Neuroprotective effect of diazoxide on brain injury induced by cerebral ischemia/reperfusion during deep hypothermia. J Neurol Sci. 2008;268:18-27. [PMID: 18068190 DOI: 10.1016/j.jns.2007.10.029]

Deep Hypothermic Low Flow Results in Multiple Aspects of Neurological Deficits in Mice by eEF2 Hyperphosphorylation

Postoperative neurological dysfunction is a common complication caused by deep hypothermia with cerebral hypoperfusion during aortic arch surgery, but the exact pathological changes and molecular mechanisms are not yet clear. In this study, we established an adult mouse model of deep hypothermic low flow (DHLF) to simulate the ischemic-reperfusion brain injury during aortic arch surgery. The DHLF-modeled mice showed significant neurological and cognitive dysfunction, accompanied by reduced dendritic spine density and increased glial cell activation in the hippocampus and cortex. DHLF induced proteomic changes primarily involved in synaptic organization in the hippocampus and cortex, with AMPA and NMDA receptor subunits and synaptic activity-dependent proteins markedly downregulated in the hippocampus and/or cortex. Moreover, DHLF also resulted in altered proteome in mRNA translation and inhibition of eukaryotic elongation factor 2 (eEF2), a crucial regulator of translational elongation whose activity is negatively regulated via phosphorylation by eEF2 kinase (eEF2K). Importantly, the administration of the small-molecular eEF2K inhibitor A484954 ameliorated DHLF-induced neurobehavioral dysfunction, dendritic spine reduction, and glial cell activation, suggesting that eEF2K/eEF2 may be a promising therapeutic target in DHLF-induced neurological injury. Our findings revealed new evidence of pathological features, molecular mechanism, and intervention of DHLF-induced cerebral ischemia-reperfusion injury, providing promising insight for developing strategies on reducing postoperative neurological complications after aortic arch surgery.

Baicalin alleviates bleomycin-induced early pulmonary fibrosis in mice via the mitoKATP signaling pathway

Bleomycin (BLM), a frequently employed chemotherapeutic agent, exhibits restricted clinical utility owing to its pulmonary toxicity. Meanwhile, baicalin (BA)-an active ingredient extracted from the roots of Scutellaria baicalensis Georgi -has been shown to alleviate BLM-induced pulmonary fibrosis (PF). Hence, the objective of this study was to examine the protective effects of BA in the context of BLM-induced early PF in mice and elucidate the underlying mechanism(s). We established an in vivo BLM (3.5 mg/kg)-induced PF murine model and in vitro BLM (35 μM)-damaged MLE-12 cell model. On Day 14 of treatment, the levels of fibrosis and apoptosis were evaluated in mouse lungs via hydroxyproline analysis, western blotting (COL1A1, TGF-β, Bax, Bcl-2, cleaved caspase-3), and Masson, immunohistochemical (α-SMA, AIF, Cyto C), and TUNEL staining. Additionally, in vitro, apoptosis was assessed in MLE-12 cells exposed to BLM for 24 h using the Annexin V/PI assay and western blotting (Bax, Bcl-2, cleaved caspase-3, AIF, Cyto C). To elucidate the role of the mitochondrial ATP-sensitive potassium channel (mitoKATP) in the protective effect of BA, we utilised diazoxide (DZX)-a mitoKATP agonist-and 5-hydroxydecanoate sodium (5-HD)-a mitoKATP inhibitor. Results revealed the involvement of mitoKATP in the protective effect of BA in BLM-induced PF. More specifically, mitoKATP activation can attenuate BLM-induced PF progression and mitigate alveolar epithelial type II cell death by reducing mitochondrial ROS, maintaining the mitochondrial membrane potential, and impeding the mitochondrial apoptotic pathway. Collectively, the findings offer pharmacological support to use BA for the treatment or prevention of BLM-induced PF and suggest that mitoKATP might serve as an effective therapeutic target for this condition.

