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Publications

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  • Mark Nicolls

    Stanford University Professor of Pulmonary and Critical Care Medicine

Publications

    • A Cross-Species and Sex-Specific Meta-Analysis of Transcriptomic Studies of Pulmonary Hypertension.

      Zhao, L., Cunningham, C. M., Hong, J., Agarwal, S., Yuan, K., de Jesus Perez, V. A., Nicolls, M. R.

      American journal of respiratory cell and molecular biology

      ABSTRACT
      Pulmonary hypertension (PH) is a life-threatening disease characterized by pulmonary vascular remodeling and right ventricle (RV) dysfunction. Among the five PH groups, group 1 pulmonary arterial hypertension (PAH) is a particularly serious condition characterized by a poor prognosis. PAH can be in idiopathic (IPAH), associated (APAH), and heritable (HPAH) forms, and has a notable female predominance. A number of in vivo PH models in rodents together with in vitro cultured vascular cells such as pulmonary arterial endothelial cells (PAECs) and pulmonary arterial smooth muscle cells (PASMCs) derived from PAH patients have been widely used to reproduce the pathological disease features. To systematically evaluate the in vivo and in vitro efficacy of the existing PH model systems, publicly available whole transcriptome data from both humans and rodents were collected and analyzed. Subgroups of Schistosoma-induced female PH in mice and male chronic hypoxia (CH)-PH model in rats correlated well with human HPAH and IPAH lungs, respectively. A SU5416-CH (SuHx) PH model is well connected to the decompensated RVs of human PAH. Sex dimorphisms have been observed in PAH derived PAECs and PASMCs, independent of gonadal hormones. We conducted, for the first time, a meta-cohort and cross-species comparative study and identified optimal in vivo and in vitro PH model systems that recapitulate certain aspects of the human PH, which could provide novel insights into new therapeutic avenues in PH.
      https://www.ncbi.nlm.nih.gov/pubmed/39928415 https://doi.org/10.1165/rcmb.2024-0410OC
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    • Altered baseline immunological state and impaired immune response to SARS-CoV-2 mRNA vaccination in lung transplant recipients.

      Hu, M., Oliveira, A. P., Fang, Z., Feng, Y., Miranda, M., Kowli, S., Arunachalam, P. S., Vasudevan, G., Hui, H. S., Grifoni, A., Sette, A., Litvack, M., Rouphael, N., Suthar, M. S., Ji, X., Maecker, H. T., Hagan, T., Dhillon, G., Nicolls, M. R., Pulendran, B.

      Cell reports. Medicine

      ABSTRACT
      The effectiveness of COVID-19 mRNA vaccines is diminished in organ transplant patients. Using a multi-omics approach, we investigate the immunological state of lung transplant (LTX) recipients at baseline and after SARS-CoV-2 mRNA vaccination compared to healthy controls (HCs). LTX patients exhibit a baseline immune profile resembling severe COVID-19 and sepsis, characterized by elevated pro-inflammatory cytokines (e.g., EN-RAGE [also known as S100A12], interleukin [IL]-6), reduced human leukocyte antigen (HLA)-DR expression on monocytes and dendritic cells, impaired cytokine production, and increased plasma microbial products. Single-cell RNA sequencing identifies an enriched monocyte cluster in LTX patients marked by high S100A family expression and reduced cytokine and antigen presentation genes. Post vaccination, LTX patients show diminished antibody, B cell, and T cell responses, along with blunted innate immune signatures. Integrative analysis links these altered baseline immunological features to impaired vaccine responses. These findings provide critical insights into the immunosuppressed condition of LTX recipients and their reduced vaccine-induced adaptive and innate immune responses.
      https://www.ncbi.nlm.nih.gov/pubmed/40187358 https://doi.org/10.1016/j.xcrm.2025.102050
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    • Microbiome-Immune Interaction in Pulmonary Arterial Hypertension: What Have We Missed?

      Zhou, X., Tian, W., Gu, S., Rabinovitch, M., Nicolls, M. R., Snyder, M. P.

      Research (Washington, D.C.)

      ABSTRACT
      Pulmonary arterial hypertension (PAH) is a devastating disease characterized by perivascular inflammation, immune dysregulation, and vascular remodeling. Recent studies have unveiled a potential link between the gut microbiome and PAH pathogenesis, suggesting that microbial dysbiosis and increased intestinal permeability may contribute to the inflammatory pathology in PAH and ultimately disease progression. This perspective highlights the emerging evidence of the role of leaky gut in PAH, the interplay between microbiota-induced immune responses, and the activation of endogenous retroviruses like human endogenous retrovirus K. Understanding these complex interactions opens new interdisciplinary avenues for research and therapeutic interventions, potentially transforming PAH management through microbiome-targeted strategies.
      https://www.ncbi.nlm.nih.gov/pubmed/40207016 https://doi.org/10.34133/research.0669
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    • 3D Imaging Reveals Complex Microvascular Remodeling in the Right Ventricle in Pulmonary Hypertension.

      Ichimura, K., Boehm, M., Andruska, A. M., Zhang, F., Schimmel, K., Bonham, S., Kabiri, A., Kheyfets, V. O., Ichimura, S., Reddy, S., Mao, Y., Zhang, T., Wang, G., Santana, E. J., Tian, X., Essafri, I., Vinh, R., Tian, W., Nicolls, M. R., Yajima, S., Shudo, Y., MacArthur, J. W., Woo, Y. J., Metzger, R. J., Spiekerkoetter, E.

