title: Selective inhibition of cyclooxygenase-2 by C-phycocyanin, a biliprotein from Spirulina platensis.
abstract: We report data from two related assay systems (isolated enzyme assays and whole blood assays) that C-phycocyanin a biliprotein from Spirulina platensis is a selective inhibitor of cyclooxygenase-2 (COX-2) with a very low IC(50) COX-2/IC(50) COX-1 ratio (0.04). The extent of inhibition depends on the period of preincubation of phycocyanin with COX-2, but without any effect on the period of preincubation with COX-1. The IC(50) value obtained for the inhibition of COX-2 by phycocyanin is much lower (180 nM) as compared to those of celecoxib (255 nM) and rofecoxib (401 nM), the well-known selective COX-2 inhibitors. In the human whole blood assay, phycocyanin very efficiently inhibited COX-2 with an IC(50) value of 80 nM. Reduced phycocyanin and phycocyanobilin, the chromophore of phycocyanin are poor inhibitors of COX-2 without COX-2 selectivity. This suggests that apoprotein in phycocyanin plays a key role in the selective inhibition of COX-2. The present study points out that the hepatoprotective, anti-inflammatory, and anti-arthritic properties of phycocyanin reported in the literature may be due, in part, to its selective COX-2 inhibitory property, although its ability to efficiently scavenge free radicals and effectively inhibit lipid peroxidation may also be involved.
authors.affiliation: Department of Organic Chemistry, Indian Institute of Science, Bangalore, 560 012, India.
authors.forename: C M
authors.initials: CM
authors.lastname: Reddy
authors.forename: V B
authors.initials: VB
authors.lastname: Bhat
authors.forename: G
authors.initials: G
authors.lastname: Kiranmai
authors.forename: M N
authors.initials: MN
authors.lastname: Reddy
authors.forename: P
authors.initials: P
authors.lastname: Reddanna
authors.forename: K M
authors.initials: KM
authors.lastname: Madyastha
mesh_terms: D000818:Animals; D000068579:Celecoxib; D000458:Cyanobacteria / Q000737:chemistry*; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D019476:Insect Proteins / Q000378:metabolism; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007783:Lactones / Q000494:pharmacology; D008565:Membrane Proteins; D008861:Microsomes / Q000378:metabolism; D010798:Phycocyanin / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011720:Pyrazoles; D012756:Sheep; D013449:Sulfonamides / Q000494:pharmacology; D013450:Sulfones
chemical_list: C116940:Blue biliprotein, Manduca sexta; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D019476:Insect Proteins; D007527:Isoenzymes; D007783:Lactones; D008565:Membrane Proteins; D011720:Pyrazoles; D013449:Sulfonamides; D013450:Sulfones; C116926:rofecoxib; D010798:Phycocyanin; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D000068579:Celecoxib