REGULATORY MECHANISM OF EPITHELIAL CELLS ON IMMUNE RESPONSE OF MACROPHAGES TO MYCOBACTERIUM TUBERCULOSIS INFECTION

Yinghong Li^1#, Weiwei Sun^1#, Jinglei Liu¹, Haihong Pu¹, Chunlin Xu^2*

¹The Fifth Department of Internal Medicine, Affiliated Tumor Hospital of Harbin Medical University, Harbin Medical University Cancer Hospital, Harbin 150040, China - ²Department of Infectious Diseases, The Second Affiliated Hospital of Harbin Medical University,Harbin 150040, China

Objective: Explore the regulatory mechanism of epithelial cells on the macrophage immune response against Mycobacterium tuberculosis infection. 

Methods: The A549 and U937 cell lines were divided into control group (A549 cells + U937 cells), A549 infection group (A549 cells infected with H37Rv alone), U937 infection group (U937 cells infected with H37Rv alone), and co-infection group (A549 cells and U937 cells co-infected with H37Rv). TLR pathway proteins (toll like receptor 2 (TLR2), TLR6, myeloid differentiation factor 88 (MyD88), tumor necrosis factor receptor related factor 6 (TRAF6), and nuclear factor 6 (NF - α) were compared among the groups- κ B p65 (NF- κ. The expression levels of IL-6, IL-10 and TNF - α were significantly higher than those of IL-6, IL-10, and TNF - α. (TNF- α) Level A LY294002, a phosphatidylinositol 3 kinase (PI3K) inhibitor, was added to the cells of each group. The TLR pathway proteins (TLR2, TLR6, MyD88, TRAF6, NF) of each group were compared- κ B p65) and inflammatory factors (IL-6, IL-10, TNF - α) Level. 

Results: The TLR2, TLR6, MyD88, TRAF6 and NF occurrences in the U937 infection group were significantly higher than those in the control group- κ The expression of the B p65 protein in the control group was significantly higher than that in the control group (p-value<0.05). TLR2, TLR4, MyD88, TRAF6, NF in A549 infection group and co-infection group- κ The expression of the B p65 protein in the U937 infection group was significantly lower than that in the U937 infection group (p-value<0.05). In the IL-6, IL-10 and TNF in U937 infection groups- α, the levels were significantly higher than those in the control group (p-value<0.05). In the IL-6, IL-10, A549, and co-infection groups, the levels were significantly lower than those in the U937 infection group (p-value<0.05). The occurrence of Ly294002tlr2, TLR6, MyD88, TRAF6 and NF in the U937 cells were significantly increased when A549 and U937 were co-infected by LY294002- κ. The expression of the B p65 protein in the U937 infected group was significantly higher than that in the U937 infected group. LY294002 intervention in the H37Rv-infection co-culture model can reduce the overall occurrence of IL-6, IL-10, and TNF- α. Moreover, the U937 erysipelas infection could induce IL-6, IL-10, and TNF in the co-culture microenvironment. The level of IL-6 released into the microenvironment in A59 and U937 co-infection group was significantly higher than that in the U937 single infection group, which was contrary to that in the non-inhibitor group. 

Conclusion: In the anti-MTB environment of the lung epithelial cells and macrophages, epithelial cells can improve the inflammation, which is mediated by the TLR signal in macrophages and which may be realized by regulating the PI3K signal pathway.