Formation of Bradykinin: A Major Contributor to the Innate Inflammatory Response

Clinical complications in envenoming by Apis honeybee stings: insights into mechanisms, diagnosis, and pharmacological interventions

Envenoming resulting from Apis honeybee stings pose a neglected public health concern, with clinical complications ranging from mild local reactions to severe systemic manifestations. This review explores the mechanisms underlying envenoming by honeybee sting, discusses diagnostic approaches, and reviews current pharmacological interventions. This section explores the diverse clinical presentations of honeybee envenoming, including allergic and non-allergic reactions, emphasizing the need for accurate diagnosis to guide appropriate medical management. Mechanistic insights into the honeybee venom's impact on physiological systems, including the immune and cardiovascular systems, are provided to enhance understanding of the complexities of honeybee sting envenoming. Additionally, the article evaluates emerging diagnostic technologies and therapeutic strategies, providing a critical analysis of their potential contributions to improved patient outcomes. This article aims to provide current knowledge for healthcare professionals to effectively manage honeybee sting envenoming, thereby improving patient care and treatment outcomes.

Extracellular C1qbp inhibits myogenesis by suppressing NFATc1

Aging and lack of exercise are the most important etiological factors for muscle loss. We hypothesized that new factors that contribute to muscle loss could be identified from ones commonly altered in expression in aged and exercise-limited skeletal muscles. Mouse gastrocnemius muscles were subjected to mass spectrometry-based proteomic analysis. The muscle proteomes of hindlimb-unloaded and aged mice were compared to those of exercised and young mice, respectively. C1qbp expression was significantly upregulated in the muscles of both hindlimb-unloaded and aged mice. In vitro myogenic differentiation was not affected by altering intracellular C1qbp expression but was significantly suppressed upon recombinant C1qbp treatment. Additionally, recombinant C1qbp repressed the protein level but not the mRNA level of NFATc1. NFATc1 recruited the transcriptional coactivator p300, leading to the upregulation of acetylated histone H3 levels. Furthermore, NFATc1 silencing inhibited p300 recruitment, downregulated acetylated histone H3 levels, and consequently suppressed myogenic differentiation. The expression of C1qbp was inversely correlated with that of NFATc1 in the gastrocnemius muscles of exercised or hindlimb-unloaded, and young or aged mice. These findings demonstrate a novel role of extracellular C1qbp in suppressing myogenesis by inhibiting the NFATc1/p300 complex. Thus, C1qbp can serve as a novel therapeutic target for muscle loss.

Chemical modification of bradykinin-polymer conjugates for optimum delivery of nanomedicines to tumors

We recently prepared pH-responsive HPMA copolymer conjugates of bradykinin (P-BK), which release BK in response to the acidic tumor microenvironment, and found that administration of P-BK increased the tumor accumulation and therapeutic efficacy of nanomedicine. Because the release of BK from P-BK determines its onset of action, P-BKs with different release rates were prepared, and their properties were evaluated. The release kinetics were significantly altered by substitution proximal to hydrazone bond, release constant of methyl-substituted P-BK (P-MeBK) was approximately 4- and 80-fold higher than that of cyclopropyl-substituted P-BK (P-CPBK) and phenyl-substituted P-BK (P-PhBK). None of the P-BKs were active, but the release of BK restored their BK-like activity. Pre-administration of the P-BKs increased the tumor accumulation of nanomedicine in C26 tumor-bearing mice by 2- and 1.4-fold for P-MeBK and P-PhBK at 3 and 6 h. Altogether, this study provides insights into the design of pH-responsive nanodrugs with the desired release properties to target acidic lesions such as cancer and inflammation.

Kinin Receptors and Kinin-Related Gene Expression in Astrocytic Brain Tumors

Kinins are a set of peptides present in tissues that are involved in the inflammatory response and cancer progression. However, studies showing the expression of kinin receptors in human glioma samples are still incomplete and contradictory. The aim of the present study was to ascertain the expression of BDKRB1 and BDKRB2 genes, as well as the level of B1R and B2R proteins in human gliomas, depending on the degree of malignancy. Additionally, representative kinin-dependent genes with altered expression were indicated. The expression profile of kinin-dependent genes was determined using oligonucleotide microarray technique. In addition, RT-qPCR was used to assess the expression level of selected differentiating genes. The location of kinin receptors in brain gliomas was assessed using immunohistochemical methods. The oligonucleotide microarray method was used to identify 12 mRNA IDs of kinin-related genes whose expression was upregulated or downregulated in gliomas of different grades. In immunohistochemically stained samples, the concentrations of BR1 and BR2 proteins, measured by optical density, were statistically significantly higher in grade G3 vs. G2 and G4 vs. G3. Increased expression of kinin receptors BDKRB1 and BDKRB2 in brain gliomas, depending on the degree of malignancy, suggests the involvement of kinins and their receptors in the disease's pathogenesis. Quantitative assessment of mRNA BDKRB1, PRKAR1A, MAP2K, and EGFR in patients with brain tumors may hold diagnostic and therapeutic significance.

Bradykinin produced during Plasmodium falciparum erythrocytic cycle drives monocyte adhesion to human brain microvascular endothelial cells

Cerebral malaria (CM) pathogenesis is described as a multistep mechanism. In this context, monocytes have been implicated in CM pathogenesis by increasing the sequestration of infected red blood cells to the brain microvasculature. In disease, endothelial activation is followed by reduced monocyte rolling and increased adhesion. Nowadays, an important challenge is to identify potential pro-inflammatory stimuli that can modulate monocytes behavior. Our group have demonstrated that bradykinin (BK), a pro-inflammatory peptide involved in CM, is generated during the erythrocytic cycle of P. falciparum and is detected in culture supernatant (conditioned medium). Herein we investigated the role of BK in the adhesion of monocytes to endothelial cells of blood brain barrier (BBB). To address this issue human monocytic cell line (THP-1) and human brain microvascular endothelial cells (hBMECs) were used. It was observed that 20% conditioned medium from P. falciparum infected erythrocytes (Pf-iRBC sup) increased the adhesion of THP-1 cells to hBMECs. This effect was mediated by BK through the activation of B2 and B1 receptors and involves the increase in ICAM-1 expression in THP-1 cells. Additionally, it was observed that angiotensin-converting enzyme (ACE) inhibitor, captopril, enhanced the effect of both BK and Pf-iRBC sup on THP-1 adhesion. Together these data show that BK, generated during the erythrocytic cycle of P. falciparum, could play an important role in adhesion of monocytes in endothelial cells lining the BBB.

Pathophysiology of bradykinin and histamine mediated angioedema

Angioedema is characterized by swelling localized to the subcutaneous and submucosal tissues. This review provides an overview of angioedema, including the different types, triggers, and underlying pathophysiologic mechanisms. Hereditary and acquired angioedema are caused by dysregulation of the complement and kinin pathways. In contrast, drug-induced and allergic angioedema involve the activation of the immune system and release of vasoactive mediators. Recent advances in the understanding of the pathophysiology of angioedema have led to the development of targeted therapies, such as monoclonal antibodies, bradykinin receptor antagonists, and complement inhibitors, which promise to improve clinical outcomes in patients with this challenging condition. To accurately diagnose and manage angioedema, an understanding of this condition's complex and varied pathophysiology is both necessary and critical.

