Behavioral alterations induced by post-weaning isolation rearing of rats are accompanied by reduced VGF/BDNF/TrkB signaling in the hippocampus.

Post-weaning social isolation has been shown to be a relevant animal model for studying the mechanisms underlying psychopathological states induced by early-life stressful experiences. Besides extensively studied brain-derived neurotrophic factor (BDNF) and tyrosine receptor kinase B (TrkB) receptor, increasing attention is being given to a neuropeptide precursor VGF (non-acronymic). Several lines of evidence indicate an interplay between the neurotrophins and nitric oxide signaling. This study investigated the long-term consequences of post-weaning social isolation on behavior, VGF/BDNF/TrkB pathway and two isoforms of nitric oxide synthase (NOS) in the hippocampus and examined whether these effects were sex-specific. Male and female Sprague-Dawley rats were reared either in social isolation or social groups from postnatal day 21 for 9 weeks (n = 12-15/group and sex). Post-weaning social isolation induced impairments in sensorimotor gating and increased anxiety-like behavior in rats of both sexes. These behavioral alterations were accompanied by attenuated gene expression of VGF and TrkB receptor in the hippocampus. Isolation-induced reduction in VGF gene expression was more evident in male isolates. Similar changes were found in neuronal NOS (nNOS) gene expression with reduced mRNA levels in male isolates. Gene expression of BDNF and inducible NOS was not influenced by isolation rearing or sex. In addition, sex-specific patterns of VGF and nNOS gene expression in the hippocampus with higher mRNA levels in males than in females were revealed. The present study demonstrates a relationship between nNOS, VGF, BDNF, and TrkB confirming a link between nitric oxide and neurotrophins signaling pathways. Our findings indicate that long-term post-weaning social isolation alters signaling via VGF/BDNF/TrkB and nNOS that could interfere with neurodevelopmental processes which may contribute to pathological behavioral symptoms in adulthood. Future studies are needed to support this suggestion since the direct mechanistic link has not been approached in this study.

Changes in the vasoactive effects of nitric oxide, hydrogen sulfide and the structure of the rat thoracic aorta: the role of age and essential hypertension.

Several studies have already confirmed the specific vasomotor effect of hydrogen sulfide (H2S) and its interaction with the nitric oxide (NO) system in normotensive rats, but results in spontaneously hypertensive rats (SHRs) are limited. the aim of this study was to describe the age- and blood pressure-dependent effects of endogenous NO and exogenous Na2S and their interaction in vasomotor responses of the thoracic aorta (TA) in normotensive Wistar rats and SHRs. the systolic blood pressure (sBP), vasoactivity, NO-synthase (NOS) expression and activity, cystathionine gamma-lyase (CSE) expression, and geometry of the isolated TA were evaluated at 4 and 16 weeks of age. Although hypertrophy of the heart was observed in young and adult SHRs, the sBP was increased only in adulthood. the contractile responses were decreased in young as in adult SHRs with the key participation of the endogenous NO system. however, the hypotrophy in the young and the hypertrophy (mainly at the expense of extracellular matrix) in the adult SHRs were found in the TA. While unchanged in young SHRs, in adult SHRs, partially impaired endothelial function was confirmed. Nevertheless, the NO-dependent component of acetylcholine-induced relaxation was higher in both young and adult SHRs. Consistently, even though there was an age-dependent decrease in NOS activity in both strains, NOS activity was higher in both young and adult SHRs compared to age-matched normotensive rats. Application of exogenous Na2S evoked a concentration-dependent dual vasoactive effect of TAs in both strains, regardless of age. Increased sensitivity in favor of vasorelaxant responses of Na2S in prehypertensive SHRs, and an enhanced maximal vasorelaxation in adult SHR was observed. the acute NO inhibition generally increased the relaxant phase of Na2S responses; nevertheless, the development of hypertension potentiated this effect. the TA of the SHRs is endowed with a unique inherent predisposition of vasoactive mechanisms, which serve as compensatory processes during the developed stage of hypertension: the NO component and H2S signaling pathways are implicated. the decreased contractility seems to be a deleterious effect. the increased participation of the H2S system on vasorelaxation after acute NO inhibition could be considered a reserved mechanism in case of endogenous NO deficiency.

Cardiovascular effects of gasotransmitter donors.

