Rice phospholipase A superfamily: organization, phylogenetic and expression analysis during abiotic stresses and development

Background

Phospholipase A (PLA) is an important group of enzymes responsible for phospholipid hydrolysis in lipid signaling. PLAs have been implicated in abiotic stress signaling and developmental events in various plants species. Genome-wide analysis of PLA superfamily has been carried out in dicot plant Arabidopsis. A comprehensive genome-wide analysis of PLAs has not been presented yet in crop plant rice.

Methodology/Principal Findings

A comprehensive bioinformatics analysis identified a total of 31 PLA encoding genes in the rice genome, which are divided into three classes; phospholipase A₁ (PLA₁), patatin like phospholipases (pPLA) and low molecular weight secretory phospholipase A₂ (sPLA₂) based on their sequences and phylogeny. A subset of 10 rice PLAs exhibited chromosomal duplication, emphasizing the role of duplication in the expansion of this gene family in rice. Microarray expression profiling revealed a number of PLA members expressing differentially and significantly under abiotic stresses and reproductive development. Comparative expression analysis with Arabidopsis PLAs revealed a high degree of functional conservation between the orthologs in two plant species, which also indicated the vital role of PLAs in stress signaling and plant development across different plant species. Moreover, sub-cellular localization of a few candidates suggests their differential localization and functional role in the lipid signaling.

Conclusion/Significance

The comprehensive analysis and expression profiling would provide a critical platform for the functional characterization of the candidate PLA genes in crop plants.     

Determination of EGFR Endocytosis Kinetic by Auto-Regulatory Association of PLD1 with μ2

Background

Upon ligand binding, cell surface signaling receptors are internalized through a process tightly regulated by endocytic proteins and adaptor protein 2 (AP2) to orchestrate them. Although the molecular identities and roles of endocytic proteins are becoming clearer, it is still unclear what determines the receptor endocytosis kinetics which is mainly regulated by the accumulation of endocytic apparatus to the activated receptors.

Methodology/Principal Findings

Here we employed the kinetic analysis of endocytosis and adaptor recruitment to show that μ2, a subunit of AP2 interacts directly with phospholipase D (PLD)1, a receptor-associated signaling protein and this facilitates the membrane recruitment of AP2 and the endocytosis of epidermal growth factor receptor (EGFR). We also demonstrate that the PLD1-μ2 interaction requires the binding of PLD1 with phosphatidic acid, its own product.

Conclusions/Significance

These results suggest that the temporal regulation of EGFR endocytosis is achieved by auto-regulatory PLD1 which senses the receptor activation and triggers the translocation of AP2 near to the activated receptor.     

Antihypertensive treatment differentially affects vascular sphingolipid biology in spontaneously hypertensive rats

Background

We have previously shown that essential hypertension in humans and spontaneously hypertensive rats (SHR), is associated with increased levels of ceramide and marked alterations in sphingolipid biology. Pharmacological elevation of ceramide in isolated carotid arteries of SHR leads to vasoconstriction via a calcium-independent phospholipase A₂, cyclooxygenase-1 and thromboxane synthase-dependent release of thromboxane A₂. This phenomenon is almost absent in vessels from normotensive Wistar Kyoto (WKY) rats. Here we investigated whether lowering of blood pressure can reverse elevated ceramide levels and reduce ceramide-mediated contractions in SHR.

Methods and Findings

For this purpose SHR were treated for 4 weeks with the angiotensin II type 1 receptor antagonist losartan or the vasodilator hydralazine. Both drugs decreased blood pressure equally (SBP untreated SHR: 191±7 mmHg, losartan: 125±5 mmHg and hydralazine: 113±14 mmHg). The blood pressure lowering was associated with a 20–25% reduction in vascular ceramide levels and improved endothelial function of isolated carotid arteries in both groups. Interestingly, losartan, but not hydralazine treatment, markedly reduced sphingomyelinase-induced contractions. While both drugs lowered cyclooxygenase-1 expression, only losartan and not hydralazine, reduced the endothelial expression of calcium-independent phospholipase A₂. The latter finding may explain the effect of losartan treatment on sphingomyelinase-induced vascular contraction.

