Innovative techniques for developing an inclusive teaching environment.

The educational landscape is currently experiencing a growth in the diversity of the student population. Concomitantly, the scientific community continues to work toward increasing the diversity of its workforce while ensuring equity and inclusion for all. However, there is a pressing need for educators to promote these values and aspirations and embed them into their classrooms to continue to increase the diversity of the next generation of scientists. To explore this very topic, we developed and co-chaired a symposium at the 2022 Experimental Biology meeting entitled "Innovative Techniques for Developing an Inclusive Teaching Environment." This paper will share the philosophies, approaches, findings, and suggestions from the symposium speakers and will provide recommendations for educators to consider when designing new courses or evaluating and revising current courses.

Sex differences in oxidative stress and the impact on blood pressure control and cardiovascular disease.

1. In the present review, we addressed studies in humans and rats to determine the role that oxidative stress may play in mediating cardiovascular outcomes. 2. Biochemical evaluation of oxidative stress in both humans and spontaneously hypertensive rats gives equivocal results as to the relative levels in males versus females. Clinical trials with anti-oxidants in humans have not shown consistent results in protecting against detrimental cardiovascular outcomes. In spontaneously hypertensive rats (SHR), blockade studies using tempol or apocynin reduce renal oxidative stress and blood pressure in male SHR, but not in female rats. In addition, increasing oxidative stress with molsidomine increases blood pressure in male, but not female, SHR. Treatment with vitamins E and C reduces blood pressure in young male, but not aged, animals. Furthermore tempol is unable to reduce blood pressure in young male SHR in the absence of a functional nitric oxide system. 3. Neither human nor animal studies are consistent in terms of whether oxidative stress levels are higher in males or females. Furthermore, anti-oxidant therapy in humans often does not ameliorate, or even attenuate, the negative cardiovascular consequences of increased oxidative stress. Our studies in SHR shed light on why these outcomes occur.

Testosterone supplementation in aging men and women: possible impact on cardiovascular-renal disease.

Treatment of aging men and women with testosterone supplements is increasing. The supplements are given to postmenopausal women mainly to improve their libido and to aging men to improve muscle mass and bone strength, to improve libido and quality of life, to prevent and treat osteoporosis, and, with the phosphodiesterase-5 inhibitors, such as sildenafil, to treat erectile dysfunction. The increased use of testosterone supplements in aging individuals has occurred despite the fact that there have been no rigorous clinical trials examining the effects of chronic testosterone on the cardiovascular-renal disease risk. Studies in humans and animals have suggested that androgens can increase blood pressure and compromise renal function. Androgens have been shown to increase tubular sodium and water reabsorption and activate various vasoconstrictor systems in the kidney, such as the renin-angiotensin system and endothelin. There is also evidence that androgens may increase oxidative stress. Furthermore, the kidney contains the enzymes necessary to produce androgens de novo. This review presents an overview of the data from human and animal studies in which the role of androgens in promoting renal and cardiovascular diseases has been investigated.

Increasing oxidative stress with molsidomine increases blood pressure in genetically hypertensive rats but not normotensive controls.

Spontaneously hypertensive rats (SHR) have a higher level of oxidative stress and exhibit a greater depressor response to a superoxide scavenger, tempol, than normotensive Wistar-Kyoto rats (WKY). This study determined whether an increase in oxidative stress with a superoxide/NO donor, molsidomine, would amplify the blood pressure in SHR. Male SHR and WKY were given molsidomine (30 mg.kg(-1).day(-1)) or vehicle (0.01% ethanol) for 1 wk, and blood pressure, renal hemodynamics, nitrate and nitrite excretion (NOx), renal superoxide production, and expression of renal antioxidant enzymes, Mn- and Cu,Zn-SOD, catalase, and glutathione peroxidase (GPx), were measured. Renal superoxide and NOx were higher in control SHR than in WKY. Molsidomine increased superoxide by approximately 35% and NOx by 250% in both SHR and WKY. Mean arterial blood pressure (MAP) was also higher in control SHR than WKY. Molsidomine increased MAP by 14% and caused renal vasoconstriction in SHR but reduced MAP by 16%, with no effect on renal hemodynamics, in WKY. Renal expression of Mn- and Cu,Zn-SOD was not different between SHR and WKY, but expression of catalase and GPx were approximately 30% lower in kidney of SHR than WKY. The levels of Mn- and Cu,Zn-SOD were not increased with molsidomine in either WKY or SHR. Renal catalase and GPx expression was increased by 300-400% with molsidomine in WKY, but there was no effect in SHR. Increasing oxidative stress elevated blood pressure further in SHR but not WKY. WKY are likely protected because of higher bioavailable levels of NO and the ability to upregulate catalase and GPx.

