ADP-ribosyl transferase activity and gamma radiation cytotoxicity of Pseudomonas aeruginosa exotoxin A

Radwa N Morgan; Sarra E Saleh; Khaled M Aboshanab; Hala A Farrag

doi:10.1186/s13568-021-01332-3

ADP-ribosyl transferase activity and gamma radiation cytotoxicity of Pseudomonas aeruginosa exotoxin A

AMB Express. 2021 Dec 22;11(1):173. doi: 10.1186/s13568-021-01332-3.

Authors

Radwa N Morgan¹, Sarra E Saleh², Khaled M Aboshanab³, Hala A Farrag¹

Affiliations

¹ National Centre for Radiation Research and Technology (NCRRT), Drug Radiation Research Department, Egyptian Atomic Energy Authority (EAEA), Ahmed El-Zomor Street, Nasr city, Cairo, 11787, Egypt.
² Microbiology and Immunology Department, Faculty of Pharmacy, Ain Shams University, African union organization Street, Abbassia, Cairo, 11566, Egypt.
³ Microbiology and Immunology Department, Faculty of Pharmacy, Ain Shams University, African union organization Street, Abbassia, Cairo, 11566, Egypt. aboshanab2012@pharma.asu.edu.eg.

Abstract

This work explores the ADP-ribosyltransferase activity of Pseudomonas (P.) aeruginosa exotoxin A using the guanyl hydrazone derivative, nitrobenzylidine aminoguanidine (NBAG) and the impact of gamma radiation on its efficacy. Unlike the conventional detection methods, NBAG was used as the acceptor of ADP ribose moiety instead of wheat germ extract elongation factor 2. Exotoxin A was extracted from P. aeruginosa clinical isolates and screened for toxA gene using standard PCR. NBAG was synthesized using aminoguanidine bicarbonate and 4-nitrobenzaldehyde and its identity has been confirmed by UV, FTIR, Mass and ¹³C-NMR spectroscopy. The ADP-ribosyl transferase activity of exotoxin A on NBAG in the presence of Nicotinamide adenine dinucleotide (NAD⁺) was recorded using UV spectroscopy and HPLC. In vitro ADP-ribosyl transferase activity of exotoxin A protein extract was also explored by monitoring its cytotoxicity on Hep-2 cells using sulforhodamine B cytotoxicity assay. Bacterial broths were irradiated at 5, 10, 15, 24 Gy and exotoxin A protein extract activity were assessed post exposure. Exotoxin A extract exerted an ADP-ribosyltransferase ability which was depicted by the appearance of a new ʎmax after the addition of exotoxin A to NBAG/NAD⁺ mixture, fragmentation of NAD⁺ and development of new peaks in HPLC chromatograms. Intracellular enzyme activity was confirmed by the prominent cytotoxic effects of exotoxin A extract on cultured cells. In conclusion, the activity of Exotoxin A can be monitored via its ADP-ribosyltransferase activity and low doses of gamma radiation reduced its activity. Therefore, coupling radiotherapy with exotoxin A in cancer therapy should be carefully monitored.

Keywords: ADP ribosyl transferase activity; Cytotoxicity; Exotoxin A; Gamma radiation; HPLC; NBAG.