Metrifonate Research Articles

In vitro effect of metrifonate on the indices of oxidative stress in Gigantocotyle explanatum

Helminth infections in general and digenetic trematodes in particular cause a huge economic loss globally to our livestock. Gigantocotyle explanatum is a digenetic amphistome that infects the bile ducts of water buffalo and are highly prevalent in tropical and sub-tropical countries. In the present study, effects of an organophosphate compound, Metrifonate (MF) in three doses, viz., 9.4 × 10−5 M (Dose I), 14.4 × 10−5 M (Dose II), and 19.4 × 10−5 M (Dose III), have been studied in vitro, on the motility and on some enzymatic and non-enzymatic oxidative stress indices in G. explanatum. The worm's motility and their non-enzymatic oxidative stress biomarkers like lipid peroxides measured as thiobarbituric acid-reactive substances (TBARS) and reduced glutathione (GSH) were disrupted significantly in a dose-dependent manner. However, the enzymatic oxidative stress biomarkers like glutathione-S-transferase (GST) and superoxide dismutase (SOD) were affected by MF treatment in a biphasic manner. Exposure to Dose I significantly stimulated the activities of both GST and SOD, whereas exposure to Doses II and III resulted into significant inhibition in a dose-dependent manner. Our findings suggest that MF has potential to be a strong and effective anthelmintic, however, further studies in vitro as well as in vivo are needed to explore further these observations and understand the exact mode of MF action in G. explanatum and other trematodes of veterinary economic importance.

Short- and long-term effect of acetylcholinesterase inhibition on the expression and metabolism of the amyloid precursor protein.

We have investigated the acute and chronic effect of metrifonate (MTF) and dichlorvos (DDVP), respectively the prodrug and active acetylcholinesterase inhibitor, on the secretory processing of the amyloid precursor protein (APP) in SH-SY5Y neuroblastoma cells. We demonstrate that the acute treatment of SH-SY5Y cells with both compounds results in an increased secretion of the soluble fragment of APP (sAPPalpha) into the conditioned media of cells, with a pattern correlated to the level of acetycholinesterase inhibition. The regulation of APP processing in these conditions is mediated by an indirect cholinergic effect on muscarinic receptors, as demonstrated by inhibition with atropine. We have also followed APP expression and metabolism after long-term treatment with metrifonate. Treated cells showed reduced AChE activity after 24, 48 h and also following 7 days of repeated treatment, a time point at which increased AChE expression was detectable. At all time points sAPPalpha release was unaffected suggesting that enhanced sAPPalpha release by MTF is transitory, nevertheless the sensitivity of cholinergic receptors was unchanged, as indicated by the fact that cholinergic response can be elicited similarly in untreated and treated cells. APP gene expression was unaffected by long-term AChE inhibition suggesting that increased short-term sAPPalpha release does not elicit compensatory effects.

Reversible and irreversible acetylcholinesterase inhibitors cause changes in neuronal amyloid precursor protein processing and protein kinase C level in vitro

The alternative routes of cleavage of the amyloid precursor protein (APP) result in the generation and secretion of both soluble APP and β-amyloid, the latter being the main component of the amyloid deposits in the brains of individuals with Alzheimer's disease (AD). This study examined the question of whether acetylcholinesterase (AChE) inhibitors can alter the processing of APP and the level of protein kinase C (PKC) in primary rat basal forebrain cultures. Western blotting was used to test two AChE inhibitors (reversible and irreversible) for their ability to enhance the release of APP and PKC content. These inhibitors were ambenonium (AMB) and metrifonate (MTF), at different concentrations. A significant increase was found in the cell-associated APP level in a basal forebrain neuronal culture, and there was an elevation of the APP release into the medium. Increases were similarly observed in the PKC levels after AMB or MTF treatment. The results suggest that these AChE inhibitors promote the non-amyloidogenic route of APP processing, which may be due to their stimulatory effects on PKC. The PKC activation may enhance the α-secretase activity and consequently the production of the N-terminal APP. Since both a decreased level of APP secretion and a low activity and level of PKC may be involved in the pathogenesis of AD, it is concluded that the administration of AChE inhibitors to AD patients may facilitate the memory processes and exert a neuroprotective effect.

Kinetics of brain cholinesterase inhibition following metrifonate administration.

