Inactivation of SERCA2 Cys674 accelerates aortic aneurysms by suppressing PPARγ

The role of transcription factors in the pathogenesis and therapeutic targeting of vascular diseases

Transcription factors (TFs) constitute an essential component of epigenetic regulation. They contribute to the progression of vascular diseases by regulating epigenetic gene expression in several vascular diseases. Recently, numerous regulatory mechanisms related to vascular pathology, ranging from general TFs that are continuously activated to histiocyte-specific TFs that are activated under specific circumstances, have been studied. TFs participate in the progression of vascular-related diseases by epigenetically regulating vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). The Krüppel-like family (KLF) TF family is widely recognized as the foremost regulator of vascular diseases. KLF11 prevents aneurysm progression by inhibiting the apoptosis of VSMCs and enhancing their contractile function. The presence of KLF4, another crucial member, suppresses the progression of atherosclerosis (AS) and pulmonary hypertension by attenuating the formation of VSMCs-derived foam cells, ameliorating endothelial dysfunction, and inducing vasodilatory effects. However, the mechanism underlying the regulation of the progression of vascular-related diseases by TFs has remained elusive. The present study categorized the TFs involved in vascular diseases and their regulatory mechanisms to shed light on the potential pathogenesis of vascular diseases, and provide novel insights into their diagnosis and treatment.

Calcium promotes vascular smooth muscle cell phenotypic switching in Marfan syndrome

Fibrillin 1 (Fbn1) mutations cause Marfan syndrome (MFS), with aortic root dilatation, dissection, and rupture. Few studies reported the blood calcium and lipid profile of MFS, and the effect of vascular smooth muscle cell (VSMC) phenotypic switching on MFS aortic aneurysm is unclear. Here, we aimed to investigate the role of calcium-related VSMC phenotypic switching in MFS. We retrospectively collected MFS patients' clinical data, performed bioinformatics analysis to screen the enriched biological process in MFS patients and mice, and detected markers of VSMC phenotypic switching on Fbn1^C1039G/+ mice and primary aortic vascular smooth muscle cells. We found that patients with MFS have elevated blood calcium levels and dyslipidemia. Furthermore, the calcium concentration levels were increased with age in MFS mice, accompanied by the promoted VSMC phenotypic switching, and SERCA2 contributed to maintaining the contractile phenotype of VSMCs. This study provides the first evidence that the increased calcium is associated with the promoted VSMC phenotype switching in MFS. SERCA may become a novel therapeutic target for suppressing aneurysm progression in MFS.

Lathyrol promotes ER stress-induced apoptosis and proliferation inhibition in lung cancer cells by targeting SERCA2

Lathyrol is a natural product isolated from the traditional Chinese medicine Semen Euphorbiae with unknown anti-tumor effects. We found that lathyrol had significant inhibitory effect on lung cancer cells by inducing apoptosis and inhibiting proliferation. Subsequently, we demonstrated for the first time that endoplasmic reticulum (ER) stress is a key anti-tumor mechanism of lathyrol. Furthermore, we found that lathyrol can induce ER stress in lung cancer cells by upregulating the protein expression levels of GRP78, PERK, p-eIF2α, CHOP, and ATF4, and the inhibitory effect of lathyrol on lung cancer cells was significantly reversed when cells were pretreated with ER stress inhibitor. In addition, we found that inhibition of SERCA2 resulted in depletion of the ER Ca²⁺ pool followed by a sustained increase in cytoplasmic Ca²⁺ levels, eventually leading to ER stress induced tumor cell apoptosis and proliferation inhibition. Lathyrol targeted SERCA2 to cause a significant upregulation of Ca²⁺ levels, and the inhibitory effect of lathyrol on lung cancer cells was significantly reversed after pretreatment with SERCA2 agonist. Taken together, our data suggest that lathyrol exerts its anti-tumor effect primarily by targeting SERCA2. Our findings highlight the potential for lathyrol as a new candidate drug for the treatment of lung cancer.

