beta-Carotene production and its role in sclerotial differentiation of Sclerotium rolfsii

Therapeutic effects of intermittent fasting on high-fat, high-fructose diet; involvement of jejunal aquaporin 1, 3, and 7

Background

Aquaporins (AQPs) are transmembrane channel proteins. Aquaporin 1 (AQP1), Aquaporin 3 (AQP3), and Aquaporin 7 (AQP7) are expressed in the jejunum. The purpose of this study was to ascertain how a high-fat high-fructose diet (HFFD) and intermittent fasting (IF) affect AQP1, AQP3, and AQP7 expression in the rat jejunum.

Methods

Sixteen adult male rats were divided into control rats (n = 4) fed on a basal diet and water ad libitum for 12 weeks; IF control rats (n = 4) followed the IF protocol, HFFD-fed rats (n = 8) fed HFFD for eight weeks, and rats were randomized into two groups: HFFD only or HFFD and IF protocol from the beginning of the 9th week until the end of the experiment. The lipid profile values were assessed after 12 weeks. Jejunal oxidative markers (malondialdehyde and reduced glutathione) and AQP1, AQP3, and AQP7 mRNA expression were measured. Jejunal sections were used for morphometric analysis of villus length and crypt depth. Immunohistochemical evaluation of AQP1, AQP3, and AQP7 expression was also performed.

Results

IF ameliorates HFFD-induced lipid profile, oxidative stress, and jejunal morphometric changes. The results of both mRNA expression using PCR and immunohistochemistry showed a significant increase in AQP1, AQP3, and AQP7 expression in HFFD, whereas IF caused a decline in this expression.

Conclusion

These findings suggest that IF can reduce inflammation, and oxidative stress and restore jejunal morphology caused by HFFD.

De Novo RNA Sequencing and Transcriptome Analysis of Sclerotium rolfsii Gene Expression during Sclerotium Development

Sclerotium rolfsii is a destructive soil-borne fungal pathogen that causes stem rot in cultivated plants. However, little is known about the genetic basis of sclerotium development. In this study, we conducted de novo sequencing of genes from three different stages of S. rolfsii (mycelia, early sclerotium formation, and late sclerotium formation) using Illumina HiSeqTM 4000. We then determined differentially expressed genes (DEGs) across the three stages and annotated gene functions. STEM and weighted gene-co-expression network analysis were used to cluster DEGs with similar expression patterns. Our analysis yielded an average of 25,957,621 clean reads per sample (22,913,500-28,988,848). We identified 8929, 8453, and 3744 DEGs between sclerotium developmental stages 1 versus 2, 1 versus 3, and 2 versus 3, respectively. Additionally, four significantly altered gene expression profiles involved 220 genes related to sclerotium formation, and two modules were positively correlated with early and late sclerotium formation. These results were supported by the outcomes of qPCR and RNA-sequencing conducted on six genes. This is the first study to provide a gene expression map during sclerotial development in S. rolfsii, which can be used to reduce the re-infection ability of this pathogen and provide new insights into the scientific prevention and control of the disease. This study also provides a useful resource for further research on the genomics of S. rolfsii.

Light irradiation can regulate the growth characteristics and metabolites compositions of Rhodotorula mucilaginosa

Light is an important factor that can induce the growth of varieties of organisms including fungi and their secondary metabolites. The evolutions of biomass, carotenoids, lipid production, compositions and contents of fatty acid and amino acid in Rhodotorula mucilaginosa were investigated under different light irradiation conditions. The results indicated that irradiation with 1700 lx could promote the growth and glucose assimilation of R. mucilaginosa, compared to the dark control, while the trial with 3500 lx had certain inhibiting effects. The carotenoids concentrations and percentages of unsaturated fatty acid (USFA, C16:1 and C18:1) increased with the improvement of irradiation intensity. Conversely, the proportions of saturated fatty acids (C16:0, C18:0 and C20:0) were decreased. The relative contents of amino acid and total protein were reduced under illumination compared to dark control. Conclusively, irradiation could change the cell growth and metabolites of the pigmented fungus, which implied that there may be a photoinduced mode exists in R. mucilaginosa similar to that of Neurospora crassa, and it also could be applied to regulate the biosynthesis and production of valuable components such as carotenoids and USFA.

Production and extraction of carotenoids produced by microorganisms

Carotenoids are a group of isoprenoid pigments naturally synthesized by plants and microorganisms, which are applied industrially in food, cosmetic, and pharmaceutical product formulations. In addition to their use as coloring agents, carotenoids have been proposed as health additives, being able to prevent cancer, macular degradation, and cataracts. Moreover, carotenoids may also protect cells against oxidative damage, acting as an antioxidant agent. Considering the interest in greener and sustainable industrial processing, the search for natural carotenoids has increased over the last few decades. In particular, it has been suggested that the use of bioprocessing technologies can improve carotenoid production yields or, as a minimum, increase the efficiency of currently used production processes. Thus, this review provides a short but comprehensive overview of the recent biotechnological developments in carotenoid production using microorganisms. The hot topics in the field are properly addressed, from carotenoid biosynthesis to the current technologies involved in their extraction, and even highlighting the recent advances in the marketing and application of "microbial" carotenoids. It is expected that this review will improve the knowledge and understanding of the most appropriate and economic strategies for a biotechnological production of carotenoids.

