Sulforaphane inhibits NLRP3 inflammasome activation in microglia through Nrf2-mediated miRNA alteration

Effects of Strigolactones on NLRP3 Activation, Nitrosative Stress, and Antioxidant Mox Phenotype: In Vitro and In Silico Evidence

Phytohormones have significant roles in redox metabolism, inflammatory responses, and cellular survival mechanisms within the microenvironment of the mammalian brain. Herein, we identified the mammalian molecular targets of three representative strigolactone (SL) analogues structurally derived from apocarotenoids and the functional equivalent of plant hormones. All tested SL analogues have an inhibitory effect on NLRP3 inflammasome-mediated IL-1β release in murine microglial cells. However, IND and EGO10 became prominent among them due to their high potency at low micromolar doses. All SL analogues dose-dependently suppressed the release and expression of proinflammatory factors. For EGO10 and IND, IC50 values for iNOS-associated NO secretion were as low as 1.72 and 1.02 μM, respectively. In silico analyses revealed that (S)-EGO10 interacted with iNOS, NLRP3, and Keap1 ligands with the highest binding affinities among all stereoisomeric SL analogues. Although all compounds were effective in microglial Mox phenotype polarization, 4-Br-debranone exhibited a differential pattern for upregulating Nrf2-driven downstream enzymes.

Glioprotective Effects of Sulforaphane in Hypothalamus: Focus on Aging Brain

Sulforaphane is a natural compound with neuroprotective activity, but its effects on hypothalamus remain unknown. In line with this, astrocytes are critical cells to maintain brain homeostasis, and hypothalamic astrocytes are fundamental for sensing and responding to environmental changes involved in a variety of homeostatic functions. Changes in brain functionality, particularly associated with hypothalamic astrocytes, can contribute to age-related neurochemical alterations and, consequently, neurodegenerative diseases. Thus, here, we investigated the glioprotective effects of sulforaphane on hypothalamic astrocyte cultures and hypothalamic cell suspension obtained from aged Wistar rats (24 months old). Sulforaphane showed anti-inflammatory and antioxidant properties, as well as modulated the mRNA expression of astroglial markers, such as aldehyde dehydrogenase 1 family member L1, aquaporin 4, and vascular endothelial growth factor. In addition, it increased the expression and extracellular levels of trophic factors, such as glia-derived neurotrophic factor and nerve growth factor, as well as the release of brain-derived neurotrophic factor and the mRNA of TrkA, which is a receptor associated with trophic factors. Sulforaphane also modulated the expression of classical pathways associated with glioprotection, including nuclear factor erythroid-derived 2-like 2, heme oxygenase-1, nuclear factor kappa B p65 subunit, and AMP-activated protein kinase. Finally, a cell suspension with neurons and glial cells was used to confirm the predominant effect of sulforaphane in glial cells. In summary, this study indicated the anti-aging and glioprotective activities of sulforaphane in aged astrocytes.

Bioactive sulforaphane from cruciferous vegetables: advances in biosynthesis, metabolism, bioavailability, delivery, health benefits, and applications

Chronic inflammation-induced diseases (CID) are the dominant cause of death worldwide, contributing to over half of all global deaths. Sulforaphane (SFN) derived from cruciferous vegetables has been extensively studied for its multiple functional benefits in alleviating CID. This work comprehensively reviewed the biosynthesis, metabolism, bioavailability, delivery, health benefits, and applications of SFN and its potential mechanisms against CID (e.g., cancer, obesity, type 2 diabetes, et al.), and neurological disorders based on a decade of research. SFN exerts its biological functions through the hydrolysis of glucosinolates by gut microbiota, and exhibits rapid metabolism and excretion characteristics via metabolization of mercapturic acid pathway. Microencapsulation is an important way to improve the stability and targeted delivery of SFN. The health benefits of SNF against CID are attributed to the multiple regulatory mechanisms including modulating oxidative stress, inflammation, apoptosis, immune response, and intestinal homeostasis. The clinical applications of SFN and related formulations show promising potential; however, further exploration is required regarding the sources, dosages, toxicity profiles, and stability of SFN. Together, SFN is a natural product with great potential for development and application, which is crucial for the development of functional food and pharmaceutical industries.

