Effects of ischemic and remote ischemic postconditioning on apoptosis, necroptosis, pyroptosis and ferroptosis in cerebral ischemia reperfusion injury

Ischemic stroke, characterized by the loss of blood circulation in an area of the brain, leads to a range of neurological deficits and is one of the leading causes of death and disability worldwide. Despite advances in acute treatment strategies such as mechanical thrombectomy or intravenous thrombolysis, effective treatment options are limited. This leads researchers to discover new therapeutic targets. Ischemic postconditioning (PostC) is defined as a series of short ischemia-reperfusion intervals applied at the onset of reperfusion following prolonged ischemia. Remote ischemic postconditioning (RePostC) is a noninvasive approach that aims to protect vital organs affected by ischemia by interventions applied to remote areas of the body. Cellular homeostasis is important during the injury process and pro-survival/pro-death processes are activated simultaneously. Apoptosis is a caspase-dependent regulated process. Necroptosis is defined as a regulated type of cell death with a necrotic appearance. Pyroptosis is critical in the defense of physiological systems against infection and stress-related signals. Ferroptosis is a mode of cell death characterised by iron-induced lipid peroxidation. In our study, we investigated the role of apoptosis, necroptosis, pyroptosis and ferroptosis among cell death pathways in cerebral ischemia/reperfusion (I/R) injury, the protective effects of PostC and RePostC as a mechanical treatment and the effects of PostC and RePostC on Sestrin2 levels. This study was performed in 40 male Spraque Dawley rats aged 10-12 weeks. The rats were divided into 4 groups. At the beginning of reperfusion after middle cerebral artery occlusion, 3 cycles of 30 s reperfusion/10 s ischemia were performed as PostC; and 3 cycles of reperfusion-ischemia as RePostC were applied to the right hind leg for 5 min each. Protein expression levels were determined by Western blot; 2,3,5-triphenyltetrazolium chloride (TTC) staining for necrosis area and open field, vertical bar and beam walking tests were performed to evaluate locomotor activity. Cerebral I/R-induced necrosis area was significantly decreased with PostC and RePostC administration. The treatment methods applied did not cause a statistically significant difference in behavioural tests. Apoptotic protease activating factor 1 (Apaf-1), receptor-interacting serine/threonine-protein kinase 3 (RIPK3), Gasdermin D (GsdmD) and Sestrin2 (Sesn2) levels were significantly increased by IR and significantly decreased by PostC and RepostC. Long-chain fatty acyl CoA synthase 4 (ACSL4) was significantly increased by I/R and significantly decreased by RePostC treatment. The decrease with PostC treatment was not statistically significant. Hexokinase II (HK-II) level was significantly decreased by I/R, while it was significantly increased in PostC and RePostC treated groups. Apoptosis, necroptosis, pyroptosis and ferroptosis may be involved in the pathophysiological mechanism of cerebral I/R injury and inflammation may accompany this mechanism. In cerebral I/R injury, PostC and RePostC may be protective by inhibiting apoptosis, necroptosis, pyroptosis and ferroptosis and triggering anti-inflammatory mechanisms. Apaf-1, RIPK3, GsdmD and ACSL4 and HK-II, Sesn2 levels may be a potential target for the treatment of cerebral IR injury. Inducing endogenous tolerance mechanisms by PostC and RePostC administration may protect against cerebral I/R injury.