Influence of diluent on antimicrobial activity of cinnamon bark essential oil vapor against Staphylococcus aureus and Salmonella enterica on a laboratory medium and beef jerky.

The influence of chemical diluents on the antimicrobial activity of plant essential oil (EO) vapors was evaluated. We first determined if vapors generated from 22 chemical diluents not containing EO had antimicrobial activities. Ethyl ether vapor retarded the growth of S. aureus. The minimal inhibitory concentrations (MICs) and the minimal lethal concentrations (MLCs) of cinnamon bark EO vapor, which was diluted in and generated from 21 diluents, against S. aureus and S. enterica were determined. Cinnamon bark EO vapor showed significantly (P ≤ 0.05) lower MICs against S. aureus when diluted in dimethyl sulfoxide (DMSO), ethanol, ethyl acetate, or jojoba oil, and against S. enterica when diluted in DMSO, ethanol, or jojoba oil, compared to those in other diluents. We compared antimicrobial activities of cinnamon bark EO vapor diluted in DMSO, ethanol, ethyl acetate, or jojoba oil against S. aureus and S. enterica on beef jerky as a food model. Antimicrobial activity was significantly (P ≤ 0.05) higher when vaporized from DMSO. These results indicate that antimicrobial activity of cinnamon bark EO vapor may vary significantly (P ≤ 0.05) depending on the type of diluent from which it is vaporized. These observations provide basic information when developing food and food-contact surface decontamination strategies using EO vapors.

FcRγ- NK Cell Induction by Specific Cytomegalovirus and Expansion by Subclinical Viral Infections in Rhesus Macaques.

"Adaptive" NK cells, characterized by FcRγ deficiency and enhanced responsiveness to Ab-bound, virus-infected cells, have been found in certain hCMV-seropositive individuals. Because humans are exposed to numerous microbes and environmental agents, specific relationships between hCMV and FcRγ-deficient NK cells (also known as g-NK cells) have been challenging to define. Here, we show that a subgroup of rhesus CMV (RhCMV)-seropositive macaques possesses FcRγ-deficient NK cells that stably persist and display a phenotype resembling human FcRγ-deficient NK cells. Moreover, these macaque NK cells resembled human FcRγ-deficient NK cells with respect to functional characteristics, including enhanced responsiveness to RhCMV-infected target in an Ab-dependent manner and hyporesponsiveness to tumor and cytokine stimulation. These cells were not detected in specific pathogen-free (SPF) macaques free of RhCMV and six other viruses; however, experimental infection of SPF animals with RhCMV strain UCD59, but not RhCMV strain 68-1 or SIV, led to induction of FcRγ-deficient NK cells. In non-SPF macaques, coinfection by RhCMV with other common viruses was associated with higher frequencies of FcRγ-deficient NK cells. These results support a causal role for specific CMV strain(s) in the induction of FcRγ-deficient NK cells and suggest that coinfection by other viruses further expands this memory-like NK cell pool.

Highly Resilient Dual-Crosslinked Hydrogel Adhesives Based on a Dopamine-Modified Crosslinker.

Hydrogels are promising material for wound dressing and tissue engineering. However, owing to their low tissue adhesion in a moist environment and lack of flexibility, hydrogels are still not widely applied in movable parts, such as joints. Herein, we report a dual-crosslinked hydrogel adhesive using a dopamine-modified and acrylate-terminated crosslinker, tri(ethylene glycol) diacrylate-dopamine crosslinker (TDC). The covalent crosslinking was formed by photopolymerization between acrylic acid (AA) and TDC, and the noncovalent crosslinking was formed by intermolecular dopamine-dopamine and dopamine-AA interactions. Our resultant hydrogel demonstrated strong tissue adhesion in a moist environment (approximately 71 kPa) and high mechanical resilience (approximately 94%) with immediate recovery at a 200% strain rate. Moreover, it accelerated wound healing upon dressing the wound site properly. Our study provides the potential for advanced polymer synthesis by introducing a functional crosslinking agent.

Rapid Photoresponsive Switchable Pressure-Sensitive Adhesive Containing Azobenzene for the Mini-Light Emitting Diode Transfer Process.

