A polymethoxy flavonoids-rich Citrus aurantium extract ameliorates ethanol-induced liver injury through modulation of AMPK and Nrf2-related signals in a binge drinking mouse model

Determination of eleven components in rat plasma by UPLC-MS/MS and GC-MS for pharmacokinetic studies after oral administration of Citri Reticulatae Pericarpium extract

Citri Reticulatae Pericarpium (CRP) is used as common health-care food and traditional Chinese medicine (TCM), which exerts pharmacological effects, such as anti-cardiovascular, anti-tumor, anti-oxidant, anti-inflammatory, anti-virus, hepatoprotective, blood pressure-lowering and neuroprotective. In this study, reliable, and sensitive ultra-high performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) methods were developed and validated for the determination of eleven active components in rat plasma after oral administration of the CRP extract. The results of this method exhibited that the specificity, linearity (r > 0.999), precision and accuracy (the coefficient of variation (CV) < 11.5 %), recovery (52.9-107.9 %), matrix effects (63.8-107.5 %), and stability (CV < 10.8 %) met all requirements for the quantitation of plasma samples. The pharmacokinetic results showed that the Tmax of flavone glycosides was less than 0.7 h, and that of polymethoxyflavones and volatile components were within 1-7 h. Meanwhile, the area-under-the-curve (AUC) and concentration maximum (Cmax) of hesperidin, nobiletin, tangeretin, and D-limonene were higher than those of the other components, suggesting that the plasma exposure levels of these constituents were higher in CRP. The present research lays a foundation for elucidating the therapeutic material basis and provides a reference for further scientific research and clinical application of CRP.

Nobiletin Protects Against Alcoholic Liver Disease in Mice via the BMAL1-AKT-Lipogenesis Pathway

SCOPE

Alcoholic liver disease (ALD) is a global public health concern. Nobiletin, a polymethoxyflavone abundant in citrus fruits, enhances circadian rhythms and ameliorates diet-induced hepatic steatosis, but its influences on ALD are unknown. This study investigates the role of brain and muscle Arnt-like protein-1 (Bmal1), a key regulator of the circadian clock, in nobiletin-alleviated ALD.

METHODS AND RESULTS

This study uses chronic ethanol feeding plus an ethanol binge to establish ALD models in Bmal1flox/flox and Bmal1 liver-specific knockout (Bmal1LKO) mice. Nobiletin mitigates ethanol-induced liver injury (alanine aminotransferase [ALT]), glucose intolerance, hepatic apoptosis, and lipid deposition (triglyceride [TG], total cholesterol [TC]) in Bmal1flox/flox mice. Nobiletin fails to modulated liver injury (ALT, aspartate aminotransferase [AST]), apoptosis, and TG accumulation in Bmal1LKO mice. The expression of lipogenic genes (acetyl-CoA carboxylase alpha [Acaca], fatty acid synthase [Fasn]) and fatty acid oxidative genes (carnitine pamitoyltransferase [Cpt1a], cytochrome P450, family 4, subfamily a, polypeptide 10 [Cyp4a10], and cytochrome P450, family4, subfamily a, polypeptide 14 [Cyp4a14]) is inhibited, and the expression of proapoptotic genes (Bcl2 inteacting mediator of cell death [Bim]) is enhanced by ethanol in Bmal1flox/flox mice. Nobiletin antagonizes the expression of these genes in Bmal1flox/flox mice and not in Bmal1LKO mice. Nobiletin activates protein kinase B (PKB, also known as AKT) phosphorylation, increases the levels of the carbohydrate response element binding protein (ChREBP), ACC1, and FASN, and reduces the level of sterol-regulatory element binding protein 1 (SREBP1) and phosphorylation of ACC1 in a Bmal1-dependent manner.

CONCLUSION

Nobiletin alleviates ALD by increasing the expression of genes involved in fatty acid oxidation by increasing AKT phosphorylation and lipogenesis in a Bmal1-dependent manner.

Flavonoids from citrus peel display potential synergistic effects on inhibiting rumen methanogenesis and ammoniagenesis: a microbiome perspective

Flavonoids have been recognized as potential phytochemicals to reduce enteric methane (CH4) production and improve rumen nitrogen efficiency in ruminants. We evaluated whether naringin, hesperidin, their combination, or a mixed citrus flavonoid extract (CFE) as additives can inhibit methanogenesis and ammoniagenesis in dairy cows using an in vitro rumen batch refermentation system. The rumen inocula from dairy cows were incubated in batch cultures with five groups: no addition (CON), hesperidin (20 g/kg DM), naringin (20 g/kg DM), hesperidin + naringin (10 g/kg DM of hesperidin + 10 g/kg DM of naringin), and CFE (20 g/kg DM). The combination of naringin plus hesperidin and CFE achieved greater reductions in CH4 and ammonia production compared to either naringin or hesperidin alone. Microbiome analysis revealed that the decrease in CH4 emissions may have been caused by both the direct inhibitory impact of citrus flavonoids on Methanobrevibacter and a simultaneous decrease in protozoa Isotricha abundance. The relatively lower proportion of Entodinium in naringin plus hesperidin or CFE was responsible for the lower ammonia concentration. These results suggest that citrus flavonoids possess potential synergistic effects on mitigating ruminal CH4 emissions by cows and improving nitrogen utilization.

