Drug-Related Lymphedema: Mysteries, Mechanisms, and Potential Therapies

The lymphatic circulation is an important component of the circulatory system in humans, playing a critical role in the transport of lymph fluid containing proteins, white blood cells, and lipids from the interstitial space to the central venous circulation. The efficient transport of lymph fluid critically relies on the rhythmic contractions of collecting lymph vessels, which function to “pump” fluid in the distal to proximal direction through the lymphatic circulation with backflow prevented by the presence of valves. When rhythmic contractions are disrupted or valves are incompetent, the loss of lymph flow results in fluid accumulation in the interstitial space and the development of lymphedema. There is growing recognition that many pharmacological agents modify the activity of ion channels and other protein structures in lymph muscle cells to disrupt the cyclic contraction and relaxation of lymph vessels, thereby compromising lymph flow and predisposing to the development of lymphedema. The effects of different medications on lymph flow can be understood by appreciating the intricate intracellular calcium signaling that underlies the contraction and relaxation cycle of collecting lymph vessels. For example, voltage-sensitive calcium influx through long-lasting (“L-type”) calcium channels mediates the rise in cytosolic calcium concentration that triggers lymph vessel contraction. Accordingly, calcium channel antagonists that are mainstay cardiovascular medications, attenuate the cyclic influx of calcium through L-type calcium channels in lymph muscle cells, thereby disrupting rhythmic contractions and compromising lymph flow. Many other classes of medications also may contribute to the formation of lymphedema by impairing lymph flow as an off-target effect. The purpose of this review is to evaluate the evidence regarding potential mechanisms of drug-related lymphedema with an emphasis on common medications administered to treat cardiovascular diseases, metabolic disorders, and cancer. Additionally, although current pharmacological approaches used to alleviate lymphedema are largely ineffective, efforts are mounting to arrive at a deeper understanding of mechanisms that regulate lymph flow as a strategy to identify novel anti-lymphedema medications. Accordingly, this review also will provide information on studies that have explored possible anti-lymphedema therapeutics.

Flecainide Paradoxically Activates Cardiac Ryanodine Receptor Channels under Low Activity Conditions: A Potential Pro-Arrhythmic Action

Cardiac ryanodine receptor (RyR2) mutations are implicated in the potentially fatal catecholaminergic polymorphic ventricular tachycardia (CPVT) and in atrial fibrillation. CPVT has been successfully treated with flecainide monotherapy, with occasional notable exceptions. Reported actions of flecainide on cardiac sodium currents from mice carrying the pro-arrhythmic homozygotic RyR2-P2328S mutation prompted our explorations of the effects of flecainide on their RyR2 channels. Lipid bilayer electrophysiology techniques demonstrated a novel, paradoxical increase in RyR2 activity. Preceding flecainide exposure, channels were mildly activated by 1 mM luminal Ca²⁺ and 1 µM cytoplasmic Ca²⁺, with open probabilities (P_o) of 0.03 ± 0.01 (wild type, WT) or 0.096 ± 0.024 (P2328S). Open probability (P_o) increased within 0.5 to 3 min of exposure to 0.5 to 5.0 µM cytoplasmic flecainide, then declined with higher concentrations of flecainide. There were no such increases in a subset of high P_o channels with P_o ≥ 0.08, although P_o then declined with ≥5 µM (WT) or ≥50 µM flecainide (P2328S). On average, channels with P_o < 0.08 were significantly activated by 0.5 to 10 µM of flecainide (WT) or 0.5 to 50 µM of flecainide (P2328S). These results suggest that flecainide can bind to separate activation and inhibition sites on RyR2, with activation dominating in lower activity channels and inhibition dominating in more active channels.

