ACF takes the driver's seat

Upregulated Mitochondrial Dynamics Is Responsible for the Procatabolic Changes of Chondrocyte Induced by α2-Adrenergic Signal Activation

OBJECTIVE

Activation of sympathetic tone is important for cartilage degradation in osteoarthritis (OA). Recent studies reported that sympathetic signals can affect the mitochondrial function of target cells. It is unknown whether this effect exits in chondrocytes and affects chondrocyte catabolism. The contribution of mitochondrial dynamics in the activation of α2-adrenergic signal-mediated chondrocyte catabolism was investigated in this study.

DESIGN

Primary chondrocytes were stimulated with norepinephrine (NE) alone, or pretreated with an α2-adrenergic receptor (Adra2) antagonist (yohimbine) and followed by stimulation with NE. Changes in chondrocyte metabolism and their mitochondrial dynamics were investigated.

RESULTS

We demonstrated that NE stimulation induced increased gene and protein expressions of matrix metalloproteinase-3 and decreased level of aggrecan by chondrocytes. This was accompanied by upregulated mitochondriogenesis and the number of mitochondria, when compared with the vehicle-treated controls. Mitochondrial fusion and fission, and mitophagy also increased significantly in response to NE stimulation. Inhibition of Adra2 attenuated chondrocyte catabolism and mitochondrial dynamics induced by NE.

CONCLUSIONS

The present findings indicate that upregulation of mitochondrial dynamics through mitochondriogenesis, fusion, fission, and mitophagy is responsible for activation of α2-adrenergic signal-mediated chondrocyte catabolism. The hypothesis that "α2-adrenergic signal activation promotes cartilage degeneration in temporomandibular joint osteoarthritis (TMJ-OA) by upregulating mitochondrial dynamics in chondrocytes" is validated. This represents a new regulatory mechanism in the chondrocytes of TMJ-OA that inhibits abnormal activation of mitochondrial fusion and fission is a potential regulator for improving mitochondrial function and inhibiting chondrocyte injury and contrives a potentially innovative therapeutic direction for the prevention of TMJ-OA.

Matrix metalloproteinases in rheumatoid arthritis and osteoarthritis: a state of the art review

Although the pathological mechanisms involved in osteoarthritis (OA) and rheumatoid arthritis (RA) are different, the onset and progression of both diseases are associated with several analogous clinical manifestations, inflammation, and immune mechanisms. In both diseases, cartilage destruction is mediated by matrix metalloproteinases (MMPs) synthesized by chondrocytes and synovium fibroblasts. This review aims to summarize recent articles regarding the role of MMPs in OA and RA, as well as the possible methods of targeting MMPs to alleviate the degradation processes taking part in OA and RA. The novel experimental MMP-targeted treatments in OA and RA are MMP inhibitors eg. 3-B2, taraxasterol, and naringin, while other treatments aim to silence miRNAs, lncRNAs, or transcription factors. Additionally, other recent MMP-related developments include gene polymorphism of MMPs, which have been linked to OA susceptibility, and the MMP-generated neoepitope of CRP, which could serve as a biomarker of OA progression.

Transcriptome Profiling of N7-Methylguanosine Modification of Messenger RNA in Drug-Resistant Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive hematological tumor caused by the malignant transformation of myeloid progenitor cells. Although intensive chemotherapy leads to an initial therapeutic response, relapse due to drug resistance remains a significant challenge. In recent years, accumulating evidence has suggested that post-transcriptional methylation modifications are strongly associated with tumorigenesis. However, the mRNA profile of m7G modification in AML and its role in drug-resistant AML are unknown. In this study, we used MeRIP-seq technology to establish the first transcriptome-wide m7G methylome profile for AML and drug-resistant AML cells, and differences in m7G between the two groups were analyzed. In addition, bioinformatics analysis was conducted to explore the function of m7G-specific methylated transcripts. We found significant differences in m7G mRNA modification between AML and drug-resistant AML cells. Furthermore, bioinformatics analysis revealed that differential m7G-modified mRNAs were associated with a wide range of cellular functions. Importantly, down-methylated m7G modification was significantly enriched in ABC transporter-related mRNAs, which are widely recognized to play a key role in multidrug resistance. Our results provide new insights into a novel function of m7G methylation in drug resistance progression of AML.

