hinokiresinol and Brain-Ischemia

Growing evidence suggests that therapeutic strategies to modulate the post-ischemic inflammatory responses are promising approaches to improve stroke outcome. Although the endocannabinoid system has been emerged as an endogenous therapeutic target to regulate inflammation after stroke insult, the downstream mechanisms and their potentials for therapeutic intervention remain controversial. Here we identified trans- and cis-hinokiresinols as novel non-selective antagonists for two G-protein-coupled cannabinoid receptors, cannabinoid receptor type 1 and type 2. The Electric Cell-substrate Impedance Sensing and Boyden chamber migration assays using primary microglial cultures revealed that both hinokiresinols significantly inhibited an endocannabinoid, 2-arachidonoylglycerol-induced migration. Hinokiresinols modulated 2-arachidonoylglycerol-induced mitochondrial bioenergetics in microglia as evidenced by inhibition of ATP turnover and reduction in respiratory capacity, thereby resulting in impaired migration activity. In rats subjected to transient middle cerebral artery occlusion (1.5-h) followed by 24-h reperfusion, post-ischemic treatment with hinokiresinols (2 and 7-h after the onset of ischemia, 10 mg/kg) significantly reduced cerebral infarct and infiltration of ED1-positive microglial/macrophage cells into cerebral ischemic lesions in vivo. Co-administration of exogenous 2-AG (1 mg/kg, i.v., single dose at 2 h after starting MCAO) abolished the protective effect of trans-hinokiresionol. These results suggest that hinokiresinols may serve as stroke treatment by targeting the endocannabinoid system. Alteration of mitochondrial bioenergetics and consequent inhibition of inflammatory cells migration may be a novel mechanism underlying anti-ischemic effects conferred by cannabinoid receptor antagonists.

Topics: Animals; Arachidonic Acids; Brain Ischemia; Cannabinoid Receptor Agonists; Cannabinoid Receptor Antagonists; Cell Movement; Cell Respiration; Cells, Cultured; Disease Models, Animal; Endocannabinoids; Glycerides; Lignans; Macrophages; Male; Microglia; Mitochondria; Phenols; Rats

During cerebral ischemia, neurons are injured by various mechanisms including excitotoxicity, oxidative stress, and inflammatory responses. Thus, pharmacological manipulation of multiple cytotoxic pathways has been pursued for the treatment of ischemic injury. Cis-hinokiresinol, a naturally occurring phenylpropanoid, was previously reported to possess anti-oxidant, anti-inflammatory and estrogen-like activities. In the present study, we investigated anti-ischemic effects of trans- and cis-hinokiresinols using in vitro as well as in vivo experimental models. The ORAC and DPPH assays showed that two isomers had similar free radical scavenging activities. However, only trans-hinokiresinol significantly decreased neuronal injury in cultured cortical neurons exposed to oxygen-glucose deprivation (75 min) followed by re-oxygenation (9 h). The differential neuroprotective effect could be due to the stereo-specific augmentation of Cu/Zn-SOD activity by trans-hinokiresinol, when compared with cis-hinokiresinol. Similarly, in rats subjected to transient middle cerebral artery occlusion (1.5 h) followed by 24-h reperfusion, pre-ischemic treatment with trans-hinokiresinol, but not with cis-isomer, reduced cerebral infarct volume. Interestingly, however, post-ischemic treatment with both hinokiresinols (2 and 7 h after onset of ischemia) significantly reduced cerebral infarct. When administered after onset of ischemia, trans-hinokiresinol, but not its cis-isomer reduced nitrotyrosine immunoreactivity in ischemic regions. In contrast, both hinokiresinols suppressed neutrophil infiltration and IL-1β release to a similar extent. The observed differential anti-oxidant, but comparable anti-inflammatory, activities may explain the stereo-specific anti-ischemic activities and different therapeutic time windows of the hinokiresinols examined. More detailed delineation of the anti-ischemic mechanism(s) of hinokiresinols may provide a better strategy for development of efficacious regimens for cerebral ischemic stroke.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Antioxidants; Brain Ischemia; Cells, Cultured; Lignans; Male; Phenols; Rats; Rats, Sprague-Dawley; Stereoisomerism; Time Factors; Treatment Outcome