Role of Staphylococcus aureus coagulase and clumping factor in pathogenesis of experimental endocarditis.

The pathogenic role of staphylococcal coagulase and clumping factor was investigated in the rat model of endocarditis. The coagulase-producing and clumping factor-producing parent strain Staphylococcus aureus Newman and a series of mutants defective in either coagulase, clumping factor, or both were tested for their ability (i) to attach in vitro to either rat fibrinogen or platelet-fibrin clots and (ii) to produce endocarditis in rats with catheter-induced aortic vegetations. In vitro, the clumping factor-defective mutants were up to 100 times less able than the wild type strain to attach to fibrinogen and also significantly less adherent than the parents to platelet-fibrin clots. Coagulase-defective mutants, in contrast, were not altered in their in vitro adherence phenotype. The rate of in vivo infection was inoculum dependent. Clumping factor-defective mutants produced ca. 50% less endocarditis than the parent organisms when injected at inoculum sizes infecting, respectively, 40 and 80% (ID40 and ID80, respectively) of rats with the wild-type strain. This was a trend at the ID40 but was statistically significant at the ID80 (P < 0.05). Coagulase-defective bacteria were not affected in their infectivity. Complementation of a clumping factor-defective mutant with a copy of the wild-type clumping factor gene restored both its in vitro adherence and its in vivo infectivity. These results show that clumping factor plays a specific role in the pathogenesis of S. aureus endocarditis. Nevertheless, the rate of endocarditis with clumping factor-defective mutants increased with larger inocula, indicating the contribution of additional pathogenic determinants in the infective process.

Pathogenesis of streptococcal and staphylococcal endocarditis.

Although streptococcal and S. aureus IE share the same primary site of infection, their pathogenesis and clinical evolution present several major differences. Streptococci adhere to cardiac valves with pre-existing endothelial lesions. In contrast, S. aureus can colonize either damaged endothelium or invade physically intact endothelial cells. These interactions are mediated by multiple surface adhesins, some of which have been only partially characterized. Streptococci produce surface glucans (gtf and ftf), ECM adhesins (e.g., fibronectin-binding proteins, FimA), and platelet aggregating factors (phase I and phase II antigens, pblA, pblB, and pblT), all of which have been.

Pathogenesis of adult-onset Still's disease: new insights from the juvenile counterpart.

Adult-onset Still's disease (AOSD) is a rare inflammatory disease characterized by the classical triad of daily fever, arthritis, and typical salmon-colored rash. Recent accumulation of knowledge, mostly arising from hereditary autoinflammatory diseases and from the systemic-onset juvenile idiopathic arthritis (sJIA), has given raise to new hypotheses on the pathophysiology of AOSD. In this review, we first discuss on the continuum between AOSD and sJIA. Then, we summarize current hypotheses on the underlying pathogenesis: (1) an infectious hypothesis; (2) an autoinflammatory hypothesis; (3) a lymphohistiocytic hypothesis; and (4) a hyperferritinemic hypothesis. Finally, we present the recent data suggesting that patients with AOSD fall into two distinct subgroups with different courses, one with prominent systemic features and one with chronic arthritis.

Placental growth factor-1 and epithelial haemato-retinal barrier breakdown: potential implication in the pathogenesis of diabetic retinopathy.

