Expression, distribution and cellular localization of Sirtuins in the normal and ischemic brain of rodent

Abstract

Sirtuins (SIRTs) are nicotinamide adenine dinucleotide-dependent histone deacetylases. To date, seven sirtuins (SIRT1-SIRT7) have been identified in mammals. While basic knowledge of sirtuins in the brain is essential to understand the role of sirtuins in the normal and pathologic brain, only limited information is available. We investigated the distribution and cellular localization of sirtuins in the normal and ischemic brain of the rodent.

Male Sprague-Dawley (SD) rats, Wistar rats, Imprinting Control Region (ICR) mice, and C57BL/6 mice were used. Normal whole brain samples were obtained. In paraffin or frozen sections, immunohistochemistry was performed and the whole brain was examined into regions: olfactory bulb, cerebrum and cerebellum. To examine the cell types that express sirtuins, double immunofluorescence staining was performed using antibodies for each sirtuin and those for specific cell markers. Cerebral ischemia induced by 2 hr of middle cerebral artery occlusion and 22 hr of reperfusion using nylon thread. The expression of each sirtuin was compared between normal and ischemic brain areas.

SIRT1, SIRT3 and SIRT5-7 were expressed in neurons of most of regions and in oligodendrocytes of corpus callosum and internal capsule. SIRT2 was expressed in myelin. SIRT4 was expressed in vessels. As a result, sirtuins, especially SIRT5-7 were widely distributed and highly expressed in the olfactory bulb, cerebrum, and cerebellum. The expression of SIRT1 and SIRT3 in the corpus callosum and internal capsule was variable among species. SIRT2 was not expressed in the external plexiform layer of olfactory bulb and hypothalamus of cerebrum. SIRT4 was widely expressed in the entire brain areas except in the purkinje layer of cerebellum in SD rats. After induction of cerebral ischemia, SIRT4 showed significantly increased expression in the ischemic region. However, the other sirtuins were not significantly different.

Distribution and cellular localization in the rodent brain were different among sirtuins. Expression in the ischemic brain was also different. Findings of this study might provide with basic information for studying pathophysiologic role of sirtuins in the brain.