Isoproterenol induced cardiac hypertrophy: A comparison of three doses and two delivery methods in C57BL/6J mice.

Heart Failure (HF) continues to be a complex public health issue with increasing world population prevalence. Although overall mortality has decreased for HF and hypertrophic cardiomyopathy (HCM), a precursor for HF, their prevalence continues to increase annually. Because the etiology of HF and HCM is heterogeneous, it has been difficult to identify novel therapies to combat these diseases. Isoproterenol (ISP), a non-selective ß-adrenoreceptor agonist, is commonly used to induce cardiotoxicity and cause acute and chronic HCM and HF in mice. However, the variability in dose and duration of ISP treatment used in studies has made it difficult to determine the optimal combination of ISP dose and delivery method to develop a reliable ISP-induced mouse model for disease. Here we examined cardiac effects induced by ISP via subcutaneous (SQ) and SQ-minipump (SMP) infusions across 3 doses (2, 4, and 10mg/kg/day) over 2 weeks to determine whether SQ and SMP ISP delivery induced comparable disease severity in C57BL/6J mice. To assess disease, we measured body and heart weight, surface electrocardiogram (ECG), and echocardiography recordings. We found all 3 ISP doses comparably increase heart weight, but these increases are more pronounced when ISP was administered via SMP. We also found that the combination of ISP treatment and delivery method induces contrasting heart rate, RR interval, and R and S amplitudes that may place SMP treated mice at higher risk for sustained disease burden. Mice treated via SMP also had increased heart wall thickness and LV Mass, but mice treated via SQ showed greater increase in gene markers for hypertrophy and fibrosis. Overall, these data suggest that at 2 weeks, mice treated with 2, 4, or 10mg/kg/day ISP via SQ and SMP routes cause similar pathological heart phenotypes but highlight the importance of drug delivery method to induce differing disease pathways.

Incremental Benefit of Stepwise Nonpulmonary Vein Trigger Provocation During Catheter Ablation of Atrial Fibrillation.

BACKGROUND: The importance of nonpulmonary vein (PV) triggers for the initiation/recurrence of atrial fibrillation (AF) is well established. OBJECTIVES: This study sought to assess the incremental benefit of provocative maneuvers for identifying non-PV triggers. METHODS: We included consecutive patients undergoing first-time AF ablation between 2020 and 2022. The provocation protocol included step 1, identification of spontaneous non-PV triggers after cardioversion of AF and/or during sinus rhythm; step 2, isoproterenol infusion (3, 6, 12, and 20-30 µg/min); and step 3, atrial burst pacing to induce AF followed by cardioversion during residual or low-dose isoproterenol infusion or induce focal atrial tachycardia. Non-PV triggers were defined as non-PV ectopic beats triggering AF or sustained focal atrial tachycardia. RESULTS: Of 1,372 patients included, 883 (64.4%) underwent the complete stepwise provocation protocol with isoproterenol infusion and burst pacing, 334 (24.3%) isoproterenol infusion only, 77 (5.6%) burst pacing only, and 78 (5.7%) no provocative maneuvers (only step 1). Overall, 161 non-PV triggers were found in 135 (9.8%) patients. Of these, 51 (31.7%) non-PV triggers occurred spontaneously, and the remaining 110 (68.3%) required provocative maneuvers for induction. Among those receiving the complete stepwise provocation protocol, there was a 2.2-fold increase in the number of patients with non-PV triggers after isoproterenol infusion, and the addition of burst pacing after isoproterenol infusion led to a total increase of 3.6-fold with the complete stepwise provocation protocol. CONCLUSIONS: The majority of non-PV triggers require provocative maneuvers for induction. A stepwise provocation protocol consisting of isoproterenol infusion followed by burst pacing identifies a 3.6-fold higher number of patients with non-PV triggers.

Heartbeat-evoked neural response abnormalities in generalized anxiety disorder during peripheral adrenergic stimulation.

