Protective effects of curcumin against rat intestinal inflammation‑related motility disorders

Abstract

Intestinal inflammation frequently occurs alongside dysmotility, which is characterized by altered myosin light chain phosphorylation levels. Curcumin, an active component from the ginger family, is reported to confer anti‑inflammatory effects. However, the effects of curcumin on both diarrhea and constipation associated inflammation remains to be elucidated. The present study was designed to investigate the effects of curcumin on diarrhea and constipation and to determine the related mechanisms. Sprague‑Dawley rats were used to establish diarrhea and constipation models via intracolonic acetic acid (4%) instillation or cold water gavage for 2 weeks, respectively. Blood samples were collected to measure the serum levels of the cytokines TNF‑α and IL‑1β using ELISA kits. Western blotting was performed to measure NF‑κB, RhoA, Rho‑related kinase 2, phosphorylated MLC₂₀, phosphorylated myosin phosphorylated target subunit 1, 130k Da‑MLC kinase (MLCK), c‑kit tyrosine kinase protein expression, and reverse transcription‑quantitative PCR was conducted to measure MLCK expression levels. The results indicated that curcumin reversed the elevations in the pro‑inflammatory cytokines IL‑1β and TNF‑α by inhibiting the NF‑κB pathway in rats with diarrhea and constipation. The results also indicated that myosin light chain (MLC) phosphorylation in intestinal smooth muscle was positively and negatively associated with the motility of inflammation‑related diarrhea and constipation in rats, respectively. Curcumin significantly reversed the increased MLC phosphorylation in the jejunum of the rats with diarrhea, significantly enhanced the reductions in inflammatory mediators, including TNF‑α and IL‑1β, of rats with constipation and significantly ameliorated the related hyper‑motility and hypo‑motility in rats with both diarrhea and constipation. In conclusion, the potential roles of the MLC kinase, c‑kit tyrosine and Rho A/Rho‑associated kinase 2 pathways, which are involved in curcumin‑induced amelioration of inflammation‑related diarrhea and constipation, were explored in the present study. Results from the present study suggested that curcumin has potential therapeutic value for treating intestinal inflammation and inflammation‑related motility disorders.

Keywords: curcumin; NF‑κB; Rho kinase pathway; myosin light chain phosphorylation; inflammation.

Figure 1.

Chemical structure of curcumin.

Figure 2.

TNF-α and IL-1β release in DP and CP rat models and curcumin inhibits NF-κB p65 translocation in DP and CP models. Effects of curcumin on and (A) IL-1β and (B) TNF-α release in the serum of DP and CP rat models. **P<0.05 vs. Sham and ^##P<0.05 CP or DP. (C) Western blotting analysis for protein expression levels of cytoplasmic IκB. (D) Western blotting analysis for protein levels of nuclear NF-κB p65. (E) Western blotting analysis for protein levels of phosphorylated p65. **P<0.05 vs. Sham and ^##P<0.05 vs. DP or CP. IL-1β, interleukin-1β; TNF-α, tumor necrosis factor-α; DP, diarrhea-prominent; CP, constipation-prominent; Cur, curcumin; p, phosphorylated; IκB, inhibitor of NF-κB.

Figure 3.

Effect of curcumin on MLC phosphorylation in curcumin treated diarrhea- DP and CP rat models. (A) Western blotting analysis of phosphorylation levels of MLC₂₀ in CP rats. (B) Western blotting analysis of phosphorylation levels of MLC₂₀ in DP rats. **P<0.05 vs. Sham and ^##P<0.05 vs. DP or CP. DP, diarrhea-prominent; CP, constipation-prominent; Cur, curcumin; MLC, myosin light chain; p-, phosphorylated.

Figure 4.

Effect of curcumin on long and short isoform MLCK, MLCK mRNA and MYPT1 expression. (A) Western blotting analysis of protein expression levels of MLCK. (B) MLCK mRNA expression levels by RT-qPCR analysis in CP and DP rats. (C) Western blot analysis of protein expression levels of RhoA and ROCKII in CP and DP rats. (D) Western blotting analysis for protein expression levels of phosphorylated MYPT1 and total MYPT1 in CP and DP rats. **P<0.05 vs. Sham and ^##P<0.05 vs. DP or CP. DP, diarrhea-prominent; CP, constipation-prominent; Cur, curcumin; MLCK, myosin light chain kinase; ROCK II, Rho-associated kinase 2; MYPT1, myosin phosphate target subunit 1; RT-qPCR, reverse transcription-quantitative PCR; P-, phosphorylated.

Figure 5.

Effect of curcumin on protein expression levels of c-kit tyrosine kinase in the intestine of constipation-prominent and diarrhea-prominent related rat groups. **P<0.05 vs. Sham and ^##P<0.05 vs. DP or CP. DP, diarrhea-prominent; CP, constipation-prominent; Cur, curcumin.