Coastal marine organisms are increasingly exposed to co-occurring chemical effluents and opportunistic pathogens; however, the mechanisms governing their combined toxicological effects remain insufficiently resolved. This study evaluated the combined effects of olive mill wastewater (OMW) and Vibrio harveyi on Mytilus galloprovincialis, with a focus on antioxidant enzyme responses, microbial dynamics, and environmental conditions under static and flow-through exposure regimes. Mussels were exposed to sublethal OMW concentrations in the presence and absence of V. harveyi, and tissue-specific activities of the antioxidant enzymes, namely superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST), were assessed alongside bacterial abundance, dissolved oxygen concentration (DO), and pH. Under static conditions, V. harveyi persisted throughout the exposure period (4.08-4.48 log CFU/g at 48 h), coinciding with reduced DO (3.4 mg/L) and sustained elevation of antioxidant enzyme activities. In contrast, flow-through conditions promoted rapid bacterial elimination (below detection limits within 3-12 h) and stabilised environmental parameters (DO >5 mg/L), resulting in reduced antioxidant enzyme responses. OMW alone induced concentration-dependent changes in antioxidant enzyme activities, with gill SOD activity reaching 135.28 ± 8.10 U/mg protein at 5% OMW. Notably, under co-exposure conditions, 1% OMW was associated with lower antioxidant enzyme activities compared with V. harveyi exposure alone. Multivariate analyses revealed clear associations between antioxidant enzyme activities, microbial persistence, and dissolved oxygen concentration dynamics across exposure regimes. These findings indicate that short-term antioxidant enzyme response patterns differed between static and flow-through exposure regimes and highlight the importance of environmental context when interpreting biochemical responses in marine bivalves.
Caffeic acid is widely used in food and pharmaceuticals, raising concerns about its aquatic ecotoxicity. Here, we evaluated developmental toxicity in zebrafish embryos acutely exposed to caffeic acid. At 120 hpf, the LC₅₀ was 134.3 μg/mL. Subsequent exposures at 0, 40, 80, and 120 μg/mL dose-dependently increased mortality, delayed hatching, reduced growth, and induced cardiac, hepatic, and neurobehavioral abnormalities. Molecular assays revealed dysregulation of inflammation-related genes and suppressed expression of caspase3/9 with a decreased bax/bcl2 ratio, indicating an inflammatory response and inhibition of apoptosis. Transcriptomic profiling at 80 μg/mL identified 287 differentially expressed genes enriched in immune, cellular, and signal transduction pathways; protein-protein interaction analysis further suggested possible synergistic roles in DNA repair and cell cycle regulation. Collectively, our results demonstrate that caffeic acid causes multi-organ developmental toxicity at phenotypic and gene-expression levels. The findings provide a theoretical basis for understanding the toxicological mechanisms of caffeic acid and contribute to its environmental safety assessment.
Fenvalerate (FEN), a widely used an agricultural type II pyrethroid pesticide, has been found in the environment and human tissues. Nevertheless, the cardiotoxicity of FEN remains poorly understood. This study aimed to explore the cardiotoxicity of FEN and the potential cardioprotective role of resveratrol (RES, a polyphenolic antioxidant) in zebrafish. In this research, zebrafish embryos were exposed to FEN at concentrations of 0, 3.5 and 7 μg/L from 4 to 96 h post fertilization (hpf) and developmental cardiotoxicity was evaluated. The findings demonstrated that FEN significantly impaired embryonic development, with lower survival and hatching success, diminished spontaneous movement, lower heart rate and body length, as well as an elevated malformation rate. FEN induced both morphological and functional abnormalities in the heart of myl7:egfp zebrafish, along with the downregulation of genes related to cardiac development. FEN also induced oxidative stress by generating excessive reactive oxygen species and disturbing antioxidant enzyme activities, thereby triggering cardiomyocyte apoptosis via upregulated apoptotic gene expression. Remarkably, these cardiotoxic effects were effectively mitigated by RES via its antioxidation, underscoring oxidative stress and apoptosis as important mechanisms of FEN-induced cardiotoxicity in zebrafish. Overall, this study delineated the key mechanisms of FEN-triggered cardiotoxicity and identified RES as a promising candidate for therapeutic intervention.
