Bachelor of Science, China Pharmaceutical University (2010)
Doctor of Philosophy, Peking University Health Science Center (2015)
Using proteomic approaches, we uncovered a DNA damage response (DDR) function for peroxisome proliferator activated receptor gamma (PPARgamma) through its interaction with the DNA damage sensor MRE11-RAD50-NBS1 (MRN) and the E3 ubiquitin ligase UBR5. We show that PPARgamma promotes ATM signaling and is essential for UBR5 activity targeting ATM interactor (ATMIN). PPARgamma depletion increases ATMIN protein independent of transcription and suppresses DDR-induced ATM signaling. Blocking ATMIN in this context restores ATM activation and DNA repair. We illustrate the physiological relevance of PPARgamma DDR functions by using pulmonary arterial hypertension (PAH) as a model that has impaired PPARgamma signaling related to endothelial cell (EC) dysfunction and unresolved DNA damage. In pulmonary arterial ECs (PAECs) from PAH patients, we observed disrupted PPARgamma-UBR5 interaction, heightened ATMIN expression, and DNA lesions. Blocking ATMIN in PAH PAEC restores ATM activation. Thus, impaired PPARgamma DDR functions may explain the genomic instability and loss of endothelial homeostasis in PAH.
View details for DOI 10.1016/j.celrep.2019.01.013
View details for PubMedID 30699358
Amphetamine (AMPH) or methamphetamine (METH) abuse can cause oxidative damage and is a risk factor for diseases including pulmonary arterial hypertension (PAH). Pulmonary artery endothelial cells (PAECs) from AMPH-associated-PAH patients show DNA damage as judged by ?H2AX foci and DNA comet tails. We therefore hypothesized that AMPH induces DNA damage and vascular pathology by interfering with normal adaptation to an environmental perturbation causing oxidative stress. Consistent with this, we found that AMPH alone does not cause DNA damage in normoxic PAECs, but greatly amplifies DNA damage in hypoxic PAECs. The mechanism involves AMPH activation of protein phosphatase 2A, which potentiates inhibition of Akt. This increases sirtuin 1, causing deacetylation and degradation of HIF1?, thereby impairing its transcriptional activity, resulting in a reduction in pyruvate dehydrogenase kinase 1 and impaired cytochrome c oxidase 4 isoform switch. Mitochondrial oxidative phosphorylation is inappropriately enhanced and, as a result of impaired electron transport and mitochondrial ROS increase, caspase-3 is activated and DNA damage is induced. In mice given binge doses of METH followed by hypoxia, HIF1? is suppressed and pulmonary artery DNA damage foci are associated with worse pulmonary vascular remodeling. Thus, chronic AMPH/METH can induce DNA damage associated with vascular disease by subverting the adaptive responses to oxidative stress.
View details for DOI 10.1172/jci.insight.90427
View details for PubMedID 28138562
Background -Immune dysregulation has been linked to occlusive vascular remodeling in pulmonary arterial hypertension (PAH) that is hereditary, idiopathic or associated with other conditions. Circulating autoantibodies, lung perivascular lymphoid tissue and elevated cytokines have been related to PAH pathogenesis but without clear understanding of how these abnormalities are initiated, perpetuated and connected in the progression of disease. We therefore set out to identify specific target antigens in PAH lung immune complexes as a starting point toward resolving these issues to better inform future application of immunomodulatory therapies. Methods -Lung immune complexes were isolated and PAH target antigens were identified by liquid chromatography tandem mass spectrometry (LCMS), confirmed by ELISA, and localized by confocal microscopy. One PAH antigen linked to immunity and inflammation was pursued and a link to PAH pathophysiology was investigated by next generation sequencing, functional studies in cultured monocytes and endothelial cells (EC) and hemodynamic and lung studies in a rat. Results -SAM domain and HD1 domain-containing protein (SAMHD1), an innate immune factor that suppresses HIV replication was identified and confirmed as highly expressed in immune complexes from 16 hereditary and idiopathic PAH vs. 12 control lungs. Elevated SAMHD1 was localized to endothelial cells (EC), perivascular dendritic cells and macrophages and SAMHD1 antibodies were prevalent in tertiary lymphoid tissue. An unbiased screen using metagenomic sequencing related SAMHD1 to increased expression of human endogenous retrovirus K (HERV-K) in PAH vs. control lungs (n=4 each). HERV-K envelope and deoxyuridine triphosphate nucleotidohydrolase (dUTPase) mRNAs were elevated in PAH vs. control lungs (n=10) and proteins were localized to macrophages. HERV-K dUTPase induced SAMHD1 and pro-inflammatory cytokines (e.g., IL6, IL1? and TNF?) in circulating monocytes and pulmonary arterial (PA) EC, and activated B cells. Vulnerability of PAEC to apoptosis was increased by HERV-K dUTPase in an IL6 independent manner. Furthermore, three weekly injections of HERV-K dUTPase induced hemodynamic and vascular changes of pulmonary hypertension in rats (n=8), and elevated IL6. Conclusions -Our study reveals that upregulation of the endogenous retrovirus HERV-K could both initiate and sustain activation of the immune system and cause vascular changes associated with PAH.
View details for PubMedID 28935667
Idiopathic or heritable pulmonary arterial hypertension is characterized by loss and obliteration of lung vasculature. Endothelial cell dysfunction is pivotal to the pathophysiology but different causal mechanisms may reflect a need for patient-tailored therapies.Endothelial cells differentiated from induced pluripotent stem cells were compared to pulmonary arterial endothelial cells from the same patients with idiopathic or heritable pulmonary arterial hypertension, to determine whether they shared functional abnormalities and altered gene expression patterns, that differed from those in unused donor cells. We then investigated whether endothelial cells differentiated from pluripotent cells could serve as surrogates to test emerging therapies.Functional changes assessed included adhesion, migration, tube formation, and propensity to apoptosis. Expression of BMPR2 and its target, collagen IV, pSMAD1/5 signaling and transcriptomic profiles were also analyzed.Native pulmonary arterial and induced pluripotent stem cell-derived endothelial cells from idiopathic and heritable pulmonary arterial hypertension patients compared to controls, showed a similar reduction in adhesion, migration, survival, and tube formation, decreased BMPR2 and downstream signaling and collagen IV expression. Transcriptomic profiling revealed high KISS1 related to reduced migration and low CES1, to impaired survival in patient cells. A beneficial angiogenic response to potential therapies, FK-506 and Elafin, was related to reduced SLIT3, an anti-migratory factor.Despite the site of disease in the lung our study indicates that induced pluripotent stem cell derived endothelial cells are useful surrogates to uncover novel features related to disease mechanisms and to better match patients to therapies.
View details for PubMedID 27779452