Blood pressure and cognitive function: a prospective analysis among adolescents in Seychelles

Objective: An inverse relationship between blood pressure and cognitive function has been found in adults, but limited data are available in adolescents and young adults. We prospectively examined the relation between blood pressure and cognitive function in adolescence. Methods: We examined the association between BP measured at the ages of 12-15 years in school surveys and cognitive endpoints measured in the Seychelles Child Development Study at ages 17 (n=407) and 19 (n=429) years respectively. We evaluated multiple domains of cognition based on subtests of the Cambridge Neurological Test Automated Battery (CANTAB), the Woodcock Johnson Test of Scholastic Achievement (WJTA), the Finger Tapping test (FT) and the Kaufman Brief Intelligence Test (K-BIT). We used age-, sex- and height-specific z-scores of systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP). Results: Six out of the 21 cognitive endpoints tested were associated with BP. However, none of these associations were found to hold for both males and females or for different subtests within the same neurodevelopmental domain or for both SBP and DBP. Most of these associations disappeared when analyses were adjusted for selected potential confounding factors such as socio-economic status, birth weight, gestational age, body mass index, alcohol consumption, blood glucose, and total n-3 and n-6 polyunsaturated fats. Conclusions: Our findings do not support a consistent association between BP and subsequent performance on tests assessing various cognitive domains in adolescents.

Respiratory effects of an exposure to grain dust among grain workers in the Vaud region (Switzerland)

Introduction: Bioaerosols such as grain dust (GD) elicit direct immunological reactions within the human respiratory system. Workplace-dependent exposure to GD may induce asthma, chronic bronchitis, and hypersensitivity pneumonitis. Aims: To assess the clinical impact of occupational exposure to GD and to determine quantitative biological markers of bioaerosol exposure in grain workers. Methods: This longitudinal study has been conducted from summer 2012 to summer 2013, comprising 6 groups of 30 active workers with different GD exposure patterns (4 groups of grain workers, 2 control groups). Two evaluations at high- and low-exposing seasons take place, during which an occupational and a medical history are questionnaire-assessed, lung function is evaluated by spirometry, airway inflammation is measured by exhaled nitric oxide (eNO) and specific blood IgG and IgE are titrated. Results: The preliminary results are those of 2 of the 4 exposed groups, (harvesters and mill workers), compared to the control groups, at first assessment (n=100). Mean age is 38.4 [years]; 98% are male. Exposed groups differ from controls (p<0.05) in daily contact with animals (57% vs. 40%) and active smoking (39% vs. 11%). Grain workers have more respiratory (50%), nasal (57%), ocular (45%) and dermatologic (36%) occupational symptoms than controls (6.4%, 19%, 16%, 6.4% respectively, p<0.05). Lower mean peak-expiratory-flow (PEF) values (96.1 ± 18.9 vs. 108.2 ± 17.4 [% of predicted], p<0.05) and eNO values (13.9 ± 9.6 vs. 20.5 ± 14.7 [ppm], p<0.05) are observed in the exposed groups. Conclusion: Preliminary results show a higher prevalence of clinical symptoms and a lower mean PEF value in the groups exposed to GD.

Clinical characteristics and outcome of patients admitted to a medico-surgical ICU requiring non invasive ventilation (NIV) for hypercapnic respiratory failure

