Association of Prenatal Acetaminophen Exposure Measured in Meconium With Adverse Birth Outcomes in a Canadian Birth Cohort.

Background: The small number of studies examining the association of prenatal acetaminophen with birth outcomes have all relied on maternal self-report. It remains unknown whether prenatal acetaminophen exposure measured in a biological specimen is associated with birth outcomes. Objectives: To investigate the association of acetaminophen measured in meconium with birthweight, gestational age, preterm birth, size for gestational age, gestational diabetes, preeclampsia, and high blood pressure. Methods: This birth cohort from Sherbrooke, QC, Canada, included 773 live births. Mothers with no thyroid disease enrolled at their first prenatal care visit or delivery. Acetaminophen was measured in meconium for 393 children at delivery. We tested associations of prenatal acetaminophen with birthweight, preterm birth, gestational age, small and large for gestational age, gestational diabetes, preeclampsia, and high blood pressure. We imputed missing data via multiple imputation and used inverse probability weighting to account for confounding and selection bias. Results: Acetaminophen was detected in 222 meconium samples (56.5%). Prenatal acetaminophen exposure was associated with decreased birthweight by 136 g (ß = -136; 95% CI [-229, -43]), 20% increased weekly hazard of delivery (hazard ratio = 1.20; 95% CI [1.00, 1.43]), and over 60% decreased odds of being born large for gestational age (odds ratio = 0.38; 95% CI [0.20, 0.75]). Prenatal acetaminophen was not associated with small for gestational age, preterm birth, or any pregnancy complications. Conclusion: Prenatal acetaminophen was associated with adverse birth outcomes. Although unobserved confounding and confounding by indication are possible, these results warrant further investigation into adverse perinatal effects of prenatal acetaminophen exposure.

Associations of Childhood and Perinatal Blood Metals with Children's Gut Microbiomes in a Canadian Gestation Cohort.

BACKGROUND: The gut microbiome is important in modulating health in childhood. Metal exposures affect multiple health outcomes, but their ability to modify bacterial communities in children is poorly understood. OBJECTIVES: We assessed the associations of childhood and perinatal blood metal levels with childhood gut microbiome diversity, structure, species, gene family-inferred species, and potential pathway alterations. METHODS: We assessed the gut microbiome using 16S rRNA gene amplicon sequencing and shotgun metagenomic sequencing in stools collected from 6- to 7-year-old children participating in the GESTation and Environment (GESTE) cohort study. We assessed blood metal concentrations [cadmium (Cd), manganese (Mn), mercury (Hg), lead (Pb), selenium (Se)] at two time points, namely, perinatal exposures at delivery (N=70) and childhood exposures at the 6- to 7-y follow-up (N=68). We used multiple covariate-adjusted statistical models to determine microbiome associations with continuous blood metal levels, including linear regression (Shannon and Pielou alpha diversity indexes), permutational multivariate analysis of variance (adonis; beta diversity distance matrices), and multivariable association model (MaAsLin2; phylum, family, species, gene family-inferred species, and pathways). RESULTS: Children's blood Mn and Se significantly associated with microbiome phylum [e.g., Verrucomicrobiota (coef=-0.305, q=0.031; coef=0.262, q=0.084, respectively)] and children's blood Mn significantly associated with family [e.g., Eggerthellaceae (coef=-0.228, q=0.052)]-level differences. Higher relative abundance of potential pathogens (e.g., Flavonifractor plautii), beneficial species (e.g., Bifidobacterium longum, Faecalibacterium prausnitzii), and both potentially pathogenic and beneficial species (e.g., Bacteriodes vulgatus, Eubacterium rectale) inferred from gene families were associated with higher childhood or perinatal blood Cd, Hg, and Pb (q<0.1). We found significant negative associations between childhood blood Pb and acetylene degradation pathway abundance (q<0.1). Finally, neither perinatal nor childhood metal concentrations were associated with children's gut microbial inter- and intrasubject diversity. DISCUSSION: Our findings suggest both long- and short-term associations between metal exposure and the childhood gut microbiome, with stronger associations observed with more recent exposure. Future epidemiologic analyses may elucidate whether the observed changes in the microbiome relate to children's health. https://doi.org/10.1289/EHP9674.

