Peroxisome proliferator-activated receptor alpha (PPAR alpha) down-regulation in cystic fibrosis lymphocytes

IPSE, a urogenital parasite-derived immunomodulatory protein, ameliorates ifosfamide-induced hemorrhagic cystitis through downregulation of pro-inflammatory pathways

Ifosfamide and other oxazaphosphorines can result in hemorrhagic cystitis, a constellation of complications caused by acrolein metabolites. We previously showed that a single dose of IPSE (Interleukin-4-inducing principle from Schistosoma eggs), a schistosome-derived host modulatory protein, can ameliorate ifosfamide-related cystitis; however, the mechanisms underlying this urotoxicity and its prevention are not fully understood. To provide insights into IPSE’s protective mechanism, we undertook transcriptional profiling of bladders from ifosfamide-treated mice, with or without pretreatment with IPSE or IPSE-NLS (a mutant of IPSE lacking nuclear localization sequence). Ifosfamide treatment upregulated a range of proinflammatory genes. The IL-1β-TNFα-IL-6 proinflammatory cascade via NFκB and STAT3 pathways was identified as the key driver of inflammation. The NRF2-mediated oxidative stress response pathway, which regulates heme homoeostasis and expression of antioxidant enzymes, was highly activated. Anti-inflammatory cascades, namely Wnt, Hedgehog and PPAR pathways, were downregulated. IPSE drove significant downregulation of major proinflammatory pathways including the IL-1β-TNFα-IL-6 pathways, interferon signaling, and reduction in oxidative stress. IPSE-NLS reduced inflammation but not oxidative stress. Taken together, we have identified signatures of acute-phase inflammation and oxidative stress in ifosfamide-injured bladder, which are reversed by pretreatment with IPSE. This work revealed several pathways that could be therapeutically targeted to prevent ifosfamide-induced hemorrhagic cystitis.

Long-term dietary (n-3) polyunsaturated fatty acids show benefits to the lungs of Cftr F508del mice

Introduction

The pro-inflammatory status of cystic fibrosis (CF) patients promotes pulmonary colonization with opportunist and pathogenic bacteria, which is favored by a sticky mucus. Oral supplementation with (n-3) long chain polyunsaturated fatty acids (LC-PUFA) has shown anti-inflammatory effects. The aim of this study was to demonstrate the positive effects of a long-term diet enriched in (n-3) LC-PUFA on the lungs of Cftr F508del mice.

Materials and methods

Breeding CftrΔF508del/+ mice received a control diet or a diet enriched in (n-3) LC-PUFA for 5 weeks before mating, gestation and lactation. After weaning, the offspring were given the same diet as their mother until post-natal day 60. The effects of (n-3) LC-PUFA supplementation on the lungs were evaluated in homozygous Cftr F508del mice and their wild-type littermates after acute lung inflammation induced by Pseudomonas aeruginosa lipopolysaccharide (LPS) inhalation.

Results

(n-3) LC-PUFA enrichment of mothers contributes to enrichment of mammary milk and cell membrane of suckling pups. Cftr F508del mice exhibited growth retardation and lung damage with collapsed alveoli, hyperplasia of bronchial epithelial cells and inflammatory cell infiltration. The (n-3) LC-PUFA diet corrected the growth delay of Cftr F508del mice and decreased hyperplasia of bronchial epithelial cells. Besides decreasing metaplasia of Club cells after LPS inhalation, (n-3) LC-PUFA modulated lung inflammation and restricted lung damage.

Conclusion

Long-term (n-3) LC-PUFA supplementation shows moderate benefits to the lungs of Cftr F508del mice.

Stimulating effect of normal-dosing of fibrates on cell proliferation: word of warning

BACKGROUND

Fibrates are widely used hypolipidemic drugs, which serve as ligand of peroxisome proliferator-activated receptor α (PPARα). Recently, they have also been considered as potential anticancer agents. We studied effect of fibrates treatment on cell proliferation, expression of CYP2J2 and concomitant changes in expression of cell cycle regulatory proteins in three different human cell lines: HEK293, HepG2, and HT-29.

METHODS

We used WST-1 viability test, western blot and immunocytochemistry for detection of proteins of interests and analysis of cell cycle.

