Sex- and age-related differences in arterial pressure and albuminuria in mice

Hypertension disrupts the vascular clock in both sexes

Blood pressure (BP) displays a circadian rhythm and disruptions in this pattern elevate cardiovascular risk. Although both central and peripheral clock genes are implicated in these processes, the importance of vascular clock genes is not fully understood. BP, vascular reactivity, and the renin-angiotensin-aldosterone system display overt sex differences, but whether changes in circadian patterns underlie these differences is unknown. Therefore, we hypothesized that circadian rhythms and vascular clock genes would differ across sex and would be blunted by angiotensin II (ANG II)-induced hypertension. ANG II infusion elevated BP and disrupted circadian patterns similarly in both males and females. In females, an impact on heart rate (HR) and locomotor activity was revealed, whereas in males hypertension suppressed baroreflex sensitivity (BRS). A marked disruption in the vascular expression patterns of period circadian regulator 1 (Per1) and brain and muscle aryl hydrocarbon receptor nuclear translocator like protein 1 (Bmal1) was noted in both sexes. Vascular expression of the G protein-coupled estrogen receptor (Gper1) also showed diurnal synchronization in both sexes that was similar to that of Per1 and Per2 and disrupted by hypertension. In contrast, vascular expression of estrogen receptor 1 (Esr1) showed a diurnal rhythm and hypertension-induced disruption only in females. This study shows a strikingly similar impact of hypertension on BP rhythmicity, vascular clock genes, and vascular estrogen receptor expression in both sexes. We identified a greater impact of hypertension on locomotor activity and heart rate in females and on baroreflex sensitivity in males and also revealed a diurnal regulation of vascular estrogen receptors. These insights highlight the intricate ties between circadian biology, sex differences, and cardiovascular regulation.NEW & NOTEWORTHY This study reveals that ANG II-induced hypertension disrupts the circadian rhythm of blood pressure in both male and female mice, with parallel effects on vascular clock gene and estrogen receptor diurnal patterns. Notably, sex-specific responses to hypertension in terms of locomotor activity, heart rate, and baroreflex sensitivity are revealed. These findings pave the way for chronotherapeutic strategies tailored to mitigate cardiovascular risks associated with disrupted circadian rhythms in hypertension.

Epigenetic mechanisms differentially regulate blood pressure and renal dysfunction in male and female Npr1 haplotype mice

We determined the epigenetic mechanisms regulating mean arterial pressure (MAP) and renal dysfunction in guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) gene-targeted mice. The Npr1 (encoding NPRA) gene-targeted mice were treated with class 1 specific histone deacetylase inhibitor (HDACi) mocetinostat (MGCD) to determine the epigenetic changes in a sex-specific manner. Adult male and female Npr1 haplotype (1-copy; Npr1+/-), wild-type (2-copy; Npr1+/+), and gene-duplicated heterozygous (3-copy; Npr1++/+) mice were intraperitoneally injected with MGCD (2 mg/kg) for 14 days. BP, renal function, histopathology, and epigenetic changes were measured. One-copy male mice showed significantly increased MAP, renal dysfunction, and fibrosis than 2-copy and 3-copy mice. Furthermore, HDAC1/2, collagen1alpha-2 (Col1α-2), and alpha smooth muscle actin (α-SMA) were significantly increased in 1-copy mice compared with 2-copy controls. The expression of antifibrotic microRNA-133a was attenuated in 1-copy mice but to a greater extent in males than females. NF-κB was localized at significantly lower levels in cytoplasm than in the nucleus with stronger DNA binding activity in 1-copy mice. MGCD significantly lowered BP, improved creatinine clearance, and repaired renal histopathology. The inhibition of class I HDACs led to a sex-dependent distinctive stimulation of acetylated positive histone marks and inhibition of methylated repressive histone marks in Npr1 1-copy mice; however, it epigenetically lowered MAP, repaired renal fibrosis, and proteinuria and suppressed NF-kB differentially in males versus females. Our results suggest a role for epigenetic targets affecting hypertension and renal dysfunction in a sex-specific manner.

A circadian behavioral analysis suite for real-time classification of daily rhythms in complex behaviors

Measuring animal behavior over long timescales has been traditionally limited to behaviors that are easily measurable with real-time sensors. More complex behaviors have been measured over time, but these approaches are considerably more challenging due to the intensive manual effort required for scoring behaviors. Recent advances in machine learning have introduced automated behavior analysis methods, but these often overlook long-term behavioral patterns and struggle with classification in varying environmental conditions. To address this, we developed a pipeline that enables continuous, parallel recording and acquisition of animal behavior for an indefinite duration. As part of this pipeline, we applied a recent breakthrough self-supervised computer vision model to reduce training bias and overfitting and to ensure classification robustness. Our system automatically classifies animal behaviors with a performance approaching that of expert-level human labelers. Critically, classification occurs continuously, across multiple animals, and in real time. As a proof-of-concept, we used our system to record behavior from 97 mice over two weeks to test the hypothesis that sex and estrogen influence circadian rhythms in nine distinct home cage behaviors. We discovered novel sex- and estrogen-dependent differences in circadian properties of several behaviors including digging and nesting rhythms. We present a generalized version of our pipeline and novel classification model, the "circadian behavioral analysis suite," (CBAS) as a user-friendly, open-source software package that allows researchers to automatically acquire and analyze behavioral rhythms with a throughput that rivals sensor-based methods, allowing for the temporal and circadian analysis of behaviors that were previously difficult or impossible to observe.

Anatomical location, sex, and age modulate adipocyte progenitor populations in perivascular adipose tissues

Perivascular adipose tissue (PVAT) regulates vascular function due to its capacity to synthesize vasoactive products and its mechanical properties. PVATs most abundant cells are adipocytes, and their populations are maintained by the maturation of adipocyte progenitor cells (APC), which may play a pivotal role in the pathogenesis of cardiovascular diseases. However, the distribution of APC within PVAT depots, their potential variation in spatial location, and the influence of sex and age on their abundance remain unknown. We hypothesize that APC abundance in PVAT is affected by location, age, sex and that APC subtypes have specific spatial distributions. PVAT from thoracic and abdominal aorta, and mesenteric arteries, and AT from interscapular, gonadal, and subcutaneous depots from 13-week and 30-week-old females and males Pdgfrα-CreERT2 x LSL-tdTomato mice (n = 28) were analyzed. Abdominal aorta PVAT had fewer progenitors than mesenteric PVAT and gonadal AT. Aging reduced the abundance of APC in the thoracic aorta but increased their numbers in mesenteric PVAT. Females had more APC than males in mesenteric PVAT and gonadal AT depots. APC exhibited unique spatial distribution in the aorta and mesenteric PVAT where they localized neighboring vasa vasorum and arteries. APC subtypes (APC1, APC2, APC3, diff APC) were identified in all PVAT depots. Thoracic aorta PVAT APC3 were located in the adventitia while diff APC were in the parenchyma. This study identified variability in APC populations based on depot, age, and sex. The distinctive spatial distribution and the presence of diverse APC subtypes suggest that they may contribute differently to cardiovascular diseases-induced PVAT remodeling.