Structures of factor XI and prekallikrein bound to domain 6 of high-molecular weight kininogen reveal alternate domain 6 conformations and exosites

BACKGROUND

High-molecular weight kininogen (HK) circulates in plasma as a complex with zymogen prekallikrein (PK). HK is both a substrate and a cofactor for activated plasma kallikrein, and the principal exosite interactions occur between PK N-terminal apple domains and the C-terminal D6 domain of HK.

OBJECTIVES

To determine the structure of the complex formed between PK apple domains and an HKD6 fragment and compare this with the coagulation factor XI (FXI)-HK complex.

METHODS

We produced recombinant FXI and PK heavy chains (HCs) spanning all 4 apple domains. We cocrystallized PKHC (and subsequently FXIHC) with a 31-amino acid synthetic peptide spanning HK residues Ser565-Lys595 and determined the crystal structure. We also analyzed the full-length FXI-HK complex in solution using hydrogen deuterium exchange mass spectrometry.

RESULTS

The 2.3Å PKHC-HK peptide crystal structure revealed that the HKD6 sequence WIPDIQ (Trp569-Gln574) binds to the apple 1 domain and HK FNPISDFPDT (Phe582-Thr591) binds to the apple 2 domain with a flexible intervening sequence resulting in a bent double conformation. A second 3.2Å FXIHC-HK peptide crystal structure revealed a similar interaction with the apple 2 domain but an alternate, straightened conformation of the HK peptide where residues LSFN (Leu579-Asn583) interacts with a unique pocket formed between the apple 2 and 3 domains. HDX-MS of full length FXI-HK complex in solution confirmed interactions with both apple 2 and apple 3.

CONCLUSIONS

The alternate conformations and exosite binding of the HKD6 peptide likely reflects the diverging relationship of HK to the functions of PK and FXI.

The blood-retina barrier in health and disease

The blood-retina barrier (BRB) is the term used to define the properties of the retinal capillaries and the retinal pigment epithelium (RPE), which separate the systemic circulation from the retina. More specifically, the inner blood-retina barrier (iBRB) is used to describe the properties of the endothelial cells that line the microvasculature of the inner retina, while the outer blood-retina barrier (oBRB) refers to the properties of the RPE cells that separate the fenestrated choriocapillaris from the retina. The BRB is not a fixed structure; rather, it is dynamic, with its components making unique contributions to its function and structural integrity, and therefore the retina. For example, while tight junction (TJ) proteins between retinal endothelial cells are the key molecular structures in the maintenance of the iBRB, other cell types surrounding endothelial cells are also important. In fact, this overall structure is termed the neurovascular unit (NVU). The integrity of the BRB is crucial in the maintenance of a 'dry', tightly regulated retinal microenvironment through the regulation of transcellular and paracellular transport. Specifically, breakdown of TJs can result in oedema formation, a hallmark feature of many retinal diseases. Here, we will describe the oBRB briefly, with a more in-depth focus on the structure and function of the iBRB in health and diseased states. Finally, the contribution of the BRB to the pathophysiology of age-related macular degeneration (AMD), diabetic retinopathy (DR) and other rarer retinal diseases will be discussed.

COVID-19: imbalance of multiple systems during infection and importance of therapeutic choice and dosing of cardiac and anti-coagulant therapies

The renin-angiotensin-aldosterone system and its metabolites play an important role in homeostasis of body, especially the cardiovascular system. In this study, we discuss the imbalance of multiple systems during the infection and the importance of therapeutic choice, dosing, and laboratory monitoring of cardiac and anti-coagulant therapies in COVID-19 patients. The crosstalk between angiotensin, kinin-kallikrein system, as well as inflammatory and coagulation systems plays an essential role in COVID-19. Cardiac complications and coagulopathies imply the crosstalks between the mentioned systems. We believe that the blockage of bradykinin can be a good option in the management of COVID-19 and CVD in patients and that supportive treatment of respiratory and cardiologic complications is needed in COVID-19 patients. Ninety-one percent of COVID-19 patients who were admitted to hospital with a prolonged aPTT were positive for lupus anticoagulant, which increases the risk of thrombosis and prolonged aPTT. Therefore, the question that is posed at this juncture is whether it is safe to use the prophylactic dose of heparin particularly in those with elevated D-dimer levels. It should be noted that timing is of high importance in anti-coagulant therapy; therefore, we should consider the level of D-dimer, fibrinogen, drug-drug interactions, and risk factors during thromboprophylaxis administration. Fibrinogen is an independent predictor of resistance to heparin and should be considered before thromboprophylaxis. Alteplase and Futhan might be a good choice to assess the condition of heparin resistance. Finally, the treatment option, dosing, and laboratory monitoring of anticoagulant therapy are critical decisions in COVID-19 patients.

Hereditary angioedema: Pathophysiology (HAE type I, HAE type II, and HAE nC1-INH)

The pathophysiology of hereditary angioedema (HAE) in virtually all cases is the result of the uncontrolled production of the vasoactive peptide bradykinin. C1 inhibitor (C1-INH) is a serine protease inhibitor, which, under normal circumstances, is the regulator of critical enzymes that are active in the cascades that result in bradykinin generation. In the classic forms of HAE, C1-INH is not produced in sufficient quantities (<40% of normal) or the function is <40% of normal activity. The major pathway for the production of bradykinin is the "contact system," also known as the kallikrein-kinin system. This system begins with the activation of factor XII (FXII) to FXIIa, by a variety of physiologic and pathologic stimuli. FXIIa is a serine protease that binds to surfaces and cleaves prekallikrein to the active serine protease kallikrein. Kallikrein then cleaves high-molecular-weight kininogen to release the nonapeptide bradykinin. Bradykinin binds to the bradykinin β2 receptor, which increases vascular permeability and allows the flow of fluids into the extracellular space and results in angioedema. The two major enzymes generated in this cascade FXIIa and kallikrein are inhibited by C1-INH, which is the major regulator of this cascade. Failure to adequately control the production of bradykinin is thus the major mechanism for HAE. Several other types of HAE in which C1-INH is not decreased (HAE nlC1-INH) have been described. The alterations in FXII and plasminogen (also a serine protease inhibited by C1-INH) like with classic HAE are the result of dysregulation of bradykinin generation. Only genetic alterations in angiopoietin-1 may not be related to bradykinin generation, rather related to the control of the effect of bradykinin on the vascular endothelium.

Double Heterozygous Mutations (Cys247Tyr and 252delAsn) Cause Factor XII Deficiency in a Chinese Family

OBJECTIVE

 To study the molecular basis of human coagulation factor XII (FXII) deficiency in a Chinese family.

METHODS

 Routine blood coagulation indexes were detected by a one-stage clotting method, whereas FXII antigen was detected by enzyme linked immunosorbent assay. DNA sequencing was applied to find mutations in the F12 gene. Bioinformatics and conservative analyses were performed to analyze possible effects of the mutation.

RESULTS

 The proband had significantly prolonged activated partial thromboplastin time (141.9 seconds), and her FXII clotting activity was decreased to 5%. Genetic analysis revealed that the propositus carried a heterozygous missense mutation c.797G > A in exon 8 resulting in Cys247Tyr and deletion mutation c.809_811delACA in exon 9 resulting in 252delAsn. Bioinformatics results indicated that the mutation had affected the function of the protein.

CONCLUSION

 The c.797G > A heterozygous missense variation and the c.809_811delACA heterozygous deletion variation are associated with decreased FXII levels in this family, of which c.797G > A is first reported in the world.

