Citations

Endothelial dysfunction and arterial stiffening major risk factors associated with progression of atherosclerosis and increased risk of acute coronary events. Recent data suggest sirtuins may play a role in protecting against a variety age-related diseases, and we recently reported that sirtuins are reduced in the aging vasculature. The roles of SIRT3 (a deacetylase that is largely restricted to the mitochondria) in the regulation of vasomotor function and arterial stiffness, however, remains poorly understood. Therefore, we hypothesized that genetic inactivation of SIRT3 in hypercholesterolemic mice will impair endothelial function and reduce vascular compliance compared to hypercholesterolemic mice with normal levels of SIRT3. We used Ldlr -/- /ApoB 100/100 (LA) mice that were either wild-type for SIRT3 (LA-SIRT3 +/+ ) or null for SIRT3 (LA-SIRT3 -/- ) and fed a western diet for 12 months. At time of sacrifice, aorta was removed for isolated organ chamber baths to measure changes in endothelium-dependent relaxation to acetylcholine (ACH), and carotid arteries were harvested to assess changes in vascular compliance using a pressurized cannulation system. Surprisingly, losses of SIRT3 did not impair relaxation to ACH in aorta compared to LA-SIRT3 +/+ mice (38.2±4.4%, 37.0±4.4%, respectively). Furthermore, reductions in SIRT3 did not impact vascular compliance or distensibility in carotid arteries from the same animals. In conclusion, in contrast to our hypothesis, inactivation of SIRT3 does not impact vasomotor function or conduit vessel compliance in advanced atherosclerosis. Importantly, this and may be explained by a “floor-effect”, and future work examining the effect of SIRT3 overexpression on vascular function and pathology will be instrumental in determining its biological role and ultimate therapeutic utility.

Evidence continues to accumulate on the importance of endothelial progenitor cells (EPCs) in neovascularization of ischemic tissues and repair of injured endothelium. The present study was designed to determine the in vivo effect of EPCs on the vasomotor function of rabbit cerebral arteries. Isolated mononuclear cells from rabbit peripheral blood were cultured in endothelial growth medium (EGM‐2) for 7 days, yielding EPCs. Rabbits were injected intracisternally with either autologous EPCs (1x10 5 to 5x10 5 cells) or vehicle (EGM‐2) as control. After 24 hours, basilar arteries were isolated, vasomotor function was studied in organ chambers, and protein expression in the basilar arteries quantified by Western blot analysis. In rabbits treated with EPCs, contractions to either potassium chloride (80 mmol/L) or histamine (10 −9 to 10 −5 mol/L) were not affected. However, endothelium‐dependent relaxations to acetylcholine (10 −9 to 10 −5 mol/L) and endothelium‐independent relaxations to a NO donor, DEA‐NONOate (10 −9 to 10 −5 mol/L) were enhanced in basilar arteries from EPC‐treated rabbits. Western blot studies demonstrated increased expressions of cyclooxygenase‐2 and prostacyclin synthase (PGI 2 synthase) only in arteries exposed to EPCs. Results of the present study suggest that in vivo administration of EPCs could augment vasodilatation of the cerebral arteries by increasing vascular production of prostacyclin. Funded by NIH HL66958.

Erythropoietin (EPO) fosters tissue oxygenation by stimulating erythropoiesis. More recently, EPO is recognized as a tissue protective cytokine. In this study, we tested the hypothesis that EPO promotes recovery of injured vascular endothelium. A murine model of wire‐induced injury of common carotid artery was used to examine the therapeutic effect of EPO. Recombinant human EPO (1000 U/kg, s.c., biweekly) was administered for 2 weeks after which vascular reactivity of isolated carotid arteries was studied in vitro under pressurized condition using a video dimension analyzer. Changes in vascular structure were histologically assessed. Injured arteries exhibited impairment in endothelium‐dependent relaxations to acetylcholine and increased thickness of the medial cross sectional area (P<0.05; n=5–7). EPO normalized the vasorelaxant response of injured arteries to acetylcholine and prevented the increase in medial cross sectional area (30±1 x 10 ‐3 mm 2 ; P<0.05 vs. without EPO: 37±3 x 10 ‐3 mm 2 ; n=6). The number of circulating endothelial progenitor cells (EPCs), defined as CD34 + /Flk‐1 + cells in the peripheral blood, was significantly reduced 2 weeks after vascular injury (0.016±0.005%; P<0.05 vs. non‐injured control: 0.09±0.01%), but this was entirely restored by EPO (0.212±0.08%; P<0.05; n=5). Our results indicate that EPO accelerates recovery of the injured carotid artery endothelium, and such salutary effects of EPO may reflect augmentation in circulating EPCs induced by EPO.

