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.

Lipopolysaccharide (LPS), also known as an endotoxin, is derived from Gram-negative bacteria. The intravenous administration of LPS induces an inflammatory response and causes systemic inflammation, such as cytokine storm. Gram-negative bacteria that produce LPS are found in the environment and digestive tract. The mucous membrane, the primary barrier between the interior of the body and the external environment, is constantly exposed to LPS. Moreover, no toxicity is observed when administering LPS through the mucous membranes of the mouth or skin. The presence of LPS in the mucous membranes is necessary not only for maintaining health but also for inducing preventive and therapeutic effects against multiple diseases when administered orally or topically. LPS is an environmental substance that is useful when administered to mucous membranes. The general information emphasizes the role of LPS as an inflammatory substance that occurs when administered intravenously. Therefore, the valuable role of LPS is unknown. Thus, mucosal administration of LPS has received little attention, and the mechanism underlying the expression of its beneficial effects has not been fully elucidated. We proposed a comprehensive concept, the “macrophage network,” which proposes a regulatory system in which the mucosa receives environmental information, membrane-bound cytokines are expressed in phagocytes (macrophages), and these macrophages migrate distally to exert effects, such as anti-inflammatory and tissue repair effects, on distal tissues through cell-to-cell communication (juxtacrine signaling) with tissue macrophages. This macrophage network is effective not only for preventing and treating diseases but also for increasing the efficacy of pharmaceuticals. This review aims to investigate the preventive and therapeutic effects of oral and transdermal administration of LPS on various diseases and present an introduction to the concept of the macrophage network and the latest findings.

The present study examined the effects of foods containing lipopolysaccharides from Pantoea agglomerans (LPSp) on eye–nose allergic symptoms using a double-blind, placebo-controlled, randomized, parallel-group comparative research design. Sixty-three Japanese individuals aged 20–65 years with eye–nose allergic symptoms were included in this study and assigned to the LPS (480 μg/day)-containing food and placebo groups. Data on the subjective eye–nose allergic symptoms and antiallergic medication during the 8-week period were evaluated. The immunoglobulin E (IgE) and eosinophil counts were measured as indicators that may be correlated with allergy. No significant group differences were found in the change in eye–nose allergic symptoms from baseline. However, the LPS group showed a significantly shorter duration of antiallergic medication use and lower total antiallergic drug score than the placebo group. The corrected nasal allergy score calculated by taking into account the antiallergic drug score at week 8 was predominantly lower in the LPS group. The IgE to house dust and cedar pollen and eosinophil counts tended to be lower in the LPS group, and the total IgE and eosinophil counts were significantly lower in the LPS group at week 4. In conclusion, our results indicate that LPS-containing foods alleviate eye–nose allergic symptoms and consequently lower the use of antiallergic drugs (UMIN000049974).

Tissue-resident macrophages are essential for skin homeostasis. This study investigated whether lipopolysaccharide (LPS)-activated macrophages affect senescence and rejuvenation in human dermal fibroblasts. Human monocytic THP-1 cells were stimulated with Pantoea agglomerans–derived LPS (1–1000 ng/mL), and culture supernatants were collected. These were applied to two NB1RGB fibroblast populations: young, actively dividing cells (Young cells) and senescent cells with high population doubling levels and reduced proliferation (Old cells). Senescence markers P16, P21, and Ki-67 were analyzed at gene and protein levels. Conditioned medium from Old cells induced senescence in Young cells, increasing P16 and P21 expression levels. This effect was suppressed by cotreatment with LPS-activated THP-1 supernatant. Old cells treated with the LPS-activated supernatant exhibited decreased P16 and P21 levels as well as increased Ki-67 expression, indicating partial rejuvenation. These effects were not observed following treatment with unstimulated THP-1 supernatants or LPS alone. Overall, these findings suggest that secretory factors from LPS-activated macrophages can suppress cellular senescence and promote human dermal fibroblast rejuvenation, highlighting the potential role of macrophage activation in regulating cellular aging and offering a promising strategy for skin aging intervention.

In this study, the effects of foods containing lipopolysaccharide (LPS) from Pantoea agglomerans (LPSp) on immunity were preliminarily investigated using a double-blind, placebo-controlled, randomized, parallel-group comparative study design. Thirty healthy subjects aged ≥ 20 years (four males and twenty-six females; mean age 49 ± 9.2 years) were randomly assigned to the LPS-containing food group (488 μg/day; LPS) or placebo group. Each food was consumed for 8 weeks, and a subjective survey of cold symptoms (Wisconsin Upper Respiratory Symptom Questionnaire) and allergic symptoms of the eyes and nose were conducted. Phagocytic capacity and lymphocyte counts were measured as indicators of immune function. There were no significant between-group differences with respect to any of the investigated items. On sub-group analysis of eye–nose allergy symptom score, confined only to subjects who reported eye–nose allergic symptoms in previous years, the LPS group showed a trend toward milder symptoms compared to the placebo group. In addition, when the symptom scores were compared only for subjects who developed eye–nose allergies during the study period, the LPS group showed significantly lower overall scores and eye symptom scores compared to the placebo group. These results suggest that the consumption of LPS-containing foods may alleviate or prevent eye–nose allergies. There were no statistically predominant changes in hematology and blood biochemistry tests, indicating that continued consumption of LPS-containing foods is safe. (UMIN000046154).

Background/Aim: Because the skin is exposed to the external environment, it is important that wound healing processes proceed and terminate rapidly to minimize the risk of infection. A previous case report described the promotion of wound healing by transdermal administration of lipopolysaccharide derived from Pantoea agglomerans (LPSp). However, whether the wound healing–promoting effect of LPSp was due to direct activity on skin cells or indirect effects involving macrophages remained unclear. Therefore, this study investigated the wound healing–promoting effect of LPSp, particularly the promotion of keratinocyte migration. Materials and Methods: The migration of HaCaT human keratinocytes over time with and without LPSp was assayed using a cell migration assay kit. Migration was also analyzed using HaCaT cells treated with LPSp and an antibody against Toll-like receptor (TLR) 4, a receptor for LPS. Results: Addition of LPSp significantly enhanced cell migration compared to no LPSp addition. Migration was inhibited by the addition of anti-TLR4 antibody. Conclusion: LPSp acts directly on epidermal cells to promote migration and may be one mechanism by which LPSp promotes wound healing.