Ubiquitination and Deubiquitination in Oral Disease

Therapeutic potential of curcumin in regenerative dentistry

Introduction

Natural compounds have emerged as promising candidates in drug development due to their potent immunomodulatory anti-inflammatory, antibacterial, analgesic, and healing properties. They have shown significant therapeutic potential in clinical applications, such as mouth rinses, toothpastes, and localized delivery systems. The use of natural alternatives can contribute to tackling antimicrobial resistance. Among natural compounds, curcumin has gained particular attention, demonstrating robust anti-cancer, antibiotic, and anti-inflammatory activities in numerous in vivo studies, while exhibiting a favorable safety profile for the treatment of various diseases. In this study, the remedial effects of curcumin and its metabolite, tetrahydrocurcumin, on dental pulp were explored. In addition, these results were compared with our previous findings on the effects of these natural compounds on periodontal ligament and gingival epithelial cells, further broadening our understanding of their therapeutic potential in oral disease such as caries and periodontitis.

Methods

RNA sequencing was used to investigate the differentially expressed genes in dental pulp cells following treatments with curcumin and tetrahydrocurcumin.

Results

We show that treatment of dental pulp cells with 1 μM of curcumin or tetrahydrocurcumin is sufficient to promote Wnt signaling pathway in dental pulp cells. Curcumin treatment promotes the upregulation of cellular metabolism and enhances cellular response to stress. Our enrichment analysis shows that treatment with tetrahydrocurcumin modulates the extracellular matrix and angiogenesis.

Conclusions

The findings of this study highlight the cytoprotective and regenerative properties of curcumin and tetrahydrocurcumin. These properties could be leveraged as a therapeutic approach to promote tissue regeneration in oral diseases.

Ubiquitin-Proteasome System in Periodontitis: Mechanisms and Clinical Implications

The progression of periodontitis, a bacteria-driven inflammatory and bone-destructive disease, involves myriad cellular and molecular mechanisms. Protein regulation significantly influences the pathogenesis and management of periodontitis. However, research regarding its regulatory role in periodontitis remains relatively limited. The ubiquitin-proteasome system (UPS), which mainly involves ubiquitination by E3 ubiquitin ligases (E3s) and deubiquitination by deubiquitinating enzymes (DUBs), is the primary intracellular and non-lysosomal mechanism of protein degradation. Recent studies have provided compelling evidence to support the involvement of UPS in periodontitis progression. Increasing evidence indicated that E3s, such as CUL3, Nedd4-2, Synoviolin, FBXL19, PDLIM2, TRIMs and TRAFs, modulate inflammatory responses and bone resorption in periodontitis through multiple classical signalling pathways, including NLRP3, GSDMD, NF-κB, Wnt/β-catenin and Nrf2. Meanwhile, DUBs, including OTUD1, A20, CYLD, UCH-L1 and USPs, also broadly modulate periodontitis progression by regulating signalling pathways such as NF-κB, Wnt/β-catenin, NLRP3, and BMP2. Therefore, the modulation of E3s and DUBs has proven to be an effective therapy against periodontitis. This review provides a comprehensive overview of the regulatory role of ubiquitinating and deubiquitinating enzymes in periodontitis progression and the underlying mechanisms. Finally, we summarise several chemical and genetic methods that regulate UPS enzymes and pave the way for the development of targeted therapies for periodontitis.

USP39 promotes retinal pathological angiogenesis in retinopathy of prematurity by stabilizing SIRT2 expression through deubiquitination

BACKGROUND

Retinopathy of prematurity (ROP) is a major cause of childhood blindness worldwide, highlighted by retinal neovascularization. Ubiquitin is present throughout the retina. The deubiquitinating enzyme ubiquitin-specific protease 39 (USP39) has been reported to be involved in angiogenesis. Here, this study aimed to investigate the effects of USP39 on ROP and its associated mechanism.

METHODS

Hypoxia-induced human retinal microvascular endothelial cells (hRMECs) were adopted for functional analyses. Detection of mRNA and protein was conducted using quantitative real-time PCR and western blotting. Cell migration, invasion and angiogenesis were evaluated using transwell and tube formation assays. Protein interaction was determined by immunoprecipitation assay. Oxygen-induced retinopathy (OIR) mouse models were used for in vivo analysis.

