Toxic effect of heavy metals on ovarian deformities, apoptotic changes, oxidative stress, and steroid hormones in rainbow trout

Fate and Effects of Heavy Metals in Fishes: Antioxidant Defense System, miRNA/Gene Expression Response, and Histopathological Reproductive Manifestations

Heavy metal pollution is a major environmental concern and in particular for aquatic ecosystems. With heavy metals exceeding safe and recommended limits, they pose significant threats to the environment and its inhabitants, including fish. Heavy metals, when accumulated in the different organs of the fish, result in toxicity in fish by producing reactive oxygen species (ROS) through the generation of oxidizing radicals. This oxidative stress mechanism is a key factor in the detrimental effects of heavy metal pollution on aquatic life. Heavy metal exposure profoundly affects fish behavior and physiology. In this review, an attempt was made to report the effects of heavy metals on fish physiology, focusing on toxicological effects on antioxidant enzymes, microRNAs (miRNAs) and molecular genetic responses, histopathology of organs, and underlying molecular mechanisms. This review also highlighted the heavy metal impact on fish gonads (testes and ovaries) and the hormones associated with it. The detection methods and the incorporation of latest developments in AI-based technology for the detection of heavy metals are also included in this review. Understanding the above effects is important for assessing the ecological impact of heavy metal pollution and developing strategies to mitigate its adverse effects on aquatic life. Understanding the consequences listed above is important for analyzing the ecological impact of heavy metal pollution and devising measures to reduce its negative effects on aquatic life and human health.

Lead Nitrate (Pb(NO3)2) Toxicity Effects on DNA Structure and Histopathological Damage in Gills of Common Carp (Cyprinus carpio)

The toxic impact of environmentally relevant nominal sub-lethal concentration of lead nitrate (23 mg/L) on the gills of Cyprinus carpio after 30 days of exposure was assessed. Structural alterations were analyzed through histopathology, and the DNA damage rate in peripheral erythrocytes was evaluated by alkaline comet assay. A significant deviation in the gill histoarchitecture was observed compared to the control group. Significant changes, including the curling of secondary lamellae, loss of filaments, necrosis, hyperplasia, hypertrophy of cells of primary filament, and vacuolization, were found in the fish exposed to nominal sub-lethal concentration of lead nitrate. Moreover, the comet assay showed lead nitrate-induced DNA damage, evidenced by the length of the DNA "tail" in the exposed fish. The findings of this study strongly indicated that lead nitrate, even at sub-lethal levels, could significantly alter the overall physiology of the fish. This situation could lead to severe ecological consequences.

Selected micro- and macro-element associations with oxidative status markers in common carp (Cyprinus carpio) blood serum and ejaculate: a correlation study

The aim of this study was to (1) determine complex interactions between macro- and micro-elements present in blood serum and ejaculate of common carp (Cyprinus carpio), and (2) examine the association between alterations in these macro- and micro-elements with markers of oxidative stress. Blood and ejaculate from 10 male carp were collected in the summer period on the experimental pond in Kolíňany (West Slovak Lowland). Reactive oxygen species (ROS), total antioxidant capacity (TAC), protein carbonyls (PC), and malondialdehyde (MDA) levels were measured in blood serum and ejaculate using spectrophotometric methods. The amounts of elements (Ag, Al, Ba, Co, Li, Mo, Ca, K, Na, and Mg) in all samples were quantified using inductively coupled plasma optical emission spectrophotometry. Data demonstrated significant differences in elemental concentrations between blood and ejaculate, specifically significantly higher ejaculate levels were detected for Ag, Al, Ba, Co, Li, Mo, K, and Mg. Potassium was the most abundant macro-element in the ejaculate, while sodium was the most abundant in blood serum. Among the micro-elements, Al was predominant in both types of samples. It is noteworthy that oxidative status markers including ROS, TAC, and MDA were significantly higher in ejaculate indicating the presence of oxidative stress in C. carpio reproductive tissue. The positive correlations between Mg and Ca in blood serum and ejaculate suggest these elements play a functional role in metabolic and physiological processes. In contrast, the positive correlations of Ba and Al with markers of oxidative stress indicated the association of these metals with induction of oxidative stress. Our findings provide insights into the association of metals with biomarkers of physiological function as well as adverse effects in C. carpio.

