Isolation, characterization, and tissue-specific expression of GABA A receptor α1 subunit gene of Carassius auratus gibelio after avermectin treatment

Eucalyptol alleviates avermectin exposure-induced apoptosis and necroptosis of grass carp hepatocytes by regulating ROS/NLRP3 axis

The wide application of Avermectin (AVM) has caused pollution of surface water and damage to non-target organisms. A growing body of evidence supports the most prominent role of Eucalyptol (EUC) is antioxidation. To the purpose of explore the injury mechanism of Avermectin on grass carp hepatocytes and the antagonistic effect of Eucalyptol, 5.7 μM AVM and/or 20 μM EUC were used to treat grass carp hepatocytes for 24 h to establish hepatocyte exposure model. The results showed that Avermectin exposure significantly increased the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) in cells, reduced the activities of superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC). Also, the expressions of NLRP3 inflammasome-related genes including NLRP3, ASC, and Caspase-1, the necroptosis-related genes including RIPK1, RIPK3, and MLKL and apoptotic genes including Bax, Caspase-3, and Caspase-9 were all up-regulated. Meanwhile, the expressions of Caspase-8 and Bcl-2 were significantly decreased upon exposure to Avermectin. However, the toxicity was significantly alleviated with the treatment of EUC or N-acetyl-l-cysteine (NAC). The above results indicated that eucalyptol alleviated AVM exposure-induced apoptosis and necroptosis of grass carp hepatocytes by regulating the ROS/NLRP3 signaling pathway.

Pesticides at brain borders: Impact on the blood-brain barrier, neuroinflammation, and neurological risk trajectories

Pesticides are omnipresent, and they pose significant environmental and health risks. Translational studies indicate that acute exposure to high pesticide levels is detrimental, and prolonged contact with low concentrations of pesticides, as single and cocktail, could represent a risk factor for multi-organ pathophysiology, including the brain. Within this research template, we focus on pesticides' impact on the blood-brain barrier (BBB) and neuroinflammation, physical and immunological borders for the homeostatic control of the central nervous system (CNS) neuronal networks. We examine the evidence supporting a link between pre- and postnatal pesticide exposure, neuroinflammatory responses, and time-depend vulnerability footprints in the brain. Because of the pathological influence of BBB damage and inflammation on neuronal transmission from early development, varying exposures to pesticides could represent a danger, perhaps accelerating adverse neurological trajectories during aging. Refining our understanding of how pesticides influence brain barriers and borders could enable the implementation of pesticide-specific regulatory measures directly relevant to environmental neuroethics, the exposome, and one-health frameworks.

Abamectin causes cardiac dysfunction in carp via inhibiting redox equilibrium and resulting in immune inflammatory response and programmed cell death

This study aims to investigate the effects of environmentally relevant concentrations of abamectin on the cardiac function of carp and the potential mechanisms. Here, male carp were exposed to abamectin, and cardiac function-related enzymatic markers were examined. Cardiac histopathology, redox equilibrium, inflammation, and cell death were evaluated. Abamectin exposure caused cardiac dysfunction by upregulating lactate dehydrogenase (LDH), aspartate aminotransferase (AST), creatine kinase (CK), creatine Kinase MB isoenzyme (CK-MB) and white blood cells (WBCs), and decreasing red blood cells (RBCs) and hemoglobin (Hb). DHE staining and biochemical assays revealed that abamectin caused ROS release and oxidative stress by inhibiting Nrf2-ARE pathway. Histopathological and real-time fluorescence quantitative PCR (RT-qPCR) assays revealed that abamectin caused myocardial fiber swelling and inflammatory cell infiltration, enhanced pro-inflammatory cytokines tumor necrosis factor-α (Tnf-α), interleukin-1 beta (Il-1β), and Il-6 levels and attenuated anti-inflammatory cytokines Il-10 and transforming growth factor beta 1 (Tgf-β1) through activating NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome and nuclear factor kappa-B (NF-κB) pathway. Tunel staining showed that abamectin triggered cardiac apoptosis via activating p53-mediated mitochondrial apoptosis with elevated bcl2-associated X (Bax), reduced B-cell lymphoma-2 (Bcl-2), and activated Caspase-9 and Caspase-3. Immunoblot analysis revealed that abamectin activated autophagic flow by inhibiting mammalian target of rapamycin (mTOR), resulting in the conversion of LC3B from LC3-I to LC3-II, elevation of autophagy protein 5 (Atg5), and reduction of p62. Overall, abamectin caused cardiac dysfunction in carp via inhibiting redox equilibrium and resulting in immune inflammatory response and programmed cell death.

