Does the severity of the ischemic insult promote differential activation of the endoplasmic reticulum stress pathway?

ROMAN B; ESOIN F; MUNDIÑA -WEILENMANN C.; BECERRA R; SALAS M; VITTONE L.; MARIANGELO JIE; SILVESTRI A; SAID M

Buenos Aires

Congreso; Reunión Conjunta de la Sociedades de Biociencias; 2017

Sociedad Argentina de Investigación Clínica - Sociedad Argentina de Fisiología

Abstract: Restoration of coronary flow after an ischemic event rescues the heart from further damage. However, reperfusion can cause reversible contractile dysfunction and arrhythmias if the ischemic period is brief or cell death if ischemia is prolonged. Ischemia and Reperfusion (I/R) challenges the endoplasmic reticulum (ER) protein folding capacity, leading to ER stress. The adaptive response to ER stress is the unfolded protein response (UPR) and comprises three pathways which lead to different effects: 1) ATF6 induces the transcription of XBP1 and GRP78 (the main ER chaperone); 2) IRE1 produces the splicing of XBP1 (sXBP1) which also increases GRP78 expression and 3) PERK attenuates protein synthesis. If ER stress is severe or prolonged, PERK can promote the expression of the pro-apoptotic protein CHOP and IRE1the activation of caspase 12. The aim of this work was to study the UPR associated to a reversible (I/Rrev) or irreversible (I/Rirrev) I/R damage. Isolated perfused rat hearts were subjected to I/R (20/30min, I/Rrev or 30/60min, I/Rirrev). At the end of R, mRNA expression of GRP78, total XBP1, sXBP1 and CHOP (real time qRT-PCR), expression of caspase 12 (Western blot) and apoptosis (TUNEL assay) were evaluated. mRNA levels of GRP78 and sXBP1 increased in both I/R protocols vs. non-ischemic hearts (Ctrl) (I/Rrev 1.68±0.14, 4.17±0.60; I/Rirrev 1.69±0.12, 2.73±0.22 fold change respectively, n=4-10, p