Protective effects of luteolin on cognitive impairments induced by psychological stress in mice

Luteolin Mitigates D-Galactose-Induced Brain Ageing in Rats: SIRT1-Mediated Neuroprotection

Luteolin is an essential natural polyphenol found in a variety of plants. Numerous studies have supported its protective role in neurodegenerative diseases, yet the research for its therapeutic utility in D-galactose (D-gal)-induced brain ageing is still lacking. In this study, the potential neuroprotective impact of luteolin against D-gal-induced brain ageing was explored. Forty rats were randomly divided into four groups: control, luteolin, D-gal, and luteolin-administered D-gal groups. All groups were subjected to behavioural, cholinergic function, and hippocampal mitochondrial respiration assessments. Hippocampal oxidative, neuro-inflammatory, senescence and apoptotic indicators were detected. Gene expressions of SIRT1, BDNF, and RAGE were assessed. Hippocampal histopathological studies, along with GFAP and Ki67 immunoreactivity, were performed. Our results demonstrated that luteolin effectively alleviated D-gal-induced cognitive impairment and reversed cholinergic abnormalities. Furthermore, luteolin administration substantially mitigated hippocampus oxidative stress, mitochondrial dysfunction, neuro-inflammation, and senescence triggered by D-gal. Additionally, luteolin treatment considerably attenuated neuronal apoptosis and upregulated hippocampal SIRT1 mRNA expression. In conclusion, our findings revealed that luteolin administration attenuated D-gal-evoked brain senescence, improving mitochondrial function and enhancing hippocampal neuroregeneration in an ageing rat model through its antioxidant, senolytic, anti-inflammatory, and anti-apoptotic impacts, possibly due to upregulation of SIRT1. Luteolin could be a promising therapeutic modality for brain aging-associated abnormalities.

Multiple integrated social stress induces depressive-like behavioral and neural adaptations in female C57BL/6J mice

Despite women representing most of those affected by major depression, preclinical studies have focused almost exclusively on male subjects, partially due to a lack of ideal animal paradigms. As the persistent need regarding the sex balance of neuroscience research and female-specific pathology of mental disorders surges, the establishment of natural etiology-based and systematically validated animal paradigms for depression with female subjects becomes an urgent scientific problem. This study aims to establish, characterize, and validate a "Multiple Integrated Social Stress (MISS)" model of depression in female C57BL/6J mice by manipulating and integrating daily social stressors that females are experiencing. Female C57BL/6J mice randomly experienced social competition failure in tube test, modified vicarious social defeat stress, unescapable overcrowding stress followed by social isolation on each day, for ten consecutive days. Compared with their controls, female MISS mice exhibited a relatively decreased preference for social interaction and sucrose, along with increased immobility in the tail suspension test, which could last for at least one month. These MISS mice also exhibited increased levels of blood serum corticosterone, interleukin-6 L and 1β. In the pharmacological experiment, MISS-induced dysfunctions in social interaction, sucrose preference, and tail suspension tests were amended by systematically administrating a single dose of sub-anesthetic ketamine, a rapid-onset antidepressant. Compared with controls, MISS females exhibited decreased c-Fos activation in their anterior cingulate cortex, prefrontal cortex, nucleus accumbens and some other depression-related brain regions. Furthermore, 24 h after the last exposure to the paradigm, MISS mice demonstrated a decreased center zone time in the open field test and decreased open arm time in the elevated plus-maze test, indicating anxiety-like behavioral phenotypes. Interestingly, MISS mice developed an excessive nesting ability, suggesting a likely behavioral phenotype of obsessive-compulsive disorder. These data showed that the MISS paradigm was sufficient to generate pathological profiles in female mice to mimic core symptoms, serum biochemistry and neural adaptations of depression in clinical patients. The present study offers a multiple integrated natural etiology-based animal model tool for studying female stress susceptibility.

Targeting mTOR/YY1 signaling pathway by quercetin through CYP7A1-mediated cholesterol-to-bile acids conversion alleviated type 2 diabetes mellitus induced hepatic lipid accumulation

BACKGROUND

Hepatic lipid accumulation was a major promoter for the further development of non-alcoholic fatty liver disease (NAFLD) in type 2 diabetes (T2DM). mTOR/YY1 signaling pathway regulated many metabolic processes in different organs, and played an important role in hepatic lipid metabolism. Thus, targeting mTOR/YY1 signaling pathway might be a novel therapeutic strategy of T2DM-associated NALFD.

PURPOSE

To investigate the effects and the mechanism of quercetin against T2DM-associated NAFLD.

