ACE2 deficiency inhibits thoracic aortic dissection by enhancing SIRT3 mediated inhibition of inflammation and VSCMs phenotypic switch

UCP1 prevents the formation of thoracic aortic aneurysms and dissection by inhibiting the TLR4/NLRP3/IL-1β signaling pathway and VSMC phenotype switching in mice

Thoracic aortic aneurysms and dissection (TAAD) is a life-condition associated with high morbidity and mortality. Research has proven that inflammation contributes to the progression of TAAD. Mitochondrial uncoupling protein 1 (UCP1) can inhibit the release of inflammatory factors in perivascular adipose tissue (PVAT), regulate fat and inflammation, to confer vascular protection. However, whether UCP1 can ameliorate TAAD has not been clarified. In this study, aortas were harvested from organ donors and TAAD patients to explore the expression of UCP1 and Toll-like receptor 4 (TLR4)/NOD-like receptor thermal protein domain associated protein 3 (NLRP3)/interleukin-1β (IL-1β) signaling pathway. Meanwhile, in vitro and in vivo models of TAAD were constructed to clarify the impact of UCP1 expression on VSMCs and TAAD. UCP1 expression was significantly downregulated and the TLR4/NLRP3/IL-1β signaling pathway was activated in TAAD in vivo. Moreover, UCP1 inhibited the migration, invasion, apoptosis, and phenotype switching of VSMCs in vitro. UCP1 significantly blocked the β-aminopropionitrile (BAPN)-induced TAAD formation and rupture in mice, suppressed aortic dilation, elastic fiber fragmentation, and apoptosis in the aorta. It also activated the TLR4/NLRP3/IL-1β signaling pathway to alleviate aortic inflammation and prevent the degradation of systolic phenotype proteins and phenotype switching of VSMCs. These effects suggest that UCP1 may inhibit TAAD formation by blocking the TLR4/NLRP3/IL-1β signaling pathway and VSMC phenotype switching.

ACE2 deficiency protects against heme protein-induced acute kidney injury

Angiotensin-converting enzyme 2 (ACE2) exerts countervailing effects on the renin-angiotensin-aldosterone system (RAAS). ACE2 also engages the spike protein of SARS-CoV-2. ACE2 protein has been shown recently to avidly bind heme. We examined the pathobiological relevance of this heme-binding property of ACE2 by using the glycerol-induced model of heme protein-mediated AKI (HP-AKI), which is characterized by increased kidney heme content. We studied the response of ACE2-wildtype (ACE2+/y) and ACE2-deficient (ACE2-/y) mice to HP-AKI and quantitated kidney and cellular content of heme under relevant conditions. ACE2-deficient mice, compared with ACE2-wildtype mice, were significantly protected against HP-AKI as reflected by filtration markers, less histological injury, and less expression of apoptosis and ferroptosis markers. ACE2-deficient mice also evinced lesser kidney heme content and a blunted induction of HO-1. HEK293 ACE2-overexpressing cells, compared with HEK293-native cells, when exposed to heme, retained higher amounts of heme. In HP-AKI, ACE2 expression and activity were reduced, and myoglobin and heme, administered independently, reduced ACE2 expression in the otherwise intact mouse kidney. Finally, with more severe HP-AKI, the protective effect of ACE2 deficiency was attenuated. We conclude that ACE2 deficiency confers protection against HP-AKI. We suggest that this reflects the recently recognized binding of heme to ACE2, such binding serving to facilitate renal entry of heme, a known nephrotoxin. These findings uncover a novel pathway of heme-dependent acute kidney injury. This is the first demonstration of the biological relevance of chemical binding of heme by ACE2. Finally, we identify heme proteins and heme as novel determinants of ACE2 expression.NEW & NOTEWORTHY ACE2 protein binds heme, which we reasoned would promote heme entry into the kidney and, accordingly, heme protein-mediated acute kidney injury. Our findings support this hypothesis. This study is the first to demonstrate the biological relevance of ACE2-heme binding, uncover a new pathway of heme-dependent kidney injury, and identify myoglobin and heme as novel determinants of ACE2 expression. Our study explains why plasma levels of myoglobin and heme predict poor outcomes in patients with COVID-19.

Roles of Sirtuins in Cardiovascular Diseases: Mechanisms and Therapeutics

Cardiovascular diseases (CVDs) are experiencing a rapid surge and are widely recognized as the leading cause of mortality in the current aging society. Given the multifactorial etiology of CVDs, understanding the intricate molecular and cellular mechanisms is imperative. Over the past 2 decades, many scientists have focused on Sirtuins, a family of nicotinamide adenine dinucleotide-dependent deacylases. Sirtuins are highly conserved across species, from yeasts to primates, and play a crucial role in linking aging and diseases. Sirtuins participate in nearly all key physiological and pathological processes, ranging from embryogenic development to stress response and aging. Abnormal expression and activity of Sirtuins exist in many aging-related diseases, while their activation has shown efficacy in mitigating these diseases (eg, CVDs). In terms of research, this field has maintained fast, sustained growth in recent years, from fundamental studies to clinical trials. In this review, we present a comprehensive, up-to-date discussion on the biological functions of Sirtuins and their roles in regulating cardiovascular biology and CVDs. Furthermore, we highlight the latest advancements in utilizing Sirtuin-activating compounds and nicotinamide adenine dinucleotide boosters as potential pharmacological targets for preventing and treating CVDs. The key unresolved issues in the field-from the chemicobiological regulation of Sirtuins to Sirtuin-targeted CVD investigations-are also discussed. This timely review could be critical in understanding the updated knowledge of Sirtuin biology in CVDs and facilitating the clinical accessibility of Sirtuin-targeting interventions.