Accumulation of DNA methylation is associated with tumor stage in gastric cancer

BACKGROUND

The authors purpose in this study was to clarify the difference in terms of clinicopathologic features between gastric cancer (GC) with high numbers of DNA methylated genes and CpG island methylator phenotype (CIMP)-positive GC as originally defined.

METHODS

We analyzed DNA methylation of 12 tumor-related genes (hMLH1, MGMT, p16(INK4a), CDH1, RAR-beta, HLTF, RIZ1, TM, FLNc, LOX, HRASLS, HAND1) in 75 samples of GC from 75 patients, 25 samples of corresponding nonneoplastic mucosa from 25 patients, and 10 samples of normal gastric mucosa from 10 healthy young individuals by methylation-specific polymerase chain reaction (PCR) and bisulfite PCR. We also investigated CIMP status by examining the methylation of five MINT loci and p53 mutation status by PCR single-strand conformation polymorphism. We measured levels of expression of mRNAs for these 12 genes by quantitative reverse transcription PCR in 50 GC specimens.

RESULTS

The average number of methylated genes per tumor was 4.83. DNA methylation of each gene was correlated with low expression of the respective mRNA. High methylation (GC with 5 or more methylated genes) was detected in 39 (52.0%) of 75 GCs. Twenty-nine (37.8%) of 75 GCs were CIMP-positive. DNA methylation of each of the 12 genes was observed more frequently in the high-methylation group than in the low-methylation group. Methylation of 6 specific genes occurred more frequently in CIMP-positive GC than in CIMP-negative GC. Methylation of the remaining 6 genes was not correlated with CIMP-status. High methylation was found more frequently in Stage III/IV GC (26 of 40 cases, 65.0%) than in Stage I/II GC (13 of 35 cases, 37.1%, P = 0.029).CONCLUSIONS.These findings indicate that GCs with higher numbers of methylated genes have more distinct DNA methylation profiles than the originally defined CIMP-positive GCs. DNA methylation of tumor-related genes accumulates in conjunction with tumor progression.

Down-regulation of the claudin-18 gene, identified through serial analysis of gene expression data analysis, in gastric cancer with an intestinal phenotype

Gastric cancer (GC) is one of the most common malignancies worldwide. Genes whose expression is down-regulated in GC may be tumour suppressor genes. In the present study, genes with decreased expression in GC were screened for by serial analysis of gene expression (SAGE) data analysis and reverse transcription (RT)-polymerase chain reaction (PCR), and CLDN18 (encoding claudin-18) was identified. Quantitative RT-PCR revealed that expression of CLDN18 was down-regulated in 13 (56.5%) of 23 GCs. Immunostaining showed that normal gastric mucosa and Paneth cells of the duodenum expressed claudin-18 on cell membranes. Expression of claudin-18 was reduced in several intestinal metaplasias of the stomach. Of 20 samples of gastric adenoma, 18 (90.0%) showed decreased claudin-18 expression. Down-regulation of claudin-18 was observed in 84 of 146 GCs (57.5%) and correlated with poor survival in 65 advanced GCs (p = 0.0346). In addition, expression of the gastric and intestinal phenotypes of GC was examined by immunostaining for MUC5AC, MUC6, MUC2, and CD10. Of 38 GCs showing only the intestinal phenotype, down-regulation of claudin-18 was observed in 28 (73.7%), whereas in the remaining 108 GC cases, down-regulation of claudin-18 was observed in 56 (51.9%) (p = 0.0224). These results indicate that claudin-18 is a good marker of poor survival in GC. Down-regulation of claudin-18 may be involved in GCs with an intestinal phenotype, and may be an early event in gastric carcinogenesis.

Systematic search for gastric cancer-specific genes based on SAGE data: melanoma inhibitory activity and matrix metalloproteinase-10 are novel prognostic factors in patients with gastric cancer

