Effects of unsaturated fatty acids on calcium-activated potassium current in gastric myocytes of guinea pigs

AIM: To investigate the effects of exogenous unsaturated fatty acids on calcium-activated potassium current [IK(Ca)] in gastric antral circular myocytes of guinea pigs. METHODS: Gastric myocytes were isolated by collagenase from the antral circular layer of guinea pig stomach. The whole-cell patch clamp technique was used to record /K(Ca) in the isolated single smooth muscle cells with or without different concentrations of arachidonic acid (AA), linoleic acid (LA), and oleic acid (OA). RESULTS: AA at concentrations of 2,5 and 10 μmol/L markedly increased IK(Ca) in a dose-dependent manner. LA at concentrations of 5, 10 and 20 μmol/L also enhanced /K(Ca) in a dose-dependent manner. The increasing potency of AA, LA, and oleic acid (OA) on /K(Ca)at the same concentration (10μmol/L) was in the order of AA>LA>OA. AA (10 μmol/L)-induced increase of Ik(ca) was not blocked by H-7 (10 μmol/L), an inhibitor of protein kinase C (PKC), or indomethacin (10 μmol/L), an inhibitor of the cyclooxygenase pathway, and 17-octadecynoic acid (10 μmol/L), an inhibitor of the cytochrome P450 pathway, but weakened by nordihydroguaiaretic acid (10μmol/L), an inhibitor of the lipoxygenase pathway. CONCLUSION: Unsaturated fatty acids markedly increase Ik(Ca), and the enhancing potencies are related to the number of double bonds in the fatty acid chain. The lipoxygenase pathway of unsaturated fatty acid metabolism is involved in the unsaturated fatty acid-induced increase of IK(Ca) in gastric antral circular myocytes of guinea pigs.

Differential Effect of Calcium-Activated Potassium and Chloride Channels on Rat Basilar Artery Vasomotion

Spontaneous, rhythmical contractions, or vasomotion, can be recorded from cerebral vessels under both normal physiological and pathophysiological conditions. We investigated the cellular mechanisms underlying vasomotion in the cerebral basilar artery （BA） of Wistar rats. Pressure myograph video microscopy was used to study the changes in cerebral artery vessel diameter. The main results of this study were as follows： （1） The diameters of BA and middle cerebral artery （MCA） were 314.5±15.7 μm （n=15） and 233.3±10.1 μm （n=12） at 10 mmHg working pressure （P〈0.05）, respectively. Pressure-induced vasomotion occurred in BA （22/28, 78.6%）, but not in MCA （4/31, 12.9%） from 0 to 70 mmHg working pressure. As is typical for vasomotion, the contractile phase of the response was more rapid than the relaxation phase; （2） The frequency of vasomotion response and the diameter were gradually increased in BA from 0 to 70 mmHg working pressure. The amplitude of the rhythmic con- tractions was relatively constant once stable conditions were achieved. The frequency of contractions was variable and the highest value was 16.7±4.7 （n=13） per 10 min at 60 mmHg working pressure; （3） The pressure-induced vasomotion of the isolated BA was attenuated by nifedipine, NFA, 181]-GA, TEA or in Ca2＋-free medium. Nifedipine, NFA, 18^-GA or Ca2＋-free medium not only dampened vasomotion, but also kept BA in relaxation state. In contrasts, TEA kept BA in contraction state. These results sug- gest that the pressure-induced vasomotion of the isolated BA results from an interaction between Ca2＋-activated C1- channels （CaCCs） currents and Kca currents. We hypothesize that vasomotion of BA depends on the depolarizing of the vascular smooth muscle cells （VSMCs） to activate CaCCs. Depolarization in turn activates voltage-dependent Ca2＋ channels, synchronizing contractions of adjacent cells through influx of extracellular calcium and the flow of calcium through gap junctions. Subsequent calcium-induced calcium release from ryanodine-sensitive stores activates Kca channels and hyperpo- larizes VSMCs, which provides a negative feedback loop for regenerating the contractile cycle.

