Antidotal Action of Some Gold(I) Complexes toward Phosphine Toxicity.

Phosphine (PH3) poisoning continues to be a serious problem worldwide, for which there is no antidote currently available. An invertebrate model for examining potential toxicants and their putative antidotes has been used to determine if a strategy of using Au(I) complexes as phosphine-scavenging compounds may be antidotally beneficial. When Galleria mellonella larvae (or wax worms) were subjected to phosphine exposures of 4300 (±700) ppm·min over a 20 min time span, they became immobile (paralyzed) for ∼35 min. The administration of Au(I) complexes auro-sodium bisthiosulfate (AuTS), aurothioglucose (AuTG), and sodium aurothiomalate (AuTM) 5 min prior to phosphine exposure resulted in a drastic reduction in the recovery time (0-4 min). When the putative antidotes were given 10 min after the phosphine exposure, all the antidotes were therapeutic, resulting in mean recovery times of 14, 17, and 19 min for AuTS, AuTG, and AuTM, respectively. Since AuTS proved to be the best therapeutic agent in the G. mellonella model, it was subsequently tested in mice using a behavioral assessment (pole-climbing test). Mice given AuTS (50 mg/kg) 5 min prior to a 3200 (±500) ppm·min phosphine exposure exhibited behavior comparable to mice not exposed to phosphine. However, when mice were given a therapeutic dose of AuTS (50 mg/kg) 1 min after a similar phosphine exposure, only a very modest improvement in performance was observed.

Electrophysiological and molecular mechanisms of protection by iron sucrose against phosphine-induced cardiotoxicity: a time course study.

The present study was designed for determining the exact mechanism of cytotoxic action of aluminum phosphide (AlP) in the presence of iron sucrose as the proposed antidote. Rats received AlP (12 mg/kg) and iron sucrose (5-30 mg/kg) in various sets and were connected to cardiovascular monitoring device. After identification of optimum doses of AlP and iron sucrose, rats taken in 18 groups received AlP (6 mg/kg) and iron sucrose (10 mg/kg), treated at six different time points, and then their hearts were surgically removed and used for evaluating a series of mitochondrial parameters, including cell lipid peroxidation, antioxidant power, mitochondrial complex activity, ADP/ATP ratio and process of apoptosis. ECG changes of AlP poisoning, including QRS, QT, P-R, ST, BP and HR were ameliorated by iron sucrose (10 mg/kg) treatment. AlP initiated its toxicity in the heart mitochondria through reducing mitochondrial complexes (II, IV and V), which was followed by increasing lipid peroxidation and the ADP/ATP ratio and declining mitochondrial membrane integrity that ultimately resulted in cell death. AlP in acute exposure (6 mg/kg) resulted in an increase in hydroxyl radicals and lipid peroxidation in a time-dependent fashion, suggesting an interaction of delivering electrons of phosphine with mitochondrial respiratory chain and oxidative stress. Iron sucrose, as an electron receiver, can compete with mitochondrial respiratory chain complexes and divert electrons to another pathway. The present findings supported the idea that iron sucrose could normalize the activity of mitochondrial electron transfer chain and cellular ATP level as vital factors for cell escaping from AlP poisoning.

Phosphine-induced oxidative damage in rats: attenuation by melatonin.

Phosphine (PH(3)), from hydrolysis of aluminum, magnesium and zinc phosphide, is an insecticide and rodenticide. Earlier observations on PH(3)-poisoned insects, mammals and a mammalian cell line led to the proposed involvement of oxidative damage in the toxic mechanism. This investigation focused on PH(3)-induced oxidative damage in rats and antioxidants as candidate protective agents. Male Wistar rats were treated ip with PH(3) at 2 mg/kg. Thirty min later the brain, liver, and lung were analyzed for glutathione (GSH) levels and lipid peroxidation (as malondialdehyde and 4-hydroxyalkenals) and brain and lung for 8-hydroxydeoxyguanosine (8-OH-dGuo) in DNA. PH(3) caused a significant decrease in GSH concentration and elevation in lipid peroxidation in brain (36-42%), lung (32-38%) and liver (19-25%) and significant increase of 8-OH-dGuo in DNA of brain (70%) and liver (39%). Antioxidants administered ip 30 min before PH(3) were melatonin, vitamin C, and beta-carotene at 10, 30, and 6 mg/kg, respectively. The PH(3)-induced changes were significantly or completely blocked by melatonin while vitamin C and beta-carotene were less effective or inactive. These findings establish that PH(3) induces and melatonin protects against oxidative damage in the brain, lung and liver of rats and suggest the involvement of reactive oxygen species in the genotoxicity of PH(3).

Protective effects of N-acetylcysteine on aluminum phosphide-induced oxidative stress in acute human poisoning.

