Tissue kallikrein and kinins in renal disease

Comprehensive analysis of molecular mechanisms underlying kidney stones: gene expression profiles and potential diagnostic markers

Background

The study aimed to investigate the molecular mechanisms underlying kidney stones by analyzing gene expression profiles. They focused on identifying differentially expressed genes (DEGs), performing gene set enrichment analysis (GSEA), weighted gene co-expression network analysis (WGCNA), functional enrichment analysis, and screening optimal feature genes using various machine learning algorithms.

Methods

Data from the GSE73680 dataset, comprising normal renal papillary tissues and Randall's Plaque (RP) tissues, were downloaded from the GEO database. DEGs were identified using the limma R package, followed by GSEA and WGCNA to explore functional modules. Functional enrichment analysis was conducted using KEGG and Disease Ontology. Various machine learning algorithms were used for screening the most suitable feature genes, which were then assessed for their expression and diagnostic significance through Wilcoxon rank-sum tests and ROC curves. GSEA and correlation analysis were performed on optimal feature genes, and immune cell infiltration was assessed using the CIBERSORT algorithm.

Results

412 DEGs were identified, with 194 downregulated and 218 upregulated genes in kidney stone samples. GSEA revealed enriched pathways related to metabolic processes, immune response, and disease states. WGCNA identified modules correlated with kidney stones, particularly the yellow module. Functional enrichment analysis highlighted pathways involved in metabolism, immune response, and disease pathology. Through machine learning algorithms, KLK1 and MMP10 were identified as optimal feature genes, significantly upregulated in kidney stone samples, with high diagnostic value. GSEA further elucidated their biological functions and pathway associations.

Conclusion

The study comprehensively analyzed gene expression profiles to uncover molecular mechanisms underlying kidney stones. KLK1 and MMP10 were identified as potential diagnostic markers and key players in kidney stone progression. Functional enrichment analysis provided insights into their roles in metabolic processes, immune response, and disease pathology. These results contribute significantly to a better understanding of kidney stone pathogenesis and may inform future diagnostic and therapeutic strategies.

Function and structure of bradykinin receptor 2 for drug discovery

Type 2 bradykinin receptor (B2R) is an essential G protein-coupled receptor (GPCR) that regulates the cardiovascular system as a vasodepressor. Dysfunction of B2R is also closely related to cancers and hereditary angioedema (HAE). Although several B2R agonists and antagonists have been developed, icatibant is the only B2R antagonist clinically used for treating HAE. The recently determined structures of B2R have provided molecular insights into the functions and regulation of B2R, which shed light on structure-based drug design for the treatment of B2R-related diseases. In this review, we summarize the structure and function of B2R in relation to drug discovery and discuss future research directions to elucidate the remaining unknown functions of B2R dimerization.

Diabetes-induced upregulation of kallistatin levels exacerbates diabetic nephropathy via RAS activation

Kallistatin is an inhibitor of tissue kallikrein and also inhibits the Wnt pathway. Its role in diabetic nephropathy (DN) is uncertain. Here we reported that serum kallistatin levels were significantly increased in diabetic patients with DN compared to those in diabetic patients without DN and healthy controls, and positively correlated with urinary albumin excretion. In addition, renal kallistatin levels were significantly upregulated in mouse models of type 1 (Akita, OVE26) and type 2 diabetes (db/db). To unveil the effects of kallistatin on DN and its underlying mechanism, we crossed transgenic mice overexpressing kallistatin with OVE26 mice (KS‐tg/OVE). Kallistatin overexpression exacerbated albuminuria, renal fibrosis, inflammation, and oxidative stress in diabetes. Kallikrein activity was inhibited while the renin‐angiotensin system (RAS) upregulated in the kidney of KS‐tg/OVE mice compared to WT/OVE mice, suggesting a disturbed balance between the RAS and kallikrein‐kinin systems. As shown by immunostaining of endothelial makers, renal vascular densities were decreased accompanied by increased HIF‐1α and erythropoietin levels in the kidneys of KS‐tg/OVE mice. Taken together, high levels of kallistatin exacerbate DN at least partly by inducing RAS overactivation and hypoxia. The present study demonstrated a positive correlation between kallistatin levels and DN, suggesting a potential biomarker for prognosis of DN.

