Complexification of In Vitro Models of Intestinal Barriers, A True Challenge for a More Accurate Alternative Approach.

The use of cell models is common to mimic cellular and molecular events in interaction with their environment. In the case of the gut, the existing models are of particular interest to evaluate food, toxicants, or drug effects on the mucosa. To have the most accurate model, cell diversity and the complexity of the interactions must be considered. Existing models range from single-cell cultures of absorptive cells to more complex combinations of two or more cell types. This work describes the existing solutions and the challenges that remain to be solved.

How advanced are we on the consequences of oral exposure to food contaminants on the occurrence of chronic non communicable diseases?

The development of an individual during fetal life and childhood is characterized by rapid growth as well as gradual maturation of organs and systems. Beyond the nutritional intake in essential nutrients, food contaminants can permanently influence the way organs mature and function. These processes are called "programming" and play an essential role in the occurrence of non-communicable chronic diseases throughout the lifespan. Populations as pregnant women, fetuses and young children are vulnerable and particularly sensitive to food contaminants which can induce epigenetic modifications transmissible to future generations. Among these contaminants, pesticides are found in most food matrices exposing humans to cocktails of molecules through variable concentrations and duration of exposure. The Maillard reaction products (MRPs) represent other food contaminants resulting from heat treatment of food. Modern diet, rich in fats and sugars, is also rich in neoformed pathogenic compounds, Advanced Glycation End products (AGEs), the levels of which depend on the heat treatment of foods and eating habits and whose effects on health are controversial. In this review, we have chosen to present the current knowledge on the impacts of selected pesticides and MRPs, on the risk of developing during life non-communicable chronic diseases such as IBD, metabolic disorders or allergies. A large review of literature was performed via Pubmed, and the most appropriate studies were summarised.

Plasma Levels of Free NƐ-Carboxymethyllysine (CML) after Different Oral Doses of CML in Rats and after the Intake of Different Breakfasts in Humans: Postprandial Plasma Level of sRAGE in Humans.

N-carboxymethyl-lysine (CML) and other dietary advanced glycation end-products (AGEs) are chemically modified amino acids with potential toxicological effects putatively related to their affinity with the receptor for AGEs (RAGE). The goal of this study was to determine the postprandial kinetics of CML in both rodents and humans and, in the latter, to evaluate their relationship with the soluble RAGE isoforms (sRAGE). Four gavage solutions containing different forms of CML were given to rats, and blood was collected over 8 h. Three different breakfasts containing dietary CML (dCML) were administered to 20 healthy volunteers, and blood was collected over 2 h. Concentrations of CML, CEL, and lysine were quantified in plasma and human meals by LC-MS/MS, and sRAGE was determined in human plasma by ELISA. The results showed that dCML did not affect the concentrations of circulating protein-bound CML and that only free CML increased in plasma, with a postprandial peak at 90 to 120 min. In humans, the postprandial plasmatic sRAGE concentration decreased independently of the dAGE content of the breakfasts. This study confirms reports of the inverse postprandial relationship between plasmatic free CML and sRAGE, though this requires further investigation for causality to be established.

Effect of Advanced Glycation End-Products and Excessive Calorie Intake on Diet-Induced Chronic Low-Grade Inflammation Biomarkers in Murine Models.

Chronic Low-Grade Inflammation (CLGI) is a non-overt inflammatory state characterized by a continuous activation of inflammation mediators associated with metabolic diseases. It has been linked to the overconsumption of Advanced Glycation End-Products (AGEs), and/or macronutrients which lead to an increase in local and systemic pro-inflammatory biomarkers in humans and animal models. This review provides a summary of research into biomarkers of diet-induced CLGI in murine models, with a focus on AGEs and obesogenic diets, and presents the physiological effects described in the literature. Diet-induced CLGI is associated with metabolic endotoxemia, and/or gut microbiota remodeling in rodents. The mechanisms identified so far are centered on pro-inflammatory axes such as the interaction between AGEs and their main receptor AGEs (RAGE) or increased levels of lipopolysaccharide. The use of murine models has helped to elucidate the local and systemic expression of CLGI mediators. These models have enabled significant advances in identification of diet-induced CLGI biomarkers and resultant physiological effects. Some limitations on the translational (murine → humans) use of biomarkers may arise, but murine models have greatly facilitated the testing of specific dietary components. However, there remains a lack of information at the whole-organism level of organization, as well as a lack of consensus on the best biomarker for use in CLGI studies and recommendations as to future research conclude this review.

