Molecular Weight-Dependent Immunostimulative Activity of Low Molecular Weight Chitosan via Regulating NF-κB and AP-1 Signaling Pathways in RAW264.7 Macrophages.

Chitosan and its derivatives such as low molecular weight chitosans (LMWCs) have been found to possess many important biological properties, such as antioxidant and antitumor effects. In our previous study, LMWCs were found to elicit a strong immunomodulatory response in macrophages dependent on molecular weight. Herein we further investigated the molecular weight-dependent immunostimulative activity of LMWCs and elucidated its mechanism of action on RAW264.7 macrophages. LMWCs (3 kDa and 50 kDa of molecular weight) could significantly enhance the mRNA expression levels of COX-2, IL-10 and MCP-1 in a molecular weight and concentration-dependent manner. The results suggested that LMWCs elicited a significant immunomodulatory response, which was dependent on the dose and the molecular weight. Regarding the possible molecular mechanism of action, LMWCs promoted the expression of the genes of key molecules in NF-κB and AP-1 pathways, including IKKß, TRAF6 and JNK1, and induced the phosphorylation of protein IKBα in RAW264.7 macrophage. Moreover, LMWCs increased nuclear translocation of p65 and activation of activator protein-1 (AP-1, C-Jun and C-Fos) in a molecular weight-dependent manner. Taken together, our findings suggested that LMWCs exert immunostimulative activity via activation of NF-κB and AP-1 pathways in RAW264.7 macrophages in a molecular weight-dependent manner and that 3 kDa LMWC shows great potential as a novel agent for the treatment of immune suppression diseases and in future vaccines.

Bio-filler from waste shellfish shell: preparation, characterization, and its effect on the mechanical properties on polypropylene composites.

Waste shellfish shell stacking with a significant odor and toxicity which are hazardous to human constitutes a serious environmental hazard. For utilization of waste shellfish shell resource, granule of shellfish shell (SS) was prepared from waste shellfish shell by removing cuticle, crushing, grinding and shearing emulsification and was introduced as a filler to reinforce polypropylene (PP). The mechanical behavior of PP/SS composite shows a higher yield strain, yield strength, tensile strength and elongation at break than traditional commercial calcium carbonate (CC) filled PP. Yield strength of PP/SS composite with 2% SS is improved by 11.1% due to the formation of ß-crystalline PP phase. Using waste SS for producing bio-filler for filling PP is an effective and prospective measure to deal with waste SS, which is valuable for industrial production and practical application as fillers for reinforcing polymers.

[Study on the antibacterial mechanisms of copper-bearing montmorillonite].

Vibrio parahaemolyticus ATCC 27519 was chosen as indicator of aquacultural pathogenic bacteria to determine the antibacterial activity and mechanism of copper-bearing montmorillonite (Cu-MMT) in vitro. The results indicated that montmorillonite (MMT) had no antibacterial activity. The minimum inhibitory concentration (MIC) and bactericidal concentration (MBC) of Cu-MMT on Vibrio parahaemolyticus were 75 and 300 mg/L, respectively. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) of bacteria were examined and the results showed treatment with Cu-MMT could lead to significant release of intracellular enzymes from the tested bacteria suggesting that the permeability of the cell membrane increased and bacteria suffered injury. Three typical inhibitors (malonic acid, iodine acetic acid and phosphate sodium) were used to further study the inhibitory pathways of respiratory metabolism. Cu-MMT effectively inhibited respiratory metabolism of Vibrio parahaemolyticus, with the respiratory inhibition percent (I(R)) of 31.8%. The respiratory superposing inhibition percent after addition of phosphate sodium, iodine acetic acid and malonic acid was 48.6%, 27.8% and 17.5%, respectively. These results indicated that the effect of malonic acid on superposing inhibition percent of Cu-MMT for bacteria is the lowest; thus, the synergic action between Cu-MMT and malonic acid is the weakest, indicating that they inhibited the same pathway of respiratory metabolism, i.e. the TCA pathway, which is the most important pathway of carbohydrate metabolism. The atomic force microscope image of Vibrio parahaemolyticus exposed to Cu-MMT showed that Cu-MMT could rupture the bacterial cell membrane.