Doxorubicin Activates Ryanodine Receptors in Rat Lymphatic Muscle Cells to Attenuate Rhythmic Contractions and Lymph Flow

Doxorubicin is a risk factor for secondary lymphedema in cancer patients exposed to surgery or radiation. The risk is presumed to relate to its cytotoxicity. However, the present study provides initial evidence that doxorubicin directly inhibits lymph flow and this action appears distinct from its cytotoxic activity. We used real-time edge detection to track diameter changes in isolated rat mesenteric lymph vessels. Doxorubicin (0.5-20 μmol/l) progressively constricted lymph vessels and inhibited rhythmic contractions, reducing flow to 24.2% ± 7.7% of baseline. The inhibition of rhythmic contractions by doxorubicin paralleled a tonic rise in cytosolic Ca²⁺ concentration in lymphatic muscle cells, which was prevented by pharmacological antagonism of ryanodine receptors. Washout of doxorubicin partially restored lymph vessel contractions, implying a pharmacological effect. Subsequently, high-speed optical imaging was used to assess the effect of doxorubicin on rat mesenteric lymph flow in vivo. Superfusion of doxorubicin (0.05-10 μmol/l) maximally reduced volumetric lymph flow to 34% ± 11.6% of baseline. Likewise, doxorubicin (10 mg/kg) administered intravenously to establish clinically achievable plasma concentrations also maximally reduced volumetric lymph flow to 40.3% ± 6.0% of initial values. Our findings reveal that doxorubicin at plasma concentrations achieved during chemotherapy opens ryanodine receptors to induce "calcium leak" from the sarcoplasmic reticulum in lymphatic muscle cells and reduces lymph flow, an event linked to lymph vessel damage and the development of lymphedema. These results infer that pharmacological block of ryanodine receptors in lymphatic smooth muscle cells may mitigate secondary lymphedema in cancer patients subjected to doxorubicin chemotherapy. SIGNIFICANCE STATEMENT: Doxorubicin directly inhibits the rhythmic contractions of collecting lymph vessels and reduces lymph flow as a possible mechanism of secondary lymphedema, which is associated with the administration of anthracycline-based chemotherapy. The inhibitory effects of doxorubicin on rhythmic contractions and flow in isolated lymph vessels were prevented by pharmacological block of ryanodine receptors, thereby identifying the ryanodine receptor family of proteins as potential therapeutic targets for the development of new antilymphedema medications.

Time dependent response of daunorubicin on cytotoxicity, cell cycle and DNA repair in acute lymphoblastic leukaemia

BACKGROUND

Daunorubicin is commonly used in the treatment of acute lymphoblastic leukaemia (ALL). The aim of this study was to explore the kinetics of double strand break (DSB) formation of three ALL cell lines following exposure to daunorubicin and to investigate the effects of daunorubicin on the cell cycle and the protein kinases involved in specific checkpoints following DNA damage and recovery periods.

METHODS

Three ALL cell lines CCRF-CEM and MOLT-4 derived from T lymphocytes and SUP-B15 derived from B lymphocytes were examined following 4 h treatment with daunorubicin chemotherapy and 4, 12 and 24 h recovery periods. Cell viability was measured via MTT (3-(4,5-dimethylthiazol-2-yl)-2-5 diphenyltetrazolium bromide) assay, reactive oxygen species (ROS) production by flow cytometry, double stranded DNA breaks by detecting γH2AX levels while stages of the cell cycle were detected following propidium iodide staining and flow cytometry. Western blotting was used to detect specific proteins while RNA was extracted from all cell lines and converted to cDNA to sequence Ataxia-telangiectasia mutated (ATM).

RESULTS

Daunorubicin induced different degrees of toxicity in all cell lines and consistently generated reactive oxygen species. Daunorubicin was more potent at inducing DSB in MOLT-4 and CCRF-CEM cell lines while SUP-B15 cells showed delays in DSB repair and significantly more resistance to daunorubicin compared to the other cell lines as measured by γH2AX assay. Daunorubicin also causes cell cycle arrest in all three cell lines at different checkpoints at different times. These effects were not due to mutations in ATM as sequencing revealed none in any of the three cell lines. However, p53 was phosphorylated at serine 15 only in CCRF-CEM and MOLT-4 but not in SUP-B15 cells. The lack of active p53 may be correlated to the increase of SOD2 in SUP-B15 cells.

