Silver nanoparticles induce protective autophagy via Ca2+/CaMKKβ/AMPK/mTOR pathway in SH-SY5Y cells and rat brains

Integrating transcriptome and physiological analysis to reveal the essential responses of Daphnia magna to antimony trioxide nanoparticle

Antimony (Sb) pollution has already posed a severe threat to the aquatic ecosystem. However, the toxicity mechanisms of Sb on aquatic organisms are far from being elucidated. One of the crucial questions remaining unresolved is the characterization of molecular toxicity of Sb(III). Transcriptomics profiling combined with physiological characterizations was applied to investigate the response of Daphnia magna to nano-size antimony trioxide (nATO) and its soluble Sb(III) counterpart antimony potassium tartrate (APT) in the present study. Both nATO and APT induced the formation of oxidative stress, enhanced the activities of anti-oxidative enzymes, altered the metabolism of xenobiotics, increased the concentration of hydrogen sulfide (H₂S) and nitric oxide (NO), and triggered the self-protection mechanisms such as ubiquitin-mediated proteolysis. In addition, nATO and APT caused damage to the nervous system of D. magna, inhibited its locomotion and nutrient uptake in a concentration-dependent manner. Moreover, nATO exposure enhanced the autophagy activity, reflected by the up-regulated expression of hypoxia-inducible factor-1α, calmodulin-dependent protein kinase-β, and inositol-requiring enzyme 1. The present study, for the first time, depicted a global map of cellular response to nATO, provided essential information on Sb(III) toxicity to aquatic organisms, and is of great significance to the development of Sb management strategies.

Evaluation of Antidiabetic Activity of Biogenic Silver Nanoparticles Using Thymus serpyllum on Streptozotocin-Induced Diabetic BALB/c Mice

Type 2 Diabetes Mellitus is one of the most common metabolic disorders, and is characterized by abnormal blood sugar level due to impaired insulin secretion or impaired insulin action—or both. Metformin is the most commonly used drug for the treatment of Type 2 Diabetes Mellitus, but due to its slow mode of action and various side effects it shows poor and slow therapeutic response in patients. Currently, scientists are trying to tackle these limitations by developing nanomedicine. This research reports novel synthesis of silver nanoparticles using aqueous extract of Thymus serpyllum and aims to elucidate its therapeutic potential as an antidiabetic agent on streptozotocin induced diabetic BALB/c mice. Thymus serpyllum mediated silver nanoparticles were characterized through UV, SEM, XRD, and FTIR. The alpha amylase inhibition and antioxidant activity were checked through α amylase and DPPH radical scavenging assay, respectively. To check the effect of silver nanoparticles on blood glucose levels FBG, IPGTT, ITT tests were employed on STZ induced BALB/c mice. To assess the morphological changes in the anatomy of liver, pancreas, and kidney of BALB/c mice due to silver nanoparticles, histological analysis was done through H&E staining system. Finally, AMPK and IRS1 genes expression analysis was carried out via real time PCR. Silver nanoparticles were found to be spherical in shape with an average size of 42 nm. They showed an IC50 of 8 μg/mL and 10 μg/mL for α amylase and DPPH assay, respectively. Our study suggests that silver nanoparticles—specifically 10 mg/kg—cause a significant increase in the expression of AMPK and IRS1, which ultimately increase the glucose uptake in cells. Thymus serpyllum mediated silver nanoparticles possess strong antioxidant and antidiabetic potential and can further be explored as an effective and cheaper alternative option for treatment of Type 2 Diabetes Mellitus.

Nanoparticle Effects on Stress Response Pathways and Nanoparticle-Protein Interactions

Nanoparticles (NPs) are increasingly used in a wide variety of applications and products; however, NPs may affect stress response pathways and interact with proteins in biological systems. This review article will provide an overview of the beneficial and detrimental effects of NPs on stress response pathways with a focus on NP-protein interactions. Depending upon the particular NP, experimental model system, and dose and exposure conditions, the introduction of NPs may have either positive or negative effects. Cellular processes such as the development of oxidative stress, the initiation of the inflammatory response, mitochondrial function, detoxification, and alterations to signaling pathways are all affected by the introduction of NPs. In terms of tissue-specific effects, the local microenvironment can have a profound effect on whether an NP is beneficial or harmful to cells. Interactions of NPs with metal-binding proteins (zinc, copper, iron and calcium) affect both their structure and function. This review will provide insights into the current knowledge of protein-based nanotoxicology and closely examines the targets of specific NPs.

Myricetin Induces Apoptosis and Protective Autophagy through Endoplasmic Reticulum Stress in Hepatocellular Carcinoma

Myricetin, a natural flavonoid, exhibits diverse biological activities, including antitumor effects. The present study aimed to investigate the effects of myricetin on hepatocellular carcinoma (HCC) cells and explore the underlying molecular mechanisms. Our results showed that myricetin significantly inhibited cell proliferation and induced apoptosis in HCC cells. The apoptosis induced by myricetin was associated with the activation of endoplasmic reticulum (ER) stress. In addition, autophagy was enhanced in response to ER stress. Inhibition of autophagy by RNA interference or chemical inhibitors resulted in increased apoptosis in myricetin-treated HCC cells. The in vivo experiment also showed that myricetin effectively reduced tumor growth in an HCC xenograft model and that combination treatment with an autophagy inhibitor significantly enhanced this effect. These results indicated that myricetin induced apoptosis in HCC cells through the activation of ER stress. Protective autophagy was also upregulated during this process. Simultaneous inhibition of autophagy enhanced the anti-HCC activity of myricetin. Myricetin might be a promising drug candidate for HCC therapy, and the combined use of myricetin with autophagy inhibitors could be an effective therapeutic strategy.

