Synthesis of kininogen and degradation of bradykinin by PC12 cells

Reduced hepatic bradykinin degradation accounts for cold-induced BAT thermogenesis and WAT browning in male mice

An important role for liver in the regulation of adipose tissue thermogenesis upon cold exposure has been suggested; however, the underlying mechanisms remain incompletely defined. Here, we identify elevated serum bradykinin levels in response to acute cold exposure in male mice. A bolus of anti-bradykinin antibodies reduces body temperature during acute cold exposure, whereas bradykinin has the opposite effect. We demonstrate that bradykinin induces brown adipose tissue thermogenesis and white adipose tissue browning, and bradykinin increases uncoupling protein 1 (UCP1) expression in adipose tissue. The bradykinin B2 receptor (B2R), adrenergic signaling and nitric oxide signaling are involved in regulating bradykinin-increased UCP1 expression. Moreover, acute cold exposure inhibits hepatic prolyl endopeptidase (PREP) activity, causing reduced liver bradykinin degradation and increased serum bradykinin levels. Finally, by blocking the breakdown of bradykinin, angiotensin-converting enzyme inhibitors (ACEIs) increase serum bradykinin levels and induce brown adipose tissue thermogenesis and white adipose tissue browning via B2R. Collectively, our data provide new insights into the mechanisms underlying organ crosstalk in whole-body physiology control during cold exposure and also suggest bradykinin as a possible anti-obesity target.

The Bradykinin System Contributes to the Regulation of Prostaglandin-Endoperoxide Synthase 2 Expression in Human Amnion Fibroblasts: Implications for Term and Preterm Birth

BACKGROUND

Bradykinin (BK) and its biologically active metabolite des-Arg9 bradykinin (DABK) play a pivotal role in inflammation. Since chorioamnionitis is the leading cause of preterm birth and prostaglandin E2 (PGE2) derived from the amnion is key to labor initiation, we investigated if bradykinin peptides are part of the regulatory network of PGE2 synthesis in human amnion at parturition.

METHODS

Human amnion tissue was obtained from term and preterm birth for the study of the changes of the bradykinin system at parturition. Cultured primary human amnion fibroblasts, the major source of PGE2, were used to study the effects of bradykinin peptides on PTGS2 expression and PGE2 production as well as the effects of infection mediators on bradykinin receptors.

RESULTS

Bradykinin peptides and their receptors BDKRB1 and BDKRB2 were present in human amnion, and their abundance increased in term and preterm labor. However, transcripts of the genes encoding the bradykinin precursor and its proteolytic cleavage enzymes were hardly detectable in human amnion despite the increased abundance of bradykinin peptides in term and preterm labor, suggesting that there is an alternative source of bradykinin peptides for human amnion and their actions are enhanced in human amnion at parturition. In-vitro studies in cultured human amnion fibroblasts showed that both BK and DABK increased the expression of prostaglandin-endoperoxide synthase 2 (PTGS2), the rate-limiting enzyme in prostaglandin synthesis, and subsequent PGE2 production. These effects of BK and DABK were mediated through BDKRB2 and BDKRB1 receptors, respectively, with subsequent activation of the p38 and ERK1/2 pathways. Moreover, lipopolysaccharide (LPS) and serum amyloid A1 (SAA1), the important mediators of infectious inflammation, induced the expression of both BDKRB1 and BDKRB2 through toll-like receptor 4 (TLR4). Induction of BDKRB1 and BDKRB2 expression by LPS and SAA1 enhanced BK- or DABK-induced PTGS2 expression and PGE2 production in human amnion fibroblasts.

CONCLUSIONS

This study demonstrated for the first time that the human amnion is a target tissue of bradykinin peptides and the bradykinin system may be part of the regulatory network of PTGS2 expression and PGE2 production in human amnion fibroblasts at both term and preterm birth, which may be enhanced by infection.

