Lipopolysaccharide Activates Toll-Like Receptor 4 and Prevents Cardiac Fibroblast-to-Myofibroblast Differentiation

Abstract

Bacterial lipopolysaccharide (LPS) is a known ligand of Toll-like receptor 4 (TLR4) which is expressed in cardiac fibroblasts (CF). Differentiation of CF to cardiac myofibroblasts (CMF) is induced by transforming growth factor-β1 (TGF-β1), increasing alpha-smooth muscle actin (α-SMA) expression. In endothelial cells, an antagonist effect between LPS-induced signaling and canonical TGF-β1 signaling was described; however, it has not been studied whether in CF and CMF the expression of α-SMA induced by TGF-β1 is antagonized by LPS and the mechanism involved. In adult rat CF and CMF, α-SMA, ERK1/2, Akt, NF-κβ, Smad3, and Smad7 protein levels were determined by western blot, TGF-β isoforms by ELISA, and α-SMA stress fibers by immunocytochemistry. CF and CMF secrete the three TGF-β isoforms, and the secretion levels of TGF-β2 was affected by LPS treatment. In CF, LPS treatment decreased the protein levels of α-SMA, and this effect was prevented by TAK-242 (TLR4 inhibitor) and LY294002 (Akt inhibitor), but not by BAY 11-7082 (NF-κβ inhibitor) and PD98059 (ERK1/2 inhibitor). TGF-β1 increased α-SMA protein levels in CF, and LPS prevented partially this effect. In addition, in CMF α-SMA protein levels were decreased by LPS treatment, which was abolished by TAK-242. Finally, in CF LPS decreased the p-Smad3 phosphorylation and increased the Smad7 protein levels. LPS treatment prevents the CF-to-CMF differentiation and reverses the CMF phenotype induced by TGF-β1, through decreasing p-Smad3 and increasing Smad7 protein levels.

LPS Promotes Vascular Smooth Muscle Cells Proliferation Through the TLR4/Rac1/Akt Signalling Pathway

“…Moreover, they discuss many molecules, including microRNAs, cytokines and biochemical factors, membrane receptors, ion channels, cytoskeleton and extracellular matrix may become a promising target in VSMCs differentiation-related diseases [44]. Bolı´var et al recently reported that LPS induces TLR4 activation and prevents cardiac fibroblast-to-myofibroblast differentiation and that decreasedα-SMA expression played a role in this effect [45]. However, whether LPS-induced phenotypic modulation of VSMCs represents a new therapeutic target for proliferative vascular diseases warrants further investigation.…”

Multiscale Coupling of an Agent-Based Model of Tissue Fibrosis and a Logic-Based Model of Intracellular Signaling

“…This was accomplished by performing a parameter sweep of values for k dep while constraining k deg to satisfy the ratio determined previously and minimizing the sum of squared error (SSE) between the model fit and infarct experimental data. Wakefield et al, 1987;Campbell and Katwa, 1997;Campaner et al, 2006;Cartledge et al, 2015;Bolívar et al, 2017 k deg,latentTGFβ First-order degradation rate for latent TGFβ 5 0.0096 /hr Rollins et al, 1989 k act,latentTGFβ Activation rate of latent TGFβ to active TGFβ 5 & 6 0.045 Maeda et al, 2002;Hawinkels et al, 2007 Ancey et al, 2002;Fredj et al, 2005;Turner et al, 2007Turner et al, , 2009…”

Identification of SMAD3 as a Novel Mediator of Inflammation in Human Myometrium In Vitro

“…In addition, inflammatory insults can also impair SMAD3 expression. For example, brains affected by Alzheimer disease are associated with decreased levels of SMAD3 [ 26 ], while SMAD3 phosphorylation (i.e., activity) is reduced in proximal tubular cells stimulated with IL-1 β [ 27 ] and in cardiac fibroblasts treated with LPS [ 28 ].…”