RESUMO
The development of new models to study diabetes in invertebrates is important to ensure adherence to the 3R's principle and to expedite knowledge of the complex molecular events underlying glucose toxicity. Streptozotocin (STZ)-an alkylating and highly toxic agent that has tropism to mammalian beta cells-is used as a model of type 1 diabetes in rodents, but little is known about STZ effects in insects. Here, the cockroach; Nauphoeta cinerea was used to determine the acute toxicity of 74 and 740 nmol of STZ injection per cockroach. STZ increased the glucose content, mRNA expression of glucose transporter 1 (GLUT1) and markers of oxidative stress in the head. Fat body glycogen, insect survival, acetylcholinesterase activity, triglyceride content and viable cells in head homogenate were reduced, which may indicate a disruption in glucose utilization by the head and fat body of insects after injection of 74 and 740 nmol STZ per nymph. The glutathione S-transferase (GST) activity and reduced glutathione levels (GSH) were increased, possibly via activation of nuclear factor erythroid 2 related factor as a compensatory response against the increase in reactive oxygen species. Our data present the potential for metabolic disruption in N. cinerea by glucose analogues and opens paths for the study of brain energy metabolism in insects. We further phylogenetically demonstrated conservation between N. cinerea glucose transporter 1 and the GLUT of other insects in the Neoptera infra-class.
Assuntos
Encéfalo/metabolismo , Baratas/metabolismo , Proteínas Facilitadoras de Transporte de Glucose/metabolismo , Glucose/metabolismo , Estresse Oxidativo , Filogenia , Estreptozocina/farmacologia , Animais , Antibióticos Antineoplásicos/farmacologia , Encéfalo/efeitos dos fármacos , Baratas/efeitos dos fármacos , Baratas/genética , Proteínas Facilitadoras de Transporte de Glucose/genética , Glutationa/metabolismo , Glutationa Transferase/metabolismoRESUMO
Rhinella icterica is a poisonous toad whose toxic secretion has never been studied against entomotoxic potential. Sublethal doses of Rhinella icterica toxic secretion (RITS) were assayed in Nauphoeta cinerea cockroaches, in order to understand the physiological and behavioral parameters, over the insect central and peripheral nervous system. RITS (10⯵g/g) injections, induced behavioral impairment as evidenced by a significant decrease (38⯱â¯14%) in the distance traveled (pâ¯<â¯.05), followed by an increase (90⯱â¯6%) of immobile episodes (pâ¯<â¯.001, nâ¯=â¯28, respectively). In cockroaches semi-isolated heart preparations, RITS (16⯵g/200⯵l) induced a significant irreversible dose-dependent negative chronotropism, reaching ~40% decrease in heart rate in 20â¯min incubation. In in vivo cockroach neuromuscular preparations, RITS (20, 50 and 100⯵g/g of animal weight) induced a time-dependent inhibition of twitch tension that was complete for 20⯵g/g, in 120â¯min recordings. RITS (10⯵g/g) also induced a significant increase in the insect leg grooming activity (128⯱â¯10%, nâ¯=â¯29, pâ¯<â¯.01), but not in the antennae counterparts. The RITS increase in leg grooming activity was prevented in 90% by the pretreatment of cockroaches with phentolamine (0.1⯵g/g). The electrophysiological recordings of spontaneous neural compound action potentials showed that RITS (20⯵g/g) induced a significant increase in the number of events, as well as in the rise time and duration of the potentials. In conclusion, RITS showed to be entomotoxic, being the neuromuscular failure and cardiotoxic activity considered the main deleterious effects. The disturbance of the cockroaches' behavior together with the electrophysiological alterations, may unveil the presence of some toxic components present in the poison with inherent biotechnological potentials.
