p90RSK-ERK5 module, efferocytosis, and vulnerable plaque formation

描述（由申请人提供）：晚期动脉粥样硬化（AS）病变中形成的坏死核心是被炎性细胞包围的坏死巨噬细胞（M？）的集合，其有助于炎症、斑块破裂和血栓形成，并最终发展成易损斑块。通常，巨噬细胞的快速吞噬清除（巨噬细胞吞噬作用）可以防止坏死核心的形成，但越来越多的证据表明，巨噬细胞吞噬作用在晚期病变中是有缺陷的。虽然HMG辅酶A还原酶抑制剂（他汀类药物）1-3可以上调红细胞增多症，但红细胞增多症的综合调控机制仍不清楚。在这项研究中，我们发现他汀类药物/AC治疗激活M <$中的ERK 5激酶，并通过调理素分泌和M2 M <$极化加速细胞增殖，而这些反应在来自巨噬细胞特异性ERK 5敲除（ERK 5- MKO）小鼠的M <$中受到抑制。事实上，ERK 5-MKO/LDLR-/-小鼠显示坏死核心和AS形成增加。另一方面，血管紧张素II（AngII）激活的p90 RSK通过ERK 5 S496磷酸化抑制ERK 5转录活性，从而抑制ERK 5在M？功能中的作用。此外，M与LDLR-/-小鼠杂交的特异性野生型-p90 RSK转基因（WT-p90 RSK-MTg）表现出加速的坏死核心形成和AC形成。这表明p90 RSK和ERK 5之间的相互作用对于调节各种M？功能至关重要。因此，我们假设他汀类/ACs介导的ERK 5激酶激活是抑制AS和坏死核心形成的红细胞增多症的关键步骤，而AngII或晚期动脉粥样硬化病变中的p90 RSK激活通过抑制ERK 5抑制红细胞增多症。我们将设计实验，以解决这一假设，在体内和体外的方法。本提案的三个具体目标是：1）我们将检验以下假设：在AngII、他汀类药物或CSF-1刺激下，p90 RSK和ERK 5激活之间的平衡差异性地调节M？功能如增殖、凋亡、M1/M2表型和红细胞增多，2）我们将研究我们的假设，即由AngII或在晚期斑块中诱导的p90 RSK活化抑制ERK 5转录活性和细胞增殖，其促进AS斑块和坏死核心的形成，以及3）我们将检验ERK 5激活或抑制p90 RSK增加红细胞增多并通过Mfge 8的上调抑制AS和坏死核心形成的假设。我们的研究的意义在于提供了一个机制的理解，临床上充分描述的急性动脉粥样硬化血栓性血管疾病的心脏风险，在先进的动脉粥样硬化病变。此外，了解ERK 5介导的细胞增殖和抑制坏死核心和AS形成的作用和分子机制，应提供深入了解急性动脉粥样硬化血栓性血管疾病的原因，并可能揭示新的治疗靶点。

DESCRIPTION (provided by applicant): A necrotic core formed in an advanced atherosclerosis (AS) lesion is a collection of necrotic macrophages (M¿) surrounded by inflammatory cells, which contributes to inflammation, plaque disruption, and thrombosis, and eventually develops into a vulnerable plaque. Ordinarily, rapid phagocytic clearance (efferocytosis) by macrophages prevents necrotic core formation, but increasing evidence indicates that efferocytosis is defective in advanced lesions. Although efferocytosis can be up-regulated by HMG Co-A reductase inhibitors (statins)1-3, the comprehensive regulatory mechanism for efferocytosis remains unclear. In the study, we show that statins/ACs treatment activates ERK5 kinase in M¿ and accelerates efferocytosis via secretion of opsonins and M2 M¿ polarization, whereas these responses are inhibited in M¿ derived from macrophage specific ERK5 knock-out (ERK5- MKO) mice. Indeed, ERK5-MKO/LDLR-/- mice showed increased necrotic core and AS formation. On the other hand, p90RSK activated by angiotensin II (AngII) inhibited the ERK5 role in M¿ functions by inhibiting ERK5 transcriptional activity via ERK5 S496 phosphorylation. In addition, M¿-specific wild type-p90RSK transgenic (WT-p90RSK-MTg) crossing to LDLR-/- mice exhibited accelerated formation of necrotic core and AC formation. It suggests that the interplay between p90RSK and ERK5 are critical for the regulation of various M¿ functions. We therefore hypothesize that statin/ACs-mediated ERK5 kinase activation is a key step in efferocytosis, which inhibits AS and necrotic core formation, while p90RSK activation under AngII, or in advanced atherosclerotic lesions, inhibits efferocytosis via inhibiting ERK5. We will design experiments to address this hypothesis using an in vivo and in vitro approach. The three specific aims of this proposal are 1) We will test the hypothesis that the balance between p90RSK and ERK5 activation under AngII, statins, or CSF-1 stimulation differentially regulates M¿ functions such as proliferation, apoptosis, M1/M2 phenotypes, and efferocytosis, 2) We will investigate our hypothesis that p90RSK activation induced by AngII or in advanced plaques inhibits ERK5 transcriptional activity and efferocytosis, which promotes the formation of AS plaques and necrotic cores, and 3) We will test the hypothesis that ERK5 activation or inhibition of p90RSK increases efferocytosis and inhibits AS and necrotic core formation via up-regulation of Mfge8. The significance of our study is in providing a mechanistic understanding of the clinically well-described cardiac risk of acute athero-thrombotic vascular disease in advanced atherosclerotic lesions. Also, understanding the role and molecular mechanisms of ERK5- mediated efferocytosis and inhibition of the necrotic core and AS formation should provide insight into the cause of acute atherothrombotic vascular diseases and possibly reveal novel therapeutic targets.