Role of connexin 43 in a rat model of periodontitis-induced renal injury.

OBJECTIVES: This study aims to investigate the role of gap junction mediated by connexin 43 (Cx43) in renal injury induced by periodontitis in rats. METHODS: Twelve SPF-grade Wistar male rats were divided into a control group and a periodontitis group by using a completely random number table method, with six rats in each group. The control group rats were not treated, while the periodontitis group rats were subjected to wire ligation of the neck of their bilateral maxillary first molars to construct a periodontitis model. After 8 weeks of modeling, the rats were examined for clinical indicators of the periodontium. micro-CT scanning of the maxilla reconstructed its 3D structure and analyzed the absorption of alveolar bone. Histopathological changes in periodontal and renal tissues were detected. MitoSOX red reagent was used to determine reactive oxygen species (ROS) content in renal tissues. A biochemical reagent kit was used to detect serum oxidative stress biomarkers. Real-time fluorescent quantitative-polymerase chain reaction (qRT-PCR) was employed to determine Cx43, nuclear factor kappa-B (NF-κB) , interleukin (IL)-1ß, IL-6, BCL2-Associated X (Bax), B-lymphomatoma-2 gene (Bcl-2), and Caspase-3 mRNA were determined. Western blot analysis was used to detect Cx43, NF-κB, IL-1ß, Bax, Bcl-2 and Caspase-3 protein. RESULTS: micro-CT 3D reconstruction showed significant bone resorption of the first molar alveolar bone in the periodontitis group rats and decreased height of the alveolar ridge. The distance from the enamel cementum boundary to the top of the alveolar ridge in the periodontitis group was significantly higher than that inthe control group. The histopathological results showed a large number of inflammatory cells that infiltrated the periodontal tissue of the periodontitis group, and the alveolar bone was significantly absorbed. Rats in the periodontitis group also exhibited mild thickening of the glomerular basement membrane, dilation of the Bowman's capsule, and destruction of the brush-like edge of the renal tubules in the renal tissue. The MitoSOX red staining results showed a significant increase in ROS content in the renal tissue of the periodontitis group. The biochemical test results showed that the levels of superoxide dismutase and glutathione in the serum of rats with periodontitis decreased, while that of malondialdehyde increased. The results of qRT-PCR and Western blot showed that the expression levels of Cx43, IL-1ß, IL-6, Bax, Caspase-3 mRNA and Cx43, IL-1ß, NF-κB, Bax, Caspase-3 proteins in the periodontitis group significantly increased compared with those in the control group, while the expression levels of Bcl-2 mRNA and protein decreased. CONCLUSIONS: Periodontitis may activate NF-κB signaling molecules by upregulating the expression of Cx43 in rat kidney tissues, leading to increased levels of inflammation and apoptosis and ultimately inducing kidney injury.

The role of uncoupling protein 2 in experimental periodontitis-associated renal injury in rats.

OBJECTIVES: This study aims to explore changes in uncoupling protein 2 (UCP2) in experimental periodontitis-associated renal injury induced by ligation and investigate the effect of UCP2 on renal injury induced by periodontitis. METHODS: Twelve Wistar male rats were randomly divided into two groups: control and periodontitis groups. A periodontal model was built by ligating the maxillary first molars area with 0.2 mm orthodontic ligature wire. After 8 weeks, the intraoral condition of the rats was observed and periodontal clinical indices such as gingival bleeding index (BI), periodontal probing depth (PD), and tooth mobility (TM) were detected. The maxillary bone was scanned by Micro CT to observe the alveolar bone resorption. The tissue mineral density (TMD), bone mineral density (BMD), bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular bone separation (Tb.Sp) were recorded, and the distance from the enamel bone boundary to the alveolar crest (CEJ-ABC) of the maxillary first molar was measured. The oxidative stress indexes such as malondialdehyde, glutathione (GSH), and superoxide dismutase (SOD) were detected using frozen rat kidney tissue. The gene expression of UCP2, nuclear factor erythroid 2-related factor 2 (Nrf2), and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) was observed by quantitative real-time polymerase chain reaction (qRT-PCR) test. The gingival tissue of the rats was used for immunohistochemical staining to observe the expression of the UCP2 protein. The fixed rat kidney tissue was used for hematoxylin-eosin (HE), periodic acid-schiff (PAS), MitoSOX Red, JC-1, and immunohistochemical staining to observe the renal histopathology, the level of reactive oxygen species (ROS), the level of mitochondrial membrane potential, and the expression of UCP2, Nrf2, and PGC-1α protein. Rat serum was collected to detect renal function indices, namely, blood urea nitrogen (BUN), creatinine (Cre), and albumin (Alb). RESULTS: Compared with the control group, the periodontitis group showed red, swollen, and soft gingival tissue, with gingival probing bleeding, periodontal PD increased, tooth loosening, alveolar bone resorption, decreased TMD, BMD, BV/TV, and Tb.Th indices, and increased Tb.Sp index, CEJ-ABC, and gingival UCP2 protein expression. Compared with the control group, the levels of MDA and ROS in the kidney tissue of periodontitis rats and the gene and protein expression of UCP2 increased, and the levels of MMP, GSH, and SOD and the gene and protein expression of Nrf2 and PGC-1α decreased. Renal functional indices, namely, BUN, Cre, and Alb, were not significantly different between the two groups. CONCLUSIONS: UCP2 may play a role in renal injury induced by periodontitis through oxidative stress.

Impact of circadian clock protein Bmal1 on experimentally-induced periodontitis-associated renal injury.

OBJECTIVES: To investigate the mechanism of circadian clock protein Bmal1 (Bmal1) on renal injury with chronic periodontitis, we established an experimental rat periodontitis model. METHODS: Twelve male Wistar rats were randomly divided into control and periodontitis groups (n=6, each group). The first maxillary molars on both sides of the upper jaw of rats with periodontitis were ligated by using orthodontic ligature wires, whereas the control group received no intervention measures. After 8 weeks, clinical periodontal parameters, including probing depth, bleeding index, and tooth mobility, were evaluated in both groups. Micro-CT scanning and three-dimensional image reconstruction were performed on the maxillary bones of the rats for the assessment of alveolar bone resorption. Histopatholo-gical observations of periodontal and renal tissues were conducted using hematoxylin-eosin (HE) and periodic acid-Schiff (PAS) staining. Renal function indicators, such as creatinine, albumin, and blood urea nitrogen levels, and oxidative stress markers, including superoxide dismutase, glutathione, and malondialdehyde levels, were measured using biochemical assay kits. MitoSOX red staining was used to detect reactive oxygen species (ROS) content in the kidneys. The gene and protein expression levels of Bmal1, nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1) in rat renal tissues were assessed using real-time quantitative polymerase chain reaction (RT-qPCR) and immunohistochemical staining. RESULTS: Micro-CT and HE staining results showed significant bone resorption and attachment loss in the maxillary first molar region of the periodontitis group. Histological examination through HE and PAS staining revealed substantial histopathological damage to the renal tissues of the rats in the periodontitis group. The findings of the assessment of renal function and oxidative stress markers indicated that the periodontitis group exhibited abnormal levels of oxidative stress, whereas the renal function levels showed abnormalities without statistical significance. MitoSOX Red staining results showed that the content of ROS in the renal tissue of the periodontitis group was significantly higher than that of the control group, and RT-qPCR and immunohistochemistry results showed that the expression levels of Bmal1, Nrf2, and HO-1 in the renal tissues of the rats in the periodontitis group showed a decreasing trend. CONCLUSIONS: Circadian clock protein Bmal1 plays an important role in the oxidative damage process involved in the renal of rats with periodontitis.