[Effect of paraoxon on antioxidant system and lipid peroxidation in liver of rat]

The toxic effects of some organophosphate pesticides [Ops] which are capable to produce free radicals and induce disturbance in body antioxidant systems. Paraoxon is an OP that is the active form parathion. To evaluate the effect of paraoxon on liver antioxidant system of rat. Wister rats were randomly divided into four groups including: control [paraoxon solvent], and three groups receiving different doses of paraoxon [0.3, 0.7 and 1 mg/kg] by intraperitoneal injection. Animal were anesthetized and liver tissue removed 24 hours after injection. After hemogenation of liver tissue Superoxide Dismutase [SOD] and Catalase [CAT], Lactate Dehydrogenese [LDH] and Glutathione S- Transferase [GST] activities, Glutathione [GSH] and malondialdehyde [MDA] levels were determined by biochemical methods. Paraoxon increased CAT, LDH and SOD activities and MDA level at doses higher than 0.3 mg/kg, while GSH level was decreased significantly, as compare with the control group. GST activity was increased significantly at 0.3 and 0.7 mg/kg concentration [P<0.05], but at 1 mg/kg concentration was decreased as compare with the control group. Probably Paraoxon induced the production of free radicals and oxidative stress in a dose- dependent manner. The enhanced activity of antioxidant enzymes of liver is due to increase the detoxification capacity. Decrease of tissue GSH content indicatives of oxidative tissue injury and the increase of MDA level indicatives per oxidation that occurs in membranes of liver

[ neuroprotective effect of cannabinoid receptor agonist [WIN55,212-2] in paraoxon induced neurotoxicity in PC12 cells and N-methyl-D-aspartate receptor interaction]

Considering that cannabinoids protect neurons against neurodegeneration, in this study, the neuroprotective effect of WIN55,212-2 in paraoxon induced neurotoxicity in PC12 cells and the role of the N-methyl-D-aspartate [NMDA] receptor were evaluated. In this study PC12 cells were maintained in Dulbecco's modified eagle's medium [DMEM+F12] culture medium supplemented with 10% fetal bovine serum. The cells were treated with paraoxon [200 micro M] in the presence or absence of WIN55,212-2 [0.1 micro M], NMDA receptor agonist NMDA [100 micro M], cannabinoid receptor antagonist AM251 and NMDA receptor antagonist MK801 [1 micro M] at 15 minutes intervals. After 48 hours of exposure, cellular viability and protein expression of the CB1 receptor were evaluated in PC12 cells. Following the exposure of PC12 cells to paraoxon [200 micro M], a reduction in cell survival and protein level of the CB1 receptor was observed [p<0.01]. Treatment of the cells with WIN55,212-2 [0.1 micro M] and NMDA [100 micro M] prior to paraoxon exposure significantly elevated cell survival and protein level of the CB1 receptor [p<0.01]. Also, AM251 [1 micro M] did not inhibit the cell survival and protein level of the CB1 receptor increase induced by WIN55,212-2 [p<0.001]. However, MK801 [1 micro M] did inhibit cell survival and protein expression of the CB1 receptor increase induced by NMDA [p<0.001]. The results indicate that WIN55,212-2 and NMDA protect PC12 cells against paraoxon induced toxicity. In addition, the neuroprotective effect of WIN55,212-2 and NMDA was cannabinoid receptor-independent and NMDA receptor dependent, respectively

Paraoxonase gene polymorphism and serum paraoxonase activity: relationship with type I diabetes and nephropathy

