The aim of this study was to investigate the role of TLR2, TLR4 and MyD88 in sepsis-induced AKI. C57BL/6 TLR2−/−, TLR4−/− and MyD88−/− male mice were subjected to sepsis by cecal ligation and puncture (CLP). Twenty four hours later, kidney tissue and blood samples were collected for analysis. The TLR2−/−, TLR4−/− and MyD88−/− mice that were subjected to CLP had preserved renal morphology, and fewer areas of hypoxia and apoptosis compared with the wild-type C57BL/6 mice (WT). MyD88−/− mice were completely protected compared with the WT mice. We also observed reduced expression of proinflammatory cytokines in the kidneys of the knockout mice compared with those of the WT mice and subsequent inhibition of increased vascular permeability in the kidneys of the knockout mice. The WT mice had increased GR1+low cells migration compared with the knockout mice and decreased in GR1+high cells migration into the peritoneal cavity. The TLR2−/−, TLR4−/−, and MyD88−/− mice had lower neutrophil infiltration in the kidneys. Depletion of neutrophils in the WT mice led to protection of renal function and less inflammation in the kidneys of these mice. Innate immunity participates in polymicrobial sepsis-induced AKI, mainly through the MyD88 pathway, by leading to an increased migration of neutrophils to the kidney, increased production of proinflammatory cytokines, vascular permeability, hypoxia and apoptosis of tubular cells.

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Tubule-interstitial nephritis (TIN) results in decreased renal function and interstitial inflammation, which ultimately leads to fibrosis. Excessive adenine intake can cause TIN because xanthine dehydrogenase (XDH) can convert this purine into an insoluble compound, which precipitates in the tubuli. Innate immune sensors, such as Toll-like receptors (TLR) and inflammasome complex, play a crucial role in the initiation of inflammation. The aim of this study was to evaluate the roles of TLR-2 and -4, Myd88 and inflammasome complex in an experimental model of TIN. Here, we show that wild-type (WT) mice fed adenine-enriched food exhibited significant renal dysfunction and enhanced cellular infiltration accompanied by collagen deposition. They also presented higher gene and protein expression of pro-inflammatory cytokines. In contrast, TLR-2, -4, MyD88, ASC and Caspase-1 KO mice showed renoprotection associated with expression of inflammatory molecules at levels comparable to controls. Furthermore, treatment of WT animals with allopurinol, an XDH inhibitor, led to reduced levels of uric acid, oxidative stress, collagen deposition and a downregulation of the NF-kB signaling pathway. We concluded that MyD88 signaling and inflammasome participate in the development of TIN. Furthermore, inhibition of XDH seems to be a promising way to therapeutically target the developing inflammatory process.

Inflammation contributes to the pathogenesis of chronic kidney disease (CKD). Molecules released by the inflamed injured tissue can activate toll-like receptors (TLRs), thereby modulating macrophage and CD4(+) T-cell activity. We propose that in renal fibrogenesis, M2 macrophages are recruited and activated in a T helper subset 2 cell (T(H)2)-prone inflammatory milieu in a MyD88-dependent manner. Mice submitted to unilateral ureteral ligation (UUO) demonstrated an increase in macrophage infiltration with collagen deposition after 7 d. Conversely, TLR2, TLR4 and MyD88 knockout (KO) mice had an improved renal function together with diminished T(H)2 cytokine production and decreased fibrosis formation. Moreover, TLR2, TLR4 and MyD88 KO animals exhibited less M2 macrophage infiltration, namely interleukin (IL)-10(+) and CD206(+) CD11b(high) cells, at 7 d after surgery. We evaluated the role of a T(H)2 cytokine in this context, and observed that the absence of IL-4 was associated with better renal function, decreased IL-13 and TGF-β levels, reduced arginase activity and a decrease in fibrosis formation when compared with IL-12 KO and wild-type (WT) animals. Indeed, the better renal outcomes and the decreased fibrosis formation were restricted to the deficiency of IL-4 in the hematopoietic compartment. Finally, macrophage depletion, rather than the absence of T cells, led to reduced lesions of the glomerular filtration barrier and decreased collagen deposition. These results provide evidence that future therapeutic strategies against renal fibrosis should be accompanied by the modulation of the M1:M2 and T(H)1:T(H)2 balance, as T(H)2 and M2 cells are predictive of fibrosis toward mechanisms that are sensed by innate immune response and triggered in a MyD88-dependent pathway.