Health promotion innovations scale up: combining insights from framing and actor-network to foster reflexivity.

There are numerous hurdles down the road for successfully scaling up health promotion innovations into formal programmes. The challenges of the scaling-up process have mainly been conceived in terms of available resources and technical or management problems. However, aiming for greater impact and sustainability involves addressing new contexts and often adding actors whose perspectives may challenge established orientations. The social dimension of the scaling-up process is thus critical. Building on existing conceptualizations of interventions as dynamic networks and of evolving framing of health issues, this paper elaborates a social view of scaling up that accounts for the transformations of innovations, using framing analysis and the notion of 'expanding scaling-up networks'. First, we discuss interventions as dynamic networks. Second, we conceptualize scaling-up processes as networks in expansion within which social learning and change occur. Third, we propose combining a 'representational approach' to frame analysis and an 'interactional approach' that illustrates framing processes related to the micro-practices of leading public health actors within expanding networks. Using an example concerning equity in early childhood development, we show that this latter approach allows documenting how frames evolve in the process. Considering the process in continuity with existing conceptualizations of interventions as actor-networks and transformation of meanings enriches our conceptualization of scaling up, improves our capacity to anticipate its outcomes, and promotes reflexivity about health promotion goals and means.

[Initiating an antipsychotic drug treatment for schizophrenia: the situation in Quebec, Canada, from 1998 to 2006]. / Amorcer un traitement antipsychotique en schizophrénie : la situation au Québec de 1998 à 2006.

Objectives To describe factors associated with the following characteristics of the first prescription of an antipsychotic drug treatment (ADT): 1) prescribing physician type (psychiatrist vs. general practitioner); 2) second-generation vs. first-generation antipsychotic drug; 3) in conjunction with at least one additional antipsychotic drug (multitherapy); 4) never renewed by the patient.Methods This is a pharmacoepidemiologic study using administrative data from the Régie de l'assurance maladie du Québec (RAMQ), the public healthcare insurer in Quebec, Canada. Available data sample was exhaustive for adults with a diagnosis of schizophrenia who received an ADT under RAMQ drug coverage from 1998 to 2006. We report multiple logistic regression results.Results Among 16,225 patients who met inclusion criteria 46.2% were women and 70% were beneficiaries of governmental financial assistance. Patients who had their ADT prescribed by psychiatrists tended to be younger and were more burdened by their mental illness. Multitherapy was associated with hospitalization with a psychotic disorder as main diagnosis, lower socioeconomic status, and age between 35 and 64. Second-generation antipsychotic use became progressively more prominent during the period under study. Antipsychotic non renewal was correlated with substance use disorders and was less likely to happen following hospitalization with a psychiatric main diagnosis. Conclusions Although this study is subject to the intrinsic limitations of secondary analysis of administrative data, the database available for study was exhaustive within the Quebec healthcare system and included data from both general practice and specialized care, which allowed us to draw a relevant picture of how ADT were initiated for schizophrenia in Quebec, Canada, from 1998 to 2006. This timeframe is especially relevant since the 1990s were marked by the introduction of second-generation antipsychotics in Canada.

Apolipoprotein E isoforms disrupt long-chain fatty acid distribution in the plasma, the liver and the adipose tissue of mice.

