Serum and lymphocytic neurotrophins profiles in systemic lupus erythematosus: a case-control study

Blood Growth Factor Levels in Patients with Systemic Lupus Erythematosus: High Neuregulin-1 Is Associated with Comorbid Cardiovascular Pathology

Patients with systemic lupus erythematosus (SLE) are known to frequently suffer from comorbid cardiovascular diseases (CVDs). There are abundant data on cytokine levels and their role in the pathogenesis of SLE, while growth factors have received much less attention. The aim of this study was to analyze growth factor levels in SLE patients and their association with the presence of comorbid CVDs. The serum concentrations for the granulocyte-macrophage colony-stimulating factor (GM-CSF), nerve growth factor β (NGFβ), glial cell line-derived neurotrophic factor (GDNF), and neuregulin-1 β (NRG-1β) were determined in the SLE patients (n = 35) and healthy individuals (n = 38) by a Luminex multiplex assay. The NGFβ and NRG-1β concentrations were shown to be significantly higher in the total group of SLE patients (median [Q1-Q3]: 3.6 [1.3-4.5] and 52.5 [8.5-148], respectively) compared with the healthy individuals (2.9 [1.3-3.4] and 13.7 [4.4-42] ng/mL, respectively). The GM-CSF and GDNF levels did not differ. Interestingly, elevated NRG-1β levels were associated with the presence of CVDs, as SLE patients with CVDs had significantly higher NRG-1β levels (99 [22-242]) compared with the controls (13.7 [4.4-42]) and patients without CVDs (19 [9-80] ng/mL). The model for the binary classification of SLE patients with and without CVDs based on the NRG-1β level had an average predictive ability (AUC = 0.67). Thus, altered levels of growth factors may be associated with comorbid CVDs in SLE patients.

The 330 risk loci known for systemic lupus erythematosus (SLE): a review

An in-depth literature review of up to 2023 reveals 330 risk loci found by genetic association at p ≤ 5 × 10-8, with systemic lupus erythematosus (SLE) in at least one study of 160 pertinent publications. There are 225 loci found in East Asian (EAS), 106 in European (EU), 11 in African-American (AA), 18 Mixed American (MA), and 1 in Egyptian ancestries. Unexpectedly, most of these associations are found to date at p ≤ 5 × 10-8 in a single ancestry. However, the EAS and EU share 40 risk loci that are independently established. The great majority of the identified loci [250 (75.8%) of 330] do not contain a variant that changes an amino acid sequence. Meanwhile, most overlap with known regulatory elements in the genome [266 (80.6%) of 330], suggesting a major role for gene regulation in the genetic mechanisms of SLE. To evaluate the pathways altered by SLE-associated variants, we generated gene sets potentially regulated by SLE loci that consist of the nearest genes, published attributions, and genes predicted by computational tools. The most useful insights, at present, suggest that SLE genetic mechanisms involve (1) the regulation of both adaptive and innate immune responses including immune cell activation and differentiation; (2) the regulation of production and response to cytokines, including type I interferon; (3) apoptosis; (4) the sensing and removal of immune complexes and apoptotic particles; and (5) immune response to infections, including Epstein-Barr Virus, and symbiont microorganisms. These mechanisms affected by SLE genes involve multiple cell types, including B cells/plasma cells, T cells, dendritic cells, monocytes/macrophages, natural killer cells, neutrophils, and endothelial cells. The genetics of SLE from GWAS data reveal an incredibly complex profusion of interrelated molecular processes and interacting cells participating in SLE pathogenesis, mostly unified in the molecular regulation of inflammatory responses. These genetic associations in lupus and affected molecular pathways not only give us an understanding of the disease pathogenesis but may also help in drug discoveries for SLE treatment.

