Analytical studies of spontaneous and vasopressin-induced calcium oscillations in cultured vascular smooth muscle cells

Spontaneous and vasopressin-induced Ca2+ oscillations in cultured vascular smooth muscle (A7r5) cells were further examined and characterized. Intracellular Ca2+ concentrations ([Ca2+]i) were measured by use of a high-performance laser cytometer. When the oscillatory patterns in [Ca2+]i were analyzed with a power spectrum method, about 80% of cells exhibited spontaneous Ca2+ oscillations with the frequency of 0.02-0.5 Hz. Nifedipine abolished these repetitive spikes, whereas pinacidil partially attenuated their amplitude and frequency. When vasopressin (100 nM) was applied to A7r5 cells, there was an initial rise in [Ca2+]i, followed by a delayed sustained increase in [Ca2+]i. The one-pool, nonoscillatory model was employed to fit this biphasic change, and the difference between the observed response and the simulated response was then analyzed with a power spectral method. About 50% of cells were noted to display oscillatory patterns in [Ca2+]i after sustained increase in [Ca2+]i. The present study indicates that spontaneous Ca2+ oscillations in A7r5 cells are modulated by the activity of ATP-sensitive K+ channels and are not related to pertussis toxin-sensitive GTP-binding protein(s). On the basis of the one-pool, nonoscillatory model, it is suggested that the buffering capacity of internal stores appears to be stronger in the cells with spontaneous Ca2+ oscillations than in those in a quiescent state, and the vasopressin-mediated inhibition of accumulation by internal stores was attenuated when the cells exhibited spontaneous Ca2+ oscillations. The implementation of this minimum kinetic model integrated with a power spectrum method would be an alternative to understand the oscillating behavior in [Ca2+]i.

Dolichyl phosphate, a potent inducer of apoptosis in rat glioma C6 cells

Exposure of rat glioma C6 cells to dolichyl phosphate resulted in cell shrinkage followed by nuclear fragmentation and internucleosomal cleavage of genomic DNA, yielding ladder patterns of oligonucleosomal fragments, all characteristics of apoptosis. This phenomenon occurred in a dose and time dependent manner. Dolichol and prenol failed to induce apoptosis. The inhibitors of N-glycosylation, tunicamycin and swainsonine had no apparent effect on dolichyl phosphate-induced apoptosis. Apoptotic changes were also observed in HL-60 cells, SIRC cells and HeLa cells. Thus, dolichyl phosphate functions as a potential apoptosis inducer as well as an essential carrier lipid in the biosynthesis of N-linked glycoprotein.

Modulation of elastin expression by heparin is dependent on the growth condition of vascular smooth muscle cells: up-regulation of elastin expression by heparin in the proliferating cells is mediated by the inhibition of protein kinase C activity

The effect of heparin on elastin expression in the proliferating and quiescent phases of growth of smooth muscle cells was studied. Heparin stimulated elastin synthesis and its mRNA level 2-3 fold in the proliferating cells while it inhibited the cell proliferation. The inhibition of cell proliferation and the stimulation of elastin expression by heparin in the proliferating cells were mimicked by a potent protein kinase C antagonist, H-7, but not by H-89, W-7, and HA1004, suggesting that the effect of heparin is mediated by the inhibition of protein kinase C. In contrast, heparin inhibited elastin synthesis and its mRNA level slightly but exhibited no effect on cell proliferation in the growth-arrested cells. This result indicates that heparin reciprocally affects elastin expression depending on the growth state of smooth muscle cells. Heparin thus exerts a complex influence on elastin expression in smooth muscle cells.

Stimulation of cell proliferation and autoregulation of elastin expression by elastin peptide VPGVG in cultured chick vascular smooth muscle cells

Synthetic elastin peptides, VPGVG or its polymer (VPGVG)n, enhanced the proliferation of smooth muscle cells 1.5-fold during 48 h treatment at the concentrations over 10(-6) M or 1.0 microgram/ml, respectively. Monomeric and polymeric VPGVG sequences reduced elastin synthesis and its mRNA level to one-third and one-half of control respectively under the conditions in which the proliferation of cells were enhanced, but did not change collagen synthesis as measured by bacterial collagenase digestion. The elastin-specific autoregulation by elastin fragments may reflect the feedback regulation of elastin expression which may play an essential role in elastin metabolism under the normal and diseased conditions.

