Suppressive Effect of β-Carotene on the Development of Pulmonary Foam Cells in Rats with Hyper β-Lipoproteinemia

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Abstract
The effect of β-carotene (BC) on the development of pulmonary foam cells (PFCs) was studied in rats with diet-induced hyper β-lipoproteinemia. Rats were fed a standard diet; a hyper-β-lipoproteinemic diet (HB) consisting of the standard diet, 4% cholesterol, and 1% cholic acid; or the standard diet plus 0.1% BC; or the HB diet plus 0.1% BC diet (HBC). Rats in the HB and HBC groups developed hyper-β-lipoproteinemia, but no significant differences were observed in serum levels of total cholesterol, phospholipid, and β- lipoprotein (B-LP) between both groups. The percentages of foamy, lipid-ingested monocytes (FMs) to the number of blood monocytes (BMs), the number and size of lipid droplets in FMs, the percentages of PFCs to the number of alveolar macrophages from bronchopulmonary lavage fluid, and the score of PFC development in the lungs of rats in the HBC group were reduced compared to those of rats in the HB group. There were no differences in latex-phagocytotic activity of BMs among rats in the control, HB, BC, and HBC groups. BC suppressed the foamy transformation of BMs and development of PFCs deriving from the influx of FMs into the alveoli of hyper-β-lipoproteinemic rats. Based on the present results, it is presumed that the antioxidative property of BC may prevent an oxidative modification of B-LP under the hyper-β-lipoproteinemic condition, leading to a decrease in the uptake of oxidatively modified B-LP by BMs.