Phytic acid attenuates acetaminophen-induced hepatotoxicity via modulating iron-mediated oxidative stress and SIRT-1 expression in mice

Introduction: Administration of high doses of acetaminophen (APAP) results in liver injury. Oxidative stress and iron overload play roles in the pathogenesis of APAP-induced hepatotoxicity. The present study assessed the potential hepatoprotective effects of phytic acid (PA), a natural antioxidant and iron chelator, on APAP-induced hepatotoxicity and the possible underlying mechanism through its effects on CYP2E1 gene expression, iron homeostasis, oxidative stress, and SIRT-1 expression levels. Methods: Twenty-four adult male albino mice were used in this study. Mice were divided into four groups (six mice in each group): control, APAP-treated, PA-treated and APAP + PA-treated groups. Liver function tests, serum and liver tissue iron load were evaluated in all the study groups. Hepatic tissue homogenates were used to detect oxidative stress markers, including malondialdehyde (MDA) and reduced glutathione (GSH). Histological hepatic evaluation and immunohistochemistry of SIRT-1 were performed. Quantitative real-time PCR was used for the assessment of CYP2E1 and SIRT-1 gene expressions. APAP-induced biochemical and structural hepatic changes were reported. Results: PA administration showed beneficial effects on APAP-induced hepatotoxicity through improvements in liver functions, decreased CYP2E1 gene expression, decreased serum and liver iron load, decreased MDA, increased GSH, increased SIRT-1 expression level and improvement in hepatic architecture. Conclusion: Conclusively, PA can be considered a potential compound that can attenuate acetaminophen-induced hepatotoxicity through its role as an iron chelator and antioxidant, as well as the up-regulation of SIRT-1 and down-regulation of CYP2E1.

Modulatory effects of Moringa oleifera leaf extract on sodium nitrate-induced experimental colitis via regulation of P53, Ki-67 and PCNA biomarkers

BACKGROUND

Ulcerative colitis is a risk factor for colorectal carcinoma. Different mechanisms are related to colitis like apoptosis and hyperproliferation. Moringa oleifera leaves extract (MO) provides a promising option to overcome the risk.

PURPOSE

To examine the colonic changes in a rat model of colitis induced by sodium nitrate (SN) and study the effects of MO.

STUDY DESIGN

Eight adult male rats were allocated in each of the three group; control (distilled water), SN (100 mg/kg/day, orally via gastric gavage), and SN + MO (100 mg/kg/day, orally via gastric gavage).

METHODS

Body weight was measured after the end of the experiment. Colonic homogenates were tested for levels of oxidative stress indicators. Immunohistochemistry for P53, PCNA and Ki-67 was performed. Fresh colon specimens were used for quantitative real-time PCR for assessment of P53, PCNA and Ki-67 gene expression.

RESULTS

SN group revealed a significant decreased weight (p = 0.002). MDA and NO levels were higher with SN administration than with MO co-administration (p= 0.04, 0.01 respectively). GSH level was reduced in SN group (p = 0.02) and significantly increased with MO intake (p = 0.04). SN-induced colonic destructive changes were reversed with MO. P53, PCNA and Ki-67 levels of gene expression were reduced in SN + MO group than SN group (P = 0.007, 0.02, 0.001 respectively).

CONCLUSION

MO protected the colonic mucosa against SN-induced changes regulating apoptosis, and cell proliferation.

Potential role for vitamin D vs. intermittent fasting in controlling aquaporin-1 and aquaporin-3 expression in HFD-induced urinary bladder alterations in rats

Background: High-fat diet-induced obesity is linked to suppression of aquaporins (AQPs) expression in different tissues. Both vitamin D and intermittent fasting were identified to enhance AQPs expression. In the urinary bladder, AQP-1 and AQP-3 mRNA transcripts were identified. Vitamin D has an impact on a variety of genes that encode proteins that control cell proliferation, differentiation, and death. Aim: To assess potential benefits of vitamin D and intermittent fasting (IF) and to explore alterations to the urinary bladder triggered by high-fat diet (HFD) in a rat model of obesity. Methods: Each of the 4 groups contained six adult male albino rats; control: a standard rodent chew for 12 weeks, HFD: HFD and fructose were administered orally via gastric gavage for 12 weeks, and vitamin D: HFD and fructose were administered orally for 8 weeks, then 4 weeks of intraperitoneal injection of vitamin D (5 microns/Kg/2 days) and IF group: Received intraperitoneal injections of vitamin D (5 microns/Kg/2 days) for 4 weeks after consumption of HFD and fructose orally for 8 weeks. The serum lipid profile was conducted at end of the experiment. In the bladder homogenates, the levels of oxidative stress indicators were assessed. Quantitative real-time PCR was performed on recently collected bladder samples. AQP-1 and AQP-3 immunohistochemistry was done. Results: When compared to the HFD group, the vitamin D and IF groups both demonstrated a substantial improvement in histopathological, immunohistochemical, biochemical, and molecular markers. Conclusion: In all examined parameters, IF exceeded vitamin D as a preventive factor for the urinary bladder deterioration.

Neuroprotective effect of ranolazine improves behavioral discrepancies in a rat model of scopolamine-induced dementia

Background

Ranolazine (Rn), an antianginal agent, acts in the central nervous system and has been used as a potential treatment agent for pain and epileptic disorders. Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases and the leading factor in dementia in the elderly.

Aim

We examined the impact of Rn on scopolamine (Sco)-induced dementia in rats.

Methods

Thirty-two albino male rats were divided into four groups: control, Rn, Sco, and Rn + Sco.

Results

A significant decrease in the escape latency in the Morris water maze test after pre-treatment with Rn explained better learning and memory in rats. Additionally, Rn significantly upregulated the activities of the antioxidant enzymes in the treated group compared to the Sco group but substantially reduced acetylcholinesterase activity levels in the hippocampus. Moreover, Rn dramatically reduced interleukin-1 β (IL-1β) and IL-6 and upregulated the gene expression of brain-derived neurotrophic factor (BDNF). Furthermore, in the Sco group, the hippocampal tissue's immunohistochemical reaction of Tau and glial factor activating protein (GFAP) was significantly increased in addition to the upregulation of the Caspase-3 gene expression, which was markedly improved by pre-treatment with Rn. The majority of pyramidal neurons had large vesicular nuclei with prominent nucleoli and appeared to be more or less normal, reflecting the all-beneficial effects of Rn when the hippocampal tissue was examined under a microscope.

Conclusion

Our findings indicated that Rn, through its antioxidative, anti-inflammatory, and anti-apoptotic effects, as well as the control of the expression of GFAP, BDNF, and Tau proteins, has a novel neuroprotective impact against scopolamine-induced dementia in rats.

Probiotics Attenuate Myopathic Changes in Aging Rats via Activation of the Myogenic Stellate Cells

Aging represents a complex biological process associated with decline in skeletal muscle functions. Aging impairs satellite cells that serve as muscle progenitor cells. Probiotic supplementation may have many beneficial effects via various mechanisms. We examined the possible effects of probiotics in stimulating the proliferation of myogenic stellate cells in aging rats. Twenty-four male albino Sprague-Dawley rats were classified equally into four groups: adult control, old control, adult + probiotics, and old + probiotics. Probiotics (Lactobacillus LB) were administered gavage at a dose of 1 ml (1 × 109 CFU/ml/day) for 4 weeks. A significant increase in the relative gastrocnemius weight ratio and improvement of contractile parameters was detected in the old + probiotics group (0.6 ± 0.01) compared to the old control group (0.47 ± 0.01; P < 0.001). Probiotics significantly upregulated the activities of GSH, while NO and MDA were markedly decreased compared to control groups (P ≤ 0.001). Also, probiotics increased the mRNA and protein expressions of myogenin and CD34 (P < 0.05) as determined by real-time PCR and immunohistochemistry. Moreover, the old + probiotics group showed apparent restoration of the connective tissue spaces, reflecting the all-beneficial effects of probiotics. Our findings indicated that probiotics attenuated myopathic changes in aging rats probably through activation of the myogenic stellate cells. Probiotics improved the muscle weight, function, antioxidant activity, and myogenic transcription factors of the skeletal muscle.