Functional complementation of two splicing variants of Gustavus in Neocaridina denticulata sinensis during ovarian maturation

Gustavus, a positive regulator in arthropod reproduction, features a conserved SPRY and a C-terminal SOCS box domain and belongs to the SPSB protein family. The SPSB family, encompassing SPSB1 to SPSB4, plays pivotal roles in higher animals, including immune response, apoptosis, growth, and stress responses. In Neocaridina denticulata sinensis, alternative splicing yielded two NdGustavus isoforms, NdGusX1 and NdGusX2, with distinct expression patterns-high in ovaries and muscles, respectively, and across all ovarian germ cells. These isoforms showed similar expression dynamics during embryogenesis and significant upregulation post-copper ion exposure (P < 0.05). The in situ hybridization result elucidated that NdGusX1 and NdGusX2 were expressed across the germ cell spectrum in the ovary, with NdGusX1 showing enhanced expression in oogonia and primary oocytes. In addition, RNA interference revealed functional complementation in ovaries and potential functional differentiation in muscles. Knockdown of NdGusX1 and NdGusX2 potentially disrupted endogenous vitellogenin synthesis, regulating vitellogenesis and reducing mature oocyte volume, affecting follicular cavity occupation. This study provides a theoretical framework for understanding the biological functions of the SPSB family in crustacean ovarian maturation.

Microscopic photoplethysmography-based evaluation of cardiotoxicity in whitefish larvae induced by acute exposure to cadmium and phenol

Toxic environmental pollutants pose a health risk for both humans and animals. Accumulation of industrial contaminants in freshwater fish may become a significant threat to biodiversity. Comprehensive monitoring of the impact of environmental stressors on fish functional systems is important and use of non-invasive tools that can detect the presence of these toxicants in vivo is desirable. The blood circulatory system, by virtue of its sensitivity to the external stimuli, could be an informative indicator of chemical exposure. In this study, microscopic photoplethysmography-based approach was used to investigate the cardiac activity in broad whitefish larvae (Coregonus nasus) under acute exposure to cadmium and phenol. We identified contamination-induced abnormalities in the rhythms of the ventricle and atrium. Our results allow introducing additional endpoints to evaluate the cardiac dysfunction in fish larvae and contribute to the non-invasive evaluation of the toxic effects of industrial pollutants on bioaccumulation and aquatic life.

Chronic lead poisoning-induced budgerigar liver damage, gut microbiota dysbiosis, and metabolic disorder

Birds are sensitive to heavy metal pollution, and lead (Pb) contamination can negatively affect their liver and gut. Therefore, we used budgerigars to examine liver and gut toxicosis caused by Pb exposure in bird, and the possible toxic mechanisms. The findings showed Pb exposure increased liver weight and decreased body weight. Moreover, histopathological and immunofluorescence assay results demonstrated obvious liver damage and cell apoptosis increased in Pb- treated budgerigars. Quantitative polymerase chain reaction (qPCR) results also showed Pb caused an increase in apoptosis by inhibiting the PPAR-γ/PI3K/Akt pathway. The gut microbe analyses indicated Firmicutes, Proteobacteria, and Bacteroidetes were dominant microbial phyla, and Network analysis results shown Arthrobacter, Bradyrhizobium and Alloprevotella as the hubs of Modules I, II, and III, respectively. Phenylpropanoids and polyketides, Organoheterocyclic compounds, Organic oxygen compounds, and Organic nitrogen compounds were dominant metabolite superclasses. Tauroursodeoxycholic acid, taurochenodeoxycholic acid (sodium salt), and 2-[2-(5-bromo-2-pyridyl)diaz-1-enyl]-5-(diethylamino)phenol were significantly enriched in the Pb-treated group. It showed that 41 Kyoto Encyclopedia of Genes and Genomes (KEGG) orthologues and 183 pathways differed between the Pb-treated and control budgerigars using microbial and metabolomic data. Moreover, orthogonal partial least-squares discrimination analysis (OPLS-DA) based on microbial and metabolite indicated distinct clusters in the Pb-treated and control groups. Additionally, the correlation analysis results indicated that a positive correlation for the Pb-treated and control groups between gut microbiota and metabolomic data, respectively. Furthermore, the microenvironment of the gut and liver were found to affect each other, and this study demonstrated heavy metal especially Pb may pose serious health risks to birds through the "gut-liver axis" too.