Human serum paraoxonase-I [PON1] is physically associated with high density lippprotein [HDL] and has been implicated in the prevention of LDL lipid peroxidation. PON1 gene displays several polymorphisms that influence both its level of expression and its catalytic activity. The goal of this study was to examine the association between paraoxonase-1 [PON1] activity and gene polymorphism and the micro-vascular complications in children and adolescence suffering from type 1 DM [TIDM]. Case-control study. One study centre at a University hospital. Thirty eight patients, with type 1 diabetes [n=38], 13 patients presenting with diabetic nephropathy [mean age 18.76 +/- 5.59 years. 8 males and 5 females] and 25 without diabetic nephropathy [mean age 14.48 +/- 3.69 years. 14 males and 11 females] and 16 healthy controls [mean age 12.38 +/- 8.25 years, 10 males and 6 females]. The allele variants of PON1 gene polymorphisms in the PON1 coding region Q192R and L55M have been identified by polymerase chain reaction followed by restriction fragment length polymorphism analysis. Serum PON1 enzyme activity was measured spectrophotometrically. Serum PON1 activity was significantly decreased in complicated diabetics when compared to both non-complicated patients and the control persons [103.33 +/- 35.46 nmol/ml/min, 462.57 +/- 200.69 nmol/ml/min and 1132 +/- 317.61 nmol/ml/min respectively]. As regards PON1 Q192R polymorphism, the R allele was more frequent in complicated diabetics versus both non-complicated diabetics and controls [p=0.0113 and p=0.001 respectively]. PON1 192QR genotype is a risk factor for developing type 1 diabetes OR=7.8; 95% CI [1.12-65.7] with p=0.043. PON1 192QR genotype and 192R allele are risk factors for developing micro-vascular complications with OR =6.40 and 4.00; 95% CI [1.44.28.29] and [1.15-13.87] with p=0.01 and 0.023 respectively. In PON1 L55M polymorphism, non significant differences in the genotype or allele frequency were found between T TIDM, both complicated and non-complicated diabetics and control persons. The association of PON1 Q192R polymorphisms, lower PON1 activity and poorer diabetic control found in patients with diabetic nephropathy further support an idea of genetic factors contributing to development of vascular complications in diabetes

Effects of organophosphorus insecticides on G protein-coupled receptor kinase-2 mediated phosphorylation of M2 muscarinic receptors / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To explore the effect of organophosphorus insecticides (OPs) on G protein-coupled receptor kinase 2 mediated phosphorylation of M2 muscarinic receptors in vitro and to understand an alternative target of the OPs for human and other animals.</p><p><b>METHODS</b>The acetylcholine M2 muscarinic receptors (mAChR2) were purified from rat brain by single step affinity chromatography. In vitro experiments, the purified mAChR2, G-protein coupled receptor kinase 2 (GRK2) and the (gamma-p32) labeled ATP were incubated with paraoxon (PO), chlorpyrifos oxon (CPO) or chlorpyrifos (CPF) of varying concentrations. The proteins were separated by the polyacrylamide gel electrophoresis. The gels were dried and the phosphorylation of mAChR2 was detected with autoradiograms. Bands containing M2 receptor were excised and counted by liquid scintillation.</p><p><b>RESULTS</b>CPO inhibited phosphorylation of M2 muscarinic receptors by GRK2 with a median inhibition concentration (IC(50)) at 70 micromol/L. CPF also inhibited M2 receptors phosphorylation, but was less potent and less efficacious than that of CPO. PO and parathion (PT) had little effect on the receptor phosphorylation under the same conditions. CPO and CPF didn't inhibit the beta2 Adrenalin (beta2-AR) receptor phosphorylation also mediated by GRK2.</p><p><b>CONCLUSION</b>CPO and CPF can selectively inhibit the GRK2 mediated mAChR2 phosphorylation while PO and PT have no this effect.</p>

reactivation effect of pralidoxime in human blood on parathion and paraoxon-induced cholinesterase inhibition

In this investigation the reactivation of cholinesterases by pralidoxime in parathion and paraoxon intoxication in plasma and erythrocytes were studied. For this purpose, human plasma and erythrocytes were incubated with various concentrations of parathion [0.1-10 micro M] and paraoxon [0.03-0.3 micro M] at 37 °C for 10 min. Then, pralidoxime [10-300 micro M] was added to the samples and incubated for 10 min before cholinesterases assay. The results showed that effects of parathion and paraoxon were dose dependent. These agents inhibited more than 85% of butyrylcholinesterase [BChE] and acetylcholinesterase [AChE] activity and the inhibitory effect of paraoxon was 10 times more than parathion. BChE activity was significantly higher than the control at 100 micro M of pralidoxime and it reduced inhibitory effects of parathion to less than 50% and of paraoxon to 42% of control. When pralidoxime [10 micro M] was added to erythrocytes, the inhibitory effects of two organophosphates were reduced to less than 15%. At higher concentrations of pralidoxime [>100 micro M], both BChE and AChE activities were inhibited

Evaluation of antidotal effect of pralidoxime on prevention or reversal of a paraoxon- induced increasing response of chicken biventer cervices to electrical stimulation