RESULTS

Our results showed that at lower concentrations of all tested fibrates, viability of all tested cell lines is increased, whereas at higher concentrations, repression is apparent. Unfortunately, the viability of tested cells is predominantly increased in a range of concentration which is reached in patient plasma. This phenomenon is accompanyed by elevation of CYP2J2, increased number of cyclin E-positive cells and decreased number of Cdc25A-positive cells in all tested cell lines, and elevated cyclin A expression in HepG2 and HT-29. These changes are concentration-dependent. We suppose that increased level of CYP2J2 could explain enhanced cell proliferation in lower concentration of fibrates.

CONCLUSION

Based on our results, we suggested there is no anti-cancer effect of fibrates in tested carcinoma cell lines.

PPAR-α activation reduced LPS-induced inflammation in alveolar epithelial cells

PURPOSE OF THE STUDY

Acute respiratory distress syndrome (ARDS) represents a major cause of mortality in intensive care patients. Activation of peroxisome proliferator-activated receptor-α (PPAR-α) by fibrates, such as WY-14643 (WY), has been described to beneficially influence inflammation and experimental lung injury. The impact of PPAR-α activation on alveolar epithelial cells (AEC) has not been studied yet.

MATERIALS AND METHODS

To investigate the effect of PPAR-α activator WY in wild-type (WT) and in PPAR-α knockout (PPAR-α(-/-)) animals, mice were treated in different regimes: mice received chow enriched with or without WY for 14 days prior AEC isolation (in-vivo treatment). Furthermore, isolated AEC from both groups were subsequently cultured with or without WY (in-vitro treatment). AEC were stimulated with lipopolysaccharide (LPS). Cell culture supernatant and cell lysate were used for analysis of pro-inflammatory mediators.

RESULTS

AEC challenged with LPS showed a significantly increased generation of pro-inflammatory mediators. After in-vivo WY-exposure, AEC displayed significantly reduced concentration of TNF-α, MIP-2, and TxB2 after LPS stimulation. This beneficial effect was abrogated in PPAR-α(-/-) animals. Interestingly, sole in-vitro application of WY-14643 failed to reduce levels of pro-inflammatory mediators whereas we found an additive effect of a combined in-vivo and in-vitro PPAR-α activation. PGE2 concentration remained high after LPS challenge and was unaffected by WY treatment.

CONCLUSION

PPAR-α activation by in-vivo exposure to fibrates reduced the inflammatory response in isolated AEC. These findings may facilitate further studies investigating the translation of pharmacological PPAR-α activation into clinical therapy of ARDS.

Fenofibrate Attenuates Neutrophilic Inflammation in Airway Epithelia: Potential Drug Repurposing for Cystic Fibrosis

A hallmark of cystic fibrosis (CF) lung disease is neutrophilic airway inflammation. Elevated neutrophil counts have been associated with decreased forced expiratory volume in 1 second and poor clinical measures in patients with CF. Interleukin 8 (IL-8), epithelial neutrophil activating protein 78 (ENA-78), tumor necrosis factor alpha (TNF-α), granulocyte macrophage colony-stimulating factor (GM-CSF), and granulocyte colony-stimulating factor (G-CSF) contribute to neutrophil activation and disease pathogenesis in the airways of patients with CF. Drugs that modify the production of these chemokines in the airways could potentially benefit CF patients. Thus, we determined the effects of fenofibrate on their production in cell populations obtained from the airways. Human small airway epithelial cells and CF bronchial epithelial cells were treated with IL-1β to induce inflammation. We cotreated the cells with fenofibrate at concentrations ranging from 10 to 50 μM to determine if this drug could attenuate the inflammation. IL-8, ENA-78, TNF-α, GM-CSF, and G-CSF production were measured from the cell culture supernates by ELISA. ANOVA statistical testing was conducted using SPSS 17.0. IL-1β increased the production of each of the chemokines by several fold. Fenofibrate reduced IL-1β induced production of each of these neutrophilic chemokines at the concentrations used. IL-1β increases the production of neutrophilic chemokines in airway epithelial cells. Cotreatment with fenofibrate blunts these processes. Fenofibrate should be explored as a therapeutic option to modulate the abundant neutrophilic inflammation observed in CF.

