Bradykinin augments fibroblast-mediated contraction of released collagen gels

Bradykinin potentially stimulates cell proliferation in rabbit corneal endothelial cells through the ZO‑1/ZONAB pathway

Bradykinin (BK) has been demonstrated to induce proliferation in several types of cell in ex vivo corneas. However, the mechanisms underlying the action of BK on corneal endothelial cells (CECs) remain largely unknown. The present study aimed to investigate the effect of BK on rabbit corneal endothelial cell (RCEC) proliferation, and assess the involvement of the zonula occludens‑1(ZO‑1)/ZO‑1associated nucleic acid binding protein (ZONAB) pathway. Cell proliferation and cell cycle distribution was analyzed following treatment with BK (0.01, 0.1,1.0 or 10.0 µM) for the indicated time intervals (24, 48, 72 and 96 h), or following BK treatment combined with transfection of ZONAB‑small interfering (si)RNA for 72 h. In addition, the expression of tight junction ZO‑1, nuclear ZONAB, proliferating cell nuclear antigen(PCNA) and cyclin D1 were evaluated using western blotting or immunofluorescence. BK treatment was demonstrated to induce time‑ and concentration‑dependent cell proliferation and cell cycle progression, along with the upregulation of tight junction ZO‑1 and nuclear ZONAB, as well as PCNA and cyclin D1 protein expression. Furthermore, knockdown with ZONAB‑siRNA inhibited cell proliferation, induced cell cycle arrest and downregulated PCNA and cyclin D1 protein expression. ZONAB knockdown therefore successfully reversed the increase in proliferation induced by BK treatment. Taken together, these results suggested that BK stimulated RCEC proliferation, potentially via the ZO‑1/ZONAB pathway. The signaling paradigm disclosed in the present study potentially serves as an important therapeutic target for cornea regeneration and transplantation.

Combination of glycopyrronium and indacaterol inhibits carbachol-induced ERK5 signal in fibrotic processes

Background

Airway fibrosis is one of the pathological features of chronic obstructive pulmonary disease (COPD), and recent studies revealed that acetylcholine plays an important role in the development of airway remodeling by stimulating proliferation and collagen synthesis of lung fibroblasts. This study was designed to examine the effects of a long-acting muscarinic receptor antagonist (LAMA) glycopyrronium and a long-acting β2 adrenergic receptor agonist (LABA) indacaterol on acetylcholine-mediated fibrotic responses in lung fibroblasts.

Methods

After carbachol (CCh) or transforming growth factor-β1 (TGF-β1) exposure, the response to glycopyrronium and indacaterol was determined in vitro in fibroblasts isolated from mild-to-moderate COPD lung tissue. The ability of fibroblasts to mediate the contraction of collagen gels was assessed. The expression of α-smooth muscle actin (α-SMA) and the phosphorylation of extracellular-signal-regulated kinase 5 (ERK5) were determined by immunoblot. TGF-β1 was quantified by ELISA and acetylcholine was quantified by liquid chromatography tandem-mass spectrometry.

Results

CCh stimulated fibroblast-mediated collagen gel contraction and α-SMA expression and TGF-β1 release by fibroblasts. Blockade of autocrine TGF-β1 attenuated CCh-mediated fibrotic responses, while TGF-β1 did not stimulate acetylcholine release. Glycopyrronium plus indacaterol significantly attenuated CCh- and TGF-β1-mediated fibrotic responses through inhibition of ERK5 phosphorylation. Notably, the magnitudes of CCh- and TGF-β1-stimulated gel contraction, CCh-induced TGF-β1 release, and ERK5 phosphorylation were greater in fibroblasts isolated from COPD subjects than in those from non-smokers.

Conclusions

CCh induced TGF-β1 self-sustaining signaling loops by potentiating ERK5 signaling and promoted myofibroblast activity. This autocrine signaling mechanism may be an attractive therapeutic target to block the fibrotic response, which was modulated by the combination of glycopyrronium and indacaterol.

