Ovariectomy-Induced Arterial Stiffening Differs From Vascular Aging and Is Reversed by GPER Activation

BACKGROUND

Arterial stiffness is a cardiovascular risk factor and dramatically increases as women transition through menopause. The current study assessed whether a mouse model of menopause increases arterial stiffness in a similar manner to aging and whether activation of the G-protein-coupled estrogen receptor could reverse stiffness.

METHODS

Female C57Bl/6J mice were ovariectomized at 10 weeks of age or aged to 52 weeks, and some mice were treated with G-protein-coupled estrogen receptor agonists.

RESULTS

Ovariectomy and aging increased pulse wave velocity to a similar extent independent of changes in blood pressure. Aging increased carotid wall thickness, while ovariectomy increased material stiffness without altering vascular geometry. RNA-sequencing analysis revealed that ovariectomy downregulated smooth muscle contractile genes. The enantiomerically pure G-protein-coupled estrogen receptor agonist, LNS8801, reversed stiffness in ovariectomy mice to a greater degree than the racemic agonist G-1. In summary, ovariectomy and aging induced arterial stiffening via potentially different mechanisms. Aging was associated with inward remodeling, while ovariectomy-induced material stiffness independent of geometry and a loss of the contractile phenotype.

CONCLUSIONS

This study enhances our understanding of the impact of estrogen loss on vascular health in a murine model and warrants further studies to examine the ability of LNS8801 to improve vascular health in menopausal women.

Ovariectomy-Induced Arterial Stiffening Differs from Vascular Aging and is Reversed by GPER Activation

Arterial stiffness is a cardiovascular risk factor and dramatically increases as women transition through menopause. The current study assessed whether a mouse model of menopause increases arterial stiffness in a similar manner to aging, and whether activation of the G protein-coupled estrogen receptor (GPER) could reverse stiffness. Female C57Bl/6J mice were ovariectomized (OVX) at 10 weeks of age or aged to 52 weeks, and some mice were treated with GPER agonists. OVX and aging increased pulse wave velocity to a similar extent independent of changes in blood pressure. Aging increased carotid wall thickness, while OVX increased material stiffness without altering vascular geometry. RNA-Seq analysis revealed that OVX downregulated smooth muscle contractile genes. The enantiomerically pure GPER agonist, LNS8801, reversed stiffness in OVX mice to a greater degree than the racemic agonist G-1. In summary, OVX and aging induced arterial stiffening via potentially different mechanisms. Aging was associated with inward remodeling while OVX induced material stiffness independent of geometry and a loss of the contractile phenotype. This study helps to further our understanding of the impact of menopause on vascular health and identifies LNS8801 as a potential therapy to counteract this detrimental process in women.

Sex Differences in Vascular Aging and Impact of GPER Deletion

Aging is a nonmodifiable risk factor for cardiovascular disease associated with arterial stiffening and endothelial dysfunction. We hypothesized that sex differences exist in vascular aging processes and would be attenuated by global deletion of the G protein-coupled estrogen receptor. Blood pressure was measured by tail cuff plethysmography, pulse wave velocity (PWV) and echocardiography were assessed with high resolution ultrasound, and small vessel reactivity was measured using wire myography in adult (25 weeks) and middle-aged (57 weeks) male and female mice. Adult female mice displayed lower blood pressure and PWV, but this sex difference was absent in middle-aged mice. Aging significantly increased PWV but not blood pressure in both sexes. Adult female carotids were more distensible than males, but this sex difference was lost during aging. Acetylcholine-induced relaxation was greater in female than male mice at both ages, and only males showed aging-induced changes in cardiac hypertrophy and function. GPER deletion removed the sex difference in PWV as well as ex vivo stiffness in adult mice. The sex difference in blood pressure was absent in KO mice and was associated with endothelial dysfunction in females. These findings indicate that the impact of aging on arterial stiffening and endothelial function is not the same in male and female mice. Moreover, nongenomic estrogen signaling through GPER impacted vascular phenotype differently in male and female mice. Delineating sex differences in vascular changes during healthy aging is an important first step in improving early detection and sex-specific treatments in our aging population.

Abstract P285: Aging In Male Mice Is Characterized By Arterial Stiffening And Diastolic Dysfunction

