Tail-cuff Plethysmography Research Articles

Chronic rose oxide and exercise synergistically modulate cardiovascular and autonomic functions in hypertensive rats.

With the alarming rise in cases of arterial hypertension worldwide, there is an urgent need to develop combined therapies to mitigate this scenario. Rose oxide (RO), a monoterpene with anti-inflammatory and hypotensive properties, emerges as an alternative. The present study is the first to evaluate the effect of RO administered chronically and combined with physical exercise (swimming) since both have been reported to have beneficial impacts on hypertension. Male SHR and Wistar rats (aged 12weeks) received RO for 34 consecutive days (orally; 100mg/kg). The progression of systolic arterial pressure (SAP) was monitored through tail-cuff plethysmography. Twenty-four hours before the end of the treatment, the animals were anesthetized, and the femoral artery and vein were cannulated to record the pulsatile arterial pressure and to administer drugs, respectively. Hemodynamic and autonomic parameters and baroreflex sensitivity and intrinsic heart rate (IHR) were evaluated. Treatment with RO, administered alone or combined with exercise, reduced SAP and mean arterial pressure in SHR. The swimming protocol did not prevent increases in BP, but when combined with RO, it improved autonomic control, assessed through heart rate variability and parasympathetic tone. IHR was attenuated in SHR, and none of the treatments reversed this response. Therefore, combining RO with physical exercise may enhance their antihypertensive effects, improving autonomic function, reducing oxidative stress and inflammation, providing synergistic cardiovascular benefits, improving metabolic health, promoting a comprehensive lifestyle intervention, and potentially allowing for reduced medication dosages. This multifaceted approach could offer a more effective and sustainable strategy for managing hypertension.

Acute Chikungunya Infection Induces Vascular Dysfunction by Directly Disrupting Redox Signaling in Endothelial Cells.

Chikungunya virus (CHIKV) infection is characterized by febrile illness, severe joint pain, myalgia, and cardiovascular complications. Given that CHIKV stimulates reactive oxygen species (ROS) and pro- and anti-inflammatory cytokines, events that disrupt vascular homeostasis, we hypothesized that CHIKV induces arterial dysfunction by directly impacting redox-related mechanisms in vascular cells. Wild-type (WT) and iNOS knockout (iNOS-/-) mice were administered either CHIKV (1.0 × 106 PFU/µL) or Mock vehicle via the intracaudal route. In vivo, CHIKV infection induced vascular dysfunction (assessed by a wire myograph), decreased systolic blood pressure (tail-cuff plethysmography), increased IL-6 and IFN-γ, but not TNF-α levels (determined by ELISA), and increased protein content by Western blot. Marked contractile hyporesponsiveness to phenylephrine was observed 48 h post-infection, which was restored by endothelium removal. L-NAME, 1400W, Tiron, and iNOS gene deletion prevented phenylephrine hyporesponsiveness. CHIKV infection increased vascular nitrite concentration (Griess reaction) and superoxide anion (O2•-) generation (lucigenin chemiluminescence), and decreased hydrogen peroxide (H2O2, by Amplex Red) levels 48 h post-infection, alongside increased TBARS levels. In vitro, CHIKV infected endothelial cells (EA.hy926) and upregulated ICAM-1 and iNOS protein expression (determined by Western blot). These data support the conclusion that CHIKV-induced alterations in vascular ROS/NF-kB/iNOS/NO signaling potentially contribute to cardiovascular events associated with Chikungunya infection.

Developmental nicotine exposure alters cardiovascular structure and function in neonatal and juvenile rats.

Here we test the hypothesis that continuous nicotine exposure throughout pre- and postnatal development (developmental nicotine exposure, DNE) alters cardiovascular structure and function in neonatal and juvenile rats. Echocardiography showed that DNE reduced left ventricular mass, left ventricular outflow tract (LVOT) diameter, and posterior wall thickness, but only in females. Both male and female DNE rats had a lower end-systolic volume, higher ejection fraction, and increased fractional shortening, with unchanged stroke volume and cardiac output. Left ventricular single cardiac myocytes from male and female DNE animals exhibited increased calcium-evoked maximal tension with no effect on EC50. Tail-cuff plethysmography in awake rats showed that DNE males had lower systolic blood pressure and higher heart rate than control males. No significant changes in preload, afterload, or the in vitro renal artery response to vasodilators was observed. The results suggest that DNE enhances myocyte tension-generating capacity, possibly compensating for an unknown developmental insult, which may differ in males and females. While this adaptation maintains normal resting cardiac function, it may lead to reduced cardiac reserve, increased energy demand, and elevated oxidative stress, potentially compromising both short-and-long-term cardiovascular health in developing neonates.

