L-arginine supplementation lowers blood pressure, protein excretion and plasma lipid profile in experimental salt-induced hypertension in pregnancy: Relevance to preeclampsia

The Effectiveness of L-arginine in Clinical Conditions Associated with Hypoxia

The review summarises the data of the last 50 years on the effectiveness of the amino acid L-arginine in therapeutic practice in conditions accompanied by different-origin hypoxia. The aim of this review was to analyse the literature and our research data on the role of nitric oxide in the modulation of individual physiological reactivity to hypoxia. The review considers the possibility of eliminating methodological conflicts in the case of L-arginine, which can be solved by taking into account individual physiological reactivity (or the hypoxia resistance factor). Considerable attention is paid to genetic and epigenetic mechanisms of adaptation to hypoxia and conditions of adaptation in different models. The article presents data on the clinical effectiveness of L-arginine in cardiovascular system diseases (hypertension, atherosclerosis, coronary heart disease, etc.) and stress disorders associated with these diseases. The review presents a generalised analysis of techniques, data on L-arginine use by athletes, and the ambiguous role of NO in the physiology and pathology of hypoxic states shown via nitric oxide synthesis. Data on the protective effects of adaptation in the formation of individual high reactivity in sportsmen are demonstrated. The review demonstrates a favourable effect of supplementation with L-arginine and its application depending on mitochondrial oxidative phosphorylation processes and biochemical indices in groups of individuals with low and high capacity of adaptation to hypoxia. In individuals with high initial anti-hypoxic reserves, these favourable effects are achieved by the blockade of NO-dependent biosynthesis pathways. Therefore, the methodological tasks of physiological experiments and the therapeutic consequences of treatment should include a component depending on the basic level of physiological reactivity.

Novel therapeutic and diagnostic approaches for preeclampsia

PURPOSE OF REVIEW

This review will summarize recent findings relating to the diagnostic approach to preeclampsia and current avenues of research aimed at modifying the underlying disease process.

RECENT FINDINGS

Growing international consensus supports a broad preeclampsia definition that incorporates maternal end-organ and uteroplacental dysfunction. Recent evidence demonstrates that this definition better identifies women and babies at risk of adverse outcomes compared to the traditional definition of hypertension and proteinuria. Multiple studies have demonstrated the usefulness and cost-effectiveness of angiogenic biomarkers such as soluble fms-like tyrosine kinase-1 and placental growth factor as a clinical adjunct to diagnose and predict severity of preeclampsia associated outcomes. Current novel therapeutic approaches to preeclampsia target pathogenic pathways (e.g. antiangiogenesis) or downstream effects such as oxidative stress and nitric oxide. Recent findings relating to these promising candidates are discussed. Multicenter clinical trials are needed to evaluate their effectiveness and ability to improve fetal and maternal outcomes.

SUMMARY

We provide an updated framework of the current approaches to define and diagnose preeclampsia. Disease modifying therapies (in particular, targeting the angiogenic pathway) are being developed for the first time and promise to revolutionize the way we manage preeclampsia.

Pathophysiology of Preeclampsia and L-Arginine/L-Citrulline Supplementation as a Potential Strategy to Improve Birth Outcomes

In preeclampsia, the shallow invasion of cytotrophoblast cells to uterine spiral arteries, leading to a reduction in placental blood flow, is associated with an imbalance of proangiogenic/antiangiogenic factors to impaired nitric oxide (NO) production. Proangiogenic factors, such as vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), require NO to induce angiogenesis through antioxidant regulation mechanisms. At the same time, there are increases in antiangiogenic factors in preeclampsia, such as soluble fms-like tyrosine kinase type 1 receptor (sFIt1) and toll-like receptor 9 (TLR9), which are mechanism derivates in the reduction of NO bioavailability and oxidative stress in placenta.Different strategies have been proposed to prevent or alleviate the detrimental effects of preeclampsia. However, the only intervention to avoid the severe consequences of the disease is the interruption of pregnancy. In this scenario, different approaches have been analysed to treat preeclamptic pregnant women safely. The supplementation with amino acids is one of them, especially those associated with NO synthesis. In this review, we discuss emerging concepts in the pathogenesis of preeclampsia to highlight L-arginine and L-citrulline supplementation as potential strategies to improve birth outcomes. Clinical and experimental data concerning L-arginine and L-citrulline supplementation have shown benefits in improving NO availability in the placenta and uterine-placental circulation, prolonging pregnancy in patients with gestational hypertension and decreasing maternal blood pressure.

