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Lysophosphatidic acid (LPA) released during ischemia has diverse physiological effects via its G protein-coupled receptors, LPA[sub 1], LPA[sub 2], and LPA[sub 3] (formerly Edg-2, -4, and -7). We tested the hypothesis that selective blockade of LPA receptors affords protection from renal ischemia-reperfusion (UR) injury. By real-time PCR, LPA[sub 1-3] receptor mRNAs were expressed in mouse renal cortex, outer medulla, and inner medulla with the following rank order LPA[sub 3] = LPA[sub 2] > LPA[sub 1]. In C57BL/6 mice whose kidneys were subjected to ischemia and reperfusion, treatment with a selective LPA3 agonist, oleoyl-methoxy phosphothionate (OMPT), enhanced injury. In contrast, a dual LPA[sub 1]/LPA[sub 3]-receptor antagonist, VPC-12249, reduced UR injury, but this protective effect was lost when the antagonist was coadministered with OMPT. Interestingly, delaying administration of VPC-12249 until 30 min after the start of reperfusion did not alter its efficacy significantly. We conclude that VPC-12249 reduces renal I/R injury predominantly by LPA3 receptor blockade and could serve as a novel compound in the treatment ofischemia acute renal failure. [ABSTRACT FROM AUTHOR]

Enhanced protection from renal ischemia: Reperfusion injury with A2A -adenosine receptor activation and PDE 4 inhibition. Background. We previously demonstrated in rats and mice that agonists of A2A -adenosine receptors (A2A -ARs) reduce renal injury following ischemia-reperfusion. We now extend these studies and examine the effects of ATL-146e (formerly DWH-146e), an A2A -AR agonist, and rolipram, a type IV phosphodiesterase (PDE 4) inhibitor, on murine renal injury following ischemia-reperfusion. Methods. C57BL/6 mice were treated with rolipram, ATL-146e, or both compounds combined and were subjected to renal ischemia for 32 minutes and reperfusion for 24 to 48 hours. In vitro studies were performed on suspended and adhering human neutrophils. Results. Continuous delivery of rolipram or ATL-146e during reperfusion reduced renal injury in a dose-dependent manner. Maximal protection was observed when ATL-146e was infused for six hours during reperfusion. Elevated plasma creatinine and myeloperoxidase activity produced by ischemia-reperfusion were reduced by rolipram (0.1 ng/kg/min) and ATL-146e (10 ng/kg/min) by up to approximately 60% and 70%, respectively. Co-infusion of both compounds produced a maximum reduction of plasma creatinine of approximately 90% and myeloperoxidase activity. In vitro studies on suspended and adhering human neutrophils demonstrated that selective stimulation of A2A -ARs by ATL-146e increased cAMP accumulation, reduced oxidative activity of activated neutrophils, and decreased activated neutrophil adherence. These responses were potentiated by rolipram. Conclusions. We conclude that the combined infusion of ATL-146e and rolipram leads to enhanced renal tissue protection from ischemia-reperfusion by mechanisms that may include reduced neutrophil adherence/recruitment and release of reactive oxygen species. [ABSTRACT FROM AUTHOR]

Investigates whether selective alpha2A adenosine receptor activation reduces ischemia-reperfusion injury in the rat kidney. Effect of adenosine on neutrophils and endothelial cells; Reduction in tubular injury and ischemic necrosis after ischemia-reperfusion injury following treatment with the adenosine analog DWH-146e.

Presents information on a study which examined the effect of selective activation of A... adenosine receptors on ischemia-reperfusion injury in rat kidney. Methods of the study; Results and discussion.

T cells are activated by antigen-independent as well as antigen-dependent mechanisms during ischemia-reperfusion injury to the kidney. In the current issue, a study by Savransky et al. suggests that antigen-dependent activation of T-cell receptors further contributes to the pathogenesis of ischemia-reperfusion injury.Kidney International (2006) 69, 208–210. doi:10.1038/sj.ki.5000128 [ABSTRACT FROM AUTHOR]

