Benefit of SERCA2a gene transfer to vascular endothelial and smooth muscle cells: a new aspect in therapy of cardiovascular diseases

Calcium signaling in endothelial and vascular smooth muscle cells: sex differences and the influence of estrogens and androgens

Calcium signaling in vascular endothelial cells (ECs) and smooth muscle cells (VSMCs) is essential for the regulation of vascular tone. However, the changes to intracellular Ca2+ concentrations are often influenced by sex differences. Furthermore, a large body of evidence shows that sex hormone imbalance leads to dysregulation of Ca2+ signaling and this is a key factor in the pathogenesis of cardiovascular diseases. In this review, the effects of estrogens and androgens on vascular calcium-handling proteins are discussed, with emphasis on the associated genomic or nongenomic molecular mechanisms. The experimental models from which data were collected were also considered. The review highlights 1) in female ECs, transient receptor potential vanilloid 4 (TRPV4) and mitochondrial Ca2+ uniporter (MCU) enhance Ca2+-dependent nitric oxide (NO) generation. In males, only transient receptor potential canonical 3 (TRPC3) plays a fundamental role in this effect. 2) Female VSMCs have lower cytosolic Ca2+ levels than males due to differences in the activity and expression of stromal interaction molecule 1 (STIM1), calcium release-activated calcium modulator 1 (Orai1), calcium voltage-gated channel subunit-α1C (CaV1.2), Na+-K+-2Cl- symporter (NKCC1), and the Na+/K+-ATPase. 3) When compared with androgens, the influence of estrogens on Ca2+ homeostasis, vascular tone, and incidence of vascular disease is better documented. 4) Many studies use supraphysiological concentrations of sex hormones, which may limit the physiological relevance of outcomes. 5) Sex-dependent differences in Ca2+ signaling mean both sexes ought to be included in experimental design.

Sarco/Endoplasmic Reticulum Ca2+ ATPase 2 Activator Ameliorates Endothelial Dysfunction; Insulin Resistance in Diabetic Mice

Background: Sarco/endoplasmic reticulum Ca2+-ATPase2 (SERCA2) is impaired in various organs in animal models of diabetes. The purpose of this study was to test the effects of an allosteric SERCA2 activator (CDN1163) on glucose intolerance, hepatosteatosis, skeletal muscle function, and endothelial dysfunction in diabetic (db/db) mice. Methods: Either CDN1163 or vehicle was injected intraperitoneally into 16-week-old male control and db/db mice for 5 consecutive days. Results: SERCA2 protein expression was decreased in the aorta of db/db mice. In isometric tension measurements of aortic rings from db/db mice treated with CDN1163, acetylcholine (ACh)-induced relaxation was improved. In vivo intraperitoneal administrations of CDN 1163 also increased ACh-induced relaxation. Moreover, CDN1163 significantly decreased blood glucose in db/db mice at 60 and 120 min during a glucose tolerance test; it also decreased serum insulin levels, hepatosteatosis, and oxygen consumption in skeletal muscle during the early period of exercise in db/db mice. Conclusions: CDN1163 directly improved aortic endothelial dysfunction in db/db mice. Moreover, CDN1163 improved hepatosteatosis, skeletal muscle function, and insulin resistance in db/db mice. The activation of SERCA2 might be a strategy for the all the tissue expressed SERCA2a improvement of endothelial dysfunction and the target for the organs related to insulin resistance.

Endo-bronchial aerosolized AAV1.SERCA2a gene therapy in a pulmonary hypertension pig model: addressing the lung delivery bottleneck

A disappointing number of new therapies for pulmonary hypertension (PH) have been successfully translated to the clinic. Adeno-associated viral (AAV) gene therapy has the potential to treat the underlying pathology of PH, but the challenge remains in efficient and safe delivery. The aims of this study were i) to test the efficacy of endo-bronchial aerosolization delivery for AAV1-mediated sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) gene therapy in a PH pig model and ii) to identify the most efficient airway administration modality for in-lung gene therapy in PH. We hypothesized that delivery to the distal bronchi increases lung viral uptake and avoids virus loss in off-target compartments. In part one of the study, PH was induced in pigs by surgically banding the pulmonary veins. Two months post-surgery, 1x1013 viral genomes (vg) of AAV1.SERCA2a or saline was endo-bronchially aerosolized using a bronchoscope. Two months after aerosolization, high vg copies were detected in the lungs, accompanied by functional and morphometrical amelioration of PH. In part two of the study, we directly compared the endo-bronchial aerosolization gene delivery to the intra-tracheal aerosolization in PH pigs. Endo-bronchial delivery demonstrated higher viral expression (6,719 ± 927 vs 1,444 ± 402 vg copy/100ng DNA, p=0.0017), suggesting this delivery modality is a promising method for clinical AAV gene therapy for PH.