Evidences suggest that omega-3 fatty acid (n-3 PUFA) metabolism is imbalanced in apolipoprotein E epsilon 4 isoform carriers (APOE4). This study aimed to investigate APOE genotype-dependant modulation of FA profiles, protein and enzyme important to fatty acid (FA) metabolism in the adipose tissue, the liver and the plasma using human APOE-targeted replacement mouse-model (N=37). FA transport (FATP) and binding (FABP) protein levels in tissues and concentrations of liver carnitine palmitoyltransferase 1 (CPT1) were performed. N-3 PUFA concentration was >45% lower in the adipose tissue and liver of APOE4 mice compared to APOE3 mice. In APOE4 mice, there were higher levels of FATP and FABP in the liver and higher FATP in the adipose tissue compared to APOE2 mice. There was a trend towards higher CPT1 concentrations in APOE4 mice compared to APOE3 mice. Therefore, since APOE-isoform differences were not always in line with the unbalanced n-3 PUFA profiles in organs, other proteins may be involved in maintaining n-3 PUFA homeostasis in mice with different APOE-isoforms.

Stimulating innovative research in health promotion.

The Global Working Group on Health Promotion Research (GWG HPR) of the International Union for Health Promotion and Education (IUHPE) presents a collection of four articles illustrating innovative avenues for health promotion research. This commentary synthesizes the contributions of these articles while attempting to define the contours of research in health promotion. We propose that innovation in research involves the adoption of a reflexive approach wherein consideration of context plays different roles. The reflexive process consists of questioning what is taken for granted in the conceptualization and operationalization of research. It involves linking research findings and its theoretical foundations to characteristics and goals of the field and observed realities, while orienting reflection on specific objects. The reflexive nature of the research activity is of paramount importance for innovation in health promotion. With the publication of this series, the GWG HPR wishes to strengthen health promotion research capacity at the global level and reaffirm health promotion as a specific research domain.

Combination of prenatal immune challenge and restraint stress affects prepulse inhibition and dopaminergic/GABAergic markers.

Gestational immune challenge with the viral-like antigen poly I:C is a well-established neurodevelopmental model of schizophrenia. However, exposure to inflammation during early life may sensitize the developing brain to secondary insults and enhance the central nervous system vulnerability. To gain a better understanding of the pathophysiology of schizophrenia, we thus developed a two-hit animal model based on prenatal poly I:C immune challenge followed by restraint stress in juvenile mice. C57BL/6 gestational mice were intraperitoneally injected with poly I:C or saline at gestational day 12. Pups were then submitted or not, to restraint stress for 2h, for three consecutive days, from postnatal days 33 to 35. Prepulse inhibition (PPI) of acoustic startle response is commonly used to assess sensorimotor gating, a neural process severely disrupted in patients with schizophrenia. Our results revealed that the combination of prenatal immune challenge with poly I:C followed by a restraint stress period was able to induce a PPI disruption in 36-day-old pups, as opposed to each insult applied separately. PPI deficits were accompanied by dopaminergic and GABAergic abnormalities in the prefrontal cortex and striatum. Indeed, measurements of cortical and striatal dopamine D2 receptor (D2R) mRNA and protein levels revealed that the combination of gestational exposure to poly I:C and postnatal restraint stress induced an increase in D2R protein and mRNA levels. Likewise, the combination of both insults reduced the mRNA and protein expression levels of the 67 kDa form of glutamic acid decarboxylase (GAD67), in those two brain regions. To our knowledge, this two-hit animal model is the first in vivo model reporting PPI deficits at pubertal age. This two-hit animal model may also help in studying innovative therapies dedicated to the treatment of schizophrenia, especially in its early phase.

Antipsychotic-induced DRD2 upregulation and its prevention by α-lipoic acid in SH-SY5Y neuroblastoma cells.

