Higher-Order VLP-Based Protein Macromolecular Framework Structures Assembled via Coiled-Coil Interactions.

Hierarchical organization is one of the fundamental features observed in biological systems that allows for efficient and effective functioning. Virus-like particles (VLPs) are elegant examples of a hierarchically organized supramolecular structure, where many subunits are self-assembled to generate the functional cage-like architecture. Utilizing VLPs as building blocks to construct two- and three-dimensional (3D) higher-order structures is an emerging research area in developing functional biomimetic materials. VLPs derived from P22 bacteriophages can be repurposed as nanoreactors by encapsulating enzymes and modular units to build higher-order catalytic materials via several techniques. In this study, we have used coiled-coil peptide interactions to mediate the P22 interparticle assembly into a highly stable, amorphous protein macromolecular framework (PMF) material, where the assembly does not depend on the VLP morphology, a limitation observed in previously reported P22 PMF assemblies. Many encapsulated enzymes lose their optimum functionalities under the harsh conditions that are required for the P22 VLP morphology transitions. Therefore, the coiled-coil-based PMF provides a fitting and versatile platform for constructing functional higher-order catalytic materials compatible with sensitive enzymes. We have characterized the material properties of the PMF and utilized the disordered PMF to construct a biocatalytic 3D material performing single- and multistep catalysis.

Population Pharmacokinetic Analysis and Dosing Optimization Based on Unbound Daptomycin Concentration and Cystatin C in Nonobese Elderly Patients with Hypoalbuminemia and Chronic Kidney Disease.

PURPOSE: This study evaluated the population pharmacokinetics of daptomycin in nonobese elderly patients with hypoalbuminemia and chronic kidney disease (CKD) using the glomerular filtration rate estimated from cystatin C (eGFRcys) and estimated its optimal dose. METHODS: We performed population pharmacokinetic analysis of the unbound concentrations of daptomycin. The probability of target attainment of 90% for achieving an area under the concentration-time curve of unbound daptomycin at steady state/ minimum inhibitory concentration ratio of ≥66.6 was stochastically simulated. RESULTS: In the population pharmacokinetic analysis of 25 patients aged ≥65 years, the two-compartment model using eGFRcys and age as covariates of clearance in central compartment of unbound daptomycin were optimal. The unbound fraction rate (fu) was 0.05-0.14. According to the Monte Carlo simulation, the optimal doses for patients with eGFRcys of 20-60 mL/min and aged 65-95 years were calculated as 200-500 mg q24h. CONCLUSION: These results suggest that establishing the dose using total concentrations may result in under- or overestimation caused by alterations in fu. The optimal dose for nonobese elderly patients with hypoalbuminemia and CKD depends on eGFRcys and age, and a standard dose may be insufficient for some patients.

Synthetic Virus-like Particles for Glutathione Biosynthesis.

Protein-based nanocompartments found in nature have inspired the development of functional nanomaterials for a range of applications including delivery of catalytic activities with therapeutic effects. As glutathione (GSH) plays a vital role in metabolic adaptation and many diseases are associated with its deficiency, supplementation of GSH biosynthetic activity might be a potential therapeutic when delivered directly to the disease site. Here, we report the successful design and production of active nanoreactors capable of catalyzing the partial or complete pathway for GSH biosynthesis, which was realized by encapsulating essential enzymes of the pathway inside the virus-like particle (VLP) derived from the bacteriophage P22. These nanoreactors are the first examples of nanocages specifically designed for the biosynthesis of oligomeric biomolecules. A dense packing of enzymes is achieved within the cavities of the nanoreactors, which allows us to study enzyme behavior, in a crowded and confined environment, including enzymatic kinetics and protein stability. In addition, the biomedical utility of the nanoreactors in protection against oxidative stress was confirmed using an in vitro cell culture model. Given that P22 VLP capsid was suggested as a potential liver-tropic nanocarrier in vivo, it will be promising to test the efficacy of these GSH nanoreactors as a novel treatment for GSH-deficient hepatic diseases.

Mrakia hoshinonis sp. nov., a novel psychrophilic yeast isolated from a retreating glacier on Ellesmere Island in the Canadian High Arctic.

