Search

This study aimed to investigate the role of bone marrow stromal cell antigen-1 (Bst1; also known as CD157) in acute kidney injury (AKI). Bst1 is a cell surface molecule with various enzymatic activities and downstream intracellular signaling pathways that modulate the immune response. Previous research has linked Bst1 to diseases such as ovarian cancer, Parkinson's disease, and rheumatoid arthritis. We used bilateral ischemia-reperfusion injury (IRI) as an AKI model and created bone marrow chimeric mice to evaluate the role of Bst1 in bone marrow-derived cells. We also used flow cytometry to identify Bst1/CD157 expression in hematopoietic cells and evaluate immune cell dynamics in the kidney. The findings showed that Bst1-deficient (Bst1-/-) mice were protected against renal bilateral IRI. Bone marrow chimera experiments revealed that Bst1 expression on hematopoietic cells, but not parenchymal cells, induced renal IRI. Bst1 was mainly found in B cells and neutrophils by flow cytometry of the spleen and bone marrow. In vitro, migration of neutrophils from Bst1-/- mice was suppressed, and adoptive transfer of neutrophils from wild-type Bst1+/+ mice abolished the renal protective effect in Bst1 knockout mice. In conclusion, the study demonstrated that Bst1-/- mice are protected against renal IRI and that Bst1 expression in neutrophils plays a crucial role in inducing renal IRI. These findings suggest that targeting Bst1 in neutrophils could be a potential therapeutic strategy for AKI. NEW & NOTEWORTHY Acute kidney injury (AKI), a serious disease for which there is no effective Federal Drug Administration-approved treatment, is associated with high mortality rates. Bone marrow stromal cell antigen-1 (Bst1) is a cell surface molecule that can cause kidney fibrosis, but its role in AKI is largely unknown. Our study showed that Bst1-/- mice revealed a protective effect against renal bilateral ischemia-reperfusion injury (IRI). Adoptive transfer studies confirmed that Bst1 expression in hematopoietic cells, especially neutrophils, contributed to renal bilateral IRI. [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 S1[P.sub.1] 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 doseresponse manner with a maximal reduction of ~73 and ~69% with doses of 240 and 48 [micro]g/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 S1[P.sub.1] receptor antagonist. Furthermore, SEW-2871, a selective S1[P.sub.1] 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 S1[P.sub.1] 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 S1[P.sub.1] receptors. The mechanism of protection is not known but may be related to peripheral lymphocyte depletion or direct effects on kidney cells expressing S1[P.sub.1] receptor. FTY-720; inflammation; lymphocyte; acute renal failure

We previously demonstrated the anti-inflammatory effects and renal tissue protection in response to adenosine [A.sub.2A]-receptor ([A.sub.2A]R) activation in acute renal injury. We sought to extend these studies and determine the efficacy of [A.sub.2A]R agonists in a chronic model of renal injury. We hypothesized that [A.sub.2A] agonists mediate renal tissue protection in diabetic nephropathy by reducing glomerular inflammation. Diabetes was induced with single intravenous injection of streptozotocin in Sprague-Dawley rats (50 mg/kg). Increases in urinary albumin excretion (UAE) and plasma creatinine at week 6 in the diabetes group (26- and 6-fold over control, respectively) were markedly reduced by continuous subcutaneous administration of ATL146e (10 ng * kg * [min.sup.-1]), a selective [A.sub.2A] agonist. The increase in UAE in the diabetes group was associated with a significant reduction in the expression of slit diaphragm-associated molecules compared with control (nephrin; P < 0.05 and podocin; P < 0.005) that was reversed by ATL146e treatment. Diabetes led to an increase in urinary excretion of monocyte chemoattractant protein-1 (705% of control), TNF-[alpha] (1,586% of control), IFN-[lambda] (298% of control), kidney fibronectin mRNA (457% of control), and glomerular infiltration of macrophages (764% of control), effects significantly reduced by ATL146e treatment. Mesangial expansion and basement membrane thickness were reduced with ATL146e. To further confirm the selectivity of ATL146e, we used wild-type (WT) or [A.sub.2A] knockout ([A.sub.2A]-KO) mice. Four weeks after diabetes, UAE increased significantly in both WT and [A.sub.2A]-KO diabetic mice (3.0- and 3.3-fold over control). [A.sub.2A] agonist treatment blocked the increase in UAE in WT diabetic mice (P < 0.001), whereas it had no effect on the [A.sub.2A]-KO diabetic mice. These results demonstrate that chronic [A.sub.2A]R activation in diabetic rats 1) ameliorates histological and functional changes in kidneys induced by diabetes and 2) causes reduced inflammation associated with diabetic nephropathy. proteinuria; diabetes; macrophage; kidney; ATL146e