Assuntos
Bufonidae/fisiologia , Baratas/efeitos dos fármacos , Octopamina/farmacologia , Pele/metabolismo , Toxinas Biológicas/toxicidade , Potenciais de Ação/efeitos dos fármacos , Animais , Comportamento Animal/efeitos dos fármacos , Baratas/metabolismo , Relação Dose-Resposta a Droga , Asseio Animal/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Técnicas In Vitro , Junção Neuromuscular/efeitos dos fármacos , Octopamina/metabolismo , Fentolamina/farmacologia , Toxinas Biológicas/metabolismoRESUMO
The effects of caffeine supplementation is well documented in conventional animal models, however, in the lobster cockroaches Nauphoeta cinerea, they have not been reported. Thus, the aim of this study was to investigate the locomotor behavior and biochemical endpoints in the head of the nymphs of N. cinerea following 60 days exposure to food supplemented with 0, 0.5, 1.0, 2.5, 5.0 and 10.0â¯mg of caffeine/g of diet. The analysis of the locomotor behavior using the video-tracking software, Any-maze, for 12â¯min revealed that caffeine supplementation caused significant behavioral improvement. There was increase in distance travelled, velocity, frequency of rotation and turn angle (stereotypical behavior such as circling movements), and this was supported by the representative track plots of the path travelled by cockroaches in the open-field arena. In addition, caffeine supplementation markedly increased total thiol and non-protein thiol glutathione (GSH) levels in the heads of cockroaches, and this was in parallel with significant reduction of lipid peroxidation and free Fe(II) content. Taking together, our results indicate that long-term caffeine supplementation may exert preventive effects against oxidative stress and support the use of N. cinerea as an efficient alternative model to assess the efficacy of food molecules.
Assuntos
Biomarcadores/metabolismo , Cafeína/farmacologia , Baratas/efeitos dos fármacos , Baratas/metabolismo , Locomoção/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Animais , Dieta/métodos , Suplementos Nutricionais , Glutationa/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Modelos AnimaisRESUMO
The present study aimed to increase our understanding about the mode of toxic action of organophosphate pesticides in insects by evaluating the biochemical and neurobehavioral characteristics in Nauphoeta cinerea exposed to chlorpyrifos (CPF)-contaminated diet. The insects were exposed for 35 consecutive days to CPF at 0.078, 0.15625, 0.3125 and 0.625µg/g feed. Locomotor behavior was assessed for a 10-min trial in a novel arena and subsequently, biochemical analyses were carried out using the cockroaches' heads. In comparison to control, CPF-exposed cockroaches showed significant decreases in the total distance traveled, body rotation, turn angle and meandering, along with significant increase in the number of falls, time and episodes of immobility. The marked decrease in the exploratory profiles of CPF-exposed cockroaches was confirmed by track plots, whereas occupancy plot analyses showed a progressive dispersion at 0.15625µg/g feed group. Moreover, the heads of CPF-exposed cockroaches showed marked decrease in acetylcholinesterase activity and antioxidant status with concomitant significant elevation in dichlorofluorescein oxidation and lipid peroxidation levels in CPF-treated cockroaches. Gas Chromatography-Mass Spectrometry analyses revealed bioaccumulation of CPF in cockroaches exposed to concentrations above 0.078µg/g feed. The findings from this investigation showed N. cinerea as a value model organism for the risk assessment of environmental organophosphate contamination in insects.
Assuntos
Clorpirifos/farmacologia , Baratas/efeitos dos fármacos , Inseticidas/farmacologia , Acetilcolinesterase/efeitos dos fármacos , Animais , Baratas/metabolismo , Locomoção/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacosRESUMO
The Notch pathway is an essential regulator of cell proliferation and differentiation during development. Its involvement in insect oogenesis has been examined in insect species with meroistic ovaries, and it is known to play a fundamental role in cell fate decisions and the induction of the mitosis-to-endocycle switch in follicular cells (FCs). This work reports the functions of the main components of the Notch pathway (Notch and its ligands Delta and Serrate) during oogenesis in Blattella germanica, a phylogenetically basal species with panoistic ovary. As is revealed by RNAi-based analyses, Notch and Delta were found to contribute towards maintaining the FCs in an immature, non-apoptotic state. This ancestral function of Notch appears in opposition to the induction of transition from mitosis to endocycle that Notch exerts in Drosophila melanogaster, a change in the Notch function that might be in agreement with the evolution of the insect ovary types. Notch was also shown to play an active role in inducing ovarian follicle elongation via the regulation of the cytoskeleton. In addition, Delta and Notch interactions were seen to determine the differentiation of the posterior population of FCs. Serrate levels were found to be Notch-dependent and are involved in the control of the FC programme, although they would appear to play no crucial role in panoistic ovary oogenesis.