      Circulation research

      ABSTRACT
      Pathogenic concepts of right ventricular (RV) failure in pulmonary arterial hypertension focus on a critical loss of microvasculature. However, the methods underpinning prior studies did not take into account the 3-dimensional (3D) aspects of cardiac tissue, making accurate quantification difficult. We applied deep-tissue imaging to the pressure-overloaded RV to uncover the 3D properties of the microvascular network and determine whether deficient microvascular adaptation contributes to RV failure.Heart sections measuring 250-µm-thick were obtained from mice after pulmonary artery banding (PAB) or debanding PAB surgery and properties of the RV microvascular network were assessed using 3D imaging and quantification. Human heart tissues harvested at the time of transplantation from pulmonary arterial hypertension cases were compared with tissues from control cases with normal RV function.Longitudinal 3D assessment of PAB mouse hearts uncovered complex microvascular remodeling characterized by tortuous, shorter, thicker, highly branched vessels, and overall preserved microvascular density. This remodeling process was reversible in debanding PAB mice in which the RV function recovers over time. The remodeled microvasculature tightly wrapped around the hypertrophied cardiomyocytes to maintain a stable contact surface to cardiomyocytes as an adaptation to RV pressure overload, even in end-stage RV failure. However, microvasculature-cardiomyocyte contact was impaired in areas with interstitial fibrosis where cardiomyocytes displayed signs of hypoxia. Similar to PAB animals, microvascular density in the RV was preserved in patients with end-stage pulmonary arterial hypertension, and microvascular architectural changes appeared to vary by etiology, with patients with pulmonary veno-occlusive disease displaying a lack of microvascular complexity with uniformly short segments.3D deep tissue imaging of the failing RV in PAB mice, pulmonary hypertension rats, and patients with pulmonary arterial hypertension reveals complex microvascular changes to preserve the microvascular density and maintain a stable microvascular-cardiomyocyte contact. Our studies provide a novel framework to understand microvascular adaptation in the pressure-overloaded RV that focuses on cell-cell interaction and goes beyond the concept of capillary rarefaction.
      https://www.ncbi.nlm.nih.gov/pubmed/38770652 https://doi.org/10.1161/CIRCRESAHA.123.323546
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    • CT strain metrics allow for earlier diagnosis of bronchiolitis obliterans syndrome after hematopoietic cell transplant.

      Sharifi, H., Bertini, C. D., Alkhunaizi, M., Hernandez, M. P., Musa, Z., Borges, C., Turk, I., Bashoura, L., Dickey, B. F., Cheng, G. S., Yanik, G. A., Galban, C., Guo, H. H., Godoy, M., Reinhardt, J., Hoffman, E., Castro, M., Rondon, G., Alousi, A., Champlin, R. E., Shpall, E. J., Lu, Y., Peterson, S. W., Datta, K., Nicolls, M., Hsu, J. L., Sheshadri, A.

      Blood advances

      ABSTRACT
      Bronchiolitis obliterans syndrome (BOS) after hematopoietic cell transplantation (HCT) is associated with substantial morbidity and mortality. Quantitative CT (qCT) can help diagnose advanced BOS meeting National Institutes of Health (NIH) criteria (NIH-BOS) but has not been used to diagnose early, often asymptomatic BOS (early BOS), limiting the potential for early intervention and improved outcomes. Using Pulmonary Function Tests (PFT) to define NIH-BOS, early BOS, and mixed BOS (NIH-BOS with restrictive lung disease) in patients from two large cancer centers, we applied qCT to identify early BOS and distinguish between types of BOS. Patients with transient impairment or healthy lungs were included for comparison. PFT were done at month 0, 6, and 12. Analysis was performed with association statistics, principal component analysis, conditional inference trees (CIT), and machine learning (ML) classifier models. Our cohort included 84 allogeneic HCT recipients -- 66 BOS (NIH-defined, early, or mixed) and 18 without BOS. All qCT metrics had moderate correlation with Forced Expiratory Volume in 1 second, and each qCT metric differentiated BOS from those without BOS (non-BOS) (P < 0.0001). CIT's distinguished 94% of participants with BOS versus non-BOS, 85% early BOS versus non-BOS, 92% early BOS versus NIH-BOS. ML models diagnosed BOS with area under the curve (AUC) 0.84 (95% confidence interval [CI] 0.74-0.94) and early BOS with AUC 0.84 (95% CI 0.69 - 0.97). Quantitative CT metrics can identify individuals with early BOS, paving the way for closer monitoring and earlier treatment in this vulnerable population.
      https://www.ncbi.nlm.nih.gov/pubmed/39163616 https://doi.org/10.1182/bloodadvances.2024013748
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    • HIF2A Activation Reduces Pulmonary Angiogenesis and Promotes Vascular Remodeling in PAH by Suppressing Wnt7a Production in Pulmonary Endothelial Cells

      Mitra, A., Yi, D., Agarwal, S., Tian, A., Jiang, X., Nicolls, M. R., Zhiyu, D., Perez, V.

