Mechanisms of Endogenous Neuroprotective Effects of Astrocytes in Brain Injury

Astrocytes, once believed to serve only as “glue” for the structural support of neurons, have been demonstrated to serve critical functions for the maintenance and protection of neurons, especially under conditions of acute or chronic injury. There are at least seven distinct mechanisms by which astrocytes protect neurons from damage; these are (1) protection against glutamate toxicity, (2) protection against redox stress, (3) mediation of mitochondrial repair mechanisms, (4) protection against glucose-induced metabolic stress, (5) protection against iron toxicity, (6) modulation of the immune response in the brain, and (7) maintenance of tissue homeostasis in the presence of DNA damage. Astrocytes support these critical functions through specialized responses to stress or toxic conditions. The detoxifying activities of astrocytes are essential for maintenance of the microenvironment surrounding neurons and in whole tissue homeostasis. Improved understanding of the mechanisms by which astrocytes protect the brain could lead to the development of novel targets for the development of neuroprotective strategies

Transcriptomic Profiling and Pathway Analysis of Mesenchymal Stem Cells Following Low Dose-Rate Radiation Exposure

Low dose-rate radiation exposure can occur in medical imaging, as background from environmental or industrial radiation, and is a hazard of space travel. In contrast with high dose-rate radiation exposure that can induce acute life-threatening syndromes, chronic low-dose radiation is associated with Chronic Radiation Syndrome (CRS), which can alter environmental sensitivity. Secondary effects of chronic low dose-rate radiation exposure include circulatory, digestive, cardiovascular, and neurological diseases, as well as cancer. Here, we investigated 1–2 Gy, 0.66 cGy/h, 60Co radiation effects on primary human mesenchymal stem cells (hMSC). There was no significant induction of apoptosis or DNA damage, and cells continued to proliferate. Gene ontology (GO) analysis of transcriptome changes revealed alterations in pathways related to cellular metabolism (cholesterol, fatty acid, and glucose metabolism), extracellular matrix modification and cell adhesion/migration, and regulation of vasoconstriction and inflammation. Interestingly, there was increased hypoxia signaling and increased activation of pathways regulated by iron deficiency, but Nrf2 and related genes were reduced. The data were validated in hMSC and human lung microvascular endothelial cells using targeted qPCR and Western blotting. Notably absent in the GO analysis were alteration pathways for DNA damage response, cell cycle inhibition, senescence, and pro-inflammatory response that we previously observed for high dose-rate radiation exposure. Our findings suggest that cellular gene transcription response to low dose-rate ionizing radiation is fundamentally different compared to high-dose-rate exposure. We hypothesize that cellular response to hypoxia and iron deficiency are driving processes, upstream of the other pathway regulation

Transcriptomic Profiling and Pathway Analysis of Mesenchymal Stem Cells Following Low Dose-Rate Radiation Exposure

Low dose-rate radiation exposure can occur in medical imaging, as background from environmental or industrial radiation, and is a hazard of space travel. In contrast with high dose-rate radiation exposure that can induce acute life-threatening syndromes, chronic low-dose radiation is associated with Chronic Radiation Syndrome (CRS), which can alter environmental sensitivity. Secondary effects of chronic low dose-rate radiation exposure include circulatory, digestive, cardiovascular, and neurological diseases, as well as cancer. Here, we investigated 1–2 Gy, 0.66 cGy/h, 60Co radiation effects on primary human mesenchymal stem cells (hMSC). There was no significant induction of apoptosis or DNA damage, and cells continued to proliferate. Gene ontology (GO) analysis of transcriptome changes revealed alterations in pathways related to cellular metabolism (cholesterol, fatty acid, and glucose metabolism), extracellular matrix modification and cell adhesion/migration, and regulation of vasoconstriction and inflammation. Interestingly, there was increased hypoxia signaling and increased activation of pathways regulated by iron deficiency, but Nrf2 and related genes were reduced. The data were validated in hMSC and human lung microvascular endothelial cells using targeted qPCR and Western blotting. Notably absent in the GO analysis were alteration pathways for DNA damage response, cell cycle inhibition, senescence, and pro-inflammatory response that we previously observed for high dose-rate radiation exposure. Our findings suggest that cellular gene transcription response to low dose-rate ionizing radiation is fundamentally different compared to high-dose-rate exposure. We hypothesize that cellular response to hypoxia and iron deficiency are driving processes, upstream of the other pathway regulation

