CD14/LPS receptor exhibits lectin-like properties

We had previously shown that the specific binding of endotoxin (lipopolysaccharide, LPS) to human monocytes in the presence of serum was mediated by the polysaccharide moiety of the LPS molecule. CD14 has been identified as the main receptor for endotoxin on monocytes/macrophages. In the present report we demonstrate that the CD14 molecule exhibits lectin-like properties. Anti-CD14 monoclonal antibodies inhibited the binding of [3H]-radiolabeled Neisseria meningitidis LPS as efficiently as the homologous unlabeled LPS. Rough Escherichia coli LPS (Rc- and Re-types) could also inhibit the binding of [3H]-LPS to a similar extent, whereas lipid A had no or very weak inhibitory activity. This suggests a major contribution of the inner-core region within the LPS and particularly the Kdo sugars. The lectin-like nature of CD14 was assessed with polyanionic sugars as well as with uncharged polysaccharides. The relative efficiencies in competition were dextran sulfate > fucoidan > mannan > polygalacturonic acid = heparan sulfate ≥ heparin ≥ chondroitin sulfate. Candida albicans phospholipomannan was far more active in the competition experiment than the mannan, indicating that, besides the osidic residues, anionic charges and/or fatty acids may contribute to the interaction with the CD14 molecule. Binding of polysaccharide to CD14 was not sufficient to trigger TNFα and IL-6 production since phospholipomannan and dextran sulfate were unable to induce cytokine release. Taken together, these results demonstrate that the binding of [3H]-LPS to CD14 involves the contribution of sugars and suggest that the signals for cytokine production require additional interactions.

Ischaemic stroke subtypes and associated risk factors: a French population based study

BACKGROUND

There is little reliable population based information about the distribution of risk factors among the various ischaemic stroke subtypes, even though determining risk factor profiles is of major importance to develop targeted preventive strategies.

METHODS

The distribution of first ever ischaemic stroke subtypes was established in a prospective population based study conducted in Dijon, France (152,606 inhabitants). Cases were collected between January 2005 and December 2006, and were classified using TOAST classification. Vascular risk factors were recorded to determine a risk factor profile for each subtype.

RESULTS

332 patients with first ever ischaemic stroke (150 men and 182 women) were recorded. Adjusted incidence to world population was 54/100,000/year. The distribution of ischaemic stroke subtypes was as follows: 119 (35.8%) cases of large artery atherosclerosis, 89 (26.8%) small artery occlusions, 81 (24.4%) cardioembolisms and 43 (13%) other and undetermined causes. The most frequent vascular risk factor was hypertension, irrespective of the ischaemic stroke subtype, with a total prevalence of 62%. Using multivariate regression, a positive association between cardioembolism and age (OR 1.051; 95% CI 1.026 to 1.076; p<0.001) was demonstrated and between small artery occlusion and either high blood pressure (OR 1.86; 95% CI 1.06 to 3.27; p = 0.03) or hypercholesterolaemia (OR 2.23; 95% CI 1.33 to 3.76; p = 0.02).

CONCLUSION

This comprehensive prospective population based study has demonstrated that vascular risk factors exhibit a particular distribution according to the ischaemic stroke subtypes. These findings, as well as the great frequency of hypertension among stroke patients, have implications for prevention strategies, the design of clinical trials and the organisation of health care services.

HLA, NFKB1 and NFKBIA Gene Polymorphism Profile in Autoimmune Diabetes Mellitus Patients

Type 1 diabetes mellitus (T1DM) is one of the long-time studied autoimmune disorders. The triggering of the autoimmune process has been ascribed to various genes active in the regulation of the cytokine gene transcription including the Rel/NF-kappaB gene family. In our study the gene polymorphism of HLA class II, NFKB1 (nuclear factor of kappa light polypeptide gene enhancer in B-cells 1) and NFKBIA (inhibitor of nuclear factor kappa B) was tested. Patients were divided into the subgroups in relation to the disease type: T1DM in children, T1DM in adults, and Latent Autoimmune Diabetes in Adults (LADA). HLA-DRB1 (*)04 and HLA-DQB1 (*)0302 have been detected as risk factors for T1DM in adults and particularly in children (P<0.0001, OR=22.9 and 46.5 respectively). HLA-DRB1 (*)03 has been found as a single risk factor for LADA (P<0.0001, OR=4.9). We detected 15 alleles for the NFKB1 gene polymorphism (CA-repeats) in the Czech population. The alleles were ranging in size from 114-142 bp corresponding to 10-25 CA repeats. Frequency of the A7 allele of NFKB1 gene has been significantly increased in T1DM adults (P<0.01). There was no difference in A and a G allele frequency of NFKBIA gene between the control group and patients, but the association of the AA genotype of NFKBIA gene has been found for LADA (P<0.05). Summarizing our results we concluded that there is a high probability of association of gene polymorphism from Rel/NF-kappaB family with an autoimmune diabetes course. Due to the results obtained in the epidemiological study we have been looking also for the function significance of the genetic predisposition. No significant changes have been observed by real time PCR testing of HLA-DRB1 (*)04 gene and NFKB1 gene expression between T1DM diabetic group with different HLA, NFKB1, NFKBIA genetic background.

