Georg Wondrak

Redox Drug Discovery Targeting Skin Cancer and Solar Photodamage
The Redox Antimalarial Dihydroartemisinin Targets Human Metastatic Melanoma Cells But Not Primary Melanocytes With Induction Of Noxa Dependent Apoptosis. Source: Investigational New Drugs
May 6th, 2011 PMID: 21547369 Georg Wondrak
Recent research suggests that altered redox control of melanoma cell survival, proliferation, and invasiveness represents a chemical vulnerability that can be targeted by pharmacological modulation of cellular oxidative stress. The endoperoxide artemisinin and semisynthetic artemisinin-derivatives including dihydroartemisinin (DHA) constitute a major class of antimalarials that kill plasmodium parasites through induction of iron-dependent oxidative stress. Here, we demonstrate that DHA may serve as a redox chemotherapeutic that selectively induces melanoma cell apoptosis without compromising viability of primary human melanocytes. Cultured human metastatic melanoma cells (A375, G361, LOX) were sensitive to DHA-induced apoptosis with upregulation of cellular oxidative stress, phosphatidylserine externalization, and activational cleavage of procaspase 3. Expression array analysis revealed DHA-induced upregulation of oxidative and genotoxic stress response genes (GADD45A, GADD153, CDKN1A, PMAIP1, HMOX1, EGR1) in A375 cells. DHA exposure caused early upregulation of the BH3-only protein NOXA, a proapototic member of the Bcl2 family encoded by PMAIP1, and genetic antagonism (siRNA targeting PMAIP1) rescued melanoma cells from apoptosis indicating a causative role of NOXA-upregulation in DHA-induced melanoma cell death. Comet analysis revealed early DHA-induction of genotoxic stress accompanied by p53 activational phosphorylation (Ser 15). In primary human epidermal melanocytes, viability was not compromised by DHA, and oxidative stress, comet tail moment, and PMAIP1 (NOXA) expression remained unaltered. Taken together, these data demonstrate that metastatic melanoma cells display a specific vulnerability to DHA-induced NOXA-dependent apoptosis and suggest feasibility of future anti-melanoma intervention using artemisinin-derived clinical redox antimalarials.<br><br>
Zinc Pyrithione Impairs Zinc Homeostasis And Upregulates Stress Response Gene Expression In Reconstructed Human Epidermis. Source: Biometals : An International Journal On The Role Of Metal Ions In Biology, Biochemistry, And Medicine
March 22nd, 2011 PMID: 21424779 Georg Wondrak
Zinc ion homeostasis plays an important role in human cutaneous biology where it is involved in epidermal differentiation and barrier function, inflammatory and antimicrobial regulation, and wound healing. Zinc-based compounds designed for topical delivery therefore represent an important class of cutaneous therapeutics. Zinc pyrithione (ZnPT) is an FDA-approved microbicidal agent used worldwide in over-the-counter topical antimicrobials, and has also been examined as an investigational therapeutic targeting psoriasis and UVB-induced epidermal hyperplasia. Recently, we have demonstrated that cultured primary human skin keratinocytes display an exquisite sensitivity to nanomolar ZnPT concentrations causing induction of heat shock response gene expression and poly(ADP-ribose) polymerase (PARP)-dependent cell death (Cell Stress Chaperones 15:309-322, 2010). Here we demonstrate that ZnPT causes rapid accumulation of intracellular zinc in primary keratinocytes as observed by quantitative fluorescence microscopy and inductively coupled plasma mass spectrometry (ICP-MS), and that PARP activation, energy crisis, and genomic impairment are all antagonized by zinc chelation. In epidermal reconstructs (EpiDermâ„¢) exposed to topical ZnPT (0.1-2% in Vanicreamâ„¢), ICP-MS demonstrated rapid zinc accumulation, and expression array analysis demonstrated upregulation of stress response genes encoding metallothionein-2A (MT2A), heat shock proteins (HSPA6, HSPA1A, HSPB5, HSPA1L, DNAJA1, HSPH1, HSPD1, HSPE1), antioxidants (SOD2, GSTM3, HMOX1), and the cell cycle inhibitor p21 (CDKN1A). IHC analysis of ZnPT-treated EpiDermâ„¢ confirmed upregulation of Hsp70 and TUNEL-positivity. Taken together our data demonstrate that ZnPT impairs zinc ion homeostasis and upregulates stress response gene expression in primary keratinocytes and reconstructed human epidermis, activities that may underlie therapeutic and toxicological effects of this topical drug.<br><br>
Dcpip (2,6 Dichlorophenolindophenol) As A Genotype Directed Redox Chemotherapeutic Targeting Nqo1*2 Breast Carcinoma. Source: Free Radical Research
November 1st, 2010 PMID: 21034357 Georg Wondrak
