Inactivation of Anthracyclines by Cellular Peroxidase

Oregano essential oil modulates colonic homeostasis and intestinal barrier function in fattening bulls

Oregano essential oil (OEO) primarily contains phenolic compounds and can serve as a dietary supplement for fattening bulls. However, the precise molecular mechanism underlying this phenomenon remains largely elusive. Therefore, this study investigated the impact of adding OEO to diet on the integrity of the intestinal barrier, composition of the colonic microbiome, and production of microbial metabolites in fattening bulls. Our goal was to provide insights into the utilization of plant essential oil products in promoting gastrointestinal health and welfare in animals. We employed amplicon sequencing and metabolome sequencing techniques to investigate how dietary supplementation with OEO impacted the intestinal barrier function in bulls. The inclusion of OEO in the diet resulted in several notable effects on the colon of fattening bulls. These effects included an increase in the muscle thickness of the colon, goblet cell number, short-chain fatty acid concentrations, digestive enzyme activity, relative mRNA expression of intestinal barrier-related genes, and relative expression of the anti-inflammatory factor IL-10. Additionally, α-amylase activity and the relative mRNA expression of proinflammatory cytokines decreased. Moreover, dietary OEO supplementation increased the abundance of intestinal Bacteroides, Coprobacillus, Lachnospiraceae_UCG_001, and Faecalitalea. Metabolomic analysis indicated that OEO primarily increased the levels of 5-aminovaleric acid, 3-methoxysalicylic acid, and creatinine. In contrast, the levels of maltose, lactulose, lactose, and D-trehalose decreased. Correlation analysis showed that altered colonic microbes and metabolites affected intestinal barrier function. Taken together, these results demonstrate that OEO facilitates internal intestinal environmental homeostasis by promoting the growth of beneficial bacteria while inhibiting harmful ones.

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.

Carboxyl Group-Modified Myoglobin Induces TNF-α-Mediated Apoptosis in Leukemia Cells

Previous studies have shown that chemical modification may increase the activity of proteins or confer novel activity to proteins. Some studies have indicated that myoglobin (Mb) is cytotoxic; however, the underlying mechanisms remain unclear. In this study, we investigated whether chemical modification of the carboxyl group by semicarbazide could promote the Mb cytotoxicity in human leukemia U937 cells and the underlying mechanism of semicarbazide-modified myoglobin (SEM-Mb)-induced U937 cell death. The semicarbazide-modified Mb (SEM-Mb) induced U937 cell apoptosis via the production of cleaved caspase-8 and t-Bid, while silencing of FADD abolished this effect. These findings suggest that SEM-Mb can induce U937 cell death by activating the death receptor-mediated pathway. The SEM-Mb inhibited miR-99a expression, leading to increased NOX4 mRNA and protein expression, which promoted SIRT3 degradation, and, in turn, induced ROS-mediated p38 MAPK phosphorylation. Activated p38 MAPK stimulated miR-29a-dependent tristetraprolin (TTP) mRNA decay. Downregulation of TTP slowed TNF-α mRNA turnover, thereby increasing TNF-α protein expression. The SEM-Mb-induced decrease in cell viability and TNF-α upregulation were alleviated by abrogating the NOX4/SIRT3/ROS/p38 MAPK axis or ectopic expression of TTP. Taken together, our results demonstrated that the NOX4/SIRT3/p38 MAPK/TTP axis induces TNF-α-mediated apoptosis in U937 cells following SEM-Mb treatment. A pathway regulating p38 MAPK-mediated TNF-α expression also explains the cytotoxicity of SEM-Mb in the human leukemia cell lines HL-60, THP-1, K562, Jurkat, and ABT-199-resistant U937. Furthermore, these findings suggest that the carboxyl group-modified Mb is a potential structural template for the generation of tumoricidal proteins.

Role of Inflammation and Redox Status on Doxorubicin-Induced Cardiotoxicity in Infant and Adult CD-1 Male Mice

