Peptidoglycan primes for LPS-induced release of proinflammatory cytokines in whole human blood

The pathophysiological mechanisms involved in mixed bacterial infections caused by gram-positive and gram-negative bacteria are largely unknown. The present study examines the potential interaction between lipopolysaccharide (LPS) and peptidoglycan (PepG) in the induction of the sepsis-associated cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and IL-10 in whole human blood. Plasma values of these cytokines were measured by enzyme immunoassays and a TNF bioassay. Co-administration of PepG (10 microg/mL) or muramyl dipeptide (MDP, 1 microg/mL) with LPS (10 ng/mL) caused significantly elevated values of TNF-alpha and IL-6 in the blood that could not be obtained by the sum of the values obtained by each stimulant alone, or by 3-fold higher doses of either bacterial component alone. This phenomenon was observed 1 h after stimulation, throughout the experimental period (24 h), and with different doses of LPS and PepG. In contrast, the release of IL-10 was not influenced by the co-administration of PepG or MDP with LPS. The TNF-alpha release induced by co-administration of LPS and PepG was abrogated after pretreatment with a monoclonal antibody against CD14 (18D11). Addition of PepG or MDP to whole blood caused a 2-fold increase in the surface expression of CD14 on monocytes, as measured by flow cytometry. In contrast, LPS caused decreased expression of this receptor. Our data suggest that PepG and MDP primes human whole blood leukocytes for LPS-induced release of proinflammatory cytokines. We speculate that synergy between PepG and LPS may contribute to the pathogenesis in sepsis caused by mixed bacterial infections.

The selective guanylate cyclase inhibitor ODQ reduces multiple organ injury in rodent models of Gram-positive and Gram-negative shock

OBJECTIVE

An enhanced formation of endogenous nitric oxide contributes to the circulatory failure caused by endotoxin (lipopolysaccharide). Many of the biological actions of nitric oxide are mediated by the guanylate cyclase/cyclic guanosine 3prime;,5'-monophosphate system. We recently discovered that two cell wall components, namely lipoteichoic acid and peptidoglycan of the Gram-positive bacterium Staphylococcus aureus, synergize to cause shock and multiple organ dysfunction syndrome in the rat. Here we investigate the effects of a selective guanylate cyclase inhibitor, 1H-(1,2,4)oxadiazole(4,3-alpha)quinoxaline-1-one (ODQ), on the circulatory failure and multiple organ dysfunction syndrome (kidney, liver, lung) caused by a) coadministration of lipoteichoic acid and peptidoglycan (Gram-positive shock) or b) lipopolysaccharide (Gram-negative shock) in the anesthetized rat. Furthermore, we investigated whether ODQ scavenges superoxide anions and/or hydroxyl radicals.

DESIGN

The in vivo portion of the study was a prospective, randomized, controlled animal study. The in vitro portion included a) cultured ventricular myoblasts of the rat, H9c2(2-1) cells, and b) a cell free superoxide anion assay system.

SETTING

University-based research laboratory.

SUBJECTS

Seventy-five anesthetized, male Wistar rats were used for the in vivo study.

INTERVENTIONS

For the in vivo portion of the study, after surgical preparation, anesthetized rats were observed for 6 hrs. All rats were pretreated and received an intravenous infusion of saline (1.5 mL.kg-1.hr-1), which was maintained throughout the experiment. The rats were assigned to nine groups. Group 1 contained control rats (sham) subjected to 2 mL/kg saline intraperitoneally, 2 hrs before the experiment (n = 7). Group 2 contained control rats (sham) that received 2 mg/kg ODQ intraperitoneally, 2 hrs before the experiment (n = 9). Group 3 contained control rats (sham) that received 2 mL/kg dimethyl sulfoxide, 30% v/v in saline intraperitoneally, as a vehicle for ODQ, 2 hrs before the experiment (n = 6). In group 4 rats, Gram-positive shock was induced by coadministration of lipoteichoic acid (3 mg/kg intravenously) and peptidoglycan (10 mg/kg intravenously) (n = 10). In group 5, rats were pretreated with ODQ (as described previously) before lipoteichoic acid/peptidoglycan (n = 9). In group 6, rats were pretreated with dimethyl sulfoxide (as described previously) before lipoteichoic acid/peptidoglycan (n = 7). In group 7, Gram-negative shock was induced by lipopolysaccharide (6 mg/kg intravenously) (n = 11). In group 8, rats were pretreated with ODQ (as described previously) before lipopolysaccharide (n = 8). In group 9, rats were pretreated with dimethyl sulfoxide (as described previously) before lipopolysaccharide (n = 8). For the in vitro portion of the study, rat cells were preincubated with vehicle (saline and/or dimethyl sulfoxide) and ODQ (0.1 microM to 1 mM) for 2 hrs. The cells then were exposed to H2O2 (1 mM) for 4 hrs at 37 degrees C, after which time cell viability was determined by measuring the mitochondrial-dependent reduction of 3-(4,5-di-methyliazol-2-yl)-2,5-diphenyltetrazolium bromide to blue formazan. Next, an aqueous solution was incubated with ODQ (as described previously), and superoxide anions were produced by using a hypoxanthine/xanthine-oxidase assay. The chemiluminescence assay was used to evaluate any potential antioxidative effects of ODQ.