HIV-Associated Neurocognitive Disorder: A Look into Cellular and Molecular Pathology

Despite combined antiretroviral therapy (cART) limiting HIV replication to undetectable levels in the blood, people living with HIV continue to experience HIV-associated neurocognitive disorder (HAND). HAND is associated with neurocognitive impairment, including motor impairment, and memory loss. HIV has been detected in the brain within 8 days of estimated exposure and the mechanisms for this early entry are being actively studied. Once having entered into the central nervous system (CNS), HIV degrades the blood-brain barrier through the production of its gp120 and Tat proteins. These proteins are directly toxic to endothelial cells and neurons, and propagate inflammatory cytokines by the activation of immune cells and dysregulation of tight junction proteins. The BBB breakdown is associated with the progression of neurocognitive disease. One of the main hurdles for treatment for HAND is the latent pool of cells, which are insensitive to cART and prolong inflammation by harboring the provirus in long-lived cells that can reactivate, causing damage. Multiple strategies are being studied to combat the latent pool and HAND; however, clinically, these approaches have been insufficient and require further revisions. The goal of this paper is to aggregate the known mechanisms and challenges associated with HAND.

Nrf2 activator Diethyl Maleate attenuates ROS mediated NLRP3 inflammasome activation in murine microglia

Microglia are the tissue-resident immune cells of the central nervous system. As a part of the innate immune response, NLR Family Pyrin Domain Containing Protein 3 (NLRP3) inflammasome activation leads to cleavage of caspase-1 and triggers secretion of proinflammatory cytokines and may also result in pyroptotic cell death. Inflammasome activation plays a crucial role in inflammatory conditions; aberrant activation of inflammasome contributes to the pathogenesis of neurodegenerative diseases. Diethyl Maleate (DEM) is a promising antiinflammatory chemical to alleviate inflammasome activation. In this study, NLRP3 inflammasome was activated in N9 murine microglia via 1 µg/ml LPS (Lipopolysaccharide) for 4 h and 5 mM ATP (Adenosine 5'-triphosphate) for 1 h, respectively. We demonstrated that 1 h pretreatment of DEM attenuated NLRP3 inflammasome activation in microglial cells. Besides, mitochondrial ROS decreased upon DEM pretreatment in inflammasome-induced cells. Likewise, it ameliorated pyroptotic cell death in microglia. DEM is a potent activator of Nrf2 transcription factor, the key regulator of the antioxidant response pathway. Nrf2 has been a significant target to decrease aberrant inflammasome activation through the antioxidant compounds, including DEM. Here, we have shown that DEM increased Nrf2 translocation to the nucleus, resulting in Nrf2 target gene expression in microglia. In conclusion, DEM is a promising protective agent against NLRP3 inflammasome activation.

Unraveling the role of miRNAs in the diagnosis, progression, and therapeutic intervention of Alzheimer's disease

Alzheimer's disease (AD) is a multifaceted, advancing neurodegenerative illness that is responsible for most cases of neurological impairment and dementia in the aged population. As the disease progresses, affected individuals may experience cognitive decline, linguistic problems, affective instability, and behavioral changes. The intricate nature of AD reflects the altered molecular mechanisms participating in the affected human brain. MicroRNAs (miRNAs, miR) are essential for the intricate control of gene expression in neurobiology. miRNAs exert their influence by modulating the transcriptome of brain cells, which typically exhibit substantial genetic activity, encompassing gene transcription and mRNA production. Presently, comprehensive studies are being conducted on AD to identify miRNA-based signatures that are indicative of the disease pathophysiology. These findings can contribute to the advancement of our understanding of the mechanisms underlying this disorder and can inform the development of therapeutic interventions based on miRNA and related RNA molecules. Therefore, this comprehensive review provides a detailed holistic analysis of the latest advances discussing the emerging role of miRNAs in the progression of AD and their possible application as potential biomarkers and targets for therapeutic interventions in future studies.

