Concentrations of nucleotides, nucleosides, purine bases, oxypurines, uric acid, and neuron-specific enolase in the cerebrospinal fluid of children with sepsis

Epidemiological and Microbiome Characterization of Black Tooth Stain in Preschool Children

OBJECTIVE

To assess the epidemiologic attributes and microbial variations associated with extrinsic black tooth stain (BTS) among Chinese preschool children.

METHODS

This cross-sectional study included 250 preschool children (3-4 years) from three kindergartens in Shanghai, China. Following clinical examination, and using a case-control design, saliva and dental plaque specimens were collected from caries-free participants with (n = 21, BTS group) and without (n = 48, control group) BTS. The chi-square test and logistic regression model were used to evaluate factors associated with BTS. 16S rRNA sequencing were used to characterize the associated microbial communities.

RESULTS

BTS was detected in 12.4% of participants, with a mean of 13.7 black-stained teeth. Participants with BTS had a lower caries burden and better oral hygiene (P = 0.003). Children with less frequent intake of marmalade or honey (P = 0.033) and regular application of fluoride (P = 0.007) had a lower likelihood of having BTS. Microbiota analysis revealed 14 phyla, 35 classes, 63 orders, 113 families, 221 genera, 452 species, and 1,771 operational taxonomic units (OTUs). In terms of microbial diversity, no significant differences were observed in the saliva of the two groups (P > 0.05). Dental plaque from the BTS group exhibited higher OTU richness but lower evenness than that from the control group (Chao P = 0.006, Shannon P = 0.007, respectively) and showed a significant difference in β diversity (P = 0.002). The microbiome in the two groups was characterized by various microbial biomarkers, such as Pseudomonas fluorescens, Leptotrichia sp._HMT_212, Actinomyces sp._HMT_169, and Aggregatibacter sp._HMT_898 in plaques from the BTS group. Functional analysis of the microbial species suggested the existence of a hyperactive metabolic state on teeth surfaces with BTS plaques and revealed that ferric iron, the iron complex transport system, and the iron (III) transport system were more abundant in BTS plaque samples.

CONCLUSIONS

This study provides insights into the epidemiologic and microbial features of BTS in preschool children. The microbiome in BTS is characterized by various microbial biomarkers, which can serve as indicators for BTS diagnosis and prognosis.

Magnetic resonance spectroscopy for assessment of brain injury in the rat model of sepsis

The diagnostic value of magnetic resonance spectroscopy (MRS), T2-weighted imaging (T2WI) and serum markers of brain injury in a rat model of sepsis were investigated. Rats were randomly divided into the control group and 6, 12 and 24 h after lipopolysaccharide-injection groups. Brain morphology and metabolism were assessed with T2WI magnetic resonance imaging (MRI) and MRS. Serum and brain tissue samples were then collected to examine the concentrations of neuron-specific enolase (NSE) and S100-β protein. Brain T2WI showed no differences between the groups. N-acetylaspartate/choline (NAA/Cr) ratio measured by MRS showed different degrees of decrease in the sepsis groups, and serum NSE and S100-β concentrations were increased compared with the control group. Apoptosis rates were measured in the right hippocampal area, and there were statistically significant differences between the indicated groups and the control group (p<0.05). The correlation between apoptosis rate and NAA/Cr ratio was closer than that between apoptosis rate and NSE or S100-β (−0.925 vs. 0.434 vs. 0.517, respectively). In conclusion, MRS is a sensitive, non-invasive method to investigate complications of brain injury in septic rats, which may be utilized for the early diagnosis of brain injury caused by sepsis.

Biomarkers in septic encephalopathy: a systematic review of clinical studies

Objective

The aim of this study was to systematically review the importance of neuron-specific enolase and S100 beta for diagnosing and monitoring septic encephalopathy.

Methods

A PubMed database search was performed to identify studies that evaluated S100 beta and neuron-specific enolase serum levels in patients with sepsis and that were published between January 2000 and April 2012. Only human studies that employed an additional method of neurological assessment were selected.

Results

Nine studies were identified, seven of which associated high concentrations of S100 beta and neuron-specific enolase with the development of septic encephalopathy. Four studies also associated these concentrations with increased mortality. However, two studies did not find such an association when they evaluated S100 beta levels, and one of these studies did not observe a correlation between neuron-specific enolase and septic encephalopathy.

