Impact of JAK/STAT inhibitors on human monocyte-derived-macrophages stimulated by cigarette smoke extract and lipopolysaccharide.

The main risk factor for chronic obstructive pulmonary disease (COPD) is cigarette smoke (CS). It can alter many immune cells functions such as phagocytosis, efferocytosis and cytokine production. Cytokines play a role in the orchestration of inflammation in COPD. The JAK/STAT pathways are among the most important signalling components of cytokines. The objective of this work was to investigate the role of the JAK/STAT pathway with regard to cytokine release and microsphere uptake capacity (to minimize the non-specific scavenging) in human monocyte-derived-macrophages (MDMs). The MDMs were stimulated by cigarette smoke extract (CSE) alone or in combination with lipopolysaccharide (LPS). CSE alone was not associated with significant changes in the cytokine, with the exception of IL-8/CXCL8 production. However, CSE disturbed cytokine production in LPS-stimulated MDMs. CSE increase CXCL-8 and CCL2 release in LPS-stimulated monocyte-derived macrophages and suppressed the production of IL-6 and CXCL1 in these cells. CSE also decreased microsphere uptake capacity by MDMs. Then, CSE + LPS-stimulated MDMs were treated with two different JAK inhibitors. AG490 (specific inhibitor of JAK2) and ruxolitinib (inhibitor of JAK1 and JAK2). JAK/STAT inhibitors, particularly ruxolitinib, attenuated in cytokine production without completely inhibiting when compared with dexamethasone. On the other hand, the cells exposed to dexamethasone are nearly unable to capture the microspheres, while both JAK inhibitors do not affect the uptake capacity. In summary, our results showed the versatility of ruxolitinib which might bring a better balance disturbance of cytokine release and uptake capacity. The information regarding the distinctive effect of JAK/STAT inhibitors may be useful in the development of novel treatments for COPD.

trans-Cinnamic acid, but not p-coumaric acid or methyl cinnamate, induces fibroblast migration through PKA- and p38-MAPK signalling pathways.

AIM: Hydroxycinnamic acids their derivatives have various pharmacological properties. The hydroxycinnamic acid derivatives, methyl cinnamate, trans-cinnamic, and p-coumaric acids have been the object of study in the treatment of skin wounds. However, it is unclear whether these derivatives exert a direct beneficial effect on fibroblast function. In this study, we evaluated the effects of methyl cinnamate, trans-cinnamic, and p-coumaric acids on fibroblast migration in vitro. MATERIALS AND METHODS: NIH 3T3 and L929 fibroblast cell lines were exposed to each drug at several concentrations and the effect on cell viability, cell cycle, and extracellular matrix production were assessed by MTT assay, flow cytometry, and immunofluorescence staining, respectively. The effect on cell migration was examined using scratch assay. RESULTS: The results showed that hydroxycinnamic acid derivatives not affect cell viability, but increase fibroblast migration in the in vitro scratch-wound healing assay. They also induced an increase in S and G2/M phases accompanied by a decrease in the G0/G1 phase of the cell cycle. The cell proliferation inhibitor mitomycin C abolished the effect induced by p-coumaric acid and methyl cinnamate, indicating that only the trans-cinnamic acid stimulated migration. A transwell migration assay confirmed that trans-cinnamic acid-treated fibroblasts exhibited increased migration compared with untreated cells. trans-Cinnamic acid-induced fibroblast migration was decreased by PKA inhibitor and p38-MAPK inhibitor but not by JNK inhibitor. Additionally, trans-cinnamic acid-treated fibroblasts showed an increase in the production of laminin and collagen type I. CONCLUSION: Our study showed that trans-cinnamic acid improves fibroblast migration and modulates extracellular matrix synthesis, indicating its potential for accelerating the healing process.

Uvaol Improves the Functioning of Fibroblasts and Endothelial Cells and Accelerates the Healing of Cutaneous Wounds in Mice.

