Effects of dietary fluoranthene on nymphs of Blaptica dubia S. (Blattodea: Blaberidae)

Effect of luminescent materials on the biochemistry, ultrastructure, and rhizobial microbiota of Spirodela polyrhiza

Fluorescent materials and technologies have become widely used in scientific research, and due to the ability to convert light wavelengths, their application to photosynthetic organisms can affect their development by altering light quality. However, the impacts of fluorescent materials on aquatic plants and their environmental risks remain unclear. To assess the effects of luminescent materials on floating aquatic macrophytes and their rhizosphere microorganisms, 4-(di-p-tolylamino)benzaldehyde-A (DTB-A) and 4-(di-p-tolylamino)benzaldehyde-M (DTB-M) (emitting blue-green and orange-red light, respectively) were added individually and jointly to Spirodela polyrhiza cultures and set at different concentrations (1, 10, and 100 μM). Both DTB-A and DTB-M exhibited phytotoxicity, which increased with concentration under separate treatment. Moreover, the combined group exhibited obvious stress relief at 10 μM compared to the individually treated group. Fluorescence imaging showed that DTB-A and DTB-M were able to enter the cell matrix and organelles of plant leaves and roots. Peroxidation induced cellular damage, contributing to a decrease in superoxide dismutase (SOD) and peroxidase (POD) activities and malondialdehyde (MDA) accumulation. Decomposition of organelle structures, starch accumulation in chloroplasts, and plasmolysis were observed under the ultrastructure, disrupting photosynthetic pigment content and photosynthesis. DTB-A and DTB-M exposure resulted in growth inhibition, dry weight loss, and leaf yellowing in S. polyrhiza. A total of 3519 Operational Taxonomic Units (OTUs) were identified in the rhizosphere microbiome. The microbial communities were dominated by Alphaproteobacteria, Oxyphotobacteria, and Gammaproteobacteria, with the abundance and diversity varied significantly among treatment groups according to Shannon, Simpson, and Chao1 indices. This study revealed the stress defense response of S. polyrhiza to DTB-A and DTB-M exposures, which provides a broader perspective for the bioremediation of pollutants using aquatic plants and supports the further development of fluorescent materials for applications.

Metoprolol elicits neurobehavioral insufficiency and oxidative damage in nontarget Nauphoeta cinerea nymphs

Metoprolol, a drug for hypertension and cardiovascular diseases, has become a contaminant of emerging concern because of its frequent detection in various environmental matrices globally. The dwindling in the biodiversity of useful insects owing to increasing presence of environmental chemicals is currently a great interest to the scientific community. In the current research, the toxicological impact of ecologically relevant concentrations of metoprolol at 0, 0.05, 0.1, 0.25, and 0.5 μg/L on Nauphoeta cinerea nymphs following exposure for 42 consecutive days was evaluated. The insects' behavior was analyzed with automated video-tracking software (ANY-maze, Stoelting Co, USA) while biochemical assays were done using the midgut, head and fat body. Metoprolol-exposed nymphs exhibited significant diminutions in the path efficiency, mobility time, distance traveled, body rotation, maximum speed and turn angle cum more episodes, and time of freezing. In addition, the heat maps and track plots confirmed the metoprolol-mediated wane in the exploratory and locomotor fitness of the insects. Compared with control, metoprolol exposure decreased acetylcholinesterase activity in insects head. Antioxidant enzymes activities and glutathione level were markedly decreased whereas indices of inflammation and oxidative injury to proteins and lipids were significantly increased in head, midgut and fat body of metoprolol-exposed insects. Taken together, metoprolol exposure induces neurobehavioral insufficiency and oxido-inflammatory injury in N. cinerea nymphs. These findings suggest the potential health effects of environmental contamination with metoprolol on ecologically and economically important nontarget insects.

Perfluorooctanoic acid induces behavioral impairment and oxidative injury in Nauphoeta cinerea nymphs

Perfluorooctanoic acid (PFOA) is a persistent organic contaminant with potential health threats to both animals and humans. However, the impact of PFOA on insects, which play significant roles in ecosystems, is understudied. We evaluated the toxicological impact of ecologically relevant concentrations of PFOA (0, 25, 50, 100, and 200 µg L-1) on Nauphoeta cinerea nymphs following exposure for 42 consecutive days. We analyzed the behavior of the insects with automated video-tracking software and processed the head, midgut, and fat body for biochemical assays. PFOA-exposed insects exhibited significant reductions in locomotory abilities and an increase in freezing time. Furthermore, PFOA exposure reduced acetylcholinesterase activity in the insect head. PFOA exposure increased the activities of superoxide dismutase, glutathione peroxidase, and catalase in the head and midgut, but decreased them in the fat body. PFOA also significantly increased glutathione-S transferase activity, while decreasing glutathione levels in the head, midgut, and fat body. Additionally, PFOA exposure increased reactive oxygen and nitrogen species, nitric oxide, lipid peroxidation, and protein carbonyl contents in the head, midgut, and fat body of the insects. In conclusion, our findings indicate that PFOA exposure poses an ecological risk to Nauphoeta cinerea.