RESULTS

USP39 level was higher in hypoxia-induced hRMECs, functionally, USP39 silencing reversed hypoxia-induced migration, invasion and angiogenesis in hRMECs. In further mechanism analysis, we found that USP39 stabilized SIRT2 protein expression in hRMECs by inducing SIRT2 deubiquitination. Moreover, SIRT2 up-regulation abated hypoxia-evoked migration, invasion and angiogenesis in hRMECs. Besides that, the inhibitory effects of USP39 silencing on hypoxia-induced metastatic and angiogenic behaviors were abolished after SIRT2 overexpression. In addition, USP39 silencing blocked the activation of phosphoinositide 3-kinase (PI3K)/protein kinase B pathway (AKT) by regulating SIRT2. In vivo assay showed that levels of USP39, SIRT2, matrix metalloproteinase (MMP)-2 (MMP-2), MMP-9 and Vascular endothelial growth factor A (VEGFA) were increased in the retinas of OIR mice, while intravitreal injection of USP39 short hairpin RNA (shRNA) could reduce their expression.

CONCLUSION

USP39 stabilized SIRT2 expression by deubiquitination and promoted hypoxia-induced metastatic and angiogenic behaviors of RMECs in vitro, as well as retinal angiogenesis in vivo.

USP9X deubiquitinates TRRAP to promote glioblastoma cell proliferation and migration and M2 macrophage polarization

Glioblastoma (GBM) is the most aggressive form of brain cancer, characterized by rapid growth and invasion into surrounding brain tissue. Ubiquitin-specific protease 9X (USP9X) has emerged as a key regulator in various cancers, but its role in GBM pathogenesis remains unclear. Understanding the molecular mechanisms underlying USP9X modulation of GBM progression could unveil potential therapeutic targets for this deadly disease. The mRNA and protein levels were determined in GBM tissues and/or cells using quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting assays, respectively. Cell migration was evaluated through wound-healing assay, while cell proliferation was measured using colony formation and CCK-8 assays. Flow cytometry analysis was performed to quantify the CD206-positive macrophages to assess M2 polarization. Co-immunoprecipitation (Co-IP) assays were conducted to elucidate the association between USP9X and transformation/transcription domain-associated protein (TRRAP). Cycloheximide (CHX) treatment was used to determine the impact of USP9X on TRRAP protein stabilization. Furthermore, the effect of USP9X depletion on GBM cell malignancy was validated using a xenograft mouse model. We found that USP9X expression was elevated in GBM tissues and cells. Depletion of USP9X suppressed GBM cell migration, proliferation, and M2 macrophage polarization. Mechanistically, USP9X stabilized TRRAP through the deubiquitination pathway in GBM cells, and TRRAP mitigated the effects of USP9X silencing on GBM cell malignant phenotypes and M2 macrophage polarization. Moreover, silencing of USP9X inhibited tumor formation in vivo. Together, USP9X deubiquitinated TRRAP, thereby promoting glioblastoma cell proliferation, migration, and M2 macrophage polarization. These results highlight the potential of targeting the USP9X-TRRAP axis as a therapeutic strategy for GBM.

Recurrent aphthous stomatitis and neoplasms of the mouth and pharynx: a two-sample Mendelian randomization study

BACKGROUND

The association between recurrent aphthous stomatitis (RAS) and neoplasms of the mouth and pharynx (NOMAP) has been reported in some previous observational studies. However, causality is still confused. Our research aims to explore the relationship between RAS and NOMAP through a Mendelian randomization (MR) analysis and to explore whether RAS can serve as a risk factor for NOMAP to provide a reference for the clinical strategy.

METHODS

An exposure dataset for RAS were collected from a published study based on the UK Biobank (UKB). Outcome datasets included Genome-wide association studies (GWAS) summary statistics of NOMAP from the FinnGen datasets. The core method was inverse variance weighting (IVW). The Bonferroni correction, MR-Egger, weighted median, weighted mode, Cochcan's Q test, MR-PRESSO, and leave-one-out methods served as complementary methods.

