Independent and synergistic roles of MEK-ERK1/2 and PKC pathways in regulating functional changes in vascular tissue following flow cessation.

BACKGROUND: The MEK-ERK1/2 and PKC pathways play critical roles in regulating functional changes in tissues, but their interplay remains poorly understood. The vasculature provides an ideal model to study these pathways, particularly under conditions of flow cessation, which is highly relevant to ischemia and other cardiovascular diseases. This study examined the independent roles, additive effects, and time-dependent dynamics of MEK and PKC pathway inhibition in functional receptor upregulation. METHODS: Rat basilar arteries were cultured for 48 h with selective inhibitors targeting MEK (Trametinib), PKC (RO-317549) and their downstream ERK (Ulixertinib) and NF-kB (BMS 345541). Functional changes in ET(B) receptor responses were assessed via wire myography following stimulation with Sarafotoxin 6c (S6c). Western blot analysis quantified ERK phosphorylation, and the effects of inhibitor timing and combination treatments were evaluated. RESULTS: MEK inhibition reduced ERK phosphorylation and ET(B) receptor-mediated contractility, whereas PKC inhibition had no effect on ERK phosphorylation but significantly reduced ET(B) receptor function. Combining MEK and PKC inhibitors produced an additive effect, resulting in greater suppression of functional changes compared to single treatments. At 6 h following flow cessation, PKC inhibition effectively suppressed ET(B) receptor function, while MEK inhibition had minimal effects when introduced at this delayed time point. CONCLUSIONS: The MEK and PKC pathways independently drive functional changes in vascular tissue, particularly following flow cessation. MEK inhibition is effective early, while PKC inhibition remains effective when applied later. The additive effects observed with combined MEK and PKC inhibition indicate parallel and functionally independent pathway activation during ET(B) receptor upregulation.