Rat Model of Menopausal/Andropausal Hypertension with Different Sensitivities to Non-Genomic Antihypertensive Responses of Female and Male Sex Steroids

Introduction: Hypertension is prevalent in older women and men, but the impact of sex differences is unclear. Methods: Blood pressure (BP) was evaluated weekly for 15 weeks using tail-cuff plethysmography in intact or gonadectomized female and male rats. Similarly, gonadectomized rats were subcutaneously treated daily for 15 weeks with estradiol in females or testosterone in males. Treatment with estrogen in males and androgen in females for BP was also examined. The non-genomic antihypertensive potency and efficacy of different sex steroids were determined; catheters were implanted in the carotid artery of hypertensive rats for BP recording with bolus injections in the jugular vein at cumulative doses (1 × 10−7−1 × 10−4M kg−1 min−1) of dehydroepiandrosterone (DHEA), estradiol, testosterone, or 5β-dihydrotestosterone (5β-DHT). Results: Data showed a time-dependent increase in BP after gonadectomy in female and male rats until hypertension values were reached. Males are more sensitive to the development of hypertension than females. The increases in BP in females and males were completely prevented by estradiol or testosterone, respectively. Testosterone completely prevented hypertension in females, whereas estradiol only partially in males. Antihypertensive potencies in conscious hypertensive rats were DHEA = 5β-DHT = testosterone >> estradiol, in females and DHEA = 5β-DHT >> testosterone >> estradiol in males. The efficacy was DHEA = 5β-DHT = testosterone >> estradiol in females and 5β-DHT = DHEA >> testosterone >> estradiol in males. Conclusion: Gonadectomized males developed hypertension faster than females, suggesting that androgen deficiency plays an important role in BP reduction. Antihypertensive responses of steroids are structure-dependent; estradiol demonstrated the lowest potency, whereas 5β-DHT was a potent antihypertensive without estrogenic and androgenic actions, suggesting it is as a therapeutic candidate for controlling hypertension in both sexes.

Resistance artery vasodilator pathways involved in the antihypertensive effects of cocoa shell extract in rats exposed to fetal undernutrition.

Fetal undernutrition establishes the foundations for hypertension development, with oxidative stress being a key hallmark. A growing interest in nutraceuticals for treating hypertension and environmental waste concerns prompted the present study aiming to evaluate whether supplementation with a polyphenol enriched extract from cocoa shell (CSE), a by-product from the chocolate industry with antioxidant properties, reduces hypertension of developmental origin, thus improving mesenteric resistance artery (MRA) vasodilatation. Adult male and female offspring from rats exposed to 50% food restriction from mid-gestation (maternal undernutrition, MUN) and controls were used. Supplementation was given through a gelatine (vehicle, VEH) or containing CSE (250mgkg-1day-1) 5daysweek-1 for 3weeks. Systolic blood pressure (SBP) was assessed by tail-cuff plethysmography. MRA function was studied by wire myography, and superoxide anion and nitric oxide were investigated by fluorescent indicators and confocal microscopy. Compared to control-VEH, MUN-VEH males showed significantly higher SBP, reduced MRA as well as relaxation to ACh, sodium nitroprusside and the AMPK agonist 5-aminoimidazole-4-carboxamide riboside, but not to isoproterenol. In MUN males, endothelial endothelium-derived hyperpolarizing factor and nitric oxide were unaltered, but MRA released a vasoconstrictor prostanoid and produced higher levels of superoxide anion. CSE normalized blood pressure and improved all above-mentioned MRA alterations in MUN males without an effect on control counterparts, except the reduction of superoxide anion. MUN-VEH females were normotensive and only showed a tendency towards larger superoxide anion production, which was abolished by CSE. CSE supplementation reduces SBP improving endothelium-dependent and independent MRA vasodilatation, related to local superoxide anion reduction, being a potential nutraceutical ingredient to counteract hypertension, in addition to contributing to the circular economy. KEY POINTS: Fetal undernutrition induces hypertension in males associated with deficient resistance artery vasodilatation, being normalized by cocoa shell extract (CSE). Release of a cyclooxygenase-derived contractile factor is the main endothelial alteration, which is abolished by CSE. AMPK and soluble guanylyl cyclase-mediated relaxation are also reduced in smooth muscle cells from maternal undernutrition resistance arteries, being improved by CSE. Vascular oxidative damage caused by excess superoxide anion generation can account for impaired vasodilatation, which is improved by CSE. The capacity of CSE to improve relaxation is probably related to its antioxidant bioactive factors, and thus cocoa shell is a potential food by-product to treat hypertension.

Methamphetamine-Induced Blood Pressure Sensitization Correlates with Morphological Alterations within A1/C1 Catecholamine Neurons

Methamphetamine (METH) is a drug of abuse, which induces behavioral sensitization following repeated doses. Since METH alters blood pressure, in the present study we assessed whether systolic and diastolic blood pressure (SBP and DBP, respectively) are sensitized as well. In this context, we investigated whether alterations develop within A1/C1 neurons in the vasomotor center. C57Bl/6J male mice were administered METH (5 mg/kg, daily for 5 consecutive days). Blood pressure was measured by tail-cuff plethysmography. We found a sensitized response both to SBP and DBP, along with a significant decrease of catecholamine neurons within A1/C1 (both in the rostral and caudal ventrolateral medulla), while no changes were detected in glutamic acid decarboxylase. The decrease of catecholamine neurons was neither associated with the appearance of degeneration-related marker Fluoro-Jade B nor with altered expression of α-synuclein. Rather, it was associated with reduced free radicals and phospho-cJun and increased heat shock protein-70 and p62/sequestosome within A1/C1 cells. Blood pressure sensitization was not associated with altered arterial reactivity. These data indicate that reiterated METH administration may increase blood pressure persistently and may predispose to an increased cardiovascular response to METH. These data may be relevant to explain cardiovascular events following METH administration and stressful conditions.

