Chronic cerebral hypoperfusion (CCH) is a leading cause of disability and mortality worldwide. Restoring cerebral blood flow (CBF) through vasodilatation is particularly important in the treatment of CCH. Costunolide (Cos) is a natural sesquiterpenoid compound with vasodilatory effect, but its mechanism is unclear.
This study aimed to investigate the vasodilatory mechanism of Cos and provide a new therapeutic regimen for treating CCH.
The therapeutic effect of Cos on CCH was assessed in a rat model of permanent common carotid artery occlusion. The direct target protein for improving CBF was identified by drug affinity responsive target stability combined with quantitative differential proteomics analysis. The molecular mechanism of Cos acting on its target protein was analyzed by multidisciplinary approaches. The signalling involved was assessed using site-directed pharmacological intervention.
Cos has a significant therapeutic effect on ischemic brain injury by restoring CBF. Multifunctional calcium/calmodulin-dependent protein kinase II (CaMKII) was identified as a direct target of the natural small molecule Cos with a therapeutic effect on CCH. Mechanistic studies revealed that the α,β-unsaturated-γ-lactone ring of Cos covalently binds to the Cys116 residue of CaMKII. It then inhibits the phosphorylation of CaMKII and reduces the calcium concentration in vascular smooth muscle cells, thus playing a role in vasodilation and increasing CBF. Notably, this covalent binding between Cos and CaMKII can exert a long-term vasodilator activity.
We reported for the first time that Cos reduced ischemia-associated brain damage by covalently binding to the Cys116 residue of CaMKII, inhibiting CaMKII phosphorylation, and exerting long-term vasodilatory activity. This study not only found a new covalent inhibitor against the phosphorylation of CaMKII but also suggested that pharmacologically targeting CaMKII is a promising therapeutic strategy for CCH.

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