Ligand-based Modeling for the Prediction of Pharmacophore Features for Multi-targeted Inhibition of the Arachidonic Acid Cascade.

The single-target drugs against the arachidonic acid inflammatory pathway are associated with serious side effects, hence, as a first step towards multi-target drugs, we have studied the pharmacophoric features common to the inhibitors of 5-lipoxygenase-activating protein (FLAP), microsomal prostaglandin E-synthase 1 (mPGES-1) and leukotriene A4 hydrolase (LTA4H). FLAP and mPGES-1 shared subfamily-specific positions (SSPs) and four mPGES-1 inhibitors binding to them mapped onto the pharmacophore derived from FLAP inhibitors (Ph-FLAP). The reactions of mPGES-1 and LTA4H had high structural similarity. The pharmacophore derived from two substrate mimic inhibitors of LTA4H (Ph-LTA4H) also mapped onto three mPGES-1 inhibitors. Screening of in-house database for Ph-FLAP and Ph-LTA4H identified one compound, C1. It inhibited the production of the mPGES-1 product, prostaglandin E2 (PGE2) by 97.8±1.6 % at 50 µM in HeLa cells and can be a starting point for designing molecules inhibiting all three targets simultaneously.

Phytochemicals as multi-target inhibitors of the inflammatory pathway- A modeling and experimental study.

The arachidonic acid pathway consists of several enzymes and targeting them is favored for developing anti-inflammatory drugs. However, till date the current drugs are generally active against a single target, leading to undesirable side-effects. Phytochemicals are known to inhibit multiple targets simultaneously and hence, an attempt is made here to investigate their suitability. A pharmacophore based study is performed with three sets of reported phytochemicals namely, dual 5-LOX/mPGES1, alkaloids and FLAP inhibitors. The analysis indicated that phenylpropanoids (including ferulic acid) and benzoic acids derivatives, and berberine mapped onto these pharmacophores with three hydrophobic centroids and an acceptor feature. 2,4,5-trimethoxy (7) and 3,4-dimethoxy cinnamic acids (8) mapped onto all the three pharmacophores. Experimental studies indicated that berberine inhibited 5-LOX (100 µM) and PGE2 (50 µM) production by 72.2 and 72.0% and ferulic acid by 74.3 and 54.4% respectively. This approach offers a promising theoretical combined with experimental strategy for designing novel molecules against inflammatory enzymes.

Transcriptional Regulation of mPGES1 in Cancer: An Alternative Approach to Drug Discovery?

Prostaglandins serve as the connecting link between inflammation and cancer. mPGES1, the downstream enzyme in the prostaglandin pathway is considered a better target than COX-2 against the progression of cancer due to the cardiovascular and other complications associated with the inhibition of the latter. Despite the discovery of several compounds that inhibit mPGES1 none could enter the market as drugs because of the problems concerning specificity and unacceptable pharmacokinetic properties. Expression of mPGES1 is inducible in conditions of inflammation and hypoxia and its expression is regulated by a number of transcriptional factors. Targeting these transcription factors could be an alternative approach in the drug discovery process. In this review, the characteristics of the transcription factors, their ability to bind to the promoter of mPGES1 gene and the inhibitors against them have been discussed. The Structure Activity Relationship of the reported inhibitors is highlighted. Finally, practical challenges to further the drug development and future research directions are discussed. These novel compounds that are inhibitors of the major transcription factors are promising candidates for further development as inhibitors of mPGES1.

Inhibition of the enzymes in the leukotriene and prostaglandin pathways in inflammation by 3-aryl isocoumarins.

The biosynthesis of leukotrienes in one of the arachidonic acid pathways and PGE2 in the other by 5-LOX and mPGES1 respectively, play pivotal roles in augmenting inflammatory responses. PGE2 is known to participate in cancer pathological processes as well. Isocoumarins are natural compounds with a wide range of biological activities. In this study, 3-aryl isocoumarin derivatives are synthesized and tested against 5-LOX enzyme in vitro and PGE2 production in HeLa cells. Most of the compounds show high activity, and 1c is identified as a dual inhibitor with an IC50 of 4.6 ± 0.26 µM and 6.3 ± 0.13 µM against 5-LOX and PGE2 production respectively. Another compound 7f, exhibits an IC50 of 12.4 ± 0.14 µM against 5-LOX. Further investigations reveal that the mechanism of action of 1c and 7f against 5-LOX is mixed and competitive modes of action respectively. Thunberginol A (7c) exhibits IC50 of 15.8 ± 0.03 µM against PGE2 production. 1c and 7c inhibit the mRNA expression of mPGES1 and COX-2. The study has identified a novel scaffold, 1c with a dual inhibitory activity which can be further optimized to compete against Licofelone which is under clinical trials (with IC50 of 6.0 µM for mPGES1 & 0.2 µM for 5-LOX). To conclude, 3-aryl isocoumarin derivatives appears as promising tools to fight against inflammatory diseases as well as cancer.

Central role for PELP1 in nonandrogenic activation of the androgen receptor in prostate cancer.

The ability of 17ß-estradiol (E2) to regulate the proliferation of prostate cancer (PCa) cells in the absence of androgen is poorly understood. Here, we show the predominant estrogen receptor (ER) isoform expressed in PCa specimens and cell lines is ERß. Our data indicate that E2 induces the formation of a complex between androgen receptor (AR), ERß, and a proline-, glutamic acid-, and leucine-rich cofactor protein 1 (PELP1) in PCa cells. This protein complex is formed on AR's cognate DNA-responsive elements on the promoter in response to E2. Formation of this complex enables the transcription of AR-responsive genes in response to E2. Knockdown of PELP1, AR, or ERß blocks the assembly of this complex, blocks E2-induced genomic activation of AR-regulated genes, and blocks E2-stimulated proliferation of PCa cells. Overall, this study shows that PELP1 may enable E2-induced AR signaling by forming a protein complex between AR, ERß, and PELP1 on the DNA, leading to the proliferation of PCa cells in the absence of androgen. PELP1 may bridge the signal between E2 bound to ERß and AR and thus allow for cross talk between these steroid receptors. These data suggest a novel mechanism of AR activation in the absence of androgens in PCa cells. Our data indicate that disruption of the complex between AR and PELP1 may be a viable therapeutic strategy in advanced PCa.