Improvement of synaptic plasticity by nanoparticles and the related mechanisms: Applications and prospects

Synaptic plasticity is an important basis of learning and memory and participates in brain network remodelling after different types of brain injury (such as that caused by neurodegenerative diseases, cerebral ischaemic injury, posttraumatic stress disorder (PTSD), and psychiatric disorders). Therefore, improving synaptic plasticity is particularly important for the treatment of nervous system-related diseases. With the rapid development of nanotechnology, increasing evidence has shown that nanoparticles (NPs) can cross the blood-brain barrier (BBB) in different ways, directly or indirectly act on nerve cells, regulate synaptic plasticity, and ultimately improve nerve function. Therefore, to better elucidate the effect of NPs on synaptic plasticity, we review evidence showing that NPs can improve synaptic plasticity by regulating different influencing factors, such as neurotransmitters, receptors, presynaptic membrane proteins and postsynaptic membrane proteins, and further discuss the possible mechanism by which NPs improve synaptic plasticity. We conclude that NPs can improve synaptic plasticity and restore the function of damaged nerves by inhibiting neuroinflammation and oxidative stress, inducing autophagy, and regulating ion channels on the cell membrane. By reviewing the mechanism by which NPs regulate synaptic plasticity and the applications of NPs for the treatment of neurological diseases, we also propose directions for future research in this field and provide an important reference for follow-up research.

Aspergillus flavus-Mediated Green Synthesis of Silver Nanoparticles and Evaluation of Their Antibacterial, Anti-Candida, Acaricides, and Photocatalytic Activities

Aspergillus flavus F5 was used to reduce AgNO3 to form silver nanoparticles (Ag-NPs) that were monitored by a color change from colorless to yellowish-brown. The characterizations were achieved by UV-Vis spectroscopy, FT-IR, TEM, SEM-EDX, and XRD. Data showed that there was a successful formation of crystalline, spherical shape Ag-NPs with a particle average size of 12.5 ± 5.1 nm. The FT-IR clarified the role of various functional groups in the reducing/capping process. EDX-SEM revealed that the main component of the as-formed sample was set to be mainly Ag with a weight percentage of 46.1%. The synthesized Ag-NPs exhibit antibacterial and anti-Candida activity against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, C. glabrata, C. tropicalis, and C. parapsilosis, with inhibition zones ranging between 9.3 ± 0.5 to 20.8 ± 0.3 nm based on concentrations used and MIC values between 6.25 to 25 ppm. The mortality percentages of Tyrophagus putrescentiae mite species due to the mixing of their diet with different Ag-NPs concentrations of 0.5, 1.0, and 1.5 mg were 55.7 ± 2.1, 73.3 ± 1.5, and 87.4 ± 1.6% respectively after 20 days post-treatment. The catalytic activity of Ag-NPs to degrade methylene blue (MB) was investigated in the presence and absence of light irradiation. Data showed that a high photocatalytic degradation of MB compared with dark conditions at various times and concentrations. At a concentration of 70 mg/30 mL after 200 min., the dye removal percentages were 86.4 ± 0.4% in the presence of light irradiation versus 66.5 ± 1.1% in dark conditions.

Controlled Activation of TRPV1 Channels on Microglia to Boost Their Autophagy for Clearance of Alpha-Synuclein and Enhance Therapy of Parkinson's Disease

Parkinson's disease (PD) is characterized with accumulation of Lewy bodies with a major component of fibrillar alpha-synuclein (α-syn). Herein, boosting PD therapeutic efficacy by enhancing the autophagy of microglia to phagocytose and degrade α-syn via controlled opening of their surface TRPV1 channels with rationally designed photothermal nanoagent is reported. The Cu_{2- x} Se-anti-TRPV1 nanoparticles (CS-AT NPs) are fabricated to target the microglia and open their surface TRPV1 channels under the second near infrared (NIR-II) laser irradiation to cause influx of Ca²⁺ to activate ATG5 and Ca²⁺ /CaMKK2/AMPK/mTOR signaling pathway, which promote phagocytosis and degradation of α-syn. The CS-AT NPs are efficiently delivered by focused ultrasound into striatum of PD mice with high expression of TRPV1 receptors. The athletic ability of PD mice treated by CS-AT NPs and NIR-II irradiation is significantly improved due to the phagocytotic clearance of α-syn by microglia with enhanced autophagy. The enzyme tyrosine hydroxylase, ionized calcium binding adapter protein 1, glial fibrillary acidic protein, and pSer129-α-syn (p-α-syn) of treated PD mice are almost recovered to the normal levels of healthy mice. This study provides insights into the activation of microglial autophagy by targeting surface ion channels to improve the treatment of PD and other neurodegenerative diseases.

Recent Advancements in Plant-Derived Nanomaterials Research for Biomedical Applications

Engineering, physics, chemistry, and biology are all involved in nanotechnology, which comprises a wide variety of multidisciplinary scientific field devices. The holistic utilization of metallic nanoparticles in the disciplines of bio-engineering and bio-medicine has attracted a great deal of attention. Medical nanotechnology research can offer immense health benefits for humans. While the advantages of developing nanomaterials have been well documented, it is precisely apparent that there are still some major issues that remain unattended to those need to be resolved immediately so as to ensure that they do not adversely affect living organisms in any manner. The existence of nanoparticles gives them particular value in biology and materials science, as an emerging scientific field, with multiple applications in science and technology, especially with numerous frontiers in the development of new materials. Presented here is a review of recent noteworthy developments regarding plant-derived nanomaterials and their use in the development of medicine and biomedical applications around the world.

