Biomedical subjects

N Weissmann

Publications and source records attributed to N Weissmann.

33 records · Page 2Linked to original sources

PubMed2000

Nitric oxide (NO)-dependent but not NO-independent guanylate cyclase activation attenuates hypoxic vasoconstriction in rabbit lungs.

Hypoxic pulmonary vasoconstriction (HPV) is essential for matching lung perfusion with ventilation, thus optimizing pulmonary gas exchange. Preceding studies provided evidence for a role of both nitric oxide (NO) and superoxide/ H(2)O(2) formation in this vasoregulatory mechanism. Both agents might be operative via stimulation of guanylate cyclase with formation of the vasodilatory cyclic guanosine monophosphate (cGMP), the loss of which under conditions of hypoxia contributes to HPV. This view is challenged by the recent suggestion of increased rather than decreased superoxide/H(2)O(2) formation in hypoxia. We addressed the role of NO-dependent versus NO-independent guanylate cyclase activity in hypoxic and pharmacologically evoked vasoconstriction in perfused rabbit lungs. Two inhibitors of soluble guanylate cyclase, LY83583 (2 to 16 microM) and methylene blue (20 to 60 microM), increased baseline pulmonary artery pressure under normoxic conditions and markedly amplified the vasoconstrictor response to both hypoxia and the stable thromboxane analogue U46619. Under conditions of preblocked lung NO synthesis (N(G)-mono-methyl-L-arginine), however, additional guanylate cyclase inhibition further enhanced the vasoconstrictor response to U46619 but did not influence the strength of HPV. The selective phosphodiesterase V inhibitor Zaprinast (1 to 10 microM), used for prolongation of the cGMP half-life, reduced the hypoxia-induced pressor response to a larger extent than the pressor response to U46619. This difference was lost under conditions of preblocked NO synthesis. Equilibration of the lung perfusate with molecular NO suppressed the HPV more potently than the U46619-induced vasoconstrictor response. We conclude that NO-dependent guanylate cyclase activity has an important role in attenuating the vasoconstrictor response to alveolar hypoxia in rabbit lungs. In contrast, no evidence was obtained for a role of NO-independent cGMP formation in HPV. In this feature, HPV differs from that elicited by the thromboxane analogue U46619.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed2000

Subthreshold doses of specific phosphodiesterase type 3 and 4 inhibitors enhance the pulmonary vasodilatory response to nebulized prostacyclin with improvement in gas exchange.

Aerosolized prostacyclin (PGI(2)) has been suggested for selective pulmonary vasodilation, but its effect rapidly levels off after termination of nebulization. Stabilization of the second-messenger cAMP by phosphodiesterase (PDE) inhibition may offer a new strategy for amplification of the vasodilative response to nebulized PGI(2). In perfused rabbit lungs, continuous infusion of the thromboxane mimetic U46619 was used to establish stable pulmonary hypertension [increase in pulmonary arterial pressure (pPA) from approximately 7 to approximately 32 mm Hg], which is accompanied by progressive edema formation and severe disturbances in gas exchange with a predominance of shunt flow (increase from <2 to approximately 58%, as assessed by the multiple inert gas elimination technique). In the absence of PGI(2), dose-effect curves for intravascular and aerosol administration of the specific PDE3 inhibitor motapizone, the PDE4 inhibitor rolipram, and the dual-selective PDE3/4 inhibitor tolafentrine on pulmonary hemodynamics were established (potency rank order: rolipram > tolafentrine approximately motapizone; highest efficacy on coapplication of rolipram and motapizone). Ten-minute aerosolization of PGI(2) was chosen to effect a moderate pPA decrease (approximately 4 mm Hg; rapidly returning to prenebulization values within 10-15 min) with only a slight reduction in shunt flow (approximately 49%). Prior application of subthreshold doses of i.v. or inhaled PDE3 or PDE4 inhibitors, which per se did not affect pulmonary hemodynamics, caused prolongation of the post-PGI(2) decrease in pPA. The most effective approach, rolipram plus motapizone, amplified the maximum pPA decrease in response to PGI(2) to approximately 9 to 10 mm Hg, prolonged the post-PGI(2) vasorelaxation to >60 min, reduced the extent of lung edema formation by 50%, and decreased the shunt flow to approximately 19% (i.v. rolipram/motapizone) and 28% (aerosolized rolipram/motapizone). We conclude that lung PDE3/4 inhibition, achieved by intravascular or transbronchial administration of subthreshold doses of specific PDE inhibitors, synergistically amplifies the pulmonary vasodilatory response to inhaled PGI(2), concomitant with an improvement in ventilation-perfusion matching and a reduction in lung edema formation. The combination of nebulized PGI(2) and PDE3/4 inhibition may thus offer a new concept for selective pulmonary vasodilation, with maintenance of gas exchange in respiratory failure and pulmonary hypertension.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1999