Hypovirulence of Sclerotium rolfsii Caused by Associated RNA Mycovirus

Mycoviruses associated with hypovirulence are potential biological control agents and could be useful to study the pathogenesis of fungal host pathogens. Sclerotium rolfsii, a pathogenic fungus, causes southern blight in a wide variety of crops. In this study, we isolated a series of dsRNAs from a debilitated S. rolfsii strain, BLH-1, which had pronounced phenotypic aberrations including reduced pathogenicity, mycelial growth and deficient sclerotia production. Virus-curing and horizontal transmission experiments that eliminated or transmitted, respectively, all dsRNA elements showed that the dsRNAs were involved in the hypovirulent traits of BLH-1. Ultrastructure examination also showed hyphae fracture and cytoplasm or organelle degeneration in BLH-1 hyphal cells compared to the virus-free strain. Three assembled cDNA contigs generated from the cDNA library cloned from the purified dsRNA indicated that strain BLH-1 was infected by at least three novel mycoviruses. One has similarity to the hypovirulence-associated Sclerotinia sclerotiorum hypovirus 2 (SsHV2) in the family Hypoviridae, and the other two are related to two different unclassified dsRNA mycovirus families. To our knowledge, this is the first report of S. rolfsii hypovirulence that was correlated with its associated dsRNA.

De novo assembly and transcriptome analysis of sclerotial development in Wolfiporia cocos

Wolfiporia cocos Ryvarden et Gilbertson, a well-known medicinal fungus in the Basidiomycetes, is widely distributed in East Asia. Its dried sclerotium, which is known as Fuling in China, has been used as a traditional crude drug in Chinese traditional medicine for thousand years. However, little is known about how the sclerotium is developed at the genetic level. In this study, the de novo sequencing of sclerotia of W. cocos (S1_initial stage; S2_developmental stage and S3_mature stage) was carried out by illumina HiSeq 2000 technology. 27,438 unigenes were assembled from ~30Gbp raw data, and 12,093 unigenes were significantly annotated. The analysis of expression profiles during development returned 304 differentially expressed genes (DEGs), which were clustered into four different groups according to their expression trends. Especially for the maturation stage (S3), the sclerotium exhibited a markedly different expression profile from other stages. We further showed that peroxisome, unsaturation of fatty acids and degradation pathway were respectively prevalent in S1, S2 and S3 stages as evidenced by enrichment analysis. To our knowledge, this study represents the first report of sclerotial development transcriptomics in W. cocos. The obtained results provide novel insights into the developmental biology of the sclerotia, which is helpful for future studies about cultivation and breeding of W. cocos.

Biological roles of fungal carotenoids

Carotenoids are terpenoid pigments widespread in nature, produced by bacteria, fungi, algae and plants. They are also found in animals, which usually obtain them through the diet. Carotenoids in plants provide striking yellow, orange or red colors to fruits and flowers, and play important metabolic and physiological functions, especially relevant in photosynthesis. Their functions are less clear in non-photosynthetic microorganisms. Different fungi produce diverse carotenoids, but the mutants unable to produce them do not exhibit phenotypic alterations in the laboratory, apart of lack of pigmentation. This review summarizes the current knowledge on the functional basis for carotenoid production in fungi. Different lines of evidence support a protective role of carotenoids against oxidative stress and exposure to visible light or UV irradiation. In addition, the carotenoids are intermediary products in the biosynthesis of physiologically active apocarotenoids or derived compounds. This is the case of retinal, obtained from the symmetrical oxidative cleavage of β-carotene. Retinal is the light-absorbing prosthetic group of the rhodopsins, membrane-bound photoreceptors present also in many fungal species. In Mucorales, β-carotene is an intermediary in the synthesis of trisporoids, apocarotenoid derivatives that include the sexual hormones the trisporic acids, and they are also presumably used in the synthesis of sporopollenin polymers. In conclusion, fungi have adapted their ability to produce carotenoids for different non-essential functions, related with stress tolerance or with the synthesis of physiologically active by-products.

