Activated L-Arginine/Nitric Oxide Pathway in Pediatric Cystic Fibrosis and Its Association with Pancreatic Insufficiency, Liver Involvement and Nourishment: An Overview and New Results

Impaired Nitric Oxide Synthetase Activity in Primary Ciliary Dyskinesia-Data-Driven Hypothesis

Low nasal nitric oxide (nNO) is a typical feature of Primary Ciliary Dyskinesia (PCD). nNO is part of the PCD diagnostic algorithm due to its discriminative power against other lung diseases, such as cystic fibrosis (CF). However, the underlying pathomechanisms are elusive. To better understand NO dysregulation in PCD, the L-arginine/NO (Arg/NO) pathway in patients with PCD (pwPCD) and CF (pwCF) and in healthy control (HC) subjects was investigated. In a prospective, controlled study, we measured in 24 pwPCD, 25 age-matched pwCF, and 14 HC the concentrations of the NO precursors Arg and homoarginine (hArg), the arginase metabolite ornithine (Orn), the NO inhibitor asymmetric dimethylarginine (ADMA), and the major NO metabolites (nitrate, nitrite) in sputum, plasma, and urine using validated methods. In comparison to HC, the sputum contents (in µmol/mg) of L-Arg (PCD 18.43 vs. CF 329.46 vs. HC 9.86, p < 0.001) and of ADMA (PCD 0.055 vs. CF 0.015 vs. HC 0.010, p < 0.001) were higher. In contrast, the sputum contents (in µmol/mg) of nitrate and nitrite were lower in PCD compared to HC (nitrite 4.54 vs. 9.26, p = 0.023; nitrate 12.86 vs. 40.33, p = 0.008), but higher in CF (nitrite 16.28, p < 0.001; nitrate 56.83, p = 0.002). The metabolite concentrations in urine and plasma were similar in all groups. The results of our study indicate that PCD, unlike CF, is associated with impaired NO synthesis in the lung, presumably due to mechano-chemical uncoupling.

Biomarkers of the L-Arginine/Dimethylarginine/Nitric Oxide Pathway in People with Chronic Airflow Obstruction and Obstructive Sleep Apnoea

BACKGROUND

Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnoea (OSA) are common chronic diseases that are associated with chronic and intermittent hypoxemia, respectively. Patients affected by the overlap of COPD and OSA have a particularly unfavourable prognosis. The L-arginine/nitric oxide (NO) pathway plays an important role in regulating pulmonary vascular function. Asymmetric (ADMA) and symmetric dimethylarginine (SDMA) interfere with NO production.

METHODS

We analysed the serum concentrations of ADMA, SDMA, L-arginine, L-citrulline, and L-ornithine in a large sample of the Icelandic general population together with chronic airflow obstruction (CAO), a key physiological marker of COPD that was assessed by post-bronchodilator spirometry (FEV1/FVC < LLN). OSA risk was determined by the multivariable apnoea prediction (MAP) index.

RESULTS

713 individuals were analysed, of whom 78 (10.9%) showed CAO and 215 (30%) had MAP > 0.5. SDMA was significantly higher in individuals with CAO (0.518 [0.461-0.616] vs. 0.494 [0.441-0.565] µmol/L; p = 0.005), but ADMA was not. However, ADMA was significantly associated with decreasing FEV1 percent predicted among those with CAO (p = 0.002). ADMA was 0.50 (0.44-0.56) µmol/L in MAP ≤ 0.5 versus 0.52 (0.46-0.58) µmol/L in MAP > 0.5 (p = 0.008). SDMA was 0.49 (0.44-0.56) µmol/L versus 0.51 (0.46-0.60) µmol/L, respectively (p = 0.004). The highest values for ADMA and SDMA were observed in individuals with overlap of CAO and MAP > 0.5, which was accompanied by lower L-citrulline levels.

CONCLUSIONS

The plasma concentrations of ADMA and SDMA are elevated in COPD patients with concomitant intermittent hypoxaemia. This may account for impaired pulmonary NO production, enhanced pulmonary vasoconstriction, and disease progression.

