Nrf2 Activation: Involvement in Central Nervous System Traumatic Injuries. A Promising Therapeutic Target of Natural Compounds

Molecular mechanisms of neuroprotection: The interplay of Klotho, SIRT-1, Nrf2, and HO-1 in neurological health

Neurological disorders significantly impair neuronal function and lead to cognitive and motor deficits. This review manuscript explores the therapeutic potential of key proteins-Klotho, SIRT-1, Nrf2, and HO-1-in combating these disorders. Neurological conditions encompass neurotraumatic, neurodegenerative, and neuropsychiatric diseases, all characterized by neuronal loss and dysfunction. The complex functions of Klotho, an anti-aging protein, and SIRT-1, a histone deacetylase, highlight their roles in neuronal survival and neuroprotection through the enhancement of antioxidant defences and the modulation of stress responses. Nrf2 functions as the principal regulator of the antioxidant response, whereas HO-1 facilitates the control of oxidative stress and the resolution of inflammation. Evidence suggests that the interplay between these proteins facilitates neuroprotection by decreasing oxidative damage and promoting cognitive function. The study emphasises the significance of signalling pathways, particularly the Nrf2/HO-1 axis, which are essential in mitigating oxidative stress and inflammation linked to neurodegenerative disorders. Future therapeutic strategies must consider personalized approaches, innovative drug delivery systems, and early intervention to optimize outcomes. This review provides a comprehensive framework for understanding how targeting these pathways can mitigate the burden of neurological disorders, advancing the development of effective interventions for enhancing brain health.

Potential of integrating phytochemicals with standard treatments for enhanced outcomes in TBI

OBJECTIVE

TBI's intricate pathophysiology, which includes oxidative stress, neuroinflammation, apoptosis, and mechanical injury, makes it a serious public health concern. Although stabilization and secondary damage management are the main goals of current treatments, their efficacy is still restricted. The potential for improving patient outcomes by combining phytochemicals with traditional medicines is examined in this review.

METHODS

The study examined the neuroprotective qualities of ginsenosides, ginkgolides, resveratrol, and curcumin as well as their antioxidant and anti-inflammatory activities. Analysis was done on molecular pathways and medication delivery techniques to improve translational outcomes and drug availability for clinical practice.

RESULTS

Phytochemical substances directly influence TBI-related neurogenic pathways and functional restoration while also affecting subsequent neural damage processes. Particle-based medicine delivery platforms enhance therapeutic drug efficacy, emerging as innovative solutions for targeted drug delivery. When traditional medical therapies integrate with phytochemicals, it becomes possible to achieve better patient results through enhanced synergy.

CONCLUSION

This review uniquely integrates phytochemicals with standard TBI treatments, emphasizing advanced drug delivery strategies and their translational potential to enhance neuroprotection and clinical outcomes. Unlike previous studies, it explores novel drug delivery platforms, such as nanoparticle-based systems, and highlights the synergy between phytochemicals and conventional therapies to improve patient recovery.

7β-(3-ethyl-cis-crotonoyloxy)-1α-(2-methylbutyryloxy)-3,14-dehydro-Z-notonipetranone (ECN) attenuates inflammation and oxidative stress via MAPK, and Nrf2/HO-1 signaling in Traumatic brain injury

Traumatic brain injury (TBI) is an acquired neurological insult that has become a major cause of mortality.Hence, immediate and appropriate medical attention is essential. The present study investigated the neuroprotective effect of 7β-(3-ethyl-cis-crotonoyloxy)-1α-(2-methylbutyryloxy)-3,14-dehydro-Z-notonipetranone (ECN), a sesquiterpenoid against a weight drop model of traumatic brain injury (TBI). During the in-vitro analysis, ECN demonstrated neuroprotective potential by remarkably improving the cell viability and also provided significant protection in case of nitric oxide-evoked oxidative stress in HT22 cells. The administration of ECN significantly improved the neurological severity score, and mechanical/periorbital allodynia following TBI, when compared with the TBI-group. The level of brain edema and blood-brain barrier (BBB) disruption were also significantly reduced by ECN treatment. ECN also restored constitutional changes in the protein/lipid profile; simultaneous with histological changes in the brain in contrast to the TBI-group. It significantly ameliorated neuronal loss and also minimized the intracerebral hemorrhages arising from traumatic insult. ECN exhibited potent anti-inflammatory effects, by altering the expression of extracellular-signal-regulated kinase (ERK), p38, and activating protein-1 (AP-1) proteins. It also exhibited antioxidant effects by increasing the production levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1). Furthermore, ECN also produced an anti-apoptotic effect by downregulation of caspase3 and upregulation of B-cell lymphoma 2 (Bcl-2). It also increased the levels of antioxidants while reducing the levels of oxidative stress and inflammatory markers in comparison to the TBI-group. In short, it was concluded that ECN exhibited protective anti-inflammatory, antioxidant, and anti-apoptotic effects against trauma-induced brain injury.