Dorsal peduncular cortex activity modulates affective behavior and fear extinction in mice

The medial prefrontal cortex (mPFC) is critical to cognitive and emotional function and underlies many neuropsychiatric disorders, including mood, fear and anxiety disorders. In rodents, disruption of mPFC activity affects anxiety- and depression-like behavior, with specialized contributions from its subdivisions. The rodent mPFC is divided into the dorsomedial prefrontal cortex (dmPFC), spanning the anterior cingulate cortex (ACC) and dorsal prelimbic cortex (PL), and the ventromedial prefrontal cortex (vmPFC), which includes the ventral PL, infralimbic cortex (IL), and in some studies the dorsal peduncular cortex (DP) and dorsal tenia tecta (DTT). The DP/DTT have recently been implicated in the regulation of stress-induced sympathetic responses via projections to the hypothalamus. While many studies implicate the PL and IL in anxiety-, depression-like and fear behavior, the contribution of the DP/DTT to affective and emotional behavior remains unknown. Here, we used chemogenetics and optogenetics to bidirectionally modulate DP/DTT activity and examine its effects on affective behaviors, fear and stress responses in C57BL/6J mice. Acute chemogenetic activation of DP/DTT significantly increased anxiety-like behavior in the open field and elevated plus maze tests, as well as passive coping in the tail suspension test. DP/DTT activation also led to an increase in serum corticosterone levels and facilitated auditory fear extinction learning and retrieval. Activation of DP/DTT projections to the dorsomedial hypothalamus (DMH) acutely decreased freezing at baseline and during extinction learning, but did not alter affective behavior. These findings point to the DP/DTT as a new regulator of affective behavior and fear extinction in mice.

An evolutionarily conserved olfactory receptor is required for sex differences in blood pressure

Sex differences in blood pressure are well-established, with premenopausal women having lower blood pressure than men by ~10 millimeters of mercury; however, the underlying mechanisms are not fully understood. We report here that sex differences in blood pressure are absent in olfactory receptor 558 knockout (KO) mice. Olfr558 localizes to renin-positive cells in the kidney and to vascular smooth muscle cells. Female KOs exhibit increased blood pressure and increased pulse wave velocity. In contrast, male KO mice have decreased renin expression and activity, altered vascular reactivity, and decreased diastolic pressure. A rare OR51E1 (human ortholog) missense variant has a statistically significant sex interaction effect with diastolic blood pressure, increasing diastolic blood pressure in women but decreasing it in men. In summary, our findings demonstrate an evolutionarily conserved role for OLFR558/OR51E1 to mediate sex differences in blood pressure.

Rab4A-directed endosome traffic shapes pro-inflammatory mitochondrial metabolism in T cells via mitophagy, CD98 expression, and kynurenine-sensitive mTOR activation

Activation of the mechanistic target of rapamycin (mTOR) is a key metabolic checkpoint of pro-inflammatory T-cell development that contributes to the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE), however, the underlying mechanisms remain poorly understood. Here, we identify a functional role for Rab4A-directed endosome traffic in CD98 receptor recycling, mTOR activation, and accumulation of mitochondria that connect metabolic pathways with immune cell lineage development and lupus pathogenesis. Based on integrated analyses of gene expression, receptor traffic, and stable isotope tracing of metabolic pathways, constitutively active Rab4AQ72L exerts cell type-specific control over metabolic networks, dominantly impacting CD98-dependent kynurenine production, mTOR activation, mitochondrial electron transport and flux through the tricarboxylic acid cycle and thus expands CD4+ and CD3+CD4-CD8- double-negative T cells over CD8+ T cells, enhancing B cell activation, plasma cell development, antinuclear and antiphospholipid autoantibody production, and glomerulonephritis in lupus-prone mice. Rab4A deletion in T cells and pharmacological mTOR blockade restrain CD98 expression, mitochondrial metabolism and lineage skewing and attenuate glomerulonephritis. This study identifies Rab4A-directed endosome traffic as a multilevel regulator of T cell lineage specification during lupus pathogenesis.

KDM6A Demethylase Regulates Renal Sodium Excretion and Blood Pressure

BACKGROUND

KDM6A (Lysine-Specific Demethylase 6A) is a specific demethylase for histone 3 lysine (K) 27 trimethylation (H3K27me3). The purpose of this study is to investigate whether KDM6A in renal tubule cells plays a role in the regulation of kidney function and blood pressure.

METHODS

We first crossed Ksp-Cre+/- and KDM6Aflox/flox mice for generating inducible kidney-specific deletion of KDM6A gene.

RESULTS

Notably, conditional knockout of KDM6A gene in renal tubule cells (KDM6A-cKO) increased H3K27me3 levels which leads to a decrease in Na excretion and elevation of blood pressure. Further analysis showed that the expression of NKCC2 (Na-K-2Cl cotransporter 2) and NCC (Na-Cl cotransporters) was upregulated which contributes to impaired Na excretion in KDM6A-cKO mice. The expression of AQP2 (aquaporin 2) was also increased in KDM6A-cKO mice, which may facilitate water reabsorption in KDM6A-cKO mice. The expression of Klotho was downregulated while expression of aging markers including p53, p21, and p16 was upregulated in kidneys of KDM6A-cKO mice, indicating that deletion of KDM6A in the renal tubule cells promotes kidney aging. Interestingly, KDM6A-cKO mice developed salt-sensitive hypertension which can be rescued by treatment with Klotho. KDM6A deficiency induced salt-sensitive hypertension likely through downregulation of the Klotho/ERK (extracellular signal-regulated kinase) signaling and upregulation of the WNK (with-no-lysine kinase) signaling.

CONCLUSIONS

This study provides the first evidence that KDM6A plays an essential role in maintaining normal tubular function and blood pressure. Renal tubule cell specific KDM6A deficiency causes hypertension due to increased H3K27me3 levels and the resultant downregulation of Klotho gene expression which disrupts the Klotho/ERK/NCC/NKCC2 signaling.

Functional, Structural and Proteomic Effects of Ageing in Resistance Arteries

The normal ageing process affects resistance arteries, leading to various functional and structural changes. Systolic hypertension is a common occurrence in human ageing, and it is associated with large artery stiffening, heightened pulsatility, small artery remodeling, and damage to critical microvascular structures. Starting from young adulthood, a progressive elevation in the mean arterial pressure is evidenced by clinical and epidemiological data as well as findings from animal models. The myogenic response, a protective mechanism for the microcirculation, may face disruptions during ageing. The dysregulation of calcium entry channels (L-type, T-type, and TRP channels), dysfunction in intracellular calcium storage and extrusion mechanisms, altered expression of potassium channels, and a change in smooth muscle calcium sensitization may contribute to the age-related dysregulation of myogenic tone. Flow-mediated vasodilation, a hallmark of endothelial function, is compromised in ageing. This endothelial dysfunction is related to increased oxidative stress, lower nitric oxide bioavailability, and a low-grade inflammatory response, further exacerbating vascular dysfunction. Resistance artery remodeling in ageing emerges as a hypertrophic response of the vessel wall that is typically observed in conjunction with outward remodeling (in normotension), or as inward hypertrophic remodeling (in hypertension). The remodeling process involves oxidative stress, inflammation, reorganization of actin cytoskeletal components, and extracellular matrix fiber proteins. Reactive oxygen species (ROS) signaling and chronic low-grade inflammation play substantial roles in age-related vascular dysfunction. Due to its role in the regulation of vascular tone and structural proteins, the RhoA/Rho-kinase pathway is an important target in age-related vascular dysfunction and diseases. Understanding the intricate interplay of these factors is crucial for developing targeted interventions to mitigate the consequences of ageing on resistance arteries and enhance the overall vascular health.

Sex differences in blood pressure regulation and hypertension: renal, hemodynamic, and hormonal mechanisms

The teleology of sex differences has been argued since at least as early as Aristotle's controversial Generation of Animals more than 300 years BC, which reflects the sex bias of the time to contemporary readers. Although the question "why are the sexes different" remains a topic of debate in the present day in metaphysics, the recent emphasis on sex comparison in research studies has led to the question "how are the sexes different" being addressed in health science through numerous observational studies in both health and disease susceptibility, including blood pressure regulation and hypertension. These efforts have resulted in better understanding of differences in males and females at the molecular level that partially explain their differences in vascular function and renal sodium handling and hence blood pressure and the consequential cardiovascular and kidney disease risks in hypertension. This review focuses on clinical studies comparing differences between men and women in blood pressure over the life span and response to dietary sodium and highlights experimental models investigating sexual dimorphism in the renin-angiotensin-aldosterone, vascular, sympathetic nervous, and immune systems, endothelin, the major renal sodium transporters/exchangers/channels, and the impact of sex hormones on these systems in blood pressure homeostasis. Understanding the mechanisms governing sex differences in blood pressure regulation could guide novel therapeutic approaches in a sex-specific manner to lower cardiovascular risks in hypertension and advance personalized medicine.

