Delineating involvement of MAPK/NF-κB pathway during mitigation of permethrin-induced oxidative damage in fish gills by melatonin

Present study evaluated involvement of transcription factors during permethrin-induced gill toxicity and its amelioration by melatonin. First, adult Notoptertus notopterus females were exposed to permethrin at nominal concentrations [C: 0.0, P1: 0.34, P2: 0.68 µg/L] for 15 days followed by intramuscular melatonin administration (100 µg/kg body weight) for 7 days. Gill MDA, XO, LDH levels increased, while Na+-K+-ATPase, SDH, cytochrome C oxidase levels decreased with increasing permethrin concentrations. Glutathione, SOD, CAT, GST, GRd levels increased in P1 than C, but decreased in P2 than P1, C. Melatonin administration restored gill enzyme and antioxidant levels in P1, P2. Next, isolated gill tissues were exposed to permethrin at 25, 50 µM doses along with melatonin administration (100 μg/mL). NF-κB, NRF2, Keap1, ERK, Akt, caspases protein expression changed significantly during permethrin-induced gill damage. Melatonin administration amended permethrin-induced molecular imbalance through modulation of caspase proteins and MAPK/NF-κB signal transduction pathway via melatonin receptor 1.

Expression of genes related to antioxidation, immunity, and heat stress in Gambusia affinis exposed to the heavy metals Cu and Zn

Water pollution is an increasingly serious problem. Here, Cu and Zn ions were used as stress factors, and G. affinis served as a test organism. Fluorescence quantitative PCR was used to detect changes in the expression of antioxidant genes (SOD, GST, CAT), heat stress genes (Hsp70, Hsp90, Hspd1, Hsc70), and immune system-related genes (IL-1β, IL-8) in G. affinis exposed to Cu and Zn ions over time. To explore the toxic effects of Cu and Zn on G. affinis. The results showed that the 48 h LC₅₀ concentrations of the heavy metals Cu and Zn to G. affinis were 0.17 mg/L and 44.67 mg/L, respectively. Within 48 h, with prolonged Cu exposure, the relative expression levels of the Hsp70, Hsp90, Hspd1, Hsc70, SOD, GST, and CAT genes in the gill tissue first showed a significant increase and then gradually decreased. Gene expression peaked between 9 and 36 h. The relative expression levels of SOD and GST genes in liver tissue showed a gradual decline. Within 48 h, with prolonged Zn exposure, the expression levels of SOD, CAT, and GST genes in G. affinis first increased and then fell before finally rising. The expression levels of IL-1β and IL-8 mRNA showed varying degrees of upward trends, and the expression of IL-8 was the highest for all gill tissue. To sum up, Cu and Zn have strong toxic effects on G. affinis, which makes it possible to use G. affinis as indicator organisms for aquatic environmental pollution.

The effect of Roundup on embryonic development, early foxr1 and hsp70 gene expression and hatching of common carp (Cyprinus carpio L.)

The effects of herbicide Roundup (based on glyphosate) on the embryonic development, survival and hatching of common carp (Cyprinus carpio L.) larvae and alteration in foxr1 and hsp70 gene expression were determined. The eggs (obtained from 6 females) were fertilised and incubated in water containing 0; 1 or 10 μl L^-1 of Roundup formulation. During early embryonic development (24 and 48 h post-fertilisation - hpf), Roundup caused a statistically important decrease in the embryonic survival rate of common carp. Moreover, retardation of the hatching rate was observed in the group treated with the higher concentration of Roundup at 81 to 99 hpf. At the end of the experiment (99 hpf), an important increase in number of deformed larvae was observed in both groups treated with Roundup in comparison to the control group (52.06; 16.02 and 5.08%, respectively). Significant differences in transcript of the gene foxr1 were found in Roundup-intoxicated groups in comparison to the controls. In the case of hsp70 transcripts, no important changes in exposed groups were observed. These results showed that even small, environmentally relevant amount of Roundup present in the aquatic environment is able to affect the early life stages of common carp and change the transcripts of foxr1, which may have an adverse effect on the later proper development of the reproductive system.