Gastric cancer (GC) is one of the most common malignancies worldwide. Genes expressed only in cancer tissue will be useful molecular markers for diagnosis and may also be good therapeutic targets. However, little is known about cancer-specific genes, at least in GC. In this study, we searched for GC-specific genes by serial analysis of gene expression (SAGE) data analysis and quantitative reverse transcription (RT)-PCR. Comparing GC SAGE libraries with those of various normal tissues in the SAGEmap database, we identified 54 candidate GC-specific genes. Quantitative RT-PCR analysis of these candidates revealed that APin protein (APIN), taxol resistance-associated gene 3 (TRAG3), cytochrome P450, family 2, subfamily W, polypeptide 1 (CYP2W1), melanoma inhibitory activity (MIA), matrix metalloproteinase-10 (MMP-10), dickkopf homolog 4 (DKK4), GW112, regenerating islet-derived family, member 4 (REGIV), and HORMA domain-containing 1 (HORMAD1) were expressed much more highly in GC than in 14 kinds of normal tissues. Immunohistochemical staining for MIA, MMP-10, and DKK4 was found in 47 (31.1%), 68 (45.0%), and two (1.3%) of 151 GCs, respectively, and staining for both MIA and MMP-10 was correlated with poor prognosis in advanced GC (P=0.0001 and 0.0141, respectively). Moreover, enzyme-linked immunosorbent assay showed high levels of MMP-10 (65/69, 94.2%) in serum samples from patients with GC. Levels of MIA were raised in a small proportion of serum samples from patients with GC (4/69, 5.8%). In Boyden chamber invasion assays, MIA-transfected GC cells were up to three times more invasive than cells transfected with empty vector. Taken together, these results suggest that MMP-10 is a good marker for the detection of GC and that MIA and MMP-10 are prognostic factors for GC. As expression of MIA and MMP-10 is narrowly restricted in cancer, these two molecules may be good therapeutic targets for GC.

Differential expression of claudin-2 in normal human tissues and gastrointestinal carcinomas

Claudins are involved in the formation of tight junctions in epithelial and endothelial cells. Claudins form a family of 24 members displaying organ- and tissue-specific patterns of expression. In the present study, we evaluated the specificity of the claudin-2 expression in various normal human tissues and gastrointestinal cancers by quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry. In 14 various normal tissues, claudin-2 mRNA was expressed in the kidney, liver, pancreas, stomach, and small intestine; the highest level of which was detected in the kidney. Colorectal cancers (CRCs) expressed claudin-2 mRNA at high levels. Immunohistochemical analysis of claudin-2 in 146 gastric cancers (GCs) and 99 CRCs demonstrated claudin-2 expression in 2.1% of GCs and 25.3% of CRCs, respectively. There was no obvious correlation between claudin-2 expression and clinicopathological parameters of CRCs. These results suggest that the expression of claudin-2 may involve organ specificity, and increased expression of claudin-2 may participate in colorectal carcinogenesis.

Genes involved in invasion and metastasis of gastric cancer identified by array-based hybridization and serial analysis of gene expression

Gastric cancer (GC) is still a serious health problem and remains the second most common type of fatal cancer worldwide. Comprehensive gene expression analyses may be useful to identify genes associated with invasion/metastasis in GC. Among them, array-based hybridization and serial analysis of gene expression (SAGE) are currently the most common approaches. Over the past 3 years, several large-scale gene expression studies with array-based hybridization and SAGE have been performed and several genes have been identified. This review describes genes associated with invasion/metastasis in GC which have been identified by array-based hybridization and SAGE. We compared the expression levels of the genes identified by array-based hybridization with our SAGE data. In addition, expression of the candidate genes obtained by SAGE was further investigated by quantitative RT-PCR of 40 GC samples. MIA and GW112 were overexpressed in 10 (25%) and 22 (55%) of 40 GC samples, and the overexpression of these two genes was associated with tumor stage, respectively. We also discuss the significance of HMGB1/amphoterin in invasion and metastasis of GC.

Expression and localization of Reg IV in human neoplastic and non-neoplastic tissues: Reg IV expression is associated with intestinal and neuroendocrine differentiation in gastric adenocarcinoma

Regenerating islet-derived family, member 4 (Reg IV) is a candidate marker for cancer and inflammatory bowel disease. In the present study, immunohistochemical analysis of Reg IV was performed in various human neoplastic (n = 289) and non-neoplastic tissues. In the stomach, foveolar epithelium was negative for Reg IV, whereas goblet cells of intestinal metaplasia and neuroendocrine cells at the base of intestinal metaplasia expressed Reg IV. Neuroendocrine cells of the small intestine and colon showed strong expression of Reg IV, whereas goblet cells of the small intestine and colon showed weak or no expression of Reg IV. Insulin-producing beta cells of the endocrine pancreas were positive for Reg IV. Among 143 gastric adenocarcinomas, Reg IV expression was detected in 42 (29.4%) and was associated with both the intestinal mucin phenotype and neuroendocrine differentiation. No association was found between Reg IV expression and clinical characteristics such as tumour stage and patient prognosis. Of 36 colorectal adenocarcinomas, 13 (36.1%) were positive for Reg IV, which was associated with tumour stage (p = 0.0379, Fisher's exact test). Expression of Reg IV was detected in 14 (93.3%) of 15 colorectal carcinoid tumours. Reg IV expression was also detected in 5 (21.7%) of 23 ductal adenocarcinomas of the pancreas. In contrast, lung cancers (n = 30) and breast cancers (n = 30) did not express Reg IV. This is the first immunohistochemical analysis of the expression and distribution of Reg IV protein in human tumours. These data suggest that Reg IV is expressed by gastrointestinal and pancreatic tumours, including adenocarcinomas and carcinoid tumours, and that Reg IV is associated with intestinal and neuroendocrine differentiation of the stomach and gastric carcinoma.

