PP2A activation in vivo is sufficient to disrupt interactions among vascular Akt‐Hsp90‐eNOS (1013.16)

Abstract

We have shown in bovine aortic endothelial cells (BAECs) treated with palmitate (P) and in arteries from obese mice that protein phosphatase 2A (PP2A) associates directly with eNOS. When PP2A co‐localizes with eNOS, interactions among Akt‐Hsp90‐eNOS are disrupted, p‐eNOS/eNOS is decreased, and NO bioavailability is impaired. We hypothesized that PP2A activation is sufficient to disrupt interactions among Akt‐Hsp90‐eNOS in arteries from fat‐fed mice. To test efficacy of the in vivo PP2A inhibitor Lixte Biotechnology 1 (LB1, Setauket, NY), BAECs were treated (3h) ± 500 uM P ± 4 uM LB1. P‐induced increases (p<0.05) in PP2A activity, and reductions (p<0.05) in p‐eNOS/eNOS and NO production (ELISA and EPR), were prevented by LB1. To determine the safety / efficacy of LB1, mice were treated (1 mg/kg/day IP) ± LB1 for 21 days. PP2A activity was reduced (p<0.05) and p‐PP2A Y307 to PP2A was elevated (p<0.05) in arteries from LB1 vs. vehicle‐treated mice after 3 and 21 days. To confirm the importance of PP2A vs. other phosphatases, BAECs incubated ± PP1 (3 uM tautomycin), PP2B (100 nM cyclosporine), or PP2A (4 uM LB1) inhibition. P‐induced reductions (p<0.05) in p‐eNOS/eNOS were prevented only by LB1. Finally, 7‐week old, male C57B16 mice consumed standard (CON, n=20) or high‐fat (HF, n=20) chow for 12‐weeks. Subgroups (n=10) of CON and HF mice received IP injections of saline (vehicle; V) or LB1 for the last 14‐days. HF mice gained weight and developed peripheral glucose intolerance vs. CON mice regardless of LB1 treatment. p‐eNOS/eNOS was impaired (53±6%; p<0.05) in vascular homogenates from HF‐V vs. all groups. After eNOS immunoprecipitation (IP), the association between: (i) PP2A:eNOS increased 95±11%, and the co‐localization between (ii) Akt:eNOS decreased 53±8%, and (iii) Hsp90:eNOS decreased 56±12%, in HF‐V vs. CON mice (all p<0.05). These findings suggest that PP2A activation is sufficient to disrupt interactions among Akt‐Hsp90‐eNOS in arteries from fat‐fed mice. Grant Funding Source: ADA 7‐08‐RA‐164, ADA1‐12‐BS‐208, 2R15HL091493