Immune activation caused by vascular oxidation promotes fibrosis and hypertension

ure 1D). Aortas from 3-month-old tg sm/p22phox mice were similar to those of WT mice, but at 6 and 9 months of age, aortas from these mice demonstrated depressed pressure-diameter relationships.This was reflected by a leftward shift in the stress-strain curves (Figure 1E), indicating increased stiffness of the aortas of tg sm/p22phox mice at 6 and 9 months of age.To confirm aortic stiffening in vivo, we measured PWV as previously described (20).At 3 months of age, PWV in WT and tg sm/p22phox mice was similar; however, with aging, this parameter increased in tg sm/p22phox mice but did not significantly change in WT mice (Supplemental Figure 1; supplemental material available online with this article; doi:10.1172/JCI80761DS1).Nox1 expression and a 2-fold increase in vascular superoxide and hydrogen peroxide production (19).Masson's trichrome staining revealed minimal collagen staining in the aorta of WT mice at either 3, 6, or 9 months of age (Figure 1, A andB).In contrast, aortic adventitial collagen content was increased in the tg sm/p22phox mice at 6 and 9 months of age.Hydroxyproline analysis confirmed that aortic collagen content was increased by about 2-fold at 6 and 9 months of age in tg sm/p22phox mice (Figure 1C).Mechanical properties of the aortas of WT and tg sm/p22phox mice were studied ex vivo in a pressurized vessel apparatus.Aortas from WT mice at 3, 6, and 9 months of age demonstrated identical increases in diameter as intraluminal pressure was increased (Fig-Figure 2. Vascular oxidative stress induced by deletion of smooth muscle Sod3 promotes age-related aortic stiffening and hypertension.(A) Masson's trichrome blue staining in 3-, 6-, and 9-month-old Sod3 fl/fl Cre -and Sod3 fl/fl Smmhc-Cre mice.Tamoxifen was administered at 3 mg/20 kg in corn oil via i.p. injection at 10 weeks of age.Images are ×20 magnification.Scale bars: 100 μm.(B) Aortic hydroxyproline content.(C and D) Pressure diameter relationship and stress-strain relationships.(E and F) Blood pressure measured by radiotelemetry (n = 6-8).# P < 0.05 vs. Cre -/-; *P < 0.05 vs. Sod3 fl/fl Smmhc Cre 3 month; **P < 0.05 vs. Sod3 fl/fl Smmhc-Cre 3 month.Aortic hydroxyproline content was analyzed using 2-way ANOVA.Pressure diameter relationships, stress-strain relationships, and blood pressures were analyzed using 1-way ANOVA with repeated measures.