Pharmacological Research

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating complication of cancer treatment. CB2 cannabinoid receptor activation reduces inflammation and is an attractive therapeutic target. Antibodies targeting G protein-coupled receptors (GPCRs), like CB2, offer high specificity and peripheral-restriction, thereby minimizing off-target activity. Here, we investigated the efficacy of first-in-class CB2-specific antibody agonists (AB110 and AB120) and an isotype control (AB100) on mechanical and cold hypersensitivity induced by paclitaxel in both tumor-free and mammary (4T1) tumor-bearing female mice. These CB2 antibody agonists exhibit biased G- signaling and also reduce macrophage markers and pro-inflammatory cytokines in vitro. Paclitaxel produced behavioral hypersensitivities to mechanical and cold stimulation, which were reduced by AB110 and AB120 for approximately 48 hours post-injection in female mice. Repeated daily dosing did not lead to tolerance to the anti-allodynic effects. Prophylactic treatment with AB110 and AB120 during paclitaxel treatment delayed, but did not prevent, the development of paclitaxel-induced behavioral hypersensitivities after termination of dosing with antibody agonists. AB100 had no effect under any conditions. The anti-allodynic effects of AB120 were absent in CB2 knockout mice, confirming pharmacological specificity via CB2 receptors. Furthermore, AB120 remained effective in paclitaxel-treated tumor-bearing mice. Neither AB110 nor AB120 affected locomotor activity in otherwise naive mice. The cytotoxic activity of paclitaxel on 4T1 tumor cell line was maintained in the presence of CB2 antibody agonists in vitro. Overall, our results suggest that CB2-specific antibody agonists are promising candidates for treating CIPN, providing lasting pain relief without tolerance, off target effects or unwanted CB1-mediated motor side effects.

The serotonin 5-HT7 receptor (5-HT7R), a member of the rhodopsin-like family of G protein-coupled receptors (GPCRs) is highly expressed in the central nervous system (CNS) and represents a promising target for treating CNS disorders such as sleep disturbances, migraine, neuropsychiatric conditions, and neuropathic pain. Owing to its therapeutic potential, extensive efforts have focused on developing selective 5-HT7R ligands. In the last decades, biased signalling has emerged as a key concept in GPCR pharmacology as biased ligands can stabilize specific active states of the receptor and trigger selective activation of downstream signaling pathways. In this context, we recently identified two biased 5-HT7R ligands, Serodolin and MOA51, from different chemical series. Here, we aimed to compare the pharmacological and safety profiles of these ligands and to assess their effect on pain-related behaviors and spinal neuroinflammation. In inflammatory pain models (acid acetic writhing, formalin and CFA tests), both serodolin and MOA51 effectively attenuated pain responses to a similar extend. Furthermore, in neuropathic pain models, spinal nerve injury (SNI) and Cuff model, both ligands reversed mechanical allodynia. Interestingly, unlike pregabalin, a clinically used reference drug, neither Serodolin nor MOA51 induced apparent tolerance after 10 consecutive days of administration. Treatment with these 5-HT7R ligands also reduced spinal microglial and attenuated neuronal hyperactivity in the spinal cord. Altogether these findings highlight the potential of 5-HT7R-biased ligands as promising analgesic candidates capable of modulating neuroinflammatory processes and mitigating both inflammatory and neuropathic pain.

Withdrawal StatementThe authors have withdrawn this manuscript because the senior authors have identified inconsistencies in the data presented in this manuscript, which affect the reliability of the main conclusions. In keeping with our commitment to scientific rigor and transparency, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding authors.

The idea that the effects of drugs largely depend on subcellular target location is emerging as a novel predictive factor of their beneficial or adverse outcomes. G protein-coupled type-1 cannabinoid receptors (CB1) are regulators of several brain functions as well as the main targets of cannabinoid-based medicines. Besides their classical location at plasma membranes, CB1 receptors are present at different locations within cells, including in association to mitochondrial membranes (mtCB1). Here we report the generation and characterization of a mutant mouse line, which lack mtCB1 receptors.

