Brain-derived neurotrophic factor gene polymorphisms and serum levels in Chinese atopic dermatitis patients

Neurotrophin-4 and Brain-Derived Neurotrophic Factor Serum Levels in Renal Transplant Recipients with Chronic Pruritus

INTRODUCTION

Chronic pruritus (CP) is a common symptom defined as a sensation that provokes the desire to scratch and which lasts for at least 6 weeks. CP remains a problem for up to 21.3% of renal transplant recipients (RTRs). Our research aimed to establish the possible association between serum levels of neurotrophin-4 (NT-4) and brain-derived neurotrophic factor (BDNF) and the presence and intensity of CP in RTR.

METHODS

The study was performed on a group of 129 RTRs, who were divided according to the presence or absence of pruritus in the previous 3 days. The assessment of pruritus was performed with the use of a numeric rating scale (NRS), 4-Item Itch Questionnaire (4IIQ), and Itchy Quality of Life (Itchy QoL). A total of 129 blood samples with a volume of 9 ml were drawn from RTRs during the monthly routine control. Serum levels (pg/mL) of NT-4 and BDNF were measured by the ELISA.

RESULTS

Pruritic RTRs have statistically significantly higher serum concentrations of NT-4 serum level compared to non-pruritic RTRs (229.17 ± 143.86 pg/mL and 153.08 ± 78.19 pg/mL [p = 0.024], respectively). Moreover, a statistically significant difference between pruritic and non-pruritic RTRs with healthy controls was shown (p < 0.001 and p < 0.001, respectively). Although there was a numerically higher serum concentration of BDNF in pruritic RTRs (32.18 ± 7.31 pg/mL vs. 31.58 ± 10.84 pg/mL), the difference did not reach statistical significance. No statistically significant difference was also seen in BDNF serum levels between RTRs and healthy controls. Furthermore, there was a statistically significant, positive correlation between serum concentration of NT-4 and NRS score (p = 0.008, r = 0.357).

CONCLUSIONS

The results indicate higher NT-4 serum concentration in RTRs with pruritus compared to RTRs without pruritus. Furthermore, the study revealed a statistically significant, positive correlation between the serum concentration of NT-4 and NRS score.

Elevated Level of Serum Neurotrophin-4, but Not of Brain-Derived Neurotrophic Factor, in Patients with Chronic Kidney Disease-Associated Pruritus

Chronic kidney disease-associated pruritus (CKD-aP) is a bothersome condition that occurs in patients with advanced chronic kidney disease (CKD) and severely reduces their quality of life. Recently, much research has focused on the search for markers that are involved in the pathogenesis of CKD-aP and may become a therapeutic target. One of the suggested hypotheses is the increased activation of sensory neurons by molecules such as neurotrophins (NTs). An increased serum concentration of NTs has been demonstrated in pruritic patients, which may suggest their involvement in the pathogenesis of itch. The purpose of this study is to assess the serum concentration of neurotrophin-4 (NT-4) and brain-derived neurotrophic factor (BDNF) in hemodialysis patients. The study enrolled 126 patients undergoing dialysis. Participants were divided into 2 groups: with and without CKD-aP. NRS scale was used to evaluate itch severity. Serum levels of NT-4 and BDNF have been assessed using ELISA. The results showed a significantly higher level of NT-4 in the group with pruritus. No significant difference was reported in the serum level of BDNF between the two groups of patients. There was also no correlation between serum NT-4 nor BDNF levels and the severity of pruritus. In summary, NT-4 may play an important role in the pathophysiology of pruritus in dialysis patients. More research is needed to understand the exact mechanism by which NTs influence the pathogenesis of CKD-aP.

Seasonality and BDNF polymorphism influences depression outcome in patients with atopic dermatitis and psoriasis

OBJECTIVES

To examine the effect of seasonality and rs6265 genotype on depression outcome and brain-derived neurotrophic factor (BDNF) level with dermatitis patients from onset through remission.

