Direct mapping of ligandable tyrosines and lysines in cells with chiral sulfonyl fluoride probes

Advances in chemoproteomic technology have revealed covalent interactions between small molecules and protein nucleophiles, primarily cysteine, on a proteome-wide scale. Most chemoproteomic screening approaches are indirect, relying on competition between electrophilic fragments and a minimalist electrophilic probe with inherently limited proteome coverage. Here we develop a chemoproteomic platform for direct electrophile-site identification based on enantiomeric pairs of clickable arylsulfonyl fluoride probes. Using stereoselective site modification as a proxy for ligandability in intact cells, we identify 634 tyrosines and lysines within functionally diverse protein sites, liganded by structurally diverse probes. Among multiple validated sites, we discover a chiral probe that modifies Y228 in the MYC binding site of the epigenetic regulator WDR5, as revealed by a high-resolution crystal structure. A distinct chiral probe stimulates tumour cell phagocytosis by covalently modifying Y387 in the recently discovered immuno-oncology target APMAP. Our work provides a deep resource of ligandable tyrosines and lysines for the development of covalent chemical probes.

Reversible lysine-targeted probes reveal residence time-based kinase selectivity

The expansion of the target landscape of covalent inhibitors requires the engagement of nucleophiles beyond cysteine. Although the conserved catalytic lysine in protein kinases is an attractive candidate for a covalent approach, selectivity remains an obvious challenge. Moreover, few covalent inhibitors have been shown to engage the kinase catalytic lysine in animals. We hypothesized that reversible, lysine-targeted inhibitors could provide sustained kinase engagement in vivo, with selectivity driven in part by differences in residence time. By strategically linking benzaldehydes to a promiscuous kinase binding scaffold, we developed chemoproteomic probes that reversibly and covalently engage >200 protein kinases in cells and mice. Probe-kinase residence time was dramatically enhanced by a hydroxyl group ortho to the aldehyde. Remarkably, only a few kinases, including Aurora A, showed sustained, quasi-irreversible occupancy in vivo, the structural basis for which was revealed by X-ray crystallography. We anticipate broad application of salicylaldehyde-based probes to proteins that lack a druggable cysteine.

Discovery of Lysine-Targeted eIF4E Inhibitors through Covalent Docking

Eukaryotic translation initiation factor 4E (eIF4E) binds the m7GTP cap structure at the 5'-end of mRNAs, stimulating the translation of proteins implicated in cancer cell growth and metastasis. eIF4E is a notoriously challenging target, and most of the reported inhibitors are negatively charged guanine analogues with negligible cell permeability. To overcome these challenges, we envisioned a covalent targeting strategy. As there are no cysteines near the eIF4E cap binding site, we developed a covalent docking approach focused on lysine. Taking advantage of a "make-on-demand" virtual library, we used covalent docking to identify arylsulfonyl fluorides that target a noncatalytic lysine (Lys162) in eIF4E. Guided by cocrystal structures, we elaborated arylsulfonyl fluoride 2 to 12, which to our knowledge is the first covalent eIF4E inhibitor with cellular activity. In addition to providing a new tool for acutely inactivating eIF4E in cells, our computational approach may offer a general strategy for developing selective lysine-targeted covalent ligands.

Lysine-Targeted Inhibitors and Chemoproteomic Probes

Covalent inhibitors are widely used in drug discovery and chemical biology. Although covalent inhibitors are frequently designed to react with noncatalytic cysteines, many ligand binding sites lack an accessible cysteine. Here, we review recent advances in the chemical biology of lysine-targeted covalent inhibitors and chemoproteomic probes. By analyzing crystal structures of proteins bound to common metabolites and enzyme cofactors, we identify a large set of mostly unexplored lysines that are potentially targetable with covalent inhibitors. In addition, we describe mass spectrometry-based approaches for determining proteome-wide lysine ligandability and lysine-reactive chemoproteomic probes for assessing drug-target engagement. Finally, we discuss the design of amine-reactive inhibitors that form reversible covalent bonds with their protein targets.

Vitamin D3 affects innate immune status of European sea bass (Dicentrarchus labrax L.)

The effects of vitamin D₃ dietary administration on certain innate immune parameters on the expression of immune-related genes in head-kidney (HK) and gut were investigated in European sea bass Dicentrarchus labrax. Vitamin D₃ (vD₃) was orally administered to fish in a commercial pellet food supplemented with 0 (control); 3750; 18,750; or 37,500 U kg^-1. Furthermore, gut histology was considered. This study showed a modulation in the activities examined in fish fed with the addition of vD₃. After just 2 weeks of administration, diet supplementation with the vitamin resulted in increased phagocytic ability, while serum peroxidase content was increased in fish fed with all experimental diets after 4 weeks, no significant differences were observed in protease, anti-protease, natural haemolytic complement activities and total IgM level. At gene level, fbl and rbl transcripts were up-regulated in HK in fish fed with the highest concentration of vD₃-supplemented diets after 4 weeks, while in the gut, an up-regulation of hep gene was observed in fish fed with the different doses of vD₃. These results suggest that vD₃ may be of great interest for immunostimulatory purposes in fish farms.

The short-term effects of farmed fish food consumed by wild fish congregating outside the farms

We simulated in the laboratory the possible effects on fatty acids and immune status of wild fish arriving for the first time in the vicinity of a sea-cage fish farm, shifting their natural diet to commercial feed consumption, rich in fatty acids of vegetable origin. The flesh fatty acid profile of golden mullet specimens was altered after 2weeks of commercial feed consumption, showing an increase in fatty acids of vegetable origin. The serum peroxidase and bactericidal activities, and head-kidney leucocyte phagocytic capacity, increased after eight weeks of the new diet, while the respiratory burst activity decreased. The extent of these changes cannot be considered large enough to regard them as compromising the health status of fish. More research is needed in order to elucidate whether the rapid assimilation of the dietary fatty acids could harm the immune status of fish when feeding for longer periods than two months.