Cell cycle-dependent regulation of elastin gene in cultured chick vascular smooth-muscle cells

A study was made of the relationship between elastin expression and the proliferative state of chick vascular smooth-muscle cells. Confluent cells of primary culture brought to a quiescent state by the deprivation of serum for 72 h exhibited a 5-, 3.5- and 2-fold increase in elastin synthesis, elastin mRNA level and transcriptional activity of elastin gene respectively over those in the proliferative state. On re-addition of serum in serum-deprived culture, cells started to proliferate, and elastin synthesis, its mRNA level and transcription of the gene decreased to the level of a proliferative state within 24 h, indicating that elastin expression in smooth-muscle cells was controlled by their growth states at least in part at a transcriptional level. A comparable increase in elastin mRNA level was observed when the cell growth was arrested by suspension culture for 72 h. When the cells were synchronized at the G1/S phase with thymidine/hydroxyurea treatment, elastin expression at the G1/S phase was greater than that at the G2/M phase during cell cycling. Elastin mRNA level at the G0 phase brought about by serum-deprivation or suspension culture predominated over that at the G1/S phase during cell cycling. These results indicate that gene expression of elastin and cell cycle are tightly coupled, which is independent of the presence of serum or adhesive state, and that elastin expression could be a biochemical marker for the growth states of smooth-muscle cells.

Changes in the level of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid in cerebrospinal fluid after subarachnoid hemorrhage

A high concentration of a type of cholic acid, 7 alpha-hydroxy-3-oxo-4-cholestenoic acid, is observed in the content of chronic subdural hematoma. To investigate the possible causes, the level of this compound was measured in the cerebrospinal fluid of patients who underwent surgery for aneurysmal subarachnoid hemorrhage or non-hemorrhagic diseases. The maximum level was significantly higher in the aneurysmal subarachnoid hemorrhage patients, indicating that surgical intervention did not cause the postoperative increase in the level of this compound in the cerebrospinal fluid. Monitoring of plasma levels showed no postoperative increase. In vitro culture of a mixture of arterial blood and cerebrospinal fluid failed to show the de novo production of this compound. These results strongly suggest extrahepatic intracranial production of this cholic acid occurs in subarachnoid hemorrhage. The high concentration of this compound in both chronic subdural hematoma and subarachnoid hemorrhage suggests a possible role for 7 alpha-hydroxy-3-oxo-4-cholestenoic acid in intracranial hemorrhagic disorders.

Enhanced tropoelastin-degrading activity during cell passages in cultured smooth muscle cells

Tropoelastin expression in vascular smooth muscle cells during serial cell passages from the primary to the tertiary culture was studied. The level of tropoelastin was found to be greatly reduced as the number of cell passages increased. The translational activity and level of elastin mRNA were essentially unchanged throughout the cell passages. The reduction in tropoelastin expression was not due to the repetitive trypsin treatment nor to the prolyl hydroxylation level of the newly-synthesized elastin. A comparable decline in tropoelastin expression was also found with increasing cell division in the primary cultures plated at different cell densities. A pulse-chase experiment revealed that the newly-synthesized elastin in the tertiary culture degraded more rapidly than that in the primary culture. The culture medium harvested from the tertiary culture exhibited a higher tropoelastin-degrading activity than that from the primary culture in the test-tube. The degrading activity of the tertiary culture was inhibited by the addition of 1 mM ethylenediaminetetraacetic acid or 1 mM phenylmethylsulfonyl fluoride, but not by 1 mM N-ethylmaleimide. These results suggest that the reduction in tropoelastin expression during the cell passages from the primary to the tertiary culture is due to the enhanced tropoelastin-degrading activity of the tertiary culture. The transition to tropoelastin-degrading phenotype during cell passages may explain the biological mechanisms of smooth muscle cell migration from the media to the intima observed in the pathological conditions.

