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
ABSTRACT Pharmacists and their pharmacies have been evolving in their roles as health promoters in Brazil. Some examples are the recent legislation reaffirming the role of Brazilian pharmacies as health institutions, rather than having only a commercial profile, giving greater clarity to pharmacists about their roles as health care providers. This evolution came with the recognition that is already seen in other developed countries, confirming the need for the pharmacist as a health promoter, and not simply a dispenser of drugs in society. This study has obtained the profile and activities of community pharmacists, as well as the quality indicators of private community pharmacies throughout the State of Paraná through the application of an online survey sent to pharmacists in the state. Out of all pharmacists surveyed, 533 were part of the final analysis, being the pharmacists to complete the survey in full. Participants were mostly female (69.4%) and were, on average, 35.2 ± 9.2 years old. Of these, 60% worked in pharmacy chains and just 37% of all pharmacist respondents were issuing the Declaration of Pharmaceutical Services. The current study showed that many pharmaceutical services are not adopted by pharmacies as these services bring no significant financial reward. Regarding the structure, the Paraná State showed that pharmacies present a good overall structure. The kind of pharmacy (chain or independent) influenced the pharmaceutical services provided and the available structure, where the independent pharmacies provide a wider range of services and have better structure. This study was able to identify the profile and behaviors of pharmacists and also the quality indicators of pharmacies in Paraná State.