Garlic (Allium sativum) and Fu-ling (Poria cocos) mitigate lead toxicity by improving antioxidant defense mechanisms and chelating ability in the liver of grass carp (Ctenopharyngodon idella)

The heavy metal lead (Pb) is a contaminant widely distributed in the food chain. In this study, eight weeks of feeding containing Garlic (Allium sativum) or Fu-ling (Poria cocos) or both, markedly increased the growth index, enzyme activity, and serum index and significantly decreased muscle Pb level in grass carp (Ctenopharyngodon idella). Upon Pb exposure, the feeding Garlic or Fu-ling or both possessed the similar effects on improving the function of the antioxidant system and chelating ability. Further, the gene expressions of metal binding proteins (TF and MT-2) in the liver of the three experimental groups were significantly higher than those of the control group, which were all highly up-regulated after Pb exposure. At the same time, the activities of antioxidant enzymes (SOD and CAT) and the content of non-enzymatic substance (GSH) in the liver of the Garlic group, Fu-ling group and mixed group were stable compared to the control group after Pb exposure. Moreover, the reduction of Pb toxicity was manifested by the decrease of Pb content in the muscle, and the stable expression of heat stress proteins (HSP30 and HSP60) and immune-related genes (TNF-α and IL-1β). Taken together, the study preliminarily shows that the Garlic and Fu-ling play a role in mitigating the toxicity of Pb in grass carp.

Melatonin and its mechanism of action in the female reproductive system and related malignancies

Melatonin (N-acetyl-5-methoxytryptamine), the main product of pineal gland in vertebrates, is well known for its multifunctional role which has great influences on the reproductive system. Recent studies documented that melatonin is a powerful free radical scavenger that affects the reproductive system function and female infertility by MT1 and MT2 receptors. Furthermore, cancer researches indicate the influence of melatonin on the modulation of tumor cell signaling pathways resulting in growth inhibitor of the both in vivo/in vitro models. Cancer adjuvant therapy can also benefit from melatonin through therapeutic impact and decreasing the side effects of radiation and chemotherapy. This article reviews the scientific evidence about the influence of melatonin and its mechanism of action on the fertility potential, physiological alteration, and anticancer efficacy, during experimental and clinical studies.

Crosstalk between heat shock proteins, NRF2, NF-κB and different endogenous antioxidants during lead-induced hepatotoxicity in Puntius ticto

Present study aims to investigate interaction of molecular chaperons (heat shock protein 70, heat shock protein 90) with transcriptional factors (nuclear factor kappa B/nuclear factor E2-related factor 2/Kelch-like ECH-associated protein 1) to evaluate their role during metal induced stress in fish hepatocytes. Adult Puntius ticto were exposed to lead nitrate at 0 mg/l (control), 1/50th (0.04 mg/l) and 1/20th (0.12 mg/l) of LC₅₀ for 30 days and sacrificed to collect liver tissues. Activity of selected liver enzymes, antioxidants and metallothionein were analyzed. Levels of heat shock protein 70, heat shock protein 90, nuclear factor kappa B, nuclear factor E2-related factor 2 and Kelch-like ECH-associated protein 1 were also measured. Liver enzymes showed a significant increase (p < 0.05) in both Pb exposed groups indicating that the liver might be at risk of damage. Increased level of lipid peroxidation due to metal stress was marked by significant increase (p < 0.05) in malondialdehyde level in fish exposed to the higher Pb concentration compared to control (+ 13.7 %). Significant increase (p < 0.05) in gluthathione reductase (+ 35 %, + 39.2 %), glutathione s-transferase (+ 22.4 %, + 50.4 %) activities and decrease in reduced glutathione level (- 6.75 %, - 12.25 %) in fish exposed to both lower and higher Pb concentration compared to control also indicated metal induced oxidative damage in fish liver. Super oxide dismutase and catalase activities increased significantly (p < 0.05) during exposure to lower Pb concentration, while decreased significantly (p < 0.05) during exposure to higher Pb concentration compared to those in control. Significant (P < 0.05) increase (+ 52.63 %, + 89.47 %) in metallothionein in Pb exposed groups confirmed its role in detoxification process of the metal. Heat shock protein 70 and heat shock protein 90 expression levels increased significantly (p < 0.05) during metal exposure indicating their role as modulator of stress-induced antioxidant protein remodelling. A positive correlation between nuclear factor kappa B/nuclear factor E2-related factor 2/Kelch-like ECH-associated protein 1 with gluthathione regulatory enzymes (gluthathione reductase and glutathione s-transferase) was noted. Current study effectively illuminates the critical role of different factors (heat shock proteins/nuclear factor kappa B/nuclear factor E2-related factor 2/Kelch-like ECH-associated protein 1) to influence the expression and synthesis of antioxidants and other functional enzymes in lead-exposed fish liver.

