Effect of Chronic Blockade of the Kallikrein-Kinin System on the Development of Hypertension in Rats

Role of Kinins in Hypertension and Heart Failure

The kallikrein-kinin system (KKS) is proposed to act as a counter regulatory system against the vasopressor hormonal systems such as the renin-angiotensin system (RAS), aldosterone, and catecholamines. Evidence exists that supports the idea that the KKS is not only critical to blood pressure but may also oppose target organ damage. Kinins are generated from kininogens by tissue and plasma kallikreins. The putative role of kinins in the pathogenesis of hypertension is discussed based on human mutation cases on the KKS or rats with spontaneous mutation in the kininogen gene sequence and mouse models in which the gene expressing only one of the components of the KKS has been deleted or over-expressed. Some of the effects of kinins are mediated via activation of the B2 and/or B1 receptor and downstream signaling such as eicosanoids, nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF) and/or tissue plasminogen activator (T-PA). The role of kinins in blood pressure regulation at normal or under hypertension conditions remains debatable due to contradictory reports from various laboratories. Nevertheless, published reports are consistent on the protective and mediating roles of kinins against ischemia and cardiac preconditioning; reports also demonstrate the roles of kinins in the cardiovascular protective effects of the angiotensin-converting enzyme (ACE) and angiotensin type 1 receptor blockers (ARBs).

Danhong injection reduces vascular remodeling and up-regulates the Kallikrein-kinin system in spontaneously hypertensive rats

Although Danhong injection (DHI) is one of the most prescribed cardiovascular medicines in China, its therapeutic indications and mechanisms remain partially defined. We now identify molecular targets of DHI in resistance vasculatures and demonstrate its role in vascular function and blood pressure (BP) regulation. BP was determined in DHI, Losartan, and placebo- treated Spontaneously Hypertensive Rats (SHR) by both noninvasive and invasive measurements. Vasorelaxation was examined both in conduit and resistance vasculature by ex vivo aortic rings. Microarray analysis was performed and gene expression changes were verified by RT-qPCR and ELISA. Diastolic, systolic and mean BPs were significantly lower in DHI-treated SHR than controls by both tail-cuff and invasive BP measurements. In ex vivo rings, aortic and mesenteric vessels from SHR treated with DHI exhibited significantly greater acetylcholine-mediated relaxation. Among the 282 genes that are differentially expressed in microarray analysis, DHI treatment up-regulated the expression of kallikrein and plasma kallikrein B genes. DHI also significantly increased serum kallikrein content in SHR. Treatment with DHI significantly increased the ratio of aortic lumen to outer diameter. Therefore, the reduction of vascular remodeling and the up-regulation of Kallikrein-kinin system contribute, at least in part, to the antihypertensive effect of DHI in SHR.

Deletion of interleukin-6 prevents cardiac inflammation, fibrosis and dysfunction without affecting blood pressure in angiotensin II-high salt-induced hypertension

OBJECTIVE

Inflammation has been proposed as a key component in the development of hypertension and cardiac remodeling associated with different cardiovascular diseases. However, the role of the proinflammatory cytokine interleukin-6 in the chronic stage of hypertension is not well defined. Here, we tested the hypothesis that deletion of interleukin-6 protects against the development of hypertension, cardiac inflammation, fibrosis, remodeling and dysfunction induced by high salt diet and angiotensin II (Ang II).

METHODS

Male C57BL/6J and interleukin-6-knock out (KO) mice were implanted with telemetry devices for blood pressure (BP) measurements, fed a 4% NaCl diet, and infused with either vehicle or Ang II (90 ng/min per mouse subcutaneously) for 8 weeks. We studied BP and cardiac function by echocardiography at baseline, 4 and 8 weeks.

RESULTS

Myocyte cross-sectional area (MCSA), macrophage infiltration, and myocardial fibrosis were also assessed. BP increased similarly in both strains when treated with Ang II and high salt (Ang II-high salt); however, C57BL/6J mice developed a more severe decrease in left ventricle ejection fraction, fibrosis, and macrophage infiltration compared with interleukin-6-KO mice. No differences between strains were observed in MCSA, capillary density and MCSA to capillary density ratio.

