Reduced expression of PMCA1 is associated with increased blood pressure with age which is preceded by remodelling of resistance arteries

A role for plasma membrane Ca2+ ATPases in regulation of cellular Ca2+ homeostasis by sphingosine kinase-1

Sphingosine-1-phosphate (S1P) is a ubiquitous lipid mediator, acting via specific G-protein-coupled receptors (GPCR) and intracellularly. Previous work has shown that deletion of S1P lyase caused a chronic elevation of cytosolic [Ca2+]i and enhanced Ca2+ storage in mouse embryonic fibroblasts. Here, we studied the role of sphingosine kinase (SphK)-1 in Ca2+ signaling, using two independently generated EA.hy926 cell lines with stable knockdown of SphK1 (SphK1-KD1/2). Resting [Ca2+]i and thapsigargin-induced [Ca2+]i increases were reduced in both SphK1-KD1 and -KD2 cells. Agonist-induced [Ca2+]i increases, measured in SphK1-KD1, were blunted. In the absence of extracellular Ca2+, thapsigargin-induced [Ca2+]i increases declined rapidly, indicating enhanced removal of Ca2+ from the cytosol. In agreement, plasma membrane Ca2+ ATPase (PMCA)-1 and -4 and their auxiliary subunit, basigin, were strongly upregulated. Activation of S1P-GPCR by specific agonists or extracellular S1P did not rescue the effects of SphK1 knockdown, indicating that S1P-GPCR were not involved. Lipid measurements indicated that not only S1P but also dihydro-sphingosine, ceramides, and lactosylceramides were markedly depleted in SphK1-KD2 cells. SphK2 and S1P lyase were upregulated, suggesting enhanced flux via the sphingolipid degradation pathway. Finally, histone acetylation was enhanced in SphK1-KD2 cells, and the histone deacetylase inhibitor, vorinostat, induced upregulation of PMCA1 and basigin on mRNA and protein levels in EA.hy926 cells. These data show for the first time a transcriptional regulation of PMCA1 and basigin by S1P metabolism. It is concluded that SphK1 knockdown in EA.hy926 cells caused long-term alterations in cellular Ca2+ homeostasis by upregulating PMCA via increased histone acetylation.

Enhancement of cardiac angiogenesis in a myocardial infarction rat model using selenium alone and in combination with PTXF: the role of Akt/HIF-1α signaling pathway

Ischemic heart diseases such as myocardial infarction (MI) are a global health problem and a leading cause of mortality worldwide. Angiogenesis is an important approach for myocardial healing following ischemia. Thus, this study aimed to explore the potential cardiac angiogenic effects of selenium (Se), alone and in combination with the tumor necrosis factor-alpha inhibitor, pentoxifylline (PTXF), via Akt/HIF-1α signaling. MI was induced in rats using two subcutaneous doses of isoprenaline (ISP) at a 24-h interval (150 mg/kg). One week later, rats were orally given Se (150 µg/kg/day), PTXF (50 mg/kg/day), or Se/PTXF combination. ISP-induced myocardial damage was evident by increased HW/TL ratios, ST segment elevation, and increased serum levels of CK-MB, LDH, and troponin-I. ISP increased the cardiac levels of the lipid peroxidation marker MDA; the pro-inflammatory cytokines IL-6, IL-1β, and TNF-α; and the pro-apoptotic protein Bax and caspase-3. In contrast, the cardiac levels of the antioxidant markers GSH and SOD and the anti-apoptotic marker Bcl-2 were reduced. Furthermore, ISP markedly increased the cardiac levels of p-Akt and HIF-1α proteins and the cardiac gene expression of ANGPT-1, VEGF, and FGF-2. Treatment with Se both alone and in combination with PTXF ameliorated the ISP-induced myocardial damage and further increased cardiac angiogenesis via Akt/HIF-1α signaling. Se/PTXF combined therapy was more beneficial than individual treatments. Our study revealed for the first time the cardiac angiogenic effects of Se both alone and in combination with PTXF in myocardial infarction, suggesting that both may be promising candidates for clinical studies.

Modifying Dietary Sodium and Potassium Intake: An End to the 'Salt Wars'?

Excessive salt intake raises blood pressure, but the implications of this observation for human health have remained contentious. It has also been recognized for many years that potassium intake may mitigate the effects of salt intake on blood pressure and possibly on outcomes such as stroke. Recent large randomized intervention trials have provided strong support for the benefits of replacing salt (NaCl) with salt substitute (75% NaCl, 25% KCl) on hard outcomes, including stroke. During the same period of time, major advances have been made in understanding how the body senses and tastes salt, and how these sensations drive intake. Additionally, new insights into the complex interactions between systems that control sodium and potassium excretion by the kidneys, and the brain have highlighted the existence of a potassium switch in the kidney distal nephron. This switch seems to contribute importantly to the blood pressure-lowering effects of potassium intake. In recognition of these evolving data, the United States Food and Drug Administration is moving to permit potassium-containing salt substitutes in food manufacturing. Given that previous attempts to reduce salt consumption have not been successful, this new approach has a chance of improving health and ending the 'Salt Wars'.

