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PubMed2002

Implications of circadian gene expression in kidney, liver and the effects of fasting on pharmacogenomic studies.

Pharmacogenomics offers the potential to define metabolic pathways and to provide increased knowledge of drug actions. We studied relative levels of gene expression in the rat using a microarray with 8448 rat UniGenes (1928 known genes, 6520 unknown ESTs) in the liver and kidney as a function of time of day and then of feeding regime, which are common variables in preclinical pharmacogenomic studies. We identified 597 genes, including several key metabolic pathways, whose relative expression levels are significantly affected by time of day: expression of some was further modified by feeding state. These would have sparked interest in a pharmacogenomic study. Our study demonstrates that two common variables in pharmacogenomic studies can have dramatic effects on gene expression. This study provides investigators with baseline information for both kidney and liver with respect to 'normal' changes in gene expression influenced by time of day and feeding state. It also identifies 18 new genes that should be investigated for a role in circadian rhythms in peripheral tissues.

Animals↗
PubMed2000

Signaling from E-cadherins to the MAPK pathway by the recruitment and activation of epidermal growth factor receptors upon cell-cell contact formation.

E-cadherins are well characterized cell surface molecules expressed in epithelial cells, which play a major role in cell adhesion through the establishment of calcium-dependent homophilic interactions at sites of cell-cell contacts. They are also integral components of morphogenetic programs controlling the maintenance of the structural and functional integrity of epithelia. Accumulated evidence indicates that the E-cadherin-mediated cell adhesion system is highly regulated from inside the cells by a number of intracellular signaling pathways. Recently available information suggests that E-cadherins may also play a role in the transduction of signals from the outside of the cell to the cytoplasm. However, the nature of the biochemical routes regulated by E-cadherins is still largely unknown. In this study, we set out to explore the possibility that E-cadherins may regulate the activity of MAPK, a key signaling pathway involved in cell fate decisions, upon the formation of cell-cell contacts among neighboring cells. By using an immortalized non-tumorigenic keratinocyte cell line, HaCat, as a model system, we provide evidence that the assembly of calcium-dependent adherens junctions leads to a rapid and remarkable increase in the state of activation of MAPK and that this event is mediated by E-cadherins. Furthermore, we found that E-cadherins stimulate the MAPK pathway through the ligand-independent activation of epidermal growth factor receptors and the consequent activation of a biochemical route leading to the stimulation of MAPKs. These findings suggest that E-cadherins can initiate outside-in signal transducing pathways through the engagement of tyrosine kinase receptors for epidermal growth factor, thus providing a novel molecular mechanism whereby these cell adhesion molecules may ultimately control the fate of normal and transformed epithelial cells.

Cadherins↗
PubMed2003

A novel pathway for MuSK to induce key genes in neuromuscular synapse formation.

At the developing neuromuscular junction the Agrin receptor MuSK is the central organizer of subsynaptic differentiation induced by Agrin from the nerve. The expression of musk itself is also regulated by the nerve, but the mechanisms involved are not known. Here, we analyzed the activation of a musk promoter reporter construct in muscle fibers in vivo and in cultured myotubes, using transfection of multiple combinations of expression vectors for potential signaling components. We show that neuronal Agrin by activating MuSK regulates the expression of musk via two pathways: the Agrin-induced assembly of muscle-derived neuregulin (NRG)-1/ErbB, the pathway thought to regulate acetylcholine receptor (AChR) expression at the synapse, and via a direct shunt involving Agrin-induced activation of Rac. Both pathways converge onto the same regulatory element in the musk promoter that is also thought to confer synapse-specific expression to AChR subunit genes. In this way, a positive feedback signaling loop is established that maintains musk expression at the synapse when impulse transmission becomes functional. The same pathways are used to regulate synaptic expression of AChR epsilon. We propose that the novel pathway stabilizes the synapse early in development, whereas the NRG/ErbB pathway supports maintenance of the mature synapse.

Agrin↗
PubMed2005

LdpA: a component of the circadian clock senses redox state of the cell.

The endogenous 24-h (circadian) rhythms exhibited by the cyanobacterium Synechococcus elongatus PCC 7942 and other organisms are entrained by a variety of environmental factors. In cyanobacteria, the mechanism that transduces environmental input signals to the central oscillator of the clock is not known. An earlier study identified ldpA as a gene involved in light-dependent modulation of the circadian period, and a candidate member of a clock-entraining input pathway. Here, we report that the LdpA protein is sensitive to the redox state of the cell and exhibits electron paramagnetic resonance spectra consistent with the presence of two Fe4S4 clusters. Moreover, LdpA copurifies with proteins previously shown to be integral parts of the circadian mechanism. We also demonstrate that LdpA affects both the absolute level and light-dependent variation in abundance of CikA, a key input pathway component. The data suggest a novel input pathway to the circadian oscillator in which LdpA is a component of the clock protein complex that senses the redox state of a cell.

