Normotensive Rats Research Articles

MMP-9 expression in rat pup incisor teeth is not altered by maternal hypertension or maternal atenolol treatment during pregnancy and lactation.

Hypertension alters tooth formation and Atenolol reduces the blood pressure of spontaneously hypertensive rats (SHR) during pregnancy and lactation, and as demonstrated before, increases the microhardness of the SHR offspring's teeth. MMP-9 is overexpressed in different tissues of hypertensive animals and treatment of hypertension substances can reverse this alteration. We hypothesize hypertension alters the expression of MMP-9 in dental structures of SHR offspring and that treating female SHR with atenolol prevents this alteration. This study aimed to evaluate the expression of matrix metalloproteinase (MMP-9) in incisor teeth (IT) in male offspring of SHR (30 days old) treated or untreated with Atenolol during pregnancy and lactation. MMP-9 expression was evaluated in ameloblasts (AM), enamel matrix (EM), odontoblasts (OD), and predentin (PD) of IT through immunohistochemical reactions (immunoperoxidase). Data were analyzed by Shapiro-Wilk and Kruskal-Wallis (p < 0.05), with Dunn post-test. Histological differences were not observed between IT tissues of SHR and normotensive Wistar rats. For the first time, our data showed that MMP-9 expression in specific dental structures is not altered in SHR. Atenolol treatment increased MMP-9 immunostaining in EM of Wistar rat, however, Atenolol did not alter MMP-9 in the IT tissues of SHR. Our results demonstrated that MMP-9 expression in dental tissues is not affected by hypertension or atenolol treatment in dental tissues. If confirmed in humans, the results obtained in this study will corroborate the suggestion that MMP-9 is not a viable therapeutic target for the treatment of dental alterations associated with maternal hypertension.

Prosopis africana extract inhibits critical enzymes associated with hypertension in vitro and in cyclosporine-induced hypertensive rats

ObjectiveThis study evaluated the antihypertensive properties of leaf extracts of Prosopis africana (PA) in vitro and in hypertensive rats. MethodsEthanol (ELPA) and differential solvent fractions [ethyl-acetate (EAPA), butanol (BLPA), and aqueous (ALPA)] were prepared using standard protocols. Hypertension was induced in female albino Wistar rats intraperitoneally using cyclosporine (25 mg/kg/day) while extracts were administered via oral route. Forty female rats were grouped into 5 (n = 8). Group 1 received 2 ml distilled water, Group 2: (cyclosporine + 2 ml distilled water); Group 3: cyclosporine + captopril (10 mg/kg/day); Group 4: cyclosporine + 1000 mg/kg ELPA and Group 5: cyclosporine + 1500 mg/kg ELPA. The blood pressure of anesthetized rats was measured using LabScribe coupled to a Lab-Trax-4/24T, and the activities of angiotensin-converting enzyme (ACE), arginase, phosphodiesterase-5 (PDE-5), acetylcholinesterase (AChE) and adenosine deaminase (ADA) were evaluated using standard methods. ResultsAll the fractions exerted significantly (p < 0.05) higher ACE inhibitory effect (ELPA = 64.36 ± 0.50%; EAPA = 86.31 ± 0.60%; BLPA= 85.28 ± 2.30 % ; ALPA= 82.27 ± 2.10 % ) than the reference, lisinopril (40.22±0.50 % ); while the butanol fraction (67.05±0.40 % ) showed higher PDE-5 inhibition than the reference, sildenafil (23.06±0.70 % ). Administration of cyclosporine caused notable (p < 0.05) elevation of systolic/diastolic blood (131.00 ± 1.22/93.25 ± 1.49 mmHg) pressure plus elevated heart rate when in comparison with the normotensive rats (106.25 ± 1.65/85.25 ± 1.18 mmHg). Treatment of hypertensive rats with ELPA significantly reduced elevated activities of ACE, PDE-5, AChE, and arginase to values that are not significantly (p < 0.05) different from those of the rats treated with the reference drug. ConclusionThis result could validate the use of P. africana as an antihypertensive agent in folklore.

