Intracellular Calcium Homeostasis Research Articles

Vasorin plays a critical role in vascular smooth muscle cells and arterial functions.

Within the cardiovascular system, the protein vasorin (Vasn) is predominantly expressed by vascular smooth muscle cells (VSMCs) in the coronary arteries and the aorta. Vasn knockout (Vasn-/- ) mice die within 3 weeks of birth. In the present study, we investigated the role of vascular Vasn expression on vascular function. We used inducible Vasn knockout mice (VasnCRE-ERT KO and VasnSMMHC-CRE-ERT2 KO , in which respectively all cells or SMCs only are targeted) to analyze the consequences of total or selective Vasn loss on vascular function. Furthermore, in vivo effects were investigated in vitro using human VSMCs. The death of VasnCRE-ERT KO mice 21 days after tamoxifen injection was concomitant with decreases in blood pressure, angiotensin II levels, and vessel contractibility to phenylephrine. The VasnSMMHC-CRE-ERT2 KO mice displayed concomitant changes in vessel contractibility in response to phenylephrine and angiotensin II levels. In vitro, VASN deficiency was associated with a shift toward the SMC contractile phenotype, an increase in basal intracellular Ca2+ levels, and a decrease in the SMCs' ability to generate a calcium signal in response to carbachol or phenylephrine. Additionally, impaired endothelium-dependent relaxation (due to changes in nitric oxide signaling) was observed in all Vasn knockout mice models. Our present findings highlight the role played by Vasn SMC expression in the maintenance of vascular functions. The mechanistic experiments suggested that these effects are mediated by SMC phenotype switching and changes in intracellular calcium homeostasis, angiotensin II levels, and NO signaling.

Lipid-coated albumin-paclitaxel nanoparticles loaded with sorcin-siRNA reverse cancer chemoresistance via restoring intracellular calcium ion homeostasis

Chemoresistance is often a cause of the failure of chemotherapy in cancer treatment. Sorcin (SRI) is a soluble resistance-related calcium-binding protein involved in chemoresistant processes and is overexpressed in many chemoresistant cancer cells, including paclitaxel (PTX)-resistant ovarian cancer. Increased SRI can reduce the concentration of calcium ions in the cytosol and mitochondria and the decrease of calcium ion concentration prevents the occurrence of apoptosis. Here we examined the SRI expression in multiple cancers using a human TissueArray and found that SRI expression was significantly higher in malignant tumor tissues. Furthermore, SRI was overexpressed, while intracellular calcium concentration was decreased, in chemoresistant cancer cells. To restore intracellular calcium homeostasis and overcome chemoresistance, we developed lipid-coated albumin-PTX nanoparticles loaded with SRI-siRNA (LANP-PTX-siSRI) for PTX and SRI-siRNA co-delivery. LANP-PTX-siSRI had dual-target roles in the regulation of SRI and the delivery of PTX into chemoresistant cells. The LANP-PTX-siSRI inhibited the expression of SRI and enhanced intracellular calcium, leading to the induction of apoptosis and the inhibition of the growth of PTX-resistant cancer cells in vitro and in vivo. In addition, the mechanism study revealed that the overexpression of SRI was associated with an impaired TGF-β signaling pathway. The administration of TGF-β1 inhibited two calcium-binding proteins SRI and S100A14. In conclusion, our data unveil that restoring intracellular calcium ion homeostasis via reducing SRI expression can reverse chemoresistance. Thus, the fabricated LANP-PTX-siSRI has a potentially therapeutical application.

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-β1), 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-β1 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.

