Nitroxide Radical-Containing Redox Nanoparticles Protect Neuroblastoma SH-SY5Y Cells against 6-Hydroxydopamine Toxicity

Reactive oxygen species-scavenging nanomaterials for the prevention and treatment of age-related diseases

With increasing proportion of the elderly in the population, age-related diseases (ARD) lead to a considerable healthcare burden to society. Prevention and treatment of ARD can decrease the negative impact of aging and the burden of disease. The aging rate is closely associated with the production of high levels of reactive oxygen species (ROS). ROS-mediated oxidative stress in aging triggers aging-related changes through lipid peroxidation, protein oxidation, and DNA oxidation. Antioxidants can control autoxidation by scavenging free radicals or inhibiting their formation, thereby reducing oxidative stress. Benefiting from significant advances in nanotechnology, a large number of nanomaterials with ROS-scavenging capabilities have been developed. ROS-scavenging nanomaterials can be divided into two categories: nanomaterials as carriers for delivering ROS-scavenging drugs, and nanomaterials themselves with ROS-scavenging activity. This study summarizes the current advances in ROS-scavenging nanomaterials for prevention and treatment of ARD, highlights the potential mechanisms of the nanomaterials used and discusses the challenges and prospects for their applications.

The Cellular and Organismal Effects of Nitroxides and Nitroxide-Containing Nanoparticles

Nitroxides are stable free radicals that have antioxidant properties. They react with many types of radicals, including alkyl and peroxyl radicals. They act as mimics of superoxide dismutase and stimulate the catalase activity of hemoproteins. In some situations, they may exhibit pro-oxidant activity, mainly due to the formation of oxoammonium cations as products of their oxidation. In this review, the cellular effects of nitroxides and their effects in animal experiments and clinical trials are discussed, including the beneficial effects in various pathological situations involving oxidative stress, protective effects against UV and ionizing radiation, and prolongation of the life span of cancer-prone mice. Nitroxides were used as active components of various types of nanoparticles. The application of these nanoparticles in cellular and animal experiments is also discussed.

Induction of Oxidative Stress in SH-SY5Y Cells by Overexpression of hTau40 and Its Mitigation by Redox-Active Nanoparticles

Abnormally phosphorylated tau protein is the principal component of neurofibrillary tangles, accumulating in the brain in many neurodegenerative diseases, including Alzheimer's disease. The aim of this study was to examine whether overexpression of tau protein leads to changes in the redox status of human neuroblastoma SH-SY5Y cells. The level of reactive oxygen species (ROS) was elevated in tau-overexpressing cells (TAU cells) as compared with cells transfected with the empty vector (EP cells). The level of glutathione was increased in TAU cells, apparently due to overproduction as an adaptation to oxidative stress. The TAU cells had elevated mitochondrial mass. They were more sensitive to 6-hydroxydopamine, delphinidin, 4-amino-TEMPO, and nitroxide-containing nanoparticles (NPs) compared to EP controls. These results indicate that overexpression of the tau protein imposes oxidative stress on the cells. The nitroxide 4-amino-TEMPO and nitroxide-containing nanoparticles (NPs) mitigated oxidative stress in TAU cells, decreasing the level of ROS. Nitroxide-containing nanoparticles lowered the level of lipid peroxidation in both TAU and EP cells, suggesting that nitroxides and NPs may mitigate tau-protein-induced oxidative stress.

Evidence for Oxidative Pathways in the Pathogenesis of PD: Are Antioxidants Candidate Drugs to Ameliorate Disease Progression?

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that arises due to a complex and variable interplay between elements including age, genetic, and environmental risk factors that manifest as the loss of dopaminergic neurons. Contemporary treatments for PD do not prevent or reverse the extent of neurodegeneration that is characteristic of this disorder and accordingly, there is a strong need to develop new approaches which address the underlying disease process and provide benefit to patients with this debilitating disorder. Mitochondrial dysfunction, oxidative damage, and inflammation have been implicated as pathophysiological mechanisms underlying the selective loss of dopaminergic neurons seen in PD. However, results of studies aiming to inhibit these pathways have shown variable success, and outcomes from large-scale clinical trials are not available or report varying success for the interventions studied. Overall, the available data suggest that further development and testing of novel therapies are required to identify new potential therapies for combating PD. Herein, this review reports on the most recent development of antioxidant and anti-inflammatory approaches that have shown positive benefit in cell and animal models of disease with a focus on supplementation with natural product therapies and selected synthetic drugs.

