Programmed cell death of PC12 induced by adenovirus E1A

PC12 rat pheochromocytoma cells undergo programmed cell death or apoptosis with DNA fragmentation when deprived of serum. Here, we isolated a subclone of PC12, PC12FrR, that was resistant to DNA fragmentation in a serum-free condition. PC12FrR grew slightly faster, and had cells that were slightly larger than parental PC12 cells. Adenovirus E1A gene-transfected PC12FrR cells grew much faster than did parental PC12FrR cells in the presence of serum. In a serum-deprived condition, E1A-transfected PC12FrR cells died with DNA fragmentation, as did PC12 cells under the same conditions. These results suggest that the target(s) of E1A gene products may be involved in the mechanism(s) that regulate growth and death of neuronal cells.

A flow cytometric assay reveals a suppression of phagocytosis by rabbit defensin NP-3A in mouse peritoneal macrophages

Phagocytosis of fluorescein isothiocyanate (FITC)-labeled polystyrene microparticles by peritoneal macrophages from thioglycollate-elicited mice was examined by means of flow cytometry (FCM). This assay revealed that rabbit defensin NP-3A suppressed the phagocytosis in a dose-dependent manner. The present results suggest that NP-3 released from neutrophils is one of the mediators which modulates the activity of macrophages in response to infection.

Induction of functional interleukin-2 receptor in mouse microglia

Interleukin (IL)-2, initially discovered for its mitogenic activity on T cells, also acts on monocytes, resulting in the activation of cytokine production, superoxide production, and tumoricidal activity. Because severe brain damage was observed in IL-2-transgenic mice, this cytokine may have some influence(s) on the cells of the CNS. We investigated IL-2 receptor-bearing cells in the CNS and found that activated microglia expressed alpha-chain mRNA and immunoreactive IL-2 receptor beta-chain protein in culture. Although microglia did not express IL-2 receptors under normal culture conditions, they were induced to express these receptors by lipopolysaccharide (LPS) in a time-dependent manner. The IL-2 receptors were found to be functional because the viability and growth activity of LPS-treated microglia, but not untreated controls, increased in response to recombinant mouse IL-2 as determined by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay and bromodeoxyuridine uptake experiment, respectively. These effects of recombinant IL-2 were blocked by pretreatment with anti-mouse IL-2 receptor beta-chain antibody. Our findings suggest that activated microglia in the CNS can respond to this T cell-derived factor regulating their growth, which may be an important mechanism of communication between nervous and immune systems in physiological and pathological conditions.

Expression of glutamate transporters in cultured glial cells

Expression of mRNAs for glutamate transporter (GLT-1) and glutamate aspartate transporter (GLAST) was investigated in three different types of purified glial cells by the reverse transcriptase-polymerase chain reaction (RT-PCR). Cultured astrocytes, oligodendrocytes, and microglia expressed mRNAs for GLAST and GLT-1; mRNA for GLAST was expressed more prominently than that for GLT-1 in astrocytes. Oligodendrocytes and microglia expressed mRNAs for both GLT-1 and GLAST equally, but the expression in microglia was not prominent, suggesting glutamate uptake is not essential in microglia. In astrocytes cultured from different brain regions, GLAST mRNA was equally expressed. GLT-1 mRNA was also detected in these astrocytes, but the expression level was lower than that of GLAST.

cDNA cloning of a thromboxane A2 receptor from rat astrocytes

A cDNA clone for rat thromboxane (TX) A2 receptor was obtained from cultured astrocytes. The cDNA encodes a protein of 341 amino acids with seven putative transmembrane domains. The receptor is homologous with mouse and human TXA2 receptors at 92.7% and 71.8%, respectively. Expression of messenger RNA for the receptor was examined by reverse transcriptase-polymerase chain reaction, showing ubiquitous expression in brain glial cells such as astrocytes, oligodendrocytes and microglia.

