Synergistic induction of nuclear factor-kappaB by transforming growth factor-beta and tumour necrosis factor-alpha is mediated by protein kinase A-dependent RelA acetylation.

The TGF-beta (transforming growth factor-beta) pathway represents an important signalling pathway involved in regulating diverse biological processes, including cell proliferation, differentiation and inflammation. Despite the critical role for TGF-beta in inflammatory responses, its role in regulating NF-kappaB (nuclear factor-kappaB)-dependent inflammatory responses still remains unknown. In the present study we show that TGF-beta1 synergizes with proinflammatory cytokine TNF-alpha (tumour necrosis factor-alpha) to induce NF-kappaB activation and the resultant inflammatory response in vitro and in vivo. TGF-beta1 synergistically enhances TNF-alpha-induced NF-kappaB DNA binding activity via induction of RelA acetylation. Moreover, synergistic enhancement of TNF-alpha-induced RelA acetylation and DNA-binding activity by TGF-beta1 is mediated by PKA (protein kinase A). Thus the present study reveals a novel role for TGF-beta in inflammatory responses and provides new insight into the regulation of NF-kappaB by TGF-beta signalling.