Biomedical subjects

L M Commins

Publications and source records attributed to L M Commins.

6 recordsLinked to original sources

PubMed1993

Tumor necrosis factor-alpha activates pulmonary artery endothelial protein kinase C.

We investigated the hypothesis that tumor necrosis factor-alpha (TNF) activates pulmonary endothelial protein kinase C (PKC). Confluent bovine pulmonary artery endothelial monolayers were exposed to recombinant human TNF, and the translocation of PKC, an indicator of enzyme activation, was studied using both slot immunoblotting and immunofluorescence. For slot immunoblot analysis, membrane and cytosol lysate fractions were prepared, and PKC antigen was assessed using MC5 monoclonal anti-PKC antibody. TNF (1,000 U/ml for 15 min) induced translocation of PKC into the membrane. Immunofluorescence analysis with the MC5 antibody was also used. Monolayers treated with culture medium showed diffuse cytoplasmic fluorescence. In contrast, treatment with either TNF (1,000 U/ml for 15 min) or 1,2-dioctanoylglycerol (4 x 10(-5) M for 5 min), a diacylglycerol that activates PKC, resulted in translocation of fluorescence to the cell periphery; fine, punctate PKC-associated fluorescence was localized to the margins of cells. The TNF-induced translocation of PKC was inhibited using either IP-300 polyclonal anti-TNF antibody (indicating that the TNF effect was not due to the vehicle or contaminating endotoxin) or calphostin C (10(-6) M for 15 min), which inhibits PKC activation by interacting with the regulatory diacylglycerol-binding domain. TNF treatment had no effect on either the content of PKC, or of total protein, in the membrane + cytosol, and cycloheximide (40 microM for 5 min) did not alter the translocation of PKC induced by TNF; these results indicate that the effect of TNF on PKC translocation was related to neither de novo membrane synthesis of PKC (as opposed to translocation per se) nor nonspecific augmentation of protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1991

Scavengers of reactive oxygen intermediates do not mediate the depression of macrophage hydrogen peroxide production caused by erythrocyte phagocytosis.

Our previous studies have shown that a phagocytic challenge with IgG-coated erythrocytes (EIgG) depressed macrophage triggered H2O2 production in vitro, and in vivo there was a decrease in the survival rate following bacteremia. The phagocytosis of an equal number of IgG-coated erythrocyte ghosts had none of these effects, indicating that the contents of the erythrocytes are important for these effects. The present study evaluated the role of the scavengers of reactive oxygen intermediates within erythrocytes in the depression of H2O2 production triggered with phorbol myristate acetate following a phagocytic challenge with EIgG. Elicited rat peritoneal macrophages (PM) were challenged with EIgG prepared from normal E or E with inactivated catalase, depleted glutathione, hemoglobin converted to methemoglobin, or fixed with formaldehyde. The depression of triggered H2O2 production was similar when equal numbers of normal EIgG and EIgG with inactivated scavengers were phagocytized. When the phagocytic challenge with normal EIgG was carried out in the presence of cytochalasin B, no depression of triggered H2O2 production was observed. Cytochalasin B partially blocked the phagocytosis of EIgG, so that with larger doses of EIgG there was sufficient ingestion of EIgG to depress H2O2 production in untreated PM. These results indicate that the scavengers of reactive oxygen intermediates present in erythrocytes are neither required nor sufficient to depress H2O2 production by macrophages.

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PubMed1990

Effect of phagocytosis of erythrocytes and erythrocyte ghosts on macrophage phagocytic function and hydrogen peroxide production.

Our previous studies have shown that an in vivo phagocytic challenge with IgG-coated erythrocytes can depress Kupffer cell complement and Fc receptor function, as well as decrease the survival rate following endotoxemia and bacteremia. In an effort to better understand the mechanism underlying these in vivo findings, the present study evaluated the in vitro effects of a phagocytic challenge with either IgG-coated erythrocytes (EIgG) or erythrocyte ghosts (GIgG) on macrophage phagocytic and respiratory burst activity. Elicited rat peritoneal macrophage (PM) monolayers were challenged with varying doses of EIgG, then the noninternalized EIgG were lysed hypotonically and the monolayers incubated for an additional hour prior to determining phagocytic function and PMA-stimulated hydrogen peroxide production. Challenge of PM with 1 x 10(6) EIgG per well had no effect, but challenge with 1 x 10(7) or 1 x 10(8) EIgG per well caused a dose-dependent depression of phagocytic function or hydrogen peroxide production. GIgG were formed by hypotonically lysing EIgG bound to PM at 4 degrees C. The bound GIgG were phagocytized during a subsequent incubation at 37 degrees C. Challenge with GIgG depressed phagocytic function only with the highest challenge dose tested (1 x 10(8) per well) and did not depress hydrogen peroxide production. The observation that prior phagocytic challenge with EIgG depressed macrophage function to a greater extent than challenge with GIgG supports our previous in vivo observations. Furthermore, these studies suggest that the internalization of erythrocyte contents, and not phagocytosis per se, plays an important role in determining macrophage host defense function.