Nobiletin from citrus peel: a promising therapeutic agent for liver disease-pharmacological characteristics, mechanisms, and potential applications

Nobiletin (NOB) is a flavonoid derived from citrus peel that has potential as an alternative treatment for liver disease. Liver disease is a primary health concern globally, and there is an urgent need for effective drugs. This review summarizes the pharmacological characteristics of NOB and current in vitro and in vivo studies investigating the preventive and therapeutic effects of NOB on liver diseases and its potential mechanisms. The findings suggest that NOB has promising therapeutic potential in liver diseases. It improves liver function, reduces inflammation and oxidative stress, remodels gut microflora, ameliorates hepatocellular necrosis, steatosis, and insulin resistance, and modulates biorhythms. Nuclear factor erythroid 2-related factor 2 (Nrf2), nuclear transcription factor kappa (NF-κB), AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor α(PPAR-α), extracellular signal-regulated kinase (ERK), protein kinase B (AKT), toll-like receptor 4 (TLR4) and transcription factor EB (TFEB) signaling pathways are important molecular targets for NOB to ameliorate liver diseases. In conclusion, NOB may be a promising drug candidate for treating liver disease and can accelerate its application from the laboratory to the clinic. However, more high-quality clinical trials are required to validate its efficacy and identify its molecular mechanisms and targets.

Brain and serum metabolomic studies reveal therapeutic effects of san hua decoction in rats with ischemic stroke

San Hua Decoction (SHD) is a traditional four-herbal formula that has long been used to treat stroke. Our study used a traditional pharmacodynamic approach combined with systematic and untargeted metabolomics analyses to further investigate the therapeutic effects and potential mechanisms of SHD on ischemic stroke (IS). Male Sprague-Dawley rats were randomly divided into control, sham-operated, middle cerebral artery occlusion reperfusion (MCAO/R) model and SHD groups. The SHD group was provided with SHD (7.2 g/kg, i.g.) and the other three groups were provided with equal amounts of purified water once a day in the morning for 10 consecutive days. Our results showed that cerebral infarct volumes were reduced in the SHD group compared with the model group. Besides, SHD enhanced the activity of SOD and decreased MDA level in MCAO/R rats. Meanwhile, SHD could ameliorate pathological abnormalities by reducing neuronal damage, improving the structure of damaged neurons and reducing inflammatory cell infiltration. Metabolomic analysis of brain and serum samples with GC-MS techniques revealed 55 differential metabolites between the sham and model groups. Among them, the levels of 12 metabolites were restored after treatment with SHD. Metabolic pathway analysis showed that SHD improved the levels of 12 metabolites related to amino acid metabolism and carbohydrate metabolism, 9 of which were significantly associated with disease. SHD attenuated brain inflammation after ischemia-reperfusion. The mechanisms underlying the therapeutic effects of SHD in MCAO/R rats are related to amino acid and carbohydrate metabolism.

Citri Reticulatae Pericarpium (Chenpi): A multi-efficacy pericarp in treating cardiovascular diseases

Citri Reticulatae Pericarpium (CRP) has been utilized as a versatile medicinal herb with wide cardiovascular benefits in Asian nations for centuries. Accumulating evidence suggests that CRP and its components are effective in preventing cardiovascular diseases (CVDs) such as atherosclerosis, myocardial infarction, myocardial ischemia, arrhythmia, cardiac hypertrophy, heart failure, and hypertension. Studies show that the two most bioactive components of CRP are flavonoids and volatile oils. The cardiovascular protective effects of CRP have attracted considerable research interest due to its hypolipidemic, antiplatelet activity, antioxidant and anti-inflammatory effects. Hereby, we provide a rigorous and up-to-date overview of the cardiovascular protective properties and the potential molecular targets of CRP, and finally highlight the pharmacokinetics and the therapeutic potential of the main pharmacologically active components of CRP to treat CVDs.

Identification of hepatoprotective traditional Chinese medicines based on the structure–activity relationship, molecular network, and machine learning techniques

The efforts focused on discovering potential hepatoprotective drugs are critical for relieving the burdens caused by liver diseases. Traditional Chinese medicine (TCM) is an important resource for discovering hepatoprotective agents. Currently, there are hundreds of hepatoprotective products derived from TCM available in the literature, providing crucial clues to discover novel potential hepatoprotectants from TCMs based on predictive research. In the current study, a large-scale dataset focused on TCM-induced hepatoprotection was established, including 676 hepatoprotective ingredients and 205 hepatoprotective TCMs. Then, a comprehensive analysis based on the structure–activity relationship, molecular network, and machine learning techniques was performed at molecular and holistic TCM levels, respectively. As a result, we developed an in silico model for predicting the hepatoprotective activity of ingredients derived from TCMs, in which the accuracy exceeded 85%. In addition, we originally proposed a material basis and a drug property-based approach to identify potential hepatoprotective TCMs. Consequently, a total of 12 TCMs were predicted to hold potential hepatoprotective activity, nine of which have been proven to be beneficial to the liver in previous publications. The high rate of consistency between our predictive results and the literature reports demonstrated that our methods were technically sound and reliable. In summary, systematical predictive research focused on the hepatoprotection of TCM was conducted in this work, which would not only assist screening of potential hepatoprotectants from TCMs but also provide a novel research mode for discovering the potential activities of TCMs.

Monkfish Peptides Mitigate High Fat Diet-Induced Hepatic Steatosis in Mice

Non-alcoholic fatty liver disease (NAFLD) is a hepatic metabolic syndrome usually accompanied by fatty degeneration and functional impairment. The aim of the study was to determine whether monkfish peptides (LPs) could ameliorate high-fat diet (HFD)-induced NAFLD and its underlying mechanisms. NAFLD was induced in mice by giving them an HFD for eight weeks, after which LPs were administered in various dosages. In comparison to the HFD control group: body weight in the LP-treated groups decreased by 23–28%; triacylglycerol levels in the blood decreased by 16–35%; and low-density lipoproteins levels in the blood decreased by 23–51%. Additionally, we found that LPs elevated the activity of hepatic antioxidant enzymes and reduced the inflammatory reactions within fatty liver tissue. Investigating the effect on metabolic pathways, we found that in LP-treated mice: the levels of phospho-AMP-activated protein kinase (p-AMPK), and phospho-acetyl CoA carboxylase (p-ACC) in the AMP-activated protein kinase (AMPK) pathway were up-regulated and the levels of downstream sterol regulatory element-binding transcription factor 1 (SREBP-1) were down-regulated; lipid oxidation increased and free fatty acid (FFA) accumulation decreased (revealed by the increased carnitine palmitoyltransferase-1 (CPT-1) and the decreased fatty acid synthase (FASN) expression, respectively); the nuclear factor erythroid-2-related factor 2 (Nrf2) antioxidant pathway was activated; and the levels of heme oxygenase-1 (HO-1) and nicotinamide quinone oxidoreductase 1 (NQO1) were increased. Overall, all these findings demonstrated that LPs can improve the antioxidant capacity of liver to alleviate NAFLD progression mainly through modulating the AMPK and Nrf2 pathways, and thus it could be considered as an effective candidate in the treatment of human NAFLD.