Pravastatin, proton-pump inhibitors, metformin, micronutrients, and biologics: new horizons for the prevention or treatment of preeclampsia

There has been increasing research momentum to identify new therapeutic agents for the prevention or treatment of preeclampsia, drugs that can affect the underlying disease pathophysiology. Molecular targets of candidate treatments include oxidative stress, antiangiogenic factors, and the angiotensin, nitric oxide, and proinflammatory pathways. The proposed treatments undergoing preclinical and clinical trial evaluation are thought to act on placental or endothelial disease or both. Most have adopted the pragmatic strategy of repurposing drugs. Of all the therapeutic agents proposed, pravastatin has received the most interest. There are preclinical studies showing that it has pleiotropic actions that favorably impact on multiple molecular targets and can resolve a preeclampsia phenotype in many animal models. An early phase clinical trial suggests that it may have therapeutic activity. Several large prevention trials are planned or ongoing and, when completed, could definitively address whether pravastatin can prevent preeclampsia. Proton-pump inhibitors, metformin, and sulfasalazine are other drugs with preclinical evidence of multiple molecular actions that could resolve the pathophysiology of preeclampsia. These agents are also currently being evaluated in clinical trials. There have been many recent preclinical studies identifying the potential of numerous natural compounds to treat preeclampsia, such as plant extracts and micronutrients that have potent anti-inflammatory or antioxidant activity. Recent preclinical studies have also proposed novel molecular-targeted strategies, such as monoclonal antibodies targeting tumor necrosis factor alpha, placental growth factor, and short interfering RNA technology, to silence the gene expression of soluble fms-like tyrosine kinase-1 or angiotensinogen. Other treatment approaches that have transitioned to human trials (ranging from single-arm to phase III trials that have been completed or are ongoing) include folic acid, nitric oxide donors (such as L-arginine), recombinant antithrombin III, digoxin immune antigen-binding fragment, and melatonin. There have been case series showing the removal of circulating soluble fms-like tyrosine kinase-1 may help stabilize the disease and prolong pregnancy. Interestingly, there are case reports suggesting that monoclonal antibody eculizumab (complement inhibitor) may have therapeutic potential. If new agents are discovered that are proven to be effective in preventing or treating preeclampsia, the potential to improve global maternal and perinatal health will be significant.

L-arginine supplementation to mitigate cardiovascular effects of walking outside in the context of traffic-related air pollution in participants with elevated blood pressure: A randomized, double-blind, placebo-controlled trial

Exposure to traffic-related air pollution (TRAP) increases blood pressure (BP) and cardiovascular morbidity and mortality. We aimed to evaluate the potential efficacy of L-arginine supplementation in mitigating the adverse cardiovascular effects of adults with elevated BP walking outside under TRAP using a randomized, double-blind and placebo-controlled trial. 118 adults with elevated BP were recruited and were randomly assigned to either the placebo group or the intervention group with 9 g/day L-arginine supplementation for 2 weeks. On the 14th day, paired participants from the two groups walked along a traffic road for 2 h. Resting BP, L-arginine-nitric oxide metabolites and inflammatory biomarkers were measured before, during and after the 2 h exposure scenario, and ambulatory BP and Holter were measured during the 2 h outdoor walk. Participants in the intervention group had significantly elevated plasma L-arginine levels compared to the placebo group after supplementation. The two groups had similar exposures to traffic-related air pollutants. However, participants in the intervention group showed significant reductions of 5.3 mmHg (95% CI: -9.9, -0.7) in resting systolic BP (SBP), 4.3 mmHg (95% CI: -7.2, -1.3) in resting diastolic BP (DBP) and 4.6 mmHg (95% CI: -7.9, -1.3) in resting mean arterial pressure (MAP) at 30 min after the 2 h outdoor walk compared with the placebo group. There were also significant decreases in ambulatory SBP, DBP and MAP (7.5-9.9 mmHg, 5.3-7.6 mmHg and 4.7-7.9 mmHg, respectively) during the walk in the intervention group compared with the placebo group. There were no substantial changes in ST-segment level, L-arginine-NO metabolites and inflammatory biomarkers, and no significant associations were found between specific traffic-related air pollutants and cardiovascular health indicators. Specifically, our study shows that oral L-arginine supplementation was safe and well-tolerated, and could improve BP levels in adults with elevated BP during outside walk under TRAP.

Placental Ischemia Says "NO" to Proper NOS-Mediated Control of Vascular Tone and Blood Pressure in Preeclampsia

In this review, we first provide a brief overview of the nitric oxide synthase (NOS) isoforms and biochemistry. This is followed by describing what is known about NOS-mediated blood pressure control during normal pregnancy. Circulating nitric oxide (NO) bioavailability has been assessed by measuring its metabolites, nitrite (NO₂) and/or nitrate (NO₃), and shown to rise throughout normal pregnancy in humans and rats and decline postpartum. In contrast, placental malperfusion/ischemia leads to systemic reductions in NO bioavailability leading to maternal endothelial and vascular dysfunction with subsequent development of hypertension in PE. We end this article by describing emergent risk factors for placental malperfusion and ischemic disease and discussing strategies to target the NOS system therapeutically to increase NO bioavailability in preeclamptic patients. Throughout this discussion, we highlight the critical importance that experimental animal studies have played in our current understanding of NOS biology in normal pregnancy and their use in finding novel ways to preserve this signaling pathway to prevent the development, treat symptoms, or reduce the severity of PE.

