Intracellular Calcium Homeostasis Research Articles

Assessing the Potential of Nutraceuticals as Geroprotectors on Muscle Performance and Cognition in Aging Mice.

Aging and frailty are associated with a decline in muscle force generation, which is a direct consequence of reduced muscle quantity and quality. Among the leading contributors to aging is the generation of reactive oxygen species, the byproducts of terminal oxidation. Their negative effects can be moderated via antioxidant supplementation. Krill oil and astaxanthin (AX) are nutraceuticals with a variety of health promoting, geroprotective, anti-inflammatory, anti-diabetic and anti-fatigue effects. In this work, we examined the functional effects of these two nutraceutical agents supplemented via pelleted chow in aging mice by examining in vivo and in vitro skeletal muscle function, along with aspects of intracellular and mitochondrial calcium homeostasis, as well as cognition and spatial memory. AX diet regimen limited weight gain compared to the control group; however, this phenomenon was not accompanied by muscle tissue mass decline. On the other hand, both AX and krill oil supplementation increased force production without altering calcium homeostasis during excitation-contraction coupling mechanism or mitochondrial calcium uptake processes. We also provide evidence of improved spatial memory and learning ability in aging mice because of krill oil supplementation. Taken together, our data favors the application of antioxidant nutraceuticals as geroprotectors to improve cognition and healthy aging by virtue of improved skeletal muscle force production.

Abstract P356: Dual Dysfunction Of Kir2.1 Underlies Conduction And Excitation-contraction Coupling Defects Promoting Arrhythmias In A Mouse Model Of Andersen-tawil Syndrome Type 1

Background: Andersen-Tawil syndrome type 1 (ATS1), caused by trafficking deficient mutations in the gene KCNJ2 coding the inward rectifier K + channel Kir2.1, is associated with life-threatening arrhythmias, which in some patients resemble catecholaminergic polymorphic ventricular tachycardia (CPVT), but the mechanisms are poorly understood. We tested the hypothesis that dysfunction of two different populations of mutant Kir2.1 channels, one at the sarcolemma, and the other at the sarcoplasmic reticulum (SR) membrane, directly alters conduction and intracellular calcium dynamics, respectively, to promote the ATS1 phenotype and arrhythmias that resemble CPVT. Methods: We generated a new mouse model of ATS1 by a single i.v. injection of cardiac specific adeno-associated viral (AAV) transduction with Kir2.1 Δ314-315 . In-vivo and cellular, structural and functional analyses of the model were carried out by electrocardiogram (ECG), magnetic resonance imaging (MRI), intracardiac stimulation, patch-clamping, membrane fractionation, western blot, immunolocalization and live calcium imaging. Results: Our mouse model carrying mutant Kir2.1 Δ314-315 recapitulated the ATS1 phenotype without modifying ventricular function. On ECG, Kir2.1 Δ314-315 mice had prolonged PR, QRS and QT intervals and occasional U waves. They showed significantly slower conduction velocities than wildtype mice in response to flecaidine-induced Na + -channel blockade, additional QT prolongation in response to isoproterenol, and increased vulnerability to cardiac fibrillation. Cardiomyocytes from Kir2.1 Δ314-315 mice had significantly reduced inward rectifier K + and Na + inward currents, depolarized resting membrane potential and prolonged action potential duration. Immunolocalization in wildtype cardiomyocytes and skeletal muscle cells revealed a novel SR microdomain of functional Kir2.1 channels contributing to intracellular Ca 2+ homeostasis. Kir2.1 Δ314-315 cardiomyocytes showed defects in SR Kir2.1 localization and function, which contributed to abnormal spontaneous Ca 2+ release events. Conclusions: Cardiac-specific AAV transduction with Kir2.1 Δ314-315 in mice recapitulates the ATS1 phenotype by disrupting localization and function of Kir2.1 channels at the SR, and the Kir2.1-Na V 1.5 channelosome at the sarcolemma. These results reveal a novel dual mechanism of arrhythmogenesis in ATS1 involving defects in Kir2.1 channel trafficking and function at two different microdomains. They also provide the first demonstration at the molecular level of the mechanism underlying the overlap between ATS1 and CPVT associated with defects in intracellular calcium homeostasis.

