Oral Administration of Lipopolysaccharide Enhances Insulin Signaling-Related Factors in the KK/Ay Mouse Model of Type 2 Diabetes Mellitus.

Lipopolysaccharide (LPS), an endotoxin, induces systemic inflammation by injection and is thought to be a causative agent of chronic inflammatory diseases, including type 2 diabetes mellitus (T2DM). However, our previous studies found that oral LPS administration does not exacerbate T2DM conditions in KK/Ay mice, which is the opposite of the response from LPS injection. Therefore, this study aims to confirm that oral LPS administration does not aggravate T2DM and to investigate the possible mechanisms. In this study, KK/Ay mice with T2DM were orally administered LPS (1 mg/kg BW/day) for 8 weeks, and blood glucose parameters before and after oral administration were compared. Abnormal glucose tolerance, insulin resistance progression, and progression of T2DM symptoms were suppressed by oral LPS administration. Furthermore, the expressions of factors involved in insulin signaling, such as insulin receptor, insulin receptor substrate 1, thymoma viral proto-oncogene, and glucose transporter type 4, were upregulated in the adipose tissues of KK/Ay mice, where this effect was observed. For the first time, oral LPS administration induces the expression of adiponectin in adipose tissues, which is involved in the increased expression of these molecules. Briefly, oral LPS administration may prevent T2DM by inducing an increase in the expressions of insulin signaling-related factors based on adiponectin production in adipose tissues.

Anti-inflammatory and Insulin Signaling Phenotype Induced by Repeated Lipopolysaccharide Stimulation in 3T3-L1 Adipocytes.

BACKGROUND/AIM: Lipopolysaccharide (LPS) is thought to be a causative agent of type 2 diabetes, because it has been shown that a single LPS stimulation in vitro induces chronic inflammation and reduces insulin signaling in adipocytes. However, oral LPS administration prevents type 2 diabetes, and this effect does not correspond to a single LPS adipocyte stimulation. In this study, the response of adipocytes to single and repeated stimulation with LPS was examined. MATERIALS AND METHODS: 3T3-L1 cells were differentiated into adipocytes and stimulated with LPS once or thrice every 24 h. The expression levels of inflammatory and anti-inflammatory factors and insulin sensitivity-related factors were measured. RESULTS: Single stimulation with LPS increased the mRNA and protein expression of inflammatory factors (interleukin-6 and monocyte chemotactic protein 1), but this increase was inhibited by repeated stimulation. In contrast, the mRNA expression levels of anti-inflammatory factors (proliferator-activated receptor γ and peroxisome proliferator-activated receptor gamma coactivator1 α) were increased by repeated LPS stimulation. Additionally, the mRNA expression levels of insulin sensitivity-related factors (glucose transporter type 4, insulin receptor, insulin receptor substrate 1 and thymoma viral proto-oncogene 2) in adipocytes were increased upon repeated LPS stimulation. CONCLUSION: Repetitive LPS stimulation, unlike single stimulation of adipocytes, upregulates anti-inflammatory and insulin signaling-related factors.

Prevention of Diabetes-Associated Cognitive Dysfunction Through Oral Administration of Lipopolysaccharide Derived From Pantoea agglomerans.

Diabetes-related cognitive dysfunction (DRCD) is a serious complication induced by diabetes. However, there are currently no specific remedies for DRCD. Here, we show that streptozotocin-induced DRCD can be prevented without causing side effects through oral administration of lipopolysaccharide (LPS) derived from Pantoea agglomerans. Oral administration of LPS (OAL) prevented the cerebral cortex atrophy and tau phosphorylation induced by DRCD. Moreover, we observed that neuroprotective transformation of microglia (brain tissue-resident macrophages) is important for preventing DRCD through OAL. These findings are contrary to the general recognition of LPS as an inflammatory agent when injected systemically. Furthermore, our results strongly suggest that OAL promotes membrane-bound colony stimulating factor 1 (CSF1) expression on peripheral leukocytes, which activates the CSF1 receptor on microglia, leading to their transformation to the neuroprotective phenotype. Taken together, the present study indicates that controlling innate immune modulation through the simple and safe strategy of OAL can be an innovative prophylaxis for intractable neurological diseases such as DRCD. In a sense, for modern people living in an LPS-depleted environment, OAL is like a time machine that returns microglia to the good old LPS-abundant era.

