Hydrogen sulfide signaling: interactions with nitric oxide and reactive oxygen species.

Signaling in cells involving reactive compounds is well established. Reactive oxygen species (ROS) and nitric oxide (NO) are known to be extremely influential in the control of a range of physiological responses in many organisms, from animals to plants. Often, their generation is triggered in reaction to stress, and it is common for ROS and NO metabolism to interact to give a coordinated response. Recently, hydrogen sulfide (H2 S) has also been found to be an important signaling molecule, being shown to be involved in vascular tone in animals. Of relevance to respiration, in plants, H2 S has been shown to affect stomatal apertures and the transpiration stream, while, in animals, H2 S has been shown to be a source of electrons for ATP synthesis in mitochondria. However, in signaling, H2 S does not work in isolation, and it is likely that it will interact with both ROS and NO. This may occur at a variety of levels, from influencing the generation of such molecules, interacting directly, or competing for control of downstream signaling events. A full understanding of the impact of this toxic molecule in the control of cells requires all these factors to be taken into account.