Ischemia-reperfusion injury (IRI) is one of the major causes of acute kidney injury (AKI) and evidence supporting the involvement of both innate and adaptive immunity in renal IRI has accumulated in recent years. In addition to leukocytes, kidney endothelial cells promote inflammation after IRI by increasing adhesion molecule expression and vascular permeability. Kidney tubular epithelial cells increase complement binding and upregulate toll-like receptors, both of which lead to cytokine/chemokine production in IRI. Activation of kidney resident dendritic cells, interferon-γ-producing neutrophils, infiltrating macrophages, CD4+ T cells, B cells and invariant natural killer T cells are all implicated in the pathogenesis of AKI. The complex interplay between innate and adaptive immunity in renal IRI is still not completely understood, but major advances have been made. This review summarizes these recent advances to further our understanding of the immune mechanisms of acute kidney injury. Copyright © 2008 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Our bodies turn over billions of cells daily via apoptosis and are in turn cleared by phagocytes via the process of "efferocytosis." Defects in efferocytosis are now linked to various inflammatory diseases. Here, we designed a strategy to boost efferocytosis , denoted "chimeric receptor for efferocytosis" (CHEF). We fused a specific signaling domain within the cytoplasmic adapter protein ELMO1 to the extracellular phosphatidylserine recognition domains of the efferocytic receptors BAI1 or TIM4, generating BELMO and TELMO, respectively. CHEF-expressing phagocytes display a striking increase in efferocytosis. In mouse models of inflammation, BELMO expression attenuates colitis, hepatotoxicity, and nephrotoxicity. In mechanistic studies, BELMO increases ER-resident enzymes and chaperones to overcome protein-folding-associated toxicity, which was further validated in a model of ER-stress-induced renal ischemia-reperfusion injury. Finally, TELMO introduction after onset of kidney injury significantly reduced fibrosis. Collectively, these data advance a concept of chimeric efferocytic receptors to boost efferocytosis and dampen inflammation. [Display omitted] Design of chimeric receptors for efferocytosis (CHEF) to enhance efferocytosis Boosting efferocytosis via CHEF attenuates multiple inflammatory insults in vivo Protein folding and misfolded protein degradation are rate-limiting steps in efferocytosis CHEF expression can improve outcomes in ongoing disease Chimeric receptors comprising an extracellular phosphatidylserine recognition domain and the signalling domain of a cytoplasmic adaptor protein boost clearance of apoptotic cells in damaged tissue and improve the disease outcome. [ABSTRACT FROM AUTHOR]

The nervous and immune systems interact in complex ways to maintain homeostasis and respond to stress or injury, and rapid nerve conduction can provide instantaneous input for modulating inflammation. The inflammatory reflex referred to as the cholinergic antiinflammatory pathway regulates innate and adaptive immunity, and modulation of this reflex by vagus nerve stimulation (VNS) is effective in various inflammatory disease models, such as rheumatoid arthritis and inflammatory bowel disease. Effectiveness of VNS in these models necessitates the integration of neural signals and α7 nicotinic acetylcholine receptors (α7nAChRs) on splenic macrophages. Here, we sought to determine whether electrical stimulation of the vagus nerve attenuates kidney ischemia-reperfusion injury (IRI), which promotes the release of proinflammatory molecules. Stimulation of vagal afferents or efferents in mice 24 hours before IRI markedly attenuated acute kidney injury (AKI) and decreased plasma TNF. Furthermore, this protection was abolished in animals in which splenectomy was performed 7 days before VNS and IRI. In mice lacking α7nAChR, prior VNS did not prevent IRI. Conversely, adoptive transfer of VNS-conditioned α7nAChR splenocytes conferred protection to recipient mice subjected to IRI. Together, these results demonstrate that VNS-mediated attenuation of AKI and systemic inflammation depends on α7nAChR-positive splenocytes. [ABSTRACT FROM AUTHOR]

