We have recently reported that members of the heparin-binding group II subfamily of secretory PLA 2 s (sPLA 2 s) (types IIA and V), when transfected into 293 cells, released [ 3 H]arachidonic acid (AA) preferentially in response to interleukin-1 (IL-1) and acted as "signaling" PLA 2 s that were functionally coupled with prostaglandin biosynthesis. Here we show that these group II subfamily sPLA 2 s and the type X sPLA 2 behave in a different manner, the former being more efficiently coupled with the prostaglandin-biosynthetic pathway than the latter, in 293 transfectants. Type X sPLA 2 , which bound only minimally to cell surface proteoglycans, augmented the release of both [ 3 H]AA and [ 3 H]oleic acid in the presence of serum but not IL-1. Both types IIA and V sPLA 2 , the AA released by which was efficiently converted to prostaglandin E 2 , markedly augmented IL-1-induced expression of cyclooxygenase (COX)-2 in a heparin-sensitive fashion, whereas type X sPLA 2 lacked the ability to augment COX-2 expression, thereby exhibiting the poor prostaglandin E 2 -biosynthetic response unless either of the COX isozymes was forcibly introduced into type X sPLA 2 -expressing cells. Implication of phospholipid scramblase, an enzyme responsible for the perturbation of plasma membrane asymmetry, revealed that the scramblase-transfected cells became more sensitive to types IIA and V, but not X, sPLA 2 , releasing both [ 3 H]AA and [ 3 H]oleic acid in an IL-1-independent manner. Thus, although phospholipid scramblase-mediated alteration in plasma membrane asymmetry actually led to the increased cellular susceptibility to the group II subfamily of sPLA 2 s, several lines of evidence suggest that it does not entirely mimic their actions on cells after IL-1 signaling. Interestingly, coexpression of type IIA or V, but not X, sPLA 2 and phospholipid scramblase resulted in a marked reduction in cell growth, revealing an unexplored antiproliferative aspect of particular classes of sPLA 2 .

No abstract

Multiple 5-HT receptors contribute to effective treatments to reverse adverse effects of NMDA-RA which model psychosis and cognitive impairment.

The role of 5-hydroxytryptamine (serotonin) (5-HT) 7 receptor antagonism in the actions of atypical antipsychotic drugs (APDs), e.g., amisulpride, clozapine, and lurasidone, if any, is uncertain. We examined the ability of 5-HT 7 receptor antagonism alone and as a component of amisulpride and lurasidone to reverse deficits in rat novel object recognition (NOR) produced by subchronic treatment with the N-methyl-D-aspartate receptor antagonist phencyclidine (PCP), and we examined the ability of supplemental 5-HT 7 antagonism to augment the inability of sulpiride, haloperidol, and (1R,4R,5S,6R)-4-amino-2-oxabicyclo[3.1.0]hexane-4,6-dicarboxylic acid (LY379268), a metabotropic glutamate receptor (mGluR) 2/3 agonist, which lack 5-HT 7 antagonism, to reverse the NOR deficit. The 5-HT 7 receptor antagonist, (2R)-1-[(3-hydroxyphenyl)sulfonyl]-2-[2-(4-methyl-1-piperidinyl)ethyl]pyrrolidine (SB269970) (0.1-1 mg/kg) dose-dependently reversed PCP-induced NOR deficits. In addition, the ability of lurasidone (0.1 mg/kg) and amisulpride (3 mg/kg) to reverse this deficit was blocked by cotreatment with the 5-HT 7 receptor agonist (2S)-(ϩ)-5-(1,3,5-trimethylpyrazol-4-yl)-2-(dimethylamino)tetralin (AS19) (5-10 mg/kg), which did not affect NOR in naive rats. Sulpiride, a less potent 5-HT 7 antagonist than amisulpride, did not itself improve the PCPinduced NOR deficit. However, a subeffective dose of SB269970 (0.1 mg/kg) in combination with subeffective doses of lurasidone (0.03 mg/kg), amisulpride (1 mg/kg), or sulpiride (20 mg/kg), also reversed the PCP-induced NOR deficit. Pimavanserin, a 5-HT 2A inverse agonist, LY379268, and haloperidol did not potentiate the ability of subeffective SB269970 to improve the NOR deficit. Furthermore, the mGluR2/3 antagonist (2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl)propanoic acid (LY341495), which blocks the effect of clozapine to reverse the NOR deficit, did not block the SB269970-induced amelioration of the NOR deficit. These results suggest 5-HT 7 antagonism may contribute to the efficacy of some atypical APDs in the treatment of cognitive impairment in schizophrenia and may itself have some benefit in this regard.

