Involvement of neurotrophins and their receptors in spondyloarthritis synovitis: relation to inflammation and response to treatment

The Implications of Brain-Derived Neurotrophic Factor in the Biological Activities of Platelet-Rich Plasma

Platelet-rich plasma (PRP) is a biological blood-derived therapeutic obtained from whole blood that contains higher levels of platelets. PRP has been primarily used to mitigate joint degeneration and chronic pain in osteoarthritis (OA). This clinical applicability is based mechanistically on the release of several proteins by platelets that can restore joint homeostasis. Platelets are the primary source of brain-derived neurotrophic factor (BDNF) outside the central nervous system. Interestingly, BDNF and PRP share key biological activities with clinical applicability for OA management, such as anti-inflammatory, anti-apoptotic, and antioxidant. However, the role of BDNF in PRP therapeutic activities is still unknown. Thus, this work aimed to investigate the implications of BDNF in therapeutic outcomes provided by PRP therapy in vitro and in-vivo, using the MIA-OA animal model in male Wistar rats. Initially, the PRP was characterized, obtaining a leukocyte-poor-platelet-rich plasma (LP-PRP). Our assays indicated that platelets activated by Calcium release BDNF, and suppression of M1 macrophage polarization induced by LP-PRP depends on BDNF full-length receptor, Tropomyosin Kinase-B (TrkB). OA animals were given LP-PRP intra-articular and showed functional recovery in gait, joint pain, inflammation, and tissue damage caused by MIA. Immunohistochemistry for activating transcriptional factor-3 (ATF-3) on L4/L5 dorsal root ganglia showed the LP-PRP decreased the nerve injury induced by MIA. All these LP-PRP therapeutic activities were reversed in the presence of TrkB receptor antagonist. Our results suggest that the therapeutic effects of LP-PRP in alleviating OA symptoms in rats depend on BDNF/TrkB activity.

Nerve growth factor receptors in equine synovial membranes vary with osteoarthritic disease severity

Nerve growth factor (NGF) is a neurotrophin that has been implicated in pain signaling, apoptosis, inflammation and proliferation. The resultant effects depend on interaction with two different receptors; tyrosine kinase A (TrkA) and p75^NTR . NGF increases in synovial fluid from osteoarthritic joints, and monoclonal antibody therapy is trialed to treat osteoarthritis (OA)-related pain. Investigation of the complex and somewhat contradictory signaling pathways of NGF is conducted in neural research, but has not followed through to orthopaedic studies. The objectives of this study were to compare the expression of NGF receptors and the downstream regulator BAX in synovial membranes from joints in various stages of OA. The horse was used as a model. Synovial membranes were harvested from five healthy horses postmortem and from clinical cases with spontaneous OA undergoing arthroscopic surgery for lameness. Four horses with synovitis without gross cartilage changes, four horses with synovitis and cartilage damage, and four horses with synovitis and intracarpal fractures were included. Samples were investigated by immunohistochemistry and results showed that nuclear staining of TrkA, p75^NTR and BAX increases in OA-associated synovitis. TrkA expression increased in early disease stages whereas increases in p75^NTR were most prominent in later disease stages with cartilage damage and fibrosis. Clinical significance: Suppression of NGF may result in varied effects depending on different stages of the osteoarthritic disease process.

The Role of Brain-Derived Neurotrophic Factor in Immune-Related Diseases: A Narrative Review

Brain-derived neurotrophic factor (BDNF) is a neurotrophin regulating synaptic plasticity, neuronal excitability, and nociception. It seems to be one of the key molecules in interactions between the central nervous system and immune-related diseases, i.e., diseases with an inflammatory background of unknown etiology, such as inflammatory bowel diseases or rheumatoid arthritis. Studies show that BDNF levels might change in the tissues and serum of patients during the course of these conditions, e.g., affecting cell survival and modulating pain severity and signaling pathways involving different neurotransmitters. Immune-related conditions often feature psychiatric comorbidities, such as sleep disorders (e.g., insomnia) and symptoms of depression/anxiety; BDNF may be related as well to them as it seems to exert an influence on sleep structure; studies also show that patients with psychiatric disorders have decreased BDNF levels, which increase after treatment. BDNF also has a vital role in nociception, particularly in chronic pain, hyperalgesia, and allodynia, participating in the formation of central hypersensitization. In this review, we summarize the current knowledge on BDNF's function in immune-related diseases, sleep, and pain. We also discuss how BDNF is affected by treatment and what consequences these changes might have beyond the nervous system.

The Mechanism of Action between Pulsed Radiofrequency and Orthobiologics: Is There a Synergistic Effect?

Radiofrequency energy is a common treatment modality for chronic pain. While there are different forms of radiofrequency-based therapeutics, the common concept is the generation of an electromagnetic field in the applied area, that can result in neuromodulation (pulsed radiofrequency—PRF) or ablation. Our specific focus relates to PRF due to the possibility of modulation that is in accordance with the mechanisms of action of orthobiologics. The proposed mechanism of action of PRF pertaining to pain relief relies on a decrease in pro-inflammatory cytokines, an increase in cytosolic calcium concentration, a general effect on the immune system, and a reduction in the formation of free radical molecules. The primary known properties of orthobiologics constitute the release of growth factors, a stimulus for endogenous repair, analgesia, and improvement of the function of the injured area. In this review, we described the mechanism of action of both treatments and pertinent scientific references to the use of the combination of PRF and orthobiologics. Our hypothesis is a synergic effect with the combination of both techniques which could benefit patients and improve the life quality.

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.

Serum BDNF and cognitive dysfunction in SLE: findings from a cohort of 111 patients

OBJECTIVE

The association between brain-derived neurotrophic factor (BDNF) and neuropsychiatric systemic lupus erythematosus (NPSLE) is controversial in the literature. Cognitive dysfunction (CD) is a common, underdiagnosed NPSLE manifestation, but its pathophysiology is unknown. Thus, we investigate serum BDNF as a potential biomarker of CD in a cohort of SLE patients.

METHODS

We included 63 SLE patients, 48 NPSLE, and 57 age- and gender-matched controls (CON). All participants underwent neuropsychological assessment. Data on cardiovascular comorbidities, SLE disease activity index (SLEDAI), and Systemic Lupus International Collaborating Clinics damage index (SLICC-DI) were compiled. Multiple regression analyses evaluated predictors of serum BDNF levels.