Materials that can switch adhesive properties based on external stimuli are required in several industries for temporary bonding or transfer processes. Previously studied materials achieve this under restricted conditions (hydration, heat, and long switching times), and some materials have limitations related to reuse because of irreversible reactions or residue formation on substrates. Herein, a rapid photoresponsive switchable pressure-sensitive adhesive (PSA) fabricated using an acrylic polymer and an aliphatic monomer containing azobenzene is reported. The adhesion force of the proposed PSA can be switched by photoisomerizing the azobenzene moiety. The process induces the transition of surface energy and modulus of the PSA. Ultraviolet and visible light irradiation can switch the probe tack force from 200 to 4 kPa within 15-30 s. Adhesion switching is possible in a state wherein the PSA remains adhered to a substrate. Mini-LEDs are selectively transferred from the carrier PSA to a polydimethylsiloxane substrate following the process of partial adhesion switching of the PSA. The novel and switchable PSA, which exhibits a selective and repeatable adhesion switching property and high switching ratio when stimulated by light stimuli, may be potentially used to realize the mini-LED or micro-LED transfer processes.

Photoresponsive, switchable, pressure-sensitive adhesives: influence of UV intensity and hydrocarbon chain length of low molecular weight azobenzene compounds.

Unlike traditional adhesives with a fixed adhesive force, switchable adhesives, which have an adhesive force that can be adjusted by external stimuli, are specifically designed to be released according to user demand, or to enable the transfer of fine electronic devices. Previously developed switchable adhesives have limitations such as a slow switching rate, narrow adhesion modulation range, or the lack of reusability. Thus, we fabricated switchable pressure-sensitive adhesives (PSAs) that can overcome these limitations. The adhesive force of each switchable PSA, which comprises an azobenzene-containing acrylic polymer and low molecular weight compounds, was designed to be activated/deactivated via ultraviolet (UV) and visible light irradiation. The adhesive force and UV intensity required for the switch were found to be dependent on the aliphatic chain length of the compound. The adhesive force of the SP-C10, i.e., a switchable PSA containing a azobenzene compound with an aliphatic chain of 10 hydrocarbons, increased to 3.5 N from nearly zero in response to only 30 s of low-level (25 mW cm-2) UV irradiation. Additionally, SP-C10 did not lose its adhesive force even after 30 cycles of repeated adhesion switching. The mechanism of adhesion switching influenced by UV intensity and the structure of low molecular weight azobenzene compounds are also reported.

Defect-Induced Fluorescence of Silica Nanoparticles for Bioimaging Applications.

With biocompatibility, biodegradability, and high functionality, silica nanoparticles (SNPs) have been widely investigated for various biomedical applications. However, lack of optical fluorescence has limited the application of SNPs as a degradable imaging agent. Here, we hydrothermally synthesized fluorescent SNPs by artificially generating optically active defect centers using tetraethyl orthosilicate and (3-aminopropyl)trimethoxysilane. The synthesized SNPs demonstrated strong blue photoluminescence originating from the dioxasilyrane (=Si(O2)) and silylene (=Si:) defect centers with the aid of aminopropyl groups. Furthermore, phosphorescence was observed at 459 nm, indicating the presence of silylene in SNPs. Finally, these SNPs have been successfully utilized as a fluorescent probe for bioimaging of normal, cancer, and macrophage cells.

Site-Specific Three-Color Labeling of α-Synuclein via Conjugation to Uniquely Reactive Cysteines during Assembly by Native Chemical Ligation.

Single-molecule fluorescence is widely used to study conformational complexity in proteins, and has proven especially valuable with intrinsically disordered proteins (IDPs). Protein studies using dual-color single-molecule Förster resonance energy transfer (smFRET) are now quite common, but many could benefit from simultaneous measurement of multiple distances through multi-color labeling. Such studies, however, have suffered from limitations in site-specific incorporation of more than two dyes per polypeptide. Here we present a fully site-specific three-color labeling scheme for α-synuclein, an IDP with important putative functions and links to Parkinson disease. The convergent synthesis combines native chemical ligation with regiospecific cysteine protection of expressed protein fragments to permit highly controlled labeling via standard cysteine-maleimide chemistry, enabling more global smFRET studies. Furthermore, this modular approach is generally compatible with recombinant proteins and expandable to accommodate even more complex experiments, such as by labeling with additional colors.

Dual Unnatural Amino Acid Incorporation and Click-Chemistry Labeling to Enable Single-Molecule FRET Studies of p97 Folding.