A comprehensive review on drug repositioning against coronavirus disease 2019 (COVID19)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) is the reason for this ongoing pandemic infection diseases termed coronavirus disease 2019 (COVID-19) that has emerged since early December 2019 in Wuhan City, Hubei Province, China. In this century, it is the worst threat to international health and the economy. After 4 months of COVID-19 outbreak, there is no certain and approved medicine against it. In this public health emergency, it makes sense to investigate the possible effects of old drugs and find drug repositioning that is efficient, economical, and riskless process. Old drugs that may be effective are from different pharmacological categories, antimalarials, anthelmintics, anti-protozoal, anti-HIVs, anti-influenza, anti-hepacivirus, antineoplastics, neutralizing antibodies, immunoglobulins, and interferons. In vitro, in vivo, or preliminary trials of these drugs in the treatment of COVID-19 have been encouraging, leading to new research projects and trials to find the best drug/s. In this review, we discuss the possible mechanisms of these drugs against COVID-19. Also, it should be mentioned that in this manuscript, we discuss preliminary rationales; however, clinical trial evidence is needed to prove them. COVID-19 therapy must be based on expert clinical experience and published literature and guidelines from major health organizations. Moreover, herein, we describe current evidence that may be changed in the future.

Peptidylarginine Deiminase of Porphyromonas gingivalis Modulates the Interactions between Candida albicans Biofilm and Human Plasminogen and High-Molecular-Mass Kininogen

Microorganisms that create mixed-species biofilms in the human oral cavity include, among others, the opportunistic fungus Candida albicans and the key bacterial pathogen in periodontitis, Porphyromonas gingivalis. Both species use arsenals of virulence factors to invade the host organism and evade its immune system including peptidylarginine deiminase that citrullinates microbial and host proteins, altering their function. We assessed the effects of this modification on the interactions between the C. albicans cell surface and human plasminogen and kininogen, key components of plasma proteolytic cascades related to the maintenance of hemostasis and innate immunity. Mass spectrometry was used to identify protein citrullination, and microplate tests to quantify the binding of modified plasminogen and kininogen to C. albicans cells. Competitive radioreceptor assays tested the affinity of citrullinated kinins to their specific cellular receptors. The citrullination of surface-exposed fungal proteins reduced the level of unmodified plasminogen binding but did not affect unmodified kininogen binding. However, the modification of human proteins did not disrupt their adsorption to the unmodified fungal cells. In contrast, the citrullination of kinins exerted a significant impact on their interactions with cellular receptors reducing their affinity and thus affecting the role of kinin peptides in the development of inflammation.

Temporal map of the pig polytrauma plasma proteome with fluid resuscitation and intravenous vitamin C treatment

BACKGROUND

Fluid resuscitation plays a prominent role in stabilizing trauma patients with hemorrhagic shock yet there remains uncertainty with regard to optimal administration time, volume, and fluid composition (e.g., whole blood, component, colloids) leading to complications such as trauma-induced coagulopathies (TIC), acidosis, and poor oxygen transport. Synthetic fluids in combination with antioxidants (e.g., vitamin C) may resolve some of these problems.

OBJECTIVES

We applied quantitative mass spectrometry-based proteomics [liquid chromatography-mass spectrometry (LC-MS/MS)] to map the effects of fluid resuscitation and intravenous vitamin C (VitC) in a pig model of polytrauma (hemorrhagic shock, tissue injury, liver reperfusion, hypothermia, and comminuted bone fracture). The goal was to determine the effects of VitC on plasma protein expression, with respect to changes associated with coagulation and trauma-induced coagulopathy (TIC).

METHODS

Longitudinal blood samples were drawn from nine male Sinclair pigs at baseline, 2 h post trauma, and 0.25, 2, and 4 h post fluid resuscitation with 500 mL hydroxyethyl starch. Pigs were treated intravenously (N = 3/treatment group) with saline, 50 mg VitC/kg (Lo-VitC), or 200 mg VitC/kg (Hi-VitC) during fluid resuscitation.

RESULTS

A total of 436 plasma proteins were quantified of which 136 changed following trauma and resuscitation; 34 were associated with coagulation, complement cascade, and glycolysis. Unexpectedly, Lo-VitC and Hi-VitC treatments stabilized ADAMTS13 levels by ~4-fold (P = .056) relative to saline and enhanced ADAMTS13/von Willebrand factor (VWF) cleavage efficiency based on LC-MS/MS evidence for the semitryptic VWF cleavage product (VWF1275-1286 ).

CONCLUSIONS

This study provides the first comprehensive map of trauma-induced changes to the plasma proteome, especially with respect to proteins driving the development of TIC.

Opposing roles of inter-α-trypsin inhibitor heavy chain 4 in recurrent pregnancy loss

Background

The mechanism behind an increased risk of recurrent pregnancy loss (RPL) remains largely unknown. In our previous study, we identified that inter-α-trypsin inhibitor heavy chain 4 (ITI-H4) is highly expressed at a modified molecular weight of 36 kDa in serum derived from RPL patients. Yet, the precise molecular mechanism and pathways by which the short form of ITI-H4 carries out its function remain obscure.

Methods

Human sera and peripheral blood mononucleated cells (PBMCs) were collected from patients and normal controls to compare the expression levels of ITI-H4 and plasma kallikrein (KLKB1). Flow cytometric assay was performed to measure inflammatory markers in sera and culture supernatants. Furthermore, to investigate the functions of the two isoforms of ITI-H4, we performed migration, invasion, and proliferation assays.

Findings

In the current study, we showed that ITI-H4 as a biomarker of RPL could be regulated by KLKB1 through the IL-6 signaling cascade, indicating a novel regulatory system for inflammation in RPL. In addition, our study indicates that the two isoforms of ITI-H4 possess opposing functions on immune response, trophoblast invasion, and monocytes migration or proliferation.

Interpretation

The ITI-H4 (∆N⁶⁸⁸) might be a crucial inflammatory factor which contributes to the pathogenesis of RPL. Moreover, it is expected that this study would give some insights into potential functional mechanisms underlying RPL.

Fund

This study was supported by the Ministry of Health & Welfare of the Republic of Korea (HI18C0378) through the Korea Health Industry Development Institute.

Drug-induced Glomerulonephritis: The Spectre of Biotherapeutic and Antisense Oligonucleotide Immune Activation in the Kidney

Prevalence of immune-mediated glomerulonephritis has increased in preclinical toxicity studies, with more frequent use of biotherapeutic agents (especially antigenic humanized molecules) and antisense oligonucleotide (ASO) therapies. Immune complex disease affects a small number of study monkeys, often correlates with antidrug antibody (ADA) titers, and occurs at a dose that favors immune complex formation or impedes clearance. While preclinical glomerulonephritis often fails to correlate with evidence of glomerular or vascular injury in human clinical trials and is not considered predictive, additional animal investigative immunohistochemical work may be performed to substantiate evidence for immune complex pathogenesis. While ADA is most commonly encountered as a predisposing factor with biotherapeutic agents, complement activation may occur without circulating complexes, and other mechanisms of non-ADA immune-mediated glomerulonephritis have been observed including nonendogenous immune aggregates and immunoregulatory pharmacology. Although glomerulonephritis associated with oligonucleotide therapies has been noted occasionally in preclinical studies and more rarely with human patients, pathophysiologic mechanisms involved appear to be different between species and preclinical cases are not considered predictive for humans. ADA is not involved in oligonucleotide-associated cases, and complement fixation plays a more important role in monkeys. Recent screening of ASOs for proinflammatory activity appears to have decreased glomerulonephritis incidence preclinically.