The Cyclic Nitroxide TEMPOL Ameliorates Oxidative Stress but Not Inflammation in a Cell Model of Parkinson’s Disease

The cyclic nitroxide TEMPOL exerts anti-oxidative and anti-inflammatory effects, and thus may provide therapeutic benefit in Parkinson’s disease (PD), in which mitochondrial dysfunction, oxidative damage and inflammation have been implicated as pathophysiological mechanisms underlying the selective loss of dopaminergic neurons. Markers of oxidative stress and inflammation were investigated in a cell model of differentiated human neuroblastoma (SH-SY5Y) cells treated with the neurotoxin, 6-hydroxydopamine (6-OHDA). Treatment with TEMPOL ameliorated 6-OHDA-mediated cytotoxicity and attenuated biomarkers of oxidative stress including: mitochondrial superoxide anion free radical production, lipid peroxidation, induction of heme oxygenase 1 (HO-1) protein expression and NFκB activation. Treatment with TEMPOL abated decreased gene expression of DRD2S and DRD2L induced by 6-OHDA indicating that TEMPOL may prevent mitochondrial dysfunction and activation of pathways that result in receptor desensitization. 6-OHDA insult decreased gene expression of the antioxidant, SOD-1, and this diminution was also mitigated by TEMPOL. Activation of NFκB increased pro-inflammatory IFNy and decreased IL-6, however, TEMPOL had no effect on these inflammation mediators. Overall, this data suggests that cyclic nitroxides may preserve dopaminergic neuronal cell viability by attenuating oxidative stress and mitochondrial dysfunction, but are unable to affect inflammatory mediators that propagate cellular damage and neurodegeneration in PD.

Nanotechnology-Based Drug Delivery Strategies to Repair the Mitochondrial Function in Neuroinflammatory and Neurodegenerative Diseases

Mitochondria are vital organelles in eukaryotic cells that control diverse physiological processes related to energy production, calcium homeostasis, the generation of reactive oxygen species, and cell death. Several studies have demonstrated that structural and functional mitochondrial disturbances are involved in the development of different neuroinflammatory (NI) and neurodegenerative (ND) diseases (NI&NDDs) such as multiple sclerosis, Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Remarkably, counteracting mitochondrial impairment by genetic or pharmacologic treatment ameliorates neurodegeneration and clinical disability in animal models of these diseases. Therefore, the development of nanosystems enabling the sustained and selective delivery of mitochondria-targeted drugs is a novel and effective strategy to tackle NI&NDDs. In this review, we outline the impact of mitochondrial dysfunction associated with unbalanced mitochondrial dynamics, altered mitophagy, oxidative stress, energy deficit, and proteinopathies in NI&NDDs. In addition, we review different strategies for selective mitochondria-specific ligand targeting and discuss novel nanomaterials, nanozymes, and drug-loaded nanosystems developed to repair mitochondrial function and their therapeutic benefits protecting against oxidative stress, restoring cell energy production, preventing cell death, inhibiting protein aggregates, and improving motor and cognitive disability in cellular and animal models of different NI&NDDs.