Identification of key genes and infiltrating immune cells among acetaminophen-induced acute liver failure and HBV-associated acute liver failure

BackgroundAcute liver failure (ALF) is a life-threatening complication that is relatively uncommon. ALF causes severe hepatocyte damage and necrosis, which can lead to liver dysfunction and even multi-organ failure. A growing body of evidence suggests that immune cell infiltration and some abnormally expressed genes are associated with ALF development. However, in ALF, they have yet to be thoroughly investigated.MethodsThe Gene Expression Omnibus (GEO) database was used to obtain microarray datasets such as GSE74000, GSE120652, GSE38941, and GSE14668, which were then examined via GEO2R to determine differentially expressed genes (DEGs) associated with ALF. Metascape was employed to annotate the underlined genes using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. The mechanism of IGF1 in 2 different kinds of ALF including acetaminophen-induced ALF and hepatitis B virus (HBV)-induced ALF was studied using gene set enrichment analysis (GSEA). Next, immune cell infiltration was investigated and differentiated in ALF using CIBERSORT.ResultsSix genes (HAO2, IGF1, PLA2G7, SC5D, GNE, SLC1A1) were found to be abnormally expressed in the 2 distinct types of ALF i.e., acetaminophen-induced ALF and HBV-induced ALF. IGF1 was identified as a hub gene in ALF and was found to be associated with several developmental cascades including immune responses, inflammatory responses, and intracellular calcium homeostasis. Additionally, the number of CD4 naive T cells, CD8 T cells, and follicular helper T cells was increased in acetaminophen-induced ALF, whereas the number of activated NK cells, resting NK cells, and plasma cells was increased in HBV-induced ALF.ConclusionsThe present study determined a potential molecular target, namely IGF1, in acetaminophen-induced ALF and HBV-induced ALF, which may provide novel insights into the pathophysiology and management of ALF. Concurrently, the putative immunological pathways have been found.

Primitive Phospholamban- and Sarcolipin-like Peptides Inhibit the Sarcoplasmic Reticulum Calcium Pump SERCA.

Intracellular calcium signaling is essential for all kingdoms of life. An important part of this process is the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA), which maintains the low cytosolic calcium levels required for intracellular calcium homeostasis. In higher organisms, SERCA is regulated by a series of tissue-specific transmembrane subunits such as phospholamban in cardiac muscles and sarcolipin in skeletal muscles. These regulatory axes are so important for muscle contractility that SERCA, phospholamban, and sarcolipin are practically invariant across mammalian species. With the recent discovery of the arthropod sarcolambans, the family of calcium pump regulatory subunits appears to span more than 550 million years of evolutionary divergence from arthropods to humans. This evolutionary divergence is reflected in the peptide sequences, which vary enormously from one another and only vaguely resemble phospholamban and sarcolipin. The discovery of the sarcolambans allowed us to address two questions. How much sequence variation is tolerated in the regulation of mammalian SERCA activity by the transmembrane peptides? Do divergent peptide sequences mimic phospholamban or sarcolipin in their regulatory activities despite limited sequence similarity? We expressed and purified recombinant sarcolamban peptides from three different arthropods. The peptides were coreconstituted into proteoliposomes with mammalian SERCA1a and the effect of each peptide on the apparent calcium affinity and maximal activity of SERCA was measured. All three peptides were superinhibitors of SERCA, exhibiting either phospholamban-like or sarcolipin-like characteristics. Molecular modeling, protein-protein docking, and molecular dynamics simulations revealed novel features of the divergent peptides and their SERCA regulatory properties.

Cellular context determines primary characteristics of human TRPC5 as a cold-activated channel.

The human transient receptor potential canonical 5 (TRPC5) is a calcium-permeable, nonselective cation channel expressed in the central and peripheral nervous system and also in other tissues such as the kidney, synovium, and odontoblasts. TRPC5 has been recently confirmed to play a key role in spontaneous, inflammatory mechanical, and cold pain. Although TRPC5 activation is known to be cold sensitive, it is unclear whether this property is intrinsic to the channel protein and whether or to what extent it may be determined by the cellular environment. In this study, we explored the cold sensitivity of human TRPC5 at the single-channel level using transiently transfected HEK293T cells. Upon decreasing the temperature, the channel demonstrated prolonged mean open dwell times and a robust increase in the open probability (Po ), whereas the amplitude of unitary currents decreased ~1.5-fold per 10°C of temperature difference. In the absence of any agonists, the temperature dependence of Po was sigmoidal, with a steep slope within the temperature range of 16°C-11°C, and exhibited saturation below 8-5°C. Thermodynamic analysis revealed significant changes in enthalpy and entropy, suggesting that substantial conformational changes accompany cold-induced gating. The mutant channel T970A, in which the regulation downstream of G-protein coupled receptor signaling was abrogated, exhibited higher basal activity at room temperature and a less steep temperature response profile, with an apparent threshold below 22°C. An even more pronounced decrease in the activation threshold was observed in a mutant that disrupted the electrostatic interaction of TRPC5 with the endoplasmic reticulum calcium sensor stromal interaction molecule 1. Thus, TRPC5 exhibits features of an intrinsically cold-gated channel; its sensitivity to cold tightly depends on the phosphorylation status of the protein and intracellular calcium homeostasis.

