Method: The expression of NALP3, apoptosis-associated speck-like protein containing CARD domain (ASC) and NOD2 in erythema nodosum lesions of 25 BD patients and 25 non-BD patients were examined by immunohistochemistry. The mRNA expression of NALP3 and NOD2 were examined by RT-PCR in 20 patients with BD and as control, 10 patients with psoriasis and 10 healthy adults were studied. The altered function of inflammasomes in 20 BD patients was evaluated by measuring the release of IL-1β and TNF-α from PBMCs and monocytes after stimulation using ELISA.
Result: The immunohistochemistry results showed that the expression of NALP3 and ASC was significantly higher in BD patients. Also RT-PCR results showed similar results. However, neither immunohistochemistry nor RT-PCR results showed any difference in NOD2 expression between the groups. When PBMCs from BD patients were stimulated with LPS, IL-1β secretion significantly increased by 58 times. And with ATP, IL-1β release was even more increased by 1.6 times compared to LPS stimulation alone. Caspase-1 inhibitor decreased IL-1β release caused by LPS, however the decrease was less dramatic when ATP was added as a second stimulus. So in PBMCs, LPS stimulation caused large IL-1β release in BD patients but not in healthy controls. But with ATP, IL-1β release increase significantly in healthy controls but not in BD patients. When monocytes from BD patients were stimulated with LPS, IL-1β secretion was increased by 5 times And with ATP, IL-1β release was even more increased by 14 times compared to LPS stimulation alone. So, in BD patients, monocytes secrete impressively greater amounts of mature IL-1β following LPS stimulation, comparable to that of healthy individuals, but fail to increase IL-1β secretion in response to ATP. However, when TNF-α release was measured in a similar way, the result was independent of crosstalk between toll like receptors and NALP3 in BD patients.
Conclusion: This study reveals a role for the NALP3 inflammasome complex in BD. In normal monocytes, 2 signals are required to activate the inflammasome, thus tightly controlling IL-1β secretion but in patients, a single stimulus, which would be unable to trigger IL-1β secretion in healthy individuals, is sufficient to drive a dramatic inflammatory cascade. Modulation of the NALP3 inflammasome activity may delay the inflammatory process and chronic morbidities noticed in patients with BD.
Disclosure: E. H. Kim, None; J. Y. Shin, None; M. J. Park, None; S. Park, None; E. S. Lee, None.