Characterization of the gilthead seabream (Sparus aurata L.) immune response under a natural lymphocystis disease virus outbreak

Lymphocystis or lymphocystis disease virus (LCDV) is distributed worldwide and affects many fresh and marine water fish species. LCDV is commonly found in aquaria fish species but also in farmed fish species, among them the gilthead seabream (Sparus aurata L.). The immune status of gilthead seabream (S. aurata) specimens under a natural outbreak of LCDV was studied. The replication of the virus was demonstrated in infected fish, but not in control fish. The results showed decreased total serum IgM levels and increased innate cellular immune response (peroxidase and respiratory burst activities) of head kidney leucocytes in LCDV-infected fish, compared to the values obtained in uninfected specimens. In addition, transcription of antiviral genes (ifn and irf3) was down-regulated in the skin of LCDV-positive fish as well as genes involved in cellular immunity (csf1r, mhc2a, tcra and ighm) that were down-regulated in skin and head kidney of infected fish. By contrast, the transcription of nccrp1 was up-regulated in head kidney after LCDV infection. These present results show that head kidney leucocytes are activated to encounter the virus at the sites of replication.

Mercury Accumulation, Structural Damages, and Antioxidant and Immune Status Changes in the Gilthead Seabream (Sparus aurata L.) Exposed to Methylmercury

In aquatic systems, mercury (Hg) is an environmental contaminant that causes acute and chronic damage to multiple organs. In fish, practically all of the organic Hg found is in the form of methylmercury (MeHg), which has been associated with animal and human health problems. This study evaluates the impact of waterborne-exposure to sublethal concentrations of MeHg (10 μg L(-1)) in gilthead seabream (Sparus aurata). Hg was seen to accumulate in liver and muscle, and histopathological damage to skin and liver was detected. Fish exposed to MeHg showed a decreased biological antioxidant potential and increased levels of the reactive oxygen molecules compared with the values found in control fish (nonexposed). Increased liver antioxidant enzyme activities (superoxide dismutase and catalase) were detected in 2 day-exposed fish with respect to the values of control fish. However, fish exposed to MeHg for 10 days showed liver antioxidant enzyme levels similar to those of the control fish but had increased hepato-somatic index and histopathological alterations in liver and skin. Serum complement levels were higher in fish exposed to MeHg for 30 days than in control fish. Moreover, head-kidney leukocyte activities increased, although only phagocytosis and peroxidase activities showed a significant increase after 10 and 30 days, respectively. The data show that 30 days of exposure to waterborne MeHg provokes more significant changes in fish than a short-term exposure of 2 or 10 days.

Impact of date palm fruits extracts and probiotic enriched diet on antioxidant status, innate immune response and immune-related gene expression of European seabass (Dicentrarchus labrax)

The application of additives in the diet as plants or extracts of plants as natural and innocuous compounds has potential in aquaculture as an alternative to antibiotics and immunoprophylactics. The aim of the current study was to evaluate the potential effects of dietary supplementation of date palm fruit extracts alone or in combination with Pdp11 probiotic on serum antioxidant status, on the humoral and cellular innate immune status, as well as, on the expression levels of some immune-related genes in head-kidney and gut of European sea bass (Dicentrarchus labrax) after 2 and 4 weeks of administration. This study showed for the first time in European sea bass an immunostimulation in several of the parameters evaluated in fish fed with date palm fruits extracts enriched diet or fed with this substance in combination with Pdp 11 probiotic, mainly after 4 weeks of treatment. In the same way, dietary supplementation of mixture diet has positive effects on the expression levels of immune-related genes, chiefly in head-kidney of Dicentrarchus labrax. Therefore, the combination of both could be considered of great interest as potential additives for farmed fish.

Determination of ubiquitin fitness landscapes under different chemical stresses in a classroom setting

Ubiquitin is essential for eukaryotic life and varies in only 3 amino acid positions between yeast and humans. However, recent deep sequencing studies indicate that ubiquitin is highly tolerant to single mutations. We hypothesized that this tolerance would be reduced by chemically induced physiologic perturbations. To test this hypothesis, a class of first year UCSF graduate students employed deep mutational scanning to determine the fitness landscape of all possible single residue mutations in the presence of five different small molecule perturbations. These perturbations uncover 'shared sensitized positions' localized to areas around the hydrophobic patch and the C-terminus. In addition, we identified perturbation specific effects such as a sensitization of His68 in HU and a tolerance to mutation at Lys63 in DTT. Our data show how chemical stresses can reduce buffering effects in the ubiquitin proteasome system. Finally, this study demonstrates the potential of lab-based interdisciplinary graduate curriculum.

DOI:http://dx.doi.org/10.7554/eLife.15802.001

The ability of an organism to grow and reproduce, that is, it’s “fitness”, is determined by how its genes interact with the environment. Yeast is a model organism in which researchers can control the exact mutations present in the yeast’s genes (its genotype) and the conditions in which the yeast cells live (their environment). This allows researchers to measure how a yeast cell’s genotype and environment affect its fitness.

