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1.
Immunology ; 130(3): 388-98, 2010 Jul.
Article in English | MEDLINE | ID: mdl-20408892

ABSTRACT

SUMMARY: The cholinergic nervous system has been demonstrated to attenuate the inflammatory response during sepsis via the inhibitory action of acetylcholine (ACh) on macrophages. These findings were largely based on experimental sepsis models using endotoxin as the inducing agent. Herein, however, we report that the specific inhibition of acetylcholinesterase (AChE) renders animals more resistant to infection by a virulent strain of Salmonella enterica serovar Typhimurium, a Gram-negative enteric pathogen. Inhibition of AChE was induced by a subchronic exposure to paraoxon, a potent anti-cholinesterase metabolite of the organophosphorous compound parathion. Our findings indicate that inhibition of AChE enhanced survival of infected mice in a dose-dependent fashion and this correlated with efficient control of bacterial proliferation in target organs. Immunologically, inhibition of AChE enabled the animals to mount a more effective inflammatory anti-microbial response, and to secrete higher levels of interleukin-12, a key T helper type 1-promoting cytokine. The ACh-induced enhancement in resistance to infection was abrogated by co-administration of an oxime which can reactivate AChE. Hence, in a model of Gram-negative bacterial infection, cholinergic stimulation is shown to enhance the anti-microbial immune response leading to effective control of bacterial proliferation and enhanced animal survival.


Subject(s)
Cholinesterase Inhibitors/pharmacology , Immune System/drug effects , Salmonella Infections/microbiology , Salmonella Infections/prevention & control , Salmonella typhimurium , Acetylcholinesterase/metabolism , Animals , B-Lymphocytes/cytology , Cell Count , Cholinesterase Inhibitors/therapeutic use , Cholinesterase Reactivators/pharmacology , Concanavalin A/pharmacology , Cytokines/blood , Cytokines/metabolism , Erythrocytes/drug effects , Erythrocytes/metabolism , GPI-Linked Proteins , Immune System/immunology , Lipopolysaccharides/pharmacology , Lymph Nodes/microbiology , Macrophages/cytology , Macrophages/drug effects , Macrophages/metabolism , Male , Mice , Mice, Inbred BALB C , Nitric Oxide/metabolism , Oximes/pharmacology , Paraoxon/pharmacology , Paraoxon/therapeutic use , Pyridinium Compounds/pharmacology , Salmonella Infections/blood , Salmonella Infections/drug therapy , Salmonella typhimurium/pathogenicity , Spleen/cytology , Spleen/drug effects , Spleen/microbiology , Survival Analysis , T-Lymphocytes/cytology , T-Lymphocytes/drug effects , T-Lymphocytes/metabolism , Thymus Gland/drug effects
2.
Toxicol Appl Pharmacol ; 218(3): 215-26, 2007 Feb 01.
Article in English | MEDLINE | ID: mdl-17196234

ABSTRACT

Persistent exposure to inorganic lead (Pb) is known to adversely affect the immune system. In the present study, we assessed the effect of chronic Pb exposure on susceptibility to infection by the facultative intracellular pathogen Salmonella enterica serovar Typhimurium. Mice were exposed to 10 mM Pb-acetate in drinking water for approximately 16 weeks, resulting in a significant level of Pb in the blood (106.2+/-8.9 microg/dl). Pb exposure rendered mice susceptible to Salmonella infection, manifested by increased bacterial burden in target organs and heightened mortality. Flow cytometric analysis of the splenic cellular composition in normal and Pb-exposed mice revealed no gross alteration in the ratios of B and T lymphocytes or myeloid cells. Similarly, the capacity of B and T cells to upregulate the expression of activation antigens in response to mitogenic or inflammatory stimuli was not hindered by Pb exposure. Analysis of the ability of ex vivo-cultured splenocytes to secrete cytokines demonstrated a marked reduction in IFN-gamma and IL-12p40 production associated with Pb exposure. In contrast, secretion of IL-4 by splenocytes of Pb-treated mice was 3- to 3.6-fold higher than in normal mice. The increased capacity to produce IL-4 correlated with a shift in the in vivo anti-Salmonella antibody response from the protective IgG2a isotype to the Th2-induced IgG1 isotype. We conclude that chronic exposure to high levels of Pb results in a state of immunodeficiency which is not due to an overt cytotoxic or immunosuppressive mechanism, but rather is largely caused by a shift in immune responsiveness to Th2-type reactions.


