Activation of neuronal NADPH oxidase NOX2 promotes inflammatory neurodegeneration

Stachydrine hydrochloride reduces NOX2 activity to suppress oxidative stress levels to improve cardiac insufficiency

BACKGROUND

Oxidative stress is a significant cause in the occurrence of cardiac insufficiency. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase2 (NOX2)-derived reactive oxygen species (ROS) play a pivotal role in oxidative stress-induced excitation-contraction decoupling. Stachydrine hydrochloride (Sta) reduces pressure overload-induced cardiac insufficiency, which may be related to the NOX2-ROS pathway, as demonstrated by our earlier research. However, the mechanism through which Sta specifically affects NOX2 remains unknown.

PURPOSE

In order to investigate whether Sta plays a cardioprotective role by inhibiting NOX2 activity, we explored the specific mechanism by which Sta improves cardiac function by affecting NOX2-mediated oxidative stress in this study.

METHODS

Molecular docking and cellular thermal shift assay (CETSA) were performed to verify whether Sta can bind to individual subunits of NOX2. We induced models of cardiac insufficiency in the compensatory phase (cardiac hypertrophy) by phenylephrine (PE) in vivo and in vitro and treated with Sta and GSK2795039 (NOX2 inhibitor). Cardiac function and structure were observed by echocardiography analysis. We detected the expression and localization of NOX2 subunits and calcium channel proteins, also detected the activities of ROS and NOX2, SOD, and GSH, and observed intracardiac calcium homeostasis and systolic-diastolic function in cardiomyocytes. Secondly, we used adenovirus and adeno-associated virus transfection for cardiac-specific overexpression of NOX2 in vivo and in vitro respectively, and also treated with Sta to observe NOX2 activation indexes and ROS levels, cardiac function and cardiomyocyte function in mice.

RESULTS

Prior to our investigation, we discovered that Sta could bind to NOX2 through molecular docking and CETSA. The findings demonstrated that Sta decreased the expression levels of gp91phox and p67phox, as well as the phosphorylation levels of p47phox, and by preventing p67phox and p47phox from translocating across cell membranes. NOX2 activity inhibition by Sta suppresses ROS production. Sta reduced ROS-induced oxidation of Ca2+/calmodulin protein kinase II and modulated excitatory-contractile coupling via sarcoplasmic reticulum calcium pumps. Cardiac-specific overexpression of gp91phox promotes membrane translocation of p67phox and p47phox, increases NOX2 activity, and promotes ROS generation. Sta inhibition of gp91phox overexpression reduced the membrane translocation of p67phox and p47phox, decreased NOX2 activity and oxidative stress levels, and restored excitatory-contractor-coupled myocardial function.

CONCLUSIONS

Our study innovatively verified the key role of NOX2 in cardiac insufficiency. Sta downgrades NOX2's activity by suppressing the protein level of gp91phox and the membrane transport of p67phox and p47phox, thereby reducing myocardial oxidative stress and playing a cardioprotective role. This study was hoped to support the possibility of Sta as a cardiac function-enhancing drug in the future.

Microglial NOX2 as a therapeutic target in traumatic brain injury: Mechanisms, consequences, and potential for neuroprotection

Traumatic brain injury (TBI) is a leading cause of long-term disability worldwide, with secondary injury mechanisms, including neuroinflammation and oxidative stress, driving much of its chronic pathology. While NADPH oxidase 2 (NOX2)-mediated reactive oxygen species (ROS) production is a recognized factor in TBI, the specific role of microglial NOX2 in perpetuating oxidative and inflammatory damage remains underexplored. Addressing this gap is critical, as current therapeutic approaches primarily target acute symptoms and fail to interrupt the persistent neuroinflammation that contributes to progressive neurodegeneration. Besides NOX, other ROS-generating enzymes, such as CYP1B1, COX2, and XO, also play crucial roles in triggering oxidative stress and neuroinflammatory conditions in TBI. However, this review highlights the pathophysiological role of microglial NOX2 in TBI, focusing on its activation following injury and its impact on ROS generation, neuroinflammatory signaling, and neuronal loss. These insights reveal NOX2 as a critical driver of secondary injury, linked to worsened outcomes, particularly in aged individuals where NOX2 activation is more pronounced. In addition, this review evaluates emerging therapeutic approaches targeting NOX2, such as GSK2795039 and other selective NOX2 inhibitors, which show potential in reducing ROS levels, limiting neuroinflammation, and preserving neurological functions. By highlighting the specific role of NOX2 in microglial ROS production and secondary neurodegeneration, this study advocates for NOX2 inhibition as a promising strategy to improve TBI outcomes by addressing the unmet need for therapies targeting long-term inflammation and neuroprotection. Our review highlights the potential of NOX2-targeted interventions to disrupt the cycle of oxidative stress and inflammation, ultimately offering a pathway to mitigate the chronic impact of TBI.

