Surfactant protein-A limits Ureaplasma-mediated lung inflammation in a murine pneumonia model

Ureaplasma infections: update on epidemiology, antimicrobial resistance, and pathogenesis

Human Ureaplasma species are being increasingly recognized as opportunistic pathogens in human genitourinary tract infections, infertility, adverse pregnancy, neonatal morbidities, and other adult invasive infections. Although some general reviews have focused on the detection and clinical manifestations of Ureaplasma spp., the molecular epidemiology, antimicrobial resistance, and pathogenesis of Ureaplasma spp. have not been adequately explained. The purpose of this review is to offer valuable insights into the current understanding and future research perspectives of the molecular epidemiology, antimicrobial resistance, and pathogenesis of human Ureaplasma infections. This review summarizes the conventional culture and detection methods and the latest molecular identification technologies for Ureaplasma spp. We also reviewed the global prevalence and mechanisms of antibiotic resistance for Ureaplasma spp. Aside from regular antibiotics, novel antibiotics with outstanding in vitro antimicrobial activity against Ureaplasma spp. are described. Furthermore, we discussed the pathogenic mechanisms of Ureaplasma spp., including adhesion, proinflammatory effects, cytotoxicity, and immune escape effects, from the perspectives of pathology, related molecules, and genetics.

Sequential Exposure to Antenatal Microbial Triggers Attenuates Alveolar Growth and Pulmonary Vascular Development and Impacts Pulmonary Epithelial Stem/Progenitor Cells

Perinatal inflammatory stress is strongly associated with adverse pulmonary outcomes after preterm birth. Antenatal infections are an essential perinatal stress factor and contribute to preterm delivery, induction of lung inflammation and injury, pre-disposing preterm infants to bronchopulmonary dysplasia. Considering the polymicrobial nature of antenatal infection, which was reported to result in diverse effects and outcomes in preterm lungs, the aim was to examine the consequences of sequential inflammatory stimuli on endogenous epithelial stem/progenitor cells and vascular maturation, which are crucial drivers of lung development. Therefore, a translational ovine model of antenatal infection/inflammation with consecutive exposures to chronic and acute stimuli was used. Ovine fetuses were exposed intra-amniotically to Ureaplasma parvum 42 days (chronic stimulus) and/or to lipopolysaccharide 2 or 7 days (acute stimulus) prior to preterm delivery at 125 days of gestation. Pulmonary inflammation, endogenous epithelial stem cell populations, vascular modulators and morphology were investigated in preterm lungs. Pre-exposure to UP attenuated neutrophil infiltration in 7d LPS-exposed lungs and prevented reduction of SOX-9 expression and increased SP-B expression, which could indicate protective responses induced by re-exposure. Sequential exposures did not markedly impact stem/progenitors of the proximal airways (P63+ basal cells) compared to single exposure to LPS. In contrast, the alveolar size was increased solely in the UP+7d LPS group. In line, the most pronounced reduction of AEC2 and proliferating cells (Ki67+) was detected in these sequentially UP + 7d LPS-exposed lambs. A similar sensitization effect of UP pre-exposure was reflected by the vessel density and expression of vascular markers VEGFR-2 and Ang-1 that were significantly reduced after UP exposure prior to 2d LPS, when compared to UP and LPS exposure alone. Strikingly, while morphological changes of alveoli and vessels were seen after sequential microbial exposure, improved lung function was observed in UP, 7d LPS, and UP+7d LPS-exposed lambs. In conclusion, although sequential exposures did not markedly further impact epithelial stem/progenitor cell populations, re-exposure to an inflammatory stimulus resulted in disturbed alveolarization and abnormal pulmonary vascular development. Whether these negative effects on lung development can be rescued by the potentially protective responses observed, should be examined at later time points.

Intra-uterine experimental infection by Ureaplasma diversum induces TNF-α mediated womb inflammation in mice

Ureaplasma diversum is an opportunistic pathogen associated with uterine inflammation, impaired embryo implantation, infertility, abortions, premature birth of calves and neonatal pneumonia in cattle. It has been suggested that the intra-uterine infection by Ureaplasma diversum can cause vascular changes that hinder the success of pregnancy. Thus, the aim of this study was to evaluate the changes of intrauterine site of A/J mice in estrus or proestrus phase inoculated with Ureaplasma diversum. The infection was monitored at 24, 48 and 72 hours by the PCR methodology to detect the Ureaplasma in the inoculation site and the profile of circulating blood cells. Morphological changes, intensity of inflammation and the production of cytokines were compared. The infected mice showed local inflammation through the production of IFN-γ and TNF-α. Ureaplasma diversum infections in the reproductive tract of studied mice seemed to be associated with the production of pro-inflammatory cytokines in uterine parenchyma. The levels of TNF-α of infected mice were dependent on the bacterial load of inoculated Ureaplasma. Uterine experimental infections by Ureaplasma diversum have not been mentioned yet and herein we presented the first report of an intrauterine infection model in mice.

