Inhibition of ATM Promotes Neuronal Apoptosis through Upregulating Bim Expression / 中山大学学报(医学科学版)

@#【Abstract】 【Objective】To investigate the mechanisms implicated in ataxia telangiectasia mutated(ATM)inhibitioncaused apoptosis in the cultured cerebellar granule neurons.【Methods】Primary cerebellar granule neurons(CGN)isolated from neonatal Sprague Dawley rats of 7-8 days were divided into the following groups:25 K group(survival group),5 K group(apoptosis group)and 25 K + KU-55933 treatment group(ATM inhibition group),25 K + KU-55933 + Mithramycin A treatment group(MMA group),25 K + KU-55933 + Chromonycin A3 treatment group(CMA3 group). The protein expression of p-ATM,ATM,Bim and Caspase 3 were detected by Western Blot. The apoptotic cells with nuclear pyknosis were detected by Hoechst-staining.【Results】Compared with 25 K group,the result of western blot showed that the protein expression of Bim and Caspase 3 were increased in the ATM inhibition group(P < 0.05). Compared with 25 K group,the nuclear pyknosis rate of 5 K group and ATM inhibition group were significantly increased(P < 0.05). Inhibition of Bim by Mithramycin A or Chromomycin A3 remarkably reversed ATM inhibition-caused apoptosis.【Conclusion】Inhibition of ATM induce Bim dependent apoptosis in cultured cerebellar granule neurons.

LINGO-1-Fc Fusion Protein Prevents Apoptosis of Cerebellar Granule Neurons Induced by Low-potassium / 生物化学与生物物理进展

Three myelin proteins, Nogo-A, MAG and OMgp, transduce their neurite-outgrowth inhibitory signal through a common receptor complex: NgR/ p75NTR (or TROY). Recently, LINGO-1 is identified as another essential component and regulator for the Nogo-66 receptor/p75 signaling complex. LINGO-1 is restricted to express in CNS, neuronal LINGO-1 is shown to be involved in the signal transduction from three myelin proteins, and Lingo-1 in oligodendrocyte negatively regulates the differentiation and myelination of oligodendrocyte. To investigate the potential activity of LINGO-1 in neuronal apoptosis, LINGO-1-Fc fusion protein including the extracellular LRR and IgC2 domain, was used as functional antagonist to study its protective effect on low-potassium induced apoptosis of cerebellar granule neurons (CGNs). In judgement of the apoptotic nuclei stained by Hoechst, LINGO-1-Fc pretreatment for 2 h significantly prevents apoptosis of CGNs. Although GST-LINGO-1 protein, including the LRR domain, binds to the CGN cultures in the same way with LINGO-1-Fc, it doesn't prevent the apoptosis of CGNs. These results indicate that LINGO-1-Fc fusion protein prevents low-potassium induced apoptosis of cerebellar granule neurons in certain conditions and this activity is probably IgC2 domain dependent.

Modulation of Baseline Potassium Channels in Cerebellar Granule Neurons of Sprague-Dawley Rats by Sevoflurane / 대한마취과학회지

BACKGROUND: Volatile general anesthetics have been widely used to produce reversible unconsciousness and analgesia in clinical practice over the last one hundred years, but the basic mechanism of anesthetic action is not yet completely understood. In addition to the well known mechanism of GABAA and glycine channels, accumulating evidence indicates that neuronal baseline K+ channels are also activated by volatile anesthetics. The goal of this study was to test the hypothesis that sevoflurane, one of the newly developed volatile anesthetics, activates baseline potassium channnels in the cerebellar granule neurons of rats. METHODS: Whole cell measurement techniques were performed from cultured cerebellar granule neurons of seven day old male Sprague-Dawley rats using patch clamp techniques to see the effects of two MACs of sevoflurane on baseline K+ channels. Holding potentials were set to 20 mV and collect pulses from 90 to 90 in 10 mV increments of 300 ms duration. The electrode filling solution contained (in mM) 150 KOH, 105 aspartic acid, 3 NaCl, 10 HEPES, 86 glucose, 1 EGTA, 5 MgCl2 (pH 7.4) and standard saline were used as bath solution. The bath contained 150 NaCl, 3 KCl, 10 HEPES, 14 glucose, 1 EGTA, 5 MgCl2 (pH 7.4). RESULTS: Analysis of multiple patch clamp experiments showed the presence of outward-rectifying K+ selective ion channels with a conductance of 1.064 +/- 0.32 nS (n = 10) at depolarized potentials. Cerebellar granule neurons exhibit rapid rising, noninactivating, outward-rectifying currents. These channels are insensitive to conventional K+ channel blockers. Clinically relevant concentrations of sevoflurane (518nM) increased the baseline K+ channel outward currents from the control value by 225% in a standard saline perfusate (n = 10, P < 0.05, paired t-test). Channel activity enhanced during the duration of the exposure period to sevoflurane returned to the baseline activity level quickly upon wash. CONCLUSIONS: These outward-rectifying whole cell I V curves are consistent with the properties of tandem pore K+ channels. Activation of baseline K+ channels in central neurons by two MACs of sevoflurane causes membrane hyperpolarization and increases neuronal input conductances providing an additional inhibitory mechanism that could contribute to the overall central depressant effects of this compound.

STUDY ON APOPTOSIS INDUCED BY ELECTROMAGNETIC PULSE IN NEURONS OF CEREBELLAR GRANULAR LAYER / 解放军医学杂志

By observing apoptosis and morphological changes in primary culture of neurons from cerebellar granular layer, the neurons were irradiated with EMP (electromagnetic pulses), the possible injury mechanism was explored. The changes in death and apoptosis of the neurons were detected by MTT and flow cytometry, respectively. The slides stained with HE and TUNNEL were examined with light and fluorescence microscopy. The results showed that not only death of the neurons occurred immediately, but also apoptosis appeared after irradiation with EMP. Our conclusion is EMP can promote necrosis and apoptosis of neurons from cerebellar granular layer at early stage, which may result from DNA injury induced by EMP.

Overexpression of neuronal ARNT2 is involved in neuronal apoptosis evoked by low K~+ / 中国病理生理杂志

AIM: To observe the expression of neuronal Aryl hydrocarbon receptor nuclear translocator 2 (ARNT2) involved in neuronal apoptosis evoked by low K + and to investigate the relationship between ARNT2 and neuronal apoptosis. METHODS: After neuron apoptosis model was established, the changes of mRNA and protein of ARNT2 during apoptosis were investigated by RT-PCR and Western blotting, respectively. Immunofluorescence was analyzed by confocal microscopy to probe the subcellular localization of ARNT2. RESULTS: Induced by low K +, the expression of ARNT2 mRNA was up-regulated obviously at the point of 30 min, and peaks at the point of 1 h. This up-regulated expression lasted for 12 h, and the variation of ARNT2 protein was similar to that of mRNA. The results of immunofluorescence analyzed by confocal microscopy showed that the localization of ARNT2 protein was in the nucleus. CONCLUSION: ARNT2 locate in nuclei of normal cerebellar granule neurons of rat. During the process of apoptosis evoked by low K +, both mRNA and protein of ARNT2 are overexpressed.