RESULTS

We found no significant evidence of causal relationships between RAS and NOMAP. After applying the Bonferroni correction, the corrected P was equal to 0.00625 (0.05/1/8). The IVW method provided the sole evidence for RAS on Benign neoplasm of floor of mouth (BNFM) (OR = 2.509, 95% CI: 1.296-4.857, P = 0.006), but the subsequent MR-Egger regression method showed that this result may be due to horizontal pleiotropy (P = 0.035). The Cochran Q-test, MR-Egger regression, and MR-PRESSO did not reveal any heterogeneity or directional pleiotropy for the other outcomes.

CONCLUSIONS

In conclusion, this is the first MR analysis to investigate the relationship between RAS and NOMAP. Our research confirmed at the genetic level that no causal association has been identified between RAS and NOMAP, therefore facilitating a logical therapeutic perspective and the development of clinical therapies for them.

Ubiquitin C-terminal hydrolase L1 activation in periodontal ligament cells mediates orthodontic tooth movement via the MAPK signaling pathway

PURPOSE

Periodontal ligament cells (PDLCs) play a significant role in orthodontic force induced bone remodeling. However, the molecular mechanisms by which PDLCs respond to mechanical stimuli and influence osteoclastic activities remain unclear. This study aims to investigate the role of UCHL1, a key deubiquitinating enzyme involved in protein degradation and cellular responses, in force-treated PDLCs during orthodontic tooth movement (OTM).

MATERIALS AND METHODS

In this study, we conducted in vivo and in vitro experiments using human PDLCs and a rat model of OTM. Mechanical stress was applied to PDLCs, and UCHL1 expression was analyzed through quantitative real-time polymerase chain reaction (qPCR), Western blot, and immunofluorescence staining. UCHL1 knockdown was achieved using siRNA, and its effects on osteoclast differentiation were assessed. The role of the MAPK/ERK pathway was investigated using the MEK-specific inhibitor U0126. An animal model of OTM was established, and the impact of UCHL1 inhibitor-LDN57444 on OTM and osteoclastic activity was evaluated through micro-CT analysis, histological staining, and immunohistochemistry.

RESULTS

Mechanical force induced UCHL1 expression in PDLCs during OTM. UCHL1 knockdown downregulated the RANKL/OPG ratio in PDLCs, affecting osteoclast differentiation. LDN57444 inhibited OTM and osteoclastic activity. UCHL1 activation correlated with ERK1/2 phosphorylation in force-treated PDLCs.

CONCLUSIONS

Mechanical force mediated UCHL1 activation in PDLCs promotes osteoclast differentiation via the ERK1/2 signaling pathway during OTM.

USP7 regulates HMOX-1 via deubiquitination to suppress ferroptosis and ameliorate spinal cord injury in rats

Heme oxygenase 1 (HMOX-1) is overexpressed in spinal cord injury (SCI) and relevant to ferroptosis. Ubiquitin-specific-processing protease 7 (USP7) has unveiled its role in regulating HMOX-1 stabilization while its function in SCI remains unknown. This study is to explore the potential molecular mechanism of the USP7-HMOX-1 axis in ferroptosis in a SCI rat model. SCI was assessed with Basso, Beattie, Bresnahan locomotion evaluation, hematoxylin-eosin histological staining, and immunofluorescence detection of NeuN. Ferroptosis was assessed by detections of the iron content, malondialdehyde and glutathione levels, mitochondrial damage, and glutathione peroxidase 4, 4-hydroxynonenal, USP7, and HMOX-1 expression in spinal cord. Co-immunoprecipitation was used to detect the binding of USP7 to HMOX-1. The ubiquitination level of HMOX-1 was measured after USP7 overexpression. USP7 expression was downregulated and HMOX-1 expression was upregulated in SCI rat models. HMOX-1 or USP7 overexpression promoted motor function recovery, ameliorated spinal cord damage, increased NeuN expression, and blocked the occurrence of ferroptosis in SCI rat models. In SCI rats, USP7 directly bound to HMOX-1 and its overexpression promoted HMOX-1 expression via deubiquitination. To sum up, USP7 overexpression facilitated the expression of HMOX-1 through deubiquitination, thereby reducing ferroptosis and alleviating SCI.