Redox Regulation of Nucleotide-Binding and Oligomerization Domain-Like Receptors Inflammasome

Significance: Inflammasomes are multimeric complexes that, as part of the innate immune response, sense a wide range of pathogenic and sterile stimuli. They consist of three components, namely a sensor protein, an adaptor, and procaspase-1, which once activated result in secretion of proinflammatory interleukin (IL)-1β and IL-18 and, eventually, in a gasdermin D-dependent lytic cell death called pyroptosis. Recent Advances: Since their discovery 20 years ago, the molecular mechanisms underlying the regulation of inflammasomes have been extensively studied. Oxidative stress appears as a major contributor to modulate inflammasomes, especially NLRP3 as well as NLRP1, NLRP6, and NLRC4. Growing evidence supports the idea that the positive feedback between redox imbalance and inflammasome-driven inflammation fuels an OxInflammatory state in a variety of human pathologies. Critical Issues: The current knowledge about the redox signaling pathways involved in inflammasomes activation and functions are here highlighted. In addition, we discuss the role of this complex molecular network interaction in the onset and progression of pathological conditions including neurological and metabolic diseases as well as skin disorders, also with an insight on COVID-19-related pathology. Finally, the therapeutic strategies able to mitigate the redox-mediated inflammasome activation with synthetic and natural compounds as well as by acting on inflammasome-related post-translational modifications and microRNAs are also addressed. Future Directions: Further investigations leading to a deeper understanding of the reciprocal interaction between inflammasomes and reactive oxygen species will help identify other molecular targets for modulating their hyperactivated state, and to design novel therapeutics for chronic OxInflammatory conditions. Antioxid. Redox Signal. 39, 744-770.

Exploring the anti-inflammatory activity of sulforaphane

Dysregulation of innate immune responses can result in chronic inflammatory conditions. Glucocorticoids, the current frontline therapy, are effective immunosuppressive drugs but come with a trade-off of cumulative and serious side effects. Therefore, alternative drug options with improved safety profiles are urgently needed. Sulforaphane, a phytochemical derived from plants of the brassica family, is a potent inducer of phase II detoxification enzymes via nuclear factor-erythroid factor 2-related factor 2 (NRF2) signaling. Moreover, a growing body of evidence suggests additional diverse anti-inflammatory properties of sulforaphane through interactions with mediators of key signaling pathways and inflammatory cytokines. Multiple studies support a role for sulforaphane as a negative regulator of nuclear factor kappa-light chain enhancer of activated B cells (NF-κB) activation and subsequent cytokine release, inflammasome activation and direct regulation of the activity of macrophage migration inhibitory factor. Significantly, studies have also highlighted potential steroid-sparing activity for sulforaphane, suggesting that it may have potential as an adjunctive therapy for some inflammatory conditions. This review discusses published research on sulforaphane, including proposed mechanisms of action, and poses questions for future studies that might help progress our understanding of the potential clinical applications of this intriguing molecule.

Non-Coding RNA in Microglia Activation and Neuroinflammation in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by complex pathophysiological features. Amyloid plaques resulting from extracellular amyloid deposition and neurofibrillary tangles formed by intracellular hyperphosphorylated tau accumulation serve as primary neuropathological criteria for AD diagnosis. The activation of microglia has been closely associated with these pathological manifestations. Non-coding RNA (ncRNA), a versatile molecule involved in various cellular functions such as genetic information storage and transport, as well as catalysis of biochemical reactions, plays a crucial role in microglial activation. This review aims to investigate the regulatory role of ncRNAs in protein expression by directly targeting genes, proteins, and interactions. Furthermore, it explores the ability of ncRNAs to modulate inflammatory pathways, influence the expression of inflammatory factors, and regulate microglia activation, all of which contribute to neuroinflammation and AD. However, there are still significant controversies surrounding microglial activation and polarization. The categorization into M1 and M2 phenotypes may oversimplify the intricate and multifaceted regulatory processes in microglial response to neuroinflammation. Limited research has been conducted on the role of ncRNAs in regulating microglial activation and inducing distinct polarization states in the context of neuroinflammation. Moreover, the regulatory mechanisms through which ncRNAs govern microglial function continue to be refined. The current understanding of ncRNA regulatory pathways involved in microglial activation remains incomplete and may be influenced by spatial, temporal, and tissue-specific factors. Therefore, further in-depth investigations are warranted. In conclusion, there are ongoing debates and uncertainties regarding the activation and polarization of microglial cells, particularly concerning the categorization into M1 and M2 phenotypes. The study of ncRNA regulation in microglial activation and polarization, as well as its mechanisms, is still in its early stages and requires further investigation. However, this review offers new insights and opportunities for therapeutic approaches in AD. The development of ncRNA-based drugs may hold promise as a new direction in AD treatment.