Endometriosis is a common and debilitating neuro-inflammatory disorder that is associated with chronic pain. Definitive diagnosis is based on the presence of endometrial-like tissue (lesions) in sites outside the uterus. Kynurenine monooxygenase (KMO) is a mitochondrial enzyme of tryptophan metabolism that regulates inflammation and immunity. Here, we show that KMO is expressed in epithelial cells in human endometriosis tissue lesions and in corresponding lesions in a mouse model of endometriosis. In mice, oral treatment with the potent KMO inhibitor KNS898 induced a biochemical state of KMO blockade with accumulation of kynurenine, diversion to kynurenic acid and ablation of 3-hydroxykynurenine production. In the mouse model of endometriosis, KMO inhibition improved histological outcomes and endometriosis pain-like behaviours, even when KNS898 treatment commenced one week after initiation of lesions. Taken together, these results suggest that KMO blockade is a promising new non-hormonal therapeutic modality for endometriosis.

Psychedelic-assisted psychotherapy has over the last decade emerged as a promising treatment strategy for mental health disease, and the therapeutic potential in classical psychedelics such as psilocybin, LSD and 5-MeO-DMT is presently being pursued in a plethora of clinical trials. However, the resurgent interest in the drugs as therapeutics has also prompted a search for novel agents with more specific pharmacological activities than the rather promiscuous classical psychedelics. Here we present the results of an elaborate preclinical characterization of one such compound, LPH-5 [(S)-3-(2,5-dimethoxy-4-(trifluoromethyl)phenyl)piperidine]. LPH-5 was found to be a potent partial agonist at the 5-HT2A receptor (5-HT2AR) and to exhibit pronounced selectivity for this receptor over the related 5-HT2B and 5-HT2C receptors in a range of functional assays. LPH-5 (0.375 - 12.0 mg/kg, i.p.) dose-dependently induced head-twitch responses (HTR) in Sprague Dawley rats, with substantial 5-HT2AR engagement being observed at 0.5-1.0 mg/kg. Acute administration of LPH-5 (1.5 mg/kg, i.p.) induced robust antidepressant-like effects in Flinders Sensitive Line rats and adrenocorticotropic hormone-treated Sprague Dawley rats, and LPH-5 (0.3 and 1.5 mg/kg, i.p.) induced significant effects in a recently developed Wistar Kyoto rat model proposed to reflect the long-term antidepressant-like effects produced by psychedelics in humans. In conclusion, selective 5-HT2AR activation, as mediated here by LPH- 5, seems to hold antidepressant potential, suggesting that this activity component is key for the beneficial effects of classical psychedelics. Hence, we propose that LPH-5 and other 5-HT2AR- selective agonists could hold potential as therapeutics in psychiatric disease as a new generation of psychedelic-derived antidepressant.

Prevalence of heart failure with preserved ejection fraction (HFpEF) is increasing, while treatment options are inadequate. Hypertension and obesity-related metabolic dysfunctions contribute to HFpEF progression. Nitro-oleic acid (NO2-OA) impacts metabolic processes by improving glucose tolerance and adipocyte function. In this study, 4 week treatment with NO2-OA ameliorated diastolic dysfunction in a HFpEF mouse model induced by high-fat diet and inhibition of the endothelial nitric oxide synthase. A proteomic analysis of left ventricular tissue revealed, that one third of the identified proteins, mostly mitochondrial proteins, were upregulated in hearts of NO2-OA-treated HFpEF mice compared to controls and vehicle-treated HFpEF mice, which was confirmed by immunoblot. Activation of the 5-adenosine-monophosphate-activated-protein-kinase (AMPK) signaling pathway mediated an enhancement of mitochondrial biogenesis in hearts of NO2-OA-treated HFpEF mice. In cardiomyocytes under metabolic stress, NO2-OA increased mitochondrial protein level accompanied by enhanced oxidative phosphorylation. In conclusion, targeting mitochondrial integrity in HFpEF leads to improved diastolic function.