Gasotransmitters represent a subfamily of the endogenous gaseous signaling molecules that include nitric oxide (NO), carbon monoxide (CO), and hydrogen sulphide (H(2)S). These particular gases share many common features in their production and function, but they fulfill their physiological tasks in unique ways that differ from those of classical signaling molecules found in tissues and organs. These gasotransmitters may antagonize or potentiate each other's cellular effects at the level of their production, their downstream molecular targets and their direct interactions. All three gasotransmitters induce vasodilatation, inhibit apoptosis directly or by increasing the expression of anti-apoptotic genes, and activate antioxidants while inhibiting inflammatory actions. NO and CO may concomitantly participate in vasorelaxation, anti-inflammation and angiogenesis. NO and H(2)S collaborate in the regulation of vascular tone. Finally, H(2)S may upregulate the heme oxygenase/carbon monoxide (HO/CO) pathway during hypoxic conditions. All three gasotransmitters are produced by specific enzymes in different cell types that include cardiomyocytes, endothelial cells and smooth muscle cells. As translational research on gasotransmitters has exploded over the past years, drugs that alter the production/levels of the gasotransmitters themselves or modulate their signaling pathways are now being developed. This review is focused on the cardiovascular effects of NO, CO, and H(2)S. Moreover, their donors as drug targeting the cardiovascular system are briefly described.

Effect of melatonin on blood pressure and nitric oxide generation in rats with metabolic syndrome.

Melatonin, a multitasking indolamine, seems to be involved in a variety of physiological and metabolic processes via both receptor-mediated and receptor-independent mechanisms. The aim of our study was to find out whether melatonin can affect blood pressure (BP), nitric oxide synthase (NOS) activity, eNOS and nNOS protein expressions in rats with metabolic syndrome (SHR/cp). Rats were divided into four groups: 6-week-old male WKY andSHR/cp and age-matched WKY and SHR/cp treated with melatonin (10 mg/kg/day) for 3 weeks. BP was measured by tail-cuff plethysmography. NOS activity, eNOS and nNOS protein expressions were determined in the heart, aorta, brain cortex and cerebellum. MT(1) receptors were analyzed in the brain cortex and cerebellum. In SHR/cp rats, BP was decreased after melatonin treatment. In the same group, melatonin did not affect NOS activity and eNOS protein expression in the heart and aorta, while it increased both parameters in the brain cortex and cerebellum. Interestingly, melatonin elevated MT1 protein expression in the cerebellum. Neuronal NOS protein expression was not changed within the groups. In conclusion, increased NOS activity/eNOS upregulation in particular brain regions may contribute partially to BP decrease in SHR/cp rats after melatonin treatment. Participation of MT(1) receptors in this melatonin action may be supposed.

Effect of deuterium-depleted water on selected cardiometabolic parameters in fructose-treated rats.

Deuterium-depleted water (DDW) has a lower concentration of deuterium than occurs naturally (less than 145 ppm). While effects of DDW on cancer started to be intensively studied, the effects on cardiovascular system are completely unknown. Thus, we aimed to analyze the effects of DDW (55+/-5 ppm) administration to 12-week-old normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) treated with 15 % fructose for 6 weeks. Blood pressure (BP) and selected biochemical parameters were measured together with determination of nitric oxide synthase (NOS) activity and iNOS and eNOS protein expressions in the left ventricle (LV) and aorta. Neither DDW nor fructose had any significant effect on BP in both strains. DDW treatment decreased total cholesterol and triglyceride levels in WKY, but it was not able to prevent increase in the same parameters elevated due to fructose treatment in SHR. Both fructose and DDW increased insulin level in WKY. Fructose did not affect NOS activity either in WKY or SHR. DDW increased NOS activity in LV of both WKY and SHR, while it decreased NOS activity and iNOS expression in the aorta of SHR with or without fructose treatment. In conclusion, DDW treatment significantly modified biochemical parameters in WKY together with NOS activity elevation in the heart. On the other hand, it did not affect biochemical parameters in SHR, but decreased NOS activity elevated due to iNOS upregulation in the aorta.

Cardiac NO signalling in the metabolic syndrome.