Wet-plate culture studies of Penicillium sp. PT95 and Q1 for mass production of sclerotia

Penicillium sp. PT95 and Q1 strains were able to form abundant orange, sand-shaped sclerotia in which carotenoids were accumulated. To determine the potential availability of the wet-plate method for mass production of sclerotia, nine kinds of liquid media were used culture the PT95 and Q1 strains. The results of the wet-plate culture showed that on 25% glycerol nitrate broth medium, the growth of both strains was relatively slow, and no sclerotia were found. Q1 strain cultured on Czapek's yeast extract broth medium could not form sclerotia. On other media, both strains could form sclerotia. For PT95 strain, the highest sclerotial biomass (380 mg plate(-1) ) and carotenoids yield (20.88 µg plate(-1) ) could be obtained on Czapek's yeast extract broth and Georgiou's liquid medium, respectively. For Q1 strain, malt extract broth medium gave the highest sclerotial biomass (340 mg plate(-1) ) and omitting iron Joham's liquid medium gave the highest carotenoids yield (18.29 µg plate(-1) ). The results from this study suggest the potential usage of wet-plate method in the mass production of sclerotia of the PT95 and Q1 strains.

Sclerotial formation of Polyporus umbellatus by low temperature treatment under artificial conditions

BACKGROUND

Polyporus umbellatus sclerotia have been used as a diuretic agent in China for over two thousand years. A shortage of the natural P. umbellatus has prompted researchers to induce sclerotial formation in the laboratory.

METHODOLOGY/PRINCIPAL FINDING

P. umbellatus cultivation in a sawdust-based substrate was investigated to evaluate the effect of low temperature conditions on sclerotial formation. A phenol-sulfuric acid method was employed to determine the polysaccharide content of wild P. umbellatus sclerotia and mycelia and sclerotia grown in low-temperature treatments. In addition, reactive oxygen species (ROS) content, expressed as the fluorescence intensity of mycelia during sclerotial differentiation was determined. Analysis of ROS generation and sclerotial formation in mycelia after treatment with the antioxidants such as diphenyleneiodonium chloride (DPI), apocynin (Apo), or vitamin C were studied. Furthermore, macroscopic and microscopic characteristics of sclerotial differentiation were observed. Sclerotia were not induced by continuous cultivation at 25°C. The polysaccharide content of the artificial sclerotia is 78% of that of wild sclerotia. In the low-temperature treatment group, the fluorescent intensity of ROS was higher than that of the room temperature (25°C) group which did not induce sclerotial formation all through the cultivation. The antioxidants DPI and Apo reduced ROS levels and did not induce sclerotial formation. Although the concentration-dependent effects of vitamin C (5-15 mg mL(-1)) also reduced ROS generation and inhibited sclerotial formation, using a low concentration of vitamin C (1 mg mL(-1)) successfully induced sclerotial differentiation and increased ROS production.

CONCLUSIONS/SIGNIFICANCE

Exposure to low temperatures induced P. umbellatus sclerotial morphogenesis during cultivation. Low temperature treatment enhanced ROS in mycelia, which may be important in triggering sclerotial differentiation in P. umbellatus. Moreover, the application of antioxidants impaired ROS generation and inhibited sclerotial formation. Our findings may help to provide new insights into the biological mechanisms underlying sclerotial morphogenesis in P. umbellatus.

Neurospora crassa Light Signal Transduction Is Affected by ROS

In the ascomycete fungus Neurospora crassa blue-violet light controls the expression of genes responsible for differentiation of reproductive structures, synthesis of secondary metabolites, and the circadian oscillator activity. A major photoreceptor in Neurospora cells is WCC, a heterodimeric complex formed by the PAS-domain-containing polypeptides WC-1 and WC-2, the products of genes white collar-1 and white collar-2. The photosignal transduction is started by photochemical activity of an excited FAD molecule noncovalently bound by the LOV domain (a specialized variant of the PAS domain). The presence of zinc fingers (the GATA-recognizing sequences) in both WC-1 and WC-2 proteins suggests that they might function as transcription factors. However, a critical analysis of the phototransduction mechanism considers the existence of residual light responses upon absence of WCC or its homologs in fungi. The data presented point at endogenous ROS generated by a photon stimulus as an alternative input to pass on light signals to downstream targets.

Effects of Ganoderma lucidum on obstructive jaundice-induced oxidative stress

OBJECTIVE

Obstructive jaundice develops after occlusion of the common bile duct. Direct hyperbilirubinaemia, which occurs secondary to the condition, causes various life-threatening pathologies. Cytoprotective effects of Ganoderma lucidum (GL) have previously been shown. In this study, the effects of GL on oxidative stress and oxidant DNA damage in experimental obstructive jaundice were evaluated.

METHODS

Sixty Wistar albino adult female rats were randomly divided into six weight-matched equal groups: sham group, bile duct ligated group (BDL); after sham operation 250 mg/kg/d of GL administered group, after sham operation 500 mg/kg/d of GL administered group, after bile duct ligation 250 mg/kg/d of GL administered (GL1BDL) group, and after bile duct ligation 500 mg/kg/d of GL administered (GL2BDL) group. GL polysaccharide was orally administered to the rats via gavage tube once a day for 14 days after bile duct ligation.

