Tetracycline inhibits Porphyromonas gingivalis lipopolysaccharide‐induced lesions in vivo and TNFα processing in vitro

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Abstract
Lipopolysaccharides (LPS) are considered one of the more important virulence factors related to the pathogenesis of periodontal diseases. Based on tetracycline (TTC) ability to bind divalent metal ions, the present study was designed to examine the effect of TTC on P. gingivalis LPS-induced lesions in vivo and on LPS-induced TNF alpha production in vitro. Subcutaneous injection of 50-100 micrograms of P. gingivalis LPS into BALB/C mice induced a visible lesion within 24 h with evident tissue necrosis. Daily systemic administration of TTC for the first 4 d following LPS challenge reduced the size of the lesion, and total inhibition of lesion formation was observed in 75-100% of the treated mice. A non-related broad spectrum antibiotic, ampicillin, or the IL-1 inhibitor ML-20, had no effect on the lesion size. In order to explore some aspects of the mechanism involved, we tested the effect of TTC on LPS-induced TNF alpha secretion by human monocytes in vitro. TTC (1 mM) was found to block LPS-stimulated TNF alpha secretion. Western blotting of monocyte cytoplasmic membranes for membrane-bound TNF alpha show that TTC causes the retention of membrane-associated TNF alpha on monocyte membranes, thereby preventing the release of TNF alpha into the culture media. The results suggest the TTC is an effective in vivo therapy for preventing P. gingivalis LPS-induced subcutaneous lesion formation in the murine model. The mechanism of TTC treatment probably involves blocking the activity of metalloproteinases, including TNF alpha processing enzyme, thereby preventing LPS-induced tissue destruction.