Calcium dysregulation in heart diseases: Targeting calcium channels to achieve a correct calcium homeostasis

Intracellular calcium signaling is a universal language source shared by the most part of biological entities inside cells that, all together, give rise to physiological and functional anatomical units, the organ. Although preferentially recognized as signaling between cell life and death processes, in the heart it assumes additional relevance considered the importance of calcium cycling coupled to ATP consumption in excitation-contraction coupling. The concerted action of a plethora of exchangers, channels and pumps inward and outward calcium fluxes where needed, to convert energy and electric impulses in muscle contraction. All this without realizing it, thousands of times, every day. An improper function of those proteins (i.e., variation in expression, mutations onset, dysregulated channeling, differential protein-protein interactions) being part of this signaling network triggers a short circuit with severe acute and chronic pathological consequences reported as arrhythmias, cardiac remodeling, heart failure, reperfusion injury and cardiomyopathies. By acting with chemical, peptide-based and pharmacological modulators of these players, a correction of calcium homeostasis can be achieved accompanied by an amelioration of clinical symptoms. This review will focus on all those defects in calcium homeostasis which occur in the most common cardiac diseases, including myocardial infarction, arrhythmia, hypertrophy, heart failure and cardiomyopathies. This part will be introduced by the state of the art on the proteins involved in calcium homeostasis in cardiomyocytes and followed by the therapeutic treatments that to date, are able to target them and to revert the pathological phenotype.

Contractile Behavior of Mouse Aorta Depends on SERCA2 Isoform Distribution: Effects of Replacing SERCA2a by SERCA2b

The Sarco(endo)plasmic reticulum Ca²⁺ ATPase (SERCA) actively pumps Ca²⁺ into the sarco/endoplasmic reticulum, thereby regulating intracellular Ca²⁺ concentrations and associated physiological processes. Different SERCA isoforms have been described (SERCA1, 2, and 3) with SERCA2 playing a pivotal role in Ca²⁺ homeostasis in cardiovascular tissues. In the heart, SERCA2a is the dominant isoform and has been proposed as therapeutic target in patients with heart failure. In the vasculature, both SERCA2a and SERCA2b are expressed with SERCA2b being the predominant isoform. The physiological role of SERCA2a in the vasculature, however, remains incompletely understood. In the present study, we used gene-modified mice in which the alternative splicing of the SERCA2-encoding gene (Atp2a2), underlying the expression of SERCA2a, is prevented and SERCA2a is replaced by SERCA2b. The resulting SERCA2^b/b mice provide a unique opportunity to investigate the specific contribution of SERCA2a versus SERCA2b to vascular physiology. Aortic segments of SERCA2^b/b (SERCA2a-deficient) and SERCA2^a/b (control) mice were mounted in organ baths to evaluate vascular reactivity. SERCA2^b/b aortic rings displayed higher contractions induced by phenylephrine (1 μM). Surprisingly, the initial inositol-3-phosphate mediated phasic contraction showed a faster decay of force in SERCA2^b/b mice, while the subsequent tonic contraction was larger in SERCA2^b/b segments. Moreover, in the presence of the calcium channel blocker diltiazem (35 μM) SERCA2^b/b aortic rings showed higher contractions compared to SERCA2^a/b, suggesting that SERCA2a (deficiency) modulates the activity of non-selective cation channels. Additionally, in endothelial cell (EC)-denuded aortic segments, the SERCA-inhibitor cyclopiazonic acid (CPA) caused markedly larger contractions in SERCA2^b/b mice, while the increases of cytosolic Ca²⁺ were similar in both strains. Hence, aortas of SERCA2^b/b mice appear to have a stronger coupling of intracellular Ca²⁺ to contraction, which may be in agreement with the reported difference in intracellular localization of SERCA2a versus SERCA2b. Finally, EC-mediated relaxation by acetylcholine and ATP was assessed. Concentration-response-curves for ATP showed a higher sensitivity of aortic segments of SERCA2^b/b mice, while no difference in potency between strains were observed for acetylcholine. In summary, despite the relative low expression of SERCA2a in the murine aorta, our results point toward a distinct role in vascular physiology.