Role of Ureaplasma Respiratory Tract Colonization in Bronchopulmonary Dysplasia Pathogenesis: Current Concepts and Update

Respiratory tract colonization with the genital mycoplasma species Ureaplasma parvum and Ureaplasma urealyticum in preterm infants is a significant risk factor for bronchopulmonary dysplasia (BPD). Recent studies of the ureaplasmal genome, animal infection models, and human infants have provided a better understanding of specific virulence factors, pathogen-host interactions, and variability in genetic susceptibility that contribute to chronic infection, inflammation, and altered lung development. This review provides an update on the current evidence supporting a causal role of ureaplasma infection in BPD pathogenesis. The current status of antibiotic trials to prevent BPD in Ureaplasma-infected preterm infants is also reviewed.

The protective effect of different airway humidification liquids to lung after tracheotomy in traumatic brain injury: The role of pulmonary surfactant protein-A (SP-A)

The purpose of this study was to establish a rat model of a brain injury with tracheotomy and compared the wetting effects of different airway humidification liquids, afterward, the best airway humidification liquid was selected for the clinical trial, thus providing a theoretical basis for selecting a proper airway humidification liquid in a clinical setting. Rats were divided into a sham group, group A (0.9% NaCl), group B (0.45% NaCl), group C (0.9% NaCl+ambroxol) and group D (0.9% NaCl+Pulmicort). An established rat model of traumatic brain injury with tracheotomy was used. Brain tissue samples were taken to determine water content, while lung tissue samples were taken to determine wet/dry weight ratio (W/D), histological changes and expression levels of SP-A mRNA and SP-A protein. 30 patients with brain injury and tracheotomy were selected and divided into two groups based on the airway humidification liquid instilled in the trachea tube, 0.45% NaCl and 0.9% NaCl+ambroxol. Blood was then extracted from the patients to measure the levels of SP-A, interleukin-6 (IL-6), interleukin-8 (IL-8) and tumour necrosis factor-α (TNF-α). The difference between group C and other groups in lung W/D and expression levels of SP-A mRNA and SP-A protein was significant (P<0.05). In comparison, the histological changes showed that the lung tissue damage was smallest in group C compared to the three other groups. Aspect of patients, 0.45% NaCl group and 0.9% NaCl+ambroxol group were significantly different in the levels of SP-A, IL-6, IL-8 and TNF-α (P<0.01). In the present study, 0.9% NaCl+ambroxol promote the synthesis and secretion of pulmonary surfactant, and has anti-inflammatory and antioxidant effects, which inhibit the release of inflammatory factors and cytokines, making it an ideal airway humidification liquid.

Sex differences in the acute in vivo effects of different human SP-A variants on the mouse alveolar macrophage proteome

Surfactant protein A (SP-A) is involved in lung innate immunity. Humans have two SP-A genes, SFTPA1 and SFTPA2, each with several variants. We examined the in vivo effects of treatment with specific SP-A variants on the alveolar macrophage (AM) proteome from SP-A knockout (KO) mice. KO mice received either SP-A1, SP-A2, or both. AM were collected and their proteomes examined with 2D-DIGE. We identified 90 proteins and categorized them as related to actin/cytoskeleton, oxidative stress, protease balance/chaperones, regulation of inflammation, and regulatory/developmental processes. SP-A1 and SP-A2 had different effects on the AM proteome and these effects differed between sexes. In males more changes occurred in the oxidative stress, protease/chaperones, and inflammation groups with SP-A2 treatment than with SP-A1. In females most SP-A1-induced changes were in the actin/cytoskeletal and oxidative stress groups. We conclude that after acute SP-A1 and SP-A2 treatment, sex-specific differences were observed in the AM proteomes from KO mice, and that these sex differences differ in response to SP-A1 and SP-A2. Females are more responsive to SP-A1, whereas the gene-specific differences in males were minimal. These observations not only demonstrate the therapeutic potential of exogenous SP-A, but also illustrate sex- and gene-specific differences in the response to it.

BIOLOGICAL SIGNIFICANCE

This study shows that changes occur in the alveolar macrophage proteome in response to a single in vivo treatment with exogenous SP-A1 and/or SP-A2. We demonstrate that SP-A1 and SP-A2 have different effects on the AM proteome and that sex differences exist in the response to each SP-A1 and SP-A2 gene product. This study illustrates the potential of exogenous SP-A1 and SP-A2 treatment for the manipulation of macrophage function and indicates that the specific SP-A variant used for treatment may vary with sex and with the cellular functions being modified. The observed changes may contribute to sex differences in the incidence of some lung diseases.

