Activation of mineralocorticoid receptor by ecdysone, an adaptogenic and anabolic ecdysteroid, promotes glomerular injury and proteinuria involving overactive GSK3\u03b2 pathway signaling

Minglei Lu,Pei Wang,Rujun Gong,Andrew Brem,Lance Dworkin,Zhangsuo Liu,Yan Ge

doi:10.1038/s41598-018-29483-7

Abstract

Ecdysone is an arthropod molting hormone and has been marketed as a non-androgenic natural anabolic and adaptogen. However, the safety profile of ecdysone is largely undetermined. After ecdysone treatment for 2 weeks, mice developed albuminuria with histologic signs of glomerular injury, including hypertrophy, mesangial expansion, mild glomerulosclerosis and podocyte injury. A direct glomerulopathic activity of ecdysone seems to contribute, since addition of ecdysone to cultured glomerular cells induced cytopathic changes, including apoptosis, activation of mesangial cells, podocyte shape changes and a decreased expression of podocyte markers. To explore the molecular target responsible for the pathogenic actions, we employed an in silico modeling system of compound-protein interaction and identified mineralocorticoid receptor (MR) as one of the top-ranking proteins with putative interactions with ecdysone. The molecular structure of ecdysone was highly homologous to mineralocorticoids, like aldosterone. Moreover, ecdysone was capable of both inducing and activating MR, as evidenced by MR nuclear accumulation in glomerular cells both in vitro and in vivo following ecdysone treatment. Mechanistically, glycogen synthase kinase (GSK) 3β, which has been recently implicated in pathogenesis of glomerular injury and proteinuria, was hyperactivated in glomeruli in ecdysone-treated mice, concomitant with diverse glomerulopathic changes. In contrast, spironolactone, a selective blockade of MR, largely abolished the cytopathic effect of ecdysone in vitro and attenuated albuminuria and glomerular lesions in ecdysone treated mice, associated with a mitigated GSK3β overactivity in glomeruli. Altogether, ecdysone seems able to activate MR and thereby promote glomerular injury and proteinuria involving overactive GSK3β pathway signaling.

Highlights

Glomerular disease is one of the leading causes of progressive chronic kidney disease and loss of kidney function, culminating in end stage renal disease (ESRD)
Electron microscopy of kidney specimens revealed a variable degree of podocyte injury ranging from minimal to moderate, marked by focal podocyte foot process effacement (Fig. 1C), which was quantified by absolute count of the number of foot processes per unit length of glomerular basement membrane (Fig. 1F)
As shown by immunoblot analysis of isolated glomeruli, ecdysone-triggered albuminuria and early signs of glomerulopathy were concomitant with reduced glomerular expression of GSK3β with inhibitory phosphorylation of at serine 9, indicative of GSK3β hyperactivity. This effect was markedly abolished in animals co-treated with spironolactone. These findings suggest that mineralocorticoid receptor (MR) mediates the effect of ecdysone on eliciting podocyte dedifferentiation, glomerular cell apoptosis, mesangial activation and early signs of glomerulosclerosis possibly involving GSK3β overactivity

Summary

Introduction

Glomerular disease is one of the leading causes of progressive chronic kidney disease and loss of kidney function, culminating in end stage renal disease (ESRD). Epidemiologic evidence is still scarce to date and there are no adequate animal model studies on this topic It remains uncertain whether androgen or increased lean body mass is the exact causative factor for FSGS. This is an important issue, because in addition to androgenic steroids, many other non-androgenic anabolic supplements, like ecdysteroids, are commonly used for fitness. Ecdysteroids are one of the most common and major ingredients found in various non-androgenic fitness or adaptogenic supplements[19,20] They are steroidal insect molting hormones essential for inducing metamorphosis in arthropods, like Drosophila melanogaster, and activate the ecdysone receptor (EcR), a member of the nuclear receptor superfamily[21]. This study, by using both mice and kidney cell culture models, revealed a mineralocorticoid-like effect of ecdysone that elicits albuminuria and induces early signs of glomerular damage

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Conclusion