A novel mechanism of retinoic acid-enhanced interleukin-8 gene expression in airway epithelium

IL-8 (CXCL8) Correlations with Psychoneuroimmunological Processes and Neuropsychiatric Conditions

Interleukin-8 (IL-8/CXCL8), an essential CXC chemokine, significantly influences psychoneuroimmunological processes and affects neurological and psychiatric health. It exerts a profound effect on immune cell activation and brain function, suggesting potential roles in both neuroprotection and neuroinflammation. IL-8 production is stimulated by several factors, including reactive oxygen species (ROS) known to promote inflammation and disease progression. Additionally, CXCL8 gene polymorphisms can alter IL-8 production, leading to potential differences in disease susceptibility, progression, and severity across populations. IL-8 levels vary among neuropsychiatric conditions, demonstrating sensitivity to psychosocial stressors and disease severity. IL-8 can be detected in blood circulation, cerebrospinal fluid (CSF), and urine, making it a promising candidate for a broad-spectrum biomarker. This review highlights the need for further research on the diverse effects of IL-8 and the associated implications for personalized medicine. A thorough understanding of its complex role could lead to the development of more effective and personalized treatment strategies for neuropsychiatric conditions.

ALDH1A1 overexpression in melanoma cells promotes tumor angiogenesis by activating the IL‑8/Notch signaling cascade

ALDH1A1 is a cytosolic enzyme upregulated in tumor cells, involved in detoxifying cells from reactive aldehydes and in acquiring resistance to chemotherapeutic drugs. Its expression correlates with poor clinical outcomes in a number of cancers, including melanoma. The present study hypothesized that the increased ALDH1A1 expression and activity upregulated the release of proangiogenic factors from melanoma cells, which regulate angiogenic features in endothelial cells (ECs) through a rearrangement of the Notch pathway. In vivo, when subcutaneously implanted in immunodeficient mice, ALDH1A1 overexpressing melanoma cells displayed a higher microvessel density. In a 3D multicellular system, obtained co‑culturing melanoma cancer cells with stromal cells, including ECs, melanoma ALDH1A1 overexpression induced the recruitment of ECs into the core of the tumorspheres. By using a genes array, overexpression of ALDH1A1 in tumor cells also promoted modulation of Notch cascade gene expression in ECs, suggesting an interaction between tumor cells and ECs mediated by enrichment of angiogenic factors in the tumor microenvironment. To confirm this hypothesis, inactivation of ALDH1A1 by the pharmacological inhibitor CM037 significantly affected the release of angiogenic factors, including IL‑8, from melanoma cells. High levels of ALDH1A1, through the retinoic acid pathway, regulated the activation of NF‑kB‑p65 and IL‑8. Further, in a 2D co‑culture system, the addition of an IL‑8 neutralizing antibody to ECs co‑cultured with melanoma cells forced to express ALDH1A1 dampened endothelial angiogenic features, both at the molecular (in terms of gene and protein expression of mediators of the Notch pathway) and at the functional level (proliferation, scratch assay, tube formation and permeability). In conclusion, these findings demonstrated the existence of a link between melanoma ALDH1A1 expression and EC Notch signaling modification that results in a pro‑angiogenic phenotype. Based on the crucial role of ALDH1A1 in melanoma control of the tumor microenvironment, the enzyme seems a promising target for the development of novel drugs able to interrupt the cross‑talk between cancer (stem) cells and endothelial cells.

Effects of oral ısotretinoin on normal and wounded nasal mucosa: an experimental study

BACKGROUND

We aimed to investigate the effect of systemic isotretinoin therapy on normal and wounded nasal septal mucosa histopathologically in an experimental rabbit model.

METHODS

Circular mucosal defect with a 7 mm diameter was made in the left septum of 12 New Zealand white rabbits. The rabbits were divided into two groups (six rabbits in each group) oral isotretinoin was given with olive oil at the operation day to the first group. The control group was only oil given group. The harvested septum mucosas were divided into four groups (1-wounded-drug given side, 2-unwounded and drug-given side, 3-wounded-control and 4-unwounded-control side). The diameter of the defect, mucosal thickness, epithelial thickness, ciliated cell level, goblet cell level and inflammation were evaluated every week for 4 weeks.

RESULTS

At both wounded and normal side, thinning of normal respiratory ciliated epithelium was observed in the postoperative period. In study group at the wounded side; mean mucosal thickness was measured 139.66 µ (± 26.24), and in the control group, mean mucosal thickness was 238.33 µ (± 39.7) at the wounded side. (p < 0.001). The difference between the groups in thickness of normal septal mucosa was also statistically significant (p = 0.016) [190 µ (± 14.6) and 256.66 µ (± 44.66)]. The average cilia level was observed 1.16 in the wounded study group, while the average level was 2.33 in the wounded control group (p = 0.012). Average score measurements of the regenerated mucosa suggested that isotretinoin-given wounded animals have reduced goblet cell recovery, compared to the control both on the regenerated and unwounded mucosas (p = 0.007, p = 0.002, respectively). Inflammation was significantly higher in the wounded isotretinoin group (p = 0.018).

