Doxorubicin induces an increase of nitric oxide synthesis in rat cardiac cells that is inhibited by iron supplementation

Quantification of Nitric Oxide in Single Cells Using the Single-Probe Mass Spectrometry Technique

Nitric oxide (NO) is a small molecule that plays important roles in biological systems and human diseases. The abundance of intracellular NO is tightly related to numerous biological processes. Due to cell heterogeneity, the intracellular NO amounts significantly vary from cell to cell, and therefore, any meaningful studies need to be conducted at the single-cell level. However, measuring NO in single cells is very challenging, primarily due to the extremely small size of single cells and reactive nature of NO. In the current studies, the quantitative reaction between NO and amlodipine, a compound containing the Hantzsch ester group, was performed in live cells. The product dehydro amlodipine was then detected by the Single-probe single-cell mass spectrometry technique to quantify NO in single cells. The experimental results indicated heterogeneous distributions of intracellular NO amounts in single cells with the existence of subpopulations.

The role of inflammation and antioxidant defenses in the cardiotoxicity of doxorubicin in elderly CD-1 male mice

Doxorubicin (DOX) is a potent chemotherapeutic agent used against several cancer types. However, due to its cardiotoxic adverse effects, the use of this drug may be also life-threatening. Although most cancer patients are elderly, they are poorly represented and evaluated in pre-clinical and clinical studies. Considering this, the present work aims to evaluate inflammation and oxidative stress as the main mechanisms of DOX-induced cardiotoxicity, in an innovative approach using an experimental model constituted of elderly animals treated with a clinically relevant human cumulative dose of DOX. Elderly (18-20 months) CD-1 male mice received biweekly DOX administrations, for 3 weeks, to reach a cumulative dose of 9.0 mg/kg. One week (1W) or two months (2 M) after the last DOX administration, the heart was collected to determine both drug's short and longer cardiac adverse effects. The obtained results showed that DOX causes cardiac histological damage and fibrosis at both time points. In the 1W-DOX group, the number of nuclear factor kappa B (NF-κB) p65 immunopositive cells increased and a trend toward increased NF-κB p65 expression was seen. An increase of inducible nitric oxide synthase (iNOS) and interleukin (IL)-33 and a trend toward increased IL-6 and B-cell lymphoma-2-associated X (Bax) expression were seen after DOX. In the same group, a decrease in IL-1β, p62, and microtubule-associated protein 1A/1B-light chain 3 (LC3)-I, p38 mitogen-activated protein kinase (MAPK) expression was observed. Contrariwise, the animals sacrificed 2 M after DOX showed a significant increase in glutathione peroxidase 1 and Bax expression with persistent cardiac damage and fibrosis, while carbonylated proteins, erythroid-2-related factor 2 (Nrf2), NF-κB p65, myeloperoxidase, LC3-I, and LC3-II expression decreased. In conclusion, our study demonstrated that in an elderly mouse population, DOX induces cardiac inflammation, autophagy, and apoptosis in the heart in the short term. When kept for a longer period, oxidative-stress-linked pathways remained altered, as well as autophagy markers and tissue damage after DOX treatment, emphasizing the need for continuous post-treatment cardiac monitoring.

Doxorubicin and other anthracyclines in cancers: Activity, chemoresistance and its overcoming

Anthracyclines have been important and effective treatments against a number of cancers since their discovery. However, their use in therapy has been complicated by severe side effects and toxicity that occur during or after treatment, including cardiotoxicity. The mode of action of anthracyclines is complex, with several mechanisms proposed. It is possible that their high toxicity is due to the large set of processes involved in anthracycline action. The development of resistance is a major barrier to successful treatment when using anthracyclines. This resistance is based on a series of mechanisms that have been studied and addressed in recent years. This work provides an overview of the anthracyclines used in cancer therapy. It discusses their mechanisms of activity, toxicity, and chemoresistance, as well as the approaches used to improve their activity, decrease their toxicity, and overcome resistance.

Molecular mechanisms of endothelial remodeling under doxorubicin treatment

Doxorubicin (DOX) is an effective antineoplastic agent used to treat various types of cancers. However, its use is limited by the development of cardiotoxicity, which may result in heart failure. The exact mechanisms underlying DOX-induced cardiotoxicity are not fully understood, but recent studies have shown that endothelial-mesenchymal transition (EndMT) and endothelial damage play a crucial role in this process. EndMT is a biological process in which endothelial cells lose their characteristics and transform into mesenchymal cells, which have a fibroblast-like phenotype. This process has been shown to contribute to tissue fibrosis and remodeling in various diseases, including cancer and cardiovascular diseases. DOX-induced cardiotoxicity has been demonstrated to increase the expression of EndMT markers, suggesting that EndMT may play a critical role in the development of this condition. Furthermore, DOX-induced cardiotoxicity has been shown to cause endothelial damage, leading to the disruption of the endothelial barrier function and increased vascular permeability. This can result in the leakage of plasma proteins, leading to tissue edema and inflammation. Moreover, DOX can impair the production of nitric oxide, endothelin-1, neuregulin, thrombomodulin, thromboxane B2 etc. by endothelial cells, leading to vasoconstriction, thrombosis and further impairing cardiac function. In this regard, this review is devoted to the generalization and structuring of information about the known molecular mechanisms of endothelial remodeling under the action of DOX.

Medicinal Plants from Brazilian Cerrado Biome: Potential sources of new anti-inflammatory compounds and antitumor agents on Ehrlich carcinoma

This work describes a pharmacological screening of Brazilian medicinal plants through their anti-inflammatory and cytotoxicity activities. Cytotoxicity activity of Mouriri elliptica and Alchornea glandulosa as well as the drugs celecoxib and doxorubicin were evaluated in cultures of peritoneal macrophages. The immune system influence of these samples was analyzed by determining production/inhibition of NO, production of tumor necrosis factor-α and production of interleukin-10. Regarding the production/inhibition of NO, there was NO production by M. elliptica and NO inhibition when the cells were exposed to A. glandulosa; Macrophages generally produce more NO, plus TNF-α and less IL-10, when associated to the tumor phenomenon, characterizing the inflammation involved in cancer. A. glandulosa showed anti-inflammatory effect, inhibited NO production and it was associated with low TNF-α production, although not as low as the macrophages associated with celecoxib and doxorubicin. These cytokines were not different in animals with tumor. Celecoxib confirms its anti-inflammatory action by markedly inhibiting NO and TNF-α, but also inhibiting IL-10 which is an anti-inflammatory cytokine. Doxorubicin inhibited NO in a higher percentage in the group of animals with tumor, although the literature reports that this drug stimulates the production of NO and this collaborates with its cytotoxic effect.

