Serum cytokines in pediatric neuropsychiatric syndromes: focus on Attention Deficit Hyperactivity Disorder

Risk of Periodontitis in Adolescents With Attention Deficit Hyperactivity Disorder: A Cohort Study of 81,055 Participants

OBJECTIVES

Previous studies have demonstrated poor oral hygiene in children with attention deficit hyperactivity disorder (ADHD). However, the association between ADHD and periodontitis is still unclear.

METHODS

In all, 16,211 adolescents with ADHD and 162,110 age- and sex-matched controls participated in the study between 2001 and 2011. To identify the occurrence of periodontitis, the participants were followed up till the end of 2011. Confounding factors, including smoking, diabetes, and depressive disorder, were assessed and adjusted in the Cox regression models.

RESULTS

Adolescents with ADHD (HR: 2.29) were more likely to develop periodontitis later in life than controls. We additionally observed the beneficial effect of atomoxetine (HR: 0.42) on the periodontitis risk among adolescents with ADHD. However, this finding should be interpreted cautiously given the small sample (n = 290) of children taking atomoxetine in the present study.

CONCLUSIONS

ADHD is an independent risk factor for subsequent periodontitis development. Oral health should be closely monitored in adolescents with ADHD. Future investigation of the shared pathomechanisms between periodontitis and ADHD is warranted.

Rhynchophylline Alleviates Hyperactivity and Cognitive Flexibility Impairment Associated With Inhibition of Inflammatory Responses in Mice That Partly Lack the Dopamine Transporter Protein

BACKGROUND AND AIMS

Rhynchophylline (RHY) can alleviate some cognitive flexibility impairment and stereotyped behavior for attention-deficit hyperactivity disorder (ADHD) and Tourette syndrome (TS) patients as one of a key extract and an active ingredient in Ningdong granule (NDG), which is a Traditional Chinese medicine (TCM) preparation widely used in the treatment of ADHD and TS children in China; however, the underlying mechanism is not well understood. Therefore, this study aimed to evaluate how RHY alleviates hyperactivity and cognitive flexibility impairment while inhibiting inflammatory responses in mice that partly lack dopamine transporter protein (DAT- mice).

METHODS

Male DAT- mice were randomly divided into the RHY group (n = 8) and administered RHY (30 mg/kg) in the DAT- group (n = 8) and administered saline (i.p., 10 mL/kg) in wild-type (WT) mice as the WT control group (n = 8). Hyperactivity and cognitive flexibility impairment were evaluated by the open field test (OFT) and the Morris water maze (MWM) test. The levels of the inflammatory factors of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in cortical homogenates were tested by enzyme-linked immunosorbent assays (ELISA) after 8 weeks of treatment with RHY. In vitro, primary microglia and astrocytes extracted from the cortices of DAT- neonatal mice and WT neonatal mice were treated with lipopolysaccharide (LPS) (1 mg/mL) to induce neuroinflammatory responses and with RHY (20 mM) for 48 h. The levels of the inflammatory factors TNF-α, IL-1β, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX2) in the culture medium were measured at 6 h, 24 h, and 48 h after treatment with LPS and RHY.

RESULTS

RHY ameliorated hyperactivity and cognitive flexibility impairment in DAT- mice and inhibited the expression of the inflammatory factors TNF-α, IL-1β, iNOS, and COX-2 in microglia and astrocytes in vitro, and also inhibited the expression of TNF-α and IL-1β in cortical homogenates after 8 weeks of treatment.

CONCLUSION

RHY improved hyperactivity and cognitive flexibility impairment through inhibiting inflammatory responses in DAT- mice.

Increased Rate of Familial Mediterranean Fever in Children With ADHD: A Population-Based Case-Control Study

OBJECTIVE

There is growing evidence of involvement of inflammatory mechanisms in ADHD. Previous studies found significantly higher rates of ADHD among children with FMF. The present study examined the rate of exposure to FMF in children with a later (within a 5-year period) diagnosis of ADHD compared to non-ADHD children.

METHODS

A population-based case-control study of all children (<18 years) registered in Leumit Health Services during 01.01.2006 to 06.30.2021. All cases met ICD-9/10 criteria for ADHD. They were matched by age, sex, and socioeconomic status on a 1:2 rate to randomly selected non-ADHD controls.

RESULTS

Fifty-six (0.30%) children with ADHD (N = 18,756) were previously diagnosed with FMF compared to 65 of 37,512 controls (0.17%). A significant, independent association existed between a preceding FMF diagnosis and a later ADHD diagnosis [OR = 1.72 (95% CI 1.18-2.51); p = .003].