Effect of early decrease in the lesion size on late brain tissue loss, synaptophysin expression and functionality after a focal brain lesion in rats

The purpose of the present study is to determine the effects of early decrease in the lesion size on late brain tissue loss, synaptogenesis and functionality after a focal brain lesion in rats. The lesion was induced either to the cortex using the photothrombotic ischemic stroke or to the striatum using the malonate poisoning model. The cortical and striatal lesions amounted to 66-80 mm(3) at day 1 post-lesion and were reduced by 50% after the acute administration of dipyridyl (a liposoluble iron chelator) and aminoguanidine (an inhibitor of the inducible nitric oxide synthase), respectively. Loss of histologically intact tissue and synaptophysin expression as an indicator of synaptogenesis were examined at day 35 post-lesion. Both types of lesion resulted in synaptophysin upregulation in contralateral and ipsilateral cortical areas. On the contrary, brain tissue loss was greater after the striatal (-17%) than the cortical lesion (-5%). Synaptophysin expression and tissue loss were not different between drug- and vehicle-treated rats. Moreover, a set of standard neurological tests revealed a difference in deficit between the both types of lesion, yet only in the acute post-lesion stage. However, it did not distinguish between vehicle- and drug-treated rats whatever the lesion location. Our results indicate that late histological endpoints measurements are not recommended to probe the potential neuroprotective properties of a drug administered within the acute post-lesion stage. They also suggest that inhibition of cytotoxic mechanisms involved in lesion growth is of no clinical interest when it cannot lead to a long-term histological protection and/or increased synaptogenesis.

Flavonoid-inducible modifications to rhamnan O antigens are necessary for Rhizobium sp. strain NGR234-legume symbioses

Rhizobium sp. strain NGR234 produces a flavonoid-inducible rhamnose-rich lipopolysaccharide (LPS) that is important for the nodulation of legumes. Many of the genes encoding the rhamnan part of the molecule lie between 87 degrees and 110 degrees of pNGR234a, the symbiotic plasmid of NGR234. Computational methods suggest that 5 of the 12 open reading frames (ORFs) within this arc are involved in synthesis (and subsequent polymerization) of L-rhamnose. Two others probably play roles in the transport of carbohydrates. To evaluate the function of these ORFs, we mutated a number of them and tested the ability of the mutants to nodulate a variety of legumes. At the same time, changes in the production of surface polysaccharides (particularly the rhamnan O antigen) were examined. Deletion of rmlB to wbgA and mutation in fixF abolished rhamnan synthesis. Mutation of y4gM (a member of the ATP-binding cassette transporter family) did not abolish production of the rhamnose-rich LPS but, unexpectedly, the mutant displayed a symbiotic phenotype very similar to that of strains unable to produce the rhamnan O antigen (NGRDeltarmlB-wbgA and NGROmegafixF). At least two flavonoid-inducible regulatory pathways are involved in synthesis of the rhamnan O antigen. Mutation of either pathway reduces rhamnan production. Coordination of rhamnan synthesis with rhizobial release from infection threads is thus part of the symbiotic interaction.

Early enterocytic differentiation of HT-29 cells: biochemical changes and strength increases of adherens junctions

We have characterized the modulation of cell-cell adhesion and the structure of adherens junctions in the human colon adenocarcinoma HT-29 cell line that differentiates into enterocytes after glucose substitution for galactose in the medium. We demonstrate that differentiated cells (HT-29 Gal) rapidly established E-cadherin-mediated interactions in aggregation assays. This effect is not due to an increase in E-cadherin expression during this early stage of cell differentiation, but rather results from the maturation of preexisting adherens junctions. These junctions are characterized by the redistribution of E-cadherin to the basolateral membrane and its co-localization with the actin cytoskeleton. Subcellular fractionation studies indicate that actin-associated E-cadherins bind beta-catenin and p120ctn. Furthermore, the p120ctn/E-cadherin association is upregulated. These data reveal a cooperative interaction between p120ctn and E-cadherin that corresponds to mature functional adherens junctions able to initiate tight cell-cell adhesion required for epithelium architecture and further affirm the gatekeeper role of p120ctn.