The SGLT-2 inhibitor empagliflozin improves myocardial strain, reduces cardiac fibrosis and pro-inflammatory cytokines in non-diabetic mice treated with doxorubicin

BACKGROUND

Empagliflozin (EMPA), a selective inhibitor of the sodium glucose co-transporter 2, reduced the risk of hospitalization for heart failure and cardiovascular death in type 2 diabetic patients in the EMPA-REG OUTCOME trial. Recent trials evidenced several cardio-renal benefits of EMPA in non-diabetic patients through the involvement of biochemical pathways that are still to be deeply analysed. We aimed to evaluate the effects of EMPA on myocardial strain of non-diabetic mice treated with doxorubicin (DOXO) through the analysis of NLRP3 inflammasome and MyD88-related pathways resulting in anti-apoptotic and anti-fibrotic effects.

METHODS

Preliminary cellular studies were performed on mouse cardiomyocytes (HL-1 cell line) exposed to doxorubicin alone or combined to EMPA. The following analysis were performed: determination of cell viability (through a modified MTT assay), study of intracellular ROS production, lipid peroxidation (quantifying intracellular malondialdehyde and 4-hydroxynonenal), intracellular Ca2+ homeostasis. Moreover, pro-inflammatory studies were also performed: expression of NLRP3 inflammasome, MyD88 myddosome and p65/NF-κB associated to secretion of cytokines involved in cardiotoxicity (Interleukins 1β, 8, 6). C57Bl/6 mice were untreated (Sham, n = 6) or treated for 10 days with doxorubicin (DOXO, n = 6), EMPA (EMPA, n = 6) or doxorubicin combined to EMPA (DOXO-EMPA, n = 6). DOXO was injected intraperitoneally. Ferroptosis and xanthine oxidase were studied before and after treatments. Cardiac function studies, including EF, FS and radial/longitudinal strain were analysed through transthoracic echocardiography (Vevo 2100). Cardiac fibrosis and apoptosis were histologically studied through Picrosirius red and TUNEL assay, respectively and quantified through pro-collagen-1α1, MMP-9 and Caspase-3 expression. Tissue NLRP3, MyD88 and cytokines were also quantified before and after treatments through ELISA methods.

RESULTS

Cardiomyocytes exposed to doxorubicin increased the intracellular Ca2+ content and expression of several pro-inflammatory markers associated to cell death; co-incubation with EMPA reduced significantly the magnitude of the effects. In preclinical study, EMPA increased EF and FS compared to DOXO groups (p < 0.05), prevented the reduction of radial and longitudinal strain after 10 days of treatment with doxorubicin (RS) 30.3% in EMPA-DOXO vs 15.7% in DOXO mice; LS - 17% in EMPA-DOXO vs - 11.7% in DOXO mice (p < 0.001 for both). Significant reductions in ferroptosis, xanthine oxidase expression, cardiac fibrosis and apoptosis in EMPA associated to DOXO were also seen. A reduced expression of pro-inflammatory cytokines, NLRP3, MyD88 and NF-kB in heart, liver and kidneys was also seen in DOXO-EMPA group compared to DOXO (p < 0.001).

CONCLUSION

EMPA reduced ferroptosis, fibrosis, apoptosis and inflammation in doxorubicin-treated mice through the involvement of NLRP3 and MyD88-related pathways, resulting in significant improvements in cardiac functions. These findings provides the proof of concept for translational studies designed to reduce adverse cardiovascular outcomes in non-diabetic cancer patients treated with doxorubicin.

Oxidative stress and inflammation: determinants of anthracycline cardiotoxicity and possible therapeutic targets

Chemotherapy with anthracycline-based regimens remains a cornerstone of treatment of many solid and blood tumors but is associated with a significant risk of cardiotoxicity, which can manifest as asymptomatic left ventricular dysfunction or overt heart failure. These effects are typically dose-dependent and cumulative and may require appropriate screening strategies and cardioprotective therapies in order to minimize changes to anticancer regimens or even their discontinuation. Our current understanding of cardiac damage by anthracyclines includes a central role of oxidative stress and inflammation. The identification of these processes through circulating biomarkers or imaging techniques might then be helpful for early diagnosis and risk stratification. Furthermore, therapeutic strategies relieving oxidative stress and inflammation hold promise to prevent heart failure development or at least to mitigate cardiac damage, although further evidence is needed on their efficacy, either alone or as part of combination therapies with neurohormonal antagonists, which are the current adopted standard.

A switch in mechanism of action prevents doxorubicin-mediated cardiac damage

Cancer patients treated with doxorubicin are at risk of congestive heart failure due to doxorubicin-mediated cardiotoxicity via topoisomerase IIβ poisoning. Acute cardiac muscle damage occurs in response to the very first dose of doxorubicin, however, cardioprotection has been reported after co-treatment of doxorubicin with acyloxyalkyl ester prodrugs. The aim of this study was to examine the role played by various forms of acute cardiac damage mediated by doxorubicin and determine a mechanism for the cardioprotective effect of formaldehyde-releasing prodrug AN-9 (pivaloyloxymethyl butyrate). Doxorubicin-induced cardiac damage in BALB/c mice bearing mammary tumours was established with a single dose of doxorubicin (4 or 16 mg/kg) administered alone or in combination with AN-9 (100 mg/kg). AN-9 protected the heart from doxorubicin-induced myocardial apoptosis and also significantly reduced dsDNA breaks, independent from the level of doxorubicin biodistribution to the heart. Covalent incorporation of [¹⁴C]doxorubicin into DNA showed that the combination treatment yielded significantly higher levels of formaldehyde-mediated doxorubicin-DNA adducts compared to doxorubicin alone, yet this form of damage was associated with cardioprotection from apoptosis. The cardiac transcriptomic analysis indicates that the combination treatment initiates inflammatory response signalling pathways. Doxorubicin and AN-9 combination treatments were cardioprotective, yet preserved doxorubicin-mediated anti-tumour proliferation and apoptosis in mammary tumours. This was associated with a switch in doxorubicin action from cardiac topoisomerase IIβ poisoning to covalent-DNA adduct formation. Co-administration of doxorubicin and formaldehyde-releasing prodrugs, such as AN-9, may be a promising cardioprotective therapy while maintaining doxorubicin activity in primary mammary tumours.

