The antihypertensive action of C-phycocyanin is related to the prevention of angiotensin II-caused vascular dysfunction in chronic kidney disease.

C-phycocyanin (CPC) is a photosynthetic protein found in Arthrospira maxima with a nephroprotective and antihypertensive activity that can prevent the development of hemodynamic alterations caused by chronic kidney disease (CKD). However, the complete nutraceutical activities are still unknown. This study aims to determine if the antihypertensive effect of CPC is associated with preventing the impairment of hemodynamic variables through delaying vascular dysfunction. Twenty-four normotensive male Wistar rats were divided into four groups: (1) sham + 4 mL/kg/d vehicle (100 mM of phosphate buffer, PBS) administered by oral gavage (og), (2) sham + 100 mg/kg/d og of CPC, (3) CKD induced by 5/6 nephrectomy (CKD) + vehicle, (4) CKD + CPC. One week after surgery, the CPC treatment began and was administrated daily for four weeks. At the end treatment, animals were euthanized, and their thoracic aorta was used to determine the vascular function and expression of AT1, AT2, and Mas receptors. CKD-induced systemic arterial hypertension (SAH) and vascular dysfunction by reducing the vasorelaxant response of angiotensin 1-7 and increasing the contractile response to angiotensin II. Also, CKD increased the expression of the AT1 and AT2 receptors and reduced the Mas receptor expression. Remarkably, the treatment with CPC prevented SAH, renal function impairment, and vascular dysfunction in the angiotensin system. In conclusion, the antihypertensive activity of CPC is associated with avoiding changes in the expression of AT1, AT2, and Mas receptors, preventing vascular dysfunction development and SAH in rats with CKD.

Sodium Hydrosulfide Reverts Chronic Stress-Induced Cardiovascular Alterations by Reducing Oxidative Stress.

ABSTRACT: Chronic stress induces a group of unrecognized cardiovascular impairments, including elevated hemodynamic variables and vascular dysfunction. Moreover, hydrogen sulfide (H 2 S), a gasotransmitter that regulates the cardiovascular system decreases under chronic stress. Thus, this study assessed the impact of sodium hydrosulfide (NaHS) (H 2 S donor) on chronic restraint stress (CRS)-induced cardiovascular changes. For that purpose, male Wistar rats were restrained for 2 hours a day in a transparent acrylic tube over 8 weeks. Then, body weight, relative adrenal gland weight, serum corticosterone, H 2 S-synthesizing enzymes, endothelial nitric oxide synthetize expression, reactive oxygen species levels, lipid peroxidation, and reduced glutathione-to-oxidized glutathione (GSH 2 :GSSG) ratio were determined in the thoracic aorta. The hemodynamic variables were measured in vivo by the plethysmograph method. The vascular function was evaluated in vitro as vasorelaxant responses induced by carbachol or sodium nitroprusside, and norepinephrine (NE)-mediated vasocontractile responses in the thoracic aorta. CRS increased (1) relative adrenal gland weight; (2) hemodynamic variables; (3) vasoconstrictor responses induced by NE, (4) reactive oxygen species levels, and (5) lipid peroxidation in the thoracic aorta. In addition, CRS decreased (1) body weight; (2) vasorelaxant responses induced by carbachol; (3) GSH content, and (4) GSH 2 :GSSG ratio. Notably, NaHS administration (5.6 mg/kg) restored hemodynamic variables and lipid peroxidation and attenuated the vasoconstrictor responses induced by NE in the thoracic aorta. In addition, NaHS treatment increased relative adrenal gland weight and the GSH 2 :GSSG ratio. Taken together, our results demonstrate that NaHS alleviates CRS-induced hypertension by reducing oxidative stress and restoring vascular function in the thoracic aorta.

Hydrogen sulfide ameliorates hypertension and vascular dysfunction induced by insulin resistance in rats by reducing oxidative stress and activating eNOS.