Benzophenone-type UV filters (BPs) are widely used in personal care products and various industrial applications, resulting in their continuous release into aquatic environments. BPs have attracted significant attention as emerging contaminants because of their widespread use, structural diversity, environmental persistence, various exposure pathways, and adverse toxicological effects in aquatic organisms. Previous studies have largely focused on environmental occurrence and individual toxicological effects of BPs, whereas evidence regarding their interactions with multiple environmental stressors remains fragmented. Available evidence indicates that environmental factors and co-occurring contaminants can modify the environmental fate, bioavailability, bioaccumulation, and toxicity of BPs, resulting in antagonistic, additive, or synergistic effects depending on the stressor, organism, and exposure conditions. Therefore, this review describes the widespread distribution and toxicological effects of BPs in aquatic ecosystems, examining how environmental factors and co-occurring contaminants modify the environmental fate and toxicological effects of BPs under multi-stressor conditions. This review suggests that the ecological significance of BPs lies not only in their intrinsic toxicity but also in the way multi-stressor interactions modify their biological impacts, thereby defining directions for future ecological risk assessment.
Thyroid hormone (TH) system disruption in aquatic organisms is a major global concern, yet links between laboratory toxicity data and population-level impacts remain unclear. Here, we investigated the effects of chemically induced TH deficiency on population-relevant apical endpoints-growth, development, and reproduction-in Japanese medaka (Oryzias latipes). Medaka were exposed to propylthiouracil (PTU), a TH synthesis inhibitor, in a 21-day short-term reproduction assay and a 47-day partial life-cycle test. This approach enabled the evaluation of effects across multiple life stages and generations. PTU exposure led to reduced TH levels, thyroid histopathological changes, and upregulation of TH-related genes, confirming the sensitivity of these endpoints in medaka. In offspring from the TH-deficient group, delayed hatching and reduced growth were detected. However, investigation of larval-juvenile metamorphosis and development of the swim bladder and retina showed limited or no effects, despite their established association with TH. While reproductive output and vitellogenin levels were unaffected even under TH depletion, reduced secondary sexual characteristics in adult males and delayed testicular development in offspring were observed. These results suggest possible crosstalk between thyroid and reproductive axes, although non-specific systemic toxicity cannot be excluded. These findings indicate that TH-responsive molecular and organ-/tissue-level endpoints are not necessarily directly relevant to population-level adverse outcomes and should be interpreted carefully. Overall, this study supports the utility of medaka as a model for evaluating thyroid active substances and highlights the importance of a weight-of-evidence approach integrating diverse endpoints for the assessment of endocrine-disrupting chemicals in aquatic environments.
The co-occurrence of pesticides and antibiotics in aquatic environments has raised increasing concern because of their potential effects on aquatic organisms. Cypermethrin (CMN) and sulfamethoxazole (SMZ) are representative pyrethroid pesticides and sulfonamide antibiotics, respectively, but their combined effects on fish muscle remain poorly understood. In this study, grass carp (Ctenopharyngodon idella) were exposed to CMN (0.65 μg/L), SMZ (0.30 μg/L), or their combination for 42 days. Network toxicology, histopathology, oxidative stress assays, Western blotting, protein-protein interaction analysis, and molecular docking were used to investigate muscle injury and related molecular responses. The MIX group showed more severe pathological alterations than the single-exposure groups, including extensive myofiber disruption, fragmentation, nuclear condensation, and nuclear displacement. It also increased malondialdehyde levels, decreased total superoxide dismutase activity, and markedly altered proteins associated with endoplasmic reticulum stress. Phosphorylation of P38, JNK, and ERK was elevated, indicating enhanced MAPK signaling. Suppression of the PI3K-AKT-mTOR pathway was accompanied by increased Beclin-1 expression, an elevated LC3-II/LC3-I ratio, and decreased P62 expression, suggesting enhanced autophagy-related responses. In addition, Bax, Caspase-9, and Caspase-3 expression increased, whereas Bcl-2 expression decreased, indicating enhanced mitochondria-associated apoptotic signaling. Network analysis and molecular docking identified HSP90, HSP70, and Caspase-3 as potential core targets. These findings show that combined CMN and SMZ exposure induces severe muscle injury in grass carp, with the MIX group exhibiting the most pronounced changes in oxidative stress, endoplasmic reticulum stress, MAPK activation, autophagy, and apoptosis.
