RESUMEN
Ehrlichia chaffeensis (E. chaffeensis) has evolved eukaryotic ligand mimicry to repurpose multiple cellular signaling pathways for immune evasion. In this investigation, we demonstrate that TRP120 has a novel repetitive short linear motif (SLiM) that activates the evolutionarily conserved Hedgehog (Hh) signaling pathway to inhibit apoptosis. In silico analysis revealed that TRP120 has sequence and functional similarity with Hh ligands and a candidate Hh ligand SLiM was identified. siRNA knockdown of Hh signaling and transcriptional components significantly reduced infection. Co-immunoprecipitation and surface plasmon resonance demonstrated that rTRP120-TR interacted directly with Hh receptor Patched-2 (PTCH2). E. chaffeensis infection resulted in early upregulation of Hh transcription factor GLI-1 and regulation of Hh target genes. Moreover, soluble recombinant TRP120 (rTRP120) activated Hh and induced gene expression consistent with the eukaryotic Hh ligand. The TRP120-Hh-SLiM (NPEVLIKD) induced nuclear translocation of GLI-1 in THP-1 cells and primary human monocytes and induced a rapid and expansive activation of Hh pathway target genes. Furthermore, Hh activation was blocked by an α-TRP120-Hh-SLiM antibody. TRP120-Hh-SLiM significantly increased levels of Hh target, anti-apoptotic protein B-cell lymphoma 2 (BCL-2), and siRNA knockdown of BCL-2 dramatically inhibited infection. Blocking Hh signaling with the inhibitor Vismodegib, induced a pro-apoptotic cellular program defined by decreased mitochondria membrane potential, significant reductions in BCL-2, activation of caspase 3 and 9, and increased apoptotic cells. This study reveals a novel E. chaffeensis SLiM ligand mimetic that activates Hh signaling to maintain E. chaffeensis infection by engaging a BCL-2 anti-apoptotic cellular program.
Asunto(s)
Ehrlichia chaffeensis , Ehrlichiosis , Proteínas Bacterianas/metabolismo , Ehrlichia chaffeensis/genética , Ehrlichiosis/metabolismo , Proteínas Hedgehog/metabolismo , Interacciones Huésped-Patógeno/genética , Humanos , Ligandos , Proteínas Proto-Oncogénicas c-bcl-2/genética , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , ARN Interferente Pequeño/metabolismo , Transducción de SeñalRESUMEN
Human metapneumovirus (hMPV), a leading cause of respiratory tract infections in infants, encodes a small hydrophobic (SH) protein of unknown function. Here we show that infection of plasmacytoid dendritic cells (pDCs) with a recombinant virus lacking SH expression (rhMPV-ΔSH) enhanced the secretion of type I interferons (IFNs), which required TLR7 and MyD88 expression. HMPV SH protein inhibited TLR7/MyD88/TRAF6 signaling leading to IFN gene transcription, identifying a novel mechanism by which paramyxovirus SH proteins modulate innate immune responses.
Asunto(s)
Células Dendríticas/virología , Interferón Tipo I/metabolismo , Metapneumovirus/genética , Proteínas Oncogénicas de Retroviridae/inmunología , Células Dendríticas/inmunología , Células HEK293 , Humanos , Inmunidad Innata , Metapneumovirus/fisiología , Factor 88 de Diferenciación Mieloide/inmunología , Transducción de Señal , Receptor Toll-Like 7/inmunologíaRESUMEN
Rickettsial agents are sensed by pattern recognition receptors but lack pathogen-associated molecular patterns commonly observed in facultative intracellular bacteria. Due to these molecular features, the order Rickettsiales can be used to uncover broader principles of bacterial immunity. Here, we used the bacterium Anaplasma phagocytophilum, the agent of human granulocytic anaplasmosis, to reveal a novel microbial surveillance system. Mechanistically, we discovered that upon A. phagocytophilum infection, cytosolic phospholipase A2 cleaves arachidonic acid from phospholipids, which is converted to the eicosanoid prostaglandin E2 (PGE2) via cyclooxygenase 2 (COX2) and the membrane associated prostaglandin E synthase-1 (mPGES-1). PGE2-EP3 receptor signaling leads to activation of the NLRC4 inflammasome and secretion of interleukin (IL)-1ß and IL-18. Importantly, the receptor-interacting serine/threonine-protein kinase 2 (RIPK2) was identified as a major regulator of the immune response against A. phagocytophilum. Accordingly, mice lacking COX2 were more susceptible to A. phagocytophilum, had a defect in IL-18 secretion and exhibited splenomegaly and damage to the splenic architecture. Remarkably, Salmonella-induced NLRC4 inflammasome activation was not affected by either chemical inhibition or genetic ablation of genes associated with PGE2 biosynthesis and signaling. This divergence in immune circuitry was due to reduced levels of the PGE2-EP3 receptor during Salmonella infection when compared to A. phagocytophilum. Collectively, we reveal the existence of a functionally distinct NLRC4 inflammasome illustrated by the rickettsial agent A. phagocytophilum.