Bilirubin induces microglial NLRP3 inflammasome activation in vitro and in vivo

Despite current advancements in neonatal care, hyperbilirubinemia resulting in bilirubin-induced neurological dysfunction (BIND) continues to be one of the major reasons of mortality or lifelong disability. Although the exact mechanisms underlying brain injury upon bilirubin exposure remains unelucidated, inflammation is considered to be one of the major contributors to BIND. This study investigates the role of the NLRP3 inflammasome in bilirubin-induced injury using in vitro and in vivo models. We successfully demonstrated that the upregulation of NLRP3 expression is significantly associated with the release of active caspase-1 and IL-1β in N9 microglial cells exposed to bilirubin. Functional in vitro experiments with NLRP3 siRNA confirms that bilirubin-induced inflammasome activation and cell death are mediated by the NLRP3 inflammasome. Following injection of bilirubin into the cisterna magna of a neonatal mouse, activation of the NLRP3 inflammasome and microglia were determined by double staining with Iba1-NLRP3 and Iba1-Caspase-1. Upon injection of bilirubin into the cisterna magna, neuronal loss was significantly higher in the wild-type mouse compared to Nlrp3^-/- and Caspase-1^-/- strains. Collectively, these data indicate that NLRP3 inflammasome has a crucial role in microglial activation and bilirubin-induced neuronal damage.

Understanding the involvement of innate immunity and the Nrf2-NLRP3 axis on mitochondrial health in Parkinson's disease

Parkinson's disease (PD), a multifactorial movement disorder, is interlinked with numerous molecular pathways, including neuroinflammation, which is a critical factor in the development and progression of PD. Microglia play a central role in driving neuroinflammation through activation and overexpression of the M1 phenotype, which has a significant impact on mitochondria. Multiple regulators converge together, and among these, the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasomes have been implicated in transmitting inflammatory and deleterious components to the mitochondria. Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates the NLRP3 inflammasome and acts as the saviour of the mitochondria. Together, the NLRP3-Nrf2 axis functions in regulating mitochondrial function in the case of PD. It regulates fundamental processes such as oxidative stress, mitochondrial respiratory function, and mitochondrial dynamics. In this review, we discuss the contributions that a variety of miRNAs make to the regulation of the NLRP3 inflammasome and Nrf2, which can be used to target this important axis and contribute to the preservation of mitochondrial integrity. This axis may prove to be a crucial target for extending the lives of Parkinson's patients by deferring neuroinflammatory damage to mitochondria.

Sulforaphane attenuates microglia-mediated neuronal damage by down-regulating the ROS/autophagy/NLRP3 signal axis in fibrillar Aβ-activated microglia

The neuroinflammatory hypothesis of Alzheimer's disease (AD) posits that amyloid-beta (Aβ) phagocytosis along with subsequent lysosomal damage and NLRP3 inflammasome activation plays important roles in Aβ-induced microglia activation and microglia-induced neurotoxicity. Sulforaphane (SFN) has neuroprotective effects for AD. However, whether SFN can inhibit its cytotoxic autophagy and NLRP3 inflammasome activation in microglia remain unknown. In this study, results showed SFN played an indirect, protective role on neurons via a series of impacts on Aβ-activated microglia, including inhibition of autophagy initiation as well as autophagic lysosomal membrane permeability and subsequent NLRP3/caspase-1 inflammasomes activation. M1 phenotype polarization was also inhibited. Our results demonstrated that SFN could inhibit the cytostatic autophagy-induced NLRP3 signaling pathway in Aβ-activated microglia by decreasing reactive oxygen species (ROS) production. These results provide novel insight into the potential role of SFN in AD therapy.

NLRP3 Inflammasome: From Pathophysiology to Therapeutic Target in Major Depressive Disorder

Major depressive disorder (MDD) is a highly prevalent psychiatric disorder, whose pathophysiology has been linked to the neuroinflammatory process. The increased activity of the Nod-like receptor pyrin containing protein 3 (NLRP3) inflammasome, an intracellular multiprotein complex, is intrinsically implicated in neuroinflammation by promoting the maturation and release of proinflammatory cytokines such as interleukin (IL)-1β and IL-18. Interestingly, individuals suffering from MDD have higher expression of NLRP3 inflammasome components and proinflammatory cytokines when compared to healthy individuals. In part, intense activation of the inflammasome may be related to autophagic impairment. Noteworthy, some conventional antidepressants induce autophagy, resulting in less activation of the NLRP3 inflammasome. In addition, the fast-acting antidepressant ketamine, some bioactive compounds and physical exercise have also been shown to have anti-inflammatory properties via inflammasome inhibition. Therefore, it is suggested that modulation of inflammasome-driven pathways may have an antidepressant effect. Here, we review the role of the NLRP3 inflammasome in the pathogenesis of MDD, highlighting that pathways related to its priming and activation are potential therapeutic targets for the treatment of MDD.

