Bax-Bcl2 regulated apoptosis: morphological features of molecular localtzation

F Labat-Moleur, MD, A Negoescu, MD PhD

Laboratoire de Pathologic cellulaire, Centre Hospitalier Universitaire CHU, Grenoble, France

AIM: This investigation demonstrates for the first time the involvement of a Bax~Bcl2-dependent apoptotic process in the Graves - Basedow thyroid, a pathological condition known for its spontaneously oscillating evolution. METHODS: A continuous senes of 86 cases of surgically treated Graves' thyroids was evaluated for its content in apoptotic cells identified on histological criteria and confirmed by TUNEL (terminal desoxynucleotidyl transferase-mediated desoxyuridinc triphosphate nick end-labeling). A significant correlation was found between the various tissular features of Graves' disease (epithelial hyperplasia, cellular hypertrophy, colloid content) and the amount of apoptotic cells. RESULTS: Thus, 41 cases were characterized by tissular heterogeneity with hyperactive foci, rich in apoptosis, alternating with regressive areas lacking apoptosis. This group was best suited to illustrate the participation of apoptosis, in a tight balance with cell proliferation, to the remodeling of Graves' thyroid parenchyma and offered an exquisite model for apoptosis observation. Indeed, the thyroid follicle accumulated apoptotic cells and bodies, allowing a tentative chronological ordering of programmed cell death aspects in close correlation with Bax- - Bcl2 cellular pattern. CONCLUSION: The initiation of apoptosis would correspond to a loss of cellular cohesion, a drop in Bcl2 expression and, as suggested by our observations, a delocalization of Bax from a putative Golgi storage location (paranuclear dot) to a mitochondrial distribution (diffuse granular). Bax delocalization phenomena may explain the apoptotic effect of liposome-mediated gene transfer, an attractive method (termed lipofection) for therapeutic DNA delivery to cancer cells. Indeed, the large-scale interference between lipofection and internal cell membranes(1) can be considered as able to favor Bax delocalization and apoptosis induction. Thus, the paranuclear flax dot in nonapoptotic thyrocytes was also found in a lymphoma(2), and lipofection induces apoptosis in lymphocyte(3). REFERENCES: (1) Labat-Moleur F, Steffan AM, Brisson C, Perron H, Feugeas O, Furstenberger P, Oberling F, Brambila E, Behr JP. An electron microscopy study into the mechanism of gene transfer with lipopolyamines. Gene Ther 1996;3:1010-1017. (2) Schlaifer D, Krajewski S, Galoin S, Rigal-Huguet F, Laurent G, Massip P, Pris J, Delsol G, Reed JC, Brousset P. Immunodetection of apoptosis-regulating proteins in lymphomas from patients with and without human immunodeficiency virus. Am J Pathol 1996;149:177-185. (3) Ebert O, Finke S, Salahi A, Herrmann M. Trojaneck B, Lefterova P, Wagner B. Kircheis R, HuIm D, Schreiver F, Schmidt-Wolf IGH. Lymphocyte apoptosis: induction by gene transfer techniques. Gene Ther 1997;4, 296-302.

Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Apoptosis - Molecular Mechanisms.