CONCLUSIONS

The delay in DSB repair and lower sensitivity to daunorubicin seen in the B lymphocyte derived SUP-B15 cells could be due to loss of function of p53 that may be correlated to increased expression of SOD2 and lower ROS production.

Progression of excitation-contraction coupling defects in doxorubicin cardiotoxicity

Cardiac failure is a common complication in cancer survivors treated with anthracyclines. Here we followed up cardiac function and excitation-contraction (EC) coupling in an in vivo doxorubicin (Dox) treated mice model (iv, total dose of 10 mg/Kg divided once every three days). Cardiac function was evaluated by echocardiography at 2, 6 and 15 weeks after the last injection. While normal at 2 and 6 weeks, ejection fraction was significantly reduced at 15 weeks. In order to evaluate the underlying mechanisms, we measured [Ca²⁺]_i transients by confocal microscopy and action potentials (AP) by patch-clamp technique in cardiomyocytes isolated at these times. Three phases were observed: 1/depression and slowing of the [Ca²⁺]_i transients at 2 weeks after treatment, with occurrence of proarrhythmogenic Ca²⁺ waves, 2/compensatory state at 6 weeks, and 3/depression on [Ca²⁺]_i transients and cell contraction at 15 weeks, concomitant with in-vivo defects. These [Ca²⁺]_i transient alterations were observed without cellular hypertrophy or AP prolongation and mirrored the sarcoplasmic reticulum (SR) Ca²⁺ load variations. At the molecular level, this was associated with a decrease in the sarcoplasmic reticulum Ca²⁺ ATPase (SERCA2a) expression and enhanced RyR2 phosphorylation at the protein kinase A (PKA, pS2808) site (2 and 15 weeks). RyR2 phosphorylation at the Ca²⁺/calmodulin dependent protein kinase II (CaMKII, pS2814) site was enhanced only at 2 weeks, coinciding with the higher incidence of proarrhythmogenic Ca²⁺ waves. Our study highlighted, for the first time, the progression of Dox treatment-induced alterations in Ca²⁺ handling and identified key components of the underlying Dox cardiotoxicity. These findings should be helpful to understand the early-, intermediate-, and late- cardiotoxicity already recorded in clinic in order to prevent or treat at the subclinical level.

The paradox of the first cycle of chemotherapy-transient improvement of contractility and diastolic function after the first cycle of anthracycline-based chemotherapy: a prospective clinical trial

Aims

Breast cancer is the most common cancer among women, and anthracyclines are the most commonly administered drugs for these patients. Cardiotoxicity is one of the complications, which limits the success of this therapy. Very few studies have evaluated anthracycline toxicities within the first few hours after the first infusion, and the majority of published studies were performed in animal models. The present study aimed to evaluate changes in echocardiographic parameters in women with breast cancer 24 hours after receiving the first dose of an anthracycline.

Materials and Methods and Results

The present study included 75 chemotherapy-naive female patients without heart failure, who were diagnosed with breast cancer and were scheduled to undergo anthracycline-based chemotherapy (epirubicin and doxorubicin). During their visits to the Heart Center, the patients underwent detail echocardiographic examination, including assessment of systolic and diastolic function and longitudinal strain. There were no differences in baseline echocardiographic parameters between patients with and those without cardiotoxicity. Cardiotoxicity was observed during follow-up in 14 patients (18.7%). Improvements in left ventricular ejection fraction and global longitudinal strain were observed at 24 hours after administration of the cytotoxic agent in the subgroup of patients without further cardiotoxicity. The changes were transient and the assessment of left ventricular ejection fraction after completion of chemotherapy revealed similar values to those before the treatment.

Conclusions

The findings of our study suggest that transient improvement in contractility and systolic and diastolic function might occur 24 hours after anthracycline administration, especially in patients who do not develop cardiotoxicity.