RESULTS

Serum BDNF levels were lower in SLE and NPSLE patients than in CON (SLE 800.4 ± 502.7 vs. NPSLE 779.7 ± 426.3 vs. CON 1,345.5 ng/mL ± 438.4; p < 0.001). In addition, hypertension (B: - 192.5, SE: 84.3, 95% CI: - 359.7 to - 25.3, p = 0.024) and SLICC-DI score (B: - 75.9, SE: 27.2, 95% CI: - 129.8 to - 22, p = 0.006) were predictors of serum BDNF levels in SLE. There was no relation between BDNF levels and CD.

CONCLUSION

BDNF levels are lower in SLE patients than CON and inversely associated with hypertension and SLICC-DI scores. No association between BDNF levels and CD or NPSLE was observed in this cohort. These findings indicate that BDNF may be associated with overall burden in SLE rather than specific manifestations such as cognition impairment. Key Points • BDNF is associated with an overall burden in SLE rather than specific manifestations such as cognition dysfunction. • BDNF levels are reduced in patients with SLE, and higher SLICC-DI scores and hypertension are independent predictors of lower serum BDNF levels. • The cognitive dysfunction rate is elevated (46%) among Brazilian SLE patients.

The opposing contribution of neurotrophin-3 and nerve growth factor to orofacial heat hyperalgesia in rats

It has been proposed that neurotrophin-3 acts in a manner that is opposed to nerve growth factor, especially in the modulation of heat hyperalgesia. Injury to the constriction of the infraorbital nerve (CION) is a well-established model of trigeminal neuropathic pain that leads to robust heat, cold, and mechanical hyperalgesia. Here, we assessed the effect of local neurotrophin-3 treatment on CION-induced hyperalgesia, and we examined some mechanisms related to the effect of neurotrophin-3. Neurotrophin-3 (1 µg/50 µl) injected into the upper lip of CION rats caused a significant and long-lasting reduction of CION-induced heat hyperalgesia, but failed to affect cold and mechanical hyperalgesia. Increased levels of neurotrophin-3 were detected in the injured nerve at the time point that represents the peak of heat hyperalgesia. The anti-hyperalgesic effect of neurotrophin-3 was markedly reduced in the presence of an antagonist of TrkA receptors (K-252a, 1 μg/50 μl). Moreover, association of lower doses of neurotrophin-3 with an antibody anti-nerve growth factor resulted in a synergistic anti-hyperalgesic effect in CION rats. Local injection of nerve growth factor (3 µg/50 µl) or the TRPV1 agonist capsaicin (1 μg/50 μl), but not neurotrophin-3 injection (1 µg/50 µl), resulted in long-lasting facial heat hyperalgesia, which was both significantly reduced by previous neurotrophin-3 local treatment. In conclusion, we suggest that neurotrophin-3 is a potent modulator of facial heat hyperalgesia, which may exert an inhibitory influence on the trkA pathway. Neurotrophin-3 treatment may represent a promising approach, especially in pain conditions associated with increased levels of nerve growth factor.

In vitro affinity optimization of an anti-BDNF monoclonal antibody translates to improved potency in targeting chronic pain states in vivo

The role of brain-derived neurotrophic factor (BDNF) signaling in chronic pain has been well documented. Given the important central role of BDNF in long term plasticity and memory, we sought to engineer a high affinity, peripherally-restricted monoclonal antibody against BDNF to modulate pain. BDNF shares 100% sequence homology across human and rodents; thus, we selected chickens as an alternative immune host for initial antibody generation. Here, we describe the affinity optimization of complementarity-determining region-grafted, chicken-derived R3bH01, an anti-BDNF antibody specifically blocking the TrkB receptor interaction. Antibody optimization led to the identification of B30, which has a > 300-fold improvement in affinity based on BIAcore, an 800-fold improvement in potency in a cell-based pERK assay and demonstrates exquisite selectivity over related neurotrophins. Affinity improvements measured in vitro translated to in vivo pharmacological activity, with B30 demonstrating a 30-fold improvement in potency over parental R3bH01 in a peripheral nerve injury model. We further demonstrate that peripheral BDNF plays a role in maintaining the plasticity of sensory neurons following nerve damage, with B30 reversing neuron hyperexcitability associated with heat and mechanical stimuli in a dose-dependent fashion. In summary, our data demonstrate that effective sequestration of BDNF via a high affinity neutralizing antibody has potential utility in modulating the pathophysiological mechanisms that drive chronic pain states.

pathfindR: An R Package for Comprehensive Identification of Enriched Pathways in Omics Data Through Active Subnetworks

Pathway analysis is often the first choice for studying the mechanisms underlying a phenotype. However, conventional methods for pathway analysis do not take into account complex protein-protein interaction information, resulting in incomplete conclusions. Previously, numerous approaches that utilize protein-protein interaction information to enhance pathway analysis yielded superior results compared to conventional methods. Hereby, we present pathfindR, another approach exploiting protein-protein interaction information and the first R package for active-subnetwork-oriented pathway enrichment analyses for class comparison omics experiments. Using the list of genes obtained from an omics experiment comparing two groups of samples, pathfindR identifies active subnetworks in a protein-protein interaction network. It then performs pathway enrichment analyses on these identified subnetworks. To further reduce the complexity, it provides functionality for clustering the resulting pathways. Moreover, through a scoring function, the overall activity of each pathway in each sample can be estimated. We illustrate the capabilities of our pathway analysis method on three gene expression datasets and compare our results with those obtained from three popular pathway analysis tools. The results demonstrate that literature-supported disease-related pathways ranked higher in our approach compared to the others. Moreover, pathfindR identified additional pathways relevant to the conditions that were not identified by other tools, including pathways named after the conditions.

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.

