Recommendation for an occupational exposure limit for toluene.

The Lower Olefins and Aromatics (LOA) REACH Consortium, which includes toluene registrants in the EU, established a Working Group (WG) to conduct a review of the occupational exposure limit (OEL) for toluene. The review focussed on CNS and neuro-behavioural toxicity, ototoxicity, effects on colour vision, reproductive and developmental effects, as safety signals for these effects were identified. The WG also examined the need for a skin notation and/or a short-term exposure limit (STEL). The WG critically reviewed and discussed the strengths and weaknesses of the available published information describing the effects of toluene in animals and humans, to assess its adequacy as a potential point of departure for the establishment of an OEL for toluene and to derive an OEL. As a result, the WG recommendation for a toluene OEL is 20 ppm 8-h TWA, with a 15-min STEL of 100 ppm and a skin notation.

Application of physiologically-based pharmacokinetic modeled toluene blood concentration in the assessment of short term exposure limits.

Toluene is a volatile hydrocarbon with solvent applications in several industries. Acute neurological effects in workers exposed to toluene have been reported in various publications. To inform the basis for a toluene Short Term Exposure Limit (STEL), studies of toluene-exposed workers were modeled using customized exposure scenarios within an existing physiologically-based pharmacokinetic (PBPK) model to simulate blood concentrations during individual studies. Maximum simulated blood concentration ranged from 0.3 to 1.7 (mean = 0.74 mg/L, median = 0.73, upper 95th percentile = 1.07) at the studies identified No Observed Adverse Effect Concentration (NOAEC). Maximum simulated blood concentration ranged from 0.7 to 4.1 mg/L (mean = 1.81, median = 1.63, lower 95th percentile = 0.92) at the studies identified Lowest Observed Adverse Effect Concentration (LOAEC). The maximum blood concentration for a 100 ppm STEL-like simulation was 0.4 mg/L, at the lower end of the NOAEC range and below the 95th percentile of the LOAEC. Therefore, it appears that a STEL <100 ppm would be unnecessary to protect workers due to peak occupational exposures to toluene.

Appraisal of the human health related toxicological information available on dicyclopentadiene (DCPD) in view of assessing the substance's potential to cause endocrine disruption.

Dicyclopentadiene (DCPD) is an olefinic hydrocarbon which is manufactured and imported into the European Union (EU) at greater than 1000 tons per year. Concerns related to fetotoxic effects observed in reproductive toxicity studies at high doses led the REACH registrants to self-classify DCPD as a Category 2 reproductive toxicant under the EU CLP Regulation. DCPD was also reviewed in the European Union in the frame of an ongoing European Chemical Agency (ECHA) Community Rolling Action Plan (CoRAP) procedure and under the French National Strategy on Endocrine Disruptors (SNPE). To elucidate whether the developmental effects may be triggered by an endocrine mode of action, the Lower Olefins Sector Group (LOSG) of the European Chemical Industry Council (CEFIC) formed an ad hoc expert team to review the available scientific information pertaining to the potential endocrine activity and adversity of DCPD. Existing experimental data was complemented with structure activity modelling using ECHA-recommended (Q)SAR tools. Overall, considering the available information from (Q)SAR, mechanistic in vitro and in vivo studies, no indication of endocrine-mediated adversity was found. Hence, the available evidence supports the conclusion that DCPD does not cause developmental toxicity via an endocrine mode of action. Further work is ongoing to support this conclusion.

The short-term toxicity and metabolome of dicyclopentadiene.

Dicyclopentadiene (DCPD) was investigated in a 14-day oral rat toxicity study based on the OECD 407 guideline in combination with plasma metabolomics. Wistar rats received the compound daily via gavage at dose levels of 0, 50 and 150 mg/kg bw. The high dose induced transient clinical signs of toxicity and in males only reduced body weight gain. High dose liver changes were characterized by altered clinical chemistry parameters in both sexes and pathological changes in females. In high dose males an accumulation of alpha-2 u-globulin in the kidney was noted. Comparing the DCPD metabolome with previously established specific metabolome patterns in the MetaMap® Tox data base suggested that the high dose would result in liver enzyme induction leading to increased breakdown of thyroid hormones for males and females. An indication for liver toxicity in males was also noted. Metabolomics also suggested an effect on the functionality of the adrenals in high dose males, which together with published data, is suggestive of a stress related effect in this organ. The results of the present 14-day combined toxicity and metabolome investigations were qualitatively in line with literature data from subchronic oral studies in rats with DCPD. Importantly no other types of organ toxicity, or hormone dysregulation beyond the ones associated with liver enzyme induction and stress were indicated, again in line with results of published 90-day studies. It is therefore suggested that short term "smart" studies, combining classical toxicity with 'omics technologies, could be a 2 R (refine and reduce) new approach method allowing for the reduction of in vivo toxicity testing.