Accumulative experimental evidence suggests feasibility of chemotherapeutic intervention targeting human cancer cells by pharmacological modulation of cellular oxidative stress. Current efforts aim at personalization of redox chemotherapy through identification of predictive tumour genotypes and redox biomarkers. Based on earlier research demonstrating that anti-melanoma activity of the pro-oxidant 2,6-dichlorophenolindophenol (DCPIP) is antagonized by cellular NAD(P)H:quinone oxidoreductase (NQO1) expression, this study tested DCPIP as a genotype-directed redox chemotherapeutic targeting homozygous NQO1*2 breast carcinoma, a common missense genotype [rs1800566 polymorphism; NP_000894.1:p.Pro187Ser] encoding a functionally impaired NQO1 protein. In a panel of cultured breast carcinoma cell lines and NQO1-transfectants with differential NQO1 expression levels, homozygous NQO1*2 MDA-MB231 cells were hypersensitive to DCPIP-induced caspase-independent cell death that occurred after early onset of oxidative stress with glutathione depletion and loss of genomic integrity. Array analysis revealed upregulated expression of oxidative (GSTM3, HMOX1, EGR1), heat shock (HSPA6, HSPA1A, CRYAB) and genotoxic stress response (GADD45A, CDKN1A) genes confirmed by immunoblot detection of HO-1, Hsp70, Hsp70B', p21 and phospho-p53 (Ser15). In a murine xenograft model of human homozygous NQO1*2-breast carcinoma, systemic administration of DCPIP displayed significant anti-tumour activity, suggesting feasibility of redox chemotherapeutic intervention targeting the NQO1*2 genotype.<br><br>
The Malondialdehyde Derived Fluorophore Dhp Lysine Is A Potent Sensitizer Of Uva Induced Photooxidative Stress In Human Skin Cells. Source: Journal Of Photochemistry And Photobiology. B, Biology
July 30th, 2010 PMID: 20724175 Georg Wondrak
Light-driven electron and energy transfer involving non-DNA skin chromophores as endogenous photosensitizers induces oxidative stress in UVA-exposed human skin, a process relevant to photoaging and photocarcinogenesis. Malondialdehyde is an electrophilic dicarbonyl-species derived from membrane lipid peroxidation. Here, we present experimental evidence suggesting that the malondialdehyde-derived protein epitope dihydropyridine (DHP)-lysine is a potent endogenous UVA-photosensitizer of human skin cells. Immunohistochemical analysis revealed the abundant occurrence of malondialdehyde-derived and DHP-lysine epitopes in human skin. Using the chemically protected dihydropyridine-derivative (2S)-Boc-2-amino-6-(3,5-diformyl-4-methyl-4H-pyridin-1-yl)-hexanoic acid-t-butylester as a model of peptide-bound DHP-lysine, photodynamic inhibition of proliferation and induction of cell death were observed in human skin Hs27 fibroblasts as well as primary and HaCaT keratinocytes exposed to the combined action of UVA and DHP-lysine. DHP-lysine photosensitization induced intracellular oxidative stress, p38 MAPkinase activation, and upregulation of heme oxygenase-1 expression. Consistent with UVA-driven ROS formation from DHP-lysine, formation of superoxide, hydrogen peroxide, and singlet oxygen was detected in chemical assays, but little protection was achieved using SOD or catalase during cellular photosensitization. In contrast, inclusion of NaN(3) completely abolished DHP-photosensitization. Taken together, these data demonstrate photodynamic activity of DHP-lysine and support the hypothesis that malondialdehyde-derived protein-epitopes may function as endogenous sensitizers of UVA-induced oxidative stress in human skin.<br><br>
Hmgb1 Directed Drug Discovery Targeting Cutaneous Inflammatory Dysregulation. Source: Current Drug Metabolism
May 6th, 2010 PMID: 20406187 Georg Wondrak
Extracellular cytokine function of the non-histone nuclear protein high-mobility group box 1 (HMGB1) has recently been recognized as an important drug target for novel anti-inflammatory therapeutics. Accumulating evidence supports the mechanistic involvement of the alarmin HMGB1 in skin response to microbial infection and ultraviolet-induced solar damage. Moreover, HMGB1 modulation of inflammatory signaling and tissue remodeling is now emerging as a causative factor in wound repair, autoimmune dysregulation, and skin carcinogenesis, representing cutaneous pathologies that affect large patient populations with unmet therapeutic needs. Recent structure-based drug discovery efforts have aimed at increasing the number of small molecule- and biologics-based prototype therapeutics targeting HMGB1. Small molecule drugs that may provide therapeutic benefit through HMGB1-directed mechanisms involve HMGB1 inhibitory ligands, Toll-like receptor antagonists, RAGE antagonists, alpha7 nicotinic acetylcholine receptor agonists, G2A antagonists, serine protease inhibitors, and alpha-dicarbonyl-based soft electrophiles. Using some of these agents, pharmacological modulation of HMGB1-associated cutaneous pathology has been achieved with an acceptable toxicity profile, and preclinical proof-of-concept experimentation has demonstrated feasibility of developing HMGB1-modulators into novel systemic and topical therapeutics that target cutaneous inflammatory dysregulation.<br><br>
Glo1 Overexpression In Human Malignant Melanoma. Source: Melanoma Research
March 12th, 2010 PMID: 20093988 Georg Wondrak
