BACKGROUND: Ischemic postconditioning protects the myocardium from ischemia/recursion injury via maintaining 3-minute acidosis initially. But its effect on the skeletal muscle remains unclear. OBJECTIVE: To dynamically measure the pH values in rat skeletal muscle after ischemia, and then to simulate acidic perfusate infusion to investigate the effect of ischemic postconditioning on ischemia/reperfusion injury. METHODS: Based on the ischemia/reperfusion injury model and ischemic postconditioning protocol in previous study, dynamic measurement of pH values in rat skeletal muscle was conducted using pH instrument at the global ischemia, ischemic postconditioning (30/30 seconds) and reperfusion period, and then the acidic perfusate equivalent to pH in ischemic postconditioning period was prepared with lactic acid and normal saline. Twenty-five healthy adult male Sprague-Dawley rats were randomly divided into sham, ischemia/reperfusion, ischemic postconditioning, lactic acid, and normal saline groups (n=5 per group). Blood samples were collected to detect lactate dehydrogenase level. The samples from gastrocnemius were harvested to calculate the wet/dry ratio, level of myeloperoxidase, and infarct size through triphenyltetrazolium chloride staining. The samples from the right tibialis anterior muscle were taken to detect the expression level of Erk1/2 in the MAPK signaling pathway by western blot assay. RESULTS AND CONCLUSION: A prolonged acidic platform was detected in the early reperfusion during ischemic postconditioning, on which the pH value was 6.81±0.133, and the duration was 2 minutes and 40 seconds. The levels of lactate dehydrogenase and myeloperoxidase as well as the wet/dry ratio in the ischemic postconditioning and lactic acid groups were significantly lower than those in the ischemia/reperfusion group (P < 0.05). Western blot assay results showed that the expression level of p-Erk in the ischemic postconditioning, lactic acid and normal saline groups was significantly higher than that in the ischemia/reperfusion group (P < 0.05). Triphenyltetrazolium chloride staining results showed that compared with the ischemia/reperfusion group, the infarct area was significantly reduced in the postconditioning and lactic acid groups (P < 0.05). These findings suggest the existence of a short acidosis during ischemic postconditioning in the early reperfusion, and acidic perfusate can simulate the ischemic postconditioning and effectively attenuate ischemia/reperfusion injury in the rat skeletal muscle via activating Erk1/2 in RISK signaling pathway.

Objective To analyze the relationship between the serum B-cell activating factor (BAFF) levels and clinical characters and pathological features in children with lupus nephritis (LN). Methods ELISA was used to detect the serum BAFF (sBAFF) levels of the 54 LN children diagnosed in the First Affiliated Hospital, Sun Yat-sen University during October 1, 2014 to December 31, 2016 and with complete clinical data. According to whether glucocorticoid or immunosuppressive agents has been used at their first admission, patients were divided into treated group (n=44) and non-therapy group (n=10). According to the renal response after induction treatment for 6 months, patients were divided into remission group (n=20) and non-response group (n=34). According to whether there was renal recurrence, they were divided into recurrence group (6 cases) and non-recurrence group (48 cases). According to renal biopsy, patients were divided into class-Ⅲ, class-Ⅳ and class-Ⅴ group. Another 15 healthy children were taken as a control group. The correlations between sBAFF and clinical manifestation, laboratory examination, renal biopsy and clinical outcome were analyzed. Results (1) Compared with the control group, the sBAFF was significantly increased in LN group (t=3.821, P<0.001). Compared with the non- neuropsychiatric systemic lupus erythematosus (NPSLE) group, sBAFF was significantly increased in NPSLE group (t=2.202, P=0.032). (2) Compared with that in treated group, sBAFF was significantly higher in untreated group (LSD - t=2.309, P=0.025). Compared with non-response group, sBAFF was significantly decreased in response group (LSD-t=2.035, P=0.046). (3) No significant difference was observed between class-Ⅲ, class-Ⅳ and class-Ⅴpathological classification group (F=1.080, P=0.459). sBAFF in LN children was not significantly correlated with the active index (AI) or chronic index (CI) of Austin index (r=-0.273, P=0.063; r=0.150, P=0.314). (4) In LN children, sBAFF has positive correlation with ESR and IgG level (r=0.289, P=0.036; r=0.340, P=0.017) and negative correlation with WBC (r=-0.337, P=0.013). Multiple linear regression model showed that serum IgG level (β'=0.517, P=0.001) and renal response (β'=-0.271, P=0.037) were independent influencing factors of sBAFF level. Conclusions Renal remission and serum IgG levels in LN children are influencing factors of sBAFF levels. sBAFF is helpful to clinical assessment on renal response of LN children.