Vishal M. Balaramnavar

Drug/drug interaction of common NSAIDs with antiplatelet effect of aspirin in human platelets

Nonsteroidal anti-inflammatory drugs (NSAIDs) may interfere with the anti-platelet activity of aspirin at the level of the platelet cyclooxygenase-1 (COX-1) enzyme. In order to examine the interference of common NSAIDs with the anti-platelet activity of aspirin the human platelet rich plasma from voluntary donors was used for arachidonic acid-induced aggregation and determination of thromboxane synthesis. Further, docking studies were used to explain the molecular basis of the NSAID/aspirin interaction. The experimental results showed that celecoxib, dipyrone (active metabolite), ibuprofen, flufenamic acid, naproxen, nimesulide, oxaprozin, and piroxicam significantly interfere with the anti-platelet activity of aspirin, while diclofenac, ketorolac and acetaminophen do not. Docking studies suggested that NSAIDs forming hydrogen bonds with Ser530, Arg120, Tyr385 and other amino acids of the COX-1 hydrophobic channel interfere with antiplatelet activity of aspirin while non interfering NSAIDs do not form relevant hydrogen bond interactions within the aspirin binding site. In conclusion, docking analysis of NSAID interactions at the COX-1 active site appears useful to predict their interference with the anti-platelet activity of aspirin. The results, demonstrate that some NSAIDs do not interfere with the antiplatelet action of aspirin while many others do and provide a basis for understanding the observed differences among individual non-aspirin NSAIDs.

Rohitukine inhibits in vitro adipogenesis arresting mitotic clonal expansion and improves dyslipidemia in vivo

We developed a common feature pharmacophore model using known antiadipogenic compounds (CFPMA). We identified rohitukine, a reported chromone anticancer alkaloid as a potential hit through in silico mapping of the in-house natural product library on CFPMA. Studies were designed to assess the antiadipogenic potential of rohitukine. Rohitukine was isolated from Dysoxylum binacteriferum Hook. to ⬧95% purity. As predicted by CFPMA, rohitukine was indeed found to be an antiadipogenic molecule. Rohitukine inhibited lipid accumulation and adipogenic differentiation in a concentration- and exposure-time-dependent manner in 3T3-L1 and C3H10T1/2 cells. Rohitukine downregulated expression of PPARγ, CCAAT/enhancer binding protein α, adipocyte protein 2 (aP2), FAS, and glucose transporter 4. It also suppressed mRNA expression of LPL, sterol-regulatory element binding protein (SREBP) 1c, FAS, and aP2, the downstream targets of PPARγ. Rohitukine arrests cells in S phase during mitotic clonal expansion. Rohitukine was bioavailable, and 25.7% of orally administered compound reached systemic circulation. We evaluated the effect of rohitukine on dyslipidemia induced by high-fat diet in the hamster model. Rohitukine increased hepatic expression of liver X receptor α and decreased expression of SREBP-2 and associated targets. Rohitukine decreased hepatic and gonadal lipid accumulation and ameliorated dyslipidemia significantly. In summary, our strategy to identify a novel antiadipogenic molecule using CFPMA successfully resulted in identification of rohitukine, which confirmed antiadipogenic activity and also exhibited in vivo antidyslipidemic activity.

Pharmacophore modelling, molecular docking and virtual screening for EGFR (HER 1) tyrosine kinase inhibitors

A pharmacophore model has been developed using diverse classes of epidermal growth factor receptor (EGFR) tyrosine kinase (TK) inhibitors useful in the treatment of human tumours. Among the top 10 generated hypotheses, the second hypothesis, with one hydrogen bond acceptor, one ring aromatic and three hydrophobic features, was found to be the best on the basis of Cat Scramble validation as well as test set prediction (r training = 0.89, r test = 0.82). The model also maps well to the external test set molecules as well as clinically active molecules and corroborates the docking studies. Finally, 10 hits were identified as potential leads after virtual screening of ZINC database for EGFR TK inhibition. The study may facilitate the designing and discovery of novel EGFR TK inhibitors.