Doxorubicin (DOX) is a topoisomerase II inhibitor commonly used in the treatment of several types of cancer. Despite its efficacy, DOX can potentially cause fatal adverse effects, like cardiotoxicity. This work aimed to assess the role of inflammation in DOX-treated infant and adult mice and its possible link to underlying cardiotoxicity. Two groups of CD-1 male mice of different ages (infants or adults) were subjected to biweekly DOX administrations, to reach a cumulative dose of 18.0 mg/kg, which corresponds approximately in humans to 100.6 mg/m2 for infants and 108.9 mg/m2 for adults a clinically relevant dose in humans. The classic plasmatic markers of cardiotoxicity increased, and that damage was confirmed by histopathological findings in both groups, although it was higher in adults. Moreover, in DOX-treated adults, an increase of cardiac fibrosis was observed, which was accompanied by an increase in specific inflammatory parameters, namely, macrophage M1 and nuclear factor kappa B (NF-κB) p65 subunit, with a trend toward increased levels of the tumor necrosis factor receptor 2 (TNFR2). On the other hand, the levels of myeloperoxidase (MPO) and interleukin (IL)-6 significantly decreased in DOX-treated adult animals. In infants, a significant increase in cardiac protein carbonylation and in the levels of nuclear factor erythroid-2 related factor 2 (Nrf2) was observed. In both groups, no differences were found in the levels of tumor necrosis factor (TNF-α), IL-1β, p38 mitogen-activated protein kinase (p38 MAPK) or NF-κB p52 subunit. In conclusion, using a clinically relevant dose of DOX, our study demonstrated that cardiac effects are associated not only with the intensity of the inflammatory response but also with redox response. Adult mice seemed to be more prone to DOX-induced cardiotoxicity by mechanisms related to inflammation, while infant mice seem to be protected from the damage caused by DOX, possibly by activating such antioxidant defenses as Nrf2.

A protein-sulfosalicylic acid/boswellic acids @metal-organic framework nanocomposite as anticancer drug delivery system

The metal-organic frameworks (MOF) have shown fascinating possibilities in biomedical applications, designing a multifunctional drug delivery system based on the MOF is important. In this study, 5-sulfosalicylic acid and boswellic acids (BAs) were loaded to the pH sensitive zeolitic imidazolate framework-8 (ZIF-8) nanocomposite containing bovine serum albumin (BSA) as the center. The ZIF layer acts as a capsule for the nontoxic storage of 5-sulfosalicylic acid and boswellic acids (BAs) under physiological conditions. The results of the characterization demonstrated the performance of the nanocarrier formation. The pH-sensitive drug release of 5-sulfosalicylic acid was detected due to the innate pH-dependent stability of ZIF-8. An effective pH-sensitive drug delivery system using a 5-sulfosalicylic acid/BSA@ZIF-8, and 5-sulfosalicylic acid/BSA/BAs@ZIF-8, in which the 5-sulfosalicylicacid is not free in physiological pH but it is released at acidic pH (5.0) has been fabricated. The best biocompatibility has been found in 5-sulfosalicylic acid/BSA/BAs@ZIF-8 comparing to the 5-sulfosalicylic acid/BSA, 5-sulfosalicylic acid /BSA/BAs, and 5-sulfosalicylic acid/BSA@ZIF-8. Additionally, 5-sulfosalicylic acid/BSA /BAs@ZIF-8 exhibited higher effectiveness than other compounds against the breast cancer cell line, MCF-7, with less toxicity. It is concluded from the results of the current study that the fabricated ZIF-8 based nanocarrier may potentially provide therapeutic effects on breast cancer cells.

ABTS/PP Decolorization Assay of Antioxidant Capacity Reaction Pathways

The 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS^•+) radical cation-based assays are among the most abundant antioxidant capacity assays, together with the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-based assays according to the Scopus citation rates. The main objective of this review was to elucidate the reaction pathways that underlie the ABTS/potassium persulfate decolorization assay of antioxidant capacity. Comparative analysis of the literature data showed that there are two principal reaction pathways. Some antioxidants, at least of phenolic nature, can form coupling adducts with ABTS^•+, whereas others can undergo oxidation without coupling, thus the coupling is a specific reaction for certain antioxidants. These coupling adducts can undergo further oxidative degradation, leading to hydrazindyilidene-like and/or imine-like adducts with 3-ethyl-2-oxo-1,3-benzothiazoline-6-sulfonate and 3-ethyl-2-imino-1,3-benzothiazoline-6-sulfonate as marker compounds, respectively. The extent to which the coupling reaction contributes to the total antioxidant capacity, as well as the specificity and relevance of oxidation products, requires further in-depth elucidation. Undoubtedly, there are questions as to the overall application of this assay and this review adds to them, as specific reactions such as coupling might bias a comparison between antioxidants. Nevertheless, ABTS-based assays can still be recommended with certain reservations, particularly for tracking changes in the same antioxidant system during storage and processing.