MEASUREMENTS AND MAIN RESULTS

In vivo, administration of lipoteichoic acid/peptidoglycan or lipopolysaccharide resulted within 6 hrs in hypotension, acute renal dysfunction, hepatocellular injury, and lung injury. Pretreatment of rats with ODQ attenuated the renal dysfunction, lung injury, and hepatocellular injury caused by lipoteichoic acid/peptidoglycan or lipopolysaccharide. In vitro, administration of H2O2 (for 4 hrs) to rat cardiomyoblasts decreased mitochondrial respiration attributable to generation of hydroxyl radicals. Pretreatment of cells with ODQ did not abolish this cell injury. In addition, ODQ did not scavenge superoxide anions.

CONCLUSIONS

These results imply that ODQ, an inhibitor of guanylate cyclase, reduces the multiple organ injury and dysfunction caused by wall fragments of Gram-positive or Gram-negative bacteria in the anesthetized rat. The observed protective effects of ODQ are not attributable to the ability of ODQ to reduce the formation or the effects of superoxide anions or hydroxyl radicals.

Calpain inhibitor-1 reduces renal ischemia/reperfusion injury in the rat

BACKGROUND

Activation of the cysteine protease calpain has been implicated in renal ischemia/reperfusion (I/R) injury. The aim of this study was to investigate the effects of calpain inhibitor-1 (Cal I-1) in an in vivo model of renal I/R injury.

METHODS

Male Wistar rats were administered Cal I-1 (10 mg/kg, IP) 30 minutes before undergoing bilateral renal ischemia (45 minutes) followed by reperfusion (6 hours). Plasma concentrations of urea, creatinine, Na(+), gamma-glutamyl transferase (gamma GT), aspartate aminotransferase (AST) and urinary Na(+), glutathione S-transferase (GST), and N-acetyl-beta-D-glucosaminidase (NAG) were measured for the assessment of renal dysfunction and I/R injury. Creatinine clearance (C(Cr)) and fractional excretion of Na(+) (FE(Na)) were used as indicators of glomerular and tubular function, respectively. Kidney myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels were measured for assessment of neutrophil infiltration and lipid peroxidation, respectively. Renal sections were used for histologic grading of renal injury and for immunohistochemical localization of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2).

RESULTS

Cal I-1 significantly reduced I/R-mediated increases in urea, creatinine, gamma GT, AST, NAG, and FE(Na) and significantly improved C(Cr). Cal I-1 also significantly reduced kidney MPO activity and MDA levels. Cal I-1 also reduced histologic evidence of I/R-mediated renal damage and caused a substantial reduction in the expression of iNOS and COX-2, both of which involve activation of nuclear factor-kappa B (NF-kappa B).

CONCLUSIONS

: These results suggest that Cal I-1 reduces the renal dysfunction and injury associated with I/R of the kidney. We suggest that the mechanism could involve the inhibition of I/R-mediated activation of NF-kappa B.

Peptidoglycan and lipoteichoic acid modify monocyte phenotype in human whole blood