Deep imaging for visualizing nitric oxide in lipid droplets: discovering the relationship between nitric oxide and resistance to cancer chemotherapy drugs

A near-infrared two-photon fluorescent probe (TAN) was synthesized for selective detection and deep-depth imaging of NO in lipid droplets. All results demonstrated that NO production in lipid droplets is closely correlated with the resistance to anti-tumor drugs, and NO inhibitors can effectively improve the efficacy of chemotherapeutic agents.

Distinct influence of the anthracycline derivative doxorubicin on the differentiation efficacy of mESC-derived endothelial progenitor cells

Cardiotoxicity is a highly relevant, because often life-threatening, adverse effect of doxorubicin (Doxo)-based anticancer therapy. Here, we investigated the Doxo-response of cardiovascular stem/progenitor cells employing a mouse embryonic stem cell (mESC)-based in vitro differentiation model. Endothelial progenitor cells revealed a pronounced Doxo sensitivity as compared to mESC, differentiated endothelial-like (EC) and cardiomyocyte-like cells (CM) and CM progenitors, which rests on the activation of senescence. Doxo treatment of EC progenitors altered protein expression of individual endothelial markers, actin cytoskeleton morphology, mRNA expression of genes related to mitochondrial functions, autophagy, apoptosis, and DNA repair as well as mitochondrial DNA content, respiration and ATP production in the surviving differentiated EC progeny. By contrast, LDL uptake, ATP-stimulated Ca²⁺ release, and cytokine-stimulated ICAM-1 expression remained unaffected by the anthracycline treatment. Thus, exposure of EC progenitors to Doxo elicits isolated and persistent dysfunctions in the surviving EC progeny. In conclusion, we suggest that Doxo-induced injury of EC progenitors adds to anthracycline-induced cardiotoxicity, making this cell-type a preferential target for pharmacoprotective and regenerative strategies.

Angiotensin-converting enzyme 2 overexpression protects against doxorubicin-induced cardiomyopathy by multiple mechanisms in rats

Angiotensin-converting enzyme 2 (ACE2) is considered a potential therapeutic target of the renin-angiotensin system (RAS) for the treatment of cardiovascular diseases. We aimed to explore the effects of ACE2 overexpression on doxorubicin-induced cardiomyopathy in rats. Rats were randomly divided into treatment and control groups. The rats of treatment group were injected intraperitoneally with 6 doses of doxorubicin (2.5 mg/kg) within a period of two weeks. Two weeks after the initial injection of doxorubicin, these rats were randomly divided into Mock, Ad-EGFP, Ad-ACE2, and Cilazapril groups. The rats of Ad-EGFP and Ad-ACE2 groups received intramyocardial injection of Ad-EGFP and Ad-ACE2, respectively. The rats of Cilazapril group received cilazapril (10 mg/kg/day) via intragastric intubation. Apoptosis, inflammation, oxidative stress, cardiac function, the extent of myocardial fibrosis, and levels of ACE2, ACE, angiotensin II (AngII), and angiotensin (1–7) were evaluated. Four weeks after ACE2 gene transfer, the Ad-ACE2 group showed not only reduced apoptosis, inflammatory response, oxidative stress, left ventricular (LV) volume, extent of myocardial fibrosis and mortality of rats, but also increased LV ejection fraction and ACE2 expression level compared with the Mock and Ad-EGFP groups. ACE2 overexpression was superior to cilazapril in improving doxorubicin-induced cardiomyopathy. The putative mechanisms may involve activation of the AMPK and PI3K-AKT pathways, inhibition of the ERK pathway, decrease of TGF-β1 expression, and interactions of shifting RAS components, such as decreased myocardium AngII levels, increased myocardium Ang (1–7) levels, and reduced ACE expression. Thus, ACE2 may be a novel therapeutic approach to prevent and treat doxorubicin-induced cardiomyopathy.

Recent progress in doxorubicin-induced cardiotoxicity and protective potential of natural products

BACKGROUND

As an anthracycline antibiotic, doxorubicin (DOX) is one of the most potent and widely used chemotherapeutic agents for various types of solid tumors. Unfortunately, clinical application of this drug results in severe side effects of cardiotoxicity.

PURPOSE

We aim to review the research focused on elimination or reduction of DOX cardiotoxicity without affecting its anticancer efficacy by natural products.

METHODS

This study is based on pertinent papers that were retrieved by a selective search using relevant keywords in PubMed and ScienceDirect. The literature mainly focusing on natural products and herb extracts with therapeutic efficacies against experimental models both in vitro and in vivo was identified.

RESULTS

Current evidence revealed that multiple molecules and signaling pathways, such as oxidative stress, iron metabolism, and inflammation, are associated with DOX-induced cardiotoxicity. Based on these knowledge, various strategies were proposed, and thousands of compounds were screened. A number of natural products and herb extracts demonstrated potency in limiting DOX cardiotoxicity toward cultured cells and experimental animal models.

CONCLUSIONS

Though a panel of natural products and herb extracts demonstrate protective effects on DOX-induced cardiotoxicity in cells and animal models, their therapeutic potentials for clinical needs further investigation.

Diallyl trisulfide suppresses doxorubicin-induced cardiomyocyte apoptosis by inhibiting MAPK/NF-κB signaling through attenuation of ROS generation

BACKGROUND

Doxorubicin (Dox) is an effective anticancer agent. However, its effectiveness is limited by its cardiotoxic effects. It has also been reported that the mitogen-activated protein kinase family and NF-κB can be activated by Dox treatment. DATS has been shown to be a potent antioxidant with cardioprotective effects. We investigate whether Dox induces cardiac apoptosis through JNK- and ERK-dependent NF-κB upregulation that can be reduced by DATS treatment.

METHODS AND MATERIAL

H9c2 cells were treated with 0.5-1.5 μM Dox for 24 hours. Dox promoted apoptosis and ROS generation and inhibited viability in a dose-dependent manner. Then, the phosphorylation levels of JNK, ERK, and NF-κB evaluated by western blot were elevated. We used inhibitors of JNK, ERK, and NF-κB to determine which of these proteins were involved in Dox-induced apoptosis. Furthermore, Dox-exposed cells were treated with DATS at doses of 1, 5, and 10 μM, and the data demonstrated that ROS generation and apoptotic proteins were decreased and that ERK and NF-κB were downregulated in a dose-dependent manner. Additionally, six-week-old rats were divided into three groups (n = 6 per group) designed as an eight-week study. Normal, Dox (at dose 3.75 mg/kg by ip) administered with or without DATS (at dose 40 mg/kg by gavage) treatment groups. The results indicate that cardiac dysfunction, apoptosis, and JNK, ERK, and NF-κB activation by Dox were reversed by treatment with DATS.