Hydrogen sulfide (H2S) is a gasotransmitter implied in metabolic diseases, insulin resistance, obesity, and type 2 Diabetes Mellitus. This study aimed to determine the effect of chronic administration of sodium hydrosulfide (NaHS; inorganic H2S donor), L-Cysteine (L-Cys; substrate of H2S producing enzymes) and DL-Propargylglycine (DL-PAG; cystathionine-gamma-lyase inhibitor) on the vascular dysfunction induced by insulin resistance in rat thoracic aorta. For this purpose, 72 animals were divided into two main sets that received: 1) tap water (control group; n = 12); and 2) fructose 15% w/v in drinking water [insulin resistance group (IR); n = 60] for 20 weeks. After 16 weeks, the group 2 was divided into five subgroups (n = 12 each), which received daily i. p. injections during 4 weeks of: 1) non-treatment (control); 2) vehicle (phosphate buffer saline; PBS, 1 ml/kg); 3) NaHS (5.6 mg/kg); 4) L-Cys (300 mg/kg); and (5) DL-PAG (10 mg/kg). Hemodynamic variables, metabolic variables, vascular function, ROS levels and the expression of p-eNOS and eNOS were determined. IR induced: 1) hyperinsulinemia; 2) increased HOMA-index; 3) decreased Matsuda index; 4) hypertension, vascular dysfunction, increased ROS levels; 5) increased iNOS, and 6) decreased CSE, p-eNOS and eNOS expression. Furthermore, IR did not affect contractile responses to norepinephrine. Interestingly, NaHS and L-Cys treatment, reversed IR-induced impairments and DL-PAG treatment decreased and increased the HOMA and Matsuda index, respectively. Taken together, these results suggest that NaHS and L-Cys decrease the metabolic and vascular alterations induced by insulin resistance by reducing oxidative stress and activating eNOS. Thus, hydrogen sulfide may have a therapeutic application.

NaHS restores the vascular alterations in the renin-angiotensin system induced by hyperglycemia in rats.

Hyperglycemia (HG) impairs the renin-angiotensin system (RAS), which may contribute to vascular dysfunction. Besides, hydrogen sulfide (H2S) exerts beneficial cardiovascular effects in metabolic diseases. Therefore, our study aimed to determine the effects of chronic administration of sodium hydrosulfide (NaHS; inorganic H2S donor) and DL-Propargylglycine [DL-PAG; cystathionine-×¥-lyase (CSE) inhibitor] on the RAS-mediated vascular responses impairments observed in thoracic aortas from male diabetic Wistar rats. For that purpose, neonatal rats were divided into two groups that received: 1) citrate buffer (n = 12) or 2) streptozotocin (STZ, 70 mg/kg; n = 48) on the third postnatal day. After 12 weeks, diabetic animals were divided into 4 subgroups (n = 12 each) that received daily i.p. injections during 4 weeks of: 1) non-treatment; 2) vehicle (PBS, 1 mL/kg); 3) NaHS (5.6 mg/kg); and 4) DL-PAG (10 mg/kg). After treatments (16 weeks), blood glucose, angiotensin-(1-7) [Ang-(1-7)], and angiotensin II (Ang II) levels, vascular responses to Ang-(1-7) and Ang II, and the expression of angiotensin AT1, AT2, and Mas receptors, angiotensin converting enzyme (ACE) and ACE type 2 (ACE2) were determined. HG induced: 1) increased blood glucose levels and expression of angiotensin II AT1 receptor; 2) impaired Ang-(1-7) and Ang II mediated vascular responses; 3) decreased angiotensin levels and expression of angiotensin II AT2 and angiotensin-(1-7) Mas receptors, and ACE2; and 4) no changes in ACE expression. Interestingly, NaHS, but not DL-PAG, reversed HG-induced impairments, except for blood glucose level changes. These results suggest that NaHS restores vascular function in streptozotocin-induced HG through RAS modulation.

Hydrogen sulfide prevents the vascular dysfunction induced by severe traumatic brain injury in rats by reducing reactive oxygen species and modulating eNOS and H2S-synthesizing enzyme expression.

