Mesenchymal Stem Cells Increase Drug Tolerance of A431 Cells Only in 3D Spheroids, Not in 2D Co-Cultures.

Mesenchymal stem cells (MSCs) are an integral part of the tumor microenvironment (TME); however, their role is somewhat controversial: conflicting reports suggest that, depending on the stage of tumor development, MSCs can either support or suppress tumor growth and spread. Additionally, the influence of MSCs on drug resistance is also ambiguous. Previously, we showed that, despite MSCs proliferating significantly more slowly than cancer cells, there are chemotherapeutic drugs which proved to be similarly toxic to both cell types. Here we established 2D co-cultures and 3D co-culture spheroids from different ratios of GFP-expressing, adipose tissue-derived MSCs and A431 epidermoid carcinoma cells tagged with mCherry to investigate the effect of MSCs on cancer cell growth, survival, and drug sensitivity. We examined the cytokine secretion profile of mono- and co-cultures, explored the inner structure of the spheroids, applied MSC-(nutlin-3) and cancer cell-targeting (cisplatin) treatments separately, monitored the response with live-cell imaging and identified a new, double-fluorescent cell type emerging from these cultures. In 2D co-cultures, no effect on proliferation or drug sensitivity was observed, regardless of the changes in cytokine secretion induced by the co-culture. Conversely, 3D spheroids developed a unique internal structure consisting of MSCs, which significantly improved cancer cell survival and resilience to treatment, suggesting that physical proximity and cell-cell connections are required for MSCs to considerably affect nearby cancer cells. Our results shed light on MSC-cancer cell interactions and could help design new, better treatment options for tumors.

Genetic polymorphisms and decreased protein expression of ABCG2 urate transporters are associated with susceptibility to gout, disease severity and renal-overload hyperuricemia.

Gout is a common crystal induced disease of high personal and social burden, characterised by severe arthritis and comorbidity if untreated. Impaired function of ABCG2 transporter is causative in gout and may be responsible for renal-overload type hyperuricemia. Despite its importance, there is limited information on how clinical parameters correlate with protein expression and that with genetic changes. Urate and clinical parameters of 78 gouty patients and healthy controls were measured among standardised circumstances from a Hungarian population. ABCG2 membrane expression of red blood cells was determined by flow cytometry-based method and SNPs of this protein were analysed by TaqMan-based qPCR. The prevalence of ABCG2 functional polymorphisms in gouty and control patients were 32.1 and 13.7%, respectively. Most common SNP was Q141K while one sample with R236X, R383C and the lately described M71V were found in the gouty population. These polymorphisms showed strong linkage with decreased protein expression while the latter was also associated with higher fractional urate excretion (FUE) and urinary urate excretion (UUE). This study firstly evaluated ABCG2 protein expression in a clinically defined gouty population while also proving its associations between ABCG2 genetic changes and renal-overload hyperuricemia. The paper also highlighted relations between ABCG2 SNPs, gout susceptibility and disease severity characterised by an early onset disease with frequent flares and tophi formation.

Genetic Modulation of the GLUT1 Transporter Expression-Potential Relevance in Complex Diseases.

The human GLUT1 (SLC2A1) membrane protein is the key glucose transporter in numerous cell types, including red cells, kidney, and blood-brain barrier cells. The expression level of this protein has a role in several diseases, including cancer and Alzheimer's disease. In this work, to investigate a potential genetic modulation of the GLUT1 expression level, the protein level was measured in red cell membranes by flow cytometry, and the genetic background was analyzed by qPCR and luciferase assays. We found significant associations between red cell GLUT1 levels and four single nucleotide polymorphisms (SNP) in the coding SLC2A1 gene, that in individuals with the minor alleles of rs841848, rs1385129, and rs11537641 had increased, while those having the variant rs841847 had decreased erythrocyte GLUT1 levels. In the luciferase reporter studies performed in HEK-293T and HepG2 cells, a similar SNP-dependent modulation was observed, and lower glucose, serum, and hypoxic condition had variable, cell- and SNP-specific effects on luciferase expression. These results should contribute to a more detailed understanding of the genetic background of membrane GLUT1 expression and its potential role in associated diseases.

Selective Fluorescent Probes for High-Throughput Functional Diagnostics of the Human Multidrug Transporter P-Glycoprotein (ABCB1).

