A Combined Metabonomic and Proteomic Approach Identifies Frontal Cortex Changes in a Chronic Phencyclidine Rat Model in Relation to Human Schizophrenia Brain Pathology

Abstract

Current schizophrenia (SCZ) treatments fail to treat the broad range of manifestations associated with this devastating disorder. Thus, new translational models that reproduce the core pathological features are urgently needed to facilitate novel drug discovery efforts. Here, we report findings from the first comprehensive label-free liquid-mass spectrometry proteomic-and proton nuclear magnetic resonance-based metabonomic profiling of the rat frontal cortex after chronic phencyclidine (PCP) intervention, which induces SCZ-like symptoms. The findings were compared with results from a proteomic profiling of post-mortem prefrontal cortex from SCZ patients and with relevant findings in the literature. Through this approach, we identified proteomic alterations in glutamate-mediated Ca 2 þ signaling (Ca 2 þ /calmodulin-dependent protein kinase II, PPP3CA, and VISL1), mitochondrial function (GOT2 and PKLR), and cytoskeletal remodeling (ARP3). Metabonomic profiling revealed changes in the levels of glutamate, glutamine, glycine, pyruvate, and the Ca 2 þ regulator taurine. Effects on similar pathways were also identified in the prefrontal cortex tissue from human SCZ subjects. The discovery of similar but not identical proteomic and metabonomic alterations in the chronic PCP rat model and human brain indicates that this model recapitulates only some of the molecular alterations of the disease. This knowledge may be helpful in understanding mechanisms underlying psychosis, which, in turn, can facilitate improved therapy and drug discovery for SCZ and other psychiatric diseases. Most importantly, these molecular findings suggest that the combined use of multiple models may be required for more effective translation to studies of human SCZ.

Hippocampal Proteomic and Metabonomic Abnormalities in Neurotransmission, Oxidative Stress, and Apoptotic Pathways in a Chronic Phencyclidine Rat Model

“…Behavioural readouts were recorded as described and PCP injection induced the standard increase in locomotor activity and stereotypic movement. 43 …”

“…43 Immunoassays were calibrated using duplicate standard curves for each analyte and raw intensity measurements converted to protein concentrations using proprietary software. Multiplexed calibrators (eight levels per analyte) and controls (three levels per analyte) were used to monitor key performance parameters, such as lower limit of quantification, precision, cross-reactivity, linearity, spike-recovery, dynamic range, matrix interference, freeze-thaw stability and short-term sample stability (http://www.myriadrbm.com/technology/data-quality/).…”

“…Therefore we included key proteins of glutamatergic signalling and proteins already known to be affected by PCP treatment 39,43 or in schizophrenia. This led to validation of opposite changes in superoxide dismutase and alpha-actinin 1 (ACTN1) in frontal cortex and hippocampus.…”

“…1,[40][41][42] One extensive proteomic and metabonomic study which investigated the molecular effects in the frontal cortex of a chronic PCP rat model, only led to the identification of subtle abnormalities in proteins involved in calcium signalling and energy metabolism. 43 Here, we attempt to gain further insights into the effects of chronic PCP treatment of rats using a combination of metabonomic and proteomic profiling of rat brain tissue. Since only subtle molecular changes have been found in the frontal cortex from chronic PCP treated rats, 43 this study now analyses hippocampal tissue from cPCP treated rats to investigate how this brain region is affected, particularly considering its role in cognition and memory, social behaviour and the (negative) symptom domains.…”

“…43 Here, we attempt to gain further insights into the effects of chronic PCP treatment of rats using a combination of metabonomic and proteomic profiling of rat brain tissue. Since only subtle molecular changes have been found in the frontal cortex from chronic PCP treated rats, 43 this study now analyses hippocampal tissue from cPCP treated rats to investigate how this brain region is affected, particularly considering its role in cognition and memory, social behaviour and the (negative) symptom domains. The molecular characterisation will help to understand pathophysiological mechanisms in psychosis and schizophrenia and may facilitate future drug discovery and development by evaluating the translational validity of the model.…”