Uvaol is a natural pentacyclic triterpene that is widely found in olives and virgin olive oil, exerting various pharmacological properties. However, information remains limited about how it affects fibroblasts and endothelial cells in events associated with wound healing. Here, we report the effect of uvaol in the in vitro and in vivo healing process. We show the positive effects of uvaol on migration of fibroblasts and endothelial cells in the scratch assay. Protein synthesis of fibronectin and laminin (but not collagen type I) was improved in uvaol-treated fibroblasts. In comparison, tube formation by endothelial cells was enhanced after uvaol treatment. Mechanistically, the effects of uvaol on cell migration involved the PKA and p38-MAPK signaling pathway in endothelial cells but not in fibroblasts. Thus, the uvaol-induced migratory response was dependent on the PKA pathway. Finally, topical treatment with uvaol caused wounds to close faster than in the control treatment using experimental cutaneous wounds model in mice. In conclusion, uvaol positively affects the behavior of fibroblasts and endothelial cells, potentially promoting cutaneous healing.

Ethanol and its metabolites: update on toxicity, benefits, and focus on immunomodulatory effects.

This article summarizes recent experimental and epidemiological data on the toxic and beneficial effects of ethanol and its metabolites (acetaldehyde), and focuses on their immunomodulatory effects. The section dealing with the toxic effects of alcohol focuses on its chronic toxicity (liver disorders, carcinogenic effects, cardiovascular disorders, neuropsychic disorders, addiction and withdrawal syndrome, hematologic disorders, reprotoxicity, osteoporosis) although acute toxicity is considered. The role of oxidative metabolism of ethanol by alcohol dehydrogenase, cytochrome P450 2E1, and aldehyde dehydrogenase, as well as the impact of genetic polymorphism in its physiopathology are also highlighted. The section dealing with the beneficial effects of low to moderate alcohol consumption (on cardiovascular system, diabetes, the nervous system and sensory organs, autoimmune diseases, and rheumatology) highlights the importance of anti-inflammatory and immunomodulatory effects in these observations. This knowledge, enriched by a focus on the immunomodulatory effects of ethanol and its metabolites, in particular on the NLRP3 inflammasome pathway, might facilitate the development of treatments that can reduce ethanol's harmful effects or accentuate its beneficial effects.

Intestinally derived bacterial products stimulate development of nonalcoholic steatohepatitis.

Fatty livers are susceptible to factors that cause inflammation and fibrosis, but fat deposition and the inflammatory response can be dissociated. While nonalcoholic fatty liver disease (NAFLD), caused by pathologic fat accumulation inside the liver, can remain stable for several years, in other cases NAFLD progresses to nonalcoholic steatohepatitis (NASH), which is characterized by fat accumulation and inflammation and is not a benign condition. In this review, we discuss the NASH host cells and microbial mechanisms that stimulate inflammation and predispose the liver to hepatocyte injury and fibrotic stages via increased lipid deposition. We highlight the interactions between intestine-derived bacterial products, such as lipopolysaccharide, and nutritional models of NAFLD and/or obese individuals. The results of modulating enteric microbiota suggest that gut-derived endotoxins may be essential determinants of fibrotic progression and regression in NASH.

Endotoxin regulates matrix genes increasing reactive oxygen species generation by intercellular communication between palmitate-treated hepatocyte and stellate cell.

Previous studies have shown that gut-derived bacterial endotoxins contribute in the progression of simple steatosis to steatohepatitis, although the mechanism(s) remains inaccurate to date. As hepatic stellate cells (HSC) play a pivotal role in the accumulation of excessive extracellular matrix (ECM), leading to collagen deposition, fibrosis, and perpetuation of inflammatory response, an in vitro model was developed to investigate the crosstalk between HSC and hepatocytes (human hepatoma cell) pretreated with palmitate. Bacterial lipopolysaccharide (LPS) stimulated HSC with phosphorylation of the p38 mitogen-activated protein kinase/NF-κB pathway, while several important pro-inflammatory cytokines were upregulated in the presence of hepatocyte-HSC. Concurrently, fibrosis-related genes were regulated by palmitate and the inflammatory effect of endotoxin where cells were more exposed or sensitive to reactive oxygen species (ROS). This interaction was accompanied by increased expression of the mitochondrial master regulator, proliferator-activated receptor gamma coactivator alpha, and a cytoprotective effect of the agent N-acetylcysteine suppressing ROS production, transforming growth factor-ß1, and tissue inhibitor of metalloproteinase-1. In summary, our results demonstrate that pro-inflammatory mediators LPS-induced promote ECM rearrangement in hepatic cells transcriptionally committed to the regulation of genes encoding enzymes for fatty acid metabolism in light of differences that might require an alternative therapeutic approach targeting ROS regulation.

