Dongliang Li

Decreased Brain KATP Channel Contributes to Exacerbating Ischemic Brain Injury and the Failure of Neuroprotection by Sevoflurane Post-Conditioning in Diabetic Rats

Diabetes leads to exacerbating brain injury after ischemic stroke, but the underlying mechanisms and whether therapeutic intervention with anesthetic post-conditioning can induce neuroprotection in this population are not known. We tested the hypothesis that alteration of brain mitochondrial (mito) KATP channels might cause exacerbating brain injury after ischemic stroke and attenuate anesthetic post-conditioning induced neuroprotection in diabetes. We also examined whether hyperglycemic correction with insulin would restore anesthetic post-conditioning in diabetes. Non-diabetic rats and diabetic rats treated with or without insulin were subjected to focal cerebral ischemia for 2 h followed by 24 h of reperfusion. Post-conditioning was performed by exposure to sevoflurane for 15 min, immediately at the onset of reperfusion. The role of the mitoKATP channel was assessed by administration of a selective blocker 5-hydroxydecanoate (5-HD) before sevoflurane post-conditioning or by diazoxide (DZX), a mitoKATP channel opener, given in place of sevoflurane. Compared with non-diabetic rats, diabetic rats had larger infarct volume and worse neurological outcome at 24 h after ischemia. Sevoflurane or DZX reduced the infarct volume and improved neurological outcome in non-diabetic rats but not in diabetic rats, and the protective effects of sevoflurane in non-diabetic rats were inhibited by pretreatment with 5-HD. Molecular studies revealed that expression of Kir6.2, an important mitoKATP channel component, was decreased in the brain of diabetic rats as compared to non-diabetic rats. In contrast, hyperglycemic correction with insulin in diabetic rats normalized expression of brain Kir6.2, reduced ischemic brain damage and restored neuroprotective effects of sevoflurane post-conditioning. Our findings suggest that decreased brain mitoKATP channel contributes to exacerbating ischemic brain injury and the failure of neuroprotection by anesthetic post-conditioning in diabetes. Insulin glycemic control in diabetes may restore the neuroprotective effects of anesthetic post-conditioning by modulation of brain mitoKATP channel.

Pentoxifylline Ameliorates Cardiac Fibrosis, Pathological Hypertrophy, and Cardiac Dysfunction in Angiotensin II-induced Hypertensive Rats.

Abstract: Inflammation induces cardiac fibrosis and hypertrophy in multiple cardiovascular diseases, contributing to cardiac dysfunction. We tested the hypothesis that pentoxifylline (PTX), a phosphodiesterase inhibitor with anti-inflammatory property, would attenuate cardiac fibrosis and hypertrophy, and prevent cardiac dysfunction in angiotensin (ANG) II-induced hypertensive rats. Sprague–Dawley rats were divided into control and ANG II-infused groups treated with or without PTX for 2 weeks. PTX had no effect on ANG II-induced hypertension, but significantly attenuated cardiac fibrosis and hypertrophy, and ameliorated cardiac dysfunction in ANG II-induced hypertensive rats. In addition, ANG II-induced increase in circulating and cardiac proinflammatory cytokines were attenuated by PTX, which reduced cardiac nuclear factor-kappa B activity. Furthermore, PTX decreased cardiac expression of genetic markers important for fibrosis, hypertrophy, and endothelial dysfunction, and reduced migration and infiltration of macrophages. In contrast, PTX had no effects on the above parameters in control rats. The findings suggest that PTX ameliorates cardiac fibrosis, pathological hypertrophy, and cardiac dysfunction by suppressing inflammatory responses in angiotensin II-induced hypertension, and that these benefits were independent of the blood pressure lowering effect. The PTX by its anti-inflammatory property may be a potential therapeutic option for the prevention of cardiac remodeling and dysfunction in ANG II-induced hypertension.

Exercise training prevents the attenuation of anesthetic pre-conditioning-mediated cardioprotection in diet-induced obese rats.

Obesity abolishes anesthetic pre‐conditioning‐induced cardioprotection due to impaired reactive oxygen species (ROS)‐mediated adenosine monophosphate‐activated protein kinase (AMPK) pathway, a consequence of increased basal myocardial oxidative stress. Exercise training has been shown to attenuate obesity‐related oxidative stress.