Four strains isolated from sediment sampled at the front of a retreating glacier on northern Ellesmere Island in the Canadian high Arctic, namely JCM 32575T, JCM 32576, JCM 32577 and JCM 32578, belong to a novel psychrophilic basidiomycetous yeast species in the genus Mrakia. Molecular phylogenetic analysis indicated that these strains are most closely related to the type strains of Mrakia aquatica and Mrakianic combsii, but with 8-9 and 7-12 nt substitutions in ITS and in the D1/D2 domain of the LSU rRNA gene, respectively. The strains grew at sub-zero temperatures and in vitamin-free media, with lipase and cellulase highly active even at -3 °C. These characteristics likely allow this yeast species to grow and survive in extremely cold, oligotrophic environments, such as the fronts of retreating glaciers in the high Arctic. The name Mrakia hoshinonis sp. nov. is proposed, with type strain JCM 32575T (UAMH 11969) and MycoBank number MB 825484.

Enhancement Effect of Poly-L-ornithine on the Nasal Absorption of Water-Soluble Macromolecules in Rats.

The transnasal route for the delivery of water-soluble macromolecules, such as bioactive peptides and proteins, has attracted interest, although the use of permeation enhancers is required due to the poor permeabilities of these macromolecules across the nasal mucosa. With polycationic compounds, such as poly-L-arginine and chitosan, the nasal absorption of hydrophilic macromolecules is molecular weight- and concentration-dependently enhanced without causing cytotoxicity. In the present study, we evaluated the effect of various molecular weights and concentrations of poly-L-ornithine (PLO), a polycationic compound, on the nasal absorption and the damage to the nasal mucosa in vivo. PLO enhanced the nasal absorption of fluorescein isothiocyanate-dextran (FD-4), used as a model drug, and the bioavailability of FD-4 increased with the concentration of PLO. The enhancement effect was also dependent on the molecular weight. The administration of PLO at a concentration that sufficed for enhancing the nasal absorption had no effect on the activity of lactic dehydrogenase and the protein leakage in the nasal fluid, as indices of nasal mucosa damage. These findings suggest that a transnasal delivery system using PLO is a useful strategy for improving the nasal absorption of water-soluble macromolecules without toxicity to the nasal mucosa.

[Gender Differences in Projected Life Expectancy in Japan (2023-2047) Determined by Bayesian Age-Period-Cohort Analysis].

OBJECTIVES: In this study, we aimed to (1) determine the effects of age, period, and cohort on mortality rate trends between 1958 and 2012 in Japan and (2) assess gender differences in projected life expectancy (LE) for the 2023-2047 period. METHODS: A time trend study was conducted using age-period-cohort (APC) analysis. A Bayesian APC model was fitted to describe mortality rate trends for the 1958-2012 period and to project mortality rates for 2023-2047. LE was predicted by Chiang's method using projected mortality rates. RESULTS: Age, period, and cohort effects showed similar patterns between males and females. As time passes, gender differences in projected LE were larger among individuals over 65 years than among those under 65 years. Time series change rates of the extension of projected LE after excluding specific causes of death showed the following: smaller extension of projected LE in males in terms of mortality risk from malignant neoplasms, heart diseases, pneumonia, and accidents (under 65 years) and in females in terms of mortality risk from heart diseases, cerebrovascular diseases, and suicide (over 65 years). CONCLUSIONS: Gender differences in projected LE are expected to be smaller before middle age and to be larger among seniors. These projected gender differences stem in part from the lower mortality risk among men than among women from malignant neoplasms, heart diseases, pneumonia, and accidents (under 65 years), and among women compared to men from heart disease, cerebrovascular disease, and suicide (over 65 years).

Sortase-Mediated Ligation as a Modular Approach for the Covalent Attachment of Proteins to the Exterior of the Bacteriophage P22 Virus-like Particle.

Virus-like particles are unique platforms well suited for the construction of nanomaterials with broad-range applications. The research presented here describes the development of a modular approach for the covalent attachment of protein domains to the exterior of the versatile bacteriophage P22 virus-like particle (VLP) via a sortase-mediated ligation strategy. The bacteriophage P22 coat protein was genetically engineered to incorporate an LPETG amino acid sequence on the C-terminus, providing the peptide recognition sequence utilized by the sortase enzyme to catalyze peptide bond formation between the LPETG-tagged protein and a protein containing a polyglycine sequence on the N-terminus. Here we evaluate attachment of green fluorescent protein (GFP) and the head domain of the influenza hemagglutinin (HA) protein by genetically producing polyglycine tagged proteins. Attachment of both proteins to the exterior of the P22 VLP was found to be highly efficient as judged by SDS-PAGE densitometry. These results enlarge the tool kit for modifying the P22 VLP system and provide new insights for other VLPs that have an externally displayed C-terminus that can use the described strategy for the modular modification of their external surface for various applications.