Zinc modulates hypothalamo-pituitary-gonadal-liver axis to impair reproduction in female Mystus vittatus (Bloch, 1794)

The present study investigated the effects of zinc on the hypothalamo-pituitary-gonadal-liver (HPGL) axis of the bagrid catfish Mystus vittatus. Female fish (pre-ovulatory and ovulatory phases) were exposed to zinc sulphate at 1/10th of LC50 (5.62 mg/L) for 60 days and sacrificed at every 15-day interval to collect tissues. Zinc concentration in all tissues was significantly higher in the metal-exposed group at all exposure durations compared to control for both phases. Metallothionein (MT) levels increased in the brain, liver and ovary of fish from both phases with exposure duration. Reactive oxygen species (ROS) generation in the brain, liver and ovary tissues increased with exposure duration at both reproductive phases while serum cortisol levels in ovulatory fish increased significantly compared to pre-ovulatory. Condition factor, gonadosomatic index and hepatosomatic index decreased in Zn-exposed fish. Brain GnRH and kisspeptin levels decreased significantly in the Zn-exposed group for both phases. GnIH was significantly higher in Zn-exposed fish. Serum FSH levels in pre-ovulatory and LH levels in ovulatory fish decreased gradually with an increase in the duration of exposure. Zn exposure reduced vitellogenin (Vtg) and estradiol (E2) in the liver and ovary with an increase in duration from both phases. Ovary maturation-inducing hormone (MIH) levels showed a decrease with exposure duration in ovulatory fish. Moreover, Zn-exposed ovulatory fish showed a degenerated oocyte nucleus due to the disintegration of the nuclear membrane. It might be inferred that Zn altered the HPGL regulatory system of M. vittatus reproduction at both the pre-ovulatory and ovulatory phases.

Emerging insights into the impacts of heavy metals exposure on health, reproductive and productive performance of livestock

Heavy metals, common environmental pollutants with widespread distribution hazards and several health problems linked to them are distinguished from other toxic compounds by their bioaccumulation in living organisms. They pollute the food chain and threaten the health of animals. Biologically, heavy metals exhibit both beneficial and harmful effects. Certain essential heavy metals such as Co, Mn, Se, Zn, and Mg play crucial roles in vital physiological processes in trace amounts, while others like As, Pb, Hg, Cd, and Cu are widely recognized for their toxic properties. Regardless of their physiological functions, an excess intake of all heavy metals beyond the tolerance limit can lead to toxicity. Animals face exposure to heavy metals through contaminated feed and water, primarily as a result of anthropogenic environmental pollution. After ingestion heavy metals persist in the body for an extended duration and the nature of exposure dictates whether they induce acute or chronic, clinical or subclinical, or subtle toxicities. The toxic effects of metals lead to disruption of cellular homeostasis through the generation of free radicals that develop oxidative stress. In cases of acute heavy metal poisoning, characteristic clinical symptoms may arise, potentially culminating in the death of animals with corresponding necropsy findings. Chronic toxicities manifest as a decline in overall body condition scoring and a decrease in the production potential of animals. Elevated heavy metal levels in consumable animal products raise public health concerns. Timely diagnosis, targeted antidotes, and management strategies can significantly mitigate heavy metal impact on livestock health, productivity, and reproductive performance.

Bioaccumulation of Potentially Toxic Elements in Commercially Important Food Fish Species from Lower Gangetic Stretch: Food Security and Human Health Risk Assessment

Ganga river is the inhabitant of more than 190 fish species and important river system of India. Potentially toxic elements (PTEs) in the Gangetic riverine ecosystem are a hot environmental issue. A detailed evaluation of PTEs bioaccumulation in Gangetic fishes is required to safeguard human health. The present study investigated the bioaccumulation of PTEs (Cd, Co, Cr, Cu, Li, Ni, Pb, Se, Zn, and Mn) within 12 economic fish species (n = 72) collected from the lower Gangetic stretch. The mean concentrations of PTEs followed the order Zn > Cu > Mn > Ni > Se > Cr > Pb > Co ~ Li > Cd. Li and Se bioaccumulation were studied first time from Gangetic fishes. Results demonstrated that all the selected PTEs were below the maximum permissible limit recommended by reference standards except for Zn in L. catla and L. rohita. For all PTEs, the metal pollution index (MPI), hazard quotient (THQ), and hazard index (HI) were < 1, indicating that these PTEs do not pose a health risk to the public through the dietary intake of fish in this study area. All studied fish were acceptable in terms of carcinogenic risk (CR) from exposure to Cd, Cr, and Pb. Multivariate statistical analysis suggests that inter-correlated metals have similar dispersion properties and bioaccumulation homology within the body. This study provides a scientific basis for food safety assessment and continuous monitoring of PTEs in Gangetic fishes is suggested in the future to safeguard human health.

