Upregulation of MMP-9 Production by TNFα in Keratinocytes and Its Attenuation by Vitamin D

MMP-9, a member of the matrix metalloproteinase family that degrades collagen IV and processes chemokines and cytokines, participates in epidermal remodeling in response to stress and injury. Limited activity of MMP-9 is essential while excessive activity is deleterious to the healing process. Tumor necrosis factor (TNF alpha), a key mediator of cutaneous inflammation, is a powerful inducer of MMP-9. Calcitriol, the hormonally active vitamin D metabolite, and its analogs are known to attenuate epidermal inflammation, We aimed to examine the modulation of MMP-9 by calcitriol in TNF alpha-treated keratinocytes. The immortalized HaCaT keratinocytes were treated with TNF alpha in the absence of exogenous growth factors or active ingredients. MMP-9 production was quantified by gelatin zymography and real-time RT-PCR. Activation of signaling cascades was assessed by western blot analysis and DNA-binding activity of transcription factors was determined by EMSA. Exposure to TNF alpha markedly increased the protein and mRNA levels of MMP-9, while pretreatment with calcitriol dose dependently reduced this effect. Employing specific inhibitors we established that the induction of MMP-9 by TNF alpha was dependent on the activity of the epidermal growth factor receptor, c-jun-N-terminal kinase (JNK), NF kappa B and extracellular signal- regulated kinase-1/2. The effect of calcitriol was associated with inhibition of JNK activation and reduction of DNA-binding activities of the transcription factors activator protein-1 (AP-1) and NF kappa B following treatment with TNF alpha. By down-regulating MMP-9 levels active vitamin D derivatives may attenuate deleterious effects due to excessive TNF alpha-induced proteolytic activity associated with cutaneous inflammation. J. Cell. Physiol. J. Cell. Physiol. 222: 729-737, 2010. (C) 2009 Wiley-Liss, Inc.