High-density lipoprotein (HDL) is well-known for its cardioprotective effects, as it possesses anti-inflammatory, anti-oxidative, anti-thrombotic, and cytoprotective properties. Traditionally, studies and therapeutic approaches have focused on raising HDL cholesterol levels. Recently, it became evident that, not HDL cholesterol, but HDL composition and functionality, is probably a more fruitful target. In disorders, such as chronic kidney disease or cardiovascular diseases, it has been observed that HDL is modified and becomes dysfunctional. There are different modification that can occur, such as serum amyloid, an enrichment and oxidation, carbamylation, and glycation of key proteins. Additionally, the composition of HDL can be affected by changes to enzymes such as cholesterol ester transfer protein (CETP), lecithin-cholesterol acyltransferase (LCAT), and phospholipid transfer protein (PLTP) or by modification to other important components. This review will highlight some main modifications to HDL and discuss whether these modifications are purely a consequential result of pathology or are actually involved in the pathology itself and have a causal role. Therefore, HDL composition may present a molecular target for the amelioration of certain diseases, but more information is needed to determine to what extent HDL modifications play a causal role in disease development.

The search to improve therapies to prevent or treat cardiovascular diseases (CVDs) rages on, as CVDs remain a leading cause of death worldwide. Here, the main cause of CVDs, atherosclerosis, and its prevention, take center stage. Chemokines and their receptors have long been known to play an important role in the pathophysiological development of atherosclerosis. Their role extends from the initiation to the progression, and even the potential regression of atherosclerotic lesions. These important regulators in atherosclerosis are therefore an obvious target in the development of therapeutic strategies. A plethora of preclinical studies have assessed various possibilities for targeting chemokine signaling via various approaches, including competitive ligands and microRNAs, which have shown promising results in ameliorating atherosclerosis. Developments in the field also include detailed imaging with tracers that target specific chemokine receptors. Lastly, clinical trials revealed the potential of various therapies but still require further investigation before commencing clinical use. Although there is still a lot to be learned and investigated, it is clear that chemokines and their receptors present attractive yet extremely complex therapeutic targets. Therefore, this review will serve to provide a general overview of the connection between various chemokines and their receptors with atherosclerosis. The different developments, including mouse models and clinical trials that tackle this complex interplay will also be explored.

Proprotein convertase subtilin/kexin type 9 (PCSK9) is a protease secreted mainly by hepatocytes and in lesser quantities by intestines, pancreas, and vascular cells. Over the years, this protease has gained importance in the field of cardiovascular biology due to its regulatory action on the low-density lipoprotein receptor (LDLR). However, recently, it has also been shown that PCSK9 acts independent of LDLR to cause vascular inflammation and increase the severity of several cardiovascular disorders. We hypothesized that PCSK9 affects the expression of chemokine receptors, major mediators of inflammation, to influence cardiovascular health. However, using overexpression of PCSK9 in murine models in vivo and PCSK9 stimulation of myeloid and vascular cells in vitro did not reveal influences of PCSK9 on the expression of certain chemokine receptors that are known to be involved in the development and progression of atherosclerosis and vascular inflammation. Hence, we conclude that the inflammatory effects of PCSK9 are not associated with the here investigated chemokine receptors and additional research is required to elucidate which mechanisms mediate PCSK9 effects independent of LDLR.

BACKGROUND: Atherosclerotic cardiovascular disease, characterized by an imbalanced lipid metabolism and a dysregulated immune response, is a major cause of death worldwide. The AhR (aryl hydrocarbon receptor) is a ligand-activated transcription factor that is highly expressed in the liver and primarily known for its role in detoxification. However, recent studies suggest that the AhR also plays a key role in immune regulation, indicating that this receptor can influence the development of atherosclerosis. METHODS: Apoe ^−/− and Apoe ^−/− Ahr ^−/− mice were fed a western-type diet for 12 weeks to induce atherosclerosis. Aortic roots were analyzed for size and composition of atherosclerotic plaques. Plasma samples were characterized for inflammation and lipid levels. Liver samples were analyzed for cytokines and lipid accumulation and subjected to RNA sequencing and kinomics. A PheWAS (Phenome-Wide Association Study) was performed to identify associations of genetic AHR variants with atherosclerotic cardiovascular disease and lipid phenotypes in humans. RESULTS: The number of circulating leukocytes was increased in Apoe ^−/− Ahr ^−/− mice compared with Apoe ^−/− controls. Surprisingly, however, mice lacking Ahr showed significantly smaller plaques than Apoe ^−/− mice, which coincided with strongly reduced plasma cholesterol and triglyceride levels. The liver lipid levels showed a similar effect, indicating a key role of the AhR in lipid metabolism. RNA sequencing of the liver revealed that lipid metabolism pathways were particularly impacted in Apoe ^−/− Ahr ^−/− mice. Furthermore, through kinomics, we identified signaling pathways affected by the absence of Ahr . PheWAS analysis revealed significant associations between the AHR variant rs4410790 and lipid traits, including plasma triglycerides, LDL (low-density lipoprotein), and total cholesterol. CONCLUSIONS: Our study demonstrates a remarkable role for AhR in the pathogenesis of atherosclerosis, interfering with both lipid metabolism and inflammatory pathways. Although the underlying mechanisms remain unclear, these results demonstrate a novel and crucial role for AhR in atherosclerotic cardiovascular disease.