Loss of heterozygosity and histone hypoacetylation of the PINX1 gene are associated with reduced expression in gastric carcinoma

The expression of PINX1, a possible telomerase inhibitor and a putative tumor suppressor, has not been studied in human cancers, including gastric cancer (GC). We examined expression of PINX1 by quantitative reverse transcription (RT)-PCR in 73 cases of GC, and 45 of these cases were further studied for loss of heterozygosity (LOH) by PCR with microsatellite marker D8S277. Reduced expression (tumor vs normal ratio<0.5) of PINX1 was detected in 50 (68.5%) of 73 cases of GC. GC tissues with reduced expression of PINX1 showed significantly higher telomerase activities as measured by telomeric repeat amplification protocol than those with normal expression of PINX1 (P=0.031). LOH of PINX1 locus was detected in 15 (33.3%) of 45 cases of GC and was correlated significantly with reduced expression of PINX1 (P=0.031). Expression of PINX1 in a GC cell line, MKN-74, was induced by treatment with trichostatin A (TSA) or nicotinamide (NAM). Chromatin immunoprecipitation assay of MKN-74 cells revealed that acetylation of histone H4 in the 5' untranslated region (UTR) of PINX1 was enhanced by treatment with TSA or NAM, whereas acetylation of histone H3 was not changed by TSA or NAM. In addition, TSA or NAM treatment led to inhibition of telomerase activity in MKN-74 cells. These results indicate that LOH of PINX1 locus and hypoacetylation of histone H4 in the 5' UTR of PINX1 are associated with reduced expression of PINX1 in GC.

Histone H3 acetylation is associated with reduced p21(WAF1/CIP1) expression by gastric carcinoma

Histone acetylation appears to play an important role in transcriptional regulation. Inactivation of chromatin by histone deacetylation is involved in the transcriptional repression of several tumour suppressor genes, including p21(WAF1/CIP1). However, the in vivo status of histone acetylation in human cancers, including gastric carcinoma, is not well understood. This study shows that histone H3 in the p21(WAF1/CIP1) promoter region is hypoacetylated and that this hypoacetylation is associated with reduced p21(WAF1/CIP1) expression in gastric carcinoma specimens. Chromatin immunoprecipitation assays revealed that histone H3 was hypoacetylated in the p21(WAF1/CIP1) promoter and coding regions in 10 (34.5%) and 10 (34.5%) of 29 gastric carcinoma specimens, respectively. Hypoacetylation of histone H4 in the p21(WAF1/CIP1) promoter and coding regions was observed in 6 (20.7%) and 16 (55.2%) of 29 gastric carcinoma specimens, respectively. p21(WAF1/CIP1) mRNA levels were associated with histone H3 acetylation status in the p21(WAF1/CIP1) promoter region (p = 0.047) but not p53 mutation status (p = 0.460). In gastric carcinoma cell lines, expression of p21(WAF1/CIP1) protein was induced by trichostatin A, a histone deacetylase inhibitor. This induction was associated with hyperacetylation of histone H3 in the p21(WAF1/CIP1) promoter region. Hyperacetylation of histone H4 in the p21(WAF1/CIP1) promoter region did not appear to be associated with increased expression. Induction of p21(WAF1/CIP1) protein expression was associated with hyperacetylation of histones H3 and H4 in the p21(WAF1/CIP1) coding region. Expression of a dominant-negative mutant of p53 reduced expression of p21(WAF1/CIP1) protein. Histone H4 acetylation in both the promoter and coding regions of the p21(WAF1/CIP1) gene in cells expressing dominant-negative p53 was less than half of that in cells expressing wild-type p53, whereas histone H3 acetylation in both the promoter and coding regions was slightly reduced (by approximately 20%) in cells expressing the dominant-negative p53. These findings provide evidence that alteration of histone acetylation occurs in human cancer tissue specimens such as those from gastric carcinoma.