Changes in ischemia-modified albumin in myocardial toxicity induced by anthracycline and docetaxel chemotherapy

This study aims to evaluate differences in myocardial toxicity induced by different chemotherapy regimens. Patients were divided into 2 groups: epirubicin (EPI) combined with cyclophosphamide (EC) group and docetaxel combined with cyclophosphamide (TC) group. Changes in electrocardiograph (ECG) and ischemia-modified albumin (IMA) were determined pre- and 1, 3, and 6 courses of postchemotherapy. After the first course of chemotherapy, there was no significant difference in ECG and abnormal IMA incidence rates between the TC groups and EC groups (P > .05). After the third course and at the end of the sixth course, ECG and abnormal IMA incidence rates in the EC group were significantly higher than in the TC group (P < .05). Besides, IMA values significantly increased with the increase in chemotherapy courses in the EC group; and the value of the postsixth course was significantly higher than in the pre- and postfirst and -third courses of chemotherapy. IMA value in the postsixth course in the TC group was significantly higher than that in the pre- and postfirst and -third courses of chemotherapy. In addition, IMA values at the postfirst and -third courses of chemotherapy in the EC group were significantly higher than in the TC group. Both EC and TC chemotherapy regimens were harmful to the myocardium, and the incidence rate of myocardial damage increased with the increase of cumulative dose. Besides, the degree of myocardial damage in EC group was significantly higher than in the TC group.

A new cytoplasmic interaction between junctin and ryanodine receptor Ca2+ release channels

Junctin, a non-catalytic splice variant encoded by the aspartate-β-hydroxylase (Asph) gene, is inserted into the membrane of the sarcoplasmic reticulum (SR) Ca²⁺ store where it modifies Ca²⁺ signalling in the heart and skeletal muscle through its regulation of ryanodine receptor (RyR) Ca²⁺ release channels. Junctin is required for normal muscle function as its knockout leads to abnormal Ca²⁺ signalling, muscle dysfunction and cardiac arrhythmia. However, the nature of the molecular interaction between junctin and RyRs is largely unknown and was assumed to occur only in the SR lumen. We find that there is substantial binding of RyRs to full junctin, and the junctin luminal and, unexpectedly, cytoplasmic domains. Binding of these different junctin domains had distinct effects on RyR1 and RyR2 activity: full junctin in the luminal solution increased RyR channel activity by ∼threefold, the C-terminal luminal interaction inhibited RyR channel activity by ∼50%, and the N-terminal cytoplasmic binding produced an ∼fivefold increase in RyR activity. The cytoplasmic interaction between junctin and RyR is required for luminal binding to replicate the influence of full junctin on RyR1 and RyR2 activity. The C-terminal domain of junctin binds to residues including the S1–S2 linker of RyR1 and N-terminal domain of junctin binds between RyR1 residues 1078 and 2156.

Adverse effects of doxorubicin and its metabolic product on cardiac RyR2 and SERCA2A

The use of anthracycline chemotherapeutic drugs is restricted owing to potentially fatal cardiotoxic side effects. It has been hypothesized that anthracycline metabolites have a primary role in this cardiac dysfunction; however, information on the molecular interactions of these compounds in the heart is scarce. Here we provide novel evidence that doxorubicin and its metabolite, doxorubicinol, bind to the cardiac ryanodine receptor (RyR2) and to the sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA2A) and deleteriously alter their activity. Both drugs (0.01 μM-2.5 μM) activated single RyR2 channels, and this was reversed by drug washout. Both drugs caused a secondary inhibition of RyR2 activity that was not reversed by drug washout. Preincubation with the reducing agent dithiothreitol (DTT, 1 mM) prevented drug-induced inhibition of channel activity. Doxorubicin and doxorubicinol reduced the abundance of thiol groups on RyR2, further indicating that oxidation reactions may be involved in the actions of the compounds. Ca(2+) uptake into sarcoplasmic reticulum vesicles by SERCA2A was inhibited by doxorubicinol, but not doxorubicin. Unexpectedly, in the presence of DTT, doxorubicinol enhanced the rate of Ca(2+) uptake by SERCA2A. Together the evidence provided here shows that doxorubicin and doxorubicinol interact with RyR2 and SERCA2A in similar ways, but that the metabolite acts with greater efficacy than the parent compound. Both compounds modify RyR2 and SERCA2A activity by binding to the proteins and also act via thiol oxidation to disrupt SR Ca(2+) handling. These actions would have severe consequences on cardiomyocyte function and contribute to clinical symptoms of acute anthracycline cardiotoxicity.

