Inhibition of infarction-induced sympathetic innervation with endothelin receptor antagonism via a PI3K/GSK-3β-dependent pathway

Shikonin mitigates cyclophosphamide-induced cardiotoxicity in mice: the role of sirtuin-1, NLRP3 inflammasome, autophagy, and apoptosis

OBJECTIVES

The aim of this study was to elucidate the protective potential of shikonin (SHK) on cyclophosphamide (CP)-induced cardiotoxicity in Swiss albino mice.

METHODS

Mice received SHK in three different doses by oral gavage daily for 14 days and CP at 100 mg/kg, intraperitoneally once on the seventh day. On the 15th day, mice were euthanized, blood collected, and hearts were removed to estimate various biochemical and histopathological parameters.

KEY FINDINGS

CP significantly increased serum lactate dehydrogenase, creatine kinase-MB, troponin I and NT pro-BNP, and cardiac malondialdehyde and decreased cardiac total antioxidant capacity and Nrf2, whereas increased inflammatory markers in the cardiac tissues. CP also caused hypertrophy and fibrosis in the cardiac tissues via activation of IL6/JAK2/STAT3 while depressed SIRT1 and PI3K/p-Akt pathway with consequent increased apoptosis and dysregulation of autophagy. SHK treatment reversed these changes in a dose-dependent manner and showed a significant protective effect against CP-induced cardiotoxicity via suppressing oxidative stress, inflammation, and apoptosis with modulation of autophagy via induction of SIRT1/PI3K/p-Akt signaling.

CONCLUSIONS

Shikonin may be used as an adjuvant to cyclophosphamide in cancer treatment, but further research is needed to investigate its effects on cardiotoxicity in distinct animal cancer models.

Cardiac sympathetic hyperinnervation after myocardial infarction: a systematic review and qualitative analysis

BACKGROUND

Cardiac sympathetic hyperinnervation after myocardial infarction (MI) is associated with arrhythmogenesis and sudden cardiac death. The characteristics of cardiac sympathetic hyperinnervation remain underexposed.

OBJECTIVE

To provide a systematic review on cardiac sympathetic hyperinnervation after MI, taking into account: (1) definition, experimental model and quantification method and (2) location, amount and timing, in order to obtain an overview of current knowledge and to expose gaps in literature.

METHODS

References on cardiac sympathetic hyperinnervation were screened for inclusion. The included studies received a full-text review and quality appraisal. Relevant data on hyperinnervation were collected and qualitatively analysed.

RESULTS

Our literature search identified 60 eligible studies performed between 2000 and 2022. Cardiac hyperinnervation is generally defined as an increased sympathetic nerve density or increased number of nerves compared to another control group (100%). Studies were performed in a multitude of experimental models, but most commonly in male rats with permanent left anterior descending (LAD) artery ligation (male: 63%, rat: 68%, permanent ligation: 93%, LAD: 97%). Hyperinnervation seems to occur mainly in the borderzone. Quantification after MI was performed in regions of interest in µm2/mm2 (41%) or in percentage of nerve fibres (46%) and the reported amount showed a great variation ranging from 439 to 126,718 µm2/mm2. Hyperinnervation seems to start from three days onwards to >3 months without an evident peak, although studies on structural evaluation over time and in the chronic phase were scarce.

CONCLUSIONS

Cardiac sympathetic hyperinnervation after MI occurs mainly in the borderzone from three days onwards and remains present at later timepoints, for at least 3 months. It is most commonly studied in male rats with permanent LAD ligation. The amount of hyperinnervation differs greatly between studies, possibly due to differential quantification methods. Further studies are required that evaluate cardiac sympathetic hyperinnervation over time and in the chronic phase, in transmural sections, in the female sex, and in MI with reperfusion.

GSK-3β RNAi Lentivirus Affects Neuronal Damage and Nuclear Factor E2-Related Factor 2 (Nrf2) Expression in Cerebral Infarction Rats

We investigated the effect of GSK-3β RNAi lentivirus on neuronal damage and Nrf2 level in rats with cerebral infarction. 40 rats were assigned into sham group, CI group, Vector group and GSK-3β RNAi group followed by analysis of cell damage and oxidative stress, neurological scores, cerebral infarction volume, and brain water content as well as brain morphology by H&E staining and Nrf2 protein level by Western blot. Compared with sham group, GSK-3β mRNA in neurons of CI group and Vector group was significantly elevated (P < 0.05) with reduced level in GSK-3β RNAi group (P < 0.05); 3 hours after surgery, there was no change in neuroethology scores of rats in CI group, Vector group and GSK-3β RNAi group (P > 0.05). While 1 and 3 days later, the scores of rats were significantly improved (P < 0.05) and brain water content was reduced in GSK-3β RNAi group (P < 0.05) without difference between CI group and Vector group (P > 0.05). Compared with sham group, infarct size in CI group and Vector group was increased (P < 0.05) and reduced in GSK-3β RNAi group (P < 0.05) without difference between CI group and Vector group (P > 0.05). Meanwhile, CI group and Vector group showed significantly downregulated Nrf2, Srx1 and Trx1 proteins (P < 0.05), which were increased in GSK-3β RNAi group (P < 0.05). In conclusion, GSK-3β RNAi lentivirus can promote the expression of Nrf2 and exert an inhibitory effect on neurons of rats with cerebral infarction, therefore protecting brain tissue.

