Endotoxin-activated murine macrophage

IL-4 and IL-10 inhibit the induction of iNOS in murine macrophages in vitro (Cunha et al., 1992 Schneemann et al., 1993 Bogdan et al., 1994). Few studies, however, have focused on the effects of IL-4 and IL-10 in vivo. Thus, we have studied the effects of IL-4 and IL-10 on the production of NO by endotoxin-activated peritoneal macrophages ex vivo. 

Pycnogenol affects the activity of nitric oxide synthase and the production of nitric oxide in murine macrophages (RAW 264.7 cell line) activated by endotoxin (the lipopolysaccharide) and tumor necrosis factor (TNF)-... 

The other broad category of MSP actions on macrophages relates to mediator production. Endotoxin, or combinations of proinflammatory cytokines, causes expression of murine macrophage-inducible nitric oxide synthase, an effect that can be detected by Northern blots for the mRNA or by measurement of nitrate in the culture fluid. MSP prevents induction of NO-synthase by any of the above stimuli (Wang et al., 1994d). The inhibitory action of MSP is confined to this specific mediator. MSP did not inhibit endotoxin-induced expression of mRNA for monocyte chemoattractant protein-1. Furthermore, MSP caused secretion of IL-6 (but not IL-1 or TNFa) within 6 hr, and did not inhibit endotoxin-induced secretion of IL-1, IL-6, or TNFa (A. Skeel and E. J. Leonard, unpublished data). The in vitro modulation by MSP of endotoxin-induced NO production now has an in vivo counterpart. Concentrations of nitrate in serum of Stk / mice that received endotoxin intravenously were higher than in serum of comparably treated normal mice and at a critical endotoxin dose, only 20% of the Stk / mice survived, compared to 80% survival for normal mice (Correll et al., 1997). If MSP plays a role in the host response to endotoxemia, pro-MSP must be cleaved to biologically active MSP. Within 4 hr after i.v. administration of... 

Helicobacter pylori will infect different types of macrophages including primary human and murine macrophages and murine macrophage-like cell lines and human neutrophils isolated from peripheral blood (4,6,8,9,10,11,12,13). As noted above, endotoxin-free reagents are required to prevent unintended cell activation. In addition, tissue-culture medium must not contain penicillin or streptomycin, as these drugs compromise H. pylori viability. Thus, all phagocytes should be maintained in antibiotic-free medium or, at a minimum, transferred to antibiotic-free medium 48 h prior to infection. 

In an animal model of endotoxin pleurisy, IL-8 was found to be an important contributor to the chemotactic activity in the acute inflammatory liquids formed in response to endotoxin (14). Neutralization of IL-8 antibody inhibited the endotoxin-induced neutrophil influx by 77%. Pleural fluid from patients with paraneumonic effusions also contained significant quantities of macrophage inflammatory protein-la (MIP-la CCL-3) MIP-la antibody inhibited up to 43% of the bioactivity for mononuclear cells in pleural fluids of patients with parapneumonic effusions (18). In an animal model of Staphylococcus aureus-induc i experimal empyema, neutrophil chemokine levels of murine KC (KC) and macrophage inflammatory protein-2 (MIP-2) were found to be significantly lower in CD4 knockout mice than in CD4 wild-type mice (19,20). 

The antiendotoxin activity of cationic peptides is also related to the above uptake mechanism. Endotoxin is in fact LPS, or more precisely the lipid A portion of LPS. As mentioned above, cationic peptides bind to polyanionic LPS (70.128,129). The binding is of high affinity and cooperative (70). This binding can neutralize the ability of LPS to induce TNF in macrophage cell lines or in a murine model, and it reduces endotoxin mortality in galactosamine-sei isitized mice (130,131). 

Cloricromene (2,20 or 200 pM) inhibited the expression but not the activity of the inducible form of nitric oxide synthase in lipopolysaccharide (100 ng/ml)-stimulated murine J774 macrophages in a concentration-dependent manner (Zingarelli et al. 1993). Maximal inhibition (84.0 8.0%) was observed when cloricromene (200 pM) was added to the cells 6 h before hpopolysaccharide, whereas it was ineffective when given 6 h after endotoxin. 

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