Early exposure to food contaminants reshapes maturation of the human brain-gut-microbiota axis.

Early childhood growth and development is conditioned by the consecutive events belonging to perinatal programming. This critical window of life will be very sensitive to any event altering programming of the main body functions. Programming of gut function, which is starting right after conception, relates to a very well-established series of cellular and molecular events associating all types of cells present in this organ, including neurons, endocrine and immune cells. At birth, this machinery continues to settle with the establishment of extra connection between enteric and other systemic systems and is partially under the control of gut microbiota activity, itself being under the densification and the diversification of microorganisms' population. As thus, any environmental factor interfering on this pre-established program may have a strong incidence on body functions. For all these reasons, pregnant women, fetuses and infants will be particularly susceptible to environmental factors and especially food contaminants. In this review, we will summarize the actual understanding of the consequences of repeated low-level exposure to major food contaminants on gut homeostasis settlement and on brain/gut axis communication considering the pivotal role played by the gut microbiota during the fetal and postnatal stages and the presumed consequences of these food toxicants on the individuals especially in relation with the risks of developing later in life non-communicable chronic diseases.

Prevention of Adult Colitis by Oral Ferric Iron in Juvenile Mice Is Associated with the Inhibition of the Tbet Promoter Hypomethylation and Gene Overexpression.

Iron is an essential nutrient needed for physiological functions, particularly during the developmental period of the early childhood of at-risk populations. The purpose of this study was to investigate, in an experimental colitis, the consequences of daily oral iron ingestion in the early period on the inflammatory response, the spleen T helper (Th) profiles and the associated molecular mechanisms. Juvenile mice orally received microencapsulated ferric iron or water for 6 weeks. On adult mice, we induced a sham or experimental trinitrobenzene sulfonic acid (TNBS) moderate colitis during the last week of the experiment before sacrificing the animals 7 days later. The severity of the gut inflammation was assessed by macroscopic damage scores (MDS) and the myeloperoxidase activity (MPO). Th profiles were evaluated by the examination of the splenic gene expression of key transcription factors of the Th differentiation (Tbet, Gata3, Foxp3 and RORγ) and the methylation of their respective promoter. While TNBS-induced colitis was associated with a change of the Th profile (notably an increase in the Tbet/Gata3 ratio in the spleen), the colitis-inhibition induced by ferric iron was associated with a limitation of the splenic Th profiles perturbation. The inhibition of the splenic Tbet gene overexpression was associated with an inhibition of promoter hypomethylation. In summary, mice treated by long-term oral ferric iron in the early period of life exhibited an inhibition of colitis associated with the inhibition of the splenic Tbet promoter hypomethylation and gene overexpression.

Maillard reaction products from highly heated food prevent mast cell number increase and inflammation in a mouse model of colitis.