BackgroundThe tubule-interstitial fibrosis is the hallmark of progressive renal disease and is strongly associated with inflammation of this compartment. Heme-oxygenase-1 (HO-1) is a cytoprotective molecule that has been shown to be beneficial in various models of renal injury. However, the role of HO-1 in reversing an established renal scar has not yet been addressed.AimWe explored the ability of HO-1 to halt and reverse the establishment of fibrosis in an experimental model of chronic renal disease.MethodsSprague-Dawley male rats were subjected to unilateral ureteral obstruction (UUO) and divided into two groups: non-treated and Hemin-treated. To study the prevention of fibrosis, animals were pre-treated with Hemin at days -2 and -1 prior to UUO. To investigate whether HO-1 could reverse established fibrosis, Hemin therapy was given at days 6 and 7 post-surgery. After 7 and/or 14 days, animals were sacrificed and blood, urine and kidney tissue samples were collected for analyses. Renal function was determined by assessing the serum creatinine, inulin clearance, proteinuria/creatininuria ratio and extent of albuminuria. Arterial blood pressure was measured and fibrosis was quantified by Picrosirius staining. Gene and protein expression of pro-inflammatory and pro-fibrotic molecules, as well as HO-1 were performed.ResultsPre-treatment with Hemin upregulated HO-1 expression and significantly reduced proteinuria, albuminuria, inflammation and pro-fibrotic protein and gene expressions in animals subjected to UUO. Interestingly, the delayed treatment with Hemin was also able to reduce renal dysfunction and to decrease the expression of pro-inflammatory molecules, all in association with significantly reduced levels of fibrosis-related molecules and collagen deposition. Finally, TGF-β protein production was significantly lower in Hemin-treated animals.ConclusionTreatment with Hemin was able both to prevent the progression of fibrosis and to reverse an established renal scar. Modulation of inflammation appears to be the major mechanism behind HO-1 cytoprotection.

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Acute kidney injury (AKI) is considered an inflammatory disease in which toll-like receptors (TLRs) signaling pathways play an important role. The activation of TLRs results in production of several inflammatory cytokines leading to further renal damage. In contrast, TLRs are key players on autophagy induction, which is associated with a protective function on cisplatin-induced AKI. Hence, the present study aimed to evaluate the specific participation of TLR2 and TLR4 molecules on the development of cisplatin-induced AKI. Complementarily, we also investigated the link between TLRs and heme oxygenase-1 (HO-1), a promisor cytoprotective molecule. First, we observed that only the absence of TLR2 but not TLR4 in mice exacerbated the renal dysfunction, tissue injury and mortality rate, even under an immunologically privileged microenvironment. Second, we demonstrated that TLR2 knockout (KO) mice presented lower expression of autophagy-associated markers when compared with TLR4 KO animals. Similar parameter was confirmed , using tubular epithelial cells derived from both KO mice. To test the cross-talking between HO-1 and TLRs, hemin (an HO-1 internal inducer) was administrated in cisplatin-treated TLR2 and TLR4 KO mice and it was detected an improvement in the global renal tissue parameters. However, this protection was less evident at TLR2 KO mice. In summary, we documented that TLR2 plays a protective role in cisplatin-induced AKI progression, in part, by a mechanism associated with autophagy up-regulation, considering that its interplay with HO-1 can promote renal tissue recover.

Background/Aims: Recent evidence shows a critical role of the CD4+ T cell with the Th1/Th2 paradigm as a possible effector mechanism in ischemia and reperfusion injury. We hypothesize that a polarized Th1 activation response may negatively influence the renal IRI through its relationship with chemokine production (MCP-1) and with a protective tissue response (HO-1). Methods: We subjected mice to renal ischemia for 45 min using IL-4 and IL-12 knockout C57BL/6. We then measured serum urea levels, performed histomorphometric analysis for tubular necrosis and regeneration, and evaluated the mRNA expression of HO-1, t-bet, Gata-3 and MCP-1 by real-time PCR at 24, 48 and 120 h after surgery. Results/Conclusions: The IL-4 knockout mice had a statistically significant rise in serum urea levels post IRI compared with control animals. The IL-12-deficient mice were not affected. The IL-4-deficient mice had a statistically significant increase in tubular injury and impairment in cell regeneration. The IRI in IL-4-deficient mice was accompanied by higher levels of HO-1, t-bet and later up-regulation of MCP-1. These findings suggest that the deleterious effects of the Th1 cell involve increased production of chemokines such as MCP-1.