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Wahiduzzaman, Hassan MI, Islam A, Ahmad F. Urea Stress: Myo-inositol's efficacy to counteract destabilization of TIM-β-globin complex by urea is as good as that of the methylamine. Int J Biol Macromol 2020; 151:1108-1115. [DOI: 10.1016/j.ijbiomac.2019.10.153] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 10/15/2019] [Accepted: 10/16/2019] [Indexed: 11/29/2022]
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Costanzo JP. Overwintering adaptations and extreme freeze tolerance in a subarctic population of the wood frog, Rana sylvatica. J Comp Physiol B 2018; 189:1-15. [PMID: 30390099 DOI: 10.1007/s00360-018-1189-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 10/21/2018] [Accepted: 10/29/2018] [Indexed: 12/12/2022]
Abstract
The terrestrially hibernating wood frog (Rana sylvatica) is well-known for its iconic freeze tolerance, an overwintering adaptation that has received considerable investigation over the past 35 years. Virtually, all of this research has concerned frogs indigenous to the temperate regions of its broad range within North America. However, recent investigations have shown that frogs of subarctic populations are extremely cold hardy, being capable of surviving freezing for longer periods and at much lower temperatures as compared to conspecifics from temperate regions. Their exceptional freeze tolerance is partly supported by an enhanced cryoprotectant system that uses very high levels of urea and glucose to limit ice formation, regulate metabolism, and protect macromolecules and cellular structures from freezing/thawing stresses. In the weeks before they begin hibernating, northern frogs undertake radical physiological transitions, such as depletion of fat stores and catabolism of muscle protein, that prime the cryoprotectant system by accruing urea and stockpiling glycogen from which glucose is mobilized during freezing. Concentrations of cryoprotectants ultimately achieved in Alaskan frogs when freezing occurs vary among tissues but generally are higher than those of frogs inhabiting milder climates. This review summarizes the molecular, biochemical, and physiological adaptations permitting this northern phenotype to survive the long and harsh winters of the region.
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Affiliation(s)
- Jon P Costanzo
- Department of Biology, Miami University, 45056, Oxford, OH, USA.
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Zhang Y, Luu BE, Storey KB. FoxO4 activity is regulated by phosphorylation and the cellular environment during dehydration in the African clawed frog, Xenopus laevis. Biochim Biophys Acta Gen Subj 2018; 1862:1721-1728. [DOI: 10.1016/j.bbagen.2018.05.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 04/07/2018] [Accepted: 05/04/2018] [Indexed: 01/10/2023]
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Zhang Y, English SG, Storey KB. Regulation of nuclear factor of activated T cells (NFAT) and downstream myogenic proteins during dehydration in the African clawed frog. Mol Biol Rep 2018; 45:751-761. [PMID: 29923155 DOI: 10.1007/s11033-018-4214-8] [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: 04/30/2018] [Accepted: 06/14/2018] [Indexed: 10/28/2022]
Abstract
Xenopus laevis, otherwise known as the African clawed frog, undergoes natural dehydration of up to 30% of its total body water during the dry season in sub-Saharan Africa. To survive under these conditions, a variety of physiological and biochemical changes take place in X. laevis. We were interested in understanding the role that the calcineurin-NFAT pathway plays during dehydration stress response in the skeletal muscles of X. laevis. Immunoblotting was performed to characterize the protein levels of NFATc1-4, calcium signalling proteins, in addition to myogenic proteins (MyoD, MyoG, myomaker). In addition, DNA-protein interaction ELISAs were used to assess the binding of NFATs to their consensus binding sequence, and to identify the effect of urea on NFAT-binding. Our results showed that NFATc1 and c4 protein levels decreased during dehydration, and there were no changes in NFATc2, c3, and calcium signalling proteins. However, MyoG and myomaker both showed increases in protein levels during dehydration, thus indicating that the late myogenic program involving myoblast differentiation, but not satellite cell activation and myoblast proliferation, could be involved in preserving the skeletal muscle of X. laevis during dehydration. In addition, we observed that urea seems to reduce NFATc3-binding to DNA during control, but not during dehydration, possibly indicating that NFATc3 is protected from the denaturing effects of urea as it accumulates during dehydration. These findings expand upon our knowledge of adaptive responses to dehydration, and they identify specific protein targets that could be used to protect the skeletal muscle from damage during stress.
