Lipoproteins upregulate high affinity Fc receptors in human monocytes

Levels of expression of Fcgamma receptor IIA (CD32) are decreased on peripheral blood monocytes in patients with severe atherosclerosis

To obtain information in vivo concerning the role of Fcgamma receptors (FcgammaR) in atherosclerosis, we used quantitative flow cytometry to measure the levels of expression of FcgammaRI and FcgammaRIIA on peripheral monocytes in patients with severe atherosclerosis. Expression of several other markers was also measured. We found that differences in the levels of expression of FcgammaRI were not statistically significant when compared between patients and control subjects. For FcgammaRIIA, levels of expression were decreased in the patient group, a difference that was statistically significant. Levels of expression of CD14 and CD36 were also significantly decreased in the patient group. The decrease in expression of FcgammaRIIA was statistically significant when the effects of current cigarette smoking status or medication use, including statins, were taken into account. There was also a positive and statistically significant correlation between high-density lipoprotein-cholesterol and levels of expression of FcgammaRIIA for all subjects. In contrast, decreased levels of expression of CD14 and CD36 were strongly associated with current smoking status or statin use. In summary, levels of expression of FcgammaRIIA on peripheral blood monocytes were significantly decreased in patients with clinical atherosclerosis. Additional studies are warranted to determine if levels of expression of FcgammaRIIA have utility as a phenotypic marker for assessing relative risk of atherosclerotic disease.

Peripheral blood monocytes in psoriatic patients overproduce cytokines

Interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha) and interleukin-8 (IL-8) production by peripheral monocytes in 15 patients with psoriasis vulgaris and 13 healthy controls were investigated using an enzyme-linked immunosorbent assay. Polymorphonuclear leukocytes, mononuclear leukocytes, monocytes, lymphocytes and serum were isolated and cultured for 1, 12, 24 and 48 h in RPMI 1640 medium without fetal calf serum to release the cytokines. All cytokine levels in serum were very low in both psoriatic patients and the controls. However, a significant increase in the IL-1 alpha levels in the monocyte culture supernatants was observed in the psoriatic patients compared with that of the controls. IL-1 beta and IL-8 levels in the monocyte supernatants were also significantly increased in the psoriatic patients compared with the controls. TNF-alpha levels in the 12-h supernatants of the monocytes increased in some samples from psoriatic patients but not in the 48-h supernatants. Our study confirmed the overproduction of cytokines in the peripheral monocytes of the psoriatic patients and suggest the activation of monocytes in the patients with psoriasis.

Effect of lovastatin on cell surface expression of Fc receptors or CD14 antigen in human monocytes

Lovastatin is a widely used anticholesterolemic drug which exercises its effect by inhibiting hepatic cholesterol synthesis and up-regulating low density lipoprotein (LDL) receptors. In the present study, we determined that the drug has no adverse effects on the expression of three cell surface antigens of human monocytes, i.e. high affinity Fc receptors (Fc gamma RI), low affinity Fc receptors (Fc gamma RII) and CD14 antigen. We have shown previously these antigens are regulated by cholesterol and lipoproteins. At 0.5 micrograms/mL of culture medium, lovastatin did not reduce the percentage of receptor-positive cells or the average number of receptor molecules per cell. These observations add to the attractiveness of the drug as an anticholesterolemic agent and also indicate that endogenous cholesterol biosynthesis by monocytes is not required for expression of Fc gamma RI, Fc gamma RII, or CD14.