CCL3 Signaling in the Tumor Microenvironment.

Within the tumor microenvironment, chemokines play a key role in immune cell trafficking regulation and immune landscape formulation. CCL3 or macrophage inflammatory protein-1α (MIP-1α), an important chemokine implicated in both immune surveillance and tolerance, has emerged as a prognostic biomarker in both solid and hematological malignancies. CCL3 exerts both antitumor and pro-tumor behavior which is context dependent highlighting the complexity of the underlying interrelated signaling cascades. Current CCL3-directed therapeutic approaches are investigational and further optimization is required to increase efficacy and minimize adverse events.

The role of CCR1 and therapeutic effects of anti-CCL3 antibody in herpes simplex virus-induced Behçet's disease mouse model.

Behçet's disease (BD) is a chronic systemic inflammatory disease with unclear etiopathogenesis. Although gene variants of CC chemokine receptor type 1 (CCR1) have been reported, the protein expression of CCR1 in patients with BD remains unclear. The objective of this study was to analyze the frequencies of CCR1+ cells in a herpes simplex virus-induced mouse model of BD. The frequencies of CCR1+ cells on the surface and in the cytoplasm of peripheral blood mononuclear cells and lymph nodes were analyzed by flow cytometry. The CCR1+ cells were significantly down-regulated in BD mice compared with the normal control and symptom-free control mice. Colchicine and pentoxifylline treatment improved the symptoms of BD and increased the frequencies of CCR1+ cells in BD mice. Treatment with chemokine CC motif ligand 3 (CCL3), a ligand of CCR1, caused BD symptoms to deteriorate in 10 of 16 BD mice (62·5%) via down-regulation of CCR1+ cells. Anti-CCL3 antibody treatment ameliorated BD symptoms in 10 of 20 mice (50%) and significantly decreased the disease severity score compared with CCL3-treated BD mice (P = 0·01) via up-regulation of CCR1+ cell frequencies. In patients with BD, plasma levels of CCL3 in an active state were significantly higher than in healthy control individuals (P = 0·02). These results show that the up-regulation of CCR1+ cells was related to the control of systemic inflammation of BD in mouse models.

TiO2 nanotubes promote osteogenic differentiation of mesenchymal stem cells via regulation of lncRNA CCL3-AS.

Titanium (Ti) is widely used as orthopedic implant materials. TiO2 nanotubes (TNTs) further improve the bioactivity of Ti, which enhance the osteogenic differentiation of mesenchymal stem cells (MSCs). However, the underlying mechanism is still unclear. In this study, we verified the response of MSCs on Ti and TNT substrates and explored the regulatory mechanism of long non-coding RNAs (lncRNAs). LncRNA and mRNA expression profiles were analyzed via RNA sequencing. Differential lncRNA and mRNA expression and predicted target genes of lncRNAs were performed by bioinformatics analysis. 1075 up-regulated and 1301 down-regulated genes, 26 up-regulated and 35 down-regulated lncRNAs were obtained according to the RNA-Seq. Expression of 8 lncRNAs were verified by qPCR, which was consistent with the sequencing data. To explore the function and target gene of lncRNA, lncRNA CCL3-AS and gene CCL3 were selected for further investigation. The fluorescence staining, alkaline phosphatase (ALP) activity and CCK-8 assay were performed. Besides, expressions of runt-related transcription factor 2 (Runx2), collagen type I (Col I), osteopontin (OPN) were detected by qPCR and western blot. These results indicate that lncRNA CCL3-AS could inhibit the osteogenic differentiation and enhance cell viability of MSCs on the TNT substrates, which was dependent on the regulation of CCL3. This study supplied a comprehensive understanding for further study using lncRNA modulators to surface design of titanium for enhancing osseointegration.

Didox (3,4-dihydroxybenzohydroxamic acid) suppresses IL-33-induced cytokine production in primary mouse mast cells.

