Macrophage Inflammatory Protein-2 Secretion Research Articles

Production of macrophage inflammatory protein-2 following hypoxia/reoxygenation in glial cells

Polymorphonuclear neutrophils (PMNs) are known to mediate brain inflammation following hypoxia/reoxygenation (H/R), but the precise mechanisms leading to PMN recruitment are undefined. The alpha-chemokine macrophage inflammatory protein-2 (MIP-2) has specificity for the recruitment of PMNs. In this study, we found that 8 or 12 h of hypoxia followed by 24-h reoxygenation (H8/R24 or H12/R24) induced MIP-2 secretion in cultures of enriched microglia or mixed glia, respectively. Microglia, however, could not survive longer duration (>12 h) of hypoxia. Astrocytes did not produce any significant amount of MIP-2 even though astrocytes maintained 98-99% viability following H12/R24. We also found that microglia survived the H/R treatment better (following H24) in the presence of astrocytes (mixed glial culture) than in microglia-enriched culture. Reoxygenation for prolonged periods (3 and 5 days) following H24 resulted in progressively larger increases in MIP-2 production (20- and 60-fold, respectively) in mixed glial cultures. Immunocytochemical staining revealed that the cells expressing MIP-2 in response to H/R were microglia rather than astrocytes in mixed glial cultures. Examination of MIP-2 mRNA expression showed that H/R upregulated MIP-2 gene expression. Taken together, our data suggest that microglial cells are an important source of MIP-2 production and suggest a potential injury mechanism involving brain-derived production of MIP-2 in H/R.

Acute Effects of Inhaled Urban Particles and Ozone: Lung Morphology, Macrophage Activity, and Plasma Endothelin-1

We studied acute responses of rat lungs to inhalation of urban particulate matter and ozone. Exposure to particles (40 mg/m3 for 4 hours; mass median aerodynamic diameter, 4 to 5 microm; Ottawa urban dust, EHC-93), followed by 20 hours in clean air, did not result in acute lung injury. Nevertheless, inhalation of particles resulted in decreased production of nitric oxide (nitrite) and elevated secretion of macrophage inflammatory protein-2 from lung lavage cells. Inhalation of ozone (0.8 parts per million for 4 hours) resulted in increased neutrophils and protein in lung lavage fluid. Ozone alone also decreased phagocytosis and nitric oxide production and stimulated endothelin-1 secretion by lung lavage cells but did not modify secretion of macrophage inflammatory protein-2. Co-exposure to particles potentiated the ozone-induced septal cellularity in the central acinus but without measurable exacerbation of the ozone-related alveolar neutrophilia and permeability to protein detected by lung lavage. The enhanced septal thickening was associated with elevated production of both macrophage inflammatory protein-2 and endothelin-1 by lung lavage cells. Interestingly, inhalation of urban particulate matter increased the plasma levels of endothelin-1, but this response was not influenced by the synergistic effects of ozone and particles on centriacinar septal tissue changes. This suggests an impact of the distally distributed particulate dose on capillary endothelial production or filtration of the vasoconstrictor. Overall, equivalent patterns of effects were observed after a single exposure or three consecutive daily exposures to the pollutants. The experimental data are consistent with epidemiological evidence for acute pulmonary effects of ozone and respirable particulate matter and suggest a possible mechanism whereby cardiovascular effects may be induced by particle exposure. In a broad sense, acute biological effects of respirable particulate matter from ambient air appear related to paracrine/endocrine disruption mechanisms.

Cytokine expression in hepatocytes: role of oxidant stress.

Inflammatory mediators, including cytokines and chemokines, are associated with the pathology of chronic liver disease. Interleukin-8 (IL-8) in humans and macrophage inflammatory protein-2 (MIP-2) in rodents, both members of the C-X-C family of chemokines, are particularly potent neutrophil attractants and have been implicated in chronic liver diseases. In the liver, cytokine secretion is usually associated with non-parenchymal cells, particularly Kupffer cells. In the present studies, chemokine gene expression and secretion were investigated in hepatocytes treated with various stimulators. Using human Hep G2 cells, it was demonstrated that, in contrast to lipopolysaccharides (LPS), both tumor necrosis factor-alpha (TNF-beta) and H2O2 are potent inducers of IL-8, presumably acting via protein kinase C (PKC)-dependent pathways. MIP-2 expression occurred in freshly isolated rat hepatocytes following treatment with TNF-alpha, LPS, and to a lesser degree, H2O2. Both IL-8 and MIP-2 secretion were inhibited, although to varying degrees, by such antioxidants as TMTU, DMSO, catalase, and N-acetylcysteine. Furthermore, in vitro TNF-alpha neutralization experiments and transfection of Hep G2 cells with an IL-8 construct confirmed that TNF-alpha and H2O2 directly stimulate IL-8 secretion. RT-PCR analyses indicated that chemokine secretion induced by these agents operates via increased gene expression. Furthermore, a variety of cytokine genes were found to be expressed by hepatocytes, including MCP-1, cytokine-induced neutrophil chemoattractant (CINC), and IL-6. Taken together, these studies indicate that hepatocytes respond to biologically relevant levels of common activators, including H2O2, to produce cytokines and chemokines that contribute to pathophysiologic and repair processes in the liver.

Macrophage inflammatory protein-2: chromosomal regulation in rat small intestinal epithelial cells.

Nonpathogenic, resident bacteria participate in the pathogenesis of inflammation in the small intestine, but the molecular messages produced by such bacteria are unknown. Inflammatory responses involve the recruitment of specific leukocyte subsets. We, therefore, hypothesized that butyrate, a normal bacterial metabolite, may modulate chemokine secretion by epithelial cells, by amplifying their response to proinflammatory signals. We studied the expression of the chemokine, macrophage inflammatory protein-2 (MIP-2) by the rat small intestinal epithelial cell line, IEC-6. Cells were stimulated with lipopolysaccharide or with interleukin 1beta (IL-1beta) and incubated with sodium butyrate. Acetylation of histones was examined in Triton X acetic acid-urea gels by PAGE. Unstimulated IEC-6 cells did not secrete MIP-2. However, lipopolysaccharide and IL-1beta induced MIP-2 expression. Butyrate enhanced MIP-2 secretion both in lipopolysaccharide-stimulated and IL-1beta-stimulated enterocytes; but butyrate alone did not induce MIP-2 expression. Butyrate increased the acetylation of histones extracted from the nuclei of IEC-6 cells. Furthermore, acetylation of histones (induced by trichostatin A, a specific inhibitor of histone deacetylase) enhanced MIP-2 expression by cells stimulated with IL-1beta. In conclusion, trichostatin A reproduced the effects of butyrate on MIP-2 secretion. Butyrate, therefore, increases MIP-2 secretion in stimulated cells by increasing histone acetylation. We speculate that butyrate carries information from bacteria to epithelial cells. Epithelial cells transduce this signal through histone deacetylase, modulating the secretion of chemokines.