Effects of water extracts of Lepidium meyenii walp (maca) growing in two different places in Xinjiang on the maturation and function of dendritic cells
Objective 
To investigate the effects of water extracts of Lepidium meyenii walp (LMWE) collected from two different places in Xinjiang on the maturation and function of dendritic cells (DCs) and to evaluate their roles in immunoregulation. 
 
 
Methods 
Water extracts of LMWE growing in Tashikuergan County (Ta xian) and A La gou of Xinjiang were prepared and named as LMWE-T and LMWE-A, respectively. Bone marrow-derived DCs and splenocytes isolated from C57BL/6 mice were treated with different concentrations of polysaccharide extracts from LMWE-T/A. Effects of LMWE-T/A on the percentage and apoptosis of DC, expression of co-stimulatory molecules and secretion of cytokines were detected by flow cytometry and ELISA. MTT assay was used to analyze the proliferation of splenocytes. Changes in the functions of DC were evaluated by mixed lymphocyte reaction (MLR). 
 
 
Results 
LMWE-T/A had no influence on the percentage and viability of DC. Expression of CD40 and CD86, and secretion of TNF-α, IL-12p40 and IFN-γ were significantly increased by LMWE-T/A treatment in a dose-dependent manner. LMWE-T/A treatment enhanced the functions of DCs and also dose-dependently promoted the proliferation of splenocytes. LMWE-A was more effective than LMWE-T in promoting CD86 expression, IFN-γ secretion and splenocyte proliferation. Pretreatment with TAK-242, an inhibitor of Toll-like receptor 4 (TLR4), could significantly inhibit the regulatory effects of LMWE-T/A on CD40 expression and the secretion of TNF-α and IL-12p40. 
 
 
Conclusion 
This study shows that LMWE could promote the maturation of DC through TLR4 signaling pathway, enhance the functions of DC without side effects on DC survival, and increase the proliferation of splenocytes, indicating that LMWE has a potential immunopotentiating effect. LMWE-A has better effects than LMWE-T on immune enhancement. 
 
 
Key words: 
Lepidium meyenii walp; Dendritic cell; Co-stimulatory molecule; Cytokines; Immunoregulation