Maree H. Poniris

Dual ERK and phosphatidylinositol 3-kinase pathways control airway smooth muscle proliferation: differences in asthma

Hyperplasia of airway smooth muscle (ASM) within the bronchial wall of asthmatic patients has been well documented and is likely due to increased muscle proliferation. We have shown that ASM cells obtained from asthmatic patients proliferate faster than those obtained from non‐asthmatic patients. In ASM from non‐asthmatics, mitogens act via dual signaling pathways (both ERK‐ and PI 3‐kinase‐dependent) to control growth. In this study we are the first to examine whether dual pathways control the enhanced proliferation of ASM from asthmatics. When cells were incubated with 0.1% or 1% FBS, ERK activation was significantly greater in cells from asthmatic subjects (P < 0.05). In contrast, when cells were stimulated with 10% FBS, ERK activity was significantly greater in the non‐asthmatic cells. However, cell proliferation in asthmatic cells was still significantly higher in cells stimulated by both 1% and 10% FBS. Pharmacological inhibition revealed that although dual proliferative pathways control ASM growth in cells from non‐asthmatics stimulated with 10% FBS to an equal extent ([3H]‐thymidine incorporation reduced to 57.2 ± 6.9% by the PI 3‐kinase inhibitor LY294002 and 57.8 ± 1.1% by the ERK‐pathway inhibitor U0126); in asthmatics, the presence of a strong proliferative stimulus (10% FBS) reduces ERK activation resulting in a shift to the PI 3‐kinase pathway. The underlying mechanism appears to be upregulation of an endogenous MAPK inhibitor—MKP‐1—that constrains ERK signaling in asthmatic cells under strong mitogenic stimulation. This study suggests that the PI 3‐kinase pathway may be an attractive target for reversing hyperplasia in asthma. J. Cell. Physiol. 216: 673–679, 2008,

Asthmatic airway smooth muscle CXCL10 production: mitogen-activated protein kinase JNK involvement

CXCL10 (IP10) is involved in mast cell migration to airway smooth muscle (ASM) bundles in asthma. We aimed to investigate the role of cytokine-induced MAPK activation in CXCL10 production by ASM cells from people with and without asthma. Confluent growth-arrested ASM cells were treated with inhibitors of the MAPKs ERK, p38, and JNK and transcription factor NF-κB, or vehicle, and stimulated with IL-1β, TNF-α, or IFN-γ, alone or combined (cytomix). CXCL10 mRNA and protein, JNK, NF-κB p65 phosphorylation, and Iκ-Bα protein degradation were assessed using real-time PCR, ELISA, and immunoblotting, respectively. Cytomix, IL-1β, and TNF-α induced CXCL10 mRNA expression more rapidly in asthmatic than nonasthmatic ASM cells. IL-1β and/or TNF-α combined with IFN-γ synergistically increased asthmatic ASM cell CXCL10 release. Inhibitor effects were similar in asthmatic and nonasthmatic cells, but cytomix-induced release was least affected, with only JNK and NF-κB inhibitors halving it. Notably, JNK phosphorylation was markedly less in asthmatic compared with nonasthmatic cells. However, in both, the JNK inhibitor SP600125 reduced JNK phosphorylation and CXCL10 mRNA levels but did not affect CXCL10 mRNA stability or Iκ-Bα degradation. Together, the JNK and NF-κB inhibitors completely inhibited their CXCL10 release. We concluded that, in asthmatic compared with nonasthmatic ASM cells, JNK activation was reduced and CXCL10 gene expression was more rapid following cytomix stimulation. However, in both, JNK activation did not regulate early events leading to NF-κB activation. Thus JNK and NF-κB provide independent therapeutic targets for limiting CXCL10 production and mast cell migration to the ASM in asthma.

Doxycycline inhibits matrix metalloproteinase-2 secretion from TSC2-null mouse embryonic fibroblasts and lymphangioleiomyomatosis cells

BACKGROUND AND PURPOSE Lymphangioleiomyomatosis (LAM) is characterized by the abnormal growth of smooth muscle‐like cells (LAM cells) and cystic destruction of the lung parenchyma. LAM cell‐derived matrix metalloproteinases (MMPs) are thought to play a prominent role in the tissue destruction. The aim of this study was to determine whether doxycycline, a known MMP inhibitor, can inhibit LAM cell proliferation or mitochondrial function and/or modulate MMPs and their tissue inhibitors (TIMPs).

