Effect of silver nanomaterials on the activity of thiol-containing antioxidants

L-Cysteine: A promising nutritional supplement for alleviating anxiety disorders

Anxiety disorders are prevalent chronic psychological disease with complex pathogenic mechanisms. Current anxiolytics have limited efficacy and numerous side effects in many anxiety patients, highlighting the urgent need for new therapies. Recent research has been focusing on nutritional supplements, particularly amino acids, as potential therapies for anxiety disorders. Among these, L-Cysteine plays a crucial role in various biological processes. L-Cysteine exhibits antioxidant properties that can enhance the antioxidant functions of the central nervous system (CNS). Furthermore, metabolites of L-cysteine, such as glutathione and hydrogen sulfide have been shown to alleviate anxiety through distinct molecular mechanisms. Long-term administration of L-Cysteine has anxiolytic, antidepressant, and memory-improving effects. L-Cysteine depletion can lead to increased oxidative stress in the brain. This review delves into the potential mechanisms of L-Cysteine and its main products, glutathione (GSH) and hydrogen sulfide (H2S) in the management of anxiety and related diseases.

Oxidation Analysis of l-Cysteine with a Chiral Sensor Based on Quantum Weak Measurement

l-Cysteine, distinguished by its possession of reactive sulfhydryl groups within its molecular structure, plays a significant role in both biological systems and the pharmaceutical industry. It stands not only as a natural component integral to the constitution of glutathione but also as the principal precursor for the synthesis of l-cystine through an oxidation reaction. This study endeavors to introduce a novel approach to l-cysteine analysis, capitalizing on its optical activity, whereby an optical rotation detection system grounded in the principles of quantum weak measurement is proffered. The optical rotation angle corresponding to the concentration of chiral solutions can be accurately ascertained through spectral analysis. In practical implementation, a chiral sensing system, boasting a sensitivity of 372 nm/rad, was meticulously constructed, leveraging the concept of weak value amplification. Then, the real-time monitoring of chemical reactions involving l-cysteine and dimethyl sulfoxide was performed. Under the specific experimental conditions outlined in this investigation, it was observed that the oxidation process culminated within approximately 12 h. The application of weak measurement-based chiral sensors holds immense potential, providing robust technical support for real-time monitoring in fields such as chiral analysis and the synthesis of chiral pharmaceutical compounds.

Silver Nanoparticles Enhance Oxidative Stress, Inflammation, and Apoptosis in Liver and Kidney Tissues: Potential Protective Role of Thymoquinone

Silver nanoparticles (AgNPs) are the most common nanomaterials in consumer products. Therefore, it has been crucial to control AgNPs toxicological effects to improve their safety and increase the outcome of their applications. This work investigated the possible protective effect of thymoquinone (TQ) against AgNPs-induced hepatic and renal cytotoxicity in rats. Serum markers of liver and kidney functions as well as liver and kidney oxidative stress status, pro-inflammatory cytokines, apoptosis markers, and histopathology were assessed. TQ reversed AgNPs-induced elevation in serum liver and kidney function markers, including aspartate transaminase, alanine transaminase, urea, and creatinine. Moreover, TQ co-administration with AgNPs alleviates hepatic and renal oxidative insults by decreasing MDA and NO levels with a significant increase in the activity of antioxidant enzymes (superoxide dismutase, catalase, and glutathione recycling enzymes peroxidase and reductase) compared to AgNPs-treated rats. Besides, TQ upregulated hepatic and renal Nrf2 gene expression in AgNPs-intoxicated rats. Furthermore, TQ co-administration decreased the hepatic and renal pro-inflammatory mediators represented by IL-1β, TNF-α, TGF-β, and NF-κB levels. Besides, TQ co-administration decreased apoptotic protein (Bax) levels and increased the anti-apoptotic protein (Bcl-2) levels. These findings were confirmed by the histopathological examination of hepatic and renal tissues. Our data affirmed the protective effect of TQ against AgNPs cytotoxicity and proposed a possible mechanism of TQ antioxidant, anti-inflammatory, and anti-apoptotic effects. Consequently, we could conclude that using TQ might control AgNPs toxicological effects, improve their safety, and increase the outcome of their applications.