We examined the influence of the gram-positive cell wall products peptidoglycan (PepG) and lipoteichoic acid (LTA), compared to lipopolysaccharide (LPS), on the monocyte expression of receptors involved in antigen presentation (HLA-DR, B7.1, and B7.2), cell adhesion (intercellular adhesion molecule-1 [ICAM-1] and lymphocyte function associated antigen-3 [LFA-3]), phagocytosis (Fc gamma RI), and cell activation (CD14). We also evaluated possible influences of the immunosuppressive drugs cyclosporine A, tacrolimus, and sirolimus on the expression of these receptors. Pretreatment of whole blood for 4 h with the immunosuppressive drugs did not influence the expression of the surface receptors in normal or stimulated blood. Stimulation with both PepG and LTA caused significant up-regulation of the surface expression of ICAM-1 and HLA-DR on whole blood monocytes, similar to that obtained with LPS, whereas B7.1, B7.2, LFA-3, and Fc gamma RI were not modulated. PepG and LTA also caused increased expression of CD14, whereas LPS down-regulated this molecule. In contrast, we did not detect any significant influence of any of the bacterial products on the plasma concentration of soluble CD14. We hypothesized that the increased expression of surface CD14 in blood stimulated with PepG would prime for cellular activation by LPS. Indeed, we show that PepG and the partial PepG structure muramyl dipeptide acted in synergy with LPS to cause the release of tumor necrosis factor-alpha. The results suggest that PepG and LPS provoke partly different responses on monocyte phenotype and that CD14 may play different roles in the innate response to gram-positive and gram-negative bacteria.

Ranolazine, a partial fatty acid oxidation inhibitor, reduces myocardial infarct size and cardiac troponin T release in the rat

Ranolazine reduces cellular acetyl-CoA content via inhibition of fatty acid beta-oxidation and activates pyruvate dehydrogenase. This metabolic switch increases ATP production per mole of oxygen consumed, reduces the rise in lactic acid and acidosis, and maintains myocardial function under conditions of reduced myocardial oxygen delivery. It is still unclear whether ranolazine causes a reduction of (i) infarct size and (ii) cardiac troponin T release, in a male Wistar rat model of left anterior descending coronary artery occlusion (25 min) and reperfusion (2 h). Rats were subjected to saline infusion (n=12) or ranolazine (bolus injection: 10 mg/kg plus infusion: 9.6 mg/kg/h, n=12), 30 min prior to left anterior descending coronary artery occlusion-reperfusion, respectively. Ranolazine caused a significant reduction in myocardial infarct size of approximately 33% compared to saline control (P<0.05). In addition, infusion of ranolazine significantly attenuated the release of cardiac troponin T into the plasma from 65+/-14 (controls) to 12+/-2 ng/ml. This study demonstrates for the first time that ranolazine significantly reduces (i) infarct size and (ii) cardiac troponin T release in rats subjected to left anterior descending coronary artery occlusion-reperfusion.

Calpain inhibitor I reduces colon injury caused by dinitrobenzene sulphonic acid in the rat

BACKGROUND AND AIMS

Inflammatory bowel disease is characterised by oxidative and nitrosative stress, leucocyte infiltration, upregulation of expression of intercellular adhesion molecule 1 (ICAM-1), and upregulation of P-selectin in the colon. The aim of the present study was to examine the effects of calpain inhibitor I in rats subjected to experimental colitis.

METHODS

Colitis was induced in rats by intracolonic instillation of dinitrobenzene sulphonic acid (DNBS).

RESULTS

Rats experienced haemorrhagic diarrhoea and weight loss. Four days after administration of DNAB, the mucosa of the colon exhibited large areas of necrosis. Neutrophil infiltration (determined by histology as well as by an increase in myeloperoxidase activity in the mucosa) was associated with upregulation of ICAM-1 and P-selectin as well as high tissue levels of malondialdehyde. Immunohistochemistry for nitrotyrosine and poly (ADP-ribose) polymerase (PARP) showed intense staining in the inflamed colon. Staining of sections of colon obtained from DNBS treated rats with an anti-cyclooxygenase 2 antibody showed diffuse staining of the inflamed tissue. Furthermore, expression of inducible nitric oxide synthase was found mainly in macrophages located within the inflamed colon of DNBS treated rats. Calpain inhibitor I (5 mg/kg daily intraperitoneally) significantly reduced the degree of haemorrhagic diarrhoea and weight loss caused by administration of DNBS. Calpain inhibitor I also caused a substantial reduction in (i) degree of colon injury, (ii) rise in myeloperoxidase activity (mucosa), (iii) increase in tissue levels of malondialdehyde, (iv) increase in staining (immunohistochemistry) for nitrotyrosine and PARP, as well as (v) upregulation of ICAM-1 and P-selectin caused by DNBS in the colon.

CONCLUSION

Calpain inhibitor I reduces the degree of colitis caused by DNBS. We propose that calpain inhibitor I may be useful in the treatment of inflammatory bowel disease.