Effects of Electrotherapy on Delayed Onset Muscle Soreness (DOMS)

In this article, the reasons for the occurrence of Delayed Onset Muscle Soreness (DOMS) and the effect of electrotherapy on it were discussed. Electrotherapy is a non-invasive and easy method to treat DOMS and muscle fatigue. As a result of intense and abnormal exercise, the creatine phosphokinase enzyme in the muscle increases and DOMS occur. DOMS can be treated with electrotherapy techniques such as micro-current electrotherapy. Micro-currents devices reduce the severity of DOMS symptoms by maintaining intracellular calcium homeostasis. Devices such as Transcutaneous Electrical Nerve Stimulation (TENS) and Micro-Current Electrical Therapy (MET) belong to the category of micro-currents. The number of electrotherapy sessions after the occurrence of DOMS and the frequency of electrotherapy devices are two important factors in the treatment of DOMS. TENS conducts electrical current to the body through electrodes that attach to the skin, and helping to reduce pain by releasing endorphins, a natural painkiller, and blocking the passage of pain to the brain. MET uses resonant frequencies to aid in deeper and longer treatment, increase the body’s production of natural catalysts in the healing process, and is more useful in chronic pain than TENS. Research has shown that electrotherapy has been shown to improve DOMS symptoms.

SENP2-PLCβ4 signaling regulates neurogenesis through the maintenance of calcium homeostasis.

Neurogenesis plays a critical role in brain physiology and behavioral performance, and defective neurogenesis leads to neurological and psychiatric disorders. Here, we show that PLCβ4 expression is markedly reduced in SENP2-deficient cells and mice, resulting in decreased IP3 formation and altered intracellular calcium homeostasis. PLCβ4 stability is regulated by the SUMO-dependent ubiquitin-mediated proteolytic pathway, which is catalyzed by PIAS2α and RNF4. SUMOylated PLCβ4 is transported to the nucleus through Nup205- and RanBP2-dependent pathways and regulates nuclear signaling. Furthermore, dysregulated calcium homeostasis induced defects in neurogenesis and neuronal viability in SENP2-deficient mice. Finally, SENP2 and PLCβ4 are stimulated by starvation and oxidative stress, which maintain calcium homeostasis regulated neurogenesis. Our findings provide mechanistic insight into the critical roles of SENP2 in the regulation of PLCβ4 SUMOylation, and the involvement of SENP2-PLCβ4 axis in calcium homeostasis regulated neurogenesis under stress.

Inhibition of ultraviolet-induced sea cucumber (Stichopus japonicus) autolysis by maintaining coelomocyte intracellular calcium homeostasis

Apoptosis plays a critical role in sea cucumber autolysis. To investigate the ultraviolet (UV)-induced apoptosis, sea cucumbers with and without injection of BAPTA-AM (cytosolic calcium chelator) were exposed to UV (15 W/m2) for 30 min. The results showed that UV irradiation caused several changes in sea cucumber coelomocytes, including calcium imbalance, abnormal morphology of endoplasmic reticulum, upregulation of pro-apoptotic proteins CRT, CHOP, and caspases 9 and 3, and downregulation of anti-apoptotic protein Bcl-2. A comparison between the two groups showed that injection of the calcium chelator into sea cucumbers helped maintain coelomocyte intracellular calcium homeostasis and suppressed other abnormal changes caused by ER stress, indicating apoptosis in sea cucumbers is mediated by calcium imbalance and follows the activation of the ER stress pathway. Therefore, this study broadens understanding of the apoptotic mechanism involved in sea cucumber autolysis, which is helpful in developing preservative agents for sea cucumbers.

PTPN5 promotes follicle‐stimulating hormone secretion through regulating intracellular calcium homeostasis

Protein tyrosine phosphatase non-receptor type 5 (PTPN5), also called striatal-enriched protein tyrosine phosphatase (STEP), is highly expressed in neurons of the basal ganglia, hippocampus, cortex, and related structures, also in the pituitary. Gonadotropins are the key regulator of the reproduction in mammals. In this study, PTPN5 is detected to express in murine pituitary in a developmental manner. Moreover, the expression of PTPN5 in the pituitary is heavily reduced after ovary removal. Follicle-stimulating hormone (FSH) secretion in gonadotropes is regulated by PTPN5 via binding GnRH to GnRH-R. Two parallel signaling pathways, Gs-protein kinase A (PKA)-PTPN5 and Gq-phospholipases C (PLC)-p38 MAPK-PTPN5, cooperatively regulate GnRH-induced FSH secretion. We also show that influx of Ca2+ activates the Ca2+ -dependent phosphatase calcineurin, leading to the phosphorylation and activation of PTPN5. The intracellular release of Ca2+ is reduced via TC2153. In conclusion, blocking or knocking out of PTPN5 reduces the release of FSH in whole pituitary. Mechanically, PTPN5 regulates gonadotropes' function through regulating intracellular calcium homeostasis.

