Cellular pathophysiology of Leptospira interrogans infection in canine testicular tissue: role of the TLR4/NF-kB/JNK pathway.

Leptospirosis is a prevalent zoonotic disease in dogs. Although it is known that leptospires are primarily harboured in kidney tissues of dogs, it has been reported that they also infect testicular tissue. Leptospira interrogans causes various lesions in canine testicular tissues; however, the pathogenesis has not been clearly explained. In this study, 20 canine testicular tissue samples infected with L. interrogans were investigated for evidence of oxidative DNA damage, inflammation, apoptosis and autophagy. Ten samples of canine testicular tissue that were negative for L. interrogans were used as a positive control group. All tissues were examined by histopathological, immunohistochemistry (IHC) and immunofluorescence (IF) methods. Histopathological examination revealed that testicular tissues infected with L. interrogans had inflammation and oedema, and degeneration and necrosis of spermatocytes. In cases of severe disease, enzyme-linked immunosorbent assay, reverse transcriptase polymer chain reaction and IHC and IF indicated significant increases in levels of TLR4, NF-kB, IL-1β, TNF-α, 8-OHdG, JNK1/3, caspase-8, caspase-3, LC3A and LC3B but lower levels in milder cases. These results indicate that L. interrogans stimulated the immune system through the TLR4/NF-kB/JNK pathway in dog testicular tissues, leading to inflammation and apoptosis. The infection also caused oxidative DNA damage and autophagy.