The mineralocorticoid receptor: insights into its molecular and (patho)physiological biology

The last decade has witnessed tremendous progress in the understanding of the mineralocorticoid receptor (MR), its molecular mechanism of action, and its implications for physiology and pathophysiology. After the initial cloning of MR, and identification of its gene structure and promoters, it now appears as a major actor in protein-protein interaction networks. The role of transcriptional coregulators and the determinants of mineralocorticoid selectivity have been elucidated. Targeted oncogenesis and transgenic mouse models have identified unexpected sites of MR expression and novel roles for MR in non-epithelial tissues. These experimental approaches have contributed to the generation of new cell lines for the characterization of aldosterone signaling pathways, and have also facilitated a better understanding of MR physiology in the heart, vasculature, brain and adipose tissues. This review describes the structure, molecular mechanism of action and transcriptional regulation mediated by MR, emphasizing the most recent developments at the cellular and molecular level. Finally, through insights obtained from mouse models and human disease, its role in physiology and pathophysiology will be reviewed. Future investigations of MR biology should lead to new therapeutic strategies, modulating cell-specific actions in the management of cardiovascular disease, neuroprotection, mineralocorticoid resistance, and metabolic disorders

Prenatal Excess Glucocorticoid Exposure and Adult Affective Disorders:A Role for Serotonergic and Catecholamine Pathways

Fetal glucocorticoid exposure is a key mechanism proposed to underlie prenatal ‘programming’ of adult affective behaviours such as depression and anxiety. Indeed, the glucocorticoid metabolising enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2), which is highly expressed in the placenta and the developing fetus, acts as a protective barrier from the high maternal glucocorticoids which may alter developmental trajectories. The programmed changes resulting from maternal stress or bypass or from the inhibition of 11β-HSD2 are frequently associated with alterations in the hypothalamic-pituitary-adrenal (HPA) axis. Hence, circulating glucocorticoid levels are increased either basally or in response to stress accompanied by CNS region-specific modulations in the expression of both corticosteroid receptors (mineralocorticoid and glucocorticoid receptors). Furthermore, early-life glucocorticoid exposure also affects serotonergic and catecholamine pathways within the brain, with changes in both associated neurotransmitters and receptors. Indeed, global removal of 11β-HSD2, an enzyme that inactivates glucocorticoids, increases anxiety‐ and depressive-like behaviour in mice; however, in this case the phenotype is not accompanied by overt perturbation in the HPA axis but, intriguingly, alterations in serotonergic and catecholamine pathways are maintained in this programming model. This review addresses one of the potential adverse effects of glucocorticoid overexposure in utero, i.e. increased incidence of affective behaviours, and the mechanisms underlying these behaviours including alteration of the HPA axis and serotonergic and catecholamine pathways

[Progressive renal failure caused by lithium nephropathy]

OBJECTIVES: Study the renal consequences of lithium therapy and find out whether lithium-induced chronic renal toxicity can provoke a progressive nephropathy, leading to advanced renal failure, requiring periodical dialysis. METHODS: Fifty-three patients treated with long-term lithium salts were included in the study. They had developed chronic renal failure (creatinine clearance inferior to 80 ml/min) not due to any other cause. RESULTS: These patients had received lithium salts for a mean period of 17.7 years. The mean reduction in creatinine clearance was of 2.23 ml/min/year. Final clearance correlated negatively with the duration of lithium administration. In 7 patients treated a mean of 22 years, progression towards terminal kidney failure required periodical dialysis. Around 30% of patients exhibited mild hypercalcemia. CONCLUSION: Lithium nephropathy inducing progressive renal failure is a reality. Its prevalence in patients treated long-term with lithium should be assessed

Rat liver 11 beta-hydroxysteroid dehydrogenase complementary deoxyribonucleic acid encodes oxoreductase activity in a mineralocorticoid-responsive toad bladder cell line

The mineralocorticoid receptor displays equal affinity for aldosterone and corticosterone. It has been proposed that aldosterone selectivity in vivo is achieved by the conversion of corticosterone into its inactive metabolite 11-dehydrocorticosterone by 11 beta-hydroxysteroid dehydrogenase (11 beta HSD). To test this hypothesis, we transfected rat liver 11 beta HSD cDNA into TBM cells, a sodium-transporting cell line. These cells respond equally well to aldosterone and corticosterone, indicating that endogenous 11 beta HSD is expressed at low levels in TBM cells. Although exogenous rat liver 11 beta HSD was expressed at high levels in transfected cells, mineralocorticoid selectivity was not observed. By contrast, the biologically inactive 11-dehydrocorticosterone was readily converted into corticosterone, a potent agonist for sodium transport. Our results indicate that rat liver 11 beta HSD behaves predominantly as a reductase in TBM cells. Another 11 beta HSD isoform is likely to be responsible for the dehydrogenase reaction in aldosterone-responsive cells