The mechanism of heme oxygenase-1 action involved in the enhancement of neurotrophic factor expression

Molecular mechanisms of the effects of photodynamic therapy on the brain: A review of the literature

Malignant gliomas are the most common primary brain tumors in adults. These tumors have a diverse molecular origin and a very poor prognosis. There is a lack of effective treatment at WHO grade IV glioma, and all glioblastomas progress or recur. Current treatments including surgical intervention, radiation therapy, and chemotherapy are insufficient and can cause damage to healthy brain tissue and neurological deficits. The preservation of healthy brain tissue during therapeutic intervention is made extremely difficult by the ability of malignant gliomas to diffusely infiltrate the surrounding brain parenchyma. Photodynamic therapy (PDT) is a treatment modality for glioma that can possibly overcome the inherent shortcommings of traditional therapies. Photodynamic therapy involves the use of a photosensitizer (PS) which, upon absorption of light by photosensitized tissue, triggers photochemical reactions generating reactive oxygen species (ROS) leading to the killing of tumor cells. Research focusing on the effective use of PDT in the treatment of glioma is already underway with promising results. Clinical studies on PDT for the treatment of gliomas have shown it to be a safe therapeutic modality with acceptable levels of side effects. However, some adverse sequelae have been observed during PDT of these tumours, such as increased photosensitivity, increased intracranial pressure or transient aphasia and worsening of pre-existing neurological deficits. Although the clinical sequelae of PDT are well described, the molecular mechanisms of PDT's effects on the healthy brain have not yet been thoroughly characterized. In our work, we attempt to summarize the molecular mechanisms of the effects of photosensitization on neural tissue, brain vasculature and the blood-brain barrier (BBB). We also point to findings presenting molecular approaches to protect the healthy brain from the adverse effects of photodynamic damage.

Unraveling the dual role of bilirubin in neurological Diseases: A Comprehensive exploration of its neuroprotective and neurotoxic effects

Neurodegenerative disorders are characterized by a progressive loss of neurons, causing substantial deficits in motor and cognitive functioning. Bilirubin is a yellow by-product of heme, existing in two primary isoforms namely unconjugated and conjugated, while initially produced unconjugated isomer is lipophilic and cytotoxic in nature. At physiological levels, bilirubin has an important role in brain function by acting as a powerful antioxidant, preventing brain tissues from oxidative damage by eliminating reactive oxygen species (ROS). Additionally, it contributes to immune regulation through microglial activation, cytokine release, complement system interception, fragment crystallization (Fc) receptor modulation, and major histocompatibility complex (MHC II) expression modification, which lower the risk of inflammatory and autoimmune reactions in the central nervous system (CNS). As per the literature, serum bilirubin concentrations are associated with CNS diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), ischemic stroke, hemorrhagic stroke, traumatic brain injury (TBI), multiple sclerosis (MS), epilepsy, schizophrenia and kernicterus spectrum disorder (KSD), which causes neuronal damage, especially in regions like the basal ganglia and cerebellum, which causes movement abnormalities and cognitive deficits. The aim of this article is to explore the dual role of bilirubin as neuroprotective and neurotoxic, essential for establishing effective therapeutic outcomes for neurodegenerative diseases by looking at its cellular mechanisms and discussing how bilirubin's antioxidant properties can shield neurons and, in some situations, may induce oxidative stress and apoptosis.

Intranasal administration of mesenchymal stem cells overexpressing FGF21 demonstrates therapeutic potential in experimental Parkinson's disease

Parkinson's disease (PD) is a prevalent movement disorder characterized by mitochondrial dysfunction and dopaminergic neuronal loss in the substantia nigra of the midbrain. Currently, there are no effective treatments to cure or slow the progression of PD, highlighting an urgent need for new therapeutic strategies. Emerging evidence suggests that mesenchymal stem cells (MSCs) and fibroblast growth factor 21 (FGF21) are potential candidates for PD treatment. This study investigates a therapeutic strategy involving FGF21 delivered via mouse MSCs in the PD model of mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and dopaminergic SH-SY5Y cells exposed to 1-methyl-4-phenylpyridinium (MPP+). FGF21-overexpressing MSCs were administered intranasally, either before or after MPTP treatment in mice. Intranasally delivered FGF21-overexpressing MSCs efficiently migrated to the injured substantia nigra, ameliorated MPTP-induced PD-like motor deficits, reinstated dopaminergic neurons in the substantia nigra and nerve terminals in the striatum, as well as normalized brain-derived neurotrophic factor (BDNF) and FGF21 levels. In contrast, MSCs not overexpressing FGF21 showed limited or no impact on these parameters. In a PD cellular model of MPP+-treated SH-SY5Y cells, FGF21-overexpressing MSCs showed enhanced PD cell viability. Treatment with conditioned medium from FGF21-overexpressing MSCs or exogenous FGF21 prevented cell death, reduced mitochondrial reactive oxygen species (ROS), and restored neuroprotective proteins, including phospho-Akt, BDNF, and Bcl-2. These findings indicate that intranasal delivery of FGF21-overexpressing MSCs holds promise as a potential PD therapy, likely through activating the Akt-BDNF-Bcl-2 pathway, normalizing mitochondrial dysfunction, and mitigating dopaminergic neurodegeneration. Further clinical investigations are essential to validate these promising findings.

Using transcriptomic signatures to elucidate individual and mixture effects of inorganic arsenic and manganese in human placental trophoblast HTR-8/SVneo cells

Prenatal exposure to the toxic metal inorganic arsenic (iAs) is associated with adverse pregnancy and fetal growth outcomes. These adverse outcomes are tied to physiological disruptions in the placenta. Although iAs co-occurs in the environment with other metals such as manganese (Mn), there is a gap in the knowledge of the effects of metal mixtures on the placenta. To address this, we exposed human placental trophoblast cells to iAs, Mn, and an iAs-Mn mixture at 3 concentrations and evaluated transcriptome-wide gene expression and placental migration. We hypothesized that co-exposure to iAs-Mn in a mixture would result in a synergistic/enhanced transcriptomic effect compared to either metal alone. We also anticipated that genes involved in inflammatory or immune-related pathways would be differentially expressed in relation to the mixture compared to single-metals. The results highlight that iAs exposure alone had a stronger genomic response than Mn exposure, with 2-fold the number of differentially expressed genes (DEGs). When analyzing DEGs present across all concentrations of study, the iAs-Mn mixture resulted in the greatest number of DEGs. The results highlight that iAs exposure alone influences the expression of toll-like receptor-initiated response pathways including Triggering Receptor Expressed on Myeloid Cells-1. Exposure to Mn alone influenced the expression of Nicotinamide adenine dinucleotide biosynthesis pathways. In contrast, exposure to the iAs-Mn mixtures resulted in altered expression of inflammatory and immune response-related pathways, including the Nuclear factor erythroid 2-related factor 2 (NRF2)-mediated oxidative stress response pathway. Migration was unaffected by iAs, Mn, or the iAs-Mn mixture. These findings provide novel toxicogenomic insights into iAs- and Mn-induced placental transcriptomic dysregulations at environmentally relevant concentrations, with implications that in utero exposure to metal mixtures can influence inflammatory and immune pathways within the placenta.

Ischemia-induced endogenous Nrf2/HO-1 axis activation modulates microglial polarization and restrains ischemic brain injury

Cerebral ischemic stroke accounts for more than 80% of all stroke cases. During cerebral ischemia, reactive oxygen species produced in the ischemic brain induce oxidative stress and inflammatory responses. Nrf2 is a transcription factor responsible for regulating cellular redox balance through the induction of protective antioxidant and phase II detoxification responses. Although the induction of endogenous Nrf2/HO-1 axis activation has been observed in the ischemic brain, whether ischemia-induced endogenous Nrf2/HO-1 axis activation plays a role in modulating microglia (MG) phenotypes and restraining ischemic brain injury is not characterized and requires further exploration. To investigate that, we generated mice with Nrf2 knockdown specifically in MG to rigorously assess the role of endogenous Nrf2 activation in ischemic brain injury after stroke. Our results showed that MG-specific Nrf2 knockdown exacerbated ischemic brain injury after stroke. We found that Nrf2 knockdown altered MG phenotypes after stroke, in which increased frequency of inflammatory MG and decreased frequency of anti-inflammatory MG were detected in the ischemic brain. Moreover, we identified attenuated Nrf2/HO-1 axis activation led to increased CD68/IL-1β and suppressed CD206 expression in MG, resulting in aggravated inflammatory MG in MG-specific Nrf2 knockdown mice after stroke. Intriguingly, using type II diabetic preclinical models, we revealed that diabetic mice exhibited attenuated Nrf2/HO-1 axis activation in MG and exacerbated ischemic brain injury after stroke that phenocopy mice with MG-specific Nrf2 knockdown. Finally, the induction of exogenous Nrf2/HO-1 axis activation in MG through pharmacological approaches ameliorated ischemic brain injury in diabetic mice. In conclusion, our findings provide cellular and molecular insights demonstrating ischemia-induced endogenous Nrf2/HO-1 axis activation modulates MG phenotypes and restrains ischemic brain injury. These results further strengthen the therapeutic potential of targeting Nrf2/HO-1 axis in MG for the treatment of ischemic stroke and diabetic stroke.

