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p38α (MAPK14) critically regulates the immunological response and the production of specific cytokines and chemokines in astrocytes.

Lo U, Selvaraj V, Plane JM, Chechneva OV, Otsu K, Deng W - Sci Rep (2014)

Bottom Line: We studied the role of p38α signaling in astrocyte immune activation both in vitro and in vivo, and simultaneously examined the effects of astrocyte activation in CNS inflammation.Our results showed that specific subsets of cytokines (TNFα, IL-6) and chemokines (CCL2, CCL4, CXCL1, CXCL2, CXCL10) are critically regulated by p38α signaling in astrocytes.Together, these studies provide important insights into the critical role of p38α signaling in astrocyte immune activation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Medicine, University of California, Davis, CA, USA.

ABSTRACT
In CNS lesions, "reactive astrocytes" form a prominent cellular response. However, the nature of this astrocyte immune activity is not well understood. In order to study astrocytic immune responses to inflammation and injury, we generated mice with conditional deletion of p38α (MAPK14) in GFAP+ astrocytes. We studied the role of p38α signaling in astrocyte immune activation both in vitro and in vivo, and simultaneously examined the effects of astrocyte activation in CNS inflammation. Our results showed that specific subsets of cytokines (TNFα, IL-6) and chemokines (CCL2, CCL4, CXCL1, CXCL2, CXCL10) are critically regulated by p38α signaling in astrocytes. In an in vivo CNS inflammation model of intracerebral injection of LPS, we observed markedly attenuated astrogliosis in conditional GFAPcre p38α(-/-) mice. However, GFAPcre p38α(-/-) mice showed marked upregulation of CCL2, CCL3, CCL4, CXCL2, CXCL10, TNFα, and IL-1β compared to p38αfl/fl cohorts, suggesting that in vivo responses to LPS after GFAPcre p38α deletion are complex and involve interactions between multiple cell types. This finding was supported by a prominent increase in macrophage/microglia and neutrophil recruitment in GFAPcre p38α(-/-) mice compared to p38αfl/fl controls. Together, these studies provide important insights into the critical role of p38α signaling in astrocyte immune activation.

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Microglia/macrophages at the CNS site of injury in GFAPCrep38α−/− mice after intracerebral LPS injection (A) After intracerebral LPS injection, CD11b mRNA showed significant upregulation in GFAPcre p38α−/− mice at 12 hours (p < 0.05); this upregulation was relatively moderate and not significant in p38αfl/fl cohorts. Comparison between genotypes showed a significantly higher CD11b expression in GFAPcrep38α−/− mice p38αfl/fl cohorts at 12 hours (p < 0.05). (B) Similarly, CD68 mRNA showed significant upregulation in GFAPcre p38α−/− mice at 12 hours after LPS injection (p < 0.05); this upregulation was relatively moderate and not significant in p38αfl/fl cohorts. Comparison between genotypes showed a significantly higher CD68 expression in GFAPcrep38α−/− mice compared to p38αfl/fl cohorts at 6 and 12 hours (p < 0.05). (C) Iba1 positive cells were distributed in the brain parenchyma and were not particularly clustered at the site of injury. A more prominent distribution of Iba1 positive microglia/macrophages were observed in GFAPcre p38α−/− mice compared to p38αfl/fl cohorts at 24 hours after intracerebral LPS injection (scale bar = 100 μm). (D) Numerical quantification of Iba1 positive cells showed a significant increase in their numbers in GFAPcre p38α−/− mice compared to p38αfl/fl control mice. *p < 0.05; data represent mean ± SEM.
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f10: Microglia/macrophages at the CNS site of injury in GFAPCrep38α−/− mice after intracerebral LPS injection (A) After intracerebral LPS injection, CD11b mRNA showed significant upregulation in GFAPcre p38α−/− mice at 12 hours (p < 0.05); this upregulation was relatively moderate and not significant in p38αfl/fl cohorts. Comparison between genotypes showed a significantly higher CD11b expression in GFAPcrep38α−/− mice p38αfl/fl cohorts at 12 hours (p < 0.05). (B) Similarly, CD68 mRNA showed significant upregulation in GFAPcre p38α−/− mice at 12 hours after LPS injection (p < 0.05); this upregulation was relatively moderate and not significant in p38αfl/fl cohorts. Comparison between genotypes showed a significantly higher CD68 expression in GFAPcrep38α−/− mice compared to p38αfl/fl cohorts at 6 and 12 hours (p < 0.05). (C) Iba1 positive cells were distributed in the brain parenchyma and were not particularly clustered at the site of injury. A more prominent distribution of Iba1 positive microglia/macrophages were observed in GFAPcre p38α−/− mice compared to p38αfl/fl cohorts at 24 hours after intracerebral LPS injection (scale bar = 100 μm). (D) Numerical quantification of Iba1 positive cells showed a significant increase in their numbers in GFAPcre p38α−/− mice compared to p38αfl/fl control mice. *p < 0.05; data represent mean ± SEM.

