RESUMO
Many fungi are thought to have developed morphological and physiological adaptations to cope with exposure to UV-B radiation, but in most species, such responses and their protective effects have not been explored. Here, we study the adaptive response to UV-B radiation in the widespread, saprotrophic fungus Serpula himantioides, frequently found colonizing coniferous wood in nature. We report the morphological and chemical responses of S. himantioides to controlled intensities of UV-B radiation, under in vitro culture conditions. Ultraviolet radiation induced a decrease in the growth rate of S. himantioides but did not cause gross morphological changes. Instead, we observed accumulation of pigments near the cell wall with increasing intensities of UV-B radiation. Nuclear magnetic resonance (NMR) and high-performance liquid chromatography-mass spectrometry (HPLC-MS) analyses revealed that xerocomic acid was the main pigment present, both before and after UV-B exposure, increasing from 7 mg/liter to 15 mg/liter after exposure. We show that xerocomic acid is a photoprotective metabolite with strong antioxidant abilities, as evidenced by DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt], and oxygen radical absorbance capacity (ORAC) assays. Finally, we assessed the capacity of xerocomic acid as a photoprotective agent on HEK293 cells and observed better photoprotective properties than those of ß-carotene. Xerocomic acid is therefore a promising natural product for development as a UV-protective ingredient in cosmetic and pharmaceutical products.IMPORTANCE Our study shows the morphological and chemical responses of S. himantioides to controlled doses of UV-B radiation under in vitro culture conditions. We found that increased biosynthesis of xerocomic acid was the main strategy adopted by S. himantioides against UV-B radiation. Xerocomic acid showed strong antioxidant and photoprotective abilities, which has not previously been reported. Our results indicate that upon UV-B exposure, S. himantioides decreases its hyphal growth rate and uses this energy instead to increase the biosynthesis of xerocomic acid, which is allocated near the cell wall. This metabolic switch likely allows xerocomic acid to efficiently defend S. himantioides from UV radiation through its antioxidant and photoprotective properties. The findings further suggest that xerocomic acid is a promising candidate for development as a cosmetic ingredient to protect against UV radiation and should therefore be investigated in depth in the near future both in vitro and in vivo.
Assuntos
Brachyspira/metabolismo , Parede Celular/metabolismo , Pigmentos Biológicos/metabolismo , Raios Ultravioleta , Brachyspira/efeitos da radiação , Parede Celular/efeitos da radiação , Células HEK293 , Humanos , Pigmentos Biológicos/efeitos da radiaçãoRESUMO
BACKGROUND: Antarctic bryophytes (mosses and liverworts) are resilient to physiologically extreme environmental conditions including elevated levels of ultraviolet (UV) radiation due to depletion of stratospheric ozone. Many Antarctic bryophytes synthesise UV-B-absorbing compounds (UVAC) that are localised in their cells and cell walls, a location that is rarely investigated for UVAC in plants. This study compares the concentrations and localisation of intracellular and cell wall UVAC in Antarctic Ceratodon purpureus, Bryum pseudotriquetrum and Schistidium antarctici from the Windmill Islands, East Antarctica. RESULTS: Multiple stresses, including desiccation and naturally high UV and visible light, seemed to enhance the incorporation of total UVAC including red pigments in the cell walls of all three Antarctic species analysed. The red growth form of C. purpureus had significantly higher levels of cell wall bound and lower intracellular UVAC concentrations than its nearby green form. Microscopic and spectroscopic analyses showed that the red colouration in this species was associated with the cell wall and that these red cell walls contained less pectin and phenolic esters than the green form. All three moss species showed a natural increase in cell wall UVAC content during the growing season and a decline in these compounds in new tissue grown under less stressful conditions in the laboratory. CONCLUSIONS: UVAC and red pigments are tightly bound to the cell wall and likely have a long-term protective role in Antarctic bryophytes. Although the identity of these red pigments remains unknown, our study demonstrates the importance of investigating cell wall UVAC in plants and contributes to our current understanding of UV-protective strategies employed by particular Antarctic bryophytes. Studies such as these provide clues to how these plants survive in such extreme habitats and are helpful in predicting future survival of the species studied.
