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Mucus plugs occlude airways to obstruct airflow in asthma. Studies in patients and in mouse models show that mucus plugs occur in the context of type 2 inflammation, and studies in human airway epithelial cells (HAECs) show that IL-13-activated cells generate pathologic mucus independently of immune cells. To determine how HAECs autonomously generate pathologic mucus, we used a magnetic microwire rheometer to characterize the viscoelastic properties of mucus secreted under varying conditions. We found that normal HAEC mucus exhibited viscoelastic liquid behavior and that mucus secreted by IL-13-activated HAECs exhibited solid-like behavior caused by mucin cross-linking. In addition, IL-13-activated HAECs shows increased peroxidase activity in apical secretions, and an overlaid thiolated polymer (thiomer) solution shows an increase in solid behavior that was prevented by peroxidase inhibition. Furthermore, gene expression for thyroid peroxidase (TPO), but not lactoperoxidase (LPO), was increased in IL-13-activated HAECs and both TPO and LPO catalyze the formation of oxidant acids that cross-link thiomer solutions. Finally, gene expression for TPO in airway epithelial brushings was increased in patients with asthma with high airway mucus plug scores. Together, our results show that IL-13-activated HAECs autonomously generated pathologic mucus via peroxidase-mediated cross-linking of mucin polymers.

Chromium (Cr) is a micromineral that is involved in the metabolism of carbohydrates, lipids, ammonia, and nucleic acids; thus, its supplementation can influence the nutritional status of ruminants, and consequently, colostrum profile, since this secretion depends on products secreted by the mammary gland and elements of the maternal bloodstream. The present study investigated the influence of supplementation with Cr bound to organic molecule on the nutritional, immune, and antioxidant quality of ewe colostrum. Thirty-two multiparous Santa Ines ewes (55.3 ± 8.00 kg body weight) were randomly assigned into four groups: T1 (0.0 mg of chromium picolinate (CrPic) supplementation per ewe, n = 8), T2 (0.15 mg of CrPic per ewe, n = 9), T3 (0.30 mg of CrPic per ewe, n = 7), and T4 (0.45 mg of CrPic per ewe, n = 8). Supplementation was supplied during the breeding season, pregnancy, and lactation. Shortly after calving, the first milking colostrum was collected to determine its chemical composition, activity of lysozyme, lactoperoxidase, ceruloplasmin, catalase, glutathione peroxidase, and oxygen radical absorbance capacity. The results show that lactoperoxidase activity decreased with CrPic supplementation (P < 0.01), revealing that this micromineral reduces an important component of defense mechanism in the body. Therefore, the results of this work show that supplementation with chromium picolinate influences colostrum quality.

Lactoperoxidase (LPO) (E.C. 1.11.1.7) is a member of the superfamily of mammalian heme peroxidases that is isolated from milk, and it is the first enzyme announced to be found in milk. In addition to milk, LPO is also found in saliva, tears, and airways (airway goblet cells and submucosal glands). It contributes significantly to the self-defense of the mammal body. It catalyzes the oxidation of certain molecules such as thiocyanate (SCN−), I−, and Br− in the presence of hydrogen peroxide (H2O2). This reaction leads to the formation of antimicrobial products that have a great antimicrobial spectrum, including antibacterial, antiviral, and antifungal activity, especially hypothiocyanite (OSCN−) and hypoiodite (OI−), which are coming into prominence via their high antimicrobial activity. The lactoperoxidase system (LPOS) is the system consisting of LPO, H2O2, and SCN−. LPO has a great potential to be used in various areas such as preservation and shelf-life elongation of milk; milk products; meat; meat products; plants, including fruits and vegetables; and oral care, diagnosis, immunomodulation, and treatment of nephrotoxicity. The LPO gene, along with LPO itself, is important for animals. In the absence of the LPO gene, there is an increase in the frequency of diverse diseases, including inflammation, tumor formation, and obesity. In this review, we mentioned general information about the enzyme LPO and its potential. Chemical properties and other features of other components of the LPOS, H2O2, and SCN− were also touched on the review. To offer readers a comprehensive understanding of the enzyme’s biological significance and research progress over time, both recent and older studies have been used together. Lastly, we discussed potential applications of LPO in different areas and left future remarks in the light of recent studies.

We calculated the internal energies (ΔE) for the breakdowns of HOI, HOBr and HOCl for the first time using the principles of molecular orbital theory. The release of atomic oxygen (ATOX) from all three molecules was estimated being from 43.3 (HOCl) to 64.1 (HOI) kcal mol −1 . These internal energies are much less than the inputs required for hydroxyl anion and cationic halide productions which range from 315.0 (HOI) to 381.1 (HOCl) kcal mol −1 . These results answer the puzzle concerning the fates of the products from the halide oxidations by peroxidases. The active species were thought to be the hypohalous acids themselves or the cationic halide but ATOX has never been considered. ATOX is an electron pair accepter and an incredibly destructive species which is observed only in high energy systems. Our results have implications for mammalian immunology because the final steps for microbe disposal in mammals are destructions by one of three peroxidases; lactoperoxidase (LPO), eosinophil peroxidase (EPO) or myeloperoxidase (MPO). These all utilize H 2 O 2 and one of the halide ions; I − (LPO), Br − (EPO) or Cl − (MPO) to biosynthesize HOI, HOBr and HOCl, respectively. The low energies required for ATOX liberation from hypohalous acids explains why these are the preferred products of important mammalian peroxidases. For example, LPO is an integral enzyme of mammalian airway defence and enhanced nutritional iodine intake encourages liberal biosynthesis of HOI, which is immediately lethal to all microbes tested in vitro and in vivo.