Oxidative stress mediated by the NOX2/ROS/NF-κB signaling axis is involved in rosacea

Rosacea is a chronic inflammatory cutaneous disease characterized by a multifaceted pathogenesis. Extensive research has demonstrated that oxidative stress plays a pivotal role in the etiology of rosacea, mediating vascular alterations and inflammation cascades via the generation of reactive oxygen species (ROS). Nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) possesses the capacity to synthesize ROS and exhibits a strong correlation with diverse inflammatory processes. However, the effects of NOX2 in rosacea are unknown. Our findings revealed that NOX2 was highly expressed in rosacea. Inhibition of NOX2 improved markedly rosacea-like manifestations, encompassing reduced skin erythema and downregulated expression of pro-inflammatory cytokines and chemokines. Additionally, knockdown NOX2 in HaCaT keratinocytes significantly rescues TNF-α-induced oxidative stress and inflammation. Our study further elucidated that inhibition of NOX2 suppressed NF-κB activation in LL37-induced skin and LL37/ TNF-α-induced HaCaT keratinocytes. Our results demonstrate that NOX2 plays a proinflammatory role in rosacea by regulating the NF-κB signaling pathway.

The emerging role of oxygen redox in pathological progression of disorders

Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and Huntington disease, pose serious threats to human health, leading to substantial economic burdens on society and families. Despite extensive research, the underlying mechanisms driving these diseases remain incompletely understood, impeding effective diagnosis and treatment. In recent years, growing evidence has highlighted the crucial role of oxidative stress in the pathogenesis of various neurodegenerative diseases. However, there is still a lack of comprehensive reviews that systematically summarize the impact of mitochondrial oxidative stress on neurodegenerative diseases. This review aims to address this gap by summarizing the molecular mechanisms by which mitochondrial oxidative stress promotes the initiation and progression of neurodegenerative disorders. Furthermore, it discusses the potential of antioxidant-based therapeutic strategies for the treatment of these diseases. By shedding light on the role of mitochondrial oxidative stress in neurodegenerative diseases, this review not only serves as a valuable reference for further research on the disease mechanisms, but also offers novel perspectives for the treatment of these disorders.

NOX2 in Alzheimer's and Parkinson's disease

Alzheimer's Disease (AD), and related dementias, represent a growing concern for the worldwide population given the increased numbers of people of advanced age. Marked by significant degradation of neurological tissues and critical processes, in addition to more specific factors such as the presence of amyloid plaques and neurofibrillary tangles in AD, robust discussion is ongoing regarding the precise mechanisms by which these diseases arise. One of the major interests in recent years has been the contribution of reactive oxygen species (ROS) and, particularly, the contribution of the ROS-generating NADPH Oxidase proteins. NADPH Oxidase 2 (NOX2), the prototypical member of the family, represents a particularly interesting target for study given its close association with vascular and inflammatory processes in all tissues, including the brain, and the association of these processes with AD development and progression. In this review, we discuss the most relevant and recent work regarding the contribution of NOX2 to AD progression in neuronal, microglial, and cerebrovascular signaling. Furthermore, we will discuss the most promising NOX2-targeted therapeutics for potential AD management and treatment.

