ROLE OF SEX CHROMOSOMES IN SEXUAL DIMORPHISM OF ANGII-INDUCED ABDOMINAL AORTIC ANEURYSMS

Abdominal aortic aneurysms (AAAs), a permanent dilation in the abdominal region of the aorta, is a highly sexually dimorphic disease. AAAs prevalence is ranging from 4-10 fold higher in males than females. Defining the mechanistic basis for reduced (in females) or increased (in males) AAA formation and progression may uncover potential therapeutic targets. The majority of studies examining sexual dimorphism focus on the role of sex hormones. However, genes residing on sex chromosomes, in addition to sex hormones, may contribute to sexual dimorphism of AAAs. For example, the X chromosome contains about 5% of the whole genome, but the role of sex chromosomes genes to sexual dimorphism of cardiovascular diseases such as AAAs is largely unknown. The purpose of this study was to determine the role of sex chromosomes as mediators of sex differences for angiotensin II (AngII)-induced AAAs in hypercholesterolemic mice. We used the four core genotype murine model, which enables the creation of phenotypically normal male and female mice with an XX versus XY sex chromosome complement, to test the hypothesis that an XY sex chromosome complement promotes AngII-induced AAAs. Transgenic male mice expressing the Sry gene on an autosome, but not on the Y-chromosome, were bred to female low-density lipoprotein receptor deficient mice to create male and female mice with an XX or an XY sex chromosome complement. In females, an XY sex chromosome complement doubled the incidence and markedly increased the severity of AngII-induced AAAs. To define mechanisms, we examined gene expression patterns in abdominal aortas and demonstrated elevated expression of inflammatory genes that were linked to increased MMP activity and oxidative stress in aortas from XY females. Moreover, administration of testosterone to XY females, to mimic males, resulted in a striking level of aneurysm rupture. In males, transcriptional profiling of abdominal aortas revealed 450 genes that were influenced by sex chromosomes. Infusion of AngII to XY males resulted in diffuse pathology along the length of the aorta, while XX males developed focal AAAs, with pathology reduced by orchiectomy in both genotypes. Thoracic aortas of XY males exhibited adventitial thickening which was not exist in thoracic aortas from XX males. Following a prolonged period (3 months) of AngII infusions XY males had AAAs with expanded aortic walls, while XX males had thin walled dilated AAAs. In summary, our findings demonstrate a remarkable effect of sex chromosome complement to regulate aortic vasculature and disease development. Aside from demonstrating mechanisms of sexual dimorphism of aortic diseases, these findings indicate that chronic sex hormone therapy in the aging and transgender population may have cardiovascular ramifications. Moreover, identification of targets influenced by sex chromosomes and/or sex hormones in a manner that predicts disease development may identify sex-specific approaches to cardiovascular therapy

Sexual Dimorphism of Abdominal Aortic Aneurysms

Sex is the largest nonmodifiable risk factor for the development of abdominal aortic aneurysms (AAAs) in humans and experimental models. Data from several studies consistently demonstrate a higher AAA prevalence in males than in females, contributing to divergent recommendations for AAA screening in men and women. Despite a higher AAA prevalence in males, females have more rapid rates of aneurysm dilation, and aneurysms rupture at smaller sizes. Unfortunately, no therapies have been effective to retard aneurysm dilation in either sex. Results from experimental AAA models indicate a protective role for estrogen in AAA development and progression, while male testosterone has been demonstrated to markedly promote angiotensin II (AngII)‐induced AAAs. Potential mechanisms implicated in sex hormone regulation of AAAs include regulation of inflammation, matrix metalloproteinases, aromatase activity, oxidative stress, stem cells, and transforming growth factor‐beta. In addition to sex hormones, sex chromosomes have been implicated in diseases of the aorta. Turner\u27s syndrome (monosomy X) patients have a high incidence of thoracic aortic rupture. Recent studies indicate a novel approach to define the relative role of sex hormones versus sex chromosomes in experimental AAAs. Further studies are warranted to determine interactions between sex hormones and sex chromosomes in AAA development and progression

Exogenous 17-β Estradiol Administration Blunts Progression of Established Angiotensin II-Induced Abdominal Aortic Aneurysms in Female Ovariectomized Mice

