Melatonin Ameliorates LPS-Induced Testicular Nitro-oxidative Stress (iNOS/TNFα) and Inflammation (NF-kB/COX-2) via Modulation of SIRT-1

Abstract

Lipopolysaccharide (LPS) — an endotoxin that is being extensively used in laboratory to mimic microbial infection that adversely affects male fertility. This study investigated the protective effects of melatonin on LPS-induced testicular nitro-oxidative stress, inflammation, and associated damages in the testes of male golden hamsters, Mesocricetus auratus. Hamsters were administered with melatonin and LPS for 7 days. Testes of LPS treated hamsters showed degenerative changes (appearance of vacuoles, exfoliation, and depletion of germ cells in the seminiferous tubules), adverse effects on spermatogenesis (sperm count and viability), and steroidogenesis (declined serum and testicular testosterone). Furthermore, LPS treatment decreased melatonin content, melatonin receptor (MT1), and antioxidant potential (catalase and SOD), and simultaneously increased nitro-oxidative stress (CRP, nitrate, TNFα). LPS upregulated NF-kB, COX-2, and iNOS expressions to increase testicular inflammatory load that resulted in the decrease of germ cell proliferation and survival, thus culminating into germ cell apoptosis as indicated by AO-EB staining and caspase-3 expression. Administration of melatonin with LPS showed improved testicular histoarchitecture, sperm parameters, and testosterone level. Melatonin increased testicular antioxidant status (SOD, catalase) to counteract the LPS-induced testicular ROS and thus reduced testicular nitro-oxidative stress. Furthermore, melatonin treatment upregulated testicular SIRT-1 expression to inhibit LPS-induced inflammatory proteins, i.e., NF-kB/COX-2/iNOS expression. The rescue effect of melatonin was further supported by increased germ cell survival (Bcl-2), proliferation (PCNA), and declined apoptosis (caspase-3). In conclusion, our result demonstrated that melatonin rescued testes from LPS-induced testicular nitro-oxidative stress, inflammation, and associated damages by upregulation of SIRT-1.