Assuntos
Diferenciação Celular , Baratas/citologia , Baratas/metabolismo , Proteínas de Insetos/metabolismo , Folículo Ovariano/citologia , Transdução de Sinais , Animais , Apoptose , Proliferação de Células , Citoesqueleto/metabolismo , Feminino , Ligantes , Mitose , Interferência de RNARESUMO
Organophosphate (OP) insecticides have been used indiscriminately, based on their high dissipation rates and low residual levels in the environment. Despite the toxicity of OPs to beneficial insects is principally devoted to the acetylcholinesterase (AChE) inhibition, the physiological mechanisms underlying this activity remain poorly understood. Here we showed the pharmacological pathways that might be involved in severe alterations in the insect locomotion and grooming behaviors following sublethal administration of the OP Trichlorfon (Tn) (0.25, 0.5 and 1 µM) in Phoetalia pallida. Tn inhibited the acetylcholinesterase activity (46±6, 38±3 and 24±6 nmol NADPH/min/mg protein, n=3, p<0.05), respectively. Tn (1 µM) also increased the walking maintenance of animals (46±5 s; n=27; p<0.05). Tn caused a high increase in the time spent for this behavior (344±18 s/30 min, 388±18 s/30 min and 228±12 s/30 min, n=29-30, p<0.05, respectively). The previous treatment of the animals with different cholinergic modulators showed that pirenzepine>atropine>oxotremorine>d-tubocurarine>tropicamide>methoctramine induced a decrease on Tn (0.5 µM)-induced grooming increase, respectively in order of potency. Metoclopramide (0.4 µM), a DA-D2 selective inhibitor decreased the Tn-induced grooming activity (158±12 s/30 min; n=29; p<0.05). Nevertheless, the effect of the selective DA-D1 receptor blocker SCH 23390 (1.85 µM) on the Tn (0.5 µM)-induced grooming increase was significative and more intense than that of metoclopramide (54±6 s/30 min; n=30; p<0.05). Taken together the results suggest that a cross-talking between cholinergic M1/M3 and dopaminergic D1 receptors at the insect nervous system may play a role in the OP-mediated behavioral alterations.
Assuntos
Baratas/efeitos dos fármacos , Inseticidas/toxicidade , Transmissão Sináptica/efeitos dos fármacos , Triclorfon/toxicidade , Acetilcolinesterase/metabolismo , Animais , Encéfalo/enzimologia , Baratas/metabolismo , Asseio Animal/efeitos dos fármacos , Masculino , Atividade Motora/efeitos dos fármacosRESUMO
The adverse effects of the alga Prasiola crispa extract (PcE) were investigated in a fruit fly (Drosophila melanogaster) and cockroach (Nauphoeta cinerea) model. In flies, toxicity was assessed as mortality and biochemical alterations including acetylcholinesterase (AChE) activity and oxidative stress markers. The cardiotoxic action of PcE was also examined in a model of semi-isolated cockroach heart. The administration of PcE (2 mg/ml) to flies for 24 h resulted in a marked increase in mortality rate (7.6-fold rise compared to control). AChE activity, glutathione (GSH) levels, and hydroperoxide formation remained unchanged. Fly glutathione S-transferase (GST) and catalase (CAT) activity were significantly altered after PcE treatment. Fraction III (ethyl acetate) of PcE was significantly more toxic to flies compared to fractions I (methanol) and II (ethanol). A significant decrease was noted in cockroach semi-isolated heart function. The addition of 5,5'-dithiobis-(2-nitrobenzoic acid (DTNB), an oxidizing agent, concomitant with the extract significantly blocked this effect, suggesting that reduced compounds may be involved in the cardiotoxic action produced by PcE. Our results show for the first time the adverse effects of PcE in two insect models, Drosophila melanogaster and Nauphoetacinerea. The insecticidal properties of PcE may be related to changes in important antioxidant/detoxifying systems, as well as to changes in insect cardiac function.
