VPA and MEL induce apoptosis by inhibiting the Nrf2-ARE signaling pathway in TMZ-resistant U251 cells

Temozolomide Resistance in Glioblastoma by NRF2: Protecting the Evil

The transcription factor NRF2 is constitutively active in glioblastoma, a highly aggressive brain tumor subtype with poor prognosis. Temozolomide (TMZ) is the primary chemotherapeutic agent for this type of tumor treatment, but resistance to this drug is often observed. This review highlights the research that is demonstrating how NRF2 hyperactivation creates an environment that favors the survival of malignant cells and protects against oxidative stress and TMZ. Mechanistically, NRF2 increases drug detoxification, autophagy, DNA repair, and decreases drug accumulation and apoptotic signaling. Our review also presents potential strategies for targeting NRF2 as an adjuvant therapy to overcome TMZ chemoresistance in glioblastoma. Specific molecular pathways, including MAPKs, GSK3β, βTRCP, PI3K, AKT, and GBP, that modulate NRF2 expression leading to TMZ resistance are discussed, along with the importance of identifying NRF2 modulators to reverse TMZ resistance and develop new therapeutic targets. Despite the significant progress in understanding the role of NRF2 in GBM, there are still unanswered questions regarding its regulation and downstream effects. Future research should focus on elucidating the precise mechanisms by which NRF2 mediates resistance to TMZ, and identifying potential novel targets for therapeutic intervention.

Exploring the role of Nrf2 signaling in glioblastoma multiforme

Glioblastoma multiforme (GBM) is one of the most aggressive glial cell tumors in adults. Although current treatment options for GBM offer some therapeutic benefit, median survival remains poor and does not generally exceed 14 months. Several genes, such as isocitrate dehydrogenase (IDH) enzyme and O6-methylguanine-DNA methyltransferase (MGMT), have been implicated in pathogenesis of the disease. Treatment is often adapted based on the presence of IDH mutations and MGMT promoter methylation status. Recent GBM cell line studies have associated Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2) expression with high-grade tumors. Increased Nrf2 expression is often found in tumors with IDH-1 mutations. Nrf2 is an important transcription factor with anti-apoptotic, antioxidative, anti-inflammatory, and proliferative properties due to its complex interactions with multiple regulatory pathways. In addition, evidence suggests that Nrf2 promotes  GBM cell survival in hypoxic environment,by up-regulating hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF). Downregulation of Nrf2 has been shown to improve GBM sensitivity to chemotherapy drugs such as Temozolomide. Thus, Nrf2 could be a key regulator of GBM pathways and potential therapeutic target.  Further research efforts exploring an interplay between Nrf2 and major molecular signaling mechanisms could offer novel GBM drug candidates with a potential to significantly improve patients prognosis.

Temozolomide hexadecyl ester targeted plga nanoparticles for drug-resistant glioblastoma therapy via intranasal administration

Introduction: Temozolomide (TMZ) is the first-line drug for glioblastoma (GBM), but it is limited in clinical use due to the drug resistance, poor brain targeting, and side effects. Temozolomide hexadecyl ester (TMZ16e), a TMZ derivative with high lipophilicity, membrane permeability, and high anti-glioma properties, has the potential to reverse drug resistance. In this study, anti-ephrin type-A receptor 3 (EphA3) modified TMZ16e loaded nanoparticles (NPs) were prepared for targeted GBM therapy via intranasal administration to deliver TMZ16e to the brain, treat drug-resistant glioma effectively, and reduce peripheral toxicity.

Methods: TMZ16e loaded NPs were prepared by emulsion solvent evaporation method followed by modified with anti-EphA3 (anti-EphA3-TMZ16e-NPs). In vitro evaluations were performed by an MTT assay and flow cytometry analysis. The orthotopic nude mice models were used to evaluate the anti-glioma effect in vivo. Additionally, we investigated the anti-drug resistant mechanism by western blot analysis.

Results: The particle size of the prepared NPs was less than 200 nm, and the zeta potential of TMZ16e-NPs and anti-EphA3-TMZ16e-NPs were -23.05 ± 1.48 mV and -28.65 ± 1.20mV, respectively, which is suitable for nasal delivery. In vitro studies have shown that anti-EphA3 modification increased the cellular uptake of nanoparticles in T98G cells. The cytotoxicity in the anti-EphA3-TMZ16e-NPs treated group was significantly higher than that of the TMZ16e-NPs, TMZ16e, and TMZ groups (p < 0.01), and the cell cycle was blocked. Western blotting analysis showed that the TMZ16e-loaded NPs were able to effectively downregulate the expression level of O6-methylguanine-deoxyribonucleic acid-methyltransferase (MGMT) protein in T98G cells and reverse drug resistance. In vivo studies showed that the median survival time of tumor-bearing nude mice in the anti-EphA3-TMZ16e-NPs group was extended to 41 days, which was 1.71-fold higher than that of the saline group and the TUNEL staining results of the brain tissue section indicated that the TMZ16e-loaded NPs could elevate apoptosis in T98G cells.

