Data_Sheet_1_Mode of administration influences plasma levels of active Centella asiatica compounds in 5xFAD mice while markers of neuroinflammation remain unaltered.pdf

IntroductionA water extract of Centella asiatica (L.) Urban [Apiaceae] (CAW) has demonstrated cognitive-enhancing effects in mouse models of Alzheimer’s disease and aging, the magnitude of which is influenced by whether CAW is delivered in the drinking water or the diet. These cognitive benefits are accompanied by improvements in oxidative stress and mitochondrial function in the brain, two pathways related to the neuroinflammatory response. The effect of CAW on neuroinflammation, however, has not been directly studied. Here, we investigated the effect of CAW on neuroinflammation in 5xFAD mice and compared plasma levels of CAW’s active compounds following two modes of CAW administration.
MethodsEight-to-nine-month-old male and female 5xFAD mice and their wild-type littermates were administered CAW in their diet or drinking water (0 or 1,000 mg/kg/day) for five weeks. Immunohistochemistry was performed for β-amyloid (Aβ), glial fibrillary acidic protein (GFAP), and Griffonia simplicifolia lectin I (GSL I) in the cortex and hippocampus. Gene expression of inflammatory mediators (IL-6, TNFα, IL-1β, TREM2, AIF1, CX3CR1, CX3CL1, CD36, C3AR1, RAGE, CCR6, CD3E) was measured in the deep grey matter.
ResultsCAW decreased cortical Aβ plaque burden in female 5xFAD mice administered CAW in the drinking water but had no effect on Aβ plaques in other treatment groups. CAW did not impact elevated levels of GFAP or GSL I in 5xFAD mice, regardless of sex, brain region, or mode of CAW administration. In the deep grey matter, CAW increased C3AR1 expression in 5xFAD females administered CAW in the drinking water and decreased IL-1β expression in 5xFAD males administered CAW in the diet. CAW had no effect, however, on gene expression levels of any other inflammatory mediator in the deep grey, for either sex or mode of CAW administration. Mice administered CAW in the drinking water versus the diet had significantly higher plasma levels of CAW compounds.
DiscussionCAW had little impact on the neuroinflammatory markers selected for evaluation in the present study, suggesting that the cognitive benefits of CAW may not be mediated by an anti-inflammatory effect or that additional molecular markers are needed to fully characterize the effect of CAW on neuroinflammation.

引言：积雪草（Centella asiatica (L.) Urban，伞形科（Apiaceae））水提取物（CAW）已在阿尔茨海默病（Alzheimer’s disease）及衰老小鼠模型中被证实具有认知增强作用，其效果强弱受给药方式——经饮用水或饲料递送——的影响。该认知益处伴随脑内氧化应激与线粒体功能的改善，而这两条通路均与神经炎症反应相关。然而，目前尚未有研究直接探讨CAW对神经炎症的作用。本研究旨在探究CAW对5xFAD小鼠神经炎症的影响，并对比两种给药方式下CAW活性成分的血浆水平。
方法：选取8~9月龄的雄性和雌性5xFAD小鼠及其野生型同窝仔鼠，分别通过饲料或饮用水给予CAW（剂量为0或1000 mg/kg/天），持续5周。对皮层和海马组织开展β淀粉样蛋白（β-amyloid, Aβ）、胶质纤维酸性蛋白（glial fibrillary acidic protein, GFAP）以及简射草凝集素I（Griffonia simplicifolia lectin I, GSL I）的免疫组织化学检测。在深部灰质中检测炎症介质白细胞介素6（interleukin 6, IL-6）、肿瘤坏死因子α（tumor necrosis factor α, TNFα）、白细胞介素1β（interleukin 1β, IL-1β）、髓系细胞触发受体2（triggering receptor expressed on myeloid cells 2, TREM2）、AIF1、CX3CR1、CX3CL1、CD36、C3AR1、晚期糖基化终末产物受体（receptor for advanced glycation end products, RAGE）、CCR6、CD3E的基因表达水平。
结果：经饮用水给药的雌性5xFAD小鼠中，CAW可降低皮层Aβ斑块负荷，但其余给药组的Aβ斑块水平未受影响。无论性别、脑区或给药方式，CAW均未改变5xFAD小鼠体内升高的GFAP或GSL I水平。在深部灰质中，经饮用水给药的雌性5xFAD小鼠体内，CAW可上调C3AR1的表达；而经饲料给药的雄性5xFAD小鼠体内，CAW可下调IL-1β的表达。其余炎症介质的基因表达水平均未受CAW影响，且不受性别或给药方式的影响。与经饲料给药的小鼠相比，经饮用水给药的小鼠体内CAW活性成分的血浆水平显著更高。
讨论：本研究中，CAW对所选的神经炎症标志物几乎无影响，这提示CAW的认知益处可能并非通过抗炎作用介导，或是需要选取更多的分子标志物才能全面表征CAW对神经炎症的作用。