While IgE is considered the primary mediator of mast cell activation, IL-33 contributes substantially in asthma, allergic rhinitis, and atopic dermatitis. To develop effective treatments for allergic disease, it is important to understand the role of therapeutic agents on IL-33 activation. We examined the effect of Didox (3,4-dihydroxybenzohydroxamic acid), an antioxidant and ribonucleotide reductase (RNR) inhibitor, on IL-33-mediated mast cell activation. Didox suppressed IL-6, IL-13, TNF, and MIP-1α (CCL3) production in bone marrow derived mast cells following IL-33 activation. This suppression was observed in different genetic backgrounds and extended to peritoneal mast cells. The antioxidant N-acetylcysteine mimicked the suppression of Didox, albeit at a much higher dose, while the RNR inhibitor hydroxyurea had no effect. Didox substantially suppressed IL-33-mediated NFκB and AP-1 transcriptional activities. These results suggest that Didox attenuates IL-33-induced mast cell activation and should be further studied as a potential therapeutic agent for inflammatory diseases involving IL-33.

Peripherally administered orexin improves survival of mice with endotoxin shock.

Sepsis is a systemic inflammatory response to infection, accounting for the most common cause of death in intensive care units. Here, we report that peripheral administration of the hypothalamic neuropeptide orexin improves the survival of mice with lipopolysaccharide (LPS) induced endotoxin shock, a well-studied septic shock model. The effect is accompanied by a suppression of excessive cytokine production and an increase of catecholamines and corticosterone. We found that peripherally administered orexin penetrates the blood-brain barrier under endotoxin shock, and that central administration of orexin also suppresses the cytokine production and improves the survival, indicating orexin's direct action in the central nervous system (CNS). Orexin helps restore body temperature and potentiates cardiovascular function in LPS-injected mice. Pleiotropic modulation of inflammatory response by orexin through the CNS may constitute a novel therapeutic approach for septic shock.

Leukaemogenic effects of Ptpn11 activating mutations in the stem cell microenvironment.

Germline activating mutations of the protein tyrosine phosphatase SHP2 (encoded by PTPN11), a positive regulator of the RAS signalling pathway, are found in 50% of patients with Noonan syndrome. These patients have an increased risk of developing leukaemia, especially juvenile myelomonocytic leukaemia (JMML), a childhood myeloproliferative neoplasm (MPN). Previous studies have demonstrated that mutations in Ptpn11 induce a JMML-like MPN through cell-autonomous mechanisms that are dependent on Shp2 catalytic activity. However, the effect of these mutations in the bone marrow microenvironment remains unclear. Here we report that Ptpn11 activating mutations in the mouse bone marrow microenvironment promote the development and progression of MPN through profound detrimental effects on haematopoietic stem cells (HSCs). Ptpn11 mutations in mesenchymal stem/progenitor cells and osteoprogenitors, but not in differentiated osteoblasts or endothelial cells, cause excessive production of the CC chemokine CCL3 (also known as MIP-1α), which recruits monocytes to the area in which HSCs also reside. Consequently, HSCs are hyperactivated by interleukin-1ß and possibly other proinflammatory cytokines produced by monocytes, leading to exacerbated MPN and to donor-cell-derived MPN following stem cell transplantation. Remarkably, administration of CCL3 receptor antagonists effectively reverses MPN development induced by the Ptpn11-mutated bone marrow microenvironment. This study reveals the critical contribution of Ptpn11 mutations in the bone marrow microenvironment to leukaemogenesis and identifies CCL3 as a potential therapeutic target for controlling leukaemic progression in Noonan syndrome and for improving stem cell transplantation therapy in Noonan-syndrome-associated leukaemias.

CCL3 promotes angiogenesis by dysregulation of miR-374b/ VEGF-A axis in human osteosarcoma cells.

