Poster Presentation 23rd Annual Lorne Proteomics Symposium 2018

ERK1/2 is a key regulator of early myocardial ischemic damage (#129)

Desmond K Li 1 2 , Lauren E Smith 1 2 , Melanie Y White 1 2 3 , Stuart J Cordwell 1 2 3 4
  1. Discipline of Pathology, School of Medical Sciences, The University of Sydney, Sydney, NSW, Australia
  2. Charles Perkins Centre, The University of Sydney, Sydney, NSW, Australia
  3. School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, Australia
  4. Sydney Mass Spectrometry, The University of Sydney, Sydney, NSW, Australia

Cardiovascular disease is one of the leading causes of death with ischemic heart disease (IHD) the largest contributor. The long-term outcomes following IHD are directly attributable to the duration of ischemic insult, with short periods of ischemia (<20 mins) producing reversible contractile dysfunction, while prolonged ischemia (>30 mins) results in irreversible contractile injury. In previous studies we utilised large-scale phosphoproteomics to monitor the activation/repression of signalling pathways over an ischemic time course spanning 0-60 minutes. ERK1/2 was identified to be significantly upregulated within the first 2 minutes of ischemia only, suggesting a significant role of ERK1/2 during reversible ischemic damage. To investigate the importance of ERK1/2 during the early phases of ischemia, an upstream MEK inhibitor (U0126) was introduced during the ischemic period, with subsequent reperfusion to monitor the return of contractile function. Hearts were subject to one of the following conditions; 2 minutes of ischemia with/without U0126 (2I, 2IU); 2 minutes of ischemia with/without U0126 followed by 5 minutes of normal reperfusion (2I/5R, 2IU/5R) or; 2IU followed by 5 minutes of reperfusion with U0126 (2IU/5RU). Haemodynamic comparison showed that 2IU/5R had significantly poorer function compared to 2I/5R (54.8% ± 7.3 % RPP vs 93.1% ± 2.8% RPP ) while 2IU/5RU did not (86.8% ±9.2%), suggesting that ERK1/2 inhibition during ischemia and reperfusion has no effect on function. If ERK1/2 is inhibited during ischemia but re-activated during reperfusion it causes significant deterioration of contractile function. This suggests activation of a compensatory mechanism/signalling pathway in the absence of ERK1/2 activity. Using a combination of phosphoproteomics and Western Blot, we found that AMPK contributed in a compensatory way to ERK1/2 inhibition. The ability to activate AMPK, appears to circumvent the need for ERK1/2 regulation, however activation of both AMPK and ERK1/2 is detrimental to the heart, leading to poor functional outcomes.