It is well documented that metabolic syndrome (i.e. a group of risk factors, such as abdominal obesity, elevated blood pressure, elevated fasting plasma glucose, high serum triglycerides and low cholesterol level in high-density lipoprotein), which raises the risk for heart disease and diabetes, is associated with increased reactive oxygen and nitrogen species (ROS/RNS) generation. ROS/RNS can modulate cardiac NO signalling and trigger various adaptive changes in NOS and antioxidant enzyme expressions/activities. While initially these changes may represent protective mechanisms in metabolic syndrome, later with more prolonged oxidative, nitrosative and nitrative stress, these are often exhausted, eventually favouring myocardial RNS generation and decreased NO bioavailability. The increased oxidative and nitrative stress also impairs the NO-soluble guanylate cyclase (sGC) signalling pathway, limiting the ability of NO to exert its fundamental signalling roles in the heart. Enhanced ROS/RNS generation in the presence of risk factors also facilitates activation of redox-dependent transcriptional factors such as NF-κB, promoting myocardial expression of various pro-inflammatory mediators, and eventually the development of cardiac dysfunction and remodelling. While the dysregulation of NO signalling may interfere with the therapeutic efficacy of conventional drugs used in the management of metabolic syndrome, the modulation of NO signalling may also be responsible for the therapeutic benefits of already proven or recently developed treatment approaches, such as ACE inhibitors, certain ß-blockers, and sGC activators. Better understanding of the above-mentioned pathological processes may ultimately lead to more successful therapeutic approaches to overcome metabolic syndrome and its pathological consequences in cardiac NO signalling.

Long-term effect of losartan administration on blood pressure, heart and structure of coronary artery of young spontaneously hypertensive rats.

Alterations in geometry and structure of coronary arteries have marked consequences on blood flow to the respective area. We evaluated long-term effect of losartan on blood pressure (BP), heart weight/body weight (HW/BW), geometry and structure of septal branch of coronary artery (RS) of young SHR and Wistar rats. Four-week-old Wistar rats and SHR were used. Losartan was administered (20 mg/kg/day) in drinking water by gavage for 5 weeks. BP was measured by plethysmographic method. Cardiovascular system was perfused with a fixative (120 mm Hg). RS was processed for electron microscopy. Wall thickness of intima + media (WT), inner diameter (ID), cross-sectional area of intima + media (CSA), volume densities (VD) of endothelial cells (EC), extracellular matrix (ECM) of intima, smooth muscle cells (SMC) and ECM of media were evaluated. BP of 4-week-old SHR did not differ from that of Wistar rats. BP, HW/BW, WT, CSA, WT/ID, CSAs of SMC, ECM of media were increased in 9-week-old SHR, whereas their VD and CSA of EC were decreased. Losartan administration decreased BP and HW/BW in both groups. Geometry of RS was affected only in SHR (reduction of WT, CSA, WT/ID and increased of ID, circumferential tension, VD and CSA of EC). Losartan administration reduced BP and myocardial mass in both groups and beneficially affected geometry and structure of coronary artery in SHR.

Long-term effects of early administered sildenafil and NO donor on the cardiovascular system of SHR.

We evaluated the long-term effect of NO-donor, pentaerythrityl tetranitrate (Petn), and sildenafil citrate (sildenafil) on the cardiovascular system of the spontaneously hypertensive rat (SHR). Petn (100 mg/kg/day) and sildenafil (10 mg/kg/day) were administered to SHR individually or together from week 4 (pre-hypertensive period) to week 9 of age. Blood pressure (BP) was measured using a plethysmographic method. The animals were perfused with a glutaraldehyde fixative (120 mmHg). Carotid (AC) and coronary artery (RS) were processed according to electron microscopy procedure. Geometry of the arteries was measured on semi-thin sections using light microscopy. Administration of Petn and sildenafil to SHR individually or together did not prevent an increase of BP, but evoked a decrease of cardiac hypertrophy. Petn and sildenafil affected the geometry of RS and AC differently. In the RS, an increase of inner diameter (ID) without an increase of wall thickness (WT) resulted in increased WT/ID and circumferential stress. In the AC, changes in ID were accompanied by changes in WT and, thereby, WT/ID and circumferential stress remained unchanged. The arterial wall mass of both arteries was increased. The data suggest that administration of the NO donor, Petn, and/or sildenafil does not result in a beneficial effect on the myocardium or on the geometry of the carotid and coronary arteries.

Hereditary hypertriglyceridemic rat: a suitable model of cardiovascular disease and metabolic syndrome?

Hypertriglyceridemia and hypertension seem to be very important cardiovascular risk factors. The Prague hereditary hypertriglyceridemic (hHTG) rat was developed as a model of human hypertriglyceridemia. It was demonstrated that these rats are not obese, they are hypertensive and insulin resistant and they have some disturbances in glucose metabolism. Several QTLs were identified for blood pressure, its particular components (dependent on major vasoactive systems) and plasma triglycerides throughout the genome of hHTG rats by using of F(2) hybrids strategy. It is evident that hHTG rats are a suitable model for the study of metabolic disturbances in relation to blood pressure as well as for the search of genetic determinants of these abnormalities. Numerous abnormalities of blood pressure regulation as well as alterations in the structure and function of cardiovascular apparatus (heart, conduit and resistance arteries) were found in hHTG rats. A special attention was paid to possible changes in the efficiency of various vasoactive systems such as nitric oxide, renin-angiotensin-aldosterone system and sympathetic nervous system, which seem to contribute substantially to cardiovascular and/or metabolic abnormalities observed in Prague hereditary hypertriglyceridemic rats.

