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- Belladonna Alkaloid Intoxication: The 10-Year Experience of a Large Tertiary Care Pediatric Hospital. [JOURNAL ARTICLE]
- Am J Ther 2013 Nov 20.
The belladonna alkaloids can be isolated from a number of plants, which contain hallucinogens that represent a serious danger to infants, children, and adolescents. Roots, leaves, and fruits of the plant contain the alkaloids atropine, hyoscyamine, and scopolamine, which can lead to an anticholinergic toxidrome; however, not all characteristics of the toxidrome are necessarily present in each case of poisoning. A retrospective chart review of all children seen following anticholinergic ingestions, between April 2001 and November 2010, at the Hospital for Sick Children in Toronto. Ten children, with a mean age of 15.5 years (range, 15-18 years), were identified; 5 had used jimsonweed and the others had a variety of tablets containing atropine. All 10 presented with severe anticholinergic symptoms and 2 with suicide attempts. Treatments included charcoal, benzodiazepines, haloperidol, and physostigmine, and 2 patients were intubated. Ingestion and subsequent severe anticholinergic toxidrome occurred exclusively in adolescents. It is important to educate this age group regarding the toxicity and potential risks associated with the recreational use of these plants and substances. Physostigmine can help in both the diagnosis and management of patients intoxicated with these substances.
- Alkaloids as a source of potential anticholinesterase inhibitors for the treatment of Alzheimer's disease. [Journal Article]
- J Pharm Pharmacol 2013 Dec; 65(12):1701-25.
The inhibition of acetylcholinesterase (AChE), the key enzyme in the breakdown of acetylcholine, is currently the main pharmacological strategy available for Alzheimer's disease (AD). In this sense, many alkaloids isolated from natural sources, such as physostigmine, have been long recognized as acetyl- and butyrylcholinesterase (BChE) inhibitors. Since the approval of galantamine for the treatment of AD patients, the search for new anticholinesterase alkaloids has escalated, leading to promising candidates such as huperzine A. This review aims to summarize recent advances in current knowledge on alkaloids as AChE and BChE inhibitors, highlighting structure-activity relationship (SAR) and docking studies.Natural alkaloids belonging to the steroidal/triterpenoidal, quinolizidine, isoquinoline and indole classes, mainly distributed within Buxaceae, Amaryllidaceae and Lycopodiaceae, are considered important sources of alkaloids with anti-enzymatic properties. Investigations into the possible SARs for some active compounds are based on molecular modelling studies, predicting the mode of interaction of the molecules with amino acid residues in the active site of the enzymes. Following this view, an increasing interest in achieving more potent and effective analogues makes alkaloids good chemical templates for the development of new cholinesterase inhibitors.The anticholinesterase activity of alkaloids, together with their structural diversity and physicochemical properties, makes them good candidate agents for the treatment of AD.
- Nature as a source of metabolites with cholinesterase-inhibitory activity: an approach to Alzheimer's disease treatment. [Journal Article]
- J Pharm Pharmacol 2013 Dec; 65(12):1681-700.
Alzheimer's disease (AD) is the most common cause of dementia, being responsible for high healthcare costs and familial hardships. Despite the efforts of researchers, no treatment able to delay or stop AD progress exists. Currently, the available treatments are only symptomatic, cholinesterase inhibitors being the most widely used drugs. Here we describe several natural compounds with anticholinesterase (acetylcholinesterase and butyrylcholinesterase) activity and also some synthetic compounds whose structures are based on those of natural compounds.Galantamine and rivastigmine are two cholinesterase inhibitors used in therapeutics: galantamine is a natural alkaloid that was extracted for the first time from Galanthus nivalis L., while rivastigmine is a synthetic alkaloid, the structure of which is modelled on that of natural physostigmine. Alkaloids include a high number of compounds with anticholinesterases activity at the submicromolar range. Quinones and stilbenes are less well studied regarding cholinesterase inhibition, although some of them, such as sargaquinoic acid or (+)-α-viniferin, show promising activity. Among flavonoids, flavones and isoflavones are the most potent compounds. Xanthones and monoterpenes are generally weak cholinesterase inhibitors.Nature is an almost endless source of bioactive compounds. Several natural compounds have anticholinesterase activity and others can be used as leader compounds for the synthesis of new drugs.
