Counterprotective effect of erythrocytes in experimental bacterial peritonitis is due to scavenging of nitric oxide and reactive oxygen intermediates

Abstract

Erythrocytes (RBC) in the peritoneal cavity significantly increase the lethality of bacterial peritonitis. The lethality is known to be associated with, and perhaps due to, increased bacterial counts in the peritoneal cavity. The mechanism is unknown. In this study, we investigated the hypothesis that RBC scavenge reactive oxygen intermediates (ROI) and nitric oxide (NO), so that the counterprotective effect is due to a loss of the microbiostatic activity of both ROI and NO. To study this effect, rats were subjected to a peritoneal inoculation of live Escherichia coli without RBC (nonlethal dose) or with RBC (lethal dose). The adjuvant effect of RBC was not modified by N G-monomethyl-L-arginine (NMA, an NO synthase inhibitor), superoxide dismutase, catalase, mannitol, or a combination of these agents. Furthermore, the increased number of bacteria in the peritoneal cavity in the presence of RBC was unaffected by these treatments. The administration of NMA with bacteria alone (no RBC) converted a nonlethal model into a lethal one associated with higher intraperitoneal bacterial counts. A similar effect was seen with superoxide dismutase and catalase but not with mannitol. During bacterial peritonitis in the absence of RBC, superoxide and NO formation (determined by the total nitrite plus nitrate formed) was detected in the ascites and inducible NO synthase mRNA expression was present in the peritoneal cells. In the absence of RBC, superoxide was detected and oxidation of dihydrorhodamine to rhodamine was observed, indicating that peroxynitrite was produced. Both were blocked by the inclusion of RBC. Preinjection with a low inoculum of killed bacteria protected the rats from a subsequent lethal peritoneal bacterial challenge; this effect was reversed by scavenging ROI and NO. The protective effect of killed bacterial pretreatment was lost when RBC were placed in the peritoneal cavity. In vitro bactericidal activity of NO-and ROI-generating macrophages was also inhibited by RBC or by inhibiting ROI and NO formation. Taken together, these data are consistent with the hypothesis that RBC can impair bacterial clearance by removing both NO and ROI, suggesting that NO in combination with superoxide may be important to the antimicrobial defenses of the peritoneal cavity.

Effect of pentaglobin and piperacillin on survival in a rat model of faecal peritonitis: importance of intervention timings

“…Recently, several intestigators have observed protective effect of antioxidants against peritonitis‐induced lipid peroxidation in rats ( 42, 43). On the other hand, Kim et al ( 44) have suggested an important role of ROS in antimicrobial defences of the peritoneal cavity in experimental peritonitis. Thus, a fine balance between the generation of ROS and antioxidant defences in vivo is important.…”

The diagnostic and predictive value of ascites nitric oxide levels in patients with spontaneous bacterial peritonitis

“…A recent study, performed in normal rats with experimental bacterial peritonitis, demonstrated that one of the mechanisms by which erythrocytes can impair bacterial clearance is by inhibiting NO formation, thereby demonstrating that NO has an important protective role in the pathogenesis of bacterial peritonitis. 5 There is limited information on the role of NO in the diagnosis or in the prevention of SBP, an infection of ascites almost exclusive of cirrhosis. Experiments in cirrhotic rats, in which a NO synthesis inhibitor is placed in the peritoneal cavity, shows an extraordinary rate of infection of 100% compared with no infection in controls, 6 suggesting that NO is in fact protective of SBP.…”

“…A study performed in a small number of patients with alcoholic liver disease showed that serum nitrate levels were higher in patients with SBP compared with patients without infection. 4 On the other hand, experimental studies suggest that NO may have a protective role in the pathogenesis of SBP, 5,6 and therefore, ascites NO levels could also be used as a predictor of the development of SBP.…”

Inhibition of Protein Synthesis by Nitric Oxide Correlates with Cytostatic Activity: Nitric Oxide Induces Phosphorylation of Initiation Factor eIF-2α

“…NG-monomethyl-L-arginine (NMA) was purchased from Cyclopss (Salt Lake City, UT). Red blood cells were isolated as previously described (6). Adenoviral vectors carrying either the cDNA for human iNOS or ,B-galactosidase (lacZ) were prepared and tested as previously described (29).…”

“…Nitric oxide (NO) is generated from the amino acid L-arginine by three known NO synthase other factors. Induced NO is cytostatic or even cytotoxic to some cell types (4,5) and has been shown to inhibit microbial growth (6). Mechanisms thought to be responsible for the cytostasis and cytotoxicity include direct inhibition of ribonucleotide reductase (7) as well as inhibition of key metabolic enzymes (8,9).…”