Keene C Dirk, Chang Rubens, Stephen Christina, Nivison Mary, Nutt Samuel E, Look Amy, Breyer Richard M, Horner Phillip J, Hevner Robert, Montine Thomas J
Department of Pathology, University of Washington, Box 359791, Seattle, WA 98104, USA.
Am J Pathol. 2009 Jun;174(6):2300-9. doi: 10.2353/ajpath.2009.081153. Epub 2009 Apr 23.
Prostaglandin E2 is one of several eicosanoid products of the cyclooxygenase isozymes and is a key regulator of innate immune responses; it also possesses paracrine effects on mature neurons. The prostaglandin E2 receptor family consists of four subtypes of which EP1 and EP2 are known to be expressed by microglia. Lipopolysaccharide (LPS)-induced innate immune activation leads to the degeneration of intermediate progenitor cells (IPCs) that are destined for neuronal maturation in the hippocampal subgranular zone (SGZ); these cells can be identified by the expression of the transcription factor T-box brain gene 2 (Tbr2). Importantly, depletion of LPS-induced IPCs from the SGZ is suppressed by cyclooxygenase inhibitors. We therefore tested the hypothesis that either EP1 or EP2 is critical to LPS-induced depletion of Tbr2+ IPCs from the SGZ. Expression of either EP1 or EP2 was necessary for Toll-like receptor 4-dependent innate immune-mediated depletion of these Tbr2+ IPCs in mice. Moreover, EP1 activation was directly toxic to murine adult hippocampal progenitor cells; EP2 was not expressed by these cells. Finally, EP1 modulated the response of murine primary microglia cultures to LPS but in a manner distinct from EP2. These results indicate that prostaglandin E2 signaling via either EP1 or EP2 is largely to completely necessary for Toll-like receptor 4-dependent depletion of IPCs from the SGZ and suggest further pharmacological strategies to protect this important neurogenic niche.
前列腺素E2是环氧化酶同工酶产生的几种类花生酸产物之一,是先天免疫反应的关键调节因子;它对成熟神经元也具有旁分泌作用。前列腺素E2受体家族由四种亚型组成,其中已知小胶质细胞表达EP1和EP2。脂多糖(LPS)诱导的先天免疫激活导致海马颗粒下区(SGZ)中注定要进行神经元成熟的中间祖细胞(IPC)退化;这些细胞可通过转录因子T-box脑基因2(Tbr2)的表达来识别。重要的是,环氧化酶抑制剂可抑制SGZ中LPS诱导的IPC的耗竭。因此,我们检验了以下假设:EP1或EP2对LPS诱导的SGZ中Tbr2+ IPC的耗竭至关重要。在小鼠中,Toll样受体4依赖性先天免疫介导的这些Tbr2+ IPC的耗竭需要EP1或EP2的表达。此外,EP1激活对成年小鼠海马祖细胞具有直接毒性;这些细胞不表达EP2。最后,EP1调节小鼠原代小胶质细胞培养物对LPS的反应,但方式与EP2不同。这些结果表明,通过EP1或EP2的前列腺素E2信号传导在很大程度上至完全是Toll样受体4依赖性SGZ中IPC耗竭所必需的,并提出了进一步保护这一重要神经源性微环境的药理学策略。