SERCA2 dysfunction triggers hypertension by interrupting mitochondrial homeostasis and provoking oxidative stress.

BACKGROUND AND AIM: Sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) is critical in maintaining Ca2+ homeostasis. The cysteine 674 (C674) is the key redox regulatory cysteine in regulating SERCA2 activity, which is irreversibly oxidized in the renal cortex of hypertensive mice. We have reported that the substitution of C674 by serine causes SERCA2 dysfunction and increases blood pressure by induction of endoplasmic reticulum stress (ERS). This study is to explore whether the dysfunction of SERCA2 causes hypertension by interrupting mitochondrial homeostasis and inducing oxidative stress. METHODS & RESULTS: We used heterozygous SERCA2 C674S gene mutation knock-in (SKI) mice, where one copy of C674 was substituted by serine to represent partial C674 oxidation. In renal proximal tubule (RPT) cells, the substitution of C674 by serine decreased mitochondrial Ca2+ content, increased mitochondrial membrane potential, ATP content, and reactive oxygen species (ROS), which could be reversed by ERS inhibitor 4-phenylbutyric acid or SERCA2 agonist CDN1163. In SKI RPT cells, the redox modulator Tempol alleviated oxidative stress, downregulated the protein expression of ERS markers and soluble epoxide hydrolase, upregulated the protein expression of dopamine D1 receptor, and reduced Na+/K+- ATPase activity. In SKI mice, SERCA2 agonists CDN1163 and [6]-Gingerol, or the redox modulator Tempol increased urine output and lowered blood pressure. CONCLUSION: The irreversible oxidation of C674 is not only an indicator of increased ROS, but also further inducing oxidative stress to cause hypertension. Activation of SERCA2 or inhibition of oxidative stress is beneficial to alleviate hypertension caused by SERCA2 dysfunction.

CDN1163 alleviates SERCA2 dysfunction-induced pulmonary vascular remodeling by inhibiting the phenotypic transition of pulmonary artery smooth muscle cells.

BACKGROUND AND PURPOSE: Substitution of Cys674 (C674) in the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) causes SERCA2 dysfunction which leads to activated inositol requiring enzyme 1 alpha (IRE1α) and spliced X-box binding protein 1 (XBP1s) pathway accelerating cell proliferation of pulmonary artery smooth muscle cells (PASMCs) followed by significant pulmonary vascular remodeling resembling human pulmonary hypertension. Based on this knowledge, we intend to investigate other potential mechanisms involved in SERCA2 dysfunction-induced pulmonary vascular remodeling. EXPERIMENTAL APPROACH: Heterozygous SERCA2 C674S knock-in (SKI) mice of which half of cysteine in 674 was substituted by serine to mimic the partial irreversible oxidation of C674 were used. The lungs of SKI mice and their littermate wild-type mice were collected for PASMC culture, protein expression, and pulmonary vascular remodeling analysis. RESULTS: SERCA2 dysfunction increased intracellular Ca2+ levels, which activated Ca2+-dependent calcineurin (CaN) and promoted the nuclear translocation and protein expression of the nuclear factor of activated T-lymphocytes 4 (NFAT4) in an IRE1α/XBP1s pathway-independent manner. In SKI PASMCs, the scavenge of intracellular Ca2+ by BAPTA-AM or inhibition of CaN by cyclosporin A can prevent PASMC phenotypic transition. CDN1163, a SERCA2 agonist, suppressed the activation of CaN/NFAT4 and IRE1α/XBP1s pathways, reversed the protein expression of PASMC phenotypic transition markers and cell cycle-related proteins, and inhibited cell proliferation and migration when given to SKI PASMCs. Furthermore, CDN1163 ameliorated pulmonary vascular remodeling in SKI mice. CONCLUSIONS AND IMPLICATIONS: SERCA2 dysfunction promotes PASMC phenotypic transition and pulmonary vascular remodeling by multiple mechanisms, which could be improved by SERCA2 agonist CDN1163.