Environmental accumulation of excessive molybdenum (Mo) and cadmium (Cd) exerts detrimental effects on organisms. The TLR4/MyD88/NF-κB signaling cascade is classified as a core pathway responsible for regulating inflammatory responses in organisms. To elucidate the mechanism by which combined Mo and Cd exposure induces sheep spleen injury and clarify how the TLR4/MyD88/NF-κB pathway modulates this pathological process, we constructed both in vivo and in vitro models. Mo and/or Cd exposure induces splenic histological changes and mitochondrial ultrastructural damage. Notably, mRNA transcript and protein abundances of TLR4/MyD88/NF-κB pathway-related molecules and pro-inflammatory cytokines were significantly elevated in sheep splenic tissue. Concurrently, this tissue showed a marked drop in T-SOD and CAT activity, in contrast to the significant increase in MDA and H2O2 concentrations. In parallel, observations from the in vitro assay showed that single or combined treatment with Mo and Cd significantly upregulated the expression of TLR4/MyD88/NF-κB pathway-associated molecules, accompanied by elevated ROS levels and exacerbated lipid peroxidation in splenic lymphocytes. We further observed a substantial decrease in antioxidant enzyme activities, alongside a significant reduction in immunoglobulin levels in treated cells' supernatant. Importantly, application of a TLR4 inhibitor effectively mitigated the Mo- and/or Cd-induced damage to splenic lymphocytes along with associated oxidative lesions. It simultaneously inhibited ROS production, downregulated pro-inflammatory cytokine expression, and increased immunoglobulin levels in the experimental model. Collectively, our findings indicate that combined Mo and Cd exposure induces splenic inflammatory responses and oxidative stress-mediated lymphocyte injury by activating the TLR4/MyD88/NF-κB signaling cascade.
Nitrite accumulation represents a major stressor in the intensive aquaculture of Litopenaeus vannamei. Increasing water salinity (by NaCl supplementation) is one of the conventional alleviation strategies. However, this study found that under conditions providing equivalent Cl- concentration, MgCl2 was more effective than NaCl in alleviating nitrite toxicity. To elucidate the specific protective mechanism of magnesium ions (Mg2+), a stress experiment under an equimolar chloride background was designed, including NaCl and MgCl2 treatment groups. Survival analysis, histopathology, oxidative stress indicators, and combined transcriptomic and metabolomic approaches were comprehensively employed for evaluation. The results demonstrated that, compared with the NaCl group, MgCl2 treatment significantly improved shrimp survival, reduced hepatopancreatic tissue damage and apoptosis, and accelerated the clearance of nitrite in vivo. At the molecular level, the beneficial effect of Mg2+ was primarily achieved through a dual synergistic pathway: First, it systematically up-regulated genes and metabolites related to cofactor biosynthesis, providing critical support for cellular metabolism under stress. Second, it directed adaptive reprogramming of the glycerophospholipid metabolism pathway, enhancing resistance to oxidative damage by stabilizing cell membrane structure. This coordinated regulation of metabolic support systems and membrane stability enabled the organism to manage oxidative stress via an economical and efficient "prevention-stabilization" mode, rather than passively activating high-energy-consuming antioxidant defenses. This study reveals, at both physiological and multi-omics levels, the unique cytoprotective mechanism of Mg2+ against acute aquatic toxicants in crustaceans, providing an important theoretical foundation for developing novel and efficient nitrite alleviation strategies based on Mg2+ regulation.