Subject(s)
Disease Susceptibility/chemically induced , Immunity, Cellular/drug effects , Interleukin-4/metabolism , Organometallic Compounds/toxicity , Salmonella typhi/pathogenicity , Th2 Cells/drug effects , Animals , Disease Models, Animal , Disease Susceptibility/immunology , Disease Susceptibility/metabolism , Dose-Response Relationship, Drug , Immunity, Cellular/immunology , Male , Mice , Mice, Inbred C3H , Salmonella Infections, Animal , Salmonella typhi/immunology , Spleen/drug effects , Spleen/immunology , Spleen/metabolism , Th2 Cells/immunology , Th2 Cells/metabolism
3.
Arch Toxicol ; 80(11): 777-84, 2006 Nov.
Article in English | MEDLINE | ID: mdl-16598495

ABSTRACT

Pyridostigmine (PSTG) is a carbamate inhibitor of cholinesterases. Carbamates are known to confer some protection from the lethal effects of (some) organophosphorus compounds. Recently, based on animal data, the FDA approved oral PSTG for pre-exposure treatment of soman. The purpose of the study was to quantify in vivo the effect of PSTG pre-treatment on survival in rats exposed to the organophosphate paraoxon (POX) with and without subsequent reactivator (pralidoxime) treatment. POX is a highly toxic non-neuropathic ethyl organophospate. Pralidoxime (PRX) is the enzyme reactivator used by some NATO armies. The prospective, controlled animal (rat) study included Group 1 that received 1 micromol POX ( approximately LD(75)); Group 2 that received 1 micromol PSTG followed 30 min later by 1 micromol POX; Group 3 that received 1 micromol PSTG followed 30 min later by 1 micromol POX and 50 micromol PRX; Group 4 that received 1 micromol POX and 50 micromol PRX; Group 5 that received 1 micromol PSTG; Group 6 that received 50 micromol PRX and Group 7 that received 1 micromol PSTG followed 30 min later by 50 micromol PRX. Each group contained six rats. The experiment was repeated twelve times (12 cycles). All substances were applied i.p. From surviving animals of eight cycles tail blood was taken for red blood cell acetylcholinesterase (RBC-AChE) measurements. The animals were monitored for 48 h and mortality (survival time) was recorded. RBC-AChE activities were determined. Mortality was analysed using Kaplan-Meier plots. Both PSTG and PRX statistically significantly decreased organophosphate induced mortality in the described model. While the same applies to their combination the decrease in mortality when using both PSTG and PRX is less than that achieved with their single use (but not significantly so). While certainly further work using different organophosphorus compounds and animal species are needed before a final conclusion is reached, the animal data presented does not support the combined use of PSTG and PRX.


Subject(s)
Cholinesterase Inhibitors/toxicity , Cholinesterase Reactivators/administration & dosage , Paraoxon/toxicity , Pralidoxime Compounds/administration & dosage , Pyridostigmine Bromide/administration & dosage , Animals , Cholinesterase Reactivators/therapeutic use , Cholinesterases/blood , Drug Administration Schedule , Erythrocytes/drug effects , Erythrocytes/enzymology , Female , Male , Pralidoxime Compounds/blood , Pralidoxime Compounds/pharmacokinetics , Pralidoxime Compounds/therapeutic use , Pyridostigmine Bromide/therapeutic use , Rats , Rats, Wistar
4.
World J Gastroenterol ; 11(27): 4154-60, 2005 Jul 21.
Article in English | MEDLINE | ID: mdl-16015682

