Objective: To observe the effects of rapamycin on glucose-induced autophagy and apoptosis of corpus cavernosum smooth muscle cells (CCSMC) in SD rats.
Methods: After primary isolation, purification and identification, CCSMCs were treated with glucose at 5.6, 10, 20, 30 and 40 mmol/L for 48 hours. The autophagy flow was detected in the cells transfected with mCherry-GFP-LC3B double fluorescent adenovirus, the protein and mRNA expressions of autophagy-related gene 5 (ATG5), microtubule-associated protein 1 light chain 3 (LC3), P62 and Beclin-1 determined by Western blot and PCR and the apoptosis of the CCSMC measured by flow cytometry, followed by detection of the changes in the protein and mRNA levels of LC3, Beclin-1 and P62 and the apoptosis of the cells after 2-hour pretreatment with 600 nmol/L rapamycin and then 48-hour treatment with 40 mmol/L glucose.
Results: Autophagy was observed in the CCSMCs treated with different concentrations of glucose, the strongest in the 10 mmol/L group (P < 0.05) and then gradually decreasing with the increase of glucose concentration (P < 0.05). The apoptosis rate of the CCSMCs was remarkably increased in a concentration-dependent manner after treated with glucose (P < 0.01) though with no statistically significant difference between the 5.6 and 10 mmol/L groups (P = 0.302). After pretreatment with rapamycin, the expression of the LC3 protein and those of the Beclin-1 protein and mRNA were markedly up-regulated (P < 0.05), while those of the P62 protein and mRNA remarkably down-regulated (P < 0.05), indicating the enhancement of autophagy, and the apoptosis rate of the CCSMCs dramatically decreased (P < 0.01).
Conclusions: In vitro culture of CCSMCs with glucose within a certain range of concentration can promote autophagy, inhibit the apoptosis and thus have a protective effect on the cells, but when the proper concentration exceeded, it may also reduce autophagy, promote the apoptosis and consequently affect the vitality and function of CCSMCs.
Keywords: apoptosis; autophagy; corpus cavernosum smooth muscle cell; rapamycin; rat; erectile dysfunction.