METHODS

Atopic dermatitis (AD, 56) and psoriasis (PS, 33) patients and healthy controls (HC, 49) were recruited over the 2014 calendar year. Patients were subdivided by immunoglobulin E (IgE) sensitivity (AD only), season and rs6265 genotype. Assessments were performed at onset and week 10 (Hamilton Depression Rating Scale [HAM-D], SCORAD/PASI, IgE, BDNF). Patients received standard corticosteroid and antihistamine interventions.

RESULTS

All patients responded to corticosteroid treatment. Seasonally differential outcomes were observed in all groups. HAM-D was elevated at onset and improved over 10 weeks: AD cohort 1 (autumn/winter, AD-1) patients improved and AD cohort 2 (spring/summer, AD-2) patients remained elevated. BDNF levels were elevated in AD and seasonal differential: AD-2 declined at 10 weeks, whereas AD-1 remained high (intrinsic AD) or elevated further (extrinsic AD). PS cohort 2 declined to below control at 10 weeks. AD Val/Val had persistently elevated HAM-D and AD Val/Met were either normal (AD-1) or persistently elevated (AD-2).

CONCLUSIONS

Findings presented here suggest a strong influence of seasonality on depression outcome and BDNF expression in AD and PS and likely reflect separate patient populations which differentially respond to environment-based stressors.

Serum biomarkers for allergy in children

A large number of studies investigating various biomarkers for allergy have been published over the past decades. The aim of this review was to evaluate these biomarkers on their diagnostic and/or predictive value. To this date, no single or specific biomarker for allergy has been identified. As allergy is not one disease, but a collection of a number of allergic conditions, it is more plausible a combination of clinical history, clinical readouts, and diagnostic markers will be needed.

Molecular Mechanisms of Cutaneous Inflammatory Disorder: Atopic Dermatitis

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease resulting from interactions between genetic susceptibility and environmental factors. The pathogenesis of AD is poorly understood, and the treatment of recalcitrant AD is still challenging. There is accumulating evidence for new gene polymorphisms related to the epidermal barrier function and innate and adaptive immunity in patients with AD. Newly-found T cells and dendritic cell subsets, cytokines, chemokines and signaling pathways have extended our understanding of the molecular pathomechanism underlying AD. Genetic changes caused by environmental factors have been shown to contribute to the pathogenesis of AD. We herein present a review of the genetics, epigenetics, barrier dysfunction and immunological abnormalities in AD with a focus on updated molecular biology.

Genetic polymorphisms and the adequacy of brain stimulation: state of the art

INTRODUCTION

Heterogeneity of therapeutic response to brain stimulation techniques has inspired scientists to uncover the secrets to success or failure of these projects. Genetic polymorphisms are one of the major causes of this heterogeneity.

AREAS COVERED

More than twenty genetic variants within more than ten genes (e.g. BDNF, COMT, DRD2, TRPV1, 5-HT1A, 5-HHT, P2RX7, VEGF, TPH1, TPH2, ACE, APOE, GNB3, NET, NMDA receptors, and RGS4) have been investigated, among which the BDNF gene and its polymorphism, Val66Met, is the best documented variant. We review the genotypic combinations, which are reported to interact with the work of brain stimulation, of which the DRD2 C957T polymorphism is the most prominent type. Finally, implications of transcranial magnetic stimulation in deciphering the interaction between genetic background (e.g. SCN1A and 5-HTT) and drugs (e.g. carbamazepine and citalopram) at the cortical excitability level is explained. Expert commentary: Studies are ongoing to find missing factors responsible for heterogeneity of response to brain stimulation techniques. Further knowledge about genetic factors affecting the therapeutic response to brain stimulation techniques might provide helpful guidelines for choosing ideal candidates for treatment.