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Affiliation(s)
- Yichi Zhang
- Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada.,Department of Molecular Biology, Hamon Center for Regenerative Science and Medicine, Sen. Paul D. Wellstone Muscular Dystrophy Cooperative Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Simon G English
- Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada
| | - Kenneth B Storey
- Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada.
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Peña-Villalobos I, Narváez C, Sabat P. Metabolic cost of osmoregulation in a hypertonic environment in the invasive African clawed frog Xenopus laevis. Biol Open 2016; 5:955-61. [PMID: 27334694 PMCID: PMC4958268 DOI: 10.1242/bio.016543] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 05/31/2016] [Indexed: 12/26/2022] Open
Abstract
Studies of aquatic invertebrates reveal that salinity affects feeding and growth rates, reproduction, survival, and diversity. Little is known, however, about how salinity impacts the energy budget of vertebrates and amphibians in particular. The few studies focused on this topic in vertebrates suggest that the ingestion of salts and the resulting osmoregulatory activity is energetically expensive. We analyzed the effect of saline acclimation on standard metabolic rates (SMR) and the activities of metabolic enzymes of internal organs and osmoregulatory variables (plasma osmolality and urea plasma level) in females of Xenopus laevis by means of acclimating individuals to an isosmotic (235 mOsm NaCl; ISO group) and hyper-osmotic (340 mOsm NaCl; HYP group) environment for 40 days. After acclimation, we found that total and mass-specific SMR was approximately 80% higher in the HYP group than those found in the ISO group. These changes were accompanied by higher citrate synthase activities in liver and heart in the HYP group than in the ISO group. Furthermore, we found a significant and positive correlation between metabolic rates and plasma urea, and citrate synthase activity in liver and heart. These results support the notion that the cost of osmoregulation is probably common in most animal species and suggest the existence of a functional association between metabolic rates and the adjustments in osmoregulatory physiology, such as blood distribution and urea synthesis.
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Affiliation(s)
- Isaac Peña-Villalobos
- Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago 7800003, Chile
| | - Cristóbal Narváez
- Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago 7800003, Chile
| | - Pablo Sabat
- Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Santiago 7800003, Chile Center of Applied Ecology and Sustainability (CAPES), Pontificia Universidad Católica de Chile, Santiago 6513677, Chile
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Childers CL, Storey KB. Post-translational Regulation of Hexokinase Function and Protein Stability in the Aestivating Frog Xenopus laevis. Protein J 2016; 35:61-71. [DOI: 10.1007/s10930-016-9647-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Cryoprotectants and extreme freeze tolerance in a subarctic population of the wood frog. PLoS One 2015; 10:e0117234. [PMID: 25688861 PMCID: PMC4331536 DOI: 10.1371/journal.pone.0117234] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 12/19/2014] [Indexed: 01/29/2023] Open
Abstract
Wood frogs (Rana sylvatica) exhibit marked geographic variation in freeze tolerance, with subarctic populations tolerating experimental freezing to temperatures at least 10-13 degrees Celsius below the lethal limits for conspecifics from more temperate locales. We determined how seasonal responses enhance the cryoprotectant system in these northern frogs, and also investigated their physiological responses to somatic freezing at extreme temperatures. Alaskan frogs collected in late summer had plasma urea levels near 10 μmol ml-1, but this level rose during preparation for winter to 85.5 ± 2.9 μmol ml-1 (mean ± SEM) in frogs that remained fully hydrated, and to 186.9 ± 12.4 μmol ml-1 in frogs held under a restricted moisture regime. An osmolality gap indicated that the plasma of winter-conditioned frogs contained an as yet unidentified osmolyte(s) that contributed about 75 mOsmol kg-1 to total osmotic pressure. Experimental freezing to -8°C, either directly or following three cycles of freezing/thawing between -4 and 0°C, or -16°C increased the liver's synthesis of glucose and, to a lesser extent, urea. Concomitantly, organs shed up to one-half (skeletal muscle) or two-thirds (liver) of their water, with cryoprotectant in the remaining fluid reaching concentrations as high as 0.2 and 2.1 M, respectively. Freeze/thaw cycling, which was readily survived by winter-conditioned frogs, greatly increased hepatic glycogenolysis and delivery of glucose (but not urea) to skeletal muscle. We conclude that cryoprotectant accrual in anticipation of and in response to freezing have been greatly enhanced and contribute to extreme freeze tolerance in northern R. sylvatica.
