Aortic pathology from protein kinase G activation is prevented by an antioxidant vitamin B12 analog

Abstract

People heterozygous for an activating mutation in protein kinase G1 ( PRKG1 , p.Arg177Gln) develop thoracic aortic aneurysms and dissections (TAAD) as young adults. Here we report that mice heterozygous for the mutation have a three-fold increase in basal protein kinase G (PKG) activity, and develop age-dependent aortic dilation. Prkg1 R177Q/+ aortas show increased smooth muscle cell apoptosis, elastin fiber breaks, and oxidative stress compared to aortas from wild type littermates. Transverse aortic constriction (TAC)—to increase wall stress in the ascending aorta—induces severe aortic pathology and mortality from aortic rupture in young mutant mice. The free radical-neutralizing vitamin B 12 -analog cobinamide completely prevents age-related aortic wall degeneration, and the unrelated anti-oxidant N-acetylcysteine ameliorates TAC-induced pathology. Thus, increased basal PKG activity induces oxidative stress in the aorta, raising concern about the widespread clinical use of PKG-activating drugs. Cobinamide could be a treatment for aortic aneurysms where oxidative stress contributes to the disease, including Marfan syndrome.

Aortic disease in Marfan syndrome is caused by overactivation of sGC-PRKG signaling by NO

“…In this scenario, high NO and superoxide anion levels would generate peroxynitrite, leading to nitrosative stress accompanied by Tyr/Trp-nitration and S-nytrosylation of proteins and oxidative damage to other biomolecules 18 . Oxidative stress has been linked to syndromic and nonsyndromic familial aortic diseases 28,56 ; moreover, in MFS mice redox stress is associated with NOX4 (NADPH oxidase 4), which is upregulated in the aortas of MFS patients and whose deficiency protects MFS mice from elastic-fiber fragmentation and aortic dilation 28 .…”

“…Tissue levels of pVASP-S239 could also be used to determine if PRKG activation is a signature of other TAADs. Recent findings show that a gain-of-function mutation in the human PRKG1 gene generates a constitutively activated kinase and predisposes to TAA in affected families; moreover, the equivalent activating mutation in heterozygous mice (Prkg1 R177Q/+ mice) triggers an age-dependent aortic dilation 56,70,71 . In affected families, the increased PRKG1 activity stimulates myosin regulatory light chain phosphatase, which can alter VSMC contractility 71 .…”

“…An essential role of NO-sGC-PRKG signaling in aortopathy does not exclude roles in the disease for NOS2-derived signals independent of this pathway. Indeed, oxidants such as NOS2derived superoxide anion can also activate PRKG 29 , and signals downstream of PRKG involving oxidative stress and JNK activation have been shown to mediate aortopathy in Prkg1 R177Q/+ mice, in which antioxidants prevent age-dependent aortic dilation 56 . However, the action of PRKG appears to be mediated mainly through its regulation of contractility via myosin light chain phosphatase activation and decreased calcium influx in VSMCs 44,72 .…”

Reactive Oxygen Species and Oxidative Stress in the Pathogenesis and Progression of Genetic Diseases of the Connective Tissue

“…PRKG1 encodes for cGMP-dependent protein kinase 1, which is an essential mediator of VSMC tone through NO/cGMP-signaling. Here, basal protein kinase G (PKG) activity was significantly increased in mice carrying the PRKG1 mutation, which leads to oxidative stress, increased VSMC apoptosis, and elastin fiber breaks [ 212 ].…”

“…This is the case of cobinamide, an analog of the free radical-neutralizing vitamin B 12 , which prevented aortic wall degeneration in a heterozygous mutant mouse for protein kinase G1 (PRKG1) that leads to its overactivation. The antioxidant N-acetylcysteine also ameliorated the aortopathy in these mutant mice [ 212 ]. Another promising example comes from the use of resveratrol in MFS [ 234 ].…”