Conclusion

In summary, this study corroborates the importance of sphingolipid biology in blood pressure control and specifically shows that blood pressure lowering reduces vascular ceramide levels in SHR and that losartan treatment, but not blood pressure lowering per se, reduces ceramide-mediated arterial contractions.     

Impact of RTS,S/AS02A and RTS,S/AS01B on Genotypes of P. falciparum in Adults Participating in a Malaria Vaccine Clinical Trial

Objective

RTS,S, a candidate vaccine for malaria, is a recombinant protein expressed in yeast containing part of the circumsporozoite protein (CSP) sequence of 3D7 strain of Plasmodium falciparum linked to the hepatitis B surface antigen in a hybrid protein. The RTS,S antigen is formulated with GSK Biologicals'' proprietary Adjuvant Systems AS02_A or AS01_B. A recent trial of the RTS,S/AS02_A and RTS,S/AS01_B vaccines evaluated safety, immunogenicity and impact on the development of parasitemia of the two formulations. Parasite isolates from this study were used to determine the molecular impact of RTS,S/AS02_A and RTS,S/AS01_B on the multiplicity of infection (MOI) and the csp allelic characteristics of subsequent parasitemias.

Design

The distribution of csp sequences and the MOI of the infecting strains were examined at baseline and in break-through infections from vaccinated individuals and from those receiving a non-malarial vaccine.

Setting

The study was conducted in Kombewa District, western Kenya.

Participants

Semi-immune adults from the three study arms provided isolates at baseline and during break-through infections.

Outcome

Parasite isolates used for determining MOI and divergence of csp T cell–epitopes were 191 at baseline and 87 from break-through infections.

Results

Grouping recipients of RTS,S/AS01_A and RTS,S/AS02_B together, vaccine recipients identified as parasite-positive by microscopy contained significantly fewer parasite genotypes than recipients of the rabies vaccine comparator (median in pooled RTS,S groups: 3 versus 4 in controls, P = 0.0313). When analyzed separately, parasitaemic individuals in the RTS,S/AS01_B group, but not the RTS,S/AS02_A group, were found to have significantly fewer genotypes than the comparator group. Two individual amino acids found in the vaccine construct (Q339 in Th2R and D371 in Th3R) were observed to differ in incidence between vaccine and comparator groups but in different directions; parasites harboring Q339 were less common among pooled RTS,S/AS vaccine recipients than among recipients of rabies vaccine, whereas parasites with D371 were more common among the RTS,S/AS groups.

Conclusions

It is concluded that both RTS,S/AS vaccines reduce multiplicity of infection. Our results do not support the hypothesis that RTS,S/AS vaccines elicit preferential effects against pfcsp alleles with sequence similarity to the 3D7 pfcsp sequence employed in the vaccine construct.     

Enhanced clathrin-dependent endocytosis in the absence of calnexin

Background

Calnexin, together with calreticulin, constitute the calnexin/calreticulin cycle. Calnexin is a type I endoplasmic reticulum integral membrane protein and molecular chaperone responsible for the folding and quality control of newly-synthesized (glyco)proteins. The endoplasmic reticulum luminal domain of calnexin is responsible for lectin-like activity and interaction with nascent polypeptide chains. The role of the C-terminal, cytoplasmic portion of calnexin is not clear.

Methodology/Principal Findings

Using yeast two hybrid screen and immunoprecipitation techniques, we showed that the Src homology 3-domain growth factor receptor-bound 2-like (Endophilin) interacting protein 1 (SGIP1), a neuronal specific regulator of endocytosis, forms complexes with the C-terminal cytoplasmic domain of calnexin. The calnexin cytoplasmic C-tail interacts with SGIP1 C-terminal domains containing the adaptor complexes medium subunit (Adap-Comp-Sub) region. Calnexin-deficient cells have enhanced clathrin-dependent endocytosis in neuronal cells and mouse neuronal system. This is reversed by expression of full length calnexin or calnexin C-tail.

