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Endothelial cells injury and pro-inflammation cytokines release are the initial steps of hyperhomocysteinemia (HHcy)-associated vascular inflammation. Pyroptosis is a newly identified pro-inflammation form of programmed cell death, causing cell lysis and IL-1β release, and characterized by the caspases-induced cleavage of its effector molecule gasdermins (GSDMs). However, the effect of homocysteine (Hcy) on endothelial cells pyroptosis and the underlying mechanisms have not been fully defined. We have previously reported that Hcy induces vascular endothelial inflammation accompanied by the increase of high mobility group box-1 protein (HMGB1) and lysosomal cysteine protease cathepsin V in endothelial cells, and other studies have shown that HMGB1 or cathepsins are involved in activation of NLRP3 inflammasome and caspase-1. Here, we investigated the role of HMGB1 and cathepsin V in the process of Hcy-induced pyroptosis. We observed an increase in plasma IL-1β levels in HHcy patients and mice models, cathepsin V inhibitor reduced the plasma IL-1β levels and cleavage of GSDMD full-length into GSDMD N-terminal in the thoracic aorta of hyperhomocysteinemia mice. Using cultured HUVECs, we observed that Hcy promoted GSDMD N-terminal expression, silencing GSDMD or HMGB1 rescued Hcy-induced pyroptosis. HMGB1 also increased GSDMD N-terminal expression, and silencing cathepsin V reversed HMGB1-induced pyroptosis. HMGB1 could increase lysosome permeability, and silencing cathepsin V attenuated HMGB1-induced activation of caspase-1. In conclusion, this study has delineated a novel mechanism that HMGB1 mediated Hcy-induced endothelial cells pyroptosis partly via cathepsin V-dependent pathway., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

It is well-established that homocysteine (Hcy) is an independent risk factor for atherosclerosis. Hcy can promote vascular smooth muscle cell (VSMC) proliferation, it plays a key role in neointimal formation and thus contribute to arteriosclerosis. However, the molecular mechanism on VSMCs proliferation underlying atherosclerosis is not well elucidated. Mitofusin-2 (MFN2) is an important transmembrane GTPase in the mitochondrial outer membrane and it can block cells in the G0/G1 stage of the cell cycle. To investigate the contribution of aberrant MFN2 transcription in Hcy-induced VSMCs proliferation and the underlying mechanisms. Cell cycle analysis revealed a decreased proportion of VSMCs in G0/G1 and an increased proportion in S phase in atherosclerotic plaque of APOE -/- mice with hyperhomocystinaemia (HHcy) as well as in VSMCs exposed to Hcy in vitro. The DNA methylation level of MFN2 promoter was obviously increased in VSMCs treated with Hcy, leading to suppressed promoter activity and low expression of MFN2. In addition, we found that the expression of c-Myc was increased in atherosclerotic plaque and VSMCs treated with Hcy. Further study showed that c-Myc indirectly regulates MFN2 expression is duo to the binding of c-Myc to DNMT1 promoter up-regulates DNMT1 expression leading to DNA hypermethylation of MFN2 promoter, thereby inhibits MFN2 expression in VSMCs treated with Hcy. In conclusion, our study demonstrated that Hcy-induced hypermethylation of MFN2 promoter inhibits the transcription of MFN2, leading to VSMCs proliferation in plaque formation, and the increased binding of c-Myc to DNMT1 promoter is a new and relevant molecular mechanism., (© 2019 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)

Endothelial inflammation plays an important role in hyperhomocysteinemia (HHcy)-associated vascular diseases. High mobility group box 1 (HMGB1) is a pro-inflammatory danger molecule produced by endothelial cells. However, whether HMGB1 is involved in vascular endothelial inflammation of HHcy is poorly understood. Neuropilin-1 (NRP1) mediates inflammatory response and activates mitogen-activated protein kinases (MAPKs) pathway that has been reported to be involved in regulation of HMGB1. The aim of this study was to determine the alteration of HMGB1 in HHcy, and the role of NRP1 in regulation of endothelial HMGB1 under high homocysteine (Hcy) condition. In the present study, we first observed that the plasma level of HMGB1 was elevated in HHcy patients and an experimental rat model, and increased HMGB1 was also observed in the thoracic aorta of an HHcy rat model. HMGB1 was induced by Hcy accompanied with upregulated NRP1 in vascular endothelial cells. Overexpression of NRP1 promoted expression and secretion of HMGB1 and endothelial inflammation; knockdown of NRP1 inhibited HMGB1 and endothelial inflammation induced by Hcy, which partially regulated through p38 MAPK pathway. Furthermore, NRP1 inhibitor ATWLPPR reduced plasma HMGB1 level and expression of HMGB1 in the thoracic aorta of HHcy rats. In conclusion, our data suggested that Hcy requires NRP1 to regulate expression and secretion of HMGB1. The present study provides the evidence for inhibition of NRP1 and HMGB1 to be the novel therapeutic targets of vascular endothelial inflammation in HHcy in the future. NEW & NOTEWORTHY This study shows for the first time to our knowledge that the plasma level of high mobility group box 1 (HMGB1) is elevated in hyperhomocysteinemia (HHcy) patients, and homocysteine promotes expression and secretion of HMGB1 partially regulated by neuropilin-1 in endothelial cells, which is involved in endothelial inflammation. Most importantly, these new findings will provide a potential therapeutic strategy for vascular endothelial inflammation in HHcy.