Age-Associated Changes in Endothelial Transcriptome and Epigenetic Landscapes Correlate With Elevated Risk of Cerebral Microbleeds

Background Stroke is a leading global cause of human death and disability, with advanced aging associated with elevated incidences of stroke. Despite high mortality and morbidity of stroke, the mechanisms leading to blood-brain barrier dysfunction and development of stroke with age are poorly understood. In the vasculature of brain, endothelial cells (ECs) constitute the core component of the blood-brain barrier and provide a physical barrier composed of tight junctions, adherens junctions, and basement membrane. Methods and Results We show, in mice, the incidents of intracerebral bleeding increases with age. After isolating an enriched population of cerebral ECs from murine brains at 2, 6, 12, 18, and 24 months, we studied age-associated changes in gene expression. The study reveals age-dependent dysregulation of 1388 genes, including many involved in the maintenance of the blood-brain barrier and vascular integrity. We also investigated age-dependent changes on the levels of CpG methylation and accessible chromatin in cerebral ECs. Our study reveals correlations between age-dependent changes in chromatin structure and gene expression, whereas the dynamics of DNA methylation changes are different. Conclusions We find significant age-dependent downregulation of the Aplnr gene along with age-dependent reduction in chromatin accessibility of promoter region of the Aplnr gene in cerebral ECs. Aplnr is associated with positive regulation of vasodilation and is implicated in vascular health. Altogether, our data suggest a potential role of the apelinergic axis involving the ligand apelin and its receptor to be critical in maintenance of the blood-brain barrier and vascular integrity.

Ageing-associated phenotypes in mice

Ageing is a continuous process in life featuring progressive damage accumulation that leads to physiological decline, functional deterioration and ultimately death of an organism. Based on the relatively close anatomical and physiological similarity to humans, the mouse has been proven as a valuable model organism in ageing research over the last decades. In this review, we survey methods and tools currently in use to assess ageing phenotypes in mice. We summarize a range of ageing-associated alterations detectable at two major levels of analysis: (1) physiology and pathophysiology and (2) molecular biomarkers. Age-sensitive phenotypes provided in this article may serve to inform future studies targeting various aspects of organismal ageing in mice. In addition, we discuss conceptual and technical challenges faced by previous ageing studies in mice and, where possible, provide recommendations on how to resolve some of these issues.

Insights into the Role of a Cardiomyopathy-Causing Genetic Variant in ACTN2

Pathogenic variants in ACTN2, coding for alpha-actinin 2, are known to be rare causes of Hypertrophic Cardiomyopathy. However, little is known about the underlying disease mechanisms. Adult heterozygous mice carrying the Actn2 p.Met228Thr variant were phenotyped by echocardiography. For homozygous mice, viable E15.5 embryonic hearts were analysed by High Resolution Episcopic Microscopy and wholemount staining, complemented by unbiased proteomics, qPCR and Western blotting. Heterozygous Actn2 p.Met228Thr mice have no overt phenotype. Only mature males show molecular parameters indicative of cardiomyopathy. By contrast, the variant is embryonically lethal in the homozygous setting and E15.5 hearts show multiple morphological abnormalities. Molecular analyses, including unbiased proteomics, identified quantitative abnormalities in sarcomeric parameters, cell-cycle defects and mitochondrial dysfunction. The mutant alpha-actinin protein is found to be destabilised, associated with increased activity of the ubiquitin-proteasomal system. This missense variant in alpha-actinin renders the protein less stable. In response, the ubiquitin-proteasomal system is activated; a mechanism that has been implicated in cardiomyopathies previously. In parallel, a lack of functional alpha-actinin is thought to cause energetic defects through mitochondrial dysfunction. This seems, together with cell-cycle defects, the likely cause of the death of the embryos. The defects also have wide-ranging morphological consequences.

The effect of sex and age on ex vivo cardiac electrophysiology: insight from a guinea pig model

Highlighting the importance of sex as a biological variable, we recently reported sex differences in guinea pig in vivo electrocardiogram (ECG) measurements. However, substantial inconsistencies exist in this animal model, with conflicting reports of sex-specific differences in cardiac electrophysiology observed in vivo and in vitro. Herein, we evaluated whether sexual dimorphism persists in ex vivo preparations, using an isolated intact heart preparation. Pseudo-ECG recordings were collected in conjunction with dual optical mapping of transmembrane voltage and intracellular calcium from Langendorff-perfused hearts. In contrast to our in vivo results, we did not observe sex-specific differences in ECG parameters collected from isolated hearts. Furthermore, we observed significant age-specific differences in action potential duration (APD) and Ca2+ transient duration (CaD) during both normal sinus rhythm (NSR) and in response to dynamic pacing but only a modest sex-specific difference in CaD30. Similarly, the alternans fluctuation coefficient, conduction velocity during sinus rhythm or in response to pacing, and electrophysiology parameters (atrioventricular nodal effective refractory period, Wenckebach cycle length) were comparable between males and females. Results of our study suggest that the observed sex-specific differences in in vivo ECG parameters from guinea pigs are diminished in ex vivo isolated heart preparations, although age-specific patterns are prevalent. To assess sex as a biological variable in cardiac electrophysiology, a comprehensive approach may be necessary using both in vitro measurements from cardiomyocyte or intact heart preparations with secondary follow-up in vivo studies.NEW & NOTEWORTHY We evaluated whether the guinea pig heart has intrinsic sex-specific differences in cardiac electrophysiology. Although we observed sex-specific differences in in vivo ECGs, these differences did not persist ex vivo. Using a whole heart model, we observed similar APD, CaD, conduction velocity, and alternans susceptibility in males and females. We conclude that sex-specific differences in guinea pig cardiac electrophysiology are likely influenced by the in vivo environment and less dependent on the intrinsic electrical properties of the heart.

Telotristat ethyl reverses myxomatous changes in mice mitral valves

Rationale

Myxomatous mitral valve degeneration is a common pathological manifestation of mitral valve regurgitation, with or without valvular prolapse. In addition to similarities between naturally occurring and serotonergic valve degeneration, an increasing body of evidence has recently suggested that serotonin signaling is a regulator of degenerative valvulopathies. Studies have found that serotonin can be synthesized locally by valvular cells and serotonin receptors in turn may be activated to promote signaling. Recently, telotristat ethyl (TE) has been introduced as a treatment for carcinoid disease, by selectively inhibiting tryptophan hydroxylase 1, the rate-limiting enzyme in peripheral serotonin synthesis. TE provides a unique tool to test inhibition of serotonin synthesis in vivo, without impacting brain serotonin, to further confirm the role of local serotonin synthesis on heart valves.

Objective

To confirm the link between serotonin and myxomatous valvular disease in vivo.

Methods and results

A hypertension-induced myxomatous mitral valve disease mouse model was employed to test the effect of TE on valvular degeneration. Circulating serotonin and local serotonin in valve tissues were tested by enzyme immunoassay and immunohistochemistry, respectively. TE was administrated in two modes: (1) parallel with angiotensin II (A2); (2) post A2 treatment. Myxomatous changes were successfully recapitulated in hypertensive mice, as determined by ECM remodeling, myofibroblast transformation, and serotonin signaling activation. These changes were at least partially reversed upon TE administration.

Conclusion

This study provides the first evidence of TE as a potential therapeutic for myxomatous mitral disease, either used to prevent or reverse myxomatous degeneration.

