Differential adriamycin distribution to blood components

Drug transport by red blood cells

This review focuses on the role of human red blood cells (RBCs) as drug carriers. First, a general introduction about RBC physiology is provided, followed by the presentation of several cases in which RBCs act as natural carriers of drugs. This is due to the presence of several binding sites within the same RBCs and is regulated by the diffusion of selected compounds through the RBC membrane and by the presence of influx and efflux transporters. The balance between the influx/efflux and the affinity for these binding sites will finally affect drug partitioning. Thereafter, a brief mention of the pharmacokinetic profile of drugs with such a partitioning is given. Finally, some examples in which these natural features of human RBCs can be further exploited to engineer RBCs by the encapsulation of drugs, metabolites, or target proteins are reported. For instance, metabolic pathways can be powered by increasing key metabolites (i.e., 2,3-bisphosphoglycerate) that affect oxygen release potentially useful in transfusion medicine. On the other hand, the RBC pre-loading of recombinant immunophilins permits increasing the binding and transport of immunosuppressive drugs. In conclusion, RBCs are natural carriers for different kinds of metabolites and several drugs. However, they can be opportunely further modified to optimize and improve their ability to perform as drug vehicles.

Exploring the Interplay between Drug Release and Targeting of Lipid-Like Polymer Nanoparticles Loaded with Doxorubicin

Targeted delivery of doxorubicin still poses a challenge with regards to the quantities reaching the target site as well as the specificity of the uptake. In the present approach, two colloidal nanocarrier systems, NanoCore-6.4 and NanoCore-7.4, loaded with doxorubicin and characterized by different drug release behaviors were evaluated in vitro and in vivo. The nanoparticles utilize a specific surface design to modulate the lipid corona by attracting blood-borne apolipoproteins involved in the endogenous transport of chylomicrons across the blood–brain barrier. When applying this strategy, the fine balance between drug release and carrier accumulation is responsible for targeted delivery. Drug release experiments in an aqueous medium resulted in a difference in drug release of approximately 20%, while a 10% difference was found in human serum. This difference affected the partitioning of doxorubicin in human blood and was reflected by the outcome of the pharmacokinetic study in rats. For the fast-releasing formulation NanoCore-6.4, the AUC_0→1h was significantly lower (2999.1 ng × h/mL) than the one of NanoCore-7.4 (3589.5 ng × h/mL). A compartmental analysis using the physiologically-based nanocarrier biopharmaceutics model indicated a significant difference in the release behavior and targeting capability. A fraction of approximately 7.310–7.615% of NanoCore-7.4 was available for drug targeting, while for NanoCore-6.4 only 5.740–6.057% of the injected doxorubicin was accumulated. Although the targeting capabilities indicate bioequivalent behavior, they provide evidence for the quality-by-design approach followed in formulation development.

Sample Extraction and Simultaneous Chromatographic Quantitation of Doxorubicin and Mitomycin C Following Drug Combination Delivery in Nanoparticles to Tumor-bearing Mice

Combination chemotherapy is frequently used in the clinic for cancer treatment; however, associated adverse effects to normal tissue may limit its therapeutic benefit. Nanoparticle-based drug combination has been shown to mitigate the problems encountered by free drug combination therapy. Our previous studies have shown that the combination of two anticancer drugs, doxorubicin (DOX) and mitomycin C (MMC), produced a synergistic effect against both murine and human breast cancer cells in vitro. DOX and MMC co-loaded polymer-lipid hybrid nanoparticles (DMPLN) bypassed various efflux transporter pumps that confer multidrug resistance and demonstrated enhanced efficacy in breast tumor models. Compared to conventional solution forms, such superior efficacy of DMPLN was attributed to the synchronized pharmacokinetics of DOX and MMC and increased intracellular drug bioavailability within tumor cells enabled by the nanocarrier PLN. To evaluate the pharmacokinetics and bio-distribution of co-administered DOX and MMC in both free solution and nanoparticle forms, a simple and efficient multi-drug analysis method using reverse-phase high performance liquid chromatography (HPLC) was developed. In contrast to previously reported methods that analyzed DOX or MMC individually in the plasma, this new HPLC method is able to simultaneously quantitate DOX, MMC and a major cardio-toxic DOX metabolite, doxorubicinol (DOXol), in various biological matrices (e.g., whole blood, breast tumor, and heart). A dual fluorescent and ultraviolet absorbent probe 4-methylumbelliferone (4-MU) was used as an internal standard (I.S.) for one-step detection of multiple drug analysis with different detection wavelengths. This method was successfully applied to determine the concentrations of DOX and MMC delivered by both nanoparticle and solution approaches in whole blood and various tissues in an orthotopic breast tumor murine model. The analytical method presented is a useful tool for pre-clinical analysis of nanoparticle-based delivery of drug combinations.