Bacterial Proteins↗
PubMed2026

The Health Benefits of Exercise: Molecular and Cellular Mechanisms.

Exercise is a low-cost lifestyle intervention that can prevent and alleviate various diseases. It is a potent physiological stimulus that activates conserved molecular signaling pathways. Through the coordinated integration of multiple molecules, pathways, and systems, it leads to systemic health benefits. However, most studies focus on individual systems or molecular mechanisms, lacking systematic integration of the cross-system regulation induced by exercise. We summarize the molecular mechanisms of exercise in the musculoskeletal, cardiovascular, nervous systems, among others. Exercise induces the release of exerkines (e.g., irisin, interleukin-6, and brain-derived neurotrophic factor) and extracellular vesicles, which activate key signaling pathways to enhance mitochondrial function, metabolism and physiological adaptation, while suppressing inflammation and oxidative stress, thereby alleviating diseases and delaying aging through cross-system coordination. We further explore exercise-induced adaptive regulation in extreme environments, including microgravity, hyperbaria, and hypoxia, offering a multifaceted perspective on organismal health regulation. Finally, we outline the prospects and challenges of multiomics, artificial intelligence-driven precision medicine, personalized exercise prescriptions, and exercise mimetics. Overall, this review provides a more integrated perspective on the molecular basis of exercise and offers directions for future mechanistic and translational studies.

exercise↗
PubMed2003

Chemoresistance in human ovarian cancer: the role of apoptotic regulators.

Ovarian cancer is among the most lethal of all malignancies in women. While chemotherapy is the preferred treatment modality, chemoresistance severely limits treatment success. Recent evidence suggests that deregulation of key pro- and anti-apoptotic pathways is a key factor in the onset and maintenance of chemoresistance. Furthermore, the discovery of novel interactions between these pathways suggests that chemoresistance may be multi-factorial. Ultimately, the decision of the cancer cell to live or die in response to a chemotherapeutic agent is a consequence of the overall apoptotic capacity of that cell. In this review, we discuss the biochemical pathways believed to promote cell survival and how they modulate chemosensitivity. We then conclude with some new research directions by which the fundamental mechanisms of chemoresistance can be elucidated.

Antineoplastic Agents↗
PubMed1996

The Rev Axis of HIV-1 and Its Associated Host Cofactors: A Viral Window onto the Workings of Eukaryotic Posttranscriptional RNA Processing.

The Rev axis of HIV is one of two key autoregulatory pathways required for viral replication and pathogenesis. The viral Rev protein interacts with its RNA target sequence, the RRE, to overcome the inhibitory effects of constitutive repressor sequences and promote nucleocytoplasmic transport and expression of viral RNAs. The Rev axis is the subject of intense scrutiny not only because it plays a central role in the viral life cycle, but also because it offers a window onto the workings of key mechanisms of posttranscriptional regulation, including splicing, polyadenylation, degradation, transport, and translation. Recent reports have conclusively demonstrated a central role for transport in the Rev mechanism and have identified cellular factors that are good candidates for mediating the transport phenomena. Other potentially involved cellular factors are being investigated. Much of the apparent heterogeneity in the observed effects of Rev may actually derive from heterogeneity in the constitutive repressor sequences rather than from heterogeneity in the mechanism of action of Rev per se. Copyright 1996 S. Karger AG, Basel

Journal Article↗
PubMed2005

Loss of mitogen-activated protein kinase kinase kinase 4 (MEKK4) results in enhanced apoptosis and defective neural tube development.