Effect of zinc and copper ions on cadmium-induced toxicity in rat cultured cortical neurons

BackgroundCadmium is a highly toxic heavy metal that is capable of accumulating in the body and causing neurodegeneration. However, the effect of other trace elements on Cd2+ toxicity is currently poorly understood. The aim of this work was to study the effect of Zn2+ and Cu2+ ions on cadmium-induced death of neurons in the cerebral cortex. MethodsThe work was performed on rat cortical primary cultures. The MTT test was used to determine the cytotoxicity effects. Analysis of intracellular Ca2+ concentration was assessed by the Fluo-4 AM calcium indicator that exhibit an increase in fluorescence upon binding Ca2+. MitoSOX Red (mitochondrial superoxide indicator) was used to measuring mitochondrial ROS content in live cells. ResultsIn this article, we show that the administration of CdCl2 (0.005–0.02 mM) for 48 h induced an increase in dose-dependent death rate of cultured cortical neurons. Mature neurons were more sensitive to the damaging effects of Cd2+ than immature ones. ZnCl2 (0.01–0.03 mM) significantly protected neurons from this toxic effect. In contrast to ZnCl2, CuCl2 (0.01 mM) increased cadmium neurotoxicity. Using Fluo-4 AM, measurements of intracellular calcium ions demonstrated that 24 h-exposure to Cd2+ induced intensive increase in Fluo-4 fluorescence in neurons, which was significantly reduced by zinc ions. CuCl2 increased the cadmium-induced Fluo-4 and MitoSOX Red fluorescence in neurons. The chelator of intracellular Ca2+ BAPTA significantly decreased Cd2+-induced intensive increase in Fluo-4 fluorescence in cells. ConclusionThe data obtained by us indicate that Zn2+ and Cu2+ can affect the neurotoxicity of cadmium in different directions: Zn2+ weaken the violation of intracellular calcium homeostasis caused by cadmium, preventing cell death, while Cu2+ potentiate the increase in the level of free intracellular calcium induced by cadmium and the development of mitochondrial dysfunction with an increase in the production of free radicals in differentiated cultured neurons of the cerebral cortex, which ultimately stimulates cytotoxicity.

Endoplasmic Reticulum Stress and the Unfolded Protein Response in Cerebral Ischemia/Reperfusion Injury.

Ischemic stroke is an acute cerebrovascular disease characterized by sudden interruption of blood flow in a certain part of the brain, leading to serious disability and death. At present, treatment methods for ischemic stroke are limited to thrombolysis or thrombus removal, but the treatment window is very narrow. However, recovery of cerebral blood circulation further causes cerebral ischemia/reperfusion injury (CIRI). The endoplasmic reticulum (ER) plays an important role in protein secretion, membrane protein folding, transportation, and maintenance of intracellular calcium homeostasis. Endoplasmic reticulum stress (ERS) plays a crucial role in cerebral ischemia pathophysiology. Mild ERS helps improve cell tolerance and restore cell homeostasis; however, excessive or long-term ERS causes apoptotic pathway activation. Specifically, the protein kinase R-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), and inositol-requiring enzyme 1 (IRE1) pathways are significantly activated following initiation of the unfolded protein response (UPR). CIRI-induced apoptosis leads to nerve cell death, which ultimately aggravates neurological deficits in patients. Therefore, it is necessary and important to comprehensively explore the mechanism of ERS in CIRI to identify methods for preserving brain cells and neuronal function after ischemia.