The crosstalk between oxidative stress and DNA damage induces neural stem cell senescence by HO-1/PARP1 non-canonical pathway

Neural stem cells play a crucial role in maintaining brain homeostasis. Neural stem cells senescence can lead to the decline of nerve repair and regeneration, causing brain aging and neurodegenerative diseases. However, the mechanism underlying neural stem cells senescence remains poorly understood. In this study, we report a novel HO-1/PARP1 non-canonical pathway highlighting how oxidative stress triggers the DNA damage response, ultimately leading to premature cellular senescence in neural stem cells. HO-1 acts as a sensor for oxidative stress, while PARP1 functions as a sensor for DNA damage. The simultaneous expression and molecular interaction of these two sensors can initiate a crosstalk of oxidative stress and DNA damage response processes, leading to the vicious cycle. The persistent activation of this pathway contributes to the senescence of neural stem cells, which in turn plays a crucial role in the progression of neurodegenerative diseases. Consequently, targeting this novel signaling pathway holds promise for the development of innovative therapeutic strategies and targets aimed at mitigating neural stem cells senescence-related disorders.

Mitigating effect of ferulic acid on di-(2-ethylhexyl) phthalate-induced neurocognitive dysfunction in male rats with a comprehensive in silico survey

Di-(2-ethylhexyl) phthalate (DEHP) is the most abundant phthalate threatening public health-induced neurotoxicity. This neurotoxicity is associated with behavioral and biochemical deficits in male rats. Our study investigated the neuroprotective effect of ferulic acid (FA) on male rats exposed to DEHP. Thirty-two male Wistar rats were assigned to four groups. Group I control rats received corn oil, group II intoxicated rats received 300 mg/kg of DEHP, group III received 300 mg/kg of DEHP + 50 mg/kg of FA, and group IV received 50 mg/kg of FA, all agents administrated daily per os for 30 days. Anxiety-like behavior, spatial working memory, and recognition memory were assessed. Also, brain oxidative stress biomarkers, including brain malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide (NO), superoxide dismutase (SOD), brain-derived neurotrophic factor (BDNF) as well as heme oxygenase-1 (HO-1) were measured. Moreover, brain histopathology examinations associated with immunohistochemistry determination of brain caspase-3 were also evaluated. Furthermore, docking simulation was adapted to understand the inhibitory role of FA on caspase-3 and NO synthase. Compared to DEHP-intoxicated rats, FA-treated rats displayed improved cognitive memory associated with a reduced anxious state. Also, the redox state was maintained with increased BNDF levels. These changes were confirmed by restoring the normal architecture of brain tissue and a decrement in the immunohistochemistry caspase-3. In conclusion, FA has potent antioxidant and antiapoptotic properties that confirm the neuroprotective activity of FA, with a possible prospect for its therapeutic capabilities and nutritional supplement value.

A novel hydrogel containing 4-methylcatechol for skin regeneration: in vitro and in vivo study

Skin damages are usual physical injuries and different studies have been done to improve wound healing. Hydrogel due to its properties like a moist environment and cooling wound site is a good option for wound treatment. In this study, we evaluated the consequence of using alginate/chitosan hydrogel contained various dosages of 4-Methylcatechol (0, 0.1, 1% (W/W)) on wound healing. After hydrogel fabrication, different tests like SEM, swelling, release, weight loss, and hemo- and cytocompatibility were done to characterize fabricated hydrogels. Finally, the rat model was used to assess Alginate/Chitosan hydrogel's therapeutic function containing 0.1 and 1% of 4-Methylcatechol. The pore size of hydrogel was between 24.5 ± 9 and 62.1 ± 11.63 µm and about 90% of hydrogel was lost after 14 days in the weight loss test. Blood compatibility and MTT assay showed that hydrogels were nontoxic and improved cell proliferation. In vivo test showed that Alginate/Chitosan/0.1%4-Methylcatechol improved wound healing and the results were significantly better than the gauze-treated wound. Our results showed dose depending effect of 4-Methylcatechol on wound healing. This study shows the treatment effect of 4-Methylcatechol on wound healing and the possibility of using it for treating skin injuries.

LAR Downregulation Protects the Astrocytic U251 and Cocultured SH-SY5Y Cells in a Rotenone-Induced Parkinson's Disease Cell Model

Leukocyte common antigen-related protein tyrosine phosphatase (LAR) is a member of the protein tyrosine phosphatase family that serves as a key regulator of cellular survival. It is also involved in neurodevelopment and brain disorders. This study was designed to investigate the role of LAR in a cell-based model of Parkinson's disease (PD) in which U251 and SH-SY5Y cells were used as models of astrocytes and dopaminergic neurons, respectively. Cell viability, cell death, cell morphology, protein phosphorylation and expression, ATP levels, reactive oxygen species (ROS) generation, and mitochondrial membrane potential were analyzed in the wild-type (WT) and heterozygous LAR-knockout astrocytoma U251 cells to assess the cell state, signal transduction, and mitochondrial function. LAR downregulation showed a protective effect in rotenone-exposed U251 cells by increasing cell viability, reducing cell mortality, and restoring appropriate cellular morphology. LAR downregulation enhanced IGF-1R phosphorylation and downstream signal transduction as evidenced by increases in the Akt and GSK-3β phosphorylation, as well as the upregulation of NRF2 and HO-1. The downregulation of LAR also augmented DJ-1 levels in these cells. The enhanced Akt and GSK-3β phosphorylation contributed to a reduced Bax/Bcl2 ratio and suppressed apoptosis after rotenone exposure. Heterozygous LAR-knockout U251 cells exhibited higher mitochondrial function evidenced by increased mitochondrial membrane potential, ATP contents, and reduced ROS production compared to the WT cells following rotenone exposure. Further studies showed that the astrocytic protection mediated by the heterozygous knockout of LAR was associated with the activation of Akt. A specific Akt inhibitor, MK2206, reduced the cell viability, Akt and GSK3β phosphorylation, and HO-1 and NRF2 expression in U251 cells exposed to rotenone. Astrocytes provide structural and metabolic support to maintain neuronal health. Astrocytic glial cell-derived neurotrophic factor (GDNF) production is vital for dopaminergic neuron survival. Heterozygous LAR-knockout U251 cells produced higher amounts of GDNF than the WT cells. The SH-SY5Y cells cocultured with heterozygous LAR-knockout U251 cells exhibited greater viability than that of cells cocultured with WT U251 cells in response to rotenone. Together, these findings demonstrate that the heterozygous knockout of LAR in astrocytes can play a key role in protecting both astrocytic cells and cocultured neurons in a rotenone-induced cell-based model of PD. This neuroprotective effect is attributable to the augmentation of IGF1R-Akt-GDNF signaling and the maintenance of astrocytic mitochondrial function.

Effects of two different exercise paradigms on cardiac function, BDNF-TrkB expression, and myocardial protection in the presence and absence of Western diet

Background

Brain-derived neurotrophic factor (BDNF) -tropomyosin-related kinase receptor B (TrkB) signaling is a vital regulator of myocardial performance. Here, we tested the impact of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on heart function, metabolic parameters, and serum/cardiac BDNF (with its TrkB receptor) in animals fed a Western (WD) or regular diet (ND). Further, myocardial expression of pro-inflammatory cytokine interleukin-18 (IL-18) and cardioprotective molecule heme oxygens-1 (HO-1) were monitored.

Methods

Wistar rats were divided into HIIT, MICT, and sedentary (SED), all fed a WD or ND, for 12 weeks. Heart function, protein expression, and serum factors were assessed via echocardiography, western blotting, and ELISA, respectively.

Results

WD plus SED caused insulin resistance, dyslipidemia, visceral fat deposition, serum BDNF depletion as well as cardiac upregulation of IL-18 and downregulation of HO-1, without affecting, heart function and BDNF-TrkB expression. The cardiometabolic risk factors, serum BDNF losses, and IL-18 overexpression were similarly obviated by HIIT and MICT, although HO-1 expression was boosted by HIIT exclusively (even in ND). HIIT enhanced heart function, regardless of the diet. HIIT augmented cardiac BDNF expression, with a significant difference between ND and WD. Likewise, HIIT instigated TrkB expression only in ND.

