Col4a1 mutation in mice causes defects in vascular function and low blood pressure associated with reduced red blood cell volume.
Collagen type IV is the major structural component of the basement membrane and COL4A1 mutations cause adult small vessel disease, familial porencephaly and hereditary angiopathy with nephropathy aneurysm and cramps (HANAC) syndrome. Here, we show that animals with a Col4a1 missense mutation (Col4a1(+/Raw)) display focal detachment of the endothelium from the media and age-dependent defects in vascular function including a reduced response to nor-epinephrine. Age-dependent hypersensitivity to acetylcholine is abolished by inhibition of nitric oxide synthase (NOS) activity, indicating that Col4a1 mutations affect vasorelaxation mediated by endothelium-derived nitric oxide (NO). These defects are associated with a reduction in basal NOS activity and the development of heightened NO sensitivity of the smooth muscle. The vascular function defects are physiologically relevant as they maintain in part the hypotension in mutant animals, which is primarily associated with a reduced red blood cell volume due to a reduction in red blood cell number, rather than defects in kidney function. To understand the molecular mechanism underlying these vascular defects, we examined the deposition of collagen type IV in the basement membrane, and found it to be defective. Interestingly, this mutation also leads to activation of the unfolded protein response. In summary, our results indicate that mutations in COL4A1 result in a complex vascular phenotype encompassing defects in maintenance of vascular tone, endothelial cell function and blood pressure regulation.
Van Agtmael
Tom
T
Faculty of Biomedical and Life Sciences, University of Glasgow, University Avenue, Glasgow G12 8QQ, UK. tom.van.agtmael@bio.gla.ac.uk
Bailey
Matthew A
MA
Schlötzer-Schrehardt
Ursula
U
Craigie
Eilidh
E
Jackson
Ian J
IJ
Brownstein
David G
DG
Megson
Ian L
IL
Mullins
John J
JJ
D000818:Animals; D000831:Animals, Newborn; D001808:Blood Vessels / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology* / Q000648:ultrastructure; D002543:Cerebral Hemorrhage / Q000097:blood / Q000150:complications / Q000473:pathology / Q000503:physiopathology; D024141:Collagen Type IV / Q000235:genetics*; D006152:Cyclic GMP / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D004911:Erythrocyte Volume / Q000502:physiology*; D006706:Homeostasis / Q000187:drug effects; D007022:Hypotension / Q000097:blood* / Q000150:complications / Q000503:physiopathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology / Q000648:ultrastructure; D009154:Mutation / Q000235:genetics*; D009569:Nitric Oxide / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D056811:Unfolded Protein Response / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
D024141:Collagen Type IV; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP