Effect of atorvastatin on asthma control and airway inflammation : a randomised controlled trial

Background Statins are inhibitors of the rate-limiting enzyme, 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, in cholesterol biosynthesis. As such, they have been widely used in clinical practice as cholesterol lowering agents to reduce morbidity and mortality from coronary artery disease. There is evidence from clinical studies and in vitro experiments that statins have additional anti-inflammatory properties in atherosclerotic disease, which are unrelated to their lipid lowering activity. Clinical studies have previously suggested that statins might show a beneficial clinical effect in inflammatory diseases, such as rheumatoid arthritis and multiple sclerosis. Furthermore, preliminary data obtained in models of pulmonary inflammation suggest that the effects manifest in rheumatoid patients can be achieved also in asthma. A proof of concept study was designed to test the hypothesis that atorvastatin improves asthma control and airway inflammation in adults with asthma. Methods Fifty four adults with allergic asthma were recruited to a 22-week crossover randomised controlled trial comparing the effect on asthma control and airway inflammation of oral atorvastatin 40 mg daily with that of a matched placebo. Each treatment was administered for 8 weeks separated by a 6-week washout period. The primary outcome was morning peak expiratory flow. Secondary outcomes included spirometry, asthma control questionnaire (ACQ) score, asthma quality of life questionnaire (AQLQ), provocation concentration to methacholine (PC20) and inflammatory markers: exhaled nitric oxide, sputum differential cell count, sputum supernatant and serum inflammatory markers such as interleukin-6 (IL-6), IL-5, IL-8, sICAM-1, TNF-α, leukotriene B4 (LTB4) and high sensitivity C-reactive protein (hsCRP), and blood lymphocyte proliferation. Results At 8 weeks, the change in mean morning PEF, as compared with baseline, did not differ between the atorvastatin and placebo treatment periods [mean difference -0.5 L/min, 95% CI -10.6 to 9.6, p=0.921]. No statistically significant effect of atorvastatin was seen in evening PEF, or methacholine responsiveness (PC20). Out of all spirometry results, only post-salbutamol FVC showed a statistically significant result, which was slightly lower in the atorvastatin group [treatment difference -0.1L, 95% CI -0.2 to 0.0, p=0.037]. There was also no change in ACQ or AQLQ. No change was seen in exhaled nitric oxide. The total cell counts recovered from sputum were similar after atorvastatin compared to after placebo treatment. After 8 weeks, the mean absolute and relative sputum macrophage count was significantly reduced after atorvastatin compared to placebo [mean absolute difference -44.9x104 cells, 95% CI -80.1 to -9.7, p=0.029]. There was a reciprocal increase in the relative proportion of sputum neutrophils [mean proportion difference 13.1%, 95% CI 1.8 to 24.4, p=0.025], but there were no significant changes in the absolute count of these cells or the counts and proportions of the other sputum cell phenotypes under atorvastatin treatment. The sputum concentrations of inflammatory cytokines and mediators were similar after atorvastatin compared to after placebo treatment other than LTB4 which was significantly reduced [mean difference -88.1 pg/mL, 95% CI -156.4 to -19.9, p=0.014]. No significant difference was seen in the concentration of any serum marker of inflammation between atorvastatin and placebo treatment periods. The change in hsCRP was of borderline significance [mean difference -0.65 mg/L, 95% CI -1.38 to 0.09, p=0.082], but there were no changes in sICAM-1, TNF-α, IL-5, IL-6 and IL-8. There was no significant difference in lymphocyte proliferation. The biochemical effects of atorvastatin therapy were reflected in significant reduction in concentration of serum lipids; cholesterol (mean difference -1.71 mmol/l, 95% CI -1.94 to -1.48 p