Intracellular pH regulation of CA1 neurons in Na(+)/H(+) isoform 1 mutant mice.
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To understand the role of Na(+)/H(+) exchanger 1 (NHE1) in intracellular pH (pH(i)) regulation and neuronal function, we took advantage of natural knockout mice lacking NHE1, the most ubiquitously and densely expressed NHE isoform in the central nervous system (CNS). CA1 neurons from both wild-type (WT) and NHE1 mutant mice were studied by continuous monitoring of pH(i), using the fluorescent indicator carboxy-seminaphthorhodafluor-1 (SNARF-1) and confocal microscopy. In the nominal absence of CO(2)/HCO(3)(-), steady-state pH(i) was higher in WT neurons than in mutant neurons. Using the NH(4)Cl prepulse technique, we also show that H(+) flux in WT neurons was much greater than in mutant neurons. The recovery from acid load was blocked in WT neurons, but not in mutant neurons, by removal of Na(+) from the extracellular solution or by using 100 microM 3-(methylsulfonyl-4-piperidino-benzoyl)-guanidine methanesulfonate (HOE 694) in HEPES buffer. Surprisingly, in the presence of CO(2)/HCO(3)(-), the difference in H(+) flux between WT and mutant mice was even more exaggerated, with a difference of more than 250 microM/s between them at pH 6.6. H(+) flux in CO(2)/HCO(3)(-) was responsive to diisothiocyanato-stilbene-2, 2'-disulfonate (DIDS) in the WT but not in the mutant. We conclude that (a) the absence of NHE1 in the mutant neurons tended to cause lower steady-state pH(i) and, perhaps more importantly, markedly reduced the rate of recovery from an acid load; and (b) this difference in the rate of recovery between mutant and WT neurons was surprisingly larger in the presence, rather than in the absence, of HCO(3)(-), indicating that the presence of NHE1 is essential for the regulation and/or functional expression of both HCO(3)(-)-dependent and -independent transporters in neurons. (+info)
The vasodilator action of nebivolol in forearm vasculature of subjects with essential hypertension.
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AIMS: Brachial artery administration of nebivolol increases forearm blood flow in normotensive subjects through activation of the L-arginine/NO pathway. The aim of the present study was to investigate the effect of brachial artery administration of nebivolol in subjects with essential hypertension. METHODS: We studied eight patients with uncomplicated essential hypertension and serum cholesterol less than 6.9 mmol l-1. Antihypertensive medication was discontinued 2 weeks before the study in previously treated patients. Following cannulation of the left brachial artery, saline was infused to establish baseline blood flow, followed by increasing doses of nebivolol (88.5, 177 and 354 microg min-1, each dose for 6 min), followed by saline for 12 min, followed by a 30 min infusion of L-NMMA (2 mg min-1 ). During the final 18 min of the L-NMMA infusion, nebivolol was coinfused using the same doses as before. Forearm blood flow was measured in both arms using venous occlusion plethysmography. RESULTS: Blood flow in the noninfused arm did not change significantly throughout the study. In the infused arm blood flow increased significantly in a dose-related manner during the first series of nebivolol infusions from 2.76+/-0.39 ml min-1-1 100 ml forearm-1 during the baseline period to 4.40+/-0.60 ml min-1-1 100 ml forearm-1 (mean+/-s.e. mean, n=8, P=0.0003 by anova ). L-NMMA antagonized the vasodilator effect of nebivolol: baseline blood flow in the infused arm was 2.41+/-0.53 ml min-1 100 ml forearm-1 and 2.94+/-0.42 ml min-1 100 ml forearm-1 during coinfusion of the top dose of nebivolol with L-NMMA (P=0.0006 for an effect of L-NMMA on nebivolol response). There were no serious adverse events. CONCLUSIONS: Nebivolol causes vasodilation in the forearm vascular bed in subjects with essential hypertension. Since this response is antagonized by L-NMMA, the vasodilatation is probably caused by activation of the L-arg/NO pathway. (+info)
Mode of action of anhydrofulvic acid against Candida utilis ATCC 42402 under acidic condition.
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The mode of action of anhydrofulvic acid against Candida utilis ATCC 42402 was investigated under acidic conditions. Anhydrofulvic acid inhibited the incorporation of radioactive precursors into DNA, RNA, protein and lipid fractions. Although it did not induce leakage of intracellular materials from the treated cells, it had inhibitory effects on both endogenous and exogenous cellular respiration. Moreover, it inhibited mitochondrial respiration of Candida utilis ATCC 42402 using both succinate and cytochrome c as respiratory substrates, but not using NADH. Unexpectedly, the inhibition against isolated mitochondria was observed at pH 7.0. These results suggested that the action site against the respiratory inhibition of anhydrofulvic acid might be involved in succinate dehydrogenase, complex II in the mitochondrial electron transport chain of the yeast cells. Judging from the inhibitory effect of anhydrofulvic acid on mitochondria detected at pH 7.0, it was postulated that the antifungal activity at a low pH level might depend on the elevation of drug permeability to the cell membrane under acidic conditions. (+info)
Effect of combined treatment with the pure antiestrogen EM-800 and radiotherapy on the growth of human ZR-75-1 breast cancer xenografts in nude mice.
