Synthesis and Mechanistic Studies of a Novel Homoisoflavanone Inhibitor of Endothelial Cell Growth

Abstract

Preventing pathological ocular angiogenesis is key to treating retinopathy of prematurity, diabetic retinopathy and age-related macular degeneration. At present there is no small molecule drug on the market to target this process and hence there is a pressing need for developing novel small molecules that can replace or complement the present surgical and biologic therapies for these neovascular eye diseases. Previously, an antiangiogenic homoisoflavanone was isolated from the bulb of a medicinal orchid, Cremastra appendiculata. In this study, we present the synthesis of a novel homoisoflavanone isomer of this compound. Our compound, SH-11052, has antiproliferative activity against human umbilical vein endothelial cells, and also against more ocular disease-relevant human retinal microvascular endothelial cells (HRECs). Tube formation and cell cycle progression of HRECs were inhibited by SH-11052, but the compound did not induce apoptosis at effective concentrations. SH-11052 also decreased TNF-α induced p38 MAPK phosphorylation in these cells. Intriguingly, SH-11052 blocked TNF-α induced IκB-α degradation, and therefore decreased NF-κB nuclear translocation. It decreased the expression of NF-κB target genes and the pro-angiogenic or pro-inflammatory markers VCAM-1, CCL2, IL8, and PTGS2. In addition SH-11052 inhibited VEGF induced activation of Akt but not VEGF receptor autophosphorylation. Based on these results we propose that SH-11052 inhibits inflammation induced angiogenesis by blocking both TNF-α and VEGF mediated pathways, two major pathways involved in pathological angiogenesis. Synthesis of this novel homoisoflavanone opens the door to structure-activity relationship studies of this class of compound and further evaluation of its mechanism and potential to complement existing antiangiogenic drugs.

Synthesis and Biological Evaluation of Novel Homoisoflavonoids for Retinal Neovascularization

“…Finally, it blocks nuclear translocation of NF-κB and production of inflammatory cytokines. 7, 16 The search for direct molecular targets is underway. However, since its exact mechanism of action remains unknown, a cell-based analysis of efficacy is the most appropriate route to developing novel derivatives.…”

The first synthesis of the antiangiogenic homoisoflavanone, cremastranone

“…During our previous synthetic approach toward cremastranone, the regioisomer (SH-11052, 2 ) was generated due to the challenge of selective deprotection of methyl phenyl ethers. 18 Herein, we describe a short and efficient synthesis of cremastranone ( 1 ) featuring a solution to the issue of selective deprotection of the methyl phenyl ether. Moreover, we show for the first time that synthetic cremastranone has biological properties consistent with the natural-source compound, in a disease relevant cell model.…”

Design, synthesis and biological evaluation of photoaffinity probes of antiangiogenic homoisoflavonoids

“…25–28 It inhibits ocular angiogenesis, without substantial toxicity, in mouse models of laser-induced choroidal neovascularization (L-CNV) and oxygen-induced retinopathy (OIR). These animal models recapitulate features of the blinding eye diseases wet age-related macular degeneration and retinopathy of prematurity, respectively.…”

“…30, 31 Finally, it blocks nuclear translocation of NF-κB and production of inflammatory cytokines. 25, 31, 32 Seeking more potent and selective compounds than cremastranone, we identified SH-11037 which is observed to have novel antiangiogenic activity against human retinal microvascular endothelial cells (HRECs) and blocks neovascularization in the OIR and L-CNV models. 27, 33 Although the studies of mechanisms and medicinal chemistry could contribute to many therapeutic facets of the antiangiogenic homoisoflavonoids, their exact mechanisms of action and cellular targets remain unknown, so the search for direct interacting proteins is valuable.…”

“…25–27 The phenolic OH on the C-3′ position was alkylated with tert -butyl bromoacetate under basic conditions, followed by the acidic treatment of the ester 12 to afford the carboxylic acid 13 . Finally, the carboxylic acid 13 was coupled with the intermediate 10 by HBTU-mediated amidation to provide the desired photoaffinity probe 3 in moderate yield.…”