Western diet consumption promotes vascular remodeling in non-senescent mice consistent with accelerated senescence, but does not modify vascular morphology in senescent ones

Transient cerebral ischaemia alters mesenteric arteries in hypertensive rats: Limited reversal despite suberoylanilide hydroxamic acid cerebroprotection

Stroke induces brain injury, especially severe in hypertensive patients, and elevates mortality rates through non-neurological complications. However, the potential effects of a transient ischaemic episode on the peripheral vasculature of hypertensive individuals remain unclear. We investigated whether transient cerebral ischaemia (90 min)/reperfusion (1 or 8 days) induces alterations in mesenteric resistance artery (MRA) properties in adult male spontaneously hypertensive rats (SHR). In addition, we assessed whether the reported cerebroprotective effects of suberoylanilide hydroxamic acid (SAHA; 50 mg/kg; administered intraperitoneally at 1, 4, or 6 h after reperfusion onset) extend over several days and include beneficial effects on MRAs. Functional and structural properties of MRAs were examined at 1- and 8-days post-stroke. Nuclei distribution, collagen content, and oxidative stress were assessed. Ischaemic brain damage was evaluated longitudinally using magnetic resonance imaging. Following stroke, MRAs from SHR exhibited non-reversible impaired contractile responses to the thromboxane A2 receptor agonist U46619. Stroke increased the MRA cross-sectional area, wall thickness, and wall/lm ratio due to augmented collagen deposition. These changes were partially sustained 8 days later. SAHA did not improve U46619-induced contractions but mitigated stroke-induced oxidative stress and collagen deposition, preventing MRA remodelling at 24 h of reperfusion. Furthermore, SAHA induced sustained cerebroprotective effects over 8 days, including reduced brain infarct and oedema, and improved neurological scores. However, SAHA had minimal impact on chronic MRA contractile impairments and remodelling. These findings suggest that stroke causes MRA changes in hypertensive subjects. While SAHA treatment offers sustained protection against brain damage, it cannot fully restore MRA alterations.

Sirt1 overexpression attenuates Western-style diet-induced aortic stiffening in mice

Increased arterial stiffness is a cardiovascular disease risk factor in the setting of advancing age and Western diet (WD) induced obesity. Increases in large artery stiffness, as measured by pulse wave velocity (PWV), occur within 8 weeks of WD feeding in mice. Sirtuin-1 (Sirt1), a NAD-dependent deacetylase, regulates cellular metabolic activity and activation of this protein has been associated with vasoprotection in aged mice. The aim of the study was to elucidate the effect of global Sirt1 overexpression (Sirttg ) on WD-induced arterial stiffening. Sirt1 overexpression did not influence PWV in normal chow (NC) fed mice. However, PWV was higher in wild-type (WT) mice (p < 0.04), but not in Sirttg mice, after 12 weeks of WD and this effect was independent of changes in blood pressure or the passive pressure diameter relation in the carotid artery. Overexpression of Sirt1 was associated with lower collagen and higher elastin mRNA expression in the aorta of WD fed mice (both p < 0.05). Although MMP2 and MMP3 mRNA were both upregulated in WT mice after WD (both p < 0.05), this effect was reversed in Sirttg mice compared to WT mice fed WD (both p < 0.05). Surprisingly, histologically assessed collagen and elastin quality were unchanged in the aortas of WT or Sirttg mice after WD. However, Sirttg mice were protected from WD-induced glucose intolerance, although there was no difference in insulin tolerance between groups. These findings demonstrate a vasoprotective effect of Sirt1 overexpression that limits the increase in arterial stiffness in response to consumption of a WD.

