Acute Alcohol Exposure Exerts Anti-Inflammatory Effects by Inhibiting IκB Kinase Activity and p65 Phosphorylation in Human Monocytes

Abstract

Acute alcohol use is associated with impaired immune responses and decreased proinflammatory cytokine production. Our earlier studies have shown that acute alcohol intake inhibits NF-κB DNA binding in an IκBα-independent manner. We report using human peripheral blood monocytes and Chinese hamster ovary cells transfected with CD14 cells that acute alcohol treatment in vitro exerts NF-κB inhibition by disrupting phosphorylation of p65. Immunoprecipitation of p65 and IκBα revealed that acute alcohol exposure for 1 h decreased NF-κB-IκBα complexes in the cytoplasm. Phosphorylation of p65 at Ser536 is mediated by IκB kinase (IKK)β and is required for NF-κB-dependent cellular responses. We show that acute alcohol treatment decreased LPS-induced IKKα and IKKβ activity resulting in decreased phosphorylation of p65 at Ser536. Furthermore, nuclear expression of IKKα increased after alcohol treatment, which may contribute to inhibition of NF-κB. Decreased phosphorylation of nuclear p65 at Ser276 was likely not due to alcohol-induced inhibition of protein kinase A and mitogen- and stress-activated protein kinase-1 activity. Although decreased IκBα phosphorylation after acute alcohol treatment was attributable to reduced IKKβ activity, degradation of IκBα during alcohol exposure was IKKβ-independent. Alcohol-induced degradation of IκBα in the presence of a 26S proteasome inhibitor suggested proteasome-independent IκBα degradation. Collectively, our studies suggest that acute alcohol exposure modulates IκBα-independent NF-κB activity primarily by affecting phosphorylation of p65. These findings further implicate an important role for IKKβ in the acute effects of alcohol in immune cells.