Differential expression of Bcl-2 and Bax during gastric ischemia-reperfusion of rats

AIM: To investigate expression of Bcl-2 and Bax in gastric ischemia-reperfusion (GI-R) and involvement of extracellular signal-regulated kinase (ERK) 1/2 activation. METHODS: The GI-R model was established by ligature of the celiac artery for 30 min and reperfusion in SpragueDawley rats. Rats were assigned to groups in accordance with their evaluation period: control, 0, 0.5, 1, 3, 6, 24, 48, and 72 h. Expression and distribution of Bcl-2 and Bax proteins were analyzed by immunohistochemistry and western blotting in gastric tissue samples after sacrifice. RESULTS: Compared with controls, the percentage of positive cells and protein levels of Bcl-2 decreased inthe early phases of reperfusion, reached its minimum at 1 h (P < 0.05); it then increased, reaching its peak at 24 h of reperfusion (P < 0.05). The pattern of Bax expression was opposite to that of Bcl-2. Bax expression increased after reperfusion, with its peak at 1 h of reperfusion (P < 0.05), and then it decreased gradually to a minimum at 24 h after reperfusion (P < 0.05). On the other hand, inhibition of activation of ERK1/2 induced by PD98059, a specific upstream MEK inhibitor, had significant effects on Bcl-2 and Bax in GI-R. Compared with GI-R treatment only at 3 h of reperfusion, PD98059 reduced the number of Bcl-2 positive cells (0.58% of R3h group, P < 0.05) and Bcl-2 protein level (74% of R3h group, P < 0.05) but increased the number of Bax-positive cells (1.33-fold vs R3h group, P < 0.05) and Bax protein level (1.35-fold of R3h group, P < 0.05). CONCLUSION: These results indicated that the Bcl-2 and Bax played a pivotal role in the gastric mucosal I-R injury and repair by activation of ERK1/2.

Effects of hypothalamic paraventricular nuclei on apoptosis and proliferation of gastric mucosal cells induced by ischemia/reperfusion in rats

AIM: To investigate the effects of electrical stimulation of hypothalamic paraventricular nuclei (PVN) on gastric mucosal cellular apoptosis and proliferation induced by gastric ischemia/reperfusion (I/R) injury. METHODS: For different experimental purposes, stimulating electrode plantation or electrolytic destruction of the PVN was applied, then the animals' GI/R injury model was established by clamping the celiac artery for 30min and allowing reperfusing the artery for 30min, 1h, 3h or 6h respectively. Then histological, immunohistochemistry methods were used to assess the gastric mucosal damage index, the gastric mucosal cellular apoptosis and proliferation at different times. RESULTS: The electrical stimulation of PVN significantly attenuated the GI/R injury at 30 min, 1h and 3h after reperfusion. The electrical stimulation of PVN decreased gastric mucosal apoptosis and increased gastric mucosal proliferation. The electrolytic destruction of the PVN could eliminate the protective effects of electrical stimulation of PVN on GI/R injury. These results indicated that the PVN participated in the regulation of GI/R injury as a specific area in the brain, exerting protective effects against the GI/R injury, and the protection was associated with the inhibition of cellular apoptosis and the promotion of gastric mucosal proliferation. CONCLUSION: Stimulating PVN significantly inhibits the gastric mucosal cellular apoptosis and promots gastric mucosal cellular proliferation. This may explain the protective mechanisms of electrical stimulation of PVN against GI/R injury.

Preparation and application of polyclonal antibodies against KSHV v-cyclin

We prepared rabbit polyclonal antibodies against Kaposi＇s sarcoma-associated herpesvirus （KSHV）-encoded v- cyclin （ORF 72） and detected the natural viral protein using these polyclonal antibodies. Three antigenic polypep- tides of v-cyclin were designed and synthesized. A fragment of the v-cyclin gene was cloned into a eukaryotic expression vector pEF-MCS-Flag-IRES/Puro to construct a recombinant vector, pEF v-cyclin. Then, pEF v-cyclin was transfected into 293T and EA.hy926 cells to obtain v-cyclin-Flag fusion proteins. Six New Zealand white rabbits were immunized with KLH-conjugated peptides to generate polyclonal antibodies against v-cyclin. The polyclonal antibodies were then characterized by ELISA and Western blotting assays. Finally, the polyclonal anti- bodies against v-cyclin were used to detect natural viral protein expressed in BCBL-1, BC-3, and JSC-1 cells. The results showed that using the Flag antibody, v-cyclin-Flag fusion protein was detected in 293T and EA.hy926 cells transfected with pEF-v-cyclin. Furthermore, ELISA showed that the titer of the induced polyclonal rabbit anti-v- cyclin antibodies was higher than 1：8,000. In Western blotting assays, the antibodies reacted specifically with the v-cyclin-Flag fusion protein as well as the natural viral protein. The recombinant expression vector pEF-v-cyclin was constructed successfully, and the polyclonal antibodies prepared can be used for various biological tests in- cluding ELISA and Western blotting assays.

