PubMed Health⌕ Search

Biomedical subjects

C R Gardner

Publications and source records attributed to C R Gardner.

At least 37 records · Page 2Linked to original sources
PubMed1996

Biphasic actions of the benzodiazepine receptor inverse agonist RU34347 in the rat cerebellar slice.

We have characterised the biphasic response of the benzodiazepine receptor inverse agonist RU34347 in the rat cerebellar slice preparation using extracellular electrophysiological recordings from Purkinje cells. RU34347 (10 fM-10 nM) produced an increase in GABA(A)-mediated inhibition at between 10 fM and 10 nM, a response normally associated with benzodiazepine agonists. This response was biphasic, being dose dependent between 10 fM and the peak effect at 10 pM, and inversely related to concentration between 100 pM and 10 nM. Associated with this increase in inhibition was a decrease in firing rate, also showing a biphasic concentration-response relationship. The agonist-like response was composed of two elements, an initial increase occurring after 5 min followed by a slow decline over the next 20 min. This second, declining, phase was more evident at higher concentrations of RU34347. The peak effect seen at 10 pM was fully antagonised by 1 microM flumazenil, a benzodiazepine receptor antagonist. This concentration of flumazenil also antagonised the decrease in firing rate induced by 10 pM RU34347. The response to 10 nM RU34347 was further characterised since the largest second phase decline was demonstrated at this concentration. 10 nM flumazenil fully antagonised the second, declining, phase of the response, but not the magnitude of the initial increase. A partial antagonism of the peak effect was seen with 1 microM flumazenil, and a full antagonism at 10 microM flumazenil. This effect was similar to that observed with Ro15-4513 in a previous study. Therefore, we investigated the binding of RU34347 to diazepam-insensitive benzodiazepine receptors. [3H]Ro15-4513 was displaced by Ro15-4513, flumazenil and Ro19-4603, but not by RU34347. Therefore, although the electrophysiological data correlate well with that previously reported for Ro15-4513, RU34347 does not displace Ro15-4513 binding at the diazepam-insensitive benzodiazepine receptor. Therefore, either both ligands bind to complimentary sites on the same receptor complex, or both induce a similar physiological response through an action on different receptors.

Animals↗
PubMed1996

Reduction of cerebellar GABAA responses by interleukin-1 (IL-1) through an indomethacin insensitive mechanism.

Recently, a role of IL-1 in the central nervous system has been described, principally a fever-inducing effect in the hypothalamus through a prostaglandin second messenger system. IL-1 has also been shown to potentiate gamma-aminobutyric acid (GABAA) responses in embryonic chick neurones. This study describes the investigation of the effect of IL-1 on GABAA responses within the in vitro rat cerebellar slice, a preparation containing intact neuronal circuitry. Stimulation of the area of passage of paralleled fibres produced a pure GABAA inhibition of the spontaneous firing of Purkinje cells. 5 and 10 ng/ml IL-1 produced a reduction in the duration of inhibition 10 min after beginning perfusion of IL-1. This effect reversed within 15 min of washing out the IL-1. 10 ng/ml IL-1 also reduced the effects of exogenously-applied GABA (0.1 mM) with the same time course. In the presence of 1 uM indomethacin, there was no change in the effect of the IL-1. It can therefore be concluded that the reduction in cerebellar GABAA responses by IL-1 is not mediated by the indomethacin-sensitive prostaglandin second messenger system.

Animals↗
PubMed1996

Hypothermia as an indicator of the acute effects of lipopolysaccharides: comparison with serum levels of IL1 beta, IL6 and TNF alpha.