Acetaminophen (APAP), also known as paracetamol, is the only antipyretic and analgesic agent that can be administered to pregnant women. In addition to hepatotoxicity in cases of an overdose, the developmental neurotoxicity of APAP has been reported in model organisms. In this study, developing zebrafish were used to assess the neurotoxic effects of waterborne APAP exposure (0.039-2.5 mM). At 120 h post-fertilization (hpf), the spontaneous swimming distance was significantly reduced at all tested APAP concentrations under alternating light-dark conditions. Touch-evoked escape velocity, which assesses the motor function, was not significantly reduced at any concentration and it increased at moderate APAP doses. The optokinetic response was only reduced at 2.5 mM APAP concentrations, suggesting that the decrease in spontaneous swimming at low APAP doses is unlikely to be due to motor or visual impairments. Vibration-evoked responses, indicative of the sensory function, were slightly but significantly diminished at 0.625 and 2.5 mM APAP concentrations. At 72 hpf, acridine orange and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining showed that exposure to 2.5 mM APAP resulted in regulated cell death in the cerebellum, retina, and dorsal trunk. Some APAP-induced cell death in the dorsal trunk was confirmed to be of neuronal origin using Tg(eno2:Cerulean) transgenic zebrafish. N-acetylcysteine, a well-known antioxidant and antidote for APAP toxicosis in humans, partially attenuated APAP-induced cell death. These results suggest that APAP induces developmental neurobehavioral and sensory organ toxicity in the absence of detectable regulated cell death under the present experimental conditions.
The serine-hydrolase esterases-acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and carboxylesterase (CarbE)-mediate xenobiotic detoxification and lipid metabolism, yet their comparative kinetics and regulatory mechanisms remain largely unknown in Neotropical fish. Here, we provide the first integrated kinetic and mechanistic characterization of AChE, BChE, and CarbE in the serum and liver of three ecologically and commercially important Characiform fish: curimbatá (Prochilodus lineatus), pacu (Piaractus mesopotamicus), and piavussu (Leporinus macrocephalus). The dominant serum esterase was species-specific: CarbE predominated in curimbatá (Vmax = 29.85 U·mL-1) and pacu (4.69 U·mL-1), whereas piavussu serum was dominated by BChE (17.87 U·mL-1). Selective-inhibitor profiling confirmed the B-esterase identity of serum CarbE, which was inhibited by the organophosphate methyl-paraoxon with approximately 10-fold higher potency in curimbatá than in pacu (IC50 = 74 vs. 691 nM), indicating interspecific differences in organophosphate-scavenging capacity. Semi-purified CarbE fractions from the two species were biochemically distinct (49 vs. 56 kDa; Vmax = 3426 vs. 330 U·mg-1 protein). Pacu CarbE hydrolyzed p-nitrophenyl palmitate (p-NPP) in serum and liver microsomes, demonstrating long-chain ester hydrolase activity, and the microsomal activity decreased after 42 h of hypoxia (0.5 mg O2·L-1), with a more pronounced effect during spring/summer. The lipid aldehyde 4-hydroxynonenal (4-HNE) inhibited serum CarbE more potently than the microsomal form (approximate IC50 ≈ 2 vs. ≈ 4 mM), supporting a potential link between hypoxia-associated lipid peroxidation and reduced esterase activity. These findings establish a biochemical framework for esterase function in Neotropical Characiform fish and identify 4-HNE-mediated CarbE inhibition as a candidate regulatory mechanism associated with oxygen limitation.