Abstract 315: Augmentation Of Protein O -glcnacylation By Impaired Intracellular Calcium Homeostasis Promoted Vascular Calcification

Vascular calcification is accelerated in patients with diabetes mellitus and increases risk of cardiovascular events and mortality. Wes have demonstrated elevated protein O -GlcNAcylation promotes vascular calcification in diabetes. Increased O -GlcNAcylation is linked to impaired calcium signaling, which is critical for the development of vascular calcification in both humans and animal models. The present studies determined the role of an important regulator for intracellular calcium homeostasis, the stromal interaction molecule 1 (STIM1), in regulating O -GlcNAcylation and vascular calcification. Deletion of STIM1 induced osteogenic differentiation and calcification of VSMC, which was associated with decreased expression of the SMC marker genes and increased expression of the key osteogenic transcription factor, Runx2. By generating a SMC-specific STIM1 ablation mouse model, we determined that STIM1 ablation induced vascular calcification in aortic rings cultured ex vivo and in diabetic mice injected with low-dose streptozotocin in vivo. The diabetic mide with SMC-specific STIM1 ablation also exhibited increased aortic Runx2 expression and aortic stiffness (pulse wave velocity). Mechanistically, we identified that STIM1 deficiency impaired calcium homeostasis in VSMC, increased activation of the Ca 2+ /calmodulin-dependent protein kinase II and elevation of protein O -GlcNAcylation. Increased O -GlcNAcylation by STIM1 deficiency was further demonstrated in aortic arteries from the SMC-specific STIM1 ablation mice. The essential role of O -GlcNAcylation in mediating STIM1 deficiency-induced VSMC calcification was determined using a specific inhibitor for the O -GlcNAc transferase (OGT), the enzyme adding O -GlcNAc onto proteins. Inhibition of OGT abolished STIM1 deficiency-induced elevation of O -GlcNAcylation and VSMC. In conclusion, our studies have demonstrated a causative effect of SMC-expressed STIM1 on vascular calcification and stiffness in diabetes. We have further identified a novel link connecting STIM1 deficiency-induced impairment of calcium homeostasis and elevation of protein O -GlcNAcylation in VSMC that promotes osteogenic differentiation and calcification of VSMC.

Rhynchophylline Regulates Calcium Homeostasis by Antagonizing Ryanodine Receptor 2 Phosphorylation to Improve Diabetic Cardiomyopathy.

Diabetic cardiomyopathy (DCM) is a serious complication of diabetes that can lead to heart failure and death, for which there is no effective treatment. Rhynchophylline (Rhy) is the main effective component of the Chinese herbal medicine Uncaria rhynchophylla, which mainly acts on the cardiovascular and nervous systems. However, its role in protecting against DCM remains unexplored. The present study sought to reveal the mechanism of Rhy in improving type 2 diabetes mellitus (T2DM) myocardial lesions from the perspective of regulating calcium homeostasis in cardiomyocytes. We prepared a mouse model of T2DM using a high-fat diet combined with low doses of streptozotocin. The T2DM mice were given 40 mg/kg of Rhy for 8 weeks. The results showed that Rhy can attenuate cardiac pathological changes, slow down the heart rate, decrease serum cardiac enzyme levels, reduce cardiomyocyte apoptosis, enhance cardiomyocyte contractility, and raise the calcium transient amplitude in T2DM mice. Further, Rhy downregulated the phosphorylation level of ryanodine receptor 2, upregulated the phosphorylation level of phospholamban, protected mitochondrial structure and function, and increased adenosine triphosphate levels in the cardiac tissue of T2DM mice. Our results demonstrated that Rhy may protect against myocardial damage in T2DM mice and promote cardiomyocyte contraction, and its mechanism of action seems to be related to the regulation of intracellular calcium homeostasis.