Oral Administration of Lipopolysaccharide Prevents Cognitive Impairment in Streptozotocin-induced Diabetic Mice in a Blood Glucose-independent Manner.

BACKGROUND/AIM: Diabetes is a risk factor for dementia. However, no radical preventive method for diabetes-associated dementia has yet been developed. Our previous study revealed that oral administration of lipopolysaccharide (LPS) prevents high-fat diet-induced cognitive impairment. Therefore, we investigated here whether oral administration of LPS (OAL) could also prevent diabetes-associated dementia. MATERIALS AND METHODS: Diabetic mice were produced by intraperitoneal administration of streptozotocin (STZ), and then mice were orally administered LPS. Cognitive ability was evaluated using the Morris water maze, and gene expression was analyzed in isolated microglia. RESULTS: OAL prevented STZ-induced diabetic cognitive impairment, but did not affect blood glucose levels. Moreover, OAL promoted the expression of neuroprotective genes in microglia, such as heat shock protein family 40 (HSP40) and chemokine CCL7. CONCLUSION: OAL prevents diabetes-associated dementia, potentially via promotion of HSP40 and CCL7 expression in microglia.

Prevention of streptozotocin­induced Neuro­2a cell death by C8­B4 microglia transformed with repetitive low­dose lipopolysaccharide.

Diabetes­associated neuronal dysfunction (DAND) is one of the serious complications of diabetes, but there is currently no remedy for it. Streptozotocin [2­deoxy­2­(3­methy1­3­nitrosoureido) D­glucopyranose; STZ] is one of the most well­established diabetes inducers and has been used in vivo and in vitro DAND models. The aim of the present study was to demonstrate that C8­B4 microglia transformed by the stimulus of repetitive low­dose lipopolysaccharide (LPSx3­microglia) prevent STZ­induced Neuro­2a neuronal cell death in vitro. The ELISA results showed that neurotrophin­4/5 (NT­4/5) secretion was promoted in LPSx3­microglia and the cell viability assay with trypan blue staining revealed that the culture supernatant of LPSx3­microglia prevented STZ­induced neuronal cell death. In addition, reverse transcription­quantitative PCR showed that neurons treated with the culture supernatant of LPSx3­microglia promoted the gene expression of B­cell lymphoma­extra large and glucose­dependent insulinotropic polypeptide receptor. Furthermore, the inhibition of tyrosine kinase receptor B, a receptor of NT­4/5, suppressed the neuroprotective effect of LPSx3­microglia. Taken together, the present study demonstrated that LPSx3­microglia prevent STZ­induced neuronal death and that NT­4/5 may be involved in the neuroprotective mechanism of LPSx3­microglia.

Low-dose lipopolysaccharide as an immune regulator for homeostasis maintenance in the central nervous system through transformation to neuroprotective microglia.