Ubiquitin is a protein that many organisms depend on to manage cell stress by acting as a tag that targets other proteins for degradation. Essential proteins such as ubiquitin often remain unchanged by mutation over long periods of time. As a result, these proteins evolve very slowly. Like all proteins, ubiquitin is built from a chain of amino acid molecules linked together, and the ubiquitin proteins of yeast and humans are made of almost identical sequences of amino acids.

Although ubiquitin has barely changed its sequence over evolution, previous studies have shown that – under normal growth conditions in the laboratory – most amino acids in ubiquitin can be mutated without any loss of cell fitness. This led Mavor et al. to hypothesize that treating the yeast cells with chemicals that cause cell stress might lead to amino acids in ubiquitin becoming more sensitive to mutation.

To test this idea, a class of graduate students at the University of California, San Francisco grew yeast cells with different ubiquitin mutations together, and with different chemicals that induce cell stress, and measured their growth rates. Sequencing the ubiquitin gene in the thousands of tested yeast cells revealed that three of the chemicals cause a shared set of amino acids in ubiquitin to become more sensitive to mutation.

This result suggests that these amino acids are important for the stress response, possibly by altering the ability of yeast cells to target certain proteins for degradation. Conversely, another chemical causes yeast to become more tolerant to changes in the ubiquitin sequence. The experiments also link changes in particular amino acids in ubiquitin to specific stress responses.

Mavor et al. show that many of ubquitin’s amino acids are sensitive to mutation under different stress conditions, while others can be mutated to form different amino acids without effecting fitness. By testing the effects of other chemicals, future experiments could further characterize how the yeast’s genotype and environment interact.

DOI:http://dx.doi.org/10.7554/eLife.15802.002

Modulatory effects of deltamethrin-exposure on the immune status, metabolism and oxidative stress in gilthead seabream (Sparus aurata L.)

Deltamethrin, a sintetic pyrethroid, is the insecticide that has been replacing recently to others like organochlorines, organophosphates and carbamates which are less toxic for birds and mammals, although, unfortunately, all of them are highly toxic to various non-targeted aquatic organisms including fish. In the present study, the consequences of the exposition of gilthead seabream (Sparus aurata L.) specimens to sublethal bath dose of deltamethrin (0.1 ppb) on organo-somatic indexes, immunity, seric metabolic parameters, oxidative stress and liver histology were determined after 1, 3, 7 and 14 days of exposure. Deltamethrin alters gilthead seabream immune status, the hepato-somatic index and various seric metabolic parameters since the first exposure day while important progressive deleterious morphological changes in liver were also observed. However, no statistically significant deviation was detected in the expression of oxidative stress-related genes whilst the expression of cytochrome P450 gene was up-regulated in head-kidney and liver of exposed fish. Overall, the present results indicate severe immunotoxicological and metabolic effects of deltamethrin in gilthead seabream, the species with the highest rate of production in Mediterranean aquaculture. In general, the values obtained for the tested parameters during the trial seem to indicate that specimens try to adapt to this adverse situation although the continuous presence of the toxic impede the hypothetic recovery of homoeostasis. The use of deltamethrin in the proximities of seabream farms should be carefully considered.

Accumulation, histopathology and immunotoxicological effects of waterborne cadmium on gilthead seabream (Sparus aurata)

Studies in fish have demonstrated that Cd-exposure produce skeletal deformities and alterations in tissue morphology, enzyme activities, stress response, ion regulation and immune response. In the present work, gilthead seabream (Sparus aurata) specimens were exposed to waterborne Cd (5 μM CdCl2 or 1 mg L(-1)) for 2, 10 or 30 days. Organo-somatic changes, Cd accumulation, liver histology and humoral and cellular immune responses were determined. Results showed that exposure of seabream specimens to Cd induced no alterations on spleen and liver organo-somatic indexes whilst produced progressive deleterious morphological alterations in liver and exocrine pancreas that correlated with the hepatic Cd-accumulation. Regarding the immunotoxicological potential, strikingly, Cd-exposure produced a reduction in the serum complement activity and leucocyte respiratory burst to a significant extent after 10 and 30 days whilst the serum peroxidase activity and leucocyte phagocytosis were increased at different sampling times. On the other hand, serum IgM levels and leucocyte peroxidase activity resulted unaltered. The present results seem to indicate that seabream exposed to Cd in the present conditions suffer toxicity.

Immunotoxicological effects of inorganic arsenic on gilthead seabream (Sparus aurata L.)

Arsenic (As) has been associated with multitude of animal and human health problems; however, its impact on host immune system has not been extensively investigated. In fish, there are very few works on the potential risks or problems associated to the presence of arsenic. In the present study we have evaluated the effects of exposure (30 days) to sub-lethal concentrations of arsenic (5 μM As₂O₃) in the teleost fish gilthead seabream (Sparus aurata), with special emphasis in the innate immune response. The arsenic concentration was determined using atomic fluorescence spectrometry (AFS) in liver and muscle of exposed fish showing As accumulation in the liver after 30 days of exposure. The hepatosomatic index was increased at significant extent after 10 days but returned to control values after 30 days of exposure. Histological alterations in the liver were observed including hypertrophy, vacuolization and cell-death processes. Focusing on the immunological response, the humoral immune parameters (seric IgM, complement and peroxidase activities) were no affected to a statistically significant extent. Regarding the cellular innate parameters, head-kidney leucocyte peroxidase, respiratory burst and phagocytic activities were significantly increased after 10 days of exposition compared to the control fish. Overall, As-exposure in the seabream affects the immune system. How this might interfere with fish biology, aquaculture management or human consumers warrants further investigations. This paper describes, for the first time, the immunotoxicological effects of arsenic exposure in the gilthead seabream, which is a species with the largest production in Mediterranean aquaculture.

