Saccharibacteria (TM7) in the Human Oral Microbiome

Bacteria from the Saccharibacteria phylum (formerly known as TM7) are ubiquitous members of the human oral microbiome and are part of the Candidate Phyla Radiation. Recent studies have revealed remarkable 16S rRNA diversity in environmental and mammalian host-associated members across this phylum, and their association with oral mucosal infectious diseases has been reported. However, due to their recalcitrance to conventional cultivation, TM7's physiology, lifestyle, and role in health and diseases remain elusive. The recent cultivation and characterization of Nanosynbacter lyticus type strain TM7x (HMT_952)-the first Saccharibacteria strain coisolated as an ultrasmall obligate parasite with its bacterial host from the human oral cavity-provide a rare glimpse into the novel symbiotic lifestyle of these enigmatic human-associated bacteria. TM7x is unique among all bacteria: it has an ultrasmall size and lives on the surface of its host bacterium. With a highly reduced genome, it lacks the ability to synthesize any of its own amino acids, vitamins, or cell wall precursors and must parasitize other oral bacteria. TM7x displays a highly dynamic interaction with its bacterial hosts, as reflected by the reciprocal morphologic and physiologic changes in both partners. Furthermore, depending on environmental conditions, TM7x can exhibit virulent killing of its host bacterium. Thus, Saccharibacteria potentially affect oral microbial ecology by modulating the oral microbiome structure hierarchy and functionality through affecting the bacterial host's physiology, inhibiting the host's growth dynamics, or affecting the relative abundance of the host via direct killing. At this time, several other uncharacterized members of this phylum have been detected in various human body sites at high prevalence. In the oral cavity alone, at least 6 distinct groups vary widely in relative abundance across anatomic sites. Here, we review the current knowledge on the diversity and unique biology of this recently uncovered group of ultrasmall bacteria.

Arginine Improves pH Homeostasis via Metabolism and Microbiome Modulation

Dental caries can be described as a dysbiosis of the oral microbial community, in which acidogenic, aciduric, and acid-adapted bacterial species promote a pathogenic environment, leading to demineralization. Alkali generation by oral microbes, specifically via arginine catabolic pathways, is an essential factor in maintaining plaque pH homeostasis. There is evidence that the use of arginine in dentifrices helps protect against caries. The aim of the current study was to investigate the mechanistic and ecological effect of arginine treatment on the oral microbiome and its regulation of pH dynamics, using an in vitro multispecies oral biofilm model that was previously shown to be highly reflective of the in vivo oral microbiome. Pooled saliva from 6 healthy subjects was used to generate overnight biofilms, reflecting early stages of biofilm maturation. First, we investigated the uptake of arginine by the cells of the biofilm as well as the metabolites generated. We next explored the effect of arginine on pH dynamics by pretreating biofilms with 75 mM arginine, followed by the addition of sucrose (15 mM) after 0, 6, 20, or 48 h. pH was measured at each time point and biofilms were collected for 16S sequencing and targeted arginine quantification, and supernatants were prepared for metabolomic analysis. Treatment with only sucrose led to a sustained pH drop from 7 to 4.5, while biofilms treated with sucrose after 6, 20, or 48 h of preincubation with arginine exhibited a recovery to higher pH. Arginine was detected within the cells of the biofilms, indicating active uptake, and arginine catabolites citrulline, ornithine, and putrescine were detected in supernatants, indicating active metabolism. Sequencing analysis revealed a shift in the microbial community structure in arginine-treated biofilms as well as increased species diversity. Overall, we show that arginine improved pH homeostasis through a remodeling of the oral microbial community.