Asunto(s)
Anaplasma phagocytophilum/inmunología , Proteínas Reguladoras de la Apoptosis/inmunología , Proteínas de Unión al Calcio/inmunología , Dinoprostona/inmunología , Ehrlichiosis/inmunología , Inflamasomas/inmunología , Subtipo EP3 de Receptores de Prostaglandina E/inmunología , Animales , Modelos Animales de Enfermedad , Ensayo de Inmunoadsorción Enzimática , Immunoblotting , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Reacción en Cadena en Tiempo Real de la PolimerasaRESUMEN
Human metapneumovirus (hMPV) and respiratory syncytial virus (RSV) are leading causes of upper and lower respiratory tract infections in young children and among elderly and immunocompromised patients. The pathogenesis of hMPV-induced lung disease is poorly understood. The lung macrophage population consists of alveolar macrophages (AMs) residing at the luminal surface of alveoli and interstitial macrophages present within the parenchymal lung interstitium. The involvement of AMs in innate immune responses to virus infections remains elusive. In this study, BALB/c mice depleted of AMs by intranasal instillation of dichloromethylene bisphosphonate (L-CL2MBP) liposomes were examined for disease, lung inflammation, and viral replication after infection with hMPV or RSV. hMPV-infected mice lacking AMs exhibited improved disease in terms of body weight loss, lung inflammation, airway obstruction, and hyperresponsiveness compared with AM-competent mice. AM depletion was associated with significantly reduced hMPV titers in the lungs, suggesting that hMPV required AMs for early entry and replication in the lung. In contrast, AM depletion in the context of RSV infection was characterized by an increase in viral replication, worsened disease, and inflammation, with increased airway neutrophils and inflammatory dendritic cells. Overall, lack of AMs resulted in a broad-spectrum disruption in type I IFN and certain inflammatory cytokine production, including TNF and IL-6, while causing a virus-specific alteration in the profile of several immunomodulatory cytokines, chemokines, and growth factors. Our study demonstrates that AMs have distinct roles in the context of human infections caused by members of the Paramyxoviridae family.
Asunto(s)
Pulmón/inmunología , Macrófagos Alveolares/inmunología , Metapneumovirus/patogenicidad , Infecciones por Paramyxoviridae/inmunología , Infecciones por Virus Sincitial Respiratorio/inmunología , Virus Sincitiales Respiratorios/patogenicidad , Obstrucción de las Vías Aéreas/inmunología , Obstrucción de las Vías Aéreas/fisiopatología , Obstrucción de las Vías Aéreas/virología , Animales , Células Cultivadas , Citocinas/metabolismo , Modelos Animales de Enfermedad , Humanos , Mediadores de Inflamación/metabolismo , Pulmón/metabolismo , Pulmón/fisiopatología , Pulmón/virología , Macrófagos Alveolares/metabolismo , Macrófagos Alveolares/virología , Metapneumovirus/inmunología , Ratones Endogámicos BALB C , Infecciones por Paramyxoviridae/metabolismo , Infecciones por Paramyxoviridae/fisiopatología , Infecciones por Paramyxoviridae/virología , Neumonía/inmunología , Neumonía/fisiopatología , Neumonía/virología , Infecciones por Virus Sincitial Respiratorio/metabolismo , Infecciones por Virus Sincitial Respiratorio/fisiopatología , Infecciones por Virus Sincitial Respiratorio/prevención & control , Infecciones por Virus Sincitial Respiratorio/virología , Virus Sincitiales Respiratorios/inmunología , Factores de Tiempo , Replicación ViralRESUMEN
