title: Interleukin-6: the missing element of the neurocognitive deterioration in schizophrenia? The focus on genetic underpinnings, cognitive impairment and clinical manifestation.
abstract: The influence of the immune system deregulation on the risk of schizophrenia is increasingly recognized. The aim of this study was to assess the influence of serum interleukin-6 (IL-6) level together with the polymorphism in its gene (IL6 -174G/C) and high sensitivity C-reactive protein (hsCRP) levels on clinical manifestation and cognition in schizophrenia patients. We recruited 151 patients with schizophrenia and 194 healthy control subjects. Psychopathology was evaluated using Operational Criteria for Psychotic Illness checklist, Positive and Negative Syndrome Scale (PANSS) and Scales for Assessment of Positive and Negative Symptoms. Cognitive performance in schizophrenia patients was assessed using following tests: Rey Auditory Verbal Learning Test, Trail Making Test, Verbal Fluency Tests, Stroop and subscales from Wechsler Adults Intelligence Scale-R-Pl (Similarities, Digit Symbol Coding, Digit Span Forward and Backward). Serum IL-6 and hsCRP levels were significantly higher in schizophrenia patients in comparison with healthy controls. Both hsCRP and IL-6 levels were associated with insidious psychosis onset, duration of illness and chronic schizophrenia course with deterioration. After adjustment for age, education level, number of years of completed education, illness duration, total PANSS score, depression severity and chlorpromazine equivalent, there was still a positive association between IL-6 and hsCRP levels and worse cognitive performance. The IL6 -174G/C polymorphism did not influence IL-6 level, but it was associated with the severity of positive symptoms. Our results suggest that elevated IL-6 levels may play the role in cognitive impairment and serve as potential inflammatory biomarker of deterioration in schizophrenia.
authors.affiliation: Department of Psychiatry, Wroclaw Medical University, 10 Pasteur Street, 50-367, Wrocław, Poland, dfrydecka@gmail.com.
authors.forename: Dorota
authors.initials: D
authors.lastname: Frydecka
authors.forename: Błażej
authors.initials: B
authors.lastname: Misiak
authors.forename: Edyta
authors.initials: E
authors.lastname: Pawlak-Adamska
authors.forename: Lidia
authors.initials: L
authors.lastname: Karabon
authors.forename: Anna
authors.initials: A
authors.lastname: Tomkiewicz
authors.forename: Paweł
authors.initials: P
authors.lastname: Sedlaczek
authors.forename: Andrzej
authors.initials: A
authors.lastname: Kiejna
authors.forename: Jan Aleksander
authors.initials: JA
authors.lastname: Beszłej
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism*; D003072:Cognition Disorders / Q000097:blood* / Q000209:etiology / Q000503:physiopathology; D005260:Female; D006801:Humans; D007249:Inflammation / Q000097:blood* / Q000150:complications; D015850:Interleukin-6 / Q000097:blood* / Q000235:genetics; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic; D012559:Schizophrenia / Q000097:blood* / Q000150:complications / Q000503:physiopathology; D012720:Severity of Illness Index
chemical_list: D015415:Biomarkers; C508600:IL6 protein, human; D015850:Interleukin-6; D002097:C-Reactive Protein