Anti-inflammatory Function of Ozonated Ethyl Ester of Unsaturated Fatty Acids

In this study, we investigated the anti-inflammatory properties of ozonated polyunsaturated fatty acids (PUFAs). Ozonated fatty acid ethyl esters were prepared by bubbling ozone gas into the sample solution, leading to the formation of ozonide structures. Upon treatment with RAW264 cells, ozonated fatty acid ethyl esters reduced the lipopolysaccharide (LPS)-induced nitric oxide (NO) production in a dose-dependent manner, with ozonated ethyl ester of α-linolenic acid (zLnEE) showing the strongest reduction among all samples. The mRNA expression levels of inflammatory factors, such as tumor necrosis factor-α (TNF-α), prostaglandin-endoperoxide synthase 2 (PTGS2), interleukin (IL) 1β and IL6, induced by the stimulation of LPS, were suppressed, while the oxidative stress response gene of hemeoxidase-1 (HO-1) was upregulated by zLnEE treatment. In the nuclear factor kappa B (NF-κB) reporter gene assay, NF-κB activation stimulated by TNF-α was inhibited by the addition of zLnEE. These results indicate that ozonated PUFAs have anti-inflammatory effects. Furthermore, the observed upregulation of the HO-1 mRNA levels suggests that the ozonide structure of zLnEE activates the nuclear factor erythroid 2-related factor 2 (Nrf2) - Kelch-like ECH-associated protein 1 (Keap1) pathway, thereby inducing its anti-inflammatory properties. However, the potential cytotoxic degradation products of ozonated PUFAs may be harmful to humans and further studies are needed to confirm the safety of ozonated oils.