Chemotherapeutic agents induce mitochondrial superoxide production and toxicity but do not alter respiration in skeletal muscle in vitro

Adenylosuccinic Acid Is a Non-Toxic Small Molecule In Vitro and In Vivo

Adenylosuccinic acid (ASA) is a small molecule dicarboxylate that could be a strong clinical development candidate for inherited myopathies involving dysregulated purine nucleotide metabolism. Currently, there are no published pharmacokinetic/dynamic or toxicology data available, although 10-year clinical trial data on Duchenne muscular dystrophy patients suggests it is a chronically safe drug. In this study, we tested the toxicity of ASA to cultured myoblasts in vitro and its acute systemic toxicity in mice. ASA is a non-toxic small molecule with an LD50 > 5000 mg/kg. Some background necrotic foci in the liver, kidney and gastrointestinal tract were shown that are likely incidental but warrant follow-up sub-/chronic oral exposure studies.

Recovery from FOLFOX chemotherapy-induced systemic and skeletal muscle metabolic dysfunction in mice

FOLFOX (5-fluorouracil, leucovorin, oxaliplatin) chemotherapy is used to treat colorectal cancer and can acutely induce metabolic dysfunction. However, the lasting effects on systemic and skeletal muscle metabolism after treatment cessation are poorly understood. Therefore, we investigated the acute and lasting effects of FOLFOX chemotherapy on systemic and skeletal muscle metabolism in mice. Direct effects of FOLFOX in cultured myotubes were also investigated. Male C57BL/6J mice completed four cycles (acute) of FOLFOX or PBS. Subsets were allowed to recover for 4 wk or 10 wk. Comprehensive Laboratory Animal Monitoring System (CLAMS) metabolic measurements were performed for 5 days before study endpoint. C2C12 myotubes were treated with FOLFOX for 24 hr. Acute FOLFOX attenuated body mass and body fat accretion independent of food intake or cage activity. Acute FOLFOX decreased blood glucose, oxygen consumption (V̇o2), carbon dioxide production (V̇co2), energy expenditure, and carbohydrate (CHO) oxidation. Deficits in V̇o2 and energy expenditure remained at 10 wk. CHO oxidation remained disrupted at 4 wk but returned to control levels after 10 wk. Acute FOLFOX reduced muscle COXIV enzyme activity, AMPK(T172), ULK1(S555), and LC3BII protein expression. Muscle LC3BII/I ratio was associated with altered CHO oxidation (r = 0.75, P = 0.03). In vitro, FOLFOX suppressed myotube AMPK(T172), ULK1(S555), and autophagy flux. Recovery for 4 wk normalized skeletal muscle AMPK and ULK1 phosphorylation. Our results provide evidence that FOLFOX disrupts systemic metabolism, which is not readily recoverable after treatment cessation. FOLFOX effects on skeletal muscle metabolic signaling did recover. Further investigations are warranted to prevent and treat FOLFOX-induced metabolic toxicities that negatively impact survival and life quality of patients with cancer.NEW & NOTEWORTHY The present study demonstrates that FOLFOX chemotherapy induces long-lasting deficits in systemic metabolism. Interestingly, FOLFOX modestly suppressed skeletal muscle AMPK and autophagy signaling in vivo and in vitro. The FOLFOX-induced suppression of muscle metabolic signaling recovered after treatment cessation, independent of systemic metabolic dysfunction. Future research should investigate if activating AMPK during treatment can prevent long-term toxicities to improve health and quality of life of patients with cancer and survivors.

Cachexia: A systemic consequence of progressive, unresolved disease

Cachexia, a systemic wasting condition, is considered a late consequence of diseases, including cancer, organ failure, or infections, and contributes to significant morbidity and mortality. The induction process and mechanistic progression of cachexia are incompletely understood. Refocusing academic efforts away from advanced cachexia to the etiology of cachexia may enable discoveries of new therapeutic approaches. Here, we review drivers, mechanisms, organismal predispositions, evidence for multi-organ interaction, model systems, clinical research, trials, and care provision from early onset to late cachexia. Evidence is emerging that distinct inflammatory, metabolic, and neuro-modulatory drivers can initiate processes that ultimately converge on advanced cachexia.