Subchronic administration of the N-methyl-D-aspartate receptor antagonist, phencyclidine (PCP), in rodents has been shown to produce impairment in novel object recognition (NOR), a model of visual learning and memory. We tested the hypothesis that the selective 5-HT 2A inverse agonists, pimavanserin and, would potentiate subeffective doses of atypical antipsychotic drugs (APDs) to reverse the NOR deficits. Female rats received vehicle or PCP (2 mg/kg b.i.d.) for 7 days, followed by a 7-day washout. Pimavanserin (3 mg/kg) or M100907 (1 mg/kg) alone, or four atypicial APDs, risperidone (0.05-0.1 mg/kg), melperone (1-3 mg/kg), olanzapine (1-2 mg/kg), or N-desmethylclozapine (1-2 mg/kg), and the typical APD, haloperidol (0.05-0.1 mg/kg), were administered alone, or in combination with pimavanserin or M100907, before NOR testing. The exploration times of objects during 3-min acquisition and retention trials, separated by a 1-min interval, were compared by analysis of variance. Vehicle-, but not PCP-treated, animals, explored the novel object significantly more than the familiar in the retention trial (p Ͻ 0.05-0.01). Pretreatment with the higher doses of the atypical APDs, but not pimavanserin, M100907, or haloperidol alone, reversed the effects of PCP. The effect of risperidone was blocked by haloperidol pretreatment. Coadministration of pimavanserin or M100907, with ineffective doses of the atypical APDs, but not haloperidol, also reversed the PCP-induced deficit in NOR. These results support the importance of 5-hydroxytryptamine 2A receptor blockade relative to D 2 receptor blockade in the ability of atypicals to ameliorate the effect of subchronic PCP, a putative measure of cognitive dysfunction in schizophrenia.

Decreased fibrinolytic activity has been reported in atherosclerotic cardiovascular diseases. To determine whether oxidized low-density lipoprotein (Ox-LDL), which accumulates in atherosclerotic arteries, modulates the endothelial fibrinolytic system, cultures of human umbilical vein endothelial cells were incubated with low-density lipoproteins or lipids, and levels of plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA) antigens in the conditioned medium were measured by enzyme-linked immunosorbent assay. Ox-LDL (30 ,ug protein/mL) and its extracted lipid (50 ,g cholesterol/mL) stimulated PAI-1 release by 42±3% and 29±-3% of control cultures, respectively, whereas Ox-LDL and its lipid inhibited t-PA release by 42+4% and 53 ±3% of control cultures, respectively. Native LDL and its lipid were inactive on their release. Ox-LDL depleted of hydrophilic lipids, which was prepared by the incubation with defatted albumin (an acceptor for hydrophilic lipids), lost both the stimulatory action on PAI-1 and the inhibitory action on t-PA. The extracted lipid from the incubated albumin, which has been found to accept the hydrophilic lipids from Ox-LDL, gained the stimulatory action on PAI-1 and the inhibitory action on t-PA. Ox-LDL depleted of lysophosphatidylcholine (LPC), which was prepared by the incubation with phospholipase B, lost the stimulatory effect on PAIT1, whereas the inhibitory effect on t-PA remained present in the Ox-LDL depleted of LPC. The incubation with synthetic palmitoyl LPC (10 ,uM) stimulated PAI-1 release by 85±7% of control. 25-Hydroxycholesterol (50 ,uM) and 7-ketocholesterol (50 ,uM), both of which were generated in Ox-LDL and were found to be transferable from Ox-LDL to defatted albumin by the analysis using gas chromatography-mass spectrometry, inhibited t-PA release by 26+3% and 31±3% of control cultures, respectively.

