Fluorescence lifetime imaging and phasor analysis of intracellular porphyrinic photosensitizers applied with different polymeric formulations

The fluorescence lifetime of a porphyrinic photosensitizer (PS) is an important parameter to assess the aggregation state of the PS even in complex biological environments. Aggregation-induced quenching of the PS can significantly reduce the yield of singlet oxygen generation and thus its efficiency as a medical drug in photodynamic therapy (PDT) of diseased tissues. Hydrophobicity and the tendency to form aggregates pose challenges on the development of efficient PSs and often require carrier systems. A systematic study was performed to probe the impact of PS structure and encapsulation into polymeric carriers on the fluorescence lifetime in solution and in the intracellular environment. Five different porphyrinic PSs including chlorin e6 (Ce6) derivatives and tetrakis(m-hydroxyphenyl)-porphyrin and -chlorin were studied in free form and combined with polyvinylpyrrolidone (PVP) or micelles composed of triblock-copolymers or Cremophor. Following incubation of HeLa cells with these systems, fluorescence lifetime imaging combined with phasor analysis and image segmentation was applied to study the lifetime distribution in the intracellular surrounding. The data suggest that for free PSs, the structure-dependent cell uptake pathways determine their state and emission lifetimes. PS localization in the plasma membrane yielded mostly monomers with long fluorescence lifetimes whereas the endocytic pathway with subsequent lysosomal deposition adds a short-lived component for hydrophilic anionic PSs. Prolonged incubation times led to increasing contributions from short-lived components that derive from aggregates mainly localized in the cytoplasm. Encapsulation of PSs into polymeric carriers led to monomerization and mostly fluorescence emission decays with long fluorescence lifetimes in solution. However, the efficiency depended on the binding strength that was most pronounced for PVP. In the cellular environment, PVP was able to maintain monomeric long-lived species over prolonged incubation times. This was most pronounced for Ce6 derivatives with a logP value around 4.5. Micellar encapsulation led to faster release of the PSs resulting in multiple components with long and short fluorescence lifetimes. The hydrophilic hardly aggregating PS exhibited a mostly stable invariant lifetime distribution over time with both carriers. The presented data are expected to contribute to optimized PDT treatment protocols and improved PS-carrier design for preventing intracellular fluorescence quenching. In conclusion, amphiphilic and concurrent hydrophobic PSs with high membrane affinity as well as strong binding to the carrier have best prospects to maintain their photophysical properties in vivo and serve thus as efficient photodynamic diagnosis and PDT drugs.

Association of acute thrombocytopenia with anaphylaxis

A commonly seen phenomenon in the hospital and critical care setting is anaphylaxis. This acute systemic inflammatory reaction can lead to anaphylactic shock in severe cases and potentially be fatal. The role of platelets in anaphylactic reactions is not well established; however, platelets, among other mediators such as platelet-activating factor, have been shown to promote a prothrombotic state shortly after an acute hypersensitivity reaction. In addition, the aggregation of platelets promoted by platelet-activating factor and other mediators can also lead to thrombocytopenia. We present a case of a 57-year-old woman who developed severe anaphylaxis while receiving chemotherapy with paclitaxel suspended in Cremophor, a well-known allergen. She was profoundly thrombocytopenic following the reaction and was treated with therapeutic anticoagulation, with no thrombus formation.