Frequent loss of RUNX3 expression by promoter hypermethylation in gastric carcinoma

The RUNX3 gene is a member of the Runt domain family of transcription factors that are master regulators of gene expression in major developmental pathways. Recently, lack of RUNX3 function was found to be associated with genesis and progression of gastric carcinoma. We studied methylation of CpG islands in the RUNX3 gene by methylation-specific PCR in 80 gastric carcinoma specimens, 45 corresponding non-neoplastic mucosae, and 7 gastric carcinoma cell lines. We also measured levels of RUNX3 mRNA in 50 of the gastric carcinoma cases by quantitative RT-PCR and in the gastric carcinoma cell lines by RT-PCR. Hypermethylation of the RUNX3 promoter was found in 57 (71%) of 80 gastric carcinomas, and promoter hypermethylation of RUNX3 occurred more frequently in intestinal and diffuse-adherent type tumors than in diffuse-scattered type tumors (p = 0.046). Reduced RUNX3 expression was associated with promoter hypermethylation (p = 0. 036), however, there was no correlation between RUNX3 mRNA expression levels and T grade, N grade, tumor stage, or histological type. In corresponding non-neoplastic mucosae, hypermethylation of the RUNX3 promoter was found in 38 (84%) of 45 specimens. Among seven gastric carcinoma cell lines, three cell lines (MKN-28, MKN-74, TMK-1) with diminished expression of RUNX3 had promoter methylation and three cell lines (MKN-1, MKN-7, MKN-45) with RUNX3 expression showed no promoter methylation. Our results overall suggest that transcriptional inactivation of RUNX3 by promoter hypermethylation may participate in the stomach carcinogenesis.

Frequent epigenetic inactivation of RIZ1 by promoter hypermethylation in human gastric carcinoma

The retinoblastoma protein-interacting zinc finger gene, RIZ1 (GenBank accession number U17838), is involved in chromatin-mediated gene expression and is also a target for frameshift mutation in microsatellite-unstable cancers. Methylation of the RIZ1 promoter CpG island has been shown to be a common mechanism in inactivating the RIZ1 gene in human liver and breast cancers. We investigated levels of RIZ1 mRNA in 45 gastric carcinoma tissues by quantitative RT-PCR and in gastric carcinoma cell lines by RT-PCR. In addition, we examined CpG island methylator phenotype (CIMP) status, p53 mutation status, and the correlation between promoter methylation status and RIZ1 mRNA expression. CIMP status was investigated by examining the methylation status of MINT1, MINT2, MINT12, MINT25 and MINT31. p53 mutation status was examined by PCR-single strand conformation polymorphism and promoter methylation status was examined by methylation-specific PCR. Promoter hypermethylation of the RIZ1 gene was found in 31 (69%) of 45 gastric carcinoma tissues and in 3 (21%) of 14 corresponding non-neoplastic mucosae, the incidence being significantly different (p = 0.002). None of the 12 normal gastric tissues from young non-cancer individuals showed hypermethylation. Promoter hypermethylation was associated with reduced RIZ1 expression in gastric carcinoma tissues (p = 0.029). Promoter hypermethylation of the RIZ1 gene was significantly associated with CIMP (p = 0.002). Mutation status of the p53 gene was not associated with methylation status or RIZ1 expression in gastric carcinoma. In gastric carcinoma cell lines MKN-28 and KATO-III, the RIZ1 promoter was hypermethylated and RIZ1 transcription was inactive. Treatment of these cells with demethylating agent 5-aza-2'-deoxycytidine restored RIZ1 transcription. Our results suggest that transcriptional inactivation of the RIZ1 gene by promoter hypermethylation may participate in stomach carcinogenesis.

Gene expression profile of gastric carcinoma: identification of genes and tags potentially involved in invasion, metastasis, and carcinogenesis by serial analysis of gene expression

Gastric carcinoma (GC) is one of the most common malignancies worldwide. To better understand the genetic basis of this disease, we performed serial analysis of gene expression (SAGE) on four primary GC samples and one associated lymph node metastasis. We obtained a total of 137,706 expressed tags (Gene Expression Omnibus accession number GSE 545, SAGE Hiroshima gastric cancer tissue), including 38,903 that were unique. Comparing tags from our GC libraries containing different stages and different histologies, we found several genes and tags that are potentially involved in invasion, metastasis, and carcinogenesis. Among these, we selected 27 genes and measured mRNA expression levels in an additional 46 GC samples by quantitative reverse transcription-PCR. Frequently overexpressed genes (tumor/normal ratio > 2) were COL1A1 (percentage of cases with overexpression, 78.3%), CDH17 (73.9%), APOC1 (67.4%), COL1A2 (58.7%), YF13H12 (52.2%), CEACAM6 (50.0%), APOE (50.0%), REGIV (47.8%), S100A11 (41.3%), and FUS (41.3%). Among these genes, mRNA expression levels of CDH17 and APOE were associated with depth of tumor invasion (P = 0.0060 and P = 0.0139, respectively), and those of FUS and APOE were associated with degree of lymph node metastasis (P = 0.0416 and P = 0.0006, respectively). In addition, mRNA expression levels of FUS, COL1A1, COL1A2, and APOE were associated with stage (P = 0.0414, P = 0.0156, P = 0.0395, and P = 0.0125, respectively). Quantitative reverse transcription-PCR analysis also showed a high level of REGIV expression (>100 arbitrary units) in 14 of 46 GC samples (30.4%) but not in noncancerous tissues. We detected V5-tagged RegIV protein in the culture media of cells transfected with pcDNA-RegIV-V5 by Western blot. Our results provide a list of candidate genes that are potentially involved in invasion, metastasis, and carcinogenesis of GC. REGIV may serve as a specific biomarker for GC.