Most antipsychotic (AP) drugs are dopamine (DA) D2 receptor (DRD2) antagonists and remain the main pharmacological treatment of schizophrenia. Long-term AP use can give rise to tardive dyskinesia. It has been reported that chronic treatment with APs induces DRD2 upregulation and oxidative stress, which have been associated with tardive dyskinesia. We showed previously that H2O2-induced oxidative stress increased DRD2 expression in human SH-SY5Y neuroblastoma cells. We report here the effects of AP drugs on DRD2 expression levels in the same cell line and the effects of the inhibition of oxidative phenomena by (±)-α-lipoic acid treatment. Haloperidol, a first-generation AP, induced an increase in DRD2 protein and mRNA levels, whereas amisulpride, a second-generation AP, had no significant effect. (±)-α-Lipoic acid pretreatment reversed the haloperidol-induced DRD2 upregulation in mRNA and protein levels. Furthermore, haloperidol induced a larger increase of oxidative stress biomarkers (protein carbonylation, lipid peroxidation, and superoxide anion production) than amisulpride. (±)-α-Lipoic acid also attenuated AP-induced oxidative stress. Inhibition of catecholamine synthesis by α-methyl-DL-tyrosine (AMPT) increased DRD2 expression and prevented further increase by APs. Our results suggest that haloperidol-induced DRD2 upregulation is linked to oxidative stress and provide potential mechanisms by which (±)-α-lipoic acid can be considered as a therapeutic agent to prevent and treat side effects related to the use of first-generation APs.

No relationship between the ins del polymorphism of the serotonin transporter promoter and pain perception in fibromyalgia patients and healthy controls.

BACKGROUND: In animals, decades of research have shown that serotonin (5-HT) is involved in endogenous pain inhibition systems, which are deficient in chronic pain disorders such as fibromyalgia (FM). In humans, there is preliminary evidence showing that 5-HT is involved in the FM pathophysiology. In the current endophenotyping study, we sought to investigate, for the first time in humans, the relationships between the serotonin transporter promoter region (5-HTTLPR) polymorphism and experimentally-induced pain perception/inhibition in healthy controls (HC) and FM patients. METHODS: Participants were 58 FM patients and 60 HC, who did not differ in age, sex or menstrual cycle. Thermal stimuli were used to measure pain thresholds. Pain inhibition was elicited using a tonic thermal test (Peltier thermode) administered before and after activation of the diffuse noxious inhibitory controls (DNIC) by means of a cold-pressor test (CPT). RESULTS: Thermal pain thresholds were higher in HC compared to FM patients. Pain ratings during the CPT were lower in HC, relative to FM patients. Also, DNIC efficacy was stronger in HC compared to FM patients. However, there was no relationship between 5-HTTLPR and experimentally-induced pain perception/inhibition. DISCUSSION: Our results further confirm that FM is associated with thermal hyperalgesia and deficient DNIC. However, we found no evidence showing that the 5-HTTLPR polymorphism influences pain perception and DNIC. Potential reasons for this negative result will be discussed. Further endophenotyping studies of 5-HT-related gene polymorphisms are required to ascertain the potential relationships between 5-HT and human pain perception/inhibition.

TNF-alpha system response in a rat model of very preterm brain injuries induced by lipopolysaccharide and/or hypoxia-ischemia.

OBJECTIVE: The aim of this study was to determine, with the use of a rat model, the expression of tumor necrosis factor (TNF)-alpha, its receptors, and TNF-alpha-converting enzyme in perinatal brain lesions of early premature neonates. STUDY DESIGN: Lipopolysaccharide (LPS) was injected intraperitoneally in pregnant rats at the end of gestation. At postnatal day 1, the right carotid artery was ligated and followed by exposure to hypoxia. Forebrains (n = 220) were collected to study the TNF-alpha system. RESULTS: LPS alone or combined with hypoxia-ischemia (HI) led to a slight decrease of intracerebral TNF-alpha, whereas sole HI induced no variation. TNF-alpha-converting enzyme followed the same pattern of expression as TNF-alpha. TNF receptor 1 was up-regulated in forebrains that were submitted to LPS alone or combined with HI. No variation was observed in TNF receptor 2 expression. CONCLUSION: The minimal expression of the TNF-alpha system that we observed may indicate that this pathway is not central in the pathogenesis of brain lesions in early premature neonates.

DRD3 Ser9Gly polymorphism is related to thermal pain perception and modulation in chronic widespread pain patients and healthy controls.