1. Hypothermia was investigated as a parameter indicating the severity of the acute effects of lipopolysaccharides (LPS) in BALB/c mice, and was compared with the induction of serum levels of IL1 beta, TNF alpha and IL6. 2. Hypothermia induced by low doses of LPS (10-50 micrograms/mouse IP LPS E. coli 0111:B4) peaked at 2 hr after LPS and then either plateaued (50 micrograms) or declined. LPS, 100 and 300 mu, induced greater degrees of hypothermia that plateaued or continued to increase with time for 8 hr. Higher doses of LPS induced similar levels of hypothermia until 4 hr but then continued to increase markedly until 8 hr. 3. TNF alpha levels peaked early (1-2 hr) and declined rapidly, IL6 levels peaked at 3 hr and then declined slowly, and IL1 beta levels peaked at 4 hr, declined at lower doses of LPS, plateaued at higher doses and continued to slowly increase at highest doses. 4. The peak levels of the cytokines (IL1 beta up to 4 hr) and hypothermia (4 hr) increased in relation to the dose of LPS and maximum responses were apparently achieved in all cases at 300-1000 micrograms LPS. 5. A similar parallel between hypothermia and induction of cytokines was observed in C57BL6 and OF1 mice, which were good and poor responders to LPS, respectively, and with the more potent Shigella dysenteria LPS in BALB/c mice. 6. In conclusion, hypothermia is a useful parameter for indicating the strength of the acute effects of LPS. Further studies are necessary to determine whether or not the cytokines studied here play a causative role in hypothermia.

Animals↗
PubMed1996

Stimulation of nitric oxide production in rat lung lavage cells by anti-Mac-1beta antibody: effects of ozone inhalation.

Acute inhalation of the pulmonary irritant ozone is associated with an inflammatory response characterized by increased numbers of macrophages in the lung that release elevated quantities of nitric oxide. The accumulation of phagocytes in the lung is dependent on expression of leukocyte adhesion molecules including Mac-1. In the present studies, we determined whether activation of the Mac-1 receptor is involved in regulating nitric oxide production by lung phagocytes, and whether this response is modified following acute ozone inhalation. Cells were isolated from the lung by bronchoalveolar lavage 48 h after exposure of female Sprague-Dawley rats to air or ozone (2 parts per million, for 3 h). Anti-Mac-1beta antibody, but not anti-Mac-1alpha antibody, stimulated nitric oxide production by cells from both air- and ozone-exposed animals. Cells from ozone-exposed rats produced more nitric oxide and expressed greater quantities of inducible nitric oxide synthase mRNA than did cells from air-exposed animals. Production of nitric oxide in response to anti-Mac-1beta was also found to be augmented by cross-linking of the Mac-1beta receptor. Pretreatment of lavage cells with granulocyte/macrophage colony-stimulating factor (GM-CSF), which activates phagocytes, enhanced the expression of Mac-1beta and increased anti-Mac-1beta-induced nitric oxide production by the cells. Lavage cells from ozone-exposed animals were more responsive to GM-CSF than were cells from control animals. Taken together, these data suggest that the Mac-1beta adhesion molecule may contribute to phagocyte activation and mediator release during ozone-induced inflammatory reactions in the lung.

Administration, Inhalation↗
PubMed1996

Inhibition of ozone-induced nitric oxide synthase expression in the lung by endotoxin.

Inhalation of the pulmonary irritant ozone is associated with an accumulation of macrophages in the lung. These cells, along with type II epithelial cells, are activated to release increased quantities of hydrogen peroxide and nitric oxide, two reactive mediators that have been implicated in tissue injury. In the present studies we determined whether pretreatment of rats with bacterially derived endotoxin, which modulates oxidant levels in tissues, could abrogate the effects of ozone on lung injury and nitric oxide production. Acute exposure of rats to ozone (2 parts per million, 3 h) resulted in nitric oxide production in the lung as measured by electron paramagnetic resonance spin trapping. This was correlated with expression of inducible nitric oxide synthase (iNOS) mRNA in the lung as determined by in situ hybridization. Particularly high levels of iNOS were evident in alveolar macrophages and type II cells. Alveolar macrophages isolated from ozone-treated rats also expressed increased iNOS mRNA and protein as measured by Northern and Western blotting, respectively, and produced more nitric oxide compared with cells from air-exposed animals. Treatment of rats with endotoxin (5 mg/kg, intravenously), 30 min prior to ozone, was found to abrogate ozone-induced increases in iNOS mRNA and protein expression, as well as nitric oxide production by alveolar macrophages. This was associated with a reduction in ozone-induced tissue injury as determined by levels of lung lavage fluid protein. Ozone inhalation also resulted in a reduction in intracellular glutathione in alveolar macrophages, an effect that was blocked by endotoxin administration. Taken together, these data provide evidence that the protective effects of endotoxin against ozone-induced injury are mediated, at least in part, by alterations in levels of lung oxidants and antioxidants.