In vivo assessment of molybdenum and cadmium co-induce nephrotoxicity via causing calcium homeostasis disorder and autophagy in ducks (Anas platyrhyncha)

Excess molybdenum (Mo) and cadmium (Cd) are widespread environmental and industrial metal pollutants. To evaluate the combined effects of Mo and Cd on calcium homeostasis and autophagy in duck kidneys. 160 healthy 7-day-old ducks (Anas platyrhyncha) were randomized into 4 groups and given to a basic diet, adding various doses of Mo or/and Cd for 16 weeks. On the 4th, 8th, 12th and 16th weeks, kidney tissues were collected. The study exhibited that Mo or/and Cd caused histological abnormality, reduced the activities of Ca2+ ATPase, Mg2+ ATPase, Na+-K+ ATPase and Ca2+-Mg2+ ATPase, K and Mg contents, and increased Na and Ca contents, upregulated CaMKKβ, CaMKIIɑ, CaN, IP3R, GRP78, GRP94, CRT mRNA levels and CaMKIIɑ, CaN, IP3R protein levels. Moreover, exposure to Mo or/and Cd notably promoted the amount of autophagosomes and LC3II immunofluorescence, upregulated AMPKα1, ATG5, Beclin-1, LC3A, LC3B mRNA levels and Beclin-1, LC3II/LC3I protein levels, downregulated mTOR, Dynein, P62 mRNA levels and P62 protein level. The changes of above indicators in combined group were more obvious. Overall, the results suggest that Mo and Cd co-exposure may can synergistically induce nephrotoxicity via causing calcium homeostasis disorder and autophagy in ducks.

Calcium overload and reactive oxygen species accumulation induced by selenium deficiency promote autophagy in swine small intestine

Selenium (Se) deficiency can seriously affect the small intestine of swine, and cause diarrhea in swine. However, the specific mechanism of Se deficiency-induced swine diarrhea has rarely been reported. Here, to explore the damage of Se deficiency on the calcium homeostasis and autophagy mechanism of swine, in vivo and in vitro models of swine intestinal Se deficiency were established. Twenty-four pure line castrated male Yorkshire pigs (45 d old, 12.50 ± 1.32 kg, 12 full-sibling pairs) were divided into 2 equal groups and fed Se-deficient diet (0.007 mg Se/kg) as the Se-deficiency group, or fed Se-adequate diet (0.3 mg Se/kg) as the control group for 16 weeks. The intestinal porcine enterocyte cell line (IPEC-J2) was divided into 2 groups, and cultured by Se-deficient medium as the Se-deficient group, or cultured by normal medium as the control group. Morphological observations showed that compared with the control group, intestinal cells in the Se-deficiency group were significantly damaged, and autophagosomes increased. Autophagy staining and cytoplasmic calcium staining results showed that in the Se-deficiency group, autophagy increased and calcium homeostasis was destroyed. According to the reactive oxygen species (ROS) staining results, the percentage of ROS in the Se-deficiency group was higher than that in the control group in the in vitro model. Compared with the control group, the protein and mRNA expressions of autophagy-calcium-related genes including Beclin 1, microtubule-associated proteins 1A (LC3-1), microtubule-associated proteins 1B (LC3-2), autophagy-related protein 5 (ATG5), autophagy-related protein 12 (ATG12), autophagy-related protein 16 (ATG16), mammalian target of rapamycin (mTOR), calmodulin-dependent protein kinase kinase β (CAMKK-β), adenosine 5′-monophosphate-activated protein kinase (AMPK), sarco(endo)plasmic reticulum Ca²⁺-ATPase (SERCA), and calpain in the Se-deficiency group were significantly increased which was consistent in vivo and in vitro (P < 0.05). Altogether, our results indicated that Se deficiency could destroy the calcium homeostasis of the swine small intestine to trigger cell autophagy and oxidative stress, which was helpful to explain the mechanism of Se deficiency-induced diarrhea in swine.

Silver Nanoparticles Biosynthesis, Characterization, Antimicrobial Activities, Applications, Cytotoxicity and Safety Issues: An Updated Review

Rapid advances in nanotechnology have led to its emergence as a tool for the development of green synthesized noble metal nanoparticles, especially silver nanoparticles (AgNPs), for applications in diverse fields such as human health, the environment and industry. The importance of AgNPs is because of their unique physicochemical and antimicrobial properties, with a myriad of activities that are applicable in various fields, including the pharmaceutical industry. Countries with high biodiversity require the collection and transformation of information about biological assets into processes, associations, methods and tools that must be combined with the sustainable utilization of biological diversity. Therefore, this review paper discusses the applicable studies of the biosynthesis of AgNPs and their antimicrobial activities towards microorganisms in different areas viz. medicine and agriculture. The confirmed antiviral properties of AgNPs promote their applicability for SARS-CoV-2 treatment, based on assimilating the virus’ activities with those of similar viruses via in vivo studies. In this review, an insight into the cytotoxicity and safety issues of AgNPs, along with their future prospects, is also provided.

