Synergistic activation of Src, ERK and STAT pathways in PBMCs for Staphylococcal enterotoxin A induced production of cytokines and chemokines.

Background: Staphylococcal enterotoxin A (SEA) is a well-known superantigen and stimulates human peripheral blood mononuclear cells (PBMCs) involving in the pathogenesis of inflammatory disorders and cancer. Objective: To better understand the biological activities of SEA and the possible intracellular mechanisms by which SEA plays its roles in conditions like staphylococcal inflammatory and/or autoimmune disorders and immunotherapy. Methods: Recombinant SEA (rSEA) was expressed in a prokaryotic expression system and its effects on the cytokine and chemokine production was examined by Enzyme-linked Immunospot (ELISpot) Assay and ELISA analysis. Results: In vitro experiments showed rSEA could significantly enhance secretion of a broad spectrum of cytokines and chemokines from PBMCs dose-dependently. Increased secretion of cytokines and chemokines from rSEA stimulated PBMCs was barely affected by C-C motif chemokine receptor 2 (CCR2) antagonist INCB3344. However, Src, ERK and STAT pathway inhibitors were able to successfully block the enhanced secretion of most of cytokines and chemokines produced by rSEA stimulated PBMCs. Conclusions: Our work suggested that rSEA serves as a potent stimulant of PBMCs, and induces the release of cytokines and chemokines through Src, ERK and STAT pathways upon a relatively independent network. Our work also strongly supported that Src, ERK and STAT signaling inhibitors could be effective therapeutic agents against diseases like toxic shock syndrome or infection by microbes resistant to antibiotics.