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RGS4 controls renal blood flow and inhibits cyclosporine-mediated nephrotoxicity.

ABSTRACT: Calcineurin inhibitors (CNI) are powerful immunomodulatory agents that produce marked renal dysfunction due in part to endothelin-1-mediated reductions in renal blood flow. Ligand-stimulated Gq protein signaling promotes the contraction of smooth muscle cells via phospholipase Cbeta-mediated stimulation of cytosolic calcium release. RGS4 is a GTPase activating protein that promotes the deactivation of Gq and Gi family members. To investigate the role of G protein-mediated signaling in the pathogenesis of CNI-mediated renal injury, we used mice deficient for RGS4 (rgs4(-/-)). Compared to congenic wild type control animals, rgs4(-/-) mice were intolerant of the CNI, cyclosporine (CyA), rapidly developing fatal renal failure. Rgs4(-/-) mice exhibited markedly reduced renal blood flow after CyA treatment when compared to congenic wild type control mice as measured by magnetic resonance imaging (MRI). Hypoperfusion was reversed by coadministration of CyA with the endothelin antagonist, bosentan. The MAPK/ERK pathway was activated by cyclosporine administration and was inhibited by cotreatment with bosentan. These results show that endothelin-1-mediated Gq protein signaling plays a key role in the pathogenesis of vasoconstrictive renal injury and that RGS4 antagonizes the deleterious effects of excess endothelin receptor activation in the kidney.

SUBMITTER: Siedlecki A

PROVIDER: S-EPMC3221245 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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RGS4 controls renal blood flow and inhibits cyclosporine-mediated nephrotoxicity.

Siedlecki A A Anderson J R JR Jin X X Garbow J R JR Lupu T S TS Muslin A J AJ

American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons 20091202 2

Calcineurin inhibitors (CNI) are powerful immunomodulatory agents that produce marked renal dysfunction due in part to endothelin-1-mediated reductions in renal blood flow. Ligand-stimulated Gq protein signaling promotes the contraction of smooth muscle cells via phospholipase Cbeta-mediated stimulation of cytosolic calcium release. RGS4 is a GTPase activating protein that promotes the deactivation of Gq and Gi family members. To investigate the role of G protein-mediated signaling in the pathog ...[more]

PMID: 19958325

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Project description:Calcineurin inhibitors are powerful immunosuppressants that revolutionized organ transplantation. However, non-immune effects of the calcineurin inhibitor, such as cyclosporine A (CsA), have significantly hindered their use. Specifically, nephrotoxicity, which is associated with tubulointerstitial fibrosis, inflammation, and podocyte damage, affects up to half of all transplant patients. Calcineurin is involved in many aspects of kidney development and function; therefore, mechanisms of CsA-induced nephrotoxicity are complex and not yet fully understood. MicroRNAs are short non-coding RNAs that regulate protein-coding RNA expression through post-translational repression of target messenger RNAs. MicroRNA dysregulation is known to be involved in kidney diseases including fibrosis. In this study, we compared the renal microRNA expression profiles between mice that received CsA (20 mg/kg) or vehicle daily for six weeks. The results demonstrate that CsA induces significant changes in renal microRNA expression profile. We used combined criteria of False Discovery Rate (≤0.1), fold change (≥2) and median signal strength (≥50) and identified 76 differencially expressed microRNAs. This approach identified microRNAs previously linked to renal fibrosis that includes let-7d, miR-21, miR-29, miR-30, miR-130, miR-192, and miR-200 as well as microRNAs that have not been reported to be related to nephrotoxicity or immunosuppression. Pathway analysis of microRNA/mRNA changes highlights the Wnt, TGF-β, mTOR, and VEGF pathways. The mRNA expression profiles were compared in the same samples. The change of mRNA and microRNA profiles showed close correlations. To validate that the observed microRNA and mRNA expression level changes in mice kidney tissue were directly related to CsA treatment, the expression change induced by CsA treatment of three microRNAs (miR-21, miR-186, and miR-709) and three mRNAs (BMPR1a, SMURF1 and SMAD7) were compared in HEK293 cell line. A similar trend of expression level change was induced by CsA treatment in all selected microRNAs and mRNAs in the in vitro cell model. These data provide a roadmap for future work to study the role of the known and novel candidate microRNAs in the mechanism of nephrotoxicity and their further therapeutic potential.

Project description:Chronic calcineurin inhibitor (CNI) nephrotoxicity is a major drawback in current immunosuppressive regimens. Pathology includes vascular and tubulointerstitial alterations. Although still commonly in use, cyclosporine A (CsA) is increasingly exchanged for tacrolimus (Tac) for a more favorable clinical outcome. Data on their differential pathogenetic effects in the kidney are, however, still scarce. We asked how CsA and Tac may affect adverse renal responses differentially. Methods- Wistar rats were divided into groups receiving cyclosporineÊ AÊ (n=4, target trough plasma level 3 mg/ml) and the respective vehicle (n=4, saline), or tacrolimus (Tac, FK506, n= 6, target trough plasma level 3.5 ng/ml) and the respective vehicle (n=6, DMSO/PEG500), via subcutaneously implanted osmotic minipumps for 28 days. Clinical parameters from plasma and urine samples were controlled. Animals were prepared for high-end morphological analysis, elective immunostaining, and high-throughput technology. Large scale electron microscopy (EM), confocal, stimulated emission-depletion (STED) and 3D-structured illumination (SIM) microscopy were used for pathology. Protein biochemistry, transcriptome, proteome, and phosphoproteome technologies were used to identify gene expressional differences. Results - In rats, CsA and Tac produced common as well as distinct alterations in glomeruli and tubulointerstitium. Both drugs caused cortical fibrotic foci with sclerotic glomeruli and damaged tubules. With CsA, glomerular damage was milder than with Tac. Proximal tubules showed widespread dysmorphic lysosomes with peripheral LAMP1 signal as well as autophagic and mitophagic vacuoles along with high apoptosis rate and diminished albumin uptake; megalin-dependent endocytosis was causally involved in the changes, and lysosomal exocytosis was sharply stimulated at the luminal cell pole. KIM1 signal was moderate. With Tac, these changes were far less pronounced, but the incidence of focal tubular necrosis along with intense KIM-1 signal was high. High throughput analysis showed differential changes between CsA and Tac with almost no overlap between the respective spectra. CsA caused upregulation of components of the unfolded protein response and apoptosis, whereas Tac resulted in RAS-associated stimulation and vascular deterioration. Conclusions- CNI nephrotoxicity presented with widely differing pathogenetic characteristics upon chronical CsA vs. Tac treatments. Beyond its known vascular effects, CsA markedly affected proximal tubular integrity, whereas Tac was primarily affecting vascular/glomerular components. Both medications produced comparable degrees of nephron loss and fibrosis. Results may serve to better adjust immunosuppressive treatment combinations in transplant patients.

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RGS4 controls renal blood flow and inhibits cyclosporine-mediated nephrotoxicity.

Publications

RGS4 controls renal blood flow and inhibits cyclosporine-mediated nephrotoxicity.

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