Current Programs and Incentives to Overcome Rural Physician Shortages in the United States: A Narrative Review.

Access to healthcare continues to be a top priority and prominent challenge in rural communities, with 20% of the total U.S. population living in rural areas while only 10% of physicians practice in rural areas. In response to physician shortages, a variety of programs and incentives have been implemented to recruit and retain physicians in rural areas; however, less is known about the types and structures of incentives that are offered in rural areas and how that compares to physician shortages. The purpose of our study is to conduct a narrative review of the literature to identify and compare current incentives that are offered by rural physician shortage areas to better understand how resources are being allocated to vulnerable areas. We reviewed published peer-reviewed articles from 2015-2022 to identify incentives and programs designed to address physician shortages in rural areas. We augment that review by examining the gray literature, including reports and white papers on the topic. Identified incentive programs were aggregated for comparison and translated into a map that depicts high, medium, and low levels of geographically designated Health Professional Shortage Areas (HPSAs) and the number of incentives offered by state. Surveying current literature regarding different types of incentivization strategies while comparing to primary care HPSAs provides general insights on the potential influence of incentive programs on shortages, allows easy visual review, and may provide greater awareness of available support for potential recruits. Providing a broad overview of the incentives offered in rural areas will help illuminate whether diverse and appealing incentives are offered in the most vulnerable areas and guide future efforts to address these issues.

Mining Clinical Data for Novel Posttraumatic Stress Disorder Medications.

BACKGROUND: Despite the prevalence and negative impact of posttraumatic stress disorder (PTSD), there are few medications approved by the U.S. Food and Drug Administration for treatment, and approved medications do not work well enough. We leveraged large-scale electronic health record data to identify existing medications that may be repurposed as PTSD treatments. METHODS: We constructed a mechanistic tree of all Food and Drug Administration-approved medications and used the tree-based scan statistic to identify medications associated with greater than expected levels of clinically meaningful improvement in PTSD symptoms using electronic health record data from the U.S. Department of Veterans Affairs. Our cohort included patients with a diagnosis of PTSD who had repeated symptom measurements using the PTSD Checklist over a 20-year period (N = 168,941). We calculated observed numbers based on patients taking each drug or mechanistically related class of drugs and the expected numbers based on the tree as a whole. RESULTS: Medications typically used to treat PTSD, such as the Food and Drug Administration-approved agent sertraline, were associated with improvement in PTSD symptoms, but the effects were small. Several, but not all, direct-acting antivirals used in the treatment of hepatitis C virus demonstrated a strong association with PTSD improvement. The finding was robust to a sensitivity analysis excluding patients who received established PTSD treatments, including trauma-focused psychotherapy, concurrent with hepatitis treatment. CONCLUSIONS: Our exploratory approach both demonstrated findings that are consistent with what is known about pharmacotherapy for PTSD and uncovered a novel class of medications that may improve PTSD symptoms.

The Regional Distribution of Psychiatric Residency Positions Funded by the Department of Veterans Affairs and Its Relationship to Rural Veteran Populations.

OBJECTIVE: The authors evaluated the distribution of psychiatry residency positions funded by the Department of Veterans Affairs between 2014 and 2020 with respect to geographic location and hospital patient population rurality. METHODS: The authors collected data on psychiatry residency positions from the Veterans Affairs' Office of Academic Affiliations Support Center and data on hospital-level patient rurality from the Veterans Health Administration Support Service Center. They examined the chronological and geospatial relationships between the number of residency positions deployed and the size of the rural patient populations served. RESULTS: Between 2014 and 2020, the Department of Veterans Affairs has substantially increased the number of rural hospitals hosting psychiatry residency programs, as well as the number of residency positions at those hospitals. However, several geographic regions serve high numbers of rural veterans with few or no psychiatry resident positions. CONCLUSIONS: While the VA efforts to increase psychiatry residency positions in rural areas have been partially successful, additional progress can be made increasing support for psychiatry trainees at Veterans Affairs hospitals and community-based outpatient clinics that serve large portions of the rural veteran population.

