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J Neurosci. 2014 Jan 29;34(5):1903-15. doi: 10.1523/JNEUROSCI.4043-13.2014.

Omega-3 fatty acids protect the brain against ischemic injury by activating Nrf2 and upregulating heme oxygenase 1.

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State Key Laboratory of Medical Neurobiology and Institute of Brain Science, Fudan University, Shanghai 200032, China, Department of Neurology and Center of Cerebrovascular Disease Research, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, Department of Neurology, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, Jiangsu 210008, China, Division of Pharmaceutical Sciences, Mylan School of Pharmacy, Duquesne University, Pittsburgh, Pennsylvania 15282, Department of Neurology and Key Laboratory of Cerebral Microcirculation, University of Shandong, Affiliated Hospital of Taishan Medical College, Taian, Shandong 271000, China, and Geriatric Research, Educational and Clinical Center, Veterans Affairs Pittsburgh Health Care System, Pittsburgh, Pennsylvania 15240.


Ischemic stroke is a debilitating clinical disorder that affects millions of people, yet lacks effective neuroprotective treatments. Fish oil is known to exert beneficial effects against cerebral ischemia. However, the underlying protective mechanisms are not fully understood. The present study tests the hypothesis that omega-3 polyunsaturated fatty acids (n-3 PUFAs) attenuate ischemic neuronal injury by activating nuclear factor E2-related factor 2 (Nrf2) and upregulating heme oxygenase-1 (HO-1) in both in vitro and in vivo models. We observed that pretreatment of rat primary neurons with docosahexaenoic acid (DHA) significantly reduced neuronal death following oxygen-glucose deprivation. This protection was associated with increased Nrf2 activation and HO-1 upregulation. Inhibition of HO-1 activity with tin protoporphyrin IX attenuated the protective effects of DHA. Further studies showed that 4-hydroxy-2E-hexenal (4-HHE), an end-product of peroxidation of n-3 PUFAs, was a more potent Nrf2 inducer than 4-hydroxy-2E-nonenal derived from n-6 PUFAs. In an in vivo setting, transgenic mice overexpressing fatty acid metabolism-1, an enzyme that converts n-6 PUFAs to n-3 PUFAs, were remarkably resistant to focal cerebral ischemia compared with their wild-type littermates. Regular mice fed with a fish oil-enhanced diet also demonstrated significant resistance to ischemia compared with mice fed with a regular diet. As expected, the protection was associated with HO-1 upregulation, Nrf2 activation, and 4-HHE generation. Together, our data demonstrate that n-3 PUFAs are highly effective in protecting the brain, and that the protective mechanisms involve Nrf2 activation and HO-1 upregulation by 4-HHE. Further investigation of n-3 PUFA neuroprotective mechanisms may accelerate the development of stroke therapies.

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