Ureaplasma and BPD

Ureaplasma is an organism with low virulence and is a commensal of the lower genito-urinary tract in females. From here, it can gain entry in the amniotic fluid to cause inflammation in the amniotic compartment during pregnancy. Ureaplasma spp. are the most common organisms isolated from women with chorioamnionitis. Ureaplasma spp. are associated with increased risk for preterm labor and morbidity in the preterm neonate. However, there is some controversy regarding the importance of Ureaplasma in the pathogenesis of bronchopulmonary dysplasia (BPD). This article will review the microbiology of Ureaplasma, host innate immune responses, and the pathology of lung injury in animal models of Ureaplasma chorioamnionitis. We will review epidemiological studies of Ureaplasma and BPD in preterm infants and efficacy of antibiotics in preventing preterm labor and BPD.

A TLR4-interacting SPA4 peptide inhibits LPS-induced lung inflammation

The interaction between surfactant protein-A (SP-A) and TLR4 is important for host defense. We have recently identified an SPA4 peptide region from the interface of SP-A-TLR4 complex. Here, we studied the involvement of the SPA4 peptide region in SP-A-TLR4 interaction using a two-hybrid system, and biological effects of SPA4 peptide in cell systems and a mouse model. HEK293 cells were transfected with plasmid DNAs encoding SP-A or a SP-A-mutant lacking SPA4 peptide region and TLR4. Luciferase activity was measured as the end-point of SP-A-TLR4 interaction. NF-κB activity was also assessed simultaneously. Next, the dendritic cells or mice were challenged with Escherichia coli-derived LPS and treated with SPA4 peptide. Endotoxic shock-like symptoms and inflammatory parameters (TNF-α, NF-κB, leukocyte influx) were assessed. Our results reveal that the SPA4 peptide region contributes to the SP-A-TLR4 interaction and inhibits the LPS-induced NF-κB activity and TNF-α. We also observed that the SPA4 peptide inhibits LPS-induced expression of TNF-α, nuclear localization of NF-κB-p65 and cell influx, and alleviates the endotoxic shock-like symptoms in a mouse model. Our results suggest that the anti-inflammatory activity of the SPA4 peptide through its binding to TLR4 can be of therapeutic benefit.

Current technology in the diagnosis of developmentally related lung disorders

Respiratory disorders that present in the newborn period may result from structural, functional, or acquired mechanisms that limit gas exchange between the airspace and vascular bed. Exciting new imaging, gene sequencing, mass spectrometry, and molecular and cell-based techniques are enhancing our understanding of mechanisms of disease; highlighting the complexity of interactions between genes, development, and environment in the manifestation of health and disease; and becoming part of the clinical armamentarium for the care of patients. Some of these technologies and their clinical potential are briefly reviewed in this paper.

In vivo rescue of alveolar macrophages from SP-A knockout mice with exogenous SP-A nearly restores a wild type intracellular proteome; actin involvement

BACKGROUND

Mice lacking surfactant protein-A (SP-A-/-; knockout; KO) exhibit increased vulnerability to infection and injury. Although many bronchoalveolar lavage (BAL) protein differences between KO and wild-type (WT) are rapidly reversed in KO after infection, their clinical course is still compromised. We studied the impact of SP-A on the alveolar macrophage (AM) proteome under basal conditions. Male SP-A KO mice were SP-A-treated (5 micrograms/mouse) and sacrificed in 6 or 18 hr. The AM proteomes of KO, SP-A-treated KO, and WT mice were studied by 2D-DIGE coupled with MALDI-ToF/ToF and AM actin distribution was examined by phalloidon staining.

RESULTS

We observed: a) significant differences from KO in WT or exogenous SP-A-treated in 45 of 76 identified proteins (both increases and decreases). These included actin-related/cytoskeletal proteins (involved in motility, phagocytosis, endocytosis), proteins of intracellular signaling, cell differentiation/regulation, regulation of inflammation, protease/chaperone function, and proteins related to Nrf2-mediated oxidative stress response pathway; b) SP-A-induced changes causing the AM proteome of the KO to resemble that of WT; and c) that SP-A treatment altered cell size and F-actin distribution.

CONCLUSIONS

These differences are likely to enhance AM function. The observations show for the first time that acute in vivo SP-A treatment of KO mice, under basal or unstimulated conditions, affects the expression of multiple AM proteins, alters F-actin distribution, and can restore much of the WT phenotype. We postulate that the SP-A-mediated expression profile of the AM places it in a state of "readiness" to successfully conduct its innate immune functions and ensure lung health.

