Cell-based indicator to visualize picomolar dynamics of nitric oxide release from living cells

Evaluation of Copper(II) Eriochrome Cyanine R (ECR) Complex Immobilized in Anion Exchange Membrane as a Potential Nitric Oxide Optical Sensor

The immobilization of the copper(ii) complex of Eriochrome cyanine R (Cu(ECR)2) in anion exchange membranes was investigated in the development of an optical sensor for nitric oxide (NO) gas. The change in the absorbance spectrum of Cu(ECR)2 membranes was monitored at 445 nm on exposure to NO gas and a steady-state response was obtained following a 400 s exposure time. This response was highly linear (r2 = 0.996) up to 6 ppm NO and the detection limit was calculated to be 0.848 ppm (~28.28 μM in solution). This response was 4.7 times more sensitive to changing NO gas concentrations (0–6 ppm) compared with that of Cu(ECR)2 immobilized in silicone rubber films. This response was fully reversible by resubmersion of the membranes in copper(ii) solution following NO exposure and this reversibility was extremely reproducible (0.81%, relative standard deviation, n = 3). These anion exchange membranes were more selective to NO gas rather than O2 (80:1), NO2 (3:1), and CO (7:1) and these gases were shown not to interfere with the reaction of Cu-ECR membranes with NO itself.

Optical probes for molecular processes in live cells

In this review, I summarize the development over the past several years of fluorescent and/or bioluminescent indicators to pinpoint cellular processes in living cells. These processes involve second messengers, protein phosphorylations, protein-protein interactions, protein-ligand interactions, nuclear receptor-coregulator interactions, nucleocytoplasmic trafficking of functional proteins, and protein localization.

Nitric oxide release from a single cell affects filopodial motility on growth cones of neighboring neurons

Nitric oxide (NO), a gaseous messenger, has been reported to be involved in a variety of functions in the nervous system, ranging from neuronal pathfinding to learning and memory. We have shown previously that the application of NO via NO donors to growth cones of identified Helisoma buccal neurons B5 in vitro induces an increase in filopodial length, a decrease in filopodial number, and a slowing in neurite advance. It is unclear, however, whether NO released from a physiological source would affect growth cone dynamics. Here we used cell bodies of identified neurons known to express the NO synthesizing enzyme nitric oxide synthase (NOS) as a source of constitutive NO production and tested their effect on growth cones of other cells in a sender-receiver paradigm. We showed that B5 cell bodies induced a rapid increase in filopodial length in NO-responsive growth cones, and that this effect was blocked by the NOS inhibitor 7-NI, suggesting that the effect was mediated by NO. Inhibition of soluble guanylyl cyclase (sGC) with ODQ blocked filopodial elongation induced by B5 somata, confirming that NO acted via sGC. We also demonstrate that the effect of NO was reversible and that a cell releasing NO can affect growth cones over a distance of at least 100 microm. Our results suggest that NO released from a physiological source can affect the motility of nearby growth cones and thus should be considered a signaling molecule with the potential to affect the outcome of neuronal pathfinding in vivo.