Loss of PDZK1 causes coronary artery occlusion and myocardial infarction in Paigen diet-fed apolipoprotein E deficient mice.

BACKGROUND

PDZK1 is a four PDZ-domain containing protein that binds to the carboxy terminus of the HDL receptor, scavenger receptor class B type I (SR-BI), and regulates its expression, localization and function in a tissue-specific manner. PDZK1 knockout (KO) mice are characterized by a marked reduction of SR-BI protein expression ( approximately 95%) in the liver (lesser or no reduction in other organs) with a concomitant 1.7 fold increase in plasma cholesterol. PDZK1 has been shown to be atheroprotective using the high fat/high cholesterol ('Western') diet-fed murine apolipoprotein E (apoE) KO model of atherosclerosis, presumably because of its role in promoting reverse cholesterol transport via SR-BI.

PRINCIPAL FINDINGS

Here, we have examined the effects of PDZK1 deficiency in apoE KO mice fed with the atherogenic 'Paigen' diet for three months. Relative to apoE KO, PDZK1/apoE double KO (dKO) mice showed increased plasma lipids (33% increase in total cholesterol; 49 % increase in unesterified cholesterol; and 36% increase in phospholipids) and a 26% increase in aortic root lesions. Compared to apoE KO, dKO mice exhibited substantial occlusive coronary artery disease: 375% increase in severe occlusions. Myocardial infarctions, not observed in apoE KO mice (although occasional minimal fibrosis was noted), were seen in 7 of 8 dKO mice, resulting in 12 times greater area of fibrosis in dKO cardiac muscle.

CONCLUSIONS

These results show that Paigen-diet fed PDZK1/apoE dKO mice represent a new animal model useful for studying coronary heart disease and suggest that PDZK1 may represent a valuable target for therapeutic intervention.