Predicting relapse in schizophrenia: Is BDNF a plausible biological marker?

Understanding the biological processes that underlie why patients relapse is an issue of fundamental importance to the detection and prevention of relapse in schizophrenia. Brain Derived Neurotrophic Factor (BDNF), a facilitator of brain plasticity, is reduced in patients with schizophrenia. In the present study, we examined whether decreases in plasma BDNF levels could be used as a biological predictor of relapse in schizophrenia. A total of 221 patients were prospectively evaluated for relapse over 30months in the Preventing Relapse in Schizophrenia: Oral Antipsychotics Compared to Injectables: eValuating Efficacy (PROACTIVE) study. Serial blood samples were collected at a maximum of 23 time points during the 30-month trial and BDNF levels were measured in plasma samples by ELISA. Receiver Operating Characteristic (ROC) curve analysis indicated that BDNF was not a significant predictor of relapse, hospitalization or exacerbation. Regardless of treatment group (oral second generation antipsychotic vs. long-acting injectable risperidone microspheres), baseline BDNF value did not differ significantly between those who experienced any of the adverse outcomes and those who did not. While contrary to the study hypothesis, these robust results offer little support for the use of plasma BDNF alone as a biomarker to predict relapse in schizophrenia.

Ubiquitin-proteasome dependent degradation of GABAAα1 in autism spectrum disorder.

BACKGROUND: Although the neurobiological basis of autism spectrum disorder (ASD) is not fully understood, recent studies have indicated the potential role of GABAA receptors in the pathophysiology of ASD. GABAA receptors play a crucial role in various neurodevelopmental processes and adult neuroplasticity. However, the mechanism(s) of regulation of GABAA receptors in ASD remains poorly understood. METHODS: Postmortem middle frontal gyrus tissues (13 ASD and 13 control subjects) were used. In vitro studies were performed in primary cortical neurons at days in vitro (DIV) 14. The protein levels were examined by western blotting. Immunofluorescence studies were employed for cellular localization. The gene expression was determined by RT-PCR array and qRT-PCR. RESULTS: A significant decrease in GABAAα1 protein, but not mRNA levels was found in the middle frontal gyrus of ASD subjects indicating a post-translational regulation of GABAA receptors in ASD. At the cellular level, treatment with proteasomal inhibitor, MG132, or lactacystin significantly increased GABAAα1 protein levels and Lys48-linked polyubiquitination of GABAAα1, but reduced proteasome activity in mouse primary cortical neurons (DIV 14 from E16 embryos). Moreover, treatment with betulinic acid, a proteasome activator significantly decreased GABAAα1 protein levels in cortical neurons indicating the role of polyubiquitination of GABAAα1 proteins with their subsequent proteasomal degradation in cortical neurons. Ubiquitination specific RT-PCR array followed by western blot analysis revealed a significant increase in SYVN1, an endoplasmic reticulum (ER)-associated degradation (ERAD) E3 ubiquitin ligase in the middle frontal gyrus of ASD subjects. In addition, the inhibition of proteasomal activity by MG132 increased the expression of GABAAα1 in the ER. The siRNA knockdown of SYVN1 significantly increased GABAAα1 protein levels in cortical neurons. Moreover, reduced association between SYVN1 and GABAAα1 was found in the middle frontal gyrus of ASD subjects. CONCLUSIONS: SYVN1 plays a critical role as an E3 ligase in the ubiquitin proteasome system (UPS)-mediated GABAAα1 degradation. Thus, inhibition of the ubiquitin-proteasome-mediated GABAAα1 degradation may be an important mechanism for preventing GABAAα1 turnover to maintain GABAAα1 levels and GABA signaling in ASD.