Conclusion: In conclusion, the TMZ16e-loaded NPs can be effectively delivered to the brain and targeted to gliomas, exhibiting better anti-glioma activity, indicating they possess great potential in the treatment of drug-resistant glioma.

The Role of NRF2/KEAP1 Pathway in Glioblastoma: Pharmacological Implications

Glioblastoma multiforme (GBM) grade IV glioma is the most frequent and deadly intracranial cancer. This tumor is determined by unrestrained progression, uncontroled angiogenesis, high infiltration and weak response to treatment, which is chiefly because of abnormal signaling pathways in the tumor. A member related to the Cap 'n' collar family of keypart-leucine zipper transcription agents-the transcription factor NF-E2-related factor 2 (Nrf2)-regulates adaptive protection answers by organized upregulation of many genes that produce the cytoprotective factors. In reply to cellular pressures types such as stresses, Nrf2 escapes Kelch-like ECH-related protein 1 (Keap1)-facilitated suppression, moves from the cytoplasm towards the nucleus and performs upregulation of gene expression of antioxidant responsive element (ARE). Nrf2 function is related tocontrolling many types of diseases in the human specially GBM tumor.Thus, we will review the epigeneticalregulatory actions on the Nrf2/Keap1 signaling pathway and potential therapeutic options in GBM by aiming the stimulation of Nrf2.

Valproic acid disables the Nrf2 anti-oxidant response in acute myeloid leukaemia cells enhancing reactive oxygen species-mediated killing

BACKGROUND

We previously demonstrated the in vitro killing of AML cells by the combination of the lipid-lowering agent bezafibrate (BEZ) and the contraceptive hormone medroxyprogesterone acetate (MPA). A phase II trial demonstrated in vivo safety and efficacy of BEZ and MPA (BaP) in elderly, relapsed/refractory AML and high-risk myelodysplastic syndrome (MDS) patients. However, we observed dose-limiting toxicities in a second trial that attempted to improve outcomes via escalation of BaP doses. Thus we sought to identify a third repurposed drug that potentiates activity of low dose BaP (BaP 0.1 mM).

METHODS AND RESULTS

We demonstrate that addition of a commonly used anti-epileptic, valproic acid (VAL) to low dose BaP (BaP 0.1 mM)(VBaP) enhanced killing of AML cell lines/primary AML cells to levels similar to high dose BaP (BaP 0.5 mM). Similarly, addition of VAL to BaP 0.1 mM enhanced reactive oxygen species (ROS), lipid peroxidation and inhibition of de novo fatty acid synthesis. Overexpression of Nrf2 in K562 and KG1a completely inhibited ROS production and rescued cells from VAL/BaP 0.1 mM/VBaP killing.

CONCLUSIONS

Given the good safety data of low-dose BaP in elderly/relapsed/refractory AML patients, and that VAL alone is well-tolerated, we propose VBaP as a novel therapeutic combination for AML.

Nose-to-Brain Delivery of Antioxidants as a Potential Tool for the Therapy of Neurological Diseases

Oxidative stress has a key role in the pathogenesis of neurodegenerative disorders such as Alzheimer's, Parkinson's, and Huntington's diseases and can be an important cause of the damages in cerebral ischemia. Oxidative stress arises from high levels of reactive oxygen species (ROS). Consequently, on this rational base, antioxidants (many of natural origin) are proposed as potential drugs to prevent ROS noxious actions because they can protect the target tissues from the oxidative stress. However, the potential of antioxidants is limited, owing to the presence of the blood-brain barrier (BBB), which is difficult to cross with a consequent low bioavailability of the drug into the brain after systemic (intravenous, intraperitoneal, oral) administrations. One strategy to improve the delivery of antioxidants to the brain involves the use of the so-called nose-to-brain route, with the administration of the antioxidant in specific nasal formulations and its passage to the central nervous system (CNS) mainly through the olfactory nerve way. In the current literature, many examples show encouraging results in studies carried out in cell cultures and in animal models about the potential neuroprotective effects of antioxidants when administered through the nose. This review concerns the nose-to-brain route for the brain targeting of antioxidants as a potential tool for the therapy of neurological diseases.