Preparation and Evaluation of PEGylated Poly-L-ornithine Complex as a Novel Absorption Enhancer.

Polycationic compounds, such as poly-L-arginine and poly-L-ornithine (PLO), enhance the nasal absorption of hydrophilic macromolecular drugs. However, the bio availability corresponding to the dose of these enhancers has not been obtained in an open system study, where an administered solution is transferred to the pharynx because they do not exhibit mucoadhesion/retention in the nasal cavity. In this study, we prepared PEGylated-poly-L-ornithine (PEG-PLO) and investigated the effects of PEGylation on in vitro adhesion/retention properties, permeation enhancement efficiency, and cytotoxicity. PEG-PLO bearing 3-4 polyethylene glycol (PEG) chains per PLO molecule was more retentive than unmodified PLO on an inclined plate. The permeability of a model drug, FD-4, across Caco-2 cell sheets was enhanced by PEG-PLO as well as by PLO. PLO showed cytotoxicity at high concentrations, whereas PEG-PLO did not decrease cell viability, even above the concentration giving a sufficient enhancement effect. These findings suggest that PEGylation of polycationic absorption enhancers improves their adhesion/retention and decreases their cytotoxicity, which may lead to enhancers with greater utility.

RGD targeting of human ferritin iron oxide nanoparticles enhances in vivo MRI of vascular inflammation and angiogenesis in experimental carotid disease and abdominal aortic aneurysm.

PURPOSE: To evaluate Arg-Gly-Asp (RGD)-conjugated human ferritin (HFn) iron oxide nanoparticles for in vivo magnetic resonance imaging (MRI) of vascular inflammation and angiogenesis in experimental carotid disease and abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: HFn was genetically engineered to express the RGD peptide and Fe3 O4 nanoparticles were chemically synthesized inside the engineered HFn (RGD-HFn). Macrophage-rich left carotid lesions were induced by ligation in FVB mice made hyperlipidemic and diabetic (n = 14), with the contralateral right carotid serving as control. Murine AAAs were created by continuous angiotensin II infusion in ApoE-deficient mice (n = 12), while control mice underwent saline infusion (n = 8). All mice were imaged before and after intravenous injection with either RGD-HFn-Fe3 O4 or HFn-Fe3 O4 using a gradient-echo sequence on a whole-body 3T clinical scanner, followed by histological analysis. The nanoparticle accumulation was assessed by the extent of T2*-induced carotid lumen reduction (% lumen loss) or aortic T2*-weighted signal intensity reduction (% SI [signal intensity] loss). RESULTS: RGD-HFn-Fe3 O4 was taken up more than HFn-Fe3 O4 in both the ligated left carotid arteries (% lumen loss; 69 ± 9% vs. 36 ± 7%, P = 0.01) and AAAs (% SI loss; 47 ± 6% vs. 20 ± 5%, P = 0.01). The AAA % SI loss correlated positively with AAA size (r = 0.89, P < 0.001). Histology confirmed the greater accumulation and colocalization of RGD-HFn-Fe3 O4 to both vascular macrophages and endothelial cells. CONCLUSION: RGD-HFn-Fe3 O4 enhances in vivo MRI by targeting both vascular inflammation and angiogenesis, and provides a promising translatable MRI approach to detect high-risk atherosclerotic and aneurysmal vascular diseases. LEVEL OF EVIDENCE: 1 J. Magn. Reson. Imaging 2017;45:1144-1153.

Development of a Transnasal Delivery System for Recombinant Human Growth Hormone (rhGH): Effects of the Concentration and Molecular Weight of Poly-L-arginine on the Nasal Absorption of rhGH in Rats.

A novel system for delivering recombinant human growth hormone (rhGH) that is noninvasive and has a simple method of administration is strongly desired to improve the compliance of children. The aim of this study was to investigate the potential for the intranasal (i.n.) co-administration of rhGH with poly-L-arginine (PLA) as a novel delivery system by evaluating the effects of the concentration and molecular weight of PLA on the nasal absorption of rhGH. The influence of the formation of insoluble aggregates and a soluble complex in the dosage formulation on nasal rhGH absorption was also evaluated by size-exclusion chromatography and ultrafiltration. PLA enhanced the nasal absorption of rhGH at each concentration and molecular weight examined. Nasal rhGH absorption increased dramatically when the PLA concentration was 1.0 % (w/v) due to the improved solubility of rhGH in the formulation. A delay in rhGH absorption was observed when the molecular weight of PLA was increased. This appeared to be because the increase in molecular weight caused the formation of a soluble complex. It seems that the PLA concentration affects the absorption-enhancing effect on rhGH, while the molecular weight of PLA affects the time when the maximum plasma rhGH concentration was reached (Tmax) of rhGH after i.n. administration, mainly because of the interactions among rhGH, PLA, and additives. Therefore, the transnasal rhGH delivery system using PLA is considered to be a promising alternative to subcutaneous (s.c.) injection if these interactions are sufficiently controlled.