Designing, synthesis of selective and high-affinity chalcone-benzothiazole hybrids as Brugia malayi thymidylate kinase inhibitors: In vitro validation and docking studies

In our continuing search for safe and efficacious antifilarials, a series of novel chalcone-benzothiazole hybrids have been synthesized and evaluated for their Brugia malayi thymidylate kinase (BmTMK) enzyme inhibition activity. Their selectivity towards BmTMK was studied and compared to the human TMK (HsTMK) by an in silico method. Out of seventeen derivatives, compounds 34 and 42 showed higher interactions with the BmTMK active site. MolDock docking model revealed the interactions of these two derivatives and the results corroborated well with their in vitro antifilarial activities. Our studies suggest that these hybrids are selective towards the BmTMK enzyme and may serve as potential therapeutic agents against filariasis.

Modelling the binding affinity of steroids to zebrafish sex hormone-binding globulin

The circulating endogenous steroids are transported in the bloodstream. These are bound to a highly specific sex hormone-binding globulin (SHBG) and in lower affinity to proteins such as the corticosteroid-binding protein and albumin in vertebrates, including fish. It is generally believed that the glycoprotein SHBG protects these steroids from rapid metabolic degradation and thus intervenes in its availability at the target tissues. Endocrine disrupters binding to SHBG affect the normal activity of natural steroids. Since xenobiotics are primarily released in the aquatic environment, there is a need to evaluate the binding affinity of xenosteroid mimics on fish SHBG, especially in zebrafish (Danio rerio), a small freshwater fish originating in India and widely employed in ecotoxicology, toxicology, and genetics. In this context, a zebrafish SHBG (zfSHBG) homology model was developed using the human SHBG (hSHBG) receptor structure as template. It was shown that interactions with amino acids Ser-36, Asp-59 and Thr-54 were important for binding affinity. A ligand-based pharmacophore model was also developed for both zfSHBG and hSHBG inhibitors that differentiated binders from non-binders, but also demonstrated structural requirements for zfSHBG and hSHBG ligands. The study provides insights into the mechanism of action of endocrine disruptors in zebrafish as well as providing a useful tool for identifying anthropogenic compounds inhibiting zfSHBG.

Identification of novel PTP1B inhibitors by pharmacophore based virtual screening, scaffold hopping and docking.

Design and synthesis of protein tyrosine phosphatases-1B (PTP1B) inhibitors are important for the drugs targeted to treat diabetes and obesity. The pharmacophore modeling, docking and scaffold hopping techniques have been applied to discover the novel PTP1B inhibitors. The ten prioritized compounds (115-119, 120-121, 127, 130-131) from the library of 86 compounds were synthesized and found positive in the micro molar range for PTP1B in-vitro inhibitory assays as compared to Suramin (IC50 9.5 μM). Among these five active compounds (115-119) were tested in STZ-s induced diabetic rat model and the most active compound 115 in this test, was further tested in C57BL/KsJ-db/db mice where it significantly improved OGTT along with the fasting and random blood glucose level. The treatment by the compound 115 significantly improved the insulin resistance and insulin signaling by restoring the insulin level and normalizing the serum lipid profile. Compound 115 also augmented the insulin action by modulating the expression of genes involved in insulin signaling like IRS 1-2, PI3K, PTPN1, Akt2, AMPK and PPAR-α. Western blot analysis of both skeletal muscle and liver demonstrated that proteins and intermediate enzymes of insulin signaling were also increased as compared to control group. The compound 115 was also investigated for anti-adipogenic effect on 3T3L-1 cells. The compound 115 inhibited MDI induced lipid accumulation in a dose-dependent manner. The oral bioavailability of compound 115 was ∼10.29% after 30 mg/kg oral dosing assessed in rat.

Operative conversions of 3-carboxy-4-quinolones into 3-nitro-4-quinolones via ipso-nitration: potential antifilarial agents as inhibitors of Brugia malayi thymidylate kinase

An efficient, cost effective and green methodology for ipso nitration in the synthesis of the 3-nitro derivative of 3-carboxy 4-quinolones has been developed by the quantitative use of copper acetate and silver nitrate in water. The observed regioselectivity of nitration is explained by the DFT calculations. Three of these compounds with IC50 values (2.9–3.4 μmol) against Brugia malayi thymidylate kinase may be good antifilarial agents as also evidenced by molecular docking studies.