Protective Effects of Euthyroidism Restoration on Mitochondria Function and Quality Control in Cardiac Pathophysiology

Mitochondrial dysfunctions are major contributors to heart disease onset and progression. Under ischemic injuries or cardiac overload, mitochondrial-derived oxidative stress, Ca²⁺ dis-homeostasis, and inflammation initiate cross-talking vicious cycles leading to defects of mitochondrial DNA, lipids, and proteins, concurrently resulting in fatal energy crisis and cell loss. Blunting such noxious stimuli and preserving mitochondrial homeostasis are essential to cell survival. In this context, mitochondrial quality control (MQC) represents an expanding research topic and therapeutic target in the field of cardiac physiology. MQC is a multi-tier surveillance system operating at the protein, organelle, and cell level to repair or eliminate damaged mitochondrial components and replace them by biogenesis. Novel evidence highlights the critical role of thyroid hormones (TH) in regulating multiple aspects of MQC, resulting in increased organelle turnover, improved mitochondrial bioenergetics, and the retention of cell function. In the present review, these emerging protective effects are discussed in the context of cardiac ischemia-reperfusion (IR) and heart failure, focusing on MQC as a strategy to blunt the propagation of connected dangerous signaling cascades and limit adverse remodeling. A better understanding of such TH-dependent signaling could provide insights into the development of mitochondria-targeted treatments in patients with cardiac disease.

Safety and long-term efficacy of AAV1.SERCA2a using nebulizer delivery in a pig model of pulmonary hypertension

Nebulization delivery of adeno-associated virus serotype 1 encoding sarcoplasmic reticulum Ca2+-ATPase2a (AAV1.SERCA2a) gene was examined in a Yukatan miniature swine model of chronic pulmonary hypertension (n = 13). Nebulization of AAV1.SERCA2a resulted in homogenous distribution of vectors, lower pulmonary vascular resistance, and a trend towards better long-term survival compared to control animals.

Correcting Calcium Dysregulation in Chronic Heart Failure Using SERCA2a Gene Therapy

Chronic heart failure (CHF) is a major contributor to cardiovascular disease and is the leading cause of hospitalization for those over the age of 65, which is estimated to account for close to seventy billion dollars in healthcare costs by 2030 in the US alone. The successful therapies for preventing and reversing CHF progression are urgently required. One strategy under active investigation is to restore dysregulated myocardial calcium (Ca²⁺), a hallmark of CHF. It is well established that intracellular Ca²⁺ concentrations are tightly regulated to control efficient myocardial systolic contraction and diastolic relaxation. Among the many cell surface proteins and intracellular organelles that act as the warp and woof of the regulatory network controlling intracellular Ca²⁺ signals in cardiomyocytes, sarco/endoplasmic reticulum Ca²⁺ ATPase type 2a (SERCA2a) undoubtedly plays a central role. SERCA2a is responsible for sequestrating cytosolic Ca²⁺ back into the sarcoplasmic reticulum during diastole, allowing for efficient uncoupling of actin-myosin and subsequent ventricular relaxation. Accumulating evidence has demonstrated that the expression of SERCA2a is downregulated in CHF, which subsequently contributes to severe systolic and diastolic dysfunction. Therefore, restoring SERCA2a expression and improving cardiomyocyte Ca²⁺ handling provides an excellent alternative to currently used transplantation and mechanical assist devices in the treatment of CHF. Indeed, advancements in safe and effective gene delivery techniques have led to the emergence of SERCA2a gene therapy as a potential therapeutic choice for CHF patients. This mini-review will succinctly detail the progression of SERCA2a gene therapy from its inception in plasmid and animal models, to its clinical trials in CHF patients, highlighting potential avenues for future work along the way.