The lactoperoxidase (LPO) system shows promise in the prevention of dental caries, a common chronic disease. This system has antimicrobial properties and is part of the non-specific antimicrobial immune system. Understanding the efficacy of the LPO system in the fight against biofilms could provide information on alternative strategies for the prevention and treatment of caries. In this study, the enzymatic system was modified using four different (pseudo)halide substrates (thiocyanate, thiocyanate-iodide mixture, selenocyanate, and iodide). The study evaluated the metabolic effects of applying such modifications to Streptococcus mutans; in particular: (1) biofilm formation, (2) synthesis of insoluble polysaccharides, (3) lactate synthesis, (4) glucose and sucrose consumption, (5) intracellular NAD+ and NADH concentrations, and (6) transmembrane glucose transport efficiency (PTS activity). The results showed that the LPO–iodide system had the strongest inhibitory effect on biofilm growth and lactate synthesis (complete inhibition). This was associated with an increase in the NAD+/NADH ratio and an inhibition of glucose PTS activity. The LPO–selenocyanate system showed a moderate inhibitory effect on biofilm biomass growth and lactate synthesis. The other systems showed relatively small inhibition of lactate synthesis and glucose PTS but no effect on the growth of biofilm biomass. This study provides a basis for further research on the use of alternative substrates with the LPO system, particularly the LPO–iodide system, in the prevention and control of biofilm-related diseases.

Numerous studies signify that diets rich in phytochemicals offer many beneficial functions specifically during pathologic conditions, yet their effects are often not uniform due to inter-individual variation. The host indigenous gut microbiota and their modifications of dietary phytochemicals have emerged as factors that greatly influence the efficacy of phytoceutical-based intervention. Here, we investigated the biological activities of one such active microbial metabolite, Urolithin A (UA or 3,8-dihydroxybenzo[c]chromen-6-one), which is derived from the ellagic acid (EA). Our study demonstrates that UA potently inhibits heme peroxidases i.e. myeloperoxidase (MPO) and lactoperoxidase (LPO) when compared to the parent compound EA. In addition, chrome azurol S (CAS) assay suggests that EA, but not UA, is capable of binding to Fe3+, due to its catechol-like structure, although its modest heme peroxidase inhibitory activity is abrogated upon Fe3+-binding. Interestingly, UA-mediated MPO and LPO inhibition can be prevented by innate immune protein human NGAL or its murine ortholog lipocalin 2 (Lcn2), implying the complex nature of host innate immunity-microbiota interactions. Spectral analysis indicates that UA inhibits heme peroxidase-catalyzed reaction by reverting the peroxidase back to its inactive native state. In support of these in vitro results, UA significantly reduced phorbol myristate acetate (PMA)-induced superoxide generation in neutrophils, however, EA failed to block the superoxide generation. Treatment with UA significantly reduced PMA-induced mouse ear edema and MPO activity compared to EA treated mice. Collectively, our results demonstrate that microbiota-mediated conversion of EA to UA is advantageous to both host and microbiota i.e. UA-mediated inhibition of pro-oxidant enzymes reduce tissue inflammation, mitigate non-specific killing of gut bacteria, and abrogate iron-binding property of EA, thus providing a competitive edge to the microbiota in acquiring limiting nutrient iron and thrive in the gut.

It is imperative to explore new biocompatible drugs with low toxicity for use in medicinal fields such as fighting tumors. Bovine lactoperoxidase (BLPO) stems from the most important enzymes in the bovine whey that provide a proper pattern for nano-formulation with nanomaterials. LPO is a suitable protein to be coated or adsorbed to alginate modified graphene oxide (GO-SA), which forms the modified GO-SA-LPO hybrid structure. This novel combination provides LPO stability with strong anticancer effects and boosts immunity response. The characterization results obtained from different techniques confirmed a successful LPO adsorption on the GO-SA composite surface. Moreover, nano-formulation of LPO with GO-SA composite exhibited a reduction in its size and overall charge. In addition, the experimental results showed greater LPO activity stability in the modified GO-SA-LPO nanocombination than free LPO after storage for 10 weeks at 4 °C. The in vitro study, a crucial step in the validation of our approach, demonstrated that the modified GO-SA-LPO nanocombination showed a potent anticancer selectivity toward colon cancer cell lines more than GO-SA composite or free form of LPO, which enhanced in a dose-dependent manner with high safety manner against normal cells. The apoptotic effect of this novel nanocombination was confirmed by the greatest variations in the expression of both well-known apoptosis genes (p53 and Bcl-2), severe changes in the cellular morphology, DNA fragmentation, and nuclear staining with fluorescence yellow and orange of the target cancer cells. Also, this superior efficacy of the modified GO-SA-LPO nanocombination was induced by suppressing some pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin (IL-6), and necrosis factor-kappa B (NF-ĸB). Our observations presented that the modified nanocombination of LPO may offer a novel remedy for treating colon tumors via induced apoptosis pathway, inflammation reduction, and immune response improvement.