Many cellular functions are critically dependent on the folding of complex multimeric proteins, such as p97, a hexameric multidomain AAA+ chaperone. Given the complex architecture of p97, single-molecule (sm) FRET would be a powerful tool for studying folding while avoiding ensemble averaging. However, dual site-specific labeling of such a large protein for smFRET is a significant challenge. Here, we address this issue by using bioorthogonal azide-alkyne chemistry to attach an smFRET dye pair to site-specifically incorporated unnatural amino acids, allowing us to generate p97 variants reporting on inter- or intradomain structural features. An initial proof-of-principle set of smFRET results demonstrated the strengths of this labeling method. Our results highlight this as a powerful tool for structural studies of p97 and other large protein machines.

Non-Hematopoietic ß-Arrestin1 Confers Protection Against Experimental Colitis.

ß-Arrestins are multifunctional scaffolding proteins that modulate G protein-coupled receptor (GPCR)-dependent and -independent cell signaling pathways in various types of cells. We recently demonstrated that ß-arrestin1 (ß-arr1) deficiency strikingly attenuates dextran sodium sulfate (DSS)-induced colitis in mice. Since DSS-induced colitis is in part dependent on gut epithelial injury, we examined the role of ß-arr1 in intestinal epithelial cells (IECs) using a colon epithelial cell line, SW480 cells. Surprisingly, we found that knockdown of ß-arr1 in SW480 cells enhanced epithelial cell death via a caspase-3-dependent process. To understand the in vivo relevance and potential cell type-specific role of ß-arr1 in colitis development, we generated bone marrow chimeras with ß-arr1 deficiency in either the hematopoietic or non-hematopoietic compartment. Reconstituted chimeric mice were then subjected to DSS-induced colitis. Similar to our previous findings, ß-arr1 deficiency in the hematopoietic compartment protected mice from DSS-induced colitis. However, consistent with the role of ß-arr1 in epithelial apoptosis in vitro, non-hematopoietic ß-arr1 deficiency led to an exacerbated colitis phenotype. To further understand signaling mechanisms, we examined the effect of ß-arr1 on TNF-α-mediated NFκB and MAPK pathways. Our results demonstrate that ß-arr1 has a critical role in modulating ERK, JNK and p38 MAPK pathways mediated by TNF-α in IECs. Together, our results show that ß-arr1-dependent signaling in hematopoietic and non-hematopoietic cells differentially regulates colitis pathogenesis and further demonstrates that ß-arr1 in epithelial cells inhibits TNF-α-induced cell death pathways.

Optimization of treatment with recombinant FGF-2 for proliferation and differentiation of human dental stem cells, mesenchymal stem cells, and osteoblasts.

Basic fibroblast growth factor (bFGF or FGF-2) is widely used to modulate the proliferation and differentiation of certain cell types. An expression and purification system for recombinant human FGF-2 in Escherichia coli was established for the purpose of securing a continuous supply of this protein. The purified recombinant FGF-2 significantly increased the population of human embryonic stem cells. The optimal concentrations of FGF-2 for cell proliferative induction in various adult stem cells including human dental pulp stem cells, full term human periodontal ligament stem cells, human gingival fibroblasts, mesenchymal stem cells, and osteogenic oseosarcoma were established in a dose-dependent manner. When cells were treated with recombinant FGF-2 for 6 days before osteogenic induction, the mRNA expression of the bone markers was upregulated in cells originated from human dental pulp tissue, indicating that pretreatment with FGF-2 during culture increase stem cell/progenitor population and osteogenic potential.

Probiotic L. reuteri treatment prevents bone loss in a menopausal ovariectomized mouse model.

Estrogen deficiency is a major risk factor for osteoporosis that is associated with bone inflammation and resorption. Half of women over the age of 50 will experience an osteoporosis related fracture in their lifetime, thus novel therapies are needed to combat post-menopausal bone loss. Recent studies suggest an important role for gut-bone signaling pathways and the microbiota in regulating bone health. Given that the bacterium Lactobacillus reuteri ATCC PTA 6475 (L. reuteri) secretes beneficial immunomodulatory factors, we examined if this candidate probiotic could reduce bone loss associated with estrogen deficiency in an ovariectomized (Ovx) mouse menopausal model. Strikingly, L. reuteri treatment significantly protected Ovx mice from bone loss. Osteoclast bone resorption markers and activators (Trap5 and RANKL) as well as osteoclastogenesis are significantly decreased in L. reuteri-treated mice. Consistent with this, L. reuteri suppressed Ovx-induced increases in bone marrow CD4+ T-lymphocytes (which promote osteoclastogenesis) and directly suppressed osteoclastogenesis in vitro. We also identified that L. reuteri treatment modifies microbial communities in the Ovx mouse gut. Together, our studies demonstrate that L. reuteri treatment suppresses bone resorption and loss associated with estrogen deficiency. Thus, L. reuteri treatment may be a straightforward and cost-effective approach to reduce post-menopausal bone loss.

