Endotoxin Generated Lipid Second Messengers

描述（由申请人提供）：引发和促进动脉粥样硬化形成的事件尚未明确定义，但LDL在易于病变发展的部位的血管壁中的隔离是其中之一。结合的LDL氧化成促动脉粥样硬化形式，其被清道夫受体如CD 36结合，导致不适当的细胞内脂质积累和泡沫细胞形成。 动脉粥样硬化病变可能含有肺炎衣原体，这种感染构成动脉粥样硬化的危险因素。巨噬细胞感染C.肺炎链球菌导致泡沫细胞形成，暴露于其纯化的脂多糖（LPS）也是如此。LPS如何诱导脂质积聚或刺激基因转录尚不清楚。 我们发现LPS诱导单核细胞中CD 36清道夫受体基因的表达，导致表面表达增强，并导致细胞内脂滴积聚和泡沫细胞形成。CD 36由转录因子PPARgamma控制，我们发现LPS出乎意料地激活了PPAR反应元件（PPRE）-报告基因。事实上，LPS通过其PPRE激活CD 36启动子。 PPARgamma被脂质配体激活;合成药物可以做到这一点，但高亲和力的生理PPAR 3配体是未知的。LPS不结合PPARgamma，因此它诱导内源性激动剂的形成。 我们发现，溶血磷脂酸（LPA）是一个PPARgamma配体和激动剂-提供了第一个证据，这可能是长期以来寻求这种转录因子的生理激动剂。LPA刺激PPRE驱动的报告基因，诱导CD 36表达，并将单核细胞分化为泡沫细胞。我们表明，这种信号是独立的Edg（表面LPA受体）信号在几个方面。 我们发现LPS增加细胞LPA水平，并且通过转染的LPA酰基转移酶代谢这种细胞内LPA阻断PPAR 7活化和功能。在这里，我们建议定义的方式，LPS诱导LPA积累，并确定泡沫细胞形成的细胞内核激素受体/转录因子的LPA激活的后果。知道生理配体的身份，使我们能够建立一个高通量筛选合理设计的PPARgamma抑制剂。一种不可水解的LPA类似物阻断了PPARy功能，并可能定义一类新的抗炎、抗炎剂。

DESCRIPTION (provided by applicant): The events that initiate and promote atherogenesis are not well defined, but sequestration of LDL in the vascular wall at sites prone to lesion development is one. Bound LDL oxidizes to a pro-atherogenic form that is bound by scavenger receptors like CD36, leading to inappropriate intracellular lipid accumulation and foam cell formation. Atherosclerotic lesions can contain Chlamydia pneumoniae, and such infections constitute a risk factor for atherosclerosis. Macrophage infection by C. pneumoniae results in foam cell formation, as does exposure to its purified lipopolysaccharide (LPS). How LPS induces lipid accumulation or stimulates gene transcription is unknown. We find that LPS induces expression of the CD36 scavenger receptor gene in monocytes, leading to enhanced surface expression, and to intracellular lipid droplet accumulation and foam cell formation. CD36 is controlled by the transcription factor PPARgamma, and we find that LPS, unexpectedly, activates a PPAR responsive element (PPRE)-reporter. In fact, LPS activates the CD36 promoter through its PPRE. PPARgamma is activated by lipid ligands; synthetic drugs do this, but high affinity physiologic PPAR3, ligands are unknown. LPS does not bind PPARgamma, so it induced the formation of an endogenous agonist. We find that lysophosphatidic acid (LPA) is a PPARgamma ligand and agonist --providing the first evidence that this might be the long sought after physiologic agonist for this transcription factor. LPA stimulates PPRE-driven reporters, induces CD36 expression, and differentiates monocytes to foam cells. We show this signaling is independent of Edg (surface LPA receptors) signaling in several ways. We find that LPS increases cellular LPA levels, and that metabolizing this intracellular LPA by transfected LPA acyltransferase blocks PPAR7 activation and function. Here we propose to define the way in which LPS induces LPA accumulation, and determine the consequences of LPA activation of an intracellular nuclear hormone receptor/transcription factor on foam cell formation. Knowing the identity of the physiologic ligand has allowed us to establish a high throughput screen for rationally designed PPARgamma inhibitors. One non-hydrolyzable LPA analog blocks PPARy function and might define a new class of anti-infiammatory, anti-lipidic agents.