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J B Hibbs

Publications and source records attributed to J B Hibbs.

At least 55 records · Page 3Linked to original sources
PubMed1987

Macrophage cytotoxicity: role for L-arginine deiminase and imino nitrogen oxidation to nitrite.

Previous studies have shown that cytotoxic activated macrophages cause inhibition of DNA synthesis, of mitochondrial respiration, and of aconitase activity in tumor target cells. An L-arginine-dependent biochemical pathway synthesizing L-citrulline and nitrite, coupled to an effector mechanism, is now shown to cause this pattern of metabolic inhibition. Murine cytotoxic activated macrophages synthesize L-citrulline and nitrite in the presence of L-arginine but not D-arginine. L-Citrulline and nitrite biosynthesis by cytotoxic activated macrophages is inhibited by NG-monomethyl-L-arginine, which also inhibits this cytotoxic effector mechanism. This activated macrophage cytotoxic effector system is associated with L-arginine deiminase activity, and the imino nitrogen removed from the guanido group of L-arginine by the deiminase reaction subsequently undergoes oxidation to nitrite. L-Homoarginine, an alternative substrate for this deiminase, is converted to L-homocitrulline with concurrent nitrite synthesis and similar biologic effects.

Ammonia↗
PubMed1987

L-arginine is required for expression of the activated macrophage effector mechanism causing selective metabolic inhibition in target cells.

L-Arginine is required for expression of the activated macrophage cytotoxic effector mechanism that causes inhibition of mitochondrial respiration, aconitase activity, and DNA synthesis in tumor target cells. This effector mechanism is active in the presence of L-arginine even when the cocultivation medium lacks all other amino acids and serum. Cytotoxic activated macrophage-induced inhibition of mitochondrial respiration in target cells is proportional to the concentration of L-arginine in the medium. L-Arginine must be present during the cocultivation period. Pretreatment of cytotoxic activated macrophages with L-arginine or posttreatment of the target cells after cocultivation is not effective. D-Arginine does not substitute for L-arginine and at high concentrations is a competitive inhibitor of the L-arginine-dependent effector mechanism. Other analogues that could not replace L-arginine include agmatine, argininic acid, arginine hydroxamate, and tosyl-L-arginine methyl ester. L-homoarginine, however, can effectively substitute for L-arginine. NG-monomethyl-L-arginine is a potent competitive inhibitor of this effector mechanism. High concentrations of lipopolysaccharide do not reverse inhibition of the L-arginine-dependent effector mechanism by NG-monomethyl-L-arginine. However, inhibition of the effector mechanism by NG-monomethyl-L-arginine can be overridden by increasing the concentration of L-arginine in the culture medium. We compared NGNG-dimethyl-L-arginine and NGN1G-dimethyl-L-arginine with NG-monomethyl-L-arginine as inhibitors of the L-arginine-dependent effector mechanism. The results show that the inhibitory effect of these guanidino methylated derivatives of L-arginine is highly determined by structure. Guanidine is a weak competitive inhibitor of the L-arginine-dependent effector mechanism. The requirement for L-arginine does not appear to be for protein synthesis, creatine biosynthesis, polyamine biosynthesis, or ADP ribosylation reactions. Bacterial lipopolysaccharide is effective as a second signal only when the cocultivation medium contains L-arginine, and this strict L-arginine dependency is not overridden by increasing the concentration of lipopolysaccharide. Bovine liver arginase, by competing for L-arginine in the cocultivation medium, inhibits the L-arginine-dependent activated macrophage cytotoxic effector mechanism.

Aconitate Hydratase↗
PubMed1986

Murine cytotoxic activated macrophages inhibit aconitase in tumor cells. Inhibition involves the iron-sulfur prosthetic group and is reversible.

Previous studies show that cytotoxic activated macrophages cause inhibition of DNA synthesis, inhibition of mitochondrial respiration, and loss of intracellular iron from tumor cells. Here we examine aconitase, a citric acid cycle enzyme with a catalytically active iron-sulfur cluster, to determine if iron-sulfur clusters are targets for activated macrophage-induced iron removal. Results show that aconitase activity declines dramatically in target cells after 4 h of co-cultivation with activated macrophages. Aconitase inhibition occurs simultaneously with arrest of DNA synthesis, another early activated macrophage-induced metabolic change in target cells. Dithionite partially prevents activated macrophage induced aconitase inhibition. Furthermore, incubation of injured target cells in medium supplemented with ferrous ion plus a reducing agent causes near-complete reconstitution of aconitase activity. The results show that removal of a labile iron atom from the [4Fe-4S] cluster, by a cytotoxic activated macrophage-mediated mechanism, is causally related to aconitase inhibition.

Aconitate Hydratase↗
PubMed1984

Iron depletion: possible cause of tumor cell cytotoxicity induced by activated macrophages.