Conclusions

HIIT and MICT can cope with myocardial inflammation and cardiometabolic risk factors in WD consumers and, exclusively, HIIT may grant further protection by increasing heart function, BDNF-TrkB expression, and HO-1 expression. Thus, the HIIT paradigm should be considered as a preference for subjects who require heart function to be preserved or enhanced.

Roles of Heme Oxygenase-1 in Neuroinflammation and Brain Disorders

The heme oxygenase (HO) system is believed to be a crucial mechanism for the nervous system under stress conditions. HO degrades heme to carbon monoxide, iron, and biliverdin. These heme degradation products are involved in modulating cellular redox homeostasis. The first identified isoform of the HO system, HO-1, is an inducible protein that is highly expressed in peripheral organs and barely detectable in the brain under normal conditions, whereas HO-2 is a constitutive protein that is highly expressed in the brain. Several lines of evidence indicate that HO-1 dysregulation is associated with brain inflammation and neurodegeneration, including Parkinson’s and Alzheimer’s diseases. In this review, we summarize the essential roles that the HO system plays in ensuring brain health and the molecular mechanism through which HO-1 dysfunction leads to neurodegenerative diseases and disruption of nervous system homeostasis. We also provide a summary of the herbal medicines involved in the regulation of HO-1 expression and explore the current situation regarding herbal remedies and brain disorders.

Acupuncture for Parkinson's disease: From theory to practice

Advances in molecular biology and biochemistry have improved the treatment of Parkinson's disease (PD). There has been extensive evidence on the benefit of standard treatment (e.g., deep brain stimulation, levodopa, and dopamine agonists) and acupuncture for PD. This article aims to distill the similarities and differences in the treatment concepts between Chinese and Western medicine from the perspective of reinforcing the deficiency and purging the excess, summarize the latest evidence on the benefits of acupuncture for PD from theory to practice, and propose prospective treatment options for PD.

Sulforaphane Induces Glioprotection After LPS Challenge

Sulforaphane is a natural compound that presents anti-inflammatory and antioxidant properties, including in the central nervous system (CNS). Astroglial cells are involved in several functions to maintain brain homeostasis, actively participating in the inflammatory response and antioxidant defense systems. We, herein, investigated the potential mechanisms involved in the glioprotective effects of sulforaphane in the C6 astrocyte cell line, when challenged with the inflammogen, lipopolysaccharide (LPS). Sulforaphane prevented the LPS-induced increase in the expression and/or release of pro-inflammatory mediators, possibly due to nuclear factor κB and hypoxia-inducible factor-1α activation. Sulforaphane also modulated the expressions of the Toll-like and adenosine receptors, which often mediate inflammatory processes induced by LPS. Additionally, sulforaphane increased the mRNA levels of nuclear factor erythroid-derived 2-like 2 (Nrf2) and heme oxygenase-1 (HO1), both of which mediate several cytoprotective responses. Sulforaphane also prevented the increase in NADPH oxidase activity and the elevations of superoxide and 3-nitrotyrosine that were stimulated by LPS. In addition, sulforaphane and LPS modulated superoxide dismutase activity and glutathione metabolism. Interestingly, the anti-inflammatory and antioxidant effects of sulforaphane were blocked by HO1 pharmacological inhibition, suggesting its dependence on HO1 activity. Finally, in support of a glioprotective role, sulforaphane prevented the LPS-induced decrease in glutamate uptake, glutamine synthetase activity, and glial-derived neurotrophic factor (GDNF) levels, as well as the augmentations in S100B release and Na+, K+ ATPase activity. To our knowledge, this is the first study that has comprehensively explored the glioprotective effects of sulforaphane on astroglial cells, reinforcing the beneficial effects of sulforaphane on astroglial functionality.

An Analysis of the Multifaceted Roles of Heme in the Pathogenesis of Cancer and Related Diseases

Heme is an essential prosthetic group in proteins and enzymes involved in oxygen utilization and metabolism. Heme also plays versatile and fascinating roles in regulating fundamental biological processes, ranging from aerobic respiration to drug metabolism. Increasing experimental and epidemiological data have shown that altered heme homeostasis accelerates the development and progression of common diseases, including various cancers, diabetes, vascular diseases, and Alzheimer's disease. The effects of heme on the pathogenesis of these diseases may be mediated via its action on various cellular signaling and regulatory proteins, as well as its function in cellular bioenergetics, specifically, oxidative phosphorylation (OXPHOS). Elevated heme levels in cancer cells intensify OXPHOS, leading to higher ATP generation and fueling tumorigenic functions. In contrast, lowered heme levels in neurons may reduce OXPHOS, leading to defects in bioenergetics and causing neurological deficits. Further, heme has been shown to modulate the activities of diverse cellular proteins influencing disease pathogenesis. These include BTB and CNC homology 1 (BACH1), tumor suppressor P53 protein, progesterone receptor membrane component 1 protein (PGRMC1), cystathionine-β-synthase (CBS), soluble guanylate cyclase (sGC), and nitric oxide synthases (NOS). This review provides an in-depth analysis of heme function in influencing diverse molecular and cellular processes germane to disease pathogenesis and the modes by which heme modulates the activities of cellular proteins involved in the development of cancer and other common diseases.

Carbon Monoxide Releasing Molecule-3 Enhances Heme Oxygenase-1 Induction via ROS-Dependent FoxO1 and Nrf2 in Brain Astrocytes

Carbon monoxide releasing molecule-3 (CORM-3) has been shown to protect inflammatory diseases via the upregulation of heme oxygenases-1 (HO-1). However, in rat brain astrocytes (RBA-1), the mechanisms underlying CORM-3-induced HO-1 remain poorly defined. This study used western blot, real-time PCR, and promoter activity assays to determine the levels of HO-1 expression and 2',7'-dichlorodihydrofluorescein diacetate (H₂DCFDA) and dihydroethidium (DHE) to measure reactive oxygen species (ROS). We found that CORM-3-induced HO-1 expression was mediated through ROS generation by Nox or mitochondria. The signaling components were differentiated by pharmacological inhibitors and small interfering RNA (siRNA). Subcellular fractions, immunofluorescent staining, and chromatin immunoprecipitation assay were used to evaluate the nuclear translocation and promoter binding activity of Nrf2 induced by CORM-3. The roles of mTOR and FoxO1 in CORM-3-stimulated responses are still unknown in RBA-1 cells. Our results demonstrated that transfection with siRNAs or pretreatment with pharmacological inhibitors attenuated the levels of HO-1 and phosphorylation of signaling components including Akt, mTOR, FoxO1, and Nrf2 stimulated by CORM-3. Moreover, pretreatment with N-acetyl-L-cysteine, diphenyleneiodonium chloride, apocynin, or rotenone blocked nuclear translocation and promoter binding activity of Nrf2 induced by CORM-3. The present study concluded that in RBA-1 cells, CORM-3-induced HO-1 expression is, at least partially, mediated through Nox and mitochondria/ROS-dependent PI3K/Akt/mTOR cascade to activate FoxO1 or ROS leading to activation of Nrf2 activity.

Sodium arsenite induces spatial learning and memory impairment associated with oxidative stress and activates the Nrf2/PPARγ pathway against oxidative injury in mice hippocampus

Arsenic (As) is a ubiquitous environmental and industrial toxin with known correlates of oxidative stress and cognitive deficits in the brain. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcriptional factor that represents a central cellular antioxidant defense mechanism and transcribes many antioxidant genes. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a well-known nuclear receptor to regulate lipid metabolism in many tissues, and it has been also associated with the control of oxidative stress, neuronal death, neurogenesis and differentiation. The role of Nrf2 and PPARγ in As-induced neurotoxicity is still debated. The present study was designed to investigate the neurobehavioral toxic effect of sub-chronic and middle-dose sodium arsenite exposure in mice hippocampus, as well as the response of Nrf2/PPARγ expression and influence on protein expression levels of their downstream antioxidant genes. Our results showed that mice treated with intraperitoneal injection of sodium arsenite (50 mg/kg body wt.) twice a week for 7 weeks resulted in increased generation of reactive oxygen species and impairment of spatial cognitive function. The present study also found a positive association between Nrf2/PPARγ expression in hippocampus of mice, and activation of antioxidant defenses by the evidently upregulated expression of their downstream genes, including superoxide dismutase, heme oxygenase-1 and glutathione peroxidase-3. Therefore, our findings were helpful for further understanding the role of Nrf2/PPARγ feedback loop in As-induced neurobehavioral toxicity.