Nerve Growth Factor and Autoimmune Diseases

NGF plays a crucial immunomodulatory role and increased levels are found in numerous tissues during autoimmune states. NGF directly modulates innate and adaptive immune responses of B and T cells and causes the release of neuropeptides and neurotransmitters controlling the immune system activation in inflamed tissues. Evidence suggests that NGF is involved in the pathogenesis of numerous immune diseases including autoimmune thyroiditis, chronic arthritis, multiple sclerosis, systemic lupus erythematosus, mastocytosis, and chronic granulomatous disease. Furthermore, as NGF levels have been linked to disease severity, it could be considered an optimal early biomarker to identify therapeutic approach efficacy. In conclusion, by gaining insights into how these molecules function and which cells they interact with, future studies can devise targeted therapies to address various neurological, immunological, and other disorders more effectively. This knowledge may pave the way for innovative treatments based on NGF manipulation aimed at improving the quality of life for individuals affected by diseases involving neurotrophins.

Blood levels of brain-derived neurotrophic factor (BDNF) in systemic lupus erythematous (SLE): a systematic review and meta-analysis

OBJECTIVES

BDNF has been implicated in the pathophysiology of systemic lupus erythematosus (SLE), especially its neuropsychiatric symptoms. The purpose of this study was to investigate the profile of blood BDNF levels in patients with SLE.

METHODS

We searched PubMed, EMBASE, and the Cochrane Library for papers that compared BDNF levels in SLE patients and healthy controls (HCs). The Newcastle-Ottawa scale was used to assess the quality of the included publications, and statistical analyses were carried out using R 4.0.4.

RESULTS

The final analysis included eight studies totaling 323 healthy controls and 658 SLE patients. Meta-analysis did not show statistically significant differences in blood BDNF concentrations in SLE patients compared to HCs (SMD 0.08, 95% CI [ - 1.15; 1.32], P value = 0.89). After removing outliers, there was no significant change in the results: SMD -0.3868 (95% CI [ - 1.17; 0.39], P value = 0.33. Univariate meta-regression analysis revealed that sample size, number of males, NOS score, and mean age of the SLE participants accounted for the heterogeneity of the studies (R² were 26.89%, 16.53%, 18.8%, and 49.96%, respectively).

CONCLUSION

In conclusion, our meta-analysis found no significant association between blood BDNF levels and SLE. The potential role and relevance of BDNF in SLE need to be further examined in higher quality studies.

ProBDNF and its receptors in immune-mediated inflammatory diseases: novel insights into the regulation of metabolism and mitochondria

Immune-mediated inflammatory diseases (IMIDs) consist of a common and clinically diverse group of diseases. Despite remarkable progress in the past two decades, no remission is observed in a large number of patients, and no effective treatments have been developed to prevent organ and tissue damage. Brain-derived neurotrophic factor precursor (proBDNF) and receptors, such as p75 neurotrophin receptor (p75^NTR) and sortilin, have been proposed to mediate intracellular metabolism and mitochondrial function to regulate the progression of several IMIDs. Here, the regulatory role of proBDNF and its receptors in seven typical IMIDs, including multiple sclerosis, rheumatoid arthritis, systemic lupus erythematosus, allergic asthma, type I diabetes, vasculitis, and inflammatory bowel diseases, was investigated.

Brain-Derived Neurotrophic Factor Suppressed Proinflammatory Cytokines Secretion and Enhanced MicroRNA(miR)-3168 Expression in Macrophages

We investigated the role of brain-derived neurotrophic factor (BDNF) and its signaling pathway in the proinflammatory cytokines production of macrophages. The effects of different concentrations of BDNF on proinflammatory cytokines expression and secretion in U937 cell-differentiated macrophages, and human monocyte-derived macrophages were analyzed using enzyme-linked immunosorbent assay and real-time polymerase chain reaction. The CRISPR-Cas9 system was used to knockout p75 neurotrophin receptor (p75NTR), one of the BDNF receptors. Next-generation sequencing (NGS) was conducted to search for BDNF-regulated microRNA. A very low concentration of BDNF (1 ng/mL) could suppress the secretion of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6 in lipopolysaccharide (LPS)-stimulated macrophages but did not change their mRNA expression. BDNF suppressed IL-1β and IL-6 secretion in human monocyte-derived macrophages. In U937 cells, BDNF suppressed the phosphorylation of JNK and c-Jun. The p75NTR knockout strongly suppressed IL-1β, IL-6, and TNF-α secretion in macrophages and LPS-stimulated macrophages. BDNF regulated the expression of miR-3168 with Ras-related protein Rab-11A as its target. In conclusion, BDNF suppressed proinflammatory cytokines secretion in macrophages and inhibited the phosphorylation of JNK. Knockout of p75NTR suppressed proinflammatory cytokines expression and secretion. BDNF upregulated the expression of miR-3168. The inhibition of p75NTR could be a potential strategy to control inflammation.