Functional and structural pattern of arterial responses in hereditary hypertriglyceridemic and spontaneously hypertensive rats in early stage of experimental hypertension.

It has been shown that endothelium-derived nitric oxide (NO) plays an important role in regulation of vascular tone in the prenatal and early postnatal period. The aim of this paper was to determine the reactivity and accompanying structural changes in thoracic aorta from 4-week-old spontaneously hypertensive rats (SHR) and rats with hereditary hypertriglyceridemia (hHTG) in comparison with age-matched normotensive controls. For functional studies thoracic aorta was excised, cut into rings and mounted in organ baths for measurement of isometric contractile force. For morphological studies cardiovascular system of rats was perfused with glutaraldehyde fixative (at 100 mm Hg) via cannula placed in the left ventricle. Morphological changes of thoracic aorta were measured using light microscopy. Systolic blood pressure (SBP) in SHR (98+/-1 mm Hg) did not significantly differ from that of age-matched control rats (95+/-4 mm Hg), but was slightly increased in hHTG rats (110+/-2 mm Hg, P<0.05). Heart weight/body weight ratio was higher in SHR and hHTG rats than in control group indicating the hypertrophy of the heart in both models of hypertension. Endothelium-dependent relaxation of aorta induced by acetylcholine was preserved in all groups and did not differ from that in control normotensive rats. The maximal isometric contraction of thoracic aorta to noradrenaline (NA) was reduced in hypertensive groups and the concentration-response curves to NA were shifted to the right indicating increased sensitivity of smooth muscle to NA. The values of wall thickness and cross sectional area as well as inner diameter of thoracic aorta in SHR and hHTG rats were significantly decreased in comparison to control groups. Endothelial dysfunction seems to be absent in all young rats before development of hypertension. In conclusion, our observations indicate that in early stage of experimental hypertension NO-dependent relaxation is preserved so that putative impairment of this function provides no significant pathogenic contribution to the onset of hypertension in these two experimental models.

Comparison of vascular function and structure of iliac artery in spontaneously hypertensive and hereditary hypertriglyceridemic rats.

The aim of this study was to compare the vascular reactivity and morphology of iliac artery (IA) in adult spontaneously hypertensive rats (SHR) and hereditary hypertriglyceridemic (hHTG) rats. The isolated rings of iliac artery (IA) from Wistar rats (controls), SHR and hHTG rats were used for measurement of relaxant responses to acetylcholine (ACh) and contractile responses to noradrenaline (NA). Morphological changes of IA were measured using light microscopy. Systolic blood pressure (BP) measured by plethysmographic method was increased in SHR approximately by 88 % and in hHTG rats by 44 % compared to controls. BP increase was accompanied by cardiac hypertrophy. In both SHR and hHTG groups (experimental groups) reduced relaxation to ACh and enhanced maximal contraction and sensitivity to adrenergic stimuli were observed. The sensitivity to NA in SHR was higher also in comparison with hHTG. Geometry of IA in both experimental groups revealed increased wall thickness and wall cross-sectional area, in SHR even in comparison with hHTG. Inner diameter was decreased in both experimental groups. Thus, independently of etiology, hypertension in both models was connected with impaired endothelial function accompanied by structural alterations of IA. A degree of BP elevation was associated with arterial wall hypertrophy and increased contractile sensitivity.

Differential remodeling of carotid artery in spontaneously hypertensive and hereditary hypertriglyceridemic rats.

High blood pressure, increased level of cholesterol, diabetes, hypertriglyceridemia and obesity are risk factors accompanied metabolic syndrome. The aim of the study was to compare geometry of carotid artery (AC) of 3-week-old (3w) and 52-week-old (52w) hereditary hypertriglyceridemic rats (hHTG) and spontaneously hypertensive rats (SHR) which represent a genetic model of human essential hypertension with age-matched Wistar rats. After sacrificing the rats were perfused with a glutaraldehyde fixative under the pressure 90 mm Hg (3w) and 120 mm Hg (52w) for 10 min via cannula placed into left ventricle. Middle part of AC was excised and processed according to standard electron microscopy procedure. Geometry of AC was evaluated in light microscopy. SHR vs. Wistar rats: BP of 3w did not differ, in 52w it was increased; cardiac hypertrophy was found in both ages; wall thickness (WT) and cross sectional area (CSA) in 3w did not differ, in 52w both were increased; inner diameter (ID) in 3w and 52w was decreased; WT/ID was increased in both ages. Hereditary HTG vs. Wistar rats: BP was increased in both periods; cardiac hypertrophy was observed in 3w; WT in 3w was decreased, in 52w it was increased; CSA and ID were decreased in both ages; WT/ID was increased only in 52w. Discrepancies between development of BP, cardiac hypertrophy in SHR and hHTG rats were observed. Alterations of BP were not in harmony with alterations in geometry of carotid arteries in both SHR and hHTG rats. We suggest that BP is not the main stimuli evoked hemodynamic and structural alterations of cardiovascular system in ontogenic development of SHR and hHTG rats.

