'Acridines' as New Horizons in Antifungal Treatment.

Frequent fungal infections in immunocompromised patients and mortality due to invasive mycosis are important clinical problems. Opportunistic pathogenic Candida species remain one of the leading causes of systemic mycosis worldwide. The repertoire of antifungal chemotherapeutic agents is very limited. Although new antifungal drugs such as lanosterol 14α-demethylase and ß-glucan synthase inhibitors have been introduced into clinical practice, the development of multidrug resistance has become increasingly significant. The urgency to expand the range of therapeutic options for the treatment of fungal infections has led researchers in recent decades to seek alternative antifungal targets to the conventional ones currently used. Among them, many compounds containing an acridine scaffold have been synthesized and tested. In this review, the applicability of acridines and their functional analogues acridones as antifungal agents is described. Acridine derivatives usage in photoantifungal chemotherapy, interactions with fungal transporters resulting in modulation of efflux/influx pumps and the effect of acridine derivatives on fungal topoisomerases are discussed. This article explores new perspectives on the mechanisms of antifungal acridine-peptide conjugates and acridine-based hybrid molecules to effectively combat fungal infections.

Synthesis and biological evaluation of acridine-based histone deacetylase inhibitors as multitarget agents against Alzheimer's disease.

Multitarget agents simultaneously trigger molecules in functionally complementary pathways, and are therefore considered to have potential in effectively treating Alzheimer's disease (AD), which has a complex pathogenetic mechanism. In this study, the HDAC inhibitor core is incorporated into the acetylcholine esterase (ACE) inhibitor acridine-derived moiety and resulted in compounds that exhibited higher class IIa HDAC (4, 5, 7, and 9)- and class IIb HDAC6-inhibiting activity when compared to the pan-HDAC inhibitor SAHA in clinical practice. One of these compounds, 11b, displayed greater selectivity toward HDAC6 than other isoform enzymes. In contrast, the activity of compound 6a was selective toward class IIa HDAC and HDAC6. These two compounds exhibited strong activity against Aß-aggregation as well as significantly disrupted Aß-oligomer. Additionally, 11b and 6a strongly inhibited AChE. These experimental findings demonstrate that compounds 11b and 6a are HDAC-Aß-aggregation-AChE inhibitors. Notably, they can enhance neurite outgrowth, but with no significant neurotoxicity. Further biological evaluation revealed the various cellular effects of multitarget compounds 11b and 6a, which have the potential to treat AD.

Improvement of conventional anti-cancer drugs as new tools against multidrug resistant tumors.

Multidrug resistance (MDR) is the dominant cause of the failure of cancer chemotherapy. The design of antitumor drugs that are able to evade MDR is rapidly evolving, showing that this area of biomedical research attracts great interest in the scientific community. The current review explores promising recent approaches that have been developed with the aim of circumventing or overcoming MDR. Encouraging results have been obtained in the investigation of the MDR-modulating properties of various classes of natural compounds and their analogues. Inhibition of P-gp or downregulation of its expression have proven to be the main mechanisms by which MDR can be surmounted. The use of hybrid molecules that are able to simultaneously interact with two or more cancer cell targets is currently being explored as a means to circumvent drug resistance. This strategy is based on the design of hybrid compounds that are obtained either by merging the structural features of separate drugs, or by conjugating two drugs or pharmacophores via cleavable/non-cleavable linkers. The approach is highly promising due to the pharmacokinetic and pharmacodynamic advantages that can be achieved over the independent administration of the two individual components. However, it should be stressed that the task of obtaining successful multivalent drugs is a very challenging one. The conjugation of anticancer agents with nitric oxide (NO) donors has recently been developed, creating a particular class of hybrid that can combat tumor drug resistance. Appropriate NO donors have been shown to reverse drug resistance via nitration of ABC transporters and by interfering with a number of metabolic enzymes and signaling pathways. In fact, hybrid compounds that are produced by covalently attaching NO-donors and antitumor drugs have been shown to elicit a synergistic cytotoxic effect in a variety of drug resistant cancer cell lines. Another strategy to circumvent MDR is based on nanocarrier-mediated transport and the controlled release of chemotherapeutic drugs and P-gp inhibitors. Their pharmacokinetics are governed by the nanoparticle or polymer carrier and make use of the enhanced permeation and retention (EPR) effect, which can increase selective delivery to cancer cells. These systems are usually internalized by cancer cells via endocytosis and accumulate in endosomes and lysosomes, thus preventing rapid efflux. Other modalities to combat MDR are described in this review, including the pharmaco-modulation of acridine, which is a well-known scaffold in the development of bioactive compounds, the use of natural compounds as means to reverse MDR, and the conjugation of anticancer drugs with carriers that target specific tumor-cell components. Finally, the outstanding potential of in silico structure-based methods as a means to evaluate the ability of antitumor drugs to interact with drug transporters is also highlighted in this review. Structure-based design methods, which utilize 3D structural data of proteins and their complexes with ligands, are the most effective of the in silico methods available, as they provide a prediction regarding the interaction between transport proteins and their substrates and inhibitors. The recently resolved X-ray structure of human P-gp can help predict the interaction sites of designed compounds, providing insight into their binding mode and directing possible rational modifications to prevent them from becoming P-gp drug substrates. In summary, although major efforts were invested in the search for new tools to combat drug resistant tumors, they all require further implementation and methodological development. Further investigation and progress in the abovementioned strategies will provide significant advances in the rational combat against cancer MDR.