CONCLUSION

Oral isotretinoin has negative effects on epithelial and ciliary regeneration, significantly reduces mucosal thickness and goblet cell counts of the normal and regenerated mucosa, causes severe inflammation and significant reactive changes.

The dual nature of retinoic acid in pemphigus and its therapeutic potential: Special focus on all-trans Retinoic Acid

The efficient treatment of pemphigus with no certain side effect remained a controversial issue. Although there are various options for controlling disease severity, the majority of them may cause serious side effects. Retinoic acid (RA), an active metabolite converted from vitamin A, plays an active role in immune functions. Effects of RA, especially all-trans-Retinoic Acid (ATRA) on different types of cells involved in immune responses were analyzed in vitro and in vivo. RAs could affect the differentiation of T helper (Th) cells, B cells responses, stabilization of both natural regulatory T cells (nTregs) and regulatory B cells (Bregs) populations, and regulating the expression of critical genes in immune responses. The role of RA, based on major immune cells involved in pemphigus has not been addressed so far. In this study, we sought to determine the possible effects of RA, with a special focus on ATRA in pemphigus. All the evidences of ATRA effects on the immune system were collected and their association with the pemphigus was analyzed. According to the previous results, ATRA causes a decline in Th17 populations; increase in CD4+ induced regulatory T cells (iTregs), stabilization of nTregs, and promotion of suppressive B cells, which are critical in the improvement of pemphigus. Nevertheless, it also causes shifting of the Th1:Th2 balance toward Th2 cells, which is not favorable for pemphigus patients. In conclusion, ATRA acts via different ways in pemphigus. Due to increase in the suppressive function via iTregs, nTregs, and Bregs, it is suggested that patients with pemphigus may benefit from systemic ATRA therapy. To clarify this issue, further studies, such as clinical trials are needed.

Respiratory syncytial virus interaction with human airway epithelium

Although respiratory syncytial virus (RSV) is a major human respiratory pathogen, our knowledge of how it causes disease in humans is limited. Airway epithelial cells are the primary targets of RSV infection in vivo, so the generation and exploitation of RSV infection models based on morphologically and physiologically authentic well-differentiated primary human airway epithelial cells cultured at an air-liquid interface (WD-PAECs) provide timely developments that will help to bridge this gap. Here we review the interaction of RSV with WD-PAEC cultures, the authenticity of the RSV-WD-PAEC models relative to RSV infection of human airway epithelium in vivo, and future directions for their exploitation in our quest to understand RSV pathogenesis in humans.

Differential cytopathogenesis of respiratory syncytial virus prototypic and clinical isolates in primary pediatric bronchial epithelial cells

Background

Human respiratory syncytial virus (RSV) causes severe respiratory disease in infants. Airway epithelial cells are the principle targets of RSV infection. However, the mechanisms by which it causes disease are poorly understood. Most RSV pathogenesis data are derived using laboratory-adapted prototypic strains. We hypothesized that such strains may be poorly representative of recent clinical isolates in terms of virus/host interactions in primary human bronchial epithelial cells (PBECs).

Methods

To address this hypothesis, we isolated three RSV strains from infants hospitalized with bronchiolitis and compared them with the prototypic RSV A2 in terms of cytopathology, virus growth kinetics and chemokine secretion in infected PBEC monolayers.

Results

RSV A2 rapidly obliterated the PBECs, whereas the clinical isolates caused much less cytopathology. Concomitantly, RSV A2 also grew faster and to higher titers in PBECs. Furthermore, dramatically increased secretion of IP-10 and RANTES was evident following A2 infection compared with the clinical isolates.

Conclusions

The prototypic RSV strain A2 is poorly representative of recent clinical isolates in terms of cytopathogenicity, viral growth kinetics and pro-inflammatory responses induced following infection of PBEC monolayers. Thus, the choice of RSV strain may have important implications for future RSV pathogenesis studies.

Advances in understanding the pulmonary infiltration in acute promyelocytic leukaemia

In acute promyelocytic leukaemia (APL), differentiation therapy can be complicated by the development of a differentiation syndrome (DS). Pulmonary infiltration of differentiating leukaemic cells is a key event in the development of DS. Several mediators have been identified that may promote migration and extravasation of differentiating APL cells from the bloodstream into the tissue. Adhesion of APL cells to each other and to the endothelium is induced by upregulation of the expression of adhesion molecules and constitutively active β2-integrins during differentiation therapy. The expression of chemokines and their receptors is significantly upregulated as well. Pulmonary chemokine production can trigger transendothelial migration of differentiating APL cells from the bloodstream into the underlying tissue (initiation phase of DS). Massive production of chemokines by infiltrated APL cells can further enhance transendothelial migration of differentiating APL cells, causing an uncontrollable hyperinflammatory reaction in the lung (aggravation phase), which is not efficiently switched-off by corticosteroids.

