Biology subjects

Shimoda, L.

Publications and source records attributed to Shimoda, L..

6 recordsLinked to original sources

bioRxiv2025

Na+/H+ Exchanger Isoform 1 Regulates Apoptosis Susceptibility in Pulmonary Arterial Smooth Muscle from the Sugen/Hypoxia model of Pulmonary Hypertension

Pulmonary hypertension (PH) is characterized by vascular remodeling driven in part by apoptosis-resistant pulmonary arterial smooth muscle cells (PASMCs). Na/H exchanger isoform 1 (NHE1) regulates intracellular pH and plasma membrane cytoskeleton anchoring, influencing PASMC migration and proliferation, but the role of NHE1 in apoptosis remains unclear. NHE activity and NHE1 surface expression were increased in PASMCs from the Sugen/Hypoxia (SuHx) rat model compared to controls. Despite increased endoplasmic reticulum (ER) stress at baseline, SuHx PASMCs were resistant to apoptosis following H2O2 challenge. Pharmacological inhibition of NHE activity with ethyl-isopropyl amiloride (EIPA) and silencing with siRNA restored apoptosis in SuHx PASMCs. Conversely, NHE1 overexpression in control PASMCs conferred apoptosis resistance. Expression of mutant NHE1 constructs lacking ion translocation or binding to the adaptor protein, ezrin, also reduced H2O2-induced apoptosis. Mechanistically, apoptotic stimulation with H2O2 increased p38 phosphorylation in PASMCs from control, but not SuHx, rats, indicating impaired activation of this pro-apoptotic pathway. NHE1 suppression via EIPA or siRNA restored p38 phosphorylation in SuHx PASMCs, while overexpression of NHE1 (wild-type or mutants) suppressed p38 activation following apoptotic stimulation. Inhibition of p38 with SB203580 prevented the pro-apoptotic effect of EIPA, validating a role for p38 signaling in NHE1-mediated apoptosis resistance in SuHx PASMCs. These findings identify NHE1 as necessary and sufficient for PASMC apoptosis resistance in PH, by a mechanism independent of ion transport or ezrin-binding functions but involving suppression of p38 phosphorylation. Targeting NHE1-dependent pathways may restore PASMC apoptosis and offer a novel therapeutic strategy to reverse pulmonary vascular remodeling in PH.

physiology↗

bioRxiv2024

Single-cell transcriptomics reveal diverging pathobiology and opportunities for precision targeting in scleroderma-associated versus idiopathic pulmonary arterial hypertension

IntroductionPulmonary arterial hypertension (PAH) involves progressive cellular and molecular change within the pulmonary vasculature, leading to increased vascular resistance. Current therapies targeting nitric oxide (NO), endothelin, and prostacyclin pathways yield variable treatment responses. Patients with systemic sclerosis-associated PAH (SSc-PAH) often experience worse outcomes than those with idiopathic PAH (IPAH). MethodsLung tissue samples from four SSc-PAH, four IPAH, and four failed donor specimens were obtained from the Pulmonary Hypertension Breakthrough Initiative (PHBI) lung tissue bank. Single-cell RNA sequencing (scRNAseq) was performed using the 10X Genomics Chromium Flex platform. Data normalization, clustering, and differential expression analysis were conducted using Seurat. Additional analyses included gene set enrichment analysis (GSEA), transcription factor activity analysis, and ligand-receptor signaling. Pharmacotranscriptomic screening was performed using the Connectivity Map. ResultsSSc-PAH samples showed a higher proportion of fibroblasts and dendritic cells/macrophages compared to IPAH and donor samples. GSEA revealed enriched pathways related to epithelial-to-mesenchymal transition (EMT), apoptosis, and vascular remodeling in SSc-PAH samples. There was pronounced differential gene expression across diverse pulmonary vascular cell types and in various epithelial cell types in both IPAH and SSc-PAH, with epithelial to endothelial cell signaling observed. Macrophage to endothelial cell signaling was particularly pronounced in SSc-PAH. Pharmacotranscriptomic screening identified TIE2, GSK-3, and PKC inhibitors, among other compounds, as potential drug candidates for reversing SSc-PAH gene expression signatures. DiscussionOverlapping and distinct gene expression patterns exist in SSc-PAH versus IPAH, with significant molecular differences suggesting unique pathogenic mechanisms in SSc-PAH. These findings highlight the potential for precision-targeted therapies to improve SSc-PAH patient outcomes. Future studies should validate these targets clinically and explore their therapeutic efficacy.

bioinformatics↗

bioRxiv2023

Aquaporin 1 confers apoptosis resistance in pulmonary arterial smooth muscle cells from the SU5416 hypoxia rat model

Pulmonary arterial hypertension (PAH) is a deadly condition that arises from increased pulmonary vascular resistance due to contraction and remodeling of the pulmonary arteries. The structural changes that occur in the pulmonary arteries include thickening of the medial (smooth muscle) layer resulting from increased proliferation and resistance to apoptosis. The mechanisms underlying apoptosis resistance in PAH are not fully understood. In cancer cells, high expression of aquaporin 1 (AQP1), a water channel, is associated with apoptosis resistance. We previously showed functional AQP1 protein was expressed in pulmonary arterial smooth muscle cells (PASMCs) and was upregulated in pre-clinical models of pulmonary hypertension. Whether AQP1 controls susceptibility of PASMCs to apoptosis in pre-clinical models of PAH is unknown. In this study, we used PASMCs isolated from control rats and rats exposed to SU5416 plus hypoxia (SuHx) to test the role of AQP1 in modulating apoptosis in PASMCs. We found that elevated levels of AQP1 in PASMCs from pulmonary hypertensive rats were necessary for resistance to apoptosis, and that apoptosis resistance could be conferred by increasing expression of AQP1 in PASMCs from control rats. Moreover, in exploring the downstream pathways involved, we found AQP1 levels influence the expression of Bcl-2, with enhanced AQP1 levels corresponding to increased Bcl-2 expression, resulting in reductions in the ratio of BAX to Bcl-2 as are typically associated with apoptosis resistance. These early results provide a mechanism by which AQP1 can regulate PASMC fate and suggest further investigation could provide additional clues regarding whether AQP1-mediated apoptosis resistance contributes to PAH development or progression and whether AQP1 might be a suitable target for therapy.

