Peroxisomal proliferator-activated receptor gamma (PPARγ) is a nuclear hormone receptor whose agonist, rosiglitazone has a neuroprotective effect to hippocampal neurons in pilocarpine-induced seizures. Hippocampal slice preparations treated in Mg2+ free medium can induce ictal and interictal-like epileptiform discharges, which is regarded as an in vitro model of N-methyl-D-aspartate (NMDA) receptor-mediated temporal lobe epilepsy (TLE). We applied rosiglitazone in hippocampal slices treated in Mg2+ free medium. The effects of rosiglitazone on hippocampal CA1-Schaffer collateral synaptic transmission were tested. We also examined the neuroprotective effect of rosiglitazone toward NMDA excitotoxicity on cultured hippocampal slices. Application of 10μM rosiglitazone significantly suppressed amplitude and frequency of epileptiform discharges in CA1 neurons. Pretreatment with the PPARγ antagonist GW9662 did not block the effect of rosiglitazone on suppressing discharge frequency, but reverse the effect on suppressing discharge amplitude. Application of rosiglitazone suppressed synaptic transmission in the CA1-Schaffer collateral pathway. By miniature excitatory-potential synaptic current (mEPSC) analysis, rosiglitazone significantly suppressed presynaptic neurotransmitter release. This phenomenon can be reversed by pretreating PPARγ antagonist GW9662. Also, rosiglitazone protected cultured hippocampal slices from NMDA-induced excitotoxicity. The protective effect of 10μM rosiglitazone was partially antagonized by concomitant high dose GW9662 treatment, indicating that this effect is partially mediated by PPARγ receptors. In conclusion, rosiglitazone suppressed NMDA receptor-mediated epileptiform discharges by inhibition of presynaptic neurotransmitter release. Rosiglitazone protected hippocampal slice from NMDA excitotoxicity partially by PPARγ activation. We suggest that rosiglitazone could be a potential agent to treat patients with TLE.
Complement component 2 (C2), an early member of the classical pathway, mainly participates in apoptotic cell clearance. We hypothesize that C2 polymorphism may confer genetic susceptibility to complement dysfunction in systemic lupus erythematosus (SLE). The major aim of our study was to investigate the clinical and serological associations of C2 variants in Chinese patients with SLE. The single-nucleotide polymorphism (rs2844455, G/A SNP) located in the intron region of C2 gene was genotyped by direct sequencing in 95 SLE patients and 95 matched normal control subjects. The gene expression profiles were generated by quantitative real-time polymerase chain reaction (PCR) and reverse transcription PCR. Our results showed that the AA genotype was observed more frequently in SLE patients than in normal control subjects (22.1% vs 9.5%, P < 0.05). The A allele was strongly associated with the occurrence of hair loss, photosensitivity and anti-cardiolipin antibodies; whereas, the G allele was associated with lower frequencies of these clinical presentations. Relative expression levels were significantly lower in patients with the AA genotype [median: 18.86, interquartile range (IQR) 11.36-22.43, P = 0.002] than in those with the GG genotype (35.76, IQR: 19.33-49.71). As expected, we confirmed the A allele as a risk factor for SLE development in a Chinese population, in contrast, the G allele might be a protective factor against the pathogenic autoantibody formation and cutaneous manifestations in SLE patients.
Noradrenergic neurons in the locus coeruleus referred to as locus coeruleus neurons, provide the major supply of norepinephrine to the forebrain and play important roles in behavior through regulation of wakefulness and arousal. In a previous study using brain slice preparations, we reported that locus coeruleus neurons are subject to tonic inhibition mediated by γ-aminobutyric acid B receptors (GABABRs) and that the extent of tonic inhibition varies with ambient GABA levels. Since ambient GABA in the locus coeruleus was reported to fluctuate during the sleep-wakefulness cycle, here we tested whether GABABR-mediated tonic inhibition of locus coeruleus neurons could be a mechanism underlying changes in brain arousal. We first demonstrated that GABABR-mediated tonic inhibition of locus coeruleus neurons also exists in vivo by showing that local infusion of CGP35348, a GABABR antagonist, into the locus coeruleus increased the firing rate of locus coeruleus neurons in anesthetized rats. We then showed that this manipulation accelerated the behavioral emergence of rats from deep anesthesia induced by isoflurane. Together, these observations show that GABABR-mediated tonic inhibition of locus coeruleus neurons occurs in vivo and support the idea that this effect may be important in regulating the functional state of the brain.
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