Molecular Roles of NADPH Oxidase-Mediated Oxidative Stress in Alzheimer's Disease: Isoform-Specific Contributions

Oxidative stress is linked to the pathogenesis of Alzheimer's disease (AD), a neurodegenerative disorder marked by memory impairment and cognitive decline. AD is characterized by the accumulation of amyloid-beta (Aβ) plaques and the formation of neurofibrillary tangles (NFTs) of hyperphosphorylated tau. AD is associated with an imbalance in redox states and excessive reactive oxygen species (ROS). Recent studies report that NADPH oxidase (NOX) enzymes are significant contributors to ROS generation in neurodegenerative diseases, including AD. NOX-derived ROS aggravates oxidative stress and neuroinflammation during AD. In this review, we provide the potential role of all NOX isoforms in AD pathogenesis and their respective structural involvement in AD progression, highlighting NOX enzymes as a strategic therapeutic target. A comprehensive understanding of NOX isoforms and their inhibitors could provide valuable insights into AD pathology and aid in the development of targeted treatments for AD.

Amyloid beta-activated alpha-1-syntrophin has ramifications on Rac1 activation, ROS production and neuronal cell death

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the presence of β-amyloid (Aβ)-containing extracellular neuritic plaques and phosphorylated tau-containing intracellular neurofibrillary tangles. It remains the primary neuropathological criteria for the diagnosis of AD. Additionally, several other processes are currently being recognized as significant risk factors for AD development, including the brain's susceptibility to reactive oxygen species (ROS). The ROS production is among the early signs in the progression of AD. However, the underlying mechanisms behind increased ROS production in AD remain poorly understood. We have observed SNTA1 plays critical role in regulating ROS levels in different pathological conditions. Here, we wanted to gain further insight into the role of SNTA1 in the development of AD by using IMR32 cell line. Our results show that the accumulation of Aβ plaques in Alzheimer's model neuroblastoma cells significantly increases the expression and activation of SNTA1 and MKK6 kinase. The activation of MKK6 results in the phosphorylation of SNTA1, creating a binding site for Rac1, leading to its activation and subsequent production of ROS. Excessive ROS production leads to cell cycle arrest in the G2/M phase, a hallmark of AD. Our study provides new insight into the mechanism of Aβ-mediated cell death in AD and suggests that MKK6-mediated activation of alpha-1-syntrophin promotes ROS production in neuronal cells, resulting in cell death. This study presents a mechanistic insight into Aβ-mediated cell death and could serve as a paradigm for reducing neuronal cell death in AD.

Prolactin protects hippocampal neurons against H2O2-induced neurotoxicity by suppressing BAX and NOX4 via the NF-κB signaling pathway

Reactive oxygen species (ROS) are physiological byproducts of neuronal metabolism. However, an imbalance between ROS generation and antioxidant capacity, often driven by dysregulated pro-oxidant enzymes like nicotinamide adenine dinucleotide phosphate oxidases (NOX), can result in deleterious oxidative stress. This oxidative stress is a critical factor in the pathogenesis of neurodegenerative diseases. While interventions with broad-spectrum antioxidants have demonstrated limited efficacy, the modulation of endogenous antioxidant mechanisms presents a promising therapeutic avenue. Here, we investigated the potential of the neuroprotective hormone prolactin to mitigate oxidative stress and subsequent neuronal cell death. Prolactin protected primary mouse hippocampal neurons from hydrogen peroxide (H2O2)-induced oxidative damage. Prolactin reduced ROS levels, lipid peroxidation, and apoptosis, and its effects were occluded by a specific prolactin receptor antagonist (G129R-hPRL). Mechanistically, prolactin suppressed H2O2-induced mRNA upregulation of pro-oxidative Nox4 and pro-apoptotic Bax. Moreover, prolactin induced nuclear factor kappa B (NF-κB) nuclear translocation, and the inhibition of the NF-κB signaling pathway abolished the neuroprotective and transcriptional effects of prolactin, indicating its central role in prolactin-mediated protection. Our findings indicate that prolactin exerts potent antioxidant and neuroprotective effects by modulating the expression of Nox4 and Bax, thereby reducing ROS generation and neuronal apoptosis. This study underscores the therapeutic potential of prolactin in attenuating oxidative stress and suggests a possible role in the treatment of neurodegenerative diseases.