Conclusion

S100 beta and neuron-specific enolase are promising biomarkers for diagnosing and monitoring patients with septic encephalopathy, but more research is necessary.

Adenosine is required for sustained inflammasome activation via the A₂A receptor and the HIF-1α pathway

Inflammasome pathways are important in chronic diseases, but it is not known how the signalling is sustained after initiation. Inflammasome activation is dependent on stimuli such as LPS and ATP that provide two distinct signals resulting in rapid production of IL-1β, with lack of response to repeat stimulation. Here we report that adenosine is a key regulator of inflammasome activity, increasing the duration of the inflammatory response via the A_2A receptor. Adenosine does not replace signals provided by stimuli such as LPS or ATP, but sustains inflammasome activity via a cAMP/PKA/CREB/HIF-1α pathway. In the setting of lack of IL-1β responses after previous exposure to LPS, adenosine can supersede this tolerogenic state and drive IL-1β production. These data reveal that inflammasome activity is sustained, after initial activation, by A_2A receptor-mediated signalling.

Adenosine inhibits chemotaxis and induces hepatocyte-specific genes in bone marrow mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (MSCs) have therapeutic potential in liver injury, but the signals responsible for MSC localization to sites of injury and initiation of differentiation are not known. Adenosine concentration is increased at sites of cellular injury and inflammation, and adenosine is known to signal a variety of cellular changes. We hypothesized that local elevations in the concentration of adenosine at sites of tissue injury regulate MSC homing and differentiation. Here we demonstrate that adenosine does not induce MSC chemotaxis but dramatically inhibits MSC chemotaxis in response to the chemoattractant hepatocyte growth factor (HGF). Inhibition of HGF-induced chemotaxis by adenosine requires the A2a receptor and is mediated via up-regulation of the cyclic adenosine monophosphate (AMP)/protein kinase A pathway. This results in inhibition of cytosolic calcium signaling and down-regulation of HGF-induced Rac1. Because of the important role of Rac1 in the formation of actin stress fibers, we examined the effect of adenosine on stress fiber formation and found that adenosine inhibits HGF-induced stress fiber formation. In addition, we found that adenosine induces the expression of some key endodermal and hepatocyte-specific genes in mouse and human MSCs in vitro.

CONCLUSION

We propose that the inhibition of MSC chemotaxis at sites of high adenosine concentration results in localization of MSCs to areas of cellular injury and death in the liver. We speculate that adenosine might initiate the process of differentiation of MSCs into hepatocyte-like cells.

Adenosine A(2A) receptor mediates microglial process retraction

Cell motility drives many biological processes, including immune responses and embryonic development. In the brain, microglia are immune cells that survey and scavenge brain tissue using elaborate and motile cell processes. The motility of these processes is guided by the local release of chemoattractants. However, most microglial processes retract during prolonged brain injury or disease. This hallmark of brain inflammation remains unexplained. We identified a molecular pathway in mouse and human microglia that converted ATP-driven process extension into process retraction during inflammation. This chemotactic reversal was driven by upregulation of the A(2A) adenosine receptor coincident with P2Y(12) downregulation. Thus, A(2A) receptor stimulation by adenosine, a breakdown product of extracellular ATP, caused activated microglia to assume their characteristic amoeboid morphology during brain inflammation. Our results indicate that purine nucleotides provide an opportunity for context-dependent shifts in receptor signaling. Thus, we reveal an unexpected chemotactic switch that generates a hallmark feature of CNS inflammation.

