Functional significance of the negative-feedback regulation of ATP release via pannexin-1 hemichannels under ischemic stress in astrocytes

The opening of pannexin-1 (Px1) hemichannels is regulated by the activity of P2X(7) receptors (P2X(7)Rs). At present, however, little is known about how extracellular ATP-sensitive P2X(7)Rs regulates the opening and closure of Px1 hemichannels. Several lines of evidence suggest that P2X(7)Rs are activated under pathological conditions such as ischemia, resulting in the opening of Px1 hemichannels responsible for the massive influx of Ca(2+) from the extracellular space and the release of ATP from the cytoplasm, leading to cell death. Here we show in cultured astrocytes that the suppression of the activity of P2X(7)Rs during simulated ischemia (oxygen/glucose deprivation, OGD) resulted in the opening of Px1 hemichannels, leading to the enhanced release of ATP. In addition, the suppression of the activity of P2X(7)Rs during OGD resulted in a significant increase in astrocytic damage. Both the P2X(7)Rs suppression-induced enhancement of the release of ATP and cell damage were reversed by co-treatment with blockers of Px1 hemichannels, suggesting that suppression of the activity of PX(7)Rs resulted in the opening of Px1 hemichannels. All these findings suggested the existence of a negative-feedback loop regulating the release of ATP via Px1 hemichannels; ATP-induced suppression of ATP release. The present study indicates that ATP, released through Px1 hemichannels, activates P2X(7)Rs, resulting in the closure of Px1 hemichannels during ischemia. This negative-feedback mechanism, suppressing the loss of cellular ATP and Ca(2+) influx, might contribute to the survival of astrocytes under ischemic stress.

Relationship between hand stability and the 10-Hz physiological tremor during various manual tasks

To quantify an individual's ability to perform manual operations stably, the relationship between hand stability and the 10-Hz physiological tremor was investigated. A total of 35 subjects were assessed when performing force and position control tasks, which were representative of ordinary hand movements. Hand stability was analysed as two components: the fluctuation caused by voluntary control (the control error or inaccuracy when voluntarily maintaining a position or force) and the involuntary oscillatory fluctuation (physiological tremor). The control error was defined by the standard deviation of the low frequency component. The tremor was evaluated based on the power spectrum around 10 Hz. A positive correlation between the control error and the 10-Hz tremor was observed in the finger force control tasks. A correlation between finger tremor and arm tremor also was observed; subjects showing small tremors in the finger tasks also exhibited small tremors when performing the arm tasks. Taken together, the results suggested that the 10-Hz tremor can be used as a benchmark to evaluate an individual's ability to use their hands precisely. STATEMENT OF RELEVANCE: It is important to be able to quantify an individual's ability to perform precise manual operations, such as those required for microsurgery. One important aspect is instability when applying force with a finger. The relationship between hand stability and the 10-Hz physiological tremor was investigated in this study. A correlation was found between control error (or inaccuracy when voluntarily maintaining a position or force) and the 10-Hz tremor in the finger force control tasks and the results suggest that the 10-Hz tremor can be used as a measure to evaluate an individual's ability to use their hands precisely.

The number distribution of complex shear modulus of single cells measured by atomic force microscopy

The viscoelastic properties of a large number of mouse fibroblast NIH3T3 cells (n approximately 130) were investigated by combining atomic force microscopy (AFM) with a microarray technique. In the experiments, the cells were arranged and cultured in the wells of a microarray substrate, and a force modulation mode experiment was used to measure the complex shear modulus, G*, of individual cells in a frequency range 0.5-200Hz. The frequency dependence of G* of the cells exhibited a power-law behavior and similar frequency dependencies have been observed in several cell types cultured on flat substrates. This indicated that the NIH3T3 cells cultured in the wells of a microarray have analogous structural organization to those cells cultured on flat substrates. The number distribution of both the storage and loss moduli of G* fitted well to a log-normal distribution function, whereas the power-law exponent estimated by a power-law structural damping model showed a normal distribution function. These results showed that combining AFM with a microarray technique was a suitable approach for investigating the statistics of rheological properties of living cells without the requirement of cell surface modification.

Possible involvement of extracellular ATP-P2Y purinoceptor signaling in ischemia-induced tolerance of astrocytes in culture

Extracellular adenosine 5'-triphosphate (ATP) activates specific G protein-coupled purinoceptors (P2Y), and ATP-P2Y signaling pathways induces intracellular Ca(2+) mobilization resulting in changes in the gene expression of a variety of proteins in astrocytes. This study investigated whether the exposure of cultured astrocytes to sublethal ischemia produced resistance to subsequent lethal ischemic stress, and if so, whether the extracellular ATP-P2Y signaling pathways were responsible for the tolerance. Ischemia-like insults, sublethal oxygen-glucose deprivation (sOGD), produced tolerance to subsequent lethal OGD stress in cultured astrocytes. Early during reperfusion after sOGD, the amount of extracellular ATP and the expression of both P2Y(1) and P2Y(2) receptors were increased, leading to enhanced activation of the extracellular ATP-P2Y signaling pathways. The occurrence of intracellular spontaneous Ca(2+) oscillations was also increased. In addition, sOGD treatment enhanced the expression of the phosphorylated form of extracellular signal-regulated protein kinases 1 and 2 (p-ERK 1/2), and treatment with an inhibitor of ERK significantly attenuated the sOGD-induced ischemic tolerance of astrocytes.

