Mosapride stimulates human 5-HT4-serotonin receptors in the heart.

Mosapride (4-amino-5-chloro-2-ethoxy-N-[[4-[(4-fluorophenyl) methyl]-2-morpholinyl]-methyl] benzamide) is a potent agonist at gastrointestinal 5-HT4 receptors. Mosapride is an approved drug to treat several gastric diseases. We tested the hypothesis that mosapride also stimulates 5-HT4 receptors in the heart. Mosapride increased the force of contraction and beating rate in isolated atrial preparations from mice with cardiac overexpression of human 5-HT4-serotonin receptors (5-HT4-TG). However, it is inactive in wild-type mouse hearts (WT). Mosapride was less effective and potent than serotonin in raising the force of contraction or the beating rate in 5-HT4-TG. Only in the presence of cilostamide (1 µM), a phosphodiesterase III inhibitor, mosapride, and its primary metabolite time dependently raised the force of contraction under isometric conditions in isolated paced human right atrial preparations (HAP, obtained during open heart surgery). In HAP, mosapride (10 µM) reduced serotonin-induced increases in the force of contraction. Mosapride (10 µM) shifted the concentration-response curves to serotonin in HAP to the right. These data suggest that mosapride is a partial agonist at 5-HT4-serotonin receptors in HAP.

Lysergic acid diethylamide stimulates cardiac human H2 histamine and cardiac human 5-HT4-serotonin receptors.

Lysergic acid diethylamide (LSD) is an artificial hallucinogenic drug. Thus, we hypothesized that LSD might act 5-HT4 serotonin receptors and/or H2 histamine receptors. We studied isolated electrically stimulated left atrial preparations, spontaneously beating right atrial preparations, and spontaneously beating Langendorff-perfused hearts from transgenic mice with cardiomyocyte-specific overexpression of the human 5-HT4 receptor (5-HT4-TG) or of the H2-histamine receptor (H2-TG). For comparison, we used wild type littermate mice (WT). Finally, we measured isometric force of contraction in isolated electrically stimulated muscle strips from the human right atrium obtained from patients during bypass surgery. LSD (up to 10 µM) concentration dependently increased force of contraction and beating rate in left or right atrial preparations from 5-HT4-TG (n = 6, p < 0.05) in 5-HT4-TG atrial preparations. The inotropic and chronotropic effects of LSD were antagonized by 10 µM tropisetron in 5-HT4-TG. In contrast, LSD (10 µM) increased force of contraction and beating rate in left or right atrial preparations, from H2-TG. After pre-stimulation with cilostamide (1 µM), LSD (10 µM) increased force of contraction in human atrial preparations (n = 6, p < 0.05). The contractile effects of LSD in human atrial preparations could be antagonized by 10 µM cimetidine and 1 µM GR 125487. LSD leads to H2-histamine receptor and 5-HT4-receptor mediated cardiac effects in humans.

Cantharidin and sodium fluoride attenuate the negative inotropic effects of carbachol in the isolated human atrium.

Carbachol, an agonist at muscarinic receptors, exerts a negative inotropic effect in human atrium. Carbachol can activate protein phosphatases (PP1 or PP2A). We hypothesized that cantharidin or sodium fluoride, inhibitors of PP1 and PP2A, may attenuate a negative inotropic effect of carbachol. During bypass-surgery trabeculae carneae of human atrial preparations (HAP) were obtained. These trabeculae were mounted in organ baths and electrically stimulated (1 Hz). Force of contraction was measured under isometric conditions. For comparison, we studied isolated electrically stimulated left atrial preparations (LA) from mice. Cantharidin (100 µM) and sodium fluoride (3 mM) increased force of contraction in LA (n = 5-8, p < 0.05) by 113% ± 24.5% and by 100% ± 38.2% and in HAP (n = 13-15, p < 0.05) by 625% ± 169% and by 196% ± 23.5%, respectively. Carbachol (1 µM) alone exerted a rapid transient maximum negative inotropic effect in LA (n = 6) and HAP (n = 14) to 46.9% ± 3.63% and 19.4% ± 3.74%, respectively (p < 0.05). These negative inotropic effects were smaller in LA (n = 4-6) and HAP (n = 9-12) pretreated with 100 µM cantharidin and amounted to 58.0% ± 2.27% and 59.2% ± 6.19% or 3 mM sodium fluoride to 63.7% ± 9.84% and 46.3% ± 5.69%, (p < 0.05). We suggest that carbachol, at least in part, exerts a negative inotropic effect in the human atrium by stimulating the enzymatic activity of PP1 and/or PP2A.

