The role of MAPK in drug-induced kidney injury.

This paper focuses on the role that mitogen-activated protein kinases (MAPKs) play in drug-induced kidney injury. The MAPKs, of which there are four major classes (ERK, p38, JNK, and ERK5/BMK), are signalling cascades which have been found to be broadly conserved across a wide variety of organisms. MAPKs allow effective transmission of information from the cell surface to the cytosolic or nuclear compartments. Cross talk between the MAPKs themselves and with other signalling pathways allows the cell to modulate responses to a wide variety of external stimuli. The MAPKs have been shown to play key roles in both mediating and ameliorating cellular responses to stress including xenobiotic-induced toxicity. Therefore, this paper will discuss the specific role of the MAPKs in the kidney in response to injury by a variety of xenobiotics and the potential for therapeutic intervention at the level of MAPK signalling across different types of kidney disease.

Sirolimus enhances cyclosporine a-induced cytotoxicity in human renal glomerular mesangial cells.

End Stage Renal Disease (ESRD) is an ever increasing problem worldwide. However the mechanisms underlying disease progression are not fully elucidated. This work addressed nephrotoxicity induced by the immunosuppressive agents' cyclosporine A (CsA) and sirolimus (SRL). Nephrotoxicity is the major limiting factor in long term use of CsA. SRL causes less nephrotoxicity than CsA. Therefore investigations into the differential effects of these agents may identify potential mechanisms of nephrotoxicity and means to prevent ESRD induced by therapeutic drugs. Using ELISA, Western blotting, quantitative PCR and a reporter gene assay we detailed the differential effects of CsA and SRL in human renal mesangial cells. CsA treatment increased profibrotic TGF-ß1 secretion in human mesangial cells whereas SRL did not, indicating a role for TGF-ß in CsA toxicity. However we observed a synergistic nephrotoxic effect when CsA and SRL were co-administered. These synergistic alterations may have been due to an increase in CTGF which was not evident when the immunosuppressive drugs were used alone. The CsA/SRL combination therapy significantly enhanced Smad signalling and altered the extracellular matrix regulator matrix metalloproteinase 9 (MMP-9). Inhibition of the ERK 1/2 pathway, attenuated these CsA/SRL induced alterations indicating a potentially significant role for this pathway.

Cyclosporine A--induced oxidative stress in human renal mesangial cells: a role for ERK 1/2 MAPK signaling.

Cyclosporine A (CsA) is a potent immunosuppressant used to prevent organ transplant rejection and in the treatment of autoimmune diseases. However, chronic CsA nephropathy is the major limiting factor to its widespread use. The exact mechanisms of CsA-induced renal damage remain to be fully elucidated. The objective of the current research was to examine whether CsA treatment induced any glomerular mesangial cell alterations. In this research goal, human mesangial cells (HMCs) were treated with CsA for various time points. CsA caused an increase in the production of reactive oxygen species (ROS). Microarray analysis of mesangial cells treated with CsA also indicated 282 dysregulated genes. Bioinformatic analysis of these 282 genes indicated enriched apoptotic oxidative stress, mitogen-activated protein kinase (MAPK), and transforming growth factor-ß signaling in response to CsA treatment. The focus of this study was directed on oxidative stress and MAPK signaling as potential novel mechanisms of CsA nephrotoxicity. One key contributor to oxidative stress, thioredoxin interacting protein, was significantly upregulated following CsA treatment. Inhibition of the MAPK pathway resulted in attenuation of the CsA-induced mesangial cell alterations. These findings suggest a major role for ROS, oxidative stress, and MAPK signaling in promoting CsA-induced glomerular dysfunction and subsequent nephrotoxicity.

Identification of ß2-microglobulin as a urinary biomarker for chronic allograft nephropathy using proteomic methods.