Cannabidiol causes endothelium-dependent vasorelaxation of human mesenteric arteries via CB1 activation

Aims

The protective effects of cannabidiol (CBD) have been widely shown in preclinical models and have translated into medicines for the treatment of multiple sclerosis and epilepsy. However, the direct vascular effects of CBD in humans are unknown.

Methods and results

Using wire myography, the vascular effects of CBD were assessed in human mesenteric arteries, and the mechanisms of action probed pharmacologically. CBD-induced intracellular signalling was characterized using human aortic endothelial cells (HAECs). CBD caused acute, non-recoverable vasorelaxation of human mesenteric arteries with an R_max of ∼40%. This was inhibited by cannabinoid receptor 1 (CB₁) receptor antagonists, desensitization of transient receptor potential channels using capsaicin, removal of the endothelium, and inhibition of potassium efflux. There was no role for cannabinoid receptor-2 (CB₂) receptor, peroxisome proliferator activated receptor (PPAR)γ, the novel endothelial cannabinoid receptor (CB_e), or cyclooxygenase. CBD-induced vasorelaxation was blunted in males, and in patients with type 2 diabetes or hypercholesterolemia. In HAECs, CBD significantly reduced phosphorylated JNK, NFκB, p70s6 K and STAT5, and significantly increased phosphorylated CREB, ERK1/2, and Akt levels. CBD also increased phosphorylated eNOS (ser1177), which was correlated with increased levels of ERK1/2 and Akt levels. CB₁ receptor antagonism prevented the increase in eNOS phosphorylation.

Conclusion

This study shows, for the first time, that CBD causes vasorelaxation of human mesenteric arteries via activation of CB₁ and TRP channels, and is endothelium- and nitric oxide-dependent.

Endocannabinoids modulate human blood-brain barrier permeability in vitro

Background and Purpose

Endocannabinoids alter permeability at various epithelial barriers, and cannabinoid receptors and endocannabinoid levels are elevated by stroke, with potential neuroprotective effects. We therefore explored the role of endocannabinoids in modulating blood–brain barrier (BBB) permeability in normal conditions and in an ischaemia/reperfusion model.

Experimental Approach

Human brain microvascular endothelial cell and astrocyte co-cultures modelled the BBB. Ischaemia was modelled by oxygen-glucose deprivation (OGD) and permeability was measured by transepithelial electrical resistance. Endocannabinoids or endocannabinoid-like compounds were assessed for their ability to modulate baseline permeability or OGD-induced hyperpermeability. Target sites of action were investigated using receptor antagonists and subsequently identified with real-time PCR.

Key Results

Anandamide (10 μM) and oleoylethanolamide (OEA, 10 μM) decreased BBB permeability (i.e. increased resistance). This was mediated by cannabinoid CB₂ receptors, transient receptor potential vanilloid 1 (TRPV1) channels, calcitonin gene-regulated peptide (CGRP) receptor (anandamide only) and PPARα (OEA only). Application of OEA, palmitoylethanolamide (both PPARα mediated) or virodhamine (all 10 μM) decreased the OGD-induced increase in permeability during reperfusion. 2-Arachidonoyl glycerol, noladin ether and oleamide did not affect BBB permeability in normal or OGD conditions. N-arachidonoyl-dopamine increased permeability through a cytotoxic mechanism. PPARα and γ, CB₁ receptors, TRPV1 channels and CGRP receptors were expressed in both cell types, but mRNA for CB₂ receptors was only present in astrocytes.

Conclusion and Implication

The endocannabinoids may play an important modulatory role in normal BBB physiology, and also afford protection to the BBB during ischaemic stroke, through a number of target sites.