RESULTS

The plasma malondialdehyde levels of the GL1BDL and GL2BDL groups were significantly lower than those of the BDL group (p < 0.01). The plasma 8-hydroxy-2'-deoxyguanosine levels of the GL1BDL and GL2BDL groups were significantly lower than those of the BDL group (p < 0.001). The liver tissue Cu-Zn superoxide dismutase level of the GL2BDL group was significantly higher than that of the BDL group (p < 0.05).

CONCLUSION

GL protected against DNA and liver tissue damage by reducing oxidative stress in obstructive jaundice.

Bombesin and neurotensin exert antiproliferative effects on oval cells and augment the regenerative response of the cholestatic rat liver

The regenerative capacity of the cholestatic liver is significantly attenuated. Oval cells are hepatic stem cells involved in liver's regeneration following diverse types of injury. The present study investigated the effect of the neuropeptides bombesin (BBS) and neurotensin (NT) on oval cell proliferation as well as on hepatocyte and cholangiocyte proliferation and apoptosis in the cholestatic rat liver. Seventy male Wistar rats were randomly divided into five groups: controls, sham operated, bile duct ligated (BDL), BDL+BBS (30 μg/kg/d), BDL+NT (300 μg/kg/d). Ten days later, alpha-fetoprotein (AFP) mRNA (in situ hybridization), cytokeratin-19 and Ki67 antigen expression (immunohistochemistry) and apoptosis (TUNEL) were evaluated on liver tissue samples. Cells with morphologic features of oval cells that were cytokeratin-19(+) and AFP mRNA(+) were scored in morphometric analysis and their proliferation was recorded. In addition, the proliferation and apoptotic rates of hepatocytes and cholangiocytes were determined. Alanine aminotransferase (ALT) levels and hepatic oxidative stress (lipid peroxidation and glutathione redox state) were also estimated. The neuropeptides BBS and NT significantly reduced ALT levels and hepatic oxidative stress. Both agents exerted similar and cell type-specific effects on oval cells, hepatocytes and cholangiocytes: (a) oval cell proliferation and accumulation in the cholestatic liver was attenuated, (b) hepatocyte proliferation was increased along with a decreased rate of their apoptosis and (c) cholangiocyte proliferation was attenuated and their apoptosis was increased. These observations might be of potential value in patients with extrahepatic cholestasis.

Thiol redox state and related enzymes in sclerotium-forming filamentous phytopathogenic fungi

Thiol redox state (TRS) reduced and oxidized components form profiles characteristic of each of the four main types of differentiation in the sclerotiogenic phytopathogenic fungi: loose, terminal, lateral-chained, and lateral-simple, represented by Rhizoctonia solani, Sclerotinia sclerotiorum, Sclerotium rolfsii, and Sclerotinia minor, respectively. A common feature of these fungi is that as their undifferentiated mycelium enters the differentiated state, it is accompanied by a decrease in the low oxidative stress-associated total reduced thiols and/or by an increase of the high oxidative stress-associated total oxidized thiols either in the sclerotial mycelial substrate or in its corresponding sclerotium, indicating a relationship between TRS-related oxidative stress and sclerotial differentiation. Moreover, the four studied sclerotium types exhibit high activities of TRS-related antioxidant enzymes, indicating the existence of antioxidant protection of the hyphae of the sclerotium medulla until conditions become appropriate for sclerotium germination.

Thiol redox state and oxidative stress affect sclerotial differentiation of the phytopathogenic fungi Sclerotium rolfsii and Sclerotinia sclerotiorum

AIMS

To investigate the involvement of oxidative stress and thiol redox state (TRS) in sclerotial differentiation of Sclerotium rolfsii and Sclerotinia sclerotiorum.

METHODS AND RESULTS

Oxidative stress in these fungi was assessed by lipid peroxidation, which was higher in comparison with their nonsclerotiogenic counterpart strains. TRS [measured as glutathione (GSH) and cysteine] was associated with oxidative stress and differentiation using the TRS modulator and antioxidant Nu-acetylcysteine (AcCSH) and the GSH biosynthesis inducer and inhibitor l-2-oxo-thiazolidine-4-carboxylate and L-buthionine-S,R-sulphoximine (BSO) respectively. Differentiation and oxidative stress was decreased by AcCSH in both fungi. The decrease of differentiation by BSO was not associated with oxidative stress in these fungi.

CONCLUSIONS

Differentiation and oxidative stress in both fungi depends on the availability of antioxidant noncytotoxic -SH groups and is not depended on any direct antioxidant role of GSH and its precursor cysteine.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study helps to understand the mechanism(s) of sclerotial differentiation in these agriculturally important phytopathogenic fungi and proposes that AcCSH can be used as potent fungicide by (i) acting as growth inhibiting cytotoxic oxidant and (ii) sustaining these fungi in their undifferentiated hyphal stage where they are vulnerable to degradation by soil micro-organisms.

