Reduced expression of exocytotic proteins caused by anti-cholinesterase pesticides in Brachionus calyciflorus (Rotifera: Monogononta) / Redução da expressão de proteínas de exocitose causados por pesticidas anti-colinesterase em Brachionus calyciflorus (Rotifera: Monogononta)

AbstractThe organophosphate and carbamate pesticides methyl-parathion and carbaryl have a common action mechanism: they inhibit acetylcholinesterase enzyme by blocking the transmission of nerve impulses. However, they can alter the expression of exocytotic membrane proteins (SNARE), by modifying release of neurotransmitters and other substances. This study evaluated the adverse effects of the pesticides methyl-parathion and carbaryl on expression of SNARE proteins: Syntaxin-1, Syntaxin-4 and SNAP-23 in freshwater rotifer Brachionus calyciflorus. Protein expression of these three proteins was analyzed before and after exposure to these two pesticides by Western Blot. The expression of Syntaxin-1, Syntaxin-4 and SNAP-23 proteins in B. calyciflorussignificantly decreases with increasing concentration of either pesticides. This suggests that organophosphates and carbamates have adverse effects on expression of membrane proteins of exocytosis by altering the recognition, docking and fusion of presynaptic and vesicular membranes involved in exocytosis of neurotransmitters. Our results demonstrate that the neurotoxic effect of anticholinesterase pesticides influences the interaction of syntaxins and SNAP-25 and the proper assembly of the SNARE complex.

ResumoOs pesticidas organofosforados e carbamatos metil- paration e carbaril tem um mecanismo de ação comum: eles inibem a enzima acetilcolinesterase, bloqueando a transmissão dos impulsos nervosos. No entanto, eles podem alterar a expressão de proteínas de membrana de exocitose (SNARE), através da modificação da libertação de neurotransmissores e outras substâncias. Este estudo avaliou os efeitos adversos dos pesticidas metil- paration e carbaril sobre a expressão de proteínas SNARE: Sintaxina -1, Sintaxina-4 e SNAP-23 em rotíferos de água doce Brachionus calyciflorus. A expressão destas três proteínas foi analisada antes e depois da exposição a estes dois pesticidas por Western Blot. A expressão das proteínas Sintaxina-1, Sintaxina-4 e SNAP-23 em B. calyciflorus diminui significativamente com o aumento da concentração de ambos os pesticidas. Isto sugere que os organofosfatos e carbamatos têm efeitos adversos sobre a expressão de proteínas de membrana de exocitose, alterando o reconhecimento, de encaixe e fusão de membranas pré-sinápticas e vesiculares envolvidas na exocitose de neurotransmissores. Nossos resultados demonstram que o efeito neurotóxico de pesticidas anticolinesterásicos influencia a interação de sintaxinas e SNAP-25 e a montagem correta do complexo SNARE.

comparative study of inhibition of brain and plasma cholinesterase and hepatic and plasma aliesterases in young and adult rats following exposures to three organophosphorothionate insecticides

Young rats are more sensitive than adults to a variety of Organophosphorothionate insecticides [OPS], compounds which act in vivo by inhibition of Cholinesterase and aliesterases. Little is known, however, regarding age-related differences in biochemical responses to these toxicants. The time course of Cholinesterase and aliesterases inhibit and recovery in different tissues were compared in young [14 days of age] and adult [90-100 days of -age] rats after treatment with high sublethal intraperitoneal dosages of parathion, methyl parathion or chlorpyrifos. Young rats were more sensitive than adult in all cases [high sublethal doses for parathion, methyl parathion and chlorpyrifos; young = 0.5, 5 and 10 mg/kg, i.p.; adult = 4, 12 and 60 mg/kg, i.p... respectively]. In general, the maximal inhibition of brain regions and plasma Cholinesterase activity was not immediate with parathion and chlorpyrifos, in young and adult rats, reflecting the time required for bioactivation of the phosphorothionates as well as the effectiveness of the aliesterases to inactive much of the hepatically generated oxons. In contrast, brain regions and plasma Cholinesterase activities were rapidly inhibited following administration of methyl parathion in both age groups reflecting the low sensitivity of the aliesterases to methyl paraoxon. In general, maximal plasma and brain regions Cholinesterase inhibition was similar [greater than 80 percent] in both age groups but Cholinesterase activity recovered faster in young rats. Aliesterases were inhibited to a greater extent than acetyl cholinesterase at each sampling time with parathion and chlorpyrifos in young and adult rats where the reverse was true with methyl parathion .The very prolonged inhibition of esterase activities following chlorpyrifos treatment probably results from its substantially greater lipophilicity compared to the other compouritls, which would allow it to be stored and released for gradual bioactivation The data reported indicate that young rats are more sensitive to sublethal dosages from these compounds and that high sublethal doses exposure produce extensive plasma and different brain regions cholinesterase and plasma and liver aliesterases inhibition in both age groups. Significant inhibitor- related and age-related differences in the duration of cholinesterase and aliesterases inhibition can ensue, however, following such Organophosphorothionate insecticides exposures. Additionally, under defined experimental conditions plasma cholinesterase inhibition may be a useful quantitative index for the degree of brain cholinesterase inhibition following organophosphorous exposures

Elevation of C-reactive protein in serum of Channa punctatus as an indicator of water pollution.

Effect of some pollutants like heavy metals, non-metals and pesticides on the circulating level of C-reactive protein (CRP) which is an acute phase plasma protein was studied in a freshwater murrel C. punctatus. Fish was exposed to nonlethal doses of these xenobiotics which were apparently safe. But the level of CRP detected by sensitive single radial immunodiffusion (SRID) technique showed that within 12 hr of exposure the nonlethal doses of xenobiotics could initiate the acute phase response in terms of elevated CRP titre. Heavy metals caused the acute phase within 24 hr, nonmetals and Metacid-50 within 48 hr exposure. The carbamate compound, carbaryl demonstrated a biphasic response to CRP level which may be correlated with the reversible type of anticholinesterase property of this compound while Metacid-50 is an irreversible type of anticholinesterase agent. The assessment of the CRP level in the serum of fish may be utilized as a primary bioindicator of a contaminated environment toxic enough to mount an acute phase response.