Mast Cells and Arachidonic Acid Cascade in Inflammation

Prostaglandin D2 PGD2 is a major cyclooxygenase metabolite of arachidonic acid produced by mast cells and it is released following allergen challenge in diseases, such as allergic diseases. PGD2 may act as a neuromodulator and as an allergic and inflammatory mediator. In allergic diseases, activated mast cell synthesizes prostaglandin D2 (first cyclo-oxygenate mediator) which has bronchoconstrictive and vasodilating effects and attracts several leukocytes. It has been found that activated mast cells, challenged with physiological and non- physiological secretagogues, release elevated histamine and tryptase and chymase, leukotrienes B4, C4 and D4, 5-hydroxyeicosatetraenoic acid, PGD2, Platelet Activating Factor (PAF), heparin, and high-molecular-weight neutrophil chemotactic factor and cytokines/chemokines. PGD2 exerts its biological activity through the DP and CRTH2 receptors and their cDNA cloning which were characterized 15 years ago. In this report, we revisited the biological effects of arachidonic acid compounds released by activated mast cells in allergic and inflammatory states.

Examination of periodontal pathogens in stenotic valve specimens and in whole blood samples in patients affected by aortic valve stenosis and chronic periodontitis

Periodontitis may be a risk factor for atherosclerosis and coronary heart disease. The influence of periodontal pathogens in cardiovascular diseases needs further investigation. Therefore, the aims of this clinical study are: to test the presence of periodontal bacteria DNA in aortic valves and to assess the concomitant presence of the same periodontal bacteria DNA in whole blood samples in patients affected by aortic valve stenosis and chronic periodontitis. Nineteen consecutive patients (12 males and 7 females, age: 49-85 years) were enrolled in this study after having been subjected to a complete periodontal evaluation to confirm the diagnosis of chronic periodontitis. All patients were scheduled for aortic valve replacement surgery. After clinical and microbial periodontal examination, the aortic valve tissue specimens were obtained by excision during valve replacement surgery and the patients were subjected to the whole blood sampling before the surgery. The polymerase chain reaction technology was used to detect the putative periodontal pathogens Tannerella forshytia, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Prevotella intermedia, Fusobacterium nucleatum, Campylobacter rectus, Eikenella corrodens and Treponema denticola. Neither the 19 aortic valve specimens nor the blood samples were positive for the genoma of the selected periodontal pathogens. The selected periodontal pathogens did not colonize the aortic valve of patients affected by stenosis and bacterial genoma was not present in whole blood samples. A high blood pressure at the aortic valve may prevent the adhesion and proliferation of bacterial colonies.

Vascular endothelial growth factor and e-nitric oxide synthase-mediated regenerative response occurring upon autologous and heterologous bone grafts

Bone regeneration procedures allow oral rehabilitation with dental implants also in edentulous ridges with severe bone atrophy. The integration of grafted materials with the host tissue can initiate regenerative, inflammatory and apoptotic response. Since molecular mechanisms exist at the basis of such response, the aim of this work is to investigate, by immunohistochemical analyses, the expression of proteins involved in the graft integration process, in parallel to clinical and histological modifications, occurring on sites treated with extraoral autologous bone graft deriving from the parietal region of the calvaria (eAB), intraoral autologous bone graft deriving from mandibular ramus (iAB) and heterologous bone graft from swine (hB) in human patients. In our study, the immunohistochemical expression of BSP, VEGF, eNOS in eAB samples was significantly higher (p < 0.05) compared to values recorded in iAB and hB samples. The inflammatory response, investigated by iNOS expression, was found lower in all autologous samples (eAB and iAB) compared to hB, at statistically significant values. Moreover, the expression of the pro-apoptotic molecule, Bax, resulted significantly lower (p < 0.05) in eAB than in iAB and hB samples. These values, together with the low number of apoptotic cells detected in autologous samples, suggest a good regenerative response when extraoral autologous bone graft is used in comparison to the response from the other grafts, and also suggest the use of calvaria graft as a predictable therapeutic procedure for repairing severe bone defects in oral and maxillofacial surgery, not only by clinical and biomechanical criteria, but also from a biomolecular aspect.