Sarcoplasmic reticulum calcium ATPase (SERCA) proteolysis by matrix metalloproteinase-2 contributes to vascular dysfunction in early hypertension

AimsHypertension is associated with an increased activity of matrix metalloproteinase (MMP)-2 in the vasculature, which, in turn, proteolyzes extra- and intracellular proteins that lead to vascular dysfunction. The activity of sarcoplasmic reticulum calcium ATPase (SERCA) is decreased in the aortas of hypertensive rats. Increased activity of MMP-2 proteolyzed SERCA in rat heart during ischemia and reperfusion injury, thus impairing cardiac function. Therefore, we examined whether increased activity of MMP-2 in early hypertension contributes to proteolyze SERCA in the aortas, thus leading to maladaptive vascular remodeling and dysfunction. Main methodsMale Sprague-Dawley rats were submitted to two kidney-one clip (2K-1C) or Sham surgery and treated with doxycycline. Systolic blood pressure (SBP) was assessed by tail-cuff plethysmography. After 7 days, aortas were collected for zymography assays, Western blot to SERCA, ATPase activity assay, vascular reactivity, Ki-67 immunofluorescence and hematoxylin/eosin stain. Key findingsSBP was increased in 2K-1C rats and doxycycline did not reduce it, but decreased MMP-2 activity and prevented SERCA proteolysis in aortas. Cross sectional area, media to lumen ratio and Ki-67 were all increased in the aortas of hypertensive rats and doxycycline decreased Ki-67. In 2K-1C rats, arterial relaxation to acetylcholine was impaired and doxycycline ameliorated it. Significancedoxycycline reduced MMP-2 activity in aortas of 2K-1C rats and prevented proteolysis of SERCA and its dysfunction, thus ameliorating hypertension-induced vascular dysfunction.

Abstract P178: Sex Differences in the Role of the Immune ET-1/ET A Axis in Controlling Blood Pressure during a Hypertension Challenge

Immune cells like dendritic cells (DCs) and T cells are essential for the development of hypertension. Upregulation of the vasoactive peptide endothelin-1 (ET-1) is key in the progression of hypertension. ET-1 acting via its ET A receptor raises blood pressure and promotes end-organ damage and inflammation. DCs and T cells express ET-1 receptors and respond to changing levels of ET-1. However, it is unknown whether activation of the ET-1/ET A receptor axis on DCs or T cells is critical in driving hypertension, or if a differential activation of this axis in immune cells leads to the sex differences that exist in the pathophysiology of this disease. We hypothesized that activation of the ET-1/ ET A axis on immune cells is crucial in the development of hypertension, with a more prominent role in males than females. Male and female mice lacking ET A receptor on DCs (DC ET A KO) or on T cells (T cell ET A KO) and floxed ET A control mice were given the nitric oxide synthase inhibitor L-NAME (0.5 mg/mL) in drinking water for 3 wks to induce hypertension. Systolic blood pressure (SBP) was measured 3 times/wk via tail cuff plethysmography. Glomerular filtration rate (GFR) was evaluated at baseline and after L-NAME treatment via the transcutaneous FITC-sinistrin clearance method. Absence of ET A receptor on DCs resulted in a ~10 mmHg decrease in SBP at baseline in both sexes, and this difference increased throughout the protocol in males (Floxed ET A vs. DC ET A KO: L-NAME: 150.8±6.7 vs. 130.8±2.6 mmHg, n=4/group, p=0.002), but not in females (137.4±5.7 vs. 137.2±2.4 mmHg, n=3/group). Lack of the ET A receptor on T cells led to a similar decrease of ~10 mmHg in SBP at baseline. However, the difference in SBP widened when males were challenged with L-NAME (Floxed ET A vs. T cell ET A KO: 135.2±2.0 vs. 118.0±4.1, n=11/group, p=0.003), whereas the group difference in SBP disappeared in females (131.5±4.0 vs. 132.4±4.7, n=8-9/group). Following L-NAME, GFR trended to decline in control male mice, while it increased in T cell ET A KO males. Our data suggest that activation of ET A receptors on DCs and T cells modulates SBP in response to a hypertensive insult in males, but not in females. Additionally, absence of ET-1/ ET A axis activation on T cells suggests improved renal function during hypertension. Our results suggest that the use of ET A antagonism in the clinic may be more protective during hypertension in males than females.

Abstract P447: Impact of Altered Receptor Expression On the Cardiovascular Response to Estrogen

Premenopausal women benefit from estrogen's protective effects, including lower arterial stiffness than men of the same age. Despite estrogen's protective role, menopausal hormone therapy showed no cardiovascular benefits in the Women's Health Initiative. One theory is that the response to menopausal hormone therapy is modulated by the presence of pre-existing cardiovascular disease. Estrogen signals through nuclear estrogen receptors ERα and ERβ, and the membrane-bound G protein-coupled estrogen receptor (GPER). Our lab has shown that GPER induces protective cardiovascular effects including decreased blood pressure, protection from renal damage, and attenuation of arterial remodeling. In this study, we hypothesized that GPER deletion would attenuate the protective vascular effects of estrogen after menopause. Female C57Bl/6J wildtype (wt) and global GPER knockout (ko) mice underwent ovariectomy (OVX) at 46 weeks of age and concurrently administered estrogen (E) or vehicle (Veh). Angiotensin II (Ang II; 700 ng/kg/day) infusion was used to induce hypertension either four weeks prior (Ang-E) or at the time of OVX (E-Ang) to evaluate the impact of cardiovascular diseases preceding or coinciding with menopause. Blood pressure was measured by tail-cuff plethysmography and arterial stiffness was assessed by pulse wave velocity (PWV). Statistical analysis was performed using one-way ANOVA. Ang II induced a similar level of hypertension in wt and ko mice and was not impacted by E or timing. In wt mice, PWV was significantly higher in Veh-treated compared with E-treated hypertensive animals, independent of timing (P<0.001). In contrast, PWV was not impacted by E in GPER ko mice (P=0.99). In conclusion, we found that E did not affect the hypertensive response to Ang II in both wt and GPER ko mice. GPER deletion reduced estrogen’s protection from arterial stiffening. Whether Ang II preceded or coincided with menopause did not alter the effects of E. These studies are important for determining whether cardiovascular status should be a factor when considering menopausal hormone therapy.