Animals↗
PubMed1995

Lymphocyte-mediated nitric oxide production by rat endothelial cells.

Lymphocyte migration from the blood to sites of tissue injury is mediated, in part, through the interaction of these cells with endothelial cells lining the vessel walls. The ability of endothelial cells to produce nitric oxide may be important in this process. We found that the addition of the nonspecific lymphocyte activators lipopolysaccharide (LPS) or concanavalin A (Con A) to rat hepatic endothelial cell cultures from control or endotoxemic rats markedly enhanced the ability of these cells to produce nitric oxide. In contrast, wheat germ agglutinin (WGA) and phytohemagglutinin (PHA) had no effect on nitric oxide release. Coculture of endothelial cells with lymphocyte-rich preparations of rat thymocytes or splenocytes stimulated endothelial cell nitric oxide production. This response was enhanced by LPS or Con A and to a lesser extent by WGA or PHA. In contrast to endothelial cells, thymocytes and splenocytes did not produce nitric oxide either in the presence or absence of lymphocyte mitogens. Increased production of nitric oxide by endothelial cells in response to lymphocytes and lymphocyte mitogens was due, at least in part, to increased expression of protein for an inducible form of nitric oxide synthase, as measured by Western blotting. Stimulation of endothelial cell nitric oxide production by thymocytes and splenocytes was inhibitable by the specific nitric oxide synthase inhibitor NG-monomethyl-L-arginine and dependent on cell-cell contact. Thus, nitric oxide production by endothelial cells was reduced when the lymphocytes were physically separated from the endothelial cells using cell culture inserts. We hypothesize that nitric oxide released by endothelial cells increases vascular permeability, thereby allowing the extravasation of lymphocytes into the surrounding tissue, a process that may be important in inflammation, tissue injury, and/or wound healing.

Amino Acid Oxidoreductases↗
PubMed1995

Distinct biochemical responses of hepatic macrophages and endothelial cells to platelet-activating factor during endotoxemia.

Acute endotoxemia is associated with activation of hepatic macrophages and endothelial cells. These cells release a variety of inflammatory mediators that have been implicated in tissue injury. In the present studies, we analyzed the biochemical responses of these cells to platelet-activating factor (PAF), a lipid autacoid released during hepatic inflammatory responses. To induce acute endotoxemia, rats were injected intravenously with lipopolysaccharide (LPS). Using the calcium sensitive fluorescent indicator dye Indo-1, we found that PAF induced a rapid and transient increase in intracellular calcium in both hepatic macrophages and endothelial cells. Induction of acute endotoxemia resulted in an increase in the amount of calcium mobilized by both cell types. Although endothelial cells from control rats were less responsive to PAF than macrophages, these cells were more sensitive to in vivo endotoxin. PAF was also found to cause a rapid decrease in intracellular pH in hepatic macrophages that was quantified by fluorescence image analysis using the pH sensitive dye SNAFL-calcein. This decrease occurred more rapidly in macrophages from endotoxemic rats. In cells from both control and endotoxemic rats, the effects of PAF on intracellular pH were inhibited by the specific PAF antagonist triazolam. In contrast to hepatic macrophages, PAF had no effect on intracellular pH in endothelial cells from either control or endotoxemic rats. Ligand binding studies demonstrated that both hepatic macrophages and endothelial cells possess high affinity binding sites for PAF. Macrophages expressed 6- to 7-fold more binding sites/cell than endothelial cells and exhibited a higher Kd. Whereas treatment of rats with LPS had no effect on the Kd for PAF binding to macrophages or on the number of binding sites, a significant increase in both of these receptor characteristics was observed in endothelial cells. Taken together, the present data suggest that the biochemical responses of endothelial cells and macrophages to PAF are distinct. Furthermore, cellular activation induced by PAF in endothelial cells appears to be independent of changes in intracellular pH.