AIMS/HYPOTHESIS: Disruption of the retinal pigment epithelial (RPE) barrier contributes to sub-retinal fluid and retinal oedema as observed in diabetic retinopathy. High placental growth factor (PLGF) vitreous levels have been found in diabetic patients. This work aimed to elucidate the influence of PLGF-1 on a human RPE cell line (ARPE-19) barrier in vitro and on normal rat eyes in vivo. METHODS: ARPE-19 permeability was measured using transepithelial resistance and inulin flux under stimulation of PLGF-1, vascular endothelial growth factor (VEGF)-E and VEGF 165. Using RT-PCR, we evaluated the effect of hypoxic conditions or insulin on transepithelial resistance and on PLGF-1 and VEGF receptors. The involvement of mitogen-activated protein kinase (MEK, also known as MAPK)/extracellular signal-regulated kinase (ERK, also known as EPHB2) signalling pathways under PLGF-1 stimulation was evaluated by western blot analysis and specific inhibitors. The effect of PLGF-1 on the external haemato-retinal barrier was evaluated after intravitreous injection of PLGF-1 in the rat eye; evaluation was by semi-thin analysis and zonula occludens-1 immunolocalisation on flat-mounted RPE. RESULTS: In vitro, PLGF-1 induced a reversible decrease of transepithelial resistance and enhanced tritiated inulin flux. These effects were specifically abolished by an antisense oligonucleotide directed at VEGF receptor 1. Exposure of ARPE-19 cells to hypoxic conditions or to insulin induced an upregulation of PLGF-1 expression along with increased transcellular permeability. The PLGF-1-induced RPE cell permeability involved the MEK signalling pathway. Injection of PLGF-1 in the rat eye vitreous induced an opening of the RPE tight junctions with subsequent sub-retinal fluid accumulation, retinal oedema and cytoplasm translocation of junction proteins. CONCLUSIONS/INTERPRETATION: Our results indicate that PLGF-1 may be a potential regulation target for the control of diabetic retinal and macular oedema.

A role for the transcriptional repressor ICER in the molecular pathogenesis of type 2 diabetes

