Effects of ischemic preconditioning on mitochondrial and metabolic neruoprotection: 5' adenosine monophosphate-activated protein kinase and sirtuins

Abstract

Stroke and cardiac arrest result in cerebral ischemia, a highly prevalent medical issue around the world, which is characterized by a reduction or loss of blood flow to the brain. The loss of adequate nutrient supply in the brain during ischemia results in neuronal cell death contributing to cognitive and motor deficits that are usually permanent. Current effective therapies for cerebral ischemia are only applicable after the fact. Thus, the development of preventative therapies of ischemia is imperative. A field of research that continues to show promise in developing therapies for cerebral ischemia is ischemic preconditioning (IPC). IPC is described as exposure to sublethal ischemic events, which induce adaptive changes that provide tolerance to future ischemic events. Through either transient sub-lethal ischemic events, or the actions of a preconditioning molecular mimetic, IPC typically results in augmented gene expression and cellular metabolism. A pivotal target of such changes in gene expression and metabolism is the mitochondrion. Direct and indirect effects on mitochondria by IPC can result in the activation of 5' adenosine monophosphate-activated protein kinase (AMPK), a master regulator of cellular metabolism. Changes in the activity of the posttranslational modifiers, SIRT1 and SIRT5, also contribute to the overall adaptive processes in cellular metabolism and mitochondrial functioning. In this review, we present recently collected evidence to highlight the neuroprotective interactions of mitochondria with AMPK, SIRT1, and SIRT5 in IPC. To produce this review, we utilized PubMed and previous reviews to target and to consolidate the relevant studies and lines of evidence.

Keywords: 5’ adenosine monophosphate-activated protein kinase; SIRT1; SIRT5; ischemic preconditioning; metformin.

Figure 1

Ischemic preconditioning and its mimetics activate AMPK to induce mitochondrial neuroprotective mechanisms. Ischemic preconditioning, resveratrol, and metformin have all been shown to activate AMPK through various means. Activation of AMPK induces cellular changes in mitochondrial function, mitochondrial number, and antioxidant expression. Ultimately, the activation of AMPK promotes mitochondrial neuroprotection of ischemic insult. AMPK = 5’ adenosine monophosphate-activated protein kinase, AMP = Adenosine monophosphate, ATP = Adenosine triphosphate, CI = Complex I, IPC = Ischemic preconditioning, MCP = Metformin preconditioning, Nampt = Nicotinamide phosphoribosyltransferase, Nrf2 = Nuclear factor erythroid 2-related factor, PKCε = Protein kinase C epsilon, RPC = Resveratrol preconditioning