Substitution of SERCA2 Cys674 accelerates aortic aneurysm by inducing endoplasmic reticulum stress and promoting cell apoptosis

BACKGROUND AND PURPOSE

The Cys674 residue (C674) in the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) is key to maintaining its enzyme activity. The irreversible oxidation of C674 occurs broadly in aortic aneurysms. Substitution of C674 promotes a phenotypic transition of aortic smooth muscle cells (SMCs) and exacerbates angiotensin II-induced aortic aneurysm. However, its underlying mechanism remains enigmatic.

EXPERIMENTAL APPROACH

Heterozygous SERCA2 C674S knock-in (SKI) mice, in which half of C674 was replaced by serine, were used to mimic partially irreversible oxidation of C674 thiol. The aortas of SKI mice and their littermate wild-type mice under an LDL receptor-deficient background were collected for histological and immunohistochemical analysis. Cultured aortic SMCs were used for protein expression, apoptosis analysis, and cell function studies.

KEY RESULTS

The substitution of SERCA2 C674 caused endoplasmic reticulum (ER) stress and induced SMC apoptosis. The inhibition of ER stress by 4-phenylbutyric acid (4-PBA) in SKI aortic SMCs decreased the expression of marker proteins for cell apoptosis as well as phenotypic transition, and prevented cell apoptosis, proliferation, migration, and macrophage adhesion to SMCs. 4-PBA also ameliorated angiotensin II-induced aortic aneurysm in SKI mice.

CONCLUSIONS AND IMPLICATIONS

The irreversible oxidation of SERCA2 C674 promotes the development of aortic aneurysm by inducing ER stress and subsequent SMC apoptosis. Our study illustrates that ER stress caused by oxidative inactivation of C674 is related to the pathogenesis of aortic aneurysm. Therefore, ER stress and SERCA2 are potential therapeutic targets for treating aortic aneurysm.

Construction and analysis of competing endogenous RNA network and patterns of immune infiltration in abdominal aortic aneurysm

Background

Various studies have highlighted the role of circular RNAs (circRNAs) as critical molecular regulators in cardiovascular diseases, but its role in abdominal aortic aneurysm (AAA) is unclear. This study explores the potential molecular mechanisms of AAA based on the circRNA-microRNA (miRNA)-mRNA competing endogenous RNA (ceRNA) network and immune cell infiltration patterns.

Methods

The expression profiles of circRNAs (GSE144431) and mRNAs (GSE57691 and GSE47472) were obtained from the Gene Expression Omnibus (GEO). Then, the differentially expressed circRNAs (DEcircRNAs) and mRNAs (DEmRNAs) between AAA patients and healthy control samples, and the target miRNAs of these DEmRNAs and DEcircRNAs were identified. Based on the miRNA-DEmRNAs and miRNA-DEcircRNAs pairs, the ceRNA network was constructed. Furthermore, the proportion of the 22 immune cell types in AAA patients was assessed using cell type identification by estimating relative subsets of RNA transcripts (CIBERSORT) algorithm. The expressions of key genes and immune cell infiltration were validated using clinical specimens.

Results

A total of 214 DEmRNAs were identified in the GSE57691 and GSE47472 datasets, and 517 DEcircRNAs were identified in the GSE144431 dataset. The ceRNA network included 19 circRNAs, 36 mRNAs, and 68 miRNAs. Two key genes, PPARG and FOXO1, were identified among the hub genes of the established protein-protein interaction between mRNAs in the ceRNA network. Moreover, seven types of immune cells were differentially expressed between AAA patients and healthy control samples. Hub genes in ceRNA, such as FOXO1, HSPA8, and RAB5C, positively correlated with resting CD4 memory T cells or M1 macrophages, or both.

Conclusion

In conclusion, a ceRNA interaction axis was constructed. The composition of infiltrating immune cells was analyzed in the abdominal aorta of AAA patients and healthy control samples. This may help identify potential therapeutic targets for AAA.

