Alteration in left ventricular diastolic filling and accumulation of myocardial collagen at insulin-resistant prediabetic stage of a type II diabetic rat model

BACKGROUND

Considerable controversy exists regarding impairment of cardiac function in diabetes mellitus (DM). We investigated the serial changes in left ventricular (LV) histopathology and LV filling dynamics in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which have been established as an animal model of type II DM.

METHODS AND RESULTS

In 54 OLETF and 54 non-DM rats, body weight, blood pressure, heart rate, and transmitral pulsed Doppler examinations were performed from 5 to 47 weeks of age. An oral glucose tolerance test was performed at 10, 20, and 30 weeks of age. The hearts were excised for histopathology, including immunohistochemistry and histomorphometry of collagen, and measurement of hydroxyproline at baseline and each stage of developing DM. In the prediabetic stage (15 weeks of age), in which fast blood glucose remained normal, OLETF rats manifested mild obesity, postprandial hyperglycemia, and hyperinsulinemia, and early diastolic transmitral inflow exhibited prolonged deceleration time (OLETF, 59+/-10 ms versus non-DM, 49+/-8 ms, P<0.01) and low peak velocity (OLETF, 73+/-11 cm/s versus non-DM, 88+/-11 cm/s, P<0.01). Histopathology revealed extracellular fibrosis and abundant transforming growth factor-beta(1) receptor II in LV myocytes of OLETF rats. At 15 weeks of age, the ratio of collagen area/visual field of LV wall in OLETF rats (8.3+/-1.3%) was larger than that in non-DM rats (4.9+/-1.8%, P<0.0001), and the collagen content/dry tissue weight ratio of heart was significantly higher in OLETF (2. 0+/-0.5 mg/g) than non-DM (1.3+/-0.2 mg/g, P<0.01) rats.

CONCLUSIONS

A metabolic abnormality present in the prestage of type II DM may produce LV fibrosis and alteration in cardiac function.

Organization and evolution of variable region genes of the human immunoglobulin heavy chain

We have isolated 23 different cosmid clones of the heavy-chain variable region genes (VH) of human immunoglobulin. These clones encompass about 1000 X 10(3) base-pairs of DNA containing 61 VH genes. Characterization of the 23 clones by Southern blot hybridization showed that VH genes belonging to different families were physically linked in many regions. Cluster 71, which was analyzed in detail, comprised seven VH segments arranged in the same orientation with different intervals. This clone contained internal homology regions, each carrying two VH segments of different families. Comparison of the nucleotide sequences of VH segments within each family showed that profiles of accumulation of mutations in framework (FR) and complementarity-determining (CDR) regions were different. CDR had more mutations at amino-acid-substituting positions than at silent positions, whereas FR had the reverse distribution of mutations. Five out of seven VH segments of this cluster were pseudogenes containing various mutations. VH pseudogenes were classified into two distinct groups; one with a few replacement mutations (conserved pseudogenes), and the other with rather extensive mutations (diverged pseudogenes). The possibility that conserved pseudogenes serve as a reservoir of VH segments is discussed.

Cloning of cDNA for human T-cell replacing factor (interleukin-5) and comparison with the murine homologue

We have cloned cDNA for T-cell replacing factor (interleukin-5), which replaces T-cell helper function for normal B cells which secrete immunoglobulin, from human T cell leukemia line, ATL-2, using mouse interleukin-5 cDNA as probe. Total nucleotide sequence of the cDNA (816 base pairs) was determined and compared with that of mouse interleukin-5 cDNA. The cloned cDNA encoded the interleukin-5 precursor of 134 amino acids containing an N-terminal signal sequence. Although the human interleukin-5 precursor is one amino acid longer than the murine homologue, the sizes of the mature proteins appear similar. The nucleotide and amino acid sequence homologies of the coding regions of human and murine interleukin-5 are 77% and 70%, respectively. Human interleukin-5 synthesized by the direction of the cloned cDNA induced immunoglobulin synthesis in human B cells stimulated by Staphylococcus aureus mitogen.

