Analysis of P-Glycoprotein Transport Cycle Reveals a New Way to Identify Efflux Inhibitors

Rational Design Problematics of Peptide Nucleic Acids as SARS-CoV-2 Inhibitors

The use of viral protein inhibitors has shown to be insufficiently effective in the case of highly variable SARS-CoV-2. In this work, we examined the possibility of designing agents that bind to a highly conserved region of coronavirus (+)RNA. We demonstrated that while the design of antisense RNAs is based on the complementary interaction of nitrogenous bases, it is possible to use semirigid docking methods in the case of unnatural peptide nucleic acids. The transition from N-(2-aminoethyl)glycine chain to a more conformationally rigid piperidine-containing backbone allowed us to significantly increase the affinity of structures to the target RNA.

Exploring the dynamics of the ABCB1 membrane transporter P-glycoprotein in the presence of ATP and active/non-active compounds through molecular dynamics simulations

P-glycoprotein (Pgp) is a member of the ATP-binding cassette family of transporters that confers multidrug resistance to cancer cells and is actively involved in the pharmacokinetics and toxicokinetics of a big variety of drugs. Extensive studies have provided insights into the binding of many compounds, but the precise mechanism of translocation across the membrane remains unknown; in this context, the major challenge has been to understand the basis for its polyspecificity. In this study, molecular dynamics (MD) simulations of human P-gp (hP-gp) in an explicit membrane-and-water environment were performed to investigate the dynamic behavior of the transporter in the presence of different compounds (active and inactive) in the binding pocket and ATP molecules within the nucleotide binding domains (NBDs). The complexes studied involve four compounds: cyclosporin A (CSA), amiodarone (AMI), pamidronate (APD), and valproic acid (VPA). While CSA and AMI are known to interact with P-gp, APD and VPA do not. The results highlighted how the presence of ATP notably contributed to increased flexibility of key residues in NBD1 of active systems, indicating potential conformational changes activating the translocation mechanism. MD simulations reveal how these domains adapt and respond to the presence of different substrates, as well as the influence of ATP binding on their flexibility. Furthermore, distinctive behavior was observed in the presence of active and inactive compounds, particularly in the arrangement of ATP between NBDs, supporting the proposed nucleotide sandwich dimer mechanism for ATP binding. This study provides comprehensive insights into P-gp behavior with various ligands and ATP, offering implications for drug development, toxicity assessment and demonstrating the validity of the results derived from the MD simulations.

NMR-Verified Dearomatization of 5,7-Substituted Pyrazolo[1,5-a]pyrimidines

Tetrahydropyrazolo[1,5-a]pyrimidine (THPP) is an attractive scaffold for designing biologically active compounds. The most obvious way to obtain such compounds is to reduce pyrazolopyrimidines with complex hydrides, because the pyrimidine ring is reduced in the preference over the pyrazole ring. The presence of substituents at positions five and seven of pyrazolo[1,5-a]pyrimidines complicates the set of reaction products but makes it more attractive for medicinal chemistry because four possible stereoisomers can be formed during reduction. However, the formation of only syn-isomers has been described in the literature. This article is the first report on the formation of anti-configured isomers along with syn-isomers in the reduction of model 5,7-dimethylpyrazolo[1,5-a]pyrimidine, which was confirmed by NMR. The bicyclic core in the syn-configuration was shown to be conformationally stable, which was used to estimate the long-range interproton distances using NOESY data. At the same time, long-range dipole-dipole interactions corresponding to a distance between protons of more than 6 Å were first registered and quantified. In turn, the bicyclic core in the trans-configuration represents a conformationally labile system. For these structures, an analysis of conformations observed in solutions was carried out. Our results indicate the significant potential of trans-configured tetrahydropyrazolo[1,5-a]pyrimidines for the development of active small molecules. While possessing structural lability due to the low energy of the conformational transition, they have the ability to adjust to the active site of the desired target.

Involvement and targeted intervention of benzo(a)pyrene-regulated apoptosis related proteome modification and muti-drug resistance in hepatocellular carcinoma

During the development of hepatocellular carcinoma (HCC), the mutual adaptation and interaction of HCC cells and the microenvironment play an important role. Benzo(a)pyrene (B[a]P) is a common environmental pollutant, which can induce the initiation of various malignant tumors, including HCC. However, the effects of B[a]P exposure on progression of HCC and the potential mechanisms remains largely uninvestigated. Here we found that, after the long-term exposure of HCC cells to low dose of B[a]P, it activated glucose-regulated protein 75 (GRP75), which then induced a modification of apoptosis-related proteome. Among them, we identified the X-linked inhibitor of apoptosis protein (XIAP) as a key downstream factor. XIAP further blocked the caspase cascade activation and promoted the acquisition of the anti-apoptosis abilities, ultimately leading to multi-drug resistance (MDR) in HCC. Furthermore, the abovementioned effects were markedly attenuated when we inhibited GRP75 by using 3,4-dihydroxycinnamic acid (caffeic acid, CaA). Collectively, our present study revealed the effects of B[a]P exposure on the progression of HCC, and identified GRP75 was a meaningful factor involved in.

Modulating multidrug resistance to drug-based antitumor therapies through NF-κB signaling pathway: mechanisms and perspectives

INTRODUCTION

Despite the advances made in cancer treatment in the past decades, therapeutic efficacy is still quite challenging, partially due to the emergence of multidrug resistance (MDR). It is crucial to decipher the underlying mechanisms of resistance in order to develop new therapeutic strategies for cancer patients. Previous studies have shown that activation of nuclear factor-κB (NF-κB) plays key roles in various cellular processes including proliferation, anti-apoptosis, metastasis, invasion, and chemoresistance.

AREAS COVERED

In this review, we conduct an integrated analysis of the evidence suggesting the vital roles of the NF-κB signaling pathway in MDR during chemotherapy, immunotherapy, endocrine, and targeted therapy. A literature search was performed on NF-κB and drug resistance in PubMed up to February 2023.

EXPERT OPINION

This review summarizes that the NF-κB signaling pathway exhibits a crucial role in enhancing drug resistance in chemotherapy, immunotherapy, endocrine, and targeted therapy. The application of combination therapy with existing antineoplastic drugs and a safe NF-κB inhibitor could become a promising strategy in cancer treatment. A better understanding of the pathway and mechanisms of drug resistance may help exploit safer and more effective NF-κB-targeting agents for clinical use in the future.