Effects of P. gingivalis-LPS on Pancreatic Gene Expressions in Mice

Objectives: Periodontal disease has been reported to increase a risk factor for various systemic diseases, including arteriosclerosis, diabetes and rheumatoid arthritis. There are also reports suggesting an association with pancreatic disease, but the mechanism is not clear. In this study, we examined the effect of periodontal pathogens, P. gingivalis LPS on the pancreas in a mouse model system that does not cause acute inflammation in various organs. The gene expression of the pancreas was exhaustively analyzed in this model.
Methods: Male C57BL/6J mice (8-10 weeks of age) were used. Mice were treated intraperitoneally with 5 mg/kg P. gingivalisLPS every 84 h for 1 month. Three days after the last injection, the mice were sacrificed by cervical dislocation under deep anesthesia and the pancreas was extracted. Mice treated with normal saline were used as controls. A portion of the pancreatic tissue was fixed with formaldehyde, embedded in paraffin, sliced, and observed microscopically with hematoxylin and eosin staining. Total RNA was extracted from the remaining pancreas and a microarray analysis performed. The qPCR was carried out to confirm the reproducibility of the microarray data. Results were compared by Mann-Whitney U test with P-value <0.05 accepted as statistically significant. Also, the results were assessed using the Ingenuity Pathway Analysis (IPA).
Results: 1029 probes were overexpressed more than 2-fold, and 326 were underexpressed 0.5-fold, in pancreatic cells from mice treated with LPS compared to controls. By qPCR the expression level of Ighg3 and Igk mRNAs in the experimental group were significantly higher than in the control (p<0.05). The IPA showed that the changes in gene expression induced by treatment with LPS were indicative of immunological disease.
Conclusions: These results indicate that LPS from P. gingivalis may affect immunological