Identification of Novel 2-((1-(Benzyl(2-hydroxy-2-phenylethyl)amino)-1-oxo-3-phenylpropan-2-yl)carbamoyl)benzoic Acid Analogues as BMP-2 Stimulators

The synthesis and SAR studies of 10 new chemical entities (NCEs) that have shown BMP-2 stimulation and osteoblast differentiation are reported. Among these, 2-((1-(benzyl(2-hydroxy-2-phenylethyl)amino)-1-oxo-3-phenylpropan-2-yl)carbamoyl)benzoic acid (11) was the most effective while its analogue 13 also showed good activity in inducing osteoblast BMP-2 production. Compound 11 induced osteoblast differentiation in vitro, and this effect was abrogated by a physiological BMP-2 inhibitor, noggin. It also exhibited dose dependent increase in nascent bone formation (2.16- and 3.12-fold more than the control at 1 and 5 mg/kg dose, respectively) at the fracture site in rats. At the maximum osteogenic concentration, compound 11 significantly inhibited osteoblastic proteosomal activity. This compound was safe, as it had no effect on BMP synthesis in cardiovascular tissue.

Pharmacokinetic and metabolism studies of rohitukine in rats by high performance liquid-chromatography with tandem mass spectrometry

A sensitive, selective, and rapid high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the quantification of rohitukine in rat plasma. HPLC was performed using a Symmetry-Shield C18 (5 μ, 4.6 × 150 mm) column, and isocratic elution with ammonium acetate buffer (pH4; 10 mM):methanol (08:92, v/v) at a flow rate of 0.6 mL/min. Sample clean-up involved solid phase extraction (SPE) of analyte and internal standard (phenacetin) from 100 μL plasma. The parent→product ion transitions (MRM) for analyte and IS were 306.1→245.1 m/z and 180.1→138.1 m/z respectively, and were monitored on a triple quadrupole mass spectrometer, operating in positive ion mode. The method was validated across the dynamic concentration range of 5-500 ng/mL for rohitukine, with a fast run time of 4.5 min. The analytical method measured concentrations of rohitukine with accuracy (% bias) of <±10% and precision (% RSD) of <±12%. Rohitukine was stable during the battery of stability studies viz., bench-top, auto-sampler, freeze/thaw cycles and 30 days of storage in a freezer at -70±10°C. Finally, the applicability of this assay has been successfully demonstrated in vivo pharmacokinetic and in vitro metabolism studies in Sprague-Dawley rat. This method will therefore be highly useful for future preclinical and clinical pharmacokinetic studies of rohitukine.

Curcumin-3,4-Dichloro Phenyl Pyrazole (CDPP) overcomes curcumin's low bioavailability, inhibits adipogenesis and ameliorates dyslipidemia by activating reverse cholesterol transport

BACKGROUND Adipocyte dysfunction, obesity and associated metabolic disorders are of prime healthcare concern worldwide. Among available medications, natural products and inspired molecules hold 40% space in clinically prescribed medicines. In queue, this study overcomes the drawback of curcumins low bioavailability with potent anti-adipogenic and anti-dyslipidemic activity. METHODS To evaluate the role of CDPP on adipocyte differentiation, 3T3-L1 adipocytes were used as an in-vitro model. Flow cytometry was performed for cell cycle analysis. Syrian golden hamsters were used to study pharmacokinetic profile and dyslipidemic activity exhibited by CDPP. RESULT CDPP was found to be a potent inhibitor of adipogenesis in-vitro. It blocked mitotic clonal expansion by causing cell cycle arrest. CDPP showed marked improvement in gastrointestinal stability and bioavailability in-vivo as compared to curcumin. Administration of CDPP (100mg/kg) significantly improved HFD induced dyslipidemic profile in hamsters and activated reverse cholesterol transport machinery. CONCLUSION CDPP could be used as a potential drug candidate against adipogenesis and dyslipidemia with enhanced gastrointestinal stability and bioavailability.