Cong-Yuan Xia

Selective modulation of microglia polarization to M2 phenotype for stroke treatment

Resident microglia are the major immune cells in the brain, acting as the first defense of the central nervous system. Following cerebral ischemia, microglia respond to this injury at first and transform from surveying microglia to active state. The activated microglia play a dual role in the ischemic injury, due to distinct microglia phenotypes, including deleterious M1 and neuroprotective M2. However, microglia show transient M2 phenotype followed by a shift to M1. The high ratio of M1 to M2 is significantly related to ischemic injury. Many signal pathways participate in the alternation of microglial phenotype, presenting potential therapeutic targets for selectively modulating M2 polarization of microglia. In this review, we discuss how the M2 phenotype mediates neuroprotective effects and summarize the alternation of signaling cascades that control microglial phenotype after ischemic stroke.

Nrf2 pathway activation contributes to anti-fibrosis effects of ginsenoside Rg1 in a rat model of alcohol- and CCl4-induced hepatic fibrosis.

Aim:To investigate the anti-fibrosis effects of ginsenoside Rg1 on alcohol- and CCl4-induced hepatic fibrosis in rats and to explore the mechanisms of the effects.Methods:Rats were given 6% alcohol in water and injected with CCl4 (2 mL/kg, sc) twice a week for 8 weeks. Rg1 (10, 20 and 40 mg/kg per day, po) was administered in the last 2 weeks. Hepatic fibrosis was determined by measuring serum biochemical parameters, HE staining, Massons trichromic staining, and hydroxyproline and α-SMA immunohistochemical staining of liver tissues. The activities of antioxidant enzymes, lipid peroxidation, and Nrf2 signaling pathway-related proteins (Nrf2, Ho-1 and Nqo1) in liver tissues were analyzed. Cultured hepatic stellate cells (HSCs) of rats were prepared for in vitro studies.Results:In the alcohol- and CCl4-treated rats, Rg1 administration dose-dependently suppressed the marked increases of serum ALT, AST, LDH and ALP levels, inhibited liver inflammation and HSC activation and reduced liver fibrosis scores. Rg1 significantly increased the activities of antioxidant enzymes (SOD, GSH-Px and CAT) and reduced MDA levels in liver tissues. Furthermore, Rg1 significantly increased the expression and nuclear translocation of Nrf2 that regulated the expression of many antioxidant enzymes. Treatment of the cultured HSCs with Rg1 (1 μmol/L) induced Nrf2 translocation, and suppressed CCl4-induced cell proliferation, reversed CCl4- induced changes in MDA, GPX, PCIII and HA contents in the supernatant fluid and α-SMA expression in the cells. Knockdown of Nrf2 gene diminished these actions of Rg1 in CCl4-treated HSCs in vitro.Conclusion:Rg1 exerts protective effects in a rat model of alcohol- and CCl4-induced hepatic fibrosis via promoting the nuclear translocation of Nrf2 and expression of antioxidant enzymes.

Protective effects of Forsythia suspense extract with antioxidant and anti-inflammatory properties in a model of rotenone induced neurotoxicity

The present study investigated the neuroprotective effects of Forsythia suspense extract in a rotenone-induced neurotoxic model. FS8, one of the herbal extracts, markedly protected PC12 cells against rotenone toxicity and was selected for the in vivo study. Gavage administration of FS8 (50 and 200mg/kg, but not 10mg/kg) for 25 days significantly improved the behavior function, decreased the loss of dopaminergic neurons in substantia nigra (SN), and maintained the level of dopamine in striatum after unilateral infusion of rotenone in SN. Wherein, the protective effects of FS8 at the dose of 200mg/kg were better than selegiline. Further study indicated the excellent antioxidant activity of FS8 on the 5th and 21st days after intranigral injection of rotenone. Moreover, FS8 could inhibit microglia activity and accumulation in SN, and obviously decreased the expression of pro-inflammatory molecules (IL-6, TNF-α, iNOS and COX-2), which indicated the anti-inflammatory effects of FS8. In the PI3K/Akt/NF-κB and MAPK pathways, FS8 significantly down-regulated the protein expression of p-PI3K, p-Akt, p-IκB, p-P65, cleaved Caspase 8, p-p38 and p-JNK but not p-mTOR, cleaved Caspase 3 and p-ERK. Therefore, FS8 protected dopamine neurons against rotenone toxicity via antioxidant and anti-inflammatory effects, which suggested the promising application of FS8 in the prevention and treatment of Parkinson disease.