Microglia, which are tissue-resident macrophages in the brain, play a central role in the brain innate immunity and contribute to the maintenance of brain homeostasis. Lipopolysaccharide is a component of the outer membrane of gram-negative bacteria, and activates immune cells including microglia via Toll-like receptor 4 signaling. Lipopolysaccharide is generally known as an endotoxin, as administration of high-dose lipopolysaccharide induces potent systemic inflammation. Also, it has long been recognized that lipopolysaccharide exacerbates neuroinflammation. In contrast, our study revealed that oral administration of lipopolysaccharide ameliorates Alzheimer's disease pathology and suggested that neuroprotective microglia are involved in this phenomenon. Additionally, other recent studies have accumulated evidence demonstrating that controlled immune training with low-dose lipopolysaccharide prevents neuronal damage by transforming the microglia into a neuroprotective phenotype. Therefore, lipopolysaccharide may not a mere inflammatory inducer, but an immunomodulator that can lead to neuroprotective effects in the brain. In this review, we summarized current studies regarding neuroprotective microglia transformed by immune training with lipopolysaccharide. We state that microglia transformed by lipopolysaccharide preconditioning cannot simply be characterized by their general suppression of proinflammatory mediators and general promotion of anti-inflammatory mediators, but instead must be described by their complex profile comprising various molecules related to inflammatory regulation, phagocytosis, neuroprotection, anti-apoptosis, and antioxidation. In addition, microglial transformation seems to depend on the dose of lipopolysaccharide used during immune training. Immune training of neuroprotective microglia using low-dose lipopolysaccharide, especially through oral lipopolysaccharide administration, may represent an innovative prevention or treatment for neurological diseases; however more vigorous studies are still required to properly modulate these treatments.

A Novel Anti-inflammatory Phenotype Transformed by Repetitive Low-dose Lipopolysaccharide in Primary Peritoneal Tissue-resident Macrophages.

BACKGROUND/AIM: Our previous studies suggested that oral administration of lipopolysaccharide (LPS) regulates the progression of various diseases via transformation of tissue-resident macrophages (MΦ). Recently, we characterized microglia transformed by repetitive low-dose LPS treatment (REPELL-microglia) in vitro, and this response was similar to that observed in response to oral administration of LPS in vivo. Here, we examined the characteristics of peritoneal tissue-resident MΦ (pMΦ) transformed by repetitive low-dose LPS treatment (REPELL-pMΦ). MATERIALS AND METHODS: Primary pMΦ were treated with low-dose LPS (1 ng/ml) three times; subsequently, phagocytic activity and gene expression were evaluated. RESULTS: REPELL-pMΦ exhibited high phagocytic activity and elevated expression of Arg1, Gipr, Gdnf, and Fpr2. The gene expression profiles observed in REPELL-pMΦ were distinct from those of REPELL-microglia. CONCLUSION: REPELL-pMΦ have the potential to promote clearance of xenobiotics and to suppress inflammation. The present study also demonstrates the diversity of tissue-resident MΦ transformation that reflect their tissue origin.

Attempt to Construct an In Vitro Model of Enhancement of Macrophage Phagocytosis Via Continuous Administration of LPS.

BACKGROUND: Continuous oral administration of lipopolysaccharide (LPS) enhances the phagocytic ability of macrophages, which is useful for preventing various diseases. Here, we attempted to create an in vitro model of continuous administration of LPS. MATERIALS AND METHODS: RAW264.7 cells were stimulated with LPS three times every 24 h (repeated stimulation), and phagocytic ability and inflammatory cytokine [interleukin-6 (IL6) and tumor necrosis factor-α (TNFα)] production were measured. RESULTS: The phagocytic ability was increased by a single stimulation with LPS and was maintained by repeated stimulation. IL6 production increased with a single stimulation with LPS; however, IL6 production by repeated stimulation with LPS was comparable to that of non-stimulation with LPS. On the other hand, the amount of TNFα was significantly increased by single and repeated stimulation with LPS. CONCLUSION: Repeated stimulation with LPS in RAW264.7 cells triggered a phenotype that was similar to that of macrophages after continuous oral administration of LPS. This suggests that this study model may reproduce the enhancement of macrophage phagocytosis, an effect afforded by continuous oral administration of LPS.

Mastication Affects Transcriptomes of Mouse Microglia.