Brain-derived neurotrophic factor in autoimmune inflammatory diseases (Review)

Numerous recent studies reported that brain-derived neurotrophic factor (BDNF) also exists in the peripheral blood to regulate the proliferation, differentiation and survival of lymphocytes. Besides the role of BDNF in neuron repair, circulatory BDNF also enhances the proliferation and reduces apoptosis of lymphocytes. Peripheral lymphocytes express both BDNF and its receptors. Increasing evidence has indicated that altered BDNF serum levels significantly affect patients with autoimmune inflammatory diseases and may also be linked to the pathogenesis of diseases. For instance, systemic lupus erythematosus, an autoimmune inflammatory disease involving multiple organs, is frequently linked to altered B lymphocyte function, imbalance of T-cell subpopulations and loss of immune tolerance, which dysregulates the immune regulatory network with excessive secretion of inflammatory cytokines. The present review summarized studies that suggest a potential link between circulatory BDNF and autoimmune inflammatory diseases.

Cognitive dysfunction and serum levels of brain-derived neurotrophic factor (BDNF) in primary anti-phospholipid syndrome (PAPS)

OBJECTIVES

Cognitive dysfunction (CD) is a poorly understood non-stroke central neurological manifestation in anti-phospholipid syndrome (APS). Brain-derived neurotrophic factor (BDNF) is a neurotrophin that plays an important role in neural plasticity and could potentially be a biomarker of CD in primary APS (PAPS). The aim of the study is to assess CD in PAPS patients and to evaluate its association with clinical data, anti-phospholipid antibodies and serum BDNF levels.

METHODS

This cross-sectional study compared 44 PAPS patients and 20 healthy controls matched for age, gender and education. PAPS patients and controls underwent a standardized cognitive examination. The demographic, clinical and laboratory characteristics of patients were recorded. Serum BDNF was measured by Enzyme Linked Immunosorbent.

RESULTS

Fourteen (31.8%) of the 44 patients with PAPS had CD compared with only one (5%) healthy control (P =0.019). PAPS patients presented lower serum BDNF levels when compared with controls (P =0.007). Lower levels of BDNF were associated with CD in PAPS patients (P =0.032). In the univariate analysis, a positive association was found between CD and livedo reticularis, deep vein thrombosis, stroke, seizure, smoking as well as a negative association with Mini Mental State Examination and serum BDNF. According to multivariate analysis, the only independent predictor of CD in PAPS was stroke (OR 137.06; 95% CI: 4.73, 3974.32; P =0.004).

CONCLUSIONS

CD is commonly reported in PAPS patients; however, its assessment lacks in standards and objective screening tests. The association between CD and low serum BDNF suggests that this neurotrophin can be a promising biomarker for PAPS cognitive impairment.

Peripheral blood brain-derived neurotrophic factor level and tyrosine kinase B expression on T lymphocytes in systemic lupus erythematosus: Implications for systemic involvement

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) has been reported to be involved in the pathogenesis of autoimmune diseases and tyrosine kinase B (TrkB) is the specific receptor for BDNF. Our aim in this study was to investigate serum BDNF level and TrkB expression on peripheral blood T cell surface in patients with systemic lupus erythematosus (SLE) and explore potential relationship between serum BDNF and SLE.

METHODS

Samples from fifty SLE patients and thirty healthy controls were evaluated. Serum BDNF level was measured by enzyme-linked immunosorbent assay (ELISA) and the percentages of TrkB expression on the surface of CD3 + CD4 + and CD3 + CD8 + T lymphocytes were measured by flow cytometry. The SLE patients were divided into subgroups according to whether they exhibited brain, kidney or lung involvement, and whether the disease was active or inactive.