Sex Differences in Circadian Rhythms

Sex as a biological variable is the focus of much literature and has been emphasized by the National Institutes of Health, in part, to remedy a long history of male-dominated studies in preclinical and clinical research. We propose that time-of-day is also a crucial biological variable in biomedical research. In common with sex differences, time-of-day should be considered in analyses and reported to improve reproducibility of studies and to provide the appropriate context to the conclusions. Endogenous circadian rhythms are present in virtually all living organisms, including bacteria, plants, invertebrates, and vertebrates. Virtually all physiological and behavioral processes display daily fluctuations in optimal performance that are driven by these endogenous circadian clocks; importantly, many of those circadian rhythms also show sex differences. In this review, we describe some of the documented sex differences in circadian rhythms.

SGLT2 inhibition attenuates arterial dysfunction and decreases vascular F-actin content and expression of proteins associated with oxidative stress in aged mice

Aging of the vasculature is characterized by endothelial dysfunction and arterial stiffening, two key events in the pathogenesis of cardiovascular disease (CVD). Treatment with sodium glucose transporter 2 (SGLT2) inhibitors is now known to decrease cardiovascular morbidity and mortality in type 2 diabetes. However, whether SGLT2 inhibition attenuates vascular aging is unknown. We first confirmed in a cohort of adult subjects that aging is associated with impaired endothelial function and increased arterial stiffness and that these two variables are inversely correlated. Next, we investigated whether SGLT2 inhibition with empagliflozin (Empa) ameliorates endothelial dysfunction and reduces arterial stiffness in aged mice with confirmed vascular dysfunction. Specifically, we assessed mesenteric artery endothelial function and stiffness (via flow-mediated dilation and pressure myography mechanical responses, respectively) and aortic stiffness (in vivo via pulse wave velocity and ex vivo via atomic force microscopy) in Empa-treated (14 mg/kg/day for 6 weeks) and control 80-week-old C57BL/6 J male mice. We report that Empa-treated mice exhibited improved mesenteric endothelial function compared with control, in parallel with reduced mesenteric artery and aortic stiffness. Additionally, Empa-treated mice had greater vascular endothelial nitric oxide synthase activation, lower phosphorylated cofilin, and filamentous actin content, with downregulation of pathways involved in production of reactive oxygen species. Our findings demonstrate that Empa improves endothelial function and reduces arterial stiffness in a preclinical model of aging, making SGLT2 inhibition a potential therapeutic alternative to reduce the progression of CVD in older individuals.

The renin-angiotensin system and cardiovascular autonomic control in aging

Aging is the greatest independent risk factor for developing hypertension and cardiovascular-related diseases including systolic hypertension, vascular disease, ischemic events, arrhythmias, and heart failure. Age-related cardiovascular risk is associated with dysfunction of peripheral organ systems, such as the heart and vasculature, as well as an imbalance in the autonomic nervous system characterized by increased sympathetic and decreased parasympathetic neurotransmission. Given the increasing prevalence of aged individuals worldwide, it is critical to better understand mechanisms contributing to impaired cardiovascular autonomic control in this population. In this regard, the renin-angiotensin system has emerged as an important hormonal modulator of cardiovascular function in aging, in part through modulation of autonomic pathways controlling sympathetic and parasympathetic outflow to cardiovascular end organs. This review will summarize the role of the RAS in cardiovascular autonomic control during aging, with a focus on current knowledge of angiotensin II versus angiotensin-(1-7) pathways in both rodent models and humans, pharmacological treatment strategies targeting the renin-angiotensin system, and unanswered questions for future research.

Sex differences in cardiopulmonary effects of acute bromine exposure

Accidental occupational bromine (Br>2>) exposures are common, leading to significant morbidity and mortality; however, the specific effects of Br>2> inhalation in female victims are unclear. Our studies demonstrated that acute high-concentration Br>2> inhalation is fatal, and cardiac injury and dysfunction play an important role in Br>2> toxicity in males. In this study, we exposed female Sprague Dawley rats, age-matched to those males from previously studied, to 600 ppm Br>2> for 45 min and assessed their survival, cardiopulmonary injury and cardiac function after exposure. Br>2> exposure caused serious mortality in female rats (59%) 48 h after exposure. Rats had severe clinical distress, reduced heart rates and oxygen saturation after Br>2> inhalation as was previously reported with male animals. There was significant lung injury and edema when measured 24 h after exposure. Cardiac injury biomarkers were also significantly elevated 24 h after Br>2> inhalation. Echocardiography and hemodynamic studies were also performed and revealed that the mean arterial pressure was not significantly elevated in females. Other functional cardiac parameters were also altered. Aside from the lack of elevation of blood pressure, all other changes observed in female animals were also present in male animals as reported in our previous study. These studies are important to understand the toxicity mechanisms to generate therapies and better-equip first responders to deal with these specific scenarios after bromine spill disasters.>.

Obesity and metabolic syndrome induce hyperfiltration, glomerulomegaly, and albuminuria in obese ovariectomized female mice and obese male mice

OBJECTIVE

Obese patients with metabolic syndrome have a high risk of chronic kidney disease. The prevalence of obesity, metabolic syndrome, and insulin resistance increase in women after menopause, as does the risk of chronic kidney disease. This may indicate an interaction between obesity, metabolic syndrome, and menopause in the induction of renal damage. However, the pathogenesis of kidney disease in postmenopausal obese women is poorly understood.

METHODS

We investigated the interaction of an obesogenic diet and menopause on renal dysfunction in ovariectomized and non-ovariectomized lean (n = 8 and 17) and obese (n = 12 and 20) female mice. Obese (n = 12) and lean (n = 10) male mice were also studied. Glucose metabolism, insulin resistance, and kidney function were evaluated with gold standards procedures. Changes in kidney histology and lipid deposition were analyzed. Females had a lower number of glomeruli than males at baseline.

RESULTS

Only female ovariectomized obese animals developed insulin resistance, hyperglycemia, and kidney damage, evidenced as glomerulomegaly, glomerular hyperfiltration, and increased urinary albumin excretion, despite a similar increase in weight than obese non-ovariectomized female mice. Male obese mice developed hyperglycemia, insulin resistance, and hyperfiltration without major renal histological changes. Males on high fat diet showed higher renal lipid content and females on high fat diet (ovariectomized or non-ovariectomized) showed higher total cholesterol content than males.

CONCLUSIONS

In mice, there is a clear interplay between obesity, metabolic syndrome, and menopause in the induction of kidney damage.

In Aged Females, the Enhanced Pressor Response to Angiotensin II Is Attenuated By Estrogen Replacement via an Angiotensin Type 2 Receptor-Mediated Mechanism

[Figure: see text].

Sex differences in soluble prorenin receptor in patients with type 2 diabetes

BACKGROUND

The soluble prorenin receptor (sPRR), a member of the renin-angiotensin system (RAS), is elevated in plasma of patients with preeclampsia, hypertension, chronic kidney disease (CKD), and type 2 diabetes. Our goal was to examine the relationship between sPRR and RAS activation to define whether sexual dimorphisms in sPRR might explain sex disparities in renal outcomes in patients with type 2 diabetes.

METHODS

Two hundred sixty-nine participants were included in the study (mean age, 48 ± 16 years; 42% men, 58% women), including 173 controls and 96 subjects with type 2 diabetes. In plasma and urine, we measured sPRR, plasma renin activity (PRA), and prorenin. In the urine, we also measured angiotensinogen along with other biomarkers of renal dysfunction.

RESULTS

Plasma sPRR and PRA were significantly higher in women with type 2 diabetes compared to men. In these women, plasma sPRR was positively correlated with PRA, age, and body mass index (BMI). In contrast, in men the sPRR in urine but not in plasma positively correlated with eGFR in urine, but negatively correlated with urine renin activity, plasma glucose, age, and BMI.

