Transforming growth factor-beta differently regulates urokinase type plasminogen activator and matrix metalloproteinase-9 expression in mouse macrophages; analysis of intracellular signal transduction

The role of endogenous Smad7 in regulating macrophage phenotype following myocardial infarction

Smad7 restrains TGF-β responses, and has been suggested to exert both pro- and anti-inflammatory actions that may involve effects on macrophages. Myocardial infarction triggers a macrophage-driven inflammatory response that not only plays a central role in cardiac repair, but also contributes to adverse remodeling and fibrosis. We hypothesized that macrophage Smad7 expression may regulate inflammation and fibrosis in the infarcted heart through suppression of TGF-β responses, or via TGF-independent actions. In a mouse model of myocardial infarction, infiltration with Smad7+ macrophages peaked 7 days after coronary occlusion. Myeloid cell-specific Smad7 loss in mice had no effects on homeostatic functions and did not affect baseline macrophage gene expression. RNA-seq predicted that Smad7 may promote TREM1-mediated inflammation in infarct macrophages. However, these alterations in the transcriptional profile of macrophages were associated with a modest and transient reduction in infarct myofibroblast infiltration, and did not affect dysfunction, chamber dilation, scar remodeling, collagen deposition, and macrophage recruitment. In vitro, RNA-seq and PCR arrays showed that TGF-β has profound effects on macrophage profile, attenuating pro-inflammatory cytokine/chemokine expression, modulating synthesis of matrix remodeling genes, inducing genes associated with sphingosine-1 phosphate activation and integrin signaling, and inhibiting cholesterol biosynthesis genes. However, Smad7 loss did not significantly affect TGF-β-mediated macrophage responses, modulating synthesis of only a small fraction of TGF-β-induced genes, including Itga5, Olfml3, and Fabp7. Our findings suggest a limited role for macrophage Smad7 in regulation of post-infarction inflammation and repair, and demonstrate that the anti-inflammatory effects of TGF-β in macrophages are not restrained by endogenous Smad7 induction.

Estramustine Phosphate Inhibits TGF-β-Induced Mouse Macrophage Migration and Urokinase-Type Plasminogen Activator Production

Transforming growth factor-beta (TGF-β) has been demonstrated as a key regulator of immune responses including monocyte/macrophage functions. TGF-β regulates macrophage cell migration and polarization, as well as it is shown to modulate macrophage urokinase-type plasminogen activator (uPA) production, which also contributes to macrophage chemotaxis and migration toward damaged or inflamed tissues. Microtubule (MT) cytoskeleton dynamic plays a key role during the cell motility, and any interference on the MT network profoundly affects cell migration. In this study, by using estramustine phosphate (EP), which modifies MT stability, we analysed whether tubulin cytoskeleton contributes to TGF-β-induced macrophage cell migration and uPA expression. We found out that, in the murine macrophage cell line RAW 264.7, EP at noncytotoxic concentrations inhibited cell migration and uPA expression induced by TGF-β. Moreover, EP greatly reduced the capacity of TGF-β to trigger the phosphorylation and activation of its downstream Smad3 effector. Furthermore, Smad3 activation seems to be critical for the increased cell motility. Thus, our data suggest that EP, by interfering with MT dynamics, inhibits TGF-β-induced RAW 264.7 cell migration paralleled with reduction of uPA induction, in part by disabling Smad3 activation by TGF-β.