CONCLUSION

In conclusion, absence of interleukin -6 did not alter the development of Ang II-high salt-induced hypertension and cardiac hypertrophy, but it prevented the development of cardiac dysfunction, myocardial inflammation, and fibrosis. This indicates that interleukin-6 plays an important role in hypertensive heart damage but not in the development of hypertension.

Chronic resveratrol reverses a mild angiotensin II-induced pressor effect in a rat model

Resveratrol is reported to reduce blood pressure in animal models of hypertension, but the mechanisms are unknown. We have shown that resveratrol infusion increases sodium excretion. We hypothesized that chronic ingestion of resveratrol would reduce angiotensin II (Ang II)-induced increases in blood pressure by decreasing oxidative stress and by also decreasing sodium reabsorption through a nitric oxide-dependent mechanism. We infused rats with vehicle or 80 μg Ang II/d over 4 weeks. Vehicle or Ang II-infused rats were individually housed, pair fed, and placed on a diet of normal chow or normal chow plus 146 mg resveratrol/d. Groups included 1) control, 2) resveratrol-fed, 3) Ang II-treated, and 4) Ang II plus resveratrol. Systolic blood pressure was measured by tail cuff. During the 4th week, rats were placed in metabolic caging for urine collection. NO2/NO3 and 8-isoprostane excretion were measured. Ang II increased systolic blood pressure in the 1st week by +14±5 mmHg (P<0.05) in Group 3 and +10±3 mmHg (P<0.05) in Group 4, respectively. Blood pressure was unchanged in Groups 1 and 2. After 4 weeks, blood pressure remained elevated in Group 3 rats with Ang II (+9±3 mmHg, P<0.05), but in Group 4, blood pressure was no longer elevated (+2±2 mmHg). We found no significant differences between the groups in sodium excretion or cumulative sodium balance (18.49±0.12, 17.75±0.16, 17.97±0.17, 18.46±0.18 μEq Na+/7 d in Groups 1-4, respectively). Urinary excretion of NO2/NO3 in the four groups was 1) 1631±207 μmol/24 h, 2) 1045±236 μmol/24 h, 3) 1490±161 μmol/24 h, and 4) 609±17 μmol/24 h. 8-Isoprostane excretion was 1) 63.85±19.39 nmol/24 h, 2) 73.57±22.02 nmol/24 h, 3) 100.69±37.62 nmol/24 h, and 4) 103.00±38.88 nmol/24 h. We conclude that chronic resveratrol supplementation does not blunt Ang II-increased blood pressure, and while resveratrol has mild depressor effects, these do not seem to be due to natriuresis or enhanced renal nitric oxide synthesis.

Renal (tissue) kallikrein-kinin system in the kidney and novel potential drugs for salt-sensitive hypertension

A large variety of antihypertensive drugs, such as angiotensin converting enzyme inhibitors, diuretics, and others, are prescribed to hypertensive patients, with good control of the condition. In addition, all individuals are generally believed to be salt sensitive and, thus, severe restriction of salt intake is recommended to all. Nevertheless, the physiological defense mechanisms in the kidney against excess salt intake have not been well clarified. The present review article demonstrated that the renal (tissue) kallikrein-kinin system (KKS) is ideally situated within the nephrons of the kidney, where it functions to inhibit the reabsorption of NaCl through the activation of bradykinin (BK)-B2 receptors localized along the epithelial cells of the collecting ducts (CD). Kinins generated in the CD are immediately inactivated by two kidney-specific kinin-inactivating enzymes (kininases), carboxypeptidase Y-like exopeptidase (CPY), and neutral endopeptidase (NEP). Our work demonstrated that ebelactone B and poststatin are selective inhibitors of these kininases. The reduced secretion of the urinary kallikrein is linked to the development of salt-sensitive hypertension, whereas potassium ions and ATP-sensitive potassium channel blockers ameliorate salt-sensitive hypertension by accelerating the release of renal kallikrein. On the other hand, ebelactone B and poststatin prolong the life of kinins in the CD after excess salt intake, thereby leading to the augmentation of natriuresis and diuresis, and the ensuing suppression of salt-sensitive hypertension. In conclusion, accelerators of the renal kallikrein release and selective renal kininase inhibitors are both novel types of antihypertensive agents that may be useful for treatment of salt-sensitive hypertension.

