The presence of guanosine 5'-diphospho-5'-guanosine and guanosine 5'-triphospho-5'-adenosine in brine shrimp embryos

Efficacy and safety of artificial tears containing Artemia salina extract with dinucleotides for dry eye

CLINICAL RELEVANCE

This clinical trial was conducted as part of the marketing procedures for a medical device comprising artificial tears containing Artemia salina extract with dinucleotides. These molecules previously demonstrated secretagogue properties by enhancing the production of aqueous, mucinous, and lipidic components of the tears.

BACKGROUND

After confirming the efficacy of artificial tears containing Artemia salina extract in an animal model, this study proceeded to evaluate their efficacy and safety on dry eye participants.

METHODS

A randomised controlled clinical trial was performed on 36 dry eye participants (41.6 ± 20.6 years). Half of the participants were treated with saline solution as a placebo for four weeks, while the other half were treated with artificial tears containing Artemia salina, randomly assigned. After a wash-out period of two weeks, the treatments were crossed for another four weeks. Participants were assessed at baseline and after one week, two weeks, and four weeks. Efficacy variables were: eye dryness frequency (primary), eye comfort, visual satisfaction, tear secretion, tear break-up time, corneal staining, conjunctival staining, and conjunctival hyperaemia. Safety variables were: high- and low-contrast visual acuity, intraocular pressure, and eye fundus images analysis.

RESULTS

Compared with the baseline, the saline solution showed no significant changes in any of the studied variables after four weeks of treatment (p ≥ 0.05). However, the topical instillation of the artificial tears with Artemia salina for four weeks significantly improved eye dryness frequency (p = 0.014) and corneal staining (p = 0.010). No systemic or ocular adverse events were reported during the clinical trial.

CONCLUSION

The topical instillation of artificial tears containing Artemia salina in mild to moderate dry eye participants for four weeks slightly improved their symptoms related to eye dryness frequency and reduced corneal damage, with no undesirable side effects observed.

Efficacy of Artificial Tears Based on an Extract of Artemia salina Containing Dinucleotides in a Rabbit Dry Eye Model

(1) Background: Artemia salina is a brine shrimp containing high concentrations of dinucleotides, molecules with properties for dry eye treatment. For this reason, the purpose of the study was to evaluate the effect of the artificial tears based on an extract of Artemia salina in a rabbit dry eye model. (2) Methods: A prospective and randomized study was carried out. Twenty rabbits were divided into 4 groups (n = 5, each group): healthy rabbits, dry eye rabbits, dry eye rabbits treated with hypromellose (HPMC), and dry eye rabbits treated with Artemia salina. Dry eye was induced by the topical instillation of 0.2% benzalkonium chloride. The measurements were performed before and after the treatment for 5 consecutive days. (3) Results: The topical instillation of artificial tears containing Artemia salina showed beneficial effects on tear secretion, tear break-up time, corneal staining, the density of Goblet cells, heigh of mucin cloud secreted by these cells, and mRNA levels of IL-1β and MMP9 in conjunctival cells. Compared with the HPMC, there was a statistically significant improvement (p < 0.05) with the Artemia salina in all the variables under study, except for the conjunctival hyperemia, density of Goblet cells, and mRNA levels of IL-6. (4) Conclusions: The potential of artificial tears based on Artemia salina as a secretagogue agent for dry eye treatment was confirmed, opening the door for future clinical trials and studies to extrapolate the findings for dry eye patients.

Targeted Metabolomic Assessment of the Sub-Lethal Toxicity of Halogenated Acetic Acids (HAAs) to Daphnia magna

Halogenated acetic acids (HAAs) are amongst the most frequently detected disinfection by-products in aquatic environments. Despite this, little is known about their toxicity, especially at the molecular level. The model organism Daphnia magna, which is an indicator species for freshwater ecosystems, was exposed to sub-lethal concentrations of dichloroacetic acid (DCAA), trichloroacetic acid (TCAA) and dibromoacetic acid (DBAA) for 48 h. Polar metabolites extracted from Daphnia were analyzed using liquid chromatography hyphened to a triple quadrupole mass spectrometer (LC-MS/MS). Multivariate analyses identified shifts in the metabolic profile with exposure and pathway analysis was used to identify which metabolites and associated pathways were disrupted. Exposure to all three HAAs led to significant downregulation in the nucleosides: adenosine, guanosine and inosine. Pathway analyses identified perturbations in the citric acid cycle and the purine metabolism pathways. Interestingly, chlorinated and brominated acetic acids demonstrated similar modes of action after sub-lethal acute exposure, suggesting that HAAs cause a contaminant class-based response which is independent of the type or number of halogens. As such, the identified metabolites that responded to acute HAA exposure may serve as suitable bioindicators for freshwater monitoring programs.

