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Kainic acid-induced microglial activation is attenuated in aged interleukin-18 deficient mice.

Zhang XM, Jin T, Quezada HC, Mix E, Winblad B, Zhu J - J Neuroinflammation (2010)

Bottom Line: Additionally, IL-18 participates in fundamental inflammatory processes that increase during aging.Seven days after KA treatment, degenerating neurons were detected by Nissl's method and Fluoro-Jade B staining; and microglial activation was analyzed by immunohistochemistry and flow cytometry.Deficiency of IL-18 attenuates microglial activation after KA-induced excitotoxicity in aged brain, while the net effects of IL-18 deficiency are balanced by the enhancement of other cytokines, such as TNF-alpha, IL-6 and IL-10.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurobiology, Care Sciences and Society, Karolinska Institute, Stockholm, Sweden. xingmei.zhang@ki.se

ABSTRACT

Background: Previously, we found that interleukin (IL)-18 deficiency aggravates kainic acid (KA)-induced hippocampal neurodegeneration in young C57BL/6 mice due to an over-compensation by IL-12. Additionally, IL-18 participates in fundamental inflammatory processes that increase during aging. In the present study, we were interested in the role of IL-18 in KA-induced neurodegeneration in aged female C57BL/6 mice.

Methods: Fifteen aged female IL-18 knockout (KO) and 15 age-matched wild-type (WT) mice (18 to 19 months old) were treated with KA at a dose of 25 mg/kg body weight intranasally. Seizure activities and behavioral changes were rated using a 6-point scoring system and open-field test, respectively. Seven days after KA treatment, degenerating neurons were detected by Nissl's method and Fluoro-Jade B staining; and microglial activation was analyzed by immunohistochemistry and flow cytometry.

Results: Aged female IL-18 KO and WT mice showed similar responses to treatment with KA as demonstrated by comparable seizure activities, behavioral changes and neuronal cell death. However, aged female IL-18 KO mice failed to exhibit the strong microglial activation shown in WT mice. Interestingly, even though the number of activated microglia was less in KA-treated IL-18 KO mice than in KA-treated WT mice, the proportion of microglia that expressed the cytokines tumor necrosis factor (TNF)-alpha, IL-6 and IL-10 was higher in KA-treated IL-18 KO mice.

Conclusion: Deficiency of IL-18 attenuates microglial activation after KA-induced excitotoxicity in aged brain, while the net effects of IL-18 deficiency are balanced by the enhancement of other cytokines, such as TNF-alpha, IL-6 and IL-10.

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CD11b and MHC-II expression in hippocampi of aged female mice detected by immunohistochemistry and flow cytometry. Seven days after KA treatment, the number of activated microglia was greater in WT mice (A) than in IL-18 KO mice (B) with similar neuropathological changes. Very few activated microglia were found in the hippocampi of saline-treated mice (C) and negative controls with omission of the primary antibody showed no positive staining (D). CD11b positive cells were shown as dark brown in color. By flow cytometry, microglia of hippocampi were identified as a homogeneous population of CD11b+/CD45low/moderatecells (E). The proportion of MHC-II positive cells was higher in WT mice (n = 5) than in IL-18 KO mice (n = 6) after KA treatment. Before KA delivery, there was no difference of MHC-II positive cells between the two groups (F). *P < 0.05. Bars = 100 μm.
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Figure 4: CD11b and MHC-II expression in hippocampi of aged female mice detected by immunohistochemistry and flow cytometry. Seven days after KA treatment, the number of activated microglia was greater in WT mice (A) than in IL-18 KO mice (B) with similar neuropathological changes. Very few activated microglia were found in the hippocampi of saline-treated mice (C) and negative controls with omission of the primary antibody showed no positive staining (D). CD11b positive cells were shown as dark brown in color. By flow cytometry, microglia of hippocampi were identified as a homogeneous population of CD11b+/CD45low/moderatecells (E). The proportion of MHC-II positive cells was higher in WT mice (n = 5) than in IL-18 KO mice (n = 6) after KA treatment. Before KA delivery, there was no difference of MHC-II positive cells between the two groups (F). *P < 0.05. Bars = 100 μm.

Mentions: Microglia are the main effector cells of the immune system in the central nervous system (CNS). We evaluated microglial activation by detection of the expression of CD11b and MHC-II by immunohistochemistry and flow cytometry. CD11b can detect both resting and activated microglia, while strong CD11b-immunreactive microglia show a marked cellular hypertrophy with thicker and shorter processes. Seven days after KA delivery, although both groups of mice exhibited microglial activation, the number of activated microglia of WT mice (Fig. 4A) was consistently higher than in IL-18 KO mice (Fig. 4B). Very few activated microglia were found in the hippocampi of saline-treated mice (Fig. 4C) and the negative controls with omission of the primary antibody showed no positive staining (Fig. 4D).