Properties and Roles of γδT Cells in Plasmodium yoelii nigeriensis NSM Infected C57BL/6 Mice

Background

Many kinds of immune cells are involved in malaria infection. γδT cells represent a special type of immune cell between natural and adaptive immune cells that play critical roles in anti-parasite infection.

Methods

In this study, malaria infection model was constructed. Distribution of γδT cells in various immune organs and dynamic changes of γδT cells in the spleens of C57BL/6 mice after infection were detected by flow cytometry. And activation status of γδT cells was detected by flow cytometry. Then γδT cells in naive and infected mice were sorted and performed single-cell RNA sequencing (scRNA-seq). Finally, γδTCR KO mice model was constructed and the effect of γδT cell depletion on mouse T and B cell immunity against Plasmodium infection was explored.

Results

Here, splenic γδT cells were found to increase significantly on day 14 after Plasmodium yoelii nigeriensis NSM infection in C57BL/6 mice. Higher level of CD69, ICOS and PD-1, lower level of CD62L, and decreased IFN-γ producing after stimulation by PMA and ionomycin were found in γδT cells from infected mice, compared with naive mice. Moreover, 11 clusters were identified in γδT cells by scRNA-seq based t-SNE analysis. Cluster 4, 5, and 7 in γδT cells from infected mice were found the expression of numerous genes involved in immune response. In the same time, the GO enrichment analysis revealed that the marker genes in the infection group were involved in innate and adaptive immunity, pathway enrichment analysis identified the marker genes in the infected group shared many key signalling molecules with other cells or against pathogen infection. Furthermore, increased parasitaemia, decreased numbers of RBC and PLT, and increased numbers of WBC were found in the peripheral blood from γδTCR KO mice. Finally, lower IFN-γ and CD69 expressing CD4⁺ and CD8⁺ T cells, lower B cell percentage and numbers, and less CD69 expressing B cells were found in the spleen from γδTCR KO infected mice, and lower levels of IgG and IgM antibodies in the serum were also observed than WT mice.

Conclusions

Overall, this study demonstrates the diversity of γδT cells in the spleen of Plasmodium yoelii nigeriensis NSM infected C57BL/6 mice at both the protein and RNA levels, and suggests that the expansion of γδT cells in cluster 4, 5 and 7 could promote both cellular and humoral immune responses.

PGK1 Is a Key Target for Anti-Glycolytic Therapy of Ovarian Cancer: Based on the Comprehensive Analysis of Glycolysis-Related Genes

Reprogramming of energy metabolism is a key hallmark of cancer, which provides a new research perspective for exploring the development of cancer. However, the most critical target of anti-glycolytic therapy for ovarian cancer remains unclear. Therefore, in the present study, Oncomine, GEPIA, and HPA databases, combined with clinical specimens of different histological types of ovarian cancer were used to comprehensively evaluate the expression levels of glycolysis-related metabolite transporters and enzymes in ovarian cancer. We selected phosphoglycerate kinase 1 (PGK1), which showed the greatest prognostic value in the Kaplan-Meier Plotter database, for subsequent validation. Immunochemistry assays confirmed that PGK1 was highly expressed in ovarian cancer. The PGK1 expression level was an independent risk factor for the survival and prognosis of patients with ovarian cancer. Functional analysis showed that the PGK1 expression level was positively correlated with the infiltration of neutrophils. Cell experiments confirmed that inhibiting PGK1 expression in ovarian cancer cells could reduce the epithelial-mesenchymal transition (EMT) process, resulting in loss of cell migration and invasion ability. The small molecule NG52 dose-dependently inhibited the proliferation of ovarian cancer cells. In addition, NG52 reduced the EMT process and reversed the Warburg effect by inhibiting PGK1 activity. Therefore, PGK1 is an attractive molecular target for anti-glycolytic therapy of ovarian cancer.

