Regulation of chemokine mRNA expression in a rat model of vanadium-induced pulmonary inflammation.
Environmental and occupational exposure to vanadium dusts results in toxic effects mainly confined to the respiratory system. Using a rat model of acute lung inflammation induced by intratracheal instillation of sodium metavanadate (NaVO3) at the dose of 200 microg V/kg, we investigated the relationship between the cytologic characterization of pulmonary inflammation and the expression of chemokine mRNA. Significant polymorphonuclear leukocyte (PMN) influx (P < 0.01) into the lung was noted 4 h after NaVO3 instillation, whereas alveolar macrophages (AMs) in bronchoalveolar lavage (BAL) cells appeared to decrease significantly. In contrast, neither PMNs nor AMs changed substantially 1 h after NaVO3 instillation. By Northern analysis, macrophage inflammatory protein (MIP)-2 mRNA in BAL cells increased markedly 1 h after NaVO3 instillation and reduced a little bit at 4 h, whereas MIP-1alpha mRNA in BAL cells was expressed relatively high 1 h after NaVO3 instillation, although a basal expression was detected in control group, and returned rapidly nearly to control level at 4 h. Since MIP-2 is a potent PMN chemoattractant and MIP-1alpha is a potent macrophage/monocyte chemoattractant has been well known. The facts that PMN influx was preceded by increased MIP-2 mRNA expression, suggesting that MIP-2 is involved in the development of NaVO3-induced pulmonary inflammation, whereas increased MIP-1alpha mRNA expression was followed by decreased AMs in BAL cells, suggesting AMs might be activated by MIP-1alpha, adherent to the lining surface of the airways and then resistant to be washed out. To delineate the mechanisms of transcriptional activation, we recently cloned the 5'-flanking region of the MIP-2 gene. The promotor region contains consensus binding sites for transcription factor nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1). Using electrophoretic mobility shift assay, increased nuclear NF-kappaB, not AP-1, binding activity was detected 1 h after NaVO3 instillation, which correlated with the induction of MIP-2 mRNA. p65 (Rel A) and p50 protein appears to be involved in MIP-2 NF-kappaB binding. Taken together, our studies suggest that MIP-2 is an important mediator of NaVO3-induced pulmonary inflammation in the rat model. In addition, elevated MIP-2 mRNA levels are accompanied by increased NF-kappaB binding activity in BAL cells, suggesting possible MIP-2 transcriptional regulation through NF-kappaB.
Chong
I W
IW
Department of Internal Medicine, Kaohsiung Medical University, Taiwan.
Shi
M M
MM
Love
J A
JA
Christiani
D C
DC
Paulauskis
J D
JD
D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D054405:Chemokine CCL3; D054407:Chemokine CCL4; D054426:Chemokine CXCL2; D018925:Chemokines / Q000235:genetics*; D005260:Female; D019402:Macrophage Inflammatory Proteins / Q000235:genetics; D016676:Macrophages, Alveolar / Q000473:pathology; D016328:NF-kappa B / Q000502:physiology; D009504:Neutrophils / Q000473:pathology; D011014:Pneumonia / Q000139:chemically induced* / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014638:Vanadates
D054405:Chemokine CCL3; D054407:Chemokine CCL4; D054426:Chemokine CXCL2; D018925:Chemokines; C404915:Cxcl2 protein, mouse; D019402:Macrophage Inflammatory Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; D014638:Vanadates