In previous metrifonate (MTF) studies, there has been evidence for a preferential functional effect of the drug in cortical but not in striatal regions. In the present study we investigated the kinetics of brain cholinesterase (ChE) inhibition following an acute administration of MTF (100 mg/kg) in various brain regions of young and old Fischer 344 rats. The main objective was to test the hypothesis that the functional regional selectivity, observed in previous studies, was correlated with the extent of ChE inhibition. Using Karnovsky's method for histochemical staining, the highest staining intensity in control rats was found in the striatum and hippocampus, compared to a low basal activity in the frontal and frontoparietal cortices. In the striatum of drug treated old rats, enzyme inhibition was somewhat greater than that found in young rats. However, in the hippocampus, four to eight hours following MTF administration, the inhibition was greater in young compared to old rats. The differences in the sensitivity of various brain regions towards MTF induced ChE inhibition could not be correlated with the regional variation of MTF functional effects.

Preclinical pharmacology of metrifonate.

Alzheimer's disease is a chronic neurodegenerative disorder that is characterized by memory impairment, cognitive dysfunction, behavioral disturbances, and deficits in activities of daily living. A consistent observation in these patients is that cholinergic neurons are affected and deteriorate over time, leading to decreased levels of acetylcholine (ACh). Acetylcholinesterase (AChE) inhibitors, which attempt to prevent the breakdown of ACh, may be classified as short acting, intermediate acting, and long acting based on AChE regeneration time. Metrifonate is converted by a nonenzymatic process to the long-acting cholinesterase inhibitor 2,2-dichlorovinyl dimethyl phosphate (DDVP). Acetylcholinesterase inhibition produced by metrifonate occurs rapidly, is dose dependent, can be detected by inhibition measured in red blood cells, and can be reversed by oxime administration. Metrifonate and DDVP improved performance in young rats; cognitive improvement in aged rats also was observed. Both agents were well tolerated and did not have significant effects on various preclinical pharmacologic safety tests.

Metrifonate: overview of safety and efficacy.

Metrifonate is a cholinesterase inhibitor with a long-lasting inhibition that raises brain acetylcholine levels. It is well-absorbed and has limited binding to serum proteins. In preliminary studies of its utility in the treatment of Alzheimer disease's (AD), it led to improvements of cognition or reduced the rate of decline of cognition compared with placebo. It also benefited the global function of these patients. Side effects include nausea, cramping, and diarrhea. Metrifonate has promise as a well-tolerated treatment of the symptoms of AD.

Metrifonate Improves Cognitive Function in AD

Metrifonate is an acetylcholinesterase (ACh) inhibitor that has been used in the treatment of schistosomiasis for over 30 years. It is not metabolized by the cytochrome P450 enzyme system and is associated with only mild gastrointestinal side effects. These two studies document the efficacy of metrifonate for enhancing the cognitive function of patients with Alzheimer's disease. The first study randomized 480 patients with AD to …

Effects of metrifonate on radial arm maze acquisition in middle-aged rats

The efficacy of metrifonate, a well-tolerated cholinesterase (ChE) inhibitor, in attenuating the normal aging- and corticosterone-induced impairments of radial maze performance of rats was compared. Middle-aged Fischer 344 rats were screened for their spatial orientation performance in the Morris water escape task. Good and bad performers were selected: good performers ( N=22) were treated with subcutaneous sustained-release corticosterone pellets, resulting in hippocampal cell damage and impaired spatial orientation in the radial maze; age-induced bad performers ( N=20) were tested without additional pharmacological intervention. Metrifonate (MFT), administered daily during radial maze testing, 30 min before training, at a dose of 15 mg/kg p.o., facilitated the acquisition of the task in age-impaired rats, but not in corticosterone-impaired rats.

Effects of metrifonate on impairment of learning and dysfunction of cholinergic neuronal system in basal forebrain-lesioned rats

Several studies have indicated the possibility of using cholinesterase (ChE) inhibitors as therapeutic drugs for Alzheimer's disease. Metrifonate (MTF) is an organophosphorus compound that has been used in the treatment of schistosomiasis. In this study, we investigated the effects of MTF on the impairment of learning and memory, decreased ChE activity and extracellular acetylcholine (ACh) levels in basal forebrain (BF)-lesioned rats. The oral administration of MTF improved the BF-lesion-induced impairment of performance on passive avoidance task. Further, MTF reduced ChE activity in the cerebral cortex. In vivo brain microdialysis studies showed that MTF significantly increased the release of ACh, but decreased that of choline (Ch) in the cerebral cortex of BF-lesioned rats. These results indicated that MTF ameliorates the impairment of performance on passive avoidance task in BF-lesioned rats by increasing the extracellular ACh levels by inhibiting ChE. This suggested that MTF may be useful as a therapeutic drug for Alzheimer's disease.