Activation of NADPH oxidase is a major contributor to hypertension, reactive oxygen species generation, endothelial dysfunction and increased vascular distensibility in angiotensin II (AngII)‐induced hypertension. Since exercise has been associated with increased antioxidant enzyme expression in blood vessels, we hypothesized that exercise training would improve endothelial function and vascular distensibility in mice with AngII‐induced hypertension. C57BL/6J mice received saline or AngII (1000 ng/kg/min) via osmotic minipumps, and were assigned to sedentary or treadmill exercise groups (13 m/min for 30 minutes, 5 days/week) for 14 days. Endothelium‐dependent relaxation in response to acetylcholine and arterial distensibility were assessed in carotid arteries using a pressurized arteriograph system. Gene expression was examined by qRT‐PCR. In AngII‐treated sedentary mice, endothelium‐dependent relaxation was impaired, while distensibility was higher than in saline‐infused sedentary mice. Compared to AngII‐infused sedentary mice, however, endothelium‐dependent relaxation was partially improved, and distensibility normalized in AngII‐infused exercised mice. In response to exercise, mRNA levels of SOD1 and SOD2 in aorta were increased, while mRNA levels of NOX2 were reduced. We conclude that exercise training can dramatically improve endothelial dysfunction and reverse derangements in carotid distensibility following prolonged AngII‐induced hypertension. Additional work examining mechanisms underlying our observed transcriptional changes will be critical to development of novel therapeutic targets.

The present study is aimed at investigating the contribution of endothelial nitric oxide synthase (eNOS) to erythropoietin (EPO)‐induced mobilization of stem (c‐kit + ,sca‐1 + ,lin‐1 − ; KSL) cells and hematopoietic progenitor (CD34 + ) cells. Wild type (WT) and eNOS −/− mice were injected biweekly with recombinant erythropoietin (1000 U/kg, s.c.) for 14 days. The percentage of KSL cells in spleen, bone marrow and peripheral blood were quantitated by flow cytometry (Becton Dickinson) and analyzed by Cell Quest software. The effect of EPO on number of CD34 + cells in peripheral blood was quantitated by ProCount Progenitor Cell Enumeration Kit (BD Biosciences). Treatment of eNOS −/− mice with EPO increased the percentage of KSL cells by two folds only in bone marrow and spleen, while the percentage of KSL cells in peripheral blood remained unchanged. Treatment with EPO significantly increased the number of CD34 + cells in blood of WT mice (2.75 ± 0.30 cells in WT, 38.39 ± 10.35 in WT+EPO, n=5, P<0.01). However, the number of CD34 + cells remained unchanged in blood of eNOS −/− mice (2.51 ± 1.31 in eNOS −/− , 4.65 ± 1.40 in eNOS −/− + EPO, n=5, P=ns). Results of the present study suggest that eNOS plays an important role in the mobilization of hematopoietic stem/progenitor cells by erythropoietin.

Cilostazol is an inhibitor of phosphodiesterase type III that possesses both antiplatelet and vasodilator effects. The present study aimed to determine the vasodilator effect of cilostazol in eNOS deficient (eNOS −/− ) mice. Mouse aorta was contracted with sub‐maximal concentration of phenylephrine and concentration‐dependent relaxations to cilostazol (10 −8 –10 −5 mol/L) were obtained in aortic rings, isolated from wild type and eNOS −/− mice. As previously reported, in aortas of wild type mice with intact endothelium, relaxations to cilostazol were significantly augmented as compared to aortas without endothelium. Surprisingly, genetic inactivation of eNOS significantly enhanced relaxations to cilostazol suggesting that chronic loss of nitric oxide may unmask compensatory vasodilator mechanisms significantly enhanced by the treatment with cilostazol. The augmentation of relaxations to cilostazol in aortas of eNOS −/− mice was endothelium independent and not inhibited by indomethacin, a cyclooxygenase inhibitor. Our findings support the view that patients suffering from vascular endothelial dysfunction induced by reduced availability of nitric oxide, may exhibit enhanced vasodilator reactivity to cilostazol.

Impaired endothelial function in cardiovascular disorders is mediated, in part, by uncoupling of eNOS caused by reduced availability of tetrahydrobiopterin (BH 4 ). Endothelial progenitor cells (EPCs), originating from bone marrow, contribute to repair of vascular system by either neovascularization following tissue ischemia or re‐endothelialization after endothelial injury. The contribution of BH 4 to the angiogenic function has not been studied. In the present study, we investigated the role of BH 4 in angiogenesis and mobilization of cells enriched in EPCs in hph‐1 mutant mice, a genetic model of GTP‐cyclohydrolase I deficiency. HPLC analysis revealed that enzymatic activity of GTP‐cyclohydrolase I is reduced by 65% in bone marrow of hph‐1 mice (22±4 pmol neopterin/mg/h; P<0.05 vs. wild‐type mice: 63±4 pmol/mg/h). Basal counts of cells co‐expressing CD34 and VEGFR2 (Flk‐1) were reduced in bone marrow and peripheral blood of hph‐1 mice. Fourteen days after hind limb ischemia, recovery of blood flow was significantly reduced in hph‐1 mice as compared to blood flow in ischemic limb of wild type mice. Our findings suggest that reduced bioavailability of BH 4 impairs mobilization of cells enriched in EPCs. This effect may help to explain impaired angiogenesis in hph‐1 mice.