The restorative effect of apocynin and catalase in l-arginine induced hypotension on normotensive subjects – the role of oxidative stress

L-arginine is a substrate for nitric oxide synthase (NOS) responsible for the production of NO. This investigation studied the effect of apocynin, an NADPH oxidase inhibitor and catalase, an H2O2 scavenger on L-arginine induced oxidative stress and hypotension. Forty Wistar-Kyoto rats were treated for 14 days with vehicle, L-arginine (12.5mg/ml p.o.), L-arginine+apocynin (2.5mmol/L p.o.), L-arginine+catalase (10000U/kg/day i.p.) and L-arginine plus apocynin+catalase respectively. Weekly renal functional and hemodynamic parameters were measured and kidneys harvested at the end of the study for histopathological and renal NADPH oxidase 4 (Nox4) assessments. L-arginine administration in normotensive rats decreased systolic blood pressure (120±2 vs 91±2mmHg) and heart rate (298±21 vs 254±15b/min), enhanced urinary output (21.5±4.2 vs 32±1.9ml/24h , increased creatinine clearance (1.72±0.56 vs 2.62±0.40ml/min/kg), and fractional sodium excretion (0.88±0.16 vs 1.18±0.16 %), caused proteinuria (28.10±1.93 vs 35.26±1.69mg/kg/day) and a significant decrease in renal cortical blood perfusion (292±3 vs 258±5bpu) and pulse wave velocity (3.72±0.20 vs 2.84±0.13m/s) (all P<0.05). L-arginine increased plasma malondialdehyde (by ~206 % P<0.05) and NO (by ~51 %, P<0.05) but decreased superoxide dismutase (by ~31 %, P<0.05) and total antioxidant capacity (by ~35 %, P<0.05) compared to control. Renal Nox4 mRNA activity was approximately 2.1 fold higher (P<0.05) in the L-arginine treated rats but was normalized by apocynin and apocynin plus catalase treatment. Administration of apocynin and catalase, but not catalase alone to rats fed L-arginine, restored the deranged renal function and structure, prevented hypotension and enhanced the antioxidant capacity and suppressed Nox4 expression. These findings suggest that apocynin and catalase might be used prophylactically in states of oxidative stress.

Metabolites and Hypertension: Insights into Hypertension as a Metabolic Disorder: 2019 Harriet Dustan Award

For over 100 years, essential hypertension has been researched from different perspectives ranging from genetics, physiology, and immunology to more recent ones encompassing microbiology (microbiota) as a previously underappreciated field of study contributing to the cause of hypertension. Each field of study in isolation has uniquely contributed to a variety of underlying mechanisms of blood pressure regulation. Even so, clinical management of essential hypertension has remained somewhat static. We, therefore, asked if there are any converging lines of evidence from these individual fields that could be amenable for a better clinical prognosis. Accordingly, here we present converging evidence which support the view that metabolic dysfunction underlies essential hypertension.

Resveratrol Supplementation Prevents Hypertension in Hypertensive Pregnant Rats by Increasing Sodium Excretion and Serum Nitric Oxide Level

Background

Pregnancy-induced hypertension (PIH) remains a major cause of morbidity and mortality in pregnancy worldwide. This study was designed to study the blood pressure-lowering effect of resveratrol (RES) in a salt-induced hypertensive pregnant rat model.

Methods

Forty female Sprague Dawley (SD) rats were randomized into 4 groups: Normal Preg (0.9% salt diet), Normal Preg + RES (0.9% salt diet plus daily oral RES for 4 weeks), Salt Preg (8% salt diet), and Salt Preg + RES (8% salt diet plus daily oral RES for 4 weeks). Noninvasive blood pressure was recorded on gestational days 7 and 14. On the gestational day 19, foetuses were weighed, and blood and urine samples were harvested for electrolytes and biochemical assays.

Results

RES significantly reduced SBP, DBP, and MAP on gestational days 7 and 14 in the Salt Preg + RES group compared to the Salt Preg group (all P < 0.05). Compared to the Salt Preg group, the foetal weight, serum NO level, urinary sodium, and 24 hour urine volume were significantly increased in the Salt Preg + RES group (all P < 0.05). Compared to the Salt Preg group, the foetal weight, serum NO level, urinary sodium, and 24 hour urine volume were significantly increased in the Salt Preg + RES group (all P < 0.05). Compared to the Salt Preg group, the foetal weight, serum NO level, urinary sodium, and 24 hour urine volume were significantly increased in the Salt Preg + RES group (all

Conclusions

RES decreases blood pressure in a hypertensive pregnant rat model. Increasing sodium excretion and serum nitric oxide level might be, at least part of, the underlying mechanisms.