Systemic alpha-1 adrenergic receptor inhibition reduces sperm damage in adult and aging spontaneously hypertensive rats

Decreased sperm quality has been reported in men with different clinical conditions, including aging and hypertension. In the male reproductive tract, it has been suggested that the α1-adrenergic receptor influences fertility and spermatogenesis, and important functions are also attributed to the renin–angiotensin axis, such as regulation of steroidogenesis, spermatogenesis, and sperm function. Previously, our group demonstrated impaired testicular vasomotion via α1-adrenergic receptor activation and increased hypoxia-related proteins in the testes of spontaneously hypertensive rats (SHRs) compared to Wistar normotensive rats. In this study, we aimed to investigate the effect of hypertension and inhibition of systemic α1-adrenergic receptor or angiotensin II AT1 receptor on sperm quality, sperm functional characteristics, and testicular microcirculation in rats from three different ages: young (8–10-week-old), adult (20–24-week-old) and older adult (60–66-week-old). We observed higher blood pressure in SHRs of all ages compared to age-matched Wistar rats. Lower blood pressure was observed either in prazosin or losartan-treated adult or aged SHRs. Additionally, lower sperm concentration, impaired motility and higher acrosome damage were demonstrated in SHRs. Prazosin treatment alleviated the effects of hypertension on sperm concentration and motility but not acrosome damage. Higher vasomotion was noticed in testicular blood vessels of adult and aged SHRs compared to Wistar rats. Thus, impaired sperm quality was observed in SHRs of different ages and was improved by sub-chronically blocking the α1-adrenergic receptor.

Rhythmic Contractions of Lymph Vessels and Lymph Flow Are Disrupted in Hypertensive Rats.

Hypertension increases the risk of lymphedema in patients with comorbidities, but whether hypertension directly compromises lymph vessel (LV) function and lymph flow is unclear. We compared the contractions of mesenteric LVs ex vivo and lymph flow in vivo between normotensive and Ang II (angiotensin II)-induced hypertensive rats and explored the ionic basis of contractile patterns. Key studies were recapitulated in spontaneously hypertensive rats and control Wistar-Kyoto rats. Video microscopy continuously recorded the diameters of cannulated rat mesenteric LVs, and high-speed optical imaging estimated mesenteric lymph flow in vivo. Jess capillary Western electrophoresis evaluated expression levels of ion channel proteins. Isolated LVs from Ang II-induced hypertensive rats exhibited dysrhythmic contractions, whereas LVs from both Ang II-induced hypertensive rats and spontaneously hypertensive rats exhibited reduced diastolic diameters and cross-sectional flow. Mesenteric lymph flow in vivo was 2.9-fold lower in Ang II-induced hypertensive rats compared with normotensive rats. Surprisingly, the LVs from Ang II-induced hypertensive rats expressed fewer intact L-type Ca2+ channel pore proteins and more modulatory cleaved C-terminal fragments. However, pharmacological block of voltage-gated K+ channels but not other K+ channel types in control LVs established the pattern of contractile dysfunction observed in hypertension. Jess capillary Western electrophoresis analysis confirmed a loss of Shaker-type KV1.2 channels in LVs from hypertensive rats. We provide initial evidence of lymphatic contractile dysfunction and compromised lymph flow in hypertensive rats, which may be caused by a loss of KV1.2 channels in the lymphatic muscle cells.

Therapeutic Effects of Pterocarpus santalinoides Stem Bark Aqueous Extract: Evidence from L-NAME-induced Hypertensive Wistar Rats

Aims: Ethnopharmacological information indicates that the stem bark of Pterocarpus santalinoides is used in traditional medicine to treat many diseases including hypertension. Thus, this study was designed to evaluate the therapeutic effects of the stem bark aqueous extract of Pterocarpus santalinoides (AEPS) in L-NAME-induced hypertensive rats (LNHR). Methodology: Hypertension was induced in normotensive rats by intraperitoneal administration of L-NAME (25 mg/kg/day) for 42 days. Forty-two animals were divided into two main groups: one group of seven rats (group 1) receiving distilled water (10 mL/kg) and another thirty-five rats receiving L-NAME (group 2). After three weeks of treatment, the hypertensive animals (group 2) were divided into five groups of seven rats each. Animals of the first group received distilled water, those of the second group were treated with captopril (20 mg/kg), and the three last groups received the AEPS (50, 100, and 200 mg/kg). These rats were daily treated per os with the above substances for three weeks. At the end of the experimental period (42 days), animals were anesthetized and the blood pressure and heart rate were recorded by invasive method. Afterward, the blood, aorta, and heart of each rat were collected for some biochemical and/or histological examination. Results: L-NAME administration induced hypertension, as associated with left ventricular hypertrophy, dyslipidemia, oxidative stress, hepatic and renal dysfunctions. Aqueous extract administration significantly improved all these metabolic disorders induced by L-NAME. Furthermore, the remodeling of the aortic media after NO deficiency-induced L-NAME has also been improved by Pterocarpus santalinoides aqueous extract. The therapeutic effect of AEPS against L-NAME-induced hypertension could probably be due to its antihypertensive, hypolipidemic, and antioxidant properties. Conclusion: Current results confirmed the empirical use of Pterocarpus santalinoides stem bark for the treatment of hypertension in traditional medicine.

