Current Chemical Biology - Volume 15, Issue 4, 2021

Ascorbic acid is an essential nutrient, and required for various metabolic activities in humans. Typically citrus fruits, vegetables and organ meat are good source of vitamin C. It acts as strong antioxidant and act as a scavenger in defence against free radical oxygen species. It has also contributed to rejuvenate photo aged skin. It has ability to control the pigmentation of melanin by inhibiting the enzyme tyrosinase by interacting with copper ions. It serves as a co-antioxidant with vitamin E to regenerate alpha tocopherol, thereby retards cellular damage. Ascorbic acid is deprotonated to form ascorbate anion, contributes to its prooxidant properties and act as a potential anticancer agent. It reduces the mutation rate in mismatch-repair deficient human colon cancer cells. Ascorbic acid is a phytochemical has micronutrients that act against the inflammation in arthritis. Currently, challenges lies finding most stable formulation for achieving optimum results.

Aims: This study aims to evaluate the bioactivity of dipeptidyl nitrile inhibitors of human cysteine cathepsins that could work as anticancer agents in a drug discovery and development project. Background: Human lysosomal cysteine proteases promote cancer progression, migration, and metastasis, targeted by inhibitors. Objective: Here, 19 cysteine protease inhibitors known as dipeptidyl nitriles were tested using MIA PaCa-2 pancreatic cancer cells and Balb/3T3 clone A31 non-tumoral mouse fibroblasts. Methods: In vitro assays evaluated cell migration, colony formation, inhibition of the enzymatic activity in cell lysates, and combination therapy with gemcitabine. Results: There were mixed results; the inhibitors reduced the number of colonies but did not affect the total area. Cells migrated despite enzyme inhibition by Neq0709 and Neq0712. As expected, the compounds were non-cytotoxic; they improved the potency of gemcitabine in the combined therapy assay, especially for Neq0707. Conclusion: In summary, our findings revealed the complexity of dealing with the translation from biochemical to cell-based assays in the hit-to-lead step.

Aim: We aimed to identify critical human proteins involved in cathepsin L regulation Background: It has been shown that Dengue Virus (DENV) NS1 activates cathepsin L (CTSL). The CTSL activates heparanase, which cleaves heparan sulfate proteoglycans and causes dengue pathogenesis. NS1 directly interacts with PTBP1 and Gab proteins. Gab protein activates the Ras signaling pathway. Still, no known direct interaction partners are linking GAB1 to cathepsin L. Objective: Our objective includes three main points.1-Network analysis of NS1 interacting human proteins 2- Identification of protein-drug and protein-disease interactions 3- Identification of core proteins involved in cathepsin L regulation. Method: We collected NS1 interacting Human proteins from DenHunt, Int-Act Molecular Interaction Database, Virus Mentha, Virus Pathogen Database and Analysis Resource (ViPR), and Virus MINT. We employed Pesca, cytohubba, and centiscape as the significant plug-ins in Cytoscape for network analysis. To study protein-diseases and protein-drugs interaction, we used NetworkAnalyst. Result: Based on the prior knowledge on the interaction of NS1 with GAB1 and PTBP1 human proteins, we found several core proteins that drive dengue pathogenesis. The proteins EED, NXF1, and MOV10, are the mediators between PTBP1 and CTSL. Similarly, DNM2, GRB2, PXN, PTPRC, and NTRK1 mediate GAB1 and PTBP1. The common first neighbors of MOV10, NXF1, and EED were identified, and the common primary pathways in all three subnetworks were mRNA processing and protein translation. The common interaction partners were considered for drug and disease network analysis. These proteins were; PARP1, NFKB2, HDAC2, SLC25A4, ATP5A1, EPN1, CTSL, UBR4, CLK3, and ARPC4. PARP1 was the highly connected node in the protein-drug network. The highest degree protein, LMNA, was associated with many diseases. The NXF1 is connected with LMNA. Here, we reported one essential protein, namely, NXF1 protein, which links PTBP1 with CTSL. The NXF1 is also connected with TPM3, which is connected to CTSL. Conclusion: We listed functionally important proteins which are involved in cathepsin L activation. Based on network properties, we proposed, NXF1 and TPM3 are the important high centrality proteins in dengue infection.