Associations between Variants in BDNF/BDNFOS Gene and Lumbar Disc Herniation Risk among Han Chinese People

Lumbar disc herniation (LDH) is a low back pain disorder and associated with several single nucleotide polymorphisms (SNPs). However, the role of brain-derived neurotrophic factor (BDNF) and BDNFOS gene in LDH susceptibility remains unknown. To examine whether the variants contribute to LDH, 7 SNPs were genotyped in 380 patients and 692 healthy controls among Han Chinese population. Multiple genetic models, stratification by age/gender and haploview analysis was used by calculating odds ratio (OR) and 95% confidence intervals (CIs). Rs11030064 in BDNFOS gene was associated with modified susceptibility for LDH at age ≤50 years but three loci (rs6265, rs11030104 and rs10767664) of BDNF gene increased LDH risk at age >50 years. Further, rs11030096 polymorphism in BDNFOS gene was associated with LDH the increased susceptibility of LDH in females. Haplotype analysis shown that haplotype “GCC” in the block (rs988712, rs7481311, and rs11030064) increased LDH risk (OR = 1.49, 95% CI = 1.06–2.10, p = 0.022) at age ≤50 years. However, there was no significant association between BDNF/BDNFOS gene and LDH risk in the overall before stratified analysis. For the first time, our results provide evidence on polymorphism of BDNF / BDNFOS gene associated with LDH risk in Chinese Han population.

Nerve growth factor concentrations in the synovial fluid from healthy dogs and dogs with secondary osteoarthritis

Objective: To measure the concentrations of nerve growth factor (NGF) in the synovial fluid from normal dogs and dogs with osteoarthritis (OA) secondary to common joint disorders.

Methods: Nerve growth factor synovial concentrations were measured by ELISA assay in 50 dogs divided into three groups: 12 healthy, 16 affected by acute lameness within seven days before enrolment, and 22 with chronic lameness persisting by more than one month before enrolment and accompanied by radiological signs of OA. Both acute and chronic lameness were secondary to orthopaedic diseases involving the shoulder, elbow and stifle joints. Nerve growth factor synovial concentrations were compared between means for healthy and acute groups and between the three groups using an F-test. Significance level was set at p ±0.05.

Results: Nerve growth factor was detected in all canine synovial fluid samples. However, the mean synovial NGF concentration of healthy dogs (3.65 ± 2.18 pg/ml) was not significantly different from the mean value in dogs with acute lameness (6.45 ± 2.45 pg/ml) (p ± 0.79). Conversely, the mean synovial NGF concentration in dogs with chronic lameness (20.19 ± 17.51 pg/ml) was found to be significantly higher than that found in healthy dogs (p ±0.01).

Clinical significance: This study demonstrates for the first time the presence of NGF in canine synovial fluid and its increased concentrations in dogs with chronic lameness compared to healthy dogs and dogs with acute lameness. The association between chronic lameness and raised synovial concentrations may suggest an involvement of NGF in OA inflammation and chronic pain.

NGF and Its Receptors in the Regulation of Inflammatory Response

There is growing interest in the complex relationship between the nervous and immune systems and how its alteration can affect homeostasis and result in the development of inflammatory diseases. A key mediator in cross-talk between the two systems is nerve growth factor (NGF), which can influence both neuronal cell function and immune cell activity. The up-regulation of NGF described in inflamed tissues of many diseases can regulate innervation and neuronal activity of peripheral neurons, inducing the release of immune-active neuropeptides and neurotransmitters, but can also directly influence innate and adaptive immune responses. Expression of the NGF receptors tropomyosin receptor kinase A (TrkA) and p75 neurotrophin receptor (p75NTR) is dynamically regulated in immune cells, suggesting a varying requirement for NGF depending on their state of differentiation and functional activity. NGF has a variety of effects that can be either pro-inflammatory or anti-inflammatory. This apparent contradiction can be explained by considering NGF as part of an endogenous mechanism that, while activating immune responses, also activates pathways necessary to dampen the inflammatory response and limit tissue damage. Decreases in TrkA expression, such as that recently demonstrated in immune cells of arthritis patients, might prevent the activation by NGF of regulatory feed-back mechanisms, thus contributing to the development and maintenance of chronic inflammation.

Brain-derived neurotrophic factor plasma levels are increased in older women after an acute episode of low back pain

BACKGROUND

Low back pain (LBP) is a growing public health problem in old age, and it is associated with disabling pain and depressive disorders. We compared brain-derived neurotrophic factor (BDNF) plasma levels, a key neurotrophin in pain modulation, between older women after an acute episode of LBP and age-matched pain-free controls, and investigated potential differences in BDNF levels between controls and LBP subgroups based on pain severity, presence of depressive symptoms and use of analgesic and antidepressant drugs.

METHODS

A total of 221 participants (154 with LBP and 67 pain-free) were studied. A comprehensive assessment of sociodemographic and clinical variables was conducted including pain severity (11-point NRS), depressive symptoms (GDS-15), age, body mass index, physical activity and total number of comorbidities and medications in use.

RESULTS

BDNF levels in LBP group were significantly higher than controls (7515.9±3021.2; Md=7116.0 vs 6331.8±3364.0; Md=5897.5pg/mL, P=0.005). LBP subgroups exhibited higher BDNF levels than controls, regardless of pain severity, presence of depressive symptoms and use of analgesic drugs. BDNF levels were significantly higher in LBP subgroup without use of antidepressant drugs compared to both controls and LBP subgroup with use of antidepressant drugs.

DISCUSSION

This study provides evidence that older women with acute low back pain exhibit higher BDNF plasma levels compared to pain-free controls. Subgroup comparisons suggest that use of pain-relief drugs may influence BDNF levels. The study results offer a novel target for research on mechanisms of back pain in older adults.

Fasinumab (REGN475), an antibody against nerve growth factor for the treatment of pain: results from a double-blind, placebo-controlled exploratory study in osteoarthritis of the knee

The safety, tolerability, and efficacy of fasinumab (REGN475), a fully human monoclonal antibody against nerve growth factor, was evaluated for the treatment of pain in patients with osteoarthritis (OA) of the knee. This was a 24-week, double-blind, placebo-controlled, parallel-group, repeat-dose, exploratory study. Eligible patients 40 to 75 years of age with a diagnosis of OA of the knee and moderate to severe pain were randomized 1:1:1:1 to intravenous fasinumab 0.03, 0.1, or 0.3 mg/kg or placebo and received study drug on day 1 and day 57. Pain intensity was recorded daily using the numeric rating scale. Safety and tolerability, assessed by the incidence of treatment-emergent adverse events (TEAEs), was the primary study endpoint. Secondary study endpoints included the change from baseline in daily walking knee pain and the assessment of pain, function, and stiffness using the Western Ontario and McMaster Osteoarthritis (WOMAC) index. Baseline characteristics were similar among treatment groups (N=217). After 24 weeks, the incidence of TEAEs ranged from 66.1% to 75.0% in the fasinumab groups vs. 63.6% for placebo. The most common TEAEs included arthralgia, hyperesthesia, myalgia, peripheral edema, and joint swelling. Discontinuation for TEAEs occurred in 5.6% of fasinumab patients and 3.7% of placebo patients. All 3 doses of fasinumab were associated with significant (P<.05) improvements compared with placebo in walking knee pain and WOMAC total and subscale scores. Fasinumab was generally well tolerated, and was associated with a significant reduction in walking knee pain and an improvement in function for up to 8 weeks.

