Interleukin 23 levels are increased in carotid atherosclerosis: possible role for the interleukin 23/interleukin 17 axis

BACKGROUND AND PURPOSE

Interleukin (IL)-23 is a cytokine in the IL-12 family, mainly produced by antigen-presenting cells with a central role in inflammation. We hypothesize that IL-23 is also important in atherogenesis and investigate this in a population with carotid atherosclerosis.

METHODS

Plasma levels of IL-23 were measured in patients with carotid artery stenosis and in healthy controls. The mRNA levels of IL-23 and its receptor, IL-23R, were measured in atherosclerotic plaques, nonatherosclerotic vessels, peripheral blood mononuclear cells, and plasmacytoid dendritic cells.

RESULTS

Our findings were as follows: (1) patients with carotid atherosclerosis (n=177) had significantly raised plasma levels of IL-23 when compared with healthy controls (n=24) with particularly high levels in those with the most recent symptoms. (2) mRNA levels of IL-23 and IL-23R were markedly increased in carotid plaques (n=68) when compared with nonatherosclerotic vessels (n=8-10). Immunostaining showed colocalization to plaque macrophages. (3) Patients with carotid atherosclerosis had increased mRNA levels of both IL-23 and IL-23R in plasmacytoid dendritic cells, but not in peripheral blood mononuclear cells. (4) IL-23 increased IL-17 release in monocytes and particularly in peripheral blood mononuclear cells from patients with carotid atherosclerosis, but not in cells from healthy controls. (5) IL-23 gave a prominent tumor necrosis factor release in monocytes from patients with carotid atherosclerosis but not in cells from healthy controls. (6) High plasma levels of IL-23 were associated with increased mortality during follow-up.

CONCLUSIONS

We have shown an association between IL-23 and disease progression in patients with carotid atherosclerosis, potentially involving IL-17-related mechanisms.

The CXCL13-CXCR5 axis contributes to atherosclerosis development in LDLr-/- mice by regulating myeloid development (149.1)

CXCL13 is a homeostatic chemokine instrumental in guided lymphocyte and dendritic cell trafficking towards lymphoid organs and stromal tissue. Evidence is culminating that in various chronic immune disorders extranodal CXCL13 expression at the site of inflammation contributes to the disease. Here we addressed the role of CXCL13 and its receptor CXCR5 in atherosclerosis. Bone marrow ablated LDLr-/- mice were repopulated with CXCL13 KO and CXCR5 KO bone marrow cells and after recovery fed a high-fat diet for 14 weeks. Carotid artery lesions were induced by perivascular collar placement. Both CXCL13 and CXCR5 deficiency resulted in significant attenuation of atherosclerosis, characterized by a decreased infiltration of granulocytes into the lesions. Haematopoietic deficiency of CXCR5 resulted in impaired homing of B cells and regulatory T cells towards peripheral lymph nodes. However, we didn’t observe this effect in the CXCL13 KO group. Surprisingly, FACS analysis showed a significant reduction in circulating CD11b+Ly6C+ pro-inflammatory monocytes and granulocytes both in the CXCR5 KO and CXCL13 KO group. In addition, plasma levels of M-CSF, G-CSF and RANK-L were strongly reduced. To conclude, haematopoietic deficiency of CXCL13/CXCR5 attenuates atherogenesis, probably attributable to the effects seen on Ly6Chighmonocyte and granulocyte levels in circulation. This study is the first to describe a critical role for the CXCL13/CXCR5 axis in myeloid development.

Plasmacytoid dendritic cell depletion augments CD8 T cell IFN-γ associated atherogenic responses in a mouse model of atherosclerosis. (147.18)

Plasmacytoid dendritic cells (pDC) have been shown to play a pivotal immunogenic role in viral immune responses by releasing high IFN-alpha levels upon TLR9 activation. However, evidence is culminating that pDC also play a major role in inducing immune tolerance in chronic low grade inflammation. In this study we set out to address effects of pDC depletion on atherosclerosis development. Carotid artery lesions were induced in LDLr-/- mice by perivascular collar placement. To study effects of pDC depletion on atherogenesis, a pDC depleting antibody, 120G8, was administered daily for 4 weeks. GL113 mAb was used as isotype control. pDC depletion resulted in exacerbated atherosclerosis, characterized by an increased lesion CD3+ T cell infiltration. FACS analysis showed an increase in CD3+ T cell numbers in spleen and lymph nodes with a concurrent shift towards CD8+ T cells. This was paralleled by strongly elevated plasma IFN-γ levels. Moreover, immature but not mature pDC from spleen of atherosclerotic mice expressed increased levels of IDO and PD-L1 compared to pDC from non-atherosclerotic mice. Finally, we found that pDC isolated from human UAP/SAP patients displayed reduced IFNalpha expression, while intralesional expression of IFNalpha was unaltered at later stages of disease progression. In conclusion, our data demonstrate that immature pDC act atheroprotective by dampening CD8+ T cell responses and keeping Th2/Th1 responses in check.