Evidence for a role of protein kinase C in hypoxic pulmonary vasoconstriction.

Hypoxic pulmonary vasoconstriction (HPV) matches lung perfusion to ventilation, thus optimizing gas exchange. NADPH oxidase-related superoxide anion generation has been suggested as part of the signaling response to hypoxia. Because protein kinase (PK) C activation can occur during hypoxia and PKC activation is known to be critical for NADPH oxidase stimulation in different cell types, we probed the role of PKC in hypoxic vasoconstriction in intact rabbit lungs. Control vasoconstrictor responses were elicited by angiotensin II (ANG II) and the stable thromboxane analog U-46619. Portions of the experiments were performed while NO synthesis and prostanoid generation were blocked with NG-monomethyl-L-arginine and acetylsalicylic acid to avoid confounding effects due to interference with these vasoactive mediators. The PKC inhibitor H-7 (10-50 microM) caused dose-dependent inhibition of HPV, but this agent lacked specificity because ANG II- and U-46619-induced vasoconstrictions were correspondingly suppressed. In contrast, low concentrations of the specific PKC inhibitor bisindolylmaleimide I (BIM; 1-15 microM) strongly inhibited the hypoxic vasoconstriction without any interference with the responses to the pharmacological agents. Superimposable dose-inhibition curves were also obtained for BIM when lung NO synthesis and prostanoid generation were blocked throughout the experiments. Under either condition, BIM did not affect normoxic vascular tone. The PKC activator farnesylthiotriazole (FTT), ascertained to stimulate rabbit NADPH oxidase by provocation of alveolar macrophage superoxide anion generation in vitro, caused rapid-onset, transient pressor responses in normoxic lungs. After FTT, the hypoxic vasoconstrictor response was totally suppressed, in contrast to the largely maintained pressor responses to ANG II and U-46619. The lungs became refractory even to delayed hypoxic challenges after FTT application. In conclusion, these data support the concept that activation of PKC is involved in the transduction pathway forwarding pulmonary vasoconstriction in response to alveolar hypoxia.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1999

Low-dose systemic phosphodiesterase inhibitors amplify the pulmonary vasodilatory response to inhaled prostacyclin in experimental pulmonary hypertension.

