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Angiotensin-(1-7) prevents radiation-induced inflammation in rat primary astrocytes through regulation of MAP kinase signaling.

ABSTRACT: About 500,000 new cancer patients will develop brain metastases in 2013. The primary treatment modality for these patients is partial or whole brain irradiation which leads to a progressive, irreversible cognitive impairment. Although the exact mechanisms behind this radiation-induced brain injury are unknown, neuroinflammation in glial populations is hypothesized to play a role. Blockers of the renin-angiotensin system (RAS) prevent radiation-induced cognitive impairment and modulate radiation-induced neuroinflammation. Recent studies suggest that RAS blockers may reduce inflammation by increasing endogenous concentrations of the anti-inflammatory heptapeptide angiotensin-(1-7) [Ang-(1-7)]. Ang-(1-7) binds to the AT(1-7) receptor and inhibits MAP kinase activity to prevent inflammation. This study describes the inflammatory response to radiation in astrocytes characterized by radiation-induced increases in (i) IL-1? and IL-6 gene expression; (ii) COX-2 and GFAP immunoreactivity; (iii) activation of AP-1 and NF-?B transcription factors; and (iv) PKC?, MEK, and ERK (MAP kinase) activation. Treatment with U-0126, a MEK inhibitor, demonstrates that this radiation-induced inflammation in astrocytes is mediated through the MAP kinase pathway. Ang-(1-7) inhibits radiation-induced inflammation, increases in PKC?, and MAP kinase pathway activation (phosphorylation of MEK and ERK). Additionally Ang-(1-7) treatment leads to an increase in dual specificity phosphatase 1 (DUSP1). Furthermore, treatment with sodium vanadate (Na3VO4), a phosphatase inhibitor, blocks Ang-(1-7) inhibition of radiation-induced inflammation and MAP kinase activation, suggesting that Ang-(1-7) alters phosphatase activity to inhibit radiation-induced inflammation. These data suggest that RAS blockers inhibit radiation-induced inflammation and prevent radiation-induced cognitive impairment not only by reducing Ang II but also by increasing Ang-(1-7) levels.

SUBMITTER: Moore ED

PROVIDER: S-EPMC3879043 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature

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Angiotensin-(1-7) prevents radiation-induced inflammation in rat primary astrocytes through regulation of MAP kinase signaling.

Moore Elizabeth D ED Kooshki Mitra M Metheny-Barlow Linda J LJ Gallagher Patricia E PE Robbins Mike E ME

Free radical biology & medicine 20130903

About 500,000 new cancer patients will develop brain metastases in 2013. The primary treatment modality for these patients is partial or whole brain irradiation which leads to a progressive, irreversible cognitive impairment. Although the exact mechanisms behind this radiation-induced brain injury are unknown, neuroinflammation in glial populations is hypothesized to play a role. Blockers of the renin-angiotensin system (RAS) prevent radiation-induced cognitive impairment and modulate radiation- ...[more]