VISTA deficiency attenuates antibody-induced arthritis and alters macrophage gene expression in response to simulated immune complexes.

BACKGROUND: In addition to activated T cells, the immune checkpoint inhibitor "V domain-containing Ig suppressor of T-cell activation" (VISTA) is expressed by myeloid cell types, including macrophages and neutrophils. The importance of VISTA expression by myeloid cells to antibody-induced arthritis and its potential for relevance in human disease was evaluated. METHODS: VISTA was immunolocalized in normal and arthritic human synovial tissue sections and synovial tissue lysates were subjected to western blot analysis. The collagen antibody-induced arthritis model (CAIA) was performed with DBA/1 J mice treated with antibodies against VISTA and with VISTA-deficient mice (V-KO). Total mRNA from arthritic joints, spleens, and cultured macrophages was analyzed with NanoString arrays. Cytokines secreted by splenic inflammatory macrophages were determined. In-vitro chemotaxis and signal transduction assays were performed with cultured macrophages. RESULTS: VISTA protein was localized to synovial membrane cells, neutrophils, and scattered cells in lymphocyte-rich foci and was detected by western blot analysis in normal synovium and synovium from rheumatoid arthritis patients. Deficiency of VISTA or treatment of mice with anti-VISTA monoclonal antibodies attenuated CAIA. Joint damage and MMP-3 expression were significantly reduced in V-KO mice. Surface expression of C5a receptor was reduced on monocytes, neutrophils, and cultured macrophages from V-KO. Upon Fc receptor engagement in vitro, gene expression by V-KO macrophages was altered profoundly compared to WT, including a significant induction of IL-1 receptor antagonist (IL1rn). CONCLUSIONS: VISTA expression supports immune-complex inflammation in CAIA and VISTA is expressed in human synovium. VISTA supports optimal responses to C5a and modulates macrophage responses to immune complexes.

Interleukin-1 beta and transforming growth factor-beta 3 cooperate to activate matrix metalloproteinase expression and invasiveness in A549 lung adenocarcinoma cells.

Cytokines present in the tumor microenvironment can promote the invasiveness and metastatic potential of cancer cells. We therefore investigated the effects of interleukin-1 beta (IL-1B) and transforming growth factor beta-3 (TGFB3) on the non-small cell lung carcinoma (NSCLC) cell line A549. We found that these cytokines synergistically activated matrix metalloproteinase (MMP)-1, MMP-3, and MMP-10 gene expression in these cells through mitogen-activated protein kinase (MAPK)-dependent pathways. Consistent with this, both cytokines stimulated epithelial to mesenchymal transition and MAPK-dependent invasion through Matrigel™. These studies identify IL-1B and TGFB3 as pro-invasive factors in NSCLC and potential therapeutic targets for tumor progression.

Interleukin-1ß mediates metalloproteinase-dependent renal cell carcinoma tumor cell invasion through the activation of CCAAT enhancer binding protein ß.

Effective treatment of metastatic renal cell carcinoma (RCC) remains a major medical concern, as these tumors are refractory to standard therapies and prognosis is poor. Although molecularly targeted therapies have shown some promise in the treatment of this disease, advanced RCC tumors often develop resistance to these drugs. Dissecting the molecular mechanisms underlying the progression to advanced disease is necessary to design alternative and improved treatment strategies. Tumor-associated macrophages (TAMs) found in aggressive RCC tumors produce a variety of inflammatory cytokines, including interleukin-1ß (IL-1ß). Moreover, the presence of TAMs and high serum levels of IL-1ß in RCC patients correlate with advanced disease. We hypothesized that IL-1ß in the tumor microenvironment promotes the development of aggressive RCC tumors by directing affecting tumor epithelial cells. To address this, we investigated the role of IL-1ß in mediating RCC tumor cell invasion as a measure of tumor progression. We report that IL-1ß induced tumor cell invasion of RCC cells through a process that was dependent on the activity of matrix metalloproteinases (MMPs) and was independent of migration rate. Specifically, IL-1ß induced the expression of MMP-1, MMP-3, MMP-10, and MT1-MMP in a mechanism dependent on IL-1ß activation of the transcription factor CCAAT enhancer binding protein ß (CEBPß). Consistent with its role in MMP gene expression, CEBPß knockdown significantly reduced invasion, but not migration, of RCC tumor cells. These results identify the IL-1ß /CEBPß/MMP pathway as a putative target in the design of anti-metastatic therapies for the treatment of advanced RCC.

