Immunomodulatory Effect of Chymotrypsin in CNS Is Sex-independent: Evidence of Anti-inflammatory Role for IL-17 in EAE

Multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), are inflammatory autoimmune diseases of the central nervous system. Chymotrypsin is a serine protease with immunomodulatory effect in the peripheral organs. We previously demonstrated the immunomodulatory effect of chymotrypsin in ameliorating the EAE in female Lewis rats. However, there are sex-based differences in the immune system, drug activity, and CNS structure and composition. In addition, female gender is a better prognostic indicator of MS and males are more severely affected by EAE than females. Consequently, gender may have an important impact on therapeutic effect. Therefore, in this study we investigated the anti-inflammatory effect of chymotrypsin in male Lewis rat model of EAE. The disease was induced in male Lewis rats and the animals were evaluated for weight loss and clinical signs for 14 days. Intra-CSF injection of chymotrypsin was done on day 7 and expression of mRNA for IFN-γ, IL-4, IL-17, and FoxP3 in brain, spinal cord and deep cervical lymph node were determined using a two-step real-time PCR. Administration of 0.2mg/ml chymotrypsin ameliorated the disease by decreasing IFN-γ and increasing expression of IL-4 and IL-17 at the inflammatory foci. This is consistent with anti-inflammatory effect of IL-4 and IL-17 at high concentrations. We conclude that Immunomodulatory affect of chymotrypsin in CNS is sex-independent. Our result also provides more evidence on the anti-inflammatory role of IL-17. However more research is needed to elucidate the underlying immunomodulatory role of chymotrypsin and how to increase its beneficial effect by modification of dosage and/or regimen of administration.