Human tissue kallikrein in the treatment of acute ischemic stroke

Acute ischemic stroke (AIS) remains a major cause of death and disability throughout the world. The most severe form of stroke results from large vessel occlusion of the major branches of the Circle of Willis. The treatment strategies currently available in western countries for large vessel occlusion involve rapid restoration of blood flow through removal of the offending blood clot using mechanical or pharmacological means (e.g. tissue plasma activator; tPA). This review assesses prospects for a novel pharmacological approach to enhance the availability of the natural enzyme tissue kallikrein (KLK1), an important regulator of local blood flow. KLK1 is responsible for the generation of kinins (bradykinin and kallidin), which promote local vasodilation and long-term vascularization. Moreover, KLK1 has been used clinically as a direct treatment for multiple diseases associated with impaired local blood flow including AIS. A form of human KLK1 isolated from human urine is approved in the People's Republic of China for subacute treatment of AIS. Here we review the rationale for using KLK1 as an additional pharmacological treatment for AIS by providing the biochemical mechanism as well as the human clinical data that support this approach.

Genetically‑modified stem cells in treatment of human diseases: Tissue kallikrein (KLK1)‑based targeted therapy (Review)

The tissue kallikrein-kinin system (KKS) is an endogenous multiprotein metabolic cascade which is implicated in the homeostasis of the cardiovascular, renal and central nervous system. Human tissue kallikrein (KLK1) is a serine protease, component of the KKS that has been demonstrated to exert pleiotropic beneficial effects in protection from tissue injury through its anti-inflammatory, anti-apoptotic, anti-fibrotic and anti-oxidative actions. Mesenchymal stem cells (MSCs) or endothelial progenitor cells (EPCs) constitute populations of well-characterized, readily obtainable multipotent cells with special immunomodulatory, migratory and paracrine properties rendering them appealing potential therapeutics in experimental animal models of various diseases. Genetic modification enhances their inherent properties. MSCs or EPCs are competent cellular vehicles for drug and/or gene delivery in the targeted treatment of diseases. KLK1 gene delivery using adenoviral vectors or KLK1 protein infusion into injured tissues of animal models has provided particularly encouraging results in attenuating or reversing myocardial, renal and cerebrovascular ischemic phenotype and tissue damage, thus paving the way for the administration of genetically modified MSCs or EPCs with the human tissue KLK1 gene. Engraftment of KLK1-modified MSCs and/or KLK1-modified EPCs resulted in advanced beneficial outcome regarding heart and kidney protection and recovery from ischemic insults. Collectively, findings from pre-clinical studies raise the possibility that tissue KLK1 may be a novel future therapeutic target in the treatment of a wide range of cardiovascular, cerebrovascular and renal disorders.

Tissue kallikrein-kinin therapy in hypertension and organ damage

Tissue kallikrein is a serine proteinase that cleaves low molecular weight kininogen to produce kinin peptides, which in turn activate kinin receptors to trigger multiple biological functions. In addition to its kinin-releasing activity, tissue kallikrein directly interacts with the kinin B2 receptor, protease-activated receptor-1, and gamma-epithelial Na channel. The tissue kallikrein-kinin system (KKS) elicits a wide spectrum of biological activities, including reducing hypertension, cardiac and renal damage, restenosis, ischemic stroke, and skin wound injury. Both loss-of-function and gain-of-function studies have shown that the KKS plays an important endogenous role in the protection against health pathologies. Tissue kallikrein/kinin treatment attenuates cardiovascular, renal, and brain injury by inhibiting oxidative stress, apoptosis, inflammation, hypertrophy, and fibrosis and promoting angiogenesis and neurogenesis. Approaches that augment tissue kallikrein-kinin activity might provide an effective strategy for the treatment of hypertension and associated organ damage.

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

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.

Immunohistochemical analysis of kallikrein-related peptidases in the normal kidney and renal tumors: potential clinical implications

Kallikrein-related peptidases (KLKs) have been shown to be differentially expressed in various malignancies and shown to be useful tumor markers. Previous immunohistochemistry (IHC) analysis demonstrated that KLKs 5, 6, 10, and 11 have a potential prognostic significance in renal cell carcinoma (RCC). To further explore the significance of KLKs, we examined KLKs 1, 6, 7, and 15 in different subtypes of renal tumors. KLK1 has stronger expression in high grade compared to low grade clear cell RCC. However, KLK6 and KLK7 show strong expression in low grade in contrast to high grade clear cell RCC. Furthermore, the expression of KLK7 can distinguish between oncocytoma and chromophobe RCC. Oncocytoma showed diffuse, strong granular cytoplasmic staining, but chromophobe RCC showed focal weak homogeneous cytoplasmic stain. The pattern of staining of different KLKs can also be helpful in differentiating some of the subtypes of renal tumors. Our results show the potential ability of KLKs to serve as diagnostic markers and expand previous data about the prognostic significance of KLKs in kidney cancer. In addition, our study is the first to show the ability of KLK staining to distinguish various types of kidney cancers when morphology is similar.