Human lung and monocyte-derived macrophages differ with regard to the effects of ß2-adrenoceptor agonists on cytokine release.

BACKGROUND: ß2-adrenoceptor agonists have been shown to reduce the lipopolysaccharide (LPS)-induced cytokine release by human monocyte-derived macrophages (MDMs). We compare the expression of ß2-adrenoceptors and the inhibitory effect of formoterol and salmeterol on the LPS-induced release of tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-6 and a range of chemokines (CCL2, 3, 4, and IL-8) by human lung macrophages (LMs) and MDMs. METHODS: LMs were isolated from patients undergoing resection and MDMs were obtained from blood monocytes in the presence of GM-CSF. LMs and MDMs were incubated in the absence or presence of formoterol or salmeterol prior to stimulation with LPS. The effects of formoterol were also assessed in the presence of the phosphodiesterase inhibitor roflumilast. RESULTS: LPS-induced cytokine production was higher in LMs than in MDMs. Salmeterol and formoterol exerted an inhibitory effect on the LPS-induced production of TNF-α, IL-6, CCL2, CCL3, and CCL4 in MDMs. In contrast, the ß2-adrenoceptor agonists were devoid of any effect on LMs - even in the presence of roflumilast. The expression of ß2-adrenergic receptors was detected on Western blots in MDMs but not in LMs. CONCLUSIONS: Concentrations of ß2-adrenoceptor agonists that cause relaxation of the human bronchus can inhibit cytokine production by LPS-stimulated MDMs but not by LMs.

Propolis reversed cigarette smoke-induced emphysema through macrophage alternative activation independent of Nrf2.

Chronic obstructive pulmonary disease (COPD) is an incurable and progressive disease. Emphysema is the principal manifestation of COPD, and the main cause of this condition is cigarette smoke (CS). Natural products have shown antioxidant and anti-inflammatory properties that can prevent acute lung inflammation and emphysema, but there are few reports in the literature regarding therapeutic approaches to emphysema. We hypothesized that supplementation with natural extracts would repair lung damage in emphysema caused by CS exposure. Mice were exposed to 60days of CS and then treated or not with three different natural extracts (mate tea, grape and propolis) orally for additional 60days. Histological analysis revealed significant improvements in lung histoarchitecture, with recovery of alveolar spaces in all groups treated with natural extracts. Propolis was also able to recovery alveolar septa and elastic fibers. Propolis also increased MMP-2 and decreased MMP-12 expression, favoring the process of tissue repair. Additionally, propolis recruited leukocytes, including macrophages, without ROS release. These findings led us to investigate the profile of these macrophages, and we showed that propolis could promote macrophage alternative activation, thus increasing the number of arginase-positive cells and IL-10 levels and favoring an anti-inflammatory microenvironment. We further investigated the participation of Nrf2 in lung repair, but no Nrf2 translocation to the nucleus was observed in lung cells. Proteins and enzymes related to Nrf2 were not altered, other than NQO1, which seemed to be activated by propolis in a Nrf2-independent manner. Finally, propolis downregulated IGF1 expression. In conclusion, propolis promoted lung repair in a mouse emphysema model via macrophage polarization from M1 to M2 in parallel to the downregulation of IGF1 expression in a Nrf2-independent manner.

The release of pro-inflammatory cytokines is mediated via mitogen-activated protein kinases rather than by the inflammasome signalling pathway in keratinocytes.