The N-methyl-D-aspartate receptor (NMDAR) antagonists, phencyclidine (PCP), dizocilpine (MK-801), or ketamine, given subchronically (sc) to rodents and primates, produce prolonged deficits in cognitive function, including novel object recognition (NOR), an analog of human declarative memory, one of the cognitive domains impaired in schizophrenia. Atypical antipsychotic drugs (AAPDs) have been reported to improve declarative memory in some patients with schizophrenia, as well as to ameliorate and prevent the NOR deficit in rodents following scNMDAR antagonist treatment. While the efficacy of AAPDs to improve cognitive impairment in schizophrenia (CIS) is limited, at best, and controversial, single doses of all currently available AAPDs so far tested transiently restore NOR in rodents following scNMDAR antagonist treatment. Typical antipsychotic drugs (APDs), e.g. haloperidol and perphenazine, are ineffective in this rodent model, and may be less effective as treatments of some domains of CIS. Serotonergic mechanisms, including, but not limited to serotonin (5-HT)2A and 5-HT7 antagonism, 5-HT(1A), and GABA(A) agonism, contribute to the efficacy of the AAPDs in the scNMDAR antagonist rodent models, which are relevant to the loss of GABA interneuron/hyperglutamate hypothesis of the etiology of CIS. The ability of sub-effective doses of the atypical APDs to ameliorate NOR in the scNMDAR-treated rodents can be restored by the addition of a sub-effective dose of the 5-HT(1A) partial agonist, tandospirone, or the 5-HT7 antagonist, SB269970. The mGluR2/3 agonist, LY379268, which itself is unable to restore NOR in the scNMDAR-treated rodents, can also restore NOR when given with lurasidone, an AAPD. Enhancing cortical and hippocampal dopamine and acetylcholine efflux, or both, may contribute to the restoration of NOR by the atypical APDs. Importantly, co-administration of lurasidone, tandospirone, or SB269970, with PCP, to rodents, at doses 5-10 fold greater than those acutely effective to restore NOR following scNMDAR treatment, prevents the effect of scPCP to produce an enduring deficit in NOR. This difference in dosage may be relevant to utilizing AAPDs to prevent the onset of CIS in individuals at high risk for developing schizophrenia. The scNMDAR paradigm may be useful for identifying possible means to treat and prevent CIS.

The concept that the efficacy of all antipsychotic drugs (APDs) can be explained by their action on dopamine (DA) D2 receptors is most challenged by drugs such as clozapine which target serotonin (5-HT)2A receptors as an essential component of their efficacy and tolerability. The 5-HT2A receptor, along with 5-HT1A, 5-HT 2C, 5-HT 6 or 5-HT 7 receptors, all of which are components of the mechanism of action of clozapine, represent important targets for treating multiple aspects of schizophrenia, especially psychosis and cognitive impairment. The class of atypical antipsychotic drugs (APDs), of which clozapine is the prototype, share in common more effective 5-HT 2A receptor inverse agonism and weaker interference with D2 receptor stimulation, either through D2 receptor blockade or partial D2 receptor agonism. This has led to development of a selective 5-HT2A antagonist, ACP-103 (pimavanserin), which has been found to be effective as monotherapy in L-DOPA psychosis and has promise as an add-on agent for sub-effective doses of atypical APDs. We review here the extensive preclinical evidence to support the importance of 5-HT2A receptor inverse agonism to the action of clozapine and related atypical APDs, and evidence supporting the potential of selective 5-HT2A, 5-HT 6 , and 5-HT 7, antagonists, 5-HT1A partial agonists and 5-HT2C agonists for development of drugs which ameliorate psychosis or cognitive impairment.