N -Acetyl- L-cysteine and pyrrolidine dithiocarbamate inhibited nuclear factor-kappaB activation in alveolar macrophages by different mechanisms
Abstract
Aim: To study the effects of N-acetyl-L-cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC) on the phosphorylation of IκB kinase (IKK)β, IKKα, and IκBα in alveolar macrophages (AM), and to explore the pharmacological mechanisms of NAC and PDTC as inhibitors of NF-κB activation.
Methods: AM were collected from bronchoalveolar lavage fluid from the patients with chronic obstructive pulmonary disease. The AM were incubated for 1.5 h with NAC and PDTC, and then stimulated for 90 min by either tumor necrosis factor (TNF)-α or interleukin (IL)-1.
Western blotting was used to detect the protein phosphorylation levels of IKKβ, IKKα, and IκBα. NF-κB activity was analyzed by using an electrophoretic mobility shift assay.
Results: NAC inhibited the phosphorylation of IKKβ, IKKα, and IκBα induced by TNF-α, but had no effect on the phosphorylation of IKKβ, IKKα and IκBα induced by IL-1. PDTC did not inhibit the phosphorylation of IκBα induced by TNF-α or IL-1. Similarly, NAC inhibited the activation of NF-κB induced by TNF-α, but had no effect on the activation of NF-κB induced by IL-1. PDTC significantly inhibited the activation of NF-κB induced by TNF-α and IL-1. The electrophoretic mobility shift assay also showed that PDTC and NAC do not directly inhibit NF-κB DNA binding activity in vitro.
Conclusion: PDTC prevents the degradation of IκBα via the ubiquitylation-proteasome proteolytic pathway. NAC can inhibit the processes upstream of IKK activation induced by TNF-α, which results in the decline of NF-κB activity.
Keywords:
Methods: AM were collected from bronchoalveolar lavage fluid from the patients with chronic obstructive pulmonary disease. The AM were incubated for 1.5 h with NAC and PDTC, and then stimulated for 90 min by either tumor necrosis factor (TNF)-α or interleukin (IL)-1.
Western blotting was used to detect the protein phosphorylation levels of IKKβ, IKKα, and IκBα. NF-κB activity was analyzed by using an electrophoretic mobility shift assay.
Results: NAC inhibited the phosphorylation of IKKβ, IKKα, and IκBα induced by TNF-α, but had no effect on the phosphorylation of IKKβ, IKKα and IκBα induced by IL-1. PDTC did not inhibit the phosphorylation of IκBα induced by TNF-α or IL-1. Similarly, NAC inhibited the activation of NF-κB induced by TNF-α, but had no effect on the activation of NF-κB induced by IL-1. PDTC significantly inhibited the activation of NF-κB induced by TNF-α and IL-1. The electrophoretic mobility shift assay also showed that PDTC and NAC do not directly inhibit NF-κB DNA binding activity in vitro.
Conclusion: PDTC prevents the degradation of IκBα via the ubiquitylation-proteasome proteolytic pathway. NAC can inhibit the processes upstream of IKK activation induced by TNF-α, which results in the decline of NF-κB activity.