Pentoxifylline as a modulator of anticancer drug doxorubicin. Part II: Reduction of doxorubicin DNA binding and alleviation of its biological effects

Influence of silver nanoparticles' size on their direct interactions with doxorubicin and its biological effects

Breast cancer is one of cancer's most deadly varieties. Its variability makes the development of personalized therapies very difficult. Therefore, improvement of classic chemotherapy is still one of the important challenges of cancer research. We addressed this issue applying nanotechnology to verify the influence of silver nanoparticles (AgNPs) on doxorubicin (DOX) anticancer activity and assess if the size of AgNPs affects their interactions with DOX. We employed a broad spectrum of biophysical methods, characterizing 5 and 50 nm AgNPs interactions with DOX using UV-Vis spectroscopy, dynamic light scattering, fluorescence spectroscopy, and atomic force microscopy imaging. Biological effects of observed AgNPs-DOX interactions were assessed utilizing MTT and 3D Matrigel assays on SKBR3 and MDA-MB-231 breast cancer cell lines. Obtained results indicate direct interactions between AgNPs and DOX. Furthermore, AgNPs size influences their interactions with DOX, as evidenced by differences in the heteroaggregates formation observed in biophysical experiments and further supported by in vitro biological assays. We detected reduction of tumor cell viability and/or colony sizes of the analyzed cancer cell lines, registering differences linked to the observed phenomenon. However, the effects may be limited to the outer borders of the tumor microenvironment as evidenced by the 3D model. Summing up, we observed diverse patterns of interactions and biological effects for different sizes of AgNPs with DOX providing insight how the nanoparticles' size affects their interactions with other biologically active compounds. Moreover, obtained data can be further used in experiments on the reduction of tumor size i.e. before the surgical intervention.

Activation of AMPK/mTOR-Driven Autophagy and Suppression of the HMGB1/TLR4 Pathway with Pentoxifylline Attenuates Doxorubicin-Induced Hepatic Injury in Rats

Despite being an effective chemotherapeutic agent, the clinical use of doxorubicin (DOX) is limited by several organ toxicities including hepatic injury. Pentoxifylline (PTX) is a methylxanthine derivative with marked anti-inflammatory and anti-apoptotic features. It is unknown, however, whether PTX can mitigate DOX-evoked hepatotoxicity. This study aims to explore the potential hepatoprotective impact of PTX in DOX-induced hepatic injury and the underlying molecular mechanisms. Histopathology, immunohistochemistry, and ELISA were used to examine liver tissues. The current findings revealed that PTX administration to DOX-intoxicated rats mitigated the pathological manifestations of hepatic injury, reduced microscopical damage scores, and improved serum ALT and AST markers, revealing restored hepatic cellular integrity. These favorable effects were attributed to PTX's ability to mitigate inflammation by reducing hepatic IL-1β and TNF-α levels and suppressing the pro-inflammatory HMGB1/TLR4/NF-κB axis. Moreover, PTX curtailed the hepatic apoptotic abnormalities by suppressing caspase 3 activity and lowering the Bax/Bcl-2 ratio. In tandem, PTX improved the defective autophagy events by lowering hepatic SQSTM-1/p62 accumulation and enhancing the AMPK/mTOR pathway, favoring autophagy and hepatic cell preservation. Together, for the first time, our findings demonstrate the ameliorative effect of PTX against DOX-evoked hepatotoxicity by dampening the hepatic HMGB1/TLR4/NF-κB pro-inflammatory axis and augmenting hepatic AMPK/mTOR-driven autophagy. Thus, PTX could be utilized as an adjunct agent with DOX regimens to mitigate DOX-induced hepatic injury.

Fluorescent Alloyed CdZnSeS/ZnS Nanosensor for Doxorubicin Detection

Doxorubicin (DOX) is widely used in chemotherapy as an anti-tumor drug. However, DOX is highly cardio-, neuro- and cytotoxic. For this reason, the continuous monitoring of DOX concentrations in biofluids and tissues is important. Most methods for the determination of DOX concentrations are complex and costly, and are designed to determine pure DOX. The purpose of this work is to demonstrate the capabilities of analytical nanosensors based on the quenching of the fluorescence of alloyed CdZnSeS/ZnS quantum dots (QDs) for operative DOX detection. To maximize the nanosensor quenching efficiency, the spectral features of QDs and DOX were carefully studied, and the complex nature of QD fluorescence quenching in the presence of DOX was shown. Using optimized conditions, turn-off fluorescence nanosensors for direct DOX determination in undiluted human plasma were developed. A DOX concentration of 0.5 µM in plasma was reflected in a decrease in the fluorescence intensity of QDs, stabilized with thioglycolic and 3-mercaptopropionic acids, for 5.8 and 4.4 %, respectively. The calculated Limit of Detection values were 0.08 and 0.03 μg/mL using QDs, stabilized with thioglycolic and 3-mercaptopropionic acids, respectively.

