TLR3 deficiency increases voluntary alcohol consumption

Ethanol induces interferon expression in neurons via TRAIL: role of astrocyte-to-neuron signaling

RATIONALE

Alcohol use disorder (AUD) involves dysregulation of innate immune signaling in brain. Toll-like receptor 3 (TLR3), an innate immune receptor that is upregulated in post-mortem human alcoholics, leads to induction of interferon (IFN) signaling. IFNs have been linked to depressive-like symptoms and therefore may play a role in addiction pathology. Astrocyte-neuronal signaling may contribute to maladaptation of neuronal circuits.

OBJECTIVES

In this manuscript, we examine ethanol (EtOH) induction of IFN signaling in neuronal, astrocyte, and microglial cell lines and assess astrocyte-neuronal interactions.

METHODS

U373 astrocytes, SH-SY5Y neurons, and BV2 microglia were treated with EtOH and analyzed for autocrine/paracrine IFN signaling.

RESULTS

EtOH induced TLR3, IFNβ, and IFNγ in SH-SY5Y neurons and U373 astrocytes, but not in BV2 microglia. The IFN response gene TRAIL was also strongly upregulated by TLR3 agonist Poly(I:C) and EtOH in U373 astrocytes. TRAIL blockage via neutralizing antibody prevented induction of IFNs in SH-SY5Y neurons but not in U373 astrocytes. Blocking TRAIL in conditioned media from EtOH-treated astrocytes prevented induction of IFNs in SH-SY5Y neurons. Finally, an in vivo model of chronic 10-day binge EtOH exposure in C57BL6/J mice, as well as single acute treatment with Poly(I:C), showed increased TRAIL +IR cells in both orbitofrontal and entorhinal cortex.

CONCLUSIONS

This study establishes a role of astrocyte to neuron TRAIL release in EtOH-induced IFN responses. This may contribute to alcohol associated negative affect and suggest potential therapeutic benefit of TRAIL inhibition in AUD.

Lyme and Dopaminergic Function: Hypothesizing Reduced Reward Deficiency Symptomatology by Regulating Dopamine Transmission

The principal vector of Lyme disease in the United States is Ixodes scapularis: black legged or deer ticks. There is increased evidence that those infected may be plagued by anxiety or depression as well. Researchers have identified transcripts coding for two putative cytosolic sulfotransferases in these ticks, which recognized phenolic monoamines as their substrates. It is hypothesized that protracted Lyme disease sequelae may be due to impairment of dopaminergic function of the brain reward circuitry. The subsequent recombinant proteins exhibited sulfotransferase function against two neurotransmitters: dopamine and octopamine. This, in itself, can reduce dopamine function leading to many Reward Deficiency Syndrome behaviors, including depression and possibly, anxiety. In fact, it was shown that activity of Ixosc Sult 1 and Sult 2 in the Ixodid tick salivary glands might contain inactivation of the salivation signal through sulfonation of either dopamine or octopamine. This infraction results in a number of clinically observed mood changes, such as anxiety and depression. In fact, there are common symptoms observed for both Parkinson and Lyme diseases. The importance of understanding the mechanistic and neurobiological effects of Lyme on the central nervous system (CNS) provides the basis for pro-dopamine regulation as a treatment. WC 195

Ethanol, TLR3, and TLR4 Agonists Have Unique Innate Immune Responses in Neuron-Like SH-SY5Y and Microglia-Like BV2

BACKGROUND

Ethanol (EtOH) consumption leads to an increase of proinflammatory signaling via activation of Toll-like receptors (TLRs) such as TLR3 and TLR4 that leads to kinase activation (ERK1/2, p38, TBK1), transcription factor activation (NFκB, IRF3), and increased transcription of proinflammatory cytokines such as TNF-α, IL-1β, and IL-6. This immune signaling cascade is thought to play a role in neurodegeneration and alcohol use disorders. While microglia are considered to be the primary macrophage in brain, it is unclear what if any role neurons play in EtOH-induced proinflammatory signaling.

METHODS

Microglia-like BV2 and retinoic acid-differentiated neuron-like SH-SY5Y were treated with TLR3 agonist Poly(I:C), TLR4 agonist lipopolysaccharide (LPS), or EtOH for 10 or 30 minutes to examine proinflammatory immune signaling kinase and transcription factor activation using Western blot, and for 24 hours to examine induction of proinflammatory gene mRNA using RT-PCR.

RESULTS

In BV2, both LPS and Poly(I:C) increased p-ERK1/2, p-p38, and p-NFκB by 30 minutes, whereas EtOH decreased p-ERK1/2 and increased p-IRF3. LPS, Poly(I:C), and EtOH all increased TNF-α and IL-1β mRNA, and EtOH further increased TLR2, 7, 8, and MD-2 mRNA in BV2. In SH-SY5Y, LPS had no effect on kinase or proinflammatory gene expression. However, Poly(I:C) increased p-p38 and p-IRF3, and increased expression of TNF-α, IL-1β, and IL-6, while EtOH increased p-p38, p-IRF3, p-TBK1, and p-NFκB while decreasing p-ERK1/2 and increasing expression of TLR3, 7, 8, and RAGE mRNA. HMGB1, a TLR agonist, was induced by LPS in BV2 and by EtOH in both cell types. EtOH was more potent at inducing proinflammatory gene mRNA in SH-SY5Y compared with BV2.

CONCLUSIONS

These results support a novel and unique mechanism of EtOH, TLR3, and TLR4 signaling in neuron-like SH-SY5Y and microglia-like BV2 that likely contributes to the complexity of brain neuroimmune signaling.