Abstract MP03: Perineuronal nets in the paraventricular nucleus of the hypothalamus are altered during DOCA-salt hypertension

The paraventricular nucleus of the hypothalamus (PVN) is critical to integrate peripheral signals to modulate neurohumoral and sympathetic output. During hypertension, overactivation of the PVN contributes to neurohumoral dysregulation and increased sympathetic tone. Perineuronal nets (PNNs) are lattice-like extracellular structures that surround the soma and proximal dendrites of neurons and modulate neuronal firing and circuit plasticity. These structures are expressed throughout the brain, including the hypothalamus and PVN, and are of particular interest because changes in their deposition have been associated with multiple neurological disorders including stress, PTSD, and depression. Here, we explore changes in PNNs in the PVN during DOCA-salt hypertension, a model of neurogenic hypertension, specifically testing the hypothesis that PNNs deposition would be decreased in the PVN. 5-month old male C57BL6 mice were implanted with a s.c. deoxycorticosterone acetate (DOCA) pellet and received 0.9% NaCl in the drinking water. Blood pressure was monitored twice weekly by tail-cuff plethysmography. After 21-days of DOCA-salt (n=3) and sham control (n=4), mice were perfused with 2% paraformaldehyde to quantify PNNs using the marker N-acetylgalactosamine-binding Wisteria floribunda agglutinin (WFA). We found a trend towards less WFA+ neurons in the PVN in DOCA-salt vs control (42.29 ± 7.93 neurons/mm 2 in DOCA vs 68.97 ± 10.80 in control; p=0.1231), but observed no difference in the overall PVN area that was positive for WFA+ staining (26.53 ±0.80 % in DOCA vs 29.75 ± 2.02 % in control). Next, we quantified WFA intensity (PMID 28713865) and observed a decrease in individual PNN intensity in the PVN of DOCA-salt mice (40.08 ± 7.46 vs 67.39 ± 7.42 a.u. in control), as well as a decrease in total WFA+ intensity in the PVN (26.04 ± 3.48 vs 33.80 ± 0.29 a.u. in control; p=0.0458). We conclude that PNN deposition is decreased in the PVN during DOCA-salt hypertension, a potentially important mechanism which has been previously unexplored. PNN intensity has been previously associated with neuronal firing; therefore, ongoing studies are investigating the contribution of PNNs in the PVN to sympathetic tone and blood pressure regulation during DOCA-salt hypertension.

O65 SARCOPLASMIC CALCIUM ATPASE (SERCA) PROTEOLYSIS BY MATRIX METALLOPROTEINASE (MMP)-2 CONTRIBUTES TO VASCULAR DYSFUNCTION IN EARLY HYPERTENSION

Background and objective: Hypertension-induced increased matrix metalloproteinase (MMP)-2 activity proteolyzes extra- and intracellular proteins in aortas and contributes to vascular dysfunction. MMP-2 proteolyzes sarcoplasmic reticulum calcium ATPase (SERCA) in the heart during ischemia and reperfusion injury, thus impairing cardiac function. SERCA activity is also impaired in the arteries of hypertensive animals. We investigated whether hypertension-induced increased MMP-2 activity in aorta contributes to SERCA proteolysis, vascular remodeling and dysfunction. Methods: Aortas from male Sprague-Dawley (SD) rats, incubated or not with angiotensin II (AngII) and MMP inhibitors, ONO-4817 or doxycycline (Doxy), were used for zymography and co-immunoprecipitation of SERCA with MMP-2. Male SD rats were also submitted to two kidney-one clip (2K-1C) or Sham surgery and treated with Doxy from third to seventh day post-surgery. Systolic blood pressure (SBP) was assessed basally and daily by tail-cuff plethysmography. After 7 days, aortas were collected for gel and in situ zymography, western blot to SERCA, ATPase activity assay, vascular reactivity to phenylephrine and acetylcholine, Ki-67 immunofluorescence and hematoxylin/eosin stain. A7r5 cells were incubated or not with AngII, in the presence or absence of SERCA inhibitor, tapsigargin, to assess intracellular calcium concentrations. Results: AngII increased MMP-2 activity in aortas and MMP-2 co-immunoprecipitated with SERCA. SBP was increased in 2K-1C rats and Doxy did not reduce it, but decreased MMP-2 activity and prevented SERCA proteolysis in aortas. Intracellular calcium concentrations were increased in A7r5 cells incubated with AngII and/or SERCA inhibitor, tapsigargin. Cross sectional area, media to lumen ratio and Ki-67 were all increased in the aortas of hypertensive rats and Doxy decreased Ki-67 cell proliferation. In 2K-1C rats, arterial contraction to phenylephrine was accentuated but Doxy ameliorated only the impaired relaxation to acetylcholine. Conclusion: Doxy reduced MMP-2 activity in the aortas of 2K-1C rats and prevented the ATPase activity impairment and MMP-2-induced SERCA proteolysis and vascular dysfunction.