Microglial CR3 promotes neuron ferroptosis via NOX2-mediated iron deposition in rotenone-induced experimental models of Parkinson's disease

The activation of complement receptor 3 (CR3) in microglia contributes to neurodegeneration in neurological disorders, including Parkinson's disease (PD). However, it remains unclear for mechanistic knowledge on how CR3 mediates neuronal damage. In this study, the expression of CR3 and its ligands iC3b and ICAM-1 was found to be up-regulated in the midbrain of rotenone PD mice, which was associated with elevation of iron content and disruption of balance of iron metabolism proteins. Interestingly, genetic deletion of CR3 blunted iron accumulation and recovered the expression of iron metabolism markers in response to rotenone. Furthermore, reduced lipid peroxidation, ferroptosis of dopaminergic neurons and neuroinflammation were detected in rotenone-lesioned CR3-/- mice compared with WT mice. The regulatory effect of CR3 on ferroptotic death of dopaminergic neurons was also mirrored in vitro. Mechanistic study revealed that iron accumulation in neuron but not the physiological contact between microglia and neurons was essential for microglial CR3-regulated neuronal ferroptosis. In a cell-culture system, microglial CR3 silence significantly dampened iron deposition in neuron in response to rotenone, which was accompanied by mitigated lipid peroxidation and neurodegeneration. Furthermore, ROS released from activated microglia via NOX2 was identified to couple microglial CR3-mediated iron accumulation and subsequent neuronal ferroptosis. Finally, supplementation with exogenous iron was found to recover the sensitivity of CR3-/- mice to rotenone-induced neuronal ferroptosis. Altogether, our findings suggested that microglial CR3 regulates neuron ferroptosis through NOX2 -mediated iron accumulation in experimental Parkinsonism, providing novel points of the immunopathogenesis of neurological disorders.

Electroacupuncture regulates glucose metabolism by inhibiting SGLT1 levels, inhibiting microglial polarization, and alleviating Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a common central neurodegenerative disease in middle-aged and elderly people. The progressive degeneration and death of dopaminergic neurons leads to insufficient dopamine (DA) neurotransmitters. Acupuncture and moxibustion can alleviate the aging of neurons. Therefore, studying the neuroprotective effects of electroacupuncture (EA) in PD mice is particularly important.

METHODS

Intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 20 mg/kg) was used to establish a PD mouse model, and lipopolysaccharide (LPS) was used to induce microglia polarization. Western blotting, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), Nissl staining and immunohistochemistry were used to detect neuronal apoptosis and injury, α-syn expression and microglial accumulation in PD mice. In addition, the levels of inflammatory factors were determined using enzyme-linked immunosorbent assay (ELISA). Flow cytometry was used to detect the Ca2+ content. The fluorescein isothiocyanate (FITC) labeling method was used to assess glucose uptake. A reagent kit was used to detect glucose and lactate levels.

RESULTS

MPTP induced the selective loss of DA neurons in the SN of mice, altered Ca2+ homeostasis, and induced an inflammatory response. In addition, maintaining Ca2+ homeostasis depends on the activity of transient receptor potential channel 1 (TRPC1). EA therapy promotes TRPC1 expression, which has a negative regulatory effect on sodium-glucose cotransporter 1 (SGLT1). Under the action of EA, TRPC1 protein expression increased, Ca2+ concentrations increased, and the effect of SGLT1 was inhibited, thereby facilitating glucose metabolism, blocking the activation of the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway, restraining M1 polarization of microglia, and alleviating the PD process.

CONCLUSION

EA promotes TRPC1/Ca2+ pathway activation, inhibits SGLT1-mediated regulation of glucose metabolism and PI3K/AKT pathway activation, inhibits microglial M1 polarization, and alleviates PD.

Microglia in Microbiota-Gut-Brain Axis: A Hub in Epilepsy

There is growing concern about the role of the microbiota-gut-brain axis in neurological illnesses, and it makes sense to consider microglia as a critical component of this axis in the context of epilepsy. Microglia, which reside in the central nervous system, are dynamic guardians that monitor brain homeostasis. Microglia receive information from the gut microbiota and function as hubs that may be involved in triggering epileptic seizures. Vagus nerve bridges the communication in the axis. Essential axis signaling molecules, such as gamma-aminobutyric acid, 5-hydroxytryptamin, and short-chain fatty acids, are currently under investigation for their participation in drug-resistant epilepsy (DRE). In this review, we explain how vagus nerve connects the gut microbiota to microglia in the brain and discuss the emerging concepts derived from this interaction. Understanding microbiota-gut-brain axis in epilepsy brings hope for DRE therapies. Future treatments can focus on the modulatory effect of the axis and target microglia in solving DRE.