The Neuroprotective and Neurodegeneration Effects of Heme Oxygenase-1 in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by complex pathological and biological features. Notably, extracellular amyloid-β deposits as senile plaques and intracellular aggregation of hyperphosphorylated tau as neurofibrillary tangles remain the primary premortem criterion for the diagnosis of AD. Currently, there exist no disease-modifying therapies for AD, and many clinical trials have failed to show its benefits for patients. Heme oxygenase 1 (HO-1) is a 32 kDa enzyme, which catalyzes the degradation of cellular heme to free ferrous iron, biliverdin, and carbon monoxide under stressful conditions. Several studies highlight the crucial pathological roles of HO-1 in the molecular processes of AD. The beneficial roles of HO-1 overexpression in AD brains are widely accepted due to its ability to convert pro-oxidant heme to biliverdin and bilirubin (antioxidants), which promote restoration of a suitable tissue redox microenvironment. However, the intracellular oxidative stress might be amplified by metabolites of HO-1 and exacerbate the progression of AD under certain circumstances. Several lines of evidence have demonstrated that upregulated HO-1 is linked to tauopathies, neuronal damage, and synapse aberrations in AD. Here, we review the aspects of the molecular mechanisms by which HO-1 regulates AD and the latest information on the pathobiology of AD. We further highlight the neuroprotective and neurodystrophic actions of HO-1 and the feasibility of HO-1 as a therapeutic target for AD.

CORM-3 ameliorates neurodegeneration in the amygdala and improves depression- and anxiety-like behavior in a rat model of combined traumatic brain injury and hemorrhagic shock

OBJECTIVE

Emotional disturbances characterized by depression and anxiety among survivors of traumatic brain injury (TBI) impact the quality of life severely. Currently, there is a lack of effective drug treatment for neurodegeneration induced by TBI, mainly due to failed efficacy of compounds such as corticosteroids, calcium channel blockers, and excitatory amino acid inhibitors. Thus, we sought to continue with our investigation on CORM-3, a water-soluble exogenous carbon monoxide-releasing molecule with excellent anti-inflammatory actions employed in a previous study using a rat model of combined TBI with hemorrhage shock and resuscitation (HSR).

METHODS

Rats were administrated with CORM-3 after induction of TBI and HSR and examined depressive and anxiety-like behaviors, along with cerebral function employing functional magnetic resonance imaging (MRI) 30-days post-trauma. Also, the following variables were measured: 1) neuronal pyroptosis and apoptosis 24 h post-trauma, 2) the roles of PKG-ERK1/2 signaling pathways with the use of the protein kinase G (PKG) specific inhibitor, KT5823.

RESULTS

CORM-3-treated rats displayed significant ameliorated depression- and anxiety-like behaviors, improved cerebral blood flow, and fractional anisotropy (FA), showed less neuronal pyroptosis and apoptosis in the amygdala, and upregulated the phosphorylation of Vasodilator-stimulated phosphoprotein (VASP) and ERK1/2. However, CORM-3 neuroprotective effects against trauma were only partially reversed by KT5823.

CONCLUSION

CORM-3 ameliorated the emotional deficits and neuronal death induced in the amygdala post-TBI and HSR rat model, and PKG-ERK1/2 signaling might be implicated in the underlying mechanism.

Regenerative Potential of Carbon Monoxide in Adult Neural Circuits of the Central Nervous System

Regeneration of adult neural circuits after an injury is limited in the central nervous system (CNS). Heme oxygenase (HO) is an enzyme that produces HO metabolites, such as carbon monoxide (CO), biliverdin and iron by heme degradation. CO may act as a biological signal transduction effector in CNS regeneration by stimulating neuronal intrinsic and extrinsic mechanisms as well as mitochondrial biogenesis. CO may give directions by which the injured neurovascular system switches into regeneration mode by stimulating endogenous neural stem cells and endothelial cells to produce neurons and vessels capable of replacing injured neurons and vessels in the CNS. The present review discusses the regenerative potential of CO in acute and chronic neuroinflammatory diseases of the CNS, such as stroke, traumatic brain injury, multiple sclerosis and Alzheimer’s disease and the role of signaling pathways and neurotrophic factors. CO-mediated facilitation of cellular communications may boost regeneration, consequently forming functional adult neural circuits in CNS injury.

Heme Oxygenase Dependent Bilirubin Generation in Vascular Cells: A Role in Preventing Endothelial Dysfunction in Local Tissue Microenvironment?

Among antioxidants in the human body, bilirubin has been recognized over the past 20 years to afford protection against different chronic conditions, including inflammation and cardiovascular disease. Moderate increases in plasma concentration and cellular bilirubin generation from metabolism of heme via heme oxygenase (HMOX) in virtually all tissues can modulate endothelial and vascular function and exert antioxidant and anti-inflammatory roles. This review aims to provide an up-to-date and critical overview of the molecular mechanisms by which bilirubin derived from plasma or from HMOX1 activation in vascular cells affects endothelial function. Understanding the molecular actions of bilirubin may critically improve the management not only of key cardiovascular diseases, but also provide insights into a broad spectrum of pathologies driven by endothelial dysfunction. In this context, therapeutic interventions aimed at mildly increasing serum bilirubin as well as bilirubin generated endogenously by endothelial HMOX1 should be considered.

The Nrf2/HO-1 Axis as Targets for Flavanones: Neuroprotection by Pinocembrin, Naringenin, and Eriodictyol

Flavanones are a group of flavonoids that derive from their immediate chalcone precursors through the action of chalcone isomerase enzymes. The Aromatic A and B rings, C4-keto group, and the 15-carbon flavonoid skeleton are all evident in flavanones, but a notable absence of C2-C3 double bond and a lack of oxygenation at C-3 position of the C-ring makes them distinctively different from other groups such as flavonols (e.g., quercetin). On the basis of oxygenation level in the B ring, flavanones can vary from each other as exemplified by pinocembrin (no oxygenation), naringenin (4′-hydroxyl), or eriodictyol (3′,4′-dihydroxyl substitution). These groups are generally weaker free radical scavengers as compared to quercetin and derivatives though eriodictyol has a better free radical scavenging profile within the group due to the presence of the catechol functional moiety. In this communication, their antioxidant potential through the induction of antioxidant defenses is scrutinized. These compounds as exemplified by pinocembrin could induce the nuclear factor erythroid 2-related factor 2- (Nrf2-) heme oxygenase-1 (HO-1) axis leading to amelioration of oxidative stress in cellular and animal models. Their neuroprotective effect through such mechanism is discussed.

Pioglitazone Attenuates Lipopolysaccharide-Induced Oxidative Stress, Dopaminergic Neuronal Loss and Neurobehavioral Impairment by Activating Nrf2/ARE/HO-1

The aim of the present study was to examine the neuroprotective potential of pioglitazone via activation of Nrf2/ARE-dependent HO-1 signaling pathway in chronic neuroinflammation and progressive neurodegeneration mouse model induced by lipopolysaccharide (LPS). After assessing spatial memory, anxiety and motor-coordination, TH+ neurons in substantia nigra (SN) were counted. The oxidative stress marker carbonyl protein levels and HO-1 enzyme activity were also evaluated. RT-qPCR was conducted to detect HO-1, Nrf2 and NF-κp65 mRNA expression levels and Nrf2 transcriptional activation of antioxidant response element (ARE) of HO-1 was investigated. Pioglitazone ameliorated LPS-induced dopaminergic neuronal loss, as well as mitigated neurobehavioral impairments. It enhanced Nrf2 mRNA expression, and augmented Nrf2/ARE-dependent HO-1 pathway activation by amplifying HO-1 mRNA expression. Moreover, it induced a significant decrease in NF-κB p65 mRNA expression, while reducing carbonyl protein levels and restoring the HO-1 enzyme activity. Interestingly, LPS induced Nrf2/antioxidant response element (ARE) of HO-1 activation, ultimately resulting in slight enhanced HO-1 mRNA expression. However, LPS elicited decrease in HO-1 enzyme activity. Zinc protoporphyrin-IX (ZnPPIX) administrated with pioglitazone abolished its effects in the LPS mouse model. The study results demonstrate that coordinated activation of Nrf2/ARE-dependent HO-1 pathway defense mechanism by the PPARγ agonist pioglitazone mediated its neuroprotective effects.

