Search

Aims: To evaluate the effects of chronic ethanol consumption on the development and the pathophysiology of sepsis, using an experimental model of polymicrobial peritonitis by feces i.p. injection., Methods: Forty-day-old male Wistar rats were divided into groups for two experiments: A and B. Experiment A was performed for determination of mortality rates, while experiment B was designed for biochemical analysis and measurement of cytokines before and after sepsis. In both the experiments, treated animals were exposed to a 10% ethanol solution as the single drinking source for 4 weeks, while untreated animals were exposed to tap water over the same period. Food was provided ad libitum. After this period, the animals underwent i.p. fecal injection for induction of sepsis., Results: Experiment A showed that higher doses of ethanol resulted in early mortality from sepsis that was correlated with the alcohol consumption (high dose = 85.7%, low dose = 14.3%, P = 0.027). In experiment B, cytokine analysis demonstrated important changes resulting from sepsis, which were further affected by ethanol exposure. In addition, glucose and creatinine levels decreased and increased, respectively, after sepsis, but a significant change occurred only in the ethanol group (P < 0.003 glucose, P < 0.01 creatinine). The levels of pro-inflammatory cytokines, interleukin-6 and tumor necrosis factor-α, increased after sepsis, but were less evident after ethanol exposure., Conclusion: These differences may be the result of either early mortality or an increase in the severity of the septic process. Taking into account the high mortality rate and the extreme severity of sepsis after alcohol consumption, often encouraged by advertising, a caution should be given to patients with severe infections and a history of alcohol abuse.

Lipid bodies (lipid droplets) are lipid-rich organelles with functions in cell metabolism and signaling. Here, we investigate the mechanisms of Trypanosoma cruzi-induced lipid body formation and their contributions to host-parasite interplay. We demonstrate that T. cruzi-induced lipid body formation in macrophages occurs in a Toll-like receptor 2-dependent mechanism and is potentiated by apoptotic cell uptake. Lipid body biogenesis and prostaglandin E₂ (PGE₂) production triggered by apoptotic cell uptake was largely dependent of α(v)β₃ and transforming growth factor-β signaling. T. cruzi-induced lipid bodies act as sites of increased PGE synthesis. Inhibition of lipid body biogenesis by the fatty acid synthase inhibitor C75 reversed the effects of apoptotic cells on lipid body formation, eicosanoid synthesis, and parasite replication. Our findings indicate that lipid bodies are highly regulated organelles during T. cruzi infection with roles in lipid mediator generation by macrophages and are potentially involved in T. cruzi-triggered escape mechanisms.

Protozoan parasites of the genus Leishmania frequently occur as opportunistic pathogens in human immunodeficiency virus type 1 (HIV-1)-infected individuals, but the mechanisms underlying protozoan growth in this context are poorly understood. Here, we demonstrate that the HIV-1 Tat protein drives Leishmania replication in primary human macrophages. We found that Leishmania growth doubled in HIV-1-infected macrophages and that anti-Tat antibodies reduced the exacerbated protozoan replication by 70%. Recombinant Tat increased Leishmania replication and overrode the leishmanicidal effect induced by interferon-gamma , allowing Leishmania replication even in the presence of this cytokine. Tat induced cyclooxygenase (COX)-2 expression and prostaglandin E2 (PGE2) synthesis, and a COX-2 inhibitor abolished the Tat-mediated augmentation of Leishmania replication. Moreover, PGE2 increased Leishmania growth, which was abrogated by anti-transforming growth factor (TGF)- beta1 monoclonal antibodies. Neutralization of TGF-beta1 reduced parasite growth in Leishmania-infected macrophages exposed to Tat by 50%. Our findings suggest that Tat generates a milieu permissive to Leishmania growth in individuals infected with HIV-1.

