Search Results (13)

Specificity Proteins/Krüppel-like Factors (SP/KLF family) are a conserved family of transcriptional regulators. These proteins share three highly conserved, contiguous zinc fingers in their carboxy-terminus, requisite for binding to cis elements in DNA. Each SP/KLF protein has unique primary sequence within its amino-terminal and carboxy-terminal regions, and it is these regions which interact with co-activators, co-repressors, and chromatin-modifying proteins to support the transcriptional activation and repression of target genes. Krüppel-like Factor 9 (KLF9) and Krüppel-like Factor 13 (KLF13) are two of the smallest members of the SP/KLF family, are paralogous, emerged early in metazoan evolution, and are highly conserved. Paradoxically, while most similar in primary sequence, KLF9 and KLF13 display many distinct roles in target cells. In this article, we summarize the work that has identified the roles of KLF9 (and to a lesser degree KLF13) in tumor suppression or promotion via unique effects on differentiation, pro- and anti-inflammatory pathways, oxidative stress, and tumor immune cell infiltration. We also highlight the great diversity of miRNAs, lncRNAs, and circular RNAs which provide mechanisms for the ubiquitous tumor-specific suppression of KLF9 mRNA and protein. Elucidation of KLF9 and KLF13 in cancer biology is likely to provide new inroads to the understanding of oncogenesis and its prevention and treatments. Full article

The continuum of antioxidant response dysregulation in aging/oxidative stress-driven Nlrp3 inflammasome activation-mediated inflammatory response is associated with age-related diseases. Peroxiredoxin (Prdx) 6 is a key antioxidant that provides cytoprotection by regulating redox homeostasis. Herein, using lens epithelial cells (LECs) derived from the targeted inactivation of Prdx6 gene and aging lenses, we present molecular evidence that Prdx6-deficiency causes oxidative-driven Nlrp3 inflammasome activation, resulting in pyroptosis in aging/redox active cells wherein Prdx6 availability offsets the inflammatory process. We observed that Prdx6^−/− and aging LECs harboring accumulated reactive oxygen species (ROS) showed augmented activation of Nlrp3 and bioactive inflammatory components, like Caspase-1, IL-1β, ASC and Gasdermin-D. Similar to lipopolysaccharide treatment, oxidative exposure led to further ROS amplification with increased activation of the Nlrp3 inflammasome pathway. Mechanistically, we found that oxidative stress enhanced Kruppel-like factor 9 (Klf9) expression in aging/Prdx6^−/− mLECs, leading to a Klf9-dependent increase in Nlrp3 transcription, while the elimination of ROS by the delivery of Prdx6 or by silencing Klf9 prevented the inflammatory response. Altogether, our data identify the biological significance of Prdx6 as an intrinsic checkpoint for regulating the cellular health of aging or redox active LECs and provide opportunities to develop antioxidant-based therapeutic(s) to prevent oxidative/aging-related diseases linked to aberrant Nlrp3 inflammasome activation. Full article

Over the past decade, the treatment of metastatic melanoma has improved significantly due to the development of innovative therapies, such as drugs that target the BRAF/MAPK kinase pathway and the PD-1 pathway. However, these therapies do not work for all patients, highlighting the need for additional research on the pathophysiology of melanoma. Paclitaxel is a chemotherapeutic agent used when first-line treatments are unsuccessful; however, its efficacy is limited. Since Krüppel-like factor 9 (KLF9) (antioxidant repressor) is downregulated in melanoma, we propose that restoring KLF9 levels may sensitize malignant melanoma to chemotherapeutic agents, such as paclitaxel. We used adenovirus overexpression and siRNA technologies to assess the role of KLF9 in mediating the response of malignant melanoma-derived cell lines RPMI-7951 and A375 to paclitaxel treatment. We found that increasing KLF9 levels potentiates the effectiveness of paclitaxel, as shown by apoptotic parameters such as decreased cell viability, pro-caspase-3 activation, increased number of annexin V-positive cells, and reduction in nuclear proliferation marker (KI67). These results suggest that KLF9 may be a potential target for improving chemotherapeutic response in melanoma. Full article