Role of oxidative stress in the sex differences in blood pressure in spontaneously hypertensive rats.

OBJECTIVE: The hypothesis was tested that differences in oxidative stress play a role in the sex differences in the development and maintenance of hypertension in spontaneously hypertensive rats (SHR). DESIGN AND METHODS: Male and female SHR [and Wistar-Kyoto (WKY) rats in the long-term study] (n = 6-12 per group) received tempol (30 mg/kg per day) or tap water for 6 weeks from 9 to 15 weeks of age or from birth until 15 weeks of age. Blood pressure [mean arterial pressure (MAP)] and kidney tissue F2-isoprostane (IsoP) were measured at 15 weeks of age. RESULTS: In SHR given tempol for 6 weeks, blood pressure and IsoP were reduced in males, but not in females. In SHR given tempol from birth, MAP was higher in SHR than WKY rats (SHR males, 181 +/- 2 mmHg; SHR females, 172 +/- 3 mmHg; WKY males, 100 +/- 2 mmHg; WKY females, 101 +/- 2 mmHg, P < 0.01), and tempol reduced MAP by 14% (156 +/- 3) and 26% (127 +/- 4) in male and female SHR, respectively, but had no effect on WKY rats. IsoP was higher in SHR than WKY rats and higher in male SHR than female SHR (SHR males, 5.18 +/- 0.23 ng/mg; SHR females, 3.71 +/- 0.19 ng/mg, P < 0.01; WKY males, 1.72 +/- 0.45 ng/mg; WKY females, 2.21 +/- 0.08 ng/mg, P < 0.05, compared with SHR). Tempol reduced IsoP in SHR to levels found in WKY rats, but had no effect on IsoP in WKY rats. CONCLUSIONS: Development of hypertension in SHR is mediated in part by oxidative stress independent of sex. Also, tempol is effective in reducing blood pressure in females only when given prior to the onset of hypertension.

Role of endothelin in mediating postmenopausal hypertension in a rat model.

Cardiovascular disease is the leading cause of death in women after menopause. Hypertension, a major cardiovascular risk factor, becomes more prevalent after menopause. The mechanisms responsible for the increase in blood pressure (BP) in postmenopausal women are unknown. We have recently characterized the aged, postestrous-cycling (PMR) spontaneously hypertensive rats (SHR) as a model of postmenopausal hypertension. The purpose of the present study was to determine whether endothelin plays a role in the increased BP in PMR. Premenopausal female SHR, aged 4-5 mo (YF), and PMR, aged 16 mo, were studied. Expression of preproendothelin-1 mRNA was not different in either renal cortex or medulla between PMR and YF (n = 7-8/group). In contrast, ET-1 peptide expression was significantly higher in renal cortex of PMR than in renal cortex of YF, but there was no difference in medullary ET-1. Expression of endothelin ET(A) receptor (ET(A)R) mRNA was lower in renal cortex and medulla of PMR than of YF. Additional groups of rats (n = 6-7/group) were treated for 3 wk with the ET(A)R antagonist ABT-627 (5 mg.kg(-1).day(-1)). BP was significantly higher in PMR than in YF. ET(A)R antagonist reduced BP in PMR by 20% to the level found in control YF. ET(A)R antagonist had no effect on BP in YF. These data support the hypothesis that the increase in BP in PMR is mediated in part by endothelin and the ET(A)R.

Systemic arterial pressure response to two weeks of Tempol therapy in SHR: involvement of NO, the RAS, and oxidative stress.