Ornithine decarboxylase is directly involved in mouse mammary carcinoma cell invasion in vitro

To elucidate the role of ornithine decarboxylase (ODC) in cancer cell invasion, we have compared the invasiveness of mouse mammary carcinoma, FM3A and its variant cell line, EXOD, which overproduces ODC. We have found that EXOD cells showed about 5.6-fold more invasiveness through a reconstituted basement membrane (Matrigel) compared to FM3A cells. To elucidate the underlying mechanism of increased invasiveness of EXOD cells, we analyzed gelatinase activity in conditioned media derived from FM3A and EXOD cells. EXOD cells secreted approximately 3-fold 72kDa gelatinase compared to FM3A cells. Cell attachment ability to Matrigel was also studied. Although FM3a and EXOD cells showed increased attachment to Matrigel in a dose-dependent manner, EXOD cells showed higher cell attachment ability compared to FM3A cells. Anti-72kDa gelatinase neutralizing antibody suppressed EXOD cell invasion through Matrigel. Further, antisense oligonucleotides of ODC suppressed EXOD cell invasion through Matrigel. Although the causal relationship among ODC expression, gelatinase secretion and cell attachment ability remains to be elucidated, the results suggest that both overproduction of ODC and 72kDa gelatinase secretion are directly involved in increased invasiveness of EXOD cells.

Sexual dimorphism of lipids in Harderian glands of golden hamsters

The Harderian gland of golden hamsters excretes alkyldiacylglycerol (ADG), the fatty acid and alkyl compositions of which differ between males and females. ADG in males contains mostly straight chain fatty acids, even- and odd-numbered, the major one being 15:0, while ADG in females contains iso- and anteiso-branched chain acids (34.0%). Iso-branching was found in both even- and odd-numbered acids, but anteiso-branching was found mostly in odd-numbered acids. The presence of propionic acid at the 3 position of the glycerol moiety in male ADG, and of isovaleric and 2-methylbutyric acids at the same position in female ADG was demonstrated by NMR spectrometry. Alkyl portions also exhibited sexual dimorphism in these lipids. ADG from males consisted of straight aliphatic chains, but branched chain components occupied almost half (45%) in ADG from females, and the branching resided at the iso- and anteiso-positions. The ADGs in glands from the two sexes were separated by Iatrobeads column chromatography into three and two subfractions, respectively. The fatty acid and alkyl compositions of these subfractions coincided with the above-mentioned results and with the behavior of the ADGs on thin-layer plates. These findings suggest that a sex hormone affects the metabolism of valine, leucine and isoleucine, and sexual dimorphism of ADGs occurs in the Harderian gland.

Induction of Ca2+ oscillations by vasopressin in the presence of tetraethylammonium chloride in cultured vascular smooth muscle cells

The change of cytosolic Ca2+ concentration ([Ca2+]i) caused by vasopressin was examined in indo-1-loaded A7r5 smooth muscle cells by use of the high-performance laser cytometer and ratiometric fluorescence method. Vasopressin (100 nM) caused an initial rapid rise and a delayed increase in [Ca2+]i (n = 6). However, in the presence of tetraethylammonium chloride (10 mM), vasopressin consistently triggered sustained Ca2+ oscillations which were preceded by a large peak of [Ca2+]i. The latency for the development of this huge increase in [Ca2+]i prior to the occurrence of sustained Ca2+ oscillations was always the same. The frequency and amplitude of this type of Ca2+ oscillation varied depending upon the extracellular Ca2+ concentration. Ca(2+)-free solution did not completely suppress the sustained Ca2+ oscillations, but caffeine (20 mM) effectively abolished them. The present findings indicate that in A7r5 smooth muscle cells, the sustained Ca2+ oscillations triggered by vasopressin in the presence of tetraethylammonium chloride were mainly due to Ca2+ release from IP3-sensitive Ca2+ stores and Ca2+ influx from extracellular space, and did not require the pacemaker activity derived from the surface membrane. Moreover, the vasopressin-induced change in [Ca2+]i appeared to be linked to pertussis toxin-insensitive GTP-binding protein(s).

