Endothelial dysfunction in hypercholesterolemia is corrected by L-arginine

An Overview of NO Signaling Pathways in Aging

Nitric Oxide (NO) is a potent signaling molecule involved in the regulation of various cellular mechanisms and pathways under normal and pathological conditions. NO production, its effects, and its efficacy, are extremely sensitive to aging-related changes in the cells. Herein, we review the mechanisms of NO signaling in the cardiovascular system, central nervous system (CNS), reproduction system, as well as its effects on skin, kidneys, thyroid, muscles, and on the immune system during aging. The aging-related decline in NO levels and bioavailability is also discussed in this review. The decreased NO production by endothelial nitric oxide synthase (eNOS) was revealed in the aged cardiovascular system. In the CNS, the decline of the neuronal (n)NOS production of NO was related to the impairment of memory, sleep, and cognition. NO played an important role in the aging of oocytes and aged-induced erectile dysfunction. Aging downregulated NO signaling pathways in endothelial cells resulting in skin, kidney, thyroid, and muscle disorders. Putative therapeutic agents (natural/synthetic) affecting NO signaling mechanisms in the aging process are discussed in the present study. In summary, all of the studies reviewed demonstrate that NO plays a crucial role in the cellular aging processes.

Deletion of endothelial arginase 1 does not improve vasomotor function in diabetic mice

Endothelial arginase 1 was ablated to assess whether this prevents hyperglycemia-induced endothelial dysfunction by improving arginine availability for nitric oxide production. Endothelial Arg1-deficient mice (Arg1-KOTie2 ) were generated by crossing Arg1fl/fl (controls) with Tie2Cretg/- mice and analyzed by immunohistochemistry, measurements of hemodynamics, and wire myography. Ablation was confirmed by immunohistochemistry. Mean arterial blood pressure was similar in conscious male control and Arg1-KOTie2 mice. Depletion of circulating arginine by intravenous infusion of arginase 1 or inhibition of nitric oxide synthase activity with L-NG -nitro-arginine methyl ester increased mean arterial pressure similarly in control (9 ± 2 and 34 ± 2 mmHg, respectively) and Arg1-KOTie2 mice (11 ± 3 and 38 ± 4 mmHg, respectively). Vasomotor responses were studied in isolated saphenous arteries of 12- and 34-week-old Arg1-KOTie2 and control animals by wire myography. Diabetes was induced in 10-week-old control and Arg1-KOTie2 mice with streptozotocin, and vasomotor responses were studied 10 weeks later. Optimal arterial diameter, contractile responses to phenylephrine, and relaxing responses to acetylcholine and sodium nitroprusside were similar in normoglycemic control and Arg1-KOTie2 mice. The relaxing response to acetylcholine was dependent on the availability of extracellular l-arginine. In the diabetic mice, arterial relaxation responses to endothelium-dependent hyperpolarization and to exogenous nitric oxide were impaired. The data show that endothelial ablation of arginase 1 in mice does not markedly modify smooth muscle and endothelial functions of a resistance artery under normo- and hyperglycemic conditions.

Use of Eflornithine (DFMO) in the Treatment of Early Alzheimer's Disease: A Compassionate Use, Single-Case Study