Preclinical Development of Artificial Tears Based on an Extract of Artemia Salina Containing Dinucleotides in Rabbits

PURPOSE

To evaluate the preclinical efficacy of eye drops based on an extract of Artemia salina on the ocular surface of rabbits. Tear secretion, tear break-up time and corneal staining were measured.

MATERIAL AND METHODS

A preclinical and short-term prospective study was performed. Twenty New Zealand white rabbits were divided into five groups, with four rabbits per group, each receiving a different concentration of Artemia salina. In each rabbit, an extract of Artemia salina (2%, 4%, 6%, 8% or 10%) was randomly instilled in one eye and saline solution (negative control) in the other eye. Tear secretion, tear break-up time and corneal staining were measured before and after the instillation of five drops per eye (one drop per hour) on the same day.

RESULTS

In tear secretion, there was an increase of 43.88 ± 6.73% with 4% Artemia salina in comparison with its baseline measurement (P = .049). The rest of the groups did not show differences (P ≥ 0.05). For tear break-up time, none of the groups showed differences (P ≥ 0.05), while for corneal staining score, there was an improvement of 0.88 ± 0.83 with 4% Artemia salina (P = .038) and a deterioration of 0.50 ± 0.83 with control solution (P = .008).

CONCLUSIONS

Short-term instillation of eye drops with 4% Artemia salina produced both stimulation of tear secretion and a slight improvement of physiological corneal staining. Besides, all the doses of up to 10% Artemia salina did not produce undesirable side effects on the ocular surface. Therefore, these eye drops are presented as a possible new treatment for dry eye due to their secretagogue properties and ocular surface regeneration.

Further characterization of the cathepsin L-associated protein and its gene in two species of the brine shrimp, Artemia

The major cysteine protease in embryos and larvae of the brine shrimp Artemia franciscana is a heterodimer composed of a cathepsin L-like polypeptide of 28.5 kDa and a 31.5 kDa polypeptide called the cathepsin L-associated protein or CLAP. In a previous study, CLAP was shown to be a cell adhesion protein containing two Fas I domains and two GTP/ATP binding sites known as Walker A and B motifs. Here, we have characterized CLAP and its genes to better understand the role of this protein in Artemia development. The polymerase chain reaction was used to investigate the structure of the CLAP gene in two species of Artemia, the New World bisexual diploid A. franciscana and the Old World parthenogenetic tetraploid Artemia parthenogenetica. The protein coding region of the CLAP gene from each species was 99.5% identical for a protein of 332 amino acids, while the 3' non-coding region, representing nearly 45% of the gene, was only 86% identical between the two related species. However, while the CLAP gene is intronless in A. franciscana, in A. parthenogenetica the gene contained a mini-intron of 30 base pairs in the 3' non-coding region. The sequences representing the CLAP gene in A. franciscana and A. parthenogenetica have been entered into the NCBI database as AY757920 and DQ100385, respectively. Northern blot analysis showed that while the cathepsin L gene is expressed constitutively in Artemia franciscana embryos and young larvae, the CLAP gene is not expressed in late embryos and young larvae. In contrast, Western blots indicated that CLAP is present in developing embryos and young larvae, at least to the first larval molt, supporting results obtained previously showing CLAP's resistance to degradation by its dimeric partner, cathepsin L. At the protein level we showed that the GTP/ATP binding sites in CLAP are functional with rate constants of 0.024 and 0.022 for GTP and ATP hydrolase activity, respectively. GTP but not ATP also had a slight stimulatory effect on cathepsin L activity of the heterodimeric protease containing CLAP. Our results support the hypothesis that CLAP plays an important role in targeting and expression regulation of cathepsin L activity during early development of Artemia.

Uridine 5'-polyphosphates (p4U and p5U) and uridine(5')polyphospho(5')nucleosides (Up(n)Ns) can be synthesized by UTP:glucose-1-phosphate uridylyltransferase from Saccharomyces cerevisiae

UTP:glucose-1-phosphate uridylyltransferase (EC 2.7.7.9) from Saccharomyces cerevisiae can transfer the uridylyl moiety from UDP-glucose onto tripolyphosphate (P(3)), tetrapolyphosphate (P(4)), nucleoside triphosphates (p(3)Ns) and nucleoside 5'-polyphosphates (p(4)Ns) forming uridine 5'-tetraphosphate (p(4)U), uridine 5'-pentaphosphate (p(5)U) and dinucleotides, such as Ap(4)U, Cp(4)U, Gp(4)U, Up(4)U, Ap(5)U and Gp(5)U. Unlike UDP-glucose, UDP-galactose was not a UMP donor and ADP was not a UMP acceptor. This is the first example of an enzyme that may be responsible for accumulation of dinucleoside tetraphosphates containing two pyrimidine nucleosides in vivo. Occurrence of such dinucleotides in S. cerevisiae and Escherichia coli has been previously reported (Coste et al., J. Biol. Chem. 262 (1987) 12096-12103).

