Cerebral Benefits Induced by Electrical Muscle Stimulation: Evidence from a Human and Rat Study.

Physical exercise (EX) is well established for its positive impact on brain health. However, conventional EX may not be feasible for certain individuals. In this regard, this study explores electromyostimulation (EMS) as a potential alternative for enhancing cognitive function. Conducted on both human participants and rats, the study involved two sessions of EMS applied to the quadriceps with a duration of 30 min at one-week intervals. The human subjects experienced assessments of cognition and mood, while the rats underwent histological and biochemical analyses on the prefrontal cortex, hippocampus, and quadriceps. Our findings indicated that EMS enhanced executive functions and reduced anxiety in humans. In parallel, our results from the animal studies revealed an elevation in brain-derived neurotrophic factor (BDNF), specifically in the hippocampus. Intriguingly, this increase was not associated with heightened neuronal activity or cerebral hemodynamics; instead, our data point towards a humoral interaction from muscle to brain. While no evidence of increased muscle and circulating BDNF or FNDC5/irisin pathways could be found, our data highlight lactate as a bridging signaling molecule of the muscle-brain crosstalk following EMS. In conclusion, our results suggest that EMS could be an effective alternative to conventional EX for enhancing both brain health and cognitive function.

Impact of Exercise Intensity on Cerebral BDNF Levels: Role of FNDC5/Irisin.

The positive effects of physical exercise (EX) are well known to be mediated by cerebral BDNF (brain-derived neurotrophic factor), a neurotrophin involved in learning and memory, the expression of which could be induced by circulating irisin, a peptide derived from Fibronectin type III domain-containing protein 5 (FNDC5) produced by skeletal muscle contraction. While the influence of EX modalities on cerebral BDNF expression was characterized, their effect on muscle FNDC5/Irisin expression and circulating irisin levels remains to be explored. The present study involved Wistar rats divided into four experimental groups: sedentary (SED), low- (40% of maximal aerobic speed, MAS), intermediate- (50% of MAS) and high- (70% of MAS) intensities of treadmill EX (30 min/day, 7 days). Soleus (SOL) versus gastrocnemius (GAS) FNDC5 and hippocampal BDNF expressions were evaluated by Western blotting. Additionally, muscular FNDC5/Irisin localization and serum/hippocampal irisin levels were studied by immunofluorescence and ELISA, respectively. Our findings revealed that (1) serum irisin and hippocampal BDNF levels vary with EX intensity, showing a threshold intensity at 50% of MAS; (2) hippocampal BDNF levels positively correlate with serum irisin but not with hippocampal FNDC5/Irisin; and (3) GAS, in response to EX intensity, overexpresses FNDC5/Irisin in type II muscle fibers. Altogether, peripheral FNDC5/Irisin levels likely explain EX-dependent hippocampal BDNF expression.

Brain BDNF levels are dependent on cerebrovascular endothelium-derived nitric oxide.

Scientific evidence continues to demonstrate a link between endothelial function and cognition. Besides, several studies have identified a complex interplay between nitric oxide (NO) and brain-derived neurotrophic factor (BDNF), a neurotrophin largely involved in cognition. Therefore, this study investigated the link between cerebral endothelium-derived NO and BDNF signaling. For this purpose, levels of BDNF and the phosphorylated form of endothelial NO synthase at serine 1177 (p-eNOS) were simultaneously measured in the cortex and hippocampus of rats subjected to either bilateral common carotid occlusion (n = 6), physical exercise (n = 6) or a combination of both (n = 6) as experimental approaches to modulate flow-induced NO production by the cerebrovasculature. Tropomyosin-related kinase type B (TrkB) receptors and its phosphorylated form at tyrosine 816 (p-TrkB) were also measured. Moreover, we investigated BDNF synthesis in brain slices exposed to the NO donor glyceryl trinitrate. Our results showed increased p-eNOS and BDNF levels after exercise and decreased levels after vascular occlusion as compared to corresponding controls, with a positive correlation between changes in p-eNOS and BDNF (r = 0.679). Exercise after vascular occlusion did not change levels of these proteins. Gyceryl trinitrate increased proBDNF and BDNF levels in brain slices, thus suggesting a possible causal relationship between NO and BDNF. Moreover, vascular occlusion, like exercise, resulted in increased TrkB and p-TrkB levels, whereas no change was observed with the combination of both. These results suggest that brain BDNF signaling may be dependent on cerebral endothelium-derived NO production.