CONCLUSION

DATS appears to suppress Dox-induced cardiomyocyte apoptosis by inhibiting NADPH oxidase-related ROS production and the downstream JNK/ERK/NF-κB signaling pathway; DATS may possess clinical therapeutic potential by blocking Dox-induced cardiotoxicity.

Doxorubicin-induced nitrosative stress is mitigated by vitamin C via the modulation of nitric oxide synthases

An increase in oxidative stress is suggested to be the main cause in Doxorubicin (Dox)–induced cardiotoxicity. However, there is now evidence that activation of inducible nitric oxide synthase (iNOS) and nitrosative stress are also involved. The role of vitamin C (Vit C) in the regulation of nitric oxide synthase (NOS) and reduction of nitrosative stress in Dox-induced cardiotoxicity is unknown. The present study investigated the effects of Vit C in the mitigation of Dox-induced changes in the levels of nitric oxide (NO), NOS activity, protein expression of NOS isoforms, and nitrosative stress as well as cytokines TNF-α and IL-10 in isolated cardiomyocytes. Cardiomyocytes isolated from adult Sprague-Dawley rats were segregated into four groups: 1) control, 2) Vit C (25 µM), 3) Dox (10 µM), and 4) Vit C + Dox. Dox caused a significant increase in the generation of superoxide radical (O2·−), peroxynitrite, and NO, and these effects of Dox were blunted by Vit C. Dox increased the expression of iNOS and altered protein expression as well as activation of endothelial NOS (eNOS). These changes were prevented by Vit C. Dox induced an increase in the ratio of monomeric/dimeric eNOS, promoting the production of O2·−, which was prevented by Vit C by increasing the stability of the dimeric form of eNOS. Vit C protected against the Dox-induced increase in TNFα as well as a reduction in IL-10. These results suggest that Vit C provides cardioprotection by reducing oxidative/nitrosative stress and inflammation via a modulation of Dox-induced increase in the NO levels and NOS activity.

Oxidative Damage Precedes Nitrative Damage in Adriamycin-Induced Cardiac Mitochondrial Injury

The purpose of the present study was to determine if elevated reactive oxygen (ROS)/nitrogen species (RNS) reported to be present in adriamycin (ADR)-induced cardiotoxicity actually resulted in cardiomyocyte oxidative/nitrative damage, and to quantitatively determine the time course and subcellular localization of these postulated damage products using an in vivo approach. B6C3 mice were treated with a single dose of 20 mg/kg ADR. Ultrastructural damage and levels of 4-hydroxy-2-nonenal (4HNE)-protein adducts and 3-nitrotyrosine (3NT) were analyzed. Quantitative ultrastructural damage using computerized image techniques showed cardiomyocyte injury as early as 3 hours, with mitochondria being the most extensively and progressively injured subcellular organelle. Analysis of 4HNE protein adducts by immunogold electron microscopy showed appearance of 4HNE protein adducts in mitochondria as early as 3 hours, with a peak at 6 hours and subsequent decline at 24 hours. 3NT levels were significantly increased in all subcellular compartments at 6 hours and subsequently declined at 24 hours. Our data showed ADR induced 4HNE-protein adducts in mitochondria at the same time point as when mitochondrial injury initially appeared. These results document for the first time in vivo that mitochondrial oxidative damage precedes nitrative damage. The progressive nature of mitochondrial injury suggests that mitochondria, not other subcellular organelles, are the major site of intracellular injury.

Effect of nisin and doxorubicin on DMBA-induced skin carcinogenesis--a possible adjunct therapy

In view of the emergence of multidrug-resistant cancer cells, there is a need for therapeutic alternatives. Keeping this in mind, the present study was aimed at evaluating the synergism between nisin (an antimicrobial peptide) and doxorubicin (DOX) against DMBA-induced skin carcinogenesis. The possible tumoricidal activity of the combination was evaluated in terms of animal bioassay observations, changes in hisotological architecture of skin tissues, in situ apoptosis assay (TUNEL assay) and in terms of oxidant and antioxidant status of the skin tissues. In vivo additive effect of the combination was evidenced by larger decreases in mean tumour burden and tumour volume in mice treated with the combination than those treated with the drugs alone. Histological observations indicated that nisin-DOX therapy causes chromatin condensation and marginalisation of nuclear material in skin tissues of treated mice which correlated well with the results of TUNEL assay wherein a marked increase in the rate of apoptosis was revealed in tissues treated with the combination. A slightly increased oxidative stress in response to the adjunct therapy as compared to dox-alone-treated group was revealed by levels of lipid peroxidation (LPO) and nitrite generation in skin tissue-treated mice. An almost similar marginal enhancement in superoxide dismutase levels corresponding with a decrease in catalase activity could also be observed in nisin + DOX-treated groups as compared to nisin and dox-alone-treated groups. These results point towards the possible use of nisin as an adjunct to doxorubicin may help in developing alternate strategies to combat currently developing drug resistance in cancer cells.

Total Flavonoids from Clinopodium chinense (Benth.) O. Ktze Protect against Doxorubicin-Induced Cardiotoxicity In Vitro and In Vivo

Doxorubicin has cardiotoxic effects that limit its clinical benefit in cancer patients. This study aims to investigate the protective effects of the total flavonoids from Clinopodium chinense (Benth.) O. Ktze (TFCC) against doxorubicin- (DOX-) induced cardiotoxicity. Male rats were intraperitoneally injected with a single dose of DOX (3 mg/kg) every 2 days for three injections. Heart samples were collected 2 weeks after the last DOX dose and then analyzed. DOX delayed body and heart growth and caused cardiac tissue injury, oxidative stress, apoptotic damage, mitochondrial dysfunction, and Bcl-2 expression disturbance. Similar experiments in H9C2 cardiomyocytes showed that doxorubicin reduced cell viability, increased ROS generation and DNA fragmentation, disrupted mitochondrial membrane potential, and induced apoptotic cell death. However, TFCC pretreatment suppressed all of these adverse effects of doxorubicin. Signal transduction studies indicated that TFCC suppressed DOX-induced overexpression of p53 and phosphorylation of JNK, p38, and ERK. Studies with LY294002 (a PI3K/AKT inhibitor) demonstrated that the mechanism of TFCC-induced cardioprotection also involves activation of PI3K/AKT. These findings indicated the potential clinical application of TFCC in preventing DOX-induced cardiac oxidative stress.