Inhibition of autophagy by CRMP2-derived peptide ST2-104 (R9-CBD3) via a CaMKKβ/AMPK/mTOR pathway contributes to ischemic postconditioning-induced neuroprotection against cerebral ischemia-reperfusion injury

Cerebral ischemia, a common cerebrovascular disease, is characterized by functional deficits and apoptotic cell death. Autophagy, a type of programmed cell death, plays critical roles in controlling neuronal damage and metabolic homeostasis, and has been inextricably linked to cerebral ischemia. We previously identified a short peptide aptamer from collapsin response mediator protein 2 (CRMP2), designated the Ca2+ channel-binding domain 3 (CBD3) peptide, that conferred protection against excitotoxicity and traumatic brain injury. ST2-104, a nona-arginine (R9)-fused CBD3 peptide, exerted beneficial effects on neuropathic pain and was neuroprotective in a model of Alzheimer's disease; however, the effect of ST2-104 on cerebral ischemia and its mechanism of action have not been studied. In this study, we modeled cerebral ischemia-reperfusion injury in rats with the middle cerebral artery occlusion (MCAO) as well as challenged SH-SY5Y neuroblastoma cells with glutamate to induce toxicity to interrogate the effects of ST2-104 on autophagy following ischemic/excitotoxic insults. ST2-104 reduced the infarct volume and improved the neurological score of rats subjected to MCAO. ST2-104 protected SH-SY5Y cells from death following glutamate exposure via blunting apoptosis and autophagy as well as limiting excessive calcium entry. 3-Methyladenine (3-MA), an inhibitor of autophagy, promoted the effects of ST2-104 in inhibiting apoptosis triggered by glutamate while rapamycin, an activator of autophagy, failed to do so. ST2-104 peptide reversed glutamate-induced apoptosis via inhibiting Ca2+/CaM-dependent protein kinase kinase β (CaMKKβ)-mediated autophagy, which was partly enhanced by STO-609 (an inhibitor of CaMKKβ). ST2-104 attenuated neuronal apoptosis by inhibiting autophagy through CaMKKβ/AMPK/mTOR pathway. Our results suggest that the neuroprotective effect of ST2-104 are due to actions on the crosstalk between apoptosis and autophagy via the CaMKKβ/AMPK/mTOR signaling pathway. The findings present novel insights into the potential neuroprotection of ST2-104 in cerebral ischemia.

NR4A1 enhances MKP7 expression to diminish JNK activation induced by ROS or ER-stress in pancreatic β cells for surviving

Under adverse conditions, such as sustained or chronic hyperglycemia or hyperlipidemia, ROS (reactive oxygen species) or/and ER-stress (endoplasmic reticulum stress) will be induced in pancreatic β cells. ROS or ER-stress damages β-cells even leads to apoptosis. Previously we found ROS or ER-stress resulted in JNK activation in β cells and overexpressing NR4A1 in MIN6 cells reduced JNK activation via modulating cbl-b expression and subsequent degrading the upstream JNK kinase (MKK4). To search other possible mechanisms, we found the mRNA level and protein level of MKP7 (a phosphatase for phospho-JNK) were dramatic reduced in pancreatic β cells in the islets from NR4A1 KO mice compared with that from wild type mice. To confirm what we found in animals, we applied pancreatic β cells (MIN6 cells) and found that the expression of MKP7 was increased in NR4A1-overexpression MIN6 cells. We further found that knocking down the expression of MKP7 increased the p-JNK level in pancreatic β cells upon treatment with TG or H₂O₂. After that, we figured out that NR4A1 did enhance the transactivation of the MKP7 promoter by physical association with two putative binding sites. In sum, NR4A1 attenuates JNK phosphorylation incurred by ER-stress or ROS partially via enhancing MKP7 expression, potentially decreases pancreatic β cell apoptosis induced by ROS or ER-stress. Our finding provides a clue for diabetes prevention.

Antimicrobial Efficacy of Silver Nanoparticles as Root Canal Irrigant's: A Systematic Review

Removal of microbes is imperative during endodontic therapy. Due to their antimicrobial property, silver nanoparticles have been used for endodontic irrigation of the root canals. The objective of the present study was to provide a qualitative analysis of the published literature assessing silver nanoparticles as root canal irrigants. A search of PubMed, SCOPUS, Web of Science, and Embase databases was done without any time restriction. Articles published in English were included. Data were extracted and the risk of bias was assessed. Of the 154 studies identified, after screening according to the inclusion criteria, five in vitro studies were included. The results indicate that silver nanoparticles have an anti-microbial effect to varying degrees depending on certain factors. Within the limitations of the present studies that have a moderate to low risk of bias, an antimicrobial effect of silver nanoparticles is observed. Silver nanoparticles have the potential to be used as endodontic irrigants, although their efficacy depends on particle size and the duration of contact which require further investigation.

An updated review of autophagy in ischemic stroke: From mechanisms to therapies

Stroke is a leading cause of mortality and morbidity worldwide. Understanding the underlying mechanisms is important for developing effective therapies for treating stroke. Autophagy is a self-eating cellular catabolic pathway, which plays a crucial homeostatic role in the regulation of cell survival. Increasing evidence shows that autophagy, observed in various cell types, plays a critical role in brain pathology after ischemic stroke. Therefore, the regulation of autophagy can be a potential target for ischemic stroke treatment. In the present review, we summarize the recent progress that research has made regarding autophagy and ischemic stroke, including common signaling pathways, the role of autophagic subtypes (e.g. mitophagy, pexophagy, aggrephagy, endoplasmic reticulum-phagy, and lipophagy) in ischemic stroke, as well as the current methods for autophagy detection and potential therapeutic strategy.

