American Journal of Respiratory Cell and Molecular Biology最新文献

Pulmonary hypertension (PH) patients typically present with a diminished platelet count, but the role of platelets in the development and progression of PH remains unclear. Our research has uncovered that within animal models of PH, platelet depletion or transfusion of platelets from healthy donors reduced pulmonary vascular thickening. In contrast, the transfusion of platelets from PH-affected subjects into healthy animals led to an augmentation of pulmonary vascular thickening. Transcriptomic analysis revealed that platelets from PH patients exhibited an upregulation of genes associated with cellular adhesion, platelet activation, and adhesion. Notably, the hub genes, glycoprotein IIb/IIIa (GP IIb/IIIa), were implicated in mediating platelet-endothelium adhesion through their interaction with intercellular adhesion molecule-1 (ICAM-1) on pulmonary arterial endothelial cells, triggering platelet activation and the subsequent release of platelet-derived growth factor BB (PDGF-BB). This release increased the proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs). The pharmacological targeting of ICAM-1 has been shown to mitigate PH in a murine model under hypoxic conditions; however, this ameliorative effect was not observed in thrombocytopenic mice under analogous conditions. In summary, the adhesion of platelets to the endothelium, facilitated by GP IIb/IIIa and ICAM-1, exacerbates PH by intensifying the thickening of the pulmonary vascular wall through platelet activation and PDGF-BB secretion.

Hypoxia-inducible factors (HIF-1/2) are fundamental to the development of pulmonary hypertension (PH). Prolonged hypoxia can trigger the shift from HIF-1 to HIF-2 activity, which is critical in PH progression. Ubiquitin ligases regulate HIF activity through protein degradation. However, little is known about if or how these ligases control the HIF-1/2 switch associated with PH progression. We demonstrate that STIP1 homology and U-box containing protein1 (Stub1), an E3 ubiquitin ligase, influences HIF response to hypoxia by suppressing HIF-2 and enhancing HIF-1 mRNA, protein stability, and activity. Stub1 transgenic mice exposed to prolonged hypoxia exhibited significant decreases in pulmonary vessel and right ventricular remodeling, resulting from a failure of chronic hypoxia to trigger the transition from HIF-1α to HIF-2α and activate HIF-2α. Specifically, acute hypoxia-induced the acetylation of Stub1 at lysine-287, promoting its translocation into the nucleus and selectively suppressing HIF-2 activity. Despite the deceased total Stub1 expression, the marginal increase in Stub1^K287Ac levels was sufficient for suppressing chronic hypoxia-induced HIF-2 activity in Stub1 transgenic mice. Our findings established that Stub1 acetylation regulates the putative HIF-1/2α switch driving PH progression in hypoxic and pseudohypoxic conditions.

Lysosomal dysfunction is the primary cause of various immune disorders. Transcription factor EB (TFEB) SUMOylation is critically involved in the lysosomal biogenesis. Whether TFEB SUMOylation-associated lysosomal dysfunction contributes to asthma pathogenesis remain to be determined. Here, we observed that ovalbumin (OVA)-stimulation impaired lysosomal function through TFEB SUMOylation, which leads to increased NLRP3 and inflammatory factors. Mechanistically, mutation of TFEB SUMOylation site did not abolish the ability of its nuclear translocation, but increased TFEB stability and binding capability with target genes' promoters, thereby promoting lysosomal biogenesis and bioactivity through liquid-liquid phase separation (LLPS), and thus inhibiting the production of inflammatory factors and alleviating allergic airway inflammation. Our observations demonstrate that TFEB SUMOylation interferes with lysosomal biogenesis contributing to asthma pathogenesis, lending mechanistic insight into asthmatic disease and improving our understanding of the transcriptional regulation of host immune responses.