Liposomal nitrooxy-doxorubicin: one step over caelyx in drug-resistant human cancer cells

In this work we prepared and characterized two liposomal formulations of a semisynthetic nitric oxide (NO)-releasing doxorubicin (Dox), called nitrooxy-Dox (NitDox), which we previously demonstrated to be cytotoxic in Dox-resistant human colon cancer cells. Liposomes with 38.2% (Lip A) and 19.1% (Lip B) cholesterol were synthesized: both formulations had similar size and zeta potential values and caused the same intracellular distribution of free NitDox, but Lip B accumulated and released NitDox more efficiently. In Dox-resistant human colon cancer cells, Lip A and Lip B exhibited a more favorable kinetics of drug uptake and NO release, and a stronger cytotoxicity than Dox and free NitDox. While Caelyx, one of the liposomal Dox formulations approved for breast and ovary tumors treatment, was ineffective in Dox-resistant breast/ovary cancer cells, Lip B, and to a lesser extent Lip A, still exerted a significant cytotoxicity in these cells. This event was accompanied in parallel by a higher release of NO, which caused nitration of P-glycoprotein (Pgp) and multidrug resistance related protein 1 (MRP1), two transporters involved in Dox efflux, and impaired their pump activity. By doing so, the efflux kinetics of Dox after treatment with Lip B was markedly slowed down and the intracellular accumulation of Dox was increased in breast and ovary drug-resistant cells. We propose these liposomal formulations of NitDox as new tools with a specific indication for tumors overexpressing Pgp and MRP1.

Amelioration of adriamycin-induced cardiotoxicity by Salsola kali aqueous extract is mediated by lowering oxidative stress

OBJECTIVES

To assess the cardioprotective effect of the Salsola kali aqueous extract against adriamycin (ADR)-induced cardiotoxicity in male Swiss albino mice.

METHODS

The aqueous extract of S. kali was phytochemically screened by traditional methods for different classes and further evaluated for antioxidant activity in vitro. In vivo, cardioprotective evaluation of the extract was designed to have four groups of mice: (1) control group (distilled water, orally; normal saline, intraperitoneally (i.p.)); (2) ADR group (15 mg/kg, i.p.); (3) aqueous S. kali extract (200 mg/kg, orally); and (4) ADR + S. kali group. ADR (5 mg/kg) was injected three times over 2 weeks while S. kali was orally administered daily for 3 weeks (1 week before and 2 weeks during ADR treatment). Cardioprotective properties were assessed using biochemical and histopathological approaches.

RESULTS

ADR caused a significant increase in serum enzymes (lactate dehydrogenase, creatine phosphokinase, aspartate aminotransferase, and alanine aminotransferase). Myocardial levels of malondialdehyde, nitric oxide, and reduced glutathione, as well as the activities of superoxide dismutase and catalase increased while the activities of glutathione peroxidase and glutathione S-transferase declined. Histopathological examination of heart sections revealed that ADR caused myofibrils loss, necrosis and cytoplasmic vacuolization.

DISCUSSION

Pretreatment with S. kali aqueous extract normalized serum and antioxidant enzymes minimized lipid peroxidation and cardiac damage. These results have suggested that the extract has antioxidant activity, indicating that the mechanism of cardioprotection during ADR treatment is mediated by lowering oxidative stress.

The role of nitric oxide in Doxorubicin-induced cardiotoxicity: experimental study

Objective: We evaluated the myocardial damage in rats treated with doxorubicin (DOX) alone and in combination with nitric oxide synthase (NOS) inhibitors.

Materials and Methods: Twenty-four male Sprague Dawley rats (12 weeks old, weighing 262±18 g) were randomly assigned into 4 groups (n=6). Group I was the control group. In Group II, rats were treated with intraperitoneal (ip) injections of 3 mg/kg DOX once a week for 5 weeks. In Group III, rats received weekly ip injections of 30 mg/kg L-NAME (nonspecific NOS inhibitor) 30 min before DOX injections for 5 weeks. In Group IV, rats received weekly ip injections of 3 mg/kg L-NIL (inducible NOS inhibitor) 30 min before DOX injections for 5 weeks. Rats were weighed 2 times a week. At the end of 6 weeks, hearts were excised and then fixed for light and electron microscopy evaluation and tissue lipid peroxidation (malondialdehyde). Blood samples were also obtained for measuring plasma lipid peroxidation.

Results: Weight loss was observed in Group II, Group III, and Group IV. Weight loss was statistically significant in the DOX group. Findings of myocardial damage were significantly higher in animals treated with DOX only than in the control group. Histopathological findings of cardiotoxicity in rats treated with DOX in combination with L-NAME and L-NIL were not significantly different compared with the control group. The level of plasma malondialdehyde in the DOX group (9.3±3.4 µmol/L) was higher than those of all other groups.

Conclusion: Our results showed that DOX cardiotoxicity was significantly decreased when DOX was given with NO synthase inhibitors.

Activation of PI3K-Akt through taurine is critical for propofol to protect rat cardiomyocytes from doxorubicin-induced toxicity

Myocardial toxicity is one of the major side effects of many chemotherapeutics. It has been shown that propofol can ameliorate the cardiotoxicity of chemotherapeutic agents. In this study, we intend to investigate the role of the PI3K-Akt-Bad signaling pathway in propofol relief of doxorubicin-induced oxidative stress and apoptosis in rat cardiomyocytes. Cultured neonatal rat cardiomyocytes were treated with vehicle, doxorubicin, propofol, or propofol plus doxorubicin in the presence or absence of the PI3K inhibitor LY294002. Cells were harvested 20 h post-exposure to doxorubicin followed by analysis of their cellular taurine content, oxidative/nitrative stresses, and cellular apoptosis. The activation of the PI3K-Akt pathway was analyzed by immunoblotting. FACS, TUNEL, and LDH assays showed that the viability of cardiomyocytes was markedly reduced by doxorubicin, but was improved by propofol. Doxorubicin treatment significantly elevated cellular reactive oxygen and nitrogen contents while lowering the levels of taurine, Akt, and phosphorylated Akt and Bad. The abovementioned doxorubicin-induced changes were reversed by propofol. The protective effects of propofol were abrogated by simultaneous treatment with LY294002. In conclusion, the PI3K-Akt-Bad pathway plays a critical role in conferring the protective effects of propofol against myocardial toxicity from doxorubicin.