The purpose of the present study was to estimate whole-body fatty acid and cholesterol synthesis in weight-stable adults and to determine the likely effect on the doubly-labelled water (DLW) method for measuring energy expenditure. Synthesis was measured by 2H incorporation over 14 d in six adult males in approximate energy balance following noradrenaline infusion to maximize mobilization of free fatty acid from adipose tissue. The inter-individual variation in synthesis rates was large and in one subject the proportion of free fatty acid synthesized was ten times that of the mean of the rest of the group; the fasting concentration of esterified fatty acid in this subject was five times that of the rest of the group indicating likely violation of the assumptions underlying the calculation of whole-body synthesis. After 14 d of labelling in the other five subjects, 0.9 (SEM 0.3)% of the circulating free fatty acid, 9.3 (SEM 3.0)% of the esterified fatty acid, 14.6 (SEM 2.4)% of the free cholesterol and 28.3 (SEM 3.7)% of esterified cholesterol had been synthesized de novo. A high rate of synthesis correlated with a low pre-dose 2H abundance both within and between lipid classes suggesting that natural 2H abundance variations in some lipid classes may be used to determine their metabolic origin. Whole-body synthetic rates were 8 g/d for fatty acid and 0.3-0.5 g/d for cholesterol. These values correspond to very small errors on DLW-derived estimates of CO2 production; -2.5 litres/d for fatty acid and -0.1 to -0.2 litres/d for cholesterol. These results, obtained in subjects typically consuming a diet with a lower fat and cholesterol content that the typical Western diet, suggest that the DLW method is unlikely to be affected by fatty acid and cholesterol synthesis in subjects in energy balance consuming a typical Western diet.
Asunto(s)
Colesterol/biosíntesis , Óxido de Deuterio , Metabolismo Energético , Ácidos Grasos/biosíntesis , Tejido Adiposo/metabolismo , Adulto , Composición Corporal , Óxido de Deuterio/metabolismo , Ácidos Grasos no Esterificados/biosíntesis , Humanos , Masculino , Factores de TiempoRESUMEN
Thirteen young, male adults were investigated for thermal, cardiovascular and metabolic responses to truncal cooling for 40 min. The subjects were divided into two groups [well nourished controls (WN) and chronically energy deficient (CED)] on the basis of anthropometry and socio-economic status. The CED group had significantly greater reductions in peripheral forearm blood flow and surface finger tip temperatures on exposure to cold when compared to the well nourished controls. The CED group also showed a significant rise in oxygen consumption (3.4%), while no thermogenic response was observed in the WN controls. There was no fall in deep body temperature in either group. The study suggests that chronically energy deficient subjects thermoregulate appropriately on exposure to mild cold. The deficiency in insulative body fat is made up for by evoking greater peripheral vasoconstrictor responses as well as thermogenic mechanisms. The study suggests that on exposure to cold, thermoregulation takes precedence over energy conservation in chronically energy deficient subjects.
Asunto(s)
Regulación de la Temperatura Corporal/fisiología , Sistema Cardiovascular/fisiopatología , Hipotermia/fisiopatología , Adulto , Hemodinámica , Humanos , Masculino , Oxígeno/metabolismoRESUMEN
Maximal voluntary contraction (MVC) using a handgrip dynamometer was assessed in seventy-two young adult males. The subjects were divided into two groups on the basis of a BMI of 18.5 kg/m2. The subjects with a BMI < 18.5 kg/m2 (n 38) were further divided into an underweight (UW; n 20) group and a chronically energy-deficient (CED; n 18) group. The CED subjects had significantly lower MVC (30.1, SD 5.9 kg) than either the well-nourished controls (BMI > 18.5 kg/m2: 39.8, SD 5.8 kg) or the underweight group (37.6, SD 4.9 kg). The differences between the CED and UW groups persisted even after the MVC were corrected for forearm muscle area and stature. The results suggest that MVC may be a useful functional indicator of nutritional status particularly in differentiating subjects with chronic undernutrition from individuals who are underweight and not undernourished but have similar BMI.