Living Longer or Better-Patient's Choice in Cardiac Surgery Is Gender-Dependent-A Multicenter Study.

In view of the increasing age of cardiac surgery patients, questions arise about the expected postoperative quality of life and the hoped-for prolonged life expectancy. Little is known so far about how these, respectively, are weighted by the patients concerned. This study aims to obtain information on the patients' preferences. Between 2015 and 2017, data were analyzed from 1349 consecutive patients undergoing cardiac surgery at seven heart centers in Germany. Baseline data regarding the patient's situation as well as a questionnaire regarding quality of life versus lifespan were taken preoperatively. Patients were divided by age into four groups: below 60, 60-70, 70-80, and above 80 years. As a result, when asked to decide between quality of life and length of life, about 60% of the male patients opted for quality of life, independent of their age. On the other hand, female patients' preference for quality of life increased significantly with age, from 51% in the group below sixty to 76% in the group above eighty years. This finding suggests that female patients adapt their preferences with age, whereas male patients do not. This should impact further the treatment decisions of elderly patients in cardiac surgery within a shared decision-making process.

Ergometrine stimulates histamine H2 receptors in the isolated human atrium.

Ergometrine (6aR,9R)-N-((S)-1-hydroxypropan-2-yl)-7-methyl-4,6,6a,7,8,9-hexa-hydro-indolo-[4,3-fg]chinolin-9-carboxamide or lysergide acid ß-ethanolamide or ergonovine) activates several types of serotonin and histamine receptors in the animal heart. We thus examined whether ergometrine can activate human serotonin 5-HT4 receptors (h5-HT4R) and/or human histamine H2 receptors (hH2R) in the heart of transgenic mice and/or in the human isolated atrium. Force of contraction or beating rates were studied in electrically stimulated left atrial or spontaneously beating right atrial preparations or spontaneously beating isolated retrogradely perfused hearts (Langendorff setup) of mice with cardiac specific overexpression of the h5-HT4R (5-HT4-TG) or of mice with cardiac specific overexpression of the hH2R (H2-TG) or in electrically stimulated human right atrial preparations obtained during cardiac surgery. Western blots to assess phospholamban (PLB) phosphorylation on serine 16 were performed. Ergometrine exerted concentration- and time-dependent positive inotropic effects and positive chronotropic effects in atrial preparations starting at 0.3 µM and reaching a plateau at 10 µM in H2-TGs (n = 7). This was accompanied by an increase in PLB phosphorylation at serine 16. Ergometrine up 10 µM failed to increase force of contraction in left atrial preparations from 5-HT4-TGs (n = 5). Ten micrometer ergometrine increased the force of contraction in isolated retrogradely perfused spontaneously beating heart preparations (Langendorff setup) from H2-TG but not 5-HT4-TG. In the presence of the phosphodiesterase inhibitor cilostamide (1 µM), ergometrine at 10 µM exerted positive inotropic effects in isolated electrically stimulated human right atrial preparations, obtained during cardiac surgery, and these effects were eliminated by 10 µM of the H2R antagonist cimetidine but not by 10 µM of the 5-HT4R antagonist tropisetron. Furthermore, ergometrine showed binding to human histamine H2 receptors (at 100 µM and 1 mM) using HEK cells in a recombinant expression system (pKi < 4.5, n = 3). In conclusion, we suggest that ergometrine is an agonist at cardiac human H2Rs.

OR-1896 increases force of contraction in the isolated human atrium.