P-glycoprotein (MDR1/ABCB1) controls brain accumulation and intestinal disposition of the novel TGF-ß signaling pathway inhibitor galunisertib.

Galunisertib (LY2157299), a promising small-molecule inhibitor of the transforming growth factor-beta (TGF-ß) receptor, is currently in mono- and combination therapy trials for various cancers including glioblastoma, hepatocellular carcinoma and breast cancer. Using genetically modified mouse models, we investigated the roles of the multidrug efflux transporters ABCB1 and ABCG2, the OATP1A/1B uptake transporters and the drug-metabolizing CYP3A complex in galunisertib pharmacokinetics. In vitro, galunisertib was vigorously transported by human ABCB1, and moderately by mouse Abcg2. Orally administered galunisertib (20 mg/kg) was very rapidly absorbed. Galunisertib brain-to-plasma ratios were increased by ~24-fold in Abcb1a/1b-/- and Abcb1a/1b;Abcg2-/- mice compared to wild-type mice, but not in single Abcg2-/- mice, whereas galunisertib oral availability was not markedly affected. However, recovery of galunisertib in the small intestinal lumen was strongly reduced in Abcb1a/1b-/- and Abcb1a/1b;Abcg2-/- mice. Oral coadministration of the ABCB1/ABCG2 inhibitor elacridar boosted galunisertib brain accumulation in wild-type mice to equal the levels seen in Abcb1a/1b;Abcg2-/- mice. Oatp1a/1b deficiency did not alter oral galunisertib pharmacokinetics or liver distribution. Cyp3a-/- mice showed a 1.9-fold higher plasma AUC0-1 hr than wild-type mice, but this difference disappeared over 8 hr. Also, transgenic human CYP3A4 overexpression did not significantly alter oral galunisertib pharmacokinetics. Abcb1 thus markedly restricts galunisertib brain penetration and affects its intestinal disposition, possibly through biliary excretion. Elacridar coadministration could fully inhibit both processes, without causing acute toxicity. Moreover, mouse Cyp3a, but not human CYP3A4, may eliminate galunisertib at high plasma concentrations. These insights may help to guide the further clinical development and application of galunisertib.

Anticancer activity of arborinine from Glycosmis parva leaf extract in human cervical cancer cells.

Glycosmis parva is a small shrub found in Thailand. Ethyl acetate (EtOAc) extract from its leaves has been shown to exert anticancer effects in vitro; however, the compound responsible for this activity has not been isolated and characterized. In this study, we demonstrate that arborinine, a major acridone alkaloid in the EtOAc fraction, decreased proliferation and was strongly cytotoxic to HeLa cervical cancer cells without significantly affecting normal cells. The compound also inhibited tumor spheroid growth much more potently than chemotherapeutic drugs bleomycin, gemcitabine, and cisplatin. In addition, unlike cisplatin, arborinine activated caspase-dependent apoptosis without inducing DNA damage response. We further show that arborinine strongly suppressed cancer cell migration by downregulating expression of key regulators of epithelial-mesenchymal transition. Taken together, our data provide important insights into the molecular mechanism of arborinine's anticancer activity, supporting its potential use for treating cervical cancer.

Discovery of 1,8-acridinedione derivatives as novel GCN5 inhibitors via high throughput screening.

The general control nonrepressed protein 5 (GCN5) plays a crucial role in many biological processes. Dysregulation of GCN5 has been closely related to various human diseases, especially cancers. Hence, the exploitation of small molecules targeting GCN5 is essential for drug design and academic research. Based on the amplified luminescent proximity homogeneous assay screen methodology, we performed high throughput screening and discovered a novel GCN5 inhibitor DC_G16 with 1,8-acridinedione scaffold. Structure optimization led to the identification of a highly potent inhibitor, namely DC_G16-11 with the half-maximal inhibitory concentration (IC50) value of 6.8 µM. The binding between DC_G16-11 and GCN5 was demonstrated by NMR and SPR with a KD of 4.2 µM. It could also inhibit proliferation and induce cell cycle arrest and apoptosis in cancer cells while it presented minimal effects on normal cells. Herein, DC_G16-11 could be applied as a validated chemical probe for GCN5-related biological function research and presented great potential for clinical disease treatment.