Release of adenylate kinase 2 from the mitochondrial intermembrane space during apoptosis

The release of two mitochondrial proteins, cytochrome c and apoptosis-inducing factor (AIF), into the soluble cytoplasm of cells undergoing apoptosis is well established. Using spectrophotometric determination of enzyme activity, the accumulation of adenylate kinase (AK) activity in the cytosolic fraction of apoptotic cells has also been observed recently. However, three isozymes, AK1, AK2 and AK3, have been characterized in mammalian cells and shown to be localized in the cytosol, mitochondrial intermembrane space and mitochondrial matrix, respectively, and it is unknown which one of these isozymes accumulates in the cytosol during apoptosis. We now demonstrate that in apoptotic cells only AK2 was translocated into the cytosol concomitantly with cytochrome c. The amount of AK1 in cytosol, as well as the amount of matrix-associated AK3, remained unchanged during the apoptotic process. Thus, our data suggest that only intermembrane proteins are released from mitochondria during the early phase of the apoptotic process.

Tissue-specific and developmentally regulated expression of the genes encoding adenylate kinase isozymes

Adenylate kinase (AK) is known to play an important role in homeostasis of adenine nucleotide metabolism. We isolated cDNAs for rat AK isozymes (AK1, AK2, and AK3), determined their mRNAs in rat tissues by Northern blot analysis, and measured the isozyme activities. Tissue-dependent activities of AK1 and AK2 paralleled the contents of mRNAs. Tissues with high AK1 levels showed low AK2 levels and vice versa, suggesting that tissue-specific expressions of the AK1 and AK2 genes are inversely regulated. AK3 mRNA was detected in most tissues examined, suggesting that AK3 gene expression is constitutive. We further examined developmental changes in mRNAs and enzyme activities of AK isozymes in rat skeletal muscle and liver. In the skeletal muscle, AK1 and AK3 activities started to increase at around the weaning period. AK1 mRNA accumulated at the prenatal stage and further increased during development, while AK3 mRNA was at high levels during the fetal stage and remained fairly constant during development. In the liver, AK2 and AK3 activities started to increase after birth and were further elevated during growth, whereas their mRNAs were present at relatively high levels throughout development. The physiological meanings of the tissue-specific expression of the AK isozyme genes are discussed.

Enhancement of the interleukin 2 receptor expression on T cells by multiple B-lymphotropic lymphokines

Three new human lymphokines, interleukin-5, BSF-2 and BSF-MP6, were shown to be active in the enhancement of the IL-2 receptor expression on T cells, although they do not stimulate growth of the T cells.

Molecular cloning and structure of the human transforming growth factor-beta 2 gene promoter

Genomic DNA extending over 10 kb 5' of the transforming growth factor-beta 2 (TGF-beta 2) coding region was isolated from a human lung fibroblast lambda phage library. A 5.6 kb Hind III fragment containing the 5'-untranslated region and flanking sequences was subcloned and sequenced. S1 nuclease protection analysis identified a transcriptional initiation site 1357 nucleotides 5' of the methionine initiation codon (ATG). A "TATA box" consensus sequence was identified 30 bp from this transcriptional start site; however, consensus "CAT box" sequences were not observed. Approximately 50 nucleotides of homopurine-pyrimidine [d(GA.CT)50] sequence were identified in the 5'-untranslated region, as well as two short open reading frames of 5 and 45 amino acids. Several AP-1, AP-2, CRE and SP1-like DNA consensus sequence elements were also identified surrounding the transcription initiation site. 5'-deletion mutants of the promoter region were fused to the chloramphenicol acetyl transferase (CAT) gene and promoter activity of the isolated genomic DNA was demonstrated in several cell lines. DNA constructs containing nucleotides between -508 to +63 demonstrated high levels of promoter activity. However, sequences between -778 and -508 nucleotides modulated this promoter activity in a manner which was dependent upon the cell line utilized, suggesting that regulation of TGF-beta 2 gene transcription may be dependent upon the cellular background. The TGF-beta 2 promoter is markedly different from the promoters that have been recently characterized for TGF-beta 1 and TGF-beta 3.