Val66Met polymorphism in the BDNF gene in children with bronchial asthma

OBJECTIVES

Bronchial asthma is a chronic respiratory disease characterized by airway inflammation. There is increasing evidence that neurotrophins play an important role in the development and maintenance of neurogenic airway inflammation in chronic allergic diseases.

WORKING HYPOTHESIS

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family and has several important functions in the airways. There are only a few reports on the association between genetic variations in the BDNF gene and various allergic diseases, and the results are generally conflicting. Therefore, we aimed to study the functional polymorphism Val66Met (also called rs6265 or G196A) in the BDNF gene in a group of asthmatic children and healthy controls.

STUDY DESIGN, PATIENT-SELECTION, AND METHODOLOGY

We studied 248 asthmatic patients (aged 12.28 ± 0.24 years) and 249 healthy children (aged 13.14 ± 0.48 years). Analysis of the Val66Met polymorphism of the BDNF gene was performed by polymerase chain reaction (PCR) and PCR products were digested by PmlI.

RESULTS

The prevalence of the Val66Met polymorphisms (Val/Val, Val/Met, and Met/Met) was 61.7%, 33.5%, and 4.8% in asthmatics, respectively, and 47.0%, 51.8%, and 1.2% in healthy subjects, respectively. We observed a significant association of the Met/Met variant genotype with asthmatics (OR = 4.17, 95% CI = 1.16-14.96, P = 0.018). The Val/Met genotype was protective against bronchial asthma (OR = 0.69, 95% CI = 0.48-0.99, P = 0.045), especially in girls (OR = 0.34, 95% CI = 0.20-0.59, P = 0.001).

CONCLUSION

Specific BDNF gene polymorphism may contribute to bronchial asthma susceptibility. Our study suggested the positive association between selected functional BDNF polymorphism (rs6265) and asthma in children.

Possible pathogenic role of T helper type 9 cells and interleukin (IL)-9 in atopic dermatitis

T helper type 9 (Th9) cells are a novel identified subset of CD4(+) T helper cells, which could partly contribute to allergic inflammation, while the precise contribution of Th9 cells in atopic dermatitis (AD) remains unknown. We aimed to explore the possible role of Th9 cells in AD pathogenesis. The Th9 cell percentage, transcription factor PU.1 and cytokine interleukin (IL)-9 mRNA levels, as well as IL-9 serum concentration in peripheral circulation, were measured in AD patients, psoriasis patients and healthy controls. The Th9 cell percentage, PU.1 and IL-9 expression levels of AD patients were all increased significantly compared with the other two control groups (P < 0·01), and correlated positively with SCORing Atopic Dermatitis index, serum immunoglobulin (Ig)E and thymus- and activation-regulated chemokine (TARC) levels (P < 0·05). In simple AD patients and AD patients complicated by allergic rhinitis or asthma, there were no significant differences in the Th9 cell percentage, PU.1 and IL-9 expression levels between them. At the same time, IL-9 and vascular endothelial growth factor (VEGF) mRNA levels were detected in AD lesions and normal skin samples, which were both distinctly elevated in AD lesions, and there was a positive association between them (P < 0·01). Keratinocytes were cultured with IL-9 stimulation and the secretion of VEGF was detected. IL-9 can promote the secretion of VEGF by keratinocytes in a time- and dose-dependent manner. In conclusion, the expansion of the Th9 cell subset, up-regulation of the PU.1 transcription factor and increased secretion of the IL-9 cytokine may contribute to the pathogenesis of AD, which may be supported by the increased release of VEGF by keratinocyes after IL-9 stimulation.

Reduced serum brain-derived neurotrophic factor in patients with first onset vitiligo

PURPOSE

Vitiligo is an acquired pigmentary skin disease that can cause serious cosmetic problems. There have been numerous and well established studies that have demonstrated the comorbidity of various psychiatric disorders in patients with vitiligo. However, to our knowledge, there have been no studies investigating whether a psychiatric biomarker, such as brain-derived neurotrophic factor (BDNF), is associated with vitiligo.

