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Increased fructose consumption induces metabolic-syndrome-like pathologies and modulates vasoactivity and the participation of nitric oxide (NO) and hydrogen sulfide (H2S). We investigated whether a slow-releasing H2S donor, GYY-4137, could exert beneficial activity in these conditions. We examined the effect of eight weeks of fructose intake on the blood pressure, biometric parameters, vasoactive responses, and NO and H2S pathways in fructose-fed spontaneously hypertensive rats with or without three weeks of GYY-4137 i.p. application. GYY-4137 reduced triacylglycerol levels and blood pressure, but not adiposity, and all were increased by fructose intake. Fructose intake generally enhanced endothelium-dependent vasorelaxation, decreased adrenergic contraction, and increased protein expression of interleukin-6 (IL-6), tumor necrosis factor alpha (TNFα), and concentration of conjugated dienes in the left ventricle (LV). Although GYY-4137 administration did not affect vasorelaxant responses, it restored disturbed contractility, LV oxidative damage and decreased protein expression of TNFα in fructose-fed rats. While the participation of endogenous H2S in vasoactive responses was not affected by fructose treatment, the expression of H2S-producing enzyme cystathionine β-synthase in the LV was increased, and the stimulation of the NO signaling pathway improved endothelial function in the mesenteric artery. On the other hand, chronic treatment with GYY-4137 increased the expression of H2S-producing enzyme cystathionine γ-lyase in the LV and stimulated the beneficial pro-relaxant and anti-contractile activity of endogenous H2S in thoracic aorta. Our results suggest that sulfide and nitroso signaling pathways could trigger compensatory vasoactive responses in hypertensive rats with metabolic disorder. A slow H2S-releasing donor could partially amend metabolic-related changes and trigger beneficial activity of endogenous H2S.

Reactive oxygen species are an important element of redox regulation in cells and tissues. During physiological processes, molecules undergo chemical changes caused by reduction and oxidation reactions. Free radicals are involved in interactions with other molecules, leading to oxidative stress. Oxidative stress works two ways depending on the levels of oxidizing agents and products. Excessive action of oxidizing agents damages biomolecules, while a moderate physiological level of oxidative stress (oxidative eustress) is necessary to control life processes through redox signaling required for normal cellular operation. High levels of reactive oxygen species (ROS) mediate pathological changes. Oxidative stress helps to regulate cellular phenotypes in physiological and pathological conditions. Nrf2 (nuclear factor erythroid 2-related factor 2, NFE2L2) transcription factor functions as a target nuclear receptor against oxidative stress and is a key factor in redox regulation in hypertension and cardiovascular disease. Nrf2 mediates transcriptional regulation of a variety of target genes. The Keap1-Nrf2-ARE system regulates many detoxification and antioxidant enzymes in cells after the exposure to reactive oxygen species and electrophiles. Activation of Nrf2/ARE signaling is differentially regulated during acute and chronic stress. Keap1 normally maintains Nrf2 in the cytosol and stimulates its degradation through ubiquitination. During acute oxidative stress, oxidized molecules modify the interaction of Nrf2 and Keap1, when Nrf2 is released from the cytoplasm into the nucleus where it binds to the antioxidant response element (ARE). This triggers the expression of antioxidant and detoxification genes. The consequence of long-term chronic oxidative stress is activation of glycogen synthase kinase 3beta (GSK-3beta) inhibiting Nrf2 activity and function. PPARgamma (peroxisome proliferator-activated receptor gamma) is a nuclear receptor playing an important role in the management of cardiovascular diseases, hypertension and metabolic syndrome. PPARgamma targeting of genes with peroxisome proliferator response element (PPRE) has led to the identification of several genes involved in lipid metabolism or oxidative stress. PPARgamma stimulation is triggered by endogenous and exogenous ligands - agonists and it is involved in the activation of several cellular signaling pathways involved in oxidative stress response, such as the PI3K/Akt/NOS pathway. Nrf2 and PPARgamma are linked together with their several activators and Nrf2/ARE and PPARgamma/PPRE pathways can control several types of diseases.