The roles of nitric oxide (NO) and plasma renin activity (PRA) in the depressor response to chronic administration of Tempol in spontaneously hypertensive rats (SHR) are not clear. The present study was done to determine the effect of 2 wk of Tempol treatment on blood pressure [mean arterial pressure (MAP)], oxidative stress, and PRA in the presence or absence of chronic NO synthase inhibition. SHR were divided into four groups: control, Tempol (1 mmol/l) alone, nitro-L-arginine methyl ester (L-NAME, 4.5 mg x g(-1).day(-1)) alone, and Tempol + L-NAME or 2 wk. With Tempol, MAP decreased by 22%: 191 +/- 3 and 162 +/- 21 mmHg for control and Tempol, respectively (P < 0.05). L-NAME increased MAP by 16% (222 +/- 2 mmHg, P < 0.01), and L-NAME + Tempol abolished the depressor response to Tempol (215 +/- 3 mmHg, P < 0.01). PRA was not affected by Tempol but was increased slightly with L-NAME alone and 4.4-fold with L-NAME + Tempol. Urinary nitrate/nitrite increased with Tempol and decreased with L-NAME and L-NAME + Tempol. Tempol significantly reduced oxidative stress in the presence and absence of L-NAME. In conclusion, in SHR, Tempol administration for 2 wk reduces oxidative stress in the presence or absence of NO, but in the absence of NO, Tempol is unable to reduce MAP. Therefore, NO, but not changes in PRA, plays a major role in the blood pressure-lowering effects of Tempol. These data suggest that, in hypertensive individuals with endothelial damage and chronic NO deficiency, antioxidants may be able to reduce oxidative stress but not blood pressure.

Treatment with tetrahydrobiopterin reduces blood pressure in male SHR by reducing testosterone synthesis.

Treatment with tetrahydrobiopterin (BH(4)) reduces blood pressure in spontaneously hypertensive rats (SHR). In the present study, we tested the hypothesis that chronic BH(4) reduces blood pressure in male SHR by reducing testosterone biosynthesis mediated by increasing nitric oxide (NO). Male SHR, aged 17-18 wk, intact or castrated, were treated for 1 wk with BH(4) (20 mg.kg(-1).day(-1) ip). After 1 wk, mean arterial pressure (MAP), serum testosterone, and nitrate/nitrite excretion (NO(x)) were measured. MAP was significantly higher in intact males than castrated males (179 +/- 2 vs. 155 +/- 4 mmHg, P < 0.001). In intact males, BH(4) caused a 17% reduction in MAP (148 +/- 2 mmHg), had no effect on NO(x), and reduced serum testosterone by 85% (24.09 +/- 2.37 vs. 3.72 +/- 0.73 ng/dl; P < 0.001). In castrated males, BH(4) had no effect on MAP (152 +/- 5 mmHg) but increased NO(x) by 38%. When castrated males were supplemented with testosterone, MAP increased to the same level as in intact males (180 +/- 7 mmHg), and BH(4) had no effect on MAP (182 +/- 7 mmHg) or NO(x). NO has been shown to decrease testosterone biosynthesis. Chronic sodium nitrite (70 mg.kg(-1).day(-1) x 1 wk) decreased MAP in intact males (150 +/- 4 mmHg) but had no effect on serum testosterone (21.46 +/- 3.08 ng/dl). The data suggest that BH(4) reduces testosterone synthesis and thereby reduces MAP in male SHR, an androgen-dependent model of hypertension. The mechanism(s) by which BH(4) reduces serum testosterone levels are not clear, but the data do not support a role for NO as a mediator.

Novel mechanisms responsible for postmenopausal hypertension.

Blood pressure increases in many women after menopause. Hypertension is one of the major risk factors for cardiovascular disease. However, the mechanisms responsible for the postmenopausal increase in blood pressure are yet to be elucidated. Various humoral systems have been proposed to play a role in postmenopausal hypertension, such as changes in estrogen/androgen ratios, increases in endothelin and oxidative stress, and activation of the renin-angiotensin system (RAS). In addition, obesity, type II diabetes, and activation of the sympathetic nervous system are common in postmenopausal women and may also play important roles. However, progress in elucidating the mechanisms responsible for postmenopausal hypertension has been hampered by the lack of a suitable animal model. The aging female spontaneously hypertensive rat (SHR) exhibits many of the characteristics found in postmenopausal women. In this review, some of the possible mechanisms that could play a role in postmenopausal hypertension are discussed, as well as the characteristics of the aged female SHR as a model to study.

Increased expression of vascular endothelial growth factor and capillary density in hearts of spontaneously hypertensive rats.

