Systemic blockade of proBDNF inhibited the expansion and altered the transcriptomic expression in CD3+B220+ cells in MRL/lpr lupus mice

Objectives The overexpansion of CD3+B220+ cells is the hallmark and main pathological mechanism of clinical manifestations of spontaneously developed MRL/lpr mice, which are primarily used as a mouse model of SLE. Our recent report demonstrated that blocking brain-derived neurotrophic factor precursor (proBDNF) suppressed the antibody-secreting cell differentiation and proliferation and inhibited the progression of SLE; however, the effect of proBDNF blockade on these CD3+B220+ cells in MRL/lpr mice is unclear. Methods To explore the effect of proBDNF on CD3+B220+ cells, MRL/lpr mice at 12 weeks old were intraperitoneally injected with monoclonal anti-proBDNF antibody (McAb-proB) or control IgG continuously for 8 weeks. The manifestations in mice were observed, and peripheral blood and splenocytes were collected and analysed via flow cytometry at 20 weeks old. In addition, splenic CD3+B220+ cells were subjected to RNA sequencing (RNA-seq) analysis to identify transcriptomic alterations. Results CD3+B220+ cells in peripheral blood (p=0.0101) and spleen (p<0.0001) were expanded in MRL/lpr mice. Meanwhile, inhibition of proBDNF signalling reduced the percentage of CD3+B220+ cells in peripheral blood (p=0.0036) and spleen (p=0.0280), alleviated lymphadenopathy, reduced urine protein level (p<0.0001) and increased the body weight (p=0.0493). RNA-seq revealed 501 upregulated and 206 downregulated genes in splenic CD3+B220+ cells in McAb-proB-treated MRL/lpr mice compared with IgG-treated mice. The differentially expressed genes were found to be involved in apoptosis, tumour necrosis factor signalling, and T cell differentiation and proliferation. Conclusion Systemic blockade of proBDNF inhibited the overexpansion of CD3+B220+ cells and altered their signals related to cell cycle, cell apoptosis and the immune response, which may contribute to the attenuation of disease symptoms in murine lupus.