The active component of ginseng, ginsenoside Rb1, improves erythropoiesis in models of Diamond-Blackfan anemia by targeting Nemo-like kinase.

Nemo-like kinase (NLK) is a member of the mitogen-activated protein kinase family of kinases and shares a highly conserved kinase domain with other mitogen-activated protein kinase family members. The activation of NLK contributes to the pathogenesis of Diamond-Blackfan anemia (DBA), reducing c-myb expression and mechanistic target of rapamycin activity, and is therefore a potential therapeutic target. Unlike other anemias, the hematopoietic effects of DBA are largely restricted to the erythroid lineage. Mutations in ribosomal genes induce ribosomal insufficiency and reduced protein translation, dramatically impacting early erythropoiesis in the bone marrow of patients with DBA. We sought to identify compounds that suppress NLK and increases erythropoiesis in ribosomal insufficiency. We report that the active component of ginseng, ginsenoside Rb1, suppresses NLK expression and improves erythropoiesis in in vitro models of DBA. Ginsenoside Rb1-mediated suppression of NLK occurs through the upregulation of miR-208, which binds to the 3'-UTR of NLK mRNA and targets it for degradation. We also compare ginsenoside Rb1-mediated upregulation of miR-208 with metformin-mediated upregulation of miR-26. We conclude that targeting NLK expression through miRNA binding of the unique 3'-UTR is a viable alternative to the challenges of developing small-molecule inhibitors to target the highly conserved kinase domain of this specific kinase.

Metformin-induced suppression of Nemo-like kinase improves erythropoiesis in preclinical models of Diamond-Blackfan anemia through induction of miR-26a.

Diamond-Blackfan anemia (DBA) results from haploinsufficiency of ribosomal protein subunits in hematopoietic progenitors in the earliest stages of committed erythropoiesis. Nemo-like kinase (NLK) is chronically hyperactivated in committed erythroid progenitors and precursors in multiple human and murine models of DBA. Inhibition of NLK activity and suppression of NLK expression both improve erythroid expansion in these models. Metformin is a well-tolerated drug for type 2 diabetes with multiple cellular targets. Here we demonstrate that metformin improves erythropoiesis in human and zebrafish models of DBA. Our data indicate that the effects of metformin on erythroid proliferation and differentiation are mediated by suppression of NLK expression through induction of miR-26a, which recognizes a binding site within the NLK 3' untranslated region (3'UTR) to facilitate transcript degradation. We propose that induction of miR-26a is a potentially novel approach to treatment of DBA and could improve anemia in DBA patients without the potentially adverse side effects of metformin in a DBA patient population.