RESUMO
Objective Adenosine receptor agonist NECA has a certain myocardial protection, but the specific mechanism is not clear.This paper aimed to study the effect and mechanism of NECA inhibiting endoplasmic reticulum stress to against myocardial ischemia reperfusion injury in rats.Methods 56 Wistar rats of SPF grade were selected and divided into Sham group, I/R group, NECA group and TUDCA group through random number table method.We established the isolated rat heart ischemia reperfusion model by using the Langendorff device.Sham group: heart threaded but not ligated, Kerb-Henseleit buffer continuous infusion 170min;I/R group: heart stability 20min, ischemia 30min, reperfusion 2h;NECA group and TUDCA group: heart stability 20min, ischemia 30min, reperfusion 2h, perfusion solutions containing 0.1μmol/L NECA and 30μmol/L TUDCA were respectively given at 5min before reperfusion, and ended at 30min after reperfusion.Transmission electron microscope was used to evaluate alterations of the myocardial ultrastructures.Western blot analysis was used to detected the expression levels of endoplasmic reticulum stress IREl-XBPl signaling pathway marker protein IRE1α, XBP1s.Immunohistochemical staining was used to detect the expression of IRE1α.Results The results of transmission electron microscopy showed that most of the myofilament ruptured, sarcomere contracture deformation, visible mitochondrial vacuoles degeneration in I/R group, and injury in NECA group and TUDCA group were less than the I/R group, appeared as the filaments arranged more neat, sarcoma only had mild contracture.Immunohistochemical results showed that IRE1αpositive staining was not found in the sham group, and the area of positive staining of IRE1α in I/R group was significantly increased, while the NECA group and TUDCA group were significantly decreased.Compared to the Sham group, the expression level of IRE1α and XBP1s was significantly increased in I/R group(P<0.05);but compared with the expression level of IREα and XBP1s in I/R group(1.72±0.27, 0.97±0.19), the NECA group(1.14±0.16, 0.6±0.13) and the TUDCA(1.07±0.27, 0.58±0.15) group were significantly decreased(P<0.05).Conclusion NECA can reduce endoplasmic reticulum stress through inhibiting IREl-XBPl pathway to protect the myocardium.
RESUMO
BACKGROUND: This experiments investigated the signaling cascade responsible for anti-infarct effect by an A2 adenosine receptor (AR) agonist 5'-N-Ethylcarboxaminidoadenosine (NECA). METHODS: Langendorff perfused isolated rat hearts were subjected to 30 minutes of regional ischemia and 120 minutes of reperfusion. Drugs were perfused for a period of 5 minutes before and 60 minutes after reperfusion. For comparison of cardioprotection among groups, area at necrosis (AN) and area at risk (AAR) were measured by triphenyltetrazolium chloride staining. RESULTS: NECA significantly attenuated AN/AAR (14.1 +/- 1.9%, P < 0.001) compared with control hearts (30.7 +/- 2.8%). Anti-infarct effect by NECA was attenuated by an A(2A)AR antagonist 8-(3-chlorostyryl)caffeine (23.7 +/- 3.4%, P < 0.05) and an A(2B)AR antagonist MRS1706 (29.9 +/- 3.3%, P < 0.001). Cardioprotection by NECA was blocked by a guanylyl cyclase inhibitor (23.1 +/- 2.9%, P < 0.05) and a protein kinase G (PKG) inhibitor KT5823 (30.3 +/- 3.2%, P < 0.001). Glycogen synthase kinase-3beta (GSK-3beta) inhibitor SB216763 attenuated the AN/AAR in both NECA with MRS (17.8 +/- 2.7%, P < 0.01 vs. control) and NECA with KT5823 treated hearts (8.2 +/- 1.8%, P < 0.001 vs. control). The mitochondrial permeability transition pore (mPTP) opener atractyloside also aborted NECA's anti-infarct effect (24.7 +/- 2.4% P < 0.05). CONCLUSIONS: The signaling pathway by NECA administered at reperfusion involves the activation of both A2AAR and A2BAR and cGMP/PKG pathway, which in turn depends on inactivation of GSK-3beta and inhibition of mPTP opening.