There is a pressing need for effective alternatives to opioid analgesics, the development of which requires the identification of novel anti-nociceptive drug targets. Here, we have further investigated the anti-nociceptive properties of a GPR35 agonist, cromolyn, in an in vitro model of inflammatory sensitisation. We used ratiometric Ca2+ imaging of cultured sensory neurons to examine the effect of cromolyn on prostaglandin E2 (PGE2)-mediated sensitisation of the pro-nociceptive ion channel, transient receptor potential cation channel, subfamily V, member 1 (TRPV1). The sensitisation of TRPV1 by PGE2 was inhibited by cromolyn in a GPR35-dependent manner. These observations provide further evidence in support of an anti-nociceptive role for GPR35, highlighting the potential use of GPR35 agonists as analgesics.

Early treatment of patients with confirmed COVID-19 presenting mild symptoms can reduce the number that progress to more severe disease and require hospitalization. Considering the potential for the development of drug resistance to existing therapies and the emergence of new SARS-CoV-2 variants, there is a need for an expanded armamentarium of treatment options for COVID-19. Epeleuton is a novel orally administered second-generation n-3 fatty acid with potential direct antiviral and immunomodulatory actions, and a favourable clinical safety profile. In this study we show that epeleuton inhibits SARS-CoV-2 infectious viral load, replication and disease pathology in the lungs and upper airways in the Syrian hamster model of SARS-CoV-2 infection. These data support the potential utility of epeleuton in the early treatment and prevention of SARS-CoV-2 infection. Clinical trials are needed to evaluate the efficacy of epeleuton as an outpatient treatment and prevention of COVID-19.

Effective and available therapies for the treatment of COVID-19 disease are limited. Apadenoson is a highly potent selective anti-inflammatory adenosine A2A receptor (A2AR) agonist and potential treatment option for COVID-19 patients. Apadenoson, when administered after infection with SARS CoV-2, was found to decrease weight loss, improve clinical symptoms, reduce levels of a several proinflammatory cytokines and chemokines in bronchial lavage (BAL) fluid, and promote increased survival in K18hACE2 transgenic mice. Of note, administering apadenoson after, but not prior to Covid-19 infection, caused a rapid decrease in lung viral burden. The work presented provides the foundation for further examination of these drugs as a therapy option for COVID-19. SummaryApadenoson therapy improves COVID-19 outcome

Alpha7 nicotinic acetylcholine receptors (7nAChRs) are activated in response to inflammation and modulate pain in humans and rodent models. The use of 7nAChRs agonists as a therapeutic option for inflammation and pain is challenged by unwanted effects resulting from constant activation and/or desensitization of 7nAChRs. Positive allosteric modulators (PAMs) represent a compelling alternative as they increase endogenous nicotinic transmission but do not result in progressive desensitization or loss of receptor function. In the present study, we evaluated the function of the 4R tobacco cembranoid (4R) as a PAM of 7nAChR that reduces inflammation and pain-related behaviors in mouse models of inflammatory pain. Our electrophysiological experiments show that 4R potentiates choline-evoked currents in SH-SY5Y cells overexpressing 7nAChRs in a dose-dependent manner. At the behavioral level, we show that subcutaneous administration of 4R decreases inflammation-induced thermal but not tactile hypersensitivity or formalin-induced spontaneous nociceptive responses in both male and female mice. We further show reduced inflammation-induced paw edema in 4R-treated males, with no measurable effect observed in female mice. Altogether, the results from the experiments in this study identify 4R as a PAM of 7nAChRs that reduces thermal hypersensitivity in male and female mice and inflammation in a sex-specific manner. These findings highlight the use of 4R as a potential novel treatment strategy for pain and inflammation.

