BackgroundB cell activating factor belonging to the TNF family (BAFF) is vital for B cell survival, proliferation and activation. Evidence indicates that BAFF is systemically or locally increased in glomerulonephritis (e.g. lupus nephritis, IgA nephropathy). However, the effect of BAFF on human mesangial cells is not known.MethodsThe impact of BAFF on the proliferation of a human mesangial cell line in vitro was investigated. The expression of BAFF receptor (BAFF-R) and downstream signal transduction were explored. The influence of BAFF on the expression of related genes was also studied.ResultsOur data indicated that BAFF had a proliferative effect on human mesangial cells, as supported by the results of cell proliferation assays and the inhibited expression of the pro-apoptotic gene Bim. BAFF-R was expressed on the cell membrane of human mesangial cells and blockade of BAFF/BAFF-R binding abrogated the proliferative effect of BAFF on human mesangial cells. BAFF stimulation led to rapid phosphorylation of NF-κBp65, Akt and MAPK p38 kinase in human mesangial cells, whereas it had no effect on the expression of NF-κB p100 and phosphorylation of Erk. The phosphorylation of Akt was very sensitive to blockade of BAFF/BAFF-R ligation, although activation of MAPK p38 and NF-κBp65 was not. BAFF treatment resulted in decreased expression of BAFF-R, which implied negative feedback regulation after its binding.ConclusionsBAFF promoted proliferation of human mesangial cells, which was mediated via BAFF-R. The BAFF/BAFF-R interaction triggered Akt, p65 and p38 activation, with Akt phosphorylation being tightly dependent on BAFF/BAFF-R interaction.
The roles of pDC and IFN-α have not been well defined in IgA nephropathy (IgAN). In this study, we investigated the abundance of pDCs and IFN-α in IgAN patients and the response of peripheral blood mononuclear cells (PBMCs) after stimulation of the pDC-preferred TLR9 ligand CpG2216. The effects of IFN-α on plasma cell differentiation and leukocyte migration were also investigated. Here, we found that the percentages of pDCs were increased in PBMCs of IgAN patients, than in those of healthy controls. Plasma levels of IFN-α proteins and abundance of plasma cells were higher in IgAN patients than in healthy donors. Plasma IFN-α levels were positively associated with proteinuria, renal IgM deposition, and renal tubular atrophy/interstitial fibrosis grade in IgAN patients. Ex vivo activation of TLR9 on pDCs resulted in increased IFN-α production and enhanced plasma cell differentiation in IgAN patients as compared with healthy donors. IFN-α treatment led to increased plasma cell differentiation in vitro. IFN-α also significantly promoted expression of chemokines IP-10 and MCP-1 in human mesangial cells, which subsequently facilitated the transendothelial migration of human CD4+ and CD14+ cells. In conclusion, pDC and its secreted cytokine IFN-α may play important roles in pathological changes of IgA nephropathy.
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