Microbiota restricts trafficking of bacteria to mesenteric lymph nodes by CX(3)CR1(hi) cells

The intestinal microbiota have critical roles in immune system and metabolic homeostasis, but they must be tolerated by the host to avoid inflammatory responses that can damage the epithelial barrier separating the host from the luminal contents^1-6. Breakdown of this regulation and the resulting inappropriate immune response to commensals are thought to lead to the development of inflammatory bowel diseases (IBDs) such as Crohn's disease and ulcerative colitis⁷. We hypothesized that the intestinal immune system is instructed by the microbiota to limit responses to luminal antigens. We demonstrate that, at steady state, the microbiota inhibit the transport of both commensal and pathogenic bacteria from the lumen to a key immune inductive site, the mesenteric lymph node (MLN). However, in the absence of Myd88 or under conditions of antibiotic-induced dysbiosis, non-invasive bacteria trafficked to the MLN in a CCR7-dependent manner and induced both T cell responses and IgA production. Trafficking was carried out by CX₃CR1^hi mononuclear phagocytes, an intestinal cell population previously reported to be non-migratory⁸. These findings define a central role for commensals in regulating the migration to the MLN of CX₃CR1^hi mononuclear phagocytes endowed with the ability to capture luminal bacteria, thereby compartmentalizing the intestinal immune response to avoid inflammation.

Effects of dietary inulin and heat-inactivated Bacillus subtilis on gilthead seabream (Sparus aurata L.) innate immune parameters

In the present study, a feeding trial was conducted to evaluate the effect of inulin and heat-inactivated Bacillus subtilis, single or combined, on several innate immune activities of gilthead seabream (Sparus aurata). Forty-eight specimens were randomly assigned to four dietary treatments: 0 (control), inulin (10 g/kg, prebiotic group), B. subtilis (107 cfu/g, probiotic group), or B. subtilis + inulin (107 cfu/g + 10 g/kg, synbiotic group). After two and four weeks, six fish of each group were sampled, with the main innate immune parameters (natural haemolytic complement activity, serum and leucocyte peroxidase, phagocytosis, respiratory burst, and cytotoxic activities) being determined. Inulin or heat-inactivated B. subtilis failed to significantly stimulate the innate immune parameters assayed, although some activities showed no significant increase through these treatments. A combination of inulin and B. subtilis resulted in an increase of such parameters, with the haemolytic complement activity being the only one significantly stimulated. To conclude, inulin and B. subtilis, when administered as a synbiotic, have a synergistic effect and enhance some innate immune parameters of gilthead seabream.

Viral hemorrhagic septicaemia virus (VHSV) up-regulates the cytotoxic activity and the perforin/granzyme pathway in the rainbow trout RTS11 cell line

A survey of immune-relevant genes that might be up-regulated in response to viral hemorrhagic septicaemia virus (VHSV) in the rainbow trout monocyte-macrophage cell line, RTS11, unexpectedly revealed an increased expression of perforin (PRF) and granzyme (GRZ) genes, which represent components of the major cytotoxic pathway. The natural killer-enhancing factor (NKEF), also known to modulate cytotoxic activity, was up-regulated at the gene but strikingly down-regulated at protein level. The expression of these genes was not affected in head kidney leukocytes (HKLs) infected with VHSV, leading us to evaluate the potential cytotoxic activity of RTS11 and HKLs. For the first time, the cytotoxic activity of RTS11 against xenogeneic targets has been demonstrated, although this was modest relative to HKLs. Yet the activity in RTS11 was significantly increased by VHSV, as in HKLs. This cytotoxic activity elicited by viral infection appeared to require viral gene expression because inactivated VHSV failed to increase RTS11 cytotoxic activity. As for other immune functions, RTS11 cells provide a model for further studying cytotoxic activities of fish monocyte-macrophages.

Digoxin and its derivatives suppress TH17 cell differentiation by antagonizing RORγt activity

CD4(+) T helper lymphocytes that express interleukin-17 (T(H)17 cells) have critical roles in mouse models of autoimmunity, and there is mounting evidence that they also influence inflammatory processes in humans. Genome-wide association studies in humans have linked genes involved in T(H)17 cell differentiation and function with susceptibility to Crohn's disease, rheumatoid arthritis and psoriasis. Thus, the pathway towards differentiation of T(H)17 cells and, perhaps, of related innate lymphoid cells with similar effector functions, is an attractive target for therapeutic applications. Mouse and human T(H)17 cells are distinguished by expression of the retinoic acid receptor-related orphan nuclear receptor RORγt, which is required for induction of IL-17 transcription and for the manifestation of T(H)17-dependent autoimmune disease in mice. By performing a chemical screen with an insect cell-based reporter system, we identified the cardiac glycoside digoxin as a specific inhibitor of RORγt transcriptional activity. Digoxin inhibited murine T(H)17 cell differentiation without affecting differentiation of other T cell lineages and was effective in delaying the onset and reducing the severity of autoimmune disease in mice. At high concentrations, digoxin is toxic for human cells, but non-toxic synthetic derivatives 20,22-dihydrodigoxin-21,23-diol and digoxin-21-salicylidene specifically inhibited induction of IL-17 in human CD4(+) T cells. Using these small-molecule compounds, we demonstrate that RORγt is important for the maintenance of IL-17 expression in mouse and human effector T cells. These data indicate that derivatives of digoxin can be used as chemical templates for the development of RORγt-targeted therapeutic agents that attenuate inflammatory lymphocyte function and autoimmune disease.