A case of dermatomyositis in a patient with central core disease: unusual association with autoimmunity and genetic muscle disease

BackgroundDermatomyositis is an inflammatory muscle disease caused by immune-mediated muscle injury, and central core disease (CCD) is a congenital myopathy associated with disturbed intracellular calcium homeostasis and excitation-contraction coupling. To date, CCD has not been reported to have autoantibodies or coexist with inflammatory myopathy.Case presentationHere, we described the case of a 25-year-old woman who had progressive proximal muscle weakness, myalgia, pruritic macular rash, skin ulcers, and calcinosis. Dermatomyositis was initially suspected based on the clinical symptoms accompanied by elevated muscle enzyme levels, electromyography abnormalities, and a positive antinuclear antibody test. However, the patient’s muscle biopsy revealed the characteristic findings of both dermatomyositis and CCD, suggesting that dermatomyositis occurred in this patient with previously asymptomatic CCD. The patient did not have any pathogenic gene mutations associated with congenital myopathy, including RYR1 and SEPN1 in targeted next-generation sequencing. She received high-dose glucocorticoid therapy and azathioprine with a significant improvement in muscle strength.ConclusionsWe present a case of rare coexistence of dermatomyositis and CCD. Clinicians should be aware that patients with CCD may have inflammatory myopathy that responds well to immunosuppressive therapy.

Biallelic ADGRV1 variants are associated with Rolandic epilepsy.

Rolandic epilepsy (RE) is among the most common focal epilepsies in childhood. For the majority of patients with RE and atypical RE (ARE), the etiology remains elusive. We thus screened patients with RE/ARE in order to detect disease-causing variants.. A trios-based whole-exome sequencing approach was performed in a cohort of 28 patients with RE/ARE. Clinical data and EEGs were reviewed. Variants were validated by Sanger sequencing. Two compound heterozygous missense variants p.Val272Ile/p.Asn3028Ser and p.Ala3657Val/p.Met4419Val of ADGRV1 were identified in two unrelated familial cases of RE/ARE. All the variants were in the calcium exchanger β domain and were suggested to be damaging by at least one web-based prediction tool. These variants are not present or are present at a very low minor allele frequency in the gnomAD database. Previously, biallelic ADGRV1 variants (p.Gly2756Arg and p.Glu4410Lys) have been observed in RE, consistent with the observation in this study and supporting the association between ADGRV1 variants and RE. Additionally, a de novo mutation, p.Asp668Asn, in GRIN2B was identified in a sporadic case of ARE, and a missense variant, p.Asn1551Ser, in RyR2 was identified in a family with RE with incomplete penetrance. These genes are all calcium homeostasis associated genes, suggesting the potential effect of calcium homeostasis in RE/ARE. The results from the present study suggest that the genes ADGRV1, GRIN2B, and RyR2 are associated with RE/ARE. These data link defects in neuronal intracellular calcium homeostasis to RE/ARE pathogenesis implicating that these defects plays an important role in the development of these conditions.

Airway Administration of Flagellin Regulates the Inflammatory Response to Pseudomonas aeruginosa.

Excessive lung inflammation and airway epithelial damage are hallmarks of human inflammatory lung diseases, such as cystic fibrosis (CF). Enhancement of innate immunity provides protection against pathogens while reducing lung-damaging inflammation. However, the mechanisms underlying innate immunity–mediated protection in the lung remain mysterious, in part because of the lack of appropriate animal models for these human diseases. TLR5 (Toll-like receptor 5) stimulation by its specific ligand, the bacterial protein flagellin, has been proposed to enhance protection against several respiratory infectious diseases, although other cellular events, such as calcium signaling, may also control the intensity of the innate immune response. Here, we investigated the molecular events prompted by stimulation with flagellin and its role in regulating innate immunity in the lung of the pig, which is anatomically and genetically more similar to humans than rodent models. We found that flagellin treatment modulated NF-κB signaling and intracellular calcium homeostasis in airway epithelial cells. Flagellin pretreatment reduced the NF-κB nuclear translocation and the expression of proinflammatory cytokines to a second flagellin stimulus as well as to Pseudomonas aeruginosa infection. Moreover, in vivo administration of flagellin decreased the severity of P. aeruginosa–induced pneumonia. Then we confirmed these beneficial effects of flagellin in a pathological model of CF by using ex vivo precision-cut lung slices from a CF pigz model. These results provide evidence that flagellin treatment contributes to a better regulation of the inflammatory response in inflammatory lung diseases such as CF.

