Endogenous vascular remodeling in ischemic skeletal muscle: a role for nitric oxide

Nitrosative Stress in Astronaut Skeletal Muscle in Spaceflight

Long-duration mission (LDM) astronauts from the International Space Station (ISS) (>180 ISS days) revealed a close-to-normal sarcolemmal nitric oxide synthase type-1 (NOS1) immunoexpression in myofibers together with biochemical and quantitative qPCR changes in deep calf soleus muscle. Nitro-DIGE analyses identified functional proteins (structural, metabolic, mitochondrial) that were over-nitrosylated post- vs. preflight. In a short-duration mission (SDM) astronaut (9 ISS days), s-nitrosylation of a nodal protein of the glycolytic flux, specific proteins in tricarboxylic acid (TCA) cycle, respiratory chain, and over-nitrosylation of creatine kinase M-types as signs of impaired ATP production and muscle contraction proteins were seen. S-nitrosylation of serotransferrin (TF) or carbonic anhydrase 3 (CA3b and 3c) represented signs of acute response microgravity muscle maladaptation. LDM nitrosoprofiles reflected recovery of mitochondrial activity, contraction proteins, and iron transporter TF as signs of muscle adaptation to microgravity. Nitrosated antioxidant proteins, alcohol dehydrogenase 5/S-nitrosoglutathione reductase (ADH5/GSNOR), and selenoprotein thioredoxin reductase 1 (TXNRD1) levels indicated signs of altered redox homeostasis and reduced protection from nitrosative stress in spaceflight. This work presents a novel spaceflight-generated dataset on s-nitrosylated muscle protein signatures from astronauts that helps both to better understand the structural and molecular networks associated to muscular nitrosative stress and to design countermeasures to dysfunction and impaired performance control in human spaceflight missions.

Nitric Oxide and Hydrogen Sulfide Regulation of Ischemic Vascular Growth and Remodeling

Ischemic vascular remodeling occurs in response to stenosis or arterial occlusion leading to a change in blood flow and tissue perfusion. Altered blood flow elicits a cascade of molecular and cellular physiological responses leading to vascular remodeling of the macro- and micro-circulation. Although cellular mechanisms of vascular remodeling such as arteriogenesis and angiogenesis have been studied, therapeutic approaches in these areas have had limited success due to the complexity and heterogeneous constellation of molecular signaling events regulating these processes. Understanding central molecular players of vascular remodeling should lead to a deeper understanding of this response and aid in the development of novel therapeutic strategies. Hydrogen sulfide (H₂ S) and nitric oxide (NO) are gaseous signaling molecules that are critically involved in regulating fundamental biochemical and molecular responses necessary for vascular growth and remodeling. This review examines how NO and H₂ S regulate pathophysiological mechanisms of angiogenesis and arteriogenesis, along with important chemical and experimental considerations revealed thus far. The importance of NO and H₂ S bioavailability, their synthesis enzymes and cofactors, and genetic variations associated with cardiovascular risk factors suggest that they serve as pivotal regulators of vascular remodeling responses. © 2019 American Physiological Society. Compr Physiol 9:1213-1247, 2019.

Ghrelin Promotes Functional Angiogenesis in a Mouse Model of Critical Limb Ischemia Through Activation of Proangiogenic MicroRNAs

