ATP-sensitive potassium channels:novel potential roles in Parkinson's disease

The ATP-sensitive potassium（KATP）channels which extensively distribute in diverse tissues（e.g.vascular smooth muscle,cardiac cells,and pancreas）are well-established for characteristics like vasodilatation,myocardial protection against ischemia,and insulin secretion.The aim of this review is to get insight into the novel roles of KATPchannels in Parkinson＇s disease（PD）,with consideration of the specificities KATPchannels in the central nervous system（CNS）, such as the control of neuronal excitability,action potential,mitochondrial function and neurotransmitter release.

Effect of simulated ischemia-reperfusion on I_f in sinoatrial node cells and the intervention of KATP channel opener

Objective: To study the effect of simulated ischemia-reperfusion (I/R) on If of sinoatrial node (SAN) cells and the intervention of KATP channel opener Pinacidil. Methods: The SAN cells of the neonatal rats were detached and purified 2 d before the experiment. The experimental animals were randomly divided into the control group, group of simulated I/R, group intervened with KATP channel opener Pinacidil (P+ I/R) and group intervened with KATP channel blocking agent 5-HD (5-HD + P + I/R & 5-HD + I/R). The If density of each group was measured by technique of routine whole cell patch clamp and multiple-catheter perfusion system and the If activated curve in each group was drawn. Results: ①Under different directive potentials, the If density of the SAN cells in I/R group increased significantly, compared with that in the control group ( P < 0.01); that in P + I/R group decreased significantly, compared with that in I/R group ( P < 0.01); the If density values in 5-HD + P + I/R group and 5-HD + I/R group increased significantly, compared with that in P + I/R group, but showed no significant difference with that in I/R group. ②Compared with that in the control group, the If activated curve of the SAN cells moved rightwards under ultimate activating potential, half of which was from - 108.0 ± 12.4 to - 89.5 ± 7.2 mV ( P <0.01); compared with that in I/R group, If activated curve of the SAN cells moved leftwards under ultimate activating potential, half of which was the range from -99.5± 10.8 mV (P<0.05); KATP channel blocking agent 5-HD could block the effect of Pinacdil on If activated curve. Conclusion: KATP channel opener Pinacidil can antagonize the effect of simulated I/R on the If of SAN cells, which may be beneficial to the maintenance of the relative stability of ion steady state and electrophysiological activities under condition of simulated I/R.

Transient diabetes mellitus with ABCC8 variant successfully treated with sulfonylurea:Two case reports and review of literature

BACKGROUND Transient neonatal diabetes mellitus(TNDM)is a rare form of diabetes mellitus that usually presents within the first 6 mo of life.Patients often enter remission within several months,although relapse can occur later in life.Mutations in the ABCC8 gene,which encodes the sulfonylurea receptor 1 of the ATP-sensitive potassium channel in pancreatic beta cells,are associated with TNDM and permanent neonatal diabetes.This study describes a novel de novo c.3880C>T heterozygous ABCC8 variant that causes TNDM and can be treated with sulfonylurea therapy.CASE SUMMARY We retrospectively analyzed 2 Chinese patients with TNDM who were diagnosed,treated,or referred for follow-up between September 2017 and September 2023.The patients were tested for mutations using targeted next-generation sequencing.Patients with neonatal diabetes mellitus caused by a c.3880C>T heterozygous missense variant in the ABCC8 gene have not been reported before.Both children had an onset of post-infectious diabetic ketoacidosis,which is worth noting.At a follow-up visit after discontinuing insulin injection,oral glyburide was found to be effective with no adverse reactions.CONCLUSION Early genetic testing of neonatal diabetes mellitus aids in accurate diagnosis and treatment and helps avoid daily insulin injections that may cause pain.