Modulation of the anticancer activities of paclitaxel by Cremophor micelles

The objective of this study was to determine the effect of Cremophor (CrEL) on the antineoplastic effect induced by paclitaxel (PTX). Fluorescence spectroscopy, employing pyrene as a probe, was used to determine the critical micelle concentration (CMC) of CrEL. EL4 murine thymoma cells and MDA-MB-231 human breast cancer cells were treated with PTX in different concentrations of CrEL. G2 arrest with 8 N polyploidy was observed in PTX-treated EL4 cells but not in MDA-MB-231 cells. Cell cycle analysis via propidium iodide (PI) staining showed that the frequency of G2 arrest decreased as the CrEL concentration exceeded 0.02% (w/v), demonstrating the effect of CrEL micelle formation on the antimitotic activity of PTX. CrEL was also shown to enhance PTX-induced cell death in vitro by Annexin V/PI staining. Treatment of C57BL/6 mice with PTX in a lower concentration of CrEL resulted in higher myelosuppression, decreased both Ki-67 expression and survival rate, suggesting that CrEL micelle formation above the CMC may lower the cytotoxic activity of PTX in vivo. The data obtained in this study demonstrate CrEL micelle-mediated modulation of the cell cycle and cell death induced by PTX in vitro and the antineoplastic efficacy of PTX in vivo.

Non-convulsive seizure related to Cremophor EL™-free, polymeric micelle formulation of paclitaxel: a case report

Paclitaxel is a chemotherapeutic agent that is effective against ovarian, breast, lung, and other cancers. Although peripheral neurotoxicity is among the most common side effects of paclitaxel treatment, central neurotoxicity is rarely reported. When centrally mediated side effects are observed, they are attributed to Cremophor EL™ (CrEL), a surfactant-containing vehicle used for paclitaxel administration. In the present report, we discuss the case of a 72-year-old woman with ovarian carcinoma who experienced a non-convulsive seizure following administration of a CrEL-free, polymeric micelle formulation of paclitaxel. One week after her fourth round of chemotherapy, she experienced a transient episode of aphasia for 45 minutes. Electroencephalography demonstrated epileptiform discharges. To our knowledge, this is the first reported case of seizure associated with a CrEL-free formulation of paclitaxel. Although rare, patients and clinicians should remain aware of the risk of non-convulsive seizure following infusion of this paclitaxel formulation.

Paclitaxel pre-medication: A comparison of two steroid pre-medication protocols

Purpose To evaluate and compare the rate of hypersensitivity reactions between two low-dose steroid pre-medication regimens for paclitaxel-based treatments. Methods This was a single-center, retrospective, descriptive study, comparing the incidence of hypersensitivity reactions in two different dexamethasone pre-medication regimens that took place between July 2013 to December 2014. Patients who were paclitaxel-naïve with a diagnosis of breast or gynecological cancers were included. Patients in the early termination protocol were pre-medicated with a standard pre-medication regimen and if tolerated with no hypersensitivity reaction occurrence, all pre-medications were discontinued after the first two infusions. Patients in the low-dose steroid continuation protocol were pre-medicated with lower doses of dexamethasone, and if the infusion was tolerated with no hypersensitivity reaction, dexamethasone doses were further reduced after the first two infusions. Results A total of 120 patients were included for data analysis. The hypersensitivity reaction rate in the early termination protocol group was 7% (4 out of 60 patients). The hypersensitivity reaction rate in the low-dose continuation protocol group was 5% (3 out of 60 patients). All hypersensitivity reactions occurred during the first infusion, with no hypersensitivity reactions occurring once the dexamethasone pre-medications were discontinued or dose-reduced. All of the patients who experienced a hypersensitivity reaction were successfully re-challenged with paclitaxel and were able to continue their therapy uninterrupted. Conclusion Discontinuing dexamethasone pre-medication altogether after two uneventful infusions or decreasing the dose of dexamethasone paclitaxel pre-medication are both safe alternatives to high-dose steroid pre-medications recommended in product labeling.

Intravenous tacrolimus and cyclosporine induced anaphylaxis: what is next?