Endotoxemia alters nucleotide hydrolysis in platelets of rats

Platelets play a critical role in homeostasis and blood clotting at sites of vascular injury, and also in various ways in innate immunity and inflammation. Platelets are one of the first cells to accumulate at an injured site, and local release of their secretome at some point initiate an inflammatory cascade that attracts leukocytes, activates target cells, stimulates vessel growth and repair. The level of exogenous ATP in the body may be increased in various inflammatory and shock conditions, primarily as a consequence of nucleotide release from platelets, endothelium and blood vessel cells. An increase of ATP release has been described during inflammation and this compound presents proinflammatory properties. ADP is a nucleotide known to induce changes in platelets shape and aggregation, to promote the exposure of fibrinogen-binding sites and to inhibit the stimulation of adenylate cyclase. Adenosine, the final product of the nucleotide hydrolysis, is a vasodilator and an inhibitor of platelet aggregation. There is a group of ecto-enzymes responsible for extracellular nucleotide hydrolysis named ectonucleotidases, which includes the NTPDase (nucleoside triphosphate diphosphohydrolase) family, the NPP (nucleoside pyrophosphatase/phosphodiesterase) family and an ecto-5'-nucleotidase. Therefore, we have aimed to investigate the effect of lipopolysaccharide endotoxin from Escherichia coli on ectonucleotidases in platelets from adult rats in order to better understand the role of extracellular adenine nucleotides and nucleosides in the maintenance of blood homeostasis in inflammatory processes. LPS administered in vitro was not able to alter the ATP, ADP, AMP and rho-Nph-5'-TMP hydrolysis of platelets from untreated rats in all concentrations tested (25-100 microg/ml). There was a significant decrease in ATP, ADP, AMP and rho-Nph-5'-TMP hydrolysis in rat platelets after 48 hours of LPS exposure (2 mg/Kg, i.p.). ATP and ADP hydrolysis has been reduced about 28% whereas it has been observed a significant 30% and 26% decrease on AMP and rho-Nph-5'-TMP hydrolysis. Platelet aggregation and platelet number have shown a significant decrease in LPS-treated rats (40% and 55%, respectively) when compared to control group. These results suggest that changes observed in platelet count and, consequently, in nucleotidase activities from circulatory system could alter extracellular nucleotide and nucleoside levels, which might modulate the inflammatory process.

Activities of xanthine oxidase and superoxide dismutase enzymes in rat intestinal tissues in sepsis

BACKGROUND

The aim of this study was to elucidate a possible source of oxidant stress in experimental sepsis.

METHODS

For this aim, 32 Sprague-Dawley type rats were used in the study. After all the animals underwent laparotomy, nonlethal cecum ligation and puncture (CLP) technique was used to create an experimental sepsis model in two groups (CLP-6 and CLP-48 groups). Rats in the other groups (Sham operated) were used as controls. Animals in the control-6 and CLP-6 groups were killed 6 hours after the beginning of the study whereas the other animals were killed 48 hours after the beginning. Part of the terminal ileum of each animal was removed to be used in the measurements of xanthine oxidase and superoxide dismutase enzyme activities.

RESULTS

Xanthine oxidase activity in the CLP-48 group was found to increase significantly as compared with that of the control-48 group, but superoxide dismutase activity did not change. No significant changes, however, were observed between analysis parameters in the terminal ileum tissues when obtained 6 hours after the beginning of sepsis.

CONCLUSION

Our results suggest that increased xanthine oxidase activity is one of the leading factors for the oxidant stress in the late phase of sepsis.

Lipopolysaccharide alters nucleotidase activities from lymphocytes and serum of rats

ATP exerts a proinflammatory role and induces cytokine release by acting at P2X(7) receptors. The product of ATP hydrolysis is the nucleoside adenosine, an important immunomodulator. The main source of extracellular adenosine is the hydrolysis of extracellular ATP by a group of ecto-enzymes: ENTPDase family, NPP family and ecto-5'-nucleotidase. Considering the role of ATP and adenosine in inflammatory processes, we investigated the effect of lipopolysaccharide on ectonucleotidases activities and expression in lymphocytes from mesenteric lymph nodes and serum of rats, in order to better understand the involvement of extracellular nucleotide hydrolysis in an endotoxemia model. We observed significant changes on nucleotidase activities from lymphocytes and serum of rats after in vitro and in vivo exposure to LPS. In vitro results have shown an increase on nucleotide hydrolysis in lymphocytes and a decrease on the enzyme activity of NPP in blood serum. In vivo, we observed an increase on nucleotide hydrolysis in lymphocytes and a decrease in the hydrolysis of all nucleotides tested in blood serum. After 24 and 48 h of LPS treatment, there was a reduction in NTPDase1, 2, 3 and ecto-5'-nucleotidase transcripts. These results suggest that there is a time-dependent enhancement of extracellular nucleotides metabolism in lymphocytes and blood serum after the induction of an endotoxemic model. The changes observed suggest that these enzymes can act in the regulation of extracellular nucleosides and nucleotides in a model able to trigger inflammatory process.