Postmenopausal osteoporosis (PMO), a silent disorder caused due to estrogen deficiency, is characterized by loss of bone mass and low bone mineral density. Despite advancements in treatment, current medications often fail to fully restore bone integrity and prevent fragility fractures in the osteoporotic individuals. Thus, there is a high demand of novel therapeutic modalities in dealing with osteoporosis. Interleukin-3 (IL-3), a cytokine secreted by activated T cells, emerges as a promising therapeutic candidate. The dual role of IL-3 in inhibiting osteoclast differentiation and promoting osteoblast differentiation, offers protection against bone and joint degeneration in arthritic mice. However, its role in osteoporosis is not yet delineated. Therefore, our investigation focuses on elucidating the role of IL-3 in PMO, employing both prophylactic and therapeutic strategies in ovariectomized mice, mimicking human PMO. In our study, at the onset of osteoporosis, IL-3 treatment effectively preserved trabecular bone architecture and enhanced bone mineral density in OVX mice, particularly notable in therapeutic interventions where fully developed osteoporosis was addressed. Notably, in preventive measures, IL-3 inhibited osteoclast differentiation, thereby suppressing bone resorption, while in therapeutic approaches, it enhanced osteoblast differentiation, promoting bone formation. Irrespective of gender specific, microCT analysis of IL-3-/- (KO) mice showed reduced trabecular bone development compared to its respective wild type (WT) mice, highlighting essential role of IL-3 in skeletal integrity. Moreover, IL-3 increased Treg cells population while inhibiting B cell lymphopoiesis in ovariectomized mice with no adverse effects on hematopoiesis or vital organs. In conclusion, our findings collectively underscore the potential of IL-3 as a novel therapy for PMO, offering insights into its mechanisms of action and clinical applications. One Sentence SummaryIL-3 has a dual action on bone: anti-osteoclastic and pro-osteoblastic in OVX mice, thus can be a novel therapeutic drug in treating postmenopausal osteoporosis.

Chronic pain states are challenging to control with current drug therapies. Here, we demonstrate that a single dose of psilocybin can produce a sustained anti-nociceptive effect in a model of chronic neuropathic pain in male and female mice. Psilocybin anti-nociceptive effects were mediated by 5-HT2A receptors, although additional mechanisms might also be involved. Furthermore, a single dose of psilocybin caused a significant increase in the anti-nociceptive potential of gabapentin, a widely used treatment for neuropathic pain consistent with the establishment of longer lasting changes in network processing. Overall, these findings present the first preclinical evidence that psilocybin could be a valuable approach for treating chronic pain from nerve injury and serve as a new therapeutic addition for pain management.

BackgroundArrhythmogenic Cardiomyopathy (ACM) is one of the major causes of sudden cardiac death in young adults. With the underlying patho-mechanisms not well understood, current therapeutic approaches for this genetic disease are solely symptomatic. A recent study demonstrates that loss of cell-cell adhesion is an important initial step leading to ACM. Because loss of cell-cell adhesion is considered a key initial step, we aim to identify new compounds from a drug library, which can restore intercellular adhesion and potentially serve as therapeutics for ACM. MethodsWe established a 2D cell adhesion-based high-throughput platform and screened an FDA-approved drug library. To model loss of intercellular adhesion, human cell lines deficient for the desmosomal adhesion molecule desmoglein-2 (DSG2) were employed and the revealed top candidates were validated in cells expressing different ACM patient mutations. The therapeutic potential of the top hit dexamethasone was evaluated in an inducible ACM disease mouse model using ECG, echocardiography and histology. Phospho-proteomic analysis was applied to investigate protective drug mechanisms. ResultsWe established a set-up to sensitively detect changes in cell-cell adhesion via a high-throughput platform and applied this approach to identify a large pool of adhesion-strengthening compounds in DSG2 deficient cells. The pro-adhesive effect of selected candidates was validated for different ACM patient mutations inducing defective cell cohesion. Importantly, in vivo administration of the selected top pro-adhesive drug dexamethasone rescued impaired right ventricular function in an ACM mouse model. Phospho-proteome analysis suggests modulation of AKT1/AMPK1 signaling and changes in cardiac contractility and junctional components as factors contributing to this protective effect. ConclusionsWe developed an adhesion-based high-throughput screening platform capable of identifying adhesion modulators. We revealed and validated several pro-adhesive compounds and showed a protective effect for the top candidate dexamethasone in an ACM mouse model. This indicates the potential of adhesion-strengthening compounds as therapeutic strategy in ACM and lays the basis for detailed follow-up studies. Moreover, these results and methods can be translated to other diseases with defective desmosomal adhesion. Clinical PerspectiveO_ST_ABSWhat is new?C_ST_ABSO_LIWe developed a novel high-throughput in vitro screening platform to identify compounds that strengthen cell-cell adhesion under conditions of disrupted adhesion, which is a central pathogenetic step in Arrhythmogenic Cardiomyopathy (ACM). C_LIO_LIWith aid of this screen, we identified and validated different compounds from an FDA-approved drug library, which restore disrupted cell-cell adhesion induced by ACM patient mutations including glucocorticoids such as dexamethasone. C_LIO_LIDexamethasone rescued impaired right ventricular function in a novel inducible ACM mouse model and reverted altered AKT1/AMPK1 signaling as well as changes in the phosphorylation state of components of the contractile and junctional apparatus. C_LI What are clinical implications?O_LIWe established a high-throughput cell-cell adhesion screening method as a viable tool for identifying drugs to combat ACM and other diseases featuring impaired desmosomal adhesion. C_LIO_LIWe identified the glucocorticoid dexamethasone as a promising compound to therapeutically approach ACM. C_LIO_LIThis study highlights strengthening of disrupted cell-cell adhesion as a novel therapeutic strategy to treat ACM. C_LI