CONCLUSIONS

The mechanisms underlying the association w between FMF and later ADHD diagnosis merit further elucidation.

Memory deficits and hippocampal cytokine expression in a rat model of ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a complex behavioral disorder characterized by hyperactivity, impulsivity, inattention, and deficits in working memory and time perception. While animal models have advanced our neurobiological understanding of this condition, there are limited and inconsistent data on working and elapsed time memory function. Inflammatory signaling has been identified as a key factor in memory and cognitive impairments, but its role in ADHD remains unclear. Additionally, the disproportionate investigation of male subjects in ADHD research has contributed to a poor understanding of the disorder in females. This study sought to investigate the potential connections between memory, neuroimmunology, and ADHD in both male and female animals. Specifically, we utilized the spontaneously hypertensive rat (SHR), one of the most extensively studied animal models of ADHD. Compared to their control, the Wistar-Kyoto (WKY) rat, male SHR are reported to exhibit several behavioral phenotypes associated with ADHD, including hyperactivity, impulsivity, and poor sustained attention, along with impairments in learning and memory. As the hippocampus is a key brain region for learning and memory, we examined the behavior of male and female SHR and WKY rats in two hippocampal-dependent memory tasks. Our findings revealed that SHR have delay-dependent working memory deficits that were similar to, albeit less severe than, those seen in hippocampal-lesioned rats. We also observed impairments in elapsed time processing in female SHR, particularly in the discrimination of longer time durations. To investigate the impact of inflammatory signaling on memory in these rats, we analyzed the levels of several cytokines in the dorsal and ventral hippocampus of SHR and WKY. Although we found some sex and genotype differences, concentrations were generally similar between groups. Taken together, our results indicate that SHR exhibit deficits in spatial working memory and memory for elapsed time, as well as some differences in hippocampal cytokine concentrations. These findings contribute to a better understanding of the neurobiological basis of ADHD in both sexes and may inform future research aimed at developing effective treatments for the disorder. Nonetheless, the potential mediating role of neuroinflammation in the memory symptomatology of SHR requires further investigation.

Neutrophil to lymphocyte ratio, platelet to lymphocyte ratio, and monocyte to lymphocyte ratio in ADHD: a systematic review and meta-analysis

Introduction

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder with an unclear etiology. Systemic inflammation and immune dysregulation may play a role in the pathogenesis of ADHD. Morphology-derived parameters such as neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), and monocyte to lymphocyte ratio (MLR), have been proposed as peripheral biomarkers of the immune-inflammatory process in various diseases. However, studies examining their role in ADHD remain inconclusive.

Methods

A systematic review and a meta-analysis were conducted to evaluate the association between NLR, MLR, PLR and ADHD. Relevant articles were identified, screened, and assessed for quality according to PRISMA guidelines. Moreover, a qualitative and quantitative analyses were performed.

Results

The review contained eight eligible studies, five of which were included in the meta-analysis. The meta-analysis showed that ADHD patients had higher NLR and PLR values compared to health controls. No significant difference in MLR value was observed between the two groups. Analysis in relation to ADHD subtypes showed no significant differences in inflammatory markers in any of the included studies as well. The influence of medical treatment on these ratios could not be adequately assessed due to limited data.

Conclusion

ADHD patients exhibit higher NLR and PLR than healthy controls, which may indicate the potential immune-inflammatory involvement in this disorder. Further studies on inflammatory markers and ADHD, especially those considering the impact of treatment and clinical symptoms, are essential to comprehensively understand this association.

Peripheral Inflammatory Markers in Autism Spectrum Disorder and Attention Deficit/Hyperactivity Disorder at Adolescent Age

Autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD) are associated with immune dysregulation. We aimed to estimate the pro- and anti-inflammatory activity/balance in ASD and ADHD patients at a little-studied adolescent age with respect to sex. We evaluated 20 ASD patients (5 girls, average age: 12.4 ± 1.9 y), 20 ADHD patients (5 girls, average age: 13.4 ± 1.8 y), and 20 age- and gender-matched controls (average age: 13.2 ± 1.9 y). The evaluated parameters included (1) white blood cells (WBCs), neutrophils, monocytes, lymphocytes, platelets, platelet distribution width (PDW), mean platelet volume, and derived ratios, as well as (2) cytokines-interferon-gamma, interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, and IL-10, tumor necrosis factor-alpha (TNF-α), and derived profiles and ratios. ASD adolescents showed higher levels of WBC, monocytes, IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, and IL-10, macrophages (M)1 profile, and anti-inflammatory profile than the controls, with ASD males showing higher monocytes, IL-6 and IL-10, anti-inflammatory profile, and a lower T-helper (Th)1/Th2+T-regulatory cell ratio than control males. The ADHD adolescents showed higher levels of PDW, IL-1β and IL-6, TNF-α, M1 profile, proinflammatory profile, and pro-/anti-inflammatory ratio than the controls, with ADHD females showing a higher TNF-α and pro-/anti-inflammatory ratio than the control females and ADHD males showing higher levels of IL-1β and IL-6, TNF-α, and M1 profile than the control males. Immune dysregulation appeared to be different for both neurodevelopmental disorders in adolescence.