Hyperarousal symptoms in generalized anxiety disorder (GAD) are often incongruent with the observed physiological state, suggesting that abnormal processing of interoceptive signals is a characteristic feature of the disorder. To examine the neural mechanisms underlying interoceptive dysfunction in GAD, we evaluated whether adrenergic modulation of cardiovascular signaling differentially affects the heartbeat-evoked potential (HEP), an electrophysiological marker of cardiac interoception, during concurrent electroencephalogram and functional magnetic resonance imaging (EEG-fMRI) scanning. Intravenous infusions of the peripheral adrenergic agonist isoproterenol (0.5 and 2.0 micrograms, µg) were administered in a randomized, double-blinded and placebo-controlled fashion to dynamically perturb the cardiovascular system while recording the associated EEG-fMRI responses. During the 0.5 µg isoproterenol infusion, the GAD group (n = 24) exhibited significantly larger changes in HEP amplitude in an opposite direction than the healthy comparison (HC) group (n = 24). In addition, the GAD group showed significantly larger absolute HEP amplitudes than the HC group during saline infusions, when cardiovascular tone did not increase. No significant group differences in HEP amplitude were identified during the 2.0 µg isoproterenol infusion. Using analyzable blood oxygenation level-dependent fMRI data from participants with concurrent EEG-fMRI data (21 GAD and 21 HC), we found that the aforementioned HEP effects were uncorrelated with fMRI signals in the insula, ventromedial prefrontal cortex, dorsal anterior cingulate cortex, amygdala, and somatosensory cortex, brain regions implicated in cardiac signal processing in prior fMRI studies. These findings provide additional evidence of dysfunctional cardiac interoception in GAD and identify neural processes at the electrophysiological level that may be independent from blood oxygen level-dependent responses during peripheral adrenergic stimulation.

Electrophysiological characteristics of atrial tachycardia recurrence: Relevance to catheter ablation strategies in adults with congenital heart disease.

BACKGROUND: Catheter ablation outcomes for adults with congenital heart disease (ACHD) are described, but recurrence mechanisms remain largely unknown. OBJECTIVE: The purpose of this study was to identify the electrophysiological characteristics of atrial tachycardia (AT) recurrence in ACHD. METHODS: ACHD atrial tachycardia procedures over a 10-year period were explored for AT or atrial fibrillation (AF) recurrence. RESULTS: At 299 procedures in 250 ACHD (mean age 39 ± 15 years; 130 [52%] male), 464 ATs (360 intra-atrial reentrant tachycardia, 104 focal AT; median 2 [IQR 1-3] ATs per procedure) were targeted. Complete (n = 256 [86%]) or partial (n = 37 [12%]) success was achieved in 98% of procedures. Over a median of 3.0 (IQR 1.4-5.3) years of follow-up, 67 patients (27%) developed AT/AF recurrence after the index procedure. Repeat vs index tachycardias were more often focal AT (26/69 [38%] vs 73/378 [19%]; P < .001), demonstrated longer cycle length (325 ms vs 280 ms; P = .003), required isoproterenol (34/69 [50%] vs 121/378 [32%]; P = .03), and involved the pulmonary venous atrium (PVA)/septum (26/69 [38%] vs 67/378 [18%]; P < .001). AF history (hazard ratio [HR] 2.0; interquartile range [IQR] 1.2-3.4; P = .01), incomplete success (HR 3.6; IQR 2.1-6.4; P < .001), and PVA substrate (HR 2.1; IQR 1.2-3.5; P = .006) were independently associated with AT/AF recurrence. With complete index procedure success and no AF history, 5-year actuarial freedom from AT/AF and AT alone were 77% and 80%. CONCLUSION: After catheter ablation in ACHD, repeat ATs were more frequently focal, required isoproterenol administration, or involved intra-atrial reentrant tachycardia within the PVA or atrial septum. Negative factors were partial success, index PVA substrate, and remote history of AF. These data support aggressive pharmacological provocation to eliminate all inducible tachycardias and coexisting PVA substrates at index procedures for ACHD.