Chemotherapy-induced peripheral neuropathy (CIPN) is the de facto clinical side effect that limits the administration of anti-cancer treatments. Recently, we reported that intrathecally injected bone marrow stromal cells (BMSCs) reduced nerve trauma-induced neuropathic pain in male mice via TGF-{beta}1 signaling. In this study, we examined sex-dependent pain relief mediated by intrathecally delivered BMSCs and TGF-{beta}1 in paclitaxel (PTX)-induced CIPN. BMSCs were prepared from primary cultures of male or female mice separately. A single intrathecal injection of BMSCs, prepared from male donors, completely prevented the development of PTX-evoked mechanical allodynia in male mice. However, female mice showed no analgesic response to either male or female BMSCs. Additionally, male mice did not demonstrate an analgesic response to BMSCs from female donors. Intrathecal injection of TGF-{beta}1 neutralizing antibody reversed the analgesic action of BMSCs. Interestingly, spinal administration of TGF-{beta}1 reduced mechanical allodynia in male mice but not in female mice. Ex vivo patch-clamp recordings in spinal cord slices revealed that TGF-{beta}1 inhibited PTX-induced synaptic plasticity, i.e. increase in spontaneous excitatory synaptic currents (sEPsCs), in spinal cord neurons from male mice only. Intrathecal TGF-{beta}1 increased the paw withdrawal threshold in von Frey testing in naive mice of males but not females, and the antinociceptive effect of TGF-{beta}1 in males was blocked by orchiectomy-induced androgen deficiency. Together, these findings reveal sex dimorphism in BMSC control of mechanical pain through spinal TGF-{beta}1 signaling.

The Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a central regulator of learning and memory, which poses a problem for targeting it therapeutically. Indeed, our study supports prior conclusions that long-term interference with CaMKII signaling can erase pre-formed memories. By contrast, short-term pharmacological CaMKII inhibition with tatCN19o interfered with learning in mice only mildly and transiently (for less than 1 h) and did not at all reverse pre-formed memories. This was at [≥]500fold of the dose that protected hippocampal neurons from cell death after a highly clinically relevant pig model of transient global cerebral ischemia: ventricular fibrillation followed by advanced life support and electrical defibrillation to induce return of spontaneous circulation. Of additional importance for therapeutic development, cardiovascular safety studies in mice and pig did not indicate any concerns with acute tatCN19o injection. Taken together, even though prolonged interference with CaMKII signaling can erase memory, acute short-term CaMKII inhibition with tatCN19o did not cause such retrograde amnesia that would pose a contraindication for therapy.