miR-122-5p Mediates Fluoride-Induced Osteoblast Activation by Targeting CDK4

Chronic intake of fluoride, existing in the environment, may cause endemic fluorosis, which is characterized by the occurrence of skeletal and dental fluorosis. However, the pathogenesis of fluorosis has not yet been elucidated. Abnormal osteoblast proliferation and activation have a pivotal role in bone turnover disorders which are linked to skeletal fluorosis. MicroRNAs are involved in fundamental cellular processes, including cell proliferation. Based on our previous study, population study and in vitro experiments were designed to understand the effect of miR-122-5p on osteoblast activation in skeletal fluorosis through targeting cyclin-dependent kinase 4 (CDK4). In human populations with coal-burning type fluoride exposure, the results showed that miR-122-5p was downregulated but CDK4 expression was upregulated and miR-122-5p was negatively correlated with CDK4 expression. Furthermore, in human osteoblasts treated with sodium fluoride, we demonstrated that miR-122-5p mediated osteoblast activation of skeletal fluorosis via upregulation of the CDK4 protein. In support of this, dual-luciferase reporter assay showed that miR-122-5p modulated CDK4 protein levels by targeting its 3'-untranslated region. These findings show, for the first time, that miR-122-5p may be involved in the cause and development of skeletal fluorosis by targeting CDK4.

Autophagy in fate determination of mesenchymal stem cells and bone remodeling

Mesenchymal stem cells (MSCs) have been widely exploited as promising candidates in clinical settings for bone repair and regeneration in view of their self-renewal capacity and multipotentiality. However, little is known about the mechanisms underlying their fate determination, which would illustrate their effectiveness in regenerative medicine. Recent evidence has shed light on a fundamental biological role of autophagy in the maintenance of the regenerative capability of MSCs and bone homeostasis. Autophagy has been implicated in provoking an immediately available cytoprotective mechanism in MSCs against stress, while dysfunction of autophagy impairs the function of MSCs, leading to imbalances of bone remodeling and a wide range of aging and degenerative bone diseases. This review aims to summarize the up-to-date knowledge about the effects of autophagy on MSC fate determination and its role as a stress adaptation response. Meanwhile, we highlight autophagy as a dynamic process and a double-edged sword to account for some discrepancies in the current research. We also discuss the contribution of autophagy to the regulation of bone cells and bone remodeling and emphasize its potential involvement in bone disease.

CircHIPK3 Promotes Metastasis of Gastric Cancer via miR-653-5p/miR-338-3p-NRP1 Axis Under a Long-Term Hypoxic Microenvironment

As a vital feature of the microenvironment, hypoxia, especially long-term hypoxia, is known to promote metastasis and lead to poor prognosis in solid tumors. Circular RNAs (circRNAs) participate in important processes of cell proliferation and metastasis in cancers. However, the contribution of circRNAs to metastasis under long-term hypoxia is obscure. In this study, we aim to explore specific functions of circHIPK3 in long-term hypoxia-promoting metastasis of gastric cancer (GC). The hypoxic resistant gastric cancer (HRGC) cell lines we established previously, which were tolerant to 2% O₂ conditions, were used as the long-term hypoxia model. We found that circHIPK3 was upregulated by HIF-2α in HRGC cells, and circHIPK3 facilitated the migration and invasion ability of HRGC cells. Further investigation proved that circHIPK3 promoted metastasis of HRGC cells directly by interacting with miR-653-5p and miR-338-3p to relieve the suppression of neuropilin 1 (NRP1), resulting in the activation of downstream ERK and AKT pathways. Our study identified oncogene functions of circHIPK3 under a long-term hypoxic microenvironment and the possibility of using circHIPK3 as a potential biomarker of long-term hypoxia in GC. In conclusion, circHIPK3 could promote GC metastasis via the miR-653-5p/miR-338-3p-NRP1 axis under a long-term hypoxic microenvironment.