Cardiac ryanodine receptor activation by a high Ca²⁺ store load is reversed in a reducing cytoplasmic redox environment

Here, we report the impact of redox potential on isolated cardiac ryanodine receptor (RyR2) channel activity and its response to physiological changes in luminal [Ca²⁺]. Basal leak from the sarcoplasmic reticulum is required for normal Ca²⁺ handling, but excess diastolic Ca²⁺ leak attributed to oxidative stress is thought to lower the threshold of RyR2 for spontaneous sarcoplasmic reticulum Ca²⁺ release, thus inducing arrhythmia in pathological situations. Therefore, we examined the RyR2 response to luminal [Ca²⁺] under reducing or oxidising cytoplasmic redox conditions. Unexpectedly, as luminal [Ca²⁺] increased from 0.1 to 1.5 mM, RyR2 activity declined when pretreated with cytoplasmic 1 mM DTT or buffered with GSH∶GSSG to a normal reduced cytoplasmic redox potential (−220 mV). Conversely, with 20 µM cytoplasmic 4,4′-DTDP or buffering of the redox potential to an oxidising value (−180 mV), RyR2 activity increased with increasing luminal [Ca²⁺]. The luminal redox potential was constant at −180 mV in each case. These responses to luminal [Ca²⁺] were maintained with cytoplasmic 2 mM Na₂ATP or 5 mM MgATP (1 mM free Mg²⁺). Overall, the results suggest that the redox potential in the RyR2 junctional microdomain is normally more oxidised than that of the bulk cytoplasm.

Systems pharmacology modeling: an approach to improving drug safety

Advances in systems biology in conjunction with the expansion in knowledge of drug effects and diseases present an unprecedented opportunity to extend traditional pharmacokinetic and pharmacodynamic modeling/analysis to conduct systems pharmacology modeling. Many drugs that cause liver injury and myopathies have been studied extensively. Mitochondrion-centric systems pharmacology modeling is important since drug toxicity across a large number of pharmacological classes converges to mitochondrial injury and death. Approaches to systems pharmacology modeling of drug effects need to consider drug exposure, organelle and cellular phenotypes across all key cell types of human organs, organ-specific clinical biomarkers/phenotypes, gene-drug interaction and immune responses. Systems modeling approaches, that leverage the knowledge base constructed from curating a selected list of drugs across a wide range of pharmacological classes, will provide a critically needed blueprint for making informed decisions to reduce the rate of attrition for drugs in development and increase the number of drugs with an acceptable benefit/risk ratio.

Complications of chemotherapy, a basic science update

Anthracyclines, discovered 50 years ago, are antibiotics widely used as antineoplastic agents and are among the most successful anticancer therapies ever developed to treat a wide range of cancers, including hematological malignancies, soft tissue sarcomas and solid tumors. However, some anthracyclines, including doxorubicin, exhibit major signs of cardiotoxicity that may ultimately lead to heart failure (HF). Despite intensive research on doxorubicine-induced cardiotoxicity, the underlying mechanisms responsible for doxorubicin-induced cardiotoxicity have not been fully elucidated yet. Published literature so far has focused mostly on mitochondria dysfunction with consequent oxidative stress, Ca(2+) overload, and cardiomyocyte death as doxorubicin side effects, leading to heart dysfunction. This review focuses on the current understanding of the molecular mechanisms underlying doxorubicin-induced cardiomyocyte death (i.e.: cardiomyocyte death, mitochondria metabolism and bioenergetic alteration), but we will also point to new directions of possible mechanisms, suggesting potent prior or concomitant alterations of specific signaling pathways with molecular actors directly targeted by the anticancer drugs itself (i.e. calcium homeostasis or cAMP signaling cascade). The mechanisms of anticancer cardiac toxicity may be more complex than just mitochondria dysfunction. Partnership of both basic and clinical research is needed to promote new strategies in diagnosis, therapies with concomitant cardioprotection in order to achieve cancer treatment with acceptable cardiotoxicity along life span.

