LncRNA SNHG1 alleviates myocardial ischaemia-reperfusion injury by regulating the miR-137-3p/KLF4/TRPV1 axis

AIMS

Myocardial ischaemia-reperfusion injury (MIRI) contributes to serious myocardial injury and even death. Long non-coding RNAs (lncRNAs) have been reported to play pivotal roles in the occurrence and development of MIRI. Here, the detailed molecular mechanism of lncRNA SNHG1 in MIRI was explored.

METHODS AND RESULTS

A cell model of MIRI was established through hypoxia/reoxygenation (H/R) stimulation. Cell viability and pyroptosis were evaluated utilizing MTT, PI staining, and flow cytometry. Interleukin (IL)-1β and IL-18 secretion levels were examined by ELISA. The gene and protein expression were detected by RT-qPCR and western blot, respectively. Dual luciferase reporter gene, RIP and ChIP assays were performed to analyse the molecular interactions. The results showed that lncRNA SNHG1 overexpression alleviated H/R-induced HL-1 cell pyroptosis (all P < 0.05). LncRNA SNHG1 promoted KLF4 expression by sponging miR-137-3p. miR-137-3p silencing alleviated H/R-induced pyroptosis in HL-1 cells (all P < 0.05), which was abolished by KLF4 knockdown (all P < 0.05). KLF4 activated the AKT pathway by transcriptionally activating TRPV1 in HL-1 cells (all P < 0.05). TRPV1 knockdown reversed the alleviation of SNHG1 upregulation on H/R-induced pyroptosis in HL-1 cells (all P < 0.05).

CONCLUSIONS

These results showed that lncRNA SNHG1 assuaged cardiomyocyte pyroptosis during MIRI progression by regulating the KLF4/TRPV1/AKT axis through sponging miR-137-3p. Our findings may provide novel therapeutic targets for MIRI.

miR-29a-KLF4 signaling inhibits breast tumor initiation by regulating cancer stem cells

Cancer stem cells (CSCs) are known for their potent ability to drive tumor initiation and recurrence, yet the molecular mechanisms regulating CSCs are still unclear. Our study found a positive correlation between increased levels of miR-29a and better survival rates in early-stage breast cancer patients, but a negative correlation in late-stage patients, suggesting a dual function of miR-29a in regulating breast cancer. Furthermore, miR-29a showed significant downregulation in the ALDH+ breast cancer stem cell population compared to non-stem cancer cells. Overexpression of miR-29a in human breast cancer cells reduced the proportion of CSCs, suppressed their ability to form mammospheres, and inhibited the expression of stemness genes SOX2, KLF4, and hTERT in vitro. Conversely, knockdown of miR-29a in breast cancer cells showed opposite effects. Tumor xenograft experiments revealed that miR-29a overexpression significantly inhibited tumorigenesis initiated by MDA-MB-231 cell transplantation in nude mice. We further demonstrated that Krüppel-like factor 4 (KLF4), a key gene that regulates cell stemness, was a direct target of miR-29a in breast cancer cells. miR-29a suppressed the expression of KLF4 at both mRNA and protein levels. Reintroduction of KLF4 into breast cancer cells rescued the miR-29a-induced CSC suppression phenotype. In summary, our study is the first to demonstrate that miR-29a-KLF4 signaling inhibits breast tumor initiation by regulating CSCs, which provides novel therapeutic targets for preventing breast tumor initiation.

Endothelium-specific SIRT7 targeting ameliorates pulmonary hypertension through Krüpple-like factor 4 deacetylation

AIMS

Pulmonary hypertension (PH) is a pulmonary vascular disease characterized by a high mortality rate. Pulmonary arterial endothelium cells (PAECs) serve as a primary sensor of various environmental cues, such as shear stress and hypoxia, but PAEC dysfunction may trigger vascular remodelling during the onset of PH. This study aimed to illustrate the role of Sirtuin 7 (SIRT7) in endothelial dysfunction during PH and explore the potential therapeutic strategy for PH.

METHODS AND RESULTS

SIRT7 levels were measured in human and murine experimental PH samples. Bioinformatic analysis, immunoprecipitation, and deacetylation assay were used to identify the association between SIRT7 and Krüpple-like factor 4 (KLF4), a key transcription factor essential for endothelial cell (EC) homeostasis. Sugen5416 + hypoxia (SuHx)-induced PH mouse models and cell cultures were used for the study of the therapeutic effect of SIRT7 for PH. SIRT7 level was significantly reduced in lung tissues and PAECs from PH patients and the SuHx-induced PH mouse model as compared with healthy controls. Pulmonary endothelium-specific depletion of Sirt7 increased right ventricular systolic pressure and exacerbated right ventricular hypertrophy in the SuHx-induced PH model. At the molecular level, we identified KLF4 as a downstream target of SIRT7, which deacetylated KLF4 at K228 and inhibited the ubiquitination-proteasome degradation. Thus, the SIRT7/KLF4 axis maintained PAEC homeostasis by regulating proliferation, migration, and tube formation. PAEC dysfunction was reversed by adeno-associated virus type 1 vector-mediated endothelial overexpression of Sirt7 or supplementation with nicotinamide adenine dinucleotide (NAD)+ intermediate nicotinamide riboside which activated Sirt7; both approaches successfully reversed PH phenotypes.