Symmetry Controlled, Genetic Presentation of Bioactive Proteins on the P22 Virus-like Particle Using an External Decoration Protein.

Viruses use spatial control of constituent proteins as a means of manipulating and evading host immune systems. Similarly, precise spatial control of proteins encapsulated or presented on designed nanoparticles has the potential to biomimetically amplify or shield biological interactions. Previously, we have shown the ability to encapsulate a wide range of guest proteins within the virus-like particle (VLP) from Salmonella typhimurium bacteriophage P22, including antigenic proteins from human pathogens such as influenza. Expanding on this robust encapsulation strategy, we have used the trimeric decoration protein (Dec) from bacteriophage L as a means of controlled exterior presentation on the mature P22 VLP, to which it binds with high affinity. Through genetic fusion to the C-terminus of the Dec protein, either the 17 kDa soluble region of murine CD40L or a minimal peptide designed from the binding region of the "self-marker" CD47 was independently presented on the P22 VLP capsid exterior. Both candidates retained function when presented as a Dec-fusion. Binding of the Dec domain to the P22 capsid was minimally changed across designed constructs, as measured by surface plasmon resonance, demonstrating the broad utility of this presentation strategy. Dec-mediated presentation offers a robust, modular means of decorating the exposed exterior of the P22 capsid in order to further orchestrate responses to internally functionalized VLPs within biological systems.

Age, period, and birth cohort-specific effects on cervical cancer mortality rates in Japanese women and projections for mortality rates over 20-year period (2012-2031).

OBJECTIVES: We aimed to determine the effects of age, period, and birth cohort on cervical cancer mortality rate trends in Japanese women, by age-period-cohort (APC) analysis. Additionally, we analyzed projected mortality rates. METHODS: We obtained data on the number of cervical cancer deaths in Japanese women from 1975-2011 from the national vital statistics and census population data. A cohort table of mortality rate data was analyzed on the basis of a Bayesian APC model. We also projected the mortality rates for the 2012-2031 period. RESULTS: The period effect was relatively limited, compared with the age and cohort effects. The age effect increased suddenly from 25-29 to 45-49 years of age and gently increased thereafter. An analysis of the cohort effect on mortality rate trends revealed a steep decreasing slope for birth cohorts born from 1908-1940 and a subsequent sudden increase after 1945. The mortality rate projections indicated increasing trends from 40 to 74 years of age until the year 2031. CONCLUSIONS: The age effect increased from 25-29 years of age. This could be attributable to the high human papilloma virus (HPV) infection risk and the low cervical cancer screening rate. The cohort effect changed from decreasing to increasing after the early 1940s. This might be attributable to the spread of cervical cancer screening and treatment before 1940 and the high HPV infection risk and reduced cervical cancer screening rate after 1945. The projected mortality rate indicated an increasing trend until the year 2031.

A mechanism enhancing macromolecule transport through paracellular spaces induced by Poly-L-Arginine: Poly-L-Arginine induces the internalization of tight junction proteins via clathrin-mediated endocytosis.

PURPOSE: Poly-L-arginine (PLA) enhances the paracellular permeability of the Caco-2 cell monolayer to hydrophilic macromolecules by disappearance of tight junction (TJ) proteins from cell-cell junctions. However, the mechanism of the disappearance of TJ proteins in response to PLA has been unclear. In this study, we investigated the mechanism of disappearance of TJ proteins from cell-cell junctions after the application of PLA to Caco-2 cell monolayers. METHODS: The membrane conductance (Gt), FITC-dextran (FD-4) permeability, and localization of TJ proteins were examined after the treatment of Caco-2 cell monolayers with PLA in the presence of various endocytosis inhibitors. In addition, the localization of endosome marker proteins was also observed. RESULTS: Clathrin-mediated endocytosis inhibitors suppressed the increase in Gt and Papp of FD-4 induced by PLA, and also significantly suppressed the disappearance of TJ proteins induced by PLA. Furthermore, occludin, one of the TJ proteins, colocalized with early endosome and recycling endosomes after the internalization of occludin induced by PLA, and then was recycled to the cell-cell junctions. CONCLUSION: PLA induced the transient internalization of TJ proteins in cell-cell junctions via clathrin-mediated endocytosis, subsequently increasing the permeability of the Caco-2 cell monolayer to FD-4 via a paracellular route.

