Vascular Arginase Is a Relevant Target to Improve Cerebrovascular Endothelial Dysfunction in Rheumatoid Arthritis: Evidence from the Model of Adjuvant-Induced Arthritis

International audiencemerging data revealed that rheumatoid arthritis (RA) is associated with higher risk of cerebrovascular diseases. Whereas cerebral endothelial dysfunction is acknowledged as a critical aspect of cerebrovascular diseases, its presence in RA and the mechanisms involved are currently unknown. By using the model of rat adjuvant-induced arthritis (AIA), the present study investigated cerebrovascular reactivity in pressurized middle cerebral arteries (MCA) on day 33 post-immunization. The results revealed that arthritis induced a dramatic decrease in the vasodilatory response to acetylcholine (ACh), ADP, and bradykinin (n = 7-9 arteries, p < 0.0001). By using nor-NOHA, L-NAME, BH4, and Tempol, the results showed that the reduced response to ACh relied on arginase overactivation (n = 8), low NOS activity (n = 8), BH4 deficiency (n = 9), and excessive superoxide production (n = 9). Immunohistological analysis revealed an endothelial upregulation of arginase 2 (p < 0.05, n = 5-6) and NADPH oxidase (p < 0.05, n = 5-7) while eNOS expression was unchanged in AIA (n = 6). To assess whether arginase inhibition may be a relevant therapeutic, AIA rats were treated with an arginase inhibitor (nor-NOHA, 40 mg/kg/day, i.p., n = 20 rats) daily from day 10 to day 33 post-immunization. The treatment alleviated the impaired response of MCA to endothelium-dependent agonists, through an increase in NOS signaling and a suppression of BH4 deficiency and superoxide overproduction. By contrast, it did not change the course of arthritis. In conclusion, arthritis induced a cerebrovascular endothelial dysfunction involving an imbalance in the arginase/NOS pathway. Arginase inhibition appears as a promising therapy beyond anti-rheumatic drugs for reducing the risk of cerebrovascular diseases in RA

Opposite effects of hypertension and physical exercise on cerebrovascular BDNF levels

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

International audienceThe 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 (12m/min) or high (18m/min) exercise intensity on horizontal treadmill (30min/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

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

International audienceObjective: 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(tyr816) (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(tyr816), 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

Brain-derived neurotrophic factor secreted by the cerebral endothelium: A new actor of brain function?

International audienceLow cerebral levels of brain-derived neurotrophic factor (BDNF), which plays a critical role in many brain functions, have been implicated in neurodegenerative, neurological and psychiatric diseases. Thus, increasing BDNF levels in the brain is considered an attractive possibility for the prevention/treatment of various brain diseases. To date, BDNF-based therapies have largely focused on neurons. However, given the cross-talk between endothelial cells and neurons and recent evidence that BDNF expressed by the cerebral endothelium largely accounts for BDNF levels present in the brain, it is likely that BDNF-based therapies would be most effective if they also targeted the cerebral endothelium. In this review, we summarize the available knowledge about the biology and actions of BDNF derived from endothelial cells of the cerebral microvasculature and we emphasize the remaining gaps and shortcomings

Corrigendum to “Vascular brain-derived neurotrophic factor pathway in rats with adjuvant-induced arthritis: Effect of anti-rheumatic drugs” [Atherosclerosis 274 (July 2018) 77–85]

International audienceThe Authors of the above paper regret that there was an error in the published Abstract section. The correct section is therefore published below (the word ‘lower’ has replaced the word ‘higher’ in the first sentence).Results: Vascular BDNF and full length tropomyosin-related kinase B receptor (TrkB-FL) were lower in AIA than in control rats. These changes coincided with decreased endothelial immunoreactivity in BDNF and pTrkBtyr816 and were disconnected from arthritis score. Among anti-rheumatic drugs, only prednisolone and methotrexate prevented AIA-induced vascular BDNF loss. The effect of AIA on aortic BDNF levels was reversed by an NO donor and reproduced by an NOS inhibitor. Finally, LM22A-4 induced both NO-dependent vasodilation and phosphorylation of endothelial NO synthase at serine 1177

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

International audienceINTRODUCTION: Elevation of brain-derived neurotrophic factor (BDNF) levels in the brain and 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. While 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/day for 7 consecutive days) either in a horizontal position at two different speeds to modulate intensity (experiment 1) or at three different inclinations (null, -10%, +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, pTrk, 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)

Vascular brain-derived neurotrophic factor pathway in rats with adjuvant-induced arthritis: Effect of anti-rheumatic drugs

