Synthesis and preliminary biological evaluation of gabactyzine, a benactyzine-GABA mutual prodrug, as an organophosphate antidote.

Organophosphates (OPs) are inhibitors of acetylcholinesterase and have deleterious effects on the central nervous system. Clinical manifestations of OP poisoning include convulsions, which represent an underlying toxic neuro-pathological process, leading to permanent neuronal damage. This neurotoxicity is mediated through the cholinergic, GABAergic and glutamatergic (NMDA) systems. Pharmacological interventions in OP poisoning are designed to mitigate these specific neuro-pathological pathways, using anticholinergic drugs and GABAergic agents. Benactyzine is a combined anticholinergic, anti-NMDA compound. Based on previous development of novel GABA derivatives (such as prodrugs based on perphenazine for the treatment of schizophrenia and nortriptyline against neuropathic pain), we describe the synthesis and preliminary testing of a mutual prodrug ester of benactyzine and GABA. It is assumed that once the ester crosses the blood-brain-barrier it will undergo hydrolysis, releasing benactyzine and GABA, which are expected to act synergistically. The combined release of both compounds in the brain offers several advantages over the current OP poisoning treatment protocol: improved efficacy and safety profile (where the inhibitory properties of GABA are expected to counteract the anticholinergic cognitive adverse effects of benactyzine) and enhanced chemical stability compared to benactyzine alone. We present here preliminary results of animal studies, showing promising results with early gabactyzine administration.

Prevention of organophosphate-induced chronic epilepsy by early benzodiazepine treatment.

Poisoning with organophosphates (OPs) may induce status epilepticus (SE), leading to severe brain damage. Our objectives were to investigate whether OP-induced SE leads to the emergence of spontaneous recurrent seizures (SRSs), the hallmark of chronic epilepsy, and if so, to assess the efficacy of benzodiazepine therapy following SE onset in preventing the epileptogenesis. We also explored early changes in hippocampal pyramidal cells excitability in this model. Adult rats were poisoned with the paraoxon (450µg/kg) and immediately treated with atropine (3mg/kg) and obidoxime (20mg/kg) to reduce acute mortality due to peripheral acetylcholinesterase inhibition. Electrical brain activity was assessed for two weeks during weeks 4-6 after poisoning using telemetric electrocorticographic intracranial recordings. All OP-poisoned animals developed SE, which could be suppressed by midazolam. Most (88%) rats which were not treated with midazolam developed SRSs, indicating that they have become chronically epileptic. Application of midazolam 1min following SE onset had a significant antiepileptogenic effect (only 11% of the rats became epileptic; p=0.001 compared to non-midazolam-treated rats). Applying midazolam 30min after SE onset did not significantly prevent chronic epilepsy. The electrophysiological properties of CA1 pyramidal cells, assessed electrophysiologically in hippocampal slices, were not altered by OP-induced SE. Thus we show for the first time that a single episode of OP-induced SE in rats leads to the acquisition of chronic epilepsy, and that this epileptogenic outcome can be largely prevented by immediate, but not delayed, administration of midazolam. Extrapolating these results to humans would suggest that midazolam should be provided together with atropine and an oxime in the immediate pharmacological treatment of OP poisoning.

Improved triclosan delivery by a novel silica-based nanocomposite.

In this study, we report on the design, synthesis, and full characterization of a covalently-linked, triclosan silica-based nanoparticles (T-SNPs), coated with a polyaminated shell (NH2 -T-SNPs). Various techniques are used to elucidate and rationalize the potential biological mechanism of action of these novel nanoparticles. NH2 -T-SNPs are found to be potently bactericidal with no detectable lag time for the antimicrobial activity against E. coli and S. aureus. In this context, we also prove that triclosan is the chemical agent that mediated the bactericidal activity of these chemically-modified NPs. The obtained experimental data allows us to pinpoint the actual minimal bactericidal concentrations (MBCs) of triclosan-bound NPs by quantifying intracellular triclosan concentrations. Furthermore, we conduct preliminary cytotoxicity studies, which show that triclosan bound NPs are less cytotoxic (2000 fold) in vitro compared to free-triclosan when tested with various human and mammalian cell lines. Taken together, our results further support the characterization and development of these new nanoscale materials for various biomedical applications.

