NF-κB driven cardioprotective gene programs; Hsp70.3 and cardioprotection after late ischemic preconditioning

Abstract

Rationale It has been shown that the transcription factor NF-κB is necessary for late phase cardioprotection after ischemic preconditioning (IPC) in the heart, and yet is injurious after ischemia/reperfusion (I/R). However the downstream gene expression programs that underlie the contribution of NF-κB to cardioprotection after late IPC are incompletely understood. Objective To delineate the specific genes that are regulated by NF-κB immediately after a late IPC stimulus and validate the methodology for identification of NF-κB-dependent genes that contribute to cardioprotection. Methods and Results A directed microarray analysis identified 238 genes as up or down regulated in an NF-κB-dependent manner 3.5 h after late IPC. Among these are several genes previously implicated in late IPC. Gene ontological analysis showed that the most significant group of NF-κB-dependent genes are heat shock response genes, including the genes encoding Hsp70.1 and Hsp70.3. Though an Hsp70.1/70.3 double knockout failed to exhibit cardioprotection, late IPC was intact in the Hsp70.1 single knockout. After I/R, the Hsp70.1/70.3 double knockout and the Hsp70.1 single knockout had significantly increased and reduced infarct size, respectively. Conclusions These results delineate the immediate NF-κB-dependent transcriptome after late IPC. One of the major categories of NF-κB-dependent genes induced by late IPC is the heat shock response. The results of infarct studies confirm that Hsp70.3 is protective after IPC. However, though Hsp70.1 and Hsp70.3 are coordinately regulated, their functions are opposing after I/R injury.

Cardiomyocyte-specific p65 NF-κB deletion protects the injured heart by preservation of calcium handling

“…This point is potentially important since conditional deletion of the p50 subunit has demonstrated conflicting results: worsening of postinfarction heart failure (13,24) versus ischemic cardioprotection (45). Similarly, inhibition of the p65 subunit has also produced, admittedly rare, conflicting results regarding its effect on ischemic injury (46,49). Taken together, we felt there was a need to directly assess the role of the p65 subunit not only to Fig.…”

“…However, this pattern overlooks that fact that NF-B is a vital part of our innate immunity and promotes survival signals (47). Indeed, some evidence suggests that NF-B promotes cardioprotection in models of ischemic preconditioning and coronary ligation (46,49). Central to reconciling many of these issues is enhanced understanding of the role of its principal subunit.…”

Coordinated Post-transcriptional Regulation of Hsp70.3 Gene Expression by MicroRNA and Alternative Polyadenylation

“…The Hsp70 family is among the best studied of the heat shock proteins, has been shown to be induced by many cardiac preconditioning stimuli, and plays a necessary role in the second window of protection (3)(4)(5)(6). Hsp70.1 and Hsp70.3 are two nearly identical stress-inducible Hsp70 genes present in the murine heart.…”

“…We have recently shown that NF-B-dependent expression of heat shock protein 70.3 (Hsp70.3), but not the closely related Hsp70.1, is necessary for the late phase or second window of ischemic preconditioning (IPC) cardioprotection against acute I/R in the heart (6). In fact, Hsp70.3 and Hsp70.1 appear to contribute differing functions to cell survival in the myocardium (6,7).…”

“…In fact, Hsp70.3 and Hsp70.1 appear to contribute differing functions to cell survival in the myocardium (6,7). Thus, it is important to understand the regulation of these two genes independently.…”