Dietary tannic acid attenuates elastase-induced pulmonary inflammation and emphysema in mice

Emphysema is one of the major components of chronic obstructive pulmonary disease (COPD), which is characterised by the destruction and enlargement of air spaces, leading to airflow limitation and dyspnoea, finally progressing to oxygen dependency. The alveolar wall destruction is due to chronic inflammation, oxidative stress, apoptosis, and proteinase/anti-proteinase imbalance. So far, there has been no effective therapy for patients with COPD. We evaluated the therapeutic efficacy of tannic acid (TA), a naturally occurring plant-derived polyphenol in the murine emphysema model. In C57BL/6 J mice, we established emphysema by intratracheal instillation of elastase (EL). Then, mice were treated with TA and evaluated 1 and 21 days post-EL instillation. After 24 h, TA treatment significantly reduced EL-induced histopathological alterations, infiltrating leukocytes, and gene expression of markers of inflammation and apoptosis. Similarly, after 21 days, TA treatment suppressed the mean linear intercept, gene expression of proteinases, and increased elastic fiber contents in the lungs when compared to the EL-alone group. Furthermore, EL induced the activation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor kappa light chain enhancer of activated B cells (NF-kB) p65 pathways in the lungs was suppressed by TA treatment. In summary, TA has the potential to mitigate EL-induced inflammation, apoptosis, proteinase/anti-proteinase imbalance, and subsequent emphysema in mice.

Bacterial Outer Membrane Vesicles Promote Lung Inflammatory Responses and Macrophage Activation via Multi-Signaling Pathways

Emerging evidence suggests that Gram-negative bacteria release bacterial outer membrane vesicles (OMVs) and that these play an important role in the pathogenesis of bacterial infection-mediated inflammatory responses and organ damage. Despite the fact that scattered reports have shown that OMVs released from Gram-negative bacteria may function via the TLR2/4-signaling pathway or induce pyroptosis in macrophages, our study reveals a more complex role of OMVs in the development of inflammatory lung responses and macrophage pro-inflammatory activation. We first confirmed that various types of Gram-negative bacteria release similar OMVs which prompt pro-inflammatory activation in both bone marrow-derived macrophages and lung alveolar macrophages. We further demonstrated that mice treated with OMVs via intratracheal instillation developed significant inflammatory lung responses. Using mouse inflammation and autoimmune arrays, we identified multiple altered cytokine/chemokines in both bone marrow-derived macrophages and alveolar macrophages, suggesting that OMVs have a broader spectrum of function compared to LPS. Using TLR4 knock-out cells, we found that OMVs exert more robust effects on activating macrophages compared to LPS. We next examined multiple signaling pathways, including not only cell surface antigens, but also intracellular receptors. Our results confirmed that bacterial OMVs trigger both surface protein-mediated signaling and intracellular signaling pathways, such as the S100-A8 protein-mediated pathway. In summary, our studies confirm that bacterial OMVs strongly induced macrophage pro-inflammatory activation and inflammatory lung responses via multi-signaling pathways. Bacterial OMVs should be viewed as a repertoire of pathogen-associated molecular patterns (PAMPs), exerting more robust effects than Gram-negative bacteria-derived LPS.

Caveolin-1 regulates OMV-induced macrophage pro-inflammatory activation and multiple Toll-like receptors

Macrophages (MФ), the primary cell of the innate immune system, serves as the first line of defense. During bacterial infection, Gram-negative (G-) bacteria release nanosized outer membrane vesicles (OMVs), facilitating the crosstalk between the microbe and the host. The underlying mechanisms by which OMVs induced pro-inflammatory (M1) activation are still unknown. Our study shows that OMVs caused M1 activation via modulating various toll-like receptor (TLR) expressions as they contain LPS, LTA, bacterial DNAs, and flagellins. Also, we found that caveolin-1 (cav-1), a 21-kDa scaffolding protein of caveolae and lipid rafts, plays a significant role in OMV-induced pro-inflammatory response in regulating various TLR signaling pathways. Specifically, cav-1 deletion increased the expression of OMV-induced TLRs, pro-inflammatory cytokine secretions (TNF-α and IL-1β), and the reactive oxygen species (ROS) production in MФs. Further, we examined the interaction between Cav-1 and TLR4 by immunoprecipitation, colocalization, and computational models, providing future direction to explore the role of cav-1 in OMV-induced other TLR signaling. Altogether, Cav-1 is a key regulator in OMV-induced multiple TLRs response. This study promotes future research to develop drugs by targeting the specific motif of cav-1 or TLRs against bacterial infection and macrophage-mediated inflammation.