The experiments reported here provide a possible molecular mechanism for the activated macrophage cytotoxic effect. Tumor cells that develop cytostasis and inhibition of mitochondrial respiration in response to cocultivation with activated macrophages release a significant fraction of their intracellular iron-59 content. Kinetic studies show that specific release of iron-59 from target cells begins 4-6 hours after initiating cocultivation which is the time point that inhibition of DNA synthesis is first detected. Treatment of tumor cells with metabolic inhibitors causing inhibition of respiration, protein synthesis, RNA synthesis, and DNA synthesis to a similar or greater extent than that caused by activated macrophages does not induce release of intracellular iron-59. It is significant that mitochondrial respiration and DNA replication, both strongly inhibited in target cells by activated macrophages, are metabolic pathways with enzymatic activity vulnerable to inhibition by depletion of intracellular iron.

Animals↗
PubMed1982

DNA virus-transformed hamster cell--host effector cell interactions: level of resistance to cytolysis correlated with tumorigenicity.

Spontaneously cytolytic hamster spleen cells and BCG-activated hamster macrophages were used to examine susceptibilities to nonspecific effector cell-induced lysis among 13 DNA virus-transformed hamster cell lines exhibiting four different tumorigenic phenotypes. Hamster cells transformed by adenovirus type 12 (an oncogenic adenovirus serotype) or simian virus 40 (an oncogenic papovavirus) readily induced tumors in immunocompetent syngeneic hamsters and were relatively resistant to spleen-cell-induced lysis compared to cells transformed by adenovirus type 2 (a non-oncogenic adenovirus serotype) which induced tumors only in immunoincompetent hosts. Simian virus 40-transformed cells, which possess the unusual property of efficient tumor induction in allogeneic hosts, were uniquely resistant to lysis by activated macrophages. These differential patterns of susceptibility to cytolysis suggest an association between the level of transformed cell resistance to lysis by nonspecific host effector cells and the oncogenicity of the transforming virus. Furthermore, these data suggest that tumor-cell properties, other than those commonly associated with neoplastic transformation, determine the level of susceptibility or resistance to host effector cell mechanisms.

Adenoviridae↗
PubMed1982

Macrophage fibrinolytic activity: identification of two pathways of plasmin formation by intact cells and of a plasminogen activator inhibitor.

Endotoxin-stimulated macrophages hydrolyze fibrin by a plasmin-mediated process in the absence of detectable soluble plasminogen activator (PAs). The data show that macrophages also activate plasmin by a membrane-associated plasminogen activator (PAm). In the presence of endotoxin, PAm activity increases, and plasmin is formed only by PAm. In addition, endotoxin stimulates macrophages to secrete a proteinase inhibitor that blocks PAs activity but not PAm or plasmin activity. The increased PAm activity and the PA inhibitor secretion in response to endotoxin explains the ability of intact macrophages to hydrolyze fibrin in the absence of detectable PAs. Endotoxin, 100 ng/ml, induced an intracellular PA inhibitor in cultured macrophages, and this correlated with accumulation of inhibitor in medium over the cells. The intracellular PA inhibitor was found to be 50--60 kilodaltons by gel chromatography, to be of anionic charge at pH 7.4 and to inhibit urokinase esterolytic and proteolytic activity but not preformed plasmin. These results define two pathways of plasmin formation by intact macrophages and identify the macrophage cell surface as a site of PA activity relatively protected from soluble proteinase inhibitors.

Animals↗
PubMed1980

Resistance of simian virus 40-transformed hamster cells to the cytolytic effect of activated macrophages: a possible factor in species-specific viral oncogenicity.

Simian virus 40 (SV40)-transformed hamster cells were relatively resistant to the lytic effect of activated macrophages from animals with chronic intracellular infections. Conversely, SV40-transformed mouse and rat cells and adenovirus 2-transformed hamster cells were highly susceptible to destruction by tumoricidal activated macrophages. The pattern of resistance or susceptibility of SV40-transformed rodent cells was the same whether activated macrophage effectors were obtained from mice, random-bred hamsters, or the inbred LSH hamsters from which some of the SV40-transformed hamster lines were derived. The results suggest that resistance of transformed cells to macrophage-mediated cytolysis may explain in part the species-specific oncogenicity of this DNA virus.

Animals↗
PubMed1980

Injury of neoplastic cells by murine macrophages leads to inhibition of mitochondrial respiration.

