The influence of soluble epoxide hydrolase inhibition and their PUFA-derived epoxides in osteoblast bone metabolism: an in vitro study

EpFAs are crucial mediators in resolving inflammation and regulating various biological processes. However, their activity is constrained by the rapid metabolism mediated by the soluble epoxide hydrolase (sEH), which converts EpFAs into inactive or even pro-inflammatory diols. Nevertheless, the specific effects of soluble epoxide hydrolase inhibition (sEHI) and EpFAs on osteogenic cell metabolism remain unclear. Cultures of the human immortalized osteoblast-like cell line (SAOS-2) were treated with varying concentrations (0.1–10 μM) of the potent sEHI TPPU or EpFAs (epoxyeicosatrienoic acids [EETs], epoxydocosapentaenoic acids [EDPs], and epoxyeicosatetraenoic acids [EEQs], derived from arachidonic acid [ARA], eicosapentaenoic acid [EPA], and docosahexaenoic acid [DHA], respectively). Cellular metabolic activity and proliferation were evaluated. Osteogenic potential was assessed through alkaline phosphatase activity, mineral nodule formation, and the expression of osteogenic markers, including Runx-2, Osx, Col1, Bsp, Opg, Ocn, Opn, and sEH. Treatment with TPPU and EpFAs enhanced cellular metabolic activity during the first 48 h without affecting proliferation. Alkaline phosphatase activity and mineral nodule formation assays revealed that TPPU significantly stimulated osteogenic differentiation, while EpFAs, particularly EETs, EEQs, and EDPs, promoted osteogenesis predominantly at later stages. Furthermore, TPPU modulated the expression of key osteogenic markers, enhancing differentiation. Notably, EDPs were found to disrupt the synergistic effects between sEHI and EpFAs during the mineralization process. These findings suggest that sEHI enhances mineralization and may facilitate tissue regeneration in vitro. The differential effects of EpFAs and their interplay with sEHI provide insights into potential therapeutic strategies for bone tissue engineering and regeneration.