Crosstalk Between Oxidative Stress and Endoplasmic Reticulum (ER) Stress in Endothelial Dysfunction and Aberrant Angiogenesis Associated With Diabetes: A Focus on the Protective Roles of Heme Oxygenase (HO)-1

Type-2 diabetes prevalence is continuing to rise worldwide due to physical inactivity and obesity epidemic. Diabetes and fluctuations of blood sugar are related to multiple micro- and macrovascular complications, that are attributed to oxidative stress, endoplasmic reticulum (ER) activation and inflammatory processes, which lead to endothelial dysfunction characterized, among other features, by reduced availability of nitric oxide (NO) and aberrant angiogenic capacity. Several enzymatic anti-oxidant and anti-inflammatory agents have been found to play protective roles against oxidative stress and its downstream signaling pathways. Of particular interest, heme oxygenase (HO) isoforms, specifically HO-1, have attracted much attention as major cytoprotective players in conditions associated with inflammation and oxidative stress. HO operates as a key rate-limiting enzyme in the process of degradation of the iron-containing molecule, heme, yielding the following byproducts: carbon monoxide (CO), iron, and biliverdin. Because HO-1 induction was linked to pro-oxidant states, it has been regarded as a marker of oxidative stress; however, accumulating evidence has established multiple cytoprotective roles of the enzyme in metabolic and cardiovascular disorders. The cytoprotective effects of HO-1 depend on several cellular mechanisms including the generation of bilirubin, an anti-oxidant molecule, from the degradation of heme; the induction of ferritin, a strong chelator of free iron; and the release of CO, that displays multiple anti-inflammatory and anti-apoptotic actions. The current review article describes the major molecular mechanisms contributing to endothelial dysfunction and altered angiogenesis in diabetes with a special focus on the interplay between oxidative stress and ER stress response. The review summarizes the key cytoprotective roles of HO-1 against hyperglycemia-induced endothelial dysfunction and aberrant angiogenesis and discusses the major underlying cellular mechanisms associated with its protective effects.

Regenerative Effects of Heme Oxygenase Metabolites on Neuroinflammatory Diseases

Heme oxygenase (HO) catabolizes heme to produce HO metabolites, such as carbon monoxide (CO) and bilirubin (BR), which have gained recognition as biological signal transduction effectors. The neurovascular unit refers to a highly evolved network among endothelial cells, pericytes, astrocytes, microglia, neurons, and neural stem cells in the central nervous system (CNS). Proper communication and functional circuitry in these diverse cell types is essential for effective CNS homeostasis. Neuroinflammation is associated with the vascular pathogenesis of many CNS disorders. CNS injury elicits responses from activated glia (e.g., astrocytes, oligodendrocytes, and microglia) and from damaged perivascular cells (e.g., pericytes and endothelial cells). Most brain lesions cause extensive proliferation and growth of existing glial cells around the site of injury, leading to reactions causing glial scarring, which may act as a major barrier to neuronal regrowth in the CNS. In addition, damaged perivascular cells lead to the breakdown of the blood-neural barrier, and an increase in immune activation, activated glia, and neuroinflammation. The present review discusses the regenerative role of HO metabolites, such as CO and BR, in various vascular diseases of the CNS such as stroke, traumatic brain injury, diabetic retinopathy, and Alzheimer's disease, and the role of several other signaling molecules.

Heme Oxygenase 1 in the Nervous System: Does It Favor Neuronal Cell Survival or Induce Neurodegeneration?

Heme oxygenase 1 (HO-1) up-regulation is recognized as a pivotal mechanism of cell adaptation to stress. Under control of different transcription factors but with a prominent role played by Nrf2, HO-1 induction is crucial also in nervous system response to damage. However, several lines of evidence have highlighted that HO-1 expression is associated to neuronal damage and neurodegeneration especially in Alzheimer’s and Parkinson’s diseases. In this review, we summarize the current literature regarding the role of HO-1 in nervous system pointing out different molecular mechanisms possibly responsible for HO-1 up-regulation in nervous system homeostasis and neurodegeneration.

Improved Healing after the Co-Transplantation of HO-1 and BDNF Overexpressed Mesenchymal Stem Cells in the Subacute Spinal Cord Injury of Dogs

Abundant expression of proinflammatory cytokines after a spinal cord injury (SCI) creates an inhibitory microenvironment for neuroregeneration. The mesenchymal stem cells help to mitigate the inflammation and improve neural growth and survival. For this purpose, we potentiated the function of adipose-derived mesenchymal stem cells (Ad-MSCs) by transfecting them with brain-derived neurotrophic factor (BDNF) and heme oxygenase-1 (HO-1), through a lentivirus, to produce BDNF overexpressed Ad-MSCs (BDNF-MSCs), and HO-1 overexpressed Ad-MSCs (HO-1-MSCs). Sixteen SCI beagle dogs were randomly assigned into four treatment groups. We injected both HO-1 and BDNF-overexpressed MSCs as a combination group, to selectively control inflammation and induce neuroregeneration in SCI dogs, and compared this with BDNF-MSCs, HO-1-MSCs, and GFP-MSCs injected dogs. The groups were compared in terms of improvement in canine Basso, Beattie, and Bresnahan (cBBB) score during 8 weeks of experimentation. After 8 weeks, spinal cords were harvested and subjected to western blot analysis, immunofluorescent staining, and hematoxylin and eosin (H&E) staining. The combination group showed a significant improvement in hindlimb functions, with a higher BBB score, and a robust increase in neuroregeneration, depicted by a higher expression of Tuj-1, NF-M, and GAP-43 due to a decreased expression of the inflammatory markers interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), and an increased expression of interleukin-10 (IL-10) (P ≤ 0.05). H&E staining showed more reduced intraparenchymal fibrosis in the combination group than in other groups (P ≤ 0.05). It was thus suggested that the cotransplantation of HO-1 and BDNF-MSCs is more effective in promoting the healing of SCI. HO-1-MSCs reduce inflammation, which favors BDNF-induced neuroregeneration in SCI of dogs.

Electroacupuncture Promotes Recovery of Motor Function and Reduces Dopaminergic Neuron Degeneration in Rodent Models of Parkinson's Disease

Parkinson’s disease (PD) is a common neurodegenerative disease. The pathological hallmark of PD is a progressive loss of dopaminergic neurons in the substantia nigra (SN) pars compacta in the brain, ultimately resulting in severe striatal dopamine deficiency and the development of primary motor symptoms (e.g., resting tremor, bradykinesia) in PD. Acupuncture has long been used in traditional Chinese medicine to treat PD for the control of tremor and pain. Accumulating evidence has shown that using electroacupuncture (EA) as a complementary therapy ameliorates motor symptoms of PD. However, the most appropriate timing for EA intervention and its effect on dopamine neuronal protection remain unclear. Thus, this study used the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mouse model (systemic-lesioned by intraperitoneal injection) and the 1-methyl-4-phenylpyridinium (MPP⁺)-lesioned rat model (unilateral-lesioned by intra-SN infusion) of PD, to explore the therapeutic effects and mechanisms of EA at the GB34 (Yanglingquan) and LR3 (Taichong) acupoints. We found that EA increased the latency to fall from the accelerating rotarod and improved striatal dopamine levels in the MPTP studies. In the MPP⁺ studies, EA inhibited apomorphine induced rotational behavior and locomotor activity, and demonstrated neuroprotective effects via the activation of survival pathways of Akt and brain-derived neurotrophic factor (BDNF) in the SN region. In conclusion, we observed that EA treatment reduces motor symptoms of PD and dopaminergic neurodegeneration in rodent models, whether EA is given as a pretreatment or after the initiation of disease symptoms. The results indicate that EA treatment may be an effective therapy for patients with PD.

Hippocampal Astrocyte Cultures from Adult and Aged Rats Reproduce Changes in Glial Functionality Observed in the Aging Brain

Astrocytes are dynamic cells that maintain brain homeostasis, regulate neurotransmitter systems, and process synaptic information, energy metabolism, antioxidant defenses, and inflammatory response. Aging is a biological process that is closely associated with hippocampal astrocyte dysfunction. In this sense, we demonstrated that hippocampal astrocytes from adult and aged Wistar rats reproduce the glial functionality alterations observed in aging by evaluating several senescence, glutamatergic, oxidative and inflammatory parameters commonly associated with the aging process. Here, we show that the p21 senescence-associated gene and classical astrocyte markers, such as glial fibrillary acidic protein (GFAP), vimentin, and actin, changed their expressions in adult and aged astrocytes. Age-dependent changes were also observed in glutamate transporters (glutamate aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1)) and glutamine synthetase immunolabeling and activity. Additionally, according to in vivo aging, astrocytes from adult and aged rats showed an increase in oxidative/nitrosative stress with mitochondrial dysfunction, an increase in RNA oxidation, NADPH oxidase (NOX) activity, superoxide levels, and inducible nitric oxide synthase (iNOS) expression levels. Changes in antioxidant defenses were also observed. Hippocampal astrocytes also displayed age-dependent inflammatory response with augmentation of proinflammatory cytokine levels, such as TNF-α, IL-1β, IL-6, IL-18, and messenger RNA (mRNA) levels of cyclo-oxygenase 2 (COX-2). Furthermore, these cells secrete neurotrophic factors, including glia-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), S100 calcium-binding protein B (S100B) protein, and transforming growth factor-β (TGF-β), which changed in an age-dependent manner. Classical signaling pathways associated with aging, such as nuclear factor erythroid-derived 2-like 2 (Nrf2), nuclear factor kappa B (NFκB), heme oxygenase-1 (HO-1), and p38 mitogen-activated protein kinase (MAPK), were also changed in adult and aged astrocytes and are probably related to the changes observed in senescence marker, glutamatergic metabolism, mitochondrial dysfunction, oxidative/nitrosative stress, antioxidant defenses, inflammatory response, and trophic factors release. Together, our results reinforce the role of hippocampal astrocytes as a target for understanding the mechanisms involved in aging and provide an innovative tool for studies of astrocyte roles in physiological and pathological aging brain.