Acute Disease↗
PubMed1995

The pharmacology of immunosuppressant drugs in skin transplant rejection in mice and other rodents.

1. Skin transplantation in rodents is a convenient, widely used method, particularly in mice. It is used as much as an indicator of immune responsiveness as for pharmacological studies. 2. Many differences exist in experimental protocols, both for transplantation and drug administration and in this review, the increase in graft survival time with respect to control times is used to indicate drug effects, in an attempt to account for these differences. 3. The mechanisms underlying skin graft rejection in rodents are described, emphasising the crucial role of both helper and effector T cells. 4. The pharmacology of clinically-used immunosuppressants, including CsA, FK506, rapamycin and purine or pyrimidine synthesis inhibitors, in rodent models of skin transplantation is reviewed. 5. The effects of other potential immunosuppressants and compounds modulating immune responses are described, including the effects of UV light and involvement of platelet-derived factors, prostaglandins and thromboxanes.

Animals↗
PubMed1995

Modulation of macrophage functioning abrogates the acute hepatotoxicity of acetaminophen.

Acetaminophen is a mild analgesic and antipyretic agent that is safe and effective when taken in therapeutic doses. Ingestion of overdoses, however, may lead to acute liver failure accompanied by centrilobular degeneration and necrosis. Although the toxicity of acetaminophen is generally thought to be caused by direct interaction of its reactive metabolites with cellular macromolecules, recent studies have suggested that nonparenchymal cells also may contribute to tissue injury indirectly through the release of cytotoxic mediators. We analyzed the potential role of hepatic macrophages in acetaminophen hepatotoxicity by examining the effects of modulating the activity of these cells on tissue injury. Treatment of male Long Evans Hooded rats with acetaminophen (800 mg/kg) was found to induce extensive centrilobular hepatic necrosis. Pretreatment of the rats with either dextran sulfate or gadolinium chloride, two inhibitors of hepatic macrophage functioning, completely blocked hepatic necrosis, as well as increases in serum transaminase levels induced by acetaminophen. Interestingly, treatment of rats with the macrophage activator, lipopolysaccharide (LPS), also reduced tissue injury induced by acetaminophen. To exclude the possibility that the effects of gadolinium chloride, dextran sulfate, or LPS were due to alterations in acetaminophen metabolism, we analyzed the effects of these agents on various pharmacokinetic properties of this analgesic. Dextran sulfate and gadolinium chloride had no effect on the half-life of a low dose of acetaminophen (20 mg/kg), or on the activity of any of its individual pathways of metabolism, including the formation of acetaminophen-mercapturic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaminophen↗
PubMed1994

Different functional effect of Ro 15-4513 and Ro 19-4603 on synaptic responses of Purkinje cells in the rat cerebellar slice.

Modulation of GABA-mediated neurotransmissions by Ro 15-4513 in cerebellar slices was assessed following stimulation of the parallel fibre input, which, in this preparation, preferentially activates the inhibitory interneurones innervating Purkinje cells. Peristimulus-time histogram analysis of inhibitory responses of spontaneously-active Purkinje cells showed only a decrease in the duration of inhibition induced by Ro 19-4603. This is consistent with inverse agonism on the BZ1 receptors associated with postsynaptic GABAA receptors on Purkinje cells. 1 microM Ro 15-4513 induced a similar response but 100 nM Ro 15-4513 induced a biphasic response, with an increase in duration of inhibition preceding the decrease during continued perfusion of the compound. At lower concentrations of Ro 15-4513 the increase in inhibition predominated, the minimal effective concentration being 10 pM. 1 microM flumazenil blocked both components of this response to 100 nM Ro 15-4513, but at 100 nM flumazenil only blocked the decrease in inhibition. The ability of Ro 15-4513 but not Ro 19-4603 to enhance inhibition and its relative insensitivity to 100 nM flumazenil, parallel the affinities of these compounds for diazepam-insensitive (DI) binding sites in the cerebellum. These data suggest that the enhancement of inhibition induced by Ro 15-4513 results from its inverse agonist activity on DI receptors causing disinhibition of both granule cells and their parallel fibres and increased sensitivity to the electrical stimuli inducing activation of the inhibitory interneurones innervating Purkinje cells.