Bradykinin-induced asthmatic fibroblast/myofibroblast activities via bradykinin B2 receptor and different MAPK pathways

Bradykinin drives normal lung fibroblasts into myofibroblasts, induces fibroblast proliferation and activates mitogen activated protein kinase pathways (MAPK) but its effects on bronchial fibroblasts from asthmatics (HBAFb) have not been yet studied. We studied bradykinin-induced fibroblast proliferation and differentiation and the related intracellular mechanisms in HBAFb compared to normal bronchial fibroblasts (HNBFb). Bradykinin-stimulated HBAFb and HNBFb were used to assess: bradykinin B2 receptor expression by Western blot analysis; cell proliferation by [(3)H] thymidine incorporation; α-smooth muscle actin (SMA) expression/polymerization by Western blot and immunofluorescence; epidermal growth factor (EGF) receptor, extracellular-regulated kinase (ERK) 1/2 and p38 MAPK activation by immunoprecipitation and Western blot, respectively. Constitutive bradykinin B2 receptor and α-SMA expression was higher in HBAFb as compared to HNBFb. Bradykinin increased bradykinin B2 receptor expression in HBAFb. Bradykinin, via bradykinin B2 receptor, significantly increased fibroblast proliferation at lower concentration (10(-11)M) and α-SMA expression/polymerization at higher concentration (10(-6)M) in both cells. Bradykinin increased ERK1/2 and p38 phosphorylation via bradykinin B2 receptor; EGF receptor inhibitor AG1478 and panmetalloproteinase inhibitor GM6001 blocked bradykinin-induced ERK1/2 activation but not p38 phosphorylation. Bradykinin, via bradykinin B2 receptor, induced EGF receptor phosphorylation that was suppressed by AG1478. In HBAFb AG1478, GM6001, the ERK1/2-inhibitor U0126 and the p38 inhibitor SB203580 suppressed bradykinin-induced cell proliferation, but only SB203580 reduced myofibroblast differentiation. These data indicate that bradykinin is actively involved in asthmatic bronchial fibroblast proliferation and differentiation, through MAPK pathways and EGF receptor transactivation, by which bradykinin may contribute to airway remodeling in asthma, opening new horizons for potential therapeutic implications in asthmatic patients.

Pharmacological modulation of the bradykinin-induced differentiation of human lung fibroblasts: effects of budesonide and formoterol

OBJECTIVE

Bradykinin (BK) induces differentiation of lung fibroblasts into myofibroblasts, which play an important role in extracellular matrix remodeling in the airways of asthmatic patients. It is unclear whether this process is affected by antiasthma therapies. Here, we evaluated whether a glucocorticoid, budesonide (BUD), and a long-acting β2-agonist, formoterol (FM), either alone or in combination, modified BK-induced lung fibroblast differentiation, and affected the BK-activated intracellular signaling pathways.

METHODS

Human fetal lung fibroblasts were incubated with BUD (0.001-0.1 μM) and/or FM (0.0001-0.1 μM) before exposure to BK (0.1 or 1 μM). Fibroblast differentiation into α-smooth-muscle-actin-positive (α-SMA⁺) myofibroblasts, BK2 receptor (B2R) expression, extracellular signal-regulated kinase 1/2 (ERK 1/2) phosphorylation (p-ERK1/2), intracellular Ca²⁺ concentration ([Ca²⁺]i), and p65 nuclear factor kappa B translocation were evaluated.

RESULTS

BUD (0.1 μM) and FM (0.1 μM), either alone or in combination, completely inhibited BK-induced α-SMA protein expression and decreased the numbers of α-SMA⁺ fibroblasts, with a clear reduction in α-SMA stress fibers organization. BUD also completely inhibited the increase of B2R, whereas FM with or without BUD had no effect. BK-induced increases of [Ca²⁺]i and p-ERK1/2 were significantly reduced to similar levels by BUD and FM, either alone or in combination, whereas p65 translocation was completely inhibited by all treatments.

CONCLUSION

Both BUD and FM, either alone or in combination, effectively inhibited the BK-induced differentiation of fibroblasts into α-SMA⁺ myofibroblasts and the intracellular signaling pathways involved in fibroblast activation. These results suggest that BUD and FM combination therapy has potential to inhibit fibroblast-dependent matrix remodeling in the airways of asthmatic patients.

Soft tissue mechanotransduction in wound healing and fibrosis

Recent evidence suggests that mechanical forces can significantly impact the biologic response to injury. Integrated mechanical and chemical signaling networks have been discovered that enable physical cues to regulate disease processes such as pathologic scar formation. Distinct molecular mechanisms control how tensional forces influence wound healing and fibrosis. Conceptual frameworks to understand cutaneous repair have expanded beyond traditional cell-cytokine models to include dynamic interactions driven by mechanical force and the extracellular matrix. Strategies to manipulate these biomechanical signaling networks have tremendous therapeutic potential to reduce scar formation and promote skin regeneration.

