水解磷酸脂誘導小鼠巨噬細胞介白素-1β表達，過氧化物生成，與氧化低密度脂蛋白攝入之研究

Abstract

Lysophophatidic acid (LPA) is a platelet-enriched low molecular weight lysophospholipid (LPL) with multiple biological functions. These biological activities elicited by LPA are mediated through its binding to a series of G protein-coupled receptors: LPA1, LPA2, and LPA3. IL-1β, a major pro-inflammatory cytokine secreted by multiple cell types, plays an important role in innate immunity, inflammation and tumorigenesis. Reactive oxygen species (ROS) are bacteria killing reagents and also act as a mediator in regulation of multiple signaling pathways. The relationship between ROS and inflammatory cytokine is well characterized. OxLDL uptake by macrophages, also known as fatty streak, is an important indicator in atherosclerosis. From our previous studies, we found that LPA induce IL-1β expression in mouse peritoneal macrophages. In this study, we intended to investigate the molecular mechanisms involved in LPA-regulated IL-1β expression and elucidate inflammation-related functions regulated by LPA in J774A.1 cells. By calcium imaging analysis, we found that calcium mobilization was induces immediately after 1microM LPA treatment. RT-PCR analysis showed that both LPA1 and LPA2 receptors were expressed in J774A.1 and RAW246.7 cells, another commonly used mouse macrophage cell line. Using specific pharmacological blockers and real-time PCR analysis, we delineated that LPA-induced IL-1β mRNA expression is mediated through Rho-, Gi-, NF-kappaB-, p38 MAPK-, and PI3K-dependent pathways. Furthermore, reactive oxygen species (ROS) production in J774A.1 and RAW264.7 cells was increased by LPA dosage-dependently. The LPA-induced ROS production could be partially inhibited by C3 and pertussis toxin (PTx). Furthermore, LPA-induced IL-1β and ROS also play a physiological role by regulating IL-1β expression. Last but not least, fluorescence labeled DiI-OxLDL uptake is also upregulated by LPA in J774A.1 cells. In conclusion, our results elucidated the molecular mechanisms by which LPA-induced IL-1β production and also indicated that LPA is involved in the processes of inflammation and inflammation-related disease, atherosclerosis, in mouse macrophages.