Effectiveness of melatonin to restore fish brain activity in face of permethrin induced toxicity

Present study demonstrates permethrin induced oxidative damage in fish brain and explores effectiveness of melatonin to ameliorate brain function. Adult female Notopterus notopterus were exposed to nominal permethrin concentrations at 1/20th (0.34 μg/l) and 1/10th (0.68 μg/l) of LC₅₀ for 15 days. The measured permethrin concentrations using gas chromatography (GC-ECD) were 0.28 μg/l and 0.57 μg/l, respectively. Some fish were sacrificed to collect brain tissue after 15 days of exposure. Remaining fish from both groups were administered exogenous melatonin (50 μg/kg, 100 μg/kg body weight) for 7 days and brain tissues were collected. Brain enzymes, ntioxidant factors, HSP70, HSP90, nuclear factor-kappa binding (NFkB), melatonin receptor (MT1R) proteins were measured. Permethrin treatment significantly (P < 0.05) decreased the levels of glutathione and brain enzymes. Malondialdehyde (MDA), xanthine oxidase (XO), HSPs increased at each concentration of permethrin. However, superoxide dismutase, glutathione s-transferase levels increased at low permethrin concentration followed by sharp decrease at higher concentration. Expression of NFkB and MT1R increased significantly (P < 0.05). Melatonin administration reinstated activity of brain enzymes, reduced MDA, XO levels and modulated HSPs. Melatonin also increased expression of NFkB and MT1R. Exogenous melatonin improves oxidative status in permethrin stressed fish brain. Melatonin modulates expression of HSPs that enables brain to become stress tolerant and survive by initiating NFkB translocation. Melatonin could act through melatonin receptor protein to induce synthesis of antioxidant proteins. Therefore the study successfully evaluates the potential of melatonin application for better culture and management of fish against pesticide toxicity.

Enzymatic, Non-enzymatatic Antioxidant Levels and Heat Shock Protein Expression as Indicators of Metal Induced Toxicity and Reproductive Modulation in Female Indian Major Carp Cirrhinus cirrhosus

Effects of zinc (Zn) and lead (Pb) exposure on oxidative biomarkers and heat shock protein (HSP) expression, and their possible relation to ovarian steroidogenesis in fish were investigated. Female Cirrhinus cirrhosus were exposed to 1/10th of LC₅₀ of metals for 30 days, and kept for another 30 days without metal exposure. Metal concentrations, antioxidants, HSPs, 17β-estradiol and steroidogenic enzymes were analysed in brain and ovary after 15 and 30 days of exposure and a 15 and 30 day recovery period. Activities of enzymatic and non-enzymatic antioxidants showed duration dependent variation in both exposure and recovery period. HSP70 and HSP90 expressions increased following metal exposure, with the expression being higher in brain than ovary. 17β-Estradiol, steroidogenic enzymes decreased significantly (p < 0.05) after metal exposure. The present study suggests that metals have differential and tissue specific influence on oxidative status and manipulate ovarian steroidogenesis probably through the modulation of HSPs.

Reference gene selection for quantitative gene expression analysis in black soldier fly (Hermetia illucens)

Hermetia illucens is an important resource insect for the conversion of organic waste. Quantitative PCR (qPCR) is the primary tool of gene expression analysis and a core technology of molecular biology research. Reference genes are essential for qPCR analysis; however, a stability analysis of H. illucens reference genes has not yet been carried out. To find suitable reference genes for normalizing gene expression data, the stability of eight housekeeping genes (including ATP6V1A, RPL8, EF1, Tubulin, TBP, GAPDH, Actin and RP49) was investigated under both biotic (developmental stages, tissues and sex) and abiotic (heavy metals, food, antibiotics) conditions. Gene expression data were analysed by geNorm, NormFinder, BestKeeper, and ΔCt programs. A set of specific reference genes was recommended for each experimental condition using the results of RefFinder synthesis analysis. This study offers a solid foundation for further studies of the molecular biology of H. illucens.

Physiological response of fish under variable acidic conditions: a molecular approach through the assessment of an eco-physiological marker in the brain