Dinitramine induces implantation failure by cell cycle arrest and mitochondrial dysfunction in porcine trophectoderm and luminal epithelial cells

The herbicide market is growing rapidly, as weed control is a significant challenge in agriculture. Many studies have reported the toxicity of herbicides to non-target organisms. Dinitramine is a dinitroaniline herbicide that is particularly toxic to aquatic organisms. However, little is known about the effects of dinitramine on the female reproductive system. Therefore, in the present study, we utilized porcine trophectoderm (pTr) cells and porcine endometrial luminal epithelial (pLE) cells to verify the reproductive toxicity of dinitramine. Dinitramine reduced the viability of both cell types, by triggering cell cycle arrest, especially at the sub-G1 phase, and increasing apoptosis, inhibiting DNA replication. Dinitramine disrupted intracellular calcium homeostasis and induced oxidative stress by producing reactive oxygen species, leading to the loss of mitochondrial membrane potential and alteration of mitochondrial respiration. Mitogen-activated protein kinase pathways were altered, and migration decreased in pTr and pLE cells after dinitramine treatment; the expression of pregnancy-related genes in these cells was decreased. Thus, dinitramine reduced the viability and migratory capacity of both cell types, and this could interrupt the early stages of pregnancy.

Roles of Nitric Oxide in Brain Ischemia and Reperfusion.

Brain ischemia and reperfusion (I/R) is one of the most severe clinical manifestations of ischemic stroke, placing a significant burden on both individuals and society. The only FDA-approved clinical treatment for ischemic stroke is tissue plasminogen activator (t-PA), which rapidly restores cerebral blood flow but can have severe side effects. The complex pathological process of brain I/R has been well-established in the past few years, including energy metabolism disorders, cellular acidosis, doubling of the synthesis or release of excitotoxic amino acids, intracellular calcium homeostasis, free radical production, and activation of apoptotic genes. Recently, accumulating evidence has shown that NO may be strongly related to brain I/R and involved in complex pathological processes. This review focuses on the role of endogenous NO in pathological processes in brain I/R, including neuronal cell death and blood brain barrier disruption, to explore how NO impacts specific signaling cascades and contributes to brain I/R injury. Moreover, NO can rapidly react with superoxide to produce peroxynitrite, which may also mediate brain I/R injury, which is discussed here. Finally, we reveal several therapeutic approaches strongly associated with NO and discuss their potential as a clinical treatment for ischemic stroke.

Biological Effects of Transforming Growth Factor Beta in Human Cholangiocytes.

Simple SummaryTransforming growth factor β (TGF-β) is involved in fibrosis, and contributes to the progressive pathology of cholangiopathies. However, little is known regarding the effects and signaling of TGF-β in cholangiocytes. Here, we assessed the effects of TGF-β on proliferation, cell migration and cell cycle after 24 and 48 h. Proteomic approach was used to highlight proteins involved in these biological processes. In cholangiocytes, TGF-β reduced the proliferation rate and induced cell cycle arrest in G0/G1 phase. Proteomic analysis showed a downregulation of proteins involved in Ca2+ homeostasis, including CaM kinase II subunit delta, caveolin-1, NipSnap1 and calumin. Accordingly, Gene Ontology indicated that the plasma membrane and endoplasmic reticulum are the cellular compartments most perturbed following TGF-β treatment. In conclusion, our study highlighted the connection between TGF-β and Ca2+ homeostasis in cholangiocytes, and for the first time, correlated calumin and NipSnap1 to TGF-β signaling.TGF-β is a cytokine implicated in multiple cellular responses, including cell cycle regulation, fibrogenesis, angiogenesis and immune modulation. In response to pro-inflammatory and chemotactic cytokines and growth factors, cholangiocytes prime biliary damage, characteristic of cholangiopathies and pathologies that affect biliary tree. The effects and signaling related to TGF-β in cholangiocyte remains poorly investigated. In this study, the cellular response of human cholangiocytes to TGF-β was examined. Wound-healing assay, proliferation assay and cell cycle analyses were used to monitor the changes in cholangiocyte behavior following 24 and 48 h of TGF-β stimulation. Moreover, proteomic approach was used to identify proteins modulated by TGF-β treatment. Our study highlighted a reduction in cholangiocyte proliferation and a cell cycle arrest in G0/G1 phase following TGF-β treatment. Moreover, proteomic analysis allowed the identification of four downregulated proteins (CaM kinase II subunit delta, caveolin-1, NipSnap1 and calumin) involved in Ca2+ homeostasis. Accordingly, Gene Ontology analysis highlighted that the plasma membrane and endoplasmic reticulum are the cellular compartments most affected by TGF-β. These results suggested that the effects of TGF-β in human cholangiocytes could be related to an imbalance of intracellular calcium homeostasis. In addition, for the first time, we correlated calumin and NipSnap1 to TGF-β signaling.

