OxLDL induces the release of IL-1β from primed human endothelial and smooth muscle cells via different caspase -1-dependent mechanisms.

Abstract

Atherosclerosis is characterised by abnormal lipid and cell accumulation within arterial layers that leads to disturbed blood flow. Modified cholesterol forms such as oxidised low-density lipoprotein (oxLDL) enter cells altering their phenotype, triggering over-exuberant repair and arterial occlusion, myocardial infarction or stroke. We hypothesised that oxLDL enters vascular wall cells and induces interleukin-1β (IL-1β) secretion, potentially via a caspase-1/NLRP3 mechanism. Human coronary artery endothelial cells (HCAEC) and smooth muscle cells (HCASMC), isolated from different donors, were cultured and stimulated (primed) with pro-inflammatory cytokines TNFα and IL-1α (10 ng/mL each, for 48 h), followed by incubation with human oxLDL (10-50 ug/mL) for up to 6 h. Inhibitors of caspase-1 (YVAD), NLRP3 (MCC950) and gasdermin D (disulfiram) were added 1 h before oxLDL. Cell lysates and culture supernatants were collected and analysed for IL-1β using ELISA. Microscopy imaging showed oxLDL entered stimulated cells and formed particles. OxLDL at 20 and 50 ug/mL induced the maximum release of IL-1β from stimulated HCASMCs and HCAECs, respectively, compared to control. Inhibition of either NLRP3, caspase-1 or gasdermin D significantly reduced the release of IL-1β (4-fold, P < 0.0001; 14-fold, P < 0.0001, 1.5-fold, P < 0.0003, respectively) in HCAEC. In contrast, in HCASMCs, only caspase-1 inhibition reduced the release of IL-1β (2.1-fold, P < 0.0001). HCAECs and HCASMCs elicited the release of IL-1β in response to the same stimulus via different mechanisms. In HCAECs, released IL-1β potentially exits via a GSDMD-induced membrane pore. These data suggest that caspase-1 or gasdermin D inhibition is likely to be effective vessel wall cell-specific strategies for the reduction of atherosclerosis.