Animals↗
PubMed1994

Osteopontin inhibits induction of nitric oxide synthase gene expression by inflammatory mediators in mouse kidney epithelial cells.

We report that osteopontin (OPN), a secreted, Arg-Gly-Asp-containing phosphoprotein expressed at high levels in the kidney, suppresses nitric oxide (NO) synthesis induced by the inflammatory mediators gamma-interferon and lipopolysaccharide in primary mouse kidney proximal tubule epithelial cells. Northern blot and immunofluorescence analyses of inducible nitric oxide synthase (iNOS) expression revealed that the inflammatory mediators increased iNOS mRNA and protein levels. Recombinant human OPN (purified from both mammalian cells and from Escherichia coli) inhibited this response by a process that was blocked by anti-OPN antiserum and by the peptide GRGDS, but not GRGES. The data suggest that inhibition of NO synthesis by OPN in these kidney cells is mediated by an integrin, possibly the alpha v beta 3 integrin, which is known to be an OPN receptor. NO is believed to control blood flow through the glomerulus, regulating salt and water balance, and to be important as a defense against tumor cells and infecting microorganisms. The ability of OPN to inhibit the induction of iNOS suggests that OPN may be an important regulator of the NO signaling pathway and NO-mediated cytotoxic processes.

Amino Acid Oxidoreductases↗
PubMed1994

Distinct patterns of nitric oxide production in hepatic macrophages and endothelial cells following acute exposure of rats to endotoxin.

Hepatic macrophages and endothelial cells play an important role in the clearance of endotoxin from the portal circulation. These cells are activated by endotoxin to release reactive mediators including superoxide anion, hydrogen peroxide, and nitric oxide, which have been implicated in hepatic inflammation and tissue injury. In the present studies we analyzed mechanisms regulating the production of nitric oxide by hepatic macrophages and endothelial cells following in vivo exposure to endotoxin. Rats were injected intravenously with Escherichia coli lipopolysaccharide (LPS, 5 mg/kg). Cells were isolated from the animals 48 h later by in situ perfusion of the liver with collagenase and pronase followed by differential centrifugation and centrifugal elutriation. We found that macrophages and endothelial cells from both untreated and endotoxin-treated rats readily synthesized nitric oxide following in vitro stimulation with interferon-gamma (IFN-gamma) and LPS alone and in combination. This response was dependent on l-arginine and was blocked by two nitric oxide synthase inhibitors, NG-monomethyl-l-arginine and l-canavanine. Macrophages produced more nitric oxide in response to LPS or LPS plus IFN-gamma than endothelial cells. In addition, nitric oxide production by both cell types in response to LPS plus IFN-gamma was increased after treatment of rats with endotoxin. Macrophages appeared to be more sensitive than endothelial cells to the in vivo effects of this inflammatory stimulus. Northern and Western blot analysis demonstrated that nitric oxide production by macrophages and endothelial cells in response to LPS plus IFN-gamma was due to increased expression of an inducible form of nitric oxide synthase (iNOS) mRNA and protein. Using fluorescence image analysis, iNOS protein was found to be localized in the cytoplasm of the cells. Treatment of rats with endotoxin was associated with increased expression of iNOS protein in the macrophages. The phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA) also stimulated nitric oxide production by macrophages and endothelial cells from endotoxin-treated rats, although not as effectively as LPS and IFN-gamma. Macrophages were more responsive than endothelial cells to TPA. Furthermore, depletion of the cells of glutathione using buthionine sulfoximine had no major effect on nitric oxide production by macrophages but resulted in small but significant inhibition in endothelial cells. This suggests that this sulfhydryl-containing tripeptide does not regulate intracellular levels of reactive nitrogen intermediates in activated macrophages.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Oxidoreductases↗
PubMed1994

Production of nitric oxide and peroxynitrite in the lung during acute endotoxemia.

