Physiological Concentration of H2O2 Supports Dopamine Neuronal Survival via Activation of Nrf2 Signaling in Glial Cells

Calcium bridges built by mitochondria-associated endoplasmic reticulum membranes: potential targets for neural repair in neurological diseases

The exchange of information and materials between organelles plays a crucial role in regulating cellular physiological functions and metabolic levels. Mitochondria-associated endoplasmic reticulum membranes serve as physical contact channels between the endoplasmic reticulum membrane and the mitochondrial outer membrane, formed by various proteins and protein complexes. This microstructural domain mediates several specialized functions, including calcium (Ca 2+ ) signaling, autophagy, mitochondrial morphology, oxidative stress response, and apoptosis. Notably, the dysregulation of Ca 2+ signaling mediated by mitochondria-associated endoplasmic reticulum membranes is a critical factor in the pathogenesis of neurological diseases. Certain proteins or protein complexes within these membranes directly or indirectly regulate the distance between the endoplasmic reticulum and mitochondria, as well as the transduction of Ca 2+ signaling. Conversely, Ca 2+ signaling mediated by mitochondria-associated endoplasmic reticulum membranes influences other mitochondria-associated endoplasmic reticulum membrane-associated functions. These functions can vary significantly across different neurological diseases-such as ischemic stroke, traumatic brain injury, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease-and their respective stages of progression. Targeted modulation of these disease-related pathways and functional proteins can enhance neurological function and promote the regeneration and repair of damaged neurons. Therefore, mitochondria-associated endoplasmic reticulum membranes-mediated Ca 2+ signaling plays a pivotal role in the pathological progression of neurological diseases and represents a significant potential therapeutic target. This review focuses on the effects of protein complexes in mitochondria-associated endoplasmic reticulum membranes and the distinct roles of mitochondria-associated endoplasmic reticulum membranes-mediated Ca 2+ signaling in neurological diseases, specifically highlighting the early protective effects and neuronal damage that can result from prolonged mitochondrial Ca 2+ overload or deficiency. This article provides a comprehensive analysis of the various mechanisms of Ca 2+ signaling mediated by mitochondria-associated endoplasmic reticulum membranes in neurological diseases, contributing to the exploration of potential therapeutic targets for promoting neuroprotection and nerve repair.

Actl6a regulates autophagy via Sox2-dependent Atg5 and Atg7 expression to inhibit apoptosis in spinal cord injury

INTRODUCTION

Spinal cord injury (SCI) is a severe central nervous system disorder with limited treatment options. While autophagy plays a protective role in neural repair, its regulatory mechanisms in SCI remain unclear. Actin-like protein 6A (Actl6a) influences cell fate and neural development, yet its specific role in SCI repair is not well understood. This study investigates Actl6a's function in regulating autophagy and apoptosis via the transcription factor Sox2 in SCI.

OBJECTIVES

This study aims to determine if Actl6a promotes neural survival post-SCI by regulating autophagy-related genes Atg5 and Atg7 through Sox2. It also examines how the demethylase Fto modulates Actl6a mRNA stability via m6A methylation.

METHODS

In vitro experiments were conducted using primary neurons and HT-22 hippocampal cells exposed to hydrogen peroxide (H2O2)-induced oxidative stress. Actl6a expression was manipulated by knockdown or overexpression. For in vivo studies, a rat SCI model was established with AAV-Actl6a injected at the injury site to induce Actl6a overexpression. Autophagy and apoptosis markers were analyzed using immunofluorescence, Western blotting, and qPCR. Additionally, m6A dot blot and RNA immunoprecipitation (RIP) assays were performed to assess Fto's role in regulating Actl6a mRNA methylation and stability.

RESULTS

Actl6a expression significantly decreased after SCI, resulting in increased apoptosis. Overexpressing Actl6a enhanced autophagy, reduced apoptosis, and improved neurological function in SCI models. Mechanistically, Actl6a and Sox2 collaboratively upregulated Atg5 and Atg7 expression, promoting autophagy. Fto's modulation of Actl6a mRNA stability via m6A demethylation further influenced autophagy and apoptosis.