BACKGROUND: Abdominal aortic aneurysms (AAAs) occur predominately in males. However, AAAs in females have rapid growth rates and rupture at smaller sizes. Mechanisms contributing to AAA progression in females are undefined. We defined effects of ovariectomy, with and without 17-β estradiol (E2), on progression of established angiotensin II (AngII)-induced AAAs in female mice. METHODS: We used neonatal testosterone exposures at 1 day of age to promote susceptibility to AngII-induced AAAs in adult female Ldlr-/- mice. Females were infused with AngII for 28 days to induce AAAs, and then stratified into groups that were sham, ovariectomized (Ovx, vehicle), or Ovx with E2 administration for 2 months of continued AngII infusions. Aortic lumen diameters were quantified by ultrasound and analyzed by linear mixed model, and maximal AAA diameters were analyzed by one-way ANOVA. Atherosclerosis was quantified en face in the aortic arch. AAA tissue sections were analyzed for cellular composition. We quantified effects of E2 on abdominal aortic smooth muscle cell (SMC) growth, α-actin and transforming growth factor-beta (TGF-β) production, and wound healing. RESULTS: Serum E2 concentrations were increased significantly by E2. Aortic lumen diameters increased over time in sham-operated and Ovx (vehicle) females, but not in Ovx females administered E2. At day 70, E2 administration decreased significantly aortic lumen diameters compared to Ovx vehicle and sham-operated females. Compared to Ovx females (vehicle), maximal AAA diameters were reduced significantly by E2. AAA tissue sections from Ovx females administered E2 exhibited significant increases in α-actin and decreases in neutrophils compared to Ovx females administered vehicle. In abdominal aortic SMCs, E2 resulted in a concentration-dependent increase in α-actin, elevated TGF-β, and more rapid wound healing. E2 administration to Ovx females also significantly reduced atherosclerotic lesions compared to sham-operated females. This effect was accompanied by significant reductions in serum cholesterol concentrations. CONCLUSIONS: E2 administration to Ovx females abolished progressive growth and decreased severity of AngII-induced AAAs. These effects were accompanied by increased SMC α-actin, elevated TGF-β, and reduced neutrophils. Similarly, E2 administration reduced AngII-induced atherosclerosis. These results suggest that loss of E2 in post-menopausal females may contribute to progressive growth of AAAs

Assessment of glove integrity across various dental specialties in a dental school setting

ObjectivesThis study aimed to evaluate the integrity of non-sterile, powder-free latex gloves used by dental students in various dental specialties.Materials and methodsThis cross-sectional study involved dental students from Ajman University who provided gloves during various dental specialty procedures. A total of 177 pairs of latex examination powder-free gloves were included and categorized as follows: 43 pairs (24.3%) were used in operative dentistry, 30 pairs (16.9%) in oral surgery, 28 pairs (15.8%) in endodontics, 24 pairs (13.6%) in periodontics, 21 pairs (11.9%) in pedodontics, 13 pairs (7.3%) in prosthodontics, and 18 pairs (10.2%) as control gloves. After use, glove integrity was assessed with a modified water leak test.ResultsPerforations were identified in 72 cases (40.7%) of gloves, distributed as follows: 22 cases (51.2%) in operative dentistry, 12 cases (40.0%) in oral surgery, 11 cases (39.3%) in endodontics, 11 cases (45.8%) in periodontics, 10 cases (47.6%) in pedodontics, 5 cases (38.5%) in prosthodontics, and 1 case (5.5%) in the control group. There were no statistically significant differences in the loss of glove integrity among different dental specialty procedures (χ2 = 11.899, p = 0.064) or among different glove usage durations (χ2 = 1.732, p = 0.785). However, the location of perforations in the experimental groups was statistically significant (χ2 = 34.427, p < 0.001). The most common locations were the right thumb (n = 18; 13.7%) and the right index finger (n = 17; 13%), with no perforations in the left ring finger and only one perforation in the left little finger (n = 1, 0.08%). There was a statistically significant correlation between the anticipated and actual presence of defects (χ2 = 32.875, p < 0.001).ConclusionsThe study found a high rate of glove perforations during dental procedures by undergraduate students, especially in the right thumb and index finger. To reduce cross-infection risks, strict protocols like double gloving, frequent glove changes, and covering wounds with plaster are recommended