Preventive Effect of Flavonoid Extract from the Peel of Gonggan (Citrus reticulata Blanco Var. Gonggan) on CCl4-Induced Acute Liver Injury in Mice

Objective

Citrus peel, a waste product of citrus consumption and processing, is rich in flavonoids. This study aimed to study the protective effect of flavonoid extract from the peel of gonggan (Citrus reticulata Blanco var. gonggan) on acute chemical liver injury.

Materials and Methods

We established a chemical liver injury model induced by carbon tetrachloride (CCl₄) in mice. The flavonoid composition in gonggan (Citrus reticulata Blanco var. gonggan) peel was detected by HPLC. The histopathological sections of liver, related biochemical indicators in serum and liver, and related genes were examined to evaluate the protective effect of gonggan peel flavonoid extract (GPFE).

Results

The results showed that GPFE contained narirutin, hesperidin, nobiletin, tangeretin, and 5-demethylnobiletin. After 14 days of intragastric administration of GPFE, the result showed GPFE could reduce the increase in liver index, serum alanine aminotransferase (ALT), and aspartate transaminase (AST) levels caused by CCl₄. At the same time, pathological sections of liver confirmed that GPFE alleviated the damage to liver tissue. Moreover, biochemical indicator results showed that GPFE increased the activities of superoxide dismutase (SOD) and catalase (CAT) in liver tissue and reduced the content of malondialdehyde (MDA). Also, it reduced the levels of inflammation factors: tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin (IL)-1β, and IL-6. In addition, q-PCR results showed that GPFE upregulated mRNA expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2), copper/zinc superoxide dismutase (SOD1), manganese superoxide dismutase (SOD2), glutathione peroxidase (GSH-Px), γ-glutamylcysteine synthetase (γ-GCS), CAT, and downregulated IL-6 and TNF-α mRNA expression levels. The mechanism of GPFE may be related to the inhibition of oxidative stress and inflammation.

Conclusion

The experiment indicates GPFE has a good protective effect on acute chemical liver injury in mice induced by CCl₄ via antioxidant and anti-inflammatory pathways.

Telmisartan alleviates alcohol-induced liver injury by activation of PPAR-γ/ Nrf-2 crosstalk in mice

Excessive consumption of alcohol may induce severe liver damage, in part via oxidative stress and inflammatory responses, which implicates these processes as potential therapeutic approaches. Prior literature has shown that Telmisartan (TEL) may provide protective effects, presumably mediated by its anti-oxidant and anti-inflammatory activities. The purpose of this study was to determine TEL's hepatoprotective effects and to identify its possible curative mechanisms in alcoholic liver disease. A mouse chronic alcohol plus binge feedings model was used in the current study for induction of alcoholic liver disease (ALD). Our results showed that TEL (10 mg/kg/day) has the ability to reduce serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP). TEL also increased the activity of superoxide dismutase (SOD) and glutathione (GSH) with concomitant reduction of nitric oxide (NO) malonaldehyde (MDA) in the liver homogenate. Moreover, TEL downregulated nuclear factor kappa B (NF-κB) expression and decreased liver content of interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α). These anti-inflammatory and anti-oxidant activities were associated with a significant increase in the expression of nuclear factor erythroid 2-related factor 2 (Nrf-2), peroxisome proliferator-activated receptors -γ (PPAR-γ), and heme oxygenase-1 (Hmox-1). In conclusion, TEL's hepatoprotective effects against ALD may be attributable to its anti-inflammatory and anti-oxidant activities which may be in part via the modulation of PPAR-γ/ Nrf-2/ NF-κB crosstalk.

Citrus peel derived' Poly-Methoxylated Flavones (PMF)

The prevalence of obesity has increased substantially over the last several decades and several environmental factors have accelerated this trend. Poly-methoxy flavones (PMFs) exist abundantly in the peels of citrus, and their biological activities have been broadly examined in recent years. Several studies have examined the effects of PMFs on obesity and its-related diseases. This systematic review conducted to focus on the effect of PMFs on obesity and its related conditions management. The PubMed, Google Scholar, Scopus, and Science Direct databases were searched for relevant studies published before November 2020. Out of 1,615 records screened, 16 studies met the study criteria. The range of dosage of PMFs was varied from 10 to 200 mg/kg (5-26 weeks) and 1-100 μmol (2h-8 days) across selected animal and in vitro studies, respectively. The literature reviewed shows that PMFs modulate several biological processes associated with obesity such as lipid and glucose metabolism, inflammation, energy balance, and oxidative stress by different mechanisms. All of the animal studies showed significant positive effects of PMFs on obesity by reducing body weight (e.g. reduced weight gain by 21.04%), insulin resistance, energy expenditure, inhibiting lipogenesis and reduced blood lipids (e.g. reduced total cholesterol by 23.10%, TG by 44.35% and LDL by 34.41%). The results of the reviewed in vitro studies have revealed that treatment with PMFs significantly inhibits lipid accumulation in adipocytes (e.g. reduced lipid accumulation by 55-60%) and 3T3-L1 pre-adipocyte differentiation as well by decreasing the expression of PPARγ and C/EBPα and also reduces the number and size of fat cells and reduced TG content in adipocytes by 45.67% and 23.10% and 16.08% for nobiletin, tangeretin and hesperetin, respectively. Although current evidence supports the use of PMFs as a complementary treatment in obesity, future research is needed to validate this promising treatment modality.