'What is already known' l The dysfunction of SERCA2 promotes PASMC hyperproliferation and pulmonary vascular remodeling through activation of the IRE1α/XBP1s pathway.'What this study adds' l The dysfunction of SERCA2 activates the Ca²⁺-dependent CaN-mediated NFAT4 pathway to promote the PASMC phenotypic transition.l Revitalization of SERCA2 suppresses PASMC phenotypic transition and pulmonary vascular remodeling caused by SERCA2 dysfunction.'Clinical significance' l SERCA2 dysfunction-induced pulmonary vascular remodeling involves more than one mechanism, implicating that more drugable targets are to be discovered.l SERCA2 is a potential therapeutic target for preventing pulmonary vascular remodeling.

Krüppel-like Factor 7 inhibits proliferation and migration of pulmonary smooth muscle cells via p21 activation.

The aberrant proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) are critical contributors to the pulmonary vascular remodeling that occurs during the development of Pulmonary arterial hypertension (PAH). Krüppel-like Factor 7 (KLF7) has been reported to be involved in the development of certain cardiovascular diseases. However, the role of KLF7 in PAH remains unknown. Here, we aimed to explore whether KLF7 mediates the proliferation and migration of PASMCs and its underlying mechanism. In this study, Sprague Dawley rats were exposed to 60 mg/kg monocrotaline (MCT) for 3 weeks to induce PAH and human PASMCs were stimulated with 20 ng/ml platelet-derived growth factor-BB (PDGF-BB) for 24 h to induce proliferation and migration. The mRNA and protein expression of KLF7 were significantly down-regulated in MCT-induced PAH rats and PDGF-BB-treated PASMCs. Under normal conditions, KLF7 knockdown obviously promoted PASMCs proliferation and migration, whereas KLF7 overexpression exhibited the opposite effects. Furthermore, PDGF-BB promoted the PASMCs proliferation and migration, increased the cell proportion in S phase, which was significantly attenuated by overexpression of KLF7. Mechanistic investigation indicated that KLF7 through activation its target protein, the cell cycle inhibitor p21, which finally leading to the inhibition of PASMCs growth. Consistently, UC2288, a specific inhibitor of p21, partially reversed the PASMCs proliferation inhibited by KLF7 overexpression. Taken collectively, the data suggested that KLF7 inhibits PASMCs proliferation and migration via p21 pathway and it may be used as a new therapeutic target for the PAH.

Pickering emulsion-enhanced Vibrio fischeri assay for ecotoxicity assessment of highly hydrophobic polycyclic aromatic hydrocarbons.

Accurate ecotoxicity assessment of contaminated soil is critical to public health, and the luminescent bacteria (Vibrio fischeri) method is the most commonly used. Hydrophobic compounds such as polycyclic aromatic hydrocarbons (PAHs) in soil cannot be in contact with luminescent bacteria due to their low water solubility so that the luminescence inhibitory effect cannot be observed. The underestimated biological toxicity makes the test unreliable and en-dangers public health and safety. The commonly adopted improved method of adding cosolvents has limited effect, it was only effective for low-hydrophobicity chemicals and could not be used for ecotoxicity evaluation of high-hydrophobicity chemicals. Therefore, we constructed Pickering emulsions using luminescent bacteria modified with n-dodecanol in which PAHs were dissolved in the oil phase, n-tetradecane. Then the luminescent bacteria could tightly adhere to the oil-water interface and contact PAHs. As a result, their bioluminescence was suppressed to varying degrees depending on the chemical species and concentrations. With no solubility limitation, highly hydrophobic PAHs could even completely inhibit bacterial bioluminescence, hence the toxicity information was accurately displayed and the median effect concentration (EC50) values could be calculated. This Pickering emulsion-based method was successfully applied for the accurate ecotoxicity evaluation of highly hydrophobic PAHs and soil samples contaminated with them, which all previous methods could not achieve. This method overcomes the problem of ecotoxicity evaluation of hydrophobic compounds, and has great potential for practical application, whether it is pure chemicals or various real samples from the ecological environment.

