Diethard Gemsa

Programmed Cell Death (Apoptosis) in Human Monocytes Infected by Influenza A Virus

Although infection of monocytes by influenza A virus primes for a high cytokine release, it also leads to cell death within 20-30 hours. In this brief report, we demonstrate that influenza A virus-induced monocyte killing was due to programmed cell death (apoptosis) and not to necrosis. Morphologically, chromatin condensation and margination occurred and biochemically, an apoptosis-specific internucleosomal DNA fragmentation into multimers of 180 bp (DNA ladder) was found. Induction of apoptosis and not necrosis in influenza A virus-infected monocytes may serve three purposes: 1. Virus replication is limited, 2. a priming for a high cytokine response is initiated and 3. damaging and inflammation-inducing lysosomal enzymes are held back from monocytes undergoing controlled cell death.

Induction of neutrophil-attracting chemokines in transforming rat hepatic stellate cells

BACKGROUND & AIMSnHepatic stellate cells (HSCs) play a key role in the pathogenesis of liver fibrosis. Immigrating leukocytes can potentiate the progression of liver fibrosis by release of fibrogenic mediators and cytotoxic actions. The inducible production of neutrophil chemotactic activities in HSCs was investigated to understand the underlying mechanisms responsible for the attraction of leukocytes in the pathogenesis of liver fibrosis.nnnMETHODSnCultured HSCs of different transformation grades and after transformation to myofibroblasts (MFBs) were stimulated with tumor necrosis factor (TNF)-alpha and lipopolysaccharide (LPS), respectively. Induced leukocyte chemotactic activities were evaluated by chemotaxis assays, enzyme-linked immunosorbent assay, and Northern blot analysis.nnnRESULTSnA transformation grade-dependent differential responsiveness of HSCs and MFBs was observed. TNF-alpha-inducible production of chemotactic mediators increased substantially with advancing transformation. Only transformed MFBs were LPS responsive. Macrophage inflammatory protein 2 was identified as one of the inducible chemokines.nnnCONCLUSIONSnThe results suggest that chemokines play an important role in the pathogenesis of liver fibrosis. Proinflammatory cytokines can initiate the production of chemotactic activities. The more HSCs are transformed to MFBs, e.g., by chronic injury, the more sensitive the cells become to LPS, which may lead to a vicious circle of enhanced fibrogenic and chemotactic mediator production.

Characterization of blood mononuclear cells of rheumatoid arthritis patients: I. Depressed lymphocyte proliferation and enhanced prostanoid release from monocytes

Purified blood monocytes from patients with rheumatoid arthritis released enhanced amounts of the arachidonic acid products PGE, TXB2, and 6-keto-PGFα when compared to monocytes from healthy control individuals. The proliferative response of blood lymphocytes to concanavalin A was strongly suppressed in rheumatoid arthritis patients. Suppression of lymphocyte proliferation could not be reversed by in vitro addition of indomethacin, an inhibitor of prostaglandin synthesis. However, a restoration of lymphocyte proliferation was possible by reducing the high percentage of monocytes in the mononuclear cell fraction of rheumatoid arthritis patients (50 ± 6% versus 23 ± 5% in healthy controls). Although these findings indicate that monocytes of rheumatoid arthritis patients display a “stimulated” arachidonic acid metabolism, the depressed lymphocyte response appears to be due to the high number of monocytes and not to an enhanced PGE release.

Prostaglandin synthesis in spleen cell cultures of mice injected with corynebacterium parvum.

Abstract Spleen cells of C57BL/6 mice produced high amounts of PGE in vitro when tested 5 to 10 days after injection of heat-killed C. parvum organisms. Little or no PGE was produced by spleen cells from untreated mice or from mice injected with a strain of coryneform bacteria that does not stimulate the lymphoreticular system of mice. Significant release of PGE from spleen cells of C. parvum injected mice could be detected as early as 30 min after initiating the cultures and maximal levels were usually seen after 48 hr. Treatment by indomethacin completely abolished this PGE production. Removal of the adherent population from the spleen cell suspension resulted in markedly decreased levels of PGE, but PGE release of the remaining population was never completely abolished. These data suggest that the cells responsible for most of the PGE synthesis in this system were adherent cells, presumably macrophages. The levels of PGE produced in spleen cells of C. parvum -treated mice were further increased by in vitro addition of C. parvum . This effect could also be observed after addition of zymosan particles indicating that it was not an immunologically specific effect. The reported data suggest that prostaglandins may represent important mediator molecules of the described immunostimulatory and immunosuppressive effects of C. parvum .

The effect of adrenergic drugs on serotonin metabolism in the nucleus raphe dorsalis of the rat, studied by in vivo voltammetry

The serotonin (5-HT) and norepinephrine (NE) system participate in the control of behavioural functions. The experiments were aimed at the question whether the NE system of the locus coeruleus interferes with the 5-HT activity of the nucleus raphe dorsalis and of which receptors are possibly involved. The alpha 1- and beta-adrenoceptor agonists methoxamine and isoproterenol, as well as a high dose (600 micrograms/kg i.p.) of the alpha 2-adrenoceptor agonist clonidine, increased extraneuronal 5-hydroxyindoleacetic acid (5-HIAA) levels in the nucleus raphe dorsalis as measured by in vivo voltammetry. In contrast, a low dose (60 micrograms/kg i.p.) of clonidine and the alpha 1-, alpha 2- and beta-adrenoceptor antagonists, prazosin, piperoxane, and atenolol, reduced the 5-HIAA concentration. In the locus coeruleus, the origin of NE projections to the nucleus raphe dorsalis, clonidine decreased whereas piperoxane enhanced extracellular 3,4-dihydroxyphenylacetic acid (DOPAC), an index of NE metabolism in the locus coeruleus. The results suggest that 5-HT neurotransmission in the nucleus raphe dorsalis is stimulated by the NE system of the locus coeruleus and that adrenoceptor drugs may affect 5-HT neuronal activity in addition to NE neurotransmission.