Neural tube defects (NTDs) are prevalent human birth defects. Mitogen-activated protein kinases (MAPKs), such as c-Jun N-terminal kinase (JNK), are implicated in facilitating neural tube closure, yet upstream regulators remain to be identified. Here, we show that MAP kinase kinase kinase 4 (MEKK4) is strongly expressed in the developing neuroepithelium. Mice deficient in MEKK4 develop highly penetrant NTDs that cannot be rescued by supplementation with folic acid or inositol. Unlike most mouse models of NTDs, MEKK4 mutant embryos display genetically co-segregated exencephaly and spina bifida, recapitulating the phenotypes observed in human patients. To identify downstream targets of MEKK4 during neural tube development, we examined the activity of MAP kinase kinase 4 (MKK4), a signaling intermediate between MAP kinase kinase kinase and JNK/p38. We found a significant reduction in MKK4 activity in MEKK4-deficient neuroepithelium at sites of neural tube closure. MAPK pathways are key regulators of cell apoptosis and proliferation. Analyses of the neuroepithelium in MEKK4-deficient embryos showed massively elevated apoptosis before and during neural tube closure, suggesting an antiapoptotic role for MEKK4 during development. In contrast, proliferation of MEKK4-deficient neuroepithelial cells appeared to be largely unaffected. MEKK4 therefore plays a critical role in regulating MKK4 activity and apoptotic cell death during neural tube development. Disruption of this signaling pathway may be clinically relevant to folate-resistant human NTDs.

Animals↗
PubMed2005

Effects of organochlorine insecticides on MAP kinase pathways in human HaCaT keratinocytes: key role of reactive oxygen species.

Organochlorine pesticides (OCs) are reported as potential carcinogens in humans. The aim of this study was to investigate the effects of four OCs (dieldrin, endosulfan, heptachlor, and lindane) on mitogen-activated protein kinase (MAPK) cascades and more specifically to identify the mechanism underlying OC-induced ERK1/2 activation. Organochlorine pesticides increased phosphorylated Raf, MEK1/2, ERK1/2, and c-Jun in human HaCaT cells, but they had no effect on p38 MAPK activation. Moreover, blockade of Raf, MEK1/2, or PKC activation with geldanamycin, U0126, or calphostin C inhibited ERK1/2 phosphorylation, demonstrating a PKC-Raf-MEK1/2 pathway. We also showed that these insecticides induced the production of reactive oxygen species (ROS). Pre-treatment with the antioxidant molecule N-acetyl cysteine sharply decreased the level of phospho-ERK1/2 and had no effect on Raf and MEK1/2 activation, suggesting a Raf-independent mechanism. This study indicates that OCs strongly activate the ERK1/2 pathway, and it identifies a critical role of ROS in OC-induced ERK activation, probably by stabilizing its phosphorylation.

Cell Line↗
PubMed1999

Peroxisome-proliferator regulates key enzymes of the tryptophan-NAD+ pathway.

Structually diverse peroxisome-proliferators (PPs) were investigated regarding their effects on NAD+ level and two key enzyme activities in the tryptophan (Trp)-NAD+ pathway in the liver of rats (Sprague-Dawley male) fed PP-containing diets freely for 2 weeks. All PPs, except for thyroxine, significantly increased hepatic NAD+ level in concert with hepatic hypertrophy. Activity of quinolinate phosphoribosyltransferase (QAPRTase), one of the key enzymes in the Trp-NAD+ pathway, was increased by the PPs which caused significant increase in the hepatic NAD+. On the other hand, alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase (ACMSDase), another key enzyme in the Trp-NAD+ pathway, was drastically inhibited by all PPs except for linolenic acid, which was only slightly inhibitory. Most PPs investigated activated peroxisomal marker enzymes such as palmitoyl-CoA oxidase, catalase, and PPAR-alpha(peroxisome-proliferator activated receptor-alpha)-dependent enzymes, such as malic enzyme and l-3-glycerophosphate dehydrogenase. NAD+ was also increased in the rat hepatocytes cultured in the medium supplemented with PPs. These data suggested that regulation of the key enzymes in the Trp-NAD+ pathway was associated with PPAR-alpha directly or indirectly, and as a consequence the hepatic NAD+ was increased by PPs.

Animals↗
PubMed2006

Abnormal insulin-like growth factor 1 signaling in human osteoarthritic subchondral bone osteoblasts.