Neuropeptide-induced modulation of carcinogenesis in a metastatic breast cancer cell line (MDA-MB-231LUC+)

Background

Metastatic cancer to bone is well-known to produce extreme pain. It has been suggested that the magnitude of this perceived pain is associated with disease progression and poor prognosis. These data suggest a potential cross-talk between cancer cells and nociceptors that contribute not only to pain, but also to cancer aggressiveness although the underlying mechanisms are yet to be stablished.

Methods

The in vitro dose dependent effect of neuropeptides (NPs) (substance P [SP], calcitonin gene-related peptide and neurokinin A [NKA]) and/or its combination, on the migration and invasion of MDA-MB-231^LUC+ were assessed by wound healing and collagen-based cell invasion assays, respectively. The effect of NPs on the expression of its receptors (SP [NK1] and neurokinin A receptors [NK2], CALCRL and RAMP1) and kininogen (high-molecular-weight kininogen) release to the cell culture supernatant of MDA-MB-231^LUC+, were measured using western-blot analysis and an ELISA assay, respectively. Statistical significance was tested using one-way ANOVA, repeated measures ANOVA, or the paired t-test. Post-hoc testing was performed with correction for multiple comparisons as appropriate.

Results

Our data show that NPs strongly modify the chemokinetic capabilities of a cellular line commonly used as a model of metastatic cancer to bone (MDA-MB-231^LUC+) and increased the expression of their receptors (NK1R, NK2R, RAMP1, and CALCRL) on these cells. Finally, we demonstrate that NPs also trigger the acute release of HMWK (Bradykinin precursor) by MDA-MB-231^LUC+, a molecule with both tumorigenic and pro-nociceptive activity.

Conclusions

Based on these observations we conclude that NPs exposure modulates this breast cancer cellular line aggressiveness by increasing its ability to migrate and invade new tissues. Furthermore, these results also support the pro nociceptive and cancer promoter role of the peripheral nervous system, during the initial stages of the disease.

Kinin-B2 receptor expression and activity during differentiation of embryonic rat neurospheres

Neural progenitor cells were isolated from rat fetal telencephalon and proliferate as neurospheres in the presence of EGF, FGF-2, and heparin. In the absence of these growth factors, neurospheres differentiate into neurons, astrocytes, and oligodendrocytes. Using an embryonal carcinoma cell line as in vitro differentiation model, we have already demonstrated the presence of an autocrine loop system between kinin-B2 receptor activity and secretion of its ligand bradykinin (BK) as prerequisites for final neuronal differentiation (Martins et al., J Biol Chem 2005; 280: 19576-19586). The aim of this study was to verify the activity of the kallikrein-kinin system (KKS) during neural progenitor cell differentiation. Immunofluorescence studies and flow cytometry analysis revealed increases in glial fibrillary acidic protein and beta-3 tubulin expression and decrease in the number of nestin-positive cells along neurospheres differentiation, indicating the transition of neural progenitor cells to astrocytes and neurons. Kinin-B2 receptor expression and activity, secretion of BK into the medium, and presence of high-molecular weight kininogen suggest the participation of the KKS in neurosphere differentiation. Functional kinin-B2 receptors and BK secretion indicate an autocrine loop during neurosphere differentiation to neurons, astrocytes, and oligodendrocytes, reflecting events occurring during early brain development.

Alzheimer's disease skin fibroblasts selectively express a bradykinin signaling pathway mediatingtauprotein Ser phosphorylation