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 ERK 1/2 /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., (© 2017 The British Pharmacological Society.)

Hyperhomocysteinemia (HHcy) has been associated with impaired vascular endothelial function. Our previous study demonstrated significantly higher secretion of the chemokine monocyte chemoattractant protein-1 from monocytes in response to lipopolysaccharide in patients with HHcy. In the present study, we investigated whether coronary endothelial function was damaged in patients with chronic HHcy (plasma level of homocysteine >15 μmol/l) and, if so, whether this impaired endothelial function is induced by the uncoupling of endothelial nitric oxide synthase (eNOS). When tetrahydrobiopterin levels are inadequate, eNOS is no longer coupled to l-arginine oxidation, which results in reactive oxygen species rather than nitric oxide production, thereby inducing vascular endothelial dysfunction. The 71 participants were divided into two groups, control (n = 50) and HHcy (n = 21). Quantification of coronary flow velocity reserve (CFVR) was after rest and after adenosine administration done by noninvasive Doppler echocardiography. Plasma levels of nitric oxide and tetrahydrobiopterin were significantly lower in patients with HHcy than in controls (99.54 ± 32.23 vs. 119.50 ± 37.68 μmol/l and 1.43 ± 0.46 vs. 1.73 ± 0.56 pmol/ml, all P < 0.05). Furthermore, CFVR was significantly lower in the HHcy than the control group (2.76 ± 0.49 vs. 3.09 ± 0.52, P < 0.05). In addition, plasma level of homocysteine was negatively correlated with CFVR. Chronic HHcy may contribute to coronary artery disease by inducing dysfunction of the coronary artery endothelium. The uncoupling of eNOS induced by HHcy in patients with chronic HHcy may explain this adverse effect in part.

Introduction: Fenofibrate, an agonist of peroxisome proliferator-activated receptor-α (PPAR-α), has a vascular protective effect. Aims: We investigated the effect of the PPAR-α agonist on coronary artery endothelial function in patients with hypertriglyceridemia. Methods: Fifty-eight patients with hypertriglyceridemia were divided into two groups: control (no treatment; n = 23) and fenofibrate treatment (n = 35), 200 mg/d, for 6 months. The patients had undergone rest and adenosine treatment to induce hyperemia for quantification of coronary flow velocity reserve (CFVR) by noninvasive Doppler echocardiography before treatment and at 6-month follow-up. Pulse wave velocity (PWV) was measured before treatment and at 6-month follow-up. Results: CFVR was significantly improved with fenofibrate treatment as compared with baseline level and control group (3.14 ± 0.36 vs. 2.80 ± 0.58 and 2.79 ± 0.65, P < 0.01 and 0.05, respectively), with no difference between baseline levels and untreated controls. In addition, at 6 months, plasma level of homocysteine was significantly increased with fenofibrate treatment as compared with at baseline and control group (median 18.13 [range 14.46-22.02]μmol/L vs. 14.09 [12.01-18.81] and 13.34 [9.69-17.06]μmol/L, P < 0.001 and 0.01, respectively). Furthermore, at 6 months, PWV was significantly decreased with fenofibrate treatment as compared with control group (1446 ± 136 cm/s vs. 1570 ± 203 cm/s, P < 0.05). Conclusions: Treatment with PPAR-α agonist fenofibrate significantly improved CFVR and arterial stiffness in patients with hypertriglyceridemia. This endothelial protective effect may be reduced in part by the side effect of increasing homocysteine. [ABSTRACT FROM AUTHOR]

Hyperhomocysteinemia (HHcy) has been associated with impaired vascular endothelial function. Our previous study demonstrated significantly higher secretion of the chemokine monocyte chemoattractant protein-1 from monocytes in response to lipopolysaccharide in patients with HHcy. In the present study, we investigated whether coronary endothelial function was damaged in patients with chronic HHcy (plasma level of homocysteine >15 μmol/l) and, if so, whether this impaired endothelial function is induced by the uncoupling of endothelial nitric oxide synthase (eNOS). When tetrahydrobiopterin levels are inadequate, eNOS is no longer coupled to L-arginine oxidation, which results in reactive oxygen species rather than nitric oxide production, thereby inducing vascular endothelial dysfunction. The 71 participants were divided into two groups, control (n = 50) and HHcy (n = 21). Quantification of coronary flow velocity reserve (CFVR) was after rest and after adenosine administration done by noninvasive Doppler echocardiography. Plasma levels of nitric oxide and tetrahydrobiopterin were significantly lower in patients with HHcy than in controls (99.54 ± 32.23 vs. 119.50 ± 37.68 μmol/l and 1.43 ± 0.46 vs. 1.73 ± 0.56 pmol/ml, all P < 0.05). Furthermore, CFVR was significantly lower in the HHcy than the control group (2.76 ± 0.49 vs. 3.09 ± 0.52, P < 0.05). In addition, plasma level of homocysteine was negatively correlated with CFVR. Chronic HHcy may contribute to coronary artery disease by inducing dysfunction of the coronary artery endothelium. The uncoupling of eNOS induced by HHcy in patients with chronic HHcy may explain this adverse effect in part. [ABSTRACT FROM AUTHOR]