Osteosarcoma is the most frequent bone tumor, characterized by a high metastatic potential. However, the crosstalk between chemokine (C-C motif) ligand 3 (CCL3), which facilitates tumor progression and metastasis. Vascular endothelial growth factor-A (VEGF-A), an angiogenesis inducer and a highly specific mitogen for endothelial cells, has not been well explored in human osteosarcoma. Here we demonstrate the correlation of CCL3 and VEGF-A expressions, quantified by immunohistochemistry, with the tumor stage of human osteosarcoma tissues. Furthermore, CCL3 promotes VEGF-A expression in human osteosarcoma cells that subsequently induces human endothelial progenitor cell (EPC) migration and tube formation. Phosphorylation of JNK, ERK, and p38 was found after CCL3 stimulation. In addition, JNK, ERK, and p38 inhibitors also abolished CCL3-induced VEGF-A expression and angiogenesis. We noted that CCL3 reduces the expression of miR-374b and miR-374b mimic by reversing CCL3-promoted VEGF-A expression and angiogenesis in vitro and in vivo. This study shows that CCL3 promotes VEGF-A expression and angiogenesis in human osteosarcoma cells by down-regulating miR-374b expression via JNK, ERK, and p38 signaling pathways. Thus, CCL3 may be a new molecular therapeutic target in osteosarcoma angiogenesis and metastasis.

Serum amyloid A chemoattracts immature dendritic cells and indirectly provokes monocyte chemotaxis by induction of cooperating CC and CXC chemokines.

Serum amyloid A (SAA) is an acute phase protein that is upregulated in inflammatory diseases and chemoattracts monocytes, lymphocytes, and granulocytes via its G protein-coupled receptor formyl peptide receptor like 1/formyl peptide receptor 2 (FPRL1/FPR2). Here, we demonstrated that the SAA1α isoform also chemoattracts monocyte-derived immature dendritic cells (DCs) in the Boyden and µ-slide chemotaxis assay and that its chemotactic activity for monocytes and DCs was indirectly mediated via rapid chemokine induction. Indeed, SAA1 induced significant amounts (≥5 ng/mL) of macrophage inflammatory protein-1α/CC chemokine ligand 3 (MIP-1α/CCL3) and interleukin-8/CXC chemokine ligand 8 (IL-8/CXCL8) in monocytes and DCs in a dose-dependent manner within 3 h. However, SAA1 also directly activated monocytes and DCs for signaling and chemotaxis without chemokine interference. SAA1-induced monocyte migration was nevertheless significantly prevented (60-80% inhibition) in the constant presence of desensitizing exogenous MIP-1α/CCL3, neutralizing anti-MIP-1α/CCL3 antibody, or a combination of CC chemokine receptor 1 (CCR1) and CCR5 antagonists, indicating that this endogenously produced CC chemokine was indirectly contributing to SAA1-mediated chemotaxis. Further, anti-IL-8/CXCL8 antibody neutralized SAA1-induced monocyte migration, suggesting that endogenous IL-8/CXCL8 acted in concert with MIP-1α/CCL3. This explained why SAA1 failed to synergize with exogenously added MIP-1α/CCL3 or stromal cell-derived factor-1α (SDF-1α)/CXCL12 in monocyte and DC chemotaxis. In addition to direct leukocyte activation, SAA1 induces a chemotactic cascade mediated by expression of cooperating chemokines to prolong leukocyte recruitment to the inflammatory site.

Effect of prostaglandin I2 analogs on macrophage inflammatory protein 1α in human monocytes via I prostanoid receptor and cyclic adenosine monophosphate.

