CR6 interacting factor 1 deficiency promotes endothelial inflammation by SIRT1 downregulation

Multifunctions of CRIF1 in cancers and mitochondrial dysfunction

Sustaining proliferative signaling and enabling replicative immortality are two important hallmarks of cancer. The complex of cyclin-dependent kinase (CDK) and its cyclin plays a decisive role in the transformation of the cell cycle and is also critical in the initiation and progression of cancer. CRIF1, a multifunctional factor, plays a pivotal role in a series of cell biological progresses such as cell cycle, cell proliferation, and energy metabolism. CRIF1 is best known as a negative regulator of the cell cycle, on account of directly binding to Gadd45 family proteins or CDK2. In addition, CRIF1 acts as a regulator of several transcription factors such as Nur77 and STAT3 and partly determines the proliferation of cancer cells. Many studies showed that the expression of CRIF1 is significantly altered in cancers and potentially regarded as a tumor suppressor. This suggests that targeting CRIF1 would enhance the selectivity and sensitivity of cancer treatment. Moreover, CRIF1 might be an indispensable part of mitoribosome and is involved in the regulation of OXPHOS capacity. Further, CRIF1 is thought to be a novel target for the underlying mechanism of diseases with mitochondrial dysfunctions. In summary, this review would conclude the latest aspects of studies about CRIF1 in cancers and mitochondria-related diseases, shed new light on targeted therapy, and provide a more comprehensive holistic view.

B cell-specific deletion of Crif1 drives lupus-like autoimmunity by activation of IL-17, IL-6, and pathogenic Tfh cells

OBJECTIVE

CR6-interacting factor 1 (Crif1) is a nuclear transcriptional regulator and a mitochondrial inner membrane protein; however, its functions in B lymphocytes have been poorly defined. In this study, we investigated the effects of Crif1 on B-cell metabolic regulation, cell function, and autoimmune diseases.

METHODS

Using mice with B cell-specific deletion of Crif1 (Crif1^ΔCD19 ), we assessed the relevance of Crif1 function for lupus disease parameters including anti-double-stranded DNA, cytokines, and kidney pathology. RNA sequencing was performed on B cells from Crif1^ΔCD19 mice. The phenotypic and metabolic changes in immune cells were evaluated in Crif1^ΔCD19 mice. Roquin^san/+ mice crossed with Crif1^ΔCD19 mice were monitored to assess the functionality of Crif1-deficient B cells in lupus development.

RESULTS

Crif1^ΔCD19 mice showed an autoimmune lupus-like phenotype, including high levels of autoantibodies to double-stranded DNA and severe lupus nephritis with increased mesangial hypercellularity. While loss of Crif1 in B cells showed impaired mitochondrial oxidative function, Crif1-deficient B cells promoted the production of IL-17 and IL-6 and was more potent in helping T cells develop into T follicular helper cells. In an autoimmune lupus mouse model, depletion of Crif1 in B cells exacerbated lupus severity and Crif1 overexpression prevented lupus development in Roquin^san/san mice.

CONCLUSION

These results showed that Crif1 was negatively correlated with disease severity, and overexpression of Crif1 ameliorated disease development. Our findings suggest that Crif1 is essential for preventing lupus development by maintaining B cell self-tolerance.

LncRNA Sirt1-AS upregulates Sirt1 to attenuate aging related deep venous thrombosis

Aging is associated with the increased incidence of deep venous thrombosis (DVT), resulting in significant morbidity and mortality in the elderly, but the underlying mechanism is elusive. Silent information regulator 1 (Sirt1) is linked to the senescence, inflammation, oxidative stress and platelet adhesion of endothelial cells. Here we showed that DVT was associated with the senescence of endothelium and lower expression of Sirt1. Furthermore, Sirt1 could inhibit endothelial senescence and reduce the occurrence of DVT. Interestingly, we found antisense long non-coding RNA (lncRNA Sirt1-AS) upregulated Sirt1, decreased the expression of senescence and DVT associated biomarkers in human vascular endothelial cells (HUVECs). In addition, lncRNA Sirt1-AS overexpression alleviated DVT through upregulating Sirt1 and thereby inducing Foxo3a degradation. In conclusion, our findings demonstrate that lncRNA Sirt1-AS may be a potential new biomarker for DVT.

