Hinokiresinols reduce rat cerebral ischemic injury via stereo-specific antioxidant and anti-inflammatory activities

C Ju1, S Hwang1, GS Cho1, IY Choi1, G Kondaji2, Y Choi2, WK Kim1. 1Korea University, Department of Neuroscience, College of Medicine, Seoul 136-705, Republic of Korea, 2Korea University, School of Life Sciences and Biotechnology, Seoul 136-705, Republic of Korea

During cerebral ischemia, neuronal cells are injured by various mechanisms including excitotoxicity, oxidative stress, imbalance of ions and inflammatory responses. Cis-hinokiresinol, a naturally occurring phenylpropanoid, was previously reported to possess anti-oxidant, anti-inflammatory and estrogen-like activities. However, its anti-ischemic activity still remains elusive. In the present study, therefore, we investigated the potential therapeutic effects of cis-hinokiresinol and its trans-isomer in in vitro as well as in vivo ischemic/hypoxic models. Trans-hinokiresinol, but not cis-hinokiresinol (10 μM each), significantly decreased neuronal injury in cultured cortical neurons exposed to oxygen-glucose deprivation (OGD)/re-oxygenation (R) (***P<0.001, n = 15~21). However, neither of hinokiresinols inhibited the NMDA-evoked excitotoxicity. Although both hinokiresinols possessed substantial free radical scavenging activities against peroxyl radicals, hydrogen peroxide and peroxynitrite, only trans-hinokiresinol significantly induced Cu/Zn-SOD activity (**P<0.01, n = 12), and attenuated OGD/R-evoked intracellular oxidative stress such as superoxide anion formation (***P<0.001, n = 15). When pre-treated in rats subjected to transient middle cerebral artery occlusion (MCAO) (Male Sprague-Dawley rats, 260~300g; 15 min before MCAO and 15 min after reperfusion), only trans-hinokiresinol (10 mg/kg in 5% DMSO/10% cremophor/saline, i. p.) reduced cerebral infarct volume and edema (75.01 % inhibition, ***P<0.001 and 75.70 %, *P<0.01, respectively, n = 8~14). Interestingly, however, when treated twice at 2 and 7 h after the onset of MCAO, both cis- and trans-hinokiresinols significantly reduced cerebral infarct (**P<0.01, n = 8~14). Furthermore, both hinokiresinols inhibited neutrophil infiltration into ischemic injury sites (*P<0.05, n = 3~5). In conclusion, the present data suggest that hinokiresinols exerted significant, but stereo-specific neuroprotective effects against ischemic injury, through differential anti-oxidant but comparable anti-inflammatory activities. The data demonstrated that trans-hinokiresinol possesses extended profiles in anti-oxidant activity (e.g. free radical scavenging capacity and Cu/Zn-SOD induction) than cis-isomer whereas both hinokiresinols can modulate the inflammatory response following MCAO such as neutrophil infiltration. The seeming difference in therapeutic time window of hinokiresinols could be attributed to the variance in target profiles. More detailed delineation of anti-ischemic mechanism of hinokiresinols may provide a better strategy to develop efficacious regimen for cerebral ischemic stroke.