Growth Hormone (GH)-dependent Expression of a Natural Antisense Transcript Induces Zinc Finger E-box-binding Homeobox 2 (ZEB2) in the Glomerular Podocyte

Abstract

Growth hormone (GH) excess results in structural and functional changes in the kidney and is implicated as a causative factor in the development of diabetic nephropathy (DN). Glomerular podocytes are the major barrier to the filtration of serum proteins, and altered podocyte function and/or reduced podocyte number is a key event in the pathogenesis of DN. We have previously shown that podocytes are a target for GH action. To elucidate the molecular basis for the effects of GH on the podocyte, we conducted microarray and RT-quantitative PCR analyses of immortalized human podocytes and identified zinc finger E-box-binding homeobox 2 (ZEB2) to be up-regulated in a GH dose-and time-dependent manner. We established that the GH-dependent increase in ZEB2 levels is associated with increased transcription of a ZEB2 natural antisense transcript required for efficient translation of the ZEB2 transcript. GH down-regulated expression of E-and P-cadherins, targets of ZEB2, and inhibited E-cadherin promoter activity. Mutation of ZEB2 binding sites on the E-cadherin promoter abolished this effect of GH on the E-cadherin promoter. Whereas GH increased podocyte permeability to albumin in a paracellular albumin influx assay, shRNA-mediated knockdown of ZEB2 expression abrogated this effect. We conclude that GH increases expression of ZEB2 in part by increasing expression of a ZEB2 natural antisense transcript. GH-dependent increase in ZEB2 expression results in loss of P-and E-cadherins in podocytes and increased podocyte permeability to albumin. Decreased expression of P-and E-cadherins is implicated in podocyte dysfunction and epithelial-mesenchymal transition observed in DN. We speculate that the actions of GH on ZEB2 and P-and E-cadherin expression play a role in the pathogenesis of microalbuminuria of DN. Pituitary growth hormone (GH)5 is essential for postnatal growth in mammals. In addition to growth, GH affects the metabolism of fat, protein, and carbohydrate (1). GH exerts these actions both by its direct effect on target organs and by stimulating the production of insulin-like growth factor-1 (IGF-1). At the tissue level, these pleiotropic actions of GH result from the interaction of GH with a specific cell surface receptor, the GH receptor (GHR). Whereas the GHR is ubiquitously expressed, the role and effects of GH have been most intensely investigated in organs and tissues such as liver, bone, muscle, and adipocytes in which GHR expression is substantial and are thus considered canonical targets of GH action. However, recent reports have highlighted the biological effects and physiological relevance of GH action in non-canonical targets such as the blastocyst (2), colonic epithelial cells (3), cardiomyocytes (4), and neurons (5).GH excess in both the human (acromegaly) and in transgenic animal models is characterized by significant structural and functional changes in the kidney (6 -8). An overactive GH/ GHR axis is implicated as a causative factor in the development of diabetic nephropathy (9 -11). Our previous study...

Hormone-Dependent Expression of a Steroidogenic Acute Regulatory Protein Natural Antisense Transcript in MA-10 Mouse Tumor Leydig Cells

“…Our data show that Star NAT expression reached a maximum level at 2 to 3 h after stimulation and indicate that this effect was mediated by cAMP. Our results are among the few recently described examples of effective regulation of NAT expression by hormones [69]-[72]. Sense-antisense Star RNA co-expression in MA-10 cells was demonstrated directly by RPA, suggesting that these transcripts could be coordinately regulated.…”

Reversal by Growth Hormone of Homocysteine-induced Epithelial-to-Mesenchymal Transition through Membrane Raft-Redox Signaling in Podocytes

“…This protective action of GH on EMT and consequent functional injury in podocytes was found to be due to blockade of the formation of membrane raft platforms with GHR and NADPH oxidase subunits and consequent O 2 .-production. Although there were reports that excessive endogenous production of GH as a peptide hormone secreted by the pituitary gland may be an injurious factor in pathogenesis of some diseases or pathological process such as diabetes mellitus and progressive glomerulosclerosis [24,25], this hormone is often used as a therapeutic agent for different medical conditions, some of which were approved by the U.S. Food and Drug Administration, such as cachexia [26], Turner syndrome [27], chronic renal failure [28], Prader-Willi syndrome [29], and idiopathic short stature (ISS) [30]. In addition to these and other therapeutic uses for improvement of growth in children or adults, GH has also been reported to be used for healing of large burns [31]or in obesity [32], Crohn's disease [33], chronic fatigue syndrome, aging [34] and various degenerative diseases such as Alzheimer's disease [35], multiple sclerosis [36], atherosclerosis [37] and chronic heart failure [38].…”

Epithelial–mesenchymal Transition of Glomerular Podocytes: Implications in Proteinuria

“…It was also shown that GH-induced ZEB2 suppresses SD proteins and consequently increases podocyte permeability to albumin. 37 Furthermore, we have also demonstrated that administration of GH to rats induced podocyte EMT vis-à-vis decreased podocyte count, and increased proteinuria. 38 Advanced glycation end-products (AGEs) that are derived from glucose via nonenzymatic reactions are also implicated in the pathogenesis of DN.…”