Biology subjects

Kent, K. C.

Publications and source records attributed to Kent, K. C..

5 recordsLinked to original sources

bioRxiv2020

Partnership between epigenetic reader BRD4 and transcription factor CEBPD

Vascular smooth muscle cell (SMC) state/phenotype transitions underlie neointimal hyperplasia (IH) predisposing to cardiovascular diseases. Bromodomain protein BRD4 is a histone acetylation reader and enhancer mark that co-activates transcription elongation. CCAAT enhancer binding protein delta (CEBPD) is a transcription factor typically studied in adipogenesis and immune cell differentiation. Here we investigated the association between BRD4 and CEBPD in SMC state transition. Chromatin immunoprecipitation sequencing (ChIPseq) showed enrichment of BRD4 and histone acetylation (H3K27ac) at Cebpd and enhancer in rat carotid arteries undergoing IH. In vitro, BRD4 silencing with siRNA reduced SMC expression of CEBPD. Bromodomain-1 but not bromodoamin-2 accounted for this BRD4 function. Endogenous BRD4 co-IPed with CEBPD; Cebpd promoter and enhancer DNA fragments co-IPed with CEBPD or endogenous BRD4 (ChIP-qPCR). These co-IPs were abolished by the BRD4 bromodomain blocker JQ1. TNF upregulated both BRD4 and CEBPD. Silencing CEBPD averted TNF-induced inflammatory SMC state transition (heightened IL-1{beta}, IL6, and MCP-1 mRNA levels), so did JQ1. CEBPD overexpression increased PDGFR preferentially over PDGFR{beta}; so did TNF, and JQ1 abolished TNFs effect. Our data reveal a BRD4/CEBPD partnership that promotes CEBPDs own transcription and inflammatory SMC state transition, thus shedding new light on epigenetic reader and transcription factor cooperative actions in SMC pathobiology.

cell biology↗

bioRxiv2019

Silencing epigenetic writer DOT1L attenuates intimal hyperplasia

ObjectiveHistone methyltransferases are emerging targets for epigenetic therapy. DOT1L (disruptor of telomeric silencing 1-like) is the H3K79 methylation writer. We investigated its role in the development of intimal hyperplasia (IH).\n\nApproach and ResultsIH was induced via balloon angioplasty in rat carotid arteries. DOT1L and its catalytic products H3K79me2 and H3K79me3 (immunostaining) increased by 4.69 {+/-}0.34, 2.38 {+/-}0.052, and 3.07 {+/-}0.27 fold, respectively, in injured (versus uninjured) carotid arteries at post-injury day 7. DOT1L silencing via shRNA-lentivirus infusion in injured arteries reduced DOT1L, H3K79me2, and IH at day 14 by 54.5%, 37.1%, and 76.5%, respectively. Moreover, perivascular administration of a DOT1L-selective inhibitor (EPZ5676) reduced H3K79me2, H3K79me3, and IH by 56.1%, 58.6%, and 39.9%, respectively.\n\nConclusionsDOT1L inhibition mitigates the development of IH.

pathology↗

bioRxiv2019

PERK inhibition mitigates restenosis and thrombosis - a potential low-thrombogenic anti-restenotic paradigm