The multidrug transporter ABCB1 (MDR1, Pgp) plays an important role in the absorption, distribution, metabolism, and elimination of a wide range of pharmaceutical compounds. Functional investigation of the ABCB1 expression is also essential in many diseases, including drug-resistant cancer, inflammatory conditions, or Alzheimer disease. In this study, we examined the potential interaction of the ABCB1 multidrug transporter with a group of commercially available viability dyes that are generally considered not to penetrate into intact cells. Here, we demonstrate that the slow cellular accumulation of TO-PRO™-1 (TP1) or TO-PRO™-3 (TP3) was strongly inhibited by ABCB1-dependent dye extrusion. TP1/3 dye accumulation was not affected by the presence of ABCC1 or ABCG2, while this uptake was increased to the level in the ABCB1-negative cells by a specific P-glycoprotein inhibitor, Tariquidar. We suggest that TP compounds can be used as highly sensitive, selective, non-toxic, and stable dyes to examine the functional expression and properties of the ABCB1 multidrug transporter, especially in microplate-based high-throughput flow cytometry assays. In addition, we demonstrate the applicability of the TP dyes to efficiently select and separate even a very low number of Pgp-expressing intact cells.

Potential role of the ABCG2-Q141K polymorphism in type 2 diabetes.

Type 2 diabetes mellitus (T2DM) is a complex metabolic disease and variations in multispecific membrane transporter functions may affect T2DM development, complications or treatment. In this work we have analyzed the potential effects of a major polymorphism, the Q141K variant of the ABCG2 transporter in T2DM. The ABCG2 protein is a multispecific xeno- and endobiotic transporter, affecting drug metabolism and playing a key role in uric acid extrusion. The ABCG2-Q141K variant, with reduced expression level and function, is present in 15-35% of individuals, depending on the genetic background of the population, and has been shown to significantly affect gout development. Several other diseases, including hypertension, chronic renal failure, and T2DM have also been reported to be associated with high serum uric acid levels, suggesting that ABCG2 may also play a role in these conditions. In this work we have compared relatively small cohorts (n = 203) of T2DM patients (n = 99) and healthy (n = 104) individuals regarding the major laboratory indicators of T2DM and determined the presence of the SNP rs2231142 (C421A), resulting the ABCG2-Q141K protein variant. We found significantly higher blood glucose and HbA1c levels in the T2DM patients carrying the ABCG2-Q141K variant. These findings may emphasize the potential metabolic role of ABCG2 in T2DM and indicate that further research should explore how prevention and treatment of this disease may be affected by the frequent polymorphism of ABCG2.

A Genetically Encoded Isonitrile Lysine for Orthogonal Bioorthogonal Labeling Schemes.

Bioorthogonal click-reactions represent ideal means for labeling biomolecules selectively and specifically with suitable small synthetic dyes. Genetic code expansion (GCE) technology enables efficient site-selective installation of bioorthogonal handles onto proteins of interest (POIs). Incorporation of bioorthogonalized non-canonical amino acids is a minimally perturbing means of enabling the study of proteins in their native environment. The growing demand for the multiple modification of POIs has triggered the quest for developing orthogonal bioorthogonal reactions that allow simultaneous modification of biomolecules. The recently reported bioorthogonal [4 + 1] cycloaddition reaction of bulky tetrazines and sterically demanding isonitriles has prompted us to develop a non-canonical amino acid (ncAA) bearing a suitable isonitrile function. Herein we disclose the synthesis and genetic incorporation of this ncAA together with studies aiming at assessing the mutual orthogonality between its reaction with bulky tetrazines and the inverse electron demand Diels-Alder (IEDDA) reaction of bicyclononyne (BCN) and tetrazine. Results showed that the new ncAA, bulky-isonitrile-carbamate-lysine (BICK) is efficiently and specifically incorporated into proteins by genetic code expansion, and despite the slow [4 + 1] cycloaddition, enables the labeling of outer membrane receptors such as insulin receptor (IR) with a membrane-impermeable dye. Furthermore, double labeling of protein structures in live and fixed mammalian cells was achieved using the mutually orthogonal bioorthogonal IEDDA and [4 + 1] cycloaddition reaction pair, by introducing BICK through GCE and BCN through a HaloTag technique.

Co-Transmission of Alpha-Synuclein and TPPP/p25 Inhibits Their Proteolytic Degradation in Human Cell Models.