Toll-like receptors (TLRs) are expressed in the skin and airway epithelial tissues, which are the most important sites of host-pathogen interactions. TLRs recognize the 3-D structures of pathogen-associated molecules and are therefore useful markers of the innate immune response. Here, we investigated the role of lipopolysaccharides and monosodium urate (MSU) crystals in the activation of the TLR and NOD-like receptor (NLR) pathways in human keratinocytes. Analysis of the inflammasome compounds revealed that NOD-like receptor P3 and TLR4, both of which are components of inflammasome complexes involved in the activation of interleukin (IL)-1ß, were not expressed in keratinocytes. Transcriptomic analysis showed that the combination of MSU and lipopolysaccharide priming did not elicit significant results compared to MSU treatment, which induced the expression of TLR2, IL-6 and IL-8/chemokine (C-X-C motif) ligand 8 CXCL8 in the keratinocyte cell line HaCaT. Furthermore, MSU promoted the phosphorylation of extracellular signal-regulated kinase 1/2 and MAPK14/p38α mitogen-activated protein kinases. We concluded that MSU stimulates a pro-inflammatory response in keratinocytes via mitogen-activated protein kinase pathway to induce production of IL-8/CXCL8 chemokine (C-X-C motif) ligand 8 and TLR2.

Time Course of the Phenotype of Blood and Bone Marrow Monocytes and Macrophages in the Lung after Cigarette Smoke Exposure In Vivo.

Alveolar macrophages play a central role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Monocytes are recruited from blood during inflammation and then mature into alveolar macrophages. The aim of this study was to investigate the effect of cigarette smoke (CS) at different times in lung macrophages and monocytes from blood and bone marrow in mice. Male mice (C57BL/6, n = 45) were divided into groups: control, CS 5 days, CS 14 days and CS 30 days. Five days' CS exposure induced a pronounced influx of neutrophils and macrophages in the lung associated with increased levels of keratinocyte chemoattractant (KC), tumor necrosis factor-α (TNF-α), nitric oxide (NO) and matrix metalloproteinase (MMP)-12. After 14 days of CS exposure, neutrophil recruitment and cytokine production were greatly reduced. Moreover, chronic CS exposure led to increased recruitment of macrophages (with high expression of CD206), transforming growth factor-ß (TGF-ß) production as well as no detection of TNF-α, interleukin (IL)-6 and KC. CS can also change the monocyte phenotype in the blood and bone marrow, with an increase in Ly6Clow cells. These results show for the first time that CS can change not only macrophage polarization but also monocyte. These results suggest that continued recruitment of Ly6Clow monocytes may help the distinct renewing macrophage M2 population required for COPD progression.

IL-1ß production is dependent on the activation of purinergic receptors and NLRP3 pathway in human macrophages.

The Nod-like receptor family protein 3 (NLRP3)-inflammasome pathway is known to be activated by danger signals such as monosodium urate (MSU). We investigated the role of P2 purinergic receptors in the activation of NLRP3-inflammasome pathway after MSU treatment of primary human monocyte-derived macrophages (MDMs). After initial stimulation with a low concentration of LPS (0.1 µg/ml), a 6 h treatment with MSU crystals (250, 500, and 1000 µg/ml) induced the MDMs to release IL-1ß, IL-1α, and IL-6 in a dose-dependent manner. Moreover, the caspase 1 inhibitor Z-YVAD-FMK and the cathepsin B inhibitor CA-074Me reduced production of IL-1ß in a dose-dependent manner after LPS + MSU treatment. We used real-time reverse transcription-quantitative PCR to show that treatment with LPS and MSU (500 µg/ml) induced significantly greater expression of NLRP3 and IL-1ß than after treatment with LPS. We also found that MSU treatment induced P2X purinergic receptor 7 (P2X7R) mRNA and protein expression. Furthermore, addition of the P2X7 purinergic receptor antagonist A-740003 significantly impeded IL-1ß production and pro-IL-1ß cleavage after treatment with LPS + MSU. Remarkably, RNA silencing of P2X7R (but not P2X4R) inhibited the release of IL-1ß and other M1 macrophage cytokines (such as IL-1α, IL-6, and TNF-α) from MDMs stimulated with LPS + MSU. Taken as a whole, our results show that P2 purinergic receptors and the NLRP3 inflammasome pathway are involved in the secretion of IL-1ß from MSU-stimulated human macrophages. This pathway may constitute a novel therapeutic target for controlling the inflammatory process in several associated pathologies.

Involvement of purinergic receptors and NOD-like receptor-family protein 3-inflammasome pathway in the adenosine triphosphate-induced cytokine release from macrophages.