Impact of Storage Conditions on EV Integrity/Surface Markers and Cargos

Extracellular vesicles (EVs) are small biological particles released into biofluids by every cell. Based on their size, they are classified into small EVs (<100 nm or <200 nm) and medium or large EVs (>200 nm). In recent years, EVs have garnered interest for their potential medical applications, including disease diagnosis, cell-based biotherapies, targeted drug delivery systems, and others. Currently, the long-term and short-term storage temperatures for biofluids and EVs are −80 °C and 4 °C, respectively. The storage capacity of EVs can depend on their number, size, function, temperature, duration, and freeze−thaw cycles. While these parameters are increasingly studied, the effects of preservation and storage conditions of EVs on their integrity remain to be understood. Knowledge gaps in these areas may ultimately impede the widespread applicability of EVs. Therefore, this review summarizes the current knowledge on the effect of storage conditions on EVs and their stability and critically explores prospective ways for improving long-term storage conditions to ensure EV stability.

Direct Detection of Extracellular Vesicle miRNAs Using a Single-Step RT-qPCR Assay

Extracellular vesicles (EVs) are biological carriers, and EV-associated miRNAs (EV-miRNAs) are considered as a novel biomarker in multiple diseases. Currently, the column-based purification method is used to purify miRNAs from EVs. However, this method of purification is complex, time-consuming, and expensive. Therefore, a simple and cost-effective single-step quantitative reverse transcription-polymerase chain reaction (RT-qPCR) method is required to detect the expression of EV-miRNAs. This chapter describes a protocol for directly analyzing the EV-miRNAs expression from mouse bronchoalveolar lavage fluid (BALF) and serum without going for an RNA isolation and purification step from EVs. It is an efficient method in several terms such as cost-wise, time, low expertise, and accuracy in results. This method may be helpful in diagnostic blood tests used in medical centers or research laboratories.

An overview on the role of plant-derived tannins for the treatment of lung cancer

Lung cancer is the leading cause of cancer-related death globally. Despite many advanced approaches to treat cancer, they are often ineffective due to resistance to classical anti-cancer drugs and distant metastases. Currently, alternative medicinal agents derived from plants are the major interest due to high bioavailability and fewer adverse effects. Tannins are polyphenolic compounds existing as specialized products in a wide variety of vegetables, fruits, and nuts. Many tannins have been found to possess protective properties, such as anti-inflammatory, anti-fibrotic, anti-microbial, anti-diabetic, and so on. This review aims to summarize the current knowledge addressing the anti-cancer effects of dietary tannins and their underlying molecular mechanisms. In vivo and in vitro studies provide evidences that anti-cancer effects of various tannins are predominantly mediated through negative regulation of transcription factors, growth factors, receptor kinases, and many oncogenic molecules. In addition, we also discussed the absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of tannins, clinical trial results as well as our perspective on future research with tannins.

