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Abstract Objective To explore whether Cyclic Adenosine Monophosphate (cAMP)-Epac1 signaling is activated in 1-Desamino-8-D-arginine-Vasopressin-induced Endolymphatic Hydrops (DDAVP-induced EH) and to provide new insight for further in-depth study of DDAVP-induced EH. Methods Eighteen healthy, red-eyed guinea pigs (36 ears) weighing 200-350 g were randomly divided into three groups: the control group, which received intraperitoneal injection of sterile saline (same volume as that in the other two groups) for 7 consecutive days; the DDAVP-7d group, which received intraperitoneal injection of 10 mg/mL/kg DDAVP for 7 consecutive days; and the DDAVP-14d group, which received intraperitoneal injection of 10 μg/mL/kg DDAVP for 14 consecutive days. After successful modeling, all animals were sacrificed, and cochlea tissues were collected to detect the mRNA and protein expression of the exchange protein directly activated by cAMP-1 and 2 (Epac1, Epac2), and Repressor Activator Protein-1 (Rap1) by Reverse Transcription (RT)-PCR and western blotting, respectively. Results Compared to the control group, the relative mRNA expression of Epac1, Epac2, Rap1A, and Rap1B in the cochlea tissue of the DDAVP-7d group was significantly higher (p< 0.05), while no significant difference in Rap1 GTPase activating protein (Rap1gap) mRNA expression was found between the two groups. The relative mRNA expression of Epac1, Rap1A, Rap1B, and Rap1gap in the cochlea tissue of the DDAVP-14d group was significantly higher than that of the control group (p< 0.05), while no significant difference in Epac2 mRNA expression was found between the DDAVP-14d and control groups. Comparison between the DDAVP-14d and DDAVP-7d groups showed that the DDAVP-14d group had significantly lower Epac2 and Rap1A (p< 0.05) and higher Rap1gap (p < 0.05) mRNA expression in the cochlea tissue than that of the DDAVP-7d group, while no significant differences in Epac1 and Rap1B mRNA expression were found between the two groups. Western blotting showed that Epac1 protein expression in the cochlea tissue was the highest in the DDAVP-14d group, followed by that in the DDAVP-7d group, and was the lowest in the control group, showing significant differences between groups (p< 0.05); Rap1 protein expression in the cochlea tissue was the highest in the DDAVP-7d group, followed by the DDAVP-14d group, and was the lowest in the control group, showing significant differences between groups (p< 0.05); no significant differences in Epac2 protein expression in the cochlea tissue were found among the three groups. Conclusion DDAVP upregulated Epac1 protein expression in the guinea pig cochlea, leading to activation of the inner ear cAMP-Epac1 signaling pathway. This may be an important mechanism by which DDAVP regulates endolymphatic metabolism to induce EH and affect inner ear function. Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence Level 5.
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AIM: To investigate the neuroprotective effect of ginsenoside Rg1 on rats with ischemic stroke and to investigate its mechanism of action. METHODS: Eighty-four SPF-grade SD male rats at about 13 weeks of age were randomly divided into 7 groups (n=12): sham-operated group, model group, Rg1 low-dose group, Rg1 medium-dose group, Rg1 high-dose group, Epac1 agonist group, and Epac1 inhibitor group. The model group, Rg1 low, medium and high dose groups, Epac1 agonist group and Epac1 inhibitor group were all used to establish a permanent focal cerebral ischemia rat model. Rats in the Rg1 low, medium and high dose groups were treated with 60, 120 and 240 μmol/L Rg1 administered by gavage at a fixed time every morning. The rats in the Epac1 agonist and Epac1 inhibitor groups were administered intraperitoneally at a fixed time each morning with a concentration of 1.0×10
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Increasing evidence suggests that a cyclic adenosine monophosphate (cAMP)-dependent intracellular signal drives the process of myelination. Yet, the signal transduction underlying the action of cAMP on central nervous system myelination remains undefined. In the present work, we sought to determine the role of EPAC (exchange protein activated by cAMP), a downstream effector of cAMP, in the development of the myelin sheath using EPAC1 and EPAC2 double-knockout (EPAC) mice. The results showed an age-dependent regulatory effect of EPAC1 and EPAC2 on myelin development, as their deficiency caused more myelin sheaths in postnatal early but not late adult mice. Knockout of EPAC promoted the proliferation of oligodendrocyte precursor cells and had diverse effects on myelin-related transcription factors, which in turn increased the expression of myelin-related proteins. These results indicate that EPAC proteins are negative regulators of myelination and may be promising targets for the treatment of myelin-related diseases.