Asunto(s)
Fuerza de la Mano , Trastornos Nutricionales/diagnóstico , Adolescente , Adulto , Índice de Masa Corporal , Enfermedad Crónica , Diagnóstico Diferencial , Humanos , MasculinoRESUMEN
Basal metabolic rate (BMR), thermic effect of a meal (TEM), anthropometry, and dietary intakes were measured in 18 control subjects; 18 pregnant women at 12, 24, and 34 wk gestation; and in 17 of these women at 12 and 24 wk postpartum, to uncover any metabolic economy associated with either pregnancy or lactation. Results indicated that the BMR and TEM were not associated with any energy saving either during pregnancy or lactation. Mean weight gain from 12 wk gestation to term was 11.4 +/- 3.7 kg; mean birth weight of the infants was 3.06 +/- 0.41 kg. Estimated gain in adipose tissue and fat mass were 3.1 +/- 3.6 and 2.5 +/- 2.9 kg, respectively. Energy cost of pregnancy was estimated to be 303 +/- 171 MJ. The cumulative increase in energy intake over the last two trimesters of pregnancy was 290 +/- 280 MJ, meeting a large part of the total estimated cost of pregnancy. Weight gained by infants who were exclusively breast-fed from birth to 12 wk of age was used as a proxy indicator of adequate lactational performance. The extra energy required during lactation appeared to have been met largely by increases in energy intake, rather than by any metabolic economy or increase in fat mobilization.
PIP: Researchers compared data on 18 nonpregnant, nonlactating staff and students (controls) with data on 18 pregnant women at 12, 24, and 34 weeks gestation and on 17 of these women at 12 and 24 weeks postpartum to determine any changes in maternal energy metabolism during pregnancy and lactation. All controls and cases were healthy and recruited at St. John's Medical College and Hospital in Bangalore, India. They had unlimited access to food. Mean birth weight stood at 3.06 kg. Pregnant women gained, on average, 11.4 kg between 12 weeks gestation and term. They also gained 3.1 kg of adipose tissue and 2.5 kg in fat mass during the same period. The total energy cost of pregnancy was 303 MJ. Pregnant women experienced a cumulative increase in energy intake over the last trimesters of pregnancy of 290 MJ, satisfying a considerable part of the total estimated cost of pregnancy. Neither the basal metabolic rate nor the thermic effect of a meal were related to any energy saving during pregnancy or lactation. Energy intake was significantly higher than that of controls at 24 and 34 weeks gestation (9.01 and 9.33 vs 7.58 MJ/d) and at 12 and 24 weeks postpartum (9.6 and 9.09 vs. 7.58 MJ/d) (p 0.05). The proxy indicator of adequate lactational performance was weight gain of infant between birth and 12 weeks. At 12 weeks, the body weights were similar to the 50th percentile of the NCHS weight-for-age. These findings suggest that increases in energy intake met the need for extra energy needed during lactation and that metabolic economy and increase in fat mobilization did not occur.
Asunto(s)
Ingestión de Energía , Metabolismo Energético , Lactancia/metabolismo , Embarazo/metabolismo , Adulto , Antropometría , Ingestión de Alimentos , Femenino , Humanos , India/etnología , Estado Nutricional , Consumo de Oxígeno , Periodo Posparto/metabolismo , Aumento de PesoRESUMEN
Forearm and fingertip temperature gradients were related to simultaneously measured forearm blood flow in eleven adult subjects at rest and during a mild cold stimulus. The change in temperature gradients were converted into a percentage change of the potential capacity for heat exchange and this was found to correlate well (r = 0.73: P < 0.001) with the absolute reduction in forearm blood flow.
Asunto(s)
Antebrazo/irrigación sanguínea , Temperatura Cutánea , Adolescente , Adulto , Índice de Masa Corporal , Frío , Dedos , Humanos , Masculino , Flujo Sanguíneo RegionalRESUMEN
The classification of motoneurons based on size alone may not be an absolute morphological criterion. There appears to be a fair difference in the pattern of horseradish peroxidase uptake between the phrenic and the intercostal motoneurons. Hence we would like to suggest that the gamma and the alpha motoneurons differ in the horseradish peroxidase uptake.