CSF proteome: a protein repository for potential biomarker identification

Proteomic analysis is not limited to the analysis of serum or tissues. Synovial, peritoneal, pericardial and cerebrospinal fluid represent unique proteomes for disease diagnosis and prognosis. In particular, cerebrospinal fluid serves as a rich source of putative biomarkers that are not solely limited to neurologic disorders. Peptides, proteolytic fragments and antibodies are capable of crossing the blood-brain barrier, thus providing a repository of pathologic information. Proteomic technologies such as immunoblotting, isoelectric focusing, 2D gel electrophoresis and mass spectrometry have proven useful for deciphering this unique proteome. Cerebrospinal fluid proteins are generally less abundant than their corresponding serum counterparts, necessitating the development and use of sensitive analytical techniques. This review highlights some of the promising areas of cerebrospinal fluid proteomic research and their clinical applications.

[Case report of paradoxical overdrainage of cerebrospinal fluid]

The authors describe a case of paradoxical lumboperitoneal overdrain of cerebrospinal fluid (CSF) with severe CSF hypotension syndrome in horizontal position of the patient and immediate cessation in vertical position. Ligation and then removal of lumboperitoneal shunt lead to rapid and stable disappearance of overdrain syndrome as well as concurrent left-side radicular pain syndrome in the leg.

Cerebrospinal fluid levels of opioid peptides in fibromyalgia and chronic low back pain

BACKGROUND

The mechanism(s) of nociceptive dysfunction and potential roles of opioid neurotransmitters are unresolved in the chronic pain syndromes of fibromyalgia and chronic low back pain.

METHODS

History and physical examinations, tender point examinations, and questionnaires were used to identify 14 fibromyalgia, 10 chronic low back pain and 6 normal control subjects. Lumbar punctures were performed. Met-enkephalin-Arg6-Phe7 (MEAP) and nociceptin immunoreactive materials were measured in the cerebrospinal fluid by radioimmunoassays.

RESULTS

Fibromyalgia (117.6 pg/ml; 85.9 to 149.4; mean, 95% C.I.; p = 0.009) and low back pain (92.3 pg/ml; 56.9 to 127.7; p = 0.049) groups had significantly higher MEAP than the normal control group (35.7 pg/ml; 15.0 to 56.5). MEAP was inversely correlated to systemic pain thresholds. Nociceptin was not different between groups. Systemic Complaints questionnaire responses were significantly ranked as fibromyalgia > back pain > normal. SF-36 domains demonstrated severe disability for the low back pain group, intermediate results in fibromyalgia, and high function in the normal group.

CONCLUSIONS

Fibromyalgia was distinguished by higher cerebrospinal fluid MEAP, systemic complaints, and manual tender points; intermediate SF-36 scores; and lower pain thresholds compared to the low back pain and normal groups. MEAP and systemic pain thresholds were inversely correlated in low back pain subjects. Central nervous system opioid dysfunction may contribute to pain in fibromyalgia.

Protein identification with Teflon as matrix-assisted laser desorption/ionization sample support

Protein identification is a critical step in proteomics, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) plays an important role in that identification. Polytetrafluoroethylene (Teflon) was tested as a new MALDI sample support to improve protein identification. The tryptic peptides obtained from a model protein were bound to the surface of a modified MALDI sample holder via the hydrophobic interactions that occur between the Teflon surface and the peptide ion-pairs, and the affinity of alpha-cyano-4-hydroxycinnamic acid for the peptides. During that surface-binding step, the peptide mixture was also desalted and concentrated. A greater number of matched peptides and a larger sequence coverage were obtained for the proteins when Teflon was used as the sample support compared with conventional sample preparation methods and a stainless-steel surface. In addition, the characterization of a small amount of protein was improved with Teflon. Nine silver-stained protein spots obtained from 2-D gel of a human cerebrospinal fluid (CSF) proteome were identified by this method. Among the nine protein spots, peptide 6:c3c fragment and procollagen c-proteinase enhancer were not annotated in any published 2-D map of human CSF. A Teflon MALDI sample support is a low-cost, simple, and effective method that can be used to improve the quality of the MALDI mass spectrum of a complex tryptic peptide mixture, and to achieve a higher level of reliability and success in protein identification.

Higher levels of antibodies against the psoriasis-associated antigen pso p27 in cerebrospinal fluid from patients with low back pain and sciatica

STUDY DESIGN

A prospective study comparing the presence of antibodies against the psoriasis-associated antigen pso p27 in pain-free control subjects and patients with low back pain and/or sciatica.

OBJECTIVES

To analyze the amount of local inflammation present in human lumbar disc disorders, using anti-pso p27 antibodies in the cerebrospinal fluid as a marker and to analyze whether pain intensity correlates with this marker of inflammation.

SUMMARY OF BACKGROUND DATA

Pso p27 is a major antigen in psoriasis that is also present, mostly locally, in other inflammatory disorders, such as sarcoidosis, inflammatory bowel disease, and ankylosing spondylitis, inflammation is also thought to play a major role in the generation of lumbar and radicular pain in degenerative disc disorders.

METHODS

Anti-pso p27 antibodies in cerebrospinal fluid were quantified using an indirect enzyme-linked immunosorbent assay with pso p27 obtained from patients with psoriasis for use as an antigen. Fifteen patients with spinal stenosis, 11 patients without myelographic disc herniation, 17 patients with disc herniation, and 24 pain-free patient control subjects were studied.

RESULTS

Significantly higher levels of anti-pso p27 antibodies were found in patients with myelographic signs of disc herniation than in with patients with no signs of herniation, patients with spinal stenosis, and control subjects. Patients with no known signs of disc herniation and patients with myelographic signs of spinal stenosis (< 10 mm in diameter) caused by degenerative changes, had higher levels of anti-pso p27 antibodies than did control subjects. However, these differences reached only borderline statistical significance.