Urine proteomic profiling of uranium nephrotoxicity

Uranium is used in many chemical forms in civilian and military industries and is a known nephrotoxicant. A key issue in monitoring occupational exposure is to be able to evaluate the potential damage to the body, particularly the kidney. In this study we used innovative proteomic techniques to analyse urinary protein modulation associated with acute uranium exposure in rats. Given that the rat urinary proteome has rarely been studied, we first identified 102 different proteins in normal urine, expanding the current proteome data set for this central animal in toxicology. Rats were exposed intravenously to uranyl nitrate at 2.5 and 5 mg/kg and samples were collected 24 h later. Using two complementary proteomic methods, a classic 2-DE approach and semi-quantitative SDS-PAGE-LC-MS/MS, 14 modulated proteins (7 with increased levels and 7 with decreased levels) were identified in urine after uranium exposure. Modulation of three of them was confirmed by western blot. Some of the modulated proteins corresponded to proteins already described in case of nephrotoxicity, and indicated a loss of glomerular permeability (albumin, alpha-1-antiproteinase, serotransferrin). Others revealed tubular damage, such as EGF and vitamin D-binding protein. A third category included proteins never described in urine as being associated with metal stress, such as ceruloplasmin. Urinary proteomics is thus a valuable tool to profile uranium toxicity non-invasively and could be very useful in follow-up in case of accidental exposure to uranium.

The Tissue Kallikrein Family of Serine Proteases: Functional Roles in Human Disease and Potential as Clinical Biomarkers

Prostate specific antigen (PSA) or human kallikrein 3 (hK3) has long been an effective biomarker for prostate cancer. Now, other members of the tissue kallikrein (KLK) gene family are fast becoming of clinical interest due to their potential as prognostic biomarkers. particularly for hormone dependent cancers. The tissue kallikreins are serine proteases that are encoded by highly conserved multi-gene family clusters in rodents and humans. The rat and mouse loci contain 10 and 25 functional genes, respectively, while the human locus at 19q 13.4 contains 15 genes. The structural organization and size of these genes are similar across species; all genes have 5 coding exons that encode a prepro-enzyme. Although the physiological activators of these zymogens have not been described, in vitro biochemical studies show that some kallikreins can auto-activate and others can activate each other, suggesting that the kallikreins may participate in an enzymatic cascade similar to that of the coagulation cascade. These genes are expressed, to varying degrees, in a wide range of tissues suggesting a functional involvement in a diverse range of physiological and pathophysiological processes. These include roles in normal skin desquamation and psoriatic lesions, tooth development, neural plasticity, and Alzheimer's disease (AD). Of particular interest is the expression of many kallikreins in prostate, ovarian, and breast cancers where they are emerging as useful prognostic indicators of disease progression.

Anesthesia and renal disease

PURPOSE OF REVIEW

To present and interpret the relevant research (Jan 2001-Feb 2002) which has the most important implications for clinical anesthesiology as regards the prevention of perioperative renal dysfunction and the anesthetic management of patients with renal disease.

RECENT FINDINGS

Prolonged sevoflurane anesthesia with fresh gas flow less than 1 l min is unlikely to lead to clinically significant renal injury. When used as maintenance agents for patients undergoing coronary artery bypass grafting, sevoflurane anesthesia at a fresh gas flow of 3 l min, isoflurane and propofol are associated with similar rates of postoperative renal dysfunction. Less compound A is produced with smaller soda lime containers. High flow sevoflurane anesthesia (fresh gas flow of 4-6 l min) in combination with perioperative ketorolac is unlikely to lead to renal injury. Chronic treatment with angiotensin-converting enzyme inhibitors is associated with an increased incidence of postoperative renal impairment in patients undergoing elective aortic surgery. Thoracic epidural anesthesia and postoperative analgesia are associated with a decreased incidence of renal failure in patients undergoing coronary artery bypass grafting. Compared with open surgical repair, endovascular repair of aortic aneurysm is associated with less renal injury.