Interaction of genetic liability for attention deficit hyperactivity disorder (ADHD) and perinatal inflammation contributes to ADHD symptoms in children

Objective

Genetic and environmental factors contribute to the development of Attention Deficit/Hyperactivity Disorder (ADHD). Perinatal inflammation is one of the promising environmental risk factors for ADHD, but the relationship between the genetic risk for ADHD and perinatal inflammation requires further examination.

Methods

A possible gene-environmental interaction between perinatal inflammation and ADHD polygenic risk score (ADHD-PRS) on ADHD symptoms was investigated in children aged 8-9 from the Hamamatsu Birth Cohort for Mothers and Children (N = 531). Perinatal inflammation was evaluated by the level of concentration of three cytokines assayed in umbilical cord blood. The genetic risk for ADHD was assessed by calculating ADHD-PRS for each individual using a previously collected genome-wide association study of ADHD.

Results

Perinatal inflammation (β [SE], 0.263 [0.017]; P < 0.001), ADHD-PRS (β [SE], 0.116[0.042]; P = 0.006), and an interaction between the two (β [SE], 0.031[0.011]; P = 0.010) were associated with ADHD symptoms. The association between perinatal inflammation and ADHD symptoms measured by ADHD-PRS was evident only in the two higher genetic risk groups (β [SE], 0.623[0.122]; P < 0.001 for the medium-high risk group; β [SE], 0.664[0.152]; P < 0.001 for the high-risk group).

Conclusion

Inflammation in the perinatal period both directly elevated ADHD symptoms and magnified the impact of genetic vulnerability on ADHD risk particularly among children aged 8-9 with genetically higher risk for ADHD.

C-Reactive Protein (CRP): A Potent Inflammation Biomarker in Psychiatric Disorders

An increasing number of studies have investigated the role of inflammation in psychiatric disorders, by demonstrating how an altered/dysfunctional immunological and inflammatory system may underpin a psychiatric condition. Particularly, several studies specifically investigated the role of a neuroinflammatory biomarker, named C-reactive protein (CRP), in psychiatric disorders. Overall, even though scientific literature so far published still does not appear definitive, CRP is more likely reported to be elevated in several psychiatric disorders, including schizophrenia, mood disorders, anxiety disorders and post-traumatic stress disorder. Moreover, a low-grade inflammation (CRP >3 mg/L) has been more likely observed in a subgroup of patients affected with a more severe psychopathological symptomatology, more treatment resistance and worst clinical mental illness course, strengthening the hypothesis of the need for a different clinical and prognostic characterization based on this concomitant neuroinflammatory predisposition. However, even though further research studies are needed to confirm this preliminary evidence, CRP may represent a potential clinical routine biomarker which could be integrated in the clinical routine practice to better characterize clinical picture and course as well as address clinicians towards a personalized treatment.

Clinical and Socio-Demographic Variables Associated with the Diagnosis of Long COVID Syndrome in Youth: A Population-Based Study

This study examines the demographic, clinical and socioeconomic factors associated with diagnosis of long COVID syndrome (LCS). Data of 20,601 COVID-19-positive children aged 5 to 18 years were collected between 2020 and 2021 in an Israeli database. Logistic regression analysis was used to evaluate the adjusted odds ratio for the characteristics of the COVID-19 infection and pre-COVID-19 morbidities. Children with LCS were significantly more likely to have been severely symptomatic, required hospitalization, and experienced recurrent acute infection within 180 days. In addition, children with LCS were significantly more likely to have had ADHD, chronic urticaria, and allergic rhinitis. Diagnosis of LCS is significantly associated with pre-COVID-19 ADHD diagnosis, suggesting clinicians treating ADHD children who become infected with COVID-19 remain vigilant for the possibility of LCS. Although the risk of severe COVID-19 infection and LCS in children is low, further research on possible morbidity related to LCS in children is needed.