CONCLUSION

The SIRT7/KLF4 axis ensures PAEC homeostasis, and pulmonary endothelium-specific SIRT7 targeting might constitute a PH therapeutic strategy.

Myocardial Expression of Pluripotency, Longevity, and Proinflammatory Genes in the Context of Hypercholesterolemia and Statin Treatment

Background: This study sought to assess the effect of statin therapy on myocardial inflammation in a White New Zealand rabbit model of atherogenesis. Methods: The mRNA expression levels of pro-inflammatory, pluripotency, and aging-related markers were quantified following a controlled feeding protocol and statin treatments. Results: Following high-cholesterol diet induction, we observed significant upregulation in the myocardial mRNA levels of MYD88, NF-κB, chemokines (CCL4, CCL20, and CCR2), IFN-γ, interleukins (IL-1β, IL-2, IL-4, IL-8, IL-10, and IL-18), and novel markers (klotho, KFL4, NANOG, and HIF1α). In contrast, HOXA5 expression was diminished following a hyperlipidemic diet. Both statin treatments significantly influenced the markers studied. Nevertheless, rosuvastatin administration resulted in a greater reduction in MYD88, NF-kB, chemokines (CCL4, CCL20, and CCR2), and interleukins IL-1β, IL-8, KLF4, NANOG, and HIF1α than fluvastatin. Fluvastatin, on the other hand, led to a stronger decrease in IL-4. Downregulation of IL-2 and IL-18 and upregulation of IFNβ and HOXA5 were comparable between the two statins. Notably, rosuvastatin had a stronger effect on the upregulation of klotho and IL-10. Conclusion: Overall, statin therapy significantly attenuated inflammatory, pluripotency, and klotho expression in myocardial tissue under atherogenic conditions. Our findings also highlight the differential efficacy of rosuvastatin over fluvastatin in curtailing proatherogenic inflammation, which could have profound implications for the clinical management of cardiovascular disease.

MiRNA-296-5p promotes the sensitivity of nasopharyngeal carcinoma cells to cisplatin via targeted inhibition of STAT3/KLF4 signaling axis

Improving drug sensitivity is an important strategy in chemotherapy of cancer and accumulating evidence indicates that miRNAs are involved in the regulation of drug sensitivity, but the specific mechanism is still unclear. Our previous study has found that miR-296-5p was significantly downregulated in nasopharyngeal carcinoma (NPC). Here, we aim to explore whether miR-296-5p is involved in regulating cisplatin sensitivity in NPC by regulating STAT3/KLF4 signaling axis. The cell proliferation and clonogenic capacity of NPC cells were evaluated by CCK8 Assay and plate colony assay, respectively. The Annexin V-FITC staining kit was used to determine and quantify the apoptotic cells using flow cytometry. The drug efflux ability of NPC cells were determined by Rhodamine 123 efflux experiment. The expression of miR-296-5p, apoptosis-related genes and protein in NPC cell lines were detected by qPCR and Western blot, respectively. Animal study was used to evaluate the sensitivity of NPC cells to DDP treatment in vivo. Our results showed that elevated miR-296-5p expression obviously promoted the sensitivity of NPC cells to DDP by inhibiting cell proliferation and clonogenic capacity, and inducing apoptosis. In addition, we found that miR-296-5p inhibited the expression of STAT3 and KLF4 in NPC cells, while overexpression of exogenous STAT3 reversed miR-296-5p-mediated enhancement in cell death of DDP-treated NPC cells. In vivo studies further confirmed that miR-296-5p promotes the sensitivity of NPC cells to DDP treatment. miRNA-296-5p enhances the drug sensitivity of nasopharyngeal carcinoma cells to cisplatin via STAT3/KLF4 signaling pathway.

Meningioma: current updates on genetics, classification, and mouse modeling

Meningiomas, the most common primary brain tumors in adults, are often benign and curable by surgical resection. However, a subset is of higher grade, shows aggressive growth behavior as well as brain invasion, and often recurs even after several rounds of surgery. Increasing evidence suggests that tumor classification and grading primarily based on histopathology do not always accurately predict tumor aggressiveness and recurrence behavior. The underlying biology of aggressive treatment-resistant meningiomas and the impact of specific genetic aberrations present in these high-grade tumors is still only insufficiently understood. Therefore, an in-depth research into the biology of this tumor type is warranted. More recent studies based on large-scale molecular data such as whole exome/genome sequencing, DNA methylation sequencing, and RNA sequencing have provided new insights into the biology of meningiomas and have revealed new risk factors and prognostic subtypes. The most common genetic aberration in meningiomas is functional loss of NF2 and occurs in both low- and high-grade meningiomas, whereas NF2-wildtype meningiomas are enriched for recurrent mutations in TRAF7, KLF4, AKT1, PI3KCA, and SMO and are more frequently benign. Most meningioma mouse models are based on patient-derived xenografts and only recently have new genetically engineered mouse models of meningioma been developed that will aid in the systematic evaluation of specific mutations found in meningioma and their impact on tumor behavior. In this article, we review recent advances in the understanding of meningioma biology and classification and highlight the most common genetic mutations, as well as discuss new genetically engineered mouse models of meningioma.