CONCLUSION

Actl6a, through interaction with Sox2, plays a critical role in modulating autophagy and reducing apoptosis in SCI, with Fto's m6A modification affecting Actl6a stability. This Fto/Actl6a/Sox2 axis is a promising therapeutic target for SCI repair.

Emerging role of Nrf2 in Parkinson's disease therapy: a critical reassessment

Parkinson's disease (PD) is the neurodegenerative disorder characterized by the progressive degeneration of nigrostriatal dopaminergic neurons, leading to the range of motor and non-motor symptoms. There is mounting evidence suggesting that oxidative stress, neuroinflammation and mitochondrial dysfunction play pivotal roles in the pathogenesis of PD. Current therapies only alleviate perturbed motor symptoms. Therefore, it is essential to find out new therapies that allow us to improve not only motor symptoms, but non-motor symptoms like cognitive impairment and modulate disease progression. Nuclear factor erythroid 2-related factor 2 (Nrf2) is transcription factor that regulates the expression of numerous anti-oxidants and cytoprotective genes can counteract oxidative stress, neuroinflammation and mitochondrial dysfunction, thereby potentially ameliorating PD-associated pathology. The current review discusses about the Nrf2 structure and function with special emphasis on various molecular signalling pathways involved in positive and negative modulation of Nrf2, namely Glycogen synthase kinase-3β, Phosphoinositide-3-kinase, AMP-activated protein kinase, Mitogen activated protein kinase, nuclear factor-κB and P62. Furthermore, this review highlights the various Nrf2 activators as promising therapeutic agents for slowing down the progression of PD.

Multifunctional Nanomaterials for Advancing Neural Interfaces: Recording, Stimulation, and Beyond

Neurotechnology has seen dramatic improvements in the last three decades. The major focus in the field has been to design electrical communication platforms with high spatial resolution, stability, and translatability for understanding and affecting neural pathways. The deployment of nanomaterials in bioelectronics has enhanced the capabilities of conventional approaches employing microelectrode arrays (MEAs) for electrical interfaces, allowing the construction of miniaturized, high-performance neuroelectronics (Garg, R.; et al. ACS Appl. Nano Mater. 2023, 6, 8495). While these advancements in the electrical neuronal interface have revolutionized neurotechnology both in scale and breadth, an in-depth understanding of neurons' interactions is challenging due to the complexity of the environments where the cells and tissues are laid. The activity of large, three-dimensional neuronal systems has proven difficult to accurately monitor and modulate, and chemical cell-cell communication is often completely neglected. Recent breakthroughs in nanotechnology have provided opportunities to use new nonelectric modes of communication with neurons and to significantly enhance electrical signal interface capabilities. The enhanced electrochemical activity and optical activity of nanomaterials owing to their nonbulk electronic properties and surface nanostructuring have seen extensive utilization. Nanomaterials' enhanced optical activity enables remote neural state modulation, whereas the defect-rich surfaces provide an enormous number of available electrocatalytic sites for neurochemical detection and electrochemical modulation of cell microenvironments through Faradaic processes. Such unique properties can allow multimodal neural interrogation toward generating closed-loop interfaces with access to more complete neural state descriptors. In this Account, we will review recent advances and our efforts spearheaded toward utilizing nanostructured electrodes for enhanced bidirectional interfaces with neurons, the application of unique hybrid nanomaterials for remote nongenetic optical stimulation of neurons, tunable nanomaterials for highly sensitive and selective neurotransmitter detection, and the utilization of nanomaterials as electrocatalysts toward electrochemically modulating cellular activity. We highlight applications of these technologies across cell types through nanomaterial engineering with a focus on multifunctional graphene nanostructures applied though several modes of neural modulation but also an exploration of broad material classes for maximizing the potency of closed-loop bioelectronics.

