1,721,001 research outputs found
From Sea to Skin: Is There a Future for Natural Photoprotectants?
Get PDFIn the last few decades, the thinning of the ozone layer due to increased atmospheric pollution has exacerbated the negative effects of excessive exposure to solar ultraviolet radiation (UVR), and skin cancer has become a major public health concern. In order to prevent skin damage, public health advice mainly focuses on the use of sunscreens, along with wearing protective clothing and avoiding sun exposure during peak hours. Sunscreens present on the market are topical formulations that contain a number of different synthetic, organic, and inorganic UVR filters with different absorbance profiles, which, when combined, provide broad UVR spectrum protection. However, increased evidence suggests that some of these compounds cause subtle damage to marine ecosystems. One alternative may be the use of natural products that are produced in a wide range of marine species and are mainly thought to act as a defense against UVR-mediated damage. However, their potential for human photoprotection is largely under-investigated. In this review, attention has been placed on the molecular strategies adopted by marine organisms to counteract UVR-induced negative effects and we provide a broad portrayal of the recent literature concerning marine-derived natural products having potential as natural sunscreens/photoprotectants for human skin. Their chemical structure, UVR absorption properties, and their pleiotropic role as bioactive molecules are discussed. Most studies strongly suggest that these natural products could be promising for use in biocompatible sunscreens and may represent an alternative eco-friendly approach to protect humans against UV-induced skin damage
Biochemical and functional characterization of superoxide dismutase from the psychrophilic eubacterium Pseudoalteromonas haloplanktis
No full textSuperoxide dismutase (SOD) is a metal-enzyme, catalyzing the dismutation of superoxide anion in molecular oxygen and hydrogen peroxide. It is involved in the cellular defence mechanism against the reactive and toxic products of oxygen metabolism. SODs have been classified into two main families, according to their different structural folding and metal content: the Cu/Zn family and that containing Fe or Mn in the active site. SODs isolated from extremophilic organisms are suitable models to study the structure-function relationships and the molecular and evolutive mechanisms for the adaptation of proteins to extreme environments. We have previously isolated a SOD from the hyperthermophilic archaeon Sulfolobus solfataricus (SsSOD). Its is a Fe-SOD endowed with a remarkable heat stability, its t1/2 being 2 hours at 100°C. Structural ands functional studies on the recombinant SsSOD and the analysis of some mutant and modified forms have explained several aspects about the mechanisms adopted by the enzyme to function at high temperatures. Therefore, it could be interesting to carry out similar studies also in a psychrophilic organism. In this communication we report the purification and the preliminary biochemical characterization of SOD from the psychrophilic eubacterium Pseudoalteromonas haloplanktis, isolated from Antarctic marine sediments and adapted to grow at low temperatures. SOD from P. haloplanktis (PhSOD) was purified to homogeneity from cells grown at 4°C by two chromatographic steps on a DEAE-Sepharose and HTP. The relative molecular mass of the purified enzyme, estimated by SDS-PAGE is 22,000. As SsSOD, also PhSOD shows a homotetrameric structure, as determined by gel filtration. PhSOD has a unusual thermal stability for a psychrophilic enzyme, as evaluated by its half-life of 10 min at 52°C. Similar results were obtained by UV-melting curves. The heat stability seems to be a feature possessed by a number of SODs; for instance, rat mitochondrial Mn-SOD has a a melting temperature of 87°C. Enzymatic assays showed that PhSOD has a specific activity of 6500 U/mg, The enzyme is inactivated by hydrogen peroxide and it is inhibited by sodium azide, whereas PMSF, a specific SsSOD inactivator, has no effect. According to this preliminary characterization PhSOD could be classified as a Fe-SOD. Future research plan includes the determination of the metal content and the cloning of the gene encoding PhSOD from a genomic DNA library. To this aim, a molecular probe will be designed on the basis of the amino acid sequence of some tryptic fragments of the purified protein
