2-deoxyribose deprives cultured astrocytes of their glutathione

Structural-Functional Pluralistic Modification of Silk Fibroin via MOF Bridging for Advanced Wound Care

Silk fibroin (SF) is widely used to fabricate biomaterials for skin related wound caring or monitoring, and its hydrogel state are preferred for their adaptability and easy to use. However, in-depth development of SF hydrogel is restricted by their limited mechanical strength, increased risk of infection, and inability to accelerate tissue healing. Therefore, a structure-function pluralistic modification strategy using composite system of metal organic framework (MOF) as bridge expanding SF's biomedical application is proposed. After developing the photocuring and bonding SF hydrogel, a MOF drug-loading system is utilized to enhance hydrogel's structural strength while endowing its antibacterial and angiogenic properties, yielding a multifunctional SF hydrogel. The synergy between the MOF and SF proteins at the secondary structure level gives this hydrogel reliable mechanical strength, making it suitable for conventional wound treatment, whether for closing incisions quickly or acting as adhesive dressings (five times the bonding strength of ordinary fibrin glue). Additionally, with the antibacterial and angiogenic functions getting from MOF system, this modified SF hydrogel can even treat ischemic trauma with cartilage exposure. This multiple modification should contribute to the improvement of advanced wound care, by promoting SF application in the production of tissue engineering materials.

Familial Alzheimer's Disease Lymphocytes Respond Differently Than Sporadic Cells to Oxidative Stress: Upregulated p53-p21 Signaling Linked with Presenilin 1 Mutants

Familial (FAD) and sporadic (SAD) Alzheimer's disease do not share all pathomechanisms, but knowledge on their molecular differences is limited. We previously reported that cell cycle control distinguishes lymphocytes from SAD and FAD patients. Significant differences were found in p21 levels of SAD compared to FAD lymphocytes. Since p21 can also regulate apoptosis, the aim of this study was to compare the response of FAD and SAD lymphocytes to oxidative stress like 2-deoxy-D-ribose (2dRib) treatment and to investigate the role of p21 levels in this response. We report that FAD cells bearing seven different PS1 mutations are more resistant to 2dRib-induced cell death than control or SAD cells: FAD cells showed a lower apoptosis rate and a lower depolarization of the mitochondrial membrane. Despite that basal p21 cellular content was lower in FAD than in SAD cells, in response to 2dRib, p21 mRNA and protein levels significantly increased in FAD cells. Moreover, we found a higher cytosolic accumulation of p21 in FAD cells. The transcriptional activation of p21 was shown to be dependent on p53, as it can be blocked by PFT-α, and correlated with the increased phosphorylation of p53 at Serine 15. Our results suggest that in FAD lymphocytes, the p53-mediated increase in p21 transcription, together with a shift in the nucleocytoplasmic localization of p21, confers a survival advantage against 2dRib-induced apoptosis. This compensatory mechanism is absent in SAD cells. Thus, therapeutic and diagnostic designs should take into account possible differential apoptotic responses in SAD versus FAD cells.

Glutathione-Dependent Detoxification Processes in Astrocytes

Astrocytes have a pivotal role in brain as partners of neurons in homeostatic and metabolic processes. Astrocytes also protect other types of brain cells against the toxicity of reactive oxygen species and are considered as first line of defence against the toxic potential of xenobiotics. A key component in many of the astrocytic detoxification processes is the tripeptide glutathione (GSH) which serves as electron donor in the GSH peroxidase-catalyzed reduction of peroxides. In addition, GSH is substrate in the detoxification of xenobiotics and endogenous compounds by GSH-S-transferases which generate GSH conjugates that are efficiently exported from the cells by multidrug resistance proteins. Moreover, GSH reacts with the reactive endogenous carbonyls methylglyoxal and formaldehyde to intermediates which are substrates of detoxifying enzymes. In this article we will review the current knowledge on the GSH metabolism of astrocytes with a special emphasis on GSH-dependent detoxification processes.

Glycation of glutamate cysteine ligase by 2-deoxy-d-ribose and its potential impact on chemoresistance in glioblastoma

The antioxidant glutathione (GSH) plays a critical role in maintaining intracellular redox homeostasis but in tumors the GSH biosynthetic pathway is often dysregulated, contributing to tumor resistance to radiation and chemotherapy. Glutamate-cysteine ligase (GCL) catalyzes the first and rate-limiting reaction in GSH synthesis, and enzyme function is controlled by GSH feedback inhibition or by transcriptional upregulation of the catalytic (GCLC) and modifier (GCLM) subunits. However, it has recently been reported that the activity of GCLC and the formation of GCL can be modified by reactive aldehyde products derived from lipid peroxidation. Due to the susceptibility of GCLC to posttranslational modifications by reactive aldehydes, we examined the potential for 2-deoxy-D-ribose (2dDR) to glycate GCLC and regulate enzyme activity and GCL formation. 2dDR was found to directly modify both GCLC and GCLM in vitro, resulting in a significant inhibition of GCLC and GCL enzyme activity without altering substrate affinity or feedback inhibition. 2dDR-mediated glycation also inhibited GCL subunit heterodimerization and formation of the GCL holoenzyme complex while not causing dissociation of pre-formed holoenzyme. This PTM could be of particular importance in glioblastoma (GBM) where intratumoral necrosis provides an abundance of thymidine, which can be metabolized by thymidine phosphorylase (TP) to form 2dDR. TP is expressed at high levels in human GBM tumors and shRNA knockdown of TP in U87 GBM cells results in a significant increase in cellular GCL enzymatic activity.

Gliclazide does not fully prevent 2-deoxy-D-ribose-induced oxidative damage because it does not restore glutathione content in a pancreatic β-cell line

We compared the effects of gliclazide, an antidiabetic agent with antioxidant properties, and N-acetyl-L-cysteine (NAC), a glutathione precursor, in protecting against 2-deoxy-D-ribose- (dRib-) induced oxidative damage in HIT-T15 cells. Using trypan blue staining and flow cytometry with annexin V/PI staining, gliclazide treatment slightly reversed dRib-induced cell death and apoptosis, and NAC treatment markedly reduced both measures. Likewise, flow cytometry using DHR 123 staining showed that the levels of dRib-induced reactive oxygen species (ROS) were partially suppressed by gliclazide and completely inhibited by NAC. Using electron spin resonance spectrometry, gliclazide and NAC scavenged hydroxyl radicals generated by Fenton reaction to a similar degree in a cell-free system. NAC, but not gliclazide, completely restored the intracellular glutathione depleted by dRib using monochlorobimane fluorescence and glutathione assays. Thus, gliclazide treatment suppressed dRib-induced oxidative damage in HIT-T15 cells less than NAC did because gliclazide did not restore the intracellular glutathione content as effectively as NAC. In addition, the elevation of intracellular glutathione rather than free radical scavenging might be an important mechanism for protecting against dRib-induced oxidative damage in a β-cell line.