The pathological association of alpha-synuclein (SYN) and Tubulin Polymerization Promoting Protein (TPPP/p25) is a key factor in the etiology of synucleinopathies. In normal brains, the intrinsically disordered SYN and TPPP/p25 are not found together but exist separately in neurons and oligodendrocytes, respectively; in pathological states, however, they are found in both cell types due to their cell-to-cell transmission. The autophagy degradation of the accumulated/assembled SYN has been considered as a potential therapeutic target. We have shown that the hetero-association of SYN with TPPP/p25 after their uptake from the medium by human cells (which mimics cell-to-cell transmission) inhibits both their autophagy- and the ubiquitin-proteasome system-derived elimination. These results were obtained by ELISA, Western blot, FACS and immunofluorescence confocal microscopy using human recombinant proteins and living human cells; ANOVA statistical analysis confirmed that TPPP/p25 counteracts SYN degradation by hindering the autophagy maturation at the stage of LC3B-SQSTM1/p62-derived autophagosome formation and its fusion with lysosome. Recently, fragments of TPPP/p25 that bind to the interface between the two hallmark proteins have been shown to inhibit their pathological assembly. In this work, we show that the proteolytic degradation of SYN on its own is more effective than when it is complexed with TPPP/p25. The combined strategy of TPPP/p25 fragments and proteolysis may ensure prevention and/or elimination of pathological SYN assemblies.

Alterations in erythrocyte membrane transporter expression levels in type 2 diabetic patients.

Type 2 diabetes mellitus (T2DM) is one of the most common multifactorial diseases and several membrane transporters are involved in its development, complications and treatment. We have recently developed a flow-cytometry assay panel for the quantitative determination of red cell membrane protein levels with potential relevance in diseases. Here we report a detailed phenotypic analysis of a medium scale, clinically based study on the expression of T2DM-related membrane proteins, the GLUT1, GLUT3, MCT1, URAT1, ABCA1, ABCG2 and the PMCA4 transporters in erythrocytes. By comparing age-matched control subjects and three groups of T2DM patients (recently diagnosed, successfully managed, and patients with disease-related complications), we found significant differences in the membrane expression levels of the transporters in these groups. This is a first detailed analysis of T2DM related alterations in erythrocyte membrane transporter protein levels, and the results suggest significant changes in some of the transporter expression levels in various patient groups. By performing a further, more detailed analysis of the clinical and molecular biology parameters, these data may serve as a basis of establishing new, personalized diagnostic markers helping the prevention and treatment of type 2 diabetes.

Interactions of Potential Anti-COVID-19 Compounds with Multispecific ABC and OATP Drug Transporters.

During the COVID-19 pandemic, several repurposed drugs have been proposed to alleviate the major health effects of the disease. These drugs are often applied with analgesics or non-steroid anti-inflammatory compounds, and co-morbid patients may also be treated with anticancer, cholesterol-lowering, or antidiabetic agents. Since drug ADME-tox properties may be significantly affected by multispecific transporters, in this study, we examined the interactions of the repurposed drugs with the key human multidrug transporters present in the major tissue barriers and strongly affecting the pharmacokinetics. Our in vitro studies, using a variety of model systems, explored the interactions of the antimalarial agents chloroquine and hydroxychloroquine; the antihelmintic ivermectin; and the proposed antiviral compounds ritonavir, lopinavir, favipiravir, and remdesivir with the ABCB1/Pgp, ABCG2/BCRP, and ABCC1/MRP1 exporters, as well as the organic anion-transporting polypeptide (OATP)2B1 and OATP1A2 uptake transporters. The results presented here show numerous pharmacologically relevant transporter interactions and may provide a warning on the potential toxicities of these repurposed drugs, especially in drug combinations at the clinic.

Precision-engineered reporter cell lines reveal ABCG2 regulation in live lung cancer cells.

Expression of the ABCG2 multidrug transporter is a marker of cancer stem cells and a predictor of recurrent malignant disease. Understanding how human ABCG2 expression is modulated by pharmacotherapy is crucial in guiding therapeutic recommendations and may aid rational drug development. Genome edited reporter cells are useful in investigating gene regulation and visualizing protein activity in live cells but require precise targeting to preserve native regulatory regions. Here, we describe a fluorescent reporter assay that allows the noninvasive assessment of ABCG2 regulation in human lung adenocarcinoma cells. Using CRISPR-Cas9 gene editing coupled with homology-directed repair, we targeted an EGFP coding sequence to the translational start site of ABCG2, generating ABCG2 knock-out and in situ tagged ABCG2 reporter cells. Using the engineered cell lines, we show that ABCG2 is upregulated by a number of anti-cancer medications, HDAC inhibitors, hypoxia-mimicking agents and glucocorticoids, supporting a model in which ABCG2 is under the control of a general stress response. To our knowledge, this is the first description of a fluorescent reporter assay system designed to follow the endogenous regulation of a human ABC transporter in live cells. The information gained may guide therapy recommendations and aid rational drug design.