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Human breast tumors are usually composed of heterogeneous cell populations that exhibit different sensitivities to therapeutic agents. We therefore investigated the effect of treatment with various regimens of the novel pure antiestrogen EM-800, alone or in combination with external beam radiation therapy, on the growth of human ZR-75-1 xenografts in athymic mice. The animals received a maximal dose of EM-800 (300 microg, p.o.) and/or radiotherapy at the dose of 10 Gy. 2.5 Gy fractions were administered over a 9-day period in four sessions of 13.7 min each (250-kilovolt Siemens with 2-mm aluminum filtration at 90 cm from the source origin). EM-800 was administered p.o. once daily, whereas radiotherapy was repeated every 35 days. Tumor size was expressed as a percentage of the initial tumor size, which was assigned a value of 100%. Average tumor size increased by 514% in ovariectomized mice supplemented with estrone alone for 259 days compared with the pretreatment value. Treatment with radiotherapy or EM-800 alone resulted in 11 and 73% decreases in mean tumor size, respectively, whereas combined treatment given simultaneously at the beginning caused a dramatic 98% decrease in tumor size. The start of radiotherapy on day 35 in EM-800-treated mice, or conversely, the start of EM-800 in irradiated mice at the 35-day time interval, resulted in somewhat lower, 88% and 95%, decreases in tumor size, respectively. In animals receiving EM-800 alone, 40% of tumors disappeared, thus indicating a cytotoxic effect caused by the estrogen blockade achieved with the pure antiestrogen. Eighty-six % of the original tumors disappeared under continuous combined treatment. Most importantly, no tumor reappeared under estrogenic stimulation after stopping treatment, thus indicating cure of 86% of the tumors in the group of animals who received the combination therapy. The present data indicate that combined treatment with EM-800 and radiotherapy yields a faster response, a greater decrease in tumor size, and a higher percentage of complete responses or tumor disappearance (cure) than either treatment used alone. The present data also suggest that maximal benefits are achieved when the pure antiestrogen is administered continuously, starting at the same time as radiation therapy and continued without interruption as adjuvant therapy. The present data also clearly show that efficient blockade of estrogens with a potent and pure antiestrogen is not only cytostatic but is cytotoxic and can lead to the disappearance of an important proportion of tumors or cure. (+info)
Antagonistic effects of protein kinase C alpha and delta on both transformation and phospholipase D activity mediated by the epidermal growth factor receptor.
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Downregulation of protein kinase C delta (PKC delta) by treatment with the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) transforms cells that overexpress the non-receptor class tyrosine kinase c-Src (Z. Lu et al., Mol. Cell. Biol. 17:3418-3428, 1997). We extended these studies to cells overexpressing a receptor class tyrosine kinase, the epidermal growth factor (EGF) receptor (EGFR cells); like c-Src, the EGF receptor is overexpressed in several human tumors. In contrast with expectations, downregulation of PKC isoforms with TPA did not transform the EGFR cells; however, treatment with EGF did transform these cells. Since TPA downregulates all phorbol ester-responsive PKC isoforms, we examined the effects of PKC delta- and PKC alpha-specific inhibitors and the expression of dominant negative mutants for both PKC delta and alpha. Consistent with a tumor-suppressing function for PKC delta, the PKC delta-specific inhibitor rottlerin and a dominant negative PKC delta mutant transformed the EGFR cells in the absence of EGF. In contrast, the PKC alpha-specific inhibitor Go6976 and expression of a dominant negative PKC alpha mutant blocked the transformed phenotype induced by both EGF and PKC delta inhibition. Interestingly, both rottlerin and EGF induced substantial increases in phospholipase D (PLD) activity, which is commonly elevated in response to mitogenic stimuli. The elevation of PLD activity in response to inhibiting PKC delta, like transformation, was dependent upon PKC alpha and restricted to the EGFR cells. These data demonstrate that PKC isoforms alpha and delta have antagonistic effects on both transformation and PLD activity and further support a tumor suppressor role for PKC delta that may be mediated by suppression of tyrosine kinase-dependent increases in PLD activity. (+info)
Changes in uterine ornithine decarboxylase activity and steroid receptor levels during decidualization in the rat induced by CDRI-85/287.
