Caffeic acid and caffeine attenuate toxicity associated with malonic or methylmalonic acid exposure in Drosophila melanogaster.

The deficiency in the activity of the mitochondrial enzyme methylmalonyl-CoA mutase (MCM, EC 5.4.99.2) leads to a condition called methylmalonic academia, which is characterised by the accumulation of methylmalonic (MMA), malonic (MA) or other organic acids. Importantly, we have recently found that supplementation with Ilex paraguariensis aqueous extract offered protection against toxicity associated with MMA or MA exposure to Drosophila melanogaster. Of note, caffeic acid (CA) and caffeine (CAF) were the major phytochemicals found in our Ilex paraguariensis crude extract. Therefore, here, we have exploited CA and/or CAF to test the hypothesis that supplementation with the isolated compounds (either alone or combined) could exert a protective effect against MMA or MA-induced toxicity in flies. Therefore, flies were exposed to MA (5 mM) or MMA (5 mM) and concomitantly treated with CA (1.39 µg/mL), CAF (1.27 µg/mL) or CA + CAF for 10 days for survival, and for 4 days for behavioural and biochemical assays. CA, CAF and CA + CAF treatments completely abolished the mortality associated with either MMA or MA exposure. Moreover, CA and CAF, either alone or combined, completely abolished behavioural changes, and completely protect against changes in thiobarbituric acid reactive substances (TBARS) levels, catalase (CAT) activity and MTT reduction ability, associated with MA or MMA exposure. In turn, CAF restored SOD activity in the head of flies exposed to MA or MMA. However, CA and CAF (either alone or combined) significantly decreased acetylcholinesterase (AChE) activity per se, while CAF alone protected from changes in AChE activity (in head tissue) associated with MA or MMA. Finally, CA and/or CAF were able to protect from a decrease in glucose and triglyceride levels associated with both MA and MMA exposures in haemolymph. Together, our data confirm the hypothesis that supplementation with CA and/or CAF offers protection against detrimental changes associated with MMA or MA exposure in flies, being responsible, at least in part, for the protective effect of I. paraguariensis crude extract which was reported previously.

Thimerosal inhibits Drosophila melanogaster tyrosine hydroxylase (DmTyrH) leading to changes in dopamine levels and impaired motor behavior: implications for neurotoxicity.

Thimerosal (THIM) is a well-established antifungal and antiseptic agent widely used as a preservative in vaccines. Recent studies identified the neurotoxic effects of THIM, including malfunction of the monoaminergic system. However, the underlying cytotoxic mechanisms are not well understood. Here we used the fruit fly Drosophila melanogaster to investigate the mechanisms of THIM-induced neurotoxicity. We focused on the dopaminergic system, and the rate-limiting enzyme tyrosine hydroxylase (DmTyrH), to test the hypothesis that THIM can impair dopamine (DA) homeostasis and subsequently cause dysfunction. We studied the effect of THIM by feeding 1-2 day old flies (both sexes) food supplemented with 25 µM THIM for 4 days and determined THIM-induced effects on survival, oxidative stress, and metabolic activity based on MTT assay and acetylcholinesterase (AChE) activity. Our results demonstrate that D. melanogaster exposed to THIM present changes in DmTyrH expression and activity, together with altered DA levels that led to impaired motor behavior. These phenotypes were accompanied by an increase in oxidative stress, with a decrease in MTT reduction, in AChE activity, and also in survival rate. These findings suggest an initiating and primary role for THIM-mediated DmTyrH dysfunction that leads to impaired DA function and behavioral abnormalities, ultimately causing oxidative stress-related neurotoxicity.

Treatment with pentylenetetrazole (PTZ) and 4-aminopyridine (4-AP) differently affects survival, locomotor activity, and biochemical markers in Drosophila melanogaster.

