Is it true that PDE inhibitors "block the inhibition of cAMP"? I thought PDE has to do with the inositol business instead. AxelBoldt 09:16 Sep 3, 2002 (PDT)
Luteolin is a PDE-4 inhibitor:
Eur J Pharmacol. 2009 Oct 22. [Epub ahead of print] Luteolin, a non-selective competitive inhibitor of phosphodiesterases 1-5, displaced [(3)H]-rolipram from high-affinity rolipram binding sites and reversed xylazine/ketamine-induced anesthesia. Yu MC, Chen JH, Lai CY, Han CY, Ko WC.
Department of Internal Medicine, Taipei Municipal Wan-Fang Hospital, Taiwan. The aim of the present study was to investigate the mode of action of luteolin on phisphodiesterase (PDE) 1-5, and the possible adverse effects, such as nausea, vomiting, and gastric hypersecretion, determined by replacing [(3)H]-rolipram binding and reversing xylazine/ketamine-induced anesthesia. The reversing effect was reported to occur through a presynaptic alpha(2)-adrenoceptor inhibition and trigger vomiting in ferrets. In contrast, clonidine, an alpha(2)-adrenoceptor agonist, prevented emesis induced by PDE4 inhibitors in ferrets. According to the Lineweaver-Burk analysis, luteolin (3-30muM) competitively inhibited PDE1-5 activities, with K(i) values of 15.0, 6.4, 13.9, 11.1, and 9.5muM, respectively, which did not significantly differ from each other. The equilibrium dissociation constant (K(d)) and maximal density (B(max)) for [(3)H]-rolipram binding at high-affinity rolipram binding sites of guinea pig brain cell membranes were 10.1nM and 3.7pmol/g of tissue, respectively. The EC(50) (PDE4(H)) values of luteolin and Ro 20-1724, a selective PDE4 inhibitor, for displacing 2nM [(3)H]-rolipram binding were 11.2muM and 45.6nM, respectively. The therapeutic (PDE4(H)/PDE4(L)) ratios of luteolin and Ro 20-1724 were calculated to be 0.6, and 0.004, respectively. Both luteolin (10-30mumol/kg, s.c.) and Ro 20-1724 (0.1-1mumol/kg, s.c.) significantly reversed the xylazine/ketamine-induced anesthesia in mice. Although luteolin non-selectively and competitively inhibited PDE1-5, only PDE4 inhibition contributed to a reversing effect. In conclusion, because of the low therapeutic (PDE4(H)/PDE4(L)) ratio of luteolin, the gastrointestinal adverse effects such as nausea, vomiting and gastric hypersecretion should be carefully monitored, whenever luteolin is used for treating allergies, asthma or chronic obstructive pulmonary disease.