Y-Box Binding Protein-1 Mediates Profibrotic Effects of Calcineurin Inhibitors in the Kidney

Abstract

The immunosuppressive calcineurin inhibitors (CNIs) cyclosporine A (CsA) and tacrolimus are widely used in transplant organ recipients, but in the kidney allograft, they may cause tubulointerstitial as well as mesangial fibrosis, with TGF-β believed to be a central inductor. In this study, we report that the cold-shock protein Y-box binding protein-1 (YB-1) is a TGF-β independent downstream effector in CsA- as well as in tacrolimus- but not in rapamycin-mediated activation of rat mesangial cells (rMCs). Intracellular content of YB-1 is several-fold increased in MCs following CNI treatment in vitro and in vivo in mice. This effect ensues in a time-dependent manner, and the operative concentration range encompasses therapeutically relevant doses for CNIs. The effect of CNI on cellular YB-1 content is abrogated by specific blockade of translation, whereas retarding the transcription remains ineffective. The activation of rMCs by CNIs is accomplished by generation of reactive oxygen species. In contrast to TGF-β–triggered reactive oxygen species generation, hydrogen peroxide especially could be identified as a potent inductor of YB-1 accumulation. In line with this, hindering TGF-β did not influence CNI-induced YB-1 upregulation, whereas ERK/Akt pathways are involved in CNI-mediated YB-1 expression. CsA-induced YB-1 accumulation results in mRNA stabilization and subsequent generation of collagen. Our results provide strong evidence for a CNI-dependent induction of YB-1 in MCs that contributes to renal fibrosis via regulation of its own and collagen translation.

YB-1 Is an Early and Central Mediator of Bacterial and Sterile Inflammation In Vivo

“…Prior to immunoprecipitation, polyclonal anti-YB-1 Ab and irrelevant antirabbit IgG (Cell Signaling) as negative control were covalently linked to protein A-Sepharose beads (50% suspension; Invitrogen), as described before (23). A total of 20 ml protein A-Sepharose coupled either with polyclonal anti-YB-1 Ab or nonspecific IgG incubated with 200 mg kidney cell extract from LPS-stimulated or control-untreated recombinant mesangial cells for 1.5 h at 4˚C in immunoprecipitation buffer (20 mM HEPES [pH 7.4], 100 mM potassium chloride, 5 mM magnesium acetate, 1 mM DTT, 0.025% Triton X-100, and protease inhibitors).…”

Calcineurin inhibitors in bronchiolitis obliterans syndrome following stem cell transplantation

“…CsA and FK506 both inhibit calcineurin, which is responsible for calcium-dependent signal transduction, thereby preventing the transcription of lymphokine genes, such as interleukin-2, and inhibiting T-cell activation and proliferation [32]. However, a fibrogenic effect of CsA and FK506 has been described earlier in renal allografts and in animal and in vitro models [19][20][21]. The fibrogenic effects are predominantly mediated by elevated expression of transforming growth factor-b, suppressed matrix metalloproteinase activity and augmented fibroblast collagen synthesis [20,21].…”

“…The fibrogenic effects of CsA and FK506 have been studied extensively in renal allografts [19], and are predominantly mediated by elevated expression of transforming growth factor-b [20,21]. In addition, previous data have demonstrated that CsA may directly stimulate cell proliferation [22,23], raising the possibility that calcineurin inhibitors may contribute to the development of chronic GvHD in the lung.…”

Molecular Mechanisms Underlying the Nephrotoxicity of Cisplatin, Lead Acetate and Cyclosporine: Key Roles of Myc and Smad4

“…The Ybx1 is a key regulator of cell growth, apoptosis, drug resistance, DNA repair and transcription. It has been shown that overexpression of Ybx1 via Erk/Akt pathway can monitor damage recognition and renal fibrosis of toxic agents such as Cyclosporine [48][49][50]. However, the role of Pcgf4 and Ybx1 in nephrotoxicity has not yet been fully evaluated.…”