STUDY DESIGN AND METHODS

The combine abilities of 24 flavonoid compounds with mTOR were detected by computer virtual screening (VS) and molecular modeling. mTOR/YY1 signaling pathway was examined in the liver of db/db mice, and high glucose (HG) and free fatty acid (FFA) co-cultured HepG2 cells. YY1 overexpression lentivirus vector and mTOR specific inhibitor rapamycin were used to further identify the indispensable role of mTOR/YY1 signaling pathway in quercetin's amelioration effect of hepatic lipid accumulation in vitro. Clinical studies, luciferase assay and chromatin immunoprecipitation (ChIP) assay were all carried out to investigate the potential mechanisms by which quercetin exerted its amelioration effect of hepatic lipid accumulation.

RESULTS

Quercetin had the strongest ability to combine with mTOR and could competitively occupy its binding pocked. Along with the alleviated hepatic injury by quercetin, mTOR/YY1 signaling pathway was down-regulated in vivo and in vitro. However, the alleviation effect of quercetin against hepatic lipid accumulation was inhibited by YY1 overexpression in vitro. Mechanistically, the down-regulated nuclear YY1 induced by quercetin directly bound to CYP7A1 promoter and activated its transcription, resulting in the restoration of cholesterol homeostasis via the conversion of cholesterol-to-bile acids (BAs).

CONCLUSION

The hepatoprotective effect of quercetin on T2DM-associated NAFLD was linked to the restoration of cholesterol homeostasis by the conversion of cholesterol-to-BAs via down-regulating mTOR/YY1 signaling pathway, leading to the increased CYP7A1 activity.

Exploration of the Core Pathways and Potential Targets of Luteolin Treatment on Late-Onset Depression Based on Cerebrospinal Fluid Proteomics

Cognitive deficiency is one of the fundamental characteristics of late-onset depression (LOD). Luteolin (LUT) possesses antidepressant, anti-aging, and neuroprotective properties, which can dramatically enhance cognition. The altered composition of cerebrospinal fluid (CSF), which is involved in neuronal plasticity and neurogenesis, directly reflects the physio-pathological status of the central nervous system. It is not well known whether the effect of LUT on LOD is in association with a changed CSF composition. Therefore, this study first established a rat model of LOD and then tested the therapeutic effects of LUT using several behavioral approaches. A gene set enrichment analysis (GSEA) was used to evaluate the CSF proteomics data for KEGG pathway enrichment and Gene Ontology annotation. We combined network pharmacology and differentially expressed proteins to screen for key GSEA-KEGG pathways as well as potential targets for LUT therapy for LOD. Molecular docking was adopted to verify the affinity and binding activity of LUT to these potential targets. The outcomes demonstrated that LUT improved the cognitive and depression-like behaviors in LOD rats. LUT may exert therapeutic effects on LOD through the axon guidance pathway. Five axon guidance molecules-EFNA5, EPHB4, EPHA4, SEMA7A, and NTNG-as well as UNC5B, L1CAM, and DCC, may be candidates for the LUT treatment of LOD.

Antidepressant-Like Effects of Edaravone and Minocycline: Investigation of Oxidative Stress, Neuroinflammation, Neurotrophic, and Apoptotic Pathways

Depression is a very common mental disorder and mechanism that is associated with mitochondrial dysfunction. In the present study, we examined the mechanisms of action of isolated brain mitochondria in rats with depression for the first time. This will help identify the mitochondrial protective pathways of the two drugs and shed light on new therapeutic goals for developing antidepressants. Forced swimming, tail suspension, and sucrose preference tests were used to assess depressive-like behaviors and the oxidative stress factors of brain tissue, and measure the gene expression of apoptotic and anti-apoptotic, neuroplasticity, and neuroinflammatory factors by RT-PCR and acetylcholinesterase (AChE) activity in brain tissue (hippocampus and prefrontal) and the serum levels of corticosterone and fasting blood sugar. The results showed that the separation of neonatal rats from their mothers induced depressive-like behaviors, weight loss, mitochondrial dysfunction, increased expression of genes involved in neuroinflammation, apoptosis, genes involved in the depressive process, and decreased expression of genes involved in mood in both the hippocampus and prefrontal cortex. Maternal separation increased serum corticosterone levels, caused dysfunction of the cholinergic system, and also increased AChE activity. Treatment with different concentrations of minocycline and edaravone (1, 20, and 50 mg/kg), 5MTHF, and citalopram for 14 days showed that these drugs improved depression-like behaviors and mitochondrial function. It also reduced the expression of genes involved in neuroinflammation, apoptosis, and depression and increased the expression of genes involved in mood. In conclusion, minocycline and edaravone have neuroprotective, mitochondrial protective, antioxidant, anti-inflammatory, and anti-apoptotic effects against depressive-like behaviors caused by chronic stress.

