The selective anti-IL17A monoclonal antibody secukinumab (AIN457) attenuates IL17A-induced levels of IL6 in human astrocytes.

The family of interleukin 17 receptors (IL17Rs), subtypes IL17RA-IL17RE, is targeted by the group of pro-inflammatory IL17 cytokines (IL17A-F) and moreover the newly developed anti-IL17A antibody secukinumab (AIN457) has shown promise in Phase II trials in multiple sclerosis. Here, we show that human astrocytes, isolated from a fetal cerebral cortex, express IL17RA and IL17RC and in vitro treatment with IL17A increases protein levels of IL6 in human astrocytes, which is enhanced in the presence of TNFα, as determined by homogeneous time resolved fluorescence. Studies on acutely isolated mouse astrocytes are comparable to human astrocytes although the protein levels of IL6 are lower in mouse astrocytes, which also show a lower response to IL17F and IL1ß in promoting IL6 levels. In human astrocytes, IL17A and TNFα also induce mRNA expression of IL6, IL8 and the Th17 cytokines CXCL1, CXCL2, and CCL20, with little effect on Th1 cytokines CXCL9, CXCL10, and CXCL11. The effects of IL17A are associated with nuclear translocation of the NF-κB transcription factor, as determined by immunocytochemistry, where treatment of human astrocytes with the inhibitors of the NF-κB pathway and with secukinumab inhibits the IL17A and IL17A/TNFα-induced increase in nuclear translocation of NF-κB and levels of IL6. Taken together the data shows that IL17A signaling plays a key role in regulating the levels of cytokines, such as IL6, in human astrocytes via a mechanism that involves NF-κB signaling and that selective inhibition of IL17A signaling attenuates levels of pro-inflammatory molecules in astrocytes.

Brain-specific overexpression of trace amine-associated receptor 1 alters monoaminergic neurotransmission and decreases sensitivity to amphetamine.

Trace amines (TAs) such as ß-phenylethylamine, p-tyramine, or tryptamine are biogenic amines found in the brain at low concentrations that have been implicated in various neuropsychiatric disorders like schizophrenia, depression, or attention deficit hyperactivity disorder. TAs are ligands for the recently identified trace amine-associated receptor 1 (TAAR1), an important modulator of monoamine neurotransmission. Here, we sought to investigate the consequences of TAAR1 hypersignaling by generating a transgenic mouse line overexpressing Taar1 specifically in neurons. Taar1 transgenic mice did not show overt behavioral abnormalities under baseline conditions, despite augmented extracellular levels of dopamine and noradrenaline in the accumbens nucleus (Acb) and of serotonin in the medial prefrontal cortex. In vitro, this was correlated with an elevated spontaneous firing rate of monoaminergic neurons in the ventral tegmental area, dorsal raphe nucleus, and locus coeruleus as the result of ectopic TAAR1 expression. Furthermore, Taar1 transgenic mice were hyposensitive to the psychostimulant effects of amphetamine, as it produced only a weak locomotor activation and failed to alter catecholamine release in the Acb. Attenuating TAAR1 activity with the selective partial agonist RO5073012 restored the stimulating effects of amphetamine on locomotion. Overall, these data show that Taar1 brain overexpression causes hyposensitivity to amphetamine and alterations of monoaminergic neurotransmission. These observations confirm the modulatory role of TAAR1 on monoamine activity and suggest that in vivo the receptor is either constitutively active and/or tonically activated by ambient levels of endogenous agonist(s).

Trace amine-associated receptor 1 modulates dopaminergic activity.

The recent identification of the trace amine-associated receptor (TAAR)1 provides an opportunity to dissociate the effects of trace amines on the dopamine transporter from receptor-mediated effects. To separate both effects on a physiological level, a Taar1 knockout mouse line was generated. Taar1 knockout mice display increased sensitivity to amphetamine as revealed by enhanced amphetamine-triggered increases in locomotor activity and augmented striatal release of dopamine compared with wild-type animals. Under baseline conditions, locomotion and extracellular striatal dopamine levels were similar between Taar1 knockout and wild-type mice. Electrophysiological recordings revealed an elevated spontaneous firing rate of dopaminergic neurons in the ventral tegmental area of Taar1 knock-out mice. The endogenous TAAR1 agonist p-tyramine specifically decreased the spike frequency of these neurons in wild-type but not in Taar1 knockout mice, consistent with the prominent expression of Taar1 in the ventral tegmental area. Taken together, the data reveal TAAR1 as regulator of dopaminergic neurotransmission.

Functional magnetic resonance imaging reveals similar brain activity changes in two different animal models of schizophrenia.

RATIONALE AND OBJECTIVES: In schizophrenia research, most of the functional imaging studies have been performed in psychotic patients, but little is known about brain areas involved in the expression of psychotic-like symptoms in animal models. The objective of this study was to visualize and compare brain activity abnormalities in a neurodevelopmental and a pharmacological animal model of schizophrenia. METHODS: Blood perfusion of specific brain areas, taken as indirect measure of brain activity, was investigated in adult rats following either neonatal ventral hippocampal lesion or acute administration of phencyclidine. Quantitative perfusion magnetic resonance imaging was performed on five frontal brain slices using the continuous arterial spin labeling technique. The mean perfusion was calculated in several brain structures, which were identified on anatomical images. RESULTS: Lesioned animals exhibiting deficits in prepulse inhibition of the startle reflex showed a significant blood perfusion increase in the nucleus accumbens, basolateral amygdala, ventral pallidum, entorhinal-piriform cortex, orbital prefrontal cortex, and in the bed nucleus of the stria terminalis, and a decrease of perfusion in the temporal cortex. Similar effects were seen following acute phencyclidine administration in naïve animals. CONCLUSION: Our data point out specific cortical and subcortical brain areas involved in the development of psychotic-like symptoms in two different animal models of schizophrenia. The observed brain activity abnormalities are reminiscent of classical neuroimaging findings described in schizophrenic patients.