Expression of POT1 is associated with tumor stage and telomere length in gastric carcinoma

Pot1, a telomere end-binding protein in fission yeast and human, is proposed not only to cap telomeres but also to recruit telomerase to the ends of chromosomes. No study has been performed regarding Pot1 expression status in human cancers. Thus, we examined POT1 mRNA expression in 51 gastric cancer (GC) tissues and evaluated telomere length and 3' telomeric overhang signals in 20 of the 51 GC tissues. Quantitative reverse transcription-PCR analysis showed that POT1 expression levels in the tumor relative to those in nonneoplastic mucosa (T/N ratio) were significantly higher in stage III/IV tumors than in stage I/II tumors (P = 0.005). Down-regulation of POT1 (T/n < 0.5) was observed more frequently in stage I/II GC (52.4%, 11 of 21) than in stage III/IV GC (23.3%, 7 of 30; P = 0.033), whereas up-regulation of POT1 (T/n > 2.0) was observed more frequently in stage III/IV GC (33.3%, 10 of 30) than in stage I/II GC (9.5%, 2 of 21; P = 0.048). POT1 expression levels showed decreased in accordance with telomere shortening (r = 0.713, P = 0.002). In-gel hybridization analysis showed that 3' telomeric overhang signals decreased in accordance with decreases in POT1 expression levels (r = 0.696, P = 0.002) and telomere shortening (r = 0.570, P = 0.013). Reduced POT1 expression was observed in GC cell lines with telomeres shortened by treatment with azidothymidine. In addition, inhibition of Pot1 by antisense oligonucleotides led to telomere shortening as well as inhibition of telomerase activity in GC cells. Moreover, inhibition of Pot1 decreased 3' overhang signals and increased the frequency of anaphase bridge (P = 0.0005). These data suggest that Pot1 may play an important role in regulation of telomere length and that inhibition of Pot1 may induce telomere dysfunction. Moreover, changes in POT1 expression levels may be associated with stomach carcinogenesis and GC progression.

DNA hypermethylation and histone hypoacetylation of the HLTF gene are associated with reduced expression in gastric carcinoma

The SWI/SNF proteins are ATP-dependent chromatin remodeling enzymes that have been implicated in the regulation of gene expression. Recent studies have shown that members of the SWI/SNF superfamily can function as tumor suppressor genes. DNA methylation and transcriptional inactivation of the HLTF gene, which is a homologue to the SWI/SNF genes, have been observed in colon cancer. In the present study, we studied the DNA methylation status of the HLTF gene by methylation-specific PCR in 50 gastric carcinoma tissues, and seven gastric carcinoma cell lines and compared the methylation status with the levels of HLTF mRNA expression. DNA methylation of the HLTF gene was found in 25 (50%) of 50 gastric carcinomas, and levels of HLTF mRNA were associated with methylation status of HLTF (P = 0.027; Mann-Whitney U test). No correlations were found between HLTF mRNA levels and DNA methylation and T grade, N grade, tumor stage, or histological type. In corresponding non-neoplastic mucosae, DNA methylation of the HLTF gene was found in 1 (7%) of 15 samples. The methylated allele was not detected in any of 10 normal gastric mucosae from 10 healthy volunteers. Among seven gastric carcinoma cell lines, the KATO-III cell line showed loss of HLTF mRNA expression associated with DNA methylation. This loss was rectified by treatment with both Aza-2'-deoxycytidine, a demethylating agent, and trichostatin A, a histone deacetylase inhibitor. Chromatin immunoprecipitation assay revealed that the acetylation levels of histones H3 and H4 in the 5' CpG island of the HLTF gene were inversely associated with DNA methylation status. These results suggest that transcriptional inactivation of HLTF by aberrant DNA methylation and histone deacetylation may be involved in stomach carcinogenesis through down-regulation of HLTF expression.