The introduction of multi-copy CpG motifs into an antiviral DNA vaccine strongly up-regulates its immunogenicity in fish

The protection conferred by antiviral DNA vaccines in fish is known to rely greatly on innate immune responses. Since oligodeoxynucleotides (ODNs) containing unmethylated CpG dinucleotides (CpG motifs) have been shown to induce potential innate immune responses, we have introduced several copies (either two or four) of a fragment containing multiple CpG sequences of known immunostimulatory effects into a DNA vaccine against viral hemorrhagic septicemia virus (VHSV). We have determined the effects of this introduction on the vaccine immunogenicity, measured as immune gene induction, serum neutralizing activity and antigen-dependent proliferation. When comparing the effects of the vaccine containing 2 copies of this CpG fragment (pVHSV-2CpG) or that containing 4 copies of the fragment (pVHSV-4CpG) with the original VHSV DNA vaccine (pVHSV), we found that the levels of expression of type I interferon (IFN) were significantly up-regulated in muscle and spleen when the CpG fragments were introduced. An up-regulation in the levels of MHC-I expression in spleen were also observed in response to the modified vaccines, whereas, the levels of transcription of interleukin 1β (IL-1β) were strongly reduced in comparison to the original vaccine. Important but very variable differences were also observed concerning the vaccine induction of IFN-γ. Moreover, the serum neutralizing capacity was strongly increased as fish were vaccinated with plasmids containing more CpG fragments. Taken together, all these results demonstrate a strongly increased immunogenicity of the VHSV DNA vaccine, through the introduction of this multicopy CpG fragment.

In vitro search for alternative promoters to the human immediate early cytomegalovirus (IE-cMV) to express the G gene of viral haemorrhagic septicemia virus (VHSV) in fish epithelial cells

Present DNA vaccines against fish rhabdoviruses require intramuscular injection (fish-to-fish vaccination) of their G-protein gene under the control of the human immediate early cytomegalovirus (IE-CMV) promoter, while immersion delivery (mass DNA vaccination), for instance, by using fish epithelial-specific promoters, would be more practical for aquaculture. To find fish epithelial-specific promoters alternative to the IE-CMV, a comparative study of the effectiveness of different fish promoters constitutively expressing the G gene of the viral haemorrhagic septicemia virus (VHSV) in the epithelial papulosum cyprini (EPC) cell line was performed. The study included MCV1.4 (an alternative IE-CMV promoter version), AE6 (a version of the carp beta-actin promoter), long terminal repeats (LTR) of zebrafish or walleye retroviruses, trout Mx1, carp myosin-heavy-chain and flatfish pleurocidin promoters and salmonid sleeping beauty (SB)/medaka Tol2 transposon repeats. The G-protein expression in transfected EPC cells was studied by estimating the number of cells expressing the G-protein in their membrane and the average expression level per cell. In addition, in an attempt to reduce their sizes, some regions of the MCV1.4 and AE6 promoters were deleted and expression levels compared to those observed for full-length promoters. Since both zebrafish LTR and carp AE6 promoters were the most effective regulatory sequences for expressing the VHSV G-protein in EPC cells, these sequences might be candidates for new DNA vaccine vectors for fish epithelial tissues avoiding the IE-CMV promoter. Furthermore, known transcription factor binding sites (TFBS) common to most of the fish G-expressing promoters, might enable the future design of fully synthetic or hybrid promoters with improved efficacy of VHSV G-protein expression in epithelial fish cells.

Transfection improvements of fish cell lines by using deacylated polyethylenimine of selected molecular weights

A new tool for DNA transfer to fish cell lines such as epithelioma papulosum cyprini (EPC) and rainbow trout gonad (RTG2), has been optimized by testing commercially available polyethylenimine (PEI) polymers as transfectant reagents. Deacylated 25 kDa PEI polymers were selected amongst the most active and then low toxicity deacylated PEIs fractions around 15 kDa were obtained by gel filtration chromatography to increase 3-4-fold their initial in vitro transfection efficiency. The EPC and plasmids coding for reporter genes were first used to optimize variable values for best expression by transfection with deacylated low toxicity PEI while both EPC/RTG2 and a plasmid coding for the glycoprotein G gene of the fish pathogen, viral haemorrhagic septicemia virus (VHSV) were then used to demonstrate some of their practical applications. Due to its relatively low price, defined chemical composition and availability, low toxicity deacylated PEI might be used for numerous applications for all those studying fish cell immunology in vitro as well as in vivo.

The expression profile of TLR9 mRNA and CpG ODNs immunostimulatory actions in the teleost gilthead seabream points to a major role of lymphocytes

The potential effects of synthetic unmethylated oligodeoxynucleotides (ODN) containing CpG motifs, mimicking bacterial DNA, has never been evaluated on the immune response in the teleost fish gilthead seabream (Sparus aurata), the most important fish species in Mediterranean aquaculture. First, binding and competition studies have demonstrated that binding is saturated and promiscuous, suggesting the participation of several receptors. Moreover, leucocyte cytotoxic (NCC) activity, production of ROIs (reactive oxygen intermediates), and expression of immune-relevant genes was greatly primed by ODNs. Focusing on the mechanism, the TLR9 gene is widely distributed in seabream tissues and differently regulated in vitro by several stimuli. Moreover, and for the first time in fish, TLR9 mRNA has been detected in lymphocytes as the main cell-source. To conclude, ODNs containing GACGTT, GTCGTT (optimal for mouse and human, respectively) or AACGTT motifs are the most potent inducers of seabream immunity, whilst the involvement of TLR9 is under debate.