CCAAT-enhancer-binding protein beta activation of MMP-1 gene expression in SW1353 cells: independent roles of extracellular signal-regulated and p90/ribosomal S6 kinases.

CCAAT-enhancer-binding protein beta (CEBPB) is a pluripotent transcription factor that controls inflammation, proliferation, and differentiation. We recently reported a role for CEBPB during matrix metalloproteinase (MMP) gene expression, but the mechanisms involved are poorly understood. To address this we interrogated CEBPB-dependent MMP-1 and MMP-13 gene activation in the SW1353 chondrosarcoma cell line, a well-established model of MMP gene regulation in mesenchymal cells. IL-1B treatment increased CEBPB expression in SW1353 cells over a 24-h period and knockdown of CEBPB with shRNA abrogated IL-1B-dependent MMP-1 and MMP-13 gene activation. Exogenous expression of the CEBPB isoforms LAP1 or LAP2 was sufficient to induce MMP-1 mRNA levels comparable to IL-1B-induced expression, while the truncated LIP isoform repressed IL-1B-induced MMP-1. Although exogenous CEBPB expression induced MMP-13 mRNA, the response was less robust than was observed for MMP-1. CEBPB is activated by the extracellular-regulated kinases (ERK) and RSK kinases in response to oncogenes and growth factors. We found that the MEK inhibitor U0126 and the RSK inhibitor BI-D1870 both reduced IL-1B-dependent MMP-1 gene expression in SW1353 cells. Although ERK is known to phosphorylate CEBPB on threonine 235, this residue was not required for CEBPB-dependent activation of MMP-1. In contrast, the RSK target serine 321 was required for LAP1 and LAP2-dependent activation of MMP-1. These findings establish CEBPB as a critical intermediate for IL-1B-dependent MMP gene activation and assign specific roles for the ERK and RSK kinases in this pathway.

CCAAT enhancer binding protein-beta regulates matrix metalloproteinase-1 expression in interleukin-1beta-stimulated A549 lung carcinoma cells.

Matrix metalloproteinase-1 (MMP-1) is an inflammation-inducible neutral protease that mediates extracellular matrix remodeling and promotes tumor invasion. In this study, we examined the activation of MMP-1 gene expression in A549 lung carcinoma cells stimulated with the inflammatory cytokine interleukin-1beta (IL-1beta). We found that MMP-1 mRNA levels were maximal following 16 hours of IL-1beta stimulation and that this correlated with the expression of the transcription factor CCAAT enhancer-binding protein-beta (CEBPB). Knockdown of CEBPB expression with short hairpin RNA abrogated the expression of MMP-1, MMP-3, and MMP-10 in IL-1beta-stimulated A549 cells. An established CEBP element in the MMP-1 promoter was found to be required for basal and IL-1beta-induced transcription. Electrophoresis mobility shift assays showed that CEBPB binds to this promoter element maximally 16 hours after IL-1beta stimulation. DNA affinity chromatography studies showed that the LAP1, LAP2, and LIP isoforms of CEBPB bind to the IL-1beta-responsive CEBPB site in the MMP-1 promoter. Exogenous expression of the LAP1 and LAP2 isoforms stimulated the MMP-1 promoter, whereas LIP had no effect. Phosphorylation of CEBPB at Thr(235) peaked at 16 hours in IL-1beta-stimulated cells. The MEK inhibitor U0126 inhibited this phosphorylation and reduced MMP-1 gene induction. These studies establish CEBPB as an important mediator of metalloproteinase gene activation during inflammatory responses in lung cancer cells and highlight the different regulatory roles of CEBPB isoforms.