Inhalation of aerosolized prostaglandin I(2) (PGI(2)) causes selective pulmonary vasodilation, but the effect rapidly levels off after termination of nebulization. In experimental pulmonary hypertension in intact rabbits, provoked by continuous infusion of the stable thromboxane mimetic U46619, the impact of intravenous phosphodiesterase (PDE) inhibitors on pulmonary and systemic hemodynamics was investigated in the absence and the presence of aerosolized PGI(2). We employed the monoselective inhibitors motapizone (PDE 3), rolipram (PDE 4), and zaprinast (PDE 5), as well as the dual-selective blockers zardaverine and tolafentrine (both PDE 3/4). All PDE inhibitors dose-dependently reduced the pulmonary artery pressure (Ppa), with doses for an approximately 20% decrease in pulmonary vascular resistance being 5 microgram/kg for motapizone, 25 microgram/kg for rolipram, 500 microgram/kg for zardaverine, 1 mg/kg for zaprinast, and 1 mg/kg for tolafentrine. Additive efficacy was noted when combining the monoselective 3 plus 4, 3 plus 5, and 4 plus 5 inhibitors. In parallel with the pulmonary vasorelaxant effect, all PDE inhibitors caused a decrease in systemic arterial pressure and an increase in cardiac output. Nebulized PGI(2) (56 ng/kg. min) reduced the U46619-evoked increase in Ppa by approximately 30%. This vasorelaxant effect was fully lost within 10 min after termination of PGI(2) nebulization. Coapplication of subthreshold doses of intravenous PDE inhibitors, which per se did not affect pulmonary and systemic hemodynamics, resulted in a marked prolongation of the post-PGI(2) decrease in Ppa for all blockers (motapizone at 2.2 microgram/kg, rolipram at 5.5 microgram/kg, zaprinast at 100 microgram/kg). The most effective agents, zardaverine (50 microgram/kg) and tolafentrine (100 microgram/kg), augmented the maximum Ppa drop during nebulization by approximately 30-50% and prolonged the post-PGI(2) pulmonary vasodilation to > 30 min, without affecting systemic arterial pressure and arterial oxygenation. We conclude that subthreshold systemic doses of monoselective PDE 3, 4, and 5 inhibitors and in particular dual-selective PDE 3/4 inhibitors cause significant amplification of the pulmonary vasodilatory response to inhaled PGI(2), while limiting the hypotensive effect to the pulmonary circulation. Combining nebulized PGI(2) with low-dose systemic PDE inhibitors may thus offer a therapeutic strategy to achieve selective pulmonary vasodilation in acute and chronic pulmonary hypertension.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1998

Effects of arachidonic acid metabolism on hypoxic vasoconstriction in rabbit lungs.

Hypoxic pulmonary vasoconstriction is an essential mechanism that matches lung perfusion to ventilation, thus optimising pulmonary gas exchange. Despite its pathophysiological relevance, the mechanism of hypoxic pulmonary vasoconstriction still remains enigmatic. We investigated whether arachidonic acid metabolism is involved in the regulation of hypoxic pulmonary vasoconstriction in isolated, buffer-perfused rabbit lungs. Seven inhibitors were employed to determine the contribution of different vasoactive lipoxy- and cyclooxygenase mediators as well as cytochrome P450 products on the magnitude of hypoxic pulmonary vasoconstriction. Hypoxic pulmonary vasoconstriction was not affected by (i) the cyclooxygenase inhibitor acetylsalicylic acid, (ii) the thromboxane A2 receptor antagonist BM13.505, (iii) the 5'-lipoxygenase inhibitor MK886, and (iv) the lipoxygenase and cyclooxygenase inhibitor BW755c. The hypoxia-elicited pressor response was prominently inhibited by (i) nordihydroguaiaretic acid (50-150 microM), an inhibitor of lipoxygenase and cyclooxygenase and (ii) methoxsalen (100 microM) and 1-aminobenzotriazole (1-10 mM), two inhibitors of cytochrome P450-derived metabolites. However, no specificity for the regulation of hypoxic pulmonary vasoconstriction was found, as corresponding inhibitory potency of these agents was noted when vasoconstriction was achieved by the stable thromboxane analogue U46619 under conditions of normoxia. We conclude that there is no evidence for a specific involvement of different pathways of arachidonic acid metabolism in the mechanism of hypoxic pulmonary vasoconstriction in rabbits.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗

PubMed1998

Simultaneous analysis of 4- and 5-series lipoxygenase and cytochrome P450 products from different biological sources by reversed-phase high-performance liquid chromatographic technique.

