bims-stacyt 2020-05-24 papers

Cell Mol Neurobiol. 2020 May 18.

Hypoxic Preconditioning Enhances the Efficacy of Mesenchymal Stem Cells-Derived Conditioned Medium in Switching Microglia toward Anti-inflammatory Polarization in Ischemia/Reperfusion.

Han Yu, Zhihong Xu, Gaojing Qu, Huimin Wang, Lulu Lin, Xianyu Li, Xiaolin Xie, Yifeng Lei, Xiaohua He, Yun Chen, Yinping Li.

Activation of pro-inflammatory microglia is an important mechanism of the cerebral ischemia-reperfusion (I/R)-induced neuronal injury and dysfunction. Mesenchymal stem cells (MSCs) together with their paracrine factors demonstrated curative potential in immune disorders and inflammatory diseases, as well as in ischemic diseases. However, it remains unclear whether conditioned medium from MSCs could effectively regulate the activation and polarization of microglia exposed to I/R stimulation. In this study, we investigated the effects of conditioned medium from bone marrow MSCs (BMSCs-CM) on I/R-stimulated microglia and the potential mechanism involved, as well as the way to obtain more effective BMSCs-CM. First, cell model of oxygen-glucose deprivation/reoxygenation (OGD/R) was established in microglia to mimic the I/R. BMSCs-CM from different culture conditions (normoxic: 21% O2; hypoxic: 1% O2; hypoxia preconditioning: preconditioning with 1% O2 for 24 h) was used to treat the microglia. Our results showed that BMSCs-CM effectively promoted the survival and alleviated the injury of microglia. Moreover, in microglia exposed to OGD/R, BMSCs-CM inhibited significantly the expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), CD86 and inducible nitric oxide synthase, whereas upregulated the levels of anti-inflammatory cytokine (IL-10), CD206 and Arginase-1. These results suggested that BMSCs-CM promoted the polarization of anti-inflammatory microglia. In particular, BMSCs-CM from cultures with hypoxia preconditioning was more effective in alleviating cell injury and promoting anti-inflammatory microglia polarization than BMSCs-CM from normoxic cultures and from hypoxic cultures. Furthermore, inhibition of exosomes secretion could largely mitigate these effects of BMSCs-CM. In conclusion, our results suggested that hypoxia preconditioning of BMSCs could enhance the efficacy of BMSCs-CM in alleviating OGD/R-induced injury and in promoting the anti-inflammatory polarization of microglia, and these beneficial effects of BMSCs-CM owed substantially to exosomes.

Keywords: Conditioned medium; Hypoxic preconditioning; Immune regulation; Ischemia–reperfusion injury; Mesenchymal stem cells; Microglia

DOI: https://doi.org/10.1007/s10571-020-00868-5

Biomed Res Int. 2020 ;2020 4510628

High Glucose Induces the Loss of Retinal Pericytes Partly via NLRP3-Caspase-1-GSDMD-Mediated Pyroptosis.

Jinhua Gan, Maomao Huang, Genyin Lan, Li Liu, Fangyuan Xu.

Diabetic retinopathy (DR) is one of the hallmark complications of diabetes and a leading cause of vision loss in adults. Retinal pericyte death seems to be a prominent feature in the onset of DR. Pyroptosis is an inflammatory form of programmed cell death, defined as being caspase-gasdermin-D (GSDMD)-dependent. The NOD-like receptor pyrin 3 (NLRP3) inflammasome plays an important role in mediating GSDMD activation. However, the role and mechanism of pyroptosis in the loss of retinal pericytes during the pathogenesis of DR are still unclear. In the present study, we cultured primary human retinal pericytes (HRPs) in high glucose medium; caspase-3 inhibitor DEVD, caspase-1 inhibitor YVAD, or NLRP3 inhibitor glyburide was used as intervention reagents; GSDMD was overexpressed or suppressed by transfection with an expressing vector or retroviral silencing of GSDMD, respectively. Our data showed that high glucose induced NLRP3-caspase-1-GSDMD activation and pore formation in a dose- and time-dependent manner (p < 0.05) and resulted in the inflammatory cytokines IL-1β and IL-18 and lactate dehydrogenase (LDH) release from HRPs (p < 0.05), which are all signs of HRP pyroptosis. Overexpression of GSDMD facilitated high glucose-induced pyroptosis (all p < 0.05). However, these effects were blunted by synergistically treating DEVD, YVAD, and silencing GSDMD (p < 0.05). Taken together, our results firstly revealed that high glucose induced the loss of retinal pericytes partly via NLRP3-caspase-1-GSDMD-mediated pyroptosis.

DOI: https://doi.org/10.1155/2020/4510628

Cell Rep. 2020 May 19. pii: S2211-1247(20)30612-4. [Epub ahead of print]31(7): 107659

ATF4-Induced Warburg Metabolism Drives Over-Proliferation in Drosophila.

Sebastian Sorge, Jonas Theelke, Kerem Yildirim, Helen Hertenstein, Ellen McMullen, Stephan Müller, Christian Altbürger, Stefanie Schirmeier, Ingrid Lohmann.