Effect of Short-Term Restraint Stress on the Expression of Genes Associated with the Response to Oxidative Stress in the Hypothalamus of Hypertensive ISIAH and Normotensive WAG Rats.

Normotensive and hypertensive organisms respond differently to stress factors; however, the features of the central molecular genetic mechanisms underlying the reaction of the hypertensive organism to stress have not been fully established. In this study, we examined the transcriptome profiles of the hypothalamus of hypertensive ISIAH rats, modeling a stress-sensitive form of arterial hypertension, and normotensive WAG rats at rest and after exposure to a single short-term restraint stress. It was shown that oxidative phosphorylation is the most significantly enriched process among metabolic changes in the hypothalamus of rats of both strains when exposed to a single short-term restraint stress. The analysis revealed DEGs representing both a common response to oxidative stress for both rat strains and a strain-specific response to oxidative stress for hypertensive ISIAH rats. Among the genes of the common response to oxidative stress, the most significant changes in the transcription level were observed in Nos1, Ppargc1a, Abcc1, Srxn1, Cryab, Hspb1, and Fosl1, among which Abcc1 and Nos1 are associated with hypertension, and Fosl1 and Ppargc1a encode transcription factors. The response to oxidative stress specific to hypertensive rats is associated with the activation of the Fos gene. The DEG's promoter region enrichment analysis allowed us to hypothesize that the response to oxidative stress may be mediated by the participation of the transcription factor CREB1 (Cyclic AMP-responsive element-binding protein 1) and the glucocorticoid receptor (NR3C1) under restraint stress in the hypothalamus of both rat strains. The results of the study revealed common and strain-specific features in the molecular mechanisms associated with oxidative phosphorylation and oxidative stress response in the hypothalamus of hypertensive ISIAH and normotensive WAG rats following a single short-term restraint stress. The obtained results expand the understanding of the most significant molecular targets for further research aimed at developing new therapeutic strategies for the prevention of the consequences of acute emotional stress, taking into account the hypertensive state of the patient.

The Expression of Genes CYP1A1, CYP1B1, and CYP2J3 in Distinct Regions of the Heart and Its Possible Contribution to the Development of Hypertension.

It is believed that alterations in the functioning of the cytochrome P450 (CYP), which participates in metabolic transformations of endogenous polyunsaturated fatty acids (PUFAs) (with the formation of cardioprotective or cardiotoxic products), affects the development of age-related cardiovascular diseases and reduces the effectiveness of some cardioselective drugs. For example, CYP2J2 activation or CYP1B1 inhibition protects against the cardiovascular toxicity of anticancer drugs. It is currently unclear whether CYPs capable of metabolizing arachidonic acid and ω-3 PUFAs to vasodilatory and vasoconstrictive derivatives are expressed in all heart regions. The work was performed on senescence-accelerated OXYS rats featuring elevated blood pressure, OXYSb rats (an OXYS substrain with normal blood pressure), and Wistar rats as a "healthy" control. The mRNA level was determined in the right and left ventricles, the right and left atria, and the aorta of 1-, 3-, and 12-month-old rats. We showed that all heart regions express CYPs capable of metabolizing arachidonic acid and ω-3 PUFAs and revealed significant differences between heart regions both in the mRNA level of genes CYP1B1, CYP2J3, and CYP1A1 and in the time course of expression changes with age. We noticed that expression levels of these CYPs in the heart regions and aorta differ between hypertensive OXYS rats, normotensive OXYSb rats, and healthy Wistar rats but could not detect any clear-cut patterns associated with the hypertensive status of OXYS rats.