Combined agonists act synergistically to increase mucociliary clearance in a cystic fibrosis airway model.

Mucus clearance, a primary innate defense mechanism of airways, is defective in patients with cystic fibrosis (CF) and CF animals. In previous work, the combination of a low dose of the cholinergic agonist, carbachol with forskolin or a ß adrenergic agonist, isoproterenol synergistically increased mucociliary clearance velocity (MCCV) in ferret tracheas. Importantly, the present study shows that synergistic MCCV can also be produced in CF ferrets, with increases ~ 55% of WT. Synergistic MCCV was also produced in pigs. The combined agonists increased MCCV by increasing surface fluid via multiple mechanisms: increased fluid secretion from submucosal glands, increased anion secretion across surface epithelia and decreased Na+ absorption. To avoid bronchoconstriction, the cAMP agonist was applied 30 min before carbachol. This approach to increasing mucus clearance warrants testing for safety and efficacy in humans as a potential therapeutic for muco-obstructive diseases.

1, 8-cineole protects against ISO-induced heart failure by inhibiting oxidative stress and ER stress in vitro and in vivo.

Sugemule-3 is widely adopted in clinical practice to manage cardio-cerebral diseases. 1, 8-cineole is the main ingredient of Sugemule-3, however, the underlying cellular mechanisms for its protective effect are poorly understood. 1, 8-cineole improved the survival of H9C2 cardiomyocytes during isoproterenol (ISO) injury and reduced ISO-induced apoptosis. Compared to the ISO group, 1, 8-cineole highly attenuated the generation of ISO-induced reactive oxygen species (ROS), the depolarization of △ψm, suppression of the Bax/Bcl-2 ratio, and p-caspase 3 expression, in vitro. Furthermore, 1, 8-cineole treatment in H9C2 cardiomyocytes lowered the expressions of 78-kDa glucose-regulated protein (GRP78), p-protein kinase-like ER kinase (PERK), activation of transcription factor (ATF) 4, and ER stress effector protein C/EBP and homologous protein (CHOP). These findings implied that 1, 8-cineole contribute to cardioprotection via the GRP78/CHOP pathways. Using animal models, 1, 8-cineole was revealed to markedly alleviate ISO-induced heart injury, and reduce cardiac hypertrophy, formation of the cytoplasmic vacuole, loss of myofiber, and fibrosis by inhibiting oxidative stress and ER stress. 1, 8-cineole reduces apoptosis by inhibiting signaling pathways related to oxidative stress and ER stress. These findings implicate 1, 8-cineole as a potential therapeutic target for cardiac hypertrophy-related heart diseases, including heart failure.

Betalain exerts cardioprotective and anti-inflammatory effects against the experimental model of heart failure.

Betalain is a natural plant pigment known to elicit various biological activities. However, studies on the protective effect of betalain against heart failure have not reported yet. The experimental model of heart failure was created in Wistar rats using isoproterenol (ISO). The animals were randomly assigned into four groups such as sham-control, ISO-induced heart failure, betalain pretreated before ISO induction (50 mg/kg/day), and betalain drug control group were maintained for 6 weeks. At the end of the experimental period, anti-oxidant enzymes, inflammatory markers, matrix proteins, cardiac-specific markers, and micro RNAs were elucidated using RT-PCR, and ELISA analysis. The results demonstrated that the rats induced with ISO displayed an abnormality in cardiac functions, increased oxidative stress markers (p < 0.01), inflammatory cytokines (p < 0.01) while abrogated the expression of miR-18a, and increased miR-199a. While betalain pre-treated rats prevented the cardiac failure significantly (p < 0.01) with improved anti-oxidant enzymes, abrogated the inflammatory signals with restored matrix proteins, cardiac biomarker genes, and attenuated miR-423 and miR-27 compared to heart failure rats. The results of the study suggest that the betalain treatment protected the hearts from failing via microRNA mediated activation the anti-inflammatory signaling and restoring the matrix protein modulation.

