Glucocorticoid receptor-NECAB1 axis can negatively regulate insulin secretion in pancreatic β-cells

The mechanisms of impaired glucose-induced insulin secretion from the pancreatic β-cells in obesity have not yet been completely elucidated. Here, we aimed to assess the effects of adipocyte-derived factors on the functioning of pancreatic β-cells. We prepared a conditioned medium using 3T3-L1 cell culture supernatant collected at day eight (D8CM) and then exposed the rat pancreatic β-cell line, INS-1D. We found that D8CM suppressed insulin secretion in INS-1D cells due to reduced intracellular calcium levels. This was mediated by the induction of a negative regulator of insulin secretion-NECAB1. LC-MS/MS analysis results revealed that D8CM possessed steroid hormones (cortisol, corticosterone, and cortisone). INS-1D cell exposure to cortisol or corticosterone increased Necab1 mRNA expression and significantly reduced insulin secretion. The increased expression of Necab1 and reduced insulin secretion effects from exposure to these hormones were completely abolished by inhibition of the glucocorticoid receptor (GR). NECAB1 expression was also increased in the pancreatic islets of db/db mice. We demonstrated that the upregulation of NECAB1 was dependent on GR activation, and that binding of the GR to the upstream regions of Necab1 was essential for this effect. NECAB1 may play a novel role in the adipoinsular axis and could be potentially involved in the pathophysiology of obesity-related diabetes mellitus.

Quantification of DNA methylation for carcinogenic risk estimation in patients with non-alcoholic steatohepatitis

BACKGROUND

In recent years, non-alcoholic steatohepatitis (NASH) has become the main cause of hepatocellular carcinoma (HCC). As a means of improving the treatment of NASH-related HCCs based on early detection, this study investigated the feasibility of carcinogenic risk estimation in patients with NASH.

RESULTS

Normal liver tissue (NLT), non-cancerous liver tissue showing histological findings compatible with non-alcoholic fatty liver from patients without HCC (NAFL-O), non-cancerous liver tissue showing NASH from patients without HCC (NASH-O), non-cancerous liver tissue showing non-alcoholic fatty liver from patients with HCC (NAFL-W), non-cancerous liver tissue showing NASH from patients with HCC (NASH-W) and NASH-related HCC were analyzed. An initial cohort of 171 tissue samples and a validation cohort of 55 tissue samples were used. Genome-wide DNA methylation screening using the Infinium HumanMethylation450 BeadChip and DNA methylation quantification using high-performance liquid chromatography (HPLC) with a newly developed anion-exchange column were performed. Based on the Infinium assay, 4050 CpG sites showed alterations of DNA methylation in NASH-W samples relative to NLT samples. Such alterations at the precancerous NASH stage were inherited by or strengthened in HCC samples. Receiver operating characteristic curve analysis identified 415 CpG sites discriminating NASH-W from NLT samples with area under the curve values of more than 0.95. Among them, we focused on 21 CpG sites showing more than 85% specificity, even for discrimination of NASH-W from NASH-O samples. The DNA methylation status of these 21 CpG sites was able to predict the coincidence of HCC independently from histopathological findings such as ballooning and fibrosis stage. The methylation status of 5 candidate marker CpG sites was assessed using a HPLC-based system, and for 3 of them sufficient sensitivity and specificity were successfully validated in the validation cohort. By combining these 3 CpG sites including the ZC3H3 gene, NAFL-W and NASH-W samples from which HCCs had already arisen were confirmed to show carcinogenic risk with 95% sensitivity in the validation cohort.

CONCLUSIONS

After a further prospective validation study using a larger cohort, carcinogenic risk estimation in liver biopsy specimens of patients with NASH may become clinically applicable using this HPLC-based system for quantification of DNA methylation.

Proteolytic cleavage of membrane proteins by membrane type-1 MMP regulates cancer malignant progression

Strategies to develop cancer therapies using inhibitors that target matrix metalloproteinases (MMPs), particularly membrane type-1 MMP (MT1-MMP), have failed. This is predominantly attributed to the specificity of MMP inhibitors and numerous functions of MMPs; therefore, targeting substrates with such broad specificity can lead to off-target effects. Thus, new drug development for cancer therapeutics should focus on the ability of MT1-MMP to break down substrates, such as functional cell membrane proteins, to regulate the functions of these proteins that promote tumor malignancy. In this review, we discuss the mechanism by which proteolysis of cell surface proteins by MT1-MMP promotes progression of malignant tumor cells. In addition, we discuss the two protein fragments generated by limited cleavage of erythropoietin-producing hepatoma receptor tyrosine kinase A2 (EphA2-NF, -CF), which represent a promising basis for developing new cancer therapies and diagnostic techniques.

Abstract 5703: Quantification of DNA methylation for carcinogenic risk estimation in patients with non-alcoholic steatohepatitis

Background: In recent years, non-alcoholic steatohepatitis (NASH) has become the main cause of hepatocellular carcinoma (HCC). As a means of improving the treatment of NASH-related HCCs based on early detection, this study investigated the feasibility of carcinogenic risk estimation in patients with NASH.