Antioxidant and Anti-Inflammatory Properties of Melatonin in Secondary Traumatic Brain Injury

Traumatic brain injury (TBI) is a disease resulting from external physical forces acting against the head, leading to transient or chronic damage to brain tissue. Primary brain injury is an immediate and, therefore, rather irreversible effect of trauma, while secondary brain injury results from a complex cascade of pathological processes, among which oxidative stress and neuroinflammation are the most prominent. As TBI is a significant cause of mortality and chronic disability, with high social costs all over the world, any form of therapy that may mitigate trauma-evoked brain damage is desirable. Melatonin, a sleep-wake-cycle-regulating neurohormone, exerts strong antioxidant and anti-inflammatory effects and is well tolerated when used as a drug. Due to these properties, it is very reasonable to consider melatonin as a potential therapeutic molecule for TBI treatment. This review summarizes data from in vitro studies, animal models, and clinical trials that focus on the usage of melatonin in TBI.

Nrf2 pathways in neuroprotection: Alleviating mitochondrial dysfunction and cognitive impairment in aging

Mitochondrial dysfunction and cognitive impairment are widespread phenomena among the elderly, being crucial factors that contribute to neurodegenerative diseases. Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important regulator of cellular defense systems, including that against oxidative stress. As such, increased Nrf2 activity may serve as a strategy to avert mitochondrial dysfunction and cognitive decline. Scientific data on Nrf2-mediated neuroprotection was collected from PubMed, Google Scholar, and Science Direct, specifically addressing mitochondrial dysfunction and cognitive impairment in older people. Search terms included "Nrf2", "mitochondrial dysfunction," "cognitive impairment," and "neuroprotection." Studies focusing on in vitro and in vivo models and clinical investigations were included to review Nrf2's therapeutic potential comprehensively. The relative studies have demonstrated that increased Nrf2 activity could improve mitochondrial performance, decrease oxidative pressure, and mitigate cognitive impairment. To a large extent, this is achieved through the modulation of critical cellular signalling pathways such as the Keap1/Nrf2 pathway, mitochondrial biogenesis, and neuroinflammatory responses. The present review summarizes the recent progress in comprehending the molecular mechanisms regarding the neuroprotective benefits mediated by Nrf2 through its substantial role against mitochondrial dysfunction and cognitive impairment. This review also emphasizes Nrf2-target pathways and their contribution to cognitive function improvement and rescue from mitochondria-related abnormalities as treatment strategies for neurodegenerative diseases that often affect elderly individuals.

interFLOW: maximum flow framework for the identification of factors mediating the signaling convergence of multiple receptors

Cell-cell crosstalk involves simultaneous interactions of multiple receptors and ligands, followed by downstream signaling cascades working through receptors converging at dominant transcription factors, which then integrate and propagate multiple signals into a cellular response. Single-cell RNAseq of multiple cell subsets isolated from a defined microenvironment provides us with a unique opportunity to learn about such interactions reflected in their gene expression levels. We developed the interFLOW framework to map the potential ligand-receptor interactions between different cell subsets based on a maximum flow computation in a network of protein-protein interactions (PPIs). The maximum flow approach further allows characterization of the intracellular downstream signal transduction from differentially expressed receptors towards dominant transcription factors, therefore, enabling the association between a set of receptors and their downstream activated pathways. Importantly, we were able to identify key transcription factors toward which the convergence of multiple receptor signaling pathways occurs. These identified factors have a unique role in the integration and propagation of signaling following specific cell-cell interactions.

