Ghazi HUSSEIN,*,a,b Masami NAKAMURA,b Qi ZHAO,b Tomomi IGUCHI,b Hirozo GOTO,c Ushio SANKAWA,a and Hiroshi WATANABEb
a International Research Center for Traditional Medicine, Toyama Prefecture; Toyama 939–8224, Japan: b Division of Pharmacology; and c Department of Kampo Diagnostics, Institute of Natural Medicine, Toyama Medical & Pharmaceutical University; Toyama 930–0194, Japan.
Received May 18, 2004; accepted October 5, 2004
Astaxanthin is a natural antioxidant carotenoid that occurs in a wide variety of living organisms. We investigated, for the first time, antihypertensive effects of astaxanthin (ASX-O) in spontaneously hypertensive rats (SHR). Oral administration of ASX-O for 14 d induced a significant reduction in the arterial blood pressure (BP) in SHR but not in normotensive Wistar Kyoto (WKY) strain. The long-term administration of ASX-O (50 mg/kg) for 5 weeks in stroke prone SHR (SHR-SP) induced a significant reduction in the BP. It also delayed the incidence of stroke in the SHR-SP. To investigate the action mechanism of ASX-O, the effects on PGF2α-induced contractions of rat aorta treated with NG-nitro-l-arginine methyl ester (L-NAME) were studied in vitro. ASX-O (1 to 10 µM) induced vasorelaxation mediated by nitric oxide (NO). The results suggest that the antihypertensive effect of ASX-O may be due to a NO-related mechanism. ASX-O also showed significant neuroprotective effects in ischemic mice, presumably due to its antioxidant potential. Pretreatment of the mice with ASX-O significantly shortened the latency of escaping onto the platform in the Morris water maze learning performance test. In conclusion, these results indicate that astaxanthin can exert beneficial effects in protection against hypertension and stroke and in improving memory in vascular dementia.
Key words: astaxanthin; hypertension; spontaneously hypertensive rat (SHR); carotenoid; nitric oxide (NO)
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