Pharmacological Preconditioning Using Diazoxide Regulates Store-Operated Ca2 + Channels in Adult Rat Cardiomyocytes

Glymphatic Dysfunction Induced Oxidative Stress and Neuro-Inflammation in Major Depression Disorders

Major Depression disorder (MDD) is a potentially life-threatening mental illness, however, many patients have a poor response to current treatments. Recent studies have suggested that stress- or trauma-induced oxidative stress and inflammation could be important factors involved in the development of MDD, but the mechanisms remain unclear. We showed that the glymphatic system is a recently discovered structure in the brain that may be involved in the clearance of large molecular and cell debris in extracellular space. In addition, the glymphatic system can help with the removal of reactive oxygen species (ROS) and cytokines such as IL-1β and HIF-1α. Glymphatic impairment can lead to ROS accumulation in the microenvironment, inducing cellular injury signaling and activating NLRP3 in microglia to induce inflammation and, thus, many brain diseases, including psychiatric disorders. Therefore, trauma-induced glymphatic impairment could induce oxidative stress and inflammation, and thus MDD. This paper will review recent advances with regard to stress-induced glymphatic system impairment and ROS-mediated inflammation in MDD.

STIM and Orai Mediated Regulation of Calcium Signaling in Age-Related Diseases

Tight spatiotemporal regulation of intracellular Ca²⁺ plays a critical role in regulating diverse cellular functions including cell survival, metabolism, and transcription. As a result, eukaryotic cells have developed a wide variety of mechanisms for controlling Ca²⁺ influx and efflux across the plasma membrane as well as Ca²⁺ release and uptake from intracellular stores. The STIM and Orai protein families comprising of STIM1, STIM2, Orai1, Orai2, and Orai3, are evolutionarily highly conserved proteins that are core components of all mammalian Ca²⁺ signaling systems. STIM1 and Orai1 are considered key players in the regulation of Store Operated Calcium Entry (SOCE), where release of Ca²⁺ from intracellular stores such as the Endoplasmic/Sarcoplasmic reticulum (ER/SR) triggers Ca²⁺ influx across the plasma membrane. SOCE, which has been widely characterized in non-excitable cells, plays a central role in Ca²⁺-dependent transcriptional regulation. In addition to their role in Ca²⁺ signaling, STIM1 and Orai1 have been shown to contribute to the regulation of metabolism and mitochondrial function. STIM and Orai proteins are also subject to redox modifications, which influence their activities. Considering their ubiquitous expression, there has been increasing interest in the roles of STIM and Orai proteins in excitable cells such as neurons and myocytes. While controversy remains as to the importance of SOCE in excitable cells, STIM1 and Orai1 are essential for cellular homeostasis and their disruption is linked to various diseases associated with aging such as cardiovascular disease and neurodegeneration. The recent identification of splice variants for most STIM and Orai isoforms while complicating our understanding of their function, may also provide insight into some of the current contradictions on their roles. Therefore, the goal of this review is to describe our current understanding of the molecular regulation of STIM and Orai proteins and their roles in normal physiology and diseases of aging, with a particular focus on heart disease and neurodegeneration.

Neonicotinoid insecticides triggers mitochondrial bioenergetic dysfunction via manipulating ROS-calcium influx pathway in the liver

Extensive use of neonicotinoids insecticides (NNIs) rapidly garnered widespread attention in the toxicology, since they have been found in human samples, including urine, blood, breast milk and hair. However, the precise mechanism is not completely clear regarding the NNIs-induced hepatotoxicity. In this study, we exposed male mice to three neonicotinoids (dinotefuran (DIN), nitenpyram (NIT) and acetamiprid (ACET) for 30 days. Our results showed that NNIs remarkably induced morphological damage in the liver. Simultaneously, we found that three neonicotinoids could activate the store operated Ca2+ entry (SOCE) in the liver. Further results confirmed that reactive oxide species (ROS) scavenger n-acetylcysteine (NAC) attenuated DIN-induced calcium ion (Ca2+) overload and S-phase arrest via restoring protein expression of SOCE and S phase related genes in L02 hepatocytes. Moreover, we found that NAC obviously combated mitochondrial dysfunction caused by DIN via restoring mitochondrial membrane potential. Meanwhile, DIN treatment significantly increased pyruvate content, impaired the activities of tricarboxylic acid (TCA) cycle rate-limiting enzymes and inhibited adenosine triphosphate (ATP) generation, but these effects were reversed by Serca specific activator CDN1163. Collectively, perturbation of redox states can be recognized as the center of S-phase arrest and Ca2+ overload after NNIs exposure. In this regard, Ca2+ homeostasis dysregulation is a causative event of mitochondrial bioenergetic dysfunction in the liver. These data provides a new perspective for understanding NNI-induced hepatotoxicity mechanisms.

Dantrolene hinders dengue virus-induced upregulation and translocation of calmodulin to cardiac cell nuclei

Dengue virus (DENV) infection elevates intracellular Ca²⁺ concentration ([Ca²⁺]_i), but it is unknown whether Ca²⁺ and calmodulin (CaM) are involved in DENV infection. We conducted immunofluorescence and western blot experiments and measured [Ca²⁺]_i examining the effects of DENV infection and drugs that alter Ca²⁺/CaM functions on CaM translocation, DENV2 infection, protein expression, virus-inducible STAT2 protein abundance, and CREB phosphorylation in H9c2 cells. DENV infection increased CaM expression, its nuclear translocation and NS3 and E viral proteins expression and colocalization in a manner that could be blocked by the ryanodine receptor antagonist dantrolene. DENV infection also increased CREB phosphorylation, an effect inhibited by either dantrolene or the CaM inhibitor W7. Dantrolene substantially hindered infection as assessed by focus assays in Vero cells. These results suggest that Ca²⁺ and CaM play an important role in DENV infection of cardiac cells and that dantrolene may protect against severe DENV cardiac morbidity.

The mitochondrial K-ATP channel opener diazoxide upregulates STIM1 and Orai1 via ROS and the MAPK pathway in adult rat cardiomyocytes

Background

Openers of mitochondrial adenosine triphosphate-dependent potassium (mKATP) channels like diazoxide increase reactive oxygen species (ROS) production in cardiac cells and reduce Ca²⁺ elevations produced by ischemia–reperfusion, protecting the heart from damage. In this study we tested the hypothesis that opening mKATP channels regulates expression of the major components of store-operated Ca²⁺ entry (SOCE) STIM1 and Orai1.

Results

Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and western blot experiments showed that diazoxide increased expression of STIM1 and Orai1 at the mRNA and protein levels, respectively, in adult rat cardiomyocytes. Immunofluorescence analyses revealed that diazoxide also disrupted the striated distribution pattern of STIM1. These effects were prevented by the ROS scavenger N-acetyl cysteine (NAC), the mKATP channel antagonist 5-hydroxydecanoate (5-HD), or the protein synthesis inhibitor cycloheximide (CHX). Confocal microscopy revealed that diazoxide also led to nuclear translocation of the transcription factors c-Fos and NFκB, which was also blocked by NAC or 5-HD. Finally, the MAPK pathway inhibitor UO126 attenuated diazoxide-induced upregulation of STIM1 and Orai1 expression.

Conclusions

Our results suggest that opening mitochondrial potassium ATP channels with diazoxide upregulates the expression of STIM1 and Orai1 by de novo synthesis by a mechanism that involves NFkB, c-Fos, and ROS via MAPK/ERK signaling.