AIM: To assess the effects of subchronic administration with NaHS, an exogenous H2S donor, on TBI-induced hypertension and vascular impairments. MAIN METHODS: Animals underweministration does not prevent the body weight loss but slightly imnt a lateral fluid percussion injury, and the hemodynamic variables were measured in vivo by plethysmograph method. The vascular function in vitro, the ROS levels by the DCFH-DA method and the expression of H2S-synthesizing enzymes and eNOS by Western blot were measured in isolated thoracic aortas at day 7 post-TBI. The effect of L-NAME on NaHS-induced effects in vascular function was evaluated. Brain water content was determined 7 days after trauma induction. Body weight was recorded throughout the experimental protocol, whereas the sensorimotor function was evaluated using the neuroscore test at days -1 (basal), 2, and 7 after the TBI induction. KEY FINDINGS: TBI animals showed: 1) an increase in hemodynamic variables and ROS levels in aortas; 2) vascular dysfunction; 3) sensorimotor dysfunction; and 4) a decrease in body weight, the expression of H2S-synthesizing enzymes, and eNOS phosphorylation. Interestingly, NaHS subchronic administration (3.1 mg/kg; i.p.; every 24 h for six days) prevented the development of hypertension, vascular dysfunction, and oxidative stress. L-NAME abolished NaHS-induced effects. Furthermore, NaHS treatment restored H2S-synthesizing enzymes and eNOS phosphorylation with no effect on body weight, sensorimotor impairments, or brain water content. SIGNIFICANCE: Taken together, these results demonstrate that H2S prevents TBI-induced hypertension by restoring vascular function and modulating ROS levels, H2S-synthesizing enzymes expression, and eNOS phosphorylation.

Hydrogen sulfide as a neuromodulator of the vascular tone.

Hydrogen sulfide (H2S) is a unique signaling molecule that, along with carbon monoxide and nitric oxide, belongs to the gasotransmitters family. H2S is endogenously synthesized by enzymatic and non-enzymatic pathways. Three enzymatic pathways involving cystathionine-γ-lyase, cystathionine-ß-synthetase, and 3-mercaptopyruvate sulfurtransferase are known as endogenous sources of H2S. This gaseous molecule has recently emerged as a regulator of many systems and physiological functions, including the cardiovascular system where it controls the vascular tone of small arteries. In this context, H2S leads to vasorelaxation by regulating the activity of vascular smooth muscle cells, endothelial cells, and perivascular nerves. Specifically, H2S modulates the functionality of different ion channels to inhibit the autonomic sympathetic outflow-by either central or peripheral mechanisms-or to stimulate perivascular sensory nerves. These mechanisms are particularly relevant for those pathological conditions associated with impaired neuromodulation of vascular tone. In this regard, exogenous H2S administration efficiently attenuates the increased activity of the sympathetic nervous system often seen in patients with certain pathologies. These effects of H2S on the autonomic sympathetic outflow will be the primary focus of this review. Thereafter, we will discuss the central and peripheral regulatory effects of H2S on vascular tone. Finally, we will provide the audience with a detailed summary of the current pathological implications of H2S modulation on the neural regulation of vascular tone.

Pharmacological evidence that potassium channels mediate hydrogen sulfide-induced inhibition of the vasopressor sympathetic outflow in pithed rats.

Hydrogen sulfide (H2S) is a gasotransmitter that modulates neurotransmission. Indeed, it has been recently demonstrated that H2S inhibits the sympathetic outflow in male rats, although the mechanisms remain elusive. Thus, this study evaluated the role of potassium channels on NaHS-induced sympathoinhibition. For this purpose, male and female Wistar rats were anesthetized, pithed, and cannulated. After that, animals received selective electrical stimulation of the vasopressor sympathetic outflow (T7-T9). Prior to 310 µg/kg·min NaHS i.v. continuous infusion animals received: (1) bidistilled water (tetraethylammonium, TEA; 4-aminopyridine, 4-AP; and barium chloride, BaCl2; vehicle; 1 ml/kg); (2) TEA (non-selective K+ channels blocker; 16.5 mg/kg); (3) 4-AP (non-selective voltage-dependent K+ channels blocker; 5 mg/kg); (4) BaCl2 (inward rectifier K+ channels blocker; 65 µg/kg); (5) DMF 5%, glucose 10% and NaOH 0.1 N (glibenclamide vehicle; 1 ml/kg); (6) glibenclamide (ATP-dependent K+ channels blocker; 10 mg/kg); (7) DMSO 4% (paxilline vehicle; 1 ml/kg); and (8) paxilline (large-conductance voltage- and Ca2+-activated K+ channel blocker; 90 µg/kg). The NaHS-induced sympathoinhibition was: (1) equally observed in male and female rats; (2) unaffected by vehicles; (3) reversed by the potassium channel blockers. Taken together, our results suggest that NaHS-induced sympathoinhibition does not depend on sex and it is mediated by the activation of several potassium channels.