Dim light at night (dLAN) has become a pervasive part of the modern world, and growing evidence shows its association with increased health risks. Though this link is attributed to a disturbed circadian clock, the underlying mechanisms that can explain how circadian disruption from dLAN causes negative health effects remain unclear. Here, we exposed rats to a light–dark cycle (12:12 h) with low-intensity light at night (~2 lx) for 2 and 5 weeks and explored the steady-state pattern of circulating immune cells and renal immune-related markers, which are well controlled by the circadian clock. After 5 weeks, dLAN impaired the daily variation in several types of white blood cells, especially monocytes and T cells. Two-week dLAN caused a reduction in blood monocytes and altered gene expression of macrophage marker Cd68 and monocyte-attracting chemokine Ccl2 in the kidney. Interestingly, dLAN decreased renal 3-nitrotyrosine levels and resulted in up-regulation of the main endogenous antioxidant pathways, indicating a disturbance in the renal redox balance and an activation of compensatory mechanisms. These effects paralleled the altered renal expression of the molecular clock components and increased plasma corticosterone levels. Together, our results show that chronic exposure to dLAN weakened the circadian control of daily variation of circulating immune cells and disturbed renal immune and redox homeostasis. Consequences of this dLAN-disturbed immune balance on the ability of the immune system to cope with other challenges should by clarified in further studies.

The aim of this study was to evaluate the mutual relationship among perivascular adipose tissue (PVAT) and endogenous and exogenous H2S in vasoactive responses of isolated arteries from adult normotensive (Wistar) rats and hypertriglyceridemic (HTG) rats, which are a nonobese model of metabolic syndrome. In HTG rats, mild hypertension was associated with glucose intolerance, dyslipidemia, increased amount of retroperitoneal fat, increased arterial contractility, and endothelial dysfunction associated with arterial wall injury, which was accompanied by decreased nitric oxide (NO)-synthase activity, increased expression of H2S producing enzyme, and an altered oxidative state. In HTG, endogenous H2S participated in the inhibition of endothelium-dependent vasorelaxation regardless of PVAT presence, on the other hand, aortas with preserved PVAT revealed a stronger anticontractile effect mediated at least partially by H2S. Although we observed a higher vasorelaxation induced by exogenous H2S donor in HTG rats than in Wistar rats, intact PVAT subtilized this effect. We demonstrate that, in HTG rats, endogenous H2S could manifest a dual effect depending on the type of triggered signaling pathway. H2S within the arterial wall contributes to endothelial dysfunction. On the other hand, PVAT of HTG is endowed with compensatory vasoactive mechanisms, which include stronger anti-contractile action of H2S. Nevertheless, the possible negative impact of PVAT during hypertriglyceridemia on the activity of exogenous H2S donors needs to be taken into consideration.

Deficiency of nitric oxide (NO) and oxidative stress can be a cause, a consequence, or, more often, a potentiating factor for hypertension and hypertensive renal disease. Both NO and superoxide anions are radical molecules that interact with each other, leading to oxidative damage of such organs as the kidney. In the present study, we investigated the effect of chronic-specific (neuronal NOS inhibition) and nonspecific NOS inhibition on the oxidative state and antioxidant response and associated oxidative damage of the kidney of young normotensive and hypertensive rats. Young male normotensive Wistar rats (WRs, age 4 weeks) and spontaneously hypertensive rats (SHRs, age 4 weeks) were divided into three groups for each strain by the type of administered compounds. The first group was treated with 7-nitroindazole (WR+7-NI; SHR+7-NI), the second group was treated with N(G)-nitro-L-arginine-methyl ester (WR+L-NAME; SHR+L-NAME), and the control group was treated with pure drinking water (WR; SHR) continuously for up to 6 weeks. Systolic blood pressure increased in WR+L-NAME after the first week of administration and increased slightly in SHR+L-NAME in the third week of treatment. 7-NI had no effect on blood pressure. While total NOS activity was not affected by chronic NOS inhibition in any of the WR groups, it was attenuated in SHR+7-NI and SHR+L-NAME. Nitration of proteins (3-nitrotyrosine expression) was significantly reduced in WR+7NI but not in WR+L-NAME and increased in SHR+7-NI and SHR+L-NAME. Immunoblotting analysis of SOD isoforms showed decreased SOD2 and SOD3 expressions in both WR+7-NI and WR+L-NAME followed by increased SOD activity in WR+L-NAME. Conversely, increased expression of SOD2 and SOD3 was observed in SHR+L-NAME and SHR+7-NI, respectively. SOD1 expression and total activity of SOD did not change in the SHR groups. Our results show that the antioxidant defense system plays an important role in maintaining the oxidative state during NO deficiency. While the functioning antioxidant system seeks to balance the oxidation state in the renal cortex of normotensive WRs, the impaired antioxidant activity leads to the development of oxidative damage of proteins in the kidney induced by peroxynitrite in SHRs.