Conclusions/Significance

We show that the effects of SGIP1 and calnexin C-tail on clathrin-dependent endocytosis are due to modulation of the internalization of the receptor-ligand complexes. Enhanced clathrin-dependent endocytosis in the absence of calnexin may contribute to the neurological phenotype of calnexin-deficient mice.     

Overexpression of the Auxin Binding PROTEIN1 Modulates PIN-Dependent Auxin Transport in Tobacco Cells

Background

Auxin binding protein 1 (ABP1) is a putative auxin receptor and its function is indispensable for plant growth and development. ABP1 has been shown to be involved in auxin-dependent regulation of cell division and expansion, in plasma-membrane-related processes such as changes in transmembrane potential, and in the regulation of clathrin-dependent endocytosis. However, the ABP1-regulated downstream pathway remains elusive.

Methodology/Principal Findings

Using auxin transport assays and quantitative analysis of cellular morphology we show that ABP1 regulates auxin efflux from tobacco BY-2 cells. The overexpression of ABP1can counterbalance increased auxin efflux and auxin starvation phenotypes caused by the overexpression of PIN auxin efflux carrier. Relevant mechanism involves the ABP1-controlled vesicle trafficking processes, including positive regulation of endocytosis of PIN auxin efflux carriers, as indicated by fluorescence recovery after photobleaching (FRAP) and pharmacological manipulations.

Conclusions/Significance

The findings indicate the involvement of ABP1 in control of rate of auxin transport across plasma membrane emphasizing the role of ABP1 in regulation of PIN activity at the plasma membrane, and highlighting the relevance of ABP1 for the formation of developmentally important, PIN-dependent auxin gradients.     

SCN5A Mutations in Brugada Syndrome Are Associated with Increased Cardiac Dimensions and Reduced Contractility

Background

The cardiac sodium channel (Na_v1.5) controls cardiac excitability. Accordingly, SCN5A mutations that result in loss-of-function of Na_v1.5 are associated with various inherited arrhythmia syndromes that revolve around reduced cardiac excitability, most notably Brugada syndrome (BrS). Experimental studies have indicated that Na_v1.5 interacts with the cytoskeleton and may also be involved in maintaining structural integrity of the heart. We aimed to determine whether clinical evidence may be obtained that Na_v1.5 is involved in maintaining cardiac structural integrity.

Methods

Using cardiac magnetic resonance (CMR) imaging, we compared right ventricular (RV) and left ventricular (LV) dimensions and ejection fractions between 40 BrS patients with SCN5A mutations (SCN5a-mut-positive) and 98 BrS patients without SCN5A mutations (SCN5a-mut-negative). We also studied 18 age/sex-matched healthy volunteers.

Results

SCN5a-mut-positive patients had significantly larger end-diastolic and end-systolic RV and LV volumes, and lower LV ejection fractions, than SCN5a-mut-negative patients or volunteers.

Conclusions

Loss-of-function SCN5A mutations are associated with dilatation and impairment in contractile function of both ventricles that can be detected by CMR analysis.     

Functional characterization and FTIR-based 3D modeling of full length and truncated forms of Scorpio maurus venom phospholipase A2

Background

Heterodimeric phospholipase A₂ from venom glands of Tunisian scorpion Scorpio maurus (Sm-PLGV) had been purified. It contains long and short chains linked by a disulfide bridge. Sm-PLGV exhibits hemolytic activity towards human erythrocytes and interacts with phospholipid monolayers at high surface pressure. The investigation of structure-function relationships should provide new clues to understand its activity.