IL-17 stimulates MMP-1 expression in primary human cardiac fibroblasts via p38 MAPK- and ERK1/2-dependent C/EBP-beta , NF-kappaB, and AP-1 activation.

Matrix metalloproteinases (MMPs) degrade collagen and mediate tissue remodeling. The novel cytokine IL-17 is expressed during various inflammatory conditions and modulates MMP expression. We investigated the effect of IL-17 on MMP-1 expression in primary human cardiac fibroblasts (HCF) and delineated the signaling pathways involved. HCF were treated with recombinant human IL-17. MMP-1 expression was analyzed by Northern blotting, RT-quantitative PCR, Western blotting, and ELISA; transcriptional induction and transcription factor binding by EMSA, ELISA, and reporter assay; and p38 MAPK and ERK1/2 activation by protein kinase assays and Western blotting. Signal transduction pathways were investigated using pharmacological inhibitors, small interfering RNA (siRNA), and adenoviral dominant-negative expression vectors. IL-17 stimulated MMP-1 gene transcription, net mRNA levels, protein, and promoter-reporter activity in HCF. This response was blocked by IL-17 receptor-Fc chimera and IL-17 receptor antibodies, but not by IL-6, TNF-alpha, or IL-1beta antibodies. IL-17-stimulated type I collagenase activity was inhibited by the MMP inhibitor GM-6001 and by siRNA-mediated MMP-1 knockdown. IL-17 stimulated activator protein-1 [AP-1 (c-Fos, c-Jun, and Fra-1)], NF-kappaB (p50 and p65), and CCAAT enhancer-binding protein (C/EBP)-beta DNA binding and reporter gene activities, effects attenuated by antisense oligonucleotides, siRNA-mediated knockdown, or expression of dominant-negative signaling proteins. Inhibition of AP-1, NF-kappaB, or C/EBP activation attenuated IL-17-stimulated MMP-1 expression. IL-17 induced p38 MAPK and ERK1/2 activation, and inhibition by SB-203580 and PD-98059 blunted IL-17-mediated transcription factor activation and MMP-1 expression. Our data indicate that IL-17 induces MMP-1 in human cardiac fibroblasts directly via p38 MAPK- and ERK-dependent AP-1, NF-kappaB, and C/EBP-beta activation and suggest that IL-17 may play a critical role in myocardial remodeling.

Signal transduction and cell-type specific regulation of matrix metalloproteinase gene expression: can MMPs be good for you?

An abundance of literature over the past several years indicates a growing interest in the role of matrix metalloproteinases (MMPs) in normal physiology and in disease pathology. MMPs were originally defined by their ability to degrade the extracellular matrix, but it is now well documented that their substrates extend far beyond matrix components. Recent reviews discuss the structure and function of the MMP family members, as well as the promoter sequences that control gene expression. Thus, we focus on the signal transduction pathways that confer differential cell-type expression of MMPs, as well as on some novel non-matrix degrading functions of MMPs, particularly their intracellular location where they may contribute to apoptosis. In addition, increasing data implicate MMPs as "good guys", protective agents in some cancers and in helping to resolve acute pathologic conditions. Despite the intricate and complicated roles of MMPs in physiology and pathology, the goal of designing therapeutics that can selectively target MMPs remains a major focus. Developing MMP inhibitors with targeted specificity will be difficult; success will depend on understanding the role of these enzymes in homeostasis and on the careful delineation of mechanisms by which this family of enzymes mediates disease pathology.

The synthetic triterpenoid TP-222 inhibits RANKL stimulation of osteoclastogenesis and matrix metalloproteinase-9 expression.

