Effect of the algal alkaloid caulerpin on neuropeptide Y (NPY) expression in the central nervous system (CNS) of Diplodus sargus.

Recent studies have suggested that Mediterranean indigenous fish species are affected by bioactive metabolites coming from marine invasive species via food web interactions. In particular, both physiological and behavioural changes in the white sea bream Diplodus sargus were related to caulerpin (CAU), a bisindolic alkaloid particularly abundant in the invasive alga Caulerpa cylindracea, on which the fish actively feed. Dietary administration of CAU decreased aggressiveness in D. sargus, suggesting an anxiolytic-like effect of CAU possibly mediated by endogenous anxiolytic agents. This hypothesis is supported here by the finding of a significant increase of NPY transcriptional expression in the brain of fish fed with CAU enriched food, shedding more light on the neural mechanisms behind the altered behaviour of D. sargus.

Fishing for Targets of Alien Metabolites: A Novel Peroxisome Proliferator-Activated Receptor (PPAR) Agonist from a Marine Pest.

Although the chemical warfare between invasive and native species has become a central problem in invasion biology, the molecular mechanisms by which bioactive metabolites from invasive pests influence local communities remain poorly characterized. This study demonstrates that the alkaloid caulerpin (CAU)-a bioactive component of the green alga Caulerpa cylindracea that has invaded the entire Mediterranean basin-is an agonist of peroxisome proliferator-activated receptors (PPARs). Our interdisciplinary study started with the in silico prediction of the ligand-protein interaction, which was then validated by in vivo, ex vivo and in vitro assays. On the basis of these results, we candidate CAU as a causal factor of the metabolic and behavioural disorders observed in Diplodus sargus, a native edible fish of high ecological and commercial relevance, feeding on C. cylindracea. Moreover, given the considerable interest in PPAR activators for the treatment of relevant human diseases, our findings are also discussed in terms of a possible nutraceutical/pharmacological valorisation of the invasive algal biomasses, supporting an innovative strategy for conserving biodiversity as an alternative to unrealistic campaigns for the eradication of invasive pests.

¹H NMR Spectroscopy and MVA to Evaluate the Effects of Caulerpin-Based Diet on Diplodus sargus Lipid Profiles.

The biological invasion of the green algae Caulerpa cylindracea represents a serious scientific and public issue in the Mediterranean Sea, essentially due to strong modifications both to habitat structure and native benthic communities. Although alterations in health status and changes in flesh quality of some marine species (dietary exposed to C. cylindracea) have been observed, no studies on cause-effect relationships have been carried out. Here, for the first time, through a controlled feeding experiment followed by ¹H NMR Spectroscopy and multivariate analysis (PCA, OPLS-DA), we showed that caulerpin taken with diet is directly responsible of changes observed in metabolic profile of fish flesh, including alteration of lipid metabolism, in particular with a reduction of ω3 PUFA content. The potential of caulerpin to directly modulate lipid metabolism opens up new questions about causal mechanism triggered by algal metabolite also in view of a possible exploitation in the nutraceutical/medical field.

Therapeutic effects of D-aspartate in a mouse model of multiple sclerosis.

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis. EAE is mainly mediated by adaptive and innate immune responses that leads to an inflammatory demyelization and axonal damage. The aim of the present research was to examine the therapeutic efficacy of D-aspartic acid (D-Asp) on a mouse EAE model. EAE induction was performed in female C57BL/6 mice by myelin 40 oligodendrocyte glycoprotein (35-55) in a complete Freund's adjuvant emulsion, and D-Asp was used to test its efficiency in the reduction of EAE. During the course of study, clinical evaluation was assessed, and on Day 21, post-immunization blood samples were taken from the heart of mice for the evaluation of interleukin 6 and other chemical molecules. The mice were sacrificed, and their brain and cerebellum were removed for histological analysis. Our findings indicated that D-Asp had beneficial effects on EAE by attenuation in the severity and delay in the onset of the disease. Histological analysis showed that treatment with D-Asp can reduce inflammation. Moreover, in D-Asp-treated mice, the serum level of interleukin 6 was significantly lower than that in control animals, whereas the total antioxidant capacity was significantly higher. The data indicates that D-Asp possess neuroprotective property to prevent the onset of the multiple sclerosis.

Cryptic effects of biological invasions: Reduction of the aggressive behaviour of a native fish under the influence of an "invasive" biomolecule.