Profibrotic effect of miR-33a with Akt activation in hepatic stellate cells

MicroRNAs (miRNAs) attract more attention in the pathophysiology of liver fibrosis and miR-33a has been previously demonstrated as involved in the regulation of cholesterol and lipid metabolism. Transforming growth factor-beta1 (TGF-β1) is generally accepted to be the main stimulating factor in the hepatic stellate cells (HSCs) activation, which plays an important role in hepatic fibrosis. However, the involvement and underlying mechanism of miR-33a and its role in TGF-β1-induced hepatic fibrogenesis remains unknown. Here, we investigate the role of miR-33a in the activation of immortalized human HSCs, Lx-2 cells. Our findings have shown that the expression of miR-33a with its host gene sterol regulatory element-binding protein 2 (SREBP2) was more highly expressed in activation of Lx-2 cells than in quiescent cells. The expression of miR-33a on TGF-β1-induced HSCs activation may be modulated via the activation of PI3K/Akt pathway. In addition, miR-33a significantly correlated with TGF-β1-induced expression of α1 (I) collagen (Col1A1) and α-SMA in HSCs. Bioinformatics analyses predict that peroxisome proliferator activated receptor-alpha (PPAR-α) is the potential target of miR-33a. We further found that anti-miR-33a significantly increases target gene PPAR-α mRNA and protein level, suggesting that miR-33a involved in HSCs function might be modulated by targeting PPAR-α. Finally, our results indicate that the expression of miR-33a increased with the progression of liver fibrosis. These results suggested that anti-miR-33a inhibit activation and extracellular matrix production, at least in part, via the activation of PI3K/Akt pathway and PPAR-α and anti sense of miR-33a may be a novel potential therapeutic approach for treating hepatic fibrosis in the future.

Role of Epithelial Cells in Chronic Inflammatory Lung Disease

Airborne pathogens entering the lungs first encounter the mucus layer overlaying epithelial cells as a first line of host defense [1, 2]. In addition to serving as the physical barrier to these toxic agents, intact epithelia also are major sources of various macromolecules including antimicrobial agents, antioxidants and antiproteases [3, 4] as well as proinflammatory cytokines and chemokines that initiate and amplify host defensive responses to these toxic agents [5]. Airway epithelial cells can be categorized as either ciliated or secretory [6]. Secretory cells, such as goblet cells and Clara cells, are responsible for the production and secretion of mucus along the apical epithelial surface and, in conjunction with ciliated cells, for the regulation of airway surface liquid viscosity. In addition, submucosal mucus glands connect to the airway lumen through a ciliated duct that propels mucins outward. These glands are present in the larger airways between bands of smooth muscle and cartilage. See Fig. 1.

PPARγ as a therapeutic target in cystic fibrosis

Cystic fibrosis (CF) is characterized by a proinflammatory pulmonary condition that may result from increased infections and altered intracellular metabolism in CFTR-deficient cells. The lipid-activated transcription factor peroxisome proliferator-activated receptor-γ (PPARγ) has well-established roles in immune cell function and inflammatory modulation and has been demonstrated to play an important role in the heightened inflammatory response in CF cells. Here, we summarize current literature describing PPARγ-dependent alterations of CF cells and discuss the potential of PPARγ ligands for treating CF.

DHA and EPA reverse cystic fibrosis-related FA abnormalities by suppressing FA desaturase expression and activity

Patients and models of cystic fibrosis (CF) exhibit consistent abnormalities of polyunsaturated fatty acid composition, including decreased linoleate (LA) and docosahexaenoate (DHA) and variably increased arachidonate (AA), related in part to increased expression and activity of fatty acid desaturases. These abnormalities and the consequent CF-related pathologic manifestations can be reversed in CF mouse models by dietary supplementation with DHA. However, the mechanism is unknown. This study investigates this mechanism by measuring the effect of exogenous DHA and eicosapentaenoate (EPA) supplementation on fatty acid composition and metabolism, as well as on metabolic enzyme expression, in a cell culture model of CF. We found that both DHA and EPA suppress the expression and activity of Δ5- and Δ6-desaturases, leading to decreased flux through the n-3 and n-6 PUFA metabolic pathways and decreased production of AA. The findings also uncover other metabolic abnormalities, including increased fatty acid uptake and markedly increased retroconversion of DHA to EPA, in CF cells. These results indicate that the fatty acid abnormalities of CF are related to intrinsic alterations of PUFA metabolism and that they may be reversed by supplementation with DHA and EPA.

