An update on the pathophysiology of acute and recurrent pericarditis

INTRODUCTION: Pericarditis is an inflammatory disease of the pericardium. Progress has been done in recent years in the understanding of its pathophysiology. In particular, preclinical and clinical studies have contributed to increasing our knowledge on the role of interleukin (IL)-1 and NLRP3 (NACHT, leucine-rich repeat, and pyrin domain-containing protein 3) inflammasome. EVIDENCE ACQUISITION: Information for this study has been retrieved in original articles, reviews, systematic reviews, and meta-analyses identified through PubMed using the following search terms (or combination of terms): "pericarditis," "acute pericarditis," "recurrent pericarditis," "idiopathic recurrent acute pericarditis," "autoimmunity," "autoinflammation," "outcomes." Only articles published in English were included. Additional papers identified from the reference list of the retrieved articles were also considered. EVIDENCE SYNTHESIS: Based on current evidence, pericarditis should be considered as an inflammatory reaction to various stimuli, including chemical/physical, infectious, or ischemic ones, with a viral infection being a common etiology. Interaction of pathogens or irritants with toll like receptor (TLRs) and stimulation of IL-1 receptor by IL-1 alpha and IL-1 beta leads to an increased transcription of proinflammatory genes, including those needed for NLRP3 inflammasome assembly. This pathway is confirmed indirectly by the beneficial effect of colchicine (an indirect NLRP3 inflammasome inhibitor) and IL-1 blockers in patients with recurrent pericarditis. More recently, a direct evidence of the NLRP3 inflammasome within the inflamed pericardium has been provided as well. It may, however, occur that self-antigens on the surface of mesothelial cells or microbial peptides may stimulate autoreactive T cells along with B cells producing antiheart antibodies, although less evidence is available on this. CONCLUSIONS: Some uncertainties still remain about the role of neutrophils, neutrophil extracellular traps (NETs), and pericardial interstitial cells in recurrent and constrictive pericarditis. Unraveling these aspects might have a direct impact on the development of novel targeted therapies, especially considering the increasing number of drugs targeting NETs.