OBJECTIVE: Aluminum phosphide is used as a fumigant. It produces phosphine gas (PH3). PH3 is a mitochondrial poison which inhibits cytochrome c oxidase, it leads to generation of reactive oxygen species; so one of the most important suggested mechanisms for its toxicity is induction of oxidative stress. In this regard, it could be proposed that a drug like N-acetylcysteine (NAC) as an antioxidant would improve the tolerance of aluminum phosphide-intoxicated cases. The objective of this study was to evaluate the protective effects of NAC on acute aluminum phosphide poisoning. METHODS: This was a prospective, randomized, controlled open-label trial. All patients received the same supportive treatments. NAC treatment group also received NAC. The blood thiobarbituric acid reactive substances as a marker of lipid peroxidation and total antioxidant capacity of plasma were analyzed. RESULTS: Mean ingested dose of aluminum phosphide in NAC treatment and control groups was 4.8 ± 0.9 g vs. 5.4 ± 3.3 g, respectively (p = 0.41). Significant increase in plasma malonyldialdehyde level in control group was observed (139 ± 28.2 vs. 149.6 ± 35.2 µmol/L, p = 0.02). NAC infusion in NAC treatment group significantly decreased malondialdehyde level (195.7 ± 67.4 vs. 174.6 ± 48.9 µmol/L, p = 0.03), duration of hospitalization (2.7 ± 1.8 days vs. 8.5 ± 8.2 days, p = 0.02), rate of intubation and ventilation (45.4% vs. 73.3%, p = 0.04). Mortality rate in NAC treatment and control groups were 36% and 60%, respectively with odds ratio 2.6 (0.7-10.1, 95% CI). CONCLUSION: NAC may have a therapeutic effect in acute aluminum phosphide poisoning.

Melatonin reduces phosphine-induced lipid and DNA oxidation in vitro and in vivo in rat brain.

Phosphine (PH(3)), a widely used pesticide, was found in our recent study to induce oxidative damage in the brain, liver and lung of rats. We also observed that melatonin significantly blocked this action. The present study focused on brain and the magnitude and mechanism of protection of PH(3)-induced oxidative damage by melatonin in vitro and in vivo. PH(3) in whole brain homogenate (3 mg protein/mL Tris-HCl pH 7.4 buffer) induced increasing lipid peroxidation [as malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA)] dependent on concentration (0.25-2 mM) and time (30-150 min), reaching a maximum level of 2.9-fold at 90 min after PH(3) at 1 mM. Elevation of MDA + 4-HDA levels by PH(3) at 1 mM was also observed in homogenates of cerebral cortex, cerebellum, hippocampus and hypothalamus examined individually. Melatonin at 0.1-2 mM progressively inhibited PH(3)-induced lipid peroxidation in brain and regions thereof. Additionally, PH(3) induced brain DNA oxidation in vitro and in vivo determined as 8-hydroxyguanosine (8-OH-dG). Melatonin at 1 mM significantly suppressed PH(3)-induced brain DNA oxidation in vitro. PH(3) at 4 mg/kg i.p. significantly elevated 8-OH-dG in frontal cortex and melatonin prevented it. PH(3) in vivo marginally lowered brain glutathione peroxidase activity and melatonin restored it completely. In contrast, PH(3) and melatonin both stimulated superoxide dismutase production. Brain glutathione (GSH) levels in PH(3)-treated rats were significantly reduced at 30 min and recovered gradually. It is concluded that melatonin, probably because of its free radical scavenging ability, confers marked protection against PH(3)-induced oxidative toxicity in brain.

Effect of N-acetylcysteine and L-NAME on aluminium phosphide induced cardiovascular toxicity in rats.

AIM: To investigate the protective effects of N-acetylcysteine (NAC) and Nomega-Nitro-L-arginine methyl ester (L-NAME) on aluminium phosphide (AlP) poisoning induced hemodynamic changes, myocardial oxygen free radical injury and on survival time in rats. METHODS: AlP (12.5 mg/kg) was administered intragastrically under urethane anaesthesia. The effect of pre- and post-treatment with NAC and L-NAME alone and in combination was studied on haemodynamic parameters [blood pressure (BP), heart rate (HR), and electrocardiogram (ECG)] and biochemical parameters (malonyldialdehyde, catalase, and glutathione peroxidase). RESULTS: AlP caused significant hypotension, tachycardia, ECG abnormalities, and finally marked bradycardia. The mean survival time was (90 +/- 10) min. There was significant increase in myocardial malonyldialdehyde (MDA), and decrease in catalase and glutathione peroxidase (GSH Px) levels. NAC infusion (6.25 mg . kg-1 . min-1, iv for 30 min) caused insignificant hemodynamic and biochemical changes. Pre- and post-treatment of NAC with AlP significantly increased the survival time, stabilized BP, HR, and ECG, decreased MDA and increased GSH Px levels compared to AlP group. L-NAME infusion (1 mg . kg-1 . min-1, iv for 60 min) as such caused significant rise in BP but precipitated ECG abnormalities. Pre- and post-treatment of L-NAME with AlP neither improved the survival time nor the biochemical parameters despite significant rise in BP. Co-administration of both the drugs with AlP worsened the hemodynamic and biochemical parameters with reduction in the survival time as compared to AlP. CONCLUSION: NAC increased the survival time by reducing myocardial oxidative injury whereas L-NAME showed no such protective effects in rats exposed to AlP.