Quantification of lipoxygenase and cytochrome P450 products of both arachidonic acid (AA) and eicosapentaenoic acid (EPA) is of broad interest due to the multiple biological activities of these compounds. We developed a method combining (i) solid-phase extraction, (ii) isocratic reversed-phase high-performance liquid chromatographic separation, and (iii) online photodiode array detection with spectrum analysis for identification and measurement of all main 4- and 5-series eicosanoids (leukotrienes, hydroxyeicosatetraenoic acids/hydroxyeicosapentaenoic acids, epoxyeicosatrienoic acids) within one run. With these procedures, standard mixtures of AA- and EPA-derived lipid mediators were recovered from different biological liquids, like lung perfusate, human bronchoalveolar lavage fluid, and cell supernatant with linear characteristics for each compound. Recoveries of the different lipid mediators exceeded 80% showing excellent reproducibility. Application of the method to isolated, perfused, and ventilated human lungs challenged with the calcium ionophore A23187 and to human neutrophils stimulated in the presence of arachidonic acid and eicosapentaenoic acid with N-formyl-methionyl-leucyl-phenylalanine demonstrated the generation of a large array of lipoxygenase and cytochrome P450 products. Thus, convenient quantification of 4- and 5-series eicosanoids in fluids of biological interest is achieved by a technique comprising solid-phase extraction, isocratic reversed-phase high-performance liquid chromatography, and photodiode array-based online spectrum analysis of eluting compounds.

Arachidonate 5-Lipoxygenase↗

PubMed1998

Nitro blue tetrazolium inhibits but does not mimic hypoxic vasoconstriction in isolated rabbit lungs.

It has been suggested that hypoxic pulmonary vasoconstriction (HPV) may mainly proceed via loss of normoxic vasodilation, forwarded by tonic O2-dependent formation of nitric oxide and superoxide (23). Both agents may stimulate guanylate cyclase, the latter via conversion to hydrogen peroxide and formation of compound I with catalase. We probed this hypothesis in perfused rabbit lungs, employing the superoxide scavengers superoxide dismutase (SOD), 4,5-dihydroxy-1,3-benzene disulfonic acid (Tiron), and nitro blue tetrazolium (NBT) and the catalase inhibitor aminotriazole (AT). NBT turned out to be a potent dose-dependent inhibitor of HPV in a concentration range of 200 nM to 1 microM, and superimposable dose-inhibition curves were obtained when lung synthesis of nitric oxide and vasodilatory prostanoids was preblocked by NG-monomethyl-L-arginine (L-NMMA) and acetylsalicylic acid (ASA). The NBT effect was specific because no inhibition in the vasoconstrictor responses to the stable thromboxane analog U-46619 and angiotensin II was observed. In contrast, SOD and Tiron were ineffective. AT exerted nonspecific inhibition of the hypoxia- and chemical vasoconstrictor-induced pressor responses. When applied under normoxic conditions, however, NBT alone or coapplied with L-NMMA or ASA, both for blockage of parallel vasodilatory pathways, did not mimic the hypoxia-induced vasoconstrictor response. In conclusion, the present study supports an important role for superoxide in the basic mechanism of HPV, but it questions the concept that loss of tonic vasorelaxation via this pathway is the underlying event in rabbit lungs. The mechanisms relating O2 tension-dependent superoxide and hydrogen peroxide generation to the vasoconstrictor event occurring in HPV remain to be further elucidated.

1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium ↗

PubMed1995

Hydrogen peroxide-induced increase in lung endothelial and epithelial permeability--effect of adenylate cyclase stimulation and phosphodiesterase inhibition.

