De Boer Anna A, Monk Jennifer M, Robinson Lindsay E
Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Canada.
PLoS One. 2014 Jan 20;9(1):e85037. doi: 10.1371/journal.pone.0085037. eCollection 2014.
Paracrine interactions between adipocytes and macrophages contribute to chronic inflammation in obese adipose tissue. Dietary strategies to mitigate such inflammation include long-chain polyunsaturated fatty acids, docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids, which act through PPARγ-dependent and independent pathways. We utilized an in vitro co-culture model designed to mimic the ratio of macrophages:adipocytes in obese adipose tissue, whereby murine 3T3-L1 adipocytes were cultured with RAW 264.7 macrophages in direct contact, or separated by a trans-well membrane (contact-independent mechanism), with 125 µM of albumin-complexed DHA, EPA, palmitic acid (PA), or albumin alone (control). Thus, we studied the effect of physical cell contact versus the presence of soluble factors, with or without a PPARγ antagonist (T0070907) in order to elucidate putative mechanisms. After 12 hr, DHA was the most anti-inflammatory, decreasing MCP1 and IL-6 secretion in the contact system (-57%, -63%, respectively, p ≤ 0.05) with similar effects in the trans-well system. The trans-well system allowed for isolation of cell types for inflammatory mediator analysis. DHA decreased mRNA expression (p<0.05) of Mcp1 (-7.1 fold) and increased expression of the negative regulator, Mcp1-IP (+1.5 fold). In macrophages, DHA decreased mRNA expression of pro-inflammatory M1 polarization markers (p ≤ 0.05), Nos2 (iNOS; -7 fold), Tnfα (-4.2 fold) and Nfκb (-2.3 fold), while increasing anti-inflammatory Tgfβ1 (+1.7 fold). Interestingly, the PPARγ antagonist co-administered with DHA or EPA in co-culture reduced (p ≤ 0.05) adiponectin cellular protein, without modulating other cytokines (protein or mRNA). Overall, our findings suggest that DHA may lessen the degree of MCP1 and IL-6 secreted from adipocytes, and may reduce the degree of M1 polarization of macrophages recruited to adipose tissue, thereby decreasing the intensity of pro-inflammatory cross-talk between adipocytes and macrophages in obese adipose tissue.
脂肪细胞与巨噬细胞之间的旁分泌相互作用会导致肥胖脂肪组织中的慢性炎症。减轻此类炎症的饮食策略包括长链多不饱和脂肪酸、二十二碳六烯酸（DHA）和二十碳五烯酸（EPA），它们通过PPARγ依赖性和非依赖性途径发挥作用。我们利用一种体外共培养模型来模拟肥胖脂肪组织中巨噬细胞与脂肪细胞的比例，即将小鼠3T3-L1脂肪细胞与RAW 264.7巨噬细胞直接接触培养，或通过Transwell膜隔开培养（非接触依赖性机制），同时加入125µM与白蛋白结合的DHA、EPA、棕榈酸（PA）或单独的白蛋白（对照）。因此，我们研究了细胞直接接触与可溶性因子存在的影响，以及是否添加PPARγ拮抗剂（T0070907），以阐明可能的机制。12小时后，DHA的抗炎作用最强，在接触系统中可降低MCP1和IL-6的分泌（分别降低57%和63%，p≤0.05），在Transwell系统中也有类似效果。Transwell系统可用于分离细胞类型以进行炎症介质分析。DHA可降低Mcp1的mRNA表达（p<0.05）（降低7.1倍），并增加负调节因子Mcp1-IP的表达（增加1.5倍）。在巨噬细胞中，DHA可降低促炎M1极化标志物的mRNA表达（p≤0.05），如Nos2（诱导型一氧化氮合酶；降低7倍）、Tnfα（降低4.2倍）和Nfκb（降低2.3倍），同时增加抗炎因子Tgfβ1的表达（增加1.7倍）。有趣的是，在共培养中与DHA或EPA共同使用PPARγ拮抗剂会降低脂联素细胞蛋白水平（p≤0.05），但不调节其他细胞因子（蛋白或mRNA）。总体而言，我们的研究结果表明，DHA可能会减轻脂肪细胞分泌的MCP1和IL-6的程度，并可能降低募集到脂肪组织中的巨噬细胞的M1极化程度，从而降低肥胖脂肪组织中脂肪细胞与巨噬细胞之间促炎相互作用的强度。