Transcriptional inhibition by CDK7/9 inhibitor SNS-032 suppresses tumor growth and metastasis in esophageal squamous cell carcinoma

Metastasis is one of most lethal causes that confer a poor prognosis of patients with esophageal squamous cell carcinoma (ESCC), whereas there is no available target drug for metastatic ESCC currently. In this study, we aimed to determine whether the transcriptional inhibition by CDK7/9 inhibitor SNS-032 is activity against ESCC. MTT and soft agar assays were performed to examine the influence of SNS-032 on ESCC growth in vitro. Tumor xenograft in nude mice was used to assess the antitumor activity of SNS-032 in vivo. The roles of SNS-032 in ESCC metastasis were conducted by wound healing and transwell assays in vitro, and by a lung and a popliteal lymph node metastasis model in vivo. The results showed that CDK7 and CDK9 were highly expressed in ESCC cells; SNS-032 effectively inhibited cellular viability, abrogated anchorage-independent growth, and potentiated the sensitivity to cisplatin in ESCC cells in vitro and in vivo. In addition, SNS-032 induced a mitochondrial-dependent apoptosis of ESCC cells by reducing Mcl-1 transcription. SNS-032 also potently abrogated the abilities of ESCC cell migration and invasion through transcriptional downregulation of MMP-1. Importantly, SNS-032 remarkably inhibited the growth of ESCC xenograft, increased the overall survival, as well as diminished the lung and lymph node metastasis in nude mice. Taken together, our findings highlight that the CDK7/9 inhibitor SNS-032 is a promising therapeutic agent, and warrants a clinical trial for its efficacy in ESCC patients, even those with metastasis.

Neuroprotective effect of bromelain in 6-hydroxydopamine induced in vitro model of Parkinson's disease

BACKGROUND

This study was designed to investigate the neuroprotective effects of bromelain, which is known to have anti-oxidant and anti-inflammatory properties, against the neurotoxicity (induced by 6-OHDA) in SH-SY5Y cells.

METHODS AND RESULTS

To establish Parkinson's Disease (PD) model in cell culture conditions, SH-SY5Y cells were exposed to 200 µM 6-OHDA for 1 day. Prior to 6-OHDA treatment, SH-SY5Y cells had been pre-treated with bromelain (25 µg/mL, 50 µg/mL, 75 µg/mL and 100 µg/mL). After 1 day, cell viability was determined with the 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) and lactate dehydrogenase (LDH) assays. Oxidative stress was assessed with total antioxidant capacity (TAC), total oxidant status (TOS), glutathione reductase (GR) and malondialdehyde (MDA) analyses. The effect of the bromelain in SH-SY5Ycells was also examined by 4',6-diamidino-2-phenylindole (DAPI) staining. We found that 6-OHDA increased LDH leakage, and cellular apoptosis in SH-SY5Y cells. 6-OHDA aggravated oxidative stress by increasing TOS, MDA and GR and eventually promoted apoptosis in SH-SY5Y cells, while pretreatment with bromelain attenuated these toxic effects of 6-OHDA.

CONCLUSIONS

These findings indicated that bromelain, with its neuroprotective features can be useful for neuroprotection in PD.

CdSe/ZnS Core-Shell-Type Quantum Dot Nanoparticles Disrupt the Cellular Homeostasis in Cellular Blood-Brain Barrier Models

Two immortalized brain microvascular endothelial cell lines (hCMEC/D3 and RBE4, of human and rat origin, respectively) were applied as an in vitro model of cellular elements of the blood–brain barrier in a nanotoxicological study. We evaluated the impact of CdSe/ZnS core-shell-type quantum dot nanoparticles on cellular homeostasis, using gold nanoparticles as a largely bioorthogonal control. While the investigated nanoparticles had surprisingly negligible acute cytotoxicity in the evaluated models, a multi-faceted study of barrier-related phenotypes and cell condition revealed a complex pattern of homeostasis disruption. Interestingly, some features of the paracellular barrier phenotype (transendothelial electrical resistance, tight junction protein gene expression) were improved by exposure to nanoparticles in a potential hormetic mechanism. However, mitochondrial potential and antioxidant defences largely collapsed under these conditions, paralleled by a strong pro-apoptotic shift in a significant proportion of cells (evidenced by apoptotic protein gene expression, chromosomal DNA fragmentation, and membrane phosphatidylserine exposure). Taken together, our results suggest a reactive oxygen species-mediated cellular mechanism of blood–brain barrier damage by quantum dots, which may be toxicologically significant in the face of increasing human exposure to this type of nanoparticles, both intended (in medical applications) and more often unintended (from consumer goods-derived environmental pollution).