Procalcitonin does not influence the surface expression of inflammatory receptors on whole blood leukocytes

The plasma levels of procalcitonin (PCT) are increased in patients with severe bacterial infections. Its cellular origin and potential pathophysiological function in sepsis is, however, unclear. White blood cells have recently been described to express both PCT mRNA and protein. The aim of this study was to determine whether PCT has any influence on the surface expression of receptors, relevant in inflammation, on human whole blood leukocytes under normal and septic conditions. Venous blood from healthy donors was incubated with PCT (40 ng/ml or 1200 ng/ml) alone or in combination with lipopolysaccharide (LPS, 10 ng/ml) or peptidoglycan (PepG, 10 micrograms/ml) for 6 h. The surface expression of CD14, CD54, CD64, CD80, CD86 and HLA-DR was determined by flow cytometry. We could not detect any influence of PCT on the expression of these receptors. Further studies on potential effects on other cell types during infection seem warranted.

Sirolimus interferes with the innate response to bacterial products in human whole blood by attenuation of IL-10 production

Current immunosuppressive strategies are aimed at abrogating the allospecific T-cell response against donor tissues or organs. However, little information is yet available on the potential influences of these drugs on innate immune responses. In order to address this, we have employed a whole blood model. Human whole blood was pretreated with sirolimus, cyclosporine A or tacrolimus in therapeutic as well as supra therapeutic doses, and subsequently stimulated with lipopolysaccharide (LPS), peptidoglycan (PepG) or lipoteichoic acid (LTA). Plasma cytokine analyses revealed a potent inhibitory effect of sirolimus on interleukin(IL)-10 production induced by all bacterial products tested. In contrast, cyclosporine A and tacrolimus inhibited the tumour necrosis factor (TNF)-alpha production in response to LPS, but not to PepG and LTA. Using a quantitative mRNA analyses, we also observed that sirolimus significantly decreased the IL-10 mRNA accumulation to sub-basal levels in peripheral blood mononuclear cells (PBMC). This suggests that the sirolimus inhibits IL-10 production by interfering with the IL-10 gene transcription. However, the molecular mechanism of this inhibition remains unclear. Based on the present study and observations by others, we postulate that the clinical use of the sirolimus may be associated with a dysregulated innate immune response to bacterial infection and thus an increased risk of hyperinflammation and sepsis.

A cell wall component from pathogenic and non-pathogenic gram-positive bacteria (peptidoglycan) synergises with endotoxin to cause the release of tumour necrosis factor-alpha, nitric oxide production, shock, and multiple organ injury/dysfunction in the rat

The incidence of sepsis and septic shock due to gram-positive organisms has increased dramatically over the last two decades. Interestingly, many patients with sepsis/septic shock have both gram-positive and gram-negative bacteria present in the bloodstream and these polymicrobial or "mixed" infections often have a higher mortality than infection due to a single organism. The reason for this observation is unclear. The aim of this study was to investigate whether cell wall fragments from gram-positive and gram-negative bacteria could synergise to cause the release of cytokines, shock, and organ injury/ dysfunction in vivo. Male Wistar rats were anaesthetised and received an intravenous bolus of vehicle (saline), lipopolysaccharide (LPS) from Escherichia coli (0.1 mg/kg), peptidoglycan (Pep G) from Staphylococcus aureus (S10 mg/kg), co-administration of LPS (0.1 mg/kg) and PepG from S. aureus (10 mg/kg), LPS (10 mg/kg), PepG from Bacillus subtilis, or co-administration of LPS and PepG from B. subtilis. Blood pressure and heart rate were monitored for 6 h before plasma samples were taken for the measurement of TNF-alpha, total nitrite, and biochemical indices of organ injury. Peptidoglycan from both pathogenic (S. aureus) and non-pathogenic (B. subtilis) gram-positive bacteria synergised with endotoxin to cause formation of TNF-alpha, nitrite, shock, and organ injury. Synergism between PepG and LPS may partly explain the high mortality associated with mixed bacterial infections, as well as the deleterious effects of translocation of bacteria, or their cell wall components from the gut lumen in patients with sepsis.

Beneficial effects of tempol, a membrane-permeable radical scavenger, on the multiple organ failure induced by zymosan in the rat

BACKGROUND AND METHODS

We investigated the effects of tempol, a membrane-permeable radical scavenger, on the multiple organ failure (MOF) caused by zymosan in the rat. Zymosan (500 mg/kg, suspended in saline solution, ip) enhances formation of reactive oxygen species, which contribute to the pathophysiology of MOF. After zymosan or saline administration, animals were monitored for 12 days.

