LPS/TLR4 Pathway Regulates IgA1 Secretion to Induce IgA Nephropathy.

Context:Studies have reported that the incidence and severity of IgA nephropathy (IgAN) are closely related to the imbalance of the intestinal flora. Imbalance of the intestinal flora may cause abnormalities, such as intestinal mucosal immunity or mesenteric B1 lymphocyte subsets. These can lead to an increase in immunoglobulin A (IgA) production and IgA structural changing, which can eventually cause IgA1 deposition in the glomerular mesangial area and nephritis. Objective:The study intended to explore whether the LPS/TLR4 pathway regulates mesenteric B cells, secreting Gd-IgA1 to induce IgA nephropathy. Design:The research team designed an animal study. Setting:The study took place at Department of Nephrology, Minhang Hospital, Fudan University. Animals:The animals were 60 specific pathogen free (SPF) C57BL/6 (B6, H-2b) male mice from that were 6-8 weeks old and weighed 20-25 grams. Intervention:The research team established a mouse model of IgA nephropathy. The team created five groups of mice: (1) the NC group, a normal negative control group without induced nephropathy and with no treatments; (2) the IgA nephropathy (IgAN) group, a positive control group with induced nephropathy and with no treatments; (3) the IgAN+anti-TLR4 group, an intervention group, with induced nephropathy and with a TLR4-antibody (anti-TLR4) treatment; (4) the IgAN+GEC group, an intervention group, with induced nephropathy and with treatment with glutamine enteric-coated capsules (GEC); and (5) the IgAN+anti-TLR4+GEC group, an intervention group, with induced nephropathy and with treatment with anti-TLR4 and GEC. Outcome Measures:The research team collected the blood and urine of all the mice and used an enzyme-linked immunoassay (ELISA) to analyze the levels of blood creatinine, urine protein, and urea nitrogen (BUN). The team also used the ELISA to analyze signal molecules for serum inflammation: interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), monocyte chemotactic protein 1 (MCP-1), cyclooxygenase-2 (COX2), and galactose-deficient IgA1(Gd-IgA1). The team analyzed the distribution and content of IgA+B220+B lymphocytes in the intestinal tissues of all the mice, using tissue immunofluorescence tracking technology, and used hematoxylin-eosin (HE) staining to analyze the pathological damage in the kidney tissue. For analysis of glomerular IgA deposition, the team used a tissue immunofluorescence technique, and for detection of protein expression-toll-like receptor 4 (TLR4), B-cell activating factor (BAFF), and a proliferation-inducing ligand (APRIL)-in mesenteric lymphoid tissues, the team used western blot analysis. Results:For the five groups of mice, the amount or degree of the physiological indicators and inflammatory factors that ELISA detected, the B lymphocytes and IgA sedimentation that immunofluorescence tracing measured, the kidney pathological that HE staining detected, and the expression of immune-related proteins that western blotting measured, all showed a common trend: IgAN group> IgAN+ glomerular endothelial cells (GEC) group> IgAN+anti-TLR4 group> IgAN+anti-TLR4+GEC group> NC group. Conclusions:The TLR4 antibody and GEC for the treatment of the intestinal tract can regulate and repair intestinal function, so that IgAN can also be relieved at the same time. The results supported the hypothesis that a relationship exists between IgAN and the LPS/TLR4 pathway that regulates mesenteric B cells to secrete low-glycosylated poly-IgA1, which provides a new potential therapeutic plan for IgA nephritis.