p38 MAPK mediates fibrogenic signal through smad3 phosphorylation in rat myofibroblasts

Abstract

Mikio Ni~hizawa,~ Hepatic stellate cells (HSCs) spontaneously transdifferentiate into myofibroblast (MFB) -phenotype on plastic dishes. This response recapitulates the features of activation in viva Transforming growth &tor P (TGF-P) plays a prominent role in stimulating liver fibrogenesis by MFBs. In quiescent HSCs, TGF-P signaling involves TGF-P type I receptor (TPRI)-mediated phosphorylation of serine residues within the conserved SSXS motif at the C-terminus of Smad2 and Smad3. The middle linker regions of Smad2 and Smad3 also are phosphorylated by mitogenactivated protein b a s e (MAPK). This study elucidates the change of Smad3-mediated signals during the transdifferentiation process. By using antibodies highly specific to the phosphorylated C-terminal region and the phosphorylated linker region of Smad3, we found that TGF-& dependent Smad3 phosphorylation at the C-terminal region decreased, but that the phosphorylation at the linker region increased in the process of transdifferentiation. TGF-P activated the p38 MAPK pathway, further leading to Smad3 phosphorylation at the linker region in the cultured MFBs, irrespective of Smad2. The phosphorylation promoted hetero-complex formation and nuclear translocation of Smad3 and Smad4. Once combined with TPRI-phosphorylated Smad2, the Smad3 and Smad4 complex bound to plasminogen activator inhibitor-type I promoter could enhance the transcription. In addition, Smad3 phosphorylation mediated by the activated TPRI was impaired severely in MFBs during chronic liver injury, whereas Smad3 phosphorylation at the linker region was remarkably induced by p38 MAPK pathway. In conclusion, p38 MAPK-dependent Smad3 phosphorylation promoted extracellular matrix production in MFBs both in vitro and in viva (HEPATOLOGY 2003 age as well as after their prolonged culture on plastic dishes.' This process involves changes in the cell morphology and gene expression and is characterized by the gradual loss in the retinoid content and the synthesis of a large amount of extracellular matrix (ECM) components.Transforming growth factor P (TGF-P) is an important mediator of ECM accumulation and is involved in a variety of physiologic and pathologic processes.2 In particular, the expression of TGF-/3 at high steady-state levels associated with the accelerated ECM accumulation in MFBs is a common finding in human chronic liver disease of different etiologies.3 Uncontrolled ECM accumulation mediated by TGF-P is thought to be essential for the development of liver fibrosis. However, the change of TGF-P signals during the transdifferentiation process of HSCs remains unclear.O n the other hand, recent studies over the past several years have elucidated how TGF-P initiates its response. TGF-/3 transduces the signal from its receptor to nucleus through Smads.4 The activated TGF-P type I receptor (TPRI) phosphorylates such receptor-regulated Smads 879

Src is a major signaling component for CTGF induction by TGF‐β1 in osteoblasts

“…Western blot analysis of cell lysates using these antibodies revealed a time-dependent activation of Smad 2 and Smad 3 (Figure 5A), while there was no change in total Smad 2/3 level in ROS osteoblast-like cells. Recent studies have shown that Erk could modify the linker region at Seine 213 between the MH1 and MH2 domain of R-Smads (Furukawa et al, 2003; Kamaraju and Roberts, 2005; Kretzschmar et al, 1999; Matsuura et al, 2005; Wang et al, 2009a). Therefore, we determined the phosphorylation status of linker region of Smad 3 under different conditions.…”

FGF2-mediated attenuation of myofibroblast activation is modulated by distinct MAPK signaling pathways in human dermal fibroblasts

“…Inhibition of p38 signaling has been demonstrated to attenuate fibrotic responses in vivo in experimental models of renal fibrosis [48–51], cardiac fibrosis [52, 53], and in myofibroblast activation in vitro [54–56]. Thus, our data demonstrating that p38 has the ability to not only potentiate FGF2-mediated inhibition of myofibroblast phenotypes, but also to inhibit TGFβ-mediated myofibroblast differentiation directly, add the suggestion of p38 inhibition as a potential treatment for dermal fibrosis to a growing body of literature suggesting the potential efficacy of p38 inhibition as antifibrotic therapy in various tissues.…”

Microarray expression profiles of genes in lung tissues of rats subjected to focal cerebral ischemia-induced lung injury following bone marrow-derived mesenchymal stem cell transplantation

“…It has been shown that TGF-β regulates the transformation of human lung fibroblasts into myofibroblasts through MAPK signal transduction pathways, producing extracellular matrix proteins and resulting in lung interstitial fibrosis (50). Lu et al confirmed that Smad2 plays a role in pulmonary vascular endothelial permeability induced by TGF-β1; thus, increased TGF-β1 may promote lung injury (51).…”