Grant Bledsoe

The tissue kallikrein-kinin system protects against cardiovascular and renal diseases and ischemic stroke independently of blood pressure reduction

Abstract Tissue kallikrein (hK1) cleaves low-molecular-weight kininogen to produce kinin peptide, which binds to kinin receptors and triggers a wide spectrum of biological effects. Tissue kallikrein levels are reduced in humans and in animal models with hypertension, cardiovascular and renal diseases. Transgenic mice or rats over-expressing human tissue kallikrein or kinin B2 receptor are permanently hypotensive, and somatic kallikrein gene delivery reduces blood pressure in several hypertensive rat models. Moreover, kallikrein gene delivery or kallikrein protein infusion can directly improve cardiac, renal and neurological function without blood pressure reduction. Kallikrein has pleiotropic effects in inhibiting apoptosis, inflammation, proliferation, hypertrophy and fibrosis, and promoting angiogenesis and neurogenesis in different experimental animal models. Kallikreins effects can be blocked by kinin B2 receptor antagonists. Mechanistically, tissue kallikrein/kinin leads to increased nitric oxide levels and Akt activation, and reduced reactive oxygen species formation, TGF-β1 expression, MAPK and nuclear factor-κB activation. Our studies indicate that tissue kallikrein, through the kinin B2 receptor and nitric oxide formation, can protect against oxidative damage in cardiovascular and renal diseases and ischemic stroke. These novel findings suggest that kallikrein/kinin may serve as new drug targets for the prevention and treatment of heart failure, renal disease and stroke in humans.

Kinin Infusion Prevents Renal Inflammation, Apoptosis, and Fibrosis via Inhibition of Oxidative Stress and Mitogen-Activated Protein Kinase Activity

The progression of renal disease displays several characteristics, including proteinuria, apoptosis, inflammation, and fibrosis. In this study, we investigated the effect of long-term infusion of kinin in protection against salt-induced renal damage in Dahl salt-sensitive rats. Dahl salt-sensitive rats were fed a high-salt diet for 2 weeks and were then infused with bradykinin (500 ng/h) via subcutaneously implanted minipumps for 3 weeks. Kinin infusion attenuated salt-induced impaired renal function as evidenced by reduced proteinuria, serum creatinine, and blood urea nitrogen levels without apparent effect on blood pressure. Morphological analysis indicated that kinin administration reduced salt-induced glomerular sclerosis, tubular dilatation, luminal protein cast formation, and interlobular arterial thickness. Kinin also significantly lowered collagen I, III, and IV deposition and their mRNA levels. Moreover, kinin reduced interstitial monocyte/macrophage accumulation, as well as tubular cell apoptosis and caspase-3 activity. Protection of renal injury by kinin was associated with increased renal NO levels and reduced nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate oxidase activities and superoxide generation. Suppression of oxidative stress by kinin was accompanied by reduced transforming growth factor-&bgr;1 protein and mRNA levels, as well as decreased phosphorylation of mitogen-activated protein kinases. This is the first study to demonstrate that kinin infusion can directly protect against salt-induced renal injury without blood pressure reduction by inhibiting apoptosis, inflammation, and fibrosis via suppression of oxidative stress, transforming growth factor-&bgr;1 expression, and mitogen-activated protein kinase activation.

Tissue kallikrein in cardiovascular, cerebrovascular and renal diseases and skin wound healing

Abstract Tissue kallikrein (KLK1) processes low-molecular weight kininogen to produce vasoactive kinins, which exert biological functions via kinin receptor signaling. Using various delivery approaches, we have demonstrated that tissue kallikrein through kinin B2 receptor signaling exhibits a wide spectrum of beneficial effects by reducing cardiac and renal injuries, restenosis and ischemic stroke, and by promoting angiogenesis and skin wound healing, independent of blood pressure reduction. Protection by tissue kallikrein in oxidative organ damage is attributed to the inhibition of apoptosis, inflammation, hypertrophy and fibrosis. Tissue kallikrein also enhances neovascularization in ischemic heart and limb. Moreover, tissue kallikrein/kinin infusion not only prevents but also reverses kidney injury, inflammation and fibrosis in salt-induced hypertensive rats. Furthermore, there is a wide time window for kallikrein administration in protection against ischemic brain infarction, as delayed kallikrein infusion for 24 h after cerebral ischemia in rats is effective in reducing neurological deficits, infarct size, apoptosis and inflammation. Importantly, in the clinical setting, human tissue kallikrein has been proven to be effective in the treatment of patients with acute brain infarction when injected within 48 h after stroke onset. Finally, kallikrein promotes skin wound healing and keratinocyte migration by direct activation of protease-activated receptor 1.

