Molecular Mechanisms Research Articles

Ionizing radiation inhibits zebrafish embryo hatching through induction of tissue inhibitors of metalloproteinases (TIMPs) expression.

Ionizing radiation (IR) has garnered growing attention because of its biological effects on aquatic organisms and humans. Here, we identify the most impacted organs and uncover the molecular mechanisms causing the changes in the context of vertebrate development using single-cell RNA sequencing. Alterations in cellular composition and biological functions were explored using transcriptomic profiling of zebrafish embryos exposed to 5 Gy. Single-cell RNA sequencing analyses unveiled notable shifts in the proportions of brain/central nervous system and hatching gland clusters. Although IR exposure led to increased expression of hatching enzymes, a significant but mild delay in hatching was observed following 5 Gy IR exposure. Gene Ontology analysis showed an increased expression of tissue inhibitors of metalloproteinases (TIMPs), known as matrix metalloproteinase inhibitors, which was confirmed via whole-mount in situ hybridization. Correlation analysis linked TIMPs to transcription factors cebpb and cebpd, which were significantly correlated post-IR exposure. Although no morphological changes were observed in some organs, including the brain, the study reveals substantial alterations in developing vertebrates. Notably, despite increased hatching enzymes, elevated TIMPs in the hatching gland suggest a regulatory mechanism impacting hatching activity. This research contributes to comprehending the ecological repercussions of IR exposure, emphasizing the importance of safety measures for aquatic ecosystems and overall environmental health.

1-Deoxynojirimycin affects high glucose-induced pancreatic beta-cell dysfunction through regulating CEBPA expression and AMPK pathway.

This study aims to explore the role of 1-Deoxynojirimycin (DNJ) in high glucose-induced β-cells and to further explore the molecular mechanism of DNJ effect on β-cells through network pharmacology. In the study, high glucose treatment of mouse INS-1 cells inhibited cell proliferation and insulin secretion, decreased the expression of Bcl-2 protein and Ins1 and Ins2 genes, promoted apoptosis, and increased cleaved caspase-3 and cleaved caspase-9 expression levels as well as intracellular reactive oxygen species (ROS) production. DNJ treatment significantly restored the dysfunction of INS-1 cells induced by high glucose, and DNJ showed no toxicity to normal INS-1 cells. Silencing CEBPA promoted, while overexpression of CEBPA relieved the dysfunction of pancreatic β-cells induced by high glucose. DNJ treatment partially restored the pancreatic β-cell dysfunction caused by silencing CEBPA. In conclusion, DNJ can inhibit high glucose-induced pancreatic β-cell dysfunction by promoting the expression of CEBPA.

Succinylation modification-mediated upregulation of Sp1 promotes hepatocellular carcinoma cell proliferation.

Hepatocellular carcinoma (HCC) remains one of the most prevalent malignant tumors globally, characterized by high incidence and mortality rates. Despite ongoing research, the underlying molecular mechanisms of HCC development are not yet fully understood. Utilizing bioinformatic analysis, real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR), and Western blot assays, we identified that the expression of specificity protein 1 (Sp1) was significantly elevated in HCC cells compared to normal cells. Knockdown of the Sp1 gene led to a marked reduction in the viability and clonogenic potential of HCC cells. Further investigation revealed that the succinylation level of Sp1 was also increased in HCC cells. The upregulation of Sp1 expression was attributed to its succinylation, mediated by KAT2A, with lysine (K)562 identified as the succinylation site. Additionally, KAT2A and Sp1 were found to influence the upregulation of mTOR phosphorylation. Collectively, these findings suggest that KAT2A-promoted succinylation of Sp1 enhances the proliferative capacity of HCC cells by activating the mTOR pathway, providing a theoretical foundation for potential therapeutic strategies against HCC.

Dendrobium nobile Lindl. alkaloids protect CCl4-induced acute liver injury via upregulating LAMP1 expression and activating autophagy flux.