Background: Recent genome-wide association screening (GWAS) studies have linked Alzheimer's disease (AD) neuropathology to gene networks that regulate immune function. Kan et al. recently reported that Arg1 (an anti-inflammatory gene that codes for arginase-1) is expressed in parts of the brain associated with amyloidosis prior to the onset of neuronal loss, suggesting that chronic brain arginine deprivation promotes AD-related neuropathology. They blocked arginine catabolism in their mouse AD model by administration of eflornithine (DFMO) to juvenile animals, effectively blocking the expression of AD-related amyloid pathology as the mice aged. We report results from a single-case study in which DFMO was administered, for the first time, in an attempt to slow progression of AD in a single woman with multi-domain, amnestic MCI who was unable to tolerate an acetylcholinesterase inhibitor. Methods: Patient C.S. is a 74-year old female with a 5-year history of cognitive decline who was placed on DFMO (500 mg b.i.d.) for 12 months, with amyloid PET scans (baseline and 12-months), APOE genotyping and neuropsychological exams at baseline, 3, 9, and 12 months. Results: C.S. suffered continued cognitive decline over 12 months, including progressive worsening of orientation, social functions and ability to engage in IADL's. She also showed progressive decline on measures of episodic memory and executive function. Florbetapir PET imaging yielded elevated total neocortical SUVr scores at both baseline (SUVr = 1.55) and at 12 months (SUVr = 1.69). Conclusions: We report a first attempt at using DFMO to slow AD progression. This 12-month single-case trial did not halt continued amyloidosis nor cognitive decline. Although this trial was predicated on data reported by Kan et al. (2015) showing that DFMO administered to juvenile AD-prone mice led to diminished amyloid aggregation, this attempt to treat an older mild AD patient may not be a fair test of Kan et al.'s model and results. A future trial might seek to block amyloidosis in young adults who are autosomal gene carriers for early onset AD, or perhaps in adults who are very clearly in the pre-clinical disease stage. Trial Registration: This trial was registered as a Compassionate Use IND #128888 with the United States Food and Drug Administration (FDA).

The Arginine/ADMA Ratio Is Related to the Prevention of Atherosclerotic Plaques in Hypercholesterolemic Rabbits When Giving a Combined Therapy with Atorvastatine and Arginine

Supplementation with arginine in combination with atorvastatin is more efficient in reducing the size of an atherosclerotic plaque than treatment with a statin or arginine alone in homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits. We evaluated the mechanism behind this feature by exploring the role of the arginine/asymmetric dimethylarginine (ADMA) ratio, which is the substrate and inhibitor of nitric oxide synthase (NOS) and thereby nitric oxide (NO), respectively. Methods: Rabbits were fed either an arginine diet (group A, n = 9), standard rabbit chow plus atorvastatin (group S, n = 8), standard rabbit chow plus an arginine diet with atorvastatin (group SA, n = 8) or standard rabbit chow (group C, n = 9) as control. Blood was sampled and the aorta was harvested for topographic and histological analysis. Plasma levels of arginine, ADMA, cholesterol and nitric oxide were determined and the arginine/ADMA ratio was calculated. Results: The decrease in ADMA levels over time was significantly correlated to fewer aortic lesions in the distal aorta and total aorta. The arginine/ADMA ratio was correlated to cholesterol levels and decrease in cholesterol levels over time in the SA group. A lower arginine/ADMA ratio was significantly correlated to lower NO levels in the S and C group. Discussion: A balance between arginine and ADMA is an important indicator in the prevention of the development of atherosclerotic plaques.

A clinical study about contrast nephropathy: risk factors and the role of beta blockers

Objective:

There is still a group of patient that have unpredictable risk for the development of contrast nephropathy (CN). There is also an effort to find more effficient strategies to prevent CN. Carvedilol, metoprolol and nebivolol seem to have theoretical potentials for the prevention of CN. In this study, we aimed to investigate their effects on the prevention of CN. We also aimed to define the risk factors associated with the development of CN in our study group.

Methods:

In this prospective, cross-sectional study, the patients were divided into four groups according to whether they were taking 25 mg/day carvedilol (n:56), 5 mg/day nebivolol (n:60), 50 mg/day metoprolol (n:68) or none (n:63). We made analysis to determine the agents’ efficiency on the prevention of CN. We also performed multiple logistic regression analysis including all groups to define the risk factors associated with CN.

Results:

The incidents of CN were the lowest in the carvedilol group (4%) while the worst performance occurred in those taking metoprolol (10%). The difference between the groups in terms of the development of CN did not reach statistical significance (p>0.05). Multiple logistic regression analysis showed age (p=0.003), higher triglyceride levels (p=0.011) and family history of coronary artery disease (p=0.038) to be the predictors of CN.

Conclusion:

In this study, we didn’t find any relation between the development of CN and carvedilol, metoprolol or nebivolol usage. We found age, higher levels of triglyceride and family history of coronary artery disease to be risk factors for predicting CN.

Is inflammation the cause of pre-eclampsia?