The kallikrein-kinin system as a regulator of cardiovascular and renal function

Autocrine, paracrine, endocrine, and neuroendocrine hormonal systems help regulate cardio-vascular and renal function. Any change in the balance among these systems may result in hypertension and target organ damage, whether the cause is genetic, environmental or a combination of the two. Endocrine and neuroendocrine vasopressor hormones such as the renin-angiotensin system (RAS), aldosterone, and catecholamines are important for regulation of blood pressure and pathogenesis of hypertension and target organ damage. While the role of vasodepressor autacoids such as kinins is not as well defined, there is increasing evidence that they are not only critical to blood pressure and renal function but may also oppose remodeling of the cardiovascular system. Here we will primarily be concerned with kinins, which are oligopeptides containing the aminoacid sequence of bradykinin. They are generated from precursors known as kininogens by enzymes such as tissue (glandular) and plasma kallikrein. Some of the effects of kinins are mediated via autacoids such as eicosanoids, nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF), and/or tissue plasminogen activator (tPA). Kinins help protect against cardiac ischemia and play an important part in preconditioning as well as the cardiovascular and renal protective effects of angiotensin-converting enzyme (ACE) and angiotensin type 1 receptor blockers (ARB). But the role of kinins in the pathogenesis of hypertension remains controversial. A study of Utah families revealed that a dominant kallikrein gene expressed as high urinary kallikrein excretion was associated with a decreased risk of essential hypertension. Moreover, researchers have identified a restriction fragment length polymorphism (RFLP) that distinguishes the kallikrein gene family found in one strain of spontaneously hypertensive rats (SHR) from a homologous gene in normotensive Brown Norway rats, and in recombinant inbred substrains derived from these SHR and Brown Norway rats this RFLP cosegregated with an increase in blood pressure. However, humans, rats and mice with a deficiency in one or more components of the kallikrein-kinin-system (KKS) or chronic KKS blockade do not have hypertension. In the kidney, kinins are essential for proper regulation of papillary blood flow and water and sodium excretion. B2-KO mice appear to be more sensitive to the hypertensinogenic effect of salt. Kinins are involved in the acute antihypertensive effects of ACE inhibitors but not their chronic effects (save for mineralocorticoid-salt-induced hypertension). Kinins appear to play a role in the pathogenesis of inflammatory diseases such as arthritis and skin inflammation; they act on innate immunity as mediators of inflammation by promoting maturation of dendritic cells, which activate the body's adaptive immune system and thereby stimulate mechanisms that promote inflammation. On the other hand, kinins acting via NO contribute to the vascular protective effect of ACE inhibitors during neointima formation. In myocardial infarction produced by ischemia/reperfusion, kinins help reduce infarct size following preconditioning or treatment with ACE inhibitors. In heart failure secondary to infarction, the therapeutic effects of ACE inhibitors are partially mediated by kinins via release of NO, while drugs that activate the angiotensin type 2 receptor act in part via kinins and NO. Thus kinins play an important role in regulation of cardiovascular and renal function as well as many of the beneficial effects of ACE inhibitors and ARBs on target organ damage in hypertension.

Postexercise skeletal muscle glucose transport is normal in kininogen-deficient rats

A single exercise bout stimulates skeletal muscle glucose transport (GT) in the absence or presence of insulin. It has been suggested that the kallikrein-kinin system may contribute to exercise effects on both insulin-independent and insulin-dependent GT. Plasma kininogen, a key kallikrein-kinin system component, is a protein substrate for the enzyme kallikrein and the source of the peptide bradykinin.