Aquatic ecosystems in southeastern Mexico face increasing chemical pollution, yet non-lethal molecular tools to monitor native reptile populations remain limited. We performed RNA sequencing (RNA-seq) on non-lethal caudal scute biopsies of 43 Morelet's crocodiles (Crocodylus moreletii) across six wild populations and a captive reference group. After mapping to the Alligator mississippiensis genome, 18,107 expressed genes were analyzed using multivariate, differential-expression, co-expression network, and single-sample pathway scoring approaches. Wild crocodiles showed a consistent shift along a dominant transcriptional axis contrasting dermal/extracellular matrix remodeling with epidermal-metabolic/barrier programs. A conserved core of differentially expressed genes (DEGs) and wild-associated modules were enriched for extracellular matrix organization, secretory stress handling, vesicle trafficking and adhesion pathways, while union DEGs captured site-specific alterations in lipid metabolism, ion transport, neuronal signaling and developmental processes. Integrating network connectivity, differential expression strength, statistical support, and receiver operating characteristic performance, we prioritized 10 up-regulated genes as a preliminary scute biomarker panel that discriminates wild from captive individuals. This landscape-scale scute transcriptomic framework supports non-lethal omics-based biomonitoring in crocodilians and other non-model wildlife.
Tire wear particles (TWPs), which are increasingly released into aquatic environments, pose a potential threat to aquatic organisms. Clarifying the hepatotoxic effects and mechanisms of TWP leachate is important for aquatic health protection. In this study, crucian carp (Carassius auratus) were exposed to environmentally relevant concentrations of TWP leachate for 28 days to investigate its hepatotoxic effects and potential mechanisms. The results revealed that TWP leachate exposure led to zinc accumulation in the intestine and liver. Additionally, we found that TWP leachate exposure significantly increased the hepatosomatic index, accompanied by hepatic necrosis, inflammatory cell infiltration, weakened antioxidant defense. Meanwhile, TWP leachate exposure induced gut microbiota dysbiosis, as characterized by reduced beneficial bacteria (Lactobacillus, Bacillus, Roseburia) and enriched opportunistic pathogens (Aeromonas, Mycobacterium). Furthermore, TWP leachate exposure also perturbed hepatic glycerophospholipid metabolism, fatty acid degradation, and AMPK/PPAR signaling. Transcriptome sequencing and qPCR analysis demonstrated that TWP leachate suppressed AMPK/PPAR signaling, upregulated lipogenic genes (FAS, ACC1), and activated inflammatory cytokines (TNF-α, IL-1β) in the liver. Collectively, this study suggests that TWP leachate-induced hepatotoxicity was highly associated with gut microbiota dysbiosis and AMPK/PPAR-related disruption of lipid metabolism in crucian carp. Our study provides new mechanistic insights for the ecotoxicological risks posed by chemical mixtures released from TWPs in aquatic ecosystems.
Bees are key pollinators in natural and agricultural ecosystems, yet they are increasingly affected by the intensive use of pesticides. Although not primary targets of these compounds, bees may be exposed during foraging activities. Thiamethoxam and fipronil are widely used insecticides and have been implicated in pollinator decline. Stingless bees are essential pollinators in Neotropics, making the assessment of pesticide effects on these species particularly important. This study evaluated the sublethal effects of thiamethoxam and fipronil on neural and detoxification-related enzymes in the stingless bee Melipona scutellaris. Forager bees were exposed to fipronil (LC₅₀/2 = 0.0055 and LC₅₀/5 = 0.0022 ng a.i./μL) and thiamethoxam (LC₅₀/2 = 0.027 and LC₅₀/5 = 0.010 ng a.i./μL). AChE and CaE-3 activities were assessed in the heads, while GST activity was measured in the abdomens after 1, 6, 12, 24, 48, and 96 h of exposure. Thiamethoxam promoted more pronounced alterations in AChE, CaE-3, and GST activities than fipronil, particularly at longer exposure periods. Significant Treatment vs Time interactions demonstrated that enzymatic modulation varied according to insecticide type and exposure duration, although response profiles differed among biomarkers. Alterations in AChE activity indicate disruption of cholinergic regulation, whereas changes in CaE-3 and GST activities suggest activation of detoxification and oxidative stress-related pathways. The results demonstrate that M. scutellaris exhibits marked enzymatic sensitivity to sublethal concentrations of thiamethoxam and fipronil, reinforcing the importance of incorporating sublethal endpoints into pesticide risk assessments and highlight the potential of enzymatic biomarkers as early indicators of pesticide-induced stress in stingless bees.
