[Function of bladder smooth muscle autophagy in cyclophosphamide-induced cystitis].

OBJECTIVE: To explore the existence of bladder smooth muscle autophagy and its function in cyclophosphamide (CYP) -induced cystitis. METHODS: A total of 30 Sprague-Dawley rats were randomized into control (n = 6) and experimental groups (4 h, 48 h, 72 h, 96 h, n = 24) . The experimental group received a single intraperitoneal injection of 150 mg/kg CYP in 0.6 ml saline while the control group had the same volume of saline injection. The changes of microtubule-associated protein light chain 3 (LC3), interleukin-6 (IL-6), IL-1β and tumor necrosis factor-alpha (TNF-α) proteins in bladder muscular layer were measured with Western blot. Co-location of LC3 and alpha-small muscle action (α-SMA) was detected with double-labeled immunofluorescence. Autophagic vacuoles were observed with electron microscopy. The changes in bladder inflammation were measured by hematoxylin and eosin staining. RESULTS: Autophagy was confirmed in detrusor myocytes with electron microscope, LC3 Western blot and double-labeled immunofluorescence. As compared with the control group, the expression level of LC3 in experimental groups decreased (0.08 ± 0.01 vs 0.13 ± 0.01, P < 0.05) at 4 h and increased 1.19, 0.75 and 0.20 fold (0.29 ± 0.04 vs 0.13 ± 0.01, P < 0.05; 0.23 ± 0.03 vs 0.13 ± 0.01, P < 0.05;0.16 ± 0.03 vs 0.13 ± 0.01, P > 0.05) at 48, 72 and 96 h respectively.Electron microscopy and double-labeled immunofluorescent also supported the above change of LC3 by Western blot.In addition, as compared with the control groups, IL-6, IL-1β and TNF-α and bladder histological scores of bladder muscular layer significantly increased in experimental groups (all P < 0.05) . CONCLUSIONS: Autophagy exists in bladder smooth muscle. In cyclophosphamide-induced cystitis, bladder smooth muscle autophagy activation may not be sufficient to protect bladder muscle layer inflammation in rats.