C-reactive protein aggravates myocardial ischemia/reperfusion injury through activation of extracellular-signal-regulated kinase 1/2

Background Ischemia/reperfusion injury （IRI） is an inflammatory response that occurs when tissue is reperfused following a prolonged period of ischemia. Several studies have indicated that C-reactive protein （CRP） might play an important role in inducing IRI. However, the effects of CRP on myocardial IRI and the underlying mechanisms have not been fully elucidated. This study aimed to investigate the association between CRP and myocardial IRI and the underlying mechanisms. Methods We simulated ischemia/reperfusion using oxygen-glucose deprivation/ reoxygenation （OGD/R） in neonatal Sprague-Dawley rat cardiomyocytes; reperfusion injury was induced by three hours of hypoxia with glucose and serum deprivation followed by one hour of reperfusion. Cell viability was tested with MTS assays, and cardiomyocyte damage was evaluated by lactate dehydrogenase （LDH） leakage. Mitochondrial membrane potential was measured using tetramethylrhodamine ethyl ester （TMRE） and mitochondrial permeability transition pore （mPTP） opening was measured using calcein/AM; both TMRE and caocein/AM were visualized with laser scanning confocal microscopy. In addition, we studied the signaling pathways underlying CRP-mediated ischemia/reperfusion injury via Western blot analysis. Results Compared with the simple OGD/R group, after intervention with 10 pg/mL CRP, cell viability decreased markedly （82.36 % ± 6.18% vs. 64.84% ± 4.06%, P = 0.0007）, and the LDH leakage significantly increased （145.3 U/L ± 16.06 U/L vs. 208.2 U/L ± 19.23 U/L, P = 0.0122）. CRP also activated mPTP opening and reduced mitochondrial membrane potential during myocardial ischemia/reperfusion. Pretreatment with 1 pM atorvastatin （Ator） before CRP intervention protected cardiomyocytes from IRI. Mitochondrial KATP channel opener diazoxide and mPTP inhibitor cyclosporin A also offset the effects of CRP in this process. The level of phosphorylated extracellular-signal-regulated kinase （ERK） 1/2 was significantly higher after pre-treatment with CRP compared with the OGD/R group （170.4% ± 3.00% v.v. 93.53% ± 1.94%, P 〈 0.0001）. Western blot analysis revealed that Akt expression was markedly activated （184.2% ± 6.96% vs. 122.7% ± 5.30%, P = 0.0003） and ERK 1/2 phosphorylation significantly reduced after co-treatment with Ator and CRP compared with the level after CRP pretreatment alone. Conclusions Our results suggested that CRP directly aggravates myocardial IRI in myocardial cells and that this effect is primarily mediated by inhibiting mitochondrial ATP- sensitive potassium （mitoKATp） channels and promoting mPTP opening. Ator counteracts these effects and can reduce CRP-induced IRI. One of the mechanisms of CRP-induced IRI may be related to the sustained activation of the ERK signaling pathway.

Effect of indomethacin on electrical field stimulation-induced contractions of isolated transverse and longitudinal rat gastric fundus strips

AIM: To study the effects of indomethacin on the isolated transverse and longitudinal rat gastric fundus strips.METHODS: The strips were suspended in an organ bath containing oxygenated Krebs solution, and contractile responses to electrical field stimulation were recorded on a physiograph in an isotonic manner after administration of cumulative concentrations of indomethacin. The effects of indomethacin on the strips pretreated with KATP channel modulators, diazoxide and glybenclamide were studied.RESULTS: Treatment of the transverse strips with indomethacin resulted in a concentration-dependent inhibitory response. In longitudinal strips, biphasic responses were seen, which included a stimulatory response at low concentrations of indomethacin, followed by an inhibitory response at higher concentrations.Diazoxide pre-treatment inhibited the stimulatory response of longitudinal strips. Glybenclamide pre-treatment not only blocked inhibitory effect of the low concentrations of indomethacin on transverse strips, but also increased the amplitude of contractions. Moreover, the drug decreased the amplitude of contractions in longitudinal strips.CONCLUSION: Responses of the isolated longitudinal and transverse rat gastric fundus strips to indomethacin are not similar, and are influenced by KATP channel modulators.

