Role of resident mast cells and macrophages in the neutrophil migration induced by LTB4, fMLP and C5a des arg

In the present study, we have investigated the participation of resident peritoneal cells (macrophages and mast cells) in the neutrophil migration induced in rats by the intraperitoneal administration of LTB4, fMLP or C5a des arg. The intraperitoneal injection of LTB4 (10 nmol), fMLP (10 nmol) and C5a des arg (zymosan-activated plasma, 1 ml) caused an intense neutrophil migration compared to the saline control (1,000, 1,500 and 2,000%, respectively). An 83% depletion in the number of resident cells following peritoneal lavage reduced the LTB4-stimulated neutrophil migration by 73.6% without affecting that caused by fMLP and C5a des arg. Increasing the peritoneal macrophage population (236%) by pretreating the cavities with thioglycollate enhanced the neutrophil migration induced by LTB4 (129%), but did not alter that induced by fMLP and C5a des arg. Similarly, reducing the population of peritoneal mast cells containing toluidine-blue-staining granules by subchronically pretreating the cavities with compound 48/80 diminished the LTB4-induced NM by 69% but had no effect on the responses to fMLP and C5a des arg. Pretreating the animals with dexamethasone strongly inhibited (70%) the neutrophil migration induced by the intraperitoneal injection of LTB4, fMLP and C5a des arg. Indomethacin, BW A4C and NDGA had no such effect. The incubating medium from peritoneal macrophages and mast cells stimulated with LTB4 induced neutrophil migration when injected into the peritoneal cavity of rats. This migration was strongly reduced (70%) by treating the cells with dexamethasone. In contrast, stimulating the cells with fMLP or C5a des arg did not result in the release of any promigratory activity into the incubating fluid. Our results suggest that LTB4 induces neutrophil migration via a mechanism dependent on resident mast cells and macrophages while that induced by C5a des arg and fMLP seems to be independent of such cellular involvement. The neutrophil migration induced by LTB4 is apparently mediated by factor(s) whose release is blocked by dexamethasone. fMLP and C5a appear to cause in vivo migration by the formation of a concentration gradient and by a glucocorticoid-sensitive mechanism different from that stimulated by LTB4.

The involvement of macrophage-derived tumour necrosis factor and lipoxygenase products on the neutrophil recruitment induced by Clostridium difficile toxin B

Clostridium difficile (Cd) toxins appear to mediate the inflammatory response in pseudomembranous colitis and/or colitis associated with the use of antibiotics. In contrast to Cd Toxin A (TxA), Cd Toxin B (TxB) has been reported not to promote fluid secretion or morphological damage in rabbits and hamsters and also does not induce neutrophil chemotaxis in vitro. However, TxB is about 1000 times more potent than TxA in stimulating the release of tumour necrosis factor-alpha (TNF-alpha) by cultured monocytes. In the present study, we investigated the ability of TxB to promote neutrophil migration into peritoneal cavities and subcutaneous air-pouches of rats. We also examined the role of resident peritoneal cells in this process as well as the inflammatory mediators involved. TxB caused a significant and dose-dependent neutrophil influx with a maximal response at 0.1 microgram/cavity after 4 hr. Depleting the peritoneal resident cell population by washing the peritoneal cavity or increasing this population by pretreating the animals with thioglycollate blocked and amplified the TxB-induced neutrophil migration, respectively. Pretreating the animals with MK886 (a lipoxygenase inhibitor), NDGA (a dual cyclo- and lipoxygenase inhibitor) or the glucocorticoid, dexamethasone, but not with indomethacin (a cyclo-oxygenase inhibitor), or BN52021 (a platelet-activating factor antagonist), inhibited the neutrophil migration evoked by TxB. Pretreatment with dexamethasone or the administration of anti-TNF-alpha serum into the air-pouches also significantly reduced the TxB-induced neutrophil migration. Supernatants from TxB-stimulated macrophages induced neutrophil migration when injected into the rat peritoneal cavity. This effect was attenuated by the addition of either MK886 or dexamethasone to the macrophage monolayer and by preincubating the supernatants with anti-TNF-alpha serum. TxB also stimulated the release of TNF-alpha by macrophages. Overall, these results suggest that TxB induces an intense neutrophil migration which is mediated by macrophage-derived TNF-alpha and lipoxygenase products.

