Sex-differences in physiological and oxidative stress responses and heavy metals burden in the black jaw tilapia, Sarotherodon melanotheron from a tropical freshwater dam (Nigeria)

Molecular cloning and characterization of Cu-Zn superoxide dismutase (sod1) gene in brown trout and its expression in response to acute aquaculture stressors

Aquaculture species are often exposed to acute stressors such as low water levels and handling during routine aquaculture procedures. This might result in oxidative stress by the increased reactive oxygen species (ROS)' production (e.g., superoxide anion). The harmful effects of ROS are eliminated by a defense system, referred antioxidant defense system (ADS). sod1 is the first gene involved in the ADS. Therefore, we cloned and characterized the open reading frame of the sod1 in brown trout. Then, we determined the effects of low water level and handling stress on sod1 mRNA expression in the liver and gills at 0 min, 1 and 2 h. The total RNA isolated was used to synthesize cDNA for RT-qPCR analysis. Phylogenetic tree, identity/similarity percentages, genomic organization, and conserved gene synteny analyses were applied to characterize Sod1/sod1. While low water level stress upregulated sod1 expression in the liver compared to the control group, no significant differences were observed in the gills between experimental groups. However, brown trout differently responded to handling stress at different time intervals in both tissues. Transcriptional differences were also noted between the sexes. This study contributes to the current understanding of the molecular mechanism between oxidative stress and ADS.

Sex-biased response of pollution biomarkers in fish: Insights from the killifish Poecilia vivipara

Copper ions (Cu) are one of the most frequent trace-contaminants found in Brazilian waters and, although considered as an essential element, in high concentrations can accumulate and induce toxicity. Biomarkers are important tools that can be used to assess these impacts, but to be considered trustworthy, they have to be previously tested in target organisms through laboratory studies under controlled conditions. However, many of these experiments are conducted using only males, as it is believed that the hormonal variation of females can bias the results, increasing data variability. Notwithstanding, few studies have actually tested this hypothesis, highlighting the importance of considering and measuring the role of sex in ecotoxicological studies. The aim this study was to evaluate the influence of sex on biomarkers classically used in environmental monitoring programs using the fish Poecilia vivipara as model. For this, females and males were exposed for 96 h to two Cu concentrations (9 and 20 μg/L) and a control group. In liver and gills, Cu accumulation, total antioxidant capacity (TAC) and lipid peroxidation (LPO) were evaluated. In addition, samples of peripheral blood were used for neutrophil to lymphocyte ratio determination, a measure of the onset of secondary stress. Results show that Cu hepatic accumulation did not differ between females and males, but higher levels of this metal were observed in exposed animals compared to control fish. Additionally, interactive effects were observed for hepatic LPO, as males showed elevated oxidative damage in comparison to females. Moreover, Cu exposure elevated hepatic LPO relative to control only in males, but this increase in oxidative damage was not accompanied by changes in liver TAC. On the other hand, differences in branchial Cu accumulation and LPO were not observed. Conversely, control females showed elevated TAC in comparison to control males, but Cu exposure eliminated this difference. Cu exposure also induced an increase in the N:L ratio, indicating the presence of a secondary stress response unrelated to sex. Ultimately, the findings of this study demonstrate that sex can influence the response of biomarkers that are typically used in ecotoxicological investigations in a multifaceted manner. As a result, using animals from a singular sex in such studies may result in consequential outcomes, potentially leading to underestimation or overestimation of results.

Tissue dynamics of potential toxic elements in the Pacific hake (Merluccius productus): distribution and the public health risk assessment

This study aimed to establish the distribution of As, Cd, Pb, Cu, and Zn in the main tissues (muscle, liver, gonads, and gills) of the Pacific hake (Merluccius productus) from the northern Gulf of California to establish baseline bioavailability levels in the northern stock. The results for Pb and Cd were the lowest in the studied tissues (Pb < 0.005 mg kg^-1 in the liver and gonads and 1.43 mg kg^-1 for Cd in the liver), followed by levels of Cu and As (muscle > liver > gonads > gills) and Zn with the most abundant levels in all the tissues. The sex of the organisms was not a factor that influenced the bioaccumulation and distribution of the potential toxic elements (PTEs) nor total length, except for As in gills and Cd in muscle and the liver. Important interactions among Zn and non-essential elements were established. The Pacific hake intake of PTEs was probably through the diet via bioaccumulation of the elements in their prey and less by pollution of the water column. In the muscle, a major distribution and storage of As, Zn, and Pb were observed, but in the liver, higher loads were from Cd and Cu. The maximum tolerable weekly intake must be very high to be at health risk for the essential elements and Cd. However, the population might be at risk for Pb and As consumption if more than 124 g of M. productus in adults and 35 g in children are consumed per week. Further investigations are required to understand the dynamics of PTEs in M. productus as it could be proposed as a biomonitor species.

