Seasonality effects on the inflammatory and antioxidant responses in the gilthead seabream (Sparus aurata)

Mediterranean fish such as Sparus aurata are subjected to extremes of high and low temperature favored by climate change effects, resulting to increased oxidative stress and inflammatory responses. To explore these phenomena, tnf-a and nfkb gene expression, as well as TNF-α and IL-6 levels were evaluated regarding inflammation, while sod, cat and gr gene expression, as well as SOD, GR and catalase activity levels were measured to assess antioxidant response. Findings revealed distinct tissue specific responses, dividing acclimatization phase into distinct cold and warm patterns. In highly vascular tissues (heart and red muscle) increased inflammatory levels were observed at increasing sea water temperatures, highlighting seasonality's strong oxidative effect, which cannot be ameliorated by the increased antioxidant enzymatic response. However, the decreased expression of the antioxidant genes during this period probably highlights energy allocation for processes other than antioxidant defense. An opposite pattern was exhibited in the white muscle and the liver, following the temperature pattern, with lowering levels with decreasing temperatures, probably showing a metabolic depression during decreased temperatures, and an increasing trend (mostly regarding antioxidant defense) during warming. These adjustments enlighten the adaptive responses of fish which reflect fluctuations of seasonal temperature, and the underlying thermal tolerance mechanisms during exposure to seasonal environmental oxidative stress. Understanding these responses helps scientists learn how fish cope with climate-related stress, which is important for managing fish populations and supporting sustainable aquaculture in a warming world.