Scientists discover new inhibitors of inflammation-related enzyme

Using computational tools and virtual screening, researchers at the Center for Redox Processes in Biomedicine (Redoxoma) have identified new inhibitors of the enzyme human 15-lipoxygenase-2 (h15-LOX-2). This protein plays an important role in inflammatory and metabolic processes and contributes to cellular homeostasis.

The discovery, described in the Journal of Medicinal Chemistry, could open up new avenues for investigating the biological and pathological functions of the enzyme and provide promising candidates for the development of new drugs.

"Although h15-LOX-2 is a potential biological target, it's scarcely been explored for this purpose. Our work contributes to new inhibitors that have structural diversity among themselves and with respect to inhibitors already described in the literature. What's more, they have similar drug properties according to predictions based on computational models," says Lucas Gasparello Viviani, first author of the article.

The enzyme h15-LOX-2 belongs to the family of lipoxygenases (LOXs), enzymes that catalyze the oxidation of polyunsaturated fatty acids to form specific hydroperoxides. In humans, six LOX isoforms have specialized roles in different tissues, regulating processes such as inflammation, cell proliferation and regulation of the intracellular redox state. h15-LOX-2 is predominantly expressed in macrophages, skin, cornea, lung and prostate, where it catalyzes the conversion of arachidonic acid into a compound that significantly influences inflammatory and cellular responses.

"In the inflammatory cascade, h15-LOX-2 is one of the few enzymes capable of acting on complex lipids. It can oxidize membranes and cholesterol esters, whereas most lipoxygenases act on free fatty acids. We also chose to study this enzyme because of its particularities in terms of enzymatic activity," comments Miyamoto.

Experimental validation

Virtual screening is a technique that uses computational methods to select compounds with potential biological activity from large databases. In this study, the researchers started with a database of 8 million compounds that had been pre-filtered for drug-like properties, taking into account factors such as absorption, distribution, metabolism, excretion and toxicity. They then applied sequential filters based on different methodological approaches to simplify the process.

"A very important point of this work was the use of a filter based on molecular shape similarity as a first step, based on the idea that there's shape complementarity between a low molecular mass compound—such as the inhibitor—and its binding site on the target protein. One advantage of this method is that even compounds that share the same shape can have different structures.

"Since one of our goals was to select compounds that were structurally different from existing inhibitors, this step was fundamental to the success of our approach," explained Viviani.

The specific physiological roles of h15-LOX-2 are still under investigation. The enzyme is involved in the biosynthesis of inflammatory lipid mediators and in the formation of atherosclerotic plaques. Studies indicate that the expression of the enzyme is significantly higher in atherosclerotic lesions of the human carotid artery compared to healthy arteries. In addition, evidence suggests a possible link between h15-LOX-2 and the development of certain cancers.

Moreover, h15-LOX-2 and other LOX enzymes may be involved in ferroptosis, a form of iron-dependent cell death associated with lipid peroxidation. In this case, inhibition of the enzyme may be beneficial.

The enzyme may also be involved in the regulation of cellular senescence in epithelial cells and may play a role in cholesterol homeostasis in macrophages, as described in recent studies.

Next steps

The researchers now plan to propose structural modifications to the identified compounds in order to increase their inhibitory potency.

"Another goal is to improve some physicochemical properties, such as solubility in aqueous media, which could favor their pharmacokinetic properties," says Viviani.

Miyamoto stressed that more testing is needed, saying, "In addition to improving efficiency, the inhibitors need to be tested in cells and animal models to confirm that they reach the target enzyme and work as intended."