Effect of thiol redox state modulators on oxidative stress and sclerotial differentiation of the phytopathogenic fungus Rhizoctonia solani

This study showed that sclerotial differentiation in the filamentous phytopathogenic fungus Rhizoctonia solani is directly related to oxidative stress and thiol redox state (TRS). Sclerotial differentiation is modulated by the availability of non-cytotoxic -SH groups as was shown by the inhibition of sclerorial differentiation by the TRS modulator N-acetyl cysteine (AcCSH), and not necessarily with those of the TRS reduced components glutathione (GSH) and its precursor cysteine (CSH) as indicated by the GSH-biosynthesis inducer and inhibitor L-2-oxo-thiazolidine-4-carboxylate and L-buthionine-S,R-sulfoximine, respectively. Moreover, inhibition of sclerotial differentiation was accompanied by decrease of the high oxidative stress indicators, lipid peroxidation and DNA damage in the mycelial substrate where sclerotia initials are formed, which suggests that this phenomenon is related to oxidative stress as it is predicted by our theory on sclerotial differentiation.

Sclerotial biomass and carotenoid yield of Penicillium sp. PT95 under oxidative growth conditions and in the presence of antioxidant ascorbic acid

AIMS

To determine the effect of oxidative stress and exogenous ascorbic acid on sclerotial biomass and carotenoid yield of Penicillium sp. PT95.

METHODS

In this experiment, high oxidative stress was applied by the inclusion of FeSO(4) in the growth medium and exposure to light. Low oxidative stress was applied by omitting iron from the growth medium and by incubation in the dark. Supplementation of exogenous ascorbic acid (as antioxidant) to the basal medium caused a concentration-dependent delay of sclerotial differentiation (up to 48 h), decrease of sclerotial biomass (up to 40%) and reduction of carotenoid yield (up to 91%). On the contrary, the exogenous ascorbic acid also caused a concentration-dependent decrease of lipid peroxidation in colonies of this fungus.

CONCLUSIONS

Under high oxidative stress growth condition, the sclerotial biomass and carotenoid yield of PT95 strain in each plate culture reached 305 mg and 32.94 microg, which were 1.23 and 3.71 times higher, respectively, than those at low oxidative stress growth condition. These data prompted us to consider that in order to attain higher sclerotial biomass and pigment yield, the strain PT95 should be grown under high oxidative stress and in the absence of antioxidants.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results suggest that strain PT95 may be used for solid-state fermentation of carotenoid production under high oxidative stress growth conditions.

Effect of glutathione biosynthesis-related modulators on the thiol redox state enzymes and on sclerotial differentiation of filamentous phytopathogenic fungi

In this study, sclerotial differentiation in filamentous phytopathogenic fungi, representing the four main types of sclerotia, was studied in relation to thiol redox state (TRS)-related enzymes and their substrates/products. TRS was altered by the general TRS modulator Nu-acetylcysteine (AcCSH) and by the glutathione (GSH) biosynthesis modulators L-oxo-thiazolidine-4-carboxylate (OTC), and L-buthionine-S,R-sulfoximine (BSO). This study showed that the four studied types of sclerotial differentiation are directly related with the antioxidant -SH groups of GSH and/or CSH, since the decrease of sclerotial differentiation concurred with an increase of these thiols by the GSH biosynthesis modulators AcCSH, OTC, and BSO. Supportive to that conclusion is the fact that, in general, the activities of the TRS-related enzymes GR/GPDH and Ttase decrease in the end of the undifferentiated stage due to the substitution of their antioxidant function by the antioxidant potential of the -SH group providers AcCSH and OTC. Moreover, it was found that BSO expectedly suppressed GSH biosynthesis in the tested fungi, and unexpectedly decreased their sclerotial differentiation by a dose-dependent manner typical for antioxidants. The possible antioxidant role of BSO was supported by the decrease it caused in the antioxidant enzymes GR/GPDH and Ttase. The results of this study are in accordance with our hypothesis that sclerotial differentiation in phytopathogenic fungi is induced by oxidative stress.

Effect of bombesin and neurotensin on gut barrier function in partially hepatectomized rats

AIM: To investigate the effect of regulatory peptides bombesin (BBS) and neurotensin (NT) on intestinal barrier function in partially hepatectomized rats.

METHODS: Ninety male Wistar rats were randomly divided into five groups: I (n = 10): controls, II (n = 20): sham operated, III (n = 20): partial hepatectomy 70% (PHx), IV (n = 20): PHx+BBS (30 μg/kg/d), V (n = 20): PHx+NT (300 μg/kg/d). Groups IV and V were treated for 8 days before PHx and 48 h post surgery. At the end of the experiment, on day 10, intestinal barrier function was assessed by measuring endotoxin concentrations in portal and aortic blood. Tissue sections of the terminal ileum were examined histologically and villus density, mucosal thickness, mitotic activity and apoptosis in crypts were assessed. In addition, ileal mucosa was analyzed for DNA and protein content and microbiological analysis was performed in cecal contents. To estimate intestinal oxidative stress, lipid peroxidation was determined on tissue homogenates from terminal ileum.