Citrus flavonoids and their antioxidant evaluation

The antioxidant ability is the link and bridge connecting a variety of biological activities. Citrus flavonoids play an essential role in regulating oxidative stress and are an important source of daily intake of antioxidant supplements. Many studies have shown that citrus flavonoids promote health through antioxidation. In this review, the biosynthesis, composition and distribution of citrus flavonoids were concluded. The detection methods of antioxidant capacity of citrus flavonoids were divided into four categories: chemical, cellular, animal and clinical antioxidant capacity evaluation systems. The modeling methods, applicable scenarios, and their relative merits were compared based on these four systems. The antioxidant functions of citrus flavonoids under different evaluation systems were also discussed, especially the regulation of the Nrf2-antioxidases pathway. Some shortcomings in the current research were pointed out, and some suggestions for progress were put forward.

Empagliflozin ameliorates ethanol-induced liver injury by modulating NF-κB/Nrf-2/PPAR-γ interplay in mice

BACKGROUND

Excessive alcohol intake contributes to severe liver damage involving oxidative stress and inflammatory responses, which make them promising therapeutic targets. Previous studies have demonstrated that empagliflozin (EMPA) showed cardiovascular, renal, and cerebral benefits potentially mediated through its antioxidant and anti-inflammatory actions.

AIMS

This experiment aimed to evaluate the hepatoprotective effect of EMPA on alcoholic liver disease (ALD) and the possible underlying mechanisms.

MATERIALS AND METHODS

Serum biochemical parameters and the liver contents of malondialdehyde (MDA), nitric oxide (NO), reduced glutathione (GSH), and superoxide dismutase (SOD) were measured. Real-time qPCR was conducted to determine the gene expression of peroxisome proliferator-activated receptor gamma (PPAR-γ), nuclear factor erythroid 2-related factor 2 (Nrf-2), and heme oxygenase-1 (Hmox-1). In addition, ELISA was performed to measure tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, Nrf-2, and PPAR-γ. Nuclear factor-kappa B (NF-κB) was detected by immunohistochemical staining using an anti-NF-κB p65 antibody.

KEY FINDINGS

Our results revealed that the serum levels of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase were significantly reduced by EMPA. EMPA also decreased the content of MDA and NO and increased the activities of SOD and GSH in liver homogenates. Moreover, EMPA inhibited the release of proinflammatory cytokines, including TNF-α, IL-1β, and IL-6, via the downregulation of NF-κB. These changes were associated with an improvement in histopathological deterioration. The protective effect of EMPA against oxidative stress and inflammation was associated with the upregulation of PPAR-γ, Nrf-2, and their target gene Hmox-1.

SIGNIFICANCE

EMPA showed protective activities against ethanol-induced liver injury by suppressing inflammation and oxidative stress via modulation of the NF-κB/Nrf-2/PPAR-γ axis.

Nobiletin Ameliorates NLRP3 Inflammasome-Mediated Inflammation Through Promoting Autophagy via the AMPK Pathway

Multiple lines of evidence have shown that neuroinflammation and autophagy are highly involved in the process of depression. Nobiletin (NOB) displays neuroprotective effects and anti-depressant-like effects. Given the evidence that NOB exerts anti-inflammatory effects and regulates autophagy, we investigate the anti-neuroinflammatory properties and the effect of regulating the autophagy of NOB and subsequently uncover the potential anti-depressant mechanisms of NOB. The behavioral changes of rats were observed after prolonged lipopolysaccharide (LPS) treatment and NOB administration. Rat hippocampus and BV2 cells treated by LPS and NOB were evaluated. The methods of real-time PCR analysis, Western blot, immunostaining, and adenovirus transfection were employed to determine neuroinflammation, autophagic markers, and nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) activation. Our study showed LPS enhanced the expression of pro-inflammatory cytokines and NLRP3 inflammasome activation but inhibited autophagy in both rat hippocampus and BV2 cells. NOB significantly improved the behavioral deficits and ameliorated the neuroinflammation induced by LPS in rats. Furthermore, NOB promoted autophagy and attenuated NLRP3 inflammasome activation induced by LPS, involving in the process the adenosine monophosphate-activated protein kinase (AMPK) pathway. Neuroprotective and anti-depressant actions of NOB relied on its effects of promoting autophagy and suppressing the activation of NLRP3, in which process of AMPK pathway may be involved.

Anti-inflammatory Property of AMP-activated Protein Kinase

BACKGROUND

One of the many debated topics in inflammation research is whether this scenario is really an accelerated form of human wound healing and immunityboosting or a push towards autoimmune diseases. The answer requires a better understanding of the normal inflammatory process, including the molecular pathology underlying the possible outcomes. Exciting recent investigations regarding severe human inflammatory disorders and autoimmune conditions have implicated molecular changes that are also linked to normal immunity, such as triggering factors, switching on and off, the influence of other diseases and faulty stem cell homeostasis, in disease progression and development.

METHODS

We gathered around and collected recent online researches on immunity, inflammation, inflammatory disorders and AMPK. We basically searched PubMed, Scopus and Google Scholar to assemble the studies which were published since 2010.

RESULTS

Our findings suggested that inflammation and related disorders are on the verge and interfere in the treatment of other diseases. AMPK serves as a key component that prevents various kinds of inflammatory signaling. In addition, our table and hypothetical figures may open a new door in inflammation research, which could be a greater therapeutic target for controlling diabetes, obesity, insulin resistance and preventing autoimmune diseases.

