Severe forms of coronavirus 2019 (COVID-19) disease are caused by an exaggerated systemic inflammatory response and subsequent inflammation-related coagulopathy. Anti-inflammatory treatment with low dose dexamethasone has been shown to reduce mortality in COVID-19 patients requiring oxygen therapy. However, the mechanisms of action of corticosteroids have not been extensively studied in critically ill patients in the context of COVID-19. Plasma biomarkers of inflammatory and immune responses, endothelial and platelet activation, neutrophil extracellular trap formation, and coagulopathy were compared between patients treated or not by systemic dexamethasone for severe forms of COVID-19. Dexamethasone treatment significantly reduced the inflammatory and lymphoid immune response in critical COVID-19 patients but had little effect on the myeloid immune response and no effect on endothelial activation, platelet activation, neutrophil extracellular trap formation, and coagulopathy. The benefits of low dose dexamethasone on outcome in critical COVID-19 can be partially explained by a modulation of the inflammatory response but not by reduction of coagulopathy. Future studies should explore the impact of combining dexamethasone with other immunomodulatory or anticoagulant drugs in severe COVID-19.

Acetyl-CoA carboxylase (ACC) is the first enzyme regulating de novo lipid synthesis via the carboxylation of acetyl-CoA into malonyl-CoA. The inhibition of its activity decreases lipogenesis and, in parallel, increases the acetyl-CoA content, which serves as a substrate for protein acetylation. Several findings support a role for acetylation signaling in coordinating signaling systems that drive platelet cytoskeletal changes and aggregation. Therefore, we investigated the impact of ACC inhibition on tubulin acetylation and platelet functions. Human platelets were incubated 2 h with CP640.186, a pharmacological ACC inhibitor, prior to thrombin stimulation. We have herein demonstrated that CP640.186 treatment does not affect overall platelet lipid content, yet it is associated with increased tubulin acetylation levels, both at the basal state and after thrombin stimulation. This resulted in impaired platelet aggregation. Similar results were obtained using human platelets that were pretreated with tubacin, an inhibitor of tubulin deacetylase HDAC6. In addition, both ACC and HDAC6 inhibitions block key platelet cytoskeleton signaling events, including Rac1 GTPase activation and the phosphorylation of its downstream effector, p21-activated kinase 2 (PAK2). However, neither CP640.186 nor tubacin affects thrombin-induced actin cytoskeleton remodeling, while ACC inhibition results in decreased thrombin-induced reactive oxygen species (ROS) production and extracellular signal-regulated kinase (ERK) phosphorylation. We conclude that when using washed human platelets, ACC inhibition limits tubulin deacetylation upon thrombin stimulation, which in turn impairs platelet aggregation. The mechanism involves a downregulation of the Rac1/PAK2 pathway, being independent of actin cytoskeleton.

Recent clinical trials have shown significant cardioprotective effects of antidiabetic sodium-glucose cotransporter 2 inhibitors (SGLT2i), including canagliflozin, empagliflozin, and dapagliflozin. These drugs significantly reduce hospitalizations for heart failure with reduced and preserved ejection fraction in both diabetic and non-diabetic patients. Yet, the mechanisms underlying their protective effects, beyond their glucose-lowering properties, remain poorly understood. This study aimed to elucidate the direct effects of SGLT2i on cardiac fibroblasts, key mediators of myocardial fibrosis, ventricular remodeling, and heart failure. Using primary human cardiac fibroblast cultures, we compared the impact of canagliflozin, empagliflozin, and dapagliflozin on fibroblast properties. All three inhibitors significantly prevented myofibroblast differentiation. Notably, only canagliflozin significantly reduced fibroblast proliferation and migration. While all SGLT2i increased AMP-activated protein kinase (AMPK) phosphorylation, their effects on myodifferentiation were AMPK-independent. In contrast, the effect of canagliflozin on migration was partially dependent on AMPK, as demonstrated using the AMPK inhibitor BAY-3827. These findings reveal distinct cellular effects of individual SGLT2i on cardiac fibroblasts, suggesting heterogeneous potential to modulate extracellular matrix remodeling. Among them, canagliflozin may be more potent in preventing myocardial fibrosis in the context of heart failure.