UNLABELLED: Experimental studies showed that dopamine influences pain perception in healthy volunteers. Dopamine dysfunctions have been linked to the physiopathology of fibromyalgia (FM), which is associated with hyperalgesia and deficient pain inhibition. We sought to investigate the relationships between catecholamine-related polymorphisms [dopamine-D(3) receptor (DRD3) Ser9Gly and catechol-O-methyltransferase (COMT) Val158Met] and thermal pain measures in healthy subjects and FM patients. Seventy-three subjects (37 FM patients and 36 controls) participated in this study. Thermal pain thresholds (TPTs) were measured using a Peltier thermode. Inhibitory systems were elicited using a thermal tonic pain stimulation administered before and after activation of the diffuse noxious inhibitory controls (DNIC) by means of a cold-pressor test. Genetic analyses were performed using polymerase chain reaction. Regression analyses were performed across and within groups. FM was associated with lower TPTs and deficient pain inhibition. DRD3 Ser9Gly polymorphism predicted (1) DNIC efficacy across groups and (2) thermal TPTs in FM patients. COMT Val158Met and thermal pain measures were not related. These preliminary results suggest that the DRD3 Ser9Gly polymorphism influences DNIC efficacy and TPTs and that this latter relationship is present only in FM patients. Two core psychophysical features of FM appear to be significantly influenced by limbic dopamine functioning. PERSPECTIVE: This experimental study is the first to relate DNIC and TPTs to a functional polymorphism of limbic dopamine-D3 receptors. As lowered pain thresholds and deficient pain inhibition are 2 core features of fibromyalgia, these preliminary results may help identify a subgroup of FM patients who require closer medical attention.

Role of perinatal inflammation in cerebral palsy.

Inflammatory molecules are promptly upregulated in the fetal environment and postnatally in brain-damaged subjects. Intrauterine infections and inflammation are often associated with asphyxia. This double-hit effect by combined infection or inflammation and hypoxia is therefore a frequent concomitant in neonatal brain damage. Animal models combining hypoxia and infection were recently designed to explore the mechanisms underlying brain damage in such circumstances and to look for possible neuroprotective strategies. Proinflammatory cytokines are thought to be major mediators in brain injury in neonates with perinatal asphyxia, bacterial infection, or both. Cytokines, however, could also have neuroprotective properties. The critical point in the balance between neurodamaging and neuroprotective effects of cytokines has yet to be unraveled. This understanding might help to develop new therapeutic approaches to counteract the inflammatory disequilibrium observed in the pathophysiologic mechanisms associated with brain injury.

Novel kinin B1 receptor agonists with improved pharmacological profiles.

There is some evidence to suggest that inducible kinin B1 receptors (B1R) may play beneficial and protecting roles in cardiovascular-related pathologies such as hypertension, diabetes, and ischemic organ diseases. Peptide B1R agonists bearing optimized pharmacological features (high potency, selectivity and stability toward proteolysis) hold promise as valuable therapeutic agents in the treatment of these diseases. In the present study, we used solid-phase methodology to synthesize a series of novel peptide analogues based on the sequence of Sar[dPhe(8)]desArg(9)-bradykinin, a relatively stable peptide agonist with moderate affinity for the human B1R. We evaluated the pharmacological properties of these peptides using (1) in vitro competitive binding experiments on recombinant human B1R and B2R (for index of selectivity determination) in transiently transfected human embryonic kidney 293 cells (HEK-293T cells), (2) ex vivo vasomotor assays on isolated human umbilical veins expressing endogenous human B1R, and (3) in vivo blood pressure tests using anesthetized lipopolysaccharide-immunostimulated rabbits. Key chemical modifications at the N-terminus, the positions 3 and 5 on Sar[dPhe(8)]desArg(9)-bradykinin led to potent analogues. For example, peptides 18 (SarLys[Hyp(3),Cha(5), dPhe(8)]desArg(9)-bradykinin) and 20 (SarLys[Hyp(3),Igl(5), dPhe(8)]desArg(9)-bradykinin) outperformed the parental molecule in terms of affinity, functional potency and duration of action in vitro and in vivo. These selective agonists should be valuable in future animal and human studies to investigate the potential benefits of B1R activation.

