Roles of Heme Oxygenase-1 in Neuroinflammation and Brain Disorders

Maternal social environment shapes yolk testosterone allocation and embryonic neural gene expression in tree swallows

Offspring from females breeding in competitive social environments are often exposed to more testosterone (T) during embryonic development, which can affect traits from growth to behavior in potentially adaptive ways. Despite the important role of maternally derived steroids in shaping offspring development, the molecular mechanisms driving these processes are currently unclear. Here, we use tree swallows (Tachycineta bicolor) to explore the effects of the maternal social environment on yolk T concentrations and genome-wide patterns of neural gene expression in embryos. We measured aggressive interactions among females breeding at variable densities and collected their eggs at two timepoints, including the day laid to measure yolk T concentrations and on embryonic day 11 to measure gene expression in whole brain samples. We found that females breeding in high-density sites experienced elevated rates of physical aggression and their eggs had higher yolk T concentrations. A differential gene expression and weighted gene co-expression network analysis indicated that embryos from high-density sites experienced an upregulation of genes involved in hormone, circulatory, and immune processes, and these gene expression patterns were correlated with yolk T levels and aggression. Genes implicated in neural development were additionally downregulated in embryos from high-density sites. These data highlight how early neurogenomic processes may be affected by the maternal social environment, giving rise to phenotypic plasticity in offspring.

Exploring the Comprehensive Neuroprotective and Anticancer Potential of Afzelin

Neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, Huntington's disease, and others) and cancer, seemingly disparate in their etiology and manifestation, exhibit intriguing associations in certain cellular and molecular processes. Both cancer and neurodegenerative diseases involve the deregulation of cellular processes such as apoptosis, proliferation, and DNA repair and pose a significant global health challenge. Afzelin (kaempferol 3-O-rhamnoside) is a flavonoid compound abundant in various plant sources. Afzelin exhibits a diverse range of biological activities, offering promising prospects for the treatment of diseases hallmarked by oxidative stress and deregulation of cell death pathways. Its protective potential against oxidative stress is also promising for alleviating the side effects of chemotherapy. This review explores the potential therapeutic implications of afzelin, including its capacity to mitigate oxidative stress, modulate inflammation, and promote cellular regeneration in neurodegenerative and cancer diseases.

Inflammation subsequent to mild iron excess differentially alters regional brain iron metabolism, oxidation and neuroinflammation status in mice

Iron dyshomeostasis and neuroinflammation, characteristic features of the aged brain, and exacerbated in neurodegenerative disease, may induce oxidative stress-mediated neurodegeneration. In this study, the effects of potential priming with mild systemic iron injections on subsequent lipopolysaccharide (LPS)-induced inflammation in adult C57Bl/6J mice were examined. After cognitive testing, regional brain tissues were dissected for iron (metal) measurements by total reflection X-ray fluorescence and synchrotron radiation X-Ray fluorescence-based elemental mapping; and iron regulatory, ferroptosis-related, and glia-specific protein analysis, and lipid peroxidation by western blotting. Microglial morphology and astrogliosis were assessed by immunohistochemistry. Iron only treatment enhanced cognitive performance on the novel object location task compared with iron priming and subsequent LPS-induced inflammation. LPS-induced inflammation, with or without iron treatment, attenuated hippocampal heme oxygenase-1 and augmented 4-hydroxynonenal levels. Conversely, in the cortex, elevated ferritin light chain and xCT (light chain of System Xc-) were observed in response to LPS-induced inflammation, without and with iron-priming. Increased microglial branch/process lengths and astrocyte immunoreactivity were also increased by combined iron and LPS in both the hippocampus and cortex. Here, we demonstrate iron priming and subsequent LPS-induced inflammation led to iron dyshomeostasis, compromised antioxidant function, increased lipid peroxidation and altered neuroinflammatory state in a brain region-dependent manner.

