Effect of melatonin in the antioxidant defense system in the locomotor muscles of the estuarine crab Neohelice granulata (Decapoda, Brachyura)

Effects of Photoperiod on Survival, Growth, Physiological, and Biochemical Indices of Redclaw Crayfish (Cherax quadricarinatus) Juveniles

Through a 30-day experiment, this study investigated the effects of five photoperiods (0L:24D, 6L:18D, 12L:12D, 18L:6D, and 24L:0D) on the survival, enzyme activity, body color, and growth-related gene expression of redclaw crayfish (Cherax quadricarinatus) juveniles. The results showed that C. quadricarinatus juveniles under 18L:6D and 24L:0D photoperiods exhibited the highest survival rate, which was significantly higher than the survival rates of juveniles under the other three photoperiods (p < 0.05). However, the 0L:24D group had the highest final body weight and weight gain rate, significantly surpassing those of the 12L:12D, 18L:6D, and 24L:0D groups (p < 0.05). Regarding enzyme activity and hormone levels, juveniles under the 18L:6D photoperiod exhibited relatively higher activity of superoxide dismutase (SOD), acid phosphatase (ACP), and lysozyme (LZM) enzymes than those under other photoperiods, but their levels of melatonin and cortisol were relatively low. In addition, the 24L:0D group showed the highest malondialdehyde (MDA) content. Analysis of gene expression levels revealed that retinoid X receptor (RXR) and α-amylase (α-AMY) genes in C. quadricarinatus juveniles exhibited significantly higher expression levels under the 18L:6D photoperiod than those under the other four photoperiods (p < 0.05). With increasing daylight exposure, the body color of C. quadricarinatus changed from pale blue to yellow-brown. In summary, C. quadricarinatus juveniles achieved high survival rates, good growth performance, strong antioxidant stress response, and immune defense capabilities under an 18 h photoperiod. Therefore, in the industrial seedling cultivation of redclaw crayfish, it is recommended to provide 18 h of daily light. Further, the study demonstrated the ability to manipulate the body color of C. quadricarinatus through controlled artificial photoperiods. These findings provide essential technical parameters needed for the industrial cultivation of C. quadricarinatus juveniles.

Metabolic changes in antennal glands of Caribbean spiny lobsters Panulirus argus infected by Panulirus argus virus 1 (PaV1)

Panulirus argus virus 1 (PaV1) (Family Mininucleoviridae) causes chronic and systemic infection in wild juvenile spiny lobsters Panulirus argus (Latreille, 1804), ending in death by starvation and metabolic wasting. In marine decapods, the antennal gland is involved in osmoregulation and excretion. In this compact organ, fluid is filtered from the hemolymph, and ions are reabsorbed to produce a hypotonic urine. Although PaV1 is released with the urine in infected individuals, little is known regarding the metabolic effect of PaV1 in the antennal gland. The objective of this study was to perform a comparative evaluation of the metabolic profile of the antennal gland of clinically PaV1-infected lobsters versus those with no clinical signs of infection, using proton nuclear magnetic resonance analysis. Overall, 48 compounds were identified, and the most represented metabolites were those involved in carbohydrate, amino acid, energy, and nucleotide metabolism. Most of the metabolites that were down-regulated in the infected group were essential and non-essential amino acids. Some metabolites involved in the urea cycle and carbohydrate metabolism were also altered. This study represents a first approach to the metabolic evaluation of the antennal gland. We broadly discuss alterations in the content of several proteinogenic and non-proteinogenic amino acids and other key metabolites involved in energetic and nucleotide metabolism.

CasEcR and CasMIH Genes in the Blue Crab, Callinectes sapidus: A Temporal Evaluation and Melatonin Effects