SIRT1 Activation Attenuates the Cardiac Dysfunction Induced by Endothelial Cell-Specific Deletion of CRIF1

The CR6-interacting factor1 (CRIF1) mitochondrial protein is indispensable for peptide synthesis and oxidative phosphorylation. Cardiomyocyte-specific deletion of CRIF1 showed impaired mitochondrial function and cardiomyopathy. We developed an endothelial cell-specific CRIF1 deletion mouse to ascertain whether dysfunctional endothelial CRIF1 influences cardiac function and is mediated by the antioxidant protein sirtuin 1 (SIRT1). We also examined the effect of the potent SIRT1 activator SRT1720 on cardiac dysfunction. Mice with endothelial cell-specific CRIF1 deletion showed an increased heart-to-body weight ratio, increased lethality, and markedly reduced fractional shortening of the left ventricle, resulting in severe cardiac dysfunction. Moreover, endothelial cell-specific CRIF1 deletion resulted in mitochondrial dysfunction, reduced ATP levels, inflammation, and excessive oxidative stress in heart tissues, associated with decreased SIRT1 expression. Intraperitoneal injection of SRT1720 ameliorated cardiac dysfunction by activating endothelial nitric oxide synthase, reducing oxidative stress, and inhibiting inflammation. Furthermore, the decreased endothelial junction-associated protein zonula occludens-1 in CRIF1-deleted mice was significantly recovered after SRT1720 treatment. Our results suggest that endothelial CRIF1 plays an important role in maintaining cardiac function, and that SIRT1 induction could be a therapeutic strategy for endothelial dysfunction-induced cardiac dysfunction.

Abnormal Expression of Mitochondrial Ribosomal Proteins and Their Encoding Genes with Cell Apoptosis and Diseases

Mammalian mitochondrial ribosomes translate 13 proteins encoded by mitochondrial genes, all of which play roles in the mitochondrial respiratory chain. After a long period of reconstruction, mitochondrial ribosomes are the most protein-rich ribosomes. Mitochondrial ribosomal proteins (MRPs) are encoded by nuclear genes, synthesized in the cytoplasm and then, transported to the mitochondria to be assembled into mitochondrial ribosomes. MRPs not only play a role in mitochondrial oxidative phosphorylation (OXPHOS). Moreover, they participate in the regulation of cell state as apoptosis inducing factors. Abnormal expressions of MRPs will lead to mitochondrial metabolism disorder, cell dysfunction, etc. Many researches have demonstrated the abnormal expression of MRPs in various tumors. This paper reviews the basic structure of mitochondrial ribosome, focuses on the structure and function of MRPs, and their relationships with cell apoptosis and diseases. It provides a reference for the study of the function of MRPs and the disease diagnosis and treatment.

CRIF1 overexpression facilitates tumor growth and metastasis through inducing ROS/NFκB pathway in hepatocellular carcinoma

CR6-interacting factor 1 (Crif1) is a mitochondrial protein which is required for the assembly of oxidative phosphorylation (OXPHOS) complexes. Our bioinformatics analysis based on Cancer Genome Atlas (TCGA) database revealed an aberrant overexpression of CRIF1 in hepatocellular carcinoma (HCC). However, the clinical significance and biological functions of CRIF1 are still unclear in this malignancy. Here, we report that CRIF1 is frequently overexpressed in HCC cells mainly due to the downregulation of miR-497-5p, which is associated with poor prognosis of patients with HCC. CRIF1-promoted HCC growth and metastasis by suppressing cell apoptosis and inducing cell cycle progression and epithelial to mesenchymal transition (EMT). Mechanistically, increased mitochondrial ROS production and consequently activation of the NFκB signaling pathway was found to be involved in the promotion of growth and metastasis by CRIF1 in HCC cells. In summary, CRIF1 plays an oncogenic role in HCC progression through activating ROS/NFKB pathway, implying CRIF1 as a potential prognostic factor and therapeutic target in HCC.

Sirtuins family as a target in endothelial cell dysfunction: implications for vascular ageing

The vascular endothelium is a protective barrier between the bloodstream and the vasculature that may be disrupted by different factors such as the presence of diseased states. Diseases like diabetes and obesity pose a great risk toward endothelial cell inflammation and oxidative stress, leading to endothelial cell dysfunction and thereby cardiovascular complications such as atherosclerosis. Sirtuins are NAD⁺-dependent histone deacetylases that are implicated in the pathophysiology of cardiovascular diseases, and they have been identified to be important regulators of endothelial cell function. A handful of recent studies suggest that disbalance in the regulation of endothelial sirtuins, mainly sirtuin 1 (SIRT1), contributes to endothelial cell dysfunction. Herein, we summarize how SIRT1 and other sirtuins may contribute to endothelial cell function and how presence of diseased conditions may alter their expressions to cause endothelial dysfunction. Moreover, we discuss how the beneficial effects of exercise on the endothelium are dependent on SIRT1. These mainly include regulation of signaling pathways related to endothelial nitric oxide synthase phosphorylation and nitric oxide production, mitochondrial biogenesis and mitochondria-mediated apoptotic pathways, oxidative stress and inflammatory pathways. Sirtuins as modulators of the adverse conditions in the endothelium hold a promising therapeutic potential for health conditions related to endothelial dysfunction and vascular ageing.