LPS priming-induced immune tolerance mitigates LPS-stimulated microglial activation and social avoidance behaviors in mice

In this study, we investigated the regulatory mechanisms underlying the effects of LPS tolerance on the inflammatory homeostasis of immune cells. LPS priming-induced immune tolerance downregulated cyclooxygenase-2, and lowered the production of prostaglandin-E2 in microglial cells. In addition, LPS tolerance downregulated the expression of suppressor of cytokine signaling 3, and inducible nitric oxide synthase/nitric oxide; suppressed the LPS-mediated induction of tumor necrosis factor-α, interleukin (IL)-6, and IL-1; and reduced reactive oxygen species production in microglial cells. LPS stimulation increased the levels of the adaptive response-related proteins heme oxygenase-1 and superoxide dismutase 2, and the levels of heme oxygenase-1 (HO-1) enhanced after LPS priming. Systemic administration of low-dose LPS (0.5 mg/kg) to mice for 4 consecutive days attenuated high-dose LPS (5 mg/kg)-induced inflammatory response, microglial activation, and proinflammatory cytokine expression. Moreover, repeated exposure to low-dose LPS suppressed the recruitment of peripheral monocytes or macrophages to brain regions and downregulated the expression of proinflammatory cytokines. Notably, LPS-induced social avoidance behaviors in mice were mitigated by immune tolerance. In conclusion, immune tolerance may reduce proinflammatory cytokine expression and reactive oxygen species production. Our findings provide insights into the effects of endotoxin tolerance on innate immune cells and social behaviors.

In Vitro Evaluation of the Antioxidant Capacity of 3,3-Disubstituted-3H-benzofuran-2-one Derivatives in a Cellular Model of Neurodegeneration

Oxidative stress represents a hallmark for many degenerative pathologies of the Central Nervous System. Throughout life, the constant pressure of noxious stimuli and/or episodes of traumatic events may expose the brain to a microenvironment where the non-balanced reactive oxygen species inevitably lead to neuronal loss and cognitive decline. HO-1, a 32 kDa heat-shock protein catalyzing the degradation of heme into carbon monoxide (CO), iron and biliverdin/bilirubin is considered one of the main antioxidant defense mechanisms playing pivotal roles in neuroprotection. Restoring the redox homeostasis is the goal of many natural or synthetic antioxidant molecules pursuing beneficial effects on brain functions. Here, we investigated the antioxidant capacity of four selected benzofuran-2-one derivatives in a cellular model of neurodegeneration represented by differentiated SH-SY5Y cells exposed to catechol-induced oxidative stress. Our main results highlight how all the molecules have antioxidant properties, especially compound 9, showing great abilities in reducing intracellular ROS levels and protecting differentiated SH-SY5Y cells from catechol-induced death. This compound above all seems to boost HO-1 mRNA and perinuclear HO-1 protein isoform expression when cells are exposed to the oxidative insult. Our findings open the way to consider benzofuran-2-ones as a novel and promising adjuvant antioxidant strategy for many neurodegenerative disorders.

Protective Effects of Hinokitiol on Neuronal Ferroptosis by Activating the Keap1/Nrf2/HO-1 Pathway in Traumatic Brain Injury

In this study, we investigated the effects of hinokitiol, a small-molecule natural compound, against neuronal ferroptosis after traumatic brain injury (TBI). A controlled cortical impact (CCI) mouse model and excess glutamate-treated HT-22 cells were used to study the effects of hinokitiol on TBI. Hinokitiol mitigated TBI brain tissue lesions and significantly improved neurological function. Neuron loss and iron deposition were ameliorated after hinokitiol administration. Hinokitiol alleviated excessive glutamate-induced intracellular reactive oxygen species (ROS), lipid peroxidation, and Fe2+ accumulation in HT-22. Mechanistically, hinokitiol upregulated heme oxygenase-1 (HO-1) expression, promoted nuclear factor-erythroid factor 2-related factor 2 (Nrf2) nuclear translocation, and inhibited the activation of microglia and astrocyte after TBI. These results suggest that hinokitiol has neuroprotective effects on rescuing cells from TBI-induced neuronal ferroptosis. In summary, hinokitiol is a potential therapeutic candidate for TBI by activating the Nrf2/Keap1/HO-1 signaling pathway.