Genomic structure of HTLV (human T-cell leukemia virus): detection of defective genome and its amplification in MT-2 cells

We studied the genomic structure of human T-cell leukemia virus (HTLV) in the HTLV producer cell line MT-2. Southern blotting revealed that at least eight HTLV proviruses were integrated in the chromosomes of MT-2 cells. The genomic structure of these proviruses was analyzed using fragments of cloned HTLV that were specific to gag, pol, env, pXs and U3R genes as probes. We have identified a complete genome of HTLV in MT-2 (non-defective type). However, seven of the eight proviruses had defective genomes. Provirus T2-a contains only the U3R (LTR) of HTLV and T2-b corresponds to the non-defective genome. T2-c possesses only a portion of env, and pXs and U3R. T2-d consists of gag, pol, part of env and U3R. On the other hand, T2-e, f, g and h consist of gag, pXs and U3R. Northern blotting experiments with mRNA from MT-2 cells supported the evidence of amplification of the gag-pXs gene of HTLV. 26S mRNA is considered to be a subgenomic species of 35S RNA. 32S mRNA may represent the T2-d provirus which lacks a portion of env and pXs, while 20S mRNA was a subgenomic species. The gag-pXs gene may correspond to 24S mRNA, the amount which was amplified in MT-2 cells.

Rearranged immunoglobulin heavy chain variable region (VH) pseudogene that deletes the second complementarity-determining region

We have cloned two rearranged heavy chain variable region (VH) genes from the IgG-producing human cell line CESS. The VH gene, which is linked to the mu chain constant region (C mu) gene, has two deletions at residues 45-62 and 82A-90, the former of which corresponds closely to the second complementarity-determining region (CDR2). These results could indicate that translocation of CDR2 occurred and could give support to the argument that reassortment of the V mini-genes is involved in the generation of hypervariability during evolution. However, the rearranged pseudogene could have also arisen by fortuitous deletion. The other VH gene of CESS is an expressed form and is probably linked to the C gamma gene. The diversity region (D) segments used in these rearranged V genes are less than 38% homologous to known human germline D segments, indicating the presence of more unknown germline D segments.

Enhanced expression of matrix metalloproteinase-9 in abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are characterized by structural alterations of the aortic wall resulting from degradation of collagen and elastin. Matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, show strong elastinolytic activity. We examined the levels of mRNA for MMP-2, MMP-9, membrane type (MT)-MMP-1, tissue inhibitor of metalloproteinase-1 (TIMP-1), and TIMP-2 in AAAs (n = 8), atherosclerotic occlusive diseases (AOD) (n = 8), and normal subjects (n = 8) using the reverse transcription-polymerase chain reaction (RT-PCR). We also analyzed the gelatinolytic activity of these metalloproteinases using gelatin zymography. The levels of MMP-2 and MMP-9 mRNA were increased in the AAA group compared with those in the AOD group and normal subjects. The levels for TIMP-1 and TIMP-2 mRNA in the AAA group were also higher than those in the AOD and normal groups. Only in the case of MT-MMP-1 was the difference between AAA and AOD not statistically significant. By gelatin zymography with the same samples used for RT-PCR, gelatinolytic activity of MMP-9 was elevated in all AAA tissues. The 62-kDa form of MMP-2 was elevated in both the AAA and AOD groups and did not differ significantly between them. Linear regression analysis demonstrated a significant positive correlation between mRNA levels of MMPs and those of TIMPs. These observations suggest that aneurysm formation in patients with atherosclerosis is related to the degree of MMP-9 expression.

Expression of different combinations of interleukins by human T cell leukemic cell lines that are clonally related

We have analyzed expression patterns of 7 lymphokine mRNAs by Northern blot analyses in 19 different human T cell clones derived from patients with adult T cell leukemia. However, we were not able to reveal particular combinations of lymphokine production that allowed classification of human T cells. Especially, four clonally related leukemic lines that were established independently from the same patient with adult T cell leukemia expressed different combinations of lymphokine mRNAs, indicating that the expression of various lymphokines is not fixed but rather variable even among progenies of a single T cell clone.