Intrauterine adhesion (IUA) causes menstrual disturbance and infertility. There is no effective treatment available for moderate to severe IUA cases. Stem cell-based therapy has been investigated for treating IUA but is limited in clinical applications due to issues including the precise induction of differentiation, tumorigenesis, and unclear molecular mechanisms. In our recent study, we isolated and expanded the long-term cultures of conditional reprogrammed (CR) mouse endometrial epithelial cells. Treating IUA mice with these CR cells (CRCs) restored the morphology and structure of the endometrium and significantly improved the pregnancy rate. In this study, our data with high-throughput sequencing, CRISPR knockout Ihh^−/−CRCs, and transplantation identified for the first time that the Indian hedgehog (Ihh) gene plays a critical role in the regulation of endometrial epithelial cell proliferation. We also found that aberrant activated Ihh-krüppel-like factor 9 (KLF9) signaling contributes to the inhibition of normal progesterone receptor (PR) function in IUA mice. Thus, we hypothesized that inhibition of the Ihh-KLF9 pathway may be a novel strategy to treat IUA. Our data demonstrated that treatment with the hedgehog signaling inhibitor Vismodegib restored the morphology, structure, and microenvironment of the endometrium, and greatly improved the pregnancy rate in IUA mice. This study suggests a promising application of hedgehog inhibitors as a targeted drug in the IUA clinic. Full article

Aims: Krüppel-like Factor 9 (KLF9) is a transcription factor that regulates multiple disease processes. Studies have focused on the role of KLF9 in the redox system. In this study, we aimed to explore the effect of KLF9 on diabetic cardiomyopathy. Methods and Results: Cardiac-specific overexpression or silencing of KLF9 in C57BL/6 J mice was induced with an adeno-associated virus 9 (AAV9) delivery system. Mice were also subjected to streptozotocin injection to establish a diabetic cardiomyopathy model. In addition, neonatal rat cardiomyocytes were used to assess the possible role of KLF9 in vitro by incubation with KLF9 adenovirus or small interfering RNA against KLF9. To clarify the involvement of peroxisome proliferator-activated receptors (PPARγ), mice were subjected to GW9662 injection to inhibit PPARγ. KLF9 was upregulated in the hearts of mice with diabetic cardiomyopathy and in cardiomyocytes. In addition, KLF9 overexpression in the heart deteriorated cardiac function and aggravated hypertrophic fibrosis, the inflammatory response and oxidative stress in mice with diabetic cardiomyopathy. Conversely, cardiac-specific silencing of KLF9 ameliorated cardiac dysfunction and alleviated hypertrophy, fibrosis, the cardiac inflammatory response and oxidative stress. In vitro, KLF9 silencing in cardiomyocytes enhanced inflammatory cytokine release and oxidative stress; KLF9 overexpression increased these detrimental responses. Moreover, KLF9 was found to regulate the transcription of PPARγ, which suppressed the expression and nuclear translocation of nuclear Factor E2-related Factor 2 (NRF2). In mice injected with a PPARγ inhibitor, the protective effects of KLF9 knockdown on diabetic cardiomyopathy were counteracted by GW9662 injection. Conclusions: KLF9 aggravates cardiac dysfunction, the inflammatory response and oxidative stress in mice with diabetic cardiomyopathy. KLF9 may become a therapeutic target for diabetic cardiomyopathy. Full article

Obesity, oxidative stress, and inflammation are risk factors for hepatocellular carcinoma (HCC). We examined, in mice, the effects of Krüppel-like factor 9 (KLF9) knockout on: adiposity, hepatic and systemic oxidative stress, and hepatic expression of pro-inflammatory and NOX/DUOX family genes, in a high-fat diet (HFD) context. Male and female Klf9^+/+ (wild type, WT) and Klf9^−/− (knockout, KO) mice were fed HFD (beginning at age 35 days) for 12 weeks, after which liver and adipose tissues were obtained, and serum adiponectin and leptin levels, liver fat content, and markers of oxidative stress evaluated. Klf9^−/− mice of either sex did not exhibit significant alterations in weight gain, adipocyte size, adipokine levels, or liver fat content when compared to WT counterparts. However, Klf9^−/− mice of both sexes had increased liver weight/size (hepatomegaly). This was accompanied by increased hepatic oxidative stress as indicated by decreased GSH/GSSG ratio and increased homocysteine, 3-nitrotyrosine, 3-chlorotyrosine, and 4HNE content. Decreased GSH to GSSG ratio and a trend toward increased homocysteine levels were observed in the corresponding Klf9^−/− mouse serum. Gene expression analysis showed a heightened pro-inflammatory state in livers from Klf9^−/− mice. KLF9 suppresses hepatic oxidative stress and inflammation, thus identifying potential mechanisms for KLF9 suppression of HCC and perhaps cancers of other tissues. Full article

