Carbon dioxide-sensing in organisms and its implications for human disease

Abstract

The capacity of organisms to sense changes in the levels of internal and external gases and to respond accordingly is central to a range of physiologic and pathophysiologic processes. Carbon dioxide, a primary product of oxidative metabolism is one such gas that can be sensed by both prokaryotic and eukaryotic cells and in response to altered levels, elicit the activation of multiple adaptive pathways. The outcomes of activating CO2-sensitive pathways in various species include increased virulence of fungal and bacterial pathogens, prey-seeking behavior in insects as well as taste perception, lung function, and the control of immunity in mammals. In this review, we discuss what is known about the mechanisms underpinning CO2 sensing across a range of species and consider the implications of this for physiology, disease progression, and the possibility of developing new therapeutics for inflammatory and infectious disease.

Environmental CO 2 inhibits Caenorhabditis elegans egg-laying by modulating olfactory neurons and evokes widespread changes in neural activity

“…Like gcy-9 mutants and BAGablated animals, tax-4(p678null) mutants showed severe defects in turning following a 0-5% rise in CO 2 (Fig. 1C), as would be expected if BAG was defective.…”

“…Glia also exhibit large Ca 2+ responses to CO 2 . Worms therefore may couple detection of CO 2 and other cues at the earliest stages of sensory processing. Besides avoiding CO 2 , C. elegans stops laying eggs at high CO 2 .…”

“…Many of the C. elegans sensory neurons we examined, including the AWC olfactory neurons, the ASJ and ASK gustatory neurons, and the ASH and ADL nociceptors, respond to a rise in CO 2 with a rise in Ca 2+ . In contrast, glial sheath cells harboring the sensory endings of C. elegans' major chemosensory neurons exhibit strong and sustained decreases in Ca 2+ in response to high CO 2 . Some of these CO 2 responses appear to be cell intrinsic.…”

“…Some of these CO 2 responses appear to be cell intrinsic. Worms therefore may couple detection of CO 2 to that of other cues at the earliest stages of sensory processing. We show that C. elegans persistently suppresses oviposition at high CO 2 .…”

“…Animals across phylogeny use such gradients to help detect food, conspecifics, or predators (1,2). The ubiquity of CO 2 suggests that the ecologically relevant information it communicates will depend on the dynamics of the CO 2 stimulus and on context.…”