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Harter TS, Dichiera AM, Esbaugh AJ. The physiological significance of plasma-accessible carbonic anhydrase in the respiratory systems of fishes. J Comp Physiol B 2024:10.1007/s00360-024-01562-4. [PMID: 38842596 DOI: 10.1007/s00360-024-01562-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 04/26/2024] [Accepted: 05/13/2024] [Indexed: 06/07/2024]
Abstract
Carbonic anhydrase (CA) activity is ubiquitously found in all vertebrate species, tissues and cellular compartments. Most species have plasma-accessible CA (paCA) isoforms at the respiratory surfaces, where the enzyme catalyzes the conversion of plasma bicarbonate to carbon dioxide (CO2) that can be excreted by diffusion. A notable exception are the teleost fishes that appear to lack paCA at their gills. The present review: (i) recapitulates the significance of CA activity and distribution in vertebrates; (ii) summarizes the current evidence for the presence or absence of paCA at the gills of fishes, from the basal cyclostomes to the derived teleosts and extremophiles such as the Antarctic icefishes; (iii) explores the contribution of paCA to organismal CO2 excretion in fishes; and (iv) the functional significance of its absence at the gills, for the specialized system of O2 transport in most teleosts; (v) outlines the multiplicity and isoform distribution of membrane-associated CAs in fishes and methodologies to determine their plasma-accessible orientation; and (vi) sketches a tentative time line for the evolutionary dynamics of branchial paCA distribution in the major groups of fishes. Finally, this review highlights current gaps in the knowledge on branchial paCA function and provides recommendations for future work.
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Affiliation(s)
- Till S Harter
- Department of Biology, McMaster University, Hamilton, ON, L8S 4K1, Canada.
| | - Angelina M Dichiera
- College of William and Mary, Virginia Institute of Marine Science, Gloucester Point, VA, 23062, USA
| | - Andrew J Esbaugh
- Marine Science Institute, University of Texas at Austin, Port Aransas, TX, 78373, USA
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Nelson C, Standen EM, Allen PJ, Brauner CJ. An investigation of gill and blood carbonic anhydrase characteristics in three basal actinopterygian species: alligator gar (Atractosteus spatula), white sturgeon (Acipenser transmontanus) and Senegal bichir (Polypterus senegalus). J Comp Physiol B 2024; 194:155-166. [PMID: 38459993 DOI: 10.1007/s00360-024-01539-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 12/22/2023] [Accepted: 01/19/2024] [Indexed: 03/11/2024]
Abstract
Many teleosts possess a unique set of respiratory characteristics allowing enhanced oxygen unloading to the tissues during stress. This system comprises three major components: highly pH sensitive haemoglobins (large Bohr and Root effects), rapid red blood cell (RBC) intracellular pH (pHi) protection, and a heterogeneous distribution of membrane-bound plasma-accessible carbonic anhydrase (paCA; absence in the gills). The first two components have received considerable research effort; however, the evolutionary loss of branchial paCA has received little attention. In the current study, we investigated the availability of branchial membrane-bound CA, along with several other CA-related characteristics in species belonging to three basal actinopterygian groups: the Lepisosteiformes, Acipenseriformes and Polypteriformes to assess the earlier hypothesis that Root effect haemoglobins constrain branchial paCA availability. We present the first evidence suggesting branchial membrane-bound CA presence in a basal actinopterygian species: the Senegal bichir (Polypterus senegalus) and show that like the teleosts, white sturgeon (Acipenser transmontanus) and alligator gar (Atractosteus spatula) do not possess branchial membrane-bound CA. We discuss the varying respiratory strategies for these species and propose that branchial paCA may have been lost much earlier than previously thought, likely in relation to the changes in haemoglobin buffer capacity associated with the increasing magnitude of the Bohr effect. The findings described here represent an important advancement in our understanding of the evolution of the unique system of enhanced oxygen unloading thought to be present in most teleosts, a group that encompasses half of all vertebrates.
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Affiliation(s)
| | | | - Peter J Allen
- Mississippi State University, Mississippi, 39762, USA
| | - Colin J Brauner
- University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
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Giareta EP, Hauser-Davis RA, Abilhoa V, Wosnick N. Carbonic anhydrase in elasmobranchs and implications of the current climate change scenario. Comp Biochem Physiol A Mol Integr Physiol 2023; 281:111435. [PMID: 37086909 DOI: 10.1016/j.cbpa.2023.111435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 04/16/2023] [Accepted: 04/17/2023] [Indexed: 04/24/2023]
Abstract
The enzyme carbonic anhydrase (CA) has well-known functions in acid-base balance, respiratory gas exchange, and osmoregulation in teleost fishes. However, studies concerning the role of CA in elasmobranchs are still scarce. Therefore, the aim of this study is to present the current status of CA studies in sharks and rays, as well as to identify gaps and emerging needs, in order to guide future studies. This review is organized according to the main roles of CA, with further considerations on climate change and CA effects indicated as paramount, as strategies in the face of climate change can be crucial for species response. The literature review revealed a reduction in publications on CA over the years. In addition, a historical research differentiation is noted, where the first assessments on the subject addressed investigations on basic CA functions, while the most recent studies present a comparative approach among species as well as interdisciplinary discussions, such as ecology and phylogeny. Considering that most elasmobranchs are threatened, future studies should prioritize non-lethal methodologies, in addition to expanding studies to climate change effects on CA.
