Aims: 

Proinflammatory cytokine IL-6, is produced beside immune cells in adenopituitary, and adrenal gland where it exerts local regulatory function. Adjuvant arthritis (AA) in the rat is a chronic inflammation associated with stimulation of the hypothalamic-pituitary-adrenal axis (HPA), via pro-inflammatory cytokines. These are under negative control of circulating corticosterone (CORT). Purpose of this study was to describe the relationship between activity of HPA axis, and mRNA expression of IL-6 in adenopituitaries (AP), and adrenals in chronic phase of AA in male and female rats.

Methods: 

To seven week-old, Long Evans males and females, randomly in cycle, AA was induced by injection of complete Freund's adjuvant. Control rats received vehicle. On day 23 of AA rats were decapitated. In plasma, adrenocorticotropin (ACTH) and CORT were measured by radioimmunoassay, AP, and adrenals were extracted for mRNA. The mRMA expressions for proopiomelanocortin (POMC), and IL-6 in AP and IL-6 in adrenals, were estimated by quantitative real-time PCR using TaqMan probes and primers. Paw oedema was estimated volumometricaly.

Results: 

The significant activation of HPA-axis (plasma CORT) was the same in both sexes. IL-6 mRNA expression was significantly elevated in male and female AP, and female adrenals, however in male adrenals it was significantly inhibited.

Conclusion: 

Chronic activation of HPA (namely enhanced CORT levels) during AA is not sufficient to inhibit IL-6 production in AP, or adrenals in females. The sex difference in adrenal response can not be ascribed only to the action of CORT, and warrants further study.

Supported: VZ 002162018, and GACR 305/ 06/ 0427.