Salivary Biomarkers for Parkinson's Disease: A Systematic Review with Meta-Analysis

Parkinson's Disease (PD) is a common neurodegenerative disease which manifests with motor features, such as bradykinesia, resting tremor, rigidity, and postural instability. Using the non-invasive technique of saliva collection, we designed a systematic review to answer the question "Are salivary biomarkers reliable for the diagnosis of Parkinson's Disease?". Following inclusion and exclusion criteria, 30 studies were included in this systematic review (according to the PRISMA statement guidelines). Mostly proteins were reported as potential biomarkers in saliva. Based on meta-analysis, in PD patients, salivary levels of total alpha-synuclein were significantly decreased, and those of oligomeric alpha-synuclein were significantly increased. Also, according to pooled AUC, heme oxygenase-1 demonstrated significant predictive value for saliva-based PD diagnosis. In conclusion, some potential biomarkers, especially alpha-synuclein, can be altered in the saliva of PD patients, which could be reliably useful for early diagnosis of this neurodegenerative disease differentiating other synucleopathies.

Unraveling the Interplay of Dopamine, Carbon Monoxide, and Heme Oxygenase in Neuromodulation and Cognition

The dopaminergic system plays important roles in neuromodulation, including prominent roles in complex neurological functions such as cognition, reward, motivation, and memory. Understandably, the highly complex nature of such physiological functions means that their regulation is intertwined with other signaling pathways, as has been demonstrated by numerous studies. Contrary to its public perception of being poisonous at all concentrations, carbon monoxide (CO) is produced endogenously from heme degradation by heme oxygenase (HO) as part of the physiological process of red blood cell turnover. Physiological concentrations of CO can reach high micromolar ranges in the hemoglobin bound form. Low-dose CO has shown therapeutic effects in numerous animal models, including traumatic brain injury via engaging various hemoprotein targets. As such, the HO-CO axis has been shown to offer beneficial effects in organ protection, anti-inflammation, and neuroprotection, among many others. Further, a large number of publications have shown the interactions among CO, HO, and the dopaminergic system. In this review, we critically examine such experimental evidence in a holistic fashion and in the context of a possible dopamine-HO-CO signaling axis. We hope that this Perspective will stimulate additional investigations into the molecular connectivity related to this possible axis and open doors to the development of novel therapeutics that impact the dopaminergic system.

A protein-miRNA biomic analysis approach to explore neuroprotective potential of nobiletin in human neural progenitor cells (hNPCs)

Chemical-induced neurotoxicity is increasingly recognized to accelerate the development of neurodegenerative disorders (NDs), which pose an increasing health burden to society. Attempts are being made to develop drugs that can cross the blood-brain barrier and have minimal or no side effects. Nobiletin (NOB), a polymethoxylated flavonoid with anti-oxidative and anti-inflammatory effects, has been demonstrated to be a promising compound to treat a variety of NDs. Here, we investigated the potential role of NOB in sodium arsenate (NA)-induced deregulated miRNAs and target proteins in human neural progenitor cells (hNPCs). The proteomics and microRNA (miRNA) profiling was done for different groups, namely, unexposed control, NA-exposed, NA + NOB, and NOB groups. Following the correlation analysis between deregulated miRNAs and target proteins, RT-PCR analysis was used to validate the selected genes. The proteomic analysis showed that significantly deregulated proteins were associated with neurodegeneration pathways, response to oxidative stress, RNA processing, DNA repair, and apoptotic process following exposure to NA. The OpenArray analysis confirmed that NA exposure significantly altered miRNAs that regulate P53 signaling, Wnt signaling, cell death, and cell cycle pathways. The RT-PCR validation studies concur with proteomic data as marker genes associated with autophagy and apoptosis (HO-1, SQSTM1, LC-3, Cas3, Apaf1, HSP70, and SNCA1) were altered following NA exposure. It was observed that the treatment of NOB significantly restored the deregulated miRNAs and proteins to their basal levels. Hence, it may be considered one of its neuroprotective mechanisms. Together, the findings are promising to demonstrate the potential applicability of NOB as a neuroprotectant against chemical-induced neurotoxicity.