Vanillin and pentoxifylline ameliorate isoproterenol-induced myocardial injury in rats via the Akt/HIF-1α/VEGF signaling pathway

Myocardial infarction (MI) is a major health problem associated with high morbidity and mortality. Recently, angiogenesis has emerged as a novel therapeutic approach against ischemic diseases including MI. Therefore, we aimed to investigate the potential angiogenic effects of vanillin (Van) both alone and in combination with pentoxifylline (PTX), and to examine the molecular mechanisms through which Van and PTX may ameliorate cardiac injury induced in rats including their effects on oxidative stress, inflammation and apoptosis which play a key role in MI pathogenesis. MI was induced in rats using isoproterenol (ISO) (150 mg kg^-1, SC, twice at a 24 h interval). Then, rats were treated orally with Van (150 mg kg^-1 day^-1), PTX (50 mg kg^-1 day^-1) or Van + PTX combination. ISO-induced cardiac injury was characterized by cardiac hypertrophy, ST-segment elevation and elevated serum levels of troponin-I, creatine kinase-MB and lactate dehydrogenase. Cardiac levels of the antioxidant markers GSH and SOD and the antiapoptotic protein Bcl-2 were decreased. On the other hand, cardiac levels of the oxidative stress marker malonaldehyde, the inflammatory cytokines TNF-α, IL-6 and IL-1β, the proapoptotic protein Bax, and caspase-3 were increased. Moreover, the cardiac levels of p-Akt and HIF-1α and the mRNA expression levels of the angiogenic genes VEGF, FGF-2 and ANGPT-1 were increased. Treatment with either Van or PTX ameliorated ISO-induced changes and further upregulated Akt/HIF-1α/VEGF signaling. Furthermore, Van + PTX combination was more effective than monotherapy. These findings suggest a novel therapeutic potential of Van and PTX in ameliorating MI through enhancing cardiac angiogenesis and modulating oxidative stress, inflammation and apoptosis.

Ca2+ Homeostasis by Plasma Membrane Ca2+ ATPase (PMCA) 1 Is Essential for the Development of DP Thymocytes

The strength of Ca²⁺ signaling is a hallmark of T cell activation, yet the role of Ca²⁺ homeostasis in developing T cells before expressing a mature T cell receptor is poorly understood. We aimed to unveil specific functions of the two plasma membrane Ca²⁺ ATPases expressed in T cells, PMCA1 and PMCA4. On a transcriptional and protein level we found that PMCA4 was expressed at low levels in CD4^-CD8^- double negative (DN) thymocytes and was even downregulated in subsequent stages while PMCA1 was present throughout development and upregulated in CD4⁺CD8⁺ double positive (DP) thymocytes. Mice with a targeted deletion of Pmca1 in DN3 thymocytes had an almost complete block of DP thymocyte development with an accumulation of DN4 thymocytes but severely reduced numbers of CD8⁺ immature single positive (ISP) thymocytes. The DN4 thymocytes of these mice showed strongly elevated basal cytosolic Ca²⁺ levels and a pre-mature CD5 expression, but in contrast to the DP thymocytes they were only mildly prone to apoptosis. Surprisingly, mice with a germline deletion of Pmca4 did not show any signs of altered progression through the developmental thymocyte stages, nor altered Ca²⁺ homeostasis throughout this process. PMCA1 is, therefore, non-redundant in keeping cellular Ca²⁺ levels low in the early thymocyte development required for the DN to DP transition.

PMCA1 depletion in mouse eggs amplifies calcium signaling and impacts offspring growth†

