gossypetin and morin

Death-associated protein kinase 1 (DAPK1) is a 160 kDa serine/threonine protein kinase that belongs to the Ca(2+)/calmodulin-dependent protein kinase subfamily. DAPK1 is a possible target for the treatment of acute ischemic stroke and endometrial adenocarcinomas. In the present study, we investigated the binding characteristics of 17 natural flavonoids to DAPK1 using a 1-anilinonaphthalene-8-sulfonic acid competitive binding assay and revealed that morin was the strongest binder among the selected compounds. The crystallographic analysis of DAPK1 and 7 selected flavonoid complexes revealed the structure-binding affinity relationship in atomic-level detail. It was suggested that the high affinity of morin could be accounted for by the ionic interaction between 2'-OH and K42 and that such an interaction would not take place with either cyclin-dependent protein kinases or PIM kinases because of their broader entrance regions. Thus, morin would be a more selective inhibitor of DAPK1 than either of these other types of kinases. In addition, we found that the binding of kaempferol to DAPK1 was associated with a chloride ion. The present study provides a better understanding of the molecular properties of the ATP site of DAPK1 and may be useful for the design of specific DAPK1 inhibitors.

Topics: Adenosine Triphosphate; Allosteric Site; Anilino Naphthalenesulfonates; Binding, Competitive; Crystallography, X-Ray; Death-Associated Protein Kinases; Flavonoids; Kaempferols; Protein Binding; Protein Conformation; Structure-Activity Relationship

Low density lipoproteins (LDL) can be oxidatively modified in vitro by macrophages and certain other cell types so that macrophages will take them up much faster. This process may be important in the formation of cholesterol-laden foam cells derived from macrophages in atherosclerotic lesions. In this study, we have shown that certain flavonoids, plant constituents found in the diet, are potent inhibitors of the modification of 125I-labelled LDL by macrophages, with IC50 values in the micromolar range (e.g. morin and fisetin 1 microM; quercetin and gossypetin 2 microM). The potencies of individual flavonoids in inhibiting LDL modification did not correlate with their previously determined potencies as inhibitors of 5-lipoxygenase and cyclo-oxygenase. The modification of LDL by macrophages exhibits a lag period of about 4-6 hr before enhanced uptake is detected. During this time, there is a rapid depletion in its content of alpha-tocopherol (an endogenous antioxidant found in lipoproteins) followed by a large increase in the level of hydroperoxides. The flavonoids conserved the alpha-tocopherol content of LDL and delayed the onset of detectable lipid peroxidation. Flavonoids also inhibited the cell-free oxidation of LDL mediated by CuSO4. These findings raise the possibility that flavonoids may protect LDL against oxidation in atherosclerotic lesions and may therefore be natural anti-atherosclerotic components of the diet, although this will depend to a large extent on their pharmacokinetics.

Topics: Copper; Flavonoids; Humans; Lipoproteins, LDL; Macrophages; Oxidation-Reduction; Quercetin; Time Factors