Environmental cues synchronize endogenous rhythms of many physiological processes such as hormone synthesis and secretion. Little is known about the diurnal pattern of hormones and gene expression of the Callinectes sapidus molt cycle. We aimed to investigate in the eyestalk and hepatopancreas of premolt and intermolt C. sapidus the following parameters: 1) the diurnal expression of the ecdysteroid receptor CasEcR isoforms, and the molt inhibiting hormone CasMIH; 2) the diurnal hemolymph ecdysteroid and melatonin levels; and 3) melatonin effects on the transcripts of the above-mentioned genes in intermolt C. sapidus. Ecdysteroid levels were higher in the premolt than the intermolt animals at all time points evaluated (ZTs). Premolt crabs displayed a variation of ecdysteroid concentration between time points, with a reduction at ZT17. No difference in the melatonin level was seen in either molt stage or between stages. In the eyestalk of intermolt animals, CasEcR expression oscillated, with a peak at ZT9, and premolt crabs have a reduction at ZT9; CasMIH transcripts did not vary along 24 h in either molt stage. Moreover, the evaluated eyestalk genes were more expressed at ZT9 in the intermolt than the premolt crabs. In the hepatopancreas, CasEcR expression showed a peak at ZT9 in premolt crabs. Exogenous melatonin (10⁻⁷ mol/animal) reduced the expression of both genes in the eyestalk at ZT17. In the hepatopancreas, melatonin markedly increased the expression of the CasEcR gene at ZT9. Taken altogether, our results are pioneer in demonstrating the daily oscillation of gene expression associated to molt cycle stages, as well as the daily ecdysteroid and melatonin levels and the remarkable influence of melatonin on the molt cycle of C. sapidus.

Experimental effects of cadmium on physiological response of Callinectes danae (Crustacea, Portunidae) from environments with different levels of Cd contamination

Cadmium (Cd) can adversely affect aquatic life, altering reproductive and molting processes in crustaceans. The objective of this study was to evaluate the influence of Cd on reproduction and molting in the crab Callinectes danae. Adult females were obtained from environments with different levels of pollution: low (LC), medium (MC), and high contaminated (HC) areas. Animals from LC, MC, and HC areas were exposed to 0, 0.5, and 2 mg L^-1 of CdCl₂ for 3 h. Cd bioaccumulation, oxidative stress (evaluated by antioxidant enzymes activity), and lipid peroxidation (LPX) were analyzed in mature ovaries (stage II), gills, and hepatopancreas. The expression levels of crustacean hyperglycemic hormone (CHH) and molt-inhibiting hormone (MIH) genes were quantified in the eyestalks, while 17β-estradiol (E2) and melatonin concentration were measured in the hemolymph. Cd bioaccumulated mainly in the hepatopancreas and gills, with increased E2, LPX, and antioxidant enzymes in HC compared to the LC region. Decreased CHH and MIH transcripts were observed in the animals from HC regions compared to LC and MC areas. Physiological differences were recorded, especially for bioaccumulation, oxidative stress, and hormone levels, in animals sampled in HC areas compared to LC and MC regions. In conclusion, the physiological damage triggered by Cd could be reduced due to higher levels of melatonin and antioxidant enzymes in HC areas.

Modulation of Crustacean Innate Immune Response by Amino Acids and Their Metabolites: Inferences From Other Species

Aquaculture production of crustaceans (mainly shrimp and crabs) has expanded globally, but disease outbreaks and pathogenic infections have hampered production in the last two decades. As invertebrates, crustaceans lack an adaptive immune system and mainly defend and protect themselves using their innate immune system. The immune system derives energy and metabolites from nutrients, with amino acids constituting one such source. A growing number of studies have shown that amino acids and their metabolites are involved in the activation, synthesis, proliferation, and differentiation of immune cells, as well as in the activation of immune related signaling pathways, reduction of inflammatory response and regulation of oxidative stress. Key enzymes in amino acid metabolism have also been implicated in the regulation of the immune system. Here, we reviewed the role played by amino acids and their metabolites in immune-modulation in crustaceans. Information is inferred from mammals and fish where none exists for crustaceans. Research themes are identified and the relevant research gaps highlighted for further studies.