Betulinic acid alleviates neuropathic pain induced by chronic constriction injury of the sciatic nerve in mice

Neuropathic pain refers to a type of pain that arises from primary damage and dysfunction within the nervous system. Addressing this condition presents significant challenges and complexities. Betulinic acid (BA), known for its potent antioxidative and anti-inflammatory properties, has garnered extensive attention; nevertheless, the impact upon neuropathic pain induced by CCI is still uncertain. This paper explores the analgesic effects concerning BA on mice experiencing neuropathic pain due to sciatic nerve injury. Throughout the experiment, mice with CCI received oral gavage of BA at dosages of 3, 10, and 30 mg/kg for consecutively 8 days from the 7th day post-surgery. To assess their responses, behavioral tests and sciatic functional index (SFI) evaluations were conducted on zeroth, seventh, eighth, tenth, twelveth and fourteenth day post-CCI. On day 14, histopathological examinations and measurements of biochemical markers were performed. Immunofluorescence techniques were employed to detect Nrf2 and glial cell activation, while the Western blot method was utilized to evaluate Nrf2/HO-1 protein levels and pro-inflammatory cytokine expression. The results elucidated that BA significantly alleviated hyperalgesia and allodynia, demonstrating a dose-dependent enhancement in sciatic nerve function and facilitating the recovery of sciatic nerve injury. Furthermore, BA prominently augmented the entire antioxidative capacity (T-AOC) and T-SOD levels, concomitantly reducing MDA concentrations. Notably, BA activated the Nrf2/HO-1 signaling pathway, inhibited glial cell activation, and downregulation of the expression levels of pro-inflammatory cytokines, specifically, TNF-α, IL-1β, and IL-6 were observed. As such, this study provides a basis to support BA as a candidate drug for the treatment of neuropathic pain, attributing its analgesic effects to its anti-inflammatory, antioxidative, and neuroprotective properties.

NOD-like receptor NLRC5 promotes neuroinflammation and inhibits neuronal survival in Parkinson's disease models

Parkinson's disease (PD) is mainly characterized by the progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and neuroinflammation mediated by overactivated microglia and astrocytes. NLRC5 (nucleotide-binding oligomerization domain-like receptor family caspase recruitment domain containing 5) has been reported to participate in various immune disorders, but its role in neurodegenerative diseases remains unclear. In the current study, we found that the expression of NLRC5 was increased in the nigrostriatal axis of mice with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP)-induced PD, as well as in primary astrocytes, microglia and neurons exposed to different neurotoxic stimuli. In an acute MPTP-induced PD model, NLRC5 deficiency significantly reduced dopaminergic system degeneration and ameliorated motor deficits and striatal inflammation. Furthermore, we found that NLRC5 deficiency decreased the expression of the proinflammatory genes IL-1β, IL-6, TNF-α and COX2 in primary microglia and primary astrocytes treated with neuroinflammatory stimuli and reduced the inflammatory response in mixed glial cells in response to LPS treatment. Moreover, NLRC5 deficiency suppressed activation of the NF-κB and MAPK signaling pathways and enhanced the activation of AKT-GSK-3β and AMPK signaling in mixed glial cells. Furthermore, NLRC5 deficiency increased the survival of primary neurons treated with MPP⁺ or conditioned medium from LPS-stimulated mixed glial cells and promoted activation of the NF-κB and AKT signaling pathways. Moreover, the mRNA expression of NLRC5 was decreased in the blood of PD patients compared to healthy subjects. Therefore, we suggest that NLRC5 promotes neuroinflammation and dopaminergic degeneration in PD and may serve as a marker of glial activation.

Role of Nrf2 in Parkinson's Disease: Toward New Perspectives

Parkinson's disease (PD) is one of the most common and chronic degenerative diseases in the central nervous system. The main pathology of PD formation is the progressive loss of dopaminergic neurons in substantia nigra and the formation of α-synuclein-rich Lewy bodies. The pathogenesis of PD is not caused by any single independent factor. The diversity of these independent factors of PD, such as iron accumulation, oxidative stress, neuroinflammation, mitochondrial dysfunction, age, environment, and heredity, makes the research progress of PD slow. Nrf2 has been well-known to be closely associated with the pathogenesis of PD and could regulate these induced factors development. Nrf2 activation could protect dopaminergic neurons and slow down the progression of PD. This review summarized the role of Nrf2 pathway on the pathogenesis of PD. Regulation of Nrf2 pathway might be one of the promising strategies to prevent and treat PD.

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.

