Abstract:

Objective： To explore the effect of pituitary adenylate cyclase activating polypeptide（PACAP）27 on the cyclophosphamide-induced testicular injury in the rats， and to clarify its possible mechanism. Methods Sixty SD rats were randomly divided into control group， model group， PACAP27 group and L-carnitine group， with 15 rats in each group.Except control group，the rats in other groups were treated with cyclophosphamide to establish the models and administrited with drugs. On the 3rd day after the administration， the weights of rats and the testis were weighed， and the testis index was calculated；the levels of serum follicle-stimulating hormone （FSH）， luteinizing hormone （LH） and testosterone （T） of the rats in various groups were measured by radioimmunoassay， HE staining was used to observe the pathomorphology of testis tissue of the rats in various groups； the activities of superoxide dismutase （SOD）， catalase （CAT） and the levels of malondialdehyde （MDA） in testis tissue of the rats in various groups were detected by enzyme linked immunosorbent assay（ELISA） method， TUNEL staining was used to detect the apoptotic rates of testicular tissue of the rats in various groups， and Western blotting method was used to detect the expression levels of mitochondrial apoptosis pathway-related proteins.The testicular tissue mitochondria were extracted， the opening degrees of the mitochondrial permeability transition pore （mPTP） of the rats in various groups were detected with mitochondrionl isolation reagent， and JC-1 fluorescent staining was used to detect the mitochondrial membrane potential. Results Compared with control group， the body weight， testis weight and testis index of the rats in model group were decreased （P<0.05）， the levels of FSH， LH and T in serum were decreased （P<0.05）， the activities of SOD and CAT in testis tissue were decreased （P<0.05）， the level of MDA was increased （P<0.05）， the testis tissue had obvious pathological damage， and the apoptotic rate was increased （P<0.05）， the expression levels of cytochrome C（Cyt C），B-cell lymphoma-2 associated X protein（Bax），cysteinyl aspartate specific proteinase-3（caspase-3） and cysteinyl aspartate specific proteinase-9（caspase-9） proteins were increased （P<0.05）， the expression level of B-cell lymphoma-2（Bcl-2） protein was decreased （P<0.05）， the opening degree of mPTP was enhanced （P<0.05）， and the mitochondrial membrane potential was decreased （P<0.05）. Compared with model group， the testis weights and testis indexes of the rats in PACAP27 group and L-carnitine group were increased （P<0.05）， the levels of FSH， LH and T in serum were increased （P<0.05）， the activities of SOD and CAT were increased （P<0.05）， the levels of MDA were decreased （P<0.05）， the pathological damages of testis tissue were improved， the apoptotic rates were decreased （P<0.05）， the expression levels of Cyt C， Bax， caspase-3 and caspase-9 proteins were decreased （P<0.05）， the expression levels of Bcl-2 protein were increased （P<0.05），the mPTP opening degrees were decreased（P<0.05），and the mitochondrial membrane potentials were increased （P<0.05）. Conclusion PACAP27 may alleviate cyclophosphamide-induced testicular injury in the rats by inhibiting mitochondria-dependent apoptosis pathway.

Key words: Testicular injury, Cyclophosphamide, Pituitary adenylate cyclase activating polypeptide 27, Mitochondrial-dependent apoptosis pathway