Etanercept improves endothelial function via pleiotropic effects in rat adjuvant-induced arthritis.

OBJECTIVES: To determine the effect of etanercept on endothelial dysfunction and on traditional cardiovascular (CV) risk factors in the adjuvant-induced arthritis (AIA) rat model. METHODS: At the first signs of arthritis, etanercept (10 mg/kg/3 days, s.c.) or saline was administered for 3 weeks in AIA rats. Body weights and arthritis scores were monitored daily. Endothelial function was studied in aortic rings relaxed with acetylcholine (Ach) with or without inhibitors of nitric oxide synthase (NOS), cyclo-oxygenase (COX-2), arginase, endothelium-derived hyperpolarizing factor and superoxide anions (O2 (-)°) production. Aortic expression of endothelial nitic oxide synthase (eNOS), Ser1177-phospho-eNOS, COX-2, arginase-2, p22(phox) and p47(phox) was evaluated by western blotting analysis. Blood pressure, heart rate and blood levels of triglycerides, cholesterol and glucose were measured. RESULTS: Etanercept significantly reduced arthritis score (P < 0.001). It improved Ach-induced relaxation (P < 0.05) as a result of increased NOS activity, decreased COX-2/arginase activities and decreased O2 (-)° production. These functional effects relied on increased eNOS expression and phosphorylation, and decreased COX-2, arginase-2 and p22(phox) expressions. No correlation was found between arthritis score and Ach-induced relaxation. The treatment did not change triglycerides, cholesterol and glucose levels, but significantly increased systolic blood pressure and heart rate (P < 0.05). CONCLUSION: Our data demonstrated that efficient dosage of etanercept on inflammatory symptoms improved endothelial function in AIA. This beneficial effect on endothelial function is disconnected from its impact on CV risk factors and relates to pleiotropic effects of etanercept on endothelial pathways. These results suggest that etanercept could be a good choice for patients with rheumatoid arthritis at high risk of CV events.

Electrical stimulation: a potential alternative to positively impact cerebral health?

An increasing body of evidence confirms the effectiveness of physical exercise (PE) in promoting brain health by preventing age-related cognitive decline and reducing the risk of neurodegenerative diseases. The benefits of PE are attributed to neuroplasticity processes which have been reported to enhance cerebral health. However, moderate to high-intensity PE is necessary to induce these responses and these intensities cannot always be achieved especially by people with physical limitations. As a countermeasure, electrical stimulation (ES) offers several benefits, particularly for improving physical functions, for various neurological diseases. This review aims to provide an overview of key mechanisms that could contribute to the enhancement in brain health in response to ES-induced exercise, including increases in cerebral blood flow, neuronal activity, and humoral pathways. This narrative review also focuses on the effects of ES protocols, applied to both humans and animals, on cognition. Despite a certain paucity of research when compared to the more classical aerobic exercise, it seems that ES could be of interest for improving cerebral health, particularly in people who have difficulty engaging in voluntary exercise.

Effect of stroke on arginase expression and localization in the rat brain.