PURPOSE: Chronic allograft nephropathy (CAN) remains the leading cause of renal graft loss after the first year following renal transplantation. This study aimed to identify novel urinary proteomic profiles, which could distinguish and predict CAN in susceptible individuals. EXPERIMENTAL DESIGN: The study included 34 renal transplant patients with histologically proven CAN and 36 patients with normal renal transplant function. High-throughput proteomic profiles were generated from urine samples with three different ProteinChip arrays by surface-enhanced laser-desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). Following SELDI, a biomarker pattern software analysis was performed which led to the identification of a novel biomarker pattern that could distinguish patients with CAN from those with normal renal function. RESULTS: An 11.7 kDa protein identified as ß2 microglobulin was the primary protein of this biomarker pattern, distinguishing CAN from control patients (receiver operator characteristic [ROC]=0.996). SELDI-TOF-MS comparison of purified ß2 microglobulin protein and CAN urine demonstrated identical 11.7 kDa protein peaks. Significantly, higher concentrations of 2 microglobulin were found in the urine of patients with CAN compared with the urine of normal renal function transplant recipients (p<0.001). CONCLUSIONS AND CLINICAL RELEVANCE: Although further validation in a larger more diverse patient population is required to determine if this ß2 microglobulin protein biomarker will provide a potential means of diagnosing CAN by noninvasive methods in a clinical setting, this study clearly shows a capability to stratify control and disease patients.

Identification of novel indicators of cyclosporine A nephrotoxicity in a CD-1 mouse model.

The calcineurin inhibitor cyclosporine A (CsA) is a widely used immunosuppressive agent. However, nephrotoxicity is a serious side effect observed in patients which limits clinical use of CsA. CsA nephrotoxicity is associated with tubulointerstitial injury progressing to nephropathy. This is typically diagnosed by invasive renal biopsy and is often only detected when the disease process is well advanced. Therefore identification of novel, early indicators of CsA nephrotoxicity could be clinically advantageous. This study aimed to establish a murine model of CsA nephrotoxicity and to identify urinary proteins that may indicate the onset of CsA-induced nephropathy using 2-D gel electrophoresis. CsA nephrotoxicity was induced in CD-1 mice by daily CsA administration for 4weeks. By week 4, elevated serum creatinine and proteinuria were observed after CsA treatment indicating significant renal dysfunction. Decreased cadherin-1, increased α-smooth muscle actin and fibroblast specific protein 1 in kidney tissue indicated disruption of normal tubular architecture. Alterations in podocin and uromodulin were also observed which may indicate damage to other segments of the nephron. Proteomic analysis of urine identified a number of differentially regulated proteins that may be involved in early CsA nephropathy including cadherin 1, superoxide dismutase and vinculin. These findings suggest novel mechanisms of CsA nephrotoxicity and identify novel potential markers of the disease.

Nitric oxide involvement in TNF-alpha and IL-1 beta-mediated changes in human mesangial cell MMP-9 and TIMP-1.

BACKGROUND: Mesangial cells are known to secrete metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) that are capable of disrupting the glomerular basement membrane (GBM). Disruption of the GBM appears to be an important mechanism in the renal disease process, however little is known about the mechanisms involved. Therefore we examined the potential role of nitric oxide (NO) in the regulation of MMP-9 and TIMP-1 by tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) using the human mesangial cell line (HMCL). METHODS: The HMCL was treated with various concentrations of cytokines and NO inhibitors. Activity of MMP-9 was examined by gelatin zymography and TIMP-1 expression was analysed by Western blotting. NO production was measured using the Greiss assay. RESULTS: In this study, stimulation of HMCL cells with TNF-alpha or IL-1 beta, alone or in combination, led to a substantial increase in NO production, which was shown to result from an increase in the expression of the inducible form of NOS (iNOS). Treatment of cells with the specific iNOS inhibitor L-NIL potentiated the increase in MMP-9 production induced by TNF-alpha, but prevented the suppression of TIMP-1 production observed following cytokine treatment. The NO donor, sodium nitroprusside, also stimulated a substantial increase in NO production in HMCL cells, which was associated with a reduction in basal and TNF-alpha-stimulated MMP-9 and a potentiation of the cytokine-induced decrease in TIMP-1. CONCLUSIONS: Our study provides convincing evidence of a modulatory role for NO on cytokine-induced MMP-9 and TIMP-1 production in human mesangial cells.