The bipotential glial progenitor cell line can develop into both oligodendrocytes and astrocytes in the mouse forebrain

Oligodendrocyte-type 2 astrocyte (O2A) progenitor cells in vivo might differentiate into oligodendrocytes. To examine the influence of the brain micro-environment on the differentiation, a bipotential glial cell line from the mouse cerebrum, designated OS3 cells, was implanted into the telencephalon of infant and adult mice. About a half of the OS3 cells injected into 1-week postnatal brain expressed galactocerebroside (GalC), and even myelin basic protein, which were not observed to be expressed in vitro. By contrast, in the brain over 6 months postnatally, many OS3 cells expressed glial fibrillary acidic protein, and did not express much GalC. These findings suggest that the differentiation of glial cells is controlled by stage specific factors in the brain.

Stimulation of progesterone secretion in dispersed cells of rat corpora lutea by antioxidants

Antioxidants were used to investigate the role of free radicals in control of luteal steroidogenesis. Corpora lutea from pseudopregnant rats were enzymatically dispersed, the cells were incubated with antioxidants, and progesterone production was measured. Addition of the antioxidants nordihydroguaiaretic acid (NDGA), butylated hydroxytoluene (BHT), and the gonadotropin luteinizing hormone (LH) resulted in a dose-dependent increase in progesterone secretion. However, the response pattern to these treatments differed with the age of the corpora lutea, and unlike LH neither NDGA nor BHT treatment resulted in an increase in the intracellular second messenger cAMP. Nevertheless, LH and antioxidant-induced progesterone stimulation could be blocked by the addition of either aminoglutethimide or ketoconazole, cytochrome P450 side-chain cleavage (cytochrome P450 SCC) enzyme inhibitors, which prevent the conversion of cholesterol to pregnenolone and thus block steroid hormone synthesis. Also, unlike exposure to LH, exposure to antioxidants resulted in an additional increase in progesterone production in luteal tissue saturated with 25 hydroxycholesterol, a soluble cholesterol analog which serves as a substrate for cytochrome P450 SCC. This study suggests that the site of antioxidant action in affecting progesterone secretion may be at the cytochrome P450 SCC enzyme. Based on these results and on studies in other steroid hormone-producing cells, it appears that free radicals may be involved in regulating synthesis by modulating activity of cytochrome P450 SCC enzyme in rat luteal tissue.

Fetus-specific CYP3A7 and adult-specific CYP3A4 expressed in Chinese hamster CHL cells have similar capacity to activate carcinogenic mycotoxins

To assess whether CYP3A4 and CYP3A7 have a similar capacity to activate carcinogenic mycotoxins, we established cell lines stably expressing human CYP3A4 and CYP3A7, which are adult- and fetal-specific forms of cytochrome P450 in human livers, respectively. Each cDNA was introduced into CR-119 cells which had been established by introducing guinea pig NADPH-cytochrome P450 reductase cDNA into Chinese hamster lung cells. The cell lines (4-line and 7-line) stably expressed the mRNA and the protein corresponding to CYP3A4 and CYP3A7, respectively. The concentration-response for aflatoxin B1 (AFB1) cytotoxicity in 4-line and 7-line, respectively, was compared. 4-10 and 7-40 cells were approximately 17- and 20 times more sensitive to AFB1 than the parental CR-119 cells, respectively. In addition, the sensitivities to AFB1 of both 4-10 and 7-40 cells were enhanced approximately seven times by the addition of 10 microM alpha-naphthoflavone, a known activator of CYP3A enzyme, while the sensitivities were suppressed approximately four times by the addition of 100 microM troleandomycin, which forms a metabolite intermediate complex with CYP3A enzyme. Moreover, both cell lines showed approximately 10 and 2 times higher sensitivity to sterigmatocystin and aflatoxin G1 than CR-119 cells, respectively. These results indicate that CYP3A4 and CYP3A7 have essentially similar capacities to activate AFB1, sterigmatocystin, and aflatoxin G1 to produce toxic metabolites.

cDNA cloning and characterization of a novel receptor-type protein tyrosine phosphatase expressed predominantly in the brain

