Endotoxinemia Accelerates Atherosclerosis Through Electrostatic Charge-Mediated Monocyte Adhesion.

BACKGROUND: Acute infection is a well-established risk factor of cardiovascular inflammation increasing the risk for a cardiovascular complication within the first weeks after infection. However, the nature of the processes underlying such aggravation remains unclear. Lipopolysaccharide derived from Gram-negative bacteria is a potent activator of circulating immune cells including neutrophils, which foster inflammation through discharge of neutrophil extracellular traps (NETs). Here, we use a model of endotoxinemia to link acute infection and subsequent neutrophil activation with acceleration of vascular inflammation Methods: Acute infection was mimicked by injection of a single dose of lipopolysaccharide into hypercholesterolemic mice. Atherosclerosis burden was studied by histomorphometric analysis of the aortic root. Arterial myeloid cell adhesion was quantified by intravital microscopy. RESULTS: Lipopolysaccharide treatment rapidly enhanced atherosclerotic lesion size by expansion of the lesional myeloid cell accumulation. Lipopolysaccharide treatment led to the deposition of NETs along the arterial lumen, and inhibition of NET release annulled lesion expansion during endotoxinemia, thus suggesting that NETs regulate myeloid cell recruitment. To study the mechanism of monocyte adhesion to NETs, we used in vitro adhesion assays and biophysical approaches. In these experiments, NET-resident histone H2a attracted monocytes in a receptor-independent, surface charge-dependent fashion. Therapeutic neutralization of histone H2a by antibodies or by in silico designed cyclic peptides enables us to reduce luminal monocyte adhesion and lesion expansion during endotoxinemia. CONCLUSIONS: Our study shows that NET-associated histone H2a mediates charge-dependent monocyte adhesion to NETs and accelerates atherosclerosis during endotoxinemia.

Stability of pyrrolizidine alkaloids from Senecio vernalis in grass silage under different ensilage conditions.

BACKGROUND: This study evaluated the degradation of pyrrolizidine alkaloids (PAs) from eastern groundsel (Senecio vernalis) in grass silage prepared with different inoculants. Silages were produced from ryegrass with 230 g kg-1 dry matter (DM) content and mixed with eastern groundsel (9:1; w/w fresh matter basis) containing 5.5 g kg-1 DM PA. Treatments were: CON (untreated control), LP (3.0 × 105 cfu g-1 Lactobacillus plantarum DSMZ 8862/8866) or LBLC (7.3 × 104 cfu g-1 Lactobacillus buchneri LN40177 / Lactobacillus casei LC32909), and each of the treatments in combination with 30 g kg-1 molasses. Silages were prepared in glass jars and opened after 3, 10, and 90 days. Fermentation characteristics were determined and the PAs analyzed. RESULTS: Although the levels of fermentation acids differed between treatments, results indicated good quality of all silages during 90 days. Significant time (P < 0.001) and treatment (P < 0.001) effects were observed for PAs. Concentrations of senecionine and seneciphylline decreased with molasses, declined over time, and were negatively correlated with lactic, propionic, and butyric acid, or with lactic and butyric acid in case of seneciphylline. In all silages, seneciphylline and senecionine N-oxides were undetectable after 3 days, whereas senkirkine, the most abundant PA, remained stable. CONCLUSIONS: Silage prepared from grass contaminated with eastern groundsel still contained high PA levels, and was hence a potential health hazard. Molasses supplementation reduced concentrations of senecionine and seneciphylline, while the bacterial inoculants had no effect. Other potentially toxic PA metabolites were not analyzed in the present study and further research is needed. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Externalized histone H4 orchestrates chronic inflammation by inducing lytic cell death.

The perpetuation of inflammation is an important pathophysiological contributor to the global medical burden. Chronic inflammation is promoted by non-programmed cell death1,2; however, how inflammation is instigated, its cellular and molecular mediators, and its therapeutic value are poorly defined. Here we use mouse models of atherosclerosis-a major underlying cause of mortality worldwide-to demonstrate that extracellular histone H4-mediated membrane lysis of smooth muscle cells (SMCs) triggers arterial tissue damage and inflammation. We show that activated lesional SMCs attract neutrophils, triggering the ejection of neutrophil extracellular traps that contain nuclear proteins. Among them, histone H4 binds to and lyses SMCs, leading to the destabilization of plaques; conversely, the neutralization of histone H4 prevents cell death of SMCs and stabilizes atherosclerotic lesions. Our data identify a form of cell death found at the core of chronic vascular disease that is instigated by leukocytes and can be targeted therapeutically.

Chrono-pharmacological Targeting of the CCL2-CCR2 Axis Ameliorates Atherosclerosis.

Onset of cardiovascular complications as a consequence of atherosclerosis exhibits a circadian incidence with a peak in the morning hours. Although development of atherosclerosis extends for long periods of time through arterial leukocyte recruitment, we hypothesized that discrete diurnal invasion of the arterial wall could sustain atherogenic growth. Here, we show that myeloid cell recruitment to atherosclerotic lesions oscillates with a peak during the transition from the activity to the resting phase. This diurnal phenotype is regulated by rhythmic release of myeloid cell-derived CCL2, and blockade of its signaling abolished oscillatory leukocyte adhesion. In contrast, we show that myeloid cell adhesion to microvascular beds peaks during the early activity phase. Consequently, timed pharmacological CCR2 neutralization during the activity phase caused inhibition of atherosclerosis without disturbing microvascular recruitment. These findings demonstrate that chronic inflammation of large vessels feeds on rhythmic myeloid cell recruitment, and lay the foundation for chrono-pharmacology-based therapy.