Significant research has focused on developing anti-nociceptive pain treatments by targeting specific molecular candidates. The serotonin 2A receptor (5-HT2AR) and metabotropic glutamate receptor 5 (mGluR5) are recognized as key mediators in neuropathic pain. However, the combined effects of simultaneous inhibition of these targets remain unexplored. This current study investigated the therapeutic potential of concurrently antagonizing 5-HT2AR and mGluR5. Using spinal nerve ligation (SNL) and formalin-induced pain models in male Sprague-Dawley rats, we demonstrated that the simultaneous administration of both antagonists significantly enhanced anti-allodynic and anti-nociceptive effects, resulting in increased allodynia thresholds and reduced pain-related behaviors. This dual antagonism provided pain relief comparable to that of gabapentin and morphine. Furthermore, novel small molecules designed to simultaneously antagonize 5-HT2AR and mGluR5 exerted anti-nociceptive effects by suppressing excitatory postsynaptic responses and inhibiting the phosphorylation of ERK and AKT signaling molecules. Notably, the dual antagonist maintained anti-allodynic efficacy with repeated administration, unlike morphine, which exhibited clear tolerance development with daily use. Moreover, when administered intravenously, the dual antagonist demonstrated a low potential for abuse. These findings indicate that the simultaneous antagonism of 5-HT2AR and mGluR5 represents a promising pharmacological target for the management of chronic pain. This approach may offer enhanced analgesic outcomes while reducing the risk of undesirable side effects, such as tolerance and the potential for abuse.

N-methyl-D-aspartate receptors (NMDARs) are glutamate-gated calcium-permeable excitatory channels. They have attracted great interest as potential targets for the treatment of depression in recent years. NMDARs typically assemble as heterotetramers composed of two GluN1 and two alternative GluN2 (2A-2D) subunits, the latter of which endow various subtypes with diverse gating and pharmacological properties. To date, limited molecules with GluN2 specificity have been identified to show antidepressant effects. Here, we identify a compound termed YY-23 extracted from Rhizoma Anemarrhenae allosterically inhibited the channel activities of GluN2C- or GluN2D-incorporated NMDARs, an effect that was presumably influenced by the S2 segment in the ligand-binding domain of the GluN2 subunit. We found that prefrontal GluN2D-containing NMDARs were predominantly expressed at GABAergic interneurons rather than pyramidal neurons. Furthermore, we revealed that YY-23 suppressed the activity of GluN2D-containing NMDARs and GABAergic neurotransmission in the medial prefrontal cortex (mPFC). As a consequence, this GABAergic disinhibition facilitated the excitatory transmission. Behavioural experiments showed that YY-23 acted as a rapid antidepressant in both stress-naive and stressed animal models, which was abolished in Grin2d-knockout mice. Together, our findings suggest that GluN2D-incorporated NMDARs on GABAergic interneurons might be promising therapeutic targets for the treatment of depression.