Understanding CNS Effects of Antimicrobial Drugs Using Zebrafish Models

Antimicrobial drugs represent a diverse group of widely utilized antibiotic, antifungal, antiparasitic and antiviral agents. Their growing use and clinical importance necessitate our improved understanding of physiological effects of antimicrobial drugs, including their potential effects on the central nervous system (CNS), at molecular, cellular, and behavioral levels. In addition, antimicrobial drugs can alter the composition of gut microbiota, and hence affect the gut-microbiota-brain axis, further modulating brain and behavioral processes. Complementing rodent studies, the zebrafish (Danio rerio) emerges as a powerful model system for screening various antimicrobial drugs, including probing their putative CNS effects. Here, we critically discuss recent evidence on the effects of antimicrobial drugs on brain and behavior in zebrafish, and outline future related lines of research using this aquatic model organism.

Ivermectin Increases Random-Pattern Skin Flap Survival in Rats: The Novel Role of GABAergic System

BACKGROUND

Ivermectin (IVM) was first used as an antiparasitic agent; however, the role of this drug evolved into a broad spectrum. Many mechanisms have been proposed, including interaction with the GABAergic system. Considering the presence of GABA receptor in the skin tissue and its role in ischemia-reperfusion I/R injury, we aimed to evaluate the effect of IVM through GABA receptors on random-pattern skin flap survival.

METHODS

Sixty Wistar male rats were used. Multiple doses of IVM (0.01, 0.05, 0.2, and 0.5 mg/kg) were injected intraperitoneally before the surgery. Baclofen (selective GABAB agonist) and bicuculline (selective GABAA antagonist) were administered in combination with IVM to assess the role of the GABAergic system. Histopathological evaluations, immunohistochemical staining, quantitative assessment of IL-1β and TNFα, and the expression of GABAA α1 subunit and GABAB R1 receptors were evaluated in the skin tissue.

RESULTS

IVM 0.05 mg/kg could significantly increase flap survival compared with the control group (P < 0.001). Subeffective dose of baclofen (0.1 mg/kg) had synergistic effect with the subeffective dose of IVM (0.01 mg/kg) (P < 0.001), whereas bicuculline 1 mg/kg reversed the effect of IVM (0.05 mg/kg) (P < 0.001). IVM 0.05 mg/kg could also decrease the IL-1β and TNFα levels and increase the expression of GABAA α1 subunit and GABAB R1 receptors in the flap tissue compared with the control group.

CONCLUSIONS

IVM could improve skin flap survival, probably mediated by the GABAergic pathway. Both GABAA and GABAB receptors are involved in this process. This finding may repurpose the use of old drug, "Ivermectin."

Sub-basal increases of GABA enhance the synthesis of TNF-α, TGF-β, and IL-1β in the immune system organs of the Nile tilapia

The cells of the immune and neuronal systems share different receptors for cytokines or neurotransmitters, producing feedback responses between both systems. Cytokines such as IL-1β and TNF-α can induce inflammation; however, the secretion of these molecules can be modulated by anti-inflammatory cytokines, as is the case for TGF-β, as well as by different hormones or neurotransmitters such as the γ-aminobutyric acid (GABA). In this study, we evaluated the secretion of IL-1β, TNF-α, and TGF-β under basal conditions, in the head of the kidney, spleen, thymus, and serum of the Nile tilapia, as well as their release induced by different sub-basal increases of GABA. We found that at the higher dose of GABA these cytokines were synthesised at a higher concentration compared to the control group. These results may suggest that there is feedback between both systems and that GABA plays a role in the modulation of the immune response.

Avermectin inhibits neutrophil extracellular traps release by activating PTEN demethylation to negatively regulate the PI3K-ERK pathway and reducing respiratory burst in carp

Excessive residual avermectin (AVM) in the environment can have toxic effects on non-target organisms. AVM can exert immunotoxicity by inducing genomic demethylation, but its effect on neutrophil extracellular traps (NETs) release in carp is unclear. In this study, carp neutrophils were pretreated with 5 μg/L AVM or 4 μM DNA demethylation inhibitor (aurintricarboxylic acid, ATA), alone or in combination, and then treated with 4 μM phorbol 12-myristate 13-acetate (PMA) to stimulate NETs release. The results showed that exposure of carp neutrophils to AVM significantly suppressed NETs release and MPO expression, increased ROS production, and dramatically reduced PMA-induced cellular respiratory burst. In addition, AVM could bind to the MBD2 molecule, markedly upregulate MBD2 expression to cause demethylation, and clearly activate PTEN expression, thereby inhibiting the expression of PI3K, AKT, Raf, MEK, and ERK. However, these effects were alleviated by ATA. In conclusion, our study showed that AVM could inhibit NETs release in carp by inducing demethylation of PTEN to negatively regulate NETs synthesis pathways and reducing respiratory burst level. Our findings clarify the mechanism of AVM immunotoxicity to fish and are of great significance for efforts to protect the ecological environment and human health.

