ABSTRACT
Several trypanosomatid cyclic nucleotide phosphodiesterases (PDEs) possess a unique, parasite-specific cavity near the ligand-binding region that is referred to as the P-pocket. One of these enzymes, Trypanosoma brucei PDE B1 (TbrPDEB1), is considered a drug target for the treatment of African sleeping sickness. Here, we elucidate the molecular determinants of inhibitor binding and reveal that the P-pocket is amenable to directed design. By iterative cycles of design, synthesis, and pharmacological evaluation and by elucidating the structures of inhibitor-bound TbrPDEB1, hPDE4B, and hPDE4D complexes, we have developed 4a,5,8,8a-tetrahydrophthalazinones as the first selective TbrPDEB1 inhibitor series. Two of these, 8 (NPD-008) and 9 (NPD-039), were potent ( Ki = 100 nM) TbrPDEB1 inhibitors with antitrypanosomal effects (IC50 = 5.5 and 6.7 µM, respectively). Treatment of parasites with 8 caused an increase in intracellular cyclic adenosine monophosphate (cAMP) levels and severe disruption of T. brucei cellular organization, chemically validating trypanosomal PDEs as therapeutic targets in trypanosomiasis.
Subject(s)
3',5'-Cyclic-AMP Phosphodiesterases/antagonists & inhibitors , Phosphodiesterase Inhibitors/chemistry , Phosphodiesterase Inhibitors/pharmacology , Protozoan Proteins/antagonists & inhibitors , Trypanocidal Agents/chemistry , Trypanocidal Agents/pharmacology , Trypanosoma brucei brucei/drug effects , Trypanosoma brucei brucei/enzymology , 3',5'-Cyclic-AMP Phosphodiesterases/chemistry , Amides/chemistry , Amides/pharmacology , Catalytic Domain , Inhibitory Concentration 50 , Models, Molecular , Molecular Targeted Therapy , Protozoan Proteins/chemistry , Structure-Activity RelationshipABSTRACT
OBJECTIVE: To investigate the level of expression of the cytokines interleukin (IL) -8 and IL-6 and their receptors in fallopian tubes with tubal ectopic gestation. DESIGN: Immunohistochemistry (IHC) was used to study the expression of IL-8, CXCR1, CXCR2, IL-6, and IL-6 receptor alpha in fallopian tubes with tubal ectopic gestation in comparison with normal fallopian tubes. SETTING: Hospital. PATIENT(S): We studied fallopian tubes from 50 patients with tubal ectopic gestation and normal fallopian tubes from 25 patients who had hysterectomy and bilateral salpingo-oopherectomy for uterine or ovarian lesions. INTERVENTION(S): The expression of the chemokines/cytokines and their receptors was evaluated by IHC. MAIN OUTCOME MEASURE(S): Level of expression and tissue distribution of the different antigens. RESULT(S): IHC results showed that the expression levels of IL-6 and IL-8, as well as CXCR1, were significantly up-regulated, particularly near the implantation site in fallopian tubes with tubal gestation, while the expression levels of CXCR2 and IL-6Rα were not changed in comparison with normal fallopian tubes. CONCLUSION(S): The results suggest a role for IL-6, IL-8, and CXCR1 in the pathophysiology of tubal ectopic gestation.
