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Increased levels of IL-6 are documented in asthma, but its contribution to the pathology is unknown. Asthma is characterized by airway wall thickening due to increased extracellular matrix deposition, inflammation, angiogenesis, and airway smooth muscle (ASM) mass. IL-6 binds to a specific membrane-bound receptor, IL-6 receptor-[alpha] (mIL-6R[alpha]), and subsequently to the signaling protein gp130. Alternatively, IL-6 can bind to soluble IL-6 recpetor-[alpha] (sIL-6R[alpha]) to stimulate membrane receptordeficient cells, a process called trans-signaling. We discovered that primary human ASM cells do not express mIL-6R[alpha] and, therefore, investigated the effect of IL-6 trans-signaling on the pro-remodeling phenotype of ASM. ASM required sIL-6R[alpha] to activate signal transducer and activator 3, with no differences observed between cells from asthmatic subjects compared with controls. Further analysis revealed that IL-6 alone or with sIL-6R[alpha] did not induce release of matrix-stimulating factors (including connective tissue growth factor, fibronectin, or integrins) and had no effect on mast cell adhesion to ASM or ASM proliferation. However, in the presence of sIL-6R[alpha], IL-6 increased eotaxin and VEGF release and may thereby contribute to local inflammation and vessel expansion in airway walls of asthmatic subjects. As levels of sIL-6R[alpha] are increased in asthma, this demonstration of IL-6 trans-signaling in ASM has relevance to the development of airway remodeling. soluble interleukin-6 receptor-[alpha]; gp130; signal transducer and activator 3; asthma; airway remodeling

Human airway smooth muscle (ASM) plays an immunomodulatory role in asthma. Recently, IL-17A has become of increasing interest in asthma, being found at elevated levels in asthmatic airways and emerging as playing an important role in airway neutrophilia. IL-17A predominantly exerts its neutrophil orchestrating role indirectly via the induction of cytokines by resident airway structural cells. Here, we perform an in vitro study to show that although IL-17A did not induce secretion of the CXC chemokine IL-8 from ASM cells, IL-17A significantly potentiates TNF-[alpha]-induced IL-8 protein secretion and gene expression in a concentration- and time-dependent manner (P < 0.05). Levels of IL-8 protein produced after 24 h of incubation with TNF-[alpha] were enhanced 2.7-fold in the presence of IL-17A, and conditioned media significantly enhanced neutrophil chemotaxis in vitro. As IL-17A had no effect on the activity of NF-[kappa]B, a key transcriptional regulator of IL-8 gene expression, we then examined whether IL-17A acts at the posttranscriptional level. We found that IL-17A significantly augmented TNF-[alpha]-induced IL-8 mRNA stability. Interestingly, this enhanced stability occurred via a p38 MAPK-dependent pathway. The decay of IL-8 mRNA transcripts proceeded at a significantly faster rate when cells were pretreated with the p38 MAPK inhibitor SB-203580 (-0.05763 [+ or -] 0.01964, [t.sub.1/2] = 12.0 h), compared with vehicle (-0.01030 [+ or -] 0.007963, [t.sub.1/2] = 67.3 h) [results are expressed as decay constant (means [+ or -] SE) and half-life ([t.sub.1/2] in h): P < 0.05]. Collectively, these results demonstrate that IL-17A amplifies the synthetic function of ASM cells, acting via a p38 MAPK-dependent posttranscriptional pathway to augment TNF-[alpha]-induced secretion of the potent neutrophil chemoattractant IL-8 from ASM cells. inflammation; cytokines; messenger ribonucleic acid stability; neutrophils; structural cells; airway smooth muscle: interleukin; mitogenactivated protein kinase; tumor necrosis factor; interleukin 17A