Effect of sex-steroid hormones, testosterone and estradiol, on humoral immune parameters of gilthead seabream

The role of sex-steroid hormones, testosterone (T) and 17beta-estradiol (E2), on the humoral immune parameters of the teleost gilthead seabream Sparus aurata was studied attempting to deepen on the knowledge of the immune-reproductive system interactions. Fish were injected intraperitoneally with coconut oil containing different dosages of T (0, 2, or 5 microg g(-1) body weight [bw]) or E2 (0, 1, or 2 microg g(-1) bw) and sampled 1, 3, and 7 days later. Hormonal levels and immune parameters (complement, peroxidase and antiprotease activities and IgM levels) were determined in plasma. Plasma hormone levels peaked at 1 day post-injection decreasing thereafter. Treatment with T significantly increased both complement and peroxidase activities after 3 days of injection but antiprotease activity and IgM levels remained unchanged. Treatment with E2 enhanced complement activity 1 day post-injection while decreased it after 3 and 7 days. However, peroxidase activity increased at 3 and 7 days post-injection while total IgM levels decreased. Implications of T and E2 in the immune-reproductive system interactions were discussed.

Sharpsnout sea bream (Diplodus puntazzo) humoral immune response against the parasite Enteromyxum leei (Myxozoa)

The humoral innate immune response of sharpsnout seabream Diplodus puntazzo against the myxozoan Enteromyxum leei was studied. Enteromyxosis was transmitted by cohabitation and a group of uninfected fish served as control. At 5, 12, 19, 26, 40 and 55 days post-exposure (p.e.), control and recipient fish were sampled to determine the prevalence of infection and some humoral innate immune parameters (antiprotease, antitumoral and peroxidase activities). Prevalence of infection was high from day 12 p.e. and reached 100% at days 40 and 55, when intensity of infection was medium to severe. The antiprotease activity was significantly increased in E. leei-exposed fish with respect to control fish at days 12 and 19 p.e. The serum antitumoral activity was slightly lower in recipient than in control fish at all sampling times, except at 40 days p.e., though no statistically significant differences were observed. Serum peroxidases were higher in all recipient fish than in control ones, with the highest stimulation index at 40 days p.e. Within recipient fish, no differences were detected between sampling times in any of the measured activities. The possible implication of these immune factors in the high susceptibility of D. puntazzo to this enteromyxosis is discussed.

Synthesis, structure, and physical properties of hybrid nanocomposites for solid-state dye lasers

We report on the synthesis, structural characterization, physical properties, and lasing action of two organic dyes, Rhodamine 6G (Rh6G) and Pyrromethene 597 (PM597), incorporated into new hybrid organic-inorganic materials, where the organic component was either poly(2-hydroxyethyl-methacrylate) (PHEMA) or copolymers of HEMA with methyl methacrylate (MMA), and the inorganic counterpart consisted of silica derived from hydrolysis-condensation of methyltriethoxysilane (TRIEOS) in weight proportion of up to 30%. Lasing efficiencies of up 23% and high photostabilities, with no sign of degradation in the initial laser output after 100 000 pump pulses at 10 Hz, were demonstrated when pumping the samples transversely at 534 nm with 5.5 mJ/pulse. A direct relationship could be established between the structure of the hybrid materials, analyzed by solid-state NMR, and their laser behavior. An inorganic network dominated by di-/tri- substituted silicates in a proportion approximately 35:65, corresponding to samples of HEMA with 15 and 20 wt % proportion of TRIEOS, optimizes the lasing photostability. The thermal properties of these materials, together with the high homogeneity revealed by atomic force microscopy (AFM) images, even in compounds with high silica content, indicate their microstructure to be a continuous phase, corresponding to the polymer matrix, which "traps" the silica components at molecular level via covalent bonding, with few or no silica islands.

The p.R1109X mutation in SH3TC2 gene is predominant in Spanish Gypsies with Charcot-Marie-Tooth disease type 4

Charcot-Marie-Tooth (CMT) disease type 4 (CMT4) is the name given to autosomal recessive forms of hereditary motor and sensory neuropathy (HMSN). When we began this study, three genes or loci associated with inherited peripheral neuropathies had already been identified in the European Gypsy population: HMSN-Lom (MIM 601455), HMSN-Russe (MIM 605285) and the congenital cataracts facial dysmorphism neuropathy syndrome (MIM 604168). We have carried out genetic analyses in a series of 20 Spanish Gypsy families diagnosed with a demyelinating CMT disease compatible with an autosomal recessive trait. We found the p.R148X mutation in the N-myc downstream-regulated gene 1 gene to be responsible for the HMSN-Lom in four families and also possible linkage to the HMSN-Russe locus in three others. We have also studied the CMT4C locus because of the clinical similarities and showed that in 10 families, the disease is caused by mutations located on the SH3 domain and tetratricopeptide repeats 2 (SH3TC2) gene: p.R1109X in 20 out of 21 chromosomes and p.C737_P738delinsX in only one chromosome. Moreover, the SH3TC2 p.R1109X mutation is associated with a conserved haplotype and, therefore, may be a private founder mutation for the Gypsy population. Estimation of the allelic age revealed that the SH3TC2 p.R1109X mutation may have arisen about 225 years ago, probably as the consequence of a bottleneck.

