Involvement of glutathione/glutathione S‐transferase antioxidant system in butyrate‐inhibited vascular smooth muscle cell proliferation

Abstract

Vascular smooth muscle cell (VSMC) proliferation is an important etiological factor in vascular proliferative diseases such as primary atherosclerosis, hypertension, arterial and in-stent restenosis, and transplant vasculopathy. Our studies established that butyrate, a bacterial fermentation product of dietary fiber and a chromatin modulator, is a potent inhibitor of VSMC proliferation. The cardiovascular health benefits of a high-fiber diet, the principle source of butyrate in the body, have been known for a long time, however, very little is known about the antiatherogenic potential of butyrate. Because oxidative stress plays an important role in the pathogenesis of atherosclerosis, we examined involvement of the glutathione/glutathione S-transferase (GST) antioxidant system in butyrate's inhibition of VSMC proliferation. Treatment of proliferating VSMCs with butyrate leads to the induction of several GSTs. Interestingly, our study also demonstrated the nuclear localization of GST-P1 (GST-7-7), which is considered to be a cytosolic protein; this was demonstrated using immunostaining and was corroborated by western blotting. Also, the butyrate-induced antiproliferative action, and the induction of GST-P1 and its nuclear localization are downregulated when butyrate is withdrawn. Furthermore, assessment of intracellular glutathione levels reveals their augmentation by butyrate. Conversely, butyrate treatment reduces the levels of reactive oxygen species in VSMCs. Collectively, the butyrate-treatment-related increase in glutathione content, the reduction in reactive oxygen species, the upregulation of GST and the nuclear localization of GST-P1 in growth-arrested VSMCs imply that butyrate's antiproliferative action involves modulation of the cellular redox state. Thus, induction of the glutathione/GST antioxidant system appears to have other regulatory role(s) besides detoxification and regulation of the cellular redox state, for example, cell-cycle control and cell proliferation, which are both critical to atherogenesis.

Butyrate, an HDAC inhibitor, stimulates interplay between different posttranslational modifications of histone H3 and differently alters G1-specific cell cycle proteins in vascular smooth muscle cells

“…For all experiments, VSMCs were seeded at a ratio of 1:6. One day after splitting, actively growing cells were grown in the absence or presence of 5 mM butyrate or specified concentrations of butyrate for required lengths of time [29, 34]. Culture medium was replaced every other day with fresh medium containing freshly prepared butyrate in sterile phosphate buffered saline (PBS).…”

“…The proliferation of VSMCs was measured as described previously [29, 34]. After the required period of treatment, cells were washed three times with sterile PBS and trypsinized with trypsin-EDTA.…”

Emerging Epigenetic Therapy for Vascular Proliferative Diseases

“…This elevates the strong possibility that reversing deregulated epigenetic mechanisms may be an effective treatment strategy for proliferative diseases. Incidentally, the property of HDACs, suppression of gene expression by epigenetic mechanism, has been exploited in the field of cancer to reactivate transcriptionally silent tumor suppressor gene to arrest proliferation of cancer cells and growth (Pons et al, 2009;Ranganna, et al, 2005Ranganna, et al, , 2007Sharma et al, 2010). Moreover, HDAC inhibitors (HDACi) are emerging as a new class of anticancer agents that are under clinical trials for different cancer treatment.…”

Nuclear glutathione and its functions

“…GSH регулирует экспрессию различных сетей транскрипционных программ, вовлечённых в детоксификацию, цитопротекцию и пролиферацию, и защищает клетки от дефектов, связанных с недостаточностью Nrf2 [23]. Кроме детоксификации и регуляции клеточного редокс-статуса, антиоксидантная система GSH/ГТ имеет и другие регуляторные функции, включая контроль клеточного цикла и пролиферации [24].…”

“…В норме [24] и при патологии p-ГТ часто локализована в ядре и при разных раках ассоциирована с их развитием и резистентностью к лекарствам [36,37].…”