Triphenylphosphonium Moiety Modulates Proteolytic Stability and Potentiates Neuroprotective Activity of Antioxidant Tetrapeptides in Vitro.

Rezeda A Akhmadishina,Natalia V Petrova,Marat I Kamalov,Ruslan Garifullin,Timur I Abdullin

doi:10.3389/fphar.2018.00115

Rezeda A Akhmadishina, Natalia V Petrova + Show 3 more

Open Access

https://doi.org/10.3389/fphar.2018.00115

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Abstract

Although delocalized lipophilic cations have been identified as effective cellular and mitochondrial carriers for a range of natural and synthetic drug molecules, little is known about their effects on pharmacological properties of peptides. The effect of triphenylphosphonium (TPP) cation on bioactivity of antioxidant tetrapeptides based on the model opioid YRFK motif was studied. Two tetrapeptide variants with L-arginine (YRFK) and D-arginine (YrFK) were synthesized and coupled with carboxyethyl-TPP (TPP-3) and carboxypentyl-TPP (TPP-6) units. The TPP moiety noticeably promoted YRFK cleavage by trypsin, but effectively prevented digestion of more resistant YrFK attributed, respectively, to structure-organizing and shielding effects of the TPP cation on conformational variants of the tetrapeptide motif. The TPP moiety enhanced radical scavenging activity of the modified YRFK in a model Fenton-like reaction, whereas decreased reactivity was revealed for both YrFK and its TPP derivative. The starting motifs and modified oligopeptides, especially the TPP-6 derivatives, suppressed acute oxidative stress in neuronal PC-12 cells during a brief exposure similarly with glutathione. The effect of oligopeptides was compared upon culturing of PC-12 cells with CoCl2, L-glutamic acid, or menadione to mimic physiologically relevant oxidative states. The cytoprotective activity of oligopeptides significantly depended on the type of oxidative factor, order of treatment and peptide structure. Pronounced cell-protective effect was established for the TPP-modified oligopeptides, which surpassed that of the unmodified motifs. The protease-resistant TPP-modified YrFK showed the highest activity when administered 24 h prior to the cell damage. Our results suggest that the TPP cation can be used as a modifier for small therapeutic peptides to improve their pharmacokinetic and pharmacological properties.

Highlights

Bioactive peptides are a diverse class of biomolecules with multiple functions in living organisms and great therapeutic potential
The TPP-modified oligopeptides were produced by extending the YRFK motifs with 2-carboxyethyl TPP (TPP-3) or 5-carboxypentyl TPP (TPP-6) units at the N-terminus during the synthesis (Figure 1)
According to dynamic light scattering technique, TPP-6-YRFK-NH2 and TPP-6-YrFK-NH2 formed well-defined submicron aggregates suggesting that the TPP-6 group imparted aggregative properties to the modified oligopeptides

Summary

Introduction

Bioactive peptides are a diverse class of biomolecules with multiple functions in living organisms and great therapeutic potential. Bioactive oligopeptides are being discovered among different biological species, tissues and protein resources Their specific functions encompass at least neuro- and immunoregulatory, regenerative, anticoagulant, antihypertensive, anti-inflammatory, antioxidant, antimicrobial and anticancer activities [see reviews (Guiotto et al, 2005; Anisimov and Khavinson, 2010; Kim and Wijesekara, 2010; Sah et al, 2015; Yoshikawa, 2015)]. The prooxidant activity of TPP-6-YRFK-NH2 was further decreased, and the inhibitory effect of oligopeptide toward the reaction was observed at concentrations > 250 μM (Figure 3B, 3). Attachment of the TPP-6 moiety to YrFK-NH2 almost did not alter its concentration effect on ROS generation (Figure 3B, 5), in great contrast to YRFK-NH2, suggesting that the ability of TPP-6 group to modulate antioxidant properties of the oligopeptides depends on the conformation of peptide component.

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