Arachnoid membrane as a source of sphingosine-1-phosphate that regulates mouse middle cerebral artery tone

Growing evidence indicates that perivascular tissue is critical to modulate vessel function. We hypothesized that the arachnoid membrane surrounding middle cerebral artery (MCA) regulates its function via sphingosine-1-phosphate (S1P)-induced vasoconstriction. The MCA from 3- to 9-month-old male and female wild-type (Oncine France 1 and C57BL/6) mice and sphingosine kinase 2 knockout (SphK2-/-) mice in the C57BL/6 background was mounted in pressure myographs with and without arachnoid membrane. Raman microspectroscopy and imaging were used for in situ detection of S1P. The presence of arachnoid tissue was associated with reduced external and lumen MCA diameters, and with an increase in basal tone regardless of sex and strain background. Strong S1P-positive signals were detected in the arachnoid surrounding the MCA wall in both mice models, as well as in a human post-mortem specimen. Selective S1P receptor 3 antagonist TY 52156 markedly reduced both MCA vasoconstriction induced by exogenous S1P and arachnoid-dependent basal tone increase. Compared to 3-month-old mice, the arachnoid-mediated contractile influence persisted in 9-month-old mice despite a decline in arachnoid S1P deposits. Genetic deletion of SphK2 decreased arachnoid S1P content and vasoconstriction. This is the first experimental evidence that arachnoid membrane regulates the MCA tone mediated by S1P.

Crosstalk between Peripheral Small Vessel Properties and Anxious-like Profiles: Sex, Genotype, and Interaction Effects in Mice with Normal Aging and 3×Tg-AD mice at Advanced Stages of Disease

Cardiovascular disease resulting from oxidative stress and inflammation can exacerbate Alzheimer's disease. This brief report provides the first evidence of compromised small peripheral mesenteric resistance artery (MRA) properties in 15-month-old 3xTg-AD mice. Females showed worse physiologically relevant MRA structural (increased passive external and internal diameters, cross sectional area) and functional (increased active internal diameters) alterations suggesting sex-dependent dysfunctions. At both physiological and high intraluminal pressures, vascular alterations correlated with the anxious-like behavioral profile, in a sex-dependent manner. Finally, the results unveil a crosstalk between peripheral small vessel properties and behavior in both 3xTg-AD mice and age-matched counterparts with normal aging.

Uric Acid Treatment After Stroke Prevents Long-Term Middle Cerebral Artery Remodelling and Attenuates Brain Damage in Spontaneously Hypertensive Rats

Hypertension is the most important modifiable risk factor for stroke and is associated with poorer post-stroke outcomes. The antioxidant uric acid is protective in experimental normotensive ischaemic stroke. However, it is unknown whether this treatment exerts long-term protection in hypertension. We aimed to evaluate the impact of transient intraluminal middle cerebral artery (MCA) occlusion (90 min)/reperfusion (1-15 days) on brain and vascular damage progression in adult male Wistar-Kyoto (WKY; n = 36) and spontaneously hypertensive (SHR; n = 37) rats treated (i.v./120 min post-occlusion) with uric acid (16 mg kg^-1) or vehicle (Locke's buffer). Ischaemic brain damage was assessed longitudinally with magnetic resonance imaging and properties of MCA from both hemispheres were studied 15 days after stroke. Brain lesions in WKY rats were associated with a transitory increase in circulating IL-18 and cerebrovascular oxidative stress that did not culminate in long-term MCA alterations. In SHR rats, more severe brain damage and poorer neurofunctional outcomes were coupled to higher cortical cerebral blood flow at the onset of reperfusion, a transient increase in oxidative stress and long-lasting stroke-induced MCA hypertrophic remodelling. Thus, stroke promotes larger brain and vascular damage in hypertensive rats that persists for long-time. Uric acid administered during early reperfusion attenuated short- and long-term brain injuries in both normotensive and hypertensive rats, an effect that was associated with abolishment of the acute oxidative stress response and prevention of stroke-induced long-lasting MCA remodelling in hypertension. These results suggest that uric acid might be an effective strategy to improve stroke outcomes in hypertensive subjects.

