Role of sex hormones in diabetic nephropathy

IL-17-producing T lymphocytes have been recently shown to comprise a distinct lineage of proinflammatory T helper cells, termed Th17 cells, that are major contributors to autoimmune disease. We show here that the orphan nuclear receptor RORgammat is the key transcription factor that orchestrates the differentiation of this effector cell lineage. RORgammat induces transcription of the genes encoding IL-17 and the related cytokine IL-17F in naïve CD4(+) T helper cells and is required for their expression in response to IL-6 and TGF-beta, the cytokines known to induce IL-17. Th17 cells are constitutively present throughout the intestinal lamina propria, express RORgammat, and are absent in mice deficient for RORgammat or IL-6. Mice with RORgammat-deficient T cells have attenuated autoimmune disease and lack tissue-infiltrating Th17 cells. Together, these studies suggest that RORgammat is a key regulator of immune homeostasis and highlight its potential as a therapeutic target in inflammatory diseases.

Many lines of evidence, ranging from in vitro experiments and pathological examinations to epidemiological studies, show that inflammation is a cardinal pathogenetic mechanism in diabetic nephropathy. Thus, modulation of inflammatory processes in the setting of diabetes mellitus is a matter of great interest for researchers today. The relationships between inflammation and the development and progression of diabetic nephropathy involve complex molecular networks and processes. This Review, therefore, focuses on key proinflammatory molecules and pathways implicated in the development and progression of diabetic nephropathy: the chemokines CCL2, CX3CL1 and CCL5 (also known as MCP-1, fractalkine and RANTES, respectively); the adhesion molecules intercellular adhesion molecule 1, vascular cell adhesion protein 1, endothelial cell-selective adhesion molecule, E-selectin and α-actinin 4; the transcription factor nuclear factor κB; and the inflammatory cytokines IL-1, IL-6, IL-18 and tumor necrosis factor. Advances in the understanding of the roles that these inflammatory pathways have in the context of diabetic nephropathy will facilitate the discovery of new therapeutic targets. In the next few years, promising new therapeutic strategies based on anti-inflammatory effects could be successfully translated into clinical treatments for diabetic complications, including diabetic nephropathy.

Significant advances have taken place in our knowledge of the enzymes involved in steroid hormone biosynthesis since the last comprehensive review in 1988. Major developments include the cloning, identification, and characterization of multiple isoforms of 3beta-hydroxysteroid dehydrogenase, which play a critical role in the biosynthesis of all steroid hormones and 17beta-hydroxysteroid dehydrogenase where specific isoforms are essential for the final step in active steroid hormone biosynthesis. Advances have taken place in our understanding of the unique manner that determines tissue-specific expression of P450aromatase through the utilization of alternative promoters. In recent years, evidence has been obtained for the expression of steroidogenic enzymes in the nervous system and in cardiac tissue, indicating that these tissues may be involved in the biosynthesis of steroid hormones acting in an autocrine or paracrine manner. This review presents a detailed description of the enzymes involved in the biosynthesis of active steroid hormones, with emphasis on the human and mouse enzymes and their expression in gonads, adrenal glands, and placenta.