Inhibitory Investigations of Acyl-CoA Derivatives against Human Lipoxygenase Isozymes

Abstract

Lipid metabolism is a complex process crucial for energy production resulting in high levels of acyl-coenzyme A (acyl-CoA) molecules in the cell. Acyl-CoAs have also been implicated in inflammation, which could be possibly linked to lipoxygenase (LOX) biochemistry by the observation that an acyl-CoA was bound to human platelet 12-lipoxygenase via cryo-EM. Given that LOX isozymes play a pivotal role in inflammation, a more thorough investigation of the inhibitory effects of acyl-CoAs on lipoxygenase isozymes was judged to be warranted. Subsequently, it was determined that C18 acyl-CoA derivatives were the most potent against h12-LOX, human reticulocyte 15-LOX-1 (h15-LOX-1), and human endothelial 15-LOX-2 (h15-LOX-2), while C16 acyl-CoAs were more potent against human 5-LOX. Specifically, oleoyl-CoA (18:1) was most potent against h12-LOX (IC50 = 32 μM) and h15-LOX-2 (IC50 = 0.62 μM), stearoyl-CoA against h15-LOX-1 (IC50 = 4.2 μM), and palmitoleoyl-CoA against h5-LOX (IC50 = 2.0 μM). The inhibition of h15-LOX-2 by oleoyl-CoA was further determined to be allosteric inhibition with a Ki of 82 +/− 70 nM, an α of 3.2 +/− 1, a β of 0.30 +/− 0.07, and a β/α = 0.09. Interestingly, linoleoyl-CoA (18:2) was a weak inhibitor against h5-LOX, h12-LOX, and h15-LOX-1 but a rapid substrate for h15-LOX-1, with comparable kinetic rates to free linoleic acid (kcat = 7.5 +/− 0.4 s−1, kcat/KM = 0.62 +/− 0.1 µM−1s−1). Additionally, it was determined that methylated fatty acids were not substrates but rather weak inhibitors. These findings imply a greater role for acyl-CoAs in the regulation of LOX activity in the cell, either through inhibition of novel oxylipin species or as a novel source of oxylipin-CoAs.

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

“…8 Nevertheless, only a few h15-LOX-2 inhibitors have been reported in the literature so far. 6,8,[27][28][29][30][31] Among them, nordihydroguaiaretic acid (NDGA) and some flavonoid-based compounds have been described as moderately potent and non-selective inhibitors that act by reducing the active site's catalytic iron. 28 More recently, a series of low-micromolar h15-LOX-2 inhibitors that display some selectivity against other LOXs and cyclooxygenases (COXs) have also been reported.…”

“…Six novel h15-LOX-2 inhibitors, with inhibitory potencies in the micromolar range, were identified through in vitro enzyme inhibition assays for VS experimental validation. The identified inhibitors are structurally diverse from the h15-LOX-2 inhibitors reported in the literature so far, 6,8,[27][28][29][30][31] show drug-like properties, and were predicted to interact with the more solvent-accessible arm of the U-shaped active site cavity.…”