Protopanaxtriol protects against 3-nitropropionic acid-induced oxidative stress in a rat model of Huntington's disease

Aim:Protopanaxtriol (Ppt) is extracted from Panax ginseng Mayer. In the present study, we investigated whether Ppt could protect against 3-nitropropionic acid (3-NP)-induced oxidative stress in a rat model of Huntingtons disease (HD) and explored the mechanisms of action.Methods:Male SD rats were treated with 3-NP (20 mg/kg on d 1, and 15 mg/kg on d 2–5, ip). The rats received Ppt (5, 10, and 20 mg/kg, po) daily prior to 3-NP administration. Nimodipine (12 mg/kg, po) or N-acetyl cysteine (NAC, 100 mg/kg, po) was used as positive control drugs. The body weight and behavior were monitored within 5 d. Then the animals were sacrificed, neuronal damage in striatum was estimated using Nissl staining. Hsp70 expression was detected with immunohistochemistry. Reactive oxygen species (ROS) generation was measured using dihydroethidium (DHE) staining. The levels of components in the Nrf2 pathway were measured with immunohistochemistry and Western blotting.Results:3-NP resulted in a marked reduction in the body weight and locomotion activity accompanied by progressive striatal dysfunction. In striatum, 3-NP caused ROS generation mainly in neurons rather than in astrocytes and induced Hsp70 expression. Administration of Ppt significantly alleviated 3-NP-induced changes of body weight and behavior, decreased ROS production and restored antioxidant enzymes activities in striatum. Moreover, Ppt directly scavenged free radicals, increased Nrf2 entering nucleus, and the expression of its downstream products heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidase 1 (NQO1) in striatum. Similar effects were obtained with the positive control drugs nimodipine or NAC.Conclusion:Ppt exerts a protective action against 3-NP-induced oxidative stress in the rat model of HD, which is associated with its anti-oxidant activity.

Antioxidant activities of ginsenoside Rg1 against cisplatin-induced hepatic injury through Nrf2 signaling pathway in mice

Abstract Oxidative stress is mainly caused by reactive oxygen species (ROS). The damage causes a net stress on normal organs, leading to a gradual loss of vital physiological function. ROS, such as free radicals, represent a class of molecules which are derived from the metabolism of oxygen and exist inherently. However, excessive produced ROS can damage all aerobic organisms. Ginseng is one of the most commonly used alternative herbal medicines, also as a traditional Chinese medicine. The aim of this study is to investigate the antioxidant potential function of ginsenoside Rg1 against cisplatin-caused hepatic damage. Male mice were treated with cisplatin to induce oxidative stress to mimic the side effect of anti-cancer drug cisplatin. Ginsenoside Rg1 effectively prevented against cisplatin-induced hepatotoxicity, alleviating histological lesions. Antioxidant functions of Rg1 were restrained by the activation of p62–Keap1–Nrf2 signaling pathway, simultaneously accompanied with expression of protein products. Accumulative p62 and increased activation of JNK in hepatocytes promoted the activation of Nrf2. For the other, degradation of Nrf2 was guided by tyrosine phosphorylation, ubiquitin, and Keap1. In summary, Rg1 prevents hepatotoxicity mainly by inhibiting the binding of Keap1 and Nrf2, partly by p62 accumulation, and more importantly by increasing the production of antioxidative proteins associated to Nrf2. Pharmacological activation of Nrf2 is an effective way in combating against liver injury.

