EFFECTS OF INTERLEUKIN-6, INTERLEUKIN-1, AND TUMOR NECROSIS FACTOR ON ADRENAL STEROID SECRETIONS

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Brenda Mickelson Crawford and Dr. Allan M. Judd, Zoology

Interleukin-6 (IL-6), tumor necrosis factor (TNF), and interleukin- I (IL- 1) are cytokines released in response to infection in the body. One signal of infection is lipopolysaccharide (LPS), a component of the outer coat of grain negative bacterial cells. When bacteria die, LPS circulates in the blood and stimulates the immune system to release IL- 1, IL-6, and TNF. Septic shock is a syndrome in which LPS stimulates the release of large amounts of cytokines, causing adverse effects such as severe hypotension (low blood pressure), rashes, fever, edema, and finally multiple organ failure, including the heart.

The adrenal gland releases hormones important in the body’s immune and circulatory systems. The major adrenal hormones are cortisol, aldosterone, adrenal androgens, epinephrine, and norepinephrine. It has been shown that IL-1, IL-6 and TNF affect the release of adrenal hormones. For instance, adrenal corticotropin 1,2 hormone (ACTH) (which normally stimulates the release of cortisol) has reduced activity when combined with TNF. Therefore, it is suggested that cytokine-induced effects during septic shock may be in part mediated by the cytokines effects on the adrenal hormones, which in turn affect the immune and circulatory systems.

This study investigated the effects of TNF, IL- 1, and IL-6 on the secretion of hormones from the zona fasciculata (ZF), zona reticularis (ZR) and zona glomerulosa (ZG) of the bovine adrenal gland. Bovine adrenals from the Deseret Meat Processing Plant (Spanish Fork, UT) were sterilely dissected and separated into the ZF, ZR and ZG of the adrenal cortex. The tissues were then enzymatically dispersed into single-cell suspensions using the enzyme collagenase. The cells were cultured in a medium and incubated for 4-7 days. The cells were then exposed to IL- I (0. 1-1000 ng/ml), IL-6 (0.1-1000 ng/ml), or TNF (0.1- 1000 ng/ml) in combination with either cell culture medium or cell culture medium containing ACTH (100 nM) or angiotensin II (AII) (I uM) for 24 hours. The cell culture medium was then removed and stored frozen until assayed for aldosterone, cortisol, or adrenal androgens by commercially available radioimmunoassays (RIA) (ICN Biomedical Corporation).

To measure the androgen secretion from the ZR, a common androgen, DHEA-S was measured. The DHEA-S assay worked immediately, giving reliable results. The data showed that IL-6 inhibits basal secretion of DHEA-S and indicated that IL-1 and TNF may also inhibit basal DHEA release. In the presence of the secretagogue, ACTH, all cytokines were found to inhibit DHEA secretion from the ZR.

Complications arose when performing the aldosterone RIA. By adjusting the methods, the aldosterone assay began giving reliable results. Preliminary data show that TNF may inhibit basal secretion of aldosterone. When TNF, IL-6 or IL- 1 were combined with AII, aldosterone secretion decreased, indicating that these cytokines inhibit All stimulation of the ZG.

The cortisol assay recently began working after numerous alterations of the methods. The problem was solved by performing a charcoal separation. No reliable cortisol results have yet been obtained.

Future direction of this research project includes further testing of DHEA-S basal cytokine inhibition, confirmation of aldosterone results, and commencement of cortisol radioimmunoassay using charcoal separation. The results so far look extremely promising and will lead to a published paper when complete.

References

  • 1) A.M. Judd and R.M. MacLeod. 1991. Angiotensin II increases interleukin-6 release from rat adrenal zona glomerulosa cells. Prog 1 NeuroEndocrinImmunology 4:240-247.
  • 2) A.M. Judd and R.M. MadLeod. 1995. Differential release of tumor necrosis factor and interleukin-6 from adrendal zona glomerulosa cells in vitro.
    American Journal of Physiology (Endocrinology Metabolism). 268:EII4-EI20.