Impacts of circadian rhythm and melatonin on the specific activities of immune and antioxidant enzymes of the Chinese mitten crab (Eriocheir sinensis)

Many physiological functions of crustaceans show a rhythmic change to adapt to daily environmental cycles. However, daily variation in the immune and antioxidant status and its possible correlation with circulatory melatonin levels during the daily cycle have not been reported in the Chinese mitten crab, Eriocheir sinensis. In this study, the specific activities of immune and antioxidant enzymes of E. sinensis during the 24 h cycle and its relationship with injected doses of melatonin were evaluated. The results showed that the immune parameters in the hemolymph, such as total hemolymph count, alkaline phosphatase, lysozyme, acid phosphatase, and phenol oxidase, exhibited bimodal patterns during the 24 h cycle, these parameters were synchronized with the activity of antioxidant enzymes such as malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase, and catalase. However, there was only one peak in the muscle (during 1200-1600 h) and gills (during 0400-0800 h). The survival rate reached approximately 80% in 5 days when melatonin concentrations were lower than 0.05 g/L, significantly decreasing as melatonin concentrations increased. Four hours after melatonin injection, MDA levels in the muscle and hemolymph were significantly lower than those in the control group. Eight hours after melatonin injection, SOD levels in the hemolymph were significantly higher than those in the control group. These findings highlight the importance of considering circadian regulation of innate immunity when comparing immune responses at fixed times.

Can physiological engineering/programming increase multi-generational thermal tolerance to extreme temperature events?

Organisms increasingly encounter higher frequencies of extreme weather events as a consequence of global climate change. Currently, few strategies are available to mitigate climate change effects on animals arising from acute extreme high temperature events. We tested the capacity of physiological engineering to influence the intra- and multi-generational upper thermal tolerance capacity of a model organism Artemia, subjected to extreme high temperatures. Enhancement of specific physiological regulators during development could affect thermal tolerances or life-history attributes affecting subsequent fitness. Using experimental Artemia populations we exposed F0 individuals to one of four treatments; heat hardening (28°C to 36°C, 1°C per 10 minutes), heat hardening plus serotonin (0.056 µg ml−1), heat hardening plus methionine (0.79 mg ml−1), and a control treatment. Regulator concentrations were based on previous literature. Serotonin may promote thermotolerance, acting upon metabolism and life-history. Methionine acts as a methylation agent across generations. For all groups, measurements were collected for three performance traits of individual thermal tolerance (upper sublethal thermal limit, lethal limit, and dysregulation range) over two generations. Results showed no treatment increased upper thermal limit during acute thermal stress, although serotonin-treated and methionine-treated individuals outperformed controls across multiple thermal performance traits. Additionally, some effects were evident across generations. Together these results suggest phenotypic engineering provides complex outcomes; and if implemented with heat hardening can further influence performance in multiple thermal tolerance traits, within and across generations. Potentially, such techniques could be up-scaled to provide resilience and stability in populations susceptible to extreme temperature events.

Melatonin reduces oxidative damage and upregulates heat shock protein 90 expression in cryopreserved human semen

Sperm cells can be damaged during the semen cryopreservation process, decreasing their fertilizing ability. Physical damage and oxidative stress may occur during the freeze-thawing process. Antioxidants such as the native antioxidant melatonin can potentially improve cryopreservation outcomes. In this study, we added melatonin to cryoprotectant to examine its effect on frozen-thawed human sperm. We found that adding 0.1mM melatonin to cryoprotectant significantly increased sperm viability (24.80 ± 0.46% vs. 20.97 ± 1.27%, P < 0.05) and membrane integrity (P < 0.05), and decreased intracellular reactive oxygen species and lipid peroxidation damage. Furthermore, mRNA levels of the transcription factor NF-E2-related factor-2 and its downstream genes were significantly increased. Resistance to oxidative stress was enhanced and expression of the antiapoptotic gene Bcl-2 was increased by inclusion of 0.1mM melatonin in the cryoprotectant. Moreover, 0.1mM melatonin upregulated the expression of heat shock protein 90 (HSP90), which confers resistance to stressors in frozen-thawed sperm. Results obtained upon addition of inhibitors of melatonin receptors (luzindole and 4-P-PDOT) and an HSP90 inhibitor (geldanamycin) in the cryoprotectant demonstrated that melatonin promoted HSP90 translation via the melatonin receptor MT1 and increased adenosine triphosphate levels, thus increasing the viability of thawed sperm.