ABSTRACT

AIM: To investigate the effects of leptin (1-20 microg/kg) on acidified ethanol (AE)- and indomethacin (Indo)-induced gastric lesions in rats and compare it with ranitidine, lanso-prazole, and omeprazole and to determine its mechanisms of actions. METHODS: Gastric ulcers, which were approximately 1 mm in width, formed in the glandular portion of the gastric mucosa produced by oral administration of either AE or Indo were taken as ulcer index. The inhibitory effect of subcutaneous administration of leptin, two proton pump inhibitors (PPIs) lansoprazole and omeprazole, or H(2)-receptor antagonist ranitidine 30 min before AE or Indo was evaluated. A radioimmunoassay was used to determine the PGE(2) concentration in the homogenate of the glandular portion of the stomach. We performed histological study of the glandular stomach for the evaluation of total, acidic, and sulfated mucus content. RESULTS: Subcutaneous administration of leptin, two PPIs lansoprazole and omeprazole or H(2)-receptor antagonist ranitidine 30 min before AE or Indo produced a dose-dependent and reproducible inhibition of gastric ulcers (GUs). This inhibition was found to be more potent than other antagonists used. In N(G)-nitro L-arginine methyl ester (L-NAME)-pretreated animals, the ulcer prevention ability of leptin in AE-induced ulcer was significantly reduced, compared to rats without L-NAME pretreatment. However, the ulcer prevention ability of leptin was not altered by L-NAME treatment in Indo-induced ulcers. Leptin produced a dose-dependent increase in PGE(2) level in the gastric glandular tissues. Leptin also increased mucus secretion. CONCLUSION: The results of the present study show that leptin inhibits GU formation by AE or Indo in a dose-dependent and reproducible manner in rats. The results also suggest that leptin prevents ulcer formation by increasing the activities of the cyclo-oxygenase and/or nitric oxide pathways and by increasing mucus secretion.


Subject(s)
Leptin/pharmacology , Stomach Ulcer/drug therapy , Stomach Ulcer/prevention & control , 2-Pyridinylmethylsulfinylbenzimidazoles , Animals , Anti-Ulcer Agents/pharmacology , Lansoprazole , Nitric Oxide/metabolism , Omeprazole/analogs & derivatives , Omeprazole/pharmacology , Prostaglandin-Endoperoxide Synthases/metabolism , Ranitidine/pharmacology , Rats , Rats, Wistar , Stomach Ulcer/metabolism
5.
Anesth Analg ; 100(2): 382-386, 2005 Feb.
Article in English | MEDLINE | ID: mdl-15673862

ABSTRACT

Weak and reversible inhibitors of cholinesterase(s), when coadministered in excess with a more potent inhibitor such as organophosphates, can act in a protective manner. The benzamide compound, metoclopramide, confers some protection (putatively via this mechanism) for cholinesterases against inhibition by paraoxon both in vitro and in vivo, after chronic small-dose exposure. Tiapride is a related benzamide. In this study, we compared the protection by metoclopramide and tiapride in rats acutely exposed to large doses of paraoxon with the therapeutic "gold standard," pralidoxime. Group 1 received 1 micromol paraoxon (approximately 75% lethal dose), Group 2 received 50 micromol metoclopramide, Group 3 received 50 micromol tiapride, Group 4 received 50 micromol pralidoxime, Group 5 received 1 micromol paraoxon + 50 micromol metoclopramide, Group 6 1 micromol paraoxon + 50 micromol tiapride, and Group 7 1 micromol paraoxon + 50 micromol pralidoxime. All substances were administered intraperitoneally. The animals were monitored for 48 h and mortality was recorded at 30 min, 1, 2, 3, 4, 24, and 48 h. Blood was taken for red blood cell acetylcholinesterase measurements at baseline, 30 min, 24, and 48 h. With the exception of Group 7, in which some late mortality was observed, mortality occurred mainly in the first 30 min after paraoxon administration with minimal changes occurring thereafter. Mortality at 30 min was 0% in the metoclopramide, tiapride, and pralidoxime groups and 73 +/- 20 (paraoxon), 65 +/- 15 (paraoxon + metoclopramide), 38 +/- 14 (paraoxon + tiapride), and 13 +/- 19 (paraoxon + pralidoxime). Mortality at 48 h was 75 +/- 18 (paraoxon), 67 +/- 17 (paraoxon + metoclopramide), 42 +/- 16 (paraoxon + tiapride), and 27 +/- 24 (paraoxon + pralidoxime). Metoclopramide does not significantly influence mortality after acute large-dose paraoxon exposure. Both tiapride and pralidoxime significantly decreased mortality in our model. The protection conferred by tiapride was significantly less than that conferred by pralidoxime at 30 min, but was not significantly different at 24 and 48 h.