Insulin-like growth factor (IGF)-1 is a key factor in bone homeostasis and could be involved in bone tissue sclerosis as observed in osteoarthritis (OA). Here, we compare the key signaling pathways triggered in response to IGF-1 stimulation between normal and OA osteoblasts (Obs). Primary Obs were prepared from the subchondral bone of tibial plateaus of OA patients undergoing knee replacement or from normal individuals at autopsy. Phenotypic characterization of Obs was evaluated with alkaline phosphatase and osteocalcin release. The effect of IGF-1 on cell proliferation, alkaline phosphatase and collagen synthesis was evaluated in the presence or not of 50 ng/ml IGF-1, whereas signaling was studied with proteins separated by SDS-PAGE before western blot analysis. We also used immunoprecipitation followed by western blot analysis to detect interactions between key IGF-1 signaling elements. IGF-1 receptor (IGF-1R), Shc, Grb2, insulin receptor substrate (IRS)-1, and p42/44 mitogen-activated protein kinase (MAPK) levels were similar in normal and OA Obs in the presence or absence of IGF-1. After IGF-1 stimulation, the phosphorylation of IGF-1R in normal and OA Obs was similar; however, the phosphorylation of IRS-1 was reduced in OA Ob. In addition, the PI3K pathway was activated similarly in normal and OA Obs while that for p42/44 MAPK was higher in OA Obs compared to normal. p42/44 MAPK can be triggered via an IRS-1/Syp or Grb2/Shc interaction. Interestingly, Syp was poorly phosphorylated under basal conditions in normal Obs and was rapidly phosphorylated upon IGF-1 stimulation, yet Syp showed a poor interaction with IRS-1. In contrast, Syp was highly phosphorylated in OA Obs and its interaction with IRS-1 was very strong initially, yet rapidly dropped with IGF-1 treatments. The interaction of Grb2 with IRS-1 progressively increased in response to IGF-1 in OA Obs whereas this was absent in normal Ob. IGF-1 stimulation altered alkaline phosphatase in Ob, an effect reduced in the presence of PD98059, an inhibitor of p42/44 MAPK signaling, whereas neither IGF-1 nor PD98059 had any significant effect on collagen synthesis. In contrast, cell proliferation was higher in OA Obs compared to normal under basal conditions, and IGF-1 stimulated more cell proliferation in OA Obs than in normal Ob, an effect totally dependent on p42/44 MAPK activiy. The altered response of OA Obs to IGF-1 may be due to abnormal IGF-1 signaling in these cells. This is mostly linked with abnormal IRS-1/Syp and IRS-1/Grb2 interaction in these cells.

Aged↗
PubMed2002

Protein disulfide isomerases exploit synergy between catalytic and specific binding domains.

Protein disulfide isomerases (PDIs) catalyse the formation of native disulfide bonds in protein folding pathways. The key steps involve disulfide formation and isomerization in compact folding intermediates. The high-resolution structures of the a and b domains of PDI are now known, and the overall domain architecture of PDI and its homologues can be inferred. The isolated a and a' domains of PDI are good catalysts of simple thiol-disulfide interchange reactions but require additional domains to be effective as catalysts of the rate-limiting disulfide isomerizations in protein folding pathways. The b' domain of PDI has a specific binding site for peptides and its binding properties differ in specificity between members of the PDI family. A model of PDI function can be deduced in which the domains function synergically: the b' domain binds unstructured regions of polypeptide, while the a and a' domains catalyse the chemical isomerization steps.

Animals↗
PubMed2004

Cross-talk between the interleukin-6 and prostaglandin E(2) signaling systems results in enhancement of osteoclastogenesis through effects on the osteoprotegerin/receptor activator of nuclear factor-{kappa}B (RANK) ligand/RANK system.

The osteoprotegerin (OPG)/receptor activator of nuclear factor-kappaB ligand (RANKL)/receptor activator of nuclear factor-kappaB (RANK) system is the dominant and final mediator of osteoclastogenesis. Abnormalities of this system have been implicated in the pathogenesis of many skeletal diseases. Cyclooxygenase (COX)-2 and prostaglandin (PG)E(2), a major eicosanoid product of the COX-2-catalyzed pathway, play key roles in normal bone tissue remodeling. PGE(2) exerts its actions by binding and activating the E series of prostaglandin (EP) receptor. Activation of EP(2) and EP(4) receptors is associated with PGE(2)-induced osteoclast differentiation. IL-6, a major proinflammatory cytokine, has also been reported to induce osteoclast differentiation. Although interactions between the COX-2/PGE(2) and IL-6 systems have been described in bone cells, the mechanisms underlying these cooperative signaling pathways and the possible involvement of the OPG/RANKL/RANK system have not been fully elucidated. We demonstrate that COX-2, PGE(2), and IL-6 stimulate osteoblast growth and osteoclast differentiation. Effects on osteoclast differentiation, particularly with IL-6, were most marked when osteoclast precursor cells were grown in coculture with osteoblasts, indicating a possible role of the RANK/RANKL/OPG system. COX-2 and PGE(2) stimulated osteoclastogenesis through inhibition of OPG secretion, stimulation of RANKL production by osteoblasts, and up-regulation of RANK expression in osteoclasts. PGE(2) stimulated IL-6 secretion by bone cells, whereas COX-2 inhibitors decreased this same parameter. IL-6, in turn, increased PGE(2) secretion, COX-2, and EP receptor subtype expression in bone cells. Finally, IL-6 was the mediator of PGE(2)-induced suppression of OPG production by osteoblasts. These findings provide evidence for cross-talk between the PGE(2) and IL-6 signaling enhance osteoclast differentiation via effects on the OPG/RANKL/RANK system in bone cells.

