Melatonin attenuates diabetic cardiomyopathy by increasing autophagy of cardiomyocytes via regulation of VEGF-B/GRP78/PERK signaling pathway.

AIMS: Diabetic cardiomyopathy (DCM) is a major cause of mortality in patients with diabetes, and the potential strategies for treating DCM are insufficient. Melatonin (Mel) has been shown to attenuate DCM, however, the underlying mechanism remains unclear. The role of vascular endothelial growth factor-B (VEGF-B) in DCM is little known. In present study, we aimed to investigate whether Mel alleviated DCM via regulation of VEGF-B and explored its underlying mechanisms. METHODS AND RESULTS: We found that Mel significantly alleviated cardiac dysfunction and improved autophagy of cardiomyocytes in type 1 diabetes mellitus (T1DM) induced cardiomyopathy mice. VEGF-B was highly expressed in DCM mice in comparison with normal mice, and its expression was markedly reduced after Mel treatment. Mel treatment diminished the interaction of VEGF-B and Glucose-regulated protein 78 (GRP78) and reduced the interaction of GRP78 and protein kinase RNA -like ER kinase (PERK). Furthermore, Mel increased phosphorylation of PERK and eIF2α, then up-regulated the expression of ATF4. VEGF-B-/- mice imitated the effect of Mel on wild type diabetic mice. Interestingly, injection with Recombinant adeno-associated virus serotype 9 (AAV9)-VEGF-B or administration of GSK2656157 (GSK), an inhibitor of phosphorylated PERK abolished the protective effect of Mel on DCM. Furthermore, rapamycin, an autophagy agonist displayed similar effect with Mel treatment; while 3-Methyladenine (3-MA), an autophagy inhibitor neutralized the effect of Mel on high glucose-treated neonatal rat ventricular myocytes. CONCLUSIONS: These results demonstrated that Mel attenuated DCM via increasing autophagy of cardiomyocytes, and this cardio-protective effect of Mel was dependent on VEGF-B/GRP78/PERK signaling pathway.

K2S2O8-Mediated Radical Cyclization of 1,6-Enyne for the Synthesis of Diiodonated γ-Lactams.

A novel and convenient K2S2O8-mediated diiodo cyclization of 1,6-enynes for the facile synthesis of functionalized γ-lactam derivatives has been developed. This reaction features mild and transition-metal-free conditions, which offer a green and efficient entry to synthetically important γ-lactam scaffolds. Mechanistic studies suggest that iodide radicals initiate the cascade cyclic transformation.

MCT4/Lactate Promotes PD-L1 Glycosylation in Triple-Negative Breast Cancer Cells.

Triple-negative breast cancer (TNBC) has the highest percentage of lymphocytic infiltration among breast cancer subtypes, and TNBC patients may benefit from anti-PD-1/PD-L1 immunotherapy. However, some cases whether the immune checkpoint blockade (ICB) shows low targeting efficiency have occurred and effective synergistic targets need to be found, which inspired our exploration of the co-expression analysis of MCT4 (SLC16A3) and PD-L1 (CD274) and their potential regulatory mechanisms. After bioinformatic analysis of the relationship between MCT4 and PD-L1, we validated their positive co-expression relationship in triple-negative breast cancer through multiple immunohistochemical staining (mIHC), CRISPR/Cas9, and lentiviral transduction for MCT4 knockout (sgMCT4/231 KO) or overexpression (pEGFP-N1-MCT4/231). We examined the effect of lactate treatment on PD-L1 expression in triple-negative breast cancer cells by qRT-PCR and Western blot. Combined with our results, we found that MCT4 positively regulated PD-L1 expression through discharging lactate and stabilized PD-L1 through promoting its glycosylation by the classic WNT pathway in MDA-MB-231 cells. More importantly, the high co-expression of MCT4 and PD-L1 appears to predict more effective targets for treating TNBC, which would improve immune checkpoint therapy for TNBC.

A Removable Acyl Group Promoted the Intramolecular Dehydro-Diels-Alder Reaction of Styrene-Ynes: Highly Chemoselective Synthesis of Aryldihydronaphthalene Derivatives.

A removable acyl group promoted the intramolecular didehydro-Diels-Alder reaction of styrene-ynes under mild reaction conditions is proposed. The reaction is free of metals and catalysts, is easy to perform, and exhibits good functional group tolerance, providing a highly chemoselective approach for obtaining the valuable aryldihydronaphthalene derivatives.

A mild tetradehydro-Diels-Alder reaction of aryldiyne compounds affords exclusively linear products.

The thermal tetradehydro-Diels-Alder (TDDA) reaction for the synthesis of polysubstituted aromatic compounds remains underestimated probably due to the harsh conditions and multiproduct results. Herein, a mild intramolecular TDDA reaction of aryldiyne compounds is presented with linear naphthalenes only, exhibiting good functional group tolerance. The reaction is easy to operate and amenable to multigram-scale synthesis. From the preliminary work, it was found that the mild conditions may be the key to the completely linear product in the reactions.

Glucagon-like peptide-1 receptor activation by liraglutide promotes breast cancer through NOX4/ROS/VEGF pathway.

