Faculty Collaboration Database

Hydropropidine: a novel, cell-impermeant fluorogenic probe for detecting extracellular superoxide. Free Radic Biol Med 2013 Jan;54:135-47

Date

10/12/2012

Pubmed ID

23051008

Pubmed Central ID

PMC3711142

DOI

10.1016/j.freeradbiomed.2012.09.018

Scopus ID

2-s2.0-84871920872 (requires institutional sign-in at Scopus site)   45 Citations

Abstract

Here we report the synthesis and characterization of a membrane-impermeant fluorogenic probe, hydropropidine (HPr(+)), the reduction product of propidium iodide, for detecting extracellular superoxide (O(2)(•-)). HPr(+) is a positively charged water-soluble analog of hydroethidine (HE), a fluorogenic probe commonly used for monitoring intracellular O(2)(•-). We hypothesized that the presence of a highly localized positive charge on the nitrogen atom would impede cellular uptake of HPr(+) and allow for exclusive detection of extracellular O(2)(•-). Our results indicate that O(2)(•-) reacts with HPr(+) (k=1.2×10(4) M(-1) s(-1)) to form exclusively 2-hydroxypropidium (2-OH-Pr(2+)) in cell-free and cell-based systems. This reaction is analogous to the reaction between HE and O(2)(•-) (Zhao et al., Free Radic. Biol. Med.34:1359-1368; 2003). During the course of this investigation, we also reassessed the rate constants for the reactions of O(2)(•-) with HE and its mitochondria targeted analog (Mito-HE or MitoSOX Red) and addressed the discrepancies between the present values and those reported previously by us. Our results indicate that the rate constant between O(2)(•-) and HPr(+) is slightly higher than that of HE and O(2)(•-) and is closer to that of Mito-HE and O(2)(•-). Similar to HE, HPr(+) undergoes oxidation in the presence of various oxidants (peroxynitrite-derived radicals, Fenton's reagent, and ferricytochrome c) forming the corresponding propidium dication (Pr(2+)) and the dimeric products (e.g., Pr(2+)-Pr(2+)). In contrast to HE, there was very little intracellular uptake of HPr(+). We conclude that HPr(+) is a useful probe for detecting O(2)(•-) and other one-electron oxidizing species in an extracellular milieu.

Author List

Michalski R, Zielonka J, Hardy M, Joseph J, Kalyanaraman B

Authors

Micael Joel Hardy PhD Visiting Assistant Professor in the Biophysics department at Medical College of Wisconsin
Balaraman Kalyanaraman PhD Professor in the Biophysics department at Medical College of Wisconsin
Jacek M. Zielonka PhD Assistant Professor in the Biophysics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Biological Transport, Active
Cell Line
Chromatography, High Pressure Liquid
Extracellular Space
Fluorescent Dyes
Mass Spectrometry
Mice
Oxidants
Oxidation-Reduction
Phenanthridines
Propidium
Quaternary Ammonium Compounds
Solubility
Superoxides