Truncating NFKB1 variants cause combined NLRP3 inflammasome activation and type I interferon signaling and predispose to necrotizing fasciitis.

In monogenic autoinflammatory diseases, mutations in genes regulating innate immune responses often lead to uncontrolled activation of inflammasome pathways or the type I interferon (IFN-I) response. We describe a mechanism of autoinflammation potentially predisposing patients to life-threatening necrotizing soft tissue inflammation. Six unrelated families are identified in which affected members present with necrotizing fasciitis or severe soft tissue inflammations. Exome sequencing reveals truncating monoallelic loss-of-function variants of nuclear factor κ light-chain enhancer of activated B cells (NFKB1) in affected patients. In patients' macrophages and in NFKB1-variant-bearing THP-1 cells, activation increases both interleukin (IL)-1ß secretion and IFN-I signaling. Truncation of NF-κB1 impairs autophagy, accompanied by the accumulation of reactive oxygen species and reduced degradation of inflammasome receptor nucleotide-binding oligomerization domain, leucine-rich repeat-containing protein 3 (NLRP3), and Toll/IL-1 receptor domain-containing adaptor protein inducing IFN-ß (TRIF), thus leading to combined excessive inflammasome and IFN-I activity. Many of the patients respond to anti-inflammatory treatment, and targeting IL-1ß and/or IFN-I signaling could represent a therapeutic approach for these patients.

Native and oxidised lipoproteins negatively regulate the serum amyloid A-induced NLRP3 inflammasome activation in human macrophages.

OBJECTIVES: The NLRP3 inflammasome plays a key role in arterial wall inflammation. In this study, we elucidated the role of serum lipoproteins in the regulation of NLRP3 inflammasome activation by serum amyloid A (SAA) and other inflammasome activators. METHODS: The effect of lipoproteins on the NLRP3 inflammasome activation was studied in primary human macrophages and THP-1 macrophages. The effect of oxidised low-density lipoprotein (LDL) was examined in an in vivo mouse model of SAA-induced peritoneal inflammation. RESULTS: Native and oxidised high-density lipoproteins (HDL3) and LDLs inhibited the interaction of SAA with TLR4. HDL3 and LDL inhibited the secretion of interleukin (IL)-1ß and tumor necrosis factor by reducing their transcription. Oxidised forms of these lipoproteins reduced the secretion of mature IL-1ß also by inhibiting the activation of NLRP3 inflammasome induced by SAA, ATP, nigericin and monosodium urate crystals. Specifically, oxidised LDL was found to inhibit the inflammasome complex formation. No cellular uptake of lipoproteins was required, nor intact lipoprotein particles for the inhibitory effect, as the lipid fraction of oxidised LDL was sufficient. The inhibition of NLRP3 inflammasome activation by oxidised LDL was partially dependent on autophagy. Finally, oxidised LDL inhibited the SAA-induced peritoneal inflammation and IL-1ß secretion in vivo. CONCLUSIONS: These findings reveal that both HDL3 and LDL inhibit the proinflammatory activity of SAA and this inhibition is further enhanced by lipoprotein oxidation. Thus, lipoproteins possess major anti-inflammatory functions that hinder the NLRP3 inflammasome-activating signals, particularly those exerted by SAA, which has important implications in the pathogenesis of cardiovascular diseases.

Hydroxychloroquine reduces interleukin-6 levels after myocardial infarction: The randomized, double-blind, placebo-controlled OXI pilot trial.

OBJECTIVES: To determine the anti-inflammatory effect and safety of hydroxychloroquine after acute myocardial infarction. METHOD: In this multicenter, double-blind, placebo-controlled OXI trial, 125 myocardial infarction patients were randomized at a median of 43 h after hospitalization to receive hydroxychloroquine 300 mg (n = 64) or placebo (n = 61) once daily for 6 months and, followed for an average of 32 months. Laboratory values were measured at baseline, 1, 6, and 12 months. RESULTS: The levels of interleukin-6 (IL-6) were comparable at baseline between study groups (p = 0.18). At six months, the IL-6 levels were lower in the hydroxychloroquine group (p = 0.042, between groups), and in the on-treatment analysis, the difference at this time point was even more pronounced (p = 0.019, respectively). The high-sensitivity C-reactive protein levels did not differ significantly between study groups at any time points. Eleven patients in the hydroxychloroquine group and four in the placebo group had adverse events leading to interruption or withdrawal of study medication, none of which was serious (p = 0.10, between groups). CONCLUSIONS: In patients with myocardial infarction, hydroxychloroquine reduced IL-6 levels significantly more than did placebo without causing any clinically significant adverse events. A larger randomized clinical trial is warranted to prove the potential ability of hydroxychloroquine to reduce cardiovascular endpoints after myocardial infarction.