Pentoxifylline changes the balance of immune cell population in breast tumor-infiltrating lymphocytes

Immunotherapy utilizing tumor-infiltrating lymphocytes (TILs) is a promising approach for cancer treatment. Pentoxifylline (PTXF), a xanthine derivative, exhibits antitumor properties. This study aimed to investigate the impact of PTXF on the phenotype and function of TILs and splenocytes in a triple-negative breast cancer (TNBC) mouse model. TNBC was subcutaneously induced in BALB/c mice, followed by nine intraperitoneal injections of 100 mg/kg PTXF. TILs were then isolated by enzymatic digestion of tumors and cocultured with 4T1 cells. The proportion of regulatory T cells (Tregs) and cytotoxic T cells in TILs and splenocytes was assessed using flow cytometry. Transforming growth factor (TGF)-β and interferon (IFN)-γ production in TILs and splenocytes cultures was measured by ELISA. Relative expression of t-bet, foxp3, gata-3, and ror-γt in TILs and splenocytes was evaluated using real-time PCR. Tumor growth in PTXF-treated mice was significantly lower than that in the controls (P < 0.01). The frequency of regulatory and cytotoxic TILs in PTXF-treated mice was approximately half (P < 0.01) and twice (P < 0.05) that of the control group, respectively. The level of TGF-β and IFN-γ in the supernatant of PTXF-treated TILs was decreased and increased, respectively (P < 0.05). The relative expression of t-bet and foxp3 in the PTXF-treated mice compared to controls was increased and decreased, respectively (P < 0.05). Changes in the immune cell balance were less significant in the spleen compared to the TILs. PTXF treatment could limit the tumor growth and modify the regulatory-to-cytotoxic TILs ratio, as well as cytokine balance of TILs, in favor of antitumor responses.

Pentoxifylline and thiamine ameliorate rhabdomyolysis-induced acute kidney injury in rats via suppressing TLR4/NF-κB and NLRP-3/caspase-1/gasdermin mediated-pyroptosis

Acute kidney injury (AKI) is a common complication of rhabdomyolysis (RM), a syndrome characterized by skeletal muscle damage resulting in renal tubular oxidative stress, inflammation, and activated toll like receptor-4 (TLR-4) and NOD-like receptor protein-3 (NLRP-3) inflammasome. Pyroptosis is a programmed cell death mediated by NLRP-3 leading to the activation of caspase-1 and gasdermin D (GSDMD), the hallmark of pyroptosis. This study aims to investigate the renoprotective effects of two antioxidants; pentoxifylline (PTX) and thiamine (TM) via targeting the aforementioned pathways. RM-AKI was induced in male Albino Wistar rats by intramuscular injection of glycerol (50% v/v, 10 ml/kg). PTX (100 mg/kg, oral) and TM (25 mg/kg, i.p) were administered for 12 days prior glycerol injection and continued for 3 days following induction of RM-AKI. Serum creatinine, blood urea nitrogen (BUN), creatin kinase, lipid peroxides, total antioxidant activity, inflammatory markers (tumor necrosis factor-α, interleukin-1β, and nuclear factor kappa B), TLR4, NLRP-3, caspase-1, GSDMD and c-myc (an apoptotic marker) were estimated. Compared to AKI model, co-administered drugs revealed a significant improvement in renal function and pathology as indicated by the reduction in serum creatinine, BUN and protein cast accumulation. The elevations of oxidative stress, and inflammatory markers as well as the over-expression of c-myc were alleviated. Protein levels of TLR4, NLRP3, cleaved caspase-1, and GSDMD were significantly elevated in RM-AKI model, and this elevation was attenuated by the tested drugs. In conclusion, PTX and TM could be a potential renoprotective approach for patients with RM through targeting TLR4/NF-κB and NLRP-3/caspase-1/gasdermin mediated-pyroptosis pathways.