Genome-wide analysis of DNA copy number alterations and gene expression in gastric cancer

Genomic copy number aberrations (CNAs) are believed to play a major role in the development and progression of human cancers. Although many CNAs have been reported in gastric cancer, their genome-wide transcriptional consequences are poorly understood. In this study, to reveal the impact of CNAs on genome-wide expression in gastric cancer, we analysed 30 cases of gastric cancers for their CNAs by array comparative genomic hybridization (array CGH) and 24 of these 30 cases for their expression profiles by oligonucleotide-expression microarray. We found that with the application of laser microdissection, most CNAs were detected at higher frequency than in previous studies. Notably, gain at 20q13 was detected in almost all cases (97%), suggesting that this may play an important role in the pathogenesis of gastric cancer. By comparing the array CGH data with expression profiles of the same samples, we showed that both genomic amplification and deletion strongly influence the expression of genes in altered genomic regions. Furthermore, we identified 125 candidate genes, consisting of 114 up-regulated genes located in recurrent regions (>10%) of amplification and 11 down-regulated genes located in recurrent regions of deletion. Up-regulation of several candidate genes, such as CDC6, SEC61G, ANP32E, BYSL and FDFT1, was confirmed by immunohistochemistry. Interestingly, some candidate genes were localized at genomic loci adjacent to well-known genes such as EGFR, ERBB2 and SMAD4, and concordantly deregulated by genomic alterations. Based on these results, we propose that our list of candidate genes may contain novel genes involved in the pathogenesis of advanced gastric cancer.

Disruption of the EGFR E884-R958 ion pair conserved in the human kinome differentially alters signaling and inhibitor sensitivity

Targeted therapy against epidermal growth factor receptor (EGFR) represents a major therapeutic advance in lung cancer treatment. Somatic mutations of the EGFR gene, most commonly L858R (exon 21) and short in-frame exon 19 deletions, have been found to confer enhanced sensitivity towards the inhibitors gefitinib and erlotinib. We have recently identified an EGFR mutation E884K, in combination with L858R, in a patient with advanced lung cancer who progressed on erlotinib maintenance therapy, and subsequently had leptomeningeal metastases that responded to gefitinib. The somatic E884K substitution appears to be relatively infrequent, and resulted in a mutant lysine residue that disrupts an ion pair with residue R958 in the EGFR kinase domain C-lobe, an interaction that is highly conserved within the human kinome as demonstrated by our sequence analysis and structure analysis. Our studies here, using COS-7 transfection model system, show that E884K works in concert with L858R in-cis, in a dominant fashion, to change downstream signaling, differentially induce MAPK-ERK1/2 signaling and associated cell proliferation, and differentially alter sensitivity of EGFR phosphorylation inhibition by ERBB family inhibitors in an inhibitor-specific fashion. Mutations of the conserved ion pair E884-R958 may result in conformational changes that alter kinase substrate recognition. The analogous E1271K-MET mutation conferred differential sensitivity towards preclinical MET inhibitors SU11274 (unchanged), and PHA665752 (more sensitive). Systematic bioinformatics analysis of the mutation catalog in the human kinome (COSMIC) revealed the presence of cancer-associated mutations involving the conserved E884 homologous residue, and adjacent residues at the ion pair, in known proto-oncogenes (KIT, RET, MET, FAK) and tumor suppressor gene (LKB1). Targeted therapy using small molecule inhibitors should take into account potential cooperative effects of multiple kinase mutations, and their specific effects on downstream signaling and inhibitor sensitivity. Improved efficacy of targeted kinase inhibitors may be achieved by targeting the dominant activating mutations present.

[Full-thickness pleural biopsy using an Insulation-tipped Diathermic Knife in a patient with malignant pleural mesothelioma]

A 72-year-old woman was pointed out a right pleural effusion and thickening pleura on the chest computed tomography. The patient underwent semiflexible thoracoscopy under local anesthesia at the endoscopy room. The patient was placed in the lateral decubitus position, and flexible trocar was inserted with the single puncture technique. At the macroscopic findings, the parietal pleura were thickened prominently, and patchy plaques were occasionally recognized. A standard biopsy forceps hardly grasped pleura because of presence of scar, so we performed pleural biopsy using Insulation-tipped Diathermic (IT) knife. A subpleural injection of saline containing 0.5% lidokine and 0.005% epinephrine was performed for raising the affected parietal pleura with an injection needle. After a pin hole was made, the pleural lesion was incised in a circle by manipulating the IT knife, and the incised pleura were removed. Pathology revealed extensive fibrosis and epithelial mesothelioma by the specimen. This biopsy technique using IT knife through semiflexible thoracoscopy enabled to obtain a full-thickness pleura It is thought to be useful for the diagnosis of malignant pleural mesothelioma (MPM) in which standard forceps are difficult to grasp.