Lipopolysaccharide and hypoxia/ischemia induced IL-2 expression by microglia in neonatal brain.

Using a model of perinatal brain lesions induced by lipopolysaccharide and hypoxia/ischemia, we hypothesized that interleukin-2 (IL-2), a neurotoxic cytokine, was enhanced within injured brains. We showed that lipopolysaccharide and hypoxia/ischemia enhanced both intracerebral IL-2 mRNA and protein levels, with a maximum increase upon lipopolysaccharide and hypoxia/ischemia. The lack of detectable T lymphocytes suggested the synthesis of IL-2 by neural cells. Lipopolysaccharide and hypoxia triggered IL-2 synthesis by cultured microglia with a peak after exposure to lipopolysaccharide and hypoxia. Double-labeling showed, in vivo and in vitro, that IL-2 immunoreactivity was colocalized with a microglia/macrophage marker. These results disclosed the ability of microglia to produce IL-2 and also suggest the implication of IL-2 in neural cell death triggered by perinatal lipopolysaccharide and hypoxia/ischemia exposures.

Pro-inflammatory disequilibrium of the IL-1 beta/IL-1ra ratio in an experimental model of perinatal brain damages induced by lipopolysaccharide and hypoxia-ischemia.

Bacterial infections and hypoxia/ischemia (H/I) are implicated in human neonatal brain damage leading to cerebral palsy (CP). We developed an animal model presenting similar perinatal brain damage by combining bacterial endotoxin and H/I insults. Interleukin (IL)-1beta is a mediator of brain damage and its action(s) is counteracted by its cognate anti-inflammatory IL-1 receptor antagonist (IL-1ra). We tested the hypothesis that the balance between agonist and antagonist in the IL-1 system is shifted towards inflammation in perinatal brains exposed to endotoxin and/or H/I. Lipopolysaccharide (LPS) and/or H/I enhanced both intracerebral IL-1beta mRNA and protein levels, with a maximum increase observed with combined LPS and H/I insults. Conversely, IL-1ra expression was significantly downregulated by LPS, H/I, or both combined, with a maximum magnitude of imbalance between IL-1beta and sIL-1ra noticed with the double hit. The nuclear factor (NF)kappaB component of the signaling pathway activated by IL-1beta-binding to its receptor was activated following exposure to LPS and/or H/I. We show for the first time that, perinatally, bacterial products, H/I, or both combined, induce downregulation in sIL-1ra expression concomitant with upregulation in IL-1beta. The resulting pro-inflammatory orientation in the IL-1/IL-1ra balance might play a role in the initiation of perinatal brain damages.

Subacute H2O2, but not poly(IC), upregulates dopamine D2 receptors in retinoic acid differentiated SH-SY5Y neuroblastoma.

Abnormalities of striatal dopaminergic neurotransmission play a significant role in the pathophysiology of central nervous system disorders such as movement disorders, addictions and schizophrenia. The striatum appears to be exposed to intrinsically high levels of oxidative stress (OS). Little is known, however, on the effect of OS on the regulation of the dopamine D2 receptor (DRD2), a key component of striatal dopaminergic neurotransmission. We report here on the effects of H2O2 (a canonical oxidant and non conventional messenger) and polyinosinic-polycytidylic acid (poly(IC) which elicits schizophrenia-like behaviors in newborn rodents and disrupts dopaminergic system development), on DRD2 levels in retinoic acid differentiated SH-SY5Y neuroblastoma. H2O2 elicited a significant increase in DRD2 mRNA and protein levels. Conversely, poly(IC) did not regulate DRD2 levels, although SH-SY5Y cells were confirmed to express TLR3 receptors. Under our conditions, H2O2, but not poly(IC), increased NFkappaB activation (as assessed by p65 nuclear translocation), which paralleled their effects on DRD2 levels regulation.