Abstract 23: Cognitive impairment during chronic i.c.v. angiotensin II is associated with increased tau phosphorylation in the cortex and hippocampus

Cardiovascular risk factors, such as hypertension, are recognized as important contributors to cognitive impairment and dementia, including Alzheimer’s disease (AD). However, the mechanisms underlying the detrimental effects of hypertension on the brain remain to be fully established. Angiotensin II (Ang II) has known detrimental effects on the brain, including cerebrovascular damage, sympathetic activation, and neuroinflammation. Ang II activates neuronal glycogen synthase 3b (GSK-3b), a major kinase involved in the phosphorylation of the microtubule associated protein tau. Hyperphosphorylated tau and the subsequent formation of neurofibrillary tangles are a hallmark of AD and related dementias (tauopathies). Here, we tested the central hypothesis that brain Ang II leads to cognitive impairment by increasing tau hyperphosphorylation. 3-month old male C57BL6 mice were implanted with a s.c. osmotic minipump connected to an i.c.v. cannula delivering low dose Ang II (6ng/hr) or saline for 4 weeks. Blood pressure was monitored twice weekly using tail-cuff plethysmography. During the 4 th week of infusion, mice underwent a battery of neurobehavioral testing assessing various cognitive domains including novel object recognition (recognition and short-term memory), Y-maze (spatial working memory), Barnes maze (spatial learning and long-term memory), and hippocampal/executive function (nest building). Tau phosphorylation was assessed in the cortex and hippocampus by Western blotting. Systolic blood pressure increased slightly by week 3 prior to start of behavioral tests (control: 115.3 ± 4.1 mmHg vs Ang II: 130.8 ± 4.7; n=10). We did not observe significant differences during novel object recognition (discrimination index: control: 0.49 ± 0.08 vs Ang II: 0.35 ± 0.23; n=5) or Y-maze (spontaneous alternations: control: 62.4 ± 6.1% vs Ang II: 59.0 ± 4.3%). Mice receiving i.c.v. Ang II had significantly delayed latency to find the escape hole during the Barnes maze learning trials (Treatment p=0.0006, Time p=0.0039, interaction: p=0.3028; two-way repeated measures ANOVA). The impairment in spatial learning was associated with an increase in tau phosphorylation in the cortex assessed by AT8 antibody. Ongoing studies are investigating whether this increase is mediated by activation of neuronal GSK-3b. We conclude that Ang II-mediated hyperphosphorylation of tau is a potential novel molecular mechanism driving the detrimental effects of hypertension on cognitive health.

Abstract P346: Expansion of meningeal lymphatic vessels in DOCA-salt hypertension

The meningeal lymphatic system is critical for proper brain waste clearance and maintenance of the local meningeal neuroimmune niche. Meningeal lymphatic function is impaired during aging and neurodegenerative diseases and is associated with the development of cognitive impairment. There is a bidirectional communication between meningeal lymphatic function and dural T cells, whereby the drainage of T cells into the deep cervical lymph nodes depends on functional lymphatic vessels, and meningeal lymphatic function is itself modulated by T cell derived cytokines. We have previously shown that IL-17A producing T cells accumulate in the dura during deoxycorticosterone acetate (DOCA)-salt hypertension and contribute to the impairment of neurovascular coupling and cognitive function. However, the mechanisms by which these T cells accumulate in the dura remain to be determined. Here, we tested the hypothesis that the meningeal lymphatic vessels are impaired during DOCA-salt hypertension, thus contributing to dural T cell accumulation. 12-week old C57BL6 male mice were implanted with a s.c. DOCA pellet and received 0.9% NaCl in the drinking water for 21 days (n=4). Control mice underwent a sham surgery (n=4). Blood pressure was monitored by tail-cuff plethysmography. Meningeal lymphatic vessels were assessed by immunohistochemistry using the lymphatic vessel marker LYVE1. In a separate group of mice, we assessed meningeal lymphatic function by delivering Alexa647-Ovalbumin or IgG-RPE into the cisterna magna and measuring fluorescence in the deep cervical lymph nodes one hour after injection. DOCA-salt mice developed increased systolic blood pressure (control: 117.7 ± 4.9 vs DOCA: 141.5 ± 2.9mmHg). We observed no difference in the CD31+ dural sinus area between control and DOCA-salt (control: 11.482 ± 0.718 vs DOCA: 11.816 ± 0.662 mm 2 ). We found a significant increase in LYVE1+ area surrounding the dural sinuses in DOCA-salt (control: 0.508 ± 0.039 vs DOCA: 0.816 ± 0.105 mm 2 ; p=0.0329 by unpaired two-tailed t-test) and an increase in LYVE1+/CD31+ % area (control: 4.476 ± 0.462 vs DOCA: 6.840 ± 0.609 %; p=0.0213 by unpaired two-tailed t-test) which was not different between the sagittal sinus or the transverse sinus. Contrary to our hypothesis, our data suggests that the meningeal lymphatic vessels are expanded, not retracted, during DOCA-salt hypertension. The interaction between meningeal lymphatics and dura immunity in hypertension remains to be determined.