The impact of Cytochrome P450 CYP1A2, CYP2C9, CYP2C19 and CYP2D6 genes on suicide attempt and suicide risk-a European multicentre study on treatment-resistant major depressive disorder.

Recently published data have reported associations between cytochrome P450 metabolizer status and suicidality. The aim of our study was to investigate the role of genetic polymorphisms of the cytochrome P450 genes on suicide risk and/or a personal history of suicide attempts. Two hundred forty-three major depressive disorder patients were collected in the context of a European multicentre resistant depression study and treated with antidepressants at adequate doses for at least 4 weeks. Suicidality was assessed using the Mini International Neuropsychiatric Interview and the Hamilton Rating Scale for Depression (HAM-D). Treatment response was defined as HAM-D ≤ 17 and remission as HAM-D ≤ 7 after 4 weeks of treatment with antidepressants at adequate dose. Genotyping was performed for all relevant variations of the CYP1A2 gene (*1A, *1F, *1C, *1 J, *1 K), the CYP2C9 gene (*2, *3), the CYP2C19 gene (*2, *17) and the CYP2D6 gene (*3, *4, *5, *6, *9, *19, *XN). No association between both suicide risk and personal history of suicide attempts, and the above mentioned metabolic profiles were found after multiple testing corrections. In conclusion, the investigated cytochrome gene polymorphisms do not seem to be associated with suicide risk and/or a personal history of suicide attempts, though methodological and sample size limitations do not allow definitive conclusions.

Micronucleus frequencies in lymphocytes and buccal epithelial cells from patients having head and neck cancer and their first-degree relatives.

Head and neck squamous cell carcinoma is the fifth most common cancer type worldwide. Even though it is known that the most important environmental aetiological factors for head and neck cancer (HNC) development are tobacco and alcohol, genetic susceptibility is also thought to be important. The use of biomarkers of chromosomal damage due to genetic instability in order to predict risk of cancer as well as to identify high-risk individuals is imperative. We have investigated genetic damage in patients having HNC (n = 59) and their first-degree relatives (FDRs) (n = 34) with a biomarker in two different tissues; the micronucleus (MN) test in peripheral blood lymphocytes and in exfoliated buccal cells. The mean (standard deviation) levels of MN frequencies (‰) in lymphocytes of patients, relatives and controls were 27.10 (9.52), 14.09 (5.13) and 9.00 (6.87), respectively. The mean (standard deviation) levels of MN frequencies (‰) in exfoliated buccal cells of patients, relatives and controls were 2.87 (1.16), 1.38 (0.85) and 1.23 (0.93), respectively. Our results indicated that spontaneous genetic damage in lymphocytes of patients having HNC was significantly higher than that of controls (P < 0.01) and thus genetic instability appeared to exist in lymphocytes of cancer patients. Similar findings were obtained for exfoliated buccal cell MN frequencies of cancer patients (P < 0.01). We observed that the FDRs of patients having HNC showed significantly higher chromosomal damage in terms of MN frequencies in lymphocytes when compared with those of controls (P < 0.05), thus reflecting an increased susceptibility to HNC in FDRs. However, for buccal cell MN frequencies, we could not demonstrate enhanced genetic instability in the FDRs of patients having HNC.

Associations between GSTM1 and OGG1 Ser326Cys polymorphisms and smoking on chromosomal damage and birth growth in mothers.