Cancer-associated cachexia - understanding the tumour macroenvironment and microenvironment to improve management

Cachexia is a devastating, multifactorial and often irreversible systemic syndrome characterized by substantial weight loss (mainly of skeletal muscle and adipose tissue) that occurs in around 50-80% of patients with cancer. Although this condition mainly affects skeletal muscle (which accounts for approximately 40% of total body weight), cachexia is a multi-organ syndrome that also involves white and brown adipose tissue, and organs including the bones, brain, liver, gut and heart. Notably, cachexia accounts for up to 20% of cancer-related deaths. Cancer-associated cachexia is invariably associated with systemic inflammation, anorexia and increased energy expenditure. Understanding these mechanisms is essential, and the progress achieved in this area over the past decade could help to develop new therapeutic approaches. In this Review, we examine the currently available evidence on the roles of both the tumour macroenvironment and microenvironment in cancer-associated cachexia, and provide an overview of the novel therapeutic strategies developed to manage this syndrome.

Short duration treadmill exercise improves physical function and skeletal muscle mitochondria protein expression after recovery from FOLFOX chemotherapy in male mice

FOLFOX (5-FU, leucovorin, oxaliplatin) is a chemotherapy treatment for colorectal cancer which induces toxic side effects involving fatigue, weakness, and skeletal muscle dysfunction. There is a limited understanding of the recovery from these toxicities after treatment cessation. Exercise training can improve chemotherapy-related toxicities. However, how exercise accelerates recovery and the dose required for these benefits are not well examined. The purpose of this study was to examine the effect of exercise duration on physical function, muscle mass, and mitochondria protein expression during the recovery from FOLFOX chemotherapy. 12-week-old male mice were administered four cycles of either PBS or FOLFOX over 8-weeks. Outcomes were assessed after the fourth cycle and after either 4 (short-term; STR) or 10 weeks (long-term; LTR) recovery. Subsets of mice performed 14 sessions (6 d/wk, 18 m/min, 5% grade) of 60 min/d (long) or 15 min/d (short duration) treadmill exercise during STR. Red and white gastrocnemius mRNA and protein expression were examined. FOLFOX treatment decreased run time (RT) (-53%) and grip strength (GS) (-9%) compared to PBS. FOLFOX also reduced muscle OXPHOS complexes, COXIV, and VDAC protein expression. At LTR, FOLFOX RT (-36%) and GS (-16%) remained reduced. Long- and short-duration treadmill exercise improved RT (+58% and +56%) without restoring GS in FOLFOX mice. Both exercise durations increased muscle VDAC and COXIV expression in FOLFOX mice. These data provide evidence that FOLFOX chemotherapy induces persistent deficits in physical function that can be partially reversed by short-duration aerobic exercise.

Chemotherapy-induced cachexia and model-informed dosing to preserve lean mass in cancer treatment

Although chemotherapy is a standard treatment for cancer, it comes with significant side effects. In particular, certain agents can induce severe muscle loss, known as cachexia, worsening patient quality of life and treatment outcomes. 5-fluorouracil, an anti-cancer agent used to treat several cancers, has been shown to cause muscle loss. Experimental data indicates a non-linear dose-dependence for muscle loss in mice treated with daily or week-day schedules. We present a mathematical model of chemotherapy-induced muscle wasting that captures this non-linear dose-dependence. Area-under-the-curve metrics are proposed to quantify the treatment’s effects on lean mass and tumour control. Model simulations are used to explore alternate dosing schedules, aging effects, and morphine use in chemotherapy treatment with the aim of better protecting lean mass while actively targeting the tumour, ultimately leading to improved personalization of treatment planning and improved patient quality of life.

In this paper we present a novel mathematical model for muscle loss due to cancer chemotherapy treatment. Loss of muscle mass relates to increased drug toxicity and side-effects, and to decreased patient quality of life and survival rates. With our model, we examine the therapeutic efficacy of various dosing schedules with the aim of controlling a growing tumour while also preserving lean mass. Preservation of body composition, in addition to consideration of inflammation and immune interactions, the gut microbiome, and other systemic health measures, may lead to improved patient-specific treatment plans that improve patient quality of life.

