Expression of a cytokine, interleukin-23, in experimental periapical lesions

Influence of violet LED associated or not with peroxide gel on inflammation, mineralization, and collagen fiber maturation in dentin and pulp tissue

OBJECTIVES

To evaluate the influence of violet LED, associated or not with a 17.5% hydrogen peroxide (HP) bleaching gel, on inflammation, mineralization in pulp tissue, and collagen fiber maturation in dentin and pulp tissue.

MATERIALS AND METHODS

The maxillary molars of eighty Wistar rats were distributed into four groups (n = 10): CONT - without treatment; HP - 30-minute application of 17.5% HP; LED - 20-minute application of violet LED; and HP+LED - application of PH and violet LED. Rats were euthanized and jaws were processed for histologic and immunohistochemical evaluation (IL-17, IL-23, and osteocalcin) and picrosirius red immediately after (T0), and at 7 (T1), 15 (T2), and 30 days (T3) post-treatment, with Wilcoxon, Mann-Whitney, paired T-test, and T-test (α = 0.05).

RESULTS

HP and HP+LED presented necrosis and severe inflammatory infiltrate. When compared to CONT group, LED presented severe osteocalcin (OCN) immunostaining in T2 and less immature fibers in T2 and T3.

CONCLUSION

The violet LED caused no severe damage to the pulp tissue, increased IL-17 and IL-23 expression in T0 when associated with HP, and had no influence on pulp tissue mineralization, besides accelerating the maturation of collagen fibers of dentin.

CLINICAL RELEVANCE

Violet LED therapy induced no inflammation in the pulp tissue of rats and played no role in pulp tissue fibrosis, besides accelerating the maturation of dentin collagen fibers.

Involvement of interleukin‑23 induced by Porphyromonas endodontalis lipopolysaccharide in osteoclastogenesis

Periapical lesions are characterized by the destruction of periapical bone, and occur as a result of local inflammatory responses to root canal infection by microorganisms including Porphyromonas endodontalis (P. endodontalis). P. endodontalis and its primary virulence factor, lipopolysaccharide (LPS), are associated with the development of periapical lesions and alveolar bone loss. Interleukin-23 (IL-23) is critical in the initiation and progression of periodontal disease via effects on peripheral bone metabolism. The present study investigated the expression of IL-23 in tissue where a periapical lesion was present, and the effect of P. endodontalis LPS on the expression of IL-23 in periodontal ligament (PDL) cells. Reverse transcription- quantitative polymerase chain reaction and immunohistochemistry revealed increased levels of IL-23 expression in tissue with periapical lesions compared with healthy PDL tissue. Treatment with P. endodontalis LPS increased the expression of IL-23 in the SH-9 human PDL cell line. BAY11-7082, a nuclear factor κB inhibitor, suppressed P. endodontalis LPS-induced IL-23 expression in SH-9 cells. Treatment of RAW264.7 cells with conditioned medium from P. endodontalis LPS-treated SH-9 cells promoted osteoclastogenesis. By contrast, RAW264.7 cells treated with conditioned medium from IL-23-knockdown SH-9 cells underwent reduced levels of osteoclastogenesis. The results of the present study indicated that the expression of IL-23 in PDL cells induced by P. endodontalis LPS treatment may be involved in the progression of periapical lesions via stimulation of the osteoclastogenesis process.

Cytokine-mediated bone destruction in rheumatoid arthritis

Bone homeostasis, which involves formation and resorption, is an important process for maintaining adequate bone mass in humans. Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammation and bone loss, leading to joint destruction and deformity, and is a representative disease of disrupted bone homeostasis. The bone loss and joint destruction are mediated by immunological insults by proinflammatory cytokines and various immune cells. The connection between bone and immunity has been intensely studied and comprises the emerging field of osteoimmunology. Osteoimmunology is an interdisciplinary science investigating the interplay between the skeletal and the immune systems. The main contributors in osteoimmunology are the bone effector cells, such as osteoclasts or osteoblasts, and the immune cells, particularly lymphocytes and monocytes. Physiologically, osteoclasts originate from immune cells, and immune cells regulate osteoblasts and vice versa. Pathological conditions such as RA might affect these interactions, thereby altering bone homeostasis, resulting in the unfavorable outcome of bone destruction. In this review, we describe the osteoclastogenic roles of the proinflammatory cytokines and immune cells that are important in the pathophysiology of RA.

Immunohistochemical localization of NALP3 inflammasome in experimental periapical lesions

AIM

To explore the role of NALP3 inflammasome [NALP3, its effector molecule apoptosis associated speck-like protein (ASC), caspase-1, interleukin (IL)-1β and IL-18] in the development of periapical lesions in rats.

METHODOLOGY

Periapical lesions were developed within 21 days after mandibular first molar pulp exposure in Sprague-Dawley rats. The animals were randomly sacrificed at 0, 1, 3, 7, 10, 14 and 21 days after pulpal exposure. The bilateral mandibles were extracted for histological processing, then they were haematoxylin-eosin (HE) stained to examine inflammation infiltration in the apical region and immunohistochemically examined for the NALP3 inflammasome signalling pathway. Data were analysed by one-way analysis of variance and the Pearson(') s correlation and linear tendency test.

RESULTS

NALP3 was detected in the cytoplasm of fibroblasts, monocytes, neutrophils, macrophages and vascular endothelial cells in the periapical region. From day 1 to day 21, the number of NALP3-positive cells ascended and was significantly correlated with the intensity of inflammatory infiltration (r = 0.776, P < 0.01). ASC, caspase-1, IL-1β and IL-18 were all expressed in the inflammatory periapical tissues. The positive cell counts of IL-1β and IL-18 were significantly correlated with that of NALP3, and r = 0.718, P < 0.01; r = 0.688, P < 0.01, respectively.

CONCLUSIONS

NALP3 inflammasome is expressed in the inflammatory periapical tissues. This cytokine-signalling pathway may therefore be crucial in the regulatory control of inflammatory responses in periapical tissues and the development of periapical lesions.