OR-1896 ((R)-N-(4-(4-methyl-6-oxo-1,4,5,6-tetrahydropyridazin-3-yl)phenyl)acetamide) is the main active metabolite of levosimendan. However, nobody has reported a positive inotropic effect of OR-1896 in isolated human cardiac preparations. The mechanism of action of OR-1896 remains controversial. Hence, we wanted to know whether OR-1896 exerts a positive inotropic effect in humans and what might be the underlying mechanism. Therefore, we measured the contractile effects of OR-1896 (0.01-10 µM cumulatively applied) in isolated electrically stimulated (1 Hz) human right atrial preparations (HAP) obtained during cardiac surgery. OR-1896, given alone, exerted time- and concentration-dependent positive inotropic effects; 1-µM OR-1896 increased force by 72 ± 14.7% (p < 0.05, n = 6) and shortened the time of relaxation by 10.6 ± 3.6% (p < 0.05, n = 11) in HAP started at 0.1 µM, plateaued at 1-µM OR-1896, and was antagonized by 1-µM propranolol. The maximum positive inotropic effect of OR-1896 in human right atrial preparations was less than that of 10-µM isoprenaline. EMD 57033 (10 µM), a calcium sensitizer, enhanced the force of contraction further in the additional presence of 1-µM OR-1896 by 109 ± 19% (p < 0.05, n = 4). Cilostamide (10 µM), an inhibitor of phosphodiesterase III given before OR-1896 (1 µM), blocked the positive inotropic effect of OR-1896 in HAP. Our data suggest that OR-1896 is, indeed, a positive inotropic agent in the human heart. OR-1896 acts as a PDE III inhibitor. OR-1896 is unlikely to act as a calcium sensitizer in the human heart.

Temperature alters the inotropic, chronotropic and proarrhythmic effects of histamine in atrial muscle preparations from humans and H2-receptor overexpressing mice.

We investigated whether hypothermia and hyperthermia can alter the efficacy and potency of histamine at increasing the force of cardiac contractions in mice that overexpress the human H2 receptor only in their cardiac myocytes (labelled H2-TG). Contractile studies were performed in an organ bath on isolated, electrically driven (1 Hz) left atrial preparations and spontaneously beating right atrial preparations from H2-TG mice and wild-type (WT) littermate control mice. The basal beating rate in the right atrial preparations from H2-TG mice was lowered by hypothermia (23 °C) and elevated by hyperthermia (42 °C). Furthermore, the efficacy of histamine (0.01-100 µM) at exerting positive inotropic effects was more severely attenuated in the left and right H2-TG mouse atria under hypothermia and hyperthermia than under normothermia (37 °C). Similarly, the inotropic response to histamine was attenuated under hypothermia and hyperthermia in isolated electrically stimulated (1 Hz) right atrial preparations obtained from humans undergoing cardiac surgery. The phosphorylation state of phospholamban at serine 16 at 23 °C was inferior to that at 37 °C in left atrial preparations from H2-TG mice in the presence of 10 µM histamine. In contrast, in human atrial preparations, the phosphorylation state of phospholamban at serine 16 in the presence of 100 µM histamine was lower at 42 °C than at 37 °C. Finally, under hyperthermia, we recorded more and longer lasting arrhythmias in right atrial preparations from H2-TG mice than in those from WT mice. We conclude that the inotropic effects of histamine in H2-TG mice and in human atrial preparations, as well as the chronotropic effects of histamine in H2-TG mice, are temperature dependent. Furthermore, we observed that, even without stimulation of the H2 receptors by exogenous agonists, temperature elevation can increase arrhythmias in isolated right atrial preparations from H2-TG mice. We propose that H2 receptors play a role in hyperthermia-induced supraventricular arrhythmias in human patients.

Ergotamine Stimulates Human 5-HT4-Serotonin Receptors and Human H2-Histamine Receptors in the Heart.

Ergotamine (2'-methyl-5'α-benzyl-12'-hydroxy-3',6',18-trioxoergotaman) is a tryptamine-related alkaloid from the fungus Claviceps purpurea. Ergotamine is used to treat migraine. Ergotamine can bind to and activate several types of 5-HT1-serotonin receptors. Based on the structural formula of ergotamine, we hypothesized that ergotamine might stimulate 5-HT4-serotonin receptors or H2-histamine receptors in the human heart. We observed that ergotamine exerted concentration- and time-dependent positive inotropic effects in isolated left atrial preparations in H2-TG (mouse which exhibits cardiac-specific overexpression of the human H2-histamine receptor). Similarly, ergotamine increased force of contraction in left atrial preparations from 5-HT4-TG (mouse which exhibits cardiac-specific overexpression of the human 5-HT4-serotonin receptor). An amount of 10 µM ergotamine increased the left ventricular force of contraction in isolated retrogradely perfused spontaneously beating heart preparations of both 5-HT4-TG and H2-TG. In the presence of the phosphodiesterase inhibitor cilostamide (1 µM), ergotamine 10 µM exerted positive inotropic effects in isolated electrically stimulated human right atrial preparations, obtained during cardiac surgery, that were attenuated by 10 µM of the H2-histamine receptor antagonist cimetidine, but not by 10 µM of the 5-HT4-serotonin receptor antagonist tropisetron. These data suggest that ergotamine is in principle an agonist at human 5-HT4-serotonin receptors as well at human H2-histamine receptors. Ergotamine acts as an agonist on H2-histamine receptors in the human atrium.