Pharmacokinetics of Naja sumatrana (Equatorial Spitting Cobra) Venom and Its Major Toxins in Experimentally Envenomed Rabbits

Background

The optimization of snakebite management and the use of antivenom depend greatly on the knowledge of the venom''s composition as well as its pharmacokinetics. To date, however, pharmacokinetic reports on cobra venoms and their toxins are still relatively limited. In the present study, we investigated the pharmacokinetics of Naja sumatrana (Equatorial spitting cobra) venom and its major toxins (phospholipase A₂, neurotoxin and cardiotoxin), following intravenous and intramuscular administration into rabbits.

Principal findings

The serum antigen concentration-time profile of the N. sumatrana venom and its major toxins injected intravenously fitted a two-compartment model of pharmacokinetics. The systemic clearance (91.3 ml/h), terminal phase half-life (13.6 h) and systemic bioavailability (41.9%) of N. sumatrana venom injected intramuscularly were similar to those of N. sputatrix venom determined in an earlier study. The venom neurotoxin and cardiotoxin reached their peak concentrations within 30 min following intramuscular injection, relatively faster than the phospholipase A₂ and whole venom (T_max = 2 h and 1 h, respectively). Rapid absorption of the neurotoxin and cardiotoxin from the injection site into systemic circulation indicates fast onsets of action of these principal toxins that are responsible for the early systemic manifestation of envenoming. The more prominent role of the neurotoxin in N. sumatrana systemic envenoming is further supported by its significantly higher intramuscular bioavailability (F_i.m. = 81.5%) compared to that of the phospholipase A₂ (F_i.m. = 68.6%) or cardiotoxin (F_i.m. = 45.6%). The incomplete absorption of the phospholipase A₂ and cardiotoxin may infer the toxins'' affinities for tissues at the injection site and their pathological roles in local tissue damages through synergistic interactions.

Conclusion/Significance

Our results suggest that the venom neurotoxin is absorbed very rapidly and has the highest bioavailability following intramuscular injection, supporting its role as the principal toxin in systemic envenoming.     

Histidine domain-protein tyrosine phosphatase interacts with Grb2 and GrpL

Background

Histidine domain-protein tyrosine phosphatase (HD-PTP) plays a key role in vesicle trafficking and biogenesis. Although it is a large protein with at least five distinct structural domains, only a few of its interactors are presently known, and the significance of these interactions is largely obscure.

Methodology and Results

In this study we performed a yeast two-hybrid screening using a human colon cDNA library and found that Grb2 and GrpL are binding partners of HD-PTP. Co-immunoprecipitation, pull-down and immunocytochemistry experiments confirmed the interactions. We also discovered that the central proline-rich and histidine-rich domain of HD-PTP is responsible for these interactions.

Significance

The interaction of HD-PTP with two adapters of the Grb2 family, essential for numerous signaling pathways, suggests that HD-PTP might be important for signaling through a plethora of receptors.     

PID15, a novel 6?kDa secreted peptide,mediates Naja naja venom phospholipase A2 induced apoptosis in isolated human peripheral lymphocytes

Background

Snake venoms are a complex mixture of active principles mainly peptides and proteins also including amino acids, nucleotides, free lipids, carbohydrates and metallic elements bound to proteins that interfere in several biological systems. In this study, we aimed to understand the mode of action of the apoptosis inducing ability of Naja naja venom phospholipase A₂ (NV-PLA₂) using isolated human peripheral lymphocytes.

