| Summary: | 碩士 === 國立成功大學 === 生物化學研究所 === 94 === As an gas-exchange organ, lungs are inevitably exposed to air that is contaminated with pathogens, allergens and pollutants. Host-defence mechanisms within the lungs must facilitate clearance of inhaled pathogens. The innate immune components in the lung alveolar include neutrophils, alveolar macrophages, opsonins, complements and surfactant components. Toll-like receptors (TLRs) on these antigen presenting cells (eg. macrophages and neutrophils) recognize different pathogen-associate molecular patterns (PAMPs) of inhaled pathogens. For example, unmethylated CpG dinucleotides (CpG ODN) distributed in bacterial DNA are recognized by TLR9, which leads to inflammatory cytokines (eg. TNFα) production by antigen presenting cells. Many literatures reported that surfactant proteins (SPs) regulate lung innate immunity, such as enhancing pathogen clearance by phagocytes through binding to a variety of bacteria, viruses and allergens. The carbohydrate recognition domain of SP-D was reported to bind many PAMPs, such as LPS, lipoteichoic acid, peptidoglycan, plasmic DNA and synthetic oligonucleotides. But the relationship between SP-D and CpG ODN and the immune response has not been defined. The objective of my study is to determine the role of SP-D in the modulation of TNFα production by alveolar macrophages activated by CpG ODN. Results showed that CpG ODN activated the phosphorylation of P38 and JNK MAP kinases and TNFα production in MHS cells. However, CpG ODN did not affect TLR9 expression. While MHS cells pretreated with three kinds of MAPK inhibitors, the CpG ODN-induced TNFα production was inhibited by P38 inhibitor (SB203580) and JNK inhibitor (SP600125). Which showed that P38 and JNK participated in TNFα production. Besides, IRAK-1, a joint molecular of upstream of P38 and JNK signaling, was activated and degraded by CpG ODN stimulation. Data also showed that native SP-D slightly up-regulated TNFα production under the stimulation of CpG ODN. But the recombinant SP-D composed of αhelical neck region and carbohydrate recognition domains inhibited CpG ODN-induced TNFα production significantly. While MHS cells pretreated with different dose of recombinant SP-D and then challenged with CpG ODN, the phosphorylation of P38 and JNK are inhibited by recombinant SP-D. Which led to recombinant SP-D inhibited TNFα production. In addition, IRAK-1 was protected from CpG ODN-induced degradation by recombinant SPD not native SP-D. These results demonstrated that recombinant SP-D inhibited CpG ODN-induced TNFα production via inhibition on the activity of IRAK-1, JNK and P38 MAPKs.
|
|---|