OBJECTIVE: Receptor activator of nuclear factor-kappaB ligand (RANKL) promotes osteoclast differentiation from monocyte precursors by inducing a cohort of genes, including tartrate-resistant acid phosphatase (TRAP) and matrix metalloproteinase-9 (MMP-9). A family of synthetic triterpenoids with antiinflammatory and pro-apoptotic properties was described to modulate differentiation in monocytic cell lineages. We therefore investigated the ability of the potent and bioavailable synthetic triterpenoid TP-222 to inhibit RANKL-induced osteoclast formation and MMP-9 expression from monocytic precursor cells. METHODS: Osteoclast formation was assayed by staining for TRAP-positive multinucleated cells. MMP-9 expression was measured by quantitative RT-PCR, Western blot, immunohistochemistry, and gel zymography. In vivo effects of TP-222 were assessed by daily intraperitoneal injection of 4-week-old mice for 7 days followed by measurement of osteoclast number and MMP-9 expression at the cartilage/bone junction of the epiphyseal growth plate. RESULTS: RANKL promoted and TP-222 (300 nM) inhibited osteoclast formation in cultures of RAW264.7 cells or bone marrow-derived monocytes. RANKL also induced MMP-9 expression in RAW264.7 cells and this was reduced by concurrent or subsequent addition of TP-222. TP-222 treatment significantly reduced the mean number of osteoclasts present at the cartilage/bone interface compared to vehicle-injected control mice. Morphometric analyses of tissue sections showed that TP-222 treatment reduced the amount of immunoreactive MMP-9 present in both mononucleated pre-osteoclasts and osteoclasts. CONCLUSION: Our data demonstrate that TP-222 inhibits osteoclast formation and MMP-9 expression in vitro and in vivo, and suggest that triterpenoids may be useful compounds for modulating bone resorption diseases.

Interleukin-1 beta induction of matrix metalloproteinase-1 transcription in chondrocytes requires ERK-dependent activation of CCAAT enhancer-binding protein-beta.

Interleukin-1 beta (IL-1beta) is a central mediator of inflammation and connective tissue destruction in rheumatoid arthritis. IL-1beta activates articular chondrocytes to produce matrix metalloproteinase-1 (MMP-1), an enzyme capable of dismantling the collagen scaffold of articular cartilage. To define the transcription factors and signaling intermediates that activate MMP-1 transcription in chondrocytes, we performed transient transfection of MMP-1 promoter constructs followed by reporter assays. These studies identified an IL-1beta-responsive region of the human MMP-1 promoter that contains a consensus CCAAT enhancer-binding protein (C/EBP) binding site. Deletion of this site reduced overall transcriptional activity of the MMP-1 promoter, as well as decreased fold induction by IL-1beta. IL-1beta stimulation of chondrocytes increased binding of C/EBP-beta to the MMP-1 C/EBP site. Extracellular signal regulated kinase (ERK) pathway-dependent phosphorylation of C/EBP-beta on threonine 235 activates this transcription factor. Here we show that IL-1beta stimulation of chondrocytes induced phosphorylation of C/EBP-beta on threonine 235, and that the ERK pathway inhibitor PD98059 reduced this phosphorylation. We further show that PD98059 reduces IL-1beta-induced MMP-1 mRNA expression in chondrocytes. Moreover, inhibition of the ERK pathway by expression of dominant-negative forms of ERK1 and ERK2 impaired the ability of IL-1beta to transactivate the MMP-1 promoter. Our findings demonstrate a novel role for C/EBP-beta in IL-1beta-induced connective tissue disease and define a new nuclear target for the ERK pathway in MMP-1 gene activation.

Principal component analysis for predicting transcription-factor binding motifs from array-derived data.

