Metabolite profiling, histological and oxidative stress responses in the grey mullet, Mugil cephalus exposed to the environmentally relevant concentrations of the heavy metal, Pb (NO3)2

The EU Interreg Project "GEREMIA" on waste management for the improvement of port waters: results on monitoring the health status of fish as bioindicator

Highly anthropized areas as ports represent complex scenarios that require accurate monitoring plans aimed to address the environmental status. In this context, the activities of the EU Interreg Project "GEstione dei REflui per il MIglioramento delle Acque portuali (GEREMIA)" were focused on comparing sites differently affected by human presence, as the Port of Genoa and the natural area of the S'Ena Arrubia fishpond: a panel of analyses was carried out on Mugilidae fish sampled in these two areas, aimed to address trace metal accumulation in the liver, gills, and muscle, as well as cytochrome P450 (CYP450) induction in liver and biliary polycyclic aromatic hydrocarbon (PAH) metabolites, and histopathological alterations in the liver and gills. Chemical analyses in the liver, gills, and muscle of specimens collected in the port area showed an overall higher degree of trace metal contamination compared to the natural fishpond, and similar results were obtained in terms of CYP450 induction and biliary PAH metabolites, suggesting a higher exposure to organic compounds. In addition, histopathological analyses revealed a significant alteration and then a loss of functionality of liver and gill tissue in individuals from the port. Overall, this study describes the complex environmental pollution scenario in the Port of Genoa, confirming the importance of using multidisciplinary approaches and different types of analyses to address both the presence and the effects of contaminants in marine environments.

Bioaccumulation and Bioremediation of Heavy Metals in Fishes-A Review

Heavy metals, the most potent contaminants of the environment, are discharged into the aquatic ecosystems through the effluents of several industries, resulting in serious aquatic pollution. This type of severe heavy metal contamination in aquaculture systems has attracted great attention throughout the world. These toxic heavy metals are transmitted into the food chain through their bioaccumulation in different tissues of aquatic species and have aroused serious public health concerns. Heavy metal toxicity negatively affects the growth, reproduction, and physiology of fish, which is threatening the sustainable development of the aquaculture sector. Recently, several techniques, such as adsorption, physio-biochemical, molecular, and phytoremediation mechanisms have been successfully applied to reduce the toxicants in the environment. Microorganisms, especially several bacterial species, play a key role in this bioremediation process. In this context, the present review summarizes the bioaccumulation of different heavy metals into fishes, their toxic effects, and possible bioremediation techniques to protect the fishes from heavy metal contamination. Additionally, this paper discusses existing strategies to bioremediate heavy metals from aquatic ecosystems and the scope of genetic and molecular approaches for the effective bioremediation of heavy metals.

Effects of heavy metals on fish physiology - A review

The pollution by heavy metals poses a serious threat to the aquatic environment and to the organisms if the concentration of heavy metals in the environment exceeds the safe limits. Due to their non-biodegradable and long persistence nature in the environment, heavy metals cause toxicity in fish by producing oxygen reactive species through oxidizing radical production. In this review, we investigated the effects of heavy metals on fish physiology with special emphasis on hemato-biochemical properties, immunological parameters especially hormones and enzymes, histopathology of different major organs and underlying molecular mechanisms. All those parameters are significantly affected by heavy metal exposure and are found to be important bio-monitoring tools to assess heavy metal toxicity. Hematological and biochemical alterations have been documented including cellular and nuclear abnormalities in different fish species exposed to different concentrations of heavy metals. Major fish organs (gills, liver, kidneys) including intestine, muscles showed different types of pathology specific to organs in acute and chronic exposure to different heavy metals. This study also revealed the expression of different genes involved in oxidative stress and detoxification of heavy metals. In a nutshell, this article shades light on the manipulation of fish physiology by the heavy metals and sought attention in the prevention and maintenance of aquatic environments particularly from heavy metals contaminations.

Dietary silymarin, Silybum marianum extract ameliorates cadmium chloride toxicity in common carp, Cyprinus carpio

The present study evaluated the protective effects of silymarin extract (SIE) on cadmium chloride toxicity in common carp, Cyprinus carpio. Four experimental group were considered for the experiment including: SIE0 (control): non-SIE-supplemented fish, SIE1: fish supplemented with 400 mg SIE/kg diet, SIE2: fish supplemented with1400mg SIE/kg diet, SIE3: fish supplemented with 2400 mg SIE/kg diet). Fish were fed experimental diet for 60 days and then exposed to cadmium chloride (1.5 mg/l or 25% of LC50–96 h) and antioxidant defense components and the survival rate assayed. After 60 days feeding trial, total antioxidant capacity (TAC) levels significantly increased (P<0.01) in 1400–2400 mg SIE/kg diet treatments compared to those in control and 400 mg SIE/kg diet treatment. Malondialdehyde (MDA) (P>0.01) and acetylcholinesterase (AChE) levels (P>0.01) remained unchanged during the feeding period in all treatments. Hepatic catalase (CAT) in all SIE supplemented groups and superoxide dismutase (SOD) and glutathione peroxidase (GPx) in 1400–2400 mg SIE/kg diet treatments significantly elevated (P<0.01) in response to SIE. Plasma levels of hepatic metabolic enzymes [alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), creatine kinase (CK), lactate dehydrogenase (LDH) ] remained unchanged (P>0.01) in all experimental groups over feeding period. After exposure to cadmium chloride, TAC levels were significantly elevated (P<0.01) in all experimental groups. In control and 400 mg SIE/kg diet treatment, TAC showed lower levels (P<0.01) compared to other groups. MDA levels were significantly increased (P<0.01) in control and fish supplemented with 400 and 1400 mg SIE/kg diet. TAC in the fish of 2400 mg SIE/kg diet treatment remained unchanged (P>0.01), following the exposure. CAT (P<0.01), SOD (P<0.01) and GPx (P<0.01) were significantly elevated in response to cadmium chloride in all groups. However, the treatments, 1400 and 2400 mg SIE/kg diet, showed lower increases (P<0.01) of enzymes. AChE activity (P<0.01) in the liver were significantly decreased in control and fish fed 400 and 1400 mg SIE/kg diet. Exposure to cadmium significantly increased (P<0.01) the plasma levels of ALT, AST, ALP and LDH in control and those fed 400 and 1400 mg SIE/kg diet. The findings of the current study indicated that SIE at a rate of 1400–2400mg/kg diet might enhance antioxidant defense and protect hepatocytes against toxic effects of cadmium.