Interferon-mediated reprogramming of membrane cholesterol to evade bacterial toxins.

Plasma membranes of animal cells are enriched for cholesterol. Cholesterol-dependent cytolysins (CDCs) are pore-forming toxins secreted by bacteria that target membrane cholesterol for their effector function. Phagocytes are essential for clearance of CDC-producing bacteria; however, the mechanisms by which these cells evade the deleterious effects of CDCs are largely unknown. Here, we report that interferon (IFN) signals convey resistance to CDC-induced pores on macrophages and neutrophils. We traced IFN-mediated resistance to CDCs to the rapid modulation of a specific pool of cholesterol in the plasma membrane of macrophages without changes to total cholesterol levels. Resistance to CDC-induced pore formation requires the production of the oxysterol 25-hydroxycholesterol (25HC), inhibition of cholesterol synthesis and redistribution of cholesterol to an esterified cholesterol pool. Accordingly, blocking the ability of IFN to reprogram cholesterol metabolism abrogates cellular protection and renders mice more susceptible to CDC-induced tissue damage. These studies illuminate targeted regulation of membrane cholesterol content as a host defense strategy.

RORgammat and commensal microflora are required for the differentiation of mucosal interleukin 22-producing NKp46+ cells.

The mucosal immune system of the intestine is separated from a vast array of microbes by a single layer of epithelial cells. Cues from the commensal microflora are needed to maintain epithelial homeostasis, but the molecular and cellular identities of these cues are unclear. Here we provide evidence that signals from the commensal microflora contribute to the differentiation of a lymphocyte population coexpressing stimulatory natural killer cell receptors and the transcription factor RORgammat that produced interleukin 22 (IL-22). The emergence of these IL-22-producing RORgammathiNKp46+NK1.1(int) cells depended on RORgammat expression, which indicated that these cells may have been derived from lymphoid tissue-inducer cells. IL-22 released by these cells promoted the production of antimicrobial molecules important in the maintenance of mucosal homeostasis.

Regulated expression of nuclear receptor RORγt confers distinct functional fates to NK cell receptor-expressing RORγt(+) innate lymphocytes.

Whether the recently identified innate lymphocyte population coexpressing natural killer cell receptors (NKRs) and the nuclear receptor RORγt is part of the NK or lymphoid tissue inducer (LTi) cell lineage remains unclear. By using adoptive transfer of genetically tagged LTi-like cells, we demonstrate that NKR⁻RORγt(+) innate lymphocytes but not NK cells were direct progenitors to NKR(+)RORγt(+) cells in vivo. Genetic lineage tracing revealed that the differentiation of LTi-like cells was characterized by the stable upregulation of NKRs and a progressive loss of RORγt expression. Whereas interleukin-7 (IL-7) and intestinal microbiota stabilized RORγt expression within such NKR-LTi cells, IL-12 and IL-15 accelerated RORγt loss. RORγt(+) NKR-LTi cells produced IL-22, whereas RORγt⁻ NKR-LTi cells released IFN-γ and were potent inducers of colitis. Thus, the RORγt gradient in NKR-LTi cells serves as a tunable rheostat for their functional program. Our data also define a previously unappreciated role of RORγt⁻ NKR-LTi cells for the onset or maintenance of inflammatory bowel diseases.

Biologics and atherosclerotic cardiovascular risk in rheumatoid arthritis: a review of evidence and mechanistic insights.