Metabolic adaptations to marine environments: Molecular diversity and evolution of ovothiol biosynthesis in Bacteria
No full textThe complex evolutionary history of sulfoxide synthase in ovothiol biosynthesis
No full textSulfoxide synthases are enzymes involved in the biosynthesis of small sulfur-containing natural products. Their enzymatic activity represents a unique sulfur transfer strategy in nature that is the insertion of a sulfur atom on the imidazole ring of histidine. To date, only two enzymes are known to carry out this function: the sulfoxide synthase EgtB, involved in the biosynthesis of ergothioneine in fungi and bacteria, and the 5-histidylcysteine sulfoxide synthase OvoA, involved in the biosynthesis of ovothiols, found in the eggs and biological fluids of marine invertebrates, some proteobacteria and protists. In particular, ovothiols, thanks to their unique redox properties, are probably the most intriguing marine sulfur-containing molecules. Although they have long been considered as cellular protective molecules, new evidence suggest that their biological activities and ecological role might be more complex than originally thought. Here, we investigate the evolutionary history of OvoA in Metazoa, reporting its monophyletic ancient origins, which could be traced back to the latest common ancestor of Choanozoa. Nevertheless, we show that OvoA is missing in several major extant taxa and we discuss this patchy distribution in the light of the massive genome reduction events documented in Metazoa. We also highlight two interesting cases of secondary acquisition through horizontal gene transfer, which occurred in hydrozoans and bdelloid rotifers. The evolutionary success of this metabolic pathway is probably ascribable to its role in the maintenance of cellular redox homeostasis, which enables organisms to survive in different environmental niches
Diatom-based genetic engineering system methodology for the eco-sustainable production of ovothiols
No full textThe present invention relates to the field of biotechnology, in particular it relates to the set-up of a protocol
of enzymatic engineering of the diatom species Phaeodactylum tricornutum to overexpress the biosynthetic
enzyme leading to ovothiol production. This protocol is eco-sustainable because it uses cells and nutrients
for biosynthesis and does not produce toxic side-compounds.
Microalgal biomass moreover can be exploited for additional uses after ovothiol extraction, making the
production process more cost-effective. The production of ovothiols is relevant for the pharmaceutical, nutraceutical, and cosmeceutical sectors
First evidence of dermo-protective activity of marine sulfur-containing histidine compounds
No full textAmong natural products, ovothiol (ovo), produced by marine invertebrates, bacteria, and microalgae, is receiving increasing interest for its unique antioxidant properties. Recently, ovo has been shown to exhibit anti-inflammatory activity in an in vitro model of endothelial dysfunction and in an in vivo model of liver fibrosis.The aim of this study was to evaluate the effect of ovo and its precursor 5-thiohistidine (5-thio) in comparison with ergothioneine (erg), in human skin cells and tissues upon inflammation. We used both an in vitro and ex vivo model of human skin, represented by a keratinocytes cell line (HaCaT) and skin biopsies, respectively. We observed that ovo, 5-thio, and erg were not cytotoxic in HaCaT cells, but instead exerted a protective function against TNF-alpha-induced inflammation. In order to get insights on their mechanism of action, we performed western blot analysis of ERK and JNK, as well as sub-cellular localization of Nrf2, a key mediator of the anti-inflammatory response. The results indicated that the pre-treatment with ovo, 5-thio, and erg differently affected the phosphorylation of ERK and JNK. However, all the three molecules promoted the accumulation of Nrf2 in the nucleus of HaCaT cells. In addition, gene expression analysis by RTqPCR and ELISA assays performed in ex vivo human skin tissues pre-treated with thiohistidines and then inflamed with IL-1 beta revealed a significant downregulation of IL-8, TNF-alpha and COX-2 genes and a concomitant significant decrease in the cytokines IL-6, IL-8 and TNF-alpha production. Moreover, the protective action of ovo and 5-thio resulted to be stronger when compared with dexamethasone, a corticosteroid drug currently used to treat skin inflammatory conditions.Our findings suggest that ovo and 5-thio can ameliorate skin damage and may be used to develop natural skin care products to prevent the inflammatory status induced by environmental stressors and aging.DL57/2016/CP1361/CT0006LA/P/0101/2020info:eu-repo/semantics/publishedVersio
