Dietary supplementation with nerolidol improves the antioxidant capacity and muscle fatty acid profile of Brycon amazonicus exposed to acute heat stress.

An increase in water temperature in the Amazon River has elicited concerns about commercially important fish species associated with food security, such as matrinxã (Brycon amazonicus). Studies have demonstrated the positive effects of diets supplemented with plant-based products that combat heat stress-induced oxidative damage. The aim of this study was to determine whether dietary supplementation with nerolidol prevents or reduces muscle oxidative damage and impairment of the fillet fatty acid profile of matrinxã exposed to heat stress. Plasma and muscle reactive oxygen species (ROS) and lipid peroxidation (LPO) levels were significantly higher in fish exposed to heat stress compared to fish not exposed to heat stress, while plasma superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity was significantly lower. The total content of saturated fatty acids (SFA) in fillets was significantly higher in fish exposed to heat stress compared to fish not exposed to heat stress, while he total content of polyunsaturated fatty acids (PUFA) was significantly lower. Nerolidol prevented the increase of muscle LPO and plasma ROS and LPO levels in fish exposed to heat stress, and partially prevented the increase in muscle ROS levels. Diets containing nerolidol prevented the inhibition of muscle GPx activity in fish exposed to heat stress, and partially prevented the decrease of plasma GPx activity. The nerolidol-supplemented diet prevented the increase of fillet SFA in fish exposed to heat stress, while partially preventing the decrease of PUFA. We conclude that acute heat stress at 34 °C for 72 h causes plasma and muscular oxidative damage, and that homeoviscous adaptation to maintain membrane fluidity can represent a negative impact for fish consumers. A nerolidol diet can be considered a strategy to prevent heat stress-induced oxidative damage and impairment of muscle fatty acid profiles.

Consequences of oxidative damage on the fatty acid profile in muscle of Cichlasoma amazonarum acutely exposed to copper.

Rapid industrialization results in the production of large quantities of waste that are commonly discharged into water bodies, leading to the damage of the aquatic ecosystem and freshwater organisms. Copper (Cu) can induce oxidative damage in fish muscle, the main fish portion that is consumed by humans. However, the responses of the Amazon fish Cichlasoma amazonarum and its capacity to withstand acute Cu concentrations found in Amazon water around mines remain unknown. Thus, the aim of this study was to evaluate whether exposure to Cu causes muscle oxidative stress and/or oxidative damage and impairs the fillet fatty acid profile of C. amazonarum acutely exposed to Cu found in Amazon waters around mines. Muscle reactive oxygen species and protein carbonylation levels were significantly higher in fish exposed to 1500 µg/L Cu compared with the control group, while muscle lipid peroxidation levels were significantly higher in fish exposed to 500, 750, and 1500 µg/L Cu compared with control group. Muscle antioxidant capacity against peroxyl radical's levels and glutathione peroxidase activity were significantly lower in fish exposed to 1500 µg/L Cu compared with the control group, while muscle superoxide dismutase activity was significantly lower in fish exposed to 750 and 1500 µg/L Cu compared with control group. The total content of saturated fatty acids was significantly higher in fish exposed to 1500 µg/L Cu compared with the control group, while the total content of monounsaturated fatty acids and sum of n3 fatty acids were significantly lower in fish exposed to 1500 µg/L Cu compared with control group. No significant difference was observed regarding muscle catalase, glutathione S-transferase, and glutathione reductase activities. Based on these lines of evidence, the results of this comprehensive study agree with the initial hypothesis that the exposure to Cu found in Amazon water around mines induces oxidative damage and inhibits enzymatic and non-enzymatic antioxidant response in the muscle of C. amazonarum exposed to high Cu levels. Moreover, the impairment of the fillet fatty acid profile appears to be mediated by oxidative damage, representing a negative impact on fish health.

Acute exposure to environmentally relevant concentrations of copper affects branchial and hepatic phosphoryl transfer network of Cichlasoma amazonarum: Impacts on bioenergetics homeostasis.