Differentially expressed phosphoproteins in diazoxide-pretreated ventricular myocytes by two-dimensional electrophoresis and mass spectrometry in vitro

Objectives To analyze and identify differentially expressed phosphoproteins associated with mitochondrial KATP channel opening. Methods： Adult rat ventricular myocytes were isolated, cultured, and identified, and pretreated without or with 100 μmol/L diazoxide for 10 min. Phosphoproteins prepared and enriched from the control and diazoxide-pretreated cells were separated by two-dimensional gel electrophoresis （2-DE） followed by sliver staining. The obtained interesting phosphoproteins were further identified by mass spectrometry. Results. Associated with diazoxide preconditioning, the proteins of chaperonin containing TCP-1 and hypothetical protein XP-346548 were phosphorylated significantly （P〈0. 01）, while the 94-kDa glucose-regulated protein, calpactin I heavy chain and ferritin were dephosphorylated markedly （P〈0. 01）. Conclusion： These findings suggest that cardiomyocytes undergo significant posttranslational modification via phosphorylation in a multitude of proteins in order to respond diazoxide preconditioning, and these phosphorylated protein may mediate the downstream signaling of cardioprotection by mitochondrial KATp channel opening induced by ischemic preconditioning.

Protective effect and mechanism of K_(ATp) channel opener on the sinoatrial node cells of neonatal rat cultured in simulated ischemia-reperfusion

Objective: To study the effect of KATp channel opener and its possible mechanism on the sinoatrial node cells of neonatal rats which were cultured under simulated ischemia-reperfusion. Methods: Freshly isolated sinoatrial node (SAN) cells of neonatal rats were purified and cultured for 2 d, and then they were randomly divided into the control, simulated ischemia-reperfusion group (I/R group) , group intervened with KATp channel opener pinacidil (P + I/R group), KATP Channel blocking agent 5-HD (5-HD + I/R group) , and group with the 2 agents at same time (5-HD + P + I/R group) . The survival rate of cells was measured by flow cytometry and the content of intracellular calcium in the cells of each group was detected with laser confocal microscopy. Results: ① The survival rate of SAN cells in I/R group [ (51. 79±6. 28)% ] was remarkably significantly lower than in control [ (95. 08±10. 48)% ] (P < 0.001), and very significantly lower than in P + I/R group [ (63. 77±5. 35) % ] (P<0.01), however, those of 5-HD + P + I/R group [(52. 88±6. 25)% ] and 5-HD+I/R group [ (53. 16±5. 35)% ] was significantly lower compared with that in P + I/R group (P <0. 01) ; ② When the average fluorescence intensity of sinoatrial node cells in the control was regarded as 100% , the relative fluorescence intensities of each group were: ( 374±52) % in I/R group, significantly higher than that of control (P <0. 01) ; ( 162±20)% in P + I/R group, declining significantly than that of I/R group (P<0.01); (385?6)% in 5-HD+ P + I/R group and (379±44)% in 5-HD + I/R group, increasing significantly than that of I/R group (P<0.01). Conclusion: ① Simulated ischemia-reperfusion can significantly reduce the survival rate of SAN cells, and can also lead to the overload of intracellular calcium in them.② KATp channel opener, pinacidil, exerts protective effect on the cells under simulated ischemia-reperfusion, which may be associated with the decrease of intracellular calcium loading in them.

Kaiyuqingre formula improves insulin secretion via regulating uncoupling protein-2 and KATPchannel

Background Type 2 diabetes mellitus （T2DM） results from the complex association of insulin resistance and pancreatic β-cell failure. Recent studies have shown that patients diagnosed with T2DM present with a significant decrease in β-cell function, which can be further compromised during the progression of the disease. Several mechanisms have been shown to play a role in this process such as glucotoxicity and lipotoxicity, which contribute to accelerating insulin secretion. In this regard, Chinese medicine has a certain advantage. This experiment was performed to observe the effect of a Chinese medicine named Kaiyuqingre formula （KYQRF） on β-cell function and its mechanisms of action therein. Methods High glucose was used to set up a model of β-cell function failure. At the same time, medicated serum of KYQRF with different doses were administered to the cells. Rosiglitazone was taken as a control to observe the changes in insulin secretion, ATP-sensitive K＋ channels （KATP channel） and uncoupling protein-2 （UCP-2） in each group. Results KYQRF had some effects on the insulin secretion. In a low glucose environment, no effective change in insulin secretion was observed （P 〉0.05）. However, insulin levels increased significantly when INS-1 cells were exposed to a high glucose environment （P 〈0.05）. KYQRF could also enhance cell viability （P 〈0.05） in an effect similar to rosiglitazone. Although KYQRF had no effect on inwardly rectifying potassium channels （Kir6.2） （P 〉0.05）, it could decrease the overexpression of both UCP-2 and sulfonylurea receptor 1 （P〈0.05）. Conclusion KYQRF can protect islet function by decreasing UCP-2 and sulfonylurea receptor 1.