Voluntary exposure to a toxin: the genetic influence on ethanol consumption

Ethyl alcohol is a toxin that, when consumed at high levels, produces organ damage and death. One way to prevent or ameliorate this damage in humans is to reduce the exposure of organs to alcohol by reducing alcohol ingestion. Both the propensity to consume large volumes of alcohol and the susceptibility of human organs to alcohol-induced damage exhibit a strong genetic influence. We have developed an integrative genetic/genomic approach to identify transcriptional networks that predispose complex traits, including propensity for alcohol consumption and propensity for alcohol-induced organ damage. In our approach, the phenotype is assessed in a panel of recombinant inbred (RI) rat strains, and quantitative trait locus (QTL) analysis is performed. Transcriptome data from tissues/organs of naïve RI rat strains are used to identify transcriptional networks using Weighted Gene Coexpression Network Analysis (WGCNA). Correlation of the first principal component of transcriptional coexpression modules with the phenotype across the rat strains, and overlap of QTLs for the phenotype and the QTLs for the coexpression modules (module eigengene QTL) provide the criteria for identification of the functionally related groups of genes that contribute to the phenotype (candidate modules). While we previously identified a brain transcriptional module whose QTL overlapped with a QTL for levels of alcohol consumption in HXB/BXH RI rat strains and 12 selected rat lines, this module did not account for all of the genetic variation in alcohol consumption. Our search for QTL overlap and correlation of coexpression modules with phenotype can, however, be applied to any organ in which the transcriptome has been measured, and this represents a holistic approach in the search for genetic contributors to complex traits. Previous work has implicated liver/brain interactions, particularly involving inflammatory/immune processes, as influencing alcohol consumption levels. We have now analyzed the liver transcriptome of the HXB/BXH RI rat panel in relation to the behavioral trait of alcohol consumption. We used RNA-Seq and microarray data to construct liver transcriptional networks, and identified a liver candidate transcriptional coexpression module that explained 24% of the genetic variance in voluntary alcohol consumption. The transcripts in this module focus attention on liver secretory products that influence inflammatory and immune signaling pathways. We propose that these liver secretory products can interact with brain mechanisms that affect alcohol consumption, and targeting these pathways provides a potential approach to reducing high levels of alcohol intake and also protecting the integrity of the liver and other organs.

Identification of novel loci affecting circulating chromogranins and related peptides

Chromogranins are pro-hormone secretory proteins released from neuroendocrine cells, with effects on control of blood pressure. We conducted a genome-wide association study for plasma catestatin, the catecholamine release inhibitory peptide derived from chromogranin A (CHGA), and other CHGA- or chromogranin B (CHGB)-related peptides, in 545 US and 1252 Australian subjects. This identified loci on chromosomes 4q35 and 5q34 affecting catestatin concentration (P = 3.40 × 10-30 for rs4253311 and 1.85 × 10-19 for rs2731672, respectively). Genes in these regions include the proteolytic enzymes kallikrein (KLKB1) and Factor XII (F12). In chromaffin cells, CHGA and KLKB1 proteins co-localized in catecholamine storage granules. In vitro, kallikrein cleaved recombinant human CHGA to catestatin, verified by mass spectrometry. The peptide identified from this digestion (CHGA360-373) selectively inhibited nicotinic cholinergic stimulated catecholamine release from chromaffin cells. A proteolytic cascade involving kallikrein and Factor XII cleaves chromogranins to active compounds both in vivo and in vitro.

The relevance of kalikrein-kinin system via activation of B2 receptor in LPS-induced fever in rats

PURPOSE

This study evaluated the involvement of endogenous kallikrein-kinin system and the bradykinin (BK) B₁ and B₂ receptors on LPS- induced fever and the POA cells involved in this response.

MATERIAL AND METHODS

Male Wistar rats received either i.v. (1 mg/kg), i.c.v. (20 nmol) or i.h. (2 nmol) injections of icatibant (B₂ receptor antagonist) 30 or 60 min, respectively, before the stimuli. DALBK (B₁ receptor antagonist) was given either 15min before BK (i.c.v.) or 30 min before LPS (i.v.). Captopril (5 mg/kg, sc.,) was given 1 h prior LPS or BK. Concentrations of BK and total kininogenon CSF, plasma and tissue kallikrein were evaluated. Rectal temperatures (rT) were assessed by telethermometry. Ca⁺⁺ signaling in POA cells was performed in rat pup brain tissue microcultures.

RESULTS

Icatibant reduced LPS fever while, captopril exacerbated that response, an effect abolished by icatibant. Icatibant (i.h.) reduced fever to BK (i.h.) but not that induced by LPS (i.v.). BK increased intracellular calcium concentration in neurons and astrocytes. LPS increased levels of bradykinin, tissue kallikrein and total kininogen. BK (i.c.v.) increased rT and decreased tail skin temperature. Captopril potentiated BK-induced fever an effect abolished by icatibant. DALBK reduced the fever induced by BK. BK (i.c.v.) increased the CSF PGE₂concentration. Effect abolished by indomethacin (i.p.).

CONCLUSIONS

LPS activates endogenous kalikrein-kinin system leading to production of BK, which by acting on B₂-receptors of POA cells causes prostaglandin synthesis that in turn produces fever. Thus, a kinin B₂-receptor antagonist that enters into the brain could constitute a new and interesting strategy to treat fever.

Plasma Kallikrein Mediates Vascular Endothelial Growth Factor-Induced Retinal Dysfunction and Thickening

PURPOSE

Plasma kallikrein is a serine protease and circulating component of inflammation, which exerts clinically significant effects on vasogenic edema. This study examines the role of plasma kallikrein in VEGF-induced retinal edema.

METHODS

Intravitreal injections of VEGF and saline vehicle were performed in plasma prekallikrein-deficient (KLKB1-/-) and wild-type (WT) mice, and in both rats and mice receiving a selective plasma kallikrein inhibitor, VA999272. Retinal vascular permeability (RVP) and retinal thickness were measured by Evans blue permeation and optical coherence tomography, respectively. The retinal kallikrein kinin system was examined by Western blotting and immunohistochemistry. Retinal neovascularization was investigated in KLKB1-/- and WT mice subjected to oxygen-induced retinopathy.

RESULTS

Vascular endothelial growth factor-induced RVP and retinal thickening were reduced in KLKB1-/- mice by 68% and 47%, respectively, compared to VEGF responses in WT mice. Plasma kallikrein also contributes to TNFα-induced retinal thickening, which was reduced by 52% in KLKB1-/- mice. Systemic administration of VA999272 reduced VEGF-induced retinal thickening by 57% (P < 0.001) in mice and 53% (P < 0.001) in rats, compared to vehicle-treated controls. Intravitreal injection of VEGF in WT mice increased plasma prekallikrein in the retina, which was diffusely distributed throughout the inner and outer retinal layers. Avascular and neovascular areas induced by oxygen-induced retinopathy were similar in WT and KLKB1-/- mice.

CONCLUSIONS

Vascular endothelial growth factor increases extravasation of plasma kallikrein into the retina, and plasma kallikrein is required for the full effects of VEGF on RVP and retinal thickening in rodents. Systemic plasma kallikrein inhibition may provide a therapeutic opportunity to treat VEGF-induced retina edema.