Down-regulation of PPARα in the spinal cord contributes to augmented peripheral inflammation and inflammatory hyperalgesia in diet-induced obese rats.

Obesity is associated with augmented peripheral inflammation and pain sensitivity in response to inflammatory stimulation, but the underlying mechanisms remain unclear. Emerging evidence has shown that activation of peroxisome proliferator-activated receptor-α (PPARα) in the central nervous system controls peripheral inflammation and pain. We hypothesized that obesity might down-regulate PPARα in the spinal cord, leading to enhanced peripheral inflammation and inflammatory hyperalgesia. Sprague-Dawley rats fed a high-fat diet (HF) for 12weeks developed metabolic disorder and displayed significantly decreased spinal PPARα expression and activity. Interestingly, intracerebroventricular (ICV) infusion of the PPARα activator palmitoylethanolamide (PEA) in HF-fed rats for 2weeks normalized spinal PPARα expression and activity without altering metabolic parameters. HF-fed rats were more sensitive to stimulation of the inflamed paw, and exhibited more severe paw edema following carrageenan injection, whereas HF-fed rats receiving ICV PEA had similar pain sensitivity and paw edema to LF-fed rats. No difference in the expression of inflammatory mediators or nuclear factor (NF)-κB activity was observed at baseline among groups. Carrageenan induced decreased PPARα expression and activity, increased spinal cord inflammatory mediator expression and NF-κB activity in both LF-and HF-fed rats. However, the increase was more pronounced in HF-fed rats and corrected by PEA. Intrathecal injection of small interfering RNA (siRNA) against PPARα in HF-fed rats completely abolished PEA effects on peripheral pain sensitivity and paw edema. These findings suggest that diet-induced obesity causes down-regulation of spinal PPARα, which facilitates the susceptibility to peripheral inflammatory challenge by increasing inflammatory response in the spinal cord, contributing to augmented peripheral inflammation and inflammatory hyperalgesia in obesity.

Aging causes exacerbated ischemic brain injury and failure of sevoflurane post-conditioning: role of B-cell lymphoma-2.

Aging is associated with exacerbated brain injury after ischemic stroke. Herein, we explored the possible mechanisms underlying the age-associated exacerbated brain injury after ischemic stroke and determined whether therapeutic intervention with anesthetic post-conditioning would provide neuroprotection in aged rats. Male Fisher 344 rats (young, 4 months; aged, 24 months) underwent 2h of middle cerebral artery occlusion (MCAO) followed by 24-h reperfusion, with or without sevoflurane post-conditioning for 15 min immediately at the onset of reperfusion. Compared with young rats, aged rats showed larger infarct size, worse neurological scores and more TUNEL-positive cells in the penumbral cerebral cortex at 24h after MCAO. However, edema formation and motor coordination were similar in both groups. Sevoflurane reduced the infarct size, edema formation, and TUNEL-positive cells, and improved the neurological outcome in young rats but not in aged rats. Molecular studies revealed that basal expression of the anti-apoptotic molecule B-cell lymphoma-2 (Bcl-2) in the brain was lower in aged rats compared with young rats before MCAO, while basal expression of the pro-apoptotic molecule Bcl-2-associated X protein (Bax) showed similar levels in both groups. MCAO reduced Bcl-2 expression and increased Bax expression in both groups; however, Bax increase was more pronounced in aged rats. In young rats, sevoflurane reversed the above MCAO-induced changes. In contrast, sevoflurane failed to enhance Bcl-2 expression but decreased Bax expression in aged rats. These findings suggest that aging-associated reduction in basal Bcl-2 expression in the brain contributes to increased neuronal injury by enhancing cell apoptosis after ischemic stroke. Sevoflurane post-conditioning failed to provide neuroprotection in aged rats, probably due to its inability to increase Bcl-2 levels and prevent apoptosis in the brain.

