Oil is frequently used as a solvent to inject lipophilic substances into the peritoneum of laboratory animals. Although mineral oil causes chronic peritoneal inflammation, little is known whether other oils are better suited. We show that olive, peanut, corn or mineral oil causes xanthogranulomatous inflammation with depletion of resident peritoneal macrophages. However, there were striking differences in the severity of the inflammatory response. Peanut and mineral oil caused severe chronic inflammation with persistent neutrophil and monocyte recruitment, expansion of the vasculature and fibrosis. Corn and olive oil provoked no or only mild signs of chronic inflammation. Mechanistically, the vegetal oils were taken up by macrophages leading to foam cell formation and induction of cell death. Olive oil triggered caspase-3 cleavage and apoptosis, which facilitates the resolution of inflammation. Peanut oil and, to a lesser degree, corn oil triggered caspase-1 activation and macrophage pyroptosis, which impairs the resolution of inflammation. As such, intraperitoneal oil administration can interfere with the outcome of subsequent experiments. As a proof-of-principle, intraperitoneal peanut oil injection was compared to its oral delivery in a thioglycolate-induced peritonitis model. The chronic peritoneal inflammation due to peanut oil injection impeded the proper recruitment of macrophages and the resolution of inflammation in this peritonitis model. In summary, the data indicate that it is advisable to deliver lipophilic substances like tamoxifen by oral gavage instead of intraperitoneal injection. Implications: This work contributes to the reproducibility of animal research by helping to understand some of the undesired effects observed in animal experiments.

中文翻译：

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腹腔内涂油引起局部炎症，消耗常驻腹腔巨噬细胞

油经常被用作将亲脂性物质注入实验动物腹膜的溶剂。尽管矿物油会引起慢性腹膜炎症，但对于其他油是否更适合尚知之甚少。我们表明，橄榄、花生、玉米或矿物油会导致黄色肉芽肿性炎症，并耗尽常驻腹膜巨噬细胞。然而，炎症反应的严重程度存在显着差异。花生油和矿物油会导致严重的慢性炎症，伴有中性粒细胞和单核细胞持续募集、血管扩张和纤维化。玉米和橄榄油没有或只有轻微的慢性炎症迹象。从机制上讲，植物油被巨噬细胞吸收，导致泡沫细胞形成并诱导细胞死亡。橄榄油引发 caspase-3 裂解和细胞凋亡，这有利于炎症的消退。花生油和在较小程度上的玉米油引发 caspase-1 激活和巨噬细胞焦亡，这会损害炎症的消退。因此，腹膜内油给药会干扰后续实验的结果。作为原理证明，在巯基乙酸盐诱导的腹膜炎模型中，将腹腔内花生油注射液与其口服给药进行了比较。由于花生油注射引起的慢性腹膜炎症阻碍了该腹膜炎模型中巨噬细胞的适当募集和炎症的消退。总之，数据表明通过口服管饲法而不是腹膜内注射来递送他莫昔芬等亲脂性物质是可取的。含义：