Protein tyrosine phosphatase has the potential to control various cellular events by negatively regulating the extent of tyrosine phosphorylation. Here, we report the isolation of a murine receptor protein tyrosine phosphatase, PTPBR7, which is expressed almost exclusively in the brain. Though the cytoplasmic portion of PTPBR7 reveals high similarity to HePTP/LC-PTP and STEP, these are, unlike PTPBR7, non-receptor protein tyrosine phosphatases. Unlike most receptor protein tyrosine phosphatases, PTPBR7 has only one cytoplasmic phosphatase domain, and its extracellular domain reveals no obvious structural similarity to known molecules. Thus, PTPBR7 defines a new subfamily of receptor-type protein tyrosine phosphatases. The putative extracellular domain of PTPBR7 was expressed in COS-7 cells as a chimeric fusion protein with an immunoglobulin Fc portion (PTPBR7-Fc). PTPBR7-Fc was secreted in the culture supernatant, confirming the capability of the extracellular domain of PTPBR7 to translocate across the cytoplasmic membrane. The cytoplasmic portion of PTPBR7 was expressed as a fusion protein in bacteria and was demonstrated to have catalytic activity. The expression of PTPBR7 was detectable in brain and especially in cerebellum but undetectable in liver, lung, heart, kidney, thymus, bone marrow, and spleen. In situ hybridization analysis revealed the most prominent signal in Purkinje cells. The predominant expression of PTPBR7 in the brain suggests that PTPBR7 may have role(s) in neuronal cells.

Nitric oxide induces an increased Na+ conductance in identified neurons of Aplysia

The ionic mechanism of the effects of micropressure ejections of hydroxylamine (HOA) and sodium nitroprusside (SNP), nitric oxide (NO) generators, on the membrane of identified neurons (R9-R12) of Aplysia kurodai was investigated with conventional voltage-clamp, micropressure ejection, and ion-substitution techniques. Micropressure ejection of HOA and SNP onto the neurons caused a marked depolarization in the unclamped neurons. Clamping the same neurons at their resting potential level (-60 mV) and reejecting HOA and SNP with the same dose produced a slow inward current (Ii(HOA) and Ii(SNP), 3-7 nA in amplitude, 15-60 s in duration) associated with an increase in input membrane conductance. Bath-applied hemoglobin (50 microM), a nitric oxide scavenger, almost completely blocked Ii(HOA) and Ii(SNP), and 3-isobutyl-1-methylxanthine (IBMX, 50 microM) prolonged and enhanced both Ii(HOA) and Ii(SNP). An intracellular injection of cyclic guanosine 3',5'-monophosphate (cGMP) into the same neurons produced a slow inward current (Ii(cGMP)) which resembled the responses to HOA and SNP, and this current was enhanced in IBMX. Bath-applied methylene blue (10 microM), an inhibitor of guanylate cyclase, significantly reduced Ii(HOA) and Ii(SNP). The inward currents induced by HOA, SNP and cGMP were sensitive to changes in the external Na+ concentration. These results suggest that extracellular NO can induce a slow inward current associated with an increase in Na+ conductance, mediated by an increase in intracellular cGMP.

Toxic and nontoxic effects of ouabain on the transmitter release from frog motor nerve terminals

Toxic and nontoxic effects of ouabain were investigated on frog neuromuscular preparation by measuring the mean quantal content of endplate potentials elicited during repetitive nerve stimulation. In the untreated normal muscles, application of 10 microM ouabain gave rise to a slow exponential increase in the transmitter release (toxic ouabain effect) with a certain delay. This delay was increased with either 100 microM amiloride, a Na(+)-Ca2+ exchange blocker, or the intracellular loading of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), a specific intracellular Ca2+ chelator. Measurements of frequency augmentation-potentiation (FAP) revealed a specific nontoxic effect of ouabain: 1 microM ouabain pivoted the long-linear FAP relation counter-clockwise without altering the intercept on the ordinate. Contrary to their action in the toxic effect, both 100 microM amiloride and the intracellular loading of BAPTA failed to counteract the nontoxic effect of 1 microM ouabain. The present results suggest that the toxic and nontoxic effects of ouabain are of different entities. The ouabain-sensitive subtype of Na+,K(+)-ATPase, which is abundant in neural tissues, seems to play a specific role in the process of nontoxic potentiation of transmitter release.