PMID: 24012919

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Project description:BackgroundConventional p38α inhibitors have limited efficacy in rheumatoid arthritis, possibly because p38 blockade suppresses the counter-regulatory mechanisms that limit inflammation. In contrast, targeting the upstream MAP kinase kinases, MKK3 and MKK6, partially maintains p38-mediated anti-inflammatory responses in bone marrow-derived macrophages (BMDM). In this study, we explored the mechanisms that preserve anti-inflammatory gene expression by evaluating differential regulation of IL-10 and p38-dependent anti-inflammatory genes in MKK3-/-, MKK6-/-, and p38 inhibitor-treated wildtype cells.MethodsBMDM from wild type (WT), MKK3-/-, and MKK6-/- mice were pre-treated with p38 inhibitor SB203580 (SB), JNK inhibitor SP600125 (SP), and/or ERK inhibitor PD98059 (PD) and stimulated with LPS. Supernatant protein levels were measured by multiplex bead immunoassay. mRNA expression was determined by qPCR and protein expression by Western blot analysis. De novo IL-10 mRNA synthesis was quantified in cells treated with ethynyl-uridine and LPS followed by reverse transcription and qPCR. mRNA half-life was measured in LPS-treated cells that were then incubated with actinomycin D ± SB203580.ResultsPre-treatment of WT BMDM with p38 inhibitor significantly reduced IL-10 production in the three groups, while ERK and JNK inhibitors had minimal effects. IL-10 production was significantly decreased in MKK3-/- BMDM compared with either WT or MKK6-/- cells. IL-10 mRNA expression was modestly reduced in MKK3-/- BMDM but was preserved in MKK6-/- cells compared with WT. De novo IL-10 mRNA synthesis was inhibited in MKK3-/- and p38 inhibitor pre-treated cells, but not MKK6-/- cells compared with WT. IL-10 mRNA half-life was markedly reduced in p38 inhibitor-treated WT cells while MKK-deficiency had minimal effect. DUSP1 mRNA levels were preserved in MKK-deficient cells but not in p38 inhibitor-treated WT cells. Tristetraprolin mRNA and protein levels were reduced in p38 inhibitor-treated WT cells compared with MKK6-/- cells.ConclusionUnlike p38-inhibition, the absence of MKK6 mostly preserves IL-10 and TTP protein expression in BMDM. MKK6-deficiency also spares DUSP1 and IL-1RA, which are key negative regulators of the inflammatory response. Together, these data suggest that MKK6 is a potential therapeutic target in RA.

Project description:Vascular oxidative stress and inflammation play an important role in angiotensin II-induced hypertension, and mitogen-activated protein kinases participate in these processes. We questioned whether mitogen-activated protein kinase-activated protein kinase 2 (MK2), a downstream target of p38 mitogen-activated protein kinase, is involved in angiotensin II-induced vascular responses. In vivo experiments were performed in wild-type and Mk2 knockout mice infused intravenously with angiotensin II. Angiotensin II induced a 30 mm Hg increase in mean blood pressure in wild-type that was delayed in Mk2 knockout mice. Angiotensin II increased superoxide production and vascular cell adhesion molecule-1 in blood vessels of wild-type but not in Mk2 knockout mice. Mk2 knockdown by small interfering RNA in mouse mesenteric vascular smooth muscle cells caused a 42% reduction in MK2 protein and blunted the angiotensin II-induced 40% increase of MK2 expression. Mk2 knockdown blunted angiotensin II-induced doubling of intracellular adhesion molecule-1 expression, 2.4-fold increase of nuclear p65, and 1.4-fold increase in Ets-1. Mk2 knockdown abrogated the angiotensin II-induced 4.7-fold and 1.3-fold increase of monocyte chemoattractant protein-1 mRNA and protein. Angiotensin II enhanced reactive oxygen species levels (by 29%) and nicotinamide adenine dinucleotide phosphate oxidase activity (by 48%), both abolished by Mk2 knockdown. Reduction of MK2 blocked angiotensin II-induced p47phox translocation to the membrane, associated with a 53% enhanced catalase expression. Angiotensin II-induced increase of MK2 was prevented by the nicotinamide adenine dinucleotide phosphate oxidase inhibitor Nox2ds-tat. Mk2 small interfering RNA prevented the angiotensin II-induced 30% increase of proliferation. In conclusion, MK2 plays a critical role in angiotensin II signaling, leading to hypertension, oxidative stress via activation of p47phox and inhibition of antioxidants, and vascular inflammation and proliferation.