BACKGROUND: The responses to interleukin 1 (IL-1) in human chondrocytes constitute a complex regulatory mechanism, where multiple transcription factors interact combinatorially to transcription-factor binding motifs (TFBMs). In order to select a critical set of TFBMs from genomic DNA information and an array-derived data, an efficient algorithm to solve a combinatorial optimization problem is required. Although computational approaches based on evolutionary algorithms are commonly employed, an analytical algorithm would be useful to predict TFBMs at nearly no computational cost and evaluate varying modelling conditions. Singular value decomposition (SVD) is a powerful method to derive primary components of a given matrix. Applying SVD to a promoter matrix defined from regulatory DNA sequences, we derived a novel method to predict the critical set of TFBMs. RESULTS: The promoter matrix was defined to establish a quantitative relationship between the IL-1-driven mRNA alteration and genomic DNA sequences of the IL-1 responsive genes. The matrix was decomposed with SVD, and the effects of 8 potential TFBMs (5'-CAGGC-3', 5'-CGCCC-3', 5'-CCGCC-3', 5'-ATGGG-3', 5'-GGGAA-3', 5'-CGTCC-3', 5'-AAAGG-3', and 5'-ACCCA-3') were predicted from a pool of 512 random DNA sequences. The prediction included matches to the core binding motifs of biologically known TFBMs such as AP2, SP1, EGR1, KROX, GC-BOX, ABI4, ETF, E2F, SRF, STAT, IK-1, PPARgamma, STAF, ROAZ, and NFkappaB, and their significance was evaluated numerically using Monte Carlo simulation and genetic algorithm. CONCLUSION: The described SVD-based prediction is an analytical method to provide a set of potential TFBMs involved in transcriptional regulation. The results would be useful to evaluate analytically a contribution of individual DNA sequences.

The triterpenoid CDDO inhibits expression of matrix metalloproteinase-1, matrix metalloproteinase-13 and Bcl-3 in primary human chondrocytes.

A synthetic triterpenoid, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), has been reported to have anti-inflammatory properties and to decrease the interleukin-1 (IL-1)-induced expression of matrix metalloproteinase-1 (MMP-1) and MMP-13. We have shown previously that IL-1 induces expression of the inhibitor of NF-kappaB (IkappaB) family member Bcl-3, and that this contributes to MMP-1 expression. To quantify the effects of CDDO on IL-1-induced MMP-1, MMP-13 and Bcl-3 expression, we stimulated the chondrosarcoma cell line SW-1353 and human primary chondrocytes with IL-1, in the presence or absence of CDDO. Harvested RNA was subjected to quantitative real-time reverse-transcriptase polymerase chain reaction. In SW-1353 cells, 300 nM CDDO significantly decreased the induction of MMP-1 and MMP-13 by IL-1. In human primary chondrocytes, 300 nM CDDO inhibited the induction of these genes by IL-1 to an even greater extent. In both cell types, inhibition of MMP-1 required 24 hours of pretreatment with CDDO, whereas MMP-13 could be inhibited when CDDO and IL-1 were added simultaneously to culture. In human primary chondrocytes, IL-1-induced Bcl-3 expression was inhibited when cells were pretreated with CDDO. To determine whether the inhibitory effect of CDDO on MMP worked through inhibition of Bcl-3 gene expression, SW-1353 cells stably transfected with a Bcl-3 expression plasmid were treated with IL-1 and/or CDDO, and MMP gene expression was assayed. Overexpression of Bcl-3 increased MMP-1, but not MMP-13, mRNA levels. Furthermore, overexpressed Bcl-3 could sustain the CDDO-dependent inhibition of IL-1-induced MMP-1 expression. Our data demonstrate that CDDO inhibits IL-1-induced MMP-1 and MMP-13 expression in human chondrocytes. CDDO also inhibits the expression of Bcl-3, an IL-1-responsive gene that preferentially contributes to MMP-1 gene expression.

Bcl-3 is an interleukin-1-responsive gene in chondrocytes and synovial fibroblasts that activates transcription of the matrix metalloproteinase 1 gene.

