Effect of erythromycin on cigarette-induced histone deacetylase protein expression and nuclear factor-κB activity in human macrophages in vitro

Histone deacetylases (HDACs) are families of enzymes that regulate chromatin structure and thus affect inflammatory gene expression. The anti-inflammatory properties of macrolides are well documented. However, the effects of macrolides on HDAC protein expression have not been studied. This study aimed to examine the molecular mechanism of the inflammatory responses caused by cigarette smoke extract (CSE) and the effects of erythromycin (EM) on CSE-induced HDAC protein expression in human macrophages in vitro. The cells were preincubated with EM and were then exposed to CSE. Levels of interleukin-8 (IL-8) and tumor necrosis factor-a (TNF-a) were assayed by enzyme linked immunosorbent assay (ELISA). Nuclear factor-κB (NF-κB) activity was assessed by an electrophoretic mobility shift assay. HDAC activity was measured with a colorimetric assay kit, and Western blotting was used for HDAC1, -2, -3 and NF-κB protein expression assays. The results showed that CSE causes decreases in HDAC activity and HDAC1, -2, -3 levels and upregulates NF-κB activity, resulting in increased NF-κB-dependent proinflammatory cytokine release in human macrophage cells. Moreover, EM was able to reverse the CSE-induced decline in HDAC1, -2, -3 protein expression, which was most prominent for HDAC2; these changes were associated with the suppression of both NF-κB protein expression and the production of inflammatory mediators. These results suggest that relieving inflammation with EM can be useful in therapeutic approaches for modulating intracellular nuclear signaling in chronic airway inflammatory diseases such as chronic obstructive pulmonary disease (COPD).