Introduction: Because it decreases intubation rate and mortality, NIV has become first-line treatment in case of hypercapnic respiratory failure (HRF). Whether this approach is equally successful for all categories of HRF patients is however debated. We assessed if any clinical characteristics of HRF patients were associated with NIV intensity, success, and outcome, in order to identify prognostic factors. Methods: Retrospective analysis of the clinical database (clinical information system and MDSi) of patients consecutively admitted to our medico-surgical ICU, presenting with HRF (defined as PaCO2 >50 mm Hg), and receiving NIV between January 2009 and December 2010. Demographic data, medical diagnoses (including documented chronic lung disease), reason for ICU hospitalization, recent surgical interventions, SAPS II and McCabe scores were extracted from the database. Total duration of NIV and the need for tracheal intubation during the 5 days following the first hypercapnia documentation, as well as ICU and hospital mortality were recorded. Results are reported as median [IQR]. Comparisons with Chi2 or Kruskal-Wallis tests, p <0.05 (*). Results: 164 patients were included, 45 (27.4%) of whom were intubated after 10 [2-34] hours, after having received 7 [2-19] hours of NIV. NIV successful patients received 15 [5-22] hours of NIV for up to 5 days. Intubation was correlated with increased ICU (20% vs. 3%, p <0.001) and hospital (46.7% vs. 30.2, p >0.05) mortality. Conclusions: A majority of patients requiring NIV for hypercapnic respiratory failure in our ICU have no diagnosed chronic pulmonary disease. These patients tend to have increased ICUand hospital mortality. The majority of patients were non-surgical, a feature correlated with increased hospital mortality. Beside usual predictors of severity such as age and SAPS II, absence of diagnosed chronic pulmonary disease and non-operative state appear to be associated with increased mortality. Further studies should explore whether these patients are indeed more prone to an adverse outcome and which therapeutic strategies might contribute to alter this course.

In vitro assessment of the pulmonary toxicity and gastric availability of lead-rich particles from a lead recycling plant

Epidemiological studies in urban areas have linked increasing respiratory and cardiovascular pathologies with atmospheric particulate matter (PM) from anthropic activities. However, the biological fate of metal-rich PM industrial emissions in urban areas of developed countries remains understudied. Lead toxicity and bioaccessibility assessments were therefore performed on emissions from a lead recycling plant, using complementary chemical acellular tests and toxicological assays, as a function of PM size (PM(10-2.5), PM(2.5-1) and PM(1)) and origin (furnace, refining and channeled emissions). Process PM displayed differences in metal content, granulometry, and percentage of inhalable fraction as a function of their origin. Lead gastric bioaccessibility was relatively low (maximum 25%) versus previous studies; although, because of high total lead concentrations, significant metal quantities were solubilized in simulated gastrointestinal fluids. Regardless of origin, the finest PM(1) particles induced the most significant pro-inflammatory response in human bronchial epithelial cells. Moreover, this biological response correlated with pro-oxidant potential assay results, suggesting some biological predictive value for acellular tests. Pulmonary effects from lead-rich PM could be driven by thiol complexation with either lead ions or directly on the particulate surface. Finally, health concern of PM was discussed on the basis of pro-inflammatory effects, accellular test results, and PM size distribution.

Running versus strength-based warm-up : acute effects on isometric knee extension function

This study investigated the influence of two warm-up protocols on neural and contractile parameters of knee extensors. A series of neuromuscular tests including voluntary and electrically evoked contractions were performed before and after running- (R (WU); slow running, athletic drills, and sprints) and strength-based (S (WU); bilateral 90 degrees back squats, Olympic lifting movements and reactivity exercises) warm ups (duration ~40 min) in ten-trained subjects. The estimated overall mechanical work was comparable between protocols. Maximal voluntary contraction torque (+15.6%; P < 0.01 and +10.9%; P < 0.05) and muscle activation (+10.9 and +12.9%; P < 0.05) increased to the same extent after R (WU) and S (WU), respectively. Both protocols caused a significant shortening of time to contract (-12.8 and -11.8% after R (WU) and S (WU); P < 0.05), while the other twitch parameters did not change significantly. Running- and strength-based warm ups induce similar increase in knee extensors force-generating capacity by improving the muscle activation. Both protocols have similar effects on M-wave and isometric twitch characteristics.

Multicenter, Prospective Clinical Evaluation of Respiratory Samples from Subjects at Risk for Pneumocystis jirovecii Infection by Use of a Commercial Real-Time PCR Assay.

