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Unitat de Fisiologia Animal, Departament de Biologia Cel.lular, Fisiologia i d'Immunologia, Facultat de Biociències Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona Spain1 Departament de Fisiologia, Facultat de Biologia Universitat de Barcelona, 08028, Barcelona Spain2 Great Lakes Water Institute University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, 53204 USA
(Correspondence should be addressed to L Tort; Email: lluis.tort{at}uab.cat)
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Introduction |
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Sexually immature gilthead seabream (Sparus aurata), with an average weight of 80 g, were obtained from a fish farm (Masnou, Barcelona, Spain) and maintained in a semi-closed seawater flow circuit with water at a temperature of 17 °C and a salinity of 37 % under a 12 h light:12 h darkness cycle and a density of 7 kg/m3. Blood was sampled from the caudal vein using heparinized syringes in <1 min/individual and <5 min/treatment group. Plasma was obtained by centrifugation and stored at –80 °C until analysis by RIA. To collect the seabream tissues, adult fish were killed by an excess of anesthesia (2-phenoxyethanol, (1:1000 v/v; Sigma–Aldrich, #P1126)), which is the standard method to kill fish, and the tissues were removed and immediately frozen in liquid nitrogen until analysis.
Cloning and sequencing of gilthead seabream StAR
A cDNA clone with high homology to StAR was identified in a collection of expressed sequence tags obtained from a gilthead seabream cDNA library made in 
ZAP Express III (Stratagene, Cedar Creek, TX, USA) with RNA pooled from several relevant immune tissues. This library was enriched for the sequences up-regulated after immune stimulation, and processed as described by our group (Castellana et al. personal communication). Two clones corresponding to the seabream StAR cDNA were identified, and each one was sequenced a minimum of four times in both directions using BigDye Terminator (Applied Biosystems, Foster City, CA, USA) on an ABI 3730 automated sequencer (Applied Biosystems). The full-length sequence of the StAR cDNA was obtained by overlapping the two sets of partial sequences from each clone. The sequence was confirmed by performing RT-PCR to amplify the open reading frame (ORF).
Sequence analysis
Sequence data were compiled from the National Center for Biotechnology Information (NCBI, Bethesda, MD, USA), and sequences were analyzed for similarity with other known sequences using BLAST within the ExPASy Proteomics Tools server. Alignments were performed using the Bioedit Sequence Alignment Editor (Hall 1999), which uses the CLUSTAL W algorithm (Thompson et al. 1994). The assembled full-length cDNA sequence was entered in GenBank with accession number EF640987 [GenBank] . The pI and molecular mass of seabream StAR protein were predicted using the ExPASy Proteomics Tools server of the Swiss Institute of Bioinformatics (SIB; http://www.expasy.ch/tools/; Gasteiger et al. 2003).
Analysis of StAR tissue expression
For tissue expression analysis, total RNA was isolated from a pool of tissues using Tri Reagent (Molecular Research Center Inc., Cincinnati, OH, USA) following the manufacturer's instructions. Total RNA (5 µg) was reverse transcribed with Superscript III reverse transcriptase (Invitrogen SA), according to the manufacturer's protocol. The PCRs were performed using Taq DNA polymerase (Biotools, Madrid, Spain) with 2 mM MgCl2, 800 nM primer final concentration, and 1 µl reverse-transcribed tissue RNA. The cycling conditions were as follows: 94 °C for 5 min followed by 35 cycles of 94 °C for 40 s, 59 °C for 50 s, and 72 °C for 50 s. The final step was an extension at 72 °C for 10 min. The reactions were run on 1% agarose gel and stained with ethidium bromide. Parallel RT-PCRs were carried out with specific primers against a conserved region of 18S (primers 18S forward and 18S reverse) as a control (Table 1).
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We designed an acute stress, chronic stress, and experimental infection in gilthead seabream. For the acute stress experiment, fish were chased with a net in the tank for 5 min, and sampled 1, 6, and 16 h after the stress (n=8 for each time point). Fish were killed by an excess of anesthesia (2-phenoxyethanol), and tissues and blood were obtained as described earlier. Undisturbed animals not subjected to stress were used as a control (n=8).
For the chronic stress experiments, fish (n=16) were kept for 15 days at a high density (50 kg/m3) in the tank. After that period, fish were killed by an excess of anesthesia, tissues were quickly removed and immediately frozen and blood obtained as indicated above. Undisturbed animals were used as controls (n=16).