The presenting study was investigated the associations between individual susceptibility and cigarette smoke on maternal chromosomal damage and neonatal birth growth in smoking mothers since little known about genetic susceptibility to cigarette smoke in relation to adverse pregnancy outcome such as birth growth. Sixty-one pregnant women who completed a questionnaire at Ankara Education and Research Hospital, Department of Obstetrics and Gynecology have enrolled in this study. GSTM1 and OGG1 ser326Cys gene polymorphisms were analysed by RFLP-PCR (Restriction Fragment Length Polymorphism-Polymerase Chain Reaction) as possible genetic factors affecting susceptibility to such health effects of smoking and chromosomal damage was performed by chromosomal aberration assay (CAA) in maternal blood lymphocytes. Maternal self-reported history of pregnancy smoking was informed by questionnaire declaration. Our results showed that maternal smoking had significant effect on chromosomal damage, birth weight, and length. The frequencies of CA in smokers was significantly higher than that of the nonsmokers (3.46 ± 2.06 and 2.00 ± 1.3, P = 0.001). Birth weight and length in smokers were significantly higher that of nonsmokers (3,355 g and 49.57 cm, P = 0.001; 3,639 g and 50.79 cm, P = 0.002). On the other hand, there was a slightly increased in the frequencies of CA and reduction birth weight and length in GSTM1 null and length in OGG1 variant genotypes, those differences were not statistically significant (P > 0.05); likely due to small sample size. Larger sample size needs to reach significance.

Modes of action considerations in threshold expectations for health effects of benzene.

Understanding the Mode of Action (MOA) for a chemical can help guide decisions in development of Occupational Exposure Limits (OELs). Where sufficient information exists, it can provide the OEL developer the basis for selecting either a health-based or risk-based approach. To support the development of an OEL for benzene, scientific information relevant to MOA assessment for risk-based and health-based OEL approaches was reviewed. Direct-acting mutagenicity was considered as a basis for a risk-based OEL, versus MOAs consistent with a health-based approach: indirect mutagenicity via topoisomerase II inhibition, indirect mutagenicity via reactive oxygen species generation, or an immune-based bone marrow dysfunction. Based on the evidence against direct DNA reactivity, threshold expectations for remaining MOAs, and evidence for dose rate affecting acute myeloid leukemia and myelodysplastic syndrome risk, the weight of evidence favors a health-based OEL approach. In the case of benzene, development of an OEL based on observations of earlier key events (i.e., hematologic changes and genetic toxicity) is anticipated to provide protection from later adverse outcomes such as leukemia.

Derivation of an occupational exposure limit for benzene using epidemiological study quality assessment tools.

This paper derives an occupational exposure limit for benzene using quality assessed data. Seventy-seven genotoxicity and 36 haematotoxicity studies in workers were scored for study quality with an adapted tool based on that of Vlaanderen et al., 2008 (Environ Health. Perspect. 116 1700-5). These endpoints were selected as they are the most sensitive and relevant to the proposed mode of action (MOA) and protecting against these will protect against benzene carcinogenicity. Lowest and No- Adverse Effect Concentrations (LOAECs and NOAECs) were derived from the highest quality studies (i.e. those ranked in the top tertile or top half) and further assessed as being "more certain" or "less certain". Several sensitivity analyses were conducted to assess whether alternative "high quality" constructs affected conclusions. The lowest haematotoxicity LOAECs showed effects near 2 ppm (8 h TWA), and no effects at 0.59 ppm. For genotoxicity, studies also showed effects near 2 ppm and showed no effects at about 0.69 ppm. Several sensitivity analyses supported these observations. These data define a benzene LOAEC of 2 ppm (8 h TWA) and a NOAEC of 0.5 ppm (8 h TWA). Allowing for possible subclinical effects in bone marrow not apparent in studies of peripheral blood endpoints, an OEL of 0.25 ppm (8 h TWA) is proposed.

Gemcitabine pharmacogenomics: deoxycytidine kinase and cytidylate kinase gene resequencing and functional genomics.

Gemcitabine and other cytidine antimetabolites require metabolic activation by phosphorylation. Deoxycytidine kinase (DCK) and cytidine monophosphate kinase (CMPK) catalyze these reactions. We have applied a genotype-to-phenotype strategy to study DCK and CMPK pharmacogenomics. Specifically, we resequenced DCK and CMPK using 240 DNA samples, 60 each from African-American, Caucasian-American, Han Chinese-American, and Mexican-American subjects. We observed 28 DCK polymorphisms and 28 polymorphisms in CMPK, 33 of which were novel. Expression in COS-1 cells showed that variant allozyme enzyme activities ranged from 32 to 105% of the wild type (WT) for DCK and from 78 to 112% of WT for CMPK--with no significant differences in apparent K(m) values for either enzyme except for a DCK Val24/Ser122 double variant allozyme. Relative levels of DCK and CMPK immunoreactive protein in the COS-1 cells paralleled relative levels of enzyme activity and were significantly correlated for DCK (R(p) = 0.89, P = 0.0004) but not for CMPK (R(p) = 0.82, P = 0.095). The results of an analysis of DCK and CMPK structural models were compatible with the observed functional consequences of sequence alterations in variant allozymes. We also confirmed that the CMPK protein expressed in COS-1 cells and in a rabbit reticulocyte lysate was 196 rather than 228 amino acids in length. In summary, we determined common sequence variations in DCK and CMPK and systematically evaluated their functional implications. These gene sequence differences may contribute to variations in the metabolic activation of gemcitabine and other cytidine antimetabolites.