Results: Normal liver tissue (NLT), non-cancerous liver tissue (N) showing histological findings compatible with non-alcoholic fatty liver (NAFL) from patients without HCC (NAFL-O), N showing NASH from patients without HCC (NASH-O), N showing NAFL from patients with HCC (NAFL-W), N showing NASH from patients with HCC (NASH-W) and NASH-related HCC (T) were analyzed. An initial cohort of 171 tissue samples and a validation cohort of 55 tissue samples (226 samples in total) were used. Genome-wide DNA methylation screening using the Infinium HumanMethylation450 BeadChip and DNA methylation quantification using high-performance liquid chromatography (HPLC) with a newly developed anion-exchange column were performed. Based on the Infinium assay, 4,050 CpG sites showed significant alterations of DNA methylation in 22 NASH-W samples relative to 36 NLT samples in the initial cohort, indicating that DNA methylation alterations had occurred in the NASH-W samples. On 3,234 of the 4,050 CpG sites, DNA methylation alterations in NASH-W samples relative to NLT samples were inherited by or strengthened in 22 T samples (Jonckheere-Terpstra trend test). Among the 3,234 CpG sites, receiver operating characteristic curve analysis identified 415 CpG sites discriminating NASH-W from NLT samples with area under the curve values of more than 0.95. Among the 415 CpG sites, we focused on 21 CpG sites showing more than 85% specificity, even for discrimination of NASH-W from 91 NASH-O samples. The DNA methylation status of these 21 CpG sites was able to predict the coincidence of HCC independently from histopathological findings such as ballooning and fibrosis stage (Brunt classification). The methylation status of 5 candidate marker CpG sites was assessed using a HPLC-based system, which will be easily introduced into clinical laboratories, and for 3 of them sufficient sensitivity and specificity was successfully validated in the validation cohort. By combining these 3 CpG sites including the ZC3H3 gene, of which expression alternation may affect the post-transcriptional regulation of various tumor-related genes, 10 NAFL-W and 11 NASH-W samples from which HCCs had already arisen were confirmed to show carcinogenic risk with 95% sensitivity in the validation cohort.

Conclusions: After a further prospective validation study using a larger cohort, carcinogenic risk estimation in liver biopsy specimens of patients with NASH may become clinically applicable using this HPLC-based system for quantification of DNA methylation.

Citation Format: Junko Kuramoto, Eri Arai, Mao Fujimoto, Ying Tian, Yuriko Yamada, Takuya Yotani, Satomi Makiuchi, Noboru Tsuda, Hidenori Ojima, Moto Fukai, Yosuke Seki, Kazunori Kasama, Nobuaki Funahashi, Haruhide Udagawa, Takao Nammo, Kazuki Yasuda, Akinobu Taketomi, Tatsuya Kanto, Yae Kanai. Quantification of DNA methylation for carcinogenic risk estimation in patients with non-alcoholic steatohepatitis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5703.

Effects of maternal and fetal choline concentrations on the fetal growth and placental DNA methylation of 12 target genes related to fetal growth, adipogenesis, and energy metabolism

AIM

We performed a birth cohort study involving 124 mother-infant pairs to investigate whether placental DNA methylation is associated with maternal choline status and fetal development.

METHODS

Plasma choline concentration was assayed longitudinally in the 1st and 3rd trimesters and at term-pregnancy in mothers and cord blood. Placental DNA methylation was measured for 12 target candidate genes that are related to fetal growth, adipogenesis, lipid and energy metabolism, or long interspersed nuclear elements.

RESULTS

Higher maternal plasma and cord blood choline levels at term tended to associate with lower birthweight (r = -0.246, P < 0.013; r = -0.290, P < 0.002) and body mass index (BMI) at birth (r = 0.344, P < 1E-3; r = -0.360, P < 1E-3). The correlation between maternal plasma choline level and cord blood choline level was relatively modest (r = 0.049, P = 0.639). There was an inverse correlation between placental DNA methylation at the retinoid X receptor alpha (RXRA) gene and maternal plasma choline level (r = -0.188 to r = -0.452, P = 0.043 to P < 1E-3 at three points). RXRA methylation level was positively associated with birthweight and BMI at birth (r = 0.306, P = 0.001; r = 0.390, P < 1E-3). Further, RXRA methylation was inversely correlated with RXRA gene expression level (r = 0.333, P < 1E-3).

CONCLUSION

Our results suggest that the association between maternal choline status and placental RXRA methylation represents a potential fetal programing mechanism contributing to fetal growth.

Genome-wide profiling of histone H3K27 acetylation featured fatty acid signalling in pancreatic beta cells in diet-induced obesity in mice

AIMS/HYPOTHESIS

Epigenetic regulation of gene expression has been implicated in the pathogenesis of obesity and type 2 diabetes. However, detailed information, such as key transcription factors in pancreatic beta cells that mediate environmental effects, is not yet available.

METHODS

To analyse genome-wide cis-regulatory profiles and transcriptome of pancreatic islets derived from a diet-induced obesity (DIO) mouse model, we conducted chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-Seq) of histone H3 lysine 27 acetylation (histone H3K27ac) and high-throughput RNA sequencing. Transcription factor-binding motifs enriched in differential H3K27ac regions were examined by de novo motif analysis. For the predicted transcription factors, loss of function experiments were performed by transfecting specific siRNA in INS-1, a rat beta cell line, with and without palmitate treatment. Epigenomic and transcriptional changes of possible target genes were evaluated by ChIP and quantitative RT-PCR.

