Sitagliptin Repress NALP3 Inflammasome In 3T3-L1 Cells

Background.Recent studies discovered that NALP3 plays an important role in T2DM, a disease threaten human health. Drugs targeting NALP3 and its relevant pathways in diabetes treatment are in its infancy. Our previous study indicated sitagliptin might have an inhibitive effect on NALP3. The purpose of our present study is to evaluate the inhibitive effect of sitagliptin in 3T3-L1 cells, explore the mechanisms.Methods.We grew 3T3-L1 cells and stimulated differentiation when the density of cells>90%. At the same time, drugs were added as designed:control group and sitagliptin group in various concentrations for different days. IL-1β、IL-18、IL-6、TNF-α secretion of 3T3-L1 cells was determined by enzyme-linked immune sorbent assay, ELISA. Western blot was performed to investigate the expression of NALP3 proteins. Real-time PCR was performed to assess NALP3、ASC、caspase-1 RNA expression. Western blot was performed to investigate the expression of NF-κB and IκBα proteins.Meanwhile, We grew 3T3-L1 cells and stimulated differentiation when the density of cells >90%. Drugs were added as designed for 2 days:control group, lOnM sitagliptin group, lOnM sitagliptin+10nM Exendin 9-39 group, 10nM sitagliptin+50nM Exendin 9-39 group. IL-1β、IL-18、IL-6、 TNF-α secretion of 3T3-L1 cells was determined by ELISA.Results.1. Treatment of 3T3-L1 cells with 5-100 nM of sitagliptin resulted in a dose-dependent decrease in cell IL-1β, TNF-α, IL-18, IL-6 secretion.2. Treatment of 3T3-L1 cells with 10 nM of sitagliptin for 2-10 days resulted in a time-dependent decrease in cell IL-1β, TNF-α, IL-18, IL-6 secretion.3. When cells were treated with 5-100 nM of sitagliptin, a decrease of ASC and Caspasel expression was observed. Conversely, the expression of pro-caspasel increased in a dose-dependent manner.4. When cells were treated with 10 nM of sitagliptin, a time-dependent decrease of ASC and Caspasel expression was observed. Conversely, the expression of pro-caspasel increased in a time-dependent manner.5. When cells were treated with 5-100 nM of sitagliptin, a decrease of ASC, NLRP3 and Caspasel RNA expression was observed. Conversely, the expression of pro-caspasel RNA increased in a dose-dependent manner.6. When cells were treated with 10 or 50 nM of Exendin 9-39, the decrease effect of sitagliptin in cell IL-1β, TNF-α, IL-18, IL-6 secretion was antagonized.7. When cells were treated with 10 nM of sitagliptin, a decrease of p65 protein expression was observed. Conversely, the expression of IκBα protein increased.Conclusion.Sitagliptin inhibits the IL-1β, TNF-α, IL-18 and IL-6 secretion of 3T3-L1 cells in a dose- and time-dependent manner; in the meantime, Sitagliptin inhibits ASC, Caspasel protein expression and NALP3, ASC, Caspasel mRNA expression. The results suggest sitagliptin repress NALP3 inflammasome, interleukin-1β, IL-6, IL-18, TNF-α via GLP-1 receptor in 3T3-L1 cells through NF-κB pathway.