BACKGROUND/AIM: We investigated whether mastication affects microglia, whose activity is thought to be associated with cognition and brain tumor progression. MATERIALS AND METHODS: We kept mice by feeding either a hard or soft diet for 2, 4 or 8 months. After each period, we removed the whole brains and isolated microglia. The total RNA extracted from each brain's microglia was subjected to DNA microarray analysis. RESULTS: Many genes were found to be significantly differentially expressed between hard- and soft-diet-fed mice in each group of the same feeding period. The expression of several genes involved in the regulation of actin cytoskeleton was down-regulated in the soft-diet-fed mice. CONCLUSION: Mastication may affect microglia's roles in cognition as well as their neuroimmune activity through their activity of patrolling the brain.

A unique hybrid characteristic having both pro- and anti-inflammatory phenotype transformed by repetitive low-dose lipopolysaccharide in C8-B4 microglia.

Although lipopolysaccharide (LPS) is regarded as an inducer of inflammation, previous studies have suggested that repetitive low-dose LPS has neuroprotective effects via immunomodulation of microglia, resident macrophages of brain. However, microglia transformed by the stimulus of repetitive low-dose LPS (REPELL-microglia) are not well characterized, whereas microglia transformed by repetitive high-dose LPS are well studied as an endotoxin tolerance model in which the induction of pro-inflammatory molecules is suppressed. In this study, to characterize REPELL-microglia, the gene expression and phagocytic activity of REPELL-microglia were analyzed with the murine C8-B4 microglia cell line. The REPELL-microglia were characterized by a high expression of pro-inflammatory molecules (Nos2, Ccl1, IL-12B, and CD86), anti-inflammatory molecules (IL-10, Arg1, Il13ra2, and Mrc1), and neuroprotective molecules (Ntf5, Ccl7, and Gipr). In addition, the phagocytic activity of REPELL-microglia was promoted as high as that of microglia transformed by single low-dose LPS. These results suggest the potential of REPELL-microglia for inflammatory regulation, neuroprotection, and phagocytic clearance. Moreover, this study revealed that gene expression of REPELL-microglia was distinct from that of microglia transformed by repetitive high-dose LPS treatment, suggesting the diversity of microglia transformation by different doses of LPS.

Pollen Allergy Suppression Effect by the Oral Administration of Acetic Acid Bacteria (Gluconacetobacter hansenii).

BACKGROUND/AIM: Gluconacetobacter hansenii (G. hansenii) is an acetic acid bacterium of vinegar production. Its anti-allergic effect on mice upon oral administration was examined. MATERIALS AND METHODS: The amount of LPS was measured by the Limulus reaction. Mice were sensitized by peritoneal and intranasal administration of cedar pollen and alum followed by oral administration of 30 or 150 mg/kg of heated G. hansenii cells. Pollen was administered intranasally to evaluate nasal symptoms, and at 8 weeks, IgE and IL-10 levels in blood were measured by ELISA. RESULTS: The amount of LPS in dried bacterial cells was 10.4±3.3 mg/g. In the cedar pollinosis model of mice, a significant reduction was observed in nose scratching of both groups administered with the bacterial cells (30, 150 mg/kg). CONCLUSION: G. hansenii contains LPS, and its oral administration showed an anti-allergic effect by a significant mitigation of the symptoms in a pollen allergy mouse model.

Preventive Effect of Oral Administration of Pantoea agglomerans-derived LPS in a Hypertensive Rat Model Upon Salt Loading.

BACKGROUND/AIM: Oral administration of Pantoea agglomerans-derived lipopolysaccharide (LPSp) has been reported to have a preventive effect against various lifestyle-related diseases. Therefore, we examined the preventive effect on high blood pressure, which is a kind of reserve arm for lifestyle-related diseases. MATERIALS AND METHODS: Spontaneous hypertensive rat (SHR) and WKY rat were bred from 6 to 16 weeks of age. SHR were orally administered 100 µg/kg LPSp and 0.1% NaCl, and blood pressure was measured at 6, 10, 13 and 16 weeks. Furthermore, at 16 weeks of age, blood biochemical markers were measured and microbial community composition was analyzed. RESULTS: SHRs developed hypertension with age, which was exacerbated by salt loading. Although there was almost no reduction in blood pressure in SHRs that received LPSp. It was suppressed at 13-16 weeks of age in those with salt loading. CONCLUSION: Oral administration of LPSp showed a preventive effect on salt-loaded hypertension.

