Role of glutathione biosynthesis in endothelial dysfunction and fibrosis

Abstract

Glutathione (GSH) biosynthesis is essential for cellular redox homeostasis and antioxidant defense. The rate-limiting step requires glutamate-cysteine ligase (GCL), which is composed of the catalytic (GCLc) and the modulatory (GCLm) subunits. To evaluate the contribution of GCLc to endothelial function we generated an endothelial-specific Gclc haplo-insufficient mouse model (Gclc e/+ mice). In murine lung endothelial cells (MLEC) derived from these mice we observed a 50% reduction in GCLc levels compared to lung fibroblasts from the same mice. MLEC obtained from haplo-insufficient mice showed significant reduction in GSH levels as well as increased basal and stimulated ROS levels, reduced phosphorylation of eNOS (Ser 1177) and increased eNOS S-glutathionylation, compared to MLEC from wild type (WT) mice. Studies in mesenteric arteries demonstrated impaired endothelium-dependent vasodilation in Gclc(e/+) male mice, which was corrected by pre-incubation with GSH-ethyl-ester and BH4. To study the contribution of endothelial GSH synthesis to renal fibrosis we employed the unilateral ureteral obstruction model in WT and Gclc(e/+) mice. We observed that obstructed kidneys from Gclc(e/+) mice exhibited increased deposition of fibrotic markers and reduced Nrf2 levels. We conclude that the preservation of endothelial GSH biosynthesis is not only critical for endothelial function but also in anti-fibrotic responses.

Glutathionylation: a regulatory role of glutathione in physiological processes

“…GCL limits the rate of GSH biosynthesis. It is a holoenzyme consisting of a glutamate cysteine ligase catalytic (GCLC) subunit and a regulatory glutamate cysteine ligase modifier (GCLM) subunit (56). Redox imbalance and accumulation of oxygen radicals trigger GCLC and GCLM expression, which results in elevated GCL activity ( Figure 1) and, consequently, higher GSH levels (16,24,57).…”

Sulodexide increases mRNA expression of glutathione-related genes in human umbilical endothelial cells exposed to oxygen-glucose deprivation

“…Vascular diseases related to oxidative stress, such as ischemia, are affected by endothelial dysfunction and redox imbalance with low intracellular levels of GSH [5]. Impairments in Nrf2/GSH-related genes/GSH cascades have been reported in ischemia-induced endothelial injury.…”

“…Furthermore, several antioxidants (e.g. quercetin, resveratrol) have been shown to activate Nrf2 and up-regulate GSH-dependent genes with an increase in GSH levels in ischemic endothelial cells [5].…”

“…GCL consists of a catalytic subunit (GCLc) and modifier subunit (GCLm) which are regulated independently at transcriptional and post-transcriptional levels. However, the transcriptional control of GLCc gene expression is the most important for GCL activity [5]. System x c -, a cystine/glutamate antiporter with xCT and 4F2hc subunits, facilitates the uptake of cystine, which is quickly reduced to cysteine for GSH synthesis.…”

“…GPx1 is the most abundant intracellular isoform of GPx in human endothelium. GR then converts GSSG to GSH using NADPH [5]. GPx1 and GR are regulated mainly at the level of transcription [7].…”