Lipopolysaccharide induces bacterial autophagy in epithelial keratinocytes of the gingival sulcus

Periodontopathogen-Related Cell Autophagy-A Double-Edged Sword

The periodontium is a highly organized ecosystem, and the imbalance between oral microorganisms and host defense leads to periodontal diseases. The periodontal pathogens, mainly Gram-negative anaerobic bacteria, colonize the periodontal niches or enter the blood circulation, resulting in periodontal tissue destruction and distal organ damage. This phenomenon links periodontitis with various systemic conditions, including cardiovascular diseases, malignant tumors, steatohepatitis, and Alzheimer's disease. Autophagy is an evolutionarily conserved cellular self-degradation process essential for eliminating internalized pathogens. Nowadays, increasing studies have been carried out in cells derived from periodontal tissues, immune system, and distant organs to investigate the relationship between periodontal pathogen infection and autophagy-related activities. On one hand, as a vital part of innate and adaptive immunity, autophagy actively participates in host resistance to periodontal bacterial infection. On the other, certain periodontal pathogens exploit autophagic vesicles or pathways to evade immune surveillance, therefore achieving survival within host cells. This review provides an overview of the autophagy process and focuses on periodontopathogen-related autophagy and their involvements in cells of different tissue origins, so as to comprehensively understand the role of autophagy in the occurrence and development of periodontal diseases and various periodontitis-associated systemic illnesses.

Immunohistochemical analysis with apoptosis and autophagy markers in periodontitis and peri-implantitis: Clinical comparative study

BACKGROUND AND OBJECTIVES

Recently, the terms autophagy and apoptosis have been studied on implants, especially in cell culture and in vitro studies, but in vivo evaluations are limited. The aim of this study was to compare the differences in apoptosis and autophagy intensity at the molecular and cellular level in periodontal and peri-implant diseases.

METHODS

Sixty-four biopsy samples were obtained from 52 patients, 36 female and 16 male, whose mean age was between 18 and 75, and were included in the study. The periodontitis group was defined as PG (n:30 sample) and the peri-implantitis group as IG (n:34 samples). Granulation tissues as biopsy materials were collected, and immunohistochemical analysis was performed with hematoxylin-eosin, Masson's trichrome, anti-MAP1LC3A, anti-beclin, and anti-active caspase-3 antibodies and terminal TdT-mediated dUTP-biotin nick end labeling (TUNEL) methods. The histological slide images were evaluated with the ImageJ software program. Inflammatory cell density in epithelial tissue, inflammatory cell density in connective tissue, the density of necrotic tissue debris, and collagen density in connective tissue were scored between 0 and 3 (0: none, 1: minimal, 2: moderate, 3: severe by hematoxylin-eosin and Masson's trichrome). The antibody binding reaction areas were evaluated per unit area (mm² ) in connective tissue by immunohistochemical examination.

RESULTS

As histochemical evaluations, there was no statistically significant differences the mean inflammatory cell density value in the epithelial tissue, inflammatory cell density value in the connective tissue, density value of necrotic tissue debris, collagen density value in the connective tissue between the groups. There was no statistically significant difference on immunohistochemical staining with LC3, caspase-3, Beclin-1 and TUNEL between the two groups (p > .05).

CONCLUSIONS

A higher rate of inflammatory accumulation was shown on peri-implantitis, but no difference was found between periodontitis and peri-implantitis according to autophagy and apoptosis markers. Studies with high sample sizes with different markers are needed.

