Dongming Xing

A mouse model of depression induced by repeated corticosterone injections

A rat model of depression has been recently developed by exogenous corticosterone administration. In this study, we further determined whether corticosterone administration also increased depression-like behavior in mice and explored the brain biochemical consequences of exposure to this administration paradigm. Mice received repeated injections of vehicle and 20 mg/kg of corticosterone for 1, 3 and 5 weeks, and then were subjected to the forced-swim and tail suspension tests. The results showed that repeated corticosterone injections increased immobility behavior in the forced-swim and tail suspension tests in a time-dependent manner. Meanwhile, this injection paradigm produced a time-related effect on tyrosine hydroxylase (TH) levels in the hippocampus of mice. These results are consistent with correlations in stress-induced depression models, and suggest that the repeated corticosterone injection paradigm provides a useful and reliable mouse model within which to further study the role of stress and glucocorticoids in depressive illness, as well as screen for antidepressants or preventive drugs.

Pharmacokinetic study of ellagic acid in rat after oral administration of pomegranate leaf extract

Quantification of ellagic acid, the principal bioactive component of pomegranate leaf extract, in rats plasma following oral administration of pomegranate leaf extract was achieved by using a high-performance liquid chromatographic method. The calibration curve for ellagic acid was linear (r2=0.9998) ver the concentration range 0.026-1.3 microg/ml. The intra- and inter-day assays of ellagic acid from rat plasma were less than 6.52% at concentration range from 26 to 1300 ng/ml and good overall recoveries (94.5-102.4%) were found on same concentrations. The concentration-time profile was fitted with an open two-compartment system with lag time and its max concentration of ellagic acid in plasma was 213 ng/ml only 0.55 h after oral administration extract 0.8 g/kg. The pharmacokinetic profile indicates that ellagic acid has poor absorption and rapid elimination after oral administration pomegranate leaf extract, and part of it was absorbed from stomach.

The antidepressant effect of ethanol extract of radix puerariae in mice exposed to cerebral ischemia reperfusion

In our pilot study, the depressive-like behaviors of mice exposed to cerebral ischemia reperfusion (CIR) were observed and the antidepressant effects of radix puerariae (RP; root of the Pueraria plant) extract in CIR mice were assessed because it was speculated that the neuronal damage caused by CIR played an important role in the development of poststroke depression (a common and severe complication after stroke) and the RP extract was reported to exhibit effect of neuronal protection from cerebral ischemia damage. Our studies above indicated that the RP extract markedly shortened the increased immobility time induced by CIR of male mice in the forced swimming test (FST) and tail suspension test (TST), indicating a possible antidepressant activity. Thus, the aim of the present study was to confirm the putative antidepressant effect of RP extract (75, 150, and 300 mg/kg, administered orally 24 h after the CIR) on reserpine-induced symptoms. To get further insight into the mode of antidepressant action of RP extract, biochemical examination was conducted concomitantly to examine possible involvement of the brain monoamine systems in the behavioral syndromes observed. In CIR mice, pronounced low levels of norepinephrine (NE) and 4-dihydroxyphenylacetic acid (DOPAC, a metabolite of dopamine) in the hippocampus or striatum were detected, which were reversed by RP extract, whereas no significant change of serotonin (5-HT) was detected in either CIR or RP extract-treated mice. The data suggested that the disturbance of NE and DA systems in hippocampus and striatum played more important roles in the development of depressive-like behavior of CIR mice than 5-HT system did, and RP extract ameliorated the abnormal symptoms caused by CIR, which may throw new lights on the treatment of poststroke depression.

Energy production genes sucB and ubiF are involved in persister survival and tolerance to multiple antibiotics and stresses in Escherichia coli

Persisters are a small population of slowly growing or nongrowing bacteria that are phenotypically resistant to antibiotics, but the mechanisms involved are not well understood. The aim of this study is to determine new mechanisms underlying antibiotic-tolerant persisters. The Escherichia coli deletion mutant library was screened to identify mutants that had a defect in persister survival after exposure to ampicillin for 24 h or 5 days. The identified mutants and the parent strain were subjected to minimum inhibitory concentration (MIC) and minimum bactericidal tests and antibiotic or stress conditions in exposure assays. sucB and ubiF mutants deficient in energy production were identified from the mutant screens to have defective persister survival as demonstrated by higher susceptibility to various antibiotics, including ampicillin, norfloxacin, tetracycline and gentamicin, and different stresses such as oxidative stress, acid pH and weak acid compared with the parent strain. In addition, both sucB and ubiF had a twofold lower MIC than the parent strain. The above sucB and ubiF mutant phenotypes could be complemented by their respective functional genes. Defective energy production through mutations in sucB and ubiF affects persister survival and could serve as new drug targets for persister bacteria.