Melatonin Induces Melanogenesis in Human SK-MEL-1 Melanoma Cells Involving Glycogen Synthase Kinase-3 and Reactive Oxygen Species

Melatonin is present in all living organisms where it displays a diversity of physiological functions. Attenuation of melanogenesis by melatonin has been reported in some mammals and also in rodent melanoma cells. However, melatonin may also stimulate melanogenesis in human melanoma cells through mechanisms that have not yet been revealed. Using the human melanoma cells SK-MEL-1 as a model, an increase in both tyrosinase activity and melanin was already observed at 24 h after melatonin treatment with maximal levels of both being detected at 72 h. This effect was associated with the induction in the expression of the enzymes involved in the synthesis of melanin. In this scenario, glycogen synthase kinase-3β seems to play a significant function since melatonin decreased its phosphorylation and preincubation with specific inhibitors of this protein kinase (lithium or BIO) reduced the expression and activity of tyrosinase. Blocking of PI3K/AKT pathway stimulated melanogenesis and the effect was suppressed by the inhibitors of glycogen synthase kinase-3β. Although melatonin is a recognized antioxidant, we found that it stimulates reactive oxygen species generation in SK-MEL-1 cells. These chemical species seem to be an important signal in activating the melanogenic process since the antioxidants N-acetyl-l-cysteine and glutathione decreased both the level and activity of tyrosinase stimulated by melatonin. Our results support the view that regulation of melanogenesis involves a cross-talk between several signaling pathways.

HJ22, a Novel derivative of piperine, Attenuates ibotenic acid-induced cognitive impairment, oxidativestress, apoptosis and inflammation via inhibiting the protein-protein interaction of Keap1-Nrf2

Kelch-like ECH-associated protein (Keap1)-nuclear factor erythroid-2-related factor 2 (Nrf2) protein-protein interaction has become an important drug target for the treatment of Alzheimer's disease. In this study, we found a novel piperine derivative (HJ22) synthesized by our group with great ability to bind to Keap-1 and activate Keap1-Nrf2-ARE signaling pathway in vitro, driving us to investigate the beneficial effects of HJ22 on ibotenic acid (IBO)-induced neurological disorders in rats and underlying mechanisms. Interestingly, HJ22 significantly ameliorated IBO-induced cognitive impairment in Morris water maze, Y-maze and passive avoidance tests. Moreover, HJ22 significantly attenuated cholinergic dysfunction and neuronal morphological changes via inhibiting apoptotic cell death induced by IBO. Notably, HJ22 inhibited the interaction between Keap1 and Nrf2, and subsequently up-regulated nuclear Nrf2 expression, thereby inhibiting oxidative stress and Thioredoxin-interacting protein (TXNIP)-mediated Nod-like receptor protein 3 (NLRP3) inflammasome activation. These findings demonstrated that HJ22 exhibited potent therapeutic effects against IBO-induced cognitive impairment by alleviating cholinergic damage, oxidative stress, apoptosis and neuroinflammation, which might be partly attributed to its inhibitory activity on Keap1-Nrf2 protein-protein interaction.

Combined Delivery of Temozolomide and siPLK1 Using Targeted Nanoparticles to Enhance Temozolomide Sensitivity in Glioma

INTRODUCTION

Temozolomide (TMZ) is the first-line chemotherapeutic option to treat glioma; however, its efficacy and clinical application are limited by its drug resistance properties. Polo-like kinase 1 (PLK1)-targeted therapy causes G2/M arrest and increases the sensitivity of glioma to TMZ. Therefore, to limit TMZ resistance in glioma, an angiopep-2 (A2)-modified polymeric micelle (A2PEC) embedded with TMZ and a small interfering RNA (siRNA) targeting PLK1 (siPLK1) was developed (TMZ-A2PEC/siPLK).

MATERIALS AND METHODS

TMZ was encapsulated by A2-PEG-PEI-PCL (A2PEC) through the hydrophobic interaction, and siPLK1 was complexed with the TMZ-A2PEC through electrostatic interaction. Then, an angiopep-2 (A2) modified polymeric micelle (A2PEC) embedding TMZ and siRNA targeting polo-like kinase 1 (siPLK1) was developed (TMZ-A2PEC/siPLK).

RESULTS

In vitro experiments indicated that TMZ-A2PEC/siPLK effectively enhanced the cellular uptake of TMZ and siPLK1 and resulted in significant cell apoptosis and cytotoxicity of glioma cells. In vivo experiments showed that glioma growth was inhibited, and the survival time of the animals was prolonged remarkably after TMZ-A2PEC/siPLK1 was injected via their tail vein.

DISCUSSION

The results demonstrate that the combination of TMZ and siPLK1 in A2PEC could enhance the efficacy of TMZ in treating glioma.