The Therapeutic Strategies Targeting Mitochondrial Metabolism in Cardiovascular Disease.

Cardiovascular disease (CVD) is a group of systemic disorders threatening human health with complex pathogenesis, among which mitochondrial energy metabolism reprogramming has a critical role. Mitochondria are cell organelles that fuel the energy essential for biochemical reactions and maintain normal physiological functions of the body. Mitochondrial metabolic disorders are extensively involved in the progression of CVD, especially for energy-demanding organs such as the heart. Therefore, elucidating the role of mitochondrial metabolism in the progression of CVD is of great significance to further understand the pathogenesis of CVD and explore preventive and therapeutic methods. In this review, we discuss the major factors of mitochondrial metabolism and their potential roles in the prevention and treatment of CVD. The current application of mitochondria-targeted therapeutic agents in the treatment of CVD and advances in mitochondria-targeted gene therapy technologies are also overviewed.

Monitoring of the yogurt fermentation process based on a rapid bio-luminescent chiral pattern recognition of amino acids.

The analysis of chiral α-amino acids is of great significance in asymmetric synthesis, nutrition, food science, and microbiology. However, the ability of chiral recognition is difficult to achieve. Due to the demand for expensive equipment and skilled operators, traditional methods such as high-performance liquid chromatography are limited. The previously reported methods based on chemical sensor arrays usually cannot carry out the chiral analysis. Here, we developed a novel biosensor array based on the interaction between a suite of host-based luminescent bacteria and amino acids and used linear discriminant analysis to reflect their luminescence response patterns. This biosensor array could effectively discriminate chiral amino acids, including 19 L-amino acids, their corresponding D-enantiomers, and the achiral glycine. In addition, the determination of enantiomeric purity and quantitative ability has been proved. The successful identification of a complex system containing multiple chiral amino acids further demonstrates the superiority of the bioluminescent sensor array. Moreover, this sensor array could efficiently monitor the dynamic composition of free amino acids in the process of milk fermentation. Finally, the bioluminescence response mechanism of the luminescent bacteria for the recognition of chirality was clarified. This approach possessed the advantages of facile construction, high throughput, easy operation, high accuracy and fast response.

Substitution of SERCA2 Cys674 aggravates cardiac fibrosis by promoting the transformation of cardiac fibroblasts to cardiac myofibroblasts.

Sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) is vital to maintain intracellular calcium homeostasis, and its redox Cys674 (C674) is the key to regulating activity. Our goal was to investigate whether the redox state of SERCA2 C674 is critical for cardiac fibrosis and the mechanisms involved. Heterozygous SERCA2 C674S knock-in (SKI) mice, in which half of C674 was substituted by serine, were used to mimic the partial loss of the reactive C674 thiol in pathological conditions. In cardiac fibroblasts, the substitution of C674 thiol increased Ca2+ levels in cytoplasm and mitochondria, and intracellular ROS levels, and activated calcineurin/nuclear factor of activated T-lymphocytes (NFAT) pathway, increased the protein expression of profibrotic factors TGF beta 1 (TGF-ß1), alpha smooth muscle actin, collagen I and collagen III, and promoted the transformation of cardiac fibroblasts to cardiac myofibroblasts, which could be reversed by calcineurin/NFAT inhibitor, SERCA2 agonist, or ROS scavenger. Activation of SERCA2 or scavenging ROS is beneficial to alleviate cardiac fibrosis caused by the substitution of C674. In conclusion, the partial loss of the reactive C674 thiol in the SERCA2 exacerbates cardiac fibrosis by activating the calcineurin/NFAT/TGF-ß1 pathway to promote the transformation of cardiac fibroblasts to cardiac myofibroblasts, which highlights the importance of C674 redox state in maintaining the homeostasis of cardiac fibroblasts. SERCA2 is a potential therapeutic target for the treatment of cardiac fibrosis.