Hypoxia endothelial cells-derived exosomes facilitate diabetic wound healing through improving endothelial cell function and promoting M2 macrophages polarization

It is imperative to develop and implement newer, more effective strategies to address refractory diabetic wounds. As of now, there is currently no optimal solution for these wounds. Hypoxic human umbilical vein endothelial cells (HUVECs)-derived exosomes have been postulated to promote diabetic wound healing, however, its effect and molecular mechanism need further study. In this study, we aimed to investigate whether hypoxic exosomes enhance wound healing in diabetics. Based on our high-throughput sequencing, differentially expressed lncRNAs (including 64 upregulated lncRNAs and 94 downregulated lncRNAs) were found in hypoxic exosomes compared to normoxic exosomes. Interestingly, lncHAR1B was one of the prominently upregulated lncRNAs in hypoxic exosomes, showing a notable correlation with diabetic wound healing. More specifically, hypoxic exosomes were transmitted to surrounding cells, which resulted in a significant increase in lncHAR1B level, thereby relieving the dysfunction of endothelial cells and promoting the switch from M1 to M2 macrophages under high glucose conditions. Mechanistically, lncHAR1B directly interacted with the transcription factor basic helix-loop-helix family member e23 (BHLHE23), which subsequently led to its binding to the KLF transcription factor 4 (KLF4) and promoted KLF4 expression. In our in vivo experiments, the use of hypoxic exosomes-loaded HGM-QCS hydrogels (Gel-H-Exos) resulted in rapid wound healing compared to that of normoxic exosomes-loaded HGM-QCS hydrogels (Gel-N-Exos) and diabetic groups. Consequently, our study provides potentially novel therapeutic approaches aimed at accelerating wound healing and developing a practical exosomes delivery platform.

GOLM1 Promotes Pulmonary Fibrosis through Upregulation of NEAT1

Idiopathic pulmonary fibrosis (IPF) is a lethal progressive disease with elusive molecular mechanisms and limited therapeutic options. Aberrant activation of fibroblasts is a central hallmark of lung fibrosis. Here, we report that Golgi membrane protein 1 (GOLM1, also known as GP73 or GOLPH2) was increased in the lungs of patients with pulmonary fibrosis and mice with bleomycin (BLM)-induced pulmonary fibrosis. Loss of GOLM1 inhibited proliferation, differentiation, and extracellular matrix deposition of fibroblasts, whereas overexpression of GOLM1 exerted the opposite effects. Similarly, worsening pulmonary fibrosis after BLM treatment was observed in GOLM1-knock-in mice, whereas BLM-treated Golm1-knockout mice exhibited alleviated pulmonary fibrosis and collagen deposition. Furthermore, we identified long noncoding RNA NEAT1 downstream of GOLM1 as a potential mediator of pulmonary fibrosis through increased GOLM1 expression. Depletion of NEAT1 inhibited fibroblast proliferation and extracellular matrix production and reversed the profibrotic effects of GOLM1 overexpression. Additionally, we identified KLF4 as a downstream mediator of GOLM1 signaling to NEAT1. Our findings suggest that GOLM1 plays a pivotal role in promoting pulmonary fibrosis through the GOLM1-KLF4-NEAT1 signaling axis. Targeting GOLM1 and its downstream pathways may represent a novel therapeutic strategy for treating pulmonary fibrosis.

Krupple-like factor 4 (KLF4) methylation signature in host cell in active viral keratitis with epithelial manifestation

HSV1 presents as epithelial or stromal keratitis or keratouveitis and can lead to sight-threatening complications. KLF4, a critical transcription factor, and regulator of cell growth and differentiation, is essential in corneal epithelium stratification and homeostasis. Here, we want to understand the epigenetic modification specifically the methylation status of KLF4 in epithelium samples of HSV1 keratitis patients. After obtaining consent, epithelial scrapes were collected from 7 patients with clinically diagnosed HSV1 keratitis and 7 control samples (patients undergoing photorefractive keratectomy). Genomic DNA was isolated from the collected samples using the Qiagen DNeasy Kit. Subsequently, bisulfite modification was performed. The bisulphite-modified DNA was then subjected to PCR amplification using specific primers designed to target the KLF4, ACTB gene region, allowing for the amplification of methylated and unmethylated DNA sequences. The amplified DNA products were separated and visualized on a 3% agarose gel. KLF4 hypermethylation was found in 6 out of 7 (85.71%) eyes with viral keratitis, while 1 eye showed hypomethylation compared to PRK samples. Out of these 6, there were 2 each of epithelial dendritic keratitis, epithelial geographical keratitis, and neurotrophic keratitis. The patient with hypomethylated KLF4 had a recurrent case of HSV1 keratitis with multiple dendrites and associated vesicular lesions of the lip along with a history of fever. KLF4 hypermethylation in most viral keratitis cases indicated the under functioning of KLF4 and could indicate a potential association between KLF4 hypermethylation and the development or progression of HSV1 keratitis.