Subject(s)
Cholinesterase Inhibitors/toxicity , Cholinesterase Inhibitors/therapeutic use , Metoclopramide/therapeutic use , Organophosphorus Compounds/antagonists & inhibitors , Organophosphorus Compounds/toxicity , Pralidoxime Compounds/therapeutic use , Tiapamil Hydrochloride/therapeutic use , Acetylcholinesterase/blood , Animals , Chromatography, High Pressure Liquid , Erythrocytes/drug effects , Erythrocytes/enzymology , Female , Male , Paraoxon/toxicity , Rats , Rats, Wistar
6.
Int J Neurosci ; 114(5): 607-21, 2004 May.
Article in English | MEDLINE | ID: mdl-15204067

ABSTRACT

Learning and memory are defective in the Drosophila mutant rutabaga, which has a low intracellular cyclic adenosine monophosphate (cAMP) concentration. The aim of this study was to compare modulation effects of protein kinase C activator (PKC-A) on the delayed-rectifier potassium current (IKDR) in wild-type and rutabaga neurons. IKDR was measured from cultured (2 days) wild-type and rutabaga neurons. The authors examined the effects of PKC-A on IKDR in wild-type and rutabaga neurons. IKDR was measured from neurons before and after addition of PKC-A to the external solution. IKDR was smaller in rutabaga neurons (380 +/- 25 pA) than in wild-type neurons (529 +/- 44 pA). IKDR was reduced by PKC-A more in wild-type (decreasing 55 +/- 6%) than in rutabaga (decreasing 35 +/- 8%) neurons (single-cell studies). In the presence of PKC-A, there was no difference in IKDR between wild-type (229 +/- 31 pA) and rutabaga (242 +/- 26 pA) neurons (population studies). These results indicate that PKC-A differentially affects the delayed-rectifier channel in wild-type rutabaga.


Subject(s)
Drosophila Proteins/metabolism , Enzyme Activators/pharmacology , Neurons/drug effects , Potassium Channels, Inwardly Rectifying/metabolism , Protein Kinase C/metabolism , Animals , Animals, Genetically Modified , Cells, Cultured , Drosophila , Electric Conductivity , Electrophysiology , Embryo, Nonmammalian , Genotype , Membrane Potentials/drug effects , Neurons/physiology , Patch-Clamp Techniques/methods , Potassium/metabolism , Potassium Channels, Inwardly Rectifying/drug effects
7.
Free Radic Res ; 37(4): 437-45, 2003 Apr.
Article in English | MEDLINE | ID: mdl-12747738

ABSTRACT

Chronic exposure to lead (Pb) is associated with multiorgan toxicity. The precise mechanism(s) involved, however, remains incompletely defined. The present study was undertaken to analyze the effect of Pb on the immune system and determine the ability of alpha tocopherol (AT) to reverse Pb-induced immunotoxicity. Groups of TO Mice (6 per group) were treated ip for 2 weeks with saline alone, Pb acetate alone, Pb plus AT, or with AT alone. Spleens were then analyzed for (i) cellular composition by flow cytometry, (ii) cellular response to B and T cell mitogens and (iii) production of nitric oxide (NO). Pb treatment resulted in a significant state of splenomegaly associated mainly with an influx of CD11b+ myeloid cells. Surprisingly, however, these cells exhibited no upregulation in expression of activation markers and did not produce NO. The lymphocyte mitogenic responses were inhibited by > or = 70% in Pb-treated group. Concurrent treatment with Pb and AT resulted in almost a complete reversal of Pb-induced splenic cellular influx. Despite this, however, mitogenic responses in Pb + AT treated group were approximately 50% of those observed in normal (saline-treated) controls. We conclude that (1) chronic treatment with Pb acetate induces a state of splenomegaly and decreased proliferation in response to mitogenic stimuli and (2) co-treatment with AT largely reversed the cellular influx but this was associated with only a partial improvement of the mitogenic responses. These results highlight the role of AT as a potentially effective antioxidant in the immune system.


Subject(s)
Immunosuppressive Agents/pharmacology , Lead/toxicity , alpha-Tocopherol/pharmacology , Animals , CD11b Antigen/biosynthesis , Cell Division/drug effects , Concanavalin A/pharmacology , Dose-Response Relationship, Drug , Flow Cytometry , Lead/pharmacology , Lipopolysaccharides/metabolism , Male , Mice , Nitric Oxide/metabolism , Phenotype , Spleen/cytology , Spleen/drug effects , Splenomegaly , Up-Regulation
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