The current study demonstrates oxidative damage and associated neurotoxicity following pH stress in two freshwater carp Labeo rohita and Cirrhinus cirrhosus. Carp (n = 6, 3 replicates) were exposed to four different pH (5.5, 6, 7.5, and 8) against control (pH 6.8 ± 0.05) for 7 days. After completion of treatment, levels of enzymatic (superoxide dismutase [SOD], catalase [CAT], glutathione reductase [GRd]) and non-enzymatic antioxidants (malondialdehyde [MDA], glutathione [GSH]), brain neurological parameters (Na⁺-K⁺ATPase, acetylcholinesterase [AcHE], monoamine oxidase [MAO], and nitric oxide [NO]), xanthine oxidase (XO), heat shock proteins (HSP70 and HSP90), and transcription factor NFkB were measured in carp brain. Variation in the pH caused a significant alteration in the glutathione system (glutathione and glutathione reductase), SOD-CAT system, and stress marker malondialdehyde (MDA). Xanthine oxidase was also induced significantly after pH exposure. Brain neurological parameters (MAO, NO, AChE, and Na⁺-K⁺ATPase) were significantly reduced at each pH-treated carp group though inhibition was highest at lower acidic pH (5.5). Cirrhinus cirrhosus was more affected than that of Labeo rohita. Molecular chaperon HSP70 expression was induced in all pH-treated groups though such induction was more in acid-stressed fish. HSP90 was found to increase only in acid-stressed carp brain. Expression of NFkB was elevated significantly at each treatment group except for pH 7.5. Finally, both acidic and alkaline pH in the aquatic system was found to disturb oxidative balance in carp brain which ultimately affects the neurological activity in carp. However, acidic environment in the aquatic system was more detrimental than the alkaline system regarding oxidative damage and subsequent neurotoxicity in carp brain.

Early Developmental Stress Affects Subsequent Gene Expression Response to an Acute Stress in Atlantic Salmon: An Approach for Creating Robust Fish for Aquaculture?

Stress during early life has potential to program and alter the response to stressful events and metabolism in later life. Repeated short exposure of Atlantic salmon to cold water and air during embryonic (E), post-hatch (PH) or both phases of development (EPH) has been shown to alter the methylome and transcriptome and to affect growth performance during later life compared to untreated controls (CO). The aim of this study was to investigate how the transcriptome of these fish responds to subsequent acute stress at the start feeding stage, and to describe methylation differences that might steer these changes. EPH treated fish showed the strongest down-regulation of corticotropin releasing factor 1, up-regulation of glucocorticoid receptor and 3-oxo-5-alpha-steroid 4-dehydrogenase 2 gene expression and a suppressed cortisol response 3 hr after the acute stress, differences that could influence hormesis and be affecting how EPH fish cope and recover from the stress event. Growth hormone 2 and insulin-like growth factor 1 were more strongly down-regulated following acute stress in EPH treated fish relative to E, PH and CO fish. This indicates switching away from growth toward coping with stress following stressful events in EPH fish. Genes implicated in immune function such as major histocompatibility class 1A, T-cell receptor and toll-like receptor also responded to acute stress differently in EPH treated fish, indicating that repeated stresses during early life may affect robustness. Differential DNA methylation was detected in regions mapping <500 bases from genes differentially responding to acute stress suggesting the involvement of epigenetic mechanisms. Stress treatments applied during early development therefore have potential as a husbandry tool for boosting the productivity of aquaculture by affecting how fish respond to stresses at critical stages of production.

Physiological and behavioural responses to acid and osmotic stress and effects of Mucuna extract in Guppies

Variation in pH (acidification) and salinity conditions have severe impact at different levels of biological organization in fish. Present study focused to assess the effects of acidification and salinity changes on physiological stress responses at three different levels of function: i) hormonal and oxidative response, ii) osmoregulation and iii) reproduction, in order to identify relevant biomarkers. Second objective of the study was to evaluate the efficacy of plant (Mucuna pruriens) extract for alleviating pH and salinity related stress. Guppies (Poecilia reticulata) were exposed to different pH (6.0, 5.5, 5.0) and salinity (1.5, 3.0, 4.5 ppt) for 7, 14 and 21 days. Following exposure to stress for respective duration, fish were fed diet containing methanol extract of Mucuna seeds (dose 0.80 gm/kg feed) for 7, 14 and 21 days to measure their possible recovery response. Stress hormone (cortisol), hepatic oxidative stress parameters [superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GRd), glutathione peroxidise (GPx), glutathione S-transferase (GST), malondialdehyde (MDA), glutathione (GSH)], gill osmoregulatory response (Na⁺-K⁺ATPase activity), sex steroid profiles and mating behaviours (gonopodial thrust and gestation period) were estimated. Cortisol and MDA levels increased with dose and duration of acid and salinity stress, and cortisol levels were higher in males than in females. Effect on Na⁺-K⁺ATPase activity was more intense by salinity stress rather than pH induced stress. Both acid and salinity stress reduced sex steroid levels, and mating response was highly affected by both stresses in a dose- and duration-dependent manner. Mucuna treatment reduced stress-induced alteration of cortisol, MDA, Na⁺-K⁺ATPase activity and reproductive parameters. Dietary administration of Mucuna seed extract decreased the intensity of environmental stressors at all three functional levels. Mucuna treatment was more effective against salinity stress than acid stress. Thus, cortisol, oxidative stress marker MDA and Na⁺-K⁺ATPase could be effective indicators for acid and salinity stress in wild and domestic fish populations. Dietary administration of Mucuna extract may limit the detrimental effects of acidification and salinity variations that are the inevitable outcomes expected under global climate change conditions.

