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Inflammasome-IL-1β Signaling Mediates Ethanol Inhibition of Hippocampal Neurogenesis.

Zou J, Crews FT - Front Neurosci (2012)

Bottom Line: Ethanol and neuroinflammation are known to reduce neurogenesis.Blockade of IL-1β synthesis with inflammasome inhibitors Parthenolide and Bay11708 significantly reversed ethanol inhibited neurogenesis.Furthermore, we also found that IL-1β and inflammasome proteins NALP1 and NALP3 are increased in hippocampal neurons and astrocytes in postmortem alcoholic human brain.

View Article: PubMed Central - PubMed

Affiliation: Bowles Center for Alcohol Studies, The University of North Carolina at Chapel Hill Chapel Hill, NC, USA.

ABSTRACT
Regulation of hippocampal neurogenesis is poorly understood, but appears to contribute to mood and cognition. Ethanol and neuroinflammation are known to reduce neurogenesis. We have found that ethanol induces neuroinflammation supporting the hypothesis that ethanol induction of neuroinflammation contributes to ethanol inhibition of neurogenesis. To identify the key proinflammatory molecule that may be responsible for ethanol-impaired neurogenesis we used an ex vivo model of organotypic hippocampal-entorhinal cortex brain slice cultures. Here, we demonstrated a key role of proinflammatory cytokine IL-1β signaling in mediating ethanol inhibition of neurogenesis. Ethanol inhibition of neurogenesis was reversed by neutralizing antibody to IL-1β or blockade of the IL-1β receptor with antagonist IL-1RIa. Ethanol-impaired neurogenesis is associated with strong induction of IL-1β and inflammasome proteins NALP1 and NALP3 in both neurons and astrocytes. Blockade of IL-1β synthesis with inflammasome inhibitors Parthenolide and Bay11708 significantly reversed ethanol inhibited neurogenesis. Furthermore, we also found that IL-1β and inflammasome proteins NALP1 and NALP3 are increased in hippocampal neurons and astrocytes in postmortem alcoholic human brain. Together, these novel findings demonstrate that targeting inflammasome-IL-1β signaling can normalize ethanol-impaired hippocampal neurogenesis, which may have therapeutic implications for treatment of cognitive impairment associated with hippocampal dysfunction in alcoholics.

No MeSH data available.


Related in: MedlinePlus

Ethanol induction of inflammasomes in HEC slices. RT-PCR analysis shows that ethanol exposure persistently up-regulates inflammasome NALP1 mRNA (bar graph, top). Representative confocal images are shown for cellular expression of inflammasome NALP1 and NALP3. (A,B) Double fluorescent immunostaining with NALP1 (red) and neuronal cell marker NeuN (green) show ethanol induction of NALP1 in DG granule neurons (arrows) [(A) control; (B) ethanol, original magnification 20×; insert-80×]. (C,D) Double fluorescent immunostaining with NALP1 (red) and astrocyte neuronal marker GFAP (green) show ethanol induced strong induction of NALP1 in astrocytes (yellow, arrows) [(C) control; (D) ethanol, original magnification 20×; insert-80×]. (E,F) Double fluorescent immunostaining with NALP3 (green) and astrocyte marker GFAP (red) show ethanol induction of inflammasome NALP3 in astrocytes (yellow, arrows) [(E) control; (F) ethanol, original magnification 20×; insert-80×].
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Figure 7: Ethanol induction of inflammasomes in HEC slices. RT-PCR analysis shows that ethanol exposure persistently up-regulates inflammasome NALP1 mRNA (bar graph, top). Representative confocal images are shown for cellular expression of inflammasome NALP1 and NALP3. (A,B) Double fluorescent immunostaining with NALP1 (red) and neuronal cell marker NeuN (green) show ethanol induction of NALP1 in DG granule neurons (arrows) [(A) control; (B) ethanol, original magnification 20×; insert-80×]. (C,D) Double fluorescent immunostaining with NALP1 (red) and astrocyte neuronal marker GFAP (green) show ethanol induced strong induction of NALP1 in astrocytes (yellow, arrows) [(C) control; (D) ethanol, original magnification 20×; insert-80×]. (E,F) Double fluorescent immunostaining with NALP3 (green) and astrocyte marker GFAP (red) show ethanol induction of inflammasome NALP3 in astrocytes (yellow, arrows) [(E) control; (F) ethanol, original magnification 20×; insert-80×].

Mentions: The synthesis of IL-1β, a 17.5-kDa protein, occurs through proteolytic processing of a larger precursor protein by a group of proteins that oligomerize into a common structure that include activated caspase-1, NALP proteins, and others that form a multi-protein complex called the “inflammasome” (Chakraborty et al., 2010). Therefore, we investigated the effect of ethanol on inflammasome proteins. Ethanol progressively increased inflammasome NALP1 mRNA during 4–24 h of treatment that stabilized at twofold to threefold higher levels during 24–96 h of ethanol exposure (Figure 7, bar graph). Across multiple experiments, NALP1 mRNA level was increased by 2.5- to 7-fold by ethanol after 96 h. We could not determine NALP3 mRNA due to no published primers for rat, although we did have antibodies for IHC. Protein levels assessed using immunohistochemistry indicated ethanol increased NALP1 and NALP3 expression (Figure 7). Specific cell marker immunostaining revealed that ethanol induced NALP1 in both DG granule neurons (NeuN + IR) and astrocytes (GFAP + IR; Figures 7B,D) and NALP 3 in astrocytes (Figure 7F). Western blot analysis further indicates that protein levels of short form NALP1 and caspase-1 were increased by ethanol treatment (see Figure 8). These findings provide the first evidence that ethanol induces inflammasome proteins in HEC slices that increase IL-1β levels.