Increased expression of human calcium-activated chloride channel 1 is correlated with mucus overproduction in the airways of Chinese patients with chronic obstructive pulmonary disease

Background Chronic obstructive pulmonary disease （COPD） is usually complicated with mucus overproduction in airway. Recently the increased expression of the human calcium-activated chloride channel 1 （CaCC1） was found to play an important role in mucus overproduction in the asthmatic airways. To investigate the relationship of CaCC1 and mucus overproduction in the airway of Chinese patients with COPD, the expressions of CaCC1, MUC5AC and mucus in bronchial tissues were examined. Methods Bronchial tissues were obtained from fiberoptic bronchoscopy and bronchial biopsy in West China Hospital from April to July in 2004. Twenty-five patients were diagnosed as the patients with COPD overproduction, and other 20 were the control subjects. The expressions of CaCC1, MUC5AC and mucin in bronchial tissues were detected by reverse transcriptase-polymerase chain reaction （RT-PCR）, in situ hybridization with digoxigenin （DIG）-Iabeled RNA probe, immunohistochemical and alcian blue-periodic acid Schiff （AB-PAS） staining, respectively. Results Compared with the control group, the stronger expressions of CaCC1 were further detected throughout the bronchial tissues from patients with COPD （P〈0.01）. Furthermore, the stronger expressions of the CaCC1 mRNA were related to the severity of airflow obstruction. Samples from COPD showed a stronger staining for MUC5AC than those in control subjects （P〈0.01） and AB-PAS staining revealed more mucins in COPD patients＇ submucosal gland comparing with that in control subjects （P〈0.01）. Expression levels of the CaCC1 mRNA were respectively negatively correlated with the patients＇ forced expiratory volume in one second （FEV~） / forced vital capacity （FVC） data, FEV1% predicted data, V50% predicted data, V25% predicted data （r=-0.43, r=-0.43, r=-0.35, r=-0.36, P〈0.01, P〈0.01, P〈0.05, P〈0.05）. While the expression levels of the CaCC1 mRNA were well correlated with the expression levels of the MUC5AC mRNA of airway epithelium and the PAS-AB stained area of submucosal glands （r=0.39, r=0.46, P〈0.05, P〈0.01）. Expression levels of the MUC5AC mRNA were negatively correlated with the patients＇ FEV1/FVC data （P=0.01）, FEV1% pred data （P=-0.01）, V50% predicted data, V25% predicted data（r=-0.53, r=-0.53, r=-0.48, r=-0.43, P〈0.01, P〈0.01, P〈0.01, P〈0.01）. While the expression levels of the MUC5AC mRNA were well correlated with the positively PAS-AB stained area of submucosal gland （P〈0.05）, and the correlation coefficients were 0.43. Conclusion These results suggest that the stronger gene expression of CaCC1 exists, complicated with mucus overproduction in the airwav of Chinese patients with COPD.

Effect of nitric oxide-induced tyrosine phosphorylation of calcium-activated potassium channel α subunit on vascular hyporesponsiveness in rats

Objective: To study the effect of nitric oxide-induced tyrosine phosphorylation of large-conductance calcium-activated potassium (BK Ca) channel α subunit on vascular hyporesponsiveness in rats. Methods: A total of 46 Wistar rats of either sex, weighing 250 g±20 g, were used in this study. Models of vascular hyporesponsiveness induced by hemorrhagic shock (30 mm Hg for 2 hours) in vivo and by L-arginine in vitro were established respectively. The vascular responsiveness of isolated superior mesenteric arteries to norepinephrine was observed. Tyrosine phosphorylation of BK Ca α subunit was evaluated with methods of immunoprecipitation and Western blotting. Results: In the smooth muscle cells of the superior mesenteric arteries, the expression of BK Ca α subunit tyrosine phosphorylation increased following hemorrhagic shock, and L-arginine could induce BK Ca channel α subunit tyrosine phosphorylation in a time- and dose-dependent manner. L-NAME (Nω-nitro-L-arginine-methyl-ester), a nitric oxide synthetase inhibitor, could partly restore the decreased vasoresponsiveness of the superior mesenteric arteries after hemorrhagic shock in rats. Down-regulating the protein tyrosine phosphorylation with genistein, a widely-used special protein tyrosine kinase inhibitor, could partly improve the decreased vasoresponsiveness of the superior mesenteric arteries induced by L-arginine in vitro, while up-regulating the protein tyrosine phosphorylation with Na3VO4, a protein tyrosine phosphatase inhibitor, could further decrease the nitric oxide-induced vascular hyporesponsiveness, which could be partly ameliorated by 0.1 mmol/L tetrabutylammonium chloride (TEA), a selective BK Ca inhibitor at this concentration. Conclusions: Nitric oxide can induce the tyrosine phosphorylation of BK Ca α subunit, which influences the vascular hyporesponsiveness in hemorrhagic shock rats or induced by L-arginine in vitro.

