Abstract
BackgroundPhytanic acid (PA) has been implicated in development of cancer and its defective metabolism is known to cause life-threatening conditions, such as Refsum disease, in children. To explore molecular mechanisms of phytanic acid-induced cellular pathology, we investigated its effect on NADPH oxidase (NOX) and epidermal growth factor receptor (EGFR) in rat aortic smooth muscle cells (RASMC).MethodsSmooth muscle cells were isolated from rat aortae using enzymic digestion with collagenase and elastase. Cultured RASMC were treated with varying concentrations (0.5-10 μg/ml) of phytanic acid in the presence/absence of fetal bovine serum (FBS) and/or EGFR inhibitor, AG1478. Following treatment with experimental agents, NOX activity was assayed in RASMC cultures by luminescence method. Gene expression of NOX-1 and p47phox was assessed using RT-PCR. NOX-1, p47phox and, total EGFR protein and its phosphorylated form were measured by Western blotting.ResultsTreatment of RASMC with supraphysiological concentrations (>2.5 μg/ml) of PA significantly (p < 0.01) increased the NOX activity. PA also significantly increased gene/protein expression of NOX-1 and p47phox whereas p22phox and p67phox remained unaffected. Interestingly, PA (2.5-10 μg/ml) markedly (2–3 folds) increased the total and phosphorylated EGFR. Treatment of cells with EGFR inhibitor, AG1478, significantly blocked the PA-induced enhancement of NOX activity.ConclusionsOur findings that PA transactivates EGFR and induces NOX activity in vascular smooth muscle cells provide new insights into molecular mechanisms of PA’s role in cancer and Refsum disease.
Highlights
Phytanic acid (PA) has been implicated in development of cancer and its defective metabolism is known to cause life-threatening conditions, such as Refsum disease, in children
First strand of cDNA obtained from reverse transcription was Effect of Phytanic acid on NADPH oxidase (NOX) in rat aortic smooth muscle cells (RASMC) cultures Figure 1 shows that 24 h treatment of RASMC with supra-physiological concentrations (2.5-10 μg/ml) of phytanic acid significantly (p < 0.01) increased the NOX activity irrespective of the presence or absence of fetal bovine serum (FBS) in the culture medium
In relation to the observed activation of NOX activity by phytanic acid, we examined the gene/protein expression and of various NOX components in RASMC cultures treated with phytanic acid in the presence or absence of FBS
Summary
Phytanic acid (PA) has been implicated in development of cancer and its defective metabolism is known to cause life-threatening conditions, such as Refsum disease, in children. To explore molecular mechanisms of phytanic acid-induced cellular pathology, we investigated its effect on NADPH oxidase (NOX) and epidermal growth factor receptor (EGFR) in rat aortic smooth muscle cells (RASMC). PA metabolism was recognized to be vital for human health with the identification of peroxisomal disorders, such as Zellweger syndrome and Refsum disease where supraphysiological amounts of phytanic acid were found to accumulate in body tissues and fluids of the patients [4,5,6]. Peroxisomal disorder patients with aberrant phytanic acid metabolism often experience severe clinical complications that range neurological impairment to cardiovascular anomalies [7, 8]. A number of nuclear transcription factors called peroxisome proliferator-activated receptors (PPAR), PPAR-α, have strong affinity for PA and their
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