18β-Glycyrrhetinic Acid Improves Cardiac Diastolic Function by Attenuating Intracellular Calcium Overload

Summary:Ranolazine,a late sodium current inhibitor,has been demonstrated to be effective on heart failure.18B-glycyrrhetinic acid(18β-GA)has the similar inhibitory effect on late sodium currents.However,its effect on diastolic function is still unknown.This study aimed to determine whether 18β-GA can improve the diastolic function and to explore the underlying mechanisms.Eighty male Sprague Dawley(SD)rats of Langendorff model were randomly divided into the following groups:group A,normal cardiac perfusion group;group B,ischemia-reperfusion group;group C,ischemia-reperfusion with anemoniasulcata toxinⅡ(ATX-Ⅱ);group D,ranolazine group;and group E,18β-GA group with four different concentrations.Furthermore,a pressure-overloaded rat model induced by trans-aortic constriction(TAC)was established.Echocardiography and hemodynamics were used to evaluate diastolic function at 14th day after TAC.Changes of free intracellular calcium(Ca27)concentration was indirectly detected by laser scanning confocal microscope to confirm the inhibition of late sodium currents.With the intervention of ATX-Ⅱon ischemia reperfusion injury group,5 umol/L ranolazine,and 5,10,20,40μmol/L 18β-GA could improve ATX-I-induced cardiac diastolic dysfunction.630 mg/kg glycyrrhizin tablets could improve cardiac diastolic function in the pressure-overloaded rats.18B-GA and ranolazine had similar effects on reducing the free calcium in cardiomyocytes.The study demonstrates that 18B-GA and glycyrrhizin could improve diastolic dysfunction induced by ischemia-reperfusion injury in Langendorff-perfused rat hearts and pressure-overloaded rats.The mechanism may be attributed to the inhibition of enhanced late sodium currents.

Adipose mesenchymal stem cell-derived extracellular vesicles reduce glutamate-induced excitotoxicity in the retina

Adipose mesenchymal stem cells(ADSCs)have protective effects against glutamate-induced excitotoxicity,but ADSCs are limited in use for treatment of optic nerve injury.Studies have shown that the extracellular vesicles(EVs)secreted by ADSCs(ADSC-EVs)not only have the function of ADSCs,but also have unique advantages including non-immunogenicity,low probability of abnormal growth,and easy access to target cells.In the present study,we showed that intravitreal injection of ADSC-EVs substantially reduced glutamate-induced damage to retinal morphology and electroretinography.In addition,R28 cell pretreatment with ADSC-EVs before injury inhibited glutamate-induced overload of intracellular calcium,downregulation ofα-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid receptor(AMPAR)subunit GluA2,and phosphorylation of GluA2 and protein kinase C alpha in vitro.A protein kinase C alpha agonist,12-O-tetradecanoylphorbol 13-acetate,inhibited the neuroprotective effects of ADSC-EVs on glutamate-induced R28 cells.These findings suggest that ADSCEVs ameliorate glutamate-induced excitotoxicity in the retina through inhibiting protein kinase C alpha activation.

Restoring cellular calcium homeostasis to rescue ER stress by 1,2-bis(2-aminophenoxy)ethane-N,N,N’,N’-tetraacetic acid acetoxymethyl ester-loaded lipid-mPLGA hybrid-nanoparticles for acute kidney injury therapy