Melatonin's Antineoplastic Potential Against Glioblastoma

Glioblastoma (GBM) is one of the most intransigent and aggressive brain tumors, and its treatment is extremely challenging and ineffective. To improve patients’ expectancy and quality of life, new therapeutic approaches were investigated. Melatonin is an endogenous indoleamine with an incredible variety of properties. Due to evidence demonstrating melatonin’s activity against several cancer hallmarks, there is growing interest in its use for preventing and treating cancer. In this review, we report on the potential effects of melatonin, alone or in combination with anticancer drugs, against GBM. We also summarize melatonin targets and/or the intracellular pathways involved. Moreover, we describe melatonin’s epigenetic activity responsible for its antineoplastic effects. To date, there are too few clinical studies (involving a small number of patients) investigating the antineoplastic effects of melatonin against GBM. Nevertheless, these studies described improvement of GBM patients’ quality of life and did not show significant adverse effects. In this review, we also report on studies regarding melatonin-like molecules with the tumor-suppressive properties of melatonin together with implemented pharmacokinetics. Melatonin effects and mechanisms of action against GBM require more research attention due to the unquestionably high potential of this multitasking indoleamine in clinical practice.

Increased Nose-to-Brain Delivery of Melatonin Mediated by Polycaprolactone Nanoparticles for the Treatment of Glioblastoma

PURPOSE

Intranasal administration has been extensively applied to deliver drugs to the brain. In spite of its unfavorable biopharmaceutic properties, melatonin (MLT) has demonstrated anticancer effects against glioblastoma. This study describes the nose-to-brain delivery of MLT-loaded polycaprolactone nanoparticles (MLT-NP) for the treatment of glioblastoma.

METHODS

MLT-NP were prepared by nanoprecipitation. Following intranasal administration in rats, brain targeting of the formulation was demonstrated by fluorescence tomography. Brain and plasma pharmacokinetic profiles were analyzed. Cytotoxicity against U87MG glioblastoma cells and MRC-5 non-tumor cells was evaluated.

RESULTS

MLT-NP increased the drug apparent water solubility ~35 fold. The formulation demonstrated strong activity against U87MG cells, resulting in IC50 ~2500 fold lower than that of the free drug. No cytotoxic effect was observed against non-tumor cells. Fluorescence tomography images evidenced the direct translocation of nanoparticles from nasal cavity to the brain. Intranasal administration of MLT-NP resulted in higher AUC_brain and drug targeting index compared to the free drug by either intranasal or oral route.

CONCLUSIONS

Nanoencapsulation of MLT was crucial for the selective antitumoral activity against U87MG. In vivo evaluation confirmed nose-to-brain delivery of MLT mediated by nanoparticles, highlighting the formulation as a suitable approach to improve glioblastoma therapy.

Hemin-induced platelet activation and ferroptosis is mediated through ROS-driven proteasomal activity and inflammasome activation: Protection by Melatonin

Reactive oxygen species (ROS) are capable of inducing cell death or apoptosis. Recently, we demonstrated that lipid-ROS can mediate ferroptosis and activation of human platelets. Ferroptosis is an intracellular iron-mediated cell death, distinct from classical apoptosis and necrosis, which is mediated through the accumulation of ROS, lipid peroxides and depletion of cellular GSH. Lately, we demonstrated that hemoglobin degradation product hemin induces ferroptosis in platelets via ROS and lipid peroxidation. In this study, we demonstrate that hemin-induced ferroptosis in platelets is mediated through ROS-driven proteasome activity and inflammasome activation, which were mitigated by Melatonin (MLT). Although inflammasome activation is linked with pyroptosis, it is still not clear whether ferroptosis is associated with inflammasome activation. Our study for the first time demonstrates an association of platelet activation/ferroptosis with proteasome activity and inflammasome activation. Although, high-throughput screening has recognized ferrostatin-1 (Fer-1) and liproxstatin-1 (Lip-1) as potent ferroptosis inhibitors, having an endogenous antioxidant such as MLT as ferroptosis inhibitor is of high interest. MLT is a well-known chronobiotic hormone that regulates the circadian rhythms in vertebrates. It also exhibits potent antioxidant and ROS quenching capabilities. MLT can regulate fundamental cellular functions by exhibiting cytoprotective, oncostatic, antiaging, anti-venom, and immunomodulatory activities. The ROS scavenging capacity of MLT is key for its cytoprotective and anti-apoptotic properties. Considering the anti-ferroptotic and anti-apoptotic potentials of MLT, it could be a promising clinical application to treat hemolytic, thrombotic and thrombocytopenic conditions. Therefore, we propose MLT as a pharmacological and therapeutic agent to inhibit ferroptosis and platelet activation.