The peroxisome proliferator-activated receptors (PPAR) belong to the nuclear superfamily of ligand-activated transcription factors. PPARγ acts as a nutrient sensor that regulates several homeostatic functions. Its disruption can lead to vascular pathologies, disorders of fatty acid/lipid metabolism and insulin resistance. PPARγ can modulate several signaling pathways connected with blood pressure regulation. Firstly, it affects the insulin signaling pathway and endothelial dysfunction by modulation of expression and/or phosphorylation of signaling molecules through the PI3K/Akt/eNOS or MAPK/ET-1 pathways. Secondly, it can modulate gene expression of the renin- angiotensin system – cascade proteins, which potentially slow down the progression of atherosclerosis and hypertension. Thirdly, it can modulate oxidative stress response either directly through PPAR or indirectly through Nrf2 activation. In this context, activation and functioning of PPARγ is very important in the regulation of several disorders such as diabetes mellitus, hypertension and/or metabolic syndrome.

Inhibition of nitric oxide (NO) production can influence blood pressure regulation and increase hypertension. Asymmetric dimethylarginine, ADMA, an analogue of L-arginine, can inhibit NO synthesis, impair endothelial function, and is a risk marker of cardiovascular diseases. Homocysteine (Hcy) level affects oxidative stress production of reactive oxygen species (ROS) in hypertension and also influences changes in signaling and cell damage. The present study was focused on experimental effects of exogenous NOS inhibitors and their effect on ADMA, an endogenous NOS inhibitor, homocysteine and ROS production measured as reactive oxidative metabolites (ROM). We compared effects of the two potential exogenous NO-inhibitors: NG-nitro L-arginine methyl ester (L-NAME) and 7-nitroindazole (7-NI). Levels of ADMA, Hcy, ROM and total thiols (TTL) were not changed in the L-NAME group. With 7-NI administration, we observed unchanged NOS activity in the left ventricle and a pronounced decrease of ADMA and Hcy levels, accompanied by ROM over-production in plasma. TTL/ROM ratio was more favorable than in the L-NAME group. We observed that 7-NI, an exogenous NOinhibitor, can decrease and improve the levels of ADMA, Hcy, and ROM, and increase TTL/ROM ratio in the plasma of spontaneously hypertensive rats.

Although the role of nitric oxide (NO) in essential hypertension is still unclear, the effects of long-term NO deficiency have not yet been investigated during the critical juvenile period in spontaneously hypertensive rats (SHR). We aimed to analyze the effects of chronic NO synthase (NOS) inhibition on systolic blood pressure (sBP), vasoactivity, morphological changes and superoxide level in the thoracic aorta (TA), NOS activity in different tissues, and general biomarkers of oxidative stress in plasma of young SHR. Four-week-old SHR were treated with NG-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg/day, p.o.) for 4-5 weeks. L-NAME treatment induced a transient sBP increase only, and surprisingly, slightly inhibited endothelium-dependent relaxation of TA. Hereby, the inhibition of NOS activity varied from tissue to tissue, ranging from the lowest in the TA and the kidney to the highest in the brain stem. In spite of an increased sensitivity of adrenergic receptors, the maximal adrenergic contraction of TA was unchanged, which was associated with changes in elastin arrangement and an increase in wall thickness. The production of reactive oxygen species in the TA was increased; however, the level of selected biomarkers of oxidative stress did not change. Our findings proved that the TA of young SHR responded to chronic NO deficiency by the development of adaptive mechanisms on the functional (preserved NO-derived vasorelaxation, unincreased contraction) and molecular (preserved NOS activity) level.