Effect of electroacupuncture on calcium-activated chloride channel currents in interstitial cells of Cajal in rats with diabetic gastroparesis

Objective:To investigate the mechanisms of electroacupuncture(EA)at Zusanli(ST 36),Liangmen(ST 21)and Sanyinjiao(SP 6)in intervening diabetic gastroparesis(DGP)based on calcium-activated chloride channel.Methods:Forty Sprague-Dawley rats were randomly divided into four groups,including a normal control group(group A),a model group(group B),an EA group(group C)and a metoclopramide group(group D),with 10 rats in each group.A single intraperitoneal injection of 2%streptozotocin(STZ)combined with 8-week high-glucose high-fat diet was used to establish a DGP rat model.After intervention,gastrointestinal propulsive rate was observed;the expression level of transmembrane protein 16A(TMEM16A)was examined by immunohistochemistry;the Ca2+concentration in interstitial cells of Cajal(ICCs)was detected by immunofluorescence;and whole-cell patch-clamp technique was applied to detect the current intensity of calcium-activated chloride channel(ICaCC)in ICCs in gastric antrum.Results:After modeling,the blood glucose levels in group B,group C and group D were significantly increased compared with group A(all P<0.01);after intervention,compared with group B,the blood glucose levels in group C and group D were significantly decreased(P<0.05,P<0.01);the intra-group comparison of blood glucose level between after modeling and after intervention found significant difference only in group C(P<0.01).The gastrointestinal propulsive rates in group B,group C and group D were significantly different from that in group A(P<0.01 or P<0.05);the gastrointestinal propulsive rates were markedly higher in group C and group D than in group B(P<0.01,P<0.01).The expressions of TMEM16A in group B and group C were decreased compared with group A(P<0.01,P<0.05);the expressions of TMEM16A in group C and group D were increased compared with group B(P<0.01,P<0.05).The fluorescence intensity of Ca2+was significantly lower in group B than in group A(P<0.01);the fluorescence intensity of Ca2+was significantly higher in group C and group D than in group B(P<0.01,P<0.05).ICaCC in ICCs in group B was significantly decreased compared with group A;ICaCC in group C and group D were increased compared with group B.Conclusion:EA at Zusanli(ST 36),Liangmen(ST 21)and Sanyinjiao(SP 6)can significantly improve gastrointestinal motility in DGP rats by up-regulating the ICaCC in ICCs.

Endothelium-derived Relaxing Factor Activates Calcium-activated Potassium Channels of Resistance Vessel Smooth Muscle Cells

Direct observation was made by using the patch-clamp technique with a specially designed microperfusion system to investigate the effect of acetylcholine (Ach 10^(-6) mol/L) elicited endothelium-derived relaxing factor (EDRF) on the calcium-activated potassium channel (IK(Ca))in the smooth muscle cells of mesenteric resistance vessels in Wistar rats. Activation of IK(Ca) was firstly observed by inducing the elicited EDRF or sodium nitroprusside (SNP 10^(-8) mol/L) under various clamping voltages in cell-attached configuration. While the pipette solution contained KCl 126 mmol/L and the bath solution contained KCl 5.9 mmol/L, two types of conductances of calcium-activated potassium current being 76.4±2.3 pS(mean±S.E. n = 7) and 160.3±7.5 pS (mean±S.E. n= 7) were recorded during the EDRF activation, one type of conductance being 100.5±2.8 pS (mean±S.E. n = 6) was activated by nitric oxide (NO) which is an effective component from SNP. Differences in kinetic characteristics of these channels between EDRF and NO activation were found, particularly the probability of the channel being open in EDRF activation was obviously greater than that in NO stimulation. It has been shown that the potassium channel mechanisms involved in the EDRF and NO actions might be different.

