Design, synthesis and properties of novel powerful antioxidants, glutathione analogues

Abstract

Glutathione (GSH) is the major low-molecular weight antioxidant in mammalian cells. Thus, its analogues carrying similar and/or additional positive properties might have clinical perspectives. Here, we report the design and synthesis of a library of tetrapeptidic GSH analogues called UPF peptides. Compared to cellular GSH our designed peptidic analogues showed remarkably higher hydroxyl radical scavenging ability (EC(50) of GSH: 1,231.0 +/- 311.8 microM; EC(50) of UPF peptides: from 0.03 to 35 microM) and improved antiradical efficiency towards a stable alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radical. The best of UPF peptides was 370-fold effective hydroxyl radical scavengers than melatonin (EC(50): 11.4 +/- 1.0 microM). We also found that UPF peptides do not influence the viability and membrane integrity of K562 human erythroleukemia cells even at 200 microM concentration. Dimerization of GSH and UPF peptides was compared in water and in 0.9% saline solutions. The results, together with an earlier finding that UPF1 showed protective effects in global cerebral ischemia model in rats, suggest that UPF peptides might serve both as potent antioxidants as well as leads for design of powerful non-peptidic antioxidants that correct oxidative stress-driven events.

Maintenance of glutathione levels and its importance in epigenetic regulation

“…Both compounds are linked to each other by using a covalent bond that is cleavable which regenerates the original drug with adequate bioavailability. Investigations in this type of compounds have already been reported (Ehrlich et al, 2007). In addition, as we have described, oxidative stress produces methionine sulfoxide, which is epigenetically toxic.…”

Characterization of UPF peptides, members of the glutathione analogues library, on the basis of their effects on oxidative stress-related enzymes

“…The enzyme free hydroxyl radical scavenging assay showed that substitution of g-glutamyl moiety (UPF1) with a-glutamyl moiety (UPF17) improved hydroxyl radical scavenging activity  500-fold [25].…”

“…A more detailed synthesis protocol of UPF peptides has been published before [25,28]. The purity of the peptides was !99%, as demonstrated by HPLC on an analytical Nucleosil 120-3 C18 reversed-phase column (0.4 cm)10 cm).…”

“…This modification in UPF17 sequence drastically decreased EC 50 values of hydroxyl radical elimination compared to UPF1 by Â500-times. Despite this, neither UPF1 nor UPF17 showed any toxic effects on the viability of K562 human erythroleucemia cells at concentrations of 200 mM after 24 h incubation [25]. UPF1 has already been investigated in different in vivo experimental models in rats: global brain ischemia, Langendorff model with isolated heart and was shown to possess protective effects [26,27].…”

“…We demonstrated that all members of the UPF library showed remarkably better hydroxyl radical scavenging properties than glutathione itself [25]. For the current study, we chose a pair of UPF peptides, structural analogues: UPF1 (4-methoxy-L-tyrosinyl-g-L-glutamyl-L-cysteinyl-glycine) and UPF17 (4-methoxy-L-tyrosinyl-a-L-glutamyl-L-cysteinyl-glycine).…”