Egg activation in mammals is triggered by oscillations in egg intracellular calcium (Ca2+) level. Ca2+ oscillation patterns can be modified in vitro by changing the ionic composition of culture media or in vivo by conditions affecting mitochondrial function, such as obesity and inflammation. In mice, disruption of Ca2+ oscillations in vitro impacts embryo development and offspring growth. Here we tested the hypothesis that, even without in vitro manipulation, abnormal Ca2+ signaling following fertilization impacts offspring growth. Plasma membrane Ca2+ ATPases (PMCA) extrude cytosolic Ca2+ to restore Ca2+ homeostasis. To disrupt Ca2+ signaling in vivo, we conditionally deleted PMCA1 (cKO) in oocytes. As anticipated, in vitro fertilized cKO eggs had increased Ca2+ exposure relative to controls. To assess the impact on offspring growth, cKO females were mated to wild type males to generate pups that had high Ca2+ exposure at fertilization. Because these offspring would be heterozygous, we also tested the impact of global PMCA1 heterozygosity on offspring growth. Control heterozygous pups that had normal Ca2+ at fertilization were generated by mating wild type females to heterozygous males; these control offspring weighed significantly less than their wild type siblings. However, heterozygous offspring from cKO eggs (and high Ca2+ exposure) were larger than heterozygous controls at 12 week-of-age and males had altered body composition. Our results show that global PMCA1 haploinsufficiency impacts growth and support that abnormal Ca2+ signaling after fertilization in vivo has a long-term impact on offspring weight. These findings are relevant for environmental and medical conditions affecting Ca2+ handling and for design of culture conditions and procedures for domestic animal and human assisted reproduction.

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.

Vascular calcium signalling and ageing

Changes in cellular Ca²⁺ levels have major influences on vascular function and blood pressure regulation. Vascular smooth muscle cells (SMCs) and endothelial cells (ECs) orchestrate vascular activity in distinct ways, often involving highly specific fluctuations in Ca²⁺ signalling. Ageing is a major risk factor for cardiovascular diseases, but the impact of ageing per se on vascular Ca²⁺ signalling has received insufficient attention. We reviewed the literature for age-related changes in Ca²⁺ signalling in relation to vascular structure and function. Vascular tone dysregulation in several vascular beds has been linked to abnormal expression or activity of SMC voltage-gated Ca²⁺ channels, Ca²⁺ -activated K⁺ channels or TRPC6 channels. Some of these effects were linked to altered caveolae density, microRNA expression or 20-HETE abundance. Intracellular store Ca²⁺ handling was suppressed in ageing mainly via reduced expression of intracellular Ca²⁺ release channels, and Ca²⁺ reuptake or efflux pumps. An increase in mitochondrial Ca²⁺ uptake, leading to oxidative stress, could also play a role in SMC hypercontractility and structural remodelling in ageing. In ECs, ageing entailed diverse effects on spontaneous and evoked Ca²⁺ transients, as well as structural changes at the EC-SMC interface. The concerted effects of altered Ca²⁺ signalling on myogenic tone, endothelium-dependent vasodilatation, and vascular structure are likely to contribute to blood pressure dysregulation and blood flow distribution deficits in critical organs. With the increase in the world's ageing population, future studies should be directed at solving specific ageing-induced Ca²⁺ signalling deficits to combat the imminent accelerated vascular ageing and increased risk of cardiovascular diseases.

Resveratrol Ameliorates Aortic Calcification in Ovariectomized Rats via SIRT1 Signaling

Postmenopausal women are at an increased risk of vascular calcification which is defined as the pathological deposition of minerals in the vasculature, and is strongly linked with increased cardiovascular disease risk. Since estrogen-replacement therapy is associated with increased cancer risk, there is a strong need for safer therapeutic approaches. In this study we aimed to investigate the protective and therapeutic effects of the phytoestrogen resveratrol against vascular calcification in ovariectomized rats, a preclinical model of postmenopause. Furthermore, we aimed to compare the effects of resveratrol to those of estrogen and to explore the mechanisms underpinning those effects. Treatment with resveratrol or estrogen ameliorated aortic calcification in ovariectomized rats, as shown by reduced calcium deposition in the arterial wall. Mechanistically, the effects of resveratrol and estrogen were mediated via the activation of SIRT1 signaling. SIRT1 protein expression was downregulated in the aortas of ovariectomized rats, and upregulated in rats treated with resveratrol or estrogen. Moreover, resveratrol and estrogen reduced the levels of the osteogenic markers: runt-related transcription factor 2 (RUNX2), osteocalcin and alkaline phosphatase (ALP) which have been shown to play a role during vascular calcification. Additionally, the senescence markers (p53, p16 and p21) which were also reported to play a role in the pathogenesis of vascular calcification, were reduced upon treatment with resveratrol and estrogen. In conclusion, the phytoestrogen resveratrol may be a safer alternative to estrogen, as a therapeutic approach against the progression of vascular calcification during postmenopause.