Beneficial role of rosemary extract on oxidative stress-mediated neuronal apoptosis in rotenone-induced attention deficit hyperactivity disease in juvenile rat model

BACKGROUND AND AIM

Attention deficit hyperactivity disorder (ADHD) is heterogeneous neurobehavioral disorders that co-exist with cognitive and learning deficits affecting 3-7% of children. We study the role of rosemary in the protection of the prefrontal cortical neurons against rotenone-induced ADHD in juvenile rats.

METHODS

Twenty-four juvenile rats were divided into four groups (n=6): control group, received olive oil 0.5 ml/kg/day/ I.P. for 4 weeks, rosemary group received rosemary 75 mg/kg/day/ I.P. for 4 weeks, rotenone group received rotenone 1 mg/kg/day/ I.P. dissolved in olive oil for 4 days and combined group received rotenone 1 mg/kg/day/ I.P. for 4 days and rosemary 75 mg/kg/day/ I.P. for 4 weeks.

RESULTS

Rotenone group showed higher impulsivity with reduction in the recognition index and total locomotor activity. However, combined group showed significant improvement in the recognition index and the total locomotor activity. Neurochemical analysis disclosed that rotenone decreased levels of GSH and significantly increased lipid peroxidation and oxidative stress. The administration of rosemary amended these neurochemical changes. Rotenone caused a significant increase in serum amyloid protein A and C-reactive protein levels indicating a marked state of inflammation. Rosemary ameliorated these biochemical changes. The immunohistochemical expression of tyrosine hydroxylase was decreased in the rotenone group. On the other hand, caspase-3 was increased in the rotenone group. PCR confirmed immunohistochemical results for gene expression.

CONCLUSIONS

The findings of the behavioral, neurochemical, biochemical, immunohistochemical and molecular outcomes suggested that rosemary could fight oxidative stress, inflammation and apoptosis in the prefrontal cortex of rotenone-induced ADHD in juvenile rats.

Neuroprotective effect of naringin against cerebellar changes in Alzheimer's disease through modulation of autophagy, oxidative stress and tau expression: An experimental study

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by gradual cognitive decline. Strong antioxidants that inhibit free radicals, such as polyphenols, reduce the likelihood of developing oxidative stress-related degenerative diseases such as AD. Naringin, a flavonoid found in citrus fruit shown to be neuroprotective, reduce oxidative damage and minimize histopathological changes caused by ischemic reperfusion, enhance the long-term memory in AD animal models. This work aimed to comprehend the role of naringin in the defense of the cerebellum against aluminum chloride (AlCl3)-induced AD in rats by investigating the behavioral, neurochemical, immunohistochemical, and molecular mechanisms that underpin its possible neuroprotective effects. Twenty-four adult albino rats were divided into four groups (n = 6/group): (i) Control (C) received saline per oral (p.o.), (ii) Naringin(N)-received naringin (100 mg/kg/d) p.o, (iii) AlCl3-recived AlCl3 (100 mg/kg/d) p.o and (iv) AlCl3 + Naringin (AlCl3 + N) received both AlCl3 and naringin p.o for 21 days. Behavioral tests showed an increase in the time to reach the platform in Morris water maze, indicating memory impairment in the AlCl3-treated group, but co-administration of naringin showed significant improvement. The Rotarod test demonstrated a decrease in muscle coordination in the AlCl3-treated group, while it was improved in the AlCl3 + N group. Neurochemical analysis of the hippocampus and cerebellum revealed that AlCl3 significantly increased lipid peroxidation and oxidative stress and decreased levels of reduced glutathione. Administration of naringin ameliorated these neurochemical changes via its antioxidant properties. Cerebellar immunohistochemical expression for microtubule assembly (tau protein) and oxidative stress (iNOS) increased in A1C13-treated group. On the other hand, the expression of the autophagic marker (LC3) in the cerebellum showed a marked decline in AlCl3-treated group. Western blot analysis confirmed the cerebellar immunohistochemical findings. Collectively, these findings suggested that naringin could contribute to the combat of oxidative and autophagic stress in the cerebellum of AlCl3-induced AD.

Renoprotective effect of N-acetylcystein and vitamin E in bisphenol A-induced rat nephrotoxicity; Modulators of Nrf2/ NF-κB and ROS signaling pathway

BACKGROUND AND AIM OF THE WORK

Bisphenol A (BPA) is a chemical product that is widely used as a plastic precursor. It acts directly on the kidney mitochondria, causing renal dysfunction. N-acetylcysteine is effective in protecting the kidneys from chemical-induced damage. Vitamin E is an antioxidant that protects cells from the damaging effects of free radicals. The aim of this study is to further evaluate and compare NAC and vitamin E to oppose the nephrotoxicity caused by BPA.

RESEARCH DESIGN AND METHODS

Forty-two adult male rats were divided into 7 groups:  control, BPA, NAC, vitamin E, BPA plus NAC, BPA plus vitamin E, and combined BPA, NAC and vitamin E. BPA, NAC, vitamin E were given orally at doses of 50 mg/kg, 200 mg/kg, and 1000 mg/kg respectively, for 5 weeks.

RESULTS

NAC and vitamin E groups showed improved kidney function tests and alleviated BPA-induced oxidative stress; increased GSH and decreased MDA, NO and iNOS levels. NAC and vitamin E significantly attenuated inflammation; decreased NF-κB and increased IL-4, and Nrf2, in addition there was alleviation of renal histopathology. To some extent, vitamin E administration showed significant improvement. Moreover, combined NAC and vitamin E treatment showed more significance than either NAC or vitamin E separate groups.

CONCLUSIONS

This study determined the substantial protective effects of NAC and/or vitamin E in BPA-induced nephrotoxicity through modulation of Nrf2 with subsequent improvement of oxidative stress and inflammation. The alleviation was more significant in combined NAC and vitamin E treatment mainly through their synergistic effect on Nrf2.

The impact of COVID-19 on transfusion-dependent thalassemia patients of Karachi, Pakistan: A single-center experience

Objectives

With the advent of COVID-19 in Pakistan, the already fragmented blood transfusion services (BTS) received a severe blow, putting the lives of transfusion-dependent thalassemia children on stake. This study aimed to assess the impact of the COVID-19 on blood transfusion therapy (BTT) of thalassemia patients and suggest ways to ensure safe and reliable blood supplies amid such health crises.

Material and methods

A retrospective, cross-sectional study was conducted from October 2019 (before COVID-19) to July 2020 (during COVID-19) based on the data provided by a thalassemia center, named Help International Welfare Trust, Karachi, Pakistan. SPSS version 24.0 was used for the data analysis. Data were described in the form of means and percentages.

Results

There was a significant reduction in the consumption of PRBCs bags after the emergence of COVID-19 (P = 0.002). Moreover, the number of thalassemia patients receiving BTT was dropped by 10.56% during the pandemic. There was a strong negative correlation observed between the rising cases of COVID-19 in Pakistan and the number of patients missing their therapy sessions (r = −0.914, P = 0.030). A considerable decline in the reserves of all Rhesus-negative blood groups amid the COVID-19 outbreak was also observed.

Conclusion

The COVID-19 pandemic adversely affected the already suboptimal care catered to thalassemia patients in Karachi, Pakistan. The fear of the virus contraction coupled with the lockdown and restricted mobility has disrupted the entire transfusion chain from donor to the recipient. Collaborated efforts by the government and healthcare authorities are essential to ensure sufficient blood for thalassemia patients amid the pandemic.

Extreme environments: microbiology leading to specialized metabolites

The prevalence of multidrug-resistant microbial pathogens due to the continued misuse and overuse of antibiotics in agriculture and medicine is raising the prospect of a return to the preantibiotic days of medicine at the time of diminishing numbers of drug leads. The good news is that an increased understanding of the nature and extent of microbial diversity in natural habitats coupled with the application of new technologies in microbiology and chemistry is opening up new strategies in the search for new specialized products with therapeutic properties. This review explores the premise that harsh environmental conditions in extreme biomes, notably in deserts, permafrost soils and deep-sea sediments select for micro-organisms, especially actinobacteria, cyanobacteria and fungi, with the potential to synthesize new druggable molecules. There is evidence over the past decade that micro-organisms adapted to life in extreme habitats are a rich source of new specialized metabolites. Extreme habitats by their very nature tend to be fragile hence there is a need to conserve those known to be hot-spots of novel gifted micro-organisms needed to drive drug discovery campaigns and innovative biotechnology. This review also provides an overview of microbial-derived molecules and their biological activities focusing on the period from 2010 until 2018, over this time 186 novel structures were isolated from 129 representatives of microbial taxa recovered from extreme habitats.