Socioeconomic status and the cerebellar grey matter volume. Data from a well-characterised population sample

The cerebellum is highly sensitive to adverse environmental factors throughout the life span. Socioeconomic deprivation has been associated with greater inflammatory and cardiometabolic risk, and poor neurocognitive function. Given the increasing awareness of the association between early-life adversities on cerebellar structure, we aimed to explore the relationship between early life (ESES) and current socioeconomic status (CSES) and cerebellar volume. T1-weighted MRI was used to create models of cerebellar grey matter volumes in 42 adult neurologically healthy males selected from the Psychological, Social and Biological Determinants of Ill Health study. The relationship between potential risk factors, including ESES, CSES and cerebellar grey matter volumes were examined using multiple regression techniques. We also examined if greater multisystem physiological risk index-derived from inflammatory and cardiometabolic risk markers-mediated the relationship between socioeconomic status (SES) and cerebellar grey matter volume. Both ESES and CSES explained the greatest variance in cerebellar grey matter volume, with age and alcohol use as a covariate in the model. Low CSES explained additional significant variance to low ESES on grey matter decrease. The multisystem physiological risk index mediated the relationship between both early life and current SES and grey matter volume in cerebellum. In a randomly selected sample of neurologically healthy males, poorer socioeconomic status was associated with a smaller cerebellar volume. Early and current socioeconomic status and the multisystem physiological risk index also apparently influence cerebellar volume. These findings provide data on the relationship between socioeconomic deprivation and a brain region highly sensitive to environmental factors.

The envirome and the connectome: exploring the structural noise in the human brain associated with socioeconomic deprivation

Complex cognitive functions are widely recognized to be the result of a number of brain regions working together as large-scale networks. Recently, complex network analysis has been used to characterize various structural properties of the large-scale network organization of the brain. For example, the human brain has been found to have a modular architecture i.e., regions within the network form communities (modules) with more connections between regions within the community compared to regions outside it. The aim of this study was to examine the modular and overlapping modular architecture of the brain networks using complex network analysis. We also examined the association between neighborhood level deprivation and brain network structure—modularity and gray nodes. We compared network structure derived from anatomical MRI scans of 42 middle-aged neurologically healthy men from the least (LD) and the most deprived (MD) neighborhoods of Glasgow with their corresponding random networks. Cortical morphological covariance networks were constructed from the cortical thickness derived from the MRI scans of the brain. For a given modularity threshold, networks derived from the MD group showed similar number of modules compared to their corresponding random networks, while networks derived from the LD group had more modules compared to their corresponding random networks. The MD group also had fewer gray nodes—a measure of overlapping modular structure. These results suggest that apparent structural difference in brain networks may be driven by differences in cortical thicknesses between groups. This demonstrates a structural organization that is consistent with a system that is less robust and less efficient in information processing. These findings provide some evidence of the relationship between socioeconomic deprivation and brain network topology.

Cardio-metabolic risk factors and cortical thickness in a neurologically healthy male population: Results from the psychological, social and biological determinants of ill health (pSoBid) study

INTRODUCTION

Cardio-metabolic risk factors have been associated with poor physical and mental health. Epidemiological studies have shown peripheral risk markers to be associated with poor cognitive functioning in normal healthy population and in disease. The aim of the study was to explore the relationship between cardio-metabolic risk factors and cortical thickness in a neurologically healthy middle aged population-based sample.

METHODS

T1-weighted MRI was used to create models of the cortex for calculation of regional cortical thickness in 40 adult males (average age = 50.96 years), selected from the pSoBid study. The relationship between cardio-vascular risk markers and cortical thickness across the whole brain, was examined using the general linear model. The relationship with various covariates of interest was explored.

RESULTS

Lipid fractions with greater triglyceride content (TAG, VLDL and LDL) were associated with greater cortical thickness pertaining to a number of regions in the brain. Greater C reactive protein (CRP) and intercellular adhesion molecule (ICAM-1) levels were associated with cortical thinning pertaining to perisylvian regions in the left hemisphere. Smoking status and education status were significant covariates in the model.

CONCLUSIONS

This exploratory study adds to a small body of existing literature increasingly showing a relationship between cardio-metabolic risk markers and regional cortical thickness involving a number of regions in the brain in a neurologically normal middle aged sample. A focused investigation of factors determining the inter-individual variations in regional cortical thickness in the adult brain could provide further clarity in our understanding of the relationship between cardio-metabolic factors and cortical structures.

Personality, socio-economic status and inflammation: cross-sectional, population-based study

Background

Associations between socio-economic status (SES), personality and inflammation were examined to determine whether low SES subjects scoring high on neuroticism or hostility might suffer relatively higher levels of inflammation than affluent subjects.

