Akt induces down regulation of MUC5AC production in NCI-H292 human airway epithelial cells cultured on extracellular matrix

Type IV collagen reduces MUC5AC secretion in the lungs of ovalbumin-sensitized mice

Mucin 5AC (MUC5AC) is excessively secreted in the respiratory tract of patients with asthma. Suppressing this secretion is important for improving the air passages, which facilitates easy breathing. We have previously reported that the addition of type IV collagen, a typical extracellular matrix (ECM) protein, to the culture medium for human cell lines and primary cells reduced MUC5AC secretion. In this report, we further investigated the effect of type IV collagen on MUC5AC secretion in vivo. We employed ovalbumin (OVA)-sensitized mice to model of asthma and exposed them to type IV collagen to verify the reducing effect of MUC5AC in vivo. The amount of MUC5AC in bronchoalveolar lavage fluid was examined after nebulization of type IV collagen. Hypersecretion of MUC5AC of the OVA-sensitized mice was suppressed by type IV collagen exposure in a time- and dose-dependent manner. Furthermore, type IV collagen exposure to OVA-sensitized mice decreased integrin α2 and β1 expression in the lungs and increased the levels of Akt and extracellular signal-regulated kinase (ERK) phosphorylation in the trachea. These results suggest that type IV collagen suppresses MUC5AC hypersecretion via modulating integrin expression and Akt/ERK phosphorylation in the respiratory tract of the OVA-sensitized mice.

Integrin β1 subunit regulates cellular and secreted MUC5AC and MUC5B production in NCI-H292 human lung epithelial cells

The surface of the human respiratory tract is covered with a mucus layer containing mucin 5AC (MUC5AC) and mucin 5B (MUC5B) as the main components. This layer contributes to biological defense by eliminating irritants, but excessive MUC5AC secretion by the airway epithelial cells exacerbates asthma. Therefore, regulating mucin production is important for asthma treatment. In this study, the effects of integrin β1 subunit on MUC5AC and MUC5B production were examined in NCI–H292 human lung cancer epithelial cells. When integrin β1 was overexpressed, cellular and secreted MUC5AC levels were decreased, whereas cellular MUC5B production was increased. Conversely, integrin β1 depletion using siRNA increased cellular and secreted MUC5AC production, but decreased cellular MUC5B production. Further, the activity of extracellular signal-regulated kinase (ERK), which promotes MUC5AC production, was decreased by integrin β1 overexpression and increased by its depletion. These results suggest that integrin β1 suppresses MUC5AC production and promotes MUC5B production by downregulating ERK.

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We studied the regulation of MUC5AC and MUC5B production by integrin β1 subunit.

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Integrin β1 overexpression reduced MUC5AC, but increased MUC5B levels.

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Integrin β1 depletion increased MUC5AC production and ROS level, but decreased MUC5B production.

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Integrin β1 overexpression decreased ERK activity in NCI–H292 airway cells.

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Integrin β1 downregulates ERK to suppress MUC5AC & promote MUC5B production.

Targeting the phosphoinositide-3-kinase/protein kinase B pathway in airway innate immunity

The airway innate immune system maintains the first line of defense against respiratory infections. The airway epithelium and associated immune cells protect the respiratory system from inhaled foreign organisms. These cells sense pathogens via activation of receptors like toll-like receptors and taste family 2 receptors (T2Rs) and respond by producing antimicrobials, inflammatory cytokines, and chemokines. Coordinated regulation of fluid secretion and ciliary beating facilitates clearance of pathogens via mucociliary transport. Airway cells also secrete antimicrobial peptides and radicals to directly kill microorganisms and inactivate viruses. The phosphoinositide-3-kinase/protein kinase B (Akt) kinase pathway regulates multiple cellular targets that modulate cell survival and proliferation. Akt also regulates proteins involved in innate immune pathways. Akt phosphorylates endothelial nitric oxide synthase (eNOS) enzymes expressed in airway epithelial cells. Activation of eNOS can have anti-inflammatory, anti-bacterial, and anti-viral roles. Moreover, Akt can increase the activity of the transcription factor nuclear factor erythroid 2 related factor-2 that protects cells from oxidative stress and may limit inflammation. In this review, we summarize the recent findings of non-cancerous functions of Akt signaling in airway innate host defense mechanisms, including an overview of several known downstream targets of Akt involved in innate immunity.

