Anti-Tribbles Pseudokinase 2 (TRIB2)-Immunization Modulates Hypocretin/Orexin Neuronal Functions.

Study Objectives: Recent findings showed that 16%-26% of narcolepsy patients were positive for anti-tribbles pseudokinase 2 (TRIB2) antibody, and the intracerebroventricular administration of immunoglobulin-G purified from anti-TRIB2 positive narcolepsy patients caused hypocretin/orexin neuron loss. We investigated the pathophysiological role of TRIB2 antibody using TRIB2-immunized rats and hypocretin/ataxin-3 transgenic (ataxin-3) mice. Methods: Plasma, cerebrospinal fluid (CSF), and hypothalamic tissues from TRIB2-immunized rats were collected. Anti-TRIB2 titers, hypocretin contents, mRNA expressions, the cell count of hypocretin neurons, and immunoreactivity of anti-TRIB2 antibodies on hypocretin neurons were investigated. The plasma from ataxin-3 mice was also used to determine the anti-TRIB2 antibody titer changes following the loss of hypocretin neurons. Results: TRIB2 antibody titers increased in the plasma and CSF of TRIB2-immunized rats. The hypothalamic tissue immunostained with the sera from TRIB2-immunized rats revealed positive signals in the cytoplasm of hypcretin neurons. While no changes were found regarding hypothalamic hypocretin contents or cell counts, but there were significant decreases of the hypocretin mRNA level and release into the CSF. The plasma from over 26-week-old ataxin-3 mice, at the advanced stage of hypocretin cell destruction, showed positive reactions against TRIB2 antigen, and positive plasma also reacted with murine hypothalamic hypocretin neurons. Conclusions: Our results suggest that the general activation of the immune system modulates the functions of hypocretin neurons. The absence of a change in hypocretin cell populations suggested that factors other than anti-TRIB2 antibody play a part in the loss of hypocretin neurons in narcolepsy. The increased anti-TRIB2 antibody after the destruction of hypocretin neurons suggest that anti-TRIB2 antibody in narcolepsy patients is the consequence rather than the inciting cause of hypocretin cell destruction.

Acute enhancement of non-rapid eye movement sleep in rats after drinking water contaminated with cadmium chloride.

Cadmium (Cd) is a heavy metal widely used or effused by industries. Serious environmental Cd pollution has been reported over the past two centuries, whereas the mechanisms underlying Cd-mediated diseases are not fully understood. Interestingly, an increase in reactive oxygen species (ROS) after Cd exposure has been shown. Our group has demonstrated that sleep is triggered via accumulation of ROS during neuronal activities, and we thus hypothesize the involvement of Cd poisoning in sleep-wake irregularities. In the present study, we analyzed the effects of Cd intake (1-100 ppm CdCl2 in drinking water) on rats by monitoring sleep encephalograms and locomotor activities. The results demonstrated that 100 ppm CdCl2 administration for 28 h was sufficient to increase non-rapid-eye-movement (non-REM) sleep and reduce locomotor activities during the night (the rat active phase). In contrast, free-running locomotor rhythms under constant dim red light and their re-entrainment to 12:12-h light/dark cycles were intact under chronic (1 month) 100 ppm CdCl2 administrations, suggesting a limited influence on circadian clock movements at this dosage. The relative amount of oxidized glutathione increased in the brain after the 28-h 100 ppm CdCl2 administrations similar to the levels in cultured astrocytes receiving H2O2 or CdCl2 in culture medium. Therefore, we propose Cd-induced sleep as a consequence of oxidative stress. As oxidized glutathione is an endogenous sleep substance, we suggest that Cd rapidly induces sleepiness and influences activity performance by occupying intrinsic sleep-inducing mechanisms. In conclusion, we propose increased non-REM sleep during the active phase as an index of acute Cd exposure.

Hypaphorine, an indole alkaloid from Erythrina velutina, induced sleep on normal mice.

An indole alkaloid (hypaphorine (1)) was isolated from Brazilian medicinal plant, Erythrina velutina (Leguminosae). This compound was investigated for sleep promoting effects in mice, and the results showed that it significantly increased non-rapid eye movement (NREM) sleep time during the first hour after its administration. The NREM sleep time was enhanced by 33% in the experimental mice when compared to that of the controls. This study therefore confirmed its sleep promoting property.

Hypnotic effects of total aqueous extracts of Vervain hastata (Verbenaceae) in rats.

The in vivo sedative property of the total aqueous extract of the aerial portion of Vervain hastata (Verbenaceae) (TAEV) was studied in male rats to establish its scientific basis in herbal medicine. The investigation was conducted using electroencephalogram (EEG) analysis, and the barbituric-hypnosis test. The results showed that TAEV potentiated the pentobarbital-induced hypnosis significantly by reducing sleep latency and increased sleeping time in a dose-dependent manner that was reversed by flumazenil. The EEG data demonstrated that extract administration augmented total sleep time, rapid eye movement (REM) sleep and non-REM sleep at the expense of wakefulness. The study's results clearly showed the scientific validity for the use of this plant as a sedative and possibly as a nerve tonic substance.