Pain mediators and wound healing--establishing the connection

Pain accompanies every disruption of the skin surface in a normal sensate individual. The intensity and duration of the pain varies depending on the nature of trauma, the healing trajectory and various host factors. Pain mediator release is the mechanism for pain perception following peripheral stimulus and central interpretation. The various mediators may have promoting effects on wound healing in the short term, but it appears that protracted release of these mediators may well have detrimental effects on wound healing. The exaggerated release of pain mediators may result in nociceptor hypersensitization, hyperinflammatory cellular and extracellular matrix (ECM) changes, and in some cases, the potential for a fibrotic healing pattern. This relates to an imbalance between mediators with differing healing characteristics arising in certain pathological conditions. In this respect, it may be worth examining pain mediator agonists or antagonists, not only on compassionate grounds of pain control, but relating to the potential effects on overall wound healing.

Bradykinin-mediated cell proliferation depends on transactivation of EGF receptor in corneal fibroblasts

In previous studies, bradykinin (BK) has been shown to induce cell proliferation through BK B2 receptor (B2R) via p42/p44 MAPK in Statens Seruminstitut Rabbit Corneal Cells (SIRCs). In addition to this pathway, EGFR transactivation pathway has been implicated in linking a variety of G-protein coupled receptors to MAPK cascades. Here, we further investigate whether these transactivation mechanisms participating in BK-induced cell proliferation in SIRCs. Using an immunofluorescence staining and RT-PCR, we initially characterize that SIRCs were corneal fibroblasts and predominantly expressed B2R by BK. Inhibition of p42/p44 MAPK by the inhibitors of Src, EGFR, and Akt or transfection with respective siRNAs prevents BK-induced DNA synthesis in SIRCs. The mechanisms underlying these responses were mediated through phosphorylation of Src and EGFR via the formation of Src/EGFR complex which was attenuated by PP1 and AG1478. Moreover, BK-induced p42/p44 MAPK and Akt activation was mediated through EGFR transactivation, which was diminished by the inhibitors of MMP-2/9 and heparin-binding EGF-like factor (HB-EGF). Finally, increased nuclear translocation of Akt and p42/p44 MAPK turns on early gene expression leading to cell proliferation. These results suggest that BK-induced cell proliferation is mediated through c-Src-dependent transactivation of EGFR via MMP2/9-dependent pro-HB-EGF shedding linking to activation of Akt and p42/p44 MAPK in corneal fibroblasts.

Integrin-specific mechanoresponses to compression and extension probed by cylindrical flat-ended AFM tips in lung cells

Cells from lung and other tissues are subjected to forces of opposing directions that are largely transmitted through integrin-mediated adhesions. How cells respond to force bidirectionality remains ill defined. To address this question, we nanofabricated flat-ended cylindrical Atomic Force Microscopy (AFM) tips with ~1 µm(2) cross-section area. Tips were uncoated or coated with either integrin-specific (RGD) or non-specific (RGE/BSA) molecules, brought into contact with lung epithelial cells or fibroblasts for 30 s to form focal adhesion precursors, and used to probe cell resistance to deformation in compression and extension. We found that cell resistance to compression was globally higher than to extension regardless of the tip coating. In contrast, both tip-cell adhesion strength and resistance to compression and extension were the highest when probed at integrin-specific adhesions. These integrin-specific mechanoresponses required an intact actin cytoskeleton, and were dependent on tyrosine phosphatases and Ca(2+) signaling. Cell asymmetric mechanoresponse to compression and extension remained after 5 minutes of tip-cell adhesion, revealing that asymmetric resistance to force directionality is an intrinsic property of lung cells, as in most soft tissues. Our findings provide new insights on how lung cells probe the mechanochemical properties of the microenvironment, an important process for migration, repair and tissue homeostasis.