Apigenin attenuates molecular, biochemical, and histopathological changes associated with renal impairments induced by gentamicin exposure in rats

Gentamicin (GM) is an aminoglycoside antibiotic used to treat bacterial infections. However, its application is accompanied by renal impairments. Apigenin is a flavonoid found in many edible plants with potent therapeutic values. This study was designed to elucidate the therapeutic effects of apigenin on GM-induced nephrotoxicity. Animals were injected orally with three different doses of apigenin (5 mg kg-1 day-1, 10 mg kg-1 day-1, and 20 mg kg-1 day-1). Apigenin administration abolished the alterations in the kidney index and serum levels of kidney-specific functions markers, namely blood urea nitrogen and creatinine, and KIM-1, NGAL, and cystatin C following GM exposure. Additionally, apigenin increased levels of enzymatic (glutathione reductase, glutathione peroxidase, superoxide dismutase, and catalase) and non-enzymatic antioxidant proteins (reduced glutathione) and decreased levels of lipid peroxide, nitric oxide, and downregulated nitric oxide synthase-2 in the kidney tissue following GM administration. At the molecular scope, apigenin administration was found to upregulate the mRNA expression of Nfe2l2 and Hmox1 in the kidney tissue. Moreover, apigenin administration suppressed renal inflammation and apoptosis by decreasing levels of interleukin-1β, tumor necrosis factor-alpha, nuclear factor kappa-B, Bax, and caspase-3, while increasing B-cell lymphoma-2 compared with those in GM-administered group. The recorded data suggests that apigenin treatment could be used to alleviate renal impairments associated with GM administration.

Chemical Mechanisms of Nanoparticle Radiosensitization and Radioprotection: A Review of Structure-Function Relationships Influencing Reactive Oxygen Species

Metal nanoparticles are of increasing interest with respect to radiosensitization. The physical mechanisms of dose enhancement from X-rays interacting with nanoparticles has been well described theoretically, however have been insufficient in adequately explaining radiobiological response. Further confounding experimental observations is examples of radioprotection. Consequently, other mechanisms have gained increasing attention, especially via enhanced production of reactive oxygen species (ROS) leading to chemical-based mechanisms. Despite the large number of variables differing between published studies, a consensus identifies ROS-related mechanisms as being of significant importance. Understanding the structure-function relationship in enhancing ROS generation will guide optimization of metal nanoparticle radiosensitisers with respect to maximizing oxidative damage to cancer cells. This review highlights the physico-chemical mechanisms involved in enhancing ROS, commonly used assays and experimental considerations, variables involved in enhancing ROS generation and damage to cells and identifies current gaps in the literature that deserve attention. ROS generation and the radiobiological effects are shown to be highly complex with respect to nanoparticle physico-chemical properties and their fate within cells. There are a number of potential biological targets impacted by enhancing, or scavenging, ROS which add significant complexity to directly linking specific nanoparticle properties to a macroscale radiobiological result.

Photogenerated Charge Carriers in Molybdenum Disulfide Quantum Dots with Enhanced Antibacterial Activity

Molybdenum disulfide (MoS₂) nanosheets have received considerable interest due to their superior physicochemical performances to graphene nanosheets. As the lateral size and layer thickness decrease, the formed MoS₂ quantum dots (QDs) show more promise as photocatalysts, endowing them with potential antimicrobial properties under environmental conditions. However, studies on the antibacterial photodynamic therapy of MoS₂ QDs have rarely been reported. Here, we show that MoS₂ QDs more effectively promote the creation and separation of electron-hole pair than MoS₂ nanosheets, resulting in the formation of multiple reactive oxygen species (ROS) under simulated solar light irradiation. As a result, photoexcited MoS₂ QDs show remarkably enhanced antibacterial activity, and the ROS-mediated oxidative stress plays a dominant role in the antibacterial mechanism. The in vivo experiments showed that MoS₂ QDs are efficacious in wound healing under simulated solar light irradiation and exert protective effects on normal tissues, suggesting good biocompatibility properties. Our findings provide a full description of the photochemical behavior of MoS₂ QDs and the resulting antibacterial activity, which might advance the development of MoS₂-based nanomaterials as photodynamic antibacterial agents under environmental conditions.

N-Acetylcysteine reverses silver nanoparticle intoxication in rats

The increasing use of silver nanoparticles (AgNPs) in consumer products raises the risk of human toxicity. Currently, there are no therapeutic options or established treatment protocols in cases of AgNPs intoxication. We demonstrated previously that thiol antioxidants compounds can reverse the cytotoxicity induced by AgNPs in Huh-7 hepatocarcinoma cells. Here, we investigated the use of N-acetylcysteine (NAC) against the systemic toxic effects of AgNPs (79.3 nm) in rats. Biochemical, histopathological, hematological, and oxidative parameters showed that a single intravenous injection of AgNPs (5 mg/kg b.w.) induced deleterious effects such as hepatotoxicity, potentially as a result of AgNPs accumulation in the liver. Treatment with a single intraperitoneal injection of NAC (1 g/kg b.w.) one hour after AgNPs exposure significantly attenuated all toxic effects evaluated and altered the bioaccumulation and release patterns of AgNPs in rats. The findings show that NAC may be a promising candidate for clinical management of AgNPs intoxication.