AbstractType 2 diabetes (T2D) is a metabolic disease which affects more than 200 millions people worldwide. The progression of this affection reaches nowadays epidemic proportions, owing to the constant augmentation in the frequency of overweight, obesity and sedentary. The pathogenesis of T2D is characterized by reduction in the action of insulin on its target tissues - an alteration referred as insulin resistance - and pancreatic β-cell dysfunction. This latter deterioration is defined by impairment in insulin biosynthesis and secretion, and a loss of β-cell mass by apoptosis. Environmental factors related to T2D, such as chronic elevation in glucose and free fatty acids levels, inflammatory cytokines and pro-atherogenic oxidized low- density lipoproteins (LDL), contribute to the loss of pancreatic β-cell function.In this study, we have demonstrated that the transcription factor Inducible Cyclic AMP Early Repressor (ICER) participates to the progression of both β-cell dysfunction and insulin resistance. The expression of this factor is driven by an alternative promoter and ICER protein represents therefore a truncated product of the Cyclic AMP Response Element Modulator (CREM) family which lacks transactivation domain. Consequently, the transcription factor ICER acts as a passive repressor which reduces expression of genes controlled by the cyclic AMP and Cyclic AMP Response Element Binding protein (CREB) pathway.In insulin-secreting cells, the accumulation of reactive oxygen species caused by environmental factors and notably oxidized LDL - a process known as oxidative stress - induces the transcription factor ICER. This transcriptional repressor hampers the secretory capacity of β-cells by silencing key genes of the exocytotic machinery. In addition, the factor ICER reduces the expression of the scaffold protein Islet Brain 1 (IB 1 ), thereby favouring the activation of the c-Jun N-terminal Kinase (JNK) pathway. This triggering alters in turn insulin biosynthesis and survival capacities of pancreatic β-cells.In the adipose tissue of mice and human subjects suffering from obesity, the transcription factor ICER contributes to the alteration in insulin action. The loss in ICER protein in these tissues induces a constant activation of the CREB pathway and the subsequent expression of the Activating Transcription Factor 3 (ATF3). In turn, this repressor reduces the transcript levels of the glucose transporter GLUT4 and the insulin-sensitizer peptide adiponectin, thereby contributing to the diminution in insulin action.In conclusion, these data shed light on the important role of the transcriptional repressor ICER in the pathogenesis of T2D, which contributes to both alteration in β-cell function and aggravation of insulin resistance. Consequently, a better understanding of the molecular mechanisms responsible for the alterations in ICER levels is required and could lead to develop new therapeutic strategies for the treatment of T2D.RésuméLe diabète de type 2 (DT2) est une maladie métabolique qui affecte plus de 200 millions de personnes dans le monde. La progression de cette affection atteint aujourd'hui des proportions épidémiques imputables à l'augmentation rapide dans les fréquences du surpoids, de l'obésité et de la sédentarité. La pathogenèse du DT2 se caractérise par une diminution de l'action de l'insuline sur ses tissus cibles - un processus nommé insulino-résistance - ainsi qu'une dysfonction des cellules β pancréatiques sécrétrices d'insuline. Cette dernière détérioration se définit par une réduction de la capacité de synthèse et de sécrétion de l'insuline et mène finalement à une perte de la masse de cellules β par apoptose. Des facteurs environnementaux fréquemment associés au DT2, tels l'élévation chronique des taux plasmatiques de glucose et d'acides gras libres, les cytokines pro-inflammatoires et les lipoprotéines de faible densité (LDL) oxydées, contribuent à la perte de fonction des cellules β pancréatiques.Dans cette étude, nous avons démontré que le facteur de transcription « Inducible Cyclic AMP Early Repressor » (ICER) participe à la progression de la dysfonction des cellules β pancréatiques et au développement de Pinsulino-résistance. Son expression étant gouvernée par un promoteur alternatif, la protéine d'ICER représente un produit tronqué de la famille des «Cyclic AMP Response Element Modulator » (CREM), sans domaine de transactivation. Par conséquent, le facteur ICER agit comme un répresseur passif qui réduit l'expression des gènes contrôlés par la voie de l'AMP cyclique et des « Cyclic AMP Response Element Binding protein » (CREB).Dans les cellules sécrétrices d'insuline, l'accumulation de radicaux d'oxygène libres, soutenue par les facteurs environnementaux et notamment les LDL oxydées - un processus appelé stress oxydatif- induit de manière ininterrompue le facteur de transcription ICER. Ainsi activé, ce répresseur transcriptionnel altère la capacité sécrétoire des cellules β en bloquant l'expression de gènes clés de la machinerie d'exocytose. En outre, le facteur ICER favorise l'activation de la cascade de signalisation « c-Jun N- terminal Kinase » (JNK) en réduisant l'expression de la protéine « Islet Brain 1 » (IB1), altérant ainsi les fonctions de biosynthèse de l'insuline et de survie des cellules β pancréatiques.Dans le tissu adipeux des souris et des sujets humains souffrant d'obésité, le facteur de transcription ICER contribue à l'altération de la réponse à l'insuline. La disparition de la protéine ICER dans ces tissus entraîne une activation persistante de la voie de signalisation des CREB et une induction du facteur de transcription « Activating Transcription Factor 3 » (ATF3). A son tour, le répresseur ATF3 inhibe l'expression du transporteur de glucose GLUT4 et du peptide adipocytaire insulino-sensibilisateur adiponectine, contribuant ainsi à la diminution de l'action de l'insuline en conditions d'obésité.En conclusion, à la lumière de ces résultats, le répresseur transcriptionnel ICER apparaît comme un facteur important dans la pathogenèse du DT2, en participant à la perte de fonction des cellules β pancréatiques et à l'aggravation de l'insulino-résistance. Par conséquent, l'étude des mécanismes moléculaires responsables de l'altération des niveaux du facteur ICER pourrait permettre le développement de nouvelles stratégies de traitement du DT2.Résumé didactiqueL'énergie nécessaire au bon fonctionnement de l'organisme est fournie par l'alimentation, notamment sous forme de sucres (glucides). Ceux-ci sont dégradés en glucose, lequel sera distribué aux différents organes par la circulation sanguine. Après un repas, le niveau de glucose sanguin, nommé glycémie, s'élève et favorise la sécrétion d'une hormone appelée insuline par les cellules β du pancréas. L'insuline permet, à son tour, aux organes, tels le foie, les muscles et le tissu adipeux de capter et d'utiliser le glucose ; la glycémie retrouve ainsi son niveau basai.Le diabète de type 2 (DT2) est une maladie métabolique qui affecte plus de 200 millions de personnes dans le monde. Le développement de cette affection est causée par deux processus pathologiques. D'une part, les quantités d'insuline secrétée par les cellules β pancréatiques, ainsi que la survie de ces cellules sont réduites, un phénomène connu sous le nom de dysfonction des cellules β. D'autre part, la sensibilité des tissus à l'insuline se trouve diminuée. Cette dernière altération, l'insulino-résistance, empêche le transport et l'utilisation du glucose par les tissus et mène à une accumulation de ce sucre dans le sang. Cette stagnation de glucose dans le compartiment sanguin est appelée hyperglycémie et favorise l'apparition des complications secondaires du diabète, telles que les maladies cardiovasculaires, l'insuffisance rénale, la cécité et la perte de sensibilité des extrémités.Dans cette étude, nous avons démontré que le facteur ICER qui contrôle spécifiquement l'expression de certains gènes, contribue non seulement à la dysfonction des cellules β, mais aussi au développement de l'insulino-résistance. En effet, dans les cellules β pancréatiques en conditions diabétiques, l'activation du facteur ICER altère la capacité de synthèse et de sécrétion d'insuline et réduit la survie ces cellules.Dans le tissu adipeux des souris et des sujets humains souffrant d'obésité, le facteur ICER contribue à la perte de sensibilité à l'insuline. La disparition d'ICER altère l'expression de la protéine qui capte le glucose, le transoprteur GLUT4, et l'hormone adipocytaire favorisant la sensibilité à l'insuline, nommée adiponectine. Ainsi, la perte d'ICER participe à la réduction de la captation de glucose par le tissue adipeux et au développement de l'insulino-résistance au cours de l'obésité.En conclusion, à la lumière de ces résultats, le facteur ICER apparaît comme un contributeur important à la progression du DT2, en soutenant la dysfonction des cellules β pancréatiques et l'aggravation de l'insulino-résistance. Par conséquent, l'étude des mécanismes responsables de la dérégulation du facteur ICER pourrait permettre le développement de nouvelles stratégies de traitement du DT2.

