Publications by authors named "Kathleen A Martin"

60 Publications

TET2 Protects Against VSMC Apoptosis and Intimal Thickening in Transplant Vasculopathy.

Circulation 2021 Jun 11. Epub 2021 Jun 11.

Department of Medicine (Cardiovascular Medicine), Yale University School of Medicine, New Haven, CT.

Coronary allograft vasculopathy (CAV) is a devastating sequelae of heart transplant in which arterial intimal thickening limits coronary blood flow. There are currently no targeted therapies to prevent or reduce this pathology that leads to transplant failure. Vascular smooth muscle cell (VSMC) phenotypic plasticity is critical in CAV neointima formation. TET methylcytosine dioxygenase 2 (TET2) is an important epigenetic regulator of VSMC phenotype, but the role of TET2 in the progression of CAV is unknown. We assessed TET2 expression and activity in human CAV and renal transplant samples. We also employed the sex-mismatched murine aortic graft model of graft arteriopathy (GA) in wild type and inducible smooth muscle-specific knockout mice; and studies in murine and human VSMCs using knockdown, overexpression, and transcriptomic approaches to assess the role of TET2 in VSMC responses to IFNу, a cytokine elaborated by T cells that drives CAV progression. In the present study, we found that TET2 expression and activity is negatively regulated in human CAV and renal transplant samples and in the murine aortic graft model of GA. IFNу was sufficient to repress TET2 and induce an activated VSMC phenotype . TET2 depletion mimicked the effects of IFNу, and TET2 overexpression rescued IFNу-induced dedifferentiation. VSMC-specific TET2 depletion in aortic grafts, and in the femoral wire restenosis model, resulted in increased VSMC apoptosis and medial thinning. In GA, this apoptosis was tightly correlated with proliferation. , TET2 deficient VSMCs undergo apoptosis more readily in response to IFNγ and expressed a signature of increased susceptibility to extrinsic apoptotic signaling. Notably, enhancing TET2 enzymatic activity with high-dose ascorbic acid rescued the effect of GA-induced VSMC apoptosis and intimal thickening in a TET2-dependent manner. TET2 is repressed in CAV and GA, likely mediated by IFNу. TET2 serves to protect VSMCs from apoptosis in the context of transplant vasculopathy or IFNу stimulation. Promoting TET2 activity with systemic ascorbic acid reduces VSMC apoptosis and intimal thickening. These data suggest that promoting TET2 activity in CAV may be an effective strategy for limiting CAV progression.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.120.050553DOI Listing
June 2021

Thrombocytopathy and endotheliopathy: crucial contributors to COVID-19 thromboinflammation.

Nat Rev Cardiol 2021 03 19;18(3):194-209. Epub 2020 Nov 19.

Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.

The core pathology of coronavirus disease 2019 (COVID-19) is infection of airway cells by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that results in excessive inflammation and respiratory disease, with cytokine storm and acute respiratory distress syndrome implicated in the most severe cases. Thrombotic complications are a major cause of morbidity and mortality in patients with COVID-19. Patients with pre-existing cardiovascular disease and/or traditional cardiovascular risk factors, including obesity, diabetes mellitus, hypertension and advanced age, are at the highest risk of death from COVID-19. In this Review, we summarize new lines of evidence that point to both platelet and endothelial dysfunction as essential components of COVID-19 pathology and describe the mechanisms that might account for the contribution of cardiovascular risk factors to the most severe outcomes in COVID-19. We highlight the distinct contributions of coagulopathy, thrombocytopathy and endotheliopathy to the pathogenesis of COVID-19 and discuss potential therapeutic strategies in the management of patients with COVD-19. Harnessing the expertise of the biomedical and clinical communities is imperative to expand the available therapeutics beyond anticoagulants and to target both thrombocytopathy and endotheliopathy. Only with such collaborative efforts can we better prepare for further waves and for future coronavirus-related pandemics.
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http://dx.doi.org/10.1038/s41569-020-00469-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7675396PMC
March 2021

Circular RNA CircMAP3K5 Acts as a MicroRNA-22-3p Sponge to Promote Resolution of Intimal Hyperplasia Via TET2-Mediated Smooth Muscle Cell Differentiation.

Circulation 2021 Jan 19;143(4):354-371. Epub 2020 Nov 19.

From the Institute of Pediatrics (Z.Z., L.X., J.Q., X.F., Y.L., K.L., Z.L., Y.B., W.H.T.), Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, Guangdong, China.

Background: Aberrant expression of circular RNA contributes to human diseases. Circular RNAs regulate gene expression by sequestering specific microRNAs. In this study, we investigated whether circMAP3K5 (circular mitogen-activated protein kinase 5) could act as a competing endogenous microRNA-22-3p (miR-22-3p) sponge and regulate neointimal hyperplasia.

Methods: Circular RNA profiling from genome-wide RNA sequencing data was compared between human coronary artery smooth muscle cells (SMCs) treated with or without platelet-derived growth factor. Expression levels of circMAP3K5 were assessed in human coronary arteries from autopsies on patients with dilated cardiomyopathy or coronary heart disease. The role of circMAP3K5 in intimal hyperplasia was further investigated in mice with adeno-associated virus 9-mediated circMAP3K5 transfection. SMC-specific Tet2 (ten-eleven translocation-2) knockout mice and global miR-22-3p knockout mice were used to delineate the mechanism by which circMAP3K5 attenuated neointimal hyperplasia using the femoral arterial wire injury model.

