Role of cannabinoid signalling between neurons and microglia cells in brain ageing

我们以前已经证明，在GABA能神经元上缺乏CB1受体的动物，脑老化早期伴随着海马区小胶质细胞活性的增加。这一非常出人意料的结果使我们提出了假设：(1)内源性大麻素系统在GABA能神经元和小胶质细胞之间起着通讯通道的作用；(2)神经元和小胶质细胞之间的大麻素信号对年龄相关的变化具有保护作用。为了测试这些可能性，我们将在一项纵向研究中评估小鼠在年龄相关的认知和组织学变化，这些小鼠缺乏小胶质细胞中主要的内源性大麻合成酶二酰甘油脂肪酶(DAGL)α和β。我们以前的结果也表明，小胶质细胞和GABA能神经元之间的信号减少上调了小胶质细胞的活动，并促进了老化大脑中的神经炎症。因此，我们将比较GABA特异性CB1基因敲除动物和DAGLα和DAGLβ基因敲除动物的小胶质细胞的反应性。我们还将比较GFP标记的小胶质细胞移植到野生型和不同年龄的GABA/CB1-/-小鼠海马区的运动性和形态。最后，我们假设，干扰的内源性大麻素信号导致小胶质细胞的早期发病和/或加剧衰老相关的表型。为了测试这种可能性，我们将比较不同年龄的野生型和GABA/CB1-/-动物脑中分离的小胶质细胞的脂褐素积累、表观遗传和基因表达变化的动态以及表型。

We have shown previously that there is an early onset of brain ageing accompanied with increased microglial activity in the hippocampus of animals lacking CB1 receptors on GABAergic neurons. This highly unexpected result led us to the hypotheses that (1) endocannabinoid system plays a role as communication channel between GABAergic neurons and microglia and (2) cannabinoid signaling between neurons and microglia is protective against age-related changes. To test these possibilities we will evaluate in a longitudinal study the age-related cognitive and histological changes in mice lacking the main endocannabinoid synthesizing enzyme diacylglycerol lipase (DAGL) alpha and beta from microglia. Our previous results also suggested that reduced signaling between microglia and GABAergic neurons upregulates microglial activity and promotes neuroinflammation in the ageing brain. Thus, we will compare the reactivity of microglia using organotypic hippocampal culture from GABA specific CB1 knockout and microglia specific DAGL alpha and DAGL beta knockout animals. We will also compare the motility and morphology of GFP-tagged microglia transplanted to the hippocampus of wild-type and GABA/CB1-/- mice with different age. Lastly, we hypothesize that disturbed endocannabinoid signalling leads to an early onset and/or exacerbated senescence associated phenotype in microglia. To test this possibility we will compare lipofuscin accumulation, dynamics of epigenetic and gene expression changes and the phenotype of the microglia cells isolated from the brain of wild-type and GABA/CB1-/- animals with different age.