Early in vivo MR spectroscopy findings in organophosphate-induced brain damage-potential biomarkers for short-term survival.

Organophosphates are highly toxic substances, which cause severe brain damage. The hallmark of the brain injury is major convulsions. The goal of this study was to assess the spatial and temporal MR changes in the brain of paraoxon intoxicated rats. T2-weighted MRI and ¹H-MR-spectroscopy were conducted before intoxication, 3 h, 24 h, and 8 days postintoxication. T2 prolongation mainly in the thalami and cortex was evident as early as 3 h after intoxication (4-6% increase in T2 values, P < 0.05). On spectroscopy, N-acetyl aspartate (NAA)/creatine and NAA/choline levels significantly decreased 3 h postintoxication (>20% decrease, P < 0.005), and 3 h lactate peak was evident in all intoxicated animals. On the 8th day, although very little T2 changes were evident, NAA/creatine and choline/creatine were significantly decreased (>15%, P < 0.05). Animals who succumbed had extensive cortical edema, significant higher lactate levels and a significant decrease in NAA/creatine and NAA/choline levels compared to animals which survived the experiment. Organophosphates-induced brain damage is obvious on MR data already 3 h postintoxication. In vivo spectroscopic changes are more sensitive for assessing long-term injury than T2-weighted MR imaging. Early spectroscopic findings might be used as biomarkers for the severity of the intoxication and might predict early survival.

Carbamate poisoning: treatment recommendations in the setting of a mass casualties event.

The threat of using chemical compounds by terrorists as weapons of mass casualties has been a rising concern in recent years. Carbamates, a group of reversible acetylcholinesterase inhibitors, could be potentially involved in such toxic mass casualty events because they can cause cholinergic crisis that could lead to fatality, similar to that of organophosphate poisoning. The medical management of carbamate poisoning consists of supportive measures and specific antidotal treatment, that is, the anticholinergic compound atropine. The administration of oximes, acetylcholinesterase reactivators, in carbamate poisoning is controversial because of the potential toxicity of oximes in conjunction with carbamate especially in the case of the carbamate--"carbaryl" poisoning. However, recent data suggest that this concern may be unwarranted. In this article, we review the current data regarding the pros and cons of using oximes against carbamates poisoning in a mass casualties event scenario. We also propose a new decision-making algorithm for the medical first responders in a mass casualties event suspected to be caused by a cholinergic substance (organophosphate or carbamate). According to this algorithm, treatment should consist of atropine and oxime regardless of the exact toxic compound involved. We speculate that in a mass casualties event, the benefits of using oximes outweigh the low level of potential risk.

Ammonia--when something smells wrong.

Ammonia is a common household and industrial chemical. In the medical literature and the electronic press there are many descriptions of accidental spills of anhydrous ammonia, but apart from the Chechen war, there is no evidence of its intentional use by a terrorist to date. When considering its characteristics, ammonia tankers may pose an imminent threat for a civilian population nearby. This short review attempts to highlight the main health issues and basic principles of medical management after exposure to ammonia. Ammonia can directly cause damage due to its irritating as well as alkaline properties. The management of toxic exposure to ammonia is largely supportive and there is no specific antidote. Emergency medical response on site includes rapid evacuation, life-saving procedures and decontamination if necessary and if possible. Major clinical manifestations include respiratory symptoms, such as hypoxia, bronchospasm and pulmonary edema, as well as hypovolemia and burns to the skin and eyes. The immediate medical management consists of life-saving procedures and supportive care, while broad-range antibiotics and systemic corticosteroids may have a role in preventing late onset complications.

Hydrogen fluoride--the protoplasmic poison.

HF is a corrosive mineral acid. It has extremely harmful systemic effects through any route of exposure. In dilute solutions the onset of symptoms is latent. It is important for caregivers to remember that HF has distinct clinical signs and a specific antidote, namely calcium gluconate. The industrial use of HF heightens the importance of being prepared for possible exposures. The emergency medical teams should be familiar with its symptoms, should possess the proper protective means and should be ready to respond properly in case of emergency.

Hydrazine--the space era agent.