Pioglitazone improves left ventricular diastolic function and decreases collagen accumulation in prediabetic stage of a type II diabetic rat

This study investigated the effect of pioglitazone, an insulin sensitizer, on metabolic abnormalities and oxidative stress as a cause of myocardial collagen accumulation in prediabetic rat hearts. Twenty male diabetic rats and 9 male nondiabetic age-matched rats were used. The diabetic rats were divided into two groups: diabetic treated and untreated. Pioglitazone was mixed in rat chow fed to the diabetic treated group (0.01%). Treatment duration was 5 weeks. At baseline (15 weeks) and 20 weeks of age, blood glucose, lipid, insulin, and plasma malondialdehyde-thiobarbituric acid (MDA) levels were measured and Doppler echocardiography was tracked. At 20 weeks of age, left ventricular collagen content was studied. Blood glucose, plasma insulin, and triglyceride levels in the diabetic treated group were significantly lower than those in the untreated diabetic group. Deceleration time (ms) of early diastolic inflow in the treated diabetic group decreased significantly compared with the untreated diabetic group (65 +/- 8 vs. 77 +/- 8, p < 0.01). Ratio of left ventricular weight to body weight (mg/g) and ratio of left ventricular collagen content to dry weight (mg/100 mg) were decreased in the treated diabetic group (1.5 +/- 0.1, 1.3 +/- 0.3) compared with the untreated diabetic group (1.7 +/- 0.2, p < 0.01; 1.7 +/- 0.3, p < 0.05). Plasma MDA concentration (nmol/ml) significantly decreased (2.9 +/- 0.3 at baseline to 2.3 +/- 0.3 at 20 weeks, p = 0.001) in the treated diabetic group, and was lower than that in the untreated diabetic group (3.2 +/- 0.7 at 20 weeks, p < 0.05). Pioglitazone improved glucose and lipid metabolism and reduced oxidative stress in the left ventricle, which decreased left ventricular collagen accumulation and improved left ventricular diastolic function of prediabetic rat hearts.

Prevention of doxorubicin (adriamycin)-induced cardiomyopathy by simultaneous administration of angiotensin-converting enzyme inhibitor assessed by acoustic densitometry

The purpose of our study has to determine the myocardial protective effects of the angiotensin-converting enzyme (ACE) inhibitor temocapril (TEM, 7 mg/kg/day) simultaneously administered with doxorubicin (Adriamycin). Twenty male Sprague-Dawley rats were intraperitoneally administered a cumulative dose of 15 mg/kg of doxorubicin (each dose of 1.0 mg/kg x 15) for 3 weeks, and divided into TEM-untreated and -treated rats. Seven control rats were injected with saline intraperitoneally. Body weight, hemodynamics, and echocardiographic measurements including quantitative analysis of ultrasonic integrated backscatter (IB) were obtained for 12 weeks after treatment. Finally, rats were killed for histopathologic study. At 6 weeks, end-diastolic left ventricular diameter (LVD) and percentage fractional shortening (%FS) were similar in TEM-treated and TEM-untreated rats, but cyclic variation of IB (dB) significantly decreased in TEM-untreated rats (7.3 +/- 1.2; control rats, 9.7 +/- 0.9; p < 0.01). At 12 weeks, %FS decreased in TEM-untreated rats (26.1 +/- 6.1%: TEM-treated rats, 34.2 +/- 6.2; p < 0.05), and calibrated IB (dB) in TEM-untreated rats (15.5 +/- 0.5) increased as compared with that in TEM-treated rats (12.1 +/- 0.7; p < 0.01). Interstitial collagen accumulation increased in TEM-untreated rats and was inhibited in treated rats. Simultaneous administration of TEM with doxorubicin was beneficial in preventing doxorubicin-induced myocardial damage, and myocardial tissue characterization was useful for the early detection of myocardial damage and the assessment of therapy.