Cell-mediated cytotoxicity is the main innate immune mechanism involved in the cellular defence of gilthead seabream (Teleostei: Sparidae) against Enteromyxum leei (Myxozoa)

The cellular innate immune response of gilthead seabream (Sparus aurata L.) against the myxozoan Enteromyxum leei was studied. Enteromyxosis was transmitted by maintaining uninfected fish (recipients) together with infected animals. A group of fish not exposed to the infection served as controls. After 10, 22, 38, 52 and 108 days, control and recipient fish were sampled and leucocyte subpopulations and cellular immune responses (leucocyte peroxidases, phagocytosis, respiratory burst and cytotoxicity) of the head-kidney leucocytes were determined. The percentage of acidophilic granulocytes was significantly lower in non-parasitized and parasitized recipient fish than in control fish after 22 days but no significant differences were seen between non-parasitized and parasitized recipient animals. The leucocyte peroxidase content, phagocytosis and respiratory burst activity were seen to have decreased significantly at different sampling times in both non-parasitized and parasitized recipient fish with respect to the controls, whereas cytotoxic activity was up to 2.3 times higher than in control fish. Within the recipient group, little difference was observed in the studied parameters between non-parasitized and parasitized fish. These data demonstrate that cytotoxic activity may have an important role in the defence of gilthead seabream against the myxosporean E. leei. Immunological implications of E. leei infections are discussed.

Prenatally detected double trisomy: Klinefelter and Down syndrome

Double trisomies are a rare occurrence. We report the first case of a Down and Klinefelter's syndrome (48,XXY,+21) in a fetus that was prenatally diagnosed during the 15th week of pregnancy. Even though the nasal bone was present, and the color-Doppler study of the ductus venosus and the nuchal thickness were normal, the maternal serum test results indicated an increased risk of Down syndrome and consequentially a genetic amniocentesis was performed. A 48,XXY,+21 karyotype was observed and the patient decided to terminate the pregnancy. In this case, we did not find the typical ultrasound (US) signs that would have led us to the chromosomopathy; furthermore, we emphasize the advantages of using biochemical screening which, in our case, were crucial in arriving at the correct diagnosis.

Gilthead seabream (Sparus aurataL.) innate defence against the parasiteEnteromyxum leei(Myxozoa)

The humoral innate immune response of gilthead seabream (Sparus aurataL.) against the myxozoanEnteromyxum leeihas been studied. At 10, 22, 38, 52 and 108 days of cohabitation fish were sampled to examine gut histology and to determine serum innate immune parameters and the mRNA expression of pro-inflammatory cytokines (IL-1β and TNFα) in head-kidney. The parasite was successfully transmitted to 45% of the recipient fish and prevalence reached a maximum (62·5%) at the last sampling time (108 days). Recipient fish started to die after 74 days of cohabitation. In general, alternative complement activity was higher whereas the peroxidase level was lower in recipient fish than in controls. Moreover, IL-1β mRNA expression increased while the TNFα gene expression decreased in recipient fish. These data demonstrate the involvement of complement activity in the defence mechanisms of the gilthead seabream against the myxosporeanE. leei. Within the recipient fish group, few differences were observed in the studied immune parameters betweenE. leei-parasitized and non-parasitized recipient fish. Parasitological and immunological implications ofE. leeiinfections in Mediterranean fish farms are discussed.

Total serum immunoglobulin M levels are affected by immunomodulators in seabream (Sparus aurata L.)

Immunoglobulin M (IgM) is a major component of the teleost humoral immune system. Despite the significance of IgM levels as an immune parameter, there are relatively few studies on changes induced in its total levels in serum. This study examines the effects of several immunomodulators (vitamin A, chitin, yeast cells or levamisole, which act as immunostimulants, and crowding, hypoxia or anaesthetics, which act as stressors) upon the total serum IgM levels of non-immunized gilthead seabream (Sparus aurata L.). Total serum IgM levels of fish fed with the assayed immunostimulant-supplemented diets were statistically higher than those in fish fed a non-supplemented diet, especially in the case of levamisole. On the other hand, serum IgM levels of fish subjected to different stressors were not affected by crowding, hypoxia or certain anaesthetics. However, benzocaine and a narcotic dose of 2-phenoxyethanol provoked a great reduction, while quinaldine sulphate increased IgM levels to a significant degree. These results show how the seric IgM levels can be differently affected by some immunomodulators and the important role they may play in the regulation of total circulating IgM levels in seabream. The possibility of using total serum IgM for assessing immunostimulation, disease diagnosis and stress symptoms during fish farming is discussed.

Immunostimulant properties of a cell wall-modified whole Saccharomyces cerevisiae strain administered by diet to seabream (Sparus aurata L.)

The possible differences in the immunostimulant effects between whole wild Saccharomyces cerevisiae and a mutant strain (fks-1) administered in the diet to gilthead seabream (Sparus aurata L.) were studied. Fish were fed diets containing 0 (control) or 10 g whole wild yeast or fks-1 strain per kilogram feed for 2, 4 or 6 weeks. After each sampling, the innate humoral (complement, lysozyme and peroxidases) and cellular (intracellular peroxidases, phagocytosis, respiratory burst activity and cytotoxicity) responses were determined. Among the humoral responses, serum peroxidases and complement activity were significantly decreased after 6 weeks of feeding with the fks-1 strain-supplemented diet, while lysozyme activity increased after 2 and 4 weeks of feeding the fks-1 strain. Of the cellular responses studied, phagocytosis was increased to a significant degree at all the assayed times but only by the fks-1 strain-supplemented diet, while respiratory burst activity (after 4 weeks) and natural cytotoxicity (after 4 and 6 weeks) increased with either yeast strain. The intracellular peroxidase content was not affected by the dietary supplementation of either yeast strain. These results are discussed with a view to assessing the possible use of wild and/or mutant yeast strains for immunostimulant purposes in aquaculture.

