Pertussis toxin reduces calcium influx to protect ischemic stroke in a middle cerebral artery occlusion model

Abstract

Increased calcium influx secondary to glutamate induced excitotoxicity initiates and potentiates devastating pathological changes following ischemic stroke. Pertussis toxin (PTx), a Gprotein blocker, is known to suppress intracellular calcium accumulation. We hypothesize that PTx can protect against stroke by blocking calcium influx. In a permanent middle cerebral artery occlusion model, PTx (1000 ng) was given intraperitoneally 30 min after inducing stroke. Magnetic Resonance Imaging of perfusion and T2-weighted brain scans were obtained to evaluate cerebral blood flow (CBF) and infarct volume. Primary neuronal culture was used to test glutamate induced excitotoxicity and calcium influx. We established a non-linear exponential curve model to minimize variations in animal cerebrovasculature. A reduction of 40-60% in relative CBF was a critical window where infarct volume started to increase as rCBF reduced. PTx showed maximal effects in reducing infarct volume at this window. In vitro studies further demonstrated PTx increased neuronal cell survival by decreasing glutamate-induced calcium influx into neurons and preventing neurons from apoptosis. PTx salvages the ischemic penumbra by blocking calcium influx. This provides us a new mechanism upon which experimental therapies can be explored to treat ischemic stroke.

The Role of TRPC6 in the Neuroprotection of Calycosin Against Cerebral Ischemic Injury

“…The need for developing an effective and safe treatment for acute stroke remains urgent. The pathogenesis of ischemic stroke is not fully understood; several underlying mechanisms have emerged such as excitotoxicity 4 , oxidative stress 5 , and calcium overload 6 , inflammation and apoptosis 7, 8 . Of these, calcium overload is regarded as the final common pathway of the mechanisms leading to neuronal death 9, 10 .…”

Expression of MICU1 after experimental focal cerebral ischemia in adult rats

“…Scale bar = 100 μm Previous studies showed that a rise of calcium concentration signals an increased cellular energy demand and mediates a number of pathways that can precipitate mitochondrial injury and cell death [9]. Of interest, increments in [Ca 2+ ] c are detected at the acute phases after MCAO [10][11][12]. At approximately the same time, the expression of MCU is up-regulated [13].…”

Pertussis Toxin Ameliorates Microglial Activation Associated With Ischemic Stroke

“…Neurological deficit assessments were performed by investigators who were blinded to the experimental groups, as described previously (Tang et al, 2015 ; Yin et al, 2015 ; Xie et al, 2018 ). Briefly, rating scale was used as follows: score 0 was defined as the complete absence of neurological deficit; score 1 was defined as that front paws incompletely extended and mild neurological deficit; score 2 was defined as lateral turning while walking and moderate neurological deficits; score 3 was defined as lateral jumping of animal body and severe neurological deficits; score 4 was defined as lack of “conscious” response to noxious stimuli.…”

“…PTX is used to prepare mouse model of experimental autoimmune encephalomyelitis (EAE; Tang et al, 2013 ). We previously found that low dose of PTX (50 ng/ml) may reduce neuronal calcium influx, thus minimizing neuronal damage and protecting cell viability in stroke (Tang et al, 2015 ). Although PTX, at least at a restricted dose, offers a direct protective effect on neuron, their potential pharmacologic mechanism in stroke protection may include additional key steps.…”