Topical Application Of Lipopolysaccharide Research Articles

In vivo evaluation of a lipopolysaccharide-induced ear vascular leakage model in mice using photoacoustic microscopy.

Sepsis is caused by dysregulated host inflammatory response to infection. During sepsis, early identification and monitoring of vascular leakage are pivotal for improved diagnosis, treatment, and prognosis. However, there is a lack of research on noninvasive observation of inflammation-related vascular leakage. Here, we investigate the use of photoacoustic microscopy (PAM) for in vivo visualization of lipopolysaccharide (LPS)-induced ear vascular leakage in mice using Evans blue (EB) as an indicator. A model combining needle pricking on the mouse ear, topical smearing of LPS on the mouse ear, and intravenous tail injection of EB is developed. Topical application of LPS is expected to induce local vascular leakage in skin. Inflammatory response is first validated by ex vivo histology and enzyme-linked immunosorbent assay. Then, local ear vascular leakage is confirmed by ex vivo measurement of swelling, thickening, and EB leakage. Finally, PAM for in vivo identification and evaluation of early vascular leakage using the model is demonstrated. For PAM, common excitation wavelength of 532 nm is used, and an algorithm is developed to extract quantitative metrics for EB leakage. The results show potential of PAM for noninvasive longitudinal monitoring of peripheral skin vascular leakage, which holds promise for clinical sepsis diagnosis and management.

Effect of topical application of lipopolysaccharide on contact hypersensitivity

Lipopolysaccharide (LPS) is the principal component of the outer membrane of gram-negative bacteria. The prior oral administration of LPS attenuates inflammatory responses, such as intestinal injury and atopic dermatitis, in mouse models; however, the underlying mechanism remains unclear. Here, we examined the effect of topical LPS application on allergic contact dermatitis and its mechanism of action using a murine contact hypersensitivity (CHS) model. Prolonged LPS application to the skin significantly suppressed 2,4-dinitrofluorobenzene (DNFB)-induced CHS. LPS application to the skin also reduced the phagocytosis of fluorescein isothiocyanate (FITC)-dextran by Langerhans and dendritic cells. Cutaneous cell migration into the skin-draining lymph nodes (LNs) induced by FITC painting was reduced by LPS application. During the CHS response, DNFB application induced T-cell proliferation and inflammatory cytokine production in skin-draining LNs, whereas prolonged LPS application inhibited DNFB-induced T-cell growth and interferon gamma production, indicating suppression of DNFB-induced sensitization. These results suggest that prolonged LPS application suppressed DNFB-induced sensitization and subsequently CHS response. Our findings imply that topical application of LPS may prevent allergic dermatitis such as CHS.

Impact of commensal flora on periodontal immune response to lipopolysaccharide.

Commensal flora are involved in the appropriate development of the mature immune system. However, it is unclear how commensal flora contribute to immune responses against periodontal pathogens, including the response to lipopolysaccharide (LPS). The purpose of this study was to evaluate the expression of immune responses after topical application of LPS in germ-free (GF) and specific-pathogen-free (SPF) mice. GF and SPF mice at 8weeks of age were randomly divided into four groups each: a baseline group (n=4/group) and three experimental groups (n=6/group). Experimental groups received topical application of Porphyromonas gingivalis LPS (10μg/μL) into the palatal gingival sulcus. Sampling was performed before LPS application (baseline) and at 3, 24, or 72hours after LPS application. The numbers of neutrophils, CD4+ , and CD8+ T cells in periodontal tissue were evaluated by immunohistochemistry. Expression of genes encoding cytokines, chemokines, and a transcription factor was determined by real-time PCR. SPF mice, but not GF mice, showed an increased number of CD4+ T cells in the periodontal tissue at 3hours after LPS application, compared with the number at baseline (p<0.05). Gene expressions of tumor necrosis factor-α (Tnf-α) and forkhead box protein p3 (Foxp3) was also significantly higher in the SPF mice than in the GF mice at 3hours after LPS application (p<0.05). The number of neutrophils peaked at 24hours in both GF and SPF mice. LPS-exposed SPF mice exhibited increases in the number of CD4+ T cells and in Tnf-α and Foxp3 gene expression in periodontal tissue compared with LPS-exposed GF mice.