Pre-treatment with melatonin decreases abamectin induced toxicity in a nocturnal insect Spodoptera litura (Lepidoptera: Noctuidae)

AIM

Oxidative stress is an important component of the mechanism of pesticide toxicity. The aim of the present study was to investigate the time-dependent melatonin effects against abamectin-induced oxidative stress in a S.litura model. Larvae were divided into 5 different groups; (1) control group,(2) Melatonin group (4.3×10^-5M/100ml diet), (3) Abamectin group 1.5ml/L, (4) Pre-melatonin treated group (PM) (4.3×10^-5M/100ml diet) before abamectin exposure 1.5ml/L, (5) Post-melatonin treated group (TM) after abamectin exposure. Melatonin was supplemented via artificial diet in PM and TM animals during 24h.

MAIN METHODS

Midgut, fatbody, and hemolymph, were collected for the analysis of oxidative stress markers (Total ROS, GSH, nitrite, TBARS, LPO), antioxidant enzyme levels (SOD, GST, CAT, POX, APOX) in fifth instar larvae. Midgut damage was examined by using morphological analysis.

KEY FINDINGS

Our results observed that ABA group showed significant changes (p<0.001) in the ROS and carbonyl content in midgut. The increase of antioxidant enzyme levels (SOD, CAT, POX, and APOX) in midgut was led by the continuous free radical scavenger cascade of melatonin. Significant (p<0.01) increases in CAT and APOX levels were seen in the fatbody of PM and TM treated insects.

SIGNIFICANCE

In conclusion, the results of the study revealed that abamectin toxicity generates oxidative stress in the insect, while pre-melatonin treatment reduces this damage due to its antioxidant properties, especially POX levels in midgut, fatbody, and hemolymph. Therefore, indoleamine can play a vital role curtailing the abamectin toxicity in time dependent manner in S.litura.

Effects of hypoxia and reoxygenation on the antioxidant defense system of the locomotor muscle of the crab Neohelice granulata (Decapoda, Varunidae)

Crustaceans often occur in areas with variations in oxygen and experience situations known as hypoxia and reoxygenation. Consequences of such situations are increased levels of reactive oxygen species. To avoid oxidative damage intertidal crabs appear to possess an efficient antioxidant defense system (ADS). However, to date, studies have not addressed the strategies that are adopted by the crabs when exposed to hypoxia/reoxygenation cycles. Towards this end we evaluated the ADS and the role of melatonin as an antioxidant in the locomotor muscle of the crab Neohelice granulata under conditions of severe hypoxia and reoxygenation. Total antioxidant capacity against peroxyl radicals and the enzymes superoxide dismutase, catalase, glutathione peroxidase (GPx), and glutathione-S-transferase as well as the key enzyme of glutathione synthesis, glutamate cysteine ligase (GCL), were evaluated. Furthermore, GSH, GSH/GSSG index as well as hemolymph and cellular melatonin levels were evaluated. During hypoxia, increased GPx and GCL activity and decreased GSH and mitochondrial melatonin levels were observed, but during reoxygenation catalase activity increased and cytosolic melatonin levels decreased. It appears that the ADS in the locomotor muscle of N. granulata exert a modulating effect when being confronted with hypoxia and reoxygenation to avoid oxidative stress. During hypoxia, the ADS appear to target GPX activity as well as GSH and mitochondrial melatonin. During reoxygenation, however, evidence suggests that catalase and cytosolic melatonin are involved in the recovery of the locomotor muscle from oxidative damage and the suppression of further damage.

Structures and functions of insect arylalkylamine N-acetyltransferase (iaaNAT); a key enzyme for physiological and behavioral switch in arthropods