Increased Ser phosphorylation of tau microtubule-associated protein in the brain is an early feature of Alzheimer's disease (AD) that precedes progression of the disease to frank neuronal disruption. We demonstrate that bradykinin (BK) B2 receptor activation leads to selective Ser phosphorylation of tau in skin fibroblasts from persons who have or will develop AD due to Presenilin 1 mutations or Trisomy 21, but not in skin fibroblasts from normal individuals at any age. The increased signal transduction in AD fibroblasts that culminates in tau Ser phosphorylation reflects modification of the G protein-coupled BK B2 receptors themselves. Both the BK B2 receptor modification and BK-mediated tau Ser phosphorylation are dependent on activation of protein kinase C and can be detected in fibroblasts from persons with Trisomy 21 two decades before the characteristic onset of AD. This dysregulated signaling cascade in AD may thus be expressed throughout life as an aberrant pathway in peripheral tissues more accessible than brain for molecular analysis. The sites of greatest BK B2 receptor expression in brain overlap with those areas displaying the earliest pathology in the course of AD, suggesting that BK receptor pathway dysfunction may be a molecular signature yielding information about the pathogenesis of AD.

Bradykinin receptor modulation in cellular models of aging and Alzheimer's disease

Human fibroblast cell culture systems have been used to model both molecular events associated with the aging process and the biochemical anomalies found in the aging-associated neurodegenerative disorder Alzheimer's disease (AD). We demonstrate modulation of bradykinin (BK) B2 receptors that results in Intermediate (I, Kd 2.5-5 nM) and Low (L, Kd 44 nM) receptor affinity states in two cellular model systems that target aging and aging-associated disorders: the human lung fibroblast cell line WI-38 model for cellular aging and a skin fibroblast cell line from a patient with early onset familial Alzheimer's disease. In both cellular models the generation of I and L BK B2 receptors is extremely rapid, occurring within 1 min of activation of protein kinase C (PKC) by phorbol ester. Blocking phosphoprotein phosphatase activity further augments the cellular content of I and L receptors in the Alzheimer's skin fibroblast cell line. These two lines of evidence suggest that a phosphorylation cascade modifying the receptors is responsible for the I and L states. The I and L receptors remain biologically active and enhance cellular responsiveness to elevated levels of BK that are found in tissue injury, one of the major risk factors for development of Alzheimer's disease. The Alzheimer's disease skin fibroblast cell line presents a cellular environment highly enriched in the amyloid Abeta1-42 peptide that is the hallmark of Alzheimer's plaque lesions in the brain. This Abeta-rich environment may serve to foster the signal transduction mechanism that generates I and L BK B2 receptors.

Angiotensin I-converting enzyme inhibition increases cardiac catecholamine content and reduces monoamine oxidase activity via an angiotensin type 1 receptor-mediated mechanism

Antihypertensive and cardioprotective effects of angiotensin I-converting enzyme (ACE) inhibitors are well established and have usually been attributed to the inhibition of angiotensin II (ANG)-mediated effects at vascular or ventricular (angiotensin type 1) AT(1) receptors. One other important mechanism involves ANG-induced interactions with the sympathetic nervous system, which might include alterations of cardiac catecholamine concentrations during ACE inhibition due to a modulation of monoamine oxidase (MAO) activity. Tissue catecholamines were studied in spontaneously hypertensive rats that were long-term treated with captopril (50 or 0.5 mg/kg/day), enalapril (10 or 0.1 mg/kg/day), an AT(1) receptor antagonist (candesartan-cilexetil, 3 mg/kg/day), or a calcium antagonist (mibefradil, 18 mg/kg/day). The kinetic parameters of MAO were then determined in vitro in the presence of ANG, captopril, enalaprilat, or candesartan. Noradrenaline and adrenaline contents were doubled in the left ventricle by captopril, enalapril, or candesartan independently of hypotensive potency but not in liver or cortex. In parallel, cardiac MAO activity was reduced by all doses of captopril (49/29%), enalapril (52/24%), or candesartan (38%). Mibefradil, which does not interact with the renin-angiotensin system, did not alter cardiac catecholamines or MAO activity when an equipotent antihypertensive dose was applied. In vitro MAO activity was not influenced by ANG, enalaprilat, or captopril at concentrations of up to 1 mM. It is concluded that diminished AT(1) receptor stimulation decreases cardiac MAO activity, probably by regulating MAO expression, since ANG, ACE inhibitors, and AT(1) antagonists had no effect on MAO activity in vitro. This action contributes to an increase in cardiac catecholamine content that may improve cardiac sympathetic control during therapy.