Dendrobium nobile Lindl. alkaloids (DNLA) are considered important active ingredients of Dendrobium, which have a variety of pharmacological functions. Recent studies indicate that DNLA has beneficial activity in acute liver injury. However, the specific mechanism by which DNLA produces liver protective effects is stills unclear. This study was designed to determine whether regulation of autophagy is involved in the mode of action of DNLA in liver protection. Using CCl4-induced acute liver injury (ALI) and cell culture models, the molecular mechanism of DNLA-mediated autophagy regulation was studied. The results showed that DNLA significantly improved CCl4-induced liver damage and oxidative stress, which was confirmed in AML-12 cells. DNLA promoted autophagy in cells treated with CCl4, manifested by reduced protein expressions of p62 and LC3-II. Fluorescence imaging showed a decrease in the number of autophagosomes in AML-12 cells transfected with mCherry-GFP-LC3B. In addition, DNLA inhibited lysosomal membrane permeabilization by upregulating lysosomal associated membrane protein-1 (LAMP1), thereby promoting autophagy, preventing CCl4-induced mitochondrial dysfunction, and reducing the production of mitochondrial reactive oxygen species (ROS). While pretreatment of cells with lysosomal inhibitor chloroquine weakened mitochondrial protection elicited by DNLA, overexpression of mitochondrial-targeted SOD2 in AML-12 cells significantly blocked CCl4 induced downregulation of LAMP1, thereby improving lysosome integrity and promoting lysosome dependent autophagy, suggesting that there may exist a bidirectional regulation between mitochondrial ROS and lysosome-autophagy activation. Collectively, these results demonstrated that DNLA can protect the liver injury mediated by dysregulation of lysosome-autophagy process through promoting ROS-lysosome-autophagy axis and improving mitochondrial damage.

Increased caveolin 1 by human antigen R exacerbates Porphyromonas gingivali-induced atherosclerosis by modulating oxidative stress and inflammatory responses

Objective: Many different types of infectious oral diseases have been identified clinically, including chronic periodontitis. Porphyromonas gingivalis is the main pathogen causing chronic periodontitis, which is closely related to atherosclerosis (AS) and can promote the expression levels of caveolin 1 (Cav-1) and induced ribonucleic acid (RNA)-binding protein human antigen R (HuR). However, the roles of Cav-1 and its relationship with HuR in P. gingivalis-mediated AS progression remain largely unknown. Here, we aimed to detect the role and molecular mechanisms of Cav-1 in P. gingivalis-mediated AS. Material and Methods: To investigate the role of Cav-1 in P. gingivalis-mediated AS, we infected human umbilical vein endothelial cells (HUVECs) with P. gingivalis at a multiplicity of infection of 100:1 for 6, 12, and 24 h to simulate P. gingivalis-induced AS models in vitro and then transfected them with Cav-1 small interfering RNA to silence Cav-1. Combining molecular biology experimental techniques such as cell counting kit-8 assay, enzyme-linked immunosorbent assay, immunofluorescence staining, flow cytometry, Western blotting, and Oil Red O staining, and apolipoprotein E-deficient AS model mice, the impacts of Cav-1 on cell viability, inflammation, oxidative stress, apoptosis, Cav-1 and intercellular cell adhesion molecule-1 (ICAM-1) levels, and atherosclerotic plaque formation were investigated. Then, the relationship between Cav-1 and HuR was investigated through biotin pull-down and RNA immunoprecipitation assays, reverse transcription quantitative polymerase chain reaction, and Western blot. Results: P. gingivalis can induce Cav-1 expression in a time- and dose-dependent manner (P < 0.05). This effect can inhibit the proliferation of HUVECs (P < 0.05). Cav-1 interference repressed inflammatory response, reactive oxygen species (ROS) and ICAM-1 levels, and apoptosis in the HUVECs (P < 0.05). Cav-1 messenger RNA was stabilized by HuR, which can bind to the 3’ untranslated region of Cav-1. Increase in HuR level reversed the effects of Cav-1 silencing on ROS and ICAM-1 levels and apoptosis in the HUVECs (P < 0.05). In addition, the levels of inflammatory response, oxidative stress, and atherosclerotic plaque formation induced by P. gingivalis in the mouse model were significantly reduced after Cav-1 expression was inhibited (P < 0.05). Conclusion: HuR-activated Cav-1 may promote atherosclerotic plaque formation by modulating inflammatory response and oxidative stress, leading to AS.