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

BACKGROUND

Neurotrophins play a central role in the development and maintenance of the nervous system. However, neurotrophins can also modulate B and T cell proliferation and activation, especially via autocrine loops. We hypothesized that both serum and lymphocytic neurotrophin levels may be deregulated in systemic Lupus erythematosus (SLE) and may reflect clinical symptoms of the disease.

METHODS

Neurotrophins in the serum (ELISA tests) and lymphocytes (flow cytometry) were measured in 26 SLE patients and 26 control subjects. Th1 (interferon-γ) and Th2 (IL-10) profiles and serum concentration of BAFF were assessed by ELISA in the SLE and control subjects.

FINDINGS

We have demonstrated that both NGF and BDNF serum levels are higher in SLE patients than healthy controls (p=0.003 and p<0.001), independently of Th1 or Th2 profiles. Enhanced serum NT-3 levels (p=0.003) were only found in severe lupus flares (i.e. SLEDAI ≥ 10) and significantly correlated with complement activation (decreased CH 50, Γ=-0.28, p=0.03). Furthermore, there was a negative correlation between serum NGF levels and the number of circulating T regulatory cells (Γ=0.48, p=0.01). In circulating B cells, production of both NGF and BDNF was greater in SLE patients than in healthy controls. In particular, the number of NGF-secreting B cells correlated with decreased complement levels (p=0.05). One month after SLE flare treatment, BDNF levels decreased; in contrast, NGF and NT-3 levels remained unchanged.

CONCLUSION

This study demonstrates that serum and B cell levels of both NGF and BDNF are increased in SLE, suggesting that the neurotrophin production pathway is deregulated in this disease. These results must be confirmed in a larger study with naive SLE patients, in order to avoid the potential confounding influence of prior immune-modulating treatments on neurotrophin levels.

Brain-derived neurotrophic factor is upregulated in the cervical dorsal root ganglia and spinal cord and contributes to the maintenance of pain from facet joint injury in the rat

The facet joint is commonly associated with neck and low back pain and is susceptible to loading-induced injury. Although tensile loading of the cervical facet joint has been associated with inflammation and neuronal hyperexcitability, the mechanisms of joint loading-induced pain remain unknown. Altered brain-derived neurotrophic factor (BDNF) levels are associated with a host of painful conditions, but the role of BDNF in loading-induced joint pain remains undefined. Separate groups of rats underwent a painful cervical facet joint distraction or a sham procedure. Bilateral forepaw mechanical hypersensitivity was assessed and BDNF mRNA and protein levels were quantified in the dorsal root ganglion (DRG) and spinal cord at days 1 and 7. Facet joint distraction induced significant (P < 0.001) mechanical hypersensitivity at both time points. Painful joint distraction did not alter BDNF mRNA in the DRG compared with sham levels but did significantly increase (P < 0.016) BDNF protein expression over sham in the DRG at day 7. Painful distraction also significantly increased BDNF mRNA (P = 0.031) and protein expression (P = 0.047) over sham responses in the spinal cord at day 7. In a separate study, intrathecal administration of the BDNF-sequestering molecule trkB-Fc on day 5 after injury partially attenuated behavioral sensitivity after joint distraction and reduced pERK in the spinal cord at day 7 (P < 0.045). Changes in BDNF after painful facet joint injury and the effect of spinal BDNF sequestration in partially reducing pain suggest that BDNF signaling contributes to the maintenance of loading-induced facet pain but that additional cellular responses are also likely involved.

Augmented pain behavioural responses to intra-articular injection of nerve growth factor in two animal models of osteoarthritis

OBJECTIVES

Nerve growth factor (NGF) is a promising analgesic target, particularly in osteoarthritis (OA) where existing therapies are inadequate. We hypothesised that pain responses to NGF are increased in OA joints. Here, NGF-evoked pain behaviour was compared in two rodent models of OA, and possible mechanisms underlying altered pain responses were examined.

METHODS

OA was induced in rat knees by meniscal transection (MNX) or intra-articular monosodium iodoacetate injection (MIA). Once OA pathology was fully established (day 20), we assessed pain behaviour (hindlimb weight-bearing asymmetry and hindpaw mechanical withdrawal thresholds) evoked by intra-articular injection of NGF (10 µg). Possible mechanisms underlying alterations in NGF-induced pain behaviour were explored using indomethacin pretreatment, histopathological evaluation of synovitis, and rtPCR for NGF receptor (tropomyosin receptor kinase (Trk)-A) expression in dorsal root ganglia (DRG).

RESULTS

Both the MIA and MNX models of OA displayed reduced ipsilateral weight bearing and hindpaw mechanical withdrawal thresholds, mild synovitis and increased TrkA expression in DRG. NGF injection into OA knees produced a prolonged augmentation of weight-bearing asymmetry, compared to NGF injection in non-osteoarthritic knees. However, hindpaw mechanical withdrawal thresholds were not further decreased by NGF. Pretreatment with indomethacin attenuated NGF-facilitated weight-bearing asymmetry and reversed OA-induced ipsilateral TrkA mRNA up-regulation.

CONCLUSIONS

OA knees were more sensitive to NGF-induced pain behaviour compared to non-osteoarthritic knees. Cyclo-oxygenase products may contribute to increased TrkA expression during OA development, and the subsequent increased NGF sensitivity. Treatments that reduce sensitivity to NGF have potential to improve OA pain.