Design and cellular studies of a carbon nanotube-based delivery system for a hybrid platinum-acridine anticancer agent.

A three-component drug-delivery system has been developed consisting of multi-walled carbon nanotubes (MWCNTs) coated with a non-classical platinum chemotherapeutic agent ([PtCl(NH3)2(L)]Cl (P3A1; L=N-(2-(acridin-9-ylamino)ethyl)-N-methylproprionimidamide) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)-5000] (DSPE-mPEG). The optimized P3A1-MWCNTs are colloidally stable in physiological solution and deliver more P3A1 into breast cancer cells than treatment with the free drug. Furthermore, P3A1-MWCNTs are cytotoxic to several cell models of breast cancer and induce S-phase cell cycle arrest and non-apoptotic cell death in breast cancer cells. By contrast, free P3A1 induces apoptosis and allows progression to G2/M phase. Photothermal activation of P3A1-MWCNTs to generate mild hyperthermia potentiates their cytotoxicity. These findings suggest that delivery of P3A1 to cancer cells using MWCNTs as a drug carrier may be beneficial for combination cancer chemotherapy and photothermal therapy.

Cytotoxic compounds from the fruits of Uapaca togoensis towards multifactorial drug-resistant cancer cells.

Cancer cells may rapidly acquire multidrug resistance, mainly due to the presence of adenosine triphosphate-binding cassette transporters, epidermal growth factor receptor, or mutations in the p53 tumor suppressor gene. This work was designed to assess the cytotoxicity of the methanol crude extracts and compounds from the fruits of Uapaca togoensis, namely, ß-amyryl acetate (1), 11-oxo-α-amyryl acetate (2), lupeol (3), pomolic acid (4), futokadsurin B (5), arborinin (6), and 3-O-ß-D-glucopyranosyl sitosterol (7) against nine drug sensitive and multidrug-resistant cancer cell lines. The resazurin reduction assay was used to evaluate the cytotoxicity of the fruits of U. togoensis and compounds, whilst the caspase-Glo assay was used to detect the activation of caspase enzymes by the fruits of U. togoensis and compound 6. Cell cycle, mitochondrial membrane potential, and levels of reactive oxygen species were all analyzed via flow cytometry. The acridone alkoid 6 and the crude extract from the fruits of U. togoensis were active on all of the nine tested cancer lines with IC50 values below 32 µM and 30 µg/mL, respectively. Compounds 2 and 5 showed selective activities and IC50 values below 99 µM or 42 µM, respectively, which were obtained towards 3/9 and 6/9 tested cancer cell lines. Compound 6 displayed IC50 values below 10 µM towards seven of the nine tested cancer cell lines. The IC50 values ranged from 3.55 µM (against CEM/ADR5000 cells) to 31.77 µM (against CCRF-CEM cells) for alkaloid 6 and from 0.20 µM (against CCRF-CEM cells) to 195.12 µM (against CEM/ADR5000 cells) for doxorubicin. The crude extract of the fruits of U. togoensis induced apoptosis in the CCRF-CEM leukemia cells, which was mediated by the disruption of the mitochondrial membrane potential. Compound 6 also strongly induced apoptosis in CCRF-CEM cells and cell cycle arrest in the G0/G1 and S phases. The crude extract from the fruits of this plant as well as aborinin are potential antiproliferative natural products that deserve further investigation to develop novel cytotoxic drugs to fight sensitive and otherwise drug-resistant phenotypes.

[Study of the influence of original multicomponent gels on the process of pathological scar formation using new methodological approach].

A new method of the quantitative macroscopic assessment of the process of a complex infected wound healing has been created. It was verified by example of the influence of original multicomponent gels consisting of cycloferon, amino acid glycine, glycyram (ammonium salt of glycyrrhizic acid), and vegetable oils on the process of infected wound healing and pathological scar formation. Simultaneously, the wound healing was monitored by the conventional histomorphological method. The proposed gels more effectively prevent the formation of pathological scars in comparison to reference preparation Contractubex.

Design, synthesis and evaluation of acridine and fused-quinoline derivatives as potential anti-tuberculosis agents.