Cytotoxic activated macrophages (CM) inhibited the growth of neoplastic L1210 cells in vitro but L1210 cell death was minimal to nonexistent. L1210 cells injured by CM were separated from macrophages and studied in an isolated system. CM-injured L1210 cells had an absolute requirement for glucose or another glycolyzable hexose (mannose or fructose) for at least 40 h after removal from macrophages. If the culture medium lacked sufficient concentration of one of these sugars, CM-injured L1210 cells died within 4 h. Uninjured L1210 cells cultured alone or with peptone-stimulated macrophages had no such requirement and maintained complete viability in hexoseless medium. The hexose requirement of CM-injured L1210 cells could not be fulfilled by other naturally occurring monosaccharides, glucose or mannose derivatives, or substrates that can be oxidized by mitochondria. The concentration requirements for glucose, mannose, and fructose by CM-injured L1210 cells correlated with the concentrations required to support maximal glycolysis of these sugars by other murine ascites cells. A concentration of 2-deoxy-D-glucose which completely inhibited L1210 cell glycolysis also complete prevented the ability of glucose or mannose to maintain viability of CM-injured L1210 cells. Interaction with CM led to inhibition of L1210 cell mitochondrial oxidative phosphorylation. This was supported by the findings that: (a) CM-injured L1210 cells had no Pasteur effect; their rate of aerobic glycolysis was the same as the rate of anaerobic glycolysis of uninjured L1210 cells, (b) Endogenous respiration of CM-injured L1210 cells was 15% of normal. Maximal inhibition of uninjured L1210 cell respiration by a specific mitochondrial poison (oligomycin) was nearly the same (13% of normal). It followed that CM-injured L1210 cells required hexose for chemical energy production via the glycolytic pathway. CM-induced mitochondrial injury occurred in five other neoplastic cell lines tested.

Animals↗
PubMed1979

Modulation of plasminogen activator secretion by activated macrophages: influence of serum factors and correlation with tumoricidal potential.

A high molecular weight fraction of human serum (Fr-1) was found to both inhibit macrophage tumoricidal activity and enhance plasminogen activator activity in supernates over activated macrophages in vitro. Conversely, a 40- to 90-kilodalton serine esterase (Fr-3) also found in normal human serum and endotoxin enhanced tumoricidal potential and suppressed the supernatant plasminogen activator activity. Inactivation of either Fr-1 or Fr-3 by 2-mercaptoethanol or diisopropyl fluorophosphate, respectively, abolished both biologic effects. Examination of cell-associated and culture medium plasminogen activator activity before and after acidification to inactivate proteinase inhibitors indicated that suppression of plasminogen activator activity by Fr-3 or endotoxin most likely represents modulation of macrophage plasminogen activator secretion. The findings demonstrate that activated macrophages are capable of highly coordinated biologic responses to alterations in their microenvironment and suggest that it is in fact the high potential for such responsiveness that reliably characterizes the activated macrophage. The results also suggest that an endogenous regulatory system dependent on the interaction of serine esterases may operate to regulate the functional capabilities of activated macrophages.

Animals↗
PubMed1979

Enhanced macrophage tumoricidal activity and tumor suppression or regression caused by heat-killed Candida albicans.

The growth of line-10 hepatoma in male Sewall Wright strain 2 guinea pigs was totally suppressed when tumor cells were mixed with heat-killed Candida albicans. In a significant number of animals, injection of C. albicans into established tumors 10-12 mm in diameter caused complete, rapid tumor regression. Guinea pigs whose tumors regressed or were suppressed as a result of injection of C. albicans rejected subsequent challenges at distant sites with the line-10 hepatoma, which indicated the development of systemic immunity to the tumor. Untreated control guinea pigs had positive delayed hypersensitivity reactions to intradermally injected C. albicans, which suggested prior natural exposure of the animals to C. albicans antigens. Peritoneal macrophages from mice that had received ip injections of phosphate-buffered saline (PBS) or C. albicans were not cytocidal for mouse 3T12 tumor cells in vitro. However, macrophages from the mice given injections of C. albicans, unlike those from mice given PBS, were markedly tumoricidal in the presence of 1 ng or more endotoxin/ml in vitro. These results demonstrated that heat-killed C. albicans, when inoculated into the peritoneal cavity, increased the tumoricidal potential of peritoneal macrophages.

Animals↗
PubMed1978

Modulation of macrophage tumoricidal capability by polyene antibiotics: support for membrane lipid as a regulatory determinant of macrophage function.

We have examined the effects of the sterol-binding polyene antibiotics on macrophage tumoricidal capability. Incubation for 2 hr of activated macrophages from bacillus Calmette-Guérin-infected mice with amphotericin B at 0.5--2 microgram/ml or amphotericin B methyl ester at 0.5--10 microgram/ml enhanced the capability of activated macrophages to kill 3T12 cells. These polyenes did not make normal or stimulated macrophages tumoricidal. Experiments with the ionophores gramicidin, alamethecin, nigericin, and valinomycin indicate that the ionophoretic properties of amphotericin B may not account for its enhancing effect on macrophage tumoricidal potential. Two polyenes with a smaller ring structure, filipin and pimaricin, were also ineffective suggesting that stereospecific modifications in membrane lipid organization underlie the enhancing effect of amphotericin B. The results suggest that the clinical efficacy of amphotericin B in promoting resistance to fungal disease and possibly to neoplasia may operate in part through potentiation of macrophage effector functions.

Amphotericin B↗