p21^{waf1/cip1/sdi1}as a Central Regulator of Inducible Smooth Muscle Actin Expression and Differentiation of Cardiac Fibroblasts to Myofibroblasts

Abstract

The phenotypic switch of cardiac fibroblasts (CFs) to myofibroblasts is essential for normal and pathological wound healing. Relative hyperoxic challenge during reoxygenation causes myocardial remodeling. Here, we sought to characterize the novel O(2)-sensitive molecular mechanisms responsible for triggering the differentiation of CFs to myofibroblasts. Exposure of CFs to hyperoxic challenge-induced transcription of smooth muscle actin (SMA) and enhanced the stability of both Acta2 transcript as well as of SMA protein. Both p21 deficiency as well as knockdown blunted hyperoxia-induced Acta2 and SMA response. Strikingly, overexpression of p21 alone markedly induced differentiation of CFs under normoxia. Overexpression of p21 alone induced SMA transcription by down-regulating YB1 and independent of TGFbeta1. In vivo, hyperoxic challenge induced p21-dependent differentiation of CFs to myofibroblasts in the infarct boundary region of ischemia-reperfused heart. Tissue elements were laser-captured from infarct boundary and from a noninfarct region 0.5 mm away. Reperfusion caused marked p21 induction in the infarct region. Acta2 as well as SMA expression were markedly up-regulated in CF-rich infarct boundary region. Of note, ischemia-reperfusion-induced up-regulation of Acta2 in the infarct region was completely abrogated in p21-deficient mice. This observation establishes p21 as a central regulator of reperfusion-induced phenotypic switch of CFs to myofibroblasts.

Transforming Growth Factor β1-mediated Activation of the Smooth Muscle α-Actin Gene in Human Pulmonary Myofibroblasts Is Inhibited by Tumor Necrosis Factor-α via Mitogen-activated Protein Kinase Kinase 1-dependent Induction of the Egr-1 Transcriptional Repressor

“…Repression of both myofibroblast differentiation and connective tissue biosynthesis by Egr-1 coupled with increased transcription of Egr-1-dependent genes such as interleukin (IL)-1␤, monocyte chemoattractant protein-1, intercellular adhesion molecule-1, macrophage inflammatory protein-2, 10-kDa interferon-inducible protein, and (RANTES) protein may improve wound healing efficiency because these proinflammatory cytokines and chemokines seem to collaborate with hypoxia-induced hypoxiainducible factor ␣ and vascular endothelial growth factor in the repair and expansion of microvascular networks needed to restore blood flow to damaged tissues. We recently reported that hypoxia (3% molecular oxygen) significantly repressed SM␣A gene expression in primary culture preparations of mouse cardiac fibroblasts (Roy et al, 2007). Although the role of Egr-1 in mediating transcriptional response of the SM␣A gene to hypoxia was not specifically examined in that study, we did report a positive correlation between hypoxia, SM␣A gene repression, and elevated levels of YB-1 protein in cardiac fibroblasts.…”

Hypoxic Stress Induces Transient Receptor Potential Melastatin 2 (TRPM2) Channel Expression in Adult Rat Cardiac Fibroblasts

“…Therefore, we next examined the mRNA expression levels of TRPM2 channels and KCa3.1 in cardiac fibroblasts exposed to hypoxia and normoxia. In addition, we also examined the expression levels of marker mRNAs for myofibroblasts, for example, transforming growth factor (TGF)-β1 (24), cyclin-dependent kinase inhibitor 1 (p21), and α-smooth muscle actin (α-SMA) (25), because hypoxia is known to induce differentiation from fibroblasts to myofibroblasts (6). As illustrated in Fig.…”

Correction of Aberrant NADPH Oxidase Activity in Blood-Derived Mononuclear Cells from Type II Diabetes Mellitus Patients by a Naturally Fermented Papaya Preparation

“…Data are expressed as mean -SD (n = 3) *p < 0.05 compared to non-FPP CTL. by real-time polymerase chain reaction assay using SYBR green-I (Applied Biosystems, Carlsbad, CA) as described previously (36,(38)(39)(40). b-Actin was used as the housekeeping gene.…”