CONCLUSION

The relationship between immunity and inflammation becomes easily apparent. Yet, the essence of inflammation turns out to be so startling that the theory may not be instantly established and many possible arguments are raised for its clearance. However, this study might be able to reveal some possible approaches where AMPK can reduce or prevent inflammatory disorders.

Ameliorating effect of Citrus aurantium extracts and nobiletin on β‑amyloid (1‑42)‑induced memory impairment in mice

The aim of the present study was to evaluate the neuroprotective effect of Citrus aurantium extract (CAE) and nobiletin against amyloid β 1‑42 (Aβ 1‑42)‑induced spatial learning and memory impairment in mice. After injecting Aβ 1‑42 (5 µl/2.5 min, intracerebroventricular injection), amnesic mice were orally administered CAE and nobiletin for 28 days. Memory, spatial and cognitive ability were measured using passive avoidance and a Morris water maze task. Acetylcholinesterase (AchE) activity was investigated in the hippocampus and cortex using commercial kits and the analysis of Bax, Bcl‑2, and cleaved caspase‑3 protein expression by western blot assays was used to confirm the anti‑apoptotic mechanism of CAE and nobiletin. The present study confirmed impairments in learning and memory in the Aβ‑induced neurodegenerative mice with increased AchE activity in the brain. However, the daily administration of CAE and nobiletin reduced the spatial learning deficits and increased the AchE activity in the cortex and hippocampus. Furthermore, CAE and nobiletin significantly downregulated the Bax and cleaved caspase‑3 protein expression and upregulated the Bcl‑2 and Bcl‑2/Bax expression in the cortex and hippocampus of Aβ‑treated mice. These results suggest that CAE and nobiletin exert a neuroprotective effect by regulating anti‑apoptotic mechanisms, including reduced AchE activity in the cortex and hippocampus of the cognitive deficit mouse model.

Hepatoprotective effects of an Acer tegmentosum Maxim extract through antioxidant activity and the regulation of autophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Acer tegmentosum Maxim (AT), the East Asian stripe maple, is an herb used to treat liver disease and is approved as a functional food in Korea. AT protects against hepatic disorders, atopic dermatitis, and diabetes mellitus.

AIM OF THE STUDY

We explored the mechanism of the hepatoprotective effects of AT extract in in vitro and in vivo levels.

MATERIALS AND METHODS

AT extract from Acer tegmentosum Maxim was extracted by hot water. Hepatoprotective effects of AT extract were confirmed using carbon tetrachloride (CCl₄)- or alcohol-induced mouse model, and H₂O₂- or alcohol-induced HepG2 (liver hepatocellular carcinoma cell line) cells by measuring GOT, GPT, TG, and MDA levels. Hematoxylin and eosin (H&E) staining was used to observe the pathological analysis. Cytotoxicity or protective effect of AT extract was confirmed using MTT assay in HepG2 cells. Antioxidant effect of AT extract was measured using DPPH or H₂DCFDA assay. Mechanism study of antioxidant and autophagy was carried out using western blotting and immunofluorescence analysis.

RESULTS

AT extract increased the viability of HepG2 cells treated with H₂O₂ and ethanol, and protected the liver against damage induced by CCl₄ and alcohol. The AT extract increased the levels of nuclear respiratory factor 2 (Nrf2) and heme oxygenase-1 (HO-1). The level of microtubule-associated protein light chain 3 (LC3)-Ⅱ, beclin-1, autophagy-related genes (Atg) such as Atg3 and Atg12-5 as markers of autophagy activation was also increased. Moreover, the AT extract increased activation of mitogen-activated protein kinase (MAPK), which regulated autophagy and HO-1.

CONCLUSION

Therefore, these results indicate that the AT extract has a hepatoprotective effect by increasing antioxidant activity and inducing autophagy.

Nobiletin Inhibits IL-1β-Induced Inflammation in Chondrocytes via Suppression of NF-κB Signaling and Attenuates Osteoarthritis in Mice

Osteoarthritis (OA), a common degenerative joint disease, is principally characterized by inflammation and destruction of cartilage. Nobiletin, an extract of the peel of citrus fruits, is known to have anti-inflammatory properties. However, the mechanisms by which nobiletin plays a protective role in osteoarthritis (OA) are not completely understood. In the present study, we investigated the anti-inflammatory effects of nobiletin in the progression of OA in both in vitro and in vivo experiments. Mouse chondrocytes were pretreated with nobiletin (0, 10, 20, 40 μM) for 24 h and then incubated with IL-1β (10 ng/ml, 24 h) in vitro. The generation of PGE2 and NO was evaluated by the Griess reaction and ELISAs. The protein expression of inducible nitric oxide synthase, matrix metalloproteinase-3, matrix metalloproteinase-13, A disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS5), cyclooxygenase-2, collagen II, and aggrecan was analyzed by Western blotting. Immunofluorescence and Western blot analysis were used to detect nuclear factor-κB (NF-κB) signaling molecules. Induction of proinflammatory and catabolic mediators by IL-1β stimulation of mouse chondrocytes could be partially blocked by treatment with nobiletin or ammonium pyrrolidine dithiocarbamate (an NF-κB inhibitor). Furthermore, our results indicated that nobiletin exhibited a therapeutic effect through active inhibition of the NF-κB signaling pathway. In a mouse model of OA, injection of nobiletin (20 mg/kg) every 2 days for 8 weeks after surgery inhibited cartilage destruction and synovitis. Taken together, our findings suggest that nobiletin may be a potential therapeutic agent for the treatment of OA.