Murine calcium-activated chloride channel family member 3 induces asthmatic airway inflammation independently of allergen exposure

Background Expression of murine calcium-activated chloride channel family member 3 （mCLCA3） has been reported to be increased in the airway epithelium of asthmatic mice challenged with ovalbumin （OVA）. However, its role in asthmatic airway inflammation under no OVA exposure has not yet been clarified. Methods mCLCA3 plasmids were transfected into the airways of normal BALB/c mice. mCLCA3 expression and airway inflammation in mouse lung tissue were evaluated. Cell differentials and cytokines in bronchoalveolar lavage fluid （BALF） were analyzed. The expression of mCLCA3 protein and mucus protein mucin-5 subtype AC （MUC5AC） were analyzed by Western blotting. The mRNA levels of mCLCA3, MUC5AC and interleukin-13 （IL-13） were determined quantitatively. Results mCLCA3 expression was not detected in the control group while strong immunoreactivity was detected in the OVA and mCLCA3 plasmid groups, and was strictly localized to the airway epithelium. The numbers of inflammatory cells in lung tissue and BALF were increased in both mCLCA3 plasmid and OVA groups. The protein and mRNA levels of mCLCA3 and MUC5AC in the lung tissue were significantly increased in the mCLCA3 plasmid and OVA groups compared to the control group. The level of IL-13, but not IL-4, IL-5, IFN-y, CCL2, CCL5 or CCL11, was significantly increased compared with control group in BALF in the mCLCA3 plasmid and OVA groups. The level of IL-13 in the BALF in the mCLCA3 plasmid group was much higher than that in the OVA group （P 〈0.05）. The level of mCLCA3 mRNA in lung tissue was positively correlated with the levels of MUC5AC mRNA in lung tissue, IL-13 mRNA in lung tissue, the number of eosinophils in BALF, and the content of IL-13 protein in BALE The level of IL-13 mRNA in lung tissue was positively correlated with the number of eosinophils in BALF and the level of MUC5AC mRNA in lung tissue. Conclusion These findings suggest that increased expression of a single-gene, mCLCA3, could simulate an asthma attack, and its mechanism may involve mCLCA3 overexpression up-regulating IL-13 expression.

Mechanisms underlying low [Ca^(2+)]_o-induced increased excitability of hippocampal neurons

Objective Concentration of extracellular calcium （[Ca2＋]o） in the central nervous system decreases substantially in different conditions. It results in facilitating neuronal excitability. The goal of this study is to examine the mechanisms of enhanced neuronal excitation in low [Ca2＋]o in order to provide new clues to treat the hyperexcitability diseases in clinic. Methods Whole-cell patch-clamp technique and neuron culture were used in the study. Results The firing threshold of cultured hippocampal neurons decreased markedly in low [Ca2＋]o saline. Unexpectedly, apamine and isoprenaline, antagonists of medium afterhyperpolarization （mAHP） and slow AHP （sAHP） respectively, had no statistic significant effect on excitability of neurons. TTX at a low concentration was sufficient to inhibit/Nap, which blocked the increase of firing frequency in low [Ca2＋]o. It also reduced the number of spikes in normal [Ca2＋]o. Conclusion These results suggest that in cultured hippocampal neurons, modulation of spiking threshold but not AHP may cause the increased excitability in low [Ca2＋]o.

Mechanism of persistent hyperalgesia in neuropathic pain caused by chronic constriction injury