Biological functions of connexins in the development of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a group of chronic intestinal inflammatory diseases with unknown etiology. Gap junctions composed of connexins (Cxs) have been recently validated as an important factor in the development of IBD. Under IBD-induced inflammatory response in the gut, gap junctions connect multiple signaling pathways involved in the interaction between inflammatory cells with other intestinal cells, which altogether mediate the development of IBD. This paper is a narrative review aiming to comprehensively elucidate the biological function of connexins, especially the ubiquitously and predominantly expressed Cx43, in the pathogenesis of IBD.

Matrix stiffness-dependent microglia activation in response to inflammatory cues: in situ investigation by scanning electrochemical microscopy

Microglia play a crucial role in maintaining the homeostasis of the central nervous system (CNS) by sensing and responding to mechanical and inflammatory cues in their microenvironment. However, the interplay between mechanical and inflammatory cues in regulating microglia activation remains elusive. In this work, we constructed in vitro mechanical-inflammatory coupled microenvironment models of microglia by culturing BV2 cells (a murine microglial cell line) on polyacrylamide gels with tunable stiffness and incorporating a lipopolysaccharide (LPS) to mimic the physiological and pathological microenvironment of microglia in the hippocampus. Through characterization of activation-related proteins, cytokines, and reactive oxygen species (ROS) levels, we observed that the LPS treatment induced microglia on a stiff matrix to exhibit overexpression of NOX2, higher levels of ROS and inflammatory factors compared to those on a soft matrix. Additionally, using scanning electrochemical microscopy (SECM), we performed in situ characterization and discovered that microglia on a stiff matrix promoted extracellular ROS production, leading to a disruption in their redox balance and increased susceptibility to LPS-induced ROS production. Furthermore, the respiratory activity and migration behavior of microglia were closely associated with their activation process, with the stiff matrix-LPS-induced microglia demonstrating the most pronounced changes in respiratory activity and migration ability. This work represents the first in situ and dynamic monitoring of microglia activation state alterations under a mechanical-inflammatory coupled microenvironment using SECM. Our findings shed light on matrix stiffness-dependent activation of microglia in response to an inflammatory microenvironment, providing valuable insights into the mechanisms underlying neuroinflammatory processes in the CNS.

NOX-induced oxidative stress is a primary trigger of major neurodegenerative disorders

Neurodegenerative diseases (NDDs) causing cognitive impairment and dementia are difficult to treat due to the lack of understanding of primary initiating factors. Meanwhile, major sporadic NDDs share many risk factors and exhibit similar pathologies in their early stages, indicating the existence of common initiation pathways. Glucose hypometabolism associated with oxidative stress is one such primary, early and shared pathology, and a likely major cause of detrimental disease-associated cascades; targeting this common pathology may therefore be an effective preventative strategy for most sporadic NDDs. However, its exact cause and trigger remain unclear. Recent research suggests that early oxidative stress caused by NADPH oxidase (NOX) activation is a shared initiating mechanism among major sporadic NDDs and could prove to be the long-sought ubiquitous NDD trigger. We focus on two major NDDs - Alzheimer's disease (AD) and Parkinson's disease (PD), as well as on acquired epilepsy which is an increasingly recognized comorbidity in NDDs. We also discuss available data suggesting the relevance of the proposed mechanisms to other NDDs. We delve into the commonalities among these NDDs in neuroinflammation and NOX involvement to identify potential therapeutic targets and gain a deeper understanding of the underlying causes of NDDs.

NADPH Oxidases: From Molecular Mechanisms to Current Inhibitors

NADPH oxidases (NOXs) form a family of electron-transporting membrane enzymes whose main function is reactive oxygen species (ROS) generation. Strong evidence suggests that ROS produced by NOX enzymes are major contributors to oxidative damage under pathologic conditions. Therefore, blocking the undesirable actions of these enzymes is a therapeutic strategy for treating various pathological disorders, such as cardiovascular diseases, inflammation, and cancer. To date, identification of selective NOX inhibitors is quite challenging, precluding a pharmacologic demonstration of NOX as therapeutic targets in vivo. The aim of this Perspective is to furnish an updated outlook about the small-molecule NOX inhibitors described over the last two decades. Structures, activities, and in vitro/in vivo specificity are discussed, as well as the main biological assays used.