Mechanism of action and potential applications of selective inhibition of microsomal prostaglandin E synthase-1-mediated PGE2 biosynthesis by sonlicromanol’s metabolite KH176m

Abstract

Increased prostaglandin E2 (PGE2) levels were detected in mitochondrial disease patient cells harboring nuclear gene mutations in structural subunits of complex I, using a metabolomics screening approach. The increased levels of this principal inflammation mediator normalized following exposure of KH176m, an active redox-modulator metabolite of sonlicromanol (KH176). We next demonstrated that KH176m selectively inhibited lipopolysaccharide (LPS) or interleukin-1β (IL-1β)-induced PGE2 production in control skin fibroblasts. Comparable results were obtained in the mouse macrophage-like cell line RAW264.7. KH176m selectively inhibited mPGES-1 activity, as well as the inflammation-induced expression of mPGES-1. Finally, we showed that the effect of KH176m on mPGES-1 expression is due to the inhibition of a PGE2-driven positive feedback control-loop of mPGES-1 transcriptional regulation. Based on the results obtained we discuss potential new therapeutic applications of KH176m and its clinical stage parent drug candidate sonlicromanol in mitochondrial disease and beyond.

The hyaluronan synthesis inhibitor 7-hydroxy-4-methylcoumarin inhibits LPS-induced inflammatory response in RAW 264.7 macrophage cells

“…7H-4MC reduces the release of inflammatory mediators and pro-inflammatory cytokines PGE 2 , an important inflammatory mediator, is produced from arachidonic acid by COX-2. In a variety of inflammatory cells, including macrophages, COX-2 expression is induced by cytokines and other activators, such as LPS, which results in the release of a large amount of PGE 2 at inflammatory sites [18][19]. We examined the effects of 7H-4MC on PGE 2 production, which was quantified in the supernatants of LPS-induced RAW 264.7 macrophages.…”

“…7H-4MC suppresses LPS-induced degradation of IκB-α protein In the NF-κB signaling pathway, NF-κB binds to its inhibitor protein, IκB-α, and resides in the cytoplasm of unstimulated cells. Its activation is regulated by the degradation of IκB-α, which frees NF-κB and allows its translocation to the nucleus [18][19][20]. To better demonstrate the mechanisms involved in the inhibitory effect of 7H-4MC on the LPS-induced release of inflammatory mediators, the protein levels of IκB-α were examined by western blotting.…”

Sonlicromanol’s active metabolite KH176m normalizes prostate cancer stem cell mPGES-1 overexpression and inhibits cancer spheroid growth

“…Based on our previous work in fibroblasts and macrophage-like RAW264.7 cells, addition of exogenous PGE 2 reversed the effect of KH176m on mPGES-1 expression, suggesting a PGE 2 -driven positive feedback control of mPGES-1 transcriptional regulation, which was directly inhibited by KH176m [35]. We therefore hypothesized that also in the PCa cells inhibition of mPGES-1 expression and spheroid growth by KH176m will be restored by administration of exogenous PGE 2 .…”

“…Indeed, we found that the mPGES-1 protein and mRNA expression were significantly decreased by KH176m in DU145 derived spheroids while other key genes involved in PGE 2 synthesis remained unchanged. Our recent study in fibroblasts and macrophage-like RAW264.7 cells has revealed that the effect of KH176m on mPGES-1 expression is due to the inhibition of a PGE 2 -driven positive feedback controlloop of mPGES-1 transcriptional [35]. An effect of KH176m on PGE 2 production could, however, not be determined in the spheroid cultures because the amount of PGE 2 that was secreted during their growth was below the level of detection, despite the high level of mPGES-1 present in DU145 spheroids.…”

“…Elevated mPGES-1 is considered as an important factor in determining tumorigenic potential in PCa cells [3,38]. We have recently found that KH176m can reduce the expression of inflammation induced mPGES-1 levels [35]. To investigate the effect of KH176m on cells with high constitutive levels of mPGES-1 and to establish a cell model to study functional consequences of modulating PGE 2 levels, we employed human PCa cell lines with different levels of mPGES-1.…”