Transmembrane member 16 A(TMEM16 A) is involved in many physiological functions, such as epithelial secretion, sensory conduction, nociception, control of neuronal excitability, and regulation of smooth muscle contraction, and may be important in peripheral pain transmission. To explore the role of TMEM16 A in the persistent hyperalgesia that results from chronic constriction injury-induced neuropathic pain, a rat model of the condition was established by ligating the left sciatic nerve. A TMEM16 A selective antagonist(10 μg T16 Ainh-A01) was intrathecally injected at L5–6. For measurement of thermal hyperalgesia, the drug was administered once at 14 days and thermal withdrawal latency was recorded with an analgesia meter. For measurement of other indexes, the drug was administered at 12 days,once every 6 hours, totally five times. The measurements were performed at 14 days. Western blot assay was conducted to analyze TMEM16 A expression in the L4–6 dorsal root ganglion. Immunofluorescence staining was used to detect the immunoreactivity of TMEM16 A in the L4–6 dorsal root ganglion on the injured side. Patch clamp was used to detect electrophysiological changes in the neurons in the L4–6 dorsal root ganglion. Our results demonstrated that thermal withdrawal latency was shortened in the model rats compared with control rats.Additionally, TMEM16 A expression and the number of TMEM16 A positive cells in the L4–6 dorsal root ganglion were higher in the model rats, which induced excitation of the neurons in the L4–6 dorsal root ganglion. These findings were inhibited by T16 Ainh-A01 and confirm that TMEM16 A plays a key role in persistent chronic constriction injury-induced hyperalgesia. Thus, inhibiting TMEM16 A might be a novel pharmacological intervention for neuropathic pain. All experimental protocols were approved by the Animal Ethics Committee at the First Affiliated Hospital of Shihezi University School of Medicine, China(approval No. A2017-170-01) on February 27, 2017.

Effects of Ginkgo biloba extracts with mirodenafil on the relaxation of corpus cavernosal smooth muscle and the potassium channel activity of corporal smooth muscle cells

In this study, we investigated the effects of a combination of Ginkgo biloba extracts （GBE） and phosphodiesterase type 5 （PDE-5） inhibitors on the muscular tone of the corpus cavernosum and potassium channel activity of corporal smooth muscle cells. Strips of corpus cavernosum from male New Zealand white rabbits were mounted in organ baths for isometric tension studies. After contraction with 1 × 10^-5 mol I^-1 norepinephrine, GBE （0.01-1 mg ml^-1） and mirodenafil （0.01-100 nmol I^-1） were added together into the organ bath. In electrophysiological studies, whole-cell currents were recorded by the conventional patch-clamp technique in cultured smooth muscle cells of the human corpus cavernosum. The corpus cavemosum was relaxed in response to GBE in a dose-dependent manner （from 0.64%±8.35% at 0.01 mg ml^-1 to 52.28%±11.42% at 1 mg ml^-1）. After pre-treatment with 0.03 mg ml^-1 of GBE, the relaxant effects of mirodenafil were increased at all concentrations, After tetraethylammonium （TEA） （1 mmol I^-1） administration, the increased effects were inhibited （P〈0.01）. Extracellular administration of GBE increased the whole-cell K^＋ outward currents in a dose-dependent fashion. The increase of the outward current was inhibited by I mmol 1-1 TEA. These results suggest that GBE could increase the relaxant potency of mirodenafil even at a minimally effective dose. The K＋ flow through potassium channels might be one of the mechanisms involved in this synergistic relaxation.

Activation of MRGPRB2 receptor in mouse peritoneal mast cells depends on PLC-IP3-ORAI1 pathway

OBJECTIVE A novel mast cell-specific G-protein-coupled receptor(GPCR),known as mas-related GPCR-B2(MRGPRB2),plays important roles in the immune response.The opening of ion channels mediated by MRGPRB2 activation remains unclear.METHODS AND RE⁃SULTS Calcium influx induced by activation of MRGPRB2 receptor in mouse peritoneal mast cells was related to the concentrations of calcium ions in the extracellular solution.Similarly,the volt⁃age-dependent current generated by MRGPRB2 activation was also correlated with the extracellu⁃lar calcium concentration.In addition,the in⁃creased of calcium influx or voltage-dependent current caused by activation of MrgprB2 could be blocked by U73122(PLC blocker)or 2-APB(IP3-ORAI1 blocker).Meanwhile,calcium-activated chlorine channel(TMEM16A)was involved in the generation of voltage-dependent currents in⁃duced by MRGPRB2 activation in mouse perito⁃neal mast cells.Furthermore,the degranulation of mouse peritoneal mast cells mediated by MRGPRB2 receptor could also be inhibited by U73122 or 2-APB.CONCLUSION PLC-IP3-ORAI1-TMEM16A signaling pathway was involved in MRGPRB2-mediated mast cell activation.