      ABSTRACT
      There is an unmet need for new therapeutic strategies that target alternative pathways to improve the prognosis of patients with pulmonary arterial hypertension (PAH). As immunity has been involved in the development and progression of vascular lesions in PAH, we review the potential contribution of B cells in its pathogenesis and evaluate the relevance of B cell-targeted therapies. Circulating B cell homeostasis is altered in PAH patients, with total B-cell lymphopenia, abnormal subset distribution (expansion of naive and antibody-secreting cells, reduction of memory B cells) and chronic activation. B cells are recruited to the lungs through local chemokine secretion, and activated by several mechanisms: 1) interaction with lung vascular auto-antigens through cognate B cell receptors; 2) co-stimulatory signals provided by T follicular helper (Tfh) cells (IL-21), T helper 2 (Th2) cells and mast cells (IL-4, IL-6 and IL-13); and 3) increased survival signals provided by B cell activating factor (BAFF) pathways. This activity results in the formation of germinal centres within perivascular tertiary lymphoid organs and in the local production of pathogenic autoantibodies that target the pulmonary vasculature and vascular stabilization factors (including angiotensin-II/endothelin-1 receptors and bone morphogenetic protein receptors). B cells also mediate their effects through enhanced production of pro-inflammatory cytokines, reduced anti-inflammatory properties by regulatory B cells, IgG-induced complement activation, and IgE-induced mast cell activation. Precision-medicine approaches targeting B cell immunity are a promising direction for select PAH conditions, as suggested by the efficacy of anti-CD20 therapy in experimental models and a trial of rituximab in systemic sclerosis-associated PAH.
      https://www.ncbi.nlm.nih.gov/pubmed/38575157 https://doi.org/10.1183/13993003.01518-2023
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    • CES1 Deficiency Is Associated With Endothelial Dysfunction and Metabolic Reprograming in PAH

      Agarwal, S., Heo, L., Chakraborty, A., West, J. D., Suresh, K., Nair, R. V., Nicolls, M. R., Morisseau, C., Hammock, B. D., Lafyatis, R. A., Kawut, S. M., Zamanian, R. T., Perez, V.

      ABSTRACT
      There is an unmet need for new therapeutic strategies that target alternative pathways to improve the prognosis of patients with pulmonary arterial hypertension (PAH). As immunity has been involved in the development and progression of vascular lesions in PAH, we review the potential contribution of B cells in its pathogenesis and evaluate the relevance of B cell-targeted therapies. Circulating B cell homeostasis is altered in PAH patients, with total B-cell lymphopenia, abnormal subset distribution (expansion of naive and antibody-secreting cells, reduction of memory B cells) and chronic activation. B cells are recruited to the lungs through local chemokine secretion, and activated by several mechanisms: 1) interaction with lung vascular auto-antigens through cognate B cell receptors; 2) co-stimulatory signals provided by T follicular helper (Tfh) cells (IL-21), T helper 2 (Th2) cells and mast cells (IL-4, IL-6 and IL-13); and 3) increased survival signals provided by B cell activating factor (BAFF) pathways. This activity results in the formation of germinal centres within perivascular tertiary lymphoid organs and in the local production of pathogenic autoantibodies that target the pulmonary vasculature and vascular stabilization factors (including angiotensin-II/endothelin-1 receptors and bone morphogenetic protein receptors). B cells also mediate their effects through enhanced production of pro-inflammatory cytokines, reduced anti-inflammatory properties by regulatory B cells, IgG-induced complement activation, and IgE-induced mast cell activation. Precision-medicine approaches targeting B cell immunity are a promising direction for select PAH conditions, as suggested by the efficacy of anti-CD20 therapy in experimental models and a trial of rituximab in systemic sclerosis-associated PAH.
      https://www.ncbi.nlm.nih.gov/pubmed/38575157 https://doi.org/10.1183/13993003.01518-2023
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    • Pericytes contribute to pulmonary vascular remodeling via HIF2α signaling.

      Kim, H., Liu, Y., Kim, J., Kim, Y., Klouda, T., Fisch, S., Baek, S. H., Liu, T., Dahlberg, S., Hu, C. J., Tian, W., Jiang, X., Kosmas, K., Christou, H. A., Korman, B. D., Vargas, S. O., Wu, J. C., Stenmark, K. R., Perez, V. d., Nicolls, M. R., Raby, B. A., Yuan, K.

      EMBO reports

      ABSTRACT
      Vascular remodeling is the process of structural alteration and cell rearrangement of blood vessels in response to injury and is the cause of many of the world's most afflicted cardiovascular conditions, including pulmonary arterial hypertension (PAH). Many studies have focused on the effects of vascular endothelial cells and smooth muscle cells (SMCs) during vascular remodeling, but pericytes, an indispensable cell population residing largely in capillaries, are ignored in this maladaptive process. Here, we report that hypoxia-inducible factor 2α (HIF2α) expression is increased in the lung tissues of PAH patients, and HIF2α overexpressed pericytes result in greater contractility and an impaired endothelial-pericyte interaction. Using single-cell RNAseq and hypoxia-induced pulmonary hypertension (PH) models, we show that HIF2α is a major molecular regulator for the transformation of pericytes into SMC-like cells. Pericyte-selective HIF2α overexpression in mice exacerbates PH and right ventricular hypertrophy. Temporal cellular lineage tracing shows that HIF2α overexpressing reporter NG2+ cells (pericyte-selective) relocate from capillaries to arterioles and co-express SMA. This novel insight into the crucial role of NG2+ pericytes in pulmonary vascular remodeling via HIF2α signaling suggests a potential drug target for PH.
      https://www.ncbi.nlm.nih.gov/pubmed/38243138 https://doi.org/10.1038/s44319-023-00054-w
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    • Ultrasound Neuromodulation of an Anti-Inflammatory Pathway at the Spleen Improves Experimental Pulmonary Hypertension.

      Zafeiropoulos, S., Ahmed, U., Bekiaridou, A., Jayaprakash, N., Mughrabi, I. T., Saleknezhad, N., Chadwick, C., Daytz, A., Kurata-Sato, I., Atish-Fregoso, Y., Carroll, K., Al-Abed, Y., Fudim, M., Puleo, C., Giannakoulas, G., Nicolls, M., Diamond, B., Zanos, S.