To simulate stress by infection, a concentration of 8 mg/kg of bacterial LPS was injected intraperitoneally. Fish (n=5) were killed by an excess of anesthesia (2-phenoxyethanol) at different times (6, 12, 24, 72 h) and tissues were quickly removed and immediately frozen. Blood was sampled from the caudal vein using heparinized syringes; plasma was obtained by centrifugation and stored at –80 °C until analysis by RIA. Animals injected with saline were used as controls (n=5).
Preparation of head kidney cells and in vitro assays
Gilthead seabream head kidney cells were isolated and cultured by adapting the protocol previously described for trout macrophages (Mackenzie et al. 2003). Head kidneys were dissected from seabream killed by overanesthetization in 2-phenoxyethanol and placed in PBS. Tissues were finely minced with sterile scalpel blades, passed though a pipette to disperse into small aggregates, and filtered through a cell strainer (100 µM, Falcon #352360). The resulting homogenate was allowed to settle via sedimentation on culture plates and kept at 17 °C, 5% CO2 with Dulbecco's Modified Eagle Medium (Life Technologies, #11971-025) containing high glucose, 10% heat-inactivated fetal calf serum (Gibco, #16140-071), and penicillin (100 U/ml)/streptomycin (100 µg/ml; Life Technologies).
Following isolation, cells were left undisturbed for 3 h to stabilize the cortisol levels as described previously (Rotllant et al. 2001). After this period, the head kidney cells were incubated with medium with or without ACTH (150 ng/ml) for 1, 2, 6, and 18 h. In order to check the specificity of ACTH effects on StAR gene stimulation, in another experiment we incubated the head kidney preparations with ACTH and ACTH plus 1 µM corticotropin-inhibiting peptide (CIP; Sigma–Aldrich, #A1527), an ACTH antagonist that binds to ACTH receptor without activating its signal transduction, and therefore blocking ACTH effects.
In another set of experiments, cells were incubated in medium with or without LPS (10 µg/ml) for 1, 2, 6, and 16 h. Each time condition was replicated six times on a six-well culture plate. After incubation, medium was removed, pooled for each condition, and frozen immediately for cortisol determination, and total RNA was isolated with TRI reagent following the manufacturer's instructions and pooled.
Quantitative real-time PCR
The cDNAs from the seabream tissue and head kidney preparations were used for quantitative PCR analysis using SYBR Green PCR Supermix (Bio-Rad). Results were evaluated with the ICYCLER IQ real-time detection system software (Bio-Rad). The sequences of the primers used in gene expression analysis are presented in Table 1. The total volume (20 µl) of every reaction contained 500 nM of each amplification primer, 10 µl 2xSYBR Green PCR Mix, and 5 µl of a 1:100 dilution of cDNA (1:1000 for 18S determination). Products were amplified in an ICycler IQ Real Time PCR Detection System (Bio-Rad Laboratories). Controls lacking cDNA and controls containing RNA were included. The real-time analysis consisted of 1 cycle of 95 °C for 5 min, 40 cycles of 95 °C for 10 s and 60 °C for 30 s, 1 cycle of 95 °C for 1 min, 1 cycle of 55 °C for 1 min, and a melting curve of 81 cycles (from 55 °C to 95 °C). All samples were run in triplicate and fluorescence was measured at the end of every extension step. Threshold cycle (Ct) values for each sample were expressed as ‘fold differences’, calculated relative to untreated controls and normalized to endogenous control 18S rRNA.
Cortisol measurements
For cortisol measurements, the samples were kept frozen at –20 °C until assays could be performed. Cortisol levels were measured both in plasma samples from adult fish and the culture media of head kidney cells by an RIA method (RIA) according to Rotllant et al. (2001). The antibody used for the assay was purchased from Biolink, SL (Costa Mesa, CA, USA) in a final dilution of 1:6000. Antibody cross-reactivity with cortisol is 100%. The radioactivity was quantified using a liquid scintillation counter.
Statistical analysis
For gene expression quantification by real-time PCR on in vitro assays, total RNA was pooled from six different wells for each treatment and analyzed in triplicate. Statistical significance was analyzed by one-way ANOVA followed by Tukey's post hoc test, using the software package SPSS (Chicago, IL, USA) for Windows. Differences were considered significant when P<0.05. All cortisol measurements were performed using medium of six wells per experiment on in vitro experiments and eight animals per condition on in vivo assays, and its statistical significance was analyzed by one-way ANOVA followed by Fisher's LSD post hoc test. Differences were considered significant when P<0.05.
