In the present study, we examined the role of S. aureus protein A (SpA) in inducing inflammatory response in HCECs. Exposure of HCECs to SpA induces rapid NF-κB activation and secretion of proinflammatory cytokine/chemokines (TNF-α and IL-8) in both concentration and time-dependent manner. Challenge of HCECs with live SpA − / − mutant S. aureus strains resulted in significantly reduced production of the cytokines when compared to the wild-type S. aureus strain. SpA also elicited the activation of MAP Kinases P38, ERK, but not JNK, in HCECs. SpA-induced production of proinflammatory cytokine were completely blocked by the NF-κB and p38 inhibitors and partially inhibited by the Jnk inhibitor. Pretreatment with anti-TLR2 neutralizing antibody had no effect on SpA induced inflammatory response in HCECs, suggesting that this response is independent of TLR2 signaling. Moreover, unlike TLR2 ligands, SpA failed to induce the expression of antimicrobial peptides (hBD2 and LL-37) in HCECs. These studies indicate that SpA is a S. aureus virulence factor that stimulates HCEC inflammatory response through a pathway distinct from TLR2 in HCECs.
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