Thirdhand smoke exposure causes replication stress and impaired transcription in human lung cells

Thirdhand cigarette smoke (THS) is a newly described toxin that lingers in the indoor environment long after cigarettes have been extinguished. Emerging results from both cellular and animal model studies suggest that THS is a potential human health hazard. DNA damage derived from THS exposure could have genotoxic consequences that would lead to the development of diseases. However, THS exposure-induced interference with fundamental DNA transactions such as replication and transcription, and the role of DNA repair in ameliorating such effects, remain unexplored. Here, we found that THS exposure increased the percentage of cells in S-phase, suggesting impaired S-phase progression. Key DNA damage response proteins including RPA, ATR, ATM, CHK1, and BRCA1 were activated in lung cells exposed to THS, consistent with replication stress. In addition, THS exposure caused increased 53BP1 foci, indicating DNA double-strand break induction. Consistent with these results, we observed increased micronuclei formation, a marker of genomic instability, in THS-exposed cells. Exposure to THS also caused a significant increase in phosphorylated RNA Polymerase II engaged in transcription elongation, suggesting an increase in transcription-blocking lesions. In agreement with this conclusion, ongoing RNA synthesis was very significantly reduced by THS exposure. Loss of nucleotide excision repair exacerbated the reduction in RNA synthesis, suggesting that bulky DNA adducts formed by THS are blocks to transcription. The adverse impact on both replication and transcription supports genotoxic stress as a result of THS exposure, with important implications for both cancer and other diseases.

Expression of CHD1L in colorectal cancer and its effect on colorectal cancer cell proliferation

AIM: To investigate the expression of chromodomain helicase/ATPase DNA binding protein 1-like (CHD1L) in colorectal cancer (CRC) tissues, and to assess the effect of CHD1L on CRC cell proliferation and apoptosis.

METHODS: Real-time fluorescence quantitative PCR (qRT-PCR) and immunohistochemistry were used to detect the expression of CHD1L mRNA and protein in CRC and pericarcinomatous intestine tissues (PCIT). MTT assay, colony formation assay and animal experiments were used to observe the effect of CHD1L on CRC cell proliferation. Flow cytometric assay was used to detect cell apoptosis.

RESULTS: CHD1L protein was overexpressed in 76.25% (61/80) of the CRC tissue samples. Transfection of CRC cells with an shRNA targeting CHD1L significantly reduced the expression of CHD1L mRNA and protein. MTT assay and colony formation assay showed that cell proliferation in the CHD1L knockdown group was significantly lower than that in the control group. Flow cytometry assay showed that apoptosis index in the CHD1L knockdown group was significantly increased compared with the control group. Tumor formation assay showed that tumor volume and weight in the CHD1L knockdown group were significantly less than those in the control group.

CONCLUSION: CHD1L is overexpressed in CRC tissues. Knockdown of CHD1L inhibits CRC cell proliferation and tumor growth. CHD1L may become a new target for the treatment of CRC.

Relatedness of Helicobacter pylori populations to gastric carcinogenesis

Helicobacter pylori (H. pylori) is a Gram-negative bacterium that infects half of the human population. The infection is associated with chronic inflammation of the gastric mucosa and peptic ulcers. It is also a major risk factor for gastric cancer. Phylogenetic analysis of global strains reveals there are seven populations of H. pylori, including hpAfrica1, hpAfrica2, hpEastAsia, hpEurope, hpNEAfrica, hpAsia2 and hpSahul. These populations are consistent with their geographical origins, and possibly result from geographical separation of the bacterium leading to reduced bacterial recombination in some populations. For each population, H. pylori has evolved to possess genomic contents distinguishable from others. The hpEurope population is distinct in that it has the largest genome of 1.65 mbp on average, and the highest number of coding sequences. This confers its competitive advantage over other populations but at the cost of a lower infection rate. The large genomic size could be a cause of the frequent occurrence of the deletion of the cag pathogenicity island in H. pylori strains from hpEurope. The incidence of gastric cancer varies among different geographical regions. This can be attributed in part to different rates of infection of H. pylori. Recent studies found that different populations of H. pylori vary in their carcinogenic potential and contribute to the variation in incidence of gastric cancer among geographical regions. This could be related to the ancestral origin of H. pylori. Further studies are indicated to investigate the bacterial factors contributing to differential virulence and their influence on the clinical features in infected individuals.