The toxic effects of copper (Cu) are linked to dysfunction of metabolism and depletion of adenosine triphosphate (ATP). Nevertheless, the effects related to phosphoryl transfer network, a network of enzymes to precise coupling of the ATP-production and ATP-consuming process for maintenance of bioenergetic, remain unknown. Therefore, the aim of this study was to determine whether the phosphoryl transfer network could be one pathway involved in the bioenergetic imbalance of Cichlasoma amazonarum exposed for 96 h to environmentally relevant concentrations of Cu found in Amazonia water around mines. Branchial mitochondrial creatine kinase (CK) activity was significantly lower in fish exposed to 1500 µg/L Cu than in the control group, while branchial cytosolic CK activity was significantly greater. Branchial (exposed to 750 and 1500 µg/L Cu) and hepatic (exposed to 1500 µg/L Cu) pyruvate kinase (PK) activity was significantly lower in fish exposed to Cu than in the control group. Branchial and hepatic ATP levels were significantly lower in fish exposed to 1500 µg/L than in the control group. Branchial reactive oxygen species (ROS) and lipid peroxidation (LPO) levels were significantly higher in fish exposed to 750 and 1500 µg/L Cu compared to control. Hepatic ROS and LPO levels were significantly higher in fish exposed to 1500 µg/L than in the control group. Branchial and hepatic Cu levels were significantly higher in fish exposed to 1500 µg/L compared to other groups. Exposure to 750 and 1500 µg/L Cu impairs bioenergetics homeostasis, which appears to be mediated by ROS overproduction and lipid peroxidation.

Dietary exposure to ochratoxin A reduces growth performance and impairs hepatic purinergic signaling in tambaqui (Colossoma macropomum).

The practice of replacing costly animal-derived proteins with more economical plant proteins has augmented the risk of mycotoxin contamination in fish feeds, including contamination with ochratoxin A (OTA). OTA is a secondary metabolite produced by molds commonly found in fish feeds that causes impairment of performance in several fish species and some hepatic biochemical alterations. However, the pathways involved in hepatic damage remain unknown and are limited to histopathological alterations. Purinergic signaling is a homeostatic system that continuously monitors the internal environment to detect injury primarily by two intercellular messengers: adenosine triphosphate (ATP) and adenosine (Ado). The objective of this study was to determine whether OTA-contaminated feed induces the release of nucleotides in the extracellular milieu, as well as whether ectoenzymes modulate ATP pro-inflammatory effects in liver of tambaqui (Colossoma macropomum). Final mean weight, weight gain (WG), and liver weight were significantly lower in tambaqui fed feeds containing 1.6 and 2.4 mg OTA/kg feed than in the control group. Liver ATP and Ado levels were significantly higher in tambaqui fed feeds containing 1.6 and 2.4 mg OTA/kg feed compared with control, while no significant difference was observed regarding adenosine diphosphate and adenosine monophosphate levels. Hepatic triphosphate diphosphohydrolase (NTPDase) activity (for ATP) was significantly greater in tambaqui fed feeds containing 1.6 and 2.4 mg OTA/kg feed compared with control, while adenosine deaminase (ADA) activity was lower. No significant difference was observed with respect to hepatic NTPDase activity (for ADP) or for 5'-nucleotidase activity. Finally, levels of liver metabolites of nitric oxide were significantly higher in tambaqui fed feeds containing 1.6 and 2.4 mg OTA/kg feed than in the control group. Based on these data, exposure to 1.6 and 2.4 mg OTA/kg feed impaired tambaqui growth performance associated with final mean weight and WG. Levels of two important intercellular messengers, ATP and Ado, increased in the extracellular space as a consequence of hepatic damage, exerting opposite immune responses. Finally, liver NTPDase and ADA activities were altered to modulate ATP and Ado levels, respectively, exerting anti-inflammatory effects to counteract OTA-induced hepatic injury.

Disturbance of oxidant/antioxidant status and impairment on fillet fatty acid profiles in Brycon amazonicus subjected to acute heat stress.

Amazon fish are vulnerable to climate change. Current temperature increases in Amazonian rivers are likely to continue in the coming years. Elevated temperatures impair homeostasis and subject fish to oxidative stress; nevertheless, the effects of elevated temperature on plasma and muscle oxidative stress as well as fillet fatty acid composition in matrinxã (Brycon amazonicus) remain unknown. Therefore, the aims of the present study were to determine whether antioxidant system is able to withstand acute thermal stress to avoid plasma and muscle oxidative damage and to determine the manner in which matrinxã adjust their muscle fatty acid metabolism in a response to acute heat stress. We exposed juvenile matrinxã to four temperatures (28 °C as control and 30, 32, and 34 °C) for 72 h and observed the effects on plasma and muscle oxidant/antioxidant status and on fatty acid composition. Plasma reactive oxygen species (ROS) and lipid peroxidation (LPO) levels were significantly higher in matrinxã exposed to 34 °C compared with the control group, while they were significantly higher in the muscle of matrinxã exposed to 32 °C and 34 °C compared with the control group. Superoxide dismutase (SOD) activity and total antioxidant capacity (TAC) levels were significantly lower in the plasma and muscle of matrinxã exposed to 34 °C compared with the control group. Plasma glutathione peroxidase (GPx) activity was significantly lower in matrinxã exposed to 32 and 34 °C compared with the control group, while it was significantly lower in the muscle of matrinxã exposed to 34 °C. The total content of saturated fatty acid (SFA) was significantly higher in the fillet of matrinxã exposed to 34 °C compared with the control group, while the total content of polyunsaturated fatty acid (PUFA) was significantly lower. Based on this evidence, we conclude that acute heat stress at 32 °C and 34 °C causes plasma and muscular oxidative stress, and the enzymatic and non-enzymatic antioxidant system is unable to prevent oxidative damage. Moreover, increased levels of total SFA and decreased levels of PUFA occur in an attempt to withstand heat stress and maintain membrane fluidity; nevertheless, these responses can represent negative impacts for consumers.

