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

Abstract

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.

Metabolomic Biomarkers to Predict and Diagnose Cystic Fibrosis Pulmonary Exacerbations: A Systematic Review

“…Based on available data, it remains unclear if exhaled NO is lower during PEx compared to stable state as the studies performed to date have been relatively small and the findings have been inconsistent ( 17 , 19 ). Metabolites of NO, including nitrate and nitrite, do not appear to be consistently higher or lower during PEx when sampled from saliva, plasma or urine but nitrates were lower in sputum in two studies but the differences were not statistically significant when compared to stable CF subjects ( 12 , 16 ). Arginine, an amino acid that acts as a substrate to form NO, was not significantly higher in sputum during PEx ( 16 ) but another study demonstrated its potential to predict PEx when elevated in EBC ( 31 ).…”

“…Metabolites of NO, including nitrate and nitrite, do not appear to be consistently higher or lower during PEx when sampled from saliva, plasma or urine but nitrates were lower in sputum in two studies but the differences were not statistically significant when compared to stable CF subjects ( 12 , 16 ). Arginine, an amino acid that acts as a substrate to form NO, was not significantly higher in sputum during PEx ( 16 ) but another study demonstrated its potential to predict PEx when elevated in EBC ( 31 ). Contrary to the increase in airway sampling, plasma arginine was lower in CF PEx compared to healthy controls ( 13 ) but was not significantly lower than stable CF samples ( 16 ).…”

“…For sputum, putrescine was consistently higher in PEx compared to healthly control and stable CF samples ( 15 , 26 ) but only the comparison to healthy control samples was statistically significant. Sputum nitrate was consistently lower in PEx compared to stable CF samples in two studies, but the differences were not statistically significant ( 12 , 16 ).…”

“…Plasma methionine was found to be lower in PEx compared to stable CF samples in two studies ( 7 , 13 ), with one comparison being statistically significant ( 7 ). Three studies ( 7 , 13 , 16 ) found lower plasma arginine levels in PEx compared to healthy control or stable CF samples, but only the comparison to healthy controls was statistically significant ( 13 ). Plasma histidine, phenylalanine, and tryptophan levels were lower in PEx compared to healthy control samples in two separate studies ( 7 , 13 ) but these were not compared to stable CF samples.…”

“…Arginine, an amino acid that acts as a substrate to form NO, was not significantly higher in sputum during PEx ( 16 ) but another study demonstrated its potential to predict PEx when elevated in EBC ( 31 ). Contrary to the increase in airway sampling, plasma arginine was lower in CF PEx compared to healthy controls ( 13 ) but was not significantly lower than stable CF samples ( 16 ).…”