The Effect Of Endurance Training-induced Phenotypic Changes Of Rat Adrenal Medulla Chromaffin Cells On EIB

Objective:The purpose of this study is to clarify the effect of endurance exercise on the structure and function of adrenal medulla chromaffin cells and the role of it in the pathogenesis of exercise-induced bronchoconstriction.Methods:Rats were subjected to moderate-intensity or high-intensity treadmill training, after that they were exposed to NGF antiserum intervention, exhaustive exercise or ovalbumin (OVA) intervention (sensitization and challenge).120male Sprague-Dawley rats were randomly divided into15groups(n=8per group):1) control group;2) exhaustive exercise group (ExhEx group);3) moderate-intensity training group (MoTr group);4) MoTr+NGF antiserum group (MoTrN group);5) MoTr+exhaustive exercise group (MoTr+ExhEx group);6) MoTr+NGF antiserum+exhaustive exercise group (MoTrN+ExhEx group);7) high-intensity training group (HiTr group);8) HiTr+NGF antiserum group (HiTrN group);9) HiTr+exhaustive exercise group (HiTr+ExhEx group);10) HiTr+NGF antiserum+exhaustive exercise group (HiTrN+ExhEx group);11) OVA-treated group (OVA group);12) OVA-treated+MoTr group (OVA+MoTr group);13) OVA-treated+MoTr+NGF antiserum group (OVA+MoTrN group);14) OVA-treated+HiTr group (OVA+HiTr group);15) OVA-treated+HiTr+NGF antiserum (OVA+HiTrN group). Airway resistance and white cell differential counting in broncholalveolar lavage fluid were measured. Epinephrine (EPI), nerve growth factor (NGF), corticosterone (CORT) levels in serum of rats were tested by ELISA. Histopathology structure of rat bronchopulmonary tissue and adrenal medulla were observed under light microscope. Ultrastructure of adrenal medulla chromaffin cells under transmission electron microscope was studied. The expression of phenylethanolamine N-methyl transferase (PNMT) and peripherin in adrenal medulla tissue of rat were measured by immunohistochemistry. Western blot was used to study the protein content of p-ERK/ERK、p-p38/p38, p-JNK/JNK and peripherin in rat adrenal tissue. Real-time PCR and western blot were used to test the expressions of mRNA and protein of JMJD3and Mash1, respectively.Results:1. Compared to control group and MoTr group, the infiltrated lymphocyte count and the airway resistance were significantly increased in the HiTr group. In the HiTr group, examination of adrenal medulla cells revealed a vacuolar degeneration、decreased chromaffin granules, and outgrowth of cell processes. HiTr intervention up-regulated circulating NGF level and peripherin level in adrenal medulla, but down-regulated phenylethanolamine N-methyl transferase level in adrenal medulla and circulating EPI level. The levels of p-ERK1/2, JMJD3, and Mash1were significantly increased, but the levels of p-p38and p-JNK were significantly decreased in adrenal medulla in rats of HiTr group. Injection of NGF antiserum reversed these pathophysiological changes observed in rats of HiTr group.2. Compared to control group, the airway resistance were significantly increased in ExhEx group. In ExhEx group, examination of adrenal medulla cells showed an extension of blood sinusoid in adrenal medulla. Exhaustive exercise up-regulated circulating NGF、EPI levels and PNMT、p-ERK levels in adrenal medulla, but did not affect the levels of circulating NGF and JMJD3、Mash1in adrenal medulla. Compared to HiTr group, the infiltrated lymphocyte count in airway and the airway resistance were significantly increased in HiTr+ExhEx group. The levels of peripherin, p-Erkl/2, JMJD3, and Mash1were significantly increased, but the levels of circulating EPI、CORT、NGF were not significantly altered in adrenal medulla in HiTr+ExhEx group. After injection of NGF antiserum, these pathophysiological changes observed in HiTrN+ExhEx group were ameliorated by contrast to HiTr+ExhEx group. 3. Compared to control group and HiTr group, OVA intervention significantly increased the infiltration of various inflammatory cells including lymphocytes, macrophages, eosinophils and neutrophils in bronchoalveolar lavage. OVA intervention significantly increased airway resistance and the serum NGF level, however, decreased the CORT level. Compared to control group, examination of adrenal medulla cells revealed decreased chromaffin granules, and outgrowth of cell processes. Besides, OVA intervention up-regulated peripherin、 p-ERK/ERK、JMJD3、Mashl levels in adrenal medulla, but down-regulated PNMT level in adrenal medulla and circulating EPI level. OVA+HiTr interventions significantly enhanced most of the effects of OVA intervention. Injection of NGF antiserum and moderate-intensity training reversed these changes observed in HiTr and/or OVA rats.Conclusion:1. High-intensity training could provoke neuron phenotypic changes of rat adrenal medulla chromaffin cells through NGF-induced upregulating p-ERK-JMJD3-Mashl pathway.2. Exhaustive exercise could cause bronchoconstriction of rats in high-intensity training group, which is related to the decreased circumlation EPI level due to neuron phenotypic changes of adrenal medulla chromaffin cells. 3. The interaction of high-intensity training and OVA intervention could exacerbate neuron phenotypic changes of adrenal medulla chromaffin cells; however, moderate-intensity training has partly reversal effect on the phenotypic changes.38figures,14tables,67references.