Vitamin-regulated cytokines and growth factors in the CNS and elsewhere

There is a growing awareness that natural vitamins (with the only exception of pantothenic acid) positively or negatively modulate the synthesis of some cytokines and growth factors in the CNS, and various mammalian cells and organs. As natural vitamins are micronutrients in the human diet, studying their effects can be considered a part of nutritional genomics or nutrigenomics. A given vitamin selectively modifies the synthesis of only a few cytokines and/or growth factors, although the same cytokine and/or growth factor may be regulated by more than one vitamin. These effects seem to be independent of the effects of vitamins as coenzymes and/or reducing agents, and seem to occur mainly at genomic and/or epigenetic level, and/or by modulating NF-kappaB activity. Although most of the studies reviewed here have been based on cultured cell lines, but their findings have been confirmed by some key in vivo studies. The CNS seems to be particularly involved and is severely affected by most avitaminoses, especially in the case of vitamin B(12). However, the vitamin-induced changes in cytokine and growth factor synthesis may initiate a cascade of events that can affect the function, differentiation, and morphology of the cells and/or structures not only in the CNS, but also elsewhere because most natural vitamins, cytokines, and growth factors cross the blood-brain barrier. As cytokines are essential to CNS-immune and CNS-hormone system communications, natural vitamins also interact with these circuits. Further studies of such vitamin-mediated effects could lead to vitamins being used for the treatment of diseases which, although not true avitaminoses, involve an imbalance in cytokine and/or growth factor synthesis.

Retinoic acid prevents virus-induced airway hyperreactivity and M2 receptor dysfunction via anti-inflammatory and antiviral effects

Inhibitory M(2) muscarinic receptors on airway parasympathetic nerves normally limit acetylcholine release. Viral infections decrease M(2) receptor function, increasing vagally mediated bronchoconstriction. Since retinoic acid deficiency causes M(2) receptor dysfunction, we tested whether retinoic acid would prevent virus-induced airway hyperreactivity and prevent M(2) receptor dysfunction. Guinea pigs infected with parainfluenza virus were hyperreactive to electrical stimulation of the vagus nerves, but not to intravenous acetylcholine, indicating that hyperreactivity was due to increased release of acetylcholine from parasympathetic nerves. The muscarinic agonist pilocarpine, which inhibits vagally mediated bronchoconstriction in control animals, no longer inhibited vagally induced bronchoconstriction, demonstrating M(2) receptor dysfunction. Treatment with all-trans retinoic acid (1 mg/kg) prevented virus-induced hyperreactivity and M(2) receptor dysfunction. However, retinoic acid also significantly reduced viral titers in the lungs and attenuated virus-induced lung inflammation. In vitro, retinoic acid decreased M(2) receptor mRNA expression in both human neuroblastoma cells and primary cultures of airway parasympathetic neurons. Thus, the protective effects of retinoic acid on airway function during viral infection appear to be due to anti-inflammatory and antiviral mechanisms, rather than to direct effects on M(2) receptor gene expression.

The non-human primate as a model for studying COPD and asthma

This review evaluates the current status of information regarding the nonhuman primate as an experimental model for defining mechanisms of chronic airways disease in humans, using the concept of the epithelial-mesenchymal trophic unit (EMTU) as a basis for comparison with other laboratory species. All of the cellular and acellular compartments within the walls of tracheobronchial airways which interact as the EMTU are present throughout the airway tree in human and nonhuman primates. The epithelial compartment contains mucous goblet and basal cells in the surface epithelium and submucosal glands within the wall. The interstitial compartment of primates has a prominent subepithelial basement membrane zone (BMZ) with an attenuated fibroblast sheath and cartilage throughout the tree. In primates, there is an extensive transition zone between distal conducting airways and lung parenchyma composed of numerous generations of respiratory bronchioles. None of these features are characteristic of intrapulmonary airways in rodents, whose airways do share ciliated cells, smooth muscle cells, nerve networks, vasculature and inflammatory cell populations with primates. While the numbers of intrapulmonary airway branches are similar for most mammals, branching patterns, which dictate distribution of inhaled materials, are more uniform (dichotomous) in primates and less so (monopodial) in rodents. Development of tracheobronchial airways (both differentiation of the EMTU and overall growth) occurs over an extensive postnatal period (months to years) in primates and a comparably shorter time period (2-3 weeks) in rodents. As with allergic airways disease in humans, experimental exposure of nonhuman primates to a known human allergen, house dust mite, produces extensive remodeling of all compartments of the EMTU: mucous goblet cell hyperplasia, epithelial sloughing, basement membrane zone (BMZ) thickening and reorganization, altered attenuated fibroblast function, subepithelial fibrosis and smooth muscle thickening. Experimental allergic airways disease in nonhuman primates also shares other features with asthmatic humans: positive skin test to allergen; allergen-specific circulating IgE; airway hyper responsiveness to allergen, histamine and methacholine; increased eosinophils, IGE positive cells and mucins in airway exudate; and migratory leukocyte accumulations in the airway wall and lumen. Experimental exposure of nonhuman primates to reactive gases, such as ozone, produces the chronic respiratory bronchiolitis and other airway alterations associated with restricted airflow and chronic respiratory bronchiolitis characteristic of COPD in young smokers. We conclude that nonhuman primate models are appropriate for defining mechanisms as they relate to allergic airways disease and COPD in humans.