Methods

In a cross-sectional design, 666 subjects were recruited from areas of high (most deprived – “MD”) and low (least deprived – “LD”) deprivation. IL-6, ICAM-1, CRP and fibrinogen were measured along with demographic and health-behaviour variables, and personality traits of neuroticism, extraversion and psychoticism (hostility). Regression models assessed the prediction of inflammation as a function of personality, deprivation and their interaction.

Results

Levels of CRP and IL-6 were an increasing function of neuroticism and extraversion only in LD subjects opposite trends were seen in MD subjects. The result was ascribed parsimoniously to an inflammatory ceiling effect or, more speculatively, to SES-related health-behaviour differences. Psychoticism was strongly associated with ICAM-1 in both MD and LD subjects.

Conclusions

The association between neuroticism, CRP and IL-6 may be reduced in MD subjects confirming speculation that the association differs across population sub-groups. The association between psychoticism and ICAM-1 supports evidence that hostility has adverse effects upon the endothelium, with consequences for cardiovascular health. Health interventions may be more effective by accounting for personality-related effects upon biological processes.

Soluble ST2 associates with diabetes but not established cardiovascular risk factors: a new inflammatory pathway of relevance to diabetes?

Preliminary data mostly from animal models suggest the sST2/IL-33 pathway may have causal relevance for vascular disease and diabetes and thus point to a potential novel inflammatory link to cardiometabolic disease. However, the characterisation of sST2 levels in terms of metabolic or vascular risk in man is completely lacking. We sought to address this gap via a comprehensive analysis of risk factor and vascular correlates of sST2 in a cross-sectional study (pSoBid). We measured sST2 in plasma in 639 subjects and comprehensively related it to cardiovascular and diabetes risk factors and imaged atherosclerosis measures. Circulating sST2 levels increased with age, were lower in women and in highest earners. After adjusting for age and gender, sST2 levels associated strongly with markers of diabetes, including triglycerides [effect estimate (EE) per 1 standard deviation increase in sST2:1.05 [95%CI 1.01,1.10]), liver function (alanine aminotransaminase [ALT] and γ-glutamyl transferase [GGT]: EE 1.05 [1.01,1.09] and 1.13 [1.07,1.19] respectively), glucose (1.02 [1.00,1.03]) and sICAM-1 (1.05 [1.02,1.07]). However, sST2 levels were not related to smoking, cholesterol, blood pressure, or atheroma (carotid intima media thickness, plaque presence). These results suggest that sST2 levels, in individuals largely without vascular disease, are related principally to markers associated with diabetes and ectopic fat and add support for a role of sST2 in diabetes. Further mechanistic studies determining how sST2 is linked to diabetes pathways may offer new insights into the inflammatory paradigm for type 2 diabetes.

Early life socioeconomic status, chronic physiological stress and hippocampal N-acetyl aspartate concentrations

OBJECTIVE

Early life socioeconomic deprivation has been associated with cognitive and behavioural changes that persist through towards adulthood. In this study, we investigated whether early life socioeconomic status is associated with changes in the hippocampus N-acetyl aspartate (NAA), using the non-invasive technique of magnetic resonance spectroscopy (MRS).

METHODS

We performed proton magnetic resonance spectroscopy ((1)H-MRS) of the hippocampus at 3T in 30 adult males, selected from the PSOBID cohort. We conducted multiple regression analysis to examine the relationship between early socioeconomic status (SES) and concentration of N-acetyl-aspartate in the hippocampus. We also examined whether the relationship between these variables was mediated by markers of chronic physiological stress.

RESULTS

Greater socioeconomic deprivation was associated with lower hippocampal NAA concentrations bilaterally. The relationship between early life SES and hippocampal NAA concentrations was mediated by allostatic load index - a marker of chronic physiological stress.

CONCLUSIONS

Greater early life socioeconomic deprivation was associated with lower concentrations of NAA reflecting lesser neuronal integrity. This relationship was mediated by greater physiological stress. Further work, to better understand the biological processes underlying the effects of poverty, physiological stress on hippocampal metabolites is necessary.

Interaction of personality traits with social deprivation in determining mental wellbeing and health behaviours

BACKGROUND

Associations between personality traits, mental wellbeing and good health behaviours were examined to understand further the social and psychological context of the health divide.