Astragaloside IV Regulates Expression of ATP-sensitive Potassium Channel Subunits after Ischemia-reperfusion in Rat Ventricular Cardiomyocytes

Objective: Astragaloside IV (AsIV) is the major effective component extracted from the Chinese herb Astragalus membranaceus, which has been widely used to treat cardiovascular disease. Recent studies have shown that AsIV can potentially protect the heart from myocardial ischemic injury, but the mechanisms of action are unknown. ATP-sensitive potassium (KATP) channels are activated during ischemia and exert a compensatory protective effect on cardiomyocytes. We therefore examined the effects of AsIV on KATP channel currents and channel expression in isolated rat ventricular cardiomyocytes after ischemia-reperfusion injury. Methods: Forty Wistar rats were divided into five groups: control group, ischemia-reperfusion (IP) group, IP + glibenclamide group, IP + pinacidil group and IP + AsIV group. The ischemia-reperfusion injury model was established in enzymatically isolated ventricular cardiomyocytes by perfusion with calcium-free Tyrode solution for 10 min, arrest for 30 min, and reperfusion for 45 min. The different drugs were applied for 10-15 min, and the KATP channel current (IKATP) was recorded with voltage-clamp mode by whole-cell patch-clamp technique. Protein and mRNA expression of the KATP channel subunits Kir6.1, Kir6.2, SUR2A and SUR2B was quantified using western blotting and real-time PCR. Results: The KATP current in IP group was significantly greater than that in control group (211.45±33.67 vs 83.51±23.67 pA; P<0.01). Glibenclamide (10 μmol/L) blocked KATP currents, whereas both AsIV (1 mg/L) and the known channel opener pinacidil (50 μmol/L) significantly increased IKATP (P<0.05). Consistent with this, AsIV significantly up-regulated protein and mRNA expression of Kir6.1, Kir6.2, SUR2A, SUR2B (P<0.01 vs IP group). Conclusion: The protective effects of AsIV in ischemia-reperfusion injury may be related to the up-regulation of several KATP channel subunits and facilitation of KATP currents.

Effect of electronic stimulation at Neiguan(PC 6) acupoint on gene expression of adenosine triphosphate-sensitive potassium channel and protein kinases in rats with myocardial ischemia

OBJECTIVE:To investigate the effects of electronic stimulation at acupoints Neiguan(PC 6) and Lieque(LU 7) on the gene expression of the adenosine triphosphate(ATP)-Sensitive potassium channel(KATP:Kir6.1,Kir6.2,SUR2 A,and SUR2B) and protein kinases(PKA,PKG,and PKCβ2) in myocardial cells of rats with myocardial ischemia(Ml) induced by isoproterenol(ISO).METHODS:Rats were randomly divided into a control,model,Neiguan(PC 6),Lieque(LU 7),and non-acupoint groups.The Ml model was established by injecting rats with ISO.Electro-acupuncture treatment was given to the acupuncture groups,once a day for 7 days.Gene expression was analyzed with real-time PCR.RESULTS:The gene expression of KATP and protein kinases in the model group was higher than those in the control group(P < 0.05).After acupuncture treatment,the KATP and protein kinase expression levels were significantly lower in the Neiguan(PC 6)and Lieque(LU 7) groups compared with the model group[P < 0.05).The Neiguan(PC 6) group lowered these levels significantly more than that of the Lieque(LU 7) group(P < 0.05).No significant differences were observed between the model and non-acupoint groups(P > 0.05).CONCLUSION:Our findings suggest that electronic needling of Neiguan(PC 6) can both reduce the gene expression of KATP and protein kinases in rats with ISO-induced Ml.

