Covalent modification of cyclooxygenase-2 (COX-2) by 2-acetoxyphenyl alkyl sulfides, a new class of selective COX-2 inactivators.
All of the selective COX-2 inhibitors described to date inhibit the isoform by binding tightly but noncovalently at the substrate binding site. Recently, we reported the first account of selective covalent modification of COX-2 by a novel inactivator, 2-acetoxyphenyl hept-2-ynyl sulfide (70) (Science 1998, 280, 1268-1270). Compound 70 selectively inactivates COX-2 by acetylating the same serine residue that aspirin acetylates. This paper describes the extensive structure-activity relationship (SAR) studies on the initial lead compound 2-acetoxyphenyl methyl sulfide (36) that led to the discovery of 70. Extension of the S-alkyl chain in 36 with higher alkyl homologues led to significant increases in inhibitory potency. The heptyl chain in 2-acetoxyphenyl heptyl sulfide (46) was optimum for COX-2 inhibitory potency, and introduction of a triple bond in the heptyl chain (compound 70) led to further increments in potency and selectivity. The alkynyl analogues were more potent and selective COX-2 inhibitors than the corresponding alkyl homologues. Sulfides were more potent and selective COX-2 inhibitors than the corresponding sulfoxides or sulfones or other heteroatom-containing compounds. In addition to inhibiting purified COX-2, 36, 46, and 70 also inhibited COX-2 activity in murine macrophages. Analogue 36 which displayed moderate potency and selectivity against purified human COX-2 was a potent inhibitor of COX-2 activity in the mouse macrophages. Tryptic digestion and peptide mapping of COX-2 reacted with [1-14C-acetyl]-36 indicated that selective COX-2 inhibition by 36 also resulted in the acetylation of Ser516. That COX-2 inhibition by aspirin resulted from the acetylation of Ser516 was confirmed by tryptic digestion and peptide mapping of COX-2 labeled with [1-14C-acetyl]salicyclic acid. The efficacy of the sulfides in inhibiting COX-2 activity in inflammatory cells, our recent results on the selectivity of 70 in attenuating growth of COX-2-expressing colon cancer cells, and its selectivity for inhibition of COX-2 over COX-1 in vivo indicate that this novel class of covalent modifiers may serve as potential therapeutic agents in inflammatory and proliferative disorders.
Kalgutkar
A S
AS
A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry and Chemistry, Center in Molecular Toxicology and The Vanderbilt Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Kozak
K R
KR
Crews
B C
BC
Hochgesang
G P
GP
Marnett
L J
LJ
D000107:Acetylation; D000114:Acetylene / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D000480:Alkynes; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D003110:Colonic Neoplasms / Q000201:enzymology / Q000473:pathology; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D015232:Dinoprostone / Q000037:antagonists & inhibitors; D005122:Exudates and Transudates / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology; D008565:Membrane Proteins; D051379:Mice; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D051381:Rats; D012756:Sheep; D013329:Structure-Activity Relationship; D013440:Sulfides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D013929:Thromboxane B2 / Q000097:blood; D014407:Tumor Cells, Cultured
D000480:Alkynes; D000894:Anti-Inflammatory Agents, Non-Steroidal; D000970:Antineoplastic Agents; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; D013440:Sulfides; C112390:o-(acetoxyphenyl)hept-2-ynyl sulfide; D013929:Thromboxane B2; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone; D000114:Acetylene