Accumulating evidence indicates that an important event in the tissue response in periodontal disease is the recruitment of polymorphonuclear leukocytes (PMN). This study investigated immunohistochemical expression of CXC-chemokines, including macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant-2 (CINC-2) in rat periodontal tissue at 1 and 3 hours and 1, 2, 3 and 7 days after topical application of lipopolysaccharide (LPS; 5 mg/ml in saline) from E. Coli into the rat molar gingival sulcus. In normal periodontal tissues before LPS application, a small number of MIP-2 and CINC-2 positive cells were seen in junctional epithelium (JE) especially in its coronal half. After topical application of LPS, a prominent increase of MIP-2 and CINC-2 positive JE cells was observed. Almost all JE cells strongly expressed them at day 1 and day 2, and then the number of chemokine-positive cells returned to normal at day 7. Corresponding to these chemokine expressions, LPS application induced a significant increase in number of PMNs in sub-JE area at 1 hour (P <0.01) and 3 hours (P <0.05) and a significant increase in JE area at 1 day(P< 0.05) and 2 days (P <0.01), indicating a dynamic flow of PMNs from the sub-JE area into JE.

These findings indicated that JE cells produced MIP-2 and CINC-2 in response to LPS stimulation and suggested that MIP-2 and CINC-2 may be responsible for PMN migration toward the periodontal pathogen and may play an important role in the initiation of inflammation and subsequent periodontal tissue destruction.