Characterization of natural bioactive compounds produced by isolated bacteria from compost of aromatic plants

AIMS

This study aimed to highlight the importance of compost from aromatic plants as a stunning source for several bio active compounds generated from their inhabited thermophilic bacteria. Some of the isolated compounds could have a potential role in the treatment of microbial infections.

METHODS AND RESULTS

A total of forty different thermophilic bacteria were isolated from compost samples during their thermophilic stage. These isolates were tested for their antimicrobial capabilities against different Gram-positive and -negative bacteria using agar diffusion and double layer agar methods. The potential isolates were further identified based on morphological, biochemical and 16S rRNA gene sequencing methods. They were subjected to submerged state fermentation and the total crude metabolites were recovered using ethyl acetate (EtOAc) extraction. All bioactive metabolites were identified using liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS). It was observed that 2 out of 40 isolates were remarkably active against Gram-positive bacteria. These isolates were genetically identified as Bacillus species and their different active metabolites were characterized in the EtOAc extracts using LC-HRMS.

CONCLUSION

Liquid chromatography coupled with high-resolution mass spectrometry analysis of EtOAc extracts revealed the presence of active metabolites that are responsible for antimicrobial activities.

SIGNIFICANCE AND IMPACT OF THE STUDY

To the best of our knowledge, this is the first time to identify bioactive antimicrobial metabolites from retrieved compost micro-organisms in Egypt. So, compost could be a beneficial area for research as a reliable and continuous natural source for different uncountable communities of bacteria.

Influence of foliar spray of ethephon and water stress on the essential oil composition and impact on the cytotoxic activity of Thymus vulgaris aerial parts

Thymus vulgaris, (Lamiaceae), essential oils composition and yield, were found to be greatly influenced by water stress and growth enhancers. Therefore, three controlled cultivation conditions were applied to achieve the highest essential oil productivity of T. vulgaris. The essential oils obtained by hydro-distillation of the aerial parts were analyzed using (GC-MS). The tested plant subjected to drought showed a 66% increase in the essential oil yield, while those subjected to drought stress and foliar spray showed 57.1% increase and the regularly irrigated group with foliar spraying showed 23.8% increase relative to the control group. The cytotoxic activity of T. vulgaris essential oils was evaluated against lung (A-549), colon (HCT-116), intestinal (CACO₂) and breast (MCF-7) carcinoma using the cell viability assay. The lowest IC₅₀ values 0.44 and 0.33 μg/mL were seen against (HCT-116) and (CACO₂) cells respectively. These IC₅₀ values were lower than that of doxorubicin used as reference drug.

Early indications of ANIT-induced cholestatic liver injury: Alteration of hepatocyte polarization and bile acid homeostasis

Hepatocyte polarization is essential for biliary secretion, and loss of polarity causes bile secretory failure and hepatotoxicity. Here, we showed that alpha-naphthyl isothiocyanate (ANIT)-induced liver injury was accompanied by the dynamic interruption of bile acid homeostasis in rat plasma, liver and bile, which was characterized by the redistribution of bile acids in plasma and bile and a small range of fluctuations in the liver. Molecular mechanism studies indicated that these factors are dynamically mediated by the disruption of bile acid transporters and hepatic tight junctions. Dynamic changes in tight junction (TJ) permeability were observed by hepatobiliary barrier function assessment. Hepatocyte polarization was disrupted by ANIT before the development of cholestatic hepatotoxicity and alteration of bile acid metabolic profiles, which were assayed by high-performance liquid chromatography-tandem mass spectrometry, further verifying TJ deficiency. S1PR1 activation with SEW2871 reduced ANIT-induced liver injury by reducing the total serum bile acid concentration, liver functional enzyme activity and inflammation. Our data suggest that hepatocyte polarization plays an important role in maintaining bile acid homeostasis before the development of cholestatic hepatotoxicity and that TJs were more prominent in the early stage of cholestasis. S1PR1 may be a potential target for the prevention of drug-induced cholestatic liver injury.

TP73, an under-appreciated player in non-Hodgkin lymphoma pathogenesis and management

The TP73 gene is a member of the TP53 family with high structural homology to p53 and capable of transactivating p53 target genes. The TP73 gene locus which is highly conserved and complex, encodes for two classes of isoforms TAp73 (tumor suppressor isoforms containing the transactivation domain) and ΔNp73 (oncogenic isoforms, truncated and lacking the transactivation domain) with opposing effects. The balance between TAp73 and ΔNp73 isoforms and their harmony with other members of the TP73 family regulate various cellular responses such as apoptosis, autophagy, proliferation, and differentiation. The transcriptionally active isoforms of p73 are capable of inducing apoptosis in cancer cells independent of p53 status. Unlike p53, p73 is rarely mutated in cancers, however, the ratio of ΔNp73:TAp73 is frequently up-regulated in many carcinomas and is indicative of poor prognosis. Moreover, p73 is an important determinant of chemosensitivity and radiosensitivity, the two major treatment modalities for lymphoma. In the current review, we will provide an overview of recent progress discussing the role of TP73 in cancer, specifically addressing its relevance to lymphomagenesis, progression, therapy resistance, and its potential as a novel therapeutic target.

EPR dosimetric properties of radiation--formed radicals in arginine monohydrochloride

Arginine monohydrochloride rods (3×10 mm) were irradiated with (60)Co γ-rays to study radicals for dosimetric materials with Electron Paramagnetic Resonance (EPR). The rods have significant signal which develops upon irradiation and the intensity of signal increases upon the increase in irradiation dose. The rods can be used in the dose range from 5 to 120 KGy. The temperature coefficient was found to equal +0.22% °C(-1). The dose response, influence of humidity and post-irradiation storage at different conditions are discussed. The overall uncertainty for calibration of arginine monohydrochloride rode dosimeters at 2σ was found to be 2.85%.

Direct fed microbial supplementation repartitions host energy to the immune system

Direct fed microbials and probiotics are used to promote health in livestock and poultry; however, their mechanism of action is still poorly understood. We previously reported that direct fed microbial supplementation in young broilers reduced ileal respiration without changing whole-body energy expenditure. The current studies were conducted to further investigate the effects of a direct fed microbial on energy metabolism in different tissues of broilers. One hundred ninety-two 1-d-old broiler chicks (16 chicks/pen) were randomly assigned to 2 dietary groups: standard control starter diet (CSD) and CSD plus direct fed microbial (DFMD; 0.3%) with 6 pens/treatment. Body weight, feed consumption, whole-body energy expenditure, organ mass, tissue respiration rates, and peripheral blood mononuclear cell (PBMC) ATP concentrations were measured to estimate changes in energy metabolism. No differences in whole body energy expenditure or BW gain were observed; however, decreased ileal O(2) respiration (P < 0.05) was measured in DFMD fed broilers. In contrast, the respiration rate of the thymus in those broilers was increased (P < 0.05). The PBMC from DFMD fed broilers had increased ATP concentrations and exhibited increased ATP turnover (P < 0.01). To determine if the increased energy consumption by PBMC corresponded with an altered immune response, broilers were immunized with sheep red blood cells (SRBC) and assayed for differences in their humoral response. The DFMD-fed broilers had a faster rate of antigen specific IgG production (P < 0.05) and an increase in total IgA (P < 0.05). Collectively, these data indicate that supplementation with the direct fed microbial used in this study resulted in energy re-partitioning to the immune system and an increase in antibody production independent of changes in whole body metabolism or growth performance.