Aging is a nonmodifiable risk factor for cardiovascular mortality and is associated with arterial stiffening and cardiac dysfunction. In this study, we hypothesized that aging would decrease vascular compliance and cardiac function in male mice. Tail-cuff plethysmography was used to measure blood pressure, pulse wave velocity (PWV) for arterial stiffness, echocardiography for systolic and diastolic cardiac function, and wire myography for vessel reactivity in mature adult (25 weeks) and middle-aged (57 weeks) C57Bl/6 mice. Data was analyzed by t-test or 2-way ANOVA, and P<0.05 was considered significant. While there was no difference in blood pressure, PWV was higher in middle-aged male mice (1.8 ± 0.04 m/s vs. 1.2 ± 0.05 m/s; P<0.001) and associated with increased left ventricular (LV) posterior wall thickness (1.4 ± 0.07 mm vs. 1.1 ± 0.13 mm; P=0.03), and LV mass (172 ± 8 mg vs. 158 ± 20 mg; P=0.04). The ratio of early to late filling velocities, a measure of diastolic function, was lower in middle-age (1.6 ± 0.07 vs. 2.7 ± 0.37; P<0.001). Carotid artery histological analysis indicated that middle-aged mice had a greater collagen-to-elastin ratio along with decreased amounts of smooth muscle and thin collagen (P<0.05). Mesenteric artery contraction to PGF2α (446 ± 15% vs. 378 ± 14%; P=0.02) as well as relaxation to sodium nitroprusside (55 ± 7% vs. 31 ± 7%; P<0.01) were both blunted in the middle-aged group. The current study demonstrates that aging in male mice increases arterial stiffening and LV remodeling while decreasing diastolic and vascular function, independent of increased blood pressure. Future studies will investigate whether strategies that counteract arterial stiffness in the absence of changes in blood pressure can protect from cardiovascular aging.

Experiences with rotavirus vaccines: can we improve rotavirus vaccine impact in developing countries?

Rotavirus vaccines have been introduced into over 95 countries globally and demonstrate substantial impact in reducing diarrheal mortality and diarrheal hospitalizations in young children. The vaccines are also considered by WHO as “very cost effective” interventions for young children, particularly in countries with high diarrheal disease burden. Yet the full potential impact of rotavirus immunization is yet to be realized. Large countries with big birth cohorts and where disease burden is high in Africa and Asia have not yet implemented rotavirus vaccines at all or at scale. Significant advances have been made demonstrating the impact of the vaccines in low- and lower-middle income countries, yet the modest effectiveness of the vaccines in these settings is challenging. Current research highlights these challenges and considers alternative strategies to overcome them, including alternative immunization schedules and host factors that may inform us of new opportunities.

Trolox enhances the anti-lymphoma effects of arsenic trioxide, while protecting against liver toxicity

Arsenic trioxide (As2O3) is an effective therapy in acute promyelocytic leukemia (APL), but its use in other malignancies is limited by the higher concentrations required to induce apoptosis. We have reported that trolox, an analogue of alpha-tocopherol, increases As2O3-mediated apoptosis in a variety of APL, myeloma and breast cancer cell lines, while non-malignant cells may be protected. In the present study, we extended previous results to show that trolox increases As2O3-mediated apoptosis in the P388 lymphoma cell line in vitro, as evidenced by decrease of mitochondrial membrane potential and release of cytochrome c. We then sought to determine whether this combination can enhance antitumor effects while protecting normal cells in vivo. In BDF1 mice, trolox treatment decreased As2O3-induced hepatomegaly, markers of oxidative stress and hepatocellular damage. In P388 tumor-bearing mice, As2O3 treatment prolonged survival, and the addition of trolox provided a further significant increase in lifespan. In addition, the combination of As2O3 and trolox inhibited metastatic spread, and protected the tumor-bearing mice from As2O3 liver toxicity. Our results suggest, for the first time, that trolox might prevent some of the clinical manifestations of As2O3-related toxicity while increasing its pro-apoptotic capacity and clinical efficacy in hematological malignancies.

Intracisternally injected galanin-(1-15) modulates the cardiovascular responses of galanin-(1-29) and the 5-HT1A receptor agonist 8-OH-DPAT

In view of the demonstration of specific binding sites for [125I]galanin-(1-15) in several brain areas including the nucleus of the solitary tract, possibly indicating the existence of multiple galanin receptor subtypes, the effects of intracisternal injections of galanin-(1-15) on cardiovascular parameters were studied. The effects of co-injections of galanin-(1-15) and galanin-(1-29) and co-injections of galanin-(1-15) and the 5-HT1A receptor agonist 8-OH-2-(di-n-propylamino)tetralin (8-OH-DPAT) were also evaluated. Galanin-(1-15) produced a significant increase in mean arterial blood pressure (maximum effect 10% at 3 nmol of galanin-(1-15)) and in heart rate (maximum effect 12% at 1 nmol). When threshold doses of galanin-(1-15) (0.1 nmol) and galanin-(1-29) (3 nmol) were injected simultaneously they elicited an increase in mean arterial blood pressure. The vasodepressor response induced by an ED50 dose of 8-OH-DPAT (6 nmol) was not modulated by a threshold dose of galanin-(1-15), but the increase in heart rate area induced by galanin-(1-15) alone was no longer observed. When threshold doses of both galanin-(1-15) and 8-OH-DPAT (0.3 nmol) were co-injected a vasodepressor response developed and on heart rate a tachycardic response was seen in the peak effects and the overall tachycardic response induced by galanin-(1-15) was sustained. The results show a different role for galanin-(1-15) as compared with galanin-(1-29) in central cardiovascular control.(ABSTRACT TRUNCATED AT 250 WORDS)