Early pathogenesis of ischemia-reperfusion(I/R)-induced acute kidney injury(AKI)is dominated by intracellular calcium overload,which induces oxidative stress,intracellular energy metabolism disorder,inflammatory activation,and a series of pathologic cascaded reactions that are closely intertwined with self-amplifying and interactive feedback loops,ultimately resulting in cell damage and kidney failure.Currently,most nanomedicines originate from the perspective of antioxidant stress,which can only quench existing reactive oxide species(ROS)but cannot prevent the continuous production of ROS,resulting in insufficient efficacy.As a safe and promising drug,BAPTA-AM is hydrolyzed into BAPTA by intracellular esterase upon entering cells,which can rapidly chelate with overloaded Ca^(2+),restoring intracellular calcium homeostasis,thus inhibiting ROS regeneration at the source.Here,we designed a KTP-targeting peptide-modified yolk-shell structure of liposome–poly(ethylene glycol)methyl ether-block-poly(L-lactide-co-glycolic)(mPLGA)hybrid nanoparticles(<100 nm),with the characteristics of high encapsulation rate,high colloid stability,facile modification,and prolonged blood circulation time.Once the BA/mPLGA@Lipo-KTP was targeted to the site of kidney injury,the cholesteryl hemisuccinate(CHEMS)in the phospholipid bilayer,as an acidic cholesterol ester,was protonated in the simulated inflammatory slightly acidic environment(pH 6.5),causing the liposomes to rupture and release the BA/mPLGA nanoparticles,which were then depolymerized by intracellular esterase.The BAPTA-AM was diffused and hydrolyzed to produce BAPTA,which can rapidly cut off the malignant loop of calcium overload/ROS generation at its source,blocking the endoplasmic reticulum(ER)apoptosis pathway(ATF4–CHOP–Bax/Bcl-2,Casp-12–Casp-3)and the inflammatory pathway(TNF-α–NF-κB–IL-6 axes),thus alleviating pathological changes in kidney tissue,thereby inhibiting the expression of renal tubular marker kidney injury molecule 1(Kim-1)(reduced by 82.9%)and also exhibiting prominent anti-apoptotic capability(TUNEL-positive ratio decreased from 40.2%to 8.3%),significantly restoring renal function.Overall,this research holds huge potential in the treatment of I/R injury-related diseases.

Aerobic exercise combined with huwentoxin-I mitigates chronic cerebral ischemia injury

Ca2＋ channel blockers have been shown to protect neurons from ischemia, and aerobic exercise has significant protective effects on a variety of chronic diseases. The present study injected huwentoxin-I （HWTX-I）, a spider peptide toxin that blocks Ca2＋ channels, into the caudal vein of a chronic cerebral ischemia mouse model, once every 2 days, for a total of 15 injections. During this time, a subgroup of mice was subjected to treadmill exercise for 5 weeks. Results showed amelioration of cortical injury and improved neurological function in mice with chronic cerebral ischemia in the HWTX-I ＋ aerobic exercise group. The combined effects of HWTX I and exercise were superior to HWTX-I or aerobic exercise alone. HWTX-I effectively activated the Notch signal transduction pathway in brain tissue. Aerobic exercise up-regulated synaptophysin mRNA expression. These results demonstrated that aerobic exercise, in combination with HWTX-I, effectively relieved neuronal injury induced by chronic cerebral ischemia via the Notch signaling pathway and promoting synaptic regeneration.

Protective effects of glutamine preconditioning on ischemia-reperfusion injury in rats

BACKGROUND:Hepatic ischemia-reperfusion injury is a common phenomenon in hepatic surgical procedures and can result in further severe damage.This study aimed to investigate the protective effects of glutamine preconditioning on hepatic ischemia-reperfusion injury in rats and its dose-dependency. METHODS:Thirty-two healthy male Wistar rats were randomly divided into four groups(n=8 per group).One group received 0.9%NaCl(control)and the other three received glutamine(Gln groups)4 hours before ischemia.The Gln groups were named GL,GM,and GH according to the glutamine dose.The liver was subjected to 1 hour of ischemia and 2 hours of reperfusion. Two hours later,the levels of alanine aminotransferase(ALT), intracellular free calcium(Ca 2+ ),and activity of Na + /K + adenosine triphosphatase(ATPase)and superoxide dismutase (SOD)were assessed,and liver tissue sections were examined under a microscope. RESULTS:The Gln and control groups differed in the concentration of intracellular free calcium(P<0.05),and the activity of Na + /K + ATPase and SOD in the Gln groups was higher than in the control group(P<0.05).The ALT level was lower in the GM and GH groups than in the control group(P<0.05).The levels of Na + /K + ATPase and SOD rose gradually with increasing glutamine dose(P<0.05),and the concentration of Ca 2+ declined gradually with increasing glutamine dose(P<0.05).The degree of hepatocyte injury was milder in the Gln groups than in the control group. CONCLUSIONS:Glutamine preconditioning protected effectively against hepatic ischemia-reperfusion injury.These protective effects were related to the dose of glutamine and due to the reduction of intracellular calcium overload and the improvements in the activity of Na + /K + ATPase and SOD.