Combination Effect of Silver Nanoparticles and Histone Deacetylases Inhibitor in Human Alveolar Basal Epithelial Cells

Although many treatment strategies have been reported for lung disease, the mechanism of combination therapy using silver nanoparticles (AgNPs) and histone deacetylases inhibitors (HDACi) remains unclear. Therefore, innovative treatment strategies are essential for addressing the therapeutic challenges of this highly aggressive lung cancer. AgNPs and HDACi seem to be the best candidates for anticancer therapy because of their anti-proliferative effect in a variety of cancer cells. First, we synthesized AgNPs using wogonin as a reducing and stabilizing agent, following which the synthesized AgNPs were characterized by various analytical techniques. The synthesized AgNPs exhibited dose- and size-dependent toxicity towards A549 cells. Interestingly, the combination of AgNPs and MS-275 significantly induces apoptosis, which was accompanied by an increased level of reactive oxygen species (ROS); leakage of lactate dehydrogenase (LDH); secretion of TNFα; dysfunction of mitochondria; accumulation autophagosomes; caspase 9/3 activation; up and down regulation of pro-apoptotic genes and anti-apoptotic genes, respectively; and eventually, induced DNA-fragmentation. Our findings suggest that AgNPs and MS-275 induce cell death in A549 lung cells via the mitochondrial-mediated intrinsic apoptotic pathway. Finally, our data show that the combination of AgNPs and MS-275 is a promising new approach for the treatment of lung cancer and our findings contribute to understanding the potential roles of AgNPs and MS-275 in pulmonary disease. However, further study is warranted to potentiate the use of this combination therapy in cancer therapy trials.

Effects of noble metal nanoparticles on the hydroxyl radical scavenging ability of dietary antioxidants

Noble metal nanoparticles (NPs) have been widely used in many consumer products. Their effects on the antioxidant activity of commercial dietary supplements have not been well evaluated. In this study, we examined the effects of gold (Au NPs), silver (Ag NPs), platinum (Pt NPs), and palladium (Pd NPs) on the hydroxyl radical (·OH) scavenging ability of three dietary supplements vitamin C (L-ascorbic acid, AA), (-)-epigallocatechin gallate (EGCG), and gallic acid (GA). By electron spin resonance (ESR) spin-trapping measurement, the results show that these noble metal NPs can inhibit the hydroxyl radical scavenging ability of these dietary supplements.

Bactericidal Effects of Silver Nanoparticles on Lactobacilli and the Underlying Mechanism

While the antibacterial properties of silver nanoparticles (AgNPs) have been demonstrated across a spectrum of bacterial pathogens, the effects of AgNPs on the beneficial bacteria are less clear. To address this issue, we compared the antibacterial activity of AgNPs against two beneficial lactobacilli ( Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus casei) and two common opportunistic pathogens ( Escherichia coli and Staphylococcus aureus). Our results demonstrate that those lactobacilli are highly susceptible to AgNPs, while the opportunistic pathogens are not. Acidic environment caused by the lactobacilli is associated with the bactericidal effects of AgNPs. Our mechanistic study suggests that the acidic growth environment of lactobacilli promotes AgNP dissolution and hydroxyl radical (•OH) overproduction. Furthermore, increases in silver ions (Ag⁺) and •OH deplete the glutathione pool inside the cell, which is associated with the increase in cellular reactive oxygen species (ROS). High levels of ROS may further induce DNA damage and lead to cell death. When E. coli and S. aureus are placed in a similar acidic environment, they also become more susceptible to AgNPs. This study provides a mechanistic description of a pH-Ag⁺-•OH bactericidal pathway and will contribute to the responsible development of products containing AgNPs.

Effects of the Usage of l-Cysteine (l-Cys) on Human Health

This review summarizes recent knowledge about the use of the amino acid l-Cysteine (l-Cys) through diet, nutritional supplements or drugs with the aim to improve human health or treat certain diseases. Three databases (PubMed, Scopus, and Web of Science) and different keywords have been used to create a database of documents published between 1950 and 2017 in scientific journals in English or Spanish. A total of 60,885 primary publications were ultimately selected to compile accurate information about the use of l-Cys in medicine and nutritional therapies and to identify the reported benefits of l-Cys on human health. The number of publications about the use of l-Cys for these purposes has increased significantly during the last two decades. This increase seems to be closely related to the rise of nutraceutical industries and personalized medicine. The main evidence reporting benefits of l-Cys usage is summarized. However, the lack of accurate information and studies based on clinical trials hampers consensus among authors. Thus, the debate about the role and effectiveness of supplements/drugs containing l-Cys is still open.