Levosimendan increases the phosphorylation state of phospholamban in the isolated human atrium.

Levosimendan (up to 10 µM) given alone failed to increase force of contraction in isolated electrically stimulated (1 Hz) left atrial (LA) preparations from wild-type mice. Only in the additional presence of 0.1 µM rolipram, an inhibitor of the activity of phosphodiesterase IV, levosimendan increased force of contraction in LA and increased the phosphorylation state of phospholamban at amino acid serine 16. Levosimendan alone increased the beating rate in isolated spontaneously beating right atrial preparations from mice and this effect was potentiated by rolipram. The positive inotropic and the positive chronotropic effects of levosimendan in mouse atrial preparations were attenuated by 10 µM propranolol. Finally, we studied the contractile effects of levosimendan in isolated electrically stimulated (1 Hz) right atrial preparations from the human atrium (HAP), obtained during cardiac surgery. We detected concentration-dependent positive inotropic effects of levosimendan alone that reached plateau at 1 µM levosimendan in HAP (n = 11). Levosimendan shortened time of tension relaxation in HAP. Cilostamide (1 µM), an inhibitor of phosphodiesterase III, or propranolol (10 µM) blocked the positive inotropic effect of levosimendan in HAP. Levosimendan (1 µM) alone increased in HAP the phosphorylation state of phospholamban. In conclusion, we present evidence that levosimendan acts via phosphodiesterase III inhibition in the human atrium leading to phospholamban phosphorylation and thus explaining the positive inotropic effects of levosimendan in HAP.

Cardiac effects of ephedrine, norephedrine, mescaline, and 3,4-methylenedioxymethamphetamine (MDMA) in mouse and human atrial preparations.

The use of recreational drugs like ephedrine, norephedrine, 3,4-methylenedioxymethamphetamine (MDMA), and mescaline can lead to intoxication and, at worst, to death. One reason for a fatal course of intoxication with these drugs might lie in cardiac arrhythmias. To the best of our knowledge, their inotropic effects have not yet been studied in isolated human cardiac preparations. Therefore, we measured inotropic effects of the hallucinogenic drugs ephedrine, norephedrine, mescaline, and MDMA in isolated mouse left atrial (mLA) and right atrial (mRA) preparations as well as in human right atrial (hRA) preparations obtained during cardiac surgery. Under these experimental conditions, ephedrine, norephedrine, and MDMA increased force of contraction (mLA, hRA) and beating rate (mRA) in a time- and concentration-dependent way, starting at 1-3 µM but these drugs were less effective than isoprenaline. Mescaline alone or in the presence of phosphodiesterase inhibitors did not increase force in mLA or hRA. The positive inotropic effects of ephedrine, norephedrine, or MDMA were accompanied by increases in the rate of tension and relaxation and by shortening of time of relaxation and, moreover, by an augmented phosphorylation state of the inhibitory subunit of troponin in hRA. All effects were greatly attenuated by cocaine (10 µM) or propranolol (10 µM) treatment. In summary, the hallucinogenic drugs ephedrine, norephedrine, and MDMA, but not mescaline, increased force of contraction and increased protein phosphorylation presumably, in part, by a release of noradrenaline in isolated human atrial preparations and thus can be regarded as indirect sympathomimetic drugs in the human atrium.

Preventive Impella® Support in High-Risk Patients Undergoing Cardiac Surgery.

BACKGROUND: Patients with severely reduced LV-EF ≤ 30% undergoing CABG have a high risk for postoperative cardiogenic shock. The optimal timing of an adequate hemodynamic support has an impact on short- and midterm mortality after CABG. This study aimed to assess the prophylactic use of the Impella pump in high-risk patients undergoing elective cardiac surgery. METHODS: In this single-center retrospective study, 14 patients with LV-EF (≤30%) undergoing cardiac surgery received a prophylactic, perioperative Impella (5.0, 5.5) support between 2020 and 2022. RESULTS: The mean age at surgery was 64.2 ± 2.6 years, the mean preoperative LV-EF was 20.7% ± 1.56%. The duration of Impella support was 4 (3-7.8) days and the 30-day survival rate was 92.85%. Acute renal failure occurred in four patients who were dialyzed on average for 1.2 ± 0.7 days. Mechanical ventilation was needed for 1.75 (0.9-2.7) days. Time to inotrope/vasopressor independence was 2 (0.97-7.25) days with a highest lactate level (24 h postoperatively) of 3.8 ± 0.6 mmol/l. Postoperative LV-EF showed a significant improvement when compared to preoperative LV-EF (29.1% ± 2.6% vs. 20.7% ± 1.56% (p = 0.022)). CONCLUSION: The prophylactic Impella application seems to be a safe approach to improve the outcomes of this patient population.