Links between food and inflammatory bowel diseases (IBDs) are often suggested, but the role of food processing has not been extensively studied. Heat treatment is known to cause the loss of nutrients and the appearance of neoformed compounds such as Maillard reaction products. Their involvement in gut inflammation is equivocal, as some may have proinflammatory effects, whereas other seem to be protective. As IBDs are associated with the recruitment of immune cells, including mast cells, we raised the hypothesis that dietary Maillard reaction products generated through heat treatment of food may limit the colitic response and its associated recruitment of mast cells. An experimental model of colitis was used in mice submitted to mildly and highly heated rodent food. Adult male mice were divided in 3 groups and received nonheated, mildly heated, or highly heated chow during 21 days. In the last week of the study, each group was split into 2 subgroups, submitted or not (controls) to dextran sulfate sodium (DSS) colitis. Weight variations, macroscopic lesions, colonic myeloperoxidase activity, and mucosal mast cell number were evaluated at the end of the experiment. Only highly heated chow significantly prevented DSS-induced weight loss, myeloperoxidase activity, and mast cell number increase in the colonic mucosa of DSS-colitic mice. We suggest that Maillard reaction products from highly heated food may limit the occurrence of inflammatory phases in IBD patients.

Repeated Oral Exposure to N ε-Carboxymethyllysine, a Maillard Reaction Product, Alleviates Gut Microbiota Dysbiosis in Colitic Mice.

BACKGROUND: Diet is suggested to participate in the etiology of inflammatory bowel diseases (IBD). Repeated exposure to Maillard reaction products (MRPs), molecules resulting from reduction reactions between amino acids and sugars during food heating, has been reported to be either potentially detrimental or beneficial to health. AIMS: The aim of this study is to determine the effect of repeated oral ingestion of N ε-carboxymethyllysine (CML), an advanced MRP, on the onset of two models of experimental IBD and on the gut microbiota composition of mice. METHODS: Mice received either saline (control) or N ε-carboxymethyllysine daily for 21 days. For the last week of treatment, each group was split into subgroups, receiving dextran sulfate sodium salt (DSS) or trinitrobenzenesulfonic acid (TNBS) to induce colitis. Intensity of inflammation was quantified, and cecal microbiota characterized by bacterial 16S ribosomal RNA (rRNA) amplicon sequencing. RESULTS: Daily oral administration of N ε-carboxymethyllysine did not induce intestinal inflammation and had limited impact on gut microbiota composition (Bacteroidaceae increase, Lachnospiraceae decrease). DSS and TNBS administration resulted in expected moderate experimental colitis with a shift of Bacteroidetes/Firmicutes ratio and a significant Proteobacteria increase but with distinct profiles: different Proteobacteria taxa for DSS, but mainly Enterobacteriaceae for TNBS. While N ε-carboxymethyllysine exposure failed to prevent the inflammatory response, it allowed maintenance of healthy gut microbiota profiles in mice treated with DSS (but not TNBS). CONCLUSIONS: Repeated oral exposure to CML limits dysbiosis in experimental colitis. IBD patients may modulate their microbiota profile by regulating the level and type of dietary MRP consumption.

Polyphenol Interactions Mitigate the Immunogenicity and Allergenicity of Gliadins.

Wheat allergy is an IgE-mediated disorder. Polyphenols, which are known to interact with certain proteins, could be used to reduce allergic reactions. This study screened several polyphenol sources for their ability to interact with gliadins, mask epitopes, and affect basophil degranulation. Polyphenol extracts from artichoke leaves, cranberries, apples, and green tea leaves were examined. Of these extracts, the first three formed insoluble complexes with gliadins. Only the cranberry and apple extracts masked epitopes in dot blot assays using anti-gliadin IgG and IgE antibodies from patients with wheat allergies. The cranberry and artichoke extracts limited cellular degranulation by reducing mouse anti-gliadin IgE recognition. In conclusion, the cranberry extract is the most effective polyphenol source at reducing the immunogenicity and allergenicity of wheat gliadins.

Maternal diet, bioactive molecules, and exercising as reprogramming tools of metabolic programming.

