Effects of sulforaphane on Toll-like receptor 4/myeloid differentiation factor 88 pathway of monocyte-derived macrophages from patients with chronic obstructive pulmonary disease

Abstract

To explore the effects of sulforaphane on Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88) pathway and its downstream inflammatory cytokines in patients with chronic obstructive pulmonary disease (COPD). From Jan. 2012 to Mar. 2013, thirty-two stable COPD patients and thirty healthy donors (non-COPD group) from the First Hospital of Lanzhou University were recruited. The peripheral blood monocytes were isolated and induced to macrophages (monocyte-derived macrophages, MDMs). The MDMs of COPD patients were divided into a blank control group, a LPS group, a sulforaphane group, a sulforaphane and LPS group (combined group), while the MDMs from the non-COPD group received no drug intervention. The number of cells in each group was 3×10(6). The mRNA and protein expression of TLR4 and MyD88 were measured with real-time PCR and Western blot. The TNF-α and IL-6 levels in the culture supernatant were measured with ELISA. Oneway ANOVA and LSD-t test were used for statistical analysis. The levels of mRNA and protein of TLR4 and MyD88 and the contents of TNF-α and IL-6 in the culture supernatant were higher in the blank control group [3.7 ± 0.5, 1.9 ± 0.4, 0.45 ± 0.18, 1.11 ± 0.65, (31 ± 4) and (43 ± 5) µg/L] than those in the non-COPD group [1.00, 1.00, 0.26 ± 0.14, 0.58 ± 0.40, (19 ± 2) and (29 ± 4) µg/L] (t = 2.19-12.11, P < 0.05 or P < 0.01). After LPS treatment (LPS group), the above parameters [5.5 ± 1.1, 3.4 ± 1.6, 0.65 ± 0.20, 1.66 ± 0.64, (47 ± 4) and (54 ± 5) µg/L] were increased as compared to those in the blank control group (t = 2.39-11.9, P < 0.05 or P < 0.01), but after sulforaphane treatment(Sulforaphane group), these parameters [2.2 ± 0.4, 1.0 ± 0.6, 0.25 ± 0.09, 0.62 ± 0.34, (20 ± 3) and (27 ± 4) µg/L] were decreased as compared to those in the blank control group (t = 2.13-8.46, P < 0.05 or P < 0.01). Similarly, these parameters in the combined group [3.2 ± 0.5, 1.5 ± 0.8, 0.33 ± 0.11, 0.77 ± 0.25, (31 ± 3) and (33 ± 4) µg/L] were also remarkably decreased as compared to those in the LPS group (t = 3.87-12.24, all P < 0.01). The TLR4/MyD88 pathway was activated and its downstream inflammatory cytokines were increased in macrophages from COPD patients. Sulforaphane could inhibit the TLR4/MyD88 pathway and reduce the releasing of downstream inflammatory cytokines, suggesting that sulforaphane may have an anti-inflammatory effect in COPD.