Because arginase and nitric oxide (NO) synthases (NOS) compete to degrade l-arginine, arginase plays a crucial role in the modulation of NO production. Moreover, the arginase 1 isoform is a marker of M2 phenotype macrophages that play a key role in tissue remodeling and resolution of inflammation. While NO has been extensively investigated in ischemic stroke, the effect of stroke on the arginase pathway is unknown. The present study focuses on arginase expression/activity and localization before and after (1, 8, 15 and 30 days) the photothrombotic ischemic stroke model. This model results in a cortical lesion that reaches maximal volume at day 1 post-stroke and then decreases as a result of astrocytic scar formation. Before stroke, arginase 1 and 2 expressions were restricted to neurons. Stroke resulted in up-regulation of arginase 1 and increased arginase activity in the region centered on the lesion where inflammatory cells are present. These changes were associated with an early and long-lasting arginase 1 up-regulation in activated macrophages and astrocytes and a delayed arginase 1 down-regulation in neurons at the vicinity of the lesion. A linear positive correlation was observed between expressions of arginase 1 and glial fibrillary acidic protein as a marker of activated astrocytes. Moreover, the pattern of arginase 1 and brain-derived neurotrophic factor (BDNF) expressions in activated astrocytes was similar. Unlike arginase 1, arginase 2 expression was not changed by stroke. In conclusion, increased arginase 1 expression is not restricted to macrophages in inflammation elicited by stroke but also occurs in activated astrocytes where it may contribute to neuroplasticity through the control of BDNF production.

Molecular mechanisms underlying physical exercise-induced brain BDNF overproduction.

Accumulating evidence supports that physical exercise (EX) is the most effective non-pharmacological strategy to improve brain health. EX prevents cognitive decline associated with age and decreases the risk of developing neurodegenerative diseases and psychiatric disorders. These positive effects of EX can be attributed to an increase in neurogenesis and neuroplastic processes, leading to learning and memory improvement. At the molecular level, there is a solid consensus to involve the neurotrophin brain-derived neurotrophic factor (BDNF) as the crucial molecule for positive EX effects on the brain. However, even though EX incontestably leads to beneficial processes through BDNF expression, cellular sources and molecular mechanisms underlying EX-induced cerebral BDNF overproduction are still being elucidated. In this context, the present review offers a summary of the different molecular mechanisms involved in brain's response to EX, with a specific focus on BDNF. It aims to provide a cohesive overview of the three main mechanisms leading to EX-induced brain BDNF production: the neuronal-dependent overexpression, the elevation of cerebral blood flow (hemodynamic hypothesis), and the exerkine signaling emanating from peripheral tissues (humoral response). By shedding light on these intricate pathways, this review seeks to contribute to the ongoing elucidation of the relationship between EX and cerebral BDNF expression, offering valuable insights into the potential therapeutic implications for brain health enhancement.

Region-Dependent Increase of Cerebral Blood Flow During Electrically Induced Contraction of the Hindlimbs in Rats.

Elevation of cerebral blood flow (CBF) may contribute to the cerebral benefits of the regular practice of physical exercise. Surprisingly, while electrically induced contraction of a large muscular mass is a potential substitute for physical exercise to improve cognition, its effect on CBF remains to be investigated. Therefore, the present study investigated CBF in the cortical area representing the hindlimb, the hippocampus and the prefrontal cortex in the same anesthetized rats subjected to either acute (30 min) or chronic (30 min for 7 days) electrically induced bilateral hindlimb contraction. While CBF in the cortical area representing the hindlimb was assessed from both laser doppler flowmetry (LDFCBF) and changes in p-eNOSSer1177 levels (p-eNOSCBF), CBF was evaluated only from changes in p-eNOSSer1177 levels in the hippocampus and the prefrontal cortex. The contribution of increased cardiac output and increased neuronal activity to CBF changes were examined. Stimulation was associated with tachycardia and no change in arterial blood pressure. It increased LDFCBF with a time- and intensity-dependent manner as well as p-eNOSCBF in the area representing the hindlimb. By contrast, p-eNOSCBF was unchanged in the two other regions. The augmentation of LDFCBF was partially reduced by atenolol (a ß1 receptor antagonist) and not reproduced by the administration of dobutamine (a ß1 receptor agonist). Levels of c-fos as a marker of neuronal activation selectively increased in the area representing the hindlimb. In conclusion, electrically induced bilateral hindlimb contraction selectively increased CBF in the cortical area representing the stimulated muscles as a result of neuronal hyperactivity and increased cardiac output. The absence of CBF changes in cognition-related brain regions does not support flow-dependent neuroplasticity in the pro-cognitive effect of electrically induced contraction of a large muscular mass.

