Crystal structures of monkey and mouse nicotinamide N-methyltransferase (NNMT) bound with end product, 1-methyl nicotinamide.

Nicotinamide N-methyltransferase (NNMT) is a S-adenosyl-l-methionine (SAM)-dependent enzyme that catalyzes N-methylation of nicotinamide (NA) and other pyridines to form N-methyl pyridinium ions. Here we report the first ternary complex X-ray crystal structures of monkey NNMT and mouse NNMT in bound form with the primary endogenous product, 1-methyl nicotinamide (MNA) and demethylated cofactor, S-adenosyl-homocysteine (SAH) determined at 2.30 Å and 1.88 Å respectively. The structural fold of these enzymes is identical to human NNMT. It is known that the primary endogenous product catalyzed by NNMT, MNA is a specific inhibitor of NNMT. Our data clearly indicates that the MNA binds to the active site and it would be trapped in the active site due to the formation of the bridge between the pole (long helix, α3) and long C-terminal loop. This might explain the mechanism of MNA acting as a feedback inhibitor of NNMT.

A New Series of Orally Bioavailable Chemokine Receptor 9 (CCR9) Antagonists; Possible Agents for the Treatment of Inflammatory Bowel Disease.

Chemokine receptor 9 (CCR9), a cell surface chemokine receptor which belongs to the G protein-coupled receptor, 7-trans-membrane superfamily, is expressed on lymphocytes in the circulation and is the key chemokine receptor that enables these cells to target the intestine. It has been proposed that CCR9 antagonism represents a means to prevent the aberrant immune response of inflammatory bowel disease in a localized and disease specific manner and one which is accessible to small molecule approaches. One possible reason why clinical studies with vercirnon, a prototype CCR9 antagonist, were not successful may be due to a relatively poor pharmacokinetic (PK) profile for the molecule. We wish to describe work aimed at producing new, orally active CCR9 antagonists based on the 1,3-dioxoisoindoline skeleton. This study led to a number of compounds that were potent in the nanomolar range and which, on optimization, resulted in several possible preclinical development candidates with excellent PK properties.

Lipopolysaccharide-induced paw edema model for detection of cytokine modulating anti-inflammatory agents.

Cytokines are critical to pathogenesis of inflammatory disorders. So inhibition of their action provides therapeutic benefits in various diseases. Although inhibition of inflammation caused by intraperitoneally administered LPS can identify cytokine modulators, this inflammatory test-agent does not allow one to determine overall anti-inflammatory potential. Functional characteristics of Carrageenan (Cara)-induced edema were valuable for identification of nonsteroidal anti-inflammatory drugs (NSAIDS). Hence, the potential of LPS-induced paw inflammation was investigated and compared to that by Cara. Stimulation of isolated rat peritoneal exudates cells (PEC) with 10 ng/ml LPS, but not Cara, induced IL-6 (3.04+/-0.2 ng/ml) and TNFalpha (1.030.09 ng/ml). At least 100 mg/ml Cara was necessary for detection of IL-6 (2.03+/-0.1 ng/ml) and TNFalpha (0.6+0.09 ng/ml) in PEC. Similar to Cara, subplantar administration of LPS-induced inflammatory paw edema in rats. LPS, but not Cara, induced TNFalpha (2.14+/-0.6 ng/ml) and IL-6 (2.9+/-0.5 ng/ml) in serum at 1 and 3 h, respectively, which returned to basal levels by 5 h. LPS-induced serum TNFalpha (sTNFalpha) levels closely paralleled paw swelling and its neutralization by anti-TNFalpha antibody or inhibition by pentoxifylline and nimesulide correlated with inhibition of inflammation. Similar to earlier reports, rofecoxib induced sTNFalpha at 30 mg/kg and exhibited pro-inflammatory effect by enhancing paw swelling. LPS-induced edema provides a useful functional model for identification of cytokine modulating anti-inflammatory agents.

PAT5A: a partial agonist of peroxisome proliferator-activated receptor gamma is a potent antidiabetic thiazolidinedione yet weakly adipogenic.

PAT5A [5-[4-[N-(2-pyridyl)-(2S)-pyrrolidine-2-methoxyl]phenylmethylene[thiazolidine-2,4-dione, malic acid salt]], a chemically distinct unsaturated thiazolidinedione, activates peroxisome proliferator-activated receptor gamma (PPARgamma) submaximally in vitro with the binding affinity approximately 10 times less than that of rosiglitazone, a highly potent thiazolidinedione. PAT5A reduces plasma glucose level and improves insulin sensitivity in insulin resistant db/db mice, similar to that of rosiglitazone, while exerting a relatively weak adipogenic effect. In contrast to rosiglitazone, PAT5A inhibits cholesterol and fatty acid biosynthesis suggesting that PAT5A possesses a unique receptor-independent non-PPAR related property. PAT5A induces qualitatively similar but quantitatively different protease digestion patterns and interacts with PPARgamma differently than rosiglitazone. PAT5A shows differential cofactor recruitment and gene activation than that of rosiglitazone. Thus, the partial agonism of PAT5A to PPARgamma together with its receptor independent effects may contribute to its antidiabetic potency similar to rosiglitazone in vivo despite reduced affinity for PPARgamma. These biological effects suggest that PAT5A is a PPARgamma modulator that activates some (insulin sensitization), but not all (adipogenesis), PPARgamma-signaling pathways.