BDNF ELISA Kit

Review: BDNF and Psychiatric Disorders -Mature BDNF quantification leads to new research strategy-

Brain-Derived Neurotrophic Factor (BDNF) is a molecule working in the development and maintenance of neurological function. BDNF has been reported to be related to various psychiatric diseases and it is also expected as a potential biomarker. The precursor (proBDNF) is processed to mature BDNF (mBNDF). ProBDNF and mBDNF have different functions, so that the specific methods for measuring each BDNF are required, respectively. This article explains the outline of BDNF and introduces our Mature BDNF ELISA Kit Wako.

Brain-Derived Neurotrophic Factor (BDNF)

BDNF is a secretory protein first isolated from the porcine brain as one of the neurotrophic factors frequently expressed in the brain by Barde et al in 1982. BDNF is the second identified neurotrophic factor in the neurotrophin family and widely expressed in the brain from the developing stage to the maturing stage of the neurological system. Enhancing neuron survival and synapse formation via high-affinity receptor Tropomyosin related kinase B (TrkB)1,2) are well-known functions of BDNF. BDNF has been getting attention in neuroscience research, as it is an important factor for the development and maintenance of neurological function.

Expectation as a biomarker

BDNF has been also reported to be deeply involved in brain-derived disorders, including psychiatric disorders3). Especially in the depression research, it is expected to be a biomarker since Karege et al first reported that serum BDNF levels in depression patients were lower than in healthy individuals4). Moreover, as depression patients not taking antidepressants show a reduction in serum BDNF, quantitation of BDNF is a possible indicator for depression treatment. Recently, meta-analyses have also unveiled a reduction in serum BDNF levels in patients with bipolar disorder and schizophrenia, as well as depression5). From all these findings, BDNF is likely to be an important factor for several psychiatric disorders even though the mechanism is not clear.

Mature BDNF and precursor BDNF

BDNF is expressed as precursor BDNF (proBDNF), transferred to the secreting site, and processed to mature BDNF (mBDNF)6) (Fig.1). ProBDNF had been thought to have no physiologic role; however, it has been discovered to have a different physiologic role from mBDNF. mBDNF induces long-term potentiation (LTP) via TrkB and enhances neurogenesis and development, whereas proBDNF induces long-term depression (LTD) via low-affinity receptor p75NTR and promotes apoptosis7) (Fig.2). The function change occurred by processing indicates that BDNF has a very complicated control system of the nerve system. Therefore, BDNF studies require detection methods that are specific to each molecule.

01897_img01.png

Figure 1. Structures of proBDNF and mBDNF
N-terminus of proBDNF is cleaved to form mBDNF.

 

01897_img02.png

Figure2. Function of proBDNF and mBDNF
ProBDNF induces apoptosis and suppress growth of neurite via p75NTR
while mBDNF induces synapse formation and growth of neurite via TrkB.

Development of detection technology of mature BDNF

Since mBDNF is truncated from proBDNF, it does not have unique amino acid sequences (Fig.1). To address this issue, we have developed Mature BDNF ELISA Kit Wako, using an antibody that specifically detects the N-terminus of mBDNF (Fig.3,4). This antibody has as low as about 10% cross-reactivity to proBDNF, enabling the detection of mBDNF with high specificity and sensitivity (Table 1). The recovery rate of the kit was more than 90% in the spike and recovery test in both human serum and plasma samples (Table 2), and it also had superior linearity in the dilution linearity test (Fig.5). We examined mBDNF in serum collected from healthy individuals, and patients with major depression, bipolar disorder, or schizophrenia. These results showed a trend that these patients had lower mBDNF levels than healthy individuals (It is not statistically significant) (Table 3). From these data, our Mature BDNF ELISA Kit Wako is expected to be a useful tool for psychiatric disorder research.

01897_img03.png

 

Figure 3. Principle of Mature BDNF ELISA kit Wako
We have successfully developed mBDNF specific ELISA kit
by utilizing antibody which detect N-terminus of mBDNF.

 

  • Standard curve range 4.1 - 1,000 pg/mL
    Specificity mBDNF*
    Sample Human serum and plasma**
    Sample volume Human serum: 10 μL
    Human plasma: 5 μL
    Assay time 4 hours
    Detection method Colorimetric method

    * Approximately 10% reaction to proBDNF
    ** This antibody can detect mouse and rat BDNF.

