Identification of isoxsuprine hydrochloride as a neuroprotectant in ischemic stroke through cell-based high-throughput screening

Formulation and Therapeutic Evaluation of Isoxsuprine-Loaded Nanoparticles against Diabetes-Associated Stroke

Ischemic stroke is the second-leading cause of death. Hyperglycemia, which is characteristic of diabetes mellitus, contributes to the development of endothelial dysfunction and increases the risk of stroke. Isoxsuprine is an efficient beta-adrenergic agonist that improves blood flow to the ischemic aria and stops the infarct core from growing. However, low bioavailability, a short biological half-life, and first-pass hepatic metabolism reduce the therapeutic efficacy of oral isoxsuprine. Therefore, the authors focused on developing isoxsuprine-loaded liposomes containing ethanol and propylene glycol (ILEP) formulation as nasal drops for the treatment of ischemic stroke in diabetic patients. Different ILEP formulations were optimized using Design Expert software, and the selected formulation was examined in vivo for its anti-stroke effect using a rat model of diabetes and stroke. The optimized ILEP, composed of 15% propylene glycol, 0.16% cholesterol, 10% ethanol, and 3.29% phospholipid, improved the sustainability, permeation, and targeting of isoxsuprine. Furthermore, the in vivo studies verified the improved neurological behavior and decreased dead shrunken neurons and vascular congestion of the rats treated with the optimized ILEP formulation, demonstrating its anti-stroke activity. In conclusion, our study found that treatment with an optimized ILEP formulation prevented the initiation and severity of stroke, especially in diabetic patients.

The β-adrenergic hypothesis of synaptic and microglial impairment in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease originating partly from amyloid β protein-induced synaptic failure. As damaging of noradrenergic neurons in the locus coeruleus (LC) occurs at the prodromal stage of AD, activation of adrenergic receptors could serve as the first line of defense against the onset of the disease. Activation of β₂ -ARs strengthens long-term potentiation (LTP) and synaptic activity, thus improving learning and memory. Physical stimulation of animals exposed to an enriched environment (EE) leads to the activation of β₂ -ARs and prevents synaptic dysfunction. EE also suppresses neuroinflammation, suggesting that β₂ -AR agonists may play a neuroprotective role. The β₂ -AR agonists used for respiratory diseases have been shown to have an anti-inflammatory effect. Epidemiological studies further support the beneficial effects of β₂ -AR agonists on several neurodegenerative diseases. Thus, I propose that β₂ -AR agonists may provide therapeutic value in combination with novel treatments for AD.

Ligustrazine exerts neuroprotective effects via circ_0008146/miR-709/Cx3cr1 axis to inhibit cell apoptosis and inflammation after cerebral ischemia/reperfusion injury

BACKGROUND

Ligustrazine is a traditional Chinese herbal medicine that has long been used to treat cerebral ischemic disorders. However, the molecular mechanisms of ligustrazine in cerebral ischemia/reperfusion (I/R) damage have not been clear elucidated. The aim of this study was to examine the neuroprotective mechanisms of ligustrazine in cerebral I/R.

METHODS

9 C57BL/6 mice were randomly divided to three groups: Sham group (n = 3), Middle cerebral artery occlusion (MCAO) group (n = 3), and MCAO + Ligustrazine group (n = 3). The neurological deficit score was evaluated, the cerebral infarct volume was measured by triphenylterazolium chloride (TTC) staining. Differentially expressed (DE) messenger RNAs (mRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) were analyzed using the R package DEseq2 based on P-value < 0.05 and Log2 |fold change (FC)| ≥ 2 in sham group vs MCAO group and MCAO group vs ligustrazine group by high-throughput sequencing. Function enrichment analysis, the protein-protein interaction (PPI) of neurogenesis related genes were performed. The neurogenesis related competitive endogenous RNA (ceRNA) network was constructed.

RESULTS

The expression of circ_0008146 was considerably higher in the MCAO group than the Sham group, and ligustrazine treatment markedly decreased the expression of circ_0008146 in MCAO. Next, the circ_0008146 ceRNA network was established, including circ_0008146-miR-709-Cx3cr1 ceRNA network. Besides, real time quantitative polymerase chain reaction (RT-qPCR) assay identified that miR-709 expression was considerably lower and Cx3cr1 expression was higher in the MCAO group than Sham group, and ligustrazine treatment markedly increased the miR-709 expression and reduced Cx3cr1 expression in MCAO. Further, silencing of circ_0008146 inhibited the concentration of Interleukin 6 (IL-6), Tumor Necrosis Factor alpha (TNF-α) and reduced neuron cell death and up-regulated miR-709 expression and down-regulated Cx3cr1 expression in Lipopolysaccharide (LPS) induced BV-2 cells. Dual-Luciferase reporter gene assay verified that circ_0008146 targeted miR-709.

CONCLUSION

Ligustrazine targets circ_0008146/miR-709/Cx3cr1 axis to inhibit cell apoptosis and inflammation after cerebral ischemia/reperfusion injury.

