Arachidonic acid 15-lipoxygenases (ALOX15) play a role in mammalian erythropoiesis but they have also been implicated in inflammatory processes. Seven intact Alox genes have been detected in the mouse reference genome and the mouse Alox15 gene is structurally similar to the orthologous genes of other mammals. However, mouse and human ALOX15 orthologs have different functional characteristics. Human ALOX15 converts C20 polyenoic fatty acids like arachidonic acid mainly to the n-6 hydroperoxide. In contrast, the n-9 hydroperoxide is the major oxygenation product formed by mouse Alox15. Previous experiments indicated that Leu353Phe exchange in recombinant mouse Alox15 humanized the catalytic properties of the enzyme. To investigate whether this functional humanization might also work in vivo and to characterize the functional consequences of mouse Alox15 humanization we generated Alox15 knock-in mice (Alox15-KI), in which the Alox15 gene was modified in such a way that the animals express the arachidonic acid 15-lipoxygenating Leu353Phe mutant instead of the arachidonic acid 12-lipoxygenating wildtype enzyme. These mice develop normally, they are fully fertile but display modified plasma oxylipidomes. In young individuals, the basic hematological parameters were not different when Alox15-KI mice and outbred wildtype controls were compared. However, when growing older male Alox15-KI mice develop signs of dysfunctional erythropoiesis such as reduced hematocrit, lower erythrocyte counts and attenuated hemoglobin concentration. These differences were paralleled by an improved ex vivo osmotic resistance of the peripheral red blood cells. Interestingly, such differences were not observed in female individuals suggesting gender specific effects. In summary, these data indicated that functional humanization of mouse Alox15 induces defective erythropoiesis in aged male individuals.

中文翻译：

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表达人源化花生四烯酸 15-脂氧合酶 (Alox15) 的敲入小鼠携带部分功能失调的红细胞生成系统

花生四烯酸 15-脂氧合酶 (ALOX15) 在哺乳动物红细胞生成中发挥作用，但它们也与炎症过程有关。在小鼠参考基因组中检测到了七个完整的Alox基因，并且小鼠Alox15基因在结构上与其他哺乳动物的直系同源基因相似。然而，小鼠和人类 ALOX15 直系同源物具有不同的功能特征。人 ALOX15 主要将花生四烯酸等 C20 多烯脂肪酸转化为 n-6 氢过氧化物。相比之下，n-9 氢过氧化物是小鼠 Alox15 形成的主要氧化产物。先前的实验表明，重组小鼠 Alox15 中的 Leu353Phe 交换使该酶的催化特性人性化。为了研究这种功能性人源化是否也可能在体内发挥作用，并表征小鼠 Alox15 人源化的功能后果，我们生成了 Alox15 敲入小鼠 (Alox15-KI)，其中 Alox15 基因经过修饰，使动物表达花生四烯酸 15-脂氧合 Leu353Phe 突变体代替花生四烯酸 12-脂氧合野生型酶。这些小鼠发育正常，具有完全的生育能力，但显示出经过修饰的血浆氧脂质体。在年轻个体中，当比较 Alox15-KI 小鼠和远交野生型对照时，基本血液学参数没有差异。然而，随着年龄的增长，雄性 Alox15-KI 小鼠会出现红细胞生成功能障碍的迹象，例如血细胞比容降低、红细胞计数降低和血红蛋白浓度减弱。这些差异与外周红细胞的离体渗透阻力的改善相一致。有趣的是，在女性个体中没有观察到这种差异，这表明存在性别特异性影响。总之，这些数据表明小鼠 Alox15 的功能性人源化会诱导老年男性个体红细胞生成缺陷。