P097 SEXUAL DIMORPHISM IN A HYPERTENSIVE MODEL OF FRUCTOSE PLUS HIGH SALT DIET

High salt diet (HSD) and fructose are both consumed in excess and contributes to hypertension (HTN). Fructose is commonly used to sweeten soft drinks, and studies have linked soft drink consumption to salt-sensitive HTN. However, full mechanisms aren’t understood. Previous data indicates that an acute fructose-enriched diet (FED) increases Na/K/2Cl cotransporter (NKCC2) activity, promoting salt-sensitive HTN in rats; however, there is no research on long-term consumption. Here, our goal was to evaluate whether a FED, coupled to HSD, can induce HTN. Given the known sex-dependent differences in salt-sensitive HTN, we also hypothesized differences between male and female mice. Male and female C57BI/6 mice (10 weeks old, n=4-6) were treated with vehicle or fructose (10% in drinking water) plus HSD (4% in food) for 28 days. Systolic blood pressure (SBP) was measured by tail-cuff plethysmography, and cardiac hypertrophy (morphometry). We performed an acute diuresis test using furosemide to inhibit NKCC2 (20 mg/kg bw, ip) at day 26, and then measured natriuresis (metabolic cages) for 2-hrs. All data are presented by mean standard deviation. Fructose+HSD increased SBP in male mice after 28 days (Veh=110.5±4.6 vs. Frucose+HSD=130.2±5.6 mmHg; p<0.01); in contrast, HTN was completely prevented in female mice (Veh=109.8±6.8 vs. Fructose+HSD=114.0±11.0 mmHg; ns). We did not observe changes in cardiac hypertrophy in either sex. We observed a significant decrease in natriuresis (∼20%) after furosemide injection in male mice (Veh=5.9±1.1 vs. Fructose+HSD=4.7±0.8 μEq/2 h/g bw; ns). Surprisingly, we observed an increase in natriuresis following furosemide injection in female mice (Veh=3.8±5.0 vs. Fructose+HSD= 7.7±2.7 μEq/2 h/g bw; p<0.01). We observed HTN in males following a FED combined with HSD, which was not associated with increased NKCC2 activation. In contrast, female mice showed a resistance to HTN, and yet an apparent increase in NKCC2 activity. This probably suggests a dysregulation of other transporters not evaluated in this work. Finally, we demonstrate that long-term FED, with HSD, induces HTN with a sexual dimorphic effect, apparently through differential renal sodium handling.

The hydrogen sulfide donor 4-carboxyphenyl-isothiocyanate decreases blood pressure and promotes cardioprotective effect through reduction of oxidative stress and nuclear factor kappa B/matrix metalloproteinase (MMP)-2 axis in hypertension

AimsOur aim was to evaluate whether the hydrogen sulfide (H2S) donor, 4-carboxyphenyl-isothiocyanate (4-CPI), exerts cardioprotective effect in the two kidney- one clip (2K-1C) rats through oxidative stress and MMP-2 activity attenuation and compare it with the classical H2S donor, Sodium Hydrosulfide (NaHS). Materials and methodsRenovascular hypertension (two kidneys-one clip; 2K-1C) was surgically induced in male Wistar rats. After two weeks, normotensive (2K) and hypertensive rats were intraperitoneally treated with vehicle (0.6 % dimethyl sulfoxide), NaHS (0.24 mg/Kg/day) or with 4-CPI (0.24 mg/Kg/day), for more 4 weeks. Systolic blood pressure (SBP) was evaluated weekly by tail-cuff plethysmography. Heart function was assessed by using the Millar catheter. Cardiac hypertrophy and fibrosis were evaluated by hematoxylin and eosin, and Picrosirius Red staining, respectively. The H2S was analyzed using WSP-1 fluorimetry and the cardiac oxidative stress was measured by lucigenin chemiluminescence and Amplex Red. MMP-2 activity was measured by in-gel gelatin or in situ zymography assays. Nox1, gp91phox, MMP-2 and the phospho-p65 subunit (Serine 279) nuclear factor kappa B (NF-κB) levels were evaluated by Western blotting. Key findings4-CPI reduced blood pressure in hypertensive rats, decreased cardiac remodeling and promoted cardioprotection through the enhancement of cardiac H2S levels. An attenuation of oxidative stress, with inactivation of the p65-NF-κB/MMP-2 axis was similarly observed after NaHS or 4-CPI treatment in 2K-1C hypertension. SignificanceH2S is a mediator that promotes cardioprotective effects and decreases blood pressure, and 4-CPI seems to be a good candidate to reverse the maladaptive remodeling and cardiac dysfunction in renovascular hypertension.

Augmentation of Nitric Oxide Deficient Hypertension by High Salt Diet Is Associated With Reduced TNF-α Receptor Type 1 Expression in the Kidneys.

High salt (HS) intake induces an augmented hypertensive response to nitric oxide (NO) inhibition, though it causes minimal changes in blood pressure (BP) in NO intact condition. The cause of such augmentation is not known. HS induces tumor necrosis factor-alpha (TNFα) production that causes natriuresis via activation of its receptor type 1 (TNFR1). We hypothesized that NO deficiency reduces renal TNFR1 activity, leading to enhanced sodium retention and hypertension. We examined the changes in renal TNFR1 protein expression (Immunohistochemistry analyses) after HS (4% NaCl) intake in wild-type mice (WT, C57BL6) treated with a NO synthase (NOS) inhibitor, nitro-l-arginine methyl ester (L-NAME; 0.05 mg/min/g; osmotic mini-pump), as well as in endothelial NOS knockout mice (eNOSKO) and compared the responses in WT mice with normal salt (NS; 0.3% NaCl) intake. BP was measured with tail-cuff plethysmography and 24-hour urine collections were made using metabolic cages. HS alone did not alter mean BP in untreated mice (76 ± 3 to 77 ± 1 mm Hg) but induced an augmented response in L-NAME treated (106 ± 1 vs. 97 ± 2 mm Hg) and in eNOSKO (107 ± 2 vs. 89 ± 3 mm Hg) mice. The percentage area of TNFR1 expression in renal tissue was higher in WT + HS (4.1 + 0.5%) than in WT + NS mice (2.7 ± 0.6%). However, TNFR1 expression was significantly lower in L-NAME treated WT + NS (0.9 ± 0.1%) and in eNOSKO + NS (1.4 ± 0.2%) than in both WT + NS and WT + HS mice. These data indicate that TNFR1 activity is downregulated in NO deficient conditions, which facilitates salt retention leading to augmented hypertension during HS intake.