Results: RNA sequencing demonstrated that treatment with platelet-derived growth factor-BB significantly reduced expression of circMAP3K5 in human coronary artery SMCs. Wire-injured mouse femoral arteries and diseased arteries from patients with coronary heart disease (where platelet-derived growth factor-BB is increased) confirmed in vivo downregulation of circMAP3K5 associated with injury and disease. Lentivirus-mediated overexpression of circMAP3K5 inhibited the proliferation of human coronary artery SMCs. In vivo adeno-associated virus 9-mediated transfection of circMap3k5 (mouse circular Map3k5) specifically inhibited SMC proliferation in the wire-injured mouse arteries, resulting in reduced neointima formation. Using a luciferase reporter assay and RNA pull-down, circMAP3K5 (human circular MAP3K5) was found to sequester miR-22-3p, which, in turn, inhibited the expression of TET2. Both in vitro and in vivo results demonstrate that the loss of miR-22-3p recapitulated the antiproliferative effect of circMap3k5 on vascular SMCs. In SMC-specific Tet2 knockout mice, loss of Tet2 abolished the circMap3k5-mediated antiproliferative effect on vascular SMCs.

Conclusions: We identify circMAP3K5 as a master regulator of TET2-mediated vascular SMC differentiation. Targeting the circMAP3K5/miR-22-3p/TET2 axis may provide a potential therapeutic strategy for diseases associated with intimal hyperplasia, including restenosis and atherosclerosis.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.120.049715DOI Listing
January 2021

Publisher Correction: Innate and plastic mechanisms for maternal behaviour in auditory cortex.

Nature 2020 Nov;587(7834):E2

Skirball Institute for Biomolecular Medicine, New York University School of Medicine, New York, NY, USA.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s41586-020-2898-0DOI Listing
November 2020

Innate and plastic mechanisms for maternal behaviour in auditory cortex.

Nature 2020 11 7;587(7834):426-431. Epub 2020 Oct 7.

Skirball Institute for Biomolecular Medicine, New York University School of Medicine, New York, NY, USA.

Infant cries evoke powerful responses in parents. Whether parental animals are intrinsically sensitive to neonatal vocalizations, or instead learn about vocal cues for parenting responses is unclear. In mice, pup-naive virgin females do not recognize the meaning of pup distress calls, but retrieve isolated pups to the nest after having been co-housed with a mother and litter. Distress calls are variable, and require co-caring virgin mice to generalize across calls for reliable retrieval. Here we show that the onset of maternal behaviour in mice results from interactions between intrinsic mechanisms and experience-dependent plasticity in the auditory cortex. In maternal females, calls with inter-syllable intervals (ISIs) from 75 to 375 milliseconds elicited pup retrieval, and cortical responses were generalized across these ISIs. By contrast, naive virgins were neuronally and behaviourally sensitized to the most common ('prototypical') ISIs. Inhibitory and excitatory neural responses were initially mismatched in the cortex of naive mice, with untuned inhibition and overly narrow excitation. During co-housing experiments, excitatory responses broadened to represent a wider range of ISIs, whereas inhibitory tuning sharpened to form a perceptual boundary. We presented synthetic calls during co-housing and observed that neurobehavioural responses adjusted to match these statistics, a process that required cortical activity and the hypothalamic oxytocin system. Neuroplastic mechanisms therefore build on an intrinsic sensitivity in the mouse auditory cortex, and enable rapid plasticity for reliable parenting behaviour.
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http://dx.doi.org/10.1038/s41586-020-2807-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7677212PMC
November 2020

Reduced Platelet miR-223 Induction in Kawasaki Disease Leads to Severe Coronary Artery Pathology Through a miR-223/PDGFRβ Vascular Smooth Muscle Cell Axis.

Circ Res 2020 09 29;127(7):855-873. Epub 2020 Jun 29.

From the Institute of Pediatrics (Y.Z., L.X., M.Z., Z.Z., Y.L., X.F., K.W., M.S., W.H.T.), Guangzhou Women and Children's Medical Centre, Guangzhou Medical University, China.

Rationale: Kawasaki disease (KD) is an acute vasculitis of early childhood that can result in permanent coronary artery structural damage. The cause for this arterial vulnerability in up to 15% of patients with KD is unknown. Vascular smooth muscle cell dedifferentiation play a key role in the pathophysiology of medial damage and aneurysm formation, recognized arterial pathology in KD. Platelet hyperreactivity is also a hallmark of KD. We recently demonstrated that uptake of platelets and platelet-derived miRNAs influences vascular smooth muscle cell phenotype in vivo.

Objective: We set out to explore whether platelet/vascular smooth muscle cell (VSMC) interactions contribute to coronary pathology in KD.

Methods And Results: We prospectively recruited and studied 242 patients with KD, 75 of whom had documented coronary artery pathology. Genome-wide miRNA sequencing and droplet digital PCR demonstrated that patient with KD platelets have significant induction of miR-223 compared with healthy controls (HCs). Platelet-derived miR-223 has recently been shown to promote vascular smooth muscle quiescence and resolution of wound healing after vessel injury. Paradoxically, patients with KD with the most severe coronary pathology (giant coronary artery aneurysms) exhibited a lack of miR-223 induction. Hyperactive platelets isolated from patients with KD are readily taken up by VSMCs, delivering functional miR-223 into the VSMCs promoting VSMC differentiation via downregulation of PDGFRβ (platelet-derived growth factor receptor β). The lack of miR-223 induction in patients with severe coronary pathology leads to persistent VSMC dedifferentiation. In a mouse model of KD ( cell wall extract injection), miR-223 knockout mice exhibited increased medial thickening, loss of contractile VSMCs in the media, and fragmentation of medial elastic fibers compared with WT mice, which demonstrated significant miR-223 induction upon cell wall extract challenge. The excessive arterial damage in the miR-223 knockout could be rescued by adoptive transfer of platelet, administration of miR-223 mimics, or the PDGFRβ inhibitor imatinib mesylate. Interestingly, miR-223 levels progressively increase with age, with the lowest levels found in <5-year-old. This provides a basis for coronary pathology susceptibility in this very young cohort.

