Inhibitory effect of arsenic trioxide on neuronal migration in vitro and its potential molecular mechanism.

Primary neuron cultures were established from the brains of neonatal rats and the effects of arsenic trioxide (As2O3) on the migration of neurons and the potential mechanism of As2O3 were investigated. Boyden chamber assay was used to detect the effect of AS2O3 on neuronal migration. Matrix metalloproteinase-2 (MMP-2) and MMP-9 RNA expression and doublecortin (DCX) protein expression were measured. Neuronal migration ability was significantly lower in the 20 µmol/L group compared with the other three groups (all p < 0.001). The expression of both MMP-2 and MMP-9 was significantly inversely correlated with As2O3 concentration. The expression of DCX was significantly higher in the control group compared with the other three groups (all p ≤ 0.003). Thus, the inhibitory effect of As2O3 on the migration of primary neurons might be related to the reduction in MMP-2 and MMP-9 activities and decrease in ß-actin and DCX expression.

Targeting estrogen receptor ß in microglia and T cells to treat experimental autoimmune encephalomyelitis.

A therapeutic goal in the treatment of certain CNS diseases, including multiple sclerosis, amyotrophic lateral sclerosis, and Parkinson disease, is to down-regulate inflammatory pathways. Inflammatory molecules produced by microglia are responsible for removal of damaged neurons, but can cause collateral damage to normal neurons located close to defective neurons. Although estrogen can inactivate microglia and inhibit the recruitment of T cells and macrophages into the CNS, there is controversy regarding which of the two estrogen receptors (ERs), ERα or ERß, mediates the beneficial effects in microglia. In this study, we found that ERß, but not ERα, is expressed in microglia. Using the experimental autoimmune encephalomyelitis (EAE) model in SJL/J mice, we evaluated the benefit of an ERß agonist as a modulator of neuroinflammation. Treatment of EAE mice with LY3201, a selective ERß agonist provided by Eli Lilly, resulted in marked reduction of activated microglia in the spinal cord. LY3201 down-regulated the nuclear transcription factor NF-κB, as well as the NF-κB-induced gene inducible nitric oxide synthase in microglia and CD3(+) T cells. In addition, LY3201 inhibited T-cell reactivity through regulation of indoleamine-2,3-dioxygenase. In the EAE model, treatment with LY3201 decreased mortality in the first 2 wk after disease onset, and also reduced the severity of symptoms in mice surviving for 4 wk. Our data show that ERß-selective agonists, by modulating the immune system in both microglia and T cells, offer promise as a useful class of drugs for treating degenerative diseases of the CNS.

Liver X receptor ß protects dopaminergic neurons in a mouse model of Parkinson disease.

Parkinson disease (PD) is a progressive neurodegenerative disease whose progression may be slowed, but at present there is no pharmacological intervention that would stop or reverse the disease. Liver X receptor ß (LXRß) is a member of the nuclear receptor super gene family expressed in the central nervous system, where it is important for cortical layering during development and survival of dopaminergic neurons throughout life. In the present study we have used the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of PD to investigate the possible use of LXRß as a target for prevention or treatment of PD. The dopaminergic neurons of the substantia nigra of LXRß(-/-) mice were much more severely affected by MPTP than were those of their WT littermates. In addition, the number of activated microglia and GFAP-positive astrocytes was higher in the substantia nigra of LXRß(-/-) mice than in WT littermates. Administration of the LXR agonist GW3965 to MPTP-treated WT mice protected against loss of dopaminergic neurons and of dopaminergic fibers projecting to the striatum, and resulted in fewer activated microglia and astroglia. Surprisingly, LXRß was not expressed in the neurons of the substantia nigra but in the microglia and astroglia. We conclude that LXR agonists may have beneficial effects in treatment of PD by modulating the cytotoxic functions of microglia.

Anxiety in liver X receptor ß knockout female mice with loss of glutamic acid decarboxylase in ventromedial prefrontal cortex.

Anxiety disorders are the most prevalent mental disorders in adolescents in the United States. Female adolescents are more likely than males to be affected with anxiety disorders, but less likely to have behavioral and substance abuse disorders. The prefrontal cortex (PFC), amygdala, and dorsal raphe are known to be involved in anxiety disorders. Inhibitory input from the PFC to the amygdala controls fear and anxiety typically originating in the amygdala, and disruption of the inhibitory input from the PFC leads to anxiety, fear, and personality changes. Recent studies have implicated liver X receptor ß (LXRß) in key neurodevelopmental processes and neurodegenerative diseases. In the present study, we used elevated plus-maze, startle and prepulse inhibition, open field, and novel object recognition tests to evaluate behavior in female LXRß KO (LXRß(-/-)) mice. We found that the female LXRß(-/-) mice were anxious with impaired behavioral responses but normal locomotion and memory. Immunohistochemistry analysis revealed decreased expression of the enzyme responsible for GABA synthesis, glutamic acid decarboxylase (65+67), in the ventromedial PFC. Expression of tryptophan hydroxylase 2 in the dorsal raphe was normal. We conclude that the anxiogenic phenotype in female LXRß(-/-) mice is caused by reduced GABAergic input from the ventromedial PFC to the amygdala.

