Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, USA.
J Neuroinflammation. 2011 Sep 24;8:121. doi: 10.1186/1742-2094-8-121.
Activation of glial cells, including astrocytes and microglia, has been implicated in the inflammatory responses underlying brain injury and neurodegenerative diseases including Alzheimer's and Parkinson's diseases. Although cultured astrocytes and microglia are capable of responding to pro-inflammatory cytokines and lipopolysaccharide (LPS) in the induction and release of inflammatory factors, no detailed analysis has been carried out to compare the induction of iNOS and sPLA2-IIA. In this study, we investigated the effects of cytokines (TNF-alpha, IL-1beta, and IFN-gamma) and LPS + IFN-gamma to induce temporal changes in cell morphology and induction of p-ERK1/2, iNOS and sPLA₂-IIA expression in immortalized rat (HAPI) and mouse (BV-2) microglial cells, immortalized rat astrocytes (DITNC), and primary microglia and astrocytes.
METHODS/RESULTS: Cytokines (TNF-alpha, IL-1beta, and IFN-gamma) and LPS + IFN-gamma induced a time-dependent increase in fine processes (filopodia) in microglial cells but not in astrocytes. Filopodia production was attributed to IFN-gamma and was dependent on ERK1/2 activation. Cytokines induced an early (15 min) and a delayed phase (1 ~ 4 h) increase in p-ERK1/2 expression in microglial cells, and the delayed phase increase corresponded to the increase in filopodia production. In general, microglial cells are more active in responding to cytokines and LPS than astrocytes in the induction of NO. Although IFN-gamma and LPS could individually induce NO, additive production was observed when IFN-gamma was added together with LPS. On the other hand, while TNF-alpha, IL-1beta, and LPS could individually induce sPLA₂-IIA mRNA and protein expression, this induction process does not require IFN-gamma. Interestingly, neither rat immortalized nor primary microglial cells were capable of responding to cytokines and LPS in the induction of sPLA2-IIA expression.
These results demonstrated the utility of BV-2 and HAPI cells as models for investigation on cytokine and LPS induction of iNOS, and DITNC astrocytes for induction of sPLA2-IIA. In addition, results further demonstrated that cytokine-induced sPLA2-IIA is attributed mainly to astrocytes and not microglial cells.
胶质细胞（包括星形胶质细胞和小胶质细胞）的激活被认为与脑损伤和神经退行性疾病（包括阿尔茨海默病和帕金森病）的炎症反应有关。虽然培养的星形胶质细胞和小胶质细胞能够对促炎细胞因子和脂多糖（LPS）做出反应，从而诱导和释放炎症因子，但尚未进行详细分析来比较诱导 iNOS 和 sPLA2-IIA 的情况。在这项研究中，我们研究了细胞因子（TNF-α、IL-1β 和 IFN-γ）和 LPS+IFN-γ对诱导大鼠（HAPI）和小鼠（BV-2）小胶质细胞、大鼠星形胶质细胞（DITNC）以及原代小胶质细胞和星形胶质细胞的细胞形态的时程变化和诱导 p-ERK1/2、iNOS 和 sPLA₂-IIA 表达的影响。
方法/结果：细胞因子（TNF-α、IL-1β 和 IFN-γ）和 LPS+IFN-γ诱导小胶质细胞中细突（丝状伪足）的时间依赖性增加，但星形胶质细胞没有。丝状伪足的产生归因于 IFN-γ，并且依赖于 ERK1/2 的激活。细胞因子诱导小胶质细胞中 p-ERK1/2 表达的早期（15 分钟）和延迟（1~4 小时）增加，延迟相增加与丝状伪足的产生相对应。一般来说，小胶质细胞比星形胶质细胞对细胞因子和 LPS 诱导 NO 的反应更为活跃。虽然 IFN-γ和 LPS 可以单独诱导 NO，但当 IFN-γ与 LPS 一起加入时，会观察到相加的产生。另一方面，虽然 TNF-α、IL-1β 和 LPS 可以单独诱导 sPLA₂-IIA mRNA 和蛋白质表达，但这种诱导过程不需要 IFN-γ。有趣的是，无论是大鼠永生化的还是原代小胶质细胞都不能对细胞因子和 LPS 诱导 sPLA2-IIA 表达做出反应。
这些结果表明 BV-2 和 HAPI 细胞可作为研究细胞因子和 LPS 诱导 iNOS 的模型，而 DITNC 星形胶质细胞可作为诱导 sPLA2-IIA 的模型。此外，结果进一步表明，细胞因子诱导的 sPLA2-IIA 主要归因于星形胶质细胞，而不是小胶质细胞。
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