The invasive green alga Caulerpa cylindracea has become an important component of the diet of the Mediterranean white seabream Diplodus sargus. As a consequence of this "exotic diet", the algal bisindolic alkaloid caulerpin accumulates in the fish tissues. Although the compound shows structural similarity to endogenous indolamines that modulate animal behaviour, the potential impact of caulerpin on fish behaviour still remains unexplored. In this report, behavioural experiments both on groups and on single fish responding towards a mirror were performed under different doses of dietary caulerpin. Differences between treated and control groups for each behaviour and for the overall aggressive pattern during the different experimental phases showed that the aggressiveness of D. sargus decreased with the administration of caulerpin. These results call the attention to a still unexplored potential ability of bioactive metabolites from marine invasive species, to alter the behaviour on native species, with putative negative effects on patterns of fish growth and population dynamics.

d-Aspartic acid ameliorates painful and neuropsychiatric changes and reduces ß-amyloid Aß1-42 peptide in a long lasting model of neuropathic pain.

Depressive symptoms and other neuropsychiatric dysfunctions are common in neurodegenerative disorders, including chronic pain and dementia. A correlation between the ß-amyloid protein accumulation and the development of depression has been suggested, however the underlying mechanisms are unknown. d-Aspartate (d-Asp) is a free d-amino acid found in the mammalian brain and involved in neurological and psychiatric processes, such as cognition and affective disorders. In this study we have investigated the effects of a repeated treatment with d-Asp in a long-lasting (12 months) model of neuropathic pain, the spared nerve injury (SNI), in mice. Specifically, we evaluated i) the pain sensitivity and related emotional/cognitive dysfunctions induced by SNI, ii) possible changes in the ß-amyloid protein accumulation in specific brain regions involved in pain mechanisms ii) possible changes in steroids level in neuropathic animals with or without d-Asp in the same brain areas. SNI mice showed an increase of the insoluble form of Aß1-42 at hippocampal level and displayed cognitive impairments, stereotypical and depressive-like behaviours. d-Asp treatment reduced abnormal behaviours and normalized the ß-amyloid protein expression. Moreover, d-Asp dramatically increased steroids level measured in the prefrontal cortex and in the hippocampus. Our findings provide new insights into pain mechanisms and suggest a possible role of ß-amyloid protein in neuropsychiatric dysfunctions associated with chronic pain.

Volatile secondary metabolites as aposematic olfactory signals and defensive weapons in aquatic environments.

Olfaction is considered a distance sense; hence, aquatic olfaction is thought to be mediated only by molecules dissolved in water. Here, we challenge this view by showing that shrimp and fish can recognize the presence of hydrophobic olfactory cues by a "tactile" form of chemoreception. We found that odiferous furanosesquiterpenes protect both the Mediterranean octocoral Maasella edwardsi and its specialist predator, the nudibranch gastropod Tritonia striata, from potential predators. Food treated with the terpenes elicited avoidance responses in the cooccurring shrimp Palaemon elegans Rejection was also induced in the shrimp by the memory recall of postingestive aversive effects (vomiting), evoked by repeatedly touching the food with chemosensory mouthparts. Consistent with their emetic properties once ingested, the compounds were highly toxic to brine shrimp. Further experiments on the zebrafish showed that this vertebrate aquatic model also avoids food treated with one of the terpenes, after having experienced gastrointestinal malaise. The fish refused the food after repeatedly touching it with their mouths. The compounds studied thus act simultaneously as (i) toxins, (ii) avoidance-learning inducers, and (iii) aposematic odorant cues. Although they produce a characteristic smell when exposed to air, the compounds are detected by direct contact with the emitter in aquatic environments and are perceived at high doses that are not compatible with their transport in water. The mouthparts of both the shrimp and the fish have thus been shown to act as "aquatic noses," supporting a substantial revision of the current definition of the chemical senses based upon spatial criteria.

Neuroanatomical relationships between FMRFamide-immunoreactive components of the nervus terminalis and the topology of olfactory bulbs in teleost fish.

The nervus terminalis (NT) is the most anterior of the vertebrate cranial nerves. In teleost fish, the NT runs across all olfactory components and shows high morphological variability within this taxon. We compare the anatomical distribution, average number and size of the FMRFamide-immunoreactive (ir) NT cells of fourteen teleost species with different positions of olfactory bulbs (OBs) with respect to the ventral telencephalic area. Based on the topology of the OBs, three different neuroanatomical organizations of the telencephalon can be defined, viz., fish having sessile (Type I), pseudosessile (short stalked; Type II) or stalked (Type III) OBs. Type III topology of OBs appears to be a feature associated with more basal species, whereas Types I and II occur in derived and in basal species. The displacement of the OBs is positively correlated with the peripheral distribution of the FMRFamide-ir NT cells. The number of cells is negatively correlated with the size of the cells. A dependence analysis related to the type of OB topology revealed a positive relationship with the number of cells and with the size of the cells, with Type I and II topologies of OBs showing significantly fewer cells and larger cells than Type III. A dendrogram based on similarities obtained by taking into account all variables under study, i.e., the number and size of the FMRFamide-ir NT cells and the topology of OBs, does not agree with the phylogenetic relationships amongst species, suggesting that divergent or convergent evolutionary phenomena produced the olfactory components studied.