Antimicrobial, Cytotoxic and Mutagenic Activity of Gemini QAS Derivatives of 1,4:3,6-Dianhydro-l-iditol

A series of quaternary diammonium salts derivatives of 1,4:3,6-dianhydro-l-iditol were synthesized, using isommanide (1,4:3,6-dianhydro-d-mannitol) as a starting material. Both aromatic (pyridine, 4-(N,N-dimethylamino)pyridine (DMAP), (3-carboxamide)pyridine; N-methylimidazole) and aliphatic (trimethylamine, N,N-dimethylhexylamine, N,N-dimethyloctylamine, N,N-dimethyldecylamine) amines were used, giving eight gemini quaternary ammonium salts (QAS). All salts were tested for their antimicrobial activity against yeasts, Candida albicans and Candida glabrata, as well as bacterial Staphylococcus aureus and Escherichia coli reference strains. Moreover, antibacterial activity against 20 isolates of S. aureus collected from patients with skin and soft tissue infections (n = 8) and strains derived from subclinical bovine mastitis milk samples (n = 12) were evaluated. Two QAS with octyl and decyl residues exhibited antimicrobial activity, whereas those with two decyl residues proved to be the most active against the tested pathogens, with MIC of 16-32, 32, and 8 µg/mL for yeast, E. coli, and S. aureus reference and clinical strains, respectively. Only QAS with decyl residues proved to be cytotoxic in MTT assay against human keratinocytes (HaCaT), IC₅₀ 12.8 ± 1.2 μg/mL. Ames test was used to assess the mutagenic potential of QAS, and none of them showed mutagenic activity in the concentration range 4-2000 µg/plate.

Modulatory Effects of Caffeine and Pentoxifylline on Aromatic Antibiotics: A Role for Hetero-Complex Formation

Antimicrobial resistance is a major healthcare threat globally. Xanthines, including caffeine and pentoxifylline, are attractive candidates for drug repurposing, given their well-established safety and pharmacological profiles. This study aimed to analyze potential interactions between xanthines and aromatic antibiotics (i.e., tetracycline and ciprofloxacin), and their impact on antibiotic antibacterial activity. UV-vis spectroscopy, statistical-thermodynamical modeling, and isothermal titration calorimetry were used to quantitatively evaluate xanthine-antibiotic interactions. The antibacterial profiles of xanthines, and xanthine-antibiotic mixtures, towards important human pathogens Staphylococcus aureus, Enterococcus faecium, Escherichia coli, Acinetobacter baumannii, Klebsiella pneumoniae, and Enterobacter cloacae were examined. Caffeine and pentoxifylline directly interact with ciprofloxacin and tetracycline, with neighborhood association constant values of 15.8-45.6 M-1 and enthalpy change values up to -4 kJ·M-1. Caffeine, used in mixtures with tested antibiotics, enhanced their antibacterial activity in most pathogens tested. However, antagonistic effects of caffeine were also observed, but only with ciprofloxacin toward Gram-positive pathogens. Xanthines interact with aromatic antibiotics at the molecular and in vitro antibacterial activity level. Given considerable exposure to caffeine and pentoxifylline, these interactions might be relevant for the effectiveness of antibacterial pharmacotherapy, and may help to identify optimal treatment regimens in the era of multidrug resistance.

Gold-Etched Silver Nanowire Endoscopy: Toward a Widely Accessible Platform for Surface-Enhanced Raman Scattering-Based Analysis in Living Cells

Recently, our group introduced the use of silver nanowires (AgNWs) as novel non-invasive endoscopic probes for detecting intracellular Raman signals. This method, although innovative and promising, relies exclusively on the plasmonic waveguiding effect for signal enhancement. It, therefore, requires sophisticated operational tools and protocols, drastically limiting its applicability. Herein, an advanced strategy is offered to significantly enhance the performance of these endoscopic probes, making this approach widely accessible and versatile for cellular studies. By uniformly forming gold structures on the smooth AgNW surface via a galvanic replacement reaction, the density of the light coupling points along the whole probe surface is drastically increased, enabling high surface-enhanced Raman scattering (SERS) efficiency upon solely focusing the excitation light on the gold-etched AgNW. The applicability of these gold-etched AgNW probes for molecular sensing in cells is demonstrated by detecting site-specific and high-resolved SERS spectra of cell compartment-labeling dyes, namely, 4',6-diamidino-2-phenylindole in the nucleus and 3,3'-dioctadecyloxacarbocyanine on the membrane. The remarkable spectral sensitivity achieved provides essential structural information of the analytes, indicating the overall potential of the proposed approach for cellular studies of drug interactions with biomolecular items.