Nutrition and lifestyle, particularly over-nutrition and lack of exercise, promote the progression and pathogenesis of obesity and metabolic diseases. Nutrition is likely the most important environmental factor that modulates the expression of genes involved in metabolic pathways and a variety of phenotypes associated with obesity and diabetes. During pregnancy, diet is a major factor that influences the organ developmental plasticity of the foetus. Experimental evidence shows that nutritional factors, including energy, fatty acids, protein, micronutrients, and folate, affect various aspects of metabolic programming. Different epigenetic mechanisms that are elicited by bioactive factors in early critical developmental ages affect the susceptibility to several diseases in adulthood. The beneficial effects promoted by exercise training are well recognised, and physical exercise may be considered one of the more prominent non-pharmacological tools that can be used to attenuate metabolic programming and to consequently ameliorate the illness provoked by metabolic diseases and reduce the prevalence of obesity, type 2 diabetes, and cardiovascular diseases. Literature on the different outcomes of unbalanced diets and the beneficial effects of some bioactive molecules during gestation and lactation on the metabolic health of offspring, as well as the potential mechanisms underlying these effects, was reviewed. The importance of the combined effects of functional nutrition and exercise as reprogramming tools of metabolic programming is discussed in depth. Finally, this review provides recommendations to healthcare providers that may aid in the control of early programming in an attempt to optimise the health of the mother and child.

Juvenile ferric iron prevents microbiota dysbiosis and colitis in adult rodents.

AIM: To assess whether juvenile chronic ferric iron ingestion limit colitis and dysbiosis at adulthood in rats and mice. METHODS: Two sets of experiments were designed. In the first set, recently weaned mice were either orally administered ferrous (Fe²âº) iron salt or ferric (Fe³âº) microencapsulated iron for 6 wk. The last week of experiments trinitrobenzene sulfonic acid (TNBS) colitis was induced. In the second set, juvenile rats received the microencapsulated ferric iron for 6 wk and were also submitted to TNBS colitis during the last week of experiments. In both sets of experiments, animals were sacrificed 7 d after TNBS instillation. Severity of the inflammation was assessed by scoring macroscopic lesions and quantifying colonic myeloperoxidase (MPO) activity. Alteration of the microflora profile was estimated using quantitative polymerase chain reaction (qPCR) by measuring the evolution of total caecal microflora, Bacteroidetes, Firmicutes and enterobacteria. RESULTS: Neither ferrous nor ferric iron daily exposures at the juvenile period result in any effect in control animals at adulthood although ferrous iron repeated administration in infancy limited weight gain. Ferrous iron was unable to limit the experimental colitis (1.71 ± 0.27 MPO U/mg protein vs 2.47 ± 0.22 MPO U/mg protein in colitic mice). In contrast, ferric iron significantly prevented the increase of MPO activity (1.64 ± 0.14 MPO U/mg protein) in TNBS-induced colitis. Moreover, this positive effect was observed at both the doses of ferric iron used (75 and 150 mg/kg per day po--6 wk). In the study we also compared, in both rats and mice, the consequences of chronic repeated low level exposure to ferric iron (75 mg/kg per day po--6 wk) on TNBS-induced colitis and its related dysbiosis. We confirmed that ferric iron limited the TNBS-induced increase of MPO activity in both the rodent species. Furthermore, we assessed the ferric iron incidence on TNBS-induced intestinal microbiota dysbiosis. At first, we needed to optimize the isolation and quantify DNA copy numbers using standard curves to perform by qPCR this interspecies comparison. Using this approach, we determined that total microflora was similar in control rats and mice and was mainly composed of Firmicutes and Bacteroidetes at a ratio of 10/1. Ferric juvenile administration did not modify the microflora profile in control animals. Total microflora numbers remained unchanged whichever experimental conditions studied. Following TNBS-induced colitis, the Firmicutes/Bacteroidetes ratio was altered resulting in a decrease of the Firmicutes numbers and an increase of the Bacteroidetes numbers typical of a gut inflammatory reaction. In parallel, the subdominant population, the enterobacteria was also increased. However, ferric iron supplementation for the juvenile period prevented the increase of Bacteroidetes and of enterobacteria numbers consecutive to the colitis in both the studied species at adulthood. CONCLUSION: Rats and mice juvenile chronic ferric iron ingestion prevents colitis and dysbiosis at adulthood as assessed by the first interspecies comparison.

