Inhibitory effect of polysaccharide of Sargassum weizhouense on PCV2 induced inflammation in mice by suppressing histone acetylation

Seaweeds are excellent source of bioactive compounds and seaweed-derived polysaccharides have demonstrated an array of biological effects. Here, we investigated the effect of polysaccharide of Sargassum weizhouense (PSW) on the inflammatory response in porcine circovirus type 2 (PCV2) infected mice and the underlying mechanism was studied according to the histone acetylation. After PCV2 infection, the levels of TNF-alpha, IL-1 beta, IL-6, IL-8, IL-10, MCP-1, COX-1, COX-2 and HAT in both serum and spleen were significantly increased (P < 0.05). The mRNA expression of TNF-alpha, IL-6, IL-10 and NF-kappa B p65 were elevated in PCV2 infected mice (P < 0.05). The HDAC content in both serum and spleen as well the mRNA expression of HDAC1 were greatly decreased (P < 0.05). PSW treatment dramatically inhibited the secretions of inflammatory cytokines and HATs, reduced mRNA expression of TNF-alpha, IL-6, IL-10 and NF-kappa B p65, but promoted HDAC secretion and mRNA expression of HDAC1 in PCV2-infected mice. The acetylation of both H3 and H4 was significantly up-regulated in PCV2-infected mice, and strongly inhibited by PSW treatment (P < 0.01). These results suggested that PCV2 mediate the equilibrium between HATs and HDACs, alternate the histone acetylation and thus DNA packaging, and then activate the transcription of inflammatory cytokines. PSW could inhibit the histone acetylation and the production of inflammatory cytokines, showing excellent potentials in improving the resistance of host against PCV2 infection.