Occlusal trauma accelerates attachment loss at the onset of experimental periodontitis in rats

Occlusal trauma is an important factor that influences the progression of periodontitis, but it is unclear whether occlusal trauma influences periodontal destruction at the onset of periodontitis. We established an experimental periodontitis model with both site-specific loss of attachment and alveolar bone resorption. The purpose of the present study was to investigate the effects of occlusal trauma on periodontal destruction, particularly loss of attachment, at the onset of experimental periodontitis. Sixty rats were used in the present study. Forty-eight rats immunized with lipopolysaccharide (LPS) intraperitoneally were divided into four groups. In the trauma (T) group, occlusal trauma was induced by placing an excessively high metal wire in the occlusal surface of the mandibular right first molar. In the inflammation (I) group, periodontal inflammation was induced by topical application of LPS into the palatal gingival sulcus of maxillary right first molars. In the trauma + inflammation (T+I) group, both trauma and periodontal inflammation were simultaneously induced. The PBS group was administered phosphate-buffered saline only. Another 12 nonimmunized rats (the n-(T+I) group) were treated as described for the T+I group. All rats were killed after 5 or 10 d, and their maxillary first molars with surrounding tissues were observed histopathologically. Loss of attachment and osteoclasts on the alveolar bone crest were investigated histopathologically. To detect immune complexes, immunohistological staining for C1qB was performed. Collagen fibers were also observed using the picrosirius red-polarization method. There were significant increases in loss of attachment and in the number of osteoclasts in the T+I group compared with the other groups. Moreover, widespread distribution of immune complexes was observed in the T + I group, and collagen fibers oriented from the root surface to the alveolar bone crest had partially disappeared in the T, T+I and n-(T+I) groups. When inflammation was combined with occlusal trauma, immune complexes were confirmed in more expanding areas than in the area of the I group without occlusal trauma, and loss of attachment at the onset of experimental periodontitis was increased. Damage of collagen fibers by occlusal trauma may elevate the permeability of the antigen through the tissue and result in expansion of the area of immune-complex formation and accelerating inflammatory reaction. The periodontal tissue destruction was thus greater in the T+I group than in the I group.

Topical Bacterial Lipopolysaccharide Application Affects Inflammatory Response and Promotes Wound Healing

The mechanisms underlying the complex and multistage wound-healing process are not yet completely understood. One of the most important and intriguing questions remaining is the effect of the interactions between wounds and the microflora that are present in wounds. In this report, we describe the first study of the effect of treating murine skin wounds with topical bacterial lipopolysaccharide (LPS), the main exogenous ligand of Toll-like receptor 4. Our findings demonstrate that LPS treatment strongly affects the wound-healing process by accelerating the resolution of inflammation, increasing macrophage infiltration, enhancing collagen synthesis, and altering the secretion of a number of mediators that are involved in the skin regeneration process. Topical LPS treatment upregulated the secretion of proinflammatory cytokines [interleukin (IL)-6, IL-1β, and leukemia inhibitory factor (LIF)] and CC-chemokines (CCL2/MCP-1, CCL7/MCP-3, CCL3/MIP-1α, and CCL5/RANTES), but not CXC-chemokines (CXCL2/MIP-2 and CXCL9/MIG). The secretion of growth factors (vascular endothelial growth factor, transforming growth factor-β1 (TGF-β1), and fibroblast growth factor 2) at the wound site was also upregulated. Taken together, these results suggest that the topical application of LPS at the wound surface affects the inflammatory process and promotes the wound healing of injured skin.