LncRNA ZFAS1 as a SERCA2a Inhibitor to Cause Intracellular Ca2+ Overload and Contractile Dysfunction in a Mouse Model of Myocardial Infarction

RATIONALE

Ca²⁺ homeostasis-a critical determinant of cardiac contractile function-is critically regulated by SERCA2a (sarcoplasmic reticulum Ca²⁺-ATPase 2a). Our previous study has identified ZFAS1 as a new lncRNA biomarker of acute myocardial infarction (MI).

OBJECTIVE

To evaluate the effects of ZFAS1 on SERCA2a and the associated Ca²⁺ homeostasis and cardiac contractile function in the setting of MI.

METHODS AND RESULTS

ZFAS1 expression was robustly increased in cytoplasm and sarcoplasmic reticulum in a mouse model of MI and a cellular model of hypoxia. Knockdown of endogenous ZFAS1 by virus-mediated silencing shRNA partially abrogated the ischemia-induced contractile dysfunction. Overexpression of ZFAS1 in otherwise normal mice created similar impairment of cardiac function as that observed in MI mice. Moreover, at the cellular level, ZFAS1 overexpression weakened the contractility of cardiac muscles. At the subcellular level, ZFAS1 deleteriously altered the Ca²⁺ transient leading to intracellular Ca²⁺ overload in cardiomyocytes. At the molecular level, ZFAS1 was found to directly bind SERCA2a protein and to limit its activity, as well as to repress its expression. The effects of ZFAS1 were readily reversible on knockdown of this lncRNA. Notably, a sequence domain of ZFAS1 gene that is conserved across species mimicked the effects of the full-length ZFAS1. Mutation of this domain or application of an antisense fragment to this conserved region efficiently canceled out the deleterious actions of ZFAS1. ZFAS1 had no significant effects on other Ca²⁺-handling regulatory proteins.

CONCLUSIONS

ZFAS1 is an endogenous SERCA2a inhibitor, acting by binding to SERCA2a protein to limit its intracellular level and inhibit its activity, and a contributor to the impairment of cardiac contractile function in MI. Therefore, anti-ZFAS1 might be considered as a new therapeutic strategy for preserving SERCA2a activity and cardiac function under pathological conditions of the heart.

Effect of lysophosphatidylglycerol on intracellular free Ca2+ concentration in A10 vascular smooth muscle cells

Although plasma levels of lysophosphatidylglycerol (LPG) are increased in hypertension, its role in the pathogenesis of vascular defects is not clear. In view of the importance of Ca²⁺ overload in causing vascular smooth muscle (VSM) dysfunction, the action of LPG on [Ca²⁺]_i in cultured A10 VSM cell line was examined by using Fura 2-AM acetoxymethyl ester technique. LPG was found to induce a concentration-dependent increase in [Ca²⁺]_i in VSM cells. This change was dependent both on the extracellular and intracellular Ca²⁺ sources, as it was reduced by 30% by EGTA, an extracellular Ca²⁺ chelator, and 70% by thapsigargin, a sarcoplasmic reticulum (SR) Ca²⁺-pump inhibitor. However the increase in [Ca²⁺]_i due to LPG was not altered by caffeine or ryanodine, which affect Ca²⁺-release through the ryanodine receptors in the SR. On the other hand, LPG-induced change in [Ca²⁺]_i was suppressed by 2-nitro-4-carboxyphenyl N,N-diphenylcarbamate, a phospholipase C (PLC) inhibitor, as well as by xestospongin and 2-aminoethoxydiphenyl borate, two inositol trisphosphate (IP3) receptor inhibitors in the SR. These observations support the view that LPG-induced increase in [Ca²⁺]_i in VSM cells is mainly a result of Ca²⁺ release from Ca²⁺ pool in the SR through PLC/IP3-sensitive signal transduction mechanism. Furthermore, it is suggested that the elevated level of LPG may induce intracellular Ca²⁺ overload and thus play a critical role in the development of vascular abnormalities.