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Results |
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A gilthead seabream (S. aurata) cDNA library made in ZAP Express III (Stratagene) from several relevant immune sources was used to clone the steroidogenic acute regulatory protein, StAR (GenBank accession number EF640987
[GenBank]
). The 1461 bp StAR full cDNA contains a 123 bp 5' UTR, an 861 bp ORF and a 477 bp 3' UTR.
Deduced amino acid sequence analysis
The S. aurata StAR gene encodes a 286 amino acid protein, which has a predicted molecular mass of 32 kDa and a pI of 9. Amino acid analysis was performed to determine the relatedness of gilthead seabream StAR to StARs from other fish (Fig. 1). At the amino acid level, seabream StAR shows the highest sequence identity to StAR protein from black bass (94%), whereas identity with rainbow trout (87%) is lower. On the other hand, seabream StAR shows about 69% identity with other vertebrate StARs, such as birds and amphibians, and a 66% sequence identity with human StAR.
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Primer sequences used in the PCR studies are shown in Table 1. Using RT-PCR, we found the StAR gene to be expressed in head kidneys and gonads. The basal expression of StAR was higher in head kidney than in gonads, and the rest of tissues showed no StAR gene expression (Fig. 2). In addition, we found no expression in muscle samples (data not shown).
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When the seabream head kidney cells were incubated with 150 ng/ml ACTH, cortisol levels in the incubation media dramatically rose after 1 h (5553% of control). After 6 h, cortisol levels were lower, although still higher than control levels (628% of control; Fig. 6B). The StAR mRNA levels measured by quantitative real-time PCR increased in ACTH-stimulated cells at 1 h (about threefold the control levels). However, after 6 h of incubation, StAR mRNA levels were lower compared with controls (Fig. 6A).
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Discussion |
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We have found StAR mRNA to be expressed in the head kidney and gonads. This finding is in agreement with previous data in several fish species where StAR is mainly expressed in the steroidogenic tissues (Bauer et al. 2000, Li et al. 2003, Goetz et al. 2004), although it is in contraposition to the results obtained in other species, where StAR mRNA expression has been described in extragonadal and extra-adrenocortical tissues, such as the brain and heart of the freshwater stingray (Nunez et al. 2005); the kidney of Atlantic croacker (Nunez & Evans 2007); the intestine, pyloric ceca, spleen, and kidney of trout (Kusakabe et al. 2002); human fetal and adult kidney (Sugawara et al. 1995); and several areas of the human brain (King et al. 2002). Therefore, StAR tissue distribution can be slightly different according to the species, and its role in these other tissues remains to be clarified.
We applied two different types of stressors (acute stress caused by chasing the fish with a net and a chronic stress by overcrowding) that caused a significant increase in the plasma cortisol levels of stressed fish compared with undisturbed fish. In the case of the acute stress, this increase was rapid and fish reached the highest cortisol levels between 1 and 6 h. After that period, cortisol levels decreased, although they were still higher than controls 16 h after the stressor. This kinetic profile is in accordance with the previously published data on salmonid fish (Pickering et al. 1982, Patino et al. 1987, Geslin & Auperin 2004) and white sucker (Bandeen & Leatherland 1997). StAR levels in our experiment did not increase significantly at any time post-stressor, a result also obtained by Geslin & Auperin (2004) in rainbow trout, who found no increase in StAR expression in the head kidney of fish chased with a net for 5 min. By contrast, these authors found that a stronger acute stress induced by anesthesia provoked a higher increase (30-fold) of cortisol levels in plasma and an increase in StAR mRNA levels in head kidney, a finding that led the authors to suggest that high levels of cortisol after stress require an activation of StAR gene, although lower levels do not. However, in the present experiment, plasma cortisol levels in stressed fish increased 160-fold, which is a very high value (about five times higher than in trout; Geslin & Auperin 2004), yet the StAR mRNA levels did not increase significantly over controls. This suggests that, although seabream is highly responsive to acute stress (as shown by cortisol levels), the StAR expression in head kidney could be regulated differently and the rise in plasma cortisol levels may be due to a different mechanism rather than increased gene transcription. For example, it is well known in mammals that StAR protein could be regulated post-transcriptionally (Fleury et al. 1998), translationally (reviewed by Stocco 1999), and/or post-translationally via serine phosphorylation by a PKA, which also results in the activation of StAR protein (Lehoux et al. 1998, Miller & Strauss 1999, Artemenko et al. 2001).