The mitochondrial electron transport chain (ETC) enables essential metabolic reactions; nonetheless, the cellular responses to defects in mitochondria and the modulation of signaling pathway outputs are not understood. We show that Notch signaling and ETC attenuation via knockdown of COX7a induces massive over-proliferation. The tumor-like growth is caused by a transcriptional response through the eIF2α-kinase PERK and ATF4, which activates the expression of metabolic enzymes, nutrient transporters, and mitochondrial chaperones. We find this stress adaptation to be beneficial for progenitor cell fitness, as it renders cells sensitive to proliferation induced by the Notch signaling pathway. Intriguingly, over-proliferation is not caused by transcriptional cooperation of Notch and ATF4, but it is mediated in part by pH changes resulting from the Warburg metabolism induced by ETC attenuation. Our results suggest that ETC function is monitored by the PERK-ATF4 pathway, which can be hijacked by growth-promoting signaling pathways, leading to oncogenic pathway activity.

Keywords: ATF4; Drosophila; ETC; ETC impairment; ISR; LDH; Notch pathway; PERK; UPR; lactate; mitochondrial electron transport chain; pH; proliferation

DOI: https://doi.org/10.1016/j.celrep.2020.107659

Brain Behav Immun. 2020 May 16. pii: S0889-1591(20)30117-3. [Epub ahead of print]

Interleukin 6-independent metabolic reprogramming as a driver of cancer-related fatigue.

Aaron J Grossberg, Elisabeth G Vichaya, Phillip S Gross, Bianca G Ford, Kiersten A Scott, Darlene Estrada, Daniel W Vermeer, Paola Vermeer, Robert Dantzer.

Fatigue is a common and debilitating symptom of cancer with few effective interventions. Cancer-related fatigue (CRF) is often associated with increases in inflammatory cytokines, however inflammation may not be requisite for this symptom, suggesting other biological mediators also play a role. Because tumors are highly metabolically active and can amplify their energetic toll via effects on distant organs, we sought to determine whether CRF could be explained by metabolic competition exacted by the tumor. We used a highly metabolically active murine E6/E7/hRas model of head and neck cancer for this purpose. Mice with or without tumors were submitted to metabolic constraints in the form of voluntary wheel running or acute overnight fasting and their adaptive behavioral (home cage activity and fasting-induced wheel running) and metabolic responses (blood glucose, ketones, and liver metabolic gene expression) were monitored. We found that the addition of running wheel was necessary to measure activity loss, used as a surrogate for fatigue in this study. Tumor-bearing mice engaged in wheel running showed a decrease in blood glucose levels and an increase in lactate accumulation in the skeletal muscle, consistent with inhibition of the Cori cycle. These changes were associated with gene expression changes in the livers consistent with increased glycolysis and suppressed gluconeogenesis. Fasting also decreased blood glucose in tumor-bearing mice, without impairing glucose or insulin tolerance. Fasting-induced increases in wheel running and ketogenesis were suppressed by tumors, which was again associated with a shift from gluconeogenic to glycolytic metabolism in the liver. Blockade of IL-6 signaling with a neutralizing antibody failed to recover any of the behavioral or metabolic outcomes. Taken together, these data indicate that metabolic competition between the tumor and the rest of the organism is an important component of fatigue and support the hypothesis of a central role for IL-6-independent hepatic metabolic reprogramming in the pathophysiology of CRF.

DOI: https://doi.org/10.1016/j.bbi.2020.05.043

PLoS One. 2020 ;15(5): e0233390

Interferon regulatory factor 7 mediates obesity-associated MCP-1 transcription.

Masashi Kuroda, Misa Nishiguchi, Naho Ugawa, Etsuko Ishikawa, Yasuyo Kawabata, Saya Okamoto, Waka Sasaki, Yumiko Miyatake, Mayu Sebe, Saeko Masumoto, Rie Tsutsumi, Nagakatsu Harada, Hiroshi Sakaue.

Hypertrophy, associated with adipocyte dysfunction, causes increased pro-inflammatory adipokine, and abnormal glucose and lipid metabolism, leading to insulin resistance and obesity-related-health problems. By combining DNA microarray and genomic data analyses to predict DNA binding motifs, we identified the transcription factor Interferon Regulatory Factor 7 (IRF7) as a possible regulator of genes related to adipocyte hypertrophy. To investigate the role of IRF7 in adipocytes, we examined gene expression patterns in 3T3-L1 cells infected with a retrovirus carrying the IRF7 gene and found that enforced IRF7 expression induced the expression of monocyte chemoattractant protein-1 (MCP-1), a key initial adipokine in the chronic inflammation of obesity. CRISPR/Cas9 mediated-suppression of IRF7 significantly reduced MCP-1 mRNA. Luciferase assays, chromatin immunoprecipitation PCR analysis and gel shift assay showed that IRF7 transactivates the MCP-1 gene by binding to its proximal Interferon Stimulation Response Element (ISRE), a putative IRF7 binding motif. IRF7 knockout mice exhibited lower expression of MCP-1 in epidydimal white adipose tissue under high-fat feeding conditions, suggesting the transcription factor is physiologically important for inducing MCP-1. Taken together, our results suggest that IRF7 transactivates MCP-1 mRNA in adipocytes, and it may be involved in the adipose tissue inflammation associated with obesity.

DOI: https://doi.org/10.1371/journal.pone.0233390