Filipin staining

Lack of stimulation of cholesteryl ester formation by exogenously added LDL is a hallmark of NPC. The assay is based on the procedure described by Vanier et al. [58]. The test is only performed after a positive filipin staining test is obtained. 

Fig. 6.7 Filipin staining for free cholesterol in field CA3 of the hippocampus. A section from a normal rat, showing light staining for free cholesterol in pyramidal neurons (arrows). B section from a rat that had been injected with kainate 1 day earlier, showing intense filipin staining in affected hippocampal neurons (arrows). Scale = 250 // m. Reproduced with kind permission from Ong et al., 2003, Brain Pathology 13 250-262. Blackwell Publishing...

The polyene macrolide filipin was isolated in 1955 from the cell culture filtrates of Sterptomyces filipinensis, and was later shown to be a mixture of four components [36]. Although too toxic for therapeutic use, the filipin complex has found widespread use as a histochemical stain for cholesterol and has even been used to quantitate cholesterol in cell membranes [37]. The flat structure of filipin III, the major component of the filipin complex, was assigned from a series of degradation studies [38]. Rychnovsky completed the structure determination by elucidating the relative and absolute stereochemistry [39]. The total synthesis plan for filipin III relied heavily on the cyanohydrin acetonide methodology discussed above. 

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