The interferon-stimulated gene factor 3 complex mediates the inhibitory effect of interferon-beta on matrix metalloproteinase-9 expression

IL6/sIL6R regulates TNFα-inflammatory response in synovial fibroblasts through modulation of transcriptional and post-transcriptional mechanisms

Introduction

The clinical efficacy of specific interleukin-6 inhibitors has confirmed the central role of IL6 in rheumatoid arthritis (RA). However the local role of IL6, in particular in synovial fibroblasts (SF) as a direct cellular target to IL6/sIL6R signal is not well characterized. The purpose of the study was to characterize the crosstalk between TNFα and IL6/sIL6R signaling to the effector pro-inflammatory response of SF.

Methods

SF lines were stimulated with either TNFα, IL6/sIL6R, or both together, for the time and dose indicated for each experiment, and where indicated, cells were treated with inhibitors actinomycin D, adalimumab, ruxolitinib and cycloheximide. mRNA expression of cytokines, chemokines and matrix metalloproteases (MMPs) were analyzed by quantitative RT-PCR. Level of IL8/CXCL8 and CCL8 in culture supernatants was measured by ELISA. Mononuclear and polymorphonuclear cells migration assays were assessed by transwell using conditioned medium from SF cultures. Statistical analyses were performed as indicated in the corresponding figure legends and a p-value < 0.05 was considered statistically significant.

Results

The stimulation of SF with IL6/sIL6R and TNFα, cooperatively promotes the expression of mono- and lymphocytic chemokines such as IL6, CCL8 and CCL2, as well as matrix degrading enzymes such as MMP1, while inhibiting the induction of central neutrophil chemokines such as IL8/CXCL8. These changes in the pattern of chemokines expression resulted in reduced polymorphonuclear (PMN) and increased mononuclear cells (MNC) chemoattraction by SF. Mechanistic analyses of the temporal expression of genes demonstrated that the cooperative regulation mediated by these two factors is mostly induced through de novo transcriptional mechanisms activated by IL6/sIL6R. Furthermore, we also demonstrate that TNFα and IL6/sIL6R cooperation is partially mediated by the expression of secondary factors signaling through JAK/STAT pathways.

Conclusions

These results point out to a highly orchestrated response to IL6 in TNFα-induced SF and provide additional insights into the role of IL6/sIL6R in the context of RA, highlighting the contribution of IL6/sIL6R to the interplay of SF with other inflammatory cells.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12860-020-00317-7.

AP-1 mediated transcriptional repression of matrix metalloproteinase-9 by recruitment of histone deacetylase 1 in response to interferon β

Matrix metalloproteinase-9 (MMP-9) is a 92 kDa zinc-dependant endopeptidase that degrades components of the extracellular matrix. Increased expression of MMP-9 is implicated in many pathological conditions including metastatic cancer, multiple sclerosis, and atherosclerosis. Although it has been widely noted that interferon-β (IFNβ) downregulates both the basal and phorbol 12-myristate 13-acetate (PMA)-induced MMP-9 expression at the transcriptional level, the molecular mechanism of this repression is poorly understood. In the present study we identify a novel mechanism for repression of MMP-9 transcription by IFNβ in HT1080 fibrosarcoma cells. Using reporter assays with promoter deletion constructs we show that IFNβ’s inhibitory effects require a region of the promoter between −154 and −72, which contains an AP-1 binding site. Chromatin immunoprecipitation (ChIP) studies indicate that IFNβ increases histone deacetylase (HDAC)-1 recruitment to the MMP-9 promoter and reduces histone H3 acetylation, in addition to reduced NF-κB recruitment. ChIP analysis shows that IFNβ induced HDAC1 recruitment to the MMP-9 promoter and IFNβ mediated transcriptional repression is lost when the AP-1 binding site is inactivated by a point mutation. Altogether, our results establish that the repression of MMP-9 transcription in response to IFNβ occurs by the recruitment of HDAC1 via the proximal AP-1 binding site.

Host Defense and the Airway Epithelium: Frontline Responses That Protect against Bacterial Invasion and Pneumonia

Airway epithelial cells are the first line of defense against invading microbes, and they protect themselves through the production of carbohydrate and protein matrices concentrated with antimicrobial products. In addition, they act as sentinels, expressing pattern recognition receptors that become activated upon sensing bacterial products and stimulate downstream recruitment and activation of immune cells which clear invading microbes. Bacterial pathogens that successfully colonize the lungs must resist these mechanisms or inhibit their production, penetrate the epithelial barrier, and be prepared to resist a barrage of inflammation. Despite the enormous task at hand, relatively few virulence factors coordinate the battle with the epithelium while simultaneously providing resistance to inflammatory cells and causing injury to the lung. Here we review mechanisms whereby airway epithelial cells recognize pathogens and activate a program of antibacterial pathways to prevent colonization of the lung, along with a few examples of how bacteria disrupt these responses to cause pneumonia.