Cuproptosis, ferroptosis and PANoptosis in tumor immune microenvironment remodeling and immunotherapy: culprits or new hope.

Normal life requires cell division to produce new cells, but cell death is necessary to maintain balance. Dysregulation of cell death can lead to the survival and proliferation of abnormal cells, promoting tumor development. Unlike apoptosis, necrosis, and autophagy, the newly recognized forms of regulated cell death (RCD) cuproptosis, ferroptosis, and PANoptosis provide novel therapeutic strategies for tumor treatment. Increasing research indicates that the death of tumor and immune cells mediated by these newly discovered forms of cell death can regulate the tumor microenvironment (TME) and influence the effectiveness of tumor immunotherapy. This review primarily elucidates the molecular mechanisms of cuproptosis, ferroptosis, and PANoptosis and their complex effects on tumor cells and the TME. This review also summarizes the exploration of nanoparticle applications in tumor therapy based on in vivo and in vitro evidence derived from the induction or inhibition of these new RCD pathways.

Single-Nucleus and Spatial Transcriptomics Revealing Host Response Differences Triggered by Mutated Virus in Severe Dengue

Dengue virus (DENV) infection causes various disease manifestations ranging from an asymptomatic state to severe, life-threatening dengue. Despite intensive research, the molecular mechanisms underlying the abnormal host responses and severe disease symptoms caused by evolved DENV strains is not fully understood. First, the spatial structure of mutant DENV was compared via in silico molecular modeling analysis. Second, employing single-nucleus and spatial RNA sequencing, we analyzed and verified transcriptome samples in uninfected, mild (NGC group), and severe (N10 group) liver tissues from murine models. In this study, we obtained a cumulatively mutated DENV-2 N10 with enhanced capability of replication and pathogenicity post 10 serial passages in Ifnra−/− mice. This variant caused severe damage in the liver, as compared with other organs. Furthermore, mutated DENV infection elicited stronger responses in hepatocytes. The critical host factor Nrg4 was identified. It dominated mainly via the activation of the NRG/ErbB pathway in mice with severe symptoms. We report on evolved N10 viruses with changes observed in different organisms and tissue. This evolutionary variant results in high replicability, severe pathogenicity, and strong responses in murine. Moreover, the host responses may play a role by activating the NRG/ErbB signaling pathway. Our findings provide a realistic framework for defining disturbed host responses at the animal model level that might be one of the main causes of severe dengue and the potential application value.

Unraveling the metabolic activities of bioactive compounds on cellular models of hepatosteatosis and adipogenesis through docking analysis with PPARs.

Obesity is associated with fatty liver disease. Available therapies show modest efficacy, and nutraceuticals with good effectiveness and safety are largely investigated. We focused on five natural compounds, three plant phenolic compounds (carvacrol, rosmarinic acid, silybin), and two thyroid hormones (T2: 3,5-diiodo-l-thyronine; T3: 3,5,3'-triiodo-L-thyronine) as comparison, to assess their beneficial effects on two cellular models of hepatosteatosis and adipogenesis. All compounds ameliorated the lipid accumulation and oxidative stress in both models, but with different potencies. The peroxisome proliferator-activated receptors (PPARs) are pivotal controllers of adipogenesis and lipid metabolism. For the main isoforms, PPARγ and PPARa, we assessed their possible binding to the compounds by molecular docking calculations, and their expression pattern by real-time PCR. All compounds bind both PPARs with different affinity, while not all compounds affect their expression. The results may clarify the distinctive molecular mechanisms underlying the action of the five compounds in the different cell models with possible applications to treat obesity.

Non-coding RNAs modulation in breast cancer radioresponse: mechanisms and therapeutic implications.