Superoxide dismutases

Superoxide dismutases (EC 1.15.1.1) are metalloenzymes that catalytically scavenge the superoxide radical. They are essential for the aerobic survival of all forms of life. There are three types of superoxide dismutase, containing manganese, iron, or copper and zinc. The copper--zinc type has generally been isolated from eukaryotic cells except for the enzyme for the symbiotic marine bacterium Photobacterium leiognathi. The copper--zinc type, from different sources, has a molecular weight of about 32 000, and is composed of two identical subunits, each containing one atom of copper and one atom of zinc. The copper participates in the catalytic activity of the enzyme, while the zinc plays only a structural role. The enzyme has been resolved reversibly. Superoxide dismutases provide protection against oxygen toxicity, against compounds that cause exacerbation of oxygen toxicity, against ionizing radiation, and also against the damaging sequelae of prolonged inflammation.

Molecular identity of the electrophoretic pattern and the major cross-reacting immunogens of Toxoplasma gondii (RH strain) and Neospora caninum

The complex electrophoretic profile of the antigenic components of Toxoplasma gondii and Neospora caninum was studied. T. gondii (RH strain) trophozoite's antigens were resolved by gel electrophoresis under denaturating condition. Resolved polypeptides were tested by immunoblotting against hyper-immune serum prepared in Boscat rabbits. Immunoblot analysis revealed 6 reactive bands, which are 158, 111, 102, 86, 55 and 33 kDa, out of 10 antigenic bands of the parasite. Concerning N. caninum trophozoite's antigens, immunoblot analysis revealed 5 reactive bands, which are 159, 119, 106, 97 & 39 kDa, out of 8 antigenic bands of the parasite. Cross reactivity trials between the 2 parasites explore 3 cross-reactive bands, indicating high antigenic similarity in between.

Characterization of the iron superoxide dismutase gene of Azotobacter vinelandii: sodB may be essential for viability

Azotobacter vinelandii contains two superoxide dismutases (SODs), a cytoplasmic iron-containing enzyme (FeSOD), and a periplasmic copper/zinc-containing enzyme (CuZnSOD). In this study, the FeSOD was found to be constitutive, while the activity of CuZnSOD increased as the culture entered the stationary phase. Total SOD (units/mg protein) in stationary phase cells grown under nitrogen-fixing conditions was not significantly different from those grown under non-nitrogen-fixing conditions. The gene encoding FeSOD (sodB) was isolated from an A. vinelandii cosmid library. A 1-kb fragment containing the coding region and 400 base pairs of upstream sequence was cloned and sequenced. The nucleotide sequence and the deduced amino acid sequence had a high degree of homology with other bacterial FeSODs, particularly with P. aeruginosa. Attempts to construct a sodB mutant by recombination of a sodB::kan insertion mutation into the multicopy chromosome of A. vinelandii were unsuccessful even in the presence of SOD mimics or nutritional supplements. These results suggest that FeSOD may be essential for the growth and survival of A. vinelandii, and that the periplasmic CuZnSOD cannot replace the function of FeSOD.

RpoS-dependent stress response and exoenzyme production in Vibrio vulnificus

Vibrio vulnificus is an estuarine bacterium capable of causing rapidly fatal infections through both ingestion and wound infection. Like other opportunistic pathogens, V. vulnificus must adapt to potentially stressful environmental changes while living freely in seawater, upon colonization of the oyster gut, and upon infection of such diverse hosts as humans and eels. In order to begin to understand the ability of V. vulnificus to respond to such stresses, we examined the role of the alternate sigma factor RpoS, which is important in stress response and virulence in many pathogens. An rpoS mutant of V. vulnificus strain C7184o was constructed by homologous recombination. The mutant strain exhibited a decreased ability to survive diverse environmental stresses, including exposure to hydrogen peroxide, hyperosmolarity, and acidic conditions. The most striking difference was a high sensitivity of the mutant to hydrogen peroxide. Albuminase, caseinase, and elastase activity were detected in the wild type but not in the mutant strain, and an additional two hydrolytic activities (collagenase and gelatinase) were reduced in the mutant strain compared to the wild type. Additionally, the motility of the rpoS mutant was severely diminished. Overall, these studies suggest that rpoS in V. vulnificus is important for adaptation to environmental changes and may have a role in virulence.

Effect of malic acid on the growth kinetics of Lactobacillus plantarum

The fermentation kinetics of Lactobacillus plantarum were studied in a specially designed broth formulated from commercially available, dehydrated components (yeast extract, trypticase, ammonium sulfate) in batch and continuous culture. During batch growth in the absence of malic acid, the specific growth rate was 0.20 h(-1). Malic acid in the medium, at 2 mM or 10 mM, increased the specific growth rate of L. plantarum to 0.34 h(-1). An increase in the maximum cell yield due to malic acid also was observed. Malic acid in the medium (12 mM) reduced the non-growth-associated (maintenance energy) coefficient and increased the biomass yield in continuous culture, based on calculations from the Luedeking and Piret model. The biomass yield coefficient was estimated as 27.4 mg or 34.3 mg cells mmol(-1) hexose in the absence or presence of malic acid, respectively. The maintenance coefficient was estimated as 3.5 mmol or 1.5 mmol hexose mg(-1) cell h(-1) in the absence or presence of malic acid. These results clearly demonstrate the energy-sparing effect of malic acid on the growth- and non-growth-associated energy requirements for L. plantarum. The quantitative energy-sparing effect of malic acid on L. plantarum has heretofore not been reported, to our knowledge.

An epidemiological study of neonatal necrotizing enterocolitis

OBJECTIVE

To study epidemiology including various risk factors incorporated in neonatal necrotizing enterocolitis in Kashmir.

METHODS

A retrospective hospital based study on 3235 neonates admitted in Neonatal Intensive Care Unit of Sheri-Kashmir Institute, were evaluated. Forty two were diagnosed as cases of Neonatal Necrotizing Enterocolitis on the basis of various clinical and radiological parameters and grouped in 3 stages as per modified Bell's classification. The case records of these 42 babies and 303 of the control group were reviewed for the purported risk factors and recorded on pretested proforma and finally statistically analyzed.

RESULTS

Over a period of 10 years, we documented necrotizing enterocolitis in 42 neonates, with an incidence of 1% of all Neonatal Intensive Care Unit admissions and 1% of all live births. Eighty one percent were less than 2000 gms and 76% less than 36 weeks of gestation. Twenty four percent had stage I disease, 33% had stage II, and 43% babies had stage III disease. Multiple risk factors were present in these babies, with significant differences among Necrotizing Enterocolitis and the control group of patients, particularly hypothermia (P < 0.001), respiratory distress (P < 0.05), polycythemia (P < 0.001) acidosis (P < 0.01), sepsis (P < 0.001), enteral feeding and asphyxia (P < 0.001). Of the 59 babies (< 2000 gms) with hypothermia (< 35 degrees C), 39% developed Necrotizing Enterocolitis, compared to 4% babies (11/278), who did not have hypothermia, statistically a significant finding. Mean birth weight and gestational age were lower than in control group (P < 0.05). The age of presentation was 5.2 +/- 4.0 days and majority (81%) presented during first week of life, most severe cases presenting earlier than the mild cases. Severity of Necrotizing Enterocolitis as per modified Bell's classification and mortality was inversely related to birth weight and gestational age. One hundred percent mortality was noted in the babies, with birth weight less than 1000 gms and gestational age less than 28 weeks. The overall mortality was 45%, for stage I, 20%; for stage II, 36% and 67% for stage III. Necrotizing Enterocolitis cases accounted for maximum mortality in Neonatal Intensive Care Unit than in control group (P < 0.001).

CONCLUSION

Recognition of factors such as prematurity, low birth weight, hypothermia, asphyxia and their timely prevention would help in reducing morbidity and mortality due to Necrotizing Enterocolitis.