Analysis of 16 studies in nine rodent models does not support the hypothesis that diabetic polyuria is a main reason of urinary bladder enlargement.

The urinary bladder is markedly enlarged in the type 1 diabetes mellitus model of streptozotocin-injected rats, which may contribute to the frequent diabetic uropathy. Much less data exists for models of type 2 diabetes. Diabetic polyuria has been proposed as the pathophysiological mechanism behind bladder enlargement. Therefore, we explored such a relationship across nine distinct rodent models of diabetes including seven models of type 2 diabetes/obesity by collecting data on bladder weight and blood glucose from 16 studies with 2-8 arms each; some studies included arms with various diets and/or pharmacological treatments. Data were analysed for bladder enlargement and for correlations between bladder weight on the one and glucose levels on the other hand. Our data confirm major bladder enlargement in streptozotocin rats and minor if any enlargement in fructose-fed rats, db/db mice and mice on a high-fat diet; enlargement was present in some of five not reported previously models. Bladder weight was correlated with blood glucose as a proxy for diabetic polyuria within some but not other models, but correlations were moderate to weak except for RIP-LCMV mice (r 2 of pooled data from all studies 0.0621). Insulin levels also failed to correlate to a meaningful extent. Various diets and medications (elafibranor, empagliflozin, linagliptin, semaglutide) had heterogeneous effects on bladder weight that often did not match their effects on glucose levels. We conclude that the presence and extent of bladder enlargement vary markedly across diabetes models, particularly type 2 diabetes models; our data do not support the idea that bladder enlargement is primarily driven by glucose levels/glucosuria.

Exogenous hydrogen sulfide restores CSE and CBS but no 3-MST protein expression in the hypothalamus and brainstem after severe traumatic brain injury.

Hydrogen sulfide (H2S) is a gasotransmitter endogenously synthesized by cystathionine-γ-lyase (CSE), cystathionine-ß-synthase (CBS), and 3-mercaptopiruvate sulfurtransferase (3-MST) enzymes. H2S exogenous administration prevents the development of hemodynamic impairments after traumatic brain injury (TBI). Since the hypothalamus and the brainstem highly regulate the cardiovascular system, this study aimed to evaluate the effect of NaHS subchronic treatment on the changes of H2S-sythesizing enzymes in those brain areas after TBI and in physiological conditions. For that purpose, animals were submitted to a lateral fluid percussion injury, and the changes in CBS, CSE, and 3-MST protein expression were measured by western blot at days 1, 2, 3, 7, and 28 in the vehicle group, and 7 and 28 days after NaHS treatment. After severe TBI induction, we found a decrease in CBS and CSE protein expression in the hypothalamus and brainstem; meanwhile, 3-MST protein expression diminished only in the hypothalamus compared to the Sham group. Remarkably, i.p. daily injections of NaHS, an H2S donor, (3.1 mg/kg) during seven days: (1) restored CBS and CSE but no 3-MST protein expression in the hypothalamus at day 28 post-TBI; (2) reestablished only CSE in brainstem 7 and 28 days after TBI; and (3) did not modify H2S-sythesizing enzymes protein expression in uninjured animals. Mainly, our results show that the NaHS effect on CBS and CSE protein expression is observed in a time- and tissue-dependent manner with no effect on 3-MST expression, which may suggest a potential role of H2S synthesis in hypothalamus and brainstem impairments observed after TBI.

Chronic administration of NaHS and L-Cysteine restores cardiovascular changes induced by high-fat diet in rats.

