Response of pituitary and spleen pro-opiomelanocortin mRNA, and spleen and thymus interleukin-1β mRNA to adjuvant arthritis in the rat

During development of adjuvant-induced arthritis (AA) in the rat, pituitary pro-opiomelanocortin (POMC) mRNA expression was increased. Pituitary POMC mRNA was much higher following adrenalectomy and AA. Spleen POMC mRNA also increased with a similar time kinetics, although the levels in the spleen were much lower than those in the pituitary. In control animals, spleen interleukin-1β (IL-1β mRNA) was undetectable, whereas AA led to the accumulation of IL-1β mRNA and the highest levels were seen in the adrenalectomised AA group. Thymic IL-1β expression was also increased in AA animals. These results suggest that AA leads to the activation of both the neuroendocrine and the immune systems and the interaction between these systems may play a role in this disease state.