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Epac, an exchange protein directly activated by cAMP, is a newly discovered guanine nucleotide exchange factor. Epac is a key factor involved in a series of cAMP mediated signaling pathways. Fibrosis disease, a common disease in clinic, usually results from excessive deposition of extracellular matrix under the stimulation of normal physiology (such as aging) or different pathogenetic factors. Epac has been reported to play an important role in fibrotic diseases, so this paper reviews this role of Epac in order to promote the research and development of Epac related mechanisms and drugs.
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OBJECTIVE In this study we explored the role of Epac1-Rap1 pathway in the acute myocardial ischemia/reperfusion injury (MIRI) in vitro and in vivo. METHODS An acute myocardial ischemia/reperfusion injury model was established by the ligation of left anterior descending coronary. Myocardial architecture, fibers and apoptosis was evaluated by the Masson trichrome staining, Sirius red staining and TUNEL assay.H9c2 cells were subjected to hypoxia for 5 h followed by 1-h reoxygen-ation in vitro.Cell viability was measured by MTT assay and cellular injury was evaluated by measuring the release of lactate dehydrogenase (LDH). Western blot, real-time PCR and immunofluorescence were used to detect the expressions of Epac1 and relative downstream molecules.RESULTS Myocardial IR-induced cardiac apoptosis and accumulation of Epac1 and Rap1 in rat IR injury model.Direct Epac activation by 8-CPT(8-(4-chlorophenylthio)-2′-O-methyl-cAMP)exacerbated cardiomyocyte death and dysfunction following hypoxia-reoxygenation(H/R),selective activation of Epac in response to H/R was evident which enriched for cytosolic/membrane proteins and mRNA. Harmacological inhibitor of Epac (ESI-09)significantly ameliorated myocardial injury with the decline of Epac expression.Epac inhibitor and agonist studies also implicated the effect of Rap1, which is downstream of Epac in this pathway. The expression of Rap1 elevated when activated by Epac agonist and was blocked by Epac inhibitor. The same result was true for myocyte CaMK-II and intracellular calcium ions activation.Moreover,ESI-09 also increased ERK1/2 phosphorylation. CONCLUSION Our study reveal that Epac1/Rap1 signaling pathway is involved in the pathogenesis of myocardial I/R injury in rats,which provides evidence on the development of therapeutic strategies target this pathway for myocardial I/R injury.
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Aim To investigate the role and mecha-nism of exchange protein directly activated by cAMP (Epac) protein in the paraventricular nucleus(PVN) of the hypothalamus in the development of inflammatory pain in rats. Methods Adult SD male rats were cho-sen to establish the model of inflammatory pain through subcutaneous injection of complete Freund's adjuvant(CFA) on the center of left hind foot. Western blot was used to detect the changes of the expression of Ep-ac protein. Thermal withdrawal latency(TWL) was ob-served after the PVN injecting 8p-CPT-2′-O-Me-cAMP (8p-CPT),the agonist of Epac. Then activated down-stream MEK1/2 protein of Epac in PVN was detected using Western blot when the potency was the strongest.Results ① Compared with normal saline(control group),TWL decreased significantly on d 1, d 3, d 5, d 7,d 9 on the ipsilateral foot of CFA group rats(P<0.01),whereas it returned to normal level in d 13;the paw mechanical withdrawal threshold(PMWT) de-creased significantly on d 6,d 8,d 10,d 12 and d 14 (P<0.05);②Compared with the control,the Epac1 protein in CFA group rats began to decrease from d 3, and significantly decreased on d 3 and d 9(P<0.05), however the expression of Epac2 had no significant change, meanwhile p-MEK1/2 protein decreased sig-nificantly on d 3(P<0.05);③Compared with micro-injection of saline into the PVN(Saline group), the heat hyperalgesia of 20 min and 1h decreased signifi-cantly and TWL increased significantly after PVN ad-ministration of 8p-CPT(8p-CPT group)(P <0.05);paraventricular nucleus p-MEK1/2 protein expression increased significantly in 30 min(P <0.05) and re-covered to normal level 2 h after administration. Con-clusion The Epac1-MEK1/2 signaling pathway in the paraventricular nucleus of the hypothalamus may be in-volved in the development of chronic inflammatory pain induced by CFA.
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Inflammatory Pain is one of the most common clinical symptom with unclear pathogenesis,which causes difficulty in patien's work and daily life. Previous studies have shown that P2X3 receptor participates in the pathological process of acute and chronic inflammatory pain. This paper focuses on the functions of P2X3 receptor in inflammatory pain and its relationship with TRPV1 receptor,inflammatory mediator and Epac-PKC signal transduction pathway,thereby provides a new thought for research and treatment of this disease.