AIMS: Scientific evidence imply the strong correlation between diabetes and breast cancer. Glucagon-like peptide-1 (GLP-1) and its analogue liraglutide, have been widely used for diabetes treatment. However, the role of GLP-1 receptor (GLP-1R) in breast cancer requires further elucidation. This study aimed to investigate the risk and the molecular mechanisms of liraglutide using in breast cancer. MATERIALS AND METHODS: Quantitative real-time polymerase chain reaction, western blot or immunohistochemistry were used to detect the expressions of GLP-1R, NADPH oxidase 4 (NOX4) and vascular endothelial growth factor (VEGF) in human triple negative breast cancer (TNBC) cells (MDA-MB-231 and MDA-MB-468) and tissues derived from BALB/cfC3H mouse bearing 4T1 cells inoculation. Cell proliferation and migration was detected using the Cell Counting Kit-8, adenosine triphosphate assay, and transwell assay, respectively. Flow cytometry was used to measure the level of reactive oxygen species (ROS). KEY FINDINGS: We found that the expression of GLP-1R increased after liraglutide treatment in breast cancer cells and the transplanted tumors. Liraglutide, at a slightly higher concentration, accelerated breast cancer progress in vitro (100 nM) and in vivo (400µg/kg) through the NOX4/ROS/VEGF signal pathway after activating GLP-1R. The GLP-1R inhibitor, Exendin (9-39), significantly inhibited the effect of liraglutide, inducing a reversed function of GLP-1R activation. SIGNIFICANCE: Our study illustrated that in an approximately toxicology context, liraglutide may promote the malignant progression of TNBC. The dosage and the phenotype of the breast cancer should be considered as important factors for the rational administration of antidiabetic drugs, especially that of liraglutide in breast cancer patients.

ZEB1 induces ROS generation through directly promoting MCT4 transcription to facilitate breast cancer.

PURPOSE: Transcription factor zinc finger E-box binding homeobox 1(ZEB1) was well-known as a transcription factor in epithelial-mesenchymal transition (EMT) process of cancer, but little is known about its role in cancer metabolism. We found metabolism-related gene monocarboxylate transporter 4 (MCT4) contained E-box motifs in its promoter region, which is the potential binding site of ZEB1. Thus, the correlation between ZEB1 and MCT4 was also investigated in this study. METHODS: Two human breast cancer cell lines MDA-MB-231 and MCF7 were used for ZEB1 and MCT4 expression by double fluorescence staining, ChIP as well as luciferase reporter. ROS levels were revealed by DCFDA and DHE fluorescence probes. The role of ZEB1/MCT4/ROS/autophagy was also determined in xenograft tumor mice model. RESULTS: MCT4 and ZEB1 were synchronously expressed in two types of breast cancer cells. Moreover, ZEB1 positively regulated the expression and the function of MCT4 through binding to the E-box motifs in MCT4' promoter. In addition, the in vitro and in vivo experiments showed that ZEB1/MCT4 in synergy promoted the growth of breast cancer through ROS generation and autophagy, which can be reversed by a MCT4 inhibitor, 7ACC1. CONCLUSION: ZEB1 directly binds to E-box elements of MCT4 promoter and enhance MCT4 expression, inducing ROS accumulation, which cooperatively resulting in breast cancer growth and shorten survival. Our findings provide a theoretical basis for interfering the metabolism in breast cancer therapeutics.

Blocking MCT4 SUMOylation inhibits the growth of breast cancer cells.

Monocarboxylate transporter 4 (MCT4) is highly expressed in various types of solid neoplasms including breast cancer (BC); however, the pro-tumor functions underlying its increased expression have not been explained. Here, we examined the roles of posttranslational modifications to MCT4 in BC, particularly SUMOylation. Our findings revealed that SUMOylation of MCT4 inhibited its degradation and stabilized MCT4 protein levels, while ubiquitination facilitated MCT4 degradation. The E3 ubiquitin ligases ß-TRCP and FBW7 interacted with MCT4 at the DSG-box and TPETS sequences, respectively, and Lys448 (K448) of MCT4 could be modified by SUMO chains. Our key finding was that K448 was crucial for MCT4 SUMOylation. Moreover, mutations of K448 abolished MCT4 expression, delaying the growth of BC. This study suggested that SUMOylation of K448 increased MCT4 levels, and mutations of K448 in MCT4 could have therapeutic significance in BC.

ZEB1 directly inhibits GPX4 transcription contributing to ROS accumulation in breast cancer cells.

PURPOSE: Prior studies have noted that zinc finger E-box binding homeobox 1 (ZEB1) is a master transcription regulator, affecting the expression of nearly 2000 genes in breast cancer cells, especially in the epithelial-mesenchymal transition (EMT) process. We now tested the role of ZEB1 on the oxidative stress of cancer cells and explored its possible mechanisms. METHODS: Two human breast cancer cell lines MDA-MB-231 and MCF7 were selected for the ROS test, PCR, immunofluorescence, Western blot, chromatin immunoprecipitation assay, luciferase assay, and enzyme assay. Mouse models experiments and bioinformatics analysis were conducted to test the indicated molecules. RESULTS: We observed ZEB1 could inhibit GPX4 transcription by binding to the E-box motifs and promote breast cancer progression by accumulating intracellular ROS. From the perspective of ROS clearance, Vitamin E enhanced GPX4 function to consume L-glutathione and eliminated excess intracellular ROS. CONCLUSIONS: ZEB1 could not only regulate EMT, but also inhibit GPX4 transcription by binding to the E-box motif. It was important to note that the ZEB1/GPX4 axis had a therapeutic effect on breast cancer metabolism.