CGRP as a potential mediator for the sexually dimorphic responses to traumatic brain injury

BACKGROUND

The outcomes of traumatic brain injury (TBI) exhibit variance contingent upon biological sex. Although female sex hormones exert neuroprotective effects, the administration of estrogen and progesterone has not yielded conclusive results. Hence, it is conceivable that additional mediators, distinct from female sex hormones, merit consideration due to their potential differential impact on TBI outcomes. Calcitonin gene-related peptide (CGRP) exhibits sexually dimorphic expression and demonstrates neuroprotective effects in acute brain injuries. In this study, we aimed to examine sex-based variations in TBI structural and functional outcomes with respect to CGRP expression.

METHODS

Male and female Sprague Dawley rats were exposed to controlled cortical impact to induce severe TBI, followed by interventions with and without CGRP inhibition. In the acute phase of TBI, the study centered on elucidating the influence of CGRP on oxidative stress, nuclear factor erythroid 2-related factor 2 (Nrf2) and endothelial nitric oxide synthase (eNOS) signaling in the peri-impact tissue. Subsequently, during the chronic phase of TBI, the investigation expanded to evaluate CGRP expression in relation to lesion volume, microvascular dysfunction, and white matter injury, as well as working and spatial memory, anxiety-like, and depression-like behaviors in subjects of both sexes.

RESULTS

Female rats exhibited elevated levels of CGRP in the peri-impact brain tissue during both baseline conditions and in the acute and chronic phases of TBI, in comparison to age-matched male counterparts. Enhanced CGRP levels in specific brain sub-regions among female rats correlated with superior structural and functional outcomes following TBI compared to their male counterparts. CGRP inhibition induced heightened oxidative stress and a reduction in the expression of Nrf2 and eNOS in both male and female rats, with the observed alteration being more pronounced in females than in males.

CONCLUSIONS

This study marks the inaugural identification of CGRP as a downstream mediator contributing to the sexually dimorphic response observed in TBI outcomes.

Targeting the adenosine A2A receptor for neuroprotection and cognitive improvement in traumatic brain injury and Parkinson's disease

Adenosine exerts its dual functions of homeostasis and neuromodulation in the brain by acting at mainly 2 G-protein coupled receptors, called A1 and A2A receptors. The adenosine A2A receptor (A2AR) antagonists have been clinically pursued for the last 2 decades, leading to final approval of the istradefylline, an A2AR antagonist, for the treatment of OFF-Parkinson's disease (PD) patients. The approval paves the way to develop novel therapeutic methods for A2AR antagonists to address 2 major unmet medical needs in PD and traumatic brain injury (TBI), namely neuroprotection or improving cognition. In this review, we first consider the evidence for aberrantly increased adenosine signaling in PD and TBI and the sufficiency of the increased A2AR signaling to trigger neurotoxicity and cognitive impairment. We further discuss the increasing preclinical data on the reversal of cognitive deficits in PD and TBI by A2AR antagonists through control of degenerative proteins and synaptotoxicity, and on protection against TBI and PD pathologies by A2AR antagonists through control of neuroinflammation. Moreover, we provide the supporting evidence from multiple human prospective epidemiological studies which revealed an inverse relation between the consumption of caffeine and the risk of developing PD and cognitive decline in aging population and Alzheimer's disease patients. Collectively, the convergence of clinical, epidemiological and experimental evidence supports the validity of A2AR as a new therapeutic target and facilitates the design of A2AR antagonists in clinical trials for disease-modifying and cognitive benefit in PD and TBI patients.

Zinc remodels mitochondrial network through SIRT3/Mfn2-dependent mitochondrial transfer in ameliorating spinal cord injury

Spinal cord injury (SCI) is a traumatic neuropathic condition that results in motor, sensory and autonomic dysfunction. Mitochondrial dysfunction caused by primary trauma is one of the critical pathogenic mechanisms. Moderate levels of zinc have antioxidant effects, promote neurogenesis and immune responses. Zinc normalises mitochondrial morphology in neurons after SCI. However, how zinc protects mitochondria within neurons is unknown. In the study, we used transwell culture, Western blot, Quantitative Real-time Polymerase Chain Reaction (QRT-PCR), ATP content detection, reactive oxygen species (ROS) activity assay, flow cytometry and immunostaining to investigate the relationship between zinc-treated microglia and injured neurons through animal and cell experiments. We found that zinc promotes mitochondrial transfer from microglia to neurons after SCI through Sirtuin 3 (SIRT3) regulation of Mitofusin 2 protein (Mfn2). It can rescue mitochondria in damaged neurons and inhibit oxidative stress, increase ATP levels and promote neuronal survival. Therefore, it can improve the recovery of motor function in SCI mice. In conclusion, our work reveals a potential mechanism to describe the communication between microglia and neurons after SCI, which may provide a new idea for future therapeutic approaches to SCI.