Kainic acid-induced microglial activation is attenuated in aged interleukin-18 deficient mice.

Zhang XM, Jin T, Quezada HC, Mix E, Winblad B, Zhu J - J Neuroinflammation (2010)

CD11b and MHC-II expression in hippocampi of aged female mice detected by immunohistochemistry and flow cytometry. Seven days after KA treatment, the number of activated microglia was greater in WT mice (A) than in IL-18 KO mice (B) with similar neuropathological changes. Very few activated microglia were found in the hippocampi of saline-treated mice (C) and negative controls with omission of the primary antibody showed no positive staining (D). CD11b positive cells were shown as dark brown in color. By flow cytometry, microglia of hippocampi were identified as a homogeneous population of CD11b+/CD45low/moderatecells (E). The proportion of MHC-II positive cells was higher in WT mice (n = 5) than in IL-18 KO mice (n = 6) after KA treatment. Before KA delivery, there was no difference of MHC-II positive cells between the two groups (F). *P < 0.05. Bars = 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 4: CD11b and MHC-II expression in hippocampi of aged female mice detected by immunohistochemistry and flow cytometry. Seven days after KA treatment, the number of activated microglia was greater in WT mice (A) than in IL-18 KO mice (B) with similar neuropathological changes. Very few activated microglia were found in the hippocampi of saline-treated mice (C) and negative controls with omission of the primary antibody showed no positive staining (D). CD11b positive cells were shown as dark brown in color. By flow cytometry, microglia of hippocampi were identified as a homogeneous population of CD11b+/CD45low/moderatecells (E). The proportion of MHC-II positive cells was higher in WT mice (n = 5) than in IL-18 KO mice (n = 6) after KA treatment. Before KA delivery, there was no difference of MHC-II positive cells between the two groups (F). *P < 0.05. Bars = 100 μm.
Mentions: Microglia are the main effector cells of the immune system in the central nervous system (CNS). We evaluated microglial activation by detection of the expression of CD11b and MHC-II by immunohistochemistry and flow cytometry. CD11b can detect both resting and activated microglia, while strong CD11b-immunreactive microglia show a marked cellular hypertrophy with thicker and shorter processes. Seven days after KA delivery, although both groups of mice exhibited microglial activation, the number of activated microglia of WT mice (Fig. 4A) was consistently higher than in IL-18 KO mice (Fig. 4B). Very few activated microglia were found in the hippocampi of saline-treated mice (Fig. 4C) and the negative controls with omission of the primary antibody showed no positive staining (Fig. 4D).

Bottom Line: Additionally, IL-18 participates in fundamental inflammatory processes that increase during aging.Seven days after KA treatment, degenerating neurons were detected by Nissl's method and Fluoro-Jade B staining; and microglial activation was analyzed by immunohistochemistry and flow cytometry.Deficiency of IL-18 attenuates microglial activation after KA-induced excitotoxicity in aged brain, while the net effects of IL-18 deficiency are balanced by the enhancement of other cytokines, such as TNF-alpha, IL-6 and IL-10.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurobiology, Care Sciences and Society, Karolinska Institute, Stockholm, Sweden. xingmei.zhang@ki.se

ABSTRACT

Background: Previously, we found that interleukin (IL)-18 deficiency aggravates kainic acid (KA)-induced hippocampal neurodegeneration in young C57BL/6 mice due to an over-compensation by IL-12. Additionally, IL-18 participates in fundamental inflammatory processes that increase during aging. In the present study, we were interested in the role of IL-18 in KA-induced neurodegeneration in aged female C57BL/6 mice.

Methods: Fifteen aged female IL-18 knockout (KO) and 15 age-matched wild-type (WT) mice (18 to 19 months old) were treated with KA at a dose of 25 mg/kg body weight intranasally. Seizure activities and behavioral changes were rated using a 6-point scoring system and open-field test, respectively. Seven days after KA treatment, degenerating neurons were detected by Nissl's method and Fluoro-Jade B staining; and microglial activation was analyzed by immunohistochemistry and flow cytometry.

Results: Aged female IL-18 KO and WT mice showed similar responses to treatment with KA as demonstrated by comparable seizure activities, behavioral changes and neuronal cell death. However, aged female IL-18 KO mice failed to exhibit the strong microglial activation shown in WT mice. Interestingly, even though the number of activated microglia was less in KA-treated IL-18 KO mice than in KA-treated WT mice, the proportion of microglia that expressed the cytokines tumor necrosis factor (TNF)-alpha, IL-6 and IL-10 was higher in KA-treated IL-18 KO mice.

Conclusion: Deficiency of IL-18 attenuates microglial activation after KA-induced excitotoxicity in aged brain, while the net effects of IL-18 deficiency are balanced by the enhancement of other cytokines, such as TNF-alpha, IL-6 and IL-10.

Show MeSH
Related in: MedlinePlus