When we exposed seabream to high density for 2 weeks, the cortisol levels in the plasma increased dramatically (threefold), a result that agrees with those obtained by other authors for many other fish species, since a prolonged elevation of plasma cortisol levels is frequently used as a marker for exposure to a chronic stressor, with the magnitude of the cortisol response generally reflecting the severity of the stressor (reviewed by Wendelaar Bonga 1997). In addition, we found that StAR mRNA levels in the head kidney of chronically stressed animals were increased threefold over controls. Interestingly, when we analyzed StAR gene expression on an individual basis, we found that some of them had much higher StAR mRNA levels and cortisol plasma levels than others (data not shown), which may correlate with the already demonstrated fact that socially subordinated individuals in small groups of fish show higher circulating cortisol levels, and therefore more stress than others (Winberg & Lepage 1998, Hoglund et al. 2000). This may be an interesting implication of StAR as a marker of fish behavior and stress. Further studies will be undertaken in this area.
We have been able to demonstrate strong in vitro effects of ACTH on mRNA levels of StAR in seabream head kidney. In the time-course experiment with seabream head kidney preparations, we found an important increase in StAR mRNA levels 1 h after treatment with 150 ng/ml ACTH, and no effect thereafter. As expected, cortisol levels were also elevated after 1 h and returned to normal levels after 18 h of incubation with ACTH (data not shown). ACTH stimulated the StAR gene expression in the seabream head kidney preparations by binding to its specific membrane receptors, as demonstrated when 1 µM CIP, an antagonist of the ACTH receptor (Li et al. 1978), effectively blocked the ACTH-stimulated StAR expression in our in vitro model, without affecting the basal levels of StAR expression. The rapid increase in cortisol levels, which we observed after ACTH treatment, is in agreement with several previous studies conducted under various experimental conditions (Donaldson 1981, Nichols & Weisbart 1984, Girard et al. 1998, Pottinger & Carrick 2001, Hagen et al. 2006). It also agrees with the previous data found in the same species, S. aurata, in our laboratory (Rotllant et al. 2001, Ganga et al. 2006) showing that ACTH caused a rapid increase in cortisol levels in superfused head kidney tissue. In addition, our results on StAR expression correlate with data from mammals showing that acute in vivo or in vitro treatment with ACTH leads to a rapid and significant increase (between 1 and 3 h after the treatment) in StAR mRNA in the adrenals (Ariyoshi et al. 1998, Fleury et al. 1998, Lehoux et al. 1998, Ivell et al. 2000, Le Roy et al. 2000). The results are also similar to other fish species, such as eel, where Li et al. (2003) found that ACTH injection increased StAR mRNA levels 1.5 h post-injection, and in trout, where Aluru et al. (2005) reported a 170% increase in interrenal StAR transcripts in response to 0.5 IU/ml ACTH after 3 h of incubation. Interestingly, recently, Hagen et al. (2006) found no rapid stimulation of StAR mRNA levels in the rainbow trout head kidney interrenal cells. They reported only a late effect after 18 h, although they used the same ACTH concentration (150 ng/ml) which they found produced the strongest peak in cortisol production.
LPS injection is the most frequently used acute stress model to mimic the fish response to an immune stressor (Balm et al. 1995, Balm 1997, Mackenzie et al. 2005). When we injected seabream with 8 mg/kg i.p. of bacterial endotoxin to induce infection, it provoked a marked rise in plasma cortisol levels similar to those previously described (Balm et al. 1995, Holland et al. 2002) and to the results previously reported (Acerete et al. 2007). This produced a cortisol peak after 6 h (threefold the controls) and a progressive decrease in cortisol until 72 h, which are similar to the results reported in rats (Grinevich et al. 2001) where a single LPS injection stimulated plasma cortisol levels. LPS injection also increased StAR gene expression in our in vivo seabream head kidney model and, together, these results confirm the previously described important role of immunoendocrine interactions in the head kidney of fish (Schreck & Bradford 1990, Weyts et al. 1999).
In contrast with the stimulatory effects of LPS in vivo, we found inhibitory effects of LPS (10 µg/ml) on in vitro cortisol production in a head kidney preparation. This is in agreement with the previous studies where LPS was not able to increase cortisol production in head kidneys (Balm et al. 1995). These authors reported that LPS (50 µg/ml) decreased the ACTH-stimulated cortisol production without being toxic to the head kidney preparations, an inhibitory effect that we observed as well. In addition, LPS incubation caused a decrease in StAR mRNA levels in the head kidney preparations, coincident with the reduction in cortisol levels that we observed. Therefore, it appears that the effects of LPS treatment may differ significantly from in vitro or in vivo treatments. Whereas in vivo, an experimental infection invokes a systemic reaction in which not only immune responses are generated but also neural and endocrine signals, both from pituitary sources and interrenal tissue; LPS administered in vitro may interfere with the local cortisol production or secretion mechanisms. One may speculate that in vivo either pituitary signals prevail in the interrenal tissue in the presence of the LPS or that circulating immune signals such as cytokines resulting from an experimental infection do not significantly affect the function of the HPI axis. Therefore, more work is in progress regarding these effects.