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Objective To investigate the role of activated cylic AMP(cAMP) signaling in chemical-induced podocyte injury.Methods Eight-weeks-old male BalB/C mice were randomly divided into three groups:control group,Adriamycin (ADR) group and Forskolin+ADR group.ADR nephropathy models were established by tail intravenous injection,and part of them were injected Forskolin,an agonist of adenylate cyclase,intraperitoneally.Phosphorylation of cAMP response element binding protein (CREB) was detected by laser confocal microscopy,morphology of foot processes were determined with transmission electron microscope,and WT-1 expression in glomeruli were detected by immunohistochemistry.Conditionally immortalized podocytes were treated with puromycin aminonucleoside (PAN),Exchange protein directly activated by cAMP (Epac) agonist 8-pCPT-2-O-Me-cAMP (2Me),protein kinase A (PKA) antagonist H89 and its agonist pCPT-cAMP(pCPT).Western blot was used to detect the expression levels of Epac,caspase3 and cleaved caspase3.PKA activity was assayed using cAMP-dependent protein kinase detection system.Cell viability was determined by a cell count kit and podocyte apoptosis was estimated by TUNEL staining.Mitochondrial membrane potential was evaluated by JC-1 staining.Results (1)Compared with ADR group,the urine albumin decreased significantly (P ＜ 0.05) among Forskolin + ADR group and the WT-1 positive cells per glomerulus increased obviously (P ＜ 0.05).(2)PAN decreased podocyte number in a time-dependent manner (P ＜ 0.05),pre-treatment with pCPT obviously inhibited PAN induced podocyte decrease (P ＜0.05),but H89 prevented the effect of pCPT in a dose-dependent manner (P ＜ 0.05).(3)JC-1 staining showed that the percentage of podocyte with green fluorescence for control,PAN and pCPT+PAN group were (12.67±2.15)％,(31.35±4.60)％ and (16.96 ± 2.51)％ respectively (P ＜ 0.05),and pretreatment with H89 inhibited the effect of pCPT (P ＜ 0.05).(4) PAN promoted podocyte apoptosis and cleaved caspase3 expression (P ＜ 0.05),and pretreatment with pCPT significantly prevented PAN-induced podocyte apoptosis and cleaved caspase3 expression (P ＜ 0.05).Conclusions cAMP signaling activation ameliorated podocyte injury in ADR nice and PAN-induced podocyte apoptosis,and cAMP/ PKA pathway may mediate these processes.
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Objective To investigate the dynamic expressions of exchange protein directly activated by cyclic adenosine monophosphate (cAMP) (Epac) in rat model of hepatic fibrosis(HF).Methods Forty-two male SD rats were divided into control group (n = 6) and model group (n = 36)which was divided into six subgroups of day 4, week 1, week 2, week 4,week 6 and week 8 with six rats in each subgroup. The rat model of HF was established by intraperitoneal injection of dimethylnitrosamine (DMN). The pathological changes of liver were observed by Hematoxylin-Eosin and Masson staining. Reverse transcription-polymerase chain reaction (RT-PCR),immunohistochemistry and Western blot were employed to detect the mRNA and protein expressions of Epac1, Epac2 and transforming gronth factor (TGF)β1 during the process of modeling and localization in the liver. The statistical analysis was done using one-factor ANOVA, LSD-t test,Dunnett T3 test and Pearson linear correlation analysis. Results Rat model of liver fibrosis was established successfully. In control group, Epac1 (0. 031 28±0. 008 96) and Epac2 protein (0.034 43±0. 002 45) mainly expressed in the cytoplasm of hepatocytes. In model group, the level of Epac1 decreased at day 4 (0. 023 97±0. 003 81) and week 1 (0. 015 81±0. 002 48) ,then began to increase at week 2 of modeling and peaked at week 6 (0. 039 54±0. 001 43), which had statistical significance compared to the control group (t= 5.47,11.58 and - 6.18, respectively; all P＜0.05). Epac2 protein expression declined after modeling, reached the lowest level at week 4 (0. 011 21 ±0. 001 32), which had statistical significance compared to the control group (t= 24. 50, P＜0. 05). TGFβ1 protein expression increased after modeling and peaked at week 4 (0. 011 30±0.001 03) which had statistical significance (t= -23. 36, P＜0. 05) compared to the control group (0. 002 08 ±0. 000 18). The expressions of Epac1, Epac2 and TGFβ1 mRNA were consistent with the trend of protein levels.Correlation analysis showed that Epac1 protein was positively correlated with the course of HF (r =0. 703, P＜0.01 ), while Epac2 protein was negatively correlated (r = - 0. 409, P＜0.05). Conclusions During the progression of HF, Epac1 expression tends to decrease firstly and increase afterwards,while Epac2 expression declines continually. Epac may be involved in the pathogenesis of HF.