Microplastics and degraded nanoplastics are widespread freshwater pollutants that pose the ecological risks to aquatic organisms, while temperature variation can modulate their environmental fate and toxicity. Therefore, understanding the combined effects of temperature variation and nano- and microplastics on Pomacea canaliculata is crucial for ecological risk assessment. In this study, P. canaliculata was exposed to 5 μm polystyrene microplastics and 20 nm polystyrene nanoplastics at 15, 25, and 35 °C for 14 days. Physiological responses were determined via an assessment of key enzyme activities (antioxidant, immune-related, and digestive) and non-targeted metabolomic profiles in the hepatopancreas. Exposure to polystyrene nano- and microplastics under varying thermal conditions altered physiological and metabolic responses in the hepatopancreas of P. canaliculata. Combined exposure significantly affected catalase, superoxide dismutase, and lipase activities, whereas acid phosphatase, alkaline phosphatase, and amylase were mainly regulated by temperature. Responses were more pronounced under high temperature, with the 35 °C plus 20 nm nanoplastics treatment showing the greatest metabolomic alterations. Size-dependent differences were also evident: 20 nm nanoplastics, particularly at 35 °C, induced higher antioxidant enzyme activities than 5 μm microplastics and were more closely associated with redox regulation, transmembrane transport, and damage clearance, whereas 5 μm microplastics were more closely related to membrane lipid metabolism and lipid-mediated signaling. These findings indicate that temperature, particularly high temperature, can reshape the toxic effects of polystyrene nano- and microplastics in P. canaliculata, highlighting the need to incorporate both thermal background and particle size into ecological risk assessment.
In this study, we investigated the toxicological mechanisms of trifloxystrobin (TFX), a widely used strobilurin fungicide, on zebrafish embryos, focusing on cardiovascular development and function. Embryos were exposed to TFX (100-500 μg/L) for 96 h. The compound exhibited high acute toxicity with a 96-h median lethal concentration (LC50) of ∼320 μg/L. At 200-300 μg/L, TFX induced bioenergetic impairment, manifested as growth retardation and nutrient retention in the yolk sac. The prevalence of pericardial edema served as a hallmark of cardiac dysfunction, prompting a detailed functional assessment. A detailed cardiovascular analysis revealed a critical hemodynamic paradox. While TFX-exposed embryos exhibited bradycardia and a compensatory increase in the ventricular ejection fraction and wall thickness, effective systemic circulation was severely compromised. An advanced regurgitation analysis demonstrated that TFX caused severe atrioventricular valve insufficiency and retrograde blood flow, leading to a significant overestimation of cardiac output when calculated by standard volumetric methods alone. An analysis of the dorsal aorta confirmed a genuine reduction in the arterial blood flow velocity, validating the presence of circulatory failure despite myocardial hyper-contractility. Mechanistically, the hemodynamic alteration was linked to significant downregulation of the klf2a flow-sensitive transcription factor, which impaired valve morphogenesis, while the concurrent upregulation of nppa, nppb, and gata4 signaled pathological cardiac stress and hypertrophy. These findings elucidate a mechano-molecular toxicity pathway for TFX and highlight the technical necessity of coupling a regurgitation analysis with peripheral flow assessment to accurately evaluate cardiac toxicity in aquatic models.