The evolution of N-acetyltransfeases (NATs) seems complex. Vertebrate arylalkylamine N-acetyltransferase (aaNAT) has been extensively studied since it leads to the synthesis of melatonin, a multifunctional neurohormone prevalent in photoreceptor cells, and is known as a chemical token of the night. Melatonin also serves as a scavenger for reactive oxygen species. This is also true with invertebrates. NAT therefore has distinct functional implications in circadian function, as timezymes (aaNAT), and also xenobiotic reactions (arylamine NAT or simply NAT). NATs belong to a broader enzyme group, the GCN5-related N-acetyltransferase superfamily. Due to low sequence homology and a seemingly fast rate of structural differentiation, the nomenclature for NATs can be confusing. The advent of bioinformatics, however, has helped to classify this group of enzymes; vertebrates have two distinct subgroups, the timezyme type and the xenobiotic type, which has a wider substrate range including imidazolamine, pharmacological drugs, environmental toxicants and even histone. Insect aaNAT (iaaNAT) form their own clade in the phylogeny, distinct from vertebrate aaNATs. Arthropods are unique, since the phylum has exoskeleton in which quinones derived from N-acetylated monoamines function in coupling chitin and arthropodins. Monoamine oxidase (MAO) activity is limited in insects, but NAT-mediated degradation prevails. However, unexpectedly iaaNAT occurs not only among arthropods but also among basal deuterostomia, and is therefore more apomorphic. Our analyses illustrate that iaaNATs has unique physiological roles but at the same time it plays a role in a timezyme function, at least in photoperiodism. Photoperiodism has been considered as a function of circadian system but the detailed molecular mechanism is not well understood. We propose a molecular hypothesis for photoperiodism in Antheraea pernyi based on the transcription regulation of NAT interlocked by the circadian system. Therefore, the enzyme plays both unique and universal roles in insects. The unique role of iaaNATs in physiological regulation urges the targeting of this system for integrated pest management (IPM). We indeed showed a successful example of chemical compound screening with reconstituted enzyme and further attempts seem promising.

Antioxidant activity stimulated by ultraviolet radiation in the nervous system of a crustacean

Ultraviolet (UV) radiation can produce biological damage, principally oxidative stress, by increasing the production of reactive oxygen species (ROS). This study evaluated biochemical impairments related to the oxidative stress induced by UVA, UVB and UVA+UVB (solar simulator-SIM) in environmental doses, during five consecutive days of exposure, in the brain and eyestalk of the crab Ucides cordatus. We evaluated these regions by sampling on the 1st, 3rd and 5th days of UV exposure for lipid peroxidation (LPO), antioxidant capacity against the peroxyl radical (ACAP), and the activities of catalase (CAT), glutathione peroxidase (GPX) and glutathione-S-transferase (GST). Immunohistochemical and immunoblotting assays were performed for anti-activated-caspase 3 in the brains. After the first day of exposure, LPO increased in the eyestalks and brains of the UV-exposed animals; ACAP, and CAT, GPX and GST activities also increased in the brains. On the third day, the LPO values in the eyestalk remained high in the UV-exposed groups, while ACAP decreased in the brain and eyestalk and CAT activity remained high in all irradiated groups in both regions. On the fifth day, LPO decreased in the eyestalk and brain of the UV-exposed groups. These results may have been a consequence of the antioxidant defense system (ADS) activity, since CAT activity was high in both regions, ACAP was high in the eyestalks of the SIM group, and GPX activity remained high in the eyestalks of the UVA and UVB groups. Immunohistochemical assays and immunoblotting showed that there was apoptosis in the brains of the UV-exposed crabs. In conclusion, environmental doses of UV can cause oxidative damage to the CNS cells, including apoptosis.

Melatonin as a signaling molecule for metabolism regulation in response to hypoxia in the crab Neohelice granulata

Melatonin has been identified in a variety of crustacean species, but its function is not as well understood as in vertebrates. The present study investigates whether melatonin has an effect on crustacean hyperglycemic hormone (CHH) gene expression, oxygen consumption (VO₂) and circulating glucose and lactate levels, in response to different dissolved-oxygen concentrations, in the crab Neohelice granulata, as well as whether these possible effects are eyestalk- or receptor-dependent. Melatonin decreased CHH expression in crabs exposed for 45 min to 6 (2, 200 or 20,000 pmol·crab⁻¹) or 2 mgO₂·L⁻¹ (200 pmol·crab⁻¹). Since luzindole (200 nmol·crab⁻¹) did not significantly (p > 0.05) alter the melatonin effect, its action does not seem to be mediated by vertebrate-typical MT1 and MT2 receptors. Melatonin (200 pmol·crab⁻¹) increased the levels of glucose and lactate in crabs exposed to 6 mgO₂·L⁻¹, and luzindole (200 nmol·crab⁻¹) decreased this effect, indicating that melatonin receptors are involved in hyperglycemia and lactemia. Melatonin showed no effect on VO₂. Interestingly, in vitro incubation of eyestalk ganglia for 45 min at 0.7 mgO₂·L⁻¹ significantly (p < 0.05) increased melatonin production in this organ. In addition, injections of melatonin significantly increased the levels of circulating melatonin in crabs exposed for 45 min to 6 (200 or 20,000 pmol·crab⁻¹), 2 (200 and 20,000 pmol·crab⁻¹) and 0.7 (200 or 20,000 pmol·crab⁻¹) mgO₂·L⁻¹. Therefore, melatonin seems to have an effect on the metabolism of N. granulata. This molecule inhibited the gene expression of CHH and caused an eyestalk- and receptor-dependent hyperglycemia, which suggests that melatonin may have a signaling role in metabolic regulation in this crab.