Chemotherapy-Induced Myopathy: The Dark Side of the Cachexia Sphere

Simple Summary

In addition to cancer-related factors, anti-cancer chemotherapy treatment can drive life-threatening body wasting in a syndrome known as cachexia. Emerging evidence has described the impact of several key chemotherapeutic agents on skeletal muscle in particular, and the mechanisms are gradually being unravelled. Despite this evidence, there remains very little research regarding therapeutic strategies to protect muscle during anti-cancer treatment and current global grand challenges focused on deciphering the cachexia conundrum fail to consider this aspect—chemotherapy-induced myopathy remains very much on the dark side of the cachexia sphere. This review explores the impact and mechanisms of, and current investigative strategies to protect against, chemotherapy-induced myopathy to illuminate this serious issue.

Abstract

Cancer cachexia is a debilitating multi-factorial wasting syndrome characterised by severe skeletal muscle wasting and dysfunction (i.e., myopathy). In the oncology setting, cachexia arises from synergistic insults from both cancer–host interactions and chemotherapy-related toxicity. The majority of studies have surrounded the cancer–host interaction side of cancer cachexia, often overlooking the capability of chemotherapy to induce cachectic myopathy. Accumulating evidence in experimental models of cachexia suggests that some chemotherapeutic agents rapidly induce cachectic myopathy, although the underlying mechanisms responsible vary between agents. Importantly, we highlight the capacity of specific chemotherapeutic agents to induce cachectic myopathy, as not all chemotherapies have been evaluated for cachexia-inducing properties—alone or in clinically compatible regimens. Furthermore, we discuss the experimental evidence surrounding therapeutic strategies that have been evaluated in chemotherapy-induced cachexia models, with particular focus on exercise interventions and adjuvant therapeutic candidates targeted at the mitochondria.

Metronomic 5-Fluorouracil Delivery Primes Skeletal Muscle for Myopathy but Does Not Cause Cachexia

Skeletal myopathy encompasses both atrophy and dysfunction and is a prominent event in cancer and chemotherapy-induced cachexia. Here, we investigate the effects of a chemotherapeutic agent, 5-fluorouracil (5FU), on skeletal muscle mass and function, and whether small-molecule therapeutic candidate, BGP-15, could be protective against the chemotoxic challenge exerted by 5FU. Additionally, we explore the molecular signature of 5FU treatment. Male Balb/c mice received metronomic tri-weekly intraperitoneal delivery of 5FU (23 mg/kg), with and without BGP-15 (15 mg/kg), 6 times in total over a 15 day treatment period. We demonstrated that neither 5FU, nor 5FU combined with BGP-15, affected body composition indices, skeletal muscle mass or function. Adjuvant BGP-15 treatment did, however, prevent the 5FU-induced phosphorylation of p38 MAPK and p65 NF-B subunit, signalling pathways involved in cell stress and inflammatory signalling, respectively. This as associated with mitoprotection. 5FU reduced the expression of the key cytoskeletal proteins, desmin and dystrophin, which was not prevented by BGP-15. Combined, these data show that metronomic delivery of 5FU does not elicit physiological consequences to skeletal muscle mass and function but is implicit in priming skeletal muscle with a molecular signature for myopathy. BGP-15 has modest protective efficacy against the molecular changes induced by 5FU.

The Paradoxical Effect of PARP Inhibitor BGP-15 on Irinotecan-Induced Cachexia and Skeletal Muscle Dysfunction

Simple Summary

Both cancer and the chemotherapy used to treat it are drivers of cachexia, a life-threatening body-wasting condition which complicates cancer treatment. Poly-(ADP-ribose) polymerase (PARP) inhibitors are currently being investigated as a treatment against cancer. Here, we present paradoxical evidence that they might also be useful for mitigating the skeletal muscle specific side-effects of anti-cancer chemotherapy or exacerbate them. BGP-15 is a small molecule PARP inhibitor which protected against irinotecan (IRI)-induced cachexia and loss of skeletal muscle mass and dysfunction in our study. However, peculiarly, BGP-15 adjuvant therapy reduced protein synthesis rates and the expression of key cytoskeletal proteins associated with the dystrophin-associated protein complex and increased matrix metalloproteinase activity, while it increased the propensity for fast-twitch muscles to tear during fatiguing contraction. Our data suggest that both IRI and BGP-15 cause structural remodeling involving proteins associated with the contractile apparatus, cytoskeleton and/or the extracellular matrix which may be only transient and ultimately beneficial or may paradoxically onset a muscular dystrophy phenotype and be detrimental if more permanent.