Glioprotective Effect of Resveratrol: an Emerging Therapeutic Role for Oligodendroglial Cells

Resveratrol is a natural polyphenol compound highly found in red wine that displays several beneficial effects on the central nervous system (CNS), preventing or slowing the progression of a wide variety of neurological diseases. Its neuroprotective role is particularly associated to modulation of antioxidant and anti-inflammatory responses in glial cells in a mechanism dependent of heme oxygenase 1 (HO-1) signaling pathway. Oligodendrocyte progenitor cells (OPC), primarily known for giving rise to mature oligodendrocytes, have emerged as dynamic cells that are also important to maintain the CNS homeostasis. In this sense, we have demonstrated that resveratrol has a protective effect on oligodendroglial functionality against lipopolysaccharide (LPS)-mediated cytotoxicity and that its glioprotective mechanism involves the nuclear factor erythroid 2-related factor 2 (Nrf2) and HO-1 pathways. LPS, through toll-like receptor 4 (TLR4), affected the release of trophic factors by OPC, including transforming growth factor beta (TGF-β), brain-derived neurotrophic factor (BDNF), and glial cell-derived neurotrophic factor (GDNF), and resveratrol reestablished the trophic factor release to control levels. Additionally, resveratrol prevented the LPS-induced increase in the intracellular reactive oxygen species (ROS) as well as the decrease in glutathione (GSH) levels and in glutamate cysteine ligase (GCL) activity, through Nrf2/HO-1 signaling pathways. Resveratrol also prevented the increase of the transcriptional activities of nuclear factor κB (NFκB) and hypoxia-inducible factor 1 alpha (HIF-1α) after LPS challenge. In summary, this is the first study showing the glioprotective effect of resveratrol on oligodendroglial cells.

Heme oxygenase-1, a novel target for the treatment of diabetic complications: focus on diabetic peripheral neuropathy

Diabetic neuropathy is a complex disorder induced by long standing diabetes. Many signaling pathways and transcription factors have been proposed to be involved in the development and progression of related processes. Years of research points to critical role of oxidative stress, neuroinflammation and apoptosis in the pathogenesis of neuropathy in diabetes. Heme oxygenase-1 (HO-1) is heat-shock protein induced under conditions of different kinds of stress and has been implicated in cellular defense against oxidative stress. HO-1 degrades heme to biliverdin, carbon monoxide (CO) and free iron. Biliverdin and CO are gaining particular interest because these two have been found to mediate most of anti-inflammatory, antioxidant and anti-apoptotic effects of HO-1. Although extensively studied in different kinds of cancers and cardiovascular conditions, role of HO-1 in diabetic neuropathy is still under investigation. In this paper, we review the unique therapeutic potential of HO-1 and its role in mitigating various pathological processes that lead to diabetic neuropathy. This review also highlights the therapeutic approaches such as pharmacological and natural inducers of HO-1, gene delivery of HO-1 or its reaction products that in future, could lead to progression of HO-1 activators through the preclinical stages of drug development to clinical trials.

Preferential Heme Oxygenase-1 Activation in Striatal Astrocytes Antagonizes Dopaminergic Neuron Degeneration in MPTP-Intoxicated Mice

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) accompanied by increased oxidative damage. Astrocytes, which are the most abundant glial cell types in the brain, possess higher antioxidant potential partially due to preferentially activated nuclear factor E2-related factor 2 genes. Heme oxygenase isoform 1 (HO-1) is crucial for the response to oxidative stress via the catabolism of heme to carbon monoxide, bilirubin, and iron. In the present study, we aimed to investigate astroglial expression of HO-1 in the SNpc, especially in the striatum of a subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mouse model of PD, and to investigate the neuroprotective effects of intraventricularly administrated HO-1 activator cobalt protoporphyrin IX (CoPPIX). The results showed that HO-1 was faintly distributed in neurons but not astrocytes in the normal SNpc and striatum. MPTP triggered a robust HO-1 response in the astrocytes of the striatum after 1-day treatment, but the HO-1 levels declined dramatically at day 3 and were completely undetectable at day 5. Intraventricular administration of CoPPIX for 8 days could preferentially activate HO-1 in astrocytes in the striatum but not SNpc. The content of striatal dopamine and its derivatives was restored in the subacute MPTP models. CoPPIX also increased the number of dopaminergic neurons and the tyrosine hydroxylase levels in the SNpc. These results suggest that inadequate HO-1 in striatal astrocytes might contribute to the limited antioxidant defense and dopaminergic neuron degeneration in PD, and preferential HO-1 activation in striatal astrocytes might be neuroprotective. The study thus sheds light on the targeting of HO-1 in striatal astrocytes for PD therapeutics.

Effect of carbon monoxide on gene expression in cerebrocortical astrocytes: Validation of reference genes for quantitative real-time PCR

Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) is a widely used technique to characterize changes in gene expression in complex cellular and tissue processes, such as cytoprotection or inflammation. The accurate assessment of changes in gene expression depends on the selection of adequate internal reference gene(s). Carbon monoxide (CO) affects several metabolic pathways and de novo protein synthesis is crucial in the cellular responses to this gasotransmitter. Herein a selection of commonly used reference genes was analyzed to identify the most suitable internal control genes to evaluate the effect of CO on gene expression in cultured cerebrocortical astrocytes. The cells were exposed to CO by treatment with CORM-A1 (CO releasing molecule A1) and four different algorithms (geNorm, NormFinder, Delta Ct and BestKeeper) were applied to evaluate the stability of eight putative reference genes. Our results indicate that Gapdh (glyceraldehyde-3-phosphate dehydrogenase) together with Ppia (peptidylpropyl isomerase A) is the most suitable gene pair for normalization of qRT-PCR results under the experimental conditions used. Pgk1 (phosphoglycerate kinase 1), Hprt1 (hypoxanthine guanine phosphoribosyl transferase I), Sdha (Succinate Dehydrogenase Complex, Subunit A), Tbp (TATA box binding protein), Actg1 (actin gamma 1) and Rn18s (18S rRNA) genes presented less stable expression profiles in cultured cortical astrocytes exposed to CORM-A1 for up to 60 min. For validation, we analyzed the effect of CO on the expression of Bdnf and bcl-2. Different results were obtained, depending on the reference genes used. A significant increase in the expression of both genes was found when the results were normalized with Gapdh and Ppia, in contrast with the results obtained when the other genes were used as reference. These findings highlight the need for a proper and accurate selection of the reference genes used in the quantification of qRT-PCR results in studies on the effect of CO in gene expression.

LC3 overexpression reduces Aβ neurotoxicity through increasing α7nAchR expression and autophagic activity in neurons and mice

Autophagy is an intracellular degradation pathway with dynamic interactions for eliminating damaged organelles and protein aggregates by lysosomal digestion. The EGFP-conjugated microtubule-associated protein 1 light chain 3 (EGFP-LC3) serves to monitor autophagic process. Extracellular β-amyloid peptide accumulation is reported as a major cause in Alzheimer's disease (AD) pathogenesis; large numbers of autophagic vacuoles accumulate in patients' brains. We previously demonstrated that extracellular Aβ (eAβ) induces strong autophagic response and α7nAChR acts as a carrier to bind with eAβ; which further inhibits Aβ-induced neurotoxicity via autophagic degradation. In the present study, we overexpressed LC3 in both neuroblastoma cells (SH-SY5Y/pEGFP-LC3) and mice (TgEGFP-LC3) to assess the effect of LC3 overexpression on Aβ neurotoxicity. SH-SY5Y/pEGFP-LC3 cells and primary cortical neuron cultures derived from E17 (embryonic day 17) TgEGFP-LC3 mice showed not only better resistance against Aβ neurotoxicity but also higher α7nAChR expression and autophagic activity than control. Administration of α-bungarotoxin (α-BTX) to block α7nAChR antagonized the neuroprotective action of SH-SY5Y/pECGF-LC3 cells, suggesting that eAβ binding with α7nAChR is an important step in Aβ detoxification. LC3 overexpression thus exerts neuroprotection through increasing α7nAChR expression for eAβ binding and further enhancing autophagic activity for Aβ clearance in vitro and in vivo.

