Epithelial chemerin-CMKLR1 signaling restricts microbiota-driven colonic neutrophilia and tumorigenesis by up-regulating lactoperoxidase.

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 antimicrobial mechanism.

Oxidation of caspase-8 by hypothiocyanous acid enables TNF-mediated necroptosis.

Necroptosis is a form of regulated cell death triggered by various host and pathogen-derived molecules during infection and inflammation. The essential step leading to necroptosis is phosphorylation of the mixed lineage kinase domain-like protein by receptor-interacting protein kinase 3. Caspase-8 cleaves receptor-interacting protein kinases to block necroptosis, so synthetic caspase inhibitors are required to study this process in experimental models. However, it is unclear how caspase-8 activity is regulated in a physiological setting. The active site cysteine of caspases is sensitive to oxidative inactivation, so we hypothesized that oxidants generated at sites of inflammation can inhibit caspase-8 and promote necroptosis. Here, we discovered that hypothiocyanous acid (HOSCN), an oxidant generated in vivo by heme peroxidases including myeloperoxidase and lactoperoxidase, is a potent caspase-8 inhibitor. We found HOSCN was able to promote necroptosis in mouse fibroblasts treated with tumor necrosis factor. We also demonstrate purified caspase-8 was inactivated by low concentrations of HOSCN, with the predominant product being a disulfide-linked dimer between Cys360 and Cys409 of the large and small catalytic subunits. We show oxidation still occurred in the presence of reducing agents, and reduction of the dimer was slow, consistent with HOSCN being a powerful physiological caspase inhibitor. While the initial oxidation product is a dimer, further modification also occurred in cells treated with HOSCN, leading to higher molecular weight caspase-8 species. Taken together, these findings indicate major disruption of caspase-8 function and suggest a novel mechanism for the promotion of necroptosis at sites of inflammation.

Dual oxidase 1 promotes antiviral innate immunity.

Dual oxidase 1 (DUOX1) is an NADPH oxidase that is highly expre-ssed 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-1ß, 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.

A newly identified flavoprotein disulfide reductase Har protects Streptococcus pneumoniae against hypothiocyanous acid.

Hypothiocyanous acid (HOSCN) is an antimicrobial oxidant produced from hydrogen peroxide and thiocyanate anions by heme peroxidases in secretory fluids such as in the human respiratory tract. Some respiratory tract pathogens display tolerance to this oxidant, which suggests that there might be therapeutic value in targeting HOSCN defense mechanisms. However, surprisingly little is known about how bacteria protect themselves from HOSCN. We hypothesized that tolerant pathogens have a flavoprotein disulfide reductase that uses NAD(P)H to directly reduce HOSCN, similar to thioredoxin reductase in mammalian cells. Here, we report the discovery of a previously uncharacterized flavoprotein disulfide reductase with HOSCN reductase activity, which we term Har (hypothiocyanous acid reductase), in Streptococcus pneumoniae, a bacterium previously found to be tolerant of HOSCN. S. pneumoniae generates large amounts of hydrogen peroxide that can be converted to HOSCN in the respiratory tract. Using deletion mutants, we demonstrate that the HOSCN reductase is dispensable for growth of S. pneumoniae in the presence of lactoperoxidase and thiocyanate. However, bacterial growth in the HOSCN-generating system was completely crippled when deletion of HOSCN reductase activity was combined with disruption of GSH import or recycling. Our findings identify a new bacterial HOSCN reductase and demonstrate a role for this protein in combination with GSH utilization to protect S. pneumoniae from HOSCN.

High dietary iodine intake may contribute to the low death rate from COVID-19 infection in Japan with activation by the lactoperoxidase system.

We draw the attention of readers and governments to the death rate from coronavirus disease 2019 in Japan, continuing as a fraction of that experienced by many other developed nations. We think this is due to the activity of the powerful, protective lactoperoxidase system (LPO) which prevents serious airborne infections. The LPO system requires iodine, which is liberally provided by the typical Japanese diet but lacking in many others. One might consider the Japanese experience an incredibly large, open-label study exhibiting the preventative power of a high-iodine diet. We predict this favourable trend will continue for Japan because deadly variants of the severe, acute respiratory syndrome coronavirus 2 will be with us, forever.