The Effect of Lipopolysaccharide-containing Moisturizing Cream on Skin Care in Patients With Mild Atopic Dermatitis.

BACKGROUND/AIM: Recently, the prevalence of atopic dermatitis (AD) has increased in developed countries. This study aimed to examine the usefulness of a moisturizing cream containing lipopolysaccharide derived from Pantoea agglomerans (LPSp) in patients with mild AD. PATIENTS AND METHODS: A moisturizing cream containing LPSp or its placebo was randomly assigned and continuously used for 4 weeks in patients with mild AD. AD severity was evaluated in a double-blind manner by a dermatologist using the Eczema Area and Severity Index (EASI) score and by the patients' self-evaluation of itching and skin condition using a visual analog scale (VAS). RESULTS: Although there was no difference in the EASI score between the two groups, the VAS scores showed significantly greater symptom alleviation in the LPSp group than in the placebo group. CONCLUSION: A moisturizing cream containing LPSp may be effective for routine skin care and could help alleviate symptoms of mild AD.

Evaluation of a Hypertensive Rat Model Using Peripheral Blood Neutrophil Activity, Phagocytic Activity and Oxidized LDL Evaluation.

BACKGROUND/AIM: A system is being developed that can be used to easily evaluate the health condition of an individual with the help of trace amounts of a blood sample by focusing on xenobiotics. The system is called "Multimodal homeostasis evaluation system" (measurement of neutrophil activity, phagocytic activity of phagocytes and quantification of oxidized LDL (OxLDL)). To elucidate the possibility of using this system as an evaluation system for the health condition of an individual, clearly explaining the changes in various diseases is essential. In this study, evaluations were carried out using hypertensive model animals. MATERIALS AND METHODS: Spontaneously hypertensive model rats SHR/NCrlCrlj and control rats WKY/NCrlCrlj were raised for 10 weeks from 6 to 16 weeks of age and their blood pressure was measured over time. Blood neutrophil activity (superoxide anion (O2•-) generation and myeloperoxidase (MPO) activity) and phagocytic activity of phagocytes was measured by our developed apparatus (a simple prototype device under development). OxLDL was measured by an ELISA kit, and biochemical markers were measured using the blood sample. RESULTS: Compared to WKY rats of the control group, systolic blood pressure, diastolic blood pressure, and mean blood pressure of SHR rats increased significantly with age. In SHR rats, there was a significant elevation in O2•- generation and MPO activity of neutrophils, alanine aminotransferase and triglycerides of blood, while phagocytic activity, OxLDL, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, total cholesterol and total-bilirubin decreased. CONCLUSION: In the hypertensive model, biochemical markers were found to have a relationship with O2•- generation, MPO activity, phagocytic activity of phagocytes, and OxLDL. This system is expected to be useful for clinical monitoring of hypertension diseases.

Dewaxed Brown Rice Feed Improves Fatty Liver in Obese and Diabetic Model Mice.