      Circulation research

      ABSTRACT
      Inflammation is pathogenically implicated in pulmonary arterial hypertension; however, it has not been adequately targeted therapeutically. We investigated whether neuromodulation of an anti-inflammatory neuroimmune pathway involving the splenic nerve using noninvasive, focused ultrasound stimulation of the spleen (sFUS) can improve experimental pulmonary hypertension.Pulmonary hypertension was induced in rats either by Sugen 5416 (20 mg/kg SQ) injection, followed by 21 (or 35) days of hypoxia (sugen/hypoxia model), or by monocrotaline (60 mg/kg IP) injection (monocrotaline model). Animals were randomized to receive either 12-minute-long sessions of sFUS daily or sham stimulation for 14 days. Catheterizations, echocardiography, indices of autonomic function, lung and heart histology and immunohistochemistry, spleen flow cytometry, and lung single-cell RNA sequencing were performed after treatment to assess the effects of sFUS.Splenic denervation right before induction of pulmonary hypertension results in a more severe disease phenotype. In both sugen/hypoxia and monocrotaline models, sFUS treatment reduces right ventricular systolic pressure by 25% to 30% compared with sham treatment, without affecting systemic pressure, and improves right ventricular function and autonomic indices. sFUS reduces wall thickness, apoptosis, and proliferation in small pulmonary arterioles, suppresses CD3+ and CD68+ cell infiltration in lungs and right ventricular fibrosis and hypertrophy and lowers BNP (brain natriuretic peptide). Beneficial effects persist for weeks after sFUS discontinuation and are more robust with early and longer treatment. Splenic denervation abolishes sFUS therapeutic benefits. sFUS partially normalizes CD68+ and CD8+ T-cell counts in the spleen and downregulates several inflammatory genes and pathways in nonclassical and classical monocytes and macrophages in the lung. Differentially expressed genes in those cell types are significantly enriched for human pulmonary arterial hypertension-associated genes.sFUS causes dose-dependent, sustained improvement of hemodynamic, autonomic, laboratory, and pathological manifestations in 2 models of experimental pulmonary hypertension. Mechanistically, sFUS normalizes immune cell populations in the spleen and downregulates inflammatory genes and pathways in the lung, many of which are relevant in human disease.
      https://www.ncbi.nlm.nih.gov/pubmed/38712557 https://doi.org/10.1161/CIRCRESAHA.123.323679
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    • Editorial: Regulatory T cells in immune-mediated diseases.

      Tran, G. T., Verma, N. D., Nicolls, M. R., Hall, B. M.

      Frontiers in immunology

      ABSTRACT
      Bronchiolitis obliterans syndrome (BOS) after hematopoietic cell transplantation (HCT) is associated with substantial morbidity and mortality. Quantitative CT (qCT) can help diagnose advanced BOS meeting National Institutes of Health (NIH) criteria (NIH-BOS) but has not been used to diagnose early, often asymptomatic BOS (early BOS), limiting the potential for early intervention and improved outcomes. Using Pulmonary Function Tests (PFT) to define NIH-BOS, early BOS, and mixed BOS (NIH-BOS with restrictive lung disease) in patients from two large cancer centers, we applied qCT to identify early BOS and distinguish between types of BOS. Patients with transient impairment or healthy lungs were included for comparison. PFT were done at month 0, 6, and 12. Analysis was performed with association statistics, principal component analysis, conditional inference trees (CIT), and machine learning (ML) classifier models. Our cohort included 84 allogeneic HCT recipients -- 66 BOS (NIH-defined, early, or mixed) and 18 without BOS. All qCT metrics had moderate correlation with Forced Expiratory Volume in 1 second, and each qCT metric differentiated BOS from those without BOS (non-BOS) (P < 0.0001). CIT's distinguished 94% of participants with BOS versus non-BOS, 85% early BOS versus non-BOS, 92% early BOS versus NIH-BOS. ML models diagnosed BOS with area under the curve (AUC) 0.84 (95% confidence interval [CI] 0.74-0.94) and early BOS with AUC 0.84 (95% CI 0.69 - 0.97). Quantitative CT metrics can identify individuals with early BOS, paving the way for closer monitoring and earlier treatment in this vulnerable population.
      https://www.ncbi.nlm.nih.gov/pubmed/39763678 https://doi.org/10.3389/fimmu.2024.1537314
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    • Rat microbial biogeography and age-dependent lactic acid bacteria in healthy lungs.

      Zhao, L., Cunningham, C. M., Andruska, A. M., Schimmel, K., Ali, M. K., Kim, D., Gu, S., Chang, J. L., Spiekerkoetter, E., Nicolls, M. R.

