| Two animal feeding experiments and one experiment in vitro were conducted to investigate the immunomodulation and its mechanism of Acanthopanax senticosus polysaccharide (ASPS) on immune function of weaned pigs.(1) Experiment1was evaluated to explore the effects of ASPS on growth and immune response in weaning piglets and the optimal dose of dietary ASPS. A total of96crossbred pigs were randomly allotted to six diets supplemented with ASPS at0,150,300,500,800, and1000mg/kg. Pigs were fed ad libitum for21days and were intramuscularly injected with OVA on d14to evaluate humoral immune response. Growth performance, blood parameters were measured on d14and21. The results showed that ADG, FCR, the number of WBC and lymphocyte, lymphocyte proliferation, concentration of CD4+lymphocyte subset, the scrum concentration of IFN-y and cortisol were changed quadratically (P<0.05) with the increased dose of dietary ASPS, IL-2was changed linearly (P<0.05). However, concentration of specific OVA antibody, IgG, IgA, IgM, IL-4, CD8+lymphocyte subset, ADFI, CD4+to CD8+were not affected (P>0.05) by ASPS. For improving growth and enhancing immune response, optimal supplementation level might be800mg/kg in weaned pigs.The result indicates that ASPS supplementation can improve growth performance and regulate cellular immunity as well as relieve stress response in weaned pigs.(2) Experiment2was conducted to further reseach the effects of ASPS on growth depression and its immunoregulatory role in pigs challenged with LPS. A2×2factorial design experiment including main factors such as dietary treatment and immunological challenge was conducted with64piglets which were assigned to two dietary treatments (each treatment was replicated in8pens). Piglets in4pens per dietary treatment were injected with LPS or sterile saline on day14and21. Blood samples were obtained3h and the next day after injection for analysis of blood parameters. The results showed that ASPS did not affect growth performance of piglets prior to LPS injection (P>0.05). From day15to21, ASPS improved ADG and ADFI (P<0.05) and has interaction relationship with LPS (P<0.05). Lymphocyte proliferation, CD4+, CD8+lymphocyte subset on day15were increased, and CD4+/CD8+was relieved to avoid increasing by ASPS(P<0.05). ASPS relieved the increased plasma concentration of IL-1β, IL-6, TNF-a, PGE2, cortisol, glucose, NEFA and a-AGP(P<0.05). GH, IGF-I, TP and IL-10were significantly increased by dietay ASPS (P<0.05). However, IL-4and insulin were not affected (P>0.05) by ASPS. This study suggests that dietary ASPS relieve growth depression through decreasing concentration of IL-1β, IL-6, and TNF-a but not controlling the activity of immune system. ASPS improve cellular immunity of stress pigs not only by direct effect on lymphocyte, but also by the indirect role through regulating the nerve-endocrine-immune system.(3) Experiment3possessed the same experimental design with (2) was used to further evaluate the immnoregulatory mechanism of ASPS on growth depression and immune function in stress pigs. Spleen was taken out from the slaughtering pigs after3h of LPS-injection on21d, using real-time fluorescent quantitative PCR to study the effect of ASPS on IL-1β, IL-6, and TNF-α mRNA gene expression. The results showed that dietary ASPS could decrease IL-1β、IL-6and TNF-α mRNA transcription in spleen(P<0.05) and showed the interaction relationship with LPS(P<0.05). namely, ASPS relieved the increasion of transcription levels of IL-6、IL-1β and TNF-α mRNA induced by LPS (P<0.05). The results suggest that ASPS play the role of immunoregulation by reducing expression level of IL-6、 IL-1β and TNF-α mRNA of spleen in stress pigs.(4) Experiment4researched the effects of ASPS in different level on signal transduction pathway of cultured peripheral blood lymphoeyte of weaned piglets. The results showed that lymphoeyte proliferation of T cell was changed quadratically (P<0.05) with the increased dose of ASPS.80、160、320μg/mL ASPS in higher dose affacted significantly(P<0.05). ASPS did not affect lymphoeyte proliferation of cultured B cell and IL-4(P>0.05). IL-2was changed quadratically (P<0.05) with the increased dose of ASPS at24h、48h and72h after culture, The concentration of NO、iNOS and NF-κB and TNF-α changed quadratically (P<0.05)with ASPS in no anti-TLR4group and they did not change in anti-TLR4group(P>0.05). ASPS improved the level of cAMP(P<0.05) and cAMP/cGMP(P<0.05), decreased the concentration of cGMP(P<0.05) at20min and60min after cultivation. The results suggest that ASPS can improve cellular immune function of cultured lymphoeyte in vitro, and it works through combinating with TLR4receptor of lymphoeyte surface and affecting the concentration of sigal molecules such as NO. cAMP、cGMP, influencing the cytokine of TNF-α by increasing the activity of NF-κB. |
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