Isolation and characterization of a dinucleoside triphosphatase from Saccharomyces cerevisiae

An enzyme able to cleave dinucleoside triphosphates has been purified 3,750-fold from Saccharomyces cerevisiae. Contrary to the enzymes previously shown to catabolize Ap4A in yeast, this enzyme is a hydrolase rather than a phosphorylase. The dinucleoside triphosphatase molecular ratio estimated by gel filtration is 55,000. Dinucleoside triphosphatase activity is strongly stimulated by the presence of divalent cations. Mn2+ displays the strongest stimulating effect, followed by Mg2+, Co2+, Cd2+, and Ca2+. The Km value for Ap3A is 5.4 microM (50 mM Tris-HCl [pH 7.8], 5 mM MgCl2, and 0.1 mM EDTA; 37 degrees C). Dinucleoside polyphosphates are substrates of this enzyme, provided that they contain more than two phosphates and that at least one of the two bases is a purine (Ap3A, Ap3G, Ap3C, Gp3G, Gp3C, m7Gp3A, m7Gp3G, Ap4A, Ap4G, Ap4C, Ap4U, Gp4G, and Ap5A are substrates; AMP, ADP, ATP, Ap2A, and Cp4U are not). Among the products, a nucleoside monophosphate is always formed. The specificity of cleavage of methylated dinucleoside triphosphates and the molecular weight of dinucleoside triphosphatase indicate that this enzyme is different from the mRNA decapping enzyme previously characterized (A. Stevens, Mol. Cell. Biol. 8:2005-2010, 1988).

Reversed-phase high-performance liquid chromatography of dinucleoside polyphosphates

The reversed-phase high-performance liquid chromatographic separation of purine dinucleoside polyphosphates on octadecyl- and phenyl-bonded silica packings using phosphate-based eluents was studied. The effects of pH, ionic strength and the content of the organic modifiers methanol and acetonitrile in the mobile phase on the retention and other chromatographic parameters are reported. The data obtained were used to establish an isocratic assay for diguanosine and diadenosine polyphosphates.

Dolichol phosphorylation occurs via a CTP-dependent reaction in Artemia larvae

The phosphorylation of dolichol in larval stages of the brine shrimp, Artemia salina, has been investigated. The dolichol kinase has been assayed in crude microsomes; the enzyme requires CTP as phosphoryl donor and calcium as divalent cation. Activity increases with both incubation time and added microsomal protein. The product of the reaction has been characterized by chromatographic and enzymatic procedures. With gamma-32P CTP as substrate, the apparent Km for CTP is 24 microM. Enzymatic activity is stimulated fivefold by exogenous dolichol. The specific activity of the enzyme increases with the frequency of molting. Dolichol kinase activity was detectable in membranes prepared from dormant Artemia cysts. The low level in dormancy may anticipate the critical role of the enzyme during hatching.

Analysis of sub-microgram quantities of nucleotides by fast atom bombardment mass spectrometry

Nucleotides of the structure P1,Pn-di(adenosine-5')-n-phosphate (n = di- through penta-) in the form of salts, and P1,P4-di(guanosine-5')tetraphosphate sodium salt have been analyzed by fast atom bombardment (FAB) mass spectrometry. A 0.2 molar solution of p-toluenesulfonic acid in glycerol has been evaluated as a matrix. In this matrix, the metal ions of the nucleotide salts are readily exchanged for protons, resulting in a simple spectrum with only one peak in the molecular ion region corresponding to the free phosphoric acid of the nucleotide plus or minus a proton (positive or negative mode), instead of the multiplicity of peaks arising from a series of metal and matrix adduct ions found with glycerol as matrix. The detection limit for analytes using this matrix is improved by a factor of ten compared to glycerol alone. It appears that the high acidity and the surfactant properties of p-toluenesulfonic acid both contribute to this result. Useful spectra are obtained from 250 ng of each of the above mentioned nucleotides, with the detection limit being somewhat lower in the positive mode. However, both positive and negative FAB spectra are useful and the results are complementary.

