Additive effects of dipyridamole and Trolox in protecting human red cells during photodynamic treatment

Concentration Dependence of the Antioxidant and Prooxidant Activity of Trolox in HeLa Cells: Involvement in the Induction of Apoptotic Volume Decrease

Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), a hydrophilic analog of vitamin E, is known for its strong antioxidant activity, being a high radical scavenger of peroxyl and alkoxyl radicals. Under particular conditions, Trolox may also exhibit prooxidant properties. The present work aimed at studying the dual antioxidant/prooxidant behavior of Trolox over a wide range of concentrations (from 2.5 to 160 µM) in HeLa cells. In particular, the study addressed the dose-dependent effects of Trolox on the oxidative cell status and vitality of HeLa cells, focusing on the potential role of the vitamin E analog in the induction of one of the first steps of the apoptotic process, Apoptotic Volume Decrease (AVD). In HeLa cells, Trolox showed significant antioxidant activity, expressed as the ability to reduce the endogenous ROS production detected by the ROS-sensitive probe 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate (CM-H₂DCFDA), at low concentrations (range: 2.5–15 µM), but exerted a dose-dependent prooxidant effect at higher concentrations after 24 h exposure. The prooxidant effect was paralleled by the reduction in cell viability due to the induction of the apoptotic process. The dual behavior, antioxidant at lower concentrations and prooxidant at higher concentrations, was evident also earlier after 2 h incubation, and it was paralleled by the isotonic shrinkage of the cells, ascribed to AVD. The use of SITS, known Cl⁻ channel blocker, was able to completely inhibit the Trolox-induced isotonic cell shrinkage, demonstrating the involvement of the vitamin E analog in the alteration of cell volume homeostasis and, in turn, in the AVD induction. In conclusion, the study shed light on the concentration dependence of the Trolox antioxidant/prooxidant activity in HeLa cells and revealed its role in the induction of one of the first events of apoptosis, AVD, at high concentrations.

Vitamin E Analogue Protects Red Blood Cells against Storage-Induced Oxidative Damage

Background

To investigate i) the effects of Trolox® or mannitol, which represent two different classes of antioxidants, on oxidative changes generated in manually isolated red blood cells (RBCs) from citrate-phosphate-dextrose (CPD) preserved whole blood, followed by up to 20 days refrigerated storage, and ii) whether Trolox supplemented to the blood bank-manufactured saline-adenine-glucose-mannitol (SAGM) preserved RBC units would offer better storage conditions compared with SAGM alone.

Methods

The percentage of hemolysis and extracellular activity of lactate dehydrogenase (LDH) was measured to assess RBC membrane integrity. Lipid peroxidation, reduced glutathione (GSH) levels and total antioxidant capacity (TAC) were quantified by thiobarbituric acid-reactive substances (TBARS), Ellman's reagent and 2, 2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS^.+) based assay, respectively.

Results

Trolox was little more effective than mannitol in protecting against progressive RBC hemolysis. Trolox (0.125-3.125 mmol/l) inhibited storage-induced leakage of LDH, lipid peroxidation, and to a lesser extent GSH depletion. Mannitol at these concentrations neither inhibited TBARS formation nor prevented GSH depletion. RBC units stored in SAGM-Trolox had significantly lower hemolysis, LDH leakage, and lipid peroxidation level compared to RBCs stored in SAGM.

Conclusion

There is evidence of the beneficial effects of supplementing RBC-additive solutions with membrane-interacting antioxidants such as vitamin E analogues.

Dolichol: A Component of the Cellular Antioxidant Machinery

Dolichol, an end product of the mevalonate pathway, has been proposed as a biomarker of aging, but its biological role, not to mention its catabolism, has not been fully understood. UV-B radiation was used to induce oxidative stress in isolated rat hepatocytes by the collagenase method. Effects on dolichol, phospholipid-bound polyunsaturated fatty acids (PL-PUFA) and known lipid soluble antioxidants [coenzyme Q (CoQ) and α-tocopherol] were studied. The increase in oxidative stress was detected by a probe sensitive to reactive oxygen species (ROS). Peroxidation of lipids was assessed by measuring the release of thiobarbituric acid reactive substances (TBARS). Dolichol, CoQ, and α-tocopherol were assessed by high-pressure liquid chromatography (HPLC), PL-PUFA by gas-liquid chromatography (GC). UV-B radiation caused an immediate increase in ROS as well as lipid peroxidation and a simultaneous decrease in the levels of dolichol and lipid soluble antioxidants. Decrease in dolichol paralleled changes in CoQ levels and was smaller to that in α-tocopherol. The addition of mevinolin, a competitive inhibitor of the enzyme 3-hydroxy-3-methylglutaryl CoA reductase (HMG-CoAR), magnified the loss of dolichol and was associated with an increase in TBARS production. Changes in PL-PUFA were minor. These findings highlight that oxidative stress has very early and similar effects on dolichol and lipid soluble antioxidants. Lower levels of dolichol are associated with enhanced peroxidation of lipids, which suggest that dolichol may have a protective role in the antioxidant machinery of cell membranes and perhaps be a key to understanding some adverse effects of statin therapy.