      Lab animal

      ABSTRACT
      The laboratory rat emerges as a useful tool for studying the interaction between the host and its microbiome. To advance principles relevant to the human microbiome, we systematically investigated and defined the multitissue microbial biogeography of healthy Fischer 344 rats across their lifespan. Microbial community profiling data were extracted and integrated with host transcriptomic data from the Sequencing Quality Control consortium. Unsupervised machine learning, correlation, taxonomic diversity and abundance analyses were performed to determine and characterize the rat microbial biogeography and identify four intertissue microbial heterogeneity patterns (P1-P4). We found that the 11 body habitats harbored a greater diversity of microbes than previously suspected. Lactic acid bacteria (LAB) abundance progressively declined in lungs from breastfed newborn to adolescence/adult, and was below detectable levels in elderly rats. Bioinformatics analyses indicate that the abundance of LAB may be modulated by the lung-immune axis. The presence and levels of LAB in lungs were further evaluated by PCR in two validation datasets. The lung, testes, thymus, kidney, adrenal and muscle niches were found to have age-dependent alterations in microbial abundance. The 357 microbial signatures were positively correlated with host genes in cell proliferation (P1), DNA damage repair (P2) and DNA transcription (P3). Our study established a link between the metabolic properties of LAB with lung microbiota maturation and development. Breastfeeding and environmental exposure influence microbiome composition and host health and longevity. The inferred rat microbial biogeography and pattern-specific microbial signatures could be useful for microbiome therapeutic approaches to human health and life quality enhancement.
      https://www.ncbi.nlm.nih.gov/pubmed/38297075 https://doi.org/10.1038/s41684-023-01322-x
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    • B cells in pulmonary arterial hypertension: friend, foe or bystander?

      Sanges, S., Tian, W., Dubucquoi, S., Chang, J. L., Collet, A., Launay, D., Nicolls, M. R.

      The European respiratory journal

      ABSTRACT
      There is an unmet need for new therapeutic strategies that target alternative pathways to improve the prognosis of patients with pulmonary arterial hypertension (PAH). As immunity has been involved in the development and progression of vascular lesions in PAH, we review the potential contribution of B cells in its pathogenesis and evaluate the relevance of B cell-targeted therapies. Circulating B cell homeostasis is altered in PAH patients, with total B-cell lymphopenia, abnormal subset distribution (expansion of naive and antibody-secreting cells, reduction of memory B cells) and chronic activation. B cells are recruited to the lungs through local chemokine secretion, and activated by several mechanisms: 1) interaction with lung vascular auto-antigens through cognate B cell receptors; 2) co-stimulatory signals provided by T follicular helper (Tfh) cells (IL-21), T helper 2 (Th2) cells and mast cells (IL-4, IL-6 and IL-13); and 3) increased survival signals provided by B cell activating factor (BAFF) pathways. This activity results in the formation of germinal centres within perivascular tertiary lymphoid organs and in the local production of pathogenic autoantibodies that target the pulmonary vasculature and vascular stabilization factors (including angiotensin-II/endothelin-1 receptors and bone morphogenetic protein receptors). B cells also mediate their effects through enhanced production of pro-inflammatory cytokines, reduced anti-inflammatory properties by regulatory B cells, IgG-induced complement activation, and IgE-induced mast cell activation. Precision-medicine approaches targeting B cell immunity are a promising direction for select PAH conditions, as suggested by the efficacy of anti-CD20 therapy in experimental models and a trial of rituximab in systemic sclerosis-associated PAH.
      https://www.ncbi.nlm.nih.gov/pubmed/38485150 https://doi.org/10.1183/13993003.01949-2023
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    • VIEWING PULMONARY HYPERTENSION THROUGH A PEDIATRIC LENS.

      Agarwal, S., Fineman, J., Cornfield, D. N., Alvira, C. M., Zamanian, R. T., Goss, K., Yuan, K., Bonnet, S., Boucherat, O., Pullamsetti, S., Alcázar, M. A., Goncharova, E., Kudryashova, T. V., Nicolls, M. R., de Jesús Pérez, V.

      The European respiratory journal

      ABSTRACT
      There is an unmet need for new therapeutic strategies that target alternative pathways to improve the prognosis of patients with pulmonary arterial hypertension (PAH). As immunity has been involved in the development and progression of vascular lesions in PAH, we review the potential contribution of B cells in its pathogenesis and evaluate the relevance of B cell-targeted therapies. Circulating B cell homeostasis is altered in PAH patients, with total B-cell lymphopenia, abnormal subset distribution (expansion of naive and antibody-secreting cells, reduction of memory B cells) and chronic activation. B cells are recruited to the lungs through local chemokine secretion, and activated by several mechanisms: 1) interaction with lung vascular auto-antigens through cognate B cell receptors; 2) co-stimulatory signals provided by T follicular helper (Tfh) cells (IL-21), T helper 2 (Th2) cells and mast cells (IL-4, IL-6 and IL-13); and 3) increased survival signals provided by B cell activating factor (BAFF) pathways. This activity results in the formation of germinal centres within perivascular tertiary lymphoid organs and in the local production of pathogenic autoantibodies that target the pulmonary vasculature and vascular stabilization factors (including angiotensin-II/endothelin-1 receptors and bone morphogenetic protein receptors). B cells also mediate their effects through enhanced production of pro-inflammatory cytokines, reduced anti-inflammatory properties by regulatory B cells, IgG-induced complement activation, and IgE-induced mast cell activation. Precision-medicine approaches targeting B cell immunity are a promising direction for select PAH conditions, as suggested by the efficacy of anti-CD20 therapy in experimental models and a trial of rituximab in systemic sclerosis-associated PAH.
      https://www.ncbi.nlm.nih.gov/pubmed/38575157 https://doi.org/10.1183/13993003.01518-2023
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    • Abnormal lymphatic S1P signaling aggravates lymphatic dysfunction and tissue inflammation.