Inflammasome-IL-1β Signaling Mediates Ethanol Inhibition of Hippocampal Neurogenesis.

Zou J, Crews FT - Front Neurosci (2012)

Ethanol induction of inflammasomes in HEC slices. RT-PCR analysis shows that ethanol exposure persistently up-regulates inflammasome NALP1 mRNA (bar graph, top). Representative confocal images are shown for cellular expression of inflammasome NALP1 and NALP3. (A,B) Double fluorescent immunostaining with NALP1 (red) and neuronal cell marker NeuN (green) show ethanol induction of NALP1 in DG granule neurons (arrows) [(A) control; (B) ethanol, original magnification 20×; insert-80×]. (C,D) Double fluorescent immunostaining with NALP1 (red) and astrocyte neuronal marker GFAP (green) show ethanol induced strong induction of NALP1 in astrocytes (yellow, arrows) [(C) control; (D) ethanol, original magnification 20×; insert-80×]. (E,F) Double fluorescent immunostaining with NALP3 (green) and astrocyte marker GFAP (red) show ethanol induction of inflammasome NALP3 in astrocytes (yellow, arrows) [(E) control; (F) ethanol, original magnification 20×; insert-80×].
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Related In: Results  -  Collection

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Figure 7: Ethanol induction of inflammasomes in HEC slices. RT-PCR analysis shows that ethanol exposure persistently up-regulates inflammasome NALP1 mRNA (bar graph, top). Representative confocal images are shown for cellular expression of inflammasome NALP1 and NALP3. (A,B) Double fluorescent immunostaining with NALP1 (red) and neuronal cell marker NeuN (green) show ethanol induction of NALP1 in DG granule neurons (arrows) [(A) control; (B) ethanol, original magnification 20×; insert-80×]. (C,D) Double fluorescent immunostaining with NALP1 (red) and astrocyte neuronal marker GFAP (green) show ethanol induced strong induction of NALP1 in astrocytes (yellow, arrows) [(C) control; (D) ethanol, original magnification 20×; insert-80×]. (E,F) Double fluorescent immunostaining with NALP3 (green) and astrocyte marker GFAP (red) show ethanol induction of inflammasome NALP3 in astrocytes (yellow, arrows) [(E) control; (F) ethanol, original magnification 20×; insert-80×].
Mentions: The synthesis of IL-1β, a 17.5-kDa protein, occurs through proteolytic processing of a larger precursor protein by a group of proteins that oligomerize into a common structure that include activated caspase-1, NALP proteins, and others that form a multi-protein complex called the “inflammasome” (Chakraborty et al., 2010). Therefore, we investigated the effect of ethanol on inflammasome proteins. Ethanol progressively increased inflammasome NALP1 mRNA during 4–24 h of treatment that stabilized at twofold to threefold higher levels during 24–96 h of ethanol exposure (Figure 7, bar graph). Across multiple experiments, NALP1 mRNA level was increased by 2.5- to 7-fold by ethanol after 96 h. We could not determine NALP3 mRNA due to no published primers for rat, although we did have antibodies for IHC. Protein levels assessed using immunohistochemistry indicated ethanol increased NALP1 and NALP3 expression (Figure 7). Specific cell marker immunostaining revealed that ethanol induced NALP1 in both DG granule neurons (NeuN + IR) and astrocytes (GFAP + IR; Figures 7B,D) and NALP 3 in astrocytes (Figure 7F). Western blot analysis further indicates that protein levels of short form NALP1 and caspase-1 were increased by ethanol treatment (see Figure 8). These findings provide the first evidence that ethanol induces inflammasome proteins in HEC slices that increase IL-1β levels.

Bottom Line: Ethanol and neuroinflammation are known to reduce neurogenesis.Blockade of IL-1β synthesis with inflammasome inhibitors Parthenolide and Bay11708 significantly reversed ethanol inhibited neurogenesis.Furthermore, we also found that IL-1β and inflammasome proteins NALP1 and NALP3 are increased in hippocampal neurons and astrocytes in postmortem alcoholic human brain.

View Article: PubMed Central - PubMed

Affiliation: Bowles Center for Alcohol Studies, The University of North Carolina at Chapel Hill Chapel Hill, NC, USA.

ABSTRACT
Regulation of hippocampal neurogenesis is poorly understood, but appears to contribute to mood and cognition. Ethanol and neuroinflammation are known to reduce neurogenesis. We have found that ethanol induces neuroinflammation supporting the hypothesis that ethanol induction of neuroinflammation contributes to ethanol inhibition of neurogenesis. To identify the key proinflammatory molecule that may be responsible for ethanol-impaired neurogenesis we used an ex vivo model of organotypic hippocampal-entorhinal cortex brain slice cultures. Here, we demonstrated a key role of proinflammatory cytokine IL-1β signaling in mediating ethanol inhibition of neurogenesis. Ethanol inhibition of neurogenesis was reversed by neutralizing antibody to IL-1β or blockade of the IL-1β receptor with antagonist IL-1RIa. Ethanol-impaired neurogenesis is associated with strong induction of IL-1β and inflammasome proteins NALP1 and NALP3 in both neurons and astrocytes. Blockade of IL-1β synthesis with inflammasome inhibitors Parthenolide and Bay11708 significantly reversed ethanol inhibited neurogenesis. Furthermore, we also found that IL-1β and inflammasome proteins NALP1 and NALP3 are increased in hippocampal neurons and astrocytes in postmortem alcoholic human brain. Together, these novel findings demonstrate that targeting inflammasome-IL-1β signaling can normalize ethanol-impaired hippocampal neurogenesis, which may have therapeutic implications for treatment of cognitive impairment associated with hippocampal dysfunction in alcoholics.

No MeSH data available.


Related in: MedlinePlus