Bacterial protease alleviate chronic liver fibrosis induced by thioacetamide through suppression of hepatic stellate cells consequently decrease its proliferative index

In chronic liver diseases, liver fibrosis occurs due to excessive extracellular matrix (ECM) protein accumulation. Approximately 2 million deaths occur yearly due to liver disease, while cirrhosis is the 11th most common cause of death. Therefore, newer compounds or biomolecules must be synthesized to treat chronic liver diseases. In this aspect, the present study focuses on the assessment of the anti-inflammatory and antioxidant impact of Bacterial Protease (BP) produced by a new mutant strain of bacteria (Bacillus cereus S6-3/UM90) and 4,4'-(2,5-dimethoxy-1,4-phenylene) bis (1-(3-ethoxy phenyl)-1H-1,2,3-triazole) (DPET) in the treatment of early stage of liver fibrosis induced by thioacetamide (TAA). Sixty male rats were divided into six groups, ten rats each as follows: (1) Control group, (2) BP group, (3) TAA group, (4) TAA-Silymarin (S) group, (5) TAA-BP group, and (6) TAA-DPET group. Liver fibrosis significantly elevated liver function ALT, AST, and ALP, as well as anti-inflammatory interleukin 6 (IL-6) and VEGF. The oxidative stress parameters (MDA, SOD, and NO) were significantly increased with a marked reduction in GSH. Expression of MAPK and MCP-1 was unregulated in the TAA group, with downregulation of Nrf₂ was observed. TAA caused histopathological alterations associated with hepatic vacuolation and fibrosis, increasing collagen fibers and high immuno-expression of VEGF. On the other hand, treatment with BP successfully improved the severe effects of TAA on the liver and restored histological architecture. Our study concluded the protective potentials of BP for attenuating liver fibrosis and could be used as adjuvant therapy for treating hepatic fibrosis.

Lower Airway Nitrogen Oxide Levels in Children with Primary Ciliary Dyskinesia Is Linked to Neutrophilic Inflammation

Treatment of primary ciliary dyskinesia pulmonary exacerbations resulted in an increase in sputum nitric oxide (NO) metabolites and decrease in neutrophilic inflammation. The association between the 2 suggests that neutrophilic inflammation contributes to airway NO deficiency in primary ciliary dyskinesia and that reducing inflammation may lead to improved airway NO homeostasis. TRIAL REGISTRY: ClinicalTrials.gov: NCT01155115.

Arginine Therapy for Lung Diseases

Nitric oxide (NO) is produced by a family of isoenzymes, nitric oxide synthases (NOSs), which all utilize L-arginine as substrate. The production of NO in the lung and airways can play a number of roles during lung development, regulates airway and vascular smooth muscle tone, and is involved in inflammatory processes and host defense. Altered L-arginine/NO homeostasis, due to the accumulation of endogenous NOS inhibitors and competition for substrate with the arginase enzymes, has been found to play a role in various conditions affecting the lung and in pulmonary diseases, such as asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), pulmonary hypertension, and bronchopulmonary dysplasia. Different therapeutic strategies to increase L-arginine levels or bioavailability are currently being explored in pre-clinical and clinical studies. These include supplementation of L-arginine or L-citrulline and inhibition of arginase.

Local and Systemic Alterations of the L-Arginine/Nitric Oxide Pathway in Sputum, Blood, and Urine of Pediatric Cystic Fibrosis Patients and Effects of Antibiotic Treatment

Alterations in the L-arginine (Arg)/nitric oxide (NO) pathway have been reported in cystic fibrosis (CF; OMIM 219700) as the result of various factors including systemic and local inflammatory activity in the airways. The aim of the present study was to evaluate the Arg/NO metabolism in pediatric CF patients with special emphasis on lung impairment and antibiotic treatment. Seventy CF patients and 78 healthy controls were included in the study. CF patients (43% male, median age 11.8 years) showed moderately impaired lung functions (FEV1 90.5 ± 19.1% (mean ± SD); 21 (30%) had a chronic Pseudomonas aeruginosa (PSA) infection, and 24 (33%) had an acute exacerbation). Plasma, urinary, and sputum concentrations of the main Arg/NO metabolites, nitrate, nitrite, Arg, homoarginine (hArg), and asymmetric dimethylarginine (ADMA) were determined in pediatric CF patients and in healthy age-matched controls. Clinical parameters in CF patients included lung function and infection with PSA. Additionally, the Arg/NO pathway in sputum samples of five CF patients was analyzed before and after routine antibiotic therapy. CF patients with low fractionally exhaled NO (FENO) showed lower plasma Arg and nitrate concentrations. During acute exacerbation, sputum Arg and hArg levels were high and dropped after antibiotic treatment: Arg: pre-antibiotics: 4.14 nmol/25 mg sputum vs. post-antibiotics: 2.33 nmol/25 mg sputum, p = 0.008; hArg: pre-antibiotics: 0.042 nmol/25 mg sputum vs. post-antibiotics: 0.029 nmol/25 mg sputum, p = 0.035. The activated Arg/NO metabolism in stable CF patients may be a result of chronic inflammation. PSA infection did not play a major role regarding these differences. Exacerbation increased and antibiotic therapy decreased sputum Arg concentrations.