      Kim, D., Tian, W., Wu, T. T., Xiang, M., Vinh, R., Chang, J., Gu, S., Lee, S., Zhu, Y., Guan, T., Schneider, E. C., Bao, E., Dixon, J. B., Kao, P., Pan, J., Rockson, S. G., Jiang, X., Nicolls, M. R.

      medRxiv : the preprint server for health sciences

      ABSTRACT
      BACKGROUND: Lymphedema is a global health problem with no effective drug treatment. Enhanced T cell immunity and abnormal lymphatic endothelial cell (LEC) signaling are promising therapeutic targets for this condition. Sphingosine-1-phosphate (S1P) mediates a key signaling pathway required for normal LEC function, and altered S1P signaling in LECs could lead to lymphatic disease and pathogenic T cell activation. Characterizing this biology is relevant for developing much-needed therapies.METHODS: Human and mouse lymphedema was studied. Lymphedema was induced in mice by surgically ligating the tail lymphatics. Lymphedematous dermal tissue was assessed for S1P signaling. To verify the role of altered S1P signaling effects in lymphatic cells, LEC-specific S1pr1 -deficient ( S1pr1 LECKO ) mice were generated. Disease progression was quantified by tail-volumetric and -histopathological measurements over time. LECs from mice and humans, with S1P signaling inhibition, were then co-cultured with CD4 T cells, followed by an analysis of CD4 T cell activation and pathway signaling. Finally, animals were treated with a monoclonal antibody specific to P-selectin to assess its efficacy in reducing lymphedema and T cell activation.RESULTS: Human and experimental lymphedema tissues exhibited decreased LEC S1P signaling through S1PR1. LEC S1pr1 loss-of-function exacerbated lymphatic vascular insufficiency, tail swelling, and increased CD4 T cell infiltration in mouse lymphedema. LECs, isolated from S1pr1 LECKO mice and co-cultured with CD4 T cells, resulted in augmented lymphocyte differentiation. Inhibiting S1PR1 signaling in human dermal LECs (HDLECs) promoted T helper type 1 and 2 (Th1 and Th2) cell differentiation through direct cell contact with lymphocytes. HDLECs with dampened S1P signaling exhibited enhanced P-selectin, an important cell adhesion molecule expressed on activated vascular cells. In vitro , P-selectin blockade reduced the activation and differentiation of Th cells co-cultured with sh S1PR1 -treated HDLECs. P-selectin-directed antibody treatment improved tail swelling and reduced Th1/Th2 immune responses in mouse lymphedema.CONCLUSION: This study suggests that reduction of the LEC S1P signaling aggravates lymphedema by enhancing LEC adhesion and amplifying pathogenic CD4 T cell responses. P-selectin inhibitors are suggested as a possible treatment for this pervasive condition.Clinical Perspective: What is New?: Lymphatic-specific S1pr1 deletion exacerbates lymphatic vessel malfunction and Th1/Th2 immune responses during lymphedema pathogenesis. S1pr1 -deficient LECs directly induce Th1/Th2 cell differentiation and decrease anti-inflammatory Treg populations. Peripheral dermal LECs affect CD4 T cell immune responses through direct cell contact.LEC P-selectin, regulated by S1PR1 signaling, affects CD4 T cell activation and differentiation.P-selectin blockade improves lymphedema tail swelling and decreases Th1/Th2 population in the diseased skin.What Are the Clinical Implications?: S1P/S1PR1 signaling in LECs regulates inflammation in lymphedema tissue.S1PR1 expression levels on LECs may be a useful biomarker for assessing predisposition to lymphatic disease, such as at-risk women undergoing mastectomyP-selectin Inhibitors may be effective for certain forms of lymphedema.
      https://www.ncbi.nlm.nih.gov/pubmed/37398237 https://doi.org/10.1101/2023.06.08.23291175
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    • Abnormal Lymphatic Sphingosine-1-Phosphate Signaling Aggravates Lymphatic Dysfunction and Tissue Inflammation.

      Kim, D., Tian, W., Wu, T. T., Xiang, M., Vinh, R., Chang, J. L., Gu, S., Lee, S., Zhu, Y., Guan, T., Schneider, E. C., Bao, E., Dixon, J. B., Kao, P., Pan, J., Rockson, S. G., Jiang, X., Nicolls, M. R.

      Circulation

      ABSTRACT
      Lymphedema is a global health problem with no effective drug treatment. Enhanced T-cell immunity and abnormal lymphatic endothelial cell (LEC) signaling are promising therapeutic targets for this condition. Sphingosine-1-phosphate (S1P) mediates a key signaling pathway required for normal LEC function, and altered S1P signaling in LECs could lead to lymphatic disease and pathogenic T-cell activation. Characterizing this biology is relevant for developing much needed therapies.Human and mouse lymphedema was studied. Lymphedema was induced in mice by surgically ligating the tail lymphatics. Lymphedematous dermal tissue was assessed for S1P signaling. To verify the role of altered S1P signaling effects in lymphatic cells, LEC-specific S1pr1-deficient (S1pr1LECKO) mice were generated. Disease progression was quantified by tail-volumetric and -histopathologic measurements over time. LECs from mice and humans, with S1P signaling inhibition, were then cocultured with CD4 T cells, followed by an analysis of CD4 T-cell activation and pathway signaling. Last, animals were treated with a monoclonal antibody specific to P-selectin to assess its efficacy in reducing lymphedema and T-cell activation.Human and experimental lymphedema tissues exhibited decreased LEC S1P signaling through S1P receptor 1 (S1PR1). LEC S1pr1 loss-of-function exacerbated lymphatic vascular insufficiency, tail swelling, and increased CD4 T-cell infiltration in mouse lymphedema. LECs, isolated from S1pr1LECKO mice and cocultured with CD4 T cells, resulted in augmented lymphocyte differentiation. Inhibiting S1PR1 signaling in human dermal LECs promoted T-helper type 1 and 2 (Th1 and Th2) cell differentiation through direct cell contact with lymphocytes. Human dermal LECs with dampened S1P signaling exhibited enhanced P-selectin, an important cell adhesion molecule expressed on activated vascular cells. In vitro, P-selectin blockade reduced the activation and differentiation of Th cells cocultured with shS1PR1-treated human dermal LECs. P-selectin-directed antibody treatment improved tail swelling and reduced Th1/Th2 immune responses in mouse lymphedema.This study suggests that reduction of the LEC S1P signaling aggravates lymphedema by enhancing LEC adhesion and amplifying pathogenic CD4 T-cell responses. P-selectin inhibitors are suggested as a possible treatment for this pervasive condition.
      https://www.ncbi.nlm.nih.gov/pubmed/37609838 https://doi.org/10.1161/CIRCULATIONAHA.123.064181
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    • Single-Cell Imaging Maps Inflammatory Cell Subsets to Pulmonary Arterial Hypertension Vasculopathy.