Effects of beta-carotene, selenium and vitamin A on in vitro polymorphonuclear leukocytic activity in peripartal buffalo (Bubalus bubalus)

The effect of different concentrations of three antioxidans on phagocytic and kill activities of blood polymorphonuclear leukocytes (PMN) isolated from buffaloes during the peripartum period (4 weeks before to 7 weeks after parturition) was investigated in this study. Two concentrations of beta-carotene and vitamin A (10(-6) and 10(-5) M) and one concentration of Se (10(-9) M) were used. Phagocytic activity of PMN treated with beta-carotene (10(-6)M) significantly enhanced (P < 0.05) after parturition (Week 0 until Week 3), whereas the kill activity of the same cells significantly (P < 0.05) increased before and after parturition (at Weeks -4, -3, -2, 0, 1, 2 and 3). The concentration of beta-carotene (10(-5) M) enhanced phagocytosis of PMN only at Weeks 0 and 1 and kill activity at Weeks -4, -3, -2, 0, and 1. Selenium (10(-9)M) significantly (P < 0.05) enhanced phagocytic activity of PMN starting from parturition (Week 0) until Week 3 postpartum. Kill activity increased significantly both before (Weeks -4, -3 and -2) and after (Weeks 0, 1, 2, 3 and 4) parturition. Vitamin A (10(-6) M) significantly enhanced phagocytic activity of PMN at Weeks 0, 1, and 2, whereas, the concentration of beta-carotene (10(-5) M) increased phagocytic activity only at Week 0. Kill activity of PMN increased significantly (P < 0.05) at Weeks -1 and 0 (10(-6)M). These results demonstrate that beta-carotene and selenium significantly enhanced phagocytic and kill activities of PMN isolated from buffaloes around parturition in vitro. Vitamin A enhanced phagocytosis and kill activities but not to the same extent as beta-carotene and selenium. Apparently, the in vitro killing activity of PMN is a distinctive function from phagocytosis and both activities may be enhanced by the use of essential nutrients, especially during the peripartum period. Moreover, beta-carotene is more effective as an antioxidant than vitamin A in enhancing the activities of phagocytic cells.

Immune regulation of ovarian function in buffaloes (Bubalus bubalus)

We studied the infiltration of different subsets of immune system cells in the ovarian parenchyma of Egyptian buffaloes during follicular and luteal phases of the estrous cycle. All subsets of leukocytes infiltrated significantly more into corpora lutea (CL) than into Graafian follicles (GF) (P < 0.01) except for plasma cells that were abundant in the GF but not observed in the CL. The number of macrophages, lymphocytes, neutrophils and eosinophils were significantly greater in mature CL than in corpora hemorrhagica (CH) or regressing CL. Moreover, the regressing CL showed significantly more macrophages, lymphocytes and neutrophils than the CH. Large antral follicles were infiltrated with larger number of leukocytes than growing preantral atretic follicles. Macrophages and neutrophils observed in large antral follicles were significantly more abundant in the theca externa than the theca interna (P < 0.01). Only plasma cells were significantly greater in number in the theca intema (P < 0.01). Leukocytes infiltrated significantly more into large mature follicles than large, growing, preantral atretic follicles (P < 0.01). Results of this study reveal the calling of leukocytes in a significant numbers inside the ovarian tissue of buffaloes around the time of ovulation and at luteolysis. It is possible that leukocytes with their powerful bioactive cytokines (IL-1, TNFalpha, GM-CSF, and INF-gamma) may assist in ovarian functions such as ovulation and luteolysis.

The effect of nitric oxide on platelets when delivered to the cardiopulmonary bypass circuit

Nitric oxide (NO) decreases platelet adhesion to foreign surfaces in the in vitro models of cardiopulmonary bypass (CPB). We hypothesized that NO, delivered into the membrane oxygenator (MO), would exert a platelet-sparing effect after CPB. Forty-seven patients scheduled for coronary artery surgery were randomized to either a NO group, in which NO (100 ppm) was delivered into the MO, or a control group, in which CPB was conducted without NO. Platelet numbers, platelet aggregation response to 2.5-20 microM adenosine diphosphate, and beta-thromboglobulin levels were measured after induction of anesthesia, after 1 h on CPB and 2 h after the end of CPB. Met-hemoglobin levels were measured during CPB. The amount of blood products administered and chest tube drainage were measured in the first postoperative 18 h. NO delivered into the MO for up to 180 min did not increase met-hemoglobin levels above 4%. NO inhibited the platelet aggregation response to 2.5 microM ADP during CPB, otherwise NO had no other detectable effect on the aggregation responses or the levels of beta-thromboglobulin. Platelet numbers were not significantly altered by NO. NO did not alter the use of blood products or chest tube drainage. In conclusion, this study suggests that NO delivered into the MO of the CPB circuit does not significantly alter platelet aggregation and numbers, and does not affect bleeding.

IMPLICATIONS

Nitric oxide affects platelet function. We demonstrated that nitric oxide delivered into the gas inflow of the cardiopulmonary bypass circuit membrane oxygenator does not significantly alter platelet numbers or function.

Isolation of immunologically active uterine luminal proteins associated with follicular and luteal phases of the ovary in buffalo (Bubalus bubalus)

Uterine luminal proteins (ULP) collected from the genital tract of buffalo during the follicular (Group F) and luteal (Group L) phases of the estrous cycle were chromatographed using sephacryl S-200 gel. Five peaks were detected in each group. Different protein concentrations (10 to 200 microg) from Peaks I and V in each group were examined for immunological activity on polymorph nuclear leukocytic cells (PMNL) in vitro. All concentrations except 10 microg of ULP Peak I (< or = 250 kDa) in Group F enhanced phagocytic activity of PMNL. Peak V (56 kDa) in the same group enhanced phagocytic activity of PMNL only at low protein concentrations (10, 20 and 40 microg protein), while at greater concentrations (80, 150 and 200 microg protein) PMNL activity was suppressed. On the other hand, all protein concentrations from Peak 1 (> or = 250 kDa) in Group L suppressed PMNL activity in a dose-dependent manner. Proteins from Peak V (31 kDa) in Group L suppressed PMNL phagocytic activity at all concentrations but not to the same extent as in Peak I. Electrophoretic analysis of Peaks I and V in both groups revealed only 3 detectable protein bands (subunits) in Peak I and 1 detectable subunit in Peak V. Several additional proteins were probably not detected. The molecular weights of the detected subunits in Peaks I and V in Group F were greater than those in Group L as indicated by SDS-PAGE analysis. The results of this study show that ULP collected from buffalo possessed proteins that modulated phagocytic activity of PMNL in vitro. Proteins collected during the follicular phase, especially Peak I, enhanced phagocytic activity of the PMNL, whereas those collected during the luteal phase (Peaks I and V) suppressed activity. Changes in the molecular weights of ULP detected in this experiment may be related to the changes in phagocytic activity of PMNL tested in vitro.

Long-term effect of growth hormone (GH) treatment on body composition in children with GH deficiency

OBJECTIVE

It is important for GH-deficient children to treat abnormal body composition associated with a metabolic consequence, not only short stature. In this study we evaluated long-term effects of GH therapy on body composition in GH-deficient boys and girls.

SUBJECTS AND METHODS

Forty-nine subjects with GH deficiency, 35 boys and 14 girls, 6 to 14 years of age, were studied. All the subjects were treated for three years with recombinant human GH at a weekly dosage of 0.5 IU/kg by subcutaneous daily injection. Body composition was measured by bioelectrical impedance analysis (BIA 101, Spectrum II 287, RJL Systems, Detroit, Mich).

RESULTS

Body fat (%) decreased significantly during the first three months of GH treatment. These values were maintained low thereafter in boys, in contrast to those which continued to tend upward in girls from the second year of the treatment. Lean body mass (kg) increased significantly with increasing extracellular water (kg) and body cell mass (kg) in both sexes during GH treatment.

CONCLUSION

Our data demonstrate that GH can reduce body fat mass in GH-deficient boys and girls. The gender difference in changes in body fat with age during the course of this study is compatible with that observed in normal children. The rapid increase in extracellular water and the gradual increase in body cell mass both contributed to the steady increase in LBM during GH treatment.