KLF4 and CD55 expression and function depend on each other

The transcription factor Kruppel-like factor 4 (KLF4) regulates the expression of immunosuppressive and anti-thrombotic proteins. Despite its importance in maintaining homeostasis, the signals that control its expression and the mechanism of its transactivation remain unclarified. CD55 [aka decay accelerating factor (DAF)], now known to be a regulator of T and B cell responses, biases between pro- and anti-inflammatory processes by controlling autocrine C3a and C5a receptor (C3ar1/C5ar1) signaling in cells. The similarity in CD55's and KLF4's regulatory effects prompted analyses of their functional relationship. In vascular endothelial cells (ECs), CD55 upregulation accompanied KLF4 expression via a p-CREB and CREB Binding Protein (CBP) mechanism. In both ECs and macrophages, CD55 expression was essential for KLF4's downregulation of pro-inflammatory/pro-coagulant proteins and upregulation of homeostatic proteins. Mechanistic studies showed that upregulation of KLF4 upregulated CD55. The upregulated CD55 in turn enabled the recruitment of p-CREB and CBP to KLF4 needed for its transcription. Activation of adenylyl cyclase resulting from repression of autocrine C3ar1/C5ar1 signaling by upregulated CD55 concurrently led to p-CREB and CBP recruitment to KLF4-regulated genes, thereby conferring KLF4's transactivation. Accordingly, silencing CD55 in statin-treated HUVEC disabled CBP transfer from the E-selectin to the eNOS promoter. Importantly, silencing CD55 downregulated KLF4's expression. It did the same in untreated HUVEC transitioning from KLF4low growth to KLF4hi contact inhibition. KLF4's and CD55's function in ECs and macrophages thus are linked via a novel mechanism of gene transactivation. Because the two proteins are co-expressed in many cell types, CD55's activity may be broadly tied to KLF4's immunosuppressive and antithrombotic activities.

4-amino-2-trifluoromethyl-phenyl retinate alleviates lipopolysaccharide-induced acute myocardial injury through activation of the KLF4/p62 axis

Ferroptosis plays a pivotal role in the pathological process of sepsis-induced cardiomyopathy (SIC). All-trans retinoic acid (ATRA) enhances the host immune response to lipopolysaccharides (LPS). This study investigated the role of 4-amino-2-trifluoromethyl-phenyl retinate (ATPR), a derivative of ATRA, in myocardial injury caused by sepsis. Male C57BL/6 mice were intraperitoneally injected with LPS to establish a sepsis model. H9c2 cells were stimulated by LPS to establish an injury model. We observed that ATPR improved myocardial injury in mice, which was presented in terms of an increased glutathione (GSH) level and reduced production of malondialdehyde (MDA), as well as an increased number of mitochondrial cristae and maintenance of the mitochondrial membrane integrity. ATPR improved cardiac function in the LPS-injured mice. It inhibited the inflammatory response as evidenced by the decreasing mRNA levels of TNF-α and IL-6. The elevated protein expression levels of Nrf2, SLC7A11, GPX4, and FTH1 in mice and H9c2 cells showed that ATPR inhibited ferroptosis. Immunoprecipitation of LPS-stimulated H9c2 cells demonstrated that ATPR increased the interaction between p62 and Keap1. ATPR upregulated the KLF4 and p62 protein expression. However, the inhibition of Nrf2 by ML385 reduced the protective effect of ATPR in LPS-treated H9c2 cells. Furthermore, we used siRNA to knock down KLF4 in H9c2 cells and found that the KLF4 knockdown eliminated the inhibition of ferroptosis by ATPR in H9c2 cells. Therefore, ATPR alleviates LPS-induced myocardial injury by inhibiting ferroptosis via the KLF4/p62 axis.

KLF4 interacts with TXNIP to modulate the pyroptosis in ulcerative colitis via regulating NLRP3 signaling

INTRODUCTION

Ulcerative colitis (UC) is one of the most common diseases in the gastrointestinal tract related to abnormal inflammation. Pyroptosis, which is characterized by the formation of inflammasome, activation of caspase-1, and separation of N- and C-terminus of gasdermin D (GSDMD), and may be involved in the pathogenesis of IBD. Krüppel-like factor 4 (KLF4) is a zinc finger transcription factor expressed in differentiated epithelial cells. KLF4 mediates proinflammatory signaling in macrophages. Here, we tested whether KLF4 is functional in pyroptosis of UC.

METHODS

In human UC tissues and/or lipopolysaccharide (LPS)/adenosine 5-triphosphate (ATP) stimulation human colon epithelial cells, KLF4, TXNIP, Cleave-Caspase-1, and GSDMD expression were detected through quantitative reverse transcription polymerase chain reaction (PCR), immunohistochemical and western blot assay. Interleukin (IL)-1β and IL-18 levels were quantified by enzyme-linked immunosorbent assay. We successfully constructed a KLF4-silenced colon epithelial cell line using an adenovirus vector. We apply the UCSC and JASPAR to predict the KLF4 binding sites in the promoter region of TXNIP.

RESULTS

In human UC tissues and/or LPS/ATP stimulation human colon epithelial cells, KLF4, TXNIP, Caspase-1, and GSDMD expression level were significantly elevated via quantitative reverse transcription PCR, immunohistochemical and western blot assay. Moreover, We identified that there is an interaction between KLF4 and TXNIP through Yeast double hybrid assay and CO-IP assay. We successfully constructed a KLF4-silenced human intestinal epithelial cell line. In LPS/ATP stimulation KLF4-silenced human intestinal epithelial cells, KLF4, TXNIP, Cleave Caspase-1, ASC, and GSDMD expression level were significantly decreased via quantitative reverse transcription PCR.

CONCLUSION

Our results confirm that KLF4 can positively regulate the expression of TXNIP and regulate the pyroptosis process of UC through the TXNIP/NLRP3 pathway.

The mechanisms of tumor necrosis factor α in regulating Krüpple-like factor 4 expression in SK-BR-3 breast cancer cells

OBJECTIVE

To explore the expression and functional role of Krüpple-like factor 4 (KLF4) protein stimulated by tumor necrosis factor α (TNF-α) in SK-BR-3 breast cancer cells.