The application of photosensitisers to tropical pathogens in the blood supply

The onset of the HIV pandemic led both to significant alterations in blood collection and screening practice and to the development of more sophisticated methods of inactivation of infectious agents from the blood supply. Photodynamic (i.e. light activated) pathogen inactivation is one such method currently in limited use in various European states. The approach is based on the generation of a burst of reactive oxygen and nitrogen species, resulting in the activation of several cell death mechanisms. However, its application to tropical pathogens is perhaps less appreciated, despite the fact that the efficacies of photoantimicrobial agents such as methylene blue were originally reported following screening against organisms such as Trypanosoma cruzi and viruses such as those responsible for dengue and yellow fever. Since the objective of pathogen inactivation is to remove both established and emerging infective agents, it is necessary for photoantimicrobial agents to be broad-spectrum in activity. While this is demonstrable in plasma and platelet fractions, the application to red blood cells is currently under investigation.

UVA-induced phenoxyl radical formation: A new cytotoxic principle in photodynamic therapy

Psoralens are regularly used in therapy in combination with ultraviolet A light irradiation (PUVA) to treat skin diseases such as psoriasis, vitiligo, and mycosis fungoides. PUVA therapy is also used within the scope of extracorporeal photopheresis to treat a variety of diseases that have a suspected involvement of pathogenic T cells, including rejection of organ transplants, graft-vs-host disease, cutaneous T cell lymphoma, and autoimmune disorders. Because psoralens are the only photosensitizers used in PUVA therapies and are considered to be responsible for a number of side effects, the identification of alternative drugs is of practical interest. Here we investigated the impact of activated Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), a hydrophilic vitamin E analog lacking the phytyl tail, as an alternative photoactivatable agent with T cell cytotoxic properties. Despite the well-known antioxidative capacity of Trolox, we found that at low UVA doses and in the presence of supraphysiological concentration of nitrite, a natural constituent of human skin, this compound selectively enhances radical-mediated cytotoxicity toward T cells but not toward human skin fibroblasts, keratinocytes, or endothelial cells. The cytotoxic mechanism comprises a reaction of Trolox with photo-decomposition products of nitrite, which leads to increased Trolox phenoxyl radical formation, increased intracellular oxidative stress, and a consecutive induction of apoptosis and necrosis in fast proliferating T cells. Thus, the identified UVA/nitrite-induced phenoxyl radical formation provides an opportunity for a new cytotoxic photodynamic therapy.

Trolox prevents osteoclastogenesis by suppressing RANKL expression and signaling

Excessive receptor activator of NF-kappaB ligand (RANKL) signaling causes enhanced osteoclast formation and bone resorption. Thus, down-regulation of RANKL expression or its downstream signals may be a therapeutic approach to the treatment of pathological bone loss. In this study, we investigated the effects of Trolox, a water-soluble vitamin E analogue, on osteoclastogenesis and RANKL signaling. Trolox potently inhibited interleukin-1-induced osteoclast formation in bone marrow cell-osteoblast coculture by abrogating RANKL induction in osteoblasts. This RANKL reduction was attributed to the reduced production of prostaglandin E(2) via a down-regulation of cyclooxygenase-2 activity. We also found that Trolox inhibited osteoclast formation from bone marrow macrophages induced by macrophage colony-stimulating factor plus RANKL in a reversible manner. Trolox was effective only when present during the early stage of culture, which implies that it targets early osteoclast precursors. Pretreatment with Trolox did not affect RANKL-induced early signaling pathways, including MAPKs, NF-kappaB, and Akt. We found that Trolox down-regulated the induction by RANKL of c-Fos protein by suppressing its translation. Ectopic overexpression of c-Fos rescued the inhibition of osteoclastogenesis by Trolox in bone marrow macrophages. Trolox also suppressed interleukin-1-induced osteoclast formation and bone loss in mouse calvarial bone. Taken together, our findings indicate that Trolox prevents osteoclast formation and bone loss by inhibiting both RANKL induction in osteoblasts and c-Fos expression in osteoclast precursors.

A novel arsenical has antitumor activity toward As2O3-resistant and MRP1/ABCC1-overexpressing cell lines

Inorganic arsenic trioxide (As(2)O(3)) is a highly effective treatment for acute promyelocytic leukemia (APL). However, other cancers do not respond well to this form of arsenic at clinically achievable doses. We tested a novel arsenical, S-dimethylarsino-glutathione (darinaparsin) for efficacy in various malignancies in vitro. Darinaparsin is significantly more potent than As(2)O(3) at mediating apoptosis in various malignant cell lines and is highly active against APL cells derived for As(2)O(3) resistance. We provide evidence that darinaparsin triggers apoptosis by inducing signaling pathways that do not completely overlap with As(2)O(3). We show that darinaparsin induces apoptosis and oxidative stress to a greater extent than As(2)O(3), although like As(2)O(3), darinaparsin-induced toxicity is c-Jun NH(2)-terminal kinase-dependent. However, darinaparsin does not induce promyelocytic leukemia/retinoic acid receptor alpha (PML/RAR alpha) degradation or rearrange PML nuclear bodies in APL cells, nor is its toxicity increased by glutathione depletion. Darinaparsin treatment results in higher intracellular arsenic accumulation when compared to As(2)O(3) treatment. This may be explained by our finding that As(2)O(3), but not darinaparsin, is efficiently exported by ABCC1, suggesting increased therapeutic efficacy of darinaparsin in ABCC1-overexpressing tumors. Our studies indicate that darinaparsin efficiently kills tumor cells with increased antioxidant capacity and drug exporters and suggest that darinaparsin may have a broader therapeutic spectrum than As(2)O(3).

