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Basolateral tocopherol secretion to apoA1, but not to HDL, is vitamer selective in Caco‐2 monolayers
Author(s) -
Nicod Nathalie Marie,
Parker Robert Stanley
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a354-a
Subject(s) - abca1 , secretion , chemistry , abcg1 , caco 2 , biophysics , medicine , endocrinology , transporter , biochemistry , biology , cell , gene
There is evidence for both chylomicron (CM)‐dependent and CM‐independent mechanisms of lipid secretion by the small intestine. We utilized differentiated Caco‐2 monolayers grown on transwells to investigate the relative contributions and extent of vitamer discrimination in tocopherol (TOH) secretion by these two mechanisms. Inhibition of CM secretion by BMS201038 showed that that this pathway accounted for 85% of total basolateral TOH secretion and lacked selectivity between different TOHs. In CM‐inhibited monolayers, LXR activation by T0901317 (T) induced ATP‐binding cassette transporter (ABC) A1 expression and basolateral secretion of TOHs to apoA1 in a vitamer selective manner (α‐ > β‐ >δ‐TOH). In the absence of T, ABCA1 was undetectable and addition of apoA1 had no effect, indicating the presence of another CM‐independent means of TOH secretion. ABCG1 was expressed in Caco‐2 monolayers but was not induced by T. TOH secretion to HDL occurred without selectivity and was not influenced by treatment with T, indicating that ABCG1 might facilitate TOH secretion to HDL. Addition of LDL had no effect on TOH secretion, while the presence of 1% BSA in the basolateral media enhanced δ‐TOH secretion significantly more than that of α‐TOH. We conclude that there are multiple CM‐independent pathways by which TOHs are secreted from CaCo‐2 monolayers, each with different extent of selectivity for different Vitamin E forms.