Value of Serum Sirtuin-1 (SIRT1) Levels and SIRT1 Gene Variants in Periodontitis Patients

Morinda officinalis polysaccharides inhibit the expression and activity of NOD-like receptor thermal protein domain associated protein 3 in inflammatory periodontal ligament cells by upregulating silent information regulator sirtuin 1

OBJECTIVES

This study aims to investigate the effect of morinda officinalis polysaccharides (MOP) in inflammatory microenvironment on the expression of silent information regulator sirtuin 1 (SIRT1) and NOD-like receptor thermal protein domain associated protein 3 (NLRP3) in periodontal ligament cells.

METHODS

Thirty rats were randomly divided into control group (n=6) and model group (n=24). The model group used orthodontic wire ligation to establish periodontitis, and six rats from each group were killed after 3 weeks. The successful modeling was confirmed by Micro-CT. The remaining rats in the model group were randomly divided into natural recovery group, normal saline (NS) group, and MOP group. In the MOP group, MOP [200 mg/(kg·3d), 50 µL for 4 weeks] was injected into the palatal side of the left maxillary first molar of the rats, while the NS group was injected with equal volume of NS. The natural recovery group did not undergo any treatment. The left maxilla tissues of the rats were collected, and pathological changes in perio-dontal ligament cells were observed by hematoxylin-eosin (HE) staining. The expression of SIRT1 and NLRP3 was detected by immunohistochemistry. Cultivate periodontal ligament fibroblasts in vitro and detect the effect of MOP on cell activity using CCK-8. The 4th generation cells were divided into control group, inflammation group (10 µg/mL lipopolysaccharide), and experimental group (5 µmol/L MOP, 5 µmol/L MOP+10 µg/mL lipopolysaccharide). The expression of SIRT1 and NLRP3 was detected by quantitative realtime polymerase chain reaction (qRT-PCR) and Western blot analyses. The acetylation of NLRP3 and the contents of interleukin (IL)-1β and IL-18 were detected by immunoprecipitation and enzyme-linked immunosorbent assay, respectively. Statistical analysis of data was conducted using Prism 9.0 software.

RESULTS

In the vivo experiments, the expression of NLRP3 and SIRT1 in the MOP group decreased significantly compared with that in the natural recovery group and NS group, while the expression of SIRT1 increased (P<0.05) and inflammatory cell infiltration decreased. In the in vitro experiments, the expression of NLRP3 mRNA and protein in the inflammation group increased (P<0.05), while the expression of SIRT1 significantly decreased (P<0.01); MOP upregulated the expression of SIRT1 in inflammatory cells (P<0.05), reduced the expression of NLRP3 and its acetylation level significantly (P<0.05), suppressed the content of IL-1β and IL-18 in the supernatant (P<0.01).

CONCLUSIONS

The SIRT1 expression decreased, and that of NLRP3 expression increased in inflammatory periodontal ligament cells. MOP intervention promoted SIRT1 expression, resulting in the inhibition of NLRP3. Meanwhile, the acetylation level of NLRP3 reduced through deacetylation, leading to the decreased activity of NLRP3. Thus, MOP acted as inflammatory suppressor.

Oxidative stress and inflammation regulation of sirtuins: New insights into common oral diseases

Sirtuins are a family of nicotinamide adenine dinucleotide (NAD)⁺-dependent histone deacetylases, comprising seven members SIRT1-SIRT7. Sirtuins have been extensively studied in regulating ageing and age-related diseases. Sirtuins are also pivotal modulators in oxidative stress and inflammation, as they can regulate the expression and activation of downstream transcriptional factors (such as Forkhead box protein O3 (FOXO3a), nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-kappa B (NF-κB)) as well as antioxidant enzymes, through epigenetic modification and post-translational modification. Most importantly, studies have shown that aberrant sirtuins are involved in the pathogenesis of infectious and inflammatory oral diseases, and oral cancer. In this review, we provide a comprehensive overview of the regulatory patterns of sirtuins at multiple levels, and the essential roles of sirtuins in regulating inflammation, oxidative stress, and bone metabolism. We summarize the involvement of sirtuins in several oral diseases such as periodontitis, apical periodontitis, pulpitis, oral candidiasis, oral herpesvirus infections, dental fluorosis, and oral cancer. At last, we discuss the potential utilization of sirtuins as therapeutic targets in oral diseases.