RESULTS

Treatment of rats with tempol (10, 30, or 100 mg/kg ip, 1 and 6 hrs after zymosan) attenuated the peritoneal exudation and the migration of polymorphonuclear cells caused by zymosan in a dose-dependent fashion. Tempol also attenuated the lung, liver, and intestinal injury (histology) as well as the increase in the concentrations of myeloperoxidase and malondialdehyde caused by zymosan in the lung, liver, and intestine. Immunohistochemical analysis for nitrotyrosine and for poly(adenosine 5'-diphosphate-ribose)synthetase demonstrated a positive staining in lung, liver, and intestine from zymosan-treated rats. The degree of staining for nitrotyrosine and for poly(adenosine 5'-diphosphate-ribose) synthetase was markedly reduced in tissue sections obtained from zymosan-treated rats that had received tempol (100 mg/kg ip). Furthermore, treatment of rats with tempol significantly reduced the following: a) the formation of peroxynitrite, b) the DNA damage, c) the impairment in mitochondrial respiration, and d) the decrease in the cellular concentration of oxidized nicotinamide adenine dinucleotide observed in macrophages harvested from the peritoneal cavity of rats treated with zymosan.

CONCLUSION

This study provides the first evidence that tempol, a small molecule that permeates biological membranes and scavenges reactive oxygen species, attenuates the degree of MOF associated with zymosan-induced peritonitis in the rat.

Calpain inhibitor I reduces the activation of nuclear factor-kappaB and organ injury/dysfunction in hemorrhagic shock

There is limited evidence that inhibition of the activity of the cytosolic cysteine protease calpain reduces ischemia/reperfusion injury. The multiple organ injury associated with hemorrhagic shock is due at least in part to ischemia (during hemorrhage) and reperfusion (during resuscitation) of target organs. Here we investigate the effects of calpain inhibitor I on the organ injury (kidney, liver, pancreas, lung, intestine) and dysfunction (kidney) associated with hemorrhagic shock in the anesthetized rat. Hemorrhage and resuscitation with shed blood resulted in an increase in calpain activity (heart), activation of NF-kappaB (kidney), expression of iNOS and COX-2 (kidney), and the development of multiple organ injury and dysfunction, all of which were attenuated by calpain inhibitor I (10 mg/kg i.p.), administered 30 min prior to hemorrhage. Chymostatin, a serine protease inhibitor that does not prevent the activation of NF-kappaB, had no effect on the organ injury/failure caused by hemorrhagic shock. Pretreatment (for 1 h) of murine macrophages or rat aortic smooth muscle cells (activated with endotoxin) with calpain inhibitor I attenuated the binding of activated NF-kappaB to DNA and the degradation of IkappaBalpha, IkappaBbeta, and IkappaBvarepsilon. Selective inhibition of iNOS activity with L-NIL reduced the circulatory failure and liver injury, while selective inhibition of COX-2 activity with SC58635 reduced the renal dysfunction and liver injury caused by hemorrhagic shock. Thus, we provide evidence that the mechanisms by which calpain inhibitor I reduces the circulatory failure as well as the organ injury and dysfunction in hemorrhagic shock include 1) inhibition of calpain activity, 2) inhibition of the activation of NF-kappaB and thus prevention of the expression of NFkappaB-dependent genes, 3) prevention of the expression of iNOS, and 4) prevention of the expression of COX-2. Inhibition of calpain activity may represent a novel therapeutic approach for the therapy of hemorrhagic shock.

Calpain inhibitor I reduces the development of acute and chronic inflammation

There is limited evidence that inhibition of the activity of the protease calpain I reduces inflammation. Here we investigate the effects of calpain inhibitor I in animal models of acute and chronic inflammation (carrageenan-induced pleurisy and collagen-induced arthritis). We report here for the first time that calpain inhibitor I (given at 5, 10, or 20 mg/kg i.p. in the pleurisy model or at 5 mg/kg i.p every 48 hours in the arthritis model) exerts potent anti-inflammatory effects (eg, inhibition of pleural exudate formation, mononuclear cell infiltration, delayed the development of the clinical signs and histological injury) in vivo. Furthermore, calpain inhibitor I reduced (1) the staining for nitrotyrosine and poly (ADP-ribose) polymerase (immunohistochemistry) and (2) the expression of inducible nitric oxide synthase and cyclooxygenase-2 in the lungs of carrageenan-treated rats and in joints from collagen-treated rats. Thus, prevention of the activation of calpain I reduces the development of acute and chronic inflammation. Inhibition of calpain I activity may represent a novel therapeutic approach for the therapy of inflammation.