Inactivation of Presenilin in inhibitory neurons results in decreased GABAergic responses and enhanced synaptic plasticity

Mutations in the Presenilin genes are the major genetic cause of Alzheimer's disease (AD). Presenilin (PS) is highly expressed in the hippocampus, which is particularly vulnerable in AD. Previous studies of PS function in the hippocampus, however, focused exclusively on excitatory neurons. Whether PS regulates inhibitory neuronal function remained unknown. In the current study, we investigate PS function in GABAergic neurons by performing whole-cell and field-potential electrophysiological recordings using acute hippocampal slices from inhibitory neuron-specific PS conditional double knockout (IN-PS cDKO) mice at 2 months of age, before the onset of age-dependent loss of interneurons. We found that the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) is reduced in hippocampal CA1 neurons of IN-PS cDKO mice, whereas the amplitude of sIPSCs is normal. Moreover, the efficacy of inhibitory neurotransmission as assessed with synaptic input/output relations for evoked mono- and di-synaptic IPSCs is markedly lowered in hippocampal CA1 neurons of IN-PS cDKO mice. Consistent with these findings, IN-PS cDKO mice display enhanced paired-pulse facilitation, frequency facilitation and long-term potentiation in the Schaffer collateral-CA1 pathway. Interestingly, depletion of intracellular Ca2+ stores by inhibition of sarcoendoplasmic reticulum Ca2+ ATPase results in a reduction of IPSC amplitude in control hippocampal neurons but not in IN-PS cDKO neurons, suggesting that impaired intracellular calcium homeostasis in the absence of PS may contribute to the deficiencies in inhibitory neurotransmission. Furthermore, the amplitude of IPSCs induced by short trains of presynaptic stimulation and paired-pulse ratio are decreased in IN-PS cDKO mice. These findings show that inactivation of PS in interneurons results in decreased GABAergic responses and enhanced synaptic plasticity in the hippocampus, providing additional evidence for the importance of PS in the regulation of synaptic plasticity and calcium homeostasis.

S100A6 represses Calu-6 lung cancer cells growth via inhibiting cell proliferation, migration, invasion and enhancing apoptosis.

S100 calcium binding protein A6 (S100A6) has been reported to involve in many kinds of cancers through regulating intracellular calcium homeostasis. Previous studies found that S100A6 increased in lung cancer patients' plasma and pleural effusion. This study focused on its function in Calu‐6 lung cancer cells. S100A6 gene was transferred into Calu‐6 lung cancer cell line by lentivirus vector, the empty vector transfected cells and the blank cells were set as control groups. MTT was evaluating cell proliferation. The transwell assay was reflecting cell migration and cell invasion. The flow cytometric analysis was detecting cell apoptosis and cell cycle of three groups (Calu‐6, Calu‐6/neo, Calu‐6/S100A6). Nude mouse tumorigenicity was then applied to evaluate S100A6's effect on cellular tumorigenicity. Compared with control groups, Calu‐6/S100A6 cells showed a weakening trend in the cell behaviours of proliferation, migration and invasiveness, while had an enhancement of cell apoptosis, with all P < .05. The cell cycle of Calu‐6/S100A6 cells had a reduction of S phase and an increase of G1 phase (P < .05). In animal study, after 5 weeks of cell injection, the tumour bulk of Calu‐6/S100A6 group was smaller than controls, with P < .05. Our results demonstrate S100A6 inhibits the growth of Calu‐6 lung cancer cells, as well as impairs Calu‐6's ability in tumorigenesis. At cellular level, S100A6 is supposed to act as a tumour suppressor gene in lung cancer.