Substitution of the SERCA2 Cys674 reactive thiol accelerates atherosclerosis by inducing endoplasmic reticulum stress and inflammation.

BACKGROUND AND PURPOSE: The cysteine674 (C674) thiol of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 is easily and irreversibly oxidized under atherosclerotic conditions. However, the contribution of the C674 thiol redox status in the development of atherosclerosis remains unclear. Our goal was to elucidate the possible mechanism involved. EXPERIMENTAL APPROACH: Heterozygous SERCA2 C674S knock-in mice in which half of the C674 was substituted by serine (S674) were used to mimic the removal of the reactive C674 thiol, which occurs under pathological conditions. Bone marrow-derived macrophages (BMDMs) and cardiac endothelial cells (ECs) were used for intracellular Ca2+ , macrophage adhesion, and protein expression analysis. The whole aorta and aortic root were isolated for histological analysis. KEY RESULTS: Cell culture studies suggest the partial substitution of SERCA2 C674 increased intracellular Ca2+ levels and induced ER stress in both BMDMs and ECs. The release of proinflammatory factors and macrophage adhesion increased in SKI BMDMs. In ECs, overexpression of S674 induced endothelial inflammation and promoted macrophage recruitment. SKI mice developed more severe atherosclerotic plaque and macrophage accumulation. Additionally, 4-phenyl butyric acid, an ER stress inhibitor, suppressed ER stress and inflammatory responses in BMDMs and ECs, and alleviated atherosclerosis in SKI mice. CONCLUSIONS AND IMPLICATIONS: The substitution of SERCA2 C674 thiol accelerates the development of atherosclerosis by inducing ER stress and inflammation. Our findings highlight the importance of SERCA2 C674 redox state in the context of atherosclerosis and open up a novel therapeutic strategy to combat atherosclerosis.

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.

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.

Cross-Talk between Mechanosensitive Ion Channels and Calcium Regulatory Proteins in Cardiovascular Health and Disease.

Mechanosensitive ion channels are widely expressed in the cardiovascular system. They translate mechanical forces including shear stress and stretch into biological signals. The most prominent biological signal through which the cardiovascular physiological activity is initiated or maintained are intracellular calcium ions (Ca2+). Growing evidence show that the Ca2+ entry mediated by mechanosensitive ion channels is also precisely regulated by a variety of key proteins which are distributed in the cell membrane or endoplasmic reticulum. Recent studies have revealed that mechanosensitive ion channels can even physically interact with Ca2+ regulatory proteins and these interactions have wide implications for physiology and pathophysiology. Therefore, this paper reviews the cross-talk between mechanosensitive ion channels and some key Ca2+ regulatory proteins in the maintenance of calcium homeostasis and its relevance to cardiovascular health and disease.

Ectopic Overexpression of PPARγ2 in the Heart Determines Differences in Hypertrophic Cardiomyopathy After Treatment With Different Thiazolidinediones in a Mouse Model of Diabetes.

