Increased interleukin 18 activity in adolescents with early-onset psychosis is associated with cortisol and depressive symptoms.

OBJECTIVE: Evidence indicates that the pathophysiology of adult psychosis involves immune dysregulation, but its associations with stress are often not considered. The inflammatory cytokine interleukin (IL)-18, which is elevated in adult schizophrenia, is suggested to be sensitive to stress. We compared the associations of IL-18 with cortisol and clinical variables in adolescents with early-onset psychosis (EOP) aged 12-18 years and age-matched healthy controls (HC). METHOD: We measured serum IL-18, IL-18 binding protein (IL-18BP), IL-18 receptor accessory protein (IL-18RAP), IL-18 receptor 1 (IL-18R1) and cortisol, and calculated the IL-18/IL-18BP ratio in patients (n = 31) and HC (n = 60). Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale and depressive symptoms by the Mood and Feelings Questionnaire-Child version (MFQ-C). Bivariate correlation analysis was used to explore relationships between IL-18/IL-18BP ratio and cortisol, depression and other clinical characteristics. Hierarchical multiple linear regression analysis was used to assess their individual contributions to the variance of the IL-18/IL-18BP ratio. RESULTS: Patients had significantly higher IL-18 levels and IL-18/IL-18BP ratios than HC, but similar IL-18BP, IL-18RAP and IL-18R1. Both cortisol (R2 change = 0.05) and the MFQ-C score (R2 change = 0.09) contributed significantly to the variance in IL-18/IL-18BP ratios after controlling for confounders. CONCLUSION: We found increased IL-18 system activity in adolescents with EOP. Cortisol and depressive symptoms each contributed to the variance in the IL-18/IL-18BP ratio. Our findings support activation of inflammatory pathways in adolescent psychosis and suggest interactions between stress, inflammation and depressive symptoms in EOP.

IL18RAP polymorphisms and its plasma levels in patients with Lumbar disc degeneration.

OBJECTIVES: Lumbar disc degeneration (LDD) is a common musculoskeletal disorder. Interleukin 18 Receptor Accessory Protein (IL18RAP) gene is involved in disc degeneration and inflammatory processes like matrix degeneration. Hence, this study was performed to understand the role of 2 IL18RAP (rs1420106 and rs917997) polymorphisms and IL18RAP plasma levels in lumbar disc degeneration (LDD) in Indian population. PATIENTS AND METHODS: 200 LDD patients and 200 healthy controls were recruited for the study. Genotyping was performed using allelic discrimination assay. IL18RAP levels were measured by ELISA. RESULTS: rs1420106 polymorphism did not follow Hardy Weinberg equilibrium, so it was not considered for association analysis. There was a significant association among females in CT genotype of rs917997 in LDD (p = 0.041). Also, among subjects with no history of alcohol consumption, CT allele was found to be significantly associated and had a protective effect (OR = 0.61). The plasma levels of IL18RAP were also measured. There was no significant difference in IL18RAP levels between patients and controls. CONCLUSION: Overall, rs917997 polymorphism did not show any significant difference between patients and controls (p = 0.77). However, it showed a protective role in females and patients with no history of alcohol consumption in Indian population and there was no association between polymorphisms and IL18RAP plasma levels.

Potential involvement of the interleukin-18 pathway in schizophrenia.

OBJECTIVE: Accumulating evidence implicates inflammatory cytokines in the development of psychiatric disorders, including schizophrenia (SZ). IL-18 is one of cytokines that plays a crucial role in immune response and neurodevelopment. We aimed to investigate potential genetic alterations of the cytokine system underpinning SZ. METHODS: We tested the association of genetic variants within the cytokine-cytokine receptor interaction (CCRI) pathway with SZ, using GWAS-derived data involving 768 adult SZ patients and 1348 controls, and replicated the association of IL18R1 rs1035130 with SZ in an independent sample of 1957 adult patients and 1509 controls. We compared expression levels of IL18, IL18R1 and IL18RAP in peripheral blood of a cohort of adolescent participants (<18 years), including 14 early-onset SZ patients and 13 healthy controls. Furthermore, we carried out a cis-eQTL (expression Quantitative Trait Loci) and a cis-mQTL (Methylation Quantitative Trait Loci) analysis for IL18R1 rs1035130. RESULTS: In the discovery stage, we detected association signals within two IL18 pathway genes, IL18R1 and IL18RAP, with the most significant marker being IL18R1 rs1035130 (P = 1.84E-7, OR = 0.70). In the validation stage, we found rs1035130 was associated with SZ (P = 0.028, OR = 0.89). Expressions of IL18 and IL18R1 were altered in blood of SZ patients compared with 13 controls. Furthermore, cis-QTL analyses indicated that rs1035130 was associated with an eQTL and 5 mQTLs. CONCLUSION: Our findings suggest the alteration of IL18 pathway may contribute to the psychopathology of SZ.

Increased expression of interleukin-18 receptor in blood cells of subjects with mild cognitive impairment and Alzheimer's disease.

Inflammation has been proposed as a leading force in neurodegeneration and Interleukin (IL)-18 is a pro-inflammatory cytokine which is suggested to be implicated in Alzheimer's disease (AD). However, the meaning of the IL-18 participation in this disease is still unclear. Since IL-18 activity is mediated by its heterodimeric receptor complex IL-18Rα/ß, we evaluated the presence of both IL-18R chains on peripheral blood cells of AD patients, as well as in individuals with Mild Cognitive Impairment (MCI), at increased risk to develop AD. More specifically, we compared the levels of CD14(+) monocytes and CD3(+) T-lymphocytes bearing IL-18Rα and ß chains in the two groups of patients with those in healthy control subjects, both before and after in vitro cell treatment with lipopolysaccharide (LPS). While no differences in the levels of monocytes and T-lymphocytes bearing IL-18Rα chain were found among the three groups, either in untreated and LPS-treated conditions, the IL-18Rß chain expression appeared differently regulated in MCI and AD patients, as compared to controls. In particular, the amount of IL-18Rß-bearing monocytes was similar among the three groups at unstimulated conditions, while after LPS treatment it was increased in MCI vs. controls. A significant increase of IL-18Rß-bearing T-lymphocytes was also observed in MCI and AD vs. controls, both in untreated and LPS-stimulated conditions. Our findings indicate that the expression of IL-18R complex on blood cells is perturbed in AD and even more markedly in its preclinical state of MCI, confirming that an increased peripheral activity of IL-18 may be involved in the early phase of AD pathophysiology.

Newly identified genetic risk variants for celiac disease related to the immune response.

Our genome-wide association study of celiac disease previously identified risk variants in the IL2-IL21 region. To identify additional risk variants, we genotyped 1,020 of the most strongly associated non-HLA markers in an additional 1,643 cases and 3,406 controls. Through joint analysis including the genome-wide association study data (767 cases, 1,422 controls), we identified seven previously unknown risk regions (P < 5 x 10(-7)). Six regions harbor genes controlling immune responses, including CCR3, IL12A, IL18RAP, RGS1, SH2B3 (nsSNP rs3184504) and TAGAP. Whole-blood IL18RAP mRNA expression correlated with IL18RAP genotype. Type 1 diabetes and celiac disease share HLA-DQ, IL2-IL21, CCR3 and SH2B3 risk regions. Thus, this extensive genome-wide association follow-up study has identified additional celiac disease risk variants in relevant biological pathways.