Mentions: Using CD11b and CD68 as specific markers for macrophages/microglia, we examined the inflammation site after intracerebral LPS injection in p38αfl/fl and GFAPcrep38α−/− mice. A significant upregulation of CD11b and CD68 mRNA was observed in GFAPcrep38α−/− mice that increased with time and peaked at 12 hours after intracerebral LPS injection (p < 0.05); a relatively moderate but also significant upregulation of CD11b and CD68 was also seen in the p38αfl/fl cohorts after LPS injection (p < 0.05). Interestingly, this upregulation of CD11b in GFAPcre p38α−/− mice was significantly higher than that observed in control p38αfl/fl mice at 6 hours after LPS injection (p < 0.05; Fig. 10A). However, while the CD11b expression level for both genotypes dropped down at 24 hours after LPS injection, we observed significantly lower CD11b levels in GFAPcre p38α−/− mice at this time point, compared to p38αfl/fl cohorts (p < 0.05; Fig. 10A). Corresponding with the expression pattern of CD11b, significantly higher expression levels of CD68 was observed in GFAPcrep38α−/− mice at 6 and 12 hours after LPS injection, compared to p38αfl/fl cohorts (p < 0.05; Fig. 10B). This observation corroborated that both primer sets accurately identified a specific cell type. Taken together, increased upregulation of CD11b and CD68 indicates either a more prominent CNS microglial proliferation and/or a greater number of macrophage infiltrations in the brain of GFAPcrep38α−/− mice. To examine the specific tissue pathologies associated with intracerebral LPS injections, we performed immunohistochemistry for Iba1-positive macrophages/microglia in the CNS of both GFAPcre p38α−/− and p38αfl/fl mice. Massive concentrations of macrophages/microglia were found present at the injection site in both p38αfl/fl and GFAPcre p38α−/− mice (Fig. 10C). Quantification of Iba1 positive cells in this immunopathology revealed that significantly higher number of macrophages/microglia were present in the brain parenchyma of GFAPcrep38α−/− mice compared to p38αfl/fl cohorts 24 hours after intracerebral LPS injection (p < 0.05; Fig. 10D). Together, the differential effects between GFAPcrep38α−/− and p38αfl/fl mice highlight an important facet for p38α signaling in CNS inflammation.


p38α (MAPK14) critically regulates the immunological response and the production of specific cytokines and chemokines in astrocytes.

Lo U, Selvaraj V, Plane JM, Chechneva OV, Otsu K, Deng W - Sci Rep (2014)

Microglia/macrophages at the CNS site of injury in GFAPCrep38α−/− mice after intracerebral LPS injection (A) After intracerebral LPS injection, CD11b mRNA showed significant upregulation in GFAPcre p38α−/− mice at 12 hours (p < 0.05); this upregulation was relatively moderate and not significant in p38αfl/fl cohorts. Comparison between genotypes showed a significantly higher CD11b expression in GFAPcrep38α−/− mice p38αfl/fl cohorts at 12 hours (p < 0.05). (B) Similarly, CD68 mRNA showed significant upregulation in GFAPcre p38α−/− mice at 12 hours after LPS injection (p < 0.05); this upregulation was relatively moderate and not significant in p38αfl/fl cohorts. Comparison between genotypes showed a significantly higher CD68 expression in GFAPcrep38α−/− mice compared to p38αfl/fl cohorts at 6 and 12 hours (p < 0.05). (C) Iba1 positive cells were distributed in the brain parenchyma and were not particularly clustered at the site of injury. A more prominent distribution of Iba1 positive microglia/macrophages were observed in GFAPcre p38α−/− mice compared to p38αfl/fl cohorts at 24 hours after intracerebral LPS injection (scale bar = 100 μm). (D) Numerical quantification of Iba1 positive cells showed a significant increase in their numbers in GFAPcre p38α−/− mice compared to p38αfl/fl control mice. *p < 0.05; data represent mean ± SEM.
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Related In: Results  -  Collection