Inhibition of double stranded RNA dependent protein kinase (PKR) abrogates isoproterenol induced myocardial ischemia in vitro in cultured cardiomyocytes and in vivo in wistar rats.

Protein kinase R (PKR) plays a main role in inflammation, insulin resistance, and glucose balance. It is activated by various stress signals and is key mediators of diabetes and associated complications. In the present study, we investigated the effect of PKR inhibition on myocardial dysfunction, inflammatory, cell death and interrelated signalling pathways in isoproterenol induced myocardial ischemia in vivo in wistar rats and in vitro in cultured cardiomyocytes. H9C2 rat cardiomyocytes were treated with 10 µM Isoproterenol (ISO). For in vivo studies, rats were divided into 4 groups: control, ischemic group (ISO), preventive group, curative group and each group consist of 8 rats. Myocardial Ischemia (MI) was induced with two subsequent doses of ISO (100 mg/kg, s.c.). The rats were treated with PKR inhibitor, C16 (166.5 µg/kg, i.p.) for 14 days. Heart rate, systolic, diastolic and mean arterial pressures were measured by non-invasive BP apparatus. Cardiac biomarkers were measured by commercial kits. Ischemic Zone, Morphological abnormalities and fibrosis of heart was detected by TTC, haematoxylin & eosin staining, Masson's and Sirius red staining respectively. Protein expression was done by western blotting and immune histochemistry. mRNA expression was done by RT-PCR. MI was characterized by declined myocardial performance along with elevation of cardiac biomarkers and associated with increased expression of PKR, oxidative-nitrosative stress, activated various inflammatory pathways (nuclear factor kappa light chain enhancer of activated B cells -NF-κB); Mitogen-activated protein kinases-MAPK; c-Jun N-terminal kinase-JNK), increased expression of inflammatory markers (Tumour necrosis factor alpha-TNF-α), markers of fibrosis (Alpha smooth muscle actin -α-SMA; Transforming growth factor beta-TGF-ß), enhanced cell death (Ischemic zone) and increased expression of extracellular regulated-kinases (ERK-1/2) and advanced glycation end products (AGE's). Interestingly, inhibition of PKR attenuated myocardial dysfunction, cardiac fibrosis, oxidative/nitrosative stress, inflammation, cell death, and inter-related signalling pathways. Our findings report that inhibition of PKR improves the ischemic mediated inflammation, apoptosis, cardiac hypertrophy and fibrosis in MI induced rats. Hence, inhibition of PKR might be one of intervention therapy for the treatment of myocardial ischemia.

Andrographolide protects against isoproterenol-induced myocardial infarction in rats through inhibition of L-type Ca2+ and increase of cardiac transient outward K+ currents.

Myocardial infarction (MI) is the irreversible injury of the myocardium caused by prolonged myocardial ischemia and is a major cause of heart failure and eventual death among ischemic patients. The present study assessed the protective potentials of andrographolide against isoproterenol-induced myocardial infarction in rats. Animals were randomly divided into four groups: Control (Ctr) group received 0.9% saline solution once daily for 21 days, Isoproterenol (Iso) group received 0.9% saline solution once daily for 19 days followed by 80 mg/kg/day of isoproterenol hydrochloride solution on day 20 and 21, Andrographolide (Andro) group received 20 mg/kg/day of andrographolide for 21 days, and Andrographolide plus Isoproterenol (Andro + Iso) group received 20 mg/kg/day of andrographolide for 21 days with co-administration of 80 mg/kg/day of isoproterenol hydrochloride solution on day 20 and 21. After all treatments, cardiac-specific parameters that define cardiac health and early subacute MI were measured in all groups using both biophysical and pharmacological assay methods. Isoproterenol administration significantly (P < 0.05) increased cardiac mass indexes, systemic cardiac biomarkers, infarct size and caused cardiac histological alterations; significantly (P < 0.05) increased heart rate, QRS & QTc intervals and caused ST-segment elevation; significantly (P < 0.05) increased myocytes shortening, action potential duration (APD), L-type Ca2+ current (ICa,L) density and significantly (P < 0.05) decreased transient outward K+ current (Ito) density typical of the early subacute MI. Interestingly, pretreatment with andrographolide prevented and or minimized these anomalies, notably, by reducing ICa,L density and increasing Ito density significantly. Therefore, andrographolide could be seen as a promising therapeutic agent capable of making the heart resistant to early subacute infarction and it could be used as template for the development of semisynthetic drug(s) for cardiac protection against MI.

