Interplay between inflammation and neural plasticity: Both immune activation and suppression impair LTP and BDNF expression

Brain Behav Immun. 2019 Oct;81:484-494. doi: 10.1016/j.bbi.2019.07.003. Epub 2019 Jul 4.

Abstract

An increasing number of studies show that both inflammation and neural plasticity act as key players in the vulnerability and recovery from psychiatric disorders and neurodegenerative diseases. However, the interplay between these two players has been limitedly explored. In fact, while a few studies reported an immune activation, others conveyed an immune suppression, associated with an impairment in neural plasticity. Therefore, we hypothesized that deviations in inflammatory levels in both directions may impair neural plasticity. We tested this hypothesis experimentally, by acute treatment of C57BL/6 adult male mice with different doses of two inflammatory modulators: lipopolysaccharide (LPS), an endotoxin, and ibuprofen (IBU), a nonselective cyclooxygenase inhibitor, which are respectively a pro- and an anti-inflammatory agent. The results showed that LPS and IBU have different effects on behavior and inflammatory response. LPS treatment induced a reduction of body temperature, a decrease of body weight and a reduced food and liquid intake. In addition, it led to increased levels of inflammatory markers expression, both in the total hippocampus and in isolated microglia cells, including Interleukin (IL)-1β, and enhanced the concentration of prostaglandin E2 (PGE2). On the other hand, IBU increased the level of anti-inflammatory markers, decreased tryptophan 2,3-dioxygenase (TDO2), the first step in the kynurenine pathway known to be activated during inflammatory conditions, and PGE2 levels. Though LPS and IBU administration differently affected mediators related with pro- or anti-inflammatory responses, they produced overlapping effects on neural plasticity. Indeed, higher doses of both LPS and IBU induced a statistically significant decrease in the amplitude of long-term potentiation (LTP), in Brain-Derived Neurotrophic Factor (BDNF) expression levels and in the phosphorylation of the AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor subunit GluR1, compared to the control group. Such effect appears to be dose-dependent since only the higher, but not the lower, dose of both compounds led to a plasticity impairment. Overall, the present findings indicate that acute treatment with pro- and anti-inflammatory agents impair neural plasticity in a dose dependent manner.

Keywords: Cytokines; IL-1β; Ibuprofen; Inflammatory level; LPS; LTP; NSAIDs; Neuroplasticity; Neurotrophin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Inflammatory Agents / pharmacology
  • Brain-Derived Neurotrophic Factor / biosynthesis*
  • Brain-Derived Neurotrophic Factor / metabolism
  • Cyclooxygenase Inhibitors / pharmacology
  • Cytokines / immunology
  • Cytokines / metabolism
  • Dinoprostone / metabolism
  • Hippocampus / drug effects
  • Hippocampus / metabolism
  • Ibuprofen / pharmacology
  • Inflammation / immunology
  • Inflammation / metabolism*
  • Interleukin-1beta / metabolism
  • Kynurenine / metabolism
  • Lipopolysaccharides / pharmacology
  • Long-Term Potentiation / drug effects
  • Long-Term Potentiation / physiology*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Microglia / drug effects
  • Microglia / metabolism
  • Neuronal Plasticity / immunology
  • Neuronal Plasticity / physiology*
  • Signal Transduction / drug effects
  • Tumor Necrosis Factor-alpha / immunology
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Anti-Inflammatory Agents
  • Bdnf protein, mouse
  • Brain-Derived Neurotrophic Factor
  • Cyclooxygenase Inhibitors
  • Cytokines
  • Interleukin-1beta
  • Lipopolysaccharides
  • Tumor Necrosis Factor-alpha
  • Kynurenine
  • Dinoprostone
  • Ibuprofen