Interleukin-17A modulates human airway epithelial responses to human rhinovirus infection

Human rhinovirus (HRV) infections are associated with exacerbations of asthma and chronic obstructive pulmonary disease that are characterized by a selective neutrophil infiltration. IL-17A, a cytokine derived primarily from activated T cells, has been linked to neutrophilic inflammation of the airways. We hypothesized that IL-17A alters the response of HRV-infected epithelial cells to modulate airway inflammatory cell populations. IL-17A synergistically enhanced HRV-16-induced epithelial production of the neutrophil chemoattractant, IL-8, as well as human beta-defensin-2 (HBD-2), a chemoattractant for immature dendritic cells and memory T cells, but suppressed viral production of the eosinophil chemoattractant, RANTES. These effects were not due to alterations of viral uptake or replication by IL-17A. The synergy between HRV-16 and IL-17A for IL-8 protein production was both dose- and time-dependent. IL-8 induction by IL-17A or HRV-16, alone and in combination, was reduced by inhibitors of the p38 and p44/42 MAPK pathways. By contrast, induction of HBD-2 depended on the activation of the p38 and JNK pathways. The ability of IL-17A to synergistically enhance HRV-induced IL-8 is mediated posttranscriptionally, since IL-8 promoter activation by the combination of the two stimuli was merely additive, whereas the combination of IL-17A and HRV-16 led to stabilization of IL-8 mRNA. Similarly, stimulation of HBD-2 promoter constructs by the combination of IL-17A and HRV-16 was no more than the sum of the individual responses. Further studies are needed to examine HBD-2 mRNA stability. Taken together, these data represent the first demonstration that IL-17A can modify epithelial responses to HRV in a manner that would be expected to favor the recruitment of neutrophils, immature dendritic cells, and memory T cells to the airways.

Role of interleukin-8 and growth-regulated oncogene-α in the chemotactic migration of all-trans retinoic acid-treated promyelocytic leukemic cells toward alveolar epithelial cells*

OBJECTIVE

Although all-trans retinoic acid (ATRA) can treat acute promyelocytic leukemia (APL), it also causes retinoic acid syndrome with presentations similar to acute respiratory distress syndrome. We investigated the role of interleukin (IL)-8 and growth-regulated oncogene (GRO)-alpha in the chemotactic transmigration of ATRA-treated NB4 (ATRA-NB4) APL cells toward A549 alveolar epithelial cells.

DESIGN

An in vitro human cell culture study.

SETTING

University hospital research laboratories.

SUBJECTS

NB4 and A549 cells.

INTERVENTIONS

NB4 and A549 cells were separately cultured with ATRA and/or dexamethasone for 1-3 days. NB4 or ATRA-NB4 cells were then placed in an upper insert and co-incubated with A549 cells or their conditioned medium located in a lower plate.

MEASUREMENTS AND MAIN RESULTS

ATRA stimulated NB4 cells to transmigrate toward the A549 cells in a time- and dose-dependent manner. Replacement of A459 condition medium by its original medium abrogated this transmigration. Only A549 cells constitutively secreted GRO-alpha, and both A549 and NB4 cells constitutively secreted IL-8, which was enhanced by ATRA. Exogenous administration of IL-8 or GRO-alpha also promoted the ATRA-NB4 transmigration. The binding assay demonstrated that ATRA-NB4 cells bound IL-8, but not GRO-alpha, more avidly. Pretreatment with antibodies directed against IL-8 and GRO-alpha receptors reduced ATRA-NB4 transmigration by about 60%. Dexamethasone did not suppress their IL-8 secretion and transmigration in ATRA-NB4 cells, but when applied to A549 cells, IL-8 secretion was suppressed but not GRO-alpha secretion, and there was attenuation of ATRA-NB4 transmigration.

