Sulindac sulfide suppresses 5-lipoxygenase at clinically relevant concentrations.

Sulindac is a non-selective inhibitor of cyclooxygenases (COX) used to treat inflammation and pain. Additionally, non-COX targets may account for the drug's chemo-preventive efficacy against colorectal cancer and reduced gastrointestinal toxicity. Here, we demonstrate that the pharmacologically active metabolite of sulindac, sulindac sulfide (SSi), targets 5-lipoxygenase (5-LO), the key enzyme in the biosynthesis of proinflammatory leukotrienes (LTs). SSi inhibited 5-LO in ionophore A23187- and LPS/fMLP-stimulated human polymorphonuclear leukocytes (IC(50) approximately 8-10 microM). Importantly, SSi efficiently suppressed 5-LO in human whole blood at clinically relevant plasma levels (IC(50) = 18.7 microM). SSi was 5-LO-selective as no inhibition of related lipoxygenases (12-LO, 15-LO) was observed. The sulindac prodrug and the other metabolite, sulindac sulfone (SSo), failed to inhibit 5-LO. Mechanistic analysis demonstrated that SSi directly suppresses 5-LO with an IC(50) of 20 muM. Together, these findings may provide a novel molecular basis to explain the COX-independent pharmacological effects of sulindac under therapy.

Licofelone suppresses prostaglandin E2 formation by interference with the inducible microsomal prostaglandin E2 synthase-1.

The anti-inflammatory drug licofelone [=ML3000; 2-[6-(4-chlorophenyl)-2,2-dimethyl-7-phenyl-2,3-dihydro-1H-pyrrolizin-5-yl] acetic acid], currently undergoing phase III trials for osteoarthritis, inhibits the prostaglandin (PG) and leukotriene biosynthetic pathway. Licofelone was reported to suppress the formation of PGE(2) in various cell-based test systems, but the underlying molecular mechanisms are not entirely clear. Here, we examined the direct interference of licofelone with enzymes participating in PGE(2) biosynthesis, that is, cyclooxygenase (COX)-1 and COX-2 as well as microsomal PGE(2) synthase (mPGES)-1. Licofelone concentration-dependently inhibited isolated COX-1 (IC(50) = 0.8 microM), whereas isolated COX-2 was less affected (IC(50) > 30 microM). However, licofelone efficiently blocked the conversion of PGH(2) to PGE(2) mediated by mPGES-1 (IC(50) = 6 microM) derived from microsomes of interleukin-1beta-treated A549 cells, being about equipotent to 3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-dimethylpropanoic acid (MK-886), a well recognized mPGES-1 inhibitor. In intact interleukin-1beta-treated A549 cells, licofelone potently (IC(50) < 1 microM) blocked formation of PGE(2) in response to calcimycin (A23187) plus exogenous arachidonic acid, but the concomitant generation of 6-keto PGF(1alpha), used as a biomarker for COX-2 activity, was not inhibited. We conclude that licofelone suppresses inflammatory PGE(2) formation preferentially by inhibiting mPGES-1 at concentrations that do not affect COX-2, implying an attractive and thus far unique molecular pharmacological dynamics as inhibitor of COX-1, the 5-lipoxygenase pathway, and of mPGES-1.

Structural optimization and biological evaluation of 2-substituted 5-hydroxyindole-3-carboxylates as potent inhibitors of human 5-lipoxygenase.

Pharmacological suppression of leukotriene biosynthesis by inhibitors of 5-lipoxygenase (5-LO) is a strategy to intervene with inflammatory and allergic disorders. We recently presented 2-amino-5-hydroxy-1H-indoles as efficient 5-LO inhibitors in cell-based and cell-free assays. Structural optimization led to novel benzo[g]indole-3-carboxylates exemplified by ethyl 2-(3-chlorobenzyl)-5-hydroxy-1H-benzo[g]indole-3-carboxylate (compound 11a), which inhibits 5-LO activity in human neutrophils and recombinant human 5-LO with IC(50) values of 0.23 and 0.086 microM, respectively. Notably, 11a efficiently blocks 5-LO product formation in human whole blood assays (IC(50) = 0.83-1.6 microM) and significantly prevented leukotriene B(4) production in pleural exudates of carrageenan-treated rats, associated with reduced severity of pleurisy. Together, on the basis of their high potency against 5-LO and the marked efficacy in biological systems, these novel and straightforward benzo[g]indole-3-carboxylates may have potential as anti-inflammatory therapeutics.