Paradoxical protection from atherosclerosis and thrombosis in a mouse model of sickle cell disease.

Sickle cell disease (SCD) is associated with vascular complications including premature stroke. The role of atherothrombosis in these vascular complications is unclear. To determine the effect of SCD on atherosclerosis and thrombosis, mice with SCD along with controls were generated by transplantation of bone marrow from mice carrying the homozygous sickle cell mutation (Hbb(hßs/hßs) ) or wild-type mice (Hbb(+/+) ) into C57BL6/J or apolipoprotein E deficient (Apoe(-/-) ) recipient mice. At the time of sacrifice, 23-28 weeks following bone marrow transplantation, anaemia, reticulocytosis, and splenomegaly were present in mice receiving Hbb(hßs/hßs) bone marrow compared with control mice. Analysis of atherosclerosis involving the aortic root revealed reduced atherosclerotic lesion area with reduced macrophage content and increased collagen content in Apoe(-/-) , Hbb(hßs/hßs) mice compared to Apoe(-/-) , Hbb(+/+) mice. In a carotid thrombosis model, the time to thrombosis was prolonged in Hbb(hßs/hßs) mice compared to Hbb(+/+) mice. This apparent protective effect of SCD on atherosclerosis and thrombosis was diminished by inhibition of heme oxygenase-1 (HMOX1) using zinc protoporphyrin IX. We conclude that SCD in mice is paradoxically protective against atherosclerosis and thrombosis, highlighting the complexity of vascular events in SCD. This protective effect is at least partially mediated by induction of HMOX1.

Obesity-induced endothelial dysfunction is prevented by deficiency of P-selectin glycoprotein ligand-1.

Endothelial dysfunction precedes atherosclerosis and represents an important link between obesity and cardiovascular events. Strategies designed to prevent endothelial dysfunction may therefore reduce the cardiovascular complications triggered by obesity. We tested the hypothesis that deficiency of P-selectin glycoprotein ligand-1 (Psgl-1) would improve the endothelial dysfunction associated with obesity. Psgl-1-deficient (Psgl-1(-/-)) and wild-type (Psgl-1(+/+)) mice were fed standard chow or a high-fat, high-sucrose diet (diet-induced obesity [DIO]) for 10 weeks. DIO increased mesenteric perivascular adipose tissue (mPVAT) macrophage content and vascular oxidative stress in Psgl-1(+/+) mice but not in Psgl-1(-/-) mice. Pressure myography using mesenteric arteries demonstrated that relaxation responses to acetylcholine were significantly impaired in DIO Psgl-1(+/+) mice, whereas DIO Psgl-1(-/-) mice were protected from endothelial dysfunction with similar relaxation responses to Psgl-1(+/+) or Psgl-1(-/-) mice fed standard chow. The superoxide scavenger 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy (TEMPOL) partially recovered impaired endothelial function induced by DIO. A neutralizing Psgl-1 antibody was also effective in preventing endothelial dysfunction and reducing mPVAT macrophage content induced by DIO. These results indicate that obesity in mice leads to PVAT inflammation and endothelial dysfunction that is prevented by Psgl-1 deficiency. Psgl-1 inhibition may be a useful treatment strategy for targeting vascular disease associated with obesity.