The Effects of Ananas comosus L. Leaves on Diabetic-Dyslipidemic Rats Induced by Alloxan and a High-Fat/High-Cholesterol Diet

The aim of this study is to demonstrate the effects of Ananas comosus L. leaves on diabetic-dyslipidemic rats. Hypoglycemic and hypolipidemic activities of the ethanolic extract of Ananas comosus L. leaves (EEACL) were evaluated in normal and alloxan-induced diabetic rats by oral glucose tolerance test and an olive oil load test. Anti-diabetic, anti-hyperlipidemic and anti-oxidative activities of EEACL were also investigated in diabetic-dyslipidemic rats induced by alloxan and a high-fat/high-cholesterol diet. EEACL at the dose of 0.40 g/kg significantly inhibited the increase in blood glucose in diabetic rats in oral glucose tolerance test, but did not cause any hypoglycerimic activity in normal rats. It also significantly inhibited the increase in postprandial triglycerides (TG) levels in both normal and diabetic rats in olive oil load test. After 15 days of treatment of diabetic dyslipidemic rats, EEACL significantly decreased blood glucose (-51.0%, P < 0.01), TG (-50.1%, P < 0.01), TC (-23.3%, P < 0.01), LDL-c (-47.9%, P < 0.01) and glycated albumin (-25.4%, P < 0.01) levels, significantly increased serum high-density lipoprotein cholesterol levels (66.2%, P < 0.01) and prevented lower body weight of diabetes (11.8%, P < 0.05), significantly lowered lipid peroxidation productions of blood (-27.8%, P < 0.01), brain (-31.6%, P < 0.05), liver (-44.5%, P < 0.01) and kidneys (-72.2%, P < 0.05) compared with those in untreated diabetic dyslipidemic rats. These data suggest that EEACL has anti-diabetic, anti-dyslipidemic and anti-oxidative activities, which may be developed into a new plant medicine for treatment of diabetes and its complications.

PI3K p55γ promoter activity enhancement is involved in the anti-apoptotic effect of berberine against cerebral ischemia-reperfusion.

Berberine is a candidate clinical neuroprotective agent against ischemic stroke. In the present study, we examined the influence of the PI3K/Akt pathway in mediating the anti-apoptotic effects of berberine. Oxygen-glucose deprivation and reoxygenation of nerve growth factor-differentiated PC12 cells and primary neurons, and bilateral common carotid artery occlusion in mice were used as in vitro and in vivo ischemia models. We found that the anti-apoptotic effects of berberine against ischemia were indeed mediated by the increased phosphor-activation of Akt (higher p-Akt to total Akt), leading to the intensified phosphorylation of Bad and the decreased cleavage of the pro-apoptotic protease caspase-3. Berberine action is specific for PI3K, rather than the upstream receptor tyrosine kinase. The anti-apoptotic effect is maintained in the presence of tyrosine kinase inhibitor genistein and the epidermal growth factor receptor inhibitor PD153035, but is suppressed by the PI3K inhibitor Ly294002 and the Akt inhibitor Akti-1/2.The unique PI3K regulatory subunit p55γ was upregulated by berberine during ischemia-reperfusion and was not blocked by these inhibitors. We constructed a reporter plasmid to detect PI3K p55γ promoter activity and found that berberine enhanced PI3K p55γ promoter activity during cerebral ischemia-reperfusion.

