Molecular and Cellular Regulation of Pineal Organ Responses

Falcón, Jack; Bœuf, Gilles

doi:10.1016/s1546-5098(06)25006-4

Cited by 35 publications

(69 citation statements)

References 198 publications

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“…Teleost fish have two different genes encoding for AANAT: aanat1 and aanat2 . However, at least in pike and rainbow trout only the aanat2 gene is expressed in the pineal organ, with no orthologue in other vertebrate classes (Falcón et al, 2007a). The aanat2 expression has been shown to follow daily variations, with the higher values occurring during the scotophase , and presumably it is involved in pineal organ melatonin synthesis.…”

Section: Discussionmentioning

confidence: 99%

“…This hormone is not stored and its plasma concentration reflects the synthesizing capacity of the gland, which is higher during darkness (Falcón, 1999). Daily rhythms of circulating melatonin are believed to entrain the temporal co-ordination of a number of physiological processes associated with daily and seasonal rhythms, including locomotor and feeding behaviours, reproduction and smoltification, among others (Porter et al, 1998;Bromage et al, 2001;López-Olmeda et al, 2006;Falcón et al, 2007a;Falcón et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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Changes in plasma melatonin levels and pineal organ melatonin synthesis following acclimation of rainbow trout (Oncorhynchus mykiss) to different water salinities

López‐Patiño

Rodrı́guez-Illamola

Gesto

et al. 2011

Journal of Experimental Biology

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SUMMARYMelatonin has been suggested to play a role in fish osmoregulation, and in salmonids has been related to the timing of adaptive mechanisms during smolting. It has been described that acclimation to different environmental salinities alters levels of circulating melatonin in a number of fish species, including rainbow trout. However, nothing is known regarding salinity effects on melatonin synthesis in the pineal organ, which is the main source of rhythmically produced and secreted melatonin in blood. In the present study we have evaluated, in rainbow trout, the effects of acclimation to different salinities on day and night plasma melatonin values and pineal organ melatonin synthesis. Groups of freshwater (FW)-adapted rainbow trout were placed in tanks with four different levels of water salinity (FW, 6, 12, 18 p.p.t.; parts per thousand) and maintained for 6h or 5days. Melatonin content in plasma and pineal organs, as well as the pineal content of serotonin (5-HT) and its main oxidative metabolite (5-hydroxyindole-3-acetic acid; 5-HIAA) were measured by high performance liquid chromatography. In addition, day-night changes in pineal organ arylalkylamine N-acetyltransferase (AANAT2) activity and aanat2 gene expression were studied. Plasma osmolalities were found to be higher in rainbow trout exposed to all salinity levels compared with the control FW groups. A salinity-dependent increase in melatonin content was found in both plasma and pineal organs. This effect was observed during the night, and was related to an increase in aanat2 mRNA abundance and AANAT2 enzyme activity, both of which also occurred during the day. Also, the levels of indoles (5-HT, 5-HIAA) in the pineal organ were negatively affected by increasing water salinity, which seems to be related to the higher recruitment of 5-HT as a substrate for the increased melatonin synthesis. A stimulatory effect of salinity on pineal aanat2 mRNA expression was also identified. These results indicate that increased external salinity promotes melatonin synthesis in the pineal organ of rainbow trout by enhancing synthesis of AANAT protein independently of its regulation by light. The possibility that pineal melatonin is a target for hormones involved in the response of fish to osmotic challenge is discussed, as well as the potential role of melatonin in the timing of osmoregulatory processes.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Changes in plasma melatonin levels and pineal organ melatonin synthesis following acclimation of rainbow trout (Oncorhynchus mykiss) to different water salinities

López‐Patiño

Rodrı́guez-Illamola

Gesto

et al. 2011

Journal of Experimental Biology

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“…Melatonin from the pineal gland is a hormonal messenger of daily and annual day-night cycles (photoperiod), and is released at night into the blood and cerebrospinal fluid. Melatonin is produced from serotonin in two enzymatic steps: arylalkylamine N-acetyltransferase (AANAT; EC 2.3.1.87) catalyzes the conversion of serotonin into N-acetylserotonin, which is then methylated by hydroxyindole-Omethyltransferase (HIOMT; EC 2.1.1.4) to produce melatonin (Falcón, 1999;Falcón et al, 2007;Klein et al, 1997). Variations in pineal AANAT activity are responsible for the rhythmic secretion of melatonin.…”

Section: Introductionmentioning

confidence: 99%

“…Variations in pineal AANAT activity are responsible for the rhythmic secretion of melatonin. Teleosts possess two AANAT subfamilies, AANAT1 and AANAT2, which are preferentially expressed in the retina and the pineal gland, respectively (Falcón, 1999;Falcón et al, 2007). The existence of multiple AANATs in teleosts is likely to result from a whole genome duplication that occurred shortly after the divergence of teleosts from the main tetrapod lineage (Volff, 2005).…”

Section: Introductionmentioning

confidence: 99%

Unique arylalkylamine N-acetyltransferase-2 polymorphism in Salmonids and profound variations in thermal stability and catalytic efficiency conferred by two residues

Cazaméa-Catalan

Magnanou

Helland

et al. 2013

Journal of Experimental Biology

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SUMMARYMelatonin contributes to synchronizing major biological and behavioral functions with cyclic changes in the environment. Arylalkylamine N-acetyltransferase (AANAT) is responsible for a daily rhythm in melatonin secretion. Teleost possess two enzyme forms, AANAT1 and AANAT2, preferentially expressed in the retina and the pineal gland, respectively. The concomitant action of light and temperature shapes the daily and seasonal changes in melatonin secretion: the former controls duration while the latter modulates amplitude. Investigating the respective roles of light and temperature is particularly relevant in the context of global warming, which is likely to affect the way fish decode and anticipate seasonal changes, with dramatic consequences on their physiology and behavior. Here we investigated the impact of temperature on pineal melatonin secretion of a migratory species, the Arctic charr (Salvelinus alpinus), the northernmost living and cold-adapted salmonid. We show that temperature directly impacts melatonin production in cultured pineal glands. We also show that one organ expresses two AANAT2 transcripts displaying high similarity between them and with trout Oncorhynchus mykiss AANAT2, differing by only two amino acid sites. We compared the kinetics and 3D models of these enzymes as well as of a chimeric construct, particularly with regard to their response to temperature. Our study brings interesting and new information on the evolutionary diversity of AANAT enzymes in teleosts and the role played by specific residues in the catalytic properties of the enzymes.

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“…In fish, photosensitive and multioscillatory units have been identified in nervous and peripheral tissues [5]. However, there is evidence that the master circadian clocks are located in photoreceptor cells of the eyes and pineal organ [6,7] and perhaps in the hypothalamus, the nuclei of which receive nonvisual input from the retina [8][9][10][11] (Figure 1a). The relative strength and coupling of each of these 'oscillators' is species dependent [12].…”

Section: Introductionmentioning

confidence: 99%