Calcineurin as a Multifunctional Regulator: Unraveling Novel Functions in Fungal Stress Responses, Hyphal Growth, Drug Resistance, and Pathogenesis.

Calcineurin signaling plays diverse roles in fungi in regulating stress responses, morphogenesis and pathogenesis. Although calcineurin signaling is conserved among fungi, recent studies indicate important divergences in calcineurin-dependent cellular functions among different human fungal pathogens. Fungal pathogens utilize the calcineurin pathway to effectively survive the host environment and cause life-threatening infections. The immunosuppressive calcineurin inhibitors (FK506 and cyclosporine A) are active against fungi, making targeting calcineurin a promising antifungal drug development strategy. Here we summarize current knowledge on calcineurin in yeasts and filamentous fungi, and review the importance of understanding fungal-specific attributes of calcineurin to decipher fungal pathogenesis and develop novel antifungal therapeutic approaches.

Molecular pathogenesis of spondylocheirodysplastic Ehlers-Danlos syndrome caused by mutant ZIP13 proteins.

The zinc transporter protein ZIP13 plays critical roles in bone, tooth, and connective tissue development, and its dysfunction is responsible for the spondylocheirodysplastic form of Ehlers-Danlos syndrome (SCD-EDS, OMIM 612350). Here, we report the molecular pathogenic mechanism of SCD-EDS caused by two different mutant ZIP13 proteins found in human patients: ZIP13(G64D), in which Gly at amino acid position 64 is replaced by Asp, and ZIP13(ΔFLA), which contains a deletion of Phe-Leu-Ala. We demonstrated that both the ZIP13(G64D) and ZIP13(ΔFLA) protein levels are decreased by degradation via the valosin-containing protein (VCP)-linked ubiquitin proteasome pathway. The inhibition of degradation pathways rescued the protein expression levels, resulting in improved intracellular Zn homeostasis. Our findings uncover the pathogenic mechanisms elicited by mutant ZIP13 proteins. Further elucidation of these degradation processes may lead to novel therapeutic targets for SCD-EDS.