Long-term prospective study of body composition and lipid profiles during and after growth hormone (GH) treatment in children with GH deficiency: gender-specific metabolic effects

GH has many effects on metabolism in addition to promoting growth. We studied changes in body composition and lipid profiles during and after GH treatment in 94 children with GH deficiency. Sixty-two subjects (46 boys and 16 girls) were evaluated at the beginning and during 36 months of GH treatment. The other 32 (21 boys and 11 girls) who had already been treated with GH were examined after the discontinuation of GH for a 6-month period. The height SD scores at the beginning and the discontinuation of GH treatment were -2.81 and -1.34 in boys and -3.14 and -1.38 in girls, respectively. The percent body fat (BF) significantly decreased from 16.5% to 11.7% in boys and from 16.7% to 11.6% in girls during the first 6 months of GH treatment (P < 0.01). BF subsequently remained constant in boys, but started to increase in girls from the 18th month of treatment. Lean body mass (kilograms) increased linearly throughout the treatment in both sexes (P < 0.01). Mean total cholesterol (TC) values decreased as a result of marked declines in low density lipoprotein cholesterol in both sexes, although statistical significance was detected only in boys (P < 0.01). High density lipoprotein cholesterol (HDLC) and apolipoprotein AI (Apo-AI) rapidly increased only in boys (P < 0.01). Triglyceride, Apo-AII, Apo-B, Apo-CII, Apo-CIII, Apo-E, and lipoprotein(a) showed no significant changes compared with baseline levels. Mean TC/HDLC and Apo-B/Apo-AI ratios decreased during treatment in both sexes, but the difference from baseline was significant only in boys (P < 0.01). After discontinuation of GH treatment, BF increased, and lean body mass decreased in boys (P < 0.01), whereas these variables did not change in girls. TC and low density lipoprotein cholesterol increased in boys within 6 months of discontinuing GH (P < 0.05). Other lipoproteins did not change in either sex, except for lipoprotein(a), which decreased significantly 6 months after the cessation of GH treatment in boys (P < 0.01). The mean TC/HDLC and Apo-B/Apo-AI ratios increased in boys slightly, but insignificantly. We concluded that GH treatment has beneficial effects on body composition and lipid profiles in both boys and girls with GH deficiency, although there are considerable gender differences. These beneficial effects of GH were reversed after the discontinuation of GH treatment, suggesting an important role of GH for GH-deficient children in the maintenance of normal metabolism even after the completion of linear growth.

Mechanism of regulation of 8-hydroxyguanine endonuclease by oxidative stress: roles of FNR, ArcA, and Fur

We found previously that 8-hydroxyguanine (oh8Gua) endonuclease in E. coli is induced in response to oxidative stress in a fashion similar to the oxidative response of the Mn-superoxide dismutase (MnSOD). In this study, attempts were made to identify the genes involved in the co-regulation of E. coli endonuclease and MnSOD (sodA). oh8Gua nuclease is induced by molecular oxygen and a superoxide radical generator (paraquat) but not by H2O2, suggesting that the regulation of this endonuclease is dependent on SoxRS but independent of OxyR. This enzyme was induced by paraquat in all of the soxRS mutant strains used (soxR-, soxS- and soxRc), whereas glucose-6-phosphate dehydrogenase (a member of the soxRS regulon) showed the expected responses; therefore, this possibility was excluded. The presence of metal chelators in the growth medium caused the induction of this enzyme, and this induction was suppressed by the addition of Fe++. Consistent with this finding, this enzyme was expressed under anaerobiosis in all of the mutant strains of fnr in particular, as well as fur, arcA, and combinations thereof. These findings suggest that the oxidative regulation of oh8Gua endonuclease is under control of fnr, fur, and arcA, where fnr plays a predominant role. The multiple involvement of regulatory genes as well as co-regulation with antioxidant enzyme will enhance the efficiency of cellular growth and survival in the aerobic environment.

Characterization of superoxide dismutase in Streptococcus thermophilus

Streptococcus thermophilus AO54 possesses a single manganese-containing superoxide dismutase (MnSOD). The enzyme was found to be insensitive to cyanide or to a modified H2O2 treatment. The enzyme is expressed in a growth-phase-dependent fashion, increasing three- to fourfold upon entry into stationary phase. The specific activity for MnSOD was the same under anaerobic or aerobic conditions and was not induced by the presence of paraquat under aerobic conditions.

Body composition, atherogenic risk factors and apolipoproteins following growth hormone treatment

We studied the change in atherogenic risk factors in 27 children, 21 boys and 6 girls, 6 to 14 years of age, with growth hormone deficiency during 12 months of growth hormone replacement therapy. Changes in body composition and lipid profile during growth hormone treatment were evaluated. The atherogenic index was calculated using the equation [(total cholesterol- high-density lipoprotein cholesterol)(apolipoprotein B)]/[(apolipoprotein AI)(high-density lipoprotein cholesterol)]. Body fat decreased (p < 0.01), associated with an increase in lean body mass (p < 0.01). Total cholesterol and high-density lipoprotein cholesterol showed no significant changes. The atherogenic index significantly decreased from 1.44 +/- 0.60 to 1.09 +/- 0.52 (p < 0.01) after 12 months. Apolipoproteins CII and CIII increased throughout the study period (p < 0.01). Lipoprotein(a) and apolipoproteins AI, B and B/AI ratio did not change significantly. In conclusion, growth hormone treatment improved body composition and reduced atherogenic risk factors in children with growth hormone deficiency.

Binding of integration host factor (IHF) to the Escherichia coli sodA gene and its role in the regulation of a sodA-lacZ fusion gene

We used the electrophoretic mobility-shift assay to reveal specific DNA-protein interactions between DNA fragments containing the sodA promoter and proteins present in Escherichia coli cell-free extracts. We have shown specific binding of several E. coli proteins to sodA promoter sequences and identified one of these proteins as the integration host factor (IHF). Mobility-shift experiments with cell-free extracts prepared from himA (IHF-negative) mutant strains lacked a specific DNA-protein band relative to shifts made with wild-type extracts. Several potential IHF-binding sites were identified in the sodA promoter region. Purified IHF was found to bind specifically to DNA fragments containing the sodA promoter. Further evidence presented suggests that IHF binds to multiple sites in the sodA promoter. We have also investigated the transcriptional regulation of sodA by monitoring the expression of a sodA-lacZ fusion gene in an IHF-negative E. coli strain under different growth conditions. Under aerobic conditions, a deletion in himA (IHF subunit alpha) resulted in a 60% increase in sodA expression, while having no effect on induction by paraquat. The same deletion in himA did not cause derepression of sodA-lacZ during anaerobic growth, but resulted in an increased response (about twofold) to the presence of 2,2'-dipyridyl compared to the isogenic wild-type strain.

Stability of Escherichia coli sodA mRNA and identification of the transcriptional start site(s) under different environmental and oxidative stresses

Manganese-containing superoxide dismutase (MnSOD-sodA) in Escherichia coli (E. coli) is regulated at the transcriptional level as observed in studies using both operon and gene fusions. In this paper we examine the regulation of sodA gene at the level of mRNA. We examine the effects of several aerobic inducing conditions (i.e., nalidixic acid, paraquat, or 2,2'-dipyridyl) on mRNA stability, transcription initiation, and translation. The half-life of sodA mRNA was found to be approximately 3-4 min, showing no differences in mRNA stability between induced and uninduced cells. We also found, by reverse transcriptase, that the second putative promoter is not functional under normal or stress conditions, and the amount of mRNA was found to be proportional to active MnSOD. Thus, these results indicate that under oxidative stress/inducing conditions, the increase in aerobic transcription of sodA occurs from only one transcription start site without affecting the stability of sodA mRNA. In addition, the 1:1 ratio found between increases in sodA mRNA and active MnSOD suggests that no translational regulation occurs aerobically.