Glyoxalase I [lactoylglutathione lyase (EC encoded by GLO1] is a ubiquitous cellular defense enzyme involved in the detoxification of methylglyoxal, a cytotoxic byproduct of glycolysis. Accumulative evidence suggests an important role of GLO1 expression in protection against methylglyoxal-dependent protein adduction and cellular damage associated with diabetes, cancer, and chronological aging. On the basis of the hypothesis that GLO1 upregulation may play a functional role in glycolytic adaptations of cancer cells, we examined GLO1 expression status in human melanoma tissue. Quantitative reverse transcription polymerase chain reaction analysis of a cDNA tissue array containing 40 human melanoma tissues (stages III and IV) and 13 healthy controls revealed pronounced upregulation of GLO1 expression at the mRNA level. Immunohistochemical analysis of a melanoma tissue microarray confirmed upregulation of glyoxalase I protein levels in malignant melanoma tissue versus healthy human skin. Consistent with an essential role of GLO1 in melanoma cell defense against methylglyoxal cytotoxicity, siRNA interference targeting GLO1-expression (siGLO1) sensitized A375 and G361 human metastatic melanoma cells towards the antiproliferative, apoptogenic, and oxidative stress-inducing activity of exogenous methylglyoxal. Protein adduction by methylglyoxal was increased in siGLO1-transfected cells as revealed by immunodetection using a monoclonal antibody directed against the major methylglyoxal-derived epitope argpyrimidine that detected a single band of methylglyoxal-adducted protein in human LOX, G361, and A375 total cell lysates. Using two-dimensional proteomics followed by mass spectrometry the methylglyoxal-adducted protein was identified as heat shock protein 27 (Hsp27; HSPB1). Taken together, our data suggest a function of GLO1 in the regulation of detoxification and target adduction by the glycolytic byproduct methylglyoxal in malignant melanoma.<br><br>
Redox Directed Cancer Therapeutics: Molecular Mechanisms And Opportunities. Source: Antioxidants & Redox Signaling
November 5th, 2009 PMID: 19496700 Georg Wondrak
Redox dysregulation originating from metabolic alterations and dependence on mitogenic and survival signaling through reactive oxygen species represents a specific vulnerability of malignant cells that can be selectively targeted by redox chemotherapeutics. This review will present an update on drug discovery, target identification, and mechanisms of action of experimental redox chemotherapeutics with a focus on pro- and antioxidant redox modulators now in advanced phases of preclinal and clinical development. Recent research indicates that numerous oncogenes and tumor suppressor genes exert their functions in part through redox mechanisms amenable to pharmacological intervention by redox chemotherapeutics. The pleiotropic action of many redox chemotherapeutics that involves simultaneous modulation of multiple redox sensitive targets can overcome cancer cell drug resistance originating from redundancy of oncogenic signaling and rapid mutation.Moreover, some redox chemotherapeutics may function according to the concept of synthetic lethality (i.e., drug cytotoxicity is confined to cancer cells that display loss of function mutations in tumor suppressor genes or upregulation of oncogene expression). The impressive number of ongoing clinical trials that examine therapeutic performance of novel redox drugs in cancer patients demonstrates that redox chemotherapy has made the crucial transition from bench to bedside.<br><br>
The Topical Antimicrobial Zinc Pyrithione Is A Heat Shock Response Inducer That Causes Dna Damage And Parp Dependent Energy Crisis In Human Skin Cells. Source: Cell Stress & Chaperones
October 7th, 2009 PMID: 19809895 Georg Wondrak
The differentiated epidermis of human skin serves as an essential barrier against environmental insults from physical, chemical, and biological sources. Zinc pyrithione (ZnPT) is an FDA-approved microbicidal agent used worldwide in clinical antiseptic products, over-the-counter topical antimicrobials, and cosmetic consumer products including antidandruff shampoos. Here we demonstrate for the first time that cultured primary human skin keratinocytes and melanocytes display an exquisite vulnerability to nanomolar concentrations of ZnPT resulting in pronounced induction of heat shock response gene expression and impaired genomic integrity. In keratinocytes treated with nanomolar concentrations of ZnPT, expression array analysis revealed massive upregulation of genes encoding heat shock proteins (HSPA6, HSPA1A, HSPB5, HMOX1, HSPA1L, and DNAJA1) further confirmed by immunodetection. Moreover, ZnPT treatment induced rapid depletion of cellular ATP levels and formation of poly(ADP-ribose) polymers. Consistent with an involvement of poly(ADP-ribose) polymerase (PARP) in ZnPT-induced energy crisis, ATP depletion could be antagonized by pharmacological inhibition of PARP. This result was independently confirmed using PARP-1 knockout mouse embryonic fibroblasts that were resistant to ATP depletion and cytotoxicity resulting from ZnPT exposure. In keratinocytes and melanocytes, single-cell gel electrophoresis and flow cytometric detection of gamma-H2A.X revealed rapid induction of DNA damage in response to ZnPT detectable before general loss of cell viability occurred through caspase-independent pathways. Combined with earlier experimental evidence that documents penetration of ZnPT through mammalian skin, our findings raise the possibility that this topical antimicrobial may target and compromise keratinocytes and melanocytes in intact human skin.<br><br>
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