Early Stage Functions of Mitochondrial Autophagy and Oxidative Stress in Acetaminophen‐Induced Liver Injury

Mitochondria go through frequent cycles of fusion and fission, a process required for mitochondrial quality control by eliminating ROS‐damaged mitochondria through mitochondrial autophagy. Acetaminophen (APAP) overdose can cause liver injury in animals and human beings by inducing mitochondrial damage, which need to be further evaluated. The aim of the current study is to assess the changes between oxidative damage mitophagy in vivo and in vitro, which mimics APAP‐induced liver injury (AILI) in humans. Liver damage was monitored by measuring the levels of biochemical indexes. Proteins associated with oxidative stress were inspected by western blot analysis. After given APAP to both Nrf2−/− and wild‐type mice, Nrf2−/− mice were highly susceptible to APAP induced liver injury. Actually, rapamycin promoted the process of autophagy, reducing the formation of giant mitochondria and lipid droplets. Both tBHQ and NAC protected hepatic cells, promoting Nrf2 translocation into nucleus and increasing the expression of downstream enzymes and proteins. C57BL/6 mice with stabilized Nrf2 had increased hepatic up‐regulation of Nrf2 and other antioxidant enzymes, and reduced the mitochondria dysfunction. Interestingly, APAP‐induced mitochondrial changes of Drp1; however, the initiation of mitochondria fission was inhibited by MDIVI‐1, causing much more serious hepatic impairment. In the early stage of AILI, Nrf2 played a protective role in antioxidant activity while mitophagy protected against oxidative stress damage by the scavenging function. Promoting that both Drp1 and Nrf2 could be a promising new approach to reduce AILI. J. Cell. Biochem. 118: 3130–3141, 2017.

Bibenzyl compound 20c protects against endoplasmic reticulum stress in tunicamycin-treated PC12 cells in vitro

Aim:Accumulation of α-synuclein (α-syn) in the brain is a characteristic of Parkinsons disease (PD). In this study, we investigated whether treatment with tunicamycin, an endoplasmic reticulum (ER) stress inducer, led to the accumulation of α-syn in PC12 cells, and where α-syn protein was accumulated, and finally, whether bibenzyl compound 20c, a novel compound isolated from Gastrodia elata (Tian ma), could alleviate the accumulation of α-syn and ER stress activation in tunicamycin-treated PC12 cells.Methods:PC12 cells were treated with tunicamycin for different time (6 h, 12 h, 24 h, 48 h). Cell viability was determined by a MTT assay. Subcellular fractions of ER and mitochondria were extracted with the Tissue Endoplasmic reticulum Isolation Kit. The levels of α-syn protein and ER-stress-associated downstream chaperones were detected using Western blots and immunofluorescence.Results:Treatment of PC12 cells with tunicamycin (0.5–10 μg/mL) dose-dependently increased the accumulation of α-syn monomer (19 kDa) and oligomer (55 kDa), and decreased the cell viability. Accumulation of the two forms of α-syn was observed in both the ER and mitochondria with increasing treatment time. Co-treatment with 20c (10−5 mol/L) significantly increased the viability of tunicamycin-treated cells, reduced the level of α-syn protein and suppressed ER stress activation in the cells, evidenced by the reductions in phosphorylation of eIF2α and expression of spliced ATF6 and XBP1.Conclusion:Tunicamycin treatment caused accumulation of α-syn monomer and oligomer in PC12 cells. Bibenzyl compound 20c reduces the accumulation of α-syn and inhibits the activation of ER stress, which protected PC12 cells against the toxicity induced by tunicamycin.

Autophagic flux regulates microglial phenotype according to the time of oxygen-glucose deprivation/reperfusion.