Effective clearance of intracellular Leishmania major in vivo requires Pten in macrophages

Leishmaniases are a major international public health problem, and macrophages are crucial for host resistance to this parasite. To determine if phosphatase and tensin homologue deleted on chromosome ten (Pten), a negative regulator of the PI3K pathway, plays a role in macrophage-mediated resistance to Leishmania, we generated C57BL/6 mice lacking Pten specifically in macrophages (LysMCrePten(flox/flox) mice). Examination of lesions resulting from Leishmania major infection showed that LysMCrePten(flox/flox) mice were more susceptible to the parasite than wild-type (WT) mice in the early phase of the infection, but were eventually able to eliminate the pathogen. In vitro Pten-deficient macrophages showed a reduced ability to kill parasites in response to IFN-gamma treatment, possibly because the mutant cells exhibited decreased TNF secretion that correlated with reductions in inducible nitric oxide synthase expression and nitric oxide production. In response to various TLR ligands, Pten-deficient macrophages produced less TNF and IL-12 but more IL-10 than WT cells. However, analysis of cells in the lymph nodes draining L. major inoculation sites indicated that both LysMCrePten(flox/flox) and WT mice developed normal Th1 responses following L. major infection, in line with the ability of LysMCrePten(flox/flox) mice to eventually eliminate the parasite. Our results indicate that the efficient clearance of intracellular parasites requires Pten in macrophages.

Hypermethylation of p16 gene promoter correlates with loss of p16 expression that results in poorer prognosis in esophageal squamous cell carcinomas

The purpose of this study was to analyze loss of p16 expression and its relationship to hypermethylation, clinicopathological parameters and prognosis in patients with esophageal squamous cell carcinoma (ESCC). Tissue samples from 60 ESCC were subjected to histological analysis. Immunohistochemical staining for p16 expression was performed. DNA was extracted from these primary esophageal tumors and from sera from another 38 ESCC patients. The DNA was modified with bisulfite and analyzed for p16 promoter methylation by methylation-specific polymerase chain reaction. Twelve out of the 60 tumors (20%) were methylated at the p16 promoter and 48 tumors (80%) were unmethylated. There were no significant correlations between the methylation of the p16 promoter and clinicopathological parameters. Immunohistochemical staining revealed that 41 of the 60 tumors (68.3%) were p16-negative and 19 tumors (31.7%) were p16-positive. The correlation between negative p16 immunohistochemical staining and methylation was statistically significant (P = 0.0084). No instances of p16 methylation and p16 positive immunostaining were found. There was a close correlation between loss of p16 expression and poorer prognosis in ESCC (P = 0.0517 in overall survival, P = 0.0478 in disease-free survival). The p16 gene promoter hypermethylation was detected in the serum of two of 38 (5.2%) patients with ESCC. This indicates that p16 promoter methylation suppresses p16 expression and that the loss of expression has a close relationship with poor prognosis in patients with ESCC. The present results may lead to the development of new therapeutic strategies, such as p16(INK4A) gene therapy, to treat patients with ESCC.

Fluctuations in the concentration of extracellular ATP synchronized with intracellular Ca(2+) oscillatory rhythm in cultured cardiac myocytes

Isolated and cultured neonatal cardiac myocytes contract spontaneously and cyclically. The intracellular concentration of free Ca(2+) also changes rhythmically in association with the rhythmic contraction of myocytes (Ca(2+) oscillation). Both the contraction and Ca(2+) oscillatory rhythms are synchronized among myocytes, and intercellular communication via gap junctions has been considered primarily responsible for the synchronization. However, a recent study has demonstrated that intercellular communication via extracellular ATP-purinoceptor signaling is also involved in the intercellular synchronization of intracellular Ca(2+) oscillation. In this study, we aim to elucidate whether the concentration of extracellular ATP changes cyclically and contributes to the intercellular synchronization of Ca(2+) oscillation among myocytes. In almost all the cultured cardiac myocytes at four days in vitro (4 DIV), intracellular Ca(2+) oscillations were synchronized with each other. The simultaneous measurement of the concentration of extracellular ATP and intracellular Ca(2+) revealed the extracellular concentration of ATP actually oscillated concurrently with the intracellular Ca(2+) oscillation. In addition, power spectrum and cross-correlation analyses suggested that the treatment of cultured cardiac myocytes with suramin, a blocker of P2 purinoceptors, resulted in the asynchronization of Ca(2+) oscillatory rhythms among cardiac myocytes. Treatment with suramin also resulted in a significant decrease in the amplitudes of the cyclic changes in both intracellular Ca(2+) and extracellular ATP. Taken together, the present study demonstrated the possibility that the concentration of extracellular ATP changes cyclically in association with intracellular Ca(2+), contributing to the intercellular synchronization of Ca(2+) oscillation among cultured cardiac myocytes.