A Novel Mechanism of Tissue Inhibitor of Metalloproteinases-1 Activation by Interleukin-1 in Primary Human Astrocytes

Abstract

Reactive astrogliosis is the gliotic response to brain injury with activated astrocytes and microglia being the major effector cells. These cells secrete inflammatory cytokines, proteinases, and proteinase inhibitors that influence extracellular matrix (ECM) remodeling. In astrocytes, the expression of tissue inhibitor of metalloproteinases-1 (TIMP-1) is up-regulated by interleukin-1 (IL-1), which is a major neuroinflammatory cytokine. We report that IL-1 activates TIMP-1 expression via both the IKK/NF-B and MEK3/6/p38/ATF-2 pathways in astrocytes. The activation of the TIMP-1 gene can be blocked by using pharmacological inhibitors, including BAY11-7082 and SB202190, overexpression of the dominant-negative inhibitor of NF-B (IB␣SR), or by the knock-down of p65 subunit of NF-B. Binding of activated NF-B (p50/p65 heterodimer) and ATF-2 (homodimer) to two novel regulatory elements located ؊2.7 and ؊2.2 kb upstream of the TIMP-1 transcription start site, respectively, is required for full IL-1-responsiveness. Mutational analysis of these regulatory elements and their weak activity when linked to the minimal tk promoter suggest that cooperative binding is required to activate transcription. In contrast to astrocytes, we observed that TIMP-1 is expressed at lower levels in gliomas and is not regulated by IL-1. We provide evidence that the lack of TIMP-1 activation in gliomas results from either dysfunctional IKK/NF-B or MEK3/6/p38/ATF-2 activation by IL-1. In summary, we propose a novel mechanism of TIMP-1 regulation, which ensures an increased supply of the inhibitor after brain injury, and limits ECM degradation. This mechanism does not function in gliomas, and may in part explain the increased invasiveness of glioma cells.The remodeling of the extracellular matrix (ECM), 2 including the degradation of the ECM by matrix metalloproteinases (MMPs) and its subsequent resynthesis, is critical during normal physiological processes, such as angiogenesis, embryonic development, organ morphogenesis, bone remodeling, and ovulation (1, 2). During these processes the proteolytic activity of MMPs is tightly controlled at the transcriptional level by growth factors, hormones, and cytokines, and at the protein level by proteolytic cleavage of inactive zymogens, and the inhibition by specific inhibitors, including tissue inhibitors of metalloproteinases (TIMPs) (2). The delicate balance between the activities of MMPs and TIMPs is critical to limit deleterious outcomes of uncontrolled degradation, which is manifested in pathological conditions such as periodontal disease, arthritis, tumor cell invasion, fibrosis, and neurodegenerative disorders (2-4). These pathological conditions often represent chronic inflammatory diseases suggesting that inflammatory mediators, including inflammatory cytokines, may disrupt the intricate balance between MMPs and TIMPs.In the central nervous system (CNS), infection and injury induce a histopathological response known as reactive astrogliosis, which is the primary cause of regenerative failure in ...

Differential vesicular distribution and trafficking of MMP‐2, MMP‐9, and their inhibitors in astrocytes

“…Using Western blotting, we also show TIMP-1, but not TIMP-2, induction in LPStreated astrocytes, in agreement with previous results in glial cultures (Liu et al, 2007;Liuzzi et al, 2004;Wilczynska et al, 2006). Also, a number of in vivo results, including from our laboratory, indicate that TIMP-1 is induced at high levels in reactive astrocytes (Jaworski, 2000;Rivera et al, 1997Rivera et al, , 2002Wilczynska et al, 2006).…”

“…The apparent discrepancy between these results and our data showing clear MMP-9 expression and LPS-driven upregulation in astrocytes may result from fundamental differences between primary cells and stem cells, which undergo in vivo and in vitro differentiation, respectively, and may be related to differential expression by primary and stem cells of CD14 or LPS-binding protein (LBP), both important for LPS-induced effects in cells (Guillemin et al, 1997;Kitchens, 2000). Using Western blotting, we also show TIMP-1, but not TIMP-2, induction in LPStreated astrocytes, in agreement with previous results in glial cultures (Liu et al, 2007;Liuzzi et al, 2004;Wilczynska et al, 2006). Also, a number of in vivo results, including from our laboratory, indicate that TIMP-1 is induced at high levels in reactive astrocytes (Jaworski, 2000;Rivera et al, 1997Rivera et al, , 2002Wilczynska et al, 2006).…”

Aldosterone Induces Tissue Inhibitor of Metalloproteinases-1 Expression and Further Contributes to Collagen Accumulation

“…26 To determine whether aldosterone induces TIMP-1 expression via the effect of NF-κB or AP-1, we used NF-κB and AP-1 decoy oligodeoxynucleotides to block the downstream response. Human cardiac fibroblasts were pretreated with decoy oligodeoxynucleotides before 10 -6 M aldosterone treatment, and the results showed that the aldosterone-induced expressions of protein and TIMP-1 mRNA were both suppressed by NF-κB decoy oligodeoxynucleotide, but not by AP-1 decoy oligodeoxynucleotide ( Figure 3A-3B).…”

A new role for NF-κB in angiogenesis inhibition

“…10 Next to the MMPs, plasmin is a broad-spectrum protease that also hydrolyzes many extracellular proteins, the most notable of which is fibrin. Plasmin is produced from an inactive precursor called plasminogen.…”