Limitations and Challenges of Antioxidant Therapy

Our bodies are constantly exposed to or producing free radicals nearly on a daily basis. These highly reactive molecules are generated through a variety of internal and external processes and pathways within the body. If these free radicals are not neutralized by antioxidants, they can lead to a state of oxidative stress, which has been linked to a wide range of severe and debilitating disorders affecting various systems in the human body. This involves neurodegenerative diseases, diabetes, atherosclerosis, fatty liver, inflammation, and aging. Thankfully, the human body is armed with a repertoire of powerful antioxidants with different natures and modes of action. The recent decades witnessed the publication of enormous papers proving antioxidant activity of a novel synthesized compound, plant extract, or a purified drug in vitro, in vivo, and even on human beings. However, the efficacy of antioxidant therapies in clinical trials, including selenium, vitamin C, vitamin E, and vitamin A, has been notably inconsistent. This inconsistency can be primarily ascribed to different factors related to the nature of free radical generation, purpose and the specific type of therapy employed, and the intricate oxidative stress connected network, among others. Collectively, these factors will be explored in this review article to decipher the observed shortcomings in the application of antioxidant therapies within clinical settings.

Enhancing Cisplatin Efficacy with Low Toxicity in Solid Breast Cancer Cells Using pH-Charge-Reversal Sericin-Based Nanocarriers: Development, Characterization, and In Vitro Biological Assessment

Platinum-based chemotherapeutic agents are widely employed in cancer treatment because of their effectiveness in targeting DNA. However, this indiscriminate action often affects both cancerous and normal cells, leading to severe side effects and highlighting the need for innovative approaches in achieving precise drug delivery. Nanotechnology presents a promising avenue for addressing these challenges. Protein-based nanocarriers exhibit promising capabilities in the realm of cancer drug delivery with silk sericin nanoparticles standing out as a leading contender. This investigation focuses on creating a sericin-based nanocarrier (SNC) featuring surface charge reversal designed to effectively transport cisplatin (Cispt-SNC) into MCF-7 breast cancer cells. Utilizing AutoDock4.2, our molecular docking analyses identified key amino acids and revealed distinctive conformational clusters, providing insights into the drug-protein interaction landscape and highlighting the potential of sericin as a carrier for controlled drug release. The careful optimization and fabrication of sericin as the carrier material were achieved through flash nanoprecipitation, a straightforward and reproducible method that is devoid of intricate equipment. The physicochemical properties of SNCs and Cispt-SNCs, particularly concerning size, surface charge, and morphology, were evaluated using dynamic light scattering (DLS) and scanning electron microscopy (SEM). Chemical and conformational analyses of the nanocarriers were conducted using Fourier-transform infrared spectroscopy (FTIR) and circular dichroism (CD), and elemental composition analysis was performed through energy-dispersive X-ray spectroscopy (EDX). This approach aimed to achieve the smallest nanoparticle size for Cispt-SNCs (180 nm) and high drug encapsulation efficiency (84%) at an optimal sericin concentration of 0.1% (w/v), maintaining a negative net charge at a physiological pH (7.4). Cellular uptake and cytotoxicity were investigated in MCF-7 breast cancer cells. SNCs demonstrated stability and exhibited a pH-dependent drug release behavior, aligning with the mildly acidic tumor microenvironment (pH 6.0-7.0). Efficient cellular uptake of Cispt-SNC, along with DNA fragmentation and chromatin condensation, was found at pH 6, leading to cell apoptosis. These results collectively indicate the potential of SNCs for achieving controlled drug release in a tumor-specific context. Our in vitro studies reveal the cytotoxicity of both cisplatin and Cispt-SNCs on MCF-7 cells. Cisplatin significantly reduced cell viability at 10 μM concentration (IC50), and the unique combination of sericin and cisplatin showcased enhanced cell viability compared to cisplatin alone, suggesting that controlled drug release is indicated by a gradient decrease in cell viability and highlighting SNCs as promising carriers. The study underscores the promise of protein-based nanocarriers in advancing targeted drug delivery for cancer therapy.

CuII Pyrazolyl-Benzimidazole Dinuclear Complexes with Remarkable Antioxidant Activity

Three dinuclear coordination complexes generated from 1-n-butyl-2-((5-methyl-1H-pyrazole-3-yl)methyl)-1H-benzimidazole (L), have been synthesized and characterized spectroscopically and structurally by single crystal X-ray diffraction analysis. Reaction with iron(II) chloride and then copper(II) nitrate led to a co-crystal containing 78 % of [Cu(NO3 )(μ-Cl)(L')]2 (C1 ) and 22 % of [Cu(NO3 )(μ-NO3 )(L')]2 (C2 ), where L was oxidized to a new ligand L' . A mechanism is provided. Reaction with copper chloride led to the dinuclear complex [Cu(Cl)(μ-Cl)(L)]2 (C3 ). The presence of N-H⋅⋅⋅O and C-H⋅⋅⋅O intermolecular interactions in the crystal structure of C1 and C2 , and C-H⋅⋅⋅N and C-H⋅⋅⋅Cl hydrogen bonding in the crystal structure of C3 led to supramolecular structures that were confirmed by Hirshfeld surface analysis. The ligands and their complexes were tested for free radical scavenging activity and ferric reducing antioxidant power. The complex C1 /C2 shows remarkable antioxidant activities as compared to the ligand L and reference compounds.