CR6 interacting factor 1 deficiency induces premature senescence via SIRT3 inhibition in endothelial cells

Vascular endothelial cell senescence is an important cause of cardiac-related diseases. Mitochondrial reactive oxygen species (mtROS) have been implicated in cellular senescence and multiple cardiovascular disorders. CR6 interacting factor 1 (CRIF1) deficiency has been shown to increase mtROS via the inhibition of mitochondrial oxidative phosphorylation; however, the mechanisms by which mtROS regulates vascular endothelial senescence have not been thoroughly explored. The goal of this study was to investigate the effects of CRIF1 deficiency on endothelial senescence and to elucidate the underlying mechanisms. CRIF1 deficiency was shown to increase the activity of senescence-associated β-galactosidase along with increased expression of phosphorylated p53, p21, and p16 proteins. Cell cycle arrested in the G0/G1 phase were identified in CRIF1-deficient cells using the flow cytometry. Furthermore, CRIF1 deficiency was also shown to increase cellular senescence by reducing the expression of Sirtuin 3 (SIRT3) via ubiquitin-mediated degradation of transcription factors PGC1α and NRF2. Downregulation of CRIF1 also attenuated the function of mitochondrial antioxidant enzymes including manganese superoxide dismutase (MnSOD), Foxo3a, nicotinamide-adenine dinucleotide phosphate, and glutathione via the suppression of SIRT3. Interestingly, overexpression of SIRT3 in CRIF1-deficient endothelial cells not only reduced mtROS levels by elevating expression of the antioxidant enzyme MnSOD but also decreased the expression of cell senescence markers. Taken together, these results suggest that CRIF1 deficiency induces vascular endothelial cell senescence via ubiquitin-mediated degradation of the transcription coactivators PGC1α and NRF2, resulting in decreased expression of SIRT3.

Far-Infrared-Emitting Sericite Board Upregulates Endothelial Nitric Oxide Synthase Activity through Increasing Biosynthesis of Tetrahydrobiopterin in Endothelial Cells

Far-infrared ray (FIR) therapy has been reported to exert beneficial effects on cardiovascular function by elevating endothelial nitric oxide synthesis (eNOS) activity and nitric oxide (NO) production. Tetrahydrobiopterin (BH₄) is a key determinant of eNOS-dependent NO synthesis in vascular endothelial cells. However, whether BH₄ synthesis is associated with the effects of FIR on eNOS/NO production has not yet been investigated. In this study, we investigated the effects of FIR on BH₄-dependent eNOS/NO production and vascular function. We used FIR-emitting sericite boards as an experimental material and placed human umbilical vein endothelial cells (HUVECs) and Sprague–Dawley rats on the boards with or without FIR irradiation and then evaluated vascular relaxation by detecting NO generation, BH₄ synthesis, and Akt/eNOS activation. Our results showed that FIR radiation significantly enhanced Akt/eNOS phosphorylation and NO production in human endothelial cells and aorta tissues. FIR can also induce BH₄ storage by elevating levels of enzymes (e.g., guanosine triphosphate cyclohydrolase-1, 6-pyruvoyl tetrahydrobiopterin synthase, sepiapterin reductase, and dihydrofolate reductase), which ultimately results in NO production. These results indicate that FIR upregulated eNOS-dependent NO generation via BH₄ synthesis and Akt phosphorylation, which contributes to the regulation of vascular function. This might develop potential clinical application of FIR to treat vascular diseases by augmenting the BH₄/NO pathway.

Isocitrate dehydrogenase 2 deficiency induces endothelial inflammation via p66sh-mediated mitochondrial oxidative stress

Isocitrate dehydrogenase 2 (IDH2) is an essential enzyme in the mitochondrial antioxidant system, which produces nicotinamide adenine dinucleotide phosphate, and thereby defends against oxidative stress. We have shown that IDH2 downregulation results in mitochondrial dysfunction and reactive oxygen species (ROS) generation in mouse endothelial cells. The redox enzyme p66shc is a key factor in regulating the level of ROS in endothelial cells. In this study, we hypothesized that IDH2 knockdown-induced mitochondrial dysfunction stimulates endothelial inflammation, which might be regulated by p66shc-mediated oxidative stress. Our results showed that IDH2 downregulation led to mitochondrial dysfunction by decreasing the expression of mitochondrial oxidative phosphorylation complexes I, II, and IV, reducing oxygen consumption, and depolarizing mitochondrial membrane potential in human umbilical vein endothelial cells (HUVECs). The dysfunction not only increased mitochondrial ROS levels but also activated p66shc expression in HUVECs and IDH2 knockout mice. IDH2 deficiency increased intercellular adhesion molecule (ICAM)-1 expression and mRNA levels of pro-inflammatory cytokines (tumor necrosis factor [TNF]-α, and interleukin [IL]-1β) in HUVECs. The mRNA expression of ICAM-1 in endothelial cells and plasma levels of TNF-α and IL-1β were also markedly elevated in IDH2 knockout mice. However, p66shc knockdown rescued IDH2 deficiency-induced mitochondrial ROS levels, monocyte adhesion, ICAM-1, TNF-α, and IL-1β expression in HUVECs. These findings suggest that IDH2 deficiency induced endothelial inflammation via p66shc-mediated mitochondrial oxidative stress.