Cyclosporine upregulates KLF4 in vascular smooth muscle cells and drives phenotypic modulation in vivo

Abstract

Cyclosporine‐A (CSA, a calcineurin inhibitor) is a fungus‐derived immunosuppressant that blocks proliferation of lymphocytes. CSA has also been shown to block both vascular smooth muscle cell (SMC) proliferation in culture and vessel neointimal formation following injury in vivo. The molecular and pathological effects of CSA on SMCs are not fully understood. We show here that CSA increased SMC expression of Krüppel like factor 4 (KLF4) mRNA and protein. KLF4 is a transcription factor that regulates SMC phenotype. KLF4 inhibits proliferation, promotes migration, and suppresses SMC differentiation marker genes. We show that CSA suppressed SMC differentiation markers SM α‐actin (ACTA2), transgelin (TAGLN), smoothelin (SMTN), and myocardin (MYOCD), but increased cyclin‐dependent kinase inhibitor‐1A (CDKN1A) & matrix metalloproteinase‐3 (MMP3). CSA treatment of rat carotid arteries in vivo resulted in acute and transient suppression of ACTA2, TAGLN, SMTN, MYOCD, & SM myosin heavy chain (MYH11) mRNA. Conversely, tumor suppressor genes KLF4, p53, & CDKN1A were increased, as well as MMP3, MMP9, & collagen‐VIII (COL8). CSA‐treated arteries showed breakdown of the internal elastic lamina and pathological reorientation of SMCs. KLF4 immunostaining in SMCs and endothelial cells was increased. In conclusion, CSA increases KLF4 expression and promotes SMC phenotypic modulation in vivo. Sources of support: APS UGSRF, APS post‐doc, NIH HL81682, AHA SDG.