Species-specific regulation of angiogenesis by glucocorticoids reveals contrasting effects on inflammatory and angiogenic pathways

Glucocorticoids are potent inhibitors of angiogenesis in the rodent in vivo and in vitro but the mechanism by which this occurs has not been determined. Administration of glucocorticoids is used to treat a number of conditions in horses but the angiogenic response of equine vessels to glucocorticoids and, therefore, the potential role of glucocorticoids in pathogenesis and treatment of equine disease, is unknown. This study addressed the hypothesis that glucocorticoids would be angiostatic both in equine and murine blood vessels.The mouse aortic ring model of angiogenesis was adapted to assess the effects of cortisol in equine vessels. Vessel rings were cultured under basal conditions or exposed to: foetal bovine serum (FBS; 3%); cortisol (600 nM), cortisol (600nM) plus FBS (3%), cortisol (600nM) plus either the glucocorticoid receptor antagonist RU486 or the mineralocorticoid receptor antagonist spironolactone. In murine aortae cortisol inhibited and FBS stimulated new vessel growth. In contrast, in equine blood vessels FBS alone had no effect but cortisol alone, or in combination with FBS, dramatically increased new vessel growth compared with controls. This effect was blocked by glucocorticoid receptor antagonism but not by mineralocorticoid antagonism. The transcriptomes of murine and equine angiogenesis demonstrated cortisol-induced down-regulation of inflammatory pathways in both species but up-regulation of pro-angiogenic pathways selectively in the horse. Genes up-regulated in the horse and down-regulated in mice were associated with the extracellular matrix. These data call into question our understanding of glucocorticoids as angiostatic in every species and may be of clinical relevance in the horse.糖皮质激素（glucocorticoids）在啮齿类动物的体内及体外实验中均为强效的血管生成抑制剂，但其发挥作用的具体分子机制迄今尚未阐明。临床中常通过施用糖皮质激素治疗马类的多种病症，但马类血管对糖皮质激素的血管生成应答，以及糖皮质激素在马类疾病发病机制与治疗中的潜在作用，目前仍不明确。本研究针对“糖皮质激素对马类及鼠类血管均具有血管生成抑制作用”这一假说展开探究。本研究改良了小鼠主动脉环血管生成模型，以此评估皮质醇（cortisol）对马类血管的作用效果。血管环在基础培养条件下进行培养，或分别接受以下处理：胎牛血清（foetal bovine serum, FBS；3%）、皮质醇（600 nM）、皮质醇联合3%胎牛血清，以及600 nM皮质醇分别联合糖皮质激素受体拮抗剂RU486或盐皮质激素受体拮抗剂螺内酯（spironolactone）。在小鼠主动脉样本中，皮质醇可抑制新生血管生成，而胎牛血清则可促进新生血管生长。与之相反，在马类血管样本中，单独使用胎牛血清无明显促血管生成效果，但单独使用皮质醇，或皮质醇联合胎牛血清处理，均较对照组显著促进了新生血管生成。该促血管生成效应可被糖皮质激素受体拮抗作用阻断，但盐皮质激素受体拮抗作用无法产生类似阻断效果。鼠类与马类血管生成的转录组分析结果显示，皮质醇可在两个物种中均下调炎症相关通路，但仅在马类中选择性上调促血管生成通路。在马类中上调、在鼠类中下调的基因，均与细胞外基质密切相关。本研究数据对“糖皮质激素在所有物种中均为血管生成抑制剂”这一传统认知提出了质疑，其结果或对马类疾病的临床诊疗具有参考价值。