Tacrolimus and cyclosporine have been used in various formulations, but their hypersensitivity reactions are rare in practice. Castor oil derivatives are nonionic surfactants used in aqueous preparations of hydrophobic active pharmaceutical ingredients. Castor oil derivatives that can be used as additives to tacrolimus and cyclosporine may play a role in the development of hypersensitivity reactions, especially anaphylaxis. Various immunologic and nonimmunologic mechanisms have been implicated in hypersensitivity reactions induced by castor oil derivatives. Physicians should be aware that not only the drug itself, but also its additives or metabolites could induce hypersensitivity reactions. We report a case of anaphylaxis caused by vitamin K (phytonadine), serotonin antagonist (granisetron), intravenous tacrolimus, and cyclosporine. Interestingly, the patient tolerated oral cyclosporine, which did not contain Cremophor EL or polysorbate 80.

Interfacial electron-shuttling processes across KolliphorEL monolayer grafted electrodes

Covalently grafted KolliphorEL (a poly(ethylene glycol)-based transporter molecule for hydrophobic water-insoluble drugs; MW, ca. 2486; diameter, ca. 3 nm) at the surface of a glassy-carbon electrode strongly affects the rate of electron transfer for aqueous redox systems such as Fe(CN)6(3-/4-). XPS data confirm monolayer grafting after electrochemical anodization in pure KolliphorEL. On the basis of voltammetry and impedance measurements, the charge transfer process for the Fe(CN)6(3-/4-) probe molecule is completely blocked after KolliphorEL grafting and in the absence of a "guest". However, in the presence of low concentrations of suitable ferrocene derivatives as guests, mediated electron transfer across the monolayer via a shuttle mechanism is observed. The resulting amplification of the ferrocene electroanalytical signal is investigated systematically and compared for five ferrocene derivatives. The low-concentration electron shuttle efficiency decreases in the following sequence: (dimethylaminomethyl)ferrocene > n-butyl ferrocene > ferrocene dimethanol > ferroceneacetonitrile > ferroceneacetic acid.

Nonconvulsive status epilepticus secondary to paclitaxel administration

Nonconvulsive status epilepticus (NCSE) can be triggered by metabolic disturbances and drugs in adults without previous epilepsy. We present the case of a 51-year-old woman without previous history of epilepsy and recently diagnosed with infiltrating lobular breast carcinoma. Following the administration of paclitaxel-cremophor, she presented a striking disinhibited behavior with episodic spatial disorientation, emotional indifference, and irritability. Urgent EEG was consistent with NCSE. Clinical improvement and resolution of EEG abnormalities were observed following the administration of intravenous levetiracetam and lacosamide. Other causes of NCSE were ruled out, and antiepileptic drugs were slowly tapered off without new episodes of abnormal behavior after three months of follow-up. We have reported the first case of NCSE secondary to paclitaxel-cremophor. Neurologists and oncologists should consider NCSE as an unusual complication of treatment with paclitaxel-cremophor in patients without a history of epilepsy.

Nab-paclitaxel-associated photosensitivity: report in a woman with non-small cell lung cancer and review of taxane-related photodermatoses

BACKGROUND

Taxanes [paclitaxel, nab-paclitaxel (Abraxane, Celgene Corp, USA), and docetaxel]-used in the treatment of lung, breast, and head and neck cancers-have been associated with cutaneous adverse effects, including photodermatoses.

PURPOSE

We describe a woman with non-small cell lung cancer who developed a photodistributed dermatitis associated with her nab-paclitaxel therapy and review photodermatoses in patients receiving taxanes.

MATERIALS AND METHODS

The features of a woman with a nab-paclitaxel-associated photodistributed dermatitis are presented and the literature on nab-paclitaxel-associated photosensitivity is reviewed.

RESULTS

Our patient developed nab-paclitaxel-associated photodistributed dermatitis on the sun-exposed surfaces of her upper extremities, which was exacerbated with each course of nab-paclitaxel. Biopsies revealed an interface dermatitis and laboratory studies were negative for lupus erythematosus and dermatomyositis. Her condition improved following topical corticosteroid cream application and strict avoidance of sunlight.