Salivary Biomarkers for Alzheimer's Disease: A Systematic Review with Meta-Analysis

Alzheimer's Disease (AD) is the most common neurodegenerative disease which manifests with progressive cognitive impairment, leading to dementia. Considering the noninvasive collection of saliva, we designed the systematic review to answer the question "Are salivary biomarkers reliable for the diagnosis of Alzheimer's Disease?" Following the inclusion and exclusion criteria, 30 studies were included in this systematic review (according to the PRISMA statement guidelines). Potential biomarkers include mainly proteins, metabolites and even miRNAs. Based on meta-analysis, in AD patients, salivary levels of beta-amyloid42 and p-tau levels were significantly increased, and t-tau and lactoferrin were decreased at borderline statistical significance. However, according to pooled AUC, lactoferrin and beta-amyloid42 showed a significant predictive value for salivary-based AD diagnosis. In conclusion, potential markers such as beta-amyloid42, tau and lactoferrin can be detected in the saliva of AD patients, which could reliably support the early diagnosis of this neurodegenerative disease.

Oxygen metabolism abnormality and Alzheimer's disease: An update

Oxygen metabolism abnormality plays a crucial role in the pathogenesis of Alzheimer's disease (AD) via several mechanisms, including hypoxia, oxidative stress, and mitochondrial dysfunction. Hypoxia condition usually results from living in a high-altitude habitat, cardiovascular and cerebrovascular diseases, and chronic obstructive sleep apnea. Chronic hypoxia has been identified as a significant risk factor for AD, showing an aggravation of various pathological components of AD, such as amyloid β-protein (Aβ) metabolism, tau phosphorylation, mitochondrial dysfunction, and neuroinflammation. It is known that hypoxia and excessive hyperoxia can both result in oxidative stress and mitochondrial dysfunction. Oxidative stress and mitochondrial dysfunction can increase Aβ and tau phosphorylation, and Aβ and tau proteins can lead to redox imbalance, thus forming a vicious cycle and exacerbating AD pathology. Hyperbaric oxygen therapy (HBOT) is a non-invasive intervention known for its capacity to significantly enhance cerebral oxygenation levels, which can significantly attenuate Aβ aggregation, tau phosphorylation, and neuroinflammation. However, further investigation is imperative to determine the optimal oxygen pressure, duration of exposure, and frequency of HBOT sessions. In this review, we explore the prospects of oxygen metabolism in AD, with the aim of enhancing our understanding of the underlying molecular mechanisms in AD. Current research aimed at attenuating abnormalities in oxygen metabolism holds promise for providing novel therapeutic approaches for AD.

4-methoxycinnamyl p-coumarate reduces neuroinflammation by blocking NF-κB, MAPK, and Akt/GSK-3β pathways and enhancing Nrf2/HO-1 signaling cascade in microglial cells

The active compound, 4-methoxycinnamyl p-coumarate (MCC), derived from the rhizome of Etlingera pavieana (Pierre ex Gagnep) R.M.Sm., has been shown to exert anti-inflammatory effects in several inflammatory models. However, its effects on microglial cells remain elusive. In the current study, we aimed to investigate the anti-neuroinflammatory activities of MCC and determine the potential mechanisms underlying its action on lipopolysaccharide (LPS)-induced BV2 microglial cells. Our results revealed that MCC significantly reduced the secretion of nitric oxide (NO) and prostaglandin E2, concomitantly inhibiting the expression levels of inducible NO synthase and cyclooxygenase-2 mRNA and proteins. Additionally, MCC effectively decreased the production of reactive oxygen species in LPS-induced BV2 microglial cells. MCC also attenuates the activation of NF-κB by suppressing the phosphorylation of IκBα and NF-κB p65 subunits and by blocking the nuclear translocation of NF-κB p65 subunits. Furthermore, MCC significantly reduced the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), and protein kinase B (Akt)/glycogen synthase kinase-3β (GSK-3β). In addition, MCC markedly increased the expression of heme oxygenase-1 (HO-1) by upregulating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. Collectively, our findings suggest that the anti-inflammatory activities of MCC could be attributed to its ability to suppress the activation of NF-κB, MAPK, and Akt/GSK-3β while enhancing that of Nrf2-mediated HO-1. Accordingly, MCC has promising therapeutic potential to treat neuroinflammation-related diseases.