Oxidation of anti-thyroid drugs and their selenium analogs by ABTS radical cation.

Lactoperoxidase was previously used as a model enzyme to test the inhibitory activity of selenium analogs of anti-thyroid drugs with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as a substrate. Peroxidases oxidize ABTS to a metastable radical ABTS•+, which is readily reduced by many antioxidants, including thiol-containing compounds, and it has been used for decades to measure antioxidant activity in biological samples. We showed that anti-thyroid drugs 6-n-propyl-2-thiouracil, methimazole, and selenium analogs of methimazole also reduced it rapidly. This reaction may explain the anti-thyroid action of many other compounds, particularly natural antioxidants, which may reduce the oxidized form of iodine and/or tyrosyl radicals generated by thyroid peroxidase thus decreasing the production of thyroid hormones. However, influence of selenium analogs of methimazole on the rate of hydrogen peroxide consumption during oxidation of ABTS by lactoperoxidase was moderate. Direct hydrogen peroxide reduction, proposed before as their mechanism of action, cannot therefore account for the observed inhibitory effects. 1-Methylimidazole-2-selone and its diselenide were oxidized by ABTS•+ to relatively stable seleninic acid, which decomposed slowly to selenite and 1-methylimidazole. In contrast, oxidation of 1,3-dimethylimidazole-2-selone gave selenite and 1,3-dimethylimidazolium cation. Accumulation of the corresponding seleninic acid was not observed.

Synthesis and characterization of supermacroporous cryogel with immobilized p-aminobenzenesulfonamide as affinity ligand for the purification of lactoperoxidase from whey.

This study proposed the development of a monolithic supermacroporous affinity column for direct capture of lactoperoxidase, a glycoprotein present in milk, whey, and colostrum, with several applications due to its wide antimicrobial activity. A poly(acrylamide)-based cryogel was produced by radical co-polymerization of monomers in frozen aqueous solution and activated with p-aminobenzenesulfonamide as a ligand for specific interaction with the lactoperoxidase. The axial liquid dispersion coefficients at different liquid flow rates were determined by measuring residence time distributions using the tracer pulse-response method. The axial dispersion coefficient was low and the height equivalent to theoretical plate was not dependent on the flow velocity. The adsorptive capacity of affinity cryogel was studied as a function of flow velocity and the best condition was 0.9 cm/min. The response surface methodology was applied to optimize the capture of the enzyme, as a function of pH and salt concentration. Higher purification factor value was found at a salt concentration of 80 mmol/L and pH of 8.0 (p < 0.05). There was no influence of the variables under study on the yield (p > 0.05). The results indicated that affinity cryogel is a promising chromatography support for the use in high-throughput one-step purification of lactoperoxidase from whey.

Screening of in Vitro Inhibition of Lactoperoxidase Enzyme by Methyl Benzoate Derivatives with Molecular Docking Studies.

Lactoperoxidase enzyme (LPO) is secreted from salivary, mammary, and other mucosal glands including the bronchi, lungs, and nose, which had functions as a natural and the first line of defense towards viruses and bacteria. In this study, methyl benzoates were examined in LPO enzyme activity. Methyl benzoates are used as precursors in the synthesis of aminobenzohydrazides used as LPO inhibitors. For this purpose, LPO was purified in a single step using sepharose-4B-l-tyrosine-sulfanilamide affinity gel chromatography with a yield of 9.91 % from cow milk. Also, some inhibition parameters including the half maximal inhibitory concentration (IC50 ) value and an inhibition constant (Ki ) values of methyl benzoates were determined. These compounds inhibited LPO with Ki values ranging from 0.033±0.004 to 1540.011±460.020 µM. Compound 1 a (methyl 2-amino-3-bromobenzoate) showed the best inhibition (Ki =0.033±0.004 µM). The most potent inhibitor (1 a) showed with a docking score of -3.36 kcal/mol and an MM-GBSA value of -25.05 kcal/mol, of these methyl benzoate derivatives (1 a-16 a) series are established H-bond within the binding cavity with residues Asp108 (distance of 1.79 Å), Ala114 (distance of 2.64 Å), and His351 (distance of 2.12 Å).