Postcoital testing after the use of a bio-adhesive acid buffering gel (ACIDFORM) and a 2% nonoxynol-9 product

ACIDFORM is a gel already shown to be safe in vaginal use during six consecutive days through colposcopic observation. A randomized, blinded, crossover study was carried out to compare the spermicidal effect of ACIDFORM to that of a commercial 2% nonoxynol-9 (N-9) product. Twenty sexually active, sterilized women, aged 19-45 years, with regular cycles, normal gynecological exam, no previous sexually transmitted infection (STI) and stable partner willing to undergo four postcoital tests (PCTs) at midcycle during four different menstrual cycles, were enrolled in the study. Known allergy to N-9 or ACIDFORM, oligospermic partner, chronic diseases, use of hormones, previous treatment for STI or presence of STI at screening tests were criteria for exclusion. ACIDFORM or N-9 product administered 0-30 min precoitus or ACIDFORM given 8-10 h precoitus significantly reduced the mean number of progressively motile sperm compared to control cycles (0.19, 0.07, 0.75 vs. 17.94, respectively, p<.05, Wilcoxon test). All treated cycles had five or fewer progressively motile sperm in midcycle cervical mucus, confirming in vivo the spermicidal effect of ACIDFORM previously observed in vitro and in animal models.

Vaginal safety after use of a bioadhesive, acid-buffering, microbicidal contraceptive gel (ACIDFORM) and a 2% nonoxynol-9 product

BACKGROUND

ACIDFORM is a microbicidal and contraceptive candidate with strong buffering capacity.

METHODS

This was a Phase I blinded, randomized and crossover clinical study on two products, ACIDFORM and a commercial nonoxynol-9 (N-9) product (2%), evaluating their vaginal safety in 20 couples aged between 19 and 45 years. The women had regular menses, underwent previous tubal ligation, were not breast-feeding, had no vaginal sign and symptom and were in a stable partnership; both partners had no previous STI. Colposcopy, vaginal microbiology, inflammation markers and subject complaints were studied after coitus. Women were randomly assigned sequentially to receive ACIDFORM 0-30 min (0-30 min before intercourse), ACIDFORM 8-10 h (8-10 h before intercourse) or N-9 0-30 min after a control cycle.

RESULTS

Mild/moderate vulvar irritation was observed in five postcoital test colposcopies, burning and pruritus were reported in six treated cycles and non-irritation-related symptoms were found in five cycles with different treatments. No difference in vaginal pH, Nugent scores, H2O2-producing lactobacillus or leukocytes and interleukin 6 in the cervicovaginal lavage was found between the treatment and control cycles.

CONCLUSIONS

ACIDFORM appears to be safe for clinical use once a day. There is a potential spermicidal-microbicidal role for ACIDFORM as a vaginal flora helper or as a vehicle for products, except N-9.

Role of pertussis toxin A subunit in neutrophil migration and vascular permeability

The anti-inflammatory activity of pertussis toxin (Ptx) was compared to that of a noncatalytic mutant of pertussis toxin (9K/129G; Ptxm), which contains two amino acid substitutions in the A protomer, by using a rat model of inflammation. The toxins were administered intravenously 1 h prior to the injection of inflammatory stimuli. Ptx, but not Ptxm, inhibited neutrophil migration into peritoneal cavities in response to formyl-methionyl-leucyl-phenylalanine and lipopolysaccharide. The inhibitory effect of Ptx on neutrophil migration could not be explained by the ability of the toxin to induce leukopenia or neutropenia. The increase in skin vascular permeability induced by leukotriene B4, a powerful neutrophil chemotactic agent, was also inhibited only by Ptx. On the other hand, the increase in skin vascular permeability induced by histamine was potentiated by both toxins. These data show that Ptx inhibits neutrophil-mediated inflammation in vivo and that this effect is dependent on the ADP-ribosyltransferase activity of the A protomer.

Role of tumor necrosis factor and nitric oxide in the cytotoxic effects of Clostridium difficile toxin A and toxin B on macrophages

Clostridium difficile, the bacterium involved in antibiotic-associated colitis, produces two exotoxins, toxin A (TxA) and toxin B (TxB). Although these toxins are well recognized as being cytotoxic to several mammalian cell types, the mechanisms involved are not fully understood. The aim of the present investigation was to examine the cytotoxicity of TxA and TxB to peritoneal macrophages in culture and to investigate whether tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) are involved in the process. As a control, the effect of E. coli LPS was also investigated. TxA, TxB and LPS were dose-dependently cytotoxic to macrophage monolayers, with TxB being the most potent. All of the toxins stimulated the release of TNF-alpha from macrophages. TxB was again the most active in inducing this response. The TNF-alpha released appears to be involved in the action of LPS and TxA, but not of TxB, since a mAb against TNF-alpha inhibited the cytotoxicity of the former two but had no effect on the latter. NO is not involved in the effects of TxA and TxB since these toxins did not induce the production of this mediator in macrophages, even in the presence of IFN-gamma. In addition, L-imino-ethyl-L-ornithine (L-NIO), a NO synthase inhibitor, did not modify the macrophage death caused by TxA or TxB. Although LPS was able to induce the production of high amounts of NO, NO did not mediate the LPS cytotoxicity since L-NIO did not influence the degree of macrophage death caused by LPS. TxA and TxB therefore appear to exert cytotoxic effects on cultured macrophages by different mechanisms. TNF-alpha is involved in TxA and LPS-mediated cytotoxicity but not in the toxicity caused by TxB. NO is not involved in the killing action of any of these toxins.