Doxycycline-regulated co-expression of GDNF and TH in PC12 cells

Current gene therapy models for Parkinson's disease (PD) have adapted two treatment strategies. One is to restore dopamine (DA) production by delivering the genes of DA-synthesizing enzymes such as tyrosine hydroxylase (TH) to the striatum to relieve motor symptoms of PD. Another is to block or slow down progressive degenerative changes by delivering neurotrophic factors such as glial cell line-derived neurotrophic factor (GDNF) to protect the remained neurons. To test the assumption that the combination of the two strategies may have a compound or synergistic effect, we had constructed tetracycline-inducible (tet-off) AAV vector carrying GDNF and TH. After co-transfection of PC12 cells with this vector and the inducer plasmid, the expression of GDNF and TH protected these cells from 1-methyl-4-phenyl-pyridinium-induced injury, and significantly increased the content of dopamine in GDNF/TH-expressing cells compared with the control. Furthermore, mRNA expression of GDNF and TH could be effectively and reversibly regulated by doxycycline (Dox) and the function of GDNF and TH could be repressed by Dox. These results suggest that the tet-off AAV vector carrying GDNF and TH may be a useful tool for gene therapy in the treatment of PD.

Up-regulation of the expression of cocaine and amphetamine-regulated transcript peptide by electroacupuncture in the arcuate nucleus of diet-induced obese rats

It was reported that acupuncture or electro-acupuncture (EA) is effective in reducing the body weight for obese patients, although the mechanisms remain obscure. In a previous study, we have found that rats fed with high-fat (HIF) diet developed diet-induced obesity (DIO) with a concomitant decrease in the hypothalamic content of the cocaine and amphetamine-regulated transcript (CART) peptide, a peptide with anorexiogenic effect. To assess the central effect of EA on DIO rat, we revealed that EA up-regulated the expression of CART peptide in the arcuate nucleus (ARC) of the DIO rats. After feeding with HIF diet for 14 weeks, the DIO rats received EA stimulation three times per week for 4 weeks. The expression of CART peptide in ARC was measured using immunohistochemistry. The plasma ACTH was measured with ELISA. EA caused a reduction of both body weight and energy intake in DIO rats and increased the expression of CART peptide in ARC. The plasma ACTH was increased in response to restraint stress, but EA produced no further increase in ACTH levels. The results suggest that EA can up-regulate the expression of CART peptide to approach normal level, resulting in an inhibition of food intake and a reduction of body weight in DIO rats.

Triptolide protects dopaminergic neurons from inflammation-mediated damage induced by lipopolysaccharide intranigral injection

Converging lines of evidence suggest that neuroinflammatory processes may account for the progressive death of dopaminergic neurons in Parkinson's disease (PD). Therefore, anti-inflammatory strategies have attracted much interest for their potential to prevent further deterioration of PD. Our previous study showed that triptolide, a traditional Chinese herbal compound with anti-inflammatory and immunosuppressive properties, protected dopaminergic neurons from lipopolysaccharide (LPS)-induced damage in primary embryonic midbrain cell cultures. To examine further if triptolide can protect dopaminergic neurons from inflammation-mediated damage in vivo, microglial activation and injury of dopaminergic neurons were induced by LPS intranigral injection, and the effects of triptolide treatment on microglial activation and survival ratio and function of dopaminergic neurons were investigated. Our results demonstrated that microglial activation induced by a single intranigral dose of 10 mug of LPS reduced the survival ratio of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the substantia nigra pars compacta (SNpc) to 29% and the content of dopamine (DA) in striatum to 37% of the non-injected side. Intriguingly, treatment with triptolide of 5 mug/kg for 24 days once per day dramatically improved the survival rate of TH-ir neurons in the SNpc to 79% of the non-injected side. Meanwhile, treatment with triptolide of 1 or 5 mug/kg for 24 days once per day significantly improved DA level in striatum to 70% and 68% of the non-injected side, respectively. Complement receptor 3 (CR3) immunohistochemical staining revealed that triptolide treatment potently inhibited LPS-elicited deleterious activation of microglia in SNpc. The excessive production of cytokines, such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta, was significantly abolished by triptolide administration. These results, together with our previous data in vitro, highly suggest the effectiveness of triptolide in protecting dopaminergic neurons against inflammatory challenge.

Electro-acupuncture stimulation protects dopaminergic neurons from inflammation-mediated damage in medial forebrain bundle-transected rats