[Some peculiarities in the manifestation of oxidative stress and current status of antioxidant system in adolescents of different age groups with obesity, complicated by insulin resistance and without it]

The study has shown that neuroendocrine obesity in adolescents is associated with the formation of oxidative stress which is more pronounced in early than in late puberty. Obesity with concomitant insulin resistance increases manifestations of oxidative stress accompanied by a compensatory increase in the activity of catabolic enzymes and reduced capacity of the defense antioxidant system in late puberty. These alterations may be caused by age-related changes in hormonal secretion under conditions of insulin resistance in late puberty.

Melatonin: neuritogenesis and neuroprotective effects in crustacean x-organ cells

Melatonin has both neuritogenic and neuroprotective effects in mammalian cell lines such as neuroblastoma cells. The mechanisms of action include receptor-coupled processes, direct binding and modulation of calmodulin and protein kinase C, and direct scavenging of free radicals. While melatonin is produced in invertebrates and has influences on their physiology and behavior, little is known about its mechanisms of action. We studied the influence of melatonin on neuritogenesis in well-differentiated, extensively-arborized crustacean x-organ neurosecretory neurons. Melatonin significantly increased neurite area in the first 24h of culture. The more physiological concentrations, 1 nM and 1 pM, increased area at 48 h also, whereas the pharmacological 1 μM concentration appeared to have desensitizing effects by this time. Luzindole, a vertebrate melatonin receptor antagonist, had surprising and significant agonist-like effects in these invertebrate cells. Melatonin receptors have not yet been studied in invertebrates. However, the presence of membrane-bound receptors in this population of crustacean neurons is indicated by this study. Melatonin also has significant neuroprotective effects, reversing the inhibition of neuritogenesis by 200 and 500 μM hydrogen peroxide. Because this is at least in part a direct action not requiring a receptor, melatonin's protection from oxidative stress is not surprisingly phylogenetically-conserved.

The effects of UV radiation on the visual system of the crab Neohelice granulata: a protective role of melatonin

The first and main target-structure of ultraviolet (UV) radiation in animals is the body surface, including the skin and eyes. Here, we investigated cell damage in the visual system of the crab Neohelice granulata acclimated to constant light and exposed to UVA or UVB at 12:00 h for 30 min. The reactive oxygen species (ROS) production, antioxidant capacity against peroxyl radicals (ACAP), lipid peroxidation (LPO) damage, catalase (CAT) activity, and the melatonin immunohistochemical reactivity in the eyestalks were evaluated. The animals that received melatonin and were exposed to UVA and UVB radiation showed a decreased ROS concentration (p<0.05).The ACAP test showed a decrease (p<0.05) in their values when the animals received 2 pmol/crab of melatonin (physiological dose) before the exposure to UVA radiation. The animals exposed to UVB radiation after receiving the same dose of melatonin showed an increase (p<0.05) in the ACAP test compared with the animals exposed to UVB radiation after receiving only crab physiological saline. The CAT activity increased (p<0.05) in the animals that received melatonin and were exposed to UVA and UVB radiation. Animals exposed to UVA and UVB displayed an increase (p<0.05) in the LPO levels, whereas animals treated with melatonin showed lower (p<0.05) LPO levels when irradiated. The results indicate that the specific oxidative parameters altered by UV radiation can be modulated by a physiological dose of melatonin. Moreover, the melatonin regularly produced by virtually all eyestalk cells suggests that it may function to modulate the noxious effects of radiation, at least in the crab N. granulata.