Prophylactic Antihypertensive Effect of Extract of Simarouba glauca on Salt-Load Induced Hypertension in Normotensive Male Wistar Rat

Simarouba glauca has been reported to demonstrate a wide range of medicinal properties; including folklore management of hypertension disorder. The current study focused on the application of aqueous leaf extract of Simarouba glauca (AESG) as a potential prophylactic anti-hypertensive agent in male Wistar rats, following salt-load induced hypertension. A total of 15 experimental adult male Wistar rats weighing between 184 and 244 g were used for the study. The rats were allotted into five (5) groups of 25, 50, and 100 mgkg-1 body weight AESG; group that received 8 % NaCl for one week to induce hypertension; replaced with 0.9 % NaCl daily in drinking water for 4 weeks; the normotensive group, received food and water only ad libitum. Body weights and relevant hemodynamics were obtained weekly for four weeks, using the non-invasive (tail-cuff) MRBP system according to the method described by Bunag and Butterfield. Biochemical evaluation and histopathology investigation were conducted on blood plasma and relevant tissues respectively after 4 weeks according to previously established and reported methods; data were analyzed with GraphPad Prism, version 9 and presented as mean ± Standard Deviation. The results indicated that salt-load elicited significant weight loss; elevated hemodynamics; particularly, systolic and diastolic blood pressures; altered relevant biochemical indicators of hepatic and renal functions. Inversely, groups pre-treated with respective dose of AESG exponentially gained weight, significantly prevented alterations of hemodynamics and mitigated relevant biochemical indicators and pathological changes in relevant organs. Pre-treatment with AESG; particularly at 50 mgkg-1, remarkably demonstrated significant anti-hypertensive potential.

Exaggerated postnatal surge of orexin neurons and the effects of elimination of excess orexin on blood pressure and exaggerated chemoreflex in spontaneously hypertensive rats.

An overactive orexin (OX) system is associated with neurogenic hypertension and an exaggerated chemoreflex in spontaneously hypertensive rats (SHRs). However, the chronology and mechanism of this association is unclear. We hypothesized that increased postnatal neurogenesis of OX neurons in SHRs precedes and contributes to the aberrant increase in mean arterial blood pressure (MAP) and the exaggerated response to hypercapnia during postnatal development. Using immunohistochemical methods and bromodeoxyuridine, we mapped the timeline of orexin neuron neurogenesis and maturation during early postnatal development. We then used whole-body plethysmography with EEG and EMG to map the development of mean arterial pressure (MAP) and state regulation. Finally, we used OX-targeted saporin toxin to determine the effects of eliminating excess OX neurons on the elevated MAP and exaggerated chemoreflex in adult SHRs. We found that both SHRs and Wistar-Kyoto (WKY) rats experienced postnatal increases in OX neurons. However, SHRs experienced a greater increase than WKY rats before P15, which led to significantly more OX neurons in SHRs than age-matched WKY controls by P15-16 (3,720 ± 780 vs. 2,406 ± 363, p = 0.005). We found that neurogenesis, as evidenced by BrdU staining in OX-positive neurons, was the primary contributor to the excess OX neurons in SHRs during early postnatal development. While SHRs develop more OX neurons by P15-16, SHRs and normotensive WKY control rats have similar MAP during postnatal development until P25 in wakefulness (81.6 ± 6.6 vs. 67.5 ± 6.8mmHg, p = 0.006) and sleep (79.3 ± 6.1 vs. 66.6 ± 6.5, p = 0.009), about 10 days after the surge of OX neurons. By selectively eliminating excess (∼30%) OX neurons in SHRs, we saw a significantly lowered MAP and hypercapnic ventilatory chemoreflex compared to non-lesioned SHRs at P40. Additionally, we found unique signatures in state indicative of the attention defecit phenotype commonly associated with this model. We suggest that the postnatal increase of OX neurons, primarily attributed to exaggerated postnatal OX neurogenesis, may be necessary for the development of higher MAP and exaggerated chemoreflex in SHRs, and modulation of the overactive OX system may have a potential therapeutic effect during the pre-hypertensive period.

L-Arginine and Taurisolo® Effects on Brain Hypoperfusion-Reperfusion Damage in Hypertensive Rats.