Current therapeutic strategies for the treatment of critical limb ischemia (CLI) have only limited success. Recent in vitro evidence in the literature, using cell lines, proposes that the peptide hormone ghrelin may have angiogenic properties. In this study, we aim to investigate if ghrelin could promote postischemic angiogenesis in a mouse model of CLI and, further, identify the mechanistic pathway(s) that underpin ghrelin's proangiogenic properties. CLI was induced in male CD1 mice by femoral artery ligation. Animals were then randomized to receive either vehicle or acylated ghrelin (150 μg/kg sc) for 14 consecutive days. Subsequently, synchrotron radiation microangiography was used to assess hindlimb perfusion. Subsequent tissue samples were collected for molecular and histological analysis. Ghrelin treatment markedly improved limb perfusion by promoting the generation of new capillaries and arterioles (internal diameter less than 50 μm) within the ischemic hindlimb that were both structurally and functionally normal; evident by robust endothelium-dependent vasodilatory responses to acetylcholine. Molecular analysis revealed that ghrelin's angiogenic properties were linked to activation of prosurvival Akt/vascular endothelial growth factor/Bcl-2 signaling cascade, thus reducing the apoptotic cell death and subsequent fibrosis. Further, ghrelin treatment activated proangiogenic (miR-126 and miR-132) and antifibrotic (miR-30a) microRNAs (miRs) while inhibiting antiangiogenic (miR-92a and miR-206) miRs. Importantly, in vitro knockdown of key proangiogenic miRs (miR-126 and miR-132) inhibited the angiogenic potential of ghrelin. These results therefore suggest that clinical use of ghrelin for the early treatment of CLI may be a promising and potent inducer of reparative vascularization through modulation of key molecular factors.

The association of plasma vitamin A and E levels with coronary collateral circulation

OBJECTIVE

To investigate if plasma levels of vitamin A and E have an association with coronary collateral development.

METHODS

A total of 189 patients who underwent coronary angiography and had total occlusion in at least one major epicardial coronary artery were enrolled in the study. To classify coronary collateral circulation (CCC), the Rentrop scoring system was used. Patients were classified as having poor CCC (Rentrop grades 0-1) or good CCC (Rentrop grades 2-3), and all patients were also screened for hypertension, hypercholesterolemia, diabetes, and smoking history.

RESULTS

There were no differences in plasma vitamin A and E levels between the two groups (vitamin A: 2.37 ± 0.65 vs. 2.35 ± 0.78, p = 0.253; vitamin E: 47.1 ± 12.8 vs. 44.6 ± 15.1, p = 0.082), and plasma vitamin A and E levels were not associated with CCC. Serum high-sensitivity C-reactive protein (hs-CRP) levels were significantly higher in patients with poor CCC (4.68 ± 2.52 vs. 3.89 ± 1.78, p = 0.001). The higher frequency of diabetes and higher serum hs-CRP levels were found to be an independent predictor for poor CCC (odds ratio = 2.44, p = 0.006; odds ratio = 1.24, p = 0.007, respectively). And a higher frequency of total occluded RCA was found to be a positive predictor for good CCC (odds ratio = 2.36, p = 0.06) in a multivariate logistic regression analysis.

CONCLUSIONS

We found that serum hs-CRP levels, presence of diabetes, and total occlusion of RCA have an effect on coronary collateral development. We found no correlation between plasma vitamin A and E levels and CCC.

Far red/near infrared light treatment promotes femoral artery collateralization in the ischemic hindlimb

Nitric oxide (NO) is a crucial mediator of hindlimb collateralization and angiogenesis. Within tissues there are nitrosyl-heme proteins which have the potential to generate NO under conditions of hypoxia or low pH. Low level irradiation of blood and muscle with light in the far red/near infrared spectrum (670 nm, R/NIR) facilitates NO release. Therefore, we assessed the impact of red light exposure on the stimulation of femoral artery collateralization. Rabbits and mice underwent unilateral resection of the femoral artery and chronic R/NIR treatment. The direct NO scavenger carboxy-PTIO and the nitric oxide synthase (NOS) inhibitor L-NAME were also administered in the presence of R/NIR. DAF fluorescence assessed R/NIR changes in NO levels within endothelial cells. In vitro measures of R/NIR induced angiogenesis were assessed by endothelial cell proliferation and migration. R/NIR significantly increased collateral vessel number which could not be attenuated with L-NAME. R/NIR induced collateralization was abolished with c-PTIO. In vitro, NO production increased in endothelial cells with R/NIR exposure, and this finding was independent of NOS inhibition. Similarly R/NIR induced proliferation and tube formation in a NO dependent manner. Finally, nitrite supplementation accelerated R/NIR collateralization in wild type C57Bl/6 mice. In an eNOS deficient transgenic mouse model, R/NIR restores collateral development. In conclusion, R/NIR increases NO levels independent of NOS activity, and leads to the observed enhancement of hindlimb collateralization.