International audienceBackground and aims: In rheumatoid arthritis, the control of both disease activity and standard cardiovascular (CV) risk factors is expected to attenuate the increased CV risk. Evidence that brain-derived neurotrophic factor (BDNF) plays a role in vascular biology led us to investigate the vascular BDNF pathway in arthritis rats as well as the interaction between endothelial nitric oxide (NO) and BDNF production.Methods: The aortic BDNF pathway was studied in rats with adjuvant-induced arthritis, (AIA) using Western blot and immunohistochemical analysis. Control of arthritis score was achieved by administration (for 3 weeks) of an equipotent dosage of etanercept, prednisolone, methotrexate, celecoxib or diclofenac. Aortas were exposed to an NO donor or an NO synthase inhibitor and vasoreactivity experiments were performed using LM22A-4 as a TrkB agonist.Results: Vascular BDNF and full length tropomyosin-related kinase B receptor (TrkB-FL) were higher in AIA than in control rats. These changes coincided with decreased endothelial immunoreactivity in BDNF and pTrkBtyr816 and were disconnected from arthritis score. Among anti-rheumatic drugs, only prednisolone and methotrexate prevented AIA-induced vascular BDNF loss. The effect of AIA on aortic BDNF levels was reversed by an NO donor and reproduced by an NOS inhibitor. Finally, LM22A-4 induced both NO-dependent vasodilation and phosphorylation of endothelial NO synthase at serine 1177.Conclusions: Our study identified changes in the BDNF/TrkB pathway as a disease activity-independent component of AIA-associated changes in endothelial phenotype. It provides new perspectives in the understanding and management of the high CV risk reported in rheumatoid arthritis

Relevance of Post-Stroke Circulating BDNF Levels as a Prognostic Biomarker of Stroke Outcome. Impact of rt-PA Treatment

International audienceThe recombinant form of tissue plasminogen activator (rt-PA) is the only curative treatment for ischemic stroke. Recently, t-PA has been linked to the metabolism of brain-derived neurotrophic factor (BDNF), a major neurotrophin involved in post-stroke neuroplasticity. Thus, the objective of our study was to investigate the impact of rt-PA treatment on post-stroke circulating BDNF levels in humans and in animals. Serum BDNF levels and t-PA/plasmin activity were measured at hospital admission and at up to 90 days in stroke patients receiving (n = 24) or not (n = 14) rt-PA perfusion. We investigated the relationships between serum BDNF with concurrent t-PA/plasmin activity, neurological outcomes and cardiovascular scores at admission. In parallel, serum BDNF levels and t-PA/plasmin activity were assessed before and after (1, 4 and 24h) the induction of ischemic stroke in rats. Our study revealed higher serum BDNF levels and better neurological outcome in rt-PA-treated than non-treated patients. However, serum BDNF levels did not predict stroke outcome when the whole cohort of stroke patients was analyzed. By contrast, serum BDNF levels when measured at admission and at day 90 correlated with cardiovascular scores, and those at day 1 correlated with serum t-PA/plasmin activity in the whole cohort of patients whereas no association could be found in the rt-PA-treated group. In rats devoid of cardiovascular risk, no difference in post-stroke serum BDNF levels was detected between rt-PA- and vehicle-treated animals and no correlation was found between serum BDNF levels and t-PA/plasmin activity. Overall, the data suggest that serum BDNF levels may not be useful as a prognostic biomarker of stroke outcome and that endothelial dysfunction could be a confounding factor when serum BDNF levels after stroke are used to reflect of brain BDNF levels

''Comparative Effect of Treadmill Exercise on Mature BDNF Production in Control versus Stroke Rats''

Quirie, Aurore | Hervieu, Marie | Garnier, Philippe | Demougeot, Celine | Mossiat, Claude | Bertrand, Nathalie | Martin, Alain | Marie, Christine | Prigent-Tessier, AnneInternational audience''Physical exercise constitutes an innovative strategy to treat deficits associated with stroke through the promotion of BDNF-dependent neuroplasticity. However, there is no consensus on the optimal intensity/duration of exercise. In addition, whether previous stroke changes the effect of exercise on the brain is not known. Therefore, the present study compared the effects of a clinically-relevant form of exercise on cerebral BDNF levels and localization in control versus stroke rats. For this purpose, treadmill exercise (0.3 m/s, 30 min/day, for 7 consecutive days) was started in rats with a cortical ischemic stroke after complete maturation of the lesion or in control rats. Sedentary rats were run in parallel. Mature and proBDNF levels were measured on the day following the last boot of exercise using Western blotting analysis. Total BDNF levels were simultaneously measured using ELISA tests. As compared to the striatum and the hippocampus, the cortex was the most responsive region to exercise. In this region, exercise resulted in a comparable increase in the production of mature BDNF in intact and stroke rats but increased proBDNF levels only in intact rats. Importantly, levels of mature BDNF and synaptophysin were strongly correlated. These changes in BDNF metabolism coincided with the appearance of intense BDNF labeling in the endothelium of cortical vessels. Notably, ELISA tests failed to detect changes in BDNF forms. Our results suggest that control beings can be used to find conditions of exercise that will result in increased mBDNF levels in stroke beings. They also suggest cerebral endothelium as a potential source of BDNF after exercise and highlight the importance to specifically measure the mature form of BDNF to assess BDNF-dependent plasticity in relation with exercise.'