Dissecting Abdominal Aortic Aneurysm Is Aggravated by Genetic Inactivation of LIGHT (TNFSF14)

Genetically Predicted Vascular Proteins and Risk of Intracranial Aneurysms: A Mendelian Randomization Study

The relationship between vascular proteins (VPs) and intracranial aneurysms (IAs) has not been fully elucidated. We used Mendelian randomization (MR) analysis to explore the effect of VPs on IAs. Dataset of aneurysmal subarachnoid hemorrhage (aSAH) [5140 cases and 71,934 controls] and unruptured intracranial aneurysm (uIA) [2070 cases and 71,934 controls] were obtained from individuals of European ancestry. Univariate MR was used to explore the associations between 90 VPs and IAs. Then, we performed multivariate MR (MVMR) to further investigate the identified VP-to-IA estimates. Two-sample MR showed that TNFSF14 was inversely associated with aSAH (odds ratio [OR] = 0.831, 95% CI: 0.713-0.969, p = 0.018). IL-16 (OR = 1.218, 95% CI: 1.032-1.438, p = 0.020) and AgRP (OR = 1.394, 95% CI: 1.048-1.855, p = 0.023) were positively associated with aSAH. HBEGF (OR = 0.642, 95% CI: 0.461-0.894, p = 0.009), MCP-1 (OR = 1.537, 95% CI: 1.007-2.344, p = 0.046), and CX3CL1 (OR = 0.762, 95% CI: 0.581-0.999, 0.049 < p < 0.050) were associated with uIA risk. The MVMR showed that the TNFSF14-to-aSAH estimate remained statistically significant after adjustment for past tobacco smoking, alcohol consumption, systolic blood pressure and body mass index. Our study indicated that low serum TNFSF14 levels might be a potential risk factor for IA rupture. Five VPs (HBEGF, MCP-1, IL-6, CX3CL1, and AgRP) are associated with the risk of IAs (both uIA and aSAH).

Light deficiency in Apoe-/-mice increases atheroma plaque size and vulnerability by modulating local immunity

Previous research suggests a potential involvement of the cytokine LIGHT (TNFSF14) in atherosclerosis. In this study, the genetic inactivation of Light in Apolipoprotein E deficient mice (male and female C57BL) augmented plaque size and vulnerability while decreasing Treg cells. Human and mouse transcriptomic results demonstrated deranged immune pathways in human atheromas with low LIGHT expression levels and in Light-deficient murine atheromas. In agreement with this, in vitro LIGHT-treatment of human lymphocytes, induced an elevation of Treg cell prevalence while proteomic analysis showed a downregulation of apoptotic and leukocyte cytotoxic pathways. Consistently, Light-deficient mouse lesions displayed increased plaque apoptosis and detrimental adventitial T-lymphocyte aggregates. Altogether suggested that LIGHT could promote a Treg prevalence in the local immunity to prevent the generation of vulnerable plaques via decreased cytotoxic microenvironment and apoptosis. Light gene delivery in Apoe-/-Light-/- mice, through bone marrow transplantation approaches, consistently diminished lesion size and restored local plaque immunity. Altogether demonstrate that Light-deficiency promotes atheroma plaque progression, at least in part through local loss of immune homeostasis and increased apoptosis. This study suggest that therapies based on the local delivery of LIGHT within plaques might therefore prevent immune cell derangement and advanced atherosclerosis.

Cellular, Molecular and Clinical Aspects of Aortic Aneurysm-Vascular Physiology and Pathophysiology

A disturbance of the structure of the aortic wall results in the formation of aortic aneurysm, which is characterized by a significant bulge on the vessel surface that may have consequences, such as distention and finally rupture. Abdominal aortic aneurysm (AAA) is a major pathological condition because it affects approximately 8% of elderly men and 1.5% of elderly women. The pathogenesis of AAA involves multiple interlocking mechanisms, including inflammation, immune cell activation, protein degradation and cellular malalignments. The expression of inflammatory factors, such as cytokines and chemokines, induce the infiltration of inflammatory cells into the wall of the aorta, including macrophages, natural killer cells (NK cells) and T and B lymphocytes. Protein degradation occurs with a high expression not only of matrix metalloproteinases (MMPs) but also of neutrophil gelatinase-associated lipocalin (NGAL), interferon gamma (IFN-γ) and chymases. The loss of extracellular matrix (ECM) due to cell apoptosis and phenotype switching reduces tissue density and may contribute to AAA. It is important to consider the key mechanisms of initiating and promoting AAA to achieve better preventative and therapeutic outcomes.

Vascular smooth muscle cell phenotype is modulated by ligands of the lymphotoxin β receptor and the tumor necrosis factor receptor

OBJECTIVE

Vascular smooth muscle cells (VSMCs) undergo a phenotypic-switching process during the generation of unstable atheroma plaques. In this investigation, the potential implication of the tumor necrosis factor superfamily (TNFSF) ligands, in the gene expression signature associated with VSMC plasticity was studied.

MATERIAL AND METHODS

Human aortic (ha)VSMCs were obtained commercially and treated with the cytokine TNFSF14, also called LIGHT, the lymphotoxin alpha (LTα), the heterotrimer LTα₁β₂ or with vehicle for 72h. The effect of the different treatments on gene expression was analyzed by quantitative PCR and included the study of genes associated with myofibroblast-like cell function, osteochondrogenesis, pluripotency, lymphorganogenesis and macrophage-like cell function.

RESULTS

HaVSMCs displayed a change in myofibroblast-like cell genes which consisted in reduced COL1A1 and TGFB1 mRNA levels when treated with LTα or LIGHT and with augmented MMP9 expression levels when treated with LTα. LTα and LIGHT treatments also diminished the expression of genes associated with osteochondrogenesis and pluripotency SOX9, CKIT, and KLF4. By contrary, all the above genes were no affected by the treatment with the trimer LTα₁β₂. In addition, haVSMC treatment with LTα, LTα₁β₂ and LIGHT altered lymphorganogenic cytokine gene expression which consisted of augmented CCL20 and CCL21 mRNA levels by LTα and a reduction in the gene expression of CCL21 and CXCL13 by LIGHT and LTα₁β₂ respectively. Neither, LTα or LIGHT or LTα₁β₂ treatments affected the expression of macrophage-like cell markers in haVSMC.

CONCLUSIONS

Altogether, indicates that the TNFSF ligands through their interconnected network of signaling, are important in the preservation of VSMC identity against the acquisition of a genetic expression signature compatible with functional cellular plasticity.