Safety Assessment of the Modified Lactoperoxidase System-In Vitro Studies on Human Gingival Fibroblasts.

One strategy in caries prevention is to inhibit the formation of cariogenic biofilms. Attempts are being made to develop oral hygiene products enriched with various antimicrobial agents. One of them is lactoperoxidase-an enzyme that can oxidise (pseudo)halide ions to reactive products with antimicrobial activity. Currently, commercially available products utilise thiocyanate as a substrate; however, several alternatives that are oxidised to products with greater antimicrobial potential have been found. In this study, toxicity against human gingival fibroblasts of the lactoperoxidase system was evaluated using four different (pseudo)halide substrate systems-thiocyanate, iodide, selenocyanate, and a mixture of thiocyanate and iodide. For this purpose, cells were treated with the systems and then apoptosis, cell cycle, intracellular glutathione concentration, and mitochondrial superoxide production were assessed. The results showed that each system, after generating 250 µM of the product, inhibited cell divisions, increased apoptosis, and increased the percentage of dead cells. It was concluded that the mechanism of the observed phenomena was not related to increased superoxide production or the depletion of glutathione concentration. These findings emphasised the need for the further in vitro and in vivo toxicity investigation of the modified lactoperoxidase system to assess its safety and the possibility of use in oral hygiene products.

Modified Lactoperoxidase System as a Promising Anticaries Agent: In Vitro Studies on Streptococcus mutans Biofilms.

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.

Resistance of Streptococcus pneumoniae to Hypothiocyanous Acid Generated by Host Peroxidases.

Streptococcus pneumoniae is a serious human respiratory pathogen. It generates hydrogen peroxide (H2O2) as part of its normal metabolism, yet it lacks enzymes that remove this oxidant. Here we show that lactoperoxidase and myeloperoxidase, two host enzymes present in the respiratory tract, convert bacterial H2O2 into HOSCN that S. pneumoniae can resist. We found that incubation of S. pneumoniae with myeloperoxidase in chloride-rich buffer killed the bacteria due to formation of toxic hypochlorous acid (HOCl). However, the addition of physiological concentrations of thiocyanate protected the bacteria. Similarly, S. pneumoniae remained viable in the presence of lactoperoxidase and thiocyanate even though the majority of bacterial H2O2 was converted to hypothiocyanous acid (HOSCN). S. pneumoniae and Pseudomonas aeruginosa, another respiratory pathogen, were similarly sensitive to H2O2 and HOCl. In contrast, S. pneumoniae tolerated much higher doses of HOSCN than P. aeruginosa. When associated with neutrophil extracellular traps (NETs), S. pneumoniae continued to generate H2O2, which was converted to HOCl by myeloperoxidase (MPO) present on NETs. However, there was no loss in bacterial viability because HOCl was scavenged by the NET proteins. We conclude that at sites of infection, bacteria will be protected from HOCl by thiocyanate and extracellular proteins including those associated with NETs. Resistance to HOSCN may give S. pneumoniae a survival advantage over other pathogenic bacteria. Understanding the mechanisms by which S. pneumoniae protects itself from HOSCN may reveal novel strategies for limiting the colonization and pathogenicity of this deadly pathogen.

Synthesis and Characterization of Biotene: A New 2D Natural Oxide From Biotite.

In this work, the synthesis and characterization of ultrathin metal oxide, called biotene, using liquid-phase exfoliation from naturally abundant biotite are demonstrated. The atomically thin biotene is used for energy harvesting using its flexoelectric response under multiple bending. The effective flexoelectric response increases due to the presence of surface charges, and the voltage increases up to ≈8 V, with a high mechano-sensitivity of 0.79 V N-1 for normal force. This flexoelectric response is further validated by density functional theory (DFT) simulations. The atomically thin biotene shows an increased response in the magnetic field and thermal heating. The synthesis of two-dimensional (2D) metal-oxide biotene suggests a wealth of future 2D-oxide material for energy generation and energy harvesting applications.

