Remote Ischemic Pre-Conditioning Attenuates Adverse Cardiac Remodeling and Mortality Following Doxorubicin Administration in Mice

Is There a Mitochondrial Protection via Remote Ischemic Conditioning in Settings of Anticancer Therapy Cardiotoxicity?

PURPOSE OF REVIEW

To provide an overview of (a) protective effects on mitochondria induced by remote ischemic conditioning (RIC) and (b) mitochondrial damage caused by anticancer therapy. We then discuss the available results of studies on mitochondrial protection via RIC in anticancer therapy-induced cardiotoxicity.

RECENT FINDINGS

In three experimental studies in healthy mice and pigs, there was a RIC-mediated protection against anthracycline-induced cardiotoxicity and there was some evidence of improved mitochondrial function with RIC. The RIC-mediated protection was not confirmed in the two available studies in cancer patients. In adult cancer patients, RIC was associated with an adverse outcome. There are no data on mitochondrial function in cancer patients. Studies in tumor-bearing animals are needed to determine whether RIC does not interfere with the anticancer properties of the drugs and whether RIC actually improves mitochondrial function, ultimately resulting in improved cardiac function.

NMNATs expression inhibition mediated NAD+ deficiency plays a critical role in doxorubicin-induced hepatotoxicity in mice

Doxorubicin (DOX) is one of the most widely used antineoplastic drugs with known cardiotoxicity while other organ toxicity, such as hepatotoxicity is not well defined. This study was to explore the role of nicotinamide adenine dinucleotide (NAD+) in DOX-induced hepatotoxicity. DOX (20 mg/kg) induced acute liver injury and oxidative stress in C57BL/6 J mice at 48 h. Notably, the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and NAD(P)H dehydrogenase quinone 1 (NQO1) were downregulated. NAD+ deficiency was confirmed due to DOX exposure. Mechanistically, the downregulation of nicotinamide mononucleotide adenylyl transferase 1 (NMNAT1), NMNAT2 and NMNAT3, while no alteration of nicotinamide phosphoribosyl transferase was proved. As a consequence of NAD+ deficiency, the expression of poly-ADP-ribose polymerase1 (PARP1), CD38 and Sirtuin1 (SIRT1) were reduced. Furthermore, supplementation of NAD+ (200 mg/kg/day) or its precursor nicotinamide mononucleotide (NMN) (500 mg/kg/day) alleviated liver injury, attenuated oxidative stress, and elevated the downregulation of Nrf2 and NQO1. More importantly, compromised expression of NMNAT1-3, PARP1, CD38 and SIRT1 were improved by NAD+ and NMN. In conclusion, NAD+ deficiency due to NMNATs expression inhibition may attribute to the pathogenesis of DOX-induced hepatotoxicity, thus providing new insights for mitigating DOX side effects.

m6A demethylase ALKBH5 attenuates doxorubicin-induced cardiotoxicity via posttranscriptional stabilization of Rasal3

The clinical application of anthracyclines such as doxorubicin (DOX) is limited due to their cardiotoxicity. N6-methyladenosine (m⁶A) plays an essential role in numerous biological processes. However, the roles of m⁶A and m⁶A demethylase ALKBH5 in DOX-induced cardiotoxicity (DIC) remain unclear. In this research, DIC models were constructed using Alkbh5-knockout (KO), Alkbh5-knockin (KI), and Alkbh5-myocardial-specific knockout (ALKBH5^{flox/flox, αMyHC-Cre}) mice. Cardiac function and DOX-mediated signal transduction were investigated. As a result, both Alkbh5 whole-body KO and myocardial-specific KO mice had increased mortality, decreased cardiac function, and aggravated DIC injury with severe myocardial mitochondrial damage. Conversely, ALKBH5 overexpression alleviated DOX-mediated mitochondrial injury, increased survival, and improved myocardial function. Mechanistically, ALKBH5 regulated the expression of Rasal3 in an m⁶A-dependent manner through posttranscriptional mRNA regulation and reduced Rasal3 mRNA stability, thus activating RAS3, inhibiting apoptosis through the RAS/RAF/ERK signaling pathway, and alleviating DIC injury. These findings indicate the potential therapeutic effect of ALKBH5 on DIC.

Current State of Pediatric Cardio-Oncology: A Review

The landscape of pediatric oncology has dramatically changed over the course of the past several decades with five-year survival rates surpassing 80%. Anthracycline therapy has been the cornerstone of many chemotherapy regimens for pediatric patients since its introduction in the 1960s, and recent improved survival has been in large part due to advancements in chemotherapy, refinement of supportive care treatments, and development of novel therapeutics such as small molecule inhibitors, chimeric antigen receptor T-cell therapy, and immune checkpoint inhibitors. Unfortunately, many cancer-targeted therapies can lead to acute and chronic cardiovascular pathologies. The range of cardiotoxicity can vary but includes symptomatic or asymptotic heart failure, arrhythmias, coronary artery disease, valvar disease, pericardial disease, hypertension, and peripheral vascular disease. There is lack of data guiding primary prevention and treatment strategies in the pediatric population, which leads to substantial practice variability. Several important future research directions have been identified, including as they relate to cardiac disease, prevention strategies, management of cardiovascular risk factors, risk prediction, early detection, and the role of genetic susceptibility in development of cardiotoxicity. Continued collaborative research will be key in advancing the field. The ideal model for pediatric cardio-oncology is a proactive partnership between pediatric cardiologists and oncologists in order to better understand, treat, and ideally prevent cardiac disease in pediatric oncology patients.

