Neutrophils as major drivers of increased atherosclerosis in a murine model of chronic colitis

Background

Recent findings showed a higher risk of premature atherosclerosis and cardiovascular events in patients with inflammatory bowel disease (IBD) especially during acute flare of the chronic disease. The underlying mechanisms remain to be defined since traditional risk factors such as hypercholesterinemia are not present in these patients.

Purpose

The present study aimed to unravel the underlying pathomechanisms of enhanced atherogenesis and -progression in a murine model of colitis.

Methods

Chronic colitis was induced in male Apolipoprotein E-deficient mice (Apoe−/−) using dextran sodium sulphate (DSS) in drinking water for 2,3 or 5 cycles, while the control group received regular drinking water. Each cycle consisted of 6 days DSS application and two weeks of recovery. Aortic atherosclerotic plaque burden was determined by en face Oil Red O staining and immune cell subsets were analysed by flow cytometry in the circulation, the bone marrow, and the aorta. Neutrophil depletion was performed via i.p injection of a Ly6G-depleting antibody or respective isotype control. Bone marrow-derived neutrophils were further analysed by transcriptome analysis.

Results

Similar to IBD patients, mice with chronic colitis exhibited an increased aortic plaque burden after 15 weeks of treatment despite the absence of classical risk factors. Over time, both circulating and aortic neutrophils showed an oscillatory detection pattern with the first significant increase after the 2nd DSS administration whereby the second increase after the 3rd DSS cycle was even stronger. Also, pro-inflammatory cytokines were elevated in the plasma and specifically G-CSF showed the same oscillatory pattern with increased plasma level already after the 2nd DSS administration and an even stronger increase after the 3rd thereby pointing towards alterations in bone marrow hematopoiesis. In line, flow cytometric analyses confirmed a greater rise of hematopoietic stem and even myeloid progenitor cells compared with the 2nd DSS application in IBD mice after 3rd treatment. scRNA-Seq analysis of progenitor cells revealed changes in cell differentiation towards neutrophils and upregulation of proinflammatory genes in isolated neutrophils of DSS-treated mice. These neutrophils showed also a more adhesive phenotype revealed by increased mRNA expression of Glg1 and Selplg. Accordingly, also Sele mRNA was increased in the aorta. The reduction of circulating neutrophils by an anti-Ly6G antibody during the acute phases of colitis reduced the aortic plaque burden compared to isotype treaded mice.

Conclusion

The current findings suggest detrimental effects of chronic colitis on atherogenesis and -progression in Apoe−/− mice via increased differentiation of myeloid cells into neutrophils and the promotion of a more adhesive and proinflammatory phenotype. These modified neutrophils may act as initiators of atherogenesis by promoting the invasion of immune cells into the aortic wall.

Funding Acknowledgement

Type of funding sources: None.

Endothelial hyaluronan synthase 3 aggravates acute colitis in an experimental model of inflammatory bowel disease

The association between hyaluronan (HA) accumulation and increased inflammation in the colon suggests that HA is a potential therapeutic target in inflammatory bowel disease (IBD). However, whether patients with IBD would benefit from interference with HA synthesis is unknown. Here, we used pharmacological and genetic approaches to investigate the impact of systemic and partial blockade of HA synthesis in the Dextran Sodium Sulfate (DSS)-induced colitis model. To systemically inhibit HA production, we used 4-Methylumbelliferone (4-MU), whereas genetic approaches included the generation of mice with global or inducible cell-type specific deficiency in the Hyaluronan synthase 3 (Has3). We found that 4-MU treatment did not ameliorate but exacerbated disease severity characterized by increased body weight loss and enhanced colon tissue destruction compared to control mice without colitis. In contrast, global Has3 deficiency had a profound protective effect as reflected by a low colitis score and reduced infiltration of immune cells into the colon. To get further mechanistic insight into the proinflammatory role of HAS3, we deleted Has3 in a cell-type specific manner. Interestingly, while lack of Has3 expression in intestinal epithelial and smooth muscle cells had no effect or was rather proinflammatory, mice with Has3 deficiency in the endothelium were strongly protected against acute colitis. We conclude that endothelium-derived HAS3 plays a critical role in driving experimental colitis, warranting future studies on cell type-specific therapeutic interference with HA production in human IBD.

[Survey of sensory perception and patients' subjective assessment of the application of nasal sprays - the nasal-spray-sensoric-scale]

AIM

The Nasal Spray Evaluation Questionnaire is a standardized means to evaluate hedonicity of nasal sprays in the English speaking countries. To date, there is no such questionnaire for German speaking patients. The here presented study aimed at evaluating the translated questionnaire. Three nasal sprays were tested and the questionnaire was used to estimate sensory hedonicity. Finally, the questionnaire was improved and can now serve as a standardized means to measure nasal sensory perceptions.

MATERIAL AND METHODS

The questionnaire was literally translated from English to German. There were three groups of 60 patients each presenting with the sensation of a 'dry nose' to a secondary medical center with a board certified otolaryngologist. The ingredients of the three different nasal sprays varied only in one phytotherapeutic addition. The first evaluation of the nasal spray was conducted immediately after application of the nasal spray, and two minutes after application. A third and optional telephone survey was performed several days later after continuous use of the spray.

RESULTS

The different evaluations of nasal sprays were already lined out after the first questionnaire. It could serve as a new, reliable and reproduceable tool for the evaluation of nasal sensory perceptions.

DISCUSSION

The questionnaire served as an adequate tool to estimate hedonicity of nasal sprays. First results of the German version show, however, that it could facilitate the evaluation by restructuring the questionnaire. Continuously marking good grades with high points (maximum 100) and negative answers with low points (minimum 0 points) will unify and simplify the questionnaire.

CONCLUSION

The translation of the Nasal Spray Evaluation Questionnaire into a German version can serve as a new standard tool for measuring nasal sensation.