Endothelial cells are an important source of BDNF in rat skeletal muscle.

BDNF (brain-derived neurotrophic factor) is present in skeletal muscle, controlling muscular metabolism, strength and regeneration processes. However, there is no consensus on BDNF cellular source. Furthermore, while endothelial tissue expresses BDNF in large amount, whether endothelial cells inside muscle expressed BDNF has never been explored. The aim of the present study was to provide a comprehensive analysis of BDNF localization in rat skeletal muscle. Cellular localization of BDNF and activated Tropomyosin-related kinase B (TrkB) receptors was studied by immunohistochemical analysis on soleus (SOL) and gastrocnemius (GAS). BDNF and activated TrkB levels were also measured in muscle homogenates using Western blot analysis and/or Elisa tests. The results revealed BDNF immunostaining in all cell types examined with a prominent staining in endothelial cells and a stronger staining in type II than type I muscular fibers. Endothelial cells but not other cells displayed easily detectable activated TrkB receptor expression. Levels of BDNF and activated TrkB receptors were higher in SOL than GAS. In conclusion, endothelial cells are an important and still unexplored source of BDNF present in skeletal muscle. Endothelial BDNF expression likely explains why oxidative muscle exhibits higher BDNF levels than glycolytic muscle despite higher the BDNF expression by type II fibers.

Tofacitinib improved peripheral endothelial dysfunction and brain-derived neurotrophic factor levels in the rat adjuvant-induced arthritis model.

This study aimed to explore the effect of Tofacitinib on endothelial dysfunction and cerebral levels of brain-derived neurotrophic factor (BDNF) in the adjuvant-induced arthritis (AIA) rat model. Tofacitinib (10 mg/kg twice a day) or vehicle was administered from the first signs of inflammation. Arthritis scores were daily monitored while other parameters including endothelial function assessed from aortic rings, radiographic scores, blood pressure, heart rate, circulating levels of triglycerides, cholesterol, and interleukin (IL)-1ß, tumor necrosis factor-α (TNF-α), IL-17A, and cerebral BDNF levels were determined after 3 weeks of treatment. A group of non-AIA rats served as controls. In AIA rats, as compared with vehicle, Tofacitinib significantly reduced arthritis and radiographic scores, decreased total cholesterol and low-density lipoprotein cholesterol (LDL-C), but changed neither blood pressure nor heart rate and proinflammatory cytokines levels. It also fully restored acetylcholine (Ach)-induced relaxation (p < 0.05) through increased nitric oxide (NO) synthase activity, reduced BH4 deficiency and O2 -° production, decreased cyclo-oxygenase-2 (COX-2)/arginase activities, and enhanced endothelium-derived hyperpolarizing factor (EDHF) production. These effects translated into a decrease in atherogenic index and an elevation of BDNF levels in the prefrontal cortex (p < 0.05) and hippocampus (p < 0.001). The present study identified Tofacitinib as an efficient therapeutic option to reduce cardiovascular risk and improve BDNF-dependent cognition in arthritis.

Brain-derived neurotrophic factor is a full endothelium-derived factor in rats.