The phosphoinositide 3′‐kinase p110δ modulates contractile protein production and IL‐6 release in human airway smooth muscle

Transforming growth factor (TGF) β1 increases pro‐inflammatory cytokines and contractile protein expression by human airway smooth muscle (ASM) cells, which could augment airway inflammation and hyperresponsiveness. Phosphoinositide 3′ kinase (PI3K) is one of the signaling pathways implicated in TGFβ1 stimulation, and may be altered in asthmatic airways. This study compared the expression of PI3K isoforms by ASM cells from donors with asthma (A), chronic obstructive pulmonary disease (COPD), or neither disease (NA), and investigated the role of PI3K isoforms in the production of TGFβ1 induced pro‐inflammatory cytokine and contractile proteins in ASM cells. A cells expressed higher basal levels of p110δ mRNA compared to NA and COPD cells; however COPD cells produced more p110δ protein. TGFβ1 increased 110δ mRNA expression to the same extent in the three groups. Neither the p110δ inhibitor IC87114 (1, 10, 30 µM), the p110β inhibitor TGX221 (0.1, 1, 10 µM) nor the PI3K pan inhibitor LY294002 (3, 10 µM) had any effect on basal IL‐6, calponin or smooth muscle α‐actin (α‐SMA) expression. However, TGFβ1 increased calponin and α‐SMA expression was inhibited by IC87114 and LY294002 in all three groups. IC87114, TGX221, and LY294002 reduced TGFβ1 induced IL‐6 release in a dose related manner in all groups of ASM cells. PI3K p110δ is important for TGFβ1 induced production of the contractile proteins calponin and α‐SMA and the proinflammatory cytokine IL‐6 in ASM cells, and may therefore be relevant as a potential therapeutic target to treat both inflammation and airway remodeling. J. Cell. Physiol. 227: 3044–3052, 2012.

In vitro studies of lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is associated with abnormal airway smooth muscle that leads to the characteristic pathology of lung nodule formation and destruction of lung tissue. The current authors have previously identified abnormal behaviour of airway smooth muscle cells from patients with asthma. In this study, cells and tissue sections derived from patients with LAM (n = 7), asthma (n = 8), and nonasthmatic controls (n = 9) were compared. The presence of the antigen human melanosome (HM)B-45 was investigated, along with the proliferation and release of extracellular matrix proteins, release of endogenous prostaglandin E2 (PGE2), vascular endothelial growth factor and connective tissue growth factor, and the expression of integrins. Positive HMB-45 staining was found in all LAM patients and no controls. Proliferation of LAM cells was not different from control cells nor was its inhibition by β-agonists, corticosteroids, rapamycin or PGE2. However, endogenous PGE2 levels were markedly decreased in LAM cells, and this was associated with decreased expression of the inducible form of cyclooxygenase (COX-2). The increased levels of connective tissue growth factor seen in asthma cells were not observed in LAM. Elastin mRNA in response to transforming growth factor-β stimulation was markedly lower in LAM cells than either asthma or control cells. In conclusion, lymphangioleiomyomatosis cells exhibit abnormal properties in vitro that may contribute to pathophysiology and symptomatology in patients with lymphangioleiomyomatosis.

Combined Beta-agonists and corticosteroids do not inhibit extracellular matrix protein production in vitro

Background. Persistent asthma is characterized by airway remodeling. Whereas we have previously shown that neither β 2-agonists nor corticosteroids inhibit extracellular matrix (ECM) protein release from airway smooth muscle (ASM) cells, the effect of their combination is unknown and this forms the rationale for the present study. Methods. ASM cells from people with and without asthma were stimulated with TGFβ1 (1 ng/ml) with or without budesonide (10−8 M) and formoterol (10−10 and 10−8 M), and fibronectin expression and IL-6 release were measured by ELISA. Bronchial rings from nonasthmatic individuals were incubated with TGFβ1 (1 ng/ml) with or without the drugs, and fibronectin expression was measured using immunohistochemistry. Results. Budesonide stimulated fibronectin deposition, in the presence or absence of TGFβ1, and this was partially reversed by formoterol (10−8 M) in both asthmatic and nonasthmatic cells. Budesonide and formoterol in combination failed to inhibit TGFβ-induced fibronectin in either cell type. A similar pattern of expression of fibronectin was seen in bronchial rings. TGFβ1-induced IL-6 release was inhibited by the combination of drugs. Conclusion. Current combination asthma therapies are unable to prevent or reverse remodeling events regulated by ASM cells.