Atg5 knockdown induces age-dependent cardiomyopathy which can be rescued by repeated remote ischemic conditioning

Altered autophagy is implicated in several human cardiovascular diseases. Remote ischemic conditioning (RIC) is cardioprotective in multiple cardiovascular injury models and modifies autophagy signaling, but its effect in cardiomyopathy induced by gene manipulation has not been reported. To investigate the cardiac effects of chronically reduced autophagy as a result of Atg5 knockdown and assess whether RIC can rescue the phenotype. Atg5 knockdown was induced with tamoxifen for 14 days in cardiac-specific conditional Atg5 flox mice. Autophagy proteins and cardiac function were evaluated by Western blot and echocardiography, respectively. RIC was induced by cyclical hindlimb ischemia and reperfusion using a tourniquet. RIC or sham procedure was performed daily during tamoxifen induction and, in separate experiments, chronically 3 times per week for 8 weeks. Cardiac responses were assessed by end of the study. Cardiac-specific knockdown of Atg5 reduced protein levels by 70% and was associated with a significant increase in mTOR, a reduction of LC3-II and increased upstream autophagy proteins including LC3-I, P62, and Beclin. The changes in biochemical markers were associated with development of an age-related cardiomyopathy during the 17-month follow-up indicated by increased heart weight body weight ratio, progressive decline in cardiac function, and premature death. RIC increased cardiac ATG5 and rescued some of the Atg5 knockdown-induced cardiomyopathy phenotype and associated morphological remodeling. We conclude that cardiac-specific Atg5 knockdown leads to the development of age-related cardiomyopathy. RIC reverses the molecular and structural phenotype when administered both acutely and chronically.

Analgesic effect of central relaxin receptor activation on persistent inflammatory pain in mice: behavioral and neurochemical data

Supplemental Digital Content is Available in the Text. Relaxin peptide analogues produce strong but transient analgesia in inflammatory pain in mouse. Relaxin and its RXFP1 receptor represent a new peptidergic system that modulates pain processing in the forebrain areas.

Introduction:

The relaxin peptide signaling system is involved in diverse physiological processes, but its possible roles in the brain, including nociception, are largely unexplored.

Objective:

In light of abundant expression of relaxin receptor (RXFP1) mRNA/protein in brain regions involved in pain processing, we investigated the effects of central RXFP1 activation on nociceptive behavior in a mouse model of inflammatory pain and examined the neurochemical phenotype and connectivity of relaxin and RXFP1 mRNA-positive neurons.

Methods:

Mice were injected with Complete Freund Adjuvant (CFA) into a hind paw. After 4 days, the RXFP1 agonist peptides, H2-relaxin or B7-33, ± the RXFP1 antagonist, B-R13/17K-H2, were injected into the lateral cerebral ventricle, and mechanical and thermal sensitivity were assessed at 30 to 120 minutes. Relaxin and RXFP1 mRNA in excitatory and inhibitory neurons were examined using multiplex, fluorescent in situ hybridization. Relaxin-containing neurons were detected using immunohistochemistry and their projections assessed using fluorogold retrograde tract-tracing.

Results:

Both H2-relaxin and B7-33 produced a strong, but transient, reduction in mechanical and thermal sensitivity of the CFA-injected hind paw alone, at 30 minutes postinjection. Notably, coinjection of B-R13/17K-H2 blocked mechanical, but not thermal, analgesia. In the claustrum, cingulate cortex, and subiculum, RXFP1 mRNA was expressed in excitatory neurons. Relaxin immunoreactivity was detected in neurons in forebrain and midbrain areas involved in pain processing and sending projections to the RXFP1-rich, claustrum and cingulate cortex. No changes were detected in CFA mice.

Conclusion:

Our study identified a previously unexplored peptidergic system that can control pain processing in the brain and produce analgesia.

Remote ischaemic preconditioning ameliorates anthracycline-induced cardiotoxicity and preserves mitochondrial integrity

AIMS

Anthracycline-induced cardiotoxicity (AIC) is a serious adverse effect among cancer patients. A central mechanism of AIC is irreversible mitochondrial damage. Despite major efforts, there are currently no effective therapies able to prevent AIC.