cell biology↗

bioRxiv2023

A Novel Interaction Between Aquaporin 1 and Caspase-3 in Pulmonary Arterial Smooth Muscle Cells

Pulmonary arterial hypertension (PAH) is a disease in which remodeling of the precapillary pulmonary vasculature leads to hyperplasia and hypertrophy of the muscular vascular wall, and the formation of vaso-occlusive lesions. These pathologic changes are predominantly due to abnormal proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), enhanced cellular functions that have been linked to increases in the cell membrane protein aquaporin-1 (AQP1). However, the mechanisms underlying increased AQP1 abundance have not been fully elucidated. Here we present data that establishes a novel interaction between AQP1 and the proteolytic enzyme caspase-3. In silico analysis of the AQP1 protein reveals two caspase-3 cleavage sites on its c-terminal tail, proximal to known ubiquitin sites. Using biotin proximity ligase techniques, we establish that AQP1 and caspase-3 interact in both HEK293A cells and rat PASMCs. Furthermore, we demonstrate that AQP1 levels increase and decrease with enhanced caspase-3 activity and inhibition respectively. Ultimately, further work characterizing this interaction could provide the foundation for novel PAH therapeutics.

cell biology↗

bioRxiv2021

Ca2+ Mediates HIF-dependent Upregulation of Aquaporin 1 in Pulmonary Arterial Smooth Muscle Cells

Prolonged exposure to hypoxia causes structural remodeling and sustained contraction of the pulmonary vasculature, resulting in the development of pulmonary hypertension. Both pulmonary arterial smooth muscle cell (PASMC) proliferation and migration contribute to the vascular remodeling. We previously showed that the protein expression of aquaporin 1 (AQP1), a membrane water channel protein, is elevated in PASMCs during following in vivo or in vitro exposure to hypoxia. Studies in other cell types suggest that AQP1 is a direct transcriptional target of hypoxia inducible factor (HIF)-1. Moreover, we and others have shown that an increase in intracellular calcium concentration ([Ca2+]i) is a hallmark of hypoxic exposure in PASMCs. Thus, we wanted to determine whether HIF regulates AQP1 in PASMCs and, if so, whether the process occurred via transcriptional regulation or was Ca2+-dependent. PASMCs were exposed to hypoxia, incubated with DMOG, which inhibits HIF protein degradation or infected with constitutively active forms of HIF-1 or HIF-2. Hypoxia, DMOG and HIF1/2 produced a time-dependent increase in AQP1 protein, but not mRNA. Interestingly, incubation with increasing HIF1/2a levels and DMOG increased [Ca2+]i in PASMCs, and this elevation was prevented by the voltage-gated Ca2+ channel inhibitor, verapamil (VER) and nonselective cation channel inhibitor SKF96365 (SKF). VER and SKF also blocked upregulation of AQP1 protein by DMOG or HIF1/2, but had no effect on expression of GLUT1, a canonical HIF transcriptional target. Silencing of AQP1 abrogated increases in PASMC migration and proliferation induced by HIF1/2, suggesting induction of AQP1 protein by HIF1/2 has a functional outcome in these cells. Thus, our results show that contrary to reports in other cell types, in PASMCs, AQP1 does not appear to be a direct target for HIF transcriptional regulation. Instead, AQP1 protein may be upregulated by a mechanism involving HIF-dependent increases in [Ca2+]i.

cell biology↗

bioRxiv2021

MK2 Expression Promotes Non-Small Cell Lung Cancer Cell Death and Predicts Survival

Non-small cell lung cancers demonstrate intrinsic resistance to cell death even in response to chemotherapy. Previous work suggested that defective nuclear translocation of active caspase 3 may play a role in resistance to cell death. Separately, our group has identified that mitogen activated protein kinase activated protein kinase 2 (MK2) is required for nuclear translocation of active caspase 3 in the execution of apoptosis. This study demonstrates a relatively low expression of MK2 in non-small cell lung carcinoma cell lines compared to small cell carcinoma cell lines. Further, overexpression of MK2 in non-small cell lung carcinoma cell lines results in increased caspase 3 activity and caspase 3 mediated cell death. Higher MK2 transcript levels were observed in patients with earlier-stage non-small cell lung cancer. Higher expression of MK2 is associated with better survival in patients with early stage non-small cell lung cancer across two independent clinical datasets. Using data sets spanning multiple cancer types, we observed improved survival with higher MK2 expression was unique to lung adenocarcinoma. Mechanistically, MK2 promotes nuclear translocation of caspase 3 leading to PARP1 cleavage and execution of cell death. While MK2 can directly phosphorylate caspase 3, neither phosphorylation status of caspase 3 nor the kinase activity of MK2 impacts caspase 3 activation, nuclear translocation and execution of cell death. Rather, a non-kinase function of MK2, specifically trafficking via its nuclear localization sequence, is required for caspase 3 mediated cell death. In summary this study highlights the importance of a non-enzymatic function of MK2 in the execution of apoptosis, which may be leveraged in the adjunctive treatment of NSCLC or other conditions where regulation of apoptosis is crucial.

cancer biology↗