Activation of protein kinase Cξ is essential for cytokine-induced metalloproteinase-1, -3, and -9 secretion from rabbit smooth muscle cells and inhibits proliferation

Abstract

Several matrix metalloproteinases (MMPs), including MMP-1, -3, and -9, mediate matrix destruction during chronic inflammatory diseases such as arthritis and atherosclerosis. MMP up-regulation by inflammatory cytokines involves interactions between several transcription factors, including activator protein-1 and nuclear factor κB (NF-κB). The upstream regulatory pathways are less well understood. We investigated the role of isoforms of protein kinase C (PKC) in basic fibroblast growth factor- and interleukin-1α-mediated MMP production from cultured rabbit aortic smooth muscle cells. A synthetic PKC inhibitor, RO318220, inhibited MMP-1, -3, and -9 production by 89 ± 3, 75 ± 18, and 89 ± 9%, respectively. However, down-regulation of conventional and novel isoforms did not inhibit but rather increased MMP-9 production by 48 ± 16%, implicating an atypical PKC isoform. Consistent with this, PKCξ protein levels and activity were stimulated 3.3- and 13-fold, respectively, by basic fibroblast growth factor plus interleukin-1α and antisense oligonucleotides to PKCξ significantly decreased MMP-9 formation by 62 ± 18% compared with scrambled sequences. Moreover, adenovirus-mediated overexpression of a dominant-negative (DN) PKCξ reduced MMP-1, -3, and -9 production by 78 ± 9, 76 ± 8, and 76 ± 5%, respectively. DN-PKCξ inhibited NF-κB DNA binding but did not affect ERK1/2 activation or AP-1 binding. Antisense PKCξ oligonucleotides and DN-PKCξ stimulated cell proliferation by 89 ± 14% (n = 4) and 305 ± 74% (n = 3), respectively (both p < 0.05). Our results show that PKCξ is essential for cytokine-induced up-regulation of MMP-1, -3, and -9, most likely by activating NF-κB. Selective inhibition of PKCξ is therefore a possible strategy to inhibit MMP production in inflammatory diseases such as atherosclerosis.