METHODS

In a cross-sectional study, 666 subjects recruited from areas of high and low socioeconomic deprivation had personality traits and mental wellbeing assessed, and lifestyle behaviours quantified. Regression models (using deprivation as a moderating variable) assessed the extent to which personality traits and mental wellbeing predicted health behaviour.

RESULTS

Deprived (vs. affluent) subjects exhibited similar levels of extraversion but higher levels of neuroticism and psychoticism, more hopelessness, less sense of coherence, lower self-esteem and lower self-efficacy (all P< 0.001). They ate less fruit and vegetables, smoked more and took less aerobic exercise (all P< 0.001). In the deprived group, personality traits were significantly more important predictors of mental wellbeing than in the least deprived group (P< 0.01 for interaction), and mental wellbeing and extraversion appeared more strongly related to good health behaviours.

CONCLUSIONS

Persistence of a social divide in health may be related to interactions between personality, mental wellbeing and the adoption of good health behaviours in deprived areas. Effectiveness of health messages may be enhanced by accommodating the variation in the levels of extraversion, neuroticism, hopelessness and sense of coherence.

Socio-economic status is associated with epigenetic differences in the pSoBid cohort

BACKGROUND

Epigenetic programming and epigenetic mechanisms driven by environmental factors are thought to play an important role in human health and ageing. Global DNA methylation has been postulated as an epigenetic marker for epidemiological studies as it is reflective of changes in gene expression linked to disease. How epigenetic mechanisms are affected by psychological, sociological and biological determinants of health still remains unclear. The aim of this study was to investigate the relationship between socio-economic and lifestyle factors and epigenetic status, as measured by global DNA methylation content, in the pSoBid cohort, which is characterized by an extreme socio-economic and health gradient.

METHODS

DNA was extracted from peripheral blood leukocytes using the Maxwell® 16 System and Maxwell® 16 Blood DNA Purification kit (Promega, UK). Global DNA methylation was assessed using Methylamp™ Global DNA Methylation Quantification Ultra kit (Epigentek, USA). Associations between global DNA methylation and socio-economic and lifestyle factors were investigated in linear regression models.

RESULTS

Global DNA hypomethylation was observed in the most socio-economically deprived subjects. Job status demonstrated a similar relationship, with manual workers having 24% lower DNA methylation content than non-manual. Additionally, associations were found between global DNA methylation content and biomarkers of cardiovascular disease (CVD) and inflammation, including fibrinogen and interleukin-6 (IL-6), after adjustment for socio-economic factors.

CONCLUSIONS

This study has indicated an association between epigenetic status and socio-economic status (SES). This relationship has direct implications for population health and is reflected in further associations between global DNA methylation content and emerging biomarkers of CVD.

Using DGGE profiling to develop a novel culture medium suitable for oral microbial communities

More than 700 bacterial species have been detected in the human oral cavity. They form highly organized microbial communities and are responsible for many oral infectious diseases, such as dental caries and periodontal disease. The prevention and treatment of these diseases require a comprehensive knowledge of oral microbial communities, which largely relies on culture-dependent methods to provide detailed phenotypic and physiological analysis of these communities. However, most of the currently available laboratory media can only selectively support the growth of a limited number of bacterial species within these communities, and fail to sustain the original oral microbial diversity. In this study, using denaturing gradient gel electrophoresis (DGGE) as an index to systematically survey and analyse the selectivity of commonly used laboratory media, we developed a new medium (SHI medium) by combining the ingredients of several selected media that can support different subpopulations within the original oral microbial community derived from pooled saliva. DGGE and 454 pyrosequencing analysis showed that SHI medium was capable of supporting a more diversified community with a microbial profile closer to that of the original oral microbiota. Furthermore, 454 pyrosequencing revealed that SHI medium supported the growth of many oral species that have not before been cultured. Crystal violet assay and the confocal laser scanning microscope analysis indicated that, compared with other media, SHI medium is able to support a more complex saliva-derived biofilm with higher biomass yield and more diverse species. This DGGE-guided method could also be used to develop novel media for other complex microbial communities.

Early life socioeconomic adversity is associated in adult life with chronic inflammation, carotid atherosclerosis, poorer lung function and decreased cognitive performance: a cross-sectional, population-based study

BACKGROUND

Socioeconomic gradients in health persist despite public health campaigns and improvements in healthcare. The Psychosocial and Biological Determinants of Ill-health (pSoBid) study was designed to uncover novel biomarkers of chronic disease that may help explain pathways between socioeconomic adversity and poorer physical and mental health.