Roles of manganese and iron in the regulation of the biosynthesis of manganese-superoxide dismutase in Escherichia coli

Aerobic life-style offers both benefits and risks to living cells. The major risk comes from the formation of reactive oxygen intermediates (i.e. superoxide radical, O2-; hydrogen peroxide, H2O2; and hydroxyl radical, OH.) during normal oxygen metabolism. However, living cells are able to cope with oxygen toxicity by virtue of a unique set of antioxidant enzymes that scavenge O2- and H2O2, and prevent the formation OH.. Superoxide dismutases (SODs; EC 1.15.1.1) are metalloenzymes essential for aerobic survival. Escherichia coli contains two forms of this enzyme: an iron-containing enzyme (FeSOD) and a manganese-containing enzyme (MnSOD). In E. coli, MnSOD biosynthesis is under rigorous control. The enzyme is induced in response to a variety of environmental stress conditions including exposure to oxygen, redox cycling compounds such as paraquat which exacerbate the level of intracellular superoxide radicals, iron chelation (i.e. iron deprivation), and oxidants. A model for the regulation of the MnSOD has been proposed in which the MnSOD gene (sodA) is negatively regulated at the level of transcription by an iron-containing redox-sensitive repressor protein. The effect of iron-chelation most probably results in removal of the iron necessary for repressor activity. Recent studies have shown that sodA expression is regulated by three iron-dependent regulatory proteins, Fur (ferric uptake regulation), Fnr (fumarate nitrate regulation) and SoxR (superoxide regulon), and by the ArcA/ArcB (aerobic respiration control) system. The potential Fur-, Fnr- and ArcA-binding sites in the sodA promoter region have been identified by using different cis-acting regulatory mutations that caused anaerobic derepression of the gene.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of fur on the transcriptional and post-transcriptional regulation of MnSOD gene (sodA) in Escherichia coli

Earlier studies have shown that the Fur (ferric uptake regulation) protein acts as an anaerobic/aerobic repressor of MnSOD (sodA) expression. We found that the aerobic expression of sodA::lacZ fusion in a Fur- background to be threefold higher than in a Fur+ background. This effect of fur mutation was not seen in a strain harboring the sodA+ gene instead of the sodA::lacZ fusion. However, we observed a proportionate increase in the concentrations of sodA::lacZ and sodA+ mRNAs in response to a mutation in the fur gene. These data suggest that the formation of active MnSOD is dependent on a functional fur gene. Indeed, we found that in a fur mutant iron was incorporated into SodA in place of manganese, thus creating inactive and/or partially active forms of the enzyme (i.e., Fe2SodA and/or Mn,FeSodA, respectively), resulting in little or no increase in total MnSOD activity. Thus, Fur plays the role of a repressor at the transcriptional level, but it also plays an indirect role at the post-transcriptional level where it affects the maturation of SodA into a fully active enzyme, Mn2SodA (MnSOD).

Transcriptional activation of Mn-superoxide dismutase gene (sodA) of Escherichia coli by MnCl2

Transcription of the manganese-superoxide dismutase gene (sodA) in Escherichia coli was shown to be activated by manganese. Addition of MnCl2 increased the expression of beta-galactosidase from a sodA::lacZ protein fusion and increased the concentration of mRNA transcribed from sodA+ and sodA::lacZ constructs. The stimulatory affect of manganese on the expression of sodA::lacZ was greatly reduced (i.e., > 90%) in a strain harboring a fur mutation. We also found that manganese was capable of altering DNA topology. These results show that Mn2+ causes activation of sodA transcription.

Characterization of regulatory mutations causing anaerobic derepression of the sodA gene in Escherichia coli K12: cooperation between cis- and trans-acting regulatory loci

The genetic loci leading to anaerobic derepression of a sodA::lacZ protein fusion in a UV-generated mutant strain (UV14) of Escherichia coli were identified. The mutant (UV14) was found to harbour two altered loci: one is in the trans-regulatory gene fnr (fumarate nitrate reduction) where leucine-129 was changed to glutamine (fnr14), and the second (sodA14) is in the promoter region (cis) of the sodA gene apparently affecting the binding of the Fur (ferric uptake regulation) protein. Introduction of an fnr+ gene into UV14 restored anaerobic repression of sodA::lacZ and restored the ability of the cells to reduce nitrate. However, when either the fnr14 or the sodA14 mutation was introduced into an otherwise wild-type background, only slight anaerobic derepression of sodA was observed. When both the cis- and trans-acting mutations (i.e. sodA14 and fnr14) were combined simultaneously in an otherwise wild-type background, the specific activity of sodA::lacZ expression was comparable to that of the original mutant strain (UV14). Furthermore, a genetically confirmed fur fnr double mutant was also similarly derepressed in anaerobic sodA::lacZ expression. The data presented suggest that the cis-mutation in UV14 (sodA14) affects the Fur-binding site in the sodA promoter, while having no effect on Fnr or Arc mediated repression. Also, a second putative Fnr-binding site that straddles the ribosomal binding-site was identified in the sodA gene.

Characterization of cis-acting regulatory mutations causing anaerobic expression of the sodA gene in Escherichia coli

The biosynthesis of Mn-containing superoxide dismutase is regulated in response to stimuli that affect the redox potential of the cell. To further investigate the mode of regulation of the gene (sodA) encoding this enzyme, cis-acting regulatory mutations in a strain containing a sodA::lacZ gene fusion were studied. The mutant strains expressed beta-galactosidase under anaerobic conditions, whereas the wild-type did not. Furthermore, the mutants were not induced in response to the presence of iron chelator, 2,2'-dipyridyl, or to the redox cycling compound, paraquat. The wild-type, however, did respond to these effectors. In vivo cloning was used to isolate the cis-acting regulatory elements from the mutants (NC4 and NC5). Replacement of the wild-type 5'-regulatory region with either of the mutants' cis-acting regulatory element resulted in the anaerobic expression of active Mn-superoxide dismutase. Sequence and restriction analysis revealed the presence of an IS2 insertion element in the promoter region of one of the mutants (NC5). This insertion caused the displacement of the 5'-regulatory region of sodA and the formation of a functional hybrid promoter consisting of the resident-10 region from sodA and -35 from IS2. The second mutation (from NC4) was similarly analyzed, and an IS5 element was identified. The insertion site of IS5 (in NC4) was 6 bp (5'-TTAATT-3') upstream from the IS2 site (in NC5). Anaerobic expression of sodA in NC4 was lower than in NC5. This difference was almost eliminated in an arc- background, suggesting that the sequence 5'-TTAATT-3' might be essential for negative regulation by ArcA.

Cloning and expression of the manganese superoxide dismutase gene of Escherichia coli in Lactococcus lactis and Lactobacillus gasseri

The Escherichia coli sodA gene encoding the antioxidant enzyme Mn-containing superoxide dismutase (MnSOD), was cloned in the expression vector pMG36e. This vector has a multiple cloning site downstream of a promoter and Shine-Dalgarno sequences derived from Lactococcus. The protein-coding region of sodA from E. coli was amplified by the polymerase chain reaction, using a thermocycler and Taq DNA polymerase before cloning into pMG36e. When introduced into E. coli, the recombinant plasmid expressed the predicted fusion protein, both in the presence and absence of oxygen. The expression of the fusion protein in E. coli was verified by SOD assays, activity gels and Western blots. The recombinant plasmid was also introduced into Lactococcus lactis, which contains a resident SOD, and into Lactobacillus gasseri, which is devoid of SOD. Transformed lactococci expressed an active SodA fusion protein plus an active hybrid protein composed of subunits of the Lactococcus and the recombinant E. coli enzymes. Transformants of L. gasseri expressed only the fusion SodA protein, which was enzymatically active.

Transcriptional regulation of Mn-superoxide dismutase gene (sodA) of Escherichia coli is stimulated by DNA gyrase inhibitors

The expression of manganese-containing superoxide dismutase (sodA) in Escherichia coli using sodA::lacZ gene fusion was found to be stimulated by DNA gyrase inhibitors, nalidixic acid, or coumermycin A1. Aerobically, the gyrase inhibitors increased the expression of sodA::lacZ in the presence or absence of either paraquat or the iron chelator 2,2'-dipyridyl. The concentrations of the inhibitors used were found to reduce DNA supercoiling. Treatment of wild-type cells (sodA+) with nalidixic acid increased the transcription of MnSOD mRNA. Anaerobically, the expression of sodA::lacZ in wild-type cells was not affected by nalidixic acid. However, nalidixic acid had a stimulatory effect on the anaerobic expression of sodA::lacZ in cells preinduced by the iron chelator as well as in mutants derepressed in sodA expression by virtue of their lacking the trans-acting repressor proteins or the cis-acting regulatory elements needed for sodA regulation. The results indicate that the effect of DNA gyrase inhibitors is secondary to the cis- and trans-regulatory elements of sodA and suggest that changes in DNA topology may affect transcriptional regulation of sodA.