Acute and chronic hypertension causes cerebral vasculopathy, increasing the risk of ischemia and stroke. Our study aimed to compare the effects of arterial pressure reduction on the pial microvascular responses induced by hypoperfusion and reperfusion in spontaneously hypertensive Wistar rats, desamethasone-induced hypertensive Wistar rats and age-matched normotensive Wistar rats fed for 3 months with a normal diet or normal diet supplemented with L-arginine or Taurisolo® or L-arginine plus Taurisolo®. At the end of treatments, the rats were submitted to bilateral occlusion of common carotid arteries for 30 min and reperfusion. The microvascular parameters investigated in vivo through a cranial window were: arteriolar diameter changes, permeability increase, leukocyte adhesion to venular walls and percentage of capillaries perfused. Hypoperfusion-reperfusion caused in all rats marked microvascular changes. L-arginine treatment was effective in reducing arterial blood pressure causing vasodilation but did not significantly reduce the damage induced by hypoperfusion-reperfusion. Taurisolo® treatment was less effective in reducing blood pressure but prevented microvascular damage from hypoperfusion-reperfusion. L-arginine plus Taurisolo® maintained blood pressure levels within the physiological range and protected the pial microcirculation from hypoperfusion-reperfusion-induced microvascular injuries. Therefore, the blood pressure reduction is not the only fundamental aspect to protect the cerebral circulation from hypoperfusion-reperfusion damage.

Comparative Analysis of the Protective Effect of Naringenin on Cardiovascular Parameters of Normotensive and Hypertensive Rats Subjected to the Myocardial Infarction Model.

Background: Cardiovascular diseases rank as the top global cause of mortality, particularly acute myocardial infarction (MI). MI arises from the blockage of a coronary artery, which disrupts blood flow and results in tissue death. Among therapeutic approaches, bioactives from medicinal plants emerge as promising for the development of new medicines. Objectives: This study explored the effects of naringenin (NAR 100 mg/kg), a flavonoid found in citrus fruits, in normotensive (NTR) and spontaneously hypertensive (SHR) rats, both subjected to isoproterenol (ISO 85 mg/kg)-induced MI. Results: Post-treatment assessments indicated that NAR reduced blood pressure and minimized clot formation, particularly notable in the SHR group, which helps mitigate damage related to hypertension and ISO exposure. Additionally, NAR effectively restored KCl-induced contractility in the aortas of both NTR and SHR groups. NAR treatment reduced reduced glutathione (GSH) and lipid hydroperoxides (LOOH) values and recovered the activity of the antioxidant enzymes catalase (CAT) and glutathione-s-transferase (GST) in NTR groups. Moreover, myocardial damage assessed through histological analyses was reduced in groups treated with NAR. Conclusions: The results highlight significant pathophysiological differences between the groups, suggesting that NAR has protective potential against ISO-induced cardiac damage, warranting further investigation into its protective effects and mechanisms.

Modulation of Blood Pressure through Microbiome Exchange between Milan Normotensive and Hypertensive Rat Strains

Modulation of Blood Pressure through Microbiome Exchange between Milan Normotensive and Hypertensive Rat Strains

Right Ventricular Hypertrophy in Spontaneously Hypertensive Rats (SHR/NHsd) Is Associated with Inter-Individual Variations of the Pulmonary Endothelin System.

Spontaneously hypertensive rats (SHRs) develop severe hypertension and subsequently left ventricular hypertrophy. Whether they also develop right ventricular hypertrophy is not clear. We analyzed 76 female SHRs (strain SHR/NHsd) and observed severe right ventricular hypertrophy in 7% of these rats (SHR-RVH). Right ventricular hypertrophy did not correlate with the age of the rats and was already seen in one rat at the pre-hypertensive state. The current study investigated the molecular fingerprint of the lung and right ventricle from SHR-RVH and compared this first to SHRs that did develop left but not right ventricular hypertrophy, and second to normotensive rats without hypertrophy. Rats with right ventricular hypertrophy had a decreased expression of the endothelin-B receptor (EDNRB) in the lung, together with an increased protein content of endothelin-1 and an increased expression of ACTA2A. Furthermore, in the right ventricle, a down-regulation of the endothelin-A receptor (EDNRA) was found, consistent with a mild phenotype. The data suggest that in a sub-group of SHR/NHsd rats, low expression of the endothelin clearance receptor (endothelin-B receptor) in the lung triggers an increase in vascular resistance to the right ventricle that then triggers hypertrophy. Our study is the first description of a genetic variant in a defined SHR strain.

Anatomic and functional evidence for renal autonomic innervation in normotensive and hypertensive rats.