Pneumocystis jirovecii pneumonia (PCP) is a common opportunistic infection. Microscopic diagnosis, including diagnosis using the Merifluor-Pneumocystis direct fluorescent antigen (MP-DFA) test, has limitations. Real-time PCR may assist in diagnosis, but no commercially validated real-time PCR assay has been available to date. MycAssay Pneumocystis is a commercial assay that targets the P. jirovecii mitochondrial large subunit (analytical detection limit, ≤3.5 copies/μl of sample). A multicenter trial recruited 110 subjects: 54 with transplants (40 with lung transplants), 32 with nonmalignant conditions, 13 with leukemia, and 11 with solid tumors; 9 were HIV positive. A total of 110 respiratory samples (92% of which were bronchoalveolar lavage [BAL] specimens) were analyzed by PCR. Performance was characterized relative to investigator-determined clinical diagnosis of PCP (including local diagnostic tests), and PCR results were compared with MP-DFA test results for 83 subjects. Thirteen of 14 subjects with PCP and 9/96 without PCP (including 5 undergoing BAL surveillance after lung transplantation) had positive PCR results; sensitivity, specificity, and positive and negative predictive values (PPV and NPV, respectively) were 93%, 91%, 59%, and 99%, respectively. Fourteen of 83 subjects for whom PCR and MP-DFA test results were available had PCP; PCR sensitivity, specificity, PPV, and NPV were 93%, 90%, 65%, and 98%, respectively, and MP-DFA test sensitivity, specificity, PPV, and NPV were 93%, 100%, 100%, and 98%. Of the 9 PCR-positive subjects without PCP, 1 later developed PCP. The PCR diagnostic assay compares well with clinical diagnosis using nonmolecular methods. Additional positive results compared with the MP-DFA test may reflect low-level infection or colonization.

Structure-function characterization and optimization of a plant-derived antibacterial peptide.

Crushed seeds of the Moringa oleifera tree have been used traditionally as natural flocculants to clarify drinking water. We previously showed that one of the seed peptides mediates both the sedimentation of suspended particles such as bacterial cells and a direct bactericidal activity, raising the possibility that the two activities might be related. In this study, the conformational modeling of the peptide was coupled to a functional analysis of synthetic derivatives. This indicated that partly overlapping structural determinants mediate the sedimentation and antibacterial activities. Sedimentation requires a positively charged, glutamine-rich portion of the peptide that aggregates bacterial cells. The bactericidal activity was localized to a sequence prone to form a helix-loop-helix structural motif. Amino acid substitution showed that the bactericidal activity requires hydrophobic proline residues within the protruding loop. Vital dye staining indicated that treatment with peptides containing this motif results in bacterial membrane damage. Assembly of multiple copies of this structural motif into a branched peptide enhanced antibacterial activity, since low concentrations effectively kill bacteria such as Pseudomonas aeruginosa and Streptococcus pyogenes without displaying a toxic effect on human red blood cells. This study thus identifies a synthetic peptide with potent antibacterial activity against specific human pathogens. It also suggests partly distinct molecular mechanisms for each activity. Sedimentation may result from coupled flocculation and coagulation effects, while the bactericidal activity would require bacterial membrane destabilization by a hydrophobic loop.

Respiratory effects of an exposure to grain dust among grain workers in the Vaud region (Switzerland)

Introduction: Bioaerosols such as grain dust, via biologically active agents, elicit local inflammation and direct immunological reactions within the human respiratory system. Workplace-dependent exposure to grain dust (GD) may thus induce asthma, chronic bronchitis, and hypersensitivity pneumonitis. The aim of this study is to assess the clinical impact of occupational exposure to GD and to determine quantitative biological markers of bioaerosol exposure in grain workers. Methods: This longitudinal study has been conducted from summer 2012, to summer 2013, comprising 6 groups of 30 active workers with different GD exposure patterns (4 groups of grain workers, 2 control groups). After obtaining informed consent, two evaluations at high- and low-exposing seasons take place, during which an occupational history and a detailed medical history are questionnaire-assessed, lung function is evaluated by spirometry, airway inflammation is measured by exhaled nitric oxide (eNO), and specific blood IgG and IgE are titrated. The preliminary results presented hereafter are those of two of the four exposed groups, namely harvesters and mill workers, compared to the control groups, at first assessment (n=100). Results: Mean age is 38.4 [years]; 98% are male. Exposed groups differ from controls (p<0.05) in daily contact with animals (57% vs. 40%) and active smoking (39% vs. 11%). Grain workers have more respiratory (50%), nasal (57%), ocular (45%), dermatologic (36%) and systemic (20%) occupational symptoms than controls (6.4%, 19%, 16%, 6.4%, 1.6% respectively, p<0.05). Lower mean peak-expiratory-flow (PEF) values (96.1 ± 18.9 vs. 108.2 ± 17.4 [% of predicted], p<0.05) and eNO values (13.9 ± 9.6 vs. 20.5 ± 14.7 [ppm], p<0.05) are observed in the exposed groups. Conclusion: Preliminary results show a higher prevalence of clinical symptoms and a lower mean PEF value in the exposed groups. Detailed supplementary analyses are pending.