Influence of patient characteristics on preventive service delivery and general practitioners' preventive performance indicators: A study in patients with hypertension or diabetes mellitus from Hungary.

BACKGROUND: Regular primary healthcare (PHC) performance monitoring to produce a set of performance indicators for provider effectiveness is a fundamental method for improving guideline adherence but there are potential negative impacts of the inadequate application of this approach. Since performance indicators can reflect patient characteristics and working environments, as well as PHC team contributions, inadequate monitoring practices can reduce their effectiveness in the prevention of cardiometabolic disorders. OBJECTIVES: To describe the influence of patients' characteristics on performance indicators of PHC preventive practices in patients with hypertension or diabetes mellitus. METHODS: This cross-sectional analysis was based on a network of 165 collaborating GPs. A random sample of 4320 adults was selected from GP's patient lists. The response rate was 97.3% in this survey. Sociodemographic status, lifestyle, health attitudes and the use of recommended preventive PHC services were surveyed by questionnaire. The relationship between the use of preventive services and patient characteristics were analysed using hierarchical regression models in a subsample of 1659 survey participants with a known diagnosis of hypertension or diabetes mellitus. RESULTS: Rates of PHC service utilization varied from 18.0% to 97.9%, and less than half (median: 44.4%; IQR: 30.8-62.5) of necessary services were used by patients. Patient attitude was as strong of an influencing factor as demographic properties but was remarkably weaker than patient socioeconomic status. CONCLUSION: These findings emphasize that PHC performance indicators have to be evaluated concerning patient characteristics.

Clinically relevant mutations in the ABCG2 transporter uncovered by genetic analysis linked to erythrocyte membrane protein expression.

The ABCG2 membrane protein is a key xeno- and endobiotic transporter, modulating the absorption and metabolism of pharmacological agents and causing multidrug resistance in cancer. ABCG2 is also involved in uric acid elimination and its impaired function is causative in gout. Analysis of ABCG2 expression in the erythrocyte membranes of healthy volunteers and gout patients showed an enrichment of lower expression levels in the patients. By genetic screening based on protein expression, we found a relatively frequent, novel ABCG2 mutation (ABCG2-M71V), which, according to cellular expression studies, causes reduced protein expression, although with preserved transporter capability. Molecular dynamics simulations indicated a stumbled dynamics of the mutant protein, while ABCG2-M71V expression in vitro could be corrected by therapeutically relevant small molecules. These results suggest that personalized medicine should consider this newly discovered ABCG2 mutation, and genetic analysis linked to protein expression provides a new tool to uncover clinically important mutations in membrane proteins.

A new fluorescent dye accumulation assay for parallel measurements of the ABCG2, ABCB1 and ABCC1 multidrug transporter functions.

ABC multidrug transporters are key players in cancer multidrug resistance and in general xenobiotic elimination, thus their functional assays provide important tools for research and diagnostic applications. In this study we have examined the potential interactions of three key human ABC multidrug transporters with PhenGreen diacetate (PGD), a cell permeable fluorescent metal ion indicator. The non-fluorescent, hydrophobic PGD rapidly enters the cells and, after cleavage by cellular esterases, in the absence of quenching metal ions, PhenGreen (PG) becomes highly fluorescent. We found that in cells expressing functional ABCG2, ABCB1, or ABCC1 transporters, cellular PG fluorescence is strongly reduced. This fluorescence signal in the presence of specific transporter inhibitors is increased to the fluorescence levels in the control cells. Thus the PG accumulation assay is a new, unique tool for the parallel determination of the function of the ABCG2, ABCB1, and ABCC1 multidrug transporters. Since PG has very low cellular toxicity, the PG accumulation assay also allows the selection, separation and culturing of selected cell populations expressing either of these transporters.

Proteasome Subunit Beta Type 1 P11A Polymorphism Is a New Prognostic Marker in Multiple Myeloma.

