Objectives

To establish a safe and tolerable dose of sulforaphane that effects in vivo antioxidants via Nrf2 for development as a potential novel treatment for patients with COPD.

Background

Chronic Obstructive Pulmonary Disease (COPD), caused primarily by smoking, is the third leading cause of death in the United States and world-wide. Surprisingly, there are few treatments available to address the pathobiology of COPD other than cessation of smoking. The development and progression of COPD are associated with increased inflammatory response(s) and increased oxidative stress in the lung. Thus, one approach to the development of novel therapies is the stimulation of endogenous antioxidant defense mechanisms.

Nuclear factor erythroid-2-related factor 2 (Nrf2) is a transcription factor activated by oxidative stress. Nrf2 activity promotes anti-oxidant enzymes, and anti-oxidant enzymes play key roles in cellular defenses. Sulforaphane, a derivative of broccoli and other cruciferous vegetables, has been shown to stimulate Nrf2 activity in both in vivo and in vitro experiments. For example, activation of Nrf2 protected mice from developing emphysema after chronic smoke exposure and decreased oxidative stress. Similarly, activation of Nrf2 in human COPD lung cells resulted in decreased oxidative stress. Therefore, this study was designed to assess whether daily ingestion of sulforaphane by COPD patients for four weeks increased Nrf2 activity in alveolar macrophages and bronchial epithelial cells.

Participants

Participants were required to be 40 years or older with physician diagnosed COPD who were able to tolerate repeated bronchoscopies. Eligible participants were required to have an active or previous smoking habit of 10 or more pack-years, a post bronchodilator FEV1/FVC ratio less than 0.70, and a percent predicted FEV1 of 40–80%.

Exclusion criteria included significant co-morbidities, allergies, and/or medical history that would interfere with study participation or interpretation of the results, current use of warfarin, child-bearing potential with lack of adequate contraception, and inadequate FEV1 or FEV1/FVC results.

There were a total of 89 participants randomized to one of three treatment arms. Of these, 31 participants were randomized to the placebo arm, and 29 participants were randomized to the each of the sulforaphane arms. One participant withdrew from the placebo arm, therefore, a total of 88 participants completed the study.

Design

Participants were assigned to receive sulforaphane at 25 micromoles (4.4mg), sulforaphane at 150 micromoles (26.6 mg), or placebo (microcellulose) once daily by mouth. Computer-generated treatment assignments were blinded to participants, clinical staff, and study staff. Doses were back-filled with methylcellulose and presented in similar capsules to compensate for appearance and weight differences in sulforaphane and placebo treatments arms.

There were a total of five study visits over the six-week study period. Prior to randomization, participants were assessed for eligibility, which included baseline data collection. Participants provided medical histories, underwent a physical examination, pre-and-post bronchodilator spirometry, lung volume measurements, carbon monoxide diffusing capacity (DLCO), and pulse oximetry over the six-week study period. Follow up data and biospecimens were collected at the final visit, which was targeted for four weeks after randomization. Two fiberoptic bronchoscopies were performed under sedation to collect endobronchial brushings and bronchoalveolar lavage used to isolate alveolar macrophages and bronchial epithelial cells. The first bronchoscopy was performed on the day of randomization, and the second bronchoscopy was performed the day after the final visit. In addition, nasal brushings were obtained prior to bronchoscopy to isolate nasal epithelial cells.

The primary outcomes were changes in Nrf2 target gene expression at four weeks in alveolar macrophages and bronchial epithelial cells. The target genes for the primary outcome were NQ01, H01, AKR1C1, and AKR1C3. Secondary outcomes included the evaluation of: expression of other genes in the Nrf2/Keap1 pathway (e.g. Nrf2, KEAP1, and SLPI), markers of oxidative stress (e.g. isoprostane and thiobarbituric acid reactive substances) in plasma and expired breath condensate, and cytokine profiles in bronchoalveolar lavage fluid.

Conclusions

Sulforaphane administered at four weeks doses of 25umoles and 150umoles to patients with COPD did not significantly increase Nrf2 target gene expression in alveolar macrophages or bronchial epithelial cells. In addition, changes in oxidative stress markers and the expression of other genes in the Nrf2/Keap1 pathway were not statistically significant between the treatment groups.

Wise RA, Holbrook JT, Criner G, et al. Lack of Effect of Oral Sulforaphane Administration on Nrf2 Expression in COPD: A Randomized, Double-Blind, Placebo Controlled Trial. Vij N, ed. PLoS ONE. 2016; 11(11):e0163716. doi:10.1371/journal.pone.0163716.

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