Reactive oxygen species (ROS) are signalling molecules used to regulate cellular metabolism and homeostasis. However, excessive ROS production causes oxidative stress, one of the main mechanisms associated with the origin and progression of neurodegenerative disorders such as Parkinson’s disease. NRF2 (Nuclear Factor-Erythroid 2 Like 2) is a transcription factor that orchestrates the cellular response to oxidative stress. The regulation of NRF2 signalling has been shown to be a promising strategy to modulate the progression of the neurodegeneration associated to Parkinson’s disease. The NRF2 pathway has been shown to be affected in patients with this disease, and activation of NRF2 has neuroprotective effects in preclinical models, demonstrating the therapeutic potential of this pathway. In this review, we highlight recent advances regarding the regulation of NRF2, including the effect of Angiotensin II as an endogenous signalling molecule able to regulate ROS production and oxidative stress in dopaminergic neurons. The genes regulated and the downstream effects of activation, with special focus on Kruppel Like Factor 9 (KLF9) transcription factor, provide clues about the mechanisms involved in the neurodegenerative process as well as future therapeutic approaches. Full article

Krüppel-associated box zinc finger proteins (KRAB-ZFPs) constitute the largest family of transcriptional factors exerting co-repressor functions in mammalian cells. In general, KRAB-ZFPs have a dual structure. They may bind to specific DNA sequences via zinc finger motifs and recruit a repressive complex through the KRAB domain. Such a complex mediates histone deacetylation, trimethylation of histone 3 at lysine 9 (H3K9me3), and subsequent heterochromatization. Nevertheless, apart from their repressive role, KRAB-ZFPs may also co-activate gene transcription, likely through interaction with other factors implicated in transcriptional control. KRAB-ZFPs play essential roles in various biological processes, including development, imprinting, retroelement silencing, and carcinogenesis. Cancer cells possess multiple genomic, epigenomic, and transcriptomic aberrations. A growing number of data indicates that the expression of many KRAB-ZFPs is altered in several tumor types, in which they may act as oncogenes or tumor suppressors. Hereby, we review the available literature describing the oncogenic and suppressive roles of various KRAB-ZFPs in cancer. We focused on their association with the clinicopathological features and treatment response, as well as their influence on the cancer cell phenotype. Moreover, we summarized the identified upstream and downstream molecular mechanisms that may govern the functioning of KRAB-ZFPs in a cancer setting. Full article

Qin Pi (Fraxinus chinensis Roxb.) is commercially used in healthcare products for the improvement of intestinal function and gouty arthritis in many countries. Three new secoiridoid glucosides, (8E)-4′′-O-methylligstroside (1), (8E)-4′′-O-methyldemethylligstroside (2), and 3′′,4′′-di-O-methyl-demethyloleuropein (3), have been isolated from the stem bark of Fraxinus chinensis, together with 23 known compounds (4–26). The structures of the new compounds were established by spectroscopic analyses (1D, 2D NMR, IR, UV, and HRESIMS). Among the isolated compounds, (8E)-4′′-O-methylligstroside (1), (8E)-4′′-O-methyldemethylligstroside (2), 3′′,4′′-di-O-methyldemethyloleuropein (3), oleuropein (6), aesculetin (9), isoscopoletin (11), aesculetin dimethyl ester (12), fraxetin (14), tyrosol (21), 4-hydroxyphenethyl acetate (22), and (+)-pinoresinol (24) exhibited inhibition (IC₅₀ ≤ 7.65 μg/mL) of superoxide anion generation by human neutrophils in response to formyl-L-methionyl-L-leuckyl-L-phenylalanine/cytochalasin B (fMLP/CB). Compounds 1, 9, 11, 14, 21, and 22 inhibited fMLP/CB-induced elastase release with IC₅₀ ≤ 3.23 μg/mL. In addition, compounds 2, 9, 11, 14, and 21 showed potent inhibition with IC₅₀ values ≤ 27.11 μM, against lipopolysaccharide (LPS)-induced nitric oxide (NO) generation. The well-known proinflammatory cytokines, tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6), were also inhibited by compounds 1, 9, and 14. Compounds 1, 9, and 14 displayed an anti-inflammatory effect against NO, TNF-α, and IL-6 through the inhibition of activation of MAPKs and IκBα in LPS-activated macrophages. In addition, compounds 1, 9, and 14 stimulated anti-inflammatory M2 phenotype by elevating the expression of arginase 1 and Krüppel-like factor 4 (KLF4). The above results suggested that compounds 1, 9, and 14 could be considered as potential compounds for further development of NO production-targeted anti-inflammatory agents. Full article