RESULTS: BBS or NT administration significantly reduced portal and systemic endotoxemia observed 48 h after partial hepatectomy. In hepatectomized rats (group III), a trend towards induction of mucosal atrophy was observed, demonstrated by the reduction of villus density, mucosal thickness, protein content and significant reduction of DNA, while these alterations were reversed by regulatory peptides administration. This trophic effect of BBS and NT was accompanied by induction of mitoses above control levels and a significant reduction of apoptosis in intestinal crypts. Intestinal lipid peroxidation was found significantly lower in PHx group and regulatory peptides exerted an antioxidant action, further decreasing this parameter of oxidative stress. The bacterial population of E. coli and aerobic Gram (+) cocci was increased in cecal content of hepatectomized rats, while this parameter was not affected by the administration of BBS or NT.

CONCLUSION: Gut regulatory peptides BBS and NT improve intestinal barrier function and reduce endotoxemia in experimental partial hepatectomy. This effect is, at least in part, mediated by their trophic, antiapoptotic, mitogenic, and antioxidant effect on the intestinal epithelium. This observation might be of potential value in patients undergoing liver resection.

Effect of oxidative stress and exogenous beta-carotene on sclerotial differentiation and carotenoid yield of Penicillium sp. PT95

AIMS

To determine the effect of oxidative stress and exogenous beta-carotene on sclerotial differentiation and carotenoid yield of Penicillium sp. PT95.

METHODS AND RESULTS

In this experiment, high oxidative stress was applied by inclusion of FeCl(3) (10 micromol l(-1)) in the growth medium and by light exposure. Low oxidative stress was applied by omitting iron from the growth medium and by incubation in the dark. Supplementation of exogenous beta-carotene (as antioxidant) to the basal medium caused a concentration-dependent delay of sclerotial differentiation (up to 72 h), decrease of sclerotial biomass (up to 43%) and reduction of carotenoid yield (up to 92%). On the contrary, the exogenous beta-carotene also caused a concentration-dependent decrease of lipid peroxidation in colonies of this fungus.

CONCLUSIONS

Under high oxidative stress growth condition, the sclerotial biomass and carotenoid yield of PT95 strain in each plate culture reached 141 mg and 30.03 microg, which were 1.53 and 3.51 times higher respectively, than that at low oxidative stress growth condition.

SIGNIFICANCE AND IMPACT OF THE STUDY

These data prompted us to consider that in order to attain higher sclerotial biomass and pigment yield, the strain PT95 should be grown under high oxidative stress and in the absence of antioxidants.

Gut regulatory peptides bombesin and neurotensin reduce hepatic oxidative stress and histological alterations in bile duct ligated rats

Gut regulatory peptides bombesin (BBS) and neurotensin (NT) exert a wide spectrum of biological actions on gastrointestinal tissues and we have previously shown that they improve intestinal barrier function and oxidative stress in experimentally jaundiced rats. In the present study, we explored their potential action on liver histology and oxidative status in bile duct ligated rats. Seventy male Wistar rats were randomly divided into five groups: controls, sham operated, bile duct ligated (BDL), BDL + BBS (10 microg/kg, s.c. x3), BDL + NT (300 microg/kg, i.p.). At the end of the experiment, on day 10, serum total bilirubin and alanine aminotransferase (ALT) levels were determined and endotoxin was measured in portal and aortic blood. Liver tissue samples were examined histologically for evaluation of the ratio of portal tracts presenting changes of obstructive cholangiopathy and neutrophils' number in portal tracts. In addition, hepatic oxidative status was estimated on liver homogenates by measurements of lipid peroxidation (malondialdehyde), protein oxidation (protein carbonyl groups) and thiol redox state [reduced glutathione (GSH), oxidized glutathione (GSSG), total non-protein mixed disulfides (NPSSR) and protein thiols (PSH)]. Administration of BBS or NT significantly reduced portal and aortic endotoxaemia observed in obstructive jaundice. Both agents significantly ameliorated liver injury, as demonstrated by improvement of obstructive cholangiopathy and reduction of ALT. This effect was accompanied by prevention of lipid peroxidation, protein oxidation and decrease of the oxidized forms GSSG and NPSSR. Moreover, neutrophil accumulation in portal tracts was significantly decreased. In conclusion, this study shows that gut regulatory peptides BBS and NT reduce cholestatic liver injury, exerting protective effects on portal tract architecture, neutrophil infiltration and hepatic oxidative stress in bile duct ligated rats.