Conclusions: Platelet-derived miR-223 (through PDGFRβ inhibition) promotes VSMC differentiation and resolution of KD induced vascular injury. Lack of miR-223 induction leads to severe coronary pathology characterized by VSMC dedifferentiation and medial damage. Detection of platelet-derived miR-223 in patients with KD (at the time of diagnosis) may identify patients at greatest risk of coronary artery pathology. Moreover, targeting platelet miR-223 or VSMC PDGFRβ represents potential therapeutic strategies to alleviate coronary pathology in KD. Graphic Abstract: A graphic abstract is available for this article.
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http://dx.doi.org/10.1161/CIRCRESAHA.120.316951DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7486265PMC
September 2020

TCF21: Flipping the Phenotypic Switch in SMC.

Circ Res 2020 02 13;126(4):530-532. Epub 2020 Feb 13.

From the Departments of Medicine and Pharmacology, Yale University School of Medicine, New Haven, CT.

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http://dx.doi.org/10.1161/CIRCRESAHA.120.316533DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7041869PMC
February 2020

Mitochondrial MsrB2 serves as a switch and transducer for mitophagy.

EMBO Mol Med 2019 08 8;11(8):e10409. Epub 2019 Jul 8.

Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.

Mitophagy can selectively remove damaged toxic mitochondria, protecting a cell from apoptosis. The molecular spatial-temporal mechanisms governing autophagosomal selection of reactive oxygen species (ROS)-damaged mitochondria, particularly in a platelet (no genomic DNA for transcriptional regulation), remain unclear. We now report that the mitochondrial matrix protein MsrB2 plays an important role in switching on mitophagy by reducing Parkin methionine oxidation (MetO), and transducing mitophagy through ubiquitination by Parkin and interacting with LC3. This biochemical signaling only occurs at damaged mitochondria where MsrB2 is released from the mitochondrial matrix. MsrB2 platelet-specific knockout and in vivo peptide inhibition of the MsrB2/LC3 interaction lead to reduced mitophagy and increased platelet apoptosis. Pathophysiological importance is highlighted in human subjects, where increased MsrB2 expression in diabetes mellitus leads to increased platelet mitophagy, and in platelets from Parkinson's disease patients, where reduced MsrB2 expression is associated with reduced mitophagy. Moreover, Parkin mutations at Met192 are associated with Parkinson's disease, highlighting the structural sensitivity at the Met192 position. Release of the enzyme MsrB2 from damaged mitochondria, initiating autophagosome formation, represents a novel regulatory mechanism for oxidative stress-induced mitophagy.
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http://dx.doi.org/10.15252/emmm.201910409DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6685081PMC
August 2019

Age associated non-linear regulation of redox homeostasis in the anucleate platelet: Implications for CVD risk patients.

EBioMedicine 2019 Jun 24;44:28-40. Epub 2019 May 24.

Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, 300 George St Level 7, New Haven, CT 06511, United States of America. Electronic address:

Background: Aging is a complex physiological phenomenon, intricately associated with cardiovascular pathologies, where platelets play a central pathophysiological role. Although antiplatelets are commonly employed to prevent and treat major adverse cardiovascular events, aging associated intraplatelet changes remain largely unexplored.

Methods: Platelets were studied in high cardiovascular risk patients (aged 40-100 years) comparing them to younger healthy subjects. This was followed by cross sectional and longitudinal mice studies. Flow cytometry, biochemical and molecular assays were used to study platelets comprehensively.

Findings: CVD Patients were categorized in the age groups 40-59, 60-79, and 80-100 years. Progressive decline in platelet health was observed in the 40-79 years age cohort, marked by increase in oxidative stress, hyperactivation and apoptotic markers. Paradoxically, this was reversed in patients aged above 79 years and the improved platelet phenotype was associated with lower oxidative damage. The platelets from the very old (80-100 year) group were found to be preloaded with increased antioxidants, which also contributed to higher resistance against induced redox insults. Cross sectional mouse studies excluded the effect of comorbidities and medications. Longitudinal mouse studies implicate an adaptive increase in antioxidant levels as the mechanism.

Interpretation: We report a novel age associated, non-linear redox regulation in platelets in both humans and mice. In advanced age, there occurs an adaptive increase in platelet antioxidants, reducing the intracellular ROS and leading to a healthier platelet phenotype. Clinically, our results advocate the use of less aggressive antiplatelet therapies for CVD in the elderly population. FUND: Study funded by NIH-NHLBI, RO1-HL122815 and RO1-HL115247.
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http://dx.doi.org/10.1016/j.ebiom.2019.05.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6604369PMC
June 2019

Hippo and Hyperplasia.

Circ Res 2019 04;124(9):1282-1284

From the Departments of Medicine and Pharmacology, Yale University School of Medicine, New Haven, CT.

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http://dx.doi.org/10.1161/CIRCRESAHA.119.314968DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7081792PMC
April 2019

Promoters to Study Vascular Smooth Muscle.