In conclusion, we have isolated a cDNA from seabream that encodes a protein very similar in form and function to StAR in other vertebrates. It is expressed in head kidney and gonads, and while fish under acute stress showed increased cortisol levels but no changes in StAR mRNA expression, a chronic stress provoked a marked increase in StAR expression and cortisol levels. Moreover, ACTH caused a rapid increase in cortisol and StAR mRNA levels in the head kidney cells in vitro, whereas LPS infection stimulated StAR expression in vivo but was inhibitory in vitro. All these data together show that seabream StAR expression and cortisol production in interrenal cells can be highly affected by different stress conditions (acute/chronic as well as stress by infection) and provides new data on the important relationship between the immune and endocrine systems in fish.
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Acknowledgements |
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References |
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Aluru N, Renaud R, Leatherland JF & Vijayan MM 2005 Ah receptor-mediated impairment of interrenal steroidogenesis involves StAR protein and P450scc gene attenuation in rainbow trout. Toxicological Sciences 84 260–269.
Arakane F, Sugawara T, Nishino H, Liu Z, Holt JA, Pain D, Stocco DM, Miller WL & Strauss JF 1996 Steroidogenic acute regulatory protein (StAR) retains activity in the absence of its mitochondrial import sequence: implications for the mechanism of StAR action. PNAS 93 13731–13736.
Arakane F, King SR, Du Y, Kallen CB, Walsh LP, Watari H, Stocco DM & Strauss JF 1997 Phosphorylation of steroidogenic acute regulatory protein (StAR) modulates its steroidogenic activity. Journal of Biological Chemistry 272 32656–32662.
Ariyoshi N, Kim YC, Artemenko I, Bhattacharyya KK & Jefcoate CR 1998 Characterization of the rat Star gene that encodes the predominant 3.5-kilobase pair mRNA. ACTH stimulation of adrenal steroids in vivo precedes elevation of Star mRNA and protein. Journal of Biological Chemistry 273 7610–7619.
Artemenko IP, Zhao D, Hales DB, Hales KH & Jefcoate CR 2001 Mitochondrial processing of newly synthesized steroidogenic acute regulatory protein (StAR), but not total StAR, mediates cholesterol transfer to cytochrome P450 side chain cleavage enzyme in adrenal cells. Journal of Biological Chemistry 276 46583–46596.
Balm PHM 1997 Immune–endocrine interactions. In Fish Stress and Health in Aquaculture , pp 195–221. Eds GK Iwama, AD Pickering, JP Sumpter, CB Schreck & NM Ruane. Cambridge, UK: Cambridge University Press.
Balm PHM, van Lieshout E, Lokate J & Wendelaar-Bonga SE 1995 Bacterial lipopolysaccharide (LPS) and interleukin 1 (IL-1) exert multiple physiological effects in the tilapia Oreochromis mossambicus (Teleostei). Journal of Comparative Physiology. B 165 85–92.[CrossRef][Medline]
Bandeen A & Leatherland JF 1997 Transportation and handling stress of white suckers raised in cages. Aquaculture International 5 385–396.[CrossRef][Web of Science]
Bauer MP, Bridgham JT, Langenau DM, Johnson AL & Goetz FW 2000 Conservation of steroidogenic acute regulatory (StAR) protein structure and expression in vertebrates. Molecular and Cellular Endocrinology 168 119–125.[CrossRef][Web of Science][Medline]
Carsia RV & John-Alder H 2003 Seasonal alterations in adrenocortical cell function associated with stress-responsiveness and sex in the eastern fence lizard (Sceloporus undulatus). Hormones and Behavior 43 408–420.[CrossRef][Medline]
Carsia RV, Scanes CG & Malamed S 1984 Self-suppression of corticosteroidogenesis: evidence for a role of adrenal 5 alpha-reductase. Endocrinology 115 2464–2472.
Clark BJ, Wells J, King SR & Stocco DM 1994 The purification, cloning, and expression of a novel luteinizing hormone-induced mitochondrial protein in MA-10 mouse Leydig tumor cells. Characterization of the steroidogenic acute regulatory protein (StAR). Journal of Biological Chemistry 269 28314–28322.