SUMMARY

Sevoflurane anesthesia at low or high fresh gas flow rates is probably no more injurious to the kidneys than other commonly used maintenance agents. Chronic angiotensin-converting enzyme inhibition may increase perioperative renal dysfunction. The use of thoracic epidural anesthesia and analgesia may reduce the incidence of postoperative renal failure.

The role of the renal kallikrein-kinin system in diabetic nephropathy

PURPOSE OF REVIEW

Diabetic nephropathy is one of the most common complications in diabetes mellitus. Multiple pathogenic mechanisms are now believed to contribute to this disease, including inflammatory cytokines, autacoids and oxidative stress. Numerous studies have shown that the kallikrein-kinin system may be involved in these mechanisms. This review focuses on recent research advance on the potential role of the kallikrein-kinin system in the development of diabetic nephropathy, and its clinical relevance.

RECENT FINDINGS

A collection of recent studies has shown that angiotensin-converting enzyme inhibitors, which inhibit angiotensin II formation and degradation of bradykinin, and vasopeptidase inhibitors attenuated the development of diabetic nephropathy in experimental animals and clinical settings. The role of the kallikrein-kinin system in diabetes is further supported by findings that diabetic nephropathy is worsened in diabetic mice lacking bradykinin B2 receptors. Although long-acting bradykinin B2 receptor agonists have been shown to have renal protective effects, their therapeutic benefits have not been well studied.

SUMMARY

Current experimental investigations demonstrated that pharmacological intervention of the kallikrein-kinin system improved renal conditions in diabetes mellitus. These findings suggest that the kallikrein-kinin system may be a therapeutic target in preventing and treating diabetic nephropathy.

Pharmacological enhancement of the kallikrein-kinin system promotes anti-fibrotic responses in human mesangial cells

The aim of the present study was to investigate whether pharmacological enhancement of the renal kallikrein-kinin system using the vasopeptidase inhibitor omapatrilat plays a direct role in modulating the fibrotic responses of human mesangial cells to injury. Treatment with 40 micromol/L omapatrilat was able to reduce macrophage-conditioned medium (MPCM)-induced fibronectin levels without affecting mRNA expression. MPCM injury also suppressed kallikrein and low molecular weight kininogen mRNA. Omapatrilat was able to attenuate this suppression. Bradykinin levels in contrast were increased by MPCM and treatment with omapatrilat further augmented levels. Co-incubation with the bradykinin B2 receptor antagonist HOE 140 attenuated the omapatrilat-induced lowering of fibronectin. Moreover, inhibition of cGMP release had a similar effect. Paradoxically, RT-PCR and Southern blotting demonstrated that bradykinin B2 receptor mRNA levels were down regulated in response to omapatrilat. Western blotting supported this data. Supernatant levels of tissue plasminogen activator (tPA), a product of bradykinin stimulation, were decreased by omapatrilat while cell associated tPA levels were increased. Matrix metalloproteinase-9 (MMP-9) mRNA expression was up regulated by omapatrilat treatment, although no difference in active zymogen levels was observed. In conclusion enhancement of kallikrein-kinin system appears to play a direct role in promoting anti-fibrotic responses in MPCM-injured human mesangial cells.

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-beta1 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-beta1 expression, and mitogen-activated protein kinase activation.

Cellular distribution of human tissue kallikreins: immunohistochemical localization

We have studied the immunohistochemical expression (IE) of eight non-tissue-specific human kallikreins (hKs) (hK5, 6, 7, 10, 11, 12, 13, and 14) in different normal tissues. The IE was always cytoplasmic, showing a characteristic pattern in some tissues. Comparison of the IE of all hKs studied in the different tissues revealed no major differences, suggesting that they share a common mode of regulation. Furthermore, hKs were immunohistochemically revealed in a variety of tissues, indicating that no protein is tissue-specific (except for hK2 and hK3, which have tissue-restricted expression). In general, our results correspond well with data from RT-PCR and ELISA assays. Glandular epithelia constitute the main kallikrein IE sites, and the staining in their secretions confirms that these proteases are secreted. A variety of other tissues express the proteins as well. We have also immunohistochemically evaluated all the above hKs in several malignant tissues. Tumors arising from tissues expressing kallikreins tested positive. Corresponding to the IE in normal glandular tissues, most hKs were expressed in adenocarcinomas. The prognostic value of several hKs was studied in series of prostate, renal cell, colon and urothelial carcinomas.

