Airway hypoxia in lung transplantation
CURRENT OPINION IN PHYSIOLOGY
2019; 7: 21–26
Phenotypically-Silent Bone Morphogenetic Protein Receptor 2 (Bmpr2) Mutations Predispose Rats to Inflammation-Induced Pulmonary Arterial Hypertension by Enhancing The Risk for Neointimal Transformation.
Endothelial HIF-2alpha is Required for the Maintenance of Airway Microvasculature.
Bmpr2 mutations are critical risk factors for hereditary pulmonary arterial hypertension (hPAH) with approximately 20% of carriers developing disease. There is an unmet medical need to understand how environmental factors, such as inflammation, render Bmpr2 mutants susceptible to PAH. Overexpressing 5-lipoxygenase (5-LO) provokes lung inflammation and transient PAH in Bmpr2+/- mice. Accordingly, 5-LO and its metabolite, leukotriene B4 (LTB4), are candidates for the 'second hit'. The purpose of this study was to determine how 5-LO-mediated pulmonary inflammation synergized with phenotypically-silent Bmpr2 defects to elicit significant pulmonary vascular disease in rats.Monoallelic Bmpr2 mutant rats were generated and found phenotypically normal for up to one year of observation. To evaluate whether a second hit would elicit disease, animals were exposed to 5-LO-expressing adenovirus (AdAlox5), monocrotaline, SU5416, SU5416 with chronic hypoxia or chronic hypoxia alone. Bmpr2-mutant hPAH patient samples were assessed for neointimal 5-LO expression. Pulmonary artery endothelial cells (PAECs) with impaired BMPR2 signaling were exposed to increased 5-LO-mediated inflammation and were assessed for phenotypic and transcriptomic changes.Lung inflammation, induced by intratracheal delivery of AdAlox5, elicited severe PAH with intimal remodeling in Bmpr2+/- rats but not in their wild-type littermates. Neointimal lesions in the diseased Bmpr2+/- rats gained endogenous 5-LO expression associated with elevated LTB4 biosynthesis. Bmpr2-mutant hPAH patients similarly expressed 5-LO in the neointimal cells. In vitro, BMPR2 deficiency, compounded by 5-LO-mediated inflammation, generated apoptosis-resistant, and proliferative PAECs with mesenchymal characteristics. These transformed cells expressed nuclear envelope-localized 5-LO consistent with induced LTB4 production, as well as a transcriptomic signature similar to clinical disease, including upregulated NF-κB, IL-6, and TGF-β signaling pathways. The reversal of PAH and vasculopathy in Bmpr2 mutants by TGF-β antagonism suggests that TGF-β is critical for neointimal transformation.In a new 'two-hit' model of disease, lung inflammation induced severe PAH pathology in Bmpr2+/- rats. Endothelial transformation required the activation of canonical and noncanonical TGF-β signaling pathways and was characterized by 5-LO nuclear envelope translocation with enhanced LTB4 production. This study offers one explanation of how an environmental injury unleashes the destructive potential of an otherwise-silent genetic mutation.
View details for DOI 10.1161/CIRCULATIONAHA.119.040629
View details for PubMedID 31462075
Microhemorrhage-associated tissue iron enhances the risk forAspergillus fumigatusinvasion in a mouse model of airway transplantation.
Science translational medicine
2018; 10 (429)
BACKGROUND: Hypoxia-inducible factors (HIFs), especially HIF-1alpha and HIF-2alpha, are key mediators of the adaptive response to hypoxic stress and play essential roles in maintaining lung homeostasis. Human and animal genetics studies confirm that abnormal HIF correlates with pulmonary vascular pathology and chronic lung diseases, but it remains unclear whether endothelial cell (EC) HIF production is essential for microvascular health. The large airway has an ideal circulatory bed for evaluating histologic changes and physiology in genetically-modified rodents.METHODS: The tracheal microvasculature of mice, with conditionally-deleted or overexpressed HIF-1alpha or HIF-2alpha, was evaluated for anatomy, perfusion, and permeability. Angiogenic signaling studies assessed vascular changes attributable to dysregulated HIF expression. An orthotopic tracheal transplantation model further evaluated the contribution of individual HIF isoforms in airway ECs.RESULTS: The genetic deletion of Hif-2alpha, but not Hif-1alpha, caused tracheal EC apoptosis, diminished pericyte coverage, reduced vascular perfusion, defective barrier function, overlying epithelial abnormalities and subepithelial fibrotic remodeling. HIF-2alpha promoted microvascular integrity in airways through endothelial angiopoietin-1/TIE2 signaling and Notch activity. In functional tracheal transplants, HIF-2alpha deficiency in airway donors accelerated graft microvascular loss, whereas HIF-2alpha or angiopoietin-1 overexpression prolonged transplant microvascular perfusion. Augmented endothelial HIF-2alpha in transplant donors promoted airway microvascular integrity and diminished alloimmune inflammation.CONCLUSIONS: Our findings reveal that the constitutive expression of endothelial HIF-2alpha is required for airway microvascular health.
View details for PubMedID 30586708
Combined heart lung transplantation: an updated review of the current literature.