Relevance of death receptors in nervous system: role in the pathogenesis of neurodegenerative diseases and targets for therapy

L’apoptosi és un procés fisiològic que controla el nombre de cèl·lules en organismes superiors. L’apoptosi està estrictament regulada i s’ha vist que està implicada en la patogènesi d’algunes malalties del sistema nerviós. En aquest sentit, un excés de mort cel·lular contribueix a les malalties neurodegenerati- ves, mentre que, el seu dèficit és una de les raons del desenvolupament de tumors. El punt principal de regulació del procés apoptòtic és l’activació de les caspases, cisteïna-proteases que tenen especificitat pels residus aspàrtic. Les caspases es poden activar per dos mecanismes principals: (1) alliberament de citocrom C dels mitocondris alterats al citoplasma i (2) l’activació dels receptors de la membrana anomenats receptors de mort (DR, de l’anglès death receptor). Aquests receptors s’han caracteritzat extensament en el sistema immunitari, mentre que en el sistema nerviós les seves funcions són encara desconegudes. El present article se centra en el paper dels DR en la patogènesi de malalties neurodegeneratives i suggereix el seu potencial des del punt de vista terapèutic. També es descriuen diverses molècules intracel·lulars caracteritzades per la seva habilitat en la modulació dels DR. Entre elles, presentem dues noves proteïnes – lifeguard i FAIM – que s’expressen específicament al sistema nerviós.

A systems view of risk factors for knee osteoarthritis reveals insights into the pathogenesis of the disease.

Early detection of osteoarthritis (OA) remains a critical yet unsolved multifaceted problem. To address the multifaceted nature of OA a systems model was developed to consolidate a number of observations on the biological, mechanical and structural components of OA and identify features common to the primary risk factors for OA (aging, obesity and joint trauma) that are present prior to the development of clinical OA. This analysis supports a unified view of the pathogenesis of OA such that the risk for developing OA emerges when one of the components of the disease (e.g., mechanical) becomes abnormal, and it is the interaction with the other components (e.g., biological and/or structural) that influences the ultimate convergence to cartilage breakdown and progression to clinical OA. The model, applied in a stimulus-response format, demonstrated that a mechanical stimulus at baseline can enhance the sensitivity of a biomarker to predict cartilage thinning in a 5 year follow-up in patients with knee OA. The systems approach provides new insight into the pathogenesis of the disease and offers the basis for developing multidisciplinary studies to address early detection and treatment at a stage in the disease where disease modification has the greatest potential for a successful outcome.

Leri's pleonosteosis, a congenital rheumatic disease, results from microduplication at 8q22.1 encompassing GDF6 and SDC2 and provides insight into systemic sclerosis pathogenesis.

OBJECTIVES: Leri's pleonosteosis (LP) is an autosomal dominant rheumatic condition characterised by flexion contractures of the interphalangeal joints, limited motion of multiple joints, and short broad metacarpals, metatarsals and phalanges. Scleroderma-like skin thickening can be seen in some individuals with LP. We undertook a study to characterise the phenotype of LP and identify its genetic basis. METHODS AND RESULTS: Whole-genome single-nucleotide polymorphism genotyping in two families with LP defined microduplications of chromosome 8q22.1 as the cause of this condition. Expression analysis of dermal fibroblasts from affected individuals showed overexpression of two genes, GDF6 and SDC2, within the duplicated region, leading to dysregulation of genes that encode proteins of the extracellular matrix and downstream players in the transforming growth factor (TGF)-β pathway. Western blot analysis revealed markedly decreased inhibitory SMAD6 levels in patients with LP. Furthermore, in a cohort of 330 systemic sclerosis cases, we show that the minor allele of a missense SDC2 variant, p.Ser71Thr, could confer protection against disease (p<1×10(-5)). CONCLUSIONS: Our work identifies the genetic cause of LP in these two families, demonstrates the phenotypic range of the condition, implicates dysregulation of extracellular matrix homoeostasis genes in its pathogenesis, and highlights the link between TGF-β/SMAD signalling, growth/differentiation factor 6 and syndecan-2. We propose that LP is an additional member of the growing 'TGF-β-pathies' group of musculoskeletal disorders, which includes Myhre syndrome, acromicric dysplasia, geleophysic dysplasias, Weill-Marchesani syndromes and stiff skin syndrome. Identification of a systemic sclerosis-protective SDC2 variant lays the foundation for exploration of the role of syndecan-2 in systemic sclerosis in the future.

