Ischemic preconditioning in pigs: a causal role for signal transducer and activator of transcription 3

Abstract

Ischemic preconditioning (IPC), i.e., brief episodes of nonlethal myocardial ischemia-reperfusion (I/R) before sustained ischemia with subsequent reperfusion, reduces infarct size in all species tested so far, including humans. In rodents, the cardioprotective signal transduction causally involves an activation of Akt, ERK1/2, and STAT3. However, there are apparent species differences in the signal transduction between rodents and larger mammals such as pigs, where data on IPC's signal transduction are inconsistent for Akt and ERK1/2. The role of STAT3 has not yet been analyzed. Pigs were subjected to 60 min of left anterior descending coronary artery occlusion and 180 min of reperfusion without or with IPC (2 cycles of 3-min occlusion separated by 2 min of reperfusion 15 min before sustained I/R). Infarct size was analyzed by triphenyl tetrazolium chloride staining, and Akt, ERK1/2, and STAT3 phosphorylation was quantified in myocardial biopsies taken at baseline and early reperfusion. AG490 was used to block the STAT3 signaling pathway. IPC reduced infarct size (%area at risk; mean ± SE, I/R, 45 ± 3 vs. IPC, 18 ± 3, < 0.05). Akt and ERK1/2 phosphorylation was increased at early reperfusion without and with IPC. In contrast, STAT3 phosphorylation at early reperfusion was only increased with IPC (%baseline; mean ± SE, I/R, 126 ± 29 vs. IPC, 408 ± 147, < 0.05). AG490 prevented the IPC-related increase of STAT3 phosphorylation at reperfusion (%baseline; mean ± SE, 82 ± 12) and abolished IPC's cardioprotection (%area at risk; mean ± SE, 35 ± 4). In pigs, increased phosphorylation of STAT3 is causally involved, whereas Akt and ERK1/2 seem to play no role in IPC's cardioprotection. In pig hearts in situ, ischemic preconditioning (IPC) causally involves increased phosphorylation of STAT3, whereas Akt and ERK1/2 play no role for cardioprotection. The cardioprotective signal transduction of IPC is similar to that of ischemic postconditioning and remote IPC in pigs.

Humoral transfer and intramyocardial signal transduction of protection by remote ischemic perconditioning in pigs, rats, and mice

“…In pigs, RPER is mediated through an ATP-sensitive K ϩ channel-dependent mechanism and blocked by glibenclamide (32). In a very recent study from our laboratory, we found the infarct size reduction by RPER associated with increased phosphorylation of STAT3 during reperfusion (20) very similar to remote (34) and local (8) ischemic preconditioning and also to ischemic postconditioning (14). In that study, the protection by RPER became evident by an attenuation of ST segment elevation after the RPER procedure but during still ongoing coronary occlusion, indicating that RPER protects not only from reperfusion injury but also from ischemic injury (20).…”

Larger infarct size but equal protection by ischemic conditioning in septum and anterior free wall of pigs with LAD occlusion

“…The algorithms for the cardioprotective maneuvers have been adapted from published maneuvers in clinical settings [IPC (Buyukates et al ), RIPC (Munk et al ), RPER (Bøtker et al ), POCO (Staat et al )] with slight modifications. These maneuvers robustly reduced IS in our prior studies (Skyschally et al ; Skyschally et al ; Gent et al ; Kleinbongard et al ). We therefore did not modify the algorithms in number and duration of ischemia/reperfusion cycles to further optimize the magnitude of IS reduction (Johnsen et al ).…”

“…The underlying data were retrospectively analyzed from experiments performed in a single institution over a period of 6 years. Such approach has been used by others before (Rossello et al 2018) and is in line with the 3R (Skyschally et al 2013;Skyschally et al 2015;Gent et al 2017;Kleinbongard et al 2018). We therefore did not modify the algorithms in number and duration of ischemia/reperfusion cycles to further optimize the magnitude of IS reduction (Johnsen et al 2016).…”

“…The experiments were performed between November 2012 and November 2018, and their results have already been reported in a different context (Skyschally et al 2013;Skyschally et al 2015;Gent et al 2017;Kleinbongard et al 2018;Skyschally et al 2018;Lieder et al 2018). All experiments were performed in healthy G€ ottingen minipigs (male, body weight:~30 kg, age: 12-14 months; Ellegaard, Dalmose, Denmark).…”

“…We determined AAR and IS in the septum and anterior free wall after proximal LAD occlusion. In addition, we analyzed and compared the magnitude of cardioprotection by local ischemic preconditioning (Gent et al ), ischemic postconditioning (Skyschally et al ), remote ischemic preconditioning (Skyschally et al ), and remote ischemic perconditioning (Kleinbongard et al ; Skyschally et al ) in the septum and anterior free wall.…”