Expression and preliminary characterization of recombinant human tissue kallikrein in egg white of laying hens

Human tissue kallikrein (hK1) plays an important role in regulation of blood pressure, electrolyte and glucose transport, and renal function. To evaluate the feasibility of expression of recombinant human tissue kallikrein (rhK1) in the egg whites of laying hens, human tissue kallikrein gene (hKLK1) cDNA was subcloned into the chicken oviduct-specific expression vector (pOV3), and the resultant recombinant vector pOV3K was injected into laying hens via wing vein after mixing with polyethyleneimine. Following injection twice with the recombinant vector, the enzymatic activity at a maximal level of 59 U/mL was detected in the egg whites, which lasted for more than 7 d. The expression level of rhK1 in the egg whites in the 3-mg group was relatively higher than that in the 2-mg group, but the significant differences were identified on d 7 and 8 (P < 0.05). Ten days after the primary injection, the hens were reinjected with the same dose of the vector, and even higher enzymatic activity was detected in their egg whites. Two different breeds of hen were tested with no difference in expression level found (P > 0.05). Western blot analysis of the egg whites from vector-injected hens showed the rhK1 was recognized by a polyclonal antibody specific for hK1 with molecular weights of 37 and 43 kDa, which probably corresponded to the mature and preenzyme, respectively. Biochemical studies showed that the recombinant enzyme had a similar thermostability, optimal pH, hypotensive effect, and sensitivity to different ions to the natural enzymes in human and porcine tissues. These data indicate that the chicken oviduct-specific transient expression system can produce relatively high level and authentic recombinant enzyme with a potential for further development for therapeutic use.

Reversal of renal fibrosis, inflammation, and glomerular hypertrophy by kallikrein gene delivery

Evidence suggests that the progression of renal fibrosis is a reversible process. Because inflammation plays a crucial role in the development of renal injury, we examined the effect of kallikrein and activation of the kinin B2 receptor on the reversal of salt-induced inflammation and renal fibrosis in Dahl salt-sensitive (DSS) rats. Four weeks after high salt loading, when renal injury was apparent, adenovirus harboring the human tissue kallikrein gene was injected into DSS rats. To determine the role of the B2 receptor in mediating the actions of kallikrein, icatibant, a kinin B2 receptor antagonist, was infused with kallikrein gene delivery. Two weeks after adenovirus injection, salt-induced glomerular sclerosis, tubular protein cast formation, and monocyte/ macrophage accumulation in the kidney were notably reversed by kallikrein. Decreased intercellular adhesion molecule-1 expression paralleled this observation. Kallikrein gene delivery also dramatically reduced collagens I, III, and IV and reticulin deposition, accompanied by a decline in myofibroblast accumulation and transforming growth factor-beta(1) expression. Moreover, kallikrein reversed salt-induced glomerular hypertrophy and inhibited the increase in levels of the cell cycle-inhibitory proteins p21 and p27. These protective actions of kallikrein were abolished by icatibant, indicating a B2 receptor-mediated event. In addition, kallikrein protected against salt-induced renal injury by diminishing urinary protein and blood urea nitrogen levels. Furthermore, kallikrein gene delivery restored nitric oxide production and suppressed NADH oxidase activity and superoxide generation. These results indicate that tissue kallikrein, through the kinin B2 receptor, reverses salt-induced inflammation, renal fibrosis, and glomerular hypertrophy via suppression of oxidative stress.

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

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. Kallikrein's 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-beta1 expression, MAPK and nuclear factor-kappaB 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.

International union of pharmacology. XLV. Classification of the kinin receptor family: from molecular mechanisms to pathophysiological consequences

