Docosahexaenoic acid impacts macrophage phenotype subsets and phagolysosomal membrane permeability with particle exposure

Inhalation of particles results in pulmonary inflammation; however, treatments are currently lacking. Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid shown to exhibit anti-inflammatory capabilities. The impact of DHA on particle-induced inflammation is unclear; therefore, the aim of this study was to examine the hypothesis that DHA downregulates macrophage inflammatory responses by altering phagolysosomal membrane permeability (LMP) and shifting macrophage phenotype. Isolated Balb/c alveolar macrophages (AM) were polarized into M1, M2a, M2b, or M2c phenotypes in vitro, treated with DHA, and exposed to a multi-walled carbon nanotube (MWNCT) or crystalline silica (SiO2). Results showed minimal cytotoxicity, robust effects for silica particle uptake, and LMP differences between phenotypes. Docosahexaenoic acid prevented these effects to the greatest extent in M2c phenotype. To determine if DHA affected inflammation similarly in vivo, Balb/c mice were placed on a control or 1% DHA diet for 3 weeks, instilled with the same particles, and assessed 24 hr following instillation. Data demonstrated that in contrast to in vitro findings, DHA increased pulmonary inflammation and LMP. These results suggest that pulmonary responses in vivo may not necessarily be predicted from single-cell responses in vitro.

颗粒物吸入可引发肺部炎症，但目前尚无针对性治疗手段。二十二碳六烯酸（Docosahexaenoic Acid, DHA）是一种ω-3多不饱和脂肪酸，已被证实具备抗炎活性。目前DHA对颗粒物诱导炎症的作用尚不明确，因此本研究旨在验证以下假说：DHA可通过改变吞噬溶酶体膜通透性（Phagolysosomal Membrane Permeability, LMP）并重塑巨噬细胞表型，下调巨噬细胞的炎症应答。本研究体外分离巴尔贝/c（Balb/c）小鼠肺泡巨噬细胞（Alveolar Macrophages, AM），将其极化为M1、M2a、M2b或M2c表型，经DHA处理后分别暴露于多壁碳纳米管（Multi-walled Carbon Nanotube, MWNCT）或结晶二氧化硅（Crystalline Silica, SiO2）。实验结果显示，细胞毒性极低，二氧化硅颗粒摄取效果显著，且不同巨噬细胞表型间的LMP存在差异。二十二碳六烯酸对M2c表型巨噬细胞的上述异常改变抑制效果最为显著。为验证DHA在体内是否可产生类似的抗炎效果，本研究将巴尔贝/c小鼠分为两组，分别饲喂基础饲料与含1% DHA的饲料，持续3周后经气道滴入上述颗粒物，并于滴注后24小时进行检测评估。体内实验数据显示，与体外实验结果相反，DHA反而加重了肺部炎症并提升了LMP水平。上述结果表明，体外单细胞实验结果未必能够准确预测体内肺部的实际应答反应。