Characterization of purinergic receptor 2 signaling in podocytes from diabetic kidneys

SummaryGrowing evidence suggests that renal purinergic signaling undergoes significant remodeling during pathophysiological conditions such as diabetes. This study examined the renal P2 receptor profile and ATP-mediated calcium response from podocytes in glomeruli from kidneys with type 1 or type 2 diabetic kidney disease (DKD), using type 2 diabetic nephropathy (T2DN) rats and streptozotocin-injected Dahl salt-sensitive (type 1 diabetes) rats. A dramatic increase in the ATP-mediated intracellular calcium flux in podocytes was observed in both models. Pharmacological inhibition established that P2X4 and P2X7 are the major receptors contributing to the augmented ATP-mediated intracellular calcium signaling in diabetic podocytes. The transition in purinergic receptor composition from metabotropic to ionotropic may disrupt intracellular calcium homeostasis in podocytes resulting in their dysfunction and potentially further aggravating DKD progression.

The Relevance of Amyloid β-Calmodulin Complexation in Neurons and Brain Degeneration in Alzheimer’s Disease

Intraneuronal amyloid β (Aβ) oligomer accumulation precedes the appearance of amyloid plaques or neurofibrillary tangles and is neurotoxic. In Alzheimer’s disease (AD)-affected brains, intraneuronal Aβ oligomers can derive from Aβ peptide production within the neuron and, also, from vicinal neurons or reactive glial cells. Calcium homeostasis dysregulation and neuronal excitability alterations are widely accepted to play a key role in Aβ neurotoxicity in AD. However, the identification of primary Aβ-target proteins, in which functional impairment initiating cytosolic calcium homeostasis dysregulation and the critical point of no return are still pending issues. The micromolar concentration of calmodulin (CaM) in neurons and its high affinity for neurotoxic Aβ peptides (dissociation constant ≈ 1 nM) highlight a novel function of CaM, i.e., the buffering of free Aβ concentrations in the low nanomolar range. In turn, the concentration of Aβ-CaM complexes within neurons will increase as a function of time after the induction of Aβ production, and free Aβ will rise sharply when accumulated Aβ exceeds all available CaM. Thus, Aβ-CaM complexation could also play a major role in neuronal calcium signaling mediated by calmodulin-binding proteins by Aβ; a point that has been overlooked until now. In this review, we address the implications of Aβ-CaM complexation in the formation of neurotoxic Aβ oligomers, in the alteration of intracellular calcium homeostasis induced by Aβ, and of dysregulation of the calcium-dependent neuronal activity and excitability induced by Aβ.

Acute Knockdown of MG29 in Mouse Muscle Cells Reveals Signaling Mechanisms Associated with Polyunsaturated Fatty Acid (PUFA) – Implications for Sarcopenia

Estimates of humans with sarcopenia (i.e., the age related loss of muscle loss and strength) ranges from 30% to over 70% depending on the age group, and specific population studied. Mitsugumin 29 (MG29), a muscle-specific protein, is a member of the synaptophysin-like protein family (SYPL2) that contain MAL and related proteins for vesicle trafficking and membrane link (MARVEL) domains. MG29 is important for the formation of the transverse-tubule (TT) system in skeletal muscles, efficient signaling between RyR1 and the store-operated Ca2+ entry (SOCE) machinery, and maintenance of lipid content of the sarcolemmal membrane. Our previous in vivo studies using a global knockout model of MG29 suggested a role of MG29 in the aging decline in muscle function. To avoid potential adaptive effects of the global absence of MG29, we also tested the siRNA-mediated acute knockdown of MG29 in mouse primary skeletal muscle cells, which led to extensive myogenic changes characterized by increased myogenic differentiation that led to abnormally thinner and longer myotubes. To examine the mechanistic basis of these changes, we measured changes in lipid signaling following knockdown of MG29. We collected both cell culture medium and cell homogenates 72 h after siRNA transfection, and applied a custom-targeted LC/MS lipidomics approach to quantify specific Lipid Signaling Mediators (LMs) in cell culture media and we used our customized skeletal muscle-specific RT-qPCR gene array to investigate specific genes showing alteration expression following acute MG29 knockdown. Compared with negative control siRNA treated cells, in MG29 siRNA treated cells, the cell culture media levels of arachidonoylethanolamine (AEA), oleoylethanolamide (OEA) increased significantly (p < 0.05) and the levels of prostaglandin D2 (PGD2), 9,10-DiHOME, 9-HOTrE, 9-HODE decreased significantly (p < 0.05). In addition, the PCR gene array revealed that in MG29 siRNA treated cells the expression of Cacna1s, RyR3, Btk and Sod3 increased 2.6 ± 0.48, 4.5 ± 0.89, 2.7 ± 0.51 and 6.5 ± 1.06 fold, respectively, while Fkbp1b and Ccl2 decreased 2.8 ± 0.38 and 7.3 ± 1.74 fold, respectively. These genes have function in calcium signaling and homeostasis and oxidative stress as well as inflammation and immune-regulation. We conclude that MG29 modulation of myogenic differentiation occurs via a complex signaling mechanism related to changes in LMs derived from polyunsaturated fatty acid (PUFA). This study further positions MG29 as an important regulator of signaling pathways associated with intracellular calcium homeostasis, oxidative stress, and inflammation, which emphasizes the role of MG29 as an orchestrator of alterations in skeletal muscle during sarcopenia.

