The molecular mechanisms of acute kidney injury (AKI) remain unclear. Toll-like receptors (TLRs), widely expressed on leukocytes and kidney epithelial cells, regulate innate and adaptive immune responses. The present study examined the role of TLR signaling in cisplatin-induced AKI. Cisplatin-treated wildtype mice had significantly more renal dysfunction, histologic damage, and leukocytes infiltrating the kidney than similarly treated mice with a targeted deletion of TLR4 [Tlr4(Ϫ/Ϫ)]. Levels of cytokines in serum, kidney, and urine were increased significantly in cisplatin-treated wild-type mice compared with saline-treated wild-type mice and cisplatin-treated Tlr4(Ϫ/Ϫ) mice. Activation of JNK and p38, which was associated with cisplatin-induced renal injury in wild-type mice, was significantly blunted in Tlr4(Ϫ/Ϫ) mice. Using bone marrow chimeric mice, it was determined that renal parenchymal TLR4, rather than myeloid TLR4, mediated the nephrotoxic effects of cisplatin. Therefore, activation of TLR4 on renal parenchymal cells may activate p38 MAPK pathways, leading to increased production of inflammatory cytokines, such as TNF-␣ and subsequent kidney injury. Targeting the TLR4 signaling pathways may be a feasible therapeutic strategy to prevent cisplatin-induced AKI in humans.

Meprins are metalloendopeptidases expressed by leukocytes in the lamina propria of the human inflamed bowel, that degrade extracellular matrix proteins in vitro implicating them in leukocyte transmigration events. The aims of these studies were to 1) examine the expression of meprins in the mouse mesenteric lymph node, 2) determine whether macrophages express meprins, and 3) determine whether deletion of the meprin β gene (Mep-1β) mitigated the ability of leukocytes to disseminate through extracellular matrix in vitro. These studies show that meprin α and β are expressed in leukocytes of the mouse mesenteric lymph node, and meprin α, but not β, decreased during intestinal inflammation. Deletion of Mep-1β gene decreased the ability of leukocytes to migrate through matrigel compared with wild-type leukocytes. Meprin β, but not α, was detected in cortical and medullary macrophages of the lymph node. Thus overall, meprin β is expressed by leukocytes in the draining lymph node of the intestine, regardless of the inflammatory status of the animal, and is likely to contribute to leukocyte transmigration events important to intestinal immune responses. Thus, the expression of meprins by leukocytes of the intestinal immune system may have important implications for diseases such as inflammatory bowel diseases, which are aggravated by leukocyte infiltration.

toxicity of the cancer chemotherapeutic agent cisplatin is acute renal failure. Sepsis is a common cause of acute renal failure in humans and patients who receive cisplatin are at increased risk for sepsis. Accordingly, this study examined the interactions between cisplatin and endotoxin in vivo with respect to renal function and cytokine production. Mice were treated with either a single dose of cisplatin or two doses of LPS administered 24 h apart, or both agents in combination. Administration of 10 mg/kg cisplatin had no effect on blood urea nitrogen or creatinine levels throughout the course of the study. LPS resulted in a modest rise in blood urea nitrogen at 24 and 48 h, which returned to normal by 72 h. In contrast, mice treated with both cisplatin and LPS developed severe renal failure and an increase in mortality. Urine, but not serum, TNF-␣ levels showed a synergistic increase by cisplatin and LPS. Urinary IL-6, MCP-1, KC, and GM-CSF also showed a synergistic increase with cisplatinϩLPS treatment. The renal dysfunction induced by cisplatinϩLPS was completely dependent on TLR4 signaling and partially dependent on TNF-␣ production. Increased cytokine production was associated with a moderate increase in infiltrating leukocytes which was not different between cisplatinϩLPS and LPS alone. These results indicate that cisplatin and LPS act synergistically to produce nephrotoxicity which may involve proinflammatory cytokine production.tumor necrosis factor-␣; Toll-like receptor 4; sepsis; acute renal failure; cytokines ACUTE RENAL FAILURE can develop in a variety of clinical situations such as ischemia, sepsis, and administration of nephrotoxic agents. Studies using experimental models of acute renal failure have identified a large number of putative pathophysiological mediators (33, 35). The majority of these studies have employed models of acute renal injury subsequent to a single renal insult (20). However, acute renal failure in humans often occurs in complex clinical settings in which patients may be exposed to a number of different renal insults (35). It has been suggested that the failure in humans of therapeutic interventions based on single-insult animal studies may be due, in part, to the multiplicity of renal insults in human acute renal failure (12,20).Sepsis is a common cause of acute renal failure, accounting for up to 60% of cases in some series (2, 32). TNF-␣ is an important mediator of the systemic and renal effects of sepsis (3,15). The production of TNF-␣ in sepsis results from the activation of TLR receptors by bacterial products such as endotoxin (1, 4, 5). In previous animal studies, we and others (27,29,30,36,37) also demonstrated an important role for TNF-␣ in the pathogenesis of cisplatin-induced renal injury. Inhibition of TNF-␣ production or action markedly reduced the nephrotoxicity of cisplatin (29,30). Against this background, Zager et al. (44) reported that treatment of mice with both cisplatin and endotoxin resulted in augmented production of proinflammatory cytokines, includin...

Meprins are membrane-bound and secreted metalloproteinases consisting of alpha- and/or beta-subunits that are highly expressed in mouse kidney proximal tubules. Previous studies have implied that the meprin alpha/beta-isoform is deleterious when renal tissue is subjected to ischemia-reperfusion (I/R). To delineate the roles of the meprin isoforms in renal disease, we subjected mice deficient in meprin-beta (KO) and their wild-type (WT) counterparts to I/R. WT mice were markedly more susceptible to renal injury after I/R than the meprin-beta KO mice as determined by blood urea nitrogen levels. Urinary levels of inflammatory cytokines IL-6 and KC (CXCL1) were significantly higher in WT compared with meprin-beta KO mice by 6 h post-I/R. At 96 h postischemia, kidney mRNA expression levels for tumor necrosis factor-alpha, transforming growth factor-beta, inducible nitric oxide synthase, and heat shock protein-27 were significantly higher in the WT than meprin-beta KO mice. For WT mice subjected to I/R, there was a rapid (3 h) redistribution of meprin beta-subunits in cells in S3 segments of proximal tubules, followed by shedding of apical cell membrane and detachment of cells. These studies indicate that meprin-beta is important in the pathogenesis of renal injury following I/R and that the redistribution of active meprin-alpha/beta is a major contributor to renal injury and subsequent inflammation.