Inhibition of central sympathetic nervous tone improves cardiomyocyte contraction by increasing the response of beta 2-adrenergic receptor in aged rats

In the present study,selective β1-adrenergic receptor antagonist CGP20712A and selective β2-adrenergic receptor antagonist ICI 118551 were administered to isolated cardiomyocytes from young （4-6 months）,aged （18-20 months）,and clonidine-pretreated aged （18-20 months） Sprague-Dawley rats.Cardiomyocyte contraction amplitude was measured to assess cardiomyocyte response to the β-adrenergic receptor agonist,isoprenaline.CGP20712A reduced cardiomyocyte contraction amplitude in young and aged groups and significantly reduced contraction amplitude in cells from young rats.ICI 118551 had no effect on cardiomyocyte contraction amplitude in young rats,but significantly decreased contraction amplitude in the aged groups,in particular in the clonidine-pretreated aged rats.Results demonstrated that reduced central sympathetic tone improved cardiomyocyte contraction in aged rats by improving the response of β2-adrenergic receptor to isoprenaline.

Oxidative stress induces gastric submucosal arteriolar dysfunction in the elderly

AIM:To evaluate human gastric submucosal vascular dysfunction and its mechanism during the aging process.METHODS:Twenty male patients undergoing subtotal gastrectomy were enrolled in this study.Young and elderly patient groups aged 25-40 years and 60-85 years,respectively,were included.Inclusion criteria were:no clinical evidence of cardiovascular,renal or diabetic diseases.Conventional clinical examinations were carried out.After surgery,gastric submucosal arteries were immediately dissected free of fat and connective tissue.Vascular responses to acetylcholine(ACh)and sodium nitroprusside(SNP)were measured by isolated vascular perfusion.Morphological changes in the gastric mucosal vessels were observed by hematoxylin and eosin(HE)staining and Verhoeff van Gieson(EVG)staining.The expression of xanthine oxidase(XO)and manganese-superoxide dismutase(Mn-SOD)was assessed by Western blotting analysis.The malondialdehyde(MDA)and hydrogen peroxide(H2O2)content and the activities of superoxide dismutase(SOD)and glutathione peroxidase(GSH-Px)were determined according to commercial kits.RESULTS:The overall structure of vessel walls was shown by HE and EVG staining,respectively.Disruption of the internal elastic lamina or neointimal layers was not observed in vessels from young or elderly patients;however,cell layer number in the vessel wall increased significantly in the elderly group.Compared with submucosal arteries in young patients,the amount of vascular collagen fibers,lumen diameter and media cross-sectional area were significantly increased in elderly patients.Ach-and SNP-induced vasodilatation in elderly arterioles was significantly decreased compared with that of gastric submucosal arterioles from young patients.Compared with the young group,the expression of XO and the contents of MDA and H2O2in gastric submucosal arterioles were increased in the elderly group.In addition,the expression of Mn-SOD and the activities of SOD and GSH-Px in the elderly group decreased significantly compared with those in the young group.CONCLUSION:Gastric vascular dysfunction and senescence may be associated with increased oxidative stress and decreased antioxidative defense in the aging process.

Apelin-13 as a novel target for intervention in secondary injury after traumatic brain injury

The adipocytokine,apelin-13,is an abundantly expressed peptide in the nervous system.Apelin-13 protects the brain against ischemia/reperfusion injury and attenuates traumatic brain injury by suppressing autophagy.However,secondary apelin-13 effects on traumatic brain injury-induced neural cell death and blood-brain barrier integrity are still not clear.Here,we found that apelin-13 significantly decreases cerebral water content,mitigates blood-brain barrier destruction,reduces aquaporin-4 expression,diminishes caspase-3 and Bax expression in the cerebral cortex and hippocampus,and reduces apoptosis.These results show that apelin-13 attenuates secondary injury after traumatic brain injury and exerts a neuroprotective effect.

