Fibroblasts synthesize kininogen in response to inflammatory mediators

The kinin-kallikrein system: physiological roles, pathophysiology and its relationship to cancer biomarkers

The kinin-kallikrein system (KKS) is an endogenous multiprotein cascade, the activation of which leads to triggering of the intrinsic coagulation pathway and enzymatic hydrolysis of kininogens with the consequent release of bradykinin-related peptides. This system plays a crucial role in inflammation, vasodilation, smooth muscle contraction, cardioprotection, vascular permeability, blood pressure control, coagulation and pain. In this review, we will outline the physiology and pathophysiology of the KKS and also highlight the association of this system with carcinogenesis and cancer progression.

Expression of kininogen genes by rat cardiomyocytes

To determine the existence of the kallikrein-kinin system in the heart, we have studied in vitro and in vivo whether rat heart expresses kininogens (KGNs). The reverse transcription-polymerase chain reaction (RT-PCR) for KGN mRNAs demonstrated that the cardiac tissue of adult male rats expresses T-KGN mRNA but not high-molecular-weight (H-) KGN mRNA. An intravenous injection of lipopolysaccharide (LPS) resulted in a significant increase in T-KGN mRNA levels of rat heart within 12 h. Polyacrylamide gel electrophoresis of cDNA products generated by RT-PCR from heart mRNA using primers specific for either T- or low-molecular-weigh (L-) KGN revealed that rat heart expressed not only T-KGN gene but also L-KGN gene, and that LPS injection exclusively stimulated the expression of T-KGN but not of L-KGN gene. T-KGN mRNA was also detected in cultured myocytes derived from fetal rat heart, and the expression was markedly enhanced by an addition of LPS to cultures. These results demonstrated that rat cardiomyocytes are the source of T- and L-KGNs but not of H-KGN, and that their expression of T-KGN mRNA is stimulated by LPS, probably via LPS-receptor CD14.

Kininogen expression by rat vascular smooth muscle cells: stimulation by lipopolysaccharide and angiotensin II

To identify the presence of a local kallikrein-kinin system in vascular wall, we have studied whether rat vascular smooth muscle cells (VSMC) express kininogen in vitro and in vivo. Western blots using anti-T-kininogen antibody revealed the presence of T-kininogen in conditioned medium of cultured VSMC. T-Kininogen secretion by VSMC was markedly enhanced by the addition of lipopolysaccharide (LPS), angiotensin II (AII) and phorbol 12-myristate 13-acetate (PMA) to the culture. Experiments using specific inhibitors for protein kinases and on the PMA-induced down-regulation of protein kinase C suggested that a protein kinase C-dependent or unidentified pathway is involved in AII or LPS action, respectively. The intravenous injection of LPS (0.5 mg/kg) resulted in an increase in T-kininogen mRNA levels in the vascular smooth muscle of rat aorta, peaking at 16 h. Polyacrylamide gel electrophoresis of cDNA products generated by reverse transcription-polymerase chain reaction (RT-PCR) from aortic mRNA using primers specific for either T- or low-molecular-weight kininogen revealed that rat vascular smooth muscle expressed T-kininogen gene but not low-molecular-weight kininogen gene, and that LPS exclusively stimulated T-kininogen expression. The mRNA for high-molecular-weight kininogen was undetectable in either aortic smooth muscle or cultured VSMC by means of RT-PCR analysis. RT-PCR using specific primers for rat tissue kallikrein genes showed that aortic smooth muscle expressed KLK1 (true kallikrein) mRNA, but not KLK10 (T-kininogenase) mRNA. These results demonstrated that rat VSMC are a source of T-kininogen but not of low-molecular-weight- or high-molecular-weight kininogen, in contrast to the expression of true kallikrein but not of T-kininogenase by these cells.