Mitochondrial-targeting nitrooxy-doxorubicin: a new approach to overcome drug resistance

In previous studies, we showed that nitric oxide (NO) donors and synthetic doxorubicins (DOXs) modified with moieties containing NO-releasing groups--such as nitrooxy-DOX (NitDOX) or 3-phenylsulfonylfuroxan-DOX (FurDOX)--overcome drug resistance by decreasing the activity of ATP-binding cassette (ABC) transporters that can extrude the drug. Here, we have investigated the biochemical mechanisms by which NitDOX and FurDOX exert antitumor effects. Both NitDOX and FurDOX were more cytotoxic than DOX against drug-resistant cells. Interestingly, NitDOX exhibited a faster uptake and an extranuclear distribution. NitDOX was preferentially localized in the mitochondria, where it nitrated and inhibited the mitochondria-associated ABC transporters, decreased the flux through the tricarboxylic acid cycle, slowed down the activity of complex I, lowered the synthesis of ATP, induced oxidative and nitrosative stress, and elicited the release of cytochrome c and the activation of caspase-9 and -3 in DOX-resistant cells. We suggest that NitDOX may represent the prototype of a new class of multifunctional anthracyclines, which have cellular targets different from conventional anthracyclines and greater efficacy against drug-resistant tumors.

Doxorubicin induces cytotoxicity through upregulation of pERK-dependent ATF3

Although doxorubicin is commonly used in the treatment of many cancer types, its use in chemotherapy has been limited, largely because of its severe side effects, including cardiotoxicity and nephrotoxicity. In this study, we aimed to identify the mechanism of doxorubicin-induced cytotoxicity by using the human kidney proximal tubule cell line HK-2. Furthermore, we investigated the role of activating transcription factor 3 (ATF3) as a mediator of doxorubicin-induced cytotoxicity by using wild-type mouse embryonic fibroblasts (MEF) cells and ATF3 knockout (KO) cells. In HK-2 cells, doxorubicin decreased cell viability in a dose-dependent manner and induced an increase in cells in the sub G1 and G2/M phases at all doses. Doxorubicin treatment showed the following dose-dependent effects: increase in the secretion of tumor necrosis factor alpha; decrease in the expression of phosphorylated protein kinase A and Bcl-2; and increase in the expression of phosphorylated signal transducer and activator of transcription 3, phosphorylated extracellular signal-regulated kinase (ERK), and ATF3. Based on these results, we suggest that doxorubicin induces cytotoxicity through an ERK-dependent pathway, and ATF3 plays a pivotal role as a transcriptional regulator in this process.

Propofol ameliorates doxorubicin-induced oxidative stress and cellular apoptosis in rat cardiomyocytes

BACKGROUND

Propofol is an anesthetic with pluripotent cytoprotective properties against various extrinsic insults. This study was designed to examine whether this agent could also ameliorate the infamous toxicity of doxorubicin, a widely-used chemotherapeutic agent against a variety of cancer diseases, on myocardial cells.

METHODS

Cultured neonatal rat cardiomyocytes were administrated with vehicle, doxorubicin (1μM), propofol (1μM), or propofol plus doxorubicin (given 1h post propofol). After 24h, cells were harvested and specific analyses regarding oxidative/nitrative stress and cellular apoptosis were conducted.

RESULTS

Trypan blue exclusion and MTT assays disclosed that viability of cardiomyocytes was significantly reduced by doxorubicin. Contents of reactive oxygen and nitrogen species were increased and antioxidant enzymes SOD1, SOD2, and GPx were decreased in these doxorubicin-treated cells. Mitochondrial dehydrogenase activity and membrane potential were also depressed, along with activation of key effectors downstream of mitochondrion-dependent apoptotic signaling. Besides, abundance of p53 was elevated and cleavage of PKC-δ was induced in these myocardial cells. In contrast, all of the above oxidative, nitrative and pro-apoptotic events could be suppressed by propofol pretreatment.

CONCLUSIONS

Propofol could extensively counteract oxidative/nitrative and multiple apoptotic effects of doxorubicin in the heart; hence, this anesthetic may serve as an adjuvant agent to assuage the untoward cardiac effects of doxorubicin in clinical application.

Mitochondrial superoxide dismutase--signals of distinction

Mitochondrial superoxide dismutase (MnSOD) neutralizes the highly reactive superoxide radical (O(2)(˙-)), the first member in a plethora of mitochondrial reactive oxygen species (ROS). Over the past decades, research has extended the prevailing view of mitochondrion well beyond the generation of cellular energy to include its importance in cell survival and cell death. In the normal state of a cell, endogenous antioxidant enzyme systems maintain the level of reactive oxygen species generated by the mitochondrial respiratory chain. Mammalian mitochondria are important to the production of reactive oxygen species, which underlie oxidative damage in many pathological conditions and contribute to retrograde redox signaling from the organelle to the cytosol and nucleus. Mitochondria are further implicated in various metabolic and aging-related diseases that are now postulated to be caused by misregulation of physiological systems rather than pure accumulation of oxidative damage. Thus, the signaling mechanisms within mitochondria, and between the organelle and its environment, have gained interest as potential drug targets. Here, we discuss redox events in mitochondria that lead to retrograde signaling, the role of redox events in disease, and their potential to serve as therapeutic targets.

Nitric oxide donor doxorubicins accumulate into Doxorubicin-resistant human colon cancer cells inducing cytotoxicity

Products 4 and 5, obtained by conjugation of doxorubicin with nitric oxide (NO) donor nitrooxy and phenylsulfonyl furoxan moieties, respectively, accumulate in doxorubicin-resistant human colon cancer cells (HT29-dx), inducing high cytotoxicity. This behavior parallels the ability of the compounds to generate NO, detected as nitrite, in these cells. Preliminary immunoblotting studies suggest that the mechanism that underlies the cytotoxic effect could involve inhibition of cellular drug efflux due to nitration of tyrosine residues of the MRP3 protein pump.

iNOS activity is necessary for the cytotoxic and immunogenic effects of doxorubicin in human colon cancer cells

BACKGROUND

Doxorubicin is one of the few chemotherapeutic drugs able to exert both cytotoxic and pro-immunogenic effects against cancer cells. Following the drug administration, the intracellular protein calreticulin is translocated with an unknown mechanism onto the plasma membrane, where it triggers the phagocytosis of tumour cells by dendritic cells. Moreover doxorubicin up-regulates the inducible nitric oxide (NO) synthase (iNOS) gene in cancer cells, leading to huge amounts of NO, which in turn acts as a mediator of the drug toxicity and as a chemosensitizer agent in colon cancer. Indeed by nitrating tyrosine on the multidrug resistance related protein 3, NO decreases the doxorubicin efflux from tumour cells and enhances the drug toxicity. It is not clear if NO, beside playing a role in chemosensitivity, may also play a role in doxorubicin pro-immunogenic effects. To clarify this issue, we compared the doxorubicin-sensitive human colon cancer HT29 cells with the drug-resistant HT29-dx cells and the HT29 cells silenced for iNOS (HT29 iNOS-).

