MAPK3 and infection: This study demonstrates that (i) in 0.25 mM NaO-treated bMECs, the IIR is not mediated by TLR2, and its signaling pathway (MAPKs and TF) is impaired, and (ii) 1 mM NaO treatment activates bMECs via the TLR2/p38/JNK/ERK1/2 pathway prior to infection, which might be involved in the 1 mM NaO-reduced S. aureus internalization into bMECs.