Noise Induced Depression-Like Behavior, Neuroinflammation and Synaptic Plasticity Impairments: The Protective Effects of Luteolin

Noise is a kind of sound that causes agitation and harms human health. Studies have shown that noise can lead to neuroinflammation, damage to synaptic plasticity and altered levels of neurotransmitters that may result in depression. The present study demonstrated that luteolin exerted antidepressant-like effects by improving neuroinflammation in a mouse model of noise-induced depression. Luteolin significantly alleviated noise-induced depression-like behavior. Notably, luteolin treatment not only remarkably ameliorated noise-induced inflammation in the hippocampus and prefrontal cortex, but also increased synapsin. Furthermore, luteolin treatment significantly increased the contents of serum 5-hydroxytryptamine and norepinephrine in noise-induced mice. In sum, luteolin exerts antidepressant effects indepression-like mice caused by noise, which can serve as a potential agent for the treatment of chronic noise-induced depression.

Behaviors Related to Psychiatric Disorders and Pain Perception in C57BL/6J Mice During Different Phases of Estrous Cycle

Robust sex difference among humans regarding psychiatry- and pain-related behaviors is being researched; however, the use of female mice in preclinical research is relatively rare due to an unchecked potential behavioral variation over the estrous cycle. In the present study, a battery of psychiatry- and pain-related behaviors are examined under physiological condition in female C57BL/6J mice over different estrous cycle phases: proestrus, estrous, metestrous, diestrous. Our behavioral results reveal that there is no significant difference over different phases of the estrous cycle in social interaction test, sucrose preference test, tail suspension test, open field test, marble burying test, novelty-suppressed feeding test, Hargreaves thermal pain test, and Von Frey mechanical pain test. These findings implicate those psychiatry- and pain-related behaviors in normal female C57BL/6J mice appear to be relatively consistent throughout the estrous cycle; the estrous cycle might not be a main contributor to female C57BL/6J mice’s variability of behaviors.

Neuroprotective effects of flavone luteolin in neuroinflammation and neurotrauma

Neuroinflammation leads to neurodegeneration, cognitive defects, and neurodegenerative disorders. Neurotrauma/traumatic brain injury (TBI) can cause activation of glial cells, neurons, and neuroimmune cells in the brain to release neuroinflammatory mediators. Neurotrauma leads to immediate primary brain damage (direct damage), neuroinflammatory responses, neuroinflammation, and late secondary brain damage (indirect) through neuroinflammatory mechanism. Secondary brain damage leads to chronic inflammation and the onset and progression of neurodegenerative diseases. Currently, there are no effective and specific therapeutic options to treat these brain damages or neurodegenerative diseases. Flavone luteolin is an important natural polyphenol present in several plants that show anti-inflammatory, antioxidant, anticancer, cytoprotective, and macrophage polarization effects. In this short review article, we have reviewed the neuroprotective effects of luteolin in neurotrauma and neurodegenerative disorders and pathways involved in this mechanism. We have collected data for this study from publications in the PubMed using the keywords luteolin and mast cells, neuroinflammation, neurodegenerative diseases, and TBI. Recent reports suggest that luteolin suppresses systemic and neuroinflammatory responses in Coronavirus disease 2019 (COVID-19). Studies have shown that luteolin exhibits neuroprotective effects through various mechanisms, including suppressing immune cell activation, such as mast cells, and inflammatory mediators released from these cells. In addition, luteolin can suppress neuroinflammatory response, activation of microglia and astrocytes, oxidative stress, neuroinflammation, and the severity of neuroinflammatory diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, and TBI pathogenesis. In conclusion, luteolin can improve cognitive decline and enhance neuroprotection in neurodegenerative diseases, TBI, and stroke.