Recently, we demonstrated that peroxisome proliferator-activated receptor-[alpha] (PPAR[alpha]) ligand ameliorates cisplatin-induced acute renal failure (ARF) by preventing inhibition of substrate oxidation, and also by preventing apoptosis and necrosis of the proximal tubule (Li S, Bhatt R, Megyesi J, Gokden N, Shah SV, and Portilla D. Am J Physiol Renal Physiol 287: F990-F998, 2004). In the following studies, we examined the protective effect of PPAR[alpha] ligand on cisplatin-induced inflammatory responses during ARF. Mice subjected to a single intraperitoneal injection of cisplatin developed ARF at day 3. Cisplatin increased mRNA and protein expression of TNF-[micro] RANTES, and also upregulated endothelial adhesion molecules ICAM-1/VCAM-1 and chemokine receptors CCR1/CCR5. Cisplatin also led to neutrophil infiltration in the corticomedullary region. Pretreatment of wild-type mice with WY-14,643, a fibrate class of PPAR[alpha] ligands, before cisplatin signifcantly suppressed cisplatin-induced upregulation of cytokine/chemokine expression, prevented neutrophil accumulation, and ameliorated renal dysfunction. In contrast, treatment with PPAR[alpha] ligand before cisplatin did not prevent cytokine/chemokine production, neutrophil accumulation, and did not protect kidney function in PPAR[alpha] null mice. In addition, we observed that cisplatin-induced NF-[kappa]B binding activity in nuclear extracts from wild-type mice was markedly reduced by treatment with PPAR[alpha] ligand. These results demonstrate that PPAR[alpha] exerts an anti-inflammatory effect in kidney tissue by a mechanism that includes inhibition of NF-[kappa]B DNA binding activity, and this effect results in inhibition of neutrophil infiltration, cytokine/chemokine release, and amelioration of cisplatin-induced ARF. peroxisome proliferator-activated receptor-[alpha]; inflammation; cisplatin; acute renal failure

The role of monocytes/ macrophages in the pathogenesis of ischemia-reperfusion injury (IRI) is unknown. We sought to determine whether activation of macrophage adenosine 2A ([A.sub.2A]) receptors ([A.sub.2A]RS) mediates tissue protection. We subjected C57B1/6 mice infused with clodronate [dichloromethylene bisphosphonate ([Cl.sub.2]MBP)] 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 [Cl.sub.2]MBP (26% of control). Adoptive transfer of murine RAW 264.7 cells reconstituted injury, an effect blocked significantly by [A.sub.2A] agonists (27% of plasma creatinine from mice reconstituted with macrophages). Macrophages subjected to [A.sub.2A] 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 [A.sub.2A] agonists (20% of vehicle treatment). Finally, the [A.sub.2A] agonist effect on IRI was blocked in macrophage-depleted [A.sub.2A]-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-[beta] mRNA induction. However, [A.sub.2A] agonist-mediated tissue protection is independent of IL-6 and TGF-[beta] mRNA. We conclude that the full extent of IRI requires macrophages and that [A.sub.2A] agonist-mediated tissue protection is independent of activation of macrophage [A.sub.2A]RS. small interfering RNA: clodronate; adoptive transfer; inflammation: acute renal failure