Project description:Fatty liver hemorrhagic syndrome (FLHS) in laying hens, a nutritional metabolic disorder disease, can lead to the decline of laying rate, shortening of laying peak period and increase of mortality, which seriously constrain the sustainable development of layer industry. Until now, there is no effective strategies can prevent and control the occurrence of fatty liver hemorrhagic syndrome in laying hens. The AMP-activated protein kinase (AMPK), a major sensor of cellular energy status, acts a crucial role in regulating lipid metabolism, oxidative stress and inflammatory responses in body. However, the potential molecular mechanisms about AMP-activated protein kinase signal in controlling the occurrence of fatty liver hemorrhagic syndrome are remain unclear. In present study, we found that the phosphorylated AMP-activated protein kinase (Thr172) protein level was markedly reduced in palmitic acid plus oleic acid (PO)-induced primary chicken hepatocytes. Moreover, blocked AMP-activated protein kinase signal by AMP-activated protein kinase inhibitor compound C obviously exacerbated lipid metabolism disorders, oxidative stress and inflammatory response triggered by palmitic acid plus oleic acid in primary chicken hepatocytes. Nevertheless, the lipid metabolism disorders, oxidative stress and inflammatory response challenged by palmitic acid plus oleic acid were obviously alleviated through activation of AMP-activated protein kinase signal with AMP-activated protein kinase activator AICAR in hepatocytes. In addition, we found that the beneficial effects of AMP-activated protein kinase signal in relieving lipid metabolism disorders, oxidative stress and inflammatory response are achieved by activating the nuclear factor erythroid 2-related factor 2 (NRF-2)/kelch-like ECH-associated protein 1 (KEAP1) pathway and inhibiting the NF-κB pathway in PO-stimulated primary chicken hepatocytes. Collectively, our data demonstrated that AMP-activated protein kinase acts as a potential target for the prevention of fatty liver hemorrhagic syndrome occurrence in laying hens.

Project description:IntroductionExposure to space conditions during crewed long-term exploration missions can cause several health risks for astronauts. Space radiation, isolation and microgravity are major limiting factors. The role of astrocytes in cognitive disturbances by space radiation is unknown. Astrocytes' response toward low linear energy transfer (LET) X-rays and high-LET carbon (12C) and iron (56Fe) ions was compared to reveal possible effects of space-relevant high-LET radiation. Since astronauts are exposed to ionizing radiation and microgravity during space missions, the effect of simulated microgravity on DNA damage induction and repair was investigated.MethodsPrimary murine cortical astrocytes were irradiated with different doses of X-rays, 12C and 56Fe ions at the heavy ion accelerator GSI. DNA damage and repair (γH2AX, 53BP1), cell proliferation (Ki-67), astrocytes' reactivity (GFAP) and NF-κB pathway activation (p65) were analyzed by immunofluorescence microscopy. Cell cycle progression was investigated by flow cytometry of DNA content. Gene expression changes after exposure to X- rays were investigated by mRNA-sequencing. RT-qPCR for several genes of interest was performed with RNA from X-rays- and heavy-ion-irradiated astrocytes: Cdkn1a, Cdkn2a, Gfap, Tnf, Il1β, Il6, and Tgfβ1. Levels of the pro inflammatory cytokine IL-6 were determined using ELISA. DNA damage response was investigated after exposure to X-rays followed by incubation on a 2D clinostat to simulate the conditions of microgravity.ResultsAstrocytes showed distinct responses toward the three different radiation qualities. Induction of radiation-induced DNA double strand breaks (DSBs) and the respective repair was dose-, LET- and time-dependent. Simulated microgravity had no significant influence on DNA DSB repair. Proliferation and cell cycle progression was not affected by radiation qualities examined in this study. Astrocytes expressed IL-6 and GFAP with constitutive NF-κB activity independent of radiation exposure. mRNA sequencing of X-irradiated astrocytes revealed downregulation of 66 genes involved in DNA damage response and repair, mitosis, proliferation and cell cycle regulation.DiscussionIn conclusion, primary murine astrocytes are DNA repair proficient irrespective of radiation quality. Only minor gene expression changes were observed after X-ray exposure and reactivity was not induced. Co-culture of astrocytes with microglial cells, brain organoids or organotypic brain slice culture experiments might reveal whether astrocytes show a more pronounced radiation response in more complex network architectures in the presence of other neuronal cell types.

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Angiotensin-(1-7) prevents radiation-induced inflammation in rat primary astrocytes through regulation of MAP kinase signaling.

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Angiotensin-(1-7) prevents radiation-induced inflammation in rat primary astrocytes through regulation of MAP kinase signaling.

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