Natural killer cell development and maturation in aged mice.

The effect of aging on natural killer cell homeostasis is not well studied in humans or in animal models. We compared natural killer (NK) cells from young and aged mice to investigate age-related defects in NK cell distribution and development. Our findings indicate aged mice have reduced NK cells in most peripheral tissues, but not in bone marrow. Reduction of NK cells in periphery was attributed to a reduction of the most mature CD11b(+) CD27(-) NK cells. Apoptosis was not found to explain this specific reduction of mature NK cells. Analysis of NK cell development in bone marrow revealed that aged NK cells progress normally through early stages of development, but a smaller percentage of aged NK cells achieved terminal maturation. Less mature NK cells in aged bone marrow correlated with reduced proliferation of immature NK cells. We propose that advanced age impairs bone marrow maturation of NK cells, possibly affecting homeostasis of NK cells in peripheral tissues. These alterations in NK cell maturational status have critical consequences for NK cell function in advanced age: reduction of the mature circulating NK cells in peripheral tissues of aged mice affects their overall capacity to patrol and eliminate cancerous and viral infected cells.

Lithium chloride induces TNFα in mouse macrophages via MEK-ERK-dependent pathway.

Lithium (Li) is one of the currently prescribed drugs for bipolar disorders (BPDs) and has many neuro-regulatory and immune-modulating properties. Because many neuro-pathological diseases including BPDs have been associated with some level of inflammation, Li's effect on inflammation may have some crucial consequences. Even though Li has been shown to have pro- and anti-inflammatory activities in different cell models, mechanisms involved in these effects are not well understood. Moreover, Li's effect on inflammation in the presence of activators of Toll-like receptors (TLRs), especially TLR-2 (that activates MyD88-dependent pathway) and TLR-3 (that activates TRIF-dependent pathway) is not known. Here we tested the role of Li in the presence and absence of TLR2, and TLR3 on MAPK and NFκB pathways and the consequent production of tumor necrosis factor-α (TNFα) in Raw264.7 macrophages. Our results indicate that Li enhances TNFα production both in the absence and presence of TLR stimulation. Interestingly, Li differentially modulates MAPK and NFκB pathways in the absence and presence of TLR2/3 ligands. Our results further indicate that the effect of Li on TNFα occurs at the post-transcriptional level. Together, these studies demonstrate that Li induces TNFα production in macrophages and that it modulates signaling at different levels depending on the presence or absence of TLR2/3 stimulation.

Reyranella soli sp. nov., isolated from forest soil, and emended description of the genus Reyranella Pagnier et al. 2011.

A Gram-stain-negative, non-motile, rod-shaped bacterial strain, designated KIS14-15(T), was isolated from forest soil of Baengnyeong Island in the Yellow Sea in Korea and its taxonomic position was investigated by using a polyphasic study. Strain KIS14-15(T) grew optimally at 30 °C, at pH 6.0-7.0 and without NaCl. In the neighbour-joining phylogenetic tree based on 16S rRNA gene sequences, strain KIS14-15(T) formed a cluster with the strains of Reyranella massiliensis with a bootstrap resampling value of 100%. Strain KIS14-15(T) exhibited 16S rRNA gene sequence similarity values of 98.0% to R. massiliensis 521(T) and of less than 89% to the type strains of other taxa. The mean level of DNA-DNA relatedness between strain KIS14-15(T) and R. massiliensis KACC 16548(T) was 21% (reciprocal, 24%). The predominant ubiquinone found in strain KIS14-15(T) and R. massiliensis KACC 16548(T) was ubiquinone-10 (Q-10). The predominant fatty acids of strain KIS14-15(T) and R. massiliensis KACC 16548(T) were C(18:1)ω7c, C(18:1) 2-OH and 11-methyl C(18:1)ω7c. Total polar lipids of strain KIS14-15(T) were phosphatidylmonomethylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unknown aminolipid and one unknown lipid. Differential phenotypic properties, together with phylogenetic and genetic distinctiveness, demonstrated that strain KIS14-15(T) is distinguishable from R. massiliensis. On the basis of the data presented, strain KIS14-15(T) is considered to represent a novel species of the genus Reyranella, for which the name Reyranella soli sp. nov. is proposed. The type strain is KIS14-15(T) ( = KACC 13034(T) =NBRC 108950(T)).