METHODS

SK-BR-3 cells were stimulated with various concentrations of TNF-α at 0, 1, 5, 10, and 20 ng/mL. Expression levels of KLF4 protein were detected by Western blotting. In the detection of apoptosis, flow cytometry, and DAPI staining were used for detecting the level of apoptosis.

RESULTS

KLF4 expression was markedly elevated following stimulation of SK-BR-3 with TNF-α. At the same time, the expression of KLF4 protein increased gradually with the increase of TNF-α stimulation concentration. TNF-α stimulation of SK-BR-3 cells increased apoptosis as measured by apoptosis levels. By overexpressing KLF4 protein in SK-BR-3 cells, it similarly increased apoptosis and promoted cell death of SK-BR-3 cells.

CONCLUSION

TNF-α promotes KLF4 expression, while TNF-α promotes apoptosis in SK-BR-3 cells, a process that may be due to elevated KLF4 protein expression.

Role of lipid metabolism gene KLF4 in osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a common degenerative disease of joints, which can appear in almost any joint of the body. Therefore, the widespread occurrence of this disease has a huge impact on the lives of patients around the world. As an important part of metabolism, lipid metabolism is closely related to the occurrence and development of osteoarthritis.

METHOD

We screened UGCG and KLF4 based on weighted co-expression network analysis (WGCNA) and SVM-REF analysis. The data from Gene Expression Omnibus (GEO) and single-cell data verified the expression of these two genes. We analyzed KLF4-related genes and established a diagnosis model of OA related to lipid metabolism through the least absolute shrinkage and selection operator (LASSO) analysis. RT-PCR was used to verify the expression of KLF4 in osteoarthritis.

RESULTS

Ten important lipid metabolism related genes (LMRGs) in OA were obtained. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that they are involve in the formation of immune microenvironment in osteoarthritis. CIBERSORT analysis revealed that there were significant differences in the immune microenvironment between osteoarthritis patients and normal controls. RT-PCR results showed that the expression of KLF4 in OA samples was lower than that in normal samples. The diagnostic model can be used to diagnose OA patients well.

CONCLUSIONS

Overall, we demonstrated the potential relationship between the abnormal lipid metabolism and the pathological process of OA. Finally, we identified KLF4 as our significant LMRG and constructed a KLF4-related scoring model to accurately diagnose OA. In conclusion, therapy strategies targeting on regulating lipid metabolism may become a key factor in treating OA. Key Points (a) We identified the significant LMRG KLF4 and constructed a novel KLF4-related scoring model for the accuracy diagnosis of OA. (b) The potential relationship between lipid metabolism and the immune microenvironment in OA was demonstrated in our research. (c) The relationship of lipid metabolism and OA has been further improved in our research and provided novel insight for the diagnosis and therapy for OA patients.

KLF4 facilitates chromatin accessibility remodeling in porcine early embryos

Chromatin accessibility remodeling driven by pioneer factors is critical for the development of early embryos. Current studies have illustrated several pioneer factors as being important for agricultural animals, but what are the pioneer factors and how the pioneer factors remodel the chromatin accessibility in porcine early embryos is not clear. By employing low-input DNase-seq (liDNase-seq), we profiled the landscapes of chromatin accessibility in porcine early embryos and uncovered a unique chromatin accessibility reprogramming pattern during porcine preimplantation development. Our data revealed that KLF4 played critical roles in remodeling chromatin accessibility in porcine early embryos. Knocking down of KLF4 led to the reduction of chromatin accessibility in early embryos, whereas KLF4 overexpression promoted the chromatin openness in porcine blastocysts. Furthermore, KLF4 deficiency resulted in mitochondrial dysfunction and developmental failure of porcine embryos. In addition, we found that overexpression of KLF4 in blastocysts promoted lipid droplet accumulation, whereas knockdown of KLF4 disrupted this process. Taken together, our study revealed the chromatin accessibility dynamics and identified KLF4 as a key regulator in chromatin accessibility and cellular metabolism during porcine preimplantation embryo development.

KLF4 targets RAB26 and decreases 5-FU resistance through inhibiting autophagy in colon cancer

BACKGROUND

Accumulating studies demonstrated that resistance of colon cancer (CC) to 5-fluorouracil (5-FU) contributes to adverse prognosis. We investigated how Kruppel-like factor 4 (KLF4) affected 5-FU resistance and autophagy in CC cells.

METHODS

KLF4 expression and its downstream target gene RAB26 in CC tissues was analyzed by bioinformatics analysis, and the effect of abnormal KLF4 expression on prognoses of CC patients was predicted. Luciferase reporter assay detected the targeted relationship between KLF4 and RAB26. The viability and apoptosis of CC cells were analyzed by CCK-8 and flow cytometry. The formation of intracellular autophagosomes was detected by confocal laser scanning microscopy and immunofluorescence staining. The mRNA and protein levels were assayed by qRT-PCR and western blot. A xenograft animal model was constructed to verify the function of KLF4. Rescue assay was employed to verify whether KLF4/RAB26 could affect 5-FU resistance in CC cells through autophagy.

