Background: RNA interference (RNAi) is a regulatory mechanism conserved in higher eukaryotes. The RNAi pathway generates small interfering RNA (siRNA) or micro RNA (miRNA) from either long double stranded stretches of RNA or RNA hairpins, respectively. The siRNA or miRNA then guides an effector complex to a homologous sequence of mRNA and regulates suppression of gene expression through one of several mechanisms. The suppression of gene expression through these mechanisms serves to regulate endogenous gene expression and protect the cell from foreign nucleic acids. There is growing evidence that many viruses have developed in the context of RNAi and express either a suppressor of RNAi or their own viral miRNA.

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Both the risk and the rate of development of atherosclerosis are increased in diabetics, but the mechanisms involved are unknown. Here we report a glucose-mediated increase in CD36 mRNA translation efficiency that results in increased expression of the macrophage scavenger receptor CD36. Expression of CD36 was increased in endarterectomy lesions from patients with a history of hyperglycemia. Macrophages that were differentiated from human peripheral blood monocytes in the presence of high glucose concentrations showed increased expression of cell-surface CD36 secondary to an increase in translational efficiency of CD36 mRNA. We obtained similar data from primary cells isolated from human vascular lesions, and we found that glucose sensitivity is a function of ribosomal reinitiation following translation of an upstream open reading frame (uORF). Increased translation of macrophage CD36 transcript under high glucose conditions provides a mechanism for accelerated atherosclerosis in diabetics.

The TAR microRNA is expressed in all stages of the viral life cycle, can be detected in latently infected cells, and represents a mechanism wherein the virus extends the life of the infected cell for the purpose of increasing viral replication.

Age-related progression of cardiovascular disease is by far the largest health problem in the US and involves vascular damage, progressive vascular fibrosis and the accumulation of lipid-rich atherosclerotic lesions. Advanced lesions can restrict flow to key organs and can trigger occlusive thrombosis resulting in a stroke or myocardial infarction. Transforming growth factor-beta (TGF-β) is a major orchestrator of the fibroproliferative response to tissue damage. In the early stages of repair, TGF-β is released from platelets and activated from matrix reservoirs; it then stimulates the chemotaxis of repair cells, modulates immunity and inflammation and induces matrix production. At later stages, it negatively regulates fibrosis through its strong antiproliferative and apoptotic effects on fibrotic cells. In advanced lesions, TGF-β might be important in arterial calcification, commonly referred to as “hardening of the arteries”. Because TGF-β can signal through multiple pathways, namely the SMADs, a MAPK pathway and the Rho/ROCK pathways, selective defects in TGF-β signaling can disrupt otherwise coordinated pathways of tissue regeneration. TGF-β is known to control cell proliferation, cell migration, matrix synthesis, wound contraction, calcification and the immune response, all being major components of the atherosclerotic process. However, many of the effects of TGF-β are essential to normal tissue repair and thus, TGF-β is often thought to be “atheroprotective”. The present review attempts to parse systematically the known effects of TGF-β on both the major risk factors for atherosclerosis and to isolate the role of TGF-β in the many component pathways involved in atherogenesis.

BackgroundThe function of the non-coding portion of the human genome remains one of the most important questions of our time. Its vast complexity is exemplified by the recent identification of an unusual and notable component of the transcriptome - very long intergenic non-coding RNAs, termed vlincRNAs.ResultsHere we identify 2,147 vlincRNAs covering 10 percent of our genome. We show they are present not only in cancerous cells, but also in primary cells and normal human tissues, and are controlled by canonical promoters. Furthermore, vlincRNA promoters frequently originate from within endogenous retroviral sequences. Strikingly, the number of vlincRNAs expressed from endogenous retroviral promoters strongly correlates with pluripotency or the degree of malignant transformation. These results suggest a previously unknown connection between the pluripotent state and cancer via retroviral repeat-driven expression of vlincRNAs. Finally, we show that vlincRNAs can be syntenically conserved in humans and mouse and their depletion using RNAi can cause apoptosis in cancerous cells.ConclusionsThese intriguing observations suggest that vlincRNAs could create a framework that combines many existing short ESTs and lincRNAs into a landscape of very long transcripts functioning in the regulation of gene expression in the nucleus. Certain types of vlincRNAs participate at specific stages of normal development and, based on analysis of a limited set of cancerous and primary cell lines, they appear to be co-opted by cancer-associated transcriptional programs. This provides additional understanding of transcriptome regulation during the malignant state, and could lead to additional targets and options for its reversal.

Cells proliferating from human atherosclerotic lesions are resistant to the antiproliferative effect of TGF-␤ 1, a key factor in wound repair. DNA from human atherosclerotic and restenotic lesions was used to test the hypothesis that microsatellite instability leads to specific loss of the Type II receptor for TGF-␤ 1 (T ␤ R-II), causing acquired resistance to TGF-␤ 1. High fidelity PCR and restriction analysis was adapted to analyze deletions in an A 10 microsatellite within T ␤ R-II. DNA from lesions, and cells grown from lesions, showed acquired 1 and 2 bp deletions in T ␤ R-II, while microsatellites in the hMSH3 and hMSH6 genes, and hypermutable regions of p53 were unaffected. Sequencing confirmed that these deletions occurred principally in the replication error-prone A 10 microsatellite region, though nonmicrosatellite mutations were observed. The mutations could be identified within specific patches of the lesion, while the surrounding tissue, or unaffected arteries, exhibited the wild-type genotype. This microsatellite deletion causes frameshift loss of receptor function, and thus, resistance to the antiproliferative and apoptotic effects of TGF-␤ 1. We propose that microsatellite instability in T ␤ R-II disables growth inhibitory pathways, allowing monoclonal selection of a disease-prone cell type within some vascular lesions. ( J. Clin. Invest. 1997.

Immune factors influencing progression to active tuberculosis (TB) remain poorly defined. In this study, we investigated the expression of immunoregulatory cytokines and receptors by using lung bronchoalveolar lavage cells obtained from patients with pulmonary TB, patients with other lung diseases (OLD patients), and healthy volunteers (VOL) by using reverse transcriptase PCR, a transforming growth factor ␤ (TGF-␤) bioactivity assay, and an enzyme immunoassay. TB patients were significantly more likely than OLD patients to coexpress TGF-␤ receptor I (RI) and RII mRNA, as well as interleukin-10 (IL-10) mRNA (thereby indicating the state of active gene transcription in the alveolar cells at harvest). In contrast, gamma interferon (IFN-␥) and IL-2 mRNA was seen in both TB and OLD patients. Likewise, significantly elevated pulmonary steady-state protein levels of IL-10, IFN-␥, and bioactive TGF-␤ were found in TB patients versus those in OLD patients and VOL. These data suggest that the combined production of the immunosuppressants IL-10 and TGF-␤, as well as coexpression of TGF-␤ RI and RII (required for cellular response to TGF-␤), may act to down-modulate host anti-Mycobacterium tuberculosis immunity and thereby allow uncontrolled bacterial replication and overt disease. Delineating the underlying mechanisms of M. tuberculosis-triggered expression of these immune elements may provide a molecular-level understanding of TB immunopathogenesis.