DNA repair gene polymorphisms and bladder cancer susceptibility in a Turkish population.

BACKGROUND: Occupational exposure and life style preferences, such as smoking are the main known environmental susceptibility factors for bladder cancer. A growing list of chemicals has been shown to induce oxidative DNA damage. Base excision repair (BER) genes (X-ray repair cross complementing 1, XRCC1 and human 8-oxoguanine DNA glycosylase 1, OGG1) may play a key role in maintaining genome integrity and preventing cancer development. MATERIALS AND METHODS: We tested whether polymorphisms in XRCC1 and OGG1 are associated with bladder cancer risk by using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) assay. In addition, the possible modifying affect of cigarette smoking was evaluated. RESULTS: No studies, to date, have examined the association between genetic polymorphisms in DNA repair genes and bladder cancer susceptibility, in the Turkish population. We found the OGG1 Cys326Cys genotype to be more frequent among bladder cancer patients (odds ratio (OR): 2.41 (95% CI, 1.36-4.25)). However, in the case of XRCC1, there was no significant difference in susceptibility to bladder cancer development between patients with the Arg399 and these with the Gln399 allele (OR. 0.72 (95% CI, 0.41-1.26)). CONCLUSION: Our data showed that OGG1 genetic polymorphisms might be useful as prognostic genetic markers for bladder cancer in the clinical setting.

Polymorphisms related to estrogen and xenobiotic metabolism in healthy Turkish women.

BACKGROUND: Polymorphisms which are inherited alterations in the activity of cytochrome P450 1B1 (CYP1B1), catechol O-methyltransferase (COMT), manganese superoxide dismutase (MnSOD) hold the potential to define differences in estrogen metabolism and, thereby, possibly explain inter-individual differences in cancer susceptibility associated with estrogen-mediated carcinogenesis. METHODS: The CYP1B1 (L432V), COMT (V158M), MnSOD (Ala-9Val) genotypes, to examine estrogen metabolism and the influence of age of menarche/menopause, were determined by using different polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) based on genotyping assays. RESULTS: Women who carried CYP1B1 *3 and COMT-L alleles had an earlier age at menarche than the women who carried wild alleles (chi2 = 4.57, p = 0.032), whereas I did not observe any correlation in women with all mutant alleles. Also, CYP1B1 *3 and COMT-H genotypes were common among postmenopausal women with a body mass index (BMI) > 27 kg/m2 (Fisher exact test, p = 0.044). CONCLUSIONS: To my knowledge, this is the first genetic study on the association of these genes with susceptibility in Turkish women. Although the small sample size of each combination of estrogen metabolizing, results suggest that the CYP1B1 *3 and COMT-L alleles influence age at menarche in healthy Turkish women.

Lack of association between RNASEL Arg462Gln variant and the risk of breast cancer.

BACKGROUND: The RNASEL G1385A variant was recently found to be implicated in the development of prostate cancer. Considering the function of RNase L and the pleiotropic effects of mutations associated with cancer, we sought to investigate whether the RNASEL G1385A variant is a risk factor for breast cancer. PATIENTS AND METHODS: A total of 453 breast cancer patients and 382 age- and sex-matched controls from Greece and Turkey were analyzed. Genotyping for the RNASEL G1385A variant was performed using an Amplification Refractory Mutation System (ARMS). RESULTS: Statistical evaluation of the RNASEL G1385A genotype distribution among breast cancer patients and controls revealed no significant association between the presence of the risk genotype and the occurrence of breast cancer. CONCLUSION: Although an increasing number of studies report an association between the RNASEL G1385A variant and prostate cancer risk; this variant does not appear to be implicated in the development of breast cancer.

Chromosomal aberrations under basal conditions and after treatment with X-ray in human lymphocytes as related to the GSTM1 genotype.