Importance of Altered Levels of SERCA, IP3R, and RyR in Vascular Smooth Muscle Cell

Calcium cycling between the sarcoplasmic reticulum (SR) and the cytosol via the sarco-/endoplasmic reticulum Ca-ATPase (SERCA) pump, inositol-1,4,5-triphosphate receptor (IP₃R), and Ryanodine receptor (RyR), plays a major role in agonist-induced intracellular calcium ([Ca²⁺]_cyt) dynamics in vascular smooth muscle cells (VSMC). Levels of these calcium handling proteins in SR get altered under disease conditions. We have developed a mathematical model to understand the significance of altered levels of SERCA, IP₃R, and RyR on the intracellular calcium dynamics of VSMC and to understand how variation in protein levels that arise due to diabetes contribute to different VSMC behavior and thus vascular disease. SR is modeled as a single continuous entity with homogeneous intra-SR calcium. Model results show that agonist-induced intracellular calcium dynamics can be modified by changing the levels of SERCA, IP₃R, and/or RyR. Lowering SERCA level will enable intracellular calcium oscillations at low agonist concentrations whereas lowered levels of IP₃R and RyR need higher agonist concentration for intracellular calcium oscillations. This research suggests that reduced SERCA level is the main factor responsible for the reduced intracellular calcium transients and contractility in VSMCs.

Activation of M3 cholinoceptors attenuates vascular injury after ischaemia/reperfusion by inhibiting the Ca2+/calmodulin-dependent protein kinase II pathway

BACKGROUND AND PURPOSE

The activation of M3 cholinoceptors (M3 receptors) by choline reduces cardiovascular risk, but it is unclear whether these receptors can regulate ischaemia/reperfusion (I/R)-induced vascular injury. Thus, the primary goal of the present study was to explore the effects of choline on the function of mesenteric arteries following I/R, with a major focus on Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) regulation.

EXPERIMENTAL APPROACH

Rats were given choline (10 mg · kg(-1), i.v.) and then the superior mesenteric artery was occluded for 60 min (ischaemia), followed by 90 min of reperfusion. The M3 receptor antagonist, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), was injected (0.12 μg · kg(-1), i.v.) 5 min prior to choline treatment. Vascular function was examined in rings of mesenteric arteries isolated after the reperfusion procedure. Vascular superoxide anion production, CaMKII and the levels of Ca(2+)-cycling proteins were also assessed.

KEY RESULTS

Choline treatment attenuated I/R-induced vascular dysfunction, blocked elevations in the levels of reactive oxygen species (ROS) and decreased the up-regulated expression of oxidised CaMKII and phosphorylated CaMKII. In addition, choline reversed the abnormal expression of Ca(2+)-cycling proteins, including Na(+)Ca(2+) exchanger, inositol 1,4,5-trisphosphate receptor, sarcoplasmic reticulum Ca(2+)-ATPase and phospholamban. All of these cholinergic effects of choline were abolished by 4-DAMP.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that inhibition of the ROS-mediated CaMKII pathway and modulation of Ca(2+)-cycling proteins may be novel mechanisms underlying choline-induced vascular protection. These results represent a significant addition to the understanding of the pharmacological roles of M3 receptors in the vasculature, providing a new therapeutic strategy for I/R-induced vascular injury.

Effect of adenovirus‑mediated uPA gene transduction on the fibrinolytic activity of human umbilical vein endothelial cells

The present study aimed to investigate the effect of adenovirus‑mediated urokinase‑type plasminogen activator (uPA) transduction on uPA expression and fibrinolytic activity in human umbilical vein endothelial cells (HUVECs). Recombinant adenovirus vectors containing the human uPA gene were constructed and transduced into HUVECs. The expression and fibrinolytic activity of uPA was then assessed in HUVECs using western blot analysis, ELISA and colorimetric assay. The experiments were performed in three groups: The ad/uPa (n=3), ad/neg control (n=3) and blank control (n=3) groups. Western blot analysis revealed that uPA protein expression in the HUVECs in the ad/uPa group was significantly increased compared with those in the ad/neg control or blank groups (P<0.01). The uPA protein levels in the supernatant of the three groups were 379.40±2.46, 240.01±1.16 and 256.10±3.04 ng/l, respectively, showing that the uPA protein levels were significantly higher in the supernatant in the ad/uPa group compared with those in the ad/neg control or blank groups. uPA activity was determined using a colorimetric method and was found to be 40238.49±5755 IU/mg in the HUVECs in the ad/uPa group, which was significantly higher than that in the HUVECs in the ad/neg control (6180.03±942.38 IU/mg) or blank groups (3346.06±928.81 IU/mg) (both P<0.01). These findings suggested that transduction of the uPA gene increased uPA protein expression and fibrinolytic activity in HUVECs.