Histone acetylation and gastrointestinal carcinogenesis

The importance of altered histone acetylation in gastrointestinal carcinogenesis, especially in relation to invasion and metastasis, is described. Histone acetylation and chromatin remodeling linked with CpG island methylation play a major role in epigenetic regulation of gene expression. Acetylation of histones through an imbalance of histone acetyltransferases and deacetylases disrupts nucleosome structure, which leads to DNA relaxation and subsequent increase in accessibility to transcription factors. The expression of acetylated histone H4 is reduced in a majority of gastric and colorectal cancers, indicating the low level of global histone acetylation in tumor cells. Moreover, reduced histone acetylation is significantly associated with depth of tumor invasion and nodal metastasis of gastrointestinal cancers. A histone deacetylase inhibitor, trichostatin A (TSA), induces growth arrest and apoptosis and suppresses invasion of cancer cells. Treatment with TSA, which is followed by increased histone acetylation in the promoters, induces the expression of many genes that are suppressors of invasion and metastasis, including tissue inhibitors of metalloproteinase and nm23H1/H2, in addition to negative cell cycle regulators and apoptosis-related molecules. Our approach, serial analysis of gene expression (SAGE), enabled us to identify a gene that is a novel candidate for a metastasis suppressor, whose expression is induced by histone acetylation. These findings suggest that, by modifying gene expression, histone deacetylation may participate not only in tumorigenesis but also in invasion and metastasis. Therefore, histone acetylation should be a promising target for cancer therapy, especially against invasive and metastatic disease, but also for cancer prevention.

Correlation of inhaled nitric-oxide induced reduction of pulmonary artery pressure and vascular changes

The purpose of the present study was to determine the relationship between hypertensive pulmonary vascular remodelling and the changes in mean pulmonary artery pressure (mPAP) during low-dose nitric oxide (NO) inhalation. Rats were exposed to chronic hypobaric hypoxia (air at 50.5 kPa (380 mmHg), 10% oxygen, for 5-29 days) to induce chronic pulmonary hypertension (PH) with pulmonary vascular structural changes. After the chronic hypoxic exposure, the rats had an indwelling pulmonary artery catheter inserted and changes in mPAP with NO were correlated to morphometrical analysis of pulmonary vascular changes. All concentrations of inhaled NO (0.1-2.0 parts per million) reduced mPAP with a similar per cent reduction from baseline mPAP in PH rats, while no changes were observed in control rats. During NO inhalation in PH rats, the absolute value of the decrease in mPAP, but not per cent reduction in mPAP, significantly correlated with baseline mPAP, the percentage of muscularised arteries at the alveolar wall level and at the alveolar duct level, and the per cent medial wall thickness of muscularised arteries. In the chronic hypoxic pulmonary hypertension model, the severity of pulmonary vascular remodelling did not alter the reactivity of the pulmonary arteries to nitric oxide and might, in part, determine the magnitude of nitric-oxide induced absolute reduction in mean pulmonary artery pressure.

Ultrafiltration of the priming blood before cardiopulmonary bypass attenuates inflammatory response and improves postoperative clinical course in pediatric patients

The priming solution using in cardiopulmonary bypass (CPB) for infants undergoing cardiac surgery includes considerable amounts of stored blood. Our objective was to test the hypothesis that ultrafiltration (UF) of the stored blood before CPB reduces the unfavorable effects of stored blood and the production of inflammatory cytokines. Fifty pediatric patients with congenital heart defects took part in this study. The patients were randomly divided into two groups: the UF (27 pediatric patients who received UF) and control (23 pediatric patients who did not receive UF) groups. UF was performed with a polysulphone ultrafiltrator before CPB. Blood samples were collected immediately before, during, and 1 h after CPB. The levels of cytokines (TNF-alpha, IL-1beta, IL-8), NH3, and bradykinin were determined. The serum concentrations of NH3 and bradykinin decreased significantly after UF. Compared with the control group, the UF group had significantly lower cytokine production. Water balance in UF group was better than that of control group. The UF group received significantly less inotropic support and shorter duration of ventilator support and ICU stay. We conclude that removal of bradykinin and a decrease in the levels of NH3, potassium, and pH play a significant role in reducing water retention and postoperative lung injury. UF of the blood used to prime the circuit for CPB is a safe and efficient method for use in open heart surgery in small pediatric patients.

Heterodimer formation between the antimicrobial peptides magainin 2 and PGLa in lipid bilayers: a cross-linking study

The antimicrobial peptides magainin 2 and PGLa, isolated from the skin of the African clawed frog Xenopus laevis, show marked synergism [Westerhoff, H. V., Zasloff, M., Rosner, J. L., Hendler, R. W., de Waal, A., Vaz Gomes, A., Jongsma, A. P. M., Riethorst, A., and Juretic, D. (1995) Eur. J. Biochem. 228, 257-264]. We suggested previously that these peptides form a potent heterodimer composed of either parallel or antiparallel helices in membranes [Matsuzaki, K., Mitani, Y., Akada, K., Murase, O., Yoneyama, S., Zasloff, M., and Miyajima, K. (1998) Biochemistry 37, 15144-15153]. To detect the putative heterodimer by chemical cross-linking, analogues of magainin 2 and PGLa with a Cys residue at either terminus were synthesized. These cross-linking experiments suggested that both peptides form a parallel heterodimer in membranes composed of phosphatidylglycerol/phosphatidylcholine but not in either buffer or a helix-promoting 2,2,2-trifluoroethanol/buffer mixture. The isolated parallel heterodimers exhibited an order of magnitude higher membrane permeabilization activity compared with the monomeric species, indicating that the observed synergism is due to heterodimer formation.