The peroxisome proliferator-activated receptor-α agonist, BAY PP1, attenuates renal fibrosis in rats

Recent studies have shown renoprotective effects of the peroxisome proliferator-activated receptor-α (PPAR-α), but its role in kidney fibrosis is unknown. In order to gain insight into this, we examined the effect of a novel PPAR-α agonist, BAY PP1, in two rat models of renal fibrosis: unilateral ureteral obstruction and the 5/6 nephrectomy. In healthy animals, PPAR-α was expressed in tubular but not in interstitial cells. Upon induction of fibrosis, PPAR-α was significantly downregulated, and treatment with BAY PP1 significantly restored its expression. During ureteral obstruction, treatment with BAY PP1 significantly reduced tubulointerstitial fibrosis, proliferation of interstitial fibroblasts, and TGF-β(1) expression. Treatment with a less potent PPAR-α agonist, fenofibrate, had no effects. Treatment with BAY PP1, initiated in established disease in the 5/6 nephrectomy, halted the decline of renal function and significantly ameliorated renal fibrosis. In vitro, BAY PP1 had no direct effect on renal fibroblasts but reduced collagen, fibronectin, and TGF-β(1) expression in tubular cells. Conditioned media of BAY PP1-treated tubular cells reduced fibroblast proliferation. Thus, renal fibrosis is characterized by a reduction of PPAR-α expression, and treatment with BAY PP1 restores PPAR-α expression and ameliorates renal fibrosis by modulating the cross-talk between tubular cells and fibroblasts. Hence, potent PPAR-α agonists might be useful in the treatment of renal fibrosis.

The Role of PPARs in Lung Fibrosis

Pulmonary fibrosis is a group of disorders characterized by accumulation of scar tissue in the lung interstitium, resulting in loss of alveolar function, destruction of normal lung architecture, and respiratory distress. Some types of fibrosis respond to corticosteroids, but for many there are no effective treatments. Prognosis varies but can be poor. For example, patients with idiopathic pulmonary fibrosis (IPF) have a median survival of only 2.9 years. Prognosis may be better in patients with some other types of pulmonary fibrosis, and there is variability in survival even among individuals with biopsy-proven IPF. Evidence is accumulating that the peroxisome proliferator-activated receptors (PPARs) play important roles in regulating processes related to fibrogenesis, including cellular differentiation, inflammation, and wound healing. PPARα agonists, including the hypolidipemic fibrate drugs, inhibit the production of collagen by hepatic stellate cells and inhibit liver, kidney, and cardiac fibrosis in animal models. In the mouse model of lung fibrosis induced by bleomycin, a PPARα agonist significantly inhibited the fibrotic response, while PPARα knockout mice developed more serious fibrosis. PPARβ/δ appears to play a critical role in regulating the transition from inflammation to wound healing. PPARβ/δ agonists inhibit lung fibroblast proliferation and enhance the antifibrotic properties of PPARγ agonists. PPARγ ligands oppose the profibrotic effect of TGF-β, which induces differentiation of fibroblasts to myofibroblasts, a critical effector cell in fibrosis. PPARγ ligands, including the thiazolidinedione class of antidiabetic drugs, effectively inhibit lung fibrosis in vitro and in animal models. The clinical availability of potent and selective PPARα and PPARγ agonists should facilitate rapid development of successful treatment strategies based on current and ongoing research.

Peroxisome proliferator activated receptor ligands as regulators of airway inflammation and remodelling in chronic lung disease

Inflammation is a major component in the pathology of chronic lung diseases, including asthma. Anti-inflammatory treatment with corticosteroids is not effective in all patients. Thus, new therapeutic options are required to control diverse cellular functions that are currently not optimally targeted by these drugs in order to inhibit inflammation and its sequelae in lung disease. Peroxisome proliferator activated receptors (PPARs), originally characterised as regulators of lipid and glucose metabolism, offer marked potential in this respect. PPARs are expressed in both lung infiltrating and resident immune and inflammatory cells, as well as in resident and structural cells in the lungs, and play critical roles in the regulation of airway inflammation. In vitro, endogenous and synthetic ligands for PPARs regulate expression and release of proinflammatory cytokines and chemoattractants, and cell proliferation and survival. In murine models of allergen-induced inflammation, PPARα and PPARγ ligands reduce the influx of inflammatory cells, cytokine and mucus production, collagen deposition, and airways hyperresponsiveness. The activity profiles of PPAR ligands differ to corticosteroids, supporting the hypothesis that PPARs comprise additional therapeutic targets to mimimise the contribution of inflammation to airway remodelling and dysfunction.

