An efficient two-photon fluorescent probe for measuring γ-glutamyltranspeptidase activity during the oxidative stress process in tumor cells and tissues

Abstract

Oxidative stress, a disturbance in the balance between oxidant/antioxidant ratios, is associated with cancer, aging, inflammation, neurodegenerative diseases and other conditions. γ-Glutamyltranspeptidase (GGT) is a redox-related enzyme that plays a key role in mitigating the effects of oxidative stress by maintaining cellular glutathione (GSH) metabolism and homeostasis. Therefore, oxidative stress will upregulate the intracellular GGT level. To better understand the major pathophysiological resist mechanism to oxidative injury in mediating many disease states, we designed and synthesized a novel two-photon (TP) fluorescent turn-on probe, Np-Glu, for GGT detection and bioimaging. Under the optimized conditions, Np-Glu exhibited remarkable fluorescence enhancement (150-fold), good selectivity and high sensitivity (LOD is 0.033 U L), with a wide linear concentration range (0-50 U L). More importantly, the probe Np-Glu was successfully applied in one-photon and TP fluorescence imaging of GGT activity in an oxidative stress model in living cells and tissues, suggesting Np-Glu as an ideal indicator for clinical and biological samples.

The mercapturic acid pathway

“…Examples of three classes of imaging probes, most of which are c-Glu amides that are activated by GGT, have been reported: (1) probes that release a fluorescent product or precursor (Iwatate et al 2018;Li et al 2018;Ou-Yang et al 2018;Liu et al 2018a;Luo et al 2018b); (2) probes that release a ratiometric fluorescent product (Liu et al 2018b); and (3) probes that release bioluminescent products (Hai et al 2017). GGTactivated fluorescent probes for imaging intracellular GGT that are suitable for one-photon confocal microscopy have been described but technical issues limit their applicability (Wang et al 2017b, and references cited therein). N 5 -(6- (Benzo[d]thiazol-2-yl)naphthalen-2-yl)glutamine (215, Figure 19), which is biotransformed by GGT to 2-aminonaphthalene 216 (Figure 19), has been developed as a probe suitable for two-photon microscopy (Wang et al 2017b).…”

“…GGTactivated fluorescent probes for imaging intracellular GGT that are suitable for one-photon confocal microscopy have been described but technical issues limit their applicability (Wang et al 2017b, and references cited therein). N 5 -(6- (Benzo[d]thiazol-2-yl)naphthalen-2-yl)glutamine (215, Figure 19), which is biotransformed by GGT to 2-aminonaphthalene 216 (Figure 19), has been developed as a probe suitable for two-photon microscopy (Wang et al 2017b). c-N-Substituted Gln 215 (Figure 19) was successfully used to image GGT in HepG2 cells, in normal rat liver slices, and in mouse liver cancer tissue slices.…”

Recent Advances in the Development of Optical Imaging Probes for γ‐Glutamyltranspeptidase

“…Lately,W ang et al employed an aphthalene derivative with al arge TPAc ross-section and high fluorescenceq uantum yield to design another GGT-activatable two-photon fluorescence imagingp robe (16), which was able to measure the GGT activity in living tumor cells undergoing oxidative stress. [34] In addition, at wo-photon fluorescencei maging probe (17)c apable of targetingc ancerc ells through GGT-activation and real-time imaging of DNA damage in cancer cells through sequential reactionw ith N-acetyltransferase (NAT) was also reported by Zhang et al [35] Although these two-photon fluorescence imaging probes showed good ability to detect GGT activityi nl iving cells and zebrafish larva, the fluorescencee mission at visible wavelengths still suffered from limited penetration depth rela-tive to the NIR fluorescencep robe (e.g.,p robes 13 and 14). Their applicationf or the noninvasive detection of GGT activity in living large animals(e.g.,mice) was still challenging.…”

“…Lately, Wang et al. employed a naphthalene derivative with a large TPA cross‐section and high fluorescence quantum yield to design another GGT‐activatable two‐photon fluorescence imaging probe ( 16 ), which was able to measure the GGT activity in living tumor cells undergoing oxidative stress . In addition, a two‐photon fluorescence imaging probe ( 17 ) capable of targeting cancer cells through GGT‐activation and real‐time imaging of DNA damage in cancer cells through sequential reaction with N ‐acetyltransferase (NAT) was also reported by Zhang et al .…”

Lighting-Up Tumor for Assisting Resection via Spraying NIR Fluorescent Probe of γ-Glutamyltranspeptidas

“…γ-glutamyltranspeptidase (γ-GGT; EC 2.3.2.2), an over-expression enzyme associated with the growth and progression of ovarian, liver, colon and breast cancer compared to normal tissue (De Young et al, 1978 ; Shinozuka et al, 1979 ; Rao et al, 1986 ), plays important roles in many physiological and pathological processes (Pompella et al, 2006 ; Strasak et al, 2010 ), which is regarded as an important target for analysis and imaging in vitro or in vivo (Li et al, 2015b , 2016c ; Wang et al, 2015 , 2017b ; Park et al, 2016a , b ; Zhang et al, 2016a , b ; Liu et al, 2018 ). However, rarely related fluorescent probe could be qualified for the identification tumor by tracking the activity of γ-GGT enzyme in vivo (Urano et al, 2011 ), especially for NIR emission property, possessing good performances of avoiding auto-fluorescence and deeper tissue penetration (Gu et al, 2016a ).…”