The effect of heated breathing circuit on body temperature and humidity of anesthetic gas in major burns.

BACKGROUND: Cold and dry gas mixtures during general anesthesia cause the impairment of cilliary function and hypothermia. Hypothermia and pulmonary complications are critical for the patients with major burn. We examined the effect of heated breathing circuit (HBC) about temperature and humidity with major burned patients. METHODS: Sixty patients with major burn over total body surface area 25% scheduled for escharectomy and skin graft were enrolled. We randomly assigned patients to receiving HBC (HBC group) or conventional breathing circuit (control group) during general anesthesia. The esophageal temperature of the patients and the temperature and the absolute humidity of the circuit were recorded every 15 min after endotracheal intubation up to 180 min. RESULTS: There was no significant difference of the core temperature between two groups during anesthesia. The relative humidity of HBC group was significantly greater compared to control group (98% vs. 48%, P < 0.01). In both groups, all measured temperatures were significantly lower than that after intubation. CONCLUSIONS: The use of HBC helped maintain airway humidity, however it did not have the effect to minimize a body temperature drop in major burns.

ß-Arrestin-1 deficiency protects mice from experimental colitis.

ß-Arrestins are intracellular scaffolding proteins that modulate specific cell signaling pathways. Recent studies, in both cell culture and in vivo models, have demonstrated an important role for ß-arrestin-1 in inflammation. However, the role of ß-arrestin-1 in the pathogenesis of inflammatory bowel disease (IBD) is not known. Our goal was to investigate the role of ß-arrestin-1 in IBD using mouse models of colitis. To this end, we subjected wild-type (WT) and ß-arrestin-1 knockout (ß-arr-1(-/-)) mice to colitis induced by trinitrobenzenesulfonic acid or dextran sulfate sodium and examined the clinical signs, gross pathology, and histopathology of the colon, as well as inflammatory components. The ß-arr-1(-/-) mice displayed significantly attenuated colitis, compared with WT mice, in both models. Consistent with the phenotypic observations, histological examination of the colon revealed attenuated disease pathology in the ß-arr-1(-/-) mice. Our results further demonstrate that ß-arr-1(-/-) mice are deficient in IL-6 expression in the colon, but have higher expression of the anti-inflammatory IL-10 family of cytokines. Our results also demonstrate diminished ERK and NFκB pathways in the colons of ß-arr-1(-/-) mice, compared with WT mice. Taken together, our results demonstrate that decreased IL-6 production and enhanced IL-10 and IL-22 production in ß-arrestin-1-deficient mice likely lead to attenuated gut inflammation.

Identification of human NK cells that are deficient for signaling adaptor FcRγ and specialized for antibody-dependent immune functions.

NK cells respond to tumor and virus-infected cells directly through several activation receptors, including natural cytotoxicity receptors, or indirectly through the activating Fc receptor CD16 for antibody-coated cells. Triggering of NK-cell effector functions through these receptors depends on physically associated transmembrane signaling adaptors, such as FcRγ (also known as FcεRIγ) and CD3ζ, both of which have been traditionally believed to be expressed by all mature NK cells. However, we have identified a distinct subset of human NK cells that are deficient for FcRγ expression but express normal levels of CD3ζ. FcRγ-deficient NK cells were readily detectable in about one-third of the healthy individuals examined. The deficiency was confined to the CD56(dim) population and was due to low FcRγ mRNA. FcRγ-deficient NK cells displayed dramatically reduced expression of the natural cytotoxicity receptors NKp46 and NKp30 but still expressed substantial levels of CD16. Compared to FcRγ-expressing NK cells, FcRγ-deficient NK cells showed poor direct reactivity toward tumor targets as measured by cytokine production and degranulation. Unexpectedly, however, FcRγ-deficient NK cells exhibited significantly more robust responsiveness upon stimulation through CD16, particularly for cytokine production, compared to FcRγ-expressing NK cells. Thus, our study reveals FcRγ-deficient NK cells as a novel subset of human NK cells that have remarkably potent responses toward antibody-coated targets. These findings also illustrate a differential contribution of FcRγ and CD3ζ for the expression and functional activity of their associated receptors.

Role of myeloid-specific G-protein coupled receptor kinase-2 in sepsis.