Chronic salt-loading downregulates large-conductance Ca^(2+)-activated potassium channel in mesenteric arterial smooth muscle cells from SD rats

Objective Large-conductance calcium-activated potassium(BKCa)channel modulates vascular smooth muscle tone.In the present study,we tested the hypothesis that salt,one of the factors which significantly influence blood pressure(BP),can regulate BKCa activity and then elevate blood pressure.Methods Male Sprague-Dawley rats aged 6 weeks were randomized into high salt diet group(HS)and control group,fed with high salt diet(containing 5% NaCl)and standard rat chow(containing 0.4% NaCl)respectively for 16 weeks.Tail systolic blood pressure(SBP),body weight(BW)and 24-hour urinary output were tested every 4 weeks.Content of urinary Na+ was detected using flame spectrophotometrical method.At the end of 16 weeks,all the rats were killed,the mesenteric arteries were obtained,and single mesenteric smooth muscle cells were isolated at once.The resting membrane potential(Em),the total potassium currents and the currents after perfusion with TEA solution of the cells were all recorded by whole cell patch clamp.The transcriptions of BKCa channel α and β1 subunits in mesenteric arterial vascular smooth muscle cells(VSMC)of each group were calculated by real-time RT-PCR.Results There was no difference in SBP and BW at each stage between control group and HS group;the urinary Na+ level in HS animals was elevated significantly after 4 weeks.The negative values of Em in HS group VSMCs were reduced compared with those in the control group.Transcriptions of β1 subunit of BKCa channels were decreased in HS group,but α subunit transcriptions did not differ between the two groups.Whole cell potassium currents did not differ between HS and control groups,but BKCa currents of HS group VSMCs were lower than those of control group ones.Conclusion Even without elevating SBP,salt-loading can still modulate the expression and activity of BKCa channel in the mesenteric arterial VSMC and elevate vascular tone.

Glutamate-releasing BEST1 channel is a new target for neuroprotection against ischemic stroke with wide time window

Many efforts have been made to understand excitotoxicity and develop neuroprotectants for the therapy of ischemic stroke.The narrow treatment time window is still to be solved.Given that the ischemic core expanded over days,treatment with an extended time window is anticipated.Bestrophin1(BEST1)belongs to a bestrophin family of calcium-activated chloride channels.We revealed an increase in neuronal BEST1 expression and function within the peri-infarct from 8 to 48 h after ischemic stroke in mice.Interfering the protein expression or inhibiting the channel function of BEST1 by genetic manipulation displayed neuroprotective effects and improved motor functional deficits.Using electrophysiological recordings,we demonstrated that extrasynaptic glutamate release through BEST1 channel resulted in delayed excitotoxicity.Finally,we confirmed the therapeutic efficacy of pharmacological inhibition of BEST1 during 6—72 h post-ischemia in rodents.This delayed treatment prevented the expansion of infarct volume and the exacerbation of neurological functions.Our study identifies the glutamatereleasing BEST1 channel as a potential therapeutic target against ischemic stroke with a wide time window.

Forensic Significance of Messenger RNA and Protein Expression of Genes Downstream of Hypoxia Inducible Factor 2 in Myocardial Tissue for Death Discrimination