Silver Nanoparticles Induced Oxidative Stress and Mitochondrial Injuries Mediated Autophagy in HC11 Cells Through Akt/AMPK/mTOR Pathway

Silver nanoparticles (AgNPs) are widely used in industrial products, and they have good antibacterial properties, with potential for prevention and treatment of cow mastitis. However, concerns exist about the cytotoxicity of AgNPs. Thus, we have studied the role of autophagy in AgNP-induced cytotoxicity in mouse HC11 mammary epithelium cells. We found that AgNPs injured HC11 cells, with release of lactate dehydrogenase (LDH). AgNPs also induced autophagy in HC11 cells, which was associated with oxidative stress, as indicated by increased reactive oxygen species (ROS) and increased expression of hemoxygenase-1(HO-1) and Nrf2. Mitochondria were altered by AgNPs: mitochondrial membrane potential (MMP) was decreased and the expression of PINK1 and Parkin was increased. AgNPs also increased the expression of p-AMPK and decreased the expression of p-Akt and p-mTOR. The addition of 3-methyl adenine inhibited autophagy and enhanced the cytotoxicity of AgNPs, indicating that autophagy is protective against AgNP-induced cell death. In summary, AgNPs induced protective autophagy in HC11 cells via the Akt/AMPK/mTOR pathway, associated with cellular oxidative stress and mitochondrial alterations. Our research confirms that AgNPs may damage the breast tissue in clinical applications and should be used with caution. Further research is necessary to clarify whether the damage caused by AgNPs will affect the lactation function of the mammary glands and possible residues in milk.

The application of multifunctional nanomaterials in Alzheimer's disease: A potential theranostics strategy

By virtue of their small size, nanomaterials can cross the blood-brain barrier and, when modified to target specific cells or regions, can achieve high bioavailability at the intended site of action. Modified nanomaterials are therefore promising agents for the diagnosis and treatment of neurodegenerative diseases such as Alzheimer's disease (AD). Here we review the roles and mechanisms of action of nanomaterials in AD. First, we discuss the general characteristics of nanomaterials and their application to nanomedicine. Then, we summarize recent studies on the diagnosis and treatment of AD using modified nanomaterials. These studies indicate that using nanomaterials is a potential strategy for AD treatment by slowing the progression of AD through enhanced therapeutic effects.

The impact of silver nanoparticles phytosynthesized with Viburnum opulus L. extract on the ultrastrastructure and cell death in the testis of offspring rats

AIM

To investigate the effects of prenatal exposure to AgNPs obtained by green synthesis with Viburnum opulus L. extract on the testis in male offspring rats.

MATERIAL AND METHODS

Two different doses of AgNPs (0.8 and 1.5 mg/kg b.w.) and vehicle (PBS) were administered to Wistar female rats on days 3-14 of gestation. At 6 weeks after birth, the ultrastructural changes in correlation with the amount of silver as well as the parameters of oxidative stress, inflammation and cell death mechanisms in the testis of male offspring were evaluated.

RESULTS

AgNPs administered during pregnancy crossed the placental and testicular barriers and induced oxidative stress, DNA damage and autophagy as mechanism of cell toxicity. The markers of inflammation and apoptosis decreased after AgNPs exposure while the NFkB activation increased. TEM examination revealed important ultrastructural changes of Sertoli cells, numerous vacuoles and cytoplasmic changes suggestive of the cell's evolution towards necrosis.

CONCLUSION

Phytoreduced silver nanoparticles with polyphenols from Viburnum opulus L. fruit extract, administered during the embryological development of the male gonad, have testicular toxic effects in offspring even at 6 weeks after birth.

Silver nanoparticles achieve cytotoxicity against breast cancer by regulating long-chain noncoding RNA XLOC_006390-mediated pathway

The specific cytotoxic effect of nanoparticles on tumor cells may be used in future antitumor clinical applications. Silver nanoparticles (AgNPs) have been reported to have potent cytotoxic effect, but the mechanism is unclear. Here, AgNPs were synthesized, and the particle average size was 63.1 ± 8.3 nm and showed a nearly circular shape, which were determined by transmission electron microscopy and field emission scanning electron microscopy. The selected area electron diffraction patterns showed that the nanoparticles were crystalline. The energy-dispersive X-ray spectrum proved that silver is the main component of nanoparticles. The AgNPs showed potent cytotoxicity in breast cancer cells, no matter whether they were tamoxifen sensitive or resistant. Next, we found that a long noncoding RNA, XLOC_006390, was decreased in AgNPs-treated breast cancer cells, coupled to inhibited cell proliferation, altered cell cycle and apoptotic phenotype. Downstream of AgNPs, XLOC_006390 was recognized to target miR-338-3p and modulate the SOX4 expression. This signaling pathway also mediates the AgNPs function of sensitizing tamoxifen-resistant breast cancer cells to tamoxifen. These results provide a new clue for the antitumor mechanism of AgNPs, and a new way for drug development by using AgNPs.

All That Glitters Is Not Silver-A New Look at Microbiological and Medical Applications of Silver Nanoparticles

Silver and its nanoparticles (AgNPs) have different faces, providing different applications. In recent years, the number of positive nanosilver applications has increased substantially. It has been proven that AgNPs inhibit the growth and survival of bacteria, including human and animal pathogens, as well as fungi, protozoa and arthropods. Silver nanoparticles are known from their antiviral and anti-cancer properties; however, they are also very popular in medical and pharmaceutical nanoengineering as carriers for precise delivery of therapeutic compounds, in the diagnostics of different diseases and in optics and chemistry, where they act as sensors, conductors and substrates for various syntheses. The activity of AgNPs has not been fully discovered; therefore, we need interdisciplinary research to fulfil this knowledge. New forms of products with silver will certainly find application in the future treatment of many complicated and difficult to treat diseases. There is still a lack of appropriate and precise legal condition regarding the circulation of nanomaterials and the rules governing their safety use. The relatively low toxicity, relative biocompatibility and selectivity of nanoparticle interaction combined with the unusual biological properties allow their use in animal production as well as in bioengineering and medicine. Despite a quite big knowledge on this topic, there is still a need to organize the data on AgNPs in relation to specific microorganisms such as bacteria, viruses or fungi. We decided to put this knowledge together and try to show positive and negative effects on prokaryotic and eukaryotic cells.