Background The brain stem contains important nuclei that control cardiovascular function via the sympathetic nervous system (SNS), which is strongly influenced by nitric oxide. Its biological activity is also largely determined by oxygen free radicals. Despite many experimental studies, the role of AT1R-NAD(P)H oxidase-superoxide pathway in NO-deficiency is not yet sufficiently clarified. We determined changes in free radical signaling and antioxidant and detoxification response in the brain stem of young and adult Wistar rats during chronic administration of exogenous NO inhibitors. Methods Young (4 weeks) and adult (10 weeks) Wistar rats were treated with 7-nitroindazole (7-NI group, 10 mg/kg/day), a specific nNOS inhibitor, with NG-nitro-L-arginine-methyl ester (L-NAME group, 50 mg/kg/day), a nonspecific NOS inhibitor, and with drinking water (Control group) during 6 weeks. Systolic blood pressure was measured by non-invasive plethysmography. Expression of genes (AT1R, AT2R, p22phox, SOD and NOS isoforms, HO-1, MDR1a, housekeeper GAPDH) was identified by real-time PCR. NOS activity was detected by conversion of [3H]-L-arginine to [3H]-L-citrulline and SOD activity was measured using UV VIS spectroscopy. Results We observed a blood pressure elevation and decrease in NOS activity only after L-NAME application in both age groups. Gene expression of nNOS (youngs) and eNOS (adults) in the brain stem decreased after both inhibitors. The radical signaling pathway triggered by AT1R and p22phox was elevated in L-NAME adults, but not in young rats. Moreover, L-NAME-induced NOS inhibition increased antioxidant response, as indicated by the observed elevation of mRNA SOD3, HO-1, AT2R and MDR1a in adult rats. 7-NI did not have a significant effect on AT1R-NADPH oxidase-superoxide pathway, yet it affected antioxidant response of mRNA expression of SOD1 and stimulated total activity of SOD in young rats and mRNA expression of AT2R in adult rats. Conclusion Our results show that chronic NOS inhibition by two different NOS inhibitors has age-dependent effect on radical signaling and antioxidant/detoxificant response in Wistar rats. While 7-NI had neuroprotective effect in the brain stem of young Wistar rats, L-NAME- induced NOS inhibition evoked activation of AT1R-NAD(P)H oxidase pathway in adult Wistar rats. Triggering of the radical pathway was followed by activation of protective compensation mechanism at the gene expression level. Electronic supplementary material The online version of this article (doi:10.1186/s12929-017-0366-4) contains supplementary material, which is available to authorized users.

Blood pressure (BP) is one of the principal vital signs. The regulation of normal BP is critical for maintaining the normal functioning of an organism. The structure of the BP regulation in vertebrates, including humans, is very complex and it is not yet fully understood. There are several BP regulation subsystems which interact together. In this study, we analysed and modelled the role of the most important BP regulation systems (sympathetic nervous system, renin-angiotensin-aldosterone system, L-Arginine/nitric oxide) as well as the role of reactive oxygen species, the imbalance of which is implied in the development of hypertension disease. Our aim is to design a dynamic model of the BP regulation in normotensive rats, which can help us better understand the complex process of BP regulation. The BP responses were measured in conscious rats after acute stress with or without the application of selected drugs, which can inhibit particular regulation subsystems. Linear dynamic models of particular regulation subsystems were identified using genetic algorithms. Each subsystem is a feedback loop, which contains both the system dynamics and the controller. We describe the simulation-based identification procedure of these particular models as well as of the entire BP regulation system.

This study investigated the influence of chronic crowding stress on nitric oxide (NO) production, vascular function and oxidative status in young Wistar-Kyoto (WKY), borderline hypertensive (BHR) and spontaneously hypertensive (SHR) female rats. Five-week old rats were exposed to crowding for two weeks. Crowding elevated plasma corticosterone(P<0.05)and accelerated BP (P<0.01versus basal) only in BHR. NO production and superoxide concentration were significantly higher in the aortas of control BHR and SHR versus WKY. Total acetylcholine (ACh)-induced relaxation in the femoral artery was reduced in control SHR versus WKY and BHR, and stress did not affect it significantly in any genotype. The attenuation of ACh-induced relaxation in SHR versus WKY was associated with reduction of its NO-independent component. Crowding elevated NO production in all strains investigated but superoxide concentration was increased only in WKY, which resulted in reduced NO-dependent relaxation in WKY. In crowded BHR and SHR, superoxide concentration was either unchanged or reduced, respectively, but NO-dependent relaxation was unchanged in both BHR and SHR versus their respective control group. This study points to genotype-related differences in stress vulnerability in young female rats. The most pronounced negative influence of stress was observed in BHR despite preserved endothelial function.

