Enhanced expression of P2X4 purinoceptors in pyramidal neurons of the rat hippocampal CA1 region may be involved ischemia-reperfusion injury

The role of the ATP-adenosine axis in ischemic stroke

In ischemic stroke, the primary neuronal injury caused by the disruption of energy supply is further exacerbated by secondary sterile inflammation. The inflammatory cascade is largely initiated by the purine adenosine triphosphate (ATP) which is extensively released to the interstitial space during brain ischemia and functions as an extracellular danger signaling molecule. By engaging P2 receptors, extracellular ATP activates microglia leading to cytokine and chemokine production and subsequent immune cell recruitment from the periphery which further amplifies post-stroke inflammation. The ectonucleotidases CD39 and CD73 shape and balance the inflammatory environment by stepwise degrading extracellular ATP to adenosine which itself has neuroprotective and anti-inflammatory signaling properties. The neuroprotective effects of adenosine are mainly mediated through A₁ receptors and inhibition of glutamatergic excitotoxicity, while the anti-inflammatory capacities of adenosine have been primarily attributed to A_2A receptor activation on infiltrating immune cells in the subacute phase after stroke. In this review, we summarize the current state of knowledge on the ATP-adenosine axis in ischemic stroke, discuss contradictory results, and point out potential pitfalls towards translating therapeutic approaches from rodent stroke models to human patients.

Purinergic signaling: a potential therapeutic target for ischemic stroke

Pathogenesis of ischemic stroke is mainly characterized by thrombosis and neuroinflammation. Purinergic signaling pathway constitutes adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and adenosine (ADO). ATP is hydrolyzed to ADP and then to AMP by extracellular nucleotidase CD39; AMP is subsequently converted to adenosine by CD73. All these nucleotides and nucleosides act on purinergic receptors protecting against thrombosis and inhibit inflammation. In addition, many physical methods have been found to play a neuroprotective role through purinergic signaling. This review mainly introduces the role and potential mechanism of purinergic signalings in the treatment of ischemic stroke, so as to provide reference for seeking new treatment methods for stroke.

ATP ion channel P2X purinergic receptors in inflammation response

Different studies have confirmed that P2X purinergic receptors play a key role in inflammation. Activation of P2X purinergic receptors can release inflammatory cytokines and participate in the progression of inflammatory diseases. In an inflammatory microenvironment, cells can release a large amount of ATP to activate P2X receptors, open non-selective cation channels, activate multiple intracellular signaling, release multiple inflammatory cytokines, amplify inflammatory response. While P2X4 and P2X7 receptors play an important role in the process of inflammation. P2X4 receptor can mediate the activation of microglia involved in neuroinflammation, and P2X7 receptor can mediate different inflammatory cells to mediate the progression of tissue-wide inflammation. At present, the role of P2X receptors in inflammatory response has been widely recognized and affirmed. Therefore, in this paper, we discussed the role of P2X receptors-mediated inflammation. Moreover, we also described the effects of some antagonists (such as A-438079, 5-BDBD, A-804598, A-839977, and A-740003) on inflammation relief by antagonizing the activities of P2X receptors.

Xuesaitong Combined with Dexmedetomidine Improves Cerebral Ischemia-Reperfusion Injury in Rats by Activating Keap1/Nrf2 Signaling and Mitophagy in Hippocampal Tissue

Ischemic stroke is the most common type of cerebrovascular disease with high mortality and poor prognosis, and cerebral ischemia-reperfusion (CI/R) injury is the main murderer. Here, we attempted to explore the effects and mechanism of Xuesaitong (XST) combined with dexmedetomidine (Dex) on CI/R injury in rats. First, a rat model of CI/R injury was constructed via the middle cerebral artery occlusion (MCAO) method and treated with XST and Dex alone or in combination. Then, on the 5th and 10th days of treatment, the neurological impairment was assessed using the modified neurological severity scores (mNSS), the 8-arm radial maze test (8ARMT), novel object recognition test (NORT), and fear conditioning test (FCT). H&E staining was performed to observe the pathological changes of the hippocampus. ELISA and related kits were used to assess the monoamine neurotransmitters and antioxidant enzyme activities in the hippocampus. The ATP, mitochondrial membrane potential levels, and qRT-PCR of genes related to mitochondrial function were determined to assess mitochondrial functions in the hippocampus and western blot to determine Keap1/Nrf2 signaling pathway and mitophagy-related protein expression. The results showed that XST combined with Dex significantly reduced mNSS, improved spatial memory and learning deficits, and enhanced fear memory and cognitive memory ability in CI/R rats, which was superior to single-drug treatment. Moreover, XST combined with Dex treatment improved hippocampal histopathological damage; significantly increased the levels of monoamine neurotransmitters, neurotrophic factors, ATP, and mitochondrial membrane potential; and upregulated the activities of antioxidant enzymes and the expression of mitophagy-related proteins in the hippocampus of CI/R rats. XST combined with Dex treatment also activated the Keap1/Nrf2 signaling and upregulated the protein expression of downstream antioxidant enzymes HO-1 and NQ. Altogether, this study showed that a combination of XST and Dex could activate the Keap1/Nrf2 signaling and mitophagy to protect rats from CI/R-related neurological impairment.

Contribution of P2X purinergic receptor in cerebral ischemia injury

The development of cerebral ischemia involves brain damage and abnormal changes in brain function, which can cause neurosensory and motor dysfunction, and bring serious consequences to patients. P2X purinergic receptors are expressed in nerve cells and immune cells, and are mainly expressed in microglia. The P2X4 and P2X7 receptors in the P2X purinergic receptors play a significant role in regulating the activity of microglia. Moreover, ATP-P2X purine information transmission is involved in the progression of neurological diseases, including the release of pro-inflammatory factors, driving factors and cytokines after cerebral ischemia injury, inducing inflammation, and aggravating cerebral ischemia injury. P2X receptors activation can mediate the information exchange between microglia and neurons, induce neuronal apoptosis, and aggravate neurological dysfunction after cerebral ischemia. However, inhibiting the activation of P2X receptors, reducing their expression, inhibiting the activation of microglia, and has the effect of protecting nerve function. In this paper, we discussed the relationship between P2X receptors and nervous system function and the role of microglia activation inducing cerebral ischemia injury. Additionally, we explored the potential role of P2X receptors in the progression of cerebral ischemic injury and their potential pharmacological targets for the treatment of cerebral ischemic injury.