Involvement of endoplasmic reticulum and histone proteins in immunomodulation by TLR4-interacting SPA4 peptide against Escherichia coli.

Pulmonary host defense is critical for the control of lung infection and inflammation. An increased expression and activity of Toll-like receptor 4 (TLR4) induce phagocytic uptake/clearance and inflammation against Gram-negative bacteria. In this study, we addressed the mechanistic aspect of the immunomodulatory activity of the TLR4-interacting SPA4 peptide (amino acid sequence GDFRYSDGTPVNYTNWYRGE) against Escherichia coli. Binding of the SPA4 peptide to bacteria and direct anti-bacterial effects were investigated using flow cytometric, microscopic, and bacteriological methods. The bacterial uptake and inflammatory cytokine response were studied in dendritic cells expressing endogenous basal level of TLR4 or overexpressing TLR4. The subcellular distribution and co-localization of TLR4 and bacteria were investigated by immunocytochemistry. Furthermore, we studied the cellular expression and co-localization of endoplasmic reticulum (ER) molecules (calnexin and ER membrane protein complex subunit 1; EMC1) with lysosomal-associated membrane protein 1 (LAMP1) in cells infected with E. coli and treated with the SPA4 peptide. Simultaneously, the expression of histone H2A protein was quantitated by immunoblotting. Our results demonstrate no binding or direct killing of the bacteria by SPA4 peptide. Instead, it induces the uptake and localization of E. coli in the phagolysosomes for lysis and simultaneously suppresses the secreted levels of TNF-α. Overexpression of TLR4 further augments the pro-phagocytic and anti-inflammatory activity of SPA4 peptide. A time-dependent change in subcellular distribution of TLR4 and an increased co-localization of TLR4 with E. coli in SPA4 peptide-treated cells suggest an enhanced recognition and internalization of bacteria in conjugation with TLR4. Furthermore, an increased co-localization of calnexin and EMC1 with LAMP1 indicates the involvement of ER in pro-phagocytic activity of SPA4 peptide. Simultaneous reduction in secreted amounts of TNF-α coincides with suppressed histone H2A protein expression in the SPA4 peptide-treated cells. These results provide initial insights into the plausible role of ER and histones in the TLR4-immunomodulatory activity of SPA4 peptide against Gram-negative bacteria.

Stability and structure-activity relationship of the SPA4 peptide under ambient and stressed conditions of lung injury.

Lung inflammation and injuries are major health problems. The SPA4 peptide (amino acid sequence GDFRYSDGTPVNYTNWYRGE) binds to Toll-like receptor-4 and exerts anti-inflammatory activity. In this study, we have determined the stability of the structure and structure-activity relationship of the SPA4 peptide under ambient and stressed conditions of lung injury. The SPA4 peptide was maintained at different pH and temperatures, in solutions of different ionic strengths, and simulated lung fluids. The primary and secondary structure of the SPA4 peptide was determined by ultraviolet-visible (UV-VIS) and circular dichroism (CD) spectroscopy. The activity of the SPA4 peptide was determined by measurement of secreted levels of chemokine C-X-C motif ligand 1/keratinocyte-derived chemokine (CXCL1/KC) and lactate by primary mouse lung epithelial cells against lipopolysaccharide (LPS) stimuli. Our results demonstrate the stability of the structure of the SPA4 peptide at room temperature and 4 °C over 10 days. The original UV-VIS spectra of the SPA4 peptide followed a typical pattern when incubated in solutions of pH 5.7, 7.0, and 8.0 at different temperatures, simulated lung fluids, and most of the chemical components. Slight shifts in the absorbance peaks, derivative values, and vibrational fine structures were noted in the fourth-derivative spectra of the SPA4 peptide under some conditions. An increased level of lactate is the hallmark of lung injury. The SPA4 peptide on its own and in the presence of lactate exerts anti-inflammatory activity. The primary and secondary structure and the activity of the SPA4 peptide remain intact when pre-incubated in 2 mM sodium lactate solution. The results provide important insights about the stability and structure-activity relationship of the SPA4 peptide.

Effects of SPA4 peptide on lipopolysaccharide-disrupted lung epithelial barrier, injury, and function in a human cell system and mouse model of lung injury.

