Haojun Xuan

Peptide Inhibitor of CXCL4–CCL5 Heterodimer Formation, MKEY, Inhibits Experimental Aortic Aneurysm Initiation and Progression

Objective—Macrophages are critical contributors to abdominal aortic aneurysm (AAA) disease. We examined the ability of MKEY, a peptide inhibitor of CXCL4–CCL5 interaction, to influence AAA progression in murine models. Approach and Results—AAAs were created in 10-week-old male C57BL/6J mice by transient infrarenal aortic porcine pancreatic elastase infusion. Mice were treated with MKEY via intravenous injection either (1) before porcine pancreatic elastase infusion or (2) after aneurysm initiation. Immunostaining demonstrated CCL5 and CCR5 expression on aneurysmal aortae and mural monocytes/macrophages, respectively. MKEY treatment partially inhibited migration of adaptively transferred leukocytes into aneurysmal aortae in recipient mice. Although all vehicle-pretreated mice developed AAAs, aneurysms formed in only 60% (3/5) and 14% (1/7) of mice pretreated with MKEY at 10 and 20 mg/kg, respectively. MKEY pretreatment reduced aortic diameter enlargement, preserved medial elastin fibers and smooth muscle cells, and attenuated mural macrophage infiltration, angiogenesis, and aortic metalloproteinase 2 and 9 expression after porcine pancreatic elastase infusion. MKEY initiated after porcine pancreatic elastase infusion also stabilized or reduced enlargement of existing AAAs. Finally, MKEY treatment was effective in limiting AAA formation after angiotensin II infusion in apolipoprotein E–deficient mice. Conclusion—MKEY suppresses AAA formation and progression in 2 complementary experimental models. Peptide inhibition of CXCL4–CCL5 interactions may represent a viable translational strategy to limit progression of human AAA disease.

Hypoxia-inducible factor 1 in clinical and experimental aortic aneurysm disease

OBJECTIVE Mural angiogenesis and macrophage accumulation are two pathologic hallmarks of abdominal aortic aneurysm (AAA) disease. The heterodimeric transcription factor hypoxia-inducible factor 1 (HIF-1) is an essential regulator of angiogenesis and macrophage function. In this study, we investigated HIF-1 expression and activity in clinical and experimental AAA disease. METHODS Human aortic samples were obtained from 24 AAA patients and six organ donors during open abdominal surgery. Experimental AAAs were created in 10-week-old male C57BL/6J mice by transient intra-aortic infusion of porcine pancreatic elastase (PPE). Expression of HIF-1α and its target gene messenger RNA (mRNA) levels were assessed in aneurysmal and control aortae. The HIF-1α inhibitors 2-methoxyestradiol and digoxin, the prolyl hydroxylase domain-containing protein (PHD) inhibitors cobalt chloride and JNJ-42041935, and the vehicle alone as control were administered daily to mice at varying time points beginning before or after PPE infusion. Influences on experimental AAA formation and progression were assessed by serial transabdominal ultrasound measurements of aortic diameter and histopathologic analysis at sacrifice. RESULTS The mRNA levels for HIF-1α, vascular endothelial growth factor A, glucose transporter 1, and matrix metalloproteinase 2 were significantly increased in both human and experimental aneurysm tissue. Tissue immunostaining detected more HIF-1α protein in both human and experimental aneurysmal aortae compared with respective control aortae. Treatment with either HIF-1α inhibitor, beginning before or after PPE infusion, prevented enlargement of experimental aneurysms. Both HIF-1α inhibition regimens attenuated medial elastin degradation, smooth muscle cell depletion, and mural angiogenesis and the accumulation of macrophages, T cells, and B cells. Whereas mRNA levels for PHD1 and PHD2 were elevated in experimental aneurysmal aortae, pharmacologic inhibition of PHDs had limited effect on experimental aneurysm progression. CONCLUSIONS Expression of HIF-1α and its target genes is increased in human and experimental AAAs. Treatment with HIF-1α inhibitors limits experimental AAA progression, with histologic evidence of attenuated mural leukocyte infiltration and angiogenesis. These findings underscore the potential significance of HIF-1α in aneurysm pathogenesis and as a target for pharmacologic suppression of AAA disease.

Pathogenic and Therapeutic Significance of Angiotensin II Type I Receptor in Abdominal Aortic Aneurysms

BACKGROUND Abdominal aortic aneurysm (AAA) is a chronic degenerative inflammatory disease. Multi-factors including genetic, environmental and lifestyle factors determine the onsets and progression of AAAs. Currently surgical repair remains the only effective aneurysm treatment, but no pharmacological therapy is available for limiting further enlargement of small AAAs and fetal rupture. OBJECTIVE This article is to review our current understanding of angiotensin II (Ang II) and its type 1 receptor (AT1) in AAA pathogenesis as well as the translational potential of AT1 receptor blocker (ARB) treatment for treating clinical AAA disease. RESULTS While many pathways or molecules have been shown to associate with AAA formation and progression, accumulating evidence indicates the most significant importance of peptide hormone Ang II and its receptor AT1 in AAA pathogenesis and suggests the translational value of targeting inhibition of AT1 in treating clinical AAA disease. This review summarized the influences of AT1 deficiency and pharmacological ARB treatment on experimental AAAs. A discussion has also been made on whether and how ARB medication in AAA patients changes the natural course of clinical AAAs, including aneurysm enlargement rate, rupture and AAA-specific mortality. Additionally, we provided information on two registered clinical trials which are to test the efficacy of telmisartan and valsartan in limiting small AAA enlargement. CONCLUSION Ang II/AT1 pathway plays a critical role in aneurysmal pathogenesis. Targeting AT1 via ARB will help establishing novel pharmacological therapies for limiting continuous enlargement of small AAAs in patients.