Microglial phenotype alternation is a potential novel pathogenic mechanism for cerebral ischemia. Cerebral ischemia induced autophagy aggravates inflammation and neural injury. However, the effect of autophagy in the modulation of microglial phenotype is still unknown. In this study, we investigated the role of autophagic flux in the alternation of microglial phenotype following oxygen glucose deprivation/reperfusion (OGD/R) in BV-2 cells. Inhibition of autophagic flux by NH4Cl exposure significantly increased the level of microtubule-associated protein 1 light chain 3 (LC3)-II and p62 in control and OGD/R (12h, 24h and 48h) groups, but did not change their expression in OGD/R 72h group, indicating that autophagic flux was inhibited at OGD/R 72h. Once autophagic flux was inhibited at OGD/R 72h or at OGD/R 24h (with NH4Cl), BV-2 cells mainly showed M1 phenotype with increased tumor necrosis factor alpha (TNF-α), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and decreased M2 markers including interleukin-10 (IL-10), Arginase 1 (Arg-1), and brain derived neurotrophic factor (BDNF). Further study indicated that inhibition of autophagic flux activated NF-κB pathway and decreased the activity of cAMP-response element binding protein (CREB), which contributed to the alternation of microglial phenotype. Therefore, inhibition of autophagic flux regulated the alternation of microglial phenotype by modulating the balance between NF-κB and CREB.

Ginsenoside Rg1 alleviates corticosterone-induced dysfunction of gap junctions in astrocytes

ETHNOPHARMACOLOGICAL RELEVANCE Ginsenoside Rg1 (Rg1), one of the major bioactive ingredients of Panax ginseng C. A. Mey, has neuroprotective effects in animal models of depression, but the mechanism underlying these effects is still largely unknown AIM OF THE STUDY: Gap junction intercellular communication (GJIC) dysfunction is a potentially novel pathogenic mechanism for depression. Thus, we investigated that whether antidepressant-like effects of Rg1 were related to GJIC. MATERIALS AND METHODS Primary rat prefrontal cortical and hippocampal astrocytes cultures were treated with 50μM CORT for 24h to induce gap junction damage. Rg1 (0.1, 1, or 10μM) or fluoxetine (1μM) was added 1h prior to CORT treatment. A scrape loading and dye transfer assay was performed to identify the functional capacity of gap junctions. Western blot was used to detect the expression and phosphorylation of connexin43 (Cx43), the major component of gap junctions. RESULTS Treatment of primary astrocytes with CORT for 24h inhibited GJIC, decreased total Cx43 expression, and increased the phosphorylation of Cx43 at serine368 in a dose-dependent manner. Pre-treatment with 1μM and 10μM Rg1 significantly improved GJIC in CORT-treated astrocytes from the prefrontal cortex and hippocampus, respectively, and this was accompanied by upregulation of Cx43 expression and downregulation of Cx43 phosphorylation. CONCLUSION These findings provide the first evidence indicating that Rg1 can alleviate CORT-induced gap junction dysfunction, which may have clinical significance in the treatment of depression.

Rg1 Attenuates alcoholic hepatic damage through regulating AMP-activated protein kinase and nuclear factor erythroid 2-related factor 2 signal pathways

Abstract Rg1 has shown multiple pharmacological activities and been considered to be evaluated for hepatic protective activity, as Rg1 could modulate different pathways in various diseases. Herein we assessed its effect and potential mechanism in a newly modified ethanol model. C57BL/6 mice were fed with Lieber-DeCarli liquid diet containing ethanol or isocaloric maltose dextrin as control diet with or without Rg1. Meanwhile, bicyclol was treated as positive drug to compare the efficacy of Rg1 against alcoholic hepatotoxicity. According to our data, Rg1 indeed improved the survival rate and lowered the abnormal high levels of serum parameters. H&E and Oil Red O staining indicated that the condition of liver damage was mitigated by Rg1 administration. Furthermore, AMPK and Nrf2 pathways were all modulated at both RNA and protein levels. In accordance with these findings, Rg1 effectively protected against alcoholic liver injury, possibly by modulating metabolism, suppressing oxidative stress, and enhancing oxidant defense systems of Nrf2 pathway. In vitro, Rg1 has no cell toxicity and promotes Nrf2 translocate into nuclear. In summary, we demonstrate that Rg1 is a potent activator of Nrf2 pathway, and could therefore be applied for prevention of hepatic damage.