| Backround and Objective: Coronary heart disease was clinically commondiseases. Adenosine triphosphate （ATP） played an important role in signaltransmission via acting on purinergic receptors. Previous research study in ourlaboratory showed that the expressions of P2X2, P2X3and P2X2/3receptors wereenhanced after myocardial ischemic injury in superior cervical ganglia（SCG） andstellate ganglia （SG）, thereby strengthening the activity of sympathetic postganglionicneurons, increasing blood pressure and heart rate in sympathetic excitability reflex.P2X7receptor is involved in some function and diseases. It is not clear whetherP2X7receptor of cervical sympathetic ganglia plays a role in the signal transmissionof myocardial ischemic injury. This study observed the role of P2X7receptors in thesignal transmission of sympathetic excitability reflex caused by myocardial ischemiaand provided new therapeutic targets for the prevention and treatment of coronaryheart disease.Methods: Myocardial ischemic rat model was used in our study. Rats wererandomly divided into the control group, myocardial ischemic group, sham group andmyocardial ischemic rats treated with P2X7receptor antagonist （oxATP） group. Thestudies were as follows:⑴The myocardial ischemic injury rat model was establishedby ligating the left anterior descending coronary artery. Electrocardiogram （ECG） andHE stain of cardiac tissue were used to observe the changes of heart function andcardiac tissue in myocardial ischemic rats.⑵The blood pressure and heart rates weremonitored by non-invasive blood pressure determinator in control group, myocardialischemic group, sham group and myocardial ischemic rats treated with oxATP group.⑶Creatine kinase （CK）, creatine kinase isoform MB （CK-MB）, lactatedehydrogenase （LDH） and cardiac troponin I （cTn-I）（cardiac markers） weremeasured in control group, myocardial ischemic group, sham group and myocardialischemic rats treated with oxATP group.⑷The coexpressions of P2X7receptor andtyrosine hydroxylase （TH） antibody in rat SCG, SG neurons and myocardialsympathetic nerves of different groups were detected by double-labelled immuno- fluorescence.⑸The expression of P2X7receptor protein in rat SCG, SG neurons andcardiac tissue were analyzed by immunohistochemistry and western blotting in eachgroup. The expression of ERK and p-ERK was analyzed by western blotting in eachgroup.⑹The expression of P2X7receptor mRNA in rat SCG and SG neurons wereanalyzed by in situ hybridization（ISH）method.（7）The concentration of IL-6andTNF-α in blood serum was measured by ELISA.Results:⑴After ligating the left coronary anterior descending coronary artery,ST segment of ECG in myocardial ischemic rats was highly upward. After7and30days, the abnormal Q wave appeared obviously in myocardial ischemic rats. HE stainin myocardial ischemic rats showed myocardial atrophy, fibrosis significant bleedingor necrosis. After treated with oxATP, abnormal changes in ECG and myocardialtissue induced by myocardial ischemia were improved.⑵Compared with the data incontrol group, sham group and myocardial ischemic rats treated with oxATP group,the systolic blood pressure, diastolic blood pressure and heart rate in the myocardialischemic group rats were increased （n=5）（p<0.05）. Systolic blood pressure, diastolicblood pressure in control group, sham group and myocardial ischemic rats treatedwith oxATP group were no significant differences （n=5）（p>0.05）.⑶Compared withdata in control group, sham group and myocardial ischemic rats treated with oxATPgroup, CK, CK-MB, LDH and cTn-I of blood serum in the myocardial ischemicgroup rats were increased（n=5）（p<0.05）.⑷Double-labelled immunofluorescenceresults showed that P2X7receptors and TH antibody were co-expressed in SCG, SGsympathetic neurons and cardiac sympathetic nerves. The co-expressed cell of P2X7receptors and TH antibody in myocardial ischemic group exhibited more intensestaining than those in control group, sham group and myocardial ischemic rats treatedwith oxATP group. No difference was found in control group, sham group andmyocardial ischemic rats treated with oxATP group.⑸The expression value of P2X7immunoreactivity in SCG and SG neurons was studied by immunohistochemistry. InSCG and SG neurons, the integrated optical density （IOD） of P2X7receptorexpression in myocardial ischemic group was significantly higher than that in controlgroup, sham group and myocardial ischemic rats treated with oxATP group （n=10）（p<0.05）. No difference was found in the intensity of P2X7receptor in control group, sham group and myocardial ischemic rats treated with oxATP group （n=10）（p>0.05）.⑹The P2X7protein level was analyzed by western blotting. The IOD of P2X7proteinexpression （normalized to each β-actin internal control） in SCG, SG neurons andcardiac tissue of myocardial ischemic group was significantly higher than that incontrol group, sham group and myocardial ischemic rats treated with oxATP group（n=10）（p<0.05）. No difference was found in control group, sham group andmyocardial ischemic rats treated with oxATP group （n=10）（p>0.05）. The IOD ofp-ERK1/2protein expression in myocardial ischemic group was significantly higherthan those in control, sham and myocardial ischemic rats treated with oxATP group（p<0.05）. No difference was found among control, sham and myocardial ischemic ratstreated with oxATP group （p>0.05）. There is no difference in ERK1/2proteinexpression between each group （p>0.05）.⑺The levels of P2X7mRNA were studiedby ISH. The average ODs of P2X7receptor mRNA in the SCG and SG in myocardialischemic group was significantly higher than those in control group, sham group andmyocardial ischemic rats treated with oxATP group （n=10）（p<0.05）. No differencewas found in control group, sham group and myocardial ischemic rats treated withoxATP group （n=10）（p>0.05）.（8） ELISA results show that the concentration of IL-6and TNF-α in myocardial ischemic group was significantly higher than those incontrol group, sham group and myocardial ischemic rats treated with oxATP group（p<0.05）. No difference was found in the concentration of TNF-α and IL-6amongcontrol group, sham group and myocardial ischemic rats treated with oxATP group（p>0.05）.Conclusions: Expressions of P2X7receptors in the superior cervical, stellatesympathetic ganglia and cardiac sympathetic nerves of myocardial ischemic rats wereincreased. Expressions of P2X7receptors in SCG, SG and cardiac sympathetic nervesin myocardial ischemic rats were decreased after treated by P2X7receptor antagonist（oxATP）. oxATP may inhibit the excitation transmission of cervical sympatheticnerves and then systolic blood pressure reduced, heart rate slowed down inmyocardial ischemic injury rats. P2X7receptors in SCG, SG and cardiac sympatheticnerves were involved in the sympathetic reflex process mediated by myocardialischemic nociceptive signal. |
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