The frequency of chromosomal aberrations (CAs) was evaluated in blood lymphocytes from 18 healthy subjects. Basal CA frequencies were not significantly different in GSTM1 positive and GSTM1 null subjects (P>0.05), whereas they were considerably higher in smokers than in non-smokers. After 1 Gy dose of X-ray challenge of blood samples, CA frequencies were significantly higher in GSTM1 null subjects, compared to GSTM1 positive subjects (P<0.005), and in smokers, compared to non-smokers. These effects are ascribed to the influence of GSTM1 genotype and of smoking status on DNA repair capacities. As the induction of CAs are associated with carcinogenesis, the challenge assay is able to detect enhanced susceptibility for CA caused by genetic predisposition of DNA repair deficiency.

Catechol-O-methyltransferase (COMT) pharmacogenetics in the treatment response phenotypes of major depressive disorder (MDD).

Psychiatry is a specialty where the application of pharmacogenomics approaches is made to the study of interindividual differences in response to antidepressants. It is highly applied for improving patient treatment. Major depressive disorder (MDD) is a common and complex disorder resulting from genetic and environmental interactions. Less than 40% of patients with MDD achieve remission, and even after several treatment trials, one in three patients do not fully recover from MDD. Many clinical and genomic association studies suggested that the catechol-O-methyltransferase (COMT) gene region was an important genetic locus for psychiatric disorders, because of the proposed relationship between its function in catecholaminergic neurotransmission and individual response to antidepressants, and vulnerability to psychiatric disorders. Although a number of COMT single nucleotide polymorphisms (SNPs) were observed, the Val108/158Met (rs4680) polymorphism in exon 4 resulted in a change in the enzyme structure which has been intensively investigated in relation to its role of enzyme activity and processes of prefrontal cortex functions in cognition. As serotonin interacts with dopamine and dopamine availability is influenced by COMT SNPs, an association between the COMT gene and response to treatment, based on the various pharmacogenetics/pharmacogenomics studies about COMT gene published to date, is explored in this overview.

The role of GSTM1, GSTT1, GSTP1, and OGG1 polymorphisms in type 2 diabetes mellitus risk: a case-control study in a Turkish population.

The aim of the present study was to investigate the role of some polymorphisms in GSTs (GSTM1, GSTT1 and GSTP1) which are very important protective mechanisms against oxidative stress and in OGG1 gene which is important in DNA repair, against the risk of type 2 diabetes mellitus (T2DM). 127 T2DM and 127 control subjects were included in the study. DNA was extracted from whole blood. Analyses of GSTM1 and GSTT1 gene polymorphisms were performed by allele specific PCR and those of GSTP1 Ile105Val and OGG1 Ser326Cys by PCR-RFLP. Our data showed that GSTM1 null genotype frequency had a 2-6 times statistically significant increase in a patient group (OR=3.841, 95% CI=2.280-6.469, p<0.001) but no significance with GSTT1 null/positive and GSTP1 Ile105Val genotypes was observed. When T2DM patients with OGG1 Ser326Cys polymorphism were compared with patients with a wild genotype, a 2-3 times statistically significant increase has been observed (OR 1.858, 95% CI=1.099-3.141, p=0.021). The combined effect of GSTM1 null and OGG1 variant genotype frequencies has shown to be statistically significant. Similarly, the risk of T2DM was statistically increased with GSTM1 null (OR=3.841, 95% CI=2.28-6.469), GSTT1 null+GSTP1 (H+M) (OR=4.118, 95% CI=1.327-12.778) and GSTM1 null+OGG1 (H+M) (OR=3.322, 95% CI=1.898-5.816) and GSTT1 null+OGG1 (H+M) (OR=2.179, 95% CI=1.083-4.386) as compared to the control group. According to our study results, it has been observed that the combined evaluation of GSTM1-GSTT1-GSTP1 and OGG1 Ser326Cys gene polymorphisms can be used as candidate genes in the etiology of T2DM, especially in the development of T2DM.

Assessment of individual susceptibility to baseline DNA and cytogenetic damage in a healthy Turkish population: evaluation with lifestyle factors.