Long maximal incremental tests accurately assess aerobic fitness in class II and III obese men.

This study aimed to compare two different maximal incremental tests with different time durations [a maximal incremental ramp test with a short time duration (8-12 min) (STest) and a maximal incremental test with a longer time duration (20-25 min) (LTest)] to investigate whether an LTest accurately assesses aerobic fitness in class II and III obese men. Twenty obese men (BMI≥35 kg.m-2) without secondary pathologies (mean±SE; 36.7±1.9 yr; 41.8±0.7 kg*m-2) completed an STest (warm-up: 40 W; increment: 20 W*min-1) and an LTest [warm-up: 20% of the peak power output (PPO) reached during the STest; increment: 10% PPO every 5 min until 70% PPO was reached or until the respiratory exchange ratio reached 1.0, followed by 15 W.min-1 until exhaustion] on a cycle-ergometer to assess the peak oxygen uptake [Formula: see text] and peak heart rate (HRpeak) of each test. There were no significant differences in [Formula: see text] (STest: 3.1±0.1 L*min-1; LTest: 3.0±0.1 L*min-1) and HRpeak (STest: 174±4 bpm; LTest: 173±4 bpm) between the two tests. Bland-Altman plot analyses showed good agreement and Pearson product-moment and intra-class correlation coefficients showed a strong correlation between [Formula: see text] (r=0.81 for both; p≤0.001) and HRpeak (r=0.95 for both; p≤0.001) during both tests. [Formula: see text] and HRpeak assessments were not compromised by test duration in class II and III obese men. Therefore, we suggest that the LTest is a feasible test that accurately assesses aerobic fitness and may allow for the exercise intensity prescription and individualization that will lead to improved therapeutic approaches in treating obesity and severe obesity.

Upper and lower respiratory tract viral infections and acute graft rejection in lung transplant recipients.

Background: Lung transplant recipients are frequently exposed to respiratory viruses and are particularly at risk for severe complications. The aim of this study was to assess the association among the presence of a respiratory virus detected by molecular assays in bronchoalveolar lavage (BAL) fluid, respiratory symptoms, and acute rejection in adult lung transplant recipients. Methods: Upper (nasopharyngeal swab) and lower (BAL) respiratory tract specimens from 77 lung transplant recipients enrolled in a cohort study and undergoing bronchoscopy with BAL and transbronchial biopsies were screened using 17 different polymerase chain reaction-based assays. Result: BAL fluid and biopsy specimens from 343 bronchoscopic procedures performed in 77 patients were analyzed. We also compared paired nasopharyngeal and BAL fluid specimens collected in a subgroup of 283 cases. The overall viral positivity rate was 29.3% in the upper respiratory tract specimens and 17.2% in the BAL samples (). We observed a significant association P < .001 between the presence of respiratory symptoms and positive viral detection in the lower respiratory tract (Pp. 012). Conversely, acute rejection was not associated with the presence of viral infection (odds ratio, 0.41; 95% confidence interval, 0.20-0.88). The recovery of lung function was significantly slower when acute rejection and viral infection were both present. Conclusions: A temporal relationship exists between acute respiratory symptoms and positive viral nucleic acid detection in BAL fluid from lung transplant recipients. We provide evidence suggesting that respiratory viruses are not associated with acute graft rejection during the acute phase of infection.

