We scanned throughout chromosome 21 to assess genetic associations with late-onset Alzheimer disease (AD) using 374 Japanese patients and 375 population-based controls, because trisomy 21 is known to ...be associated with early deposition of β-amyloid (Aβ) in the brain. Among 417 markers spanning 33 Mb, 22 markers showed associations with either the allele or the genotype frequency (P < 0.05). Logistic regression analysis with age, sex and apolipoprotein E (APOE)-varepsilon4 dose supported genetic risk of 17 markers, of which eight markers were linked to the SAMSN1, PRSS7, NCAM2, RUNX1, DYRK1A and KCNJ6 genes. In logistic regression, the DYRK1A (dual-specificity tyrosine-regulated kinase 1A) gene, located in the Down syndrome critical region, showed the highest significance OR = 2.99 (95% CI: 1.72-5.19), P = 0.001, whereas the RUNX1 gene showed a high odds ratio OR = 23.3 (95% CI: 2.76-196.5), P = 0.038. DYRK1A mRNA level in the hippocampus was significantly elevated in patients with AD when compared with pathological controls (P < 0.01). DYRK1A mRNA level was upregulated along with an increase in the Aβ-level in the brain of transgenic mice, overproducing Aβ at 9 months of age. In neuroblastoma cells, Aβ induced an increase in the DYRK1A transcript, which also led to tau phosphorylation at Thr212 under the overexpression of tau. Therefore, the upregulation of DYRK1A transcription results from Aβ loading, further leading to tau phosphorylation. Our result indicates that DYRK1A could be a key molecule bridging between β-amyloid production and tau phosphorylation in AD.
Endothelin (ET), a vasoconstrictive peptide, acts as an anti-apoptotic factor, and endothelin receptor B (ET
B receptor) is associated with neuronal survival in the brain. Human group IIA secretory ...phospholipase A
2 (sPLA
2-IIA) is expressed in the cerebral cortex after brain ischemia and causes neuronal cell death via apoptosis. In primary cultures of rat cortical neurons, we investigated the effects of an ET
B receptor agonist, ET-3, on sPLA
2-IIA-induced cell death. sPLA
2-IIA caused neuronal cell death in a concentration- and time-dependent manner. ET-3 significantly prevented neurons from undergoing sPLA
2-IIA-induced cell death. These agonists reversed sPLA
2-IIA-induced apoptotic features such as the condensation of chromatin and the fragmentation of DNA. Before cell death, sPLA
2-IIA potentiated the influx of Ca
2+ into neurons. Blockers of the L-type voltage-dependent calcium channel (L-VSCC) not only suppressed the Ca
2+ influx, but also exhibited neuroprotective effects. As well as L-VSCC blockers, ET-3 significantly prevented neurons from sPLA
2-IIA-induced Ca
2+ influx. An ET
B receptor antagonist, BQ788, inhibited the effects of ET-3. The present cortical cultures contained few non-neuronal cells, indicating that the ET
B receptor agonist affected the survival of neurons directly, but not indirectly via non-neuronal cells. In conclusion, we demonstrate that the ET
B receptor agonist rescues cortical neurons from sPLA
2-IIA-induced apoptosis. Furthermore, the present study suggests that the inhibition of L-VSCC contributes to the neuroprotective effects of the ET
B receptor agonist.
Alzheimer's disease (AD) is a neurodegenerative affliction associated with memory dysfunction. Senile plaques are a pathological hallmark of AD, and amyloid beta (Abeta) peptides are a major ...component of these plaques. Abeta peptides are derived from proteolytic cleavage of the Abeta protein precursor (APP) by beta- and gamma-secretases to generate two principal species, Abeta1-40 and Abeta1-42. We have developed antibodies against the N- and C-termini of these peptides, and an ELISA for accurate and sensitive quantitative assessment. Sandwich ELISA composed of N-terminus (Abeta1) end-specific antibody, clone 82E1, and C-termini end-specific antibodies, and clones 1A10 and 1C3 for Abeta40 and Abeta42, respectively, detects full-length Abeta1-40 and 1-42 with a sensitivity in the sub single digit fmol/ml (equivalent to single digit pg/ml) range with no cross-reactivity to APP. A combination of C-termini antibodies and an antibody against the middle region of Abeta detects mouse Abeta in non-transgenic mouse brains.
Secretory phospholipase A(2) (sPLA(2)) exhibits neurotoxicity in the central nervous system. There are high-affinity binding sites of the porcine pancreatic group IB sPLA(2) (sPLA(2)-IB) in the ...brain. sPLA(2)-IB causes neuronal cell death via apoptosis in the rat cerebral cortex. Although apoptosis is triggered by an influx of Ca(2+) into neurons, it has not yet been ascertained whether the Ca(2+) influx is associated with the neurotoxicity of sPLA(2)-IB. We thus examined the possible involvement of Ca(2+) in the neurotoxicity of sPLA(2)-IB in the primary culture of rat cortical neurons. sPLA(2)-IB induced neuronal cell death in a concentration- and time-dependent manner. This death was accompanied by condensed chromatin and fragmented DNA, exhibiting apoptotic features. Before apoptosis, sPLA(2)-IB markedly enhanced the influx of Ca(2+) into neurons. A calcium chelator suppressed neurons from sPLA(2)-IB-induced neuronal cell death in a concentration-dependent manner. An L-type voltage-sensitive Ca(2+) channel (L-VSCC) blocker significantly protected the sPLA(2)-IB-potentiated influx of Ca(2+). On the other hand, blockers of N-VSCC and P/Q-VSCC did not. An L-VSCC blocker protected neurons from sPLA(2)-IB-induced neuronal cell death. In addition, the L-VSCC blocker ameliorated the apoptotic features of sPLA(2)-IB-treated neurons. Neither an N-VSCC blocker nor P/Q-VSCC blockers affected the neurotoxicity of the enzyme. In conclusion, these findings demonstrate that the influx of Ca(2+) into neurons play an important role in the neurotoxicity of sPLA(2)-IB. Furthermore, the present study suggests that L-VSCC contribute to the sPLA(2)-IB-potentiated influx of Ca(2+) into neurons.