RESULTS

KLF4 and RAB26 were lowly expressed in CC. KLF4 correlated with patients' survival. KLF4 was down-regulated in 5-FU resistant CC cells. KLF4 overexpression suppressed the proliferation and 5-FU resistance of CC cells, and inhibited LC3 II/I expression and autophagosome formation. Autophagy activator Rapamycin or sh-RAB26 treatment reversed the impact of KLF4 overexpression on 5-FU resistance. In vivo assay verified that KLF4 inhibited 5-FU resistance in CC cells. Rescue experiments revealed that KLF4 targeted RAB26 to inhibit CC cell autophagy, resulting in decreasing the resistance to 5-FU.

CONCLUSION

KLF4 strengthened the sensitivity of CC cells to 5-FU by targeting RAB26 to restrain autophagy pathway.

Ovarian Tumor Domain-Containing 7B Attenuates Pathological Cardiac Hypertrophy by Inhibiting Ubiquitination and Degradation of Krüppel-Like Factor 4

BACKGROUND

Cardiac hypertrophy (CH) is a well-established risk factor for many cardiovascular diseases and a primary cause of mortality and morbidity among older adults. Currently, no pharmacological interventions have been specifically tailored to treat CH. OTUD7B (ovarian tumor domain-containing 7B) is a member of the ovarian tumor-related protease (OTU) family that regulates many important cell signaling pathways. However, the role of OTUD7B in the development of CH is unclear. Therefore, we investigated the role of OTUD7B in CH.

METHODS AND RESULTS

OTUD7B knockout mice were used to assay the role of OTUD7B in CH after transverse aortic coarctation surgery. We further assayed the specific functions of OTUD7B in isolated neonatal rat cardiomyocytes. We found that OTUD7B expression decreased in hypertrophic mice hearts and phenylephrine-stimulated neonatal rat cardiomyocytes. Furthermore, OTUD7B deficiency exacerbated transverse aortic coarctation surgery-induced myocardial hypertrophy, abnormal cardiac function, and fibrosis. In cardiac myocytes, OTUD7B knockdown promoted phenylephrine stimulation-induced myocardial hypertrophy, whereas OTUD7B overexpression had the opposite effect. An immunoprecipitation-mass spectrometry analysis showed that OTUD7B directly binds to KLF4 (Krüppel-like factor 4). Additional molecular experiments showed that OTUD7B impedes KLF4 degradation by inhibiting lysine residue at 48 site-linked ubiquitination and suppressing myocardial hypertrophy by activating the serine/threonine kinase pathway.

CONCLUSIONS

These results demonstrate that the OTUD7B-KLF4 axis is a novel molecular target for CH treatment.

Effect of overexpression of KLF4 on the growth and development of hair follicles in mice

Hair follicle growth is cyclical, and hair cycle dysfunction can lead to hair follicle-related disorders, including alopecia and hirsutism. The objective was to investigate the influence and underlying mechanism of Krüppel-like factor 4 (KLF4) overexpression on hair follicle growth and development in C57BL/6 mice. To provide a theoretical basis for the biological functions of KLF4 gene in hair follicle development and hair follicle cycle, mice were assigned to three groups: experimental, overexpressing KLF4 (Ad-KLF4); control, expressing green fluorescent protein (Ad-NC); and blank, no treatment. Fur was removed from the dorsal surface, and the mice were intradermally injected with 25 μL 1 × 1010 PFU/mL adenovirus vector (Ad-KLF4 or Ad-NC) at three points. Samples were collected for molecular biological and histological analysis. It was found that mRNA and protein levels of Wnt pathway-associated factors β-catenin, LEF1, hair follicle cell proliferation-related factor Ki67, and hair follicle inner caledrin marker AE15 were all significantly greater in the Ad-NC and blank groups than in Ad-KLF4 mice (P < 0.01). These findings were confirmed by immunohistochemical analysis. Hair growth was monitored photographically for 14 days, showing an absence of growth in the injected region of the KLF4-overexpressing mice in contrast to non-overexpressing areas where hair growth was normal. HE staining showed that hair follicles in the blank and Ad-NC mice were normal, while those in the KLF4-overexpressing areas remained in telogen or early anagen with spherical dermal papillae situated at the edge of the dermis and subcutaneous tissue without an inner heel sheath. In conclusion, it was found that KLF4 downregulated key Wnt/β-catenin-associated factors during follicular regeneration in mice, reducing both follicular development and growth.

Hypoxia-sensitive cells trigger NK cell activation via the KLF4-ASH1L-ICAM-1 axis, contributing to impairment in the rat epididymis

Male infertility is a global health problem especially prevalent in high-altitude regions. The epididymis is essential for sperm maturation, but the influence of environmental cues on its reshaping remains poorly understood. Here, we use single-cell transcriptomics to track the cellular profiles of epidydimal cells in rats raised under normoxia or extended hypoxia. The results show that hypoxia impairs epididymal function, evident in reduced epithelial cells, compromised blood-epididymis barrier integrity, and increased natural killer cells. Through combined analysis of gene-regulatory networks and cell-cell interaction maps, we identify epididymal hypoxia-sensitive cells that communicate with natural killer (NK) cells via increased intercellular adhesion molecule 1 (ICAM-1) driven by KLF4 recruitment of the histone methyltransferase ASL1L to the Icam1 promoter. Taken together, our study offers a detailed blueprint of epididymal changes during hypoxia and defines a KLF4-ALSH1L-ICAM-1 axis contributing to NK cell activation, yielding a potential treatment targeting hypoxia-induced infertility.

