JAK2/STAT3 Signaling Pathway Modulates Acute Methylmercury Toxicity in the Mouse Astrocyte C8-D1A Cell Line

Methylmercury (MeHg), an environmental pollutant, reaches the human body predominantly through contaminated fish consumption, potentially leading to severe neurological disorders. Upon ingestion MeHg reaches the brain and selectively accumulates in astrocytes. The activation of nuclear factor erythroid 2-related factor 2 (Nrf2) has been identified as a key early response to MeHg-induced oxidative injury, positioning it as a potential therapeutic target. However, recent studies suggest that Nrf2 activation alone may not be sufficient to mitigate MeHg toxicity, indicating the existence of other protective mechanisms. The signal transducer and activator of transcription 3 (STAT3) signaling pathway, known for its role in cell growth and survival, has emerged as a potential player in redox homeostasis. In this study, we investigated the role of STAT3 in acute (≤ 24 h) MeHg-induced neurotoxicity. MeHg exposure induced STAT3 expression in C8-D1A astrocytic cells. Our data demonstrated that pharmacological inhibition of STAT3 using AG490 or C188-9 exacerbated MeHg-induced cell death and compromised antioxidant responses. Furthermore, to fully characterize the role of STAT3 in oxidative stress, we used two different antioxidants, N-acetylcysteine (NAC) and Trolox. Conversely, reactive oxygen species (ROS)-scavenging antioxidants partially ameliorated STAT3 activation, suggesting that MeHg-induced STAT3 activation is mediated, at least in part, by mechanisms independent of ROS. Our findings suggest that STAT3 contributes to neuroprotection against MeHg exposure in astrocytes and is, at least in part, regulated by the increase in ROS levels within these cells.