ABSTRACT
The ABCG2 transporter plays a pivotal role in multidrug resistance, however, no clinical trial using specific ABCG2 inhibitors have been successful. Although ABC transporters actively extrude a wide variety of substrates, photodynamic therapeutic agents with porphyrinic scaffolds are exclusively transported by ABCG2. In this work, we describe for the first time a porphyrin derivative (4B) inhibitor of ABCG2 and capable to overcome multidrug resistance in vitro. The inhibition was time-dependent and 4B was not itself transported by ABCG2. Independently of the substrate, the porphyrin 4B showed an IC50 value of 1.6 µM and a mixed type of inhibition. This compound inhibited the ATPase activity and increased the binding of the conformational-sensitive antibody 5D3. A thermostability assay confirmed allosteric protein changes triggered by the porphyrin. Long-timescale molecular dynamics simulations revealed a different behavior between the ABCG2 porphyrinic substrate pheophorbide a and the porphyrin 4B. Pheophorbide a was able to bind in three different protein sites but 4B showed one binding conformation with a strong ionic interaction with GLU446. The inhibition was selective toward ABCG2, since no inhibition was observed for P-glycoprotein and MRP1. Finally, this compound successfully chemosensitized cells that overexpress ABCG2. These findings reinforce that substrates may be a privileged source of chemical scaffolds for identification of new inhibitors of multidrug resistance-linked ABC transporters.
Subject(s)
ATP Binding Cassette Transporter, Subfamily G, Member 2/antagonists & inhibitors , Adenosine Triphosphatases/antagonists & inhibitors , Enzyme Inhibitors/pharmacology , Neoplasm Proteins/antagonists & inhibitors , Porphyrins/pharmacology , ATP Binding Cassette Transporter, Subfamily G, Member 2/chemistry , ATP Binding Cassette Transporter, Subfamily G, Member 2/metabolism , Adenosine Triphosphatases/chemistry , Adenosine Triphosphatases/metabolism , Cell Line, Tumor , Drug Evaluation, Preclinical , Drug Resistance, Multiple/drug effects , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/metabolism , HEK293 Cells , Humans , Irinotecan/pharmacology , Molecular Docking Simulation , Molecular Dynamics Simulation , Molecular Structure , Neoplasm Proteins/chemistry , Neoplasm Proteins/metabolism , Porphyrins/chemistry , Porphyrins/metabolism , Protein Binding , Protein Conformation/drug effectsABSTRACT
Lignin is an important raw material for the sustainable biorefineries and also the forerunner of high-value added products, such as biocomposite for chemical, pharmaceutical and cement industries. Oil palm empty fruit bunches (OPEFB) were used for lignin preparation by successive treatment with 1% (w/w) H2SO4 at 121°C for 60 min and 2.5% NaOH at 121°C for 80 min resulting in the high lignin yield of 28.89%, corresponding to 68.82% of the original lignin. The lignin obtained was characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The results indicated a lignin with molecular masses ramping from 4500 kDa to 12,580 kDa. FTIR and NMR of these lignins showed more syringyl and p-hydroxyphenyl than guaiacyl units. Moderate acid/alkaline treatment provided lignin with high industrial potential and acid hydrolyzates rich in fermentable sugars and highly porous cellulosic fibers.
Subject(s)
Arecaceae/metabolism , Biotechnology/methods , Fruit/metabolism , Lignin/metabolism , Plant Oils/metabolism , Sodium Hydroxide/pharmacology , Sulfuric Acids/pharmacology , Arecaceae/drug effects , Arecaceae/ultrastructure , Carbon-13 Magnetic Resonance Spectroscopy , Fruit/drug effects , Fruit/ultrastructure , Molecular Weight , Palm Oil , Proton Magnetic Resonance Spectroscopy , Spectroscopy, Fourier Transform InfraredABSTRACT
The DL-galactan hybrid C2S-3, isolated from the red seaweed Cryptonemia crenulata (Halymeniaceae, Halymeniales), is a potent and selective inhibitor of the multiplication of diverse strains of DENV-2 in Vero cells with higher effectiveness than the reference polysaccharide heparin. The presence of the compound either only at virus adsorption or at virus internalization exerted a significant and dose-dependent inhibition in DENV-2 plaque number. The compound failed to inactivate DENV-2 directly by incubation of virus before cell infection as well as to induce a refractory state by cell pretreatment. Thus, the inhibitory effect was exclusively exerted through a blockade in virus multiplication during the infectious process. When the entry of DENV-2 particles into the cell is bypassed, as occurs in virus RNA transfection, the polysaccharide C2S-3 failed to block the completion of the multiplication cycle. Furthermore, the antiviral properties of C2S-3 are not correlated with anticoagulant activity.
Subject(s)
Antiviral Agents/pharmacology , Dengue Virus/drug effects , Eukaryota/chemistry , Galactans/pharmacology , Animals , Antiviral Agents/chemistry , Chlorocebus aethiops , Dose-Response Relationship, Drug , Galactans/chemistry , Molecular Structure , Vero CellsABSTRACT
This study presents the chemical composition and antiviral activity against herpes simplex virus type 1 (HSV-1) and 2 (HSV-2) of sulfated galactan crude extracts and main fractions obtained from two red seaweeds collected in Brazil, Gymnogongrus griffithsiae and Cryptonemia crenulata. Most of the eighteen tested products, including homogeneous kappa/iota/nu carrageenan and DL-galactan hybrid, exhibited antiherpetic activity with inhibitory concentration 50% (IC50) values in the range 0.5-5.6 microg/ml, as determined in a virus plaque reduction assay in Vero cells. The galactans lacked cytotoxic effects and showed a broad spectrum of antiviral activity against HSV-1 and HSV-2. No direct virus inactivation was observed after virion treatment with the galactans. The mode of action of these compounds could be mainly ascribed to an inhibitory effect on virus adsorption. Most importantly, a significant protection against a murine vaginal infection with HSV-2 was afforded by topical treatment with the sulfated galactans.