Synergistic enhancement and hepatoprotective effect of combination of total phenolic extracts of Citrus aurantium L. and methotrexate for treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune inflammatory disorder characterized by joint destruction and bone damage. Methotrexate (MTX) is recommended as the first-line disease-modifying agent for the treatment of RA. However, the clinical efficacy of MTX is limited due to its low response and side effects, especially hepatotoxicity. Total phenolic extracts of Citrus aurantium L. (TPE-CA) are rich in dietary bioactive flavonoids, which show beneficial effects on liver health and are regarded as therapeutic tools against inflammatory diseases. In this study, the efficacy of MTX, alone or in combination with TPE-CA, for the treatment of collagen-induced arthritis and protection against hepatic injury in rats was investigated. TPE-CA and MTX combination effectively reduced the inflammatory symptoms and joint damage by inhibiting the NF-κB pathway. Moreover, TPE-CA significantly ameliorated MTX-induced chronic hepatic injury by enhancing antioxidant enzymes activities, suppressing hepatic cytochrome P450 2E1 expression, and modulating the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 pathway. This combination regimen not only provided synergistic enhancement but also exhibited hepatoprotective effect against chemically induced chronic hepatotoxicity. This could be an alternative strategy to improve the low response of MTX in RA treatment.

Cilostazol protects hepatocytes against alcohol-induced apoptosis via activation of AMPK pathway

Alcoholic liver disease (ALD) is a worldwide health problem and hepatocyte apoptosis has been associated with the development/progression of ALD. However, no definite effective pharmacotherapy for ALD is currently available. Cilostazol, a selective type III phosphodiesterase inhibitor has been shown to protect hepatocytes from ethanol-induced apoptosis. In the present study, the underlying mechanisms for the protective effects of cilostazol were examined. Primary rat hepatocytes were treated with ethanol in the presence or absence of cilostazol. Cell viability and intracellular cAMP were measured. Apoptosis was detected by Hoechst staining, TUNEL assay, and caspase-3 activity assay. The roles of cAMP and AMP-activated protein kinase (AMPK) pathways in the action of CTZ were explored using pharmacological inhibitors and siRNAs. Liver from mice received ethanol (5 g/kg body weight) by oral gavage following cilostazol treatment intraperitoneally was obtained for measurement of apoptosis and activation of AMPK pathway. Cilostazol inhibited ethanol-induced hepatocyte apoptosis and potentiated the increases in cAMP level induced by forskolin. However, the anti-apoptotic effect of cilostazol was not reversed by an inhibitor of adenylyl cyclase. Interestingly, cilostazol activated AMPK and increased the level of LC3-II, a marker of autophagy. The inhibition of AMPK abolished the effects of cilostazol on LC3-II expression and apoptosis. Moreover, the inhibition of LKB1 and CaMKK2, upstream kinases of AMPK, dampened cilostazol-inhibited apoptosis as well as AMPK activation. In conclusion, cilostazol protected hepatocytes from apoptosis induced by ethanol mainly via AMPK pathway which is regulated by both LKB1 and CaMKK2. Our results suggest that cilostazol may have potential as a promising therapeutic drug for treatment of ALD.

NRF2 mitigates acute alcohol-induced hepatic and pancreatic injury in mice

Binge alcohol drinking is an important health concern and well-known risk factor for the development of numerous disorders. Oxidative stress plays a critical role in the pathogenesis of acute alcoholism. Nuclear factor erythroid 2 like 2 (NRF2) is a master regulator of cellular adaptive response to oxidative insults. However, the role of NRF2 in acute alcoholism and associated pathologies remains unclear. We found that Nrf2-knockout (Nrf2-KO) mice had exaggerated hypoglycemia and hypothermia and increased mortality compared to wildtype mice after binge ethanol exposure. This phenotype was partially rescued by providing warm environment and/or glucose administration. Acute high dose of alcohol exposure resulted in substantially worsened liver and pancreatic injuries in Nrf2-KO mice. Importantly, deficiency of Nrf2 allowed severe pancreatitis and pancreatic β-cell injury with increased insulin secretion and/or leaking during binge ethanol exposure, which contributed to hypoglycemia. In contrast, a clinically used NRF2 activator dimethyl fumarate (DMF) protected against hypoglycemia and lethality induced by acute ethanol exposure. Furthermore, Nrf2-KO mice likely had defective hepatic acetaldehyde metabolism. Taken together, NRF2 plays an important protective role against acute binge alcohol-induced hepatic and pancreatic damage, which may be partially attributable to its primary regulating role in antioxidant response and impact on ethanol metabolism.

Targeting Nrf-2 is a promising intervention approach for the prevention of ethanol-induced liver disease

Alcoholic liver disease (ALD) remains to be a worldwide health problem. It is generally accepted that oxidative stress plays critical roles in the pathogenesis of ALD, and antioxidant therapy represents a logical strategy for the prevention and treatment of ALD. Nuclear factor erythroid-derived 2-like 2 (NFE2L2 or Nrf-2) is essential for the antioxidant responsive element (ARE)-mediated induction of endogenous antioxidant enzymes such as heme oxygenase 1 (HO-1) and glutamate-cysteine ligase [GCL, the rate-limiting enzyme in the synthesis of glutathione (GSH)]. Activation of Nrf-2 pathway by genetic manipulation or pharmacological agents has been demonstrated to provide protection against ALD, which suggests that targeting Nrf-2 may be a promising approach for the prevention and treatment of ALD. Herein, we review the relevant literature about the potential hepatoprotective roles of Nrf-2 activation against ALD.

Nrf2 in alcoholic liver disease

Alcoholic liver disease (ALD) is a leading cause of morbidity and mortality of liver disorders and a major health issue globally. ALD refers to a spectrum of liver pathologies ranging from steatosis, steatohepatitis, fibrosis, cirrhosis and even hepatocellular carcinoma. Various mechanisms, including oxidative stress, protein and DNA modification, inflammation and impaired lipid metabolism, have been implicated in the pathogenesis of ALD. Further, reactive oxygen species (ROS) in particular, have been identified as a key component in the initiation and progression of ALD. Nuclear factor erythroid 2 like 2 (Nrf2) is a master regulator of the intracellular adaptive antioxidant response to oxidative stress, and aids in the detoxification of a variety of toxicants. Given its cytoprotective role, Nrf2 has been extensively studied as a therapeutic target for ALD. Paradoxically, however, emerging evidence have revealed that Nrf2 may be implicated in the progression of ALD. In this review, we summarize the role of Nrf2 in the development of ALD and discuss the underlying mechanisms. Clearly, more comprehensive studies with proper animal and cell models and in human are needed to verify the potential therapeutic role of Nrf2 in ALD.