Effects of metrifonate and tacrine in the spatial morris task and modified irwin test: Evaluation of the efficacy/safety profile in rats

AbstractIn the present study we investigated the efficacy/safety profile of the cholinesterase inhibitors metrifonate (MTF) and tacrine [tetrahydroaminoacridine (THA)]. We tested the efficacy of MTF (12, 39, and 120 μmol/kg po) and THA (1.3, 4.3, and 13 μmol/kg po) in the spatial Morris task in 19‐month‐old rats. The modified Irwin test was used to evaluate the safety of both drugs, using in 19‐month‐old rats. In this observation test, higher doses of MTF (39, 120, and 390 μmol/kg) and THA (4.3, 13, and 43 μmol/kg) were tested. MTF was found to improve the performance of rats in the spatial Morris task. Independent of dose, MTF‐treated rats performed better than vehicle‐treated rats in the Morris task during the 2nd week of testing. THA treatment (1.3 μmol/kg) had only a minor effect on the spatial discrimination performance, i.e., effect on the probe trial after 2 weeks of training. In the modified Irwin test, both MTF and THA dose dependently induced side effects which were classified as being typically cholinergic. The threshold dose for the occurrence of side effects for acutely administered MTF and THA was 39 and 4.3 μmol/kg, respectively. Remarkably, repeated administration of 390 μmol/kg MTF (5 day treatment) resulted in fewer side effects. This was not observed for THA treatment. The data of the present study indicate that the efficacy/safety profile of MTF is more favorable than that of THA. © 1995 Wiley‐Liss, Inc.

Metrifonate effects on acetylcholine and biogenic amines in rat cortex

The effect of systemic and local administration of metrifonate (MTF), a long-acting cholinesterase inhibitor (ChEl) on extracellular levels of acetylcholine (ACh), norepinephrine (NE), dopamine (DA) and serotonin (5-HT) was investigated in the rat cortex by using transcortical microdialysis. Metrifonate (20, 40, and 80 mg/kg, s.c.) increased ACh levels in a dose-dependent manner above the baseline. Two consecutive administrations (80 mg/kg) enhanced ACh levels producing two similar patterns of elevation. A significant increase in NE was also seen at 80 mg/kg. Systemic administration (20 mg/kg) of MTF produced a significant increase of DA levels. Local cortical perfusion of MTF through the probe caused a significant but slow increase of ACh as well as an increase of NE levels. Compared to NE, the elevation of DA was more rapid and more long-lasting. The cortical levels of 5-HT were not modified by MTF given by either route. These results support the concept of MTF being a potential drug for treatment of Alzheimer disease (AD).

High-performance liquid chromatographic method using ultraviolet detection for measuring metrifonate and dichlorvos levels in human plasma

We report high-performance liquid chromatographic methods using ultraviolet detection, developed for the first time in our laboratory with sensitivity to detect clinically significant concentrations of metrifonate (MTF), an experimental drug for Alzheimer disease, and its active anticholinesterase metabolite, dichlorvos (DDVP). The determination limit of the method for MTF and DDVP was 1 μg/ml and 40 ng/ml, respectively. Stability of MTF and DDVP at various temperatures in water, buffered solutions and in human plasma were also studied.

Effect of acute and chronic cholinesterase inhibition on biogenic amines in rat brain

The effects of five cholinesterase inhibitors on forebrain monoamine and their metabolite levels, and on forebrain and plasma cholinesterase (ChE) activity in rat were studied in acute and chronic conditions. Acute tetrahydroaminoacridine (THA) dosing caused lower brain (68%) and higher plasma (90%) ChE inhibition than the other drugs studied and increased levels of brain dihydroxyphenylacetic acid (DOPAC) (236%), homovanillic acid (HVA) (197%) and 5-hydroxyindoleacetic acid (5-HIAA) (130%). Acute physostigmine (PHY) administration caused a 215% increase in brain DOPAC content. Despite high brain ChE inhibition induced by metrifonate (MTF), dichlorvos (DDVP) or naled no changes in brain noradrenaline (NA), dopamine (DA) or serotonin (5-HT) occurred due to treatment with the study drugs in the acute study. In the chronic 10-day study THA or PHY caused no substantial ChE inhibition in brain when measured 18 hours after the last dose, whereas MTF induced 74% ChE inhibition. Long-term treatment with THA or MTF caused no changes in monoamine levels, but PHY treatment resulted in slightly increased 5-HT values. These results suggest that MTF, DDVP and naled seem to act solely by cholinergic mechanisms. However, the central neuropharmacological mechanism of action of THA and PHY may involve changes in cholinergic as well as dopaminergic and serotoninergic systems.

Metrifonate may have a place

Metrifonate may have a place