Assuntos
Briófitas/metabolismo , Briófitas/efeitos da radiação , Parede Celular/metabolismo , Parede Celular/efeitos da radiação , Pigmentos Biológicos/metabolismo , Pigmentos Biológicos/efeitos da radiação , Raios Ultravioleta , Análise de Variância , Regiões Antárticas , Briófitas/citologia , Cromatografia Líquida de Alta Pressão , Microscopia Confocal , Pigmentação/efeitos da radiação , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Estações do Ano , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Fatores de TempoRESUMO
BACKGROUND: Antarctic bryophytes (mosses and liverworts) are resilient to physiologically extreme environmental conditions including elevated levels of ultraviolet (UV) radiation due to depletion of stratospheric ozone. Many Antarctic bryophytes synthesise UV-B-absorbing compounds (UVAC) that are localised in their cells and cell walls, a location that is rarely investigated for UVAC in plants. This study compares the concentrations and localisation of intracellular and cell wall UVAC in Antarctic Ceratodon purpureus, Bryum pseudotriquetrum and Schistidium antarctici from the Windmill Islands, East Antarctica. RESULTS: Multiple stresses, including desiccation and naturally high UV and visible light, seemed to enhance the incorporation of total UVAC including red pigments in the cell walls of all three Antarctic species analysed. The red growth form of C. purpureus had significantly higher levels of cell wall bound and lower intracellular UVAC concentrations than its nearby green form. Microscopic and spectroscopic analyses showed that the red colouration in this species was associated with the cell wall and that these red cell walls contained less pectin and phenolic esters than the green form. All three moss species showed a natural increase in cell wall UVAC content during the growing season and a decline in these compounds in new tissue grown under less stressful conditions in the laboratory. CONCLUSIONS: UVAC and red pigments are tightly bound to the cell wall and likely have a long-term protective role in Antarctic bryophytes. Although the identity of these red pigments remains unknown, our study demonstrates the importance of investigating cell wall UVAC in plants and contributes to our current understanding of UV-protective strategies employed by particular Antarctic bryophytes. Studies such as these provide clues to how these plants survive in such extreme habitats and are helpful in predicting future survival of the species studied.
Assuntos
Pigmentos Biológicos/efeitos da radiação , Pigmentos Biológicos/metabolismo , Raios Ultravioleta , Parede Celular/efeitos da radiação , Parede Celular/metabolismo , Briófitas/efeitos da radiação , Briófitas/metabolismo , Estações do Ano , Fatores de Tempo , Pigmentação/efeitos da radiação , Análise de Variância , Cromatografia Líquida de Alta Pressão , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Folhas de Planta/efeitos da radiação , Folhas de Planta/metabolismo , Microscopia Confocal , Briófitas/citologia , Regiões AntárticasRESUMO
The effect of ultraviolet (UV) radiation and copper (Cu) on apical segments of Pterocladiella capillacea was examined under two different conditions of radiation, PAR (control) and PAR+UVA+UVB (PAR+UVAB), and three copper concentrations, ranging from 0 (control) to 0.62, 1.25 and 2.50 µm. Algae were exposed in vitro to photosynthetically active radiation (PAR) at 70 µmol photons m(-2) s(-1) , PAR + UVB at 0.35 W m(-2) and PAR +UVA at 0.70 W m(-2) during a 12-h photocycle for 3 h each day for 7 days. The effects of radiation and copper on growth rates, content of photosynthetic pigments and photosynthetic performance were analyzed. In addition, samples were processed for light and transmission electron microscopy. The content of photosynthetic pigments decreased after exposure to radiation and Cu. Compared with PAR radiation and copper treatments modified the kinetics patterns of the photosynthesis/irradiance curve. The treatments also caused changes in the ultrastructure of cortical and subcortical cells, including increased cell wall thickness and accumulation of plastoglobuli, as well as changes in the organization of chloroplasts. The results indicate that the synergistic interaction between UV radiation and Cu in P. capillacea, led to the failure of protective mechanisms and causing more drastic changes and cellular imbalances.