The synthesis of twelve acridine and polycyclic acridine derivatives prepared via the Friedländer reaction is described. The one-pot reactions of 2-amino-5-chloro or 5-nitro-benzophenones and a variety of cyclanones and indanones were carried out in a MW oven under TFA catalysis in good yields. The products were designed according natural antituberculosis products and were evaluated for growth inhibitory activity towards Mycobacterium tuberculosis H37Rv (Mtb) through the National Institute of Allergy and Infectious Diseases (NIAID, USA). Three of them underwent additional testings. The cyclopenta[b]quinoline derivative 9 and the acridine derivative 13 showed remarkable MIC values against the rifampin resistant strain. The former exhibited bactericidal activity at 50 µg/mL, its intracellular activity is similar to rifampin and it was not cytotoxic at low concentrations so it can be considered a new lead compound.

Two new acridone alkaloids from the branch of Atalantia buxifolia and their biological activity.

Two new acridone alkaloids, 3-methoxy-1,4,5-trihydroxy-10-methylacridone (1) and 2,3-dimethoxy-1,4,5-trihydroxy-10-methylacridone (2), were isolated from the ethanol extract of the branch of Atalantia buxifolia. Their structures were elucidated by spectroscopic methods including 1D and 2D NMR. Compounds 1 and 2 exhibited significant antibacterial activity against Staphylococcus aureus and weak inhibitory effect on acetylcholinesterase.

New acridone from the wood of Citrus reticulata Blanco.

A new acridone, named citruscridone (1) together with five known compounds were isolated from the wood of Citrus reticulata Blanco. Their structures were established based on spectroscopic evidence. The antibacterial and antifungal activities of the wood extracts and pure compounds were evaluated.

[Role of cycloferon and interferon-alphain apoptosis regulation in neuroendocrinal system on aging].

A detailed analysis of the literature data gives contradictory information about the role of interferon-alpha in the regulation of apoptosis, while there are almost no data on the participation of cycloferon in this process. Results of original experiments in recent years showed that exogenous interferon-alpha is not apoptosis protector in hypothalamic neurons on aging. The treatment with interferon-alpha activates dystrophic processes in neurosecretory cells of aged mice. However, endogenous interferon induced by cycloferon leads to a decrease in the apoptosis of hypothalamic neurons in both young and old animals. Antiapoptotic activity of interferon-alpha and cycloferon has been found in aged animals under stress condition. Thus, the role of immunomodulators in apoptosis regulation in hypothalamic neurons depends on the age and the type of immunomodulators. This fact opens new prospects for the clinical use of interferon-alpha and cycloferon.

Mechanism-based CYP2D6 inactivation by acridone alkaloids of Indonesian medicinal plant Lunasia amara.

Fourteen acridone alkaloids isolated from Lunasia amara Blanco were tested for their mechanism-based inhibition on human liver microsomal dextromethorphan O-demethylation activity, a prototype marker for cytochrome P450 2D6 (CYP2D6). Among the 14 compounds, 5-hydroxygraveroline (1), 8-methoxyifflaiamine (2), lunamarine (3), and lunine (12) increased their inhibitory activity with increasing preincubation time. Then, we further examined the possibility of mechanism-based inhibition on 5-hydroxygraveroline (1) and lunamarine (3), which showed the potent inhibition. Further investigations on 1 and 3 showed that the characteristic time- and concentration-dependent inhibition, which required a catalytic step with NADPH, was not protected by nucleophiles, and was decreased by the presence of a competitive inhibitor. Thus, 1 and 3 were concluded as mechanism-based inactivators of CYP2D6.

The effects of a telomere destabilizing agent on cancer cell-cycle dynamics--integrated modelling and experiments.

The pentacyclic acridinium salt RHPS4 displays anti-tumour properties in vitro as well as in vivo and is potentially cell-cycle specific. We have collected experimental data and formulated a compartmental model using ordinary differential equations to investigate how the compound affects cells in each stage of the cell cycle. In addition to a control case in which no drug was used, we treated colorectal cancer cells with three different concentrations of the drug and fitted simulations from our models to experimental observations. We found that RHPS4 caused a concentration-dependent, marked cell death in treated cells, which is best modelled by allowing the rate parameters corresponding to cell death to be sigmoidal functions of time. We have shown that the model is "identifiable", meaning that, at least in principle, the parameter values can be determined from observable quantities. We find that at low concentrations RHPS4 primarily affects the cells in the G(2)/M phase, and that the drug has a delayed effect with the delay decreasing at larger doses. Since the drug diffuses into the nucleus, the observed delayed effect of the compound is unexpected and is a novel finding of our research into this compound.