Through producing a variety of cytotoxic factors upon activation, microglia are believed to participate in the mediation of neurodegeneration. Intervention against microglial activation may therefore exert a neuroprotective effect. Our previous study has shown that the electro-acupuncture (EA) stimulation at 100 Hz can protect axotomized dopaminergic neurons from degeneration. To explore the underlying mechanism, the effects of 100 Hz EA stimulation on medial forebrain bundle (MFB) axotomy-induced microglial activation were investigated. Complement receptor 3 (CR3) immunohistochemical staining revealed that 24 sessions of 100 Hz EA stimulation (28 days after MFB transection) significantly inhibited the activation of microglia in the substantia nigra pars compacta (SNpc) induced by MFB transection. Moreover, 100 Hz EA stimulation obviously inhibited the upregulation of the levels of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta mRNA in the ventral midbrains in MFB-transected rats, as revealed by reverse transcriptase polymerase chain reaction (RT-PCR). ED1 immunohistochemical staining showed that a large number of macrophages appeared in the substantia nigra (SN) 14 days after MFB transection. The number of macrophages decreased by 47% in the rats that received 12 sessions of EA simulation after MFB transection. These data indicate that the neuroprotective role of 100 Hz EA stimulation on dopaminergic neurons in MFB-transected rats is likely to be mediated by suppressing axotomy-induced inflammatory responses. Taken together with our previous results, this study suggests that the neuroprotective effect of EA on the dopaminergic neurons may stem from the collaboration of its anti-inflammatory and neurotrophic actions.

Triptolide, a Chinese herbal extract, protects dopaminergic neurons from inflammation-mediated damage through inhibition of microglial activation

Mounting lines of evidence have suggested that brain inflammation participates in the pathogenesis of Parkinson's disease. Triptolide is one of the major active components of Chinese herb Tripterygium wilfordii Hook F, which possesses potent anti-inflammatory and immunosuppressive properties. We found that triptolide concentration-dependently attenuated the lipopolysaccharide (LPS)-induced decrease in [3H]dopamine uptake and loss of tyrosine hydroxylase-immunoreactive neurons in primary mesencephalic neuron/glia mixed culture. Triptolide also blocked LPS-induced activation of microglia and excessive production of TNFalpha and NO. Our data suggests that triptolide may protect dopaminergic neurons from LPS-induced injury and its efficiency in inhibiting microglia activation may underlie the mechanism.

[Effect of Chinese herb Tripterygium wilfordii Hook F monomer triptolide on apoptosis of PC12 cells induced by Abeta1-42]

Recent studies indicate that beta-amyloid (Abeta) is the key factor to cause neuronal degeneration in Alzheimer's disease (AD). In the present study, we set up an Abeta induced PC12 cell damage modle and studied the protective effect and related mechanisms of T(10), monomer extracted from Chinese herb Tripterygium wilfordii Hook F. PC12 cells were treated with different concentrations of Abeta (5x10(-4), 5x10(-3), 5x10(-2), 5x10(-1), 5, 50 micromol/L) for 48 h, cell viability was detected by MTT conversion. The apoptotic rate of PC12 cells was quantitatively determined using FACS assay. After PC12 cells were treated with 1x10(-11) mol/L T(10) for 48 h and then co-treated with 50 micromol/LAbetafor 48 h, the apoptotic rate and the change in intracellular Ca(2+) concentration of PC12 cells were analyzed by FACS assay and confocal, respectively. It was found that 5 micromol/L Abeta decreased the cell viability to 66.3% and 50 micromol/L Abeta decreased it to 55.1%, significantly different from that of the control group. After treatment with 50 micromol/L Abeta for 48 h, the apoptotic rate of PC12 cells increased obviously. The apoptotic rate was 5.37% in the control group, while after treatment with 0.5, 5 and 50 micromol/L Abeta for 48 h, the apoptotic rate of PC12 cells went up to 10.19%, 8.02% and 16.63%, respectively. At the same time, the concentration of intracellular Ca(2+) increased greatly after treatment with 50 micromol/L Abeta for 48 h. At the concentration of 1x10(-11) mol/L T(10) remarkably inhibited the apoptosis induced by 50 micromol/L Abeta. In the naive group, the apoptotic rate was 4.83%. The apoptotic rate went up to 17.24% after treatment with 50 micromol/L Abeta for 48 h. After co-treatment with 1x10(-11) mol/L T(10) and 50 micromol/L Abeta, the apoptotic rate decreased to 8.91%, significantly different from that of the control group. At the same time, at the concentration of 1x10(-11 )mol/L T(10) remarkably inhibited the increase of intracellular Ca(2+) concentration induced by Abeta. The results indicate that T(10) has obvious protective effect on PC12 cells, which may be related to the inhibition of the cell apoptosis and increment of intracellular Ca(2+) concentration induced by Abeta.

Triptolide inhibits TNF-alpha, IL-1 beta and NO production in primary microglial cultures

Microglia are believed to participate in the mediation of neurodegeneration through producing a variety of cytotoxic factors upon activation. Pharmacological intervention in microglial activation may therefore exert a neuroprotective effect. In exploring pharmacological agents that can affect microglial activation, we found in this study that triptolide possesses a powerful inhibitory influence over microglia. Pretreatment with triptolide was able to dose-dependently reduce the lipopolysaccharide (LPS)-induced nitrite accumulation and tumor necrosis factor-alpha and interleukin-1beta release from LPS-activated microglia as revealed by Griess reaction and ELISA, respectively. Triptolide reduced LPS-stimulated mRNA expression of all three inflammatory factors. The results obtained from this study demonstrate that triptolide can inhibit inflammatory responses of microglia to inflammatory stimulation via a mechanism involving the inhibition of the synthesis and release of inflammatory factors.