Assuntos
Parede Celular/efeitos da radiação , Cloroplastos/efeitos da radiação , Cobre/toxicidade , Fótons , Fotossíntese/efeitos da radiação , Rodófitas/efeitos da radiação , Parede Celular/efeitos dos fármacos , Parede Celular/ultraestrutura , Clorofila/biossíntese , Clorofila A , Cloroplastos/efeitos dos fármacos , Cloroplastos/fisiologia , Cloroplastos/ultraestrutura , Microscopia Eletrônica de Transmissão , Fotoperíodo , Fotossíntese/efeitos dos fármacos , Fotossíntese/fisiologia , Ficobiliproteínas/biossíntese , Pigmentos Biológicos/biossíntese , Rodófitas/efeitos dos fármacos , Rodófitas/fisiologia , Rodófitas/ultraestrutura , Raios UltravioletaRESUMO
This study investigated the effects of radiation (PAR+UVA+UVB) on the development and growth rates (GRs) of young gametophytes of Gelidium floridanum. In addition, photosynthetic pigments were quantified, carotenoids identified, and photosynthetic performance assessed. Over a period of 3 days, young gametophytes were cultivated under laboratory conditions and exposed to photosynthetically active radiation (PAR) at 80 µmol photons m(-2) s(-1) and PAR+UVA (0.70 W m(-2))+UVB (0.35 W m(-2)) for 3 h per day. The samples were processed for light and electron microscopy to analyze the ultrastructure features, as well as carry out metabolic studies of GRs, quantify the content of photosynthetic pigments, identify carotenoids and assess photosynthetic performance. PAR+UVA+UVB promoted increase in cell wall thickness, accumulation of floridean starch grains in the cytoplasm and disruption of chloroplast internal organization. Algae exposed to PAR+UVA+UVB also showed a reduction in GR of 97%. Photosynthetic pigments, in particular, phycoerythrin and allophycocyanin contents, decreased significantly from UV radiation exposure. This result agrees with the decrease in photosynthetic performance observed after exposure to ultraviolet radiation, as measured by a decrease in the electron transport rate (ETR), where values of ETRmax declined approximately 44.71%. It can be concluded that radiation is a factor that affects the young gametophytes of G. floridanum at this stage of development.
Assuntos
Elétrons , Gametogênese Vegetal/efeitos da radiação , Fotossíntese/efeitos da radiação , Rodófitas/efeitos da radiação , Carotenoides/biossíntese , Parede Celular/efeitos da radiação , Parede Celular/ultraestrutura , Clorofila/biossíntese , Transporte de Elétrons/efeitos da radiação , Gametogênese Vegetal/fisiologia , Microscopia Eletrônica , Fotossíntese/fisiologia , Ficocianina/antagonistas & inibidores , Ficocianina/biossíntese , Ficoeritrina/antagonistas & inibidores , Ficoeritrina/biossíntese , Rodófitas/crescimento & desenvolvimento , Rodófitas/metabolismo , Rodófitas/ultraestrutura , Raios UltravioletaRESUMO
Opportunistic fungal pathogens may cause an array of superficial infections or serious invasive infections, especially in immunocompromised patients. Cryptococcus neoformans is a pathogen causing cryptococcosis in HIV/AIDS patients, but treatment is limited due to the relative lack of potent antifungal agents. Photodynamic inactivation (PDI) uses the combination of non-toxic dyes called photosensitizers and harmless visible light, which produces singlet oxygen and other reactive oxygen species that produce cell inactivation and death. We report the use of five structurally unrelated photosensitizers (methylene blue, Rose Bengal, selenium derivative of a Nile blue dye, a cationic fullerene and a conjugate between poly-L-lysine and chlorin(e6)) combined with appropriate wavelengths of light to inactivate C. neoformans. Mutants lacking capsule and laccase, and culture conditions that favoured melanin production were used to probe the mechanisms of PDI and the effect of virulence factors. The presence of cell wall, laccase and melanin tended to protect against PDI, but the choice of the appropriate photosensitizers and dosimetry was able to overcome this resistance.