Spirulina non-protein components induce BDNF gene transcription via HO-1 activity in C6 glioma cells

Blue-green algae are known to contain biologically active proteins and non-protein substances and considered as useful materials for manufacturing the nutritional supplements. Particularly, Spirulina has been reported to contain a variety of antioxidants, such as flavonoids, carotenoids, and vitamin C, thereby exerting their protective effects against the oxidative damage to the cells. In addition to their antioxidant actions, polyphenolic compounds have been speculated to cause the protection of neuronal cells and the recovery of neurologic function in the brain through the production of brain-derived neurotrophic factor (BDNF) in glial cells. Then, the protein-deprived extract was prepared by removing the most part of protein components from aqueous extract of Spirulina platensis, and the effect of this extract on BDNF gene transcription was examined in C6 glioma cells. Consequently, the protein-deprived extract was shown to cause the elevation of BDNF mRNA levels following the expression of heme oxygenase-1 (HO-1) in the glioma cells. Therefore, the non-protein components of S. platensis are considered to stimulate BDNF gene transcription through the HO-1 induction in glial cells, thus proposing a potential ability of the algae to indirectly modulate the brain function through the glial cell activity.

How do Chinese medicines that tonify the kidney inhibit dopaminergic neuron apoptosis?

Wistar rats were intragastrically perfused with Chinese medicines used for tonifying the kidney. These included 0.180 g/mL of Herba Epimedii (Epimedium), Semen Cuscutae (Dodder Seed), or Herba Cistanches (Desertliving Cistanche), 0.04 mg/mL monoamine oxidase-B inhibitor selegiline, or distilled water for 14 consecutive days to prepare drug-containing serum or blank serum. MES23.5 cells in the logarithmic phase were cultured in media supplemented with 15% drug-containing serum for 24 hours, followed by incubation in culture solution containing 100 μmol/L H2O2 for 3 hours. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and flow tometry results showed that all drug-containing serums improved the survival rate of H2O2-injured MES23.5 cells, inhibited pro-apoptotic FasL and caspase-3 expression, promoted anti-apoptotic Bcl-2 expression. However, drug-containing serums had little influence on Fas expression in H2O2-injured MES23.5 cells. Enzyme-linked immunosorbent assay results showed that serum containing Herba Cistanches or Herba Epimedii increased the expression of nerve growth factor, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor in injured MES23.5 cells; serum containing Semen Cuscutae only increased brain-derived neurotrophic factor expression; while expression of the above neurotrophic factors remained the same in cells treated with serum containing selegiline. These findings indicate that Chinese medicines used to tonify the kidney can protect nerve cells by regulating the expression of apoptosis-related factors and neuro-trophic factors in MES23.5 cells.

Neural HO-1/sterol interactions in vivo: implications for Alzheimer's disease

BACKGROUND

Up-regulation of heme oxygenase-1 (HO-1) and altered cholesterol (CH) metabolism are characteristic of Alzheimer-diseased (AD) neural tissues. We previously provided evidence of significant HO-1/sterol interactions in vitro (cultured rat astroglia) and in post-mortem human AD brain (Religious Orders Study).

METHODS

The current experiments were designed to further delineate these interactions in vivo by comparing the behavior of HO-1/sterol interactions in two mouse models; (1) a novel HO-1 transgenic mouse (GFAP.HMOX1) engineered to selectively express human HO-1 in the astrocytic compartment and (2) the previously described triple transgenic AD mouse (3xTg-AD). In samples of frontal cortex, total CH, CH precursors and relevant oxysterols were quantified by gas chromatography-mass spectrometry (GC-MS) and HO-1 protein expression was assessed by ELISA. The relationships of HO-1 expression to total CH, CH precursors and total oxysterols were determined for both mouse models using linear regression analysis.

RESULTS

HO-1 expression is increased in GFAP.HMOX1 mice relative to wild type and in 11-12-month-old 3xTg-AD mice (with AD-like phenotype) relative to control mice and 5-6-month-old 3xTg-AD mice (no AD-like phenotype). Total oxysterols significantly decreased as HO-1 expression increased in GFAP.HMOX1 mice expressing high levels of HO-1, whereas total oxysterols increased as HO-1 expression increased in aged 3xTg-AD mice. Total CH and total CH precursors increased as HO-1 protein expression increased in 11-12-month-old 3xTg-AD mice relative to 5-6-month old 3xTg-AD mice.

CONCLUSIONS

Our findings indicate a differential impact of HO-1 on patterns of brain sterol and redox homeostasis that is contingent on the presence or absence of AD-like neuropathology. These data provide fresh insight concerning the regulation of sterol homeostasis within the aging and degenerating CNS which may inform the development of novel therapeutic and preventive strategies for the management of AD and related conditions.

Eating habits modulate short term memory and epigenetical regulation of brain derived neurotrophic factor in hippocampus of low- and high running capacity rats

Exercise capacity and dietary restriction (DR) are linked to improved quality of life, including enhanced brain function and neuro-protection. Brain derived neurotrophic factor (BDNF) is one of the key proteins involved in the beneficial effects of exercise on brain. Low capacity runner (LCR) and high capacity runner (HCR) rats were subjected to DR in order to investigate the regulation of BDNF. HCR-DR rats out-performed other groups in a passive avoidance test. BDNF content increased significantly in the hippocampus of HCR-DR groups compared to control groups (p<0.05). The acetylation of H3 increased significantly only in the LCR-DR group. However, chip-assay revealed that the specific binding between acetylated histone H3 and BNDF promoter was increased in both LCR-DR and HCR-DR groups. In spite of these increases in binding, at the transcriptional level only, the LCR-DR group showed an increase in BDNF mRNA content. Additionally, DR also induced the activity of cAMP response element-binding protein (CREB), while the content of SIRT1 was not altered. Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) was elevated in HCR-DR groups. But, based on the levels of nuclear respiratory factor-1 and cytocrome c oxidase, it appears that DR did not cause mitochondrial biogenesis. The data suggest that DR-mediated induction of BDNF levels includes chromatin remodeling. Moreover, DR does not induce mitochondrial biogenesis in the hippocampus of LCR/HCR rats. DR results in different responses to a passive avoidance test, and BDNF regulation in LCR and HCR rats.

Management of the aging risk factor for Parkinson's disease

The aging risk factor for Parkinson's disease is described in terms of specific disease markers including mitochondrial and gene dysfunctions relevant to energy metabolism. This review details evidence for the ability of nutritional agents to manage these aging risk factors. The combination of alpha lipoic acid, acetyl-l-carnitine, coenzyme Q10, and melatonin supports energy metabolism via carbohydrate and fatty acid utilization, assists electron transport and adenosine triphosphate synthesis, counters oxidative and nitrosative stress, and raises defenses against protein misfolding, inflammatory stimuli, iron, and other endogenous or xenobiotic toxins. These effects are supported by gene expression via the antioxidant response element (ARE; Keap/Nrf2 pathway), and by peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1 alpha), a transcription coactivator, which regulates gene expression for energy metabolism and mitochondrial biogenesis, and maintains the structural integrity of mitochondria. The effectiveness and synergies of the combination against disease risks are discussed in relation to gene action, dopamine cell loss, and the accumulation and spread of pathology via misfolded alpha-synuclein. In addition there are potential synergies to support a neurorestorative role via glial derived neurotrophic factor expression.

Neuroprotective activity of peripherally administered liver growth factor in a rat model of Parkinson's disease

Liver growth factor (LGF) is a hepatic mitogen purified some years ago that promotes proliferation of different cell types and the regeneration of damaged tissues, including brain tissue. Considering the possibility that LGF could be used as a therapeutic agent in Parkinson’s disease, we analyzed its potential neuroregenerative and/or neuroprotective activity when peripherally administered to unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rats. For these studies, rats subjected to nigrostriatal lesions were treated intraperitoneally twice a week with LGF (5 microg/rat) for 3 weeks. Animals were sacrificed 4 weeks after the last LGF treatment. The results show that LGF stimulates sprouting of tyrosine hydroxylase-positive terminals and increases tyrosine hydroxylase and dopamine transporter expression, as well as dopamine levels in the denervated striatum of 6-OHDA-lesioned rats. In this structure, LGF activates microglia and raises tumor necrosis factor-alpha protein levels, which have been reported to have a role in neuroregeneration and neuroprotection. Besides, LGF stimulates the phosphorylation of MAPK/ERK1/2 and CREB, and regulates the expression of proteins which are critical for cell survival such as Bcl2 and Akt. Because LGF partially protects dopamine neurons from 6-OHDA neurotoxicity in the substantia nigra, and reduces motor deficits in these animals, we propose LGF as a novel factor that may be useful in the treatment of Parkinson’s disease.