Hydrazine is considered a dangerous toxic compound. It is flammable, easily ignitable and may explode upon contact with different materials, including clothing. As a volatile liquid, it affects mainly the upper respiratory tract, mucous membranes and skin. The characteristics and availability of this agent warrant our attention. Medical personnel should be familiar with its properties, major health effects and the treatment needed. The key principles in treating hydrazine victims include protection from further exposure and aggressive antidotal treatment with pyridoxine (vitamin B6), as well as supportive treatment as required. Finally, medical teams should also be equipped with the proper protection measures (appropriate suits, gloves and breathing apparatuses) in order to avoid secondary exposure of themselves and others.

Novel prodrugs of tegafur that display improved anticancer activity and antiangiogenic properties.

New and more potent prodrugs of the 5-fluorouracyl family derived by hydroxymethylation or acyloxymethylation of 5-fluoro-1-(tetrahydro-2-furanyl)-2,4(1H,3H)-pyrimidinedione (tegafur, 1) are described. The anticancer activity of the butyroyloxymethyl-tegafur derivative 3 and not that of tegafur was attenuated by the antioxidant N-acetylcysteine, suggesting that the increased activity of the prodrug is in part mediated by an increase of reactive oxygen species. Compound 3 in an in vitro matrigel assay was found to be a more potent antiangiogenic agent than tegafur. In vivo 3 was significantly more potent than tegafur in inhibiting 4T1 breast carcinoma lung metastases and growth of HT-29 human colon carcinoma tumors in a mouse xenograft. In summary, the multifunctional prodrugs of tegafur display selectivity toward cancer cells, antiangiogenic activity, and anticancer activities in vitro and in vivo, superior to those of tegafur. 5-fluoro-1-(tetrahydro-2-furanyl)-2,4(1 H,3 H)-pyrimidinedione (tegafur, 1), the oral prodrug of 5-FU, has been widely used for treatment of gastrointestinal malignancies with modest efficacy. The aim of this study was to develop and characterize new and more potent prodrugs of the 5-FU family derived by hydroxymethylation or acyloxymethylation of tegafur. Comparison between the effect of tegafur and the new prodrugs on the viability of a variety of cancer cell lines showed that the IC50 and IC90 values of the novel prodrugs were 5-10-fold lower than those of tegafur. While significant differences between the IC50 values of tegafur were observed between the sensitive HT-29 and the resistant LS-1034 colon cancer cell lines, the prodrugs affected them to a similar degree, suggesting that they overcame drug resistance. The increased potency of the prodrugs could be attributed to the antiproliferative contribution imparted by formaldehyde and butyric acid, released upon metabolic degradation. The anticancer activity of the butyroyloxymethyl-tegafur derivative 3 and not that of tegafur was attenuated by the antioxidant N-acetylcysteine, suggesting that the increased activity of the prodrug is in part mediated by an increase of reactive oxygen species. Compound 3 in an in vitro matrigel assay was found to be a more potent antiangiogenic agent than tegafur. In vivo 3 was significantly more potent than tegafur in inhibiting 4T1 breast carcinoma lung metastases and growth of HT-29 human colon carcinoma tumors in a mouse xenograft. In summary, the multifunctional prodrugs of tegafur display selectivity toward cancer cells, antiangiogenic activity and anticancer activities in vitro and in vivo, superior to those of tegafur.

Osmium tetroxide: a new kind of weapon.

OsO4 is a powerful oxidizer. It affects mainly the skin and mucous membranes. Although unsuitable for a large-scale terrorist attack, mainly due to its scarcity, it could be used in small-scale attacks. The small quantity contained in a vial would cause irritation to the eyes, nose, throat and skin. Combining the agent with an explosive material will probably destroy most of it, chemically. Thus, releasing the chemical without using explosives may be considerably more dangerous. Medical management is mainly symptomatic. As soon as the chemical enters the body, it rapidly reacts with the tissues in contact. Medical personnel should be aware of its poisonous effects and be equally familiar with the necessary self-protection measures and the treatment protocols.

Bromine--the red cloud approaching.

Bromine is a strong and prevalent irritating agent that can spread both as liquid and as fumes. It has a characteristic reddish-brown color. The mainstay of the medical management is supportive and symptomatic therapy that should be given as soon as possible to prevent further damage. Medical personnel, especially the emergency department staff, should be familiar with its health effects, including the safety precautions needed when caring for casualties following such an exposure.