Kallistatin attenuates endothelial apoptosis through inhibition of oxidative stress and activation of Akt-eNOS signaling

Kallistatin is a regulator of vascular homeostasis capable of controlling a wide spectrum of biological actions in the cardiovascular and renal systems. We previously reported that kallistatin inhibited intracellular reactive oxygen species formation in cultured cardiac and renal cells. The present study was aimed to investigate the role and mechanisms of kallistatin in protection against oxidative stress-induced vascular injury and endothelial cell apoptosis. We found that kallistatin gene delivery significantly attenuated aortic superoxide formation and glomerular capillary loss in hypertensive DOCA-salt rats. In cultured endothelial cells, kallistatin suppressed TNF-α-induced cellular apoptosis, and the effect was blocked by the pharmacological inhibition of phosphatidylinositol 3-kinase and nitric oxide synthase (NOS) and by the knockdown of endothelial NOS (eNOS) expression. The transduction of endothelial cells with adenovirus expressing dominant-negative Akt abolished the protective effect of kallistatin on endothelial apoptosis and caspase activity. In addition, kallistatin inhibited TNF-α-induced reactive oxygen species formation and NADPH oxidase activity, and these effects were attenuated by phosphatidylinositol 3-kinase and NOS inhibition. Kallistatin also prevented the induction of Bim protein and mRNA expression by oxidative stress. Moreover, the downregulation of forkhead box O 1 (FOXO1) and Bim expression suppressed TNF-α-mediated endothelial cell death. Furthermore, the antiapoptotic actions of kallistatin were accompanied by Akt-mediated FOXO1 and eNOS phosphorylation, as well as increased NOS activity. These findings indicate a novel role of kallistatin in the protection against vascular injury and oxidative stress-induced endothelial apoptosis via the activation of Akt-dependent eNOS signaling.

Intermedin ameliorates vascular and renal injury by inhibition of oxidative stress

Intermedin (IMD) is a newly discovered peptide related to calcitonin gene-related peptide and adrenomedullin, and has been shown to reduce blood pressure and reactive oxygen species formation in vivo. In this study, we determined whether IMD exerts vascular and renal protection in DOCA-salt hypertensive rats by intravenous injection of adenovirus harboring the human IMD gene. Expression of human IMD was detected in the rat kidney via immunohistochemistry. IMD administration significantly lowered blood pressure, increased urine volume, and restored creatinine clearance. IMD also dramatically decreased superoxide formation and media thickness in the aorta. Vascular injury in the kidney was reduced by IMD gene delivery as evidenced by the prevention of glomerular and peritubular capillary loss. Moreover, IMD lessened morphological damage of the renal tubulointerstitium and reduced glomerular injury and hypertrophy. Attenuation of inflammatory cell accumulation in the kidney by IMD was accompanied by inhibition of p38MAPK activation and intercellular adhesion molecule 1 expression. In addition, IMD gene transfer resulted in a marked decline in myofibroblast and collagen accumulation in association with decreased transforming growth factor-beta1 levels. Furthermore, IMD increased nitric oxide excretion in the urine and lowered the amount of lipid peroxidation. These results demonstrate that IMD is a powerful renal protective agent with pleiotropic effects by preventing endothelial cell loss, kidney damage, inflammation, and fibrosis in hypertensive DOCA-salt rats via inhibition of oxidative stress and proinflammatory mediator pathways.

Role of tissue kallikrein in prevention and recovery of gentamicin-induced renal injury.

Gentamicin is an aminoglycoside antibiotic that induces severe nephrotoxicity and acute renal failure. In the current project, we investigated the protective effects of tissue kallikrein (TK) protein administration (1 mug/h via osmotic minipumps) on kidney damage, apoptosis, and inflammation both during and after a 10-day regimen of gentamicin (80 mg/kg body weight/day sc) in Sprague-Dawley rats. TK infusion during gentamicin treatment significantly attenuated drug-induced renal dysfunction, cortical damage, and apoptosis. Moreover, TK reduced inflammatory cell accumulation in conjunction with diminished superoxide production and decreased expression of tumor necrosis factor-alpha, monocyte chemoattractant protein-1, and intercellular adhesion molecule-1. The protective effects of TK were blocked by coinfusion of icatibant (1.3 mug/h), indicating a kinin B2 receptor-mediated signaling event. After cessation of gentamicin treatment, TK infusion for 2 weeks completely restored kidney histology and morphology comparable to that of saline-treated animals. Furthermore, TK reduced gentamicin-induced renal dysfunction and fibrosis as evidenced by decreased myofibroblast and collagen accumulation in the kidney. In vitro, gentamicin increased the number of apoptotic cells and caspase-3 activity, but decreased phosphorylation of the prosurvival kinase Akt, in immortalized rat proximal tubular cells; addition of TK and bradykinin prevented these effects. In conclusion, our findings indicate that kallikrein/kinin prevents and promotes recovery of gentamicin-induced renal injury by inhibiting apoptosis, inflammatory cell recruitment, and fibrotic lesions through suppression of oxidative stress and proinflammatory mediator expression in animals during and after gentamicin treatment.

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.

