Bradykinin-stimulated p42/p44 MAPK activation associated with cell proliferation in corneal keratocytes

Bradykinin (BK) is released into the tear-film in ocular allergic patients. BK has been shown to exert mitogenic effects on several cell types. However, the mechanisms underlying its action on corneal keratocytes (CKs) were largely unknown. This study was to investigate the mitogenic effect of BK on rabbit CKs linked to activation of p42/p44 mitogen-activated protein kinase (MAPK), assessed by [H-3]thymidine incorporation and Western blotting analysis, respectively. BK stimulated [H-3]thymidine incorporation and p42/p44 MAPK phosphorylation in a time- and concentration-dependent manner. Pretreatment with pertussis toxin attenuated the BK-induced responses. BK-stimulated responses were attenuated by inhibitors of selective B-2 receptor (Hoe 140), phosphatidylinositol (PI)-PLC (U73122), an intracellular Ca2+ chelator (BAPTA/AM), PKC (GF109203X), tyrosine kinase (genistein), and MEK1/2 (PD98059). BK also stimulated translocation of p42/p44 MAPK into nucleus and led to expression of c-fos and c-jun in CKs. These results demonstrate that in CKs, BK-stimulated phosphorylation of p42/p44 MAPK is mediated through the activation of BK B-2 receptors and leads to cell proliferation. (C) 2003 Elsevier Inc. All rights reserved.