Takahashi 2019 Arch Biochem Biophys

Takahashi T, Mine Y, Okamoto T (2019) Extracellular coenzyme Q10 (CoQ10) is reduced to ubiquinol-10 by intact Hep G2 cells independent of intracellular CoQ10 reduction. Arch Biochem Biophys 672:108067.

» PMID: 31400302 Open Access

Takahashi Takayuki, Mine Yukitoshi, Okamoto Tadashi (2019) Arch Biochem Biophys

Abstract: Coenzyme Q₁₀ (CoQ₁₀) is an essential factor in the mitochondrial respiratory chain and is closely associated with ATP production in humans. It is known that orally administered CoQ₁₀ in humans is rapidly reduced, and most is detected as a reduced form, ubiquinol-10 (CoQ₁₀H₂), in serum. However, the mechanism of exogenous CoQ₁₀ reduction in vivo is unclear. Therefore, in order to clarify how CoQ₁₀ is reduced to CoQ₁₀H₂, we conducted a study using human liver cancer cell line Hep G2 cells, which show strong intracellular CoQ₁₀-reducing activity. When intact cells were incubated with CoQ₁₀, the exogenously added CoQ₁₀ was incorporated into the cells, time-, concentration-, and temperature-dependently, and 50-80% of that was detected as CoQ₁₀H₂. On the other hand, a part of the extracellular CoQ₁₀ was also detected as CoQ₁₀H₂, and the amount was greater than that of the intracellular CoQ₁₀H₂. Furthermore, the CoQ₁₀-loaded cells did not leak the intracellular CoQ₁₀H₂ (or CoQ₁₀) to the outside of the cells, and modulation of the extracellular CoQ₁₀H₂ amount had little effect on the intracellular CoQ₁₀ or CoQ₁₀H₂ contents, suggesting the existence of an individual mechanism of CoQ₁₀ reduction inside and outside the cells. Moreover, intact cells could reduce CoQ₁₀ in low-density lipoprotein to CoQ₁₀H₂. Therefore, we concluded that a novel CoQ₁₀-reducing mechanism may exist in the plasma membrane, probably the outer surface, of Hep G2 cells, and it may work to reduce extracellular CoQ₁₀ and/or maintain extracellular CoQ₁₀H₂. • Keywords: Coenzyme Q(10), Hep G2, Low-density lipoprotein, Membrane, Reduction, Ubiquinonol-10 • Bioblast editor: Plangger M

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