Restraint stress up-regulates lectin-like oxidized low-density lipoprotein receptor-1 in aorta of apolipoprotein E-deficient mice

Pharmacological modulation of vascular ageing: A review from VascAgeNet

Vascular ageing, characterized by structural and functional changes in blood vessels of which arterial stiffness and endothelial dysfunction are key components, is associated with increased risk of cardiovascular and other age-related diseases. As the global population continues to age, understanding the underlying mechanisms and developing effective therapeutic interventions to mitigate vascular ageing becomes crucial for improving cardiovascular health outcomes. Therefore, this review provides an overview of the current knowledge on pharmacological modulation of vascular ageing, highlighting key strategies and promising therapeutic targets. Several molecular pathways have been identified as central players in vascular ageing, including oxidative stress and inflammation, the renin-angiotensin-aldosterone system, cellular senescence, macroautophagy, extracellular matrix remodelling, calcification, and gasotransmitter-related signalling. Pharmacological and dietary interventions targeting these pathways have shown potential in ameliorating age-related vascular changes. Nevertheless, the development and application of drugs targeting vascular ageing is complicated by various inherent challenges and limitations, such as certain preclinical methodological considerations, interactions with exercise training and sex/gender-related differences, which should be taken into account. Overall, pharmacological modulation of endothelial dysfunction and arterial stiffness as hallmarks of vascular ageing, holds great promise for improving cardiovascular health in the ageing population. Nonetheless, further research is needed to fully elucidate the underlying mechanisms and optimize the efficacy and safety of these interventions for clinical translation.

Postpartum Vascular Dysfunction in the Reduced Uteroplacental Perfusion Model of Preeclampsia

Preeclampsia is a disorder affecting 2–8% of all pregnancies, characterized by gestational hypertension (≥ 140/90 mmHg) and proteinuria (≥300 mg over 24 hours) diagnosed following the 20^th week of pregnancy, and for which there is currently no available treatment. While the precise cause of preeclampsia is unknown, placental ischemia/hypoxia resulting from abnormal trophoblast invasion and maternal endothelial dysfunction are central characteristics. Preeclampsia is a major cause of both maternal and fetal morbidity and mortality in the perinatal period. In addition, women who have experienced preeclampsia are more likely to suffer cardiovascular disease later in life. The cause of this elevation in cardiovascular risk postpartum, however, is unknown. We hypothesize that there may be lasting vascular dysfunction following exposure to reduced uteroplacental perfusion during pregnancy that may contribute to increased cardiovascular risk postpartum. Using the rat reduced utero-placental perfusion pressure (RUPP) model of preeclampsia, blood pressure was assessed in dams at gestational day 20, one and three months postpartum. Mesenteric artery and aortic function were assessed using wire myography. We demonstrated hypertension and increased mesenteric artery responses to phenylephrine at gestational day 20, with the latter due to a decreased contribution of nitric oxide without any change in methylcholine-induced relaxation. At one month postpartum, we demonstrated a small but significant vasoconstrictive phenotype that was due to an underlying loss of basal nitric oxide contribution. At three months postpartum, endothelium-dependent relaxation of the aorta demonstrated sensitivity to oxLDL and mesenteric arteries demonstrated decreased nitric oxide bioavailability with impaired methylcholine-induced relaxation; indicative of an early development of endothelial dysfunction. In summary, we have demonstrated impaired vascular function following exposure to a RUPP pregnancy that continued into the postpartum period; suggesting that a pregnancy complicated by preeclampsia may predispose women to later life cardiovascular disease via ongoing vascular dysfunction.