Rethinking Drugs from Chemistry to Therapeutic Opportunities: Pixantrone beyond Anthracyclines

Pixantrone (6,9-bis[(2-aminoethyl)amino]benzo[g]isoquinoline-5,10-dione) has been approved by the European Medicines Agency for the treatment of refractory or relapsed non-Hodgkin's lymphoma (NHL). It is popularly referred to as a novel aza-anthracenedione, and as such it is grouped with anthracycline-like drugs. Preclinical development of pixantrone was in fact tailored to retain the same antitumor activity as that of anthracyclines or other anthracenediones while also avoiding cardiotoxicity that dose-limits clinical use of anthracycline-like drugs. Preliminary data in laboratory animals showed that pixantrone was active, primarily in hematologic malignancies, but caused significantly less cardiotoxicity than doxorubicin or mitoxantrone. Pixantrone was cardiac tolerable also in animals pretreated with doxorubicin, which anticipated a therapeutic niche for pixantrone to treat patients with a history of prior exposure to anthracyclines. This is the case for patients with refractory/relapsed NHL. Pixantrone clinical development, regulatory approval, and penetration in clinical practice were nonetheless laborious if not similar to a rocky road. Structural and nominal similarities with mitoxantrone and anthracyclines may have caused a negative influence, possibly leading to a general perception that pixantrone is a "me-too" anthracycline. Recent insights suggest this is not the case. Pixantrone shows pharmacological and toxicological mechanisms of action that are difficult to reconcile with anthracycline-like drugs. Pixantrone is a new drug with its own characteristics. For example, pixantrone causes mis-segregation of genomic material in cancer cells and inhibits formation of toxic anthracycline metabolites in cardiac cells. Understanding the differences between pixantrone and anthracyclines or mitoxantrone may help one to appreciate how it worked in the phase 3 study that led to its approval in Europe and how it might work in many more patients in everyday clinical practice, were it properly perceived as a drug with its own characteristics and therapeutic potential. The road is rocky but not a dead-end.

Role of Drug Metabolism in the Cytotoxicity and Clinical Efficacy of Anthracyclines

Many clinical studies involving anti-tumor agents neglect to consider how these agents are metabolized within the host and whether the creation of specific metabolites alters drug therapeutic properties or toxic side effects. However, this is not the case for the anthracycline class of chemotherapy drugs. This review describes the various enzymes involved in the one electron (semi-quinone) or two electron (hydroxylation) reduction of anthracyclines, or in their reductive deglycosidation into deoxyaglycones. The effects of these reductions on drug antitumor efficacy and toxic side effects are also discussed. Current evidence suggests that the one electron reduction of anthracyclines augments both their tumor toxicity and their toxicity towards the host, in particular their cardiotoxicity. In contrast, the two electron reduction (hydroxylation) of anthracyclines strongly reduces their ability to kill tumor cells, while augmenting cardiotoxicity through their accumulation within cardiomyocytes and their direct effects on excitation/contraction coupling within the myocytes. The reductive deglycosidation of anthracyclines appears to inactivate the drug and only occurs under rare, anaerobic conditions. This knowledge has resulted in the identification of important new approaches to improve the therapeutic index of anthracyclines, in particular by inhibiting their cardiotoxicity. The true utility of these approaches in the management of cancer patients undergoing anthracycline-based chemotherapy remains unclear, although one such agent (the iron chelator dexrazoxane) has recently been approved for clinical use.

Extension of lifespan and protection against oxidative stress by an antioxidant herb mixture complex (KPG-7) in Caenorhabditis elegans

Excessive generation of reactive oxygen species within cells results in oxidative stress. Furthermore, accumulation of reactive oxygen species has been shown to reduce cell longevity. Many dietary supplements are believed to have anti-aging effects. The herb mixture KPG-7 contains several components with antioxidant activity. We aim to clarify the mechanisms responsible for the antioxidant activity of KPG-7 and to establish whether KPG-7 has an anti-aging effect. We examined whether dietary supplementation with KPG-7 could provide protection against oxidative stress, extend lifespan, and delay aging in Caenorhabditis elegans (C. elegans). We found that KPG-7 extended lifespan and delayed aging in adult C. elegans. The expression of oxidation resistance 1 protein was induced by juglone and this effect was significantly suppressed in KPG-7-treated. In addition, the amount of oxidized protein was significantly lower in KPG-7-treated worms than untreated worms. Furthermore, locomotive activity was increased in C. elegans at 3 days of age following the treatment with KPG-7. On the other hand, the level of cellular ATP was lower at 3 days of age in worms treated with KPG-7 than in untreated worms. KPG-7 increases lifespan and delays aging in C. elegans, well corresponding to its activity to protect against oxidative stress.