METHODS

We examined links between indicators of early life adversity, possible intermediary phenotypes, and markers of ill health in adult subjects (n = 666) recruited from affluent and deprived areas. Classical and novel risk factors for chronic disease (lung function and atherosclerosis) and for cognitive performance were assessed, and associations sought with early life variables including conditions in the parental home, family size and leg length.

RESULTS

Associations were observed between father's occupation, childhood home status (owner-occupier; overcrowding) and biomarkers of chronic inflammation and endothelial activation in adults (C reactive protein, interleukin 6, intercellular adhesion molecule; P < 0.0001) but not number of siblings and leg length. Lung function (forced expiratory volume in 1 second) and cognition (Choice Reaction Time, the Stroop test, Auditory Verbal Learning Test) were likewise related to early life conditions (P < 0.001). In multivariate models inclusion of inflammatory variables reduced the impact and independence of early life conditions on lung function and measures of cognitive ability. Including variables of adult socioeconomic status attenuated the early life associations with disease biomarkers.

CONCLUSIONS

Adverse levels of biomarkers of ill health in adults appear to be influenced by father's occupation and childhood home conditions. Chronic inflammation and endothelial activation may in part act as intermediary phenotypes in this complex relationship. Reducing the 'health divide' requires that these life course determinants are taken into account.

Role of outer-membrane cytochromes MtrC and OmcA in the biomineralization of ferrihydrite by Shewanella oneidensis MR-1

In an effort to improve the understanding of electron transfer mechanisms at the microbe-mineral interface, Shewanella oneidensis MR-1 mutants with in-frame deletions of outer-membrane cytochromes (OMCs), MtrC and OmcA, were characterized for the ability to reduce ferrihydrite (FH) using a suite of microscopic, spectroscopic, and biochemical techniques. Analysis of purified recombinant proteins demonstrated that both cytochromes undergo rapid electron exchange with FH in vitro with MtrC displaying faster transfer rates than OmcA. Immunomicroscopy with cytochrome-specific antibodies revealed that MtrC co-localizes with iron solids on the cell surface while OmcA exhibits a more diffuse distribution over the cell surface. After 3-day incubation of MR-1 with FH, pronounced reductive transformation mineral products were visible by electron microscopy. Upon further incubation, the predominant phases identified were ferrous phosphates including vivianite [Fe(3)(PO(4))(2)x8H(2)O] and a switzerite-like phase [Mn(3),Fe(3)(PO(4))(2)x7H(2)O] that were heavily colonized by MR-1 cells with surface-exposed outer-membrane cytochromes. In the absence of both MtrC and OmcA, the cells ability to reduce FH was significantly hindered and no mineral transformation products were detected. Collectively, these results highlight the importance of the outer-membrane cytochromes in the reductive transformation of FH and support a role for direct electron transfer from the OMCs at the cell surface to the mineral.

Oxygen-dependent autoaggregation in Shewanella oneidensis MR-1

In aerobic chemostat cultures maintained at 50% dissolved O(2) tension (3.5 mg l(-1) dissolved O(2)), Shewanella oneidensis strain MR-1 rapidly aggregated upon addition of 0.68 mM CaCl(2) and retained this multicellular phenotype at high dilution rates. Confocal microscopy analysis of the extracellular matrix material contributing to the stability of the aggregate structures revealed the presence of extracellular DNA, protein and glycoconjugates. Upon onset of O(2)-limited growth (dissolved O(2) below detection) however, the Ca(2+)-supplemented chemostat cultures of strain MR-1 rapidly disaggregated and grew as motile dispersed cells. Global transcriptome analysis comparing aerobic aggregated to O(2)-limited unaggregated cells identified genes encoding cell-to-cell and cell-to-surface adhesion factors whose transcription increased upon exposure to increased O(2) concentrations. The aerobic aggregated cells also revealed increased expression of putative anaerobic electron transfer and homologues of metal reduction genes, including mtrD (SO1782), mtrE (SO1781) and mtrF (SO1780). Our data indicate that mechanisms involved in autoaggregation of MR-1 are dependent on the function of pilD gene which encodes a putative prepilin peptidase. Mutants of S. oneidensis strain MR-1 deficient in PilD and associated pathways, including type IV and Msh pili biogenesis, displayed a moderate increase in sensitivity to H(2)O(2). Taken together, our evidence indicates that aggregate formation in S. oneidensis MR-1 may serve as an alternative or an addition to biochemical detoxification to reduce the oxidative stress associated with production of reactive oxygen species during aerobic metabolism while facilitating the development of hypoxic conditions within the aggregate interior.