CONCLUSIONS

IL-8 and GRO-alpha secreted from alveolar epithelial cells play an important role in the cell-cell interaction involved in the chemotactic transmigration of ATRA-treated APL cells toward alveolar epithelial cells.

Cell culture models of the respiratory tract relevant to pulmonary drug delivery

The respiratory tract holds promise as an alternative site of drug delivery due to fast absorption and rapid onset of drug action, with avoidance of hepatic and intestinal first-pass metabolism as an additional benefit compared to oral drug delivery. At present, the pharmaceutical industry increasingly relies on appropriate in vitro models for the faster evaluation of drug absorption and metabolism as an alternative to animal testing. This article reviews the various existing cell culture systems that may be applied as in vitro models of the human air-blood barrier, for instance, in order to enable the screening of large numbers of new drug candidates at low cost with high reliability and within a short time span. Apart from such screening, cell culture-based in vitro systems may also contribute to improve our understanding of the mechanisms of drug transport across such epithelial tissues, and the mechanisms of action how advanced drug carriers, such as nanoparticles or liposomes, can help to overcome these barriers. After all, the increasing use and acceptance of such in vitro models may lead to a significant acceleration of the drug development process by facilitating the progress into clinical studies and product registration.

All-trans-retinoic acid induces interleukin-8 via the nuclear factor-kappaB and p38 mitogen-activated protein kinase pathways in normal human keratinocytes

Retinoic acid derivatives have been used successfully for the treatment of various dermatoses, such as psoriasis; however, topical application of these compounds often elicits skin irritation. We hypothesized that this irritation was as a result of the local production of interleukin-8 (IL-8). To test this hypothesis, we investigated whether all-trans-retinoic acid (ATRA) induced IL-8 production in normal human keratinocytes. Stimulation with 10(-7) M ATRA enhanced IL-8 mRNA expression and induced IL-8 production. We also studied the intracellular signaling mechanisms of ATRA-induced IL-8 production in keratinocytes. ATRA increased the expression of RelA (p65), RelB, nuclear factor (NF)-kappaB2 (p52), and NF-kappaB1 (p50), and elevated the DNA-binding activity of p65 and phosphorylation of inhibitor kappaB (IkappaB) alpha. Introduction of a dominant-negative mutant of IkappaBalpha completely abolished ATRA-induced IL-8 production, which indicates that this process is NF-kappaB-dependent. We also studied the role of the p38 mitogen-activated protein kinase (MAPK) pathway in this phenomenon. ATRA phosphorylated the p38 MAPK, and SB202180 inhibited ATRA-induced IL-8 production, which indicates that the p38 MAPK is also involved in ATRA-induced IL-8 production. In summary, ATRA induces IL-8 production in both NF-kappaB- and p38 MAPK-dependent manners in normal human keratinocytes.

Retinoids in nephrology: Promises and pitfalls

BACKGROUND

Retinoids, a family of vitamin A metabolites or analogs, play an important role in regulating cell proliferation, differentiation, and apoptosis.

METHODS

The biological importance of retinoids in the kidney and the potential of retinoids in the treatment of renal diseases are reviewed.

RESULTS

Vitamin A deficiency and mutations of retinoid nuclear receptors cause abnormalities in fetal kidneys, which might predispose to adult diseases such as hypertension. Further, the therapeutic value of retinoids in animal models of kidney diseases, such as lupus nephritis, puromycin aminonucleoside nephrosis, anti-glomerular basement membrane nephritis, mesangioproliferative nephritis, and acute renal allograft rejection has been unveiled recently. Retinoids target mesangial cells, podocytes, tubular epithelial cells, interstitial fibroblasts, as well as lymphocytes and macrophages. The anti-inflammation, anti-coagulation effects, and the proliferation- and immunity-modulating actions of retinoids, have been widely appreciated. Our recent in vitro data revealed a direct antifibrotic effect and a cytoprotective effect of retinoids in various renal cell types. In animal studies, the adverse effects of retinoids are generally minimal; however, the clinical use of retinoids in other diseases points to some major side effects. In addition, in vitro, retinoids can induce lipid accumulation in smooth muscle cells and macrophages and increase expression of some proinflammatory molecules, indicating that their clinical toxicity profile in the setting of renal diseases needs to be better understood.

CONCLUSION

Retinoids not only are important in renal development, but also show promise as a new generation of renal medication and deserve to be tested in clinical trials to clarify their full potential.