Most of what is known on vascular brain-derived neurotrophic factor (BDNF) derived from experiments on cultured endothelial cells. Therefore, the present study compared BDNF levels/localization in artery (aorta) vs vein (vena cava) from a same territory in rats either sedentary (SED) or exposed to treadmill exercise (EX) as a mean to stimulate endogenous endothelial nitric oxide (NO) production. In SED rats, for both artery and vein, BDNF was strongly expressed by endothelial cells, while only a faint and scattered expression was observed throughout the media. Endothelial and muscular BDNF staining as vascular BDNF protein levels were however higher in artery than in vein, while BDNF mRNA levels did not differ between vessels. Irrespective of the vessels, EX resulted in an increase (+50%) in BDNF protein levels with no change in BDNF mRNA levels, a selective endothelial BDNF overexpression (x4) and an increase in vascular levels of tropomyosin related kinase B receptors (TrkB) phosphorylated at tyrosine 816 (p-TrkBTyr816). Endothelial expressions of BDNF and p-TrkBTyr816 were positively associated when SED and EX rats were simultaneously examined. The results incite to consider endothelial BDNF as a full and NO-dependent endothelium-derived factor that exerts autocrine effects.

The effect of exercise on memory and BDNF signaling is dependent on intensity.

The aims of the present study were to investigate in brain of adult rats (1) whether exercise-induced activation of brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase B (TrkB) pathway is dependent on exercise intensity modality and (2) whether exercise-induced improvement of memory is proportional to this pathway activation. Wistar rats were subjected to low (12 m/min) or high (18 m/min) exercise intensity on horizontal treadmill (30 min/day, 7 consecutive days) that corresponds to ~ 40 and 70% of maximal aerobic speed, respectively. Animals treated with scopolamine to induce memory impairment were subjected to novel object recognition test to assess potential improvement in cognitive function. Expressions of BDNF, phosphorylated TrkB receptors, synaptophysin (a marker of synaptogenesis), c-fos (a neuronal activity marker) and phosphorylated endothelial nitric oxide synthase (a cerebral blood flow marker) were measured in prefrontal cortex and hippocampus of different groups of rats. In terms of cognition, our data reported that only the most intense exercise improves memory performance. Our data also revealed that BDNF pathway is dependent on intensity modality of exercise with a gradual effect in hippocampus whereas only the highest intensity leads to this pathway activation in prefrontal cortex. Our study revealed that memory improvement through BDNF pathway activation is dependent on exercise intensity. While reporting that our protocol is sufficient to improve cognition in animals with impaired memory, our data suggest that prefrontal cortex is possibly a more suitable structure than hippocampus when neuroplastic markers are used to mirror potential improvement in memory performance.

Brain-derived Neurotrophic Factor Pathway after Downhill and Uphill Training in Rats.

INTRODUCTION: The elevation of brain-derived neurotrophic factor (BDNF) levels in the brain and the subsequent phosphorylation of its cognate tropomyosin-related kinase B (TrkB) receptors at tyrosine 816 (pTrkB) are largely involved in the positive effect of aerobic exercise on brain functioning. Although BDNF levels were reported to increase in proportion with exercise intensity, the effect of the type of contraction is unknown. Therefore, the cerebral BDNF/TrkB pathway was investigated after uphill and downhill treadmill activities at equivalent intensity to preferentially induce eccentric and concentric contractions, respectively. METHODS: A treadmill activity (30 min·d for seven consecutive days) either in a horizontal position at two different speeds to modulate intensity (experiment 1) or at three different inclinations (null, -10%, and +5%) but at equivalent intensity to modulate the type of contraction (experiment 2) was induced in rats. Both experiments included sedentary rats. Levels of BDNF, pTrkB, synaptophysin (marker of synaptogenesis), endothelial nitric oxide synthase phosphorylated at serine 1177 (peNOS), and c-fos levels (indicators of elevation in blood flow in the cerebrovasculature and neuronal activity, respectively) were measured in motor- and cognition-related brain regions using Western blotting analysis. RESULTS: Experiment 1 indicated that treadmill activity induces an intensity-dependent increase in peNOS, c-fos, and BDNF levels. Experiment 2 showed that intensity of exercise as well as activation of the cerebral BDNF pathway, and synaptogenesis did not differ among horizontal, uphill, and downhill treadmill activities. CONCLUSION: The cerebral response of the BDNF pathway to a treadmill activity is dependent on exercise intensity, but not on the type of contraction (eccentric vs concentric).