     

    Figure 4. Overview of Mature BDNF ELISA kit Wako

  • 01897_img04.png

 

Table 1. Comparison of commercial mBDNF ELISA kit

FUJIFILM Wako Company A Company B Company C
Cross-reactivity to proBDNF Approx. 10% Approx. 10% Approx. 15% Approx. 50%
Minimum concentration of assay range 4.1 pg/mL 62.5 pg/mL 15.6 pg/mL 15.0 pg/mL

 

01897_img05.png

Figure 5. Dilution linearity test
Superior linearity in dilution linearity test was observed.

 

 

Table 2. Spike and recovery test in human serum and plasma

Sample Spike mBDNF
(pg/mL)
Assay value
(pg/mL)
Recovery volume
(pg/mL)
Receovery
(%)
Sample Spike mBDNF
(pg/mL)
Assay value
(pg/mL)
Recovery volume
(pg/mL)
Receovery
(%)
Human Serum 1 0 330 Human Plasma 1 0 156
100 423 93.0 93.0 100 252 96.0 96.0
250 581 251 100 250 407 251 100
500 817 487 97.4 500 661 505 101
Human Serum 2 0 56.6 Human Plasma 2 0 66.0
50 106 49.4 98.8 50 115 49.0 98.0
100 154 97.4 97.4 100 164 98.0 98.0
200 257 200 100 200 276 210 105
300 363 306 102 300 369 303 101

 

 

Table 3. Measurement of mBDNF in serum from healthy individuals and patients with major depression, bipolar disorder, or schizophrenia

  • Healthy Control (n=6)
    No. Sex Age Assay value
    (ng/mL)
    1 F 48 14.5
    2 F 50 22.8
    3 F 54 20
    4 F 47 18.5
    5 F 42 13.8
    6 F 60 19.1
  • Major depression (n=6)
    No. Sex Age Assay value
    (ng/mL)
    1 F 66 15.7
    2 F 38 18.1
    3 F 43 10
    4 F 52 16.6
    5 F 41 22.3
    6 F 58 15.1
  • Bipolar disorder (n=4)
    No. Sex Age Assay value
    (ng/mL)
    1 F 46 16.5
    2 F 52 20.9
    3 F 52 11.5
    4 F 52 11.5
  • Schizophrenia (n=4)
    No. Sex Age Assay value
    (ng/mL)
    1 F 36 17.9
    2 F 53 23.0
    3 F 55 14.6
    4 F 51 10.8
Healthy Control Major depression Bipolar disorder Schizophrenia
18.1±3.41 16.3±4.02 15.1±4.53 16.6±5.17

(ng/mL)

Conclusion

The number of psychiatric disorder patients has been increasing and the research in the area has been vigorous. BDNF has been reported to be related to various disorders and getting attention. Our Mature BDNF ELISA Kit Wako is a novel detection technology for mBDNF. We hope our kit contributes to psychiatric disorder research.

References

    1. Schinder and Poo, The neurotrophin hypothesis for synaptic plasticity. Trends Neurosci 23 (12) : 639-645 (2000)
    2. Huang and Reichardt, Neurotrophins: Roles in neuronal development and function. Annu. Annu Rev Neurosci 24 : 677-736 (2001).
    3. Hempstead, Brain-derived neurotrophic factor: three ligands, many actions.Trans Am Clin Clim Assoc 126 : 9-19 (2015).
    4. Karege et al., Decreased Serum Brain-Derived Neurotrophic Factor Levels in Major Depressed Patients. Psychiatry Res 109 (2) : 143-148 (2002).
    5. Cattaneo et al., The human BDNF gene: peripheral gene expression and protein levels as biomarkers for psychiatric disorders. Transl Psychiatry 6 (11) : e958 (2016).
    6. Lessmann and Brigadski, Mechanisms, Locations, and Kinetics of Synaptic BDNF Secretion : An Update. Neurosci Res 65 (1) : 11-22 (2009).
    7. Barker, Whither proBDNF Nat Neurosci 12 (2) : 105-106 (2009).

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