Exogenous S100A8 protein inhibits PDGF-induced migration of airway smooth muscle cells in a RAGE-dependent manner

Stressed out - The role of oxidative stress in airway smooth muscle dysfunction in asthma and COPD

The airway smooth muscle (ASM) surrounding the airways is dysfunctional in both asthma and chronic obstructive pulmonary disease (COPD), exhibiting; increased contraction, increased mass, increased inflammatory mediator release and decreased corticosteroid responsiveness. Due to this dysfunction, ASM is a key contributor to symptoms in patients that remain symptomatic despite optimal provision of currently available treatments. There is a significant body of research investigating the effects of oxidative stress/ROS on ASM behaviour, falling into the following categories; cigarette smoke and associated compounds, air pollutants, aero-allergens, asthma and COPD relevant mediators, and the anti-oxidant Nrf2/HO-1 signalling pathway. However, despite a number of recent reviews addressing the role of oxidative stress/ROS in asthma and COPD, the potential contribution of oxidative stress/ROS-related ASM dysfunction to asthma and COPD pathophysiology has not been comprehensively reviewed. We provide a thorough review of studies that have used primary airway, bronchial or tracheal smooth muscle cells to investigate the role of oxidative stress/ROS in ASM dysfunction and consider how they could contribute to the pathophysiology of asthma and COPD. We summarise the current state of play with regards to clinical trials/development of agents targeting oxidative stress and associated limitations, and the adverse effects of oxidative stress on the efficacy of current therapies, with reference to ASM related studies where appropriate. We also identify limitations in the current knowledge of the role of oxidative stress/ROS in ASM dysfunction and identify areas for future research.

Inhibitory Effect of S100A11 on Airway Smooth Muscle Contraction and Airway Hyperresponsiveness

OBJECTIVE

S100A11 is a member of the S100 calcium-binding protein family and has intracellular and extracellular regulatory activities. We previously reported that S100A11 was differentially expressed in the respiratory tracts of asthmatic rats as compared with normal controls. Here, we aimed to analyze the potential of S100A11 to regulate both allergen-induced airway hyperresponsiveness (AHR) as well as acetylcholine (ACh)-induced hypercontractility of airway smooth muscle (ASM) and contraction of ASM cells (ASMCs).

METHODS

Purified recombinant rat S100A11 protein (rS100A11) was administered to OVA-sensitized and challenged rats and then the AHR of animals was measured. The relaxation effects of rS100A11 on ASM were detected using isolated tracheal rings and primary ASMCs. The expression levels of un-phosphorylated myosin light chain (MLC) and phosphorylated MLC in ASMCs were analyzed using Western blotting.

RESULTS

Treatment with rS100A11 attenuated AHR in the rats. ASM contraction assays showed that rS100A11 reduced the contractile responses of isolated tracheal rings and primary ASMCs treated with ACh. In addition, rS100A11 markedly decreased the ACh-induced phosphorylation of the myosin light chain in ASMCs. Moreover, rS100A11 also suppressed the contractile response of tracheal rings in calcium-free buffer medium.

CONCLUSION

These results indicate that S100A11 protein can relieve AHR by relaxing ASM independently of extracellular calcium. Our data support the idea that S100A11 is a potential therapeutic target for reducing airway resistance in asthma patients.

The axis of the receptor for advanced glycation endproducts in asthma and allergic airway disease

Asthma is a generalized term that describes a scope of distinct pathologic phenotypes of variable severity, which share a common complication of reversible airflow obstruction. Asthma is estimated to affect almost 400 million people worldwide, and nearly ten percent of asthmatics have what is considered "severe" disease. The majority of moderate to severe asthmatics present with a "type 2-high" (T2-hi) phenotypic signature, which pathologically is driven by the type 2 cytokines Interleukin-(IL)-4, IL-5, and IL-13. However, "type 2-low" (T2-lo) phenotypic signatures are often associated with more severe, steroid-refractory neutrophilic asthma. A wide range of clinical and experimental studies have found that the receptor for advanced glycation endproducts (RAGE) plays a significant role in the pathogenesis of asthma and allergic airway disease (AAD). Current experimental data indicates that RAGE is a critical mediator of the type 2 inflammatory reactions which drive the development of T2-hi AAD. However, clinical studies demonstrate that increased RAGE ligands and signaling strongly correlate with asthma severity, especially in severe neutrophilic asthma. This review presents an overview of the current understandings of RAGE in asthma pathogenesis, its role as a biomarker of disease, and future implications for mechanistic studies, and potential therapeutic intervention strategies.