Adenosine inhibits cytosolic calcium signals and chemotaxis in hepatic stellate cells

Adenosine is produced during cellular hypoxia and apoptosis, resulting in elevated tissue levels at sites of injury. Adenosine is also known to regulate a number of cellular responses to injury, but its role in hepatic stellate cell (HSC) biology and liver fibrosis is poorly understood. We tested the effect of adenosine on the cytosolic Ca2+ concentration, chemotaxis, and upregulation of activation markers in HSCs. We showed that adenosine did not induce an increase in the cytosolic Ca2+ concentration in LX-2 cells and, in addition, inhibited increases in the cytosolic Ca2+ concentration in response to ATP and PDGF. Using a Transwell system, we showed that adenosine strongly inhibited PDGF-induced HSC chemotaxis in a dose-dependent manner. This inhibition was mediated via the A(2a) receptor, was reversible, was reproduced by forskolin, and was blocked by the adenylate cyclase inhibitor 2,5-dideoxyadenosine. Adenosine also upregulated the production of TGF-beta and collagen I mRNA. In conclusion, adenosine reversibly inhibits Ca2+ fluxes and chemotaxis of HSCs and upregulates TGF-beta and collagen I mRNA. We propose that adenosine provides 1) a "stop" signal to HSCs when they reach sites of tissue injury with high adenosine concentrations and 2) stimulates transdifferentiation of HSCs by upregulating collagen and TGF-beta production.

Can cerebrospinal fluid uric acid levels differentiate intraventricular hemorrhage from traumatic tap?

OBJECTIVE

To measure blood and cerebrospinal fluid (CSF) uric acid (UA) levels of neonates with intraventricular hemorrhage (IVH), and to examine whether or not UA can be used to differentiate traumatic tap from IVH.

MATERIAL AND METHODS

The control group (n = 19, group I) consisted of neonates presenting with signs requiring analysis of CSF but whose CSF indices proved to be normal. Traumatic taps (n = 15, group II) were mimicked by adding 2 drops of homologous blood to normal CSF samples. The IVH group (n = 21, group III) consisted of neonates who had been diagnosed by cranial ultrasonography or computed tomography scans. Data are presented as median (range).

RESULTS

There was no significant difference between groups with respect to serum UA levels. While no significant difference was observed between CSF UA levels of the control [0.6 (0.1-1.8) mg/dl] and traumatic tap group [0.5 (0.3-1.1) mg/dl], the IVH group [1.6 (0.7-6.9) mg/dl] was found to have significantly higher CSF UA levels than groups I and II. Furthermore, although there were significant correlations between serum and CSF UA levels in the control and traumatic tap groups, no correlation was observed in the IVH group.

CONCLUSION

CSF UA levels are increased in neonates with IVH and they may be used to differentiate a real hemorrhage from a traumatic tap.

Differential requirement for A2a and A3 adenosine receptors for the protective effect of inosine in vivo

Inosine is an endogenous nucleoside with immunosuppressive properties that is known to inhibit the accumulation of proinflammatory cytokines and protect mice from endotoxin-induced inflammation and lung tissue damage. There are no known receptors specific for inosine, but A3 adenosine receptors (A3Rs) have been shown to bind inosine, resulting in mast cell degranulation and increased vascular permeability. The present study specifically addresses the requirement for A2aR and/or A3R for the protective effect of inosine in 2 experimental in vivo models of inflammatory disease. The data show that A3R is essential for protection against ConA-induced fulminant hepatitis since only A3R-expressing mice were protected by inosine whereas wild-type and A2aR-deficient mice exhibited severe liver damage even after administration of inosine. In addition, we show in a model of LPS-induced endotoxemia that inosine protected both A2aR-/- and A3R-/- mice from inflammation, but not A2aA3R double-null mice, indicating that in this model both A2aR and A3R were used by inosine. Thus, we demonstrate that A2a and A3 adenosine receptors are differentially utilized by inosine for the down-regulation of tissue damage under different inflammatory conditions in vivo.

The critical role of adenosine A2A receptors in downregulation of inflammation and immunity in the pathogenesis of infectious diseases

Adenosine can be described as a retaliatory metabolite, the production and release of which is usually enhanced under adverse environmental conditions. Binding via specific receptors, adenosine activates endogenous protective mechanisms aiming at the restoration of tissue homeostasis. While adenosinergic downregulation of tissue damage is beneficial in acute inflammation, chronic suppression of the immune system by adenosine may account for immunoparalysis in long-term septic patients.