Tissue Inhibitor of Metalloproteinases–3 Moderates the Proinflammatory Status of Macrophages

Abstract

Tissue inhibitor of metalloproteinases-3 (TIMP-3) has emerged as a key mediator of inflammation. Recently, we reported that the resolution of inflammation is impaired in Timp3 2/2 mice after bleomycininduced lung injury. Here, we demonstrate that after LPS instillation (another model of acute lung injury), Timp32/2 mice demonstrate enhanced and persistent neutrophilia, increased numbers of infiltrated macrophages, and delayed weight gain, compared with wild-type (WT) mice. Because macrophages possess broad immune functions and can differentiate into cells that either stimulate inflammation (M1 macrophages) or are immunosuppressive (M2 macrophages), we examined whether TIMP-3 influences macrophage polarization. Comparisons of the global gene expression of unstimulated or LPS-stimulated bone marrow-derived macrophages (BMDMs) from WT and Timp3 2/2 mice revealed that Timp3 2/2 BMDMs exhibited an increased expression of genes associated with proinflammatory (M1) macrophages, including Il6, Il12, Nos2, and Ccl2. Microarray analyses also revealed a baseline difference in gene expression between WT and Timp3 2/2 BMDMs, suggesting altered macrophage differentiation. Furthermore, the treatment of Timp3 2/2 BMDMs with recombinant TIMP-3 rescued this altered gene expression. We also examined macrophage function, and found that Timp3 2/2 M1 cells exhibit significantly more neutrophil chemotactic activity and significantly less soluble Fas ligand-induced caspase-3/7 activity, a marker of apoptosis, compared with WT M1 cells. Macrophage differentiation into immunosuppressive M2 cells is mediated by exposure to IL-4/IL-13, and we found that Timp3 2/2 M2 macrophages demonstrated a lower expression of genes associated with an anti-inflammatory phenotype, compared with WT M2 cells. Collectively, these findings indicate that TIMP-3 functions to moderate the differentiation of macrophages into proinflammatory (M1) cells.Keywords: resolution of inflammation; macrophage; metalloproteinase; lung injury Several immunosuppressive mechanisms have evolved to ensure that acute, generally beneficial inflammation does not progress to chronic, destructive inflammation. Beyond reversal of the initiating event (e.g., bacterial clearance and wound closure), active host processes, such as the release of the anti-inflammatory cytokines IL-4, IL-10, and IL-13, among other processes (1), actively repress the proinflammatory properties of various cell types. Macrophages, through their ability to clear neutrophils and release anti-inflammatory cytokines, are thought to be important in the resolution of inflammation (2).Generally speaking, macrophages are key effectors promoting the shift from a proinflammatory to an anti-inflammatory environment, and can be broadly classified into two groups: classically activated (M1) and alternatively activated (M2) macrophages, which can be further subdivided into specialized M2 groups (3). M1 macrophages are induced by proinflammatory Th1 cytokines, such as IFN-g, and are characterized by the production of proinfl...

The role of TIMPs in regulation of extracellular matrix proteolysis

“…For example, in mice lacking TIMP3, fibrosis is enhanced following bleomycin-induced injury, suggesting that the presence of TIMP3 would actually restrict ECM deposition [58]. While the mechanism leading to this fibrosis remains to be determined, Timp3 −/− mice have impaired resolution of inflammation following lung injury, which could contribute to the enhanced fibrotic response [58,59].…”

Stromelysin-2 (MMP10) Moderates Inflammation by Controlling Macrophage Activation

“…For example, MMP12 and MMP28, both macrophage products, either promote or restrict macrophage influx into lung (10, 11), and MMP8 promotes M2 polarization (12). In addition, we reported that MMP28 and TIMP3, an MMP inhibitor, moderate M1 activation of macrophages in models of lung infection and fibrosis (13, 14). As their name implies, MMPs are thought to degrade extracellular matrix proteins, a function that is indeed performed by some members (15–17).…”

ADAM-family metalloproteinases in lung inflammation: potential therapeutic targets

“…Furthermore, TIMP3 deficiency prolongs bleomycin-induced lung inflammation with alveolar neutrophilia and prevents resolution of inflammation (53). In LPS-induced lung inflammation, lack of TIMP-3 was associated with increased macrophage polarization into the inflammatory M1 phenotype (52). Although TIMP3 seems to attenuate proinflammatory events in the lung, it is not clear to what extent this is mediated by the inhibition of ADAM17 or other metalloproteinases (Table 2).…”