Selective inhibition of JAK2/STAT1 signaling and iNOS expression mediates the anti-inflammatory effects of coniferyl aldehyde

Urgent needs still exist for selective control of excessive inflammation. Despite the therapeutic potential of natural compounds against inflammation-associated chronic conditions, lack of specific molecular targets renders these bioactive compounds difficult for further development. Here we examined the bioactivity of coniferyl aldehyde (CA), a natural phenolic compound found in several dietary substances and medicinal plants, elucidating its efficacy both in vivo and in vitro with underlying molecular mechanisms. IFN-g/TNF-a-stimulated human keratinocytes and lipopolysaccharide (LPS)-stimulated murine macrophages were used to examine the effect of CA in vitro and to elucidate the underlying mechanisms. In vivo models of phorbol 12-myristate 13-acetate (TPA)-induced ear edema and carrageenan (CRG)-induced paw edema were employed to investigate the topical and systemic antiinflammatory effects of CA, respectively. CA significantly reduced nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression in LPS-stimulated macrophages. While nuclear factorkB (NF-kB) and mitogen-activated protein kinase (MAPKs) pathways, the representative cellular pathways for iNOS induction, were not affected by CA, phosphorylation of Janus kinase 2 (JAK2) and signal Transducers and Activators of Transcription 1 (STAT1) and subsequent nuclear translocation of p-STAT1 were significantly decreased by CA. The effect of CA on JAK2-STAT1-iNOS axis was also observed in human keratinocytes stimulated with IFN-g/TNF-a. Topical application of CA to mice produced signifi- cant protection against TPA-induced ear edema along with suppressed epidermal hyperproliferation and leucocyte infiltration. Systemic administration of CA significantly reduced CRG-induced paw edema in rats, where CRG-induced iNOS expression and STAT1 phosphorylation were decreased by CA. In summary, CA has significant anti-inflammatory properties both in vitro and in vivo, mediated by significant selective inhibition of JAK2-STAT1-iNOS signaling. CA is an attractive novel candidate for treating in- flammatory diseases associated with excessive production of NO.