Activated microglia provide a neuroprotective role by balancing glial cell-line derived neurotrophic factor and tumor necrosis factor-α secretion after subacute cerebral ischemia

Microglia are the major immune cells in the central nervous system and play a key role in brain injury pathology. However, the role of activated microglia after subacute cerebral ischemia (SCI) remains unknown. To address this issue, we established a permanent middle cerebral artery occlusion (pMCAO) rat model and treated pMCAO rats with N-(6-oxo-5,6-dihydro-phenanthridin-2-yl)-N,N-dimethylacetamide (PJ34) (an inhibitor of microglial activation), or with vehicle alone. Finally, we determined the differences between the PJ34-and vehicle-treated rats with respect to neurological deficits, infarct volume, neuronal loss and the expression of CD11b (a marker of microglial activation), glial cell line-derived neurotrophic factor (GDNF) and tumor necrosis factor-α (TNF-α) at 1, 3 and 7 days after treatment. We found that the PJ34-treated rats had more severe neurological deficits and a larger infarct volume and exhibited a decreased CD11b expression, more neuronal loss, decreased expression of GDNF mRNA and protein but increased expression of TNF-α mRNA and protein compared with the vehicle-treated rats at 3 and 7 days after treatment. These results indicate that activated microglia provide a neuroprotective role through balancing GDNF and TNF-α expression following SCI.

Caffeic acid phenethyl ester protects nigral dopaminergic neurons via dual mechanisms involving haem oxygenase-1 and brain-derived neurotrophic factor

BACKGROUND AND PURPOSE

Caffeic acid phenethyl ester (CAPE) is a component of honey bee propolis that can induce expression of haem oxygenase-1 (HO-1). Because HO-1 induction has been suggested to protect dopaminergic neurons in the substantia nigra, we examined the effect of CAPE in experimental models of dopaminergic neurodegeneration.

EXPERIMENTAL APPROACH

Neuroprotective effect of CAPE was investigated in rat organotypic midbrain slice cultures and in vivo, using a mouse model of dopaminergic neurodegeneration induced by intranigral injection of LPS and intrastriatal injection of 6-hydroxydopamine.

KEY RESULTS

CAPE protected dopaminergic neurons in slice cultures from IFN-γ/LPS-induced injury. The effect of CAPE was inhibited by zinc protoporphyrin IX, an HO-1 inhibitor, and by neutralizing antibody against brain-derived neurotrophic factor (BDNF). A p38 MAPK inhibitor SB203580 prevented activation of NF-E2-related factor 2, attenuated increased expression of HO-1 and BDNF, and blocked the neuroprotective actions of CAPE. In the LPS-injected mouse model, daily intraperitoneal administration of CAPE protected dopaminergic neurons, up-regulated HO-1 and BDNF, and reduced the increase of activated microglia/macrophages. Neuroprotective effects of CAPE against LPS-induced injury was prevented by zinc protoporphyrin IX or anti-BDNF antibody. CAPE protected dopaminergic neurons and alleviated methamphetamine-induced rotational behaviour also in 6-hydroxydopamine hemiparkinsonian mice.

CONCLUSION AND IMPLICATIONS

CAPE is a novel type of neuroprotective agent whose actions are mediated by both HO-1 and BDNF. These findings may provide novel clues to develop neuroprotective agents for treatment of neurodegenerative disorders.

Protective action of nipradilol mediated through S-nitrosylation of Keap1 and HO-1 induction in retinal ganglion cells

Nipradilol (Nip), which has α1- and β-adrenoceptor antagonist and nitric oxide (NO)-donating properties, has clinically been used as an anti-glaucomatous agent in Japan. NO mediates cellular signaling pathways that regulate physiological functions. The major signaling mechanisms mediated by NO are cGMP-dependent signaling and protein S-nitrosylation-dependent signalings. Nip has been described as having neuroprotective effects through cGMP-dependent pathway in retinal ganglion cells (RGCs). However, the effect seems to be partial. On the other hand, whether Nip can prevent cell death through S-nitrosylation is not yet clarified. In this study, we therefore focused on the neuroprotective mechanism of Nip through S-nitrosylation. Nip showed a dramatic neuroprotective effect against oxidative stress-induced death of RGC-5 cells. However, denitro-nipradilol, which does not have NO-donating properties, was not protective against oxidative stress. Furthermore, an NO scavenger significantly reversed the protective action of Nip against oxidative stress. In addition, we demonstrated that α1- or β-adrenoceptor antagonists (prazosin or timolol) did not show any neuroprotective effect against oxidative stress in RGC-5 cells. We also demonstrated that Nip induced the expression of the NO-dependent antioxidant enzyme, heme oxygenase-1 (HO-1). S-nitrosylation of Kelch-like ECH-associated protein by Nip was shown to contribute to the translocation of NF-E2-related factor 2 to the nucleus, and triggered transcriptional activation of HO-1. Furthermore, RGC death and levels of 4-hydroxy-2-nonenal (4HNE) were increased after optic nerve injury in vivo. Pretreatment with Nip significantly suppressed RGC death and accumulation of 4HNE after injury through an HO-1 activity-dependent mechanism. These data demonstrate a novel neuroprotective action of Nip against oxidative stress-induced RGC death in vitro and in vivo.

Isoliquiritigenin isolated from licorice Glycyrrhiza uralensis prevents 6-hydroxydopamine-induced apoptosis in dopaminergic neurons

Licorice (Glycyrrhiza uralensis) is a medicinal herb containing various bioactive components implicated in antioxidative, anti-inflammatory, antiviral, and neuroprotective effects, but the effects of licorice against Parkinson's disease (PD)-related dopaminergic cell death have not been studied. In this study, we investigated the protective effects of isoliquiritigenin (ISL) isolated from Glycyrrhiza uralensis on 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in a dopaminergic cell line, SN4741. ISL (1 µM) significantly attenuated 6-OHDA (50 µM)-induced reactive oxygen species (ROS) and nitric oxide (NO) generation and apoptotic cell death. ISL pretreatment effectively suppressed 6-OHDA-mediated upregulation of Bax, p-c-Jun N-terminal kinase (JNK), p-p38 mitogen-activated protein (MAP) kinase, cytochrome c release, and caspase 3 activation. In addition, ISL significantly attenuated 6-OHDA-induced Bcl-2, brain-derived neurotrophic factor (BDNF), and mitochondrial membrane potential (MMP) reduction. Pharmacological inhibitors of the phosphatidylinositol 3-kinase (PI3K)-Akt/protein kinase B (PKB) pathway reversed ISL-mediated neuroprotection against 6-OHDA toxicity in SN4741 cells. These results provide the first evidence that ISL can protect dopaminergic cells under oxidative stress conditions by regulating the apoptotic process.

Involvement of phosphatidylinositol 3-kinase/Akt on basic fibroblast growth factor-induced glial cell line-derived neurotrophic factor release from rat glioma cells

Basic fibroblast growth factor (FGF-2) has a neuroprotective effect. Astrocytes support neurons by releasing neurotrophic factors including glial cell line-derived neurotrophic factor (GDNF). FGF-2 stimulates GDNF synthesis in astrocytes and the release. It has been reported that FGF-2 induces the activation of p44/p42 mitogen-activated protein (MAP) kinase, stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and p38 MAP kinase in C6 glioma cells, and that FGF-2 stimulates GDNF release through p44/p42 MAP kinase or SAPK/JNK, but not p38 MAP kinase. In the present study, we investigated the exact mechanism of FGF-2-induced GDNF release from C6 cells. FGF-2 induced the phosphorylation of Akt and its substrate, glycogen synthase kinase 3β (GSK3β) in addition to three MAP kinases in these cells. FGF-2-stimulated release of GDNF was suppressed by wortmannin (a phosphatidylinositol 3 (PI3)-kinase inhibitor) or LY294002 (another PI3-kinase inhibitor). The FGF-2-induced GDNF release from PI3-kinase-downregulated C6 cells was decreased compared with that in control siRNA-transfected cells. PD98059 (an inhibitor of MEK 1/2) or SP600125 (an inhibitor of SAPK/JNK), which suppressed FGF-2-induced phosphorylation of p44/p42 MAP kinase or SAPK/JNK respectively, did not affect FGF-2-induced Akt phosphorylation. Wortmannin or LY294002, which attenuated FGF-2-induced phosphorylation of Akt and GSK3β, had no effect on FGF-2-induced phosphorylation of p44/p42 MAP kinase or SAPK/JNK. These results strongly suggest that the PI3-kinase/Akt pathway plays a positive role in FGF-2-stimulated GDNF release independently of p44/p42 MAP kinase or SAPK/JNK in C6 glioma cells.