Ischemia-reperfusion (I/R) injury occurs as a result of restoring blood flow to previously hypoperfused vessels or after tissue transplantation and is characterized by inflammation and microvascular occlusion. We report here that 4-{3-[6-amino-9-(5-ethylcarbamoyl-3,4-dihydroxy-tetrahydro-furan-2-yl) -9H-purin-2-yl]-prop-2-ynyl}-cyclohexanecarboxylic acid methyl ester (ATL146e), a selective agonist of the A2A adenosine receptor ([A.sub.2a]AR), profoundly protects mouse liver from I/R injury when administered at the time of reperfusion, and protection is blocked by the antagonist ZM241385. ATL146e lowers liver damage by 90% as assessed by serum glutamyl pyruvic transaminase and reduces hepatic edema and MPO. Most protection remains if ATL146e treatment is delayed for 1 h but disappears when delayed for 4 h after the start of reperfusion. In mice lacking the [A.sub.2A]AR gene, protection by ATL1465e is lost and ischemic injury of short duration is exacerbated compared with wild-type mice, suggesting a protective role for endogenous adenosine. I/R injury causes induction of hepatic transcripts for IL-1[alpha], IL-I[beta], IL-1Ra, IL-6, IL-10, IL-18, INF-[beta], INF-[gamma] regulated on activation, normal T cell expressed, and presumably secreted (RANTES), major intrinsic protein (MIP)-1[alpha], MIP-2, IFN-[gamma]-inducible protein (IP)-10, and monocyte chemotactic protein (MCP)-1 that are suppressed by administering ATL146e to wild-type but not to [A.sub.2A]AR knockout mice. RANTES, MCP-1, and IP-10 are notable as induced chemokines that are chemotactic to T lymphocytes. The induction of cytokines may contribute to transient lympbopenia and neutrophilia that occur after liver I/R injury. We conclude that most damage after hepatic ischemia occurs during reperfusion and can be blocked by [A.sub.2A]AR activation. We speculate that inhibition of chemokine and cytokine production limits inflammation and contributes to tissue protection by the [A.sub.2A]AR agonist ATL146e. adenosine receptor; [A.sub.2A] adenosine receptor knockout mice; P1 purinergic; receptors; regulated on activation, normal T cell expressed, and presumably excreted; monocyte chemotactic protein-1; interferon-[gamma]-inducible protein-10

Lysophosphatidic acid (LPA) released during ischemia has diverse physiological effects via its G protein-coupled receptors, LP[A.sub.1], LP[A.sub.2], and LP[A.sub.3] (formerly Edg-2, -4, and -7). We tested the hypothesis that selective blockade of LPA receptors affords protection from renal ischemia-reperfusion (I/R) injury. By real-time PCR, LP[A.sub.1-3] receptor mRNAs were expressed in mouse renal cortex, outer medulla, and inner medulla with the following rank order LP[A.sub.3] = LP[A.sub.2] > LP[A.sub.1]. In C57BL/6 mice whose kidneys were subjected to ischemia and reperfusion, treatment with a selective LP[A.sub.3] agonist, oleoyl-methoxy phosphothionate (OMPT), enhanced injury. In contrast, a dual LP[A.sub.1]/LP[A.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 LP[A.sub.3] receptor blockade and could serve as a novel compound in the treatment ofischemia acute renal failure. VPC-12249; oleoyl-methoxy phosphothionate; kidney; acute renal failure

[A.sub.2A] adenosine receptor: a novel therapeutic target in renal disease. Am J Physiol Renal Physiol 282: F10-F18, 2002.--Present strategies in the treatment of inflammatory renal injury have focused on developing agents that specifically target individual mechanisms thought to contribute toward the pathogenesis of the disease. Such an approach is hindered by redundancies in the inflammatory cascade, rendering intervention suboptimal. The [A.sub.2A] adenosine receptor ([A.sub.2A]-AR) is a member of the family of guanine nucleotide binding proteins and has become a focus of major interest primarily because of its ability to broadly inactivate the inflammatory cascade. This review summarizes our present knowledge regarding the molecular biology and pharmacology of [A.sub.2A]-ARs as well as the physiological effects of activation of [A.sub.2A]-ARs in the kidney. We also review our recent experience in targeting this receptor subtype in abrogating the inflammatory cascade in ischemia-reperfusion injury. inflammation; ATL-146e; ZM-243185; ischemia-reperfusion; acute renal failure

Research shows that biochemical adenylyl cyclase activity occurs in the basolateral and apical regions of bovine renal epithelial LLC-PK1 cells. Experiments designed to demonstrate the regulatory properties of adenylyl cyclase via Guanine protein-coupled nucleotide binding receptors are described. Immunolocalization and immunofluorescence techniques are used.

