Sarcolemmal ATP-sensitive potassium channel protects cardiac myocytes against lipopolysaccharide-induced apoptosis

The significant mechanism and treatments of cell death in heatstroke

With global warming, extreme environmental heat is becoming a social issue of concern, which can cause adverse health results including heatstroke (HS). Severe heat stress is characterized by cell death of direct heat damage, excessive inflammatory responses, and coagulation disorders that can lead to multiple organ dysfunction (MODS) and even death. However, the significant pathophysiological mechanism and treatment of HS are still not fully clear. Various modes of cell death, including apoptosis, pyroptosis, ferroptosis, necroptosis and PANoptosis are involved in MODS induced by heatstroke. In this review, we summarized molecular mechanism, key transcriptional regulation as for HSF1, NRF2, NF-κB and PARP-1, and potential therapies of cell death resulting in CNS, liver, intestine, reproductive system and kidney injury induced by heat stress. Understanding the mechanism of cell death provides new targets to protect multi-organ function in HS.

Functional Regulation of KATP Channels and Mutant Insight Into Clinical Therapeutic Strategies in Cardiovascular Diseases

ATP-sensitive potassium channels (K_ATP channels) play pivotal roles in excitable cells and link cellular metabolism with membrane excitability. The action potential converts electricity into dynamics by ion channel-mediated ion exchange to generate systole, involved in every heartbeat. Activation of the K_ATP channel repolarizes the membrane potential and decreases early afterdepolarization (EAD)-mediated arrhythmias. K_ATP channels in cardiomyocytes have less function under physiological conditions but they open during severe and prolonged anoxia due to a reduced ATP/ADP ratio, lessening cellular excitability and thus preventing action potential generation and cell contraction. Small active molecules activate and enhance the opening of the K_ATP channel, which induces the repolarization of the membrane and decreases the occurrence of malignant arrhythmia. Accumulated evidence indicates that mutation of K_ATP channels deteriorates the regulatory roles in mutation-related diseases. However, patients with mutations in K_ATP channels still have no efficient treatment. Hence, in this study, we describe the role of K_ATP channels and subunits in angiocardiopathy, summarize the mutations of the K_ATP channels and the functional regulation of small active molecules in K_ATP channels, elucidate the potential mechanisms of mutant K_ATP channels and provide insight into clinical therapeutic strategies.

Effects of extracellular histones on left ventricular diastolic function and potential mechanisms in mice with sepsis

OBJECTIVE

Extracellular histone (EH) is involved in the development of septic myocardial injury (SMI). In this study, we explored whether EH could induce left ventricular diastolic dysfunction (LVDD) in sepsis, and investigated the potential mechanisms through in vivo and in vitro experiments using animal models.

METHODS

The ratio between E-wave and A-wave (E/A ratio), left ventricular end diastolic volume, and isovolumic relaxation time (IVRT) were measured in cecal ligation and perforation (CLP)- and EH-treated male C57BL/6J mice using echocardiography. The protein and mRNA levels of apoptosis-related proteins (cleaved caspase-3, Bcl-2, and Bax) and cardiac troponin T (cTnT) in the left ventricular tissue/cardiomyocytes were measured using enzyme-linked immunosorbent assay, qRT-PCR, and western blotting. Cardiomyocyte apoptosis was detected by flow cytometry.

RESULTS

CLP mice presented with LVDD, which was accompanied by increased circulating histones, cTnT and Bax protein levels. Circulating histones were correlated with cTnT, Bax, IVRT, and E/A ratio in CLP mice. Intraperitoneal injection of EH resulted in LVDD in mice. EH induced cardiomyocyte apoptosis, and histone neutralizing agents improved SMI and protected mice against CLP- and EH-induced death.

CONCLUSION

EH is involved in septic LVDD, and this alteration might be associated with EH-induced apoptosis. EH may serve as a potential therapeutic target for SMI.