Effects of intracoronary low-dose enalaprilat as an adjunct to primary percutaneous transluminal coronary angiography in acute myocardial infarction

Bradykinin accumulation is a potent cardioprotective mechanism underlying angiotensin-converting enzyme (ACE) inhibition in ischemia and/or reperfusion injury. There is, however, concern about treatment with ACE inhibitors in the very early phase of acute myocardial infarction (AMI) due to adverse systemic hemodynamic effects. We tested the hypothesis that cardiac bradykinin metabolism can be influenced by very low doses of intracoronary ACE inhibitors without harmful systemic effects in patients with AMI. Twenty-two patients with AMI in Killip classes II to III who underwent primary percutaneous transluminal coronary angiography (PTCA) were randomized to intracoronary enalaprilat (50 microg) or saline, given immediately after reopening of the infarct-related artery. Hemodynamics and electrocardiograms were monitored continuously and samples for determination of ACE activity, angiotensin II, bradykinin, kininogen, and cardiac marker proteins were collected from pulmonary arterial and central venous blood. Enalaprilat had no adverse effects on systemic hemodynamics, but rather stabilized arterial pressure and cardiac rhythm during reperfusion. Enalaprilat induced a 70% reduction of ACE activity and a significant increase of bradykinin in pulmonary arterial blood. Angiotensin II was not significantly affected by enalaprilat either in pulmonary arterial or in central venous blood. Myoglobin release was lower and the duration of reperfusion arrhythmias was significantly reduced in the enalaprilat group (p <0.05). Thus, in this pilot study, intracoronary enalaprilat infusion in the infarct-related artery is feasible in the setting of primary angioplasty and is safe and well tolerated. Effective cardiac ACE inhibition can be achieved by low-dose intracoronary enalaprilat, which primarily causes a potentiation of bradykinin.

Radioiodination of the stable metabolic fragment of bradykinin, RPPGF

Arg-Pro-Pro-Gly-Phe (RPPGF, BK[1-5]), is a stable metabolite of the peptide hormone bradykinin. Considering the short half-life of bradykinin (BK, approximately 15 secs), RPPGF has been used as a marker for BK's endogenous generation. A lack of a radioiodinated RPPGF has precluded the development of a radioimmunoassay for this peptide. The present study describes a two-step reaction that allows for the incorporation of 125I into the aromatic ring of the phenylalanine of RPPGF. This radioiodinated analog is recognized by an antibody to RPPGF, demonstrating its utility for the development of a radioimmunoassay for measurements of RPPGF, a stable metabolic product of bradykinin.

Pharmacology and cardiovascular implications of the kinin-kallikrein system

Kinins are peptide hormones that can exert a significant influence on the regulation of blood pressure and vascular tone due to their vasodilatatory, natriuretic and growth modulating activity. Their cardiovascular involvement in physiological and pathophysiological situations has been studied intensively since inhibitors for angiotensin I-converting enzyme and selective receptor antagonists have become available for pharmacologically potentiating or inhibiting kinin-mediated reactions. Molecular biological analysis and the establishment of genetically modified animal models have also allowed newer information to be acquired on this subject. In this review, the components and cardiovascularly relevant mechanisms of the kinin-kallikrein system shall be described. Organ-specific effects concerning the kidneys, the vascular system, the heart and nervous tissue shall also be illustrated. On this issue, the physiological functions and pathophysiological implications of the kinin-kallikrein system should be clearly distinguished from the many, mostly endothelium-mediated protective effects which occur during ACE inhibition due to the potentiation of kinin effects. Finally, a view shall also be cast upon newly discovered targets of action, which could be exploited for therapeutically altering the kinin-kallikrein system.