Regulation of the muscle-specific expression and function of an ascidian T-box gene, As-T2

The Tbx6 T-box genes are expressed in somite precursor cells of vertebrate embryos and are essential for the differentiation of paraxial mesoderm. However, it is unclear how spatial regulation of the gene expression is controlled and how the genes function to promote muscle differentiation. The Tbx6-related gene As-T2 of the ascidian Halocynthia roretzi is first expressed very transiently in endodermal cells around the 32-∼44-cell stage, is then expressed distinctly and continuously in muscle precursor cells, and later in epidermal cells situated in the distal tip region of the elongating tail. We now show that inhibition of As-T2-mediated transcriptional activation by microinjection of As-T2/EnR into one-cell embryos resulted in suppression of the expression of the muscle-specific actin gene (HrMA4) and myosin heavy chain gene (HrMHC), but the injection did not affect the differentiation of endodermal cells or tail tip cells, suggesting that the primary function of As-T2 is associated with muscle cell differentiation. The 5′ flanking region of As-T2 contains two promoter modules that regulate its specific expression: a distal module that responsible for its specific expression in the tail, and a proximal module required for its muscle-specific expression. Around the proximal module, there are two putative T protein-binding motifs (TTCACACTT). Co-injection of an As-T2/lacZ construct with or without the T-binding motifs together with As-T2 mRNA revealed that these motifs are essential for autoregulatory activation of the gene itself. In addition, we found that the minimal promoter regions of HrMA4 and HrMHC contain T-binding motifs. Co-injection of HrMA4/lacZ or HrMHC/lacZ containing the T-binding motifs along with As-T2 mRNA revealed that As-T2 protein binds to these motifs to upregulate the gene activity. Taking into account the recent finding of maternal molecules for muscle differentiation, we propose a model for a genetic cascade that includes As-T2 as a regulator of muscle cell differentiation in the ascidian embryo.

Moving-table reduced-dose gadolinium-enhanced three-dimensional magnetic resonance angiography: velocity-dependent method with three-phase gadolinium infusion

The purpose of this study was to develop a method for reducing gadolinium dose and suppressing venous overlap in moving-table three-dimensional (3D) magnetic resonance (MR) angiography from the abdomen to the feet. Thirty-one patients underwent three-phase infusion of 16-18 mL of gadolinium: infusion rates and imaging times were determined after taking into account mean blood flow velocity, so that image acquisition was synchronized with peak arterial enhancement at both the first and third stations (velocity-dependent method). Twenty-three other patients underwent slow infusion of 38 mL of gadolinium with fixed acquisition time (high-dose method). The image quality for the two methods was compared. The velocity-dependent method produced good image quality with significantly less venous overlap than the high-dose method, especially in the below-the-knee region (P <.001). The velocity-dependent method provides satisfactory MR angiograms using 16-18 mL of gadolinium in patients having various blood flow velocities.

Cross talk of the interferon-alpha/beta signalling complex with gp130 for effective interleukin-6 signalling

BACKGROUND

Signalling cross talk provides a molecular basis for modulating a given signalling pathway by another, and it is often critical for regulating cellular responses elicited by cytokines. Previously, we reported on the critical role of the IFN-alpha/beta signalling complex, generated by spontaneously produced IFN-alpha/beta, in efficient IFN-gamma signalling.

RESULTS

In the present study, we have demonstrated that the IFN-alpha/beta signalling complex also contributes to efficient IL-6 signalling. In fact, IL-6-induced activation of the Stat1 and Stat3 transcription factors is markedly diminished in the absence of the IFN-alpha/beta signalling complex. The induction of several target genes for these factors is also diminished, both in vitro and in vivo. We provide evidence that the cytoplasmic tyrosine residues of IFNAR-1, which remains phosphorylated by a weak IFN-alpha/beta stimulation, provide docking sites for Stat1 and Stat3 to form homo- or heterodimers following IL-6 stimulation. Furthermore, a chemical cross-linking experiment revealed that IFNAR-1 and gp130, a common signal transducer for the IL-6 family of cytokines, exist in close proximity.

