Study on the regulation of Pleurocidin in LPS-induced inflammatory responses

• Main Authors: Jia-Jing Yang, 楊佳靜
• Other Authors: Chung-Da Yang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/49278681493104950916

碩士 === 國立屏東科技大學 === 動物疫苗科技研究所 === 100 === Lipopolysaccharide (LPS) is the major molecular component of the outer membrane of Gram-negative bacteria and it also recognized by the immune system as a marker for the detection of bacterial pathogen invasion. During bacterial invasion, released LPS stimulates immune cells and causes inflammatory responses even sepsis accompanied by secreting a large amount of pro-inflammatory cytokines such as TNF-. Antimicrobial peptides (AMPs) are cationic peptides and have been considered to play important roles in the innate defense mechanisms of most living organisms including plants, insects, fish, amphibians and mammals. They are also known to possess potent antimicrobial activity against bacteria, fungi, and even viruses. Pleurocidin (Ple) is a cationic -helical AMP derived from the skin mucous of the winter flounder (Pleuronectes americanus) and can inhibit the growth of a broad spectrum of microbes through membrane disruption. Many studies have suggested that AMPs have LPS-neutralizing activity to decrease TNF- associated inflammatory responses in host. In our study, we used mouse model to examine whether Ple could neutralize the LPS-induced inflammatory response. We found that TNF- secretion was significantly reduced in mouse macrophage cell line RAW 264.7 after co-stimulated with LPS (80 pg/ml) and Ple (80 g/ml) for 4 hours. In addition, after intraperitoneal injection (IP) with LPS 0.1g/mouse and Ple 0.1 mg/mouse, TNF- secretion was significantly decreased in mouse serum. Therefore, Ple showed the negative regulation of LPS-induced TNF- secretion in vitro and vivo. We further studied the signal transduction of the negative regulation in Raw 264.7 cells. We demonstrated that the negative regulation was induced via ERK (Extracellular signal-regulated kinase) of MAPK (Mitogen-activated protein kinases) signal pathway. Taken together, Ple can inhibit LPS-induced TNF- secretion through the ERK of MAPK signal pathway and further suppress excessive inflammatory response. Keywords: Lipopolysaccharide, Antimicrobial peptides, Pleurocidin, Inflammatory responses