Type IV collagen reduces mucin 5AC secretion in three-dimensional cultured human primary airway epithelial cells

Mucin 5AC (MUC5AC) hypersecretion induces airway narrowing in patients with asthma, which leads to breathing problems. We investigated the regulation of MUC5AC secretion by extracellular matrix (ECM) proteins in human primary airway epithelial cells from patients with asthma. The addition of type IV collagen to three-dimensional cultured human primary airway epithelial cells, which mimics the airway surface, reduced MUC5AC secretion in the medium, while the addition of laminin increased MUC5AC secretion. Furthermore, the addition of fibronectin did not affect MUC5AC secretion. In particular, the repeated addition of a low concentration of type IV collagen demonstrated a cumulative effect on the reduction in MUC5AC secretion. Human primary cells incubated with type IV collagen showed downregulated extracellular signal-regulated kinase (ERK) activity, which induced MUC5AC hypersecretion but did not affect Akt activity. These results suggest that the addition of type IV collagen to the apical surface of primary cells downregulates MUC5AC secretion and has a cumulative effect on MUC5AC secretion which might be effected via the ERK signaling pathway.

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We studied the regulation of MUC5AC secretion by extracellular matrix proteins.

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The addition of type IV collagen reduced MUC5AC secretion in primary airway cells.

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The repeated addition of a low concentration of collagen reduced MUC5AC secretion.

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Type IV collagen induced the downregulation of ERK which induces MUC5AC secretion.

Purification, Characterization of Two Polysaccharides from Pinelliae Rhizoma Praeparatum Cum Alumine and Their Anti-Inflammatory Effects on Mucus Secretion of Airway Epithelium

Pinelliae Rhizoma Praeparatum cum Alumine (PRPCA) is an important traditional processed herbal medicine mainly used for treating phlegm in China for more than 2000 years. In our previous studies, extraction optimization, characterization, and bioactivities of total polysaccharides from PRPCA were investigated. In this study, further purification of these polysaccharides was performed. Two polysaccharides named neutral fraction of total polysaccharides-II (TPN-II) and acidic fraction of total polysaccharides-II (TPA-II) were obtained by gradient ion-exchange chromatography followed by gel-permeation chromatography. Results of scanning electron microscopy (SEM) analysis in the present study showed that TPN-II had a tight structure with a rough and uneven surface, while TPA-II had a relative homogeneous surface and a loose structure. Further studies indicated that TPN-II was a homosaccharide mainly composed by glucose with a molecular weight of 8.0 kDa. TPA-II was mainly composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose and arabinose in a molar ratio of 2.1, 2.3, 1.7, 10.6, 2.6, 14.2, and 2.5, with a molecular weight of 1250 kDa. The nuclear magnetic resonance (NMR) results indicated that α and β form glycoside bonds existed in TPN-II and TPA-II, and TPN-II was composed of α-glucopyranose. In addition, both purified polysaccharides have significant anti-inflammatory effects on mucus secretion of human airway epithelial NCI-H292 cells without cytotoxicity. Compared with TPN-II, TPA-II exhibited more significant anti-inflammatory effects on lipopolysaccharide (LPS)-induced airway inflammation by regulating levels of interleukin-4 (IL-4) and interferon-γ (IFN-γ) and inhibiting mucus secretion. The results suggest that polysaccharides from PRPCA could be explored as therapeutic agents in treating inflammation and over secretion of mucus in asthma.

MUC5B mucin production is upregulated by fibronectin and laminin in human lung epithelial cells via the integrin and ERK dependent pathway

MUC5B mucin is a principal component of airway mucus and plays a key role in biodefense. We investigated the regulation of MUC5B production using the signals from extracellular matrix (ECM) components in NCI-H292 human lung epithelial cells. We found that MUC5B production in NCI-H292 cells cultured on fibronectin or laminin increased by 4-5-fold, with the increase occurring in a dose- and time-dependent manner. In contrast, MUC5B production was unchanged on type-IV collagen. Inhibition of integrin β1 induced upregulation of MUC5B and MUC5AC; however, inhibition of p38 MAPK did not show any remarkable change in overproduced MUC5B. Inhibition of extracellular signal-regulated kinase (ERK) pathway or the transcription factor NF-κB induced the recovery of overproduced MUC5B on fibronectin and laminin. These results suggest that MUC5B production can be regulated by ECM components and that MUC5B is upregulated by fibronectin and laminin via the integrin, ERK, and NF-κB dependent pathway.