Adenosine triphosphate (ATP) has been described as a danger signal activating the NOD-like receptor-family protein 3 (NLRP3)-inflammasome leading to the pro-inflammatory cytokine, interleukin (IL)-1ß, release in the lung. The NLRP3-inflammasome pathway has been previously described to be involved in experimental collagen deposition and the development of pulmonary fibrosis. The aim of the present study was to investigate the role of the NLRP3 inflammasome pathway and P2X7 purinergic receptor in the activation of human macrophages in vitro by ATP. We showed that adenosine 5'-[γ-thio]triphosphate tetralithium salt (ATPγS) and 2',3'-O-(4-benzoylbenzoyl) adenosine 5'-triphosphate (BzATP), two stable analogs of ATP, are able to potentiate the release of IL-1ß from human monocyte-derived macrophages induced by low concentration of lipopolysaccharide (LPS). However, in the same conditions no increase in IL-1α and IL-6 was observed. Immunochemistry has shown that human macrophages natively express NLRP3 and purinergic P2X7 receptors (P2X7 R). NLRP3 and IL-1ß mRNA expression were induced from LPS-primed macrophages, but also after 5-h treatment of BzATP as analysed by reverse transcription quantitative polymerase chain reaction. However, other inflammasome pathways (NLRP1, NLRP2, NLRC4, NLRP6 and AIM2) and P2X7 R were not induced by BzATP. We observed that P2X7 R antagonists, A-438079 and A-740003, were able to reduce the release of IL-1ß, but not of IL-1α and IL-6 from macrophages stimulated by ATPγS or BzATP. The present results showed the involvement of the P2X7 R-NLRP3 inflammasome pathway in the secretion of IL-1ß from ATP-stimulated human macrophages, and suggest that P2X7 R were not involved in IL-1α and IL-6 release. This study also points out that repression of the P2X7 R represents a novel potential therapeutic approach to control fibrosis in lung injury.

Effects of the nerve growth factor and its carrier protein on the inflammatory response from human monocytes.

BACKGROUND: The nerve growth factor (NGF) has been previously shown to be involved in cellular proliferation, differentiation, survival, or wound healing. This factor displays a variety of biological effects that yet remain to be explored. Previous data on cell lines show a pro-inflammatory role of NGF on monocytes. OBJECTIVES: The objective of the study was to investigate the pro-inflammatory effect of NGF, using a model of fresh human monocytes. METHODS: Monocytes obtained from PBMC were exposed to NGF at various concentrations. Alternatively, monocytes were exposed to BSA, the NGF carrier protein without the NGF. Gene expression and cytokine release in the supernatant were monitored. RESULTS: We found that NGF increased the expression of pro-inflammatory, chemotactic, and remodeling genes such as interleukin (IL)-1ß, IL-6, tumor necrosis factor (TNF)-α, and C-X-C motif ligand (CXCL)8. The protein levels of CXCL8 and matrix metalloproteinase (MMP)-9 were also increased in the cell supernatants following NGF exposure. BSA alone was found to drive part of this response, bringing nuance to the inflammatory potential of the NGF. CONCLUSION: These data suggest that NGF is able to enhance monocyte inflammatory responses once cells are stimulated with another signal but is possibly not able to directly activate it. This could have implications for example in patients with bacterial infections, where NGF could worsen the local inflammation by over-activating immune cells.

IL-1R1/MyD88 signaling is critical for elastase-induced lung inflammation and emphysema.

Lung emphysema and fibrosis are severe complications of chronic obstructive pulmonary disease, and uncontrolled protease activation may be involved in the pathogenesis. Using experimental elastase-induced acute inflammation, we demonstrate here that inflammation and development of emphysema is IL-1R1 and Toll/IL-1R signal transduction adaptor MyD88 dependent; however, TLR recognition is dispensable in this model. Elastase induces IL-1beta, TNF-alpha, keratinocyte-derived chemokine, and IL-6 secretion and neutrophil recruitment in the lung, which is drastically reduced in the absence of IL-1R1 or MyD88. Further, tissue destruction with emphysema and fibrosis is attenuated in the lungs of IL-1R1- and MyD88-deficient mice. Specific blockade of IL-1 by IL-1R antagonist diminishes acute inflammation and emphysema. Finally, IL-1beta production and inflammation are reduced in mice deficient for the NALP3 inflammasome component apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and we identified uric acid, which is produced upon elastase-induced lung injury, as an activator of the NALP3/ASC inflammasome. In conclusion, elastase-mediated lung pathology depends on inflammasome activation with IL-1beta production. IL-1beta therefore represents a critical mediator and a possible therapeutic target of lung inflammation leading to emphysema.