Abstract

Chemotherapy-induced muscle wasting and dysfunction is a contributing factor to cachexia alongside cancer and increases the risk of morbidity and mortality. Here, we investigate the effects of the chemotherapeutic agent irinotecan (IRI) on skeletal muscle mass and function and whether BGP-15 (a poly-(ADP-ribose) polymerase-1 (PARP-1) inhibitor and heat shock protein co-inducer) adjuvant therapy could protect against IRI-induced skeletal myopathy. Healthy 6-week-old male Balb/C mice (n = 24; 8/group) were treated with six intraperitoneal injections of either vehicle, IRI (30 mg/kg) or BGP-15 adjuvant therapy (IRI+BGP; 15 mg/kg) over two weeks. IRI reduced lean and tibialis anterior mass, which were attenuated by IRI+BGP treatment. Remarkably, IRI reduced muscle protein synthesis, while IRI+BGP reduced protein synthesis further. These changes occurred in the absence of a change in crude markers of mammalian/mechanistic target of rapamycin (mTOR) Complex 1 (mTORC1) signaling and protein degradation. Interestingly, the cytoskeletal protein dystrophin was reduced in both IRI- and IRI+BGP-treated mice, while IRI+BGP treatment also decreased β-dystroglycan, suggesting significant remodeling of the cytoskeleton. IRI reduced absolute force production of the soleus and extensor digitorum longus (EDL) muscles, while IRI+BGP rescued absolute force production of the soleus and strongly trended to rescue force output of the EDL (p = 0.06), which was associated with improvements in mass. During the fatiguing stimulation, IRI+BGP-treated EDL muscles were somewhat susceptible to rupture at the musculotendinous junction, likely due to BGP-15’s capacity to maintain the rate of force development within a weakened environment characterized by significant structural remodeling. Our paradoxical data highlight that BGP-15 has some therapeutic advantage by attenuating IRI-induced skeletal myopathy; however, its effects on the remodeling of the cytoskeleton and extracellular matrix, which appear to make fast-twitch muscles more prone to tearing during contraction, could suggest the induction of muscular dystrophy and, thus, require further characterization.

Nitric Oxide (NO) and Duchenne Muscular Dystrophy: NO Way to Go?

The discordance between pre-clinical success and clinical failure of treatment options for Duchenne Muscular Dystrophy (DMD) is significant. The termination of clinical trials investigating the phosphodiesterase inhibitors, sildenafil and tadalafil (which prolong the second messenger molecule of nitric oxide (NO) signaling), are prime examples of this. Both attenuated key dystrophic features in the mdx mouse model of DMD yet failed to modulate primary outcomes in clinical settings. We have previously attempted to modulate NO signaling via chronic nitrate supplementation of the mdx mouse but failed to demonstrate beneficial modulation of key dystrophic features (i.e., metabolism). Instead, we observed increased muscle damage and nitrosative stress which exacerbated MD. Here, we highlight that acute nitrite treatment of human DMD myoblasts is also detrimental and suggest strategies for moving forward with NO replacement therapy in DMD.

Sodium nitrate co-supplementation does not exacerbate low dose metronomic doxorubicin-induced cachexia in healthy mice

The purpose of this study was to determine whether (1) sodium nitrate (SN) treatment progressed or alleviated doxorubicin (DOX)-induced cachexia and muscle wasting; and (2) if a more-clinically relevant low-dose metronomic (LDM) DOX treatment regimen compared to the high dosage bolus commonly used in animal research, was sufficient to induce cachexia in mice. Six-week old male Balb/C mice (n = 16) were treated with three intraperitoneal injections of either vehicle (0.9% NaCl; VEH) or DOX (4 mg/kg) over one week. To test the hypothesis that sodium nitrate treatment could protect against DOX-induced symptomology, a group of mice (n = 8) were treated with 1 mM NaNO₃ in drinking water during DOX (4 mg/kg) treatment (DOX + SN). Body composition indices were assessed using echoMRI scanning, whilst physical and metabolic activity were assessed via indirect calorimetry, before and after the treatment regimen. Skeletal and cardiac muscles were excised to investigate histological and molecular parameters. LDM DOX treatment induced cachexia with significant impacts on both body and lean mass, and fatigue/malaise (i.e. it reduced voluntary wheel running and energy expenditure) that was associated with oxidative/nitrostative stress sufficient to induce the molecular cytotoxic stress regulator, nuclear factor erythroid-2-related factor 2 (NRF-2). SN co-treatment afforded no therapeutic potential, nor did it promote the wasting of lean tissue. Our data re-affirm a cardioprotective effect for SN against DOX-induced collagen deposition. In our mouse model, SN protected against LDM DOX-induced cardiac fibrosis but had no effect on cachexia at the conclusion of the regimen.