Tempol, a membrane-permeable radical scavenger, reduces dinitrobenzene sulfonic acid-induced colitis

Inflammatory bowel disease is characterized by oxidative and nitrosative stress, leukocyte infiltration, and up-regulation of intercellular adhesion molecule 1 (ICAM-1) expression in the colon. The aim of the present study was to examine the effects of tempol, a membrane-permeable radical scavenger, in rats subjected to experimental colitis. Colitis was induced in rats by intracolonic instillation of dinitrobenzene sulfonic acid. Rats experienced bloody diarrhea and significant loss of body weight. At 4 days after the administration of dinitrobenzene sulfonic acid, the colon injury comprised of large areas of mucosal necrosis. Neutrophil infiltration (measured as increase in myeloperoxidase activity in the mucosa) was associated with up-regulation of ICAM-1 and expression of P-selectin and high levels of malondialdehyde (an indicator of lipid peroxidation). Immunohistochemistry for nitrotyrosine and poly (ADP-ribose) synthetase showed an intense staining in the inflamed colon. Treatment of rats with tempol (15 mg/kg daily i.p.) significantly reduced the appearance of diarrhea and the loss in body weight. This was associated with a remarkable amelioration of the disruption of the colonic architecture as well as a significant reduction in the degree of both neutrophil infiltration and lipid peroxidation in the inflamed colon. Tempol also reduced the appearance of nitrotyrosine and poly (ADP-ribose) synthetase immunoreactivity in the colon as well as the up-regulation of ICAM-1 and P-selectin. The results of this study suggest that membrane-permeable radical scavengers, such as tempol, exert beneficial effects in experimental colitis and may, hence, be useful in the treatment of inflammatory bowel disease.

The tyrosine kinase inhibitor tyrphostin AG 126 reduced the development of colitis in the rat

Inflammatory bowel disease is characterized by oxidative and nitrosative stress, leukocyte infiltration, up-regulation of the expression of intercellular adhesion molecule-1 (ICAM-1), and up-regulation of P-selectin in the colon. Here we investigate the effects of the tyrosine kinase inhibitor, Tyrphostin AG 126, in rats subjected to experimental colitis. Colitis was induced in rats by intracolonic instillation of dinitrobenzene sulfonic acid (DNBS). Rats experienced hemorrhagic diarrhea and weight loss. Four days after administration of DNBS, the mucosa of the colon exhibited large areas of necrosis. Neutrophil infiltration (determined by histology as well as an increase in myeloperoxidase activity in the mucosa) was associated with up-regulation of ICAM-1 and P-selectin, as well as high tissue levels of malondialdehyde. Immunohistochemistry for nitrotyrosine and poly(ADP-ribose) polymerase showed an intense staining in the inflamed colon. Staining with an anti-COX-2 antibody of sections of colon obtained from DNBS-treated rats showed a diffuse staining of the inflamed tissue. Furthermore, expression of inducible nitric oxide synthase was found mainly in macrophages located within the inflamed colon of DNBS-treated rats. Tyrphostin AG 126 (5 mg/kg daily ip) significantly reduced the degree of hemorrhagic diarrhea and weight loss caused by administration of DNBS. Tyrphostin AG 126 also caused a substantial reduction of (1) the phosphorylation of tyrosine residues of proteins (immunoblots of inflamed colon), (2) the degree of colonic injury, (3) the rise in myeloperoxidase activity (mucosa), (4) the increase in the tissue levels of malondialdehyde, (5) the increase in staining (immunohistochemistry) for nitrotyrosine and poly(ADP-ribose) polymerase, as well as (6) the up-regulation of ICAM-1 and P-selectin caused by DNBS in the colon. Thus, we provide the first evidence that the tyrosine kinase inhibitor Tyrphostin AG126 reduces the degree of colitis caused by DNBS.