AIMS: Inflammation plays critical roles in atherosclerosis. Chemokines are responsible for leukocyte trafficking and involve in inflammatory diseases. Macrophage inflammatory protein 1α (MIP-1α) has been implicated in atherosclerotic lesion formation. Prostaglandin I2 (PGI2) analog, used in pulmonary hypertension, has been reported to have anti-inflammatory functions. However, little is known about its role in the MIP-1α production in human monocytes. METHODS: We investigated the effects of 3 conventional (iloprost, beraprost, and treprostinil) and 1 new (ONO-1301) PGI2 analogs, on the expression of MIP-1α expression in human monocytes. Human primary monocytes from control subjects and THP-1 cell line were treated with PGI2 analogs, with or without lipopolysaccharide (LPS) stimulation. Supernatants were harvested to measure MIP-1α levels by enzyme-linked immunosorbent assay. To explore which receptors involved the effects of PGI2 analogs on the expression of MIP-1α expression, I prostanoid (IP) and E prostanoid, peroxisome proliferator-activated receptor (PPAR)-α, and PPAR-r receptor antagonists were used to pretreat THP-1 cells. Forskolin, a cyclic adenosine monophosphate (cAMP) activator, was also used to further confirm the cAMP involvement on the effect of PGI2 analogs in MIP-1α production. RESULTS: Three PGI2 analogs could suppress LPS-induced MIP-1α production in THP-1 cells and human primary monocytes. ONO-1301 had a similar effect. CAY 10449, an IP receptor antagonist, could reverse the suppressive effects on MIP-1α production of iloprost. Forskolin, a cAMP activator, also suppressed MIP-1α production in THP-1 cells. CONCLUSIONS: Prostaglandin I2 analogs suppressed LPS-induced MIP-1α production in human monocytes via the IP receptor and cAMP pathway. The PGI2 analog may be potential in the treatment for atherosclerosis.

Quercetin suppresses MIP-1α-induced adipose inflammation by downregulating its receptors CCR1/CCR5 and inhibiting inflammatory signaling.

Obesity-induced inflammation is characterized by recruitment of adipose tissue macrophages that release inflammatory cytokines and chemokines. MIP-1α (macrophage inflammatory protein 1α)/CCL3, a CC chemokine, induces monocyte/macrophage infiltration and thus is implicated in obesity-induced adipose inflammation. Quercetin has been shown to modulate obesity-induced inflammation, but the mechanism of its action remains unclear. Here we demonstrate that quercetin decreases MIP-1α release from adipocytes and macrophages and from cocultured adipocytes/macrophages; it also opposes MIP-1α-induced macrophage infiltration and activation. The inhibitory action of quercetin on the MIP-1α-induced inflammatory responses of macrophages is mediated by downregulation of CCR1/CCR5, and inhibition of activation of JNK, p38 mitogen-activated-protein kinase (MAPK), and IKK as well as IκBα degradation. These findings suggest that quercetin may be a useful agent against obesity-induced adipose tissue inflammation.

Atorvastatin inhibits the 5-lipoxygenase pathway and expression of CCL3 to alleviate atherosclerotic lesions in atherosclerotic ApoE knockout mice.

BACKGROUND: The 5-lipoxygenase (5-LO) pathway and the chemokine CCL3 are involved in the inflammatory processes of atherosclerosis. Statins have shown cholesterol-independent pleiotropic effects on antiimmune and antiinflammatory responses in atherosclerosis. We postulated that this effect may be associated with the 5-LO pathway and CCL3. METHODS AND RESULTS: ApoE knockout mice were randomized into control group (normal diet), atherosclerosis group (high-cholesterol diet), and atorvastatin group (high-cholesterol diet and atorvastatin). Sixteen weeks later, aortic roots were stained with hematoxylin and eosin. Total cholesterol and low-density lipoprotein cholesterol were measured by the enzymatic methods. The gene and protein expressions of 5-LO and CCL3 were detected separately through real-time reverse transcription polymerase chain reaction and western blotting analyses. The serum levels of leukotriene B4 and leukotriene D4 were measured by enzyme-linked immunosorbent assay. All mice have atherosclerotic plaques, mice in the control group have only tiny atherosclerotic plaques, but mice in the atherosclerosis group and atorvastatin group have typical atherosclerotic plaques. The corrected plaque areas (plaque area/luminal area) of the aortas of mice in the atorvastatin group were significantly decreased compared with those of the atherosclerosis group. The serum cholesterol levels of the atorvastatin group were not of significant difference compared with those of the atherosclerosis group. The gene and protein expressions of 5-LO and CCL3 in the aortas, as well as the serum levels of leukotriene B4 and leukotriene D4 in atorvastatin group, were markedly reduced compared with those of the atherosclerosis group. CONCLUSION: These data suggested that atorvastatin significantly alleviated atherosclerotic lesions by inhibiting the 5-LO pathway and down regulating the expression of CCL3 in ApoE-/- mice.