Obstructive sleep apnoea increases lipolysis and deteriorates glucose homeostasis in patients with type 2 diabetes mellitus.

Obstructive sleep apnoea (OSA) is associated with type 2 diabetes mellitus (T2DM). However, mechanisms mediating association between these two conditions remain unclear. This study investigated, whether the OSA-associated changes in adipose tissue lipolysis might contribute to impaired glucose homeostasis in patient with T2DM. Thirty-five matched subjects were recruited into three groups: T2DM + severe OSA (T2DM + OSA, n = 11), T2DM with mild/no OSA (T2DM, n = 10) and healthy controls (n = 14). Subcutaneous abdominal adipose tissue microdialysis assessed spontaneous, epinephrine- and isoprenaline-stimulated lipolysis. Glucose metabolism was assessed by intravenous glucose tolerance test. Spontaneous lipolysis was higher in the T2DM + OSA compared with the T2DM (60.34 ± 23.40 vs. 42.53 ± 10.16 µmol/L, p = 0.013), as well as epinephrine-stimulated lipolysis (236.84 ± 103.90 vs. 167.39 ± 52.17 µmol/L, p < 0.001). Isoprenaline-stimulated lipolysis was unaffected by the presence of OSA (p = 0.750). The α2 anti-lipolytic effect was decreased in T2DM + OSA by 59% and 315% compared with T2DM and controls (p = 0.045 and p = 0.007, respectively). The severity of OSA (AHI) was positively associated with spontaneous (p = 0.037) and epinephrine-stimulated (p = 0.026) lipolysis. The α2-adrenergic anti-lipolytic effect (p = 0.043) decreased with increasing AHI. Spontaneous lipolysis was positively associated with Insulin resistance (r = 0.50, p = 0.002). Epinephrine-stimulated lipolysis was negatively associated with the Disposition index (r = - 0.34, p = 0.048). AHI was positively associated with Insulin resistance (p = 0.017) and negatively with the Disposition index (p = 0.038). Severe OSA in patients with T2DM increased adipose tissue lipolysis, probably due to inhibition of the α2-adrenergic anti-lipolytic effect. We suggest that dysregulated lipolysis might contribute to OSA-associated impairments in insulin secretion and sensitivity.

The cardioprotective effect of microRNA-103 inhibitor against isoprenaline-induced myocardial infarction in mice through targeting FADD/RIPK pathway.

OBJECTIVE: The current study investigates the effect of the innovative phosphorothioate modified backbone locked nucleic acid (LNA) of microRNA-103 (miR-103) specifically designed for systemic delivery in the silencing of miR-103 in experimentally induced myocardial infarction (MI). MicroRNA-103 is a small non-coding RNA which regulates Fas-associated protein with death domain (FADD) gene expression, which is a negative regulator for necroptosis occurs during the progression of MI. MATERIALS AND METHODS: Experimental male mice were allocated into three groups; the first group received normal saline, the second group was injected with isoprenaline and served as the infarcted control, while the third group was treated with LNA miR-103 power inhibitor before isoprenaline injection. Blood and heart samples were used for biochemical analysis of miR-103, FADD, receptor-interacting protein kinase (RIPK), nuclear factor-κß, tumor necrosis factor-α, interleukin-6, troponin-I and creatine kinase-MB (CK-MB) as well as the histological examination of heart tissue. RESULTS: The treated mice showed marked improvement in the troponin-I and CK-MB levels with almost normal histological structure of heart tissue. Significant inhibition of miR-103 accompanied by increased FADD expression and markedly decreased expression of the other biomarkers were observed in the hearts of the treated mice. CONCLUSIONS: LNA miR-103 inhibitor is a potent cardioprotective agent and can be a promising treatment against MI through targeting FADD/RIPK pathway.

