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Background and Purpose: Vascular inflammation, including the expression of inflammatory cytokines in endothelial cells, plays a critical role in hyperhomocysteinaemia-associated vascular diseases. Cathepsin V, specifically expressed in humans, is involved in vascular diseases through its elastolytic and collagenolytic activities. The aim of this study was to determine the effects of cathepsin V on l-homocysteine-induced vascular inflammation.Experimental Approach: A high methionine diet-induced hyperhomocysteinaemic mouse model was used to assess cathepsin V expression and vascular inflammation. Cultures of HUVECs were challenged with l-homocysteine and the cathepsin L/V inhibitor SID to assess the pro-inflammatory effects of cathepsin V. Transfection and antisense techniques were utilized to investigate the effects of cathepsin V on the dual-specificity protein phosphatases (DUSPs) and MAPK pathways.Key Results: Cathepsin L (human cathepsin V homologous) was increased in the thoracic aorta endothelial cells of hyperhomocysteinaemic mice; l-homocysteine promoted cathepsin V expression in HUVECs. SID suppressed the activity of cathepsin V and reversed the up-regulation of inflammatory cytokines (IL-6, IL-8 and TNF-α), adhesion and chemotaxis of leukocytes and vascular inflammation induced by l-homocysteine in vivo and in vitro. Increased cathepsin V promoted the degradation of DUSP6 and DUSP7, phosphorylation and subsequent nuclear translocation of ERK1/2, phosphorylation of STAT1 and expression of IL-6, IL-8 and TNF-α.Conclusions and Implications: This study has identified a novel mechanism, which shows that l-homocysteine-induced upregulation of cathepsin V mediates vascular endothelial inflammation under high homocysteine condition partly via ERK1/2 /STAT1 pathway. This mechanism could represent a potential therapeutic target in hyperaemia-associated vascular diseases.Linked Articles: This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc. [ABSTRACT FROM AUTHOR]

Adenosine deaminase acting on RNA 1 (ADAR1) has been shown to participate in the regulation of endothelial cells (ECs), as well as local and systemic inflammatory responses. Here, we find that bacterial lipopolysaccharide (LPS)-induced upregulation of ADAR1 in lung ECs is impaired in aged mice, an animal model with high rates of sepsis and mortality. Endothelial cell-specific ADAR1 knockout (ADAR1 ECKO ) mice suffer from higher mortality rates, aggravated lung injury, and increased vascular permeability under LPS challenge. In primary ADAR1 knockout ECs, expression of the melanoma differentiation-associated gene 5 (MDA5), a downstream effector of ADAR1, is significantly elevated. MDA5 knockout completely rescues the postnatal offspring death of ADAR1 ECKO mice. However, there is no reduction in mortality or apoptosis in lung cells of ADAR1 ECKO /MDA5 -/- mice challenged with LPS, indicating the involvement of an MDA5-independent mechanism in this process., (© 2020 Federation of European Biochemical Societies.)