Neutrophil-derived hydrogen peroxide (H2O2) is believed to play an important role in inflammatory lung injury. We investigated the influence of pharmacological agents that increase intracellular c-AMP levels on endothelial and epithelial leakage in response to intravascular H2O2 challenge in buffer-perfused rabbit lungs. Endothelial permeability was assessed by determination of the capillary filtration coefficient (Kfc) and lung weight gain. Measurement of the clearance rate of inhaled aerosolized technetium-99m-labeled diethylenetriamine pentaacetic acid ([99mTc]DTPA) from the lungs into the perfusion fluid was used as an index of alveolar epithelial permeability. Experiments were performed in the presence of acetylsalicylic acid to suppress H2O2-induced lung prostanoid generation and concomitant vasoconstriction. Under these conditions, H2O2 admixture to the perfusate (250 microM) caused a greater than eight-fold increase in Kfc values, resulting in > 30 g lung weight gain within 30 min in the absence of any significant vasopressor response. Pretreatment with the adenylate cyclase activators prostaglandin E1 (0.1 microM) and forskolin (0.1 microM), the dual phosphodiesterase type III/IV inhibitor zardaverine (10 microM) as well as combinations of these drugs all caused a nearly complete suppression of this early Kfc increase; and severe edema formation (> 30 g) was retarded to approximately 50-55 min. In addition to the microvascular leakage response, H2O2 caused a four- to five-fold increase in the [99mTc]DTPA clearance rate, starting within 15 min and culminating after approximately 35 min. Adenylate cyclase activation reduced this epithelial leakage response by approximately 30%, whereas zardaverine exerted no significant effect. We conclude that both microvascular endothelial and alveolar epithelial barrier function are severely compromised by intravascular H2O2 challenge in intact lungs. Pharmacological approaches to increase c-AMP levels, including both adenylate cyclase activation and phosphodiesterase inhibition, partially block the endothelial response and, to a lesser extent, the epithelial response.

Adenylyl Cyclases↗

PubMed1995

Hypoxic vasoconstriction in buffer-perfused rabbit lungs.

Isolated rabbit lungs were buffer-perfused under constant flow-conditions with separate control of alveolar (PAO2) and mixed venous (PvO2) O2 tension. Alveolar hypoxia caused an increase in pulmonary artery pressure (PAP) with sigmoidal dose-dependency. Erythrocytes increased the strength of the hypoxic pulmonary vasoconstriction (HPV). The contractile and vasorelaxant responses to the onset and release of alveolar hypoxia, respectively, occurred within seconds. Kinetics of the PAP increase, but not the magnitude of response, were related to the velocity of PAO2 decline. In contrast, changes in PvO2, both in the absence and presence of erythrocytes, did neither provoke any pressor response nor amplify the response to concomitant alveolar hypoxia. Repeatedly performed HPV manoeuvres revealed excellent reproducibility, and long-term alveolar hypoxia (90 min) provoked a biphasic pressor response. We conclude that the isolated rabbit lung is a feasible model for the characterization of hypoxic vasoconstriction, with specific features hitherto not described for perfused lungs of other species.

Animals↗

PubMed1995

Effects of NADPH oxidase inhibitors on hypoxic vasoconstriction in buffer-perfused rabbit lungs.

The involvement of NADPH oxidase in hypoxic pulmonary vasoconstriction (HPV) was investigated in buffer-perfused rabbit lungs, employing the inhibitors diphenyleneiodonium (DPI) and apocynin. Responses to the vasoconstrictors U-46619 and angiotensin II (ANG II) were used to test specificity. Lung nitric oxide (NO) generation was assessed by on-line monitoring of NO exhalation (chemiluminescence), and the efficacy of DPI and apocynin on the NADPH oxidase-dependent O2- generation was quantified in alveolar macrophages by fluorescent-activated cell sorter technique. In a concentration range between 1 and 5 mM, apocynin inhibited macrophage respiratory burst and HPV but similarly suppressed U-46619-induced vasoconstrictor responses. DPI inhibited macrophage O2- generation in concentrations > or = 0.5 microM. At doses between 0.5 and 1.5 microM, DPI blocked lung NO generation, thereby increasing HPV. At higher doses (4 microM), in contrast, DPI fully blocked the hypoxia-induced pressor responses, whereas the vasoconstrictor responses to U-46619 and [Asn1, Val5] ANG II were not diminished. In the presence of NG-monomethyl-L-arginine, used to block lung NO generation throughout, DPI exhibited only the monophasic selective inhibition of HPV. We conclude that apocynin lacks specificity for HPV, but DPI, in addition to inhibiting lung NO generation, causes selective blockade of the hypoxia-induced vasoconstriction. This finding supports the hypothesis that an NADPH oxidase is involved in hypoxia sensing or specific signal transduction events underlying HPV.

