Inhibition of C-Jun N-Terminal Kinase 1, but Not c-Jun N-Terminal Kinase 2, Suppresses Apoptosis Induced by Ischemia/Reoxygenation in Rat Cardiac Myocytes

Abstract

In the present study, rat cardiac myocytes were used as an in vitro ischemia/reperfusion injury model to delineate the role of c-Jun N-terminal kinase (JNK) 1 and JNK2 isoforms in ischemia/reoxygenation-induced apoptosis using an antisense approach. Exposure of rat cardiac myocytes to ischemia did not induce apoptosis as detected by staining with either acridine orange/ethidium bromide or annexin-V-fluorescein/propidium iodide. In contrast, a time-dependent increase in the number of apoptotic cells was noted after reoxygenation of ischemic myocytes, whereas the level of necrotic cells remained unaltered. Reoxygenation, but not ischemia alone, also caused a time-dependent increase in JNK activation that preceded apoptosis induction. Treatment of cardiac myocytes with antisense (AS) oligonucleotides that specifically targeted either JNK1 or JNK2 significantly reduced both mRNA and protein expression of the target isoform but had no effect on the expression of the alternate isoform. Pretreatment of cardiac myocytes with JNK1 AS, but not JNK2 AS, resulted in almost complete attenuation of reoxygenation-induced apoptosis. Furthermore, control oligonucleotides for JNK1 AS or JNK2 AS had no effect on JNK mRNA or protein expression or reoxygenation-induced apoptosis, indicating a sequence-specific mode of action. Additional studies revealed that apoptosis induced by other JNK-activating stimuli, including ceramide, heat shock, and UV irradiation, was partly suppressed after treatment with JNK1 AS but not JNK2 AS. These findings demonstrate that the JNK1 isoform plays a preferential role in apoptosis induced by ischemia/reoxygenation as well as diverse JNK-activating cellular stresses.

Heat Shock Transcription Factor 1 Protects Cardiomyocytes From Ischemia/Reperfusion Injury

“…23,24 Activation of Akt has been reported to protect cardiomyocytes against various stresses, such as oxidative stress 25 and the ischemia/ reperfusion injury, 26 whereas JNK has been indicated to induce apoptosis during ischemia/reoxygenation in rat cardiomyocytes. 27 In the present study, ischemia/reperfusion activated more Akt and less JNK in the transgenic heart than the wild-type one. HSP90 has been reported to bind to Akt and promote activation of Akt through inhibition of protein phosphatase 2A.…”

Targeted Activation of c-Jun N-terminal Kinase in Vivo Induces Restrictive Cardiomyopathy and Conduction Defects

“…Several studies support a protective role for JNK activation in cultured myocytes (43)(44)(45)(46), whereas others have shown JNK signaling to be proapoptotic in the setting of oxidative stress (9,47). Recent studies have begun to examine the role of JNK in cardiomyocyte apoptosis in vivo.…”

Cellular response to oxidative stress: Signaling for suicide and survival*

“…Nonetheless, such strategies have supported a role for JNK in mediating apoptosis in many models of oxidative stress (Zanke et al, 1996;Turner et al, 1998;Wang et al, 1998;Yin et al, 2000). Another approach that has provided support for the role of JNK in mediating apoptosis by oxidative stress is the use of antisense oligonucleotides possessing high specificity for different JNK isoforms (Garay et al, 2000;Hreniuk et al, 2001). In these studies, JNK1 but not JNK2 has been implicated in oxidant-induced apoptosis.…”