Does Uromodulin Play a Role in Tacrolimus-Mediated Upregulation of the Sodium Chloride Cotransporter?

Background: Tacrolimus, a calcineurin inhibitor (CNI), is a medication commonly prescribed to prevent organ transplant rejection. However, chronic CNI use has several adverse effects, including hypertension. Recent studies have revealed that the renal sodium chloride cotransporter (NCC) mediates tacrolimus-induced hypertension. However, the mechanisms underlying NCC upregulation are not fully understood. Previous studies indicate that uromodulin plays a key role in renal ion channel regulation. As such, we hypothesize that uromodulin mediates tacrolimus induced NCC upregulation. Experimental Design: To test this hypothesis, male C57BL/6 mice received tacrolimus (10 mg/kg/day) or vehicle (ethanol/DMSO/saline) for 21 consecutive days via intraperitoneal injection. The impact of tacrolimus on systolic blood pressure (BP) was monitored by tail-cuff plethysmography. To examine uromodulin and NCC expression, kidneys were harvested and processed for immunohistochemistry. Results: Compared to the BP of vehicle-treated mice (120 mm Hg ± 4.252), mice administered tacrolimus had significant increases in BP (170 mm Hg ± 3.528). Furthermore, tacrolimus treatment increased phosphorylated NCC (pNCC) and uromodulin expression. Conclusions: These results indicate that tacrolimus-induced hypertension is accompanied by pNCC and uromodulin upregulation in distal convoluted tubules. Significance: Overall, these findings highlight uromodulin as a possible regulator of NCC. Funding: R21 DK119879, R01 DK-133698, R25DK07838. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Angiotensin II-induced cardiac dysfunction and fibrosis is prevented by cardiomyocyte-specific overexpression of Larp6

Introduction: La ribonucleoprotein 6, Translational Regulator (Larp6) is a multifunctional mRNA binding protein most well described for its pro-fibrotic action to increase type I collagen mRNA half-life, translation, and deposition. In the heart, the actions of Larp6 are not described. Interestingly, Larp6 is expressed in cardiomyocytes which are not primarily involved in cardiac fibrosis. To investigate the role of cardiomyocyte Larp6 in cardiac function and remodeling, we generated a cardiomyocyte-specific Larp6 overexpressing (OE) transgenic mouse model and determined its role at (i) baseline and (ii) following hypertensive challenge with angiotensin II (Ang II). We hypothesized that cardiomyocyte-specific Larp6 OE exacerbates Ang II-induced cardiac remodeling and dysfunction. Methods: Cross-sectional studies were performed from 2-8 months of age in male and female Larp6 OE and wildtype (WT) littermates. Baseline cardiac function was assessed by 7-T MRI and echocardiography. In a separate set of mice (10 mo of age), hypertension was induced via Ang II infusion by osmotic minipump (1000 ng/kg/min) or vehicle. Blood pressure (BP) was assessed 14-17 days post-infusion via tail-cuff plethysmography, cardiac function by echocardiography after 21 days, and the heart prepared for histochemistry. Differences in endpoints were determined by two-way ANOVA with Tukey post hoc and a significant p-value cutoff of 0.05. Results: Baseline studies revealed Larp6 OE had no significant effect on cardiac function (7-T MRI), BP, or gross morphology in either sex across timepoints. At 10 months of age, histochemistry revealed increased cardiomyocyte Larp6 protein expression and mild, but significant, interstitial fibrosis in unstressed Larp6 OE mice. In 10-month-old mice, Ang II infusion similarly increased BP and induced cardiac hypertrophy in both male and female Larp6 OE and WT mice. Further, Ang II induced systolic dysfunction and cardiac fibrosis in WT mice. Unexpectedly, Larp6 OE prevented Ang II-mediated interstitial fibrotic remodeling and decreases in ejection fraction, fractional shortening, and cardiac output independent of sex. Of note, Larp6 OE did not protect against Ang II-induced perivascular fibrosis, suggesting the anti-fibrotic effect was localized around the cardiomyocytes. Conclusion: Taken together, these data support a pro-fibrotic action of cardiomyocyte Larp6 in unstressed mice. Despite this impact at baseline, cardiomyocyte-specific Larp6 OE is suffcient to prevent Ang II-induced cardiac fibrosis and dysfunction, independent of BP and sex. This unexpected result, contrary to our hypothesis, suggests that targeting cardiomyocyte Larp6 signaling may represent a new therapeutic avenue to treat hypertensive heart disease. R01 HL136386, NIDDK DK130243, SRCS (IK6BX004016), BX005845, and R21 AA029747. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Deletion of dipeptidyl peptidase 4 attenuates angiotensin II-induced blood pressure rise and enhances NHE3 phosphorylation at serine 552 in the kidneys of male and female mice