Synthesis of hybrid bisnucleoside 5',5"'-P1,P4-tetraphosphates by aminoacyl-tRNA synthetases

Aminoacyl tRNA synthetases, by means of a back reaction, are able to synthesize certain 5', 5"'-P1, P4-bisnucleoside tetraphosphates of biological importance, such as Ap4A. Here it is shown that HisRS and TrpRS (Bacillus stearothermophilus) and AlaRS (E. coli) also synthesize the hybrid compounds Ap4G, Ap4C, and Ap4U. GlnRS (E. coli) is unable to synthesize any of the above compounds. AlaRS synthesizes Ap4U very poorly, and Ap4C and Ap4G almost as effectively as Ap4A. HisRS and TrpRS synthesize Ap4G, Ap4U and Ap3U quite effectively, and Ap4C very poorly. The fact that hybrid bisnucleoside tetraphosphates can be made by the same enzymes, and at rates comparable to Ap4A, suggests that these compounds may also occur in vivo.

Catabolism of bis(5'-nucleosidyl) oligophosphates in Escherichia coli: metal requirements and substrate specificity of homogeneous diadenosine-5',5'''-P1,P4-tetraphosphate pyrophosphohydrolase

Diadenosine-5',5'''-P1,P4-tetraphosphate pyrophosphohydrolase (diadenosinetetraphosphatase) from Escherichia coli strain EM20031 has been purified 5000-fold from 4 kg of wet cells. It produces 2.4 mg of homogeneous enzyme with a yield of 3.1%. The enzyme activity in the reaction of ADP production from Ap4A is 250 s-1 [37 degrees C, 50 mM tris(hydroxymethyl)aminomethane, pH 7.8, 50 microM Ap4A, 0.5 microM ethylenediaminetetraacetic acid (EDTA), and 50 microM CoCl2]. The enzyme is a single polypeptide chain of Mr 33K, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and high-performance gel permeation chromatography. Dinucleoside polyphosphates are substrates provided they contain more than two phosphates (Ap4A, Ap4G, Ap4C, Gp4G, Ap3A, Ap3G, Ap3C, Gp3G, Gp3C, Ap5A, Ap6A, and dAp4dA are substrates; Ap2A, NAD, and NADP are not). Among the products, a nucleoside diphosphate is always formed. ATP, GTP, CTP, UTP, dATP, dGTP, dCTP, and dTTP are not substrates; Ap4 is. Addition of Co2+ (50 microM) to the reaction buffer containing 0.5 microM EDTA strongly stimulates Ap4A hydrolysis (stimulation 2500-fold). With 50 microM MnCl2, the stimulation is 900-fold. Ca2+, Fe2+, and Mg2+ have no effect. The Km for Ap4A is 22 microM with Co2+ and 12 microM with Mn2+. The added metals have similar effects on the hydrolysis of Ap3A into ADP + AMP. However, in the latter case, the stimulation by Co2+ is small, and the maximum stimulation brought by Mn2+ is 9 times that brought by Co2+. Exposure of the enzyme to Zn2+ (5 microM), prior to the assay or within the reaction mixture containing Co2+, causes a marked inhibition of Ap4A hydrolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Messenger RNA during early embryogenesis in Artemia salina: altered translatability and sequence complexity

RNA from developing embryos of Artemia salina (5, 10, and 20 h after re-initiation of development) was translated 3-10 times more efficiently in a rabbit reticulocyte lysate cell-free protein synthesizing system than RNA from dormant gastrulae. The latter did not appear to contain any significant amount of translation inhibitor activity. Ninety percent of the translatable activity in dormant gastrulae was recovered as poly(A)--RNA, whereas 80% of that in post-gastrular developing embryos was present as poly(A)+-RNA. The size of most polypeptides coded for by dormant gastrular RNA was less than 130,000 daltons whereas the size of those coded for by developing embryonic RNA was up to 200,000 daltons, which correlated with a corresponding shift to poly A-containing RNA of higher molecular weight. Two major polypeptides of about 37,000 daltons coded for by dormant gastrular RNA disappeared at 20 h after resumption of development. Hybridization of complementary DNA (cDNA) to a 1000-fold excess of the homologous poly(A)+-RNA revealed the presence of three complexity classes of mRNA. Forty-five percent, 30%, and 25% of RNA in dormant gastrulae were present as high, middle, and low abundance classes comprising about 10, 80, and 9700 species, respectively whereas in the nauplii there were 10, 150, and 7900 species of high, middle, and low abundancy sequences, respectively. Heterologous hybridizations using cDNA complementary to highly abundant messenger population of nauplii (isolated by chromatography on hydroxyapatite) to poly(A)+-RNA from dormant cysts showed considerably divergence in this class of messengers from the two developmental stages. Re-initiation of development of dormant Artemia gastrulae is thus characterized by a "re-programming" seen as a simultaneous and rapid increase in the polyadenylation and translatability of poly(A)+-RNA accompanied by a qualitative change in its sequence complexity.