CONCLUSIONS

In patients with type 2 diabetes, sPRR contributes to RAS stimulation in a sex-dependent fashion. In diabetic women, increased plasma sPRR parallels the activation of systemic RAS; while in diabetic men, decreased sPRR in urine matches intrarenal RAS stimulation. sPRR might be a potential indicator of intrarenal RAS activation and renal dysfunction in men and women with type 2 diabetes.

Sex-Dependent End-of-Life Mental and Vascular Scenarios for Compensatory Mechanisms in Mice with Normal and AD-Neurodegenerative Aging

Life expectancy decreases with aging, with cardiovascular, mental health, and neurodegenerative disorders strongly contributing to the total disability-adjusted life years. Interestingly, the morbidity/mortality paradox points to females having a worse healthy life expectancy. Since bidirectional interactions between cardiovascular and Alzheimer’s diseases (AD) have been reported, the study of this emerging field is promising. In the present work, we further explored the cardiovascular–brain interactions in mice survivors of two cohorts of non-transgenic and 3xTg-AD mice, including both sexes, to investigate the frailty/survival through their life span. Survival, monitored from birth, showed exceptionally worse mortality rates in females than males, independently of the genotype. This mortality selection provided a “survivors” cohort that could unveil brain–cardiovascular interaction mechanisms relevant for normal and neurodegenerative aging processes restricted to long-lived animals. The results show sex-dependent distinct physical (worse in 3xTg-AD males), neuropsychiatric-like and cognitive phenotypes (worse in 3xTg-AD females), and hypothalamic–pituitary–adrenal (HPA) axis activation (higher in females), with higher cerebral blood flow and improved cardiovascular phenotype in 3xTg-AD female mice survivors. The present study provides an experimental scenario to study the suggested potential compensatory hemodynamic mechanisms in end-of-life dementia, which is sex-dependent and can be a target for pharmacological and non-pharmacological interventions.

Insulin-regulated aminopeptidase deficiency impairs cardiovascular adaptations and placental development during pregnancy

Insulin-regulated aminopeptidase (IRAP), an enzyme that cleaves vasoactive peptides including oxytocin and vasopressin, is suggested to play a role in pregnancy and the onset of preeclampsia. Our aim was to examine the contribution of IRAP to arterial pressure regulation and placental development during pregnancy in mice. Mean arterial pressure and heart rate were measured via radiotelemetry in 12-week-old female wild-type and IRAP knockout mice. Females were time-mated with males of the same genotype. Placentae were collected at embryonic day 18.5 for histological analysis. Basal heart rate was ∼40 bpm lower in IRAP knockout females compared with wild-type females. The increase in heart rate across gestation was greater in IRAP knockout females than wild-type females. Neither basal nor gestational mean arterial pressure was different between wildtype and IRAP knockout females. Urine output and water intake of IRAP knockout mice were ∼45% less than wild-type mice at late gestation. IRAP deficiency had no effect on fetal weight. Morphological assessment of placentae revealed that IRAP deficiency was associated with reduced labyrinth surface area and accumulation of glycogen in the junctional zone. Our data demonstrate that IRAP deficiency alters maternal fluid handling and impairs placental labyrinth expansion at late gestation, indicating that IRAP contributes to the normal adaptions to pregnancy.

Effect of gender on transition of normo- to microalbuminuria under angiotensin receptor blocker therapy in diabetes

Highlights In normoalbuminuric diabetic patients at low cardiovascular risk, the risk of transition from normo- to microalbuminuria is lower in women, despite the nonprotective effects of the angiotensin receptor blocker olmesartan. Additional methods of assessment of albuminuria in clinical studies (eg, measurements of albumin and creatinine excretion rate) should be implemented or the actually accepted higher urine albumin creatinine ratio (UACR) cutoff values for microalbuminuria in women reconsidered.

Multifaceted Benefit of Whole Blood Versus Lactated Ringer's Resuscitation After Traumatic Brain Injury and Hemorrhagic Shock in Mice

BACKGROUND

Despite increasing use in hemorrhagic shock (HS), whole blood (WB) resuscitation for polytrauma with traumatic brain injury (TBI) is largely unexplored. Current TBI guidelines recommend crystalloid for prehospital resuscitation. Although WB outperforms lactated Ringer's (LR) in increasing mean arterial pressure (MAP) in TBI + HS models, effects on brain tissue oxygenation (PbtO₂), and optimal MAP remain undefined.

METHODS

C57BL/6 mice (n = 72) underwent controlled cortical impact followed by HS (MAP = 25-27 mmHg). Ipsilateral hippocampal PbtO₂ (n = 40) was measured by microelectrode. Mice were assigned to four groups (n = 18/group) for "prehospital" resuscitation (90 min) with LR or autologous WB, and target MAPs of 60 or 70 mmHg (LR₆₀, WB₆₀, LR₇₀, WB₇₀). Additional LR (10 ml/kg) was bolused every 5 min for MAP below target.

RESULTS

LR requirements in WB₆₀ (7.2 ± 5.0 mL/kg) and WB₇₀ (28.3 ± 9.6 mL/kg) were markedly lower than in LR₆₀ (132.8 ± 5.8 mL/kg) or LR₇₀ (152.2 ± 4.8 mL/kg; all p < 0.001). WB₇₀ MAP (72.5 ± 2.9 mmHg) was higher than LR₇₀ (59.8 ± 4.0 mmHg, p < 0.001). WB₆₀ MAP (68.7 ± 4.6 mmHg) was higher than LR₆₀ (53.5 ± 3.2 mmHg, p < 0.001). PbtO₂ was higher in WB₆₀ (43.8 ± 11.6 mmHg) vs either LR₆₀ (25.9 ± 13.0 mmHg, p = 0.04) or LR₇₀ (24.1 ± 8.1 mmHg, p = 0.001). PbtO₂ in WB₇₀ (40.7 ± 8.8 mmHg) was higher than in LR₇₀ (p = 0.007). Despite higher MAP in WB₇₀ vs WB₆₀ (p = .002), PbtO₂ was similar.

CONCLUSION

WB resuscitation after TBI + HS results in robust improvements in brain oxygenation while minimizing fluid volume when compared to standard LR resuscitation. WB resuscitation may allow for a lower prehospital MAP without compromising brain oxygenation when compared to LR resuscitation. Further studies evaluating the effects of these physiologic benefits on outcome after TBI with HS are warranted, to eventually inform clinical trials.

Angiotensin-(1-7) Improves Integrated Cardiometabolic Function in Aged Mice

Angiotensin (Ang)-(1-7) is a beneficial renin–angiotensin system (RAS) hormone that elicits protective cardiometabolic effects in young animal models of hypertension, obesity, and metabolic syndrome. The impact of Ang-(1-7) on cardiovascular and metabolic outcomes during aging, however, remains unexplored. This study tested the hypothesis that Ang-(1-7) attenuates age-related elevations in blood pressure and insulin resistance in mice. Young adult (two-month-old) and aged (16-month-old) male C57BL/6J mice received Ang-(1-7) (400 ng/kg/min) or saline for six-weeks via a subcutaneous osmotic mini-pump. Arterial blood pressure and metabolic function indices (body composition, insulin sensitivity, and glucose tolerance) were measured at the end of treatment. Adipose and cardiac tissue masses and cardiac RAS, sympathetic and inflammatory marker gene expression were also measured. We found that chronic Ang-(1-7) treatment decreased systolic and mean blood pressure, with a similar trend for diastolic blood pressure. Ang-(1-7) also improved insulin sensitivity in aged mice to levels in young mice, without effects on glucose tolerance or body composition. The blood pressure–lowering effects of Ang-(1-7) in aged mice were associated with reduced sympathetic outflow to the heart. These findings suggest Ang-(1-7) may provide a novel pharmacological target to improve age-related cardiometabolic risk.