Mobilization of hematopoietic progenitor cells is predictive of functional recovery in stroke. In the present study, alterations in progenitor cell counts were studied in an experimental model of subarachnoid hemorrhage (SAH)‐induced cerebral vasospasm in rabbits. Injection of autologous arterial blood into cisterna magna resulted in significant vasospasm of the basilar arteries forty eight hours following injection. Concomitantly, the number of hematopoietic progenitor cells (CD34 + cells) and CD34 + /Flk‐1 + cells, believed to be enriched in endothelial progenitor cells (EPCs), were significantly increased in the peripheral blood. The levels of the chemokine stromal cell‐derived factor‐1α (SDF‐1α), known to play a key role in the recruitment and retention of CXCR4 + ‐progenitor cells, significantly increased in the plasma of rabbits subjected to SAH. However, levels of SDF‐1α in the cerebrospinal fluid as well as the content of SDF‐1α in the spastic basilar arteries remained unaffected forty eight hours after SAH. In summary, cerebral vasospasm was accompanied by mobilization of hematopoietic progenitor cells and EPCs. We speculate that the pathogenesis of cerebral vasospasm following SAH may be mediated, in part, by impaired recruitment and homing of CXCR4 + ‐ progenitor cells.

AbstractAging and obesity increase multimorbidity and disability risk, and determining interventions for reversing healthspan decline is a critical public health priority. Exercise and time‐restricted feeding (TRF) benefit multiple health parameters when initiated in early life, but their efficacy and safety when initiated at older ages are uncertain. Here, we tested the effects of exercise versus TRF in diet‐induced obese, aged mice from 20 to 24 months of age. We characterized healthspan across key domains: body composition, physical, metabolic, and cardiovascular function, activity of daily living (ADL) behavior, and pathology. We demonstrate that both exercise and TRF improved aspects of body composition. Exercise uniquely benefited physical function, and TRF uniquely benefited metabolism, ADL behavior, and circulating indicators of liver pathology. No adverse outcomes were observed in exercised mice, but in contrast, lean mass and cardiovascular maladaptations were observed following TRF. Through a composite index of benefits and risks, we conclude the net healthspan benefits afforded by exercise are more favorable than those of TRF. Extrapolating to obese older adults, exercise is a safe and effective option for healthspan improvement, but additional comprehensive studies are warranted before recommending TRF.

ABSTRACT Recent studies have demonstrated an effect of neurotrophins, particularly brain‐derived neurotrophic factor (BDNF), on airway contractility [ via increased airway smooth muscle (ASM) intracellular calcium [Ca 2+ ] i ] and remodeling (ASM proliferation and extracellular matrix formation) in the context of airway disease. In the present study, we examined the role of BDNF in allergen‐induced airway inflammation using 2 transgenic models: 1 ) tropomyosin‐related kinase B (TrkB) conditional knockin (TrkBKI) mice allowing for inducible, reversible disruption of BDNF receptor kinase activity by administration of 1NMPP1, a PP1 derivative, and 2) smooth muscle‐specific BDNF knockout (BDNF fl/fl /SMMHCll Cre/0 ) mice. Adult mice were intranasally challenged with PBS or mixed allergen ( Altemaria alternata, Aspergillus fumigatus , house dust mite, and ovalbumin) for 4 wk. Our data show that administration of 1NMPP1 in TrkBKI mice during the 4‐wk allergen challenge blunted airway hyper‐responsiveness (AHR) and reduced fibronectin mRNA expression in ASM layers but did not reduce inflammation per se . Smooth muscle‐specific deletion of BDNF reduced AHR and blunted airway fibrosis but did not significantly alter airway inflammation. Together, our novel data indicate that TrkB signaling is a key modulator of AHR and that smooth muscle‐derived BDNF mediates these effects during allergic airway inflammation.—Britt, R. D., Jr., Thompson, M. A., Wicher, S. A., Manlove, L. J., Roesler, A., Fang, Y.‐H., Roos, C., Smith, L., Miller, J. D., Pabelick, C. M., Prakash, Y. S. Smooth muscle brain‐derived neurotrophic factor contributes to airway hyperreactivity in a mouse model of allergic asthma. FASEB J. 33, 3024–3034 (2019). www.fasebj.org