Comprehensive study of baicalin down-regulating NOD2 receptor expression of neurons with oxygen-glucose deprivation in vitro and cerebral ischemia-reperfusion in vivo

Cerebral ischemia-reperfusion can activate several transcription factors and lead to inflammatory reactions, which related to pattern recognition receptors with immune activating functions. NOD2 (nucleotide-binding oligomerization domain protein 2) is one of the receptors involved in innate immune response and is genetically associated with several inflammatory reactions. Since baicalin has the pharmacological effects of anti-inflammation and protection of brain from cerebral ischemia-reperfusion, we studied baicalins effect on NOD2/TNFα in the cell of oxygen-glucose deprivation (OGD) in vitro and the mice of cerebral ischemia-reperfusion in vivo. The results showed that NOD2 and TNFα were up regulated in the cells with oxygen-glucose deprivation, not only in BV2 cells, but also in both of PC12 cells and primary neuron cells, which suggested NOD2 could express directly in neuron while OGD treatment. Baicalin (10 μg/ml) could effectively down regulate the expression of NOD2 and TNFα in both mRNA and protein levels. Meanwhile, baicalin (50 mg/kg, i.p.) could also down regulate the expression of NOD2 and TNFα in protein levels significantly, in which agreed with its effect in vitro study. These data demonstrated that targeting on NOD2 especially in neurons directly was possibly attributed to the neural-protective effect of baicalin in the injury of cerebral ischemia-reperfusion.

Effect of berberine on cell cycle arrest and cell survival during cerebral ischemia and reperfusion and correlations with p53/cyclin D1 and PI3K/Akt

Berberine acted as a natural medicine with multiple pharmacological activities. In the present study, we examined the effect of berberine against cerebral ischemia damage from cell cycle arrest and cell survival. Oxygen-glucose deprivation of PC12 cells and primary neurons, and carotid artery ligation in mice were used as in vitro and in vivo cerebral ischemia models. We found that the effect of berberine on cell cycle arrest during ischemia was mediated by decreased p53 and cyclin D1, increased phosphorylation of Bad (higher expression of p-Bad and higher ratio of p-Bad to Bad) and decreased cleavage of caspase 3. Meanwhile, berberine activated the PI3K/Akt pathway during the reperfusion, especially the phosphor-activation of Akt, to promote the cell survival. The neural protective effect of berberine was remained in the presence of inhibitor of mitogen-activated protein/extracellular signal-regulated kinase (MEK), but was suppressed by the inhibitors of PI3K and Akt. We demonstrated that berberine induced cell cycle arrest and cell survival to resist cerebral ischemia injury.

Comprehensive Study in the Inhibitory Effect of Berberine on Gene Transcription, Including TATA Box

Berberine (BBR) is an established natural DNA intercalator with numerous pharmacological functions. However, currently there are neither detailed reports concerning the distribution of this alkaloid in living cells nor reports concerning the relationship between BBRs association with DNA and the function of DNA. Here we report that the distribution of BBR within the nucleus can be observed 30 minutes after drug administration, and that the content of berberine in the nucleus peaks at around 4 µmol, which is twelve hours after drug administration. The spatial conformation of DNA and chromatin was altered immediately after their association with BBR. Moreover, this association can effectively suppress the transcription of DNA in living cell systems and cell-free systems. Electrophoretic mobility shift assays (EMSA) demonstrated further that BBR can inhibit the association between the TATA binding protein (TBP) and the TATA box in the promoter, and this finding was also attained in living cells by chromatin immunoprecipitation (ChIP). Based on results from this study, we hypothesize that berberine can suppress the transcription of DNA in living cell systems, especially suppressing the association between TBP and the TATA box by binding with DNA and, thus, inhibiting TATA box-dependent gene expression in a non-specific way. This novel study has significantly expanded the sphere of knowledge concerning berberines pharmacological effects, beginning at its paramount initial interaction with the TATA box.

Comparative study of the effect of baicalin and its natural analogs on neurons with oxygen and glucose deprivation involving innate immune reaction of TLR2/TNFα.

This work is to study the baicalin and its three analogs, baicalin, wogonoside, and wogonin, on the protective effect of neuron from oxygen-glucose deprivation (OGD) and toll-like receptor 2 (TLR2) expression in OGD damage. The results showed that baicalin and its three analogs did protect neurons from OGD damage and downregulated protein level of TLR2. D-Glucopyranosiduronic acid on site 7 in the structure played a core of cytotoxicity of these flavonoid analogs. The methoxyl group on carbon 8 of the structure had the relation with TLR2 protein expression, as well as the anti-inflammation. In addition, we detected caspase3 and antioxidation capability, to investigate the effect of four analogs on cell apoptosis and total antioxidation competence in OGD model.