Abstract 12521: Intracellular Fatty Acid Balance Regulated by Elovl6 Plays a Notable Phenotypic Response of Vascular Smooth Muscle Cells via AMPK-KLF4-Dependent Signaling
Introduction: Krüppel-like factor 4 (KLF4) is a transcription factor controlling differentiation and proliferation of vascular smooth muscle cells (VSMC). We recently showed that disruption of elongation of long chain fatty acids 6 (Elovl6), rate-limiting enzyme catalyzing the elongation of saturated and monounsaturated, suppressed VSMC proliferation and differentiation via AMP-activated protein kinase (AMPK) activation. However, little is known about the role of KLF4 in passing metabolic stress on to the regulating VSMC proliferation and differentiation.
Hypothesis: We examine whether KLF4 is involved in the suppression of Elovl6-disrupted VSMC proliferation.
Methods and Results: Immunohistochemical staining of aorta revealed that KLF4 expression was markedly increased in Elovl6-null (Elovl6-/-) mice compared with wild-type mice. Western blot analysis also showed that the KLF4 expression was markedly induced in human aortic smooth muscle cell (HASMC) with siRNA-mediated Elovl6 depletion and in Elovl6-/- mouse aorta. Previous study demonstrated that Elovl6 depletion in VSMC altered long chain fatty acid (LCFA) composition in which palmitate was increased and oleate was decreased. Accordingly, palmitate increased and oleate decreased KLF4 expression. To clarify the effects of KLF4 on cell-cycle regulatory gene expressions and cell proliferation, we examined a siRNA-mediated knockdown of KLF4 in HASMC. The expression of SMα-actin and SM22α genes were decreased in siKLF4-introduced HASMC, and siElovl6-triggered inhibition of cell proliferation was partially recovered by concomitant treatment of siKLF4. Elovl6 depletion in HASMC markedly induced p53 phosphorylation and p21 expression, whereas depletion of KLF4 abrogated the induction of these proteins. We further identified the treatment with AMPK activator (AICAR) significantly induced KLF4 expression, whereas AMPK inhibitor (compound C) markedly inhibited the AICAR-induced or Elovl6-knockdown-induced KLF4 expression.
Conclusions: Overall, our results indicate that KLF4 is activated by metabolic stress triggered by perturbed intracellular LCFA composition and AMPK-KLF4 axis plays an indispensable role in controlling VSMC proliferation and differentiation
Author Disclosures: H. Matsui: None. H. Sunaga: None. T. Iso: None. N. Koitabashi: None. T. Matsuzaka: None. H. Shimano: None. T. Yokoyama: None. M. Kurabayashi: None.
- © 2016 by American Heart Association, Inc.