Fragment-based design of small molecule PCSK9 inhibitors using simulated annealing of chemical potential simulations

PCSK9 is a protein secreted by the liver that binds to the low-density lipoprotein receptor (LDLR), causing LDLR internalization, decreasing the clearance of circulating LDL particles. Mutations in PCSK9 that strengthen its interactions with LDLR result in familial hypercholesterolemia (FH) and early onset atherosclerosis, while nonsense mutations of PCSK9 result in cardio-protective hypocholesterolemia. These observations led to PCSK9 inhibition for cholesterol lowering becoming a high-interest therapeutic target, with antibody drugs reaching the market. An orally-available small molecule drug is highly desirable, but inhibiting the PCSK9/LDLR protein-protein interaction (PPI) has proven challenging. Alternate approaches to finding good lead candidates are needed. Motivated by the FH mutation data on PCSK9, we found that modeling the PCSK9/LDLR interface revealed extensive electron delocalization between and within the protein partners. Based on this, we hypothesized that compounds assembled from chemical fragments could achieve the affinity required to inhibit the PCSK9/LDLR PPI if they were selected to interact with PCSK9 in a way that, like LDLR, also involves significant fractional charge transfer to form partially covalent bonds. To identify such fragments, Simulated Annealing of Chemical Potential (SACP) fragment simulations were run on multiple PCSK9 structures, using optimized partial charges for the protein. We designed a small molecule, composed of several fragments, predicted to interact at two sites on the PCSK9. This compound inhibits the PPI with 1 μM affinity. Further, we designed two similar small molecules where one allows charge delocalization though a linker and the other doesn’t. The first inhibitor with charge delocalization enhances LDLR surface expression by 60% at 10 nM, two orders of magnitude more potent than the EGF domain of LDLR. The other enhances LDLR expression by only 50% at 1 μM. This supports our conjecture that fragments can have surprisingly outsized efficacy in breaking PPI’s by achieving fractional charge transfer leading to partially covalent bonding.

The theory of interceptor-protector action of DNA binding drugs

The review discusses the theory of interceptor-protector action (the IPA theory) as the new self-consistent biophysical theory establishing a quantitative interrelation between parameters measured in independent physico-chemical experiment and in vitro biological experiment for the class of DNA binding drugs. The elements of the theory provide complete algorithm of analysis, which may potentially be applied to any system of DNA targeting aromatic drugs. Such analytical schemes, apart from extension of current scientific knowledge, are important in the context of rational drug design for managing drug's response by changing the physico-chemical parameters of molecular complexation.

Hetero-association models of non-covalent molecular complexation

The present review discusses the current state-of-the-art in building models enabling the description of non-covalent equilibrium complexation of different types of molecules in solution, which results in the formation of supramolecular structures different in length and composition (hetero-association or supramolecular multicomponent co-polymerisation). The description is focused on standard physical and chemical quantities such as experimental observables and equilibrium parameters of interaction (equilibrium constants and concentrations). The major partial cases of the hetero-association models, such as finite and indefinite isodesmic and cooperative complexations, and Benesi-Hildebrand and Langmuir adsorption models are considered. Future challenges in the development of the hetero-association models are provided.

Interactions of newly synthesized platinum nanoparticles with ICR-191 and their potential application

One of the greatest challenges of modern medicine is to find cheaper and easier ways to produce transporters for biologically active substances, which will provide selective and efficient drug delivery to the target cells, while causing low toxicity towards healthy cells. Currently, metal-based nanoparticles are considered a successful and viable solution to this problem. In this work, we propose the use of novel synthesis method of platinum nanoparticles (PtNPs) connected with their precise biophysical characterization and assessment of their potential toxicity. To work as an efficient nanodelivery platform, nanoparticles should interact with the desired active compounds spontaneously and non-covalently. We investigated possible direct interactions of PtNPs with ICR-191, a model acridine mutagen with well-established biophysical properties and mutagenic activity, by Dynamic Light Scattering, fluorescence spectroscopy, and Isothermal Titration Calorimetry. Moreover, to determine the biological activity of ICR-191-PtNPs aggregates, we employed Ames mutagenicity test, eukaryotic cell line analysis and toxicity test against the model organism Caenorhabditis elegans. PtNPs' interesting physicochemical properties associated to the lack of toxicity in a tested range of concentrations, as well as their ability to modulate ICR-191 biological activity, suggest that these particles successfully work as potential delivery platforms for different biologically active substances.