Invasive pulmonary disease due to the moldAspergillus fumigatuscan be life-threatening in lung transplant recipients, but the risk factors remain poorly understood. To study this process, we used a tracheal allograft mouse model that recapitulates large airway changes observed in patients undergoing lung transplantation. We report that microhemorrhage-related iron content may be a major determinant ofA. fumigatusinvasion and, consequently, its virulence. Invasive growth was increased during progressive alloimmune-mediated graft rejection associated with high concentrations of ferric iron in the graft. The role of iron inA. fumigatusinvasive growth was further confirmed by showing that this invasive phenotype was increased in tracheal transplants from donor mice lacking the hemochromatosis gene (Hfe
). The invasive phenotype was also increased in mouse syngrafts treated with topical iron solution and in allograft recipients receiving deferoxamine, a chelator that increases iron bioavailability to the mold. The invasive growth of the iron-intolerantA. fumigatusdouble-knockout mutant (ΔsreA/ΔcccA) was lower than that of the wild-type mold. Alloimmune-mediated microvascular damage and iron overload did not appear to impair the host's immune response. In human lung transplant recipients, positive staining for iron in lung transplant tissue was more commonly seen in endobronchial biopsy sections from transplanted airways than in biopsies from the patients' own airways. Collectively, these data identify iron as a major determinant ofA. fumigatusinvasive growth and a potential target to treat or preventA. fumigatusinfections in lung transplant patients.
View details for PubMedID 29467298
Aspergillus-related pulmonary diseases in lung transplantation
2017; 55 (1): 96-102
Heart lung transplantation is a viable treatment option for patients with many end stage heart and lung pathologies. However, given the complex nature of the procedure, it is imperative that patients are selected appropriately and the clinician is aware of the many unique aspects in management of this population. This review seeks to describe updated organ selection policies, peri and postoperative management strategies, monitoring of graft function, and clinical outcomes for patients following combined heart-lung transplantation in the current era.
View details for DOI 10.1097/TP.0000000000001820
View details for PubMedID 28505026
Lung transplantation following death by drowning: a review of the current literature.
2016; 30 (10): 1195-1197
While lung transplantation is an attractive treatment option for many end stage lung diseases, the relatively high 5-year mortality continues to be a significant limiting factor. Among the foremost reasons for this is the eventual development of obstructive chronic lung allograft dysfunction. Infections, which the lung allograft is especially prone to, are a major risk factor. Specifically, the Aspergillus species cause a higher burden of disease among lung transplant recipients, due to unique risk factors, such as relative hypoxemia. However, these risk factors also provide unique opportunities for treatment and preventative strategies, as outlined in this review.
View details for DOI 10.1093/mmy/myw121
View details for Web of Science ID 000393896500013
Elevated Troponin? Take Heart and Reconsider!
2016; 9 (6)
Central venous catheters: incidence and predictive factors of venous thrombosis
2015; 84 (1): 21-28
While multiple donor characteristics have been cited as ideal for lung transplantation, there are minimal widely accepted exclusion criteria. One criterion that many centers view with hesitation is death by drowning. However, recent literature suggests such donors may result in acceptable outcomes following transplation. This review highlights a case of a patient who underwent successful bilateral lung transplant from a donor following a drowning event. A review of the current literature is presented, concluding with a new proposed set of favorable donor criteria following death by drowning. This article is protected by copyright. All rights reserved.
View details for DOI 10.1111/ctr.12822
View details for PubMedID 27447443
Initial Commitment to Pre-Exposure Prophylaxis and Circumcision for HIV Prevention amongst Indian Truck Drivers
2010; 5 (7)
Central venous catheter access in an acute setting can be a challenge given underlying disease and risk for venous thrombosis. Peripherally inserted central venous catheters (PICCs) are commonly placed but limit sites for fistula creation in patients with chronic renal failure (CKD). The aim of this study is to determine the incidence of venous thrombosis from small bore internal jugular (SBIJ) and PICC line placement. This investigation identifies populations of patients who may not be ideal candidates for a PICC and highlights the importance of peripheral vein preservation in patients with renal failure.A venous Doppler ultrasound was performed at the time of SBIJ insertion and removal to evaluate for thrombosis in the internal jugular vein. Data was collected pre- and post-intervention to ascertain if increased vein preservation knowledge amongst the healthcare team led to less use of PICCs. Demographic factors were collected in the SBIJ and PICC groups and risk factor analysis was completed.1,122 subjects had PICC placement and 23 had SBIJ placement. The incidence of thrombosis in the PICC group was 10%. One patient with an SBIJ had evidence of central vein thrombosis when the catheter was removed. Univariate and multivariate analysis demonstrated a history of transplant, and the indication of total parenteral nutrition was associated with thrombosis (p<0.001). The decrease in PICCs placed in patients with CKD 6 months before and after intervention was significant (p<0.05).There are subsets of patients ith high risk for thrombosis who may not be ideal candidates for a PICC.
View details for DOI 10.5414/CN108347
View details for Web of Science ID 000364530900003
View details for PubMedID 25997503
View details for PubMedCentralID PMC4750112
Studies of HIV prevention interventions such as pre-exposure prophylaxis (PREP) and circumcision in India are limited. The present study sought to investigate Indian truck-drivers initial commitment to PREP and circumcision utilizing the AIDS Risk Reduction Model. Ninety truck-drivers completed an in-depth qualitative interview and provided a blood sample for HIV and HSV-2 testing. Truck-drivers exhibited low levels of initial commitment towards PREP and even lower for circumcision. However, potential leverage points for increasing commitment were realized in fear of infecting family rather than self, self-perceptions of risk, and for PREP focusing on cultural beliefs towards medication and physicians. Cost was a major barrier to both HIV prevention interventions. Despite these barriers, our findings suggest that the ARRM may be useful in identifying several leverage points that may be used by peers, health care providers and public health field workers to enhance initial commitment to novel HIV prevention interventions in India.
View details for DOI 10.1371/journal.pone.0011922
View details for Web of Science ID 000280520300031
View details for PubMedID 20689602
View details for PubMedCentralID PMC2912853