PDZK1 prevents neointima formation via suppression of breakpoint cluster region kinase in vascular smooth muscle

PDZK1 regulated by miR-145-5p protects against endothelial cell apoptosis and diabetic retinopathy by targeting mitochondrial function

Mitochondria are a focus of biomedical research because of their role in apoptosis and diabetic retinopathy (DR) initiation and progression. However, the detailed mechanisms underlying mitochondrial disorders and endothelial dysfunction during DR remain elusive. We identified PDZ domain containing 1 (PDZK1) as a key factor linking endothelial mitochondrial dysfunction and cell apoptosis during DR progression. PDZK1 was downregulated by high concentrations of glucose in human retinal capillary endothelial cells (HRCECs) and decreased in serum from patients with DR. PDZK1 knockout induced endothelial cell apoptosis and an irregular and disordered arrangement of retinal cells, aggravating DR. Moreover, PDZK1 loss impaired endothelial mitochondrial function with accumulated damaged mitochondria, decreased mitochondrial DNA (mtDNA) content, and increased reactive oxygen species (ROS) production. Mechanistically, mRNA sequencing showed that PDZK1 deficiency in endothelial cells interfered with mitochondrial function by increasing ATF4 (Activating Transcription Factor 4) expression. Further studies showed that PDZK1 was inhibited by miR-145-5p. The expression of miR-145-5p was significantly upregulated in the serum of patients with DR and HRCECs with high glucose concentration, leading to endothelial dysfunction and DR progression. Our results suggested that PDZK1 deficiency is crucial in mediating retinal endothelial cell apoptosis and is associated with mitochondrial dysfunction. PDZK1 overexpression by upstream miRNA, or its downstream molecule, ATF4, may represent novel therapeutic approaches for DR treatment.

Reduction of In-Stent Restenosis by Cholesteryl Ester Transfer Protein Inhibition

OBJECTIVE

Angioplasty and stent implantation, the most common treatment for atherosclerotic lesions, have a significant failure rate because of restenosis. This study asks whether increasing plasma high-density lipoprotein (HDL) levels by inhibiting cholesteryl ester transfer protein activity with the anacetrapib analog, des-fluoro-anacetrapib, prevents stent-induced neointimal hyperplasia.

APPROACH AND RESULTS

New Zealand White rabbits received normal chow or chow supplemented with 0.14% (wt/wt) des-fluoro-anacetrapib for 6 weeks. Iliac artery endothelial denudation and bare metal steel stent deployment were performed after 2 weeks of des-fluoro-anacetrapib treatment. The animals were euthanized 4 weeks poststent deployment. Relative to control, dietary supplementation with des-fluoro-anacetrapib reduced plasma cholesteryl ester transfer protein activity and increased plasma apolipoprotein A-I and HDL cholesterol levels by 53±6.3% and 120±19%, respectively. Non-HDL cholesterol levels were unaffected. Des-fluoro-anacetrapib treatment reduced the intimal area of the stented arteries by 43±5.6% (P<0.001), the media area was unchanged, and the arterial lumen area increased by 12±2.4% (P<0.05). Des-fluoro-anacetrapib treatment inhibited vascular smooth muscle cell proliferation by 41±4.5% (P<0.001). Incubation of isolated HDLs from des-fluoro-anacetrapib-treated animals with human aortic smooth muscle cells at apolipoprotein A-I concentrations comparable to their plasma levels inhibited cell proliferation and migration. These effects were dependent on scavenger receptor-B1, the adaptor protein PDZ domain-containing protein 1, and phosphatidylinositol-3-kinase/Akt activation. HDLs from des-fluoro-anacetrapib-treated animals also inhibited proinflammatory cytokine-induced human aortic smooth muscle cell proliferation and stent-induced vascular inflammation.

CONCLUSIONS

Inhibiting cholesteryl ester transfer protein activity in New Zealand White rabbits with iliac artery balloon injury and stent deployment increases HDL levels, inhibits vascular smooth muscle cell proliferation, and reduces neointimal hyperplasia in an scavenger receptor-B1, PDZ domain-containing protein 1- and phosphatidylinositol-3-kinase/Akt-dependent manner.

SR-B1 and PDZK1: partners in HDL regulation

PURPOSE OF REVIEW

To outline the roles of SR-B1 and PDZK1 in hepatic selective HDL cholesterol uptake and reverse cholesterol transport and the consequences for atherosclerosis development.

RECENT FINDINGS

Much of our understanding of the physiological roles of SR-B1 and PDZK1 in HDL metabolism and atherosclerosis comes from studies of genetically manipulated mice. These show SR-B1 and PDZK1 play key roles in HDL metabolism and protection against atherosclerosis. The recent identification of rare loss of function mutations in the human SCARB1 gene verifies that it plays similar roles in HDL metabolism in humans. Other rare mutations in both the human SCARB1 and PDZK1 genes remain to be characterized but may have potentially devastating consequences to SR-B1 function.

SUMMARY

Identification of carriers of rare mutations in human SCARB1 and PDZK1 that impair the function of their gene products and characterization of the effects of these mutations on HDL cholesterol levels and atherosclerosis will add to our understanding of the importance of HDL function and cholesterol flux, as opposed to HDL-cholesterol levels, per se, for protection against cardiovascular disease.