Microbiological and Biochemical Effectiveness of an Antiseptic Gel on the Bacterial Contamination of the Inner Space of Dental Implants: A 3-Month Human Longitudinal Study

Microbial penetration inside the implant's internal cavity produces a bacterial reservoir that is associated with an area of inflamed connective tissue facing the fixture-abutment junction. The aim of this clinical trial is to evaluate the effectiveness of a 1% chlorhexidine gel on the internal bacterial contamination of implants with screw-retained abutments and on the level of AST secreted in peri-implant crevicular fluid. Twenty-five patients (aged 29 to 58 years) each received one implant. Three months after the end of the restorative treatment, and immediately after a clinical and radiographic examination and the abutment removal, microbiological samples were obtained from the internal part of each fixture and biochemical samples were collected by peri-implant sulci. The patients were then divided into two groups: the control (CG; n=10) and test (TG; n=15) groups. The CG had the abutment screwed into place and the crown cemented without any further intervention. In contrast, before the abutment placement and screw tightening, the TG had the internal part of the fixture filled with a 1% chlorhexidine gel. Three months later, the same clinical, microbiological and biochemical procedures were repeated in both groups. Total bacterial count, specific pathogens and AST activity were detected. The clinical parameters remained stable throughout the study. From baseline to the 3-month examination, the total bacterial counts underwent a significant reduction only in the TG. In contrast, the AST activity showed a significant increase in the CG. The administration of a 1% chlorhexidine gel appears to be an effective method for the reduction of bacterial colonization of the implant cavity and for safeguarding the health status of peri-implant tissue over a 3-month administration period.

Stimulation of CCL2 (MCP-1) and CCL2 mRNA by substance P in LAD2 human mast cells

Chemokines are cytokines with chemotactic properties on inflammatory cells and other cell types. Chemokine (C-C motif) ligand 2 (CCL2), which is also called monocyte chemotactic protein 1 (MCP-1), is a potent chemotactic molecule that attracts lymphocytes, monocytes, mast cells, and memory T cells, but not neutrophils. CCL2/MCP-1 represents a link between the activation of monocytes, lymphocytes, basophils, mast cells, and eosinophils in inflammatory disorders, such as the late-phase allergic reaction. This C-C chemokine also plays a role in regulating Th-cell cytokine production and leukocyte trafficking. Laboratory of allergic diseases (LAD) cells is the first reported human mast cell line that closely resembles a primary culture of CD34+-derived human mast cells. These cells were cultured in vitro and treated with different concentrations of substance P (SP) for the production of CCL2/MCP-1. We used calcium ionophore as a positive control for stimulating transcription and translation of CCL2/MCP-1. The stimulation of SP on CCL2/MCP-1 was statistically significant (P < 0.05) compared with the control (untreated cells). In this study, we determined the expression and secretion of CCL2/MCP-1 from SP-activated LAD2 human mast cells in vitro. The levels of CCL2/MCP-1 from SP-activated LAD2 human mast cells were higher at 10 microM and at 18 h incubation compared with controls. This effect was also revealed on CCL2/MCP-1 messenger RNA (mRNA) expression, as determined by reverse transcriptase polymerase chain reaction (RT-PCR) analysis. Our data suggest that SP is an important neurotransmitter that can stimulate the chemokine CCL2, which plays a fundamental role in inflammation by recruiting inflammatory cells to specific cites.

Osteoblast apoptosis in periodontal disease: role of TNF-related apoptosis-inducing ligand

Periodontal disease (Pd) is characterized by an increased osteoclast resorption and a decreased osteoblast (OB) bone formation. OBs obtained from alveolar bone of Periodontitis patients (Pp) undergo apoptosis in the presence of TNF-related apoptosis-inducing ligand (TRAIL). We studied the intracellular apoptotic pathway induced by TRAIL; TRAIL death (DR4, DR5) and decoy (DcR1, DcR2) receptors expression in Periodontitis patients OBs (PpOBs), and we measured the concentration of TRAIL in the serum of Pp. We demonstrated that DNA fragmentation and activation of caspase-8 and caspase-3 in PpOBs, following TRAIL stimulation, occurred in shorter time; moreover, a higher amount of both caspases was activated in order to direct OBs. Down-regulation of DcR2 in PpOBs was demonstrated and high TRAIL levels were detected in the serum of Pp. In conclusion, our data suggest that PpOBs are more sensitive to TRAIL-induced apoptosis when compared to the control group. The down-regulation of DcR2 possibly leads to an imbalanced ratio between death and decoy receptors. Our findings highlight a role of TRAIL in the pathogenesis of Pd.