The opposite effect of tapinarof between IMQ and IL-23 induced psoriasis mouse models.

Tapinarof is an aryl hydrocarbon receptor (AHR) ligand which is used to treat plaque psoriasis in adults. However, the underlying mechanism is not yet fully understood. In this study, we applied two of the most studied psoriasis mouse models: topical application of imiquimod (IMQ) and subcutaneous injection of IL-23. Although both models successfully induced psoriasis-like lesions in mice, tapinarof had a completely opposite effect on the two models. Tapinarof decreased the expression of multiple essential cytokines involved in the pathological IL-23/IL-17/IL-22 axis and ameliorated IMQ-induced psoriatic dermatitis, inhibiting keratinocyte proliferation and abnormal differentiation. However, in the IL-23-injection-model, tapinarof instead aggravated the disease. Here, tapinarof increased epidermal thickness and differentiated epidermal dysplasia in mice. Our data suggest that tapinarof may have different effects on varied types of psoriasis.

Hepatic PPARα function is controlled by polyubiquitination and proteasome-mediated degradation through the coordinated actions of PAQR3 and HUWE1.

Peroxisome proliferator-activated receptor α (PPARα) is a key transcriptional factor that regulates hepatic lipid catabolism by stimulating fatty acid oxidation and ketogenesis in an adaptive response to nutrient starvation. However, how PPARα is regulated by posttranslational modification is poorly understood. In this study, we identified that progestin and adipoQ receptor 3 (PAQR3) promotes PPARα ubiquitination through the E3 ubiquitin ligase HUWE1, thereby negatively modulating PPARα functions both in vitro and in vivo. Adenovirus-mediated Paqr3 knockdown and liver-specific deletion of the Paqr3 gene reduced hepatic triglyceride levels while increasing fatty acid oxidation and ketogenesis upon fasting. PAQR3 deficiency enhanced the fasting-induced expression of PPARα target genes, including those involved in fatty acid oxidation and fibroblast growth factor 21, a key molecule that mediates the metabolism-modulating effects of PPARα. PAQR3 directly interacted with PPARα and increased the polyubiquitination and proteasome-mediated degradation of PPARα. Furthermore, the E3 ubiquitin ligase HUWE1 was identified to mediate PPARα polyubiquitination. Additionally, PAQR3 enhanced the interaction between HUWE1 and PPARα. CONCLUSION: Ubiquitination modification through the coordinated action of PAQR3 with HUWE1 plays a crucial role in regulating the activity of PPARα in response to starvation. (Hepatology 2018;68:289-303).

PAQR4 has a tumorigenic effect in human breast cancers in association with reduced CDK4 degradation.

Progestin and adipoQ receptor 4 (PAQR4) is a member of the PAQR family, and the members within this family are involved in the regulation of a number of biological processes including metabolism and cancer development. The potential function of PAQR4 in human cancers is unknown. Analysis of ONCOMINE database reveals that PAQR4 is highly expressed in human breast cancers. We confirmed this finding by analyzing 82 human breast cancers samples. PAQR4 mRNA level was significantly upregulated in human breast cancer samples compared with their corresponding para-cancerous histological normal tissues (P < 0.0001). The mRNA level of PAQR4 was negatively correlated with disease-free survival (P < 0.0001) and overall survival of the patients (P = 0.001). Knockdown of PAQR4 in human breast cancer cells SUM159 and MCF7 suppressed cell proliferation. In contrast, overexpression of PAQR4 in SUM159 cells enhanced cell proliferation and colony formation. In a tumor xenograft model, overexpression of PAQR4 promoted tumor growth of SUM159 cells in vivo, while PAQR4 knockdown suppressed the tumor growth. PAQR4 was able to negatively regulate cyclin-dependent kinases 4 (CDK4) protein level in the breast cancer cells. Knockdown of PAQR4 accelerated degradation of CDK4 together with upregulation of CDK4 polyubiquitination. On the other hand, overexpression of PAQR4 slowed down CDK4 protein degradation and reduced CDK4 polyubiquitination. Collectively, these data at the cellular, animal and human levels indicate that PAQR4 has a tumorigenic effect on human breast cancers, and such effect is associated with a modulatory activity of PAQR4 on protein degradation of CDK4.

Intermittent caloric restriction with a modified fasting-mimicking diet ameliorates autoimmunity and promotes recovery in a mouse model of multiple sclerosis.

