Objective: To investigate the mechanism of immune response in mouse macrophage induced by Pneumococcal heat shock protein 40 (HSP40).
Methods: After recombinant HSP40 (rHSP40) underwent expression detection and purification, lipopolysaccharide (LPS) was removed from it. Then rHSP40 was used to stimulate bone marrow derived macrophages (BMDMs) derived from C57BL/6 wild-type mice. The mRNA levels of tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), IL-1β, IL-23p19, IL-12p40, IL-12p35 and IL-10 in BMDMs were determined by reverse transcription PCR; the expressions of TNF-α, IL-6 and IL-12p40 were measured by ELISA. After stimulated by rHSP40, the levels of TNF-α and IL-6 expressed by wide-type, TLR2-/- and TLR4-/- BMDMs were detected by ELISA. The effects of the pretreatment of mitogen-activated protein kinases (MAPK) inhibitors on the secretion of TNF-α and IL-6 induced by rHSP40 were also evaluated by ELISA in BMDMs. The phosphorylation levels of p38MAPK and c-Jun N-terminal kinase (JNK) were determined by Western blotting.
Results: The rHSP40 protein reached a purity of more than 90%. It significantly enhanced the phosphorylation levels of p38MAPK and JNK as well as the expressions of TNF-α and IL-6. The p38MAPK and JNK inhibitors significantly suppressed the expressions of TNF-α and IL-6. The expressions of TNF-α and IL-6 in TLR4-/- BMDMs significantly decreased compared with wide-type BMDMs.
Conclusion: HSP40-induced immune response of mouse macrophages is regulated by p38MAPK and JNK signaling pathways, and this induction process depends on TLR4.