Transfection of Vein Grafts with Early Growth Response Factor-1 Oligodeoxynucleotide Decoy: Effects on Stem-Cell Genes and Toll-like Receptor-Mediated Inflammation

The long-term patency of vein grafts is challenged by intimal hyperplasia. We sought to explore the intricate relationships between the transcription factor Egr-1, toll-like receptors (TLRs), and stem cell genes and also assessed oligodeoxynucleotide decoys (ODNs) as a strategy to prevent vein graft failures. A total of 42 New Zealand white rabbits were fed hyperlipidemic chow and classified into three groups. A double-stranded Egr-1 ODN was synthesized and infused in vein grafts prior to anastomosis with the common carotid artery. All vein grafts were retrieved at the conclusion of the predefined experimental period. Real-time quantitative polymerase chain reaction was performed to estimate expression patterns for several genes of interest. MYD88, TLR2-4, TLR8, NF-kB, TNF-α, IFNβ, and IFNγ; chemokines CCL4, CCL20, CCR2; numerous interleukins; and stem cell genes KFL4, NANOG, HOXA5, and HIF1α were universally downregulated in the ODN arm compared with the controls. By understanding these multifaceted interactions, our study offers actionable insights that may pave the way for innovative interventions in vascular reconstructions.

MiR-497-3p induces Premature ovarian failure by targeting KLF4 to inactivate Klotho/PI3K/AKT/mTOR signaling pathway

BACKGROUND

Premature ovarian failure (POF), as a gynecological endocrine disease, features the manifestation of irregular menstruation, amenorrhea, infertility and perimenopausal syndrome. MicroRNAs (miRNAs) have been reported to modulate POF. However, the specific regulatory mechanism of miR-497-3p in POF remain unclear.

METHODS

Quantitative reverse transcription-PCR (RT-qPCR) and western blot were implemented to analyze RNA and protein levels, respectively. Comet assay was performed for the detection of DNA damage. Flow cytometry analysis and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays were performed to measure apoptosis of CTX-induced KGN cell (POF cell model). Bioinformatics was utilized to screen out the downstream mRNAs potentially regulated by miR-497-3p. Chromatin immunoprecipitation (ChIP) assay, luciferase reporter assay and RNA pulldown assays were performed to demonstrate the interaction between miR-497-3p and Kruppel-like factor 4 (KLF4) or between KLF4 and Klotho (KL). Rescue assays were performed to verify the involvement of Klotho in miR-497-3p-mediated functions of POF cell model.

RESULTS

MiR-497-3p was upregulated in CTX-treated KGN cells. Knockdown of miR-497-3p could reverse the promoting effects of CTX on DNA damage and cell apoptosis. MiR-497-3p negatively regulated Klotho expression by directly targeting the transcription activator KLF4. KLF4 activated Klotho transcription. MiR-497-3p inactivated PI3K/AKT/mTOR signaling pathway through KLF4/Klotho axis. Klotho knockdown reversed the effects of MiR-497-3p on the functions of POF cell model.

CONCLUSION

MiR-497-3p promotes DNA damage and apoptosis in CTX-treated KGN cells by targeting KLF4 to downregulate Klotho and inactivate the PI3K/AKT/mTOR signaling pathway. This study unveils novel mechanisms associated with cell functional changes in POF and may enrich therapeutic strategy for POF.

Protective effects of KLF4 on blood-brain barrier and oxidative stress after cerebral ischemia-reperfusion in rats through the Nrf2/Trx1 pathway

PURPOSE

To investigate the role of KLF4 in CI/R injury and whether Nrf2/Trx1 axis acted as a downstream pathway of KLF4 to exert the protective role in blood-brain barrier destruction after CI/R.

METHODS

The tMCAO rat model in vivo was constructed and received the intracerebroventricular injection of 5 μg/kg and 10 μg/kg rhKLF4 before operation. TTC, brain water content, neurological function, ELISA, behavioral tests, HE, TUNEL, and qRT-PCR were performed to detect the protective role of KLF4 on CIR. Double-fluorescence staining and western blot were performed to determine the localization and spatiotemporal expression in brain tissues. Furthermore, we also analyzed the effect of KLF4 on the blood-brain barrier (BBB) and related mechanisms in vivo and in vitro. Nrf2 inhibitor tretinoin was applied, which was intraperitoneally injected into CIR rat. Evans blue staining was conducted. In vitro OGD/R models of bEnd.3 cells were also established, and received KLF4 overexpressed transfection and 12.5 µM tretinoin incubation. The permeability of bEnd.3 cells was evaluated by TEER and FITC-dextran leakage. BBB-related factors and oxidative stress were also analyzed, respectively. The tubular ability of KLF4 on OGD/R bEnd3 cells was also evaluated.

RESULTS

In vivo study confirmed that KLF4 was expressed in astrocyte, and its content increased with time. KLF4 protected against brain injury caused by cerebral ischemia-reperfusion, reduced cerebral infarction area and oxidative stress levels, and promoted the recovery of behavioral ability in rats. Simultaneously, mechanism experiments confirmed that the repair effect of KLF4 on cerebral ischemia-reperfusion injury was closely related to the Nrf2/Trx1 pathway. KLF4 exerted the neuroprotective effect through upregulating Nrf2/Trx1 pathway. Consistent with in vivo animal study, in vitro study also confirmed the effect of KLF4 on the permeability of bEnd.3 cells after OGD/R injury through Nrf2/Trx1 pathway.