Oral tetrahydrobiopterin improves the beneficial effect of adenoviral-mediated eNOS gene transfer after induction of hindlimb ischemia

We tested the hypothesis that oral supplementation with the endothelial nitric oxide synthase (eNOS) cofactor tetrahydrobiopterin (BH(4)) improved the therapeutic efficacy of eNOS gene transfer in the ischemic rat hindlimb. BH(4) or vehicle were begun 1 week before induction of hindlimb ischemia, whereas recombinant adenovirus containing bovine eNOS cDNA (AdeNOS) or vehicle [phosphate-buffered saline (PBS)] was infused intra-arterially into the ischemic hindlimb 10 days after induction of ischemia. Rats receiving co-treatment with dietary BH(4) and eNOS gene transfer (the [eNOS, +BH(4)] group) had greater eNOS expression, phospho-eNOS expression (Ser(1177)), Ca(2+)-dependent NOS activity, and nitrite + nitrate concentrations in the ischemic gastrocnemius than did rats receiving AdeNOS alone. The [eNOS, +BH(4)] group demonstrated less nitrotyrosine and a higher ratio of reduced:oxidized glutathione (GSH:GSSG) in the ischemic gastrocnemius muscle than did rats receiving AdeNOS alone. The [eNOS, +BH(4)] group had greater flow recovery and a higher capillary:myocyte ratio in the ischemic hindlimb than did rats receiving AdeNOS alone. Finally, the [eNOS,+BH(4)] group had less necrosis of hindlimb muscles than rats given AdeNOS alone. We conclude that adjunctive dietary therapy with BH(4) increases the beneficial effects of eNOS gene transfer within the ischemic gastrocnemius muscle, as evidenced by increased nitric oxide (NO) production, diminished oxidative stress, enhanced flow recovery, and reduced necrosis.

The relation between endothelial dependent flow mediated dilation of the brachial artery and coronary collateral development - a cross sectional study

BACKGROUND

Endothelial dysfunction is thought to be a potential mechanism for the decreased presence of coronary collaterals. The aim of the study was to investigate the association between systemic endothelial function and the extent of coronary collaterals.

METHODS

We investigated the association between endothelial function assessed via flow mediated dilation (FMD) of the brachial artery following reactive hyperemia and the extent of coronary collaterals graded from 0 to 3 according to Rentrop classification in a cohort of 171 consecutive patients who had high grade coronary stenosis or occlusion on their angiograms.

RESULTS

Mean age was 61 years and 75% were males. Of the 171 patients 88 (51%) had well developed collaterals (grades of 2 or 3) whereas 83 (49%) had impaired collateral development (grades of 0 or 1). Patients with poor collaterals were significantly more likely to have diabetes (p = 0.001), but less likely to have used statins (p = 0.083). FMD measurements were not significantly different among good and poor collateral groups (11.5 +/- 5.6 vs. 10.4 +/- 6.2% respectively, p = 0.214). Nitroglycerin mediated dilation was also similar (13.4 +/- 5.9 vs. 12.8 +/- 6.5%, p = 0.521).

CONCLUSION

No significant association was found between the extent of angiographically visible coronary collaterals and systemic endothelial function assessed by FMD of the brachial artery.

Association of paraoxonase activity and coronary collateral flow

OBJECTIVES

Paraoxonase is a high-density lipoprotein-bound antioxidant enzyme that inhibits atherosclerosis and endothelial dysfunction. Coronary collateral flow is a crucial clinical entity with significant impact on the cardiovascular morbidity and mortality. This study sought to determine the relationship between the degree of angiographically visible coronary collateral circulation and serum paraoxonase activity.

METHODS

The study population included 98 patients (mean age=57.9+/-10.1 years, 65 men) with angiographically documented total occlusion in one of the major coronary arteries. Development of collaterals was classified by Rentrop's method. Patients were defined as having poorly developed collaterals for Rentrop grades 0 and 1 or well-developed collaterals for Rentrop grades 2 and 3. Serum paraoxonase and arylesterase activities were measured spectrophotometrically.

