Tissue inhibitor of metalloproteinase-2 inhibits burn-induced derangements and hyperpermeability in microvascular endothelial cells.

BACKGROUND: Burns induce microvascular hyperpermeability. We hypothesize that this occurs partly through an imbalance between matrix metalloproteinases (MMPs) and endogenous MMP inhibitors such as tissue inhibitors of metalloproteinases (TIMPs), and that such derangements can be attenuated with the use of TIMP-2. METHOD: Rats underwent either sham or burn: serum and tissue were collected. Western blot was used to examine MMP-9 and TIMP-2 levels and MMP activity was assayed from lung tissue. Rat lung microvascular endothelial cells were used to assess monolayer permeability and evaluate the adherens junction proteins ß-catenin, vascular endothelial cadherin and filamentous actin after exposure to burn serum ± TIMP-2. RESULTS: Lung tissue from burn animals showed increased MMP activity, decreased levels of TIMP-2, and no difference in levels of active MMP-9 in burn vs control groups. Burn serum increased monolayer permeability, damaged adherens junction proteins, and incited actin stress fiber formation; TIMP-2 attenuated these derangements. CONCLUSIONS: Burns may lower TIMP-2 levels and increase MMP activity and that TIMP-2 application in vitro may attenuate burn-induced hyperpermeability and decreases damage to endothelial structural proteins. These links warrant further investigation.

Tumor necrosis factor-α disruption of brain endothelial cell barrier is mediated through matrix metalloproteinase-9.

Traumatic brain injuries cause vascular hyperpermeability. Tumor necrosis factor-α (TNF-α), matrix metalloproteinase-9 (MMP-9), and caspase-3 may be important in these processes but the relationship between them has not been investigated. We hypothesized that TNF-α regulates caspase-3-mediated hyperpermeability and blood brain barrier damage and hyperpermeability directly or indirectly via activation of MMP-9. To test this, rat brain microvascular endothelial cells were treated with TNF-α with or without inhibition of MMP-9. Monolayer permeability was measured, zonula occludens-1 and F-actin configuration were examined, and MMP-9 and caspase-3 activities were quantified. TNF-α increased monolayer permeability, damaged zonula occludens-1, induced filamentous-actin stress fiber formation, and increased both MMP-9 and caspase-3 activities. Inhibition of MMP-9 attenuated these changes. These data highlight a novel link between TNF-α and MMP-9 and show that TNF-α regulated caspase-3-mediated hyperpermeability and vascular damage may be linked to MMP-9 in vitro. These findings augment the understanding of traumatic brain injury and pave the way for improved treatment.