Kaposin-B Enhances the PROX1 mRNA Stability during Lymphatic Reprogramming of Vascular Endothelial Cells by Kaposi's Sarcoma Herpes Virus

Kaposi's sarcoma (KS) is the most common cancer among HIV-positive patients. Histogenetic origin of KS has long been elusive due to a mixed expression of both blood and lymphatic endothelial markers in KS tumor cells. However, we and others discovered that Kaposi's sarcoma herpes virus (KSHV) induces lymphatic reprogramming of blood vascular endothelial cells by upregulating PROX1, which functions as the master regulator for lymphatic endothelial differentiation. Here, we demonstrate that the KSHV latent gene kaposin-B enhances the PROX1 mRNA stability and plays an important role in KSHV-mediated PROX1 upregulation. We found that PROX1 mRNA contains a canonical AU-rich element (ARE) in its 3′-untranslated region that promotes PROX1 mRNA turnover and that kaposin-B stimulates cytoplasmic accumulation of the ARE-binding protein HuR through activation of the p38/MK2 pathway. Moreover, HuR binds to and stabilizes PROX1 mRNA through its ARE and is necessary for KSHV-mediated PROX1 mRNA stabilization. Together, our study demonstrates that kaposin-B plays a key role in PROX1 upregulation during lymphatic reprogramming of blood vascular endothelial cells by KSHV

Somatic mutations reveal clonal cell populations in atherosclerotic plaques

ABSTRACTIn recent years, the potential involvement of clonal cell populations in atherosclerosis has emerged.Evidence from independent research groups unambiguously showed that smooth muscle cells clonally expand in experimental atherosclerosis, and clonal hematopoiesis of indeterminate potential (CHIP) was identified as a novel independent risk factor for atherosclerotic cardiovascular disease. However, whether clonal cell populations contribute to human atherosclerotic lesions remains elusive.In this study, we performed deep whole-exome sequencing of 32 segments from 14 carotid plaques of patients undergoing carotid endatherectomy. We unveiled a landscape of somatic mutations confined to plaque tissue (i.e., not detected in patient-matched buffy coats). Based on variant allele frequencies, we estimated that individual locally expanded clones contributed with up to 15% of plaque segment cell content. In addition, seven patients were CHIP carriers and in several of these patients, hematopoietic clones comprised over 30% of the cell population of plaque segments.Taken together, we provide evidence that somatic mutations and clonal cell populations (expanded locally or invading from the circulation) are inherent features of atherosclerosis.</jats:p

Ccn2 deficiency causes smooth muscle cell de-differentiation and severe atherosclerosis in hyperlipidemic mice

ABSTRACTCellular communication network factor 2 (CCN2/CTGF) is a matricellular protein with an established role in fibrotic diseases and cancers, and therapies targeting CCN2 is currently in Phase II and III clinical trials for idiopathic pulmonary fibrosis, pancreatic cancer and Duchenne Muscular Dystrophy. Recent studies have highlighed a protective role of CCN2 in aortic aneurysm disease, but its role in atherosclerosis remains to be investigated.We identified arteries as having the highest relative expression ofCCN2across 54 human tissues. In aortas,CCN2was among the highest expressed genes, andin situhybridization of human internal thoracic arteries revealed vascular smooth muscle cells (SMCs) as its principal source.Hypothesizing a role for CCN2 in SMC phenotype maintenance and athero-protection, we investigated inducible Ccn2 knockout (Ccn2Δ/Δ) mice in normo- and hyper-lipidemic settings. Induction of hyperlipidemia by single intravenous injection of 1·1011viral genomes of rAAV8-D377Y-mPcsk9 combined with 24 weeks of western type diet resulted in severe enlargement (3-5-fold increase of relative aorta mass compared to wildtype littermates,p&lt; 0.0001) and whitening ofCcn2Δ/Δaortas. Oil Red O-staining ofen faceprepared thoracic aortas showed a marked increase in atherosclerosis inCcn2Δ/Δmice as compared to wildtype littermates (75% vs. 10% Oil Red O-positive aortic area,p&lt; 0.0001). Transcriptomic profiling of cultivated SMCs derived from aortas of normolipidemic mice showed signatures of dedifferentiation (reduced expression ofe.g. Myocd, Acta2andMyh11) and modulation toward a synthetic, pro-inflammatory phenotype ofCcn2Δ/ΔSMCs. These effects were verifiedin vivoand inCCN2-silenced human aortic SMCs. Taken together, we find that CCN2 plays a critical athero-protective role in artery tissues, likely through maintaining SMCs in a differentiated, contractile phenotype.</jats:p

The hypoxia avoidance behaviour of juvenile Atlantic cod (Gadus morhua L.) depends on the provision and pressure level of an O2 refuge

The frequency of low O(2) (hypoxia) has increased in coastal marine areas but how fish avoid deleterious water masses is not yet clear. To assess whether the presence and oxygen pressure (PO(2)) level of an O(2) refuge affects the hypoxia avoidance behaviour of fish, individual Atlantic cod (Gadus morhua L.) were exposed to a range of O(2) choices in a 2-way choice chamber at 11.4 degrees C over two different experiments. Cod in the first experiment were allowed access to a fixed O(2) refuge (fully air-saturated seawater) whilst oxygen pressure (PO(2)) on the other side was reduced in steps to a critically low level, i.e. 4.3 kPa-a point where cod can no longer regulate O(2) consumption. Under these conditions, cod did not avoid any level of hypoxia and fish swimming speed also remained unchanged. In contrast, strong avoidance reactions were exhibited in a second experiment when fish were again exposed to 4.3 kPa but the safety, i.e. PO(2), of the refuge was reduced. Fish not only spent less time at 4.3 kPa as a result of fewer sampling visits but they also swam at considerably slower speeds. The presence of an avoidance response was thus strongly related to refuge PO(2) and it is unlikely that cod, and possibly other fish species, would enter low O(2) to feed in the wild if a sufficiently safe O(2) refuge was not available. It is therefore hypothesized that the feeding range of fish may be heavily compressed if hypoxia expands and intensifies in future years.The frequency of low O(2) (hypoxia) has increased in coastal marine areas but how fish avoid deleterious water masses is not yet clear. To assess whether the presence and oxygen pressure (PO(2)) level of an O(2) refuge affects the hypoxia avoidance behaviour of fish, individual Atlantic cod (Gadus morhua L.) were exposed to a range of O(2) choices in a 2-way choice chamber at 11.4 degrees C over two different experiments. Cod in the first experiment were allowed access to a fixed O(2) refuge (fully air-saturated seawater) whilst oxygen pressure (PO(2)) on the other side was reduced in steps to a critically low level, i.e. 4.3 kPa-a point where cod can no longer regulate O(2) consumption. Under these conditions, cod did not avoid any level of hypoxia and fish swimming speed also remained unchanged. In contrast, strong avoidance reactions were exhibited in a second experiment when fish were again exposed to 4.3 kPa but the safety, i.e. PO(2), of the refuge was reduced. Fish not only spent less time at 4.3 kPa as a result of fewer sampling visits but they also swam at considerably slower speeds. The presence of an avoidance response was thus strongly related to refuge PO(2) and it is unlikely that cod, and possibly other fish species, would enter low O(2) to feed in the wild if a sufficiently safe O(2) refuge was not available. It is therefore hypothesized that the feeding range of fish may be heavily compressed if hypoxia expands and intensifies in future years