Renal denervation (RDN) has been used for treating resistant hypertension. A few recent studies have shown vagal innervation of kidneys causing confusion. This study aimed to provide anatomical and functional evidence for renal autonomic innervation. Experiments were performed in male Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). Pseudorabies virus (PRV) in the paraventricular nucleus and rostral ventrolateral medulla was prevented by bilateral RDN, but not subdiaphragmatic vagotomy. PRV did not appear in the dorsal motor nucleus of the vagus and nucleus tractus solitarii 72 h after renal injection of PRV. Adrenergic fibers were approximately seven times more than cholinergic fibers in the main renal artery (MRA) and its first (1RA) and second grade (2RA) branches. Adrenergic fibers in 1RA were more than those in MRA and 2RA. Tyrosine hydroxylase immunoreactivity in these arteries was higher in SHR than in WKY. Norepinephrine (NE) increased and α-receptor antagonist reduced vascular ring tension of renal arteries. The effect of NE was greater in 1RA and 2RA than in MRA, which was prevented by α-receptor antagonist. Acetylcholine (ACh) or blockage of β-receptors, M receptors, or N receptors had no significant effects on vascular ring tension and the effect of NE. Renal blood flow was reduced by electrical stimulation of renal nerves but not affected by stimulation of the subdiaphragmatic vagus. These results provide anatomical and functional evidence that kidneys are innervated and renal blood flow is regulated by renal sympathetic nerves rather than the vagus. Renal vasoconstriction is regulated by NE and adrenergic fibers rather than ACh or cholinergic fibers in WKY and SHR.NEW & NOTEWORTHY Kidneys are innervated by renal nerves rather than the vagus. Adrenergic fibers in renal arteries are about seven times more than cholinergic fibers. Renal vasoconstriction is regulated by norepinephrine and adrenergic fibers rather than acetylcholine or cholinergic fibers. Renal blood flow is regulated by renal sympathetic nerves and is not affected by the vagus. These findings provide anatomical and functional evidence for renal autonomic innervation in normotensive and hypertensive rats.

In vivo hypotensive effect of a chemically characterised extract from the leaves of Lippia alba (Mill.) N.E.Br

Lippia alba (erva-cidreira) is often mentioned in Brazilian ethnopharmacological studies. Although its leaves have been used to treat hypertension, few studies have evaluated its hypotensive effects. This work aimed to evaluate the haemodynamic effects of Lippia alba methanolic extract and to characterise its chemical composition. Normotensive rats received an intravenous injection of L. alba extract. Systolic, diastolic, mean arterial pressures, and electrocardiographic data were analysed.1H-qNMR and LC-MS were used to assess the chemical composition. L. alba extract had significant hypotensive effects on systolic, diastolic, and mean arterial pressure. Acteoside was identified as major compound (292.6 ± 2.7 mg/g). Sixty-one other compounds were tentatively identified, mainly phenylethanoids, flavonoids, and iridoids. L. alba extract reduces systolic, diastolic, mean arterial pressure, and appears to be associated with a reduction in heart rate. Acteoside, a known hypotensive compound, may be responsible for these effects, but other structurally similar minority compounds may also contribute.

Anti-oxidative mesoporous polydopamine-based hypotensive nano-eyedrop for improved glaucoma management

Conventional hypotensive eye drops remain suboptimal for glaucoma management, primarily due to their limited intraocular bioavailability and the growing concern regarding ocular surface side effects. Therefore, there is an urgent need to develop innovative intraocular pressure (IOP)-lowering formulations that not only possess enhanced corneal penetration ability but also provide ocular surface protection. Herein, anti-oxidative mesoporous polydopamine nanoparticles (MPDA NPs) were explored as a nano-carrier for Brimonidine to address the above issues. Nearly monodisperse MPDA NPs with obvious nanopores were successfully prepared by template-removal method and used for encapsulation of Brimonidine benefiting from their high specific surface area. Interestingly, the PEGylated and drug loaded MPDA-PEG@Brim NPs showed a near neutral surface charge, which is expected to enhance intraocular drug delivery. Consequently, much higher concentration of Brimonidine in the aqueous humor was found after topical administration of MPDA-PEG@Brim nano-dispersion as compared to free Brimonidine solution. Accordingly, superior IOP reduction effect was achieved for the nano-formulation in both hypertensive and normotensive rat eyes. Moreover, MPDA-PEG NPs showed good capability in scavenging diverse free radicals, alleviating intracellular oxidative stress, and mitigating ocular surface oxidative level in a mouse model of preservative-induced dry eye. In addition, the excellent biosafety of this novel Brimonidine nanodrug was confirmed both in vitro and in vivo. Therefore, the present work may shed light on the development of next generation hypotensive formulations for extended ocular surface protection and glaucoma management.

