Electrophysiological characteristics of the rat azygos vein under electrical pacing and adrenergic stimulation

Stable Gastric Pentadecapeptide BPC 157 as Useful Cytoprotective Peptide Therapy in the Heart Disturbances, Myocardial Infarction, Heart Failure, Pulmonary Hypertension, Arrhythmias, and Thrombosis Presentation

In heart disturbances, stable gastric pentadecapeptide BPC 157 especial therapy effects combine the therapy of myocardial infarction, heart failure, pulmonary hypertension arrhythmias, and thrombosis prevention and reversal. The shared therapy effect occurred as part of its even larger cytoprotection (cardioprotection) therapy effect (direct epithelial cell protection; direct endothelium cell protection) that BPC 157 exerts as a novel cytoprotection mediator, which is native and stable in human gastric juice, as well as easily applicable. Accordingly, there is interaction with many molecular pathways, combining maintained endothelium function and maintained thrombocytes function, which counteracted thrombocytopenia in rats that underwent major vessel occlusion and deep vein thrombosis and counteracted thrombosis in all vascular studies; the coagulation pathways were not affected. These appeared as having modulatory effects on NO-system (NO-release, NOS-inhibition, NO-over-stimulation all affected), controlling vasomotor tone and the activation of the Src-Caveolin-1-eNOS pathway and modulatory effects on the prostaglandins system (BPC 157 counteracted NSAIDs toxicity, counteracted bleeding, thrombocytopenia, and in particular, leaky gut syndrome). As an essential novelty noted in the vascular studies, there was the activation of the collateral pathways. This might be the upgrading of the minor vessel to take over the function of the disabled major vessel, competing with and counteracting the Virchow triad circumstances devastatingly present, making possible the recruitment of collateral blood vessels, compensating vessel occlusion and reestablishing the blood flow or bypassing the occluded or ruptured vessel. As a part of the counteraction of the severe vessel and multiorgan failure syndrome, counteracted were the brain, lung, liver, kidney, gastrointestinal lesions, and in particular, the counteraction of the heart arrhythmias and infarction.

α1-adrenergic receptors accompanied by GATA4 expression are related to proarrhythmic conduction and automaticity in rat interatrial septum

The development of interatrial septum (IAS) is a complicated process, which continues during postnatal life. The hypertrophic signals in developing heart are mediated among others by α-adrenergic pathways. These facts suggest the presence of specific electrophysiological features in developing IAS. This study was aimed to investigate the electrical activity in the tissue preparations of IAS from rat heart in normal conditions and under stimulation of adrenoreceptors. Intracellular recording of electrical activity revealed less negative level of resting membrane potential in IAS if compared to myocardium of left atrium. In normal conditions, non-paced IAS preparations were quiescent, but noradrenaline (10^-5 M) and phenylephrine (10^-5 M) induced spontaneous action potentials, which could be abolished by α1-blocker prazosin (10^-5 M), but not β1-blocker atenolol (10^-5 M). Optical mapping showed drastic phenylephrine-induced slowing of conduction in adult rat IAS. The α1-dependent ectopic automaticity of IAS myocardium might be explained by immunohistochemical data indicating the presence of transcription factor GATA4 and abundant α1A-adrenoreceptors in myocytes from adult rat IAS. An elevated sensitivity to adrenergic stimulation due to involvement of α1-adrenergic pathways may underlie increased proarrhythmic potential of adult IAS at least in rats.

Therapy Effect of the Stable Gastric Pentadecapeptide BPC 157 on Acute Pancreatitis as Vascular Failure-Induced Severe Peripheral and Central Syndrome in Rats

