N-acetyl-l-cysteine protects porcine oocytes undergoing meiotic resumption from heat stress

•GVBD oocytes undergoing meiotic resumption are much sensitive to HS.•GVBD-specific HS disorganizes oocyte spindle assembly and inhibits ERK signaling.•GVBD-specific HS induces erroneous H3K27me3 modification in oocytes.•NAC protects oocyte cellular and molecular events against GVBD-specific HS.•NAC rescues impaired oocyte developmental potential following GVBD-specific HS. Heat stress (HS) is a notable risk factor for female reproductive performance. In particular, impaired oocyte maturation was thought to contribute largely to the HS-induced reproductive dysfunctions. In this study, we confirmed that oocytes undergoing GVBD were much susceptible to HS, and thus compromising subsequent embryonic development. Using N-acetyl-l-cysteine (NAC), we found supplementation of a relatively high dose NAC during in vitro maturation, can protect oocytes from HS-induced complications, and thus rescuing impaired embryonic development. Further analysis indicated that mechanisms responsible for protecting GVBD oocytes from HS by NAC may include: (1) reversing disorganized spindle assembly and inhibited extracellular signal–regulated kinase (ERK) signaling; (2) correcting erroneous H3K27me3 modification and dysregulated expression of imprinted genes; (3) alleviating increased intraoocyte reactive oxygen species accumulation and apoptosis initiation. Our study, focusing on the oocyte meiotic maturation, may provide a safe and promising strategy for protecting reproductive sows under environmental hyperthermal conditions.