Lipoteichoic acid from Staphylococcus aureus induced expression of MMP-9 in human middle ear epithelial cells

Abstract

Change in matrix metalloproteinases (MMPs) and regulation of their tissue inhibitors of metalloproteinases (TIMPs) could play certain role in the pathogenesis of otitis media. This study was designed to evaluate the modulation of MMPs and TIMPs in middle ear epithelium by lipoteichoic acid (LTA) isolated from Staphylococcus aureus.Human middle ear epithelial cells (HMEE) were treated with LTA. Changes of MMP and TIMP and signal transduction were examined by PCR, ELISA, zymography and western blot. LTA isolated from S. aureus increased MMP-9 mRNA expression and secretion in HMEEC, whereas no effect on the expressions of MMP-1, 2, 3, 7 and TIMP-1, 2 was observed. Only the extracellular signal-regulated kinases (ERK) 1/2 of mitogen-activated protein kinase (MAPK) pathway was activated by LTA. And the MEK1/2 inhibitor prevented the expression of MMP-9 by LTA.LTA increased the activity of MMP-9, not TIMPs in middle ear epithelia, suggesting that disturbed balance between MMP-9 and TIMPs could play an active role in LTA-induced otitis media.