Assuntos
Coinfecção/microbiologia , Criptococose/microbiologia , Cryptococcus neoformans/efeitos dos fármacos , Fármacos Fotossensibilizantes/administração & dosagem , Antifúngicos/administração & dosagem , Parede Celular/efeitos dos fármacos , Parede Celular/efeitos da radiação , Coinfecção/fisiopatologia , Coinfecção/virologia , Criptococose/genética , Criptococose/fisiopatologia , Cryptococcus neoformans/genética , Cryptococcus neoformans/patogenicidade , Cryptococcus neoformans/efeitos da radiação , HIV/patogenicidade , Infecções por HIV/complicações , Infecções por HIV/microbiologia , Infecções por HIV/virologia , Humanos , Hospedeiro Imunocomprometido/efeitos dos fármacos , Hospedeiro Imunocomprometido/efeitos da radiação , Luz , Espécies Reativas de Oxigênio/metabolismoRESUMO
The objective of this study was to evaluate whether Candida albicans exhibits altered pathogenicity characteristics following sublethal antimicrobial photodynamic inactivation (APDI) and if such alterations are maintained in the daughter cells. C. albicans was exposed to sublethal APDI by using methylene blue (MB) as a photosensitizer (0.05 mM) combined with a GaAlAs diode laser (λ 660 nm, 75 mW/cm(2), 9 to 27 J/cm(2)). In vitro, we evaluated APDI effects on C. albicans growth, germ tube formation, sensitivity to oxidative and osmotic stress, cell wall integrity, and fluconazole susceptibility. In vivo, we evaluated C. albicans pathogenicity with a mouse model of systemic infection. Animal survival was evaluated daily. Sublethal MB-mediated APDI reduced the growth rate and the ability of C. albicans to form germ tubes compared to untreated cells (P < 0.05). Survival of mice systemically infected with C. albicans pretreated with APDI was significantly increased compared to mice infected with untreated yeast (P < 0.05). APDI increased C. albicans sensitivity to sodium dodecyl sulfate, caffeine, and hydrogen peroxide. The MIC for fluconazole for C. albicans was also reduced following sublethal MB-mediated APDI. However, none of those pathogenic parameters was altered in daughter cells of C. albicans submitted to APDI. These data suggest that APDI may inhibit virulence factors and reduce in vivo pathogenicity of C. albicans. The absence of alterations in daughter cells indicates that APDI effects are transitory. The MIC reduction for fluconazole following APDI suggests that this antifungal could be combined with APDI to treat C. albicans infections.
Assuntos
Candida albicans/efeitos dos fármacos , Candidíase/tratamento farmacológico , Azul de Metileno/farmacologia , Fármacos Fotossensibilizantes/farmacologia , Fatores de Virulência/antagonistas & inibidores , Animais , Antifúngicos/farmacologia , Candida albicans/crescimento & desenvolvimento , Candida albicans/patogenicidade , Candida albicans/efeitos da radiação , Candidíase/microbiologia , Candidíase/mortalidade , Parede Celular/efeitos dos fármacos , Parede Celular/efeitos da radiação , Feminino , Fluconazol/farmacologia , Padrões de Herança , Lasers Semicondutores , Luz , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Pressão Osmótica , Estresse Oxidativo , Análise de Sobrevida , Fatores de Virulência/metabolismoRESUMO
Paracoccidioides brasiliensis is a thermally dimorphic fungus agent of paracoccidioidomycosis, a deep-seated systemic infection of humans with high prevalence in Latin America. Until now no vaccine has been reported. Ionizing radiation can be used to attenuate pathogens for vaccine development and we have successfully attenuated yeast cells of P. brasiliensis by gamma irradiation. The aim of the present study was to examine at ultrastructural level the effects of gamma irradiation attenuation on the morphology of P. brasiliensis yeast cells. Paracoccidioides brasiliensis (strain Pb-18) cultures were irradiated with a dose of 6.5 kGy. The irradiated cells were examined by scanning and also transmission electron microscopy. When examined 2 h after the irradiation by scanning electron microscopy, the 6.5 kGy irradiated cells presented deep folds or were collapsed. These lesions were reversible since when examined 48 h after irradiation the yeast had recovered the usual morphology. The transmission electron microscopy showed that the irradiated cells plasma membrane and cell wall were intact and preserved. Remarkable changes were found in the nucleus that was frequently in a very electrondense form. An extensive DNA fragmentation was produced by the gamma irradiation treatment.