Silver nanoparticles induced cytotoxicity in HT22 cells through autophagy and apoptosis via PI3K/AKT/mTOR signaling pathway

With the widespread application and inevitable environmental exposure, silver nanoparticles (AgNPs) can be accumulated in various organs. More serious concerns are raised on the biological safety and potential toxicity of AgNPs in the central nervous system (CNS), especially in the hippocampus. This study aimed to investigate the biological effects and the role of PI3K/AKT/mTOR signaling pathway in AgNPs mediated cytotoxicity using the mouse hippocampal neuronal cell line (HT22 cells). AgNPs reduced cell viability and induced membrane leakage in a dose-dependent manner, determined by the MTT and LDH assay. In doses of 25, 50, 100 μg mL^-1 for 24 h, AgNPs promoted the excessive production of reactive oxygen species (ROS) and caused the oxidative stress in HT22 cells. AgNPs induced autophagy, determined by the transmission electron microscopy observation, upregulation of LC3 II/I and downregulation of p62 expression levels. The mechanistic investigation showed that the PI3K/AKT/mTOR signaling pathway was activated by phosphorylation, which was enrolled in an AgNP-induced autophagy process. AgNPs could further trigger the apoptosis by upregulation of caspase-3 and Bax and downregulation of Bcl-2 in HT22 cells. These results revealed AgNP-induced cytotoxicity in HT22 cells, which was mediated by autophagy and apoptosis via the PI3K/AKT/mTOR signaling pathway. The study could provide the experimental evidence and explanation for the potential neurotoxicity triggered by AgNPs in vitro.

Yi-Zhi-Fang-Dai Formula Exerts a Protective Effect on the Injury of Tight Junction Scaffold Proteins in Vitro and in Vivo by Mediating Autophagy through Regulation of the RAGE/CaMKKβ/AMPK/mTOR Pathway

Alzheimer's disease (AD) is a chronic neurodegeneration disease that is closely related to the abnormal tight junction scaffold proteins (TJ) proteins of the blood-brain barrier (BBB). Recently, Yi-Zhi-Fang-Dai Formula (YZFDF) had exerted a neuronal protective effect against amyloid peptide (Aβ) toxicity. Still, the therapeutic mechanism of YZFDF in restoring Aβ-induced injury of TJ proteins (ZO-1, Occludin, and Claudin-5) remains unclear. This study aimed to explore the underlying mechanism of YZFDF in alleviating the injury of TJ proteins. We examined the impacts of YZFDF on autophagy-related proteins and the histopathology of Aβ in the APP/PS1 double-transgenic male mice. We then performed the free intracellular calcium levels [Ca²⁺]i analysis and the cognitive behavior test of the AD model. Our results showed that YZFDF ameliorated the injury of TJ proteins by reducing the mRNA transcription and expression of the receptor for advanced glycation end-products (RAGE), the levels of [Ca²⁺]i, calmodulin-dependent protein kinase β (CaMKKβ), phosphorylated AMP-activated protein kinase (AMPK). Accordingly, YZFDF increased the expression of the phosphorylated mammalian targets of rapamycin (mTOR), leading to inhibition of autophagy (downregulated LC3 and upregulated P62). Moreover, the Aβ_1-42 oligomers-induced alterations of autophagy in murine mouse brain capillary (bEnd.3) cells were blocked by RAGE small interfering RNA (siRNA). These results suggest that YZFDF restored TJ proteins' injury by suppressing autophagy via RAGE signaling. Furthermore, YZFDF reduced the pathological precipitation of Aβ in the hippocampus, and improved cognitive behavior impairment of the AD model suggested that YZFDF might be a potential therapeutic candidate for treating AD through RAGE/CaMKKβ/AMPK/mTOR-regulated autophagy pathway.

Green Biosynthesized Silver Nanoparticles With Aqueous Extracts of Ginkgo Biloba Induce Apoptosis via Mitochondrial Pathway in Cervical Cancer Cells

Biosynthetic silver nanoparticles (AgNPs), specifically formed using medicinal plant extracts, have recently exhibited a remarkable therapeutic effect due to their anticancer potential. Here, we synthesized AgNPs using an aqueous extract of Ginkgo biloba leaves and evaluated its activity against cervical cancer (CCa) and the related molecular mechanisms. The physiochemical properties of the AgNPs were measured by ultraviolet-visible spectrophotometry, nanometre particle size analyzer and transmission electron microscopy. The AgNPs effects on cell proliferation and apoptosis were investigated through MTT, MTS, and colony formation assay; Hoechst 33258 staining; and flow cytometry. The intracellular ROS and oxidative stress levels were assessed using the appropriate commercial kits. Apoptosis-related protein levels were determined by western blotting. We prepared a series of different sized ginkgo extract synthesized AgNPs (GB-AgNPs), and the smallest mean particle size was 40.2 ± 1.2 nm with low polydispersity (0.091 ± 0.011), zeta potential values showed -34.56 mV. Compared to the controls, the GB-AgNP treatment inhibited the cell proliferation and induced the apoptosis of HeLa and SiHa cells. In addition, GB-AgNP treatment led to markedly increased levels of intracellular ROS, the release of cytochrome c (Cyt C) from mitochondria into the cytosol and the cleavage of caspase -9 and -3 in both CCa cell lines. Moreover, NAC, an ROS scavenger, eliminated the effect of GB-AgNPs on the HeLa and SiHa cells. This study reveals that GB-AgNPs suppresses cancer cell proliferation and induces apoptosis by upregulating intracellular ROS generation and inducing the activation of the caspase-dependent mitochondrial apoptotic pathway in CCa cells. Thus, GB-AgNPs may be a potential alternative drug for CCa therapy.

