TXNDC5 Governs Extracellular Matrix Homeostasis in Pulmonary Hypertension
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BACKGROUND
Pulmonary hypertension (PH) is characterized by vascular remodeling without effective treatments. The initiation and progression of PH are heavily influenced by the dysfunction of pulmonary artery endothelial cells. Thioredoxin domain containing 5 (TXNDC5), a member of the protein disulfide isomerases (PDI) family, catalyzes the formation and rearrangement of disulfide bonds in proteins, crucial for endothelial cell function and maintaining vascular homeostasis in cardiovascular diseases, yet its role in PH remains unclear.
METHODS
Label-free proteomics was used to reveal the PDI protein expression profile in hypoxic PH patients. Multiplex immunofluorescence and Western blot analyses were performed to investigate the pathological role of TXNDC5. Mice with adeno-associated virus-mediated lung endothelial TXNDC5 overexpression, global knockout, and endothelial ablation of TXNDC5 were used to study the role of TXNDC5 in rodent PH models. In vitro experiments with cultured pulmonary arterial endothelial cells and bioinformatics assays were used to elucidate the underlying mechanisms. Pharmacological inhibition and endothelial-targeted TXNDC5 gene therapy were evaluated for their effects in PH.
RESULTS
TXNDC5 was significantly upregulated in the lungs of both PH patients and rodent models, with prominent expression in the endothelial layer of remodeled distal pulmonary arteries. Overexpression of TXNDC5 exacerbated Sugen5416/hypoxia (SuHx)-induced pulmonary artery remodeling, increased right ventricular systolic pressure, and right ventricular hypertrophy. Global or endothelial-specific deficiency of TXNDC5 exerted protective efficacy against the SuHx challenge. RNA sequencing and protein-protein interaction analysis revealed TXNDC5 as a potential regulator of extracellular matrix (ECM) homeostasis, with biglycan (BGN) identified as a critical downstream effector. TXNDC5 required BGN to regulate the ubiquitination of HIF-1α/2α, resulting in its abnormal accumulation to drive PH development. E64FC26, a TXNDC5 inhibitor, and endothelial-targeted TXNDC5 gene therapy exhibited therapeutic efficacy in SuHx-induced PH rats.
CONCLUSIONS
Our study reveals that TXNDC5 is a main modulator to regulate ECM homeostasis and may serve as a promising target for the treatment of PH.
Graphic Abstract
The role of TXNDC5 in regulating ECM homeostasis during PH. In the healthy state, BGN folding is properly maintained and HIF-1α/2α is rapidly degraded. During PH, TXNDC5 is upregulated, leading to excessive accumulation of BGN and impaired ubiquitination-mediated degradation of HIF-1α/2α, resulting in an imbalance in ECM homeostasis and contributing to vascular remodeling. Pharmacological or genetic inhibition of TXNDC5 restores BGN folding capacity and facilitates HIF-1α/2α degradation, thereby reestablishing ECM homeostasis and attenuating PH progression.