Modulation of left ventricular hypertrophy in spontaneously hypertensive rats by acetylcholinesterase and ACE inhibitors: physiological, biochemical, and proteomic studies

BackgroundThe consequences at the molecular level and the mechanisms involved in a possible cardioprotective effect of antihypertensive treatment are not yet fully understood. Here, the efficacy of pyridostigmine (PYR) and trandolapril (TRA) as antihypertensive and antihypertrophic agents was investigated and compared in hypertensive SHR and normotensive WKY rats. In parallel, we investigated the effects of these drugs on myocardial β-adrenergic and cholinergic signaling pathways and protein expression profiles.MethodsAge-matched male SHR and WKY rats were chronically (8 weeks) treated with PYR or TRA in drinking water. Blood pressure (BP) and heart rate (HR) were monitored telemetrically prior to tissue sampling for biochemical analysis. Baroreceptor reflex sensitivity (BRS) and methylatropine HR response as a measure of vagal tone were evaluated in separate groups of animals.ResultsPYR slightly lowered BP and HR in SHR rats during the dark phase of the day, while TRA effectively reduced BP during the light and dark phases without affecting HR. PYR enhanced BRS and improved vagal tone. There were no significant alterations in myocardial β-adrenergic and cholinergic signaling, with the exception of decreased forskolin-stimulated adenylyl cyclase (AC) activity in SHR rats, which was restored by TRA. Proteomic analysis revealed numerous differences induced by both treatments. Notable were changes in TGFβ-related signaling pathways as well as proteins involved in modifying hemodynamic parameters and cardiac hypertrophy.ConclusionsPYR is able to slightly decrease BP and HR in SHR rats but effectively increase BRS through vagal potentiation. The specific differences in protein expression profiles in rat myocardium induced by treatment with PYR and TRA reflect different mechanisms of action of these two agents at the molecular level.

P178 CENTRAL OR PERIPHERAL INJECTION OF A FORMULATION CONTAINING THE ANGIOTENSINERGIC DIPEPTIDE ASP-ARG REDUCES ARTERIAL PRESSURE AND CARDIAC INOTROPY IN HYPERTENSIVE RATS

Background and objective: Acute injection of Angiotensin 1-2 [Ang-(1-2)] reduced arterial pressure and heart rate, and improved coronary perfusion in normotensive and hypertensive rats. Formulations that confer stability and protection against proteolysis are requisites to the feasibility peptides. Next, we evaluated in rats the cardiovascular effects of peripheral or central injections of a complex containing Ang-(1-2) surrounded by a cyclodextrin. Methods: Ethics committee approval by CEUA-FOAr/UNESP 15/2022. We used male Holtzman rats that underwent 2 kidneys, 1 clip (2K1C) hypertension or sham surgery. Six weeks later, rats were separated in different experimental sets (n=4-6 per group) and were instrumented for intracerebroventricular (i.c.v.) and intravenous (i.v.) injections while recording arterial and cardiac left ventricular pressures. The dipeptide was injected i.c.v. (1, 25, 50 and 250pmol/2 μL) or i.v. (25mmol/0.1 mL). Results: dipeptide i.c.v. (25, 50 or 250pmol) reduced arterial pressure of normotensive rats (Δ=-20±3, -20±1 and -18±7mmHg respectively, P&lt;0.05 vs. baseline). In 2K1C, the antihypertensive effect was observed at all doses (Δ=-19±4, -26±5, -19±3 and -17±1mmHg respectively, P&lt;0.05 vs. baseline). I.v. injection of the dipeptide evoked slight increase in arterial pressure (Δ=7±3mmHg; P&lt;0.05 vs. baseline) that was accompanied by a positive inotropic effect (Δ=524±159mmHg/s; P&lt;0.05 vs. baseline). In 2K1C, this same injection reduced arterial and ventricular pressures (Δ=-14±4 and -20±1mmHg respectively, P&lt;0.05 vs. baseline), and caused negative inotropy (ΔLVdP/dtmax=-1140±170mmHg/s; P&lt;0.05 vs. baseline). I.c.v. injection of dipeptide in anesthetized normotensive rats discretely increased arterial and ventricular pressures, while in 2K1C group it reduced arterial and ventricular pressures (Δ=-17±3 and -18±4mmHg respectively, P&lt;0.05 vs. baseline). The ratio between the variations in contractility and mean arterial pressure revealed afterload-independent inotropic effects, i.e, the dipeptide directly affects heart performance of 2K1C. Conclusions: The formulation containing Asp1-Arg2 reduces arterial pressure and modulates cardiac function during hypertension. Whether Ang-(1-2) acts through some antagonism on Angiotensin II receptors or other paths remain to be investigated. Support: CONFAP-FAPESP/FAPEG 2019/24154-3, PROPe-UNESP 13/2022, CNPq-404079/2021-0 and FAPEG-202310267000206.

