TGF-beta potentiates airway smooth muscle responsiveness to bradykinin.
The molecular mechanisms by which bradykinin induces excessive airway obstruction in asthmatics remain unknown. Transforming growth factor (TGF)-beta has been involved in regulating airway inflammation and remodeling in asthma, although it is unknown whether TGF-beta can modulate bradykinin-associated bronchial hyperresponsiveness. To test whether TGF-beta directly modulates airway smooth muscle (ASM) responsiveness to bradykinin, isolated murine tracheal rings were used to assess whether TGF-beta alters ASM contractile responsiveness to bradykinin. Interestingly, we found TGF-beta-treated murine rings (12.5 ng/ml, 18 h) exhibited increased expression of bradykinin 2 (B(2)) receptors and became hyperreactive to bradykinin, as shown by increases in maximal contractile responses and receptor distribution. We investigated the effect of TGF-beta on bradykinin-evoked calcium signals since calcium is a key molecule regulating ASM excitation-contraction coupling. We reported that TGF-beta, in a dose- (0.5-10 ng/ml) and time- (2-24 h) dependent manner, increased mRNA and protein expression of the B(2) receptor in cultured human ASM cells. Maximal B(2) receptor protein expression that colocalized with CD44, a marker of membrane cell surface, occurred after 18 h of TGF-beta treatment and was further confirmed using fluorescence microscopy. TGF-beta (2.5 ng/ml, 18 h) also increased bradykinin-induced intracellular calcium mobilization in fura-2-loaded ASM cells. TGF-beta-mediated enhancement of calcium mobilization was not attenuated with indomethacin, a cyclooxygenase inhibitor. These data demonstrate for the first time that TGF-beta may play a role in mediating airway hyperresponsiveness to bradykinin seen in asthmatics by enhancing ASM contractile responsiveness to bradykinin, possibly as a result of increased B(2) receptor expression and signaling.
Kim
Jenny H
JH
Pulmonary, Allergy, and Critical Care Division, Dept. of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Jain
Deepika
D
Tliba
Omar
O
Yang
Bei
B
Jester
William F
WF
Panettieri
Reynold A
RA
Amrani
Yassine
Y
Puré
Ellen
E
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004357:Drug Synergism; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology; D008168:Lung / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D043782:Receptor, Bradykinin B2 / Q000378:metabolism; D012130:Respiratory Hypersensitivity / Q000503:physiopathology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D043782:Receptor, Bradykinin B2; D016212:Transforming Growth Factor beta; D001920:Bradykinin; D002118:Calcium; D007213:Indomethacin