Molecular mechanisms and proteomics of renal tissue repair in recovery after nephrotoxicity

Acute renal failure (ARF) is the generic term for an abrupt and sustained decrease in renal function resulting in retention of nitrogenous (urea and creatinine) and non-nitrogenous waste products in the body. Development of drug-induced ARF in hospital settings continues to be associated with poor outcomes. A greater understanding of the potential mechanisms to prevent and/or recover from acute tubular necrosis, ARF and death is needed.; Previous studies with male Swiss Webster mice have shown that renal injury initiated by a lethal dose of S-(1,2-dichlorovinyl)-L-cysteine (DCVC) progresses due to inhibition of cell division and hence renal repair, leading to ARF and death in mice. Renal injury initiated by low to moderate doses of DCVC is repaired by timely and adequate stimulation of renal cell division, tubular repair, restoration of renal structure and function leading to survival of mice. Recent studies have established that mice primed with a low dose of DCVC (15 mg/kg, ip) 72 h before administration of a normally lethal dose (75 mg/kg, ip), are protected from ARF and death (nephro-autoprotection). It has been shown that renal cell division and tissue repair stimulated by the low dose are sustained even after the lethal dose administration resulting in survival from ARF and death. Sustained activation of ERK1/2 by a low dose (15 mg/kg, ip) of DCVC 72 h before administration of a lethal dose of DCVC (75 mg/kg, ip) enhances renal cell division and protects mice against acute renal failure and death (autoprotection). We hypothesized that: (1) cyclin-CDK system/pRB-mediated signaling events downstream to ERK1/2 would be stimulated with low dose of DCVC and inhibited with the lethal dose of DCVC, respectively; (2) however, the priming dose relieves the block on compensatory tissue repair by upregulation of cyclin-CDK system/pRB-mediated signaling mechanisms downstream of ERK1/2 even after the high dose administration; (3) the DCVC autoprotection against the lethal dose would be abolished if low dose-stimulated cell division and tissue repair are blocked; and (4) several fold downregulation of various mitochondrial proteins involved in cellular energetics, stress response/chaperon, proteins involved in protein turnover and repair, and proteins involved in renal injury/repair with lethal dose alone is prevented by priming in the autoprotected animals. Objectives of this study are (1) to test the hypothesis of activation of transcription factors; increased expression of GI/S cyclins, cyclin dependent kinases (CDKs), and CDK inhibitors (CKIs) downstream of ERK1/2 following DCVC-induced ARF in autoprotection. (2) to test the hypothesis that renal cell division induced by the low priming dose is the critical mechanism of this autoprotection, by antimitotic intervention with colchicine (1.5 mg CLC/kg, ip). (3) and to generate a protein expression profile after DCVC in low dose, high dose, and autoprotected groups by using proteomics approach.; Administration of the lethal dose alone to male SW mice caused a general downregulation or an unsustainable increase, in transcriptional and post-transcriptional events thereby preventing G1/S transition of renal cell cycle. Phosphorylation of IkappaBalpha was inhibited resulting in limited nuclear translocation of NFkappaB. However, cyclin D1 expression was high probably due to transcriptional cooperation of AP-1. Cyclin D1/cyclin-dependent kinase 4 (cdk4)-cdk6 system mediated phosphorylation of retinoblastoma protein was downregulated due to overexpression of p16 at 24 h after exposure to the lethal dose alone. Inhibition of S-phase stimulation was confirmed by proliferating cell nuclear antigen assay (PCNA). This inhibitory response was prevented if a low priming dose of DCVC was administered, 72 h prior to administration of the lethal dose due to promitogenic effect of the low dose. NFkappaB-DNA binding was no longer limited if the mice were pretreated with the priming dose. Cyclin D1/cdk4...