S100A4 is secreted by airway smooth muscle tissues and activates inflammatory signaling pathways via receptors for advanced glycation end products

S100A4 is a low-molecular-mass (12 kDa) EF-hand Ca²⁺-binding S100 protein that is expressed in a broad range of normal tissue and cell types. S100A4 can be secreted from some cells to act in an autocrine or paracrine fashion on target cells and tissues. S100A4 has been reported in the extracellular fluids of subjects with several inflammatory diseases, including asthma. Airway smooth muscle plays a critical role in airway inflammation by synthesizing and secreting inflammatory cytokines. We hypothesized that S100A4 may play an immunomodulatory role in airway smooth muscle. Trachealis smooth muscle tissues were stimulated with recombinant His-S100A4, and the effects on inflammatory responses were evaluated. S100A4 induced the activation of Akt and NF-κB and stimulated eotaxin secretion. It also increased the expression of RAGE and endogenous S100A4 in airway tissues. Stimulation of airway smooth muscle tissues with IL-13 or TNF-α induced the secretion of S100A4 from the tissues and promoted the expression of endogenous receptors for advanced glycation end products (RAGE) and S100A4. The role of RAGE in mediating the responses to S100A4A was evaluated by expressing a mutant nonfunctional RAGE (RAGEΔcyto) in tracheal muscle tissues and by treating tissues with a RAGE inhibitor. S100A4 did not activate NF-κB or Akt in tissues that were expressing RAGEΔcyto or treated with a RAGE inhibitor, indicating that S100A4 mediates its effects by acting on RAGE. Our results demonstrate that inflammatory mediators stimulate the synthesis and secretion of S100A4 in airway smooth muscle tissues and that extracellular S100A4 acts via RAGE to mediate airway smooth muscle inflammation.

Role of Platelet-Derived Growth Factor (PDGF) in Asthma as an Immunoregulatory Factor Mediating Airway Remodeling and Possible Pharmacological Target

Asthma is a chronic and heterogenic disease of the respiratory system, one of the most common lung diseases worldwide. The underlying pathologies, which are chronic inflammatory process and airway remodeling (AR), are mediated by numerous cells and cytokines. Particularly interesting in this field is the platelet-derived growth factor (PDGF), one of the members of the human growth factor family. In this article, the authors analyze the available data on the role of PDGF in asthma in experimental models and in human research. PDGF is expressed in airway by various cells contributing to asthma pathogenesis—mast cells, eosinophils, and airway epithelial cells. Research confirms the thesis that this factor is also secreted by these cells in the course of asthma. The main effects of PDGF on bronchi are the proliferation of airway smooth muscle (ASM) cells, migration of ASM cells into the epithelium and enhanced collagen synthesis by lung fibroblasts. The importance of AR in asthma is well recognized and new therapies should also aim to manage it, possibly targeting PDGFRs. Further studies on new and already existing drugs, mediating the PDGF signaling and related to asthma are necessary. Several promising drugs from the tyrosine kinase inhibitors group, including nilotinib, imatinib masitinib, and sunitinib, are currently being clinically tested and other molecules are likely to emerge in this field.

[Effect of acupuncture on TGF-β1/Smads pathway in mice with airway remodeling mic]

OBJECTIVE

To investigate the effect of acupuncture on TGF-β1/Smads signaling pathway in the lung tissue of mice with airway remodeling.

METHODS

Thirty specific pathogen-free mice were randomly divided into blank group, model group and acupuncture group (n=10). Mouse models of asthma were established in the model group and the acupuncture group, and the mice in the latter group received 7 acupuncture therapies (at bilateral Fei Shu, Da Zhui and Zu Sanli, 20 min each time) every other day, starting on the 10th day after the modeling. At 24 h after the last acupuncture, the mice were subjected to inhalation of 1% OVA for 3 days, and 24 h after the last challenge, the mice were given methacholine chloride (Mch) inhalation at different concentrations for measurement of lung resistance using a noninvasive stroke volume meter. HE staining was used to observe the pathological changes in the lung tissues, and TGF-β1 levels in the the bronchoalveolar lavage fluid (BALF) and serum were detected using ELISA; Western blotting was used to detect the differential protein expressions in the airway smooth muscles between the two groups. The airway smooth muscle cells were isolated from the mice in the acupuncture group and treated with a TGF- β1 inhibitor (LY2157299), and the relative expressions of type-Ⅰ and Smads proteins were detected using Western blotting.