Metabolism and pharmacokinetics of indacaterol in humans

The metabolism, pharmacokinetics, and excretion of [(14)C]indacaterol were investigated in healthy male subjects. Although indacaterol is administered to patients via inhalation, the dose in this study was administered orally. This was done to avoid the complications and concerns associated with the administration of a radiolabeled compound via the inhalation route. The submilligram doses administered in this study made metabolite identification and structural elucidation by mass spectrometry especially challenging. In serum, the mean t(max), C(max), and AUC(0-last) values were 1.75 h, 0.47 ng/ml, and 1.81 ng · h/ml for indacaterol and 2.5 h, 1.4 ngEq/ml, and 27.2 ngEq · h/ml for total radioactivity. Unmodified indacaterol was the most abundant drug-related compound in the serum, contributing 30% to the total radioactivity in the AUC(0-24h) pools, whereas monohydroxylated indacaterol (P26.9), the glucuronide conjugate of P26.9 (P19), and the 8-O-glucuronide conjugate of indacaterol (P37) were the most abundant metabolites, with each contributing 4 to 13%. In addition, the N-glucuronide (2-amino) conjugate (P37.7) and two metabolites (P38.2 and P39) that resulted from the cleavage about the aminoethanol group linking the hydroxyquinolinone and diethylindane moieties had a combined contribution of 12.5%. For all four subjects in the study, ≥90% of the radioactivity dose was recovered in the excreta (85% in feces and 10% in urine, mean values). In feces, unmodified indacaterol and metabolite P26.9 were the most abundant drug-related compounds (54 and 17% of the dose, respectively). In urine, unmodified indacaterol accounted for ∼0.3% of the dose, with no single metabolite accounting for >1.3%.

The importance of myeloperoxidase in apocynin-mediated NADPH oxidase inhibition

Apocynin is widely used as an inhibitor of the NADPH oxidase. Since myeloperoxidase (MPO) has been considered as essential for the mechanism of action of apocynin, here we used cells with different levels of MPO and compared their sensitivity to apocynin. HL-60 cells were differentiated with DMSO or IFNγ/TNFα and compared with peripheral mononuclear (PBMC) and polymorphonuclear cells (PMN). The relative MPO activity was PBMC = HL60 DMSO < HL60 IFNγ < PMN. Apocynin inhibited the intracellular reactive oxygen species production by PMN (80%) and IFNγ/TNFα-differentiated HL-60 cells (45%) but showed a minor effect in PBMC and DMSO differentiated HL-60 cells (20%). The addition of azide decreased the efficiency of apocynin in PMN and the addition of peroxidase increased the inhibition in PBMC. We also determined the gene expression of the components gp91phox, p47phox, p22phox and p67phox in the resting cells. Apocynin did not change gp91phox, p47phox or p22phox gene expression in nonstimulated PBMC, HL60 DMSO, HL60 IFNγ/TNFα, and PMN and has a subtle increase in p67phox in HL60 IFNγ/TNFα. The results from this work suggest that a rational search for better inhibitors of NADPH oxidase in leukocytes should include a correlation with their affinity as substrates for MPO.

Doxorubicin inhibits oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) by a lactoperoxidase/H(2)O(2) system by reacting with ABTS-derived radical

The effect of doxorubicin on oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) by lactoperoxidase and hydrogen peroxide has been investigated. It was found that: (1) oxidation of ABTS to its radical cation (ABTS*(+)) is inhibited by doxorubicin as evidenced by its induction of a lag period, duration of which depends on doxorubicin concentration; (2) the inhibition is due to doxorubicin hydroquinone reducing the ABTS*(+) radical (stoichiometry 1: 1.8); (3) concomitant with the ABTS*(+) reduction is oxidation of doxorubicin; only when the doxorubicin concentration decreases to a near zero level, net oxidation of ABTS could be detected; (4) oxidation of doxorubicin leads to its degradation to 3-methoxysalicylic acid and 3-methoxyphthalic acid; (5) the efficacy of doxorubicin to quench ABTS*(+) is similar to the efficacy of p-hydroquinone, glutathione and Trolox C. These observations support the assertion that under certain conditions doxorubicin can function as an antioxidant. They also suggest that interaction of doxorubicin with oxidants may lead to its oxidative degradation.

