Induction of VEGF and MMP-9 Expression by Toll-like Receptor 2/4 in Human Endothelial Cells Infected with Chlamydia Pneumoniae

Matrix metalloproteinases (MMP) are a family of host-derived enzymes involved in the turnover of extracellular matrix (ECM) molecules, and, in particular, it is demonstrated that the 92 KDa gelatinase MMP-9 is often expressed in atherosclerotic plaques by macrophages and smooth muscle cells. Recent evidence supports a role of Toll-like receptor (TLR) signaling in the development of atherosclerosis lesions. In this study, we analyzed the TLR2/TLR4 expression in HUVEC infected with C. pneumoniae and correlated it to the production of VEGF and MMP-9. The results obtained showed an increased VEGF and MMP-9 production correlated with a time-dependent increase in cellular proliferation in HUVEC infected with C. pneumoniae at a multiplicity of infection (MOI) of 2 IFU/cell. HUVEC preincubated with VEGF antibody did not release MMP-9, as detected by zymography assessment and ELISA assay. In addition, we demonstrated that TLR2/TLR4 are expressed in HUVEC infected with viable microorganisms (25% and 17%, respectively), while UV-inactivated microorganisms induced a lesser expression (20% and 11%, respectively) compared to control cells and HUVEC exposed to heat-killed bacteria showed a percentage of TLR-expressing cells similar to the control cells. In addition, the cells preincubated for 60 min with TLR2/TLR4 neutralizing antibodies showed a decrease in C. pneumonia-induced VEGF and MMP-9 production.