To elucidate a genetic predisposition to major depressive disorder, we investigated two polymorphisms (−31T/C and −511C/T) in the interleukin-1beta promoter region in patients who suffered from major recurrent depression. The aim of the current work was to compare alleles and genotype layout between patients with major recurrent depression and healthy people. We would like to indicate such combination of genotypes which corresponds with major recurrent depression. Correlations between genotypes for analyzed polymorphisms and number of episodes, number of points in Hamilton Depression Rating Scale, and age of onset were investigated as well. The study group consisted of 94 patients diagnosed with major recurrent depression. The control group included 206 healthy individuals. Both groups involved representatives of Caucasian population. Genotyping of polymorphisms was performed by using PCR-RFLP technique. A specific haplotype, composed of the C allele at −31 and the T allele at −511, has a tendency to have a statistically significant difference (p = 0.064) between patients and control group. Correspondence analysis revealed that genotype T/T at −31 and genotype C/C at −511 are associated with major recurrent depression. No association was found between genotypes for studied polymorphic sites and number of episodes, number of points in Hamilton Depression Rating Scale, and age of onset.

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Major depression disorder (MDD) is the most widespread mental disorder. Selective serotonin reuptake inhibitors (SSRIs) are used as first-line MDD treatment but are effective in <70% of patients. Thus, biomarkers for the early identification of treatment-resistant (TR) MDD patients are needed for prioritizing them for alternative therapeutics. SSRI-induced inhibition of the growth of peripheral blood mononuclear cells (PBMCs) is mediated via their target, the serotonin transporter (SERT). Here, we examined whether antidepressant drug-induced inhibition of the growth of PBMCs differed between MDD patients and healthy controls. PBMCs from well-characterized 33 treatment-sensitive (TS) and 33 TR MDD patients, and 24 healthy volunteers were studied. Dose-dependent inhibition of PBMCs growth was observed for both the non-SSRI antidepressant mirtazapine and the SSRI antidepressant paroxetine. Significantly lower sensitivities to 20 μm paroxetine were observed in MDD compared with control PBMCs prior to treatment onset (13% and 46%, respectively; P<0.05). Following antidepressant drug treatment for 4 or 7 weeks, the ex vivo paroxetine sensitivity increased to control levels in PBMCs from TS but not from TR MDD patients. This suggests that the low ex vivo paroxetine sensitivity phenotype reflects a state marker of depression. A significantly lower expression of integrin beta-3 (ITGB3), a co-factor of the SERT, was observed in the PBMCs of MDD patients prior to treatment onset compared with healthy controls, and may explain their lower paroxetine sensitivity. Further studies with larger cohorts are required for clarifying the potential of reduced PBMCs paroxetine sensitivity and lower ITGB3 expression as MDD biomarkers.

Activation of the inflammatory response system is related to the pathogenesis of schizophrenia. Higher plasma levels of IL-1B have been detected in schizophrenic patients therefore, the IL-1B gene has been considered as a candidate gene for schizophrenia (Laurent et al., 1997;Katila et al., 1999). To examine a genetic predisposition to schizophrenia, the authors investigated two polymorphisms: -31T/C (rs1143627) and -511C/T (rs16944) in the IL-1B promoter region. The patient group included 143 unrelated individuals [67 (46.8%) women and 76 (53.2%) men, mean age 42.2±12.2 years (M = 42.0; range: 20-65)]. All patients fulfilled the Diagnostic and Statistical Manual of Mental Disorders, 4th ed., Text Revision criteria for paranoid schizophrenia. The diagnosis was made by two independent psychiatrists. The control group included 206 healthy, unrelated individuals [75 (36.4%) women and 131 (63.6%) men whose average age was 42.2±8.8 years (M = 43.0; range: 20-61)]. The inclusion criteria involved a verification by a direct interview to determine whether the participants had any current psychiatric problems or a family history of psychiatric or neurological disorders. The individuals in both groups were of Caucasian Polish origin living in the Silesia region.The genomic DNA was isolated from whole-blood samples. The genotypes were determined using the PCR-RFLP method. For the -31T/C polymorphic site, the 420 bp PCR fragment was amplified and products were digested as described in Borkowska et al. (2011). For the -511C/T polymorphic site, the 304 bp PCR fragment was amplified and products were digested as described in Katila et al. (1999).