      Ferrian, S., Cao, A., McCaffrey, E. F., Saito, T., Greenwald, N. F., Nicolls, M. R., Bruce, T., Zamanian, R. T., Del Rosario, P., Rabinovitch, M., Angelo, M.

      American journal of respiratory and critical care medicine

      ABSTRACT
      Rationale: Elucidating the immune landscape within and surrounding pulmonary arteries (PAs) is critical in understanding immune-driven vascular pathology in pulmonary arterial hypertension (PAH). Although more severe vascular pathology is often observed in hereditary (H)PAH patients with BMPR2 mutations, the involvement of specific immune cell subsets remains unclear. Methods: We used cutting-edge multiplexed ion beam imaging by time-of-flight (MIBI-TOF) to compare PAs and adjacent tissue in PAH lungs (idiopathic (I)PAH and HPAH) with unused donor lungs. Measurements: We quantified immune cells' proximity and abundance, focusing on those linked to vascular pathology, and evaluated their impact on pulmonary arterial smooth muscle cells (SMCs) and endothelial cells (ECs). Results: Distinct immune infiltration patterns emerged between PAH subtypes, with intramural involvement independently linked to PA occlusive changes. Notably, we identified monocyte-derived dendritic cells (mo-DCs) within PA subendothelial and adventitial regions, influencing vascular remodeling by promoting SMC proliferation and suppressing endothelial gene expression across PAH subtypes. In HPAH patients, pronounced immune dysregulation encircled PA walls, characterized by heightened perivascular inflammation involving TIM-3+ T cells. This correlated with an expanded DC subset expressing IDO-1, TIM-3, and SAMHD1, alongside increased neutrophils, SMCs, and α-SMA+ECs, reinforcing the severity of pulmonary vascular lesions. Conclusions: This study presents the first architectural map of PAH lungs, connecting immune subsets not only with specific PA lesions but also with heightened severity in HPAH compared to IPAH. Our findings emphasize the therapeutic potential of targeting mo-DCs, neutrophils, cellular interactions, and immune responses to alleviate severe vascular pathology in IPAH and HPAH.
      https://www.ncbi.nlm.nih.gov/pubmed/37934691 https://doi.org/10.1164/rccm.202209-1761OC
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    • Endotyping COPD: hypoxia-inducible factor-2 as a molecular "switch" between the vascular and airway phenotypes?

      Myronenko, O., Foris, V., Crnkovic, S., Olschewski, A., Rocha, S., Nicolls, M. R., Olschewski, H.

      European respiratory review : an official journal of the European Respiratory Society

      ABSTRACT
      COPD is a heterogeneous disease with multiple clinical phenotypes. COPD endotypes can be determined by different expressions of hypoxia-inducible factors (HIFs), which, in combination with individual susceptibility and environmental factors, may cause predominant airway or vascular changes in the lung. The pulmonary vascular phenotype is relatively rare among COPD patients and characterised by out-of-proportion pulmonary hypertension (PH) and low diffusing capacity of the lung for carbon monoxide, but only mild-to-moderate airway obstruction. Its histologic feature, severe remodelling of the small pulmonary arteries, can be mediated by HIF-2 overexpression in experimental PH models. HIF-2 is not only involved in the vascular remodelling but also in the parenchyma destruction. Endothelial cells from human emphysema lungs express reduced HIF-2α levels, and the deletion of pulmonary endothelial Hif-2α leads to emphysema in mice. This means that both upregulation and downregulation of HIF-2 have adverse effects and that HIF-2 may represent a molecular "switch" between the development of the vascular and airway phenotypes in COPD. The mechanisms of HIF-2 dysregulation in the lung are only partly understood. HIF-2 levels may be controlled by NAD(P)H oxidases via iron- and redox-dependent mechanisms. A better understanding of these mechanisms may lead to the development of new therapeutic targets.
      https://www.ncbi.nlm.nih.gov/pubmed/36631133 https://doi.org/10.1183/16000617.0173-2022
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    • Using an Unsupervised Learning Ensemble to Identify and Evaluate PAH Immune Phenotypes Longitudinally During Disease Progression

      Sweatt, A., Hedlin, H. K., Haddad, F., Lawrie, A., Desai, M., Khatri, P., Nicolls, M. R., Rabinovitch, M., Zamanian, R. T.