Oxidative Imbalance as a Crucial Factor in Inflammatory Lung Diseases: Could Antioxidant Treatment Constitute a New Therapeutic Strategy?

Inflammatory lung disease results in a high global burden of death and disability. There are no effective treatments for the most severe forms of many inflammatory lung diseases, such as chronic obstructive pulmonary disease, emphysema, corticosteroid-resistant asthma, and coronavirus disease 2019; hence, new treatment options are required. Here, we review the role of oxidative imbalance in the development of difficult-to-treat inflammatory lung diseases. The inflammation-induced overproduction of reactive oxygen species (ROS) means that endogenous antioxidants may not be sufficient to prevent oxidative damage, resulting in an oxidative imbalance in the lung. In turn, intracellular signaling events trigger the production of proinflammatory mediators that perpetuate and aggravate the inflammatory response and may lead to tissue damage. The production of high levels of ROS in inflammatory lung diseases can induce the phosphorylation of mitogen-activated protein kinases, the inactivation of phosphoinositide 3-kinase (PI3K) signaling and histone deacetylase 2, a decrease in glucocorticoid binding to its receptor, and thus resistance to glucocorticoid treatment. Hence, antioxidant treatment might be a therapeutic option for inflammatory lung diseases. Preclinical studies have shown that antioxidants (alone or combined with anti-inflammatory drugs) are effective in the treatment of inflammatory lung diseases, although the clinical evidence of efficacy is weaker. Despite the high level of evidence for the efficacy of antioxidants in the treatment of inflammatory lung diseases, the discovery and clinical investigation of safer, more efficacious compounds are now a priority.

A therapeutic oxygen carrier isolated from Arenicola marina decreases amanitin-induced hepatotoxicity.

The amanitins (namely α- and ß-amanitin) contained in certain mushrooms are bicyclic octapeptides that, when ingested, are responsible for potentially lethal hepatotoxicity. M101 is an extracellular hemoglobin extracted from the marine worm Arenicola marina. It has intrinsic Cu/Zn-SOD-like activity and is currently used as an oxygen carrier in organ preservation solutions. Our present results suggest that M101 might be effective in reducing amanitin-induced hepatotoxicity and may have potential for therapeutic development.

Local administration of p-coumaric acid decreases lipopolysaccharide-induced acute lung injury in mice: In vitro and in silico studies.

Acute lung injury (ALI) remains to cause a high rate of mortality in critically ill patients. It is known that inflammation is a key factor in the pathogenesis of lipopolysaccharide (LPS)-induced ALI, which makes it a relevant approach to the treatment of ALI. In this study, we evaluated the potential of nasally instilled p-coumaric acid to prevent LPS-induced ALI in mice, by evaluating its effects on cellular and molecular targets involved in inflammatory response via in vitro and in silico approaches. Our results demonstrated that p-coumaric acid reduced both neutrophil accumulation and pro-inflammatory cytokine abundance, and simultaneously increased IL-10 production at the site of inflammation, potentially contributing to protection against LPS-induced ALI in mice. In the in vitro experiments, we observed inhibitory effects of p-coumaric acid against IL-6 and IL-8 production in stimulated A549 cells, as well as reactive oxygen species generation by neutrophils. In addition, p-coumaric acid treatment decreased neutrophil adhesion on the TNF-α-stimulated endothelial cells. According to the in silico predictions, p-coumaric acid reached stable interactions with both the ATP-binding site of IKKß as well as the regions within LFA-1, critical for interaction with ICAM-1, thereby suppressing the production of proinflammatory mediators and hindering the neutrophil infiltration, respectively. Collectively, these findings indicate that p-coumaric acid is a promising anti-inflammatory agent that can be used for developing a pharmaceutical drug for the treatment of ALI and other inflammatory disorders.