MicroRNA profiling of cystic fibrosis intestinal disease in mice

Cystic fibrosis (CF) intestinal disease is characterized by alterations in processes such as proliferation and apoptosis which are known to be regulated in part by microRNAs. Herein, we completed microRNA expression profiling of the intestinal tissue from the cystic fibrosis mouse model of cystic fibrosis transmembrane conductance regulator (Cftr) deficient mice (BALBc/J Cftr(tm1UNC)), relative to that of wildtype littermates, to determine whether changes in microRNA expression level are part of this phenotype. We identified 24 microRNAs to be significantly differentially expressed in tissue from CF mice compared to wildtype, with the higher expression in tissue from CF mice. These data were confirmed with real time PCR measurements. A comparison of the list of genes previously reported to have decreased expression in the BALB×C57BL/6J F2 CF intestine to that of genes putatively targeted by the 24 microRNAs, determined from target prediction software, revealed 155 of the 759 genes of the expression profile (20.4%) to overlap with predicted targets, which is significantly more than the 100 genes expected by chance (p=1×10(-8)). Pathway analysis identified these common genes to function in phosphatase and tensin homolog-, protein kinase A-, phosphoinositide-3 kinase/Akt- and peroxisome proliferator-activated receptor alpha/retinoid X receptor alpha signaling pathways, among others, and through real time PCR experiments genes of these pathways were demonstrated to have lower expression in the BALB CF intestine. We conclude that altered microRNA expression is a feature which putatively influences both metabolic abnormalities and the altered tissue homeostasis component of CF intestinal disease.

High-Dose Ibuprofen in Cystic Fibrosis

Cystic Fibrosis (CF) is the most common lethal genetic disorder in North America and Europe. Most patients succumb to progressive lung disease characterized by an exaggerated neutrophilic inflammation. In animal models of chronic infection, high-dose ibuprofen was demonstrated to reduce inflammation without hindering bacterial clearance. This led to two clinical trials, which demonstrated a benefit in slowing the progression of lung disease in CF. However, concerns about potential adverse effects have limited the use of high-dose ibuprofen in CF patients. There are a variety of potential mechanisms to account for the observed clinical benefit. A better understanding of these mechanisms could potentially lead to more targeted and better-tolerated anti-inflammatory therapies.

N-Acylhomoserine lactone-mediated quorum sensing: a twist in the tail and a blow for host immunity

Communication through quorum sensing (QS) enables bacterial populations to coordinate their behavior. Recent work on N-acylhomoserine lactone-mediated QS has revealed that some soil bacteria exploit host-derived substrates to generate an alternative N-substituted homoserine lactone. New light has also been shed on the mechanism by which N-(3-oxo-dodecanoyl)-L-homoserine lactone modulates host inflammatory signaling pathways to promote bacterial survival.

Dislipidemia relacionada à fibrose cística

Esse artigo tem por objetivo rever o conhecimento atual sobre a fisiopatologia, o diagnóstico e a abordagem da dislipidemia relacionada à fibrose cística (DFC). A pesquisa bibliográfica utilizou os bancos de dados Medline e Literatura Latino-Americana e do Caribe em Ciências da Saúde (1987-2007), selecionando os artigos mais relevantes sobre o tema. A DFC é caracterizada por hipertrigliceridemia e/ou hipocolesterolemia e deficiência de ácidos graxos essenciais. Seus principais fatores de risco são: insuficiência pancreática, dieta rica em carboidratos, hepatopatias, estado inflamatório e corticoterapia. Não existem recomendações específicas sobre a triagem, que habitualmente é realizada a partir do diagnóstico e, em intervalos regulares, com maior freqüência, nos indivíduos pertencentes aos grupos de risco. O tratamento inclui: dieta balanceada, reposição de micronutrientes, vitaminas e fibras, além de exercício físico regular de acordo com a tolerância individual. Na grande maioria dos casos, a hipertrigliceridemia da DFC não atinge valores que indiquem o uso de hipolipemiantes. Conclui-se que existem poucos trabalhos na literatura sobre a freqüência, etiologia e manejo da DFC. A recomendações preventivas e terapêuticas para a hipertrigliceridemia são extrapoladas de diretrizes para indivíduos sem fibrose cística. Mais pesquisas são necessárias para investigar a associação da deficiência de ácidos graxos essenciais com a fisiopatologia da fibrose cística. Como a hipertrigliceridemia é um importante fator de risco para doença arterial coronariana, estudos prospectivos irão contribuir para o melhor entendimento da história natural dessa complicação bem como definir maneiras de preveni-la e tratá-la.

