The role of transforming growth factor Beta-2, Beta-3 in mediating apoptosis in the murine intestinal mucosa

Abstract

Apoptosis is especially relevant in the gastrointestinal tract because the mammalian intestinal mucosa undergoes continual epithelial regeneration. Most recently, we confirmed the proapoptotic role of endogenous transforming growth factor (TGF)-beta in the developing chick retina as well as in chick ciliary, dorsal root, and spinal motor neurons. In the present study, we determined to establish the role of TGF-beta2 and TGF-beta3 in mediating apoptosis in non-neuronal tissue by analyzing the intestinal mucosa of Tgfbeta2(+/-) and Tgfbeta3(+/-) heterozygous mice. Intestinal localization of TGF-beta2 and TGF-beta3 isoforms and antiapoptotic molecules Bcl-xL and Bcl-2 was examined immunocytochemically and by Western blot analysis. Apoptosis was detected by enzyme-linked immunosorbent assay and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling, and proliferation was detected by proliferating cell nuclear antigen stains. TGF-beta2 was detected in endocrine cells, whereas TGF-beta3 was predominantly found in goblet cells. Programmed cell death was significantly reduced in the intestinal mucosa of Tgfbeta2(+/-) and Tgfbeta3(+/-) heterozygous mice. This decrease in apoptosis was accompanied by an increase in villus length; proliferation, however, seemed to remain unchanged. The level of Bcl-xL and Bcl-2 was significantly up-regulated in Tgfbeta2(+/-) and Tgfbeta3(+/-) mice. Our data show that TGF-beta2 and TGF-beta3 play an important role in mediating apoptosis in the intestinal mucosa and regulating apoptosis-associated proteins Bcl-xL and Bcl-2 in vivo.