Relaxant effect of prostaglandin D(2)--receptor DP agonist on liver myofibroblast contraction

Increased intrahepatic resistance causes portal hypertension in cirrhosis. Liver myofibroblasts (MFs) are now regarded as the principle cells involved in sinusoidal blood flow regulation. Many other prostaglandin-receptor agonists have been reported to regulate liver MF contraction, but the role of the prostaglandin D(2)-receptor DP is unknown. In this study, we investigated the effect of a synthetic agonist of prostanoid DP receptor, BW245C, on contractile properties of primary rat liver MFs. Collagen gel contraction assay revealed that BW245C alone (1 and 10 µM) did not induce contraction but induced cell relaxation. Pretreatment with BW245C (10 µM, 30 min) attenuated bradykinin (100 nM)-induced liver MF contraction. Elevation of [Ca(2+)](i) induced by bradykinin (100 nM) was partially suppressed by BW245C pretreatment (10 µM, 3 min). BW245C (1 and 10 µM) significantly increased intracellular cAMP level in a dose-dependent manner. Pretreatment with forskolin (30 - 300 nM, 30 min) and dibutyryl-cAMP (3 - 30 µM, 30 min) significantly reduced bradykinin-induced contraction. Furthermore, a protein kinase A (PKA) inhibitor KT5720 (10 nM to 1 µM, 30 min) blocked the relaxant effect of BW245C. These results suggest that prostanoid DP receptor agonism inhibits bradykinin-induced [Ca(2+)](i) elevation and contraction through cAMP-PKA signal activation in rat liver MFs.

Use of a three-dimensional cell culture model to study airway smooth muscle-mast cell interactions in airway remodeling

Increased airway smooth muscle (ASM) mass and infiltration by mast cells are key features of airway remodeling in asthma. We describe a model to investigate the relationship between ASM, the extracellular matrix, mast cells, and airway remodeling. ASM cells were cultured in a three-dimensional (3-D) collagen I gel (3-D culture) alone or with mast cells. Immunocytochemistry and Western blotting of ASM in 3-D cultures revealed a spindle-shaped morphology and significantly lower alpha-smooth muscle actin and vimentin expression than in ASM cultured in monolayers on collagen type I or plastic (2-D culture). In 3-D cultures, basal ASM proliferation, examined by Ki67 immunocytochemistry, was reduced to 33 +/- 7% (P < 0.05) of that in 2-D cultures. The presence of mast cells in cocultures increased ASM proliferation by 1.8-fold (P < 0.05). Gelatin zymography revealed more active matrix metalloproteinase (MMP)-2 in 3-D than in 2-D culture supernatants over 7 days. Functional MMP activity was examined by gel contraction. The spontaneous gel contraction over 7 days was significantly inhibited by the MMP inhibitor ilomastat. Mast cell coculture enhanced ASM gel contraction by 22 +/- 16% (not significant). Our model shows that ASM has different morphology, with lower contractile protein expression and basal proliferation in 3-D culture. Compared with standard techniques, ASM synthetic function, as shown by MMP production and activity, is sustained over longer periods. The presence of mast cells in the 3-D model enhanced ASM proliferation and MMP production. Airway remodeling in asthma may be more accurately modeled by our system than by standard culture systems.

Eosinophil cationic protein stimulates TGF-beta1 release by human lung fibroblasts in vitro

Eosinophilic inflammation and airway remodeling are features of asthma. Eosinophil cationic protein (ECP) is released by activated eosinophils and transforming growth factor (TGF)-beta(1) has major functions in the fibrotic process. We therefore hypothesized that ECP stimulates TGF-beta(1) release by human lung fibroblasts. Fibroblasts in monolayer displayed a constitutive release of TGF-beta(1), which increased in presence of ECP (436 +/- 60 vs. 365 +/- 48 pg/ml at 48 h; P < 0.01). mRNA expression of TGF-beta(1) was almost twofold in ECP-stimulated fibroblasts. ECP in three-dimensional cultures stimulated both TGF-beta(1) release (180 +/- 61 vs. 137 +/- 54 pg/ml; P < 0.01) and fibroblast-mediated collagen gel contraction (28 vs. 39% of initial gel area at 48 h; P < 0.001). ECP stimulates TGF-beta(1)-release by human lung fibroblasts, suggesting a potential mechanism for eosinophils in the fibrotic response. This may be an important mechanism by which ECP promotes remodeling of extra cellular matrix leading to airway fibrosis in asthmatics.