The relationships between neuroglial and neuronal changes in Alzheimer's disease, and the related controversies II:

Since the original description of Alzheimer´s disease (AD), research into this condition has mainly focused on assessing the alterations to neurons associated with dementia, and those to the circuits in which they are involved. In most of the studies on human brains and in many models of AD, the glial cells accompanying these neurons undergo concomitant alterations that aggravate the course of neurodegeneration. As a result, these changes to neuroglial cells are now included in all the "pathogenic cascades" described in AD. Accordingly, astrogliosis and microgliosis, the main components of neuroinflammation, have been integrated into all the pathogenic theories of this disease, as discussed in this part of the two-part monograph that follows an accompanying article on gliopathogenesis and glioprotection. This initial reflection verified the implication of alterations to the neuroglia in AD, suggesting that these cells may also represent therapeutic targets to prevent neurodegeneration. In this second part of the monograph, we will analyze the possibilities of acting on glial cells to prevent or treat the neurodegeneration that is the hallmark of AD and other pathologies. Evidence of the potential of different pharmacological, non-pharmacological, cell and gene therapies (widely treated) to prevent or treat this disease is now forthcoming, in most cases as adjuncts to other therapies. A comprehensive AD multimodal therapy is proposed in which neuronal and neuroglial pharmacological treatments are jointly considered, as well as the use of new cell and gene therapies and non-pharmacological therapies that tend to slow down the progress of dementia.

Immunomodulatory Effects of (R)-Sulforaphane on LPS-Activated Murine Immune Cells: Molecular Signaling Pathways and Epigenetic Changes in Histone Markers

The aim of this study was to explore the immunomodulatory effects of the natural enantiomer (R)-Sulforaphane (SFN) and the possible signaling pathways involved in an ex vivo model of LPS-stimulated murine peritoneal macrophages. Furthermore, we studied the epigenetic changes induced by (R)-SFN as well as the post-translational modifications of histone H3 (H3K9me3 and H3K18ac) in relation to the production of cytokines in murine splenocytes after LPS stimulation. (R)-SFN was able to modulate the inflammatory response and oxidative stress induced by LPS stimulation in murine peritoneal macrophages through the inhibition of reactive oxygen species (ROS), nitric oxide (NO) and cytokine (IL-1β, IL-6, IL-17, IL-18 and TNF-α) production by down-regulating the expression of pro-inflammatory enzymes (iNOS, COX-2 and mPGES-1). We also found that activation of the Nrf-2/HO-1 axis and inhibition of the JAK2/STAT-3, MAPK, canonical and non-canonical inflammasome signaling pathways could have been responsible for the immunomodulatory effects of (R)-SFN. Furthermore, (R)-SFN modulated epigenetic modifications through histone methylation (H3K9me3) and deacetylation (H3K18ac) in LPS-activated spleen cells. Collectively, our results suggest that (R)-SFN could be a promising epinutraceutical compound for the management of immunoinflammatory diseases.

Microglia Pyroptosis: A Candidate Target for Neurological Diseases Treatment

In addition to its profound implications in the fight against cancer, pyroptosis have important role in the regulation of neuronal injury. Microglia are not only central members of the immune regulation of the central nervous system (CNS), but are also involved in the development and homeostatic maintenance of the nervous system. Under various pathological overstimulation, microglia pyroptosis contributes to the massive release of intracellular inflammatory mediators leading to neuroinflammation and ultimately to neuronal damages. In addition, microglia pyroptosis lead to further neurological damage by decreasing the ability to cleanse harmful substances. The pathogenic roles of microglia in a variety of CNS diseases such as neurodegenerative diseases, stroke, multiple sclerosis and depression, and many other neurological disorders have been gradually unveiled. In the context of different neurological disorders, inhibition of microglia pyroptosis by targeting NOD-like receptor family pyrin domain containing (NLRP) 3, caspase-1 and gasdermins (GSDMs) by various chemical agents as well as natural products significantly improve the symptoms or outcome in animal models. This study will provide new ideas for immunomodulatory treatment of CNS diseases.

