Expression and characterization of rat kallikrein-binding protein in Escherichia coli

AKT Mediates Adiponectin-Dependent Regulation of VSMC Phenotype

Adiponectin (adipoq), the most abundant hormone in circulation, has many beneficial effects on the cardiovascular system, in part by preserving the contractile phenotype of vascular smooth muscle cells (VSMCs). However, the lack of adiponectin or its receptor and treatment with recombinant adiponectin have shown contradictory effects on plaque in mice. RNA sequence of Adipoq+/+ and adipoq-/- VSMCs from male aortas identified a critical role for adiponectin in AKT signaling, the extracellular matrix (ECM), and TGF-β signaling. Upregulation of AKT activity mediated proliferation and migration of adipoq-/- cells. Activation of AMPK with metformin or AdipoRon reduced AKT-dependent proliferation and migration of adipoq-/- cells but did not improve the expression of contractile genes. Adiponectin deficiency impaired oxidative phosphorylation (OXPHOS), increased expression of glycolytic enzymes, and elevated mitochondrial reactive oxygen species (ROS) (superoxide, and hydrogen peroxide). Anti-atherogenic mechanisms targeted the ECM in adipoq-/- cells, downregulating MMP2 and 9 and upregulating decorin (DCN) and elastin (ELN). In vivo, the main sex differences in protein expression in aortas involved a more robust upregulation of MMP3 in females than males. Females also showed a reduction in DCN, which was not affected in males. Our study uncovered the AKT/MAPK/TGF-β network as a central regulator of VSMC phenotype.

Depletion of endogenous kallistatin exacerbates renal and cardiovascular oxidative stress, inflammation, and organ remodeling

Kallistatin (KS) levels are reduced in the kidney and blood vessels under oxidative stress conditions. To determine the function of endogenous KS in the renal and cardiovascular systems, KS levels were depleted by daily injection of anti-rat KS antibody into DOCA-salt hypertensive rats for 10 days. Administration of anti-KS antibody resulted in reduced KS levels in the circulation but increased levels of serum thiobarbituric acid reactive substances (an indicator of lipid peroxidation) as well as superoxide formation in the aorta. Moreover, anti-KS antibody injection resulted in increased NADH oxidase activity and superoxide production but decreased nitric oxide levels in the kidney and heart. Endogenous KS blockade aggravated renal dysfunction, damage, hypertrophy, inflammation, and fibrosis as evidenced by decreased creatinine clearance and increased serum creatinine, blood urea nitrogen and urinary protein levels, tubular dilation, protein cast formation, glomerulosclerosis, glomerular enlargement, inflammatory cell accumulation, and collagen deposition. In addition, rats receiving anti-KS antibody had enhanced cardiac injury as indicated by cardiomyocyte hypertrophy, inflammation, myofibroblast accumulation, and fibrosis. Renal and cardiac injury caused by endogenous KS depletion was accompanied by increases in the expression of the proinflammatory genes tumor necrosis factor-α and intercellular adhesion molecule-1 and the profibrotic genes collagen I and III, transforming growth factor-β, and tissue inhibitor of metalloproteinase-1. Taken together, these results implicate an important role for endogenous KS in protection against salt-induced renal and cardiovascular injury in rats by suppressing oxidative stress, inflammation, hypertrophy, and fibrosis.

Pivotal role of JNK-dependent FOXO1 activation in downregulation of kallistatin expression by oxidative stress

Oxidative stress has been shown to suppress endothelial nitric oxide synthase expression through activation of the transcription factor forkhead box O 1 (FOXO1) in cultured endothelial cells. We previously reported that circulating kallistatin levels are markedly reduced in rats with chronic oxidative organ damage. In this study, we investigated the potential role of oxidative stress in suppression of kallistatin expression via FOXO1 activation. In Dahl salt-sensitive (DSS) rats, we found that high salt intake induced a time-dependent correlation of increased thiobarbituric acid reactive substances (TBARS, an indicator of lipid peroxidation) with reduced serum kallistatin levels. Moreover, salt loading provoked an elevation of in situ aortic superoxide formation in association with reduced kallistatin levels. Expression of kallistatin was identified in cultured endothelial cells by immunocytochemistry and flow cytometry; however, H(2)O(2) dose-dependently lowered kallistatin mRNA and protein levels as determined by real-time PCR and Western blot, respectively. Downregulation of kallistatin synthesis by oxidative stress was restored by knockdown of FOXO1 expression with small-interfering RNA. H(2)O(2) rapidly induced FOXO1 nuclear translocation, but the effect was blocked by c-Jun NH(2)-terminal kinase (JNK) inhibitor. Inhibition of JNK by pharmacological inhibitor or small-interfering RNA reversed H(2)O(2)'s effect on kallistatin expression in endothelial cells. This study demonstrates that an inverse relationship exists between oxidative stress and kallistatin levels in the circulation and blood vessels and that kallistatin expression is negatively regulated by oxidative stress via JNK-dependent FOXO1 activation in cultured endothelial cells.

Kallikrein-binding protein suppresses growth of hepatocellular carcinoma by anti-angiogenic activity

Effect of kallikrein-binding protein (KBP), an endogenous angiogenic inhibitor, on the growth of hepatocellular carcinoma and the possible mechanism were investigated. KBP inhibited proliferation and induced apoptosis of endothelial cells, but had no effect on the proliferation and apoptosis of hepatocarcinoma cell line HepG2. Intraperitoneal injection of KBP significantly suppressed the tumor growth and inhibited intratumoral neovascularization both in grafted hepatocarcinoma mice and xenografted hepatocarcinoma athymic mice. Moreover, KBP reduced expression of VEGF and HIF-1alpha nuclear translocation in HepG2 cells and xenografts. Down-regulation of VEGF in tumor cells through inhibiting HIF-1alpha may represent a novel mechanism for the anti-angiogenic and anti-tumor activity of KBP.