Effect of Cholic Acid on Fetal Cardiac Myocytes in Intrahepatic Choliestasis of Pregnancy

This study examined the effect of cholic acid （CA） on cultured cardiac myoeytes （CMs） from neonatal rats with an attempt to explore the possible mechanism of sudden fetal death in intra- hepatic cholestasis of pregnancy （ICP）. Inverted microscopy was performed to detect the impact of CA on the beating rates of rat CMs. MTT method was used to study the effect of CA on the viability of CMs. CMs cultured in vitro were incubated with 10 ~maol/L Ca2＋-sensitive fluorescence indicator fluo-3/AM. The fluorescence signals of free calcium induced by CA were measured under a laser scanning confocal microscope. The results showed that CA decreased the beating rates of the CMs in a dose-dependent manner. CA could suppress the activities of CMs in a time- and dose-dependent manner. CA increased the concentration of intracellular free calcium in a dose-dependent manner. Our study suggested that CA could inhibit the activity of CMs by causing calcium overload, thereby leading to the sudden fetal death in ICP.

Recombinant AAV-mediated Expression of Human BDNF Protects Neurons against Cell Apoptosis in Aβ-induced Neuronal Damage Model

The human brain-derived neurotrophic factor (hBDNF) gene was cloned by polymerase chain reaction and the recombinant adeno-associated viral vector inserted with hBDNF gene (AAV-hBDNF) was constructed. Cultured rat hippocampal neurons were treated with Aβ25-35 and se- rued as the experimental Aβ-induced neuronal damage model (AD model), and the AD model was infected with AAV-hBDNF to explore neuroprotective effects of expression of BDNF. Cell viability was assayed by MTT. The expression of bcl-2 anti-apoptosis protein was detected by immunocyto- chemical staining. The change of intracellular free Ca ion ([Ca2+]i) was measured by laser scanning confocal microscopy. The results showed that BDNF had protective effects against Aβ-induced neu- ronal damage. The expression of the bcl-2 anti-apoptosis protein was raised significantly and the bal- ance of [Ca2+]i was maintained in the AAV-hBDNF treatment group as compared with AD model group. These data suggested that recombinant AAV mediated a stable expression of hBDNF in cul- tured hippocampal neurons and resulted in significant neuron protective effects in AD model. The BDNF may reduce neuron apoptosis through increasing the expression of the bcl-2 anti-apoptosis protein and inhibiting intracellular calcium overload. The viral vector-mediated gene expression of BDNF may pave the way of a novel therapeutic strategy for the treatment of neurodegenerative dis- eases such as Alzheimer’s disease.

Does closure of acid-sensing ion channels reduce ischemia/reperfusion injury in the rat brain?