Carvacrol treatment opens Kir6.2 ATP-dependent potassium channels and prevents apoptosis on rat testis following ischemia-reperfusion injury model

Testicular torsion is a urological problem that causes subfertility and testicular damage in males. Testis torsion and detorsion lead to ischemia–reperfusion (IR) injury in the testis. Testicular IR injury causes the increase of reactive oxygen species (ROS), oxidative stress (OS) and germ cell-specific apoptosis. In this study, we aimed to investigate whether Carvacrol has a protective effect on testicular IR injury and its effects on Kir6.2 channels, which is a member of adenosine triphosphate (ATP)-dependent potassium channels. In the study, 2–4 months old 36 albino Wistar rats were used. For experimental testicular IR model, the left testis was rotated counterclockwise at 720° for two hours, and after two hours following torsion, detorsion was performed. Carvacrol was dissolved in 5% Dimethyl Sulfoxide (DMSO) at a dose of 73 mg/kg and half an hour before detorsion, 0.2 mL was administered intraperitoneally. In testicular tissues, caspase 3 and Kir6.2 immunoexpressions were examined. Serum malondialdehyde (MDA) and testosterone levels were measured. Apoptotic cells and serum MDA levels were significantly decreased and Kir6.2 activation was significantly increased in Carvacrol-administrated IR group. As a result of our study, Carvacrol may activates Kir6.2 channels and inhibits apoptosis and may have a protective effect on testicular IR injury.

Upregulation of UCP2 Expression Protects against LPS-Induced Oxidative Stress and Apoptosis in Cardiomyocytes

Uncoupling protein 2 (UCP2) has a cardioprotective role under septic conditions, but the underlying mechanism remains unclear. This study aimed at investigating the effects of UCP2 on the oxidative stress and apoptosis of cardiomyocytes induced by lipopolysaccharide (LPS). First, LPS increased UCP2 expression in cardiomyocytes in a time-dependent manner. LPS increased the production of lactate dehydrogenase (LDH), reactive oxygen species (ROS), and malondialdehyde (MDA) and decreased the level of superoxide dismutase (SOD). However, UCP2 knockdown increased the LPS-induced cardiac injury and oxidative stress. In addition, LPS damaged the mitochondrial ultrastructure and led to the disruption of mitochondrial membrane potential (MMP), as well as the release of mitochondrial cytochrome c. UCP2 knockdown aggravated mitochondrial injury and the release of mitochondrial cytochrome c. LPS increased the protein levels of Bax and cleaved-caspase-3, decreased the protein level of Bcl-2, and upregulated the protein level of mitogen-activated protein kinase. However, upon UCP2 knockdown, the protein levels of Bax and cleaved-caspase-3 increased even further, and the protein level of Bcl-2 was further decreased. The protein level of phosphorylated p38 was also further enhanced. Thus, UCP2 protects against LPS-induced oxidative stress and apoptosis in cardiomyocytes.

Dexmedetomidine Protects Against Multi-Organ Dysfunction Induced by Heatstroke via Sustaining The Intestinal Integrity

Previous studies have indicated that gut-derived endotoxin played a pivotal role for aggravating systemic inflammatory response to multi-organ dysfunction under heatstroke. Dexmedetomidine (DEX) could protect against inflammation and multi-organ injury in various scenarios. The aim of this study was to explore the protective effect of DEX on heatstroke and the mechanism involved. Male C57BL/6 mice were placed in a controlled climate chamber (40 ± 1°C) until the maximum core temperature (Tc, Max) of 42.7°C, the received criterion of heatstroke, was attained, DEX (25 μg/kg) or 0.9% saline was injected intraperitoneally immediately. The results showed that DEX could significantly attenuate multi-organ injury induced by heatstroke, simultaneously decrease levels of serum inflammatory cytokines through inhibiting the intestinal nuclear factor-κB activation. Furthermore, to assess the effects of DEX on intestine mucosal barrier under heatstroke, the levels of plasma endotoxin, FD4, and D-lactate were detected and the expression of tight junction proteins occludin and ZO-1 was analyzed by western blot and immunohistochemistry. Meanwhile, transmission electron microscopy was employed to confirm the ultrastructure of intestine. Interestingly, we found that DEX decreased the intestinal permeability and sustained the integrity of intestinal barrier. Finally, to evaluate the anti-apoptosis effect of DEX, the pro-apoptotic protein Bax and anti-apoptotic protein Bcl-2 were analyzed by western blot, and terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling (TUNEL) staining was conducted. The results showed that DEX decreased TUNEL-positive cells induced by heatstroke in a Bax/Bcl-2-related manner. Taken together, our results indicate that DEX could protect against inflammation and multi-organ injury induced by heatstroke via sustaining the intestinal integrity.