Hypercapnic acidosis attenuates pulmonary epithelial wound repair by an NF-kappaB dependent mechanism.

BACKGROUND: Hypercapnic acidosis exerts protective effects in acute lung injury but may also slow cellular repair. These effects may be mediated via inhibition of nuclear factor-kappaB (NF-kappaB), a pivotal transcriptional regulator in inflammation and repair. OBJECTIVES: To determine the effects of hypercapnic acidosis in pulmonary epithelial wound repair, to elucidate the role of NF-kappaB and to examine the mechanisms by which these effects are mediated. METHODS: Confluent small airway epithelial cell, human bronchial epithelial cell and type II alveolar A549 cell monolayers were subjected to wound injury under conditions of hypercapnic acidosis (pH 7.0, carbon dioxide tension (P(CO(2))) 11 kPa) or normocapnia (pH 7.37, P(CO(2)) 5.5 kPa) and the rate of healing determined. Subsequent experiments investigated the role of hypercapnia versus acidosis and elucidated the role of NF-kappaB and mitogen-activated protein kinases. The roles of cellular mitosis versus migration and of matrix metalloproteinases in mediating these effects were then determined. RESULTS: Hypercapnic acidosis reduced wound closure (mean (SD) 33 (6.3)% vs 64 (5.9)%, p<0.01) and reduced activation of NF-kappaB compared with normocapnia. Buffering of the acidosis did not alter this inhibitory effect. Prior inhibition of NF-kappaB activation occluded the effect of hypercapnic acidosis. Inhibition of ERK, JNK and P38 did not modulate wound healing. Hypercapnic acidosis reduced epithelial cell migration but did not alter mitosis, and reduced matrix metalloproteinase-1 while increasing concentrations of tissue inhibitor of metalloproteinase-2. CONCLUSIONS: Hypercapnic acidosis inhibits pulmonary epithelial wound healing by reducing cell migration via an NF-kappaB dependent mechanism that may involve alterations in matrix metalloproteinase activity.

Matrix metalloproteinase-3 differences in oral and skin fibroblasts.

While skin wounds heal by scarring, wounds of oral mucosa show privileged healing with minimal scar formation. Our hypothesis was that phenotypic differences between oral and skin fibroblasts underlie these differences in healing. The aims of this study were to compare MMP-3 expression by oral and skin fibroblasts and investigate a role for MMP-3 in mediating collagen gel contraction. Oral fibroblasts induced significantly greater gel contraction than did paired skin cells. Inhibition of MMP activity significantly inhibited gel contraction by both cell types. Specific inhibition of MMP-3 activity reduced gel contraction by oral, but not skin, fibroblasts. Oral fibroblasts produced significantly higher levels of MMP-3 than did skin fibroblasts at all levels studied. TGF-beta1 and -beta3 isoforms stimulated MMP-3 expression at mRNA, protein, and activity levels by both fibroblast populations. Results suggest that increased MMP-3 production by oral fibroblasts may underlie the differences in wound-healing outcome seen in skin and oral mucosa.

Regulation of keratinocyte growth factor and scatter factor in cyclosporin-induced gingival overgrowth.

BACKGROUND: Epithelial proliferation is a histological characteristic of drug-induced gingival overgrowth. Keratinocyte growth factor (KGF) and scatter factor (SF) are fibroblast-derived growth factors with potent mitogenic and motogenic effects on epithelial cells, and, therefore, could be involved in the pathogenesis of gingival overgrowth. The aims of this study were to investigate: (i) the effects of cyclosporin on KGF and SF expression by gingival fibroblasts; and (ii) the expression levels of KGF and SF mRNA in normal and overgrown gingival tissue. METHODS: The KGF and SF protein production was determined by enzyme-linked immunosorbent assay. Relative levels of KGF and SF mRNA expression were determined using semi-quantitative reverse transcriptase polymerase chain reaction. Expression levels in biopsies of normal and overgrown gum were also determined. RESULTS: In overgrown fibroblasts, 500 ng/ml cyclosporin significantly inhibited KGF and SF mRNA and protein while 2000 ng/ml cyclosporin induced a stimulatory effect. In normal cells cyclosporin significantly increased both KGF and SF. KGF and SF mRNA was detected in both normal and overgrown tissues with a tendency towards increased expression levels in overgrown tissue. CONCLUSION: These results suggest that KGF and SF may have an important role in cyclosporin-induced gingival overgrowth.