Temporal changes in free iron levels after brain ischemia Relevance to the timing of iron chelation therapy in stroke.

Whereas iron chelators have been proposed as therapeutic agents in stroke, changes in free iron levels have never been explored after focal brain ischemia. Therefore, free and total iron levels in cortical tissue and free iron levels in plasma were measured before and after (1, 4 and 24h) photothrombotic occlusion of cortical vessels in rats. Brain ferritin expression and localization were also investigated before and after (24, 72 and 192 h) occlusion. The results showed that free iron remained below detectable levels in plasma and that the lesion exhibited high levels of free and total iron. As compared to contralateral values, free iron levels in ischemic core and penumbra increased (+50%) at 1h and returned to control values at 4h post-occlusion. In contrast, the increase in total iron levels (+20-30%) was long-lasting, but confined to the ischemic core. A time-dependent increase in the expression of both chains of ferritin was detected in regions that previously exhibited free iron accumulation. Finally, ischemic damage was reduced by the liposoluble iron chelator 2,2'-dipyridyl (20 mg/kg, i.p.) when injected 15 min or 1 h post-occlusion, yet not later (4 h). In conclusion, our results show that focal brain ischemia results in an early and transient elevation in free iron levels in the ischemic tissue and suggest that free iron excess does not originate in blood. They also highlight the importance of starting iron chelation therapy as soon as possible after stroke.

Beneficial effect of dipyridyl, a liposoluble iron chelator against focal cerebral ischemia: in vivo and in vitro evidence of protection of cerebral endothelial cells.

Whereas iron chelators were shown to induce neuroprotection against brain injury, the effect of iron chelators on ischemia-induced damage of cerebral endothelium is largely unknown. Our objective was to explore the endothelioprotective effect of the lipophilic iron chelator dipyridyl (DP) (i) in vitro on the death of cerebral endothelial cells (CECs) subjected to intracellular iron loading and (ii) in vivo on the ischemia-induced blood-brain barrier (BBB) disruption. When given shortly after iron exposure or brain ischemia, DP prevented the death of CECs and diminished BBB disruption, respectively, whereas a delayed administration of DP was associated with a lower CECs protection. Interestingly, when given preventively, DP also abrogated the death of CECs and reduced BBB disruption. However, a long delay between DP treatment and iron exposure led to a higher protection, suggesting a preconditioning effect of DP. Accordingly, prevention of hydroxyl radical formation through iron chelation cannot explain alone the beneficial effect of preventive DP treatment. Our findings showing that DP failed to induce the potentially cytoprotective proteins, heme oxygenase-1 and manganese superoxide dismutase, suggest that other proteins participate to the preconditioning effect of DP. To conclude, the curative and preventive effects of DP evidenced in this study suggest that iron chelation therapy represents a favorable and effective approach to increase BBB resistance towards ischemic injury.

Decidual prolactin silences the expression of genes detrimental to pregnancy.

