Neutrophils are required for the DNA synthetic response of human lymphocytes to mevalonic acid: evidence suggesting that a nonsterol product of mevalonate is involved.

Abstract

Communicated by Leon 0. Jacobson, January 25, 1982 ABSTRACT Human peripheral blood lymphocytes, in the presence of human neutrophils, initiate DNA synthesis and cell cycling when exposed to mevalonic acid. The ability of lymphocytes to respond in this manner is a radiosensitive property of the cells, whereas the help provided by neutrophils is maintained despite their prior exposure to x-irradiation. Other organic acid anions, including precursors of mevalonic acid biosynthesis and a variety ofproducts ofmevalonate metabolism, fail to initiate DNA synthesis when added to human lymphocytes. Because only the metabolically active R(-) enantiomer of mevalonic acid initiates lymphocyte DNA synthesis, we presume that physiological pathways of mevalonate metabolism are involved. The response to mevalonic acid of ML-236B (compactin)-inhibited lymphocytes is increased, and the threshold concentration ofmevalonate at which lymphocyte DNA synthesis first appears is decreased, when the cells are cultured in lipoprotein-containing (as opposed to lipoprotein-depleted) medium. The response to mevalonic acid oflymphocytes cultured in lipoprotein-depleted medium can be enhanced by addition to the cultures of low density lipoprotein but not by addition of high density lipoprotein. Based upon the flux diversion hypothesis of mevalonate metabolism, these observations suggest that a nonsterol product of mevalonate metabolism may be responsible for the initiation oflymphocyte DNA synthesis by mevalonic acid.

Obligatory Relationship Between the Sterol Biosynthetic Pathway and DNA Synthesis and Cellular Proliferation in Glial Primary Cultures

“…2 ) . This degree of inhibition of sterol synthesis by mevinolin added to the glial primary cultures is comparable to the inhibition that has been reported with addition of analogous competitive inhibitors of HMG-CoA reductase to cultures of nonneural cell types (Brown et al, 1978;Kaneko et al, 1978;Habenicht et al, 1980;Heiniger and Marshall, 1982;Larson et al, 1982;Perkins et al, 1982;Quesney-Huneeus et al, 1983;Fairbanks et al, 1984) and C-6 glioma cells (Volpe and Obert, 1982;Bhat and Volpe, 1983).…”

“…Thus, after it was reported that DNA synthesis in mitogenically stimulated lymphocytes is prevented by inhibition of sterol synthesis (Chen et al, 1975), investigation of both cloned smooth muscle cells and fibroblasts demonstrated that inhibition of HMG-CoA reductase resulted in a growth arrest that was reversed when mevalonate, but not cholesterol, was added to the culture medium (Habenicht et al, 1980). Further studies of lymphocytes (Larson et al, 1982;Perkins et a]., 1982) also suggested that mevalonate, rather than cholesterol, is the critical intermediate required for the initiation of DNA synthesis. However, another study of stimulated lymphocytes indicated that cholesterol itself was sufficient to restore proliferation when sterol synthesis was inhibited (Heiniger and Marshall, 1982).…”

“…However, the mechanisms regulating cellular proliferation in neural tissue remain largely unknown. During the past decade, several investigators have used a variety of cultured nonneural cell types, including lymphocytes (Chen et al, 1975;Cuthbert and Lipsky, 1981;Larson et al, 1982;Perkins et al, 1982), fibroblasts (Fairbanks et al, 1984), smooth muscle cells (Habenicht et al, 1980), and baby hamster kidney cells (Quesney-Huneeus et al, 1983), in efforts to elucidate the relationships among DNA synthesis, cellular proliferation, and the sterol biosynthetic pathway. This pathway provides cholesterol as its major product, as well as other quantitatively minor intermediates such as ubiquinone, dolichol, and isopentenyl pyrophosphate, known to have essential and diverse roles in cellular metabolism (Saito and Silbert, 1979;Brown and Goldstein, 1980).…”

Cytochalasin B is a potent mitogen for chronic lymphocytic leukemia cells in vitro.

“…Two patients were studied three times and four patients were studied twice and a significant mitogenic response to cytochalasin B was observed in each instance. In experiments with lymphocytes from 11 patients, the response to cytochalasin B exceeded that of the same cell suspension to either 50 jAg/ml Con A (six cases), 10 jig/ml PHA (six cases), or 0.5 jig/ml PWM (all 11 patients). With cells from eight patients the response to cytochalasin B exceeded that to 100 ng/ml PMA.…”

Synchronization of mammalian cells by Lovastatin

“…This agent suppresses the synthesis of mevalonic acid by competitively and reversibly inhibiting 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, the enzyme required for conversion of HMG-CoA to mevalonic acid [11]. In addition to inhibition of mevalonate synthesis, Lovastatin or compactin, another fungal toxin [12], also inhibits DNA replication [13][14][15][16][17][18], DNA replication is restored by the addition of mevalonate, the product of the reaction catalyzed by HMG-CoA reductase.…”