A sub-pathway based method to identify candidate agents for Ankylosing Spondylitis

The need for new therapeutics for Ankylosing Spondylitis (AS) is highlighted by the general lack of efficacy for most agents currently available for this disease. Many recent studies have detailed molecular pathways in AS, and several molecule-targeting agents are undergoing evaluation. We aimed to explore the mechanism of AS and identify biologically active small molecules capable of targeting the sub-pathways which were disregulated in the development of AS. By using the GSE25101 microarray data accessible from the Gene Expression Omnibus database, we first identified the differentially expressed genes (DEGs) between AS samples and healthy controls, followed by the sub-pathway enrichment analysis of the DEGs. In addition, we propose the use of an approach based on targeting sub-pathways to identify potential agents for AS. A total of 3,280 genes were identified as being significantly different between patients and controls with p-values < 0.1. Our study showed that neurotrophic signaling pathway and some immune-associated pathways may be involved in the development of AS. Besides, our bioinformatics analysis revealed a total of 15 small molecules which may play a role in perturbing the development of AS. Our study proposes the use of an approach based on targeting sub-pathways to identify potential agents for AS. Candidate agents identified by our approach may provide the groundwork for a combination therapy approach for AS.

Measurements in the Blood of BDNF for RA Patients and in Response to Anti-TNF Treatment Help Us to Clarify the Magnitude of Centrally Related Pain and to Explain the Relief of This Pain upon Treatment

Brain-derived neurotrophic factor (BDNF) is a neurotrophin with functions related to neuronal survival/proliferation processes and inflammation. BDNF is also an important central pain mediator. The levels of BDNF have been found to be high for RA patients with severe disease and to become lowered in response to anti-TNF treatment. New information says that the levels of BDNF in the blood parallel the BDNF concentrations in the brain and that BDNF can pass the blood-brain barrier. Furthermore, most of the circulating BDNF is produced in the brain. Habitual and regular exercise, in contrast to temporary exercise, does also lead to a lowering of BDNF blood levels. Both anti-TNF treatment and habitual and regular exercise do have pain-relieving effects. It might be that the pain-relieving effect of anti-TNF treatment is related to an affection of central neuronal regions, hereby influencing BDNF production. Measurements of BDNF in the blood help us to clarify the magnitude of centrally related pain for RA patients and help us to explain the relief of this pain in response to anti-TNF treatment.

Linkage and association study of neurotrophins and their receptors as novel susceptibility genes for childhood IgA nephropathy

Neurotrophins (NTs) and their receptors (NTRs) are known to be important for pathogenesis of various inflammatory diseases that occur in not only neuronal but also nonneuronal tissues, including kidney. Here, we investigated association between childhood IgA nephropathy (IgAN) and single nucleotide polymorphisms (SNPs) of genes encoding NTs [nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF)] and NTRs [nerve growth factor receptor (NGFR) and neurotrophic tyrosine kinase receptor 1-3 (NTRK1-3)]. The genotyping data of 197 patients and 289 control subjects revealed significant association between NGF SNP rs11102930 and presence of IgAN. Patient subgroup analysis revealed that that the presence of nephrotic range proteinuria (>40 mg/m/h) was associated with rs6334 of NTRK1 and rs11030104, rs7103411, rs7103873, and rs6484320 of BDNF. Significant genotype differences were observed in podocyte foot process effacement for rs1187321 and rs1187323 of NTRK2. Furthermore, some SNPs showed significantly different genotype distribution between patients with or without pathologically advanced disease markers, specifically in rs6334 of NTRK1. Our results suggest that SNPs of NTs and NTRs are associated with susceptibility, pathological advancement, podocyte foot process effacement, and development of proteinuria in childhood IgAN.

Emerging drugs for psoriatic arthritis

IMPORTANCE OF THE FIELD

The socioeconomic burden of psoriatic arthritis (PsA) is considerable and not different from that of rheumatoid arthritis. Current treatment options do not always allow reaching the therapeutic objectives consisting of the remission of symptoms and prevention of the appearance of damage in the early stage of PsA or the blocking of PsA progression in the established cases.

AREAS COVERED IN THIS REVIEW

After reviewing the current treatment choices, we examine the new drugs in clinical Phase II and III trials for PsA up to January 2010. Information was mainly obtained from the network of international clinical trial registries.

WHAT THE READER WILL GAIN

The current management of PsA includes NSAIDs, corticosteroids, disease-modifying antirheumatic drugs (DMARDs) and anti-TNF-alpha blocking agents. These last drugs are more effective than traditional DMARDs on symptoms/signs of inflammation, quality of life and function and can inhibit the progression of the structural joint damage. Recent advancement in the knowledge of the immunopathogenesis of PsA has permitted the development of novel drugs including new TNF-alpha blockers, IL-1, -6, -12, -23 and -17 inhibitors, co-stimulator modulation inhibitors, B-cell depleting agents, small molecules and receptor activator of NF-kappaB/receptor activator of NF-kappaB ligand inhibitors.

TAKE HOME MESSAGE

The currently available anti-TNF-alpha blocking agents have revolutionized the management of PsA. However, there is a need for more effective and safer drugs.

Serum neurotrophin profile in systemic sclerosis

Background

Neurotrophins (NTs) are able to activate lymphocytes and fibroblasts; they can modulate angiogenesis and sympathic vascular function. Thus, they can be implicated in the three pathogenic processes of systemic sclerosis (SSc). The aims of this study are to determine blood levels of Nerve Growth Factor (NGF), Brain-Derived Neurotrophic Factor (BDNF) and Neurotrophin-3 (NT-3) in SSc and to correlate them with clinical and biological data.

Methods

Serum samples were obtained from 55 SSc patients and 32 control subjects to measure NTs levels by ELISA and to determine their relationships with SSc profiles.

Findings

Serum NGF levels were higher in SSc patients (288.26±170.34 pg/mL) than in control subjects (170.34±50.8 pg/mL, p<0.001) and correlated with gammaglobulins levels and the presence of both anti-cardiolipin and anti-Scl-70 antibodies (p<0.05). In contrast, BDNF levels were lower in SSc patients than in controls (1121.9±158.1 vs 1372.9±190.9 pg/mL, p<0.0001), especially in pulmonary arterial hypertension and diffuse SSc as compared to limited forms (all p<0.05). NT-3 levels were similar in SSc and in the control group (2657.2±2296 vs 2959.3±2555 pg/mL, NS). BDNF levels correlated negatively with increased NGF levels in the SSc group (and not in controls).