Results

Human peripheral lymphocytes when incubated with Naja naja venom phospholipase A₂ (NV-PLA₂) induced up to 68% DNA fragmentation. The dialysed conditioned media obtained by incubating lymphocytes with NV-PLA₂ at 15^th min induced 44% DNA fragmentation, referred to as cmlp-active. Cmlp-active showed 20.5% increased protein concentration than the corresponding control condition media cmlp-c-15. Test for creatine kinase activity in cmlp-active proved negative and negligible amount of lactate dehydrogenase did not show significant DNA fragmentation. Fractionation of cmlp-active on Sephadex G-25 showed two peaks, major peak induced 38% DNA fragmentation, which was further rechromatographed on Sephadex G-25. The single peak obtained was named PID15 (Phospholipase A ₂ Induced DNA fragmentation factor secreted at 15 ^th min). Q-Tof MS/MS analysis of PID-15 showed it is a 6 kDa peptide. PID15 sequence analysis gave 40 amino acids in the following order, msilpcknvs iwvikdtaas dkevvlgsdr aikflylatg. The homology search for the sequence revealed it to be an Apoptosis Inducing Factor (AIF).

Conclusion

Results indicate that the secretion of PID15 is dependent on concentration of NV-PLA₂ treatment, incubation time and also on temperature and the probable membrane origin of PID15 and not of cytosolic origin with apoptosis inducing ability.     

Characterization of Yeast Extracellular Vesicles: Evidence for the Participation of Different Pathways of Cellular Traffic in Vesicle Biogenesis

Background

Extracellular vesicles in yeast cells are involved in the molecular traffic across the cell wall. In yeast pathogens, these vesicles have been implicated in the transport of proteins, lipids, polysaccharide and pigments to the extracellular space. Cellular pathways required for the biogenesis of yeast extracellular vesicles are largely unknown.

Methodology/Principal Findings

We characterized extracellular vesicle production in wild type (WT) and mutant strains of the model yeast Saccharomyces cerevisiae using transmission electron microscopy in combination with light scattering analysis, lipid extraction and proteomics. WT cells and mutants with defective expression of Sec4p, a secretory vesicle-associated Rab GTPase essential for Golgi-derived exocytosis, or Snf7p, which is involved in multivesicular body (MVB) formation, were analyzed in parallel. Bilayered vesicles with diameters at the 100–300 nm range were found in extracellular fractions from yeast cultures. Proteomic analysis of vesicular fractions from the cells aforementioned and additional mutants with defects in conventional secretion pathways (sec1-1, fusion of Golgi-derived exocytic vesicles with the plasma membrane; bos1-1, vesicle targeting to the Golgi complex) or MVB functionality (vps23, late endosomal trafficking) revealed a complex and interrelated protein collection. Semi-quantitative analysis of protein abundance revealed that mutations in both MVB- and Golgi-derived pathways affected the composition of yeast extracellular vesicles, but none abrogated vesicle production. Lipid analysis revealed that mutants with defects in Golgi-related components of the secretory pathway had slower vesicle release kinetics, as inferred from intracellular accumulation of sterols and reduced detection of these lipids in vesicle fractions in comparison with WT cells.

Conclusions/Significance

Our results suggest that both conventional and unconventional pathways of secretion are required for biogenesis of extracellular vesicles, which demonstrate the complexity of this process in the biology of yeast cells.     

Perinatal Caffeine,Acting on Maternal Adenosine A1 Receptors,Causes Long-Lasting Behavioral Changes in Mouse Offspring

Background

There are lingering concerns about caffeine consumption during pregnancy or the early postnatal period, partly because there may be long-lasting behavioral changes after caffeine exposure early in life.

Methodology/Principal Findings

We show that pregnant wild type (WT) mice given modest doses of caffeine (0.3 g/l in drinking water) gave birth to offspring that as adults exhibited increased locomotor activity in an open field. The offspring also responded to cocaine challenge with greater locomotor activity than mice not perinatally exposed to caffeine. We performed the same behavioral experiments on mice heterozygous for adenosine A₁ receptor gene (A₁RHz). In these mice signaling via adenosine A₁ receptors is reduced to about the same degree as after modest consumption of caffeine. A₁RHz mice had a behavioral profile similar to WT mice perinatally exposed to caffeine. Furthermore, it appeared that the mother''s genotype, not offspring''s, was critical for behavioral changes in adult offspring. Thus, if the mother partially lacked A₁ receptors the offspring displayed more hyperactivity and responded more strongly to cocaine stimulation as adults than did mice of a WT mother, regardless of their genotype. This indicates that long-term behavioral alterations in the offspring result from the maternal effect of caffeine, and not a direct effect on fetus. WT offspring from WT mother but having a A₁R Hz grandmother preserved higher locomotor response to cocaine.