Comments on the Discussion Forum: Oromucosal immunomodulation as clinical spectrum mitigating factor in SARS-CoV-2 infection.

The mammalian lactoperoxidase system, consisting of lactoperoxidase and the H2 O2 -producing enzyme duox, is our first line of defence against airborne microbes. This system catalyses the production of hypoiodite and hypoiodous acid in the presence of sufficient iodine. These products are highly efficient at destroying the H1N1 virus and the respiratory syncytial virus (RSV). Japan has not been affected as much as other nations during the COVID-19 pandemic (death rate about 10% of the United States), and we think this is due to a diet high in iodine. With this in mind, we suggest four actions to prevent SARS-CoV-2 infections. First, health professionals should study the preventative effect of increasing iodine in the diets of the aged, institutionalized, diabetics andsmokers. Second, the recommended daily intake (RDI) for iodine should be significantly increased, to at least double, the current RDI. Governments should encourage the use and distribution of cheap iodized salts, kelp and seaweed. Third, more research should be done around the physiology and the protective effects of the lactoperoxidase system. Finally, the degradation products of the SARS-CoV-2 viral particle by hypoiodite and hypoiodous acid should be characterized; portions of the damaged particle are likely to elicit stronger immunity and better vaccines.

Salivary Proteins as Dental Caries Biomarkers: A Systematic Review.

Salivary proteins play an important role in repairing mechanisms of damaged tissues and the maintenance of oral health. However, there is a dearth of information in the literature regarding the concentrations of salivary proteins in caries-free (CF) and caries-active (CA) subjects. Hence, this systematic review was conducted to update our previous systematic review published in 2013 that aimed to assess the association between caries and salivary proteins by comparing CF and CA individuals. Thereby, evaluating the possibility of whether salivary proteins can be regarded as biomarkers for caries. An extensive search of studies was conducted using PubMed, EMBASE, Clarivate Analytics' Web of Science, and Elsevier's Scopus between July 2012 and January 2022, without any language restriction. Manual searching in Google Scholar and evaluation of bibliographies of the included studies were also undertaken. The Newcastle-Ottawa Scale was used to assess the risk of bias (RoB) within the included studies. Of 22 included studies, 1,551 human subjects (range: 30-213 participants) were recruited, of which 848 individuals (54.7%) were CA and 703 (45.3%) were CF. Regarding the utilization of DMFT as the caries index, high variability was observed across different articles. A statistically significant increase in the salivary levels of alpha-amylase, acidic proline-rich protein-1, histatin-5, lactoperoxidase, and mucin-1 was found in CA patients, while the salivary levels of carbonic anhydrase 6, proteinase-3, and statherin were observed to be significantly increased in CF subjects. Conflicting results were found regarding the salivary levels of immunoglobulin A and total proteins among CA and CF subjects. The included studies were categorized as low RoB (n = 15), medium RoB (n = 4), and high RoB (n = 3). Due to significant heterogeneity among the included studies, no meta-analysis could be performed. In conclusion, the salivary levels of protein(s) might be a useful biomarker for caries diagnosis, especially alpha-amylase, acidic proline-rich protein-1, histatin-5, lactoperoxidase, mucin-1, carbonic anhydrase 6, proteinase-3, and statherin. However, their diagnostic value must be verified by large-scale prospective studies.

Nanoformulation approach for improved antimicrobial activity of bovine lactoperoxidase.

Lactoperoxidase (LPO) is a glycosylated antimicrobial protein present in milk with a molecular mass of 78 kDa. LPO is included in many biological processes and is well-known to have biocidal actions, acting as an active antibiotic and antiviral agent. The wide spectrum biocidal activity of LPO is mediated via a definite inhibitory system named lactoperoxidase system which plays a potent role in the innate immune response. With the current advancement in nanotechnology, nanoformulations can be developed for stabilizing and potentiating the activity of LPO for several applications. In the research described in this Research Communication, fresh LPO purified from bovine mammary gland secretions was used for nanoparticle synthesis using a simple thermal process at different pH and temperatures. The round-shaped nanoparticles (average size 229 nm) were successfully synthesized at pH 7.0 and a temperature of 75°C. These nanoparticles were tested against four different bacterial species namely S. flexineri, P. aeruginosa, S. aureus, and E. coli. The prepared nanoparticles exhibited strong inhibition of the growth against all four bacterial species as stated by their MIC and ZOI values. These results may help in increasing the efficiency of lactoperoxidase system and will assist in identifying novel avenues to enhance the stability and antimicrobial function of LPO in drug discovery and industrial processes.

