title: Specific in vitro binding of a new (99m)Tc-radiolabeled derivative of the C-terminal decapeptide of prothymosin alpha on human neutrophils.
abstract: Prothymosin alpha (ProTα) is a conserved mammalian polypeptide with intracellular functions associated with cell proliferation and apoptosis and an extracellular role associated with immunopotentiation. The N-terminal fragment [1-28], which is identical with the immunostimulating peptide thymosin α1 (Tα1), was earlier considered as the immunoactive region of the polypeptide; however, recent data suggest that ProTα may exert a discrete immunomodulating action through its central or C-terminal region, via targeting Toll-like receptor- 4 (TLR4). In this work, a derivative of the C-terminal fragment ProTα[100-109] (ProTα-D1) that can be radiolabeled with (99m)Tc was developed. The biological activity of the non-radioactive (185/187)rhenium-complex of this derivative ([(185/187)Re]ProTα-D1, structurally similar with [(99m)Tc]ProTα-D1) was verified through suitable in vitro bioassays on human neutrophils. Subsequent cell-binding studies revealed specific, time-dependent and saturable binding of [(99m)Tc]ProTα-D1 on neutrophils, which was inhibited by intact ProTα and ProTα[100-109], as well as by a "prototype" TLR4-ligand (lipopolysaccharide from Escherichia coli). Overall, our results support the existence of ProTα-binding sites on human neutrophils, recognizing [(99m)Tc]ProTα-D1, which might involve TLR4. [(99m)Tc]ProTα-D1 may be a useful tool for conducting further in vitro and in vivo studies, aiming to elucidate the extracellular mode of action of ProTα and, eventually, develop ProTα-based immunotherapeutics.
authors: Institute of Nuclear and Radiological Sciences & Technology, Energy and Safety (INRaSTES), National Center for Scientific Research "Demokritos", Athens 15310, Greece.
authors: Chrysoula-Evangelia
authors: CE
authors: Karachaliou
authors: Institute of Nuclear and Radiological Sciences & Technology, Energy and Safety (INRaSTES), National Center for Scientific Research "Demokritos", Athens 15310, Greece.
authors: Christos
authors: C
authors: Liolios
authors: Institute of Nuclear and Radiological Sciences & Technology, Energy and Safety (INRaSTES), National Center for Scientific Research "Demokritos", Athens 15310, Greece.
authors: Charalampos
authors: C
authors: Triantis
authors: Institute of Nuclear and Radiological Sciences & Technology, Energy and Safety (INRaSTES), National Center for Scientific Research "Demokritos", Athens 15310, Greece.
authors: Christos
authors: C
authors: Zikos
authors: Faculty of Biology, University of Athens, Athens 15784, Greece.
authors: Pinelopi
authors: P
authors: Samara
authors: Faculty of Biology, University of Athens, Athens 15784, Greece.
authors: Ourania E
authors: OE
authors: Tsitsilonis
authors: Interfaculty Institute of Biochemistry, University of Tuebingen, Tuebingen 72076, Germany.
authors: Hubert
authors: H
authors: Kalbacher
authors: Interfaculty Institute of Biochemistry, University of Tuebingen, Tuebingen 72076, Germany.
authors: Wolfgang
authors: W
authors: Voelter
authors: Institute of Nuclear and Radiological Sciences & Technology, Energy and Safety (INRaSTES), National Center for Scientific Research "Demokritos", Athens 15310, Greece.
authors: Minas
authors: M
authors: Papadopoulos
authors: Institute of Nuclear and Radiological Sciences & Technology, Energy and Safety (INRaSTES), National Center for Scientific Research "Demokritos", Athens 15310, Greece.
authors: Ioannis
authors: I
authors: Pirmettis
authors: Institute of Nuclear and Radiological Sciences & Technology, Energy and Safety (INRaSTES), National Center for Scientific Research "Demokritos", Athens 15310, Greece. Electronic address: livanlts@rrp.demokritos.gr.
authors: Evangelia
authors: E
authors: Livaniou
mesh_terms: D006801:Humans; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D011498:Protein Precursors / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D017556:Technetium Compounds; D013947:Thymosin / Q000031:analogs & derivatives* / Q000494:pharmacology; D051197:Toll-Like Receptor 4 / Q000378:metabolism
chemical_list: D011498:Protein Precursors; D017382:Reactive Oxygen Species; C495345:TLR4 protein, human; D017556:Technetium Compounds; D051197:Toll-Like Receptor 4; C040782:prothymosin alpha; D013947:Thymosin
keywords: (99m)Tc-radiolabeling; Cell-binding studies; Human neutrophils; Prothymosin alpha (ProTα); Synthetic ProTα-fragments