BACKGROUND/AIM: Dewaxed brown rice has macrophage activation ability via TLR4 and contains a high amount of lipopolysaccharides (LPS). It is expected that dewaxed brown rice can help prevent lifestyle diseases. In this study, the anti-obesity effect of dewaxed brown rice was investigated using obese and diabetic model mice. MATERIALS AND METHODS: Dewaxed brown rice and white rice were polished and powdered by Toyo Rice Co. Diet pellets were prepared (AIN-93) with 50% dewaxed brown rice or white rice powder and fed to type II diabetic model KK-Ay mice for 10 weeks. Weight and fasting blood glucose were measured every week, and whole blood and liver was collected on the final day for the evaluation of biochemical data. RESULTS: A 20% reduction in body weight was found in the dewaxed brown rice feed and white rice feed groups compared to the normal feed group. Fasting blood glucose increased in the normal-diet group, but on the other hand, the blood glucose in the white rice and the dewaxed brown rice feed group was almost constant. Dewaxed brown rice feed group of plasma ALT and AST, liver TG and T-CHO were significantly lower than that of the control and the white rice feed group. CONCLUSION: Dewaxed brown rice feed has an anti-obesity effect to suppress increasing body weight, fasting blood glucose, and an effect of suppressing fatty liver.

Oral administration of Pantoea agglomerans-derived lipopolysaccharide prevents metabolic dysfunction and Alzheimer's disease-related memory loss in senescence-accelerated prone 8 (SAMP8) mice fed a high-fat diet.

The pathogenesis of Alzheimer's disease (AD) remains unclear, but an imbalance between the production and clearance of amyloid-ß (Aß) peptides is known to play a critical role in AD progression. A promising preventative approach is to enhance the normal Aß clearance activity of brain phagocytes such as microglia. In mice, the intraperitoneal injection of Toll-like receptor 4 agonist was shown to enhance Aß clearance and exhibit a preventative effect on AD-related pathology. Our previous clinical study demonstrated that orally administered Pantoea agglomerans-derived lipopolysaccharide (LPSp) exhibited an LDL (low-density lipoprotein)-lowering effect in human volunteers with hyperlipidemia, a known risk factor for AD. In vitro studies have shown that LPSp treatment increases Aß phagocytosis by microglial cells; however it is still unclear whether orally administered LPSp exhibits a preventive effect on AD progression. We show here that in senescence-accelerated prone 8 (SAMP8) mice fed a high-fat diet, oral administration of LPSp at 0.3 or 1 mg/kg body weight·day for 18 weeks significantly improved glucose metabolism and lipid profiles. The LPSp treatment also reduced pro-inflammatory cytokine expression and oxidative-burst activity in the peripheral blood. Moreover, LPSp significantly reduced brain Aß burden and memory impairment as seen in the water maze test, although we could not confirm a significant enhancement of Aß phagocytosis in microglia isolated from the brains after treatment. Taken together, our results show that LPSp holds promise as a preventative therapy for AD or AD-related diseases induced by impairment of metabolic functions.

Oral administration of Pantoea agglomerans-derived lipopolysaccharide prevents development of atherosclerosis in high-fat diet-fed apoE-deficient mice via ameliorating hyperlipidemia, pro-inflammatory mediators and oxidative responses.

Pantoea agglomerans (P. agglomerans) is a Gram-negative bacterium that grows symbiotically with various edible plants, and the oral or sublingual administration of lipopolysaccharide derived from P. agglomerans (LPSp) have been suggested to contribute to prevention of immune-related diseases. Our previous study indicated that orally administered LPSp was shown to exhibit an LDL-lowering effect in hyperlipidemic volunteers; however, a preventive effect of LPSp on atherosclerosis is unclear. The present study attempted to evaluate the anti-atherosclerotic effect by LPSp in a mouse model of high-fat diet (HFD)-induced atherosclerosis. For 16 weeks, apoE-deficient mice were fed an HFD and received drinking water containing LPSp (0.3 or 1 mg/kg body weight/day). The results showed that the orally administered LPSp decreased body weight. A significant reduction in atherosclerotic plaque deposition was observed even with the lower dose of LPSp. The biochemical analyses showed that LPSp markedly improved glucose tolerance and reduced plasma LDL and oxidized LDL levels. In addition, LPSp significantly reduced the production of pro-inflammatory mediators including MCP-1 (in the plasma), TNF-α and IL-6 (in the colon), and decreased the oxidative burst activities in the peripheral blood sample. Taken together, these results suggest the possibility that oral administration of LPSp can effectively ameliorate HFD-induced hyperlipidemia and inflammatory/oxidative responses to prevent atherosclerosis and related metabolic disorders.