SiONx Coating Regulates Mesenchymal Stem Cell Antioxidant Capacity via Nuclear Erythroid Factor 2 Activity under Toxic Oxidative Stress Conditions

Healing in compromised and complicated bone defects is often prolonged and delayed due to the lack of bioactivity of the fixation device, secondary infections, and associated oxidative stress. Here, we propose amorphous silicon oxynitride (SiONx) as a coating for the fixation devices to improve both bioactivity and bacteriostatic activity and reduce oxidative stress. We aimed to study the effect of increasing the N/O ratio in the SiONx to fine-tune the cellular activity and the antioxidant effect via the NRF2 pathway under oxidative stress conditions. The in vitro studies involved using human mesenchymal stem cells (MSCs) to examine the effect of SiONx coatings on osteogenesis with and without toxic oxidative stress. Additionally, bacterial growth on SiONx surfaces was studied using methicillin-resistant Staphylococcus aureus (MRSA) colonies. NRF2 siRNA transfection was performed on the hMSCs (NRF2-KD) to study the antioxidant response to silicon ions. The SiONx implant surfaces showed a >4-fold decrease in bacterial growth vs. bare titanium as a control. Increasing the N/O ratio in the SiONx implants increased the alkaline phosphatase activity >1.5 times, and the other osteogenic markers (osteocalcin, RUNX2, and Osterix) were increased >2-fold under normal conditions. Increasing the N/O ratio in SiONx enhanced the protective effects and improved cell viability against toxic oxidative stress conditions. There was a significant increase in osteocalcin activity compared to the uncoated group, along with increased antioxidant activity under oxidative stress conditions. In NRF2-KD cells, there was a stunted effect on the upregulation of antioxidant markers by silicon ions, indicating a role for NRF2. In conclusion, the SiONx coatings studied here displayed bacteriostatic properties. These materials promoted osteogenic markers under toxic oxidative stress conditions while also enhancing antioxidant NRF2 activity. These results indicate the potential of SiONx coatings to induce in vivo bone regeneration in a challenging oxidative stress environment.

NRF2 Activation by AR-20007 Preserves Renal Tubular Epithelial Cells from Antimycin A-Induced Cell Death via Glutathione Metabolism Regulation

Oxidative stress plays a crucial role in the development and progression of various kidney diseases. Nuclear factor erythroid 2-related factor 2 (NRF2) is the primary transcription factor that protects cells from oxidative stress by regulating cytoprotective genes including those involved in the antioxidant glutathione (GSH) pathway. GSH maintains cellular redox status and affects redox signaling, cell proliferation, and cell death. Antimycin A, an inhibitor of complex III of the electron transport chain, causes oxidative stress and reduces GSH levels. In this study, we induced mitochondrial damage in rat renal proximal tubular cells using antimycin A and investigated cellular viability and levels of NRF2 and GSH. Treatment with antimycin A altered the expression of antioxidant genes, including reduction in the transcription of glutathione-cysteine ligase subunits (Gclc and Gclm) and glutathione reductase (Gsr1), followed by a reduction in total GSH content with a concomitant decrease in NRF2 protein expression. AR-20007, previously described as an NRF2 activator, stabilizes and increases NRF2 protein expression in cells. By stimulating NRF2, AR-20007 increased the expression of antioxidant and detoxifying enzymes, thereby enhancing protection against oxidative stress induced by antimycin A. These data suggest that NRF2 activation effectively inhibits antimycin A-induced oxidative stress and that NRF2 may be a promising therapeutic target for preventing cell death during acute kidney injury.