XX Sex Chromosome Complement Promotes Atherosclerosis in Mice

Men and women differ in circulating lipids and coronary artery disease (CAD). While sex hormones such as estrogens decrease CAD risk, hormone replacement therapy increases risk. Biological sex is determined by sex hormones and chromosomes, but effects of sex chromosomes on circulating lipids and atherosclerosis are unknown. Here, we use mouse models to separate effects of sex chromosomes and hormones on atherosclerosis, circulating lipids and intestinal fat metabolism. We assess atherosclerosis in multiple models and experimental paradigms that distinguish effects of sex chromosomes, and male or female gonads. Pro-atherogenic lipids and atherosclerosis are greater in XX than XY mice, indicating a primary effect of sex chromosomes. Small intestine expression of enzymes involved in lipid absorption and chylomicron assembly are greater in XX male and female mice with higher intestinal lipids. Together, our results show that an XX sex chromosome complement promotes the bioavailability of dietary fat to accelerate atherosclerosis

Abstract 454: An XX Sex Chromosome Complement, in the Presence of Testosterone, Markedly Promotes Angiotensin II-Induced Abdominal Aortic Aneurysms in Hypercholesterolemic Male Mice

Objective: Male sex is a strong risk factor for abdominal aortic aneurysms (AAAs). Similarly, angiotensin II (AngII)-induced AAAs exhibit a 4-fold higher prevalence in male compared to female hypercholesterolemic mice, which is abolished by removal of testosterone. We recently demonstrated that acute administration of testosterone to neonatal female mice markedly promoted their adult susceptibility to AngII-induced AAAs in the absence of a requirement for adult testosterone. In this study, we tested the hypothesis that testosterone acts through the sex chromosome complement (SCC) to promote AngII-induced AAAs. Methods and Results: Male transgenic mice with deletion of Sry from the Y-chromosome expressing Sry on autosomes (8-12 weeks of age) were bred to female Ldlr-/- mice to generate male mice with an XY or an XX SCC. Mice were fed a western diet and segregated into sham and orchiectomized (ORC) groups. Two weeks later, mice were implanted with osmotic micropumps to infuse AngII (1,000 ng/kg/min) for 28 days. Internal abdominal aortic lumen diameters were significantly larger in sham XX versus XY male mice at day 27 (XX, 1.77 ± 0.08; XY, 1.59 ± 0.05, p= 0.019). Castration decreased internal aortic lumen diameters in both genotypes, eliminating group differences (p=0.389). AAA external diameters were significantly increased in sham XX versus XY males (XX, 2.12 ± 0.17; XY, 1.55 ± 0.12, p=0.004), and this effect was abolished by castration. The presence of an additional X chromosome increased AAA incidence from 75% to 95% (p=0.136) and rupture rate from 11% to 30% (p=0.238). In contrast, an XY SCC promoted AngII-induced atherosclerosis (ORC: XY, 32.1 ± 6.5%; XX, 14.9 ± 1.6%, p=0.02), and this effect was reversed by castration (sham, XY: 19.4 ± 4.2, p=0.036). Conclusion: These results demonstrate that testosterone acts at an XX SCC to markedly promote the severity of AngII-induced AAAs in male mice. In contrast, testosterone acts at an XY SCC to protect against AngII-induced atherosclerosis in male mice. These results demonstrate, for the first time, that complex interactions between sex hormones and sex chromosomes diversely influence vascular diseases promoted by AngII. </jats:p

Abstract 249: Male Mice with XX Sex Chromosome Complement Exhibit Reduced Angiotensin II-Induced Hypertension and Atherosclerosis

