The endocannabinoids are a family of bioactive lipids that activate CB 1 cannabinoid receptors in the brain and exert intense emotional and cognitive effects. Here, we have examined the role of endocannabinoid signaling in psychotic states by measuring levels of the endocannabinoid anandamide in cerebrospinal fluid (CSF) of acute paranoid-type schizophrenic patients. We found that CSF anandamide levels are eight-fold higher in antipsychotic-naïve first-episode paranoid schizophrenics (n ¼ 47) than healthy controls (n ¼ 84), dementia patients (n ¼ 13) or affective disorder patients (n ¼ 22). Such an alteration is absent in schizophrenics treated with 'typical' antipsychotics (n ¼ 37), which antagonize dopamine D 2 -like receptors, but not in those treated with 'atypical' antipsychotics (n ¼ 34), which preferentially antagonize 5HT 2A receptors. Furthermore, we found that, in nonmedicated acute schizophrenics, CSF anandamide is negatively correlated with psychotic symptoms (r S ¼ À0.452, P ¼ 0.001). The results suggest that anandamide elevation in acute paranoid schizophrenia may reflect a compensatory adaptation to the disease state.

Phosphoinositides are membrane-delimited regulators of protein function and control many different cellular targets. The differentially phosphorylated isoforms have distinct concentrations in various subcellular membranes, which can change dynamically in response to cellular signaling events. Maintenance and dynamics of phosphoinositide levels involve a complex set of enzymes, among them phospholipases and lipid kinases and phosphatases. Recently, a novel type of phosphoinositide-converting protein (termed Ci-VSP) that contains a voltage sensor domain was isolated. It was already shown that Ci-VSP can alter phosphoinositide levels in a voltage-dependent manner. However, the exact enzymatic reaction catalyzed by Ci-VSP is not known. We used fluorescent phosphoinositidebinding probes and total internal reflection microscopy together with patch-clamp measurements from living cells to delineate substrates and products of Ci-VSP. Upon activation of Ci-VSP by membrane depolarization, membrane association of phosphatidylinositol (PI) (4,5)P 2 -and PI(3,4,5)P 3 -specific binding domains decreased, revealing consumption of these phosphoinositides by Ci-VSP. Depletion of PI(4,5)P 2 was coincident with an increase in membrane PI(4)P. Similarly, PI(3,4)P 2 was generated during depletion of PI(3,4,5)P 3 . These results suggest that Ci-VSP acts as a 5-phosphatase of PI(4,5)P 2 and PI(3,4,5)P 3 . Phosphoinositides (PIs)2 are minor components of all cell membranes and have important and diverse roles in the control of protein function and as organelle-specific membrane labels.Via dynamic concentration changes that result from breakdown or interconversion of PI isoforms, PIs act as bona fide second messengers (reviewed in Ref. 1). PI dynamics can occur in response to a huge variety of cellular events, including the activation of plasma membrane receptors.Knowledge of cellular PI signaling has dramatically increased over the last years. Much of this progress derives from the characterization of a complex set of enzymes that generate, interconvert, and degrade the various PI isoforms (2) and from the introduction of genetically encoded lipid probes that allow the tracking of the dynamics of specific PI isoforms by live cell fluorescence microscopy (3).Further research into two aspects of PI signaling appears particularly promising. First, PI homeostasis and dynamic modulation require the tight spatiotemporal regulation of lipid kinases and phosphatases, which is largely unexplored. The second issue concerns analysis of downstream targets of PI signaling. Because cellular events that change [PI] usually involve other signaling pathways, defining the role of PIs is often not straightforward.Both aspects of PI-related cell biology should benefit from methods for isoform-specific alteration of [PI]. Rapid and reversible manipulation of [PI] is particularly important because effects of long-term alteration of PI levels by overexpression or knockdown of PI-converting enzymes (e.g. Refs. 4 and 5) may be difficult to interpret. Thus, effe...

Background: Previous studies have shown that cerebrospinal fluid (CSF) from schizophrenic patients contains significantly higher levels of the endogenous cannabinoid anandamide than does CSF from healthy volunteers. Moreover, CSF anandamide levels correlated inversely with psychotic symptoms, suggesting that anandamide release in the central nervous system (CNS) may serve as an adaptive mechanism countering neurotransmitter abnormalities in acute psychoses. In the present study we examined whether cannabis use may alter such a mechanism. Methods: We used liquid chromatography/mass spectrometry (LC/MS) to measure anandamide levels in serum and CSF from firstepisode, antipsychotic-naïve schizophrenics (n = 47) and healthy volunteers (n = 81). Based on reported patterns of cannabis use and urine Δ 9 -tetrahydrocannabinol (Δ 9 -THC) tests, each subject group was further divided into two subgroups: 'low-frequency' and 'high-frequency' cannabis users (lifetime use ≤5 times and N20 times, respectively). Serum Δ 9 -THC was investigated to determine acute use and three patients were excluded from the analysis due to detectable Δ 9 -THC levels in serum. Results: Schizophrenic low-frequency cannabis users (n = 25) exhibited N 10-fold higher CSF anandamide levels than did schizophrenic high-frequency users (n = 19, p = 0.008), healthy low-frequency (n = 55, p b 0.001) or high-frequency users (n = 26, p b 0.001). In contrast, no significant differences in serum anandamide levels were found among the four subgroups. CSF anandamide levels and disease symptoms were negatively correlated in both user groups. Conclusions:The results indicate that frequent cannabis exposure may down-regulate anandamide signaling in the CNS of schizophrenic patients, but not of healthy individuals. Thus, our findings suggest that alterations in endocannabinoid signaling might be an important component of the mechanism through which cannabis impacts mental health.