Inhibition of mitogen-activated proliferation of human peripheral lymphocytes in vitro by propionic acid.

Recurrent infections are common features in patients affected by propionic acidaemia (McKusick 232000) and methylmalonic acidaemia (McKusick 251000). Since these disorders are biochemically characterized by tissue accumulation of propionic acid and methylmalonic acid respectively, it is possible that these compounds may act as immunosuppressants. We therefore investigated the effect of propionate and methylmalonate on cellular growth of human peripheral lymphocytes stimulated in vitro by phytohaemagglutinin, concanavalin A and pokeweed mitogen, a recognized test of cellular immunocompetence. Lymphocytes were cultured in flat-bottomed 96-well microplates at 37 degrees C for 96 h (phytohaemagglutinin and concanavalin A) or 144 h (pokeweed mitogen) in the presence of one mitogen at different concentrations and of one acid added at doses of 1.0, 2.5 or 5.0 mM. Cell blastogenesis was measured by the incorporation of tritiated thymidine into cellular DNA and compared with that of identical cultures with no acid added (controls). A consistent and progressive inhibitory effect of propionic acid with increasing concentrations in culture was identified with all mitogens and was more pronounced with pokeweed mitogen. Lymphocyte blastogenesis was not altered in the presence of methylmalonic acid. The effect of propionate was observed only when the drug was added at the beginning (phytohaemagglutinin-activated) or until 24 h (concanavalin A- and pokeweed mitogen-activated) of culture. The viability of lymphocytes after treatment with the drug, as assessed by the Trypan Blue exclusion test, revealed no change when compared with the same untreated lymphocytes, indicating no lymphocytotoxic activity. In conclusion, propionic acid, which accumulates in tissues of patients with propionic acidaemia, causes 'in vitro' immunosuppression, which may be related to the recurrent infections characteristic of these patients.

Inhibition of in-vitro lymphocyte transformation by the isoquinoline alkaloid berberine.

Berberine is an isoquinoline alkaloid with multiple pharmacological actions, including an anti-inflammatory activity. The effects of berberine on in-vitro cellular proliferation of human peripheral lymphocytes stimulated with phytohaemagglutinin, concanavalin A and pokeweed mitogen were studied. Mononuclear cells were cultured in flat-bottomed 96-well microplates at 37 degrees C for 96-144 h in the presence of one mitogen at different concentrations and the alkaloid at doses of 2.5 to 20 microg mL-1. The mitogen-induced response of lymphocytes was evaluated from the extent of the incorporation of [3H]thymidine into cells in-vitro. A consistent and progressive inhibitory influence of berberine with increasing concentrations in culture was identified with all mitogens and was more pronounced with pokeweed mitogen. The effect of berberine was observed in phytohaemagglutinin (PHA)-and concanavalin A-activated lymphocytes when the drug was added during the first 24 h of culture, whereas the same effect occurred throughout the incubation period in pokeweed mitogen-stimulated cells. The viability of lymphocytes following treatment with the drug, as assessed by the trypan blue exclusion test, revealed no change when compared with the same untreated lymphocytes, indicating no lymphocytotoxic activity. We conclude that some effects of berberine, especially its anti-inflammatory action, may arise in part from the inhibition of DNA-synthesis in activated lymphocytes.