We revealed the therapy effect of the stable gastric pentadecapeptide BPC 157 (10 μg/kg, 10 ng/kg ig or po) with specific activation of the collateral rescuing pathways, the azygos vein, on bile duct ligation in particular, and acute pancreatitis as local disturbances (i.e., improved gross and microscopy presentation, decreased amylase level). Additionally, we revealed the therapy’s effect on the acute pancreatitis as vascular failure and multiorgan failure, both peripherally and centrally following “occlusion-like” syndrome, major intoxication (alcohol, lithium), maintained severe intra-abdominal hypertension, and myocardial infarction, or occlusion syndrome, and major vessel occlusion. The application-sacrifice periods were ligation times of 0–30 min, 0–5 h, 0–24 h (cured periods, early regimen) and 4.30 h–5 h, 5 h–24 h (cured periods, delayed regimen). Otherwise, bile duct-ligated rats commonly presented intracranial (superior sagittal sinus), portal and caval hypertension and aortal hypotension, gross brain swelling, hemorrhage and lesions, heart dysfunction, lung lesions, liver and kidney failure, gastrointestinal lesions, and severe arterial and venous thrombosis, peripherally and centrally. Unless antagonized with the key effect of BPC 157 regimens, reversal of the inferior caval and superior mesenteric vein congestion and reversal of the failed azygos vein activated azygos vein-recruited direct delivery to rescue the inferior-superior caval vein pathway; these were all antecedent to acute pancreatitis major lesions (i.e., acinar, fat necrosis, hemorrhage). These lesions appeared in the later period, but were markedly attenuated/eliminated (i.e., hemorrhage) in BPC 157-treated rats. To summarize, while the innate vicious cycle may be peripheral (bile duct ligation), or central (rapidly developed brain disturbances), or peripheral and central, BPC 157 resolved acute pancreatitis and its adjacent syndrome.

Stable Gastric Pentadecapeptide BPC 157 May Counteract Myocardial Infarction Induced by Isoprenaline in Rats

We revealed that the stable gastric pentadecapeptide BPC 157, a useful peptide therapy against isoprenaline myocardial infarction, as well as against isoprenaline myocardial reinfarction, may follow the counteraction of the recently described occlusion-like syndrome, induced peripherally and centrally, which was described for the first time in isoprenaline-treated rats. BPC 157 (10 ng/kg, 10 µg/kg i.p.), L-NAME (5 mg/kg i.p.), and L-arginine (200 mg/kg i.p.) were given alone or together at (i) 30 min before or, alternatively, (ii) at 5 min after isoprenaline (75 or 150 mg/kg s.c.). At 30 min after isoprenaline 75 mg/kg s.c., we noted an early multiorgan failure (brain, heart, lung, liver, kidney and gastrointestinal lesions), thrombosis, intracranial (superior sagittal sinus) hypertension, portal and caval hypertension, and aortal hypotension, in its full presentation (or attenuated by BPC 157 therapy (given at 5 min after isoprenaline) via activation of the azygos vein). Further, we studied isoprenaline (75 or 150 mg/kg s.c.) myocardial infarction (1 challenge) and reinfarction (isoprenaline at 0 h and 24 h, 2 challenges) in rats (assessed at the end of the subsequent 24 h period). BPC 157 reduced levels of all necrosis markers, CK, CK-MB, LDH, and cTnT, and attenuated gross (no visible infarcted area) and histological damage, ECG (no ST-T ischemic changes), and echocardiography (preservation of systolic left ventricular function) damage induced by isoprenaline. Its effect was associated with a significant decrease in oxidative stress parameters and likely maintained NO system function, providing that BPC 157 interacted with eNOS and COX2 gene expression in a particular way and counteracted the noxious effect of the NOS-blocker, L-NAME.

Automatic Activity Arising in Cardiac Muscle Sleeves of the Pulmonary Vein

Ectopic activity in the pulmonary vein cardiac muscle sleeves can both induce and maintain human atrial fibrillation. A central issue in any study of the pulmonary veins is their difference from the left atrial cardiac muscle. Here, we attempt to summarize the physiological phenomena underlying the occurrence of ectopic electrical activity in animal pulmonary veins. We emphasize that the activation of multiple signaling pathways influencing not only myocyte electrophysiology but also the means of excitation–contraction coupling may be required for the initiation of triggered or automatic activity. We also gather information regarding not only the large-scale structure of cardiac muscle sleeves but also recent studies suggesting that cellular heterogeneity may contribute to the generation of arrythmogenic phenomena and to the distinction between pulmonary vein and left atrial heart muscle.

