CircDCBLD2 alleviates liver fibrosis by regulating ferroptosis via facilitating STUB1-mediated PARK7 ubiquitination degradation

BACKGROUND

Liver fibrosis can progress to cirrhosis and hepatic carcinoma without treatment. CircDCBLD2 was found to be downregulated in liver fibrosis. However, the precise underlying mechanism requires further investigation.

METHODS

qRT-PCR, Western blot, and immunohistochemistry assays were used to detect the related molecule levels. HE, Masson's trichrome, and Sirius Red staining were used to assess the pathological changes in mice's liver tissues. Flow cytometric analysis and commercial kit were used to assess the levels of lipid reactive oxygen species (ROS), malonaldehyde (MDA), glutathione (GSH), and iron. Cell viability was assessed by MTT. Immunoprecipitation was used to study the ubiquitination of PARK7. Mitophagy was determined by immunostaining and confocal imaging. RIP and Co-IP assays were used to assess the interactions of circDCBLD2/HuR, HuR/STUB1, and STUB1/PARK7. Fluorescence in situ hybridization and immunofluorescence staining were used to assess the co-localization of circDCBLD2 and HuR.

RESULTS

CircDCBLD2 was downregulated, whereas PARK7 was upregulated in liver fibrosis. Ferroptosis activators increased circDCBLD2 while decreasing PARK7 in hepatic stellate cells (HSCs) and mice with liver fibrosis. CircDCBLD2 overexpression reduced cell viability and GSH, PARK7, and GPX4 expression in erastin-treated HSCs while increasing MDA and iron levels, whereas circDCBLD2 knockdown had the opposite effect. CircDCBLD2 overexpression increased STUB1-mediated PARK7 ubiquitination by promoting HuR-STUB1 binding and thus increasing STUB1 mRNA stability. PARK7 overexpression or HuR knockdown reversed the effects of circDCBLD2 overexpression on HSC activation and ferroptosis. CircDCBLD2 reduced liver fibrosis in mice by inhibiting PARK7.

CONCLUSION

CircDCBLD2 overexpression increased PARK7 ubiquitination degradation by upregulating STUB1 through its interaction with HuR, inhibiting HSC activation and promoting HSC ferroptosis, ultimately enhancing liver fibrosis.

DJ-1 modulates Nrf2-mediated MRP1 expression by activating Wnt3a/β-catenin signalling in A549 cells exposed to cigarette smoke extract and LPS

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is an inflammatory disease characterized by airway obstruction and abnormal inflammatory responses. Multidrug resistance-related protein 1 (MRP1) can reduce lung inflammation and damage by excreting various toxic exogenous substances and certain pro-inflammatory molecules.

AIMS

We studied whether DJ-1 modulates nuclear factor erythroid 2-related factor 2 (Nrf2) by activating the Wnt3a/β-catenin signalling pathway to further regulate MRP1 expression and pulmonary antioxidant defences in alveolar epithelial (A549) cells treated with smoke extract (CSE) and lipopolysaccharide (LPS).

MAIN METHODS

Marker expression was studied by western blot analysis, quantitative real-time PCR and immunofluorescence staining of A549 cells.

KEY FINDINGS

A549 cells exposed to CSE and LPS showed downregulation of DJ-1, Wnt3a, MRP1 and haem oxygenase-1 (HO-1) and upregulation of inflammatory factors. Additionally, Nrf2 protein levels were significantly decreased, while there was no change in Nrf2 mRNA levels. Overexpression of DJ-1 and Wnt3a activated Nrf2 signalling, increased MRP1 and HO-1 levels and decreased IL-6 protein expression, while knockdown of DJ-1 and Wnt3a had the opposite effects. Furthermore, DJ-1 overexpression and DJ-1 knockdown increased and decreased, respectively, the levels of Wnt3a and β-catenin. Interestingly, Nrf2 and Wnt3a deficiency reduced the protective effects of Wnt3a and DJ-1, respectively, in A549 cells. However, the levels of DJ-1 and Wnt3a were not altered by Wnt3a and Nrf2 deletion, respectively.

SIGNIFICANCE

In A549 cells treated with CSE and LPS, DJ-1 regulates Nrf2-mediated MRP1 expression and antioxidant defences by activating the Wnt3a/β-catenin signalling pathway. These findings may provide potential therapeutic targets for COPD intervention.

[Effect of DJ-1 silencing by RNA interference on growth of xenografted human laryngeal squamous cell carcinoma Hep-2 cells in nude mice]

Objective: To investigate the effect of silencing DJ-1 on xenografted human laryngeal squamous cell carcinoma (LSCC) Hep-2 cells in nude mice. Methods: Xenograft model of human LSCC was established by subcutaneous transplantation of Hep-2 cells in 24 nude mice. The LSCC-bearing nude mice were randomly divided into 3 groups (n=8 in each):DJ-1 siRNA low dose group and DJ-1 siRNA high dose group were injected in tumors with 20 μg of DJ-1 siRNA or 40 μg of DJ-1 siRNA in 50 μL, respectively; control group was injected with 5% glucose solution in 50 μL, twice a week for 3 weeks. The weight and size of tumors were measured before injection. The animals were sacrificed 48 h after the final treatment, and the tumors were harvested and weighed. The apoptosis and proliferation of tumor cells were determined; the expressions of Caspase-3 and Ki-67 in tumor specimens were detected with immunohistochemistry. The expression of DJ-1, PTEN, survivin mRNA and protein in tumor tissues were detected by RT-PCR and Western blotting, respectively. Results: Tumor weight in low dose group[(0.66±0.15)g] and high dose group[(0.48±0.11)g] were significantly lower than that in control group[(0.83±0.16)g, all P<0.05]. The inhibition rates of low dose group and high dose group were (20.48±0.18)% and (42.16±0.13)%, respectively. Immunohistochemistry showed that the expression of Caspase-3 was increased and Ki-67 was reduced in tumor specimens, compared with the control group (all P<0.05). RT-PCR and Western blot results showed that in low dose group and high dose group the mRNA and protein expression of DJ-1 and survivin significantly decreased (all P<0.05), while PTEN mRNA and protein content increased (all P<0.05). Conclusion: High dose DJ-1 siRNA can inhibit the tumor growth in human LSCC xenograft nude mouse model, which indicates that down-regulating DJ-1 and survivin, and up-regulating PTEN expression may lead to blockage of PI3K-PKB/Akt signaling pathway and promoting tumor cell apoptosis.