Immunomodulatory activity of semen Ziziphi Spinosae protein: a potential plant protein functional food raw material

Semen Ziziphi Spinosae protein (SZSP) is a new plant protein resource with good food functional properties and health care function. However, the biological activity of SZSP has not been further studied, which greatly limits the development and utilization of SZSP in the food industry. The aim of this study was to investigate the protective effect of SZSP on immunosuppressed mice and its inhibitory effect on immune-stimulated RAW264.7 cells. The results demonstrated that SZSP remarkably improved the immunomodulatory secretion in serum (interleukin-2, tumor necrosis factor-alpha [TNF-alpha], interferon-gamma, immunoglobulin-A, immunoglobulin-G, immunoglobulin-M) and primary macrophages (nitric oxide, interleukin-1 beta, TNF-alpha) and promoted the NK-cell killing activity of primary splenocytes in CTX-induced immunosuppression mice. Immunohistochemical analysis results indicated that the secretion of CD4+ and CD8+ in the spleen and thymus can be regulated by SZSP, leading to inhibition of the damage induced by cyclophosphamide in mice. Meanwhile, in order to clarify the immunomodulatory mechanism of SZSP, we showed that SZSP significantly inhibited the secretion of NO, interleukin-6, and TNF-alpha and reduced the phosphorylation expression of p-ERK, p-JNK, and p-I kappa B alpha in lipopolysaccharide-stimulated RAW264.7 cells. Therefore, the immunomodulatory effect of SZSP may be related to the activation of MAPKs and NF-kappa B signaling pathways. Based on the above studies, the preliminary purification of SZSP was continued, and S1F2G1 with immunomodulatory activity was obtained. Taken together, SZSP has an immunoregulatory effect in vivo and in vitro and may be a favorable candidate of functional food raw material for regulating immune responses.

Automated summary

This study aimed to investigate the protective effect of Semen Ziziphi Spinosae protein (SZSP) on immunosuppressed mice and its inhibitory effect on immune-stimulated RAW264.7 cells. The results showed that SZSP significantly improved immunomodulatory secretion and promoted NK-cell killing activity. Additionally, SZSP was found to regulate CD4+ and CD8+ secretion and inhibit damage induced by cyclophosphamide. It also inhibited the secretion of certain molecules and reduced the phosphorylation expression of specific proteins in lipopolysaccharide-stimulated cells. Therefore, SZSP has an immunoregulatory effect and may be a favorable candidate for functional food.