Advanced Glycation End Product (AGE) and Soluble Receptor of AGE (sRAGE) Levels in Relation to Periodontitis Severity and as Putative 3-Year Outcome Predictors in Patients Undergoing Coronary Artery Bypass Grafting (CABG).

Tissue concentrations of advanced glycation end product (AGE) and peripheral soluble receptor of AGE (sRAGE) levels may be associated with periodontitis severity. Both parameters and periodontitis might serve as outcome predictors for patients undergoing coronary artery bypass grafting (CABG). This study aimed to investigate possible associations between periodontitis and AGE/sRAGE. Ultimately, we wanted to examine whether AGE, sRAGE, and severe periodontitis are associated with the incidence of new cardiovascular events within 3 years of follow-up after CABG. Ninety-five patients with coronary vascular disease (CVD) (age 69 years, 88.3% males) needing CABG surgery were included. Periodontal diagnosis was made according to the guidelines of the "Centers for Disease Control and Prevention (CDC)" (2007) and staged according to the new classification of periodontal diseases (2018). AGE tissue concentrations were assessed as skin autofluorescence (sAF). sRAGE levels were determined by using a commercially available enzyme-linked immunoabsorbance assay (ELISA) kit. Univariate and multivariate baseline and survival analyses were carried out with Mann-Whitney U test, Chi² test, Kaplan-Meier curves with Log-Rank test, and logistic and Cox regression. sAF was identified as an independent risk indicator for severe periodontitis with respect to the cofactors age, gender, plaque index, and diabetes (adjusted odds ratio [OR] = 2.9, p = 0.028). The degree of subgingival inflammation assessed as a percentage of sites with bleeding on probing (BOP) was inversely correlated with sRAGE concentration (r = -0.189, p = 0.034). Both sAF (Hazard Ratio [HR] = 2.4, p = 0.004) and sRAGE (HR = 1.9, p = 0.031) increased the crude risk for new adverse events after CABG. The occurrence of severe periodontitis trends towards a higher risk for new cardiovascular events (HR = 1.8, p = 0.115). Applying multivariate Cox regression, only peripheral arterial disease (adjusted HR = 2.7, p = 0.006) and history of myocardial infarction (adjusted HR = 2.8, p = 0.010) proved to be independent risk factors for cardiovascular outcome. We conclude that sAF may represent a new, independent risk indicator for severe periodontitis. In contrast, sAF, sRAGE, and severe periodontitis were not independent prognostic factors for postoperative outcome in patients undergoing CABG.

Campylobacter Species of the Oral Microbiota as Prognostic Factor for Cardiovascular Outcome after Coronary Artery Bypass Grafting Surgery.

BACKGROUND: The oral microbiota has been implicated in a variety of systemic diseases, including cardiovascular (CV) disease. The main objective of this study (DRKS-ID: DRKS00015776) was to evaluate the prognostic importance of the oral microbiota for further CV events in patients undergoing coronary artery bypass grafting surgery (3-year follow-up). METHODS: In this longitudinal cohort study, 102 CV patients were enrolled, of whom 95 completed the 3-year follow-up. The CV outcome was assessed using the major adverse cardiac and cerebrovascular events criteria. To evaluate subgingival colonization, 16S rRNA genes were amplified, targeting the V3/V4 region (Illumina MiSeq). RESULTS: Regarding the specific number of operational taxonomic units (OTUs), no significant differences in CV outcome were determined (alpha diversity, Shannon index). In linear discriminant analyses and t-tests, the disease-specific differences in the beta diversity of the microbiota composition were evaluated. It was evident that bacteria species of the genus Campylobacter were significantly more prevalent in patients with a secondary CV event (p = 0.015). This hierarchical order also includes Campylobacter rectus, which is considered to be of comprehensive importance in both periodontal and CV diseases. CONCLUSIONS: Here, we proved that subgingival occurrence of Campylobacter species has prognostic relevance for cardiovascular outcomes in CV patients undergoing coronary artery bypass grafting.