Asymmetric dimethylarginine (ADMA) can elevate inhibition of NO synthesis as a risk marker of cardiovascular diseases. Reactive oxygen metabolites (ROM) inhibit elevated ADMA level and is connected with homocysteine (Hcy). In our study we focused on ADMA and Hcy level changes and ROM in plasma of young spontaneously hypertensive rats (SHR) in chronic treatment by NO-sythase inhibitors (L-NAME and 7-nitroindazole). HPLC method with fluorescence detection has been used to analyse the levels of ADMA. Detection of Hcy has been measured by UV absorbance 340 nm (Analytx, Slovakia). Reactive oxygen metabolites – dROMs assay and Total thiols levels -TTL assay and TTL vs. ROM level in plasma was detected by clinical autoanalyzer UnicelDxC 800 (Beckman-Coulter, Netherlands). ADMA level, Hcy level, ROM and TTL has not been changed in the L-NAME. In 7-NI group was observed markedly decrease the ADMA overproduction, which was correlated with Hcy level decrease and redox status of ROM in plasma. Changes among total TTL and ROM production (TTL/ROM) has been improved redox level in 7-NI group comparing to L-NAME. It has been observed that 7-NI can influence decrease of ADMA,=Hcy, ROS level and improved TTL/ROM in SHR.

Endogenous and exogenous testosterone affects several behavioural traits as shown in human and animal studies. The effects of testosterone can be mediated via androgen or oestrogen receptors, but also via rapid non-genomic effects. The aim of this study was to evaluate whether a single testosterone injection has effects, mediated via the androgen receptor, on anxiety in intact male rats. We hypothesised that administration of testosterone will have an anxiolytic effect, mediated by the androgen receptor. Intact adult male Wistar rats were divided into groups: control, flutamide, testosterone and testosterone with flutamide. Testosterone and flutamide (as an androgen receptor blocker) were applied once, intramuscularly, at a dose of 5mg/kg. Twenty four hours later, rats underwent the following behavioural tests to analyse anxiety: open field test, elevated plus maze and light-dark box. Testosterone was measured in plasma to confirm elevated levels in groups that received testosterone. The levels of testosterone were 2.5-3 fold higher amongst rats administered with testosterone compared to controls. Flutamide did not affect plasma testosterone concentrations. Testosterone administration had no effect on anxiety in the open field and elevated plus maze. In the light-dark transition task, testosterone increased the time spent in the light part of the maze by 80%, an effect which was blocked by flutamide, and which was in support of our hypothesis. Flutamide-treated rats spent more time in the central square of the open field. Using the light-dark box we have shown that a single injection of testosterone decreases anxiety in adult male rats. This effect of increased testosterone was mediated via the androgen receptor as flutamide blocked the anxiolytic effect of exogenous testosterone. Treatment with flutamide blocked the effects of endogenous testosterone and had anxiolytic effects in the open field, suggesting a non-linear relationship between genomic effects of T and anxiety.

The results from different authors regarding testosterone and cognitive research show controversial results. One of the reasons may be the form of testosterone used in the experiment. The aim of our study was to evaluate the testosterone levels in plasma and its kinetics after the single application of either a long-acting or a short-acting form of this hormone. Twenty female and twenty male adult Wistar rats were divided into two groups that were either gonadectomized or not. The two groups were divided into 4 subgroups depending on whether the animals received testosterone propionate or testosterone isobutyrate intramuscularly. Samples for analysis were collected before and at 2, 4, 24, 48, 72, 96 and 168 h after injection. The results showed significant differences in the dynamics between rapid and depot forms of testosterone, together with the rebound effect and hormonal negative feedback. These aspects of testosterone kinetics need to be considered when planning experiments on the physiology of testosterone.