Organ malfunctions in patients with leptospirosis have been associated with the bacterial glycolipoprotein endotoxin and with its nonesterified unsaturated fatty acid (NEUFA) components. We examined the involvement of NEUFAs in the pathophysiological processes of leptospirosis. Patients showed a moderate increase in serum concentrations of oleic and linoleic acids but an important decrease in serum concentrations of albumin. A highly significant correlation between serum concentrations of creatinine or total bilirubin and the oleic-plus-linoleic acid : albumin ratio was revealed. We used the Na(+),K(+)-ATPase inhibitory property of NEUFAs to test the capacity of serum to prevent the cytotoxic effects of NEUFAs in vitro. Albumin solutions and serum samples from healthy volunteers, but not serum samples from severely affected patients, were able to revert the Na(+),K(+)-ATPase inhibition by oleic acid. On the basis of these data, we defined a "serum protection factor" that can be helpful in predicting NEUFA toxicity. Our data support the concept that the administration of human albumin to patients may be helpful in severe leptospirosis cases.

A role for catecholamines in the regulation of the blood neutrophilia induced by intravenous (i.v.) injection of lipopolysaccharide (LPS; 250 micrograms/kg) was examined in Wistar rats by means of surgical adrenalectomy or pretreatment with adrenergic and dopaminergic antagonists into naive animals. Treatment of animals with a single dose (250 micrograms/kg) of LPS caused a dramatic increase in the number of circulating neutrophils concomitant with a decrease in the number of these cells in the bone marrow. These effects were partially reversed when catecholamine stores were depleted with reserpine. It was found that neither adrenalectomy nor pretreatment with the dopaminergic antagonists, chlorpromazine and pimozide, affected the changes in neutrophil counts induced by LPS. The injection of the alpha 1/alpha 2-adrenoceptor antagonist, phentolamine, and the selective alpha 1-adrenoceptor antagonist, prazosin, significantly decreased blood neutrophilia induced by LPS. However, neither the selective alpha 2-adrenoceptor antagonist, yohimbine, nor the beta-adrenoceptor antagonist, propranolol, had any effect on LPS response. Taken together, these findings support the hypothesis that the catecholamine norepinephrine plays a role in the regulation of the LPS-induced neutrophilia through activation of alpha 1-adrenoceptors.

In this study we investigated the involvement of inflammatory cells in the pleural accumulation of eosinophils induced by lipopolysaccharide (LPS). Intrathoracic (i.t.) injection of LPS (250 ng/cavity) into rats induced a significant eosinophil accumulation that developed within 24 h, was maximal at 48 h, and returned to control values within 120 h. This eosinophil influx was preceded by a huge neutrophil influx within 4 h and accompanied by a mononuclear cell accumulation between 24 and 48 h. Pretreatment with an antineutrophil monoclonal antibody (RP-3, 2 ml per animal) selectively reduced the number of circulating neutrophils within 8 h but failed to alter the LPS-induced eosinophilia. Similarly, platelet depletion with an anti-rat platelet antiserum did not alter the LPS-induced eosinophil accumulation. Cyclosporine (50 mg/kg, 12 and 2 h before) partially inhibited (51%) the LPS-induced pleural eosinophilia, whereas the eosinophilia was not changed by prior degranulation of pleural mast cells with polymyxin B (10 micrograms/cavity, 24 h before). Moreover, selective depletion of T lymphocytes using an anti-Thy 1.0 monoclonal antibody significantly inhibited the eosinophilia triggered by LPS. The i.t. injection of liposomes containing dichloromethylene diphosphonate significantly reduced (65%) the number of resident macrophages after 5 days. Under this condition, the eosinophil infiltration induced by LPS was completely inhibited. Accordingly, the i.t. injection of supernatant from macrophage monolayers, obtained from the pleural cavities of LPS-injected rats, into naive recipient animals led to a twofold increase in the number of pleural eosinophils. In conclusion, our data suggest an important role for resident macrophages and T lymphocytes in the eosinophil accumulation induced by LPS.

