Expression of matrix metalloproteinase gelatinases A and B by cultured epithelial cells from human bronchial explants.

To investigate the role of human bronchial epithelial cells (HBECs) in the maintenance and remodeling of the extracellular matrix, we evaluated the expression by HBECs of 72- and 92-kDa gelatinases under basal conditions and after exposure to bacterial lipopolysaccharides (LPS). Confluent HBECs from explants were cultured in plastic dishes coated with type I and III collagens. Gelatin zymography of HBEC-conditioned media showed constitutive major 92-kDa and minor 72-kDa gelatinases recognized by specific human antibodies and totally inhibited by the metalloproteinase inhibitor EDTA. The identification of the two matrix metalloproteinases was confirmed by quantitative reverse transcription-polymerase chain reaction. Identical patterns of gelatinase expression were observed with repetitive primary cultures issued from the same explants. Zymography showed that exposure of HBECs to LPS induced 2- and 20-fold increases in 92-kDa gelatinase production and activation, respectively, as well as a smaller increase in activated 68-kDa gelatinase. With [3H]gelatin substrate, elevated metallogelatinolytic activity (138 microgram of hydrolyzed gelatin/48 h/10(6) cells) was also observed, whereas no activity was detected in the absence of LPS. A human epithelial cell line (16HBE14o-) exhibited the same basal profile of gelatinase activity, but this profile remained unchanged after exposure to LPS. Quantitative reverse transcription-polymerase chain reaction demonstrated only minimal changes in 92-kDa mRNA levels in response to LPS, but the half-life of 92-kDa gelatinase mRNA was increased with exposure to LPS. In contrast, concomitant slight increases in 72-kDa gelatinase protein and mRNA were found, suggesting that the control mechanisms regulating the expression of 92- and 72-kDa gelatinases by HBECs in response to LPS are divergent. All these data allowed us to propose that HBECs may be actively involved in the physiological and physiopathological remodeling of the airway basement membrane.