Beneficial Effects of Flavonoids on Skeletal Muscle Health: A Systematic Review and Meta-Analysis.

Skeletal muscle (SkM) is a highly dynamic tissue that responds to physiological adaptations or pathological conditions, and SkM mitochondria play a major role in bioenergetics, regulation of intracellular calcium homeostasis, pro-oxidant/antioxidant balance, and apoptosis. Flavonoids are polyphenolic compounds with the ability to modulate molecular pathways implicated in the development of mitochondrial myopathy. Therefore, it is pertinent to explore its potential application in conditions such as aging, disuse, denervation, diabetes, obesity, and cancer. To evaluate preclinical and clinical effects of flavonoids on SkM structure and function. We performed a systematic review of published studies, with no date restrictions applied, using PubMed and Scopus. The following search terms were used: "flavonoids" OR "flavanols" OR "flavones" OR "anthocyanidins" OR "flavanones" OR "flavan-3-ols" OR "catechins" OR "epicatechin" OR "(-)-epicatechin" AND "skeletal muscle." The studies included in this review were preclinical studies, clinical trials, controlled clinical trials, and randomized-controlled trials that investigated the influence of flavonoids on SkM health. Three authors, independently, assessed trials for the review. Any disagreement was resolved by consensus. The use of flavonoids could be a potential tool for the prevention of muscle loss. Their effects on metabolism and on mitochondria function suggest their use as muscle regulators.

New Insights in CaVβ Subunits: Role in the Regulation of Gene Expression and Cellular Homeostasis.

The voltage-gated calcium channels (CaVs or VGCCs) are fundamental regulators of intracellular calcium homeostasis. When electrical activity induces their activation, the influx of calcium that they mediate or their interaction with intracellular players leads to changes in intracellular Ca2+ levels which regulate many processes such as contraction, secretion and gene expression, depending on the cell type. The essential component of the pore channel is the CaVα1 subunit. However, the fine-tuning of Ca2+-dependent signals is guaranteed by the modulatory role of the auxiliary subunits β, α2δ, and γ of the CaVs. In particular, four different CaVβ proteins (CaVβ1, CaVβ2, CaVβ3, and CaVβ4) are encoded by four different genes in mammalians, each of them displaying several splice variants. Some of these isoforms have been described in regulating CaVα1 docking and stability at the membrane and controlling the channel complex’s conformational changes. In addition, emerging evidences have highlighted other properties of the CaVβ subunits, independently of α1 and non-correlated to its channel or voltage sensing functions. This review summarizes the recent findings reporting novel roles of the auxiliary CaVβ subunits and in particular their direct or indirect implication in regulating gene expression in different cellular contexts.

Liraglutide Attenuates Hepatic Ischemia-Reperfusion Injury by Modulating Macrophage Polarization.