Conclusions/Significance

We suggest that perinatal caffeine, by acting on adenosine A₁ receptors in the mother, causes long-lasting behavioral changes in the offspring that even manifest themselves in the second generation.     

Admission Lipoprotein-Associated Phospholipase A2 Activity Is Not Associated with Long-Term Clinical Outcomes after ST-Segment Elevation Myocardial Infarction

Background

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) activity is a biomarker predicting cardiovascular diseases in a real-world. However, the prognostic value in patients undergoing primary percutaneous coronary intervention (pPCI) for ST-segment elevation myocardial infarction (STEMI) on long-term clinical outcomes is unknown.

Methods

Lp-PLA₂ activity was measured in samples obtained prior to pPCI from consecutive STEMI patients in a high-volume intervention center from 2005 until 2007. Five years all-cause mortality was estimated with the Kaplan-Meier method and compared among tertiles of Lp-PLA2 activity during complete follow-up and with a landmark at 30 days. In a subpopulation clinical endpoints were assessed at three years. The prognostic value of Lp-PLA₂, in addition to the Thrombolysis In Myocardial Infarction or multimarker risk score, was assessed in multivariable Cox regression.

Results

The cohort (n = 987) was divided into tertiles (low <144, intermediate 144–179, and high >179 nmol/min/mL). Among the tertiles differences in baseline characteristics associated with long-term mortality were observed. However, no significant differences in five years mortality in association with Lp-PLA₂ activity levels were found; intermediate versus low Lp-PLA₂ (HR 0.97; CI 95% 0.68–1.40; p = 0.88) or high versus low Lp-PLA₂ (HR 0.75; CI 95% 0.51–1.11; p = 0.15). Both in a landmark analysis and after adjustments for the established risk scores and selection of cases with biomarkers obtained, non-significant differences among the tertiles were observed. In the subpopulation no significant differences in clinical endpoints were observed among the tertiles.

Conclusion

Lp-PLA₂ activity levels at admission prior to pPCI in STEMI patients are not associated with the incidence of short and/or long-term clinical endpoints. Lp-PLA₂ as an independent and clinically useful biomarker in the risk stratification of STEMI patients still remains to be proven.     

Mitochondrial inhibitory factor 1 (IF1) is present in human serum and is positively correlated with HDL-cholesterol

Background

Mitochondrial ATP synthase is expressed as a plasma membrane receptor for apolipoprotein A-I (apoA-I), the major protein component in High Density Lipoproteins (HDL). On hepatocytes, apoA-I binds to cell surface ATP synthase (namely ecto-F₁-ATPase) and stimulates its ATPase activity, generating extracellular ADP. This production of extracellular ADP activates a P2Y₁₃-mediated HDL endocytosis pathway. Conversely, exogenous IF1, classically known as a natural mitochondrial specific inhibitor of F₁-ATPase activity, inhibits ecto-F₁-ATPase activity and decreases HDL endocytosis by both human hepatocytes and perfused rat liver.

Methodology/Principal Findings

Since recent reports also described the presence of IF1 at the plasma membrane of different cell types, we investigated whether IF1 is present in the systemic circulation in humans. We first unambiguously detected IF1 in human serum by immunoprecipitation and mass spectrometry. We then set up a competitive ELISA assay in order to quantify its level in human serum. Analyses of IF1 levels in 100 normolipemic male subjects evidenced a normal distribution, with a median value of 0.49 µg/mL and a 95% confidence interval of 0.22–0.82 µg/mL. Correlations between IF1 levels and serum lipid levels demonstrated that serum IF1 levels are positively correlated with HDL-cholesterol and negatively with triglycerides (TG).