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CDRI-85/287 is an anti-estrogen and interferes with decidualization in the rat uterus. In this study, uterine estrogen receptor (ER) and progesterone receptor (PR) levels were determined during the inhibition of decidualization. The effect of 85/287 on uterine ornithine decarboxylate (ODC) activity (a marker enzyme for decidualization) was also studied, using immature ovariectomized rats divided into four different groups: control, 2.5mg/kg 85/287 only; 1 microg estradiol only; and 85/287 + estradiol. Pseudopregnant rats were administered 85/287 (2.5mg/kg p.o.) on day 3 post-coitum. Deciduoma was induced in one of the uterine horns on day 4 and animals were autopsied 18h post-traumatization. Both ERs and PRs showed an increase in traumatized horns compared with non-traumatized. In the 85/287-treated uterus, there was a reduction in cytosolic ERs in both traumatized horns. However, nuclear ER and PR levels increased in both horns under the influence of 85/287. Similarly, in a tamoxifen (0.03mg/kg)-treated group a decline was noticed in cytosolic ER with a mild increase in nuclear PR. Total ER content, expressed per 100 microg DNA, showed a decline in 85/287- or tamoxifen-treated rats. However, no significant alterations were observed in total PR levels in non-traumatized horns. In an immature rat model, 85/287 caused a significant (>50%) reduction in estradiol-induced ODC activity. These findings suggest that the decidualization inhibitory activity of 85/287 may be attributed to inhibition of certain timed biochemical events and genomic/non-genomic actions of estrogens in the rat uterus. (+info)
Activation of leukotriene synthesis in human neutrophils by exogenous arachidonic acid: inhibition by adenosine A(2a) receptor agonists and crucial role of autocrine activation by leukotriene B(4).
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We report here that the apparent inability of isolated human polymorphonuclear leukocytes (PMNs) to efficiently transform arachidonic acid (AA) is the consequence of A(2a) receptor engagement by endogenous adenosine accumulating in incubation media. Indeed, when adenosine is eliminated from PMN suspensions by the addition of adenosine deaminase, or when cells are incubated with adenosine A(2a) receptor antagonists, important quantities (40-80 pmol/10(6) cells) of 5-lipoxygenase products are synthesized by PMN incubated with 1 to 5 microM exogenous AA. The selective A(2a) receptor agonist CGS21680 was a very potent inhibitor of the AA-induced leukotriene (LT) synthesis, showing an IC(50) of approximately 1 nM. The mechanism of AA-induced stimulation of LT synthesis observed in the absence of extracellular adenosine was investigated. In adenosine deaminase-treated PMN, exogenous AA induced Ca(2+) mobilization and the translocation of 5-lipoxygenase to nuclear structures. A time lag of 20 to 60 s (variable between PMN preparations) was observed consistently between the addition of AA and the elevation of intracellular Ca(2+) concentration (and LT synthesis), indicating that AA itself did not trigger the Ca(2+) mobilization in PMN. This AA-induced Ca(2+) mobilization, as well as the corresponding 5-lipoxygenase translocation and stimulation of LT synthesis, was blocked efficiently by the LT synthesis inhibitor MK0591, the LTB(4) receptor antagonists CP105696 and LY223982, and the LTA(4) hydrolase inhibitor SC57461A. These data demonstrate that AA is a highly potent and effective activator of LT synthesis and acts through a mechanism that requires an autocrine stimulatory loop by LTB(4). (+info)
Effects of the antiestrogen EM-800 (SCH 57050) and cyclophosphamide alone and in combination on growth of human ZR-75-1 breast cancer xenografts in nude mice.
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Human breast cancer proliferates as heterogeneous cell populations that exhibit different sensitivities to therapeutic agents. A logical approach to control these different cancer cell populations is the use of combined treatment with agents that block cell proliferation or induce apoptosis via different mechanisms. We therefore investigated the effect of treatment with the novel pure antiestrogen EM-800, alone or in combination with chemotherapy, on the growth of ZR-75-1 human breast tumors in nude mice, a well-recognized model of human breast cancer. Mice bearing estrone-releasing silastic implants as estrogenic stimulus received EM-800 or cyclophosphamide alone or in combination for 227 days. Cyclophosphamide (256 mg/kg/2 weeks) was administered by i.p. injection in 64 mg/kg fractions over 4 consecutive days with repetition of the cycle every 14 days. EM-800 was administered p.o. once daily at the maximally effective dose of 300 microg/mouse. After 227 days of treatment, average tumor size in mice receiving estrone alone was 192% higher than pretreatment. The average tumor size of mice treated with chemotherapy was reduced by 47%, whereas on the other hand, EM-800 caused a 81% decrease of the value of the same parameter. The combined treatment (EM-800 + cyclophosphamide), on the other hand, resulted in a 95% decrease in tumor size compared with control estrogen alone. In fact, EM-800 alone decreased tumor size to 55% of the value at the start of treatment, whereas the addition of cyclophosphamide to the antiestrogen further decreased tumor size to as low as 15% of the pretreatment value. The combination of EM-800 and cyclophosphamide resulted in 95% of complete or partial responses compared with 61 and 27% with EM-800 and cyclophosphamide alone, respectively. In fact, in the combination therapy group, only one tumor remained stable, while 17 regressed >50% and four disappeared. It is noteworthy that no tumor progressed with EM-800 alone or in combination with cyclophosphamide. The present data show, for the first time, that the addition of cyclophosphamide to a pure antiestrogen used at a maximal dose causes a more potent inhibition of human breast tumor growth, thus suggesting that combined treatment using a maximal dose of a pure antiestrogen and a chemotherapeutic agent(s), two classes of compounds having different mechanisms of action, could further improve breast cancer therapy above the results achieved with a potent and pure antiestrogen alone in estrogen-sensitive breast cancer. (+info)