Modulation Of GSH Levels Research Articles

PRIMA-1MET-induced neuroblastoma cell death is modulated by p53 and mycn through glutathione level

BackgroundNeuroblastoma is the most common extracranial solid tumor in children. This cancer has a low frequency of TP53 mutations and its downstream pathway is usually intact. This study assessed the efficacy of the p53 activator, PRIMA-1MET, in inducing neuroblastoma cell death.MethodsCellTiter 2.0 was used to study susceptibility and specificity of NB cell lines to PRIMA-1MET. Real-time PCR and western blot were used to assess the most common p53 transactivation targets. Induction of p53 and Noxa, and inhibition of Cas3/7, were used to assess impact on cell death after PRIMA-1MET treatment. Flow cytometry was used to analyze cell cycle phase and induction of apoptosis, reactive oxygen species, and the collapse of mitochondrial membrane potential.ResultsNeuroblastoma cell lines were at least four times more susceptible to PRIMA-1MET than were primary fibroblasts and keratinocyte cell lines. PRIMA-1MET induced cell death rapidly and in all cell cycle phases. Although PRIMA-1MET activated p53 transactivation activity, p53’s role is likely limited because its main targets remained unaffected, whereas pan-caspase inhibitor demonstrated no ability to prevent cell death. PRIMA-1MET induced oxidative stress and modulated the methionine/cysteine/glutathione axis. Variations of MYCN and p53 modulated intracellular levels of GSH and resulted in increased/decreased sensitivity of PRIMA-1MET. PRIMA-1MET inhibited thioredoxin reductase, but the effect of PRIMA-1MET was not altered by thioredoxin inhibition.ConclusionsPRIMA-1MET could be a promising new agent to treat neuroblastoma because it demonstrated good anti-tumor action. Although p53 is involved in PRIMA-1MET-mediated cell death, our results suggest that direct interaction with p53 has a limited role in neuroblastoma but rather acts through modulation of GSH levels.

Harnessing drug resistance: Using ABC transporter proteins to target cancer cells

The ATP-binding cassette (ABC) class of proteins is one of the most functionally diverse transporter families found in biological systems. Although the abundance of ABC proteins varies between species, they are highly conserved in sequence and often demonstrate similar functions across prokaryotic and eukaryotic organisms. Beginning with a brief summary of the events leading to our present day knowledge of ABC transporters, the purpose of this review is to discuss the potential for utilizing ABC transporters as a means for cellular glutathione (GSH) modulation. GSH is one of the most abundant thiol antioxidants in cells. It is involved in cellular division, protein and DNA synthesis, maintenance of cellular redox status and xenobiotic metabolism. Cellular GSH levels are often altered in many disease states including cancer. Over the past two decades there has been considerable emphasis on methods to sensitize cancer cells to chemotherapeutics and radiation therapy by GSH depletion. We contend that ABC transporters, particularly multi-drug resistant proteins (MRPs), may be used as therapeutic targets for applications aimed at modulation of GSH levels. This review will emphasize MRP-mediated modulation of intracellular GSH levels as a potential alternative and adjunctive approach for cancer therapy.

Modulation of GSH levels in ABCC1 expressing tumor cells triggers apoptosis through oxidative stress

The over-expression of ABCC1 transmembrane protein has been shown to cause multidrug resistance in tumor cell lines. ABCC1 is a member of the ABC transmembrane proteins that function as efflux pumps with diverse substrate specificity. Several endogenous cell metabolites, including the leukotriene C4 (LTC 4) and glutathione (GSH) are substrates for ABCC1 protein. ABCC1 expression in certain tumor cells was demonstrated to confer hypersensitivity to glutathione modulating agents. In this report we have investigated the mechanism of collateral sensitivity seen in tumor cells over-expressing ABCC1 protein. The results of this study show that ABCC1 expression in tumor cells correlates with their hypersensitivity to various glutathione modulating agents, as demonstrated in H69AR-drug selected and HeLa/ABCC1-transfectant cells. This effect was triggered either through inhibition of GSH synthesis with BSO or by increasing ABCC1-mediated GSH transport with verapamil or apigenin. In addition, our results show that the hypersensitivity of ABCC1-expressing cells to BSO, verapamil or apigenin was preceded by an increase in reactive oxygen species (or ROS). A decrease in GSH level is also observed prior the increase in ROS. In addition, we show that hypersensitivity to the BSO, verapamil or apigenin leads to tumor cell death by apoptosis. Together, the results of this study demonstrate that ABCC1 potentiates oxidative stress in tumor cells through reductions in cellular GSH levels.

Elimination of Ehrlich tumours by ATP-induced growth inhibition, glutathione depletion and X-rays

ATP-induced tumour growth inhibition is accompanied by a selective decrease in the content of the tripeptide glutathione (GSH) within the cancer cells in vivo. Depletion of cellular GSH sensitizes tumours to chemotherapy and radiation, but the usefulness of this depletion depends on whether the levels of GSH can be reduced in the tumour relative to normal tissues. We report here that administration of ATP in combination with diethylmaleate and X-rays leads to complete regression of 95% of Ehrlich ascites tumours in mice. This shows that an aggressive tumour can be eliminated by using a therapy based on modulation of GSH levels in cancer cells.

Importance of glutathione in the acquisition and maintenance of sperm nuclear decondensing activity in maturing hamster oocytes

Sperm nuclear decondensing activity in mammalian oocytes is dependent upon the maturational state of the oocyte. It is maximal in mature, metaphase II oocytes and minimal or absent in immature germinal vesicle (GV) and fertilized pronuclear oocytes. Previous studies suggested that this difference may be due to the relative ability of an oocyte to reduce the protamine disulfide bonds in the sperm nucleus. The results of this study show that mature hamster oocytes contain significantly more glutathione (GSH), about 8 m M, and hence more disulfide reducing power, as compared with GV (4 m M) or pronuclear (6 m M) oocytes. Furthermore, the acquisition of sperm nuclear decondensing activity by maturing oocytes can be prevented or delayed by blocking GSH synthesis with l-buthionine- S,R-sulfoximine during the early stages of oocyte maturation. This is the first evidence that modulation of GSH levels during oocyte maturation and fertilization may be a mechanism by which sperm nuclear decondensing activity is regulated.