👤 Lies van Baarle

Gastrointestinal (GI) motility is controlled by the coordinated activity of enteric neurons, glial cells, and resident muscularis macrophages (mMφs). Apolipoprotein E (ApoE) is highly expressed in mMφs, but its functional role in the gut remains unclear. We hypothesized that mMφ-derived ApoE regulates intestinal motility under physiological and stress conditions. Global ApoE knockout mice, bone marrow chimeras, and macrophage-specific ApoE-deficient mice were used to assess the impact of ApoE loss on gut transit, immune response, and neuromuscular integrity in both homeostatic and postoperative ileus (POI) settings. (1) Single-cell RNA sequencing revealed that muscularis macrophages highly express ApoE, with further upregulation after intestinal manipulation. (2) Bone marrow chimera experiments showed that hematopoietic-derived ApoE only partially contribute to the maintenance of gut motility. (3) Global ApoE deficiency led to mild impairment of intestinal transit and increased glial activation, accompanied by an expansion of the macrophage population and elevated gene expression of inflammatory cytokines. (4) Macrophage-specific deletion of ApoE did not affect gastrointestinal transit or tissue morphology under normal conditions. Although highly expressed and dynamically regulated in muscularis macrophages, ApoE is largely dispensable for intestinal neuromuscular function at baseline and during postoperative ileus. Show less

Disruption of circadian rhythm by means of shift work has been associated with cardiovascular disease in humans. However, causality and underlying mechanisms have not yet been established. In this study, we exposed hyperlipidemic APOE*3-Leiden.CETP mice to either regular light-dark cycles, weekly 6 hours phase advances or delays, or weekly alternating light-dark cycles (12 hours shifts), as a well-established model for shift work. We found that mice exposed to 15 weeks of alternating light-dark cycles displayed a striking increase in atherosclerosis, with an approximately twofold increase in lesion size and severity, while mice exposed to phase advances and delays showed a milder circadian disruption and no significant effect on atherosclerosis development. We observed a higher lesion macrophage content in mice exposed to alternating light-dark cycles without obvious changes in plasma lipids, suggesting involvement of the immune system. Moreover, while no changes in the number or activation status of circulating monocytes and other immune cells were observed, we identified increased markers for inflammation, oxidative stress, and chemoattraction in the vessel wall. Altogether, this is the first study to show that circadian disruption by shifting light-dark cycles directly aggravates atherosclerosis development. Show less