Abstract 18414: Malat1 Regulates the Inflammatory Response of Endothelial Cells
Laminar blood flow has an anti-inflammatory effect on endothelial cells (ECs) and prevents local atherosclerotic lesion formation. Long non-coding RNAs (lncRNAs) have been described to play a role in many biological processes, including epigenetic regulation of gene expression. We previously showed that the lncRNA MALAT1 is highly expressed in ECs and plays a role in angiogenesis. Since we showed that MALAT1 is induced by anti-inflammatory laminar shear stress (3.4+0.6 fold), we assessed whether MALAT1 regulates the inflammatory response of ECs. Therefore, we used several siRNAs and LNA GapmeRs to specifically silence MALAT1. We noticed that targeting different regions of MALAT1 showed opposite effects on TNFα-induced inflammatory response. Whereas 3 different siRNAs and GapmeRs directed against the 5’end enhanced the TNFα-induced expression of E-selectin, VCAM1 and ICAM1, a GapmeR directed against the 3’end reduced the inflammatory response of ECs (Fig.1).
To determine whether these effects are due to targeting of different transcript variants, we designed different PCR primers and identified a novel 1.3 kb 5’ variant of MALAT1, which was confirmed by deep sequencing. Interestingly, the two transcript variants are inversely regulated in human atherosclerotic plaques. Whereas the anti-inflammatory 1.3 kb 5’ variant was down-regulated in advanced plaques in AHA classification type 3 vs. 4 (42%+9%), the long pro-inflammatory variant was increased (158+28%).
We further characterized MALAT1 variants and showed that both are transcribed by RNA Polymerase II and are nuclear localized. RNA-IP experiments showed that the short MALAT1 variant binds to Histone H3 whereas the long MALAT1 predominantly binds to H3K27me3 suggesting that the variants exhibit different epigenetic effects.
In summary, our data identify for the first time a new 5′ variant of MALAT1, which reduced EC activation by TNFα, whereas the long MALAT1 augments the inflammatory activation of ECs.
Author Disclosures: K. Michalik: None. D. John: None. W. Chen: None. S. Uchida: None. A. Schober: None. C. Weber: None. R.A. Boon: None. S. Dimmeler: None.
- © 2014 by American Heart Association, Inc.