Evaluation of the effects of absorption enhancers on Caco-2 cell monolayers by using a pore permeation model involving two different sizes.

We applied a parallel pore permeation model based on the Renkin molecular sieving function by using two different-sized pathways to analyze the permeation-enhancing effects of poly-L-arginine (PLA) or a mixed system of spermine (SPM) and sodium taurocholate (STC). Four paracellular markers were simultaneously applied to Caco-2 cell monolayers, and a set of apparent permeability coefficient (P) values was used to obtain membrane parameters. For PLA treatment, the pore occupancy/length ratio (ε/L) of the large pathways increased while the pore radius (R) did not, suggesting that the number of large pathways for the relatively large hydrophilic molecules in the monolayers could be increased by the addition of PLA. In contrast, application of the mixed system comprising SPM and STC significantly increased not only the R of the large pathways but also ε/L of the small pathways. Such changes in membrane parameters could be related to the enhancing mechanism of these compounds. The simulation curves for molecular weight (MW)-P calculated from the membrane parameters could be used to predict the P of drugs with different MWs.

Effect of poly-L-arginine on intestinal absorption of hydrophilic macromolecules in rats.

We have already reported that poly-L-arginine (PLA) remarkably enhanced the in vivo nasal absorption of hydrophilic macromolecules without producing any significant epithelial damage in rats. In the present study, we examined whether PLA could enhance the absorption of a model hydrophilic macromolecule, fluorescein isothiocyanate-dextran (FD-4), across the intestinal mucosa, as well as the nasal mucosa, by an in situ closed-loop method using the rat intestine. PLA was found to enhance the intestinal absorption of FD-4 in a concentration-dependent manner within the concentrations investigated in this study, but segment-specific differences were found to be associated with this effect (ileum>jejunum>duodenum≧colon). The factors responsible for the segment-specific differences were also investigated by intestinal absorption studies using aprotinin, a trypsin inhibitor, and an analysis of the expression of occludin, a tight junction protein. In the small intestine, the differences in the effect of PLA on the absorption of FD-4 may be related to the enzymatic degradation of PLA. In the colon, the reduced effect of PLA on the absorption of FD-4 may be related to the smaller surface area for absorption and the higher expression of occludin compared with other segments.

Poly-L-arginine-Induced internalization of tight junction proteins increases the paracellular permeability of the Caco-2 cell monolayer to hydrophilic macromolecules.

We investigated whether poly-L-arginine (PLA) enhances the paracellular permeability of the Caco-2 monolayer to hydrophilic macromolecules and clarified the disposition of tight junction (TJ) proteins. The transepithelial electrical resistance (TEER) and fluorescein isothiocyanate (FITC)-dextran (FD-4) permeation were determined after treatment with PLA. TJ proteins were visualized using immunofluorescence microscopy after PLA exposure and depletion, and their expression levels were determined. The barrier function of TJs was also evaluated by measuring the alterations in the TEER and in the localization of TJ proteins. PLA induced an increase in hydrophilic macromolecule, FD-4, permeation through Caco-2 cell monolayers and a decrease in the TEER in a concentration-dependent manner, without any significant impact on the cell viability. This increased paracellular permeability induced by PLA was found to be internalized of claudin-4, ZO-1, tricellulin and mainly occludin from cell-cell junction to the subcellular space. ZO-1 appeared to play an important role in the reconstitution of TJ strand structures following PLA depletion. These results indicate that the PLA led to the internalization of TJ proteins to the subcellular space, subsequently increasing the permeability of the Caco-2 cell monolayer to FD-4 via a paracellular route.

RGD-conjugated human ferritin nanoparticles for imaging vascular inflammation and angiogenesis in experimental carotid and aortic disease.