Synthesis and in vitro evaluation of 7-methoxy-N-(pent-4-enyl)-1,2,3,4-tetrahydroacridin-9-amine-new tacrine derivate with cholinergic properties.

Cholinesterase inhibitors are, so far, the only successful strategy for the symptomatic treatment of Alzheimer's disease. Tacrine (THA) is a potent acetylcholinesterase inhibitor that was used in the treatment of Alzheimer's disease for a long time. However, the clinical use of THA was hampered by its low therapeutic index, short half-life and liver toxicity. 7-Methoxytacrine (7-MEOTA) is equally pharmacological active compound with lower toxicity compared to THA. In this Letter, the synthesis, biological activity and molecular modelling of elimination by-product isolated during synthesis of 7-MEOTA based bis-alkylene linked compound is described.

Anti-leishmanial activity of plant-derived acridones, flavaglines, and sulfur-containing amides.

Visceral and cutaneous leishmaniases are an important public health problem in endemic geographic regions in 88 countries worldwide, with around 12 million infected people. Treatment options are limited due to toxicity and teratogenicity of the available drugs, response problems in HIV/Leishmania co-infections, and upcoming resistances. In this study, we investigated the anti-leishmanial activity of 13 plant-derived compounds in vitro aiming to find new drug candidates. Toxicity of the compounds was evaluated in human primary hepatocytes, and hemolytic activity was examined in freshly isolated erythrocytes. Two acridones, 5-hydroxynoracronycine and yukocitrine, two flavaglines, aglafoline and rocaglamide, and the sulfur-containing amide methyldambullin showed promising anti-leishmanial activities with 50% effective concentrations (EC50s) of 34.84, 29.76, 7.45, 16.45, and 6.29 µM, respectively. Hepatotoxic activities of 5-hydroxynoracronycine, yukocitrine, and methyldambullin were significantly lower compared to miltefosine and lower or equal compared to artesunate, whereas the ones of rocaglamide and aglafoline were slightly higher compared to miltefosine and significantly higher compared to artesunate. None of the compounds showed hemolytic activity.

Synthesis and in vitro evaluation of N-(Bromobut-3-en-2-yl)-7-methoxy-1,2,3,4-tetrahydroacridin-9-amine as a cholinesterase inhibitor with regard to Alzheimer's disease treatment.

A new tacrine based cholinesterase inhibitor, N-(bromobut-3-en-2-yl)-7-methoxy-1,2,3,4-tetrahydroacridin-9-amine (1), was designed and synthesized to interact with specific regions of human acetylcholinesterase and human butyrylcholinesterase. Its inhibitory ability towards cholinesterases was determined and compared to tacrine (THA) and 9-amino-7-methoxy-1,2,3,4-tetrahydroacridine (7-MEOTA). The assessment of IC50 values revealed 1 as a weak inhibitor of both tested enzymes.

The transport of gastrodin in Caco-2 cells and uptake in Bcap37 and Bcap37/MDR1 cells.

Gastrodin (GAS) is the major bioactive component of the extracts from the rhizome of Gastrodia elata Blume. The aim of this study is to investigate the transport of GAS in Caco-2 cells and the interaction of P-glycoprotein and GAS. The apparent permeability coefficients (Papp) of GAS were measured as a function of directions and concentrations. It was demonstrated that the efflux ratio was < 2.0 over the range of 50-500 micromol x L(-1) of GAS from bi-directional transport studies. The transport rate of GAS was dependent on the concentrations. Papp of GAS was not affected by transport directions, GAS concentration or the classical inhibitors of P-glycoprotein (verapamil and GF 120918). The cellular accumulation of GAS in Bcap37/MDR1 cells transected with hMDR1 gene, was similar to that in Bcap37 cells. The accumulation in both cell lines was concentration dependent. GAS did not affect the accumulation of Rhodamine 123 in Bcap37/MDR1 cells over the range of 50-500 micromol x L(-1). It indicated that the transport of GAS in Caco-2 cell monolayers mainly is by passive paracellular transport pathway. P-glycoprotein did not participate in the absorption of GAS in the intestine or the transport across the blood-brain barrier.

Synthesis of monomeric and dimeric acridine compounds as potential therapeutics in Alzheimer and prion diseases.

Starting from substituted 9-chloroacridines, a series of quinacrine and spacered dimeric acridine compounds was prepared. Their ability to interrupt the protein association of prion- and Alzheimer-specific proteins and Ab peptides was explored using a fast screening system based on FACS analysis. The bis-acridines displayed a higher activity than the corresponding monomers. Among these derivatives, best results were obtained with the 2,4-dimethoxy-6-nitro compound 7h for Abeta-peptides and the 2-methoxy-6-nitro compound 7f for PrP.