BACKGROUND: Cytogenetic biomarkers are most frequently used well-established endpoints in human population studies with their sensitivity for measuring exposure to genotoxic agents. They have an important role as early predictors of cancer risk. Identification of individual genotypes of metabolic gene polymorphisms helps to understand the modulation of cancer susceptibility by environmental exposures, such as cigarette smoking and other lifestyle factors. AIM: To evaluate individual susceptibility to chemicals, we determined individual DNA damage related to glutathione S-transferase (GST) genotypes (GSTM1, GSTT1, and GSTP1) in a Turkish population. METHODS: Peripheral blood lymphocytes (PBL) and DNA samples of 127 subjects were analyzed for the presence of DNA damage, using single-cell gel electrophoresis (the Comet assay), and for cytogenetic parameters (chromosomal aberrations [CAs], bleomycin-induced CA, and a cytokinesis-blocked micronucleus assay), and the polymerase chain reaction/restriction fragment length polymorphism method, respectively. RESULTS: Individuals carrying a GSTT1-null allele showed higher frequencies of CA and micronucleus (MN) (p=0.026, p=0.003, respectively), whereas the GSTM1-null and GSTP1 mutant genotypes did not show any differences in cytogenetic parameters. Our findings demonstrated that none of the lifestyle factors (smoking, alcohol drinking, dietary habits, vitamin intake, and physical activity), except for vitamin intake (p=0.002), were significantly associated with the studied cytogenetic parameters. CONCLUSION: Our results suggest that the GSTT1 gene polymorphism may influence the baseline cytogenetic frequency in a healthy population.

Influence of COX-2 and OXTR polymorphisms on treatment outcome in treatment resistant depression.

Inflammatory pathways play a crucial role in the pathomechanisms of antidepressant efficacy. The aim of this study was to investigate whether a set of single nucleotide polymorphisms (SNPs) within cyclooxygenase-2 (COX-2, rs5275 and rs20417) and oxytocin receptor (OXTR, rs53576 and rs2254298) genes was associated with antidepressant treatment resistance, response or remission. Three hundred seventy-two patients were recruited in the context of a multicenter resistant depression study. They were genotyped for COX-2 and OXTR SNPs. Treatment resistance (according to two different definitions), response and remission were recorded. We did not observe any association between the genotypes or alleles of the selected SNPs within COX-2 and OXTR genes and treatment resistance, response and remission in the whole sample. Our results are consistent with those of some studies but not with those of other ones. Indeed, several factors could be involved in the discrepancy observed across studies. They include sample size, environmental factors, differences in ethnicity, different study designs, and different definitions of treatment resistance.

COMT and age at onset in mood disorders: a replication and extension study.

Our study aims at replicating our previous finding of an association between COMT rs4680 G/A polymorphism and early onset major depression (MD). We included 462 MD, 147 bipolar disorders (BD) subjects and 295 healthy controls. We could partially replicate previous findings. In particular, rs4680 GG+AG genotypes were more represented in the subgroup of early onset MD patients (p=0.04). Additionally, we observed an association between rs737865 alleles and early onset MD (p=0.04). Rs4680 genotype was associated with early onset BD as well (p=0.01). In conclusion, we partially replicated our previous findings confirming a possible influence of COMT variants in MD and BD, particularly in early onset subjects, though not with the same risk genotypes.

Brain-derived neurotrophic factor gene polymorphisms: influence on treatment response phenotypes of major depressive disorder.

Brain-derived neurotrophic factor (BDNF), a member of the nerve growth factor family of neurotrophins, has pivotal roles in neuronal survival, proliferation, and synaptic plasticity in the brain. Both clinical and pharmacological studies have implicated the common single nucleotide polymorphism (SNP) at position 196, Val66Met in the pathophysiology of major depressive disorder (MDD), and antidepressant response. However, inconsistent results were found between Val66Met (rs6265) polymorphism and treatment response phenotypes in genetic association studies. The functional Val66Met polymorphism and seven other tagging SNP markers selected to capture the major allelic variations across BDNF locus were analyzed in depressed patients, treated with antidepressants, and 76 control patients. Two hundred and six patients with Diagnostic and Statistical Manual of Mental Disorders-IV MDD were recruited for this study and genotyped for eight BDNF tagging SNPs (rs11030096, rs925946, rs10501087,rs6265, rs12273363, rs908867, rs1491850, and rs1491851)to investigate the functional impact of genotypes/haplotypes in the susceptibility of depression and on treatment response. None of the eight SNPs, including the rs6265, were significantly associated with MDD after permutation correction. However, we found an association for rs10501087, rs6265 with nonresponse to antidepressant treatment (corrected permutation P:0.03599; 0.0399 and power: 0.1420; 0.1492, respectively).Analysis of each two-marker, three-marker, and four-marker sliding window haplotypes showed significance in haplotype combinations. Especially rs10501087 (C), rs6265 (A), and rs149,1850 (C) together or with the other SNP haplotypes showed a similar pattern in all treatment response phenotypes. Despite the limited power of analysis, our results suggest that these three SNPs may play a role in antidepressant treatment response phenotypes in MDD.