PPARγ plays an important role in kidney physiology of cardiovascular system, contributes in hypertension and signaling pathways. In our study we focused on the effect of PPARγ agonist pioglitazone (PIO) on the RAS, redox regulation, NOS activities, redox regulation and ADMA levels in two models of young borderline hypertensive (BHR) and spontaneously hypertensive (SHR) rats. Gene expression was detected by qRT-PCR. Protein level was determined using Western blot analysis. Superoxide dismutase (SOD) and nitric oxide synthase (NOS) activities was determined spectrophotometrically and with radioactive method. ADMA levels has been analysed by HPLC method with fluorescence detection. PIO decreased (in BHR) and slowed blood pressure development (in SHR). Gene and protein expressions of NOS isoforms and total NOS activities was improved in both experimental rats and affected ADMA changes. In AT1R/NADPH - oxidase pathway the treatment was not significantly influenced, but mRNA expression in Mas, AT2R receptors and redox regulation (Nrf2 and SOD isoforms) was up-regulated. The largest effect of PPARγ has been observed in SOD1, SOD3 and Mas receptor genes in different way: SOD1 was increased in SHR and Mas receptor in BHR rats.

Dysregulation of redox- sensitive signaling plays an important role in develompment of hypertension. PPAR gamma belongs to nuclear receptors and is a potent nutritional sensor and redox regulator. In our study we focused on the role of PPAR gamma activation of RAS/ROS regulation, and antioxidant response in spontaneously hypertensive rats (SHR). Treatment was performed by gavage with PPAR gamma agonist pioglitazone (PIO - 10 mg/kg/day, 10 days). Treatment with PPAR gamma agonist PIO in influenced blood pressure, redox- sensitive responses, lipid profile and homocystein level in age- dependent manner. The improvement parameters in hypertension and redox regulation have been observed in young animals, but not in adult SHR rats. PIO treatment influenced redox regulation (gene expression of Nrf2 and SOD isoforms) correlated with SOD a CAT activity and NO bioavailibility. PPAR gamma activation has been corelated with downregulation of and AT1R - RAS axis and „up-regulation“ of AT2R and Mas receptor. This most sensitive tissue responses in RAS/ROS signaling and NO level have been found primary in kidney of young hypertensive rats.

PPARγ receptor plays an important role in oxidative stress response. Its agonists can influence vascular contractility in experimental hypertension. Our study was focused on the effects of a PPARγ agonist pioglitazone (PIO) on blood pressure regulation, vasoactivity of vessels, and redox-sensitive signaling at the central (brainstem, BS) and peripheral (left ventricle, LV) levels in young prehypertensive rats. 5-week-old SHR were treated either with PIO (10 mg/kg/day, 2 weeks) or with saline using gastric gavage. Administration of PIO significantly slowed down blood pressure increase and improved lipid profile and aortic relaxation after insulin stimulation. A significant increase in PPARγ expression was found only in BS, not in LV. PIO treatment did not influence NOS changes, but had tissue-dependent effect on SOD regulation and increased SOD activity, observed in LV. The treatment with PIO differentially affected also the levels of other intracellular signaling components: Akt kinase increased in the the BS, while β-catenin level was down-regulated in the BS and up-regulated in the LV. We found that the lowering of blood pressure in young SHR can be connected with insulin sensitivity of vessels and that β-catenin and SOD levels are important agents mediating PIO effects in the BS and LV., PPAR Research, 2013, ISSN:1687-4757, ISSN:1687-4765

Reactive oxygen species (ROS) are products of normal cellular metabolism and derive from various sources in different cellular compartments. Oxidative stress resultant from imbalance between ROS generation and antioxidant defense mechanisms is important in pathogenesis of cardiovascular diseases, such as hypertension, heart failure, atherosclerosis, diabetes, and cardiac hypertrophy. In this review we focus on hypertension and address sources of cellular ROS generation, mechanisms involved in regulation of radical homeostasis, superoxide dismutase isoforms in pathophysiology of hypertension; as well as radical intracellular signaling and phosphorylation processes in proteins of the affected cardiovascular tissues. Finally, we discuss the transcriptional factors involved in redox-sensitive gene transcription and antioxidant response, as well as their roles in hypertension.