BackgroundDrug-eluting stents (DES) represent the main-stream management of restenosis following treatments of occlusive cardiovascular diseases. However, DES cannot eliminate instent restenosis yet exacerbate thrombogenic risks. To achieve dual inhibition of restenotic smooth muscle cell (SMC) de-differentiation/proliferation and thrombogenic endothelial cell (EC) dysfunction, a common target in both cell types, has been long-sought after. We evaluated the potential of protein kinase RNA-like endoplasmic reticulum kinase (PERK) as such a target for low-thrombogenic anti-restenotic intervention.\n\nMethods and ResultsWe used a rat angioplasty model of restenosis and a FeCl3-induced mouse model of thrombosis. Loss-or gain-of-function was achieved by PERK inhibition (GSK2606414, siRNA) or overexpression (adenovirus). Restenosis was robustly mitigated by GSK2606414 administered either via injected (i.v.) lesion-homing platelet membrane-coated nanoclusters or a perivascular hydrogel; it was enhanced by PERK transgene. Whereas PERK inhibition blocked, its overexpression exacerbated PDGF-induced human aortic SMC de-differentiation (reduced smooth muscle -actin or SMA) and proliferation (BrdU incorporation). Further, PERK activity promoted STAT3 activation but inhibited SRF transcriptional (luciferase) activity; its protein co-immunoprecipitated with STAT3 and also MRTF-A, the SRF activator for SMA transcription. Importantly, PERK inhibition also prevented TNF-induced impairment of human EC growth and upregulation of thrombogenic tissue factor, both in vitro and ex vivo. In vivo, oral gavage of GSK2606414 preserved ~50% of the normal blood flow 60 min after FeCl3-induced vascular injury.\n\nConclusionsPERK inhibition is dual beneficial in mitigating restenosis and thrombosis, thus implicating a potential design for anti-restenotic intervention to overcome the thrombogenicity of DES.

pathology↗

bioRxiv2019

A non-canonical role of polo-like kinase-4 in adventitial fibroblast cell type transition

A divergent member of the polo-like kinase family, PLK4 is known for its canonical role in centriole duplication. Its non-canonical function and regulators are poorly defined. Here we investigated PLK4s activation and expression and regulations thereof in rat adventitial fibroblast cell-type transition induced by platelet-derived growth factor (PDGF-AA).\n\nExperiments using siRNA and selective inhibitor (centrinone-B) revealed a role for PLK4 not only in AA-induced proliferation/migration, but also in serum response factor (SRF) activation and smooth muscle -actin expression. PDGFR (receptor) inhibition abrogated AA-stimulated PLK4 activation (phosphorylation) and expression; P38 inhibition (siRNA, inhibitor) downstream of PDGFR also mitigated PLK4 activation. Furthermore, transcription of PLK4 (and PDGFR) was repressed by pan-inhibition of the bromodomain/extraterminal family of chromatin-bookmark readers (BRD2, BRD3, BRD4), an effect determined herein as mainly mediated by BRD4. In vivo, periadventitial administration of centrinone-B reduced collagen content and thickness of the adventitia in a rat model of carotid artery injury.\n\nIn summary, we have identified a non-canonical role for PLK4 in SRF activation and its regulations by BRD4/PDGFR-dominated pathways. Results in this study suggest PLK4 inhibition as a potential anti-fibrotic intervention.

cell biology↗

bioRxiv2019

The BD2 domain of BRD4 is a determinant in EndoMT and vein graft neointima formation

BackgroundVein-graft bypass is commonly performed to overcome atherosclerosis but is limited by high failure rates, principally due to neointimal wall thickening. Recent studies reveal that endothelial-mesenchymal transition (EndoMT) is critical for vein-graft neointima formation. BETs are a family of Bromo/ExtraTerminal domains-containing epigenetic reader proteins (BRD2, BRD3, BRD4). They bind acetylated histones through their unique tandem bromodomains (BD1, BD2), facilitating transcriptional complex formation and cell-state transitions. The role for BETs, including individual BRDs and their unique BDs, is not well understood in EndoMT and neointimal formation.\n\nMethods and ResultsRepression of BRD4 expression abrogated TGF{beta}1-induced EndoMT, with greater effects than BRD2 or BRD3 knockdown. An inhibitor selective for BD2 in all BETs, but not that for BD1, blocked EndoMT. Moreover, expression of a dominant-negative BRD4-specific BD2 fully abolished EndoMT. Concordantly, BRD4 knockdown repressed TGF{beta}1-stimulated increase of ZEB1 protein - a transcription factor integral in EndoMT. In vivo, lentiviral gene transfer of either BRD4 shRNA or dominant negative BRD4-specific BD2 mitigated neointimal development in rat jugular veins grafted to carotid arteries.\n\nConclusionsOur data reveal the BD2 domain of BRD4 as a determinant driving EndoMT in vitro and neointimal formation in vivo. These findings provide new insight into BET biology, while offering prospects of specific BET domain targeting as an approach to limiting neointima and extending vein graft patency.

pathology↗