Assuntos
Clorófitas/toxicidade , Baratas/efeitos dos fármacos , Drosophila melanogaster/efeitos dos fármacos , Inseticidas/toxicidade , Extratos Vegetais/toxicidade , Acetilcolinesterase/metabolismo , Animais , Biomarcadores/metabolismo , Baratas/metabolismo , Relação Dose-Resposta a Droga , Drosophila melanogaster/metabolismo , Glutationa/metabolismo , Coração/efeitos dos fármacos , Coração/fisiopatologia , Peróxido de Hidrogênio/metabolismo , Masculino , Estresse Oxidativo/efeitos dos fármacosRESUMO
Organic and inorganic forms of mercury are highly neurotoxic environmental contaminants. The exact mechanisms involved in mercury neurotoxicity are still unclear. Oxidative stress appears to play central role in this process. In this study, we aimed to validate an insect-based model for the investigation of oxidative stress during mercury poisoning of lobster cockroach Nauphoeta cinerea. The advantages of using insects in basic toxicological studies include the easier handling, rapid proliferation/growing and absence of ethical issues, comparing to rodent-based models. Insects received solutions of HgCl2 (10, 20 and 40mgL(-1) in drinking water) for 7d. 24h after mercury exposure, animals were euthanized and head tissue samples were prepared for oxidative stress related biochemical determinations. Mercury exposure caused a concentration dependent decrease in survival rate. Cholinesterase activity was unchanged. Catalase activity was substantially impaired after mercury treatment 40mgL(-1). Likewise, GST had a significant decrease, comparing to control. Peroxidase and thioredoxin reductase activity was inhibited at concentrations of 20mgL(-1) and 40mgL(-1) comparing to control. These results were accompanied by decreased GSH levels and increased hydroperoxide and TBARS formation. In conclusion, our results show that mercuric compounds are able to induce oxidative stress signs in insect by modulating survival rate as well as inducing impairments on important antioxidant systems. In addition, our data demonstrates for the first time that Nauphoeta cinerea represents an interesting animal model to investigate mercury toxicity and indicates that the GSH and thioredoxin antioxidant systems plays central role in Hg induced toxicity in insects.
Assuntos
Cloreto de Mercúrio/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Animais , Baratas/efeitos dos fármacos , Baratas/metabolismo , Glutationa Transferase/metabolismo , Dose Letal Mediana , Cloreto de Mercúrio/química , Modelos Biológicos , Peroxidases/metabolismo , Tiorredoxina Dissulfeto Redutase/metabolismo , Poluentes Químicos da Água/químicaRESUMO
In vivo and in vitro synthesis of chitin in Triatoma infestans was studied. For in vivo experiments, [14C] sugars were injected through the abdominal wall. Maximal incorporation of radioactivity into the cuticle was attained immediately after the ecdysis. The identification of in vivo synthesized chitin was performed by the enzymatic hydrolysis of the alkali-insoluble material from the cuticle with Helix chitinase. The main water-soluble compound obtained was N-acetylglucosamine as demonstrated by chromatographic procedures. In vitro synthesis of chitin was carried out with enzymatic crude extracts from Triatoma infestans, and UDP-N-acetylglucosamine was used as "source" of glycosyl moieties. Higher amounts of [14C] N-acetylglucosamine incorporation to chitin than those previously reported by others, were obtained. The identity of the product was confirmed in a similar way as that from in vivo synthesis. Radioactivity was also found in a liposoluble fraction concomitantly with chitin synthesis. This compound had an anionic behavior, was acid labile and had similar chromatographic properties as dolichol pyrophosphate N-acetylglucosamine obtained with pig liver extracts. Knowledge about dolichol phosphate sugars mediated glycoprotein synthesis in eukaryotes, suggests the involvement of this type of N-acetylglucosaminyl-phospholipid in macromolecule "building" even in insects.