Immunohistochemistry of a polyclonal antibody developed specifically for B-subtype alpha(sub 2)-adrenergic receptor demonstrates specific alpha(sub 2B)-AR-like immunoreactivity in the basolateral membranes of proximal convoluted/straight tubules of kidneys. This immunoreactivity seems to be in response to dietary potassium restriction, and the effects of stimulation of alpha(sub 2B)-ARs are restricted mainly to the proximal tubule. The experiments are conducted on adult male Sprague-Dawley rats by allowing them a potassium-deficient diet and free access to tap water.

Surface binding experiments, competitive binding analyses and Northern blot analysis of Madin-Darby canine kidney (MDCK) cells to characterize the endogenous alpha2 adrenergic receptor (AR) subtype expression in the cells reveal that a clone of the MDCK cells contains high A-subtype expression of alpha2-AR in the apical membrane and intracellular compartments. The cell surface of the MDCK cells contain 63% of the A-subtype while the basolateral membrane has no A-subtype expression. Localization of the alpha(2A)-AR subtype indicates its role in regulating de novo cell surface expression.

Experiments on anesthetized rats exposed to potassium-deficient diet reveals that potassium depletion enhances the alpha2-adrenergic receptor B subtype expression while the alpha2a-adrenergic receptor expression remains unaltered. The potassium depletion leads to an impairment of the urinary concentrating mechanisms.

The acyl-CoA synthetase medium-chain family member 2 (Acsm2) gene was first identified and cloned by our group as a kidney-specific "KS" gene. However, its expression pattern and function remain to be clarified. In the present study, we found that the Acsm2 gene was expressed specifically and at a high level in normal adult kidneys. Expression of Acsm2 in kidneys followed a maturational pattern: it was low in newborn mice and increased with kidney development and maturation. In situ hybridization and immunohistochemistry revealed that Acsm2 was expressed specifically in proximal tubular cells of adult kidneys. Data from the Encyclopedia of DNA Elements database revealed that the Acsm2 gene locus in the mouse has specific histone modifications related to the active transcription of the gene exclusively in kidney cells. Following acute kidney injury, partial unilateral ureteral obstruction, and chronic kidney diseases, expression of Acsm2 in the proximal tubules was significantly decreased. In human samples, the expression pattern of ACSM2A, a homolog of mouse Acsm2, was similar to that in mice, and its expression decreased with several types of renal injuries. These results indicate that the expression of Acsm2 parallels the structural and functional maturation of proximal tubular cells. Downregulation of its expression in several models of kidney disease suggests that Acms2 may serve as a novel marker of proximal tubular injury and/or dysfunction. [ABSTRACT FROM AUTHOR]

Acute kidney injury (AKI) is an important clinical disorder with high prevalence, serious consequences, and limited therapeutic options. Modulation of neuroimmune interaction by non-pharmacological methods is emerging as a novel strategy for treating inflammatory diseases, including AKI. Recently, pulsed ultrasound (US) treatment was shown to protect from AKI by stimulating the cholinergic anti-inflammatory pathway. Because of the relatively simple, portable, and noninvasive nature of US procedures, US stimulation may be a valuable therapeutic option for treating inflammatory conditions. This review discusses potential impacts of US bioeffects on the nervous system and how this may generate feedback onto the immune system. We also discuss recent evidence supporting the use of US as a means to treat AKI and other inflammatory diseases. [ABSTRACT FROM AUTHOR]