Cytokine Hemoadsorption During Cardiac Surgery Versus Standard Surgical Care for Infective Endocarditis (REMOVE): Results From a Multicenter Randomized Controlled Trial.

BACKGROUND: Cardiac surgery often represents the only treatment option in patients with infective endocarditis (IE). However, IE surgery may lead to a sudden release of inflammatory mediators, which is associated with postoperative organ dysfunction. We investigated the effect of hemoadsorption during IE surgery on postoperative organ dysfunction. METHODS: This multicenter, randomized, nonblinded, controlled trial assigned patients undergoing cardiac surgery for IE to hemoadsorption (integration of CytoSorb to cardiopulmonary bypass) or control. The primary outcome (change in sequential organ failure assessment score [ΔSOFA]) was defined as the difference between the mean total postoperative SOFA score, calculated maximally to the 9th postoperative day, and the basal SOFA score. The analysis was by modified intention to treat. A predefined intergroup comparison was performed using a linear mixed model for ΔSOFA including surgeon and baseline SOFA score as fixed effect covariates and with the surgical center as random effect. The SOFA score assesses dysfunction in 6 organ systems, each scored from 0 to 4. Higher scores indicate worsening dysfunction. Secondary outcomes were 30-day mortality, duration of mechanical ventilation, and vasopressor and renal replacement therapy. Cytokines were measured in the first 50 patients. RESULTS: Between January 17, 2018, and January 31, 2020, a total of 288 patients were randomly assigned to hemoadsorption (n=142) or control (n=146). Four patients in the hemoadsorption and 2 in the control group were excluded because they did not undergo surgery. The primary outcome, ΔSOFA, did not differ between the hemoadsorption and the control group (1.79±3.75 and 1.93±3.53, respectively; 95% CI, -1.30 to 0.83; P=0.6766). Mortality at 30 days (21% hemoadsorption versus 22% control; P=0.782), duration of mechanical ventilation, and vasopressor and renal replacement therapy did not differ between groups. Levels of interleukin-1ß and interleukin-18 at the end of integration of hemoadsorption to cardiopulmonary bypass were significantly lower in the hemoadsorption than in the control group. CONCLUSIONS: This randomized trial failed to demonstrate a reduction in postoperative organ dysfunction through intraoperative hemoadsorption in patients undergoing cardiac surgery for IE. Although hemoadsorption reduced plasma cytokines at the end of cardiopulmonary bypass, there was no difference in any of the clinically relevant outcome measures. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT03266302.

Non-Invasive Assessment of Locally Overexpressed Human Adenosine 2A Receptors in the Heart of Transgenic Mice.

A2A adenosine receptors (A2A-AR) have a cardio-protective function upon ischemia and reperfusion, but on the other hand, their stimulation could lead to arrhythmias. Our aim was to investigate the potential use of the PET radiotracer [18F]FLUDA to non-invasively determine the A2A-AR availability for diagnosis of the A2AR status. Therefore, we compared mice with cardiomyocyte-specific overexpression of the human A2A-AR (A2A-AR TG) with the respective wild type (WT). We determined: (1) the functional impact of the selective A2AR ligand FLUDA on the contractile function of atrial mouse samples, (2) the binding parameters (Bmax and KD) of [18F]FLUDA on mouse and human atrial tissue samples by autoradiographic studies, and (3) investigated the in vivo uptake of the radiotracer by dynamic PET imaging in A2A-AR TG and WT. After A2A-AR stimulation by the A2A-AR agonist CGS 21680 in isolated atrial preparations, antagonistic effects of FLUDA were found in A2A-AR-TG animals but not in WT. Radiolabelled [18F]FLUDA exhibited a KD of 5.9 ± 1.6 nM and a Bmax of 455 ± 78 fmol/mg protein in cardiac samples of A2A-AR TG, whereas in WT, as well as in human atrial preparations, only low specific binding was found. Dynamic PET studies revealed a significantly higher initial uptake of [18F]FLUDA into the myocardium of A2A-AR TG compared to WT. The hA2A-AR-specific binding of [18F]FLUDA in vivo was verified by pre-administration of the highly affine A2AAR-specific antagonist istradefylline. Conclusion: [18F]FLUDA is a promising PET probe for the non-invasive assessment of the A2A-AR as a marker for pathologies linked to an increased A2A-AR density in the heart, as shown in patients with heart failure.