PURPOSE: Inflammation and angiogenesis are important contributors to vascular disease. We evaluated imaging both of these biological processes, using Arg-Gly-Asp (RGD)-conjugated human ferritin nanoparticles (HFn), in experimental carotid and abdominal aortic aneurysm (AAA) disease. PROCEDURES: Macrophage-rich carotid lesions were induced by ligation in hyperlipidemic and diabetic FVB mice (n = 16). AAAs were induced by angiotensin II infusion in apoE(-/-) mice (n=10). HFn, with or without RGD peptide, was labeled with Cy5.5 and injected intravenously for near-infrared fluorescence imaging. RESULTS: RGD-HFn showed significantly higher signal than HFn in diseased carotids and AAAs relative to non-diseased regions, both in situ (carotid: 1.88 ± 0.30 vs. 1.17 ± 0.10, p = 0.04; AAA: 2.59 ± 0.24 vs. 1.82 ± 0.16, p = 0.03) and ex vivo. Histology showed RGD-HFn colocalized with macrophages in carotids and both macrophages and neoangiogenesis in AAA lesions. CONCLUSIONS: RGD-HFn enhances vascular molecular imaging by targeting both vascular inflammation and angiogenesis, and allows more comprehensive detection of high-risk atherosclerotic and aneurysmal vascular diseases.

Protein cage nanoparticles bearing the LyP-1 peptide for enhanced imaging of macrophage-rich vascular lesions.

Cage-like protein nanoparticles are promising platforms for cell- and tissue-specific targeted delivery of imaging and therapeutic agents. Here, we have successfully modified the 12 nm small heat shock protein from Methanococcus jannaschii (MjHsp) to detect atherosclerotic plaque lesions in a mouse model system. As macrophages are centrally involved in the initiation and progression of atherosclerosis, targeted imaging of macrophages is valuable to assess the biologic status of the blood vessel wall. LyP-1, a nine residue peptide, has been shown to target tumor-associated macrophages. Thus, LyP-1 was genetically incorporated onto the exterior surface of MjHsp, while a fluorescent molecule (Cy5.5) was conjugated on the interior cavity. This bioengineered protein cage, LyP-Hsp, exhibited enhanced affinity to macrophage in vitro. Furthermore, in vivo injection of LyP-Hsp allowed visualization of macrophage-rich murine carotid lesions by in situ and ex vivo fluorescence imaging. These results demonstrate the potential of LyP-1-conjugated protein cages as nanoscale platforms for delivery of imaging agents for the diagnosis of atherosclerosis.

Human ferritin cages for imaging vascular macrophages.

Atherosclerosis is a leading cause of death worldwide. Macrophages are key components of vascular inflammation, which contributes to the development and complications of atherosclerosis. Ferritin, an iron storage and transport protein, has been found to accumulate in macrophages in human atherosclerotic plaques. We hypothesized that ferritin could serve as an intrinsic nano-platform to target delivery of imaging agents to vascular macrophages to detect high-risk atherosclerotic plaques. Here we show that engineered human ferritin protein cages, either conjugated to the fluorescent Cy5.5 molecule or encapsulating a magnetite nanoparticle, are taken up in vivo by macrophages in murine atherosclerotic carotid arteries and can be imaged by fluorescence and magnetic resonance imaging. These results indicate that human ferritin can serve as a nanoparticle platform to image vascular inflammation in vivo.

Oral nitrite ameliorates dextran sulfate sodium-induced acute experimental colitis in mice.

Inflammatory bowel diseases (IBDs) such as Crohn's disease and ulcerative colitis are chronic inflammatory disorders of the intestinal tract with excessive production of cytokines, adhesion molecules, and reactive oxygen species. Although nitric oxide (NO) is reported to be involved in the onset and progression of IBDs, it remains controversial as to whether NO is toxic or protective in experimental colitis. We investigated the effects of oral nitrite as a NO donor on dextran sulfate sodium (DSS)-induced acute colitis in mice. Mice were fed DSS in their drinking water with or without nitrite for up to 7days. The severity of colitis was assessed by disease activity index (DAI) observed over the experimental period, as well as by the other parameters, including colon lengths, hematocrit levels, and histological scores at day 7. DSS treatment induced severe colitis by day 7 with exacerbation in DAI and histological scores. We first observed a significant decrease in colonic nitrite levels and increase in colonic TNF-alpha expression at day 3 after DSS treatment, followed by increased colonic myeloperoxidase (MPO) activity and increased colonic expressions of both inducible NO synthase (iNOS) and heme oxygenase-1 (HO-1) at day 7. Oral nitrite supplementation to colitis mice reversed colonic nitrite levels and TNF-alpha expression to that of normal control mice at day 3, resulting in the reduction of MPO activity as well as iNOS and HO-1 expressions in colonic tissues with clinical and histological improvements at day 7. These results suggest that oral nitrite inhibits inflammatory process of DSS-induced experimental colitis by supplying nitrite-derived NO instead of impaired colonic NOS activity.