Human vascular smooth muscle cell proliferation and migration contribute to vascular remodeling in pulmonary hypertension and atherosclerosis. The precise mechanisms that regulate structural remodeling of the vessel wall remain unknown. This study tests the hypothesis that phosphatidylinositol 3-kinase (PI3K) activation is both necessary and sufficient to mediate human pulmonary vascular smooth muscle (PVSM) cell proliferation and migration. Microinjection of human PVSM cells with a dominant-negative class IA PI3K inhibited platelet-derived growth factor (PDGF)-induced DNA synthesis by 65% (P < 0.001; [chi square] analysis) compared with cells microinjected with control plasmid, whereas microinjection of cells with a constitutively active class IA PI3K (p110*-CA) was sufficient to induce DNA synthesis (mitotic index of p110*-CA-microinjected cells was 15% vs. 3% in control cells; P < 0.01). Transfection of PVSM cells with p110*-CA was also sufficient to promote human PVSM cell migration. In parallel experiments, stimulation of human PVSM cells with PDGF induced PI3K-dependent activation of Akt, p70 S6 kinase, and ribosomal protein S6 but not mitogen-activated protein kinase. PDGF-induced proliferation and migration was inhibited by LY-294002. These results demonstrate that PI3K signaling is both necessary and sufficient to mediate human PVSM cell proliferation and migration and suggest that the activation of PI3K may play an important role in vascular remodeling. phosphatidylinositol 3-kinase; hypertension; Akt; S6K1; ribosomal protein S6

Page, Severine, Alaina J. Ammit, Judith L. Black, and Carol L. Armour. Human mast cell and airway smooth muscle cell interactions: implications for asthma. Am J Physiol Lung Cell Mol Physiol 281: L1313-L1323, 2001.--Asthma is characterized by inflammation, hyper-responsiveness, and remodeling of the airway. Human mast cells (HMCs) play a central role in all of these changes by releasing mediators that cause exaggerated bronchoconstriction, induce human airway smooth muscle (HASM) cell proliferation, and recruit and activate inflammatory cells. Moreover, the number of HMCs present on asthmatic HASM is increased compared with that on nonasthmatic HASM. HASM cells also have the potential to actively participate in the inflammatory process by synthesizing cytokines and chemokines and expressing surface molecules, which have the capacity to perpetuate the inflammatory mechanisms present in asthma. This review specifically examines how the mediators of HMCs have the capacity to modulate many functions of HASM; how the synthetic function of HASM, particularly through the release and expression of stem cell factor, has the potential to influence HMC number and activation in an extraordinarily potent and proinfiammatory manner; and how these interactions between HMCs and HASM have potential consequences for airway structure and inflammation relevant to the disease process of asthma. contraction; proliferation; remodeling; inflammation; cytokines

Many lung diseases are characterized by fibrosis, leading to impaired tissue patency and reduced lung function. Development of fibrotic tissue depends on two-way interaction between the cells and the extra-cellular matrix (ECM). Concentration-dependent increased stiffening of the ECM is sensed by the cells, which in turn increases intracellular contraction and pulling on the matrix causing matrix reorganization and further stiffening. It is generally accepted that the inflammatory cytokine growth factor β1 (TGF-β1) is a major driver of lung fibrosis through the stimulation of ECM production. However, TGF-β1 also regulates the expression of members of the tropomyosin (Tm) family of actin associating proteins that mediate ECM reorganization through intracellular-generated forces. Thus, TGF-β1 may mediate the bi-directional signaling between cells and the ECM that promotes tissue fibrosis. Using combinations of cytokine stimulation, mRNA, protein profiling and cellular contractility assays with human lung fibroblasts, we show that concomitant induction of key Tm isoforms and ECM by TGF-β1, significantly accelerates fibrotic phenotypes. Knocking down Tpm2.1 reduces fibroblast-mediated collagen gel contraction. Collectively, the data suggest combined ECM secretion and actin cytoskeleton contractility primes the tissue for enhanced fibrosis. Our study suggests that Tms are at the nexus of inflammation and tissue stiffening. Small molecules targeting specific Tm isoforms have recently been designed; thus targeting Tpm2.1 may represent a novel therapeutic target in lung fibrosis. [ABSTRACT FROM AUTHOR]