Clark BJ, Soo SC, Caron KM, Ikeda Y, Parker KL & Stocco DM 1995 Hormonal and developmental regulation of the steroidogenic acute regulatory protein. Molecular Endocrinology 9 1346–1355.
Donaldson EM 1981 The pituitary–interrenal axis as an indicator of stress in fish. In Stress in Fish , pp 11–47. Eds AD Pickering. New York: Academic Press Co.
Fleury A, Cloutier M, Ducharme L, Lefebvre A, LeHoux J & LeHoux JG 1996 Adrenocorticotropin regulates the level of the steroidogenic acute regulatory (StAR) protein mRNA in hamster adrenals. Endocrine Research 22 515–520.[Web of Science][Medline]
Fleury A, Ducharme L & Lehoux JG 1998 In vivo effects of adrenocorticotrophin on the expression of the hamster steroidogenic acute regulatory protein. Journal of Molecular Endocrinology 21 131–139.[Abstract]
Ganga R, Tort L, Acerete L, Montero D & Izquierdo MS 2006 Modulation of ACTH-induced cortisol release by polyunsaturated fatty acids in interrenal cells from gilthead seabream, Sparus aurata. Journal of Endocrinology 190 39–45.
Gasteiger E, Gattiker A, Hoogland C, Ivanyi I, Appel RD & Bairoch A 2003 ExPASy: the proteomics server for in-depth protein knowledge and analysis. Nucleic Acids Research 31 3784–3788.
Geslin M & Auperin B 2004 Relationship between changes in mRNAs of the genes encoding steroidogenic acute regulatory protein and P450 cholesterol side chain cleavage in head kidney and plasma levels of cortisol in response to different kinds of acute stress in the rainbow trout (Oncorhynchus mykiss). General and Comparative Endocrinology 135 70–80.[CrossRef][Web of Science][Medline]
Girard C, Brodeur JC & Hontela A 1998 Responsiveness of the interrenal tissue of yellow perch (Perca flavescens) from contaminated sites to an ACTH challenge test in vivo. Canadian Journal of Fisheries and Aquatic Sciences 55 438–450.
Goetz FW, Norberg B, McCauley L & Iliev DB 2004 Characterization of the cod (Gadus morhua) steroidogenic acute regulatory protein (StAR) sheds light on StAR gene structure in fish. Comparative Biochemistry and Physiology, Part B 137 351–362.[CrossRef]
Grinevich V, Ma XM, Herman JP, Jezova D, Akmayev I & Aguilera G 2001 Effect of repeated lipopolysaccharide administration on tissue cytokine expression and hypothalamic–pituitary–adrenal axis activity in rats. Journal of Neuroendocrinology 13 711–723.[CrossRef][Web of Science][Medline]
Hagen IJ, Kusakabe M & Young G 2006 Effects of ACTH and cAMP on steroidogenic acute regulatory protein and P450 11beta-hydroxylase messenger RNAs in rainbow trout interrenal cells: relationship with in vitro cortisol production. General and Comparative Endocrinology 145 254–262.[CrossRef][Web of Science][Medline]
Hall TA 1999 BioEdit: a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. Nucleic Acids Symposium Series 41 95–98.
Hoglund E, Balm PH & Winberg S 2000 Skin darkening, a potential social signal in subordinate arctic charr (Salvelinus alpinus): the regulatory role of brain monoamines and pro-opiomelanocortin-derived peptides. Journal of Experimental Biology 203 1711–1721.[Abstract]
Holland JW, Pottinger TG & Secombes CJ 2002 Recombinant interleukin -1β activates the hypothalamic–pituitary–interrenal axis in rainbow trout, Oncorhynchus mykiss. Journal of Endocrinology 175 261–267.[Abstract]
Ivell R, Tillman G, Wang H, Nicol M, Stewart PM, Bartlick B, Walther N, Mason JL & Morley SD 2000 Acute regulation of the bovine gene for the steroidogenic acute regulatory protein in ovarian theca and adrenocortical cells. Journal of Molecular Endocrinology 24 109–118.[Abstract]
Kallen CB, Arakane F, Christenson LK, Watari H, Devoto L & Strauss JF 1998 Unveiling the mechanism of action and regulation of the steroidogenic acute regulatory protein. Molecular and Cellular Endocrinology 145 39–45.[CrossRef][Web of Science][Medline]
King SR, Manna PR, Ishii T, Syapin PJ, Ginsberg SD, Wilson K, Walsh LP, Parker KL, Stocco DM, Smith RG et al. 2002 An essential component in steroid synthesis, the steroidogenic acute regulatory protein, is expressed in discrete regions of the brain. Journal of Neuroscience 22 10613–10620.