Disrupted epithelial barrier, fluid accumulation, inflammation, and compromised physiology are hallmarks of lung injury. Here we investigated the structural stability of the Toll-like receptor-4 (TLR4)-interacting SPA4 peptide, its effect on Pseudomonas aeruginosa lipopolysaccharide (LPS)-disrupted epithelial barrier in a human cell system, and lung injury markers in a mouse model of LPS-induced lung inflammation. The structural properties of SPA4 peptide were investigated using circular dichroism and UV-VIS spectroscopy. The transepithelial electrical resistance (TEER), an indicator of barrier function, was measured after the cells were challenged with 1 µg/ml LPS and treated with 10 or 100 µM SPA4 peptide. The expression and localization of tight junction proteins were studied by immunoblotting and immunocytochemistry, respectively. Mice were intratracheally challenged with 5 µg LPS per g body weight and treated with 50 µg SPA4 peptide. The lung wet/dry weight ratios or edema, surfactant protein-D (SP-D) levels in serum, lung function, tissue injury, body weights, and temperature, and survival were determined as study parameters. The spectroscopy results demonstrated that the structure was maintained among different batches of SPA4 peptide throughout the study. Treatment with 100 µM SPA4 peptide restored the LPS-disrupted epithelial barrier, which correlated with the localization pattern of Zonula Occludens (ZO)-1 and occludin proteins. Correspondingly, SPA4 peptide treatment helped suppress the lung edema and levels of serum SP-D, improved some of the lung function parameters, and reduced the mortality risk against LPS challenge. Our results suggest that the anti-inflammatory activity of the SPA4 peptide facilitates the resolution of lung pathology.

Tight Junctions, the Epithelial Barrier, and Toll-like Receptor-4 During Lung Injury.

Lung epithelium is constantly exposed to the environment and is critically important for the orchestration of initial responses to infectious organisms, toxins, and allergic stimuli, and maintenance of normal gaseous exchange and pulmonary function. The integrity of lung epithelium, fluid balance, and transport of molecules is dictated by the tight junctions (TJs). The TJs are formed between adjacent cells. We have focused on the topic of the TJ structure and function in lung epithelial cells. This review includes a summary of the last twenty years of literature reports published on the disrupted TJs and epithelial barrier in various lung conditions and expression and regulation of specific TJ proteins against pathogenic stimuli. We discuss the molecular signaling and crosstalk among signaling pathways that control the TJ structure and function. The Toll-like receptor-4 (TLR4) recognizes the pathogen- and damage-associated molecular patterns released during lung injury and inflammation and coordinates cellular responses. The molecular aspects of TLR4 signaling in the context of TJs or the epithelial barrier are not fully known. We describe the current knowledge and possible networking of the TLR4-signaling with cellular and molecular mechanisms of TJs, lung epithelial barrier function, and resistance to treatment strategies.

Analysis of influenza virus-induced perturbation in autophagic flux and its modulation during Vitamin D3 mediated anti-apoptotic signaling.

Vitamin D3/Calcitriol supplementation in humans is associated with reduced incidence and severity during influenza A virus (IAV) infection. Apoptosis in response to IAV infection is a major contributor to host cell death and tissue damage; however, its modulation by Vitamin D3 remains unclear. In this study, we demonstrate the efficacy of Vitamin D3 in preventing apoptosis induction by pandemic influenza A (H1N1)pdm09 virus in human alveolar cells (A549). Human alveolar epithelial cell line A549 was used to assess the cytotoxic effects of IAV infection. Immunoblotting and fluorescence microscopy were used to study apoptosis and autophagy. The results of the present study demonstrate that IAV induces apoptosis by subversion of host autophagy via down-regulating components of autophagic machinery involved in autophagosome-lysosome fusion and lysosomal activity. Vitamin D3 restores the autophagic flux inhibited by IAV by upregulating the expression of Syntaxin-17 (STX17) and V-type proton ATPase subunit (ATP6V0A2) thereby causing a concomitant decrease in cellular apoptosis via a Vitamin D3 receptor (VDR) dependent mechanism. The present study suggests that Vitamin D3 is a potentially useful agent for limiting IAV-induced cellular injury via its pro-autophagic action.

Time-restricted feeding reduces high-fat diet associated placental inflammation and limits adverse effects on fetal organ development.

