Neuroprotection of exercise: P2X4R and P2X7R regulate BDNF actions.

The neurotrophin brain-derived neurotrophic factor (BDNF), which acts as a transducer, is responsible for improving cerebral stroke, neuropathic pain, and depression. Exercise can alter extracellular nucleotide levels and purinergic receptors in central nervous system (CNS) structures. This inevitably activates or inhibits the expression of BDNF via purinergic receptors, particularly the P2X receptor (P2XR), to alleviate pathological progression. In addition, the significant involvement of sensitive P2X4R in mediating increased BDNF and p38-MAPK for intracerebral hemorrhage and pain hypersensitivity has been reported. Moreover, archetypal P2X7R blockade induces mouse antidepressant-like behavior and analgesia by BDNF release. This review summarizes BDNF-mediated neural effects via purinergic receptors, speculates that P2X4R and P2X7R could be priming molecules in exercise-mediated changes in BDNF, and provides strategies for the protective mechanism of exercise in neurogenic disease.

[The role of clock gene BMAL1 in exercise-induced skeletal muscle injury recovery].

Objective: To investigate the role of clock gene BMAL1 in exercise-induced skeletal muscle injury recovery. Methods: Two hundred and eight 8-week-old SD rats were randomly divided into the control group (Group C, n=104) and the exercise group (Group E, n=104). Group E performed a 90-minute downhill run on the treadmill. After exercise, the gastrocnemius muscle of 8 rats in Group C and Group E were collected at 0 h, 6 h, 12 h, 18 h, 24 h, 30 h, 36 h, 42 h, 48 h, 54 h, 60 h, 66 h and 72 h. The expression of skeletal muscle core clock gene, BMAL1 was measured by real-time fluorescence quantitative PCR. The parameters of fitting cosine curve were obtained by cosine analysis software circacompare (R package), and the change trend of rhythmic oscillation was analyzed. The ultrastructure of skeletal muscle fibers was observed by transmission electron microscope. The expressions of skeletal muscle BMAL1 and DESMIN were detected by Western blot; Immunofluorescence was used to observe the localization and contents of BMAL1 and DESMIN. Results: In Group C, three complete circadian rhythm cycles of mRNA BMAL1 were observed within 72 hours; in Group E, the circadian rhythm of BMAL1 mRNA disappeared at 0 h～24 h. Compared with Group C, the expression level of BMAL1 mRNA was significantly increased at 0 h, 6 h, 12 h, and 18 h after exercise in Group E (P＜0.05), and the expression of BMAL1 protein was significantly increased at 0 h and 12 h after exercise(P＜0.05), and recovered to the level of that in Group C from 24 h to 72 h(P＞0.05). The expression of DESMIN protein was decreased at 0 h and 12 h after exercise(P＜0.05), gradually increased at 24 h, increased significantly at 48 h(P＜0.01), and recovered to the control level at 72 h (P＞0.05). In Group E, BMAL1 and DESMIN were co-localized at 0 h, 12 h, and 24 h after exercise; the colocalization at 0 h～24 h showed a trend of first decreasing and then increasing, and the fluorescence intensity at 24 h reached the highest value. Conclusion: The post-exercise clock gene BMAL1 may be involved in the enhanced synergy of regulating the cytoskeletal protein DESMIN, it is thus related to the promotion of muscle fiber structure recovery.

[Effects of acupuncture on endoplasmic reticulum pathway in exercise-induced skeletal muscle damage in rats and its mechanism].

Objective: To observe the effects of acupuncture on the endoplasmic reticulum (ER) functional enzymes sarcoplasmic reticulum Ca2+-ATPase (SERCA), protein disulfide isomerase (PDI), glucose-regulated protein 78(GRP78) and PERK pathways in rats with exercise-induced skeletal muscle damage, and to explore the mechanisms of acupuncture in preventing and treating exercise-induced skeletal muscle damage. Methods: Eight-week-old male SD rats were randomly divided into control group (group C, n=6), exercise group (group E, n=30), acupuncture group (group A, n=30) and exercise acupuncture group (group EA, n=30). Among them, the E and EA group were established an exercise-induced skeletal muscle damage model by a single eccentric exercise, and acupuncture intervention was applied 0.5 cm above the Achilles tendon of the rat's calf immediately after EA exercise, and in group A, acupuncture intervention was applied during the same period. Each group was divided into 0 h/12 h/24 h/48 h/72 h (n=6) according to different sampling time points after exercise and acupuncture intervention, and soleus muscle was collected at the corresponding time for index test. The ultrastructure of muscle fibers was observed by transmission electron microscopy; the contents of SERCA and PDI were determined by ELISA; and the expressions of ER stress marker proteins GRP78 and p-PERK and p-eIF2α were detected by Western blot. Results: Compared with group C, there were no significant differences in the indicators of group A at all time points (P＞ 0.05), the ultrastructure of muscle fibers in group E showed different damages, SERCA content was significantly decreased from 0 h to 48 h (P＜0.05), PDI content was significantly increased from 0 h to 72 h (P＜0.05), GRP78 expression was significantly increased from 0 h to 72 h (P＜0.05), p-PERK expression was significantly increased from 0 h to 24 h (P＜0.05), and p-eIF2α expression was consistent with p-PERK. Compared with the corresponding times in group E, the ultrastructure of muscle fibers in group EA was significantly alleviated, SERCA content was significantly increased from 48 h and 72 h (P＜0.05), PDI content was significantly increased from 0 h to 72 h (P＜0.05), and GRP78 expression was significantly decreased from 0 h to 72 h (P＜0.05). Conclusion: Acupuncture can effectively ameliorate exercise-induced skeletal muscle damage and alleviate ER stress after a large load eccentric exercise. The mechanism of them may be related to the up-regulation of protein disulfide isomerase PDI and the inhibition of ER stress PERK pathway.