Effects of 3 months continuous intake of supplement containing Pantoea agglomerans LPS to maintain normal bloodstream in adults: Parallel double-blind randomized controlled study.

In this study, the effects on the maintenance of normal bloodstream by lipopolysaccharide (LPS) were investigated in the parallel-group randomized double-blind study using supplement containing Pantoea agglomerans LPS (201.5 µg/tablet as LPS). Screening was previously performed in the implementation of the study. Adult males and females with normal value to borderline (healthy subjects) in the hematologic parameters, for which reference values were given, were chosen in this study. The period of ingestion of the supplement was 3 months. As the result, a significant decrease in the rate of change (the ratio when the baseline was 1) of HbA1c, which is a glycative stress marker, was found in the group which ingested LPS supplement after 3 months. Also, a significant increase in the number of fingertip capillary vessels was found compared with the control group. From these results, the effects of the maintenance of bloodstream by ingestion of LPS were shown.

Characterization of the O-antigen polysaccharide derived from Pantoea agglomerans IG1 lipopolysaccharide.

A polysaccharide fraction was isolated from the Pantoea agglomerans IG1 lipopolysaccharide (IP-PA1), and its O-antigenic polysaccharide was characterized by chemical analyses and 1D and 2D 1H and 13C NMR spectroscopy. The polysaccharide is composed of linear tetrasaccharide repeating units, consisting of glucose and rhamnose, where 40% of one of the rhamnose residues is substituted with glucose: →2)-α-l-Rhap-(1→6)-α-d-Glcp-(1→2)-[ß-d-Glcp-(1→3)]0.4-α-l-Rhap-(1→2)-α-l-Rhap-(1→.

Measurement of the Phagocytic Activity of Human Peripheral Blood Using a Highly Sensitive Fluorometric Detection Device Without Hemolysis.

BACKGROUND/AIM: Phagocytes recognize pathogens that enter the body as well as other abnormal and foreign materials that may exist within an organism (such as dead cells, oxidized lipids, and denatured proteins), and phagocytose and eliminate them to maintain a healthy state. In a previous study a simple prototype device was used, under development by Hamamatsu Photonics (Prototype), that detects fluorescence to determine the phagocytic activity of the murine macrophage cell line J774.1. The present study aimed to determine whether it was possible to detect phagocytic activity in a slight amount of human peripheral blood without using hemolysis. MATERIALS AND METHODS: Three microliters of human peripheral blood was drawn from the fingertip and mixed with 30 µg of pH-sensitive fluorescent particles. The fluorescence intensity of the human peripheral blood sample was then measured using the Prototype in development, cultured for 2 h at 37°C, and then re-measured. The phagocytes were observed under fluorescence microscopy and the phagocytosis rate of CD11b-positive cells was verified with a flow cytometer. RESULT: The phagocytic activity of non-hemolyzed human peripheral blood was measured using the Prototype under development; fluorescence after phagocytosis was detected. Furthermore, this was confirmed by both fluorescence microscopy and flow cytometry. The precision of the measurements of human peripheral blood phagocytic activity was verified with the Prototype using samples from three healthy individuals. The relationship between blood sugar levels and phagocytic activity before and after meal times was determined. Concerning exercise, phagocytic activity tended to decrease, although salivary amylase level increased in the healthy individual examined after exercise. CONCLUSION: The simple Prototype can measure phagocytic activity in a small amount of peripheral blood without hemolysis. The device allows for rapid and minimally-invasive detection of changes in phagocytic activity, which has conventionally been difficult. These findings provide promising evidence that assessment of individual phagocytic capacity can be made easier using this novel device.