PURPOSE

This study aimed to determine whether the postexercise (PEX) increase in insulin-dependent or insulin-independent GT is reduced in rats deficient in plasma kininogen versus normal rats.

METHODS

Male Brown Norway (BN) and Brown Norway Katholiek (BNK; plasma kininogen-deficient) rats were studied. BN and BNK rats were assigned to exercise (4×30-min swim) or sedentary (SED) groups. Rats were anesthetized immediately (0hPEX) or 3 h (3hPEX) after exercise. For 0hPEX and 0hSED rats, one epitrochlearis muscle per rat was used for AMPK phosphorylation and muscle glycogen analyses. The contralateral muscle was incubated with [H]-3-O-methylglucose (3-MG) for GT assay. For 3hPEX and 3hSED rats, one muscle from each rat was incubated without insulin, and the contralateral muscle was incubated with 60 μU·mL insulin, and both muscles were incubated with 3-MG for GT measurement.

RESULTS

For 0hPEX versus 0hSED, both BN and BNK rats had greater insulin-independent GT and AMPK phosphorylation with reduced glycogen after exercise. No genotype effects were found 0hPEX. There was a significant main effect of exercise (3hPEX>3hSED) and no interaction between exercise and genotype for basal or insulin-stimulated GT.

CONCLUSIONS

Plasma kininogen deficiency did not alter insulin-independent GT, AMPK phosphorylation, or glycogen depletion 0hPEX or insulin-dependent GT 3hPEX, suggesting that normal plasma kininogen is not essential for these important exercise effects.

A Novel Category of Anti-Hypertensive Drugs for Treating Salt-Sensitive Hypertension on the Basis of a New Development Concept

Terrestrial animals must conserve water and NaCl to survive dry environments. The kidney reabsorbs 95% of the sodium filtered from the glomeruli before sodium reaches the distal connecting tubules. Excess sodium intake requires the renal kallikrein-kinin system for additional excretion. Renal kallikrein is secreted from the distal connecting tubule cells of the kidney, and its substrates, low molecular kininogen, from the principal cells of the cortical collecting ducts (CD). Formed kinins inhibit reabsorption of NaCl through bradykinin (BK)-B₂ receptors, localized along the CD. Degradation pathway of BK by kinin-destroying enzymes in urine differs completely from that in plasma, so that ACE inhibitors are ineffective. Urinary BK is destroyed mainly by a carboxypeptidase-Y-like exopeptidase (CPY) and partly by a neutral endopeptidase (NEP). Inhibitors of CPY and NEP, ebelactone B and poststatin, respectively, were found. Renal kallikrein secretion is accelerated by potassium and ATP-sensitive potassium (KATP) channel blockers, such as PNU-37883A. Ebelactone B prevents DOCA-salt hypertension in rats. Only high salt intake causes hypertension in animals deficient in BK-B2 receptors, tissue kallikrein, or kininogen. Hypertensive patients, and spontaneously hypertensive rats, excrete less kallikrein than normal subjects, irrespective of races, and become salt-sensitive. Ebelactone B, poststatin, and KATP channel blockers could become novel antihypertensive drugs by increase in urinary kinin levels. Roles of kinin in cardiovascular diseases were discussed.

Lack of glutathione peroxidase 1 accelerates cardiac-specific hypertrophy and dysfunction in angiotensin II hypertension