RESULTS

After long-term feeding with a high-fat diet, C57BL/6J mice were obese and mildly glucose intolerant. Among 39,350 islet cis-regulatory regions, 13,369 and 4610 elements showed increase and decrease in ChIP-Seq signals, respectively, significantly associated with global change in gene expression. Remarkably, increased H3K27ac showed a distinctive genomic localisation, mainly in the proximal-promoter regions, revealing enriched elements for nuclear respiratory factor 1 (NRF1), GA repeat binding protein α (GABPA) and myocyte enhancer factor 2A (MEF2A) by de novo motif analysis, whereas decreased H3K27ac was enriched for v-maf musculoaponeurotic fibrosarcoma oncogene family protein K (MAFK), a known negative regulator of beta cells. By siRNA-mediated knockdown of NRF1, GABPA or MEF2A we found that INS-1 cells exhibited downregulation of fatty acid β-oxidation genes in parallel with decrease in the associated H3K27ac. Furthermore, in line with the epigenome in DIO mice, palmitate treatment caused increase in H3K27ac and induction of β-oxidation genes; these responses were blunted when NRF1, GABPA or MEF2A were suppressed.

CONCLUSIONS/INTERPRETATION

These results suggest novel roles for DNA-binding proteins and fatty acid signalling in obesity-induced epigenomic regulation of beta cell function.

DATA AVAILABILITY

The next-generation sequencing data in the present study were deposited at ArrayExpress. RNA-Seq: Dataset name: ERR2538129 (Control), ERR2538130 (Diet-induced obesity) Repository name and number: E-MTAB-6718 - RNA-Seq of pancreatic islets derived from mice fed a long-term high-fat diet against chow-fed controls. ChIP-Seq: Dataset name: ERR2538131 (Control), ERR2538132 (Diet-induced obesity) Repository name and number: E-MTAB-6719 - H3K27ac ChIP-Seq of pancreatic islets derived from mice fed a long-term high-fat diet (HFD) against chow-fed controls.

Abstract 5320: Genome-wide DNA methylation analysis during nonalcoholic steatohepatitis-related multistage hepatocarcinogenesis: Comparison with hepatitis virus-related carcinogenesis

Aim: The aim of this study was to clarify the significance of DNA methylation alterations during non-alcoholic steatohepatitis (NASH)-related hepatocarcinogenesis. Background: The incidence of NASH, a precancerous condition for hepatocellular carcinoma (HCC), has shown an alarming increase in recent years. Although significance of DNA methylation alterations in NASH has been studies in animal models, only a limited number of papers focusing on genome-wide DNA methylation analysis in a cohort of patients with NASH and NASH-related HCC have been reported. It would be informative to understand the significance of DNA methylation alterations in NASH-related hepatocarcinogenesis, especially at the precancerous stage. Methods: Single-CpG-resolution genome-wide DNA methylation analysis was performed on 264 liver tissue samples, i.e. 55 samples of normal liver tissue (NLT), 113 samples of non-cancerous liver tissue showing NASH (NASH-N), 22 samples of NASH-related HCC (NASH-T), 37 samples of non-cancerous liver tissue showing chronic hepatitis or cirrhosis associated with Hepatitis B Virus (HBV) or Hepatitis C Virus (HCV) infection (viral-N) and 37 samples of HCC associated with HBV or HCV infection (viral-T). Results: After Bonferroni correction, 3,331 probes showed significant DNA methylation alterations in NASH-N samples as compared with NLT samples. Principal component analysis using the 3,331 probes revealed distinct DNA methylation profiles of NASH-N samples that were different from those of NLT samples and viral-N samples. Receiver operating characteristic curve analysis identified 194 probes that were able to discriminate NASH-N samples from viral-N samples with area under the curve values of more than 0.95, again indicating that the DNA methylation status of NASH was clearly different from that of viral hepatitis and cirrhosis. Jonckheere-Terptsra trend test revealed that DNA methylation alterations in NASH-N samples from patients without HCC were inherited by or strengthened in NASH-N samples from patients with HCC, and then inherited by or further strengthened in NASH-T themselves. NASH- and NASH-related HCC-specific DNA methylation alterations, which were not evident in viral-N and viral-T samples, were observed in tumor-related genes, such as the WHSC1 gene which encodes a histone H3 lysine 36 methyltransferase and the WDR6 gene which encodes a WD repeat family protein implicated in cell growth arrest, and were frequently associated with mRNA expression abnormalities. Conclusion: These data suggested that NASH-specific DNA methylation alterations observed at the precancerous stage were shown to be inherited by NASH-T and may continuously participate in NASH-related multistage hepatocarcingenesis, at least partly via alterations in the expression of the affected genes.

Citation Format: Junko Kuramoto, Eri Arai, Ying Tian, Nobuaki Funahashi, Masaki Hiramoto, Takao Nammo, Yuichi Nozaki, Yoriko Takahashi, Nanako Ito, Ayako Shibuya, Hidenori Ojima, Aoi Sukeda, Yosuke Seki, Kazunori Kasama, Kazuki Yasuda, Yae Kanai. Genome-wide DNA methylation analysis during nonalcoholic steatohepatitis-related multistage hepatocarcinogenesis: Comparison with hepatitis virus-related carcinogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5320.