Comparison of ELISA and HPLC for the determination of desmosine or isodesmosine in aortic tissue elastin

We developed a rapid and simple method for estimating tissue elastin content by measuring desmosine (D) in tissue hydrolysates by competitive ELISA. We compared the ELISA previously reported HPLC methods. When D or isodesmosine (ID) in hydrolysate of the same elastin preparation were measured by the two different methods, a good linear relationship was obtained (r = 0.854 for human aorta or r = 0.938 for rabbit aorta, respectively). The ELISA method can detect as little as 6 pmol/ml and it may be useful in monitoring elastin metabolism in patients with various connective tissue diseases.

Important contribution of the methylene part of LTB4 toward binding affinity to the LTB4 receptors and rise in intracellular-free calcium concentration

In order to examine a role of the C(16)-C(20) methylene part of leukotriene B4 (LTB4) toward the activation of leukocytes, we synthesized the LTB4-analogues in which the length of the C(16)-C(20) part of LTB4 is varied systematically while the two hydroxyl groups at C(5) and C(12) positions and the 6(Z), 8(E), 10(E) conjugated triene unit remained untouched. We examined their binding affinity to the LTB4 receptors present in the rat polymorphonuclear leukocytes (PMNLs) and their ability to raise intracellular-free calcium concentration ([Ca2+]i) in the rat PMNLs loaded with fura-2. As the length of the chain of LTB4 was increased or decreased one by one, the binding affinity to the LTB4 receptors diminished, and the analogues of more than three carbon atoms shorter chain were of about three log order less activity than LTB4. The biological potency as assessed in [Ca2+]i rises pararelled that of the binding affinity to the PMNL membrane. These results indicate that the C(16)-C(20) part of LTB4 plays important role for the activity. In a similar way we prepared the LTB4-analogues of a different chain length between C(2)-C(4) of LTB4 and tested their biological activity. We found that the C(2)-C(4) part of LTB4 also affects the activity.

Distribution of cholinergic neuron-specific gangliosides (GT1a alpha and GQ1b alpha) in the rat central nervous system

A newly developed mouse monoclonal antibody, GGR-41, was used to localize a novel species of gangliosides, GT1a alpha and GQ1b alpha, in the rat central nervous system. Intense immunoreactivity was found in the neuropil of the spinal cord dorsal horn, spinal trigeminal nucleus, solitary tract nucleus, superior colliculus, interpeduncular nucleus, hypothalamus and septal area. The results suggest that GT1a alpha and GQ1b alpha are expressed in the nerve terminals of a certain population of cholinergic fibers.

Biosynthetic pathway for a new series of gangliosides, GT1a alpha and GQ1b alpha

A new class of gangliosides, GT1a alpha and GQ1b alpha, were initially identified as cholinergic neuron-specific antigens in bovine brain. These gangliosides have in common alpha 2-6 NeuAc linked to the GalNAc residue in the gangliotetraose core structure. In this study, we have determined the biosynthetic pathways of GT1a alpha and GQ1b alpha using rat liver Golgi fraction. The results showed that GT1a alpha and GQ1b alpha were synthesized from GD1a and GT1b, respectively, by the action of a GalNAc alpha 2-6 sialyltransferase. It was also demonstrated that these two gangliosides were found to exist as extremely minor components in rat liver.

Two species of antiganglioside antibodies in a patient with a pharyngeal-cervical-brachial variant of Guillain-Barré syndrome

A patient with a pharyngeal-cervical-brachial variant of Guillain-Barré syndrome had anti-GT1a and anti-GD1a antibodies (IgG) in the serum. The activities of anti-GT1a antibodies were stronger than anti-GD1a antibodies and their activities declined later in the clinical course. These two different antibodies bound independently to each ganglioside in an absorption study with polystyrene beads coated with GT1a or GD1a.

[Effect of traditional Chinese medicine (dai-saiko-to) on experimental calcinosis]

To clarify the anti-calcinosis actions of traditional Chinese medicine (Dai: Dai-saiko-to) and estradiol benzoate (E2), 7-week or retired (about 6-months-old) female rats were treated with Vit. D2 (1.75 x 10(5) I.U./kg b.w./day) for 4 days, and then were fed a basal diet containing Dai (at ten times the medical dose in humans) or were injected i.p. with E2 (at the medical dose in humans) for 6 weeks. The following results were obtained: 1) Dai did not improve Ca and P metabolism in experimental calcinosis of 7-week female rats; 2) in retired female rats, Dai decreased both P in the heart and the ratio of Ca to P in bone, similar to the treatment with E2. Dai, as well as E2, seemed to nomalize Ca and P metabolism disturbed by Vit. D2 treatment.