Further evidence for the anti-inflammatory activity of oleocanthal: inhibition of MIP-1α and IL-6 in J774 macrophages and in ATDC5 chondrocytes.

AIMS: Given the relevance of degenerative joint diseases in our society, the development of a novel pharmacologic intervention is a critically important public health goal. Recently, oleocanthal, a polyphenolic natural compound from extra virgin olive oil, has emerged as a potential therapeutic weapon for the treatment of inflammatory degenerative diseases. The goal of this study was to further evaluate the anti-inflammatory activity of oleocanthal in murine macrophages J774 and murine chondrocytes ATDC5 with a particular focus on the inhibition of gene expression of pro-inflammatory factors such as MIP-1α and IL-6. MAIN METHODS: ATDC5 murine chondrogenic cells and murine macrophages J774 were used. J774 macrophages were tested with different doses of oleocanthal and cell viability was evaluated using the MTT assay. Western blot analysis was carried on in J774 cells using anti NOS2 antibody. Nitrite accumulation was determined in culture supernatant using the Griess reaction. MIP-1α and IL-6 mRNA levels were determined using SYBR Green-based quantitative RT-PCR. MIP-1α and IL-6 protein levels were evaluated using specific ELISA assay. Several cytokines, involved in the inflammatory response, were also tested by BioPlex assay. KEY FINDINGS: First, oleocanthal inhibits LPS-induced NO production in J774 macrophages, without affecting cell viability. Moreover, it inhibits MIP-1α and IL-6 mRNA expression, as well as protein synthesis, in both ATDC5 chondrocytes and J774 macrophages. Oleocanthal also inhibits IL-1ß, TNF-α and GM-CSF protein synthesis from LPS-stimulated macrophages. SIGNIFICANCE: Our data confirm a clear potent role of oleocanthal as anti-inflammatory therapeutic agent for future treatment of arthritis or other inflammatory diseases.

Blockade of lymphocyte chemotaxis in visceral graft-versus-host disease.

BACKGROUND: Graft-versus-host disease (GVHD) is a major barrier to successful allogeneic hematopoietic stem-cell transplantation (HSCT). The chemokine receptor CCR5 appears to play a role in alloreactivity. We tested whether CCR5 blockade would be safe and limit GVHD in humans. METHODS: We tested the in vitro effect of the CCR5 antagonist maraviroc on lymphocyte function and chemotaxis. We then enrolled 38 high-risk patients in a single-group phase 1 and 2 study of reduced-intensity allogeneic HSCT that combined maraviroc with standard GVHD prophylaxis. RESULTS: Maraviroc inhibited CCR5 internalization and lymphocyte chemotaxis in vitro without impairing T-cell function or formation of hematopoietic-cell colonies. In 35 patients who could be evaluated, the cumulative incidence rate (±SE) of grade II to IV acute GVHD was low at 14.7±6.2% on day 100 and 23.6±7.4% on day 180. Acute liver and gut GVHD were not observed before day 100 and remained uncommon before day 180, resulting in a low cumulative incidence of grade III or IV GVHD on day 180 (5.9±4.1%). The 1-year rate of death that was not preceded by disease relapse was 11.7±5.6% without excessive rates of relapse or infection. Serum from patients receiving maraviroc prevented CCR5 internalization by CCL5 and blocked T-cell chemotaxis in vitro, providing evidence of antichemotactic activity. CONCLUSIONS: In this study, inhibition of lymphocyte trafficking was a specific and potentially effective new strategy to prevent visceral acute GVHD. (Funded by Pfizer and others; ClinicalTrials.gov number, NCT00948753.).

CCR1 as a target for multiple myeloma.