Luteolin delays photoreceptor degeneration in a mouse model of retinitis pigmentosa

Luteolin is neuroprotective for retinal ganglion cells and retinal pigment epithelial cells after oxidative injury, whereby it can inhibit microglial neurotoxicity. Therefore, luteolin holds the potential to be useful for treatment of retinal diseases. The purpose of this study was to investigate whether luteolin exhibits neuroprotective effects on rod cells in rd10 mice, a slow photoreceptor-degenerative model of retinitis pigmentosa. Luteolin (100 mg/kg) intraperitoneally injected daily from postnatal day 14 (P14) to P25 significantly enhanced the visual performance and retinal light responses of rd10 mice at P25. Moreover, it increased the survival of photoreceptors and improved retinal structure. Mechanistically, luteolin treatment attenuated increases in reactive oxygen species, photoreceptor apoptosis, and reactive gliosis; increased mRNA levels of anti-inflammatory cytokines while lowering that of pro-inflammatory and chemoattractant cytokines; and lowered the ratio of phospho-JNK/JNK. Application of the JNK inhibitor SP600125 exerted a similar protective effect to luteolin, suggesting that luteolin delays photoreceptor degeneration and functional deterioration in rd10 mice through regulation of retinal oxidation and inflammation by inhibiting the JNK pathway. Therefore, luteolin may be useful as a supplementary treatment for retinitis pigmentosa. This study was approved by the Qualified Ethics Committee of Jinan University, China (approval No. IACUC-20181217-02) on December 17, 2018.

Diosmetin Mitigates Cognitive and Memory Impairment Provoked by Chronic Unpredictable Mild Stress in Mice

Materials and Methods

In the present experimental study, male NMRI mice were exposed to chronic unpredictable mild stress (CUMS) paradigm for 35 days. Diosmetin (at doses of 10, 20, and 40 mg/kg. i.p.) or diosmetin solvent (normal saline + DMSO, 1 ml/kg; i.p.) was administered 30 min before stress induction. After 28 days, memory and cognitive performance were assessed by shuttle box and novel object recognition tests. Finally, antioxidant capacity (FRAP) and malondialdehyde (MDA) level of serum and brain, and serum corticosterone level were evaluated.

Results

Behavioral tests showed that CUMS significantly reduced the secondary latency in passive avoidance memory test and diagnosis index in novel object recognition test compared to the control group (P < 0.001), whereas treatment with diosmetin (20 and 40 mg/kg) significantly improved memory performance in the two tests (P < 0.001). In addition, diosmetin (40 mg/kg) could pronouncedly suppress increase in serum corticosterone levels, reduction in antioxidant capacity, and production of excess MDA caused by CUMS compared to the control group (P < 0.01, P < 0.001, and P < 0.001, respectively).

Conclusion

Chronic stress can impair memory and cognition and treatment with diosmetin can partly improve this disorder in male mice by increasing the antioxidant capacity of brain tissue and serum and improving serum corticosterone levels.

Galantamine improves cognition, hippocampal inflammation, and synaptic plasticity impairments induced by lipopolysaccharide in mice

BACKGROUND

Neuroinflammation plays an important role in the onset and progression of neurodegenerative diseases such as Alzheimer's disease. Lipopolysaccharide (LPS, endotoxin) levels are higher in the brains of Alzheimer's disease patients and are associated with neuroinflammation and cognitive decline, while neural cholinergic signaling controls inflammation. This study aimed to examine the efficacy of galantamine, a clinically approved cholinergic agent, in alleviating LPS-induced neuroinflammation and cognitive decline as well as the associated mechanism.

METHODS

Mice were treated with galantamine (4 mg/kg, intraperitoneal injection) for 14 days prior to LPS exposure (intracerebroventricular injection). Cognitive tests were performed, including the Morris water maze and step-through tests. mRNA expression of the microglial marker (CD11b), astrocytic marker (GFAP), and pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) were examined in the hippocampus by quantitative RT-PCR. The inflammatory signaling molecule, nuclear factor-kappa B (NF-κB p65), and synapse-associated proteins (synaptophysin, SYN, and postsynaptic density protein 95, PSD-95) were examined in the hippocampus by western blotting. Furthermore, NF-κB p65 levels in microglial cells and hippocampal neurons were examined in response to LPS and galantamine.

RESULTS

Galantamine treatment prevented LPS-induced deficits in spatial learning and memory as well as memory acquisition of the passive avoidance response. Galantamine decreased the expression of microglia and astrocyte markers (CD11b and GFAP), pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α), and NF-κB p65 in the hippocampus of LPS-exposed mice. Furthermore, galantamine ameliorated LPS-induced loss of synapse-associated proteins (SYN and PSD-95) in the hippocampus. In the in vitro study, LPS increased NF-κB p65 levels in microglia (BV-2 cells); the supernatant of LPS-stimulated microglia (Mi-sup), but not LPS, decreased the viability of hippocampal neuronal cells (HT-22 cells) and increased NF-κB p65 levels as well as expression of pro-inflammatory cytokines (IL-1β, IL-6) in HT-22 cells. Importantly, galantamine reduced the inflammatory response not only in the BV-2 microglia cell line, but also in the HT-22 hippocampal neuronal cell line.