Conclusion

Low BDNF serum levels were not previously documented in SSc, particularly in the diffuse SSc subset and in patients with pulmonary hypertension or anti-Scl-70 antibodies. The negative correlation between NGF and BDNF levels observed in SSc and not in healthy controls could be implicated in sympathic vascular dysfunction in SSc.

Obesity: genes, brain, gut, and environment

Obesity, which is assuming alarming proportions, has been attributed to genetic factors, hypothalamic dysfunction, and intestinal gut bacteria and an increase in the consumption of energy-dense food. Obesity predisposes to the development of type 2 diabetes mellitus, hypertension, coronary heart disease, and certain forms of cancer. Recent studies have shown that the intestinal bacteria in obese humans and mice differ from those in lean that could trigger a low-grade systemic inflammation. Consumption of a calorie-dense diet that initiates and perpetuates obesity could be due to failure of homeostatic mechanisms that regulate appetite, food consumption, and energy balance. Hypothalamic factors that regulate energy needs of the body, control appetite and satiety, and gut bacteria that participate in food digestion play a critical role in the onset of obesity. Incretins, cholecystokinin, brain-derived neurotrophic factor, leptin, long-chain fatty acid coenzyme A, endocannabinoids and vagal neurotransmitter acetylcholine play a role in the regulation of energy intake, glucose homeostasis, insulin secretion, and pathobiology of obesity and type 2 diabetes mellitus. Thus, there is a cross-talk among the gut, liver, pancreas, adipose tissue, and hypothalamus. Based on these evidences, it is clear that management of obesity needs a multifactorial approach.

New data favouring that neurotrophins are of importance in arthritis

Neurotrophins are important in inflammation. In an article in Arthritis Research & Therapy, Barthel and collaborators give new information on the existence of neurotrophin production in the synovial tissue of arthritic joints. These findings, together with other recent findings, stress that neurotrophins should be considered important factors in arthritis. This is reinforced by the facts that they are also produced by articular chondrocytes and that receptors for these are present in the synovial tissue and on chondrocytes. The importance of neurotrophins in joints should be further studied, including examinations on the efficacy of interfering with their effects in arthritis.

Absence of a classically activated macrophage cytokine signature in peripheral spondylarthritis, including psoriatic arthritis

OBJECTIVE

Peripheral spondylarthritis (SpA) is characterized by macrophages that express CD163, a marker of alternative activation (M2). The purpose of this study was to assess whether this differential infiltration with macrophage subsets was associated with a different local inflammatory milieu in SpA as compared with rheumatoid arthritis (RA).

METHODS

The effect of SpA and RA synovial fluid (SF) on macrophage polarization was tested in vitro on normal peripheral blood monocytes. SF levels of classically activated macrophage (M1)-derived and alternatively activated macrophage (M2)-derived mediators were analyzed by enzyme-linked immunosorbent assay and multiparameter Luminex bead assay in 47 patients with non-psoriatic SpA, 55 with RA, and 15 with psoriatic arthritis (PsA). Paired synovial biopsy samples were analyzed histologically.

RESULTS

SF from SpA patients promoted preferential expression of the M2 markers CD163 and CD200R in vitro, even if SF levels of the prototypical M2-polarizing factors (interleukin-4 [IL-4], IL-13, and IL-10) were not increased as compared with those in RA SF. Despite a similar degree of overall joint inflammation in SpA and RA, SpA synovitis displayed strongly reduced SF levels of M1-derived, but not M2-derived, mediators, such as tumor necrosis factor alpha (TNFalpha), IL-1beta, IL-12p70, and interferon-gamma-inducible protein 10. SF levels of M1-derived mediators correlated well with peripheral joint inflammation in RA, but neither these mediators nor IL-1alpha and IL-17 did so in SpA. Of interest, the SF cytokine profile in PsA, a more destructive subtype of SpA, was similar to that in non-psoriatic SpA.

CONCLUSION

The local inflammatory milieu is clearly different in SpA as compared with RA peripheral arthritis. Synovitis in SpA, including that in PsA, is characterized by a selective decrease in M1-derived proinflammatory mediators, such as TNFalpha and IL-1beta.

Nerve growth factor and receptor expression in rheumatoid arthritis and spondyloarthritis

Introduction

We previously described the presence of nerve growth factor receptors in the inflamed synovial compartment. Here we investigated the presence of the corresponding nerve growth factors, with special focus on nerve growth factor (NGF).

Methods

mRNA expression levels of four ligands (NGF, brain derived growth factor (BDNF), neurotrophin (NT)-3, NT-4) and their four corresponding receptors (tyrosine kinase (trk) A, trkB, trkC, NGFRp75) were determined in the synovial fluid (SF) cells of 9 patients with rheumatoid arthritis (RA) and 16 with spondyloarthritis (SpA) and compared with 7 osteoarthritis (OA) patients. NGF was also determined in synovial tissue (ST) biopsies of 10 RA and 10 SpA patients. The production of NGF by monocytes and lymphocytes was assessed by flow cytometry of SF cells, synovial tissue derived fibroblast-like synoviocytes (FLS) were assessed by ELISA on culture supernatant.

Results

SF cell analysis revealed a clear BDNF and NGF mRNA expression, with significantly higher NGF expression in RA and SpA patients than in the OA group. NGF expression was higher in ST samples of RA as compared to SpA. Using intracellular FACS analysis, we could demonstrate the presence of the NGF protein in the two inflammatory arthritis groups on both CD3+ T lymphocytes and CD14+ cells, i.e. monocytes/macrophages, whereas cultured FLS did not produce NGF in vitro.

Conclusions

Neurotrophins and especially NGF are expressed in the synovial fluid and tissue of patients with peripheral synovitis. The presence of neurotrophins as well as their receptors, in particular the NGF/trkA-p75 axis in peripheral synovitis warrants further functional investigation of their active involvement in chronic inflammatory arthritis.

The regulatory role of nerve growth factor and its receptor system in fibroblast-like synovial cells

OBJECTIVES

Investigating the role of nerve growth factor (NGF) and its receptors (NGF-R) in inflammatory diseases is an active field of research. Inflammatory diseases of the joint are the commonest cause of human morbidity but very little is known about the effect of NGF on synovial tissue biology. Here we have studied NGF/NGF-R and their functional significance on cultured fibroblast-like synovial cells (FLS) collected from the synovial tissue of five healthy subjects.