—Progressive tubulointerstitial fibrosis may occur after acute kidney injury due to persistent inflammation. Purinergic signaling by 5'-ectonucleotidase, CD73, an enzyme that converts AMP to adenosine on the extracellular surface, can suppress inflammation. The role of CD73 in progressive kidney fibrosis has not been elucidated. We evaluated the effect of deletion of CD73 from kidney perivascular cells (including pericytes and/or fibroblasts of the Foxd1+ lineage) on fibrosis. Perivascular cell expression of CD73 was necessary to suppress inflammation and prevent kidney fibrosis in Foxd1CreCD73fl/fl mice evaluated 14 days after unilateral ischemia-reperfusion injury or folic acid treatment (250 mg/kg). Kidneys of Foxd1CreCD73fl/fl mice had greater collagen deposition, expression of proinflammatory markers (including various macrophage markers), and platelet-derived growth factor recepetor- immunoreactivity than CD73fl/fl mice. Kidney dysfunction and fibrosis were rescued by administration of soluble CD73 or by macrophage deletion. Isolated CD73-/- kidney pericytes displayed an activated phenotype (increased proliferation and α-smooth muscle actin mRNA expression) compared with wild-type controls. In conclusion, CD73 in perivascular cells may act to suppress myofibroblast transformation and influence macrophages to promote a wound healing response. These results suggest that the purinergic signaling pathway in the kidney interstitial microenvironment orchestrates perivascular cells and macrophages to suppress inflammation and prevent progressive fibrosis. [ABSTRACT FROM AUTHOR]

Okusa, Mark D., Joel Linden, Liping Huang, Jayson M. Rieger, Timothy L. Macdonald, and Long P. Huynh. [A.sub.2A] adenosine receptor-mediated inhibition of renal injury and neutrophil adhesion. Am J Physiol Renal Physiol 279: FS09-F818, 2000.--We sought to determine the mechanisms responsible for the reduced renal tissue injury by agonists of [A.sub.2A] adenosine receptors ([A.sub.2A]-ARs) in models of ischemia-reperfusion (I/R) injury. DWH-146e, a selective [A.sub.2A]-AR agonist, was administered subcutaneously to Sprague-Dawley rats and C57BL/6 mice via osmotic minipumps, and animals were subjected to I/R. I/R led to an increase in plasma creatinine and kidney neutrophil infiltration. Infusion of DWH-146e at 10 ng [multiplied by] [kg.sup.-1] [multiplied by] [min.sup.-1] produced a 70% reduction in plasma creatinine as well as a decrease in neutrophil density in outer medulla and cortex and myeloperoxidase activity in the reperfused kidney. Myeloperoxidase activity in kidney correlated with the degree of renal injury. P-selectin and intercellular adhesion molecule 1 (ICAM-1) immunoreactivity were most prominent in endothelial cells of peritubular capillaries and interlobular arteries of cortex and outer and inner medulla of vehicle-treated mice whose kidneys were subjected to I/R. DWH-146e treatment led to a pronounced decrease in P-selectin- and ICAM-1-like immunoreactivity. These data are consistent with our hypothesis that [A.sub.2A]-AR agonists limit I/R injury due to an inhibitory effect on neutrophil adhesion. acute renal failure; neutrophil-endothelial cell interaction; intercellualr adhesion molecule 1; P-selectin

Okusa, Mark D., Joel Linden, Timothy Macdonald, and Liping Huang. Selective [A.sub.2A] adenosine receptor activation reduces ischemia-reperfusion injury in rat kidney. Am. J. Physiol. 277 (Renal Physiol. 46): F404-F412, 1999.--[A.sub.2A] adenosine receptors ([A.sub.2A]-ARs) are known modulators of renal hemodynamics and potent inhibitors of inflammation. We sought to determine whether selective activation of [A.sub.2A]-Ars protects kidneys from ischemia-reperfusion injury. The ester derivative of DWH-146 (DWH-146e), a selective [A.sub.2A] agonist, was found to be more potent and selective for [A.sub.2A]-ARs than the prototype compound CGS-21680. Osmotic minipumps were implanted subcutaneously to infuse into rats either vehicle or DWH-146e (0.004 [Micro]g [multiplied by] [kg.sup.-1] [multiplied by] [min.sup.-1]), during and after ischemia-reperfusion injury. Following 24 and 48 h of reperfusion, the rise in serum creatinine and blood urea nitrogen for vehicle-treated rats was substantially elevated compared with DWH-146e-treated rats. Histological examination revealed widespread tubular epithelial necrosis and vascular congestion in the outer medulla of vehicle-treated compared with DWH-146e-treated animals. ZM-241385, a selective [A.sub.2A] antagonist, blocked the protective effect of DWH-146e. Delaying administration of DWH-146e until the initiation of reperfusion also decreased serum creatinine. We conclude that 1) selective [A.sub.2A]-AR activation by DWH-146e reduces ischemia-reperfusion injury in rat kidneys, 2) the effect of DWH-146e is [A.sub.2A] receptor mediated, and 3) the protective effects are mediated by preventing injury during the reperfusion period. acute renal failure; ischemia; inflammation; DWH-146 ester; ZM-241385