Effects of tempol, a membrane-permeable radical scavenger, in a gerbil model of brain injury

There is evidence that the excessive generation of reactive-oxygen radicals contributes to the brain injury associated with transient, cerebral ischemia. This study investigates the effects of tempol, a small, water-soluble molecule, that crosses biological membranes, on the brain injury caused by bilateral occlusion and reperfusion of both common carotid arteries in the gerbil (BCO). Treatment of gerbils with tempol (30 mg/kg i.p. at 30 min prior to reperfusion and at 1 and 6 h after the onset of reperfusion) reduced the formation of post-ischemic brain oedema. Tempol also attenuated the increase in the cerebral levels of malondialdehyde (MDA) and the hippocampal levels of myeloperoxidase (MPO) caused by cerebral ischemia and reperfusion. The immunohistochemical analysis of the hippocampal region of brains subjected to ischemia-reperfusion exhibited positive staining for nitrotyrosine (an indicator of the generation of peroxynitrite) and poly(ADP-ribose) synthetase (PARS) (an indicator of the activation of this nuclear enzyme secondary to single strand breaks in DNA). In gerbils subjected to BCO, which were treated with tempol, the degree of staining for nitrotyrosine and PARS was markedly reduced. Tempol increased survival and reduced the hyperactivity (secondary to the ischemia-induced neurodegeneration) caused by cerebral ischemia and reperfusion. The loss of neurons from the pyramidal layer of the CA1 region caused by ischemia and reperfusion was also attenuated by treatment of gerbils with tempol. This is the first evidence that the membrane-permeable, radical scavenger tempol reduces the cerebral injury caused by transient, cerebral ischemia in vivo.

Beneficial effects of tempol, a membrane-permeable radical scavenger, in a rodent model of splanchnic artery occlusion and reperfusion

The aim of the present study was to investigate the effects of tempol, a membrane-permeable radical scavenger, in rats subjected to splanchnic artery occlusion shock (SAO). Rats subjected to SAO developed a significant decrease in mean arterial blood pressure, a significant increase in tissue myeloperoxidase activity, and a marked injury to the distal ileum. SAO shock resulted in 100% mortality at 2 h after reperfusion. At 60 min after reperfusion, a marked increase in the immunoreactivity to nitrotyrosine and to poly (ADP-ribose) synthetase was observed in the necrotic ileum of rats with SAO. Staining of sections of the ileum obtained from SAO-shocked rats with anti-intercellular adhesion molecule (ICAM-1) and anti-P-selectin antibodies resulted in diffuse staining. Tempol (30 mg/kg bolus injection 5 min prior to reperfusion, followed by an infusion of 30 mg/kg/h intravenously) attenuated 1) the infiltration of the reperfused intestine with neutrophils, 2) the lipid peroxidation, 3) the production of peroxynitrite, 4) the degree of P-selectin and ICAM-1 staining in tissue sections from SAO-shocked rats, 5) histological signs of bowel injury, and 6) mortality at 2 h after reperfusion. Taken together, our results clearly demonstrate that the intracellular radical scavenger tempol reduces the intestinal injury of rats subjected SAO shock.

Tempol, a membrane-permeable radical scavenger, reduces oxidant stress-mediated renal dysfunction and injury in the rat

BACKGROUND

The generation of reactive oxygen species (ROS) contributes to the pathogenesis of renal ischemia-reperfusion injury. The aim of this study was to investigate the effects of tempol in (1) an in vivo rat model of renal ischemia/reperfusion injury and on (2) cellular injury and death of rat renal proximal tubular (PT) cells exposed to oxidant stress in the form of hydrogen peroxide (H2O2).

METHODS

Male Wistar rats underwent bilateral renal pedicle clamping for 45 minutes followed by reperfusion for six hours. Tempol (30 mg/kg/h), desferrioxamine (DEF; 40 mg/kg/h), or a combination of tempol (30 mg/kg/h) and DEF (40 mg/kg/h) were administered prior to and throughout reperfusion. Plasma concentrations of urea, creatinine, Na+, gamma-glutamyl transferase (gammaGT), aspartate aminotransferase (AST), and urinary Na+ and N-acetyl-beta-D-glucosaminidase (NAG) were measured for the assessment of renal function and reperfusion injury. Kidney myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels were measured for assessment of polymorphonuclear (PMN) cell infiltration and lipid peroxidation, respectively. Renal sections were used for histologic grading of renal injury and for immunohistochemical localization of nitrotyrosine and poly(ADP-ribose) synthetase (PARS). Primary cultures of rat PT cells were incubated with H2O2 (1 mmol/L for 4 h) either in the absence or presence of increasing concentrations of tempol (0.03 to 10 mmol/L), DEF (0.03 to 10 mmol/L), or a combination of tempol (3 mmol/L) or DEF (3 mmol/L). PT cell injury and death were determined by evaluating mitochondrial respiration and lactate dehydrogenase (LDH) release, respectively.