Dipeptidyl peptidase 4 (DPP4) physically associates with the Na+/H+ exchanger isoform3 (NHE3), and DPP4 inhibitors reduce NHE3-dependent sodium reabsorption in the renal proximal tubule. Angiotensin II (Ang II) is a key mediator of sodium and water retention by the kidneys, partly through the activation of proximal tubule NHE3. Recent studies from our group reveled that Ang II activates DPP4 by, both in vivo and in vitro, and that inhibition of several canonical and non-canonical pathways can suppress this activation. However, the impact of this interaction on renal sodium handling and blood pressure remains unclear. This study aimed to test the hypothesis that DPP4 deletion mitigates the blood pressure elevation induced by Ang II in male and female mice, at least partly due to the downregulation of NHE3 in the renal proximal tubule. Male and female mice with global DPP4 deletion or wild-type controls were acutely administered either a pressor dose of Ang II (1000 ng/kg/minute) or saline. Blood pressure was measured before and one hour after the administration of Ang II or saline by tail-cuff plethysmography. Kidneys were subsequently collected for protein homogenate preparation. Increased DPP4 activity was observed in response to acute Ang II stimulation in both male and female wild-type mice, with female mice exhibiting higher basal DPP4 activity. As expected, DPP4 knockout mice exhibited minimal DPP4 activity. Baseline blood pressure did not differ significantly between male wild-type and DPP4 knockout mice or between females. In line with our hypothesis, both male and female DPP4 knockout mice displayed a reduced increase in blood pressure in response to acute Ang II administration compared to their wild-type counterparts. Furthermore, the phosphorylation of NHE3 at serine 552 (pS552-NHE3), a surrogate marker of NHE3 inhibition, was higher in wild-type females than males. Interestingly, pS552-NHE3 was fivefold higher in male DPP4 knockout mice and threefold higher in female DPP4 knockout mice compared to their wild-type counterparts. Additionally, the increase in pS552-NHE3 one hour after Ang II administration was higher in males (1208 ± 119 vs. 544 ± 54 %, P < 0.01) and females (385 ± 18 vs. 271 ± 27%, P < 0.01) DPP4 knockout mice compared to wild-type animals. Moreover, ERK, a well-known effector of the AT1R signaling cascade, was phosphorylated in a similar manner as NHE3 in response to Ang II in males but not in females. In conclusion, our data demonstrate that the absence of DPP4 reduces the rise in blood pressure induced by acute Ang II stimulation, possibly through Ang II/AT1R signaling pathways influencing phosphorylation of downstream effectors such as NHE3. Furthermore, we observe significant sex differences in Ang II effects on DPP4 activity, and AT1R signaling cascades. FAPESP 2021/14524-3 NIDDKD - K08DK115886. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Epithelial Na+ Channel Is a Zn2+ Sensitive Renal Na+ Reabsorption Pathway that Mediates Zn2+ Deficiency-induced Hypertension

Background: Zinc (Zn2+) deficiency (ZnD) is comorbid with many chronic diseases including kidney disease and diabetes. Individuals in these vulnerable populations have a higher prevalence of hypertension. Recently, we reported that ZnD induces hypertension by promoting renal Na+ reabsorption. However, the renal Na+ reabsorption mechanisms involved continue to be identified. The renal epithelial Na+ channel (ENaC) plays an essential role in regulating whole-body Na+ and water balance and is involved in hypertension. We hypothesize that ENaC is a Zn2+-sensitive channel that mediates ZnD-induced hypertension. Experimental Design: To establish the role of ENaC in ZnD-induced hypertension, WT C57Bl/6 mice were switched from a Zn2+ adequate to a Zn2+ deficient diet for 10 weeks. During weeks 9 and 10, mice were treated with benzamil, an ENaC inhibitor. Systolic blood pressure (BP) was monitored by tail-cuff plethysmography; Renal ENaC expression was examined by immunohistochemistry and Western blot. To authenticate the Zn2+ sensitivity of ENaC, mouse distal convoluted tubule cells (mDCT) were treated with a Zn2+ chelator (TPEN) or vehicle (ethanol) for 24 hours. A subset of TPEN-treated cellular monolayers were supplemented with Zn2+ for 24 hours to replete intracellular Zn2+. Cellular ENaC expression was examined by Western blot analysis. Results: 1) Blood pressure: Compared to Zn2+ adequate mice (101.4 mm Hg ± 4.225), Zn2+ deficient mice had increased BP (154.6 mm Hg ± 2.422). However, benzamil treatment lowered BP (115.0 mm Hg ± 4.626) of Zn2+ deficient mice. 2)Immunohistochemistry: Next, Zn2+ effects on ENaC expression were examined. In Zn2+ deficient mice, αENaC protein abundance significantly increased compared with Zn2+ adequate mice. 3) Western blot analysis: To directly investigate Zn2+effects on ENaC expression, in vitro studies were performed using mDCT cells. Western blot analysis showed that TPEN-induced ZnD stimulated both αENaC and βENaC protein expression. Conclusion: Collectively, our findings reveal that (1) ENaC is a Zn2+ sensitive renal Na+ reabsorption pathway and (2) ENaC mediates ZnD-induced hypertension. Significance: Understanding the renal mechanisms by which Zn2+ regulates blood pressure may have an important therapeutic impact on hypertension. Funding: R21 DK119879, R01 DK-133698 (National Institute of Diabetes and Digestive and Kidney Diseases); R25DK078381 (NIH NIDDK STEP-UP program);1742339 (National Science Foundation ASK Program). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.