Analysis of structure and gene expression in developing kidneys of male and female rats exposed to low protein diets in utero

A maternal low protein (LP) diet in rodents often results in low nephron endowment and renal pathophysiology in adult life, with outcomes often differing between male and female offspring. Precisely how a maternal LP diet results in low nephron endowment is unknown. We conducted morphological and molecular studies of branching morphogenesis and nephrogenesis to identify mechanisms and timepoints that might give rise to low nephron endowment. Sprague-Dawley rats were fed a normal protein (19.4% protein, NP) or LP (9% protein) diet for 3 weeks prior to mating and throughout gestation. Embryonic day 14.25 (E14.25) kidneys from males and females were either cultured for 2 days after which branching morphogenesis was quantified, or frozen for gene expression analysis. Real-time PCR was used to quantify expression of key nephrogenesis and branching morphogenesis genes at E14.25 and 17.25. At E17.25, nephron number was determined in fixed tissue. There was no effect of either maternal diet or sex on branching morphogenesis. Nephron number at E17.25 was 14% lower in male and female LP offspring than in NP controls. At E14.25 expression levels of genes involved in branching morphogenesis (Gfrα1, Bmp4, Gdnf) and nephrogenesis (Hnf4a, Pax2, Wnt4) were similar in the dietary groups, but significant differences between sexes were identified. At E17.25, expression of Gfrα1, Gdnf, Bmp4, Pax2 and Six2 was lower in LP offspring than NP offspring, in both male and female offspring. These findings provide new insights into how a LP diet leads to low nephron endowment and renal sexual dimorphism.

Non-Invasive Ultrasound Detection of Cerebrovascular Changes in a Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) can induce changes in vascular architecture. Although ultrasound metrics such as pulsatility index (PI) are sensitive to changes in hemodynamic resistance downstream from major arteries, these metrics depend on features unrelated to vessel architecture, such as blood pressure and heart rate. In contrast, input impedance and reflection coefficient that are derived from wave reflection theory seek to minimize the effects of altered cardiac output or heart rate. In this article, we investigate the use of ultrasound to assess changes in vascular impedance and wave reflection in the common carotid arteries of mice exposed to a controlled cortical impact. Focusing on the first harmonics of the reflected waves, the impedance phase was increased ipsilaterally in impacted mice compared with shams, whereas the magnitude of the impedance was unchanged. In contrast, PI was reduced bilaterally. Interestingly, PI and the first harmonic magnitude of input impedance in the carotid artery were correlated on the contralateral but not ipsilateral side. We investigated the use of these metrics to classify mice as sham or TBI, finding an area under the receiver operating characteristic curve ipsilaterally of 0.792 (confidence interval [CI]: 0.648-0.936) for correct classification with first harmonic impedance magnitude and phase as predictors and 0.716 (CI: 0.553-0.879) using carotid artery PI and diameter as predictors. Overall, the findings support the use of wave reflection analysis as a more specific measure of vascular changes following TBI and motivate the translation of this approach for monitoring vascular changes in humans affected by TBI.

Report of the National Heart, Lung, and Blood Institute Working Group on Hypertension: Barriers to Translation

The National Heart, Lung, and Blood Institute convened a multidisciplinary working group of hypertension researchers on December 6 to 7, 2018, in Bethesda, MD, to share current scientific knowledge in hypertension and to identify barriers to translation of basic into clinical science/trials and implementation of clinical science into clinical care of patients with hypertension. The goals of the working group were (1) to provide an overview of recent discoveries that may be ready for testing in preclinical and clinical studies; (2) to identify gaps in knowledge that impede translation; (3) to highlight the most promising scientific areas in which to pursue translation; (4) to identify key challenges and barriers for moving basic science discoveries into translation, clinical studies, and trials; and (5) to identify roadblocks for effective dissemination and implementation of basic and clinical science in real-world settings. The working group addressed issues that were responsive to many of the objectives of the National Heart, Lung, and Blood Institute Strategic Vision. The working group identified major barriers and opportunities for translating research to improved control of hypertension. This review summarizes the discussion and recommendations of the working group.

Urinary angiotensinogen increases in the absence of overt renal injury in high fat diet-induced type 2 diabetic mice

AIM OF THE STUDY

During type 2 diabetes (T2D) and hypertension there is stimulation of renal proximal tubule angiotensinogen (AGT), but whether urinary excretion of AGT (uAGT) is an indicator of glomerular damage or intrarenal RAS activation is unclear. We tested the hypothesis that elevations in uAGT can be detected in the absence of albuminuria in a mouse model of T2D.

METHODS

Male C57BL/6 mice (N = 10) were fed a high fat (HFD; 45% Kcal from fat) for 28 weeks, and the metabolic phenotype including body weight, blood pressures, glucose, insulin, ippGTT, HOMA-IR, and cholesterol was examined. In addition, kidney Ang II content and reactive oxygen species (ROS) was measured along with urinary albumin, creatinine, Ang II, and AGT.

RESULTS

All parameters consistent with T2D were present in mice after 12-14 weeks on the HFD. Systolic BP increased after 18 weeks in HFD but not NFD mice. Intrarenal ROS and Ang II concentrations were also increased in HFD mice. Remarkably, these changes paralleled the augmentation uAGT excretion (3.66 ± 0.50 vs. 0.92 ± 0.13 ng/mg by week 29; P < 0.01), which occurred in the absence of overt albuminuria.

CONCLUSIONS

In HFD-induced T2D mice, increases in uAGT occur in the absence of overt renal injury, indicating that this biomarker accurately detects early intrarenal RAS activation.

Maternal hypoxia developmentally programs low podocyte endowment in male, but not female offspring

Fetal hypoxia is a common complication of pregnancy. We have previously reported that maternal hypoxia in late gestation in mice gives rise to male offspring with reduced nephron number, while females have normal nephron number. Male offspring later develop proteinuria and renal pathology, including glomerular pathology, whereas female offspring are unaffected. Given the central role of podocyte depletion in glomerular and renal pathology, we examined whether maternal hypoxia resulted in low podocyte endowment in offspring. Pregnant CD1 mice were allocated at embryonic day 14.5 to normoxic (21% oxygen) or hypoxic (12% oxygen) conditions. At postnatal day 21, kidneys from mice were immersion fixed, and one mid-hilar slice per kidney was immunostained with antibodies directed against p57 and synaptopodin for podocyte identification. Slices were cleared and imaged with a multiphoton microscope for podometric analysis. Male hypoxic offspring had significantly lower birth weight, nephron number, and podocyte endowment than normoxic male offspring (podocyte number; normoxic 62.86 ± 2.26 podocytes per glomerulus, hypoxic 53.38 ± 2.25; p < .01, mean ± SEM). In contrast, hypoxic female offspring had low birth weight but their nephron and podocyte endowment was the same as normoxic female offspring (podocyte number; normoxic 62.38 ± 1.86 podocytes per glomerulus, hypoxic 61.81 ± 1.80; p = .88). To the best of our knowledge, this is the first report of developmentally programmed low podocyte endowment. Given the well-known association between podocyte depletion in adulthood and glomerular pathology, we postulate that podocyte endowment may place offspring at risk of renal disease in adulthood, and explain the greater vulnerability of male offspring.