Hydrogen sulfide plays an important role in the regulation of the cardiovascular system, insulin secretion, and glucose homeostasis. The aim of the present study was to examine the effects of chronic treatment with sodium hydrosulfide (NaHS), L-Cysteine (L-Cys) and DL-Propargylglycine (DL-PAG) on the changes induced by a high-fat diet (HFD) in zoometric and metabolic variables as well as cardiovascular changes such as hypertension and sympathetic hyperactivity. For this purpose, male Wistar rats were fed a normal fat diet (NFD) or HFD for 12 weeks. Next, the HFD rats were divided into 5 subgroups which received daily i.p. injections during 4 weeks of: (1) nothing (no injection, Control); (2) vehicle (PBS; 1ml/kg); (3) NaHS (5.6 mg/kg); (4) L-Cys (300mg/kg); or (5) DL-PAG (1mg/kg). Then, an oral glucose tolerance test, hormone serum levels and blood pressure were determined. The cardiovascular responses to stimulation of the vasopressor sympathetic tone or intravenous administration of the agonists noradrenaline (α1/2-adrenoceptors), methoxamine (α1-adrenoceptors) and UK 14,304 (α2-adrenoceptors) were determined in pithed rats. Lastly, the heart, liver and adipose tissue were weighted. HFD significantly increased: (1) zoometric variables, which were decreased by NaHS and L-Cys; (2) metabolic variables, ameliorated by DL-PAG; (3) haemodynamic variables, which were reversed by NaHS and L-Cys; and (4) the vasopressor responses induced by sympathetic stimulation, which were diminished by NaHS and L-Cys. In conclusion, chronic treatment with NaHS and L-Cys are effective in reducing adipose tissue and ameliorating the cardiovascular changes induced by obesity; meanwhile, DL-PAG ameliorates metabolic variables.

Pharmacological evidence that metformin blocks the vasopressor responses mediated by stimulation of α1- and α2-adrenoceptors in pithed rats.

It has been reported that metformin reduces blood pressure although the mechanisms have not been described. Indeed, several mechanisms could be implicated including the interaction with α-adrenoceptors or inhibition of sympathetic outflow. Therefore, this study was designed to determine the capability of metformin to block the vasopressor responses induced by α1/2-adrenoceptor agonists or selective electrical stimulation of sympathetic outflow. For this purpose, Wistar male rats were anesthetized, pithed and cannulated for selective preganglionic stimulation of the vasopressor sympathetic outflow or drugs administration. The effect of i.v. bolus injection of metformin (180 and 310mg/kg) or its vehicle (bidistilled water) was studied on the vasopressor responses induced by: (1) selective sympathetic stimulation (0.03-3Hz); (2) exogenous noradrenaline (0.03-3µg/kg); (3) methoxamine (1-100µg/kg); and (4) UK 14,304 (0.1-30µg/kg). The tachycardic responses to noradrenaline were also investigated in presence of metformin. The vasopressor responses induced by selective electrical stimulation of sympathetic outflow were diminished by metformin (180 and 310mg/kg) and remained unchanged in presence of vehicle. Moreover, the vasopressor responses induced by exogenous noradrenaline, methoxamine and UK 14,304 were dose-dependently inhibited by i.v. bolus injections of metformin (180 and 310mg/kg) and were not affected by vehicle. Metformin practically did not block the tachycardic responses to noradrenaline except at the dose of 3µg/kg. Taken together, these results demonstrate that metformin is capable to block vascular α1/2-adrenoceptors but not cardiac ß-adrenoceptors. Thus, this mechanism could contribute, at least in part, on the hypotensive responses induced by metformin.

Pharmacological evidence that NaHS inhibits the vasopressor responses induced by stimulation of the preganglionic sympathetic outflow in pithed rats.

It has been reported that i.v. administration of NaHS, a donor of H2S, elicited dose-dependent hypotension although the mechanisms are not completely understood. In this regard, several mechanisms could be involved including the inhibition of the vasopressor sympathetic outflow. Thus, this study was designed to determine the potential capability of NaHS to mediate inhibition of the vasopressor responses induced by preganglionic sympathetic stimulation. For this purpose, Wistar rats were anaesthetised, pithed and cannulated for drug administration. In animals pre-treated with gallamine, the effect of i.v. infusion of NaHS (310 and 560µg/kgmin) or its vehicle (phosphate buffer) was determined on the vasopressor responses induced by: (1) sympathetic stimulation (0.03-10Hz); (2) i.v. bolus injections of exogenous noradrenaline (0.03-3µg/kg); or (3) methoxamine (1-100µg/kg). The vasopressor responses induced by preganglionic sympathetic stimulation were dose-dependently inhibited by i.v. infusion of NaHS (310 and 560µg/kgmin), but not by vehicle, particularly at high frequencies. In marked contrast, the vasopressor responses to exogenous noradrenaline or methoxamine were not inhibited by the above doses of NaHS or its vehicle. The above results, taken together, demonstrate that NaHS inhibited the vasopressor responses induced by preganglionic sympathetic outflow by a prejunctional mechanism. This is the first evidence demonstrating this effect by NaHS that may contribute, at least in part, to the hypotension induced by NaHS.