Effect of engineered superparamagnetic iron oxide nanoparticles in targeted cardiac precursor cell delivery by MRI.

A scientific approach is presented describing the fabrication of nanoprobe (GloTrack) that can act as cardiac precursor label to segregate cells from cardiac/non cardiac origins and traced by magnetic resonance imaging (MRI). Signal regulatory protein alpha (SIRPA) and kinase domain receptor (KDR) recognizing antibodies, form a layer on super paramagnetic iron oxide nanoparticle - poly-ethylene glycol (SPION-PEG) complex, and bind to protein expressed on the surface of cardiac muscle cells. Physical attributes size, distribution, labelling efficiency, echocardiogram (ECG) changes and bio-distribution by MRI were analysed. The results indicate that GloTrack has an average size of 471 nm, exhibits negative potential and promotes labelling efficiency. The bio-distribution of GloTrack in in vivo experiments was traceable in 7T MRI showing high accumulation of GloTrack in cardiac muscles as compared to the liver and spleen. ECG data revealed that GloTrack segregated cardiac precursors has the potential benefit in treating heart failure, thereby paving way in the development of minimal cell manipulation with targeted cell delivery approaches.

Usefulness of an isoproterenol infusion to differentiate a left atrial appendage thrombus in a patient with nonvalvular atrial fibrillation.

A 78-year-old male with a history of a cardiac embolic stroke due to persistent AF and cerebral bleeding (CHADS2 score 4, HAS-BLED score 4) was referred to our hospital to implant a left atrial appendage (LAA) closure (LAAC) device. A trans esophageal echocardiography was performed and a high echoic lesion that was difficult to differentiate the spontaneous echo contrast or thrombus was found in the LAA cavity. After isoproterenol infusion, a high echoic lesion disappeared and we confirmed that it was not an LAA thrombus. Successful LAAC device implantation was performed without any thromboembolic events.

A multiscale model of cardiac concentric hypertrophy incorporating both mechanical and hormonal drivers of growth.

Growth and remodeling in the heart is driven by a combination of mechanical and hormonal signals that produce different patterns of growth in response to exercise, pregnancy, and various pathologies. In particular, increases in afterload lead to concentric hypertrophy, a thickening of the walls that increases the contractile ability of the heart while reducing wall stress. In the current study, we constructed a multiscale model of cardiac hypertrophy that connects a finite-element model representing the mechanics of the growing left ventricle to a cell-level network model of hypertrophic signaling pathways that accounts for changes in both mechanics and hormones. We first tuned our model to capture published in vivo growth trends for isoproterenol infusion, which stimulates ß-adrenergic signaling pathways without altering mechanics, and for transverse aortic constriction (TAC), which involves both elevated mechanics and altered hormone levels. We then predicted the attenuation of TAC-induced hypertrophy by two distinct genetic interventions (transgenic Gq-coupled receptor inhibitor overexpression and norepinephrine knock-out) and by two pharmacologic interventions (angiotensin receptor blocker losartan and ß-blocker propranolol) and compared our predictions to published in vivo data for each intervention. Our multiscale model captured the experimental data trends reasonably well for all conditions simulated. We also found that when prescribing realistic changes in mechanics and hormones associated with TAC, the hormonal inputs were responsible for the majority of the growth predicted by the multiscale model and were necessary in order to capture the effect of the interventions for TAC.

Efficacy of isoproterenol in the evaluation of dormant conduction and arrhythmogenic foci identification in atrial fibrillation ablation.