Arterioscler Thromb Vasc Biol 2019 04;39(4):603-612

From the Department of Medicine, Section of Cardiovascular Medicine (R.C., F.Z.S., A.C.C., D.M.G., K.A.M.).

Smooth muscle cells (SMCs) are a critical component of blood vessel walls that provide structural support, regulate vascular tone, and allow for vascular remodeling. These cells also exhibit a remarkable plasticity that contributes to vascular growth and repair but also to cardiovascular pathologies, including atherosclerosis, intimal hyperplasia and restenosis, aneurysm, and transplant vasculopathy. Mouse models have been an important tool for the study of SMC functions. The development of smooth muscle-expressing Cre-driver lines has allowed for exciting discoveries, including recent advances revealing the diversity of phenotypes derived from mature SMC transdifferentiation in vivo using inducible CreER lines. We review SMC-targeting Cre lines driven by the Myh11, Tagln, and Acta2 promoters, including important technical considerations associated with these models. Limitations that can complicate study of the vasculature include expression in visceral SMCs leading to confounding phenotypes, and expression in multiple nonsmooth muscle cell types, such as Acta2-Cre expression in myofibroblasts. Notably, the frequently employed Tagln/ SM22α- Cre driver expresses in the embryonic heart but can also confer expression in nonmuscular cells including perivascular adipocytes and their precursors, myeloid cells, and platelets, with important implications for interpretation of cardiovascular phenotypes. With new Cre-driver lines under development and the increasing use of fate mapping methods, we are entering an exciting new era in SMC research.
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http://dx.doi.org/10.1161/ATVBAHA.119.312449DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6527360PMC
April 2019

Platelet-derived miR-223 promotes a phenotypic switch in arterial injury repair.

J Clin Invest 2019 03 18;129(3):1372-1386. Epub 2019 Feb 18.

Institute of Pediatrics, Guangzhou Women and Children's Medical Center, Guangzhou Medical University, Guangzhou, China.

Upon arterial injury, endothelial denudation leads to platelet activation and delivery of multiple agents (e.g., TXA2, PDGF), promoting VSMC dedifferentiation and proliferation (intimal hyperplasia) during injury repair. The process of resolution of vessel injury repair, and prevention of excessive repair (switching VSMCs back to a differentiated quiescent state), is poorly understood. We now report that internalization of APs by VSMCs promotes resolution of arterial injury by switching on VSMC quiescence. Ex vivo and in vivo studies using lineage tracing reporter mice (PF4-cre × mT/mG) demonstrated uptake of GFP-labeled platelets (mG) by mTomato red-labeled VSMCs (mT) upon arterial wire injury. Genome-wide miRNA sequencing of VSMCs cocultured with APs identified significant increases in platelet-derived miR-223. miR-223 appears to directly target PDGFRβ (in VSMCs), reversing the injury-induced dedifferentiation. Upon arterial injury, platelet miR-223-KO mice exhibited increased intimal hyperplasia, whereas miR-223 mimics reduced intimal hyperplasia. Diabetic mice with reduced expression of miR-223 exhibited enhanced VSMC dedifferentiation and proliferation and increased intimal hyperplasia. Our results suggest that horizontal transfer of platelet-derived miRNAs into VSMCs provides a novel mechanism for regulating VSMC phenotypic switching. Platelets thus play a dual role in vascular injury repair, initiating an immediate repair process and, concurrently, a delayed process to prevent excessive repair.
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http://dx.doi.org/10.1172/JCI124508DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6391113PMC
March 2019

LMO7 Is a Negative Feedback Regulator of Transforming Growth Factor β Signaling and Fibrosis.

Circulation 2019 01;139(5):679-693

Departments of Medicine (Cardiovascular Medicine) (Y.X., A.C.O., Y.J., K.A.M., J.H.), Yale University, New Haven, CT.

Background: Vascular smooth muscle cells (SMCs) synthesize extracellular matrix (ECM) that contributes to tissue remodeling after revascularization interventions. The cytokine transforming growth factor β (TGF-β) is induced on tissue injury and regulates tissue remodeling and wound healing, but dysregulated signaling results in excess ECM deposition and fibrosis. The LIM (Lin11, Isl-1 & Mec-3) domain protein LIM domain only 7 (LMO7) is a TGF-β1 target gene in hepatoma cells, but its role in vascular physiology and fibrosis is unknown.

Methods: We use carotid ligation and femoral artery denudation models in mice with global or inducible smooth muscle-specific deletion of LMO7, and knockout, knockdown, overexpression, and mutagenesis approaches in mouse and human SMC, and human arteriovenous fistula and cardiac allograft vasculopathy samples to assess the role of LMO7 in neointima and fibrosis.

Results: We demonstrate that LMO7 is induced postinjury and by TGF-β in SMC in vitro. Global or SMC-specific LMO7 deletion enhanced neointimal formation, TGF-β signaling, ECM deposition, and proliferation in vascular injury models. LMO7 loss of function in human and mouse SMC enhanced ECM protein expression at baseline and after TGF-β treatment. TGF-β neutralization or receptor antagonism prevented the exacerbated neointimal formation and ECM synthesis conferred by loss of LMO7. Notably, loss of LMO7 coordinately amplified TGF-β signaling by inducing expression of Tgfb1 mRNA, TGF-β protein, αv and β3 integrins that promote activation of latent TGF-β, and downstream effectors SMAD3 phosphorylation and connective tissue growth factor. Mechanistically, the LMO7 LIM domain interacts with activator protein 1 transcription factor subunits c-FOS and c-JUN and promotes their ubiquitination and degradation, disrupting activator protein 1-dependent TGF-β autoinduction. Importantly, preliminary studies suggest that LMO7 is upregulated in human intimal hyperplastic arteriovenous fistula and cardiac allograft vasculopathy samples, and inversely correlates with SMAD3 phosphorylation in cardiac allograft vasculopathy.