METHODS

NGF/NGF-R expression was determined in the basal condition and after stimulation with tumour necrosis factor (TNF)alpha and interleukin (IL)-1beta by enzyme-linked immunosorbent assay (ELISA) and fluorescence-activated cell sorting (FACS). Proliferation studies were performed by cell count, hexosaminidase assay, and the MTT assay. The synovial fluid (SF) NGF level was studied by ELISA in 12 psoriatic arthritis (PsA), 14 rheumatoid arthritis (RA), and 10 osteoarthritis (OA) patients.

RESULTS

FACS studies showed that unstimulated FLS expressed low levels of NGF and the high-affinity NGF-tyrosine kinase receptor TrkA, and TNFalpha and IL-1beta increased NGF and TrkA expression in FLS. NGF (100 ng/mL) increased FLS proliferation by 400% compared to the control (medium only). The NGF level was significantly higher in the PsA group (365.5+/-85.2 pg/mL) than in the RA (120+/-35 pg/mL) and OA groups (30+/-6 pg/mL).

CONCLUSIONS

Upregulation of NGF/TrkA in proinflammatory cytokine-activated FLS, the mitogenic effect of NGF on FLS, and the increased NGF level in SF of inflammatory arthritis suggest that there is cross-talk between NGF/NGF-R and FLS. These results also suggest that dysregulated production of NGF may lead to synovial cell proliferation and thus could influence the inflammatory and proliferative cascades of inflammatory arthritis.

Cardiovascular actions of neurotrophins

Neurotrophins were christened in consideration of their actions on the nervous system and, for a long time, they were the exclusive interest of neuroscientists. However, more recently, this family of proteins has been shown to possess essential cardiovascular functions. During cardiovascular development, neurotrophins and their receptors are essential factors in the formation of the heart and critical regulator of vascular development. Postnatally, neurotrophins control the survival of endothelial cells, vascular smooth muscle cells, and cardiomyocytes and regulate angiogenesis and vasculogenesis, by autocrine and paracrine mechanisms. Recent studies suggest the capacity of neurotrophins, via their tropomyosin-kinase receptors, to promote therapeutic neovascularization in animal models of hindlimb ischemia. Conversely, the neurotrophin low-affinity p75(NTR) receptor induces apoptosis of endothelial cells and vascular smooth muscle cells and impairs angiogenesis. Finally, nerve growth factor looks particularly promising in treating microvascular complications of diabetes or reducing cardiomyocyte apoptosis in the infarcted heart. These seminal discoveries have fuelled basic and translational research and thus opened a new field of investigation in cardiovascular medicine and therapeutics. Here, we review recent progress on the molecular signaling and roles played by neurotrophins in cardiovascular development, function, and pathology, and we discuss therapeutic potential of strategies based on neurotrophin manipulation.

Identification of interleukin-7 as a candidate disease mediator in spondylarthritis

OBJECTIVE

Understanding of the molecular pathophysiology of spondylarthritis (SpA) remains largely elusive. This is related both to the complexity of the disease (axial versus peripheral disease, inflammation versus tissue remodeling) and to the difficulty in obtaining samples from primary disease sites. This study was undertaken to explore a gene expression approach for identifying novel candidate mediators of SpA.

METHODS

Sacroiliac joint fluid aspirates from 3 SpA patients with active sacroiliitis were studied by microarray analysis. The expression of selected candidate molecules in peripheral synovitis was confirmed by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

Microarray analysis identified 4 sacroiliitis gene clusters, containing a total of 47 messenger RNA (mRNA) transcripts. Two clusters contained genes expressed in all sacroiliitis samples, corresponding to both known and unsuspected candidate mediators of SpA pathology. These included proinflammatory molecules as well as molecules involved in tissue remodeling, such as transforming growth factor beta2. Of the novel candidate genes selected for confirmation, interleukin-7 (IL-7) mRNA expression was higher in SpA peripheral synovial fluid and synovial tissue samples than in osteoarthritis samples, and similar to expression in rheumatoid arthritis (RA) samples. At the protein level, synovial fluid IL-7 levels were even higher in SpA than in RA, despite lower levels of tumor necrosis factor alpha and IL-1beta.

CONCLUSION

In the present study, both known and unsuspected candidate mediators of SpA pathogenesis were identified, including IL-7. The specific overexpression of IL-7 at sites of peripheral synovitis in SpA suggests that further functional investigations of the role of this cytokine in SpA pathogenesis are warranted.

Expression and regulation of neurotrophins in the nondegenerate and degenerate human intervertebral disc

Introduction

The neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) have been identified in the human intervertebral disc (IVD) and have been implicated in the mechanisms associated with nerve ingrowth and nociception in degeneration of the IVD. The aim of the current study was to investigate an association between neurotrophin expression in the IVD and the severity of disc degeneration, including the effect of disc-related proinflammatory cytokines on neurotrophin and neuropeptide expression in cells derived from the human IVD.

Methods

Immunohistochemical analysis was performed to examine the expression of NGF, BDNF and their high-affinity receptors Trk-A and Trk-B in human IVD samples, divided into three categories: non-degenerate, moderate degeneration and severe degeneration. In order to study the effect of disc-related cytokines on neurotrophin/neuropeptide gene expression, nucleus pulposus cells derived from non-degenerate and degenerate IVD samples were seeded in alginate and were stimulated with either IL-1β or TNFα for 48 hours. RNA was extracted, cDNA was synthesised and quantitative real-time PCR was performed to examine the expression of NGF, BDNF and substance P.

Results

Immunohistochemistry showed expression of NGF and BDNF in the native chondrocyte-like cells in all regions of the IVD and in all grades of degeneration. Interestingly only BDNF significantly increased with the severity of degeneration (P < 0.05). Similar expression was observed for Trk-A and Trk-B, although no association with disease severity was demonstrated. In cultured human nucleus pulposus cells, stimulation with IL-1β led to significant increases in NGF and BDNF gene expression (P < 0.05). Treatment with TNFα was associated with an upregulation of substance P expression only.

Conclusion

Our findings show that both the annulus fibrosus and nucleus pulposus cells of the IVD express the neurotrophins NGF and BDNF, factors that may influence and enhance innervation and pain in the degenerate IVD. Expression of Trk-A and Trk-B by cells of the nondegenerate and degenerate IVD suggests an autocrine role for neurotrophins in regulation of disc cell biology. Furthermore, modulation of neurotrophin expression by IL-1β and modulation of substance P expression by TNFα, coupled with their increased expression in the degenerate IVD, highlights novel roles for these cytokines in regulating nerve ingrowth in the degenerate IVD and associated back pain.