Avermectin stress varied structure and function of gut microbial community in Lymantria dispar asiatica (Lepidoptera: Lymantriidae) larvae

Lymantria dispar asiatica is a globally distributed herbivorous pest. Avermectin is a highly effective, broad-spectrum insecticide. In this study, fourth instar L. dispar asiatica larvae were exposed to a LC₃₀ dose of avermectin. The structure and function of larval gut microbial community was analyzed to examine how gut microbiota in L. dispar asiatica larvae responded to avermectin stress. Results showed that the structure and function of gut microbial community in L. dispar asiatica larvae were varied by avermectin stress. To be precise, more than half quantity of the observed Optical Taxonomic Units (OTUs) showed significantly different abundances under avermectin stress. Linear discriminant analysis effect size (LEfSe) suggested nine bacterial genera and 12 fungal genera contributed to the different gut microbial community structure in L. dispar asiatica larvae. Gut microbial function classification (PICRUSt and FUNGuild) suggested that three bacterial function categories and a fungal function guild were significantly increased, and two fungal function guilds were significantly decreased by avermectin stress. This study furthers our understanding of the physiology of L. dispar asiatica larvae under avermectin stress, and is an essential step towards future development of potential pesticide targets.

Interaction of insecticides with heteromeric GABA-gated chloride channels from zebrafish Danio rerio (Hamilton)

The ionotropic GABA_A receptor (GABA_AR) is the main fast inhibitory post-synaptic receptor and is also an important insecticidal target. Effect of insecticides on fish has attracted intensive attention. However, no systematic study on heteromeric zebrafish GABA_AR expressed in oocytes has been reported to date. In this study, the α1 subunit, the β2S subunit lacking 47 amino acid residues compared with the β2L subunit, and the γ2 subunit having five transmembrane domains were isolated from zebrafish Danio rerio. The responses of homomeric and heteromeric (α1, β2S and γ2) channels to agonists and GABA_AR-targeted compounds were detected with two-electrode voltage clamp. Dose-dependent responses were observed in heteromeric α1β2S, β2Sγ2, and α1β2Sγ2 GABAR channels with EC₅₀ values at 21.75, 6291, and 33.69 μM for GABA-induced current and 3.28, 155.5, and 3.79 mM for β-alanine-induced current, respectively. However, no response was induced by benzamidine in all GABAR channels. Abamectin, dieldrin, fluralaner and fipronil could strongly inhibited GABA-induced inward current ≥50% at 10^-6 M, while α-endosulfan, flufiprole and ethiprole only inhibited GABA-induced current <50%. This study has clarified the interaction of insecticides with the heteromeric GABA_AR channel, which could help us further explore the potential function and toxicological importance of GABA_ARs from D. rerio.

Identification of Carassius auratus gibelio liver cell proteins interacting with the GABAA receptor γ2 subunit using a yeast two-hybrid system

The γ-aminobutyric acid type A (GABA_A) receptor is an important pentameric inhibitory neurotransmitter receptor, and the γ2 subunit of this receptor plays a key role in potentiation of the GABA_A response. We previously detected that the expression of GABA_A receptor in the livers of Carassius auratus gibelio significantly increased after medication (avermectin and difloxacin treatment). In order to better understand the mechanism of action of the GABA_A receptor γ2 subunit in the livers of C. auratus gibelio, we constructed a C. auratus gibelio liver cDNA library (the titer value of 1.2 × 10⁶ cfu/mL) and identified the proteins that interact with the GABA_A receptor γ2 subunit by using a yeast two-hybrid assay. The yeast two-hybrid screening yielded seven positive clones, namely, prelid3b, cdc42, sgk1, spg21, proteasome, chia.5, and AP-3 complex subunit beta-1, all of which have been annotated by the NCBI database. The functions of these proteins are complex; therefore, additional studies are required to determine the specific interactions of these proteins with the GABA_A receptor γ2 subunit in the liver of C. auratus gibelio. Although the interactions identified by the yeast two-hybrid system should be considered as preliminary results, the findings of this study may provide further direction and a foundation for future research focusing on the mechanisms of the GABA_A receptor γ2 subunit in C. auratus gibelio livers.