Tubular Deficiency of Heterogeneous Nuclear Ribonucleoprotein F Elevates Systolic Blood Pressure and Induces Glycosuria in Mice

We reported previously that overexpression of heterogeneous nuclear ribonucleoprotein F (Hnrnpf) in renal proximal tubular cells (RPTCs) suppresses angiotensinogen (Agt) expression, and attenuates systemic hypertension and renal injury in diabetic Hnrnpf-transgenic (Tg) mice. We thus hypothesized that deletion of Hnrnpf in the renal proximal tubules (RPT) of mice would worsen systemic hypertension and kidney injury, perhaps revealing novel mechanism(s). Tubule-specific Hnrnpf knockout (KO) mice were generated by crossbreeding Pax8-Cre mice with floxed Hnrnpf mice on a C57BL/6 background. Both male and female KO mice exhibited elevated systolic blood pressure, increased urinary albumin/creatinine ratio, tubulo-interstitial fibrosis and glycosuria without changes in blood glucose or glomerular filtration rate compared with control littermates. However, glycosuria disappeared in male KO mice at the age of 12 weeks, while female KO mice had persistent glycosuria. Agt expression was elevated, whereas sodium-glucose co-transporter 2 (Sglt2) expression was down-regulated in RPTs of both male and female KO mice as compared to control littermates. In vitro, KO of HNRNPF in human RPTCs (HK-2) by CRISPR gRNA up-regulated AGT and down-regulated SGLT2 expression. The Sglt2 inhibitor canagliflozin treatment had no effect on Agt and Sglt2 expression in HK-2 and in RPTCs of wild-type mice but induced glycosuria. Our results demonstrate that Hnrnpf plays a role in the development of hypertension and glycosuria through modulation of renal Agt and Sglt2 expression in mice, respectively.

Heterogeneous Cellular Contributions to Elastic Laminae Formation in Arterial Wall Development

RATIONALE

Elastin is an important ECM (extracellular matrix) protein in large and small arteries. Vascular smooth muscle cells (SMCs) produce the layered elastic laminae found in elastic arteries but synthesize little elastin in muscular arteries. However, muscular arteries have a well-defined internal elastic lamina (IEL) that separates endothelial cells (ECs) from SMCs. The extent to which ECs contribute elastin to the IEL is unknown.

OBJECTIVE

To use targeted elastin (Eln) deletion in mice to explore the relative contributions of SMCs and ECs to elastic laminae formation in different arteries.

METHODS AND RESULTS

We used SMC- and EC-specific Cre recombinase transgenes with a novel floxed Eln allele to focus gene inactivation in mice. Inactivation of Eln in SMCs using Sm22aCre resulted in depletion of elastic laminae in the arterial wall with the exception of the IEL and SMC clusters in the outer media near the adventitia. Inactivation of elastin in ECs using Tie2Cre or Cdh5Cre resulted in normal medial elastin and a typical IEL in elastic arteries. In contrast, the IEL was absent or severely disrupted in muscular arteries. Interruptions in the IEL resulted in neointimal formation in the ascending aorta but not in muscular arteries.

CONCLUSIONS

Combined with lineage-specific fate mapping systems, our knockout results document an unexpected heterogeneity in vascular cells that produce the elastic laminae. SMCs and ECs can independently form an IEL in most elastic arteries, whereas ECs are the major source of elastin for the IEL in muscular and resistance arteries. Neointimal formation at IEL disruptions in the ascending aorta confirms that the IEL is a critical physical barrier between SMCs and ECs in the large elastic arteries. Our studies provide new information about how SMCs and ECs contribute elastin to the arterial wall and how local elastic laminae defects may contribute to cardiovascular disease.

Chronic exposure to gamma irradiation at low-dose rates accelerates blood pressure decline associated with aging in female B6C3F1 mice

PURPOSE

Many studies are focusing on the biological effects of gamma irradiation at low-dose rates. Studies have shown that chronic exposure to gamma irradiation at low-dose rates shortened the lifespan of mice due to neoplasm formation. The aim of this study was to clarify the physiological effects of long-term exposure to gamma irradiation at low-dose rates in mice, measured with noninvasive parameters such as blood pressure.

MATERIALS AND METHODS

Specific-pathogen-free female B6C3F₁ mice were irradiated with gamma rays at a low dose of 20 mGy/day - a dose rate shown to shorten the life span in previous studies. The blood pressure parameters (systolic, diastolic, and mean blood pressure), heart rate, tail blood volume, and blood flow of the mice were measured every 7 weeks. Age-matched, non-irradiated mice were used as controls.

RESULTS AND CONCLUSION

The blood pressure levels of the irradiated mice decreased at an earlier age compared to the non-irradiated control mice. The expression levels of the marker genes of aging that are also associated with regulation of blood pressure showed significant differences between non-irradiated and irradiated mice. These results indicated that long-term exposure to gamma irradiation at low-dose rates induce the expression levels of Rap1a and reduces Panx1 and Sirt3, which may have contributed to the accelerated blood pressure decline in female mice.

Predominant Role of Nuclear Versus Membrane Estrogen Receptor α in Arterial Protection: Implications for Estrogen Receptor α Modulation in Cardiovascular Prevention/Safety

BACKGROUND

Although estrogen receptor α (ERα) acts primarily as a transcription factor, it can also elicit membrane-initiated steroid signaling. Pharmacological tools and transgenic mouse models previously highlighted the key role of ERα membrane-initiated steroid signaling in 2 actions of estrogens in the endothelium: increase in NO production and acceleration of reendothelialization.

METHODS AND RESULTS

Using mice with ERα mutated at cysteine 451 (ERaC451A), recognized as the key palmitoylation site required for ERα plasma membrane location, and mice with disruption of nuclear actions because of inactivation of activation function 2 (ERaAF20 = ERaAF2°), we sought to fully characterize the respective roles of nuclear versus membrane-initiated steroid signaling in the arterial protection conferred by ERα. ERaC451A mice were fully responsive to estrogens to prevent atheroma and angiotensin II-induced hypertension as well as to allow flow-mediated arteriolar remodeling. By contrast, ERαAF20 mice were unresponsive to estrogens for these beneficial vascular effects. Accordingly, selective activation of nuclear ERα with estetrol was able to prevent hypertension and to restore flow-mediated arteriolar remodeling.

CONCLUSIONS

Altogether, these results reveal an unexpected prominent role of nuclear ERα in the vasculoprotective action of estrogens with major implications in medicine, particularly for selective nuclear ERα agonist, such as estetrol, which is currently under development as a new oral contraceptive and for hormone replacement therapy in menopausal women.

Compromised microvascular oxygen delivery increases brain tissue vulnerability with age

Despite the possible role of impaired cerebral tissue oxygenation in age-related cognition decline, much is still unknown about the changes in brain tissue pO₂ with age. Using a detailed investigation of the age-related changes in cerebral tissue oxygenation in the barrel cortex of healthy, awake aged mice, we demonstrate decreased arteriolar and tissue pO₂ with age. These changes are exacerbated after middle-age. We further uncovered evidence of the presence of hypoxic micro-pockets in the cortex of awake old mice. Our data suggests that from young to middle-age, a well-regulated capillary oxygen supply maintains the oxygen availability in cerebral tissue, despite decreased tissue pO₂ next to arterioles. After middle-age, due to decreased hematocrit, reduced capillary density and higher capillary transit time heterogeneity, the capillary network fails to compensate for larger decreases in arterial pO₂. The substantial decrease in brain tissue pO₂, and the presence of hypoxic micro-pockets after middle-age are of significant importance, as these factors may be related to cognitive decline in elderly people.