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Katzenback BA, Dawson NJ, Storey KB. Purification and characterization of a urea sensitive lactate dehydrogenase from the liver of the African clawed frog, Xenopus laevis. J Comp Physiol B 2014; 184:601-11. [PMID: 24651940 DOI: 10.1007/s00360-014-0824-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 02/27/2014] [Accepted: 03/04/2014] [Indexed: 10/25/2022]
Abstract
The African clawed frog, Xenopus laevis, is able to withstand extremely arid conditions by estivating, in conjunction with dehydration tolerance and urea accumulation. Estivating X. laevis reduce their metabolic rate and recruit anaerobic glycolysis, driven by lactate dehydrogenase (LDH; E.C. 1.1.1.27) enzymes that reversibly convert pyruvate and NADH to lactate and NAD(+), to meet newly established ATP demands. The present study investigated purified LDH from the liver of dehydrated and control X. laevis. LDH from dehydrated liver showed a significantly higher K m for L-lactate (1.74 fold), NAD(+) (2.41 fold), and pyruvate (1.78 fold) in comparison to LDH from the liver of control frogs. In the presence of physiological levels of urea found in dehydrated animals, the K m values obtained for dehydrated LDH all returned to control LDH K m values. Dot blot analysis showed post-translational modifications may be responsible for the kinetic modification as the dehydrated form of LDH showed more phosphorylated serine residues (1.54 fold), less methylated lysine residues (0.43 fold), and a higher level of ubiquitination (1.90 fold) in comparison to control LDH. The physiological consequence of dehydration-induced LDH modification appears to adjust LDH function in conjunction with urea levels in dehydrated frogs. When urea levels are high during dehydration, LDH retains its normal function. Yet, as urea levels drop during rehydration, LDH function is reduced, possibly shunting pyruvate to the TCA cycle.
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Affiliation(s)
- Barbara A Katzenback
- Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada,
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Craig SS, Craig SA, Ganio MS, Maresh CM, Horrace G, da Costa KA, Zeisel SH. The betaine content of sweat from adolescent females. J Int Soc Sports Nutr 2010; 7:3. [PMID: 20205750 PMCID: PMC2822829 DOI: 10.1186/1550-2783-7-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 01/22/2010] [Indexed: 11/25/2022] Open
Abstract
Background This study was developed to establish whether betaine was present in the sweat of females and to determine any correlations with other sweat components. Methods Sweat patches were placed on eight trained adolescent Highland dancers (age = 13.6 ± 2.3 yr), who then participated in a dance class for 2 hours. Patches were removed, and the sweat recovered via centrifugation. The sweat was subsequently analyzed for betaine, choline, sodium, potassium, chloride, lactate, glucose, urea and ammonia. Results Betaine was present in the sweat of all subjects (232 ± 84 μmol·L-1), which is higher than typically found in plasma. The concentration of several sweat components were correlated, in particular betaine with most other measured components. Conclusion Betaine, an osmoprotectant and methyl donor, is a component of sweat that may be lost from the body in significant amounts.