One of the most toxic effects of organophosphate [OP] poisoning has been the paralysis of skeletal muscles that can lead to paralysis of respiratory muscles and death. However, oximes are the only antidotes available to reverse or prevent such toxic effects of OP insecticides and nerve chemical warfare agents. In the present study, the effect of different concentrations of paraoxon [as an OP] on the function of skeletal muscle and reversal or prevention of these effects by an oxime [pralidoxime, 2-PAM] were studied in chicken biventer cervices nerve-muscle preparation using twitch tension recording technique. For this purpose, twitches of the biventer cervices were evoked by stimulating the motor nerve at 0. 1 Hz with pulses of 0.2 msec duration and a voltage of greater than that required to produce maximum response. Twitches and contractures were recorded isotonically using Narco Biosystems. The results showed that paraoxon [0.1 micro M] induced a great increase [more than 100%] in the twitch amplitude, while higher concentrations [0.3 and 1 micro M] could induce partial or total contractures. In this study, paraoxon at a concentration of 0.1 micro M was used to examine the capability of pralidoxime to reverse or prevent its effects. Pralidoxime at doses of 300 and 100 micro M almost fully reversed [when it was used as post treatment] or prevented [when it was used as pretreatment or at the same time as toxin] the effect of paraoxon. While oxime at doses of 30 and 10 micro M could only reverse or reduce this effect to about 25 and 75% respectively, pralidoxime alone had no significant effect on the function of the muscle. These results suggest that this method is of high value in studying the functional effects of OPs on skeletal muscle tissues and the reversal effects of antidotes, and pralidoxime by itself can fully reverse such effects

Evaluation of the HI-6 ability on reversal or prevention of paraoxon-induced changes in the function of Chichen Biventer cervices nerve-muscle preparation

Paralysis of skeletal muscles,which can lead to paralysis of respiratory muscles and death, is one of the most toxic effects of organophosphates [Ops],and oximes are almost the only known antidotes that can reverse or prevent such toxic effects. In the present research work, possible reversal or preventive effect of different concentrations of the relatively new oxime [HI-6] on paraoxon-induced changes on function of skeletal muscle of chicken biventer cervices [CBC] nerve- muscle preparation were studied using twitch tension recording technique. This is experimental study. For this purpose,twitches of the CBC muscle were evoked by stimulating the motor nerve at 0.1 Hz with pulses of 0.2 msec duration and a voltage of greater than that required to produce the maximum response. Twitches were recorded isotonically using Narco Biosystem. Our prior findings revealed that paraoxon at a concentration of 0.1 micro M induces a significant increase [more than 100%] in the twitch amplitude, and therefore, this concentration was used to examine the efficacy of HI-6 to reverse or prevent such effects. HI-6 at 1000 micro M could almost fully reverse [when it was used as post treatment] or prevent [when it was used as pretreatment or at the same time as toxin] the effect of paraoxon. It could also reverse or reduce this effect to about 25%, 50% and 75% at 300,100 and 30 micro M, respectively. Furthermore, HI-6 at 10 micro M produced no significant preventive or reversal effect. However, HI-6 alone at 1000 micro M increased the twitch amplitude by about 20%.These data indicated that HI-6 could be recognized as an antidote of paraoxon, although it may have other effects at high concentrations

Serum paraoxonase level in Saudi obese people

The objective of this study is that, obese Saudi groups are prone to atherosclerosis more than non-obese due to lower level of serum paraoxonase activity. Patients and Sixty-two [62] subjects; 37 obese [19 males, 18 females] and 25 control groups [non-obese] [13 males, 12 females] at King Abdulaziz University Hospital, Jeddah, KSA - age range of 29 - 68 years. All obese groups have their body mass index [BMI] above 30. For both groups' complete medical examination was done, total cholesterol, triglycerides, LDL and HDL cholesterol, C-reactive protein and serum paraoxonase level was measured. Results showed that there was a significant difference in serum paraoxonase level, being much higher in non-obese groups compared to lower serum paraoxonase level in obese groups [p<0.05]. Serum paraoxonase is a marker of increasing susceptibility of the obese groups to atherosclerosis

Hydrolysis of organophosphorus compounds by an esterase isozyme from insecticide resistant pest Helicoverpa armigera.

Esterase activity of resistant and susceptible H. armigera were compared in gels with different substrate such as naphthyl acetate, naphthyl phosphate, paraoxon and monocrotophos. Whole body extract of resistant H. armigera hydrolyzed paraoxon, monocrotophos and naphthyl phosphate in gels. Resistant H. armigera showed high esterase, phosphatase and paraoxon hydrolase activity compared to susceptible ones.