Topical application of lipopolysaccharide into gingival sulcus promotes periodontal destruction in rats immunized with lipopolysaccharide

The causes of periodontitis are bacteria and the host immune system, but the role of the immune system in the onset and progression of periodontal disease is still unclear. Our previous report showed that the formation of an immune complex in the gingival sulcus induces periodontal destruction. This study was carried out to investigate how the immune system, particularly immunization, is involved in periodontal destruction. Animals immunized intraperitoneally with lipopolysaccharide (LPS) were used as the immunized group. The nonimmunized group received only phosphate-buffered saline. LPS was applied daily onto the palatal gingival sulcus in both groups 1 d after the booster injection. Serum levels of anti-LPS IgG were determined. Loss of attachment and the level of alveolar bone were histopathologically and histometrically investigated. RANKL-bearing cells and the expression of C1qB were immunohistologically evaluated. The serum levels of anti-LPS IgG were elevated in the early experimental period in the immunized group. There were significant increases in loss of attachment, level of alveolar bone and the number of RANKL-bearing cells in the immunized group. C1qB was observed in the junctional epithelium and adjacent connective tissue. The nonimmunized group showed similar findings at and after the time when the serum level of anti-LPS IgG was elevated. Topical application of LPS as an antigen induced periodontal destruction when the serum level of anti-LPS IgG was elevated in rats immunized with LPS. The presence of C1qB suggests that the formation of immune complexes is involved in this destruction.

Initial Apical Migration of Junctional Epithelium in Rats Following Application of Lipopolysaccharide and Proteases

Apical migration of junctional epithelium (JE) occurs in association with periodontal pocket formation. The aim of this study was to investigate the gingival changes occurring during apical migration of the JE following application of factors associated with inflammatory periodontal disease pathogenesis. Six-week-old male Wistar rats were divided into six groups: three experimental groups to investigate gingival changes following 2, 4, and 8 weeks topical application of lipopolysaccharide (LPS) and proteases and three control groups using pyrogen-free water. After 2, 4 or 8 weeks, nuclear DNA fragmentation was detected in periodontal ligament (PDL) fibroblasts using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) method, and proliferative activities of the basal cells and fibroblasts were evaluated through expression of proliferating cell nuclear antigen (PCNA). Collagen destruction was examined histologically. Gingiva treated with LPS and proteases showed an increase in PCNA-positive basal cells but not the fibroblasts. Collagen destruction was observed at 2 weeks; apical migration of the JE and TUNEL-positive fibroblasts was seen at 4 weeks. Following application of LPS and proteases to rat gingival sulci, the apical migration of the JE appears to occur simultaneously with the apoptosis of PDL fibroblasts, which in turn follows proliferation of the basal cells and collagen destruction.

Immuno-localization of COX-1 and COX-2 in the rat molar periodontal tissue after topical application of lipopolysaccharide

Up-regulation of prostaglandin E 2 (PGE 2) production in the periodontal tissue is considered to be important for periodontal tissue destruction. The purpose of the study was to demonstrate the dynamic changes of immuno-localization of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in rat periodontal tissue after topical application of lipopolysaccharide (LPS: 5 mg/ml in physiological saline) from Escherichia coli into the rat molar gingival sulcus. In the normal periodontal tissue, small numbers of junctional epithelium (JE) cells and numerous osteocytes embedded in alveolar bone constitutively expressed COX-1. The COX-1 expression was not effected by LPS application. JE cells, especially in the coronal portion of JE also expressed COX-2. LPS application induced the JE cells with consequent transient expression of COX-2 with a peak at day 1. These findings suggest that JE cells may play a critical role in first defense line against LPS challenge and PGE 2 from JE cells may be responsible for the initiation of periodontal inflammation. In the deep periodontal tissue, cementoblasts and osteoblasts showed constitutive expression of COX-2, which may be induced by continuous cyclic tension force due to occlusal pressure. LPS application caused a transient up-regulation of COX-2 expression in periodontal ligament fibroblasts, cementoblasts and osteoblasts. It is suggested that the inducible production of PGE 2 via COX-2 by these cells may be associated with connective tissue destruction and alveolar bone resorption.