Nano-enabled pesticide (NanoPs) formulations have emerged as promising alternative to conventional pesticides by improving ingredient stability, delivery, and controlled release. However, their unique physicochemical properties also influence interactions with soil microorganisms, raising concerns regarding ecological safety and long-term impacts on soil ecosystem functions. This review has critically synthesized the current knowledge about NanoPs-microbiome interactions with a focus on biochemical mechanisms underlying microbial responses and implications for pesticide fate and transformation. We review how the properties of NPs (e.g., particle size, surface charge, coatings, dissolution, and eco-corona formation) influence mobility, bioavailability, and microbial exposure. Mechanistic evidence of oxidative stress, membrane damage, enzyme inhibition, metal-ion-mediated toxicity and quorum sensing interference is critically synthesized to elucidate biochemical basis of NanoPs-induced microbial responses. Recent advances in high throughput sequencing and multi-omics technologies are also used to assess changes in microbial diversity, community composition, functional redundancy, microbial interaction networks and ecosystem resilience. The review further compares conventional and nano-formulated pesticides, highlighting differences in microbial toxicity, degradation kinetics, transformation pathways, and metabolite profiles. Current challenges associated with environmental fate assessment, standardized ecotoxicological testing, and microbiome-informed risk evaluation are critically discussed. Emerging opportunities for integrating metagenomics, artificial intelligence, and predictive modelling into environmental risk assessment are also highlighted. Finally, we propose a future research framework centered on microbiome-informed safe-by-design NanoPs, standardized testing protocols, and long-term field validation to support development of environmentally responsible nano-enabled crop protection technologies while preserving soil biodiversity and ecosystem functions.
Artificial light at night (ALAN), a form of physical pollution with growing global impacts, has been shown to induce various adverse effects on terrestrial organisms. However, studies on the effects of ALAN on aquatic organisms, particularly fish during early life stages, remain limited. In this study, zebrafish embryos were exposed to ALAN at 0, 25, 75, and 225 lx until 144 hours post-fertilization (hpf) with manipulated circadian cycles (light/dark or light/ALAN) to assess alterations in development, survival, behavior, and the monoaminergic system. The results showed that ALAN exerted no significant effects on the survival rate, hatching time, or blood flow velocity (at 72 hpf) of zebrafish embryos/larvae, but increased the embryonic heart rate (at 48 hpf) under the 75 and 225 lx conditions. Concurrently, the eye area of zebrafish exhibited a progressive reduction, accompanied by a decreased optokinetic response (OKR). Moreover, ALAN exposure decreased locomotor activity and induced marked anxiety-like behavior in zebrafish larvae. Biochemical analysis revealed significantly decreased levels of DA and its metabolites in zebrafish, which were associated with the observed physiological and behavioral deficits. In addition, the visual deficits induced by ALAN were closely linked to the behavioral alterations in zebrafish larvae. In summary, ALAN exposure is closely linked to the dopaminergic pathway, which correlates with disrupted early-life development and behavioral impairments in zebrafish. These findings highlight the potential risks that nocturnal light pollution poses to aquatic ecosystems, particularly in urbanized areas.
Mitochondria integrate energy metabolism and redox signaling through NAD(P)H-dependent processes that regulate reactive oxygen species (ROS) production. While the thermodynamic relationship between NAD(P)H redox state and hydrogen peroxide (H₂O₂) emission is well-established under physiological conditions, how environmental stressors disrupt this coupling remains poorly understood. This study investigated how exposure to copper (Cu), cadmium (Cd), and zinc (Zn), individually and in binary mixtures, affects the coupling between NAD(P)H redox state and H₂O₂ emission in rainbow trout (Oncorhynchus mykiss) heart mitochondria. Using substrate-specific assays and electron transport system inhibitors, we quantified NAD(P)H autofluorescence and H₂O₂ production at five redox sites associated with 2-oxoacid dehydrogenases and complex I. Results revealed that effects of metals were highly context-dependent, varying with substrate type, redox site, metal concentration, and co-exposure conditions, with antagonism predominating in binary mixtures. Under control conditions, NAD(P)H redox state and H₂O₂ emission were moderately correlated (R2 = 0.53 for all sites and R2 = 0.41 for whole pathways), with the correlation being stronger for site-specific measurements. Cu and Cd predominantly oxidized NAD(P)H pool, decreasing the degree of reduction by up to 94% whereas Zn frequently increased NAD(P)H reduction. Effects on H₂O₂ emission were complex, with metals exhibiting biphasic patterns at several sites. Critically, metals exposure weakened the positive correlation between NAD(P)H redox state and H₂O₂ emission, lowering the overall R2 to 0.36 and site-specific values to 0.00-0.28. These findings demonstrate that metals do not simply impose uniform oxidative stress but rather alter ROS production through mechanisms that decouple it from NAD(P)H redox status.