C1-Inhibitor Decreases the Release of Vasculitis-Like Chemotactic Endothelial Microvesicles

The kinin system is activated during vasculitis and may contribute to chronic inflammation. C1-inhibitor is the main inhibitor of the kinin system. In this study, we investigated the presence of the kinin B1 receptor on endothelial microvesicles and its contribution to the inflammatory process. Compared with controls (n=15), patients with acute vasculitis (n=12) had markedly higher levels of circulating endothelial microvesicles, identified by flow cytometry analysis, and significantly more microvesicles that were positive for the kinin B1 receptor (P<0.001). Compared with microvesicles from wild-type cells, B1 receptor-positive microvesicles derived from transfected human embryonic kidney cells induced a significant neutrophil chemotactic effect, and a B1 receptor antagonist blocked this effect. Likewise, patient plasma induced neutrophil chemotaxis, an effect decreased by reduction of microvesicle levels and by blocking the B1 receptor. We used a perfusion system to study the effect of patient plasma (n=6) and control plasma (n=6) on the release of microvesicles from glomerular endothelial cells. Patient samples induced the release of significantly more B1 receptor-positive endothelial microvesicles than control samples, an effect abrogated by reduction of the microvesicles in the perfused samples. Perfusion of C1-inhibitor-depleted plasma over glomerular endothelial cells promoted excessive release of B1 receptor-positive endothelial microvesicles compared with normal plasma, an effect significantly decreased by addition of C1-inhibitor or B1 receptor-antagonist. Thus, B1 receptor-positive endothelial microvesicles may contribute to chronic inflammation by inducing neutrophil chemotaxis, and the reduction of these microvesicles by C1-inhibitor should be explored as a potential treatment for neutrophil-induced inflammation.

Depletion of coagulation factor XII ameliorates brain pathology and cognitive impairment in Alzheimer disease mice

Vascular abnormalities and inflammation are found in many Alzheimer disease (AD) patients, but whether these changes play a causative role in AD is not clear. The factor XII (FXII) -initiated contact system can trigger both vascular pathology and inflammation and is activated in AD patients and AD mice. We have investigated the role of the contact system in AD pathogenesis. Cleavage of high-molecular-weight kininogen (HK), a marker for activation of the inflammatory arm of the contact system, is increased in a mouse model of AD, and this cleavage is temporally correlated with the onset of brain inflammation. Depletion of FXII in AD mice inhibited HK cleavage in plasma and reduced neuroinflammation, fibrinogen deposition, and neurodegeneration in the brain. Moreover, FXII-depleted AD mice showed better cognitive function than untreated AD mice. These results indicate that FXII-mediated contact system activation contributes to AD pathogenesis, and therefore this system may offer novel targets for AD treatment.

Factor XI deficiency enhances the pulmonary allergic response to house dust mite in mice independent of factor XII

Asthma is associated with activation of coagulation in the airways. The coagulation system can be initiated via the extrinsic tissue factor-dependent pathway or via the intrinsic pathway, in which the central player factor XI (FXI) can be either activated via active factor XII (FXIIa) or via thrombin. We aimed to determine the role of the intrinsic coagulation system and its possible route of activation in allergic lung inflammation induced by the clinically relevant human allergen house dust mite (HDM). Wild-type (WT), FXI knockout (KO), and FXII KO mice were subjected to repeated exposure to HDM via the airways, and inflammatory responses were compared. FXI KO mice showed increased influx of eosinophils into lung tissue, accompanied by elevated local levels of the main eosinophil chemoattractant eotaxin. Although gross lung pathology and airway mucus production did not differ between groups, FXI KO mice displayed an impaired endothelial/epithelial barrier function, as reflected by elevated levels of total protein and IgM in bronchoalveolar lavage fluid. FXI KO mice had a stronger systemic IgE response with an almost completely absent HDM-specific IgG₁ response. The phenotype of FXII KO mice was, except for a higher HDM-specific IgG₁ response, similar to that of WT mice. In conclusion, FXI attenuates part of the allergic response to repeated administration of HDM in the airways by a mechanism that is independent of activation via FXII.

Proteinases, Their Extracellular Targets, and Inflammatory Signaling

Given that over 2% of the human genome codes for proteolytic enzymes and their inhibitors, it is not surprising that proteinases serve many physiologic-pathophysiological roles. In this context, we provide an overview of proteolytic mechanisms regulating inflammation, with a focus on cell signaling stimulated by the generation of inflammatory peptides; activation of the proteinase-activated receptor (PAR) family of G protein-coupled receptors (GPCR), with a mechanism in common with adhesion-triggered GPCRs (ADGRs); and by proteolytic ion channel regulation. These mechanisms are considered in the much wider context that proteolytic mechanisms serve, including the processing of growth factors and their receptors, the regulation of matrix-integrin signaling, and the generation and release of membrane-tethered receptor ligands. These signaling mechanisms are relevant for inflammatory, neurodegenerative, and cardiovascular diseases as well as for cancer. We propose that the inflammation-triggering proteinases and their proteolytically generated substrates represent attractive therapeutic targets and we discuss appropriate targeting strategies.

Pharmacology of Bradykinin-Evoked Coughing in Guinea Pigs

Bradykinin has been implicated as a mediator of the acute pathophysiological and inflammatory consequences of respiratory tract infections and in exacerbations of chronic diseases such as asthma. Bradykinin may also be a trigger for the coughing associated with these and other conditions. We have thus set out to evaluate the pharmacology of bradykinin-evoked coughing in guinea pigs. When inhaled, bradykinin induced paroxysmal coughing that was abolished by the bradykinin B2 receptor antagonist HOE 140. These cough responses rapidly desensitized, consistent with reports of B2 receptor desensitization. Bradykinin-evoked cough was potentiated by inhibition of both neutral endopeptidase and angiotensin-converting enzyme (with thiorphan and captopril, respectively), but was largely unaffected by muscarinic or thromboxane receptor blockade (atropine and ICI 192605), cyclooxygenase, or nitric oxide synthase inhibition (meclofenamic acid and N(G)-nitro-L-arginine). Calcium influx studies in bronchopulmonary vagal afferent neurons dissociated from vagal sensory ganglia indicated that the tachykinin-containing C-fibers arising from the jugular ganglia mediate bradykinin-evoked coughing. Also implicating the jugular C-fibers was the observation that simultaneous blockade of neurokinin2 (NK2; SR48968) and NK3 (SR142801 or SB223412) receptors nearly abolished the bradykinin-evoked cough responses. The data suggest that bradykinin induces coughing in guinea pigs by activating B2 receptors on bronchopulmonary C-fibers. We speculate that therapeutics targeting the actions of bradykinin may prove useful in the treatment of cough.

Inflammatory Changes and Coagulopathy in Multiply Injured Patients

Severe tissue trauma leads to an early activation of several danger recognition systems, including the complement and the coagulation system, often resulting in an overwhelming almost synchronic pro- and anti-inflammatory response of the host. Although the immune response is associated with beneficial effects at the site of injury including the elimination of exogenous and endogenous danger molecules as well as the initiation of regenerative processes, an exaggerated systemic inflammatory response significantly contributes to posttraumatic complications such as multiple organ failure (MOF) and early death. Besides pre-existing physical conditions, age, gender, and underlying comorbidities, surgical and anesthesiological management after injury is decisive for outcome. Improvements in surgical intensive care have increased number of patients who survive the initial phase after trauma. However, instead of progressing to normal recovery, patients often pass into persistent inflammation, immunosuppression, and catabolism syndrome (PICS). The characterization and management of PICS will require new strategies for direct monitoring and therapeutic intervention into the patient’s immune function. In this chapter, we describe various factors involved in the inflammatory changes after trauma and aim to understand how these factors interact to progress to systemic inflammation, MOF, and PICS.

