Abstract
AIM: To investigate the role of signal transducer and activator of transcription 3 (STAT3) and peroxisome proliferator-activated receptor-γ (PPAR-γ) in the pathogenesis of ulcerative colitis (UC) in mice, and the effect of curcumin on STAT3 pathway, cyclooxygenase-2 (COX-2), and peroxisome proliferator-activated receptor γ (PPAR-γ) in UC.
METHODS: Sixty female BALB/c mice were randomly and equally divided into six groups: A (normal group), B (model group), C [dexamethasone intervention group, 1.5 mg/(kg•d)], L [low dose curcumin group, 25 mg/(kg•d)], M [medium dose curcumin group, 50 mg/(kg•d)], and H (high dose curcumin group, 100 mg/(kg•d)]. UC was induced in mice with dextran sodium sulfate. Disease activity index (DAI) scores were calculated in UC mice. HE staining was performed for observing colonic histological changes. PPAR-γ and STAT3 expression was detected by immunohistochemistry. The expression of COX-2 was detected by ELISA, the expression of p-STAT3 was detected by Western blot, and the expression of STAT3 mRNA was detected by RT-PCR.
RESULTS: Mice in group B showed symptoms and histological changes consistent with UC standards. DAI and histological scores in group B were higher than those in group A, but compared with group B, DAI and histological scores in groups C, L, M and H showed varying degrees of decrease. Immunohistochemical results showed that the expression of PPAR-γ in mouse colon in group B was lower than that in group A (23.15 ± 2.33 vs 42.07 ± 3.82, P < 0.01). The expression of STAT3 in mouse colon in group B was significantly higher than that in groups A, C, L, M and H (66.36 ± 6.08 vs 28.25 ± 2.84, 29.84 ± 3.32, 45.26 ± 5.42, 29.02 ± 3.28, 21.22 ± 3.30, P < 0.01). The expression of COX-2 in mouse colon in groups C, L, M and H was lower than that in group B (P < 0.01). The expression of p-STAT3 in mouse colon in group B was significantly higher than that in group A, but lower than that in groups C, L, M and H (P < 0.05). The expression of STAT3 mRNA in mouse colon in group B was significantly higher than that in group A, but lower than that in groups C, L, M and H (P < 0.05).
CONCLUSION: STAT3 and PPAR-γ may participate in the pathogenesis of UC. The mechanism of curcumin for treating UC may be through increasing the expression of PPAR-γ, inhibiting STAT3 signaling pathway, reducing the release of COX-2, decreasing neutrophil infiltration and thus attenuating colonic mucosa damage.
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