PTZ is a convulsive agent that acts via selective blockage of GABAA receptor channels, whereas 4-AP leads to a convulsive episode via blockage of K+ channels. However, the mechanism(s) by which pentylenetetrazole (PTZ) and 4-aminopyridine (4-AP) cause toxicity to Drosophila melanogaster needs to be properly explored, once it will help in establishing an alternative model for development of proper therapeutic strategies and also to counteract the changes associated with exposure to both epileptic drugs. For the purpose, we investigated the effects of exposure (48 h) to PTZ (60 mM) and/or 4-AP (20 mM) on survival, locomotor performance, and biochemical markers in the body and/or head of flies. 4-AP-fed flies presented a higher incidence of mortality and a worse performance in the open field test as compared to non-treated flies. 4-AP also caused a significant increase in the reactive species (RS) and protein carbonyl (PC) content in the body and head. Also a significant increase in catalase and acetylcholinesterase (AChE) activities was observed in the body. In the same vein, PTZ exposure resulted in a significant increase in RS, thiobarbituric acid reactive substances (TBARS), PC content, and catalase activity in the body. PTZ exposure also caused a significant increase in AChE activity both in body and head. It is important to note that PTZ-treated flies also down-regulated the NRF2 expression. Moreover, both 4AP- and PTZ-fed flies presented a significant decrease in MTT reduction, down-regulation, and inhibition of SOD in body. However, SOD was significantly more active in the head of both 4-AP and PTZ-treated flies. Our findings provide evidence regarding the toxicological potential of both PTZ and/or 4-AP to flies. This model will help in decoding the underlying toxicological mechanisms of the stated drugs. It will also help to properly investigate the therapeutic strategies and to counteract the drastic changes associated with both epileptogenic drugs.

In vitro and in silico antioxidant and toxicological activities of Achyrocline satureioides.

ETHNOPHARMACOLOGICAL RELEVANCE: Achyrocline satureioides ("macela or marcela") is a medicinal plant, traditionally collected in "Good Friday" before sunrise. In traditional medicine, dried flowers of A. satureioides are used as anti-dyspeptic, antispasmodic and anti-inflammatory. AIM OF THE STUDY: To evaluate the phytochemical profile and to present an in vitro and in silico approach about toxicity and antioxidant potential of A. satureioides flowers extract and its major phytoconstituents. MATERIALS AND METHODS: Plant were collected according to the popular tradition. Extract were obtained by infusion and analyzed from high-performance liquid chromatography. Toxicity was evaluated in Artemia salina and human lymphocytes. Extract antioxidant activity was determined with total antioxidant capacity, DPPH• and ABTS+• scavenging, ferric reducing antioxidant power, deoxyribose degradation assay, and thiobarbituric acid reactive substances (TBA-RS) assay. TBA-RS inhibitions were evaluated in brain of rats for A. satureioides extract and its major phytoconstituents. Predictions of activity spectra for substances and in silico toxicity evaluation from major phytoconstituents were performed via computer simulation. RESULTS: Chromatographic data indicated isoquercitrin, quercetin and caffeic acid as main compounds in flowers extract. Toxicity tests demonstrated a very low toxic potential of A. satureioides. Extract exhibited antioxidant activities in low concentrations. Both extract and major phytochemicals standards showed protection against lipid peroxidation in brain of rats. Computer simulations pointed some biological activities in agreement with traditional use, as well as some experimental results found in this work. Moreover, in silico toxic predictions showed that the A. satureioides major compounds had low probability for toxic risk. CONCLUSION: Our results indicate that A. satureioides infusion possesses low toxicological potential and an effective antioxidant activity. These findings confirm the traditional use of this plant in the folk medicine.

Scientific Performance of Brazilian Researchers in Pharmacology with grants from CNPq: A comparative study within the Brazilian categories.

In Brazil, scientific performance of researchers is one important criteria for decision-making in grant allocation. In this context, this study aimed to evaluate and compare the profile of 82 seniors' investigators (graded as level 1A-D) which were receiving CNPq (National Council for Scientific and Technological Development) productivity grant in Pharmacology, by analyzing the pattern of citation of their papers and h-index. Total documents, citations (with and without self-citations) and h-index (with and without self-citations) were retrieved from the Scopus database. The results indicated a clear difference among researchers from the higher categories (1A and 1B) in most of the parameters analyzed. However, no noticeable differentiation was found between researchers from grant category 1C and 1D. The results presented here may inform the scientific community and the grant agencies on the profile of PQ 1(A-D) fellows of Pharmacology, and may help to define new differences within CNPq grant categories, and consequently, a better allocation of grants.