- Unusual Acetylation-Dependent Reaction Cascade in the Biosynthesis of the Pyrroloindole Drug Physostigmine. [JOURNAL ARTICLE]
- Angew Chem Int Ed Engl 2013 Nov 13.
Physostigmine is a parasympathomimetic drug used to treat a variety of neurological disorders, including Alzheimer's disease and glaucoma. Because of its potent biological activity and unique pyrroloindole skeleton, physostigmine has been the target of many organic syntheses. However, the biosynthesis of physostigmine has been relatively understudied. In this study, we identified a biosynthetic gene cluster for physostigmine by genome mining. The 8.5 kb gene cluster encodes eight proteins (PsmA-H), seven of which are required for the synthesis of physostigmine from 5-hydroxytryptophan, as shown by in vitro total reconstitution. Further genetic and enzymatic studies enabled us to delineate the biosynthetic pathway for physostigmine. The pathway features an unusual reaction cascade consisting of highly coordinated methylation and acetylation/deacetylation reactions.
- Pharmacological Cholinergic Stimulation as a Therapeutic Tool in Experimental Necrotizing Pancreatitis. [JOURNAL ARTICLE]
- Pancreas 2013 Nov 7.
The endogenous immune response is influenced by the stimulation of the vagal nerve. Stimulation or ablation has a direct impact on the release of pro- and anti-inflammatory mediators. In the progression of acute pancreatitis from local to systemic disease, these mediators play a pivotal role. This study evaluates the effect of pharmacologic stimulation of the cholinergic system on pancreatic damage in experimental necrotizing pancreatitis.Experimental severe necrotizing pancreatitis was induced in male Wistar rats using the glycodeoxycholic acid model. Animals with acute pancreatitis (n = 6) were compared with animals with acute pancreatitis and prophylactic or therapeutic pharmacologic activation of the cholinergic system using nicotine, physostigmine, or neostigmine (n = 36). Twelve hours after the induction of acute pancreatitis, morphological damage as well as the myeloperoxidase levels of the pancreas and the serum levels of high-mobility group box 1 protein were evaluated.Prophylactic and delayed therapeutic application of nicotine, physostigmine, or neostigmine significantly attenuated the severity of acute pancreatitis 12 hours after the induction of severe necrotizing pancreatitis compared with untreated controls as evaluated with histological scores, myeloperoxidase, and high-mobility group box 1 levels (P < 0.05).Stimulation of the cholinergic system is useful to attenuate damage in experimental acute pancreatitis. Not only prophylactic but also delayed application was effective in the present study.
- The toxicology investigators consortium case registry-the 2012 experience. [Journal Article]
- J Med Toxicol 2013 Dec; 9(4):380-404.