Role of mitogen-activated protein kinases in the regulation of paraventricular nucleus to gastric ischemia-reperfusion injuries

Background We investigated the role in electrical stimulations of paraventricular nucleus （PVN） on gastric mucosal cells and the activity of mitogen-activated protein kinases （MAPKs） family members induced by gastric ischemia-reperfusion （GI-R）. And we elucidated the molecular mechanisms of the protection of PVN from GI-R injuries. Methods Sprague-Dawley rats were divided randomly into 4 groups： Group I, the sham-operated GI-R control group; Group II, the sham-operated electrical stimulations to PVN ＋ sham-operated GI-R control group; Group III, the GI-R group; and Group IV, the electrical stimulations to PVN ＋ GI-R group. In all of the experiments, the PVN was stimulated prior to the induction of GI-R. The GI-R model was established by clamping the celiac artery for 30 minutes to induce ischemia and then was released to allow reperfusion for 30 minutes, 1 hour, 3 hours and 6 hours, respectively. The gastric mucosal cellular apoptosis, proliferation, and the expression and activity of MAPKs protein were observed by immunohistochemistry and Western blotting, respectively. Results Compared with the GI-R group, the application of electrical stimulations in the PVN significantly depressed gastric mucosal cellular apoptosis and enhanced gastric mucosal cellular proliferation following the 30-minute, 1-hour and 3-hour intervals of reperfusion; it also promoted the activation of p-ERK during the early phase of reperfusion but inhibited the activation of p-JNK1/2 and p-p38 following the 30-minute, 1-hour and 3-hour intervals of reperfusion. Conclusions The protection of PVN against GI-R injuries may attribute to the inhibition of apoptosis and the promotion of the proliferation of gastric mucosal cells during GI-R. This protective effect is mediated by activating the ERK pathway and depressing the JNK, the JNK. p38 MAPK oathwavs of the oastric mucosal cells.

Reducing the oxidative stress mediates the cardioprotection of bicyclol against ischemia-reperfusion injury in rats

Objective:To investigate the beneficial effect of bicyclol on rat hearts subjected to ischemia-reperfusion(IR) injuries and its possible mechanism.Methods:Male Sprague-Dawley rats were intragastrically administered with bicyclol(25,50 or 100 mg/(kg·d)) for 3 d.Myocardial IR was produced by occlusion of the coronary artery for 1 h and reperfusion for 3 h.Left ventricular hemodynamics was continuously monitored.At the end of reperfusion,myocardial infarct was measured by 2,3,5-triphenyltetrazolium chloride(TTC) staining,and serum lactate dehydrogenase(LDH) level and myocardial superoxide dismutase(SOD) activity were determined by spectrophotometry.Isolated ventricular myocytes from adult rats were exposed to 60 min anoxia and 30 min reoxygenation to simulate IR injuries.After reperfusion,cell viability was determined with trypan blue;reactive oxygen species(ROS) and mitochondrial membrane potential of the cardiomyocytes were measured with the fluorescent probe.The mitochondrial permeability transition pore(mPTP) opening induced by Ca2+(200 μmol/L) was measured with the absorbance at 520 nm in the isolated myocardial mitochondria.Results:Low dose of bicyclol(25 mg/(kg·d)) had no significant improving effect on all cardiac parameters,whereas pretreatment with high bicyclol markedly reduced the myocardial infarct and improved the left ventricular contractility in the myocardium exposed to IR(P<0.05).Medium dose of bicyclol(50 mg/(kg·d)) markedly improved the myocardial contractility,left ventricular myocyte viability,and SOD activity,as well decreased infarct size,serum LDH level,ROS production,and mitochondrial membrane potential in rat myocardium exposed to IR.The reduction of ventricular myocyte viability in IR group was inhibited by pretreatment with 50 and 100 mg/(kg·d) bicyclol(P<0.05 vs.IR),but not by 25 mg/(kg·d) bicyclol.The opening of mPTP evoked by Ca2+ was significantly inhibited by medium bicyclol.Conclusions:Bicyclol exerts cardioprotection against IR injury,at least,via reducing oxidative stress and its subsequent mPTP opening.