Animals↗
PubMed2005

Proteomic analysis of enriched microsomal fractions from GS-NS0 murine myeloma cells with varying secreted recombinant monoclonal antibody productivities.

The folding, transport and modification of recombinant proteins in the constitutive secretory pathway of eukaryotic cell expression systems are reported to be a bottleneck in their production. We have utilised a proteomic approach to investigate the processes catalysed by proteins constituting the secretory pathway to further our understanding of those processes involved in high-level antibody secretion. We used GS-NS0 cell populations differing in qmAb to prepare enriched microsome fractions from each cell population at mid-exponential growth phase. These were analysed by 2-D PAGE to characterise the microsome protein component and test the hypothesis that bottlenecks in recombinant protein synthesis exist in these compartments, which are alleviated in high producers by the up-regulation of key secretory pathway proteins. Proteins whose abundance changed in a statistically significant manner with increasing qmAb were involved in a range of cellular functions: energy metabolism, mAb folding/assembly, cytoskeletal organisation and protein turnover. Amongst these were BiP and PDI, chaperones resident in the ER that interact with nascent immunoglobulins during their folding/assembly. However, our results suggest that there are diverse mechanisms by which these cells achieve qmAb. The results imply that cell-engineering strategies for improving qmAb should target proteins associated with altered functional phenotype identified in this study.

Animals↗
PubMed2006

Endostatin influences endothelial morphology via the activated ERK1/2-kinase endothelial morphology and signal transduction.

Endostatin, the proteolytic fragment of collagen XVIII, is known to be a potent inhibitor of angiogenesis. However, to date, only limited knowledge exists with regard to the effects of endostatin on vessel morphology and the underlying signaling pathway. The aim of the present work was therefore to determine the impact of endostatin and its collagen XV analogue restin on vessel development during wound healing and embryonic angio- and vasculogenesis. Time lapse experiments and electron microscopy demonstrate similar morphological changes evoked by endostatin and the ERK1/2-kinase inhibitor PD98059. Furthermore, we show that ERK1/2 phosphorylation, a crucial signaling event in vascular morphogenesis, is regulated by endostatin via the protein phosphatase 2A PP2A. These findings provide new insight into a key signaling pathway of vascular remodeling evoked by a matrix-derived factor.

Angiogenesis Inhibitors↗
PubMed2026

Decoding protein signatures and protein interactions in oral potentially malignant disorders: a systematic review and network analysis.