Molecular cloning and structure of the human interleukin 2 receptor gene

We have cloned the IL-2 receptor gene from human genomic DNA libraries using IL-2 receptor cDNA as probe. The genomic DNA segments that hybridized with cDNA were subcloned in M13 phages and their sequences were determined. The nucleotide sequences showed that the IL-2 receptor gene was encoded by eight exons and that the coding region sequences agreed completely with that of the IL-2 receptor cDNA cloned from a cell line derived from adult T cell leukemia (ATL), in which IL-2 receptors are expressed abnormally. The nucleotide sequence of the 5'-flanking region had a putative promotor region, which had some homology with the human IL-2 gene. Transcription initiation sites were clustered about 25 bp 3' to the TATA box as assessed by primer extension analysis. These sites for normal and ATL T cells were the same. Exons 2 and 4 encoding the extracytoplasmic portion had significant homology, suggesting that the two exons are derived by duplication of an ancestral exon. Exon 2 contained six cysteine residues, four of which are conserved at the corresponding positions in exon 4.

Role of interleukin-2 and interferon-gamma in inducing production of IgG subclasses in lymphocytes of human newborns

Unlike lymphocytes from adults, lymphocytes from cord blood of neonates cannot synthesize immunoglobulin G (IgG) in response to pokeweed mitogen (PWM). By using this mitogen in concert with interferon-gamma (IFN-gamma), interleukin-2 (IL-2), or interleukin-6 (IL-6), we studied the induction of IgG subclass molecules in lymphocytes of human neonates. IFN-gamma induced a limited, but substantial, enhancement of IgG2 production by neonatal lymphocytes. IL-2 dose dependently increased the production of each neonatal IgG subclass, whereas IL-6 did not. However, in adult lymphocytes, and under specific conditions, IL-6 or IL-2 each increased the production of all four IgG subclasses. Early in the culture IFN-gamma synergized with IL-2 during the latter or whole culture period to enhance cord blood IgG2 levels. This finding contrasted with the adult IgG2 synthesis synergistically up-regulated by IFN-gamma and IL-6. IL-2 caused a graded increase in immunoglobulin production in neonatal lymphocytes with IgG3 being the highest and IgG2 the lowest, thus corresponding to the differential increase of serum levels of IgG3/IgG1 and IgG4/IgG2 early in childhood. Results suggest that IL-2, but not IL-6, is critical to the development of human IgG subclass production.

Structure and expression of human mitochondrial adenylate kinase targeted to the mitochondrial matrix

The previously isolated cDNA encoding human adenylate kinase (AK) isozyme 3 was recently renamed AK4. Consequently, human AK3 cDNA remains to be identified and we have little information about the functional relationship between human AK3 and AK4. In pursuit of the physiological roles of both the AK3 and AK4 proteins, we first isolated an authentic human AK3 cDNA and compared their expression. Nucleotide sequencing revealed that the cDNA encoded a 227-amino-acid protein, with a deduced molecular mass of 25.6 kDa, that shares greater homology with the AK3 cDNAs isolated from bovine and rat than that from human. We named the isolated cDNA AK3. Northern-blot analysis revealed that AK3 mRNA was present in all tissues examined, and was highly expressed in heart, skeletal muscle and liver, moderately expressed in pancreas and kidney, and weakly expressed in placenta, brain and lung. On the other hand, we found that human AK4 mRNA was highly expressed in kidney, moderately expressed in heart and liver and weakly expressed in brain. Western-blot analysis demonstrated expression profiles of AK3 and AK4 that were similar to their mRNA expression patterns in each tissue. Over expression of AK3, but not AK4, in both Escherichia coli CV2, a temperature-sensitive AK mutant, and a human embryonic kidney-derived cell line, HEK-293, not only produced significant GTP:AMP phosphotransferase (AK3) activity, but also complemented the CV2 cells at 42 degrees C. Subcellular and submitochondrial fractionation analysis demonstrated that both AK3 and AK4 are localized in the mitochondrial matrix.

The nm23-H1 gene as a predictor of sensitivity to chemotherapeutic agents in oesophageal squamous cell carcinoma