The effect of interferon-α on the expression of cytochrome P450 3A4 in human hepatoma cells

Interferon α (IFNα) is used to treat malignancies and chronic viral infections. It has been found to decrease the rate of drug metabolism by acting on cytochrome P450 enzymes, but no studies have investigated the consequences of IFNα treatment on the CYP3A4 isoform, responsible for the metabolism of a majority of drugs. In this study, we have examined the effect of IFNα on CYP3A4 catalytic activity and expression in human hepatoma cells. We found that IFNα inhibits CYP3A4 activity and rapidly down-regulates the expression of CYP3A4, independent of de novo protein synthesis. Pharmacologic inhibitors and a dominant-negative mutant expression plasmid were used to dissect the molecular pathway required for CYP3A4 suppression, revealing roles for Jak1 and Stat1 and eliminating the involvement of the p38 mitogen-activated and extracellular regulated kinases. Treatment of hepatoma cells with IFNα did not affect the nuclear localization or relative abundance of Sp1 and Sp3 transcription factors, suggesting that the suppression of CYP3A4 by IFNα does not result from inhibitory Sp3 out-competing Sp1. To our knowledge, this is the first report that IFNα down-regulates CYP3A4 expression largely through the JAK-STAT pathway. Since IFNα suppresses CYP3A4 expression, caution is warranted when IFNα is administered in combination with CYP3A4 substrates to avoid the occurrence of adverse drug interactions.

TLR4 through IFN-β promotes low molecular mass hyaluronan-induced neutrophil apoptosis

Intratracheal administration of low molecular mass (LMM) hyaluronan (200 kDa) results in greater neutrophil infiltration in the lungs of TLR4(-/-) mice compared with that in wild-type mice. In general, enhanced neutrophil infiltration in tissue is due to cell influx; however, neutrophil apoptosis also plays an important role. We have assessed the effects of TLR4 in the regulation of neutrophil apoptosis in response to administration of LMM hyaluronan. We found that apoptosis of inflammatory neutrophils is impaired in TLR4(-/-) mice, an effect that depends upon the IFN-β-mediated TRAIL/TRAILR system. IFN-β levels were decreased in LMM hyaluronan-treated TLR4-deficient neutrophils. The treatment of inflammatory neutrophils with IFN-β enhanced the levels of TRAIL and TRAILR 2. LMM hyaluronan-induced inflammatory neutrophil apoptosis was substantially prevented by anti-TRAIL neutralizing mAb. We conclude that decreased IFN-β levels decrease the activity of the TRAIL/TRAILR system in TLR4-deficient neutrophils, leading to impaired apoptosis of neutrophils and resulting in abnormal accumulation of neutrophils in the lungs of LMM hyaluronan-treated mice. Thus, TLR4 plays a novel homeostatic role in noninfectious lung inflammation by accelerating the elimination of inflammatory neutrophils.

IFN-beta inhibits dendritic cell migration through STAT-1-mediated transcriptional suppression of CCR7 and matrix metalloproteinase 9

IFN-beta is an approved therapeutic option for the treatment of multiple sclerosis. The molecular mechanisms underlying the effects of IFN-beta in multiple sclerosis are not fully understood. Migration of dendritic cells (DCs) from the inflammatory site to draining lymph nodes for Ag presentation and activation of naive T cells and to the CNS for reactivation of encephalitogenic T cells requires CCR7 and matrix metalloproteinase (MMP)-9 expression. This article reports for the first time that IFN-beta inhibits CCR7 expression and MMP-9 production in mature DCs and reduces their migratory capacity. The effect of IFN-beta is mediated through STAT-1. In vivo treatment with IFN-beta results in lower numbers of DCs migrating to the draining lymph node following exposure to FITC and in reduced expression of CCR7 and MMP-9 in splenic CD11c(+) DCs following LPS administration. IFN-beta and IFN-gamma share the same properties in terms of their effects on CCR7, MMP-9, and DC migration, but they have opposite effects on IL-12 production. In addition, IFN-beta-treated DCs have a significantly reduced capacity for activating CD4(+) T cells and generating IFN-gamma-producing Th1 cells. The suppression of mature DC migration through negative regulation of CCR7 and MMP-9 expression represents a novel mechanism for the therapeutic effect of IFN-beta.

Staphylococcus aureus activates type I IFN signaling in mice and humans through the Xr repeated sequences of protein A

The activation of type I IFN signaling is a major component of host defense against viral infection, but it is not typically associated with immune responses to extracellular bacterial pathogens. Using mouse and human airway epithelial cells, we have demonstrated that Staphylococcus aureus activates type I IFN signaling, which contributes to its virulence as a respiratory pathogen. This response was dependent on the expression of protein A and, more specifically, the Xr domain, a short sequence-repeat region encoded by DNA that consists of repeated 24-bp sequences that are the basis of an internationally used epidemiological typing scheme. Protein A was endocytosed by airway epithelial cells and subsequently induced IFN-beta expression, JAK-STAT signaling, and IL-6 production. Mice lacking IFN-alpha/beta receptor 1 (IFNAR-deficient mice), which are incapable of responding to type I IFNs, were substantially protected against lethal S. aureus pneumonia compared with wild-type control mice. The profound immunological consequences of IFN-beta signaling, particularly in the lung, may help to explain the conservation of multiple copies of the Xr domain of protein A in S. aureus strains and the importance of protein A as a virulence factor in the pathogenesis of staphylococcal pneumonia.