Deficiency of plasminogen activator inhibitor 2 in plasma of patients with hereditary angioedema with normal C1 inhibitor levels

BACKGROUND

Hereditary angioedema with normal C1 inhibitor levels (HAE-N) is associated with a Factor XII mutation in 30% of subjects; however, the role of this mutation in the pathogenesis of angioedema is unclear.

OBJECTIVE

We sought evidence of abnormalities in the pathways of bradykinin formation and bradykinin degradation in the plasma of patients with HAE-N both with and without the mutation.

METHODS

Bradykinin was added to plasma, and its rate of degradation was measured by using ELISA. Plasma autoactivation was assessed by using a chromogenic assay of kallikrein formation. Plasminogen activator inhibitors (PAIs) 1 and 2 were also measured by means of ELISA.

RESULTS

PAI-1 levels varied from 0.1 to 4.5 ng/mL (mean, 2.4 ng/mL) in 23 control subjects, from 0.0 to 2 ng/mL (mean, 0.54 ng/mL) in patients with HAE-N with a Factor XII mutation (12 samples), and from 0.0 to 3.7 ng/mL (mean, 1.03 ng/mL) in patients with HAE-N without a Factor XII mutation (11 samples). PAI-2 levels varied from 25 to 87 ng/mL (mean, 53.8 ng/mL) in control subjects and were 0 to 25 ng/mL (mean, 4.3 ng/mL) in patients with HAE-N with or without the Factor XII mutation. Autoactivation at a 1:2 dilution was abnormally high in 8 of 17 patients with HAE-N (4 in each subcategory) and could be corrected by supplemental C1 inhibitor in 4 of them. Bradykinin degradation was markedly abnormal in 1 of 23 patients with HAE-N and normal in the remaining 22 patients.

CONCLUSIONS

Bradykinin degradation was normal in all but 1 of 23 patients with HAE-N studied. By contrast, there was a marked abnormality in PAI-2 levels in patients with HAE-N that is not seen in patients with C1 inhibitor deficiency. PAI-1 levels varied considerably, but a statistically significant difference was not seen. A link between excessive fibrinolysis and bradykinin generation that is estrogen dependent is suggested.

Kinin release from human kininogen by 10 aspartic proteases produced by pathogenic yeast Candida albicans

Background

Candida albicans yeast produces 10 distinct secreted aspartic proteases (Saps), which are some of the most important virulence factors of this pathogenic fungus. One of the suggested roles of Saps is their deregulating effect on various proteolytic cascades that constitute the major homeostatic systems in human hosts, including blood coagulation, fibrinolysis, and kallikrein-kinin systems. This study compared the characteristics of the action of all 10 Saps on human kininogens, which results in generating proinflammatory bradykinin-related peptides (kinins).

Results

Recombinant forms of Saps, heterologously overexpressed in Pichia pastoris were applied. Except for Sap7 and Sap10, all Saps effectively cleaved the kininogens, with the highest hydrolytic activity toward the low-molecular-mass form (LK). Sap1–6 and 8 produced a biologically active kinin—Met-Lys-bradykinin—and Sap3 was exceptional in terms of the kinin-releasing yield (>60% LK at pH 5.0 after 24 hours). Des-Arg¹-bradykinin was released from LK by Sap9 at a comparably high yield, but this peptide was assumed to be biologically inactive because it was unable to interact with cellular B2-type kinin receptors. However, the collaborative actions of Sap9 and Sap1, −2, −4–6, and −8 on LK rerouted kininogen cleavage toward the high-yield release of the biologically active Met-Lys-bradykinin.

Conclusions

Our present results, together with the available data on the expression of individual SAP genes in candidal infection models, suggest a biological potential of Saps to produce kinins at the infection foci. The kinin release during candidiasis can involve predominant and complementary contributions of two different Sap3- and Sap9-dependent mechanisms.

Recent insights into the role of the contact pathway in thrombo-inflammatory disorders

The contact pathway of coagulation consists of the proteins factor XI, factor XII, prekallikrein, and high-molecular-weight kininogen. Activation of the contact system leads to procoagulant and proinflammatory reactions. The contact system is essential for surface-initiated coagulation, as exemplified by aPTT, but there is probably no role for the contact system in initiating physiologic in vivo coagulation. However, over the last few years, there has been renewed interest, especially because of experimental evidence suggesting that the contact system contributes to thrombosis. Knockout mice deficient in one of the contact proteins were protected against artificially induced thrombosis. Furthermore, inhibiting agents such as monoclonal antibodies, antisense oligonucleotides, and small molecules were found to prevent thrombosis in rodents and primates in both venous and arterial vascular beds. Although it remains to be established whether targeting the contact system will be effective in humans and which of the contact factors is the best target for anticoagulation, it would constitute a promising approach for future effective and safe antithrombotic therapy.

Recent insights into the role of the contact pathway in thrombo-inflammatory disorders

The contact pathway of coagulation consists of the proteins factor XI, factor XII, prekallikrein, and high-molecular-weight kininogen. Activation of the contact system leads to procoagulant and proinflammatory reactions. The contact system is essential for surface-initiated coagulation, as exemplified by aPTT, but there is probably no role for the contact system in initiating physiologic in vivo coagulation. However, over the last few years, there has been renewed interest, especially because of experimental evidence suggesting that the contact system contributes to thrombosis. Knockout mice deficient in one of the contact proteins were protected against artificially induced thrombosis. Furthermore, inhibiting agents such as monoclonal antibodies, antisense oligonucleotides, and small molecules were found to prevent thrombosis in rodents and primates in both venous and arterial vascular beds. Although it remains to be established whether targeting the contact system will be effective in humans and which of the contact factors is the best target for anticoagulation, it would constitute a promising approach for future effective and safe antithrombotic therapy.

Single-chain factor XII exhibits activity when complexed to polyphosphate

BACKGROUND

The mechanism underpinning factor XII autoactivation was originally characterized with non-physiological surfaces, such as dextran sulfate (DS), ellagic acid, and kaolin. Several 'natural' anionic activating surfaces, such as platelet polyphosphate (polyP), have now been identified.

OBJECTIVE

To analyze the autoactivation of FXII by polyP of a similar length to that found in platelets (polyP70 ).

METHODS AND RESULTS

PolyP70 showed similar efficacy to DS in stimulating autoactivation of FXII, as detected with amidolytic substrate. Western blotting revealed different forms of FXII with the two activating surfaces: two-chain αFXIIa was formed with DS, whereas single-chain FXII (scFXII; 80 kDa) was formed with polyP70 . Dissociation of scFXII from polyP70 abrogated amidolytic activity, suggesting reversible exposure of the active site. Activity of scFXII-polyP70 was enhanced by Zn(2+) and was sensitive to NaCl concentration. A bell-shaped concentration response to polyP70 was evident, as is typical of surface-mediated reactions. Reaction of scFXII-polyP70 with various concentrations of S2302 generated a sigmoidal curve, in contrast to a hyperbolic curve for αFXIIa, from which a Hill coefficient of 3.67 was derived, indicative of positive cooperative binding. scFXII-polyP70 was more sensitive to inhibition by H-d-Pro-Phe-Arg-chloromethylketone and corn trypsin inhibitor than αFXIIa, but inhibition profiles for C1-inhibitor were similar. Active scFXII-polyP70 was also able to cleave its physiological targets FXI and prekallikrein to their active forms.