Breast cancer is the most frequent type of cancer in women, with significant incidence and fatality rates. Radiation therapy is an important therapeutic option for breast cancer patients. However, tumor cells' resistance to radiation can limit therapy efficacy, resulting in recurrence and death. Non-coding RNAs (ncRNAs) are aclass of small RNA molecules that do not translate into proteins but can affect the translation of target mRNA. Several investigations on breast cancer have demonstrated abnormal expression of ncRNAs in response to radiation. Non-coding RNAs are essential in controlling numerous processes such as DNA damage response, cancer stem cell pathways, cell cycle regulation, cell death, and inflammation. Dysregulation of ncRNAs after irradiation influences radiosensitivity or radioresistance of breast cancer cells. Understanding the molecular mechanisms underlying Radiation response can lead to innovative treatment ways to reduce breast cancer radioresistance and increase radiotherapy's efficacy. This review summarizes current research on ncRNA dysregulation following irradiation and analyzes ncRNAs' function and mechanism in modifying breast cancer cell radiosensitivity and radioresistance.

CORRECTION OF ENDOTHELIAL DYSFUNCTION WITH SULFAPORIN IN HYPERCHOLESTEROLEMIC RABBITS

In animals with experimental hypercholesterolemia, depending on the time of survey, we observed activation of smooth muscle cells and macrophages, causing development of inflammation in the intima, as evidenced by high levels of C-reactive protein (CRP), endothelin-1, and homocysteine. The aim of the study was to investigate the molecular mechanisms of endothelial dysfunction in HCH and the possibility of their correction with sulfaporin. Material and methods of the study Experiments were conducted on 46 Chinchilla rabbits with an average weight of 2.5–3.0 kg, kept on a standard diet. The model of experimental HCH in animals was reproduced by orally administering cholesterol (CS) dissolved in sunflower oil in a ratio of 0.2 g per 1 kg of body weight daily for 3 months. The development of hypercholesterolemia was assessed by the increase in the level of totalcholesterol (TC), low-density lipoproteins (LDL) and high-density lipoproteins (HDL), which were determined on a biochemical analyzer. Results of the study. In this case, a progressive increase in the homocysteine level was established: an increase of 1.72 (P < 0.01); 2.33 (P < 0.001) and 2.89 (P < 0.001) times, respectively, for the periods of cholesterol administration of 1, 2 and 3 months. Considering that hyperhomocysteinemia enhances the capture of LDL by endothelial cells, it was of interest to study the relationship between these indicators. The studies showed that with a cholesterol level in LDL of 2.38 ± 0.27 mmol / l, the homocysteine content is 3.46 ± 0.25 pg / ml. With a cholesterol level in LDL of 4.08 ± 0.10; 5.97 ± 0.09 and 6.48 ± 0.11 mmol/l, the homocysteine content increases to 5.96 ± 0.05; 8.07 ± 0.43 and 9.99 ± 0.17 pg/ml, respectively. Conclusions. Hypercholesterolemia is manifested by activation of smooth muscle cells and macrophages, causing the development of inflammation in the intima, which is confirmed by high levels of CRP, endothelin-1, homocysteine.

Exploring the role of Fusobacterium nucleatum in colorectal cancer: implications for tumor proliferation and chemoresistance.

Fusobacterium nucleatum (Fn) has been extensively studied for its connection to colorectal cancer (CRC) and its potential role in chemotherapy resistance. Studies indicate that Fn is commonly found in CRC tissues and is associated with unfavorable prognosis and treatment failure. It has been shown that Fn promotes chemoresistance by affecting autophagy, a cellular process that helps cells survive under stressful conditions. Additionally, Fn targets specific signaling pathways that activate particular microRNAs and modulate the response to chemotherapy. Understanding the current molecular mechanisms and investigating the importance of Fn-inducing chemoresistance could provide valuable insights for developing novel therapies. This review surveys the role of Fn in tumor proliferation, metastasis, and chemoresistance in CRC, focusing on its effects on the tumor microenvironment, gene expression, and resistance to conventional chemotherapy drugs. It also discusses the therapeutic implications of targeting Fn in CRC treatment and highlights the need for further research.

Tumor-derived EBV-miR-BART2-5p promotes nasopharyngeal carcinoma metastasis by inducing pre-metastatic endothelial cell pyroptosis.