RESULTS

The mice in the model showed obvious tracheal fistula with airway pathologies including lumen narrowing, bronchial mucosa thickening, dissociation of the epithelial cells, and thickening of the alveolar septum and airway smooth muscles. These pathological changes were obviously milder in the acupuncture group. The asthmatic mice exhibited significantly increased lung resistance in positive correlation with Mch concentration. Serum TGF-β1 level was significantly elevated in asthmatic mice (P < 0.05); TGF-β1 levels in the serum and BALF were significantly lower in the acupuncture group than in the model group (P < 0.05). In the model group, the expressions of α-SMA, TGF-β1 and Smads in the airway smooth muscles were significantly higher than those in the other two groups (both P < 0.05). In cultured airway smooth muscle cells, the expressions of type-Ⅰ and Smads were significantly higher in cells treated with LY2157299 than in the control cells (P>0.05).

CONCLUSIONS

Acupuncture can inhibit airway remodeling by inhibiting the expression of airway TGF-β1 and down-regulating the expression of Smads and α-SMA to reduce airway inflammatory response. Airway expressions of type-Ⅰ and Smads proteins remain high after inhibiting TGF-β1. Acupuncture may control asthma progression through the TGF-β1/Smads pathway.

Paeoniflorin inhibits PDGF‑BB‑induced human airway smooth muscle cell growth and migration

Abnormal proliferation and migration of airway smooth muscle cells (ASMCs) is important in the progression of asthma. Paeoniflorin (PF), one of the major active ingredients of Paeonia lactiflora, has been reported to exhibit anti‑asthmatic effects. However, the effects of PF in the regulation of platelet‑derived growth factor (PDGF)‑BB‑induced ASMC proliferation and migration remain unknown. The present study was designed to investigate the effects of PF on human ASMCs and the underlying mechanism. The results demonstrated that PF treatment significantly reduced the numbers of live ASMC cells and their PDGF‑BB‑induced migration. PF treatment also suppressed PDGF‑BB‑induced α‑smooth muscle actin expression in ASMCs. Furthermore, pretreatment with PF reduced PDGF‑BB‑induced phosphorylation of phosphoinositide 3‑kinase (PI3K) and AKT serine/threonine kinase 1 (Akt) in ASMCs. In conclusion, the present study demonstrated for the first time that PF inhibited ASMC growth and migration induced by PDGF‑BB, and that this effect may be partly due to inhibition of the PI3K/Akt signaling pathway. The results provide novel information regarding the role of PF as a potential therapeutic agent for the treatment of asthma.

S100A8 inhibits PDGF-induced proliferation of airway smooth muscle cells dependent on the receptor for advanced glycation end-products

Background

Airway remodeling is a key feature of asthma, characterized by increased proliferation of airway smooth muscle cells (ASMCs). S100A8 is a calcium-binding protein with a potential to regulate cell proliferation. Here, the effect of exogenous S100A8 protein on the proliferation of ASMCs induced by platelet-derived growth factor (PDGF) and the underlying molecular mechanism was investigated.

Methods

Rat ASMCs were cultured with or without a neutralizing antibody to the receptor for advanced glycation end-products (RAGE), a potential receptor for S100A8 protein. Purified recombinant rat S100A8 protein was then added into the cultured cells, and the proliferation of ASMCs induced by PDGF was detected by colorimetric-based WST-8 assay and ampedance-based xCELLigence proliferation assay. The expression levels of RAGE in ASMCs were analyzed using western blotting assay.

Results

Results showed that exogenous S100A8 inhibited the PDGF-induced proliferation of rat ASMCs in a dose-dependent manner with the maximal effect at 1 μg/ml in vitro. Furthermore, when ASMCs was pre-treated with anti-RAGE neutralizing antibody, the inhibitory effect of S100A8 on PDGF-induced proliferation was significantly suppressed. In addition, neither the treatment with S100A8 or PDGF alone nor the pre-treatment with rS100A8 followed by PDGF stimulation affected the expression levels of RAGE.

Conclusions

Our study demonstrated that S100A8 inhibits PDGF-induced ASMCs proliferation in a manner dependent on membrane receptor RAGE.

S100A8 protein attenuates airway hyperresponsiveness by suppressing the contraction of airway smooth muscle

Airway hyperresponsiveness (AHR) is a major clinical problem in allergic asthma mainly caused by the hypercontractility of airway smooth muscles (ASM). S100A8 is an important member of the S100 calcium-binding protein family with a potential to regulate cell contractility. Here, we analyze the potential of S100A8 to regulate allergen-induced AHR and ASM contraction. Treatment with recombinant S100A8 (rS100A8) diminished airway hyperresponsiveness in OVA-sensitized rats. ASM contraction assays showed that rS100A8 reduced hypercontractility in both isolated tracheal rings and primary ASM cells treated by acetylcholine. rS100A8 markedly rescued the phosphorylation level of myosin light chain induced by acetylcholine in ASM cells. These results show that rS100A8 plays a protective role in regulating AHR in asthma by inhibiting ASM contraction. These results support S100A8 as a novel therapeutic target to control ASM contraction in asthma.