A type 2 diabetes-associated SNP in KCNQ1 (rs163184) modulates the binding activity of the locus for Sp3 and Lsd1/Kdm1a, potentially affecting CDKN1C expression

Although genome-wide association studies have shown that potassium voltage-gated channel subfamily Q member 1 (KCNQ1) is one of the genes that is most significantly associated with type 2 diabetes mellitus (T2DM), functionally annotating disease-associated single nucleotide polymorphisms (SNPs) remains a challenge. Recently, our group described a novel strategy to identify proteins that bind to SNP-containing loci in an allele-specific manner. The present study successfully applied this strategy to investigate rs163184, a T2DM susceptibility SNP located in the intronic region of KCNQ1. Comparative analysis of DNA-binding proteins revealed that the binding activities for the genomic region containing SNP rs163184 differed between alleles for several proteins, including Sp3 and Lsd1/Kdm1a. Sp3 preferentially bound to the non-risk rs163184 allele and stimulated transcriptional activity in an artificial promoter containing this region. Lsd1/Kdm1a was identified to be preferentially recruited to the non-risk allele of the rs163184 region and reduced Sp3-dependent transcriptional activity in the artificial promoter. In addition, expression of the nearby cyclin‑dependent kinase inhibitor 1C (CDKN1C) gene was revealed to be upregulated after SP3 knockdown in cells that possessed non-risk alleles. This suggests that CDKN1C is potentially one of the functional targets of SNP rs163184, which modulates the binding activity of the locus for Sp3 and Lsd1/Kdm1a.

Genome-wide DNA methylation analysis during non-alcoholic steatohepatitis-related multistage hepatocarcinogenesis: comparison with hepatitis virus-related carcinogenesis

The aim of this study was to clarify the significance of DNA methylation alterations during non-alcoholic steatohepatitis (NASH)-related hepatocarcinogenesis. Single-CpG-resolution genome-wide DNA methylation analysis was performed on 264 liver tissue samples using the Illumina Infinium HumanMethylation450 BeadChip. After Bonferroni correction, 3331 probes showed significant DNA methylation alterations in 113 samples of non-cancerous liver tissue showing NASH (NASH-N) as compared with 55 samples of normal liver tissue (NLT). Principal component analysis using the 3331 probes revealed distinct DNA methylation profiles of NASH-N samples that were different from those of NLT samples and 37 samples of non-cancerous liver tissue showing chronic hepatitis or cirrhosis associated with hepatitis B virus (HBV) or hepatitis C virus (HCV) infection (viral-N). Receiver operating characteristic curve analysis identified 194 probes that were able to discriminate NASH-N samples from viral-N samples with area under the curve values of more than 0.95. Jonckheere-Terptsra trend test revealed that DNA methylation alterations in NASH-N samples from patients without hepatocellular carcinoma (HCC) were inherited by or strengthened in NASH-N samples from patients with HCC, and then inherited by or further strengthened in 22 samples of NASH-related HCC (NASH-T) themselves. NASH- and NASH-related HCC-specific DNA methylation alterations, which were not evident in viral-N samples and 37 samples of HCC associated with HBV or HCV infection, were observed in tumor-related genes, such as WHSC1, and were frequently associated with mRNA expression abnormalities. These data suggested that NASH-specific DNA methylation alterations may participate in NASH-related multistage hepatocarcinogenesis.

Demethylation of the MafB promoter in a compromised β-cell model

Recent studies suggest that dedifferentiation of pancreatic β-cells is involved in compromised β-cell function in diabetes mellitus. We have previously shown that the promoter activity of MafB, which is expressed in α-cells of adult islets and immature β-cells in embryonic pancreas but not in mature β-cells in mice, is increased in compromised β-cells of diabetic model mice. Here, we investigated a rat β-cell line of INS1 cells with late-passage numbers, which showed extremely low expression of MafA and insulin, as an in vitro model of compromised β-cells. In these INS1 cells, the mRNA expression and the promoter activity of MafB were upregulated compared with the early-passage ('conventional') INS1 cells. Analysis of the MafB promoter in these late-passage INS1 cells revealed that specific CpG sites in the MafB promoter were partially demethylated. The reporter assay revealed that the unmethylated promoter activity of the 373 bp region containing these CpG sites was higher than the in vitro methylated promoter activity. These results suggest that the chronic culture of the rat β-cell line resulted in partial DNA demethylation of the MafB promoter, which may have a role in MafB promoter activation and possible dedifferentiation in our compromised β-cell model.

Functional characterization of the vitamin K2 biosynthetic enzyme UBIAD1

UbiA prenyltransferase domain-containing protein 1 (UBIAD1) plays a significant role in vitamin K₂ (MK-4) synthesis. We investigated the enzymological properties of UBIAD1 using microsomal fractions from Sf9 cells expressing UBIAD1 by analysing MK-4 biosynthetic activity. With regard to UBIAD1 enzyme reaction conditions, highest MK-4 synthetic activity was demonstrated under basic conditions at a pH between 8.5 and 9.0, with a DTT ≥0.1 mM. In addition, we found that geranyl pyrophosphate and farnesyl pyrophosphate were also recognized as a side-chain source and served as a substrate for prenylation. Furthermore, lipophilic statins were found to directly inhibit the enzymatic activity of UBIAD1. We analysed the aminoacid sequences homologies across the menA and UbiA families to identify conserved structural features of UBIAD1 proteins and focused on four highly conserved domains. We prepared protein mutants deficient in the four conserved domains to evaluate enzyme activity. Because no enzyme activity was detected in the mutants deficient in the UBIAD1 conserved domains, these four domains were considered to play an essential role in enzymatic activity. We also measured enzyme activities using point mutants of the highly conserved aminoacids in these domains to elucidate their respective functions. We found that the conserved domain I is a substrate recognition site that undergoes a structural change after substrate binding. The conserved domain II is a redox domain site containing a CxxC motif. The conserved domain III is a hinge region important as a catalytic site for the UBIAD1 enzyme. The conserved domain IV is a binding site for Mg²⁺/isoprenyl side-chain. In this study, we provide a molecular mapping of the enzymological properties of UBIAD1.

