Novel Long Noncoding RNA HEAT4 Affects Monocyte Subtypes, Reducing Inflammation and Promoting Vascular Healing.

BACKGROUND: Activation of the immune system contributes to cardiovascular diseases. The role of human-specific long noncoding RNAs in cardioimmunology is poorly understood. METHODS: Single-cell sequencing in peripheral blood mononuclear cells revealed a novel human-specific long noncoding RNA called HEAT4 (heart failure-associated transcript 4). HEAT4 expression was assessed in several in vitro and ex vivo models of immune cell activation, as well as in the blood of patients with heart failure (HF), acute myocardial infarction, or cardiogenic shock. The transcriptional regulation of HEAT4 was verified through cytokine treatment and single-cell sequencing. Loss-of-function and gain-of-function studies and multiple RNA-protein interaction assays uncovered a mechanistic role of HEAT4 in the monocyte anti-inflammatory gene program. HEAT4 expression and function was characterized in a vascular injury model in NOD.CB17-Prkdc scid/Rj mice. RESULTS: HEAT4 expression was increased in the blood of patients with HF, acute myocardial infarction, or cardiogenic shock. HEAT4 levels distinguished patients with HF from people without HF and predicted all-cause mortality in a cohort of patients with HF over 7 years of follow-up. Monocytes, particularly anti-inflammatory CD16+ monocytes, which are increased in patients with HF, are the primary source of HEAT4 expression in the blood. HEAT4 is transcriptionally activated by treatment with anti-inflammatory interleukin-10. HEAT4 activates anti-inflammatory and inhibits proinflammatory gene expression. Increased HEAT4 levels result in a shift toward more CD16+ monocytes. HEAT4 binds to S100A9, causing a monocyte subtype switch, thereby reducing inflammation. As a result, HEAT4 improves endothelial barrier integrity during inflammation and promotes vascular healing after injury in mice. CONCLUSIONS: These results characterize a novel endogenous anti-inflammatory pathway that involves the conversion of monocyte subtypes into anti-inflammatory CD16+ monocytes. The data identify a novel function for the class of long noncoding RNAs by preventing protein secretion and suggest long noncoding RNAs as potential targets for interventions in the field of cardioimmunology.

Leptin treatment has vasculo-protective effects in lipodystrophic mice.

Lipodystrophy syndromes (LDs) are characterized by loss of adipose tissue, metabolic complications such as dyslipidemia, insulin resistance, and fatty liver disease, as well as accelerated atherosclerosis. As a result of adipose tissue deficiency, the systemic concentration of the adipokine leptin is reduced. A current promising therapeutic option for patients with LD is treatment with recombinant leptin (metreleptin), resulting in reduced risk of mortality. Here, we investigate the effects of leptin on endothelial to mesenchymal transition (EndMT), which impair the functional properties of endothelial cells and promotes atherogenesis in LD. Leptin treatment reduced inflammation and TGF-ß2-induced expression of mesenchymal genes and prevented impairment of endothelial barrier function. Treatment of lipodystrophic- and atherosclerosis-prone animals (Ldlr-/-; aP2-nSrebp1c-Tg) with leptin reduced macrophage accumulation in atherosclerotic lesions, vascular plaque protrusion, and the number of endothelial cells with mesenchymal gene expression, confirming a reduction in EndMT in LD after leptin treatment. Treatment with leptin inhibited LD-mediated induction of the proatherosclerotic cytokine growth/differentiation factor 15 (GDF15). Inhibition of GDF15 reduced EndMT induction triggered by plasma from patients with LD. Our study reveals that in addition to the effects on adipose tissue function, leptin treatment exerts beneficial effects protecting endothelial function and identity in LD by reducing GDF15.

Rubella virus infection in endothelial cells reduces angiogenesis via interferon beta-induced CXCL10.

Rubella virus (RuV) infection during pregnancy can lead to abortion, stillbirth, and embryonic defects, resulting in congenital rubella syndrome (CRS). It is estimated that there are still 100,000 cases of CRS per year in developing regions with a mortality rate of over 30%. The molecular pathomechanisms remain largely unexplored. Placental endothelial cells (EC) are frequently infected with RuV. RuV reduced the angiogenic and migratory capacity of primary human EC, as confirmed by treatment of EC with serum from RuV IgM-positive patients. Next generation sequencing analysis revealed the induction of antiviral interferon (IFN) type I and III and CXCL10. The RuV-induced transcriptional profile resembled the effects of IFN-ß treatment. The RuV-mediated inhibition of angiogenesis was reversed by treatment with blocking and neutralizing antibodies targeting CXCL10 and the IFN-ß receptor. The data identify an important role for antiviral IFN-mediated induction of CXCL10 in the control of EC function during RuV infection.