Pomelo peel oil alleviates cerebral NLRP3 inflammasome activation in a cardiopulmonary resuscitation rat model.

The NLR family pyrin domain-containing 3 (NLRP3) inflammasome, which is composed of NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC) and pro-caspase-1 protein complexes, is activated by the reactive oxygen species (ROS) that are associated with ischemia-reperfusion (I/R) and are involved in brain damage. Pomelo peel oil (PPO) exhibits antioxidant activity. However, it is unclear whether PPO is able to attenuate NLRP3 inflammasome-induced inflammation and pyroptosis. Healthy male Sprague-Dawley rats were subjected to 7 min of cardiac arrest via trans-esophageal electrical stimulation, followed by cardiopulmonary resuscitation (CPR). The rats were then treated with PPO prior to reperfusion for 24 h. Hematoxylin and eosin staining was used to evaluate brain tissue and cell damage. In the brain tissues, reactive oxygen species (ROS) were assayed, immunofluorescence was used to analyze the expression of NLRP3 and western blotting was performed to determine the expression levels of neuroenolase (NSE), NF-κB, interleukin-1ß (IL-1ß), gasdermin D (GSDMD) and the NLRP3 inflammasome. Treatment of the rats with PPO significantly decreased the pathological damage of the brain tissue and reduced the expression of NSE, production of ROS and secretion of NF-κB, NLRP3, IL-1ß and GSDMD. In conclusion, these results demonstrate the ability of PPO to protect the brain against I/R injury in rats after CPR by a mechanism involving inhibition of the inflammation and pyroptosis mediated by NLRP3 inflammasome activation.

Inhibition of extracellular signal-regulated kinase/calpain-2 pathway reduces neuroinflammation and necroptosis after cerebral ischemia-reperfusion injury in a rat model of cardiac arrest.

BACKGROUND: Cerebral ischemia-reperfusion injury (CIRI) is the leading cause of poor neurological prognosis after cardiopulmonary resuscitation (CPR). We previously reported that the extracellular signal-regulated kinase (ERK) activation mediates CIRI. Here, we explored the potential ERK/calpain-2 pathway role in CIRI using a rat model of cardiac arrest (CA). METHODS: Adult male Sprague-Dawley rats suffered from CA/CPR-induced CIRI, received saline, DMSO, PD98059 (ERK1/2 inhibitor, 0.3 mg/kg), or MDL28170 (calpain inhibitor, 3.0 mg/kg) after spontaneous circulation recovery. The survival rate and the neurological deficit score (NDS) were utilized to assess the brain function. Hematoxylin stain, Nissl staining, and transmission electron microscopy were used to evaluate the neuron injury. The expression levels of p-ERK, ERK, calpain-2, neuroinflammation-related markers (GFAP, Iba1, IL-1ß, TNF-α), and necroptosis proteins (TNFR1, RIPK1, RIPK3, p-MLKL, and MLKL) in the brain tissues were determined by western blotting and immunohistochemistry. Fluorescent multiplex immunohistochemistry was used to analyze the p-ERK, calpain-2, and RIPK3 co-expression in neurons, and RIPK3 expression levels in microglia or astrocytes. RESULTS: At 24 h after CA/CPR, the rats in the saline-treated and DMSO groups presented with injury tissue morphology, low NDS, ERK/calpain-2 pathway activation, and inflammatory cytokine and necroptosis protein over-expression in the brain tissue. After PD98059 and MDL28170 treatment, the brain function was improved, while inflammatory response and necroptosis were suppressed by ERK/calpain-2 pathway inhibition. CONCLUSION: Inflammation activation and necroptosis involved in CA/CPR-induced CIRI were regulated by the ERK/calpain-2 signaling pathway. Inhibition of that pathway can reduce neuroinflammation and necroptosis after CIRI in the CA model rats.

Pomelo Peel Volatile Oil Alleviates Neuroinflammation on Focal Cerebral Ischemia Reperfusion Injury Rats via Inhibiting TLR4/NF-κB Signaling Pathway.

BACKGROUND: Restoration of blood flow during ischemic stroke leads to Cerebral Ischemia- Reperfusion Injury (CIRI) by activating neuroinflammatory cascades. Pomelo Peel Volatile Oil (PPVO) extracted from Citrus maxima (Burm.) from the genus Rutaceae, comprises some antiinflammatory ingredients, such as limonene and ß-myrcene. OBJECTIVE: The present study aimed to investigate the potential effect of PPVO on alleviating CIRI related to the Toll-like receptor 4/nuclear factor-kappa B (TLR4/NF-κB) pathway. METHODS: Transient middle cerebral artery occlusion/reperfusion (tMCAO/R) was performed on 65 rats, which were then distributed into five groups (n = 13/group) depending on the intervention they received: Normal Saline (NS) group, normal Glycerin (GL) group, low-dose PPVO (LP, 10mg/kg) group, high-dose PPVO (HP, 30 mg/kg) group, and Sham-operated (SH) group. Neurological Deficit Scores (NDSs) and histological changes were evaluated. Infarct volumes were measured by 2,3,5- Triphenyltetrazolium Chloride (TTC) staining. The expression of TLR4 and neutrophil infiltration were detected by Immunofluorescence (IF) staining. Moreover, the downstream molecules of the TLR4/NF-κB signaling pathway, such as IL-6, IL-1ß, TNF-α, p-IκB/IκB, and p-NF-κB p65/NF-κB p65 were analyzed by Western Blot (WB). RESULTS AND DISCUSSION: The results showed that PPVO (30 mg/kg) significantly decreased infarct volumes, improved neurological deficits and pathologic changes, inhibited TLR4/NF-κB signaling pathway suppressed neutrophil infiltration, and suppressed pro-inflammatory cytokine release. CONCLUSION: It can be concluded that PPVO may alleviate neuroinflammation and protect against CIRI via inhibiting the TLR4/NF-κB signaling pathway.