Nobiletin alleviates endometriosis via down-regulating NF-κB activity in endometriosis mouse model

Nobiletin exhibits protective potential on inflammation and inhibits the activation of transcription factors nuclear factor-κB (NF-κB). However, its effects on the progression of endometriosis remain unsettled. The present study aimed to explore the in vivo alleviation of nobiletin on endometriosis and its mechanism of action. The mouse model of endometriosis was established and administered with nobiletin. The ectopic lesion size was measured and the hotplate test was performed to assess the amelioration of nobiletin on endometriosis. The expression of proliferation and angiogenesis relevant genes including proliferating cell nuclear antigen (PCNA), vascular endothelial growth factor (VEGF), and E-cadherin was measured by immunostaining and the mRNA expression of proinflammatory mediators including interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, matrix metalloproteinases (MMP)-1, and MMP-3 was measured by RT-PCR. The change of NF-κB activity in endometriotic cells was evaluated by Western blotting and confirmed by luciferase assay. Administration of nobiletin significantly reduced lesions size and pain in endometriosis mice. Nobiletin significantly altered the expression of PCNA, VEGF, and E-cadherin in ectopic endometrium, as well as the levels of IL-6, IL-1β, TNF-α, MMP-1, and MMP-3. Nobiletin also showed remarkably impairment on the activation of NF-κB in promoting endometriotic cells, likely targeting on the activity of IκB kinases (IKKs). The present study provides the first evidence that nobiletin exerts protection on endometriosis via inhibition the activation of NF-κB, specifically on the activity of IκB kinases.

An Overview on Citrus aurantium L.: Its Functions as Food Ingredient and Therapeutic Agent

Citrus aurantium L. (Rutaceae), commonly known as bitter orange, possesses multiple therapeutic potentials. These biological credentials include anticancer, antianxiety, antiobesity, antibacterial, antioxidant, pesticidal, and antidiabetic activities. The essential oil of C. aurantium was reported to display marked pharmacological effects and great variation in chemical composition depending on growing locations but mostly contained limonene, linalool, and β-myrcene. Phytochemically, C. aurantium is rich in p-synephrine, an alkaloid, and many health-giving secondary metabolites such as flavonoids. Animal studies have demonstrated a low affinity of p-synephrine for adrenergic receptors and an even lower affinity in human models. The present review focuses on the different biological activities of the C. aurantium in animal and human models in the form of extract and its pure secondary metabolites. Finally, it is concluded that both the extract and isolated compounds have no unwanted effects in human at therapeutic doses and, therefore, can confidently be used in various dietary formulations.

The Potential and Action Mechanism of Polyphenols in the Treatment of Liver Diseases

Liver disease, involving a wide range of liver pathologies from fatty liver, hepatitis, and fibrosis to cirrhosis and hepatocellular carcinoma, is a serious health problem worldwide. In recent years, many natural foods and herbs with abundant phytochemicals have been proposed as health supplementation for patients with hepatic disorders. As an important category of phytochemicals, natural polyphenols have attracted increasing attention as potential agents for the prevention and treatment of liver diseases. The striking capacities in remitting oxidative stress, lipid metabolism, insulin resistance, and inflammation put polyphenols in the spotlight for the therapies of liver diseases. It has been reported that many polyphenols from a wide range of foods and herbs exert therapeutic effects on liver injuries via complicated mechanisms. Therefore, it is necessary to have a systematical review to sort out current researches to help better understand the potentials of polyphenols in liver diseases. In this review, we aim to summarize and update the existing evidence of natural polyphenols in the treatment of various liver diseases by in vitro, in vivo, and clinical studies, while special attention is paid to the action mechanisms.

Safety, Efficacy, and Mechanistic Studies Regarding Citrus aurantium (Bitter Orange) Extract and p-Synephrine

Citrus aurantium L. (bitter orange) extracts that contain p-synephrine as the primary protoalkaloid are widely used for weight loss/weight management, sports performance, appetite control, energy, and mental focus and cognition. Questions have been raised about the safety of p-synephrine because it has some structural similarity to ephedrine. This review focuses on current human, animal, in vitro, and mechanistic studies that address the safety, efficacy, and mechanisms of action of bitter orange extracts and p-synephrine. Numerous studies have been conducted with respect to p-synephrine and bitter orange extract because ephedra and ephedrine were banned from use in dietary supplements in 2004. Approximately 30 human studies indicate that p-synephrine and bitter orange extracts do not result in cardiovascular effects and do not act as stimulants at commonly used doses. Mechanistic studies suggest that p-synephrine exerts its effects through multiple actions, which are discussed. Because p-synephrine exhibits greater adrenergic receptor binding in rodents than humans, data from animals cannot be directly extrapolated to humans. This review, as well as several other assessments published in recent years, has concluded that bitter orange extract and p-synephrine are safe for use in dietary supplements and foods at the commonly used doses. Copyright © 2017 The Authors Phytotherapy Research Published by John Wiley & Sons Ltd.

Effect of nobiletin on the MAPK/NF-κB signaling pathway in the synovial membrane of rats with arthritis induced by collagen

Nobiletin (5,6,7,8,3′,4′-hexamethoxyflavone) is a natural compound in the fruit peel of citrus fruit in the Rutaceae family.