Objective: Hypertension and atherosclerosis exhibit sexual dimorphism, partially ascribed to effects of sex hormones. However, recent studies suggest that sex chromosome complement may also contribute to sexual dimorphism of these diseases. The renin-angiotensin system has been suggested to contribute to sexual dimorphism of hypertension and atherosclerosis. However, the relative contribution of sex hormones, versus chromosomes, in the regulation of angiotensin II (AngII)-mediated responses is unknown. We hypothesized that the presence of an XX chromosome complement in male hyperlipidemic mice would reduce AngII-induced hypertension and atherosclerosis. Methods and Results: Male Ldlr-/- mice with an Sry mutation but with an Sry transgene on autosomes were bred to Ldlr-/- females to generate XY or XX males. Male XY or XX mice were segregated to sham-operated or orchiectomized (ORC) groups and fed a high fat diet (42% kcal from fat). Two weeks later, mice were infused with AngII (1,000 ng/kg/min) for 4 weeks. In the presence of sex hormones (sham groups), systolic blood pressure (SBP) was significantly lower in AngII-infused XX than XY males (XY, 136 ± 4; XX, 119 ± 4 mmHg, p=0.024). In XY males, ORC had no significant effect on SBP compared to sham (ORC XY, 129 ± 6 mmHg; p=0.48). However, following castration of XX males, SBP significantly increased (ORC XX 135 ± 3 mmHg; p =0.002). In XY males, ORC resulted in a significant increase in atherosclerotic lesion surface area in the aortic arch (sham, 19 ± 4; ORC, 32 ± 7%; p=0.04). In contrast, ORC had no significant effect on lesion surface area in XX males (sham, 17 ± 3; ORC, 15 ± 2%; p=0.53). Moreover, in the absence of sex hormones, lesion surface area was markedly increased in XY compared to XX males (XY, 32 ± 7; XX, 15 ± 2%; p=0.002). Conclusions: These results demonstrate that effects of testosterone to regulate AngII-induced hypertension and atherosclerosis are dependent on sex chromosome complement. In XY males, testosterone protects against AngII-induced atherosclerosis. In XX males, testosterone protects against AngII-induced hypertension. Moreover, there is pronounced effect of XY chromosome complement to promote AngII-induced atherosclerosis in males. </jats:p

Pancreatic AT1aR Deficiency Decreases Insulin Secretion in Obese C57BL/6 Mice

Abstract BACKGROUND Previously, we demonstrated that obese mice have marked elevations in systemic concentrations of angiotensin II (AngII). Drugs that inhibit the renin–angiotensin system (RAS), including angiotensin type 1 receptor (AT1R) antagonists, have been reported to delay the onset of type 2 diabetes (T2D), suggesting improvements in insulin sensitivity or regulation of pancreatic insulin secretion. Pancreatic islets possess components of the RAS, including AT1R, but it is unclear if AngII acts at islets to regulate insulin secretion during the development of T2D. METHODS We deleted AT1aR from pancreatic islets and examined effects on insulin secretion in mice fed a low-fat (LF) or high-fat (HF) diet. In separate studies, to exacerbate the system, we infused HF-fed mice of each genotype with AngII. RESULTS Pancreatic AT1aR deficiency impaired glucose tolerance and elevated plasma glucose concentrations in HF, but not LF-fed mice. In HF-fed mice, high glucose increased insulin secretion from islets of AT1aRfl/fl, but not AT1aRpdx mice. In AngII-infused mice, following glucose challenge, plasma glucose or insulin concentrations were not significantly different between genotypes. Moreover, high glucose stimulated insulin secretion from islets of AT1aRfl/fl and AT1aRpdx mice, presumably related to weight loss, and improved insulin sensitivity in both groups of AngII-infused HF-fed mice. CONCLUSIONS Our results suggest that during the adaptive response to insulin resistance from HF feeding, AngII promotes insulin secretion from islets through an AT1aR mechanism. These results suggest the timing of initiation of AT1R blockade may be important in the progression from prediabetes to T2D with β-cell failure. </jats:sec

Abstract 209: An XX Sex Chromosome Complement Promotes the Development of Obesity, Hypercholesterolemia and Atherosclerosis in Male and Female <i> Ldlr ^-/- </i> Mice Fed a Western Diet