Pleiotropic activity of nerve growth factor in regulating cardiac functions and counteracting pathogenesis

Cardiac innervation density generally reflects the levels of nerve growth factor (NGF) produced by the heart—changes in NGF expression within the heart and vasculature contribute to neuronal remodelling (e.g. sympathetic hyperinnervation or denervation). Its synthesis and release are altered under different pathological conditions. Although NGF is well known for its survival effects on neurons, it is clear that these effects are more wide ranging. Recent studies reported both in vitro and in vivo evidence for beneficial actions of NGF on cardiomyocytes in normal and pathological hearts, including prosurvival and antiapoptotic effects. NGF also plays an important role in the crosstalk between the nervous and cardiovascular systems. It was the first neurotrophin to be implicated in postnatal angiogenesis and vasculogenesis by autocrine and paracrine mechanisms. In connection with these unique cardiovascular properties of NGF, we have provided comprehensive insight into its function and potential effect of NGF underlying heart sustainable/failure conditions. This review aims to summarize the recent data on the effects of NGF on various cardiovascular neuronal and non‐neuronal functions. Understanding these mechanisms with respect to the diversity of NGF functions may be crucial for developing novel therapeutic strategies, including NGF action mechanism‐guided therapies.

ArrhythmoGenoPharmacoTherapy

This review is focusing on the understanding of various factors and components governing and controlling the occurrence of ventricular arrhythmias including (i) the role of various ion channel-related changes in the action potential (AP), (ii) electrocardiograms (ECGs), (iii) some important arrhythmogenic mediators of reperfusion, and pharmacological approaches to their attenuation. The transmembrane potential in myocardial cells is depending on the cellular concentrations of several ions including sodium, calcium, and potassium on both sides of the cell membrane and active or inactive stages of ion channels. The movements of Na+, K+, and Ca2+ via cell membranes produce various currents that provoke AP, determining the cardiac cycle and heart function. A specific channel has its own type of gate, and it is opening and closing under specific transmembrane voltage, ionic, or metabolic conditions. APs of sinoatrial (SA) node, atrioventricular (AV) node, and Purkinje cells determine the pacemaker activity (depolarization phase 4) of the heart, leading to the surface manifestation, registration, and evaluation of ECG waves in both animal models and humans. AP and ECG changes are key factors in arrhythmogenesis, and the analysis of these changes serve for the clarification of the mechanisms of antiarrhythmic drugs. The classification of antiarrhythmic drugs may be based on their electrophysiological properties emphasizing the connection between basic electrophysiological activities and antiarrhythmic properties. The review also summarizes some important mechanisms of ventricular arrhythmias in the ischemic/reperfused myocardium and permits an assessment of antiarrhythmic potential of drugs used for pharmacotherapy under experimental and clinical conditions.

Interaction between Endothelin-1 and Left Stellate Ganglion Activation: A Potential Mechanism of Malignant Ventricular Arrhythmia during Myocardial Ischemia

Endothelin-1 (ET-1) is synthesized primarily by endothelial cells. ET-1 administration in vivo enhances the cardiac sympathetic afferent reflex and sympathetic activity. Previous studies have shown that sympathetic hyperactivity promotes malignant ventricular arrhythmia (VA). The aim of this study was to investigate whether ET-1 could activate the left stellate ganglion (LSG) and promote malignant VA. Twelve male beagle dogs who received local microinjections of saline (control, n = 6) and ET-1 into the LSG (n = 6) were included. The ventricular effective refractory period (ERP), LSG function, and LSG activity were measured at different time points. VA was continuously recorded for 1 h after left anterior descending occlusion (LADO), and LSG tissues were then collected for molecular detection. Compared to that of the control group, local ET-1 microinjection significantly decreased the ERP and increased the occurrence of VA. In addition, local microinjection of ET-1 increased the function and activity of the LSG in the normal and ischemic hearts. The expression levels of proinflammatory cytokines and the protein expression of c-fos and nerve growth factor (NGF) in the LSG were also increased. More importantly, endothelin A receptor (ETA-R) expression was found in the LSG, and its signaling was significantly activated in the ET-1 group. LSG activation induced by local ET-1 microinjection aggravates LADO-induced VA. Activated ETA-R signaling and the upregulation of proinflammatory cytokines in the LSG may be responsible for these effects.