CONCLUSIONS

Autoactivation of FXII by polyP, of the size found in platelets, proceeds via an active single-chain intermediate. scFXII-polyP70 shows activity towards physiological substrates, and may represent the primary event in initiating contact activation in vivo.

Formation, Clearance, Deposition, Pathogenicity, and Identification of Biopharmaceutical-related Immune Complexes

Vascular inflammation, infusion reactions, glomerulopathies, and other potentially adverse effects may be observed in laboratory animals, including monkeys, on toxicity studies of therapeutic monoclonal antibodies and recombinant human protein drugs. Histopathologic and immunohistochemical (IHC) evaluation suggests these effects may be mediated by deposition of immune complexes (ICs) containing the drug, endogenous immunoglobulin, and/or complement components in the affected tissues. ICs may be observed in glomerulus, blood vessels, synovium, lung, liver, skin, eye, choroid plexus, or other tissues or bound to neutrophils, monocytes/macrophages, or platelets. IC deposition may activate complement, kinin, and/or coagulation/fibrinolytic pathways and result in a systemic proinflammatory response. IC clearance is biphasic in humans and monkeys (first from plasma to liver and/or spleen, second from liver or spleen). IC deposition/clearance is affected by IC composition, immunomodulation, and/or complement activation. Case studies are presented from toxicity study monkeys or rats and indicate IHC-IC deposition patterns similar to those predicted by experimental studies of IC-mediated reactions to heterologous protein administration to monkeys and other species. The IHC-staining patterns are consistent with findings associated with generalized and localized IC-associated pathology in humans. However, manifestations of immunogenicity in preclinical species are generally not considered predictive to humans.

Allergic responses and aryl hydrocarbon receptor novel pathway of mast cell activation

The activation of the transcription factor aryl hydrocarbon receptor (AhR) is modulated by a wide variety of xenobiotics and ligands deriving from products of metabolism. The study of the contribution of AhR to allergic diseases has gained much interest in recent years. Here we discuss the role that environmental factors and metabolic products, particularly acting on AhR-expressing mast cells (MCs), could have in the development of local allergic/atopic response. Thus, this review will cover: a brief overview of the AhR mechanism of action in the immune system; a description of different AhR ligands and their effects to IgE-mediated MC activation in the allergic response, with particular attention to the role of IL-17; a discussion about the potential involvement of AhR in immune tolerance; and a conclusion on human diseases in which direct AhR activation of MC might have a major impact.

Bradykinin analysis revived--a validated method for determination of its stable metabolite in whole blood by LC-MS/MS

Investigation of bradykinin involvement in diseases like hereditary angioedema has been greatly hindered by its rapid metabolism and generation, induced by sampling. Because of this, reliable measurements of bradykinin have yet to be introduced in clinical practice. Prevention of bradykinin generation during sampling, and determination of the in vivo generated stable metabolite BK1-5, should allow a reliable indirect measure of bradykinin involvement. An LC-MS/MS method has been developed to determine BK1-5 in human whole blood. The method inactivates metabolizing enzymes with ethanol, followed by solid phase extraction (C18), separation (C8) and detection (linear ion trap) through the transitions 287.25→320.20 (y3, quantifier), 408.20 (b4, qualifier) for BK1-5, and 292.17→330.20 (y3, quantifier), 408.20 (b4, qualifier) for the heavy labelled internal standard. The method showed acceptable linearity (n=3, r(2)=0.994), intra-run precision (CV<15%), inter-run precision (CV<15%) and accuracy (CV<14%), without matrix effects. LLOQ was 265.5 pmol L(-1) and LOD was 35.4 pmol L(-1). The method was used on blood samples from patients with hereditary angioedema, where BK1-5 was measured during attacks and in remision. The samples showed elevated concentrations (up to 1.7 nmol L(-1) during attacks and 265.5 pmol L(-1) in remission) compared to healthy volunteers (<35.4 pmol L(-1)). This is the first time BK1-5 in hereditary angioedema patients has been measured.

The kallikrein-kinin system in diabetic retinopathy

Diabetic retinopathy (DR) is a major microvascular complication associated with type 1 and type 2 diabetes mellitus, which can lead to visual impairment and blindness. Current treatment strategies for DR are mostly limited to laser therapies, steroids, and anti-VEGF agents, which are often associated with unwanted side effects leading to further complications. Recent evidence suggests that kinins play a primary role in the development of DR through enhanced vascular permeability, leukocytes infiltration, and other inflammatory mechanisms. These deleterious effects are mediated by kinin B1 and B2 receptors, which are expressed in diabetic human and rodent retina. Importantly, kinin B1 receptor is virtually absent in sane tissue, yet it is induced and upregulated in diabetic retina. These peptides belong to the kallikrein-kinin system (KKS), which contains two separate and independent pathways of regulated serine proteases, namely plasma kallikrein (PK) and tissue kallikrein (TK) that are involved in the biosynthesis of bradykinin (BK) and kallidin (Lys-BK), respectively. Hence, ocular inhibition of kallikreins or antagonism of kinin receptors offers new therapeutic avenues in the treatment and management of DR. Herein, we present an overview of the principal features and known inflammatory mechanisms associated with DR along with the current therapeutic approaches and put special emphasis on the KKS as a new and promising therapeutic target due to its link with key pathways directly associated with the development of DR.

Soluble gC1qR is an autocrine signal that induces B1R expression on endothelial cells

Bradykinin (BK) is one of the most potent vasodilator agonists known and belongs to the kinin family of proinflammatory peptides. BK induces its activity via two G protein-coupled receptors: BK receptor 1 (B1R) and BK receptor 2. Although BK receptor 2 is constitutively expressed on endothelial cells (ECs), B1R is induced by IL-1β. The C1q receptor, receptor for the globular heads of C1q (gC1qR), which plays a role in BK generation, is expressed on activated ECs and is also secreted as soluble gC1qR (sgC1qR). Because sgC1qR can bind to ECs, we hypothesized that it may also serve as an autocrine/paracrine signal for the induction of B1R expression. In this study, we show that gC1qR binds to ECs via a highly conserved domain consisting of residues 174-180, as assessed by solid-phase binding assay and deconvolution fluorescence microscopy. Incubation of ECs (24 h, 37 °C) with sgC1qR resulted in enhancement of B1R expression, whereas incubation with gC1qR lacking aa 174-180 and 154-162 had a diminished effect. Binding of sgC1qR to ECs was through surface-bound fibrinogen and was inhibited by anti-fibrinogen. In summary, our data suggest that, at sites of inflammation, sgC1qR can enhance vascular permeability by upregulation of B1R expression through de novo synthesis, as well as rapid translocation of preformed B1R.

Plasma kallikrein-kinin system and diabetic retinopathy

Diabetic retinopathy (DR) occurs, to some extent, in most people with at least 20 years' duration of diabetes mellitus. The progression of DR to its sight-threatening stages is usually associated with the worsening of underlying retinal vascular dysfunction and disease. The plasma kallikrein-kinin system (KKS) is activated during vascular injury, where it mediates important functions in innate inflammation, blood flow, and coagulation. Recent findings from human vitreous proteomics and experimental studies on diabetic animal models have implicated the KKS in contributing to DR. Vitreous fluid from people with advanced stages of DR contains increased levels of plasma KKS components, including plasma kallikrein (PK), coagulation factor XII, and high-molecular-weight kininogen. Both bradykinin B1 and B2 receptor isoforms (B1R and B2R, respectively) are expressed in human retina, and retinal B1R levels are increased in diabetic rodents. The activation of the intraocular KKS induces retinal vascular permeability, vasodilation, and retinal thickening, and these responses are exacerbated in diabetic rats. Preclinical studies have shown that the administration of PK inhibitors and B1R antagonists to diabetic rats ameliorates retinal vascular hyperpermeability and inflammation. These findings suggest that components of plasma KKS are potential therapeutic targets for diabetic macular edema.