Cardiac side effects of anticancer treatments: new mechanistic insights

Damage to heart cells leading to heart failure is a known complication of well-established cancer therapies including anthracycline antibiotics and radiation therapy, and the cardiovascular complications of these therapies has been controlled in large part through dose limitations and modifications of delivery methods. Recent research into the cellular and molecular mechanisms for the cardiovascular effects of these therapies may lead to other cardioprotective strategies that improve effectiveness of cancer treatments. Newer cancer therapies that have been developed based upon specifically targeting oncogene signaling also have been associated with heart failure. Rapid development of a detailed understanding of how these agents cause cardiac dysfunction promises to improve outcomes in cancer patients, as well as stimulate concepts of cardiovascular homeostasis that will likely accelerate development of cardiovascular therapies.

The impact of doxorubicin and dexrazoxane injection of prepubertal female rats on pregnancy outcome and cardiac function postpartum

Childhood cancer survivors can develop significant cardiac dysfunction in adulthood as a consequence of their cancer treatment. Studies have linked heart failure during pregnancy to childhood doxorubicin (DOX) exposure. We hypothesized that DOX injection would reduce cardiac function peripartum and that DOX-treated dams would show greater cardiac remodeling postweaning. Weanling female Sprague-Dawley rats were injected with phospate-buffered saline, DOX (3 mg/kg), or DOX plus the cardioprotectant dexrazoxane (DEX; 60 mg/kg) and followed for 2 pregnancies. DOX and DOX:DEX dams were fertile, but had fewer pups and more pup losses. Echocardiography, 1-day postpartum after each pregnancy, revealed greater increases in cardiac mass and eccentric hypertrophy in DOX-treated dams and early dilation in DOX:DEX dams. The expression of calcium homeostasis proteins can change after DOX treatment and cardiac remodeling. SERCA2a expression did not change. Reductions in phospholamban and phospho-serine 16-specific phospholamban expression in DOX dams were not relieved by DEX coinjection. DOX binds and inactivates calsequestrin 2 expression so increased calsequestrin 2 expression in DOX:DEX-treated dams suggests some DEX compensation. The eccentric hypertrophy and dilation development, despite compensatory changes in proteins controlling calcium cycling, suggest DOX damage with repeat pregnancy that was not alleviated fully by DEX.

Calsequestrin 2 and arrhythmias

Calsequestrin is the most abundant Ca-binding protein of the specialized endoplasmic reticulum found in muscle, the sarcoplasmic reticulum (SR). Calsequestrin binds Ca with high capacity and low affinity and importantly contributes to the mobilization of Ca during each contraction both in skeletal and cardiac muscle. Surprisingly, mutations in the gene encoding the cardiac isoform of calsequestrin (Casq2) have been associated with an inherited form of ventricular arrhythmia triggered by emotional or physical stress termed catecholaminergic polymorphic ventricular tachycardia (CPVT). Despite normal cardiac contractility and normal resting ECG, CPVT patients present with a high risk of sudden death at a young age. Here, we review recent new insights regarding the role of calsequestrin in genetic and acquired arrhythmia disorders. Mouse models of CPVT have shed light on the pathophysiological mechanism underlying CPVT. Casq2 is not only a Ca-storing protein as initially hypothesized, but it has a far more complex function in Ca handling and regulating SR Ca release channels. The functional importance of Casq2 interactions with other SR proteins and the importance of alterations in Casq2 trafficking are also being investigated. Reports of altered Casq2 trafficking in animal models of acquired heart diseases such as heart failure suggest that Casq2 may contribute to arrhythmia risk beyond genetic forms of Casq2 dysfunction.