Research ReportCilostazol reduces ischemic brain damage partly by inducing metallothionein-1 and -2
Introduction
The metallothioneins (MTs) are a family of four low molecular weight, metal-binding proteins with a high cystein content, known as MT-1, MT-2, MT-3, and MT-4 (Hamer, 1986). In adult mice, MT-1 and MT-2 are found in all organs, MT-3 is expressed mainly in the brain (Palmiter et al., 1992), and MT-4 is most abundant in certain stratified squamous epithelial tissues (Quaife et al., 1994). Previous studies suggest that MT-1 and -2 serve as important regulators of metal homeostasis, and also as a source of zinc for incorporation into proteins, including transcription factors (Zeng et al., 1991, Palmiter, 1998). MT-1 and -2 are able to prevent zinc deficiency and toxicity in vivo (Dalton et al., 1996, Kelly et al., 1996, Lee et al., 1996), and have also been proposed to function as detoxifiers of other reactive metals and free radicals (Thornalley and Vasak, 1985, Liu et al., 1991, Liu et al., 1995). Interestingly, MT-1 isoform-overexpressing transgenic mice apparently possess a degree of protection against neuronal damage in a cerebral ischemia reperfusion model (Van Lookeren Campagne et al., 1999), and MT-1,2-knock-out mice have larger infarcts than wild-type mice after 2 h transient focal ischemia (Trendelenburg et al., 2002).
Cilostazol, an antiplatelet drug used to treat intermittent claudication, has been reported to increase the intracellular level of cyclic AMP by inhibiting its hydrolysis by type III phosphodiesterase. Its principal actions include inhibition of platelet aggregation (Kimura et al., 1985, Kohda et al., 1999), antithrombosis in feline cerebral ischemia, and vasodilation via mediation of increased cyclic AMP level (Tanaka et al., 1989). Recently, Lee et al. (2005) found that cilostazol has a neuroprotective effect against cerebral infarcts in rat brains subjected to middle cerebral artery (MCA) occlusion followed by 24 h reperfusion, and that this effect is exerted via antioxidant and antiapoptotic actions. Since Michael and Robert (1989) noted that dibutyryl cyclic AMP increased significantly liver MT-1 and -2, it seemed possible that cilostazol might reduce ischemic brain damage at least partly by inducing MT-1 and -2.
The purposes of this study, on mice, were therefore to examine (1) whether cilostazol induces MT-1 and -2 in the brain and (2) whether cilostazol reduces, via an MT-related mechanism, the brain damage occurring after permanent MCA occlusion.
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Physiological variables
There was no significant difference between the vehicle and cilostazol groups in the following physiological variables: mean arterial blood pressure, blood pH, partial pressures of carbon dioxide (PaCO2) and oxygen (PaO2), and regional cerebral blood flow (rCBF) in the core area whether they were measured before or after 30 min ischemia (Table 1).
Effect of cilostazol on infarct size and volume
Animals injected i.p. with cilostazol at 30 mg/kg, at 12 h before, 1 h before, and just after the induction of focal ischemia showed no behavioral
Discussion
We examined the neuroprotective effects of cilostazol after 24 h permanent MCA occlusion in mice, and we explored the possible underlying mechanism by examining MT-1 and -2 induction in vivo. Cilostazol-treated mice showed significantly smaller infarct area and volume (vs. vehicle-treated mice) at 24 h after MCA occlusion, the trend being stronger in the cortex than in the subcortex (including the striatum). The expressions of MT-1 and -2 mRNAs were increased in the cortex of cilostazol-treated
Animal preparation
The experimental designs, and all procedures, were conducted in accordance with the Animal Care Guidelines of the Animal Experimental Committee of Gifu Pharmaceutical University. Male C57BL/6J type mice (body weight, 24–28 g) were housed at controlled room temperature (24.5–25.0 °C), with a 12/12-h light/dark cycle. Mouse food pellets and tap water were provided ad libitum.
Drugs
Cilostazol {6-[4-(1-cyclohexy-1H-tetrazol-5-yl)butoxyl]-3,4-dihydro-2-(1H)-quinolinone} was kindly gifted by Otsuka
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2011, Ageing Research ReviewsCitation Excerpt :It is also interesting to note that MTF-1 overexpression in nervous tissue was sufficient to increase lifespan, since recent studies in mice have highlighted the nervous system as a domain in which anti-apoptotic functions of MT can influence phenotypes related to aging (Ebadi et al., 2005; Hands et al., 2010; Leung et al., 2010). In particular, MT has a neuroprotective role against several forms of brain injury (e.g., cerebral ischemia) and is also able to augment the regenerative capacity of astrocytes (Wakida et al., 2006; Leung et al., 2010). Additionally, transgenic MT overexpression confers resistance to parkinsonism in multiple mouse models of Parkinson's disease (Ebadi et al., 2005), and the overexpression of MT3 in HeLa cells reduced the polyQ toxicity that is associated with Huntington's disease (Hands et al., 2010).
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2009, NeuroscienceCitation Excerpt :In addition, MT-2 mRNA was prominently induced in the spinal cord. This is also similar to the phenomenon observed in the rat brain with focal cerebral ischemia (Wakida et al., 2006). The induction of MT isoforms seems to be similarly regulated by various stimuli and stresses.