Phosphorylation of MAP4 (p-MAP4) causes cardiac remodeling, with the cardiac microvascular endothelium being considered a vital mediator of this process. In the current study, we investigated the mechanism underlying p-MAP4 influences on cardiac microvascular density. We firstly confirmed elevated MAP4 phosphorylation in the myocardium of MAP4 knock-in (KI) mice. When compared with the corresponding control group, we detected the decreased expression of CD31, CD34, VEGFA, VEGFR2, ANG2, and TIE2 in the myocardium of MAP4 KI mice, accompanied by a reduced plasma concentration of VEGF. Moreover, we observed apoptosis and mitochondrial disruption in the cardiac microvascular endothelium of MAP4 KI animals. Consistently, we noted a decreased cardiac microvascular density, measured by CD31 and lectin staining, in MAP4 KI mice. To explore the underlying mechanism, we targeted the NLRP3-related pyroptosis and found increased expression of the corresponding proteins, including NLRP3, ASC, mature IL-1β, IL-18, and GSDMD-N in the myocardium of MAP4 KI mice. Furthermore, we utilized a MAP4 (Glu) adenovirus to mimic cellular p-MAP4. After incubating HUVECs with MAP4 (Glu) adenovirus, the angiogenic ability was inhibited, and NLRP3-related pyroptosis were significantly activated. Moreover, both cytotoxicity and PI signal were upregulated by the MAP4 (Glu) adenovirus. Finally, NLRP3 inflammasome blockage alleviated the inhibited angiogenic ability induced by MAP4 (Glu) adenovirus. These results demonstrated that p-MAP4 reduced cardiac microvascular density by activating NLRP3-related pyroptosis in both young and aged mice. We thus managed to provide clues explaining MAP4 phosphorylation-induced cardiac remodeling and enriched current knowledge regarding the role of MAP4.

MAP4 (p-MAP4) 的磷酸化导致心脏重塑，心脏微血管内皮被认为是这一过程的重要介质。在目前的研究中，我们研究了 p-MAP4 对心脏微血管密度影响的潜在机制。我们首先证实了 MAP4 敲入 (KI) 小鼠心肌中 MAP4 磷酸化升高。与相应的对照组相比，我们检测到 MAP4 KI 小鼠心肌中 CD31、CD34、VEGFA、VEGFR2、ANG2 和 TIE2 的表达降低，并伴有血浆 VEGF 浓度降低。此外，我们观察到 MAP4 KI 动物心脏微血管内皮细胞凋亡和线粒体破坏。一致地，我们注意到在 MAP4 KI 小鼠中通过 CD31 和凝集素染色测量的心脏微血管密度降低。为了探索潜在的机制，我们针对 NLRP3 相关的细胞焦亡，发现相应蛋白质的表达增加，包括 NLRP3、ASC、成熟的 IL-1β、IL-18 和 GSDMD-N 在 MAP4 KI 小鼠的心肌中。此外，我们利用 MAP4 (Glu) 腺病毒来模拟细胞 p-MAP4。HUVECs与MAP4（Glu）腺病毒孵育后，血管生成能力被抑制，NLRP3相关的细胞焦亡被显着激活。此外，细胞毒性和 PI 信号都被 MAP4 (Glu) 腺病毒上调。最后，NLRP3 炎症小体阻断减轻了由 MAP4 (Glu) 腺病毒诱导的血管生成能力受到抑制。这些结果表明 p-MAP4 通过激活年轻和老年小鼠的 NLRP3 相关细胞焦亡来降低心脏微血管密度。