Hydrogen sulfide ameliorates aging-associated changes in the kidney

Aging is associated with replacement of normal kidney parenchyma by fibrosis. Because hydrogen sulfide (H₂S) ameliorates kidney fibrosis in disease models, we examined its status in the aging kidney. In the first study, we examined kidney cortical H₂S metabolism and signaling pathways related to synthesis of proteins including matrix proteins in young and old male C57BL/6 mice. In old mice, increase in renal cortical content of matrix protein involved in fibrosis was associated with decreased H₂S generation and AMPK activity, and activation of insulin receptor (IR)/IRS-2-Akt-mTORC1-mRNA translation signaling axis that can lead to increase in protein synthesis. In the second study, we randomized 18-19 month-old male C57BL/6 mice to receive 30 μmol/L sodium hydrosulfide (NaHS) in drinking water vs. water alone (control) for 5 months. Administration of NaHS increased plasma free sulfide levels. NaHS inhibited the increase in kidney cortical content of matrix proteins involved in fibrosis and ameliorated glomerulosclerosis. NaHS restored AMPK activity and inhibited activation of IR/IRS-2-Akt-mTORC1-mRNA translation axis. NaHS inhibited age-related increase in kidney cortical content of p21, IL-1β, and IL-6, components of the senescence-associated secretory phenotype. NaHS abolished increase in urinary albumin excretion seen in control mice and reduced serum cystatin C levels suggesting improved glomerular clearance function. We conclude that aging-induced changes in the kidney are associated with H₂S deficiency. Administration of H₂S ameliorates aging-induced kidney changes probably by inhibiting signaling pathways leading to matrix protein synthesis.

Orphan receptor GPR37L1 contributes to the sexual dimorphism of central cardiovascular control

Background

Over 100 mammalian G protein-coupled receptors are yet to be matched with endogenous ligands; these so-called orphans are prospective drug targets for the treatment of disease. GPR37L1 is one such orphan, abundant in the brain and detectable as mRNA in the heart and kidney. GPR37L1 ablation was reported to cause hypertension and left ventricular hypertrophy, and thus, we sought to further define the role of GPR37L1 in blood pressure homeostasis.

Methods

We investigated the cardiovascular effects of GPR37L1 using wild-type (GPR37L1^wt/wt) and null (GPR37L1^KO/KO) mice established on a C57BL/6J background, both under baseline conditions and during AngII infusion. We profiled GPR37L1 tissue expression, examining the endogenous receptor by immunoblotting and a β-galactosidase reporter mouse by immunohistochemistry.

Results

GPR37L1 protein was abundant in the brain but not detectable in the heart and kidney. We measured blood pressure in GPR37L1^wt/wt and GPR37L1^KO/KO mice and found that deletion of GPR37L1 causes a female-specific increase in systolic, diastolic, and mean arterial pressures. When challenged with short-term AngII infusion, only male GPR37L1^KO/KO mice developed exacerbated left ventricular hypertrophy and evidence of heart failure, while the female GPR37L1^KO/KO mice were protected from cardiac fibrosis.

Conclusions

Despite its absence in the heart and kidney, GPR37L1 regulates baseline blood pressure in female mice and is crucial for cardiovascular compensatory responses in males. The expression of GPR37L1 in the brain, yet absence from peripheral cardiovascular tissues, suggests this orphan receptor is a hitherto unknown contributor to central cardiovascular control.

Electronic supplementary material

The online version of this article (10.1186/s13293-018-0173-y) contains supplementary material, which is available to authorized users.

Sex-specific differences in hypertension and associated cardiovascular disease

Although intrinsic mechanisms that regulate arterial blood pressure (BP) are similar in men and women, marked variations exist at the molecular, cellular and tissue levels. These physiological disparities between the sexes likely contribute to differences in disease onset, susceptibility, prevalence and treatment responses. Key systems that are important in the development of hypertension and cardiovascular disease (CVD), including the sympathetic nervous system, the renin-angiotensin-aldosterone system and the immune system, are differentially activated in males and females. Biological age also contributes to sexual dimorphism, as premenopausal women experience a higher degree of cardioprotection than men of similar age. Furthermore, sex hormones such as oestrogen and testosterone as well as sex chromosome complement likely contribute to sex differences in BP and CVD. At the cellular level, differences in cell senescence pathways may contribute to increased longevity in women and may also limit organ damage caused by hypertension. In addition, many lifestyle and environmental factors - such as smoking, alcohol consumption and diet - may influence BP and CVD in a sex-specific manner. Evidence suggests that cardioprotection in women is lost under conditions of obesity and type 2 diabetes mellitus. Treatment strategies for hypertension and CVD that are tailored according to sex could lead to improved outcomes for affected patients.

Relaxin contributes to the regulation of arterial pressure in adult female mice

Relaxin is increasingly being recognized as a potent vasodilatory and antifibrotic hormone. Given that relaxin is present in the circulation during the luteal phase of the menstrual cycle and during pregnancy, when arterial pressure is lowest in women, relaxin may contribute to the relative cardiovascular protection observed in premenopausal women as compared with age-matched men and postmenopausal women. In the present study, we investigated the contribution of relaxin to the normal regulation of arterial pressure in adult female and male mice and during pregnancy. Mean arterial pressure (MAP) was measured via radiotelemetry in 14-week-old male and female wild-type (WT; C67BL/6xSv129) and relaxin knockout (KO) mice. Thereafter, female mice were time-mated with a (non-telemetered) male of the same genotype and MAP was measured throughout gestation. Basal MAP was ∼10 mmHg lower in WT females than males (P<0.05). Relaxin deficiency increased basal MAP in females (P<0.05 vs WT female), but not males. As expected, MAP decreased during gestation in WT mice. Conversely, in relaxin KO mice, arterial pressure increased during mid and late gestation (P<0.05 as compared with WT). Moreover, relaxin deficiency impaired gestational weight gain and reduced litter size. This is the first study to (i) demonstrate that relaxin contributes to the sexual dimorphism of arterial pressure in mice and (ii) document the changes in the arterial pressure profile of pregnant relaxin KO mice. Understanding the mechanisms that underlie the regulation of arterial pressure in premenopausal females may uncover new strategies to treat hypertension in women (non-pregnant and pregnant) and men.

Prostacyclin does not affect sweating but induces skin vasodilatation to a greater extent in older versus younger women: roles of NO and KCa channels

NEW FINDINGS

What is the central question of this study? It remains unknown whether ageing modulates prostacyclin-induced cutaneous vasodilatation in women. What is the main finding and its importance? Prostacyclin induced cutaneous vasodilatation, albeit the magnitude of increase at lower concentrations of prostacyclin was greater in older relative to young women. This response was associated with greater contributions of nitric oxide synthase and calcium-activated potassium channels. Our results suggest that administration of prostacyclin might be an effective therapy to reverse microvascular hypoperfusion, especially in older women. We previously reported that prostacyclin induces cutaneous vasodilatation but not sweating in younger and older men. Furthermore, we demonstrated that nitric oxide synthase and calcium-activated potassium (K_Ca ) channels contribute to the prostacyclin-induced cutaneous vasodilatation in younger men, although these contributions are diminished in older men. Given that the effects of ageing might differ between men and women, the above results cannot simply be applied to women. In this study, cutaneous vascular conductance and sweat rate were evaluated in younger (mean ± SD, 22 ± 3 years old) and older (55 ± 7 years old) women (10 per group) at four intradermal forearm skin sites treated as follows: (i) lactated Ringer solution without any drug (control); (ii) 10 mm N^G -nitro-l-arginine (l-NNA), a non-specific nitric oxide synthase inhibitor; (iii) 50 mm tetraethylammonium (TEA), a non-specific K_Ca channel blocker; or (iv) 10 mm l-NNA plus 50 mm TEA. All four sites were co-administered with prostacyclin in an incremental manner (0.04, 0.4, 4, 40 and 400 μm, each for 25 min). Surprisingly, increases in cutaneous vascular conductance in response to 0.04-4 μm prostacyclin were greater in older relative to younger women (all P ≤ 0.05), and these age-related differences were diminished when both l-NNA and TEA were administered simultaneously (all P > 0.05). No effect on sweat rate was observed in either group (all concentrations, P > 0.05). We show that although prostacyclin does not mediate sweating, it induces cutaneous vasodilatation, and this response elicited by lower concentrations of prostacyclin is greater in older relative to younger women. This greater cutaneous vasodilatation in older women is likely to be attributable to nitric oxide synthase- and K_Ca channel-dependent mechanisms.