CONCLUSIONS

These findings indicate that galantamine could be a promising treatment to improve endotoxin-induced cognitive decline and neuroinflammation in neurodegenerative diseases.

Luteolin rescues pentylenetetrazole-induced cognitive impairment in epileptic rats by reducing oxidative stress and activating PKA/CREB/BDNF signaling

Most antiepileptic drugs (AEDs) interfere with cognitive function, and there is therefore an urgent need for AEDs that are effective but do not have this side effect. Various studies have reported the antiinflammatory and cytoprotective properties of the natural flavonoid luteolin (LU); however, none has examined systematically its antiseizure potential. The current study investigated the effects of LU on pentylenetetrazole (PTZ)-induced cognitive impairment in rats and the underlying mechanisms. Seizures were induced in rats by daily injection of PTZ for 36 days. Two other groups were pretreated with LU (50 or 100 mg/kg/day by oral administration) 30 min prior to PTZ administration. Seizure severity was scored, and cognitive function was tested in the Morris water maze. Neuronal damage, mitochondrial generation of reactive oxygen species, oxidative stress, phosphoactivation of the protein kinase A (PKA)-cyclic AMP response element-binding protein (CREB) pathway, and brain-derived neurotrophic factor (BDNF) expression were measured in the hippocampus. Pretreatment with LU suppressed seizure induction, duration, and severity following PTZ injection, reversed cognitive impairment, reduced neuronal and oxidative stress damage, and increased phosphoactivation of PKA and CREB as well as BDNF expression. These results indicate that LU should be further investigated as a treatment for epilepsy.

Neuroprotection of luteolin against methylmercury-induced toxicity in lobster cockroach Nauphoeta cinerea

Luteolin (3', 4', 5, 7-tetrahydroxyflavone) is a polyphenolic compound found in foods of plant origin and has been reported to possess antioxidant and neuroprotective properties. However, there is dearth of information on the beneficial effects of luteolin on methylmercury (MeHg), a long-established neurotoxic compound in animals and humans. This study evaluated the effect of luteolin on MeHg-induced behavioral and biochemical deficits, using lobster cockroach Nauphoeta cinerea as an alternative and complementary animal model. The insects were exposed for 35 consecutive days to either MeHg alone (0.05 mg/g feed) or in combination with luteolin at 0.25, 0.5 and 1.0 mg/g feed. Locomotor behavior was assessed using video-tracking software during a 10-min trial in a novel arena and subsequently, biochemical analyses were carried out using the cockroaches' heads. Luteolin supplementation dose-dependently reversed the MeHg-induced locomotor deficits and enhanced the exploratory profiles of MeHg-exposed cockroaches as confirmed by track and occupancy plot analyses. Luteolin reversed the MeHg-induced acetylcholinesterase activity inhibition, decreased dichlorofluorescein oxidation and lipid peroxidation levels, but increased total thiol level and catalase and glutathione S-transferase activities in the treated cockroaches. In conclusion, luteolin prevented oxidative stress indices and neurobehavioral deficits in a Nauphoeta cinerea model of MeHg toxicity.

Protective effect of the orientin on noise-induced cognitive impairments in mice

There is increasing evidence that chronic noise stress impairs cognition and induces oxidative stress in the brain. Recently, orientin, a phenolic compound abundant in some fruits, millet, and herbs, has been shown to have antioxidant properties. This study investigated the potential effects of orientin against chronic noise-induced cognitive decline and its underlying mechanisms. A moderate-intensity noise exposure model was used to investigate the effects of orientin on behavior and biochemical alterations in mice. After 3 weeks of the noise exposure, the mice were treated with orientin (20mg/kg and 40 mg/kg, oral gavage) for 3 weeks. The chronic noise exposure impaired the learning and memory in mice in the Morris water maze and step-through tests. The noise exposure also decreased exploration and interest in a novel environment in the open field test. The administration of orientin significantly reversed noise-induced alterations in these behavior tests. Moreover, the orientin treatment significantly improved the noise-induced alteration of serum corticosterone and catecholamine levels and oxidative stress in the hippocampus and prefrontal cortex. Furthermore, the orientin treatment ameliorated the noise-induced decrease in brain-derived neurotrophic factor and synapse-associated proteins (synaptophysin and postsynaptic density protein 95) in the hippocampus and prefrontal cortex. Thus, orientin exerts protective effects on noise-induced cognitive decline in mice, specifically by improving central oxidative stress, neurotransmission, and increases synapse-associated proteins. Therefore, supplementation with orientin-enriched food or fruit could be beneficial as a preventive strategy for chronic noise-induced cognitive decline.