YY1 positively regulates human UBIAD1 expression

Vitamin K is involved in bone formation and blood coagulation. Natural vitamin K compounds are composed of the plant form phylloquinone (vitamin K1) and a series of bacterial menaquionones (MK-n; vitamin K2). Menadione (vitamin K3) is an artificial vitamin K compound. MK-4 contains 4-isoprenyl as a side group in the 2-methyl-1,4-naphthoquinone common structure and has various bioactivities. UbiA prenyltransferase domain containing 1 (UBIAD1 or TERE1) is the menaquinone-4 biosynthetic enzyme. UBIAD1 transcript expression significantly decreases in patients with prostate carcinoma and overexpressing UBIAD1 inhibits proliferation of a tumour cell line. UBIAD1 mRNA expression is ubiquitous in mouse tissues, and higher UBIAD1 mRNA expression levels are detected in the brain, heart, kidneys and pancreas. Several functions of UBIAD1 have been reported; however, regulation of the human UBIAD1 gene has not been elucidated. Here we report cloning and characterisation of the human UBIAD1 promoter. A 5' rapid amplification of cDNA ends analysis revealed that the main transcriptional start site was 306 nucleotides upstream of the translation initiation codon. Deletion and mutation analyses revealed the functional importance of the YY1 consensus motif. Electrophoretic gel mobility shift and chromatin immunoprecipitation assays demonstrated that YY1 binds the UBIAD1 promoter in vitro and in vivo. In addition, YY1 small interfering RNA decreased endogenous UBIAD1 mRNA expression and UBIAD1 conversion activity. These results suggest that YY1 up-regulates UBIAD1 expression and UBIAD1 conversion activity through the UBIAD1 promoter.

Generation and characterization of MafA-Kusabira Orange mice

MafA and MafB are basic leucine zipper transcription factors expressed in mature pancreatic β- and α-cells, respectively. MafA is not only an insulin gene transcription factor but is also critical for the maturation and maintenance of β-cell function, whereas MafB is expressed in immature β-cells during development and in compromised β-cells in diabetes. In this study, we developed a mouse model to easily trace the promoter activity of MafA in β-cells as a tool for studying β-cell differentiation, maturation, regeneration and function using the expression of the fluorescent protein Kusabira Orange (KOr) driven by the BAC-mafA promoter. The expression of KOr was highly restricted to β-cells in the transgenic pancreas. By crossing MafA-KOr mice with MafB(GFP/+) reporter mice, simultaneous monitoring of MafA and MafB expressions in the isolated islets was successfully performed. This system can be a useful tool for examining dynamic changes in the differentiation and function of pancreatic islets by visualizing the expressions of MafA and MafB.

Vitamin K2 biosynthetic enzyme, UBIAD1 is essential for embryonic development of mice

UbiA prenyltransferase domain containing 1 (UBIAD1) is a novel vitamin K₂ biosynthetic enzyme screened and identified from the human genome database. UBIAD1 has recently been shown to catalyse the biosynthesis of Coenzyme Q10 (CoQ10) in zebrafish and human cells. To investigate the function of UBIAD1 in vivo, we attempted to generate mice lacking Ubiad1, a homolog of human UBIAD1, by gene targeting. Ubiad1-deficient (Ubiad1^−/−) mouse embryos failed to survive beyond embryonic day 7.5, exhibiting small-sized body and gastrulation arrest. Ubiad1^−/− embryonic stem (ES) cells failed to synthesize vitamin K₂ but were able to synthesize CoQ9, similar to wild-type ES cells. Ubiad1^+/− mice developed normally, exhibiting normal growth and fertility. Vitamin K₂ tissue levels and synthesis activity were approximately half of those in the wild-type, whereas CoQ9 tissue levels and synthesis activity were similar to those in the wild-type. Similarly, UBIAD1 expression and vitamin K₂ synthesis activity of mouse embryonic fibroblasts prepared from Ubiad1^+/− E15.5 embryos were approximately half of those in the wild-type, whereas CoQ9 levels and synthesis activity were similar to those in the wild-type. Ubiad1^−/− mouse embryos failed to be rescued, but their embryonic lifespans were extended to term by oral administration of MK-4 or CoQ10 to pregnant Ubiad1^+/− mice. These results suggest that UBIAD1 is responsible for vitamin K₂ synthesis but may not be responsible for CoQ9 synthesis in mice. We propose that UBIAD1 plays a pivotal role in embryonic development by synthesizing vitamin K₂, but may have additional functions beyond the biosynthesis of vitamin K₂.

Endothelial cell-specific expression of roundabout 4 is regulated by differential DNA methylation of the proximal promoter

OBJECTIVE

The molecular basis of endothelial cell (EC)-specific gene expression is poorly understood. Roundabout 4 (Robo4) is expressed exclusively in ECs. We previously reported that the 3-kb 5'-flanking region of the human Robo4 gene contains information for lineage-specific expression in the ECs. Our studies implicated a critical role for GA-binding protein and specificity protein 1 (SP1) in mediating overall expression levels. However, these transcription factors are also expressed in non-ECs. In this study, we tested the hypothesis that epigenetic mechanisms contribute to EC-specific Robo4 gene expression.