Oxidant-injured airway epithelial cells upregulate thioredoxin but do not produce interleukin-8

We tested the hypothesis that oxidant-injured cells upregulate thioredoxin, whereas oxidant-stressed, but not injured, cells upregulate interleukin (IL)-8 after injury. We exposed primary human tracheobronchial epithelial cells and transformed human bronchial epithelial cells (BEAS-2B S.6) to 0, 200, 400, or 600 microM H(2)O(2) for 1 h followed by an additional 7 h of incubation. Subsequently, the cells were double-labeled with markers of injury (either Ethidium Homodimer-1 for cellular injury or MitoTracker dye for functional mitochondria) or oxidant stress (5-[and 6]-chloromethyl-2',7'-dicholorodihydrofluorescein diacetate) and antibodies specific for the chemoattractants IL-8 or thioredoxin. We found significant inverse relationships between numbers and stained chemoattractant volumes of IL-8 and thioredoxin-positive cells with increasing H(2)O(2) dose. Cells with mitochondrial injury produced thioredoxin but not IL-8, and oxidant-stressed cells were more likely to produce thioredoxin than IL-8. Isolated human neutrophils were more likely to colocalize with thioredoxin-positive BEAS-2B S.6 cells than thioredoxin-negative cells. The H(2)O(2) injury did not induce significant apoptosis in the BEAS-2B S.6 cells as measured by caspase 3 activation. We conclude that oxidant-injured and stressed airway epithelial cells upregulate thioredoxin, but produce little IL-8, which may be important in airway epithelial cell-mediated multistep navigation of neutrophils to sites of oxidant injury.

Retinoic acid inhibits interleukin-4-induced eotaxin production in a human bronchial epithelial cell line

Retinoic acid (RA) is known to accelerate wound healing and induce cell differentiation. All- trans RA (ATRA) exerts its effect by binding retinoic acid receptors, which are members of the nuclear receptor family. We investigated whether RA can alter expression of eotaxin, a potent eosinophil chemoattractant that is regulated by the transcription factors signal transducer and activator of transcription 6 (STAT6) and NF-κB. We examined the effects of RA on eotaxin expression in a human bronchial epithelial cell line BEAS-2B. ATRA and its stereodimer 9- cis retinoic acid (9- cis RA) inhibited IL-4-induced release of eotaxin at 10-6M by 78.0 and 52.0%, respectively ( P < 0.05). ATRA and 9- cis RA also significantly inhibited IL-4-induced eotaxin mRNA expression at 10-6M by 52.3 and 53.5%, respectively ( P < 0.05). In contrast, neither ATRA nor 9- cis RA had any effects on TNF-α-induced eotaxin production. In transfection studies using eotaxin promoter luciferase plasmids, the inhibitory effect of ATRA on IL-4-induced eotaxin production was confirmed at the transcriptional level. Interestingly, ATRA had no effects on IL-4-induced tyrosine phosphorylation, nuclear translocation, or DNA binding activity of STAT6. Activating protein-1 was not involved in ATRA-mediated transrepression of eotaxin with IL-4 stimulation. The mechanism of the inhibitory effect of ATRA on IL-4-induced eotaxin production in human bronchial epithelial cells has not been elucidated but does not appear to be due to an effect on STAT6 activation. These findings raise the possibility that RA may reduce eosinophilic airway inflammation, one of the prominent pathological features of allergic diseases such as bronchial asthma.

Retinoic acid fails to reverse emphysema in adult mouse models

BACKGROUND

Previous work has shown that all-trans-retinoic acid reverses elastase induced emphysema in rats. Since there is currently no effective treatment for pulmonary emphysema, the effect of retinoic acid should be further investigated in other adult species. A study was undertaken using two murine models of emphysema to evaluate the effect of retinoic acid.

METHODS

The models used were an elastase induced emphysema model for acute alveolar destruction and a tumour necrosis factor (TNF)-alpha transgenic mouse which exhibits chronic air space enlargement, loss of elastic recoil, increased lung volume, and pulmonary hypertension comparable to human pulmonary emphysema. All-trans-retinoic acid (2 mg/kg) was injected for 12 successive days after the establishment of emphysema. The effects of treatment were evaluated using physiological and morphometric analyses.

RESULTS

In contrast to the rat, administration of all-trans-retinoic acid in these murine models did not improve the emphysema. Moreover, worsening of emphysema was observed in TNF-alpha transgenic mice treated with all-trans-retinoic acid. The level of keratinocyte chemoattractant (KC), a CXC chemokine, in bronchoalveolar lavage fluid was increased in TNF-alpha transgenic mice following retinoic acid treatment. These data raise the possibility that retinoic acid causes deterioration of emphysema by promoting inflammation in this model.

CONCLUSIONS

In these models, retinoic acid did not show positive effects on emphysema. The effect of retinoic acid in the treatment of pulmonary emphysema remains controversial, and further studies are required to determine its physiological effects under a variety of experimental conditions.