Effect of sodium tanshinone IIA sulfonate treatment in a rat model of preeclampsia

Preeclampsia is a disorder of pregnancy with a significant impact on maternal and fetal health. The complexity of this multifactorial condition has precluded development of effective therapies and, although many potential pathways have been investigated, the etiology still requires clarification. Our group has investigated the scavenger lectin-like oxidized LDL (LOX-1) receptor, which may respond to factors released from the distressed placenta that contribute to the vascular pathologies observed in preeclampsia. Given the known beneficial effects of sodium tanshinone IIA sulfonate (STS; a component of Salvia miltiorrhiza) on vasodilation, reduction of oxidative stress, and lipid profiles, we have investigated its role as a potential treatment strategy. We hypothesized that STS would improve vascular endothelial function and, combined with a reduction in oxidative stress, would improve pregnancy outcomes in a rat model of preeclampsia (reduced uteroplacental perfusion pressure, RUPP). We further hypothesized this may occur via the action of STS on the LOX-1 and/or platelet-activating factor (PAF) receptor axes. The RUPP model increased maternal blood pressure, vascular oxidative stress, and involvement of the vascular PAF receptor. Treatment with STS during pregnancy decreased both oxidative stress and involvement of the PAF receptor; however, it also increased involvement of the LOX-1 receptor, which is in line with the concept that scavenger receptors, such as LOX-1 and PAF, are upregulated in response to ligand binding and/or under pathological conditions. In this model of preeclampsia, however, the vascular actions of STS did not lead to improvements in pregnancy outcome such as fetal biometrics or maternal blood pressure.

Occlusal disharmony accelerates the initiation of atherosclerosis in apoE knockout rats

Background

Psychosocial stress is one of the risk factors for atherosclerosis. As occlusal disharmony induces psychological stress, we hypothesized that psychological stress by occlusal disharmony accelerates atherosclerosis. The aim of this study was to investigate the effects of occlusal disharmony on the initiation of atherosclerosis in apolipoprotein E (apoE) knockout rats.

Methods

Fourteen male apoE-knockout rats (age; 8 weeks) (Sprague–Dawley strain background) were divided into two groups of seven rats: the occlusal disharmony group and the no treatment (control) group. In the occlusal disharmony group, the maxillary molar cusps were cut off for the 8-week experimental period.

Results

In the occlusal disharmony group, the percentages of the area of total aortic lumen occupied by plaques and lipid were significantly higher than those in the control group (p < 0.05, t-test). The occlusal disharmony group also showed significantly higher serum levels of very low-density lipoprotein-cholesterol (VLDL) and low-density lipoprotein-cholesterol (LDL), plasma levels of corticosterone (1.9, 1.3 and 1.3 times, respectively), higher aortic protein expression levels of vascular cell adhesion molecule-1 (VCAM1) and intercellular adhesion molecule-1 (ICAM1) (1.5 and 1.4 times, respectively), and higher aortic gene expression of levels of VCAM1 and Toll-like receptor 4 (TLR4) (1.9 and 4.3 times, respectively), as compared to the control group (p < 0.05). However, there were no significant differences in serum levels of oxidized LDL, reactive oxygen metabolites and C-reactive protein between the two groups.

Conclusion

In apoE knockout rats, occlusal disharmony may induce VCAM1, ICAM1 and TLR4 expression and accelerate the initiation of atherosclerosis.

Effects of acute and chronic psychological stress on platelet aggregation in mice

Although psychological stress has long been known to alter cardiovascular function, there have been few studies on the effect of psychological stress on platelets, which play a pivotal role in cardiovascular disease. In the present study, we investigated the effects of acute and chronic psychological stress on the aggregation of platelets and platelet cytosolic free calcium concentration ([Ca(2+)]i). Mice were subjected to both transportation stress (exposure to novel environment, psychological stress) and restraint stress (psychological stress) for 2 h (acute stress) or 3 weeks (2 h/day) (chronic stress). In addition, adrenalectomized mice were subjected to similar chronic stress (both transportation and restraint stress for 3 weeks). The aggregation of platelets from mice and [Ca(2+)]i was determined by light transmission assay and fura-2 fluorescence assay, respectively. Although acute stress had no effect on agonist-induced platelet aggregation, chronic stress enhanced the ability of the platelet agonists thrombin and ADP to stimulate platelet aggregation. However, chronic stress failed to enhance agonist-induced increase in [Ca(2+)]i. Adrenalectomy blocked chronic stress-induced enhancement of platelet aggregation. These results suggest that chronic, but not acute, psychological stress enhances agonist-stimulated platelet aggregation independently of [Ca(2+)]i increase, and the enhancement may be mediated by stress hormones secreted from the adrenal glands.

