p90RSK-ERK5 module, efferocytosis, and vulnerable plaque formation

描述（由申请人提供）：在晚期动脉粥样硬化（AS）病变中形成的坏死核心是由炎症细胞包围的坏死巨噬细胞（MΦ）集合，导致炎症、斑块破坏和血栓形成，并最终发展成易损斑块。通常，巨噬细胞的快速吞噬清除（efferocytosis）可以阻止坏死核心的形成，但越来越多的证据表明，在晚期病变中，efferocytosis是有缺陷的。尽管HMG Co-A还原酶抑制剂（他汀类药物）可以上调efferocytosis 1-3，但对efferocytosis的综合调控机制尚不清楚。在研究中，我们发现他汀类药物/ACs治疗激活MΦ中的ERK5激酶，并通过分泌调理素和M2 MΦ极化加速efferocytosis，而这些反应在巨噬细胞特异性ERK5敲除（ERK5- MKO）小鼠MΦ中被抑制。事实上，ERK5-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p90RSK通过ERK5 S496磷酸化抑制ERK5的转录活性，从而抑制ERK5在MΦ功能中的作用。此外，MΦ-specific野生型p90rsk转基因（WT-p90RSK-MTg）与LDLR-/-小鼠杂交后，坏死核的形成和AC的形成加速。这表明p90RSK和ERK5之间的相互作用对各种MΦ功能的调节至关重要。因此，我们假设他汀类药物/ acs介导的ERK5激酶激活是efferocytosis的关键步骤，可以抑制AS和坏死核心的形成，而AngII或晚期动脉粥样硬化病变中的p90RSK激活通过抑制ERK5来抑制efferocytosis。我们将设计实验，用体内和体外的方法来解决这一假设。本研究的三个具体目的是：1)我们将验证在AngII、他汀类药物或CSF-1刺激下p90RSK和ERK5激活之间的平衡对MΦ功能（如增殖、凋亡、M1/M2表型和efferocytosis）的差异调节；2)我们将研究我们的假设，即AngII或晚期斑块诱导的p90RSK激活抑制ERK5转录活性和efferocytosis。3)我们将验证ERK5激活或抑制p90RSK通过上调Mfge8增加efferocysis并抑制AS和坏死核心形成的假设。我们的研究的意义在于提供了对晚期动脉粥样硬化病变中急性动脉粥样硬化性血栓性血管疾病的临床良好描述的心脏风险的机制理解。此外，了解ERK5介导的efferocytosis的作用和分子机制，以及对坏死核心和AS形成的抑制，将有助于深入了解急性动脉粥样硬化性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 (MΦ) 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 MΦ and accelerates efferocytosis via secretion of opsonins and M2 MΦ polarization, whereas these responses are inhibited in MΦ 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 MΦ functions by inhibiting ERK5 transcriptional activity via ERK5 S496 phosphorylation. In addition, MΦ-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 MΦ 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 MΦ 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.