      ABSTRACT
      COPD is a heterogeneous disease with multiple clinical phenotypes. COPD endotypes can be determined by different expressions of hypoxia-inducible factors (HIFs), which, in combination with individual susceptibility and environmental factors, may cause predominant airway or vascular changes in the lung. The pulmonary vascular phenotype is relatively rare among COPD patients and characterised by out-of-proportion pulmonary hypertension (PH) and low diffusing capacity of the lung for carbon monoxide, but only mild-to-moderate airway obstruction. Its histologic feature, severe remodelling of the small pulmonary arteries, can be mediated by HIF-2 overexpression in experimental PH models. HIF-2 is not only involved in the vascular remodelling but also in the parenchyma destruction. Endothelial cells from human emphysema lungs express reduced HIF-2α levels, and the deletion of pulmonary endothelial Hif-2α leads to emphysema in mice. This means that both upregulation and downregulation of HIF-2 have adverse effects and that HIF-2 may represent a molecular "switch" between the development of the vascular and airway phenotypes in COPD. The mechanisms of HIF-2 dysregulation in the lung are only partly understood. HIF-2 levels may be controlled by NAD(P)H oxidases via iron- and redox-dependent mechanisms. A better understanding of these mechanisms may lead to the development of new therapeutic targets.
      https://www.ncbi.nlm.nih.gov/pubmed/36631133 https://doi.org/10.1183/16000617.0173-2022
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    • A Selective Leukotriene B4 Antagonist, Acebilustat, for Treatment of Outpatients With COVID-19 Disease: A Randomized, Double-blind, Placebo-controlled Phase 2 Trial

      Levitt, J. E., Hedlin, H., Duong, S., Lu, D., Lee, J., Elkarra, N., Pinsky, B., Heffernan, E., Springman, E., Bonilla, H., Parsonnet, J., Zamanian, R. T., Langguth, J., Bollyky, J., Khosla, C., Nicolls, M. R., Desai, M., Moss, R., Rogers, A.

      ABSTRACT
      COPD is a heterogeneous disease with multiple clinical phenotypes. COPD endotypes can be determined by different expressions of hypoxia-inducible factors (HIFs), which, in combination with individual susceptibility and environmental factors, may cause predominant airway or vascular changes in the lung. The pulmonary vascular phenotype is relatively rare among COPD patients and characterised by out-of-proportion pulmonary hypertension (PH) and low diffusing capacity of the lung for carbon monoxide, but only mild-to-moderate airway obstruction. Its histologic feature, severe remodelling of the small pulmonary arteries, can be mediated by HIF-2 overexpression in experimental PH models. HIF-2 is not only involved in the vascular remodelling but also in the parenchyma destruction. Endothelial cells from human emphysema lungs express reduced HIF-2α levels, and the deletion of pulmonary endothelial Hif-2α leads to emphysema in mice. This means that both upregulation and downregulation of HIF-2 have adverse effects and that HIF-2 may represent a molecular "switch" between the development of the vascular and airway phenotypes in COPD. The mechanisms of HIF-2 dysregulation in the lung are only partly understood. HIF-2 levels may be controlled by NAD(P)H oxidases via iron- and redox-dependent mechanisms. A better understanding of these mechanisms may lead to the development of new therapeutic targets.
      https://www.ncbi.nlm.nih.gov/pubmed/36631133 https://doi.org/10.1183/16000617.0173-2022
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    • Evaluation of acebilustat, a selective inhibitor of leukotriene B4 biosynthesis, for treatment of outpatients with mild-moderate COVID-19 disease: A randomized, double-blind, placebo- controlled Phase 2 trial.

      Levitt, J. E., Hedlin, H., Duong, S., Lu, D., Lee, J., Bunning, B., Elkarra, N., Pinsky, B. A., Heffernan, E., Springman, E., Moss, R. B., Bonilla, H. F., Parsonnet, J., Zamanian, R. T., Langguth, J. J., Bollyky, J., Khosla, C., Nicolls, M. R., Desai, M., Rogers, A. J.

      Clinical infectious diseases : an official publication of the Infectious Diseases Society of America

      ABSTRACT
      The vast majority of COVID-19 disease occurs in outpatients where treatment is limited to anti-virals for high-risk subgroups. Acebilustat, a leukotriene B4 (LTB4) inhibitor, has potential to reduce inflammation and symptom duration.In a single-center trial spanning Delta and Omicron variants, outpatients were randomized to 100 mg of oral acebilustat or placebo for 28 days. Patients reported daily symptoms via electronic query through Day 28 with phone follow-up on Day 120 and collected nasal swabs on Days 1-10. The primary outcome was sustained symptom resolution to Day 28. Secondary 28-day outcomes included time to first symptom resolution, area under the curve (AUC) of longitudinal daily symptom scores; duration of viral shedding through Day 10; and symptoms on Day 120.Sixty participants were randomized to each study arm. At enrollment, median duration and number of symptoms were 4 (IQR 3-5) days and 9 (IQR 7-11) symptoms. Most patients (90%) were vaccinated with 73% having neutralizing antibodies. A minority (44%) of participants (35% in the acebilustat arm and 53% in placebo) had sustained symptom resolution at Day 28 (HR 0.6, 95% CI 0.34-1.04, p = 0.07 favoring placebo). There was no difference in mean AUC of symptom scores over 28 days (difference in mean of AUC 9.4, 95% CI -42.1-60.9, p=0.72). Acebilustat did not impact viral shedding or symptoms at Day 120.Sustained symptoms through Day 28 were common in this low-risk population. Despite this, LTB4 antagonism with acebilustat did not shorten symptom duration in outpatients with COVID-19.
      https://www.ncbi.nlm.nih.gov/pubmed/36996150 https://doi.org/10.1093/cid/ciad187
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