Silicate ions as soluble form of bioactive ceramics alleviate aortic aneurysm and dissection

Aortic aneurysm and dissection (AAD) are leading causes of death in the elderly. Recent studies have demonstrated that silicate ions can manipulate multiple cells, especially vascular-related cells. We demonstrated in this study that silicate ions as soluble form of bioactive ceramics effectively alleviated aortic aneurysm and dissection in both Ang II and β-BAPN induced AAD models. Different from the single targeting therapeutic drug approaches, the bioactive ceramic derived approach attributes to the effect of bioactive silicate ions on the inhibition of the AAD progression through regulating the local vascular microenvironment of aorta systematically in a multi-functional way. The in vitro experiments revealed that silicate ions did not only alleviate senescence and inflammation of the mouse aortic endothelial cells, enhance M2 polarization of mouse bone marrow-derived macrophages, and reduce apoptosis of mouse aortic smooth muscle cells, but also regulate their interactions. The in vivo studies further confirm that silicate ions could effectively alleviate senescence, inflammation, and cell apoptosis of aortas, accomplished with reduced aortic dilation, collagen deposition, and elastin laminae degradation. This bioactive ceramic derived therapy provides a potential new treatment strategy in attenuating AAD progression.

The substitution of SERCA2 redox cysteine 674 promotes pulmonary vascular remodeling by activating IRE1α/XBP1s pathway

Pulmonary hypertension (PH) is a life-threatening disease characterized by pulmonary vascular remodeling, in which hyperproliferation of pulmonary artery smooth muscle cells (PASMCs) plays an important role. The cysteine 674 (C674) in the sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2 (SERCA2) is the critical redox regulatory cysteine to regulate SERCA2 activity. Heterozygous SERCA2 C674S knock-in mice (SKI), where one copy of C674 was substituted by serine to represent partial C674 oxidative inactivation, developed significant pulmonary vascular remodeling resembling human PH, and their right ventricular systolic pressure modestly increased with age. In PASMCs, substitution of C674 activated inositol requiring enzyme 1 alpha (IRE1α) and spliced X-box binding protein 1 (XBP1s) pathway, accelerated cell cycle and cell proliferation, which reversed by IRE1α/XBP1s pathway inhibitor 4μ8C. In addition, suppressing the IRE1α/XBP1s pathway prevented pulmonary vascular remodeling caused by substitution of C674. Similar to SERCA2a, SERCA2b is also important to restrict the proliferation of PASMCs. Our study articulates the causal effect of C674 oxidative inactivation on the development of pulmonary vascular remodeling and PH, emphasizing the importance of C674 in restricting PASMC proliferation to maintain pulmonary vascular homeostasis. Moreover, the IRE1α/XBP1s pathway and SERCA2 might be potential targets for PH therapy.

Double-edged sword of diabetes mellitus for abdominal aortic aneurysm

INTRODUCTION

Diabetes mellitus (DM) has been proved to contribute to multiple comorbidities that are risk factors for abdominal aortic aneurysm (AAA). Remarkably, evidences from epidemiologic studies have demonstrated a negative association between the two disease states. On the other hand, hyperglycemic state was linked to post-operative morbidities following AAA repair. This review aims to provide a thorough picture on the double-edged nature of DM and major hypoglycemic medications on prevalence, growth rate and rupture of AAA, as well as DM-associated prognosis post AAA repair.

METHODS

We performed a comprehensive search in electronic databases to look for literatures demonstrating the association between DM and AAA. The primary focus of the literature search was on the impact of DM on the morbidity, enlargement and rupture rate, as well as post-operative complications of AAA. The role of antidiabetic medications was also explored.

RESULTS

Retrospective epidemiological studies and large database researches associated the presence of DM with decreased prevalence, slower expansion and limited rupture rate of AAA. Major hypoglycemic drugs exert similar protective effect as DM against AAA by targeting pathological hallmarks involved in AAA formation and progression, which were demonstrated predominantly by animal studies. Nevertheless, presence of DM or postoperative hyperglycemia was linked to poorer short-term and long-term prognosis, primarily due to greater risk of infection, longer duration of hospital stays and death.

CONCLUSION

While DM is a positive factor in the formation and progression of AAA, it is also associated with higher risk of negative outcomes following AAA repair. Concomitant use of antidiabetic medications may contribute to the protective mechanism of DM in AAA, but further studies are still warranted to explore their role following AAA repair.