PubMed · 8451021
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D S Goodin. 1993. Corticosteroids and optic neuritis.. https://doi.org/10.1212/wnl.43.3_part_1.632-a
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Dietary exposure to vomitoxin (VT) results in hyperelevated serum IgA and IgA nephropathy in mice. To assess the possible role of cytokines in this IgA dysregulation, the effects of a single oral exposure in B6C3F1 male mice to 0, 5 or 25 mg/kg BW VT on production of IgA and cytokines in Peyer's patch (PP) and spleen cell cultures were evaluated. IgA levels were increased significantly in PP cell cultures prepared from mice at 2 or 24 h after oral exposure to VT and subsequently stimulated with phorbol myristate acetate (PMA) and ionomycin (ION) or with lipopolysaccharide (LPS). Significant effects on IgA production were not observed in spleen cell cultures. Since cytokines such as IL-2, IL-4, IL-5 and IL-6 have been shown to promote IgA production, the effect of the same VT exposure regimen on secretion of these mediators was determined in PP and spleen cultures. Supernatant IL-2 and IL-4 levels were unaffected by the prior treatment of animals with VT. In contrast, IL-5 levels were increased significantly in 7-day PP cell cultures obtained 2 h after VT exposure both with and without PMA + ION exposure but not in other cultures. IL-6 levels were increased significantly in LPS-treated cultures prepared from PP at 2 and 24 h following exposure to VT. IL-6 levels were also elevated significantly in both PMA + ION or LPS treated cultures from spleen isolated at 2 h but not 24 h post VT exposure. To determine whether IL-5 or IL-6 play a role in IgA hyperelevation in vitro, PP and spleen cells from mice obtained 2 h after exposure to 25 mg/kg VT were cultured in the presence of neutralizing cytokine antibodies (Abs) and IgA production was monitored. Consistent with IL-5's previously documented role in IgA production, anti-IL-5 decreased IgA levels to background in cultures of both control and VT-exposed PP or spleen cells in the presence of either PMA + ION or LPS. Similar results were seen with addition of anti-IL-6. IgA levels were decreased to a lesser extent in PP cells cultured with LPS and in spleen cells cultured with PMA + ION from VT-exposed mice to which anti-IL-2 Ab was added. Thus, the potential for enhanced IgA production exists in lymphocytes as early as 2 h and as late as 24 h after a single oral exposure to VT and this may be related to the increased capacity to secrete helper cytokines of T cell and macrophage origin. Taken together, the results suggest that the superinduction of cytokine expression may, in part, be responsible for upregulation of IgA secretion in mice exposed orally to VT.
Hypothermia is a commonly reported thermoregulatory response in rodents acutely exposed to organophosphates (OP); however, our laboratory has recently found a delayed hyperthermic response following the initial hypothermia when exposed to the OP, chlorpyrifos. It is well known that rodents display tolerance to OP-induced hypothermia but little is known about tolerance to OP-induced hyperthermia. Twenty female rats of the Long-Evans strain were made tolerant to chlorpyrifos by administering 0 or 10 mg/g chlorpyrifos by gavage daily for four days. Core temperature (T[c]) and motor activity (MA) were monitored continuously by telemetry. Twenty-four hours after the fourth 10 mg/kg injection, the animals were administered a challenge dose of 25 mg/kg chlorpyrifos or corn oil while the telemetry data were monitored for the next 72 h. Non-tolerant rats displayed an initial hypothermic response with reduced MA followed by a delayed increase in T(c) 24 h after exposure. The tolerant animals displayed a blunted hypothermic response with virtually no change in MA, but a delayed increase in T(c) similar to that of non-tolerant animals. The hyperthermic response of the non-tolerant animals persisted for two days, whereas the tolerant animals recovered by the second day. The data indicate that tolerance to the hypothermic and hyperthermic effects of chlorpyrifos involve separate neurochemical pathways.
The intravenous administration of lipopolysaccharide (LPS) to rats results in liver lesions characterized by the infiltration of both platelets and neutrophils into the liver and by midzonal hepatocellular necrosis. The liver injury is dependent on neutrophils, platelets and the coagulation system, as removal or inhibition of any of these components inhibits the development of hepatocellular necrosis. Platelet activating factor (PAF) and the cysteinyl leukotrienes (LTs) are potent inflammatory lipids that are critical for the development of some LPS-mediated alterations. To test the hypothesis that PAF, alone or in combination with LTs, contributes to the development of liver injury during LPS exposure, we conducted studies with the PAF receptor antagonist, WEB 2086, and the 5-lipoxygenase inhibitor, Zileuton. Female, Sprague-Dawley rats were pretreated with WEB 2086 (10 mg/kg, i.p.) alone or with Zileuton (40 mg/kg, p.o.) 1 h before the administration of LPS (4 mg/kg, i.v.) or its saline vehicle. Treatment with WEB 2086, alone or in combination with Zileuton, did not inhibit LPS-mediated hepatic neutrophil infiltration or liver injury, as assessed by histologic evaluation and increases in plasma alanine aminotransferase activity. Pretreatment with these agents also had no effect on the activation of the coagulation system or on the thrombocytopenia induced by LPS. These results suggest that PAF, alone or in combination with 5-lipoxygenase products, is not a critical mediator of LPS-induced hepatocellular injury in this model.