Treponema pallidum enhances human monocyte migration and invasion by dysregulating the MMP/TIMP balance.

Although the infiltration of monocytes into local lesions is an obvious pathological manifestation in the pathogenesis of syphilis, little is known about the role of metalloproteinase (MMP)/tissue inhibitor of metalloproteinases (TIMP) imbalance in the migration/invasion of THP-1 cells induced by Treponema pallidum (T. pallidum). The influence of T. pallidum on the invasion and migration of THP-1 cells was evaluated. Changes in the MMP/TIMP balance and the mechanisms underlying the involvement of the MAPK and NF-κB signaling pathways in this process were explored. T. pallidum induced the migration/invasion of THP-1 cells and the mRNA and protein expression of MMP-1, MMP-9 and TIMP-1. The mRNA expression of TIMP-2 was reduced, and the protein expression of TIMP-2 was not changed. The MMP-1/TIMP-1, MMP-1/TIMP-2, MMP-9/TIMP-1 and MMP-9/TIMP-2 ratios were increased. Inhibition of JNK, MEK/ERK, p38 MAPK and NF-κB significantly decreased the MMP/TIMP ratio and ultimately suppressed the migration/invasion of THP-1 cells. These findings revealed that MMP/TIMP imbalances induced by T. pallidum enhanced THP-1 cell migration and invasion via MAPK and NF-κB signaling pathway activation, which revealed a novel step in syphilis pathophysiology.