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OP013. Status of ER stress and autophagy in Crohn's disease: From genetics to functional read-outs

K. Nys1, W. Vanhove1, I. Cleynen1, M. Ferrante1, G. Van Assche1, P. Rutgeerts1, P. Agostinis2, S. Vermeire1, 1Department of Clinical and Experimental Medicine, KU Leuven, Translational Research in GastroIntestinal Disorders, Leuven, Belgium, 2KU Leuven, Cellular & Molecular Medicine, Leuven, Belgium

Background

The imminent introduction of new therapeutic classes for inflammatory bowel disease patients emphasizes the need for efficient personalized medicine. Large-scale studies have identified several stress and inflammatory signaling pathways to be important during Crohn's disease (CD) and ulcerative colitis (UC) pathogenesis. However, it remains unclear if and how the identified genetic variants correlate with a functional response. Therefore, we aimed to study the association of CD-associated genetic variants with deficiencies in myeloid cell function isolated from patients samples.

Methods

Peripheral blood-myeloid cells, isolated from 182 individuals (36 healthy controls and 146 CD patients), all genotyped by immunochip, were exposed to an inflammatory stimulus (LPS), ER stress (thapsigargin) or autophagy modulation (inhibition with chloroquine). We assessed the correlation of immune function, ER stress and autophagy of the myeloid cells with CD-associated genetic variants linked to innate immunity (NOD2), ER stress (XBP1, ORMDL3) and autophagy genes (ATG16L1, IRGM, ULK1, MTMR-3, LRRK2) in patients and controls.

Results

Compared to healthy individuals, CD patients showed a significant increase of LPS-induced cytokine levels [TNF, IL-6/10/1beta secretion: 29.4–139% median increase, p = 0.01–0.04]; increased levels of Bip (300% basal median increase, p = 0.02; 173.1% median increase with added stress, p = 0.02), an important ER chaperone, and 22.1% increased accumulation of p62 (p = 0.04), an autophagy-related tagging protein, after autophagy inhibition. When comparing patients according to their genetic risk load, “high genetic risk” patients (>7 risk alleles, corresponding to Q4 of the distribution of risk alleles; n = 98) had a 4.6–45.1% increased release of TNF and IL-6/10/1beta after LPS exposure, increased ER stress (21.7% basal; 39.9% with added stress) and 14.6% decreased autophagic activity (p = 0.03) compared to ‘low genetic risk’ patients (<4 risk alleles, corresponding to Q1 of the distribution of risk alleles; n = 57). Moreover, for individual risk loci such as ATG16L1, IRGM, MTMR-3, XBP1, ORMDL3 and NOD2 an augmented LPS-induced cytokine release was observed with increasing risk alleles.

Conclusion

Our data suggest that blood-myeloid cells from CD patients typically show a more severe LPS-induced cytokine response, increased unresolved ER stress and increased autophagic demand. Our study also indicates that the burden of risk alleles, in these pathways or in individual susceptibility loci, correlates with the LPS-induced cytokine response, the level of ER stress and the autophagic rate. These findings highlight the promising potential of using these functional read-outs for personalized management of Crohn's disease.