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Affiliation(s)
| | - Rachel Ann Hauser-Davis
- Laboratório de Avaliação e Promoção da Saúde Ambiental, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, Brazil
| | - Vinícius Abilhoa
- Programa de Pós-Graduação em Zoologia, Universidade Federal do Paraná, Curitiba, Brazil
| | - Natascha Wosnick
- Programa de Pós-Graduação em Zoologia, Universidade Federal do Paraná, Curitiba, Brazil
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Giacomin M, Drummond JM, Supuran CT, Goss GG. The roles of plasma accessible and cytosolic carbonic anhydrases in bicarbonate (HCO 3-) excretion in Pacific hagfish (Eptatretus stoutii). J Comp Physiol B 2022; 192:713-725. [PMID: 36098803 DOI: 10.1007/s00360-022-01459-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 08/08/2022] [Accepted: 08/23/2022] [Indexed: 11/29/2022]
Abstract
Pacific hagfish (Eptatretus stoutii) are marine scavengers and feed on decaying animal carrion by burrowing their bodies inside rotten carcasses where they are exposed to several threatening environmental stressors, including hypercapnia (high partial pressures of CO2). Hagfish possess a remarkable capacity to tolerate hypercapnia, and their ability to recover from acid-base disturbances is well known. To deal with the metabolic acidosis resulting from exposure to high CO2, hagfish can mount a rapid elevation of plasma HCO3- concentration (hypercarbia). Once PCO2 is restored, hagfish quickly excrete their HCO3- load, a process that likely involves the enzyme carbonic anhydrase (CA), which catalyzes HCO3- dehydration into CO2 at the hagfish gills. We aimed to characterize the role of branchial CA in CO2/HCO3- clearance from the plasma at the gills of E. stoutii, under control and high PCO2 (hypercapnic) exposure conditions. We assessed the relative contributions of plasma accessible versus intracellular (cytosolic) CA to gill HCO3- excretion by measuring in situ [14C]-HCO3- fluxes. To accomplish this, we employed a novel surgical technique of individual gill pouch arterial perfusion combined with perifusion of the gill afferent to efferent water ducts. [14C]-HCO3- efflux was measured at the gills of fish exposed to control, hypercapnic (48 h) and recovery from hypercapnia conditions (6 h), in the presence of two well-known pharmacological inhibitors of CA, the membrane impermeant C18 (targets membrane bound, plasma accessible CA) and membrane-permeant acetazolamide, which targets all forms of CA, including extracellular and intracellular cytosolic CAs. C18 did not affect HCO3- flux in control fish, whereas acetazolamide resulted in a significant reduction of 72%. In hypercapnic fish, HCO3- fluxes were much higher and perfusion with acetazolamide caused a reduction of HCO3- flux by 38%. The same pattern was observed for fish in recovery, where in all three experimental conditions, there was no significant inhibition of plasma-accessible CA. We also observed no change in CA enzyme activity (measured in vitro) in any of the experimental PCO2 conditions. In summary, our data suggests that there are additional pathways for HCO3- excretion at the gills of hagfish that are independent of plasma-accessible CA.
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Affiliation(s)
- Marina Giacomin
- Department of Biological Sciences, University of Alberta, CW 405, Biological Sciences Bldg., Edmonton, AB, T6G 2E9, Canada. .,Bamfield Marine Science Centre, Bamfield, BC, V0R 1B0, Canada.