Heavy metals research in Nigeria: a review of studies and prioritization of research needs

Nigeria is experiencing continuous economic and industrial transformations, typical of many developing nations. In addition to its well-established oil industry, which is infamous for exuding various kinds of pollutants, there are increased mining operations, indiscriminate disposal and burning of wastes, illegal oil refinery and terroristic insurgency, all poised to increase the levels of heavy metal contaminants in the Nigerian environment. A recent revelation indicates that about 2 million people in South-western Nigeria alone could potentially be poisoned by lead (Pb) and mercury (Hg), emanating from illegal mining operations. This further underscores the importance of investigations of toxic trace metal levels in the country. The current review of 148 research articles was conducted to provide an understanding of the scope of heavy metals research in Nigeria and to prioritize needed research. The review recognized that the scope of heavy metals studies has been wide, covering matrices such as cosmetics, human blood, hair, medicines, foods, beverages, water, air, soil and crude oil. However, important toxic metals, especially mercury (Hg), arsenic (As) and antimony (Sb), are largely under-investigated. Also, there is a need for more studies to be conducted in the northern part of the country. Furthermore, studies need to focus on marine environments rather than the freshwater ecosystems alone. Techniques such as the inductively coupled plasma-optical emission spectrometry (ICP-OES) and particle-induced X-ray emission (PIXE) analyses are herein recommended to bridge the data gap and to overcome limitations in trace metals analyses in the Nigerian total environment.

Heavy Metals in Unprocessed or Minimally Processed Foods Consumed by Humans Worldwide: A Scoping Review

Heavy metals (HM) can be accumulated along the food chain; their presence in food is a global concern for human health because some of them are toxic even at low concentrations. Unprocessed or minimally processed foods are good sources of different nutrients, so their safety and quality composition should be guaranteed in the most natural form that is obtained for human consumption. The objective of this scoping review (ScR) is to summarize the existing evidence about the presence of HM content (arsenic (As), lead (Pb), cadmium (Cd), mercury (Hg), methylmercury (MeHg), and aluminum (Al)) in unprocessed or minimally processed foods for human consumption worldwide during the period of 2011–2020. As a second objective, we identified reported HM values in food with respect to Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) International Food Standards for Maximum Limits (MLs) for contaminants in food. This ScR was conducted in accordance with the Joanna Briggs Institute (JBI) methodology and PRISMA Extension for Scoping Reviews (PRISMA-ScR); advance searches were performed in PubMed, ScienceDirect and FAO AGRIS (Agricultural Science and Technology Information) databases by two reviewers who independently performed literature searches with specific eligibility criteria. We classified individual foods in food groups and subgroups according to the Global Individual Information Food Consumption Data Tool (FAO/WHO GIFT). We homologated all the reported HM units to parts per million (ppm) to determine the weighted mean HM concentration per country and food group/subgroup of the articles included. Then, we compared HM concentration findings with FAO/WHO MLs. Finally, we used a Geographic Information System (GIS) to present our findings. Using our search strategy, we included 152 articles. Asia was the continent with the highest number of publications (n = 79, 51.3%), with China being the country with the largest number of studies (n = 34). Fish and shellfish (n = 58), followed by vegetables (n = 39) and cereals (n = 38), were the food groups studied the most. Fish (n = 42), rice (n = 33), and leafy (n = 28) and fruiting vegetables (n = 29) were the most studied food subgroups. With respect to the HM of interest, Cd was the most analyzed, followed by Pb, As, Hg and Al. Finally, we found that many of the HM concentrations reported exceeded the FAO/OMS MLs established for Cd, Pb and As globally in all food groups, mainly in vegetables, followed by the roots and tubers, and cereals food groups. Our study highlights the presence of HM in the most natural forms of food around the world, in concentrations that, in fact, exceed the MLs, which affects food safety and could represent a human health risk. In countries with regulations on these topics, a monitoring system is recommended to evaluate and monitor compliance with national standards. For countries without a regulation system, it is recommended to adopt international guidelines, such as those of FAO, and implement a monitoring system that supervises national compliance. In both cases, the information must be disseminated to the population to create social awareness. This is especially important to protect the population from the consumption of internal production and for the international markets of the globalized world.

