Cognitive functioning and cerebrospinal fluid concentrations of neuropeptides for patients with good neurological outcomes after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Many patients exhibit cognitive disturbances after aneurysmal subarachnoid hemorrhage (SAH). Structural and functional neuroimaging has failed to demonstrate any correlation with these complaints. This study was performed to investigate whether neuropeptide concentrations in cerebrospinal fluid could be related to cognitive disturbances after SAH.

METHODS

Lumbar cerebrospinal fluid was obtained, 3 to 6 months after surgery, from 17 patients who experienced good outcomes after aneurysmal SAH. The samples were analyzed for various neuropeptides using radioimmunoassays, and the peptide concentrations were evaluated in relation to scores on standardized neuropsychological tests.

RESULTS

The neuropsychological test results were normal for eight individuals, whereas the remaining nine patients exhibited various degrees of cognitive impairment. There was no correlation between the concentrations of arginine vasopressin or neuropeptide Y and test performance. However, significant correlations between cognitive impairment and elevated levels of beta-endorphins (P = 0.02), corticotropin-releasing factor (P = 0.004), and delta sleep-inducing peptide (P = 0.045) were noted.

CONCLUSION

Patients with cognitive impairments after aneurysmal SAH exhibited higher cerebrospinal fluid concentrations of endorphins, corticotropin-releasing factor, and delta sleep-inducing peptide than did those with normal capacity. This is probably attributable to diffuse derangement of transmitter release in the brain, resulting from the insult or ensuing complications, although a secondary increase in corticotropin-releasing factor concentrations caused by increased stress during the testing because of reduced cognitive capacity cannot be excluded.

Cerebrospinal fluid neuropeptides in Alzheimer's disease and vascular dementia

Cerebrospinal fluid (CSF) levels of several neuropeptides have been suggested as candidate markers in neurodegenerative disorders. We have examined the levels of corticotropin-releasing hormone (CRH), beta-endorphine (BEND), delta sleep-inducing peptide (DSIP), somatostatin (SRIF), and neuropeptide Y (NPY) in CSF samples obtained under highly standardized conditions from healthy aged controls and from patients suffering from Alzheimer's disease (AD) or vascular dementia (VAD). The influence of some potentially confounding factors was evaluated. CRH and BEND were markedly decreased in both AD and VAD patients, and BEND levels correlated negatively with degree of dementia within the patient population. SRIF was decreased in both AD and VAD patients. DSIP was slightly increased in AD, but not in VAD. NPY did not differ between groups. For none of the peptides did CSF concentrations correlate significantly with duration of illness, nor, with the exception of BEND, with its degree. Present data do not support the hypothesis that specific neuropeptide changes occur in different neurodegenerative disorders, but are in agreement with previous reports suggesting that neuropeptide systems are differentially affected by neurodegeneration.

Delta sleep-inducing-peptide-like immunoreactivity (DSIP-LI) and delta sleep in schizophrenic volunteers

Delta sleep-inducing-peptide (DSIP) has been reported to increase sleep in subjects with insomnia. The authors studied cerebrospinal fluid (CSF) DSIP-like immunoreactivity (DSIP-LI) in 15 drug-free male subjects with a DSM-IIIR diagnosis of schizophrenia. The subjects underwent a lumbar puncture and three nights of polysomnography. CSF DSIP-LI was significantly correlated with polysomnography the night before the LP: with stage 3 sleep (p = 0.05), stage 3 and delta (stages 3 + 4) sleep during the first nonrapid eye movement NREM period (p = 0.02 and p = 0.05, respectively) and the ratio of the first and second NREM period (p < 0.05), and negatively with stage 2% sleep (p < 0.05). Whether this first report of a potential relationship between CSF DSIP-LI and slow-wave sleep in man might be generalized to sleep in nonpsychiatric subjects awaits further study.