Oxidative stress and hematological profiles of advanced breast cancer patients subjected to paclitaxel or doxorubicin chemotherapy

Several adverse effects of chemotherapy treatments have been described, and most of these effects are associated with direct interactions between blood cells and indirect effects generated during the oxidative metabolism of antineoplastic drugs. In this study we evaluated the oxidative systemic status and hematological profiles of breast cancer patients with advanced ductal infiltrative carcinoma treated with doxorubicin (DOX) or paclitaxel (PTX) within 1 h after chemotherapy. Blood analyses included evaluation of hemogram, pro-oxidative markers, and antioxidant status. The results showed that advanced breast cancer diseased (AD) patients without previous chemotherapy presented anemia and high oxidative stress status characterized by elevated levels of lipid peroxidation and nitric oxide, and reduced catalase activity when compared with controls. DOX-treated patients exhibited increased anemia and reduced antioxidant status, which was revealed by decreases in reduced glutathione levels and the total antioxidant capacity of plasma; however, these changes did not lead to further increases in lipid peroxidation or carbonyl proteins when compared with the AD group. PTX-treated patients also showed increased anemia, lactate dehydrogenase leakage, and enhanced lipid peroxidation. These data reveal for the first time that patients subjected to chemotherapy with DOX or PTX present immediate systemic oxidative stress and red blood cell oxidative injury with anemia development. These findings provide a new perspective on the systemic redox state of AD and patients subjected to chemotherapy regarding oxidative stress enhancement and its possible involvement in the aggravation of chronic anemia.

Human Red Blood Cells: Rheological Aspects, Uptake, and Release of Cytotoxic Drugs

The shape of a normal human red blood cell (RBC) is well known: under resting conditions it is that of a biconcave discocyte. However, RBCs can easily undergo transformation to other shapes with stomatocytes and echinocytes as extremes. Various anticancer agents, generally reactive and labile substances, e.g., oxazaphosphorines and fluoropyrimidines, can induce severe deformation of shape. Shape changes in erythrocytes can induce rheological disturbances, which occasionally have pathophysiological consequences. It is difficult to estimate the impact of shape changes on the in vivo behavior of agents of biological interest. However, it has been demonstrated for various anticancer agents that erythrocytes fulfill an important role in their uptake, transport, and release. Moreover, some anticancer agents are capable of influencing important transporters such as MRP and GLUT-1. Monitoring of erythrocyte concentrations of certain cytotoxic agents is therefore of interest as the data generated can have a predictive outcome for therapeutic efficacy. This is true for cyclophosphamide, ifosfamide, lometrexol, and 6-mercaptopurine, as well as MRP and GLUT-1 mediated agents.

Role of red blood cells in pharmacokinetics of chemotherapeutic agents

After oral or parenteral administration of chemotherapeutic agents, these drugs are transported to the tissues by the blood in different fractions: plasma water, plasma proteins or cells. Erythrocytes may play an important role in the storage, transport and metabolism of chemotherapeutic agents. Anthracyclines, ifosfamide and its metabolites, and topoisomerase I and I/II inhibitors are incorporated in red blood cells. They may be transported to the tumour tissue and mobilised from the erythrocyte by different active or passive transport mechanisms. Erythrocytes may also be used as carriers for drugs such as asparaginase. This leads to a decreased toxicity profile. Finally, it has been shown that red blood cells are important in the transport and metabolism of mercaptopurine. The erythrocyte concentration of mercaptopurine has a prognostic value in the treatment of childhood acute lymphoblastic leukemia. In this review, the role of red blood cells for various anticancer drugs is further discussed.

Chromatographic analysis of anticancer drugs

The present review on the methods for the analysis of anticancer drugs should be seen as an addition to the excellent work of Eksborg and Ehrsson published half a decade ago in this journal (Vol. 340, p.31). The style and format have been followed closely, with the focus again on chromatographic techniques. We felt it important to add a list of compound (group) structures as a service to the reader. Methods have been reviewed for alkylating agents, platinum compounds, antitumour antibiotics, antimetabolites, alkaloids, suramin, 1-hydroxy-3-amino-propylidene-1,1-bisphosphonate and tamoxifen.