Extravasation is a key step in tumor metastasis. Epstein‒Barr virus (EBV) plays a crucial role in nasopharyngeal carcinoma (NPC) metastasis. However, the functions and molecular mechanisms of EBV during tumor cell extravasation remains unclear. Here, we showed that the expression of pyroptosis-associated proteins is greater in the endothelial cells of metastatic NPC tissues than in those of nontumor tissues Exosomes derived from NPC cells promoted endothelial cell pyroptosis, vascular permeability, and tumor cell extravasation. Moreover, we found that BART2-5p is abundant in serum exosomes from NPC patients with metastasis and NPC cells, and that it regulates endothelial cell pyroptosis in pre-metastatic organs via MRE11A. Exosomes containing a BART2-5p inhibitor and AAV-MRE11A attenuated endothelial cell pyroptosis and tumor metastasis. Moreover, in the endothelial cells of metastatic tissues from NPC patients, the BART2-5p level was positively associated with pyroptosis-related protein expression. Collectively, our findings suggest that exosomal BART2-5p is involved in pre-metastatic niche formation, identifying secreted BART2-5p as a potential therapeutic target for NPC metastasis. Implications: The finding that secreted BART2-5p is involved in pre-metastatic niche formation may aid the development of potential therapeutic target for NPC metastasis.

A Pleiotropic Nanomedicine Mitigates Splenic Hyperplasia, Ineffective Erythropoiesis, G6PDH Anomaly through Redox Buffering in Preclinical Mice Model.

Here, we present a pleiotropic nanomedicine-a smart, functionalized redox buffering nanoparticle-that may be used to treat hematological diseases, associated splenic hyperplasia, and issues related to restricted erythropoiesis. With a diameter of 5-7 nm, the spherical nanomaterial is made of manganese oxide and citrate. Here, we have produced the novel nanomaterial and, using cutting-edge electron microscopic and spectroscopic techniques, extensively assessed its redox buffering potential in vitrowith its structural integrity. Using an appropriate animal model (phenyl hydrazine, PHz, intoxicated C57BL/6J mice), we assessed the therapeutic efficacy of the redox buffering nanomedicine in the treatment of anemia and related consequences. We have further investigated the intricate molecular mechanism of the nanomedicine and its therapeutic impact, which includes increased erythropoiesis and G6PDH production, decreased inflammatory responses, mitigation of splenic hyperplasia, and synergistic intracellular redox-buffering. To the best of our knowledge, our studies would find relevance in the innovative management of anemia, decreased erythropoiesis, and splenic hyperplasia.

Computational Identification of Milk Trait Regulation Through Transcription Factor Cooperation in Murciano-Granadina Goats

The Murciano-Granadina goat (MUG) is a renowned dairy breed, known for its adaptability and resilience, as well as for its exceptional milk traits characterized by high protein and fat content, along with low somatic cell counts. These traits are governed by complex biological processes, crucial in shaping phenotypic diversity. Thus, it is imperative to explore the factors regulating milk production and lactation for this breed. In this study, we investigated the genetic architecture of seven milk traits in MUGs, employing a two-step computational analysis to examine genotype–phenotype associations. Initially, a random forest algorithm identified the relative importance of each single-nucleotide polymorphism (SNP) in determining the traits of interest. The second step applied an information theory-based approach to exploring the complex genetic architecture of quantitative milk traits, focusing on epistatic interactions that may have been overlooked in the first step. These approaches allowed us to identify an almost distinct set of candidate genes for each trait. In contrast, by analyzing the promoter regions of these genes, we revealed common regulatory networks among the milk traits under study. These findings are crucial for understanding the molecular mechanisms underlying gene regulation, and they highlight the pivotal role of transcription factors (TFs) and their preferential interactions in the development of these traits. Notably, TFs such as DBP, HAND1E47, HOXA4, PPARA, and THAP1 were consistently identified for all traits, highlighting their important roles in immunity within the mammary gland and milk production during lactation.

Pathogenic proteotoxicity of cryptic splicing is alleviated by ubiquitination and ER-phagy.