Tumouricidal activity of gilthead seabream (Sparus aurata L.) natural cytotoxic cells: the role played in vitro and in vivo by retinol acetate

The natural cytotoxic activity of gilthead seabream head-kidney leucocytes was evaluated after in vitro incubation with retinol acetate as vitamin A source, and in samples taken from specimens receiving an intraperitoneal injection or a diet supplemented with this vitamin. Isolated leucocytes were incubated with 0 to 10(-10)m all-trans-retinol acetate-supplemented culture medium for 0, 6 or 24h and assayed for their tumouricidal activity which was found to increase for all the assayed concentrations and incubation times. Seabream specimens were intraperitoneally injected with 0 (control), 1.75 or 5.25 micro g retinol acetate 100 g(-1) biomass and sampled 1, 3 or 5 days post-injection. Leucocyte natural cytotoxic activity increased in a dose-dependent manner 1 and 3 days post-injection. When fish were fed a commercial diet supplemented with 0 (control), 50, 150 or 300 mg retinol acetate kg(-1) diet for 1, 2, 4 or 6 weeks, only fish which had been fed the highest supplement for 2 weeks showed any increase in head-kidney leucocyte cytotoxic activity. Serum was isolated and analysed for all-trans-retinol concentration by reverse-phase high-pressure-liquid-chromatography. The normal level was about 0.4 micro g ml(-1) serum, while treatment for 1 to 4 weeks with vitamin A increased this level. In conclusion, retinol acetate increases gilthead seabream head-kidney leucocyte cytotoxic activity both in vitro and in vivo.

Mutations in GDAP1: autosomal recessive CMT with demyelination and axonopathy

BACKGROUND

Mutations in the ganglioside-induced differentiation-associated protein 1 gene (GDAP1) were recently shown to be responsible for autosomal recessive (AR) demyelinating Charcot-Marie-Tooth disease (CMT) type 4A (CMT4A) as well as AR axonal CMT with vocal cord paralysis.

METHODS

The coding region of GDAP1 was screened for the presence of mutations in seven families with AR CMT in which the patients were homozygous for markers of the CMT4A locus at chromosome 8q21.1.

RESULTS

A nonsense mutation was detected in exon 5 (c.581C>G, S194X), a 1-bp deletion in exon 6 (c.786delG, G262fsX284), and a missense mutation in exon 6 (c.844C>T, R282C).

CONCLUSIONS

Mutations in GDAP1 are a frequent cause of AR CMT. They result in an early-onset, severe clinical phenotype. The range of nerve conduction velocities (NCV) is variable. Some patients have normal or near normal NCV, suggesting an axonal neuropathy, whereas others have severely slowed NCV compatible with demyelination. The peripheral nerve biopsy findings are equally variable and show features of demyelination and axonal degeneration.

Levamisole is a potent enhancer of gilthead seabream natural cytotoxic activity

Gilthead seabream (Sparus aurata L.) head-kidney (HK) leucocytes were incubated with 10(3) to 10(-4) ng levamisole/ml for 4, 24 or 48 h and then assayed for their natural cytotoxic activity against xenogeneic tumor cells. This activity was slightly increased after 24 h of incubation. In a second experiment, fish specimens were fed 0, 75, 150 or 300 mg levamisole/kg diet for 10 consecutive days. The fish were then fed a commercial non-supplemented diet and sampled 0, 1, 2, 3, 4 and 6 weeks post-administration of levamisole. The cytotoxic activity was found increased along the experiment and remained greatly enhanced at the end. In conclusion, levamisole enhanced seabream natural cytotoxic cell activity both in vitro and in vivo and had a great and lasting action when administered by feeding.

Changes in some innate defence parameters of seabream (Sparus aurata L.) induced by retinol acetate

The effects of high doses of dietary or intraperitoneally (i.p.) injected retinol acetate on the gilthead seabream (Sparus aurata L.) innate immune system were studied. Gilthead seabream specimens were fed a commercial non-supplemented diet containing 1.75 mg of vitamin A kg(-1) (as control) or the same diet supplemented with 50, 150 or 300 mg of retinol acetate kg(-1) (as vitamin A source). After 1, 2, 4 or 6 weeks, serum samples and head-kidney leucocytes were obtained from each fish. Serum lysozyme activity and myeloperoxidase (MPO) content were unaffected by the vitamin A diet content. The phagocytic and respiratory burst activities of head-kidney leucocytes were established, as well as their myeloperoxidase content. While phagocytosis was not enhanced by dietary vitamin A intake and was even slightly decreased after 2 weeks, respiratory burst activity was enhanced in specimens fed supplements of 150 and 300 mg retinol acetate kg(-1) diet for 1 or 2 weeks. Leucocyte MPO content was also enhanced when seabream were fed the highest vitamin A dose for 2 or 4 weeks and after being fed the 150 or 50 mg supplemented diets for 4 or 6 weeks, respectively. Three different groups of seabream were i.p. injected with 1 ml of phosphate buffer containing an amount of retinol acetate equivalent to the daily dietary supplements from the first experiment (0-control-, 0.05 or 0.30 mg 100 g(-1) biomass). Both injection doses of retinol acetate were toxic for the gilthead seabream which showed hypervitaminic effects. These data show that retinol acetate plays an important role in the gilthead seabream nonspecific cellular immune system due to its antioxidant properties. They also point to the importance of the way in which it is administered, by dietary uptake or intraperitoneal injection.