BACKGROUND: Proteomic profiling offers thorough insights into protein structure and function, as well as it acts as an essential approach for analyzing molecular changes at the tissue level. However, because of the proteome's diversity and dynamic nature, biomarker discovery remains challenging. By combining proteomics with bioinformatics, the level of understanding in relation to molecular interactions and disease processes can be improved. Through an integrative approach, few limitations can be addressed, thereby promoting proteomic profiling for the discovery of new therapeutic targets and novel biomarkers for a variety of disorders. AIM: To identify differentially expressed protein markers and their key molecular pathways associated with Oral Potentially Malignant Disorders. METHODS: Systematic Review was conducted following the PRISMA guidelines and the protocol registered in the International Prospective Register of Systematic Reviews (PROSPERO) with the registration ID number CRD42024557545. A comprehensive literature review was performed using electronic databases, yielding 12,797, studies from which 15 eligible articles were selected. The Newcastle-Ottawa Scale was used to assess the risk of bias. Vote counting was performed to identify proteins reported in more than one study. A bipartite network was constructed using Cytoscape to identify shared and disease-specific protein markers. Lesion-wise protein-protein interaction networks were generated using STRING and analysed in Cytoscape to identify highly interconnected hub proteins, and pathway enrichment analysis for these hubs was performed using Reactome. RESULTS: A total of fifteen studies (Leukoplakia (LK) - n = 1, Proliferative Verrucous Leukoplakia (PVL) - n = 2, Oral Submucous Fibrosis (OSMF) - n = 7, and Oral Lichen Planus (OLP) - n = 5) were included. The Newcastle-Ottawa Scale was used to evaluate methodological quality and the quality of studies included in this systematic review was high for 4 articles and moderate in the remaining 11. The most commonly employed technique was mass spectrometry. A total of 318 candidate proteins (LK - 14, PVL - 82, OSMF - 172, and OLP - 50) were identified across the oral potentially malignant disorders. Key markers identified through vote counting included ERO1A, NUCB1, RHOA, and IL36A for PVL; LUM, KRT1, KRT9, ALB, and VIM for OSMF; and ALB, LYZ, HP, HBB, and AMY1A for OLP. The bipartite network showed that OSMF and OLP shared the highest number of proteins, indicating the strongest overlap among lesions. Network analysis further highlighted distinct hub proteins for each lesion: for LK- AMY1A, AMY1B and APOA1; for PVL- CFL1, RHOA and CDC42; for OSMF- HSP90AA1, ENO1 and SERPINA1; and for OLP- HP, B2M, and ORM1. Lesion-specific pathway enrichment revealed that LK was associated with epithelial differentiation, PVL with oncogenic signaling, OSMF with stress-driven fibrosis, and OLP with immune-mediated inflammation. CONCLUSIONS: Proteomic expression offers insights into disease pathogenesis by identifying important molecular changes across OPMDs. However, the majority of biomarkers are still in the exploratory stage due to the considerable variation in lesion types, sample sources, proteomic techniques, and reporting systems. In order to create reliable and clinically applicable biomarkers, future studies should concentrate on combining multi-omics techniques with large-scale, standardized cohorts.

Humans↗
PubMed1998

Signal transduction in hepatic stellate cells.

Hepatic stellate cells (HSC) are presently regarded as one of the key cell types involved in the progression of liver fibrosis and in the related pathophysiological and clinical complications. Following acute or chronic liver tissue damage, HSC undergo a process of activation towards a phenotype characterised by increased proliferation, motility, contractility and synthesis of extracellular matrix (ECM) components. Several factors have been shown to play a key role in the promotion of the full-blown picture of activated HSC. These include extensive changes in the composition and organisation of the ECM, the secretion of several growth factors, cytokines, chemokines, products of oxidative stress and other soluble factors. It is evident that each cellular response to extracellular stimuli must be framed in a scenario where different forces modulate one another and result in a prevalent biological effect. Along these lines, the identification and characterisation of intracellular signalling pathways activated by different stimuli in HSC represent a mandatory step. In this review article we have made an attempt to summarise recent acquisitions to our knowledge of the involvement of different intracellular signalling pathways in key aspects of HSC biology.

Animals↗
PubMed2003

IL-13-induced changes in the goblet cell density of human bronchial epithelial cell cultures: MAP kinase and phosphatidylinositol 3-kinase regulation.

In addition to a direct proinflammatory role, IL-13 has been demonstrated to induce a goblet cell metaplastic phenotype in the airway epithelium in vivo. We have studied the direct effects of IL-13 (and IL-4) on well-differentiated, air-liquid interface cultures of human bronchial epithelial cells (HBEs) and provide a quantitative assessment of the development of a mucus hypersecretory phenotype induced by these cytokines. Using Alcian blue staining of goblet cells and immunohistochemical detection of MUC5AC, we found that IL-13 (and IL-4) induced increases in the goblet cell density (GCD) of the HBE cultures. The effects of these cytokines were critically dependent on concentration: 1 ng/ml routinely induced a 5- to 10-fold increase in GCD that was associated with a hypersecretory ion transport phenotype. Paradoxically, 10 ng/ml of either cytokine induced a profound reduction in GCD. Removal of EGF from the culture media or treatment of the cells with AG-1478 [a potent inhibitor of EGF receptor tyrosine kinase (EGFR-TK)] demonstrated that the EGFR-TK pathway was key to the regulation of the basal GCD but that it was not involved in the IL-13-driven increase. The IL-13-driven increase in GCD was, however, sensitive to inhibition of MEK (PD-98059, U-0126), p38 MAPK (SB-202190), and phosphatidylinositol (PtdIns) 3-kinase (LY-294002). These data support the concept that IL-13 is in part able to induce a mucus hypersecretory phenotype through a direct interaction with the airway epithelium and that MAP kinase and PtdIns 3-kinase signaling pathways are involved.

Bronchi↗