Selective mGluR1 Negative Allosteric Modulator Reduces Blood-Brain Barrier Permeability and Cerebral Edema After Experimental Subarachnoid Hemorrhage.

The blood-brain barrier (BBB) disruption leads to the vasogenic brain edema and contributes to the early brain injury (EBI) after subarachnoid hemorrhage (SAH). However, the mechanisms underlying the BBB damage following SAH are poorly understood. Here we reported that the neurotransmitter glutamate of cerebrospinal fluid (CSF) was dramatically increased in SAH patients with symptoms of cerebral edema. Using the rat SAH model, we found that SAH caused the increase of CSF glutamate level and BBB permeability in EBI, intracerebroventricular injection of exogenous glutamate deteriorated BBB damage and cerebral edema, while intraperitoneally injection of metabotropic glutamate receptor 1(mGluR1) negative allosteric modulator JNJ16259685 significantly attenuated SAH-induced BBB damage and cerebral edema. In an in vitro BBB model, we showed that glutamate increased monolayer permeability of human brain microvascular endothelial cells (HBMEC), whereas JNJ16259685 preserved glutamate-damaged BBB integrity in HBMEC. Mechanically, glutamate downregulated the level and phosphorylation of vasodilator-stimulated phosphoprotein (VASP), decreased the tight junction protein occludin, and increased AQP4 expression at 72 h after SAH. However, JNJ16259685 significantly increased VASP, p-VASP, and occludin, and reduced AQP level at 72 h after SAH. Altogether, our results suggest an important role of glutamate in disruption of BBB function and inhibition of mGluR1 with JNJ16259685 reduced BBB damage and cerebral edema after SAH.