Cholesterol sulfate: a naturally-occurring inhibitor of cholesterol side-chain cleavage which functions at the level of intramitochondrial cholesterol translocation

Determination of plasma cholesterol sulfate by LC-APCI-MS/MS in the context of pediatric autism

Cholesterol sulfate (CS) has various biological functions. Previously, plasma CS was measured primarily as a means to diagnose X-linked ichthyosis; however, a recent hypothesis suggests that CS deficiency might be related to autism. As such, an assay capable of measuring both very high (in the case of X-linked ichthyosis) and very low (in the case of autism) plasma CS levels is required. Here we describe a novel LC-APCI-MS/MS method for the determination of CS in human plasma, and we propose normal CS ranges for children, based on studies of a local population of normal Chinese children between the ages of 2 and 10. In addition, we have used this method to measure plasma CS in autistic children. CS was isolated by solid-phase extraction, and quantified by isotope-dilution LC-APCI-MS/MS in negative ion mode monitoring 465.3>97.1 m/z (CS) and 472.3>97.1 m/z (CS-d7). Mean recovery of the assay ranged from 88.1 to 112.7%; within- and between-run imprecisions have CVs less than 7.2 and 8.1%, respectively. The assay was linear up to at least 100 µmol L(-1). The reference interval of plasma CS in males (range: 1.16-4.23 µmol L(-1)) was found to be higher than in females (range: 0.86-3.20 µmol L(-1)). Comparison of normal and autistic children showed no statistically significant difference in the plasma CS level. In conclusion, a robust LC-APCI-MS/MS method for plasma CS was developed, and a pediatric reference interval was derived from applying the method to normal and autistic children.

The Effects of Cholesterol-3-sulfate (CH-3S) on the Phosphorylation of Human C3a (hC3a) in Vitro and on the Ability of hC3a to Induce Vascular Permeability in Rats

The phosphorylation of human C3a (hC3a, anaphylatoxin) by two distinct protein kinases (PKA and CK-I) and the effect of cholesterol-3-sulfate (CH-3S) on this phosphorylation were biochemically investigated in vitro. It was found that (i) hC3a functions as a phosphate acceptor for PKA and CK-I, but not for CK-II; (ii) the CK-I-mediated phosphorylation of hC3a requires the presence of 3 microM CH-3S in a manner similar to the phosphorylation of HMG1 (CH-3S-binding protein) by CK-I; and (iii) CH-3S inhibits the PKA-mediated phosphorylation of hC3a in a dose-dependent manner (ID50=approximately 2 microM). As expected, hC3a containing high levels of Arg- and Lys-residues stimulated approx. 3-fold CK-II activity (phosphorylation of alpha-casein) in vitro. However, no significant effect of hC3a on CK-II activity was observed when hC3a was preincubated with CH-3S or fully phosphorylated by PKA in vitro. Furthermore, preincubation of hC3a with CH-3S diminished the ability of hC3a to induce vascular permeability in rats. The results provided here suggest that (i) hC3a is a CH-3S-binding protein; and (ii) CH-3S functions as a potent inhibitor for its physiological activities, including phosphorylation by PKA and CK-I, in vitro.

Cholesterol sulfate in human physiology: what's it all about?

Cholesterol sulfate is quantitatively the most important known sterol sulfate in human plasma, where it is present in a concentration that overlaps that of the other abundant circulating steroid sulfate, dehydroepiandrosterone (DHEA) sulfate. Although these sulfolipids have similar production and metabolic clearance rates, they arise from distinct sources and are metabolized by different pathways. While the function of DHEA sulfate remains an enigma, cholesterol sulfate has emerged as an important regulatory molecule. Cholesterol sulfate is a component of cell membranes where it has a stabilizing role, e.g., protecting erythrocytes from osmotic lysis and regulating sperm capacitation. It is present in platelet membranes where it supports platelet adhesion. Cholesterol sulfate can regulate the activity of serine proteases, e.g., those involved in blood clotting, fibrinolysis, and epidermal cell adhesion. As a result of its ability to regulate the activity of selective protein kinase C isoforms and modulate the specificity of phosphatidylinositol 3-kinase, cholesterol sulfate is involved in signal transduction. Cholesterol sulfate functions in keratinocyte differentiation, inducing genes that encode for key components involved in development of the barrier. The accumulating evidence demonstrating a regulatory function for cholesterol sulfate appears solid; the challenge now is to work out the molecular mechanisms whereby this interesting molecule carries out its various roles.

Cholesterol sulfate: a new adhesive molecule for platelets

BACKGROUND

Cholesterol 3-sulfate is present on a variety of cells and in human LDL, and it has been found in atherosclerotic lesions of human aorta. Its precise biological role has not yet been described.

METHODS AND RESULTS

In this study, we investigated the interaction of platelets with cholesterol sulfate. Platelets adhered in a concentration-dependent and saturable manner to cholesterol sulfate but did not adhere to cholesterol, cholesterol acetate, estrone sulfate, or dehydroepiandrosterone sulfate, suggesting that the specificity of this interaction is determined not only by the cholesterol moiety but also by the sulfate group. This adhesion did not increase after platelet activation, and it was not cation-dependent. Soluble cholesterol sulfate inhibited adhesion in a concentration-dependent manner. However, antibodies against glycoprotein Ib, glycoprotein IIb/IIIa, CD36, P-selectin, von Willebrand factor, or thrombospondin had no significant effect on platelet adhesion to cholesterol sulfate. Perfusion of whole blood in a parallel-plate flow chamber resulted in the rapid and progressive adhesion of platelets to cholesterol sulfate but not to cholesterol acetate or estrone sulfate.

CONCLUSIONS

Cholesterol sulfate supports platelet adhesion and may be one of the factors determining the prothrombotic potential of atherosclerotic lesions.