P181 AGE-RELATED CHANGES IN THE PROTECTIVE AXIS OF THE RENIN-ANGIOTENSIN SYSTEM IN THE BRAIN OF NORMOTENSIVE AND SPONTANEOUSLY HYPERTENSIVE RATS

Background and Objective. Aging is a major risk factor for the development of hypertension, that leads to end organ damage and cognitive dysfunction. The axis of the renin-angiotensin system composed of angiotensin (Ang) (1-7) the Mas receptor (MasR) and angiotensin converting enzyme 2 (ACE2) plays a cerebroprotective role by increasing blood flow, angiogenesis and improving cognitive function among others. Evidence on the expression of this axis with age is limited. We investigated Ang-(1-7)/Mas/ACE2 axis in different areas of the brain from normotensive and spontaneously hypertensive rats (SHR). Methods. Hypothalamus (HT), brainstem (BS), hippocampus (HC) and cerebral cortex (CC) were isolated from Wistar normotensive rats and SHR of 1, 3 and 12 months. Ang-(1-7) levels were measured by radioimmunoassay and ACE2 and MasR abundance was determined by immunoblotting. Results. Ang-(1-7) levels decreased with age in all the areas from normotensive rats and in CC from SHR, while it increased from 1 to 3 months but then decreased at 12 months in BS, HC and HT from SHR. There was no difference in Ang-(1-7) levels between normotensive and SHR except at 1 month of age where Ang-(1-7) levels were lower in BS, HC and HT but the same in CC from SHR compared to normotensive rats. MasR and ACE2 expression did not change with age in all the investigated areas from normotensive rats and in CC from SHR. However, MasR and ACE2 increased with age in HC from SHR and they were higher than in normotensive rats. Conclusions. Our results showed changes in the expression of the brain Ang-(1-7)/Mas/ACE2 axis which may contribute to deleterious functions observed in the brain with age.

Abstract P300: Modulation of Osmolyte Levels by ACE Inhibitors and SGLT-2 Inhibitors in Normotensive Rats

Hypertension is associated with disturbances in the water-electrolyte balance, leading to changes in osmotic pressure. Osmolytes, such as taurine among other compounds, play a critical role in maintaining cellular integrity under osmotic stress. This study evaluated the effects of ACE inhibitors (ACE-I) and SGLT-2 inhibitors (SGLT2i) on osmolyte homeostasis. Twelve-week-old male Sprague-Dawley (SD, n = 38) rats were divided into five groups: control (water), low and high doses of canagliflozin, and low and high doses of captopril. Metabolic studies were conducted in metabolic cages. Using liquid chromatography coupled with mass spectrometry (LC-MS), we measured osmolyte concentrations in blood, urine, kidney, liver and heart tissues. The obtained results demonstrated significant increases in liver taurine concentrations (13.34 ± 1.39 vs. 10.49 ± 1.45, p=0.029) and urinary taurine excretion (25.08 ± 2.81 vs. 16.54 ± 3.77, p=0.001) in the high-dose canagliflozin group compared to controls. Both treatments enhanced the total urinary excretion of L-alanine, β-alanine, choline, glycine, taurine, and carnitine. Additionally, canagliflozin increased the excretion of betaine and glycerophosphorylcholine (GPC). A reduction in serum β-alanine was noted in the captopril-treated rats. These findings highlight the novel effects of SGLT-2 inhibitors and ACE-I on osmolyte levels in normotensive rats, suggesting potential mechanisms contributing to their cardioprotective effects. Further research is required to elucidate the clinical significance of osmolyte changes in enhancing the protective effects of these drug classes.