Background: As a heterodimeric transcription factor, hypoxia-inducible factor 2 alpha subunit (HIF2A), is an important member of the HIF family. It plays a significant role in the hypoxia adaptation process by regulating the different types of downstream transcription factors and auxiliary regulatory factors. HIF2A-related factors are believed to participate in the progression of myocardial injury or myocardial ischemia, support the protection of ischemic myocardium, and provide guiding significance for the diagnosis and discrimination of sudden cardiac death in forensic pathology. Aim and Objectives: This study aimed to explore the discriminability and applicability of HIF2A-related factors in myocardial infarction cases compared with other causes of death, provide further insights for the forensic diagnosis of heart failure (HF) cases with myocardial infarction, and support the clinical treatment of patients with HF after myocardial infarction. Materials and Methods: The relative expression levels of HIF2A, amphiregulin (AREG), potassium large conductance calcium-activated channel subfamily M β1 (KCNMB1), peroxisome proliferator-activated receptor α (PPARA), vascular endothelial growth factor (VEGF), and VEGFR2 messenger RNAs (mRNAs) in myocardial tissue samples were performed using quantitative reverse transcriptase-polymerase chain reaction. A partial least squares-discriminant analysis model was constructed to select the indicators with better identification effects for myocardial infarction cases. The protein levels of HIF2A, AREG, KCNMB1, and PPARA were further detected by immunohistochemistry. The forensic autopsy cases (27 cases in total, postmortem interval <72 h) included seven cases of acute myocardial infarction and ten cases of myocardial ischemia. There were ten cases in the control group, including four cases of traffic injury, one case of injury by fall from height, and five cases of blunt force injury. Results: Characteristic results were observed in the myocardial ischemia/infarction samples. Compared with the control group, the relative mRNA expression levels of AREG, KCNMB1, and PPARA were significantly increased during the progression of myocardial ischemia, but this was not observed for HIF2A, VEGF, or VEGFR2 mRNA. Immunohistochemistry assays further verified the expression levels of the related factors at the protein level, and H and E staining showed signs of angiogenesis and inflammation in the ischemia/infarction group. Conclusions: By controlling the expression of downstream target genes (AREG, KCNMB1, and PPARA) during myocardial cell hypoxia adaptation, HIF2A has a potential significance in the diagnosis of myocardial infarction in forensic medicine. We believe that HIF2A, AREG, KCNMB1, and PPARA can be used as molecular pathological biomarkers for the discrimination of causes of death in myocardial infarction cases.

Modulation of the activity of dopaminergic neurons by SK channels:a potential target for the treatment of Parkinson's disease?

SK channels are small conductance calcium-activated potassium channels that are widely expressed in different neurons with distinct subtypes.They play an important role in modulating synaptic plasticity,dopaminergic neurotransmission, and learning and memory.The present review was mainly focused on the recent findings on the contradictory roles of SK channels in modulating dopaminergic neurons in substantia nigra and in the pathogenesis of Parkinson＇s disease （PD） . Besides,whether modulation of SK channels could be a potential target for PD treatment was also discussed.

The Involvement of Ca^2＋ Signal Pathways in Distal Colonic Myocytes in a Rat Model of Dextran Sulfate Sodium-induced Colitis

Background： Disrupted Ca2＋ homeostasis contributes to the development of colonic dysmotility in ulcerative colitis （UC）, but the underlying mechanisms are unknown. This study aimed to examine the alteration of colonic smooth muscle （SM） Ca2＋ signaling and Ca2＋ handling proteins in a rat model of dextran sulfate sodium （DSS）-induced UC. Methods： Male Sprague-Dawley rats were randomly divided into control （n = 18） and DSS （n = 17） groups. Acute colitis was induced by 5% DSS in the drinking water for 7 days. Contractility of colonic SM strips （controls, n = 8 and DSS, n = 7） was measured in an organ bath. Cytosolic resting Ca2＋ levels （n = 3 in each group） and Ca2＋ transients （n = 3 in each group） were measured in single colonic SM cells. Ca2＋ handling protein expression was determined by Western blotting （n = 4 in each group）. Differences between control and DSS groups were analyzed by a two-sample independent t-test. Results： Average tension and amplitude of spontaneous contractions of colonic muscle strips were significantly enhanced in DSS-treated rats compared with controls （1.25 ± 0.08 g vs. 0.96 - 0.05 g, P = 0.007; and 2.67 - 0.62 g vs. 0.52 ±0.10 g, P= 0.013）. Average tensions of carbachol-evoked contractions were much weaker in the DSS group （1.08 ±0.10 g vs. 1.80 ±0.19 g, P = 0.006）. Spontaneous Ca2＋ transients were observed in more SM cells from DSS-treated rats （15/30 cells） than from controls （5/36 cells）. Peak caffeine-induced intracellular Ca2＋ release was lower in SM cells of DSS-treated rats than controls （0.413 ±0.046 vs. 0.548 ±0.041, P = 0.033）. Finally, several Ca2＋ handling proteins in colonic SM were altered by DSS treatment, including sarcoplasmic reticulum calcium-transporting ATPase 2a downregulation and phospholamban and inositol 1,4,5-trisphosphate receptor 1 upregulation. Conclusions： Impaired intracellular Ca2＋ signaling of colonic SM, caused by alteration of Ca2＋ handing proteins, contribute to colonic dysmotility in DSS-induced UC.