RESULTS

Serum BDNF levels in SLE patients were decreased when compared to the controls (p < 0.001). Comparing with the SLE individuals without systemic involvement, the BDNF levels were decreased in SLE patients with lupus nephritis (p = 0.042) and in SLE patients with neuropsychiatric manifestations (p = 0.04). On the other hand, the BDNF level was significantly increased in the inactive SLE group (p < 0.001) compared to the active SLE group. In addition, the percentages of TrkB expression on CD3 + CD4 + and CD3 + CD8 + T cell surface in SLE were significantly higher (p < 0.001; p < 0.001, respectively) than that in the controls.

CONCLUSIONS

Serum BDNF level combined with TrkB expression on T cell surface can reflect SLE activity. It is possible that BDNF may be used as a potential serological biomarker for disease activity of SLE. In addition, the significant decrease in serum BDNF level may imply systemic involvement of SLE, as well as, possibly, differentiate neuropsychiatric SLE from hormone-induced mental disorders.

Toward the Existence of a Sympathetic Neuroplasticity Adaptive Mechanism Influencing the Immune Response. A Hypothetical View-Part I

The nervous system exerts a profound influence on the function of the immune system (IS), mainly through the sympathetic arm of the autonomic nervous system. In fact, the sympathetic nervous system richly innervates secondary lymphoid organs (SLOs) such as the spleen and lymph nodes. For decades, different research groups working in the field have consistently reported changes in the sympathetic innervation of the SLOs during the activation of the IS, which are characterized by a decreased noradrenergic activity and retraction of these fibers. Most of these groups interpreted these changes as a pathological phenomenon, referred to as "damage" or "injury" of the noradrenergic fibers. Some of them postulated that this "injury" was probably due to toxic effects of released endogenous mediators. Others, working on animal models of chronic stimulation of the IS, linked it to the very chronic nature of processes. Unlike these views, this first part of the present work reviews evidence which supports the hypothesis of a specific adaptive mechanism of neural plasticity from sympathetic fibers innervating SLOs, encompassing structural and functional changes of noradrenergic nerves. This plasticity mechanism would involve segmental retraction and degeneration of these fibers during the activation of the IS with subsequent regeneration once the steady state is recovered. The candidate molecules likely to mediate this phenomenon are also here introduced. The second part will extend this view as to the potential changes in sympathetic innervation likely to occur in inflamed non-lymphoid peripheral tissues and its possible immunological implications.

Peripheral levels of brain-derived neurotrophic factor and S100B in neuropsychiatric systemic lupus erythematous

BACKGROUND

The aim of this study was to investigate serum S100B and brain-derived neurotrophic factor (BDNF) in systemic lupus erythematous (SLE) patients, with and without neuropsychiatric (NP) manifestation activity.

METHODS

We assessed 47 SLE patients and 20 selected healthy individuals. Disease activity was assessed according to the SLE disease activity index (SLEDAI). Serum BDNF and S100B were measured by enzyme-linked immunosorbent assay.

RESULTS

Serum S100B protein was significantly higher in SLE patients. BDNF levels were significantly decreased in active SLE, when compared with inactive SLE, but not when compared with controls. S100B was clearly higher in the NPSLE group, when compared with the non-NPSLE or control groups. Receiver operating characteristic analysis of S100B revealed an area under the curve of 0.706 that discriminated NPSLE patients with peripheral polyneuropathy.

CONCLUSIONS

Our findings reinforce the use of serum S100B as a biomarker in SLE, particularly for NPSLE. Moreover, we found a strong association between serum S100B and peripheral neuropathy, indicating a specific utility for this biomarker in SLE that warrants clinical investigation.

Serum levels of brain-derived neurotrophic factor are associated with depressive symptoms in patients with systemic lupus erythematosus

OBJECTIVE

The aim of this study was to explore potential relationships between serum BDNF levels and depression in systemic lupus erythematosus (SLE) patients.

METHODS

We included 208 consecutive SLE patients and 100 age-and sex-matched healthy controls. The presence of depressive symptoms was determined through the Beck Depression Inventory-II (BDI-II) score.