Immunolocalization of CXC chemokine and recruitment of polymorphonuclear leukocytes in the rat molar periodontal tissue after topical application of lipopolysaccharide.

This study investigated the recruitment of polymorphonuclear leukocytes (PMNs) and the immunolocalization of CXC chemokines, including macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant-2 (CINC-2) in rat periodontal tissue after topical application of lipopolysaccharide (LPS; 5 mg/ml) from Escherichia coli into the rat molar gingival sulcus. In normal periodontal tissues, a small number of MIP-2- and CINC-2-positive cells were seen in junctional epithelium (JE), especially in its coronal half. After topical application of LPS, a prominent increase of MIP-2- and CINC-2-positive JE cells was observed. Almost all JE cells strongly expressed them at day 1 and day 2, and then the number of chemokine-positive cells returned to normal at day 7. Corresponding to these chemokine expressions, LPS application induced a significant increase in the number of PMNs in the sub-JE area from 1 h to 2 days and a significant increase in JE area from 3 h to 5 days, indicating a dynamic flow of PMNs from the sub-JE area into JE. These findings indicated that JE cells produced MIP-2 and CINC-2 in response to LPS stimulation and suggested that MIP-2 and CINC-2 may be responsible for PMN migration toward the periodontal pathogen and may play an important role in the initiation of inflammation and subsequent periodontal tissue destruction.

Cytokine expression in rat molar gingival periodontal tissues after topical application of lipopolysaccharide.

It is well known that proinflammatory cytokines produced by host cells play an important role in periodontal tissue destruction. However, the localization of the cytokines in in vivo periodontal tissues during development of periodontal disease has not been determined. Immunohistochemical expression of proinflammatory cytokines including IL-1alpha, IL-1beta, and TNF-alpha was examined at 1 and 3 h, and 1, 2, 3, and 7 days after topical application of lipopolysaccharide (LPS; 5 mg/ml in physiological saline) from E. coli into the rat molar gingival sulcus. In the normal periodontal tissues, a small number of cytokine-positive epithelial cells were seen in the junctional epithelium (JE), oral sulcular and oral gingival epithelium, in addition to macrophages infiltrating in the subjunctional epithelial area and osteoblasts lining the alveolar bone surface. Epithelial remnants of Malassez existing throughout periodontal ligament were intensely positive for IL-1beta but negative for the other two cytokines. At 3 h after the LPS treatment, almost all cells in the JE were strongly positive for the cytokines examined. In addition, several cytokine-positive cells, including neutrophils, macrophages, and fibroblasts, were seen in the subjunctional epithelial connective tissue. At day 2, expression of the cytokines in the JE gradually decreased, while cytokine-positive cells in the connective tissue increased in number. Positive staining of the cytokines was seen in osteoclasts and preosteoclasts which appeared along the alveolar bone margin in this period. The number of cytokine-positive cells decreased by day 7. These findings indicate that, in addition to macrophages, neutrophils, and fibroblasts, the JE cells are a potent source of TNF-alpha, IL-1alpha, and IL-1beta reacting to LPS application, and suggest that JE cells may play an important role in the first line of defense against LPS challenge, and the proinflammatory cytokines transiently produced by various host cells may be involved in the initiation of inflammation and subsequent periodontal tissue destruction.

Distribution of macrophage lineage cells in rat gingival tissue after topical application of lipopolysaccharide: an immunohistochemical study using monoclonal antibodies: OX6, ED1 and ED2.