The clinical controversy of rosiglitazone as a hypoglycemic agent is potentially associated with heart failure, mainly due to its potent activation of peroxisome proliferator-activated receptor γ (PPARγ). PPARγ partial agonists showed superior pharmacological profiles to rosiglitazone. This study compared differences in cardiac morphology and function of the PPARγ partial agonist CMHX008 with rosiglitazone. High-fat diet (HFD) induced obese mice, ob/ob mice and cardiomyocytes overexpressing PPARγ2 were treated with CMHX008 or rosiglitazone. Heart function, myocardial morphology, and hypertrophy-related gene expression were examined. Clinical information from patients with type 2 diabetes mellitus (T2DM) who had taken rosiglitazone and undergone Doppler echocardiography was collected. HFD and ob/ob mice significantly developed cardiac contractile dysfunction, with upregulated PPARγ2 protein levels in heart tissues. Cardiomyocytes of HFD and ob/ob mice were disorderly arranged, the cell areas expanded, and collagen accumulated. In vitro cardiomyocytes overexpressing PPARγ2 displayed obvious structural abnormalities and high mRNA levels of ANP and BNP, critical cardiac hypertrophy-related genes. HFD-fed mice treated with rosiglitazone or CMHX008 had significantly improved cardiac function, but rosiglitazone induced higher expression of ANP and ßMHC and hypertrophic cardiomyopathy, while CMHX008 did not. Patients with T2DM taking rosiglitazone exhibited increased thickness of the posterior wall and the ventricular septum, suggesting cardiac hypertrophy. Our findings show that diabetic cardiomyopathy was associated with ectopic overexpression of PPARγ2. The full agonist rosiglitazone prevents cardiac dysfunction at the expense of compensatory hypertrophy, while the partial agonist CMHX008 shared a comparable protective effect without altering the structure of cardiomyocytes.

Inactivation of cysteine 674 in the sarcoplasmic/endoplasmic reticulum calcium ATPase 2 causes retinopathy in the mouse.

Diabetic retinopathy is a multifactorial microvascular complication, and its pathogenesis hasn't been fully elucidated. The irreversible oxidation of cysteine 674 (C674) in the sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2) was increased in the type 1 diabetic retinal vasculature. SERCA2 C674S knock-in (SKI) mouse line that half of C674 was replaced by serine 674 (S674) was used to study the effect of C674 inactivation on retinopathy. Compared with wild type (WT) mice, SKI mice had increased number of acellular capillaries and pericyte loss similar to those in type 1 diabetic WT mice. In the retina of SKI mice, pro-apoptotic proteins and intracellular Ca2+-dependent signaling pathways increased, while anti-apoptotic proteins and vessel density decreased. In endothelial cells, C674 inactivation increased the expression of pro-apoptotic proteins, damaged mitochondria, and induced cell apoptosis. These results suggest that a possible mechanism of retinopathy induced by type 1 diabetes is the interruption of calcium homeostasis in the retina by oxidation of C674. C674 is a key to maintain retinal health. Its inactivation can cause retinopathy similar to type 1 diabetes by promoting apoptosis. SERCA2 might be a potential target for the prevention and treatment of diabetic retinopathy.

Inactivation of SERCA2 Cys674 accelerates aortic aneurysms by suppressing PPARγ.

BACKGROUND AND PURPOSE: Inactivation of Cys674 (C674) in the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) causes intracellular Ca2+ accumulation, which activates calcineurin-mediated nuclear factor of activated T-lymphocytes (NFAT)/NF-κB pathways, and results in the phenotypic modulation of smooth muscle cells (SMCs) to accelerate angiotensin II-induced aortic aneurysms. Our goal was to investigate the mechanism involved. EXPERIMENTAL APPROACH: We used heterozygous SERCA2 C674S knock-in (SKI) mice, where half of C674 was substituted by serine, to mimic partial irreversible oxidation of C674. The aortas of SKI mice and their littermate wild-type mice were collected for RNA sequencing, cell culture, protein expression, luciferase activity and aortic aneurysm analysis. KEY RESULTS: Inactivation of C674 inhibited the promoter activity and protein expression of PPARγ, which could be reversed by inhibitors of calcineurin or NF-κB. In SKI SMCs, inhibition of NF-κB by pyrrolidinedithiocarbamic acid (PDTC) or overexpression of PPARγ2 reversed the protein expression of SMC phenotypic modulation markers and inhibited cell proliferation, migration, and macrophage adhesion to SMCs. Pioglitazone, a PPARγ agonist, blocked the activation of NFAT/NF-κB, reversed the protein expression of SMC phenotypic modulation markers, and inhibited cell proliferation, migration, and macrophage adhesion to SMCs in SKI SMCs. Furthermore, pioglitazone also ameliorated angiotensin II-induced aortic aneurysms in SKI mice. CONCLUSIONS AND IMPLICATIONS: The inactivation of SERCA2 C674 promotes the development of aortic aneurysms by disrupting the balance between PPARγ and NFAT/NF-κB. Our study highlights the importance of C674 redox status in regulating PPARγ to maintain aortic homeostasis.