From transcriptome to cytome: integrating cytometric profiling, multivariate cluster, and prediction analyses for a phenotypical classification of inflammatory diseases

Gene expression studies of peripheral blood cells in inflammatory diseases revealed a large array of new antigens as potential biomarkers useful for diagnosis, prognosis, and therapy stratification. Generally, their validation on the protein level remains mainly restricted to a more hypothesis-driven manner. State-of-the-art multicolor flow cytometry make it attractive to validate candidate genes at the protein and single cell level combined with a detailed immunophenotyping of blood cell subsets. We developed multicolor staining panels including up to 50 different monoclonal antibodies that allowed the assessment of several hundreds of phenotypical parameters in a few milliliters of peripheral blood. Up to 10 different surface antigens were measured simultaneously by the combination of seven different fluorescence colors. In a pilot study blood samples of ankylosing spondylitis (AS) patients were compared with normal donors (ND). A special focus was set on the establishment of suitable bioinformatic strategy for storing and analyzing hundreds of phenotypical parameters obtained from a single blood sample. We could establish a set of multicolor stainings that allowed monitoring of all major leukocyte populations and their corresponding subtypes in peripheral blood. In addition, antigens involved in complement and antibody binding, cell migration, and activation were acquired. The feasibility of our cytometric profiling approach was demonstrated by a successful classification of AS samples with a reduced subset of 80 statistically significant parameters, which are partially involved in antigen presentation and cell migration. Furthermore, these parameters allowed an error-free prediction of independent AS and ND samples originally not included for parameter selection. This study demonstrates a new level of multiparametric analysis in the post-transcriptomic era. The integration of an appropriate bioinformatic solution as presented here by the combination of a custom-made Access database along with cluster- and prediction-analysis tools predestine our approach to promote the human cytome project.

BDNF in RA: downregulated in plasma following anti-TNF treatment but no correlation with inflammatory parameters

The involvement of brain-derived neurotrophic factor (BDNF) in rheumatoid arthritis (RA) is largely unknown. The distribution of BDNF and its associated receptors, TrkB and p75, in the synovial tissue of patients with RA was examined and contrasted with that in patients with osteoarthritis (OA). Additionally, levels of BDNF in both synovial tissue and synovial fluid were measured. Furthermore, the effects of anti-tumour necrosis factor (anti-TNF; infliximab) treatment on BDNF levels in the plasma of RA patients were analysed. Cells in the synovium showed immunoreactivity for BDNF and BDNF-, p75- and TrkB-receptor immunoreactions were seen in nerve fibres of nerve fascicles and in association with sensory corpuscles. The levels of BDNF in synovial tissue were not correlated with the number of inflammatory cells observed microscopically or with levels of TNFalpha. Nor did the BDNF levels in synovial fluid correlate with erythrocyte sedimentation rate (ESR) or white blood cell counts. Anti-TNF treatment lead to a decrease in plasma levels of BDNF 14 weeks after the initiation of anti-TNF therapy, i.e., 8 weeks after the last infusion. Higher levels of BDNF were observed in RA patients at baseline compared with those for healthy individuals. However, the levels of BDNF in plasma of patients treated with anti-TNF did not correlate with the changes in ESR or a disease activity score. The clinical significance of this study is that anti-TNF treatment influences plasma levels of BDNF although there was no evidence that BDNF levels correlate with inflammatory parameters in either infliximab-treated or non-infliximab-treated patients with RA. Instead it is likely that sources other than inflammatory cells, including nerve structures, are important sources of BDNF and that the effects of anti-TNF treatment on BDNF levels may be related to effects on circulating and various local cells and/or BDNF-containing neurons.

Nerve growth factor and brain-derived neurotrophic factor levels in patients with rheumatoid arthritis treated with TNF-alpha blockers

Twenty consecutive rheumatoid arthritis (RA) patients (mean age 50.4 +/- 10.5 years; 17 females; mean disease duration 5.78 +/- 3.75 years) enrolled for tumor necrosis factor-alpha (TNF-alpha) blockers therapy (10 infliximab and 10 etanercept) were selected. Before starting therapy, 3 and 6 months thereafter all patients were evaluated for disease activity score (DAS), erythrocyte sedimentation rate (ESR), serum levels of C-reactive protein (CRP), interleukin-6 (IL-6), nerve growth factor (NGF), and brain-derived neurotrophic factor (BDNF). After 3 and 6 months a significant reduction in DAS, ESR, CRP, and IL-6 was observed, whereas no significant differences of NGF and BDNF serum levels were found. These preliminary results confirm that TNF-alpha blockers significantly improve disease activity and inflammation in RA; nevertheless further studies are needed to explain the mechanisms regulating NGF and BDNF release in RA patients treated with TNF-alpha blockers.

BDNF: a missing link between sympathetic dysfunction and inflammatory disease?

Nerve growth factor (NGF) plays a role in sympathetic neuron integrity and survival. Brain-derived neurotrophic factor (BDNF) also has trophic effects on sympathetic neurons. We report here the serendipitous finding that co-treatment of hippocampus with BDNF and the NGF antagonist TrkA-Fc leads to perivascular inflammation and marked vasoconstriction. This effect is not observed with either reagent alone or in combination with other control proteins. Because NGF supports sympathetic neuron health, we tested the hypothesis that BDNF combined with sympathetic compromise caused this effect. Superior cervical ganglia were removed bilaterally with concurrent BDNF infusion into hippocampus. Perivascular inflammation was observed at 3 days, but not 12 days post treatment, when sympathetic terminals had receded, suggesting that the presence of these terminals was necessary for inflammation. Since sympathetic dysfunction may lead to compensatory overactivity of norepinephrine (NE) signaling, we co-infused BDNF with NE in the hippocampus and observed perivascular inflammation. In humans, sympathetic overactivity has been reported in a variety of vascular diseases. Some of these diseases, e.g. primary Raynaud's, are not accompanied by serious inflammatory disease whereas others, such as scleroderma and systemic lupus, are. We speculate that BDNF may contribute to the transformation of sympathetic dysfunction to inflammatory disease.