New Hematological Parameters as Inflammatory Biomarkers: Systemic Immune Inflammation Index, Platerethritis, and Platelet Distribution Width in Patients with Adult Attention Deficit Hyperactivity Disorder

OBJECTIVES

The potential role of neuroinflammation in adult attention deficit hyperactivity disorder (ADHD) patients has been investigated with peripheral hemogram-related inflammatory markers. Systemic immune inflammation index (SII) is defined as a new index that has been developed for the balance of inflammatory and immune status.

METHODS

Our study was based on a prospective routine complete blood count(CBC) analysis of 74 Adult ADHD patients and 70 healthy participants. The DSM-5-Clinician version and Barratt impulsivity scale-11 were used to evaluate the participants.

RESULTS

There was no statistical difference in the comparison of the SII ratios, platelet distribution width (PDW), and plateretritis (PCT) (p>0.05 for each) in a group of a young adults with ADHD and in a comparison control group. These inflammatory indicators were found to be similar between patients newly diagnosed with ADHD (n=40) and patients using methylphenidate (n=34) (p>0.05 for each). The relationship between ADHD clinical symptoms and severity and inflammation was evaluated. A significant negative correlation was observed between attention deficit scores and PCT (r=-0.301, p=0.009). A positive significant correlation was found between hyperactivity scores and SII (r=0.247, p=0.034). A significant positive correlation was found between Barrat motor scores and PDW(r=241, p=0.038). In the regression analysis, the PCT variable changed the attention deficit variable (β=.33, t(70)= -2.703, p=.009, pr ²= .094) predicted negatively and significantly.

CONCLUSIONS

We demonstrated the association of SII, which is independently associated with adverse outcomes in many diseases, and the severity of hyperactivity symptoms in adult ADHD. The fact that PCT predicts attention deficit negatively and decisively shows the importance of inflammatory assessments specific to clinical presentations. The critical importance of platelets in inflammatory processes in ADHD has been demonstrated once again with inflammatory markers such as SII, PLT, and PDW, which can be accessed by an easily applicable complete blood count method.

Gut microbiota and plasma cytokine levels in patients with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a common childhood mental disorder with undetermined pathophysiological mechanisms. The gut microbiota and immunological dysfunction may influence brain functions and social behaviours. In the current study, we aimed to explore the correlation of gut microbiome imbalance and inflammation in the pathophysiology of ADHD. Forty-one children with ADHD and thirty-nine healthy-control (HC) individuals were recruited. Faecal samples from all participants were collected and submitted for 16 S rRNA V3-V4 amplicon microbiome sequencing analysis. The plasma levels of 10 cytokines, including TNF-α, IL-6, IL-1β, IL-2, IL-10, IL-13, IL-17A, IFN-α2, IFN-γ, and MCP-1, were determined using a custom-made sandwich enzyme-linked immunosorbent assay (ELISA) developed by Luminex Flowmetrix. There was no significant difference between the ADHD and HC groups in species diversity in the faeces, as determined with α-diversity and β-diversity analysis. In the ADHD group, three differentially abundant taxonomic clades at the genus level were observed, namely Agathobacter, Anaerostipes, and Lachnospiraceae. Top differentially abundant bacteria and representative biological pathways were identified in children with ADHD using linear discriminant analysis (LDA) effect size (LEfSe), and the phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) analysis, respectively. The plasma levels of TNF-α were significantly lower in children with ADHD than in HCs. Within the ADHD group, the levels of TNF-α were negatively correlated with ADHD symptoms and diversity of the gut microbiome. Our study provides new insights into the association between gut microbiome dysbiosis and immune dysregulation, which may contribute to the pathophysiology of ADHD.

The association between heightened ADHD symptoms and cytokine and fatty acid concentrations during pregnancy

OBJECTIVE

Previous research conducted with samples of children suggest that individuals with attention-deficit/hyperactivity disorder (ADHD) have altered fatty acid concentrations and may have increased systemic inflammation. Whether these differences are also apparent in other populations of individuals with heightened ADHD symptoms (e.g., pregnant adults) is unknown. The goal of the current study was to examine whether there are ADHD-associated differences in polyunsaturated fatty acid concentrations or pro-inflammatory cytokine concentrations during pregnancy, a developmental period when fatty acid concentrations and systemic inflammation have implications for the health of both the pregnant person and the developing child. We hypothesized that plasma levels of the ratio of omega-6s to omega-3s (n-6:n-3) and plasma inflammatory cytokine levels would be higher in individuals with heightened ADHD symptoms, consistent with previous findings in children with ADHD.