Mitochondrial electron transfer chain complexes inhibition by different organochalcogens.

Mitochondrial dysfunction plays a pivotal role in the cell toxicology and death decision. The aim of the present study was to investigate the effect of three organocompounds (ebselen [Ebs], diphenyl diselenide [(PhSe)(2)] and diphenyl ditelluride [(PhTe)(2)]) on mitochondrial complexes (I, II, I-III, II-III and IV) activity from rat liver and kidney to determine their potential role as molecular targets of organochalcogens. All studied organochalcogens caused a statistically significant inhibition of the mitochondrial complex I activity. Ebs and (PhTe)(2) caused a statistically significant inhibition of the mitochondrial complex II activity in both hepatic and renal membranes. Hepatic mitochondrial complex II activity was practically unchanged by (PhSe)(2), whereas it significantly inhibited renal complex II activity. Mitochondrial complex IV activity was practically unchanged by the organochalcogens. Furthermore, organochalcogens inhibited the mitochondrial respiration supported by complex I or complex II substrates. The inhibitory effect of Ebs, (PhSe)(2) and (PhTe)(2) on mitochondrial complex I was prevented by NADH, but it was not prevented by catalase (CAT) and/or superoxide dismutase (SOD). Additionally, the organochalcogens-induced inhibition of complex I and II was completely reversed by reduced glutathione (GSH). In conclusion, Ebs, (PhSe)(2) and (PhTe)(2) were more effective inhibitors of renal and hepatic mitochondrial complex I than complex II, whereas complexes III and IV were little modified by these compounds. Taking into account the presented results, we suggest that organochalcogen-induced mitochondrial complexes I and II inhibition can be mediated by their thiol oxidation activity, i.e., Ebs, (PhSe)(2) and (PhTe)(2) can oxidize critical thiol groups from mitochondrial complexes I and II. So, mitochondrial dysfunction can be considered an important factor in the toxicity of Ebs, (PhSe)(2) and (PhTe)(2).

Protective effect of Melissa officinalis aqueous extract against Mn-induced oxidative stress in chronically exposed mice.

Manganese (Mn) is an essential element for biological systems; however occupational exposure to high levels of this metal may lead to neurodegenerative disorders, resembling Parkinson's disease (PD). While its mechanisms of neurotoxicity have yet to be fully understood, oxidative stress plays a critical role. Thus, the main goal of this study was to investigate the efficacy of aqueous extract of Melissa officinalis in attenuating Mn-induced brain oxidative stress in mice. Sixteen male mice were randomly divided into two groups and treated for 3 months: the first group consumed tap water (control group) and the second group was treated with Mn (50 mg/kg/day for habituation during the first 15 days followed by 100 mg/kg/day for additional 75 days) in the drinking water. After 3 months both groups were sub divided (n=4 per group) and treated for additional 3 months with Mn and/or M. officinalis in the drinking water. The first group (control) was treated with water and served as control; the second group (M. officinalis) was treated with M. officinalis (100 mg/kg/day); the third group was treated with Mn (100 mg/kg/day); the fourth group (Mn+M. officinalis) was treated with both Mn and M. officinalis (100 mg/kg/day each). Mn-treated mice showed a significant increase in thiobarbituric acid reactive species (TBARS) levels (a marker of oxidative stress) in both the hippocampus and striatum. These changes were accompanied by a decrease in total thiol content in the hippocampus and a significant increase in antioxidant enzyme activity (superoxide dismutase and catalase) in the hippocampus, striatum, cortex and cerebellum. Co-treatment with M. officinalis aqueous extract in Mn-treated mice significantly inhibited the antioxidant enzyme activities and attenuated the oxidative damage (TBARS and decreased total thiol levels). These results establish that M. officinalis aqueous extract possesses potent antioxidative properties, validating its efficacy in attenuating Mn-induced oxidative stress in the mouse brain.