Acetophenones↗

PubMed1995

On-line measurement of nitric oxide generation in buffer-perfused rabbit lungs.

In buffer-perfused rabbit lungs, the mixed expired gas was continuously analyzed for nitric oxide (NO) by chemiluminescence detection, and recovery data in dependency of the alveolar O2 tension were established. A small aliquot of the lung effluent was continuously forwarded to a reaction vessel in which the NO decomposition products nitrite, peroxynitrite, and nitrate [summarized as NOx; acidic vanadium (III) chloride reagent] or nitrite (acidic sodium iodide reagent) were quantitatively reduced back to NO, which was then transferred to a second chemiluminescence detector. Under baseline conditions, the perfused lungs continuously released 2.2 +/- 0.21 nmol/min of NO (n = 10) into the gas space. NO was permanently liberated into the intravascular compartment at 7.0 +/- 0.3 nmol/min (n = 4). According to a very low buffer-gas partition coefficient of NO (estimated to be 0.0292 +/- 0.005 in separate equilibration experiments), NO aerated into the prelung perfusate largely escaped into the alveolar space within one lung passage, whereas only low percentages of inhaled NO were detected as NOx in the buffer medium. Immediate increase of lung NO generation in response to A-23187 challenge and inhibition by NG-monomethyl-L-arginine were demonstrated. In conclusion, in buffer-perfused lungs, total NO generation may be monitored by continuous analysis of NO exhalation and perfusate NOx accumulation.

Animals↗

PubMed1995

Nitric oxide generation and hypoxic vasoconstriction in buffer-perfused rabbit lungs.

Nitric oxide generation and hypoxic vasoconstriction in buffer-perfused rabbit lungs. J. Appl. Physiol. 78(4): 1509-1515, 1995.--We investigated the role of nitric oxide (NO) generation in hypoxic pulmonary vasoconstriction in buffer-perfused rabbit lungs. Exhaled NO was detected by chemiluminescence, and intravascular NO release was quantified as perfusate accumulation of nitrite, peroxynitrite, and nitrate (NOx). Under baseline conditions, exhaled NO was 45.3 +/- 4.1 parts per billion (1.8 +/- 0.2 nmol/min), and lung NOx release into the perfusate was 4.1 +/- 0.4 nmol/min. Alveolar hypoxia (alveolar PO2 of approximately 23 Torr) induced readily reproducible pressor responses preceded by a sharp drop in exhaled NO concentration. In contrast, perfusate NOx accumulation was not affected. Vasoconstrictor responses to U-46619 and angiotensin II were not accompanied by a decrease in NO exhalation. NG-monomethyl-L-arginine dose-dependently suppressed NO exhalation and amplified pressor responses to hypoxia > U-46619 and angiotensin II. In conclusion, portions of baseline NO generation originating from sites with ready access to the gaseous space sharply decrease in response to alveolar hypoxia, whereas the intravascular release of NO is unchanged. Such differential regulation of lung NO synthesis in response to hypoxia may suggest a complex role in the regulation or modulation of hypoxic pulmonary vasoconstriction.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1987

Deoxyspergualin, a potent antitumor agent: further studies on the cytobiological mode of action.

Under otherwise identical conditions, deoxyspergualin preferentially inhibits the growth of the T-cell leukemia line L5178y; an effective dose for a 50% inhibition (ED50) of 0.0007 microM was determined. A much weaker cytostatic activity was found for murine lymphocytes (ED50: approximately 25 microM) and for CV-1 monkey kidney cells (ED50: 16.3 microM). Deoxyspergualin causes biphasic and differential effects on DNA metabolism of murine T and B lymphocytes. At lower concentrations (0.3 approximately 5 microM) the [3H]TdR incorporation into nonactivated or lipopolysaccharide-activated lymphocytes is significantly stimulated by the compounds; this effect was not observed with lymphocyte cultures stimulated with concanavalin A. This change of TdR incorporation rates was found to parallel with the variations of DNA polymerase alpha activity. Deoxyspergualin causes an additive effect together with bleomycin and a significant synergistic cytostatic effect in combination with avarol and avarone. Moreover, it is reported that deoxyspergualin causes neither a selective inhibitory effect on DNA-, RNA- or protein synthesis nor an alteration of the intracellular distribution pattern of the Ro and La antigens. However, detailed enzymic studies revealed that deoxyspergualin reduces DNA polymerase alpha but not beta activity in lymphocytes at the ED50 concentration of this compound. These results support previous documentations that deoxyspergualin is of potential clinical usefulness (a) in treatment of certain tumors and (b) in organ transplantation.

