Rottlerin, a PKC-delta Inhibitor, Strongly Suppresses Cell Cycle Progression in Vascular Smooth Muscle Cell Through AMPK Activation.

Motoshima, Hiroyuki; Kojima, Kanou; Igata, Motoyuki; Tsutsumi, Atsuyuki; Kondo, Tatsuya; Matsumura, Takeshi; Furukawa, Noboru; Tsuruzoe, Kaku; Nishikawa, Takeshi; Araki, Eiichi

Vascular smooth muscle cell (VSMC) proliferation is a critical event in the development and progression of atherosclerosis. Since protein kinase C (PKC) activation has been proposed to be involved in atherosclerosis as well as diabetic vascular complications, reagents, which can inhibit both PKC activity and VSMC growth, are considered to be beneficial for diabetic patients. We first screened a set of PKC inhibitors to suppress VSMC proliferation effectively by cell proliferation assay. Among PKC inhibitors we tested, rottlerin, a PKC-delta inhibitor, showed a prominent suppressive effect. Next, we investigated the levels of protein expression and/or phosphorylation of several molecules which are involved in cell cycle progression. PDGF stimulates Rb phosphorylation and increases cyclin D1 expression, both of which are known to occur at late-G1 phase and to be important for cell proliferation. Rottlerin strongly suppressed both Rb phospborylation and cyclin D1 induction stimulated by PDGF. These results indicate that rottlerin induces G1 arrest in VSMCs. Furthermore, we found that rottlerin strongly and continuously phosphorylated AMP-activated protein kinase (AMPK) and its downstream target, acethyl Co-enzyme carboxylase (ACC), suggesting the activation of AMPK, which we recently demonstrated to be a strong suppressor of VSMC proliferation (Circ Res. 97:837-844; 2005). In isolated rabbit aortic strips, PDGF also increased PKC-delta activity and Rb phosphorylation at 24 hours, and rottlerin completely inhibited these events. Decreased Rb phosphorylation in aortic strips treated with rottlerin was associated with the phosphorylation of AMPK and ACC. These data suggest that rottlerin suppresses cell cycle progression, at least in part, through activation of AMPK. Therefore, rottlerin and its derivatives may be useful for the prevention of vascular diseases associated with diabetes.

ENZYME inhibitors; PROTEIN kinase C; CELL proliferation; VASCULAR smooth muscle; MUSCLE cells; ATHEROSCLEROSIS; DIABETES complications; LABORATORY rabbits

Diabetes, 2007, Vol 56, pA599

0012-1797

Academic Journal