Diagnostic des maladies infectieuses: place des "point of care tests" (POCT) [Use of POCT (point of care tests) in the diagnosis of infectious diseases]

Les POCT (point of care tests) ont un grand potentiel d'utilisation en médecine infectieuse ambulatoire grâce à leur rapidité d'exécution, leur impact sur l'administration d'antibiotiques et sur le diagnostic de certaines maladies transmissibles. Certains tests sont utilisés depuis plusieurs années (détection de Streptococcus pyogenes lors d'angine, anticorps anti-VIH, antigène urinaire de S. pneumoniae, antigène de Plasmodium falciparum). De nouvelles indications concernent les infections respiratoires, les diarrhées infantiles (rotavirus, E. coli entérohémorragique) et les infections sexuellement transmissibles. Des POCT, basés sur la détection d'acides nucléiques, viennent d'être introduits (streptocoque du groupe B chez la femme enceinte avant l'accouchement et la détection du portage de staphylocoque doré résistant à la méticilline). POCT have a great potential in ambulatory infectious diseases diagnosis, due to their impact on antibiotic administration and on communicable diseases prevention. Some are in use for long (S. pyogenes antigen, HIV antibodies) or short time (S. pneumoniae antigen, P. falciparum). The additional major indications will be community-acquired lower respiratory tract infections, infectious diarrhoea in children (rotavirus, enterotoxigenic E. coli), and hopefully sexually transmitted infections. Easy to use, these tests based on antigen-antibody reaction allow a rapid diagnosis in less than one hour; the new generation of POCT relying on nucleic acid detection are just introduced in practice (detection of GBS in pregnant women, carriage of MRSA), and will be extended to many pathogens

Influence of compliance to respiratory weaning consensus conference criteria on respiratory outcome within 48h after planned extubation

INTRODUCTION. A two-step assessment (readiness to wean (RW) followed by spontaneousbreathing trial (SBT)) of predefined criteria is recommended before planned extubation(PE)1.OBJECTIVES. We aimed to evaluate if compliance to all guideline criteria was associatedwith better respiratory outcome within 48 h after PE.METHODS. The data (extracted from our clinical information system) of 458 consecutivepatients who underwent PE after C48 h of invasive ventilation in our medico-surgical ICUwere analyzed. We evaluated compliance with guidelines [1] regarding respiratory rate, tidalvolume, PaO2, FiO2, PEEP, PaCO2, pH, heart rate, systolic arterial pressure and arrhythmiaduringRWand SBT assessment (RW and SBT within 2 h). A patient was classified as RW+ ifallRWcriteria were fulfilled andRW-if at least 1 criterion was violated. The same approachwas used to define SBT+ and SBT- patients. During the 48 h following PE, we assessed theoccurrence of post-PE respiratory failure (PRF) (defined as the presence of at least 1 consensuscriterion of respiratory failure [1]), reintubation (after NIV failure or because of immediateintubation criteria) and cumulative duration of post-PE ventilation (PPEV = Post-PE invasive+ non-invasive ventilation). ICU mortality was recorded. Comparisons for variousoutcomes were performed by Chi-square and t tests.RESULTS. All consensus criteria were fulfilled in 77.3% of the patients during RW and in68.1% of the patients during SBT.[Compliance to weaning criteria and outcome]N = 458 PRF (%) Reintubation (%) PPEV (min) ICU mortality (%)All patients 53.5 10.0 542 ± 664 6.1RW+ 50.0 9.3 490 ± 626 5.4RW- 65.4* 12.5 718 ± 757** 8.7SBT+ 52.6 8.0 498 ± 594 6.7SBT- 55.5 14.4*** 637 ± 788**** 4.8Occurrence of PRF only was not associated with increased ICU mortality: 4.2 versus 7.8%,p = 0.11. By contrast, ICU mortality was significantly increased in patients requiring reintubation:21.7 versus 4.4%. p\0.001; * p = 0.006 RW+ versus RW-; ** p = 0.003RW+ versus RW-; *** p = 0.035 SBT+ versus SBT-; **** p = 0.030 SBT+ versusSBTCONCLUSIONS.In our ICU, compliance to all criteria of the two-step published approach ofrespiratory weaning was not optimal but reintubation rate was comparable to published data.Compliance with consensus conference guidelines was associated with lower reintubation rateand shorter PPEV but not with ICU mortality. As mortality was increased by reintubation,more sensitive and specific criteria to predict the risk of reintubation are probably needed.REFERENCE. Boles JM, et al. Eur Respir J 2007;29:1033-56.