Targeting Nrf2 signaling pathway by quercetin in the prevention and treatment of neurological disorders: An overview and update on new developments

BACKGROUND

Neurological disorders (NLDs) are widely acknowledged as a significant public health concern worldwide. Stroke, Alzheimer's disease (AD), and traumatic brain injury (TBI) are three of these disorders that have sparked major study attention. Neurological dysfunction, protein buildup, oxidation and neuronal injury, and aberrant mitochondria are all prevalent neuropathological hallmarks of these disorders. The signaling cascade of nuclear factor erythroid 2 related factor 2 (Nrf2) shares all of them as a common target. Several studies have found that overexpression of Nrf2 is a promising treatment method in NLDs. Effective treatment of these disorders continues to be a universal concern regardless of various medicines. In order to treat a variety of neurological problems, organic remedies may provide an alternative treatment. It has been demonstrated that polyphenols like quercetin (Que) offer considerable capabilities for treating NLDs. One of Que's greatest key targets, Nrf2, has the capacity to control the production of a number of cytoprotective enzymes that exhibit neuroprotective, detoxifying, and antioxidative effects. Additionally, Que enhanced the expression of Nrf2 and inhibited alterations in the shape and death of neurons in the hippocampus.

OBJECTIVE

In this review, we have focused on Que's medicinal prospects as a neuroprotective drug.

METHODS

PubMed, Scopus, Science Direct, and Google Scholar were used to search articles for this study.

RESULTS

The findings of this research demonstrate that (1) Que protected the blood-brain barrier via stimulating Nrf2 in animal stroke, which alleviated ischemic reperfusion and motor dysfunction. (2) By triggering the Nrf2 pathway, Que reduced the neuroinflammation and oxidative damage brought on by TBI in the cortex. (3) In an experimental model of AD, Que enhanced cognitive function by decreasing A1-4, antioxidant activity, and Nrf2 levels in the brain.

CONCLUSION

We discuss recent research on Que-mediated Nrf2 expression in the management of several NLDs in this paper.

Chemical and biological versatility of pyrazolo[3,4-d]pyrimidines: one scaffold, multiple modes of action

Plain language summary Pyrazolo[3,4-d]pyrimidines are chemical compounds possessing remarkable versatility and significance in both biological and chemical contexts. These compounds are composed of specific arrangements of atoms, forming a unique ring structure, which is able to form bonds in a similar way as purines do. In the realm of chemistry, pyrazolo[3,4-d]pyrimidines showcase impressive flexibility due to their ability to easily react with various molecules, opening avenues for the creation of novel compounds with diverse properties for potential applications in medicinal chemistry. In a biological context, pyrazolo[3,4-d]pyrimidines play a crucial role due to their interaction with proteins such as enzymes. In fact, these compounds can impact various biological processes, including cancer cell proliferation, oxidative stress and inflammation. This has led to investigations into their potential as therapeutic agents: by designing pyrazolo[3,4-d]pyrimidines with specific biological targets in mind, new drugs can be developed for the effective treatment of a range of medical conditions. Finally, novel administration tools (e.g., nanomaterials and functionalized liposomes) are being studied as effective ways to overcome the main unwanted characteristics of pyrazolo[3,4-d]pyrimidines (scarce solubility and off-target side effects), thereby increasing their efficacy and specificity toward cell targets. In conclusion, pyrazolo[3,4-d]pyrimidines are fascinating molecules with a dual role in chemistry and biology. Their adaptability in chemical reactions makes them valuable building blocks for designing new compounds with diverse applications. Additionally, their interaction with biological molecules holds promise for the development of innovative medicines. Ongoing research into the properties and behaviors of these compounds could lead to significant advancements in both scientific fields.

Medicinal Chemistry Insights into the Development of Small-Molecule Kelch-Like ECH-Associated Protein 1-Nuclear Factor Erythroid 2-Related Factor 2 (Keap1-Nrf2) Protein-Protein Interaction Inhibitors

Oxidative stress has been implicated in a wide range of pathological conditions. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) exerts a central role in regulating the cellular defense system against oxidative and electrophilic insults. Nonelectrophilic inhibition of the protein-protein interaction (PPI) between Kelch-like ECH-associated protein 1 (Keap1) and Nrf2 has become a promising approach to activate Nrf2. Recently, multiple drug discovery strategies have facilitated the development of small-molecule Keap1-Nrf2 PPI inhibitors with potent activity and favorable drug-like properties. In this Perspective, we summarize the latest progress of small-molecule Keap1-Nrf2 PPI inhibitors from medicinal chemistry insights and discuss future prospects and challenges in this field.