INTRODUCTION: By directing cell trafficking, differentiation and growth, chemokines modulate the immune response and are involved in the pathogenesis of autoimmune diseases and cancers, including multiple myeloma (MM). MM, the second most common hematological malignancy in the US, is characterized by disordered plasma cell growth within the bone marrow microenvironment. CCL3 and its receptors, CCR1 in particular, play a central role in the pathogenesis of MM and MM-induced osteolytic bone disease. AREAS COVERED: This review describes the functional role of CCR1 in MM and the preclinical results observed with CCR1 antagonists. CCL3 and CCR1 stimulate tumor growth, both directly and indirectly, via upregulation of cell adhesion and cytokine secretion. In addition, they modulate the osteoclast/osteoblast balance, by inducing osteoclast differentiation and inhibiting osteoblast function. Targeting either ligand or receptor reverses these effects, leading to in vivo tumor burden control and prevention of osteolysis, as confirmed in both murine and humanized mouse models. EXPERT OPINION: These promising data set the stage for clinical trials to assess the effects of CCR1 inhibitors in MM. The success of these studies depends on the development of novel antagonists with improved chemical/physical properties and careful selection of the patient population who may benefit the most from these agents.

Diclofenac, a selective COX-2 inhibitor, inhibits DMH-induced colon tumorigenesis through suppression of MCP-1, MIP-1α and VEGF.

Angiogenesis is a physiological process involving growth of new blood vessels from pre-existing ones; however, it also plays a critical role in tumor progression. It favors the transition from hyperplasia to neoplasia, that is, from a state of cellular multiplication to uncontrolled proliferation. Therefore targeting angiogenesis will be profitable as a mechanism to inhibit tumor's lifeline. Further, it is important to understand the cross-communication between vascular endothelial growth factor (VEGF)-master switch in angiogenesis and other molecules in the neoplastic and pro-inflammatory milieu. We studied the role of two important chemokines [monocyte chemoattractant protein (MCP)-1 and macrophage inflammatory protein (MIP)-lα] alongwith VEGF and matrix metalloproteinases (MMPs) in non-steroidal anti-inflammatory drugs (NSAIDs)-induced chemopreventive effect in experimental colon cancer in rat. 1,2-Dimethylhydrazine (DMH, 30 mg/kg body weight, subcutaneously (s.c.) once-a-week) for 18 wk was used as pro-carcinogen and diclofenac (8 mg/kg body weight, orally daily) as the preferential cyclooxygenase-2 (COX-2) inhibitor. Expression of COX-2 and VEGF was found to be significantly elevated in the DMH-treated group as compared to the control, which was lowered notably by Diclofenac co-administration with DMH. Gelatin zymography showed prominent MMP-9 activity in the DMH-treated rats, while the activity was nearly absent in all the other groups. Expression of MCP-1 was found to be markedly increased whereas MIP-1α expression was found to be decreased in colonic mucosa from DMH-treated rats, which was reversed in the DMH + Diclofenac group. Our results indicate potential role of chemokines alongwith VEGF in angiogenesis in DMH-induced cancer and its chemoprevention with diclofenac.

Therapeutic effects of evasin-1, a chemokine binding protein, in bleomycin-induced pulmonary fibrosis.

CC chemokines play an important role in the pathogenesis of idiopathic pulmonary fibrosis. Few studies have evaluated the efficacy of therapeutically targeting CC chemokines and their receptors during interstitial lung diseases. In the present study, the therapeutic effects of Evasin-1, a tick-derived chemokine-binding protein that has high affinity for CCL3/microphage inflammatory protein (MIP)-1α, was investigated in a murine model of bleomycin-induced lung fibrosis. CCL3/MIP-1α concentrations in lung homogenates increased significantly with time after bleomycin challenge, and this was accompanied by increased number of leukocytes and elevated levels of CCL2/monocyte chemoattractant protein (MCP)-1, CCL5/regulated upon activation, normal T cell expressed and secreted, TNF-α and transforming growth factor-ß(1), and pulmonary fibrosis. Administration of evasin-1 on a preventive (from the day of bleomycin administration) or therapeutic (from Day 8 after bleomycin) schedule decreased number of leukocytes in the lung, reduced levels of TNF-α and transforming growth factor-ß(1), and attenuated lung fibrosis. These protective effects were similar to those observed in CCL3/MIP-1α-deficient mice. In conclusion, targeting CCL3/MIP-1α by treatment with evasin-1 is beneficial in the context of bleomycin-induced lung injury, even when treatment is started after the fibrogenic insult. Mechanistically, evasin-1 treatment was associated with decreased recruitment of leukocytes and production of fibrogenic cytokines. Modulation of CCL3/MIP-1α function by evasin-1 could be useful for the treatment of idiopathic pulmonary fibrosis.