Nitric oxide is a short-lived cytotoxic mediator that has been implicated in the pathogenesis of endotoxin-induced tissue injury and septic shock. In the present studies we determined whether this mediator is produced in the lung during acute endotoxemia. We found that intravenous injection of rats with bacterially derived lipopolysaccharide (LPS), a condition that induces acute endotoxemia, caused a time-dependent increase in inducible nitric oxide synthase (iNOS) mRNA expression in the lung, which reached a maximum after 24 h. This was correlated with nitric oxide production in the lung as measured by electron paramagnetic spin trapping, which was detectable within 6 h. Alveolar macrophages (AMs) and interstitial macrophages (IMs) isolated from rats 6-12 h after induction of acute endotoxemia were also found to exhibit increased nitric oxide production in response to in vitro stimulation with interferon-gamma (IFN-gamma) and LPS measured by nitrite accumulation in the culture medium. The effects of acute endotoxemia on nitric oxide production by these cells were, however, transient and returned to control levels by 24 h in AMs and 36 h in IMs. Interestingly, although nitrite accumulation in the culture medium of IMs isolated 48 h after induction of acute endotoxemia and stimulated with low concentrations of IFN-gamma and LPS was reduced, when compared with cells from control animals, these cells, as well as AMs, continued to express high levels of iNOS protein and mRNA. This was correlated with increased peroxynitrite production by the cells. Peroxynitrite has been shown to act as a nitrating agent and can generate nitrotyrosine residues in proteins. Using a specific antibody and immunohistochemistry, we found evidence of nitrotyrosine residues in sections of lungs 48 h after treatment of rats with endotoxin. These data suggest that nitric oxide produced by IMs and AMs can react with superoxide anion to form peroxynitrite. Taken together, the present studies demonstrate that AMs and IMs are activated following acute endotoxemia to produce reactive nitrogen intermediates and that both cell types contribute to inflammatory responses in the lung.

Amino Acid Oxidoreductases↗
PubMed1994

The effects of RU 33965 and RU 34030, two new 3-cyclopropyl carbonyl imidazobenzodiazepines, on GABAA receptor-mediated synaptic transmission in cerebellar slices in the rat.

1. Two 3-cyclopropyl carbonyl imidazobenzodiazepines, RU 33965 and RU 34030, were tested for their ability to modulate GABAA synaptic transmission in rat cerebellar slices. The action of the full benzodiazepine agonist RU 32007 and the inverse agonist Ro19-4603 were tested for comparison. 2. Extracellular recordings were made from the Purkinje cell layer of the cerebellar slices and inhibition induced by just threshold electrical stimulation of the parallel fibres was bicuculline sensitive. 3. The major effect of RU 32007 when examined at 100 nM and 1 microM was to increase the GABAA mediated inhibition in the slice. 4. In contrast the major effect of the inverse agonist Ro19-4603 was to reduce the period of inhibition. 5. RU 33965 and RU 34030 at 10 and 1 microM respectively either had little effect on GABAA mediated inhibition or decreased it slightly. 6. RU 34030, 1 microM, abolished the agonist effect of RU 32007, 1 microM. 7. The effects of RU 32007 and Ro19-4603 were abolished by the benzodiazepine antagonist flumazenil. 8. It is concluded that both RU 33965 and RU 34030 have marginal inverse agonist properties.

Animals↗
PubMed1993

Induction of functionally active platelet-activating factor receptors in rat alveolar macrophages.