RESULTS

Statistically significant differences between well and poorly developed collateral groups in respect to serum low-density lipoprotein cholesterol level (P=0.046), and serum paraoxonase (P=0.001), and arylesterase (P=0.014) activities were present. Serum low-density lipoprotein cholesterol level (chi=4.15, beta=-0.347, P=0.032) and serum paraoxonase activity (chi=10.43, beta=0.008, P=0.022) were independent predictors of well-developed coronary collateral flow. Serum paraoxonase activity gradually increased from collateral grade 0 to collateral grade 3 (analysis of variance P=0.003). Serum paraoxonase (r=0.362 and P<0.001) and arylesterase (r=0.245 and P=0.015) activities were both correlated with collateral flow grade.

CONCLUSION

Findings of this study suggest that serum paraoxonase activity is independently associated with the degree of coronary collateral flow and reduced serum paraoxonase activity might represent a biochemical marker of impaired coronary collateral flow.

Optimization of adenovirus-mediated endothelial nitric oxide synthase delivery in rat hindlimb ischemia

Adenovirus-mediated overexpression of endothelial nitric oxide synthase (eNOS) induces collateral artery development and substantially increases blood flow after induction of experimental acute hindlimb ischemia. However, the optimal technique of gene delivery for this or any other form of gene therapy in limb ischemia is still unknown. The purpose of this study was to determine the effect of the two most commonly used techniques, intra-arterial and intramuscular injection, on blood flow recovery, collateral artery development, and preservation of muscle mass. We compared intra-arterial injection under vascular isolation, intra-arterial injection under transient vascular occlusion, and intramuscular injection of phosphate buffered saline (PBS) or adenovirus encoding either the eNOS (AdeNOS) or LacZ (AdlacZ) gene after induction of acute hindlimb ischemia. Delivery of AdeNOS by both intra-arterial injection techniques increased eNOS activity (22.30 versus 10.56, P<0.01), blood flow (0.90+/-0.02 versus 0.69+/-0.07, P<0.001) and collateral artery development (17.56484 versus 13.74259, P<0.05) more than by intramuscular delivery. Intra-arterial injection under transient vascular occlusion led to better preservation of muscle mass, muscle architecture, and clinical ischemic index, but led to greater transgene expression in distant organs and contralateral limb muscles. Intra-arterial injection of AdeNOS under transient vascular occlusion is the optimal technique to reverse severe hindlimb ischemia in the rat. This is the first systematic comparison of different delivery techniques used in gene therapy of experimental hindlimb ischemia.

Differential expression of nitric oxide synthases (NOS 1-3) in human skeletal muscle following exercise countermeasure during 12 weeks of bed rest

Adaptive changes of major body systems in astronauts during spaceflight can be simulated by strict anti-orthostatic head-down tilt (HDT) bed rest (BR), a ground-based microgravity (microG) model that provides a meaningful opportunity to study atrophy mechanisms and possible countermeasures under controlled experimental conditions. As nitric oxide (NO) signaling is linked to muscle activity, we investigated altered expression of the three major isoforms of nitric oxide synthase (NOS 1-3) at cellular compartments during prolonged HDT BR without (control group) and with resistance exercise interventions (exercise group) using a flywheel ergometer (FWE). Atrophy detected in mixed (fast-slow) m. vastus lateralis (VL) and slow-type m. soleus (SOL) myofiber Types I and II (minus 35-40% of myofiber cross-sectional area) was prevented by FWE training. Concomitant to muscle atrophy, reduced NOS 1 protein and immunostaining was found in VL not in SOL biopsies. In trained VL, NOS 1 protein and immunostaining at myofibers II were significantly increased at the end of BR. Exercise altered NOS 2/caveolin 3 co-immunostaining patterns of subsarcolemmal focal accumulations in VL or SOL myofibers, which suggests reorganization of sarcolemmal microdomains. In trained VL, increased capillary-to-fiber (C/F) ratio and NOS 3 protein content were documented. Activity-linked NO signaling may be widespread in skeletal muscle cellular compartments that may be directly or indirectly impacted by adequate exercise countermeasure protocols to offset the negative effects induced by disuse, immobilization, or extended exposure to microgravity.