RNA splicing enables the functional adaptation of cells to changing contexts. Impaired splicing has been associated with diseases, including retinitis pigmentosa, but the underlying molecular mechanisms and cellular responses remain poorly understood. In this work, we report that deficiency of ubiquitin-specific protease 39 (USP39) in human cell lines, zebrafish larvae, and mice led to impaired spliceosome assembly and a cytotoxic splicing profile characterized by the use of cryptic 5' splice sites. Disruptive cryptic variants evaded messenger RNA (mRNA) surveillance pathways and were translated into misfolded proteins, which caused proteotoxic aggregates, endoplasmic reticulum (ER) stress, and, ultimately, cell death. The detrimental consequence of splicing-induced proteotoxicity could be mitigated by up-regulating the ubiquitin-proteasome system and selective autophagy. Our findings provide insight into the molecular pathogenesis of spliceosome-associated diseases.

Microglia contribute to the production of the amyloidogenic ABri peptide in familial British dementia.

Mutations in ITM2B cause familial British, Danish, Chinese, and Korean dementias. In familial British dementia (FBD), a mutation in the stop codon of the ITM2B gene (also known as BRI2) causes a C-terminal cleavage fragment of the ITM2B/BRI2 protein to be extended by 11 amino acids. This fragment, termed amyloid-Bri (ABri), is highly insoluble and forms extracellular plaques in the brain. ABri plaques are accompanied by tau pathology, neuronal cell death and progressive dementia, with striking parallels to the aetiology and pathogenesis of Alzheimer's disease. The molecular mechanisms underpinning FBD are ill-defined. Using patient-derived induced pluripotent stem cells, we show that expression of ITM2B/BRI2 is 34-fold higher in microglia than neurons and 15-fold higher in microglia compared with astrocytes. This cell-specific enrichment is supported by expression data from both mouse and human brain tissue. ITM2B/BRI2 protein levels are higher in iPSC-microglia compared with neurons and astrocytes. The ABri peptide was detected in patient iPSC-derived microglial lysates and conditioned media but was undetectable in patient-derived neurons and control microglia. The pathological examination of post-mortem tissue supports the presence of ABri in microglia that are in proximity to pre-amyloid deposits. Finally, gene co-expression analysis supports a role for ITM2B/BRI2 in disease-associated microglial responses. These data demonstrate that microglia are major contributors to the production of amyloid forming peptides in FBD, potentially acting as instigators of neurodegeneration. Additionally, these data also suggest ITM2B/BRI2 may be part of a microglial response to disease, motivating further investigations of its role in microglial activation. These data have implications for our understanding of the role of microgliaand the innate immune response in the pathogenesis of FBD and other neurodegenerative dementias including Alzheimer's disease.

LincROR promotes tumor growth of colorectal cancer through the miR-145/WNT2B/WNT10A/Wnt/β-catenin regulatory axis.

Colorectal cancer (CRC) is a prevalent form of malignant tumor, and the current clinical treatments are far from satisfactory. Identifying new therapeutic targets is therefore essential for clinical practices. The long intergenic non-protein coding RNA lincROR has been shown to play a significant role in the tumorigenesis of various cancers. However, the molecular mechanism underlying lincROR-mediated CRC tumorigenesis remains unclear. In the present study, we found that knockdown of lincROR significantly inhibited cell viability in vitro, while its overexpression promoted tumor growth in vivo. Mechanistically, lincROR acted as a miRNA sponge for miR-145, thereby elevating the expression of the target genes WNT2B and WNT10A. The overexpression of WNT2B and WNT10A definitely activated the Wnt/β-catenin pathway, thus led to promoting tumorigenesis in CRC. In summary, our findings identified lincROR as a novel activator of the Wnt/β-catenin pathway by serving as a miRNA sponge for miR-145 and facilitating tumorigenesis, which suggests that lincROR may be a potential therapeutic target for CRC patients.

High-quality genome assembly and annotation of the crested gecko (Correlophus ciliatus).

Correlophus ciliatus, or the crested gecko, is widely kept as a pet in many countries around the world due to its ease to care and bred and its high survival rate. However, there is limited number of genomic studies on the crested gecko. In this study, we generated a high-quality chromosome-level genome assembly of the crested gecko by combining Nanopore, Illumina, and Hi-C data. The genome assemble has a size of 1.66 Gb, with scaffold N50 of 109.97 Mb, and 99.52% of the scaffold anchored on 19 chromosomes. The BUSCO analysis indicated a gene completeness of 90.3% (n=7,480), including 6,673 (89.2%) single-copy genes and 84 (1.1%) duplicated genes. Additionally, we identified 21,065 protein-coding genes using the MAKER3 annotation toolkit, with 41.98% (697.51 Mb) consisting of repetitive elements. Among these, 21,037 genes were validated through InterProScan5. Our study is the first to report a chromosome-level genome for the crested gecko. It provides valuable genomic resources for understanding molecular mechanisms under many interesting traits of the species.

