On the importance of albumin binding for the flux of 7α-hydroxy-3-oxo-4-cholestenoic acid in the brain.

We confirmed previous findings by a Japanese group that there is an accumulation of 7α-hydroxy-3-oxo-4-cholestenoic acid (7-Hoca) in human subdural hematomas. The accumulation correlated with the time from the bleeding to the sample collection. We present evidence that these accumulations are likely to be caused by the strong affinity of 7-Hoca to albumin and the marked difference between plasma and brain with respect to levels of albumin. In the circulation, 80-90% of 7-Hoca is bound to albumin with a ratio between the steroid acid and albumin of ∼1.4 ng/mg. In cerebrospinal fluid (CSF), the ratio between 7-Hoca and albumin is ∼30 ng/mg. When albumin or hemolyzed blood in a dialysis bag was exposed to CSF, there was a flux of 7-Hoca from CSF to the albumin. We suggest that the major explanation for accumulation of 7-Hoca in subdural hematoma is a flux from the brain into the hematoma due to the high affinity to albumin and the high capacity of 7-Hoca to pass biomembranes. We discuss the possibility that the markedly different ratios between 7-Hoca and albumin in circulation and brain can explain the flux of 7-Hoca from the brain into circulation against a concentration gradient.

7α-hydroxy-3-oxo-4-cholestenoic acid in cerebrospinal fluid reflects the integrity of the blood-brain barrier.

There is a continuous flux of the oxysterol 27-hydroxycholesterol (27-OHC) from the circulation across the blood-brain barrier (BBB) into the brain. The major metabolite of 27-OHC in the brain is 7α-hydroxy-3-oxo-4-cholestenoic acid (7-HOCA). We confirm a recent report describing the presence of this metabolite in cerebrospinal fluid (CSF) at a relatively high concentration. A simple and accurate method was developed for assay of 7-HOCA in CSF based on isotope dilution-mass spectrometry and use of (2)H4-labeled internal standard. The concentration of this metabolite was found to be markedly increased in CSF from patients with a dysfunctional BBB. There was a high correlation between the levels of 7-HOCA in CSF and the CSF/serum albumin ratio. The concentration of 7-HOCA in CSF was not significantly affected by neurodegeneration. Our findings suggest that 7-HOCA could be used as a diagnostic marker for conditions with a dysfunctional BBB.

Changes in the level of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid in cerebrospinal fluid after subarachnoid hemorrhage.

A high concentration of a type of cholic acid, 7 alpha-hydroxy-3-oxo-4-cholestenoic acid, is observed in the content of chronic subdural hematoma. To investigate the possible causes, the level of this compound was measured in the cerebrospinal fluid of patients who underwent surgery for aneurysmal subarachnoid hemorrhage or non-hemorrhagic diseases. The maximum level was significantly higher in the aneurysmal subarachnoid hemorrhage patients, indicating that surgical intervention did not cause the postoperative increase in the level of this compound in the cerebrospinal fluid. Monitoring of plasma levels showed no postoperative increase. In vitro culture of a mixture of arterial blood and cerebrospinal fluid failed to show the de novo production of this compound. These results strongly suggest extrahepatic intracranial production of this cholic acid occurs in subarachnoid hemorrhage. The high concentration of this compound in both chronic subdural hematoma and subarachnoid hemorrhage suggests a possible role for 7 alpha-hydroxy-3-oxo-4-cholestenoic acid in intracranial hemorrhagic disorders.

Identification of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid in chronic subdural hematoma.

We detected a novel kind of bile acid in the content of chronic subdural hematoma. This substance was specifically found in chronic subdural hematoma, and not in subdural hygroma, which is pathologically similar except for the lack of capsular membrane. The compound was identified as 7 alpha-hydroxy-3-oxo-4-cholestenoic acid by high performance liquid chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectrometry. The structure was confirmed by the comparison with the chemically synthesized compound. The average contents in chronic subdural hematoma were 658.09 +/- 137.53 ng/ml, while those in normal human plasma were 126.27 +/- 17.73 ng/ml. It was not detected in normal cerebrospinal fluid. The higher level in chronic subdural hematoma than human plasma strongly suggests the local, extrahepatic production of this type of C27 bile acids.