Kinins are proinflammatory peptides that mediate numerous vascular and pain responses to tissue injury. Two pharmacologically distinct kinin receptor subtypes have been identified and characterized for these peptides, which are named B1 and B2 and belong to the rhodopsin family of G protein-coupled receptors. The B2 receptor mediates the action of bradykinin (BK) and lysyl-bradykinin (Lys-BK), the first set of bioactive kinins formed in response to injury from kininogen precursors through the actions of plasma and tissue kallikreins, whereas the B(1) receptor mediates the action of des-Arg9-BK and Lys-des-Arg9-BK, the second set of bioactive kinins formed through the actions of carboxypeptidases on BK and Lys-BK, respectively. The B2 receptor is ubiquitous and constitutively expressed, whereas the B1 receptor is expressed at a very low level in healthy tissues but induced following injury by various proinflammatory cytokines such as interleukin-1beta. Both receptors act through G alpha(q) to stimulate phospholipase C beta followed by phosphoinositide hydrolysis and intracellular free Ca2+ mobilization and through G alpha(i) to inhibit adenylate cyclase and stimulate the mitogen-activated protein kinase pathways. The use of mice lacking each receptor gene and various specific peptidic and nonpeptidic antagonists have implicated both B1 and B2 receptors as potential therapeutic targets in several pathophysiological events related to inflammation such as pain, sepsis, allergic asthma, rhinitis, and edema, as well as diabetes and cancer. This review is a comprehensive presentation of our current understanding of these receptors in terms of molecular and cell biology, physiology, pharmacology, and involvement in human disease and drug development.

Kallikrein–kinin in stroke, cardiovascular and renal disease

Tissue kallikrein, a serine proteinase, produces the potent vasodilator kinin peptide from kininogen substrate. The levels of tissue kallikrein are reduced in humans and animal models with hypertension, cardiovascular and renal disease. Using transgenic and somatic gene transfer approaches, we investigated the role of the tissue kallikrein-kinin system in cardiovascular, renal and central nervous systems. A single injection of the human tissue kallikrein gene in plasmid DNA or an adenoviral vector resulted in a prolonged reduction of blood pressure and attenuation of hypertrophy and fibrosis in the heart and kidney of several hypertensive animal models. Furthermore, enhanced kallikrein-kinin levels after gene transfer exerted beneficial effects, with protection against cardiac remodelling, renal injuries, restenosis, cerebral infarction and neurological deficits in normotensive animal models without haemodynamic effects, indicating direct actions of kallikrein independent of its ability to lower blood pressure. The effects of kallikrein were mediated by the kinin B2 receptor, as the specific B2 receptor antagonist icatibant abolished the actions of kallikrein. Moreover, kallikrein-kinin exhibited pleiotropic effects by inhibiting apoptosis, inflammation, hypertrophy and fibrosis, and promoting angiogenesis and neurogenesis in the heart, kidney, brain and blood vessel. Exogenous administration of kallikrein also led to increased nitric oxide (NO)/cGMP and cAMP levels, and reduced NAD(P)H oxidase activities, superoxide formation and pro-inflammatory cytokine levels. These results indicate a novel role of kallikrein-kinin through the kinin B2 receptor as an antioxidant and anti-inflammatory agent in protection against stroke, cardiovascular and renal disease, and may uncover new drug targets for the prevention and treatment of heart failure, vascular injury, end-stage renal disease and stroke in humans.

Visualisation of transforming growth factor-β1, tissue kallikrein, and kinin and transforming growth factor-β receptors on human clear-cell renal carcinoma cells

Transforming growth factor-beta1 (TGF-beta1) has a biphasic effect on the growth of renal epithelial cells. In transformed cells, TGF-beta1 appears to accelerate the proliferation of malignant cells. The diverse cellular functions of TGF-beta1 are regulated by three high-affinity serine/threonine kinase receptors, namely TbetaRI, TbetaRII and TbetaRIII. The renal serine protease tissue kallikrein acts on its endogenous protein substrate kininogen to form kinin peptides. The cellular actions of kinins are mediated through B1 and B2 G protein-coupled rhodopsin receptors. Both kinin peptides and TGF-beta1 are mitogenic, and therefore may play an important role in carcinogenesis. Experiments were designed to immunolabel tissue kallikrein, TGF-beta1, TbetaRII, TbetaRIII and kinin receptors using specific antibodies on serial sections of normal kidney and clear-cell renal carcinoma (CCRC) tissue, which included both the tumour and the adjacent renal parenchyma. The essential result was the localisation of tissue kallikrein, kinin B 1 and B 2 receptors and TGF-beta1 primarily on the cell membranes of CCRC cells. In the distal and proximal tubules of the renal parenchyma adjacent to the carcinoma (RPTAC), immunolabelling for tissue kallikrein was reduced, but the expression of kinin B1 and B2 receptors was enhanced. Immunolabelling for TbetaRII and TbetaRIII was more pronounced in the proximal tubules of the tissue adjacent to the carcinoma when compared to the normal kidney. The expression of tissue kallikrein, kinin receptors, and TbetaRII and TbetaRIII may be relevant to the parenchymal invasion and metastasis of clear-cell renal carcinoma.