Changes in heme oxygenase level during development affect the adult life of Drosophila melanogaster

Heme oxygenase (HO) has been shown to control various cellular processes in both mammals and Drosophila melanogaster. Here, we investigated how changes in HO levels in neurons and glial cells during development affect adult flies, by using the TARGET Drosophila system to manipulate the expression of the ho gene. The obtained data showed differences in adult survival, maximum lifespan, climbing, locomotor activity, and sleep, which depended on the level of HO (after ho up-regulation or downregulation), the timing of expression (chronic or at specific developmental stages), cell types (neurons or glia), sex (males or females), and age of flies. In addition to ho, the effects of changing the mRNA level of the Drosophila CNC factor gene (NRF2 homolog in mammals and master regulator of HO), were also examined to compare with those observed after changing ho expression. We showed that HO levels in neurons and glia must be maintained at an appropriate physiological level during development to ensure the well-being of adults. We also found that the downregulation of ho in either neurons or glia in the brain is compensated by ho expressed in the retina.

Biliverdin as a disease-modifying agent: An integrated viewpoint

Biliverdin is one of the three by-products of heme oxygenase (HO) activity, the others being ferrous iron and carbon monoxide. Under physiological conditions, once formed in the cell, BV is reduced to bilirubin (BR) by the biliverdin reductase (BVR). However, if BVR is inhibited by either genetic variants, as occurs in the Inuit ethnicity, or dioxin intoxication, BV accumulates in cells giving rise to a clinical syndrome known as green jaundice. Preclinical studies have demonstrated that BV not only has a direct antioxidant effect by scavenging free radicals, but also targets many signal transduction pathways, such as BVR, soluble guanylyl cyclase, and the aryl hydrocarbon receptor. Through these direct and indirect mechanisms, BV has shown beneficial roles in ischemia/reperfusion-related diseases, inflammatory diseases, graft-versus-host disease, viral infections and cancer. Unfortunately, no clinical data are available to confirm these potential therapeutic effects and the kinetics of exogenous BV in humans is unknown. These limitations have so far excluded the possibility of transforming BV from a mere by-product of heme degradation into a disease-modifying agent. A closer collaboration between basic and clinical researchers would be advantageous to overcome these issues and promote translational research on BV in free radical-induced diseases.

An RNAi-Mediated Reduction in Transcription Factor Nrf-2 Blocks the Positive Effects of Dimethyl Fumarate on Metabolic Stress in Alzheimer's Disease

The prevalence of obesity is rapidly rising around the world, and this will have a significant impact on our society as it is believed to be one of the leading causes of death. One of the main causes of these occurrences is added sugar consumption, which is associated with a higher risk of obesity, heart disease, diabetes, and brain illnesses such as Alzheimer's disease (AD). To this purpose, excess sugar might worsen oxidative damage and brain inflammation: two neuropathological signs of AD. Dimethyl fumarate (DMF) is an orally accessible methyl ester of fumaric acid with putative neuroprotective and immunomodulatory properties. In addition, DMF stimulates the nuclear factor erythroid 2-related factor 2 (Nrf-2), a key regulator of the antioxidant response mechanism in cells. The aim of the current study was to assess the potential therapeutic benefits of DMF in an in vitro model of metabolic stress induced by high and low sugar levels. We discovered that DMF reversed the negative impacts of high and low glucose exposure on the viability and oxidative stress of SH-SY5Y cells. Mechanistically, DMF's actions were mediated by Nrf-2. To this end, we discovered that DMF boosted the expression of the Nrf-2-regulated genes heme-oxygenase-1 (HO1) and manganese superoxide dismutase (MnSOD). More importantly, we found that inhibiting Nrf-2 expression prevented DMF's positive effects. Our combined findings suggest that DMF may be a valuable support for treatments for metabolic diseases.