Gender differences in whole body fat oxidation kinetics during exercise

Introduction Discrepancies appear in studies comparing fat oxidation between men and women during exercise (1). Therefore, this study aimed to quantitatively describe and compare whole body fat oxidation kinetics between genders during exercise using a sinusoidal model (SIN) (2). Methods Twelve men and 11 women matched for age, body mass index (23.4±0.6 kg.m-2 and 21.5±0.8 kg.m-2, respectively) and aerobic fitness [maximal oxygen uptake ( ) (58.5±1.6 mL.kg FFM-1.min-1 and 55.3±2.0 mL.kg FFM-1.min-1, respectively) and power output ( ) per kilogram of fat-free mass (FFM)] performed submaximal incremental tests (Incr) with 5-min stages and 7.5% increment on a cycle ergometer. Respiratory and HR values were averaged over the last 2 minutes of each stage. All female study participants were eumenorrheic, reported regular menstrual cycles (28.6 ± 0.8 days) and were not taking oral contraceptives (OC) or other forms of exogenous ovarian hormones. Women were studied in the early follicular phase (FP) of their menstrual cycle (between days 3 and 8, where day 1 is the first day of menses). Fat oxidation rates were determined using indirect calorimetry and plotted as a function of exercise intensity. The SIN model (2), which includes three independent variables (dilatation, symmetry, translation), was used to mathematically describe fat oxidation kinetics and to determine the intensity (Fatmax) eliciting the maximal fat oxidation (MFO). Results During Incr, women exhibited greater fat oxidation rates from 35 to 85% , MFO (6.6 ± 0.9 vs. 4.5 ± 0.3 mgkg FFM-1min-1) and Fatmax (58.1 ± 1.9 vs. 50.0 ± 2.7% ) (P<0.05) than men. While men and women showed similar global shapes of fat oxidation kinetics in terms of dilatation and symmetry (P>0.05), the fat oxidation curve tended to be shifted towards higher exercise intensities in women (rightward translation, P=0.08). Conclusion These results showed that women, eumenorrheic, not taking OC and tested in FP, have a greater reliance on fat oxidation than men during submaximal exercise, but they also indicate that this greater fat oxidation is shifted towards higher exercise intensities in women compared with men. References 1. Blaak E. Gender differences in fat metabolism. Curr Opin Clin Nutr Metab Care 4: 499-502, 2001. 2. Cheneviere X, Malatesta D, Peters EM, and Borrani F. A mathematical model to describe fat oxidation kinetics during graded exercise. Med Sci Sports Exerc 41: 1615-1625, 2009.

Site-specific coupling between vascular wall thickness and function: an observational MRI study of vessel wall thickening and stiffening in hypertension.

OBJECTIVES: The objective of this study was to evaluate associations between aortic pulse wave velocity (PWV) and aortic and carotid vessel wall thickness (VWT) using cardiovascular magnetic resonance imaging (MRI) in patients with hypertension as compared with healthy adult volunteers. MATERIALS AND METHODS: Local medical ethics approval was obtained and the participants gave informed consent. Fifteen patients with hypertension (5 men and 10 women; mean [SD] age, 49 [14] years) and 15 age- and sex-matched healthy volunteers were prospectively included and compared. All participants underwent MRI examination for measuring aortic and carotid VWT and aortic PWV with well-validated MRI techniques at 1.5- and 3-T MRI systems: PWV was assessed from velocity-encoded MRI and VWT was assessed by using dual-inversion black-blood gradient-echo imaging techniques. Paired t tests were used for testing differences between the volunteers and the patients and Pearson correlation (r) and univariable and multivariable stepwise linear regression analyses were used to test associations between aortic and carotid arterial wall thickness and stiffness. RESULTS: Mean values for aortic PWV and aortic and carotid VWT (indexed for body surface area [BSA]) were all significantly higher in patients with hypertension as compared with the healthy volunteers (ie, aortic PWV, 7.0 ± 1.4 m/s vs 5.7 ± 1.3 m/s; aortic VWT/BSA, 0.12 ± 0.03 mL/m vs 0.10 ± 0.03 mL/m; carotid VWT/BSA, 0.04 ± 0.01 mL/m vs 0.03 ± 0.01 mL/m; all P < 0.01). Aortic PWV was highly correlated with aortic VWT/BSA (r = 0.76 and P = 0.002 in the patients vs r = 0.63 and P = 0.02 in the volunteers), and in the patients, aortic PWV was moderately correlated with carotid VWT/BSA (r = 0.50; P = 0.04). In the volunteers, correlation between aortic PWV and carotid VWT/BSA was not significant (r = 0.40; P = 0.13). In addition, aortic VWT/BSA was significantly correlated with carotid VWT/BSA, in both the patients (r = 0.60; P = 0.005) and volunteers (r = 0.57; P = 0.007). CONCLUSIONS: In the patients with hypertension and the healthy volunteers, the aortic PWV is associated more strongly with aortic wall thickness than with carotid wall thickness, reflecting site-specific coupling between vascular wall thickness and function.