Monocyte/macrophage recruitment correlates strongly with the progression of renal impairment in diabetic nephropathy (DN). C-C chemokine receptor (CCR)2 regulates monocyte/macrophage migration into injured tissues. However, the direct role of CCR2-mediated monocyte/macrophage recruitment in diabetic kidney disease remains unclear. We report that pharmacological blockade or genetic deficiency of CCR2 confers kidney protection in Ins2Akita and streptozotocin (STZ)-induced diabetic kidney disease. Blocking CCR2 using the selective CCR2 antagonist RS504393 for 12 wk in Ins2Akita mice significantly attenuated albuminuria, the increase in blood urea nitrogen and plasma creatinine, histological changes, and glomerular macrophage recruitment compared with vehicle. Furthermore, mice lacking CCR2 (CCR2-/-) mimicked CCR2 blockade by reducing albuminuria and displaying less fibronectin mRNA expression and inflammatory cytokine production compared with CCR2+/+ mice, despite comparable blood glucose levels. Bone marrow-derived monocytes from CCR2+/+ or CCR2-/- mice adoptively transferred into CCR2-/- mice reversed the renal tissue-protective effect in diabetic CCR2-/- mice as evaluated by increased urinary albumin excretion and kidney macrophage recruitment, indicating that CCR2 is not required for monocyte migration from the circulation into diabetic kidneys. These findings provide evidence that CCR2 is necessary for monocyte/macrophage-induced diabetic renal injury and suggest that blocking CCR2 could be a novel therapeutic approach in the treatment of DN. [ABSTRACT FROM AUTHOR]

We previously demonstrated the anti-inflammatory effects and renal tissue protection in response to adenosine A2A-receptor (A2AR) activation in acute renal injury. We sought to extend these studies and determine the efficacy of A2AR agonists in a chronic model of renal injury. We hypothesized that A2A agonists mediate renal tissue protection in diabetic nephropathy by reducing glomerular inflammation. Diabetes was induced with single intravenous injection of streptozotocin in Sprague-Dawley rats (50 mg/kg). Increases in urinary albumin excretion (UAE) and plasma creatinine at week 6 in the diabetes group (26- and 6-fold over control, respectively) were markedly reduced by continuous subcutaneous administration of ATL146e (10 ng·kg-1·min-1), a selective A2A agonist. The increase in UAE in the diabetes group was associated with a significant reduction in the expression of slit diaphragm-associated molecules compared with control (nephrin; P < 0.05 and podocin; P < 0.005) that was reversed by ATL146e treatment. Diabetes led to an increase in urinary excretion of monocyte chemoattractant protein-1 (705% of control), TNF-α (1,586% of control), IFN-γ (298% of control), kidney fibronectin mRNA (457% of control), and glomerular infiltration of macrophages (764% of control), effects significantly reduced by ATL146e treatment. Mesangial expansion and basement membrane thickness were reduced with ATL146e. To further confirm the selectivity of ATL146e, we used wild-type (WT) or A2A knockout (A2A-KO) mice. Four weeks after diabetes, UAE increased significantly in both WT and A2A-KO diabetic mice (3.0- and 3.3-fold over control). A2A agonist treatment blocked the increase in UAE in WT diabetic mice (P < 0.001), whereas it had no effect on the A2A-KO diabetic mice. These results demonstrate that chronic A2AR activation in diabetic rats 1) ameliorates histological and functional changes in kidneys induced by diabetes and 2) causes reduced inflammation associated with diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Recently, we demonstrated that peroxisome proliferator-activated receptor-α (PPARα) ligand ameliorates cisplatin-induced acute renal failure (ARF) by preventing inhibition of substrate oxidation, and also by preventing apoptosis and necrosis of the proximal tubule (Li S, Bhatt R, Megyesi J, Gokden N, Shah SV, and Portilla D. Am J Physiol Renal Physiol 287: F990–F998, 2004). In the following studies, we examined the protective effect of PPARα ligand on cisplatin-induced inflammatory responses during ARF. Mice subjected to a single intraperitoneal injection of cisplatin developed ARF at day 3. Cisplatin increased mRNA and protein expression of TNF-α, RANTES, and also upregulated endothelial adhesion molecules ICAM-1/VCAM-1 and chemokine receptors CCR1/CCR5. Cisplatin also led to neutrophil infiltration in the corticomedullary region. Pretreatment of wild-type mice with WY-14,643, a fibrate class of PPARα ligands, before cisplatin significantly suppressed cisplatin-induced upregulation of cytokine/chemokine expression, prevented neutrophil accumulation, and ameliorated renal dysfunction. In contrast, treatment with PPARα ligand before cisplatin did not prevent cytokine/chemokine production, neutrophil accumulation, and did not protect kidney function in PPARα null mice. In addition, we observed that cisplatin-induced NF-κB binding activity in nuclear extracts from wild-type mice was markedly reduced by treatment with PPARα ligand. These results demonstrate that PPARα exerts an anti-inflammatory effect in kidney tissue by a mechanism that includes inhibition of NF-κB DNA binding activity, and this effect results in inhibition of neutrophil infiltration, cytokine/chemokine release, and amelioration of cisplatin-induced ARF. [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]