UBE2T promotes glioblastoma malignancy through ubiquitination-mediated degradation of RPL6

Glioblastoma (GBM) is the most frequent and aggressive malignant glioma. Due to patients' poor prognosis, it is of great clinical significance to determine new targets that may improve GBM treatment. In the present study, we showed that ubiquitin (Ub)-conjugating enzyme E2T (UBE2T) was significantly overexpressed in GBM and could promote proliferation, invasion, and inhibit apoptosis of GBM cells. Mechanistically, UBE2T functioned as the Ub enzyme of ribosomal protein L6 (RPL6) and induced the ubiquitination and degradation of RPL6 in an E3 ligase-independent manner through direct modification by K48-linked polyubiquitination, thus contributing to the malignant progression of GBM cells. Furthermore, inhibiting the expression of RPL6 by UBE2T could not only reduce the expression of wild-type p53, but also enhance the gain-of-function of mutant p53. Moreover, knockdown of UBE2T in LN229 cells obviously suppressed tumor growth in LN229 xenograft mouse models. Collectively, our study demonstrated that UBE2T promotes GBM malignancy through ubiquitination-mediated degradation of RPL6 regardless of the p53 mutation status. It will provide new candidates for molecular biomarkers and therapeutic targets for clinical application in GBM.

Prevalence of periodontal disease in middle-aged and elderly patients and its influencing factors

OBJECTIVE

To explore the prevalence of periodontal disease in middle-aged and elderly patients and analyze its influencing factors.

METHODS

A total of 521 patients admitted to the Department of Stomatology of Fuyang District Chinese Medicine Hospital of Hangzhou from January 2019 to January 2022 were retrospectively collected as study subjects, including 176 patients aged 35-44 years old, 175 patients aged 45-64 years old, and 170 patients aged 65-74 years old. Community Periodontal Index (CPI) probe was used to detect gingival bleeding, periodontal pockets and attachment loss, and the prevalence of periodontal disease and its influencing factors were analyzed.

RESULTS

In the age group of 35-44, gingival bleeding was detected in 165 (93.75%) cases and dental calculus was detected in 176 (100.00%) cases; in the age group of 45-64, gingival bleeding was detected in 163 (93.14%) cases and dental calculus was detected in 161 (92.00%) cases; in the age group of 65-74, gingival bleeding was detected in 150 (88.24%) cases and dental calculus was detected in 162 (95.29%) cases. There were statistically significant differences in the detection rates of shallow periodontal pockets, deep periodontal pockets, and loss of periodontal attachment among the three groups (P<0.05). There wasalso asignificant difference in the detection rate of periodontitis among the three groups (P<0.05). Univariate analysis showed that gender, age, place of residence, smoking, alcohol consumption, brushing frequency, and dental cleaning in the past year were all associated with the occurrence of periodontitis (P<0.05). Logistic multi-factor regression analysis showed that age was a risk factor for the development of periodontitis in middle-aged and elderly patients (P<0.05).

CONCLUSION

The prevalence of periodontal disease in middle-aged and elderly individuals is high, with a high prevalence of gingival bleeding and shallow periodontal pockets. Age is an influencing factor on the incidence of periodontitis in middle-aged and elderly individuals.

USP44 accelerates the growth of T-cell acute lymphoblastic leukemia through interacting with WDR5 and repressing its ubiquitination

T-cell acute lymphoblastic leukemia (T-ALL) is a common hematologic malignancy. Based on the data from GSE66638 and GSE141140, T-ALL patients depicted a higher USP44 level. However, its role in T-ALL is still unclear. In the present study, we investigated the role of USP44 in T-ALL growth. USP44 overexpression elevated the proliferation of CCRF-CEM cells, while USP44 knockdown suppressed the proliferation of Jurkat and MOLT-4 cells. In addition, USP44 accelerated the cell cycle progression, with boosted cyclinD and PCNA levels. However, USP44 knockdown induced apoptosis in Jurkat and MOLT-4 cells, with an upheaval among cleaved caspase-3 and PARP levels. Mechanistically, USP44 co-localized and interacted with WDR5, leading to the repression of its ubiquitination and degradation. Interestingly, WDR5 overexpression abolished the apoptosis induced by USP44 knockdown. Consistently, the in vivo study revealed that USP44 knockdown restricted the leukemic engraftments in the bone marrow and spleens and reduced the infiltration of T-ALL cells in the livers and lungs. In conclusion, this study indicated that USP44 enhanced the growth of T-ALL through interacting with WDR5 and repressing its ubiquitination. This study highlights the potential use of USP44 as a therapeutic target of T-ALL.