CONCLUSION

Chemotherapy can be associated with adverse mucocutaneous events, including dermatoses on sun-exposed areas of the skin. Paclitaxel and nab-paclitaxel have both been associated with photodermatoses, including dermatitis, erythema multiforme, onycholysis, and subacute cutaneous lupus erythematosus. Strict avoidance of sun exposure, topical or oral corticosteroids, and/or discontinuation of the drug results in improvement with progressive resolution of symptoms and skin lesions. Development of photodermatoses is not an absolute contraindication to continuing chemotherapy, provided that the cutaneous condition resolves with dermatosis-directed treatment and the patient avoids sun exposure.

Kolliphor surfactants affect solubilization and bioavailability of fenofibrate. Studies of in vitro digestion and absorption in rats

Selection of excipients for drug formulations requires both intellectual and experimental considerations as many of the used excipients are affected by physiological factors, e.g., they may be digested by pancreatic enzymes in the gastrointestinal tract. In the present paper we have looked systematically into the differences between Kolliphor ELP, EL, and RH40 and how they affect the bioavailability of fenofibrate, through pharmacokinetic studies in rats and in vitro lipolysis studies. The study design was made as simple as possible to avoid confounding factors, for which reason the tested formulations only comprised an aqueous micellar solution of the model drug (fenofibrate) in varying concentrations (2-25% (w/v)) of the three tested surfactants. Increased concentrations of Kolliphor ELP and EL led to increased fenofibrate AUC0-24h values. For the Kolliphor RH40 formulations, an apparent fenofibrate absorption optimum was seen at 15% (w/v) surfactant, displaying both the highest AUC0-24h and Cmax. The reduced absorption of fenofibrate from the formulation containing the highest level of surfactant (25% w/v) was thought to be caused by some degree of trapping within Kolliphor RH40 micelles. In vitro, Kolliphor ELP and EL were found to be more prone to digestion than Kolliphor RH40, though not affecting the in vivo results. The highest fenofibrate bioavailability was attained from formulations with high Kolliphor ELP/EL levels (25% (w/v)), indicating that these surfactants are the better choice for solubilizing fenofibrate in order to increase the absorption upon oral administration. Due to drug dependent effects of the different types of Kolliphor, more studies are recommended in order to understand which type of Kolliphor is best suited for a given drug.

Systemic toxicity induced by paclitaxel in vivo is associated with the solvent cremophor EL through oxidative stress-driven mechanisms

The toxic effects of paclitaxel (PTX) and its solubilizing agent cremophor EL (CREL) have been well established in vitro; however, the in vivo mechanisms underlying this toxicity remain unclear. Thus, the aim of this study was to analyze the in vivo toxicity induced by infusion of PTX and CREL and to investigate the involvement of oxidative stress as a potential mechanism for this toxicity. We treated male Wistar rats with PTX and/or CREL for 1h using human-equivalent doses (PTX+CREL/ethanol+NaCl 175mg/m(2) or CREL+ethanol+NaCl) and sacrificed immediately or 24h after these drug infusions to systemic biochemical evaluations. Hidrosoluble vitamin E (vitE, Trolox) was added as a control in some groups. The oxidative profile was determined by measuring erythrocyte and plasma lipid peroxidation, superoxide dismutase and catalase activities, reduced glutathione (GSH) levels, red blood cell (RBC) counts, hemoglobin profile, plasma total radical-trapping antioxidant parameter (TRAP), plasma lipid peroxidation, nitric oxide levels and malondialdehyde levels. Our findings showed that CREL infusion triggered immediate high plasma lipid peroxidation and augmented TRAP, while PTX caused immediate TRAP consumption and metahemoglobin formation. Pronounced oxidative effects were detected 24h after infusion, when CREL treatment enhanced RBC counts and plasma lipid peroxidation, increased catalase activity, and decreased TRAP levels. On the other hand, after 24h, PTX-infused rats showed reduced catalase activity and reduced metahemoglobin levels. These data indicate the existence of a continuous oxidative stress generation during CREL-PTX treatment and highlight CREL as primarily responsible for the in vivo oxidative damage to RBCs.