Direct effects of dexamethasone on human podocytes

Abstract

Glucocorticoids are widely used in the treatment of human glomerular diseases, but their mode of action is poorly understood particularly in steroid-sensitive nephrotic syndrome, which is most common in childhood and is characterized by a lack of inflammation in the kidney. The podocyte is a key cell in the glomerulus in health and disease: until recently, human podocytes have been difficult to study in vitro. We have developed a conditionally immortalized human podocyte cell line transfected with a temperature-sensitive simian virus 40 transgene: when the transgene is inactivated in vitro, these cells adopt the phenotype of differentiated podocytes. We have used these cells to evaluate, using immunocytochemistry, reverse transcriptase-polymerase chain reaction, and Western blotting, direct effects of the glucocorticoid dexamethasone at concentrations designed to mimic in vivo therapeutic corticosteroid levels. Dexamethasone upregulated expression of nephrin and tubulin-alpha, and downregulated vascular endothelial growth factor. Effects on cell cycle were complex with downregulation of cyclin kinase inhibitor p21 and augmentation of podocyte survival, without any effect on apoptosis. We report cytokine production by human podocytes, especially interleukin (IL)-6 and -8; IL-6 expression was suppressed by dexamethasone. These potent direct effects on podocytes illustrate a novel mode of action of glucocorticoids and suggest potential new therapeutic strategies for glomerular disease.

Comparison of Methylprednisolone Plus Prednisolone with Prednisolone Alone as Initial Treatment in Adult-Onset Minimal Change Disease

“…In addition to its immunomodulatory effect, corticosteroid directly affects the gene expression of podocytes (31). Dexamethasone promotes the expression of nephrin and other proteinuria-associated factors in human podocytes in a dose-dependent fashion within a range corresponding to the intravenous mPSL therapy used in this study (31). Thus, the effectiveness of mPSL +PSL in this study may be partly ascribed to the higher initial dose of corticosteroid, which normalized podocyte function more strongly.…”

“…Although the precise MCD pathogenesis remains unknown, immunologic perturbations, especially in T cells (26), and subsequent injury to glomerular podocytes (27), including reduced expression of nephrin (28)(29)(30), lead to massive proteinuria in MCD. In addition to its immunomodulatory effect, corticosteroid directly affects the gene expression of podocytes (31). Dexamethasone promotes the expression of nephrin and other proteinuria-associated factors in human podocytes in a dose-dependent fashion within a range corresponding to the intravenous mPSL therapy used in this study (31).…”

Focal Segmental Glomerulosclerosis

“…For APOL1 FSGS, response rates to glucocorticoids are probably similar to those seen in primary FSGS, although the data are limited (83). The mechanism by which glucocorticoids affect podocytes are poorly understood; these agents are known to have direct effects on cultured podocytes (132). Recently, it has been suggested that these agents can expand the population of myeloid-derived suppressor cells that downregulate T cell function (133).…”

Induction of Podocyte VEGF164 Overexpression at Different Stages of Development Causes Congenital Nephrosis or Steroid-Resistant Nephrotic Syndrome

“…Recent reports indicate that dexamethasone induces transcriptional activation of nephrin and enhances nephrin expression in vitro, suggesting that this mechanism could be involved in the steroid response observed in minimal change disease. 24 To test the hypothesis that enhanced podocyte VEGF causes proteinuria in developing mice by disrupting nephrin signaling we developed an inducible mouse model of moderate podocyte VEGF 164 overexpression. Here we examined the phenotypes resulting from podocyte VEGF 164 excess at two developmental stages: during organogenesis and in the newborn mouse.…”