Edema in Oral Mucosa after LPS or Cytokine Exposure

Lowering of interstitial fluid pressure (P(if)) is an important factor that explains the rapid edema formation in acute inflammation in loose connective tissues. Lipopolysaccharide (LPS) and the pro-inflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) are pathogenetic in gingivitis. To test if these substances induce lowering of P(if) in rat oral mucosa, we measured P(if) with a micropuncture technique. IL-1beta and TNF-alpha caused lowering of P(if), whereas LPS induced an immediate increase in P(if), followed by lowering after 40 min. Measurements of fluid volume distribution showed a significant change in interstitial fluid volume (V(i)) 1.5 hr after LPS exposure as V(i) changed from 0.41 +/- 0.02 to 0.51 +/- 0.03 mL/g wet weight (p < 0.05), confirming edema. These findings show that LPS, IL-1beta, and TNF-alpha induce lowering of P(if) in the rat oral mucosa and contribute to edema formation in LPS-induced gingivitis.