Meeting Abstract

P1.157  Saturday, Jan. 4 15:30  Doxycycline inhibits intestinal remodeling during Xenopus laevis metamorphosis DAVIS, T*; LIANO, J; BACHMAN, N; INGALLS, J; KITTS, J; HORN, R; MILLER, B; TEMKIN, M; SCHREIBER, A.M.; St. Lawrence University, NY aschreiber@stlawu.edu

Metamorphosis of the herbivorous tadpole into a carnivorous frog is accompanied by an abrupt remodeling of the gut: the intestine shortens by 75%, the connective tissue and smooth muscle layers thicken, enteric neuronal cell bodies form clusters, and the lumen becomes highly involuted. Virtually all aspects of amphibian metamorphosis are mediated by thyroid hormone (TH), and the mRNAs of several matrixmetalloprotease (MMPs) are known to be upregulated directly (stromelysin-3) or indirectly (gelatinase A and MT1-MMP) in the gut mesenchyme by TH. The influence of MMP enzymatic activity on intestinal remodeling has not been well-described. Here we show that treatment of pre-metamorphic tadpoles (Nieuwkoop and Faber stage 50 and 54) with a broad-spectrum inhibitor of MMP activity (doxycycline, DOXY) inhibits virtually all aspects of intestinal remodeling, including shortening, thickening of the mesenchyme and smooth muscle layers, enteric neuronal clustering and changes in axonal cable diameter, and development of involutions on the lumen compared with controls following treatment with TH (3 nM triiodothyronine) for 4 days. In order to rule out the possibility that DOXY may function in part by inhibiting MMP transcription, mRNA for stromelysin-3 was measured by qRT-PCR. Stromelysin-3 mRNA synthesis from tadpole intestines treated simultaneously with TH+DOXY were not different compared with TH alone. These findings directly support the hypothesis that an upregulation of TH-responsive MMP activity during metamorphosis mediates diverse changes that accompany intestinal remodeling. Ongoing experiments are being conducted to also verify that DOXY does not inhibit MMP translation, and instead functions specifically as an inhibitor of MMP activity.