Exercise Preconditioning Attenuates Neurological Injury by Preserving Old and Newly Formed HSP72-Containing Neurons in Focal Brain Ischemia Rats

Abstract

Background: Exercise preconditioning (EP + ) is a useful and important procedure for the prevention of stroke. We aimed to ascertain whether EP + protects against ischemic brain injury by preserving heat shock protein (HSP) 72-containing neurons in ischemic brain tissues. Methods: Adult male Sprague-Dawley rats (n=240) were used to assess the contribution of HSP72-containing neurons to the neuroprotective effects of EP + on ischemic brain injury caused by transient middle cerebral artery occlusion. Results: Significant (P<0.05) increases in the percentages of both old HSP72-containing neurons (NeuN+HSP72 double positive cells) (18~20% vs. 40~50%) and newly formed HSP72-containing neurons (BrdU+NeuN+HSP72 triple positive cells); (2~3% vs. 16~20%) after 3 weeks of exercise coincided with significant (P<0.05) reductions in brain ischemia volume (250 mm 3 vs. 100 mm 3 ), brain edema (78% vs. 74% brain water content), blood-brain barrier disruption (1.5 μg/g vs. 0.7 μg/g tissue Evans Blue dye extravasation) and neurological motor deficits (neurological severity scores of 12 vs. 6 and maximal angles of 60° vs. 20°) in brain ischemia rats. Reductions in the percentages of both old (from 40~50% to 10~12%) and newly formed (from 18~20% to 5~7%) HSP72-containing neurons by gene silencing with an intracerebral injection of pSUPER small interfering RNA showed a significant (P<0.05) reversal in the neuroprotective outcomes. Our data provide an inverse correlation between the EP + -mediated increases in both old and newly formed HSP72-containing neurons and the extent of cerebral ischemic injury. Conclusions: The percentages of both old and newly formed HSP72-containing neurons are inversely correlated with the outcomes of ischemic brain injury. Additionally, preischemic treadmill exercise improves the outcomes of ischemic brain injury by preserving both the old and newly formed HSP72-containing neurons in rats.

Mechanisms of Preconditioning Exercise-Induced Neurovascular Protection in Stroke

“…These mechanisms may involve but not limited to: (1) reducing the poststroke inflammation by reducing the expression and activity of inflammatory cytokines like TNFα, TLRs, and NF-κB after stroke; [44][45][46][47][48][49][50][51][52][53] (2) increasing angiogenesis and neovascularization through increasing the expression of VEGF and VEGF receptors, caveolin, and angiopoietin in the brain; [56][57][58] (3) increasing the BBB integrity and reducing disruption through reducing the post-stroke expression of MMPs and increasing the expression of integrins proteins; [46][47][48]54,55 (4) increasing post-stroke CBF by increasing eNOS activation and NO production; [62][63][64] and (5) increasing neurogenesis and reducing neuronal apoptosis through activation of HIF-1α, HSPs, BDNF, and inhibition of glutamate and caspase activities. [68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86] It is obvious that the preconditioning exercise-induced protection is due to multiple intermeshing mechanisms and pathways. The interplay between these different mechanisms and molecules in the signaling pathways can be the main cause of the ultimate neurovas...…”

“…Collectively, these actions will inhibit cerebral inflammation, cell death, and BBB disruption. [46][47][48][84][85][86] Inhibition of glutamate-induced excitotoxicity by exercise, may lead to reduction in neuronal apoptosis and cell death. [68][69][70][71][72][73][74][75][76] This may be due to reduced calcium ion intracellular influx, increased Bcl2, and reduced Bax leading to reduction in caspases activity, mainly caspase 3.…”

“…They found that preconditioning exercise for 3 weeks caused a significant increase in the expression of HSP-70 and reduction in the expression of Bax and apoptosis inducing factor (AIF). 85 In 2019, Wang et al 86 showed that preconditioning treadmill training for 3 weeks before stroke significantly reduced infarct size, brain edema, and neurological deficits. This was attributed to the exercise-induced increase in the number of old and newly formed HSP-72 containing neurons.…”

“…This was attributed to the exercise-induced increase in the number of old and newly formed HSP-72 containing neurons. 86…”

Neuroprotective Effect of Physical Activity in Ischemic Stroke: Focus on the Neurovascular Unit

“…Recent studies have discovered that exercise can exert a neuroprotective effect on cerebral ischemia by regulating HSP-70 (HSP-72). Wang Y. L. et al (2019) demonstrated that the percentage of HSP-72-containing neurons are tightly associated with a degree of ischemic stroke-induced brain injury, and exercise preconditioning can help improve neurological function post-stroke by preserving both the old and newly formed HSP-72-containing neurons. Liebelt et al (2010) found that the expression of Bax and apoptosis-inducing factor (AIF) were reduced, while levels of Bcl-x(L) were increased in response to stroke after exercise.…”