Role of the epithelial sodium channel (ENaC) in the epidermal barrier function of the skin

Abstract In humans, the skin is the largest organ of the body, covering up to 2m2 and weighing up to 4kg in an average adult. Its function is to preserve the body from external insults and also to retain water inside. This barrier function termed epidermal permeability barrier (EPB) is localized in the functional part of the skin: the epidermis. For this, evolution has built a complex structure of cells and lipids sealing the surface, the stratum corneum. The formation of this structure is finely tuned since it is not only formed once at birth, but renewed all life long. This active process gives a high plasticity and reactivity to skin, but also leads to various pathologies. ENaC is a sodium channel extensively studied in organs like kidney and lung due to its importance in regulating sodium homeostasis and fluid volume. It is composed of three subunits α, ß and r which are forming sodium selective channel through the cell membrane. Its presence in the skin has been demonstrated, but little is known about its physiological role. Previous work has shown that αENaC knockout mice displayed an abnormal epidermis, suggesting a role in differentiation processes that might be implicated in the EPB. The principal aim of this thesis has been to study the consequences for EPB function in mice deficient for αENaC by molecular and physiological means and to investigate the underlying molecular mechanisms. Here, the barrier function of αENaC knockout pups is impaired. Apparently not immediately after birth (permeability test) but 24h later, when evident water loss differences appeared compared to wildtypes. Neither the structural proteins of the epithelium nor the tights junctions showed any obvious alterations. In contrary, stratum corneum lipid disorders are most likely responsible for the barrier defect, accompanied by an impairment of skin surface acidification. To analyze in details this EPB defect, several hypotheses have been proposed: reduced sensibility to calcium which is the key activator far epidermal formation, or modification of ENaC-mediated ion fluxes/currents inside the epidermis. The cellular localization of ENaC and the action in the skin of CAPl, a positive regulator of ENaC, have been also studied in details. In summary, this study clearly demonstrates that ENaC is a key player in the EPB maintenance, because αENaC knockout pups are not able to adapt to the new environment (ex utero) as efficiently as the wildtypes, most likely due to impaired of sodium handling inside the epidermis. Résumé Chez l'homme, la peau est le plus grand organe, couvrant presque 2m2 et pesant près de 4kg chez l'adulte. Sa fonction principale est de protéger l'organisme des agressions extérieures mais également de conserver l'eau à l'intérieur du corps. Cette fonction nommée barrière épithéliale est localisée dans la partie fonctionnelle de la peau : l'épiderme. A cette fin, l'évolution s'est dotée d'une structure complexe composée de cellules et de lipides recouvrant la surface, la couche cornée. Sa formation est finement régulée, car elle n'est pas seulement produite à la naissance mais constamment renouvelée tout au long de la vie, ce qui lui confère une grande plasticité mais ce qui est également la cause de nombreuses pathologies. ENaC est un canal sodique très étudié dans le rein et le poumon pour son importance dans la régulation de l'homéostasie sodique et la régulation du volume du milieu intérieur. Il est composé de 3 sous unités, α, ß et y qui forment un pore sélectif pour le sodium dans les membranes. Ce canal est présent dans la peau mais sa fonction n'y est pas connue. Des travaux précédents ont pu montrer que les souris dont le gène codant pour αENaC a été invalidé présentent un épiderme pathologique, suggérant un rôle dans la différentiation et pourrait même être impliqué dans la barrière