Endothelial Nox4 dysfunction aggravates atherosclerosis by inducing endoplasmic reticulum stress and soluble epoxide hydrolase.

BACKGROUND AND AIMS: Our previous findings have demonstrated the protective effect of endothelial Nox4-based NADPH oxidase on atherosclerosis. One of the possible mechanisms is the inhibition of soluble epoxide hydrolase (sEH), a proinflammatory and atherogenic factor. Our goal was to investigate whether in vivo inhibition of sEH by 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) alleviates endothelial Nox4 dysfunction caused atherosclerosis and the regulatory mechanism of endothelial Nox4 on sEH. METHODS: & results: We used endothelial human Nox4 dominant-negative (EDN) transgenic mice in ApoE deficient background to mimic the dysfunction of endothelial Nox4 in atherosclerosis-prone conditions. In EDN aortic endothelium, sEH and the inflammatory marker vascular cell adhesion molecule 1 (VCAM1) were upregulated. TPPU reduced atherosclerotic lesions in EDN mice. In EDN endothelial cells (ECs), the endoplasmic reticulum (ER) stress markers (BIP, IRE1α, phosphorylation of PERK, ATF6) were upregulated, and they can be suppressed by ER stress inhibitor 4-phenyl butyric acid (4-PBA). In EDN ECs, 4-PBA downregulated the expression of sEH and VCAM1, suppressed inflammation, and its application in vivo reduced atherosclerotic lesions of EDN mice. CONCLUSIONS: Endothelial Nox4 dysfunction upregulated sEH to enhance inflammation, probably by its induction of ER stress. Inhibition of ER stress or sEH is beneficial to alleviate atherosclerosis caused by endothelial Nox4 dysfunction.

Redox-Resistant SERCA [Sarco(endo)plasmic Reticulum Calcium ATPase] Attenuates Oxidant-Stimulated Mitochondrial Calcium and Apoptosis in Cardiac Myocytes and Pressure Overload-Induced Myocardial Failure in Mice.

BACKGROUND: SERCA [sarco(endo)plasmic reticulum calcium ATPase] is regulated by oxidative posttranslational modifications at cysteine 674 (C674). Because sarcoplasmic reticulum (SR) calcium has been shown to play a critical role in mediating mitochondrial dysfunction in response to reactive oxygen species, we hypothesized that SERCA oxidation at C674 would modulate the effects of reactive oxygen species on mitochondrial calcium and mitochondria-dependent apoptosis in cardiac myocytes. METHODS: Adult rat ventricular myocytes expressing wild-type SERCA2b or a redox-insensitive mutant in which C674 is replaced by serine (C674S) were exposed to H2O2 (100 µmol/Lµ). Free mitochondrial calcium concentration was measured in adult rat ventricular myocytes with a genetically targeted fluorescent probe, and SR calcium content was assessed by measuring caffeine-stimulated release. Mice with heterozygous knock-in of the SERCA C674S mutation were subjected to chronic ascending aortic constriction. RESULTS: In adult rat ventricular myocytes expressing wild-type SERCA, H2O2 caused a 25% increase in mitochondrial calcium concentration that was associated with a 50% decrease in SR calcium content, both of which were prevented by the ryanodine receptor inhibitor tetracaine. In cells expressing the C674S mutant, basal SR calcium content was decreased by 31% and the H2O2-stimulated rise in mitochondrial calcium concentration was attenuated by 40%. In wild-type cells, H2O2 caused cytochrome c release and apoptosis, both of which were prevented in C674S-expressing cells. In myocytes from SERCA knock-in mice, basal SERCA activity and SR calcium content were decreased. To test the effect of C674 oxidation on apoptosis in vivo, SERCA knock-in mice were subjected to chronic ascending aortic constriction. In wild-type mice, ascending aortic constriction caused myocyte apoptosis, LV dilation, and systolic failure, all of which were inhibited in SERCA knock-in mice. CONCLUSIONS: Redox activation of SERCA C674 regulates basal SR calcium content, thereby mediating the pathologic reactive oxygen species-stimulated rise in mitochondrial calcium required for myocyte apoptosis and myocardial failure.