Regulatory roles of Fnr, Fur, and Arc in expression of manganese-containing superoxide dismutase in Escherichia coli

Transcriptional regulation of the sodA gene, encoding the manganese superoxide dismutase (superoxide: superoxide oxidoreductase, EC 1.15.1.1) of Escherichia coli, was studied by monitoring expression of sodA-lacZ in different genetic backgrounds and under different growth conditions. Mutations in the fnr gene were found to affect aerobic and anaerobic expression of sodA-lacZ. Potential Fnr-binding sites were identified in the promoter region of sodA. Strains harboring simultaneous mutations in arcA/B and fur expressed sodA-lacZ under anaerobic growth conditions but were still inducible by iron chelators. However, in the triple mutants (fnr fur arcA/B) sodA-lacZ was fully expressed under anaerobiosis and was not further induced by the presence of 2,2'-dipyridyl, nitrate, or oxidants. On the other hand, aerobic expression of sodA-lacZ from a Fur-strain was approximately 3.8-fold higher than that from the wild-type strain but was diminished by introducing mutations in fnr or arcA/B. In conclusion, Fnr, Arc, and Fur act as anaerobic repressors of sodA. Furthermore, the regulation of sodA by Fur (ferric uptake regulation protein), Arc (aerobic respiratory control), and Fnr (fumarate nitrate reduction/regulator of anaerobic respiration) is independent of the superoxide response regulon SoxRS.

Acid Tolerance of Leuconostoc mesenteroides and Lactobacillus plantarum

In this study, we determined the internal cellular pH response of Leuconostoc mesenteroides and Lactobacillus plantarum to the external pH created by the microorganisms themselves or by lactic or acetic acids and their salts added to the growth medium. Growth of Leuconostoc mesenteroides stopped when its internal pH reached 5.4 to 5.7, and growth of L. plantarum stopped when its internal pH reached 4.6 to 4.8. Variation in growth medium composition or pH did not alter the growth-limiting internal pH reached by these microorganisms. L. plantarum maintained its pH gradient in the presence of either 160 mM sodium acetate or sodium lactate down to an external pH of 3.0 with either acid. In contrast, the ΔpH of Leuconostoc mesenteroides was zero at pH 4.0 with acetate and 5.0 with lactate. No differences were found between d -(−)- and l -(+)-lactic acid for the limiting internal pH for growth of either microorganism. The comparatively low growth-limiting internal pH and ability to maintain a pH gradient at high organic acid concentration may contribute to the ability of L. plantarum to terminate vegetable fermentations.

Use of site-directed mutagenesis to identify an upstream regulatory sequence of sodA gene of Escherichia coli K-12

Mn-containing superoxide dismutase (SodA; superoxide:superoxide oxidoreductase, EC 1.15.1.1) biosynthesis in Escherichia coli is regulated by several environmental stimuli. The DNA sequence of sodA shows the presence of a potential binding site for a regulatory protein(s) at the -35 region. To explore the possible role of this region in the regulation of sodA, we used oligonucleotide-directed site-specific mutagenesis to change the sequence of nucleotides -48 through -44 from 5'-GGCAT-3' to 5'-TTACG-3'. We studied the effect of this altered sequence on the expression of sodA. The data showed that the altered sequence resulted in the constitutive expression of the gene. Thus, E. coli harboring a plasmid containing the mutated sodA gene (pSNM6) were uninducible by paraquat in aerobiosis or by 2,2'-dipyridyl in aerobiosis or anaerobiosis. Furthermore, a multicopy plasmid containing the mutated sodA failed to titrate the repressor molecules present in an E. coli strain carrying the sodA-lacZ fusion. In contrast, multicopy plasmids containing the wild-type sodA gene were able to titrate the repressor protein and to cause the anaerobic induction of beta-galactosidase in this sodA-lacZ fusion strain. These results indicate that the region within and around the mutated sequence probably plays an important role in sodA regulation and that the mutation disrupts a sequence that interacts with the repressor.

An electron spin resonance study of oxyradical generation in superoxide dismutase- and catalase-deficient mutants of Escherichia coli K-12

The response of superoxide dismutase- and catalase-deficient strains of Escherichia coli to redox active compounds was examined by electron spin resonance. Levels of radicals formed in response to pyocyanine in situ were extremely low and were found to be predominantly extracellular, even in a strain completely deficient in both superoxide dismutase and catalase. In cell-free extracts of superoxide dismutase-minus strains incubated with NADPH and pyocyanine, the primary accumulating radical was the superoxide anion (O2-), although low levels of the hydroxyl radical (.OH) were also detected. In contrast, extracts from strains lacking catalase were found to accumulate higher levels of hydroxyl radicals.

Effect of temperature and htpR on the biosynthesis of superoxide dismutase in Escherichia coli

The synthesis of Mn- and FeSODs in response to temperature changes was examined in strains of Escherichia coli with different mutations in sod and htpR genes. Growth at or shift to elevated temperatures induced FeSOD but not MnSOD. The induction of FeSOD by heat was inhibited by chloramphenicol and was independent of the heat shock (htpR-controlled) regulon. FeSOD was more stable at 42 degrees C than was MnSOD.

Induction of the manganese-containing superoxide dismutase in Escherichia coli is independent of the oxidative stress (oxyR-controlled) regulon

The synthesis of manganese-superoxide dismutase in response to hydrogen peroxide and to paraquat was examined in strains of Escherichia coli with different mutations in the oxyR gene. Hydrogen peroxide treatment did not induce manganese-superoxide dismutase, but did induce the oxyR regulon. Paraquat induced this enzyme in a strain compromised in its ability to induce the defense response against oxidative stress (oxyR deletion) as well as in a strain that is constitutive and overexpresses the oxyR regulon. Catalase (HPI), but not manganese-superoxide dismutase, was over-expressed under anaerobic conditions in a strain harboring a constitutive oxyR mutation. The data clearly demonstrate that the induction of manganese-superoxide dismutase is independent of the oxyR-controlled regulon.

Response of hydroperoxidase and superoxide dismutase deficient mutants of Escherichia coli K-12 to oxidative stress

In Escherichia coli, the coordinate action of two antioxidant enzymes, superoxide dismutase and hydroperoxidase (catalase), protect the cell from the deleterious effects of oxyradicals generated during normal aerobic respiration. To evaluate the relative importance of these two classes of enzymes, strains of E. coli deficient in superoxide dismutase and (or) hydroperoxidase were constructed by generalized transduction and their physiological responses to oxygen and oxidant stress examined. Superoxide dismutase was found to be more important than hydroperoxidase in preventing oxygen-dependent growth inhibition and mutagenesis, and in reducing sensitivity to redox-active compounds known to generate the superoxide anion. However, both types of enzymes were required for an effective defense against chemical oxidants that generate superoxide radicals and hydrogen peroxide.

Transcriptional regulation of katE in Escherichia coli K-12

Escherichia coli produces two distinct species of catalase, hydroperoxidases I and II, which differ in kinetic properties and regulation. To further examine catalase regulation, a lacZ fusion was placed into one of the genes that is involved in catalase synthesis. Transductional mapping revealed the fusion to be either allelic with or very close to katE, a locus which together with katF controls the synthesis of the aerobically inducible hydroperoxidase (hydroperoxidase II). katE was expressed under anaerobic conditions at levels that were approximately one-fourth of those found in aerobically grown cells and was found to be induced to higher levels in early-stationary-phase cells relative to levels of exponentially growing cells under both anaerobic and aerobic conditions. katE was fully expressed in air and was not further induced when the growth medium was sparged with 100% oxygen. Expression of katE was unaffected by the addition of hydrogen peroxide or by the presence of additional lesions in oxyR or sodA, indicating that it is not part of the oxyR regulon. When katF::Tn10 was introduced into a katE::lacZ strain, beta-galactosidase synthesis was largely eliminated and was no longer inducible, suggesting that katF is a positive regulator of katE expression.