Single low-dose administration of pharmacological inhibitor of mitogen-activated ERK kinase to the adventitia of the injured rat carotid artery suppresses neointima formation and inhibits nuclear ERK signaling.

Arterial injury has been reported to activate the mitogen-activated ERK kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway. Pharmacological MEK inhibition was previously shown to inhibit injury-induced neointima formation in rodent models, but inhibitor compounds were administered either locally at a high dose or systemic treatment was performed over an extended period of time. Aim of this study was, therefore, to explore the efficiency of single low-dose administration of the MEK inhibitor PD98059 on neointima formation in the injured rat carotid artery. The second aim of the study was to analyse treatment effects on MEK-dependent signaling and protein expression. PD98059 (at doses of 10 and 40 nmol) was administered to the adventitia immediately after injury using Pluronic gel as drug carrier. Compared to untreated controls, PD98059 treatment (10 nmol) resulted in significant reductions of neointima-to-media ratio (by 66%) and injury-induced lumen loss (by 53%). Conversely, lumen was increased by 33% in PD98059-treated arteries. There were no significant differences between the 10 and 40 nmol treatment groups. Dual ERK1/2 phosphorylation, and also ERK1/2 protein expression, was significantly inhibited by PD98059 treatment. Expression of the transcription factor Ets-1, a nuclear target protein of ERK1/2 was significantly suppressed in PD98059-treated arteries. Attenuation of neointima formation was associated with significantly decreased expression of the proliferation marker PCNA. In contrast, we did not find biochemical evidence of increased apoptosis in PD98059-treated arteries. Our data show that the single adventitial administration of low-dose MEK inhibitor PD98059 is sufficient to suppress neointima formation in injured arteries.