Acidosis is a common characteristic of brain damage. Because studies have shown that permeable Ca2＋-acid-sensing ion channels can mediate the toxic effects of calcium ions, they have become new targets against pain and various intracranial diseases. However, the mechanism associated with expression of these channels remains unclear. This study sought to observe the expression characteristics of permeable Ca2＋-acid-sensing ion channels during different reperfusion inflows in rats after cerebral ischemia. The rat models were randomly divided into three groups： adaptive ischemia/reperfusion group, one-time ischemia/reperfusion group, and severe cerebral ischemic injury group. Western blot assays and immunofluorescence staining results exhibited that when compared with the one-time ischemia/reperfusion group, acid-sensing ion channel 3 and Bcl-x/I expression decreased in the adaptive ischemia/reperfusion group. Calmodulin expression was lowest in the adaptive ischemia/reperfusion group. Following adaptive reperfusion, common carotid artery flow was close to normal, and the pH value improved. Results verified that adaptive reperfusion following cerebral ischemia can suppress acid-sensing ion channel 3 expression, significantly reduce Ca2＋ influx, inhibit calcium overload, and diminish Ca2＋ toxicity. The effects of adaptive ischemia/reperfusion on suppressing cell apoptosis and relieving brain damage were better than that of one-time ischemia/reperfusion.

Dantrolene enhances the protective effect of hypothermia on cerebral cortex neurons

Therapeutic hypothermia is the most promising non-pharmacological neuroprotective strategy against ischemic injury. However, shivering is the most common adverse reaction. Many studies have shown that dantrolene is neuroprotective in in vitro and in vivo ischemic injury models. In addition to its neuroprotective effect, dantrolene neutralizes the adverse reaction of hypothermia. Dantrolene may be an effective adjunctive therapy to enhance the neuroprotection of hypothermia in treating ischemic stroke. Cortical neurons isolated from rat fetuses were exposed to 90 minutes of oxygen-glucose deprivation followed by reoxygenation. Neurons were treated with 40 μM dantrolene, hypothermia（at 33°C）, or the combination of both for 12 hours. Results revealed that the combination of dantrolene and hypothermia increased neuronal survival and the mitochondrial membrane potential, and reduced intracellular active oxygen cytoplasmic histone-associated DNA fragmentation, and apoptosis. Furthermore, improvements in cell morphology were observed. The combined treatment enhanced these responses compared with either treatment alone. These findings indicate that dantrolene may be used as an effective adjunctive therapy to enhance the neuroprotective effects of hypothermia in ischemic stroke.

SENP2-mediated SERCA2a deSUMOylation increases calcium overload in cardiomyocytes to aggravate myocardial ischemia/reperfusion injury

Background:Sarcoplasmic reticulum calcium ATPase 2a(SERCA2a)is a key protein that maintains myocardial Ca2+homeostasis.The present study aimed to investigate the mechanism underlying the SERCA2a-SUMOylation(small ubiquitinlike modifier)process after ischemia/reperfusion injury(I/RI)in vitro and in vivo.Methods:Calcium transient and systolic/diastolic function of cardiomyocytes isolated from Serca2a knockout(KO)and wildtype mice with I/RI were compared.SUMO-relevant protein expression and localization were detected by quantitative real-time PCR(RT-qPCR),Western blotting,and immunofluorescence in vitro and in vivo.Serca2a-SUMOylation,infarct size,and cardiac function of Senp1 or Senp2 overexpressed/suppressed adenovirus infected cardiomyocytes,were detected by immunoprecipitation,triphenyltetrazolium chloride(TTC)-Evans blue staining,and echocardiography respectively.Results:The results showed that the changes of Fura-2 fluorescence intensity and contraction amplitude of cardiomyocytes decreased in the I/RI groups and were further reduced in the Serca2a KO+I/RI groups.Senp1 and Senp2 messenger ribose nucleic acid(mRNA)and protein expression levels in vivo and in cardiomyocytes were highest at 6 h and declined at 12 h after I/RI.However,the highest levels in HL-1 cells were recorded at 12 h.Senp2 expression increased in the cytoplasm,unlike that of Senp1.Inhibition of Senp2 protein reversed the I/RI-induced Serca2a-SUMOylation decline,reduced the infarction area,and improved cardiac function,while inhibition of Senp1 protein could not restore the above indicators.Conclusion:I/RI activated Senp1 and Senp2 protein expression,which promoted Serca2a-deSUMOylation,while inhibition of Senp2 expression reversed Serca2a-SUMOylation and improved cardiac function.