Targeting Ca2 + Handling Proteins for the Treatment of Heart Failure and Arrhythmias

Diseases of the heart, such as heart failure and cardiac arrhythmias, are a growing socio-economic burden. Calcium (Ca²⁺) dysregulation is key hallmark of the failing myocardium and has long been touted as a potential therapeutic target in the treatment of a variety of cardiovascular diseases (CVD). In the heart, Ca²⁺ is essential for maintaining normal cardiac function through the generation of the cardiac action potential and its involvement in excitation contraction coupling. As such, the proteins which regulate Ca²⁺ cycling and signaling play a vital role in maintaining Ca²⁺ homeostasis. Changes to the expression levels and function of Ca²⁺-channels, pumps and associated intracellular handling proteins contribute to altered Ca²⁺ homeostasis in CVD. The remodeling of Ca²⁺-handling proteins therefore results in impaired Ca²⁺ cycling, Ca²⁺ leak from the sarcoplasmic reticulum and reduced Ca²⁺ clearance, all of which contributes to increased intracellular Ca²⁺. Currently, approved treatments for targeting Ca²⁺ handling dysfunction in CVD are focused on Ca²⁺ channel blockers. However, whilst Ca²⁺ channel blockers have been successful in the treatment of some arrhythmic disorders, they are not universally prescribed to heart failure patients owing to their ability to depress cardiac function. Despite the progress in CVD treatments, there remains a clear need for novel therapeutic approaches which are able to reverse pathophysiology associated with heart failure and arrhythmias. Given that heart failure and cardiac arrhythmias are closely associated with altered Ca²⁺ homeostasis, this review will address the molecular changes to proteins associated with both Ca²⁺-handling and -signaling; their potential as novel therapeutic targets will be discussed in the context of pre-clinical and, where available, clinical data.

5-Hydroxy-l-tryptophan Promotes the Milk Calcium Level via the miR-99a-3p/ATP2B1 Axis in Goat Mammary Epithelial Cells

5-Hydroxy-l-tryptophan (5-HTP) is the primary product that converts l-tryptophan into 5-hydroxytryptamine by a rate-limiting enzyme. Our previous study found that 5-HTP could promote the intracellular calcium level in goat mammary epithelial cells (GMECs). Herein, first, dairy goats were injected with 5-HTP or saline daily from 7 days before delivery, and the calcium level in colostrum of 5-HTP-injected goats was significantly higher than that of saline-injected goats. Moreover, miR-99a-3p expression was significantly increased after 5-HTP treatment from transcriptome sequencing analysis and quantitative real-time polymerase chain reaction. In addition, it was found that ATP2B1 is one of the target genes of miR-99a-3p predicted by bioinformatic methods, which plays a crucial role in the maintenance of intracellular calcium homeostasis of mammary epithelial cells. Next, we confirmed that miR-99a-3p could increase the intracellular calcium level via decreasing ATP2B1 in GMECs. Taken together, we draw the conclusion that 5-HTP promotes the calcium level in colostrum possibly by increasing intracellular calcium of mammary epithelial cells induced by the miR-99a-3p/ATP2B1 axis.

Genes of the cGMP-PKG-Ca2+ signaling pathway are alternatively spliced in cardiomyopathy: Role of RBFOX2

Aberrations in the cGMP-PKG-Ca2+ pathway are implicated in cardiovascular complications of diverse etiologies, though involved molecular mechanisms are not understood. We performed RNA-Seq analysis to profile global changes in gene expression and exon splicing in Chagas disease (ChD) murine myocardium. Ingenuity-Pathway-Analysis of transcriptome dataset identified 26 differentially expressed genes associated with increased mobilization and cellular levels of Ca2+ in ChD hearts. Mixture-of-isoforms and Enrichr KEGG pathway analyses of the RNA-Seq datasets from ChD (this study) and diabetic (previous study) murine hearts identified alternative splicing (AS) in eleven genes (Arhgef10, Atp2b1, Atp2a3, Cacna1c, Itpr1, Mef2a, Mef2d, Pde2a, Plcb1, Plcb4, and Ppp1r12a) of the cGMP-PKG-Ca2+ pathway in diseased hearts. AS of these genes was validated by an exon exclusion-inclusion assay. Further, Arhgef10, Atp2b1, Mef2a, Mef2d, Plcb1, and Ppp1r12a genes consisted RBFOX2 (RNA-binding protein) binding-site clusters, determined by analyzing the RBFOX2 CLIP-Seq dataset. H9c2 rat heart cells transfected with Rbfox2 (vs. scrambled) siRNA confirmed that expression of Rbfox2 is essential for proper exon splicing of genes of the cGMP-PKG-Ca2+ pathway. We conclude that changes in gene expression may influence the Ca2+ mobilization pathway in ChD, and AS impacts the genes involved in cGMP/PKG/Ca2+ signaling pathway in ChD and diabetes. Our findings suggest that ChD patients with diabetes may be at increased risk of cardiomyopathy and heart failure and provide novel ways to restore cGMP-PKG regulated signaling networks via correcting splicing patterns of key factors using oligonucleotide-based therapies for the treatment of cardiovascular complications.