épithéliale. Le but de cette thèse fut l'étude de la barrière dans ces souris knockouts avec des méthodes moléculaires et physiologiques et la caractérisation des mécanismes moléculaire impliqués. Dans ce travail, il a été montré que les souris mutantes présentaient un défaut de la barrière. Ce défaut n'est pas visible immédiatement à la naissance (test de perméabilité), mais 24h plus tard, lorsque les tests de perte d'eau transépithéliale montrent une différence évidente avec les animaux contrôles. Ni les protéines de structures ni les jonctions serrées de l'épiderme ne présentaient d'imperfections majeures. A l'inverse, les lipides de la couche cornée présentaient un problème de maturation (expliquant le phénotype de la barrière), certainement consécutif au défaut d'acidification à la surface de la peau que nous avons observé. D'autres mécanismes ont été explorées afin d'investiguer cette anomalie de la barrière, comme la réduction de sensibilité au calcium qui est le principal activateur de la formation de l'épiderme, ou la modification des flux d'ions entre les couches de l'épiderme. La localisation cellulaire d'ENaC, et l'action de son activateur CAPl ont également été étudiés en détails. En résumé, cette étude démontre clairement qu'ENaC est un acteur important dans la formation de la barrière épithéliale, car la peau des knockouts ne s'adapte pas aussi bien que celle des sauvages au nouvel environnement ex utero à cause de la fonction d'ENaC dans les mouvements de sodium au sein même de l'épiderme. Résumé tout public Chez l'homme, la peau est le plus grand organe, couvrant presque 2m2 et pesant près de 4kg chez l'adulte. Sa fonction principale est de protéger l'organisme des agressions extérieures mais également de conserver l'eau à l'intérieur du corps. Cette fonction nommée barrière épithéliale est localisée dans la partie fonctionnelle de la peau : l'épiderme. A cette fin, l'évolution s'est dotée d'une structure complexe composée de cellules et de lipides recouvrant la surface, la couche cornée. Sa formation est finement régulée, car elle n'est pas seulement produite à la naissance mais constamment renouvelée tout au long de la vie, ce qui lui confère une grande plasticité mais ce qui est également la cause de nombreuses maladies. ENaC est une protéine formant un canal qui permet le passage sélectif de l'ion sodium à travers la paroi des cellules. Il est très étudié dans le rein pour son importance dans la récupération du sel lors de la concentration de l'urine. Ce canal est présent dans la peau mais sa fonction n'y est pas connue. Des travaux précédents ont pu montrer que les souris où le gène codant pour αENaC a été invalidé présentent un épiderme pathologique, suggérant un rôle dans la peau et plus particulièrement la fonction de barrière de l'épiderme. Le but de cette thèse fut l'étude de la fonction de barrière dans ces souris mutantes, au niveau tissulaire et cellulaire. Dans ce travail, il a été montré que les souris mutantes présentaient une peau plus perméable que celle des animaux contrôles, grâce à une machine mesurant la perte d'eau à travers la peau. Ce défaut n'est visible que 24h après la naissance, mais nous avons pu montrer que les animaux mutants perdaient quasiment 2 fois plus d'eau que les contrôles. Au niveau moléculaire, nous avons pu montrer que ce défaut provenait d'un problème de maturation des lipides qui composent la barrière de la peau. Cette maturation est incomplète vraisemblablement à cause d'un défaut de mouvement des ions dans les couches les plus superficielles de l'épiderme, et cela à cause de l'absence du canal ENaC. En résumé, cette étude démontre clairement qu'ENaC est un acteur important dans la formation de la barrière épithéliale, car la peau des mutants ne s'adapte pas aussi bien que celle des sauvages au nouvel environnement ex utero à cause de la fonction d'ENaC dans les mouvements de sodium au sein même de l'épiderme.