Dietary interventions such as fasting have been proved to be effective in the prevention of metabolic and autoimmune diseases as well as aging-related conditions. The complicated interaction between nutrition and immunity has drawn wide attention in recent years. In this study, we investigated the therapeutic effect of intermittent caloric restriction on autoimmune encephalomyelitis (EAE), a model of multiple sclerosis, in mice. EAE was induced by immunization of C57BL/6 mice with myelin oligodendrocyte glycoprotein 35-55 peptide. After the EAE symptoms became obvious at the 4th week post-immunization, the mice were administered with a modified fasting-mimicking diet (FMD) at 1/3 cal of control for 3 days, followed by ad libitum with normal chow for 4 days. A total of two cycles of FMD was applied. Compared with the mice without receiving caloric restriction, the mice using FMD had significant decreases in EAE severity, immune cell infiltration in spinal cord and CNS demyelination. FMD administration also reversed EAE-mediated CNS accumulation of total CD4+ T cells and in particular, IFN-γ-producing CD4+ T cells. Moreover, FMD application elevated the cell proliferation rate in CNS and enhanced expression of brain-derived neurotrophic factor (BDNF) and remyelination markers. In conclusion, our results indicate that intermittent caloric restriction using the modified FMD was effective in the treatment of EAE through ameliorating inflammatory response and promoting recovery of the damaged tissue.

Intermittent administration of a fasting-mimicking diet intervenes in diabetes progression, restores ß cells and reconstructs gut microbiota in mice.

Fasting and especially intermittent fasting have been shown to be an effective intervention in many diseases, such as obesity and diabetes. The fasting-mimicking diet (FMD) has recently been found to ameliorate metabolic disorders. To investigate the effect of a new type of low-protein low-carbohydrate FMD on diabetes, we tested an FMD in db/db mice, a genetic model of type 2 diabetes. The diet was administered every other week for a total of 8 weeks. The intermittent FMD normalized blood glucose levels in db/db mice, with significant improvements in insulin sensitivity and ß cell function. The FMD also reduced hepatic steatosis in the mice. Deterioration of pancreatic islets and the loss of ß cells in the diabetic mice were prevented by the FMD. The expression of ß cell progenitor marker Ngn3 was increased by the FMD. In addition, the FMD led to the reconstruction of gut microbiota. Intermittent application of the FMD increased the genera of Parabacteroides and Blautia while reducing Prevotellaceae, Alistipes and Ruminococcaceae. The changes in these bacteria were also correlated with the fasting blood glucose levels of the mice. Furthermore, intermittent FMD was able to reduce fasting blood glucose level and increase ß cells in STZ-induced type 1 diabetic mouse model. In conclusion, our study provides evidence that the intermittent application of an FMD is able to effectively intervene in the progression of diabetes in mice.

Subcellular distribution of RAD23B controls XPC degradation and DNA damage repair in response to chemotherapy drugs.

The RAD23B-XPC complex in the nucleus plays a key role in the initial damage recognition during global genome nucleotide excision repair (NER). Within the complex, XPC, a product of Xeroderma pigmentosum C, recognizes and interacts with the unpaired bases in the undamaged DNA strand, while RAD23B stabilizes XPC. However, how RAD23B is regulated by other factors is not well known. We report here a mode of spatial regulation of RAD23B that controls XPC stability and DNA damage repair. We first identified that RAD23B was able to directly associate with PAQR3, a newly-discovered tumor suppressor implicated in many types of human cancers. PAQR3 reduced the protein level of XPC, together with accelerated degradation and enhanced polyubiquitination of XPC. Mechanistically, PAQR3 reduces nucleic distribution of RAD23B by tethering it to the Golgi apparatus, thus diminishing the amount of RAD23B proteins available to interact with XPC in the nucleus. The viability of gastric cancer cells upon treatment with chemotherapy drugs including etoposide, cisplatin and doxorubicin was reduced by PAQR3 overexpression, but enhanced by PAQR3 knockdown. The degree of DNA damage induced by these drugs, as measured by immunoblotting with γ-H2AX, was elevated by PAQR3 overexpression and lessened by PAQR3 knockdown. Furthermore, a synthetic peptide comprising the N-terminus of PAQR3 was able to recapitulate the activity of PAQR3 in reducing XPC stability and enhancing chemotherapy drug-induced DNA damage. In conclusion, our study reveals that RAD23B is controlled by subcellular compartmentation, thus affecting XPC-mediated DNA damage repair in cancer cells.