Activation of macrophages

Phorbol ester synergistically increases interferon regulatory factor-1 and inducible nitric oxide synthase induction in interferon-gamma-treated RAW 264.7 cells

The roles of PKC in iNOS induction by IFN-gamma have been shown in some cell types. The effect of a PKC activator, phorbol ester, in iNOS induction is thought to be due to multiple mechanisms, and it is necessary to examine the involvement of phorbol ester on IFN-gamma-induced iNOS in detail. In the present study, we investigated the mechanisms of phorbol ester on IFN-gamma-induced iNOS in RAW 264.7 cells. PMA synergistically increased iNOS activity, protein and mRNA levels in IFN-gamma-treated RAW 264.7 cells. PMA together with IFN-gamma increased iNOS mRNA without affecting the iNOS mRNA degradation, suggesting that the synergistic effect of PMA on IFN-gamma-induced iNOS mRNA production may depend on the elevation of the transcription rate rather than a prolongation of mRNA stability. The DNA binding proteins that are involved in the regulation of iNOS expression are mainly NF-kappa B and IRF-1. IRF-1 transcriptionally regulates many IFN-inducible genes such as iNOS whose promoter contains an IRF-1 binding site. PMA might modulate iNOS induction as a cosignal with IFN-gamma in RAW 264.7 cells because the synergistic effect of PMA was mediated through IRF-1, rather than NF-kappa B. Ro 31-8220, a PKC inhibitor, decreased iNOS activity, protein, mRNA levels and IRF-1 activity, indicating that the effect of PMA on iNOS induction might occur via the PKC pathway. It is evidence that PKC plays an important role in IRF-1 activation and that phorbol ester has a synergistic effect on iNOS induction through IRF-1 activation in IFN-gamma-treated RAW 264.7 cells. The synergistic effect of PMA on IFN-gamma-induced IRF-1 binding activity was observed in macrophage cell line J774 cells as well as RAW 264.7 cells, but not in thioglycollate-elicited peritoneal macrophages.

Production of H2O2 by alveolar macrophages in experimental allergic alveolitis

Experimental extrinsic allergic alveolitis (EAA) was induced in guinea pigs with Saccharopolyspora rectivirgula. Bronchoalveolar lavages were performed before inducing EAA (day 1, BAL 1), on day 23 (BAL 2), and on day 48 (BAL 3). The number of cells/ml in lavage fluid was increased at BAL 2 (4.79 x 10(6) and BAL 3 (4.29 x 10(6)) compared with BAL 1 (0.56 x 10(6)). The number of major cell types increased simultaneously, neutrophil becoming the predominant cell type over alveolar macrophages (AM). The production of H2O2 by AM was measured at the different phases of EAA. Adherent AM were either non-stimulated or triggered with phorbol myristate acetate (PMA), zymosan. S. rectivirgula opsonized with normal guinea pig serum (SRNS), or S. rectivirgula opsonized with guinea pig anti-S, rectivirgula serum (SRAS). Stimulated AM produced larger quantities of H2O2 than unstimulated cells, PMA being the most potent stimulus. At day 1, AM stimulated with S. rectivirgula and zymosan produced similar quantities of H2O2. After the induction of the disease, AM stimulated with S. rectivirgula produced larger quantities of H2O2 than with zymosan. Production of H2O2 by AM stimulated with S. rectivirgula or PMA, respectively, stayed the same at day 1 and 23, but increased sharply for both stimuli at day 48. There was no difference between H2O2 production by AM triggered with SRNS or with SRAS.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of macrophages by endotoxin results in the reactivation of a persistent herpes simplex virus infection

Previous work has shown that splenic macrophages derived from herpes simplex virus (HSV)-resistant C57BL/6 mice undergo a persistent HSV infection which is characterized by the continuous release of infectious virus particles from a small subpopulation of infected cells. Treatment of persistently infected macrophages for 2 weeks with lipopolysaccharide (LPS) resulted in an increase of HSV yield and in virus-induced cytopathic effects. HSV was also reactivated by treatment of macrophage cultures with lipid A or tumour necrosis factor (TNF). Like macrophages of C57BL/6 origin, cells from LPS-hyporesponsive C3H/HeJ mice could be persistently infected with HSV. These cells were resistant to LPS-induced virus reactivation. The results show that macrophages derived from C57BL/6 mice are rendered susceptible to lytic HSV infection by treatment with LPS or TNF. Thus, these substances may interfere with persistent HSV infection which can be established due to genetically controlled properties of the host.

A method for bronchoalveolar lavage in live pigs

In order to isolate porcine alveolar macrophages and to quantitatively study the components of recovered lung fluid, a bronchoalveolar lavage technique in living pigs was developed. Lung lavage was performed after introducing a catheter through the mouth via the trachea in the diaphragmatical lobe. Thirty ml of phosphate-buffered saline (PBS) was introduced into the lung and the fluid was aspirated after one minute. Following this, another 15 ml of PBS was introduced into the lung and aspirated after one minute. The recovered volume of the second lavage averaged 15 ml (+/- 0.4 S.E.M.). Cells thus obtained from specific-pathogen-free (SPF) pigs were composed of 98% macrophages. Lavage fluids from conventionally bred pigs contained 67% macrophages, 17% neutrophilic granulocytes and about 16% lymphocytes, demonstrated by their morphology and acid phosphatase activity. The viability of the recovered cells was over 98% in both SPF and conventionally bred pigs. The dilution of the aspirated lung liquid was determined by using methylene blue in the introduced fluid. The calculated dilution factor of the recovered lavage fluid was 0.58 (S.E.M. 0.02). No influence was noticed on the number or composition of cells nor on the dilution factor when lung lavage was done in SPF pigs twice a week during a four week period. The protein concentration in lavage fluid from SPF pigs was 142 (SD +/- 26) mcg/ml. In conventionally bred pigs, however, a wide variation (276 +/- 229 mcg/ml) in protein content was noted. Lavage fluid supernatant of some animals had a bactericidal effect on Haemophilus pleuropneumoniae strain 13261, whereas no bactericidal effect was noted in other lavage samples.