Molecular Mechanisms of Neuroimmune Crosstalk in the Pathogenesis of Stroke

Stroke disrupts the homeostatic balance within the brain and is associated with a significant accumulation of necrotic cellular debris, fluid, and peripheral immune cells in the central nervous system (CNS). Additionally, cells, antigens, and other factors exit the brain into the periphery via damaged blood–brain barrier cells, glymphatic transport mechanisms, and lymphatic vessels, which dramatically influence the systemic immune response and lead to complex neuroimmune communication. As a result, the immunological response after stroke is a highly dynamic event that involves communication between multiple organ systems and cell types, with significant consequences on not only the initial stroke tissue injury but long-term recovery in the CNS. In this review, we discuss the complex immunological and physiological interactions that occur after stroke with a focus on how the peripheral immune system and CNS communicate to regulate post-stroke brain homeostasis. First, we discuss the post-stroke immune cascade across different contexts as well as homeostatic regulation within the brain. Then, we focus on the lymphatic vessels surrounding the brain and their ability to coordinate both immune response and fluid homeostasis within the brain after stroke. Finally, we discuss how therapeutic manipulation of peripheral systems may provide new mechanisms to treat stroke injury.

Chirality of β2-agonists. An overview of pharmacological activity, stereoselective analysis, and synthesis

β2-Agonists (β2-adrenergic agonists, bronchodilatants, and sympathomimetic drugs) are a group of drugs that are mainly used in asthma and obstructive pulmonary diseases. In practice, the substances used to contain one or more stereogenic centers in their structure and their enantiomers exhibit different pharmacological properties. In terms of bronchodilatory activity, (R)-enantiomers showed higher activity. The investigation of stereoselectivity in action and disposition of chiral drugs together with the preparation of pure enantiomer drugs calls for efficient stereoselective analytical methods. The overview focuses on the stereoselectivity in pharmacodynamics and pharmacokinetics of β2-agonists and summarizes the stereoselective analytical methods for the enantioseparation of racemic beta-agonists (HPLC, LC-MS, GC, TLC, CE). Some methods of the stereoselective synthesis for β2-agonists preparation are also presented.

Vasodilation Elicited by Isoxsuprine, Identified by High-Throughput Virtual Screening of Compound Libraries, Involves Activation of the NO/cGMP and H₂S/KATP Pathways and Blockade of α₁-Adrenoceptors and Calcium Channels

Recently, our research group demonstrated that uvaol and ursolic acid increase NO and H₂S production in aortic tissue. Molecular docking studies showed that both compounds bind with high affinity to endothelial NO synthase (eNOS) and cystathionine gamma-lyase (CSE). The aim of this study was to identify hits with high binding affinity for the triterpene binding-allosteric sites of eNOS and CSE and to evaluate their vasodilator effect. Additionally, the mechanism of action of the most potent compound was explored. A high-throughput virtual screening (HTVS) of 107,373 compounds, obtained from four ZINC database libraries, was performed employing the crystallographic structures of eNOS and CSE. Among the nine top-scoring ligands, isoxsuprine showed the most potent vasodilator effect. Pharmacological evaluation, employing the rat aorta model, indicated that the vasodilation produced by this compound involved activation of the NO/cGMP and H₂S/K_ATP signaling pathways and blockade of α₁-adrenoceptors and L-type voltage-dependent Ca²⁺ channels. Incubation of aorta homogenates in the presence of isoxsuprine caused 2-fold greater levels of H₂S, which supported our preliminary in silico data. This study provides evidence to propose that the vasodilator effect of isoxsuprine involves various mechanisms, which highlights its potential to treat a wide variety of cardiovascular diseases.

Matrix-derived inflammatory mediator N-acetyl proline-glycine-proline is neurotoxic and upregulated in brain after ischemic stroke

Background

N-acetyl proline-glycine-proline (ac-PGP) is a matrix-derived chemokine produced through the proteolytic destruction of collagen by matrix metalloproteinases (MMPs). While upregulation and activation of MMPs and concomitant degradation of the extracellular matrix are known to be associated with neurological injury in ischemic stroke, the production of ac-PGP in stroke brain and its effects on neurons have not been investigated.

Findings

We examined the effects of ac-PGP on primary cortical neurons and found that it binds neuronal CXCR2 receptors, activates extracellular signal-regulated kinase 1/2 (ERK1/2), and induces apoptosis associated with caspase-3 cleavage in a dose-dependent manner. After transient ischemic stroke in rats, ac-PGP was significantly upregulated in infarcted brain tissue.

Conclusions

The production of ac-PGP in brain in ischemia/reperfusion injury and its propensity to induce apoptosis in neurons may link MMP-mediated destruction of the extracellular matrix and opening of the blood-brain barrier to progressive neurodegeneration associated with the initiation and propagation of inflammation. Ac-PGP may be a novel neurotoxic inflammatory mediator involved in sustained inflammation and neurodegeneration in stroke and other neurological disorders associated with activation of MMPs.

Transient middle cerebral artery occlusion with complete reperfusion in spontaneously hypertensive rats

Middle cerebral artery occlusion (MCAO) by the intraluminal suture method is widely used to model ischemic stroke in rats. Current methods include transection or ligation of the external carotid or common carotid artery and thus result in partial restoration of perfusion after transient MCAO. Since incomplete reperfusion may influence recovery and thus confound studies of the impact of neuroprotective compounds and therapies on outcomes after stroke, we have devised a novel method to induce transient MCAO with complete reperfusion. Advantages of the method include: MCAO is achieved through insertion of an intraluminal suture into the internal carotid artery through the common carotid artery.At the end of the occlusion period, the suture is withdrawn and the incision in the common carotid artery is closed with cyanoacrylate tissue adhesive and complete reperfusion is established.No residual subcutaneous sutures remain during recovery.Vasculature is restored to the preoperative state.