Genetic investigation of fibromuscular dysplasia identifies risk loci and shared genetics with common cardiovascular diseases

Fibromuscular dysplasia (FMD) is a non-atherosclerotic arteriopathy of unknown etiology, affecting mostly middle-aged women. It is characterized by stenotic lesions of the vascular wall in middle-size arteries, sometimes associated with dissection, aneurysm or tortuosity. We aim at identifying genetic causes of FMD to better understand its mechanism and relation with other vasculopathies. We report results from the first genome-wide association meta-analysis of six studies including 1962 FMD cases and 7100 controls. We integrated genetic association with arterial gene expression using transcriptome-wide association analysis. To identify FMD associated variants located in regulatory elements, we determined open chromatin regions in artery-derived primary cells using ATAC-Seq and estimated heritability and genetic correlation of FMD with other vascular traits and diseases using LD Score regression. We found an estimate of SNP-based heritability compatible with a polygenic feature for FMD and report four robustly associated loci (PHACTR1, LRP1, ATP2B1, and LIMA1). Transcriptome-wide association analysis in arteries identified one additional locus (SLC24A3). We found that FMD associated variants were located in arterial-specific regulatory elements. Target genes were broadly involved in mechanisms related to actin cytoskeleton and intracellular calcium homeostasis, central to vascular contraction. We found significant genetic overlap between FMD and blood pressure, although hypertension was not confounding the genetic association with FMD. We also report an important genetic overlap with migraine, intracranial aneurysm, coronary artery disease and LDL cholesterol. We identified several loci related to vascular contraction, suggesting that altered vascular tonicity may play a role in the pathogenesis of FMD. We find that FMD is genetically close to several vascular diseases where vascular integrity is impaired.

Gene network analyses unveil possible molecular basis underlying drug-induced glaucoma

BackgroundDrug-induced glaucoma (DIG) is a kind of serious adverse drug reaction that can cause irreversible blindness. Up-to-date, the molecular mechanism of DIG largely remains unclear yet due to the medical complexity of glaucoma onset.MethodsIn this study, we conducted data mining of tremendous historical adverse drug events and genome-wide drug-regulated gene signatures to identify glaucoma-associated drugs. Upon these drugs, we carried out serial network analyses, including the weighted gene co-expression network analysis (WGCNA), to illustrate the gene interaction network underlying DIG. Furthermore, we applied pathogenic risk assessment to discover potential biomarker genes for DIG.ResultsAs the results, we discovered 13 highly glaucoma-associated drugs, a glaucoma-related gene network, and 55 glaucoma-susceptible genes. These genes likely played central roles in triggering DIGs via an integrative mechanism of phototransduction dysfunction, intracellular calcium homeostasis disruption, and retinal ganglion cell death. Further pathogenic risk analysis manifested that a panel of nine genes, particularly OTOF gene, could serve as potential biomarkers for early-onset DIG prognosis.ConclusionsThis study elucidates the possible molecular basis underlying DIGs systematically for the first time. It also provides prognosis clues for early-onset glaucoma and thus assists in designing better therapeutic regimens.

