Elmadbouh, Ibrahim

Abstract Endothelial-to-mesenchymal transition (EndMT) is a biological process through which lung vascular endothelial cells (ECs) transdifferentiate into mesenchymal-like cells. EndMT has recently been implicated in the development and progression of pulmonary vascular remodeling in pulmonary hypertension (PH); however, its underlying regulatory mechanisms remain incompletely understood. MicroRNAs (miRNAs) are key post-transcriptional regulators of EC gene expression and cellular responses to various stimuli. Notably, microRNA-153 (miR-153) has been shown to directly target SNAI1 to modulate epithelial-to-mesenchymal transition (EMT), a process closely related to EndMT and extensively studied in cancer. Whether miR-153 also participates in EndMT regulation, however, remains unknown. In this study, we demonstrate that 72-hour hypoxic exposure induces SNAI1-mediated EndMT in human lung vascular ECs. Hypoxia also increased cell proliferation and disrupted intercellular junctions, leading to enhanced endothelial permeability. Reduced miR-153 expression was observed in both hypoxia- and TGF-β1-induced EndMT, as well as in ECs isolated from PH patients exhibiting an EndMT phenotype. Similar to hypoxia, TGF-β1 promoted EC permeability. Loss of miR-153 enhanced SNAI1-mediated EndMT, endothelial survival, and permeability under normoxic conditions, whereas miR-153 overexpression attenuated EndMT induced by hypoxia or TGF-β1. However, miR-153 restoration did not completely restore endothelial barrier integrity disrupted by these stimuli. In vitro findings were validated in experimental PH model. In conclusion, miR-153 serves as a critical regulator of EndMT, maintaining endothelial identity and barrier function. Therapeutic delivery of miR-153 may therefore represent a novel strategy to inhibit EndMT and attenuate pulmonary vascular remodeling in PH.

Abstract RATIONALE: Endothelial-to-mesenchymal transition (EndMT) is a cellular process in which endothelial cells (ECs) transition into mesenchymal cells, a mechanism recently linked to pulmonary vascular remodeling in pulmonary hypertension (PH). However, the regulatory mechanisms driving EndMT in PH remain largely undefined. MicroRNA-153 (miR-153), a small non-coding RNA, regulates gene expression by targeting the 3'-untranslated region (3'-UTR) of mRNA, affecting mRNA translation and stability. This study investigates miR-153's role in modulating EndMT in PH. METHODS: Human lung vascular endothelial cells (LVECs) were isolated from healthy individuals and patients with idiopathic pulmonary arterial hypertension (IPAH). In vitro, normal LVECs were exposed to hypoxia (3% O₂) for 72 hours or treated with TGF-β1 (10 ng/mL) for 7 days to induce EndMT. Levels of miR-153 and EndMT markers were quantified by qPCR, Western blotting, or immunostaining. Proliferation and apoptosis of ECs were assessed using EdU and TUNEL assays, respectively. LVECs were transfected with miR-153 inhibitor or mimic, then exposed to normoxic or hypoxic conditions, respectively for 72 hours. In vivo, mice were subjected to either hypoxia (10% O₂ for 6 weeks, Hx-PH) or Sugen5416/hypoxia (20 mg/kg i.p. plus 10% O₂ for 6 weeks, SuHx-PH) to induce PH. The PH phenotype in mice was evaluated by hemodynamic measurements and histological analysis of H&E-stained lung tissues. RESULTS:In silico analysis identified miR-153 as a direct regulator of human SNAI1 and SNAI2 genes via binding to their 3'-UTR. Downregulation of miR-153 in IPAH LVECs was correlated with elevated SNAI1/2 expression, increased EndMT, and higher proliferation compared to normal LVECs. Hypoxia or TGF-β1 treatment reduced miR-153 expression, increased EndMT transcription factors (SNAI1/2), mesenchymal markers (SM-22, vimentin), and reduced EC markers (CD31, VE-cadherin). In normoxic LVECs, miR-153 inhibition significantly upregulated SNAI1/2, increased EndMT and EC proliferation, and reduced apoptosis. Conversely, miR-153 mimic abolished hypoxia- and TGF-β1-induced EndMT. Overexpression of miR-153 attenuated hypoxia-induced EC survival. In PH mouse models, reduced miR-153 levels were associated with activated SNAI1/2, EndMT, and pulmonary vascular remodeling. CONCLUSIONS: Downregulation of miR-153 drives phenotypic transition of LVECs to proliferative mesenchymal cells via SNAI-mediated EndMT, contributing to pulmonary vascular remodeling and PH. Therefore, miR-153 could be a potential therapeutic target for PH treatment.

EndMT has been reported to contribute to the pathogenesis of PAH. In this study, we aimed to determine the role of Ca 2+ signaling in the development of EndMT in human lung vascular endothelial cells. Our data suggest that TGF-β 1 requires store-operated Ca 2+ entry through STIM1/Orai channels to induce SNAI-mediated EndMT. For the first time, we demonstrated that TGF-β 1 -induced EndMT is a Ca 2+ -dependent event, whereas inhibition of STIM1/Orai interaction attenuated EndMT in response to TGF-β 1 .

Abstract Through its classic ATP‐dependent ion‐pumping function, basolateral Na/K‐ATPase (NKA) generates the Na + gradient that drives apical Na + reabsorption in the renal proximal tubule (RPT), primarily through the Na + /H + exchanger (NHE3). Accordingly, activation of NKA‐mediated ion transport decreases natriuresis through activation of basolateral (NKA) and apical (NHE3) Na + reabsorption. In contrast, activation of the more recently discovered NKA signaling function triggers cellular redistribution of RPT NKA and NHE3 and decreases Na + reabsorption. We used gene targeting to test the respective contributions of NKA signaling and ion pumping to the overall regulation of RPT Na + reabsorption. Knockdown of RPT NKA in cells and mice increased membrane NHE3 and Na + /HCO 3 − cotransporter (NBCe1A). Urine output and absolute Na + excretion decreased by 65%, driven by increased RPT Na + reabsorption (as indicated by decreased lithium clearance and unchanged glomerular filtration rate), and accompanied by elevated blood pressure. This hyper reabsorptive phenotype was rescued upon crossing with RPT NHE3 −/− mice, confirming the importance of NKA/NHE3 coupling. Hence, NKA signaling exerts a tonic inhibition on Na + reabsorption by regulating key apical and basolateral Na + transporters. This action, lifted upon NKA genetic suppression, tonically counteracts NKA's ATP‐driven function of basolateral Na + reabsorption. Strikingly, NKA signaling is not only physiologically relevant but it also appears to be functionally dominant over NKA ion pumping in the control of RPT reabsorption.