Anti-Galectin-2 antibody treatment reduces atherosclerotic plaque size and alters macrophage polarity

Background  Galectins have numerous cellular functions in immunity and inflammation. Short-term galectin-2 (Gal-2) blockade in ischemia-induced arteriogenesis shifts macrophages to an anti-inflammatory phenotype and improves perfusion. Gal-2 may also affect other macrophage-related cardiovascular diseases.

Objectives  This study aims to elucidate the effects of Gal-2 inhibition in atherosclerosis.

Methods   ApoE ^−/− mice were given a high-cholesterol diet (HCD) for 12 weeks. After 6 weeks of HCD, intermediate atherosclerotic plaques were present. To study the effects of anti-Gal-2 nanobody treatment on the progression of existing atherosclerosis, treatment with two llama-derived anti-Gal-2 nanobodies (clones 2H8 and 2C10), or vehicle was given for the remaining 6 weeks.

Results  Gal-2 inhibition reduced the progression of existing atherosclerosis. Atherosclerotic plaque area in the aortic root was decreased, especially so in mice treated with 2C10 nanobodies. This clone showed reduced atherosclerosis severity as reflected by a decrease in fibrous cap atheromas in addition to decreases in plaque size.

The number of plaque resident macrophages was unchanged; however, there was a significant increase in the fraction of CD206 ⁺ macrophages. 2C10 treatment also increased plaque α-smooth muscle content, and Gal-2 may have a role in modulating the inflammatory status of smooth muscle cells. Remarkably, both treatments reduced serum cholesterol concentrations including reductions in very low-density lipoprotein, low-density lipoprotein, and high-density lipoprotein while triglyceride concentrations were unchanged.

Conclusion  Prolonged and frequent treatment with anti-Gal-2 nanobodies reduced plaque size, slowed plaque progression, and modified the phenotype of plaque macrophages toward an anti-inflammatory profile. These results hold promise for future macrophage modulating therapeutic interventions that promote arteriogenesis and reduce atherosclerosis.

Glucocorticoid-induced tumour necrosis factor receptor family-related protein (GITR) drives atherosclerosis in mice and is associated with an unstable plaque phenotype and cerebrovascular events in humans

AIMS

GITR-a co-stimulatory immune checkpoint protein-is known for both its activating and regulating effects on T-cells. As atherosclerosis bears features of chronic inflammation and autoimmunity, we investigated the relevance of GITR in cardiovascular disease (CVD).

METHODS AND RESULTS

GITR expression was elevated in carotid endarterectomy specimens obtained from patients with cerebrovascular events (n = 100) compared to asymptomatic patients (n = 93) and correlated with parameters of plaque vulnerability, including plaque macrophage, lipid and glycophorin A content, and levels of interleukin (IL)-6, IL-12, and C-C-chemokine ligand 2. Soluble GITR levels were elevated in plasma from subjects with CVD compared to healthy controls. Plaque area in 28-week-old Gitr-/-Apoe-/- mice was reduced, and plaques had a favourable phenotype with less macrophages, a smaller necrotic core and a thicker fibrous cap. GITR deficiency did not affect the lymphoid population. RNA sequencing of Gitr-/-Apoe-/- and Apoe-/- monocytes and macrophages revealed altered pathways of cell migration, activation, and mitochondrial function. Indeed, Gitr-/-Apoe-/- monocytes displayed decreased integrin levels, reduced recruitment to endothelium, and produced less reactive oxygen species. Likewise, GITR-deficient macrophages produced less cytokines and had a reduced migratory capacity.

CONCLUSION

Our data reveal a novel role for the immune checkpoint GITR in driving myeloid cell recruitment and activation in atherosclerosis, thereby inducing plaque growth and vulnerability. In humans, elevated GITR expression in carotid plaques is associated with a vulnerable plaque phenotype and adverse cerebrovascular events. GITR has the potential to become a novel therapeutic target in atherosclerosis as it reduces myeloid cell recruitment to the arterial wall and impedes atherosclerosis progression.

Prolactin does not affect human platelet aggregation or secretion

Platelets play an important role in the development of plaque formation and in the events after rupture of the atherosclerotic plaque, leading to atherothrombosis. Multiple hormones, either in excess or when deficient, are involved in the development of atherothrombotic disease, but, to which extent such hormones affect platelet function, is still controversial. It was the objective of this study to assess the ability of the pituitary hormone prolactin to affect platelet functions. Venous blood was collected from six healthy males. Platelet activation was studied by (i) flow cytometry in whole blood (exposure of P-selectin as a measure of platelet secretion, and binding of PAC-1 as a measure of ligand-binding conformation of αIIbβ3), and by (ii) optical aggregation and whole blood aggregation. All studies were performed without and with exposure to several concentrations of ADP (0.1, 0.5 and 1.0 μM) and prolactin (50 and 1,000 μg/l). The presence of the prolactin receptor was investigated by Western blot and flow cytometry. In response to either 50 or 1,000 μg/l prolactin, no evidence of platelet activation or aggregation was found. In addition, ADP-induced platelet activation or aggregation was not enhanced by prolactin. Finally, prolactin receptors could not be detected on the surface of platelets. The present data indicate that prolactin does not directly modulate platelet function.