Selenium nanoparticles ameliorate Brassica napus L. cadmium toxicity by inhibiting the respiratory burst and scavenging reactive oxygen species

Cadmium (Cd) is a widely distributed soil contaminant which induces oxidative damage and is therefore toxic to plants. Although selenium oxyanions such as selenite (SeO32-) and selenate (SeO42-) can alleviate Cd stress to plants, it is not known whether selenium nanoparticles (SeNPs) are able to do the same. The present study demonstrated the positive impact of both SeNPs and SeO32- on Brassica napus L. growth under conditions of Cd stress. Underlying mechanisms were elucidated using an oxidative stress detection assay, whole-genome RNA sequencing, and RT-qPCR. Application of selenium, especially in the form of SeNPs, decreased Cd-induced reactive oxygen species production by inhibiting the expression of NADPH oxidases (BnaRBOHC, BnaRBOHD1, and BnaRBOHF1) and glycolate oxidase (BnaGLO), thereby decreasing oxidative protein and membrane lipid damage. In addition, SeNPs improved resistance to Cd stress by decreasing Cd accumulation, maintaining intracellular calcium homeostasis, promoting disulfide bond formation, and restoring the waxy outer layer of the leaf surface. Although both forms of selenium decreased Cd toxicity, the beneficial concentration range was more extensive for SeNPs than for SeO32-.

Calcineurin-mediated intracellular organelle calcium homeostasis is required for the survival of fungal pathogens upon extracellular calcium stimuli

ABSTRACT In eukaryotes, calcium not only is an essential mineral nutrient but also serves as an intracellular second messenger that is necessary for many physiological processes. Previous studies showed that the protein phosphatase-calcineurin protects fungi from toxicity caused by the extracellular calcium; however, little is known about how calcineurin mediates the cellular physiology process for this function. In this study, by monitoring intracellular calcium, particularly by tracking vacuolar calcium dynamics in living cells through a novel procedure using modified aequorin, we found that calcineurin dysfunction systematically caused abnormal intracellular calcium homeostasis in cytosol, mitochondria, and vacuole, leading to drastic autophagy, global organelle fragmentation accompanied with the increased expression of cell death-related enzymes, and cell death upon extracellular calcium stimuli. Notably, all detectable defective phenotypes seen with calcineurin mutants can be significantly suppressed by alleviating a cytosolic calcium overload or increasing vacuolar calcium storage capacity, suggesting toxicity of exogenous calcium to calcineurin mutants is tightly associated with abnormal cytosolic calcium accumulation and vacuolar calcium storage capacity deficiency. Our findings provide insights into how the original recognized antifungal drug target-calcineurin regulates intracellular calcium homeostasis for cell survival and may have important implications for antifungal therapy and clinical drug administration.

Bortezomib Inhibits Hypoxia-Induced Proliferation by Suppressing Caveolin-1/SOCE/[Ca2+]i Signaling Axis in Human PASMCs.

Background Previous studies have demonstrated the ubiquitin-proteasome inhibitor bortezomib (BTZ) can effectively alleviate hypoxia-induced pulmonary hypertension (HPH) by suppressing the intracellular calcium homeostasis in pulmonary arterial smooth muscle cells (PASMCs). Further evaluation showed that the antiproliferation roles of BTZ are mainly mediated by inhibition of the intracellular calcium homeostasis. Caveolin-1 belongs to one of the key regulators of the intracellular calcium homeostasis in PASMCs, which can regulate the store-operated calcium entry (SOCE). However, the effects of BTZ on Caveolin-1 remain unclear. Methods Primarily cultured human PASMCs were used as the cell model. CCK-8 assay was performed to assess the PASMCs proliferation. Western blotting and real-time qPCR were used to detect the mRNA and protein expressions. Fura-2-based fluorescence imaging experiments were used to determine the intracellular calcium concentration ([Ca2+]i). The protein synthesis inhibitor cycloheximide (CHX) was utilized to determine the protein degradation process. Results Firstly, in cultured human PASMCs, treatment of BTZ for 24 or 60 hours significantly downregulates Caveolin-1 at both mRNA and protein levels. Secondly, in the presence CHX, BTZ treatment also leads to downregulated protein expression and fastened protein degradation of Caveolin-1, indicating that BTZ can promote the Caveolin-1 protein degradation, other than the BTZ on Caveolin-1 mRNA transcription. Then, BTZ significantly attenuates the hypoxia-elevated baseline [Ca2+]i, SOCE, and cell proliferation. Conclusion We firstly observed that the ubiquitin-proteasome inhibitor BTZ can inhibit the Caveolin-1 expression at both mRNA transcription and protein degradation processes, providing new mechanistic basis of BTZ on PASMC proliferation.

Upregulation of Piezo1 (Piezo Type Mechanosensitive Ion Channel Component 1) Enhances the Intracellular Free Calcium in Pulmonary Arterial Smooth Muscle Cells From Idiopathic Pulmonary Arterial Hypertension Patients.

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