Clonal determination of uterine leiomyomas by analyzing differential inactivation of the X-chromosome-linked phosphoglycerokinase gene

To investigate the clonality of uterine leiomyomas, we developed a PCR-based method involving the differential inactivation of the X-chromosome-linked phosphoglycerokinase (PGK) gene. Small DNA samples of 22 leiomyomas from 9 Japanese patients, showing heterozygosity at the BstXI site of the PGK gene, were digested with the methylation-sensitive restriction enzyme HpaII. Only the inactive (methylated) PGK gene allele was selectively amplified by PCR followed by digestion with BstXI and electrophoresis. All leiomyoma samples consisted of a single type of inactive allele, even though alleles were detected that were specific to each nodule. The results indicated that all leiomyoma nodules were unicellular in origin but independently generated in the uterus.

Cytokine network in the central nervous system and its roles in growth and differentiation of glial and neuronal cells

Cells resident within the central nervous system (CNS) can synthesize, secrete and respond to inflammatory cytokines not only contributing to the responses to injury or immunological challenge within the CNS, but also regulating their own growth and differentiation potential. The actions and cell communication via cytokines in the CNS are designated as the CNS cytokine network, in which microglia and astrocytes play the central roles. To further characterize the CNS cytokine network we investigated the differences in roles of these cells, and found that microglia might contribute to the early phase of cytokine production reaction and that astrocytes might contribute the late phase of the reaction. We also investigated roles of inhibitory cytokines such as TGF beta, IL-4, and IL-10, and showed that each might play a distinct role in the inhibitory regulation in the CNS. We summarized our previous report about cellular distribution of cytokine receptors in the CNS cells and discussed their roles in the CNS cytokine network. Finally, we investigated that expression of IL-6 and IL-2 receptors in neuronal and oligodendrocytic differentiation, respectively. From these results, we discussed the features of the CNS cytokine network.

Effects of inhibitors of ouabain-sensitive Na+, K(+)-ATPase and Li+ ions on the neuromuscular transmission of the frog

The effect of blockade of ouabain-sensitive alpha 2 and alpha 3 (neural type) isozymes of Na+, K(+)-ATPase was investigated on frog neuromuscular preparations by recording the frequency augmentation-potentiation (FAP) of the endplate potential, an electrophysiological and neuropharmacological technique to analyze the drug actions on the release process of the readily releasable transmitter quanta. Erythrosin B, which was thought to selectively inhibit the neural type Na+, K(+)-ATPase, pivoted the log-linear FAP relation counterclockwise without altering the intercept on the ordinate. Chlormadinone had a similar action. An increase in the concentration of extracellular K+ ions pivoted the FAP relation clockwise with a concomitant upward shift of the intercept on the ordinate, and low K+ Ringer's solution produced an inverse effect. In contrast, Li+ ions shifted the FAP relation upwards dose-dependently leaving its slope unchanged. Cinnarizine, a blocker for inositol-1,4,5-trisphosphate-induced Ca2+ release, and 5,5'-dimethyl-1,2-bis(2-amino-phenoxy)ethane-N,N,N',N'-tetraacetic acid, a specific intracellular Ca2+ chelator, significantly antagonized the potentiating action of Li+. The ouabain-sensitive neural type Na+, K(+)-ATPase isozyme, which is abundant in neural tissues, seems to play an important role in stimulation frequency-dependent modulation of the quantal transmitter release such as FAP.

Production of interleukin-10 by mouse glial cells in culture

In this study, we examined the production of IL-10 by glial cells in vitro. IL-10 was detected in the culture supernatants of microglia and in the cell lysate of astrocytes by enzyme-linked immunosorbent assay. We also detected IL-10 mRNA and IL-10 receptor mRNA in both microglia and astrocytes. The expression of IL-10 mRNA, as well as the production of IL-10 protein, was enhanced by the stimulation of these cells with lipopolysaccharide(LPS). Recombinant IL-10 effectively suppressed both LPS-induced cytokine production and IFN-gamma-induced class II major histocompatibility complex antigen expression by microglia. These results suggest that IL-10 is produced in the CNS and plays a role as an inhibitory regulator in the CNS cytokine network.