To discuss the role of macrophage lineage cells on the periodontal tissue destruction, we immunohistochemically examined the phenotype and the dynamics of macrophage lineage cells 1 or 3 h or 1, 2, 3 or 7 d after topical application of LPS (5 mg/ml in physiological saline) from the rat gingival sulcus using 3 monoclonal antibodies: OX6 (antigen-presenting cells), ED1 (monocytes, macrophages and dendritic cells) and ED2 (resident macrophages). We could detect at least 3 different types of macrophage lineage cells, namely OX6+/ED1+/ED2- dendritic cells and exudate macrophages and ED2+ resident macrophages. After LPS application the majority of macrophage lineage cells accumulated in the subjunctional epithelial area were newly extravasated OX6+/ED1+/ED2- dendritic cells or macrophages. The number of these cells increased progressively with time and reached a maximum level at d 2. On the other hand, number and tissue distribution of ED2+ resident macrophages did not change. These results indicate that several types of macrophage lineage cells exist in rat gingival tissue and suggest that dendritic cells and exudate macrophages transiently accumulated after LPS application are responsible for various host immune response and tissue destruction caused by LPS.

Effect of lipopolysaccharide on the permeability and reactivity of the cerebral microcirculation: role of inducible nitric oxide synthase

The goal of this study was to examine the effect of lipopolysaccharide on the permeability of the blood–brain barrier and reactivity of cerebral arterioles. We examined the pial microcirculation in rats using intravital fluorescence microscopy. Permeability of the blood–brain barrier (clearance of fluorescent-labeled dextran; molecular weight 10,000 Da; FITC-dextran-10K) and diameter of pial arterioles were measured in the absence and presence of topical application of vehicle (saline) or lipopolysaccharide (200 ng/ml). During superfusion with vehicle, clearance of FITC-dextran-10K from pial vessels was minimal, and diameter of pial arterioles remained constant. Topical application of lipopolysaccharide (200 ng/ml) produced an increase in clearance of FITC-dextran-10K and dilated pial arterioles. To determine whether lipopolysaccharide-induced changes in permeability of the blood–brain barrier and dilatation of cerebral arterioles was related to the synthesis/release of inducible nitric oxide, we examined the effects of aminoguanidine (0.5 mM). Aminoguanidine inhibited lipopolysaccharide-induced increases in permeability of the blood–brain barrier and dilatation of cerebral arterioles. The findings of the present study suggest that lipopolysaccharide increases permeability of the blood–brain barrier and diameter of pial arterioles via the activation of inducible nitric oxide synthase.

Distribution of macrophage lineage cells in rat gingival tissue after topical application of lipopolysaccharide: an immunohistochemical study using monoclonal antibodies: 0X6, ED1 and ED2

To discuss the role of macrophage lineage cells on the periodontal tissue destruction, we immunohistochemically examined the phenotype and the dynamics of macrophage lineage cells 1 or 3 h or 1, 2, 3 or 7 d after topical application of LPS (5 mg/ml in physiological saline) from the rat gingival sulcus using 3 monoclonal antibodies: OX6 (antigen‐presenting cells), EDI (monocytes, macrophages and dendritic cells) and ED2 (resident macrophages). We could detect at least 3 different types of macrophage lineage cells, namely 0X6+ /ED1+ /ED2− dendritic cells and exudate macrophages and ED2+ resident macrophages. After LPS application the majority of macrophage lineage cells accumulated in the subjunctional epithelial area were newly extravasated 0X6+/EDI+/ED2− dendritic cells or macrophages. The number of these cells increased progressively with time and reached a maximum level at d 2. On the other hand, number and tissue distribution of ED2+ resident macrophages did not change. These results indicate that several types of macrophage lineage cells exist in rat gingival tissue and suggest that dendritic cells and exudate macrophages transiently accumulated after LPS application are responsible for various host immune response and tissue destruction caused by LPS.

Reactive change in proliferative activity of the junctional epithelium after topical application of lipopolysaccharide.