Ischemia-reperfusion injury (IRI) is a common complication associated with liver surgery, and macrophages play an important role in hepatic IRI. Liraglutide, a glucagon-like peptide-1 (GLP-1) analog primarily used to treat type 2 diabetes and obesity, regulates intracellular calcium homeostasis and protects the cardiomyocytes from injury; however, its role in hepatic IRI is not yet fully understood. This study aimed to investigate whether liraglutide can protect the liver from IRI and determine the possible underlying mechanisms. Our results showed that liraglutide pretreatment significantly alleviated the liver damage caused by ischemia-reperfusion (I/R), as evidenced by H&E staining, serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, and TUNEL staining. Furthermore, the levels of inflammatory cytokines elicited by I/R were distinctly suppressed by liraglutide pretreatment, accompanied by significant reduction in TNF-α, IL-1β, and IL-6 levels. Furthermore, pretreatment with liraglutide markedly inhibited macrophage type I (M1) polarization during hepatic IRI, as revealed by the significant reduction in CD68+ levels in Kupffer cells (KCs) detected via flow cytometry. However, the protective effects of liraglutide on hepatic IRI were partly diminished in GLP-1 receptor-knockout (GLP-1R-/-) mice. Furthermore, in an in vitro study, we assessed the role of liraglutide in macrophage polarization by examining the expression profiles of M1 in bone marrow-derived macrophages (BMDMs) from GLP-1R-/- and C57BL/6J mice. Consistent with the results of the in vivo study, liraglutide treatment attenuated the LPS-induced M1 polarization and reduced the expression of M1 markers. However, the inhibitory effect of liraglutide on LPS-induced M1 polarization was largely abolished in BMDMs from GLP-1R-/- mice. Collectively, our study indicates that liraglutide can ameliorate hepatic IRI by inhibiting macrophage polarization towards an inflammatory phenotype via GLP-1R. Its protective effect against liver IRI suggests that liraglutide may serve as a potential drug for the clinical treatment of liver IRI.

Dysfunction of cAMP–Protein Kinase A–Calcium Signaling Axis in Striatal Medium Spiny Neurons: A Role in Schizophrenia and Huntington’s Disease Neuropathology

BackgroundStriatal medium spiny neurons (MSNs) are preferentially lost in Huntington’s disease. Genomic studies also implicate a direct role for MSNs in schizophrenia, a psychiatric disorder known to involve cortical neuron dysfunction. It remains unknown whether the two diseases share similar MSN pathogenesis or if neuronal deficits can be attributed to cell type–dependent biological pathways. Transcription factor BCL11B, which is expressed by all MSNs and deep layer cortical neurons, was recently proposed to drive selective neurodegeneration in Huntington’s disease and identified as a candidate risk gene in schizophrenia. MethodsUsing human stem cell–derived neurons lacking BCL11B as a model, we investigated cellular pathology in MSNs and cortical neurons in the context of these disorders. Integrative analyses between differentially expressed transcripts and published genome-wide association study datasets identified cell type–specific disease-related phenotypes. ResultsWe uncover a role for BCL11B in calcium homeostasis in both neuronal types, while deficits in mitochondrial function and PKA (protein kinase A)–dependent calcium transients are detected only in MSNs. Moreover, BCL11B-deficient MSNs display abnormal responses to glutamate and fail to integrate dopaminergic and glutamatergic stimulation, a key feature of striatal neurons in vivo. Gene enrichment analysis reveals overrepresentation of disorder risk genes among BCL11B-regulated pathways, primarily relating to cAMP-PKA-calcium signaling axis and synaptic signaling. ConclusionsOur study indicates that Huntington’s disease and schizophrenia are likely to share neuronal pathophysiology where dysregulation of intracellular calcium homeostasis is found in both striatal and cortical neurons. In contrast, reduction in PKA signaling and abnormal dopamine/glutamate receptor signaling is largely specific to MSNs.