Exercises in Hot and Humid Environment Caused Liver Injury in a Rat Model

Objective To investigate injury pattern during intense exercises in hot and humid environment particularly on liver in a rat exertional heat stroke model. Methods We randomly divided 30 rats into a control group (CG), a normal temperature (25±2°C, 60%±5% humidity) exercise group (NTEG) and a high temperature and high humidity (35±2°C, 80%±10% humidity) exercising group (HTEG), each comprising 10 animals. The NTEG and HTEG rats were forced to run in a treadmill for 1 hour maximum at 20 rpm. We analyzed liver cells of all three groups with JC-1 dye and flow cytometry for apoptosis rates in addition to liver tissue 8 - hydroxy deoxyguanosine (8 - OhdG) and blood serum IL–6, tumor necrosis factor alpha (TNF-α), alanine aminotransferase ALT, aspartate amino transferase (AST), serum creatinine (CREA), blood urea nitrogen (BUN), lactate dehydrogenase (LDH), creatine phosphate kinase (CK) concentrations. Result Compared with NTEG rats, beside reduced exercise tolerance (60±5 vs. 15±3 minutes) (pu200a=u200a0.002) the 8-OhdG liver tissue concentrations were significantly higher (pu200a=u200a0.040) in the HTEG rats. The HTEG developed more organ tissue damage and cellular fragmentations of liver cells. In both exercise groups TNF-α and IL-6 serum concentrations were enhanced significantly (p<0.001) being highest in the HTEG animals. Serum ALT, AST, LDH, CREA, BUN and CK concentrations were significantly enhance in both exercise groups. Conclusion In our exertional heat stroke rat model, we found tissue damage particularly in livers during exercises in hot and humid environment that was related to inflammation, oxidative stress and apoptosis.

TIPE1 suppresses invasion and migration through down-regulating Wnt/β-catenin pathway in gastric cancer

Epithelial–mesenchymal transition (EMT) plays an important role in the invasiveness and metastasis of gastric cancer. Therefore, identifying key molecules involved in EMT will provide new therapeutic strategy for treating patients with gastric cancer. TIPE1 is a newly identified member of the TIPE (TNFAIP8) family, and its contributions to progression and metastasis have not been evaluated. In this study, we found that the levels of TIPE1 were significantly reduced and inversely correlated with differentiation status and distant metastasis in primary gastric cancer tissues. We further observed overexpression of TIPE1 in aggressive gastric cancer cell lines decreased their metastatic properties both in vitro and in vivo as demonstrated by markedly inhibiting EMT and metastasis of gastric cancer cells in nude mice. Consistently, gene silencing of TIPE1 in well‐differentiated gastric cancer cell line (AGS) inhibited these processes. Mechanistically, we found that TIPE1‐medicated Wnt/β‐catenin signalling was one of the critical signal transduction pathways that link TIPE1 to EMT inhibition. Importantly, TIPE1 dramatically restrained the expression and activities of MMP2 and MMP9 which are demonstrated to promote tumour progression and are implicated in EMT. Collectively, these findings provide new evidence for a better understanding of the biological activities of TIPE1 in progression and metastasis of gastric cancer and suggest that TIPE1 may be an innovative diagnostic and therapeutic target of gastric cancer.

Sevoflurane Induces Exaggerated and Persistent Cognitive Decline in a Type II Diabetic Rat Model by Aggregating Hippocampal Inflammation

Recent studies show that a moderate duration of sevoflurane, one of the most commonly used volatile anesthetics in clinical practice, does not induce cognitive impairment in animals under physiological conditions. However, the influence of sevoflurane on cognitive function under diabetic conditions remains unclear. The aim of this study was to determine whether sevoflurane causes cognitive decline in a rat model of type 2 diabetes mellitus (DM) and if so, to explore a possible underlying mechanism. Diabetic Goto–Kakizaki (GK) rats and non-diabetic Wistar rats underwent 2.6% sevoflurane for 4 h or sham (control) exposure. Cognitive function and hippocampal inflammation were assessed 1 week and 5 months after sevoflurane or sham exposure. Compared with Wistar control rats, GK control rats exhibited shorter freezing times in Trace fear conditioning task 1 week after exposure, took longer to locate the submerged platform and had shorter dwell-time in the target quadrant in Morris Water Maze task 5 months after exposure. GK rats that received sevoflurane not only exhibited less freezing times 1 week after exposure, but also spent more time to locate the submerged platform and had less dwell-time in the target quadrant, compared with GK control rats. Molecular studies revealed that the levels of pro-inflammatory cytokines and activated microglia in the hippocampus were higher in GK control rats than those in Wistar control rats at both time points and were further increased in GK rats receiving sevoflurane. Wistar rats that received sevoflurane and Wistar control rats did not differ in any cognitive performance and molecular assessment. The results suggest that diabetic GK rats exhibit cognitive dysfunction probably due to increased hippocampal inflammation, and that sevoflurane induces exaggerated and persistent cognitive decline in GK rat by aggregating hippocampal inflammation.

