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

Function and application of brain‑derived neurotrophic factor precursors (Review)

Brain‑derived neurotrophic factor precursor (proBDNF) plays a critical role in the pathogenesis and progression of various human diseases. Through its interaction with p75NTR and sortilin receptors, proBDNF promotes apoptosis, impairs synaptic plasticity, and contributes to the regulation of immune system function, inflammatory responses and cellular metabolic processes. proBDNF is widely distributed throughout the body, and as such, extensive research has demonstrated that proBDNF is significantly associated with the pathophysiological mechanisms underlying several diseases. In the present review, the mechanisms by which proBDNF contributes to different diseases are summarized to highlight its potential therapeutic and diagnostic implications. Specifically, the role of proBDNF in cognitive disorders, focusing on its effects on synaptic function and neural network dynamics, while analyzing the cascade reactions involving proBDNF and downstream effector molecules in inflammatory diseases, to elucidate its bidirectional regulatory effects in tumor initiation and progression. Furthermore, the function of proBDNF in neurogenesis, the mechanism by which it regulates the memory of fear, and enhances individual behavioral flexibility is discussed. Finally, the potential of proBDNF as a biomarker for disease diagnosis and the therapeutic prospects of targeting it using monoclonal antibodies are highlighted while also proposing future research directions. The present review can serve as a reference for translational medical research on proBDNF and its receptors.

ω-3 polyunsaturated fatty acid alleviates systemic lupus erythematosus by suppressing autoimmunity in a murine model

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune inflammatory disease that damages multiple organs by the production of autoantibodies. Numerous research studies have demonstrated the anti-inflammatory effects of ω-3 polyunsaturated fatty acids (PUFAs). A diet rich in ω-3 PUFAs reduces chronic inflammatory and autoimmune conditions. Herein, we investigated the protective effect of ω-3 PUFAs against autoimmune injury in SLE. In a TMPD-induced mouse model of SLE, supplementation with eicosapentaenoic acid (EPA)-rich (97%) fish oil was found to alleviate systemic autoimmune phenotypes such as ascites, lipogranulomas and serum dsDNA levels. In addition, EPA also significantly improved renal manifestations, reducing proteinuria, glomerulonephritis, and immune complex deposition. Mechanistically, ω-3 PUFAs were shown to modulate the differentiation of B lymphocyte subsets of primary splenic lymphocytes in the spontaneous murine lupus model MRL/MpJ-Faslpr in vitro, specifically that both EPA and DHA suppressed the number of total B cells, B1B2 cells and plasma cells. Concurrently, they were also found to promote the secretion of the anti-inflammatory cytokine IL10, mainly produced by Breg and Treg cells. Thus, nutritional supplementation with ω-3 PUFAs can regulate B cell's differentiation and anti-inflammatory function and strongly prevent autoimmune responses and lupus nephritis. The diets balance between ω-6 and ω-3 PUFAs intake may represent a promising treatment strategy to prevent or delay the onset of SLE.

Expression of proBDNF/p75NTR in peripheral blood lymphocytes of patients with sepsis and its impact on lymphocyte differentiation

OBJECTIVES

Sepsis is a life-threatening organ dysfunction caused by the host's imbalanced response to infection. Due to lack of effective treatments, it has always been the difficulty and focus of clinical treatment of sepsis. Studies have shown that pro-brain-derived neurotrophic factor (proBDNF) binds to the high-affinity total neurotrophic factor p75 neurotrophin receptor (p75NTR), which activates downstream signaling cascades and disrupts immunological inflammation and plays an important role in the progression of sepsis. This study aims to explore the expression changes of lymphocyte-derived proBDNF/p75NTR in patients with sepsis and its effect on lymphocyte differentiation.

METHODS

From the healthy donors (control group, n=40) and sepsis patients (sepsis group, n=40) admitted to the hospital for the first time, peripheral blood samples and blood routine clinical detection indicators were obtained. By using flow cytometry, the proportion of lymphocyte subsets and their expression of proBDNF/p75NTR were examined. The peripheral blood lymphocytes were isolated from the control group and incubated with lipopolysaccharide (LPS). Flow cytometry analysis technology was used to detect the expression of proBDNF/p75NTR on LPS-treated lymphocyte subsets. On this basis, we investigated the effects on lymphocyte differentiation by inhibiting p75NTR.

RESULTS

White blood cell count, neutrophil count, and neutrophil percentage of the patients in the sepsis group at admission were significantly higher than those in the control group; on the contrary, lymphocyte count and lymphocyte percentage in the sepsis group were lower than those in the control group (all P<0.001). The patients in the sepsis group had considerably greater neutrophil/lymphocyte and monocyte/lymphocyte ratios than those in the control group (both P<0.05). In the peripheral blood of sepsis patients, proBDNF expression was upregulated on CD19+ B cells, whereas p75NTR expression was elevated on B cells, CD4+ T cells, and CD8+ T cells (all P<0.05). ProBDNF/p75NTR expression was upregulated by LPS stimulation in vitro in peripheral blood cells of the control group (P<0.05), and this tendency was similar to the expression alterations in peripheral lymphocytes of the sepsis group. Inhibition of p75NTR increased CD4+ T cell and CD19+ B cell percentages, cytokine expression of IL-4 and IL-10, and reduced IL-1β and IL-6 production (all P<0.05).

CONCLUSIONS

The immunosuppressive state of sepsis patients is indicated by a reduction in lymphocyte count and an increase in the proportion of inactive neutrophils. ProBDNF/p75NTR expression is upregulated in the peripheral blood lymphocytes of sepsis patients, and p75NTR inhibition may control lymphocyte differentiation involved in sepsis progression.

ProBDNF and its receptors in immune-mediated inflammatory diseases: novel insights into the regulation of metabolism and mitochondria

Immune-mediated inflammatory diseases (IMIDs) consist of a common and clinically diverse group of diseases. Despite remarkable progress in the past two decades, no remission is observed in a large number of patients, and no effective treatments have been developed to prevent organ and tissue damage. Brain-derived neurotrophic factor precursor (proBDNF) and receptors, such as p75 neurotrophin receptor (p75^NTR) and sortilin, have been proposed to mediate intracellular metabolism and mitochondrial function to regulate the progression of several IMIDs. Here, the regulatory role of proBDNF and its receptors in seven typical IMIDs, including multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, allergic asthma, type I diabetes, vasculitis, and inflammatory bowel diseases, was investigated.