Abstract 17225: Extracellular Signal-Regulated Kinase 1/2 is Essential for Lipocalin-2 Signaling in Endothelial Cells
Introduction: Lipocalin-2 (Lcn2) is an acute phase protein and a marker of kidney injury. Recently, elevated Lcn2-levels have been reported in heart failure and myocardial infarction. Moreover, stimulation of breast cancer angiogenesis was observed. Thus, we hypothesized that Lcn2 may be a regulator of vascular function and a target for the treatment of ischemic vascular disorders.
Methods/Results: In-vitro Lcn2 mediated proliferation of human umbilical vein endothelial cells (HUVEC; rel. proliferation Lcn2 10 nM vs. ctr.: 1.4±0.09, n=3, P<0.001) and human coronary artery endothelial cells (HCAEC; rel. proliferation Lcn2 10 nM vs. ctr.: 1.3±0.07, n=3, P<0.01) as determined by BrdU-incorporation. In the in-vitro matrigel assay stimulation of HUVEC (1.4 fold vs. ctr., n=3, P<0.01) and HCAEC (1.6 fold vs. ctr., n=3, P<0.001) with Lcn2 resulted in a significant induction of capillary like tube formation. All effects were similar to vascular endothelial growth factor (VEGF). Mechanistically these results can be traced back to phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). Real-time PCR analyses revealed expression of Lcn2 and its receptor by endothelial cells (EC) as well as a hypoxia-dependent up-regulation (rel. Lcn2 mRNA hypoxia vs. normoxia 1.6±0.2, P<0.05; rel. Lcn2-receptor mRNA hypoxia vs. normoxia 2.6±0.2, P<0.001).
In the mouse aortic ring assay Lcn2-treatment resulted in a significant outgrowth of EC similar to VEGF. In the hind limb ischemia (HLI) model Lcn2 -/- mice showed an impressive phenotype. After induction of HLI we detected significantly more tissue defects compared to wild type (WT) mice. The ischemia-related lesions were more severe as determined by necrosis score (necrosis score Lcn2 -/- 1.8±0.2 vs. WT 0.7±0.2, n=5, P<0.01) and amputation rate was significantly higher. In ischemic hind limbs of Lcn2 -/- mice ERK1/2-phosphorylation was almost abrogated which might be an underlying mechanism. Transplantation of WT-bone marrow to irradiated Lcn2 -/- mice didn’t influence the outcome suggesting that observed effects are rather endothelium-dependent than influenced by an inflammatory response.
Conclusion: Lcn2 might be a promising therapeutic factor for the treatment of ischemic vascular disorders.
Author Disclosures: M. Theurl: None. A. Schroll: None. I. Theurl: None. D. Lener: None. W. Franz: None. G. Weiss: None. R. Kirchmair: None.
- © 2014 by American Heart Association, Inc.