Secretory phospholipase A 2 inhibitor PX-18 preserves microvascular reactivity after cerebral ischemia in piglets

Abstract

Cerebral ischemia/reperfusion (I/R) results in cellular energy failure and dysfunction of the neurovascular unit that contribute to subsequent neuronal cell death in the neonate. PX-18 is a putative neuroprotective inhibitor of secretory phospholipase A 2 (sPLA 2) but its in vivo testing has been limited by its poor solubility. Our purpose was to assess whether PX-18 preserved neuronal–vascular reactivity to I/R-sensitive endothelium-dependent (hypercapnia, bradykinin) and/or neuron-dependent (N-methyl- d-aspartate; NMDA) stimuli. To make the drug available for in vivo studies, PX-18 was formulated as a 3% nanosuspension applying high pressure homogenization. Newborn piglets (1-day old, n = 40) were anesthetized and ventilated, and cerebrovascular reactivity to the above stimuli was determined by measuring changes in pial arteriolar diameters using the closed cranial window/intravital videomicroscopy technique. Intravenous infusion of PX-18 nanosuspension (6 mg/kg, 20 min) did not affect baseline arteriolar diameters, or hypercapnia-, bradykinin-, or NMDA-induced pial arteriolar vasodilation under normoxic conditions. Global cerebral ischemia (10 min) followed by 1 h of reperfusion significantly attenuated hypercapnia-, bradykinin-, and NMDA-induced vasodilation in untreated or vehicle-treated controls. However, PX-18 resulted in nearly full preservation of cerebrovascular reactivity to all these stimuli. In conclusion, inhibition of sPLA 2 by PX-18 improves neurovascular function both at the neuronal and the microvascular level following I/R. This effect of PX-18 likely contributes to its neuroprotective effect.