Interaction between Pyridostigmine Bromide and Oxidative Stress (original) (raw)
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Pyridostigmine bromide and its relation to Gulf War illness
Toxin Reviews, 2018
Pyridostigmine bromide acts as a reversible cholinesterase inhibitor that is used at relatively high doses in treatment of Myasthenia gravis and in low dose regimens as prophylaxis against nerve agents poisoning during the Gulf War. The manifestation of late nonspecific symptoms commonly called Gulf War illness has led to the discussion about the role of pyridostigmine bromide in the pathogenesis of this illness. In our study, we described plasma absorption profile of pyridostigmine bromide after p.o. administration in rats; subsequently, changes in blood biochemical and oxidative stress markers were measured. Pyridostigmine bromide was applied p.o. at the dose of 5.82 mg/kg b.w. according to the previously published recommendations. The absorption of pyridostigmine was relatively fast; the C max in plasma was 110.20 ± 15.12 ng/ml at T max of 197.12 ± 17.14 min. The bioavailability expressed as AUC total was 44,348 ± 7608 min ng/ml. The prolongation of pyridostigmine in circulation is in agreement with relatively long half-life that was 179.00 ± 28.54 min. Several blood biochemical markers were altered, including glucose, creatinine, creatine kinase, alanine aminotransferase, aspartate aminotransferase, interleukin-6, triglycerides, and cholesterol. However, the changes could be considered as mild. Thiobarbituric acid reactive substances and ferric reducing ability of plasma indicate suppression of basal metabolism. The results of blood biochemical and oxidative stress markers imply that long-term use might possibly change the basal metabolism and cause cellular damage with inflammatory changes.
Pretreatment with Pyridostigmine Bromide Does not Induce Cellular Toxicity
Soldiers are exposed to multiple stress conditions adverse psychological, physico-chemical and environmental conditions during warfare which can result in significant physical and chemical alterations in the biological system. The effects of carbamate (pyridostigmine bromide, PB) pretreatment prior to physiological stress and organophosphorous compound, DFP (diisopropylfluorophosphate) exposure have been investigated on rats. This study attempts to decipher the level of cellular toxicity imparted by PB pretreatment by assessing drug efflux transportation of the PB or DFP and possible genotoxicity with respect to chromosomal aberrations, in addition to total antioxidant status (TAS) of blood under such circumstances. Total antioxidant status was observed to be more than 50% potentiated with sign-free dose of PB. Immunohistochemical studies show that drug efflux transporter P-glycoprotein receptors were not quantitatively upregulated by physical stress or hyperthermia or hypothermia or sign-free dosage (0.075 mg/Kg after intramuscular injection) of the xenobiotic pyridostigmine bromide. Treatment with high doses (8-16mg/ml) of PB on alternate days for a week caused 10-20% increase in the receptor count, indicating the toxicity level. Further, sign-free dose of pyridostigmine does not induce genotoxicity as far as chromosomal breakage is concerned. In silico docking studies show that the pyridostigmine molecule binds with maximum affinity to asparagine(1235), threonine(1199) and arginine(1229) in the C-terminal half of the P-glycoprotein. So, pretreatment with sign-free dose of pyridostigmine bromide offers sufficient protection from stress against organophosphorous DFP exposure as observed from these molecular studies and does not significantly alterP-glycoprotein receptors quantitatively.
Effects of Pyridostigmine bromide on SH-SY5Y cells: An in vitro neuroblastoma neurotoxicity model
Mutation Research/Genetic Toxicology and Environmental Mutagenesis, 2017
Pyridostigmine bromide (PB) is a reversible acetylcholinesterase (AChE) inhibitor and the first-choice for the treatment of symptoms associated with myasthenia gravis and other neuromuscular junction disorders. However, evidence suggested that PB could be associated with the Gulf War Illness characterised by the presence of fatigue, headaches, cognitive dysfunction, and musculoskeletal respiratory and gastrointestinal disturbances. Given that a potential neurotoxic effect of PB has not yet been completely elucidated, the present investigation used neural SH-SY5Y cells to evaluate the effect of PB on the cellular viability, cell apoptosis, modulation of the cell cycle, oxidative stress, and genotoxicity variables, which indicate neurodegeneration. As expected, a PB concentration curve based on the therapeutic dose of the drug showed an inhibition of the AChE activity. However, this effect was transient and did not involve differential AChE gene regulation by PB. These results confirmed that undifferentiated SH-SY5Y cells can be used as a cholinergic in vitro model. In general, PB did not trigger oxidative stress, and at a slightly higher PB concentration (80 ng/mL), higher levels of protein carbonylation and DNA damage were detected, as determined by the marker 8-deoxyguanosine. The PB genotoxic effects at 80 ng/mL were confirmed by the upregulation of the p53 and DNA methyltransferase 1 (DNMT1) genes, which are associated with cellular DNA repair. PB at 40 ng/mL, which is the minimal therapeutic dose, led to higher cell proliferation and mitochondrial activity compared with the control group. The effects of PB were corroborated by the upregulation of the telomerase gene. In summary, despite the methodological constrains related to the in vitro protocols, our results suggested that exposure of neural cells to PB, without other chemical and physical stressors did not cause extensive toxicity or indicate any neurodegeneration patterns.
