Kumar Premranjan, Rao G Nageswar, Pal Bibhuti Bhusan, Pal Arttatrana
School of Biotechnology, KIIT University, Bhubaneswar 751024, India.
Department of Ophthalmology, Kalinga Institute of Medical Sciences, KIIT University, Bhubaneswar 751024, India.
Int J Biochem Cell Biol. 2014 Aug;53:302-19. doi: 10.1016/j.biocel.2014.05.038. Epub 2014 Jun 4.
Glial cells are very important for normal brain function and alterations in their activity due to hyperglycemia, could contribute to diabetes-related cognitive dysfunction. Oxidative insults often cause rapid changes in almost all cells including glial cells. However, pathophysiologic mechanisms that lead to diabetic complications are not completely elucidated. Therefore, we examined whether elevated glucose levels directly or indirectly disrupt antioxidant defense mechanisms causing alterations in signaling pathways, cell cycle dysregulation, and reactive oxygen/nitrogen species-mediated apoptosis in glial cells. Findings of this study demonstrated that exposure of glial cells to high glucose markedly induces cellular and molecular injuries, as evidenced by elevated levels of reactive oxygen/nitrogen species, biomolecules damage, cell cycle dysregulation, decrease in antioxidant enzymes, and decrease in cell viability. Pretreatment of cells with N-acetyl-L-cysteine reduced high glucose-induced cytotoxicity by increasing the levels of antioxidant enzymes, and decreasing the number of apoptotic cells. Further, at molecular level high glucose treatment resulted in a significant increase in phosphorylation of Akt, MAPKs, tuberin, down regulation of 8-oxoG-DNA glycosylase and increase in 8-hydroxydeoxyguanosine accumulations. Pretreatment of cells with N-acetyl-L-cysteine, phosphatidylinositol3-kinase/Akt and ERK1/2 inhibitors completely abolished the apoptotic effects of high glucose. Moreover, N-acetyl-L-cysteine significantly inhibited reactive oxygen/nitrogen species generation, elevated antioxidants levels, inhibited Akt, ERK1/2, tuberin phosphorylation, decreased 8-hydroxydeoxyguanosine accumulation and upregulated 8-oxoG-DNA glycosylase expression. Our results demonstrate that high glucose induces apoptosis and inhibits proliferation of glial cells, which may be mediated by the phosphorylation of tuberin, down regulation of 8-oxoG-DNA glycosylase and 8-hydroxydeoxyguanosine accumulation via activation of Akt and ERK1/2MAPK pathways.
神经胶质细胞对正常脑功能非常重要，因高血糖导致其活性改变，可能会引发糖尿病相关的认知功能障碍。氧化损伤通常会导致包括神经胶质细胞在内的几乎所有细胞迅速发生变化。然而，导致糖尿病并发症的病理生理机制尚未完全阐明。因此，我们研究了血糖水平升高是否直接或间接破坏抗氧化防御机制，从而导致神经胶质细胞信号通路改变、细胞周期失调以及活性氧/氮物种介导的细胞凋亡。本研究结果表明，将神经胶质细胞暴露于高糖环境中会显著诱导细胞和分子损伤，活性氧/氮物种水平升高、生物分子损伤、细胞周期失调、抗氧化酶减少以及细胞活力下降均证明了这一点。用N-乙酰-L-半胱氨酸预处理细胞可通过提高抗氧化酶水平和减少凋亡细胞数量来降低高糖诱导的细胞毒性。此外，在分子水平上，高糖处理导致Akt、丝裂原活化蛋白激酶（MAPKs）、结节性硬化蛋白磷酸化显著增加，8-氧代鸟嘌呤-DNA糖基化酶下调以及8-羟基脱氧鸟苷积累增加。用N-乙酰-L-半胱氨酸、磷脂酰肌醇3-激酶/Akt和ERK1/2抑制剂预处理细胞可完全消除高糖的凋亡作用。此外，N-乙酰-L-半胱氨酸显著抑制活性氧/氮物种的产生，提高抗氧化剂水平，抑制Akt、ERK1/2、结节性硬化蛋白磷酸化，减少8-羟基脱氧鸟苷积累并上调8-氧代鸟嘌呤-DNA糖基化酶表达。我们的结果表明，高糖诱导神经胶质细胞凋亡并抑制其增殖，这可能是通过激活Akt和ERK1/2丝裂原活化蛋白激酶途径，导致结节性硬化蛋白磷酸化、8-氧代鸟嘌呤-DNA糖基化酶下调以及8-羟基脱氧鸟苷积累介导的。