Metal Accumulation and DNA Damage in Oreochromis niloticus and Clarias gariepinus After Chronic Exposure to Discharges of the Batts Drain: Potential Risk to Human Health

The present work showed the impact of long-term exposure to the Batts drain's discharges on O. niloticus and C. gariepinus fish species. The accumulation level of Cu, Zn, Fe, Cd, Pb and Al in five vital tissues was markedly elevated near the Batts drain (site2) compared to the samples from the reference site (site 1). At the same site, C. gariepinus displayed the highest accumulation capacities when compared to O. niloticus. Based on the metal pollution index, livers and kidneys, followed by gills, showed the maximum overall metal load. The degree of DNA damage (assessed by comet and diphenylamine assays) was relative to the accumulated metals in tissues with species and site specification. The values of the hazard index for human consumption showed that the studied metals were within safe values at normal consumption rates. While harmful health consequences were observed at the habitual consumption level at site 2.

Acute effects of antimony exposure on adult zebrafish (Danio rerio): From an oxidative stress and intestinal microbiota perspective

The rapid development of the textile industry has resulted in a large influx of wastewater production. The "national discharge standards of water pollutants for dyeing and finishing of textile industry (GB4287-2012)" stipulates that the discharge of total Sb from textile industry effluent must be < 0.10 mg/L, but it is difficult to meet the standard at present. Antimony is potentially carcinogenic, and the pathogenic mechanism of antimony is poorly understood. In this study, the acute toxic effects of various concentrations of antimony on adult zebrafish (Danio rerio) were investigated, including effects on oxidative stress, neurotransmitters and intestinal microbiota. The activities of catalase (CAT), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), superoxide dismutase (SOD), total antioxidant capacity (T-AOC) and acetylcholinesterase (AChE) were measured in zebrafish muscle and intestine tissue samples. In addition, intestinal microbial community composition and diversity of zebrafish were also analyzed. The results demonstrated that SOD, CAT and GSH-Px activities in the zebrafish gut showed a decreasing and then increasing trend with antimony concentration increasing. SOD, CAT and MDA in zebrafish muscle decreased with increasing exposure time. GSH-Px activities increased with increasing exposure time. T-AOC increased and then decreased. In addition, antimony exposure was neurotoxic to zebrafish, and a significant decrease in AChE activity was found in the intestine with increased exposure time. The neurotoxicity caused by antimony in the high concentration group (40 mg/L) was stronger than that in low concentration groups (10 mg/L and 20 mg/L). Notably, antimony exposure caused increases in the relative abundance of phyla Fusobacteriota and Actinomycetes, but decreases in the relative abundance of the phyla Firmicutes and Proteobacteria in zebrafish intestine. These outcomes will advance our understanding of antimony-induced biotoxicity, environmental problems, and health hazards. In conclusion, this study shows that acute exposure of antimony to zebrafish induces host oxidative stress and neurotoxicity, dysregulates the intestinal microbiota, showing adverse effects on the health and gut microbiota of zebrafish.

Sex biased effect of acute heat shock on the antioxidant system of non-native round goby Neogobius melanostomus

Monitoring oxidative stress biomarkers has become a powerful and common tool to estimate organismal condition and response to endogenous and environmental factors. In the present study, we used round goby (Neogobius melanostomus) from non-native European populations, as a model species to test sex differences in oxidative stress biomarkers. Considering sex differences in reproductive investment, we hypothesized that males would display lower resistance to abiotic stress. Fish were exposed to a heat shock (temperature elevated by 10°C) for 1h, 6h, and 12h and catalase activity (CAT), reduced glutathione (GSH), total antioxidant capacity (TAC) and lipid peroxidation (LPO) were measured in liver and muscle tissues. Liver of males was significantly more responsive compared to liver of females in all tested parameters. GSH was found to be the most responsive to heat stress exposure in both sexes. The results supported our hypothesis that male reproductive investment (territoriality, courtship, and brood care) and likelihood of only a single spawning period in their lifetime influenced on higher sensitivity of their antioxidant defence. On the other hand, for females antioxidant defence is considered more important to survive the environmental changes and successfully reproduce in the next season. Our experiments exposed fish to acute thermal stress. Further research should determine the effects of exposure to chronic thermal stress to corroborate our understanding on sex differences in antioxidant defence in the round goby.