Toxicological Sciences, 2002
Pyridostigmine, a carbamate cholinesterase (ChE) inhibitor, has been used for decades in the treatment of the autoimmune disorder myasthenia gravis and was used prophylactically to protect soldiers from possible organophosphorus nerve agent exposures during the Persian Gulf War. Pyridostigmine is a charged, quaternary compound and thus would not be expected to easily pass the blood-brain barrier. Some studies have suggested, however, that stress may alter blood-brain barrier integrity and allow pyridostigmine to enter the brain. We evaluated the effects of acute and repeated restraint stress on functional signs of cholinergic toxicity (i.e., autonomic dysfunction and involuntary movements) and brain regional cholinesterase inhibition following either acute or repeated pyridostigmine exposures. The acute, oral maximumtolerated dosage (MTD) of pyridostigmine was estimated at 30 mg/kg. Peak ChE inhibition in whole blood occurred from 0.5 to 4 h after MTD exposure, whereas minimal (<20%) brain ChE inhibition was noted. For acute restraint studies, rats were either (1) restrained for 90 min and then given pyridostigmine (30 mg/kg, po), (2) given pyridostigmine and immediately restrained for 60 min, or (3) restrained for 3 h, given pyridostigmine, and restrained for an additional 60 min. In all cases, rats were evaluated for cholinergic toxicity (SLUD signs and involuntary movements) and sacrificed 1 h after pyridostigmine treatment. Plasma corticosterone was significantly elevated immediately after a single 60-min session of acute restraint stress, but returned to control levels by 1 and 3 h later. Pyridostigmine-induced toxicity was not enhanced nor was brain ChE inhibition altered by acute restraint stress. Blood-brain barrier permeability, assessed by accumulation of horseradish peroxidase in brain regions following intracardiac injection, was not increased by restraint stress. For repeated restraint studies, rats were given pyridostigmine (0, 3, or 10 mg/kg/ day) immediately prior to daily restraint (60 min) for 14 consecutive days. Plasma corticosterone was elevated at 1 and 7 days but not at 14 days. Pyridostigmine-treated rats in both dosage groups exhibited slight signs of toxicity for the first 3-5 days, after which cholinergic signs dissipated. Repeated restraint had little effect on functional signs of pyridostigmine toxicity, however. Whole blood and diaphragm ChE were markedly reduced 1 h after the last treatment, but stress had no influence on ChE inhibition in either peripheral or central tissues. The results suggest that acute and repeated restraint stress have little effect on pyridostigmine neurotoxicity or apparent entry of pyridostigmine into the brain.
Psychopharmacology, 2002
Questions have been raised about the role pyridostigmine bromide (PB) plays in the etiology of Gulf War veterans' illnesses. There is a need to understand better the physiological and behavioral effects of this drug, particularly at the 30-mg/8-h regimen recommended by the US Military. Objective: To perform a double-blind, cross-over, dose-response study of PB in 67 healthy, young volunteers (31 women, 36 men). Methods: Volunteers were initially trained on a standardized test battery. Supervised administration of placebo (PL) and PB (every 8 h/5 days) occurred in each of two dosing weeks, separated by a non-dosing week. One group received 30 mg PB and PL, and the other 60 mg PB and PL. In each dosing week, the battery was performed after the first pill and again when steady-state plasma PB levels were achieved. Results: PB was associated with an overall improvement in reaction time on tests of memory and attention, and with a reduction in RMS error on a tracking task. PB slowed heart rate and decreased the high frequency component of heart rate variability (HF HRV). Dose-response effects were found only for HF HRV, and RMS error. The extent of cholinesterase inhibition was directly related to the magnitude of the HF HRV decrease, and was predicted by the weight-normalized PB dose. Cholinesterase inhibition was not related to the extent or severity of reported drug side effects. Conclusions: PB does not appear to have detrimental physiological or performance consequences at the recommended 30-mg dose, or at twice that dose, when evaluated under non-stressful laboratory conditions.