Glutathione peroxidase 1 (Gpx1) plays an important role in cellular defense by converting hydrogen peroxide and organic hydroperoxides to nonreactive products, and Gpx1(-/-) mice, which are characterized by reduced tissue glutathione peroxidase activity, are known to exhibit enhanced oxidative stress. Peroxides participate in tissue injury, as well as the hypertrophy of cultured cells, yet the role of Gpx1 to prevent end organ damage in cardiovascular tissue is not clear. We postulated that Gpx1 deletion would potentiate both aortic and cardiac hypertrophy, as well as mean arterial blood pressure, in response to angiotensin II (AngII). Our results show that short-term AngII markedly increased left ventricular mass, myocyte cross-sectional area, and interventricular septum thickness and decreased shortening fraction in Gpx1(-/-) mice as compared with wild-type animals. On the other hand, AngII resulted in a similar increase in mean arterial blood pressure in wild-type and Gpx1(-/-) mice. Collagen deposition increased in response to AngII, but no differences were found between strains. Vascular hypertrophy increased to the same extent in Gpx1(-/-) and wild-type mice. Collectively, our results indicate that Gpx1 deficiency accelerates cardiac hypertrophy and dysfunction but has no effect on vascular hypertrophy and mean arterial blood pressure and suggest a major role for Gpx1 in cardiac dysfunction in AngII-dependent hypertension.

Gender-specific association between the kininogen 1 gene variants and essential hypertension in Chinese Han population

BACKGROUND

Kininogens serve as the precursors of potent vasoactive kinin peptides and also function as cysteine proteinase inhibitors.

METHOD

Given its potential role in blood pressure homeostasis, a tagging single nucleotide polymorphism (SNP) based case-control study was conducted to explore the association between kininogen 1 gene common variants and essential hypertension in Chinese Han population. Four tagging SNPs were selected on the basis of the HapMap database and further genotyped in 2411 patients with essential hypertension and 2348 controls from the International Collaborative Study of Cardiovascular Disease in Asia (InterASIA in China).

RESULTS

A significant gender-specific association between the kininogen 1 gene common variants and essential hypertension was observed. In male, but not female participants, rs2304456 CC genotype and rs4686799 TT genotype were significantly related to hypertension [odds ratio (OR) = 2.20, 95% confidence interval (CI): 1.24-3.90, P = 0.007 and OR = 1.31, 95% CI: 1.04-1.66, P = 0.025, respectively]. The haplotypes G-C-C-T and the A-A-T-T were significantly associated with essential hypertension in the male population with adjusted OR 1.43 (P < 0.001) and OR 1.24 (P = 0.001), respectively. The haplotype G-A-C-T was in significant association with essential hypertension (OR = 1.42, P = 0.003) as well as systolic blood pressure (P = 0.005) and diastolic blood pressure (P = 0.015).

CONCLUSION

This is the first association study of the kininogen 1 gene with essential hypertension. Both single-locus and haplotype analyses indicated the kininogen 1 gene was associated with essential hypertension and blood pressure traits in the Chinese male population.

The kallikrein-kinin system in health and in diseases of the kidney

Since kallikrein was discovered as a vasodilatory substance in human urine, the kallikrein-kinin system (KKS) has been considered to play a physiological role in controlling blood pressure. Gene targeting experiments in mice in which the KKS has been inactivated to varying degrees have, however, questioned this role, because basal blood pressures are not altered. Rather, these experiments have shown that the KKS has a different and important role in preventing changes associated with normal senescence in mice, and in reducing the nephropathy and accelerated senescence-associated phenotypes induced in mice by diabetes. Other experiments have shown that the KKS suppresses mitochondrial respiration, partly by nitric oxide and prostaglandins, and that this suppression may be a key to understanding how the KKS influences senescence-related diseases. Here we review the logical progression and experimental data leading to these conclusions, and discuss their relevance to human conditions.

Are all individuals equally sensitive in the blood pressure to high salt intake? (Review article)

It has been reported that only one-third of normotensive subjects and half of hypertensive patients are salt-sensitive. Many causes of salt-sensitivity have been proposed. Our suggestion is that a reduced urinary kallikrein level may be one cause, since mutant kininogen-deficient rats, which cannot generate kinin in the urine, are salt-sensitive. Renal kallikrein is secreted by the connecting tubule cells of the kidney, which are located just distal to the macula densa or the tubuloglomerular feedback system. Excess amounts of sodium taken overflow into the distal tubules and are reabsorbed in the collecting ducts. Kinins generated inhibit sodium reabsorption in the collecting ducts. Both blacks and whites with essential hypertension excrete less urinary kallikrein than do their normotensive counterparts, but the mean value in "normotensive blacks" were not different from that in "hypertensive whites". African-Americans consume less potassium than whites. Potassium and ATP-sensitive potassium channel blockers are releasers of renal kallikrein. In a small-scale study, sodium loading caused more increase in the systolic blood pressure in urinary low-kallikrein group than in urinary high-kallikrein group. Large-scale clinical studies, under strict control of potassium intake, are needed to elucidate the relationship between salt-sensitivity and urinary kallikrein levels.