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Costanzo JP, Lee RE. Urea loading enhances freezing survival and postfreeze recovery in a terrestrially hibernating frog. ACTA ACUST UNITED AC 2008; 211:2969-75. [PMID: 18775934 DOI: 10.1242/jeb.019695] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We tested the hypothesis that urea, an osmolyte accumulated early in hibernation, functions as a cryoprotectant in the freeze-tolerant wood frog, Rana sylvatica. Relative to saline-treated, normouremic (10 micromol ml(-1)) frogs, individuals rendered hyperuremic (70 micromol ml(-1)) by administration of an aqueous urea solution exhibited significantly higher survival (100% versus 64%) following freezing at -4 degrees C, a potentially lethal temperature. Hyperuremic frogs also had lower plasma levels of intracellular proteins (lactate dehydrogenase, creatine kinase, hemoglobin), which presumably escaped from damaged cells, and more quickly recovered neurobehavioral functions following thawing. Experimental freezing-thawing did not alter tissue urea concentrations, but did elevate glucose levels in the blood and organs of all frogs. When measured 24 h after thawing commenced, glucose concentrations were markedly higher in urea-loaded frogs as compared to saline-treated ones, possibly because elevated urea retarded glucose clearance. Like other low-molecular-mass cryoprotectants, urea colligatively reduces both the amount of ice forming within the body and the osmotic dehydration of cells. In addition, by virtue of certain non-colligative properties, it may bestow additional protection from freeze-thaw damage not afforded by glucose.
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Affiliation(s)
- Jon P Costanzo
- Department of Zoology, Miami University, Oxford, OH 45056, USA.
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Schiller TM, Costanzo JP, Lee RE. Urea production capacity in the wood frog (Rana sylvatica) varies with season and experimentally induced hyperuremia. ACTA ACUST UNITED AC 2008; 309:484-93. [DOI: 10.1002/jez.479] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Muir TJ, Costanzo JP, Lee RE. Osmotic and metabolic responses to dehydration and urea-loading in a dormant, terrestrially hibernating frog. J Comp Physiol B 2007; 177:917-26. [PMID: 17661060 DOI: 10.1007/s00360-007-0190-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Revised: 06/29/2007] [Accepted: 07/03/2007] [Indexed: 10/23/2022]
Abstract
Physiological responses to dehydration in amphibians are reasonably well documented, although little work has addressed this problem in hibernating animals. We investigated osmotic and metabolic responses to experimental manipulation of hydration state in the wood frog (Rana sylvatica), a terrestrial hibernator that encounters low environmental water potential during autumn and winter. In winter-conditioned frogs, plasma osmolality varied inversely with body water content (range 69-79%, fresh mass) primarily due to increases in sodium and chloride concentrations, as well as accumulation of glucose and urea. Decreased hydration was accompanied by a marked reduction in the resting rate of oxygen consumption, which was inversely correlated with plasma osmolality and urea concentration. In a separate experiment, resting rates of oxygen consumption in fully hydrated frogs receiving injections of saline or saline containing urea did not differ initially; however, upon dehydration, metabolic rates decreased sooner in the urea-loaded frogs than in control frogs. Our findings suggest an important role for urea, acting in concert with dehydration, in the metabolic regulation and energy conservation of hibernating R. sylvatica.
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Affiliation(s)
- Timothy J Muir
- Department of Zoology, Miami University, Oxford, OH 45056, USA.
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Abstract
SUMMARYThe role of urea as a balancing osmolyte in osmotic adaptation is well known, but this `waste product' also has myriad other functions in diverse taxa. We report that urea plays an important, previously undocumented role in freezing tolerance of the wood frog (Rana sylvatica), a northern woodland species that hibernates terrestrially in sites where dehydration and freezing may occur. Wood frogs inhabiting an outdoor enclosure accumulated urea to 65 mmol l-1 in autumn and early winter, when soil moisture was scarce, but subsequently urea levels fell to ∼2 mmol l-1 as the availability of environmental water increased. Laboratory experiments showed that hibernating R. sylvatica can accumulate at least 90 mmol l-1 urea under relatively dry, warm conditions. During experimental freezing, frogs synthesized glucose but did not accumulate additional urea. Nevertheless, the concentrations of urea and glucose in some tissues were similar. We tested urea's efficacy as a cryoprotectant by measuring lysis and lactate dehydrogenase (LDH) leakage in samples of R. sylvaticaerythrocytes frozen/thawed in the presence of physiological levels of urea or other osmolytes. In conferring protection against freeze/thaw damage, urea was comparable to glycerol and as good as or better than glucose, cryoprotectants found in freeze-tolerant frogs and other animals. Urea treatment also improved the viability of intact tissues frozen in vitro, as demonstrated by post-thaw measures of metabolic activity and LDH leakage. Collectively, our findings suggest that urea functions both as an osmoprotectant and a cryoprotectant in terrestrially hibernating amphibians.