BACKGROUND: Proteasome subunit beta type 1 (PSMB1) rs12717 polymorphism, a single nucleotide polymorphism with unknown functional effect, was recently reported to influence response to bortezomib-based therapy in follicular lymphoma. PATIENTS AND METHODS: We retrospectively analyzed the prognostic impact of this polymorphism in 211 consecutively diagnosed multiple myeloma cases, and performed in vitro experiments to look into its functional consequences. RESULTS: On univariate analysis, patients carrying the variant G allele showed significantly shorter progression-free survival (PFS) with a pattern suggestive of a gene-dose effect (PFS 26.4, 22.3, and 16.4 months in C/C, C/G, and G/G patients, respectively, P = .002). On multivariate analysis, carrying the G/G genotype was a significant independent risk factor for relapse (hazard ratio [HR] 2.29, P < .001) with a similar trend in C/G carriers (HR 1.33, P = .097) when compared with the major allele carrier C/C cohort. Our subsequent in vitro analyses demonstrated significantly reduced protease activity in proteasomes of individuals with G/G genotype compared with that of C/C carriers, despite that PSMB1 expression and proteasome assembly remained unaltered. Bortezomib exhibited a lower inhibitory capacity on the caspase- and trypsin-like activity of proteasomes from G/G individuals. CONCLUSION: Our results show that carriership of PSMB1 rs12717 minor allele is predictive for suboptimal response with bortezomib treatment, which could be explained by less active proteasomes that are less sensitive to bortezomib, and myeloma cells consequently relying on other escape mechanisms to cope with the abundance of misfolded proteins.

Decreased calcium pump expression in human erythrocytes is connected to a minor haplotype in the ATP2B4 gene.

Plasma membrane Ca2+-ATPases are key calcium exporter proteins in most tissues, and PMCA4b is the main calcium transporter in the human red blood cells (RBCs). In order to assess the expression level of PMCA4b, we have developed a flow cytometry and specific antibody binding method to quantitatively detect this protein in the erythrocyte membrane. Interestingly, we found several healthy volunteers showing significantly reduced expression of RBC-PMCA4b. Western blot analysis of isolated RBC membranes confirmed this observation, and indicated that there are no compensatory alterations in other PMCA isoforms. In addition, reduced PMCA4b levels correlated with a lower calcium extrusion capacity in these erythrocytes. When exploring the potential genetic background of the reduced PMCA4b levels, we found no missense mutations in the ATP2B4 coding regions, while a formerly unrecognized minor haplotype in the predicted second promoter region closely correlated with lower erythrocyte PMCA4b protein levels. In recent GWA studies, SNPs in this ATP2B4 haplotype have been linked to reduced mean corpuscular hemoglobin concentrations (MCHC), and to protection against malaria infection. Our data suggest that an altered regulation of gene expression is responsible for the reduced RBC-PMCA4b levels that is probably linked to the development of human disease-related phenotypes.

Different Paths to Different Strategies? Unique Associations Among Facets of the Dark Triad, Empathy, and Trait Emotional Intelligence.

Emotional deficits, such as limited empathy, are considered a fundamental aspect of the Dark Triad traits (narcissism, Machiavellianism, and psychopathy). However, the nature and extent of such deficiencies seem to vary among dark personalities. By applying multidimensional measures of empathy, emotional intelligence, and the Dark Triad, we aimed to investigate in more detail how individuals high in various dark traits understand and evaluate emotions. Results indicated that each trait, and, moreover, each facet thereof entailed unique emotional deficiencies. Narcissism was positively associated with trait emotional intelligence, whereas the secondary factor of psychopathy was associated negatively. With respect to empathy, only primary psychopathy was linked to an overall deficit, while a positive relationship was found between Machiavellianism and the perspective-taking facet of cognitive empathy. We argue that the specific emotional limitations of the Dark Triad traits might contribute to the successful deployment of different socially aversive strategies.

Delivery of cardio-metabolic preventive services to Hungarian Roma of different socio-economic strata.