METHODS AND RESULTS

Bisulfite sequencing analysis indicated that the proximal promoter of Robo4 is methylated in non-ECs but not in ECs. Treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine increased Robo4 gene expression in non-ECs but not in ECs. Proximal promoter methylation significantly decreased the promoter activity in ECs. Electrophoretic mobility shift assays showed that DNA methylation of the proximal promoter inhibited SP1 binding to the -42 SP1 site. In DNase hypersensitivity assays, chromatin condensation of the Robo4 promoter was observed in some but not all nonexpressing cell types. In Hprt (hypoxanthine phosphoribosyltransferase)-targeted mice, a 0.3-kb proximal promoter directed cell-type-specific expression in the endothelium. Bisulfite sequencing analysis using embryonic stem cell-derived mesodermal cells and ECs indicated that the EC-specific methylation pattern of the promoter is determined by demethylation during differentiation and that binding of GA-binding protein and SP1 to the proximal promoter is not essential for demethylation.

CONCLUSIONS

The EC-specific DNA methylation pattern of the Robo4 proximal promoter is determined during cell differentiation and contributes to regulation of EC-specific Robo4 gene expression.

A three-kilobase fragment of the human Robo4 promoter directs cell type-specific expression in endothelium

Robo4, a member of the roundabout family, is expressed exclusively in endothelial cells and has been implicated in endothelial cell migration and angiogenesis. Here we report the cloning and characterization of the human Robo4 promoter. The 3-kb 5'-flanking region directs endothelial cell-specific expression in vitro. Deletion and mutation analyses revealed the functional importance of two 12-bp palindromic DNA sequences at -2528 and -2941, 2 SP1 consensus motifs at -42 and -153, and an ETS consensus motif at -119. In electrophoretic mobility shift assays using supershifting antibodies, the SP1 motifs bound SP1 protein, whereas the ETS site bound a heterodimeric member of the ETS family, GA binding protein (GABP). These DNA-protein interactions were confirmed by chromatin immunoprecipitation assays. Transfection of primary human endothelial cells with small interfering RNA against GABP and SP1 resulted in a significant (approximately 50%) reduction in endogenous Robo4 mRNA expression. The 3-kb Robo4 promoter was coupled to LacZ, and the resulting cassette was introduced into the Hprt locus of mice by homologous recombination. Reporter gene activity was observed in the vasculature of adult organs (particularly in microvessels), tumor xenografts, and embryos, where it colocalized with the endothelial cell-specific marker CD31. LacZ mRNA levels in adult tissues and tumors correlated with mRNA levels for endogenous Robo4, CD31, and vascular endothelial cadherin. Moreover, the pattern of reporter gene expression was similar to that observed in mice in which LacZ was knocked into the endogenous Robo4 locus. Together, these data suggest that 3-kb upstream promoter of human Robo4 contains information for cell type-specific expression in the intact endothelium.

Oral delivery of synthetic eel calcitonin, elcatonin, in rats

This study was designed to develop an oral dosage form of elcatonin (EC), a hypocalcemic peptide. The EC absorption was estimated by the reduction in plasma calcium concentrations. When EC was orally coadministered with nitroso-N-acetyl-D,L-penicillamine (SNAP, 4.0 mg) and 0.02% Carbopol solution or with taurocholate (20 mM) and 0.02% Carbopol solution, the lowering effect was increased compared with that after EC alone, but the F values (0.32 and 0.30%) were extremely small. The oral administration of the mucoadhesive emulsion, which was prepared by coating the W/O/W emulsion with 0.1% Carbopol, enhanced the calcium lowering effect, with the F value of 0.43%. The strong mucoadhesion of the mucoadhesive emulsion to the gastrointestinal mucosa was observed. A capsule containing EC (500 microg), taurocholate (6 mg) and lyophilized Carbopol (3.5 mg) administered orally gave a sustained but comparatively small calcium lowering effect. In the in vitro enzymatic hydrolysis experiment, EC was more rapidly hydrolyzed in the intestinal fluid than in the mucosal extract. The combination of 20 mM taurocholate with 0.02% Carbopol showed the greatest inhibitory effect in both fluid and extract. These data indicated that EC was effectively absorbed through the intestinal wall, but the peptide was dominantly degraded by proteolytic enzymes in the GI tract. These results will offer a potential approach to the oral delivery of EC.