A Low Dose of Nanoparticulate Silver Induces Mitochondrial Dysfunction and Autophagy in Adult Rat Brain

Extensive incorporation of silver nanoparticles (AgNPs) into many medical and consumer products has raised concerns about biosafety. Since nanosilver accumulates persistently in the central nervous system, it is important to assess its neurotoxic impacts. We investigated a model of prolonged exposure of adult rats to a low environmentally relevant dose of AgNPs (0.2 mg/kg b.w.). Ultrastructural analysis revealed pathological alterations in mitochondria such as swelling and cristolysis. Besides, elongated forms of mitochondria were present. Level of adenosine triphosphate was not altered after exposure, although a partial drop of mitochondrial membrane potential was noted. Induction of autophagy with only early autophagic forms was observed in AgNP-exposed rat brains as evidenced by ultrastructural markers. Increased expression of two protein markers of autophagy, beclin 1 and microtubule-associated proteins 1A/1B light chain 3B (MAP LC3-II), was observed, indicating induction of autophagy. Expression of lysosome-related Rab 7 protein and cathepsin B did not change, suggesting inhibition of physiological flux of autophagy. Our results show that exposure to a low, environmentally relevant dose of AgNPs leads to induction of autophagy in adult rat brain in response to partial mitochondrial dysfunction and to simultaneous interfering with an autophagic pathway. The cell compensates for the defective autophagy mechanism via development of enhanced mitochondrial biodynamic.

Nanoparticles induce autophagy via mTOR pathway inhibition and reactive oxygen species generation

Due to their unique physicochemical properties, nanoparticles (NPs) have been increasingly developed for use in various fields. However, there has been both growing negative concerns with toxicity and positive realization of opportunities in nanomedicine, coming from the growing understanding of the associations between NPs and the human body, particularly relating to their cellular autophagic effects. This review summarizes NP-induced autophagy via the modulation of the mTOR signaling pathway and other associated signals including AMPK and ERK and also demonstrates how reactive oxygen species generation greatly underlies the regulation processes. The perspectives in this review aim to contribute to NP design, particularly in consideration of nanotoxicity and the potential for the precise application of NPs in nanomedicine.

Dual role of oxidative stress-JNK activation in autophagy and apoptosis induced by nickel oxide nanoparticles in human cancer cells

Nickel oxide nanoparticles (NiO-NPs) are an important group of nanoparticles with increasing applications in many aspects of industry. At present, there is evidence demonstrating the cytotoxic characteristics of NiO-NPs, while the involvement of autophagy in the cytotoxicity of NiO-NPs has not been reported. In this study, we aimed to study the role of autophagy in the cytotoxicity of NiO-NPs and the underlying regulatory mechanisms. First, we provided evidence that NiO-NPs induce autophagy in human cancer cells. Second, we found that the enhanced autophagic flux by NiO-NPs via the generation of intracellular reactive oxygen species (ROS) from mitochondria and the subsequent activation of the JNK pathway. Third, we demonstrated that the activation of JNK is a main force in mediating NiO-NPs-induced apoptosis. Finally, we demonstrated that the autophagic response plays an important protective role against the cytotoxic effect of NiO-NPs. Therefore, this study identifies the dual role of oxidative stress-JNK activation in the biological effects of NiO-NPs via promoting autophagy and mediating apoptosis. Understanding the protective role of autophagy and the underlying mechanism is important for the potential application of NiO-NPs in the biomedical industry.

Adaptive changes induced by noble-metal nanostructures in vitro and in vivo

The unique features of noble-metal nanostructures (NMNs) are leading to unprecedented expansion of research and exploration of their application in therapeutics, diagnostics and bioimaging fields. With the ever-growing applications of NMNs, both therapeutic and environmental NMNs are likely to be exposed to tissues and organs, requiring careful studies towards their biological effects in vitro and in vivo. Upon NMNs exposure, tissues and cells may undergo a series of adaptive changes both in morphology and function. At the cellular level, the accumulation of NMNs in various subcellular organelles including lysosomes, endoplasmic reticulum, Golgi apparatus, mitochondria, and nucleus may interfere with their functions, causing changes in a variety of cellular functions, such as digestion, protein synthesis and secretion, energy metabolism, mitochondrial respiration, and proliferation. In animals, retention of NMNs in metabolic-, respiratory-, immune-related, and other organs can trigger significant physiological and pathological changes to these organs and influence their functions. Exploring how NMNs interact with tissues and cells and the underlying mechanisms are of vital importance for their future applications. Here, we illustrate the characteristics of NMNs-induced adaptive changes both in vitro and in vivo. Potential strategies in the design of NMNs are also discussed to take advantage of beneficial adaptive changes and avoid unfavorable changes for the proper implementation of these nanoplatforms.

The Antibacterial Mechanism of Silver Nanoparticles and Its Application in Dentistry

Nanotechnology has recently emerged as a rapidly growing field with numerous biomedical science applications. At the same time, silver has been adopted as an antimicrobial material and disinfectant that is relatively free of adverse effects. Silver nanoparticles possess a broad spectrum of antibacterial, antifungal and antiviral properties. Silver nanoparticles have the ability to penetrate bacterial cell walls, changing the structure of cell membranes and even resulting in cell death. Their efficacy is due not only to their nanoscale size but also to their large ratio of surface area to volume. They can increase the permeability of cell membranes, produce reactive oxygen species, and interrupt replication of deoxyribonucleic acid by releasing silver ions. Researchers have studied silver nanoparticles as antimicrobial agents in dentistry. For instance, silver nanoparticles can be incorporated into acrylic resins for fabrication of removable dentures in prosthetic treatment, composite resin in restorative treatment, irrigating solution and obturation material in endodontic treatment, adhesive materials in orthodontic treatment, membrane for guided tissue regeneration in periodontal treatment, and titanium coating in dental implant treatment. Although not all authorities have acknowledged the safety of silver nanoparticles, no systemic toxicity of ingested silver nanoparticles has been reported. A broad concern is their potential hazard if they are released into the environment. However, the interaction of nanoparticles with toxic materials and organic compounds can either increase or reduce their toxicity. This paper provides an overview of the antibacterial use of silver nanoparticles in dentistry, highlighting their antibacterial mechanism, potential applications and safety in clinical treatment.