Purine levels and purinergic signaling in plasma and spleen of Brycon amazonicus exposed to acute heat thermal stress: An attempt to regulate the immune response.

Amazon fish are vulnerable to climate change. Several lines of evidence suggest that the temperature of Amazonian rivers will increase in the coming years. Elevated temperature disturbs homeostasis and subjects fish to physiological stress; however, the effects of temperature on immunity remain poorly understood, particularly those effects involving purinergic signaling. This system fine-tunes the inflammatory and immune responses triggered by stress. Therefore, the aims of this study were to determine whether acute heat stress induces the release of nucleotides into extracellular compartment and to determine whether purinergic enzymes modulate the proinflammatory effects of adenosine triphosphate (ATP) in plasma and spleen of matrinxã (Brycon amazonicus) exposed to acute heat stress. We exposed juvenile matrinxã to four temperature regimes (28 °C as control, 30, 32 and 34 °C) for 72 h and observed the effects on purinergic signaling. Plasma cortisol levels were significantly higher in fish exposed to 34 °C than in the control group, while spleen ATP, adenosine diphosphate (ADP) and adenosine monophosphate (AMP) levels were significantly higher in this group than in controls. Activities of spleen nucleoside triphosphate diphosphohydrolase (NTPDase) and 5'-nucleotidase were significantly higher in fish exposed to 34 °C than those of the control group, while spleen interleukin-1 (IL-1) and interleukin-6 (IL-6) levels were higher in this same group than in the control group. No significant differences were observed between the groups regarding plasma parameters. Based on these data, we concluded that acute heat stress at 34 °C caused physiological stress in matrinxã, manifesting as elevated plasma cortisol levels. The most important finding is that purinergic enzymes were modulated, though not efficiently, in response to the excessive release of nucleotides into the extracellular space. In summary, the purinergic signaling pathway may be involved in the impairment of immune and inflammatory responses in matrinxã exposed acutely to 34 °C.

Dietary ochratoxin A (OTA) decreases growth performance and impairs muscle antioxidant system and meat fatty acid profiles in juvenile tambaqui (Colossoma macropomum).

Plant-based ingredients are successfully replacing fishmeal in fish feeds. However, this practice increases the risk of feed contamination by mycotoxins that reduce production and heath associated with oxidative damage. The aim of this study was to determine whether feed contaminated with environmentally relevant concentrations of ochratoxin A (OTA) causes muscle oxidative damage in tambaqui (Colossoma macropomum), and to determine whether this feed impairs fatty acid profiles in fish meat. Final mean weight, weight gain, daily weight gain, feed efficiency, and specific growth rate were significantly lower in fish fed 1.6 and 2.4 mg OTA/kg compared to those fed basal diet, while feed conversion was significantly higher in these same groups compared to the basal group. Levels of reactive oxygen species and lipid peroxidation in muscle were significantly higher in fish fed 1.6 and 2.4 mg OTA/kg compared to those in the basal group. Likewise, muscle superoxide dismutase and glutathione peroxidase activities were significantly higher in fish fed 1.6 and 2.4 mg OTA/kg then in those fed basal feed. The total content of saturated fatty acids was significantly higher, and total content of polyunsaturated fatty acids was significantly lower in fish fed 2.4 mg OTA/kg compared to those fed basal feed. Taken together, the data suggest that OTA-contaminated feed induces oxidative damage and disturbs enzymatic and non-enzymatic antioxidant responses in tambaqui meat. The perturbations of fatty acid profiles in fish meat appears to mediated by oxidative damage, representing negative impact on fish health and presenting concerns for consumers of fish.