Although the main role of prolactin (PRL) in pregnant rodents is to sustain progesterone production by the corpus luteum, progesterone treatment of PRL or PRL receptor (PRL-R) null mice is unable to prevent fetal loss. We have previously shown that the rat decidua is a site of PRL production and action. In this report, we examined the hypothesis, using PRL null mice and rat decidual cell culture, that the absence of this hormone leads to the expression in the decidua of genes detrimental to pregnancy. The results show that decidual growth is normal in PRL null mice treated with PRL, progesterone, or their combination. However, the decidua of mice treated with progesterone starts expressing IL-6 and 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD), two proteins absent from the decidua of wild-type mice and involved, respectively, in inflammation and progesterone catabolism. The expression of both IL-6 and 20alpha-HSD is prevented by PRL treatment. Our results further suggest that PRL inhibition of 20alpha-HSD expression is at the level of transcription and that decidual PRL (dPRL) inhibits 20alpha-HSD promoter activity. Inhibitors of Janus kinase 2 (Jak2) but not other kinases prevent dPRL down-regulation of the 20alpha-HSD promoter. Furthermore, cotransfection of the 20alpha-HSD promoter with expression vectors of constitutively active PRL-R, Jak2, or signal transducer and activator of transcription 5b (Stat5b) leads to substantial inhibition of promoter activity. Taken together, our investigation provides an explanation for the inability of progesterone to sustain pregnancy in PRL null mice and suggests that dPRL plays an important role in pregnancy by repressing the expression of IL-6 and 20alpha-HSD in the decidua. The study also demonstrates that PRL signals through the Jak2/Stat5 pathway to down-regulate 20alpha-HSD expression in the decidua.

Time course of vascular arginase expression and activity in spontaneously hypertensive rats.

There is growing evidence that vascular arginase plays a role in pathophysiology of vascular diseases. We recently reported high arginase activity/expression in young adult hypertensive spontaneously hypertensive rats (SHR). The aim of the present study was to characterize the time course of arginase pathway abnormalities in SHR and to explore the contributing role of hemodynamics and inflammation. Experiments were conducted on 5, 10, 19 and 26-week-old SHR and their age-matched control Wistar Kyoto (WKY) rats. Arginase activity as well as expression of arginase I, arginase II, endothelial and inducible NOS were determined in aortic tissue extracts. Levels of L-arginine, NO catabolites and IL-6 (a marker of inflammation) were measured in plasma. Arginase activity/expression was also measured in 10-week-old SHR previously treated with hydralazine (20 mg/kg/day, per os, for 5 weeks). As compared to WKY, SHR exhibited high vascular arginase I and II expression from prehypertensive to established stages of hypertension. However, a mismatch between expression and activity was observed at the prehypertensive stage. Arginase expression was not related either to plasma IL-6 levels or to expression of NOS. Prevention of hypertension by hydralazine significantly blunted arginase upregulation and restored arginase activity. Importantly, arginase activity and blood pressure (BP) correlated in SHR. In conclusion, our results demonstrate that arginase upregulation precedes blood pressure rising and identify elevated blood pressure as a contributing factor of arginase dysregulation in genetic hypertension. They also demonstrated a close relationship between arginase activity and BP, thus making arginase a promising target for antihypertensive therapy.

Effects of a chronic l-arginine supplementation on the arginase pathway in aged rats.

While ageing is frequently associated with l-arginine deficiency, clinical and experimental studies provided controversial data on the interest of a chronic l-arginine supplementation with beneficial, no or even deleterious effects. It was hypothesized that these discrepancies might relate to a deviation of l-arginine metabolism towards production of l-ornithine rather than nitric oxide as a result of age-induced increase in arginase activity. This study investigated the effect of ageing on arginase activity/expression in target tissues and determined whether l-arginine supplementation modulated the effect of ageing on arginase activity. Arginase activity and expression were measured in the heart, vessel, brain, lung, kidney and liver in young rats (3-months old) and aged Wistar rats (22-24-months-old) with or without l-arginine supplementation (2.25% in drinking water for 6weeks). Plasma levels of l-arginine and l-ornithine were quantified in order to calculate the plasma l-arginine/l-ornithine ratio, considered as a reflection of arginase activity. Cardiovascular parameters (blood pressure, heart rate) and aortic vascular reactivity were also studied. Ageing dramatically reduced plasma l-arginine and l-arginine/l-ornithine ratio, decreased liver and kidney arginase activities but did not change activities in other tissues. l-Arginine supplementation normalized plasma l-arginine and l-arginine/l-ornithine ratio, improved endothelial function and decreased systolic blood pressure. These effects were associated with decreased arginase activity in aorta along with no change in the other tissues except in the lung in which activity was increased. A strong mismatch was therefore observed between arginase activity and expression in analyzed tissues. The present study reveals that ageing selectively changes arginase activity in clearance tissues, but does not support a role of the arginase pathway in the potential deleterious effect of the l-arginine supplementation in aged patients. Moreover, our data argue against the use of the measurement of plasma l-arginine/l-ornithine ratio to estimate arginase activity in aged patients.