Kallikrein-binding protein inhibits retinal neovascularization and decreases vascular leakage

AIMS/HYPOTHESIS

Kallikrein-binding protein (KBP) is a serine proteinase inhibitor (serpin). It specifically binds to tissue kallikrein and inhibits kallikrein activity. Our study was designed to test its effects on retinal neovascularization and vascular permeability.

METHODS

Endothelial cell proliferation was determined by [(3)H] thymidine incorporation assay and apoptosis quantified by Annexin V staining and flow cytometry. Effect on retinal neovascularization was determined by fluorescein angiography and count of pre-retinal vascular cells in an oxygen-induced retinopathy (OIR) model. Vascular permeability was assayed by the Evans blue method. Vascular endothelial growth factor (VEGF) was measured by Western blot analysis and ELISA.

RESULTS

Kallikrein-binding protein specifically inhibited proliferation and induced apoptosis in retinal capillary endothelial cells. Intravitreal injection of KBP inhibited retinal neovascularization in an OIR model. Moreover, KBP decreased vascular leakage in the retina, iris and choroid in rats with OIR. Blockade of kinin receptors by specific antagonists showed significantly weaker inhibition of endothelial cells, when compared to that of KBP, suggesting that the anti-angiogenic activity of KBP is not through inhibiting kallikrein activity or kinin production. KBP competed with (125)I-VEGF for binding to endothelial cells and down-regulated VEGF production in endothelial cells and in the retina of the OIR rat model.

CONCLUSION/INTERPRETATION

Kallikrein-binding protein is a multi-functional serpin, and its vascular activities are independent of its interactions with the kallikrein-kinin system. Inhibition of VEGF binding to its receptors and down-regulation of VEGF expression could represent a mechanism for the vascular activities of KBP.

Identification and characterization of two promoters of rat kallikrein-binding protein gene

Rat kallikrein-binding protein (RKBP) is a serine proteinase inhibitor (serpin) which binds to and inhibits tissue kallikrein activity [1,2]. In this study, we have sequenced and identified two promoter regions of the RKBP gene (RKBP). One promoter is located in the 5' flanking region (P1) of the gene and the other is located in the first intron (P2). Both promoters contain a consensus TATA and CAAT box. These RKBP promoters were fused with a chloramphenicol acetyltransferase (CAT) reporter gene and their promoter activities were determined by measuring CAT levels using a specific ELISA. The P1 promoter exhibited high promoter activities in Hep3B hepatoma cells but not in La-fibroblastoma cells, indicating its tissue-specificity. By deletion analysis, we have identified a negative regulatory element of the P1 promoter between -739 and -472, and defined a minimal sequence between -183 and -2 for maintaining the intact promoter activity. The P2 promoter showed a strong activity only when linked to an SV40 enhancer. Activity of the P1 promoter can be induced by growth hormone in Hep3B cells. Gel retardation assay has identified 5 DNA fragments which were bound by nuclear proteins from rat liver. Two DNA fragments are in the 5' flanking region, one contains a putative glucocorticoid and growth hormone response element and the other one contains a CAAT box and two putative AP-1 binding sites. The remaining three are in the first intron and contain a putative thyroid hormone response element, a putative GATA site and three consensus CAAT boxes, respectively. Nuclear proteins from the kidney showed that spontaneously hypertensive rats (SHR) have a distinct trans-acting factor which binds with the DNA fragment containing the glucocorticoid and growth hormone response elements, as compared with normotensive rats. This result indicates that different trans-acting factors in the kidney of SHR may contribute to the decreased RKBP expression in these hypertensive rats.

Intramuscular delivery of rat kallikrein-binding protein gene reverses hypotension in transgenic mice expressing human tissue kallikrein

The tissue kallikrein-kinin system has been postulated to play a role in blood pressure regulation. The activity of tissue kallikrein is controlled by a number of factors in vivo. Rat kallikrein-binding protein (RKBP) is a serine proteinase inhibitor which binds to and inhibits tissue kallikrein's activity in vitro. We have recently developed several hypotensive transgenic mouse lines which express human tissue kallikrein. In order to investigate the role of RKBP in blood pressure regulation, we delivered the RKBP to these transgenic mice by intramuscular injection. Expression of the RKBP was detected in skeletal muscle by reverse transcription-polymerase chain reaction and Southern blot analysis at 10, 20, 30, and 40 days post-injection. Immunoreactive RKBP levels in the muscle and serum of these mice were quantified by a RKBP-specific enzyme-linked immunosorbent assay and Western blot analysis. The levels of RKBP mRNA and immunoreactive protein were detectable at 10 days post-injection and increased significantly at 20 and 30 days. During this period, RKBP delivery significantly increased systemic blood pressure in the kallikrein transgenic mice to a level comparable to that of normotensive control mice. The RKBP and vector DNA delivery had no effect on the blood pressure of normotensive control mice. No serum antibodies to RKBP or its DNA were detected in the mice 40 days post injection. These results suggest that the increase of systemic blood pressure by RKBP delivery in these hypotensive transgenic mice may be mediated by inhibiting tissue kallikrein activity.