Endothelin and the heart in health and diseases

Endothelin-1 (ET-1), a 21-amino acid peptide, was initially identified in 1988 as a potent vasoconstrictor and pressor substance isolated from the culture supernatant of porcine aortic endothelial cells. From human genomic DNA analysis, two other family peptides, ET-2 and ET-3, were found. They showed different effects and distribution, suggesting that each peptide may play separate roles in different organs. In the heart, ET-1 also causes positive inotropic and chronotropic responses and hypertrophic activity of the cardiomyocytes. ETs act via activation of two receptor subtypes, ET_A and ET_B receptors, both of which are coupled to various GTP-binding proteins depending on cell types. Endogenous ET-1 may be involved in progression of various cardiovascular diseases. ET antagonists are currently used clinically in the treatment for patients with pulmonary hypertension, and are considered to have further target diseases as heart failure, cardiac hypertrophy and other cardiac diseases, renal diseases, systemic hypertension, and cerebral vasospasm.

MicroRNA-146b induces the PI3K/Akt/NF-κB signaling pathway to reduce vascular inflammation and apoptosis in myocardial infarction by targeting PTEN

The aim of the present study was to investigate the function of microRNA-146b on myocardial infarction and the mechanism. An MTT assay, Annexin V/propidium iodide (PI) apoptosis assay, ELISA kits, western blot analysis and a caspase-3/8 activity assay were used to measure cell growth, vascular apoptosis inflammatory factors, and the B-cell lymphoma 2-associated X protein (Bax), phosphatase and tensin homolog (PTEN), phosphoinositide 3-kinase (PI3K)/Akt/nuclear factor (NF)-κB signaling pathway. The expression of microRNA-146b was downregulated in the myocardial infarction rat model, compared with the control group. In an in vitro model of myocardial infarction, the downregulation of microRNA-146b increased inflammatory factors, vascular apoptosis, caspase-3/8 activity and the protein expression of Bax. MicroRNA-146b reduced vascular apoptosis, caspase-3/8 activity and the protein expression of Bax. MicroRNA-146b also regulated the PI3K/Akt/NF-κB signaling pathway to mediate vascular inflammation and apoptosis in myocardial infarction by PTEN. A PI3K inhibitor decreased the effect of microRNA-146b on vascular inflammation and apoptosis following myocardial infarction. In conclusion, microRNA-146b mediated vascular inflammation and apoptosis in patients with myocardial infarction, which may be associated with activation of the PI3K/Akt/NF-κB signaling pathway by PTEN.

Molecular mechanism involved in cyclophosphamide-induced cardiotoxicity: Old drug with a new vision

Cyclophosphamide (CP) is an important anticancer drug which belongs to the class of alkylating agent. Cyclophosphamide is mostly used in bone marrow transplantation, rheumatoid arthritis, lupus erythematosus, multiple sclerosis, neuroblastoma and other types of cancer. Dose-related cardiotoxicity is a limiting factor for its use. CP-induced cardiotoxicity ranges from 7 to 28% and mortality ranges from 11 to 43% at the therapeutic dose of 170-180 mg/kg, i.v. CP undergoes hepatic metabolism that results in the production of aldophosphamide. Aldophosphamide decomposes into phosphoramide mustard & acrolein. Phosphoramide is an active neoplastic agent, and acrolein is a toxic metabolite which acts on the myocardium and endothelial cells. This is the first review article that talks about cyclophosphamide-induced cardiotoxicity and the different signaling pathways involved in its pathogenicity. Based on the available literature, CP is accountable for cardiomyocytes energy pool alteration by affecting the heart fatty acid binding proteins (H-FABP). CP has been found associated with cardiomyocytes apoptosis, inflammation, endothelial dysfunction, calcium dysregulation, endoplasmic reticulum damage, and mitochondrial damage. Molecular mechanism of cardiotoxicity has been discussed in detail through crosstalk of Nrf2/ARE, Akt/GSK-3β/NFAT/calcineurin, p53/p38MAPK, NF-kB/TLR-4, and Phospholamban/SERCA-2a signaling pathway. Based on the available literature we support the fact that metabolites of CP are responsible for cardiotoxicity due to depletion of antioxidants/ATP level, altered contractility, damaged endothelium and enhanced pro-inflammatory/pro-apoptotic activities resulting into cardiomyopathy, myocardial infarction, and heart failure. Dose adjustment, elimination/excretion of acrolein and maintenance of endogenous antioxidant pool could be the therapeutic approach to mitigate the toxicities.