Doxorubicin degradation in cardiomyocytes

Antitumor therapy with the anthracycline doxorubicin is limited by a severe cardiotoxicity, which seems to correlate with the cardiac levels of doxorubicin and its metabolization to reactive oxygen species. Previous biochemical studies showed that hydrogen peroxide-activated myoglobin caused an oxidative degradation of doxorubicin; however, a pharmacological evaluation of this metabolic pathway was precluded by the lack of safe and specific inhibitors of doxorubicin degradation. We found that tert-butoxycarbonyl-alanine inhibited doxorubicin degradation induced in vitro by hydrogen peroxide-activated oxyferrous myoglobin. When assessed in H9c2 cardiomyocytes, tert-butoxycarbonyl-alanine neither stimulated the cellular uptake of doxorubicin nor diminished its efflux; moreover, tert-butoxycarbonyl-alanine did not cause toxicity per se nor did it augment the toxicity induced by hydrogen peroxide or chemical agents that increased the cellular levels of reactive oxygen species. Nonetheless, tert-butoxycarbonyl-alanine increased the cellular levels of doxorubicin, its conversion to reactive oxygen species, and its concentration-related toxicity. tert-Butoxycarbonyl-alanine also aggravated the toxicity of a degradation-prone anthracycline analog, daunorubicin, but it caused a minor effect on the toxicity of a degradation-resistant analog, aclarubicin. These results suggested that tert-butoxycarbonyl-alanine increased the cellular levels and toxicity of doxorubicin by inhibiting its oxidative degradation to harmless products. Accordingly, doxorubicin samples that had been oxidized in vitro with hydrogen peroxide and oxyferrous myoglobin lacked toxicity to cardiomyocytes. The effects of tert-butoxycarbonyl-alanine were most evident at 0.1 to 1 microM doxorubicin, which may be relevant to clinical conditions. These studies identify an oxidative degradation of doxorubicin as a possible salvage mechanism for diminishing its levels and toxicity in cardiomyocytes.

Inactivation of anthracyclines by serum heme proteins

We have previously shown that the anticancer agent doxorubicin undergoes oxidation and inactivation when exposed to myeloperoxidase-containing human leukemia HL-60 cells, or to isolated myeloperoxidase, in the presence of hydrogen peroxide and nitrite. In the current study we report that commercial fetal bovine serum (FBS) alone oxidizes doxorubicin in the presence of hydrogen peroxide and that nitrite accelerates this oxidation. The efficacy of inactivation was dependent on the concentration of serum present; no reaction was observed when hydrogen peroxide or serum was omitted. Peroxidase activity assays, based on oxidation of 3,3',5,5'-tetramethylbenzidine, confirmed the presence of a peroxidase in the sera from several suppliers. The peroxidative activity was contained in the >10000 MW fraction. We also found that hemoglobin, a heme protein likely to be present in commercial FBS, is capable of oxidizing doxorubicin in the presence of hydrogen peroxide and that nitrite further stimulates the reaction. In contrast to intact doxorubicin, the serum + hydrogen peroxide + nitrite treated drug appeared to be nontoxic for PC3 human prostate cancer cells. Together, this study shows that (pseudo)peroxidases present in sera catalyze oxidation of doxorubicin by hydrogen peroxide and that this diminishes the tumoricidal activity of the anthracycline, at least in in vitro settings. Finally, this study also points out that addition of H2O2 to media containing FBS will stimulate peroxidase-type of reactions, which may affect cytotoxic properties of studied compounds.

Oxidation of anthracyclines by peroxidase metabolites of salicylic Acid

Oxidation of anthracyclines leads to their degradation and inactivation. This process is carried out by peroxidases in the presence of a catalytic cofactor, a good peroxidase substrate. Here, we investigated the effect of salicylic acid, a commonly used anti-inflammatory and analgesic agent, on the peroxidative metabolism of anthracyclines. We report that at pharmacologically relevant concentrations, salicylic acid stimulates oxidation of daunorubicin and doxorubicin by myeloperoxidase and lactoperoxidase systems and that efficacy of the process increases markedly on changing the pH from 7 to 5. This pH dependence is positively correlated with the ease with which salicylic acid itself undergoes metabolic oxidation and involves the neutral form of the acid (pKa = 2.98). When salicylic acid reacted with a peroxidase and H2O2 at acid pH (anthracyclines omitted), a new metabolite with absorption maximum at 412 nm was formed. This metabolite reacted with anthracyclines causing their oxidation. It was tentatively assigned to biphenyl quinone, formed by oxidation of biphenol produced by dimerization of salicylic acid-derived phenoxyl radicals. The formation of this product was inhibited in a concentration-dependent manner by the anthracyclines, suggesting their scavenging of the salicylate phenoxyl radicals. Altogether, this study demonstrates that oxidation of anthracyclines is mediated by peroxidase metabolites of salicylic acid, such as phenoxyl radicals and the biphenol quinone. Given that cancer patients undergoing anthracycline chemotherapy may be administered salicylic acid-based drugs to control pain and fever, our results suggest that liberated salicylic acid could interfere with anticancer and/or cardiotoxic actions of the anthracyclines.