Detection of integrins in human cataract lens epithelial cells and two mammalian lens epithelial cell lines

AIM

To compare the incidence of various integrin subunits in human cataract anterior lens epithelial cells (A-LEC) and in two mammalian LEC lines.

METHODS

Circular sections of anterior capsules with attached LEC were obtained during cataract surgery. Integrin subunits were immunolocalised in these anterior LEC and in a human and rabbit LEC line, using four monoclonal antibodies specific for subunits alpha2, alpha3, and alpha5, and beta subunit 2.

RESULTS

All of these subunits were found in at least a proportion A-LEC samples as follows: alpha2 71%, alpha3 92%, alpha5 62%, and beta2 24%. The human LEC line was immunoreactive for alpha2 and alpha3 only. The rabbit lens epithelial cell line was immunoreactive for alpha5 but there was no staining for alpha2, alpha3, or beta2.

CONCLUSION

The A-LEC and mammalian LEC lines showed a similarity in their pattern of integrin expression. As these integrins are receptors for extracellular matrix (ECM) components, they are likely to be associated with the attachment and migration of LECs that precedes capsular opacification. Therefore these cell lines may be useful in the elucidation of mechanisms involved the pathogenesis of capsule opacification.

Divergent roles of nitrergic and prostanoid pathways in chronic joint inflammation

BACKGROUND

Nitrergic and prostanoid pathways have both been implicated in inflammatory processes.

OBJECTIVE

To investigate their respective contributions in a rat model of chronic arthritis.

METHODS

Male Wistar rats (n = 4-6/group) received either an intra-articular injection of 2% carrageenan/4% kaolin (C/K) or intra- and periarticular injections of Freund's complete adjuvant (FCA; 10 mg/ml M tuberculosis). Joint diameter, urinary nitric oxide metabolites (NO(x)), and prostaglandin E(2) (PGE(2)) levels were measured as indices of the inflammatory process. A prophylactic and therapeutic (day 5) dose ranging study of an inducible nitric oxide synthase inhibitor, L-N-(1-iminoethyl)-lysine (L-NIL), and a cyclo-oxygenase-2 (COX-2) inhibitor, SC-236, was performed with the drugs given subcutaneously. Submaximal doses were identified and used for combination studies. Appropriate vehicle controls were included.

RESULTS

L-NIL and SC-236 dose dependently inhibited C/K induced acute joint swelling, the magnitude being greatest when they were given in combination. Both prophylactic and therapeutic administration of SC-236 in the FCA induced model of chronic arthritis produced a dose dependent reduction in all the measures assessed. However, although L-NIL demonstrated similar dose dependent inhibition of urinary NO(x) and PGE(2) levels, joint swelling was significantly exacerbated in this model. Co-administration of the inhibitors nullified the benefits of SC-236.

CONCLUSION

Whereas COX-2 derived prostaglandins are proinflammatory in both acute and chronic joint inflammation, NO seems to have divergent roles, being anti-inflammatory in chronic and proinflammatory in acute joint inflammation.

Combined inhibition of nitrergic and prostanoid pathways in J774 macrophages

OBJECTIVES

Nitric oxide and prostaglandins are both implicated in the pathogenesis of inflammatory conditions such as rheumatoid arthritis (RA). The hypothesis that simultaneous inhibition of nitric oxide synthase (NOS) and cyclooxygenase (COX) was more effective than inhibition of either enzyme alone was tested.

METHODS

J774 macrophages were pre-incubated with L-NAME and/or indomethacin, prior to activation with LPS (10 micrograms/ml).