Smooth muscle NADPH oxidase 4 promotes angiotensin II-induced aortic aneurysm and atherosclerosis by regulating osteopontin.

BACKGROUND AND AIMS: Angiotensin II (Ang II) is commonly used to induce aortic aneurysm and atherosclerosis in animal models. Ang II upregulates NADPH oxidase isoform Nox4 in aortic smooth muscle cells (SMCs) in mice. However, whether smooth muscle Nox4 is directly involved in Ang II-induced aortic aneurysm and atherosclerosis is unclear. METHODS & RESULTS: To address this, we used smooth muscle-specific Nox4 dominant-negative (SDN) transgenic mice, in which Nox4 activity is constitutively inhibited. In non-transgenic (NTg) mice, Ang II increased the expression of proteins known to contribute to both aortic aneurysm and atherosclerosis, namely osteopontin (OPN), collagen type I&III (Col I&III), matrix metalloproteinase 2 (MMP2), and vascular cell adhesion molecule 1 (VCAM1), which were all significantly downregulated in SDN mice. The number and size of Ang II-induced aorta collateral aneurysms and atherosclerotic lesions in the renal artery and aortic root of SDN mice were significantly decreased compared to NTg mice, and directly correlated with a decrease in OPN expression. Replenishing OPN in SDN SMCs, increased the expression of Col I&III, MMP2, and VCAM1, and promoted SMC proliferation, migration, and inflammation. CONCLUSIONS: Our data demonstrate that smooth muscle Nox4 directly promotes the development of Ang II-induced aortic aneurysm and atherosclerosis, at least in part, through regulating OPN expression.

Inactivation of cysteine 674 in the SERCA2 accelerates experimental aortic aneurysm.

Sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) is vital to maintain intracellular calcium homeostasis. SERCA2 cysteine 674 (C674) is highly conservative and its irreversible oxidation is upregulated in human and mouse aortic aneurysms, especially in smooth muscle cells (SMCs). The contribution of SERCA2 and its redox C674 in the development of aortic aneurysm remains enigmatic. Objective: Our goal was to investigate the contribution of inactivation of C674 to the development of aortic aneurysm and the mechanisms involved. Approach and results: Using SERCA2 C674S knock-in (SKI) mouse line, in which half of C674 was substituted by serine 674 (S674) to represent partial irreversible oxidation of C674 in aortic aneurysm, we found that in aortic SMCs the replacement of C674 by S674 resulted in SMC phenotypic modulation. In SKI SMCs, the increased intracellular calcium activated calcium-dependent calcineurin, which promoted the nuclear translocation of nuclear factor of activated T-lymphocytes (NFAT) and nuclear factor kappa-B (NFκB), while inhibition of calcineurin blocked SMC phenotypic modulation. Besides, the replacement of C674 by S674 accelerated angiotensin II-induced aortic aneurysm. Conclusions: Our results indicate that the inactivation of C674 by causing the accumulation of intracellular calcium to activate calcineurin-mediated NFAT/NFκB pathways, resulted in SMC phenotypic modulation to accelerate aortic aneurysm, which highlights the importance of C674 redox state in the development of aortic aneurysms.