title: Tissue kallikrein mediates pro-inflammatory pathways and activation of protease-activated receptor-4 in proximal tubular epithelial cells.
abstract: Tissue kallikrein (KLK1) expression is up-regulated in human diabetic kidney tissue and induced by high glucose (HG) in human proximal tubular epithelial cells (PTEC). Since the kallikrein-kinin system (KKS) has been linked to cellular inflammatory process in many diseases, it is likely that KLK1 expression may mediate the inflammatory process during the development of diabetic nephropathy. In this study, we explored the role of KLK1 in tubular pro-inflammatory responses under the diabetic milieu. Recombinant KLK1 stimulated the production of inflammatory cytokines in PTEC via the activation of p42/44 and p38 MAPK signaling pathways. Molecular knockdown of endogenous KLK1 expression by siRNA transfection in PTEC attenuated advanced glycation end-products (AGE)-induced IL-8 and ICAM-1 productions in vitro. Interestingly, exposure of PTEC to KLK1 induced the expression of protease-activated receptors (PARs). There was a 2.9-fold increase in PAR-4, 1.4-fold increase in PAR-1 and 1.2-fold increase in PAR-2 mRNA levels. Activation of PAR-4 by a selective agonist was found to elicit the pro-inflammatory and pro-fibrotic phenotypes in PTEC while blockade of the receptor by specific antagonist attenuated high glucose-induced IL-6, CCL-2, CTGF and collagen IV expression. Calcium mobilization by the PAR-4 agonist in PTEC was desensitized by pretreatment with KLK1. Consistent with these in vitro findings, there was a markedly up-regulation of tubular PAR-4 expression in human diabetic renal cortical tissues. Together, these results suggest that up-regulation of KLK1 in tubular epithelial cells may mediate pro-inflammatory pathway and PAR activation during diabetic nephropathy and provide a new therapeutic target for further investigation.
authors.affiliation: Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong.
authors.forename: Wai Han
authors.initials: WH
authors.lastname: Yiu
authors.affiliation: Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong.
authors.forename: Dickson W L
authors.initials: DW
authors.lastname: Wong
authors.affiliation: Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong.
authors.forename: Loretta Y Y
authors.initials: LY
authors.lastname: Chan
authors.affiliation: Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong.
authors.forename: Joseph C K
authors.initials: JC
authors.lastname: Leung
authors.affiliation: Department of Pathology, Queen Mary Hospital, The University of Hong Kong, Hong Kong.
authors.forename: Kwok Wah
authors.initials: KW
authors.lastname: Chan
authors.affiliation: Department of Medicine and Therapeutics, and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong.
authors.forename: Hui Yao
authors.initials: HY
authors.lastname: Lan
authors.affiliation: Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong.
authors.forename: Kar Neng
authors.initials: KN
authors.lastname: Lai
authors.affiliation: Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong.
authors.forename: Sydney C W
authors.initials: SC
authors.lastname: Tang
mesh_terms: D000704:Analysis of Variance; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D003920:Diabetes Mellitus / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007249:Inflammation / Q000503:physiopathology*; D016209:Interleukin-8 / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D044462:Receptors, Proteinase-Activated / Q000378:metabolism; D018179:Receptors, Thrombin / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D020840:Tissue Kallikreins / Q000235:genetics / Q000378:metabolism*
chemical_list: D016207:Cytokines; D017931:DNA Primers; D016209:Interleukin-8; D034741:RNA, Small Interfering; D044462:Receptors, Proteinase-Activated; D018179:Receptors, Thrombin; D020840:Tissue Kallikreins; C112908:protease-activated receptor 4; D002118:Calcium