CONCLUSION

Collectively, KLF4 played neuroprotective role in CIR induced MCAO and OGD/R, and the beneficial effects of KLF4 was partly linked to Nrf2/Trx1 pathway.

Experimental study of the mechanism of induction of conjunctival goblet cell hyperexpression using CHIR-99021 in vitro

A component of the tear film, mucin is produced by conjunctival goblet cells and is crucial to preserving the tear film's stability. Severe thermal burns, chemical burns, and severe ocular surface diseases can cause extensive damage to the conjunctiva, destroy the secretory function of goblet cells, and affect the stability of the tear film and integrity of the ocular surface. Currently, the expansion efficiency of goblet cells in vitro is low. In this study, we observed that rabbit conjunctival epithelial cells exhibited dense colony morphology after stimulation with the Wnt/β-catenin signaling pathway activator CHIR-99021 and promoted the differentiation of conjunctival goblet cells and the expression of its specific marker Muc5ac, among which the best induction effect was observed after 72 h in vitro culture with 5 μmol/L CHIR-99021. Under optimal culture conditions, CHIR-99021 increased the expression levels of the Wnt/β-catenin signaling pathway factors Frzb, β-catenin, SAM pointed domain containing ETS transcription factor, and glycogen synthase kinase-3β and the levels of the Notch signaling pathway factors Notch1 and Krüppel-like factor 4 while decreasing the expression levels of Jagged-1 and Hes1. The expression level of ABCG2, a marker of epithelial stem cells, was raised to keep rabbit conjunctival epithelial cells from self-renewing. Our study showed that CHIR-99021 stimulation successfully activated the Wnt/β-catenin signaling pathway and conjunctival goblet cell differentiation was stimulated, in which the Notch signaling pathway played a combined role. Those results provide a novel idea for the expansion of goblet cells in vitro.

Inhibition of miR-25 Ameliorates Cardiac Dysfunction and Fibrosis by Restoring Krüppel-like Factor 4 Expression

Cardiac hypertrophy is an adaptive response to various pathological insults, including hypertension. However, sustained hypertrophy can cause impaired calcium regulation, cardiac dysfunction, and remodeling, accompanied by cardiac fibrosis. Our previous study identified miR-25 as a regulator of SERCA2a, and found that the inhibition of miR-25 improved cardiac function and reduced fibrosis by restoring SERCA2a expression in a murine heart failure model. However, the precise mechanism underlying the reduction in fibrosis following miR-25 inhibition remains unclear. Therefore, we postulate that miR-25 may have additional targets that contribute to regulating cardiac fibrosis. Using in silico analysis, Krüppel-like factor 4 (KLF4) was identified as an additional target of miR-25. Further experiments confirmed that KLF4 was directly targeted by miR-25 and that its expression was reduced by long-term treatment with Angiotensin II, a major hypertrophic inducer. Subsequently, treatment with an miR-25 inhibitor alleviated the cardiac dysfunction, fibrosis, and inflammation induced by Angiotensin II (Ang II). These findings indicate that inhibiting miR-25 not only enhances calcium cycling and cardiac function via SERCA2a restoration but also reduces fibrosis by restoring KLF4 expression. Therefore, targeting miR-25 may be a promising therapeutic strategy for treating hypertensive heart diseases.

HOXA1 participates in VSMC-to-macrophage-like cell transformation via regulation of NF-κB p65 and KLF4: a potential mechanism of atherosclerosis pathogenesis

BACKGROUND

Macrophage-like transformation of vascular smooth muscle cells (VSMCs) is a risk factor of atherosclerosis (AS) progression. Transcription factor homeobox A1 (HOXA1) plays functional roles in differentiation and development. This study aims to explore the role of HOXA1 in VSMC transformation, thereby providing evidence for the potential mechanism of AS pathogenesis.

METHODS

High fat diet (HFD)-fed apolipoprotein E knockout (ApoE^-/-) mice were applied as an in vivo model to imitate AS, while 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POV-PC)-treated VSMCs were applied as an in vitro model. Recombinant adeno-associated-virus-1 (AAV-1) vectors that express short-hairpin RNAs targeting HOXA1, herein referred as AAV1-shHOXA1, were generated for the loss-of-function experiments throughout the study.

RESULTS

In the aortic root of AS mice, lipid deposition was severer and HOXA1 expression was higher than the wide-type mice fed with normal diet or HFD. Silencing of HOXA1 inhibited the AS-induced weight gain, inflammatory response, serum and liver lipid metabolism disorder and atherosclerotic plaque formation. Besides, lesions from AS mice with HOXA1 knockdown showed less trans-differentiation of VSMCs to macrophage-like cells, along with a suppression of krüppel-like factor 4 (KLF4) and nuclear factor (NF)-κB RelA (p65) expression. In vitro experiments consistently confirmed that HOXA1 knockdown suppressed lipid accumulation, VSMC-to-macrophage phenotypic switch and inflammation in POV-PC-treated VSMCs. Mechanism investigations further illustrated that HOXA1 transcriptionally activated RelA and KLF4 to participate in the pathological manifestations of VSMCs.

CONCLUSIONS

HOXA1 participates in AS progression by regulating VSMCs plasticity via regulation of NF-κB p65 and KLF4. HOXA1 has the potential to be a biomarker or therapeutic target for AS.