It has been proposed that either excessive inflammation or an imbalance in angiogenic factors cause pre-eclampsia. In the present review, the arguments for and against the role of inflammation and/or angiogenic imbalance as the cause of pre-eclampsia are discussed on the basis of the Bradford–Hill criteria for disease causation. Although both angiogenic imbalance and systemic inflammation are implicated in pre-eclampsia, the absence of temporality of inflammatory markers with pre-eclampsia challenges the concept that excessive inflammation is the cause of pre-eclampsia. In contrast, the elevation of anti-angiogenic factors that precede the clinical signs of pre-eclampsia fulfils the criterion of temporality. The second most important criterion is the dose–response relationship. Although such a relationship has not been proven between pro-inflammatory cytokines and pre-eclampsia, high levels of anti-angiogenic factors have been shown to correlate with increased incidence and disease severity, hence satisfying this condition. Finally, as the removal of circulating sFlt-1 (soluble Fms-like tyrosine kinase receptor-1) from pre-eclamptic patients significantly improves the clinical outcome, it fulfils the Hill's experiment principle, which states that removal of the cause by an appropriate experimental regimen should ameliorate the condition. In contrast, treatment with high doses of corticosteroid fails to improve maternal outcome in pre-eclampsia, despite suppressing inflammation. Inflammation may enhance the pathology induced by the imbalance in the angiogenic factors, but does not by itself cause pre-eclampsia. Development of therapies based on the angiogenic and cytoprotective mechanisms seems more promising.

Vascular Nitric Oxide: Formation and Function

Nitric oxide (NO) is a structurally simple, highly versatile molecule that was originally discovered over 30 years ago as an endothelium-derived relaxing factor. In addition to its vasorelaxing effects, NO is now recognized as a key determinant of vascular health, exerting antiplatelet, antithrombotic, and anti-inflammatory properties within the vasculature. This short-lived molecule exerts its inhibitory effect on vascular smooth muscle cells and platelets largely through cyclic guanosine monophosphate-dependent mechanisms, resulting in a multitude of molecular effects by which platelet activation and aggregation are prevented. The biosynthesis of NO occurs via the catalytic activity of NO synthase, an oxidoreductase found in many cell types. NO insufficiency can be attributed to limited substrate/cofactor availability as well as interactions with reactive oxygen species. Impaired NO bioavailability represents the central feature of endothelial dysfunction, a common abnormality found in many vascular diseases. In this review, we present an overview of NO synthesis and biochemistry, discuss the mechanisms of action of NO in regulating platelet and endothelial function, and review the effects of vascular disease states on NO bioavailability.

Effect of atherosclerosis on transmural convection an arterial ultrastructure. Implications for local intravascular drug delivery

Local infusion of agents through perforated catheters may reduce neointimal formation following vascular angioplasty. Such treatment will succeed only if the drug is retained within the arterial intima long enough to promote repair. Drugs will be dispersed throughout the wall predominantly by transmural convection instead of diffusion if the Peclet number, Pe = J (1-delta f)/P, is greater than unity, where J is the transmural fluid flow per unit surface area and delta(f) and P are the reflection and permeability coefficients to the drug, respectively. Although the targets of local drug delivery will be atherosclerotic vessels, little is known about the transport properties of these vessels. Accordingly, we evaluated the effects of hypercholesterolemia and atherosclerosis on J per unit pressure (hydraulic conductance, Lp) and on ultrastructure in femoral arteries. Measurements were made at 30, 60, and 90 mm Hg in anesthetized New Zealand white rabbits fed a normal diet (n = 6) and after 3 weeks of lipid feeding (n = 19). Atherosclerosis was induced in six lipid-fed animals by air desiccation of a femoral artery. Hydraulic conductance was significantly greater in vessels from hypercholesterolemic than from normal animals and decreased with pressure only in hypercholesterolemic arteries. Atherosclerosis did not augment hydraulic conductance compared with hypercholesterolemia alone. Electron microscopic examination demonstrated damaged endothelium in hypercholesterolemic arteries and both altered endothelium and less tightly packed medial tissue, compared with controls, in atherosclerotic vessels, at least at lower pressures. Peclet numbers for macromolecules exceeded unity for all three groups of arteries and reached 0.3 to 0.4 for molecules as small as heparin. Thus, convection plays a dominant role in the distribution of macromolecular agents following local delivery and may result in their rapid transport to the adventitia in the femoral artery.