RESULTS

LPS significantly increased NO2-; PGE2 and TNF-alpha levels by 24 h. Quantitative real-time PCR demonstrated a dose-dependent reduction in the expression of COX-2 in the presence of increasing doses of L-NAME. NO2- and PGE2 production were inhibited in a dose-dependent manner by either indomethacin or L-NAME. Combined administration of L-NAME and indomethacin produced a significantly greater inhibition of NO2- and PGE2 than either inhibitor alone.

CONCLUSION

The data supports the therapeutic potential of combined inhibition of the prostanoid and nitrergic systems as an anti-inflammatory treatment strategy and supports the progression of this work into models of arthritis.

Expression of constitutive but not inducible cyclooxygenase maintains articular perfusion in the rat knee

Experiments were performed in the normal rat knee joint to investigate the role of different isoforms of cyclooxygenase (COX) in the regulation of basal joint blood flow. Laser Doppler imaging (LDI) was used to measure articular perfusion, and reverse transcriptase polymerase chain reaction (RT-PCR) for the detection of COX-1 and COX-2 mRNA in joint tissue. Intravenous infusion of indomethacin (a non-selective inhibitor of COX; 0.34 nmol min(-1)) over 40 min produced a time dependent increase in articular vascular resistance (maximum 22.5 % at 40 min; P < 0.0001, one-way ANOVA) whereas vehicle over a similar time period had no effect in a control group. An equimolar concentration of a highly selective inhibitor for COX-2, SC-236, was administered in a further group of rats but this did not increase articular vascular resistance. While there was no significant difference between the response to vehicle and SC-236 (two-way ANOVA; P = 0.686, n = 6) the response to indomethacin was significantly greater than vehicle or SC-236 (two-way Anova; P < 0.0001, n = 6). COX-1, but not COX-2, was detectable by RT-PCR in all joint tissue samples examined (n = 4). The results of this study indicate that prostaglandins (PGs) play an important role in the maintenance of basal perfusion in the rat knee joint, with COX-1 being the physiologically relevant isoform. Experimental Physiology (2001) 86.2, 191-197.

Isolation and characterization of a chromium-reducing bacterium from a chromated copper arsenate-contaminated site

A Gram-negative bacterium (CRB5) was isolated from a chromium-contaminated site that was capable of reducing hexavalent chromium to an insoluble precipitate, thereby removing this toxic chromium species from solution. Analysis of the 16S rRNA from the isolate revealed that it was a pseudomonad with high similarity to Pseudomaonas synxantha. CRB5 was tolerant to high concentrations of chromate (500 mg l(-1)) and can reduce Cr(VI) under aerobic and anaerobic conditions. It also exhibited a broad range of reduction efficiencies under minimal nutrient conditions at temperatures between 4 degrees C and 37 degrees C and at pH levels from 4 to 9. As reduction increased, so did total cellular protein, indicating that cell growth was a requirement for reduction. Under low nutrient conditions with CRB5 or when using non-sterile contaminated groundwater from the site, reduction of Cr(VI) was followed by a increase in solution turbidity as a result of the formation of fine-grained Cr(III) precipitates, most probably chromium hydroxide mineral phases such as Cr(OH)3. Chromium adsorption and precipitation, as observed by transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM/EDS), revealed that the surfaces of the cells were uniformly stained with bound Cr(III) and amorphous precipitates (as determined by selected area electron diffraction; SAED). A mass balance of chromium in a batch bioreactor revealed that up to 30% of the total Cr was as settable precipitates or bound to cells.

Umbilical cord endothelial cells expressing large T antigen: comparison with primary cultures and effect of cell age

A number of human endothelial cell lines from umbilical cord cells (HUVECs) have been generated by transfection with SV40 large T and small t antigen sequences. Comparison of these lines with primary cultures of HUVECs has been carried out by monitoring the expression of a number of endothelial cell markers with specific regard to cell age. The secreted levels of the protein plasminogen activator inhibitor (PAI) was found to be significantly reduced in SV40-transfected cells when compared to untransfected controls. Tissue plasminogen activator (tPA) and urokinase (uPA) levels were unchanged. As cells entered crisis, there was a rapid and significant increase in the levels of tPA, uPA, and PAl and this was observed for all clones screened. The endothelial cell marker von Willebrand Factor (vWF) was found intracellularly and was also secreted into the medium. The levels were not altered between transfected and untransfected cells. Angiotensin converting enzyme (ACE) activity was maintained in cell lines at levels found in nonimmortalized HUVECs. Both isoforms (alpha and beta) of IL-1 (interleukin-1) increased as cells approached crisis, and the presence of these cytokines may be responsible for the increased levels of tPA, PAI, and uPA. With one exception, the ability of the transfected cells to produce prostacyclin (PGI2) was lost by all clones.