Investigates the effect of A[sub 2A] adenosine receptors (A[sub 2A]AR) activation on protection of the liver from ischemia-reperfusion (I/R) injury and determines whether suppression of hepatic inflammatory chemokine production plays a role in this protection. Demonstration that the selective agonist of the A[sub 2a]AR produces a protection of wild-type C57BL/6 mice from liver I/R injury that is absent in congenic animals lacking the A[sub 2A]AR gene.

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]

Focuses on the characteristics of the A[sub 2A] adenosine receptor and its potential in treating and preventing renal diseases. Pharmacology and molecular biology of receptors; Localization and functional effects of receptors in kidney; Comparative affinities of A[sub 2A] ligands for human adenosine receptor subtypes and signaling elements.

Discusses a study which determined the mechanisms responsible for the reduced renal tissue injury by agonists of adenosine receptors. Methods; Results; Discussion.

The article discusses an article on distant organ injury following acute kidney injury published within the issue including one by Hassoun and colleagues and another by Hoke and others.

Progressive tubulointerstitial fibrosis may occur after acute kidney injury due to persistent inflammation. Purinergic signaling by 5'-ectonucleotidase, CD73, an enzyme that converts AMP to adenosine on the extracellular surface, can suppress inflammation. The role of CD73 in progressive kidney fibrosis has not been elucidated. We evaluated the effect of deletion of CD73 from kidney perivascular cells (including pericytes and/or fibroblasts of the Foxd1 + lineage) on fibrosis. Perivascular cell expression of CD73 was necessary to suppress inflammation and prevent kidney fibrosis in Foxd1CreCD73 fl/fl mice evaluated 14 days after unilateral ischemia-reperfusion injury or folic acid treatment (250 mg/kg). Kidneys of Foxd1CreCD73 fl/fl mice had greater collagen deposition, expression of proinflammatory markers (including various macrophage markers), and platelet-derived growth factor recepetor-β immunoreactivity than CD73 fl/fl mice. Kidney dysfunction and fibrosis were rescued by administration of soluble CD73 or by macrophage deletion. Isolated CD73 -/- kidney pericytes displayed an activated phenotype (increased proliferation and α-smooth muscle actin mRNA expression) compared with wild-type controls. In conclusion, CD73 in perivascular cells may act to suppress myofibroblast transformation and influence macrophages to promote a wound healing response. These results suggest that the purinergic signaling pathway in the kidney interstitial microenvironment orchestrates perivascular cells and macrophages to suppress inflammation and prevent progressive fibrosis.