PATIENTS AND METHODS

This study was conducted in Namık Kemal University Medical Faculty, Departments of Dermatology and Psychiatry between January 2013 and September 2014. After meeting inclusion and exclusion criteria, serum BDNF levels were assayed in 57 patients with first onset vitiligo and no known current or past psychiatric disorder and compared with BDNF levels in 58 age and sex matched healthy subjects.

RESULTS

The age and female/male ratios were similar between groups. The mean values of serum BDNF were 1.57±0.97 ng/dL and 2.37±1.73 ng/dL in the vitiligo group and in the healthy control group, respectively. The mean BDNF level was significantly higher in the healthy control group compared with the vitiligo group (t=2.76, P=0.007).

CONCLUSION

This is the first study to compare serum BDNF levels between patients with vitiligo and healthy subjects. The reduced level of serum BDNF in patients with vitiligo may be directly related to the etiology of vitiligo or associated with the high percentage of psychiatric disorders in that patient population. Further studies are needed to support our preliminary results.

The Imbalance of Th17 cells and CD4(+) CD25(high) Foxp3(+) Treg cells in patients with atopic dermatitis

BACKGROUND

Th17/Treg imbalance is involved in several autoimmune, inflammatory and allergic reactions. Nevertheless, the possible contribution of Th17/Treg imbalance in atopic dermatitis (AD) remains unknown.

OBJECTIVE

To explore the possible role of Th17/Treg imbalance in AD.

METHODS

Th17 and Treg cells percentage in peripheral blood mononuclear cells (PBMCs) and skin specimens, specific transcription factor retinoic acid-related orphan receptor (ROR)γt and Foxp3 mRNA levels in PBMCs, as well as Th17- and Treg-related cytokines mRNA levels in PBMCs, serum concentrations, and expression levels in PBMCs culture supernatant after recombinant Dermatophagoides pteronyssinus antigen stimulation were detected in AD patients. Controls included patients with psoriasis, allergic contact dermatitis (ACD) and healthy donors.

RESULTS

Th17 cells percentage, RORγt, IL-17 and IL-23 levels in peripheral circulation of AD patients were significantly higher than those in ACD patients and healthy controls, but lower than those of psoriasis patients. Treg cells percentage, Foxp3 and TGF-β mRNA levels were reduced in AD patients compared with healthy controls, while there were no significant differences among AD, ACD and psoriasis patients. Th17 cells percentage, IL-17 and IL-23 levels were increased, while Treg cells percentage and TGF-β level were decreased in AD lesion and PBMCs culture supernatant respectively. There was a negative association between Th17 and Treg cells percentage in AD patients. AD severity score positively correlated with Th17 cells percentage and Th17/Treg ratio, while negatively correlated with Treg cells percentage. Serum IgE levels positively correlated with Th17/Treg ratio.

CONCLUSION

In AD, there exists an immune imbalance in Th17 and Treg cells, which may contribute to its pathogenesis and development.

An update on the genetics of atopic dermatitis: scratching the surface in 2009

A genetic basis for atopic dermatitis (AD) has long been recognized. Historic documents allude to family history of disease as a risk factor. Before characterization of the human genome, heritability studies combined with family-based linkage studies supported the definition of AD as a complex trait in that interactions between genes and environmental factors and the interplay between multiple genes contribute to disease manifestation. A summary of more than 100 published reports on genetic association studies through mid-2009 implicates 81 genes, in 46 of which at least 1 positive association with AD has been demonstrated. Of these, the gene encoding filaggrin (FLG) has been most consistently replicated. Most candidate gene studies to date have focused on adaptive and innate immune response genes, but there is increasing interest in skin barrier dysfunction genes. This review examines the methods that have been used to identify susceptibility genes for AD and how the underlying pathology of this disease has been used to select candidate genes. Current challenges and the potential effect of new technologies are discussed.