Utility of cockroach as a model organism in the assessment of toxicological impacts of environmental pollutants

Environmental pollution is a global concern because of its associated risks to human health and ecosystem. The bio-monitoring of environmental health has attracted much attention in recent years and efforts to minimize environmental contamination as well as to delineate toxicological mechanisms related to toxic exposure are essential to improve the health conditions of both humans and animals. This review aims to substantiate the need and advantages in utilizing cockroaches as a complementary, non-mammalian model to further understand the noxious impact of environmental contaminants on humans and animals. We discuss recent advances in neurotoxicology, immunotoxicology, reproductive and developmental toxicology, environmental forensic entomotoxicology, and environmental toxicology that corroborate the utility of the cockroach (Periplaneta americana, Blaptica dubia, Blattella germanica and Nauphoeta cinerea) in addressing toxicological mechanisms as well as a sensor of environmental pollution. Indeed, recent improvements in behavioural assessment and the detection of potential biomarkers allow for the recognition of phenotypic alterations in cockroaches following exposure to toxic chemicals namely saxitoxin, methylmercury, polychlorinated biphenyls, electromagnetic fields, pharmaceuticals, polycyclic aromatic hydrocarbon, chemical warfare agents and nanoparticles. The review provides a state-of-the-art update on the current utility of cockroach models in various aspects of toxicology as well as discusses the potential limitations and future perspectives.

Chronic ciprofloxacin and atrazine co-exposure aggravates locomotor and exploratory deficits in non-target detritivore speckled cockroach (Nauphoeta cinerea)

The global detection of ciprofloxacin and atrazine in soil is linked to intensive anthropogenic activities in agriculture and inadvertent discharge of industrial wastes to the environment. Nauphoeta cinerea is a terrestrial insect with cosmopolitan distribution and great environmental function. The current study probed the neurobehavioral and cellular responses of N. cinerea singly and jointly exposed to atrazine (1.0 and 0.5 μg g^-1 feed) and ciprofloxacin (0.5 and 0.25 μg g^-1 feed) for 63 days. Results demonstrated that the reductions in the body rotation, maximum speed, turn angle, path efficiency, distance traveled, episodes, and time of mobility induced by atrazine or ciprofloxacin per se was exacerbated in the co-exposure group. The altered exploratory and locomotor in insects singly and jointly exposed to ciprofloxacin and atrazine were verified by track plots and heat maps. Furthermore, we observed a decrease in acetylcholinesterase and anti-oxidative enzyme activities with concomitant elevation in the levels of lipid peroxidation, nitric oxide, and reactive oxygen and nitrogen species were significantly intensified in the midgut, hemolymph, and head of insects co-exposed to ciprofloxacin and atrazine. In conclusion, exposure to binary mixtures of ciprofloxacin and atrazine elicited greater locomotor and exploratory deficits than upon exposure to the individual compound by inhibiting acetylcholinesterase activity and induction of oxido-inflammatory stress responses in the insects. N. cinerea may be a usable model insect for checking contaminants of ecological risks.

Toxicological outcome of exposure to psychoactive drugs carbamazepine and diazepam on non-target insect Nauphoeta cinerea

The continuous detection of human pharmaceuticals during environmental biomonitoring is a global concern because of the menaces they may exert on non-target organisms. Carbamazepine (CBZ) and diazepam (DZP) are commonly prescribed psychotropic drugs which have been reported to coexist in the environment globally. Nauphoeta cinerea is a common insect with high ecological impact. This study elucidated the influence of co-exposure to DZP (0.5 and 1.0 μg kg^-1 diet) and CBZ (1.5 and 3.0 μg kg^-1 diet) for 42 days on the behavior and biochemical responses in Nauphoeta cinerea. Results showed that DZP alone did not induce adverse effect on the behavior and antioxidant status in the exposed insects. However, exposure to CBZ alone and binary mixtures of DZP and CBZ significantly decreased locomotor and exploratory accomplishments evidenced by decreased mobile episodes, total mobile time, maximum speed, total distance traveled, absolute turn angle, body rotation and path efficiency in comparison with control. The decline observed in the exploratory activities of insects fed with CBZ alone and the mixtures was confirmed by track plots and heat maps. Further, acetylcholinesterase and antioxidant enzyme activities decreased significantly whereas reactive oxygen and nitrogen species, nitric oxide and lipid peroxidation levels increased significantly in the hemolymph, head and midgut of insects exposed to CBZ alone and the mixtures. Collectively, CBZ alone and binary mixtures of CBZ and DZP caused neurotoxicity via induction of inflammatory and oxidative stress in insects. Nauphoeta cinerea may be a potential non-target insect model for monitoring ecotoxicological hazard of pharmaceuticals.