Conclusions: LMO7 is induced by TGF-β and serves to limit vascular fibrotic responses through negative feedback regulation of the TGF-β pathway. This mechanism has important implications for intimal hyperplasia, wound healing, and fibrotic diseases.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.118.034615DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6371979PMC
January 2019

TCF7L2 (Transcription Factor 7-Like 2) Regulation of GATA6 (GATA-Binding Protein 6)-Dependent and -Independent Vascular Smooth Muscle Cell Plasticity and Intimal Hyperplasia.

Arterioscler Thromb Vasc Biol 2019 02;39(2):250-262

From the Yale Cardiovascular Research Center (R.S., H.R., Y.X., N.L., N,B., L.H., F.E., J.Z., G.G., K.A.M., A.M.), Yale School of Medicine, New Haven, CT.

Objective- TCF7L2 (transcription factor 7-like 2) is a Wnt-regulated transcription factor that maintains stemness and promotes proliferation in embryonic tissues and adult stem cells. Mice with a coronary artery disease-linked mutation in Wnt-coreceptor LRP6 (LDL receptor-related protein 6) exhibit vascular smooth muscle cell dedifferentiation and obstructive coronary artery disease, which are paradoxically associated with reduced TCF7L2 expression. We conducted a comprehensive study to explore the role of TCF7L2 in vascular smooth muscle cell differentiation and protection against intimal hyperplasia. Approach and Results- Using multiple mouse models, we demonstrate here that TCF7L2 promotes differentiation and inhibits proliferation of vascular smooth muscle cells. TCF7L2 accomplishes these effects by stabilization of GATA6 (GATA-binding protein 6) and upregulation of SM-MHC (smooth muscle cell myosin heavy chain) and cell cycle inhibitors. Accordingly, TCF7L2 haploinsufficient mice exhibited increased susceptibility to injury-induced hyperplasia, while mice overexpressing TCF7L2 were protected against injury-induced intimal hyperplasia compared with wild-type littermates. Consequently, the overexpression of TCF7L2 in LRP6 mutant mice rescued the injury-induced intimal hyperplasia. Conclusions- Our novel findings imply cell type-specific functional role of TCF7L2 and provide critical insight into mechanisms underlying the pathogenesis of intimal hyperplasia.
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http://dx.doi.org/10.1161/ATVBAHA.118.311830DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6365015PMC
February 2019

Technical Feasibility of a Murine Model of Sleeve Gastrectomy with Ileal Transposition.

Obes Surg 2019 02;29(2):593-600

Yale University School of Medicine, New Haven, CT, 06511, USA.

Background: Sleeve gastrectomy with ileal transposition has been shown to be superior to sleeve gastrectomy alone for promoting weight loss in rat and porcine models. The absence of a mouse model for this procedure has impeded efforts to understand the molecular physiology underlying its efficacy. This study demonstrates the long-term survivability of sleeve gastrectomy with ileal transposition in mice.

Materials And Methods: In this study of technical feasibility, a sleeve gastrectomy with ileal transposition (SGIT), sleeve gastrectomy (SG), or sham surgery (SH) was performed on 7- to 8-week-old C57Bl/6J mice (n = 8 for each). To evaluate long-term survivability, mice were placed on an obesogenic diet and weighed weekly for 10 weeks. The intestinal identity of the transposed segment was assessed with gene expression analysis of duodenal-, jejunal-, and ileal-specific hormones using quantitative polymerase chain reaction.

Results: Overall, SGIT better prevented weight gain than the SG or sham procedures (10-week post-operative weight: SH 45.3 ± 1.0 g, SG 41.25 ± 1.6 g, SGIT 35.4 ± 0.8 g). Gene expression pattern analysis of three markers of intestinal identity (gastrin, cholecystokinin, and peptide YY) suggests that the ileal identity of the transposed segment is maintained 10 weeks after transposition.

Conclusions: We demonstrate for the first time a reproducible mouse model of sleeve gastrectomy with ileal transposition. Future studies utilizing this model will expand our understanding of the molecular pathways through which the hindgut regulates satiety.
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http://dx.doi.org/10.1007/s11695-018-3555-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6365182PMC
February 2019

Diabetes Exacerbates Myocardial Ischemia/Reperfusion Injury by Down-Regulation of MicroRNA and Up-Regulation of O-GlcNAcylation.

JACC Basic Transl Sci 2018 Jun 16;3(3):350-362. Epub 2018 May 16.

Shanghai East Hospital, School of Life Sciences and Technology, Advanced Institute of Translational Medicine, Tongji University, Shanghai, China.

Management for patients with diabetes experiencing myocardial infarction remains a challenge. Here the authors show that hyperglycemia- and hyperinsulinemia-induced microRNA-24 (miR-24) reduction and O-GlcNAcylation in the diabetic heart contribute to poor survival and increased infarct size in diabetic myocardial ischemia/reperfusion (I/R). In a mouse model of myocardial I/R, pharmacological or genetic overexpression of miR-24 in hearts significantly reduced myocardial infarct size. Experimental validation revealed that miR-24 targets multiple key proteins, including O-GlcNac transferase, ATG4A, and BIM, to coordinately protect the myocardium from I/R injury. These results establish miR-24 as a promising therapeutic candidate for diabetic I/R injury.
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http://dx.doi.org/10.1016/j.jacbts.2018.01.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6058960PMC
June 2018

Respecting boundaries: CTCF, chromatin structural organization, and heart failure.