Anti-asthmatic effects of tannic acid from Chinese natural gall nuts in a mouse model of allergic asthma

Asthma is a chronic inflammatory disease of the airways, which is characterized by infiltration of inflammatory cells, airway hyperresponsiveness (AHR), and airway remodeling. This study aimed to explore the role and mechanism of tannic acid (TA), a naturally occurring plant-derived polyphenol, in murine asthma model. BALB/c mice were given ovalbumin (OVA) to establish an allergic asthma model. The results revealed that TA treatment significantly decreased OVA-induced AHR, inflammatory cells infiltration, and the expression of various inflammatory mediators (Th2 and Th1 cytokines, eotaxin, and total IgE). Additionally, TA treatment also attenuated increases in mucins (Muc5ac and Muc5b) expression, mucus production in airway goblet cells, mast cells infiltration, and airway remodeling induced by OVA exposure. Furthermore, OVA-induced NF-κB (nuclear factor- kappa B) activation and cell adhesion molecules expression in the lungs was suppressed by TA treatment. In conclusion, TA effectively attenuated AHR, inflammatory response, and airway remodeling in OVA-challenged asthmatic mice. Therefore, TA may be a potential therapeutic option against allergic asthma in clinical settings.

Therapeutic potential of plant-derived tannins in non-malignant respiratory diseases

Respiratory diseases are the major cause of human illness and death around the world. Despite advances in detection and treatment, very few classes of safe and effective therapy have been introduced to date. At present, phytochemicals are getting more attention because of their diverse beneficial activities and minimal toxicity. Tannins are polyphenolic secondary metabolites with high molecular weights, which are naturally present in a wide variety of fruits, vegetables, cereals, and leguminous seeds. Many tannins are endowed with well-recognized protective properties, such as anti-cancer, anti-microbial, anti-oxidant, anti-hyperglycemic, and many others. This review summarizes a large body of experimental evidence implicating that tannins are helpful in tackling a wide range of non-malignant respiratory diseases including acute lung injury (ALI), pulmonary fibrosis, asthma, pulmonary hypertension, and chronic obstructive pulmonary disease (COPD). Mechanistic pathways by which various classes of tannins execute their beneficial effects are discussed. In addition, clinical trials and our perspective on future research with tannins are also reviewed.

Tannic acid alleviates experimental pulmonary fibrosis in mice by inhibiting inflammatory response and fibrotic process

Pulmonary fibrosis (PF) is a chronic and irreversible scarring disease in the lung with limited treatment options. Therefore, it is critical to identify new therapeutic options. This study was undertaken to identify the effects of tannic acid (TA), a naturally occurring dietary polyphenol, in a mouse model of PF. Bleomycin (BLM) was intratracheally administered to induce PF. Administration of TA significantly reduced BLM-induced histological alterations, inflammatory cell infiltration and the levels of various inflammatory mediators (nitric oxide, leukotriene B₄ and cytokines). Additionally, treatment with TA also impaired BLM-mediated increases in pro-fibrotic (transforming growth factor-β1) and fibrotic markers (alpha-smooth muscle actin, vimentin, collagen 1 alpha and fibronectin) expression. Further investigation indicated that BLM-induced phosphorylation of Erk1/2 (extracellular signal-regulated kinases 1 and 2) in lungs was suppressed by TA treatment. Findings of this study suggest that TA has the potential to mitigate PF through inhibiting the inflammatory response and fibrotic process in lungs and that TA might be useful for the treatment of PF in clinical practice.

Enhanced Photoelectrochemical Water Splitting Behaviour of Tuned Band Gap CdSe QDs Sensitized LaB₆

We report the fabrication of tuned band gap quantum dots sensitized LaB₆ hybrid nanostructures and their application as a photoanode for photoelectrochemical water splitting. The lanthanum hexaboride (LaB₆) obtained by molten salt electrolysis method is sensitized with different sized CdSe quantum dots, which form a multiple-level hierarchical heterostructure and such design enhance the light absorption and charge carrier separation, which in turn showed higher photocurrent density compared to that of pristine LaB₆. When LaB₆ is sensitized with CdSe quantum dots of different band gaps, which have the absorption in the green and red (530 and 605 nm) regions in visible light, developed a ten times higher photocurrent density (11.0 mA cm(−2)) compared to that of pristine LaB6 (0.5 mA cm(−2) at 0.75 V vs. Ag/AgCl) in 1 M Na₂S electrolyte under illumination. These results prove that the tuned band gap quantum dots sensitized LaB₆ heterostructures are an ideal candidate for a photoanode in solar water splitting applications.