Immunomodulatory effects of a polysaccharide from Solanum nigrum Linne through TLR4-MyD88 signaling pathway

Solanum nigrum Linne polysaccharide (SNLP), an active ingredient from Solanum nigrum Linne, has been proposed to inhibit tumor growth and display immunomodulatory activity. However, the molecular mechanism related to immune regulation remains unclear. In the present study, a homogeneous polysaccharide (SNLP-1) was extracted, the immune effects and the underlying molecular mechanisms were investigated. The immunomodulatory activity assay in vitro showed that SNLP-1 promoted the release of NO and TNF-α and IL-6 secretion in macrophages. In tumor-bearing mice, SNLP-1 could improve immune function including increasing the spleen index, thymus index and inducing Th1 responses mediated by IL-2, IFN-γ, and TNF, as well as decreasing the tumor weight. Furthermore, SNLP-1 elevated the expression of the critical nodes in the TLR4-Myd88 signaling pathways in vitro and in vivo. These results indicated that TLR4-MyD88 signal pathway may be one of the signal pathways of immune regulation of SNLP-1.