Gas6, a product of the growth-arrest-specific gene 6, protects cortical neurons from amyloid β protein (Aβ)-induced apoptosis. Neuronal apoptosis is also caused by human group IIA secretory ...phospholipase A
2 (sPLA
2-IIA), which is expressed in the cerebral cortex after brain ischemia. sPLA
2-IIA induces Ca
2+ influx via L-type voltage-sensitive calcium channels (L-VSCCs), leading to its neurotoxicity. In the present study, we investigated effects of Gas6 on sPLA
2-IIA-induced cell death in primary cultures of rat cortical neurons. sPLA
2-IIA caused neuronal cell death in a concentration- and time-dependent manner. Gas6 significantly prevented neurons from sPLA
2-IIA-induced cell death. Gas6 suppressed sPLA
2-IIA-induced apoptotic features such as the condensation of chromatin and the fragmentation of DNA. Prior to cell death, sPLA
2-IIA increased the influx of Ca
2+ into neurons through L-VSCCs. Gas6 significantly inhibited the sPLA
2-IIA-induced Ca
2+ influx. The blocker of L-VSCCs also suppressed sPLA
2-IIA-induced neuronal cell death. The cortical cultures contained few non-neuronal cells, indicating that Gas6 affected the survival of neurons directly, but not indirectly via non-neuronal cells. In conclusion, we demonstrate that Gas6 rescues cortical neurons from sPLA
2-IIA-induced apoptosis. Furthermore, the present study indicates that inhibition of L-VSCC contributes to the neuroprotective effect of Gas6.
Secretory phospholipase A
2 (sPLA
2) exhibits neurotoxicity in the central nervous system. There are high-affinity binding sites of the porcine pancreatic group IB sPLA
2 (sPLA
2-IB) in the brain. ...sPLA
2-IB causes neuronal cell death via apoptosis in the rat cerebral cortex. Although apoptosis is triggered by an influx of Ca
2+ into neurons, it has not yet been ascertained whether the Ca
2+ influx is associated with the neurotoxicity of sPLA
2-IB. We thus examined the possible involvement of Ca
2+ in the neurotoxicity of sPLA
2-IB in the primary culture of rat cortical neurons. sPLA
2-IB induced neuronal cell death in a concentration- and time-dependent manner. This death was accompanied by condensed chromatin and fragmented DNA, exhibiting apoptotic features. Before apoptosis, sPLA
2-IB markedly enhanced the influx of Ca
2+ into neurons. A calcium chelator suppressed neurons from sPLA
2-IB-induced neuronal cell death in a concentration-dependent manner. An L-type voltage-sensitive Ca
2+ channel (L-VSCC) blocker significantly protected the sPLA
2-IB-potentiated influx of Ca
2+. On the other hand, blockers of N-VSCC and P/Q-VSCC did not. An L-VSCC blocker protected neurons from sPLA
2-IB-induced neuronal cell death. In addition, the L-VSCC blocker ameliorated the apoptotic features of sPLA
2-IB-treated neurons. Neither an N-VSCC blocker nor P/Q-VSCC blockers affected the neurotoxicity of the enzyme. In conclusion, these findings demonstrate that the influx of Ca
2+ into neurons play an important role in the neurotoxicity of sPLA
2-IB. Furthermore, the present study suggests that L-VSCC contribute to the sPLA
2-IB-potentiated influx of Ca
2+ into neurons.
Amyloid β protein (Aβ) deposits are found in the striatum of patients with Alzheimer disease (AD) showing extrapyramidal motor dysfunction, but neuronal cell loss has not yet been detected. To ...clarify how Aβ impairs motor function, we analyzed intrastriatally Aβ-injected rats. Unilateral injection of Aβ(25-35) enhanced apomorphine-induced circling in an ipsilateral direction, indicating ipsilateral dysfunction of dopaminergic nigrostriatal pathways. Volumes of lesion in the Aβ(25-35)-injected striata were significantly higher than those in the saline-injected ones. The correlation between lesion volume and circling behavior was close to significance, but slightly too low, suggesting the possible involvement of other factors in the striatal dysfunction. Aβ(25-35) significantly elevated the level of thromboxane A
2 (TXA
2). A stable TXA
2 agonist, U46619, enhanced circling behavior, and TXA
2 receptor antagonists attenuated U46619- and Aβ(25-35)-enhanced circling behavior. This study demonstrated that Aβ(25-35) impairs the motor function of dopaminergic neurons via neuronal cell loss and TXA
2. It also sheds light on the therapeutic potential of TXA
2 receptor blockers for the neurotoxicity of Aβ.
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