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Browsing by Author "Hoggatt, April"
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Item Deletion of P2Y2 receptor reveals a role for lymphotoxin-α in fatty streak formation(Elsevier, 2016-10) Aian, Shaomin; Hoggatt, April; Jones-Hall, Yava L.; Ware, Carl F.; Herring, Paul; Seye, Cheikh I.; Department of Cellular & Integrative Physiology, IU School of MedicineBackground Lymphotoxin alpha (LTα) is expressed in human atherosclerotic lesions and genetic variations in the LTα pathway have been linked to myocardial infarction. Activation of the P2Y2 nucleotide receptor (P2Y2R) regulates the production of LTα. in vitro. We aimed to uncover a potential pathway linking purinergic receptor to LTα-mediated inflammatory processes pivotal to the early stages of atherosclerosis in apolipoprotein E (ApoE−/−) deficient mice. Methods and results En face immunostaining revealed that P2Y2R and VCAM-1 are preferentially expressed in the atherosclerosis prone site of the mouse aortic sinus. Deletion of the P2Y2R gene suppresses VCAM-1 expression. Compared with ApoE−/− mice, ApoE−/− mice lacking the P2Y2R gene (ApoE−/−/P2Y2R−/−) did not develop fatty streak lesions when fed a standard chow diet for 15 weeks. Systemic and CD4+ T cell production of the pro-inflammatory cytokine lymphotoxin-alpha (LTα) were specifically inhibited in ApoE−/−/P2Y2R−/−mice. Anti-LTα preventive treatment was initiated in ApoE−/− mice with intraperitoneal administration of recombinant human tumor necrosis factor receptor 1 fusion protein (TNFR1-Fc) on 5 consecutive days before the disease onset. Remarkably, none of the TNFR1:Fc-treated ApoE−/− mice exhibited atherosclerotic lesions at any developmental stage. Significance ApoE−/− mice deficient in P2Y2R exhibit low endothelial cell VCAM-1 levels, decreased production of LTα and delayed onset of atherosclerosis. These data suggest that targeting this nucleotide receptor could be an effective therapeutic approach in atherosclerosis.Item Endothelial Cell-Specific Deletion of P2Y2 Receptor Promotes Plaque Stability in Atherosclerosis-Susceptible ApoE-Null Mice(American Heart Association, 2017-01) Xingjuan, Chen; Qian, Shaomin; Hoggatt, April; Tang, Hongying; Hacker, Timothy A.; Obukhov, Alexander G.; Herring, Paul B.; Seye, Cheikh I.; Cellular and Integrative Physiology, School of MedicineOBJECTIVE: Nucleotide P2Y2 receptor (P2Y2R) contributes to vascular inflammation by increasing vascular cell adhesion molecule-1 expression in endothelial cells (EC), and global P2Y2R deficiency prevents fatty streak formation in apolipoprotein E null (ApoE-/-) mice. Because P2Y2R is ubiquitously expressed in vascular cells, we investigated the contribution of endothelial P2Y2R in the pathogenesis of atherosclerosis. APPROACH AND RESULTS: EC-specific P2Y2R-deficient mice were generated by breeding VEcadherin5-Cre mice with the P2Y2R floxed mice. Endothelial P2Y2R deficiency reduced endothelial nitric oxide synthase activity and significantly altered ATP- and UTP (uridine 5'-triphosphate)-induced vasorelaxation without affecting vasodilatory responses to acetylcholine. Telemetric blood pressure and echocardiography measurements indicated that EC-specific P2Y2R-deficient mice did not develop hypertension. We investigated the role of endothelial P2Y2R in the development of atherosclerotic lesions by crossing the EC-specific P2Y2R knockout mice onto an ApoE-/- background and evaluated lesion development after feeding a standard chow diet for 25 weeks. Histopathologic examination demonstrated reduced atherosclerotic lesions in the aortic sinus and entire aorta, decreased macrophage infiltration, and increased smooth muscle cell and collagen content, leading to the formation of a subendothelial fibrous cap in EC-specific P2Y2R-deficient ApoE-/- mice. Expression and proteolytic activity of matrix metalloproteinase-2 was significantly reduced in atherosclerotic lesions from EC-specific P2Y2R-deficient ApoE-/- mice. Furthermore, EC-specific P2Y2R deficiency inhibited nitric oxide production, leading to significant increase in smooth muscle cell migration out of aortic explants. CONCLUSIONS: EC-specific P2Y2R deficiency reduces atherosclerotic burden and promotes plaque stability in ApoE-/- mice through impaired macrophage infiltration acting together with reduced matrix metalloproteinase-2 activity and increased smooth muscle cell migration.Item Expression of a Degradation‐Resistant β‐Catenin Mutant in Osteocytes Protects the Skeleton From Mechanodeprivation‐Induced Bone Wasting(Wiley, 2019) Bullock, Whitney A.; Hoggatt, April; Horan, Daniel J.; Lewis, Karl; Yokota, Hiroki; Hann, Steven; Warman, Matthew L.; Sebastian, Aimy; Loots, Gabriela G.; Pavalko, Fredrick M.; Robling, Alexander G.; Anatomy and Cell Biology, IU School of MedicineMechanical stimulation is a key regulator of bone mass, maintenance, and turnover. Wnt signaling is a key regulator of mechanotransduction in bone, but the role of β‐catenin—an intracellular signaling node in the canonical Wnt pathway—in disuse mechanotransduction is not defined. Using the β‐catenin exon 3 flox (constitutively active [CA]) mouse model, in conjunction with a tamoxifen‐inducible, osteocyte‐selective Cre driver, we evaluated the effects of degradation‐resistant β‐catenin on bone properties during disuse. We hypothesized that if β‐catenin plays an important role in Wnt‐mediated osteoprotection, then artificial stabilization