IT IS WELL ESTABLISHED THAT apical migration of junctional epithelium (JE) along a root surface is an important factor in periodontal pocket formation and deepening. However, the exact mechanism and, more specifically, the role of inflammatory products in influencing the activity of cells within the JE is not known. To address this issue lipopolysaccharide (LPS) was applied topically into rat molar gingival sulcus and then tissues evaluated immunohistochemically for expression of proliferating cell nuclear antigen (PCNA). Tissues were prepared for histological analysis at designated times. Histologically, infiltration of neutrophils with associated edema was noted in JE and gingival connective tissues 6 hours after LPS application and was prominent at 12 hours. These inflammatory changes persisted in the 2- and 3-day specimens, and disappeared at 5 days. In normal gingiva, before the LPS application, the JE showed few PCNA positive cells, while almost all cells in the basal and suprabasal cell layers of the oral gingival epithelium and the oral sulcular epithelium were PCNA positive. No increase in the number of PCNA positive cells in the JE beyond zero time was observed at 6 and 12 hours after LPS application. One day after LPS application, PCNA positive cells appeared in the basal cell layer of the JE, with a continued increase number of PCNA positive cells in the JE continued at 2 and 3 days. By day 5 the number of PCNA positive cells were decreasing with return to a normal range by 7 days. These results showed that 1) under normal physiological conditions, cells within the JE have minimal mitotic activity and 2) the JE cells can enter the proliferating cell cycle when exposed to LPS, and suggest that the enhanced proliferating activity in the JE is an important factor for the deepening of the periodontal pocket, if the connective tissue attachment is broken down.

Enhanced collagen phagocytosis by rat molar periodontal fibroblasts after topical application of lipopolysaccharide--ultrastructural observations and morphometric analysis.

To investigate the effect of lipopolysaccharide (LPS) on phagocytic activity of collagen fibrils by periodontal fibroblasts, we studied rat molar gingival connective tissue and periodontal ligament under light and electron microscopy after topical application of LPS (5 mg/ml in physiological salt solution (PS)) on the gingival sulcus. Phagocytic activity of collagen fibrils by fibroblasts was evaluated by counting the number of collagen-containing vacuoles inside fibroblasts that were present within a defined area (1200 microns2). Values obtained from fibroblasts in the subepithelial connective tissue, the region near the alveolar crest, and the middle region of periodontal tissue were compared. Periodontal ligament fibroblasts showed increased phagocytosis of the collagen fibrils from 3 hours to 1 day after topical LPS application, but no differences were observed in the gingival tissue. The intracytoplasmic vacuoles containing collagen fibrils were of various sizes and shapes, showing positive for acid phosphatase and/or alkaline phosphatase reaction. Collagen phagocytic activity of the fibroblasts in the middle region of the periodontal ligament also increased after PS treatment. However, this was significantly less than that observed in LPS-treated animals (p less than 0.01). This study indicates that LPS may enhance the degradation of collagen by stimulating the phagocytic activity of the periodontal ligament fibroblasts.

Light and Electron Microscopic Studies of Experimentally-Induced Pathologic Changes in the Rat Periodontal Tissue

Morphological changes in periodontal tissues following topical application of lipopolysaccharide (LPS) or prostaglandin E2 (PGE2) were examined in Wistar rats by light and electron microscopy. Ultrastructural demonstration of acid phosphatase and immunohistochemical localization of lysozyme in these tissues were also studied. The number of osteoclasts along the alveolar bone facing the periodontal ligament was counted. After topical application of LPS, degeneration and necrosis of the junctional epithelial cells, gingival fibroblasts, and alveolar osteoblasts were observed, as were increased bone resorption by osteoclasts and enhanced phagocytosis of collagen fibrils by fibroblasts. LPS appears to traverse easily through the junctional epithelium into the underlying gingival connective tissues. There it can cause destruction of deeper periodontal tissues by activating alveolar bone resorption and by enhancing the phagocytosis of collagen fibrils. PGE2 topically applied induced similar morphological changes. Possible participation of PGE2 in the induction of these LPS-related changes is discussed.