Identification of new mutations in sterol 27-hydroxylase gene in Japanese patients with cerebrotendinous xanthomatosis (CTX)

Cerebrotendinous xanthomatosis (CTX) is a hereditary sterol storage disease associated with accumulation of cholesterol and cholestanol in various tissues, especially tendons and neural tissues. The biochemical defect that causes CTX is a deficiency of the mitochondrial sterol 27-hydroxylase which oxidizes the side chain of cholesterol in connection with formation of bile acids. Japan has a relatively high prevalence of CTX and more cases of the disease are found here than in any other country. In the present study two new different point mutations are described in the heme-ligand binding domain of the sterol 27-hydroxylase gene in three Japanese CTX patients and one CTX heterozygote. Two of the homozygotes as well as the heterozygote subject have a single base substitution of A for G at codon 441 [CGG (Arg) to CAG (Gln)]. Another homozygote has a transition of C to T at codon 441 [CGG (Arg) to TGG (Trp)]. These two different mutations result in two restriction fragment length polymorphisms (RFLPs) for the enzymes StuI or HpaII. We also assayed sterol 27-hydroxylase activity using skin fibroblasts derived from three CTX patients, one CTX heterozygote, and normal subjects. While two of the homozygous subjects have undetectable levels of the enzyme activity, one homozygous subject and one heterozygous subject have decreased levels of the enzyme activity, about 1.4% and 10% of normal, respectively. The results suggest that the newly identified point mutations in the sterol 27-hydroxylase gene could account for the sterol 27-hydroxylase deficiency in the Japanese CTX patients.

Biochemical analyses of macromolecular matrix components in patients with pseudoxanthoma elasticum

Two cases of pseudoxanthoma elasticum (PXE) were reported. Biochemical studies of collagen, glycosaminoglycan, and elastin content were performed using skin specimens from affected lesions. Hydroxyproline content was reduced approximately 46% and 24% in cases 1 and 2, respectively. The reduction in collagen content resulted from the reduction in the lower dermis, not from that in the upper dermis. Glycosaminoglycan content in PXE was also decreased, with a slight increase in the ratio of hyaluronic acid to dermatan sulfate. Isodesmosine content in PXE was increased 3.2- and 2.2-fold in cases 1 and 2, respectively. These results suggest that the major and primary biochemical changes in PXE are an increase in elastin content.

1-Alkyl-2,3-diacylglycerol synthesis in primary culture cells of guinea pig harderian gland

Using a primary culture system of guinea pig Harderian gland cells, we investigated the metabolism of a unique lipid: 1-alkyl-2,3-diacylglycerol containing methyl-branched fatty acids. The cells were obtained by collagenase digestion, and cells with lipid-droplets were collected by two-step centrifugation. We cultured these cells, and examined their lipid and fatty acid compositions. The de novo synthesis of lipids in these cells was studied as to the incorporation of [1(2)-14C]acetate and [U-14C]glucose. The major lipid proved to be 1-alkyl-2,3-diacylglycerol, as in tissue, and it contained a large amount of methylbranched fatty acids specific to this gland. The incorporation of [14C]acetate and [14C]glucose into 1-alkyl-2,3-diacylglycerol in the cultured cells amounted to 79.7 and 88.2% of the total incorporation into the lipid fraction, respectively. The incorporation of [14C]acetate into fatty acids in the cultured cells was detected for the chain lengths of C14 to C25. The activities of glycerol-3-phosphate dehydrogenase in the cultured cells and Harderian gland were lower than that in adipose tissue. These results confirm that cultured cells reflect the lipid metabolism originating in the Harderian gland and show that this culture system can serve as one part of the armamentarium for further study of this unique lipid metabolism.