Inhibitory effect of vasoactive intestinal peptide (VIP) on phagocytosis in mouse peritoneal macrophages

The effect of VIP on phagocytosis in peritoneal macrophages was examined by means of flow cytometry (FCM). This assay revealed that VIP suppressed phagocytosis in a dose-dependent manner. VIP(1-12) did not suppress phagocytosis. VIP(10-28) was more suppressive than VIP(1-28). A known VIP-antagonist (N-Ac-Tyr1,D-Phe2)-growth hormone-releasing factor (GRF) (1-29)-NH2 suppressed phagocytosis less than VIP. Control phagocytosis was partially suppressed in Ca(2+)-free solution. Phagocytosis was suppressed by VIP further in Ca(2+)-free solution than in the normal solution. Phagocytosis was suppressed in a known phosphodiesterase inhibitor IBMX-containing solution. The degree of suppression by VIP was the same in the presence or the absence of IBMX. These results suggest that VIP suppresses extracellular Ca(2+)-dependent and -independent phagocytosis, that the C-terminal fragment of VIP is essential for VIP action, that the suppression is mediated by cAMP and that the inhibition of macrophage phagocytosis by VIP is one of the mechanisms which modulates immune responses by the nervous system.

Molecular cloning and functional expression of a mouse cytochrome P-450 (Cyp3a-13): examination of Cyp3a-13 enzyme to activate aflatoxin B1 (AFB1)

A cDNA encoding a novel member of the cytochrome P-450 superfamily, Cyp3a-13, has been isolated from mouse liver cDNA library by hybridization screening. The Cyp3a-13 encoded 503 amino acid residues and shared 71% amino acid identity with Cyp3a-11. When Cyp3a-13 cDNA was expressed in CR119 cells which had been established as a cell line stably expressing NADPH-cytochrome P-450 reductase cDNA of guinea pigs, aflatoxin B1-dependent cytotoxicity was observed. This cytotoxicity was enhanced by alpha-naphthoflavone (7,8-benzoflavone), which is known to augment the CYP3A enzymatic activity. The results indicate that CYP3A in mice, which are relatively insensitive to aflatoxin B1, can activate aflatoxin B1 to a genotoxic product.

Induction of MHC class II antigen expression on murine microglia by interleukin-3

The effects of various cytokines on MHC class II antigen expression were examined in murine microglia. Interleukin-3 (IL-3), as well as interferon-gamma (IFN-gamma), induced MHC class II antigen expression on these cells. IL-3 additionally enhanced MHC class II antigen expression induced by IFN-gamma. The induction of MHC class II antigen expression by IL-3 was not mediated via IFN-gamma production, because the effect was not blocked by antibodies to IFN-gamma. In contrast, granulocyte-macrophage colony-stimulating factor (GM-CSF) did not affect the expression of MHC class II antigen on naive cells and down-regulated IFN-gamma-mediated induction of MHC class II antigen expression on microglia. Because IL-3 and GM-CSF are apparently produced in the central nervous system, MHC class II antigen expression on microglia may be regulated by these cytokines synthesized in the central nervous system.

Implantation and growth of epidermal growth factor (EGF) receptor expressing human ovarian cancer xenografts in nude mice is dependent on EGF

BACKGROUND

The importance of epidermal growth factor (EGF) receptor-dependent growth has not been clarified for in vivo growth of primary human ovarian cancers.

METHODS

Seventeen primary human ovarian cancer tissue samples were examined for the presence of EGF receptors by a 125I-EGF-binding study. Three groups of mice were inoculated with EGF receptor expressing and not-expressing cancer tissues. The groups were as follows: control group, Sx group (mice that underwent sialoadenectomy; EGF depleted mice), and Sx+EGF (EGF-replaced) group. The ability of the inoculated tissues to implant and grow then was studied.

RESULTS

Of the 17 primary ovarian cancers, 12 expressed EGF receptors and 5 did not. Eight of 12 EGF-receptor expressing cancer tissues implanted and formed growing tumors in control animals. None implanted in the Sx animals. Epidermal growth factor receptor-expressing cancers implanted in Sx animals that received EGF administration. Two of five EGF receptor-negative ovarian cancers implanted and grew in both control and Sx animals.