Effects of P25 TiO2 Nanoparticles on the Free Radical-Scavenging Ability of Antioxidants upon Their Exposure to Simulated Sunlight

Although nanosized ingredients, including TiO₂ nanoparticles (NPs), can be found in a wide range of consumer products, little is known about the effects these particles have on other active compounds in product matrices. These NPs can interact with reactive oxygen species (ROS), potentially disrupting or canceling the benefits expected from antioxidants. We used electron spin resonance spectrometry to assess changes in the antioxidant capacities of six dietary antioxidants (ascorbic acid, α-tocopherol, glutathione, cysteine, epicatechin, and epicatechin gallate) during exposure to P25 TiO₂ and/or simulated sunlight. Specifically, we determined the ability of these antioxidants to scavenge 1-diphenyl-2-picryl-hydrazyl radical, superoxide radical, and hydroxyl radical. Exposure to simulated sunlight alone did not lead to noticeable changes in radical-scavenging abilities; however, in combination with P25 TiO₂ NPs, the scavenging abilities of most antioxidants were weakened. We found glutathione to be the most resistant to treatment with sunlight and NPs among these six antioxidants.

Platinum nanoparticles inhibit antioxidant effects of vitamin C via ascorbate oxidase-mimetic activity

Pt nanoparticles with ascorbate oxidase-mimetic activity inhibit the cytoprotective effect of vitamin C on cells challenged by H₂O₂.

Silver nanoparticles affect glucose metabolism in hepatoma cells through production of reactive oxygen species

The silver nanoparticle (AgNP) is a candidate for anticancer therapy because of its effects on cell survival and signaling. Although numerous reports are available regarding their effect on cell death, the effect of AgNPs on metabolism is not well understood. In this study, we investigated the effect of AgNPs on glucose metabolism in hepatoma cell lines. Lactate release from both HepG2 and Huh7 cells was reduced with 5 nm AgNPs as early as 1 hour after treatment, when cell death did not occur. Treatment with 5 nm AgNPs decreased glucose consumption in HepG2 cells but not in Huh7 cells. Treatment with 5 nm AgNPs reduced nuclear factor erythroid 2-like 2 expression in both cell types without affecting its activation at the early time points after AgNPs’ treatment. Increased reactive oxygen species (ROS) production was detected 1 hour after 5 nm AgNPs’ treatment, and lactate release was restored in the presence of an ROS scavenger. Our results suggest that 5 nm AgNPs affect glucose metabolism by producing ROS.

Differential cytotoxic and radiosensitizing effects of silver nanoparticles on triple-negative breast cancer and non-triple-negative breast cells

Identification of differential sensitivity of cancer cells as compared to normal cells has the potential to reveal a therapeutic window for the use of silver nanoparticles (AgNPs) as a therapeutic agent for cancer therapy. Exposure to AgNPs is known to cause dose-dependent toxicities, including induction of oxidative stress and DNA damage, which can lead to cell death. Triple-negative breast cancer (TNBC) subtypes are more vulnerable to agents that cause oxidative stress and DNA damage than are other breast cancer subtypes. We hypothesized that TNBC may be susceptible to AgNP cytotoxicity, a potential vulnerability that could be exploited for the development of new therapeutic agents. We show that AgNPs are highly cytotoxic toward TNBC cells at doses that have little effect on nontumorigenic breast cells or cells derived from liver, kidney, and monocyte lineages. AgNPs induced more DNA and oxidative damage in TNBC cells than in other breast cells. In vitro and in vivo studies showed that AgNPs reduce TNBC growth and improve radiation therapy. These studies show that unmodified AgNPs act as a self-therapeutic agent with a combination of selective cytotoxicity and radiation dose-enhancement effects in TNBC at doses that are nontoxic to noncancerous breast and other cells.

Increased DNA damage and oxidative stress among silver jewelry workers

Silver has long been valued as a precious metal, and it is used to make ornaments, jewelry, high-value tableware, utensils, and currency coins. Human exposures to silver and silver compounds can occur oral, dermal, or by inhalation. In this study, we investigated genotoxic and oxidative effects of silver exposure among silver jewelry workers. DNA damage in peripheral mononuclear leukocytes was measured by using the comet assay. Serum total antioxidative status (TAS), total oxidative status (TOS), total thiol contents, and ceruloplasmin levels were measured by using colorimetric methods among silver jewelry workers. Moreover, oxidative stress index (OSI) was calculated. Results were compared with non-exposed healthy subjects. The mean values of mononuclear leukocyte DNA damage were significantly higher than control subjects (p < 0.001). Serum TOS, OSI, and ceruloplasmin levels were also found to be higher in silver particles exposed group than those of non-exposed group (p < 0.001, p < 0.001, p < 0.01, respectively). However, serum TAS levels and total thiol contents of silver exposed group were found significantly lower (p < 0.05, p < 0.001, respectively). Exposure to silver particles among silver jewelry workers caused oxidative stress and accumulation of severe DNA damage.