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f10: Microglia/macrophages at the CNS site of injury in GFAPCrep38α−/− mice after intracerebral LPS injection (A) After intracerebral LPS injection, CD11b mRNA showed significant upregulation in GFAPcre p38α−/− mice at 12 hours (p < 0.05); this upregulation was relatively moderate and not significant in p38αfl/fl cohorts. Comparison between genotypes showed a significantly higher CD11b expression in GFAPcrep38α−/− mice p38αfl/fl cohorts at 12 hours (p < 0.05). (B) Similarly, CD68 mRNA showed significant upregulation in GFAPcre p38α−/− mice at 12 hours after LPS injection (p < 0.05); this upregulation was relatively moderate and not significant in p38αfl/fl cohorts. Comparison between genotypes showed a significantly higher CD68 expression in GFAPcrep38α−/− mice compared to p38αfl/fl cohorts at 6 and 12 hours (p < 0.05). (C) Iba1 positive cells were distributed in the brain parenchyma and were not particularly clustered at the site of injury. A more prominent distribution of Iba1 positive microglia/macrophages were observed in GFAPcre p38α−/− mice compared to p38αfl/fl cohorts at 24 hours after intracerebral LPS injection (scale bar = 100 μm). (D) Numerical quantification of Iba1 positive cells showed a significant increase in their numbers in GFAPcre p38α−/− mice compared to p38αfl/fl control mice. *p < 0.05; data represent mean ± SEM.
Mentions: Using CD11b and CD68 as specific markers for macrophages/microglia, we examined the inflammation site after intracerebral LPS injection in p38αfl/fl and GFAPcrep38α−/− mice. A significant upregulation of CD11b and CD68 mRNA was observed in GFAPcrep38α−/− mice that increased with time and peaked at 12 hours after intracerebral LPS injection (p < 0.05); a relatively moderate but also significant upregulation of CD11b and CD68 was also seen in the p38αfl/fl cohorts after LPS injection (p < 0.05). Interestingly, this upregulation of CD11b in GFAPcre p38α−/− mice was significantly higher than that observed in control p38αfl/fl mice at 6 hours after LPS injection (p < 0.05; Fig. 10A). However, while the CD11b expression level for both genotypes dropped down at 24 hours after LPS injection, we observed significantly lower CD11b levels in GFAPcre p38α−/− mice at this time point, compared to p38αfl/fl cohorts (p < 0.05; Fig. 10A). Corresponding with the expression pattern of CD11b, significantly higher expression levels of CD68 was observed in GFAPcrep38α−/− mice at 6 and 12 hours after LPS injection, compared to p38αfl/fl cohorts (p < 0.05; Fig. 10B). This observation corroborated that both primer sets accurately identified a specific cell type. Taken together, increased upregulation of CD11b and CD68 indicates either a more prominent CNS microglial proliferation and/or a greater number of macrophage infiltrations in the brain of GFAPcrep38α−/− mice. To examine the specific tissue pathologies associated with intracerebral LPS injections, we performed immunohistochemistry for Iba1-positive macrophages/microglia in the CNS of both GFAPcre p38α−/− and p38αfl/fl mice. Massive concentrations of macrophages/microglia were found present at the injection site in both p38αfl/fl and GFAPcre p38α−/− mice (Fig. 10C). Quantification of Iba1 positive cells in this immunopathology revealed that significantly higher number of macrophages/microglia were present in the brain parenchyma of GFAPcrep38α−/− mice compared to p38αfl/fl cohorts 24 hours after intracerebral LPS injection (p < 0.05; Fig. 10D). Together, the differential effects between GFAPcrep38α−/− and p38αfl/fl mice highlight an important facet for p38α signaling in CNS inflammation.

Bottom Line: We studied the role of p38α signaling in astrocyte immune activation both in vitro and in vivo, and simultaneously examined the effects of astrocyte activation in CNS inflammation.Our results showed that specific subsets of cytokines (TNFα, IL-6) and chemokines (CCL2, CCL4, CXCL1, CXCL2, CXCL10) are critically regulated by p38α signaling in astrocytes.Together, these studies provide important insights into the critical role of p38α signaling in astrocyte immune activation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Medicine, University of California, Davis, CA, USA.

ABSTRACT
In CNS lesions, "reactive astrocytes" form a prominent cellular response. However, the nature of this astrocyte immune activity is not well understood. In order to study astrocytic immune responses to inflammation and injury, we generated mice with conditional deletion of p38α (MAPK14) in GFAP+ astrocytes. We studied the role of p38α signaling in astrocyte immune activation both in vitro and in vivo, and simultaneously examined the effects of astrocyte activation in CNS inflammation. Our results showed that specific subsets of cytokines (TNFα, IL-6) and chemokines (CCL2, CCL4, CXCL1, CXCL2, CXCL10) are critically regulated by p38α signaling in astrocytes. In an in vivo CNS inflammation model of intracerebral injection of LPS, we observed markedly attenuated astrogliosis in conditional GFAPcre p38α(-/-) mice. However, GFAPcre p38α(-/-) mice showed marked upregulation of CCL2, CCL3, CCL4, CXCL2, CXCL10, TNFα, and IL-1β compared to p38αfl/fl cohorts, suggesting that in vivo responses to LPS after GFAPcre p38α deletion are complex and involve interactions between multiple cell types. This finding was supported by a prominent increase in macrophage/microglia and neutrophil recruitment in GFAPcre p38α(-/-) mice compared to p38αfl/fl controls. Together, these studies provide important insights into the critical role of p38α signaling in astrocyte immune activation.

Show MeSH
Related in: MedlinePlus