Expert consensus document: European Consensus Statement on congenital hypogonadotropic hypogonadism-pathogenesis, diagnosis and treatment.

Congenital hypogonadotropic hypogonadism (CHH) is a rare disorder caused by the deficient production, secretion or action of gonadotropin-releasing hormone (GnRH), which is the master hormone regulating the reproductive axis. CHH is clinically and genetically heterogeneous, with >25 different causal genes identified to date. Clinically, the disorder is characterized by an absence of puberty and infertility. The association of CHH with a defective sense of smell (anosmia or hyposmia), which is found in ∼50% of patients with CHH is termed Kallmann syndrome and results from incomplete embryonic migration of GnRH-synthesizing neurons. CHH can be challenging to diagnose, particularly when attempting to differentiate it from constitutional delay of puberty. A timely diagnosis and treatment to induce puberty can be beneficial for sexual, bone and metabolic health, and might help minimize some of the psychological effects of CHH. In most cases, fertility can be induced using specialized treatment regimens and several predictors of outcome have been identified. Patients typically require lifelong treatment, yet ∼10-20% of patients exhibit a spontaneous recovery of reproductive function. This Consensus Statement summarizes approaches for the diagnosis and treatment of CHH and discusses important unanswered questions in the field.

Periodic Fever, Aphthous Stomatitis, Pharyngitis, and Cervical Adenitis (PFAPA) Syndrome: a Review of the Pathogenesis.

PFAPA syndrome represents the most common cause of recurrent fever in children in European populations, and it is characterized by recurrent episodes of high fever, pharyngitis, cervical adenitis, and aphthous stomatitis. Many possible causative factors have been explored so far, including infectious agents, immunologic mechanisms and genetic predisposition, but the exact etiology remains unclear. Recent findings demonstrate a dysregulation of different components of innate immunity during PFAPA flares, such as monocytes, neutrophils, complement, and pro-inflammatory cytokines, especially IL-1β, suggesting an inflammasome-mediated innate immune system activation and supporting the hypothesis of an autoinflammatory disease. Moreover, in contrast with previous considerations, the strong familial clustering suggests a potential genetic origin rather than a sporadic disease. In addition, the presence of variants in inflammasome-related genes, mostly in NLRP3 and MEFV, suggests a possible role of inflammasome-composing genes in PFAPA pathogenesis. However, none of these variants seem to be relevant, alone, to its etiology, indicating a high genetic heterogeneity as well as an oligogenic or polygenic genetic background.

Inheritance of resistance to powdery mildew in pea and pathogenesis-related aspects

The inheritance of resistance to powdery mildew in the pea cultivar MK-10 and some histological aspects of infection were assessed. For the inheritance study, F1, F2, backcrosses and F3 generations of MK-10 crossed with two susceptible populations were evaluated. Histological evaluations included percentage of germinated conidia, percentage of conidia that formed appresoria, percentage of conidia that established colonies, and number of haustoria per colony. Segregation ratios obtained in the resistance inheritance study were compared by Chi-square (ײ) test and the histological data were analyzed by Tukey's test at 5% probability. It was concluded that resistance of MK-10 to powdery mildew is due to a pair of recessive alleles since it is expressed in the pre-penetration stage and completed by post-penetration localized cellular death, characteristic of the presence of the pair of recessive alleles er1er1.