Repeated stress in combination with pyridostigmine
Behavioural Brain Research, 2009
Since their return from the first Persian Gulf War, some veterans have complained of a variety of symptoms that were designated as "Gulf War Illness" (GWI). Among other factors, pyridostigmine, used as a prophylaxis treatment against intoxication by nerve agents, has been proposed by many authors as a cause of late social and/or cognitive dysfunction related to GWI. One of the hypotheses placed to explain these behavioural disorders is that operational stress has modified the side effects of pyridostigmine given to soldiers. In an attempt to establish an experimental model of GWI to evaluate the long-term behavioural effects of pyridostigmine administered in stressful conditions, we have developed a new model of repeated stress based on the pole-climbing avoidance technique. We used it to evaluate the effects of pyridostigmine treatment combined to repeated stress over the months following the end of the treatment. We observed that this stress induces impulsiveness and aggressiveness in adult male rat. Moreover, pyridostigmine treatment administered daily 30 min before each stressful session amplifies these behavioural disorders and induces long-term learning dysfunction and slight but significant decrease in phosphocholine level in hippocampus. This suggests that repeated administration of pyridostigmine combined to pole-climbing avoidance (PCA) stress conditions can induce adverse effects in rat central nervous system.
Pharmacology Biochemistry and Behavior, 2003
Experiments were performed to determine the effect of chronic low-dose pyridostigmine bromide (PB) treatment on blood acetylcholinesterase (AChE), cardiovascular (CV) function, and behavior in C57BL/6J male mice. Chronic carotid arterial catheters were used for long-term CV measurements and for collection of blood samples. Separate groups of mice were used for behavioral open field tests. PB was administered subcutaneously using osmotic minipumps at 1 and 3 mg/kg/day for 7 days. Blood pressure and heart rate (HR) were measured continuously for 24 h before treatment and on Days 3 and 7 after minipump insertion. Blood samples were collected on the same days. Mean arterial pressure (MAP) of the control group was 108 ± 2 and 104 ± 2 mm Hg during the dark and light periods, respectively. HR was 510 ± 18 and 493 ± 19 beats/min during the dark and light periods, respectively. PB treatment had no effect on MAP or HR in either dark or light period. Basal AChE activity was 0.42 ± 0.1 mmol/min/ml, with no changes observed with PB at 1 mg/kg/day. The higher PB dose (3 mg/kg/day) decreased blood AChE activity by 85% on Day 7. Despite the reduction in blood AChE activity, there were no alterations in open field behaviors (locomotor activity, rearing, distance traveled, rest time, number of entries, and pokes). In conclusion, chronic low-dose PB exposure decreased blood AChE activity but had no effect on CV function or behavior in mice. D
Toxicological Sciences, 2004
The effect of the organophosphorous insecticide paraoxon on the integrity of the blood-brain barrier (BBB) and permeability of pyridostigmine (PYR), a peripheral inhibitor of cholinesterase activity, was examined in Long Evans rats. The integrity of the BBB was examined by measuring the number of capillaries leaking horseradish peroxidase, which was injected into the heart. Treatment with paraoxon at 100 g/kg, intramuscularly, resulted in a 3-to 4-fold increase in the number of leaky capillaries in young rats (25 to 30 days old) but not in older rats (90 days old). Interestingly, young rats treated with PYR (30 mg/kg, po) 50 min before treatment with paraoxon showed an inhibited effect of paraoxon on the BBB. Furthermore, no increase in the degree of inhibition of acetylcholinesterase activity was observed in young rats treated with PYR before paraoxon compared with young rats treated with paraoxon alone. Cholinergic toxicity, as assessed by changes in behavior, was not observed in young rats treated with paraoxon alone; but, slight signs of cholinergic toxicity were observed in rats treated with PYR. Young rats treated with both PYR and paraoxon did not exhibit more extensive signs of toxicity than rats treated with paraoxon alone or PYR alone. The results indicate that treatment with paraoxon can compromise BBB permeability at dosages that do not induce cholinergic toxicity, but only in young rats. Also, PYR pre-exposure appears to protect the BBB from the paraoxon-induced alterations.