Adipose tissue–secreted extracellular vesicles (EVs) containing microRNAs (miRNAs) convey intercellular message signaling. The biogenesis of EV‐miRNAs from perivascular adipose tissue (PVAT) and their roles in intercellular communication in response to obesity‐associated inflammation have not yet been fully explored. By feeding mice a high‐fat diet for 16 wk, we established obesity‐associated, chronic low‐grade inflammation in PVAT, characterized as hypertrophy of perivascular adipocytes, decreased adipogenesis, and proinflammatory macrophage infiltration. We show that PVAT‐derived EVs and their encapsulated miRNAs can be taken up into vascular smooth muscle cells (VSMCs) in vivo and in vitro. miR‐221‐3p is one of the highly enriched miRNAs in obese PVAT and PVAT‐derived EVs. Transfer and direct overexpression of miR‐221‐3p dramatically enhances VSMC proliferation and migration. Peroxisome proliferator–activated receptor γ coactivator 1α is identified as a miR‐221‐3p target in VSMC phenotypic modulation. Obese mice secrete abundant miRNA‐containing EVs, evoking inflammatory responses in PVAT and vascular phenotypic switching in abdominal aorta of lean mice. Local delivery of miR‐221‐3p mimic in femoral artery causes vascular dysfunction by suppressing the contractile genes in the arterial wall. Our findings provide an EV–miR‐221‐3p–mediated mechanism by which PVAT triggers an early‐stage vascular remodeling in the context of obesity‐associated inflammation.—Li, X., Ballantyne, L. L., Yu, Y., Funk, C. D. Perivascular adipose tissue–derived extracellular vesicle miR‐221‐3p mediates vascular remodeling. FASEB J. 33, 12704–12722 (2019). http://www.fasebj.org

Arginase deficiency is a rare autosomal recessive disorder resulting from a loss of the liver arginase isoform, arginase 1 (ARG1), which is the final step in the urea cycle for detoxifying ammonia. ARG1 deficiency leads to hyperargininemia, characterized by progressive neurological impairment, persistent growth retardation and infrequent episodes of hyperammonemia. Using the Cre/loxP-directed conditional gene knockout system, we generated an inducible Arg1-deficient mouse model by crossing “floxed” Arg1 mice with CreERT2 mice. The resulting mice (Arg-Cre) die about two weeks after tamoxifen administration regardless of the starting age of inducing the knockout. These treated mice were nearly devoid of Arg1 mRNA, protein and liver arginase activity, and exhibited symptoms of hyperammonemia. Plasma amino acid analysis revealed pronounced hyperargininemia and significant alterations in amino acid and guanidino compound metabolism, including increased citrulline and guanidinoacetic acid. Despite no alteration in ornithine levels, concentrations of other amino acids such as proline and the branched-chain amino acids were reduced. In summary, we have generated and characterized an inducible Arg1-deficient mouse model exhibiting several pathologic manifestations of hyperargininemia. This model should prove useful for exploring potential treatment options of ARG1 deficiency.

Cysteinyl leukotrienes (CysLTs) are potent inflammatory mediators that predominantly exert their effects by binding to cysteinyl leukotriene receptors of the G protein-coupled receptor family. CysLT receptor 2 (CysLT 2 R), expressed in endothelial cells of some vascular beds, has been implicated in a variety of cardiovascular functions. Endothelium-specific overexpression of human CysLT 2 R in transgenic mice (hEC-CysLT 2 R) greatly increases myocardial infarction damage. Investigation of this receptor, however, has been hindered by the lack of selective pharmacological antagonists. Here, we describe the characterization of 3-(((3-carboxycyclohexyl)amino)carbonyl)-4-(3-(4-(4-phenoxybutoxy)phenyl)-propoxy)benzoic acid (BayCysLT 2 ) and explore the selective effects of this compound in attenuating myocardial ischemia/reperfusion damage and vascular leakage. Using a recently developed ␤-galactosidase-␤-arrestin complementation assay for CysLT 2 R activity (Mol Pharmacol 79: 270-278, 2011), we determined BayCysLT 2 to be ϳ20-fold more potent than the nonselective dual CysLT receptor 1 (CysLT 1 R)/ CysLT 2 R antagonist 4-(((1R,2E,4E,6Z,9Z)-1-((1S)-4-carboxy-1-hydroxybutyl)-2,4,6,9-pentadecatetraen-1-yl)thio)benzoic acid (Bayu9773) (IC 50 274 nM versus 4.6 M, respectively). Intracellular calcium mobilization in response to cysteinyl leukotriene administration showed that BayCysLT 2 was Ͼ500-fold more selective for CysLT 2 R compared with CysLT 1 R. Intraperitoneal injection of BayCysLT 2 in mice significantly attenuated leukotriene D 4 -induced Evans blue dye leakage in the murine ear vasculature. BayCysLT 2 administration either before or after ischemia/reperfusion attenuated the aforementioned increased myocardial infarction damage in hECCysLT 2 R mice. Finally, decreased neutrophil infiltration and leukocyte adhesion molecule mRNA expression were observed in mice treated with antagonist compared with untreated controls. In conclusion, we present the characterization of a potent and selective antagonist for CysLT 2 R that is useful for discerning biological activities of this receptor.