Antioxidative Effect of Luteolin Pretreatment on Simulated Ischemia/Reperfusion Injury in Cardiomyocyte and Perfused Rat Heart

Objective：To investigate the antioxidative effect and mechanism of luteolin on rat cardiomyocytes and isolated hearts fol owed by simulated ischemia/reperfusion（SI/R） injury. Methods：The left ventricular cardiomyocytes and the isolated hearts from adult rats were subjected to SI/R injury. The experiment groups included control, SI/R, luteolin ＋ SI/R（Lut ＋ SI/R）, vitamin E（Vit E） ＋ SI/R, and LY294002 ＋ luteolin ＋ SI/R（LY ＋ Lut ＋ SI/R） groups. Cell viability, shortening amplitude, lactate dehydrogenase（LDH） release, superoxide dismutase（SOD） activity, the production of reactive oxygen species（ROS） and malondialdehyde（MDA）, expression levels of Akt, phosphorylated Akt, NOX2（gp91phox）, NOX2 m RNA, mitogen-activated protein kinase（p38 MAPK） and phosphorylated p38 MAPK were al measured after 3-h simulated ischemia and 2-h simulated reperfusion procedure in cardiomyocytes. Vit E was used as a standard control. The contractile function of isolated hearts was further observed after they were subjected to 30-min global ischemia and 120-min reperfusion. Results：Pretreatment with 8-μmol/L luteolin substantially increased cel viability and shortening amplitude, while reducing evidence of oxidative stress-induced damage in the cel s. In addition, the expression of NOX2, NOX2 m RNA and phosphorylation of p38 MAPK were al downregulated. Furthermore, pretreatment with 40-μmol/L luteolin improved the recovery of myocardial contractile function fol owing SI/R-induced injury, and luteolin markedly increased phosphorylation of Akt. However, all of the above effects were partially inhibited by the phosphatidylinositol 3-kinase（PI3K） inhibitor, LY294002. Conclusions：Luteolin prevents SI/R-induced myocardial damage by reducing oxidative stress-induced injury in isolated rat hearts and cardiomyocytes, and the cardioprotection induced by luteolin was partial y mediated by the PI3K/Akt pathway.

Effect of oxytocin on gastric ischemia-reperfusion injury in rats

The effect of peripherally administered oxytocin(OT)on gastric ischemia-reperfusion injury(GI-RI)and its possible mechanism were investigated.The Sprague-Dawley(SD)rats were randomly divided into different treatment groups(n=6).The animal GI-RI model was established by clamping the celiac artery for 30 min to induce ischemia and then released to allow reperfusion for 1 h,and the degree of GI-RI was assessed by scoring the gastric mucosal damage index(GMDI),the gastric fluid output,gastric fluid output,gastric acidity were measured and the surgical preparations of vagotomy and sympathectomy were used to investigate the possible mechanism of OT on GI-RI.The results were as follows.Compared with the control group(NS plus GI-R only,GMDI 121.33P10.40,n=6),the intra peritoneal(ip)administration of oxytocin(20,100μg/0.5 mL)obviously attenuated GI-RI(P<0.05),GMDI were 82.33P14.26,53.5P5.58 respectively(n=6);the gastric fluid output and the gastric acidity(evaluated by pH)of the control group were(430.17P87.36)μL,1.55P0.25(n=6),and those of the OT group were(102.45P48.00)μL,2.65P0.40(n=6)res pectively;differences had statistical significance(P<0.01).The effect of oxytocin was reversed by atosiban,a selective oxytocin receptor antagonist.The GMDI of the group given atosiban 10 min before OT was 138.17P24.06(n=6),which had no significant difference with the control group.Oxytocin further attenuated GI-RI after vagotomy and sympathectomy(GMDI 6.83P8.89,29.67P5.54,n=6),compared with the GI-R group and the oxytocin group(P<0.01).These results indicated that the oxytocin could significantly protect gastric mucosal against injury induced by ischemia-reperfusion,and the oxytocin receptor was involved.This effect of oxytocin may be mediated through the vagus and sympathetic nerve,and then lead to the reduction of gastric juice output and the depression of gastric acidity.