The peroxisome proliferator-activated receptor α agonist fenofibrate decreases airway reactivity to methacholine and increases endothelial nitric oxide synthase phosphorylation in mouse lung.

In the present study, we have investigated the effect of the peroxisome proliferator-activated receptor α (PPARα) agonist fenofibrate on airway reactivity and the role of the endothelial nitric oxide synthase (eNOS)/NO pathway in this effect. Airway reactivity to methacholine was assessed in C57BL/6 mice treated or not with fenofibrate by whole-body plethysmography. In some experiments, animals were administered with the NOS inhibitor L-NAME, one hour before airway reactivity measurement. Expression and phosphorylation of eNOS were evaluated in lung homogenates from fenofibrate and control animals using Western blotting. Fenofibrate dose and time dependently decreased airway reactivity to methacholine in mice. A statistically significant (P < 0.05) reduction was observed after a treatment of 10 days with a dose of 3 or 15 mg/day fenofibrate. Mice treated with fenofibrate and administered with l-NAME exhibited similar reactivity to methacholine than vehicle-treated mice administered with the NOS inhibitor, suggesting that NO mediates fenofibrate-induced decrease in airway reactivity. eNOS levels remained unchanged in the lung from mice treated with fenofibrate, but phosphorylation of the enzyme at Ser-1177 was increased by 118% (P < 0.05). Taken together, our data demonstrate that fenofibrate downregulates airway reactivity to methacholine in the mouse and suggest that this effect could involve an increase in NO generation through an enhanced eNOS phosphorylation.

Suppression of allergen-induced airway inflammation and immune response by the peroxisome proliferator-activated receptor-alpha agonist fenofibrate.

In the present study, we have assessed the effect of the peroxisome proliferator-activated receptor-alpha (PPARalpha) agonist fenofibrate on allergen-induced airway inflammation and immune response. C57BL/6 or PPARalpha knock-out (PPARalpha(-/-)) mice were sensitized with ovalbumin and challenged with ovalbumin alone or with ovalbumin+lipopolysaccharides. Fenofibrate was administered to allergen-exposed animals during challenge only or from the day prior to sensitization to the end of challenge. Inflammation and immune response were assessed by determining cell counts and cytokine levels in bronchoalveolar lavage fluids, expression of the transcription factors Gata-3 and T-bet in lung tissue and ovalbumin-specific IgE and IgG2a in serum. Treatment with fenofibrate (0.15-15 mg/day) during allergen challenge dose-dependently reduced airway inflammatory cell infiltrate induced by ovalbumin in C57BL/6 mice. Reduction reached 74.3% (P<0.001) in animals treated with 15 mg/day of the PPARalpha agonist, whereas this treatment failed to suppress cell infiltrate induced by allergen in PPARalpha(-/-) mice. In addition, when administered from the day prior to sensitization to the end of challenge, fenofibrate (15 mg/day) triggered switching of the immune response to allergen towards a Th1 profile, as evidenced by an increase in IgG2a levels, a reduction in IL(interleukin)-4 and IL-5 together with an increase in interferon-gamma, and a decrease in Gata-3/T-bet expression ratio. Upon challenge with ovalbumin+lipopolysaccharides, sensitized mice developed a severe inflammatory response characterized by infiltration of eosinophils, neutrophils, lymphocytes and macrophages and by increased release of IL-4, IL-5, tumor necrosis factor-alpha, macrophage-inflammatory protein-2 and monocyte chemoattractant protein-1. Administration of fenofibrate during allergen challenge dramatically reduced all responses. In conclusion, our data clearly demonstrate that fenofibrate exhibits an anti-inflammatory activity in allergic asthma, including in severe conditions, and that the PPARalpha agonist is also capable of switching the immune response to allergen towards a Th1 profile when given from the day prior to sensitization.