BACKGROUND: Catheter ablation for atrial fibrillation (AF) is an established therapy. However, postoperative recurrence is a serious issue caused by the reconduction of the isolated pulmonary veins (PV) and the onset of non-PV foci. The objectives of this study were to elucidate dormant conduction, confirm PV arrhythmia substrate, induce non-PV foci after PV isolation, and assess the acute efficacy of high dose isoproterenol (ISP) when administered in addition to adenosine. METHODS: The study consisted of 100 patients with drug-refractory AF (paroxysmal and persistent) who underwent ablation therapy (either radio-frequency or cryoballoon ablation) as the first-line of therapy at our hospital. All patients first underwent PV isolation (PVI) and were administered adenosine followed by ISP (6 µg × 5 min). The effects were observed, and the therapeutic strategy was evaluated. RESULTS: Persistent dormant conduction due to ISP administration was observed in 13 patients. In over half of the patients, arrhythmia substrates were identified in the PV. Ten patients presented with persistent PV firing. The ablation of non-PV foci was additionally performed in 23 patients. CONCLUSIONS: We found that dormant conduction, as a result of ISP administration, is persistent and ISP is useful when performing an ablation. In addition, ISP administration is useful for the identification of PV arrhythmia substrates and induction of non-PV foci. However, the effectiveness of ISP may be partially due to the complementary effect of adenosine, and, therefore, a combination of the two drugs seems preferable.

Regenerative Potential of a Suspension and Spheroids of Multipotent Mesenchymal Stromal Cells from Human Umbilical Cord on the Model of Myocardial Infarction in Rats.

Regenerative potential of multipotent mesenchymal stromal cells from the human umbilical cord (MMSC-UC) in the suspension and spheroid form was revealed during the progression of experimental small focal myocardial infarction in rats. In isoproterenol-induced myocardial infarction, foci of necrosis and inflammatory infiltrate and at later terms fibrosis foci were found mainly in the left ventricle of rat heart. In rats receiving MMSC-UC, destructive changes in the myocardium, fibrous scars, and inflammatory process were less pronounced. MMSC-UC also contributed to normalization of the morphofunctional parameters of the heart. Spheroids exhibited higher efficiency in comparison with cell suspension.

Effects of ß-adrenergic stimulation on fetal heart rate, heart rate variability, and T-wave elevation during brief umbilical cord occlusions in fetal sheep.

Circulating catecholamines are critical for fetal adaptation to hypoxia by regulating fetal heart rate (FHR) and promoting myocardial contractility and peripheral vasoconstriction. They have been hypothesized to contribute to changes in FHR variability (FHRV) and T-wave morphology, clinical indexes of fetal well-being during labor. ß-Adrenergic blockade with propranolol does not affect FHRV during labor-like hypoxemia and only attenuated the increase in T-wave height between the episodes of hypoxemia. To further investigate the potential role of catecholamines, we investigated whether pharmacological ß-adrenergic stimulation could increase FHRV and T-wave elevation during intermittent labor-like hypoxemia. Nineteen chronically instrumented fetal sheep at 0.85 of gestation received isoprenaline hydrochloride (n = 7) or saline (control, n = 12), followed by three 1-min complete umbilical cord occlusions (UCOs) separated by 4-min reperfusion periods. Before the UCOs, infusion of isoprenaline increased FHR (P < 0.001), absolute-T/QRS ratio (P < 0.001), and one measure of FHRV [root-mean-square of successive RR interval differences (RMSSD), P < 0.05]. UCOs triggered deep FHR decelerations. During UCOs, isoprenaline was associated with increased FHR (P < 0.001) and absolute-T/QRS ratio (P < 0.05), but no effect on T/QRS ratio was observed when normalized to baseline before UCOs (normalized-T/QRS ratio). Between UCOs, isoprenaline increased FHR (P < 0.001) and absolute-T/QRS ratio (P < 0.05) but did not affect normalized-T/QRS ratio or any measures of FHRV. Arterial pressure was not affected by isoprenaline at any point. Our findings indicate that circulating catecholamines regulate FHR but not FHRV during labor-like hypoxemia and promote T-wave elevation between but not during intermittent fetal hypoxemia.