Antibacterial and antiplaque efficacy of a lactoperoxidase-thiocyanate-hydrogen-peroxide-system-containing lozenge.

BACKGROUND: Antimicrobial agents are considered valuable adjuncts to mechanical methods of plaque control. However, their long-term use can be limited because of side effects. Therefore, using physiological substances is promising due to no risk of development, for example, of microbial resistances, allergies or DNA damaging. The lactoperoxidase-thiocyanate-hydrogen peroxide system (LPO-system) is a highly effective antimicrobial system. This study aimed to evaluate in a randomized study with a four-replicate cross-over design the effectiveness of two oral hygiene lozenges containing LPO-system in oral hygiene. RESULTS: After using the mouth rinse as positive control (A) and allocated test lozenges (B) (0.083% H2O2) & (C) (0.04% H2O2) for 4 days instead of the normal oral hygiene procedures (tooth brushing etc.), Listerine rinse (A) was statistically significantly more effective than the LPO-system-lozenge with 0.083% H2O2, the LPO-system-lozenge with 0.04% H2O2, and the placebo lozenge (D) in inhibiting plaque. Lozenges B and C were statistically significantly more effective than the placebo lozenge, but no statistically significant differences could be observed between them. The LPO-system-lozenge (B) reduced statistically significantly more S. mutans than the LPO-system-lozenge with (C) and the placebo lozenge (D). The LPO-system-lozenge (C) reduced statistically significantly more Lactobacilli than Listerine (A), the LPO-system-lozenge (B) and the placebo lozenge (D). There were no statistically significant differences in the total CFUs between Listerine rinse, the LPO-system-lozenge with 0.083% H2O2 (B), the LPO-system-lozenge with 0.04% H2O2 (C), and the placebo lozenge (D). On day 5 there were no differences of the OSCN--values between all A, B, C, and D. However, the SCN--values increased over the days in both LPO-system-lozenges (B/C). The statistically significant differences between B/C and A/D on day 5 were as followed: A to B p = 0.0268; A to C p = 0.0035; B to D p = 0.0051; C to D p = 0.0007. Only in the group of Listerine (A) increased the NO3-/NO2--quotient over the test time, which indicates a reduction of nitrate-reducing bacteria. On Day 5 the statistically significant difference between A and B was p = 0.0123. CONCLUSIONS: The results indicate that lozenges containing a complete LPO-system, inhibiting plaque regrowth and reducing cariogenic bacteria, may be used in the daily oral hygiene.

Potassium-induced partial inhibition of lactoperoxidase: structure of the complex of lactoperoxidase with potassium ion at 2.20 Å resolution.

Lactoperoxidase, a heme-containing glycoprotein, catalyzes the oxidation of thiocyanate by hydrogen peroxide into hypothiocyanite which acts as an antibacterial agent. The prosthetic heme moiety is attached to the protein through two ester linkages via Glu258 and Asp108. In lactoperoxidase, the substrate-binding site is formed on the distal heme side. To study the effect of physiologically important potassium ion on the structure and function of lactoperoxidase, the fresh protein samples were isolated from yak (Bos grunniens) colostrum and purified to homogeneity. The biochemical studies with potassium fluoride showed a significant reduction in the catalytic activity. Lactoperoxidase was crystallized using 200 mM ammonium nitrate and 20% PEG-3350 at pH 6.0. The crystals of LPO were soaked in the solution of potassium fluoride and used for the X-ray intensity data collection. Structure determination at 2.20 Å resolution revealed the presence of a potassium ion in the distal heme cavity. Structure determination further revealed that the propionic chain attached to pyrrole ring C of the heme moiety, was disordered into two components each having an occupancy of 0.5. One component occupied a position similar to the normally observed position of propionic chain while the second component was found in the distal heme cavity. The potassium ion in the distal heme cavity formed five coordinate bonds with two oxygen atoms of propionic moiety, Nε2 atom of His109 and two oxygen atoms of water molecules. The presence of potassium ion in the distal heme cavity hampered the catalytic activity of lactoperoxidase.

