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Evidence for inflammation-mediated memory dysfunction in gastropods: putative PLA2 and COX inhibitors abolish long-term memory failure induced by systemic immune challenges.

Hermann PM, Park D, Beaulieu E, Wildering WC - BMC Neurosci (2013)

Bottom Line: This study investigated the effect of biologically realistic challenges of L. stagnalis host defense response system on LTM function and potential involvement of PLA2, COX and LOX therein.This effect dissipated within 24 hrs after treatment.Our findings underwrite the rapidly expanding view of neuroinflammatory processes as a fundamental, evolutionary conserved cause of cognitive and other nervous system disorders.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB T2N 1N4, Canada.

ABSTRACT

Background: Previous studies associate lipid peroxidation with long-term memory (LTM) failure in a gastropod model (Lymnaea stagnalis) of associative learning and memory. This process involves activation of Phospholipase A2 (PLA2), an enzyme mediating the release of fatty acids such as arachidonic acid that form the precursor for a variety of pro-inflammatory lipid metabolites. This study investigated the effect of biologically realistic challenges of L. stagnalis host defense response system on LTM function and potential involvement of PLA2, COX and LOX therein.

Results: Systemic immune challenges by means of β-glucan laminarin injections induced elevated H2O2 release from L. stagnalis circulatory immune cells within 3 hrs of treatment. This effect dissipated within 24 hrs after treatment. Laminarin exposure has no direct effect on neuronal activity. Laminarin injections disrupted LTM formation if training followed within 1 hr after injection but had no behavioural impact if training started 24 hrs after treatment. Intermediate term memory was not affected by laminarin injection. Chemosensory and motor functions underpinning the feeding response involved in this learning model were not affected by laminarin injection. Laminarin's suppression of LTM induction was reversed by treatment with aristolochic acid, a PLA2 inhibitor, or indomethacin, a putative COX inhibitor, but not by treatment with nordihydro-guaiaretic acid, a putative LOX inhibitor.

Conclusions: A systemic immune challenge administered shortly before behavioural training impairs associative LTM function in our model that can be countered with putative inhibitors of PLA2 and COX, but not LOX. As such, this study establishes a mechanistic link between the state of activity of this gastropod's innate immune system and higher order nervous system function. Our findings underwrite the rapidly expanding view of neuroinflammatory processes as a fundamental, evolutionary conserved cause of cognitive and other nervous system disorders.

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No effect of aristolochic acid or indomethacin on laminarin induced H2O2 release by haemocytes. Isolated haemocytes pre-incubated for 30 minutes with either aristolochic acid or indomethacin before being challenged with laminarin showed a similar H2O2 production compared to haemocytes pre-treated with vehicle only.
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Figure 8: No effect of aristolochic acid or indomethacin on laminarin induced H2O2 release by haemocytes. Isolated haemocytes pre-incubated for 30 minutes with either aristolochic acid or indomethacin before being challenged with laminarin showed a similar H2O2 production compared to haemocytes pre-treated with vehicle only.

Mentions: The effects of aristolochic acid and indomethacin described above may arise from inhibition of laminarin-induced processes at the level of immunocytes or the level of the nervous system. Thus next we explicitly tested the former possibility by measuring the impact of both compounds on laminarin induced H2O2 release by isolated haemocytes. Amplex Red fluorescence was very similar in laminarin activated haemocytes that were pre-treated with either aristolochic acid or indomethacin when compared to haemocytes pre-treated with vehicle-only (Figure 8; ANOVA; F2,8 = 0.401, p = 0.69).


Evidence for inflammation-mediated memory dysfunction in gastropods: putative PLA2 and COX inhibitors abolish long-term memory failure induced by systemic immune challenges.

Hermann PM, Park D, Beaulieu E, Wildering WC - BMC Neurosci (2013)

No effect of aristolochic acid or indomethacin on laminarin induced H2O2 release by haemocytes. Isolated haemocytes pre-incubated for 30 minutes with either aristolochic acid or indomethacin before being challenged with laminarin showed a similar H2O2 production compared to haemocytes pre-treated with vehicle only.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750374&req=5

Figure 8: No effect of aristolochic acid or indomethacin on laminarin induced H2O2 release by haemocytes. Isolated haemocytes pre-incubated for 30 minutes with either aristolochic acid or indomethacin before being challenged with laminarin showed a similar H2O2 production compared to haemocytes pre-treated with vehicle only.
Mentions: The effects of aristolochic acid and indomethacin described above may arise from inhibition of laminarin-induced processes at the level of immunocytes or the level of the nervous system. Thus next we explicitly tested the former possibility by measuring the impact of both compounds on laminarin induced H2O2 release by isolated haemocytes. Amplex Red fluorescence was very similar in laminarin activated haemocytes that were pre-treated with either aristolochic acid or indomethacin when compared to haemocytes pre-treated with vehicle-only (Figure 8; ANOVA; F2,8 = 0.401, p = 0.69).

Bottom Line: This study investigated the effect of biologically realistic challenges of L. stagnalis host defense response system on LTM function and potential involvement of PLA2, COX and LOX therein.This effect dissipated within 24 hrs after treatment.Our findings underwrite the rapidly expanding view of neuroinflammatory processes as a fundamental, evolutionary conserved cause of cognitive and other nervous system disorders.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Faculty of Science, University of Calgary, Calgary, AB T2N 1N4, Canada.

ABSTRACT

Background: Previous studies associate lipid peroxidation with long-term memory (LTM) failure in a gastropod model (Lymnaea stagnalis) of associative learning and memory. This process involves activation of Phospholipase A2 (PLA2), an enzyme mediating the release of fatty acids such as arachidonic acid that form the precursor for a variety of pro-inflammatory lipid metabolites. This study investigated the effect of biologically realistic challenges of L. stagnalis host defense response system on LTM function and potential involvement of PLA2, COX and LOX therein.

Results: Systemic immune challenges by means of β-glucan laminarin injections induced elevated H2O2 release from L. stagnalis circulatory immune cells within 3 hrs of treatment. This effect dissipated within 24 hrs after treatment. Laminarin exposure has no direct effect on neuronal activity. Laminarin injections disrupted LTM formation if training followed within 1 hr after injection but had no behavioural impact if training started 24 hrs after treatment. Intermediate term memory was not affected by laminarin injection. Chemosensory and motor functions underpinning the feeding response involved in this learning model were not affected by laminarin injection. Laminarin's suppression of LTM induction was reversed by treatment with aristolochic acid, a PLA2 inhibitor, or indomethacin, a putative COX inhibitor, but not by treatment with nordihydro-guaiaretic acid, a putative LOX inhibitor.

Conclusions: A systemic immune challenge administered shortly before behavioural training impairs associative LTM function in our model that can be countered with putative inhibitors of PLA2 and COX, but not LOX. As such, this study establishes a mechanistic link between the state of activity of this gastropod's innate immune system and higher order nervous system function. Our findings underwrite the rapidly expanding view of neuroinflammatory processes as a fundamental, evolutionary conserved cause of cognitive and other nervous system disorders.

Show MeSH
Related in: MedlinePlus