Discovery of endogenous nitroxyl as a new redox player in Arabidopsis thaliana

Abstract

Nitroxyl (HNO) is the one-electron reduced and protonated congener of nitric oxide (•NO), owning a distinct chemical profile. Based on real-time detection, we demonstrate that HNO is endogenously formed in Arabidopsis. Senescence and hypoxia induce shifts in the redox balance, triggering HNO decay or formation mediated by non-enzymatic •NO/HNO interconversion with cellular reductants. The stimuli-dependent HNO generation supports or competes with •NO signalling, depending on the local redox environment.

Versatile Metalloporphyrin‐Based Electrochemical Sensing Applications: From Small Gasotransmitters to Macromolecules

“…In this context, the corresponding author of this review developed an electrochemical azanone (HNO) sensor based on the covalent bonding of cobalt(III) meso ‐tetra[3‐( p– acetylthiopropoxy)phenyl] porphyrin (CoP, Figure 5) to a gold electrode . The method is based on the reaction of CoP with azanone to form a CoPNO − adduct, which upon oxidation, gives rise to a current intensity signal proportional to the bulk HNO concentration [103–106] …”

“…Using this information and adjusting the potential to values that oxidize CoIII(P)NO − (0.8 V vs. SCE), HNO can be detected by amperometric techniques. Among the analytical properties of the device, the selectivity towards azanone and the deficiency of interference with NO and other RNOS, the linear response in the nM to μM range, the compatibility with biological media, and the real‐time response that allows studying the kinetics of the reactions involving azanone can be highlighted [103–106] …”

“…The method is based on the reaction of CoP with azanone to form a CoPNO À adduct, which upon oxidation, gives rise to a current intensity signal proportional to the bulk HNO concentration. [103][104][105][106] Due to the self-assembled CoP on the gold surface (SAM formation), a 400 mV decrease in the Co(III)/Co(II) couple is observed, so there is a significant difference in the redox potential for the corresponding process between the porphyrins: free and coordinate with NO/NO À . The resulting first oxidation process occurs at � 0.4 V for Co(III)/Co(II) and 0.83 V for CoIII(P)NO/CoIII(P)NO À in an aqueous medium (vs. SCE, see Figure 6A).…”

“…Among the analytical properties of the device, the selectivity towards azanone and the deficiency of interference with NO and other RNOS, the linear response in the nM to μM range, the compatibility with biological media, and the real-time response that allows studying the kinetics of the reactions involving azanone can be highlighted. [103][104][105][106] With this device, it is possible to obtain kinetic information on reactions involving azanone at low (nanomolar) and even micromolar concentrations in the presence of interferents (including NO and other RNOS), in aerobic and anaerobic media. [100,[108][109][110] The electrode can also be used in living tissues (Figure 6B), such as cell cultures, with the advantage that it can be inserted into the culture plate and removed after measurements without disturbing or contaminating the tissue.…”

Stabilization of a Heme-HNO Model Complex Using a Bulky Bis-Picket Fence Porphyrin and Reactivity Studies with NO

“…On the other hand, HNO is a potent antialcoholism drug due to its ability to irreversibly inhibit thiol-containing enzymes such as mitochondrial aldehyde dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase . Other research suggests that HNO can act as a potential anticancer agent by triggering cancer cell apoptosis and reducing tumor growth. − Recently, endogenous HNO production has been demonstrated in plants …”