Effect of paraoxon and chlorpyrifos on the nicotinic autoreceptor function in rat cortical synaptosomes / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To explore the effect of organophosphorus insecticides (OPs) on the nicotinic autoreceptor function (NAF) in rat cortical synaptosomes and to understand alternative target of the OPs for human and other animals.</p><p><b>METHODS</b>In vitro experiment, synaptosomes from the rats were incubated with [(3)H] choline and then superfused with physiological buffer. The [(3)H] acetylcholine release from the synaptosomes after the addition of paraoxon or chlorpyrifos to the superfusion system was recorded and the changes of NAF were calculated. In vivo experiment, NAF and acetylcholinesterase (AChE) activity in the cortical synaptosomes in the adult rats dosed with chlorpyrifos were also determined 96 h after OPs treatment.</p><p><b>RESULTS</b>Paraoxon caused slight effect on NAF (average inhibition rate: < 23%) while chlorpyrifos oxon caused > 100% of inhibition on NAF in vitro. Chlorpyrifos markedly reduced NAF by 66% 96 h after treatment and inhibited the AChE activity by 91% in vivo.</p><p><b>CONCLUSION</b>The OPs may have different effects on the NAF of rat cortical synaptosomes while chlorpyrifos may certainly inhibit the NAF in cortical synaptosomes of adult rats.</p>

Reactivation and aging of acetylcholinesterase in human brain inhibited by phoxim and phoxim oxon in vitro / 中华预防医学杂志

<p><b>OBJECTIVE</b>Inhibition of acetylcholinesterase (AChE) in human brain caused by phoxim or phoxim oxon, their reactivation with oxime and aging of phosphorylated AChE were studied and compared in vitro.</p><p><b>METHODS</b>Micro-colorispectrophotometric assay was used to determine the activity of AChE.</p><p><b>RESULTS</b>The pI(50) of inhibition of AChE in human brain by phoxim and phoxim oxon were 5.39 and 5.77, respectively, whereas the pI(90) were 4.60 and 5.00, respectively. The reactivation rate of 0.1 mmol/L of pralidoxime (2-PAM), obidoxime (LüH(6)), trimedoxime (TMB-4) and pyramidoxime (HI-6) for phoxim-inhibited AChE in human brain was 65%, 97%, 91% and 56%, respectively, and their reactivation rate for phoxim oxon-inhibited AChE in human brain was 97%, 87%, 99% and 89%, respectively. The optimal reactivator for phoxim and phoxim oxon-inhibited AChEs was LüH(6) and TMB-4, respectively. The half aging time of phoxim and phoxim oxon inhibited phosphorylated AChEs were 39 and 28 hours, respectively, and the 99% aging time were 256 and 186 hours, respectively.</p><p><b>CONCLUSIONS</b>LüH(6) or TMB-4 should be used at the earlier as possible after poisoning with phoxim and phoxim oxon, and the reactivator should be consecutively used for more than seven days, even after their acute symptoms have been well controlled.</p>

Efecto del parathion sobre el índice de apoptosis en hepatocitos de ratones CF1 / Effect of parathion on the apoptosis of CF1 mouse hepatocytes

El las últimas décadas el uso masivo de agropesticidas órganofosforados, como Parathion y Malathion, ha permitido el control de plagas en la producción hortofrutícola, mejorando la productividad e incrementando la oferta de alimentos de mayor calidad. Sin embargo, pese a su efectividad, estos compuestos químicos son potenciales causantes de daños morfológicos y genéticos, de alto riesgo para la Salud Humana y animal (Draper, 1985; Rodríguez y Bustos-Obregón, 2000). El parathion© (PT), inhibidor de la aceltilcolinesterasa, se metaboliza en hígado, pulmón y cerebro. El efecto tóxico se debe a un proceso de desulfuración oxidativa hepática, que transforma el PT en paraoxon (PO), siendo éste su metabolito activo (Chambers y Chambers, 1990; Siller et al., 1997). El objetivo del presente trabajo es evaluar los efectos de una dosis única de PT sobre los índices de apoptosis en hepatocitos de ratón CFI. Se usaron ratones macho CFI de 8 a 10 semanas, con un peso promedio de 30 g, a los cuales se les aplicó una dosis intraperitoneal única de PT de 20 mg/Kg de peso (Sobarzo y Bustos-Obregón, 2000). Posteriormente fueron sacrificados a 1, 8, 16, 28 y 50 días postratamiento. El análisis histológico del hígado se realizó mediante microscopía óptica sobre cortes teñidos con hematoxilina/eosina en que se analizó la presencia y frecuencia de hepatocitos apoptóticos. Los resultados obtenidos permiten demostrar el efecto del PT sobre el hepatocito con un aumento estadísticamente significativo de apoptosis. Se postula que el PT es carcinogénico, que bloquea o modifica la capacidad de replicación de los hepatocitos, alterando la susceptibilidad del tejido hepático (Fausto, 2000; Metcalfe y Streuli, 1997). Se concluye que el PT tiene un efecto tóxico, aún en dosis consideradas bajas, aumentando significativamente los índices de eventos apoptóticos, alterando el ciclo celular y afectando la histofisiología del tejido hepático