Molecular evolution of ovothiol biosynthesis in animal life reveals diversity of the natural antioxidant ovothiols in Cnidaria
Get PDFSulfoxide synthase OvoA is the key enzyme involved in the biosynthesis of ovothiols (OSHs), secondary metabolites endowed with unique antioxidant properties. Understanding the evolution of such enzymes and the diversity of their metabolites should reveal fundamental mechanisms governing redox signaling and environmental adaptation. “Early-branching” animals such as Cnidaria display unique molecular diversity and symbiotic relationships responsible for the biosynthesis of natural products, however, they have been neglected in previous research on antioxidants and OSHs. In this work, we have integrated genome and transcriptome mining with biochemical analyses to study the evolution and diversification of OSHs biosynthesis in cnidarians. By tracing the history of the ovoA gene, we inferred its loss in the latest common ancestor of Medusozoa, followed by the acquisition of a unique ovoB/ovoA chimaeric gene in Hydrozoa, likely through a horizontal gene transfer from dinoflagellate donors. While Anthozoa (corals and anemones), bearing canonical ovoA genes, produced a striking variety of OSHs (A, B, and C), the multifunctional enzyme in Hydrozoa was related to OSH B biosynthesis, as shown in Clytia hemisphaerica. Surprisingly, the ovoA-lacking jellyfish Aurelia aurita and Pelagia noctiluca also displayed OSHs, and we provided evidence of their incorporation from external sources. Finally, transcriptome mining revealed ovoA conserved expression pattern during larval development from Cnidaria to more evolved organisms and its regulation by external stimuli, such as UV exposure. The results of our study shed light on the origin and diversification of OSH biosynthesis in basal animals and highlight the importance of redox-active molecules from ancient metazoans as cnidarians to vertebrates
Sulfur-containing histidine compounds inhibit gamma-glutamyl transpeptidase activity in human cancer cells
No full textGamma-glutamyl transpeptidase (GGT) is an enzyme located on the surface of cellular membranes and involved in glutathione metabolism and maintenance of redox homeostasis. High GGT expression on tumor cells is associated with increased cell proliferation and resistance against chemotherapy. GGT inhibitors evaluated so far in clinical trials are too toxic for human use. In this study, using enzyme kinetics analyses, we demonstrate that ovothiols, 5(Nπ)-methyl thiohistidines of marine origin, act as non-competitive inhibitors of GGT with an apparent Ki of 21 μM, when we fixed the concentrations of the donor substrate. We found that these compounds are more potent than the known GGT inhibitor 6-diazo-5-oxo-L-norleucine and are not toxic toward human embryonic cells. In particular, cellular process-specific fluorescence-based assays revealed that ovothiols induce a mixed cell-death phenotype of apoptosis and autophagy in GGT-overexpressing cell lines, including human liver cancer and chronic B leukemic cells. The findings of our study provide the basis for further development of 5-thiohistidines as therapeutics for GGT-positive tumors and highlight that GGT inhibition is involved in autophagy
Structure, Stability and flexibility of a psychrophilic iron superoxide dismutase
No full textThe Antarctic eubacterium Pseudoalteromonas haloplanktis (Ph) produces a cold-active iron superoxide dismutase (SOD). PhSOD is a homodimeric enzyme, that displays a high catalytic activity even at low temperature. The structure, stability and dynamics of PhSOD have been determined and compared with those of its mesophilic counterpart from E. coli (EcSOD). PhSOD was found to have structure and stability very similar to Ec-SOD. However, the psychrophilic protein shows an increased flexibility of the active site with respect to its mesophilic homologue. Two PhSOD mutants (C57S and C57R) have been also characterized. The C57R mutation significantly alters the half-denaturation temperature of the protein. The structural and dynamic changes induced by this mutation with respect to the C57S and wild-type structure were correlated with modifications in the thermal stability of the mutant. Altogether these data illustrate how evolution can adjust psychrophilic enzyme sequences to alter the flexibility, without compromising the overall protein structure
- …
