Effect of Doxycycline on Progression of Arterial Calcification in the Noninvasive Treatment of Abdominal Aortic Aneurysm Clinical Trial (N-TA(3)CT).

BACKGROUND: Doxycycline has been shown to prevent arterial calcification via attenuation of matrix metalloproteinases (MMP) in preclinical models. We assessed the effects of doxycycline on progression of arterial calcification in patients enrolled in the Non-Invasive Treatment of Abdominal Aortic Aneurysm Clinical Trial (N-TA3CT). METHODS: Two hundred and sixty-one patients were randomized to 100 mg doxycycline twice daily or placebo. Arterial calcification was measured in abdominal vessels on noncontrast computed tomography scans. Patients with baseline computed tomography scan and 1 or more follow-up scans within the 2-year study were included for analysis. For individual arteries, mean change in iliofemoral artery calcification over time was calculated via linear regression. Serum MMP-3 and MMP-9 levels were measured at baseline and 6 months. RESULTS: Sixty-five patients in the doxycycline and 66 in the placebo arm were included in this analysis. Baseline characteristics between the groups were similar. The unadjusted mean change in iliofemoral calcium score per year trended toward higher values in patients treated with doxycycline compared with placebo (322 ± 399 units/year vs. 217 ± 307 units/year, P = 0.09). After 6 months, changes in serum MMP-3 and MMP-9 levels were not significantly different between study arms. CONCLUSIONS: In patients with small aortic aneurysm, treatment with doxycycline 100 mg twice daily did not decrease circulating levels of the matrix degrading enzymes MMP-3 and 9 or alter the progression of arterial calcification.

Deletion of CCR2 but not CCR5 or CXCR3 inhibits aortic aneurysm formation.

BACKGROUND: Microscopic analysis of abdominal aortic aneurysms (AAAs) demonstrates an abundance of infiltrating leukocytes. The chemokine receptors CCR2, CCR5, and CXCR3 are associated with pathways implicated previously in aneurysm pathogenesis. We hypothesized that genetic deletions of CCR2, CCR5, and CXCR3 would limit leukocyte infiltration and aneurysm formation in a mouse model of AAA. METHODS: CCR2(-/-), CCR5(-/-), CXCR3(-/-), and control mice of the same genetic background were subject to periaortic application of calcium chloride. Aortic diameters were measured before aneurysm induction and at harvest 6 weeks later. Diameters were compared using the Mann-Whitney test. Aortas were stained with H&E and trichrome for histologic analysis. Aortic MMP-2 and MMP-9 activities were measured using zymography. RESULTS: Aneurysm formation was attenuated in CCR2(-/-) mice with the final mean aortic diameter less than that of the control mice (P < .01). Histology revealed preservation of the lamellar architecture and decreased inflammatory cells. Aortic MMP-2 and MMP-9 levels were decreased in CCR2(-/-) mice. CCR5(-/-) and CXCR3(-/-) mice demonstrated no protection from aneurysm formation, which was corroborated by the tissue histology showing similar inflammatory cell infiltration and elastin degradation. CONCLUSIONS: The CCR2 receptor is involved directly in AAA formation, whereas the CCR5 and CXCR3 receptors are not.

Mitochondrial defects and oxidative damage in patients with peripheral arterial disease.

Abnormal mitochondrial function is present in patients with peripheral arterial disease and may contribute to its clinical manifestations. However, the specific biochemical mitochondrial defects and their association with increased oxidative stress have not been fully characterized. Gastrocnemius muscle was obtained from peripheral arterial disease patients (n = 25) and age-matched controls (n = 16) and mitochondrial parameters were measured. Complexes I through IV of the electron transport chain were individually evaluated to assess for isolated defects. Muscle was also evaluated for protein and lipid oxidative changes by measuring the levels of protein carbonyls, lipid hydroperoxides, and total 4-hydroxy-2-nonenal binding and for the activities of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase. Mitochondrial electron transport chain complexes I, III, and IV in arterial disease patients demonstrated significant reductions in enzymatic activities and mitochondrial respiration compared to controls. Oxidative stress biomarker analysis demonstrated significantly increased levels of protein carbonyls, lipid hydroperoxides, and 4-hydroxy-2-nonenal compared to control muscle. Antioxidant enzyme activities were altered, with a significant decrease in superoxide dismutase activity and significant increases in catalase and glutathione peroxidase. Peripheral arterial disease is associated with abnormal mitochondrial function and evidence of significant oxidative stress.