Figure S6 from Multiomic-Based Molecular Landscape of FaDu Xenograft Tumors in Mice after a Combinatorial Treatment with Radiation and an HSP90 Inhibitor Identifies Adaptation-Induced Targets of Resistance and Therapeutic Intervention

Supplemental Figure S6: Graphs of proteins and phosphoproteins that previously showed impact on cancer proliferation or death. Trends towards significance only. Normalized to intensity. For JUN, microarray data showed that Drug Week 2 and Drug+Rad Week 1 were significantly decreased ([FC} > 2, p < 0.05) compared to respective Untreated tumors.</p

Figure S2 from Multiomic-Based Molecular Landscape of FaDu Xenograft Tumors in Mice after a Combinatorial Treatment with Radiation and an HSP90 Inhibitor Identifies Adaptation-Induced Targets of Resistance and Therapeutic Intervention

Supplemental Figure S2: IPA pathway highlights genes relevant to Organismal Death, Viral Infection and Vasculogenesis for Treatment groups at Week 1 compared to Control Day 1. Significantly altered genes (2-fold change, p < 0.01) are shown. White indicates no significant change, Red indicates upregulation, Blue indicates downregulation. Black arrows indicate genes of interest. Drug+Rad and Drug alone caused significantly more gene up/down regulation than Rad alone. More genes exist in these pathways than are displayed, for ease of visualization only genes which showed significant changes in expression in at least 2 treatment groups are presented. Genes may be relevant to more than one pathway (PLAUR) is relevant to Organismal Death and Vasculogenesis, but to avoid redundancy is shown once.</p

Figure S5 from Multiomic-Based Molecular Landscape of FaDu Xenograft Tumors in Mice after a Combinatorial Treatment with Radiation and an HSP90 Inhibitor Identifies Adaptation-Induced Targets of Resistance and Therapeutic Intervention

Supplemental Figure S5. Proteomic and Phospho-proteomic comparison of changes observed comparing UT_Wk1 to UT_Wk2 (A), Treated Week 1 to UT_Wk1 (B) and Treated Week 2 to UT_Wk2 (C). Trends towards significance only. Normalized to intensity. No notable change is shown in white, upregulation is red, downregulation is blue. Supplemental Figure 4A indicates change in UT_Wk2 compared to UT_Wk1, interestingly p53 and PDL-1 protein expression decrease over three days. Supplemental Figure 6A indicates change in Untreated Week 2 compared to Untreated Week 1, interestingly p53 and PDL-1 protein expression show a decreasing trend.</p

Figure S3 from Multiomic-Based Molecular Landscape of FaDu Xenograft Tumors in Mice after a Combinatorial Treatment with Radiation and an HSP90 Inhibitor Identifies Adaptation-Induced Targets of Resistance and Therapeutic Intervention

Supplemental Figure S3: IPA pathway highlights genes relevant to, Cell Migration, Angiogenesis and Morbidity or mortality for Treatment groups at Week 2 compared to Untreated Week 2. Significantly altered genes ([2-fold change, p < 0.01) are shown. White indicates no significant changes, Red indicates upregulation, Blue indicates downregulation. Black arrows indicate genes of interest. More genes exist in these pathways than are displayed, for ease of visualization only genes which showed significant changes in expression in at least 2 treatment groups are presented. Genes may be relevant to more than one pathway (PLAUR) is relevant to Organismal Death and Vasculogenesis, but to avoid redundancy is shown once.</p

Table S1 from Multiomic-Based Molecular Landscape of FaDu Xenograft Tumors in Mice after a Combinatorial Treatment with Radiation and an HSP90 Inhibitor Identifies Adaptation-Induced Targets of Resistance and Therapeutic Intervention

Supplementary Table of phosphoproteomic data</p

Figure S1 from Multiomic-Based Molecular Landscape of FaDu Xenograft Tumors in Mice after a Combinatorial Treatment with Radiation and an HSP90 Inhibitor Identifies Adaptation-Induced Targets of Resistance and Therapeutic Intervention

Supplemental Figure S1: IPA pathway highlights genes relevant to Organismal Death, Viral infection and Vasculogenesis for Untreated groups at Week 1 and Week 2 compared to Control Day 1. Significantly altered genes (2-fold change, p < 0.01) are shown. White indicates no significant change, Red indicates upregulation, Blue indicates downregulation. Black arrows indicate genes of interest.</p