Reduction of dendritic spines and elevation of GABAergic signaling in the brains of mice treated with an estrogen receptor ß ligand.

An estrogen receptor (ER) ß ligand (LY3201) with a preference for ERß over ERα was administered in s.c. pellets releasing 0.04 mg/d. The brains of these mice were examined 3 d after treatment had begun. Although estradiol-17ß is known to increase spine density and glutaminergic signaling, as measured by Golgi staining, a clear reduction in spines was evident on the dendritic branches in LY3201-treated mice but no morphological alteration and no difference in the number of dendritic spines on dendritic stems were observed. In the LY3201-treatment group, there was higher expression of glutamic acid decarboxylase (GAD) in layer V of cortex and in the CA1 of hippocampus, more GAD(+) terminals surrounding the pyramidal neurons and less glutamate receptor (NMDAR) on the neurons in layer V. There were no alterations in expression of Iba1 or in Olig2 or CNPase. However, GFAP(+) astrocytes were increased in the LY3201-treatment group. There were also more projections characteristic of activated astrocytes and increased expression of glutamine synthetase (GS). No expression of ERß was detectable in the nuclei of astrocytes. Clearly, LY3201 caused a shift in the balance between excitatory and inhibitory neurotransmission in favor of inhibition. This shift was due in part to increased synthesis of GABA and increased removal of glutamate from the synaptic cleft by astrocytes. The data reveal that treatment with a selective ERß agonist results in changes opposite to those reported in estradiol-17ß-treated mice and suggests that ERα and ERß play opposing roles in the brain.

Liver X receptor beta and thyroid hormone receptor alpha in brain cortical layering.

In the past year, two members of the nuclear receptor family, liver X receptor beta (LXRbeta) and thyroid hormone receptor alpha (TRalpha), have been found to be essential for correct migration of neurons in the developing cortex in mouse embryos. TRalpha and LXRbeta bind to identical response elements on DNA and sometimes regulate the same genes. The reason for the migration defect in the LXRbeta(-/-) mouse and the possibility that TRalpha may be involved are the subjects of the present study. At E15.5, expression of reelin and VLDLR was similar but expression of apolipoprotein E receptor 2 (ApoER2) (the reelin receptor) was much lower in LXRbeta(-/-) than in WT mice. Knockout of ApoER2 is known to lead to abnormal cortical lamination. Surprisingly, by postnatal day 14 (P14), no morphological abnormalities were detectable in the cortex of LXRbeta(-/-) mice and ApoER2 expression was much stronger than in WT controls. Thus, a postnatal mechanism leads to increase in ApoER2 expression by P14. TRalpha also regulates ApoER2. In both WT and LXRbeta(-/-) mice, expression of TRalpha was high at postnatal day 2. By P14 it was reduced to low levels in WT mice but was still abundantly expressed in the cortex of LXRbeta(-/-) mice. Based on the present data we hypothesize that reduction in the level of ApoER2 is the reason for the retarded migration of later-born neurons in LXRbeta(-/-) mice but that as thyroid hormone (TH) increases after birth the neurons do find their correct place in the cortex.

[Therapeutic effect of hypoxia-inducible factor-1alpha on focal cerebral ischemia: experiment with rats].

OBJECTIVE: To construct a recombinant adenoviral vector carrying HIF-1alpha gene and explore the therapeutic effect of HIF-1alpha on focal cerebral ischemia in adult rats. METHODS: The AdEasy System was used to construct the recombinant adenoviral vector carrying HIF-1alpha gene and green fluorescent protein and PCR was used to identify the HIF-1alpha gene. Middle cerebral artery occlusion (MCAo) and reperfusion models were established and divided into Ad-HIF-1alpha group, Ad group and NS group. After Ad-HIF-1alpha, Ad and NS were injected into the ischemic ventricle, expression of Ad-HIF-1alpha was observed and its therapeutic effect was evaluated by 2, 3, 5-triphenyltetrazolium chloride (TTC) staining and neurological severity scores. RESULTS: GFP expression distributed apart from the ventricle and reached a peak at 14 days and persisted for about 4 weeks under fluorescent microscope. The neurological severity scores was 2.4 +/- 0.5 at 24 h in Ad-HIF-1alpha group and there was no statistical significance compared with Ad group (2.6 +/- 0.5) and NS group (2.7 +/- 0.7) (P > 0.05). The scores were 1.6 +/- 0.7 at 48 h and 0.9 +/- 0.6 at 72 h in Ad-HIF-1alpha group, and there were statistical significance compared with Ad group (2.9 +/- 0.6 and 3.2 +/- 0.6 respectively) and NS group (3.0 +/- 0.7 and 3.2 +/- 0.8) (P < 0.05). The infarct volume was 81.2 mm(3) +/- 1.4 mm(3) at 72 h in Ad-HIF-1alpha group and there was statistical significance compared with Ad group (173.9 mm(3) +/- 1.3 mm(3)) and NS group (171.7 mm(3) +/- 6.2 mm(3)) (P < 0.05). CONCLUSION: HIF-1alpha gene had definite therapeutic effect on focal cerebral ischemia in adult rats, which settles a foundation for next HIF-1alpha gene study and clinic application.