A temperature-ultrasound sensitive nanoparticle delivery system for exploring central neuroinflammation mechanism in stroke-heart syndrome.

Background: Cardiovascular events secondary to stroke-collectively classified as stroke-heart syndrome-greatly impair the patient's prognosis, however its underlying mechanism has yet to be determined. To investigate the mechanism of central neuroinflammation and its effects on stroke-heart syndrome, a temperature-ultrasound responsive brain-targeted drug delivery system, DATS/MION-LPE, was synthesized to specifically study neuroinflammation in the mouse middle cerebral artery occlusion (MCAO) model.

Results: The specific polymer of DATS/MION-LPE can close the nanoparticle pores at 37 °C, restricting drug release in the circulation. After the nanoparticles were targeted to brains, the polymer can be cleaved under external ultrasound irradiation, reopening the nanoparticle pores and allowing drug release, therefore directly managing the neuroinflammation. After a stroke, a significant cerebral inflammation occurred, with elevated IL-1β and pyrin domain-containing 3 (NLRP3) inflammasome. Accordingly, significantly increased histone deacetylase 6 (HDAC6) and decreased sirtuin 1 (SIRT1) were observed. An antagonistic relationship between HDAC6 and SIRT1 was found, which can jointly regulate the cerebral NLRP3 expression. The systemic IL-1β and ATP levels were increased after the stroke, accompanied by a significant heart injury including contractile dysfunction, elevated IL-1β levels, and oxidative stress. Meanwhile, neuroinflammation can trigger sympathetic nervous overexcitation with associated heart damage. DATS/MION-LPE can targetedly effect on ischemic brain, exhibiting cerebral and cardiac protective effects including downregulated cerebral NLRP3 and HDAC6 expressions, upregulated SIRT1 expressions in brain, reduced IL-1β and ATP in circulation, and alleviated cardiac impairment.

Conclusion: This study introduced the key role of neuroinflammation in stroke-heart syndrome and first investigated the crucial HDAC6/SIRT1-NLRP3 circuit in this process. Heart injury secondary to stroke is mediated by neuroinflammation induced systemic inflammatory responses and sympathoexcitation. DATS/MION-LPE is a unique tool and effective therapeutic agent, which provides new insights into combinational heart and cardiac protection.