Relevance of the mevalonate biosynthetic pathway in the regulation of bone marrow mesenchymal stromal cell-mediated effects on T-cell proliferation and B-cell survival.
BACKGROUND
Bone marrow mesenchymal stromal cells can suppress T-lymphocyte proliferation but promote survival of normal and malignant B cells, thus representing a possible target for new therapeutic schemes. Here we defined the effects of cholesterol synthesis inhibitors on the interaction between these mesenchymal stromal cells and T or B lymphocytes.


METHODS
We exposed mesenchymal stromal cells to inhibitors, such as fluvastatin, of the 3-hydroxy-3-methylglutaryl-coenzyme A reductase, responsible for the synthesis of mevalonate, the precursor of cholesterol. Also, these cells were treated with manumycin A, a farnesyl transferase inhibitor which blocks the mevalonate-dependent isoprenylation of small guanosin triphosphate binding proteins. First, mesenchymal stromal cell morphology, cytoskeleton assembly, cell cycle, survival and cytokine production were evaluated. Then, these cells were co-cultured with either T or B lymphocytes and we analyzed: 1) the inhibition of T-cell proliferation to mitogenic stimuli; 2) B-cell survival.


RESULTS
Fluvastatin altered the assembly of actin microfilaments, inactivated RhoA guanosin triphosphate binding protein, inhibited the S-phase of the cell cycle, induced apoptosis in a small fraction of cells but preserved cytokine production. Preincubation of mesenchymal stromal cells with fluvastatin, or manumycin A, down-regulated the expression of adhesion molecules, reduced cell-to-cell interactions and prevented the inhibition exerted by these stromal cells on CD3/T-cell receptor-induced lymphocyte proliferation. Mevalonic acid could revert morphological, phenotypic and functional effects of fluvastatin. Finally, fluvastatin significantly reduced the mesenchymal stromal cells-mediated rescue of B cells in the presence of dexamethasone, although it did not function in the absence of corticosteroids.


CONCLUSIONS
Fluvastatin-mediated effects on bone marrow mesenchymal stromal cells were conceivably due to the inhibition of isoprenylation of small guanosin triphosphate binding proteins, occurring for the lack of mevalonate. Altogether these findings suggest that drugs acting on the mevalonate biosynthetic pathway can regulate mesenchymal stromal cell-induced T-cell suppression and B-lymphocyte survival.
Musso
Alessandra
A
Molecular Oncology and Angiogenesis, Department of Translational Oncology, National Institute for Cancer Research Genoa, Genoa, Italy. alessandro.poggi@istge.it
Zocchi
Maria Raffaella
MR
Poggi
Alessandro
A
D000199:Actins / Q000378:metabolism; D000214:Acyl Coenzyme A / Q000037:antagonists & inhibitors; D017209:Apoptosis / Q000187:drug effects; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism*; D002450:Cell Communication / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology; D005434:Flow Cytometry; D000077340:Fluvastatin; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000378:metabolism*; D008798:Mevalonic Acid / Q000378:metabolism*; D017368:Protein Prenylation; D017154:Stromal Cells / Q000187:drug effects / Q000378:metabolism*; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein
D000199:Actins; D000214:Acyl Coenzyme A; D005229:Fatty Acids, Monounsaturated; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007211:Indoles; C008047:3-hydroxy-3-methylglutaryl-coenzyme A; D000077340:Fluvastatin; D020742:rhoA GTP-Binding Protein; D008798:Mevalonic Acid