RESULTS

The serum BDNF levels were significantly (P<0.0001) higher in SLE patients as compared to normal controls. There was a negative correlation between levels of BDNF and the SLE disease activity index 2000 (SLEDAI-2K) (r=-0.349, P<0.0001). Depression (defined as BDI-II score≥18) was identified in 54 SLE patients (26.0%, 95%CI: 20%-31.9%). The serum BDNF levels were significantly lower in depression patients at the time of admission as compared with patients without depression [27.6(IQR, 23.2-30.4)ng/ml vs. 36.2(IQR, 31.7-42.3)ng/ml; P<0.0001]. Compared with the first quartile of serum BDNF levels, the second quartile OR for depression was 0.72 (95% CI, 0.61-0.80, P=0.033). For the third and fourth quartiles, it was 0.42 (95% CI, 0.33-0.52, P=0.002) and 0.16 (95% CI, 0.09-0.24; P<0.001).

CONCLUSION

Serum BDNF levels are decreased in SLE patients with depressive symptoms. In SLE, serum BNDF levels are independently associated with depressive disorders, suggesting the role of neurotrophic factors in depression.

Immune Cell Neurotrophin Production Is Associated with Subcortical Brain Atrophy in Neuropsychiatric Systemic Lupus Erythematosus Patients

OBJECTIVE

Central nervous system (CNS) involvement in systemic lupus erythematosus (SLE) remains poorly understood. Damage within the CNS is driven by the autoimmune response; however, immunopathophysiology of neuropsychiatric (NP) SLE is multifactorial. Immune cell neurotrophin production could be neuroprotective against autoimmunity-driven CNS damage, as has been shown in multiple sclerosis. The aim of this study was to establish whether immune cell neurotrophin production is associated with damage severity in NPSLE.

METHODS

Selected neurotrophins (BDNF, NGF, NT-3, and NT-4/5) were measured with ELISA within peripheral blood mononuclear cells (PBMCs) isolated from 38 NPSLE patients matched with 39 healthy controls. Subcortical and cortical structure volumes were segmented with the Freesurfer 5.3 pipeline on T1-weighted isotropic images acquired on a 1.5-T MRI scanner.

RESULTS

BDNF and NGF levels in PBMCs were reduced in NPSLE compared to the healthy population. The PBMC BDNF level was associated with reduced thalamus, caudate, and putamen volumes. The NGF level correlated with lateral ventricles enlargement and thalamic volume loss.

CONCLUSIONS

In NPSLE, immune cell BDNF and NGF levels are linked with subcortical atrophy. Higher BDNF levels are associated with higher midsagittal atrophy, which may reflect compensatory mechanisms, upregulating BDNF when neuroprotection is needed. These data require further confirmation.

Participation of the neutrophin brain-derived neurotrophic factor in neuropsychiatric systemic lupus erythematosus

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) is associated with the pathogenesis of several neuropsychiatric (NP) diseases, but there are few studies involving SLE. The aim of this study was to investigate whether plasma BDNF levels are associated with disease activity in SLE patients with severe NPSLE and non-NPSLE manifestations.

METHODS

We assessed 131 SLE patients and 24 randomly selected healthy individuals. SLE patients were evaluated in a cross-sectional study allocated according to the presence or not of NP manifestations and disease activity: (i) active NPSLE (n = 40), (ii) inactive NPSLE (n = 26), (iii) active SLE (n = 29) and (iv) inactive SLE (n = 36). In addition, NPSLE patients (n = 40) were evaluated before and after treatment. Disease activity was assessed according to the SLEDAI score. The plasma BDNF was measured by ELISA.

RESULTS

BDNF levels were increased in inactive NPSLE when compared with active SLE and controls (P < 0.0001). We observed similar findings in inactive SLE when compared with active SLE (P < 0.0001). In addition, we found an inverse correlation between plasma BDNF levels and the SLEDAI (r = -0.54, P < 0.0001) and a positive correlation with complement levels. We also observed an increase in BDNF levels in parallel with the improvement in NP symptoms.

CONCLUSION

Plasma BDNF level is increased in SLE patients and this increase is independent of the occurrence of NP manifestations. In addition, plasma BDNF levels increased with control of SLE activity, which points to the potential use of BDNF as a biomarker of response to treatment.