Advancing Raman microspectroscopy for cellular and subcellular analysis: towards in vitro high-content spectralomic analysis

In the confocal mode, Raman microspectroscopy can profile the biochemical content of biological cells at a subcellular level, and any changes to it by exogenous agents, such as therapeutic drugs or toxicants. As an exploration of the potential of the technique as a high-content, label-free analysis technique, this report reviews work to monitor the spectroscopic signatures associated with the uptake and response pathways of commercial chemotherapeutic agents and polymeric nanoparticles by human lung cells. It is demonstrated that the signatures are reproducible and characteristic of the cellular event, and can be used, for example, to identify the mode of action of the agent as well as the subsequent cell death pathway, and even mechanisms of cellular resistance. Data mining approaches are discussed and a spectralomics approach is proposed.

Antifibrotic effects of pentoxifylline improve the efficacy of gemcitabine in human pancreatic tumor xenografts

We investigated the combinatorial effects of pentoxifylline (PTX) on the efficacy of gemcitabine (GEM) in a human pancreatic tumor xenograft model. PTX significantly improved the efficacy of GEM, as shown by a 50% reduction in tumor growth rate at 4 weeks of treatment compared with that in animals given GEM alone. The fluorescent drug doxorubicin (DOX) was used to test whether drug delivery was improved by PTX, contributing to the improved efficacy of GEM. PTX given for 2 weeks prior to giving DOX improved drug distribution by 1.8‐ to 2.2‐fold with no changes in vessel density, suggesting that improvement in drug delivery was not related to the vascular mechanism. Instead, collagen I content in tumor stroma was significantly reduced, as was the expression of alpha‐smooth muscle actin of cancer‐associated fibroblasts and connective tissue growth factor (CTGF) by PTX pretreatment. Overall, our data demonstrated that increased efficacy of GEM by PTX was associated with improved drug delivery to tumor tissue, which may be attributed to decreased expression of CTGF and subsequent reduction in the stromal collagen matrix in the pancreatic ductal adenocarcinoma tumor. These results support the usefulness of PTX in combination with chemotherapy for targeting drug delivery barriers associated with the stromal matrix, which should be further evaluated for clinical development.

Thermoresponsive supramolecular micellar drug delivery system based on star-linear pseudo-block polymer consisting of β-cyclodextrin-poly(N-isopropylacrylamide) and adamantyl-poly(ethylene glycol)

Chemotherapy is facing several limitations such as low water solubility of anticancer drugs and multidrug resistance (MDR) in cancer cells. To overcome these limitations, a thermoresponsive micellar drug delivery system formed by a non-covalently connected supramolecular block polymer was developed. The system is based on the host-guest interaction between a well-defined β-cyclodextrin (β-CD) based poly(N-isopropylacrylamide) star host polymer and an adamantyl-containing poly(ethylene glycol) (Ad-PEG) guest polymer. The structures of the host and guest polymers were characterized by ¹H and ¹³C NMR, GPC and FTIR. Subsequently, they formed a pseudo-block copolymer via inclusion complexation between β-CD core and adamantyl-moiety, which was confirmed by 2D NMR. The thermoresponsive micellization of the copolymer was investigated by UV-vis spectroscopy, DLS and TEM. At 37°C, the copolymer at a concentration of 0.2mg/mL in PBS formed micelles with a hydrodynamic diameter of ca. 282nm. The anticancer drug, doxorubicin (DOX), was successfully loaded into the core of the micelles with a loading level of 6% and loading efficiency of 17%. The blank polymer micelles showed good biocompatibility in cell cytotoxicity studies. Moreover, the DOX-loaded micelles demonstrated superior therapeutic effects in AT3B-1-N (MDR-) and AT3B-1 (MDR+) cell lines as compared to free DOX control, overcoming MDR in cancer cells.

Establishment of an Immortalized Skin Keratinocyte Cell Line Derived from the Animal Model Mastomys coucha

In the present report we describe the establishment of a spontaneous immortalized skin keratinocyte cell line derived from the skin of the multimammate rodent Mastomys coucha. These animals are used in preclinical studies for a variety of human diseases such as infections with nematodes, bacteria and papillomaviruses, especially regarding cutaneous manifestations such as non-melanoma skin cancer. Here we characterize the cells in terms of their origin and cytogenetic features. Searching for genomic signatures, a spontaneous mutation in the splicing donor sequence of Trp53 (G to A transition at the first position of intron 7) could be detected. This point mutation leads to alternative splicing and to a premature stop codon, resulting in a truncated and, in turn, undetectable form of p53, probably contributing to the process of immortalization. Mastomys coucha-derived skin keratinocytes can be used as an in vitro system to investigate molecular and immunological aspects of infectious agent interactions with their host cells.