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P090 Differences in expression of G protein–coupled receptor 55 (GPR55) in patients with Crohn’s disease and ulcerative colitis

M. Wlodarczyk*1, A. Sobolewska-Włodarczyk1, A. Cygankiewicz2, D. Jacenik2, W. Krajewska3, K. Stec-Michalska1, A. Piechota-Polanczyk4, J. Fichna4, M. Wisniewska-Jarosinska1

1Medical University of Lodz, Department of Gastroenterology, Lodz, Poland, 2University of Lodz, Department of Cytobiochemistry, Lodz, Poland, 3University of Lodz, Cytobiochemistry, Lodz, Poland, 4Medical University of Lodz, Department of Biochemistry, Lodz, Poland

Background

G protein–coupled receptor 55 (GPR55) is a newly discovered cannabinoid (CB) receptor, which has been qualified as part of the endogenous CB system along with ‘classical’ receptors CB1 and CB2. There is a growing interest in the possible use of CB receptor agonists in the treatment of inflammation and abdominal pain. Here we attempted at establishing the levels of GPR55 expression in colonic tissue of inflammatory bowel disease (IBD) patients and healthy controls, and its potential implication in IBD treatment.

Methods

Enrolled in the study were 50 IBD patients: n = 21 with Crohn’s disease (CD) and n = 16 with ulcerative colitis (UC), 19 women and 18 men. Controls consisted of 13 healthy non-IBD patients. In each subject, 2 biopsies were taken from different left-side colonic locations. In IBD patients, biopsies both from endoscopically inflamed and non-inflamed areas were drawn and confirmed in histopatological examination. GPR55 mRNA and protein expression were measured using real-time RT-polymerase chain reaction (PCR), and Western blot, respectively.

Results

GPR55 expression on mRNA and protein level was detected in all samples tested. The level of GPR55 mRNA expression in non-inflamed colonic areas was comparable in all analysed groups (p = 0.2438). However, in the inflamed tissues, GPR55 mRNA expression was statistically significantly higher (6.9 fold) in CD patients compared with UC (105 014 ± 17 772 vs 15 310 ± 2 039; 
p < 0.0001) (Figure 1).

The CD patients manifested higher (12.5 fold) GPR55 mRNA expression in inflamed compared with non-inflamed colonic tissues (105 014 ± 17 772 vs 8 425 ± 2 075; p < 0.0001). In contrast, the analysis of GPR55 mRNA expression in UC patients revealed no statistically significant differences between inflamed and non-inflamed colonic tissue samples (15 310 ± 2 039 vs 29 552 ± 11 583; p = 0.7170). The GPR55 protein expression was detected in all tested colonic tissues. However, there were similar levels of GPR55 protein expression in non-inflamed colonic tissues in all analysed groups (p = 0.3121). No statistical differences in GPR55 expression at protein level amongst inflamed colonic tissues were observed (781.5 ± 90.3 vs 669.3 ± 58.1; p = 0.3208). Finally, no statically significant differences in GPR55 protein expression levels in unaffected compared with inflamed colonic tissue were observed in CD (781.5 ± 90.3 vs 745.4 ± 79.3; p = 0.7095) and UC (669.3 ± 58.1 vs 544.6 ± 98.5; p = 0.4885) patients.

Conclusion

Different patterns of expression of GPR55 at mRNA levels were observed in IBD patients. We speculate that GPR55 is crucial for the mucosal inflammatory processes in IBD, particularly in CD and may affect disease severity, as well as response to treatment. The GPR55 receptors may become an attractive target for novel therapeutic strategies in IBD.