Iijima, T. S. | Search bioRxiv

bioRxiv2024

Comparative study of Ergosterol and 7-dehydrocholesterol and their Endoperoxides: Generation, Identification and Impact in Phospholipid Membranes and Melanoma Cells

Melanoma is an aggressive cancer that has attracted attention in recent years due to its high mortality rate of 80%. Damage caused by oxidative stress generated by radical (type I reaction) and singlet oxygen, 1O2 (type II reaction) oxidative reactions may induce cancer. Thus, studies that aim to unveil the mechanism that drives these oxidative damage processes become relevant. Ergosterol, an analogue of 7-dehydrocholesterol, important in the structure of cell membranes, is widely explored in cancer treatment. However, to date little is known about the impact of different oxidative reactions on these sterols in melanoma treatment, and conflicting results about their effectiveness complicates the understanding of their role in oxidative damage. Our results highlight differences among ergosterol, 7-dehydrocholesterol (7-DHC) and cholesterol in membrane properties when subjected to distinct oxidative reactions. Furthermore, we conducted a comparative study exploring the mechanisms of cell damage by photodynamic treatment in A375 melanoma. Notably, endoperoxides from ergosterol and 7-DHC generated by 1O2 showed superior efficacy in reducing the viability of A375 cells compared to their precursor molecules. We also describe a step-by-step process to produce and identify endoperoxides derived from ergosterol and 7-DHC. While further studies are needed, this work provides new insights for understanding cancer cell death induced by different oxidative reactions in the presence of biologically relevant sterols.

biochemistry↗

bioRxiv2024

Identification of novel human 15-lipoxygenase-2 (h15-LOX-2) inhibitors using a virtual screening approach

The human 15-lipoxygenase-2 (h15-LOX-2) is a non-heme iron-containing enzyme that catalyzes the regio- and stereospecific oxygenation of polyunsaturated fatty acids, mainly arachidonic acid, and is implicated in the biosynthesis of pro- and anti-inflammatory lipid mediators. The biological roles of h15-LOX-2 have not been completely unveiled, but it has been suggested that high expression levels of h15-LOX-2 are related to the pathogenesis of atherosclerosis and of some types of cancer. Inhibitors of h15-LOX-2 might be helpful for a deeper understanding of its roles in physiological and pathophysiological processes, in addition to representing potential drug candidates for treating human diseases. Nevertheless, only a few h15-LOX-2 inhibitors have been reported in the literature to date. Here, aiming to search for novel h15-LOX-2 inhibitors, we used a virtual screening (VS) approach, consisting of four consecutive filters (shape-based matching, 2D structural "dissimilarity", docking, and careful visual inspection), which were applied to a "curated" version of the ZINC database, pre-filtered for potential drug-like compounds. Six novel h15- LOX-2 inhibitors, with inhibitory potencies in the micromolar range, were identified. Ki values were determined for two inhibitors, compounds 10 [Ki = (16.4 {+/-} 8.1) M] and 13 [Ki = (15.1 {+/-} 7.6) M], which showed a mixed-type mechanism of inhibition. According to docking predictions, the identified inhibitors occupy the more solvent-exposed arm of the U-shaped h15-LOX-2 active sites cavity, possibly blocking the access of the substrate to the active site. The identified inhibitors are structurally different from the few h15-LOX-2 inhibitors reported in the literature, in addition to fulfilling drug-like criteria. Overall, our results provide a valuable contribution to the search for novel inhibitors of h15-LOX-2, a so-far underexploited target enzyme.

biochemistry↗