Expression and localization of diacylglycerol kinase isozymes and enzymatic features in rat lung

Diacylglycerol kinase (DGK) catalyzes phosphorylation of diacylglycerol to generate phosphatidic acid, and both molecules are known to serve as second messengers as well as important intermediates for the synthesis of various lipids. In this study, we investigated the spatiotemporal expression patterns of DGK isozymes together with the developmental changes of the mRNA expression and enzymatic property in rat lung. Northern blot and RT-PCR analyses showed that mRNAs for DGKalpha, -epsilon, and -zeta were detected in the lung. By immunohistochemical examination, DGKalpha and -zeta were shown to be coexpressed in alveolar type II cells and macrophages. Interestingly, these isozymes were localized at distinct subcellular locations, i.e., DGKalpha in the cytoplasm and DGKzeta in the nucleus, suggesting different roles for these isozymes. In the developing lung, the expression for DGKalpha and -zeta was transiently elevated on embryonic day 21 (E21) to levels approximately two- to threefold higher than on postnatal day 0 (P0). On the other hand, the expression for DGKepsilon was inversely elevated approximately twofold on P0 compared with that on E21. These unique changes in the expression pattern during the perinatal period suggest that each isozyme may play a distinct role in the adaptation of the lung to air or oxygen breathing at birth.

The effect of eosinophils on collagen gel contraction and implications for tissue remodelling

Asthma is characterized by an eosinophilic inflammation and a subepithelial fibrosis in the airways. Eosinophils contain several cytotoxic substances, such as eosinophil cationic protein (ECP), which can promote inflammation and cause tissue damage. This has generated the hypothesis that eosinophils may drive remodelling of extracellular matrix (ECM). To investigate the role of eosinophils we used an in vitro model for remodelling, the three-dimensional collagen gel contraction assay. Two sources of eosinophils were used in this study, isolated human peripheral eosinophils (purity > 95%) and stimulated [interleukin (IL)-5, IL-3 and granulocyte macrophage-colony stimulating factor (GM-CSF)] HL-60 clone 15 cells. Human eosinophils or HL-60 cells were cast together with human lung fibroblasts (HFL1) in type I collagen gels. Both types of eosinophils augmented fibroblast-mediated collagen gel contraction in a time and concentration-dependent manner. At 48 h, the gel area in HFL1/eosinophil co-culture was 46.5% +/- 0.5 (mean +/- s.e.m.) of initial area and in HFL1 culture 52.3% +/- 0.1 (P < 0.001). Respective figures for HFL1/stimulated HL-60 co-culture and HFL1 culture only were 44.1% +/- 0.5 and 52.4% +/- 0.4 (P < 0.001). The release of ECP was increased when fibroblasts were cultured with eosinophils compared to eosinophils cultured alone. In addition, native ECP added to fibroblast gel cultures also augmented contraction. Our results suggest that eosinophils may interact with mesenchymal cells, promoting remodelling of ECM and that ECP constitutes one potential eosinophil-derived mediator driving this process. We conclude that this may be one important mechanism by which eosinophil-ECM interactions will lead to airway tissue remodelling in asthma.

Platelets stimulate fibroblast-mediated contraction of collagen gels

BACKGROUND

Platelets are thought to play a role in a variety of inflammatory conditions in the lung, some of which may lead to fibrosis. In the current study we tested the hypothesis that whole platelets and platelet lysate can mediate remodelling of extracellular matrix in vitro by affecting fibroblast-mediated contraction of a collagen gel. We also sought to determine to what extent platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) contribute to this effect.

METHODS

Washed platelets, isolated from healthy blood donors, and platelet lysate (freezing and thawing), were cast together with human lung fibroblasts in three-dimensional collagen gels. The gels were then released and cultured for four days. PDGF and TGF-beta1 concentrations were measured in culture supernatants by ELISA.

RESULTS

Both platelets and platelet lysate augmented fibroblast-mediated gel contraction in a time and concentration dependent manner (19.9% +/- 0.1 (mean +/- SEM) of initial area vs. 48.0% +/- 0.4 at 48 hours; P < 0.001 and 41.5% +/- 0.6 vs. 60.6% +/- 0.3 at 48 hours; P < 0.001, respectively). Fixed platelets had no effect in the system. Both TGF-beta1 and PDGF-AA/AB were released in co-culture. PDGF-AA/AB had a maximum release at 24 hours whereas TGF-beta1 release increased with longer culture periods. Neutralising antibodies to these mediators partially inhibited platelet-induced gel contraction.

CONCLUSION

We conclude that platelets may promote remodelling of extracellular matrix in vitro and that PDGF and TGF-beta partially mediate this effect, also indicating a role for other mediators. The findings may be an important mechanism in regulating repair processes after injury.