Role of N-acetyl-seryl-aspartyl-lysyl-proline in the antifibrotic and anti-inflammatory effects of the angiotensin-converting enzyme inhibitor captopril in hypertension

Angiotensin-converting enzyme inhibitors (ACEis) are known to have antifibrotic effects on the heart and kidney in both animal models and humans. N-acetyl-seryl-aspartyl-lysyl-proline is a natural inhibitor of proliferation of hematopoietic stem cells and a natural substrate of ACEi that was reported to prevent cardiac and renal fibrosis in vivo. However, it is not clear whether N-acetyl-seryl-aspartyl-lysyl-proline participates in the antifibrotic effects of ACEi. To clarify this issue, we used a model of aldosterone-salt-induced hypertension in rats treated with the ACEi captopril either alone or combined with an anti-N-acetyl-seryl-aspartyl-lysyl-proline monoclonal antibody. These hypertensive rats had the following: (1) left ventricular and renal hypertrophy, as well as increased collagen deposition in the left ventricular and the kidney; (2) glomerular matrix expansion; and (3) increased ED1-positive cells and enhanced phosphorylated-p42/44 mitogen-activated protein kinase in the left ventricle and kidney. The ACEi alone significantly lowered systolic blood pressure (P=0.008) with no effect on organ hypertrophy; it significantly lowered left ventricular collagen content, and this effect was blocked by the monoclonal antibody as confirmed by the histological data. As expected, the ACEi significantly decreased renal collagen deposition and glomerular matrix expansion, and these effects were attenuated by the monoclonal antibody. Likewise, the ACEi significantly decreased ED1-positive cells and inhibited p42/44 mitogen-activated protein kinase phosphorylation in the left ventricle and kidney, and these effects were blocked by the monoclonal antibody. We concluded that in aldosterone-salt-induced hypertension, the antifibrotic effect of ACEi on the heart and kidney, is partially mediated by N-acetyl-seryl-aspartyl-lysyl-proline, resulting in decreased inflammatory cell infiltration and p42/44 mitogen-activated protein kinase activation.

Genetically altered animal models in the kallikrein-kinin system

Transgenic and gene-targeting technologies allowing the generation of genetically altered animal models have greatly advanced our understanding of the function of specific genes. This is also true for the kallikrein-kinin system (KKS), in which some, but not yet all, components have been functionally characterized using such techniques. The first genetically altered animal model for a KKS component was supplied by nature, the brown Norway rat carrying an inactivating mutation in the kininogen gene. Mice deficient in tissue kallikrein, B1 and B2 receptors, some kinin-degrading enzymes, and factor XII followed, together with transgenic rat and mouse strains overexpressing tissue kallikrein, B1 and B2 receptors, and degrading enzymes. There are still no animal models with genetic alterations in plasma kallikrein, kininases I and some other degrading enzymes. The models have confirmed an important role of the KKS in cardiovascular pathology, inflammation, and pain, and have partially elucidated the distinct function of the two receptors. This created the basis for rational decisions concerning the putative use of kinin receptor agonists and antagonists in therapeutic applications. However, a more thorough analysis of the existing models and the generation of new, more sophisticated transgenic models will be necessary to clarify the still elusive issue as to where and by which mechanisms the kinins exert their actions.