Deletion of Microfibrillar-Associated Protein 4 Attenuates Left Ventricular Remodeling and Dysfunction in Heart Failure.

Background Cardiac remodeling predisposes individuals to heart failure if the burden is not solved, and heart failure is a growing cause of morbidity and mortality worldwide. The cardiac extracellular matrix not only provides structural support, but also is a core aspect of the myocardial response to various biomechanical stresses and heart failure. MFAP4 (microfibrillar-associated protein 4) is an integrin ligand located in the extracellular matrix, whose biological functions in the heart remain poorly understood. In the current study we aimed to test the role of MFAP4 in cardiac remodeling. Methods and Results MFAP4-deficient (MFAP4-/-) and wild-type mice were subjected to aortic banding surgery and isoproterenol to establish models of cardiac remodeling. We also evaluated the functional effects of MFAP4 on cardiac hypertrophy, fibrosis, and cardiac electrical remodeling. The expression of MFAP4 was increased in the animal cardiac remodeling models induced by pressure overload and isoproterenol. After challenge of 8 weeks of aortic banding or 2 weeks of intraperitoneal isoproterenol, MFAP4-/- mice exhibited lower levels of cardiac fibrosis and fewer ventricular arrhythmias than wild-type mice. However, there was no significant effect on cardiomyocyte hypertrophy. In addition, there was no significant difference in cardiac fibrosis severity, hypertrophy, or ventricular arrhythmia incidence between wild-type-sham and knockout-sham mice. Conclusions These findings are the first to demonstrate that MFAP4 deficiency inhibits cardiac fibrosis and ventricular arrhythmias after challenge with 8 weeks of aortic banding or 2 weeks of intraperitoneal isoproterenol but does not significantly affect the hypertrophy response. In addition, MFAP4 deficiency had no significant effect on cardiac fibrosis, hypertrophy, or ventricular arrhythmia in the sham group in this study.

Preparation of Ginkgolide Solid Dispersions with Low-Molecular-Weight Chitosan and Assessment of their Protective Effect on Isoproterenol- Induced Myocardial Injury.

BACKGROUND: Ginkgolides are widely used in cardio-protective therapy; however, poor bioavailability currently limits their application. OBJECTIVE: The purpose of this study was to demonstrate whether solid dispersions prepared with Low- Molecular-Weight Chitosan (LMWC) could improve the protective effect of ginkgolides on Myocardial Injury (MI). METHODS: Ginkgolide Solid Dispersions (GKSD) were prepared with LMWC. Their properties were then characterized using differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. In vivo pharmacokinetic studies were performed in rats, and the protective effect of GKSD on MI was investigated by western blotting and immunohistochemical analyses. RESULTS: Drug dissolution testing showed that GDSD were released at a significantly higher rate than ginkgolides, dissolved by alternative methods, suggesting that LMWC facilitates the release of ginkgolides. Differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy all showed that GKSD was amorphous. In-vivo testing revealed larger AUC0-t, higher Cmax, and shorter Tmax for GKSD compared to that in original ginkgolides. Myocardial injury was induced in rats with isoproterenol to test the protective effect of GKSD. GKSD alleviated MI and reduced myocardial fibrosis, as observed by Hematoxylin and Eosin staining. Compared with the crude drug group, the secretion of malonyl dialdehyde and nitric oxide and expression of NOX-2 and NOX-4 were lower. The activities of the cardiac marker enzymes SOD, CAT, GPX, GPX-1, and GSH were higher in GKSD-administered rats, indicating a beneficial effect of GKSD in eliminating free radicals during myocardial injury. Additionally, western blotting and immunohistochemical analysis showed that GKSD markedly reduced the expression of signaling proteins RHOA, ROCK1, ROCK2, and RAC1. CONCLUSION: Solid dispersions prepared with low molecular weight chitosan improved the oral bioavailability of ginkgolide and enhanced its protective effect on myocardial injury.