Introduction: Cardiovascular disease is a leading comorbidity in rheumatoid arthritis. Timely introduction of biologic therapies in a treat-to-target approach has optimized disease-related outcomes and attenuated accrual of comorbidities, including cardiovascular risk.Areas covered: A literature search in MEDLINE (via PubMed) was performed between January 2009 and November 2020. This manuscript explores recent developments in atherosclerotic cardiovascular risk in RA compared with non-RA individuals; it synopsizes differences in vascular function and inflammation, prevalence, burden, vulnerability, and progression of atherosclerotic plaque and their underlying cellular and molecular mechanisms. Finally, it reviews the recent literature on cardioprotective benefits of biologics and draws mechanistic links with inhibition of new plaque formation, stabilization of high-risk lesions and improvement in endothelial function, arterial stiffness, lipid metabolism, and traditional cardiac risk factors.Expert opinion: Increasing evidence points to a solid cardioprotective influence of earlier, longer, and ongoing use of biologic treatments in RA. Nevertheless, the precise mechanistic effects of plaque progression and remodeling, vascular stiffness, endothelial dysfunction, lipid metabolism, and traditional cardiac risk factors are less rigorously characterized.

Beta-2-glycoprotein-I IgA antibodies predict coronary plaque progression in rheumatoid arthritis.

OBJECTIVES: To evaluate whether anti-Beta-2-Glycoprotein-I (anti-ß2GPI) IgA antibodies associate with progression of coronary atherosclerosis and cardiovascular disease (CVD) events in rheumatoid arthritis (RA). METHODS: One hundred-fifty patients underwent plaque evaluation (total, non-calcified, mixed and calcified) with coronary computed tomography angiography; 101 were re-imaged within 6.9±0.3 years to assess progression. The Framingham-D'Agostino score assessed cardiovascular risk. Coronary artery calcium (CAC) and segment involvement score quantified plaque burden. RESULTS: Anti-ß2GPI IgA were seen in 45 (30%) patients. Despite no link to baseline plaque burden, anti-ß2GPI IgA associated with segment involvement score increase (adjusted-RR=1.64 [95%CI 1.02-2.63]), CAC change (adjusted-ß=0.33 [95%CI 0.002-0.656]) and developing new extensive or obstructive plaque at follow-up (adjusted-OR=4.24 [95%CI 1.30-13.87]). Adding anti-ß2GPI IgA to logistic regression models with conventional risk factors predicting plaque progression outcomes increased Area under the receiver-operator curve and improved Net Reclassification and Integrated Discrimination Improvement indices (all P<0.05). In per-segment analyses, anti-ß2GPI IgA predicted mixed plaque formation (adjusted-OR=3.20 [95%CI 1.01-10.09]) and lower likelihood of transition of mixed to calcified plaque (adjusted-OR=0.19 [95%CI 0.04-0.96]). Anti-ß2GPI IgA moderated the effect of C-reactive protein on CAC change such that C-reactive protein associated with CAC change (ß=0.26 [95%CI 0.14-0.38]) and CVD risk (adjusted-HR=1.89 [95%CI 1.02-3.51]) only in anti-ß2GPI IgA positive patients. CONCLUSION: Anti-ß2GPI IgA addition to clinical risk models improved prediction accuracy of CAC, plaque progression and transition to extensive/obstructive disease. They associated with new high-risk mixed plaques and delayed healing to calcified lesions. Anti-ß2GPI IgA further modified the effect of inflammation on plaque progression and CVD events.

Toll-Like Receptors Induce Signal-Specific Reprogramming of the Macrophage Lipidome.

Macrophages reprogram their lipid metabolism in response to activation signals. However, a systems-level understanding of how different pro-inflammatory stimuli reshape the macrophage lipidome is lacking. Here, we use complementary "shotgun" and isotope tracer mass spectrometry approaches to define the changes in lipid biosynthesis, import, and composition of macrophages induced by various Toll-like receptors (TLRs) and inflammatory cytokines. "Shotgun" lipidomics data revealed that different TLRs and cytokines induce macrophages to acquire distinct lipidomes, indicating their specificity in reshaping lipid composition. Mechanistic studies showed that differential reprogramming of lipid composition is mediated by the opposing effects of MyD88- and TRIF-interferon-signaling pathways. Finally, we applied these insights to show that perturbing reprogramming of lipid composition can enhance inflammation and promote host defense to bacterial challenge. These studies provide a framework for understanding how inflammatory stimuli reprogram lipid composition of macrophages while providing a knowledge platform to exploit differential lipidomics to influence immunity.