Signal transducer and activator of transcription 1 (STAT1) is essential for chromium silencing of gene induction in human airway epithelial cells

Hexavalent chromium (Cr(VI)) promotes lung injury and pulmonary diseases through poorly defined mechanisms that may involve the silencing of inducible protective genes. The current study investigated the hypothesis that Cr(VI) actively signals through a signal transducer and activator of transcription 1 (STAT1)-dependent pathway to silence nickel (Ni)-induced expression of vascular endothelial cell growth factor A (VEGFA), an important mediator of lung injury and repair. In human bronchial airway epithelial (BEAS-2B) cells, Ni-induced VEGFA transcription by stimulating an extracellular regulated kinase (ERK) signaling cascade that involved Src kinase-activated Sp1 transactivation, as well as increased hypoxia-inducible factor-1 alpha (HIF-1 alpha) stabilization and DNA binding. Ni-stimulated ERK, Src, and HIF-1 alpha activities, as well as Ni-induced VEGFA transcript levels were inhibited in Cr(VI)-exposed cells. We previously demonstrated that Cr(VI) stimulates STAT1 to suppress VEGFA expression. In BEAS-2B cells stably expressing STAT1 short hairpin RNA, Cr(VI) increased VEGFA transcript levels and Sp1 transactivation. Moreover, in the absence of STAT1, Cr(VI), and Ni coexposures positively interacted to further increase VEGFA transcripts. This study demonstrates that metal-stimulated signaling cascades interact to regulate transcription and induction of adaptive or repair responses in airway cells. In addition, the data implicate STAT1 as a rate limiting mediator of Cr(VI)-stimulated gene regulation and suggest that cells lacking STAT1, such as many tumor cell lines, have opposite responses to Cr(VI) relative to normal cells.

Transcriptional activation of human matrix metalloproteinase-9 gene expression by multiple co-activators

Matrix metalloproteinase-9 (MMP-9), a proteolytic enzyme for matrix proteins, chemokines and cytokines, is a major target in cancer and autoimmune diseases, since it is aberrantly upregulated. To control MMP-9 expression in pathological conditions, it is necessary to understand the regulatory mechanisms of MMP-9 expression. MMP-9 gene expression is regulated primarily at the transcriptional level. In this study, we investigated the role of multiple co-activators in regulating MMP-9 transcription. We demonstrate that multiple transcriptional co-activators are involved in MMP-9 promoter activation, including CBP/p300, PCAF, CARM1 and GRIP1. Furthermore, enhancement of MMP-9 promoter activity requires the histone acetyltransferase activity of PCAF but not that of CBP/p300, and the methyltransferase activity of CARM1. More importantly, these co-activators are able to activate MMP-9 promoter activity independently, and function in a synergistic manner. Significant synergy was observed among CARM1, p300 and GRIP1, which is dependent on the interaction of p300 and CARM1 with the AD1 and AD2 domains of GRIP1, respectively. This suggests the formation of a ternary co-activator complex on the MMP-9 promoter. Chromatin immunoprecipitation assays demonstrate that these co-activators associate with the endogenous MMP-9 promoter, and that siRNA knockdown of expression of these co-activators reduces endogenous MMP-9 expression. Taken together, these studies demonstrate a new level of transcriptional regulation of MMP-9 expression by the cooperative action of co-activators.

Type I interferons as anti-inflammatory mediators

The type I interferons (IFNs), IFN-alpha and IFN-beta, are cytokines that have antiviral, antiproliferative, and immunomodulatory activities. Data are now emerging that suggest that type I IFNs are also important mediators of anti-inflammatory responses. These findings, largely driven by studies to explain the beneficial effects of IFN-beta in the treatment of multiple sclerosis, an autoimmune disease of the central nervous system, offer a number of mechanisms for the anti-inflammatory properties of type I IFNs. Type I IFNs, through their ability to induce the immunosuppressive cytokine interleukin-10 (IL-10), mediate the inhibition of proinflammatory gene products. In addition, type I IFNs induce other immunosuppressive mediators such as suppressor of cytokine signaling-1 (SOCS-1) and tristetrapolin (TTP), which act by divergent mechanisms to restore homeostasis to the immune system. Furthermore, type I IFNs mediate anti-inflammatory and protective effects in a variety of autoimmune disease models such as experimental colitis, experimental allergic encephalomyelitis, experimental arthritis, and neonatal inflammation. Here, we discuss the molecular basis for the anti-inflammatory properties of type I IFNs and their therapeutic potential in autoimmune and inflammatory diseases.