Animals↗

PubMed1985

Mitogenic potentials of bestatin, amastatin, arphamenines A and B, FK-156 and FK-565 on spleen lymphocytes.

The following aminopeptidase (AP) activities were found to be associated with the surface of mouse spleen cells: Leu-AP (138 pmol/10(5) cells X minute) and AP-B (16 pmol/10(5) cells X minute with Lys-beta-naphthylamide as substrate and 21 pmol/10(5) cells X minute with Arg-beta-naphthylamide substrate); AP-A activity was not detected by the assay system applied. The immunoactive peptide bestatin inhibited the Leu-AP, while AP-B activity decreased in the presence of both arphamenines A and B and bestatin. No effects on these enzymes were caused by amastatin (an AP-A inhibitor), FK-156, FK-565 and Bu-2743E; the latter peptide turned out to be not an inhibitor of cell surface associated microsomal Leu-AP but an inhibitor of cytosolic Leu-AP. The immunoactive peptides bestatin, arphamenines A and B, and amastatin increased [3H]thymidine incorporation into spleen cells containing lymphocytes and macrophages. These mitogenic actions were not observed when macrophages were removed from the cultures or the cells had been stimulated with ConA or LPS. The lactoyl- and heptanoyl peptides FK-156 and FK-565 caused a mitogenic action on lymphocytes independently of the presence of macrophages. The inhibitor of cytosolic Leu-AP did not change the incorporation into lymphocytes.

Adjuvants, Immunologic↗

PubMedDate not supplied

Cytostatic activity of aeroplysinin-1 against lymphoma and epithelioma cells.

(+/-)-Aeroplysinin-1, an optically active 1,2-dihydroarene-1,2-diol, was isolated from the marine sponges Verongia aerophoba (+-isomer) and Ianthella ardis (- -isomer). For the experiments presented we used the +-isomer from Verongia aerophoba. Here we describe the hitherto unknown biological and pharmacological property of this compound to display pronounced anticancer activity against L5178y mouse lymphoma cells (ED50: 0.5 microM). Friend erythroleukemia cells (ED50: 0.7 microM), human mamma carcinoma cells (ED50: 0.3 microM) and human colon carcinoma cells (ED50: 3.0 microM) in vitro. Furthermore, aeroplysinin caused a preferential inhibition of [3H]thymidine (dThd) incorporation rates in L5178y mouse lymphoma cells if compared with murine spleen lymphocytes in vitro. At concentrations between 1.1 and 28.5 microM, the [3H]dThd incorporation rates in L5178y cells were suppressed to 28%-0% but only to 78%-18% in murine spleen lymphocytes. The same differential effect in vitro was found with the following epithelial cells: 14.70 microM of the compound were required to inhibit normal human fibroblasts to 50%, but only 2.9 microM in the assays with human malign keratinocytes or malignant melanoma cells to observe the same inhibitory effect. Moreover, aeroplysinin-1 displayed antileukemic activity in vivo using the L5178y cell/NMRI mouse system; administered at a dose of 50 mg/kg for five consecutive days, the T/C (%) value was determined to be 338. Preliminary toxicology studies revealed an acute LD50 of 202 mg/kg and a subacute LD50 of 150 mg/kg. Aeroplysinin-1 is neither a direct mutagen nor a premutagen in the umu/Salmonella typhimurium test system.

Acetonitriles↗