RESULTS

In both HT29-dx and HT29 iNOS- cells, doxorubicin did not induce NO synthesis, had a lower intracellular accumulation and a lower toxicity. Moreover the drug failed to promote the translocation of calreticulin and the phagocytosis of HT29-dx and HT29 iNOS-cells, which resulted both chemoresistant and immunoresistant. However, if NO levels were exogenously increased by sodium nitroprusside, the chemosensitivity to doxorubicin was restored in HT29 iNOS-cells. In parallel the NO donor per se was sufficient to induce the exposure of calreticulin and to increase the phagocytosis of HT29 iNOS- cells by DCs and their functional maturation, thus mimicking the pro-immunogenic effects exerted by doxorubicin in the parental drug-sensitive HT29 cells.

CONCLUSION

Our data suggest that chemo- and immuno-resistance to anthracyclines are associated in colon cancer cells and rely on a common mechanism, that is the inability of doxorubicin to induce iNOS. Therefore NO donors might represent a promising strategy to restore both chemosensitivity and immunosensitivity to doxorubicin in resistant cells.

Mitochondrial and nuclear p53 localization in cardiomyocytes: redox modulation by doxorubicin (Adriamycin)?

Reactive oxygen (ROS) and nitrogen species (RNS) generation have been proposed to be an important mechanism of doxorubicin (Adriamycin; ADR)-induced cardiotoxicity and cardiomyocyte apoptosis, processes that may be mediated by p53 protein. We note that ADR treatment resulted in increased levels of p53 protein in cardiomyocyte mitochondria and nuclei. Modulation of the cardiomyocyte redox state in genetically engineered mice by modulation of enzymes involved in metabolism of ROS/RNS, manganese superoxide dismutase (MnSOD), or inducible nitric oxide synthase (iNOS), or a combination of these, regulated levels of mitochondrial/nuclear p53 in cardiomyocytes after ADR administration. These observations led to the hypothesis that mitochondrial/nuclear p53 localization and function in the cardiomyocyte response to ADR may be regulated through redox-dependent mechanism(s).

Melatonin protects against epirubicin-induced cardiotoxicity

We investigated the cytoprotective effect of melatonin in epirubicin-induced cardiotoxicity using four experimental groups of male Wistar rats: untreated control rats, epirubicin-treated rats, epirubicin+melatonin-treated rats, and melatonin-treated rats. We examined the histopathological and biochemical effects of melatonin on the epirubicin-induced changes and measured the levels of the lipid peroxidation end-product (malondialdehyde, MDA), an indicator of nitric oxide (NO) synthesis (nitrite/nitrate production), and reduced glutathione (GSH) in the heart. We also studied the extracellular matrix components (fibronectin, laminin) in the heart. Vacuole formation, mitochondrial deformation and degeneration, and disordered myofibrillary structures were detected ultrastructurally in the epirubicin-treated group. The degeneration was reduced in the heart tissues of the epirubicin+melatonin group. Epirubicin increased the nitrite/nitrate production, but did not change the MDA and GSH levels significantly. Melatonin treatment lowered the nitrite/nitrate concentrations, while increasing the GSH levels, which exceeded the levels in epirubicin+melatonin-treated rats. We conclude that the epirubicin increased the nitrozative stress, not the oxidative stress, in heart tissue, and the cardioprotective effect of melatonin was partially attributed to the suppression of epirubicin-induced nitrozative stress. These results suggest that melatonin partially protects against epirubicin-induced cardiotoxicity.

Inactivation of Anthracyclines by Cellular Peroxidase

The anticancer anthracyclines, doxorubicin and daunorubicin, are highly cytotoxic to both cancer and normal cells. In this work, we have investigated the capacity of cellular myeloperoxidase to inactivate these agents. We show that incubation of human leukemia HL-60 cells with the anthracyclines in the presence of hydrogen peroxide and nitrite causes irreversible oxidation of the drugs, suggesting an extensive modification of their chromophores. Methimazole, 4-aminobenzoic acid hydrazide, or azide inhibits the reaction, suggesting that it is mediated by the cellular myeloperoxidase, an enzyme naturally present in large amounts in HL-60 cells. In contrast to the intact drugs, the oxidatively transformed anthracyclines were substantially less cytotoxic for HL-60 (assayed by apoptosis) and PC3 prostate cancer cells and H9c2 rat cardiac myoblasts in vitro (assayed by clonogenic survival), indicating that the oxidative metabolism of these agents leads to their inactivation. Using tandem mass spectrometry, we identified two specific metabolic products of the anthracycline degradation, 3-methoxyphthalic acid and 3-methoxysalicylic acid. These two metabolic products were obtained as authentic compounds and were nontoxic to HL-60 leukemic cells and cardiac myocytes. These findings may have important implications for the cellular pharmacology of anthracyclines and for clinical oncology.

