Acridin-9-yl exchange: A proposal for the action of some 9-aminoacridine drugs

Can Zeolite-Supporting Acridines Boost Their Anticancer Performance?

Acridine and its derivatives (9-chloroacridine and 9-aminoacridine) are investigated here, supported on FAU type zeolite Y, as a delivery system of anticancer agents. FTIR/Raman spectroscopy and electron microscopy revealed successful drug loading on the zeolite surface, while spectrofluorimetry was employed for drug quantification. The effects of the tested compounds on cell viability were evaluated using in vitro methylthiazol-tetrazolium (MTT) colorimetric technique against human colorectal carcinoma (cell line HCT-116) and MRC-5 fibroblasts. Zeolite structure remained unchanged during homogeneous drug impregnation with achieved drug loadings in the 18-21 mg/g range. The highest drug release, in the µM concentration range, with favourable kinetics was established for zeolite-supported 9-aminoacridine. The acridine delivery via zeolite carrier is viewed in terms of solvation energy and zeolite adsorption sites. The cytotoxic effect of supported acridines on HCT-116 cells reveals that the zeolite carrier improves toxicity, while the highest efficiency is displayed by zeolite-impregnated 9-aminoacridine. The 9-aminoacridine delivery via zeolite carrier favours healthy tissue preservation while accompanying increased toxicity toward cancer cells. Cytotoxicity results are well correlated with theoretical modelling and release study, providing promising results for applicative purposes.

Amino acid or peptide conjugates of acridine/acridone and quinoline/quinolone-containing drugs. A critical examination of their clinical effectiveness within a twenty-year timeframe in antitumor chemotherapy and treatment of infectious diseases

Acridines/acridones, quinolines/quinolones (chromophores) and their derivatives constitute extremely important family of compounds in current medicine. Great significance of the compounds is connected with antimicrobial and antitumor activities. Combining these features together in one drug seems to be long-term benefit, especially in oncology therapy. The attractiveness of the chromophore drugs is still enhanced by elimination their toxicity and improvement not only selectivity, specificity but also bioavailability. The best results are reached by conjugation to natural peptides. This paper highlights significant advance in the study of amino acid or peptide chromophore conjugates that provide highly encouraging data for novel drug development. The structures and clinical significance of amino acid or peptide chromophore conjugates are widely discussed.

Quinacrine promotes replication and conformational mutation of chronic wasting disease prions

Quinacrine's ability to reduce levels of pathogenic prion protein (PrP(Sc)) in mouse cells infected with experimentally adapted prions led to several unsuccessful clinical studies in patients with prion diseases, a 10-y investment to understand its mechanism of action, and the production of related compounds with expectations of greater efficacy. We show here, in stark contrast to this reported inhibitory effect, that quinacrine enhances deer and elk PrP(Sc) accumulation and promotes propagation of prions causing chronic wasting disease (CWD), a fatal, transmissible, neurodegenerative disorder of cervids of uncertain zoonotic potential. Surprisingly, despite increased prion titers in quinacrine-treated cells, transmission of the resulting prions produced prolonged incubation times and altered PrP(Sc) deposition patterns in the brains of diseased transgenic mice. This unexpected outcome is consistent with quinacrine affecting the intrinsic properties of the CWD prion. Accordingly, quinacrine-treated CWD prions were comprised of an altered PrP(Sc) conformation. Our findings provide convincing evidence for drug-induced conformational mutation of prions without the prerequisite of generating drug-resistant variants of the original strain. More specifically, they show that a drug capable of restraining prions in one species/strain setting, and consequently used to treat human prion diseases, improves replicative ability in another and therefore force reconsideration of current strategies to screen antiprion compounds.

Discriminating between cellular and misfolded prion protein by using affinity to 9-aminoacridine compounds

Quinacrine and related 9-aminoacridine compounds are effective in eliminating the alternatively folded prion protein, termed PrP(Sc), from scrapie-infected cultured cells. Clinical evaluations of quinacrine for the treatment of human prion diseases are progressing in the absence of a clear understanding of the molecular mechanism by which prion replication is blocked. Here, insight into the mode of action of 9-aminoacridine compounds was sought by using a chemical proteomics approach to target identification. Cellular macromolecules that bind 9-aminoacridine ligands were affinity-purified from tissue lysates by using a 9-aminoacridine-functionalized solid-phase matrix. Although the 9-aminoacridine matrix was conformationally selective for PrP(Sc), it was inefficient: approximately 5 % of PrP(Sc) was bound under conditions that did not support binding of the cellular isoform, PrP(C). Our findings suggest that 9-aminoacridine compounds may reduce the PrP(Sc) burden either by occluding epitopes necessary for templating on the surface of PrP(Sc) or by altering the stability of PrP(Sc) oligomers, where a one-to-one stoichiometry is not necessary.