Contribution of glucose and glutamine to hypoxia-induced lipid synthesis decreases, while contribution of acetate increases, during 3T3-L1 differentiation.

The molecular mechanisms linking obstructive sleep apnea syndrome (OSA) to obesity and the development of metabolic diseases are still poorly understood. The role of hypoxia (a characteristic feature of OSA) in excessive fat accumulation has been proposed. The present study investigated the possible effects of hypoxia (4% oxygen) on de novo lipogenesis by tracking the major carbon sources in differentiating 3T3-L1 adipocytes. Gas-permeable cultuware was employed to cultivate 3T3-L1 adipocytes in hypoxia (4%) for 7 or 14 days of differentiation. We investigated the contribution of glutamine, glucose or acetate using 13C or 14C labelled carbons to the newly synthesized lipid pool, changes in intracellular lipid content after inhibiting citrate- or acetate-dependent pathways and gene expression of involved key enzymes. The results demonstrate that, in differentiating adipocytes, hypoxia decreased the synthesis of lipids from glucose (44.1 ± 8.8 to 27.5 ± 3.0 pmol/mg of protein, p < 0.01) and partially decreased the contribution of glutamine metabolized through the reverse tricarboxylic acid cycle (4.6% ± 0.2-4.2% ± 0.1%, p < 0.01). Conversely, the contribution of acetate, a citrate- and mitochondria-independent source of carbons, increased upon hypoxia (356.5 ± 71.4 to 649.8 ± 117.5 pmol/mg of protein, p < 0.01). Further, inhibiting the citrate- or acetate-dependent pathways decreased the intracellular lipid content by 58% and 73%, respectively (p < 0.01) showing the importance of de novo lipogenesis in hypoxia-exposed adipocytes. Altogether, hypoxia modified the utilization of carbon sources, leading to alterations in de novo lipogenesis in differentiating adipocytes and increased intracellular lipid content.

Comparative analyses of RNA-seq and phytohormone data of sweetpotatoes inoculated with Dickeya dadantii causing bacterial stem and root rot of sweetpotato.

Bacterial stem and root rot (BSRR) in sweetpotato caused by Dickeya dadantii is one of the ten major diseases of sweetpotatoes in China. However, the molecular mechanism underlying the resistance of sweetpotato to D. dadantii remains unclear. This study adopted a resistance identification assay that conformed Guangshu87 (GS87) as BSRR-resistant and Xinxiang (XX) as susceptible. Compared to XX, GS87 effectively prevented the invasion and dissemination of D. dadantii in planta. An RNA sequencing (RNA-seq) analysis identified 54,844 expressed unigenes between GS87 and XX at four different stages. Further, it revealed that GS87 was more able to regulate the expressions of more unigenes after the inoculation with D. dadantii, including resistance (R) and transcription factors (TF) genes. Moreover, content measurements of disease resistance-related phytohormones showed that both jasmonic acids (JAs) and salicylic acids (SAs) accumulated in D. dadantii-inoculated sweetpotatoes, and JAs may negatively regulate sweetpotato resistance against D. dadantii and accumulated faster than SAs. Meanwhile, determinations of ROS production rate and relevant enzymatic/non-enzymatic activity highlighted the vital roles of reactive oxygen species (ROS) and superoxide dismutase (SOD) in confering GS87 resistance against D. dadantii. Additionally, several hub genes with high connectivity were highlighted through Protein-Protein interaction (PPI) network analysis. In summary, the findings in this study contribute to the understanding of the different responses of resistant and susceptible sweetpotato cultivars to D. dadantii infection, and it also provide the first insight into the relevant candidate genes and phytohormones involved in the resistance of sweetpotato to D. dadantii.