OBJECTIVE: The role of VEGF in vascular remodeling of target organs exposed to chronic hypertension is poorly understood. The authors compared capillary density (CD), capillary-to-fiber ratio (C/F), and VEGF mRNA expression in the hearts (left ventricle [LV]), and skeletal muscles (soleus and anterior tibialis [AT]) of 18-week-old male spontaneously hypertensive rats (SHR) and age-matched male Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats. METHODS: CD or C/F in LV, soleus, and AT of SHR, WKY, and SD rats was determined by analysis of randomly acquired digital images of cryosections stained with FITC-conjugated GS-I lectin. VEGF mRNA expressions in the tissues were determined by Northern blot. RESULTS: VEGF mRNA expressions in LV of SHR were 3.84- and 5.05-fold higher, compared to SD and WKY rats, respectively (n = 6; p < .01). There were no significant differences in VEGF mRNA expression in soleus or AT among SHR, WKY, and SD rats (p > .05). CD in LV of SHR (4975 +/- 167) was significantly higher than WKY or SD rats, 4151 +/- 169 and 3807 +/- 187 mm(-2), respectively (p < .05). In LV of SHR, C/F increased (35%) more significantly than CD (increased 20%), compared to WKY rats. CD, or C/F in soleus or AT of SHR was similar to that observed in WKY or 8D rats. CONCLUSIONS: VEGF expression, CD, and C/F in the heart (LV) of SHR are significantly increased, compared to WKY and SD rats. The data are consistent with the possibility that VEGF may contribute to capillary growth as a compensatory response to hypertension.

Gender difference in response to thromboxane A2/prostaglandin H2 receptor antagonism in spontaneously hypertensive rats.

BACKGROUND: Blood pressure (BP) is typically higher in men than in women. As in humans, BP is higher in male spontaneously hypertensive rats (SHRs) than in female SHRs. The mechanism(s) responsible for the higher BP in men and male rats has not been elucidated. OBJECTIVE: The present study tested the hypothesis that thromboxane and/or the thromboxane A(2)/prostaglandin H(2) receptor (TxR) plays a role in the gender difference in BP in SHRs. METHODS: Male and female SHRs were treated with the TxR antagonist SQ29548 (2 microg/kg/min into the jugular vein) via minipump for 2 weeks; mean arterial pressure (MAP) and renal hemodynamic function were measured. To determine whether thromboxane played a role in the higher MAP in SHRs, male and female rats were treated with the thromboxane synthase inhibitor (TxI) furegrelate, 30 mug/kg/min, via minipump, for 2 weeks. RESULTS: MAP was reduced with TxR antagonism in male but not in female SHRs. In addition, TxR antagonism in males caused renal vasodilation with increases in glomerular filtration rate and renal plasma flow, and reductions in renal vascular resistance. In contrast, MAP was not affected by the TxI in either males or females. CONCLUSION: These data support a role for TxR, but not thromboxane, in mediating the gender difference in BP in SHRs.

Role of androgens in mediating renal injury in aging SHR.

Men have an increased risk of cardiovascular and renal diseases and develop greater renal injury despite similar levels of blood pressure when compared with women. The mechanisms responsible for this predisposition are unknown. Using the spontaneously hypertensive rat (SHR), we have found that androgens play an important role in the development of hypertension in young male SHR. However, the role that androgens play in age-related renal injury and dysfunction in SHR is unknown. Our hypothesis was that despite reductions in serum testosterone with age, androgens mediate renal injury and dysfunction in male SHR. Male SHR were castrated at 8 months of age, studied at 18 months of age, and compared with age-matched, intact males and young intact males (4 months). Serum testosterone was reduced by 30% in aging males compared with young SHR. With castration, blood pressure (mean arterial pressure [MAP]) was decreased by >20 mm Hg compared with old males, glomerular filtration rate (GFR) was increased by >35%, and renal vascular resistance (RVR) was reduced by >40%. MAP, GFR, and RVR in castrated, old males were similar to values in young males. With castration, glomerular sclerosis was reversed and proteinuria was also decreased by >80% when compared with old intact males. In addition, in castrated old males, plasma renin activity was decreased by 30% compared with old males and by 60% compared with young rats. The data support the hypothesis that despite a reduction in testosterone with age, androgens play an important role in age-related renal injury and dysfunction in SHR.

Characterization of an animal model of postmenopausal hypertension in spontaneously hypertensive rats.