Role of macrophage cytokines in influenza A virus infections

Human monocytes and murine macrophages were found to be susceptible to infection by influenza A virus. Although virus replication was low, infection led to cell death which was characterized by an extreme intracellular vacuolization. Most importantly, influenza A virus infection was accompanied by a particular pattern of cytokine release. Whereas IL-1 beta, IL-6 and TNF-alpha production was dependent on exposure to infectious virus, IFN-alpha/beta release was also induced by UV-inactivated virus. Although influenza A virus infection alone induced a substantial cytokine mRNA accumulation, translation into bioactive cytokine protein was rather limited. However, addition of low LPS concentrations was capable of strongly potentiating cytokine release from virus-infected cells. Thus, in a first step, an influenza A virus infection primes mononuclear phagocytes by leading to an accumulation of cytokine mRNA which, in a second step, may be readily translated into bioactive cytokines when triggering signals such as LPS are available. These findings suggest that influenza A virus represents an ultimately fatal macrophage activating factor which, when inducing moderate amounts of cytokines, may be beneficial by mounting an immediate antiviral response, but which may cause adverse effects when cytokine release is highly elevated by bacterial products.

Stress-induced changes of extracellular 5-hydroxyindoleacetic acid concentrations followed in the nucleus raphe dorsalis and the frontal cortex of the rat

In the present paper, the effect of different stressors on extracellular 5-hydroxyindoleacetic acid (5-HIAA) concentrations in the frontal cortex and the N. raphe dorsalis (NRD) of the rat were studied. The following stressful procedures were used: Immobilization, 10 min, cold, 20 min, and forced exercise in a rotating wheel, 2h. These procedures were compared with a handling procedure, 10 min. The extracellular 5-HIAA concentration was followed by in vivo voltammetry with carbon multifibre electrodes in the awake animal. Handling had no significant effect on extracellular 5-HIAA concentrations neither in the frontal cortex nor the NRD, whereas immobilization and cold evoked significant increases in both brain areas. During and after forced exercise a significant increase was measurable only in the frontal cortex, while extracellular 5-HIAA concentrations were unchanged in the NRD. Since it is very likely that the modulation of the activity of the central serotoninergic system under stressful conditions is closely connected with changes in behaviour and temperature regulation, we compared our findings on extracellular 5-HIAA levels during stress with the effect of the 5-HT1A agonist (+)-8-hydroxy-2-(di-n-propylamino)tetraline (8-OH-DPAT), a substance known to reduce body temperature. The i.p. injection of a low dose decrease significantly both, the extracellular 5-HIAA concentration in the NRD and body temperature. Our results suggest that the serotoninergic activation in the frontal cortex may prove to be a general response to stress which could function perhaps as a part of the central coping mechanism, whereas serotonin (5-HT) in the NRD may modulate specific regulatory responses such as body temperature.

Ionophore A23187 raises cyclic AMP levels in macrophages by stimulating prostaglandin E formation.

Abstract The calcium ionophore A23187 rapidly increased cAMP in rat peritoneal macrophages. The cAMP accumulation required extracellular Ca 2+ and could be inhibited by indomethacin. Determinations of prostaglandins in the incubation medium revealed that the ionophore A23187 induced a rapid release of prostaglandin E (PGE) and prostaglandin F (PGF). Synthesis of PGE and PGF occurred only in the presence of extracellular Ca 2+ but was not found to depend on a translocation of Ca 2+ into the cells. The data suggest a direct perturbation of the cell membrane by the ionophore A23187, leading to a release of prostaglandins which mediate an increase of cAMP.

Membrane perturbation and stimulation of arachidonic acid metabolism

This review is a short account on the current knowledge of the arachidonic acid metabolism in macrophages. Different stimuli of the cyclooxygenase system are presented, pro- as well as antiinflammatory effects of prostaglandin E2 (PGE2) are described and the role of PGE2 as a suppressor molecule of activated macrophages is discussed in the context of immunoregulation.

Histopathological changes in enlarged thoracic lymph nodes during the development of silicosis in rats.

Silicosis is primarily a fibrotic lung disease which also affects the draining lymph nodes. In the present study, we examined the lymph nodes of rats from 2 weeks to 52 weeks after an 8-day silica aerosol exposure. Parallel to the typical silicotic changes in the lungs, profound alterations occurred in both posterior mediastinal lymph nodes. The weight of the lymph nodes progressively increased from 3.5-fold to 35-fold at 52 weeks after silica exposure. The weight increase was accompanied by an early increase of T cells and preferentially of CD4+ cells at 2 weeks, which converted into a B cell increase at 6 weeks. Histologically, a leukocyte influx without apparent structural changes was noted at 2 weeks whereas at 6 weeks, germinal centers and T cell regions were disappearing and macrophages accumulated in granuloma-like structures which were randomly scattered throughout the lymphoid tissue. Within the granulomas, macrophages were detected that carried ingested silica particles without apparent signs of degeneration or apoptosis. At 52 weeks after silica exposure, macrophage granulomas persisted without induction of fibrosis in both lymph nodes, and T and B cells were now evenly distributed within the tissue. These data extend our previous findings on lymphocyte and macrophage activation and indicate that the early and marked disorganization of draining lymph node structures may contribute to the immune abnormalities in silicosis.