Anthracycline antitumour agents. A review of physicochemical, analytical and stability properties

A review of physicochemical and analytical properties of anthracycline antitumour agents is presented. The following subjects are discussed: protolytic equilibria, partition and partition coefficients, self-association, adsorptive properties, metal complexation, spectroscopy and chromatography. Furthermore, the stability of anthracyclines in solutions, in pharmaceutical preparations and in biological media is discussed.

Adriamycin cardiomyopathy: implications of cellular changes in a canine model with mild impairment of left ventricular function

The present study has examined early cellular effects of chronic adriamycin administration to dogs using a protocol (1 mg/kg/week to a total cumulative dose of 240 mg/m2) producing significant but small reductions in ejection fraction and stroke volume as determined echocardiographically prior to the development of clinical or radiological manifestations of heart failure. At this early phase of cardiomyopathy, significant reduction (P less than 0.05) in sarcoplasmic reticulum Ca2+, K+-ATPase was observed without any change in mitochondrial, lysosomal or sarcolemmal marker enzymes. Myocardial calcium (P less than 0.01) and glutathione (P less than 0.001) levels were increased significantly. Detailed analysis of myocardial phospholipid profiles failed to show any significant differences between control and treated dogs. In contrast, red cell membranes showed increased phosphatidylcholine (PC) and decreased phosphatidylserine (PS) contents, resulting in a significant increase in PC/PS ratio (P less than 0.05). No significant changes were detected in activities of catalase, superoxide dismutase or glutathione peroxidase in erythrocytes or myocardial tissue from control and adriamycin-treated animals. A significant (P less than 0.05) elevation in plasma sialic acid was observed following adriamycin treatment. Our results suggest that early adriamycin-induced damage is unlikely to result from alterations in cellular processes protecting tissues against oxidant injury. Regression analysis indicated that, of the various abnormalities observed, only the elevated myocardial calcium levels and the increases in plasma sialic acid correlated with the degree of myocardial functional impairment. Our findings suggest the presence of sarcolemmal alterations in Ca2+ handling in early adriamycin-induced myocardial injury and indicate that measurement of plasma sialic acid should be further investigated as a possible noninvasive indicator of impending adriamycin cardiotoxicity.

Toxic effects of chemicals: difficulties in extrapolating data from animals to man

This review attempts an analysis of the major components which make it extremely difficult to extrapolate toxicological data obtained with chemicals from animals to man. A first problem concerns the use of doses to express the unit of comparison across animal species; the dose is a parameter exogenous to the body and when a chemical enters the body concentrations should be utilized. There is in fact evidence that for several chemicals equal doses in different animal species do not mean equal concentrations in blood or tissues. Concentrations of chemicals should be measured for extrapolation purposes as close as possible to the site of the toxic effect. A second problem regards the fact that several chemical are transformed in the body into other chemical species--sometimes few and sometimes many--and some of these species (active metabolites) display biological activity in some cases higher than different from or antagonistic to those of the parent compounds. Some of these metabolites are highly reactive and therefore bind to body components, particularly macromolecules such as proteins and nucleic acids. There is evidence that metabolism is quantitatively and/or qualitatively different in various animal species. A third problem concerns the difference in various animal species in the biological substrates on which chemicals exert their toxic effects. Equal concentrations of chemicals and their metabolites do not mean equal toxic effects across animal species because endogenous metabolic processes, cell permeability, enzymes, and receptors are not necessarily the same in animals and man. To overcome these difficulties there is a need for closer integration of different disciplines in the toxicological evaluation of chemicals. A scientific rather than a routine approach in toxicology is emphasized.

Pharmacokinetics and toxicity testing

The pharmacokinetic basis for the design of toxicity tests is discussed with reference to the absorption and clearance of drugs. The absorption and clearance of a wide range of drugs by laboratory animals and man has been examined and reviewed to provide a firm basis against which new drugs can be compared. Some pitfalls in either the empirical approach to toxicology or the incorrect interpretation of kinetic data are highlighted. An approach is outlined for the rational application of animal pharmacokinetic data in the assessment of the safety in man of a new therapeutic agent.