Search

Objective: Growth factors [transforming growth factor-β (TGF-β), epidermal growth factor (EGF), endothelin-1 (ET-1)] stimulate proteoglycan synthesis resulting in retention and accumulation of low density lipoprotein (LDL) in vessel intima and leading to atherosclerosis development. This study investigated the role of ET-1 on the expression of CHSY1, proteoglycan synthesizing enzyme, through both EGF and TGF-β receptor transactivation in human vascular smooth muscle cells (VSMCs). Also, we explored the involvement of NADPH oxidase (NOX), an important intermediate of redox signaling, in ET-1 transactivated EGF receptor (EGFR) through endothelin receptors. Materials and Methods: In this experimental study, phosphorylated ERK1/2 and CHSY1 protein levels in the human VSMCs were measured by Western blot analysis using anti phospho-ERK1/2 (Thr202/Tyr204) and anti CHSY1 antibodies. Results: ET-1 (100 nM) and EGF (100 ng/ml) stimulated ERK1/2 phosphorylation and inhibited in the presence of bosentan (ET receptor inhibitor), AG1478 (EGFR inhibitor), and DPI (NOX antagonist). Also, ET-1 treatment increased CHSY1 enzyme level; this response was suppressed by bosentan, AG1478, DPI, and SB431542, TGF-β receptor antagonist. This study revealed that ET-1 increases expression of CHSY1 through transactivation of EGF and TGF-β receptors. Conclusion: Transactivation through the EGF receptor mediated by phospho-ERK1/2 leads to expression of CHSY1 protein. EGF receptor transactivation by ET-1 is shown for the first time, to be dependent on NOX enzymes.

Objective Dysregulation of cholesterol metabolism in the brain is responsible for many lipid storage disorders, including Niemann-Pick disease type C (NPC). Here, we have investigated whether cyclodextrin (CD) and apolipoprotein A-I (apoA-I) induce the same signal to inhibit cell cholesterol accumulation by focusing on the main proteins involved in cholesterol homeostasis in response to CD and apoA-I treatment. Materials and Methods In this experimental study, astrocytes were treated with apoA-I or CD and then lysed in RIPA buffer. We used Western blot to detect protein levels of 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HMGCR) and ATP-binding cassette transporter A1 (ABCA1). Cell cholesterol content and cholesterol release in the medium were also measured. Results ApoA-I induced a significant increase in ABCA1 and a mild increase in HMGCR protein level, whereas CD caused a significant increase in HMGCR with a significant decrease in ABCA1. Both apoA-I and CD increased cholesterol release in the medium. A mild, but not significant increase, in cell cholesterol content was seen by apoA-I; however, a significant increase in cell cholesterol was detected when the astrocytes were treated with CD. Conclusion CD, like apoA-I, depletes cellular cholesterol. This depletion occurs in a different way from apoA-I that is through cholesterol efflux. Depletion of cell cholesterol with CDs led to reduced protein levels of ABCA1 along with increased HMGCR and accumulation of cell cholesterol. This suggested that CDs, unlike apoA-I, could impair the balance between cholesterol synthesis and release, and interfere with cellular function that depends on ABCA1.

In recent years, Trans Fatty Acids have shown a strong correlation with cardiovascular disease. However, the mechanisms explaining their atherogenicity are still unclear. ABCA1, which is involved in the reverse cholesterol transport pathway, has been considered as a new therapeutic target for cardiovascular disease. In vitro studies of the effects of PPAR-γ on lipid homeostasis in macrophage cells suggested a role for PPAR-γ in the regulation of ABCA1-dependent cholesterol efflux to apoA-I pathway. Thus, in this study we examined the effect of elaidic acid (EA) as the most abundant TFA on expression of ABCA1 and PPAR-γ in RAW 264.7 mouse macrophage cell line. Accordingly, after determining appropriate concentrations of EA using MTT, RAW 264.7 cells were treated with different concentrations of EA, and at the end, gene expression was assayed by Real-Time PCR. Our results shown that the expression of ABCA1 decreased in the treated group in comparison with the control group by 1.7, 2.3, and 5.1 fold, after 12 h treatment for 0.5, 1, and 2 mM EA concentration respectively. In addition, after 24 h treatment with EA, the rate of decreasing ABCA1 expression was 2.1, 2.6, 5.7 fold, respectively (P < 0.01). However, EA had no significant effect on PPAR-γ mRNA expression. Therefore, it could be concluded that the atherogenic effect of EA may be mediated by reducing ABCA1 expression in RAW 264.7 cells; however, this reduction has not mediated through altering PPAR-γ expression., EXCLI Journal;Vol. 17 2018