Immune and stress responses are closely interconnected, with glucocorticoids modulating neutrophil number and activity, and cytokines influencing stress response. Neutrophils, due to their role as primary responders to infection, high sensitivity to glucocorticoid fluctuations, and critical involvement in gut microbiota homeostasis, were selected as the central focus of this study. We examined how antibiotic-induced dysbiosis affects the hypothalamus-pituitary-interrenal (HPI) axis and stress-related neutrophil dynamics in common carp (Cyprinus carpio L.). We analyzed the expression of stress-related genes and characterized neutrophil maturation and function within the hematopoietic niche. Dysbiotic fish exposed to acute stress exhibited significantly elevated cortisol levels compared to stressed fish with intact microbiota. Notably, even non-stressed dysbiotic fish showed increased cortisol level, indicating that microbiota disruption alone impairs HPI axis regulation. Antibiotic-treated and stressed fish displayed upregulation of il1β, gcsfr, cxcl8_l2, and cxcr1, suggesting enhanced granulopoiesis and neutrophil mobilization. However, systemic neutrophilia was attenuated in dysbiotic fish regardless of stress exposure. Transcriptomic profiling of neutrophils from dysbiotic, stressed fish revealed downregulation of mpx and cxcr4, and upregulation of mmp9, mhc1, trb, nlrp12, dhx58, irf3, irf7 and stat1, indicating altered maturation, increased migratory potential, and possible neutrophil-T cell interactions. In contrast, stressed fish with intact microbiota exhibited anti-apoptotic signatures and suppression of antiviral pathways. Across all stressed and dysbiotic groups, neutrophil phagocytic activity was significantly reduced. These findings underscore the pivotal role of gut microbiota in modulating stress responses, neutrophil development and trafficking, and immune function in vertebrates.
The adrenergic system is known for its ability to influence various physiological and metabolic processes; however, its involvement in thyroid function in non-mammalian vertebrates remains poorly explored. Adult male lizards were treated with β-adrenergic agonists (isoproterenol, terbutaline, and L-isopropylamino-3-(2-thiazoloxy)-2-propanol) and the α-adrenergic antagonist (phentolamine). The effects of β-adrenergic agonists and the α-adrenergic antagonist administered as single and repeated injections were evaluated on plasma TSH, thyroid hormones, hepatic 5′-T4 ORD (type II monodeiodinase) activity, hepatic thyroid hormone contents, blood glucose levels, and thyroid gland histology. β-adrenergic stimulation produced a dose-dependent decrease in plasma TSH, accompanied by significant increases in circulating T3 and T4 levels. These changes were associated with enhanced hepatic monodeiodinase activity, increased hepatic T3 content, reduced hepatic T4 levels, and histological features indicative of thyroid activation. Repeated administrations amplified these effects. In contrast, phentolamine treatment increased plasma TSH levels but reduced circulating and hepatic T3, increased hepatic T4, and tended to decrease deiodinase activity, indicating impaired peripheral thyroid hormone activation. Histological analysis showed reduced follicular synthetic activity, although colloid resorption vacuoles were still present. IPT treatment produced no significant effects. All treatments induced hyperglycaemia, with stronger responses after repeated administrations, suggesting coordinated regulation of thyroid function and energy metabolism by adrenergic pathways. The results demonstrate that β-adrenergic signaling promotes thyroid activation and peripheral hormone conversion, whereas α-adrenergic blockade disrupts thyroid hormone homeostasis. These findings highlight a key role of adrenergic mechanisms in the neuroendocrine and metabolic regulation of reptiles, supporting their importance in physiological adaptation to environmental variability.