Activation of phospholipase A2 by the human endothelin receptor in Chinese hamster ovary cells involves Gi protein-mediated calcium influx

The signalling pathways used by the human endothelin A receptor to activate phospholipase A2 in Chinese hamster ovary cells were investigated. Pertussis toxin caused a partial but significant reduction in endothelin-1-induced arachidonic acid release although cAMP-dependent kinase inhibitors did not mimic its action. Extracellular calcium and its entry into the cell was essential for activation of phospholipase A2 as its removal from media or incubation with an intracellular calcium chelator-reduced activation. Nifedipine had no effect on endothelin-1-induced arachidonic acid release while divalent cations caused a significant reduction indicating the possible role of CRAC. Thapsigargin caused an increase in arachidonic acid release which was completely inhibited by pertussis toxin treatment. This further supports the involvement of CRAC in calcium influx and activation of phospholipase A2 by the human endothelin A receptor.

Cell-based assay for functional screening of compounds active at the human endothelin A receptor

We have developed a cell based assay for the functional screening of chemical libraries for novel chemical entities active at the human endothelin A (ET(A)) receptor. The assay is relatively inexpensive, suitable for dealing with large number of samples, and simple to operate; it generates results quickly. We achieved this by expressing the cDNA for the receptor in mammalian cell lines and determining whether coupling to pIA(A) occurred through the quantification of released radiolabeled arachidonic acid (AA) into the culture medium. Significant coupling was observed only when the receptor was expressed in the Chinese hamster ovary (CHO) line DG44. The assay could distinguish between ET(A)r agonists and antagonists, and the IC50 (the concentration that inhibits maximum response by 50%) values obtained were similar to those from other sources of receptor. The ET(B) receptor-selective agonist BQ3020 did not stimulate AA release, indicating that the assay can also discriminate between receptor subtypes.

Production of immortal human endothelial cell lines by strontium phosphate transfection and electroporation of SV40 sequences

Eleven human endothelial cell lines have been produced by introducing sequences from the DNA tumor virus SV40 into human umbilical vein endothelial cells either by strontium phosphate coprecipitation or electroporation. The resultant lines were confirmed as being endothelial in origin by their production of endothelial-specific von Willebrand factor. The growth characteristics of the different lines in normal and reduced levels of serum was determined, as was their cellular response to endothelial cell growth supplement in combination with heparin, basic fibroblast growth factor, transforming growth factor-alpha, and epidermal growth factor.

Improved techniques for immortalizing animal cells

The use of cultured mammalian cells for assessing potential new drugs and for basic biological research is increasing, since it facilitates the large-scale screening of candidate drugs and reduces the need for animal experimentation. In this review, the technology and tools required for producing cell lines of interest are described, and possible areas of research that will enhance the application of this rapidly expanding area of biotechnology are discussed.

Phenotypic modification of human glioma and non-small cell lung carcinoma by glucocorticoids and other agents

Glucocorticoids are cytostatic for human glioma grown at a high cell density in cell culture. The effect is not cytotoxic, appears to involve a modification of the cell surface, and has been detected with methyl prednisolone, dexamethasone, and beta-methasone. Glucocorticoids were also found to reduce malignancy-associated properties (plasminogen activator and endothelial mitogenesis) and enhance differentiation (glutamyl synthetase activity and high affinity GABA uptake). Cytostasis was also seen at high cell densities in non-small cell lung carcinoma with a concomitant reduction in plasminogen activator activity and endothelial mitogenesis. Preliminary data on surfactant production in A549 cells suggests that the repression of malignancy-associated properties is accompanied by an increase in cell differentiation. Treatment of the WIL adenocarcinoma gown as a xenograft in nude mice caused total cessation of growth and massive central necrosis in the tumor.