The Role of the NLRP3 Inflammasome in Mediating Glomerular and Tubular Injury in Diabetic Nephropathy

The NOD-like receptor protein 3 (NLRP3) inflammasome is a multi-protein signalling complex integral to the chronic inflammatory response, activated in response to sterile and non-sterile cellular damage. The assembly and activation of the NLRP3 inflammasome comprise a two-step process involving nuclear factor kappa B (NFkB)-mediated priming, followed by canonical, non-canonical or alternative signalling pathways. These result in the maturation and release of inflammatory cytokines interleukin 1 beta (IL1ß) and interleukin-18 (IL18), which are associated with chronic inflammatory conditions including diabetic kidney disease. Diabetic nephropathy is a condition affecting ∼40% of people with diabetes, the key underlying pathology of which is tubulointerstitial inflammation and fibrosis. There is growing evidence to suggest the involvement of the NLRP3 inflammasome in this chronic inflammation. Early deterioration of kidney function begins in the glomerulus, with tubular inflammation dictating the progression of late-stage disease. Priming and activation of the NLRP3 inflammasome have been linked to several clinical markers of nephropathy including proteinuria and albuminuria, in addition to morphological changes including mesangial expansion. Treatment options for diabetic nephropathy are limited, and research that examines the impact of directly targeting the NLRP3 inflammasome, or associated downstream components are beginning to gain favour, with several agents currently in clinical trials. This review will explore a role for NLRP3 inflammasome activation and signalling in mediating inflammation in diabetic nephropathy, specifically in the glomerulus and proximal tubule, before briefly describing the current position of therapeutic research in this field.

Nrf2 signaling in the oxidative stress response after spinal cord injury

Spinal cord injury (SCI) is a central nervous system trauma that can cause severe neurological impairment. A series of pathological and physiological changes after SCI (e.g., inflammation, oxidative stress, apoptosis, and mitochondrial dysfunction) promotes further deterioration of the microenvironment at the site of injury, leading to aggravation of neurological function. The multifunctional transcription factor NF-E2 related factor 2 (Nrf2) has long been considered a key factor in antioxidant stress. Therefore, Nrf2 may be an ideal therapeutic target for SCI. A comprehensive understanding of the function and regulatory mechanism of Nrf2 in the pathophysiology of SCI will aid in the development of targeted therapeutic strategies for SCI. This review discusses the roles of Nrf2 in SCI, with the aim of aiding in further elucidation of SCI pathophysiology and in efforts to provide Nrf2-targeted strategies for the treatment of SCI.

Targeting NLRP3 Inflammasome With Nrf2 Inducers in Central Nervous System Disorders

The NLRP3 inflammasome is an intracellular multiprotein complex that plays an essential role in the innate immune system by identifying and eliminating a plethora of endogenous and exogenous threats to the host. Upon activation of the NLRP3 complex, pro-inflammatory cytokines are processed and released. Furthermore, activation of the NLRP3 inflammasome complex can induce pyroptotic cell death, thereby propagating the inflammatory response. The aberrant activity and detrimental effects of NLRP3 inflammasome activation have been associated with cardiovascular, neurodegenerative, metabolic, and inflammatory diseases. Therefore, clinical strategies targeting the inhibition of the self-propelled NLRP3 inflammasome activation are required. The transcription factor Nrf2 regulates cellular stress response, controlling the redox equilibrium, metabolic programming, and inflammation. The Nrf2 pathway participates in anti-oxidative, cytoprotective, and anti-inflammatory activities. This prominent regulator, through pharmacologic activation, could provide a therapeutic strategy for the diseases to the etiology and pathogenesis of which NLRP3 inflammasome contributes. In this review, current knowledge on NLRP3 inflammasome activation and Nrf2 pathways is presented; the relationship between NLRP3 inflammasome signaling and Nrf2 pathway, as well as the pre/clinical use of Nrf2 activators against NLRP3 inflammasome activation in disorders of the central nervous system, are thoroughly described. Cumulative evidence points out therapeutic use of Nrf2 activators against NLRP3 inflammasome activation or diseases that NLRP3 inflammasome contributes to would be advantageous to prevent inflammatory conditions; however, the side effects of these molecules should be kept in mind before applying them to clinical practice.