Use of a Red Cell Band 3-Ligand/Antioxidant to Improve Red Cell Storage Properties Following Virucidal Phototeatment with Chalcogenoxanthylium Photosensitizers

The efficacy of two chalcogenoxanthylium photosensitizers to reduce pathogens in red cell suspensions while maintaining red cell storage properties was investigated in the presence and absence of the red cell band-3 ligand and antioxidant, dipyridamole (DP). In the presence of DP, both sensitizers, TMR-S and DJD-42, displayed potent virucidal photoactivity (>6 log10) and species-dependent bactericidal activities that ranged from 0.6 to 8.7 log10. Addition of DP to red cell suspensions containing TMR-S or DJD-42 reduced Day 42 photo-induced hemolysis by approximately eight-fold and four-fold, respectively. Red cell binding studies revealed only a small degree of competition between DP and TMR-S, and no competition between DP with DJD-42 for binding to red cell membranes, suggesting that protection of red cells by DP in this system may primarily stem from its antioxidant properties.

The development of phenothiazinium photosensitisers

Methylene blue has been widely used since the late 19th century in biomedical research, and was the lead compound in several important clinical areas, including therapeutics for malaria and schizophrenia. The photodynamic therapy (PDT) of cancer and, more recently, of microbial infection (photodynamic antimicrobial chemotherapy (PACT)) has also employed methylene blue and its congeners, among other chemical types, due to the low human toxicities and efficient photosensitising properties of the group. However, little work has been carried out in terms of derivative and structure-activity development, most reports covering standard, commercially available compounds. This review deals with the evolution of phenothiazinium photosensitisers for both PACT and PDT use.

Trolox selectively enhances arsenic-mediated oxidative stress and apoptosis in APL and other malignant cell lines

Although arsenic trioxide (As2O3) is an effective therapy in acute promyelocytic leukemia (APL), its use in other malignancies is limited by the toxicity of concentrations required to induce apoptosis in non-APL tumor cells. We looked for agents that would synergize with As2O3 to induce apoptosis in malignant cells, but not in normal cells. We found that trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), a widely known antioxidant, enhances As2O3-mediated apoptosis in APL, myeloma, and breast cancer cells. Treatment with As2O3 and trolox increased intracellular oxidative stress, as evidenced by heme oxygenase-1 (HO-1) protein levels, c-Jun terminal kinase (JNK) activation, and protein and lipid oxidation. The synergistic effects of trolox may be specific to As2O3, as trolox does not add to toxicity induced by other chemotherapeutic drugs. We explored the mechanism of this synergy using electron paramagnetic resonance and observed the formation of trolox radicals when trolox was combined with As2O3, but not with doxorubicin. Importantly, trolox protected nonmalignant cells from As2O3-mediated cytotoxicity. Our data provide the first evidence that trolox may extend the therapeutic spectrum of As2O3. Furthermore, the combination of As2O3 and trolox shows potential specificity for tumor cells, suggesting it may not increase the toxicity associated with As2O3 monotherapy in vivo.

Laser-assisted optical rotational cell analyzer measurements reveal early changes in human RBC deformability induced by photodynamic treatment

BACKGROUND

The ability to deform is important for circulating RBCs in vivo, and earlier studies showed that this property can objectively be measured in vitro by the LORCA. In this study it was investigated whether photodynamic treatment of human RBCs (meant to inactivate contaminating pathogens) affects deformability.

STUDY DESIGN AND METHODS

WBC-reduced RBC suspensions (30% Hct) were treated with 1,9-dimethylmethylene blue (DMMB) and red light. Changes in deformability were analyzed by LORCA measurements, in which elongation of the cells is measured at increasing shear stress. The effect of DMMB concentration and light dose was determined as well as the interfering effect of two scavengers of reactive oxygen species, that is, dipyridamole and Trolox.

RESULTS

Photodynamic treatment with DMMB resulted in clear changes in RBC deformability. Deformability changes occurred before onset of hemolysis. Under relatively mild treatment conditions, especially deformability at low shear stress was decreased, whereas deformability changes at high shear stress only occurred under harsher treatment conditions. Inclusion of dipyridamole and/or Trolox primarily prevented deformability changes at high shear stress.

CONCLUSION

LORCA measurements can effectively be used to detect changes in deformability that are induced by photodynamic treatment of human RBCs. A change in deformability represents an early marker of RBC damage under these conditions.