Abstract Body (Do not enter title and authors here): Background. Pericarditis is the inflammation of the pericardial sac, and it has been associated with the activation of the NLRP3 inflammasome, which regulates Interleukin-1β (IL-1β) release. The use of prednisolone (Pred), a potent anti-inflammatory glucocorticoid, has been associated with relapse, and in patients with systemic lupus erythematosus, with increased risk of pericarditis.
Hypothesis. We aimed to assess the effects of Pred on the NLRP3 inflammasome activation and IL-1β release in cultured macrophages. We hypothesized that long-term Pred treatment fails to inhibit IL-1β release.
Methods. J774A.1 mouse macrophages were primed with lipopolysaccharide (LPS, 1 µg/mL, 6h) to mimic pro-inflammatory conditions, followed by treatment with Pred (10, 1, or 0.1 µM) for 24 h, and then by NLRP3 activation with Adenosine triphosphate (ATP, 5 mM, 30 min). To study the short- and long-term preventive effects of Pred, cells were treated with Pred (10, 1, or 0.1 µM) for 24 hours and 4 weeks, respectively, prior to LPS and ATP. IL-1β concentration was measured by Enzyme-linked immunosorbent assay (ELISA).
Results. When administered after LPS, Pred showed a dose-dependent reduction in IL-1β at 24 h (in pg/ml, LPS+ATP 1136±12, Pred 10 µM 299±5, Pred 1 µM 294±7, Pred 0.1 µM 439±6; all p<0.0001, Fig 1A). Similarly, when Pred was administered 24 h prior to LPS, it showed a dose-dependent reduction in IL-1β release (in pg/ml, LPS+ATP 983±2, Pred 10 µM 31±1, Pred 1 µM 57±3, Pred 0.1 µM 402±4; all p<0.0001, Fig 1B). Paradoxically, long-term Pred pre-treatment for 4 weeks significantly increased IL-1β levels at all tested doses (in pg/ml, LPS+ATP 632±78, Pred 10 µM 734±17, Pred 1 µM 923±25, Pred 0.1 µM 763±74; all p<0.01, Fig 1C).
Conclusion. Short-term Pred exhibits a dose-dependent inhibitory effect on IL-1β release in macrophages, interfering with inflammasome triggering, whereas long-term exposure to Pred exacerbates IL-1β release. This paradoxical difference in effect may help explain both the loss of efficacy of glucocorticoids over time and the increased recurrence of pericarditis observed in patients undergoing prolonged prednisone therapy. Further studies are warranted to clarify the underlying mechanisms.