Worsening fluid retention in a patient with hereditary angioedema and end-stage renal disease

A 60-year-old woman who was diagnosed with hereditary angioedema (HAE) developed nephrotic syndrome, with end-stage renal disease (ESRD) occurring about 2.5 years later. During her slide toward ESRD, she experienced three severe episodes of angioedema that each resulted in significant fluid retention. Though the therapeutic administration of C1-inhibitor concentrate was effective in controlling her angioedema, seemed ineffective in preventing her from developing ESRD requiring hemodialysis treatment. We theorized that the patient's low colloid osmolality and glomerular perfusion were important facilitators of her attacks of angioedema.

Leukocytic cell sources of airway tissue kallikrein

Lung tissue kallikrein (TK) is a serine proteinase that putatively plays a role in the pathophysiology of asthma by generating kallidin and bradykinin, mediators that contribute to airway hyperresponsiveness. In previous studies we observed biphasic increases in TK activity in bronchoalveolar lavage fluid following airway allergen challenge in allergic sheep. Although glandular TK is likely a major source of the initial increase in TK, the sources of the late increases in TK that are associated with the development of airway hyperresponsiveness may be dependent on activated resident and recruited inflammatory cells including alveolar macrophages (AMs) and neutrophils (PMNs). These cells increase concomitantly with the late increases in TK activity. To test this hypothesis, we obtained AMs from bronchoalveolar lavage fluid and PMNs and monocytes (precursors of AMs) from sheep blood and determined whether these cells contained TK and whether these same cells could release TK upon activation. Using confocal microscopy, immunocytochemical techniques, and enzyme activity assays, we found that all three cell types contained and secreted TK. All three cell types demonstrated basal release of TK, which could be increased after stimulation with zymosan. In addition, PMNs also released TK in the presence of phorbol ester, suggesting multiple secretory pathways in these cells. Furthermore, we showed that human monocytes also contain and secrete TK. We conclude that in the airways, monocytes, PMNs, and AMs may contribute to increased TK activity. Knowing the sources of TK in the airways could be important in understanding the mechanisms of inflammation that contribute to the pathophysiology of asthma and may help in the development of new therapies to control the disease.

Kallikrein cascade and cytokines in inflamed joints

Rheumatoid arthritis is a chronic multi-system disease of unknown aetiology. The current hypothesis is that an unknown antigen triggers an autoimmune response in a genetically susceptible individual. The predominant pathological change is that of an inflammatory synovitis, characterised by cellular infiltrates and angiogenesis, with subsequent bone and cartilage destruction. These pathological changes are as a result of the activation of a variety of cells, inflammatory mediators, and effector molecules. The pro-inflammatory kinins and cytokines appear to play a central role in the pathogenesis of rheumatoid arthritis. Sufficient evidence exists that establishes a key role for the kallikrein-kinin cascade in inflamed joints. In addition, there appears to be an inter-relationship between cytokines and kinins in the inflammatory process. Kinins induce the release of cytokines, and cytokines have been shown to augment the effects of kinins. This may lead to an enhancement and perpetuation of the inflammatory process. In this review, we report a first study, correlating markers of disease with the kallikrein-kinin cascade and with cytokines.

The effect of ketorolac and sevoflurane anesthesia on renal glomerular and tubular function

We assessed the renal effects of the combination of ketorolac and sevoflurane anesthesia by using sensitive and specific markers of renal proximal and distal tubular and glomerular function. Thirty women (ASA physical status I and II) undergoing breast surgery received either ketorolac 30 mg IM or saline at premedication, at the end, and 6 h after anesthesia maintained with sevoflurane. Peak levels of serum fluoride at 2 h after the end of anesthesia were 30.1 micromol/L (21.0-50.0 micromol/L) in the Ketorolac group and 33.3 micromol/L (13.0-38.0 micromol/L) in the Control group (mean and range, not significant). Urine alpha1-microglobulin indexed to urine creatinine was increased from 2 h after the start of anesthesia until the first postoperative day in the Ketorolac group (peak level, 0.8 +/- 0.4 mg/mmol; upper limit of normal, 0.7 mg/mmol) but did not change in the Control group. Urine glutathione-S-transferase (GST)-alpha indexed to urine creatinine (GST-alpha/creatinine) and GST-pi/creatinine were increased 2 h after anesthesia and returned to baseline values thereafter in both groups. There were no changes in serum cystatin C and urine kallikrein or urine output per hour between groups. The perioperative administration of ketorolac to healthy, well hydrated patients anesthetized with sevoflurane did not produce renal glomerular or tubular dysfunction.

