👤 Stephen Zewinger

Coexistent CKD and cardiovascular diseases are highly prevalent in Western populations and account for substantial mortality. We recently found that apolipoprotein C-3 (ApoC3), a major constituent of triglyceride-rich lipoproteins, induces sterile systemic inflammation by activating the NOD-like receptor protein-3 (NLRP3) inflammasome in human monocytes via an alternative pathway. To identify posttranslational modifications of ApoC3 in patients with CKD, we used mass spectrometry to analyze ApoC3 from such patients and from healthy individuals. We determined the effects of posttranslationally modified ApoC3 on monocyte inflammatory response in vitro, as well as in humanized mice subjected to unilateral ureter ligation (a kidney fibrosis model) and in a humanized mouse model for vascular injury and regeneration. Finally, we conducted a prospective observational trial of 543 patients with CKD to explore the association of posttranslationally modified ApoC3 with renal and cardiovascular events in such patients. We identified significant posttranslational guanidinylation of ApoC3 (gApoC3) in patients with CKD. We also found that mechanistically, guanidine and urea induce guanidinylation of ApoC3. A 2D-proteomic analysis revealed that gApoC3 accumulated in kidneys and plasma in a CKD mouse model (mice fed an adenine-rich diet). In addition, gApoC3 augmented the proinflammatory effects of ApoC3 in monocytes in vitro . In humanized mice, gApoC3 promoted kidney tissue fibrosis and impeded vascular regeneration. In CKD patients, higher gApoC3 plasma levels (as determined by mass spectrometry) were associated with increased mortality as well as with renal and cardiovascular events. Guanidinylation of ApoC3 represents a novel pathogenic mechanism in CKD and CKD-associated vascular injury, pointing to gApoC3 as a potential therapeutic target. Show less

Very rare loss-of-function mutations in the apolipoprotein C3 (APOC3) gene have been associated with low circulating apoC-III, low triglycerides, and reduced cardiovascular risk. We aimed to analyze the impact of common APOC3 variants on key parameters of lipid metabolism and coronary artery disease in the largest sample so far. Common variants in APOC3 were tested for associations with circulating apoC-III, lipids, and apolipoprotein B (apoB) in 3041 participants of the LUdwigshafen RIsk and Cardiovascular health study (LURIC). These variants were then tested for associations with coronary artery disease in a meta-analysis comprising up to 332,389 participants of the CARDIOGRAMplusC4D consortium and the UK Biobank. The mean (standard deviation) apoC-III concentration was 14.6 (5.1) mg/dl. Seven common variants in APOC3 (rs734104, rs4520, rs5142, rs5141, rs5130, rs5128, and rs4225) were associated with circulating apoC-III (all p < 0.05). The alleles that modestly raised apoC-III were also associated with markedly higher total triglycerides and very low density lipoprotein (VLDL) triglycerides and cholesterol (all p < 0.05), but not with low density lipoprotein (LDL) cholesterol and total apoB (all p > 0.05). These variants were not associated with coronary artery disease in the CARDIOGRAMplusC4D consortium and the UK Biobank (all p > 0.1). Modest, genetically caused elevations of apoC-III are associated with a marked increase of triglyceride-rich lipoproteins but not with an increase of LDL cholesterol, total apoB, and coronary artery disease. Whether effective inhibition of apoC-III production with antisense oligomers will be instrumental to reduce cardiovascular risk remains to be demonstrated. Show less

NLRP3-inflammasome-driven inflammation is involved in the pathogenesis of a variety of diseases. Identification of endogenous inflammasome activators is essential for the development of new anti-inflammatory treatment strategies. Here, we identified that apolipoprotein C3 (ApoC3) activates the NLRP3 inflammasome in human monocytes by inducing an alternative NLRP3 inflammasome via caspase-8 and dimerization of Toll-like receptors 2 and 4. Alternative inflammasome activation in human monocytes is mediated by the Toll-like receptor adapter protein SCIMP. This triggers Lyn/Syk-dependent calcium entry and the production of reactive oxygen species, leading to activation of caspase-8. In humanized mouse models, ApoC3 activated human monocytes in vivo to impede endothelial regeneration and promote kidney injury in an NLRP3- and caspase-8-dependent manner. These data provide new insights into the regulation of the NLRP3 inflammasome and the pathophysiological role of triglyceride-rich lipoproteins containing ApoC3. Targeting ApoC3 might prevent organ damage and provide an anti-inflammatory treatment for vascular and kidney diseases. Show less