Background: Underlying mechanisms contributing to sexual dimorphism of cardiovascular diseases are not well understood. Sex hormones are primary contributors to sexual dimorphism of cardiovascular diseases. By comparison, little is known regarding the contribution of genes on sex chromosomes (XX and XY) to sexual dimorphism of cardiovascular diseases, even though the X chromosome contains around 5% of the human genome. In this study, we hypothesized that genes on sex chromosomes influence the development of obesity, hypercholesterolemia and atherosclerosis. Methods and Results: Transgenic male mice with deletion of Sry from the Y-chromosome expressing Sry on autosomes (8-12 weeks of age) were bred to female Ldlr -/- mice to generate female and male mice with an XX or an XY sex chromosome complement (FXX, FXY, MXX, MXY). Mice were fed a Western diet (Teklad TD88137) for 3 months. XX mice exhibited increased body weight compared to mice with an XY sex chromosome complement, regardless of gonadal sex (FXX, 41.2 ± 2.4; FXY, 31.7 ± 2.5 g; P&lt;0.05; MXX, 51.5 ± 1.2; MXY, 41.7 ± 1.8 g; P&lt;0.05). Moreover, XX mice had increased serum cholesterol concentrations, regardless of gonadal sex (FXX, 2501 ± 192; FXY, 890 ± 141 mg/dl; P&lt;0.05; MXX, 3814 ± 344; MXY, 1297 ± 385 mg/dl; P&lt;0.05). Elevations in serum lipids were manifest as increased VLDL and LDL-cholesterol. The extent of atherosclerosis in aortic arch was significantly increased in XX compared to XY mice (XXF, 37 ± 2.1; XYF, 20 ± 3.2; XXM, 38 ± 3.6; XYM, 24 ± 3.6 % lesion surface area; P&lt;0.05). In the aortic sinus, atherosclerotic lesion surface area was significantly increased in XX mice, regardless of gonadal sex (FXX, 60.4 x 10 4 ± 3.6 x 10 4 ; FXY, 32.4 x 10 4 ± 3.8 x 10 4 μm 2 ; P&lt;0.05; MXX, 67.1 x 10 4 ± 9.6 x 10 4 ; MXY, 36.2 x 10 4 ± 3.7 x 10 4 μm 2 ; P&lt;0.05). Conclusion: Results demonstrate that an XX sex chromosome complement promotes diet-induced obesity, hypercholesterolemia and atherosclerosis regardless of gonadal sex. Future studies will identify the role of genes on the X or Y chromosome as mechanisms for these effects. </jats:p

Abstract 100: An XY Sex Chromosome Complement in Females Confers Susceptibility and Rupture of Angiotensin II-induced Abdominal Aortic Aneurysms in Hypercholesterolemic Female Mice

Objective: We previously demonstrated that female mice are less susceptible to angiotensin II (AngII)-induced abdominal aortic aneurysms (AAAs) compared to males, a sex difference present in humans. Sex chromosome abnormalities, such as Turner’s syndrome (monosomy X), are associated with aortic vascular disease. In this study, we tested the hypothesis that an XY sex chromosome complement in females promotes AngII-induced AAAs. In addition, as previous studies demonstrated that testosterone promotes AngII-induced AAAs in male mice, we determined if testosterone would augment AAA severity in XY females. Methods and Results: Transgenic male mice with deletion of Sry from the Y-chromosome expressing Sry on autosomes (8-12 weeks of age) were bred to female Ldlr-/- mice to generate female mice with an XY or an XX sex chromosome complement. Female mice (XX and XY) were fed a Western diet and segregated into sham and ovariectomized (OVX) groups. Two weeks later, mice were implanted with osmotic minipumps to infuse AngII (1,000 ng/kg/min) for 28 days. The AAA incidence (XX sham, 40%; XX OVX 29%; XY sham, 71%; XY OVX, 57%, p=0.031) and rupture rate (XX sham, 0%; XX OVX 0%; XY sham, 35%; XY OVX, 29%, p=0.003) were significantly increased in XY compared to XX females. Internal abdominal aortic lumen diameters were significantly increased in XY OVX versus XX OVX female mice at day 27 (XY, 2.31 ± 0.14; XX, 1.58 ± 0.2, p= 0.009). Moreover, AAA external diameters were significantly increased in XY OVX versus XX OVX females (XY, 2.34 ± 0.15; XX, 1.71 ± 0.18, p=0.0004). Administration of testosterone to adult female XY mice as well as neonatal female mice markedly enhanced AAA rupture (maximum of 73%). DNA microarrays of abdominal aortas revealed that male specific genes on the Y chromosome and inflammatory genes were enriched in aortas from XY females, while genes that escape X-inactivation were enriched in aortas from XX females. Conclusion: These results demonstrate that an XY sex chromosome complement is sufficient to promote a high AAA incidence, and markedly increase AAA severity in female mice. Moreover, testosterone augmented AAA ruptures in XY females. Future studies will identify gene targets influenced by sex chromosome complement and/or testosterone. </jats:p