Chorioamnionitis stimulates angiogenesis in saccular stage fetal lungs via CC chemokines.

The fetal lung vasculature forms in tandem with developing airways. Whereas saccular airway morphogenesis is arrested in bronchopulmonary dysplasia (BPD), the potential vascular phenotype in BPD at this stage of development is less well-understood. As inflammation increases the risk of BPD and induces arrest of saccular airway morphogenesis, we tested the effects of Escherichia coli LPS on fetal mouse lung vascular development. Injecting LPS into the amniotic fluid of Tie2-lacZ endothelial reporter mice at embryonic day 15 stimulated angiogenesis in the saccular stage fetal lung mesenchyme. LPS also increased the number of endothelial cells in saccular stage fetal mouse lung explants. Inflammation appeared to directly promote vascular development, as LPS stimulated pulmonary microvascular endothelial cell angiogenesis, cell migration, and proliferation in vitro. Whereas LPS did not increase expression of VEGF, angiopoietin-1 (Ang-1), Tie2, fetal liver kinase-1 (Flk-1), fms-like tyrosine kinase-1 (Flt-1), PDGFA, PDGFB, heparin-binding EGF-like growth factor (HB-EGF), or connective tissue growth factor (CTGF), LPS did stimulate the production of the angiogenic CC chemokines macrophage inflammatory protein-1α (MIP-1α) and monocyte chemoattractant protein-1 (MCP-1). Both MIP-1α and MCP-1 increased angiogenesis in fetal mouse lung explants. In addition, inhibitory antibodies against MIP-1α and MCP-1 blocked the effects of LPS on fetal lung vascular development, suggesting these chemokines are downstream mediators of LPS-induced angiogenesis. We speculate that an inflammation-mediated surge in angiogenesis could lead to formation of aberrant alveolar capillaries in the lungs of patients developing BPD.

Matrix metalloproteinase-8 inactivates macrophage inflammatory protein-1 alpha to reduce acute lung inflammation and injury in mice.

To determine the role of matrix metalloproteinase-8 (MMP-8) in acute lung injury (ALI), we delivered LPS or bleomycin by the intratracheal route to MMP-8(-/-) mice versus wild-type (WT) mice or subjected the mice to hyperoxia (95% O(2)) and measured lung inflammation and injury at intervals. MMP-8(-/-) mice with ALI had greater increases in lung polymorphonuclear neutrophils (PMNs) and macrophage counts, measures of alveolar capillary barrier injury, lung elastance, and mortality than WT mice with ALI. Bronchoalveolar lavage fluid (BALF) from LPS-treated MMP-8(-/-) mice had more MIP-1alpha than BALF from LPS-treated WT mice, but similar levels of other pro- and anti-inflammatory mediators. MIP-1alpha(-/-) mice with ALI had less acute lung inflammation and injury than WT mice with ALI, confirming that MIP-1alpha promotes acute lung inflammation and injury in mice. Genetically deleting MIP-1alpha in MMP-8(-/-) mice reduced the increased lung inflammation and injury and mortality in MMP-8(-/-) mice with ALI. Soluble MMP-8 cleaved and inactivated MIP-1alpha in vitro, but membrane-bound MMP-8 on activated PMNs had greater MIP-1alpha-degrading activity than soluble MMP-8. High levels of membrane-bound MMP-8 were detected on lung PMNs from LPS-treated WT mice, but soluble, active MMP-8 was not detected in BALF samples. Thus, MMP-8 has novel roles in restraining lung inflammation and in limiting alveolar capillary barrier injury during ALI in mice by inactivating MIP-1alpha. In addition, membrane-bound MMP-8 on activated lung PMNs is likely to be the key bioactive form of the enzyme that limits lung inflammation and alveolar capillary barrier injury during ALI.