Hemodynamic forces regulate mural macrophage infiltration in experimental aortic aneurysms

Blood flow (BF) and wall shear stress (WSS) influence reactive oxygen species production and oxidative stress in abdominal aortic aneurysm (AAA) disease. To gain further insight into the mechanisms of hemodynamic influences on AAA inflammation, we examined aneurysm macrophage density, chemotaxis and survival under varying aortic flow conditions. Rat AAAs were created via porcine pancreatic elastase (PPE) infusion. In selected cohorts, AAA flow was increased via left common femoral arteriovenous fistula (AVF) creation (HF-AAA) or decreased by left common iliac ligation (LF-AAA). WSS was highest in HF-AAA (10.4 +/- 2.3 dyn/cm(2) vs. 2.4 +/- 0.4 and 0.5 +/- 0.2 for NF- and LF-AAA, respectively, P < 0.001) 7 days after PPE infusion, with reduced medial macrophage density and increased apoptosis. Adventitial macrophage density was not significantly influenced by flow. Monocyte chemoattractant protein-1 (MCP-1) and granulocyte-macrophage colony-stimulating factor (GM-CSF) gene expression correlated with observed macrophage densities in the media and adventitia. Luminal flow conditions regulate AAA inflammation in part via influences on medial macrophage density. Hemodynamic forces may modulate AAA inflammation and diameter enlargement via direct regulation of intimal macrophage adhesion, transmural migration or survival.

Platelets in nonresponders to epinephrine stimulation showed reduced response to ADP

It has been reported that platelets from some healthy donors did not respond to epinephrine (Epi). To identify the cause for the lack of response, we examined the alpha(2) adrenoceptor in the platelets and their signal transduction pathways. No differences in the genomic (-2076 to 1526 bp) and coding region of alpha(2A) adrenoceptor complementary DNA (cDNA) were found between the responders (R) and nonresponders (NR). No expression of alpha(2B) or alpha(2C) adrenoceptor was detected in platelets. When UK14,304 was used to induce platelet aggregation, similar effect to Epi was observed between R and NR, and any involvement of the alpha(1) and beta adrenoceptor was ruled out. Radioligand binding assay showed similar number of alpha(2) binding sites between the two groups (139+/-25/platelet vs. 145+/-37/platelets). However, platelets from NR showed a weaker response to adenosine diphosphate (ADP, 52.3+/-17.8% vs. 80.5+/-8.7% from R, P<.01). In the presence of P2Y(1) antagonist adenosine 3',5'-diphosphosulfate (A3P5PS), ADP failed to induce platelet aggregation in NR (7.8+/-4.7% vs. 64.7+/-11.2% in R, P<.01). Addition of SQ22,536 to inhibit adenylyl cyclase did not convert NR to R. These observations demonstrate that there is an impaired platelet responsiveness to ADP as well as to Epi in NR, due to a difference in downstream of the signal transduction pathway but independent of adenylyl cyclase inhibition.