Deletion of hypoxia-inducible factor-1α in myeloid lineage exaggerates angiotensin II-induced formation of abdominal aortic aneurysm

Hypoxia-inducible factor (HIF)-1α is a transcription factor that regulates various genes responding to hypoxic conditions. We previously reported that myeloid-specific activation of HIF-1α had protective effects on hypertensive cardiovascular remodelling in mice. However the role of myeloid lineage HIF-1α in the development of abdominal aortic aneurysm (AAA) has not been determined. Myeloid-specific HIF-1α knockout (HIF-1KO) mice were created using a Cre-lox recombination system in the background of apolipoprotein E-deficient (ApoE^−/−) mice. HIF-1KO and control mice were fed high-fat diet (HFD) and infused with angiotensin II (Ang II, 1800 ng/kg/min) by an osmotic mini pump for 4 weeks to induce AAA formation. Deletion of HIF-1α increased aortic external diameter (2.47±0.21 mm versus 1.80±0.28 mm in control, P=0.035). AAA formation rate (94.4% in HIF-1KO versus 81.8% in control) was not statistically significant. Elastic lamina degradation grade determined by Elastica van Gieson (EVG) staining was deteriorated in HIF-1KO mice (3.91±0.08 versus 3.25±0.31 in control, P=0.013). The number of infiltrated macrophages into the abdominal aorta was increased in HIF-1KO mice. Expression of tissue inhibitors of metalloproteinases (TIMPs) was suppressed in the aorta and peritoneal macrophages (PMs) from HIF-1KO mice compared with control mice. HIF-1α in myeloid lineage cells may have a protective role against AAA formation induced by Ang II and HFD in ApoE^−/− mice.