Coumarin and Chromen-4-one Analogues as Tautomerase Inhibitors of Macrophage Migration Inhibitory Factor: Discovery and X-ray Crystallography

Abstract

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine released from T-cells and macrophages. Although a detailed understanding of the biological functions of MIF has not yet been clarified, it is known that MIF catalyzes the tautomerization of a nonphysiological molecule, D-dopachrome. Using a structure-based computer-assisted search of two databases of commercially available compounds, we have found 14 novel tautomerase inhibitors of MIF whose K(i) values are in the range of 0.038-7.4 microM. We also have determined the crystal structure of MIF complexed with the hit compound 1. It showed that the hit compound is located in the active site of MIF containing the N-terminal proline which plays an important role in the tautomerase reaction and forms several hydrogen bonds and undergoes hydrophobic interactions. A crystallographic study also revealed that there is a hydrophobic surface which consists of Pro-33, Tyr-36, Trp-108, and Phe-113 at the rim of the active site of MIF, and molecular modeling studies indicated that several more potent hit compounds have the aromatic rings which can interact with this hydrophobic surface. To our knowledge, our compounds are the most potent tautomerase inhibitors of MIF. One of these small, drug-like molecules has been cocrystallized with MIF and binds to the active site for tautomerase activity. Molecular modeling also suggests that the other hit compounds can bind in a similar fashion.

Identification of Iguratimod as an Inhibitor of Macrophage Migration Inhibitory Factor (MIF) with Steroid-sparing Potential

“…This site has been exploited for the design and high throughput screening of small molecule inhibitors with disease-modifying potential in multiple inflammatory states (31,(35)(36)(37)(38). Using the dopachrome tautomerase assay as a foundation, research groups have discovered multiple classes of reversible MIF inhibitors, including isoxazolines (27,36,39,40), pyrimidazoles (41), coumarin and chromene analogs (42,43), and aromatic amino acid Schiff bases (44). In addition, multiple individual compounds of interest have been identified; notable among these are the Land D-isomers of the metabolic hormone T 4 , the former of which may function as an endogenous ligand of MIF (45).…”

Phenolic Hydrazones Are Potent Inhibitors of Macrophage Migration Inhibitory Factor Proinflammatory Activity and Survival Improving Agents in Sepsis

“…It has been reported by us and other workers that the amino acids, Pro-33, Tyr-36, Phe-49, Trp-108, and Phe-113, make up the second hydrophobic surface at the rim of the active site of MIF. 10,14 These residues further contribute to the hydrophobic and hydrogen bond interactions between the pharmacophore and the active site of MIF. 14 In further support of these interactions, we have previously shown that the L-amino acid Schiff bases inhibitory effect was significantly improved by five fold upon changing the amino acid residue from L-phenylalanine (IC 50 = 50 μM) to L-tyrosine (IC 50 = 10 μM), respectively.…”

“…10,14 These residues further contribute to the hydrophobic and hydrogen bond interactions between the pharmacophore and the active site of MIF. 14 In further support of these interactions, we have previously shown that the L-amino acid Schiff bases inhibitory effect was significantly improved by five fold upon changing the amino acid residue from L-phenylalanine (IC 50 = 50 μM) to L-tyrosine (IC 50 = 10 μM), respectively. This suggests that the increased potency was attributed to a hydrogen bond interaction within residues at the rim of MIF.…”

“…10 Hydrazone 6 is twelve times more potent an inhibitor than Ltryptophan Schiff base 1, so far the most potent inhibitor of MIF described in the literature. 4,[10][11][12]14,15 Recently, we have discovered that mono-fluorination of 2 improved the inhibition of MIF activity. 11 As a consequence, we synthesized the 3-fluoro, 3-chloro, and 3-bromo-4-hydroxyphenyl derivatives of the more potent hydrazone, namely the p-methoxyphenyl hydrazone (6).…”

“…Notably, compound 7 exhibits the greatest activity of all the compounds tested and is so far the most potent inhibitor of MIF described in the literature. 4,[10][11][12]14,15 Compound 7 exhibited a potent anti-inflammatory activity in vitro as demonstrated by suppression of LPS-induced macrophage activation. Moreover, a relatively low concentration of this small molecule MIF inhibitor improved survival in sepsis when treatment was initiated at 24 hours after the onset of the disease.…”