Effect of broccoli sprouts on nasal response to live attenuated influenza virus in smokers: a randomized, double-blind study

Abstract

Background: Smokers have increased susceptibility and altered innate host defense responses to influenza virus infection. Broccoli sprouts are a source of the Nrf2 activating agentsulforaphane, and short term ingestion of broccoli sprout homogenates (BSH) has been shown to reduce nasal inflammatory responses to oxidant pollutants.

Objectives: Assess the effects of BSH on nasal cytokines, virus replication, and Nrf2-dependent enzyme expression in smokers and nonsmokers.

Methods: We conducted a randomized, double-blind, placebo-controlled trial comparing the effects of BSH on serially sampled nasal lavage fluid (NLF) cytokines, viral sequence quantity, and Nrf2-dependent enzyme expression in NLF cells and biopsied epithelium. Healthy young adult smokers and nonsmokers ingested BSH or placebo (alfalfa sprout homogenate) for 4 days, designated Days -1, 0, 1, 2. On Day 0 they received standard vaccine dose of live attenuated influenza virus (LAIV) intranasally. Nasal lavage fluids and nasal biopsies were collected serially to assess response to LAIV.

Results: In area under curve analyses, post-LAIV IL-6 responses (P = 0.03) and influenza sequences (P = 0.01) were significantly reduced in NLF from BSH-treated smokers, while

Nad(p)h: quinoneoxidoreductasein NLF cells was significantly increased. In nonsmokers, a similar trend for reduction in virus quantity with BSH did not reach statistical significance.

Conclusions: In smokers, short term ingestion of broccoli sprout homogenates appears to significantly reduce some virus-induced markers of inflammation, as well as reducing virus quantity. Nutritional antioxidant interventions have promise as a safe, low-cost strategy for reducing influenza risk among smokers and other at risk populations.

Trial registration: ClinicalTrials.gov NCT01269723.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Flow diagram for recruitment and randomization of subjects for the (A) smokers and (B) nonsmokers cohorts in this study.

URI  =  upper respiratory illness.

Figure 2. IL-6 in nasal lavage fluids (NLF) and IL-6 area under curve (AUC) for Days 1–3 normalized to Day 0, for smoker and nonsmoker study groups.

Data for raw IL-6 in NLF (A, B) are shown as medians on each study day, for each treatment group. Data for AUC (C, D)are for individual subjects; bar indicates median for treatment group. During the “Treatment period” subjects received broccoli sprout homogenates (BSH) or alfalfa homogenates as control (ASH) once daily. Live attenuated influenza virus (LAIV) was inoculated nasally on Day 0, after nasal lavage. * P<.05 for bsh vs. ash.>

Figure 3. Influenza B RNA sequence quantity in nasal lavage fluid cells for (A) smokers and (B) nonsmokers.

Data are shown as medians on each study day, for each treatment group. During the “Treatment period” subjects received broccoli sprout homogenates (BSH) or placebo control (alfalfa sprout shakes) once daily. Live attenuated influenza virus (LAIV) was inoculated nasally on Day 0, after nasal lavage. (C) and (D) are area under curve data (Day 1–3, normalized to Day 0 baseline) for smokers and nonsmokers respectively. Bar indicates median for treatment group. * P<.05 for bsh vs. ash>

Figure 4. Relationship of baseline (screen day) mRNA quantity of antioxidant enzymes cells to magnitude of change in mRNA quantity after LAIV, in subjects who received BSH.

Data are shown for (A) HMOX1 and (B) NQO1 in NLF cells (AUC for Days 1–3 normalized to baseline), and for (C) HMOX1 and (D) NQO1 in nasal epithelial biopsy cells (ratio of Day 2 biopsy to screen day). Data for smokers are shown as red dots and nonsmokers as black dots. R and P values are for Spearman correlation coefficient, for smokers and nonsmokers who received BSH, considered together.