Akbulut K G, Keskin-Aktan A, Abgarmi S A, Akbulut H
Department of Physiology, School of Medicine, Gazi University, Ankara, Turkey.
Department of Physiology, School of Medicine, Afyonkarahisar Health Sciences University, Afyonkarahisar, Turkey.
Aging Brain. 2023 Jul 17;4:100087. doi: 10.1016/j.nbas.2023.100087. eCollection 2023.
Though the exact mechanisms regarding brain aging and its relation to neurodegenerative disorders are not precise, oxidative stress, the key regulators of apoptosis and autophagy, such as bcl-2 and beclin 1, seem to be the potential players in the aging of the cerebral cortex and hippocampus. As a type of nicotinamide adenine dinucleotide (NAD)-dependent deacetylases, sirtuin 2 (SIRT2) has been associated to age-related diseases. However, the exact role of SIRT2 in brain aging is not well studied. The objective of the current study was to study the role of SIRT2 inhibition on brain aging through the neuroprotective mechanisms.
We tested the effects of AGK-2, a SIRT2 inhibitor, on oxidative stress parameters, apoptosis and autophagy regulators including bcl-2, bax, beclin1 in young and old rats. 24 Wistar albino rats (3 months-old and 22 months-old) were divided into four groups; Young-Control (4% DMSO+PBS), Young-AGK-2 (10 µM/bw, ip), Aged-Control, and Aged-AGK-2. Following the 30 days of drug administration period the rats were sacrificed and the cerebral cortex, hippocampus, and cerebellum were isolated. Total antioxidant status (TAS) and total oxidant status (TOS) were measured as oxidative stress parameters in all three brain regions. SIRT2, bcl-2, and bax protein expression levels were measured by western blot and gene expression level of beclin 1, Atg5, and SIRT2 by real-time PCR.
The bcl-2, bcl-2/bax ratio, beclin 1, and TAS in the cerebral cortex of the aged group were significantly decreased; however, the TOS, oxidative stress index (OSI), and SIRT2 expression in the cerebral cortex and hippocampus increased. SIRT2 inhibition by AGK-2 reduced TOS and OSI levels in all brain regions and increased bcl-2, bcl-2/bax ratio. In aged animals, AGK-2 also increased the beclin 1 levels in the cortex and hippocampus.
Our results indicate that SIRT2 has an essential role in brain aging. The inhibition of SIRT2 by AGK-2 may increase cell survival and decrease aging related processes in the cerebral cortex and hippocampus via decreasing oxidative stress, and increasing bcl-2 and beclin 1 expression.
尽管关于大脑衰老及其与神经退行性疾病关系的确切机制尚不清楚，但氧化应激以及凋亡和自噬的关键调节因子，如bcl-2和beclin 1，似乎是大脑皮层和海马体衰老的潜在影响因素。作为一种烟酰胺腺嘌呤二核苷酸（NAD）依赖性脱乙酰酶，沉默调节蛋白2（SIRT2）与年龄相关疾病有关。然而，SIRT2在大脑衰老中的确切作用尚未得到充分研究。本研究的目的是通过神经保护机制研究SIRT2抑制对大脑衰老的作用。
我们测试了SIRT2抑制剂AGK-2对年轻和老年大鼠氧化应激参数、凋亡和自噬调节因子（包括bcl-2、bax、beclin1）的影响。将24只Wistar白化大鼠（3个月龄和22个月龄）分为四组；年轻对照组（4%二甲基亚砜+磷酸盐缓冲液）、年轻AGK-2组（10 μM/体重，腹腔注射）、老年对照组和老年AGK-2组。给药30天后处死大鼠，分离大脑皮层、海马体和小脑。在所有三个脑区测量总抗氧化状态（TAS）和总氧化状态（TOS）作为氧化应激参数。通过蛋白质印迹法测量SIRT2、bcl-2和bax蛋白表达水平，通过实时聚合酶链反应测量beclin 1、自噬相关蛋白5（Atg5）和SIRT2的基因表达水平。
老年组大脑皮层中的bcl-2、bcl-2/bax比值、beclin 1和TAS显著降低；然而，大脑皮层和海马体中的TOS、氧化应激指数（OSI）和SIRT2表达增加。AGK-2对SIRT2的抑制降低了所有脑区的TOS和OSI水平，并增加了bcl-2、bcl-2/bax比值。在老年动物中，AGK-2还增加了皮层和海马体中的beclin 1水平。
我们的结果表明SIRT2在大脑衰老中起重要作用。AGK-2对SIRT2的抑制可能通过降低氧化应激以及增加bcl-2和beclin 1表达来提高细胞存活率，并减少大脑皮层和海马体中与衰老相关的过程。