J Thorac Dis 2017 Dec;9(12):4889-4892

Yale Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT, USA.

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http://dx.doi.org/10.21037/jtd.2017.11.77DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5757032PMC
December 2017

Opposing Actions of AKT (Protein Kinase B) Isoforms in Vascular Smooth Muscle Injury and Therapeutic Response.

Arterioscler Thromb Vasc Biol 2017 12 12;37(12):2311-2321. Epub 2017 Oct 12.

From the Department of Internal Medicine, Yale Cardiovascular Research Center, Section of Cardiovascular Medicine (Y.J., Y.X., A.C.O., K.L.L., W.T., J.D., S.H.L., Y.W., J.H., K.A.M.) and Department of Pharmacology (Y.J., Y.X., A.C.O., M.Y.L., K.L.L., W.C.S., K.A.M.), Yale University, New Haven, CT; Section of Comparative Medicine and Department of Pathology, Yale University School of Medicine, New Haven, CT (X.Z.); Agnes Ginges Laboratory for Diseases of the Aorta, Centenary Institute, University of Sydney, Camperdown, Australia (R.L.); Sydney Medical School, University of Sydney, Sydney, Australia (R.L.); and Department of Physiology and Center for Metabolic Disease Research, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (J.Y.).

Objective: Drug-eluting stent delivery of mTORC1 (mechanistic target of rapamycin complex 1) inhibitors is highly effective in preventing intimal hyperplasia after coronary revascularization, but adverse effects limit their use for systemic vascular disease. Understanding the mechanism of action may lead to new treatment strategies. We have shown that rapamycin promotes vascular smooth muscle cell differentiation in an AKT2-dependent manner in vitro. Here, we investigate the roles of AKT (protein kinase B) isoforms in intimal hyperplasia.

Approach And Results: We found that germ-line-specific or smooth muscle-specific deletion of resulted in more severe intimal hyperplasia compared with control mice after arterial denudation injury. Conversely, smooth muscle-specific knockout prevented intimal hyperplasia, whereas germ-line deletion caused severe thrombosis. Notably, rapamycin prevented intimal hyperplasia in wild-type mice but had no therapeutic benefit in knockouts. We identified opposing roles for AKT1 and AKT2 isoforms in smooth muscle cell proliferation, migration, differentiation, and rapamycin response in vitro. Mechanistically, rapamycin induced (myocardin) mRNA expression. This was mediated by AKT2 phosphorylation and nuclear exclusion of FOXO4 (forkhead box O4), inhibiting its binding to the promoter.

Conclusions: Our data reveal opposing roles for AKT isoforms in smooth muscle cell remodeling. AKT2 is required for rapamycin's therapeutic inhibition of intimal hyperplasia, likely mediated in part through AKT2-specific regulation of MYOCD via FOXO4. Because AKT2 signaling is impaired in diabetes mellitus, this work has important implications for rapamycin therapy, particularly in diabetic patients.
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http://dx.doi.org/10.1161/ATVBAHA.117.310053DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5699966PMC
December 2017

Coordinating Regulation of Gene Expression in Cardiovascular Disease: Interactions between Chromatin Modifiers and Transcription Factors.

Front Cardiovasc Med 2017 6;4:19. Epub 2017 Apr 6.

Department of Medicine (Cardiovascular Medicine), Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT, USA.

Cardiovascular disease is a leading cause of death with increasing economic burden. The pathogenesis of cardiovascular diseases is complex, but can arise from genetic and/or environmental risk factors. This can lead to dysregulated gene expression in numerous cell types including cardiomyocytes, endothelial cells, vascular smooth muscle cells, and inflammatory cells. While initial studies addressed transcriptional control of gene expression, epigenetics has been increasingly appreciated to also play an important role in this process through alterations in chromatin structure and gene accessibility. Chromatin-modifying proteins including enzymes that modulate DNA methylation, histone methylation, and histone acetylation can influence gene expression in numerous ways. These chromatin modifiers and their marks can promote or prevent transcription factor recruitment to regulatory regions of genes through modifications to DNA, histones, or the transcription factors themselves. This review will focus on the emerging question of how epigenetic modifiers and transcription factors interact to coordinately regulate gene expression in cardiovascular disease. While most studies have addressed the roles of either epigenetic or transcriptional control, our understanding of the integration of these processes is only just beginning. Interrogating these interactions is challenging, and improved technical approaches will be needed to fully dissect the temporal and spatial relationships between transcription factors, chromatin modifiers, and gene expression in cardiovascular disease. We summarize the current state of the field and provide perspectives on limitations and future directions. Through studies of epigenetic and transcriptional interactions, we can advance our understanding of the basic mechanisms of cardiovascular disease pathogenesis to develop novel therapeutics.
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http://dx.doi.org/10.3389/fcvm.2017.00019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5382160PMC
April 2017

Clonal hematopoiesis associated with TET2 deficiency accelerates atherosclerosis development in mice.

Science 2017 02 19;355(6327):842-847. Epub 2017 Jan 19.

Molecular Cardiology, Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, USA.