BACKGROUND: Because the cardiovascular mortality in Hungary is high, particularly among the socio-economically deprived and the Roma, it is implied that primary health care (PHC) has a limited ability to exploit the opportunities of evidence-based preventions, and it may contribute to social health inequalities. OBJECTIVES: Our study investigated the underuse of PHC preventive services. METHODS: Random samples of adults aged 21-64 years free of hypertension and diabetes mellitus were surveyed with participation rate of 97.7% in a cross-sectional study. Data from 2199 adults were collected on socio-demographic status, ethnicity, lifestyle and history of cardio-metabolic preventive service use. Delivery rates were calculated for those aged 21-44 years and those aged 45-64 years, and the influence of socio-demographic variables was determined using multivariate logistic regression. RESULTS: Delivery rates varied between 12.79% and 99.06%, and the majority was far from 100%. Although most preventive service use was independent of education, younger participants with vocational educations underutilized problematic drinking (P = 0.011) and smoking (P = 0.027) assessments, and primary or less educated underutilized blood glucose (P = 0.001) and serum cholesterol (P = 0.005) checks. Health care measures of each lifestyle assessment (P nutrition = 0.032; P smoking = 0.021; P alcohol = 0.029) and waist circumference measurement (P = 0.047) were much less frequently used among older Roma. The blood glucose check (P = 0.001) and family history assessment (P = 0.043) were less utilized among Roma. CONCLUSIONS: The Hungarian PHC underutilizes the cardio-metabolic prevention contributing to the avoidable mortality, not generating considerably health inequalities by level of education, but contributing to the bad health status among the Roma.

Tobacco rattle virus 16K silencing suppressor binds ARGONAUTE 4 and inhibits formation of RNA silencing complexes.

The cysteine-rich 16K protein of tobacco rattle virus (TRV), the type member of the genus Tobravirus, is known to suppress RNA silencing. However, the mechanism of action of the 16K suppressor is not well understood. In this study, we used a GFP-based sensor strategy and an Agrobacterium-mediated transient assay in Nicotiana benthamiana to show that 16K was unable to inhibit the activity of existing small interfering RNA (siRNA)- and microRNA (miRNA)-programmed RNA-induced silencing effector complexes (RISCs). In contrast, 16K efficiently interfered with de novo formation of miRNA- and siRNA-guided RISCs, thus preventing cleavage of target RNA. Interestingly, we found that transiently expressed endogenous miR399 and miR172 directed sequence-specific silencing of complementary sequences of viral origin. 16K failed to bind small RNAs, although it interacted with ARGONAUTE 4, as revealed by bimolecular fluorescence complementation and immunoprecipitation assays. Site-directed mutagenesis demonstrated that highly conserved cysteine residues within the N-terminal and central regions of the 16K protein are required for protein stability and/or RNA silencing suppression.

Inconsistencies in the red blood cell membrane proteome analysis: generation of a database for research and diagnostic applications.

Based on recent results, the determination of the easily accessible red blood cell (RBC) membrane proteins may provide new diagnostic possibilities for assessing mutations, polymorphisms or regulatory alterations in diseases. However, the analysis of the current mass spectrometry-based proteomics datasets and other major databases indicates inconsistencies-the results show large scattering and only a limited overlap for the identified RBC membrane proteins. Here, we applied membrane-specific proteomics studies in human RBC, compared these results with the data in the literature, and generated a comprehensive and expandable database using all available data sources. The integrated web database now refers to proteomic, genetic and medical databases as well, and contains an unexpected large number of validated membrane proteins previously thought to be specific for other tissues and/or related to major human diseases. Since the determination of protein expression in RBC provides a method to indicate pathological alterations, our database should facilitate the development of RBC membrane biomarker platforms and provide a unique resource to aid related further research and diagnostics.

Antidepressant drugs and teenage suicide in Hungary: Time trend and seasonality analysis.

OBJECTIVE: The aim of the present study was to analyze the relationship between increasing utilization of antidepressants and lithium, and suicide rate of persons less than 20 years of age in Hungary, with particular regard to seasonal patterns. METHODS: Time trend analysis was carried out to determine the correlation between antidepressant and lithium prescription patterns in Hungarian persons under age of 20 years as well as seasonal variations within the study period from January 1998 to December 2006. RESULTS: There was a significant correlation (P = 0.03) between the eight-fold increase in antidepressant + lithium prescriptions and decreasing suicides in young Hungarian people under 20 years of age within the study period. Lithium, selective serotonin reuptake inhibitors (SSRIs) and the group of "other antidepressant drugs" rather than nonselective monoamine reuptake inhibitors and monoamine oxidase-A inhibitors were responsible for this association. No significant association could be drawn from seasonal variation with boys (P = 0.964), girls (P = 0.140), or both genders (P = 0.997). LIMITATION: Ecological study design. CONCLUSION: Our findings are in good agreement with large-scale ecological studies showing that the beneficial effect of more widely used antidepressants at a given point could appear on the level of suicide rate of the general population even among patients under the age of 20 years.