Retinoic acid syndrome in NOD/scid mice induced by injecting an acute promyelocytic leukemia cell line

All-trans retinoic acid (ATRA) induces complete remission in patients with acute promyelocytic leukemia (APL). However, ATRA sometimes causes retinoic acid syndrome (RAS) characterized by respiratory distress, pleural effusions, fever and weight gain. To investigate the pathophysiology of RAS, we generated an animal model by injecting an APL cell line, NB4, into immunodeficient mice. When NOD/scid mice were injected intravenously with fully differentiated NB4 cells (1 x 10(7)) and then given a daily administration of ATRA, three of 12 mice died of pulmonary edema within 14 days. Pathologically, dilated lung capillary vessels and alveolar effusions were observed. After the injection, NB4 cells were detected in the lung within 2 days and in the pleural effusion later on. The gene expression levels of CXC chemokines (MIP-2 and KC) and ICAM-1 were increased in the lung and heart by the ATRA administration. In immunohistochemical analyses, MIP-2 was clearly detected in alveolar macrophages of the lung in mice with RAS. Dexamethasone treatment prevented the development of RAS and decreased the CXC chemokine mRNA expression in the lung. These findings suggested that the activation of adhesion molecules for leukocytes and expression of CXC chemokines in the lung are closely involved in triggering RAS.

Up-regulated caveolin-1 accentuates the metastasis capability of lung adenocarcinoma by inducing filopodia formation

Caveolin-1, a 21- to 24-kd integral membrane protein, is primarily implicated as a tumor suppressor gene. Transformed cells normally contain reduced or no caveolin-1. Re-expression of caveolin-1 is found in advanced human and mouse prostate adenocarcinomas. To explore its potential role in tumorigenesis and tumor progression of human lung cancers, we used the well-characterized cell line (CL) series of lung adenocarcinoma cells with increasing cellular invasiveness to show that expression of caveolin-1 mRNA and protein was up-regulated with enhanced invasion/metastatic capability of CL cells. Reintroducing the caveolin-1 gene into the less invasive, caveolin-1-negative CL cells enhanced their invasive capability at least by twofold, as revealed by an in vitro chamber invasion assay. Thus, a correlation exists for both constitutive and induced expression of caveolin-1 in CL cells. Immunohistochemical examination of caveolin-1 was performed in 95 specimens obtained retrospectively from patients who had lung adenocarcinoma either with (35 patients) or without (60 patients) ipsilateral hilar/peribronchial tumor-metastasized lymph nodes. Caveolin-1 immunoreactivity was either totally absent or just barely detectable in a few lung adenocarcinoma cells from cases diagnosed as lung adenocarcinoma without regional lymph node metastasis. In contrast, increased caveolin-1 immunoreactivity both in number and intensity was detected in primary lung adenocarcinoma cells as well as in cancer cells that metastasized to regional lymph nodes from the cases diagnosed as advanced lung adenocarcinoma with nodal metastases. Multivariate analysis considering caveolin-1 immunoreactivity in addition to the established prognostic parameters such as pT stage, pN in these patients confirmed that caveolin-1 is an independent functional predictor of poor survival. We further revealed that up-regulated caveolin-1 in CL cells is necessary for mediating filopodia formation, which may enhance the invasive ability of lung adenocarcinoma cells.

BMK1 (ERK5) regulates squamous differentiation marker SPRR1B transcription in Clara-like H441 cells

Various toxicants and carcinogens upregulate the expression of small proline-rich protein 1B (SPRR1B), a squamous differentiation marker, in bronchial epithelial cells both in vivo and in vitro. We have recently shown that phorbol 13-myristate 12-acetate (PMA)-stimulated SPRR1B transcription in Clara-like H441 cells is mainly mediated by activator protein-1 (AP-1) and c-Jun N-terminal kinase-1 (JNK1). Though mitogen-activated protein kinase (MAPK) kinase (MEK)-1/2 pathway inhibitors strongly suppressed both basal and PMA-inducible SPRR1B transcription, overexpression of dominant negative (dn) forms of extracellular signal-regulated kinase (ERK)-1 and/or -2 did not have any significant effect indicating the involvement of another ERK-like MAPK in this pathway. Here, we report for the first time the involvement of ERK5 in PMA-inducible SPRR1B transcription in H441 cells. PMA significantly induced ERK5 activation in H441 cells. Overexpression of dn-ERK5 strongly suppressed both basal and PMA-inducible SPRR1B transcription, whereas wild-type ERK5 upregulated it. Consistent with this, a mutant form of MEK-5, an upstream activator of ERK5, strongly suppressed PMA-inducible promoter activity. However, coexpression of c-Jun restored promoter activation suppressed by dn-ERK5. Thus, in addition to JNK1, the activation of MEK5-ERK5 MAPK pathway probably plays a pivotal role in transcriptional regulation of AP-1-mediated SPRR1B expression in the distal bronchiolar region.

