Localization and symbiotic status of probiotics in the coral holobiont.

Corals establish symbiotic relationships with microorganisms, especially endosymbiotic photosynthetic algae. Although other microbes have been commonly detected in coral tissues, their identity and beneficial functions for their host are unclear. Here, we confirm the beneficial outcomes of the inoculation of bacteria selected as probiotics and use fluorescence in situ hybridization (FISH) to define their localization in the coral Pocillopora damicornis. Our results show the first evidence of the inherent presence of Halomonas sp. and Cobetia sp. in native coral tissues, even before their inoculation. Furthermore, the relative enrichment of these coral tissue-associated bacteria through their inoculation in corals correlates with health improvements, such as increases in photosynthetic potential, and productivity. Our study suggests the symbiotic status of Halomonas sp. and Cobetia sp. in corals by indicating their localization within coral gastrodermis and epidermis and correlating their increased relative abundance through active inoculation with beneficial outcomes for the holobiont. This knowledge is crucial to facilitate the screening and application of probiotics that may not be transient members of the coral microbiome. IMPORTANCE: Despite the promising results indicating the beneficial outcomes associated with the application of probiotics in corals and some scarce knowledge regarding the identity of bacterial cells found within the coral tissue, the correlation between these two aspects is still missing. This gap limits our understanding of the actual diversity of coral-associated bacteria and whether these symbionts are beneficial. Some researchers, for example, have been suggesting that probiotic screening should only focus on the very few known tissue-associated bacteria, such as Endozoicomonas sp., assuming that the currently tested probiotics are not tissue-associated. Here, we provide specific FISH probes for Halomonas sp. and Cobetia sp., expand our knowledge of the identity of coral-associated bacteria and confirm the probiotic status of the tested probiotics. The presence of these beneficial microorganisms for corals (BMCs) inside host tissues and gastric cavities also supports the notion that direct interactions with the host may underpin their probiotic role. This is a new breakthrough; these results argue against the possibility that the positive effects of BMCs are due to factors that are not related to a direct symbiotic interaction, for example, that the host simply feeds on inoculated bacteria or that the bacteria change the water quality.

Beta-sheet breaker peptide prevents Abeta-induced spatial memory impairments with partial reduction of amyloid deposits.

Current evidence supports the notion that beta-amyloid deposits or Abeta intermediates may be responsible for the pathogenesis in Alzheimer's disease (AD) patients. In the present work, we have assessed the neuroprotective effect of the chronic intraperitoneal administration of a five-amino-acid beta-sheet breaker peptide (iAbeta5p) on the rat behavioral deficit induced by the intrahippocampal Abeta-fibrils injection. At 1 month after the injection, animals showed a partial reduction of the amyloid deposits formed and a decreased astrocytic response around the injection site. More importantly, we report that following the iAbeta5p treatment, hippocampal-dependent spatial learning paradigms, including the standard Morris water maze and a working memory analysis, showed a significant prevention from impairments induced by Abeta deposits in the dorsal hippocampus. Thus, it is possible that a noninvasive treatment such as the one presented here with beta-sheet breaker peptides may be used as a potential therapy for AD patients.

A human prion protein peptide (PrP(59-91)) protects against copper neurotoxicity.

Human cellular prion protein (PrP(C)) is involved in several neurodegenerative disorders; however, its normal function is unknown. We report here that a synthetic peptide corresponding to the four-octarepeat sequence of the PrP(C) (PrP(59-91)) protects hippocampal neurons against copper neurotoxic effects in vivo. Using a rat bilateral intrahippocampal injection model, we found that PrP(59-91) protects against copper-induced neurotoxicity, including a recovery in spatial learning performance and a reduced neuronal cell loss and astrogliosis. Previous studies from our laboratory indicated that a tryptophan (Trp) residue plays a key role in the reduction of copper(II) to copper(I); therefore several PrP(59-91) fragments lacking histidine (His) and Trp residues were tested for their capacity to protect from copper toxicity. A PrP(59-91) peptide lacking His residue shows as much neuroprotection as the native peptide; however, PrP(59-91) without Trp residues only partially protected against copper toxicity. The neuroprotective effect not only occurs with PrP(59-91), in fact a full neuroprotection was also observed using just one octamer of the N-terminal region of prion protein. We conclude that the N-terminal tandem octarepeat of the human PrP(C) protects neurons against copper toxicity by a differential contribution of the binding (His) and reducing (Trp) copper activities of PrP(59-91). Our results are consistent with the idea that PrP(C) function is related to copper homeostasis.