Chronic inflammation in the cystic fibrosis lung: alterations in inter- and intracellular signaling

A vicious cycle of airway obstruction, infection, and inflammation continues to cause most of the morbidity and mortality in cystic fibrosis (CF). Mutations that result in decreased expression or function of the membrane Cl(-) channel, cystic fibrosis transmembrane regulator (CFTR), result in a decrease in the volume (and hence the depth) of liquid on the airway surface, impaired ciliary function, and dehydrated glandular secretions. In turn, these abnormalities contribute to a milieu, which promotes chronic infection with a limited but unique spectrum of microorganisms. Defects in CFTR also perturb regulation of several intracellular signaling pathways including signal transducers and activator of transcription, I-kappaB and nuclear factor-kappa B, and low molecular weight GTPases. Together, these abnormalities result in excessive production of NF-kappaB dependent cytokines such as interleukin (IL)-1, tumor necrosis factor (TNF), IL-6, and IL-8. There are decreased responses to interferon gamma and transforming growth factor beta leading to decreased production of iNOS and NO. Abnormalities of lipid mediators and decreased secretion of counter/regulatory cytokines have also been reported. Together, these effects combine to create a chronic inflammatory process, which damages and obstructs the airways, and eventually claims the life of the patient.

Regulation of peroxisome proliferator-activated receptor-α 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.

Fatty acid alterations and n-3 fatty acid supplementation in cystic fibrosis

Specific fatty acid alterations have been described in the blood and tissues of cystic fibrosis (CF) patients. The two most consistent alterations include decreased levels of linoleic acid (LA) and decreased levels of docosahexaenoic acid (DHA). Increased arachidonic acid (AA) release from membrane phospholipids, as well as changes in levels of AA and other monounsaturated and polyunsaturated fatty acids (PUFAs) have also been described in CF. Although mechanisms of fatty acid alterations have not yet been determined, these alterations may have an important role in the progression of the CF disease. There have been several clinical trials in which CF patients were supplemented with n-3 fatty acids. Most trials resulted in an increase in the levels of the supplemental fatty acids in the blood of CF patients in the absence of significant clinical improvement. It is recommended that future trials include a larger population of CF patients and measure multiple clinical outcomes.

PPARalpha ligands reduce PCB-induced endothelial activation: possible interactions in inflammation and atherosclerosis

Exposure to polychlorinated biphenyls (PCBs) can activate inflammatory responses in vascular endothelial cells. Activation of peroxisome proliferator-activated receptors (PPARs) by nutrients or synthetic agonists has been shown to block pro-inflammatory responses both in vitro and in vivo. Here we demonstrate that activation of PPARalpha by synthetic agonists can reduce 3,3'4,4'-tetrachlorobiphenyl (PCB77)-induced endothelial cell activation. Primary vascular endothelial cells were pretreated with the PPARalpha ligands fenofibrate or WY14643 followed by exposure to PCB77. PPARalpha activation protected endothelial cells against PCB77-induced expression of the pro-inflammatory proteins vascular cell adhesion molecule-1 (VCAM-1), cycloxygenase-2 (COX-2), and PCB77-induced expression and activity of the aryl hydrocarbon receptor (AHR) responsive cytochrome P450 1A1 (CYP1A1). Furthermore, basal AHR expression was downregulated by fenofibrate and WY14643. We also investigated the possible interactions between PCBs, and basal PPAR activity and protein expression. Treatment with PCB77 significantly reduced basal mRNA expression of PPARalpha and the PPAR responsive gene CYP4A1, as well as PPARalpha protein expression. Also, PCB77 exposure caused a significant decrease in basal PPAR-dependent reporter gene expression in MCF-7 cells. Overall, these findings suggest that PPARalpha agonists can reduce PCB77 induction of endothelial cell activation by inhibition of the AHR pathway, and that coplanar PCB induced pro-inflammatory effects could be mediated, in part, by inhibition of PPARalpha expression and function.