pH-Responsive Redox Nanoparticles Protect SH-SY5Y Cells at Lowered pH in a Cellular Model of Parkinson's Disease

The damage to SH-SY5Y cells by 6-hydroxydopamine (6-OHDA) is an established cellular model of Parkinson's disease (PD). Redox nanoparticles are a promising tool for therapy, including neurodegenerative diseases. As pH of the brain tissue at sites affected by PD is lowered down to 6.5, we studied the effect of pH-responsive redox nanoparticles (poly(ethylene glycol)-b-poly[4-(2,2,6,6-tetramethylpiperidine-1-oxyl)aminomethylstyrene]), which change their structure in a pH-dependent manner and become active below pH 7 (NRNPs pH), on the viability of SH-SY5Y cells treated with 6-OHDA at pH 6.5 and 7.4. Pretreatment of the cells with NRNPs pH (15-75 μM) prior to the 6-OHDA treatment increased their survival in a concentration-dependent manner at pH 6.5, but not at pH 7.4. Among several parameters studied (ATP and GSH content, the level of reactive oxygen species, mitochondrial potential, mitochondrial mass), only the mitochondrial mass was dose-dependently protected by NRNPs pH at pH 6.5, but not at pH 7.4. These results indicate that the action of NRNPs pH on mitochondria underlies their protective effect in this cellular model of PD. These results may have potential importance for future applications of NRNPs pH in preclinical and perhaps clinical studies.

Delphinidin Increases the Sensitivity of Ovarian Cancer Cell Lines to 3-Bromopyruvate

3-Bromopyruvic acid (3-BP) is a promising anticancer compound. Two ovary cancer (OC) cell lines, PEO1 and SKOV3, showed relatively high sensitivity to 3-BP (half maximal inhibitory concentration (IC₅₀) of 18.7 and 40.5 µM, respectively). However, the further sensitization of OC cells to 3-BP would be desirable. Delphinidin (D) has been reported to be cytotoxic for cancer cell lines. We found that D was the most toxic for PEO1 and SKOV3 cells from among several flavonoids tested. The combined action of 3-BP and D was mostly synergistic in PEO1 cells and mostly weakly antagonistic in SKOV3 cells. The viability of MRC-5 fibroblasts was not affected by both compounds at concentrations of up to 100 µM. The combined action of 3-BP and D decreased the level of ATP and of dihydroethidium (DHE)-detectable reactive oxygen species (ROS), cellular mobility and cell staining with phalloidin and Mitotracker Red in both cell lines but increased the 2’,7’-dichlorofluorescein (DCFDA)-detectable ROS level and decreased the mitochondrial membrane potential and mitochondrial mass only in PEO1 cells. The glutathione level was increased by 3-BP+D only in SKOV3 cells. These differences may contribute to the lower sensitivity of SKOV3 cells to 3-BP+D. Our results point to the possibility of sensitization of at least some OC cells to 3-BP by D.

The Antiaggregative and Antiamyloidogenic Properties of Nanoparticles: A Promising Tool for the Treatment and Diagnostics of Neurodegenerative Diseases

Due to the progressive aging of the society, the prevalence and socioeconomic burden of neurodegenerative diseases are predicted to rise. The most common neurodegenerative disorders nowadays, such as Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis, can be classified as proteinopathies. They can be either synucleinopathies, amyloidopathies, tauopathies, or TDP-43-related proteinopathies; thus, nanoparticles with a potential ability to inhibit pathological protein aggregation and/or degrade already existing aggregates can be a promising approach in the treatment of neurodegenerative diseases. As it turns out, nanoparticles can be a double-edged sword; they can either promote or inhibit protein aggregation, depending on coating, shape, size, surface charge, and concentration. In this review, we aim to emphasize the need of a breakthrough in the treatment of neurodegenerative disorders and draw attention to nanomaterials, as they can also serve as a diagnostic tool for protein aggregates or can be used in a high-throughput screening for novel antiaggregative compounds.