Surfactant protein-A and toll-like receptor-4 modulate immune functions of preterm baboon lung dendritic cell precursor cells

Lung infections are important risk factors for an increased morbidity and mortality in prematurely-delivered babies. Immaturity of the innate immune components makes them extremely susceptible to infection. Recently, we isolated lung dendritic cell (DC)-precursor cells from preterm fetal baboons. The isolated cells were found to be defective in phagocytosing Escherichia coli under basal conditions. In this study, we investigated the effects of exogenously-added purified native lung surfactant protein (SP)-A and recombinant toll-like receptor (TLR)-4-MD2 proteins on phagocytic uptake and cytokine secreting ability of fetal baboon lung DC-precursor cells. The cells were pulsed with SP-A and/or TLR4-MD2 proteins and the phagocytic function was investigated by incubating the cells with fluorescent-labeled E. coli bioparticles and analyzed by spectrofluorometry. The amounts of TNF-α secreted in cell-free supernatants were measured by ELISA. Our results demonstrate that SP-A and TLR4-MD2 proteins, whether added alone or together, induce phagocytosis of E. coli (p<0.05). The SP-A does not affect TNF-α secretion, while the TLR4-MD2 protein induces TNF-α. However, simultaneous addition of SP-A with TLR4-MD2 protein reduces the TLR4-MD2-protein induced TNF-α to basal level. In conclusion, our results indicate that an exogenous administration of SP-A can potentially induce phagocytic activity and anti-inflammatory effect in preterm babies, and help control infection and inflammation.

Pulmonary vascular and alveolar development in preterm lambs chronically colonized with Ureaplasma parvum

Ureaplasma species, the most commonly isolated microorganisms in women with chorioamnionitis, are associated with preterm delivery. Chorioamnionitis increases the risk and severity of bronchopulmonary dysplasia and persistent pulmonary hypertension in newborns. It is not known whether the timing of exposure to inflammation in utero is an important contributor to the pathogenesis of bronchopulmonary dysplasia. We hypothesized that chronic inflammation would alter the pulmonary air space and vascular development after 70 days of exposure to infection. Pregnant ewes were given intra-amniotic injection of Ureaplasma parvum serovars 3 or 6 at low (2 x 10(4) cfu) or high doses (2 x 10(7) cfu) or media (controls) at 55 days gestational age. Fetuses were delivered at 125 days (term = 150 days). U. parvum was grown from the lungs of all exposed fetuses, and neutrophils and monocytes were increased in the air spaces. Lung mRNA expression of IL-1beta and IL-8, but not IL-6, was modestly increased in U. parvum-exposed fetuses. U. parvum exposure increased surfactant and improved lung gas volumes. The changes in lung inflammation and maturation were independent of serovar or dose. Exposure to U. parvum did not change multiple indices of air space or vascular development. Parenchymal elastin and collagen content were similar between groups. Expression of several endothelial proteins and pulmonary resistance arteriolar media thickness were also not different between groups. We conclude that chronic exposure to U. parvum does not cause sustained effects on air space or vascular development in premature lambs.

Surfactant protein-A enhances ureaplasmacidal activity in vitro

BACKGROUND

Persistent respiratory tract colonization with Ureaplasma spp. in preterm infants is a significant risk factor for the development of the chronic lung disorder, bronchopulmonary dysplasia (BPD). Surfactant protein-A (SP-A), a lung collectin critical for bacterial clearance and regulating inflammation, is deficient in the preterm lung. In an experimental Ureaplasma-pneumonia model, infected SP-A deficient mice exhibited delayed bacterial clearance and an exaggerated inflammatory response compared to infected wild-type mice. The objective was to analyze the role of SP-A in Ureaplasma clearance in vitro.

SUBJECTS AND METHODS

We analyzed SP-A binding to Ureaplasma isolates and SP-A-mediated ureaplasmal phagocytosis and killing by cultured RAW 264.7 macrophages.

RESULTS

Calcium-dependent SP-A binding was similar among Ureaplasma isolates tested. Pre-incubation of RAW 264.7 cells with SP-A (10-50 μg/ml) enhanced phagocytosis of fluorescein-isothiocyanate (FITC)-labeled Ureaplasma. Surfactant protein-A also increased ureaplasmacidal activity of RAW 264.7 cells by 2.1-fold over 4 h. Pre-incubation of RAW 264.7 cells with 10 μg/ml SP-A reduced lipopolysaccharide (LPS) (100 ng/ml) and Ureaplasma (10(6) color changing units/ml)-stimulated release of tumor necrosis factor-α (TNF-α) by 46% and 43%, respectively, but did not affect transforming growth factor β(1) (TGFβ(1)) release.

CONCLUSIONS

These in vitro data confirm that SP-A is important in host defense to perinatally-acquired Ureaplasma infection.