Neuropeptides in cerebrospinal fluid in normal-pressure hydrocephalus and dementia

Delta-sleep-inducing peptide (DSIP), vasoactive intestinal peptide (VIP), peptide YY (PYY) and somatostatin (SOM) were assayed with specific radioimmunological methods in cerebrospinal fluid (CSF) of healthy volunteers, 12 patients with Alzheimer's disease (AD), 11 patients with multi-infarct dementia (MID) and 10 patients with normal-pressure hydrocephalus (NPH). Patients with NPH were reinvestigated 3 months after a ventriculoperitoneal shunt operation. DSIP, PYY and SOM levels in CSF were decreased in patients with NPH compared to controls. The CSF concentration of SOM was also significantly reduced in patients with AD. No correlations were found between the degree of dementia in any of the illnesses and the CSF concentrations of the peptides. The concentration of DSIP, VIP and SOM increased significantly in parallel to the clinical improvement after the shunt operation in NPH patients.

Passage of delta sleep-inducing peptide (DSIP) across the blood-cerebrospinal fluid barrier

Unidirectional flux of 125I-labeled DSIP at the blood-tissue interface of the blood-cerebrospinal fluid (CSF) barrier was studied in the perfused in situ choroid plexuses of the lateral ventricles of the sheep. Arterio-venous loss of 125I-radioactivity suggested a low-to-moderate permeability of the choroid epithelium to the intact peptide from the blood side. A saturable mechanism with Michaelis-Menten type kinetics with high affinity and very low capacity (approximate values: Kt = 5.0 +/- 0.4 nM; Vmax = 272 +/- 10 fmol.min-1) was demonstrated at the blood-tissue interface of the choroid plexus. The clearance of DSIP from the ventricles during ventriculo-cisternal perfusion in the rabbit indicated no significant flux of the intact peptide out of the CSF. The results suggest that DSIP crosses the blood-CSF barrier, while the system lacks the specific mechanisms for removal from the CSF found with most, if not all, amino acids and several peptides.

Comparison of DSIP- (delta sleep-inducing peptide) and P-DSIP-like (phosphorylated) immunoreactivity in cerebrospinal fluid of patients with senile dementia of Alzheimer type, multi-infarct syndrome, communicating hydrocephalus and Parkinson's disease

The concentrations of delta sleep-inducing peptide (DSIP)-like (DSIP-LI) and P-DSIP-like (phosphorylated, Ser7) immunoreactivity (P-DSIP-LI) were measured by specific radioimmunoassay in the cerebrospinal fluid (CSF) of patients with senile dementia of the Alzheimer type [SDAT, subdivided into early (S1), middle (S2) and late dementia (S3)], multi-infarct dementia (MD), Parkinson's disease (PD), vascular disease (VD) and communicating hydrocephalus (H), as well as in control patients (C1, C2). Mean DSIP-LI and P-DSIP-LI concentrations were found to be significantly higher in the elderly control group (C1, mean age 83 +/- 5 years) than in the middle-aged control group (C2, mean age 40 +/- 16 years). DSIP-LI and P-DSIP-LI were positively correlated with age in both control groups. Significant decreases of DSIP-LI compared with age-matched controls (C1) were observed for S2, S3, MD, PD, VD and H. In contrast, no significant differences corresponding to pathology were found for P-DSIP-LI.

Entry of DSIP peptides into dog CSF: role of physicochemical and pharmacokinetic parameters

Delta sleep-inducing peptide (DSIP) or one of four DSIP analogs (desTrp-DSIP, D-Ala3-DSIP, D-Ala4-DSIP, D-Ala4-DSIP-NH2), was injected IV into dogs. Samples of cerebrospinal fluid (CSF) from the posterior fossa and blood were collected simultaneously at 2, 5, 10, 20, 30, 45, and 60 min after injection and concentrations of DSIP-like material measured by radioimmunoassay (RIA). The increase in peptide concentration in the CSF correlated significantly with the increase in plasma concentration, with plasma half-life, and with peptide lipophilicity, but not with the degree of plasma protein binding or with molecular weight. An even better correlation occurred when the three factors that correlated independently were combined into a single parameter (r = 0.813, p less than 0.00005). These results demonstrate that peptides can significantly penetrate the blood-CSF barrier of the dog. For DSIP and its analogs, the degree of penetration into the CSF is highly dependent on parameters such as the level of peptide in the plasma, plasma half-life, and the lipophilicity of the peptide.