Dataset Information

Retinoic Acid Signaling Coordinates Macrophage-Dependent Injury and Repair after AKI.

ABSTRACT: Retinoic acid (RA) has been used therapeutically to reduce injury and fibrosis in models of AKI, but little is known about the regulation of this pathway and what role it has in regulating injury and repair after AKI. In these studies, we show that RA signaling is activated in mouse and zebrafish models of AKI, and that these responses limit the extent of injury and promote normal repair. These effects were mediated through a novel mechanism by which RA signaling coordinated the dynamic equilibrium of inflammatory M1 spectrum versus alternatively activated M2 spectrum macrophages. Our data suggest that locally synthesized RA represses proinflammatory macrophages, thereby reducing macrophage-dependent injury post-AKI, and activates RA signaling in injured tubular epithelium, which in turn promotes alternatively activated M2 spectrum macrophages. Because RA signaling has an essential role in kidney development but is repressed in the adult, these findings provide evidence of an embryonic signaling pathway that is reactivated after AKI and involved in reducing injury and enhancing repair.

SUBMITTER: Chiba T

PROVIDER: S-EPMC4731115 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Retinoic Acid Signaling Coordinates Macrophage-Dependent Injury and Repair after AKI.

Chiba Takuto T Skrypnyk Nataliya I NI Skvarca Lauren Brilli LB Penchev Radostin R Zhang Ke Xin KX Rochon Elizabeth R ER Fall Jessica L JL Paueksakon Paisit P Yang Haichun H Alford Catherine E CE Roman Beth L BL Zhang Ming-Zhi MZ Harris Raymond R Hukriede Neil A NA de Caestecker Mark P MP

Journal of the American Society of Nephrology : JASN 20150624 2

Retinoic acid (RA) has been used therapeutically to reduce injury and fibrosis in models of AKI, but little is known about the regulation of this pathway and what role it has in regulating injury and repair after AKI. In these studies, we show that RA signaling is activated in mouse and zebrafish models of AKI, and that these responses limit the extent of injury and promote normal repair. These effects were mediated through a novel mechanism by which RA signaling coordinated the dynamic equilibr ...[more]

PMID: 26109319

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Project description:BackgroundVitamin A is necessary for kidney development and has also been linked to regulation of solute and water homeostasis and to protection against kidney stone disease, infection, inflammation, and scarring. Most functions of vitamin A are mediated by its main active form, all-trans retinoic acid (tRA), which binds retinoic acid receptors (RARs) to modulate gene expression. We and others have recently reported that renal tRA/RAR activity is confined to the ureteric bud (UB) and collecting duct (CD) cell lineage, suggesting that endogenous tRA/RARs primarily act through regulating gene expression in these cells in embryonic and adult kidney, respectively.Methodology/principal findingsTo explore target genes of endogenous tRA/RARs, we employed the mIMCD-3 mouse inner medullary CD cell line, which is a model of CD principal cells and exhibits constitutive tRA/RAR activity as CD principal cells do in vivo. Combining antagonism of RARs, inhibition of tRA synthesis, exposure to exogenous tRA, and gene expression profiling techniques, we have identified 125 genes as candidate targets and validated 20 genes that were highly regulated (Dhrs3, Sprr1a, and Ppbp were the top three). Endogenous tRA/RARs were more important in maintaining, rather than suppressing, constitutive gene expression. Although many identified genes were expressed in UBs and/or CDs, their exact functions in this cell lineage are still poorly defined. Nevertheless, gene ontology analysis suggests that these genes are involved in kidney development, renal functioning, and regulation of tRA signaling.Conclusions/significanceA rigorous approach to defining target genes for endogenous tRA/RARs has been established. At the pan-genomic level, genes regulated by endogenous tRA/RARs in a CD cell line have been catalogued for the first time. Such a catalogue will guide further studies on molecular mediators of endogenous tRA/RARs during kidney development and in relation to renal defects associated with vitamin A deficiency.

Project description:Retinoic acid (RA), the bioactive derivative of vitamin A, is essential for vertebrate heart development. Both excess and reduced RA signaling lead to cardiovascular malformations, particularly affecting the cardiac outflow tract (OFT). The cellular mechanisms underlying the effects of RA signaling during OFT morphogenesis are not fully understood. To address this question, we used transient maternal RA supplementation to rescue the early lethality resulting from inactivation of the murine retinaldehyde dehydrogenase 2 (Raldh2) gene. By embryonic day 13.5, Raldh2-/- hearts exhibited OFT septation defects. Although cardiac neural crest cells (cNCC) were present in OFT cushions of Raldh2-/- mutant embryos, we observed that cNCC were ectopically located in the peripheral region of the endocardial cushions, closer to the myocardium rather than immediately subjacent to the endocardium. Mislocated cNCC were aligned in parallel instead of perpendicular arrays to the endocardial surface within the proximal OFT. Supernumerary mesenchyme was generated both in and ex vivo within the cushions by Raldh2-/- mutant endocardium and found in place of the cNCC in a subendocardial, medial position. Although mislocated and misoriented, mutant cNCC resembled wildtype cells in their compaction density and individually elongated shape. Our data show that RA signaling acts on cNCC orientation relative to the septation plane and position within OFT cushions during septation process. Transcriptomic analysis and pathway-specific readout suggest that up-regulation of the Bmp pathway may be responsible for increased endothelial-to-mesenchymal transition, leading thereby to displacement of cNCC. E10.5 stage embryonic mouse outflow tracts were microdissected. Four pools of four outflow tracts were established for wildtype (WT) and mutant (Raldh2-/-) embryos derived from dams whose food had been supplemented with all-trans-RA (Sigma) directly mixed into powdered food at 0.1 mg/g food and offered between E7.5 and E8.5. Total RNA was extracted using Macherey-Nagel NucleoSpinÂ® RNA columns without on-column DNase digestion.

Dataset Information

Retinoic Acid Signaling Coordinates Macrophage-Dependent Injury and Repair after AKI.

Publications

Retinoic Acid Signaling Coordinates Macrophage-Dependent Injury and Repair after AKI.

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