Chemokine expression in human 3-dimensional cultured epidermis exposed to PM2.5 collected by cyclonic separation

Fine particulate matter (PM2.5) exposure has a risk of inducing several health problems, especially in the respiratory tract. The skin is the largest organ of the human body and is therefore the primary target of PM2.5. In this study, we examined the effects of PM2.5 on the skin using a human 3-dimensional cultured epidermis model. PM2.5 was collected by cyclonic separation in Yokohama, Japan. Global analysis of 34 proteins released from the epidermis revealed that the chemokines, chemokine C-X-C motif ligand 1 (CXCL1) and interleukin 8 (IL-8), were significantly increased in response to PM2.5 exposure. These chemokines stimulated neutrophil chemotaxis in a C-X-C motif chemokine receptor 2-dependent manner. The oxidative stress and signal transducer and activator of transcription 3 pathways may be involved in the increased expression of CXCL1 and IL-8 in the human epidermis model. Interestingly, in the HaCaT human keratinocyte cell line, PM2.5 did not affect chemokine expression but did induce IL-6 expression, suggesting a different effect of PM2.5 between the epidermis model and HaCaT cells. Overall, PM2.5 could induce the epidermis to release chemokines, followed by neutrophil activation, which might cause an unregulated inflammatory reaction in the skin.

Desquamated Epithelial Cells of Unstimulated Human Whole Saliva Express Both EGF Transcript and Protein

Objective

The aim of this study was to investigate if desquamated oral epithelial cells (DOECs) express the epidermal growth factor (EGF) and if these cells thereby may contribute to salivary EGF contents.

Background

DOECs have recently been shown to harbor the antimicrobial peptide LL-37, proposing that they may also store other biologically important salivary peptides/proteins. The EGF peptide is a growth factor which plays a critical role to maintain epithelial integrity and promote epithelial healing. The EGF is produced by salivary glands, but it is not known whether DOECs contain the EGF and thereby contribute to salivary EGF levels.

Materials and Methods

DOECs were isolated from unstimulated whole saliva collected from four healthy volunteers. EGF protein expression was determined in cell lysates by dot blot and ELISA. Cellular distribution of cytokeratin, the proliferation marker Ki67, and EGF immunoreactivity were assessed by immunocytochemistry. EGF gene expression was investigated by qPCR. Expression of EGF transcript and protein in DOECs was compared to that in the human cultured keratinocyte cell line (HaCaT) cells.

Results

EGF protein expression was detected in DOEC cell lysates by both dot blot and ELISA. Strong cytoplasmic EGF immunoreactivity was observed in DOECs, although some cells showed only a weak immunoreactive signal for EGF. Moreover, DOECs, besides containing EGF protein, also expressed transcript for EGF. Interestingly, ELISA analysis revealed that EGF protein contents were higher in DOECs than in HaCaT cells. ELISA analysis also disclosed that EGF concentration was about 10 times higher in whole saliva compared to DOECs. EGF transcript expression was about 50% lower in HaCaT cells stimulated with high (10%) compared to low (0.1%) concentration of fetal bovine serum, representing growth-stimulated and growth-restricted conditions, respectively, implying that growth-stimulus exerts negative feedback on EGF gene activity in HaCaT cells.

Conclusion

Here, we show for the first time that DOECs express the EGF, arguing that these cells contribute to salivary EGF contents and hence may play a role in gingival epithelial repair and wound healing.

Interaction Between Autophagy and Porphyromonas gingivalis-Induced Inflammation

Autophagy is an immune homeostasis process induced by multiple intracellular and extracellular signals. Inflammation is a protective response to harmful stimuli such as pathogen microbial infection and body tissue damage. Porphyromonas gingivalis infection elicits both autophagy and inflammation, and dysregulation of autophagy and inflammation promotes pathology. This review focuses on the interaction between autophagy and inflammation caused by Porphyromonas gingivalis infection, aiming to elaborate on the possible mechanism involved in the interaction.

The Potential Role of Inflammation in Modulating Endogenous Hippocampal Neurogenesis After Spinal Cord Injury

Currently there are approximately 291,000 people suffering from a spinal cord injury (SCI) in the United States. SCI is associated with traumatic changes in mobility and neuralgia, as well as many other long-term chronic health complications, including metabolic disorders, diabetes mellitus, non-alcoholic steatohepatitis, osteoporosis, and elevated inflammatory markers. Due to medical advances, patients with SCI survive much longer than previously. This increase in life expectancy exposes them to novel neurological complications such as memory loss, cognitive decline, depression, and Alzheimer's disease. In fact, these usually age-associated disorders are more prevalent in people living with SCI. A common factor of these disorders is the reduction in hippocampal neurogenesis. Inflammation, which is elevated after SCI, plays a major role in modulating hippocampal neurogenesis. While there is no clear consensus on the mechanism of the decline in hippocampal neurogenesis and cognition after SCI, we will examine in this review how SCI-induced inflammation could modulate hippocampal neurogenesis and provoke age-associated neurological disorders. Thereafter, we will discuss possible therapeutic options which may mitigate the influence of SCI associated complications on hippocampal neurogenesis.