Initiation of protective autophagy in hepatocytes by gold nanorod core/silver shell nanostructures

The high reactivity of silver nanoparticles leads to their broad applications in the anti-bacterial field; however, the safety of silver nanoparticles has attracted increasing public attention. After exposure to silver nanoparticles in vivo, the liver serves as their potential deposition site; however the potential biological effects of such nanoparticles on hepatocytes at low dosages are not well understood. Here, we study the interaction between gold nanorod core/silver shell nanostructures (Au@Ag NRs) and human hepatocytes, HepG2 cells, and determine that Au@Ag NRs at sub-lethal doses can induce autophagy. After uptake, Au@Ag NRs mainly localize in the lysosomes where they release silver ions and promote the production of reactive oxygen species (ROS). The ROS then suppress the AKT-mTOR signaling pathway and activate autophagy. In addition, oxidative stress results in lysosomal impairment, causing decreased ability for lysosomal digestion. Moreover, oxidative stress also affects the structure and function of mitochondria, leading to the initiation of protective autophagy to eliminate the damaged mitochondrion. Our study shows that at sub-lethal dosages, silver nanomaterials may alter the physiological functions of hepatic cells by activating protective autophagy and cause potential health risks, indicating that cautious consideration of the safety of nanomaterials for certain applications is necessary.

Survival Mechanisms and Xenobiotic Susceptibility of Keratinocytes Exposed to Metal-Derived Nanoparticles

Metal-derived nanoparticles (Mt-NPs) are increasingly used in cosmetology due to their ultraviolet shielding (titanium dioxide [TiO₂]), antioxidant (cerium dioxide [CeO₂]), and biocidal (silver [Ag]) properties. In the absence of overt toxicity (i.e., cell death), Mt-NPs are considered safe for cosmetic applications. However, there is little understanding about the mechanisms involved in the survival of keratinocytes exposed to subtoxic levels of Mt-NPs. Human keratinocytes (HaCaT) were exposed subacutely to subtoxic concentrations (≤30 μg/mL, 48-72 h) of rutile (r) TiO₂ (cylindrical), CeO₂ (cubic) and Ag (spherical) with a core/hydrodynamic size of <50/<100 nm and >98% purity. Mt-NP uptake was indirectly quantified by changes in the light side scatter, where the kinetics (time/dose-response) suggested that the three types of Mt-NPs were similarly uptaken by keratinocytes. rTiO₂ and CeO₂, but not Ag-NPs, increased autophagy, whose inhibition prompted cell death. No increase in the steady-state levels of reactive oxygen species (ROS) was induced by exposure to any of the Mt-NPs tested. Interestingly, intracellular Ag-NP aggregates observed an increased far-red autofluorescence (≥740 nm em), which has been ascribed to their binding to thiol molecules such as glutathione (GSH). Accordingly, inhibition of GSH synthesis, but not the impairment of oxidized GSH recycling, sensitized keratinocytes to Ag-NPs suggesting that GSH homeostasis, and its direct scavenging of Ag-NPs, but not ROS, is essential for keratinocyte survival upon exposure to Ag-NP. rTiO₂ and Ag, but not CeO₂-NPs, compromised metabolic flux (glycolysis and respiration), but ATP levels were unaltered. Finally, we also observed that exposure to Mt-NPs sensitized keratinocytes to non-UV xenobiotic exposure (arsenite and paraquat). Our results demonstrate the differential contribution of autophagy and GSH homeostasis to the survival of human keratinocytes exposed to subtoxic concentrations of Mt-NPs and highlight the increased susceptibility of keratinocytes exposed to Mt-NPs to a second xenobiotic insult.

Influence of microcystins-LR (MC-LR) on autophagy in human neuroblastoma SK-N-SH cells

Microcystin-LR (MC-LR) variant exposure poses a potential health hazard to ecosystem, animals, and humans. Previously investigators showed that autophagy plays a key role in MC-LR induced cytotoxicity immortalized murine ovarian granular KK-1 cells and rat Sertoli cells. Recently exposure to MC-LR via drinking water was reported to accumulate in mouse brain with associated adverse oxidant and inflammatory responses. However, autophagy the physiological mechanism required for cells to degrade their own impaired organelles to maintain their homeostasis has not been determined with respect to MC-LR actions on the central nervous system (CNS). Thus, the aim of this study was to examine the effects of MC-LR on autophagy using human neuroblastoma SK-N-SH cells as CNS model. Data demonstrated that after treatment with 15 or 30 µmol/L MC-LR for 48 hr significantly reduced survival rate was noted in SK-N-SH cells. MC-LR increased the expression levels of autophagy-related proteins light chain 3 (LC3) II/I and p62 in SK-N-SH cells, resulting in the accumulation of LC3 and increased intracellular free calcium ion levels. Data indicated that MC-LR induced adverse effects on the CNS as evidenced by decreased cellular survival associated with inhibition of autophagy flux and consequent enhanced autophagosomes accumulation.