Proliferation Of Bronchial Smooth Muscle Cells Research Articles

CysLT1 receptor upregulation by TGF-β and IL-13 is associated with bronchial smooth muscle cell proliferation in response to LTD4

Background: Airway remodeling is a feature of chronic asthma. It involves a number of structural changes, including bronchial smooth muscle cell (BSMC) hyperplasia and hypertrophy. Cysteinyl leukotrienes (cysLTs) have been suggested to play a role in airway remodeling in addition to their numerous other physiopathologic effects. Objectives: This work was aimed at characterizing the potential modulation of CysLT1 receptor expression by cytokines and the eventual functional relevance of this modulation. Methods: Expression of CysLT1 receptor was measured by flow cytometry and immunofluorescence microscopy. Transcripts were measured by RT-PCR and BSMC proliferation by crystal violet staining. Results: When human BSMC were exposed to transforming growth factor (TGF)-β, IL-13, or IFN-γ, their expression of CysLT1 receptor was significantly augmented in a time- and concentration-dependent manner. Interestingly, IL-4 had no significant effect on CysLT1 receptor expression in BSMC. Moreover, IL-13 and IFN-γ but not TGF-β were able to increase CysLT1 mRNA levels. Finally, when BSMC were pretreated with TGF-β or IL-13 but not IFN-γ, their responsiveness to LTD4 was markedly enhanced in terms of BSMC proliferation. Whereas TGF-β, IL-13, or LTD4 alone had little effect on BSMC proliferation, preexposure of the cells to TGF-β or IL-13 for 24 hours resulted in a significant increase in proliferation in response to LTD4. The enhanced proliferation was totally prevented by pretreating the cytokine-primed BSMC with the selective CysLT1 receptor antagonist Montelukast. Conclusions: Taken together, our findings indicate a synergy between certain cytokines and cysLTs, mediated by the augmented expression of the CysLT1 receptor and subsequent LTD4-triggered BSMC proliferation. These findings support a role for cysLTs in the airway remodeling observed in asthmatic patients and may provide a rationale for preventive and therapeutic intervention.

Anti-HLA class I antibody binding to airway epithelial cells induces production of fibrogenic growth factors and apoptotic cell death: a possible mechanism for bronchiolitis obliterans syndrome

Development of anti-HLA class I antibodies is associated with bronchiolitis obliterans syndrome (BOS) after lung transplantation. BOS is characterized histologically by significant fibrosis and airway epithelial cell (AEC) apoptosis. Thus, this study was designed to determine whether anti-HLA class I antibodies can activate AECs to produce growth factors and to undergo apoptosis. KCC-266 AECs were activated with the W6/32 anti-HLA class I monoclonal antibody. Proliferation and apoptosis levels were determined after 24, 48, and 72 hours. The induction of fibroblast and bronchial smooth muscle cell proliferation by anti-HLA class I activated AECs was assessed in the presence of neutralizing antibodies against various growth factors. The anti-HLA class I induced AEC proliferation after 24 hours followed by significant induction of apoptosis after 48 hours. Anti-HLA class I activated AECs produced soluble growth factors that stimulated fibroblasts but not bronchial smooth muscle cells. The stimulation of fibroblast proliferation was inhibited by antibodies against platelet-derived growth factor, heparin-binding epidermal growth factor, insulin-like growth factor 1, and basic fibroblast growth factor. The results from this study suggest that anti-HLA class I alloantibodies may play an important role in the pathogenesis of BOS by inducing proliferation, growth factor production, and apoptotic cell death in AECs.

CysLT1 receptor upregulation by TGF-beta and IL-13, but not IL-4, is associated with bronchial smooth muscle cell proliferation in response to LTD4

CysLT1 receptor upregulation by TGF-beta and IL-13, but not IL-4, is associated with bronchial smooth muscle cell proliferation in response to LTD4

Role of capacitative Ca2+ entry in bronchial contraction and remodeling.

Asthma is characterized by airway inflammation, bronchial hyperresponsiveness, and airway obstruction by bronchospasm and bronchial wall thickening due to smooth muscle hypertrophy. A rise in cytosolic free Ca2+ concentration ([Ca2+]cyt) may serve as a shared signal transduction element that causes bronchial constriction and bronchial wall thickening in asthma. In this study, we examined whether capacitative Ca2+ entry (CCE) induced by depletion of intracellular Ca2+ stores was involved in agonist-mediated bronchial constriction and bronchial smooth muscle cell (BSMC) proliferation. In isolated bronchial rings, acetylcholine (ACh) induced a transient contraction in the absence of extracellular Ca2+ because of Ca2+ release from intracellular Ca2+ stores. Restoration of extracellular Ca2+ in the presence of atropine, an M-receptor blocker, induced a further contraction that was apparently caused by a rise in [Ca2+]cyt due to CCE. In single BSMC, amplitudes of the store depletion-activated currents (I(SOC)) and CCE were both enhanced when the cells proliferate, whereas chelation of extracellular Ca2+ with EGTA significantly inhibited the cell growth in the presence of serum. Furthermore, the mRNA expression of TRPC1, a transient receptor potential channel gene, was much greater in proliferating BSMC than in growth-arrested cells. Blockade of the store-operated Ca2+ channels by Ni2+ decreased I(SOC) and CCE and markedly attenuated BSMC proliferation. These results suggest that upregulated TRPC1 expression, increased I(SOC), enhanced CCE, and elevated [Ca2+]cyt may play important roles in mediating bronchial constriction and BSMC proliferation.

Oxygen induces S-phase growth arrest and increases p53 and p21(WAF1/CIP1) expression in human bronchial smooth-muscle cells.

Hyperoxia increases free radical production, leading to DNA damage. Recent studies indicate that oxygen augments the expression of p53 and p21(WAF1/CIP1), and increases apoptotic labeling of airway epithelial cells. Similar changes in regulatory gene products have not been reported in other pulmonary cells, nor have these changes been investigated in conjunction with alterations in cell-cycle distribution. The present study was conducted to determine whether oxygen alters the expression of p53 and p21(WAF1/CIP1) in human bronchial smooth-muscle cells (BSMC). BSMC placed in room air (RA), 40% O(2), or 95% O(2) were examined for 3 d to determine cell number, thymidine incorporation, cell-cycle distribution, and lactate dehydrogenase release. Apoptosis was assessed through the terminal deoxynucleotidyl transferase-deoxyuridine triphosphate end-nick labeling (TUNEL) technique, and p53 and p21(WAF1/CIP1) protein levels were determined through enzyme-linked immunosorbent assay. Exposure of BSMC to 95% O(2) decreased proliferation and DNA synthesis within 24 h, and was accompanied by an increase in S-phase cells (72 h; RA: 12.9 +/- 4.6%, versus 95% O(2): 34.6 +/- 7.0%; P < 0.01). By comparison, exposure to 40% O(2) resulted in decreased proliferation at 48 h without significant alterations in cell-cycle distribution. Both p53 and p21(WAF1/CIP1) levels were increased by 95% O(2), with maximal differences noted at 24 and 48 h, respectively. All atmospheres showed < 8% cell death and few TUNEL-positive cells. Our results indicate that oxygen-mediated alterations in BSMC proliferation are time- and concentration-dependent. Furthermore, high oxygen levels induce S-phase arrest and increased expression of p53 and p21(WAF1/CIP1). Activation of these genes may prevent replication without inducing apoptosis to allow for the repair of oxidative damage.