METHODS

Data (N = 68) came from a prospective study of pregnant community volunteers who were oversampled for ADHD symptoms. During the 3rd trimester, plasma concentrations of fatty acids and the pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were assessed. Dietary intake was examined in the 3rd trimester using three 24-h recalls conducted by trained dietitians and by examining plasma levels of conjugated linoleic acid (n-6) and α-linolenic acid (n-3), essential fatty acids that must come from dietary intake.

RESULTS

The group with heightened ADHD symptoms had higher n-6:n-3s (β = 0.30, p < 0.01) and higher TNF-α concentrations (β = 0.35, p < 0.001) relative to controls. There were no group differences in dietary variables, as assessed by self-report and via plasma concentrations of essential fatty acids. IL-6 was not reliably associated with ADHD status in this sample.

CONCLUSION

Pregnant individuals with ADHD, on average, had higher plasma n-6:n-3s and higher TNF-α concentrations relative to controls. A difference was not detected in their dietary intake of fatty acids or other relevant nutrients. Though these null findings are inconclusive, they are consistent with the hypothesis that ADHD-associated differences in plasma fatty acid concentrations are the result of ADHD-associated differences in fatty acid metabolism, rather than simply differences in dietary intake.

Behavioral alterations in long-term Toxoplasma gondii infection of C57BL/6 mice are associated with neuroinflammation and disruption of the blood brain barrier

The Apicomplexa protozoan Toxoplasma gondii is a mandatory intracellular parasite and the causative agent of toxoplasmosis. This illness is of medical importance due to its high prevalence worldwide and may cause neurological alterations in immunocompromised persons. In chronically infected immunocompetent individuals, this parasite forms tissue cysts mainly in the brain. In addition, T. gondii infection has been related to mental illnesses such as schizophrenia, bipolar disorder, depression, obsessive-compulsive disorder, as well as mood, personality, and other behavioral changes. In the present study, we evaluated the kinetics of behavioral alterations in a model of chronic infection, assessing anxiety, depression and exploratory behavior, and their relationship with neuroinflammation and parasite cysts in brain tissue areas, blood-brain-barrier (BBB) integrity, and cytokine status in the brain and serum. Adult female C57BL/6 mice were infected by gavage with 5 cysts of the ME-49 type II T. gondii strain, and analyzed as independent groups at 30, 60 and 90 days postinfection (dpi). Anxiety, depressive-like behavior, and hyperactivity were detected in the early (30 dpi) and long-term (60 and 90 dpi) chronic T. gondii infection, in a direct association with the presence of parasite cysts and neuroinflammation, independently of the brain tissue areas, and linked to BBB disruption. These behavioral alterations paralleled the upregulation of expression of tumor necrosis factor (TNF) and CC-chemokines (CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β and CCL5/RANTES) in the brain tissue. In addition, increased levels of interferon-gamma (IFNγ), TNF and CCL2/MCP-1 were detected in the peripheral blood, at 30 and 60 dpi. Our data suggest that the persistence of parasite cysts induces sustained neuroinflammation, and BBB disruption, thus allowing leakage of cytokines of circulating plasma into the brain tissue. Therefore, all these factors may contribute to behavioral changes (anxiety, depressive-like behavior, and hyperactivity) in chronic T. gondii infection.

CD103 Deficiency Promotes Autism (ASD) and Attention-Deficit Hyperactivity Disorder (ADHD) Behavioral Spectra and Reduces Age-Related Cognitive Decline

The incidence of autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD), which frequently co-occur, are both rising. The causes of ASD and ADHD remain elusive, even as both appear to involve perturbation of the gut-brain-immune axis. CD103 is an integrin and E-cadherin receptor most prominently expressed on CD8 T cells that reside in gut, brain, and other tissues. CD103 deficiency is well-known to impair gut immunity and resident T cell function, but it's impact on neurodevelopmental disorders has not been examined. We show here that CD8 T cells influence neural progenitor cell function, and that CD103 modulates this impact both directly and potentially by controlling CD8 levels in brain. CD103 knockout (CD103KO) mice exhibited a variety of behavioral abnormalities, including superior cognitive performance coupled with repetitive behavior, aversion to novelty and social impairment in females, with hyperactivity with delayed learning in males. Brain protein markers in female and male CD103KOs coincided with known aspects of ASD and ADHD in humans, respectively. Surprisingly, CD103 deficiency also decreased age-related cognitive decline in both sexes, albeit by distinct means. Together, our findings reveal a novel role for CD103 in brain developmental function, and identify it as a unique factor linking ASD and ADHD etiology. Our data also introduce a new animal model of combined ASD and ADHD with associated cognitive benefits, and reveal potential therapeutic targets for these disorders and age-related cognitive decline.