Pleural conditions causing exudative effusions (empyema or complicated parapneumonia), can result in pathological pleural organization leading to pleural fibrosis (PF). Pleural mesothelial cells (PMCs) undergo mesenchymal transition (MesoMT) and acquire a profibrotic phenotype characterized by increased expression of α-smooth muscle actin (α-SMA), collagen 1 (Col-1) and phenotypic changes including elongation, stress fiber formation and contraction. Using RNA sequencing analysis, we identified Tuftelin1 (Tuft1) as a novel potential target. Although Prior studies have shown that Tuft1 expression is associated with aggressive cellular phenotypes, its role in pleural fibrosis (PF) is unknown. Our prior studies show that inhibition of PI3K/Akt, mTORC2, or GSK-3β blocks MesoMT. In this study, we build on previous findings and suggest that Tuft1 plays a key role in promoting MesoMT. In human (PMCs), various mediators that induce MesoMT result in upregulation of Tuft1 expression. Furthermore, we also found that Tuft1 was increased in human pleuritis tissues and in murine models of PF compared to normal lung. In our studies, TGF-β mediated increase in Tuft1 was blocked by the GSK-3β inhibitor 9-ING-41. Knockdown of Tuft1 in vitro, blocked TGFβ mediated MesoMT. Conversely, Tuft1 overexpression induced mTORC2 signaling and promoted MesoMT in the absence of TGF-β. In vivo analyses showed that mesothelial cell-specific Tuft1 knockout mice (Tuft1PMC-/-) were protected from S. pneumoniae-mediated pleural injury. Histological analysis showed that pleural thickening and profibrotic markers were significantly reduced in Tuft1PMC-/- mice compared to WT controls. These studies strongly support therapeutic targeting of Tuft1 as a novel means to mitigate PF.

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.

Lysosomal acid sphingomyelinase (ASM; SMPD1) deficiency causes Niemann-Pick Disease (NPD) that, in Type B, manifests with interstitial lung disease and susceptibility to infections. Constitutional Smpd1 (Smpd1^-/- mice) deletion causes lung inflammation with foamy dysfunctional macrophages, but is protective against acute lung injury. It is unknown whether these manifestations are from progressive accumulation of sphingomyelin, decreased ceramide, or compensatory alterations in sphingolipid metabolism. We developed a conditional knockout mouse, Smpd1^fl/flxCAGG-CreERTM, induced by tamoxifen (5 weeks), with decreased Smpd1 expression (by 75%) and ASM activity (by up to 40%). We investigated how brief post-developmental ASM insufficiency affects lung sphingolipids and pathology including following lipopolysaccharide (LPS)-induced injury. Compared to controls, Smpd1^{fl/fl mice} exhibited modest sphingomyelin elevation with lower palmitoyl/lignoceroyl ceramide (C16/C24) ratios, increased de novo sphingolipid synthesis and sphingosine-1 phosphate levels. At 3 days following LPS instillation (20μg) control mice had increased lung (neutrophilic and monocytic) inflammation and apoptosis; Smpd1^fl/fl mice showed more exuberant inflammation with reduced apoptosis, particularly in endothelial cells. During repair (6-9 days), Smpd1^fl/fl lungs had increased cell proliferation with reduced autophagosome-tagging p62/SQSTM1. These results indicate that prior to significant lysosomal lipid storage, ASM insufficiency inhibits stress-induced lung apoptosis and promotes compensatory sphingolipid changes that favor exuberant inflammatory responses to LPS. Overall, ASM inhibition limits lung vascular injury and stimulates repair following inflammatory insults. These results provide novel insights into the function of ASM in the lung, which are relevant to understanding the pathogenesis and complications of NPD and the role of distinct sphingolipid metabolites in lung injury and repair.

Organ-specific metabolic pathways, including those related to mitochondrial metabolism, could provide insight to mechanisms underlying sepsis-induced organ dysfunction. However, it remains unclear if metabolic changes result from or precede clinical organ dysfunction. To determine if blood levels of the mitochondrial metabolites acetylcarnitine and L-carnitine correlate with organ-specific signals of sepsis-induced dysfunction, we performed a series of translational analyses of two cohorts of human sepsis and experiments using a murine model of polymicrobial sepsis. We evaluated the association between mitochondrial metabolites and clinical indices of organ function. In the blood of patients with sepsis or septic shock, we found metabolic signals of dysfunctional mitochondrial b-oxidation that were correlated with clinical measures of renal and liver dysfunction. The relevance of these findings was corroborated in an experimental model that showed distinct patterns of change in organ metabolism that correlated with the blood acetylcarnitine to L-carnitine ratio. In addition, sepsis-induced changes in organ metabolism were distinct in the liver and kidney highlighting the unique energy economies of each organ. Importantly, metabolic changes preceded changes in clinical indices of organ function and histological evidence of cellular apoptosis. Based on these findings, sepsis-induced disruption in blood levels of specific metabolites could serve as more physiologically relevant indicators of early organ dysfunction than those we presently use. These early metabolite signals provide mechanistic insights to altered metabolism that may hold the key to timely identification of impending organ dysfunction. This could lead to strategies directed at the interruption of sepsis-induced organ failure.