Abstract

Elevated extracellular D-glucose increases transforming growth factor ?1 (TGF-?1) release from human umbilical vein endothelium (HUVEC). TGF-?1, via TGF-? receptors I (T?RI) and T?RII, activates Smad2 and mitogen-activated protein kinases p44 and p42 (p42/44mapk). We studied whether D-glucose-stimulation of L-arginine transport and nitric oxide synthesis involves TGF-?1 in primary cultures of HUVEC. TGF-?1 release was higher (?1.6-fold) in 25 mM (high) compared with 5 mM (normal) D-glucose. TGF-?1 increases L-arginine transport (half maximal effect ?1.6 ng/ml) in normal D-glucose, but did not alter high D-glucose-increased L-arginine transport. TGF-?1 and high D-glucose increased hCAT-1 mRNA expression (?8-fold) and maximal transport velocity (Vmax), L-[3H]citrulline formation from L-[3H]arginine (index of NO synthesis) and endothelial NO synthase (eNOS) protein abundance, but did not alter eNOS phosphorylation. TGF-?1 and high D-glucose increased p42/44 mapk and Smad2 phosphorylation, an effect blocked by PD-98059 (MEK 1/2 inhibitor). However, TGF-?1 and high D-glucose were ineffective in cells expressing a truncated, negative dominant T?RII. High D-glucose increases L-arginine transport and eNOS expression following T?RII activation by TGF-?1 involving p42/44mapk and Smad2 in HUVEC. Thus, TGF-?1 could play a crucial role under conditions of hyperglycemia, such as gestational diabetes mellitus, which is associated with fetal endothelial dysfunction. © 2007 Wiley-Liss, Inc.