THE EXPERIMENTAL RESEARCH ON CARDIOPLEGIC SOLU-TION CONTAINING SELENIUM AND MAGNESIUM AGAINST MYOCARDIAL ISCHEMIA REPERFUSION DAMAGE

The model of this test was set up according to Langendoff isolated heart reperfusion mechanics. The experimental research was designed to observe the protective effects on ischemic andreperfuslon myocardial tissue by using ST. Thomas cardioplegic solution containing selenium andmagnesium. We conclude that using cold crystallold cardioplegic solution containing Se'+, Mg' 4 canobviously reduce ischemic and reperfusion myocardlal injury and bas an advantage of recovering myocardial runctlon after operation by observing the content or lactic dehydrogenase (LDH); creatineI,kasphoklnase CK in the coronary vessel's sinus reflux solutlonl glutatblone peroxldase (GPX); suI,eroxlde dismutase (SOD); maloydladehyde (MDA ) I Se4+ .Mg'+ .Ca'+ and cia-nging or myocardialultrastructure.

Biodegradable calcium sulfide-based nanomodulators for H_(2)S-boosted Ca^(2+)-involved synergistic cascade cancer therapy

Hydrogen sulfide(H_(2)S)is the most recently discovered gasotransmitter molecule that activates multiple intracellular signaling pathways and exerts concentration-dependent antitumor effect by interfering with mitochondrial respiration and inhibiting cellular ATP generation.Inspired by the fact that H_(2)S can also serve as a promoter for intracellular Ca^(2+)influx,tumor-specific nanomodulators(I-CaS@PP)have been constructed by encapsulating calcium sulfide(CaS)and indocyanine green(ICG)into methoxy poly(ethylene glycol)-b-poly(lactide-co-glycolide)(PLGA-PEG).I-CaS@PP can achieve tumor-specific biodegradability with high biocompatibility and pH-responsive H_(2)S release.The released H_(2)S can effectively suppress the catalase(CAT)activity and synergize with released Ca^(2+)to facilitate abnormal Ca^(2+)retention in cells,thus leading to mitochondria destruction and amplification of oxidative stress.Mitochondrial dysfunction further contributes to blocking ATP synthesis and downregulating heat shock proteins(HSPs)expression,which is beneficial to overcome the heat endurance of tumor cells and strengthen ICG-induced photothermal performance.Such a H_(2)S-boosted Ca^(2+)-involved tumor-specific therapy exhibits highly effective tumor inhibition effect with almost complete elimination within 14-day treatment,indicating the great prospect of CaS-based nanomodulators as antitumor therapeutics.

Blocking Cyclic Adenosine Diphosphate Ribose-mediated Calcium Overload Attenuates Sepsis-induced Acute Lung Injury in Rats

Background： Acute lung injury （ALI） is a common complication of sepsis that is associated with high mortality, lntracellular Ca^2＋ overload plays an important role in the pathophysiology of sepsis-induced ALl, and cyclic adenosine diphosphate ribose （cADPR） is an important regulator of intracellular Ca^2＋ mobilization. The cluster of differentiation 38 （CD38）/cADPR pathway has been found to play roles in multiple inflammatory processes but its role in sepsis-induced ALl is still unknown. This study aimed to investigate whether the CD38/cADPR signaling pathway is activated in sepsis-induced ALl and whether blocking cADPR-mediated calcium overload attenuates ALl. Methods： Septic rat models were established by cecal ligation and puncture （CLP）. Rats were divided into the sham group, the CLP group, and the CLP＋ 8-bromo-cyclic adenosine diphosphate ribose （8-Br-cADPR） group. Nicotinamide adenine dinucleotide （NAD＋）, cADPR, CD38, and intracellular Ca^2＋ levels in the lung tissues were measured at 6, 12, 24, and 48 h after CLP surgery. Lung histologic injury, tumor necrosis factor （TNF）-a, malondialdehyde （MDA） levels, and superoxide dismutase （SOD） activities were measured. Results： NAD＋, cADPR, CD38, and intracellular Ca-＋ levels in the lungs of septic rats increased significantly at 24 h after CLP surgery. Treatment with 8-Br-cADPR, a specific inhibitor of cADPR, significantly reduced intracellular Ca^2＋ levels （P = 0.007）, attenuated lung histological injury （P = 0.023）, reduced TNF-a and MDA levels （P 〈 0.001 and P = 0.002, respectively） and recovered SOD activity （P = 0.031） in the lungs of septic rats. Conclusions： The CD38/cADPR pathway is activated in the lungs of septic rats, and blocking cADPR-mediated calcium overload with 8-Br-cADPR protects against sepsis-induced ALl.