Cytoprotective Efficacy and Mechanisms of the Liposoluble Iron Chelator 2,2′-Dipyridyl in the Rat Photothrombotic Ischemic Stroke Model

We examined the efficacy of the liposoluble iron chelator 2,2'-dipyridyl (DP) in reducing histological damage in rats submitted to cerebral ischemia and the mechanisms involved in the potential cytoprotection. For this purpose, DP (20 mg/kg, i.p.) was administered 15 min before and 1 h after induction of cortical photothrombotic vascular occlusion in rat. Histological studies were performed to assess infarct volume (at days 1 and 3 postischemia) and astromicroglial activation (at day 3 postischemia). Damage to endothelial and neuronal cells was evaluated at day 1 postischemia by quantitative measurements of Evans Blue extravasation and N-acetylaspartate levels, respectively. Cerebral blood flow was recorded in the ischemic core by laser-Doppler flowmetry within the 15 min to 2 h period after photothrombosis. At 4-h postischemia, radical oxygen species (ROS) production was evaluated by measuring brain glutathione concentrations. The cortical expression of the proteins heme oxygenase-1 (HO-1) and hypoxia-inducible factor-1alpha (HIF-1alpha) was analyzed by Western blotting at day 1 postischemia. Infarct volume and ischemic damage to endothelial and neuronal cells were significantly reduced by DP treatment. This cytoprotection was associated with a reduction in ROS production, perfusion deficits, and astrocytic activation. DP treatment also resulted in significant changes in HO-1 (+100%) and HIF-1alpha (-50%) protein expression at the level of the ischemic core. These results report the efficacy of the liposoluble iron chelator DP in reducing histological damage induced by permanent focal ischemia.

Differential MnSOD and HO-1 expression in cerebral endothelial cells in response to sublethal oxidative stress

The two inducible enzymes, manganese superoxide dismutase (MnSOD) and heme-oxygenase-1 (HO-1) may participate in the cellular defense of brain endothelium against oxidative stress. The time-dependent expression of MnSOD and HO-1 mRNAs and proteins was investigated in vitro in rat cerebral endothelial cells (CEC) subjected to sublethal mild or moderate hydroxyl radical-induced oxidative stress. Mild oxidative stress induced increases in both MnSOD and HO-1 mRNA and protein expression. Moderate oxidative stress resulted in a significant reduction in HO-1 mRNA and protein expression, whereas MnSOD expression pattern was similar to that observed after mild oxidative stress. A profound protein loss of both MnSOD and HO-1 was detected 24 h after exposure of CEC to a moderate oxidative stress. The data indicate that cerebral endothelial cells respond by increasing the expression of antioxidant defense enzymes in a manner dependent on the oxidative stress intensity.

Effect of diets with different magnesium content in ischemic stroke rats

Rats fed with low (0.015%), normal (0.08%) or high (0.32%) magnesium (Mg) diet for 5-6 weeks were subjected to photothrombosis-induced infarction. As compared to normal diet, Mg deprivation increased by 45% infarct volume at 24 h after photothrombosis but did not modify the lesion at 4 h after photothrombosis. Mg supplementation did not protect from infarction whatever the time point examined. No differences in pre-ischemic systolic blood pressure and glycemia as well as in post-ischemic kaliemia, calcemia and plasma antioxidant activity were observed between groups. However, plasma total Mg level correlated with plasma antioxidant activity at 4 h after photothrombosis. These results demonstrate that brains from Mg deficient rats are more susceptible to permanent focal ischemia than rats fed with normal or high Mg diet.

Single-breath transfer factor in young healthy adults: 21% or 17.5% inspired oxygen?

For the measurement of the single-breath transfer factor of the lung for carbon monoxide (TL,CO,sb), the American Thoracic Society (ATS) recommends using a test gas with a 21% inspired fraction of oxygen (FI,O2) whereas the European Respiratory Society (ERS) expressly recommends 17-18% FI,O2. The ERS committee argues that with a higher concentration (e.g. 21%) the alveolar fraction of oxygen (and accordingly TL,CO,sb) "varies with the volume of the test gas which is inspired", that is, presumably, in proportion to the volume of the test gas that is diluted in the alveolar volume. The current study measured TL,CO,sb and the transfer coefficient (KCO,sb) in duplicate in 67 healthy adults (age 17-23 yrs) using, in random order, an inspired gas containing either 17.5% or 21% oxygen. A correction was applied for carboxyhaemoglobin, in line with ATS recommendations. As expected, TL,CO,sb was higher with 17.5% FI,O2 test gas compared with 21% FI,O2 test gas (11.98 +/- 2.68 versus 11.38 +/- 2.56 mmol x min(-1) x kPa(-1), respectively) as well as KCO,sb (1.98 +/- 0.24 versus 1.90 +/- 0.23 mmol x min(-1) x kPa(-1), respectively). The ratio of TL,CO,sb measurements was strictly independent of the residual volume/total lung capacity ratio measured with plethysmography. Hence, the rationale used by the European Respiratory Society, which utilises a 17-18% inspired fraction of oxygen test gas for single-breath transfer of the lung for carbon monoxide measurements, would appear to be unwarranted in young healthy adults.