We have previously shown that polyclonal natural IgM protects mice from renal ischemia/reperfusion injury (IRI) by inhibiting the reperfusion inflammatory response. We hypothesized that a potential mechanism involved IgM modulation of dendritic cells (DC), as we observed high IgM binding to splenic DC. To test this hypothesis, we pretreated bone marrow-derived DC (BMDC) with polyclonal murine or human IgM prior to LPS activation and demonstrated that 0.5 x 106 IgM/LPS-pretreated BMDC, when injected into wild-type C57BL/6 mice 24 h before renal ischemia, protect mice from developing renal IRI. We show that this switching of LPS-activated BMDC to a regulatory phenotype requires modulation of BMDC function that is mediated by IgM binding to nonapoptotic BMDC receptors. Regulatory BMDC require IL-10 and programmed death 1 as well as downregulation of CD40 and p65 NF-κB phosphorylation to protect in renal IRI. Blocking the programmed death ligand 1 binding site just before i.v. injection of IgM/LPS-pretreated BMDC or using IL-10 knockout BMDC fails to induce protection. Similarly, IgM/LPS-pretreated BMDC are rendered nonprotective by increasing CD40 expression and phosphorylation of p65 NF-κB. How IgM/LPS regulatory BMDC suppress in vivo ischemia-induced innate inflammation remains to be determined. However, we show that suppression is dependent on other in vivo regulatory mechanisms in the host, that is, CD25+ T cells, B cells, IL-10, and circulating IgM. There was no increase in Foxp3+ regulatory T cells in the spleen either before or after renal IRI. Collectively, these findings show that natural IgM anti-leukocyte Abs can switch BMDC to a regulatory phenotype despite the presence of LPS that ordinarily induces BMDC maturation. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) are central to innate and adaptive immunity of early kidney ischemia-reperfusion injury (IRI), and strategies to alter DC function may provide new therapeutic opportunities. Sphingosine 1-phosphate (SIP) modulates immunity through binding to its receptors (S1P1-5), and protection from kidney IRI occurs in SlP3-deficient mice. Through a series of experiments we determined that this protective effect was owing in part to differences between SlP3-sufficient and -deficient DCs. Mice lacking S1P3 on bone marrow cells were protected from IRI, and SlP3-deficient DCs displayed an immature phenotype. Wild-type (WT) but not SlP3-deficient DCs injected into mice depleted of DCs prior to kidney IR reconstituted injury. Adoptive transfer (i.e., i.v. injection) of glycolipid (Ag)-loaded WT but not SlP3-deficient DCs into WT mice exacerbated IRI, suggesting that WT but not SlP3-deficient DCs activated NKT cells. Whereas WT DC transfers activated the Thl/IFN-γ pathway, SlP3-deficient DCs activated the Th2/IL-4 pathway, and an IL-4-blocking Ab reversed protection from IRI, supporting the concept that IL-4 mediates the protective effect of SlP3-deficient DCs. Administration of SlP3-deficient DCs 7 d prior to or 3 h after IRI protected mice from IRI and suggests their potential use in cell-based therapy. We conclude that absence of DC S1P3 prevents DC maturation and promotes a Th2/IL-4 response. These findings highlight the importance of DC S1P3 in modulating NKT cell function and IRI and support development of selective S1P3 antagonists for tolerizing DCs for cell-based therapy or for systemic administration for the prevention and treatment of IRI and autoimmune diseases. [ABSTRACT FROM AUTHOR]

The IL-23/IL-17 and IL-12/IFN-gamma cytokine pathways have a role in chronic autoimmunity, which is considered mainly a dysfunction of adaptive immunity. The extent to which they contribute to innate immunity is, however, unknown. We used a mouse model of acute kidney ischemia-reperfusion injury (IRI) to test the hypothesis that early production of IL-23 and IL-12 following IRI activates downstream IL-17 and IFN-gamma signaling pathways and promotes kidney inflammation. Deficiency in IL-23, IL-17A, or IL-17 receptor (IL-17R) and mAb neutralization of CXCR2, the p19 subunit of IL-23, or IL-17A attenuated neutrophil infiltration in acute kidney IRI in mice. We further demonstrate that IL-17A produced by GR-1+ neutrophils was critical for kidney IRI in mice. Activation of the IL-12/IFN-gamma pathway and NKT cells by administering alpha-galactosylceramide-primed bone marrow-derived DCs increased IFN-gamma production following moderate IRI in WT mice but did not exacerbate injury or enhance IFN-gamma production in either Il17a-/- or Il17r-/- mice, which suggested that IL-17 signaling was proximal to IFN-gamma signaling. This was confirmed by the finding that IFN-gamma administration reversed the protection seen in Il17a-/- mice subjected to IRI, whereas IL-17A failed to reverse protection in Ifng-/- mice. These results demonstrate that the innate immune component of kidney IRI requires dual activation of the IL-12/IFN-gamma and IL-23/IL-17 signaling pathways and that neutrophil production of IL-17A is upstream of IL-12/IFN-gamma. These mechanisms might contribute to reperfusion injury in other organs. [ABSTRACT FROM AUTHOR]