Maternal nutrition has become a major public health concern over recent years and is a known predictor of adverse long-term metabolic derangement in offspring. Time-restricted feeding (TRF), wherein food consumption is restricted to the metabolically active phase of the day, is a dietary approach that improves metabolic parameters when consuming a high-fat diet (HFD). Here, we tested whether TRF could reduce maternal HFD associated inflammation and thereby mitigate defects in fetal organ developmental. Female rats were kept on following three dietary regimens; Ad libitum normal chow diet (NCD-AL), Ad libitum HFD (HFD-AL) and Time-restricted fed HFD (HFD-TRF) from 5 months prior to mating and continued throughout pregnancy. Rat dams were sacrificed at embryonic day 18.5 (ED18.5) and placental tissues from these rats were processed for the analysis of cellular apoptosis, inflammatory cytokines (TNFα and IL-6), oxidative stress, endoplasmic reticulum (ER) stress and autophagy. Furthermore, fetal hepatic triglyceride (TG) content and fetal lung maturation were assessed at ED18.5. Biochemical analysis revealed that HFD-TRF rat had significantly lower serum TG levels and body weight compared to HFD-AL rats. Additionally, TRF significantly blocked HFD-induced placental apoptosis and inflammation via minimizing cellular stress, and restoring autophagic flux. In addition, fetal hepatosteatosis and delayed fetal lung maturation induced by HFD was significantly ameliorated in HFD-TRF compared to HFD-AL. Collectively, our results suggest that reducing placental inflammation via TRF could prevent adverse fetal metabolic outcomes in pregnancies complicated by maternal obesity.

Mechanisms involved in epigenetic down-regulation of Gfap under maternal hypothyroidism.

Thyroid hormones (TH) of maternal origin are crucial regulator of mammalian brain development during embryonic period. Although maternal TH deficiency during the critical periods of embryonic neo-cortical development often results in irreversible clinical outcomes, the fundamental basis of these abnormalities at a molecular level is still obscure. One of the key developmental process affected by maternal TH insufficiency is the delay in astrocyte maturation. Glial fibrillary acidic protein (Gfap) is a predominant cell marker of mature astrocyte and is regulated by TH status. Inspite, of being a TH responsive gene during neocortical development the mechanistic basis of Gfap transcriptional regulation by TH has remained elusive. In this study using rat model of maternal hypothyroidism, we provide evidence for an epigenetic silencing of Gfap under TH insufficiency and its recovery upon TH supplementation. Our results demonstrate increased DNA methylation coupled with decreased histone acetylation at the Gfap promoter leading to suppression of Gfap expression under maternal hypothyroidism. In concordance, we also observed a significant increase in histone deacetylase (HDAC) activity in neocortex of TH deficient embryos. Collectively, these results provide novel insight into the role of TH regulated epigenetic mechanisms, including DNA methylation, and histone modifications, which are critically important in mediating precise temporal neural gene regulation.

Calcitriol [1, 25[OH]2 D3] pre- and post-treatment suppresses inflammatory response to influenza A (H1N1) infection in human lung A549 epithelial cells.

PURPOSE: Influenza viruses infect airway epithelial cells, causing respiratory distress. Immune defense is maintained by chemokine/cytokine secretions from airway epithelial cells. While moderate inflammatory response protects from ill effects, hyper-inflammatory response promotes the pathogenesis. High circulating levels of vitamin D are known to mitigate effects of infectious diseases, including respiratory infectious diseases. The question whether and how vitamin D treatment pre-/post-viral exposure modulates inflammatory response is not clear. The present study was undertaken to understand autophagy/apoptosis balance and chemokine/cytokine response to influenza A (H1N1) infection by pre- and post-1, 25-dihydroxyvitamin D3 (1,25[OH]2 D3)[calcitriol] treatment of human lung A549 epithelial cells. METHODS: Influenza A (H1N1) virus was propagated in A549 cell line, titrated using hemagglutination assay, and was used to assess effect of calcitriol. After confirming that 100 nM of calcitriol fails to clear virus, A549 cells were either pre-treated (16 h) with 100 nM or post-treated with 30 nM of 1,25[OH]2 D3 of virus inoculation (1 h). Cells after incubation at 37 °C under 5 % CO2 for 48 h were collected and subjected to RNA and protein extraction. Measurements of viability, influenza M protein, and molecular parameters of cell death and inflammatory response were performed. RESULTS: We report that treatment of these cells with 100/30 nM of 1,25[OH]2 D3 prior to/or post-H1N1 exposure does not affect viral clearance but significantly reduces autophagy and restores increased apoptosis seen on H1N1 infection back to its constitutive level. However, it significantly decreases the levels of H1N1-induced TNF-α (tumor necrosis factor-alpha), IFN-ß (interferon-beta), and IFN-stimulated gene-15 (ISG15). 1,25[OH]2 D3 treatment prior to/or post-H1N1 infection significantly down-regulates IL-8 as well as IL-6 RNA levels. These results demonstrate that calcitriol treatment suppresses the H1N1-induced transcription of the chemokines RANTES and IL-8 in epithelial cells. CONCLUSION: The findings provide support for the initiation of vitamin D supplementation program to VDD populations in reducing the severity of influenza.