Sulforaphane Modulates the Inflammation and Delays Neurodegeneration on a Retinitis Pigmentosa Mice Model

The term retinitis pigmentosa (RP) describes a large group of hereditary retinopathies. From a cellular view, retinal degeneration is prompted by an initial death of rods, followed later by cone degeneration. This cellular progressive degeneration is translated clinically in tunnel vision, which evolves to complete blindness. The mechanism underlying the photoreceptor degeneration is unknown, but several mechanisms have been pointed out as main co-stars, inflammation being one of the most relevant. Retinal inflammation is characterized by proliferation, migration, and morphological changes in glial cells, in both microglia and Müller cells, as well as the increase in the expression of inflammatory mediators. Retinal inflammation has been reported in several animal models and clinical cases of RP, but the specific role that inflammation plays in the pathology evolution remains uncertain. Sulforaphane (SFN) is an antioxidant natural compound that has shown anti-inflammatory properties, including the modulation of glial cells activation. The present work explores the effects of SFN on retinal degeneration and inflammation, analyzing the modulation of glial cells in the RP rd10 mice model. A daily dose of 20 mg/kg of sulforaphane was administered intraperitoneally to control (C57BL/6J wild type) and rd10 (Pde6brd10) mice, from postnatal day 14 to day 20. On postnatal day 21, euthanasia was performed. Histological retina samples were used to assess cellular degeneration, Müller cells, and microglia activation. SFN administration delayed the loss of photoreceptors. It also ameliorated the characteristic reactive gliosis, assessed by retinal GFAP expression. Moreover, sulforaphane treatment regulated the microglia activation state, inducing changes in the microglia morphology, migration, and expression through the retina. In addition, SFN modulated the expression of the interleukins 1β, 4, Ym1, and arginase inflammatory mediators. Surprisingly, M2 polarization marker expression was increased at P21 and was reduced by SFN treatment. To summarize, SFN administration reduced retinal neurodegeneration and modified the inflammatory profile of RP, which may contribute to the SFN neuroprotective effect.

Use of sulforaphane in COVID-19: clinical trials are needed

We read with interest the narrative review authored by Kiser et al. (2021), which discussed extensively the antioxidant effect and anti-inflammatory effect of sulforaphane, a dietary supplement found in high amounts in cruciferous vegetables that ais orally accessible and well-tolerated. Notably, in their review, the authors also discussed the potential use of sulforaphane in patients with coronavirus disease 2019 (COVID-19). Sulforaphane mediates the inhibitory effect on NLRP3 inflammasome activation and we believe that this could be the main mechanism where sulforaphane is useful for patients with COVID-19.

The Role of NLRP3 Inflammasome in Alzheimer’s Disease and Potential Therapeutic Targets

Alzheimer’s disease (AD) is a common age-related neurodegenerative disease characterized by progressive cognitive dysfunction and behavioral impairment. The typical pathological characteristics of AD are extracellular senile plaques composed of amyloid ß (Aβ) protein, intracellular neurofibrillary tangles formed by the hyperphosphorylation of the microtubule-associated protein tau, and neuron loss. In the past hundred years, although human beings have invested a lot of manpower, material and financial resources, there is no widely recognized drug for the effective prevention and clinical cure of AD in the world so far. Therefore, evaluating and exploring new drug targets for AD treatment is an important topic. At present, researchers have not stopped exploring the pathogenesis of AD, and the views on the pathogenic factors of AD are constantly changing. Multiple evidence have confirmed that chronic neuroinflammation plays a crucial role in the pathogenesis of AD. In the field of neuroinflammation, the nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a key molecular link in the AD neuroinflammatory pathway. Under the stimulation of Aβ oligomers and tau aggregates, it can lead to the assembly and activation of NLRP3 inflammasome in microglia and astrocytes in the brain, thereby causing caspase-1 activation and the secretion of IL-1β and IL-18, which ultimately triggers the pathophysiological changes and cognitive decline of AD. In this review, we summarize current literatures on the activation of NLRP3 inflammasome and activation-related regulation mechanisms, and discuss its possible roles in the pathogenesis of AD. Moreover, focusing on the NLRP3 inflammasome and combining with the upstream and downstream signaling pathway-related molecules of NLRP3 inflammasome as targets, we review the pharmacologically related targets and various methods to alleviate neuroinflammation by regulating the activation of NLRP3 inflammasome, which provides new ideas for the treatment of AD.