Bovine γ-globulin, lactoferrin, and lactoperoxidase are relevant bovine milk allergens in patients with α-Gal syndrome.

BACKGROUND: Mammalian meat is the most common trigger of the allergic reactions in patients with α-Gal syndrome (AGS). Milk and dairy, although less often, also cause a significant number of allergic manifestations. The aim of this study was to identify α-Gal-containing bovine milk proteins with allergenic properties among AGS patients. METHODS: Thirty-eight AGS patients with IgE to milk were included in the study. Milk proteins were analyzed for the presence of α-Gal and for binding by patients' IgE using immunoblot, ImmunoCAP, and inhibition ELISA. Allergenicity of milk and milk proteins was assessed by basophil activation test. RESULTS: More than half of the AGS patients reported allergic reactions to milk or dairy products. Bovine γ-globulin (BGG), lactoferrin (LF), and lactoperoxidase (LPO) were identified as α-Gal carrying proteins which were recognized by AGS patients' IgE. Whey mirrored the anti-α-Gal and IgE reactivity of BGG, LF, and LPO. Eighty-nine percent of the patients displayed IgE to BGG, 91% to LF, and 57% to LPO. Inhibition of α-Gal-specific IgE binding was achieved by BGG, LF, LPO, and whey. These proteins also activated AGS patients' basophils. Interestingly, at lower concentrations, LF was the most potent inhibitor of IgE binding, and the most potent activator of basophils. CONCLUSION: BGG, LF, and LPO were all found to be relevant milk α-Gal-containing glycoproteins that bound AGS patients' IgE antibodies and activated their basophils. These proteins are probably involved in the allergic reactions to milk in AGS patients. LPO was for the first time shown to be an allergen.

Inhibition effects of selected thiophene-2-sulfonamides on lactoperoxidase.

Lactoperoxidase (LPO, E.C.1.11.1.7) is a natural antibacterial agent which is secreted from salivary, mammary, and other mucosal glands. It is one of the crucial enzymes in biological systems, so protection of LPO activity is extremely important for the immune system. Within the scope of this study; in vitro effects of some thiophene-2-sulfonamide derivatives (1a-7a) on bovine milk LPO enzymatic activity were investigated. LPO was purified from the Sepharose-4B-L-tyrosine-5-amino-2-methylbenzenesulfonamide column prepared using affinity chromatography technique with a yield of 169.66 EU/mg specific activity in 452.44 times. As a result, 5-(2-thienylthio) thiophene-2-sulfonamide demonstrated the strongest inhibition impact among these compounds. This molecule has shown a competitive inhibition and it was determined that the IC50 value was 3.4 nM and the Ki value was 2 ± 0.6 nM.

Nanoformulation approach for improved stability and efficiency of lactoperoxidase.

Lactoperoxidase is a glycosylated protein with a molecular mass of 78 kDa, which being excreted in several mammalian secretions. Lactoperoxidase is included in many biological processes and well-known to have biocidal actions, attending as active antibiotics and antiviral agents. This wide-spectrum of biocidal activities mediates via a definite inhibitory system named lactoperoxidase system which acts a potent role in the innate immune response since its activity is not restricted by the antimicrobial effect, but might act a significant role in the hydrolysis of many toxins like aflatoxin. Hence with the current progresses in technology, nanoparticles can offer chances as an active candidate that might be utilized for stabilizing and potentiating the activity of LPO for use in several applications. Due to the variability functions of LPO, this enzyme considers an active target to be encapsulated or coated to NPs for developing novel nanocombinations with controlled surface characteristics. The development of approaches which might enhance conformational stabilization for several weeks of LPO via nanoformulation could improve the biopharmaceutical applicability of this bioactive ingredient. Nanoformulation of LPO enhances novel functions that can be useful in many biotechnological applications like food industry, cosmetic and pharmaceutical applications or to deliver and encapsulate bioactive components.