Protective effects of endurance exercise on skeletal muscle remodeling against doxorubicin-induced myotoxicity in mice

PURPOSE

Doxorubicin (DOX) is a potent anti-cancer drug that appears to have severe myotoxicity due to accumulation. The skeletal muscle has a regeneration capacity through satellite cell activation when exposed to extracellular stimulus or damage. Endurance exercise (EXE) is a therapeutic strategy that improves pathological features and contributes to muscle homeostasis. Thus, this study investigated the effect of EXE training in mitigating chronic DOX-induced myotoxicity.

METHODS

Male C57BL/6J mice were housed and allowed to acclimatize with free access to food and water. All the mice were randomly divided into four groups: sedentary control (CON, n=9), exercise training (EXE, n=9), doxorubicin treatment (DOX, n=9), doxorubicin treatment and exercise training (DOX+EXE, n=9) groups. The animals were intraperitoneally injected with 5 mg/kg/week of DOX treatment for 4 weeks, and EXE training was initiated for treadmill adaptation for 1 week and then performed for 4 weeks. Both sides of the soleus (SOL) muscle tissues were dissected and weighed after 24 hours of the last training sessions.

RESULTS

DOX chemotherapy induced an abnormal myofiber's phenotype and transition of myosin heavy chain (MHC) isoforms. The paired box 7 (PAX7) and myoblast determination protein 1 (MYOD) protein levels were triggered by DOX, while no alterations were shown for the myogenin (MYOG). DOX remarkably impaired the a-actinin (ACTN) protein, but the EXE training seems to repair it. DOX-induced myotoxicity stimulated the expression of the forkhead box O3 (FOXO3a) protein, which was accurately controlled and adjusted by the EXE training. However, the FOXO3a-mediated downstream markers were not associated with DOX and EXE.

CONCLUSION

EXE postconditioning provides protective effects against chronic DOX-induced myotoxicity, and should be recommended to alleviate cancer chemotherapy-induced late-onset myotoxicity.

A 96-well culture platform enables longitudinal analyses of engineered human skeletal muscle microtissue strength

Three-dimensional (3D) in vitro models of human skeletal muscle mimic aspects of native tissue structure and function, thereby providing a promising system for disease modeling, drug discovery or pre-clinical validation, and toxicity testing. Widespread adoption of this research approach is hindered by the lack of easy-to-use platforms that are simple to fabricate and that yield arrays of human skeletal muscle micro-tissues (hMMTs) in culture with reproducible physiological responses that can be assayed non-invasively. Here, we describe a design and methods to generate a reusable mold to fabricate a 96-well platform, referred to as MyoTACTIC, that enables bulk production of 3D hMMTs. All 96-wells and all well features are cast in a single step from the reusable mold. Non-invasive calcium transient and contractile force measurements are performed on hMMTs directly in MyoTACTIC, and unbiased force analysis occurs by a custom automated algorithm, allowing for longitudinal studies of function. Characterizations of MyoTACTIC and resulting hMMTs confirms the capability of the device to support formation of hMMTs that recapitulate biological responses. We show that hMMT contractile force mirrors expected responses to compounds shown by others to decrease (dexamethasone, cerivastatin) or increase (IGF-1) skeletal muscle strength. Since MyoTACTIC supports hMMT long-term culture, we evaluated direct influences of pancreatic cancer chemotherapeutics agents on contraction competent human skeletal muscle myotubes. A single application of a clinically relevant dose of Irinotecan decreased hMMT contractile force generation, while clear effects on myotube atrophy were observed histologically only at a higher dose. This suggests an off-target effect that may contribute to cancer associated muscle wasting, and highlights the value of the MyoTACTIC platform to non-invasively predict modulators of human skeletal muscle function.