Sphingosine-1-phosphate (S1P), produced by sphingosine kinase 1 (SphK1) or kinase 2 (SphK2), mediates biological effects through intracellular and/or extracellular mechanisms. Here we determined a role for these kinases in kidney injury of wild-type mice following ischemia–reperfusion. SphK1 but not SphK2 mRNA expression and activity increased in the kidney following injury relative to sham-operated animals. Although SphK1−/− mice had no alteration in renal function following injury, mice with a disrupted SphK2 gene (SphK2tr/tr) had histological damage and impaired function. The immune-modulating pro-drug, FTY720, an S1P agonist failed to provide protection in SphK2tr/tr mice. Injured kidneys of these mice showed increased neutrophil infiltration and neutrophil chemokine expression along with a 3- to 5-fold increase in expression of the G-protein-coupled receptor S1P3 compared to heterozygous SphK2+/tr mice. Kidney function and reduced vascular permeability were preserved in S1P3−/− compared to S1P3+/− mice after ischemia–reperfusion injury, suggesting increased S1P3 mRNA may play a role in the injury of SphK2tr/tr mice. Our study suggests that constitutive expression of SphK2 may contribute to reduced ischemia–reperfusion injury of the kidney, and its absence may enhance injury due to increased neutrophil infiltration and S1P3 activation. We also confirm that SphK2 is necessary to mediate the protective effects of FTY720.Kidney International (2009) 75, 167–175; doi:10.1038/ki.2008.400; published online 29 October 2008 [ABSTRACT FROM AUTHOR]

Chemokines and their receptors such as CCR2 and CX3CR1 mediate leukocyte adhesion and migration into injured tissue. To further define mechanisms of monocyte trafficking during kidney injury we identified two groups of F4/80-positive cells (F4/80(low) and F4/80(high)) in the normal mouse kidney that phenotypically correspond to macrophages and dendritic cells, respectively. Following ischemia and 3 h of reperfusion, there was a large influx of F4/80(low) inflamed monocytes, but not dendritic cells, into the kidney. These monocytes produced TNF-alpha, IL-6, IL-1alpha and IL-12. Ischemic injury induced in CCR2(-/-) mice or in CCR2(+/+) mice, made chimeric with CCR2(-/-) bone marrow, resulted in lower plasma creatinine levels and their kidneys had fewer infiltrated F4/80(low) macrophages compared to control mice. CX3CR1 expression contributed to monocyte recruitment into inflamed kidneys, as ischemic injury in CX3CR1(-/-) mice was reduced, with fewer F4/80(low) macrophages than controls. Monocytes transferred from CCR2(+/+) or CX3CR1(+/-) mice migrated into reperfused kidneys better than monocytes from either CCR2(-/-) or CX3CR1(-/-) mice. Adoptive transfer of monocytes from CCR2(+/+) mice, but not CCR2(-/-) mice, reversed the protective effect in CCR2(-/-) mice following ischemia-reperfusion. Egress of CD11b(+)Ly6C(high) monocytes from blood into inflamed kidneys was CCR2- and CX3CR1-dependent. Our study shows that inflamed monocyte migration, through CCR2- and CX3CR1-dependent mechanisms, plays a critical role in kidney injury following ischemia reperfusion. [ABSTRACT FROM AUTHOR]

Chemokines and their receptors such as CCR2 and CX3CR1 mediate leukocyte adhesion and migration into injured tissue. To further define mechanisms of monocyte trafficking during kidney injury we identified two groups of F4/80-positive cells (F4/80low and F4/80high) in the normal mouse kidney that phenotypically correspond to macrophages and dendritic cells, respectively. Following ischemia and 3 h of reperfusion, there was a large influx of F4/80low inflamed monocytes, but not dendritic cells, into the kidney. These monocytes produced TNF-α, IL-6, IL-1α and IL-12. Ischemic injury induced in CCR2−/− mice or in CCR2+/+ mice, made chimeric with CCR2−/− bone marrow, resulted in lower plasma creatinine levels and their kidneys had fewer infiltrated F4/80low macrophages compared to control mice. CX3CR1 expression contributed to monocyte recruitment into inflamed kidneys, as ischemic injury in CX3CR1−/− mice was reduced, with fewer F4/80low macrophages than controls. Monocytes transferred from CCR2+/+ or CX3CR1+/− mice migrated into reperfused kidneys better than monocytes from either CCR2−/− or CX3CR1−/− mice. Adoptive transfer of monocytes from CCR2+/+ mice, but not CCR2−/− mice, reversed the protective effect in CCR2−/− mice following ischemia-reperfusion. Egress of CD11b+Ly6Chigh monocytes from blood into inflamed kidneys was CCR2- and CX3CR1-dependent. Our study shows that inflamed monocyte migration, through CCR2- and CX3CR1-dependent mechanisms, plays a critical role in kidney injury following ischemia reperfusion.Kidney International (2008) 74, 1526–1537; doi:10.1038/ki.2008.500; published online 8 October 2008 [ABSTRACT FROM AUTHOR]