A comprehensive review on environmental pollutants and osteoporosis: Insights into molecular pathways

A significant problem that has an impact on community wellbeing is environmental pollution. Environmental pollution due to air, water, or soil pollutants might pose a severe risk to global health, necessitating intense scientific effort. Osteoporosis is a common chronic condition with substantial clinical implications on mortality, morbidity, and quality of life. It is closely linked to bone fractures. Worldwide, osteoporosis affects around 200 million people, and every year, there are almost 9 million fractures. There is evidence that certain environmental factors may increase the risk of osteoporosis in addition to traditional risk factors. It is crucial to understand the molecular mechanisms at play because there is a connection between osteoporosis and exposure to environmental pollutants such as heavy metals, air pollutants, endocrine disruptors, metal ions and trace elements. Hence, in this scoping review, we explore potential explanations for the link between pollutants and bone deterioration through deep insights into molecular pathways. Understanding and recognizing these pollutants as modifiable risk factors for osteoporosis would possibly help to enhance environmental policy thereby aiding in the improvement of bone health and improving patient quality of life.

Captivating Colors, Crucial Roles: Astaxanthin's Antioxidant Impact on Fish Oxidative Stress and Reproductive Performance

Fish, constantly exposed to environmental stressors due to their aquatic habitat and high metabolic rates, are susceptible to oxidative stress. This review examines the interplay between oxidative stress and fish reproduction, emphasizing the potent antioxidant properties of astaxanthin. Our primary objective is to highlight astaxanthin's role in mitigating oxidative stress during critical reproductive stages, leading to improved gamete quality, ovary development, and hormone levels. We also explore its practical applications in aquaculture, including enhanced pigmentation and overall fish health. We conducted a comprehensive literature review, analyzing studies on astaxanthin's antioxidant properties and its impact on fish reproduction. Astaxanthin, a carotenoid pigment, effectively combats reactive oxygen species, inhibiting lipid peroxidation and maintaining membrane integrity. It significantly enhances reproductive success in fish and improves overall fish health in aquaculture settings. This review reveals astaxanthin's multifaceted benefits in fish health and reproduction, offering economic advantages in aquaculture. Future research should delve into species-specific responses, optimal dosages, and the long-term effects of astaxanthin supplementation to inform sustainable aquaculture strategies.

The Behavior of Polymeric Pipes in Drinking Water Distribution System-Comparison with Other Pipe Materials

The inner walls of the drinking water distribution system (DWDS) are expected to be clean to ensure a safe quality of drinking water. Complex physical, chemical, and biological processes take place when water comes into contact with the pipe surface. This paper describes the impact of leaching different compounds from the water supply pipes into drinking water and subsequent risks. Among these compounds, there are heavy metals. It is necessary to prevent these metals from getting into the DWDS. Those compounds are susceptible to impacting the quality of the water delivered to the population either by leaching dangerous chemicals into water or by enhancing the development of microorganism growth on the pipe surface. The corrosion process of different pipe materials, scale formation mechanisms, and the impact of bacteria formed in corrosion layers are discussed. Water treatment processes and the pipe materials also affect the water composition. Pipe materials act differently in the flowing and stagnation conditions. Moreover, they age differently (e.g., metal-based pipes are subjected to corrosion while polymer-based pipes have a decreased mechanical resistance) and are susceptible to enhanced bacterial film formation. Water distribution pipes are a dynamic environment, therefore, the models that are used must consider the changes that occur over time. Mathematical modeling of the leaching process is complex and includes the description of corrosion development over time, correlated with a model for the biofilm formation and the disinfectants-corrosion products and disinfectants-biofilm interactions. The models used for these processes range from simple longitudinal dispersion models to Monte Carlo simulations and 3D modeling. This review helps to clarify what are the possible sources of compounds responsible for drinking water quality degradation. Additionally, it gives guidance on the measures that are needed to maintain stable and safe drinking water quality.