Sex-specific elemental accumulation and histopathology of pikeperch (Sander lucioperca) from Garaši reservoir (Serbia) with human health risk assessment

Accumulation of 26 elements (Ag, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Sr, and Zn) was analyzed in the gills, liver, and muscle of pikeperch males and females from Garaši reservoir using inductively coupled plasma optical emission spectrometry (ICP-OES). Histopathological (HP) changes in the gills and liver, and human health risk were also analyzed. The gills were most affected by metal pollution in both sexes. The concentrations of Hg in muscle tissue of four males, and Cd in two females and two males exceeded the maximum allowed concentrations. Statistical tests only revealed significant differences regarding the concentrations of Mg, K, and S in the muscle (higher in males) and Al, Ag, and Mn in the liver (higher in females) of individuals between sexes. Low to moderate levels of pathological changes were recorded for the gills and liver in both sexes. Significant differences between sexes were observed for inflammatory index of gills (I_GI) and HP index of gills (I_G), males had higher values compared to females, and for liver necrosis, where females had higher values compared to males. Gills were less affected by HP changes compared to the liver. There was no significant non-cancerogenic and cancerogenic health risk due to the consumption of pikeperch meat from the Garaši reservoir. However, women are under greater risk by consuming the meat of both male and female individuals, probably due to a longer lifetime and lesser body weight compared to the men.

Trace Metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) and Stable Isotope Ratios (δ13C and δ15N) in Fish from Wulungu Lake, Xinjiang, China

Wulungu Lake is a vital fishery area in Xinjiang. However, the concentration, enrichment rules, and sources of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the aquatic organisms, have rarely been investigated. The results suggest that the concentrations of As, Ni, Pb, and Zn were higher than those recommended by the national standards for edible fish in some species. Hg, Ni, Cu, Pb, Cr, and Zn in the fish were dependent on the concentration of trace metals in the water environment (p < 0.05). The body weights of the fish were significantly negatively correlated with only Hg (p < 0.05); however, their body lengths were significantly positively correlated with As, Cu, Zn, and Hg contents. Values of δ¹³C ‰ (δ¹⁵N ‰) for the entire fish food web was found to range from -19.9‰ (7.37‰) to -27.7‰ (15.9‰), indicating a wide range of trophic positions and energy sources. Based on the linear correlation, As, Cu, Cd, and Zn contents were positively correlated with δ¹⁵N (p < 0.05), and bioaccumulation was observed in the fish. The target hazard quotient (THQ) of all fish species was less than 1, indicating the absence of potential risks to human health.

The Resistance of Drosophila melanogaster to Oxidative, Genotoxic, Proteotoxic, Osmotic Stress, Infection, and Starvation Depends on Age According to the Stress Factor

We studied how aging affects the ability of Drosophila melanogaster to tolerate various types of stress factors. Data were obtained on the resistance of D. melanogaster to oxidative and genotoxic (separately paraquat, Fe³⁺, Cu²⁺, and Zn²⁺ ions), proteotoxic (hyperthermia, Cd²⁺ ions), and osmotic (NaCl) stresses, starvation, and infection with the pathological Beauveria bassiana fungus at different ages. In all cases, we observed a strong negative correlation between age and stress tolerance. The largest change in the age-dependent decline in survival occurred under oxidative and osmotic stress. In most experiments, we observed that young Drosophila females have higher stress resistance than males. We checked whether it is possible to accurately assess the biological age of D. melanogaster based on an assessment of stress tolerance. We have proposed a new approach for assessing a biological age of D. melanogaster using a two-parameter survival curve model. For the model, we used an algorithm that evaluated the quality of age prediction for different age and gender groups. The best predictions were obtained for females who were exposed to CdCl₂ and ZnCl₂ with an average error of 0.32 days and 0.36 days, respectively. For males, the best results were observed for paraquat and NaCl with an average error of 0.61 and 0.68 days, respectively. The average accuracy for all stresses in our model was 1.73 days.