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PubMed1989

Effect of ibuprofen and dexamethasone on Kupffer cell complement receptor function after endotoxemia and the phagocytosis of erythrocytes.

Depression of Kupffer cell complement receptor (CR) function is associated with several states of depressed host defense. This study was carried out to determine if ibuprofen and dexamethasone, which decrease the mortality rate following endotoxemia, could prevent the depression of CR function caused by endotoxemia and the phagocytosis of antibody-coated erythrocytes (EIgG). The depression of CR function caused by endotoxin was completely prevented by the administration of ibuprofen or dexamethasone. Thus, the ability of these drugs to prevent the depression of macrophage function may contribute to their salutory effects during endotoxin shock. In contrast to the effect with endotoxemia, the depression of CR function caused by the phagocytosis of EIgG was not modified by pretreatment with ibuprofen or dexamethasone. Additional studies demonstrated that the depression of CR function caused by EIgG was probably not due to EIgG in the blood or bound to Kupffer cells, interfering with the receptor probe for access to the CR. This study has shown that ibuprofen and dexamethasone can prevent the depression of CR function caused by endotoxin but not the depression caused by the phagocytosis of EIgG. These results suggest that different mechanisms mediate the depression of CR function caused by endotoxin and the phagocytosis of EIgG.

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PubMed1988

Effect of beta-receptor stimulation on Kupffer cell complement receptor clearance function.

The clearance function of complement receptors on Kupffer cells is depressed after several forms of experimental injury. In vitro studies have shown that stimulation of beta-receptors on macrophages causes a depression of several aspects of macrophage function. The present study evaluated the possibility that the increase in sympathetic activity associated with injury contributes to the depression of Kupffer cell complement receptor function. Complement receptor function was assessed in rats from the hepatic uptake of rat erythrocytes coated with IgM. Isoproterenol caused a depression of receptor function when infused at a rate of 5.0 and 0.5 micrograms/kg/min for 15 min but not after infusion of 0.05 micrograms/kg/min. Infusion of isoproterenol, norepinephrine, and epinephrine at 0.5 micrograms/kg/min depressed receptor function by 41%, 38%, and 29%, respectively. Beta-receptor blockade with propranolol prevented the depression of receptor function caused by isoproterenol and norepinephrine. Thermal injury depressed receptor function by 65%, and this depression was reduced to 35% by beta-receptor blockade. Therefore, stimulation of beta-receptors on macrophages by increased circulating levels of catecholamines after injury could contribute to the depression of Kupffer cell function caused by injury.

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PubMed1987

Effect of Kupffer cell phagocytosis of erythrocytes and erythrocyte ghosts on susceptibility to endotoxemia and bacteremia.

The phagocytosis of erythrocytes by macrophages has previously been shown to depress macrophage function. In this study we compared the effect of the phagocytosis of erythrocytes and erythrocyte ghosts by Kupffer cells on the duration of the depression of complement receptor clearance function and host defense against endotoxemia and bacteremia. Phagocytosis of erythrocytes and erythrocyte ghosts was induced in rats by the injection of rat erythrocytes or erythrocyte ghosts coated with anti-rat erythrocyte immunoglobulin G (EIgG and GIgG, respectively). The hepatic uptake of EIgG and GIgG (17.4 X 10(8)/100 g) occurred during the first 30 min after injection. The digestion of phagocytized EIgG and GIgG, as assessed by electron microscopy, was complete at 24 and 3 h after injection, respectively. The depression of Kupffer cell complement receptor clearance function caused by EIgG and GIgG returned to normal by 6 h after injection of EIgG and by 3 h after injection of GIgG. Phagocytosis of EIgG depressed the survival rate after endotoxemia and bacteremia when endotoxin or bacteria were injected at 30 min after EIgG. The survival rate returned to normal when the endotoxin and bacteria were injected at 12 and 6 h after the EIgG, respectively. Phagocytosis of GIgG did not depress the survival rate after endotoxemia and bacteremia. Thus, compared with erythrocytes, erythrocyte ghosts are more rapidly digested after phagocytosis, depress complement receptor function for a shorter period of time, and cause less depression of host defense. These findings indicate that the contents of erythrocytes play an important role in the impairment of host defense caused by the phagocytosis of erythrocytes by Kupffer cells.

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