Regulation of peroxisome proliferator-activated receptor-alpha expression during lung inflammation.

Peroxisome proliferator-activated receptor-alpha (PPARalpha) is implicated in the control of airway inflammation. However, little is known so far about PPARalpha expression and regulation in the lung. Our aim was to assess PPARalpha expression in the lung from normal mice, as well as to investigate its regulation during airway inflammation or in response to anti-inflammatory agents. The PPARalpha activator, fenofibrate, the glucocorticoid, dexamethasone or vehicle was administered to normal mice, to mice exposed to tumor necrosis factor-alpha (TNF-alpha) or lipopolysaccharide (LPS) or to ovalbumin (OVA)-sensitized and challenged animals. PPARalpha expression was assessed by quantifying PPARalpha mRNA levels using real-time quantitative PCR after reverse-transcription of total lung RNA. Airway inflammation was evaluated by determining total and differential cell counts, as well as TNF-alpha production in bronchoalveolar lavage fluids. PPARalpha mRNA was found at significant levels in the lung from normal mice. This expression was increased by 65% (p<0.05) and 55% (p<0.05) in animals treated with fenofibrate and dexamethasone, respectively. In mice exposed to TNF-alpha or LPS, as well as in animals sensitized and challenged with OVA, that exhibited airway inflammation, PPARalpha mRNA was decreased by 60% (p<0.05), 43% (p<0.05) and 50% (p<0.05), respectively. In mice exposed to LPS, down-regulation of PPARalpha was maximal at 4h, whereas TNF-alpha production and cell infiltration peaked at 2 and 24h, respectively. In the lung of mice exposed to LPS or OVA and treated with fenofibrate or dexamethasone, PPARalpha down-regulation was suppressed, while airway inflammation was abolished. Our data showed that PPARalpha is constitutively expressed in mouse lung and down-regulated in response to TNF-alpha or upon acute or allergic airway inflammation. Fenofibrate and dexamethasone upregulated PPARalpha in normal lung and suppressed PPARalpha down-regulation associated with airway inflammation. Taken together, our data show that PPARalpha expression is inversely regulated with lung inflammation.

Regulation of inflammation by PPARs: a future approach to treat lung inflammatory diseases?

Lung inflammatory diseases, such as acute lung injury (ALI), asthma, chronic obstructive pulmonary disease (COPD) and lung fibrosis, represent a major health problem worldwide. Although glucocorticoids are the most potent anti-inflammatory drug in asthma, they exhibit major side effects and have poor activity in lung inflammatory disorders such as ALI or COPD. Therefore, there is growing need for the development of alternative or new therapies to treat inflammation in the lung. Peroxisome proliferator-activated receptors (PPARs), including the three isotypes PPARalpha, PPARbeta (or PPARdelta) and PPARgamma, are transcription factors belonging to the nuclear hormone receptor superfamily. PPARs, and in particular PPARalpha and PPARgamma, are well known for their critical role in the regulation of energy homeostasis by controlling expression of a variety of genes involved in lipid and carbohydrate metabolism. Synthetic ligands of the two receptor isotypes, the fibrates and the thiazolidinediones, are clinically used to treat dyslipidaemia and type 2 diabetes, respectively. Recently however, PPARalpha and PPARgamma have been shown to exert a potent anti-inflammatory activity, mainly through their ability to downregulate pro-inflammatory gene expression and inflammatory cell functions. The present article reviews the current knowledge of the role of PPARalpha and PPARgamma in controlling inflammation, and presents different findings suggesting that PPARalpha and PPARgamma activators may be helpful in the treatment of lung inflammatory diseases.

Exposure to endotoxins during sensitization prevents further endotoxin-induced exacerbation of airway inflammation in a mouse model of allergic asthma.

