Bradykinin differentiates human lung fibroblasts to a myofibroblast phenotype via the B2 receptor.
BACKGROUND
The identification of factors mediating the transition of lung fibroblasts into myofibroblasts is considered fundamental in the comprehension of abnormal reparative processes. Bradykinin, a mediator known for its proinflammatory action, is able to induce cytokine production and contractility in fibroblast cultures.


OBJECTIVE
In this study the ability of bradykinin to drive fibroblast into a myofibroblast phenotype at the cellular and molecular level was evaluated.


METHODS
alpha-Smooth muscle actin (alpha-SMA) expression and TGF-beta in bradykinin stimulated fibroblasts were tested by means of flow cytometry, Western blot, and RT-PCR. Cell proliferation and collagen production were evaluated by the colorimetric methylthiazol tetrazolium assay and sirius red assay, respectively. Which bradykinin receptor mediates the expression of alpha-SMA was evaluated using selective B1 and B2 blocking agents. Furthermore, the effect of bradykinin on extracellular signal-regulated kinase 1/2 phosphorylation was explored.


RESULTS
Bradykinin caused in lung fibroblasts a significant increase in alpha-SMA at the cellular and molecular level. The B2 receptor was held responsible for this effect because a specific receptor antagonist had entirely blocked this effect. Bradykinin was able to induce fibroblast proliferation and collagen production. Bradykinin significantly activated mitogen-activated protein kinase pathway by phosphorylating extracellular signal-regulated kinase 1/2, whereas PD98059, a specific inhibitor, was able to block myofibroblast induction. Although bradykinin induced an increase of TGF-beta on fibroblasts, the blockage of this cytokine did not alter alpha-SMA expression.


CONCLUSIONS
The data support the hypothesis that bradykinin may be involved in bronchial remodeling and lung fibrosis beyond its well recognized proinflammatory activity, also suggesting a new potential therapeutic strategy to control altered reparatory processes.
Vancheri
Carlo
C
Department of Internal and Specialistic Medicine, Section of Respiratory Diseases, University of Catania, Italy.
Gili
Elisa
E
Failla
Marco
M
Mastruzzo
Claudio
C
Salinaro
Elisa Trovato
ET
Lofurno
Debora
D
Pistorio
Maria P
MP
La Rosa
Cristina
C
Caruso
Massimo
M
Crimi
Nunzio
N
D000199:Actins / Q000032:analysis*; D001920:Bradykinin / Q000494:pharmacology*; D049109:Cell Proliferation; D003094:Collagen / Q000096:biosynthesis; D005347:Fibroblasts / Q000737:chemistry / Q000166:cytology*; D006801:Humans; D008168:Lung / Q000166:cytology*; D020935:MAP Kinase Signaling System / Q000502:physiology; D009130:Muscle, Smooth / Q000737:chemistry; D010641:Phenotype; D043783:Receptor, Bradykinin B1 / Q000502:physiology; D043782:Receptor, Bradykinin B2 / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000502:physiology
D000199:Actins; D043783:Receptor, Bradykinin B1; D043782:Receptor, Bradykinin B2; D016212:Transforming Growth Factor beta; D003094:Collagen; D001920:Bradykinin