Two prostaglandin (PG) H synthases encoded by genes, colloquially known as cyclooxygenase (COX)-1 and COX-2, catalyze the formation of PG endoperoxide H, the precursor of the major prostanoids. To address the functional interchangeability of these two isoforms and their distinct roles, we have generated COX-2>COX-1 mice whereby is knocked in to the locus. We then "flipped" genes to successfully create the Reversa mouse strain, where knock-in COX-2 is expressed constitutively and knock-in COX-1 is lipopolysaccharide (LPS) inducible. In macrophages, flipping the two genes has no obvious impact on COX protein subcellular localization. COX-1 was shown to compensate for PG synthesis at high concentrations of substrate, whereas elevated LPS-induced PG production was only observed for cells expressing endogenous COX-2. Differential tissue-specific patterns of expression of the knock-in proteins were evident. Thus, platelets from COX-2>COX-1 and Reversa mice failed to express knock-in COX-2 and, therefore, thromboxane (Tx) production in vitro and urinary Tx metabolite formation in COX-2>COX-1 and Reversa mice in vivo were substantially decreased relative to WT and COX-1>COX-2 mice. Manipulation of COXs revealed isoform-specific compensatory functions and variable degrees of interchangeability for PG biosynthesis in cells/tissues.

Arginase-1 (Arg1) converts arginine to urea and ornithine in the distal step of the urea cycle in liver. We previously generated a tamoxifen-inducible Arg1 deficient mouse model (Arg1-Cre) that disrupts Arg1 expression throughout the whole body and leads to lethality ≈ 2 weeks after gene disruption. Here, we evaluate if liver-selective Arg1 loss is sufficient to recapitulate the phenotype observed in global Arg1 knockout mice, as well as to gauge the effectiveness of gene delivery or hepatocyte transplantation to rescue the phenotype. Liver-selective Arg1 deletion was induced by using an adeno-associated viral (AAV)-thyroxine binding globulin (TBG) promoter-Cre recombinase vector administered to Arg1 “floxed” mice; Arg1fl/fl). An AAV vector expressing an Arg1-enhanced green fluorescent protein (Arg1-eGFP) transgene was used for gene delivery, while intrasplenic injection of wild-type (WT) C57BL/6 hepatocytes after partial hepatectomy was used for cell delivery to “rescue” tamoxifen-treated Arg1-Cre mice. The results indicate that liver-selective loss of Arg1 (> 90% deficient) leads to a phenotype resembling the whole body knockout of Arg1 with lethality ≈ 3 weeks after Cre-induced gene disruption. Delivery of Arg1-eGFP AAV rescues more than half of Arg1 global knockout male mice (survival > 4 months) but a significant proportion still succumb to the enzyme deficiency even though liver expression and enzyme activity of the fusion protein reach levels observed in WT animals. Significant Arg1 enzyme activity from engrafted WT hepatocytes into knockout livers can be achieved but not sufficient for rescuing the lethal phenotype. This raises a conundrum relating to liver-specific expression of Arg1. On the one hand, loss of expression in this organ appears to be both necessary and sufficient to explain the lethal phenotype of the genetic disorder in mice. On the other hand, gene and cell-directed therapies suggest that rescue of extra-hepatic Arg1 expression may also be necessary for disease correction. Further studies are needed in order to illuminate the detailed mechanisms for pathogenesis of Arg1-deficiency.