METHODS AND RESULTS

Forty Large-White pigs were included. In Study 1, 20 pigs were randomized 1:1 to remote ischaemic preconditioning (RIPC, 3 cycles of 5 min leg ischaemia followed by 5 min reperfusion) or no pretreatment. RIPC was performed immediately before each intracoronary doxorubicin injections (0.45 mg/kg) given at Weeks 0, 2, 4, 6, and 8. A group of 10 pigs with no exposure to doxorubicin served as healthy controls. Pigs underwent serial cardiac magnetic resonance (CMR) exams at baseline and at Weeks 6, 8, 12, and 16, being sacrifice after that. In Study 2, 10 new pigs received 3 doxorubicin injections (with/out preceding RIPC) and were sacrificed at week 6. In Study 1, left ventricular ejection fraction (LVEF) depression was blunted animals receiving RIPC before doxorubicin (RIPC-Doxo), which had a significantly higher LVEF at Week 16 than doxorubicin treated pigs that received no pretreatment (Untreated-Doxo) (41.5 ± 9.1% vs. 32.5 ± 8.7%, P = 0.04). It was mainly due to conserved regional contractile function. In Study 2, transmission electron microscopy (TEM) at Week 6 showed fragmented mitochondria with severe morphological abnormalities in Untreated-Doxo pigs, together with upregulation of fission and autophagy proteins. At the end of the 16-week Study 1 protocol, TEM revealed overt mitochondrial fragmentation with structural fragmentation in Untreated-Doxo pigs, whereas interstitial fibrosis was less severe in RIPC+Doxo pigs.

CONCLUSION

In a translatable large-animal model of AIC, RIPC applied immediately before each doxorubicin injection resulted in preserved cardiac contractility with significantly higher long-term LVEF and less cardiac fibrosis. RIPC prevented mitochondrial fragmentation and dysregulated autophagy from AIC early stages. RIPC is a promising intervention for testing in clinical trials in AIC.

MCUb Induction Protects the Heart From Postischemic Remodeling

RATIONALE

Mitochondrial Ca2+ loading augments oxidative metabolism to match functional demands during times of increased work or injury. However, mitochondrial Ca2+ overload also directly causes mitochondrial rupture and cardiomyocyte death during ischemia-reperfusion injury by inducing mitochondrial permeability transition pore opening. The MCU (mitochondrial Ca2+ uniporter) mediates mitochondrial Ca2+ influx, and its activity is modulated by partner proteins in its molecular complex, including the MCUb subunit.

OBJECTIVE

Here, we sought to examine the function of the MCUb subunit of the MCU-complex in regulating mitochondria Ca2+ influx dynamics, acute cardiac injury, and long-term adaptation after ischemic injury.

METHODS AND RESULTS

Cardiomyocyte-specific MCUb overexpressing transgenic mice and Mcub gene-deleted (Mcub-/-) mice were generated to dissect the molecular function of this protein in the heart. We observed that MCUb protein is undetectable in the adult mouse heart at baseline, but mRNA and protein are induced after ischemia-reperfusion injury. MCUb overexpressing mice demonstrated inhibited mitochondrial Ca2+ uptake in cardiomyocytes and partial protection from ischemia-reperfusion injury by reducing mitochondrial permeability transition pore opening. Antithetically, deletion of the Mcub gene exacerbated pathological cardiac remodeling and infarct expansion after ischemic injury in association with greater mitochondrial Ca2+ uptake. Furthermore, hindlimb remote ischemic preconditioning induced MCUb expression in the heart, which was associated with decreased mitochondrial Ca2+ uptake, collectively suggesting that induction of MCUb protein in the heart is protective. Similarly, mouse embryonic fibroblasts from Mcub-/- mice were more sensitive to Ca2+ overload.

CONCLUSIONS

Our studies suggest that Mcub is a protective cardiac inducible gene that reduces mitochondrial Ca2+ influx and permeability transition pore opening after ischemic injury to reduce ongoing pathological remodeling.

Repeated Remote Ischemic Conditioning Reduces Doxorubicin-Induced Cardiotoxicity

Objectives

This study investigated the cardioprotective effect of repeated remote ischemic preconditioning (rRIC) on doxorubicin-induced cardiotoxicity in mice.

Background

Doxorubicin is an effective chemotherapeutic agent for a wide range of tumor types but its use and dosing are limited by acute and chronic cardiotoxicity. Remote ischemic conditioning (RIC) is cardioprotective in multiple cardiovascular injury models, but the effectiveness of rRIC in doxorubicin-induced cardiotoxicity has not been fully elucidated.

Methods

rRIC was performed on mice before and after doxorubicin administration. Cardiac function was assessed by echocardiography and myocardial biology was tested by molecular approaches.

Results

Doxorubicin administration induced acute cardiotoxicity, as indicated by reduced cardiac function, reduced myocyte cross-section area and increased extracellular collagen deposition, increased circulating cardiac muscle damage markers, and decreased heart weight. Doxorubicin also adversely affected other organs, including the kidney, liver, and spleen, as evaluated by circulating markers or organ weight loss. rRIC not only abrogated doxorubicin-induced cardiotoxicity (left ventricular ejection fraction, doxorubicin 47.5 ± 1.1%, doxorubicin + rRIC 51.6 ± 0.7%, p = 0.017), but also was associated with multiorgan protection. Within the myocardium, rRIC attenuated doxorubicin-induced cardiomyocyte apoptosis, reduced inflammation, and increased autophagy signaling.

Conclusions

rRIC may be a promising approach to reduce doxorubicin-induced cardiotoxicity.