An iron-dependent form of non-canonical ferroptosis induced by labile iron

Ferroptosis is a recently identified iron-dependent form of nonapoptotic cell death characterized by reactive oxygen species(ROS) generation and lipid peroxidation.Here,we report a novel iron-dependent form of ferroptosis induced by labile iron and investigate the mechanism underlying this process.We find that labile iron-induced ferroptosis is distinct from canonical ferroptosis and is linked to the mitochondrial pathway.Specifically,the mitochondrial calcium uniporter mediates the ferroptosis induced by labile iron.Interestingly,cells undergoing labile iron-induced ferroptosis exhibit cytoplasmic features of oncosis and nuclear features of apoptosis.Furthermore,labile iron-induced ferroptosis involves a unique set of genes.Finally,labile ironinduced ferroptosis was observed in liver subjected to acute iron overload in vivo.Our study reveals a novel form of ferroptosis that may be implicated in diseases caused by acute injury.

Anti-oxidation of Tanshinone Ⅱ_A and Prohibitin on Cardiomyocytes

Objective To investigate the anti-apoptotic mechanism of tanshinone ⅡA and the function of prohibitin (PHB) on myocardial cells apoptosis induced by hydrogen peroxide (H2O2). Methods Myocardial cells were primary cultured neonate rat were cultured in medium with 200 μmol/L H2O2, and the medium was supplemented with tanshinone ⅡA (1 × 10-4 mol/L) in advance for 24 h. PHB in myocardial cells was knocked down by RNA interference, and the expression level of PHB was determined by Western blotting analysis. Flow cytometric analysis was used to detect apoptosis rate, intracellular calcium concentration ([Ca2+]i), and mitochondrial membrane potential (MMP). Results H2O2-mediated cell apoptosis resulted in activation of PHB, increasing of [Ca2+]i, and decreasing of MMP. Tanshinone ⅡA profoundly inhibited myocardial cell apoptosis induced by H2O2, decreased [Ca2+]i, and increased MMP. Specific silence of PHB by siRNA down-regulated the expression level of PHB, increased apoptosis rate and [Ca2+]i, and decreased MMP. Conclusion The results demonstrate that tanshinone ⅡA could attenuate apoptosis induced by H2O2, and the activation of PHB induced by H2O2 is the major regulatory pathway of cyto-protective gene expression against oxidative stress.

P2X_7 receptors in cerebral ischemia

Cerebral ischemia is one of the most common diseases resulting in death and disability in aged people. It leads immediately to rapid energy failure, ATP depletion, and ionic imbalance, which increase extracellular ATP levels and accordingly activate P2X7 receptors. These receptors are ATP-gated cation channels and widely distributed in nerve cells, especially in the immunocompetent cells of the brain. Currently, interest in the roles of P2Xz receptors in ischemic brain injury is growing. In this review, we discuss recent research progress on the actions of P2X7 receptors, their possible mechanisms in cerebral ischemia, and the potential therapeutic value of P2X7 receptor antagonists which may provide a new target both for clinical and for research purposes.