Previous studies have implicated a critical role for G-protein coupled receptor kinase-2 (GRK2) in sepsis owing to its ability to regulate inflammatory response and chemotaxis of immune cells. We therefore, hypothesized that deletion of GRK2 in myeloid cells would significantly modulate the pathogenesis of polymicrobial sepsis. To test this hypothesis, we induced cecal ligation and puncture (CLP), in mice with myeloid-specific deletion of GRK2 and the corresponding GRK2 wild type littermates and determined the inflammatory response (IL-6 and IL-10), immune cell infiltration, bacterial load and survival. Six hours after surgery, plasma IL-6 and IL-6:IL-10 ratios were significantly enhanced in the GRK2 knockouts compared to the GRK2 wild type mice. Compared to these effects, IL-6was significantly elevated in the bronchoalveolar lavage but not in the peritoneal fluid of the GRK2 knockout mice. On the other hand, peritoneal IL-10 was significantly elevated in the GRK2 knockout mice compared to the GRK2 wild type. Even though GRK2 knockout mice exhibited an exaggerated cytokine response, there was no difference in immune cell infiltration into the primary site of infection or in bacterial clearance when compared between the GRK2 wild type and GRK2 knockout mice after surgery. Furthermore, in spite of the enhanced pro-inflammatory profile early after surgery, there was only a modest increase in mortality in the GRK2 knockout compared to the GRK2 wild type mice after CLP. Together, our studies demonstrate that myeloid-specific knockout of GRK2 renders the mice more susceptible to an early pro-inflammatory state. However, myeloid-specific GRK2 is not involved in immune cell infiltration to the primary site of infection or in bacterial clearance and does not significantly modulate mortality in the cecal ligation puncture model of polymicrobial sepsis.

The protein truncation caused by fusion of PEP-1 peptide and protective roles of transduced PEP-1-MsrA in skin cells.

PEP-1 peptide has been used for transduction of native protein into mammalian cells. This work describes the findings that the fusion of PEP-1 to target proteins led to protein truncation likely in a non-protein-specific manner. Approximately 75% of PEP-1-MsrA fusion protein was truncated in the N-terminal region of MsrA between Lys-27 and Val-28 during expression in Escherichia coli and purification. This large protein truncation was also observed in another PEP-1 fused protein, PEP-1- MsrB2, in the N-terminal region of MsrB2. The full-length PEP-1-MsrA protein was rapidly transduced into keratinocyte cells within 15 min. The transduced PEP-1-MsrA was functionally active and could protect skin cells against oxidative stress-and ultraviolet radiation-induced cell death. Collectively, our data demonstrated the protective roles of MsrA in skin cells and, moreover, may raise a concern of protein truncation caused by fusion of PEP-1 about the general use of this peptide for protein transduction.

MsrB1 (methionine-R-sulfoxide reductase 1) knock-out mice: roles of MsrB1 in redox regulation and identification of a novel selenoprotein form.

Protein oxidation has been linked to accelerated aging and is a contributing factor to many diseases. Methionine residues are particularly susceptible to oxidation, but the resulting mixture of methionine R-sulfoxide (Met-RO) and methionine S-sulfoxide (Met-SO) can be repaired by thioredoxin-dependent enzymes MsrB and MsrA, respectively. Here, we describe a knock-out mouse deficient in selenoprotein MsrB1, the main mammalian MsrB located in the cytosol and nucleus. In these mice, in addition to the deletion of 14-kDa MsrB1, a 5-kDa selenoprotein form was specifically removed. Further studies revealed that the 5-kDa protein occurred in both mouse tissues and human HEK 293 cells; was down-regulated by MsrB1 small interfering RNA, selenium deficiency, and selenocysteine tRNA mutations; and was immunoprecipitated and recognized by MsrB1 antibodies. Specific labeling with (75)Se and mass spectrometry analyses revealed that the 5-kDa selenoprotein corresponded to the C-terminal sequence of MsrB1. The MsrB1 knock-out mice lacked both 5- and 14-kDa MsrB1 forms and showed reduced MsrB activity, with the strongest effect seen in liver and kidney. In addition, MsrA activity was decreased by MsrB1 deficiency. Liver and kidney of the MsrB1 knock-out mice also showed increased levels of malondialdehyde, protein carbonyls, protein methionine sulfoxide, and oxidized glutathione as well as reduced levels of free and protein thiols, whereas these parameters were little changed in other organs examined. Overall, this study established an important contribution of MsrB1 to the redox control in mouse liver and kidney and identified a novel form of this protein.