Standardization and detailed characterization of the syngeneic Fischer/F98 glioma model.

INTRODUCTION: Adequate animal glioma models are mandatory for the pursuit of preclinical research in neuro-oncology. Many implantation models have been described, but none perfectly emulate human malignant gliomas. This work reports our experience in standardizing, optimizing and characterizing the Fischer/F98 glioma model on the clinical, pathological, radiological and metabolic aspects. MATERIALS AND METHODS: F98 cells were implanted in 70 Fischer rats, varying the quantity of cells and volume of implantation solution, and using a micro-infusion pump to minimize implantation trauma, after adequate coordinates were established. Pathological analysis consisted in hematoxylin and eosin (H&E) staining and immunohistochemistry for GFAP, vimentin, albumin, TGF-bl, TGF-b2, CD3 and CD45. Twelve animals were used for MR imaging at 5, 10, 15 and 20 days. Corresponding MR images were compared with pathological slides. Two animals underwent 18F-FDG and 11C-acetate PET studies for metabolic characterization of the tumors. RESULTS: Implantation with 1 x 10(4) cells produced a median survival of 26 days and a tumor take of 100%. Large infiltrative neoplasms with a necrotic core were seen on H&E. Numerous mitosis, peritumoral infiltrative behavior, and neovascular proliferation were also obvious. GFAP and vimentin staining was positive inside the tumor cells. Albumin staining was observed in the extracellular space around the tumors. CD3 staining was negligible. The MR images correlated the pathologic findings. 18F-FDG uptake was strong in the tumors. CONCLUSION: The standardized model described in this study behaves in a predictable and reproducible fashion, and could be considered for future pre-clinical studies. It adequately mimics the behavior of human malignant astrocytomas.

Hypotensive effects of hemopressin and bradykinin in rabbits, rats and mice. A comparative study.

Hemopressin is a novel vasoactive nonapeptide derived from hemoglobin's alpha-chain as recently reported by Rioli et al. [Rioli V, Gozzo FC, Heimann AS, Linardi A, Krieger JE, Shida CS, et al. Novel natural peptide substrates for endopeptidase 24.15, neurolysin, and angiotensin-converting enzyme. J Biol Chem 2003;278(10):8547-55]. In anesthetized male Wistar rats, this peptide exhibited hypotensive actions similar to those of bradykinin (BK) when administered intravenously (i.v.), and was found to be metabolized both in vitro and in vivo by several peptidases, including the angiotensin-converting enzyme (ACE). In this study, these findings were expanded upon by examining: (i) the degradation kinetics following incubation with ACE purified from rabbit lung and (ii) the blood pressure lowering effects of HP and BK injected i.v. or intra-arterially (i.a.) in male rabbits, rats, and mice. Our findings demonstrate that, in vitro, HP and BK are both degraded by ACE, but at different velocity rates. Furthermore, both HP and BK induced transient hypotension in all animals tested, although the responses to HP relative to the administration sites were significantly lower (by 10-100-fold) on an equimolar basis compared to those of BK. In rabbits, the decrease of blood pressure induced by HP (10-100 nmol/kg) did not differ whether it was administered i.v. or i.a., suggesting an absence of pulmonary/cardiac inactivation in contrast to BK (0.1-1 nmol/kg). The in vivo effect of HP was significantly potentiated in rabbits immunostimulated with bacterial lipopolysaccharide (LPS), but was unaffected by both the B2 receptor antagonist HOE 140 (0.1 micromol/kg) and captopril (100 microg/kg), contrary to BK. Therefore, HP acts as a weak hypotensive mediator, which does not activate kinin B2 receptors, but uses a functional site and/or signaling paths appearing to be up-regulated by LPS.