CELL-MATRIX INTERACTIONS MODULATE 92-KD GELATINASE EXPRESSION BY HUMAN BRONCHIAL EPITHELIAL-CELLS

We have previously reported that primary human bronchial epithelial ce lls (HBECs) cultured on types I + III collagen were able to differenti ally regulate the production of major constitutive 92-kD gelatinase, m inor 72-kD gelatinase, and their tissue-specific inhibitor, tissue inh ibitor of metalloproteinase-1 (TIMP-1) in response to lipopolysacchari de (LPS) or proinflammatory cytokines, suggesting that HBECs may be in volved in vivo in the active remodeling of the underlying extracellula r matrix (ECM). In this study, we examined the possible effects of spe cific type IV collagen as compared with types I + III collagen on HBEC behavior and function. We investigated 92-kD gelatinase and TIMP-1 ex pression with zymography and reverse zymography, respectively, at the protein level, and with quantitative reverse transcription-polymerase chain reaction (RT-PCR) at the mRNA level. Results showed similar morp hologic features and identical proliferation rates of HBECs in respons e to the two matrix substrates. Nevertheless, differences at the prote in and mRNA levels between HBEC cultures on type IV collagen and on ty pes I + III collagen included: (1) a lower basal level of 92-kD gelati nase production; (2) less upregulation of 92-kD gelatinase in response to LPS endotoxin or to the proinflammatory cytokines interleukin-1 be ta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha); and (3) lo ss of activation of the proforms of the 92-kD and 72-kD gelatinases. T hese findings, together with the maintenance of TIMP-1 expression, str ongly suggest that type IV collagen used as a matrix substratum is ass ociated with a homeostatic HBEC phenotype, and limits the ability of H BECs to degrade the matrix. In contrast, types I + III collagen may be associated with a matrix resorption phenotype corresponding to active matrix remodeling and repair. Thus, the ECM underlying HBECs may modu late matrix remodeling by HBECs, particularly ih response to inflammat ory processes during acute lung injury.