Epididymo-orchitis is a common disease in Bactrian camels that affects male fertility and animal husbandry development, but the regulatory mechanism of epididymo-orchitis is not clear. The present study was planned to focus on the anti-inflammatory effects of melatonin on its receptor (MT1/2) and explore the mechanism of regulation of inflammation by cryptochromes (Cry1/2) as an activating protein of MT1/2. An in vitro inflammation model was established using primary epithelial cells of the caput epididymis of six slaughtered Bactrian camels, together with an in vivo inflammation model of mice epididymo-orchitis was established to explore the role of MT1/2-Cry module in regulating inflammation. Subsequently, histological changes (H&E staining assay), protein expression (immunohistochemistry and Western blot assay), gene expression (RT-qPCR assay), cytokine levels (ELISA), and sperm malformation rates were assessed. The in vitro experimental results showed that melatonin relied on its receptor MT1/2 to inhibit the expression of inflammatory markers (CD14, TLR4, MYD88, NF-κB, IL-6, IL-18) by activating the TLR4/NF-κB signaling pathway. The performance of combination of Cry1/2 and melatonin was better than that of melatonin alone, and the anti-inflammatory effect of Cry was regulated by MT1/2. The results of in vivo inflammatory model experiments showed that melatonin improved the pathological damage of the testis and epididymis, and upregulated the expression of genes associated with germ cell structure and cell adhesion-related genes (Nectin3, PRM1, TH2B). Through Cry gene intervention and melatonin combination therapy, it was found that Cry1 and melatonin had a synergistic effect, and their combination can more effectively inhibit inflammatory responses and improve reproductive-related parameters. This study provides new potential targets and theoretical basis for the treatment of epididymo-orchitis in Bactrian camels.

To Cite This Article: Ji S, Li M, Hou J, Fang Y, Wu C, Gao Y and Zhao S, 2026. Melatonin-mediated regulation of circadian protein cryptochrome signaling in suppressing Epididymo-orchitis in Bactrian camels. Pak Vet J, 46(3): 518-531. http://dx.doi.org/10.29261/pakvetj/2026.041