1,4-Benzoquinones are well-known inhibitors of 5-lipoxygenase (5-LO, the key enzyme in leukotriene biosynthesis), but the molecular mechanisms of 5-LO inhibition is incompletely understood. Here we investigated the molecular mode of action and the pharmacological profile of the novel 1,4-benzoquinone derivative 3-((decahydronaphthalen-6-yl)methyl)-2,5-dihydroxycyclohexa-2,5-diene-1,4-dione ... [Show full abstract] (RF-Id) in vitro and its effectiveness in vivo.
Mechanistic investigations in cell-free assays using 5-LO and related enzymes within eicosanoid biosynthesis, and cell-based studies in human leukocytes and whole blood were conducted. Molecular docking of RF-Id into the 5-LO structure was performed to illustrate the molecular interference with 5-LO. The in vivo effectiveness of RF-Id was evaluated in two murine models of inflammation.
RF-Id consistently suppressed 5-LO product synthesis in human leukocytes and human whole blood (IC50 = 0.58 - 4.1 μM). RF-Id also blocked cyclooxygenase (COX)-2 activity (IC50 = 7.3 μM) but did not significantly inhibit COX-1, microsomal prostaglandin E2 synthase-1, cytosolic phospholipase A2 , or 12- and 15-LO. Although RF-Id lacks radical scavenging activity, reducing conditions govern 5-LO inhibition while cell stress impairs the efficiency. The reduced hydroquinone form of RF-Id (RED-RF-Id) allows for more bidirectional hydrogen bonds within the 5-LO substrate binding site and is more potent against 5-LO. Finally, RF-Id (0.1-1 mg kg(-1) , i.p.) caused marked anti-inflammatory activity in mice.
RF-Id represents a novel anti-inflammatory 1,4-benzoquinone that potently suppresses leukotriene biosynthesis by direct inhibition of 5-LO with effectiveness in vivo. Mechanistically, RF-Id inhibits 5-LO in nonredox fashion by discrete molecular interactions within the 5-LO active site.