Sevoflurane inhibits the migration and invasion of glioma cells by upregulating microRNA-637

Cancer cell migration and invasion are essential features of the metastatic process. Volatile anesthetic sevoflurane inhibits the migration and invasion of multiple cancer cell lines; however, its effects on glioma cells are unclear. Emerging evidence suggests that microRNAxa0(miRNA)-637 regulates glioma cell migration and invasion through the Akt1 pathway. Sevoflurane has been shown to modulate a number of miRNAs. In the present study, we examined whether sevoflurane inhibits glioma cell migration and invasion and, if so, whether these beneficial effects are mediated by miRNA-637. U251 glioma cells were treated withoutxa0(control) or with sevoflurane at low, moderate or high concentrations forxa06xa0h. To explore the molecular mechanisms, an additional group of U251 cells was treated with a miRNA‑637 inhibitor prior to treatment with a high concentration of sevoflurane. Compared with the control group, sevoflurane inhibited the migration and invasion of U251 cells in a dose-dependent manner. Molecular analyses revealed that sevoflurane increased the expression of miRNA‑637 and decreased the expression of Akt1 and phosphorylated Akt1 in a dose-dependent manner. Moreover, the inhibitory effects of sevoflurane on U251 cell migration and invasion were completely abolished by pre-treatment with miRNA‑637 inhibitor, which reversed the sevoflurane-induced reduction in the expression of Akt1 and phosphorylated Akt1 in the U251 cells. These results demonstrate that sevoflurane inhibits glioma cell migration and invasion and that these beneficial effects are mediated by the upregulation of miRNA‑637, which suppresses Akt1 expression and activity. These findings may have significant clinical implications for anesthesiologists regarding the choice of volatile anesthetic agents for the surgical resection of gliomas to prevent metastases and improve patient outcomes.

Anti-microRNA-132 causes sevoflurane‑induced neuronal apoptosis via the PI3K/AKT/FOXO3a pathway

In the present study, the mechanisms underlying the protective effects of microRNA-132 (miRNA-132) on sevoflurane-induced neuronal apoptosis were investigated. Reverse transcription-quantitative polymerase chain reaction and gene microarray hybridization were used to analyze alterations in microRNA levels. Cell viability, apoptosis and caspase-3/9 activity were measured using MTT, flow cytometry and caspase-3/9 activity kits. Immunofluorescence staining and western blot analysis were used to measure protein expression of phosphoinositide 3-kinase (PI3K) and phosphorylated (p-)AKT, forkhead box O3a (FOXO3a). In sevoflurane-induced rats, the expression of miRNA-132 was downregulated, compared with that in negative control rats. The downregulation of miRNA-132 increased neuronal apoptosis and the upregulation of miRNA-132 inhibited neuronal apoptosis in the sevoflurane-induced in vitro model. The downregulation of miRNA-132 suppressed the protein expression of PI3K and p-AKT, and suppressed the protein expression of FOXO3a in the sevoflurane-induced in vitro model. The PI3K inhibitor increased the effects of anti-miRNA-132 on neuronal apoptosis through the AKT/FOXO3a pathway in the sevoflurane-induced in vitro model. The promotion of FOXO3a inhibited the effects of anti-miRNA-132 on neuronal apoptosis through the AKT/FOXO3a pathway in the sevoflurane-induced in vitro model. These data suggested that miRNA-132 caused sevoflurane-induced neuronal apoptosis via suppression of the PI3K/AKT/FOXO3a pathway.