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107. The role of hydrogen sulphide in the control of breathing in hypoxic zebrafish (Danio rerio)

Author

Porteus, Cosima S, Abdallah, Sara J, Pollack, Jacob, Kumai, Yusuke, Kwong, Raymond W M, Yew, Hong M, Milsom, William K, and Perry, Steve F

Subjects
animal structures, Respiration, fungi, Cystathionine gamma-Lyase, Glycine, Neuroepithelial Cells, Aminooxyacetic Acid, Cystathionine beta-Synthase, Sulfides, Oxygen, Alkynes, Respiratory, Animals, Hydrogen Sulfide, Hypoxia, Zebrafish
Abstract

The current study investigated the role of hydrogen sulphide (H2S) in oxygen sensing, intracellular signalling and promotion of ventilatory responses to hypoxia in adult and larval zebrafish (Danio rerio). Both larval and adult zebrafish exhibited a dose-dependent increase in ventilation to sodium sulphide (Na2S), an H2S donor. In vertebrates, cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) are enzymes that catalyse the endogenous production of H2S. In adult zebrafish, inhibition of both CBS and CSE with aminooxyacetate (AOA) and propargyl glycine (PPG) blunted or abolished the hypoxic hyperventilation, and the addition of Na2S to the water partially rescued the effects of inhibiting endogenous H2S production. In zebrafish larvae (4 days post-fertilization), gene knockdown of either CBS or CSE using morpholinos attenuated the hypoxic ventilatory response. Furthermore, the intracellular calcium concentration of isolated neuroepithelial cells (NECs), which are putative oxygen chemoreceptors, increased significantly when these cells were exposed to 50 μm Na2S, supporting a role for H2S in Ca(2+)-evoked neurotransmitter release in these cells. Finally, immunohistochemical labelling showed that NECs dissociated from adult gill contained CBS and CSE, whereas cutaneous NECs in larval zebrafish expressed only CSE. Taken together, these data show that H2S can be produced in the putative oxygen-sensing cells of zebrafish, the NECs, in which it appears to play a pivotal role in promoting the hypoxic ventilatory response.

Published
2014

119. Inhibition of calcium uptake during hypoxia in developing zebrafish is mediated by hypoxia-inducible factor.

Author

Kwong, Raymond W. M., Kumai, Yusuke, Tzaneva, Velislava, Azzi, Estelle, Hochhold, Nina, Robertson, Cayleih, Pelster, Bernd, and Perry, Steve F.

Subjects
LOGPERCH, ANIMAL behavior, CALCIUM, HYPOXEMIA, HYPOXIA-inducible factors
Abstract

The present study investigated the potential role of hypoxia-inducible factor (HIF) in calcium homeostasis in developing zebrafish (Danio rerio). It was demonstrated that zebrafish raised in hypoxic water (30 mmHg; control, 155 mmHg PO2) until 4 days post-fertilization exhibited a substantial reduction in whole-body Ca2+ levels and Ca2+ uptake. Ca2+ uptake in hypoxia-treated fish did not return to prehypoxia (control) levels within 2 h of transfer back to normoxic water. Results from real-time PCR showed that hypoxia decreased the whole-body mRNA expression levels of the epithelial Ca2+ channel (ecac), but not plasma membrane Ca2+-ATPase (pmca2) or Na+/ Ca2+-exchanger (ncx1b). Whole-mount in situ hybridization revealed that the number of ecac-expressing ionocytes was reduced in fish raised in hypoxic water. These findings suggested that hypoxic treatment suppressed the expression of ecac, thereby reducing Ca2+ influx. To further evaluate the potential mechanisms for the effects of hypoxia on Ca2+ regulation, a functional gene knockdown approach was employed to prevent the expression of HIF-1αb during hypoxic treatment. Consistent with a role for HIF-1αb in regulating Ca2+ balance during hypoxia, the results demonstrated that the reduction of Ca2+ uptake associated with hypoxic exposurewas not observed in fish experiencing HIF-1αb knockdown. Additionally, the effects of hypoxia on reducing the number of ecac-expressing ionocytes was less pronounced in HIF-1αb-deficient fish. Overall, the current study revealed that hypoxic exposure inhibited Ca2+ uptake in developing zebrafish, probably owing to HIF-1αb-mediated suppression of ecac expression. [ABSTRACT FROM AUTHOR]

Published
2016
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135. The water channel aquaporin-1a1 facilitates movement of CO2 and ammonia in zebrafish (Danio rerio) larvae.

Author

Talbot, Krystle, Kwong, Raymond W. M., Gilmour, Kathleen M., and Perry, Steve F.

Subjects
AQUAPORINS, ZEBRA danio, LARVAE, PHENYLHYDRAZINE, PHYSIOLOGY, BEHAVIOR
Abstract

The present study tested the hypothesis that zebrafish (Danio rerio) aquaporin-1a1 (AQP1a1) serves as a multi-functional channel for the transfer of the small gaseous molecules, CO2 and ammonia, as well as water, across biological membranes. Zebrafish embryos were microinjected with a translation-blocking morpholino oligonucleotide targeted to AQP1a1. Knockdown of AQP1a1 significantly reduced rates of CO2 and ammonia excretion, as well as water fluxes, in larvae at 4 days post fertilization (dpf). Because AQP1a1 is expressed both in ionocytes present on the body surface and in red blood cells, the haemolytic agent phenylhydrazine was used to distinguish between the contributions of AQP1a1 to gas transfer in these two locations. Phenylhydrazine treatment had no effect on AQP1a1-linked excretion of CO2 or ammonia, providing evidence that AQP1a1 localized to the yolk sac epithelium, rather than red blood cell AQP1a1, is the major site of CO2 and ammonia movements. The possibility that AQP1a1 and the rhesus glycoprotein Rhcg1, which also serves as a dual CO2 and ammonia channel, act in concert to facilitate CO2 and ammonia excretion was explored. Although knockdown of each protein did not affect the abundance of mRNA and protein of the other protein under control conditions, impairment of ammonia excretion by chronic exposure to high external ammonia triggered a significant increase in the abundance of AQP1a1 mRNA and protein in 4 dpf larvae experiencing Rhcg1 knockdown. Collectively, these results suggest that AQP1a1 in zebrafish larvae facilitates the movement of CO2 and ammonia, as well as water, in a physiologically relevant fashion. [ABSTRACT FROM AUTHOR]

Published
2015
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137. Foreword

Author

Perry, Steve F., primary and Milsom, William K., additional

Published
2012
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