CONCLUSIONS

The results support those in previous reports, that inflammation probably plays an important role in degenerative disk disorders, particularly in disk herniations. That there was no correlation between pain intensity and anti-pso p27 activity indicates that the antigen is probably not essential in pain generation per se. The results may indicate that pso p27 is expressed secondary to, not as an initiator of, inflammation.

Nuclear magnetic resonance spectroscopy of cerebrospinal fluid from patients with low back pain and sciatica

STUDY DESIGN

This study was carried out to assess the metabolic differences between pain-free control subjects and patients with low back pain, either with or without disc protrusion or herniation.

OBJECTIVES

To analyze various metabolites in human cerebrospinal fluid using proton nuclear magnetic resonance spectroscopy. The potential use of this technique as an additional tool for diagnostic assessment was also evaluated.

SUMMARY OF BACKGROUND DATA

Inflammation is thought to play a major role in the generation of lumbar spine pain, a theory supported both by animal and in vitro studies. The effect of the inflammation in terms of increased metabolism has not yet been studied.

METHODS

Cerebrospinal fluid was obtained from patients by lumbar puncture, frozen, redissolved, and analyzed for metabolites by proton nuclear magnetic resonance spectroscopy.

RESULTS

Significantly lower values for several key metabolites were found in patients with low back pain or sciatica, with the lowest values in the subgroup of patients with myelographic signs of disc protrusion or herniation.

CONCLUSIONS

The results indicate a higher level of metabolic activity in patients with low back pain or sciatica compared with pain-free control subjects, with this difference being most pronounced in the subgroup of patients with myelographic evidence of disc protrusion or herniation.

Cerebrospinal fluid apolipoprotein E level is increased in late-onset Alzheimer's disease

Worldwide evidence has recently shown that the allele epsilon4 of apolipoprotein E (ApoE) is a genetic risk factor for Alzheimer's disease (AD) underlining the possible role of apoE in the physiopathology of AD. To evaluate the usefulness of apoE concentration in pathogenesis of AD, we measured the cerebrospinal fluid (CSF) levels of apoE. CSF apoE level was significantly higher in 38 patients with late-onset AD than in 31 control patients and 47 patients suffering from other neurological and related diseases. Higher levels of CSF apoE were also present in a subset of patients with meningoencephalitis, motor neuron disease, and low back pain. The increase of CSF-apoE in AD is in agreement with results from studies that find an increase of mRNA apoE in the brains of AD patients. Compared to other works, these results underline the importance and the difficulties of the selection of the controls. The CSF apoE level seems to be a reflection of neuronal damage and/or an inflammatory reaction that may be common to AD and other neurological and related diseases.

[Substance P-like immunoreactivity in cerebrospinal fluid in lumbar disc herniation]

Substance P-like immunoreactivity (SP-LI) of the cerebrospinal fluid was measured by radioimmunoassay in 40 patients with lumbar disc herniation (hernia group), and in 10 patients with no low back pain and no leg symptoms (control group). The SP-LI was significantly higher in the hernia group (5.49 +/- 3.01 pg/ml) than in the control group (2.05 +/- 0.52 pg/ml) (p < 0.01). In the hernia group, the SP-LI was significantly higher in patients with severe pain in the lower extremities than in those with only mild pain. As the SP-LI was found to be correlated with the severity of pain, it was considered to be a useful index of pain. As for the correlation of SP-LI with the hernia type, the SP-LI was significantly higher in patients with transligamentous extrusion type hernia than in those with protrusion type hernia. This result suggested that the release of substance P was increased with marked compression on the dorsal root.

Straight leg raising test and lumbar cerebrospinal fluid levels of vasoactive intestinal polypeptide and somatostatin in patients with low back pain

STUDY DESIGN

Straight leg raising was recorded before myelography in 77 patients. At myelography, samples of cerebrospinal fluid were drawn and later analyzed for neuropeptides vasoactive intestinal polypeptide and somatostatin.

OBJECTIVES

The study sought to examine correlations, if any, between a positive straight leg raising test and cerebrospinal fluid neuropeptide levels.

METHODS

The straight leg raising test was recorded for all patients before a myelography examination was performed because of intractable leg pain symptoms. Forty-seven of the patients were men and 30 were women. Cerebrospinal fluid samples were obtained from all patients upon myelography. Levels of the neuropeptides vasoactive intestinal polypeptide and somatostatin were analyzed in a blind manner by radioimmunoassay, using commercially available radioimmunoassay kits.

RESULTS

The results are compatible with previous observations that suggest cerebrospinal neuropeptide levels are altered in conjunction with neural injury or pain syndromes. In the present mixed back pain patient population, which included radicular pain symptoms due to disc herniation and lumbar stenosis, alterations in vasoactive intestinal peptide levels in particular were observed with a positive straight leg raising test.

CONCLUSIONS

Nerve root injury, as suggested by a positive straight leg raising test, appears to be neurochemically linked to altered cerebrospinal fluid vasoactive intestinal peptide levels.

CSF enkephalins in diabetic neuropathy

CSF methionine and leucine enkephalins were measured by high performance liquid chromatography and radioimmunoassay in diabetic patients with painful neuropathy (n = 22) and painless neuropathy (n = 5), and non-diabetic subjects with low back pain (n = 11). Wide variations in CSF enkephalin levels were found and they were often below the limit of detection (less than 0.1 pmol/l) in the diabetic and non-diabetic groups. The origin of CSF enkephalins is unknown and CSF levels may not reflect tissue concentrations. In conclusion, CSF enkephalin levels are difficult to interpret and do not provide useful information on the function of enkephalinergic pathways.