Acetylcholine and bradykinin enhance hypotension and affect the function of remodeled conduit arteries in SHR and SHR treated with nitric oxide donors.

Discrepancy was found between enhanced hypotension and attenuated relaxation of conduit arteries in response to acetylcholine (ACh) and bradykinin (BK) in nitric oxide (NO)-deficient hypertension. The question is whether a similar phenomenon occurs in spontaneously hypertensive rats (SHR) with a different pathogenesis. Wistar rats, SHR, and SHR treated with NO donors [molsidomine (50 mg/kg) or pentaerythritol tetranitrate (100 mg/kg), twice a day, by gavage] were studied. After 6 weeks of treatment systolic blood pressure (BP) was increased significantly in experimental groups. Under anesthesia, the carotid artery was cannulated for BP recording and the jugular vein for drug administration. The iliac artery was used for in vitro studies and determination of geometry. Compared to control, SHR showed a significantly enhanced (P < 0.01) hypotensive response to ACh (1 and 10 microg, 87.9 +/- 6.9 and 108.1 +/- 5.1 vs 35.9 +/- 4.7 and 64.0 +/- 3.3 mmHg), and BK (100 microg, 106.7 +/- 8.3 vs 53.3 +/- 5.2 mmHg). SHR receiving NO donors yielded similar results. In contrast, maximum relaxation of the iliac artery in response to ACh was attenuated in SHR (12.1 +/- 3.6 vs 74.2 +/- 8.6% in controls, P < 0.01). Iliac artery inner diameter also increased (680 +/- 46 vs 828 +/- 28 microm in controls, P < 0.01). Wall thickness, wall cross-section area, wall thickness/inner diameter ratio increased significantly (P < 0.01). No differences were found in this respect among SHR and SHR treated with NO donors. These findings demonstrated enhanced hypotension and attenuated relaxation of the conduit artery in response to NO activators in SHR and in SHR treated with NO donors, a response similar to that found in NO-deficient hypertension.

Acetylcholine and bradykinin enhance hypotension and affect the function of remodeled conduit arteries in SHR and SHR treated with nitric oxide donors

Discrepancy was found between enhanced hypotension and attenuated relaxation of conduit arteries in response to acetylcholine (ACh) and bradykinin (BK) in nitric oxide (NO)-deficient hypertension. The question is whether a similar phenomenon occurs in spontaneously hypertensive rats (SHR) with a different pathogenesis. Wistar rats, SHR, and SHR treated with NO donors [molsidomine (50 mg/kg) or pentaerythritol tetranitrate (100 mg/kg), twice a day, by gavage] were studied. After 6 weeks of treatment systolic blood pressure (BP) was increased significantly in experimental groups. Under anesthesia, the carotid artery was cannulated for BP recording and the jugular vein for drug administration. The iliac artery was used for in vitro studies and determination of geometry. Compared to control, SHR showed a significantly enhanced (P < 0.01) hypotensive response to ACh (1 and 10 æg, 87.9 ± 6.9 and 108.1 ± 5.1 vs 35.9 ± 4.7 and 64.0 ± 3.3 mmHg), and BK (100 æg, 106.7 ± 8.3 vs 53.3 ± 5.2 mmHg). SHR receiving NO donors yielded similar results. In contrast, maximum relaxation of the iliac artery in response to ACh was attenuated in SHR (12.1 ± 3.6 vs 74.2 ± 8.6 percent in controls, P < 0.01). Iliac artery inner diameter also increased (680 ± 46 vs 828 ± 28 æm in controls, P < 0.01). Wall thickness, wall cross-section area, wall thickness/inner diameter ratio increased significantly (P < 0.01). No differences were found in this respect among SHR and SHR treated with NO donors. These findings demonstrated enhanced hypotension and attenuated relaxation of the conduit artery in response to NO activators in SHR and in SHR treated with NO donors, a response similar to that found in NO-deficient hypertension.