IMPLICATIONS

Ketorolac 90 mg IM, given in divided doses over approximately 10 h to patients anesthetized with sevoflurane with a fresh gas flow rate of 4-6 L/min, did not result in clinically significant changes in renal glomerular or tubular function.

Association of a single nucleotide polymorphism in CPB2 encoding the thrombin-activable fibrinolysis inhibitor (TAF1) with blood pressure

Thrombin-activable fibrinolysis inhibitor (TAFI) is a hepatically secreted zymogen, whose substrates include bradykinin. The CPB2 gene encoding TAFI is a candidate gene for blood pressure. A recently identified single nucleotide polymorphism (SNP) in the CPB2 coding region, designated as 1057C > T, results in an amino acid change at TAFI residue 325 (Ile > Thr325). We found that the genotype based on this SNP was significantly associated with blood pressure in aboriginal Canadians. Specifically, analysis of variance showed that homozygotes for CPB2 1057T had significantly lower diastolic blood pressure than subjects with other CPB2 genotypes. CPB2 genotype accounted for approximately 3% of the total variation in diastolic blood pressure. consistent with the expected magnitude of a modest genetic effect in a complex trait such as blood pressure. Although the mechanism underlying the association is unclear, the findings are of interest because TAFI may provide a link between coagulation and blood pressure regulation.

Metalloendopeptidases EC 3.4.24.15 and EC 3.4.24.16 and bradykinin B2 receptors do not play important roles in renal wrap hypertension in rabbits

1. The aim of the present study was to determine the effects of the metalloendopeptidase (EP) 24.15 and 24.16 inhibitor N-[1-(R,S)-carboxy-3-phenylpropyl]-Ala-Aib-Tyr-p-aminobenzoate (JA-2) on haemodynamics and renal function in conscious rabbits with two-kidney, two-wrapped hypertension. We have also examined the role of endogenous bradykinin in the maintenance phase of this form of renovascular hypertension and whether inhibition of bradykinin degradation contributes to any potential effects of JA-2. 2. In two preliminary operations, rabbits were equipped with transit-time ultrasound flow probes for measuring cardiac output (CO) and renal blood flow (RBF) and had both kidneys wrapped in cellophane. Starting 4 weeks after the last operation, rabbits underwent four studies (3-5 days apart), during which they were treated with combinations of the bradykinin B2 receptor antagonist icatibant or its vehicle (1 mL/kg bodyweight 0.9% w/v NaCl) and JA-2 or its vehicle (1 mL/kg of a 5% w/v 2-hydroxypropyl-beta-cyclodextrin, 2.5% v/v dimethylsulphoxide solution). Renal function was monitored using standard renal clearance methods. 3. Icatibant (10 microg/kg) had no significant effects on systemic haemodynamic variables (mean arterial pressure, heart rate or CO), renal haemodynamic variables (RBF or glomerular filtration rate), urine flow or sodium excretion. At 5 mg/kg plus 3 mg/kg per h, JA-2 also did not affect any of these variables, either after icatibant vehicle treatment or after icatibant treatment. 4. Our data do not support major roles for endogenous bradykinin or bradykinin degradation by EP 24.15/24.16 in the control of systemic and renal haemodynamics or renal excretory function in two-kidney, two-wrapped hypertension in rabbits.

Kallikrein and kinin receptor expression in inflammation and cancer

The kallikrein family of serine proteases has been investigated in many inflammatory disorders as molecular mapping, gene characterisation and cloning of kinin receptor genes have unfolded experimentally. In the molecular events of the inflammatory response the kallikrein cascade plays a significant role, since it is considered to initiate and maintain systemic inflammatory responses and immune-modulated disorders. A primary event is the chemotactic attraction of neutrophils which deliver the kallikrein-kinin cascade to sites of cellular injury and carcinogenic transformation of cells. The present study establishes the casual involvement of the kallikrein cascade in infection, inflammatory joint disease, acute transplant rejection, renal glomerular diseases, angiogenesis and carcinoma. We provide strong evidence for new or enhanced expression of kinin B1 receptors in inflammation, and additionally the induction of kallikrein genes in angiogenesis and carcinoma. The results provide insights into possible roles of kallikrein inhibitors and kinin receptor antagonists.