OBJECTIVE: To define the role of Bcl-3, a member of the inhibitor of nuclear factor kappaB (NF-kappaB) family and a known regulator of NF-kappaB, in interleukin-1 (IL-1)-induced matrix metalloproteinase 1 (MMP-1) transcription in chondrocytes and synovial fibroblasts. METHODS: SW-1353 cells, a human chondrosarcoma cell line, were stimulated with IL-1beta, and the harvested RNA was subjected to microarray analysis and quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR). The SW-1353 cells were stimulated with IL-1 or transfected with a plasmid that constitutively expressed Bcl-3, and then MMP-1 messenger RNA (mRNA) expression was assayed by quantitative real-time RT-PCR. SW-1353 cells were transfected with antisense oligonucleotides to Bcl-3, and IL-1-induced MMP-1 mRNA expression was assayed by quantitative RT-PCR. SW-1353 cells and rabbit synovial fibroblasts were transfected with a 4.3-kb human MMP-1 promoter construct along with Bcl-3 and NF-kappaB1 expression constructs, and MMP-1 transcription was assayed. RESULTS: Microarray analysis and real-time RT-PCR showed Bcl-3 to be an IL-1beta-responsive gene in SW-1353 cells. Exogenous expression of Bcl-3 in SW-1353 cells activated MMP-1 transcription. Endogenous Bcl-3 expression was required for IL-1beta induction of MMP-1 gene expression. Bcl-3 also activated MMP-1 transcription in primary synovial fibroblasts. We showed previously that NF-kappaB1 contributes to IL-1beta induction of MMP-1 transcription in stromal cells. We showed here that Bcl-3 can cooperate with NF-kappaB1 to activate MMP-1 transcription in SW-1353 cells. CONCLUSION: These data define a new role for Bcl-3 in joint cells as an IL-1beta-responsive early gene involved in cell-mediated cartilage remodeling. Our findings implicate Bcl-3 as an important contributor to chronic inflammatory disease states, such as osteoarthritis and rheumatoid arthritis.

Transcriptional regulation of collagenase (MMP-1, MMP-13) genes in arthritis: integration of complex signaling pathways for the recruitment of gene-specific transcription factors.

Matrix metalloproteinase (MMP)-1, MMP-8 and MMP-13 are interstitial collagenases that degrade type II collagen in cartilage; this is a committed step in the progression of rheumatoid arthritis and osteoarthritis. Of these enzymes, the expression of MMP-1 and MMP-13 is substantially increased in response to IL-1 and tumor necrosis factor-alpha, and elevated levels of these collagenases are observed in arthritic tissues. Therefore, cytokine-mediated MMP-1 and MMP-13 gene regulation is an important issue in arthritis research. In this review, we discuss current models of MMP-1 and MMP-13 transcriptional regulation, with a focus on signaling intermediates and transcription factors that may be future targets for the development of new arthritis drugs.

Erk 1/2 differentially regulates the expression from the 1G/2G single nucleotide polymorphism in the MMP-1 promoter in melanoma cells.

Matrix metalloproteinase-1 (MMP-1) breaks down interstitial collagens, a major component of stromal tissue and a barrier for invading tumor cells. The degradation of collagen by MMP-1 may, therefore, provide one mechanism for facilitating tumor invasion and metastasis. Because of the potential for excessive matrix degradation, the expression of MMP-1 is tightly regulated, often by the mitogen-activated protein kinase (MAPK) pathway. The MAPK signal cascade consists of three separate pathways, the extracellular response kinase (ERK), p38 and Jun N-terminal kinase, which target proteins of the AP-1 and ETS families transcription of the gene. The MMP-1 promoter contains a single nucleotide polymorphism (SNP) at -1607 bp, which creates an ETS binding site by the addition of a guanine (5'-GGAT-3' or '2G SNP') compared to the 1G SNP (5'-GAT-3'), and enhances MMP-1 transcription. A2058 melanoma cells represent one tumor cell line that is homozygous for the 2G allele and that produces constitutively high levels of MMP-1. Thus, we used these cells to define the mechanism(s) responsible for this high level of expression. We show that inhibition of ERK 1/2 leads to the repression of MMP-1 transcription, and that both the 2G polymorphism and the adjacent AP-1 site at -1602 bp are necessary for high levels of MMP-1 transcription and for the inhibition of MMP-1 expression by PD098059, a specific ERK inhibitor. Furthermore, restoration of MMP-1 levels after ERK 1/2 inhibition requires de novo protein synthesis of a factor necessary for MMP-1 expression. Thus, this study suggests that the ERK 1/2 pathway targets the 2G polymorphism, and that the continuous synthesis of a protein(s) is necessary for the constitutive expression of MMP-1.