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Affiliation(s)
- Jon P Costanzo
- Department of Zoology, Miami University, Oxford, OH 45056, USA.
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Cowan KJ, Storey KB. Urea and KCl have differential effects on enzyme activities in liver and muscle of estivating versus nonestivating species. Biochem Cell Biol 2003; 80:745-55. [PMID: 12555807 DOI: 10.1139/o02-144] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effects of 300 mM urea or 300 mM KCl on the maximal activities of 25 enzymes of intermediary metabolism were assessed in extracts of liver and muscle from spadefoot toads (Scaphiopus couchii), leopard frogs (Rana pipiens), and rats to assess their sensitivity to these osmolytes. During estivation, toads can lose -50% of total body water, and urea, which is known for its action as a protein denaturant, accumulates to 200-300 mM. The data show that the maximal activities of toad liver enzymes were not affected when assayed in the presence of 300 mM urea in vitro whereas urea inhibited the activities of seven enzymes in frog and 11 enzymes in rat liver. High KCl affected 12 or 13 enzymes in liver of each species causing inhibition in eight or nine cases each, and for frog and rat enzymes, inhibition was frequently more pronounced than for urea. Both urea and KCl affected enzyme activities in muscle extracts of all three species, but whereas their effects were largely negative for frog and rat enzymes, the enzymes affected by urea or KCl in toad muscle were primarily activated by these osmolytes (six out of nine enzymes affected by urea and eight of 15 enzymes affected by KCl). Urea, KCl, and polyethylene glycol (a protein crowding agent) also had species-specific effects on the dissociation constant (Ka) for cAMP of protein kinase A. The data suggest that the accumulation of urea by water-stressed anurans not only contributes to minimizing cell volume reduction, but by doing so also limits the increase in intracellular ionic strength that occurs and thereby helps to minimize the potential inhibitory effects of high salts on metabolic enzymes.
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Affiliation(s)
- Kyra J Cowan
- Institute of Biochemistry and Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada
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Seibel BA, Walsh PJ. Trimethylamine oxide accumulation in marine animals: relationship to acylglycerol storagej. J Exp Biol 2002; 205:297-306. [PMID: 11854367 DOI: 10.1242/jeb.205.3.297] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Trimethylamine oxide (TMAO) is a common and compatible osmolyte in muscle tissues of marine organisms that is often credited with counteracting protein-destabilizing forces. However, the origin and synthetic pathways of TMAO are actively debated. Here, we examine the distribution of TMAO in marine animals and report a correlation between TMAO and acylglycerol storage. We put forward the hypothesis that TMAO is derived, at least in part, from the hydrolysis of phosphatidylcholine, endogenous or dietary, for storage as diacylglycerol ethers and triacylglycerols. TMAO is synthesized from the trimethylammonium moiety of choline, thus released, and is retained as a compatible solute in concentrations reflecting the amount of lipid stored in the body. A variation on this theme is proposed for sharks.
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Affiliation(s)
- Brad A Seibel
- NIEHS Marine and Freshwater Biomedical Sciences Center, Rosenstiel School of Marine and Atmospheric Science, Miami, FL 33149, USA.
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Bedford JJ, Harper JL, Leader JP, Yancey PH, Smith RA. Betaine is the principal counteracting osmolyte in tissues of the elephant fish, Callorhincus millii (Elasmobranchii, Holocephali). Comp Biochem Physiol B Biochem Mol Biol 1998. [DOI: 10.1016/s0305-0491(98)00013-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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