Sudden Cardiac Death in Diabetes and Obesity: Mechanisms and Therapeutic Strategies

Ventricular arrhythmias and sudden cardiac death (SCD) occur most frequently in the setting of coronary artery disease, cardiomyopathy and heart failure but are also increasingly observed in persons suffering from diabetes mellitus and obesity. The incidence of these metabolic disorders is rising in Western countries, but adequate prevention and treatment of arrhythmias and SCD in affected patients is limited because of our incomplete knowledge of the underlying disease mechanisms. Here, an overview is presented of the prevalence of electrophysiological disturbances, ventricular arrhythmias, and SCD in the clinical setting of diabetes and obesity. Experimental studies are reviewed, which have identified disease pathways and associated modulatory factors, in addition to pro-arrhythmic mechanisms. Key processes are discussed, including mitochondrial dysfunction, oxidative stress, cardiac structural derangements, abnormal cardiac conduction, ion channel dysfunction, prolonged repolarization, and dysregulation of intracellular sodium and calcium homeostasis. In addition, the recently identified pro-arrhythmic effects of dysregulated branched chain amino acid metabolism, a common feature in patients with metabolic disorders, are addressed. Finally, current management options are discussed in addition to the potential development of novel preventive and therapeutic strategies based on recent insight gained from translational studies.

Calcium signaling in prostate cancer cells of increasing malignancy

Calcium signaling controls a large variety of cell functions, including proliferation and apoptosis, and plays a major role in neoplastic transformation. Prostate cancer (PCa) is one of the most common malignancies in men. The transition to castration-resistant prostate cancer (CRPC), a lethal form that is still lacking an effective cure, could be influenced by fine tuning intracellular calcium ([Ca2+]i) homeostasis. This study investigates [Ca2+]i dynamics in metastatic PCa cell lines that mimic the progression of PCa to CRPC: (i) well differentiated LNCaP cells that require androgen for survival, and (ii) poorly differentiated, highly aggressive androgen-insensitive prostate cancer (AIPC) PC3 and DU145 cells. In AIPC cells, ATP induces a fast rise in [Ca2+]i, due to release from intracellular stores and sensitive to phospholipase C inhibitors, while LNCaP cells do not respond to ATP challenge. Moreover, AIPC cells showed a reduced capacity to store Ca2+ in thapsigargin-sensitive stores and limited store-operated calcium entry, with respect to androgen-dependent LNCaP cells. Finally, green tea extract causes [Ca2+]i elevation and inhibits proliferation in PC3 and DU145 cells, but is ineffective in LNCaP cells. The consequences of these differences are discussed and interpreted in this study with reference to previously proposed models for Ca2+ dependence of prostate carcinogenesis.

Nitrogen-doped graphene quantum dots induce ferroptosis through disrupting calcium homeostasis in microglia

BackgroundAlong with the wild applications of nitrogen-doped graphene quantum dots (N-GQDs) in the fields of biomedicine and neuroscience, their increasing exposure to the public and potential biosafety problem has gained more and more attention. Unfortunately, the understanding of adverse effects of N-GQDs in the central nervous system (CNS), considered as an important target of nanomaterials, is still limited.ResultsAfter we found that N-GQDs caused cell death, neuroinflammation and microglial activation in the hippocampus of mice through the ferroptosis pathway, microglia was used to assess the molecular mechanisms of N-GQDs inducing ferroptosis because it could be the primary target damaged by N-GQDs in the CNS. The microarray data suggested the participation of calcium signaling pathway in the ferroptosis induced by N-GQDs. In microglial BV2 cells, when the calcium content above the homeostatic level caused by N-GQDs was reversed, the number of cell death, ferroptosis alternations and excessive inflammatory cytokines release were all alleviated. Two calcium channels of L-type voltage-gated calcium channels (L-VGCCs) in plasma membrane and ryanodine receptor (RyR) in endoplasmic reticulum (ER) took part in N-GQDs inducing cytosolic calcium overload. L-VGCCs and RyR calcium channels were also involved in promoting the excess iron influx and triggering ER stress response, respectively, which both exert excessive ROS generation and result in the ferroptosis and inflammation in BV2 cells.ConclusionN-GQDs exposure caused ferroptosis and inflammatory responses in hippocampus of mice and cultured microglia through activating two calcium channels to disrupt intracellular calcium homeostasis. The findings not only posted an alert for biomedical applications of N-GQDs, but also highlighted an insight into mechanism researches of GQDs inducing multiple types of cell death in brain tumor therapy in the future.Graphical abstract