The susceptibility of the rat pulmonary and caval vein myocardium to the catecholamine-induced ectopy changes oppositely in postnatal development

KEY POINTS

The developmental changes of the caval (SVC) and pulmonary vein (PV) myocardium electrophysiology are traced throughout postnatal ontogenesis. The myocardium in SVC as well as in PV demonstrate age-dependent differences in the ability to maintain resting membrane potential, to manifest automaticity in a form of ectopic action potentials in basal condition and in responses to the adrenergic stimulation. Electrophysiological characteristics of two distinct types of thoracic vein myocardium change in an opposite manner during early postnatal ontogenesis with increased proarrhythmicity of pulmonary and decreased automaticity in caval veins. Predisposition of PV cardiac tissue to proarrhythmycity develops during ontogenesis in time correlation with the establishment of sympathetic innervation of the tissue. The electrophysiological properties of caval vein cardiac tissue shift from a pacemaker-like phenotype to atrial phenotype in accompaniment with sympathetic nerve growth and adrenergic receptor expression changes.

ABSTRACT

The thoracic vein myocardium is considered as a main source for atrial fibrillation initiation due to its high susceptibility to ectopic activity. The mechanism by which and when pulmonary (PV) and superior vena cava (SVC) became proarrhythmic during postnatal ontogenesis is still unknown. In this study, we traced postnatal changes of electrophysiology in a correlation with the sympathetic innervation and adrenergic receptor distribution to reveal developmental differences in proarrhythmicity occurrence in PV and SVC myocardium. A standard microelectrode technique was used to assess the changes in ability to maintain resting membrane potential (RMP), generate spontaneous action potentials (SAP) and adrenergically induced ectopy in multicellular SVC and PV preparations of rats of different postnatal ages. Immunofluorescence imaging was used to trace postnatal changes in sympathetic innervation, β1- and α1A-adrenergic receptor (AR) distribution. We revealed that the ability to generate SAP and susceptibility to adrenergic stimulation changes during postnatal ontogenesis in an opposite manner in PV and SVC myocardium. While SAP occurrence decreases with age in SVC myocardium, it significantly increases in PV cardiac tissue. PV myocardium starts to demonstrate RMP instability and proarrhythmic activity from the 14th day of postnatal life which correlates with the appearance of the sympathetic innervation of the thoracic veins. In addition, postnatal attenuation of SVC myocardium automaticity occurs concomitantly with sympathetic innervation establishment and increase in β1-ARs, but not α1A-AR levels. Our results support the contention that SVC and PV myocardium electrophysiology change during postnatal development, resulting in higher PV proarrhythmicity in adults.

Attenuation of inward rectifier potassium current contributes to the α1-adrenergic receptor-induced proarrhythmicity in the caval vein myocardium

AIM

This study is aimed at investigation of electrophysiological effects of α1-adrenoreceptor (α1-AR) stimulation in the rat superior vena cava (SVC) myocardium, which is one of the sources of proarrhythmic activity.

METHODS

α1-ARs agonists (phenylephrine-PHE or norepinephrine in presence of atenolol-NE + ATL) were applied to SVC and atrial tissue preparations or isolated cardiomyocytes, which were examined using optical mapping, glass microelectrodes or whole-cell patch clamp. α1-ARs distribution was evaluated using immunofluorescence. Kir2.X mRNA and protein level were estimated using RT-PCR and Western blotting.

RESULTS

PHE or NE + ATL application caused a significant suppression of the conduction velocity (CV) of excitation and inexcitability in SVC, an increase in the duration of electrically evoked action potentials (APs), a decrease in the maximum upstroke velocity (dV/dt_max ) and depolarization of the resting membrane potential (RMP) in SVC to a greater extent than in atria. The effects induced by α1-ARs activation in SVC were attenuated by protein kinase C inhibition (PKC). The whole-cell patch clamp revealed PHE-induced suppression of outward component of I_K1 inward rectifier current in isolated SVC, but not atrial myocytes. These effects can be mediated by α1A subtype of α-ARs found in abundance in rat SVC. The basal I_K1 level in SVC was much lower than in atria as a result of the weaker expression of Kir2.2 channels.

CONCLUSION

Therefore, the reduced density of I_K1 in rat SVC cardiomyocytes and sensitivity of this current to α1A-AR stimulation via PKC-dependent pathways might lead to proarrhythmic conduction in SVC myocardium by inducing RMP depolarization, AP prolongation, CV and dV/dt_max decrease.