Recent evidences show that peroxisome proliferator-activated receptor c (PPARc) is involved in the modulation of the amyloid-b (Ab) cascade causing Alzheimer’s disease (AD) and treatment with PPARc agonists protects against AD pathology. However, the function of PPARc steady-state activity in Ab cascade and AD pathology remains unclear. In this study, an antagonist of PPARc, GW9662, was injected into the fourth ventricle of APP/PS1 transgenic mice to inhibit PPARc activity in cerebellum. The results show that inhibition of PPARc significantly induced Ab levels in cerebellum and caused cerebellar motor dysfunction in APP/PS1 transgenic mice. Moreover, GW9662 treatment markedly decreased the cerebellar levels of insulin-degrading enzyme (IDE), which is responsible for the cellular degradation of Ab. Since cerebellum is spared from significant Ab accumulation and neurotoxicity in AD patients and animal models, these findings suggest a crucial role of PPARc steady-state activity in protection of cerebellum against AD pathology.

The effects of two polyphenols, chebulinic acid and tellimagrandin I, on DNA strand breaks mediated by H2O2/Cu(Ⅱ), hydroquinone (HQ)/Cu(Ⅱ) and H2O2/Fe(Ⅱ) in pBR322 plasmid DNA and genomic DNA of cultured MRC-5 human embryo lung fibroblasts were examined. The results demonstrated that chebulinic acid and tellimagrandin I obviously inhibited HQ/Cu(Ⅱ)-and H2O2/Cu(Ⅱ)-mediated pBR322 DNA strand breaks. When MRC-5 cells were treated with HQ/Cu(Ⅱ), the presence of chebulinic acid or tellimagrandin I inhibited HQ/Cu(Ⅱ)-mediated double strand breaks of genomic DNA. The presence of chebulinic acid or tellimagrandin I did not affect the H2O2-and HQ-mediated reduction of Cu(Ⅱ) to Cu(I). Both polyphenols could slightly inhibit H2O2/Fe(Ⅱ)-mediated plasmid DNA strand break at the lower concentration (1-10 lM), but potentiate the DNA strand break at the higher concentration (over 50 lM). These results demonstrated that chebulinic acid and tellimagrandin I possessed antioxidant action in certain conditions and exerted prooxidant action on DNA strand breaks in other conditions.

The present study established a model of RyR2 knockdown cardiomyocytes and elucidated the role of RyR2 in aconitine-induced arrhythmia. Cardiomyocytes were obtained from hearts of neonatal Sprague–Dawlay rats. siRNAs were used to down-regulate RyR2 expression. Reduction of RyR2 expression was documented by RT-PCR, western blot, and immunofluorescence. Ca2+ signals were investigated by measuring the relative intracellular Ca2+ concentration, spontaneous Ca2+ oscillations, caffeine-induced Ca2+ release, and L-type Ca2+ currents. In normal cardiomyocytes, steady and periodic spontaneous Ca2+ oscillations were observed, and the baseline [Ca2+]i remained at the low level. Exposure to 3 mMaconitine increased the frequency and decreased the amplitude of Ca2+ oscillations; the baseline [Ca2+]i and the level of caffeine-induced Ca2+ release were increased but the L-type Ca2+ currents were inhibited after application of 3 mM aconitine for 5min. In RyR2 knockdown cardiomyocytes, the steady and periodic spontaneous Ca2+ oscillations almost disappeared, but were re-induced by aconitine without affecting the baseline [Ca2+]i level; the level of caffeine-induced Ca2+ release was increased but L-type Ca2+ currents were inhibited. Alterations of RyR2 are important consequences of aconitine-stimulation and activation of RyR2 appear to have a direct relationship with aconitine-induced arrhythmias. The present study demonstrates a potential method for preventing aconitine-induced arrhythmias by inhibiting Ca2+ leakage through the sarcoplasmic reticulum RyR2 channel.

Aconitine is an effective ingredient in Aconite tuber, an important traditional Chinese medicine. Aconitine is also known to be a highly toxic diterpenoid alkaloid with arrhythmogenic effects. In the present study, we have characterized the properties of arrhythmic cytotoxicity and explored the possible mechanisms of aconitine-induced cardiomyocytes. Results show that aconitine induces significant abnormity in the spontaneous beating rate, amplitude of spontaneous oscillations and the relative intracellular Ca2+ concentration. Also, mRNA transcription levels and protein expressions of SR Ca2+ release channel RyR2 and sarcolemmal NCX were elevated in aconitine-induced cardiomyocytes. However, co-treatment with ruthenium red (RR), a RyR channel inhibitor, could reverse the aconitineinduced abnormity in intracellular Ca2+ signals. These results demonstrate that disruption of intracellular Ca2+ homeostasis in the cardiac excitation–contraction coupling (EC coupling) is a crucial mechanism of arrhythmic cytotoxicity in aconitine-induced cardiomyocytes. Moreover, certain inhibitors appear to play an important role in the detoxification of aconitine-induced Ca2+-dependent arrhythmias.

To elucidate the mechanism of nacre biomineralization, the mantle of Pinctada fucata (P. fucata) from the South China Sea was used. Using the mantle cDNA library and the ESTs we have cloned through suppression subtractive hybridization (SSH), ten novel genes including PFMG1 were obtained through nested PCR. Bioinformative results showed that PFMG1 had a high homology (40%) with Onchocerca VolVulus calcium-binding protein CBP-1 and had two EF-hand calcium-binding domains from the 81st to the 93rd amino acid and from the 98th to the 133rd amino acid in the deduced amino acid sequence. The results of multitissue RT-PCR and in situ hybridization demonstrated the high expression of PFMG1 in the mantle of P. fucata and confirmed the SSH method. The results of GST-PFMG1 on CaCO3 crystallization showed significant effects on nucleation and precipitation of CaCO3. PFMG1 was cloned into the pcDNA.3.1/myc-HisA vector and was subsequently transfected into MC3T3-E1 cells. RT-PCR revealed upregulation of the marker genes related to cell growth, differentiation, and mineralization, and BMP-2, osterix, and osteopontin were upregulated as a result. This research work suggests that PFMG1 plays an important role in the nacre biomineralization, and the SSH method can pave the way for the bulk cloning and characterization of new genes involved in biomineralization in P. fucata and may accelerate research on the mechanism of pearl formation.