RESULTS

In vivo, tempol significantly reduced the increase in urea, creatinine, gammaGT, AST, NAG, and FENa produced by renal ischemia/reperfusion, suggesting an improvement in both renal function and injury. Tempol also significantly reduced kidney MPO activity and MDA levels, indicating a reduction in PMN infiltration and lipid peroxidation, respectively. Tempol reduced the histologic evidence of renal damage associated with ischemia/reperfusion and caused a substantial reduction in the staining for nitrotyrosine and PARS, suggesting reduced nitrosative and oxidative stress. In vitro, tempol significantly attenuated H2O2-mediated decrease in mitochondrial respiration and increase in LDH release from rat PT cells, indicating a reduction in cell injury and death. Both in vivo and in vitro, the beneficial actions of tempol were similar to those obtained using the Fe2+ chelator DEF. However, coadministration of DEF and tempol did not produce any additional beneficial actions against renal ischemia/reperfusion injury or against oxidative stress-mediated PT cell injury/death.

CONCLUSION

Our results suggest that the membrane-permeable radical scavenger, tempol, reduces the renal dysfunction and injury associated with ischemia/reperfusion of the kidney.

Selective activation of E-type prostanoid(3)-receptors reduces myocardial infarct size. A novel insight into the cardioprotective effects of prostaglandins

Prostaglandins (PGs) and other eicosanoids are members of a large family of lipid mediators (autacoids). In 1978, Lefer and colleagues (Science 200, 52-55 [1978]) reported that prostacyclin reduces the myocardial tissue injury caused by coronary artery occlusion and reperfusion in the cat. Since this discovery, more than 50 papers have reported on the cardioprotective effects of vasodilator PGs, including prostacyclin. The cardioprotective effects of PGs are due in part to (1) a reduction in afterload, (2) an increase in coronary blood flow, (3) the inhibition of platelet function, and (4) the inhibition of the activation and extravasation of polymorphonuclear granulocytes. All of these effects are secondary to the activation of EP (E-type prostanoid)(2)-receptors, which activate G(s)-protein and, hence, adenylate cyclase. In addition, the protection of organs such as the heart by PGs has been attributed to a cytoprotective effect of these agents, the mechanism of which is largely unknown. We recently have discovered that certain E-type PGs, which do not activate EP(2)-receptors, also reduce myocardial infarct size, without causing a fall in blood pressure (EP(2)-receptor-mediated effects). Having provided a brief introduction into the role of eicosanoids in ischaemia-reperfusion injury of the heart, this review focuses on the recent discovery that selective agonists of EP(3)-receptors reduce myocardial infarct size, without causing haemodynamic side effects. The mechanisms of the cardioprotective effects of these agents are discussed, as are the therapeutic implications.

Peptidoglycan and lipoteichoic acid from Staphylococcus aureus induce tumor necrosis factor alpha, interleukin 6 (IL-6), and IL-10 production in both T cells and monocytes in a human whole blood model

We have examined the ability of peptidoglycan (PepG) and lipoteichoic acid (LTA) isolated from Staphylococcus aureus to induce the release of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and IL-10 in whole human blood and identified the cellular origins of these cytokines. Both PepG and LTA induced transient increases in TNF-alpha and IL-10 in plasma, with peak values at 6 and 12 h, respectively. IL-6 values increased throughout the experimental period (24 h). The TNF-alpha, IL-6, and IL-10 release induced by PepG and LTA was dose dependent. Only PepG was a potent inducer of TNF-alpha secretion. After stimulation of whole blood with PepG or LTA, very pure populations of monocytes (CD14 positive), T cells (CD2 positive), B cells (CD19 positive), and granulocytes (CD15 positive) were isolated by immunomagnetic separation and analyzed by reverse transcription-PCR for mRNA transcripts encoding TNF-alpha, IL-6, and IL-10. The TNF-alpha mRNA results were inconclusive. In contrast, PepG induced IL-6 and IL-10 mRNA accumulation in both T cells and monocytes. LTA, as well as lipopolysaccharide, induced IL-6 and IL-10 mRNA production in monocytes and possibly in T cells. Whether granulocytes and B cells produce cytokines in response to bacterial stimuli remains obscure. Blockade of the CD14 receptors with monoclonal antibodies (18D11) had no influence on the PepG-induced release of TNF-alpha but attenuated the LTA-induced release of the same cytokine. In conclusion, our data indicate that circulating T cells and monocytes contribute to cytokine production in sepsis caused by gram-positive bacteria.