The NOX/DUOX family of NADPH oxidases are transmembrane proteins generating reactive oxygen species as their primary enzymatic products. NADPH oxidase (NOX) 1–5 and Dual oxidase (DUOX) 1 and 2 are members of this family. These enzymes have several biological functions including immune defense, hormone biosynthesis, fertilization, cell proliferation and differentiation, extracellular matrix formation and vascular regulation. They are found in a variety of tissues such as the airways, salivary glands, colon, thyroid gland and lymphoid organs. The discovery of NADPH oxidases has drastically transformed our view of the biology of reactive oxygen species and oxidative stress. Roles of several isoforms including DUOX1 and DUOX2 in host innate immune defense have been implicated and are still being uncovered. DUOX enzymes highly expressed in the respiratory and salivary gland epithelium have been proposed as the major sources of hydrogen peroxide supporting mucosal oxidative antimicrobial defenses. In this review, we shortly present data on DUOX discovery, structure and function, and provide a detailed, up-to-date summary of discoveries regarding antibacterial, antiviral, antifungal, and antiparasitic functions of DUOX enzymes. We also present all the literature describing the immune functions of lactoperoxidase, an enzyme working in partnership with DUOX to produce antimicrobial substances.

Intestinal barrier immunity is essential for controlling gut microbiota without eliciting harmful immune responses, while its defect contributes to the breakdown of intestinal homeostasis and colitis development. Chemerin, which is abundantly expressed in barrier tissues, has been demonstrated to regulate tissue inflammation via CMKLR1, its functional receptor. Several studies have reported the association between increased expression of chemerin–CMKLR1 and disease severity and immunotherapy resistance in inflammatory bowel disease (IBD) patients. However, the pathophysiological role of endogenous chemerin–CMKLR1 signaling in intestinal homeostasis remains elusive. We herein demonstrated that deficiency of chemerin or intestinal epithelial cell (IEC)-specific CMKLR1 conferred high susceptibility to microbiota-driven neutrophilic colon inflammation and subsequent tumorigenesis in mice following epithelial injury. Unexpectedly, we found that lack of chemerin–CMKLR1 signaling specifically reduced expression of lactoperoxidase (LPO), a peroxidase that is predominantly expressed in colonic ECs and utilizes H₂O₂ to oxidize thiocyanates to the antibiotic compound, thereby leading to the outgrowth and mucosal invasion of gram-negative bacteria and dysregulated CXCL1/2-mediated neutrophilia. Importantly, decreased LPO expression was causally linked to aggravated microbiota-driven colitis and associated tumorigenesis, as LPO supplementation could completely rescue such phenotypes in mice deficient in epithelial chemerin–CMKLR1 signaling. Moreover, epithelial chemerin–CMKLR1 signaling is necessary for early host defense against bacterial infection in an LPO-dependent manner. Collectively, our study reveals that the chemerin–Cmklr1−/−LPO axis represents an unrecognized immune mechanism that potentiates epithelial antimicrobial defense and restricts harmful colonic neutrophilia and suggests that LPO supplementation may be beneficial for microbiota dysbiosis in IBD patients with a defective innate antimicrobialmechanism.

Dual oxidase 1 (DUOX1) is an NADPH oxidase that is highly expressed in respiratory epithelial cells and produces H₂O₂ in the airway lumen. While a line of prior in vitro observations suggested that DUOX1 works in partnership with an airway peroxidase, lactoperoxidase (LPO), to produce antimicrobial hypothiocyanite (OSCN⁻) in the airways, the in vivo role of DUOX1 in mammalian organisms has remained unproven to date. Here, we show that Duox1 promotes antiviral innate immunity in vivo. Upon influenza airway challenge, Duox1 −/− mice have enhanced mortality, morbidity, and impaired lung viral clearance. Duox1 increases the airway levels of several cytokines (IL-1β, IL-2, CCL1, CCL3, CCL11, CCL19, CCL20, CCL27, CXCL5, and CXCL11), contributes to innate immune cell recruitment, and affects epithelial apoptosis in the airways. In primary human tracheobronchial epithelial cells, OSCN⁻ is generated by LPO using DUOX1-derived H₂O₂ and inactivates several influenza strains in vitro. We also show that OSCN⁻ diminishes influenza replication and viral RNA synthesis in infected host cells that is inhibited by the H₂O₂ scavenger catalase. Binding of the influenza virus to host cells and viral entry are both reduced by OSCN⁻ in an H₂O₂-dependent manner in vitro. OSCN⁻ does not affect the neuraminidase activity or morphology of the influenza virus. Overall, this antiviral function of Duox1 identifies an in vivo role of this gene, defines the steps in the infection cycle targeted by OSCN⁻, and proposes that boosting this mechanism in vivo can have therapeutic potential in treating viral infections.