Intermedin is a new angiogenic growth factor

Intermedin (IMD) is a newly discovered peptide closely related to adrenomedullin. We recently reported that IMD gene delivery prevented kidney damage and capillary loss in a rat model of chronic renal injury. In this study, we evaluated the role of IMD in angiogenesis in the ischemic hindlimb. Adenovirus containing human IMD or control adenovirus (Ad.Null) was injected into the adductor muscles of rats immediately after femoral artery ligation. The expression of human IMD was detected in the skeletal muscle 5 days after the viral injection. Blood perfusion in the ischemic hindlimb was monitored by laser-Doppler imaging from 1 to 3 wk after gene delivery. When compared with animals receiving Ad.Null, those with IMD gene transfer resulted in a time-dependent increase in blood perfusion. IMD gene delivery also increased capillary and arteriole density in ischemic hindlimb, identified by anti-CD-31 and alpha-smooth muscle actin immunostaining. Angiogenesis promoted by IMD was confirmed by increased capillary formation and hemoglobin content in Matrigel implants containing IMD peptide in mice. In cultured endothelial cells, IMD induced cell migration and tube formation, and these effects were blocked by the inhibition of extracellular signal-regulated kinase (ERK), Akt, nitric oxide (NO) synthase (NOS), vascular endothelial growth factor receptor-2 (VEGFR-2), and anti-IMD-neutralizing antibody. IMD was found to increase the phosphorylation of ERK, Akt, and endothelial NOS, as well as to augment NO formation, VEGF, and VEGFR-2 synthesis. Taken together, these results indicate that IMD enhances angiogenesis through ERK, Akt/NOS/NO, and VEGF/VEGFR-2 signaling pathways and raises the potential of IMD gene or peptide administration in the modulation of endothelial dysfunction.

Kallistatin antagonizes Wnt/β-catenin signaling and cancer cell motility via binding to low-density lipoprotein receptor-related protein 6

Kallistatin, a plasma protein, exerts pleiotropic effects in inhibiting angiogenesis, inflammation and tumor growth. Canonical Wnt signaling is the primary pathway for oncogenesis in the mammary gland. In this study, we demonstrate that kallistatin bound to the Wnt coreceptor low-density lipoprotein receptor-related protein 6 (LRP6), thus, blocking Wnt/β-catenin signaling and Wnt-mediated growth and migration in MDA-MB-231 breast cancer cells. Kallistatin inhibited Wnt3a-induced proliferation, migration, and invasion of cultured breast cancer cells. Moreover, kallistatin was bound to LRP6 in breast cancer cells, as identified by immunoprecipitation followed by western blot. Kallistatin suppressed Wnt3a-mediated phosphorylation of LRP6 and glycogen synthase kinase-3β, and the elevation of cytosolic β-catenin levels. Furthermore, kallistatin antagonized Wnt3a-induced expression of c-Myc, cyclin D1, and vascular endothelial growth factor. These findings indicate a novel role of kallistatin in preventing breast tumor growth and mobility by direct interaction with LRP6, leading to blockade of the canonical Wnt signaling pathway.

Kallistatin inhibits TGF-β-induced endothelial-mesenchymal transition by differential regulation of microRNA-21 and eNOS expression.

Kallistatin, an endogenous protein, consists of two structural elements: active site and heparin-binding domain. Kallistatin exerts beneficial effects on fibrosis by suppressing transforming growth factor (TGF)-β synthesis in animal models. TGF-β is the most potent inducer of endothelial-mesenchymal transition (EndMT), which contributes to fibrosis and cancer. MicroRNA (miR)-21 is an important player in organ fibrosis and tumor invasion. Here we investigated the potential role of kallistatin in EndMT via modulation of miR-21 in endothelial cells. Human kallistatin treatment blocked TGF-β-induced EndMT, as evidenced by morphological changes as well as increased endothelial and reduced mesenchymal marker expression. Kallistatin also inhibited TGF-β-mediated reactive oxygen species (ROS) formation and NADPH oxidase expression and activity. Moreover, kallistatin antagonized TGF-β-induced miR-21 and Snail1 synthesis, Akt phosphorylation, NF-κB activation, and matrix metalloproteinase 2 (MMP2) synthesis and activation. Kallistatin via its heparin-binding site blocked TGF-β-induced miR-21, Snail1 expression, and ROS formation, as wild-type kallistatin, but not heparin-binding site mutant kallistatin, exerted the effect. Conversely, kallistatin through its active site stimulated the synthesis of endothelial nitric oxide synthase (eNOS), sirtuin 1 (Sirt1) and forkhead box O1 (FoxO1); however, these effects were blocked by genistein, a tyrosine kinase inhibitor. This is the first study to demonstrate that kallistatins heparin-binding site is crucial for preventing TGF-β-induced miR-21 and oxidative stress, while its active site is key for stimulating the expression of antioxidant genes via interaction with an endothelial surface tyrosine kinase. These findings reveal novel mechanisms of kallistatin in protection against fibrosis and cancer by suppressing EndMT.