BACKGROUNDMyocardial ischemia/reperfusion injury (I/RI) represents a serious clinical complication in patients after acute myocardial infarction. Ubiquitin-activating enzyme 1 (UBA1) catalyzes the initial step of ubiquitination and plays a fundamental role in regulating protein homeostasis and related diseases. This study aims to elucidate the functional contribution of UBA1 to the pathogenesis of myocardial I/RI and to uncover its underlying mechanisms. METHODSSingle-cell RNA sequencing was employed to characterize UBA1 expression in human ischemic heart tissues. Myocardial I/R injury was examined in myocardial-specific UBA1 knockout (UBA1cko) mice, UBA1-overexpressing mice (rAAV9-UBA1), and corresponding controls. Neonatal rat cardiomyocytes underwent hypoxia/reoxygenation in vitro. Cardiac function and infarction were evaluated by echocardiography and pathological staining. Protein-protein interactions were analyzed via immunoprecipitation combined with mass spectrometry. The endoplasmic reticulum-mitochondrial contact sites (ERMCSs) and mitochondrial ultrastructure were evaluated through transmission electron microscopy and confocal imaging. RESULTSUBA1 expression was significantly downregulated in human and murine ischemic myocardium, especially in cardiomyocytes. UBA1cko mice exhibited aggravated I/RI with greater infarct size, impaired function, apoptosis, elevated intracellular Ca2+ levels, mitochondrial dysfunction, and ER stress, whereas UBA1 overexpression conferred cardioprotective effects. Mechanistically, UBA1 directly bound to and ubiquitinated Pdzd8, a key ERMCS-tethering protein, thereby promoting its degradation, which inhibited ERMCS formation and improved mitochondrial dysfunction and ER stress. Moreover, knockdown of Pdzd8 via rAAV9-siRNA effectively mitigated UBA1 knockout-induced myocardial damage. Additionally, administration of auranofin (AF), a U.S. Food and Drug Administration-approved drug for treating rheumatoid arthritis, markedly alleviated myocardial I/RI via activating UBA1 in vivo and in vitro. CONCLUSIONSUBA1 confers protection against myocardial I/RI by limiting ERMCS formation through Pdzd8 ubiquitination. Activating UBA1 or targeting Pdzd8 as a potential therapeutic strategy for the treatment of ischemic heart disease. GRAPHIC ABSTRACTA graphic abstract is available for this article. Clinical PerspectiveO_ST_ABSWhat Is New?C_ST_ABSO_LIUBA1 expression is downregulated in human and murine ischemic myocardium, especially in cardiomyocytes. C_LIO_LICardiac deletion of UBA1 significantly exacerbates myocardial ischemia/reperfusion injury (I/RI), whereas cardiac UBA1 overexpression confers a marked protective effect. C_LIO_LIUBA1 interacts with Pdzd8 (PDZ domain containing 8) and facilitates its ubiquitination and subsequent degradation, which then reduces endoplasmic reticulum-mitochondria contact sites (ERMCSs) and ameliorates mitochondrial dysfunction and ER stress, protecting myocardial I/RI. C_LIO_LIPharmacological activation of UBA1 with the FDA-approved drug auranofin attenuates myocardial I/R injury and improves heart dysfunction. C_LI What Are the Clinical Implications?O_LIUBA1 represents a new therapeutic target for myocardial I/RI. C_LIO_LIActivating UBA1 or targeting Pdzd8 may offer a promising therapeutic strategy for mitigating myocardial I/RI and heart failure, underscoring its potential for clinical translation. C_LI

Chemotherapy-induced cardiotoxicity has emerged as an important focus in oncology, driven by the growing number of cancer survivors. Intensive chemotherapies (iCT) used in the treatment of acute myeloid leukemia (AML) often lead to significant adverse cardiac events, which can reduce therapeutic benefits, limit treatment options, or even necessitate discontinuation--particularly for patients with pre-existing cardiac conditions, resulting in a loss of therapeutic opportunity. This study shows that the iCT triggers severe mitochondrial dysfunction in cardiac tissue, mirroring effects seen in ischemia-reperfusion models. Specifically, iCT results in succinate accumulation and elevated reactive oxygen species production, consistent with reverse electron transport phenomenon. Importantly, these effects were entirely prevented with RET inhibitors such as malonate or S1QEL1.1. In vivo, we demonstrate that malonate administration successfully prevents iCT-induced cardiotoxicity, maintaining left ventricular ejection fraction and fibrosis levels comparable to controls. Additionally, in an MLL-AF9-driven AML model, malonate sensitized leukemic cells to iCT. These findings support the dual potential of malonate: as an OXPHOS metabolism inhibitor to overcome chemoresistance in AML, while also reducing cardiotoxic risk for already vulnerable patients. One Sentence Summary: This study demonstrates that malonate prevents chemotherapy-induced cardiotoxicity by inhibiting mitochondrial reverse electron transport (RET), preserving cardiac function, and simultaneously sensitizing AML cells to intensive chemotherapy.