A missing link between a high salt intake and blood pressure increase

It is widely accepted that a high sodium intake triggers blood pressure rise. However, only one-third of the normotensive subjects were reported to show salt-sensitivity in their blood pressure. Many factors have been proposed as causes of salt-sensitive hypertension, but none of them provides a satisfactory explanation. We propose, on the basis of accumulated data, that the reduced activity of the kallikrein-kinin system in the kidney may provide this link. Renal kallikrein is secreted by the distal connecting tubular cells and all kallikrein-kinin system components are distributed along the collecting ducts in the distal nephron. Bradykinin generated is immediately destroyed by carboxypeptidase Y-like exopeptidase and neutral endopeptidase, both quite independent from the kininases in plasma, such as angiotensin converting enzyme. The salt-sensitivity of the blood pressure depends largely upon ethnicity and potassium intake. Interestingly, potassium and ATP-sensitive potassium (K(ATP)) channel blockers accelerate renal kallikrein secretion and suppress blood pressure rises in animal hypertension models. Measurement of urinary kallikrein may become necessary in salt-sensitive normotensive and hypertensive subjects. Furthermore, pharmaceutical development of renal kallikrein releasers, such as K(ATP) channel blockers, and renal kininase inhibitors, such as ebelactone B, may lead to the development of novel antihypertensive drugs.

Kallikrein gene transfer reduces renal fibrosis, hypertrophy, and proliferation in DOCA-salt hypertensive rats

In DOCA-salt hypertension, renal kallikrein levels are increased and may play a protective role in renal injury. We investigated the effect of enhanced kallikrein levels on kidney remodeling of DOCA-salt hypertensive rats by systemic delivery of adenovirus containing human tissue kallikrein gene. Recombinant human kallikrein was detected in the urine and serum of rats after gene delivery. Kallikrein gene transfer significantly decreased DOCA- and salt-induced proteinuria, glomerular sclerosis, tubular dilatation, and luminal protein casts. Sirius red staining showed that kallikrein gene transfer reduced renal fibrosis, which was confirmed by decreased collagen I and fibronectin levels. Furthermore, kallikrein gene delivery diminished myofibroblast accumulation in the interstitium of the cortex and medulla, as well as transforming growth factor (TGF)-beta1 immunostaining in glomeruli. Western blot analysis and ELISA verified the decrease in immunoreactive TGF-beta1 levels. Kallikrein gene transfer also significantly reduced kidney weight, glomerular size, proliferating tubular epithelial cells, and macrophages/monocytes. Reduction of proliferation and hypertrophy was associated with reduced levels of the cyclin-dependent kinase inhibitor p27(Kip1), and the phosphorylation of c-Jun NH2-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK). The protective effects of kallikrein were accompanied by increased urinary nitrate/nitrite and cGMP levels, and suppression of superoxide formation. These results indicate that kallikrein protects against mineralocorticoid-induced renal fibrosis glomerular hypertrophy, and renal cell proliferation via inhibition of oxidative stress, JNK/ERK activation, and p27(Kip1) and TGF-beta1 expression.

Dualité fonctionnelle des récepteurs des kinines en physiopathologie

Kinins are autacoid peptides and central neuromediators involved in cardiovascular regulation, inflammation and pain. Their effects are mediated by two transmembrane G-protein-coupled receptors denoted as B1 and B2. While the B2 receptor is constitutive, the B1 receptor is inducible and up-regulated in the presence of cytokines, endotoxins or during tissue injury. The B2 receptor is believed to play an important role in the beneficial effects of angiotensin-1 converting enzyme inhibitors used in the treatment of cardiovascular diseases, yet it is involved in the acute phase of inflammation and of somatic and visceral pain. Conversely, the B1 receptor participates in the chronic phase of these responses and is likely to play a strategic role in diseases with a strong immune component such as rheumatoid arthritis, multiple sclerosis, septic shock and diabetes. A dual function for the B1 receptor is also reported in some pathologies in which it can exert either a protective (multiple sclerosis and septic shock) or harmful (pain and inflammation) effect. Therefore, the use of antagonists for these receptors as clinical therapeutic agents requires a rigorous evaluation of the potential side effects.