Bombesin and neurotensin reduce endotoxemia, intestinal oxidative stress, and apoptosis in experimental obstructive jaundice

OBJECTIVE

To evaluate the effect of bombesin (BBS) and neurotensin (NT) on intestinal histopathology, intestinal oxidative stress, and endotoxemia in experimental obstructive jaundice.

SUMMARY BACKGROUND DATA

Obstructive jaundice compromises gut barrier function, resulting in endotoxemia. BBS and NT, exerting various biologic actions on gastrointestinal tissues, preserve gut mucosal integrity in cases of injury or atrophy.

METHODS

Seventy male Wistar rats were randomly divided into 5 groups: I = controls, II = sham operated, III = bile duct ligation (BDL), IV = BDL + BBS (30 microg/kg/d), V = BDL + NT (300 microg/kg/d). By the end of the experiment, on day 10, endotoxin was measured in portal and aortic blood. Tissue sections of the terminal ileum were examined histologically, and villus density, mucosal thickness, mitotic activity and apoptosis in crypts were assessed. In addition, ileal mucosa was analyzed for DNA and protein content. To estimate intestinal oxidant/antioxidant equilibrium, lipid peroxidation, protein oxidation, and thiol redox state (reduced glutathione [GSH], oxidized glutathione [GSSG], total nonprotein mixed disulfides [NPSSR], protein thiols [PSH], and protein disulfides [PSSP]) were determined on tissue homogenates from the terminal ileum.

RESULTS

BBS or NT administration significantly reduced portal and systemic endotoxemia observed in obstructive jaundice. Both factors reversed obstructive jaundice-induced morphologic features of intestinal atrophy, increasing villus density and mucosal thickness. This effect was accompanied by induction of mitoses and reduction of apoptosis in intestinal crypts. Mucosal DNA and protein content were reduced, although not to significant levels, in BDL animals and restored to control levels after BBS or NT treatment. Moreover, BBS or NT administration protected the intestine in jaundiced rats against oxidative stress, as demonstrated by reduction of intestinal lipid peroxidation, increase of the antioxidant GSH, and decrease of the oxidized forms GSSG and NPSSR, while BBS additionally reduced protein oxidation as well.

CONCLUSIONS

Administration of BBS or NT in bile duct-ligated rats exerts beneficial effects on intestinal oxidative stress, cell proliferation, apoptosis, and endotoxemia. This observation might be of potential value in patients with extrahepatic cholestasis.

Oxidative state in intestine and liver after partial hepatectomy in rats. Effect of bombesin and neurotensin

OBJECTIVES

Extended liver resection is a situation with major implication of the gut-liver axis. In the present study, we aimed to investigate intestinal and liver oxidative stress after partial hepatectomy and explore the influence of exogenous administration of gut regulatory peptides bombesin (BBS) and neurotensin (NT).

DESIGN AND METHODS

Ninety male Wistar rats were randomly divided into five groups: control, sham operated, partially hepatectomized (70%), and partially hepatectomized treated with either BBS or NT. Forty-eight hours after surgery, lipid peroxidation, protein oxidation, reduced and oxidized glutathione were measured on intestinal and liver homogenates. Endotoxin levels were determined in portal and aortic blood.

RESULTS

In hepatectomized rats, all parameters of oxidative stress in remnant liver were decreased. In the intestine, oxidative protein damage was increased, while lipid peroxidation and glutathione oxidation were reduced. BBS and NT reduced protein and glutathione oxidation in both tissues and prevented lipid peroxidation in the intestine. Furthermore, portal and aortic endotoxemia were decreased in peptides-treated rats.

CONCLUSIONS

After partial hepatectomy, liver regeneration takes place under low oxidative stress, while increased oxidative damage to proteins occurs in the intestine. Gut regulatory peptides BBS and NT exert an antioxidant effect in both organs and prevent endotoxemia.

The fluorescence detection of superoxide radical using hydroethidine could be complicated by the presence of heme proteins

This study shows that hydroethidine (HE) used for the qualitative detection of superoxide anion can also be oxidized by heme proteins such as the mitochondrial cytochromes, hemoglobin, and myoglobin, forming spectrally nonhomogenous mixtures of HE-derived products of various oxidation states. All oxidation products show excitation/emission peaks (490-495/580-600 nm) near the excitation/emission peaks (475/570 nm) of the HE-superoxide oxidation product, and this may pose serious interference problems to the fluorescent detection of the superoxide radical. This paper discusses possible precautionary steps that should be taken to minimize the interfering problems in the HE-superoxide assay and suggests its use mainly for reactive oxygen species detection.

Experimental obstructive jaundice disrupts intestinal mucosal barrier by altering occludin expression: beneficial effect of bombesin and neurotensin

BACKGROUND

Little is known of the molecular events leading to increased intestinal permeability in obstructive jaundice. This study was undertaken to investigate the influence of experimental obstructive jaundice on the expression of the tight junction-associated protein occludin in the intestinal epithelium.