Functional interaction of H2-receptors and 5HT4-receptors in atrial tissues isolated from double transgenic mice and from human patients.

In the past, we generated transgenic mice that overexpress the human histamine 2 (H2)-receptor (H2-TG) or that overexpress the human serotonin 4 (5-HT4)-receptor (5-HT4-TG) in the heart. Here, we crossbred these lines of mice to generate double transgenic mice that overexpress both receptors (DT). This was done to study a conceivable interaction between these receptors in the mouse heart as a model for the human heart. When in left atria, initially, force of contraction was elevated maximally with 1 µM serotonin, and subsequently, histamine was cumulatively applied; a biphasic effect of histamine was noted: the force of contraction initially decreased, maximally at 10 nM histamine, and thereafter, the force of contraction increased again at 1 µM histamine. Notably, functional interaction between 5-HT and histamine was also identified in isolated electrically stimulated trabeculae carneae from human right atrium (obtained during cardiac surgery). These functional and biochemical data together are consistent with a joint overexpression of inotropically active H2-receptors and 5-HT4-receptors in the same mouse heart. We also describe an antagonistic interaction on the force of contraction of both receptors in the mouse atrium (DT) and in the human atrial muscle strips. We speculate that via this interaction, histamine might act as a "brake" on the cardiac actions of 5-HT via inhibitory GTP-binding proteins acting on the activity of adenylyl cyclase.

Cardiac Effects of Novel Histamine H2 Receptor Agonists.

In an integrative approach, we studied cardiac effects of recently published novel H2 receptor agonists in the heart of mice that overexpress the human H2 receptor (H2-TG mice) and littermate wild type (WT) control mice and in isolated electrically driven muscle preparations from patients undergoing cardiac surgery. Under our experimental conditions, the H2 receptor agonists UR-Po563, UR-MB-158, and UR-MB-159 increased force of contraction in left atrium from H2-TG mice with pEC50 values of 8.27, 9.38, and 8.28, respectively, but not in WT mice. Likewise, UR-Po563, UR-MB-158, and UR-MB-159 increased the beating rate in right atrium from H2-TG mice with pEC50 values of 9.01, 9.24, and 7.91, respectively, but not from WT mice. These effects could be antagonized by famotidine, a H2 receptor antagonist. UR-Po563 (1 µM) increased force of contraction in Langendorff-perfused hearts from H2-TG but not WT mice. Similarly, UR-Po563, UR-MB-158, or UR-MB-159 increased the left ventricular ejection fraction in echocardiography of H2-TG mice. Finally, UR-Po563 increased force of contraction in isolated human right atrial muscle strips. The contractile effects of UR-Po563 in H2-TG mice were accompanied by an increase in the phosphorylation state of phospholamban. In summary, we report here three recently developed agonists functionally stimulating human cardiac H2 receptors in vitro and in vivo. We speculate that these compounds might be of some merit to treat neurologic disorders if their cardiac effects are blocked by concomitantly applied receptor antagonists that cannot pass through the blood-brain barrier or might be useful to treat congestive heart failure in patients. SIGNIFICANCE STATEMENT: Recently, a new generation of histamine H2 receptor (H2R) agonists has been developed as possible treatment option for Alzheimer's disease. Here, possible cardiac (side) effects of these novel H2R agonists have been evaluated.

Cardiovascular effects of metoclopramide and domperidone on human 5-HT4-serotonin-receptors in transgenic mice and in human atrial preparations.