The mechanisms involved in renal ischemia-reperfusion injury (IRI) are complex and appear to involve the early participation of bone marrow-derived cells. T lymphocytes participate in the pathogenesis of IRI. Sphingosine 1-phosphate (S1P) induces peripheral T cell depletion. Therefore, we hypothesized that S1P1 receptor activation protects kidney from IRI. FTY-720, a non-receptor-selective sphingosine analog, was given intraperitoneally to C57BL/6 mice, and animals were subjected to ischemia for 32 min followed by reperfusion for 24 h. Plasma creatinine, blood count, myeloperoxidase (MPO) activity, and renal histology were determined. IRI led to a marked increase in plasma creatinine, MPO activity, leukocyte infiltration, and vascular permeability. FTY-720 significantly decreased plasma creatinine in a dose-response manner with a maximal reduction of ∼73 and ∼69% with doses of 240 and 48 μg/kg, respectively. MPO, leukocyte infiltration, vascular permeability, and peripheral blood lymphocyte counts were markedly decreased with FTY-720 treatment. The protective effect of FTY-720 was reversed with VPC-44116, a selective S1P1 receptor antagonist. Furthermore, SEW-2871, a selective S1P1 agonist, significantly decreased plasma creatinine in a dose-response manner with a maximal reduction of ∼70% with a dose of 10 mg/kg. Analysis of kidneys by light microscopy revealed minimal histological signs of ischemic injury with FTY-720 or SEW-2871 treatment compared with the vehicle group. Using RT-PCR, we found a time-dependent increase in the S1P1 mRNA expression following IRI that begins after 2 h with the maximum expression at ∼4 h. We conclude that the protective effect of FTY-720 is due primarily to activation of S1P1 receptors. The mechanism of protection is not known but may be related to peripheral lymphocyte depletion or direct effects on kidney cells expressing S1P1 receptor. [ABSTRACT FROM AUTHOR]

The role of monocytes/macrophages in the pathogenesis of ischemia-reperfusion injury ORB is unknown. We sought to determine whether activation of macrophage adenosine 2A (A2A) receptors (A2ARs) mediates tissue protection We subjected C57B1/6 mice infused with clodronate [dichloromethylene bisphosphonate (Cl2MBP)] to IRI (32 min of ischemia followed by 24 h of reperfusion) to deplete them of macrophages. IRI induced an elevation of plasma creatinine that was reduced with Cl2MBP (26% of control). Adoptive transfer of murine RAW 264.7 cells reconstituted injury, an effect blocked significantly by A2A agonists (27% of plasma creatinine from mice reconstituted with macrophages). Macrophages subjected to A2A knockout by small interfering RNA were adoptively transferred to macrophage-depleted mice and reconstituted injury (110% of control mice); however, the increase in plasma creatinine was blocked by A2A agonists (20% of vehicle treatment). Finally, the A2A agonist effect on IRI was blocked in macrophage-depleted A2A-knockout mice reconstituted with wild-type RAW 264.7 cells. RNase protection assays 24 h after IRI demonstrated that macrophages are required for IL-6 and TGF-β mRNA induction. However, A2A agonist-mediated tissue protection is independent of IL-6 and TGF-β mRNA. We conclude that the full extent of IRI requires macrophages and that A2A agonist-mediated tissue protection is independent of activation of macrophage A2ARs. [ABSTRACT FROM AUTHOR]

Activation of A2A adenosine receptors (A2ARs) protects kidneys from ischemia-reperfusion injury (IRI). A2ARs are expressed on bone marrow-derived (BM-derived) cells and renal smooth muscle, epithelial, and endothelial cells. To measure the contribution of A2ARs on BM-derived cells in suppressing renal IRI, we examined the effects of a selective agonist of A2ARs, ATL146e, in chimeric mice in which BM was ablated by lethal radiation and reconstituted with donor BM cells derived from GFP, A2AR-KO, or WT mice to produce GFP-->WT, A2A-KO-->WT, or WT-->WT mouse chimera. We found little or no repopulation of renal vascular endothelial cells by donor BM with or without renal IRI. ATL146e had no effect on IRI in A2A-KO mice or A2A-KO-->WT chimera, but reduced the rise in plasma creatinine from IRI by 75% in WT mice and by 60% in WT-->WT chimera. ATL146e reduced the induction of IL-6, IL-1beta, IL-1ra, and TGF-alpha mRNA in WT-->WT mice but not in A2A-KO-->WT mice. Plasma creatinine was significantly greater in A2A-KO than in WT mice after IRI, suggesting some renal protection by endogenous adenosine. We conclude that protection from renal IRI by A2AR agonists or endogenous adenosine requires activation of receptors expressed on BM-derived cells. [ABSTRACT FROM AUTHOR]