Resveratrol Inhibits NLRP3 Inflammasome-Induced Pyroptosis and miR-155 Expression in Microglia Through Sirt1/AMPK Pathway

Resveratrol is a natural polyphenolic compound with a wide range of biological activities such as antioxidant, anti-carcinogenic, anti-obesity, anti-aging, anti-inflammatory, immunomodulatory properties. Accumulating evidence suggests that resveratrol has pharmacological benefits in life-threatening diseases, including cardiovascular disease, cancer, diabetes, and neurodegenerative diseases. Resveratrol is widely known for its anti-inflammatory properties; however, signaling mechanisms of anti-inflammatory action are still elusive. Studies have illustrated that resveratrol can control different regulatory pathways by altering the expression and consequently regulatory effects of microRNAs. Our study aims to clarify the regulatory mechanisms of resveratrol in its anti-inflammatory features in the N9 microglial cell line. Our results demonstrated that resveratrol inhibits LPS- and ATP-activated NLRP3 inflammasome and protects microglial cells upon oxidative stress, proinflammatory cytokine production, and pyroptotic cell death resulting from inflammasome activation. Additionally, resveratrol inhibits nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling and activates AMPK/Sirt1 pathways. Furthermore, our results indicated that resveratrol downregulated inflammasome-induced miR-155 expression. Then, inhibition of AMPK and Sirt1 pathways has significantly reversed protective effect of resveratrol on miR-155 expression. To sum up, our results suggest that resveratrol suppresses the NLRP3 inflammasome and miR-155 expression through AMPK and Sirt1 pathways in microglia.

Inhibitory effects of sulforaphane on NLRP3 inflammasome activation

SFN, a dietary phytochemical, is a significant member of isothiocyanates present in cruciferous vegetables at high levels in broccoli. It is a well-known activator of the Nrf2/ARE antioxidant pathway. Long since, the therapeutic effects of SFN have been widely studied in several different diseases. Other than the antioxidant effect, SFN also exhibits an anti-inflammatory effect through suppression of various mechanisms, including inflammasome activation. Considerably, SFN has been demonstrated to inhibit multiple inflammasomes, including NLRP3 inflammasome. NLRP3 inflammasome induces secretion of pro-inflammatory cytokines and promotes inflammatory cell death. The release of pro-inflammatory cytokines enhances the inflammatory response, in turn leading to tissue damage. These self-propelling inflammatory responses would need modulation with exogenous therapeutic agents to suppress them. SFN is a promising candidate molecule for the mitigation of NLRP3 inflammasome activation, which has been related to the pathogenesis of numerous disorders. In this review, we have provided fundamental knowledge about Sulforaphane, elaborated its characteristics, and evidentially focused on its mechanisms of action with regard to its anti-inflammatory, anti-oxidative, and neuroprotective features. Thereafter, we have summarized both in vitro and in vivo studies regarding SFN effect on NLRP3 inflammasome activation.

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.

NRF2 as a therapeutic opportunity to impact in the molecular roadmap of ALS

Amyotrophic Lateral Sclerosis (ALS) is a devastating heterogeneous disease with still no convincing therapy. To identify the most strategically significant hallmarks for therapeutic intervention, we have performed a comprehensive transcriptomics analysis of dysregulated pathways, comparing datasets from ALS patients and healthy donors. We have identified crucial alterations in RNA metabolism, intracellular transport, vascular system, redox homeostasis, proteostasis and inflammatory responses. Interestingly, the transcription factor NRF2 (nuclear factor (erythroid-derived 2)-like 2) has significant effects in modulating these pathways. NRF2 has been classically considered as the master regulator of the antioxidant cellular response, although it is currently considered as a key component of the transduction machinery to maintain coordinated control of protein quality, inflammation, and redox homeostasis. Herein, we will summarize the data from NRF2 activators in ALS pre-clinical models as well as those that are being studied in clinical trials. As we will discuss, NRF2 is a promising target to build a coordinated transcriptional response to motor neuron injury, highlighting its therapeutic potential to combat ALS.