STUDY DESIGN

Seventy male Wistar rats were randomly divided into five groups: I, controls; II, sham-operated; III, bile duct ligation (BDL); IV, BDL+Bombesin (BBS) (30 microg/kg/d); and V, BDL+Neurotensin (NT) (300 microg/kg/d). At the end of the experiment, on day 10, endotoxin was measured in portal and aortic blood. Tissue sections of the terminal ileum were examined histologically and immunohistochemically for evaluation of occludin expression in the intestinal epithelium. Lipid peroxidation and protein oxidation were determined on tissue homogenates from terminal ileum and microbiologic analysis was performed in cecal contents.

RESULTS

Obstructive jaundice resulted in portal and aortic endotoxemia, which was significantly reduced after BBS or NT administration. In the BDL group, there was total loss of occludin expression in numerous enterocytes mainly at the upper third of the villi, while a gradient of positivity existed from crypt to tip. Occludin expression was restored to control state after treatment with BBS or NT. In addition, both peptides reduced intestinal lipid peroxidation, while BBS reduced protein oxidation as well.

CONCLUSIONS

Experimental obstructive jaundice induces regional loss of occludin expression in the intestinal epithelium, which may be a key factor contributing to the disruption of the mucosal barrier. Gut regulatory peptides BBS and NT prevent this alteration, leading to lower portal and systemic endotoxemia.

Evidence for intestinal oxidative stress in obstructive jaundice-induced gut barrier dysfunction in rats

AIM

An important factor that promotes bacterial and endotoxin translocation in obstructive jaundice is intestinal injury that causes increased permeability. However, little is known of the submicroscopic biochemical events leading to defects of the intestinal barrier. This study was undertaken to investigate the effect of experimental obstructive jaundice on intestinal lipid peroxidation, protein oxidation and thiol redox state.

METHODS

Rats were randomly divided into controls, sham operated and bile duct ligated (BDL). After 10 days, intestinal barrier function was assessed by measuring endotoxin in portal and aortic blood. Tissue samples from the terminal ileum were examined histologically and morphometrically, while other samples were homogenized for the determination of lipid peroxidation, protein oxidation and thiol redox state [reduced glutathione (GSH), oxidized glutathione (GSSG), total non-protein mixed disulphides (NPSSR), protein thiols (PSH) and protein disulphides (PSSP)].

RESULTS

Obstructive jaundice compromised intestinal barrier function leading to significant portal and systemic endotoxaemia. The intestinal mucosa in jaundiced rats was atrophic with significantly decreased villous density and total mucosal thickness. Determination of biochemical parameters of oxidative stress in the intestine showed increased lipid peroxidation and protein oxidation in BDL-rats. Thiol redox state revealed the presence of intestinal oxidative stress in jaundiced rats, indicated by a decrease in GSH and increased GSSG, NPSSR and PSSP.

CONCLUSIONS

This study shows that experimental obstructive jaundice induces intestinal oxidative stress, which may be a key factor contributing to intestinal injury and leading to endotoxin translocation.

CPTF1, a CREB-like transcription factor, is involved in the oxidative stress response in the phytopathogen Claviceps purpurea and modulates ROS level in its host Secale cereale

CPTF1, a transcription factor with significant homology to ATF/CREB bZIP factors, was identified during an expressed sequence tag (EST) analysis of in planta-expressed genes of the phytopathogen Claviceps purpurea. Using a gene-replacement approach, deletion mutants of cptf1 were created. Expression studies in axenic culture showed that the H2O2-inducible gene cpcat1 (encoding a secreted catalase) had a reduced basal expression level and no longer responded to oxidative stress in the delta cptf1 mutant. Biochemical analyses indicated that CPTF1 is a general regulator of catalase activity. Delta cptf1 mutants showed significantly reduced virulence on rye. Electron microscopical in situ localization revealed significant amounts of H2O2 in delta cptf1-infected rye epidermal tissues, indicating that the plant tissue displayed an oxidative burst-like reaction, an event not detected in wild-type infections. These data indicate that CPTF1 is involved not only in oxidative stress response in the fungus but also in modulation of the plant's defense reactions.

Beta-carotene production and sclerotial differentiation in Sclerotinia minor

Sclerotinia minor accumulates beta-carotene at levels dependent upon oxidative growth conditions and differentiation. Beta-carotene accumulation is 2.5-fold higher in differentiated mycelia at high than at low oxidative stress, and approx. 3-fold higher in differentiated than in undifferentiated mycelia. It is proposed that beta-carotene may be produced by the fungus to counteract oxidative stress that develops during growth. This is shown by the finding that exogenous beta-carotene at growth non-inhibiting concentrations causes a concentration-dependent reduction of oxidative stress (lipid and protein peroxidation) and sclerotial differentiation in this fungus. The data of this study support our hypothesis that sclerotial differentiation in phytopathogenic fungi may be induced by oxidative stress.