Performance of potential inflammatory biomarkers in peripheral blood and CSF of AD and other neurological diseases
| Marker | Function class | Systemic actions | CNS actions | Regulation in AD | Regulation in other neurological diseases | ||
| NGF | Neurotrophin | Neurotrophic | Neurotrophic | ↑ | CSF | ↑ | In CSF of major depression (DE) [1] |
| YKL-40 | Protein | – | Unclear | ↑ | CSF | ↑ | In CSF of Huntington’s disease [2] |
| ↓ | In CSF of PD and atypical Parkinsonian disorders (P+ diseases) [3] | ||||||
| ↑ | In CSF of BD [4] | ||||||
| ↑ | In CSF of MS [5] | ||||||
| IL-6 | Cytokine | Proinflammatory | Proinflammatory | ↑ | Blood | ↑ | In plasma of MS [6] |
| → | CSF | ↑ | In peripheral blood of PD [7] | ||||
| ↑ | In serum of PRES [8] | ||||||
| IL-1β | Cytokine | Proinflammatory | Proinflammatory | → | CSF | ↑ | In peripheral blood of PD [7] |
| ↑ | Blood | ||||||
| IL-10 | Cytokine | Anti-inflammatory | Unclear | ↑ | CSF | ↑ | In peripheral blood of PD [7] |
| → | Blood | ↑ | In serum of PRES [8] | ||||
| sTREM2 | Receptor | – | Neuroprotection | ↑ | CSF | ||
| α1-ACT | Protein | Proinflammatory | ↑ | CSF | |||
| ↑ | Blood | ||||||
| IL-8 | Chemokine | Proinflammatory | Proinjury | → | CSF | ↑ | In serum of RRMS [9] |
| ↓ | Blood | ||||||
| MCP-1 | Chemokine | Proinflammatory | Neurodegeneration | ↑ | CSF | ↑ | In serum of RRMS [9] |
| → | Blood | ||||||
| VILIP-1 | Protein | – | Neurodegeneration | ↑ | CSF | ||
| sTNFR | Receptor | Proinflammatory | – | ↑ | Blood | ||
| sCD40L | Protein | Proinflammatory | – | ↑ | Blood | ↑ | In peripheral blood of subarachnoid haemorrhage [10,11] |
| Prothrombotic | |||||||
| hsCRP | Protein | Proinflammatory | – | ↑ | Blood | ↑ | Associated with unfavourable clinical outcomes after acute ischaemic stroke [12] |
| TGF-β1 | Transforming growth factor | Neurotrophic | Neuroprotective | ↑ | CSF | ||
Regulation of these markers in AD demonstrated the results in this meta-analysis. Positive findings of these markers in relation to other neurological disorders are presented in the table. Relative references are provided in online supplementary material 8. Graphic symbols: ↑, increased; →, no changes; ↓, decreased.
α1-ACT, alpha1-antichymotrypsin; AD, Alzheimer’s disease; BD, bipolar disorder; CNS, central nervous system; CSF, cerebrospinal fluid; IL, interleukin; MCP-1, monocyte chemoattractant protein-1; MS, multiple sclerosis; NGF, nerve growth factor; PD, Parkinson's disease; PRES, posterior reversible encephalopathy; RRMS, relapsing-remitting MS; TGF-β1, transforming growth factor-beta; VILIP-1, visinin-like protein-1; hsCRP, high-sensitivity C reactive protein; sCD40L, soluble CD40 ligand; sTNFR, soluble tumour necrosis factor receptor; sTREM2, soluble triggering receptor expressed on myeloid cells2.