Mitochondrial dysfunction induced by different organochalchogens is mediated by thiol oxidation and is not dependent of the classical mitochondrial permeability transition pore opening.

Ebselen (Ebs) and diphenyl diselenide [(PhSe)(2)] readily oxidize thiol groups. Here we studied mitochondrial swelling changes in mitochondrial potential (Deltapsim), NAD(P)H oxidation, reactive oxygen species production, protein aggregate formation, and oxygen consumption as ending points of their in vitro toxicity. Specifically, we tested the hypothesis that organochalchogens toxicity could be associated with mitochondrial dysfunction via oxidation of vicinal thiol groups that are known to be involved in the regulation of mitochondrial permeability (Petronilli et al. J. Biol. Chem., 269; 16638; 1994). Furthermore, we investigated the possible mechanism(s) by which these organochalchogens could disrupt liver mitochondrial function. Ebs and (PhSe)(2) caused mitochondrial depolarization and swelling in a concentration-dependent manner. Furthermore, both organochalchogens caused rapid oxidation of the mitochondrial pyridine nucleotides (NAD(P)H) pool, likely reflecting the consequence and not the cause of increased mitochondrial permeability (Costantini, P., Chernyak, B. V., Petronilli, V., and Bernardi, P. (1996). Modulation of the mitochondrial permeability transition pore (PTP) by pyridine nucleotides and dithiol oxidation at two separate sites. J. Biol. Chem. 271, 6746-6751). The organochalchogens-induced mitochondrial dysfunction was prevented by the reducing agent dithiothreitol (DTT). Ebs- and (PhSe)(2)-induced mitochondrial depolarization and swelling were unchanged by ruthenium red (4microM), butylated hydroxytoluene (2.5microM), or cyclosporine A (1microM). N-ethylmaleimide enhanced the organochalchogens-induced mitochondrial depolarization, without affecting the magnitude of the swelling response. In contrast, iodoacetic acid did not modify the effects of Ebs or (PhSe)(2) on the mitochondria. Additionally, Ebs and (PhSe)(2) decreased the basal 2' 7' dichlorofluorescin diacetate (H(2)-DCFDA) oxidation and oxygen consumption rate in state 3 and increased it during the state 4 of oxidative phosphorylation and induced the formation of protein aggregates, which were prevented by DTT. However, DTT failed to reverse the formation of protein aggregates, when it was added after a preincubation of liver mitochondria with Ebs or (PhSe)(2). Similarly, DTT did not reverse the Ebs- or (PhSe)(2)-induced Deltapsim collapse or swelling, when it was added after a preincubation period of mitochondria with chalcogenides. These results show that Ebs and (PhSe)(2) can effectively induce mitochondrial dysfunction and suggest that effects of these compounds are associated with mitochondrial thiol groups oxidation. The inability of cyclosporine A to reverse the Ebs- and (PhSe)(2)-induced mitochondrial effects suggests that the redox-regulated mitochondrial permeability transition (MPT) pore was mechanistically regulated in a manner that is distinct from the classical MPT pore.

Comparative study of quercetin and its two glycoside derivatives quercitrin and rutin against methylmercury (MeHg)-induced ROS production in rat brain slices.