Gallstone formation in cholestanol-fed mice

We examined the effect of cholestanol (5 alpha-dihydrocholesterol) on cholesterol and bile acid metabolism in BALB/c mice. After feeding 1% cholestanol in the diet for 14 months, gallstones composed of 55% cholesterol and 45% cholestanol developed in 20% of the mice and were associated with mucosal inflammation and serosal vessel thickening of the gallbladder. Cholestanol concentrations increased 42-fold in the serum (0.17 versus 0.004 mg/ml) and 18-fold in the liver (0.55 versus 0.03 mg/g) as compared with control mice, whereas cholesterol declined 20 and 26% in serum and liver, respectively. Hepatic microsomal HMG-CoA reductase activity, reflecting cholesterol synthesis, rose 51% (from 7.2 to 10.9 pmol/mg/min). In contrast, hepatic microsomal cholesterol 7 alpha-hydroxylase activity, the rate-determining enzyme for bile acid synthesis, was severely depressed as compared with control mice (0.9 versus 2.2 pmol/mg/min). Discontinuing cholestanol from the diet for 1 month reduced the elevated serum and liver cholestanol concentrations and restored hepatic HMG-CoA reductase and cholesterol 7 alpha-hydroxylase activities to normal. These results demonstrate that cholestanol is absorbed, replaces cholesterol in serum and liver, causes increased cholesterol synthesis, but inhibits bile acid synthesis. The combination of increased cholesterol synthesis with decreased bile acid formation promotes gallstone formation in cholestanol-fed mice.

Initiation of DNA synthesis in a high molecular weight fraction of Xenopus egg extract

Xenopus egg extract was fractionated by gel-filtration column chromatography and DNA synthetic activity was examined using double-stranded DNA as a template. The major activity eluted had an apparent molecular mass of about 300 kDa. Product analyses showed that de novo DNA synthesis occurs with formation of replication bubbles, thereby suggesting that this fraction catalyzes the initiation of DNA replication. Activities of DNA polymerase alpha-primase and DNA helicase overlapped with the DNA synthetic activity, but the elution profiles of the enzymes differed from that of the DNA synthetic activity. Therefore, this 300-kDa fraction may contain a component which differs from the above enzymes yet is essential for initiation of DNA replication.

Three types of Gi alpha protein of the guinea-pig lung: cDNA cloning and analysis of their tissue distribution

cDNA clones encoding three types of Gi alpha, the alpha subunit of GTP-binding protein (Gi1 alpha, Gi2 alpha, and Gi3 alpha), were isolated from a cDNA library of the guinea-pig lung. Nucleotide sequence analysis revealed a high degree of homology with other mammalian Gi alpha cDNAs. By RNA blot analysis, the expression pattern of Gi1 alpha was more tissue-specific than those of other types of Gi alphas in the guinea-pig tissues examined. While Gi2 alpha and Gi3 alpha mRNAs were ubiquitously expressed in all tissues examined, Gi1 alpha mRNA was mainly expressed in the brain, lung and kidney. These results suggest that each Gi alpha protein may have a different role.

[Effects of traditional Chinese medicines (dai-saiko-to, sho-saiko-to and hachimi-zio-gan) on spontaneously diabetic rat (WBN/Kob) with experimentally induced lipid and mineral disorders]

To clarify the therapeutic effects of several traditional Chinese medicines to improve disorders of carbohydrate, lipid and mineral metabolism, spontaneously diabetic rats (WBN/Kob) were treated with Vit. D2, 1 x 10(5) I.U./kg b.w./day, for 4 days, and then fed a hyperlipidemic diet containing traditional Chinese medicines for 6 weeks. The following results were obtained: 1) In the diabetic rats, the 3 traditional Chinese medicines further decreased the blood glucose level at 120 min after glucose loading in the glucose tolerance test. 2) The drugs increased the inorganic phosphate in the liver and normalized mineral metabolic disorder. 3) Hachimi-zio-gan decreased the cholesterol content in the kidney, and Sho-saiko-to decreased the cholesterol content in the elastin fraction (elastin-cholesterol) of the kidney. Such experimental results suggest that traditional Chinese medicines may be effective against the pathological conditions of diabetes mellitus that involve disorders of lipid and mineral metabolism.