Expression of sarco (endo) plasmic reticulum calcium ATPase (SERCA) system in normal mouse cardiovascular tissues, heart failure and atherosclerosis

The sarco(endo)plasmic reticulum Ca(2+)ATPases (SERCA) system, a key regulator of calcium cycling and signaling, is composed of several isoforms. We aimed to characterize the expression of SERCA isoforms in mouse cardiovascular tissues and their modulation in cardiovascular pathologies (heart failure and/or atherosclerosis). Five isoforms (SERCA2a, 2b, 3a, 3b and 3c) were detected in the mouse heart and thoracic aorta. Absolute mRNA quantification revealed SERCA2a as the dominant isoform in the heart (~99%). Both SERCA2 isoforms co-localized in cardiomyocytes (CM) longitudinal sarcoplasmic reticulum (SR), SERCA3b was located at the junctional SR. In the aorta, SERCA2a accounted for ~91% of total SERCA and SERCA2b for ~5%. Among SERCA3, SERCA3b was the most expressed (~3.3%), mainly found in vascular smooth muscle cells (VSMC), along with SERCA2a and 2b. In failing CM, SERCA2a was down-regulated by 2-fold and re-localized from longitudinal to junctional SR. A strong down-regulation of SERCA2a was also observed in atherosclerotic vessels containing mainly synthetic VSMCs. The proportion of both SERCA2b and SERCA3b increased to 9.5% and 8.3%, respectively.

IN CONCLUSION

1) SERCA2a is the major isoform in both cardiac and vascular myocytes; 2) the expression of SERCA2a mRNA is ~30 fold higher in the heart compared to vascular tissues; and 3) nearly half the amount of SERCA2a mRNA is measured in both failing cardiomyocytes and synthetic VSMCs compared to healthy tissues, with a relocation of SERCA2a in failing cardiomyocytes. Thus, SERCA2a is the principal regulator of excitation-contraction coupling in both CMs and contractile VSMCs.

Resveratrol protects vascular smooth muscle cells against high glucose-induced oxidative stress and cell proliferation in vitro

Background

Resveratrol exhibits beneficial effects against numerous degenerative diseases at different stages of pathogenesis. This study investigated potential mechanisms and resveratrol effects on high glucose (HG)-induced oxidative stress (30 mM d-glucose, 30 min) and cell proliferation (30 mM d-glucose, 24 h) in vascular smooth muscle cells (VSMCs).

Material/Methods

Intracellular reactive oxygen species (ROS) generation was detected by 2′,7′-dichlorofluorescein diacetate (DCFH-DA). Total antioxidant capacity (TAC), malonyldialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) were measured to evaluate oxidative stress. VSMC proliferation was measured by CCK-8 assays and through propidium iodide-based cell cycle analysis. Expression of NAD(P)H oxidase, proliferation proteins, and cell signalling were assessed by immunoblot analysis.

Results

Co-treatment of primary cultures of VSMCs with 1–100 μM resveratrol decreased HG-induced ROS overproduction (P<0.05). Resveratrol also abolished HG-induced phosphorylation of oxidase subunit p47 phox and reduced HG-induced cyclin D1, cyclin E, and PCNA expression in a concentration-dependent manner. Furthermore, resveratrol (10 μM) attenuated HG-induced phosphorylation of Akt, p38 mitogen-activated protein kinase (MAPK), ERK 1/2, and JNK1/2 without affecting total levels. HG stimulation enhanced downstream IκB-α phosphorylation and NF-κB activity, and resveratrol repressed these effects.

Conclusions

Resveratrol inhibits HG-induced oxidative stress and VSMC proliferation by suppressing ROS generation, NADPH oxidase, Akt phosphorylation, p38 MAPK/JNK/ERK phosphorylation, and IκB-α and NF-κB activities.