8-Methoxypsoralen is a competitive inhibitor of glutathione S-transferase P1-1

Antifungal azoles trigger a xenobiotic detoxification pathway and chitin synthesis in Neurospora crassa

The presence of antifungal drugs is prompting the fungal microorganisms to react by mechanisms broader than the resistance. The fungi evolved mechanisms, by which they respond to various stress conditions, including the presence of antifungal compounds. In this work, we studied the response of model filamentous fungus Neurospora crassa to azole antifungals in the broader context of the adaptation mechanisms. We demonstrated the increase in expression of filamentous fungi-specific genes encoding cytochrome enzymes of CYP65 clan and plasma membrane-localized ABCC transporters. Azoles appear not to conjugate with glutathione. Surprisingly, the azoles caused changes in the hyphae organization and the amount of chitin in cell wall by the same manner that was thought to be echinocandin-specific. The response to individual azoles appeared to be influenced by the structure of azole compound (prochloraz - main outlier). Taken together, these findings demonstrate the importance of study of stress response mechanisms, specifically in filamentous fungi. Many aspects of the reaction within azoles seem to be similar, though specificities are occurring.

Xanthotoxin (8-methoxypsoralen): A review of its chemistry, pharmacology, pharmacokinetics, and toxicity

Xanthotoxin (XAT) is a natural furanocoumarins, a bioactive psoralen isolated from the fruit of the Rutaceae plant Pepper, which has received increasing attention in recent years due to its wide source and low cost. By collecting and compiling literature on XAT, the results show that XAT exhibits significant activity in the treatment of various diseases, including neuroprotection, skin repair, osteoprotection, organ protection, anticancer, antiinflammatory, antioxidative stress and antibacterial. In this paper, we review the pharmacological activity and potential molecular mechanisms of XAT for the treatment of related diseases. The data suggest that XAT can mechanistically induce ROS production and promote apoptosis through mitochondrial or endoplasmic reticulum pathways, regulate NF-κB, MAPK, JAK/STAT, Nrf2/HO-1, MAPK, AKT/mTOR, and ERK1/2 signaling pathways to exert pharmacological effects. In addition, the pharmacokinetics properties and toxicity of XAT are discussed in this paper, further elucidating the relationship between structure and efficacy. It is worth noting that data from clinical studies of XAT are still scarce, limiting the use of XAT in the clinic, and in the future, more in-depth studies are needed to determine the clinical efficacy of XAT.

The mercapturic acid pathway

The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.

Design, synthesis and cytotoxicity of the antitumor agent 1-azabicycles for chemoresistant glioblastoma cells

Twelve multi-functional pyrrolizidinones, indolizidinones and pyrroliazepinones were prepared from formal aza-[3 + 2] and aza-[3 + 3] cycloadditions of five- to seven-membered heterocyclic enaminones as diverse ambident electrophiles. The antitumor activity of these alkaloid-like compounds was investigated through an initial screening performed on human glioblastoma multiform (GBM) cell lines (GL-15, U251), on murine glioma cells line (C6) and on normal glial cells. Of the compounds tested, the new pyrrolo[1,2a]azepinone, [ethyl (3-oxo-1,2-diphenyl-6,7,8,9-tetrahydro-3H-pyrrolo[1,2a]azepin-9a(5H)-yl)acetate] or (Compound-13) exhibited selective cytotoxic effects on GBM-temozolomide resistant cells. Compound-13 exerted dose-dependent cytotoxic activity by promoting arrest of cells in the G0/G1 phase of the cell cycle in the first 24 h. The apoptotic effect observed was in a time-dependent manner. Anti-migratory effect promoted by the treatment with compound-13 was also observed. Moreover, healthy mixed glial cell cultures from rat brain exhibited no cytotoxicity effect upon exposure to compound-13. Thus, the present study paves the way for the use of compound-13 as novel antitumor scaffold candidate for glioma cell therapy.

A tyrosine-reactive irreversible inhibitor for glutathione S-transferase Pi (GSTP1)

Glutathione S-transferase Pi (GSTP1) mediates cellular defense against reactive electrophiles. Here, we report LAS17, a dichlorotriazine-containing compound that irreversibly inhibits GSTP1 and is selective for GSTP1 within cellular proteomes. Mass spectrometry and mutational studies identified Y108 as the site of modification, providing a unique mode of GSTP1 inhibition.

Role of Glutathione-S-transferases in neurological problems

INTRODUCTION

Role of Glutathione-S-transferases (GSTs) has been well explored in the cellular detoxification process, regulation of redox homeostasis and S-glutothionylation of target proteins like JNK, ASK1 etc. However, altered levels or functions of this enzyme or their subtypes have emerged in the development of several pathologies diseases such as Alzheimer's disease, Parkinson's disease, cancer and related conditions. Oxidative stress is one of the possible pathological events that contributes significantly to activation of degenerating cascades inside neuronal cells. The central nervous system is highly sensitive to oxidative stress because of low levels or capacities of antioxidant enzymes. The brain is highly metabolic in nature making it susceptible to oxidative stress. Areas covered: The present review provides a comprehensive overview of the multiple connections of GSTs within diverse neurological diseases including cancer. Furthermore, the authors have made significant efforts to discuss the regulation of different GST isoforms that have been associated with various pathological processes such as glioblastoma, Alzheimer's disease, Parkinson's disease, stroke and epilepsy. Expert opinion: Though GSTs have been one of the key areas of scientific research over the last few decades, much remains to be elucidated about their physiological functions as well as pathological involvement of GSTs and their polymorphic variants.

p53 Loss in MYC-Driven Neuroblastoma Leads to Metabolic Adaptations Supporting Radioresistance

Neuroblastoma is the most common childhood extracranial solid tumor. In high-risk cases, many of which are characterized by amplification of MYCN, outcome remains poor. Mutations in the p53 (TP53) tumor suppressor are rare at diagnosis, but evidence suggests that p53 function is often impaired in relapsed, treatment-resistant disease. To address the role of p53 loss of function in the development and pathogenesis of high-risk neuroblastoma, we generated a MYCN-driven genetically engineered mouse model in which the tamoxifen-inducible p53ER(TAM) fusion protein was expressed from a knock-in allele (Th-MYCN/Trp53(KI)). We observed no significant differences in tumor-free survival between Th-MYCN mice heterozygous for Trp53(KI) (n = 188) and Th-MYCN mice with wild-type p53 (n = 101). Conversely, the survival of Th-MYCN/Trp53(KI/KI) mice lacking functional p53 (n = 60) was greatly reduced. We found that Th-MYCN/Trp53(KI/KI) tumors were resistant to ionizing radiation (IR), as expected. However, restoration of functional p53ER(TAM) reinstated sensitivity to IR in only 50% of Th-MYCN/Trp53(KI/KI) tumors, indicating the acquisition of additional resistance mechanisms. Gene expression and metabolic analyses indicated that the principal acquired mechanism of resistance to IR in the absence of functional p53 was metabolic adaptation in response to chronic oxidative stress. Tumors exhibited increased antioxidant metabolites and upregulation of glutathione S-transferase pathway genes, including Gstp1 and Gstz1, which are associated with poor outcome in human neuroblastoma. Accordingly, glutathione depletion by buthionine sulfoximine together with restoration of p53 activity resensitized tumors to IR. Our findings highlight the complex pathways operating in relapsed neuroblastomas and the need for combination therapies that target the diverse resistance mechanisms at play. Cancer Res; 76(10); 3025-35. ©2016 AACR.