The soluble epoxide hydrolase inhibitor TPPU alleviates Aβ-mediated neuroinflammatory responses in Drosophila and cellular models of Alzheimer's disease
Authors: Sun Xiaowen , Li Wei , Li Lin , Tian Qian , Cao Qingyang , Fu Qingxi , Meng Yun , Shen Yan , Yu Jixu , Che Feng-Yuan 
Published: October 2023

Background
Alzheimer's disease (AD) is a common neurodegenerative disease, and its pathogenesis is closely associated with neuroinflammation. The control of neuroinflammation in AD is the focus of current research. sEH is increased in the brain tissues of patients with AD, and sEH induces nerve inflammation by degrading epoxyeicosatrienoic acids (EETs). Therefore, sEH inhibitor application and sEH gene knockout are effective ways to improve the bioavailability of EETs and inhibit neuroinflammation in AD. TPPU is a potent sEH inhibitor that has been shown to be effective in preclinical animal models of a variety of chronic inflammatory diseases, we want to further explore whether TPPU can alleviate AD neuroinflammation.
Methods
In this study, an Aβ42-transgenic Drosophila model was established using the GAL4/UAS system, and the protective and anti-neuroinflammatory effects of TPPU against Aβ toxicity in Drosophila were investigated. Behavioral indexes (survival time, crawling ability, and olfactory memory) and biochemical indexes MDA content and SOD content in brain tissues of Aβ42 transgenic Drosophila were detected. The mRNA expression of the inflammatory cytokines TNF, IL-1 and the gene encoding sEH (EPHX2) in the brain tissue of Aβ42 transgenic drosophila were detected by Real-time PCR. The anti-neuroinflammatory effect of TPPU and its possible mechanism were further explored by stimulating cocultures of SH-SY5Y cells and HMC3 cells with Aβ(25–35) to model neuronal cell inflammation.The cells were detected by fluorescence microscopy, ELISA, Western Blot, and Real-time PCR.
Results
In vivo drosophila model, we found that TPPU improved the survival time, crawling ability, and olfactory memory of Aβ42-transgenic Drosophila, decreased the MDA content, and increased the SOD content in the brain tissues of Aβ42-transgenic Drosophila. More importantly, TPPU reduced the mRNA expression of the inflammatory cytokines TNF and IL-1 as well as that of the gene encoding sEH (EPHX2) in the brain tissues of Aβ42-transgenic Drosophila. In cell model, we found that TPPU improved cell viability, reduced cell apoptosis, decreased lipid oxidation, inhibited oxidative damage, and enhanced oxygen free radical scavenging, thus playing a neuroprotective role. The mRNA expression of the inflammatory cytokines TNF, IL-1β, IL-6 and IL-18 was downregulated, and the mRNA expression of the M2 microglia markers CD206 and SOCS3 was upregulated by TPPU; thus, TPPU inhibited neuroinflammatory responses. TPPU exerted neuroprotective and anti-inflammatory effects by decreasing the protein expression of the sEH-encoding gene EPHX2 and increasing the levels of 11,12-EET and 14,15-EET. The inhibitory effect of TPPU on Aβ(25–35)-mediated neuroinflammation was associated with inhibition of the TLR4/NF-κB pathway and MAPK/NF-κB pathway.
Conclusion
We found that the sEH inhibitor TPPU exerts neuroprotective and anti-neuroinflammatory effects in AD models and it is expected that this drug could potentially be used for the prevention and treatment of AD.