Control of apolipoprotein E secretion in the human hepatoma cell line KYN-2

Even though it is known that apolipoprotein E (apoE) is deeply involved in major age-related disorders such as atherosclerosis or Alzheimer's disease (AD), the control of cell-specific apoE expression is still poorly understood. We compared the apoE secretion as previously described in astrocytic cell17 to hepatic cell apoE secretion. We used the human hepatoma cell line KYN-2 to better delineate the characteristics of apoE secretion and to validate it with respect to the classical human hepatoma cell line HepG2. Interleukin-1beta (IL-1beta) and interferon-gamma (IFN-gamma) significantly inhibited, while IL-2, IL-6 and tumour necrosis factor-alpha (TNF-alpha) were inactive on apoE secretion by KYN-2 as well as HepG2 cells. Cholesterol and 25-OH cholesterol had no effect, while forskolin exerted a significant inhibitory effect, on apoE secretion in KYN-2 cells. Our results suggest that the KYN-2 cell line represents an appropriate cell model, and in any case an alternative model to the HepG2 cell line, to study the control of apoE secretion. The response of KYN-2 cells to both cytokines and cholesterol differs from that found in astrocytoma cells, suggesting that blood variations of apoE concentrations in AD may not reflect the dysregulations taking place in the brain.