Tissue-specific responses of Lymantria dispar L. (Lepidoptera: Erebidae) larvae from unpolluted and polluted forests to thermal stress

In this paper the effects of increased environmental temperature on the relative growth rate (RGR) and developmental time in 5th instar L. dispar larvae originating from unpolluted and polluted forests were analyzed. As indicators of the level of generated reactive oxygen species in thermal stress, we estimated midgut and hemolymph activity of the antioxidative enzymes, superoxide dismutase (SOD) and catalase (CAT), as well as the detoxifying enzymes glutathione S-transferase (GST), carboxylesterase (CaE) and acetylcholinesterase (AChE) from the midgut and brain tissue. We also examined the influence of induced thermotolerance as a species' ability to overcome the negative effects of this stressor. In larvae originating from the unpolluted forest, the midgut is the primary location of increased SOD and CAT activity and induced thermotolerance did not modified their activity in either tissue. In larvae from the polluted forest, in both tissues SOD activity was more sensitive to an increased temperature and induced thermotolerance than CAT. Carboxylesterase responded diversely to thermal stress depending on the analyzed tissue regardless the origin of larvae, while the activity of GST and AChE in tissue depended on the origin of larvae. Induced thermotolerance modified the activity of detoxifying enzymes in larvae originating from the polluted forest. Combining the selected parameters into an integrated biomarker response (IBR) the GST, CaE and AChE battery emerged as a potential biomarker for thermal stress in L. dispar larvae.

Streptozotocin induces brain glucose metabolic changes and alters glucose transporter expression in the Lobster cockroach; Nauphoeta cinerea (Blattodea: Blaberidae)

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.

High level of methylmercury exposure causes persisted toxicity in Nauphoeta cinerea

Methylmercury (MeHg⁺) is a neurotoxicant abundantly present in the environment. The long-term effects of MeHg⁺ have been investigated in rodents, yet data on the long-term or persisted toxicity of MeHg⁺ in invertebrates is scanty. Here, we examined the acute, intermediate, and chronic effects upon dietary administration of MeHg⁺ in nymphs of Nauphoeta cinerea. Besides, the potential reversibility of the toxic effects of MeHg⁺ after a detoxification period was evaluated. Nymphs were exposed to diets containing 0 (control), 2.5, 25, and 100 μg MeHg⁺/g of diet for 10, 30, and 90 days. Additional groups of nymphs were fed with the same dose of MeHg⁺ for 30 days and then were subjected to a detoxification period for 60 days. The nymphs exposed to 100 μg MeHg⁺/g succumbed to a high mortality rate, along with multiple biochemical (increase of reactive oxygen species production and glutathione S-transferase activity, as well as decrease in the acetylcholinesterase activity) and behavioral alterations. We observed delayed mortality rate and behavioral alterations in nymphs exposed to 100 μg MeHg⁺/g for 30 days and subsequently subjected to 60 days of detoxification. However, the biochemical alterations did not persist throughout the detoxification period. In conclusion, our results established the persistent toxic effect of MeHg⁺ even after a prolonged detoxification period and evidenced the use of N. cinerea as an alternative model to study the toxicity of MeHg⁺.

Assessing the toxicant effect of spontaneously volatilized 4-vinylcyclohexane exposure in nymphs of the lobster cockroach nauphoeta cinerea

Vinylcyclohexene (VCH) is an environmental contaminant well known for its ovotoxicant effects in several organisms. However, the mechanisms underlying the toxicity of VCH as well as its harmful effects toward other organs are until unclear. In this work, we assess some endpoint signals of toxicity induced by volatilized VCH exposure using nymphs of the lobster cockroach Nauphoeta cinerea. Nymphs were exposed to VCH via inhalation for 70 days. The levels of volatilized VCH were quantified by headspace gas chromatography and the concentration varied between 3.41 and 7.03 nmol/μl. VCH inhalation caused a reduction of 35% in the survival rate of the exposed animals. Nymphs exposed to volatilized VCH for 35 and 70 days had a reduction in the body weight gain of 1.8- and 2.6-fold, respectively with a reduction in dissected head, fat body, and maturing reproductive organs. The exposure did not change water consumption, excepting on the 20th day (with a 3-fold change) and decreased the food intake significantly. Regarding biochemical markers, we found that the activity of GST from the dissected organs was increased by volatilized VCH after both 35 and 70 days of exposure. The fat body presented the most prominent GST activity especially after 35 days of exposure with 1.6-fold higher than the control group. Exposure also caused an increase in RS levels in the fat body of 1.35-fold and 1.47-fold after 35 and 70 days, respectively and did not affect the activity of the AChE from the head. Our findings support the harmful impact of volatilized VCH inhalation, highlighting the cockroach N.cinerea as a valuable insect model to investigate environmental toxicants.