Aggregatibacter Actinomycetemcomitans Induces Autophagy in Human Junctional Epithelium Keratinocytes

The adverse environmental conditions found in the periodontium during periodontitis pathogenesis stimulate local autophagy responses, mainly due to a continuous inflammatory response against the dysbiotic subgingival microbiome. The junctional epithelium represents the main site of the initial interaction between the host and the dysbiotic biofilm. Here, we investigated the role of autophagy in junctional epithelium keratinocytes (JEKs) in response to Aggregatibacter actinomycetemcomitans or its purified lipopolysaccharides (LPS). Immunofluorescence confocal analysis revealed an extensive nuclear translocation of transcription factor EB (TFEB) and consequently, an increase in autophagy markers and LC3-turnover assessed by immunoblotting and qRT-PCR. Correspondingly, challenged JEKs showed a punctuate cytosolic profile of LC3 protein contrasting with the diffuse distribution observed in untreated controls. Three-dimensional reconstructions of confocal images displayed a close association between intracellular bacteria and LC3-positive vesicles. Similarly, a close association between autophagic vesicles and the protein p62 was observed in challenged JEKs, indicating that p62 is the main adapter protein recruited during A. actinomycetemcomitans infection. Finally, the pharmacological inhibition of autophagy significantly increased the number of bacteria-infected cells as well as their death, similar to treatment with LPS. Our results indicate that A. actinomycetemcomitans infection induces autophagy in JEKs, and this homeostatic process has a cytoprotective effect on the host cells during the early stages of infection.

[Determination of some indicators of immunity and lipoperoxidation in the oral fluid in persons with a low vitamin D level.]

Oral fluid is a unique biological environment, containing a wide range of substances, coming from local and systemic sources, which makes it possible to use it as an object for assessing pathological changes in the body both at the local and systemic levels. In comparison with the traditional method of blood analysis, the advantage of evaluating the parameters of the oral fluid is the non-invasive of this method of obtaining material. All patients underwent oral fluid sampling using special plastic containers with a swab, which facilitate the selection of material, eliminating the penetration of mucin into a clean test sample, which helps to obtain more accurate analysis results. The amount of secretory IgA, lipopolysaccharide-binding protein (LBP), TBA-active products, the level of total antioxidant activity in the oral fluid in individuals with a low level of 25(OH)D before and after taking the native solution of vitamin D "Aqua Trim" were determined. The concentrations of secretory immunoglobulin A, lipopolysaccharide, binding protein and the level of total antioxidant activity are reduced in the oral fluid of people with vitamin D deficiency, but the number of intermediate products of lyoperoxidation increases. The course intake of the native solution of vitamin D (International Nonproprietary Name - Colecalciferol) normalizes the functioning of the immunity of the oral cavity and restores the balance of the "lipid peroxidation-antioxidants" system.

Bacteria Exploit Autophagy For Their Own Benefit

Autophagy is a lysosomal degradation pathway to clear long-lived proteins, protein aggregates, and damaged organelles. Certain microorganisms can be eliminated by an autophagic degradation process termed xenophagy. However, many pathogens deploy highly evolved mechanisms to evade autophagic degradation. What is more, series of pathogens have developed different strategies to exploit autophagy to ensure their survival. These bacteria could induce autophagy and/or prevent autophagosomes fusion with lysosomes through secreted effector proteins or utilizing host components, thereby maintaining the localization of the bacteria within the autophagosomes where they replicate. Here, we review the current knowledge of the mechanisms developed by the bacteria to benefit from autophagy for their survival.