Horm Metab Res 2006; 38(6): 368-376
DOI: 10.1055/s-2006-944530
Hypothesis
© Georg Thieme Verlag KG Stuttgart · New York

Cortisol Resistance in Conditions such as Asthma and the Involvement of 11β-HSD-2: A Hypothesis

E.  Pretorius1 , B.  Wallner2 , J.  Marx1
  • 1Department of Anatomy, School of Health Sciences, Medical Faculty of the University of Pretoria, South Africa
  • 2Department of Anthropology, University of Vienna, Austria
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Publication History

Received 26 September 2005

Accepted after revision 19 January 2006

Publication Date:
06 July 2006 (online)

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Abstract

The two types of corticosteroid hormones, the mineralocorticoids and glucocorticoids, act in a complementary manner and are functionally closely linked. Aldosterone and glucocorticoids express their functions through the glucocorticoid receptors (GRs; GRα and GRβ) and the mineralocorticoid receptors (MRs). Commercially available steroidal drugs used in conditions such as asthma may act on both GR and MR receptors; although glucocorticoid-receptor agonists play a fundamental role in the treatment of inflammatory conditions, prolonged exposure may have adverse effects such as the development of resistance. Glucocorticoid resistance in such conditions has been observed to be accompanied by a downregulation of GRα, a twofold decrease in GR protein half-life, downregulation of GRα mRNA expression, and enhanced expression of GRβ. Other suggestions for glucocorticoid resistance include alternative splicing of the GR gene with subsequent expression of the GRβ protein isoform, defective regulation of gene transcription of the GR gene or GR mutations, defective DNA binding and transactivating domains of the GR. In addition, we would like to suggest that dysregulation of the MR enzyme 11β-HSD-2 may be one of the causes of resistance. When expressed in cells with MRs, this enzyme’s major role is to prevent permanent occupancy of MR by glucocorticoid hormones, allowing concentration-dependent binding of aldosterone to MR. However, deficiency of the 11β-HSD isoforms (particularly 11β-HSD-2) leads to the activation of MRs by glucocorticoids rather than the glucocorticoids interacting with its “normal” receptors, the GRs. We will substantiate on support for our hypothesis in the dysregulation of this enzyme, which is typically associated with significantly higher levels of circulating plasma cortisol and elevated levels of cholesterol, little or no response to systemic glucocorticoids, and problems associated with homeostasis primarily in the distal nephron and distal colon. These are some of the symptoms typically noted in cortisol resistance.

References

E. Pretorius

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