Effect of short-term exercise training on brain-derived neurotrophic factor signaling in spontaneously hypertensive rats.

OBJECTIVE: Decreased brain-derived neurotrophic factor (BDNF) level has been reported in the hippocampus of hypertensive rats. The present study explored whether brain neurons and/or endothelial cells are targeted by hypertension with respect to BDNF expression and the potential of physical exercise to cope with hypertension. METHODS: Physical exercise was induced in spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats. The hippocampus of sedentary and exercised rats (n = 6 for each group) were used for western blots to assess proBDNF, mature BDNF (mBDNF), tropomyosin-related kinase B (TrkB), P-TrkB (TrkB phosphorylated at tyrosine 816), synaptophysin, endothelial nitric oxide synthase (eNOS) and eNOS phosphorylated at serine 1177 protein levels. BDNF and proBDNF localization in the hippocampus was studied in WKY rats, SHR and exercised SHR (n = 5 each). mBDNF and proBDNF protein levels were also assessed in hippocampal slices prepared from SHR (n = 10) that were incubated for 24 h with the nitric oxide (NO) donor glyceryl trinitrate. SBP was measured by the tail-cuff method. RESULTS: Exercise modified blood pressure neither in SHR nor WKY. As compared with WKY rats, SHR displayed decreased levels of mBDNF, P-TrkB, synaptophysin, eNOS and eNOS phosphorylated at serine 1177 but no change in proBDNF and TrkB levels. These effects coincided with low BDNF staining in both endothelial cells and neurons. Exercise improved the endothelium-derived NO system and the BDNF pathway in both strains. The NO donor increased mBDNF but decreased proBDNF levels. CONCLUSION: Our results revealed that endothelial and neuronal BDNF expressions were both impaired in hypertension and that physical exercise improved hippocampal mBDNF levels and signaling through blood pressure-independent mechanisms.

Diclofenac but not celecoxib improves endothelial function in rheumatoid arthritis: A study in adjuvant-induced arthritis.

BACKGROUND AND AIMS: We aimed at investigating the effect of celecoxib (COX-2 selective inhibitor) and diclofenac (non-selective COX inhibitor) on endothelial function, and at identifying the underlying mechanisms in adjuvant-induced arthritis (AIA). METHODS: At the first signs of AIA, diclofenac (5 mg/kg twice a day, i.p), celecoxib (3 mg/kg/day, i.p) or saline (Vehicle) was administered for 3 weeks. Endothelial function was studied in aortic rings relaxed with acetylcholine (Ach) with or without inhibitors of NOS, arginase, EDHF and superoxide anions (O2-°) production. Aortic expression of eNOS, Ser1177-phospho-eNOS, COX-2, arginase-2, p22phox and p47phox was evaluated by Western blotting analysis. Arthritis scores, blood pressure, glycaemia and serum ADMA levels were measured. RESULTS: Diclofenac and celecoxib significantly reduced arthritis score to the same extent (p<0.05). As compared to vehicle-treated AIA, celecoxib did not change whereas diclofenac improved endothelial function (p<0.05) through increased EDHF production, decreased arginase activity and expression, decreased superoxide anions production and expression of p22phox and p47phox. Diclofenac but not celecoxib significantly enhanced blood pressure and serum ADMA levels. Glycaemia was unchanged by both treatments. CONCLUSIONS: Our study reveals that the effect of NSAIDs on endothelial function cannot be extrapolated from their impact on arthritis severity and suggest that changes in blood pressure and plasma ADMA levels may not be useful to predict CV risk of NSAIDs in RA.