Cleistocalyx nervosum var. paniala Berry Seed Protects against TNF-α-Stimulated Neuroinflammation by Inducing HO-1 and Suppressing NF-κB Mechanism in BV-2 Microglial Cells

Sustained inflammatory responses have been implicated in various neurodegenerative diseases (NDDs). Cleistocalyx nervosum var. paniala (CN), an indigenous berry, has been reported to exhibit several health-beneficial properties. However, investigation of CN seeds is still limited. The objective of this study was to evaluate the protective effects of ethanolic seed extract (CNSE) and mechanisms in BV-2 mouse microglial cells using an inflammatory stimulus, TNF-α. Using LC-MS, ferulic acid, aurentiacin, brassitin, ellagic acid, and alpinetin were found in CNSE. Firstly, we examined molecular docking to elucidate its bioactive components on inflammation-related mechanisms. The results revealed that alpinetin, aurentiacin, and ellagic acid inhibited the NF-κB activation and iNOS function, while alpinetin and aurentiacin only suppressed the COX-2 function. Our cell-based investigation exhibited that cells pretreated with CNSE (5, 10, and 25 μg/mL) reduced the number of spindle cells, which was highly observed in TNF-α treatment (10 ng/mL). CNSE also obstructed TNF-α, IL-1β, and IL-6 mRNA levels and repressed the TNF-α and IL-6 releases in a culture medium of BV-2 cells. Remarkably, CNSE decreased the phosphorylated forms of ERK, p38MAPK, p65, and IκB-α related to the inhibition of NF-κB binding activity. CNSE obviously induced HO-1 protein expression. Our findings suggest that CNSE offers good potential for preventing inflammatory-related NDDs.

The dual role of heme oxygenase in regulating apoptosis in the nervous system of Drosophila melanogaster

Accumulating evidence from mammalian studies suggests the dual-faced character of heme oxygenase (HO) in oxidative stress-dependent neurodegeneration. The present study aimed to investigate both neuroprotective and neurotoxic effects of heme oxygenase after the ho gene chronic overexpression or silencing in neurons of Drosophila melanogaster. Our results showed early deaths and behavioral defects after pan-neuronal ho overexpression, while survival and climbing in a strain with pan-neuronal ho silencing were similar over time with its parental controls. We also found that HO can be pro-apoptotic or anti-apoptotic under different conditions. In young (7-day-old) flies, both the cell death activator gene (hid) expression and the initiator caspase Dronc activity increased in heads of flies when ho expression was changed. In addition, various expression levels of ho produced cell-specific degeneration. Dopaminergic (DA) neurons and retina photoreceptors are particularly vulnerable to changes in ho expression. In older (30-day-old) flies, we did not detect any further increase in hid expression or enhanced degeneration, however, we still observed high activity of the initiator caspase. In addition, we used curcumin to further show the involvement of neuronal HO in the regulation of apoptosis. Under normal conditions, curcumin induced both the expression of ho and hid, which was reversed after exposure to high-temperature stress and when supplemented in flies with ho silencing. These results indicate that neuronal HO regulates apoptosis and this process depends on ho expression level, age of flies, and cell type.

Impact of different processing methods on the phenolics and neuroprotective activity of Fragaria ananassa Duch. extracts in a D-galactose and aluminum chloride-induced rat model of aging

Age-related diseases, including dementia, are a major health concern affecting daily human life. Strawberry (Fragaria ananassa Duch.) is the most eaten fruit worldwide due to its exceptional aroma and flavor. However, it's rapid softening and decay limit its shelf-life. Freezing and boiling represent the well-known conservation methods to extend its shelf-life. Therefore, we aimed to discover the phytochemical content differences of fresh and processed strawberries associated with investigating and comparing their neuroprotective effects in a rat model of aging. Female Wistar rats were orally pretreated with fresh, boiled, and frozen F. ananassa methanolic extracts (250 mg kg-1) for 2 weeks, and then these extracts were concomitantly exposed to D-galactose [65 mg kg-1, subcutaneously (S/C)] and AlCl3 (200 mg kg-1, orally) for 6 weeks to develop aging-like symptoms. The results of UPLC/ESI-MS phytochemical profiling revealed 36 secondary metabolites, including phenolics, flavonoids, and their glycoside derivatives. Compared with boiled and frozen extracts, the fresh extract ameliorated the behavioral deficits including anxiety and cognitive dysfunction, upregulated brain HO-1 and Nrf2 levels, and markedly reduced caspase-3 and PPAR-γ levels. Moreover, LDH and miRNA-9, 124 and 132 protein expressions were reduced. The histological architecture of the brain hippocampus was restored and glial fibrillary acidic protein (GFAP) immunoexpression was downregulated. In conclusion, the fresh extract has neuroprotective activity that could have a promising role in ameliorating age-related neurodegeneration.