Paraoxonase activity and its phenotype distribution in patients with chronic renal failure and its relationship to atherosclerotic vascular diseases

Serum paraoxonase [PON[1]] is a high-density lipoprotein [HDL] associated esterase with a hypothesized role in the protection of low density lipoprotein [LDL] from oxidative stress perhaps by hydrolysing phospholipid - hydroperoxides. The present study was designed to determine the activity and phenotype distribution of serum PON[1] in patients with chronic renal failure [CRF], to elucidate the effect of regular hemodialysis on the activity of this enzyme, and hence to assess whether changes in PON[I] activity might contribute to the accelerated development of atherosclerosis. The study included 60 unrelated patients with CRF on conservative management and in need of dialysis. They were 48 males and 12 females with a mean age of 43.8 +/- 9.2 years, 22 of them had evidence of stable cardiovascular disease [CVD] and the remaining 38 had no evidence of clinical or subclinical CVD. Thirty, sex- and age-matched unrelated apparently healthy subjects served as controls. The enzyme activities were measured spectrophotometrically with paraoxon and phenylacetate as substrate for paraoxonase and arylesterase respectively with estimation of phenotype distribution. The serum PON[1] activities and phenotype distribution were determined in all subjects after inclusion in the study with another determination of serum PON[1] activity in all patients after 6 months of regular hemodialysis.Before dialysis, the serum PON[1] activity was significantly lower in CRF patients with CVD than in CRF patients without CVD [P < 0.01] and in CRF patients without CVD than in controls [P < 0.001].To assess whether the altered PON[1] activity was due to decrease in HDL or apolipoprotein A[1] [apo-A[1]] levels. The enzyme activity for the HDL [PON[1] / HDL ratio] and apo-A[1] concentrations [PON[1] / apo-A[1] ratio] were standardized.We found that both ratios were significantly lower in CRF patients than in controls [P < 0.001] and in CRF patients with CVD than in CRF patients without this disease [P < 0.01] After 6 months of regular hemodialysis, serum PON[1] activity was significantly decreased in CRF patients with and without CVD compared with before dialysis [P < 0.001, P < 0.05, respectively].It was found that PON[1] activity was trimodally distributed and no significant difference in phenotype distribution was found between the different studied groups. In conclusion, the reduced PON[1] activity in patients with CRF particularly those with CVD, either before or after 6 months of regular hemodialysis, may give rise to decreased HDL antioxidant capacity. LDL modification by lipid peroxidation might therefore be increased, contributing to the accelerated development of atherosclerosis. Interventions that preserve or enhance PON[1] activity have to be examined in future studies

Morphofunctional disturbances of human sperm after incubation with organophosphorate pesticides

The organophosphorate pesticides are highly toxic for insects and mammals, but their effects in the male reproductive tract are scarcely known. Many alterations induced by organophosphorate pesticides have been described, such as: cytogenetic alterations in germinal cells, oligozoospermia and teratozoospermia in the mouse. Parathion, the pesticide mostly utilized in Chilean agriculture, is rapidly metabolized to paraoxon, the active metabolite, in mammalian organisms. The purpose of this study is to evaluate the effect of Parathion and paraoxon on different morphological and functional parameters of the sperm. Human spermatozoa were incubated with Parathion and paraoxon at different concentrations (0.05, 0.1, 0.2, 0.4 and 0.8 mM). Vitality (tripan blue and eosin tests), acrosome reaction (triple stain test), plasma membrane integrity (HOS-test), and chromatin stability (sodium thioglycolate test) were determined. The observations were done by optical microscopy at 1000x of magnification and three hundred sperms were evaluated for each treatment. The results indicated that Parathion and paraoxon increase the percent of sperm with acrosome reaction and also increase the percentage of sperm with chromatin decondensation in a dose-dependent manner. The vitality and plasma membrane integrity decrease significantly in a dose-dependent manner. The results suggest a direct action of Parathion and paraoxon on the different parameters studied. The morphofunctionality of sperm is altered significatively, suggesting that Parathion and paraoxon, thanks to their alkylating and electrophylic properties, could act on DNA and proteins respectively, to elicit these changes