Consequences of oxidative damage and mitochondrial dysfunction on the fatty acid profile of muscle of Indian Major Carps considering metal toxicity

Current study aims to find interrelation between mitochondrial enzyme function and fatty acid profile in fish muscle and role of antioxidant agents to maintain their balance in response to metal accumulation. Fishes (Labeo rohita, Catla catla, Cirrhinus cirrhosus) were collected from two sites (Nalban Bheri and Diamond Harbour, India). Concentrations of metals (lead, cadmium, copper, nickel, zinc), enzymatic and non-enzymatic antioxidant activity (malondialdehyde, superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, glutathione S-transferase), muscle enzyme activity (acetylcholinesterase, succinate dehydrogenase, lactate dehydrogenase, Ca²⁺ATPase, AMP-deaminase, lipoamide reductase, cytochrome C oxidase, aldolase) and fatty acid composition in muscle tissues were analyzed. Metal concentrations were significantly higher (P < 0.05) in fish muscles from Nalban compared to those in Diamond Harbour. Increased activity of antioxidant enzymes was noted with diminished mitochondrial enzymes activity and altered fatty acid composition in response to higher metal accumulation. Higher metal concentration in fish muscle of Nalban seems to significantly (P < 0.05) affect poly and monounsaturated fatty acid content, possibly due to oxidative damage and accumulation of hazardous reactive oxygen species (ROS) molecules. Changes in fatty acid contents following metal accumulation were observed to be species specific. Current study is the first correlative study to illuminate the level of oxidative damage and possible consequences on muscle cellular integrity, mitochondrial functionality and flesh quality against bioaccumulation of different metals in carps. Future studies are needed to quantify the relative contributions of enzymatic and low-molecular-mass antioxidants in protecting mitochondrial function and maintenance of proper fatty acid oxidation during acclimation to long term metal exposure.

Melatonin ameliorates H2O2-induced oxidative stress through modulation of Erk/Akt/NFkB pathway

Background

Improper control on reactive oxygen species (ROS) elimination process and formation of free radicals causes tissue dysfunction. Pineal hormone melatonin is considered a potent regulator of such oxidative damage in different vertebrates. Aim of the current communication is to evaluate the levels of oxidative stress and ROS induced damage, and amelioration of oxidative status through melatonin induced activation of signaling pathways. Hepatocytes were isolated from adult Labeo rohita and exposed to H₂O₂ at three different doses (12.5, 25 and 50 µM) to observe peroxide induced damage in fish hepatocytes. Melatonin (25, 50 and 100 μg/ml) was administered against the highest dose of H₂O₂. Enzymatic and non-enzymatic antioxidants such as malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) was measured spectrophotometrically. Expression level of heat shock proteins (HSP70 and HSP90), HSPs-associated signaling molecules (Akt, ERK, cytosolic and nuclear NFkB), and melatonin receptor was also measured by western blotting analysis.

Results

H₂O₂ induced oxidative stress significantly altered (P < 0.05) MDA and GSH level, SOD and CAT activity, and up regulated HSP70 and HSP90 expression in carp hepatocytes. Signaling proteins exhibited differential modulation as revealed from their expression patterns in H₂O₂-exposed fish hepatocytes, in comparison with control hepatocytes. Melatonin treatment of H₂O₂-stressed fish hepatocytes restored basal cellular oxidative status in a dose dependent manner. Melatonin was observed to be inducer of signaling process by modulation of signaling molecules and melatonin receptor.

Conclusions

The results suggest that exogenous melatonin at the concentration of 100 µg/ml is required to improve oxidative status of the H₂O₂-stressed fish hepatocytes. In H₂O₂ exposed hepatocytes, melatonin modulates expression of HSP70 and HSP90 that enable the hepatocytes to become stress tolerant and survive by altering the actions of ERK, Akt, cytosolic and nuclear NFkB in the signal transduction pathways. Study also confirms that melatonin could act through melatonin receptor coupled to ERK/Akt signaling pathways. This understanding of the mechanism by which melatonin regulates oxidative status in the stressed hepatocytes may initiate the development of novel strategies for hepatic disease therapy in future.