Psychological stress, vascular inflammation, and atherogenesis: potential roles of circulating cytokines

Cardiovascular disease is a major cause of morbidity and mortality worldwide. Epidemiological studies have clearly demonstrated that chronic psychosocial stress increases the risk of atherosclerotic cardiovascular disease and this may involve multiple mediators and regulating pathways, whereas the precise mechanisms underlying the effects of stress on development of atherosclerosis are not completely understood. In this mini review, we summarize current information from various animal studies suggesting that stress may promote atherogenesis by stimulating vascular inflammation via elevating the level of circulating proinflammatory cytokines (such as tumor necrosis factor α and interleukin 6). Although circulating cytokines can serve as reliable biomarkers of systemic inflammation, in light of the emerging evidence, we propose that these molecules may also have a causal role in mediating stress-triggered vascular inflammatory reaction and atherogenesis. Further studies are warranted to clarify whether targeting circulating cytokines may be an effective approach to reduce the detrimental effects of chronic stress.

Effect of prenatal hypoxia in transgenic mouse models of preeclampsia and fetal growth restriction

Mice lacking endothelial nitric oxide synthase (eNOS(-)(/-)) or catechol-O-methyl transferase (COMT(-/-)) exhibit a preeclampsia-like phenotype and fetal growth restriction. We hypothesized that a hypoxic insult would result in a more severe phenotype. Pregnant eNOS(-/-), COMT(-/-) and control (C57BL/6J) mice were randomized to hypoxic (10.5% O(2)) or normal conditions (20.9% O(2)) from gestational day 10.5 to 18.5. Hypoxia increased the blood pressure in all genotypes and proteinuria in C57BL/6J and eNOS(-/-) mice. Fetal survival was significantly reduced following hypoxia, particularly in eNOS(-/-) mice. Birth weight was decreased in both C57BL/6J and COMT(-/-) mice. Placentas from COMT(-/-) mice demonstrated increased peroxynitrite. Despite similar hypoxia-induced effects on maternal blood pressure and proteinuria, eNOS(-/-) embryos have a decreased tolerance to hypoxia. Compared to C57BL/6J, COMT(-/-) mice exhibited less severe changes in proteinuria and fetal growth when exposed to prenatal hypoxia. This relative resistance to prenatal hypoxia was associated with a significant increase in placental levels of peroxynitrite.

Effect of the anti-oxidant tempol on fetal growth in a mouse model of fetal growth restriction

Fetal growth restriction (FGR) greatly increases the risk of perinatal morbidity and mortality and is associated with increased uterine artery resistance and levels of oxidative stress. There are currently no available treatments for this condition. The hypothesis that the antioxidant 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (Tempol) would improve uterine artery function and rescue fetal growth was tested in a mouse model of FGR, using the endothelial nitric oxide synthase knockout mouse (Nos3(-/-)). Pregnant Nos3(-/-) and control C57BL/6J mice were treated with the superoxide dismutase-mimetic Tempol (1 mmol/L) or vehicle from Gestational Day 12.5 to 18.5. Tempol treatment significantly increased pup weight (P < 0.05) and crown-rump length (P < 0.01) in C57BL/6J and Nos3(-/-) mice. Uterine artery resistance was increased in Nos3(-/-) mice (P < 0.05); Tempol significantly increased end diastolic velocity in Nos3(-/-) mice (P < 0.05). Superoxide production in uterine arteries did not differ between C57BL/6J and Nos3(-/-) mice but was significantly increased in placentas from Nos3(-/-) mice (P < 0.05). This was not reduced by Tempol treatment. Placental System A activity was reduced in Nos3(-/-) mice (P < 0.01); this was not improved by treatment with Tempol. Treatment of Nos3(-/-) mice with Tempol, however, was associated with reduced vascular density in the placental bed (P < 0.05). This study demonstrated that treatment with the antioxidant Tempol is able to improve fetal growth in a mouse model of FGR. This was associated with an increase in uterine artery blood flow velocity but not an improvement in uterine artery function or placental System A activity.