It is unclear whether metoclopramide and domperidone act on human cardiac serotonin 5-HT4-receptors. Therefore, we studied transgenic mice that only express the human 5-HT4 receptor in cardiomyocytes in the atrium and in the ventricle (5-HT4-TG), their wild type-littermates (WT) and isolated human atrial preparations. We found that only metoclopramide but not domperidone enhanced the force of contraction in left atrial preparations (pEC50 = 6.0 ± 0.1; n = 7) from 5-HT4-TG, isolated spontaneously beating right atrial preparations (pEC50 = 6.1 ± 0.1; n = 7) from 5-HT4-TG, Langendorff perfused hearts from 5-HT4-TG, living 5-HT4-TG and human right atrial muscle preparations obtained during bypass surgery of patients suffering from coronary heart disease. The maximum inotropic effect of metoclopramide was smaller (81 ± 2%) than that of 5-HT on the left atria from 5-HT4-TG. The maximum increase in the beating rate due to metoclopramide was 93 ± 2% of effect of 5-HT on right atrial preparations from 5-HT4-TG. Metoclopramide and domperidone were inactive in WT. We found that metoclopramide but not domperidone increased the phosphorylation state of phospholamban in the isolated perfused hearts or muscle strips of 5-HT4-TG, but not in WT. Metoclopramide, but not domperidone, shifted the positive inotropic or chronotropic effects of 5-HT in isolated left atrial and right atrial preparations from 5-HT4-TG dextrally, resp., to higher concentrations: the pEC50 of 5-HT for increase in force was in the absence of metoclopramide 8.6 ± 0.1 (n = 5) versus 8.0 ± 0.3 in the presence of 1 µM metoclopramide (n = 5; P < 0.05); and the beating rate was 7.8 ± 0.2 (n = 7) in the absence of metoclopramide versus 7.2 ± 0.1 in the presence of 1 µM metoclopramide (n = 6; P < 0.05). These results suggested that metoclopramide had an antagonistic effect on human cardiac 5-HT4 receptors. In summary, we showed that metoclopramide, but not domperidone, was a partial agonist at human cardiac 5-HT4-receptors.

Is Periodontitis a Predictor for an Adverse Outcome in Patients Undergoing Coronary Artery Bypass Grafting? A Pilot Study.

Periodontitis is a risk factor for atherosclerosis and coronary vascular disease (CVD). This research evaluated the relationship between periodontal conditions and postoperative outcome in patients who underwent coronary artery bypass grafting (CABG). A total of 101 patients with CVD (age 69 years, 88.1% males) and the necessity of CABG surgery were included. Periodontal diagnosis was made according to the guidelines of the Centers for Disease Control and Prevention (CDC, 2007). Additionally, periodontal epithelial surface area (PESA) and periodontal inflamed surface area (PISA) were determined. Multivariate survival analyses were carried out after a one-year follow-up period with Cox regression. All study subjects suffered from periodontitis (28.7% moderate, 71.3% severe). During the follow-up period, 14 patients (13.9%) experienced a new cardiovascular event (11 with angina pectoris, 2 with cardiac decompensation, and 1 with cardiac death). Severe periodontitis was not significant associated with the incidence of new events (adjusted hazard ratio, HR = 2.6; p = 0.199). Other risk factors for new events were pre-existing peripheral arterial disease (adjusted HR = 4.8, p = 0.030) and a history of myocardial infarction (HR = 6.1, p = 0.002). Periodontitis was not found to be an independent risk factor for the incidence of new cardiovascular events after CABG surgery.

The role of Saccharibacteria (TM7) in the subginival microbiome as a predictor for secondary cardiovascular events.

BACKGROUND: The composition of the subgingival microbiota is of great importance in both oral and systemic diseases. However, a possible association of the oral microbiome and cardiovascular (CV) outcome has not yet been considered in a complex model. The primary objective of the study (DRKS-ID: DRKS00015776) was to assess differences in complex subgingival bacterial composition, depending on the CV outcome in patients undergoing Coronary Artery Bypass Grafting Surgery (CABG). MATERIAL AND METHODS: We conducted a longitudinal cohort study enrolling 102 CV patients. After a one-year follow-up, the postoperative outcome was evaluated applying MACCE (Major Adverse Cardiac and Cerebrovascular Events) criteria. The complex oral microbiome was evaluated depending on CV outcome. The mathematical data processing included Qiime 2 software workflow and DADA2 pipeline as well as Human Oral Microbiome Database (HOMD) and Greengenes database classification. For identifying biomarkers distinguishing patients suffering from secondary CV events, the Cox Proportional Hazard Model for survival analysis was applied. RESULTS: In total, 19,418 Operational Taxonomic Units (OTU) were mapped according to the HOMD and Greengenes database. No significant differences in alpha and beta diversity were linked to CV outcomes (Shannon index; Principal Coordinates Analysis). No biomarker predicting secondary CV events were identified applying the area under the receiver operating characteristic curve (AUC) model. However, in survival analysis, one biomarker of Saccharibacteria phylum (class: TM7-3, order: CW040, family: F16) was associated with the incidence of a secondary CV event (p = 0.016). CONCLUSIONS: For the first time, a subgingival biomarker has been identified that supports a cardiovascular prognosis in CV patients undergoing coronary artery bypass grafting.