CONCLUSION

Growth of EGF receptor-expressing primary human ovarian cancers may be dependent on EGF in vivo.

Developmentally regulated expression of a murine receptor-type protein tyrosine phosphatase in the thymus

Reversible phosphorylation of tyrosine residues plays a crucial regulatory role in various cellular events, including differentiation and proliferation of lymphocytes. Here, we report the isolation of a murine receptor-type protein tyrosine phosphatase (PTP), mRPTP-sigma, which is expressed in both immature thymocytes and stroma cells. At least two alternatively spliced transcripts of mRPTP-sigma (T and B) were observed. mRPTP-sigma T was the dominant form in the thymus and had three Ig-like and eight fibronectin type III-like domains in the extracellular portion. mRPTP-sigma T was almost identical with RPTP-sigma/PTP NE-3/PTP-P1/CPTP1, a PTP recently cloned from rat brain, except that RPTP-sigma/PTP NE-3/PTP-P1 was about 400 amino acids shorter than mRPTP-sigma T. mRPTP-sigma B, the second form of mRPTP-sigma, was dominant in the brain and was most likely the murine counterpart of RPTP-sigma/PTP NE-3/PTP-P1. In the developing thymocytes, the expression of mRPTP-sigma was high in double negative (CD4-CD8-), low in double positive (CD4+CD8+), and marginal in single positive (SP; CD4+CD8- or CD4-CD8+) subpopulations. No upregulation of mRPTP-sigma was observed in the spleen cells stimulated with Con A. Developmental regulation of mRPTP-sigma expression suggests its involvement in the control of T lymphocyte differentiation.

Developmentally regulated expression of a murine receptor-type protein tyrosine phosphatase in the thymus

Reversible phosphorylation of tyrosine residues plays a crucial regulatory role in various cellular events, including differentiation and proliferation of lymphocytes. Here, we report the isolation of a murine receptor-type protein tyrosine phosphatase (PTP), mRPTP-sigma, which is expressed in both immature thymocytes and stroma cells. At least two alternatively spliced transcripts of mRPTP-sigma (T and B) were observed. mRPTP-sigma T was the dominant form in the thymus and had three Ig-like and eight fibronectin type III-like domains in the extracellular portion. mRPTP-sigma T was almost identical with RPTP-sigma/PTP NE-3/PTP-P1/CPTP1, a PTP recently cloned from rat brain, except that RPTP-sigma/PTP NE-3/PTP-P1 was about 400 amino acids shorter than mRPTP-sigma T. mRPTP-sigma B, the second form of mRPTP-sigma, was dominant in the brain and was most likely the murine counterpart of RPTP-sigma/PTP NE-3/PTP-P1. In the developing thymocytes, the expression of mRPTP-sigma was high in double negative (CD4-CD8-), low in double positive (CD4+CD8+), and marginal in single positive (SP; CD4+CD8- or CD4-CD8+) subpopulations. No upregulation of mRPTP-sigma was observed in the spleen cells stimulated with Con A. Developmental regulation of mRPTP-sigma expression suggests its involvement in the control of T lymphocyte differentiation.

Symptomatic middle cerebral artery stenosis and occlusion: comparison of three-dimensional time-of-flight magnetic resonance angiography with conventional angiography

The usefulness of magnetic resonance (MR) angiography using the three-dimensional time-of-flight method for the characterization of symptomatic middle cerebral artery (MCA) occlusive lesions was evaluated in 10 patients with MCA occlusion and 10 with MCA stenosis. All lesions were symptomatic and documented by conventional angiography. There was no false-negative MR angiogram that failed to demonstrate the MCA occlusive lesion. MR angiography correctly evaluated the location of lesions and the difference between stenosis and occlusion. Stenosis appeared as a focal signal loss (< 1.0 cm) of the MCA at the site of stenosis, and occlusion as a complete signal loss of the MCA distal to the site of occlusion. However, MR angiography could not distinguish diffuse stenosis and one point stenosis demonstrated by conventional angiography. MR angiography is a useful noninvasive diagnostic method for evaluating occlusive lesions of the MCA in symptomatic patients.