In 2010, the American College of Medical Toxicology (ACMT) established its Case Registry, the Toxicology Investigators Consortium (ToxIC). All cases are entered prospectively and include only suspected and confirmed toxic exposures cared for at the bedside by board-certified or board-eligible medical toxicologists at its participating sites. The primary aims of establishing this Registry include the development of a realtime toxico-surveillance system in order to identify and describe current or evolving trends in poisoning and to develop a research tool in toxicology. ToxIC allows for extraction of data from medical records from multiple sites across a national and international network. All cases seen by medical toxicologists at participating institutions were entered into the database. Information characterizing patients entered in 2012 was tabulated and data from the previous years including 2010 and 2011 were included so that cumulative numbers and trends could be described as well. The current report includes data through December 31st, 2012. During 2012, 38 sites with 68 specific institutions contributed a total of 7,269 cases to the Registry. The total number of cases entered into the Registry at the end of 2012 was 17,681. Emergency departments remained the most common source of consultation in 2012, accounting for 61 % of cases. The most common reason for consultation was for pharmaceutical overdose, which occurred in 52 % of patients including intentional (41 %) and unintentional (11 %) exposures. The most common classes of agents were sedative-hypnotics (1,422 entries in 13 % of cases) non-opioid analgesics (1,295 entries in 12 % of cases), opioids (1,086 entries in 10 % of cases) and antidepressants (1,039 entries in 10 % of cases). N-acetylcysteine (NAC) was the most common antidote administered in 2012, as it was in previous years, followed by the opioid antagonist naloxone, sodium bicarbonate, physostigmine and flumazenil. Anti-crotalid Fab fragments were administered in 109 cases or 82 % of cases in which a snake envenomation occurred. There were 57 deaths reported in the Registry in 2012. The most common associated agent alone or in combination was the non-opioid analgesic acetaminophen, being reported in 10 different cases. Other common agents and agent classes involved in death cases included ethanol, opioids, the anti-diabetic agent metformin, sedatives-hypnotics and cardiovascular agents, in particular amlodipine. There were significant trends identified during 2012. Abuse of over-the-counter medications such as dextromethorphan remains prevalent. Cases involving dextromethorphan continued to be reported at frequencies higher than other commonly abused drugs including many stimulants, phencyclidine, synthetic cannabinoids and designer amphetamines such as bath salts. And, while cases involving synthetic cannabinoids and psychoactive bath salts remained relatively constant from 2011 to 2012 several designer amphetamines and novel psychoactive substances were first reported in the Registry in 2012 including the NBOME compounds or "N-bomb" agents. LSD cases also spiked dramatically in 2012 with an 18-fold increase from 2011 although many of these cases are thought to be ultra-potent designer amphetamines misrepresented as "synthetic" LSD. The 2012 Registry included over 400 Adverse Drug Reactions (ADRs) involving 4 % of all Registry cases with 106 agents causing at least 2 ADRs. Additional data including supportive cares, decontamination, and chelating agent use are also included in the 2012 annual report. The Registry remains a valuable toxico-surveillance and research tool. The ToxIC Registry is a unique tool for identifying and characterizing confirmed cases of significant or potential toxicity or complexity to require bedside care by a medical toxicologist.
- Acetylcholinesterase inhibitors as Alzheimer therapy: From nerve toxins to neuroprotection. [JOURNAL ARTICLE]
- Eur J Med Chem 2013 Oct 6.:165-188.
Acetylcholinesterase is a member of the α/β hydrolase protein super family, with a significant role in acetylcholine-mediated neurotransmission. Research in the modulators of AChEs has moved from a potent poison (Sarin, Soman) in war times to the potent medicine (physostigmine) in peaceful times. Natural anti-AChE includes carbamates, glycoalkaloids, anatoxins derived from green algae; synthetic anti-AChE includes highly poisonous organophosphates used as nerve gases and insecticides. Recently, the role of anti-AChE was reassessed from neurotoxins to neuron-protective in the diseases characterized by impaired acetylcholine-mediated neurotransmission like Alzheimer's disease (AD). So, the AChE has been proven to be the most viable therapeutic target for the symptomatic treatment of AD. This review article gives a spectrum of strategies to design AChE inhibitors used in the Alzheimer therapy.
- Prophylactic administration of non-organophosphate cholinesterase inhibitors before acute exposure to organophosphates: assessment using terbufos sulfone. [JOURNAL ARTICLE]
- J Appl Toxicol 2013 Oct 18.