Activation of Wnt signaling rescues neurodegeneration and behavioral impairments induced by beta-amyloid fibrils.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, which is probably caused by the cytotoxic effect of the amyloid beta-peptide (Abeta). We report here molecular changes induced by Abeta, both in neuronal cells in culture and in rats injected in the dorsal hippocampus with preformed Abeta fibrils, as an in vivo model of the disease. Results indicate that in both systems, Abeta neurotoxicity resulted in the destabilization of endogenous levels of beta-catenin, a key transducer of the Wnt signaling pathway. Lithium chloride, which mimics Wnt signaling by inhibiting glycogen synthase kinase-3beta promoted the survival of post-mitotic neurons against Abeta neurotoxicity and recovered cytosolic beta-catenin to control levels. Moreover, the neurotoxic effect of Abeta fibrils was also modulated with protein kinase C agonists/inhibitors and reversed with conditioned medium containing the Wnt-3a ligand. We also examined the spatial memory performance of rats injected with preformed Abeta fibrils in the Morris water maze paradigm, and found that chronic lithium treatment protected neurodegeneration by rescuing beta-catenin levels and improved the deficit in spatial learning induced by Abeta. Our results are consistent with the idea that Abeta-dependent neurotoxicity induces a loss of function of Wnt signaling components and indicate that lithium or compounds that mimic this signaling cascade may be putative candidates for therapeutic intervention in Alzheimer's patients.

Pyridoxine deficiency and ethanol-induced liver injury.

It has been suggested that pyridoxine deficiency may potentiate ethanol-induced liver injury. Our purpose was to clarify the effect of pyridoxine deficiency on ethanol-associated liver injury by comparing liver histology, serum liver enzymes, and the viability of cultured hepatocytes from pyridoxine-deficient and pyridoxine-sufficient rats that had been chronically fed ethanol-enriched diets. Our data fail to substantiate that pyridoxine-deficient animals are more susceptible to the hepatotoxic effects of ethanol than pair-fed pyridoxine-sufficient controls. Furthermore, the addition of pyridoxine to hepatocyte cultures fails to prevent in vitro cytotoxicity of added ethanol. Pyridoxine deficiency may augment ethanol-induced enhancement of hepatic urea synthesis. These data suggest that pyridoxine deficiency may contribute to the abnormal plasma amino acid profiles and nitrogen balance of chronic alcoholics, but that it does not potentiate ethanol-induced liver injury.

Mode of death effect on rat liver iodothyronine 5' deiodinase activity: role of adenosine 3',5' monophosphate.

Liver thyronine 5'-deiodinase activity assayed in crude homogenates in the absence of dithiothreitol (DTT) is increased in rats killed by asphyxia when compared to that of animals killed by phenobarbital injection or decapitation. The addition of cyclic adenosine monophosphate leads to a consistent decrease in observed deiodinase activity, suggesting the possible involvement of this nucleotide in the regulation of this enzyme. The addition of DTT eliminates this effect and suggest a dual regulation of the enzyme by cAMP and physiological sulfhydryl compounds.

Mode of death and post-mortem time effects on 3,3',5-triiodothyronine levels--relevance to elevated post-mortem T3 levels in SIDS.

Post-mortem T3 levels have been reported to be increased in victims of SIDS. Recent animal studies suggest, however, that elevated T3 in SIDS may be a non-specific post-mortem phenomenon. Therefore, we studied the possible effects of post-mortem time on T3 levels in 10- and 20-day-old rats killed by various methods including: Sodium pentobarbital overdose, injection of KCl, cervical dislocation or asphyxia with 100% N, 95% N-5% CO2 or 100% CO2. In both age groups T3 remained unchanged or increased slightly when the animals were killed with Na Pentobarbital or KCl. Greater increases were observed when rats were killed by cervical dislocation or asphyxia (100% N, 95% N-5% CO2 or 100% CO2). T3 levels did not become elevated in asphyxiated adult rats in which the inferior vena cava was ligated immediately following death. By extension to the human infant, the results of this study support the possibility that elevated T3 levels in SIDS victims may result from post-mortem processes. However, these results also suggest that the post-mortem elevation in T3 levels may be directly related to the mode of death.