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Parkinson disease autosomal recessive, early onset 7 (PARK7 or DJ-1) is involved in multiple physiological processes and exerts anti-apoptotic effects on multiple cell types. Increased intestinal epithelial cell (IEC) apoptosis and excessive activation of the p53 signaling pathway is a hallmark of inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn's disease (CD). However, whether DJ-1 plays a role in colitis is unclear. To determine whether DJ-1 deficiency is involved in the p53 activation that results in IEC apoptosis in colitis, here we performed immunostaining, real-time PCR, and immunoblotting analyses to assess DJ-1 expression in human UC and CD samples. In the inflamed intestines of individuals with IBD, DJ-1 expression was decreased and negatively correlated with p53 expression. DJ-1 deficiency significantly aggravated colitis, evidenced by increased intestinal inflammation and exacerbated IEC apoptosis. Moreover, DJ-1 directly interacted with p53, and reduced DJ-1 levels increased p53 levels both in vivo and in vitro and were associated with decreased p53 degradation via the lysosomal pathway. We also induced experimental colitis with dextran sulfate sodium in mice and found that compared with DJ-1−/− mice, DJ-1−/−p53−/− mice have reduced apoptosis and inflammation and increased epithelial barrier integrity. Furthermore, pharmacological inhibition of p53 relieved inflammation in the DJ-1−/− mice. In conclusion, reduced DJ-1 expression promotes inflammation and IEC apoptosis via p53 in colitis, suggesting that the modulation of DJ-1 expression may be a potential therapeutic strategy for managing colitis.

BackgroundThere is no consensus on the vitamin D levels and inflammatory bowel disease (IBD).AimTo conduct a systematic review and meta-analysis to analyze the relationship between IBD and 25(OH)D, sun exposure, and latitude, and to determine whether vitamin D deficiency affects the severity of IBD.MethodsWe searched the PubMed, EBSCO, and ClinicalTrials.gov databases to identify all studies that assessed the association between 25(OH)D, sun exposure, latitude, and IBD through November 1, 2014, without language restrictions. Studies that compared 25(OH)D levels between IBD patients and controls were selected for inclusion in the meta-analysis. We calculated pooled standardized mean differences (SMDs) and odds ratios (ORs).ResultsThirteen case-control studies investigating CD and 25(OH)D levels were included, and eight studies part of above studies also investigated the relationship between UC and 25(OH)D. Both CD patients (SMD: 0.26 nmol/L, 95% confidence interval [CI]: 0.09–0.42 nmol/L) and UC patients (SMD: 0.5 nmol/L, 95% CI: 0.15–0.85 nmol/L) had lower levels of 25(OH)D than controls. In addition, CD patients and UC patients were 1.95 times (OR, 1.95; 95% CI, 1.48–2.57) and 2.02 times (OR, 2.02; 95% CI, 1.13–3.60) more likely to be 25(OH)D deficient than controls. We also included 10 studies investigating the relationship between CD activity and vitamin D. Results showed that patients with active CD (CD Activity Index≥150) were more likely to have low vitamin D levels. In addition, whether low sun exposure and high latitude were related to a high morbidity of CD need to be provided more evidence.ConclusionOur study shows that IBD patients have lower vitamin D levels. For active CD patients, vitamin D levels were low. These findings suggest that vitamin D may play an important role in the development of IBD, although a direct association could not be determined in our study.