"Reframing" dopamine signaling at the intersection of glial networks in the aged Parkinsonian brain as innate Nrf2/Wnt driver: Therapeutical implications

Dopamine (DA) signaling via G protein-coupled receptors is a multifunctional neurotransmitter and neuroendocrine-immune modulator. The DA nigrostriatal pathway, which controls the motor coordination, progressively degenerates in Parkinson's disease (PD), a most common neurodegenerative disorder (ND) characterized by a selective, age-dependent loss of substantia nigra pars compacta (SNpc) neurons, where DA itself is a primary source of oxidative stress and mitochondrial impairment, intersecting astrocyte and microglial inflammatory networks. Importantly, glia acts as a preferential neuroendocrine-immune DA target, in turn, counter-modulating inflammatory processes. With a major focus on DA intersection within the astrocyte-microglial inflammatory network in PD vulnerability, we herein first summarize the characteristics of DA signaling systems, the propensity of DA neurons to oxidative stress, and glial inflammatory triggers dictating the vulnerability to PD. Reciprocally, DA modulation of astrocytes and microglial reactivity, coupled to the synergic impact of gene-environment interactions, then constitute a further level of control regulating midbrain DA neuron (mDAn) survival/death. Not surprisingly, within this circuitry, DA converges to modulate nuclear factor erythroid 2-like 2 (Nrf2), the master regulator of cellular defense against oxidative stress and inflammation, and Wingless (Wnt)/β-catenin signaling, a key pathway for mDAn neurogenesis, neuroprotection, and immunomodulation, adding to the already complex "signaling puzzle," a novel actor in mDAn-glial regulatory machinery. Here, we propose an autoregulatory feedback system allowing DA to act as an endogenous Nrf2/Wnt innate modulator and trace the importance of DA receptor agonists applied to the clinic as immune modifiers.

NRF2 Activation and Downstream Effects: Focus on Parkinson's Disease and Brain Angiotensin

Reactive oxygen species (ROS) are signalling molecules used to regulate cellular metabolism and homeostasis. However, excessive ROS production causes oxidative stress, one of the main mechanisms associated with the origin and progression of neurodegenerative disorders such as Parkinson's disease. NRF2 (Nuclear Factor-Erythroid 2 Like 2) is a transcription factor that orchestrates the cellular response to oxidative stress. The regulation of NRF2 signalling has been shown to be a promising strategy to modulate the progression of the neurodegeneration associated to Parkinson's disease. The NRF2 pathway has been shown to be affected in patients with this disease, and activation of NRF2 has neuroprotective effects in preclinical models, demonstrating the therapeutic potential of this pathway. In this review, we highlight recent advances regarding the regulation of NRF2, including the effect of Angiotensin II as an endogenous signalling molecule able to regulate ROS production and oxidative stress in dopaminergic neurons. The genes regulated and the downstream effects of activation, with special focus on Kruppel Like Factor 9 (KLF9) transcription factor, provide clues about the mechanisms involved in the neurodegenerative process as well as future therapeutic approaches.

Regulation of Metabolic Processes by Hydrogen Peroxide Generated by NADPH Oxidases

Hydrogen peroxide (H2O2) is an important oxidizing molecule that regulates the metabolisms of aerobic organisms. Redox signaling comprises physiological oxidative stress (eustress), while excessive oxidative stress causes damage to molecules. The main enzymatic generators of H2O2 are nicotinamide adenine dinucleotide phosphate oxidases or NADPH oxidases (NOXs) and mitochondrial respiratory chains, as well as various oxidases. The NOX family is constituted of seven enzyme isoforms that produce a superoxide anion (O2−), which can be converted to H2O2 by superoxide dismutase or spontaneously. H2O2 passes through the membranes by some aquaporins (AQPs), known as peroxyporins. It diffuses through cells and tissues to initiate cellular effects, such as proliferation, the recruitment of immune cells, and cell shape changes. Therefore, it has been proposed that H2O2 has the same importance as Ca2+ or adenosine triphosphate (ATP) to act as modulators in signaling and the metabolism. The present overview focuses on the metabolic processes of liver and adipose tissue, regulated by the H2O2 generated by NOXs.