The influence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on hematological parameters during experimentally induced pleuritis in rats

Proper functioning of homeostatic mechanisms is characteristic for every healthy organism and enables adapting to environmental changes. These complicated systematic reactions can neutralize the harmful stress factors leading to various inflammatory reactions. The aim of this study was to determine dynamic changes in the inflammatory reaction after single 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) administration of 5 μg/kg body weight into rats with experimentally induced pleuritis. These changes were observed by monitoring the hematological blood parameters during inflammation. The obtained results proved that dioxins contribute to various changes in the character of the inflammatory response. TCDD administration before pleuritis initiation caused an increase of lymphocytes and significant decrease of the number of neutrophils during inflammation. The current study proved that administration of low TCDD dose (seven times lower than used in other studies) can cause thymus, spleen, or lymphatic gland atrophy. This finding indicates the toxic influence of small TCDD dose especially on the immune system.

Targeting the 'Janus face' of the B2-bradykinin receptor

INTRODUCTION

Kinins are main active mediators of the kallikrein-kinin system (KKS) via bradykinin type 1 inducible (B1R) and type 2 constitutive (B2R) receptors. B2R mediates most physiological bradykinin (BK) responses, including vasodilation, natriuresis, NO, prostaglandins release.

AREAS COVERED

The article summarizes knowledge on kinins, B2R signaling and biological functions; highlights crosstalks between B2R and renin-angiotensin system (RAS). The double role (Janus face) in physiopathology, namely the beneficial protection of the endothelium, which forms the basis for the therapeutical utilization of B2 receptor agonists, on the one side, and the involvement of B2R in inflammation or infection diseases and in pain mechanisms, which justifies the use of B2R antagonists, on the other side, is extensively analyzed.

EXPERT OPINION

For decades, the B2R has been unconsciously activated during angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) treatments. Whether direct B2R targeting with stable agonists could bring additional therapeutic benefit to RAS inhibition should be investigated. Efficacy, established in experimental models, should be confirmed by translational studies in cardiovascular pathologies, glaucoma, Duchenne cardiopathy and during brain cancer therapy. The other face of B2R is targeted by antagonists already approved to treat hereditary angioedema. The use of antagonists could be extended to other angioedema and efficacy tested against acute pain and inflammatory diseases.

Kininogen 1 and insulin-like growth factor binding protein 6: candidate serum biomarkers of proliferative vitreoretinopathy

BACKGROUND

The aim was to validate whether kininogen 1 (KNG1) or insulin-like growth factor binding protein 6 (IGFBP-6) are serum biomarkers of proliferative vitreoretinopathy (PVR).

METHODS

Samples from vitreous and corresponding serum samples were collected from patients with PVR. The donor vitreous samples and serum samples from healthy volunteers and volunteers who had undergone vitrectomies for other conditions were used as controls. The samples were subsequently analysed using Western blotting (WB) and enzyme-linked immunosorbent assay.

RESULTS

The Western blotting outcomes indicated both IGFBP-6 and KNG1 could be specifically detected in the vitreous and serum samples of patients with PVR. The concentrations of KNG1 and IGFBP-6 were significantly higher in both vitreous and serum samples from patients with severe PVR than in the samples from patients with moderate PVR. The serum concentrations of KNG1 or IGFBP-6 had decreased by the post-vitrectomy examinations. The receiver operating characteristic (ROC) analyses when the concentrations of IGFBP-6 or KNG1 were greater than 181.4 pg/ml or 441.75 ng/ml, respectively, predicted severe PVR with both a sensitivity and specificity of over 70 per cent. When the concentrations of IGFBP-6 or KNG1 were greater than 98.5 pg/ml or 88.5 ng/ml, respectively, they predicted the PVR prognosis with both a sensitivity and specificity of 80 per cent.

CONCLUSIONS

KNG1 and IGFBP-6 may be candidate serum biomarkers of PVR.

Role of plasma kallikrein in diabetes and metabolism

Plasma kallikrein (PK) is a serine protease generated from plasma prekallikrein, an abundant circulating zymogen expressed by the Klkb1 gene. The physiological actions of PK have been primarily attributed to its production of bradykinin and activation of coagulation factor XII, which promotes inflammation and the intrinsic coagulation pathway. Recent genetic, molecular, and pharmacological studies of PK have provided further insight into its role in physiology and disease. Genetic analyses have revealed common Klkb1 variants that are association with blood metabolite levels, hypertension, and coagulation. Characterisation of animal models with Klkb1 deficiency and PK inhibition have demonstrated effects on inflammation, vascular function, blood pressure regulation, thrombosis, haemostasis, and metabolism. These reports have also identified a host of PK substrates and interactions, which suggest an expanded physiological role for this protease beyond the bradykinin system and coagulation. The review summarises the mechanisms that contribute to PK activation and its emerging role in diabetes and metabolism.

Prekallikrein deficiency

Nurses often encounter abnormal laboratory assays that require them to investigate further to ensure that appropriate patient care is provided. A prolonged activated partial thromboplastin time (PTT) with a normal prothrombin time (PT) assay demand further examination, to rule out laboratory error or bleeding disorders. Prekallikrein deficiency is a rare coagulation deficiency that presents itself with a prolonged PTT and a normal PT. It was first identified in 4 of the 11 Fletcher family children in 1965, coincidentally when one of the Fletcher children was undergoing a workup for an adenoidectomy. Both the Fletcher parents had normal coagulation laboratory assays with no history of bleeding tendencies. The term Fletcher factor deficiency was used until Fletcher factor was later identified as plasma prekallikrein. A prekallikrein deficiency is inherited as an autosomal recessive trait. The purpose of this article is to provide a basic review for nurses on hemostasis, identify the 6 causes of a prolonged PTT with a normal or slightly prolonged PT, and to present 2 recently diagnosed adult cases, not previously reported in the medical literature.

Pathophysiology of genetic deficiency in tissue kallikrein activity in mouse and man

Study of mice rendered deficient in tissue kallikrein (TK) by gene inactivation and human subjects partially deficient in TK activity as consequence of an active site mutation has allowed recognising the physiological role of TK and its peptide products kinins in arterial function and in vasodilatation, in both species. TK appears as the major kinin forming enzyme in arteries, heart and kidney. Non-kinin mediated actions of TK may occur in epithelial cells in the renal tubule. In basal condition, TK deficiency induces mild defective phenotypes in the cardiovascular system and the kidney. However, in pathological situations where TK synthesis is typically increased and kinins are produced, TK deficiency has major, deleterious consequences. This has been well documented experimentally for cardiac ischaemia, diabetes renal disease, peripheral ischaemia and aldosterone-salt induced hypertension. These conditions are all aggravated by TK deficiency. The beneficial effect of ACE/kininase II inhibitors or angiotensin II AT1 receptor antagonists in cardiac ischaemia is abolished in TK-deficient mice, suggesting a prominent role for TK and kinins in the cardioprotective action of these drugs. Based on findings made in TK-deficient mice and additional evidence obtained by pharmacological or genetic inactivation of kinin receptors, development of novel therapeutic approaches relying on kinin receptor agonism may be warranted.