Human aging is associated with an increased frequency of somatic mutations in hematopoietic cells. Several of these recurrent mutations, including those in the gene encoding the epigenetic modifier enzyme TET2, promote expansion of the mutant blood cells. This clonal hematopoiesis correlates with an increased risk of atherosclerotic cardiovascular disease. We studied the effects of the expansion of -mutant cells in atherosclerosis-prone, low-density lipoprotein receptor-deficient () mice. We found that partial bone marrow reconstitution with TET2-deficient cells was sufficient for their clonal expansion and led to a marked increase in atherosclerotic plaque size. TET2-deficient macrophages exhibited an increase in NLRP3 inflammasome-mediated interleukin-1β secretion. An NLRP3 inhibitor showed greater atheroprotective activity in chimeric mice reconstituted with TET2-deficient cells than in nonchimeric mice. These results support the hypothesis that somatic mutations in blood cells play a causal role in atherosclerosis.
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http://dx.doi.org/10.1126/science.aag1381DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5542057PMC
February 2017

A New Editor of Smooth Muscle Phenotype.

Circ Res 2016 07;119(3):401-3

From the Agnes Ginges Laboratory for Diseases of the Aorta, Centenary Institute, University of Sydney, Camperdown, Australia (R.L.); Sydney Medical School, University of Sydney, Sydney, Australia (R.L.); and Section of Cardiovascular Medicine, Department of Medicine, Yale Cardiovascular Research Center (A.J.B., K.A.M.) and Department of Pharmacology, Yale School of Medicine (A.J.B., K.A.M.), Yale University, New Haven, CT.

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http://dx.doi.org/10.1161/CIRCRESAHA.116.309218DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4966897PMC
July 2016

Inducing mitophagy in diabetic platelets protects against severe oxidative stress.

EMBO Mol Med 2016 07 1;8(7):779-95. Epub 2016 Jul 1.

Section of Cardiovascular Medicine, Department of Internal Medicine, Yale Cardiovascular Research Center, Yale University School of Medicine, New Haven, CT, USA

Diabetes mellitus (DM) is a growing international concern. Considerable mortality and morbidity associated with diabetes mellitus arise predominantly from thrombotic cardiovascular events. Oxidative stress-mediated mitochondrial damage contributes significantly to enhanced thrombosis in DM A basal autophagy process has recently been described as playing an important role in normal platelet activation. We now report a substantial mitophagy induction (above basal autophagy levels) in diabetic platelets, suggesting alternative roles for autophagy in platelet pathology. Using a combination of molecular, biochemical, and imaging studies on human DM platelets, we report that platelet mitophagy induction serves as a platelet protective mechanism that responds to oxidative stress through JNK activation. By removing damaged mitochondria (mitophagy), phosphorylated p53 is reduced, preventing progression to apoptosis, and preserving platelet function. The absence of mitophagy in DM platelets results in failure to protect against oxidative stress, leading to increased thrombosis. Surprisingly, this removal of damaged mitochondria does not require contributions from transcription, as platelets lack a nucleus. The considerable energy and resources expended in "prepackaging" the complex mitophagy machinery in a short-lived normal platelet support a critical role, in anticipation of exposure to oxidative stress.
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http://dx.doi.org/10.15252/emmm.201506046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4931291PMC
July 2016

Bromodomain Blockade for Intimal Hyperplasia--A Good BET?

EBioMedicine 2015 Nov 10;2(11):1574-5. Epub 2015 Nov 10.

Department of Cardiovascular Medicine, Cardiovascular Research Center, Vascular Biology and Therapeutics, Yale University School of Medicine, United States.

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http://dx.doi.org/10.1016/j.ebiom.2015.11.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4740337PMC
November 2015

Dopamine Is Required for the Neural Representation and Control of Movement Vigor.

Cell 2015 Sep;162(6):1418-30

Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA. Electronic address:

Progressive depletion of midbrain dopamine neurons (PDD) is associated with deficits in the initiation, speed, and fluidity of voluntary movement. Models of basal ganglia function focus on initiation deficits; however, it is unclear how they account for deficits in the speed or amplitude of movement (vigor). Using an effort-based operant conditioning task for head-fixed mice, we discovered distinct functional classes of neurons in the dorsal striatum that represent movement vigor. Mice with PDD exhibited a progressive reduction in vigor, along with a selective impairment of its neural representation in striatum. Restoration of dopaminergic tone with a synthetic precursor ameliorated deficits in movement vigor and its neural representation, while suppression of striatal activity during movement was sufficient to reduce vigor. Thus, dopaminergic input to the dorsal striatum is indispensable for the emergence of striatal activity that mediates adaptive changes in movement vigor. These results suggest refined intervention strategies for Parkinson's disease.
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http://dx.doi.org/10.1016/j.cell.2015.08.014DOI Listing
September 2015

New targets to treat obesity and the metabolic syndrome.

Eur J Pharmacol 2015 Sep 19;763(Pt A):64-74. Epub 2015 May 19.

