Effect of Curcumin on Systemic T Helper 17 Cell Response; Gingival Expressions of Interleukin‐17 and Retinoic Acid Receptor‐Related Orphan Receptor γt; and Alveolar Bone Loss in Experimental Periodontitis

Background: Curcumin has anti‐inflammatory and antioxidant effects and is reported to have many biologic activities. The current study examines effect of curcumin on: 1) systemic T helper 17 (Th17) cell response; 2) gingival expressions of interleukin (IL)‐17 and retinoic acid receptor‐related orphan receptor (ROR) γt; and 3) alveolar bone loss (ABL) in experimental periodontitis. Methods: Thirty‐eight male albino Wistar rats were divided into four groups: 1) group 1 = periodontitis; 2) group 2 = periodontitis with curcumin treatment; 3) group 3 = periodontally healthy with curcumin treatment; and 4) group 4 = periodontally healthy. Curcumin was administered via oral gavage (30 mg/kg/d) for 15 days. After sacrifice via exsanguination, the following serum levels were determined using enzyme‐linked immunosorbent assay: 1) IL‐1β; 2) IL‐6; 3) IL‐17A; 4) IL‐23; and 5) transforming growth factor‐ β. Morphometric evaluation of ABL was conducted and expression levels of IL‐17 and RORγt in gingival tissues were evaluated immunohistochemically. Results: Group 2 had significantly lower ABL than group 1 ( P <0.0125). Highest expression levels of IL‐17 and RORγt were observed in group 1 and were significantly higher than those in all other groups ( P <0.0125). The only serum biochemical parameter significantly different among groups was level of IL‐23 ( P <0.05). Serum IL‐23 levels were higher in groups 1 and 2 than groups 3 and 4 ( P <0.0125); however, they were not significantly different for groups 1 and 2 ( P >0.0125). Conclusion: Curcumin seems to be a promising host modulatory agent in periodontal disease pathogenesis regarding IL‐17/IL‐23 axis, with a decreasing effect on ABL and gingival expressions of IL‐17 and RORγt.