Severe Hypertriglyceridemia Caused By Gpihbp1 Deficiency Facilitates Vascular Remodeling

BackgroundHypertriglyceridemia（HTG）,characterized by abnormally increased serum triglyceride-rich lipoprotein（TRL）levels,is increasingly recognized as an independent risk factor for atherosclerosis（AS）which plays an important role in the onset and progression of atherosclerotic cardiovascular diseases（ASCVDs）,such as coronary heart disease and stroke.However,its role in non-atherosclerotic cardiovascular diseases remains unclear.Glycosylphosphatidylinositol anchored high density lipoprotein binding protein 1（GPIHBP1）,a lipoprotein receptor exclusively expressed in the capillary endothelial cells,provides an essential platform for lipoprotein lipase-mediated hydrolysis of TRL.Loss of functional GPIHBP1 disrupts triglyceride homeostasis and causes severe HTG.AimsIn this study,Gpihbp1 knockout(Gpihbp1^-/-,GKO)mice were used to investigate whether severe HTG leads to any spontaneous non-atherosclerotic vasculopathy.Furthermore,in an angiotensionⅡ（AngⅡ）-induced hypertension model,investigation was performed to explore whether severe HTG could affect AngⅡ-induced vascular remodeling.Methods（1）Thoracic aortic rings collected from three-month-old and ten-month-old male Gpihbp1 knockout(Gpihbp1^-/-,GKO)mice and their matched littermates（Ctrl）were fixed and morphologically analyzed.Hematoxylin-eosin（H&E）staining,Mac-2immunohistochemical staining and Masson staining were used to evaluate the aortic intima-media wall thickness,proinflammatory macrophage infiltration and perivascular fibrosis,respectively.MCP-1,VCAM-1 and ICAM-1 immunofluorescent staining were used to evaluate endothelial activation,and dihydroethidium（DHE）staining to evaluate aortic oxidative stress levels.Furthermore,aortas collected from GKO and Ctrl mice were also used for real-time quantitative PCR to analyze the aortic expression of macrophage-derived proinfllammatory cytokines（Cd68,Il-1βand Il-6）,endothelial-derived chemoattractive and adhesive molecules（Mcp1,Vcam1 and Icam1）,collagen-associated genes（α-sma,Col1 and Col3）as well as oxidative stress-associated NAPDH oxidases（Nox2 and Nox4）.（2）Eight-week-old male Gpihbp1^-/-mice（GKO）and their littermates（Ctrl）were perfused with AngⅡ（1000ng/kg/min）for two weeks to induce hypertension and hypertensive vascular remodeling.Thoracic aortic rings collected from AngⅡ-infused and saline-infused mice were fixed and morphologically analyzed.Hematoxylin-eosin（H&E）staining,Mac-2 immunohistochemical staining and Masson staining were used to evaluate the aortic intima-media wall thickness,proinflammatory macrophage infiltration and perivascular fibrosis,respectively.MCP-1,VCAM-1 and ICAM-1immunofluorescent staining were used to evaluate endothelial activation,and dihydroethidium（DHE）staining to evaluate aortic oxidative stress levels.Furthermore,aortas collected from GKO and Ctrl mice were also used for real-time quantitative PCR to analyze the aortic expression of macrophage-derived proinflammatory cytokines（Cd68,Il-1βand Il-6）,endothelial-derived chemoattractive and adhesive molecules（Mcp1,Vcam1 and Icam1）,collagen-associated genes（α-sma,Col1 and Col3）as well as oxidative stress-associated NAPDH oxidases（Nox2 and Nox4）.Results（1）No significant structural change in the vasculatures was observed between three-month-old GKO and age-matched Ctrl mice.When mice reached ten-month-old,GKO mice developed spontaneous intima-media thickening with increased aortic proinflammatory macrophage infiltration and perivascular fibrosis.Furthermore,ten-month-old GKO mice presented with signs of endothelial activation and aortic oxidative stress.（2）AngⅡinfusion significantly increased blood systolic pressures in the mice.Although the AngⅡ-induced increase of blood pressures in the GKO mice was comparable with that of Ctrl mice,the AngⅡ-induced increase of aortic intima-media wall thickness,proinflammatory cell infiltration and perivascular fibrosis were all exacerbated in the GKO mice.In addition,the AngⅡ-induced increase of endothelial activation and oxidative stress were also exacerbated in the GKO mice.ConclusionsSevere HTG in GKO mice led to spontaneous vascular remodeling and promoted AngⅡ-induced vascular remodeling,indicating that HTG might contribute to the onset and progression of non-atherosclerotic vascular diseases.Endothelial activation and oxidative stress might involve in the HTG-stimulated spontaneous and stress-induced vascular remodeling process.