Nobiletin, a citrus flavonoid, activates vasodilator-stimulated phosphoprotein in human platelets through non-cyclic nucleotide-related mechanisms

Nobiletin, a bioactive polymethoxylated flavone, has been described to possess a diversity of biological effects through its antioxidant and anti-inflammatory properties. Vasodilator-stimulated phosphoprotein (VASP) is a common substrate for cyclic AMP and cyclic GMP-regulated protein kinases [i.e., cyclic AMP-dependent protein kinase (PKA; also known as protein kinase A) and cyclic GMP-dependent protein kinase (PKG; also known as protein kinase G)] and it has been shown to be directly phosphorylated by protein kinase C (PKC). In the present study, we demonstrate that VASP is phosphorylated by nobiletin in human platelets via a non-cyclic nucleotide-related mechanism. This was confirmed by the use of inhibitors of adenylate cyclase (SQ22536) and guanylate cyclase [1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ)], since they prevented VASP phosphorylation induced by nobiletin. Furthormore, this event was also not affected by specific inhibitors of PKA (H-89), PKG (KT5823) and PKC (Ro318220), representing cyclic nucleotide-dependent pathways upon nobiletin-induced VASP phosphorylation. Similarly, inhibitors of p38 mitogen-activated protein kinase (MAPK; SB203580), extracellular signal-regulated kinase 2 (ERK2; PD98059), c-Jun N-terminal kinase 1 (JNK1; SP600125), Akt (LY294002) and nuclear factor-κB (NF-κB; Bay11-7082) did not affect nobiletin-induced VASP phosphorylation. Moreover, electron spin resonance, dichlorofluorescein fluorescence and western blotting techniques revealed that nobiletin did not affect hydroxyl radicals (OH•), intracellular reactive oxygen species (ROS) and on protein carbonylation, respectively. Furthermore, the nobiletin-induced VASP phosphorylation was surprisingly reversed by the intracellular antioxidant, N-acetylcysteine (NAC), but not by the inhibitor of NADPH oxidase, diphenyleneiodonium chloride (DPI). It was surprising to observe the differential effects of nobiletin and NAC on VASP phosphorylation in human platelets, since they both have been reported to have antioxidant properties. The likely explanation for this discrepancy is that NAC may bind to allosteric sites on the receptor different from those that nobiletin binds to in human platelets. Taken together, our findings suggest that nobiletin induces VASP phosphorylation in human platelets through non-cyclic nucleotide-related mechanisms. Nevertheless, the exact mechanisms responsible for these effects need to be further confirmed in future studies.

Nobiletin promotes antioxidant and anti-inflammatory responses and elicits protection against ischemic stroke in vivo

BACKGROUND

Post-ischemic oxidative stress and inflammation play pivotal roles in the pathogenesis of ischemic stroke and may represent therapeutic targets. Nobiletin (NOB) has been reported to elicit a variety of biological effects through its anti-oxidant and anti-inflammatory properties. Our previous study has demonstrated the beneficial effect of NOB in ischemic stroke, but the underlying mechanisms remain poorly defined. We therefore further investigated the role of NOB in cerebral ischemia and its potential mechanisms.

METHODS

Adult male Sprague-Dawley rats were randomly assigned to five groups: Sham (sham-operated+0.05% Tween-80), permanent middle cerebral artery occlusion (pMCAO+0.9% saline), Vehicle (pMCAO+0.05% Tween-80), NOB-L (pMCAO+NOB 10mg/kg) and NOB-H (pMCAO+NOB 25mg/kg) groups. Rats were pre-administered intraperitoneally once daily for 3 days prior to ischemia and then received once again immediately after surgery. Neurological deficit, brain edema and infarct volume were evaluated at 24h after stroke. Immunohistochemistry, western blot and RT-qPCR were used to detect the expression of Nrf2, HO-1, SOD1, NF-κB and MMP-9. SOD1, GSH and MDA were measured by spectrophotometer.

RESULTS

Compared with Vehicle group, neurological deficits and brain edema were relieved in NOB-H group, infarct volume was lessened in both NOB-L and NOB-H groups (P<0.05). NOB significantly increased the expression of Nrf2, HO-1, SOD1 and GSH, while decreased the levels of NF-κB, MMP-9 and MDA (P<0.05).

CONCLUSION

NOB may have a neuroprotective effect on cerebral ischemia, and this protection may be through upregulating Nrf2, HO-1 and downregulating NF-κB expression.

Hepatoprotective effects of polymethoxyflavones against acute and chronic carbon tetrachloride intoxication

In the present study, we explore the protective effects of Citrus aurantium L. extract (CAE) against acute and chronic CCl4-induced hepatotoxicity. The quantitative analysis of CAE was performed using HPLC-UV to determine the nobiletin content was approximately 27%. For the acute model, the male ICR mice were orally treated with water, silymarin (positive control, 200 mg/kg) and CAE (50 and 200 mg/kg) for 3 days prior to CCl4 (1 mL/kg, 50% v/v in olive oil) IP injection. For the chronic model (n = 6/group), the mice were treated with each treatment for 28 consecutive days and CCl4 (1 mL/kg, 20%) was injected twice a week. In both the acute and chronic models, the CCl4 alone treated group showed histopathologic alterations with a significantly increase in serum hepatic enzyme levels together with a disrupted anti-oxidative status. In contrast, the CAE treatments restored pathologic alterations and recovered the oxidative status by enhancing antioxidant enzymes and reducing lipid peroxidation levels. Furthermore, CAE enhanced nuclear factor E2-related factor 2 (Nrf2) and its related cytoprotective signals, including NAD(P)H quinone oxidoreductase 1, UDP-glucuronosyltransferase, and γ-glutamylcysteine synthetase. Taken together, the present study demonstrates that CAE exerts a protective effect against CCl4-induced hepatotoxicity with its anti-oxidant, anti-inflammatory, and anti-apoptotic activity.