Role of matrix metalloproteinases in the inflammatory process of respiratory diseases.

Matrix metalloproteinases (MMPs) are a group of proteases known to regulate the turnover of extracellular matrix and thus are suggested to be important in the process of several diseases associated with tissue remodeling. Furthermore, the concept that modulation of airway remodeling including excessive proteolysis damage of the tissue, may be of interest as a basis for future treatment. Degradation of extracellular matrix is currently associated with structural and recruited cell activation and release of inflammatory mediators and MMPs. Indeed, a marked increase in their expression is observed associated with a variety of inflammatory diseases, including respiratory pathologies. In these conditions, we have to consider MMPs as therapeutic targets which can be inhibited by non-selective and/or selective inhibitors as anti-inflammatory compounds. The present review aims to discuss the potential interest of the inhibition of MMP in inflammatory diseases with a focus on respiratory diseases.

IL-1R1/MyD88 signaling and the inflammasome are essential in pulmonary inflammation and fibrosis in mice.

The molecular mechanisms of acute lung injury resulting in inflammation and fibrosis are not well established. Here we investigate the roles of the IL-1 receptor 1 (IL-1R1) and the common adaptor for Toll/IL-1R signal transduction, MyD88, in this process using a murine model of acute pulmonary injury. Bleomycin insult results in expression of neutrophil and lymphocyte chemotactic factors, chronic inflammation, remodeling, and fibrosis. We demonstrate that these end points were attenuated in the lungs of IL-1R1- and MyD88-deficient mice. Further, in bone marrow chimera experiments, bleomycin-induced inflammation required primarily MyD88 signaling from radioresistant resident cells. Exogenous rIL-1beta recapitulated a high degree of bleomycin-induced lung pathology, and specific blockade of IL-1R1 by IL-1 receptor antagonist dramatically reduced bleomycin-induced inflammation. Finally, we found that lung IL-1beta production and inflammation in response to bleomycin required ASC, an inflammasome adaptor molecule. In conclusion, bleomycin-induced lung pathology required the inflammasome and IL-1R1/MyD88 signaling, and IL-1 represented a critical effector of pathology and therapeutic target of chronic lung inflammation and fibrosis.

Uric acid is a danger signal activating NALP3 inflammasome in lung injury inflammation and fibrosis.

RATIONALE: Lung injury leads to pulmonary inflammation and fibrosis through myeloid differentiation primary response gene 88 (MyD88) and the IL-1 receptor 1 (IL-1R1) signaling pathway. The molecular mechanisms by which lung injury triggers IL-1beta production, inflammation, and fibrosis remain poorly understood. OBJECTIVES: To determine if lung injury depends on the NALP3 inflammasome and if bleomycin (BLM)-induced lung injury triggers local production of uric acid, thereby activating the NALP3 inflammasome in the lung. METHODS: Inflammation upon BLM administration was evaluated in vivo in inflammasome-deficient mice. Pulmonary uric acid accumulation, inflammation, and fibrosis were analyzed in mice treated with the inhibitor of uric acid synthesis or with uricase, which degrades uric acid. MEASUREMENTS AND MAIN RESULTS: Lung injury depends on the NALP3 inflammasome, which is triggered by uric acid locally produced in the lung upon BLM-induced DNA damage and degradation. Reduction of uric acid levels using the inhibitor of uric acid synthesis allopurinol or uricase leads to a decrease in BLM-induced IL-1beta production, lung inflammation, repair, and fibrosis. Local administration of exogenous uric acid crystals recapitulates lung inflammation and repair, which depend on the NALP3 inflammasome, MyD88, and IL-1R1 pathways and Toll-like receptor (TLR)2 and TLR4 for optimal inflammation but are independent of the IL-18 receptor. CONCLUSIONS: Uric acid released from injured cells constitutes a major endogenous danger signal that activates the NALP3 inflammasome, leading to IL-1beta production. Reducing uric acid tissue levels represents a novel therapeutic approach to control IL-1beta production and chronic inflammatory lung pathology.