Microalgal astaxanthin ameliorates cypermethrin-induced necroptosis and inflammation via targeting mitochondrial Ca2+ homeostasis and the ROS-NF-κB-RIPK3/MLKL axis in carp hepatocytes (Cyprinus carpio)

Cypermethrin is a toxic pesticide that has infiltrated water bodies due to its widespread use. This contamination has led to detrimental effects on the immune organs of aquatic species, including fish. The natural fat-soluble orange-red carotenoid, astaxanthin (MAT), derived from microalgae, possesses anti-inflammatory, antioxidant, and immunomodulatory properties. To elucidate the mechanism of CY induced damage to carp liver cells and assess the potential protective effects of MAT, we established a carp hepatocyte model exposed to CY and/or MAT. Hepatocytes from carp (Cyprinus carpio) were treated with either 8 μM CY or 60 μM MAT for 24 h. Upon exposure CY, a significant increase in reactive oxygen species (ROS) was observed alongside a diminution in the activities of key antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), suggesting an impairment of cellular antioxidant capacity. Subsequently, acridine orange/ethidium bromide (AO/EB) staining and flow cytometry analysis revealed that hepatocytes exposed to CY exhibited a higher incidence of necroptosis, associated with an elevated mitochondrial Ca²⁺ concentration, which contributed to cellular dysfunction. Furthermore, exposure to CY also activated the ROS-NF-κB-RIPK3/MLKL signaling pathway, increasing the levels of necroptosis-related regulatory factors (RIP1, RIP3, and MLKL) in hepatocytes and the expression of inflammatory genes (IL-6, IFN-γ, IL-4, IL-1β, and TNF-α), which led to immune dysfunction in hepatocytes. The immunotoxic effects induced by CY were mitigated by MAT treatment, suggesting its potential in alleviating the aforementioned changes caused by CY. Overall, the data suggested that MAT therapy could enhance hepatocyte defenses against CY-induced necroptosis and inflammatory responses by regulating mitochondrial Ca²⁺ homeostasis and inhibiting the ROS-NF-κB-RIPK3/MLKL signaling cascade. This study elucidated the potential benefits of employing MAT to protect farmed fish from agrobiological hazards during CY exposure, underscoring the practical applications of MAT in aquaculture.