| | - Jenna M Drummond
- Department of Biological Sciences, University of Alberta, CW 405, Biological Sciences Bldg., Edmonton, AB, T6G 2E9, Canada.,Bamfield Marine Science Centre, Bamfield, BC, V0R 1B0, Canada
| | - Claudiu T Supuran
- Neurofarba Department, University of Florence, Via Ugo Schiff 6, Florence, Italy
| | - Greg G Goss
- Department of Biological Sciences, University of Alberta, CW 405, Biological Sciences Bldg., Edmonton, AB, T6G 2E9, Canada.,Bamfield Marine Science Centre, Bamfield, BC, V0R 1B0, Canada
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Xin Y, Yang Z, Zhu Y, Li Y, Yu J, Zhong W, Chen Y, Lv X, Hu J, Lin J, Miao Y, Wang L. Hypoxia Induces Oxidative Injury and Apoptosis via Mediating the Nrf-2/Hippo Pathway in Blood Cells of Largemouth Bass (Micropterus salmoides). Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.841318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Investigating how aquatic animals respond to hypoxia brought about by changes in environmental temperature may be of great significance to avoid oxidative injury and maintain the quality of farmed fish in the background of global warming. Here, we investigated the effects of hypoxia on oxidative injury and environment-sensing pathway in blood cells of Micropterus salmoides. The total blood cell count (TBCC) and Giemsa staining showed that hypoxia could lead to damage of blood cells. Flow cytometry analysis confirmed that the apoptosis rate, Ca2+ level, NO production and ROS of blood cells were significantly increased under hypoxia stress. Environment-sensing pathways, such as Nrf2 pathway showed that hypoxia resulted in significant up-regulation of hiF-1 alpha subunit (Hif-1α), nuclear factor erythroid 2-related factor 2 (Nrf2) and kelch-1ike ECH- associated protein l (Keap1) expression. Meanwhile, the expression of Hippo pathway-related genes such as MOB kinase activator 1 (MOB1), large tumor suppressor homolog 1/2 (Lats1/2), yes-associated protein/transcriptional co-activator with PDZ-binding motif (YAP/TAZ), protein phosphatase 2A (PP2A) were significantly increased in blood cells after hypoxia exposure. In addition, hypoxia stress also increased the expression of catalase (CAT) and glutathione peroxidase (GPx), but decreased the expression of superoxide dismutase (SOD). Consequently, our results suggested that hypoxia could induce oxidative injury and apoptosis via mediating environment-sensing pathway such as Nrf2/Hippo pathway in blood cells of M. salmoides.
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Esbaugh AJ, Ackerly KL, Dichiera AM, Negrete B. Is hypoxia vulnerability in fishes a by-product of maximum metabolic rate? J Exp Biol 2021; 224:269306. [PMID: 34184035 DOI: 10.1242/jeb.232520] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The metabolic index concept combines metabolic data and known thermal sensitivities to estimate the factorial aerobic scope of animals in different habitats, which is valuable for understanding the metabolic demands that constrain species' geographical distributions. An important assumption of this concept is that the O2 supply capacity (which is equivalent to the rate of oxygen consumption divided by the environmental partial pressure of oxygen: ) is constant at O2 tensions above the critical O2 threshold (i.e. the where O2 uptake can no longer meet metabolic demand). This has led to the notion that hypoxia vulnerability is not a selected trait, but a by-product of selection on maximum metabolic rate. In this Commentary, we explore whether this fundamental assumption is supported among fishes. We provide evidence that O2 supply capacity is not constant in all fishes, with some species exhibiting an elevated O2 supply capacity in hypoxic environments. We further discuss the divergent selective pressures on hypoxia- and exercise-based cardiorespiratory adaptations in fishes, while also considering the implications of a hypoxia-optimized O2 supply capacity for the metabolic index concept.
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Affiliation(s)
- Andrew J Esbaugh
- University of Texas at Austin, Marine Science Institute, Port Aransas, TX 78373, USA
| | - Kerri L Ackerly
- University of Texas at Austin, Marine Science Institute, Port Aransas, TX 78373, USA
| | - Angelina M Dichiera
- University of Texas at Austin, Marine Science Institute, Port Aransas, TX 78373, USA
| | - Benjamin Negrete
- University of Texas at Austin, Marine Science Institute, Port Aransas, TX 78373, USA
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Dichiera AM, Esbaugh AJ. Red blood cell carbonic anhydrase mediates oxygen delivery via the Root effect in red drum. ACTA ACUST UNITED AC 2020; 223:223/22/jeb232991. [PMID: 33243926 DOI: 10.1242/jeb.232991] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 10/08/2020] [Indexed: 12/15/2022]
Abstract
Oxygen (O2) and carbon dioxide (CO2) transport are tightly coupled in many fishes as a result of the presence of Root effect hemoglobins (Hb), whereby reduced pH reduces O2 binding even at high O2 tensions. Red blood cell carbonic anhydrase (RBC CA) activity limits the rate of intracellular acidification, yet its role in O2 delivery has been downplayed. We developed an in vitro assay to manipulate RBC CA activity while measuring Hb-O2 offloading following a physiologically relevant CO2-induced acidification. RBC CA activity in red drum (Sciaenops ocellatus) was inhibited with ethoxzolamide by 53.7±0.5%, which prompted a significant reduction in O2 offloading rate by 54.3±5.4% (P=0.0206, two-tailed paired t-test; n=7). Conversely, a 2.03-fold increase in RBC CA activity prompted a 2.14-fold increase in O2 offloading rate (P<0.001, two-tailed paired t-test; n=8). This approximately 1:1 relationship between RBC CA activity and Hb-O2 offloading rate coincided with a similar allometric scaling exponent for RBC CA activity and maximum metabolic rate. Together, our data suggest that RBC CA is rate limiting for O2 delivery in red drum.
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Affiliation(s)
- Angelina M Dichiera
- The University of Texas at Austin Marine Science Institute, 750 Channel View Drive, Port Aransas, TX 78373, USA
| | - Andrew J Esbaugh
- The University of Texas at Austin Marine Science Institute, 750 Channel View Drive, Port Aransas, TX 78373, USA
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