Conclusions/Significance

Altogether, these data support the view that, in humans, circulating IF1 might affect HDL levels by inhibiting hepatic HDL uptake and also impact TG metabolism.     

Exendin-4 Protects Mitochondria from Reactive Oxygen Species Induced Apoptosis in Pancreatic Beta Cells

Objective

Mitochondrial oxidative stress is the basis for pancreatic β-cell apoptosis and a common pathway for numerous types of damage, including glucotoxicity and lipotoxicity. We cultivated mice pancreatic β-cell tumor Min6 cell lines in vitro and observed pancreatic β-cell apoptosis and changes in mitochondrial function before and after the addition of Exendin-4. Based on these observations, we discuss the protective role of Exendin-4 against mitochondrial oxidative damage and its relationship with Ca²⁺-independent phospholipase A2.

Methods

We established a pancreatic β-cell oxidative stress damage model using Min6 cell lines cultured in vitro with tert-buty1 hydroperoxide and hydrogen peroxide. We then added Exendin-4 to observe changes in the rate of cell apoptosis (Annexin-V-FITC-PI staining flow cytometry and DNA ladder). We detected the activity of the caspase 3 and 8 apoptotic factors, measured the mitochondrial membrane potential losses and reactive oxygen species production levels, and detected the expression of cytochrome c and Smac/DLAMO in the cytosol and mitochondria, mitochondrial Ca₂-independent phospholipase A2 and Ca²⁺-independent phospholipase A2 mRNA.

Results

The time-concentration curve showed that different percentages of apoptosis occurred at different time-concentrations in tert-buty1 hydroperoxide- and hydrogen peroxide-induced Min6 cells. Incubation with 100 µmol/l of Exendin-4 for 48 hours reduced the Min6 cell apoptosis rate (p<0.05). The mitochondrial membrane potential loss and total reactive oxygen species levels decreased (p<0.05), and the release of cytochrome c and Smac/DLAMO from the mitochondria was reduced. The study also showed that Ca²⁺-independent phospholipase A2 activity was positively related to Exendin-4 activity.

Conclusion

Exendin-4 reduces Min6 cell oxidative damage and the cell apoptosis rate, which may be related to Ca²-independent phospholipase A2.     

Synthesis and evaluation of a series of 2-substituted-5-thiopropylpiperazine (piperidine)-1,3,4-oxadiazoles derivatives as atypical antipsychotics

Background

It is important to develop novel antipsychotics that can effectively treat schizophrenia with minor side-effects. The aim of our work is to develop novel antipsychotics that act on dopamine D₂ and D₃, serotonin 5-HT_1A and 5-HT_2A receptors with low affinity for the serotonin 5-HT_2C and H₁ receptors, which can effectively cure positive symptoms, negative symptoms and cognitive impairment without the weight gain side-effect.

Methodology/Principal Findings

A series of 2-substituted-5-thiopropylpiperazine (piperidine) -1,3,4-oxadiazoles derivatives have been synthesized and the target compounds were evaluated for binding affinities to D₂, 5-HT_1A and 5-HT_2A receptors. Preliminary results indicated that compounds 14, 16 and 22 exhibited high affinities to D₂, 5-HT_1A and 5-HT_2A receptors among these compounds. Further binding tests showed that compound 22 had high affinity for D₃ receptor, and low affinity for serotonin 5-HT_2C and H₁ receptors. In addition, compound 22 inhibited apomorphine-induced climbing behavior and MK-801-induced hyperactivity with no extrapyramidal symptoms liability in mice. Moreover, compound 22 exhibited acceptable pharmacokinetic properties.

Conclusions/Significance

Compound 22 showed an atypical antipsychotic activity without liability for extrapyramidal symptoms. We anticipate compound 22 to be useful for developing a novel class of drug for the treatment of schizophrenia.