Klingbeil CK 1985 Corticosterone and aldosterone dose-dependent responses to ACTH and angiotensin II in the duck (Anas platyrhynchos). General and Comparative Endocrinology 59 382–390.[CrossRef][Web of Science][Medline]
Kusakabe M, Todo T, McQuillan HJ, Goetz FW & Young G 2002 Characterization and expression of steroidogenic acute regulatory protein and MLN64 cDNAs in trout. Endocrinology 143 2062–2070.
Lehoux JG, Fleury A & Ducharne L 1998 The acute and chronic stress effects of adrenocorticotropin on the levels of messenger ribonucleic acid and protein of steroidogenic enzymes in rat adrenal in vivo. Endocrinology 139 3913–3922.
Lehoux JG, Mathieu A, Lavigne P & Fleury A 2003 Adrenocorticotropin regulation of steroidogenic acute regulatory protein. Microscopy Research and Technique 15 288–299.
Li CH, Chung D, Yamashiro D & Lee CY 1978 Isolation, characterization and synthesis of a corticotrophin-inhibiting peptide from human pituitary glands. PNAS 75 4306–4309.
Li YY, Inoue K & Takei Y 2003 Steroidogenic acute regulatory protein in eels: cDNA cloning and effects of ACTH and seawater transfer on its mRNA expression. Zoological Science 20 211–219.[CrossRef][Web of Science][Medline]
Liu J, Heikkila P, Kahri AI & Voutilainen R 1996 Expression of the steroidogenic acute regulatory protein mRNA in adrenal tumors and cultured adrenal cells. Journal of Endocrinology 150 43–50.
Mackenzie S, Planas JV & Goetz FW 2003 LPS-stimulated expression of a tumor necrosis factor-alpha mRNA in primary trout monocytes and in vitro differentiated macrophages. Developmental and Comparative Immunology 27 393–400.[CrossRef][Web of Science][Medline]
Mackenzie S, Iliev D, Liarte C, Koskinnen H, Planas JV, Goetz FW, Molsa H, Krasnov A & Tort L 2005 Transcriptional analysis of LPS-stimulated activation of trout (Oncorhynchus mykiss) monocyte/macrophage cells in primary culture treated with cortisol. Molecular Immunology 43 1340–1348.[CrossRef][Web of Science][Medline]
Miller WL 1988 Molecular biology of steroid hormone synthesis. Endocrine Reviews 9 295–318.
Miller WL & Strauss JF 1999 Molecular pathology and mechanism of action of the steroidogenic acute regulatory, StAR. Journal of Steroid Biochemistry and Molecular Biology 69 131–141.[CrossRef][Web of Science][Medline]
Netchitailo P, Lihrmann I & Vaudry H 1984 Lack of effect of dexamethasone on corticosteroid production in the amphibian. Journal of Steroid Biochemistry 21 727–731.[CrossRef][Web of Science][Medline]
Nichols DJ & Weisbart M 1984 Plasma cortisol concentrations in Atlantic salmon, Salmo salar: episodic variations, diurnal change, and short term response to adrenocorticotrophic hormone. General and Comparative Endocrinology 56 169–176.[CrossRef][Web of Science][Medline]
Nishikawa T, Sasano H, Omura M & Suematsu S 1996 Regulation of expression of the steroidogenic acute regulatory (StAR) protein by ACTH in bovine adrenal fasciculata cells. Biochemical and Biophysical Research Communications 223 12–18.[CrossRef][Web of Science][Medline]
Nunez BS & Evans AN 2007 Hormonal regulation of the steroidogenic acute regulatory protein (StAR) in gonadal tissues of the Atlantic croaker (Micropogonias undulatus). General and Comparative Endocrinology 150 495–504.[CrossRef][Web of Science][Medline]
Nunez BS, Piermarini PM, Evans AN & Applebaum SL 2005 Cloning and characterization of cDNAs encoding steroidogenic acute regulatory protein from freshwater stingrays (Potamotrygon spp). Journal of Molecular Endocrinology 35 557–569.
