Infection with the protozoan Toxoplasma gondii induces changes in neurotransmission, neuroinflammation, and behavior, yet it remains elusive how these changes come about. In this study we investigated how norepinephrine levels are altered by infection. TINEV (Toxoplasma-induced neuronal extracellular vesicles) isolated from infected noradrenergic cells down-regulated dopamine ß-hydroxylase (DBH) gene expression in human and rodent cells. Here we report that intracerebral injection of TINEVs into the brain is sufficient to induce DBH down-regulation and distrupt catecholaminergic signalling. Further, TINEV treatment induced hypermethylation upstream of the DBH gene. An antisense lncRNA to DBH was found in purified TINEV preparations. Paracrine signalling to induce transcriptional gene silencing and DNA methylation may be a common mode to regulate neurologic function.

Infection with the protozoan Toxoplasma gondii induces changes in neurotransmission, neuroinflammation, and behavior, yet it remains elusive how these changes come about. In this study we investigated how norepinephrine levels are altered by infection. TINEV (Toxoplasma-induced neuronal extracellular vesicles) isolated from infected noradrenergic cells down-regulated dopamine ß-hydroxylase (DBH) gene expression in human and rodent cells. Here we report that intracerebral injection of TINEVs into the brain is sufficient to induce DBH down-regulation and distrupt catecholaminergic signalling. Further, TINEV treatment induced hypermethylation upstream of the DBH gene. An antisense lncRNA to DBH was found in purified TINEV preparations. Paracrine signalling to induce transcriptional gene silencing and DNA methylation may be a common mode to regulate neurologic function.

Infection with the protozoan Toxoplasma gondii induces changes in neurotransmission, neuroinflammation, and behavior. Yet, it remains elusive how these changes are wrought by the small percentage of neurons that are infected. In this study we investigated how neurotransmission is altered in uninfected neurons during infection by studying suppression of noradrenergic signalling. Noradrenergic signalling is central in modulating the neuroinflammatory response. Previous studies found decreased norepinephrine and down-regulation of the synthetic enzyme dopamine ß-hydroxylase (DBH) during chronic infection. Here, extracellular vesicles (ie. exosomes) were isolated from infected cultures that induced transcriptional gene silencing of DBH and DNA hypermethylation upstream of the DBH gene. Intracerebral injection of these extracellular vesicles induced DBH down-regulation in the locus coeruleus region of the brain and contained an antisense lncRNA. Thus, global changes invoked by signals released from infected neural cells may help explain the parasite-induced behavior changes. This novel form of paracrine signalling may apply to other neurotropic infections and enhance our understanding of regulation of neurologic functions.