Corticotropin Releasing Hormone (CRH) Antagonist Attenuates Adjuvant Induced Arthritis: Role of CRH in Peripheral Inflammation

Objective: To determine whether a corticotropin releasing hormone (CRH) type 1-specific receptor antagonist, antalarmin, would alter the progression of inflammation in adjuvant induced arthritis (AIA) susceptible LEW/N rats by blocking local CRH mediated inflammatory responses or render AIA resistant F344/N rats more susceptible to AIA by blocking central CRH, thus reducing secretion of endogenous glucocorticoids.

Methods: F344/N and LEW/N rats were assigned to either drug or vehicle groups and treated with 20 mg/kg antalarmin or vehicle alone BID for 25 days by intraperitoneal injection. Arthritis was induced in both antalarmin and vehicle treated LEW/N and F344/N rats by subcutaneous injections at the base of the tail of incomplete Freund's adjuvant containing 10 mg/ml heat killed Mycobacterium tuberculosis. Control F344/N and LEW/N rats were maintained on either antalarmin or vehicle.

Results: Chronic blockade of CRH-R1 with systemic antalarmin significantly ameliorated AIA in LEW/N rats, reducing the severity of inflammation in peripheral joints, evidenced by clinical and histopathology scores, and weight loss associated with disease onset. Antalarmin neither induced nor exacerbated arthritis expression in F344/N or LEW/N rats, despite suppression of levels of adjuvant induced corticosterone, the major antiinflammatory glucocorticoid in rats.

Conclusion: Systemic blockade of CRH-RI appeared to predominantly block peripheral proinflammatory effects of immune CRH, rather than the systemic glucocorticoid mediated antiinflammatory effects of hypothalamic CRH. Results indicate that chronic treatment with a CRH antagonist attenuates progressive inflammation induced degeneration of synovia, cartilage, and bone in arthritic joints, suggesting that antalarmin may have therapeutic potential in treatment of human autoimmune and inflammatory disorders.