Protective Effects of Iganidipine on Morphological and Functional Changes of Arteries in Hypertensive Dahl Rats

BACKGROUND: This study was performed to examine the protective effects of iganidipine, a new water-soluble calcium antagonist, on the morphological and functional changes of arteries in Dahl salt-sensitive (Dahl-S) rats. METHODS AND RESULTS: Vehicle and iganidipine were administered orally to Dahl-S rats fed a high-salt diet (HSD) for 8 weeks. Aorta, superior mesenteric arteries (SMA), and peripheral mesenteric arteries (PMA) were examined light-microscopically or electon-microscopically. Relaxant responses of isolated aorta and SMA were recorded isometrically. In rats fed HSD, blood pressure was markedly increased. Light microscopy showed intimal and medial hypertrophy, periarteritis, and narrowed arterial lumen in the PMA. Transmission and scanning electron microscopy or light microscopy showed medical thickness in the aorta and SMA and hypertrophy of endothelial cells and dilatation of the subendothelial space only in the aorta. In the SMA, both endothelium-dependent relaxation (EDR) and endothelium-independent relaxations (EIR) were reduced to a similar extent. In the aorta, the EDR was more markedly attenuated than the EIR. Iganidipine at 3 mg/kg/day showed a 24-h sustained hypotensive effect and completely prevented the morphological and functional changes in both arteries. Iganidipine at 1 mg/kg/day, which lowered blood pressure only for several hours, decreased the injuries in PMA and aortic endothelium and moderately restored the EDR in the aorta. Iganidipine at 0.3 mg/kg/day had no effects. CONCLUSIONS: In Dahl-S rats fed an HSD, iganidipine completely prevented all the changes at a sustained-hypotensive dose and prevented the injuries of PMA and aortic endothelium and the reduction of EDR in the aorta at a nonsustained hypotensive dose. Nonhemodynamic effects of iganidipine may be partly involved in its protective effects against arterial injuries.

Immunosuppressant HR-325 attenuates progression of malignant arteritis in the kidney of Dahl salt-sensitive rats

We investigated the effects of the immunosuppressant HR-325 on arterial lesions in Dahl rats with salt-induced hypertension. Forty-eight 6-wk-old Dahl salt-sensitive (DS) rats were divided into 1) a low-salt (0.3% NaCl) group, 2) a high-salt (4% NaCl) group, 3) a high-salt and low-dose (1 mg/kg) HR-325 group, and 4) a high-salt and high-dose (30 mg/kg) HR-325 group. The rats were treated for 8 wk. Various variables of renal function and morphological alterations in the kidney were assessed. Blood pressure was measured by the tail-cuff method. HR-325 significantly decreased systolic blood pressure in a dose-dependent manner throughout the study. HR-325 tended to decrease plasma creatinine level and increase creatinine clearance rate. Morphological studies revealed that HR-325 treatment strikingly resolved infiltration of immune-related cells in perivascular and intraluminal lesions, thereby decreasing the total arterial injury score by 32%. High-dose HR-325 also attenuated glomerulosclerosis and tubular injury by 35% and 34%, respectively, as compared with untreated high-salt Dahl S rats. Reduced levels of immune-related cells resulted in a decrease in urinary nitrite excretion. These data indicate that long-term treatment with the immunosuppressant HR-325 decreases systolic blood pressure in Dahl salt-sensitive rats, and that this decrease is associated particularly with resolution of infiltration of immune-related cells in arterial lesions. Hyperimmune state is responsible in part for the susceptibility of Dahl S rats to hypertensive organ damage.

Lipid metabolism and renal protection by chronic cicletanine treatment in Dahl salt-sensitive rats with salt-induced hypertension

We investigated the role of lipid metabolism in renal protection by chronic cicletanine treatment in Dahl salt-sensitive (Dahl S) rats with salt-induced hypertension. Forty-four 6-week old Dahl S rats were divided into four groups: (1) low-salt (0.3% NaCl) control group: (2) high-salt (4% NaCl) control group; (3) low-dose (10 mg/kg/day) cicletanine (CICL)-treated group given a high-salt diet; and (4) high-dose (30 mg/kg/day) cicletanine-treated group given a high-salt diet. The rats were treated for 6 weeks; blood pressure was measured by the tail-cuff method. Cicletanine significantly reduced the systolic blood pressure in a dose-dependent manner (223 mmHg in the high-salt controls vs 195 mmHg in the high-dose, high-salt group, p < 0.01). Cicletanine treatment did not affect plasma concentration of total cholesterol or triglyceride or free fatty acid; in contrast, it significantly decreased low-density lipoprotein (LDL) cholesterol and increased high-density lipoprotein (HDL) cholesterol. Morphological examination demonstrated that glomerulosclerosis in the kidney was significantly improved by 15% with high-dose cicletanine (p < 0.01). Multivariate analysis revealed that glomerular sclerosis was determined independently by LDL cholesterol levels and arterial injury score, but not by total cholesterol or HDL cholesterol levels or blood pressures. LDL cholesterol was also an independent predictor of urinary excretion of protein. Thus, it is suggested that cicletanine treatment lowers the levels of LDL cholesterol in Dahl salt-sensitive rats, and that besides blood pressure reduction, this decrease in LDL cholesterol level contributes, in part, to regression of glomerular injury in salt-induced hypertension.

Restoration of endothelial cell function by chronic cicletanine treatment in Dahl salt-sensitive rats with salt-induced hypertension