The hypothesis that methylmercury (MeHg) potently induces formation of reactive oxygen species (ROS) in the brain is supported by observations on the neuroprotective effects of various classes of antioxidants. Flavonoids have been reported to possess divalent metal chelating properties, antioxidant activities and to readily permeate the blood-brain barrier. They can also provide neuroprotection in a wide array of cellular and animal models of neurological diseases. Paradoxically, in vivo administration of quercetin displays unexpected synergistic neurotoxic effect with MeHg. Considering this controversy and the limited data on the interaction of MeHg with other flavonoids, the potential protective effect of quercetin and two of its glycoside analogs (i.e., rutin and quercitrin) against MeHg toxicity were evaluated in rat cortical brain slices. MeHg (100 microM) caused lipid peroxidation and ROS generation. Quercitrin (10 microg/mL) and quercetin (10 microg/mL) protected mitochondria from MeHg (5 microM)-induced changes. In contrast, rutin did not afford a significant protective effect against MeHg (100 microM)-induced lipid peroxidation and ROS production in cortical brain slices. MeHg-generated ROS in cortical slices was dependent upon an increase in intracellular Ca(2+) levels, because the over-production of MeHg-induced H(2)O(2) in mitochondria occurred with a concomitant increase in Ca(2+) transient. Here, we have extended the characterization of mechanisms associated with the neuroprotective effects of quercetin against MeHg-induced toxicity in isolated mitochondria, by performing an array of parallel studies in brain slices. We provide novel data establishing that (1) Ca(2+) plays a central role in MeHg toxicity and (2) in brain slices MeHg induces mitochondrial oxidative stress both via direct interaction with mitochondria (as previously reported in in vitro studies) as well as via mitochondria-independent (or indirect) mechanisms.

Guanosine and synthetic organoselenium compounds modulate methylmercury-induced oxidative stress in rat brain cortical slices: involvement of oxidative stress and glutamatergic system.

Excessive formation of reactive oxygen species (ROS) and disruption of glutamate uptake have been pointed as two key mechanisms in methylmercury-toxicity. Thus, here we investigate the involvement of glutamatergic system in methylmercury (MeHg) neurotoxicity and whether diphenyl diselenide, ebselen and guanosine could protect cortical rat brain slices from MeHg-induced ROS generation. MeHg (100 and 200 microM) increased 2',7'-dichlorodihydrofluorescin (DCFH) oxidation after 2h of exposure. At 50 microM, MeHg increased DCFH oxidation only after 5h of exposure. Guanosine (1 and 5 microM) did not caused any effect per se; however, it blocked the increase in DCFH caused by 200 or 50 microM MeHg. Ebselen (5 and 10 microM) decreased significantly the DCFH oxidation after 2 and 5h of exposure to MeHg. Diphenyl diselenide (5 microM) did not change the basal DCFH oxidation, but abolished the pro-oxidant effect of MeHg. MK-801 also abolished the pro-oxidant effect of MeHg. These results demonstrate for the first time the potential antioxidant properties of organoseleniun compounds and guanosine against MeHg-induced ROS generation after short-term exposure in a simple in vitro model. In conclusion, endogenous purine (guanosine) and two synthetic organoselenium compounds can modulate the pro-oxidant effect of MeHg in cortical brain slices.

Synthesis of telluroamino acid derivatives with remarkable GPx like activity.

A series of modular telluroamino acid derivatives with remarkable GPx-like behavior was prepared in an efficient and short two-step synthesis.

Intense exercise potentiates oxidative stress in striatum of reserpine-treated animals.

Regular physical activity exerts beneficial effects for mental and physical health, but an intense exercise can cause oxidative stress (OS) in dopaminergic regions and intensify the harmful effects of reserpine. Reserpine-induced neurotoxicity can be accessed by behavioral and biochemical evaluations. The objective of this study was to examine the effect of a gradual intensifying exercise program on an animal model of oxidative stress. Male rats were submitted to swimming sessions (1 h/day, for eleven weeks), and they were loaded gradually during the adaptation period (two weeks) with a weight corresponding to 1-7% of their body weight tied to their back. After the last training, the animals were treated with two doses of vehicle or reserpine (1 mg/kg-sc), an agent that induces orofacial dyskinesia. After behavioral evaluations, the striatum was dissected for enzymatic and biochemical assays. Development of cardiac hypertrophy demonstrated the effectiveness of the physical training. The gradual intense exercise and reserpine increased lipid peroxidation and striatal catalase activity. The results confirm the importance of catalase activity in orofacial dyskinesia which can be related to lipid peroxidation in striatal dopaminergic brain tissue. These results indicate that intense exercise can have some deleterious effect on striatal dopaminergic system.