Blood pressure (BP) increases in postmenopausal women. The mechanisms responsible are unknown. The present study was performed to characterize a model of postmenopausal hypertension in the rat and to determine the role that oxidative stress may play in mediating the postmenopausal hypertension. Spontaneously hypertensive rats were ovariectomized (ovx) or left intact (PMR) at 8 months and were aged to 18 months. These animals were compared with young females (YF; 4 or 8 months of age) and old males (18 months) for some measurements. Estradiol levels were decreased in PMR rats to levels not different from YF rats in proestrous or from old males. BP increased progressively with age in PMR rats but not in ovx or male rats, such that the gender difference in hypertension disappeared by 18 months. Glomerular filtration rate was lower in ovx and PMR rats than in YF rats. Renal plasma flow and renal vascular resistance were similar between YF and ovx rats, but lower and higher, respectively, in PMR rats. Serum testosterone increased by 60% in ovx rats and 400% in PMR rats compared with YF rats. Plasma renin activity also increased in PMR rats but not in ovx rats. Chronic treatment (for 8 months beginning at 8 months of age) of PMR rats with vitamins E and C, but not tempol, resulted in a significant reduction in BP and excretion of F2-isoprostanes. In contrast, tempol, but not vitamins E and C, reduced BP in old males. These data suggest that the PMR rats, but not ovx rats, may be a suitable model for the study of postmenopausal hypertension, and that oxidative stress plays a role in the increased BP.

Renal dysfunction after chronic blockade of nitric oxide synthesis.

The effects of the chronic inhibition of nitric oxide (NO) on renal hemodynamics and tubular function were studied in rats treated for 8 weeks with the NO synthesis inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME; 40 mg/kg/day). In addition, the effect of L-NAME administration on vasoactive systems (renin-angiotensin system, aldosterone, catecholamines, endothelin, and thromboxane A(2)) was evaluated. Chronic inhibition of NO significantly elevated blood pressure, reduced glomerular filtration rate and renal blood flow, blunted the pressure-diuresis-natriuresis response, and increased protein urine excretion. All these changes were associated with blunted nitrite production in response to acetylcholine in glomeruli. No changes were observed in the plasma levels of either renin activity, aldosterone, or endothelin in L-NAME-treated rats. Similarly, no differences were observed in the urinary excretion of thromboxane B(2) between both group of animals. By contrast, plasma concentrations of both epinephrine and norepinephrine were elevated in rats treated with L-NAME. In summary, the results show that chronic blockade of NO produced not only alterations in renal function, but also renal damage, suggesting an important renoprotective role of NO. An activation of sympathoadrenal system could participate in these renal alterations.

Nebivolol ameliorates nitric oxide deficient hypertension.

Nebivolol is a new selective beta 1-adrenoceptor antagonist with nitric oxide (NO)-releasing properties. In the present study we have analyzed whether nebivolol affects the development of the arterial hypertension that follows the chronic inhibition of nitric oxide synthesis. Nebivolol (1 mg/kg/day, 14 days) was given concurrently with the NO synthesis inhibitor Nw-nitro-L-arginine methyl ester (L-NAME, 0.1, 1, and 10 mg/kg/day, 14 days) to several groups of rats. Blood pressure, renal function, plasma renin activity (PRA), and NO activity and metabolites were measured at the end of the treatment period. L-NAME treatment alone increased mean arterial pressure dose dependently (103.5 +/- 2.4, 110.9 +/- 2.0, and 125.8 +/- 2.2 mmHg, respectively). Nebivolol completely prevented the development of arterial hypertension in the groups treated with L-NAME at the doses of 0.1 and 1 mg/kg/day and reduced the increase achieved with the L-NAME dose of 10 mg/kg/day (110.3 +/- 2.7). There were no differences in glomerular filtration rate or natriuresis between nebivolol-treated and -untreated rats. Plasma nitrates+nitrites and calcium-dependent NO synthase activity in the kidney also decreased dose dependently with L-NAME treatment and nebivolol did not significantly modify it. However, PRA was lower in all groups treated with nebivolol and L-NAME as compared to the rats receiving only L-NAME. These data indicate that nebivolol prevents the development of the arterial hypertension associated with chronic NO deficit and this effect seems to be dependent on the inhibition of renin-angiotensin system.