Metabolic activation of AMP kinase in vascular smooth muscle

Abstract

AMP-activated kinase (AMPK) is a highly conserved heterotrimeric kinase that functions as a metabolic master switch to coordinate cellular enzymes involved in carbohydrate and fat metabolism that regulate ATP conservation and synthesis. AMPK is activated by conditions that increase AMP-to-ATP ratio, such as exercise and metabolic stress. In the present study, we probed whether AMPK was expressed in vascular smooth muscle and would be activated by metabolic stress. Endothelium-denuded porcine carotid artery segments were metabolically challenged with 2-deoxyglucose (10 mM) plus N(2) (N(2)-2DG). These vessels exhibited a rapid increase in AMPK activity by 1 min that was near maximal by 20 min. AMPK inactivation on return to normal physiological saline was approximately 50% in 1 min and fully recovered by 5 min. Immunoprecipitation of the alpha(1)- and alpha(2)-catalytic subunit followed by immunoblot analysis for [P]Thr(172)-AMPK indicates that alpha(1)-AMPK accounts for all activity. Little if any alpha(2)-AMPK was detected in carotid smooth muscle. AMPK activity was not increased by contractile agonist (endothelin-1) or by the reported AMPK activators 5-aminoimidazole-4-carboxamide ribofuranoside (2 mM), metformin (2 mM), or phenformin (0.2 mM). AMPK activation by N(2)-2DG was associated with a rapid and pronounced reduction in endothelin-induced force and reduced phosphorylation of Akt and Erk 1/2. These data demonstrate that AMPK expression differs in vascular smooth muscle compared with striated muscles and that activation and inactivation after metabolic stress occur rapidly and are associated with signaling pathways that may regulate smooth-muscle contraction.

AMP-activated Protein Kinase Phosphorylates and Desensitizes Smooth Muscle Myosin Light Chain Kinase

“…AMPK was immunoprecipitated with anti-␣1-and anti-␣2-AMPK antibodies prior to AMPK assay. The AMPK catalytic ␣1-subunit isoform accounted for 90% of the total AMPK activity in ASMC lysates (data not shown), confirming results obtained with porcine carotid arteries (29). Treatment with 10 Ϫ7 M vasopressin, angiotensin II, or endothelin-1 led to AMPK activation (Fig.…”

“…*, significant difference (p Ͻ 0.05, unpaired t test) compared with the controls. stress or anoxia was found to decrease force generation in response to endothelin-1 treatment (29). The underlying mechanisms, which were not investigated, are in line with our findings.…”

Lack of direct effect of adiponectin on vascular smooth muscle cell BKCa channels or Ca2+ signaling in the regulation of small artery pressure-induced constriction

“…Thus, while AICAR causes a small (~12%) vasodilation, neither metformin nor phenformin have an effect and N 2 ‐2DG elicits a vasoconstriction (Rubin et al. 2005). A final consideration is that in our study, neither adiponectin nor the presence of intact PVAT had any effect on calcium signals (Ca 2+ sparks or waves) in intact pressurized arteries.…”

Mechanical Stretch-Induced Protection against Myocardial Ischemia-Reperfusion Injury Involves AMP-Activated Protein Kinase

“…In addition, stretch is also known to activate the AMP-activated protein kinase (AMPK) in muscle cells [12,13]. AMPK is a serine-threonine kinase, which is emerging as an important regulator of diverse cellular pathways in regulating whole-body energy metabolism.…”

“…A large number of cellular signal transduction pathways can be activated by stretch, such as the JNK, a group of MAPK, PKC, and JAK/STAT pathway [9][10][11]. It has also been suggested that stretch can activate the AMP-activated kinase (AMPK) in muscle cells [12,13].…”