BACKGROUND: We have shown previously that lipopolysaccharides (LPS) inhibited airway inflammation in allergen-sensitized and challenged mice when administered during sensitization, while exacerbating the inflammation when given upon challenge. We have here investigated the effect of LPS administered during both sensitization and challenge on airway inflammation, as well as on the profile of the T-helper (Th) response to allergen. METHODS: Mice were sensitized and challenged with ovalbumin (OVA), in the presence or absence of effective doses of LPS, namely 1 mug during sensitization and 1 ng during challenge. Inflammation was assessed by measuring cell counts and cytokine levels in bronchoalveolar lavage fluid (BALF). The profile of the Th response was determined by quantifying OVA-specific IgE and IgG2a in serum and Th1/Th2 cytokines in the culture medium of splenocytes and in BALF. RESULTS: Allergen-induced airway eosinophilia was increased in mice exposed to LPS during challenge only when compared with controls, whereas it was similarly reduced in animals exposed during sensitization only and during both sensitization and challenge. Mice exposed to LPS during sensitization only or during both sensitization and challenge also displayed a decrease in IgE and an increase in IgG2a, suggesting a switch in the immune response toward the Th1 profile. This was confirmed by quantification of Th1/Th2 cytokines in culture medium of splenocytes and in BALF. CONCLUSIONS: Our data demonstrate that exposure to endotoxins during sensitization prevents allergen-induced airway inflammation, as well as its exacerbation triggered by further exposure to endotoxins during challenge, while switching the immune response to allergen from a Th2 to a Th1 profile.

PPARalpha downregulates airway inflammation induced by lipopolysaccharide in the mouse.

BACKGROUND: Inflammation is a hallmark of acute lung injury and chronic airway diseases. In chronic airway diseases, it is associated with profound tissue remodeling. Peroxisome proliferator-activated receptor-alpha (PPARalpha) is a ligand-activated transcription factor, that belongs to the nuclear receptor family. Agonists for PPARalpha have been recently shown to reduce lipopolysaccharide (LPS)- and cytokine-induced secretion of matrix metalloproteinase-9 (MMP-9) in human monocytes and rat mesangial cells, suggesting that PPARalpha may play a beneficial role in inflammation and tissue remodeling. METHODS: We have investigated the role of PPARalpha in a mouse model of LPS-induced airway inflammation characterized by neutrophil and macrophage infiltration, by production of the chemoattractants, tumor necrosis factor-alpha (TNF-alpha), keratinocyte derived-chemokine (KC), macrophage inflammatory protein-2 (MIP-2) and monocyte chemoattractant protein-1 (MCP-1), and by increased MMP-2 and MMP-9 activity in bronchoalveolar lavage fluid (BALF). The role of PPARalpha in this model was studied using both PPARalpha-deficient mice and mice treated with the PPARalpha activator, fenofibrate. RESULTS: Upon intranasal exposure to LPS, PPARalpha-/- mice exhibited greater neutrophil and macrophage number in BALF, as well as increased levels of TNF-alpha, KC, MIP-2 and MCP-1, when compared to PPARalpha+/+ mice. PPARalpha-/- mice also displayed enhanced MMP-9 activity. Conversely, fenofibrate (0.15 to 15 mg/day) dose-dependently reduced the increase in neutrophil and macrophage number induced by LPS in wild-type mice. In animals treated with 15 mg/day fenofibrate, this effect was associated with a reduction in TNF-alpha, KC, MIP-2 and MCP-1 levels, as well as in MMP-2 and MMP-9 activity. PPARalpha-/- mice treated with 15 mg/day fenofibrate failed to exhibit decreased airway inflammatory cell infiltrate, demonstrating that PPARalpha mediates the anti-inflammatory effect of fenofibrate. CONCLUSION: Using both genetic and pharmacological approaches, our data clearly show that PPARalpha downregulates cell infiltration, chemoattractant production and enhanced MMP activity triggered by LPS in mouse lung. This suggests that PPARalpha activation may have a beneficial effect in acute or chronic inflammatory airway disorders involving neutrophils and macrophages.