Vincamine, from an antioxidant and a cerebral vasodilator to its anticancer potential

Vincamine is a naturally occurring indole alkaloid showing antioxidant activity and has been used clinically for the prevention and treatment of cerebrovascular disorders and insufficiencies. It has been well documented that antioxidants may contribute to cancer treatment, and thus, vincamine has been investigated recently for its potential antitumor activity. Vincamine was found to show cancer cell cytotoxicity and to modulate several important proteins involved in tumor growth, including acetylcholinesterase (AChE), mitogen-activated protein kinase (MAPK), nuclear factor-κB (NF-κB), nuclear factor erythroid 2-related factor 2 (Nrf2), and T-box 3 (TBX3). Several bisindole alkaloids, including vinblastine and vincristine and their synthetic derivatives, vindesine, vinflunine, and vinorelbine, have been used as clinically effective cancer chemotherapeutic agents. In the present review, the discovery and development of vincamine as a useful therapeutic agent and its antioxidant and antitumor activity are summarized, with its antioxidant-related mechanisms of anticancer potential being described. Also, discussed herein are the design of the potential vincamine-based oncolytic agents, which could contribute to the discovery of further new agents for cancer treatment.

Codelivery of resveratrol melatonin utilizing pH responsive sericin based nanocarriers inhibits the proliferation of breast cancer cell line at the different pH

Protein-based nanocarriers have demonstrated good potential for cancer drug delivery. Silk sericin nano-particle is arguably one of the best in this field. In this study, we developed a surface charge reversal sericin-based nanocarrier to co-deliver resveratrol and melatonin (MR-SNC) to MCF-7 breast cancer cells as combination therapy. MR-SNC was fabricated with various sericin concentrations via flash-nanoprecipitation as a simple and reproducible method without complicated equipment. The nanoparticles were subsequently characterized for their size, charge, morphology and shape by dynamic light scattering (DLS) and scanning electron microscope (SEM). Nanocarriers chemical and conformational analysis were done by fourier transform infrared spectroscopy (FT-IR) and circular dichroism (CD) respectively. In vitro drug release was determined at different pH values (7.45, 6.5 and 6). The cellular uptake and cytotoxicity were studies using breast cancer MCF-7 cells. MR-SNC fabricated with the lowest sericin concentration (0.1%), showed a desirable 127 nm size, with a net negative charge at physiological pH. Sericin structure was preserved entirely in the form of nano-particles. Among the three pH values we applied, the maximum in vitro drug release was at pH 6, 6.5, and 7.4, respectively. This pH dependency showed the charge reversal property of our smart nanocarrier via changing the surface charge from negative to positive in mildly acidic pH, destructing the electrostatic interactions between sericin surface amino acids. Cell viability studies demonstrated the significant toxicity of MR-SNC in MCF-7 cells at all pH values after 48 h, suggesting a synergistic effect of combination therapy with the two antioxidants. The efficient cellular uptake of MR-SNC, DNA fragmentation and chromatin condensation was found at pH 6. Nutshell, our result indicated proficient release of the entrapped drug combination from MR-SNC in an acidic environment leading to cell apoptosis. This work introduces a smart pH-responsive nano-platform for anti-breast cancer drug delivery.

The Influence of MicroRNA-31 on Oxidative Stress and Radiosensitivity in Pancreatic Ductal Adenocarcinoma

Radioresistance remains a significant challenge in treating pancreatic ductal adenocarcinoma (PDAC), contributing to the poor survival rates of this cancer. MicroRNAs (miRs) are small non-coding RNA molecules that may play an essential role in regulating radioresistance by altering the levels of oxidative stress. In this study, we investigated the role and potential mechanisms linking miR-31 to PDAC radioresistance. A pCMV-miR vector containing a miR-31 mimic was stably expressed into a miR-31-deficient PDAC cell line, BxPC-3. Additionally, a pmiRZip lentivector suppressing miR-31 was stably expressed in a miR-31 abundant PDAC cell line, Panc-1. Clonogenic assays were conducted to explore the role of miR-31 manipulation on radiosensitivity. Fluorometric ROS assays were performed to quantify ROS levels. The expression of potential miR-31 targets was measured by Western blot analysis. It was found that the manipulation of miR-31 altered the radiosensitivity in PDAC cells by regulating oxidative stress. Using online bioinformatics tools, we identified the 3'UTR of GPx8 as a predicted target of miR-31. Our study demonstrates, for the first time, that manipulating miR-31 alters GPx8 expression, regulating ROS detoxification and promoting either a radioresistant or radiosensitive phenotype. MiR-31 may represent a promising therapeutic target for altering radiosensitivity in PDAC cells.

Redox Potential of Antioxidants in Cancer Progression and Prevention

The benevolent and detrimental effects of antioxidants are much debated in clinical trials and cancer research. Several antioxidant enzymes and molecules are overexpressed in oxidative stress conditions that can damage cellular proteins, lipids, and DNA. Natural antioxidants remove excess free radical intermediates by reducing hydrogen donors or quenching singlet oxygen and delaying oxidative reactions in actively growing cancer cells. These reducing agents have the potential to hinder cancer progression only when administered at the right proportions along with chemo-/radiotherapies. Antioxidants and enzymes affect signal transduction and energy metabolism pathways for the maintenance of cellular redox status. A decline in antioxidant capacity arising from genetic mutations may increase the mitochondrial flux of free radicals resulting in misfiring of cellular signalling pathways. Often, a metabolic reprogramming arising from these mutations in metabolic enzymes leads to the overproduction of so called ’oncometabolites’ in a state of ‘pseudohypoxia’. This can inactivate several of the intracellular molecules involved in epigenetic and redox regulations, thereby increasing oxidative stress giving rise to growth advantages for cancerous cells. Undeniably, these are cell-type and Reactive Oxygen Species (ROS) specific, which is manifested as changes in the enzyme activation, differences in gene expression, cellular functions as well as cell death mechanisms. Photodynamic therapy (PDT) using light-activated photosensitizing molecules that can regulate cellular redox balance in accordance with the changes in endogenous ROS production is a solution for many of these challenges in cancer therapy.