Polysaccharide from Phellinus Igniarius activates TLR4-mediated signaling pathways in macrophages and shows immune adjuvant activity in mice.

Polysaccharide from Phellinus igniarius (PPI) is known for its immune-regulating effect with low toxicity. Toll like receptor 4 (TLR4) is important in both innate and adaptive immune responses and considered to be a promising target for new immune adjuvants. In this study, PPI was investigated for its effect on activating TLR4 in RAW264.7 and peritoneal macrophages. The adjuvant potential of PPI was evaluated in OVA-immunized mice. The results showed PPI treatment significantly increased the secretion and the mRNA expression of both MyD88 dependent and TRIF dependent cytokines. IRAK-1, a key molecule on the downstream of MyD88, was polyubiquitinated while IRF-3, another key molecule on the downstream of TRIF, was phosphorylated obviously after the treatment of PPI. The phosphorylation of molecules involved in both NF-κB pathway and MAPK pathway were significantly up-regulated after PPI treatment. In addition, the effects of PPI on the macrophages almost completely disappeared after treating the cells with the TLR4 antagonist TAK-242. Further in vivo results showed PPI significantly increased the serum OVA-specific antibody and the OVA-specific spleen cell proliferation. Taken together, PPI can specifically stimulate TLR4 and activate both MyD88 and TRIF pathways. PPI has immune adjuvant activity and may become a new potential immune adjuvant.

Oxidative DNA cleavage by Schiff base tetraazamacrocyclic oxamido nickel(II) complexes.

Nickel is considered a weak carcinogen. Some researches have shown that bound proteins or synthetic ligands may increase the toxic effect of nickel ions. A systematic study of ligand effects on the interaction between nickel complexes and DNA is necessary. Here, we compared the interactions between DNA and six closely related Schiff base tetraazamacrocyclic oxamido nickel(II) complexes NiL(1-3a,1-3b). The structure of one of the six complexes, NiL(3b) has been characterized by single crystal X-ray analysis. All of the complexes can cleave plasmid DNA under physiological conditions in the presence of H(2)O(2). NiL(3b) shows the highest DNA cleavage activity. It can convert supercoiled DNA to nicked DNA then linear DNA in a sequential manner as the complex concentration or reaction time is increased. The cleavage reaction is a typical pseudo-first-order consecutive reaction with the rate constants of 3.27+/-0.14h(-1) (k(1)) and 0.0966+/-0.0042h(-1) (k(2)), respectively, when a complex concentration of 0.6mM is used. The cleavage mechanism between the complex and plasmid DNA is likely to involve hydroxyl radicals as reactive oxygen species. Circular dichronism (CD), fluorescence spectroscopy and gel electrophoresis indicate that the complexes bind to DNA by partial intercalative and groove binding modes, but these binding interactions are not the dominant factor in determining the DNA cleavage abilities of the complexes.