lipoteichoic-acid and 3-nitrotyrosine

Acute renal failure (ARF) markedly sensitizes mice to endotoxin (LPS), as evidenced by exaggerated renal cytokine/chemokine production. This study sought to further characterize this state by testing the following: 1) does anti-inflammatory heme oxygenase-1 (HO-1) upregulation in selected ARF models prevent this response? 2) Is the ARF hyperresponsive state specifically triggered by LPS? 3) Does excess iNOS activity/protein nitrosylation participate in this phenomenon? and 4) are upregulated Toll receptors involved? Mice with either 1) rhabdomyolysis-induced ARF (massive HO-1 overexpression), 2) cisplatin nephrotoxicity, 3) or HO-1 inhibition (Sn protoporphyrin) were challenged with either LPS (a TLR4 ligand), lipoteichoic acid (LTA; a TLR2 ligand), or vehicle. Two hours later, renal and plasma TNF-alpha/mRNA, MCP-1/mRNA, renal nitrotyrosine/iNOS mRNA, and plasma cytokines were assessed. Renal TLR4 was gauged by mRNA and Western blot analysis. Both ARF models markedly hyperresponded to both LPS and LTA, culminating in exaggerated TNF-alpha, MCP-1, and iNOS/nitrotryosine increments. This was despite the fact that HO-1 exerted anti-inflammatory effects. TLR4 levels were either normal (cisplatin), or markedly depressed ( approximately 50%; rhabdomyolysis) in the ARF kidneys, despite the LPS hyperresponsive state. 1) The ARF kidney can hyperrespond to chemically dissimilar Toll ligands; 2) HO-1 does not prevent this response; 3) excess NO/protein nitrosylation can result; and 4) this hyperresponsiveness can be expressed with either normal or reduced renal TLR4 expression. This suggests that diverse signaling pathways may be involved.

Topics: Acute Kidney Injury; Animals; Chemokine CCL2; Cisplatin; Endotoxins; Glycerol; Heme Oxygenase-1; Inflammation; Kidney; Lipopolysaccharides; Male; Metalloporphyrins; Mice; Nitric Oxide Synthase Type II; Protoporphyrins; Teichoic Acids; Toll-Like Receptor 4; Tumor Necrosis Factor-alpha; Tyrosine; Up-Regulation

The aim of this study was to investigate whether in vivo administration of a low, sub-lethal dose of lipoteichoic acid (LTA), a bacterial wall-fragment derived from the Gram-positive bacterium Staphylococcus aureus, protects the kidney against the renal dysfunction and injury caused by ischemia/reperfusion (I/R).. Male Wistar rats were administered LTA from S. aureus (1 mg/kg, IP). After 24 hours, rats were subjected to bilateral renal ischemia (45 min) followed by reperfusion (6 h). Serum and urinary markers were measured for the assessment of renal function, tubular and reperfusion-injury. Renal sections were used for histological grading of renal injury and for immunohistochemical localization of P-selectin, inducible nitric oxide synthase (iNOS) and nitrotyrosine (indicative of peroxynitrite formation). Kidney myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels were measured for assessment of polymorphonuclear (PMN) cell infiltration and lipid peroxidation, respectively. Nitric oxide (NO) production was determined by measurement of plasma nitrite/nitrate levels.. LTA pretreatment significantly reduced renal dysfunction, tubular and reperfusion-injury caused by I/R of the kidney as well as histological evidence of renal injury. LTA also reduced the expression of P-selectin and kidney MPO activity associated with renal I/R. MDA levels were significantly reduced by LTA pretreatment suggesting a reduction in the lipid peroxidation and formation of reactive oxygen species (ROS). LTA pretreatment also markedly reduced both the expression of iNOS and the formation of nitrotyrosine associated with renal I/R. Although LTA significantly reduced plasma nitrite/nitrate levels associated with I/R, nitrite/nitrate levels remained at levels significantly higher than that measured from the plasma obtained from Sham-operated animals.. These data suggest, to our knowledge for the first time, that LTA pretreatment for 24 hours significantly reduces renal I/R injury. We propose that the mechanism of the protective effect involves reduction of the production of NO, ROS and peroxynitrite subsequent to reduced P-selectin and iNOS expression and PMN recruitment. However, although LTA pretreatment resulted in a reduction of iNOS expression and NO production, we hypothesize that the remaining significant levels of NO contribute to the beneficial actions provided by LTA.

Topics: Animals; Antioxidants; Cyclic N-Oxides; Kidney Diseases; Kidney Tubules; Lipopolysaccharides; Male; Malondialdehyde; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; P-Selectin; Peroxidase; Rats; Rats, Wistar; Reperfusion Injury; Spin Labels; Staphylococcus aureus; Teichoic Acids; Tyrosine

An enhanced formation of reactive oxygen species contributes to the multiple organ dysfunction syndrome (MODS) caused by endotoxin. We have recently discovered that two cell wall components, namely lipoteichoic acid (LTA) and peptidoglycan (PepG) of the gram-positive bacterium, Staphylococcus aureus, synergize to cause shock and MODS in the rat. Here, we investigate the effects of a membrane-permeable radical scavenger (tempol) on the circulatory failure and MODS (kidney, liver, lung) caused by coadministration of LTA (3 mg/kg i.v.) and PepG (10 mg/kg i.v.) in the anesthetized rat.. Prospective, randomized study.. University-based research laboratory.. Thirty-four anesthetized, male Wistar rats.. After surgical preparation, anesthetized rats were observed for 6 hrs. Control rats were given vehicle (control plus saline, 2 mL/kg bolus injection, followed by an infusion of 1.5 mL/kg i.v., n = 6) or tempol (control plus tempol, 100 mg/kg i.v. bolus injection, followed by an infusion of 30 mg/kg i.v., n = 6). Gram-positive septic shock was induced by coadministration of LTA (3 mg/kg i.v.) and PepG (10 mg/kg i.v.) (LTA/PepG plus saline, n = 12). Another group of rats was pretreated with tempol before shock was induced (LTA/PepG plus tempol, 100 mg/kg i.v. bolus injection, 15 mins before LTA/PepG administration, followed by an infusion of 30 mg/kg i.v., n = 10).. Within 6 hrs, administration of LTA/PepG resulted in hypotension, acute renal dysfunction, hepatocellular injury, pancreatic injury, and increased plasma concentrations of nitrite/nitrate. Pretreatment of rats with tempol augmented the hypotension but attenuated the renal dysfunction and the hepatocellular injury/dysfunction caused by LTA/PepG. Tempol did not affect the increase in nitrite/nitrate caused by LTA/PepG.. These results imply that an enhanced formation of reactive oxygen species (including superoxide anions) contributes to the kidney and liver injury and dysfunction caused by LTA/PepG in the anesthetized rat.

Topics: Animals; Blood Pressure; Cyclic N-Oxides; Free Radical Scavengers; Kidney; Lipopolysaccharides; Liver; Lung; Male; Multiple Organ Failure; Multiple Trauma; Nitrates; Nitrites; Peptidoglycan; Random Allocation; Rats; Rats, Wistar; Shock, Septic; Spin Labels; Staphylococcal Infections; Teichoic Acids; Tyrosine