Poisoning with organophosphorus compounds (OPCs) poses a serious threat worldwide. OPC-induced mortality can be significantly reduced by prophylactic administration of reversible acetylcholinesterase (AChE) inhibitors. The only American Food and Drug Administration (FDA)-approved substance for such pre-treatment (to soman exposure) is presently pyridostigmine, although its efficacy is controversial. In search for more efficacious and broad-spectrum alternatives, we have assessed in vivo the mortality-reducing efficacy of a group of five compounds with known AChE inhibitory activity (pyridostigmine, physostigmine, ranitidine, tacrine and K-27), when given in equitoxic dosage (25% of LD01 ) 30 min before exposure to the OPC terbufos sulfone. Protection was quantified in rats by determining the relative risk of death (RR) using Cox analysis, with RR = 1 for animals given only terbufos sulfone, but no pre-treatment. All tested AChE inhibitors reduced terbufos sulfone-induced mortality significantly (p ≤ 0.05) as compared with the non-treatment group (RR = 1: terbufos sulfone only). Best in vivo protection from terbufos sulfone-induced mortality was achieved, when K-27 was given before terbufos sulfone exposure (RR = 0.06), which was significantly (P ≤ 0.05) superior to the pre-treatment with all other tested compounds, for example tacrine (RR = 0.21), pyridostigmine (RR = 0.28), physostigmine (RR = 0.29) and ranitidine (RR = 0.33). The differences in efficacy between tacrine, pyridostigmine, physostigmine and ranitidine were not statistically significant. Prophylactic administration of an oxime (such as K-27) in case of imminent OPC exposure may be a viable option. Copyright © 2013 John Wiley & Sons, Ltd.
- Optical bioassay for measuring sublethal toxicity of insecticides in Daphnia pulex. [JOURNAL ARTICLE]
- Environ Toxicol Chem 2013 Oct 1.
Many emerging contaminants tend to be biologically active at very low concentrations, occur in water as part of complex mixtures, and impact biota in ways that are not detected using traditional toxicity tests (e.g., median lethal concentration). To evaluate emerging contaminants, the authors developed a method for detecting sublethal behavioral effects by quantifying the swimming behavior of Daphnia pulex, a model organism for studying aquatic toxicity. This optical tracking technique is capable of measuring many swimming parameters, 2 of which-cumulative distance and angular change-are presented. To validate this technique, 2 prototypical compounds that exhibit different modes of action as well as corresponding insecticides that are commonly found in surface waters were investigated. The acetylcholinesterase (AChE) inhibitor physostigmine was used as the prototypical compound for the large number of AChE inhibitor insecticides (e.g., chlorpyrifos). Nicotine was used as the prototypical compound for neonicotinoid insecticides (e.g., imidacloprid). Results demonstrate that this assay is capable of detecting sublethal behavioral effects that are concentration-dependent and that insecticides with the same mode of action yield similar results. The method can easily be scaled up to serve as a high-throughput screening tool to detect sublethal toxic effects of a variety of chemicals. This method is likely to aid in enhancing the current understanding of emerging contaminants and to serve as a novel water-quality screening tool. Environ Toxicol Chem 2014;33:XX-XX. © 2013 SETAC.
- Current Acetylcholinesterase-Inhibitors: A Neuroinformatics Perspective. [JOURNAL ARTICLE]
- CNS Neurol Disord Drug Targets 2013 Sep 19.
This review presents a concise update on the inhibitors of the neuroenzyme, Acetylcholinesterase (AChE; EC 126.96.36.199). AChE is a serine protease, which hydrolyses Acetylcholine neurotransmitter into Acetate & Choline & hence, terminates neurotransmission. Molecular interactions (mode of binding to the target enzyme), clinical applications and limitations have been summarized for each of the inhibitors discussed. Traditional inhibitors (e.g. Physostigmine, Tacrine, Donepezil, Rivastigmine etc.) as well as novel inhibitors like various Physostigmine-derivatives have been covered. This is followed by a short glimpse on inhibitors derived from nature (e.g. Huperzine A & B, Galangin). Also, a discussion on 'hybrids of pre existing drugs' has been incorporated. Furthermore, current status of therapeutic applications of AChE-inhibitors has also been summarized.