Regulation of thioredoxin gene expression by vitamin A in human airway epithelial cells

Human thioredoxin (Trx) is a 12-kD protein known to be involved in various reduction/oxidation reactions essential for cell growth and cellular injury repair. We previously demonstrated, based on nuclear run-on assay, that retinoic acid (RA) stimulated Trx gene expression in airway epithelial cells at the transcriptional level. Nucleotide sequencing of the 5'-flanking region of the human Trx gene revealed the presence of a TATA box at -28 and four RA response element (RARE)-like half sites at -426, -453, -507, and -626 nt. Transient transfection assays with a Trx promoter-reporter gene, chloramphenicol acetyltransferase (CAT), demonstrated a dose-dependent involvement of these four RARE-like half sites in RA-enhanced promoter activity. When the DNA fragment that flanks these four RARE-like half sites from -357 to -671 nt was introduced into a heterologous promoter of the tk-CAT2 vector, both basal and RA-stimulated CAT activities were observed. A site-directed mutagenesis approach demonstrated an essential role for RARE-I and RARE-II at -426 and -453 nt, respectively, and an auxiliary role for RARE-III at -507 nt in both basal and RA-stimulated CAT activities. Both in vivo and in vitro genomic footprinting experiments further demonstrated specific protein-DNA interactions in these "putative" RARE-I/II/III half sites. Gel electrophoretic mobility shift assays demonstrated specific interactions of these RARE-like half sites with the nuclear extracts obtained from RA-treated cultures. The anti-RAR-alpha antibody super-shift experiment further confirmed the interactions of RARE-I/II sites with RAR-alpha nuclear receptor. These results suggest a classic RARE/RAR interaction involved in RA-stimulated Trx gene expression in human airway epithelium.

Vitamin A, infection, and immune function

In populations where vitamin A availability from food is low, infectious diseases can precipitate vitamin A deficiency by decreasing intake, decreasing absorption, and increasing excretion. Infectious diseases that induce the acute-phase response also impair the assessment of vitamin A status by transiently depressing serum retinol concentrations. Vitamin A deficiency impairs innate immunity by impeding normal regeneration of mucosal barriers damaged by infection, and by diminishing the function of neutrophils, macrophages, and natural killer cells. Vitamin A is also required for adaptive immunity and plays a role in the development of T both-helper (Th) cells and B-cells. In particular, vitamin A deficiency diminishes antibody-mediated responses directed by Th2 cells, although some aspects of Th1-mediated immunity are also diminished. These changes in mucosal epithelial regeneration and immune function presumably account for the increased mortality seen in vitamin A-deficient infants, young children, and pregnant women in many areas of the world today.

Activation of nuclear factor-kappa b transcriptional activity in airway epithelial cells by thioredoxin but not by N-acetyl-cysteine and glutathione

Increasing evidence indicates that intracellular redox status modulates the activity of various transcriptional factors, including nuclear factor (NF)-kappa B and activator protein-1. Our laboratory has been interested in characterizing the role thioredoxin (TRX) plays in regulating cellular redox status in airway epithelium. TRX is a small, ubiquitous protein with two redox-active half-cysteine residues, -Cys-Gly-Pro-Cys, in its active center. Using primary passage-1 human tracheobronchial epithelial cell cultures and an immortalized human bronchial epithelial cell line, HBE1, we observed that tumor necrosis factor (TNF)-alpha enhanced NF-kappa B transcriptional activity. This observation was based on gel mobility shift assays and interleukin (IL)-8 promoter-reporter gene transfection studies. TNF-alpha activation coincided with translocation of NF-kappa B p65 from the cytoplasm to the nucleus. Pretreatment with N-acetyl-cysteine (NAC) (1 to 10 mM) or glutathione (1 to 10 mM) inhibited TNF-alpha-induced activation of NF-kappa B transcriptional activity and IL-8 promoter-mediated reporter gene expression. In contrast, elevated TRX protein levels in cells enhanced TNF-alpha-dependent NF-kappa B transcriptional activity and IL-8 promoter activity. This observation was independent of the manner in which TRX was elevated in cells (e.g., by cotransfection with a FLAG-TRX expression clone, or by direct exposure to commercially available human TRX protein). Localization of TRX protein by anti-TRX antibody indicated an accumulation of TRX protein in the nucleus after TNF-alpha treatment. The nuclear localization phenomenon was different from the major cytosolic accumulation of glutathione and NAC. This is the first known report demonstrating movement of TRX into the nucleus of airway epithelial cells after an inflammatory stress. These results suggest a compartment effect of thiol chemicals in the regulation of redox-dependent transcriptional activity.