The effects of chronic cicletanine (CICL) treatment on endothelial cell function were investigated in Dahl salt-sensitive (Dahl S) rats. Forty-four six-week-old Dahl S rats were divided into four groups: i) 10 Dahl S rats fed a low-salt (0.3% NaCl) diet and given vehicle, ii) 12 Dahl S rats fed a high-salt (4% NaCl) diet and given vehicle, iii) 11 low-dose (10 mg/kg body weight/d) CICL-treated Dahl S rats fed a high-salt diet, and iv) 11 high-dose (30 mg/kg body weight/d) CICL-treated Dahl S rats fed a high-salt diet. The rats were maintained on the respective salt regimen for 12 wk and treated with cicletanine for the last 6 wk, after which various parameters of endothelial cell function were determined. Systolic blood pressure, measured by the tail-cuff method, was reduced significantly by high-dose cicletanine (223 vs. 195 mmHg, p < 0.01). Scanning electron microscopy revealed that high-dose CICL attenuated endothelial injury in the aorta of Dahl S rats. Arterial lesions in the heart and glomerulosclerosis in the kidney were significantly reduced by treatment with high-dose CICL. Moreover, prostacyclin (PGI2) and prostaglandin E2 (PGE2) generation in the aortic wall was significantly increased by 28% (p < 0.005) and by 149% (p < 0.001), respectively, by high-dose CICL. Nitric oxide (NO) generation in the aortic walls was significantly increased by high-dose CICL (0.38 vs. 15.4 pmol/cm2/30 min, p < 0.001). This effect was accompanied by a 47% increase in cGMP synthesis in the vascular walls. In contrast, the synthesis of PGI2, PGE2, and NO in the kidney slices did not differ significantly among the four experimental groups. In addition, the generation of vasodilatory substances inversely correlated with the score of vascular lesions in the heart and kidney. The results suggested that the blood pressure reduction by chronic cicletanine treatment in Dahl S rats is associated with an improvement in endothelial cell function. The increased release of vasodilatory substances from endothelial cells may contribute to the blood pressure reduction and attenuation of vascular injury observed with cicletanine treatment.

[Cefepime (diHCl/L-arginine blend): intravenous continuous infusion and/or single dose subcutaneous toxicity study in rats and dogs]

To investigate single dose toxicity of cefepime (CFPM diHCl/L-arginine blend), the test drug was administered to rats [Crj: CD (SD)] of both sexes at dose levels of 500, 1,000 and 2,000 mg/kg using intravenous continuous infusion or subcutaneous injection, and to male beagle dogs at 1,000 and 2,000 mg/kg using intravenous continuous infusion. As the control, two additional groups of each animals were given either saline or L-arginine alone which was used in the test formulation to adjust pH values of CFPM diHCl solutions. The obtained results are summarized as follows: 1. Rats dosed with 2,000 mg/kg CFPM through intravenous continuous infusion showed slightly decreased spontaneous physical activity. One male rat dosed with L-arginine alone via continuous infusion also showed slightly decreased activity. Slight to severe inflammatory reactions at injection sites including sloughing of the tail were prominent at doses of 1,000 or 2,000 mg/kg of CFPM, or L-arginine alone. Average body weights of rats in the test groups of either sex were comparable to the controls in all of the dose groups of the same sex during the 14-day test period. 2. Rats receiving 2,000 mg/kg CFPM in single subcutaneous injection showed slightly diminished activities. Slight to moderate reactions occurred around the injection site (viz., hardening, depilation, scab-formation and necrosis) in rats injected any of the 3 doses of CFPM. Though body weight gains were slightly retarded in male rats receiving 2,000 mg/kg CFPM during the last half of the observation period, such weight gain retardation was not observed in rats of other dose groups.(ABSTRACT TRUNCATED AT 250 WORDS)

[Four-week repeated dose oral toxicity study of BMY-28100 in juvenile beagle dogs]

Three groups, each consisting of 3 male and 3 female juvenile beagle dogs, were orally given BMY-28100 for 4 weeks at dose levels of 50, 160 and 500 mg/kg/day, respectively. Additionally, one male and one female dogs were added to each of the control and high dose groups in order to examine the recovery, and observed for 4 weeks after withdrawal of BMY-28100. The results obtained are summarized as follows: 1. BMY-28100 provoked an increased incidence of emesis in the 500 mg/kg group during the treatment period. 2. BMY-28100 sporadically brought distention of the cecum containing considerable amounts of contents in dogs sacrificed after the 4-week administration period. However, no macroscopic or microscopic changes were observed in the cecum itself after removal of the contents. In the 500 mg/kg group, hypocellularity in the sternum bone marrow was observed in a male and a female, and thymic atrophy in a male. 3. No changes ascribed to BMY-28100 treatment were detected after the 4-week recovery period. Based upon these results, the no-effect dose level of BMY-28100 was estimated to be 160 mg/kg/day, except for effects on the cecum.

Effects of bis (tri-n-butyltin) oxide on endocrine and lymphoid organs of male rats

A total of 160 Sprague-Dawley rats averaging in body weight, were used for histopathological and biochemical studies of toxicity of bis (tri-n-butyltin) oxide (TBTO). Short-term effects and long-term effects were examined. LD50 of TBTO by gastric tubing was 197 mg/kg. The effects of a single dose of TBTO were transient, and rapid recovery followed. TBTO at a a single dose of 100 mg/kg, or a total dose of 390 to 780 mg/kg in 13 weeks, or 780 to 1,560 mg/kg in 26 weeks, caused adrenal hypertrophy, flattening of the thyroid epithelium and atrophy of the thymus and lymph nodes. A single or repeated administration induced swelling and vacuolation of aldehyde-fuchsin-positive cells in the adenohypophysis. The immunohistochemical stainability of the cytoplasm of ACTH-cells was markedly depressed 24 hours after TBTO treatment, and that of the cytoplasm of TSH-cells was enhanced. Analogous an inverse relationship was also manifested in the hormonal levels of serum: levels of cortisol were elevated, while those of T-4 and TSH were depressed.