CONCLUSIONS

The constitutive weak IFN-alpha/beta signal provides a foundation for strong cellular responses to IL-6, IFN-gamma, and possibly other cytokines. Our results also suggest the assembly of cytokine receptor subunits, which may represent a 'receptosome'-like structure, allowing the unique signalling cross talks to occur.

Polymorphonuclear leukocyte adhesion to articular cartilage is inhibited by cartilage surface macromolecules

The present studies deal with polymorphonuclear neutrophil (PMN) adhesion inhibitory properties of cartilage surface proteoglycans. Normal human PMN were used in adhesion experiments with bovine cartilage surfaces exposed to neutrophil elastase and reconstituted with fibronectin (Fn) or on plastic-bound Fn. An extract of cartilage surface small proteoglycans (SE) and purified fibromodulin (FM), decorin (DCN), biglycan (BGN), and aggrecan (AGN) on the surface of normal cartilage were used to test for inhibition of Fn-dependent cell adhesion. The PMN did not adhere to intact articular cartilage surfaces, whereas significant adhesion was measured using cartilage explants digested with elastase and reconstituted with Fn. Incubation of elastase-treated, Fn-reconstituted cartilage with 45 microg/ml SE inhibited PMN adhesion by 50.7 +/- 5.8% (P < 0.0001). Addition of 50 microg/ml purified FM to the reconstituted articular surfaces inhibited cell adhesion by 71.2 +/- 13.9% (P < 0.0001). Inhibition of PMN adhesion to plastic-bound Fn was seen with 1.7 microg/ml SE (20.4 +/- 8.0%). Maximal inhibition of 67.4 +/- 14.8% (P < 0.01) was obtained with 17.0 microg/ml SE. With FM, concentrations of 4.3 microg/ml resulted in 34.7 25.2 inhibition (P < 0.001), and maximal inhibition of 66.3 16.2% (P < 0.01) was obtained with 43.0 microg/ml. Similar results were obtained with purified bovine DCN and BGN. The main component of cartilage matrix, AGN, failed to inhibit cell adhesion significantly. The results indicate that macromolecules normally present on articular cartilage surfaces act as a barrier to PMN adhesion. Since cartilage surface proteins are susceptible to breakdown by proteases from synovial fluid inflammatory cells, we postulate that the degradation of this barrier may be responsible for increasing PMN adhesion and subsequent cartilage damage in inflammatory arthritis.

Vascular smooth muscle cell phenotypes in primary pulmonary hypertension

Primary pulmonary hypertension (PPH) is associated with specific structural alterations, including cellular intimal thickening, intimal fibrosis, and plexiform lesions. To determine the phenotypes of smooth muscle cells (SMCs) in such lesions, the authors conducted an immunohistochemical analysis of lung tissues from two patients with PPH, using two antimuscle actin antibodies, HHF35 and CGA7, and two anti-SMC myosin heavy chain markers, anti-SM1 and anti-SM2 antibodies and related antibodies. Cells that stained positive (+) with HHF35, CGA7, anti-SM1, and anti-SM2 were considered to be SMCs of a mature state. Conversely, those that stained positive with HHF35 and anti-SM1, but weakly positive (+/-) or negative (-) with CGA7 and anti-SM2, were considered to be SMCs exhibiting an immature state. Cellular intimal thickening was composed of SMCs of an immature phenotype (HHF35+, CGA7+/-, SM1+, SM2+/-), accompanied by the expression of fibronectin and the presence of macrophages; intimal fibrosis contained mature SMCs (HHF35+, CGA7+, SM1+, SM2+); and plexiform lesion consisted of proliferative endothelial cells (von Willebrand factor-positive cells, proliferating cell nuclear antigen-positive cells) and underlying immature SMCs (HHF35+, CGA7-, SM1+, SM2-) associated with fibronectin expression and macrophage infiltration. These findings suggest that smooth muscle cells with specific phenotypes may contribute to the development of specific vascular lesions in primary pulmonary hypertension.

Mastoid pneumatization of the patulous eustachian tube

The pathophysiology of the patulous eustachian tube (PET) remains unclear. The degree of mastoid cell pneumatization is considered an indicator of chronic inflammation of the middle ear. We used the mastoid cell area to investigate the relationship between past chronic inflammation of the middle ear cavity and a PET in 84 patients (20 to 83 years old). The mastoid cell size was calculated from radiographs and analyzed relative to the history of otitis media (OM). The controls were 100 normal ears. The patients' mastoid cell size was significantly suppressed versus that of the controls, in both 31 PET cases with and 53 PET cases without past OM. We surmise the possibility that the PET ears had experienced inflammation even when the patients had no history of OM and the tympanic membrane showed no OM sequelae. This study indicates the existence of some relationship between a history of chronic inflammation of the middle ear cavity and a PET.