Role of bradykinin in angiotensin-converting enzyme knockout mice

Angiotensin-converting enzyme (ACE) plays a central role in the renin-angiotensin system. Whereas ACE is responsible for the production of angiotensin II, it is also important in the elimination of bradykinin. Constitutively, the biological function of bradykinin is mediated through the bradykinin B(2) receptor. ACE knockout mice have a complicated phenotype including very low blood pressure. To investigate the role of bradykinin in the expression of the ACE knockout phenotype, we bred B(2) receptor knockout mice with ACE knockout mice, thus generating a line of mice deficient in both the B(2) receptor and ACE. Surprisingly, these mice did not differ from ACE knockout mice in blood pressure, urine concentrating ability, renal pathology, and hematocrit. Thus abnormalities of bradykinin accumulation do not play an important role in the ACE knockout phenotype. Rather, this phenotype appears due to the defective production of angiotensin II.

The renal kallikrein-kinin system: its role as a safety valve for excess sodium intake, and its attenuation as a possible etiologic factor in salt-sensitive hypertension

The distal tubules of the kidney express the full set of the components of the kallikrein-kinin system, which works independently from the plasma kallikrein-kinin system. Studies on the role of the renal kallikrein-kinin system, using congenitally kininogen-deficient Brown-Norway Katholiek rats and also bradykinin B2 receptor knockout mice, revealed that this system starts to function and to induce natriuresis and diuresis when sodium accumulates in the body as a result of excess sodium intake or aldosterone release, for example, by angiotensin II. Thus, it can be hypothesized that the system works as a safety valve for sodium accumulation. The large numbers of studies on hypertensive animal models and on essential hypertensive patients, particularly those with salt sensitivity, indicate a tendency toward the reduced excretion of urinary kallikrein, although this reduction is modified by potassium intake and impaired renal function. We hypothesize that the reduced excretion of the renal kallikrein may be attributable to a genetic defect of factor(s) in renal kallikrein secretion process and may cause salt-sensitive hypertension after salt intake.

Cardiovascular effects of peptide kinin B2 receptor antagonists in rats

Bradykinin (BK) is a vasoactive peptide reputed to play an important role in cardiovascular homeostasis. In this study, we describe the cardiovascular changes (mean blood pressure (BP) and heart rate (HR)) induced by the i.v. administration (left jugular vein) of two selective kinin B2 receptor antagonist, namely icatibant (0.1-1 micromol/kg as a bolus) and MEN1 1270 (0.1-1 micromol/kg as a bolus or 1 micromol/kg infused in 15 or 60 min), in urethane-anaesthetized or conscious rats with an indwelling catheter implanted in the right carotid artery for BP measurements. In conscious rats, icatibant at 0.1 or 0.3 micromol/kg did not change BP but at 0.1 micromol/kg increased HR at 30 min from administration. MEN1 1270 at 0.1 or 0.3 micromol/kg induced a dose-related increase in BP and a concomitant bradycardia (significant at 0.3 micromol/kg) lasting for 5 or 30 min, respectively. Icatibant at 1 micromol/kg induced a slight (P < 0.05) increase in BP that resolved in 5 min and a biphasic tachycardia (peaks at 30 and 90 min from administration). MEN1 1270 at 1 micromol/kg induced a triphasic change in HR (tachycardia in the first 5 min, bradycardia at 30 min, and tachycardia at 90 and 120 min) and a biphasic change in BP (hypotension at 15 min and hypertension at 30 min). The i.v. infusion of MEN1 1270 (1 micromol/kg in 15 or 60 min) produced hypertension, whereas HR was increased only following the 15-min infusion. In urethane-anaesthetized rats, both icatibant and MEN1 1270 (0.1 micromol/kg as a bolus) increased BP and the onset for this effect was correlated with the time course of the antagonism of BK-induced hypotension, where the effect of MEN1 1270 was more rapid than that of icatibant. These results indicate that kinin B2 receptor antagonists can induce acute cardiovascular effects, and the reason for the different haemodynamic profile between icatibant and MEN1 1270 could be putatively attributed to kinetic characteristics.