Selective platelet-activating factor (PAF) antagonists and autodesensitization to this lipid were used to investigate the role of PAF in antigen-induced pleurisy in the rat. Pleural inflammation was triggered by the intrathoracic (i.t.) injection of ovalbumin (12 micrograms/cavity) into animals actively sensitized 14 days before. Successive daily i.t. injections of PAF (1 microgram/cavity) led to selective autodesensitization, which was apparent after the third injection and maximal after the fifth. The PAF antagonists BN 52021 and WEB 2086 inhibited the late pleural eosinophil accumulation caused by antigen but, as also noted with WEB 2170, failed to modify the early antigen-induced plasma exudation and leukocyte infiltration. In contrast to the antagonists, desensitization to PAF was clearly effective against these early alterations. To further investigate this discrepancy, the antigenic challenge was performed 24 h after a single prestimulation with PAF, when sensitivity to the lipid was still intact. Under this condition, plasma exudation and cellular influx triggered by the antigen were also abrogated, indicating that this protective effect was accounted for by a mechanism other than refractoriness to PAF. Because 24 h after PAF injection only eosinophil counts remained elevated, an alternative eosinophilotactic substance was used to further study the mechanism of PAF versus antigen-induced pleural inflammation. Prior treatment with the peptide Ala-Gly-Ser-Glu (ECF-A, 20 micrograms/cavity) also inhibited the allergic pleurisy, whereas the noneosinophilotactic substances histamine (200 micrograms/cavity) and serotonin (100 micrograms/cavity) were inactive. Furthermore, drugs that share the ability to impair PAF-induced eosinophilia, including azelastine and cetirizine, prevented the inhibitory effect of PAF on the antigen-induced pleurisy. These findings suggest that PAF may account for the late eosinophilia, but not for the acute phase of the rat allergic pleurisy, which is clearly attenuated by PAF or ECF-A pretreatment.

Blood leukocyte count alterations induced by PAF-acether in anesthetized and nonanesthetized rats were investigated. Intravenous injection of increasing amounts of PAF-acether (1.5-8 micrograms/kg) in nonanesthetized animals induced dose-dependent hemoconcentration and leukocytosis. The former was apparent within 10 min, peaked from 30 min to 1 h, and diminished thereafter. The leukocytosis was noted within 30 min, was maximal at 1 h, and was over 4 h after injection of PAF-acether (4 micrograms/kg). It was characterized by a marked increase in the blood neutrophil counts under conditions in which the number of lymphocytes, monocytes, and eosinophils remained unchanged. PAF-acether-induced leukocytosis occurred in parallel with a marked decrease in the number of bone marrow nucleated cells, suggesting that the latter phenomenon may determine the former one. Leukocytosis by PAF-acether was inhibited dose-dependently by specific PAF-acether antagonists including BN 52021 (median effective dose ED50 = 4.99 mg/kg), WEB 2086 (ED50 = 4.59 mg/kg), and 48740 RP (ED50 = 9.02 mg/kg). General anesthesia by either pentobarbital, urethane, or ether inhalation, but not by ketamine, also impaired the PAF-acether-induced blood leukocytosis under conditions in which the hemoconcentration was not modified. In addition, pentobarbital-anesthetized rats did not have reduced bone marrow nucleated cell counts after PAF-acether stimulation. These findings are consistent with the assessment that PAF-acether-induced rat leukocytosis is accounted for by a bone marrow neutrophil mobilization process that is clearly suppressed in animals anesthetized by pentobarbital.

Intraplantar injections of 2-methyl-carbamate-PAF (2-MC) (0.125-16.0 micrograms/paw) into the rat paw were followed by a bell-shaped dose response curve for inflammatory oedema, with an ascending phase at 0.125-2.0 micrograms/paw, and a descending phase at 4.0-16.0 micrograms/paw. The inflammatory response to 2-MC was partially inhibited by pre-treatment with aspirin (200 mg kg-1), NDGA (100 mg kg-1), dexamethasone (0.1 mg kg-1), verapamil (50 mg kg-1) and by a specific PAF antagonist BN 52021 (5-10 mg kg-1). The cyclo-oxygenase inhibitors indomethacin (2 mg kg-1) and piroxicam (1.8 mg kg-1) as well as antihistamine meclizine (40 mg kg-1) and ranitidine (50 mg kg-1) failed to block the oedematogenic response to 2-MC. Our data suggest that 2-MC induced rat paw oedema is mediated by PAF-acether receptors and is partially dependent on arachidonate lipoxygenase pathway and extracellular Ca2+.