of β‐catenin in osteocytes would protect the limbs from disuse‐induced bone wasting. Two disuse models were tested: tail suspension, which models fluid shift, and botulinum‐toxin (botox)‐induced muscle paralysis, which models loss of muscle force. Tail suspension was associated with a significant loss of tibial bone mass and density, reduced architectural properties, and decreased bone formation indices in uninduced (control) mice, as assessed by dual‐energy X‐ray absorptiometry (DXA), micro‐computed tomography (µCT), and histomorphometry. Activation of the βcatCA allele in tail‐suspended mice resulted in little to no change in those properties; ie, these mice were protected from bone loss. Similar protective effects were observed among botox‐treated mice when the βcatCA was activated. RNAseq analysis of altered gene regulation in tail‐suspended mice yielded 35 genes, including Wnt11, Gli1, Nell1, Gdf5, and Pgf, which were significantly differentially regulated between tail‐suspended β‐catenin stabilized mice and tail‐suspended nonstabilized mice. Our findings indicate that selectively targeting/blocking of β‐catenin degradation in bone cells could have therapeutic implications in mechanically induced bone disease.Item Forkhead box F2 Regulation of Platelet-Derived Growth Factor and myocardin/Serum Response Factor Signaling is Essential for Intestinal Development(2015-03) Bolte, Craig; Ren, Xiaomeng; Tomley, Tatiana; Ustiyan, Vladimir; Pradhan, Arun; Hoggatt, April; Kalin, Tanya V.; Herring, B. Paul; Kalinichenko, Vladimir V.; Department of Cellular & Integrative Physiology, IU School of MedicineAlterations in the forkhead box F2 gene expression have been reported in numerous pathologies, and Foxf2−/− mice are perinatal lethal with multiple malformations; however, molecular mechanisms pertaining to Foxf2 signaling are severely lacking. In this study, Foxf2 requirements in murine smooth muscle cells were examined using a conditional knock-out approach. We generated novel Foxf2-floxed mice, which we bred to smMHC-Cre-eGFP mice to generate a mouse line with Foxf2 deleted specifically from smooth muscle. These mice exhibited growth retardation due to reduced intestinal length as well as inflammation and remodeling of the small intestine. Colons of Tg(smMHC-Cre-eGFP+/−);Foxf2−/− mice had expansion of the myenteric nerve plexus and increased proliferation of smooth muscle cells leading to thickening of the longitudinal smooth muscle layer. Foxf2 deficiency in colonic smooth muscle was associated with increased expression of Foxf1, PDGFa, PDGFb, PDGF receptor α, and myocardin. FOXF2 bound to promoter regions of these genes indicating direct transcriptional regulation. Foxf2 repressed Foxf1 promoter activity in co-transfection experiments. We also show that knockdown of Foxf2 in colonic smooth muscle cells in vitro and in transgenic mice increased myocardin/serum response factor signaling and increased expression of contractile proteins. Foxf2 attenuated myocardin/serum response factor signaling in smooth muscle cells through direct binding to the N-terminal region of myocardin. Our results indicate that Foxf2 signaling in smooth muscle cells is essential for intestinal development and serum response factor signaling.Item The P2Y2 nucleotide receptor is an inhibitor of vascular calcification(Elsevier, 2017-02) Qian, Shaomin; Regan, Jenna N.; Shelton, Maxwell T.; Hoggatt, April; Mohammad, Khalid S.; Herring, Paul B.; Seye, Cheikh I.; Cellular and Integrative Physiology, School of MedicineBACKGROUND AND AIMS: Mutations in the 5'-nucleotidase ecto (NT5E) gene that encodes CD73, a nucleotidase that converts AMP to adenosine, are linked to arterial calcification. However, the role of purinergic receptor signaling in the pathology of intimal calcification is not well understood. In this study, we examined whether extracellular nucleotides acting via P2Y2 receptor (P2Y2R) modulate arterial intimal calcification, a condition highly correlated with cardiovascular morbidity. METHODS: Apolipoprotein E, P2Y2R double knockout mice (ApoE-/-P2Y2R-/-) were used to determine the effect of P2Y2R deficiency on vascular calcification in vivo. Vascular smooth muscle cells (VSMC) isolated from P2Y2R-/- mice grown in high phosphate medium were used to assess the role of P2Y2R in the conversion of VSMC into osteoblasts. Luciferase-reporter assays were used to assess the effect of P2Y2R on the transcriptional activity of Runx2. RESULTS: P2Y2R deficiency in ApoE-/- mice caused extensive intimal calcification despite a significant reduction in atherosclerosis and macrophage plaque content. The ectoenzyme apyrase that degrades nucleoside di- and triphosphates accelerated high phosphate-induced calcium deposition in cultured VSMC. Expression of P2Y2R inhibits calcification in vitro inhibited the osteoblastic trans-differentiation of VSMC. Mechanistically, expression of P2Y2R inhibited Runx2 transcriptional activation of an osteocalcin promoter driven luciferase reporter gene. CONCLUSIONS: This study reveals a role for vascular P2Y2R as an inhibitor of arterial intimal calcification and provides a new mechanistic insight into the regulation of the osteoblastic trans-differentiation of SMC through P2Y2R-mediated Runx2 antagonism. Given that calcification of atherosclerotic lesions is a significant clinical problem, activating P2Y2R may be an effective therapeutic approach for treatment or prevention of vascular calcification.