Hydrogen sulfide defends against the cardiovascular risk of Nw-nitro-L-argininemethyl ester-induced hypertension in rats via the nitric oxide/endothelial nitric oxide synthase pathway

Background Dyslipidemia caused by liver injury is a significant risk factor for cardiovascular complications.Previous studies have shown that hydrogen sulfide （H2S） protects against multiple cardiovascular disease states in a similar manner as nitric oxide （NO）,and NO/endothelial nitric oxide synthase （eNOS） pathway is the key route of NO production.The purpose of this study was to investigate whether H2S can ameliorate the high blood pressure and plasma lipid profile in Nw-nitro-L-argininemethyl ester （L-NAME）-induced hypertensive rats by NO/eNOS pathway.Methods Thirty-six 4-week old Sprague-Dawley （SD） male rats were randomly assigned to 6 groups （n=6）：control group,L-NAME group,control ＋ glibenclamide group,control ＋ NaHS group,L-NAME ＋ NaHS group,and L-NAME ＋ NaHS ＋ glibenclamide group.Measurements were made of plasma triglycerides （TG）,low-density lipoprotein （LDL）,high-density lipoprotein （HDL）,total cholesterol （CHO）,glutamic-pyruvic transaminase （ALT） levels after 5 weeks.Then measurements of NO level and proteins expression of eNOS,P-eNOS,AKT,P-AKT were made in liver tissue.Results After 5 weeks of L-NAME treatment,the blood pressure,plasma TG （（1.22±0.12） mmol/L in L-NAME group vs.（0.68±0.09） mmol/L in control group; P ＜0.05） and LDL （（0.54±0.04） mmol/L in L-NAME group vs.（0.28±0.02） mmol/L in control group; P ＜0.05） concentration were significantly increased,and the plasma HDL （（0.26±0.02） mmol/L in L-NAME group vs.（0.69±0.07） mmol/L in control group; P ＜0.05） concentration significantly decreased.Meanwhile the rats treated with L-NAME exhibit dysfunctional eNOS,diminished NO levels （（1.36±0.09） mmol/g protein in L-NAME group vs.（2.34±0.06） mmol/g protein in control group; P ＜0.05） and pathological changes of the liver.H2S therapy can markedly decrease the blood pressure （（37.25±4.46） mmHg at the fifth week; P ＜0.05）,and ameliorate the plasma TG （（0.59±0.06） mmHg）,LDL （（0.32±0.04） mmHg）,and HDL （（0.46±0.03） mmHg） concentration in L-NAME ＋ NaHS group （all P ＜0.05）.H2S therapy can also restore eNOS function and NO bioavailability and attenuate the pathological changes in the liver in L-NAME-induced hypertensive rats.Conclusion H2S protects the L-NAME-induced hypertensive rats against liver injury via NO/eNOS pathway,therefore de.creases the cardiovascular risk.

The functional change of perivascular adipose tissue in hypertensive rats and its mechanisms

Background Recent studies have showed that perivascular adipose tissue （PVAT） may secrete the adventitial-derived relaxing factor （ADRF） to affect vascular function.However,the functional change of ADRF in hypertensive status is seldom studied;and the mechanisms of ADRF remain unclear.Our study examined the ADRF secreted by perivascular adipose tissue of control rats with normal blood pressure （Wistar Kyoto rats,WKY） and discussed the mechanisms of ADRF;We observed the functional change in ADRF of perivascular adipose tissue in spontaneously hypertensive rats （SHRs）.Method The two adjacent thoracic aorta rings of SHR and WKY rats were divided into naked vessel subgroup and PVAT subgroup.The differences of vascular contractility between the two subgroups induced by 10-6 mmol/L phenylephrine were compared.The effect of PVAT culture medium of WKY on the vascular tension of Fat （-） vessels was observed by liquid transfer measure.The mechanism of ADRF was determined by tool drugs.Results In WKY group,vascular contractility of Fat （＋） subgroup was lower than that of the Fat （-） subgroup （P 0.05）;while in SHR group,there was no difference between the two subgroups （P 0.05）.Transferring the incubation solution of WKY Fat （＋） subgroup to the matched Fat （-） subgroup induced rapid vasodilation.When incubating blood vessels in calcium free PSS solution,there was no significant difference of phenylephrine-induced vasoconstriction between Fat （-） and Fat （＋） subgroup.Both glibenclamide,the blocker of ATP-sensitive potassium （KATP） channel and Tetraethy-lammonium chloride （TEA）,the inhibitor of calcium-dependent potassium （KCa） channel,effectively inhibited vasodilation function of ADRF.Conclusions Perivascular adipose tissue in WKY releases ADRF which can cause vasodilation,while this function was inhibited in SHR.ADRF acts through the activation of KCa and KATP channels and calcium ion is involved.