Effects of iNOS-related NO on hearts exposed to liposoluble iron

Inducible nitric oxide synthase (iNOS) protects heart against ischemia/reperfusion injury. However, it is unknown whether the beneficial effects of iNOS are mediated by the interaction of NO with radical oxygen species (ROS). To address this issue, we examined the effects of liposoluble iron-induced ROS generation in isolated perfused hearts from rats treated with lipopolysaccharide (LPS). LPS administration (10 mg/kg, i.p., 6 h before heart removal) induced iNOS expression and increased NO production as indicated by a 3-fold elevation of nitrite level in coronary effluents relative to control hearts. An enhanced expression of hemeoxygenase 1 protein was also observed in septic hearts compared to control. Iron-induced perfusion and contractile deficits were ameliorated by LPS with more important coronary than myocardial benefits. In iron-loaded hearts, oxidative stress as measured by the 2,3 dihydroxybenzoic acid/salicylic acid concentration ratio in cardiac tissue was 23% lower in septic than in control heart although the difference did not reach significance. In addition, the presence of the NO synthase inhibitor N-nitro-L-arginine in the perfusion medium totally blocked NO production but did not reverse the protective effects of LPS. The results indicate that LPS protects from iron-induced cardiac dysfunction by mechanisms independent on ex vivo NO production and suggest that NO acts as a trigger rather than a direct mediator of the cardioprotective effects of LPS in heart exposed to iron.

Effects of a direct injection of liposoluble iron into rat striatum. Importance of the rate of iron delivery to cells

For a better understanding of the role of iron imbalance in neuropathology, a liposoluble iron complex (ferric hydroxyquinoline, FHQ) was injected into striatum of rats. The effects of two modalities of iron injections on brain damage, hydroxyl radical (*OH) production (assessed by the salicylate method coupled to microdialysis) and tissue reactive iron level (evaluated ex vivo by the propensity of the injected structure for lipid peroxidation) were examined. Rapid injection of FHQ (10 nmoles of 5 mM FHQ pH 3 solution over 1-min period) but not that of corresponding vehicle led to extensive damage associated with increased tissue free iron level in the injected region. Conversely, neither lesion nor free iron accumulation was observed after slow FHQ injection (10 nmoles of a 100 microM FHQ pH 7 solution over 1-h period) as compared to corresponding vehicle injection. Production of *OH was induced by slow FHQ injection but not by rapid FHQ injection, probably as a result of in vivo abolition of iron-induced *OH formation by acid pH. Indeed, rapid injection of FAC pH 7 (ferric ammonium citrate, 5 mM in saline) was associated with *OH formation whereas rapid injection of FAC pH 3 did not. Our results identify the rate of iron delivery to cells as an important determinant of iron toxicity and do not support a major role for extracellular *OH in damage associated with intracerebral iron injection.

Chemical preconditioning with 3-nitropropionic acid: lack of induction of neuronal tolerance in gerbil hippocampus subjected to transient forebrain ischemia

Chemical preconditioning using the mitochondrial toxin, 3-nitropropionic acid (3-NP) has been reported to induce neuroprotection against subsequent global ischemia. To investigate the underlying mechanisms, Mongolian gerbils were pretreated with either vehicle or 3-NP at the dose of 3 or 10 mg/kg, intraperitoneal, 3 days prior to a 5-min bilateral carotid artery occlusion followed by either 48 h or 7 days of blood recirculation. Neuronal damage was assessed by a cresyl violet/fuchsin acid staining. Induction of heat shock protein 72 (HSP72) and manganese superoxide dismutase (MnSOD) expression was evaluated by Western blotting. Astroglial and microglial activation was detected by immunohistochemistry (glial fibrillary acid protein) and by histochemistry (isolectin B4 staining), respectively. Present data show that the hippocampal neuronal damage induced by ischemia were of similar extent between the vehicle- and 3-NP-treated gerbils, whatever the dose tested, indicating that 3-NP did not induce tolerance to transient forebrain ischemia under our experimental conditions. The lack of difference in the post-ischemic level of HSP72 and MnSOD protein expression and in the intensity of astroglial and microglial activation represents further indirect indications of the absence of 3-NP preconditioning effect. In conclusion, although chemical preconditioning with 3-NP is a well-established phenomenon at least in vitro and in models of focal ischemia, the relevance of 3-NP as a preconditioning molecule towards global brain ischemia remains an open question.