In vitro effects of cAMP-elevating agents and glucocorticoid either alone or in combination on the production of nitric oxide, interleukin-12 and interleukin-10 in IFN-gamma- and LPS-activated mouse peritoneal macrophages

The macrophage cell surface glyceraldehyde-3-phosphate dehydrogenase is a novel transferrin receptor

The reticuloendothelial system plays a major role in iron metabolism. Despite this, the manner in which macrophages handle iron remains poorly understood. Mammalian cells utilize transferrin-dependent mechanisms to acquire iron via transferrin receptors 1 and 2 (TfR1 and TfR2) by receptor-mediated endocytosis. Here, we show for the first time that the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is localized on human and murine macrophage cell surface. The expression of this surface GAPDH is regulated by the availability of iron in the medium. We further demonstrate that this GAPDH interacts with transferrin and the GAPDH-transferrin complex is subsequently internalized into the early endosomes. Our work sheds new light on the mechanisms involved in regulation of iron, vital for controlling numerous diseases and maintaining normal immune function. Thus, we propose an entirely new avenue for investigation with respect to transferrin uptake and regulation mechanisms in macrophages.

Lipopolysaccharide-mediated protection against Klebsiella pneumoniae-induced lobar pneumonia: intranasal vs. intramuscular route of immunization

Immunoprotective potential of delivered lipopolysaccharide (LPS) preparation from Klebsiella pneumoniae was determined in a murine model of lobar pneumonia. Protection was assessed with three doses of LPS (25, 50 and 100 microg; without any adjuvant) administered intranasally or intramuscularly. After evaluation of lung tissue (bacterial load and histopathology), no significant protection was observed at 25 microg with either application. A significant decrease in lung bacterial load coupled with fall in severity of lung lesions was observed with 50 microg (again both applications). At 100 microg dose, with intramuscular route, a further decrease in the lung bacterial load was shown compared to the 50 microg dose. In contrast, 100 microg LPS, when given intranasally, resulted in a higher bacterial colonization of the lung tissue and higher lung pathology; thus we recommend intramuscular instead of the intranasal route for developing protection against K. pneumoniae-mediated pneumonia with intact LPS-based vaccines.

Expression of inflammatory markers in pig amnion after intraamniotic infection with nonpathogenic or enteropathogenic Escherichia coli

The pig amnion was in vivo intraamniotically infected with E. coli for 10 h at 80-85 d of gestation either with the nonpathogenic O86 strain or enteropathogenic O55 strain. TNF-alpha, IL-10, IL-1beta and IFN-gamma were determined in amniotic fluids by ELISA, the expression of cytokines and some other inflammatory markers was determined by immunohistochemistry. Intraamniotic infection induced high levels of TNF-alpha in amniotic fluids which correlated with bacterial virulence whereas IL-10 was induced only by O86. The IL-1beta level did not increase significantly and was expressed in all infected membranes. IFN-gamma was negligible or absent. TNF-alpha, IL-12p40, calprotectin, HSP65 and gp91phox were found by immunohistochemistry only in amnion membranes infected with the enteropathogenic strain 055.

Quantitative aspects of lipopolysaccharide and cytokine requirements to generate nitric oxide in macrophages from LPS-hyporesponsive (Lps(d)) C3H/HeJ mice

Due to a gene defect (Lps(d)), C3H/HeJ mice are known to be hyporesponsive to the immunobiological potential of lipopolysaccharide (LPS). We studied dose requirements for LPS, IFN-gamma, and cytokines TNF-alpha and IL-10 to produce nitric oxide (NO) in peritoneal macrophages (Mphi) from these animals. In contrast to the Lps(n) C3H/HeN mice, high concentrations of LPS (up to 5 microg/mL) or IFN-gamma (up to 5 ng/mL) by themselves were unable to activate NO production in C3H/HeJ Mphi. The failure to produce NO could not be overcome by addition of L-arginine or tetrahydropterin. The high-output NO biosynthesis was dose-dependently stimulated by combined administration of varying concentrations of IFN-gamma (50-5000 pg/mL) and LPS (approximately 1 ng/mL) or to a lesser extent by IFN-gamma plus TNF-alpha or TNF-alpha/IL-10. Formation of NO in C3H/HeJ MCO triggered by high concentration of LPS (approximately 1 microg/mL) given together with IFN-gamma (0.2-5 ng/mL) reached the values typical for Lps(n) C3H/HeN mice. While Mphi from C3H/HeN mice secreted TNF-alpha, IL-10, and IL-10 upon contact with a low dose of LPS (1 ng/mL), C3H/HeJ Mphi required high concentration of LPS (5 microg/mL) to enhance the secretion of the cytokines. Yet, this dose remained ineffective to stimulate IFN-gamma in Mphi from C3H/HeJ mice. It can be presumed that one of the important factors influencing their deficient ability to form NO is a failure of Mphi to produce IFN-gamma upon LPS contact.

Nitric oxide alleviates oxidative damage in the green alga Chlorella pyrenoidosa caused by UV-B radiation

The effect of ultraviolet-B radiation (UV-B; 280-320 nm) on induction of nitric oxide was estimated in the suspensions of green alga Chlorella pyrenoidosa with or without the NO scavenger N-acetyl-L-cysteine, and reductants such as 1,4-dithiothreitol, glutathione (reduced form), and ascorbic acid. Exogenously added sodium nitroprusside (NO donor), glutathione, 1,4-dithiothreitol, and ascorbic acid were able to prevent chlorophyll loss mediated by UV-B. Addition of NO to algal suspensions irradiated by UV-B increased the activity of catalase and superoxide dismutase but lowered the activity of phenylalanine ammonia-lyase. UV-B thus appears to be a strong inducer of NO production, exogenously added NO and reductants protecting the green alga against UV-B-induced oxidative damage.