Atherosclerosis is a chronic inflammatory disease of the arterial vessel wall and anti-inflammatory treatment strategies are currently pursued to lower cardiovascular disease burden. Modulation of recently discovered inactive rhomboid protein 2 (iRhom2) attenuates shedding of tumour necrosis factor-alpha (TNF-α) selectively from immune cells. The present study aims at investigating the impact of iRhom2 deficiency on the development of atherosclerosis. Low-density lipoprotein receptor (LDLR)-deficient mice with additional deficiency of iRhom2 (LDLR^−/−iRhom2^−/−) and control (LDLR^−/−) mice were fed a Western-type diet (WD) for 8 or 20 weeks to induce early or advanced atherosclerosis. Deficiency of iRhom2 resulted in a significant decrease in the size of early atherosclerotic plaques as determined in aortic root cross-sections. LDLR^−/−iRhom2^−/− mice exhibited significantly lower serum levels of TNF-α and lower circulating and hepatic levels of cholesterol and triglycerides compared to LDLR^−/− mice at 8 weeks of WD. Analyses of hepatic bile acid concentration and gene expression at 8 weeks of WD revealed that iRhom2 deficiency prevented WD-induced repression of hepatic bile acid synthesis in LDLR^−/− mice. In contrast, at 20 weeks of WD, plaque size, plaque composition, and serum levels of TNF-α or cholesterol were not different between genotypes. Modulation of inflammation by iRhom2 deficiency attenuated diet-induced hyperlipidaemia and early atherogenesis in LDLR^−/− mice. iRhom2 deficiency did not affect diet-induced plaque burden and composition in advanced atherosclerosis in LDLR^−/− mice.

Aims: To investigate how psychosocial stress contributes to accelerated thrombosis, focusing on platelet activation and hyperreactivity. The specific objective was to identify novel platelet regulators involved in stress-mediated thrombosis, with a particular emphasis on the tetraspanin CD37. Methods and results: To explore how stress contributes to platelet hyperreactivity, platelets were isolated from (i) mice that experienced chronic variable stress and stress-free controls (n = 8/group) and (ii) human subjects with self-reported high- and no-stress levels (n = 18/group), followed by RNA-sequencing. By comparing mutually expressed transcripts, a subset of genes differentially expressed following psychosocial stress was identified in both human and mouse platelets. In both mice and humans, platelet CD37 positively associates with platelet aggregation responses that underlie thrombosis, with Cd37−/− platelets exhibiting impaired integrin αIIbβ3 signalling, characterized by reduced platelet fibrinogen spreading and decreased agonist-induced αIIbβ3 activation. Consistent with a role for CD37 in regulating platelet activation responses, chimeric mice that received Cd37−/− bone marrow experienced a significantly increased time to vessel occlusion in the carotid artery FeCl3 model compared to mice reconstituted with wild-type bone marrow. CD37 deficiency did not alter haemostasis, as platelet count, coagulation metrics, prothrombin time, and partial thromboplastin time did not differ in Cd37−/− mice relative to wild-type mice. Consistent with this, bleeding time did not differ between wild-type and Cd37−/− mice following tail tip transection. Conclusion: This study provides new insights into the platelet-associated mechanisms underlying stress-mediated thrombosis. Identifying CD37 as a novel regulator of platelet activation responses offers potential therapeutic targets for reducing the thrombotic risk associated with psychosocial stress. The findings also contribute to understanding how psychosocial stress accelerates thrombotic events and underscore the importance of platelet activation in this process. Clinical trial registration: NCT02106429, NCT03022552

Inactive rhomboid protein 2 (iRhom2) regulates ADAM17-mediated shedding of tumor necrosis factor-α (TNF-α) from immune cells. We previously showed that iRhom2 deficiency attenuates early atherosclerosis in mice. This study aimed to characterize the impact of iRhom2 deficiency on macrophage phenotype and function. Bone marrow-derived macrophages (BMDMs) from iRhom2^−/− and iRhom2^+/+ mice were analyzed for proliferation, phagocytosis, survival of cytotoxic stress, and polarization. Cytokine secretion after LPS stimulation was quantified, and iRhom2 expression under atherogenic stimuli was assessed. Conditioned media from BMDMs (BMDMcM) were applied to human aortic endothelial cells (HAoECs) to evaluate adhesion molecule expression and monocyte adhesion. iRhom2 deficiency did not affect BMDM proliferation, phagocytosis, survival, or polarization marker expression. iRhom2 expression was upregulated in iRhom2^+/+ BMDMs by atherogenic stimulation. Following LPS stimulation, TNF-α secretion was decreased and IL-10 secretion was increased in iRhom2^−/− compared with iRhom2^+/+ BMDMs. HAoEC expression of adhesion molecules—ICAM-1, VCAM-1, and E-selectin—was attenuated after exposure to iRhom2^−/− compared with iRhom2^+/+ BMDMcM. Monocyte adhesion to HAoECs was reduced following treatment with iRhom2^−/− BMDMcM; TNF-α neutralization abolished this effect, indicating TNF-α dependency. iRhom2 deficiency in BMDMs selectively alters macrophage inflammatory cytokine secretion without affecting basal macrophage functions, thereby reducing endothelial activation and monocyte adhesion. These findings identify iRhom2 as a regulator of macrophage–endothelial crosstalk and a potential target to modulate inflammation in atherogenesis.