Integrated Transcriptomic and Weighted Gene Coexpression Network Analyses Identify the UCHL1-MUCL1 Axis as a Key Regulator of Endothelial Dysfunction in Sepsis.

BACKGROUND: Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, with vascular endothelial cell dysfunction playing a critical role in its pathogenesis. Endothelial injury contributes to microcirculatory failure, systemic inflammation, and multiorgan dysfunction, leading to high mortality in sepsis patients. However, the molecular mechanisms underlying vascular endothelial cell dysfunction in sepsis remain poorly understood. The study analyzed the underlying mechanism by integrating differentially expressed genes and weighted gene coexpression network analysis.

METHODS: To identify key drivers of the hyperinflammatory response in sepsis, differentially expressed genes were analyzed from the GSE46955 dataset. Weighted gene coexpression network analysis was performed to identify sepsis-associated modules. Hub genes were validated in lipopolysaccharide (LPS)-treated human umbilical vein endothelial cells (HUVECs) via quantitative real-time PCR and Western blotting. Functional assays, including enzyme-linked immunosorbent assay and flow cytometry, were conducted to investigate the role of mucin-like 1 (MUCL1) and its regulator, ubiquitin C-terminal hydrolase L1 (UCHL1), in LPS-induced endothelial injury. Coimmunoprecipitation, ubiquitination, and cycloheximide assays were performed to validate the association of MUCI and UCHL1 in HUVECs.

RESULTS: A total of 70 upregulated genes were identified, with MUCL1 emerging as a top upregulated gene significantly correlated with sepsis. LPS treatment markedly increased MUCL1 expression in HUVECs. MUCL1 knockdown attenuated LPS-induced inflammation (reduced tumor necrosis factor-alpha, interleukin 6 [IL-6], IL-8, and ICAM-1) and apoptosis. Further analysis revealed that UCHL1 stabilized MUCL1 protein by deubiquitination. UCHL1 silencing ameliorated LPS-induced effects in HUVECs; however, MUCL1 overexpression reversed these protective effects. UCHL1 silencing attenuated the activation of the β-catenin/NF-κB pathway, an effect that was associated with the regulation of MUCL1 expression.

CONCLUSIONS: The UCHL1-MUCL1 axis promoted sepsis-induced endothelial inflammation and apoptosis through the regulation of the β-catenin/nuclear factor κB pathway. Targeting MUCL1 or its regulator UCHL1 may represent a promising therapeutic strategy to mitigate vascular endothelial dysfunction in sepsis.