Department of Internal Medicine, Yale University School of Medicine, USA; Department of Genetics, Yale University School of Medicine, USA. Electronic address:

Metabolic syndrome (MetS) is a cluster ofassociated metabolic traits that collectively confer unsurpassed risk for development of cardiovascular disease (CVD) and type 2 diabetes compared to any single CVD risk factor. Truncal obesity plays an exceptionally critical role among all metabolic traits of the MetS. Consequently, the prevalence of the MetS has steadily increased with the growing epidemic of obesity. Pharmacotherapy has been available for obesity for more than one decade, but with little success in improving the metabolic profiles. The serotonergic drugs and inhibitors of pancreatic lipases were among the few drugs that were initially approved to treat obesity. At the present time, only the pancreatic lipase inhibitor orlistat is approved for long-term treatment of obesity. New classes of anti-diabetic drugs, including glucagon-like peptide 1 receptor (GLP-1R) agonists and Dipeptidyl-peptidase IV (DPP-IV) inhibitors, are currently being evaluated for their effects on obesity and metabolic traits. The genetic studies of obesity and metabolic syndrome have identified novel molecules acting on the hunger and satiety peptidergic signaling of the gut-hypothalamus axis or the melanocortin system of the brain and are promising targets for future drug development. The goal is to develop drugs that not only treat obesity, but also favorably impact its associated traits.
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http://dx.doi.org/10.1016/j.ejphar.2015.03.093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4573317PMC
September 2015

Phosphorylation of GATA-6 is required for vascular smooth muscle cell differentiation after mTORC1 inhibition.

Sci Signal 2015 May 12;8(376):ra44. Epub 2015 May 12.

Yale Cardiovascular Research Center, Vascular Biology and Therapeutics Program, and Departments of Medicine and Pharmacology, Yale University School of Medicine, New Haven, CT 06511, USA. Department of Pharmacology and Toxicology, The Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA. Department of Surgery, Section of Vascular Surgery, The Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA.

Vascular smooth muscle cells (VSMCs) undergo transcriptionally regulated reversible differentiation in growing and injured blood vessels. This dedifferentiation also contributes to VSMC hyperplasia after vascular injury, including that caused by angioplasty and stenting. Stents provide mechanical support and can contain and release rapamycin, an inhibitor of the mechanistic target of rapamycin complex 1 (mTORC1). Rapamycin suppresses VSMC hyperplasia and promotes VSMC differentiation. We report that rapamycin-induced differentiation of VSMCs required the transcription factor GATA-6. Inhibition of mTORC1 stabilized GATA-6 and promoted the nuclear accumulation of GATA-6, its binding to DNA, its transactivation of promoters encoding contractile proteins, and its inhibition of proliferation. These effects were mediated by phosphorylation of GATA-6 at Ser(290), potentially by Akt2, a kinase that is activated in VSMCs when mTORC1 is inhibited. Rapamycin induced phosphorylation of GATA-6 in wild-type mice, but not in Akt2(-/-) mice. Intimal hyperplasia after arterial injury was greater in Akt2(-/-) mice than in wild-type mice, and the exacerbated response in Akt2(-/-) mice was rescued to a greater extent by local overexpression of the wild-type or phosphomimetic (S290D) mutant GATA-6 than by that of the phosphorylation-deficient (S290A) mutant. Our data indicated that GATA-6 and Akt2 are involved in the mTORC1-mediated regulation of VSMC proliferation and differentiation. Identifying the downstream transcriptional targets of mTORC1 may provide cell type-specific drug targets to combat cardiovascular diseases associated with excessive proliferation of VSMCs.
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http://dx.doi.org/10.1126/scisignal.2005482DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4560350PMC
May 2015

Hyperglycemia repression of miR-24 coordinately upregulates endothelial cell expression and secretion of von Willebrand factor.

Blood 2015 May 26;125(22):3377-87. Epub 2015 Mar 26.

Section of Cardiovascular Medicine, Department of Internal Medicine, Yale Cardiovascular Research Center.

An elevated level of von Willebrand factor (VWF) in diabetic patients is associated with increased risk of thrombotic cardiovascular events. The underlying mechanism of how VWF expression is upregulated in diabetes mellitus is poorly understood. We now report that hyperglycemia-induced repression of microRNA-24 (miR-24) increases VWF expression and secretion in diabetes mellitus. In diabetic patients and diabetic mouse models (streptozotocin/high-fat diet-induced and db/db mice), miR-24 is reduced in both tissues and plasma. Knockdown of miR-24 in mice leads to increased VWF mRNA and protein levels and enhanced platelet tethering (spontaneous thrombosis). miR-24 tightly controls VWF levels through pleiotropic effects, including direct binding to the 3' untranslated region of VWF and targeting FURIN and the histamine H1 receptor, known regulators of VWF processing and secretion in endothelial cells. We present a novel mechanism for miR-24 downregulation through hyperglycemia-induced activation of aldose reductase, reactive oxygen species, and c-Myc. These findings support a critical role for hyperglycemic repression of miR-24 in VWF-induced pathology. miR-24 represents a novel therapeutic target to prevent adverse thrombotic events in patients with diabetes mellitus.
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http://dx.doi.org/10.1182/blood-2015-01-620278DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4447857PMC
May 2015

The magic touch: endothelial cells muscle-up adipose.

Circ Res 2014 Oct;115(9):752-4

From the Departments of Internal Medicine (K.A.M., K.K.H.) and Pharmacology (K.A.M.), Yale Cardiovascular Research Center and Vascular Biology and Therapeutics Program, Yale University, New Haven, CT.

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http://dx.doi.org/10.1161/CIRCRESAHA.114.305030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4269234PMC
October 2014

Response to letter regarding article, "ten-eleven translocation-2 (TET2) is a master regulator of smooth muscle cell plasticity".

Circulation 2014 Aug;130(8):e72

Department of Internal Medicine, Yale Cardiovascular Research Center, Section of Cardiovascular Medicine, and Department of Pharmacology, Yale University, New Haven, Connecticut.

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http://dx.doi.org/10.1161/CIRCULATIONAHA.114.010272DOI Listing
August 2014
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