Patino R, Redding JM & Schreck CB 1987 Interrenal secretion of corticosteroids and plasma cortisol and cortisone concentrations after acute stress and during seawater acclimation in juvenile coho salmon (Oncorhynchus kisutch). General and Comparative Endocrinology 68 431–439.[CrossRef][Web of Science][Medline]
Pickering AD, Pottinger TG & Christie P 1982 Recovery of the brown trout, Salmo salar L., from acute handling stress: a time-course study. Journal of Fish Biology 20 229–244.[CrossRef][Web of Science]
Pottinger TG & Carrick TR 2001 ACTH does not mediate divergent stress responsiveness in rainbow trout. Comparative Biochemistry and Physiology 129A 399–404.[CrossRef][Medline]
Rotllant J, Balm PH, Perez-Sanchez J, Wendelaar-Bonga SE & Tort L 2001 Pituitary and interrenal function in gilthead seabream (Sparus aurata L., Teleostei) after handling and confinement stress. General and Comparative Endocrinology 121 333–342.[CrossRef][Web of Science][Medline]
Le Roy C, Li JY, Stocco DM, Langlois D & Saez JM 2000 Regulation of adenocorticotropin (ACTH), angiotensin II, transforming growth factor-β and insulin-like growth factor I of bovine adrenal cell steroidogenic capacity and expression of ACTH receptor, steroidogenic acute regulatory protein, cytochrome P450c17, and 3b-hydroxysteroid dehydrogenase. Endocrinology 141 1599–1607.
Sandhoff TW, Hales DB, Hales KH & McLean MP 1998 Transcriptional regulation of the rat steroidogenic acute regulatory protein gene by steroidogenic factor 1. Endocrinology 139 4820–4831.
Schreck CB & Bradford CS 1990 Interrenal corticosteroid production: potential regulation by the immune system in the salmonid. Progress in Clinical and Biological Research 342 480–486.[Medline]
Sewer MB & Waterman MR 2003 ACTH modulation of transcription factors responsible for steroid hydroxylase gene expression in the adrenal cortex. Microscopy Research and Technique 61 300–307.[CrossRef][Web of Science][Medline]
Stocco DM 1999 Steroidogenic acute regulatory (StAR) protein: what's new? BioEssays 9 768–775.
Stocco DM 2002 Clinical disorders associated with abnormal cholesterol transport: mutations in the steroidogenic acute regulatory protein. Molecular and Cellular Endocrinology 191 19–25.[CrossRef][Web of Science][Medline]
Strauss JF, Kallen CB, Christenson LK, Watari H, Devoto L, Arakane F, Kiriakidou M & Sugawara T 1999 The steroidogenic acute regulatory protein (StAR): a window into the complexities of intracellular cholesterol trafficking. Recent Progress in Hormone Research 54 369–394.[Medline]
Sugawara T, Holt JA, Driscoll D, Strauss JF, Lin D, Miller WL, Patterson D, Clancy KP, Hart IM, Clark BJ et al. 1995 Human steroidogenic acute regulatory protein: functional activity in COS-1 cells, tissue-specific expression, and mapping of the structural gene to 8p11.2 and a pseudogene to chromosome 13. PNAS 92 4778–4782.
Sugawara T, Saito M & Fujimoto S 2000 Sp1 and SF-1 interact and cooperate in the regulation of human steroidogenic acute regulatory protein gene expression. Endocrinology 141 2895–2903.
Thompson JD, Higgins DG & Gibson TJ 1994 CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice. Nucleic Acids Research 22 4673–4680.
Tsujishita Y & Hurley JH 2000 Structure and lipid transport mechanism of a StAR-related domain. Nature Structural Biology 7 408–414.[CrossRef][Web of Science][Medline]
Watari H, Arakane F, Moog-Lutz C, Kallen CB, Tomasetto C, Gerton GL, Rio MC, Baker ME & Strauss JF 1997 MLN64 contains a domain with homology to the steroidogenic acute regulatory protein (StAR) that stimulates steroidogenesis. PNAS 94 8462–8467.
Wendelaar Bonga SE 1997 The stress response in fish. Physiological Reviews 77 591–625.
Weyts FAA, Cohen N, Flik G & Verburg-van Kemenade BML 1999 Interactions between the immune system and the hypothalamo–pituitary–interrenal axis in fish. Fish and Shellfish Immunology 9 1–20.[CrossRef]
Winberg S & Lepage O 1998 Elevation of brain 5-HT activity, POMC expression, and plasma cortisol in socially subordinate rainbow trout. American Journal of Physiology 274 R645–R654.[Web of Science][Medline]
Received in final form 29 October 2007
Accepted 2 November 2007
Made available online as an Accepted Preprint 2 November 2007
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