Oxidative stress is defined as an excessive load of reactive oxygen species (ROS), which cause ongoing or reversible damage in the body. This can occur in individual cells, and in specific body organs, and can affect the health of patients at the whole body level.
Antioxidants can chemically react with ROS to quench and thus inactivate these reactive, damaging molecules. Cystic fibrosis is characterized by oxidative stress throughout the body and chronic inflammation in the lungs. Patients with CF are deficient in the body’s major anti-oxidant, glutathione (GSH). This is thought to be due to many reasons, including dietary insufficiency, but being the major anti-oxidant of the body, GSH is highly utilized in areas of oxidative stress and inflammation. GSH serves multiple functions and is utilized by cells to regulate physiological functions such as DNA transcription, RNA translation, and subsequent protein synthesis. It is utilized to regulate protein functions and is vital in regulating dietary absorption of nutrients, storage and availability of essential proteins and fatty acids.
Oxidation reactions are essential to fight infection and are generated when neutrophils ingest bacteria to rid the body of pathogens. For reasons still unclear, in CF, the environment in the airways is strongly pro-inflammatory. After neutrophils have been recruited, neutrophil-derived oxidants are released into the airways, and contribute to ongoing tissue destruction. Oxidants, which include hydrogen peroxide, hypochlorous acid, and other damaging particles called free radicals are released and create a vicious perpetual cycle of tissue destruction.
For decades, antioxidant drugs have been utilized to supplement the diets of CF patients, with the rationale that antioxidant drugs may be useful to control both oxidative stress and excessive inflammation in CF airways. Because of this well-defined function for antioxidants, one of the most widely reiterated claims in both medicine and nutrition counseling is that anti-oxidants such as vitamin C and E, inhaled and oral NAC and GSH would prevent, or at least delay, the onset of end-stage lung disease in CF. These claims, however, have not been substantiated with appropriate placebo-controlled clinical intervention trials, until recently. While the clinical efficacies of corticosteroids and high-dose ibuprofen have been previously proved to decrease inflammation in clinical studies for CF patients, these modalities have been associated with severe side effects, limiting their long-term use. We have recently published the results of a clinical trial testing the efficacy of high doses of NAC taken orally three times a day for 6 months. We performed a placebo-controlled study involving our CF center at Stanford and 10 other CF centers from the US in which we hypothesized that treatment with high doses of NAC would lead to a decrease in the inflammation (neutrophils) in CF airways and potentially lead to clinical improvement, such as improved lung function, decreased occurrence of pulmonary exacerbations, and/or decreased use of antibiotics in that time period.
The study dose used was 900 mg of PharmaNAC™, an oral fizzy pill that was dissolved in water or juice. 70 patients were recruited and took study drug three times a day for 6 months – 3 months longer than the longest previous trials with NAC and a dose significantly higher than previous trials. Thirty-six subjects were randomized
to NAC and 34 subjects ran domized to placebo. Only six participants in the NAC group and two in the placebo group either withdrew or were lost to follow-up.
Headline Results:The baseline characteristics and randomization strata were similar between treatment groups (Table 1). The FEV1 was less than 60 percent of predicted (compared to normal) in 40 percent of subjects, and 27 percent of subjects were under 18 years of age. We detected a substantial clinical benefit in the outcome of lung function that measures obstruction: the NAC cohort maintained their baseline lung function as measured by the FEV1 (volume) and FEF25–75% (flow) throughout the 24-week period, while 4 to 6 percent declines in these measures occurred in the placebo coho
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