Background: Nicotine-metabolized product nicotine imine is suggested to play a role in metabolic changes occurring in oral cancer. There is a significant gap in the detection of oncometabolite nicotine imine in biological fluids and nails of oral cancer patients. Oncometabolites are designated as metabolites that are usually elevated in cancer cells compared to normal cells. Interestingly, a direct or indirect link is missing that establishes a role of nicotine imine in pro-cancer cellular events, including global DNA hypomethylation, a potential metabolic-epigenetic axis in oral cancer. Methods: A novel vertical tube gel electrophoresis (VTGE) system assisted purification and liquid chromatography-high resolution mass spectrometry (LC-HRMS) based identification of nicotine imine in the nails of oral cancer patients were conducted. Further, nicotine imine was evaluated for its molecular interactions with various methyltransferases, including DNA methyltransferase 1 (DNMT1), by molecular docking and molecular dynamics (MD) simulations. Results: Data suggested the presence of nicotine imine in the nails of oral cancer patients. Molecular docking and MD simulations revealed a specific binding affinity of nicotine imine with DNMT1. Binding with nicotine imine is within the CXCC regulatory domain of DNMT1, including key residues as ARG690, PRO574, VAL658, PRO692 and ALA695. Similar binding residues are displayed by DNMT1 inhibitor 5'-Aza-2'-deoxycytidine. Conclusion: Nicotine imine is suggested as a predictive biomarker for oral cancer patients, and this finding is first of its kind. Molecular docking and dynamics simulation propose the role of nicotine imine as an inhibitor of DNMT1. This work supports the involvement of synergistic pro-tumor metabolic-epigenomic axis by nicotine imine that may contribute towards potential mutagenesis of normal squamous epithelium.

Background and objectives: Quercetin is a naturally occurring phenolic compound abundantly present in plants as a secondary metabolite. The purpose of this study was to investigate the effect of quercetin on improving RINm5F β-insulinemia cell viability, glucose-stimulated insulin secretion (GSIS), and cell insulin content in the presence or absence of streptozotocin (STZ). Methods: This experimental study was conducted on RINm5F β-insulinemia cell line. The cell viability was evaluated by MTT assay. The necrosis was confirmed by flowcytometry and insulin ELISA kit was used to measure the GSIS level and cell insulin content. It should be noted that for testing of cells by 50μM of quercetin, simultaneous treatment and pre-treatment of quercetin were performed in the presence of STZ (20mM). Results: The quercetin was able to improve the viability of RINm5F cells in the presence of STZ and to increase the GSIS level and cell insulin content under STZ and glucotoxic conditions. Conclusion: The quercetin seems to have beneficial effects on β-cells, especially the synthesis and secretion of insulin. In addition to the therapeutic effect, given the low toxicity of this flavonoid and the results of this study, the quercetin as a preventive agent may play an important role in maintaining the health of β-cells in people at risk of diabetes.

Background: Nitric oxide synthase (NOS) catalyzes the formation of nitric oxide (NO) and citrulline from L-arginine, dioxygen (O2) and nicotinamide adenine dinucleotide phosphate (NADPH) in a two-step reaction, with the enzyme-bound intermediate Nω-hydroxy-L-arginine (NHA). Previous electron paramagnetic resonance (EPR) studies of NOS reaction have shown that (6R, 1'R, 2'S)-6-(l',2'-dihydroxypropyl)-5,6,7,8-tetrahydropterin (H4B) acts as a single electron donor in both steps of the reaction, resulting in transient generation of a tetrahydropterin cation radical (H4B•+). Methods: H4B•+ can also be chemically generated in strongly acidic solutions. EPR studies of chemically generated H4B•+ and similar pterin radicals date back to the 1960s. However, the reported paramagnetic parameters of H4B•+ in NOS do not seem to match the corresponding reported parameters for either H4B•+ or other pterin centered radicals chemically generated in solution. In particular, the rather isotropic hyperfine coupling of ca. 45 MHz for 1H6 of H4B•+ in NOS is at least 15 MHz larger than that of H4B•+ or any other previously studies pterin solution radical. In the work reported here, a combination of 9.5 - 9.8 GHz contentious wave (cw-) EPR, 34GHz 1H electron nuclear double resonance (ENDOR), spectral simulation and Density Functional Theory (DFT) calculations was used to investigate this seeming discrepancy. Results: A plethora of data from 9.5 - 9.8 GHz cw-EPR, 34GHz 1H ENDOR, spectral simulation and Density Functional Theory (DFT) calculations suggest that the differences in the paramagnetic parameters of the chemically generated H4B radicals in solution and those of H4B radical in NOS stems from the presence of two different conformers of the same cation radical H4B•+. Conclusion: We demonstrated that the differences in the paramagnetic parameters of the chemically generated H4B radicals in solutions and those of the H4B radicals in NOS are consistent with the presence of two different conformers of the same cation radical in the two media.