Manganese superoxide dismutase and inducible nitric oxide synthase modify early oxidative events in acute Adriamycin-induced mitochondrial toxicity

In the present study, we used genetically engineered B6C3 mice [mice overexpressing manganese superoxide dismutase (TgM(+/+)), mice in which inducible nitric oxide synthase had been inactivated (iNOSKO(-/-)), and crosses of these two genotypes] to study the role of manganese superoxide dismutase (MnSOD) and inducible nitric oxide synthase (iNOS) in the development of acute Adriamycin-induced cardiotoxicity. Both nontransgenic and genetically engineered mice were treated with 20 mg/kg Adriamycin and cardiac left ventricular tissues studied at 0, 3, 6, and 24 hours. Ultrastructural damage and levels of 4-hydroxy-2-nonenal (4HNE) protein adducts and 3-nitrotyrosine (3NT) were determined in cardiomyocytes using immunogold ultrastructural techniques. Our previous results showed that Adriamycin caused mitochondrial injury without significant nuclear or cytoplasmic damage at early time points. Interestingly, overexpression of MnSOD protected against acute mitochondrial injury, whereas deficiency in iNOS potentiated mitochondrial injury in comparison with levels of injury present in cardiomyocyte mitochondria of nontransgenic mice. In TgM(+/+) mice, there was a significant inverse correlation between mitochondrial injury and 4HNE/3NT levels at all time points analyzed, suggesting that reactive oxygen species/reactive nitrogen species damage products directly regulated acute Adriamycin-induced mitochondrial injury in these mice. The present studies are the first to directly quantify the effects of MnSOD and iNOS on mitochondrial injury during acute Adriamycin-induced cardiotoxicity and show extensive and specific patterns of posttranslational modifications of mitochondrial proteins following Adriamycin treatment.

Nitric Oxide Reverts the Resistance to Doxorubicin in Human Colon Cancer Cells by Inhibiting the Drug Efflux

Multidrug resistance (MDR) is a phenomenon by which cancer cells evade the cytotoxic effects of chemotherapeutic agents. It may occur through different mechanisms, but it often correlates with the overexpression of integral membrane transporters, such as P-glycoprotein (Pgp) and MDR-associated proteins (MRPs), with resulting decrease of drug accumulation and cellular death. Doxorubicin is a substrate of Pgp; it has been suggested that its ability to induce synthesis of nitric oxide (NO) could explain, at least in part, its cytotoxic effects. Culturing the human epithelial colon cell line HT29 in the presence of doxorubicin, we obtained a doxorubicin-resistant (HT29-dx) cell population: these cells accumulated less intracellular doxorubicin, were less sensitive to the cytotoxic effects of doxorubicin and cisplatin, overexpressed Pgp and MRP3, and exhibited a lower NO production (both under basal conditions and after doxorubicin stimulation). The resistance to doxorubicin could be reversed when HT29-dx cells were incubated with inducers of NO synthesis (cytokines mix, atorvastatin). Some NO donors increased the drug accumulation in HT29-dx cells in a guarosine-3′:5′-cyclic monophosphate–independent way; this effect was associated with a marked reduction of doxorubicin efflux rate in HT29 and HT29-dx cells, and tyrosine nitration in the MRP3 protein. Our results suggest that onset of MDR and impairment of NO synthesis are related; this finding could point to a new strategy to reverse doxorubicin resistance in human cancer.

Doxorubicine-congestive heart failure-increased big endothelin-1 plasma concentration: reversal by amlodipine, losartan, and gastric pentadecapeptide BPC157 in rat and mouse

Overall, doxorubicine-congestive heart failure (CHF) (male Wistar rats and NMRI mice; 6 challenges with doxorubicine (2.5 mg/kg, i.p.) throughout 15 days and then a 4-week-rest period) is consistently deteriorating throughout next 14 days, if not reversed or ameliorated by therapy (/kg per day): a stable gastric pentadecapeptide BPC157 (GEPPPGKPADDAGLV, MW 1419, promisingly studied for inflammatory bowel disease (Pliva; PL 10, PLD-116, PL 14736)) (10 microg, 10 ng), losartan (0.7 mg), amlodipine (0.07 mg), given intragastrically (i.g.) (once daily, rats) or in drinking water (mice). Assessed were big endothelin-1 (BET-1) and plasma enzyme levels (CK, MBCK, LDH, AST, ALT) before and after 14 days of therapy and clinical status (hypotension, increased heart rate and respiratory rate, and ascites) every 2 days. Controls (distilled water (5 ml/kg, i.g., once daily) or drinking water (2 ml/mouse per day) given throughout 14 days) exhibited additionally increased BET-1 and aggravated clinical status, while enzyme values maintained their initial increase. BPC157 (10 microg/kg) and amlodipine treatment reversed the increased BET-1 (rats, mice), AST, ALT, CK (rats, mice), and LDH (mice) values. BPC157 (10 ng/kg) and losartan opposed further increase of BET-1 (rats, mice). Losartan reduces AST, ALT, CK, and LDH serum values. BPC157 (10 ng/kg) reduces AST and ALT serum values. Clinical status of CHF-rats and -mice is accordingly improved by the BPC157 regimens and amlodipine.

The role of nitric oxide in anthracycline toxicity and prospects for pharmacologic prevention of cardiac damage

Anthracycline antibiotics are potent antitumor agents whose activity is severely limited by a cumulative dose-dependent chronic cardiotoxicity that results from the summation of multiple biochemical pathways of cellular damage, which ultimately yields to disruption of myocardiocyte integrity and loss of cardiac function. Nitric oxide (NO) is a key molecule involved in the pathophysiology of heart; dysregulation of activity of NO synthases (NOSs) and of NO metabolism seems to be a common feature in various cardiac diseases. The contribution of NO to anthracycline cardiac damage is suggested by evidence demonstrating anthracycline-mediated induction of NOS expression and NO release in heart and the ability of NOSs to promote anthracycline redox cycling to produce reactive oxygen species (ROS), including O2-* and H2O2. Overproduction of ROS and NO yields to reactive nitrogen species, particularly the powerful oxidant molecule peroxynitrite (ONOO-), which may produce the marked reduction of cardiac contractility. This review focuses on the anthracycline-mediated deregulation of NO network and presents an unifying viewpoint of the main molecular mechanisms involved in the pathogenesis of anthracycline cardiotoxicity, including iron, free radicals, and novel mechanistic notions on cardiac ceramide signaling and apoptosis. The data presented in the literature encourage the development of strategies of pharmacological manipulation of NO metabolism to be used as a novel approach to the prevention of cardiotoxicity induced by anthracyclines.

Artemisinin inhibits inducible nitric oxide synthase and nuclear factor NF-kB activation

Artemisinin is a natural product used as an alternative drug in the treatment of severe and multidrug-resistant malaria. In the present work we show that artemisinin shares with other sesquiterpene lactones the ability to inhibit the activation of the nuclear factor NF-kB: by this mechanism, artemisinin, as well as parthenolide, inhibits nitric oxide synthesis in cytokine-stimulated human astrocytoma T67 cells. These results suggest that artemisinin, in addition to its antiparasitic properties, could also exert a therapeutic effect on neurological complications of malaria.