Freshly isolated alveolar macrophages from control rats express low numbers of platelet-activating factor (PAF) receptors (4.6 x 10(3) binding sites/cell, Kd = 1.3 nM). These receptors appeared to be functionally inert in that PAF failed to induce intracellular calcium mobilization in the cells. Following brief exposure of rats to ozone (2 ppm, 3 h), a pulmonary irritant and inflammatory agent that is rapidly converted to molecular oxygen, expression of PAF receptors was markedly up-regulated on lung phagocytes (13.1 x 10(3) binding sites/cell), with no significant effect on receptor affinity (Kd = 2.0 nM). In these cells, PAF, but not lyso-PAF, an inactive analog, caused a rapid and transient rise in intracellular calcium demonstrating that the PAF receptors were functionally active. The calcium response to PAF, which was largely due to mobilization of calcium from intracellular stores, was found to be dose-dependent in the nanomolar concentration range and inhibitable by the PAF receptor antagonist triazolam. The results of these studies may be important in elucidating mechanisms of lung inflammation induced by this model irritant.

Animals↗
PubMed1993

Platelet-activating factor-induced calcium mobilization and oxidative metabolism in hepatic macrophages and endothelial cells.

Fluorescence image analysis of the calcium sensitive dye Indo-1 was used to characterize platelet-activating factor (PAF)-induced calcium mobilization in hepatic macrophages and endothelial cells. PAF, but not lyso-PAF, an inactive analog, induced a rapid and transient increase in intracellular levels of calcium that appeared to depend on the presence of extracellular calcium. In both macrophages and endothelial cells, these effects were dose dependent, reaching maximal levels with 10 nM PAF. However, the kinetics of the calcium response to PAF in macrophages and endothelial cells was distinct. The endothelial cells responded more rapidly to PAF than the macrophages (within 1 min vs. 2-3 min, respectively) and displayed longer recovery periods (4 min vs. > 10 min, respectively). In contrast, the magnitude of the response to PAF was greater in the macrophages. In both cell types, triazolam and alprazolam, two PAF antagonists, and the calcium channel blocker verapamil inhibited PAF-induced calcium mobilization. PAF also stimulated superoxide anion production alone and in combination with the macrophage activator 12-O-tetradecanoyl-phorbol-13-acetate (TPA) in both cell types. Macrophages produced more of this reactive oxygen intermediate in response to PAF and TPA than endothelial cells. Interestingly, in the absence of extracellular calcium or when verapamil was added to the cultures, superoxide anion production by the macrophages, but not the endothelial cells, was significantly reduced. These results demonstrate that, although hepatic macrophages and endothelial cells mobilize calcium in response to PAF, the characteristics of the response in each cell type are different. These differences may underlie, at least in part, distinct functional responses of the cells to PAF.

Alprazolam↗
PubMed1993

Inhibition of interleukin 1 beta induced rat and human cartilage degradation in vitro by the metalloproteinase inhibitor U27391.

Interleukin 1 induced proteoglycan loss from cartilage in vitro was prevented by a biochemical inhibitor of metalloproteinase activity. The inhibitor also partially relieved the inhibition of proteoglycan synthesis caused by interleukin 1. The loss of glycosaminoglycan by rat and human femoral head cartilage in response to human recombinant interleukin 1 beta (rhIL-1 beta) was established, and the modulation of this loss by the metalloproteinase inhibitor U27391 was investigated. Rat femoral head cartilage consistently lost glycosaminoglycan in response to rhIL-1 beta whereas only a proportion (30%) of normal human femoral head cartilage did so. Concentrations of 10-100 mumol/l U27391 inhibited the action of rhIL-1 beta on rat femoral head cartilage, reversing both the loss of glycosaminoglycan and the inhibition of glycosaminoglycan synthesis. U27391 also prevented the reduction in glycosaminoglycan content of those human femoral head cartilage explants responsive to rhIL-1 beta. Metalloproteinase inhibition therefore prevents rhIL-1 beta induced glycosaminoglycan loss by rat and human femoral head cartilage, suggesting that inhibitors of such enzymes may prove to be of therapeutic benefit in erosive diseases in humans.

Animals↗