Three new compounds, 4-geranyloxy-2-hydroxy-6-isoprenyloxybenzophenone (1), hypericumone A (2) and hypericumone B (3), were obtained from the aerial parts of Hypericum sampsonii, along with six known compounds (4–9). The structures of these compounds were determined through spectroscopic and MS analyses. Hypericumone A (2), sampsonione J (8) and otogirinin A (9) exhibited potent inhibition (IC₅₀ values ≤ 40.32 μM) against lipopolysaccharide (LPS)-induced nitric oxide (NO) generation. Otogirinin A (9) possessed the highest inhibitory effect on NO production with IC₅₀ value of 32.87 ± 1.60 μM. The well-known proinflammatory cytokine, tumor necrosis factor-alpha (TNF-α) was also inhibited by otogirinin A (9). Western blot results demonstrated that otogirinin A (9) downregulated the high expression of inducible nitric oxide synthase (iNOS). Further investigations on the mechanism showed that otogirinin A (9) blocked the phosphorylation of MAPK/JNK and IκBα, whereas it showed no effect on the phosphorylation of MAPKs/ERK and p38. In addition, otogirinin A (9) stimulated anti-inflammatory M2 phenotype by elevating the expression of arginase 1 and Krüppel-like factor 4 (KLF4). The above results suggested that otogirinin A (9) could be considered as potential compound for further development of NO production-targeted anti-inflammatory agent. Full article

tRNA-derived fragments (tRFs), a novel type of non-coding RNA derived from tRNAs, play an important part in governing gene expressions at a post-transcriptional level. To date, the regulatory mechanism of tRFs governing fat deposition and adipogenesis is completely unknown. In this study, high fat diet was employed to induce an obese rat model, and tRFs transcriptome sequencing was conducted to identify differentially expressed tRFs that response to obesity. We found out that tRF^GluTTC, which promoted preadipocyte proliferation by increasing expressions of cell cycle regulatory factors, had the highest fold change in the 296 differentially expressed tRFs. Moreover, tRF^GluTTC also suppressed preadipocyte differentiation by reducing triglyceride content and lipid accumulation, and by decreasing expressions of genes that related to fatty acid synthesis. According to results of luciferase activity analysis, tRF^GluTTC directly targeted Kruppel-like factor (KLF) 9, KLF11, and KLF12, thus significantly suppressing mRNA expressions of these target genes. Moreover, tRF^GluTTC suppressed adipogenesis, accompanying by suppressing expressions of adipogenic transcription factors (aP2, PPARγ, and C/EBPα). In conclusion, these results imply that tRF^GluTTC may act as a novel epigenetic molecule regulating adipogenesis and could provide a new strategy for the intervention treatment of obesity. Full article

Soy-leaf extracts exert their cardioprotective effects by inducing endothelium-dependent vasodilation in the arteries, and they favorably modulate the serum lipid profile. In this study, we investigated the atheroprotective effects of an ethanol extract of soy leaf (ESL) in human umbilical vein endothelial cells (HUVECs) and high-cholesterol diet (HCD)-fed low-density lipoprotein receptor deficient (LDLR−/−) mice. ESL induced the expression of Krüppel-like factor 2 (KLF2), an endothelial transcription factor, and endothelial nitric oxide synthase (eNOS), and suppressed the expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) through moderate inflammatory signal activation, not only in tumor necrosis factor-α (TNF-α)-stimulated HUVECs but also in 7-ketocholesterol (7-KC)-stimulated HUVECs. ESL supplementation reduced aortic lesion formation in Western diet-fed LDLR−/− mice by 46% (p < 0.01) compared to the HCD group. ESL also markedly decreased the aortic expression levels of VCAM-1, ICAM-1, monocyte chemotactic protein-1 (MCP-1), TNF-α, IL-6, IL-1β, matrix metallopeptidase 9 (MMP-9), and fractalkine, while the expression of KLF2 was significantly increased. These results suggest that ESL supplementation has potential for preventing HCD-induced atherosclerosis effectively. Full article

Circadian rhythms, ≈24 h oscillations in behavior and physiology, are reflected in all cells of the body and function to optimize cellular functions and meet environmental challenges associated with the solar day. This multi-oscillatory network is entrained by the master pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus, which directs an organism’s rhythmic expression of physiological functions and behavior via a hierarchical system. This system has been highly conserved throughout evolution and uses transcriptional–translational autoregulatory loops. This master clock, following environmental cues, regulates an organism’s sleep pattern, body temperature, cardiac activity and blood pressure, hormone secretion, oxygen consumption and metabolic rate. Mammalian peripheral clocks and clock gene expression have recently been discovered and are present in all nucleated cells in our body. Like other essential organ of the body, the skin also has cycles that are informed by this master regulator. In addition, skin cells have peripheral clocks that can function autonomously. First described in 2000 for skin, this review summarizes some important aspects of a rapidly growing body of research in circadian and ultradian (an oscillation that repeats multiple times during a 24 h period) cutaneous rhythms, including clock mechanisms, functional manifestations, and stimuli that entrain or disrupt normal cycling. Some specific relationships between disrupted clock signaling and consequences to skin health are discussed in more depth in the other invited articles in this IJMS issue on Sleep, Circadian Rhythm and Skin. Full article