NADPH oxidase 4 attenuates cerebral artery changes during the progression of Marfan syndrome

Marfan syndrome (MFS) is a connective tissue disorder that is often associated with the fibrillin-1 (Fbn1) gene mutation and characterized by cardiovascular alterations, predominantly ascending aortic aneurysms. Although neurovascular complications are uncommon in MFS, the improvement in Marfan patients' life expectancy is revealing other secondary alterations, potentially including neurovascular disorders. However, little is known about small-vessel pathophysiology in MFS. MFS is associated with hyperactivated transforming growth factor (TGF)-β signaling, which among numerous other downstream effectors, induces the NADPH oxidase 4 (Nox4) isoform of NADPH oxidase, a strong enzymatic source of H2O2 We hypothesized that MFS induces middle cerebral artery (MCA) alterations and that Nox4 contributes to them. MCA properties from 3-, 6-, or 9-mo-old Marfan (Fbn1(C1039G/+)) mice were compared with those from age/sex-matched wild-type littermates. At 6 mo, Marfan compared with wild-type mice developed higher MCA wall/lumen (wild-type: 0.081 ± 0.004; Marfan: 0.093 ± 0.002; 60 mmHg; P < 0.05), coupled with increased reactive oxygen species production, TGF-β, and Nox4 expression. However, wall stiffness and myogenic autoregulation did not change. To investigate the influence of Nox4 on cerebrovascular properties, we generated Marfan mice with Nox4 deficiency (Nox4(-/-)). Strikingly, Nox4 deletion in Marfan mice aggravated MCA wall thickening (cross-sectional area; Marfan: 6,660 ± 363 μm(2); Marfan Nox4(-/-): 8,795 ± 824 μm(2); 60 mmHg; P < 0.05), accompanied by decreased TGF-β expression and increased collagen deposition and Nox1 expression. These findings provide the first evidence that Nox4 mitigates cerebral artery structural changes in a murine model of MFS.

Arterial Stiffening in Western Diet-Fed Mice Is Associated with Increased Vascular Elastin, Transforming Growth Factor-β, and Plasma Neuraminidase

Consumption of excess fat and carbohydrate (Western diet, WD) is associated with alterations in the structural characteristics of blood vessels. This vascular remodeling contributes to the development of cardiovascular disease, particularly as it affects conduit and resistance arteries. Vascular remodeling is often associated with changes in the elastin-rich internal elastic lamina (IEL) and the activation of transforming growth factor (TGF)-β. In addition, obesity and type II diabetes have been associated with increased serum neuraminidase, an enzyme known to increase TGF-β cellular output. Therefore, we hypothesized that WD-feeding would induce structural modifications to the IEL of mesenteric resistance arteries in mice, and that these changes would be associated with increased levels of circulating neuraminidase and the up-regulation of elastin and TGF-β in the arterial wall. To test this hypothesis, a WD, high in fat and sugar, was used to induce obesity in mice, and the effect of this diet on the structure of mesenteric resistance arteries was investigated. 4-week old, Post-weaning mice were fed either a normal diet (ND) or WD for 16 weeks. Mechanically, arteries from WD-fed mice were stiffer and less distensible, with marginally increased wall stress for a given strain, and a significantly increased Young's modulus of elasticity. Structurally, the wall cross-sectional area and the number of fenestrae found in the internal elastic lamina (IEL) of mesenteric arteries from mice fed a WD were significantly smaller than those of arteries from the ND-fed mice. There was also a significant increase in the volume of elastin, but not collagen in arteries from the WD cohort. Plasma levels of neuraminidase and the amount of TGF-β in mesenteric arteries were elevated in mice fed a WD, while ex vivo, cultured vascular smooth muscle cells exposed to neuraminidase secreted greater amounts of tropoelastin and TGF-β than those exposed to vehicle. These data suggest that consumption of a diet high in fat and sugar causes stiffening of the vascular wall in resistance arteries through a process that may involve increased neuraminidase and TGF-β activity, elevated production of elastin, and a reduction in the size and number of fenestrae in the arterial IEL.