Studies on Cerebral Protection of Digoxin against Ischemia/Reperfusion Injury in Mice

Abstract

The present study was designed to investigate the possible neuroprotective eŠect of digoxin induced pharmacological preconditioning (PP) and its probable mechanism. Bilateral carotid artery occlusion (BCAO) of 17 min followed by reperfusion for 24 h was employed to produce ischemia and reperfusion (I/R) induced cerebral injury in male swiss albino mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was assessed using elevated plus maze test. Degree of motor incoordination was evaluated using inclined beam walking test, rota rod test and lateral push test. Digoxin (0.08 mg/kg, i.p.) was administered 24 h before surgery in a separate group of animals to induce PP. BCAO followed by reperfusion, produced signiˆcant rise in cerebral infarct size along with impairment of memory and motor coordination. Digoxin treatment produced a signiˆcant decrease in cerebral infarct size and reversal of I/R induced impairment of memory and motor incoordination. Digoxin induced neuroprotective eŠect was abolished signiˆcantly by verapamil (15 mg/kg, i.p.), a L-type calcium channel blocker, ruthenium red (3 mg/kg, s.c.), an intracellular ryanodine receptor blocker and 3,4-dichlorobenzamil (Na ＋ /Ca 2＋ exchanger inhibitor). Theseˆndings indicate that digoxin preconditioning exerts a marked neuroprotective eŠect on the ischemic brain, which is possibly linked to digitalis induced increase in intracellular calcium levels eventually leading to the activation of calcium sensitive signal transduction cascades.

Pharmacological preconditioning by milrinone: Memory preserving and neuroprotective effect in ischemia-reperfusion injury in mice

“…We therefore used the MWM test to assess memory, and assessed motor coordination via the rota-rod test, inclined beam walk test, and lateral push test. Our model of global cerebral ischemia and reperfusion increased infarct size and impaired memory as well as motor coordination, consistent with other reports Rehni et al, , 2008aRehni et al, , 2008bPateliya et al, 2008;Kaur et al, 2009aKaur et al, , 2009b. However, milrinone, a phosphodiesterase III inhibitor (Baim et al, 1983), given 24 h prior to global cerebral ischemia, dose dependently reduced infarct size and improved memory and motor coordination.…”

“…PP can be elicited by receptor agonists for adenosine, aaa-adrenergic, bradykinin, calcitonin gene related peptide (CGRP), opioid receptors (Schulz et al, 1998(Schulz et al, , 2001Rehni et al, 2008b) and ryanodine receptors (Kaur et al, 2009b). We also showed (Rehni et al, 2008b;Kaur et al, 2009b), as did others (Zhao et al, 2007), that pharmacological preconditioning exerts beneficial effects on memory dysfunction associated with cerebral ischemia/reperfusion injury.…”

“…Pharmacological activation can lead to a preconditioning-like protective effect that lasts beyond agent elimination, or pharmacological preconditioning (PP) (Rehni et al, 2008b;Kaur et al, 2009b), a clinically feasible paradigm (Yellon and Dana, 2000). PP can be elicited by receptor agonists for adenosine, aaa-adrenergic, bradykinin, calcitonin gene related peptide (CGRP), opioid receptors (Schulz et al, 1998(Schulz et al, , 2001Rehni et al, 2008b) and ryanodine receptors (Kaur et al, 2009b).…”

Autosis is a Na + ,K + -ATPase–regulated form of cell death triggered by autophagy-inducing peptides, starvation, and hypoxia–ischemia

“…Our chemical screen revealed cardiac glycosides as the most potent inhibitors of autotic cell death, and we found that they inhibited both autophagy and autotic cell death in the setting of starvation, autophagy-inducing peptide treatment, and neonatal hippocampal hypoxic-ischemic injury. The mechanism of action appears to be inhibition of the target of cardiac glycosides, Na + , K + -ATPase, as we observed similar effects with Na Previous studies have shown that neriifolin and other cardiac glycosides reduce cerebral infarct size in rodent cerebral hypoxia-ischemia models (18,24,25); however, their mechanism of neuroprotection has been unknown. Our observations suggest that inhibition of autophagy and autophagy-dependent death pathways may be a central mechanism of cardiac glycosidemediated neuroprotection.…”

“…A previous chemical screen to identify compounds that provide neuroprotection in a mouse brain slice-based model for ischemic stroke revealed neriifolin as a strong hit, and whole-animal studies have shown that neriifolin and other cardiac glycosides provide neuroprotection in neonatal models of cerebral hypoxia-ischemia (18,24,25). Given these observations, coupled with our findings described above that rat hippocampal CA3 region neurons die by autosis following hypoxia-ischemia, we evaluated whether neriifolin could protect neonatal rats against cerebral hypoxia-ischemia and reduce autosis in the hippocampal region CA3.…”