Recently, nm23-H1, an anti-metastasis gene, has been reported to correlate with sensitivity to chemotherapeutic agents including cisplatin in human breast and ovarian carcinoma cells. The aim of this study was to evaluate a role for nm23-H1 in responsiveness to cisplatin-based chemotherapy in patients with oesophageal squamous cell carcinoma (OSCC). The expression of nm23-H1 protein was examined immunohistochemically in 32 eligible patients with OSCC who underwent adjuvant chemotherapy with cisplatin, etoposide, and 5-fluorouracil after tumour resection. Fifteen (46.9%) of 32 patients were positive for nm23-H1 staining and 17 (53.1%) were negative. Both disease-free survival and overall survival rates of nm23-H1-negative patients were significantly shorter than in nm23-H1-positive patients (P < 0.01 for both). There was no significant difference in clinicopathologic characteristics between nm23-H1-positive and nm23-H1-negative groups. Multivariate analysis also showed that nm23-H1 expression was the most significant factor for overall survival of OSCC patients included in this study (P = 0.0007). To further study the role of nm23-H1, a human OSCC cell line (YES-2) was transfected with a plasmid containing a fragment of the nm23-H1 cDNA in an antisense orientation. Reduced expression of nm23-H1 protein in the antisense-transfected (AS) clones was found by Western blot analysis as compared to wild-type YES-2 and YES-2/Neo (clone transfected with the neomycin resistance gene alone). MTT (3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H tetrazolium bromide) assay showed that reduced expression of the nm23-H1 protein in AS clones was consistent with the degree of increased resistance to cisplatin but not etoposide or 5-fluorouracil. These data support the conclusion that reduced expression of nm23-H1 may be associated with resistance to cisplatin, suggesting the value of nm23-H1 expression as a prognostic marker for OSCC patients who are to undergo cisplatin-based chemotherapy.

Tumour cells engineered to secrete interleukin-15 augment anti-tumour immune responses in vivo

We examined the effect of interleukin-15 (IL-15) gene transfer into tumour cells on the host's anti-tumour response. In BALB/c mice IL-15 producing Meth-A cells (Meth-A/IL-15) underwent complete rejection, in a response characterized by massive infiltration of CD4+ T-cells and neutrophils. In contrast, Meth-A cells transfected with vector alone (Meth-A/Neo) grew rapidly. Moreover, rechallenged parental cells also were rejected in association with CD8* T-cell infiltration. However, in nude mice there was no drastic difference between Meth-A/IL-15 and Meth-A/Neo cells. These results demonstrate that IL-15-secreting tumour cells can stimulate local and systemic T-cell-dependent immunity and therefore may have a potential role in cancer therapy.

Construction of chimaeric processed immunoglobulin genes containing mouse variable and human constant region sequences

The specificity of monoclonal antibodies provides a powerful diagnostic and therapeutic tool in investigating human neoplasia. Radiological scanning and immunotherapy with mouse tumour-specific monoclonal antibodies have been applied to patients with some success, but a major problem is the neutralization of the mouse antibody induced by repeated administration of heterologous antibodies. To avoid or reduce such immune reactions, chimaeric immunoglobulins consisting of mouse variable (V) and human constant (C) regions can be synthesized. We have constructed a recombinant retrovirus DNA carrying genomic heavy-chain (H) variable-diversity joining (VH-D-JH) and C gamma 1 genes from different species and show here that the chimaeric intervening sequences are spliced out precisely. This procedure provides a useful method to construct the chimaeric mouse-human immunoglobulin gene to be expressed in Escherichia coli, yeast and animal cells. Unexpectedly, a hidden splice donor site in the 5'-flanking region of a human VH gene is used in place of the donor site of the leader sequence exon, resulting in the formation of the V region without the leader sequence.

cDNA cloning and tissue-specific expression of the gene encoding human adenylate kinase isozyme 2

We isolated two kinds of cDNAs encoding human adenylate kinase (AK) isozyme 2 from a HeLa cell cDNA library using bovine AK2 cDNA as a probe. Nucleotide sequencing revealed that the cDNAs encoded 239- and 232-amino acid proteins with deduced molecular mass of 26.5 (AK2A) and 25.6kDa (AK2B), respectively. Northern blot analysis demonstrated that AK2 mRNA is strongly expressed in liver, heart, skeletal muscle and pancreas, and moderately in kidney, placenta and brain, and weakly in lung. However, Western blot analysis showed that AK2 protein was present in large amounts in liver, heart, kidney, and in a small amount in lung, and undetectable in brain and skeletal muscle. These results suggested the presence of the tissue-specific gene-expression including post-transcriptional regulation in expression of the AK2 gene.