Diazoxide Protects against Myocardial Ischemia/Reperfusion Injury by Moderating ERS via Regulation of the miR-10a/IRE1 Pathway

Nowadays, reperfusion is still the most effective treatment for ischemic heart disease. However, cardiac reperfusion therapy would lead to reperfusion injury, which may have resulted from endoplasmic reticulum stress (ERS) during reperfusion. Diazoxide (DZ) is a highly selective mitochondrial adenosine triphosphate-sensitive potassium channel opener. Its protective effect on I/R injury has been confirmed in many organs such as the heart and brain. However, the mechanism of its protective effect has not been fully elucidated. MicroRNAs (miRNAs) are widely involved in pathologies of heart disease. In this study, we found that miR-10a expression was highly upregulated in the myocardial I/R groups, and DZ treatment significantly reduced the expression of miR-10a. More importantly, we found that DZ treatment can moderate ERS via regulation of the miR-10a/IRE1 pathway in the I/R and H/R models, thereby protecting myocardial H/R injury.

Diazoxide inhibits of ER stress‑mediated apoptosis during oxygen‑glucose deprivation in vitro and cerebral ischemia‑reperfusion in vivo

Neuroprotective strategies using diazoxide (DZX) have been demonstrated to limit ischemia/reperfusion (I/R)-induced injury and cell apoptosis. In type 2 diabetes mellitus, DZX has been reported to improve β-cell function and reduce their apoptosis, through suppressing endoplasmic reticulum (ER) stress. However, the effects of DZX on ER stress during I/R-induced neuronal apoptosis in the hippocampus remains to be elucidated. In the present study, pretreatment of hippocampal neurons with DZX was revealed to inhibit oxygen-glucose deprivation (OGD)-stimulated apoptosis in vitro and to alleviate I/R-induced hippocampal injury and behavioral deficits in rats in vivo. Furthermore, OGD and I/R were demonstrated to induce ER stress via upregulating the expression of ER stress-associated proteins, including C/EBP homologous protein, 78 kDa glucose-regulated protein and caspase-12, whereas the exogenous administration of DZX effectively downregulated ER stress-associated protein expression following OGD and I/R. In addition, DZX was revealed to significantly increase the protein expression of B-cell lymphoma (Bcl)-2 and suppress the expression of caspase-3 and Bcl-2-associated X protein. These findings suggested that DZX may protect cells against apoptosis via regulating the expression of ER stress-associated proteins in vitro and in vivo, thus enhancing the survival of hippocampal cells. The present results suggested a novel mechanism that may underlie the protective effect of DZX administration in the central nervous system.

Diazoxide protects rat vascular endothelial cells against hypoxia and cold-induced damage

The present study aimed to examine the effects of hypoxia and cold on vascular endothelial cells (VECs), as well as the protective ability of novel VECs-protective drugs against these injuries. A rat model simulating exposure to hypoxia and cold at high altitude environments was established. Based on these animal experiments, rat aortic VECs were established as injury models and exposed to hypoxia and/or adrenaline (ADR) in vitro. The results revealed that hypoxia significantly altered the levels of nitric oxide and vascular endothelial growth factor, while the cold temperature significantly increased the release of ADR and noradrenaline. Exposure to hypoxia combined with cold temperature significantly affected all these indices. In vitro experiments demonstrated that hypoxia, ADR (which was used to simulate cold in the animal experiments) and the combination of the two factors resulted in damage to the VECs and endothelial dysfunction. In addition, the results also showed that diazoxide, a highly selective mitoK_ATP opener, protected VECs against these injuries. In conclusion, hypoxia and cold temperature induced endothelial cell dysfunction and endocrine disorders, respectively. Improving endothelial function using diazoxide may be an effective therapeutic strategy in patients with altitude-associated disorders. However, the potential for clinical application requires further study.

Preconditioning in neuroprotection: From hypoxia to ischemia

Sublethal hypoxic or ischemic events can improve the tolerance of tissues, organs, and even organisms from subsequent lethal injury caused by hypoxia or ischemia. This phenomenon has been termed hypoxic or ischemic preconditioning (HPC or IPC) and is well established in the heart and the brain. This review aims to discuss HPC and IPC with respect to their historical development and advancements in our understanding of the neurochemical basis for their neuroprotective role. Through decades of collaborative research and studies of HPC and IPC in other organ systems, our understanding of HPC and IPC-induced neuroprotection has expanded to include: early- (phosphorylation targets, transporter regulation, interfering RNA) and late- (regulation of genes like EPO, VEGF, and iNOS) phase changes, regulators of programmed cell death, members of metabolic pathways, receptor modulators, and many other novel targets. The rapid acceleration in our understanding of HPC and IPC will help facilitate transition into the clinical setting.

Protective roles of intra-arterial mild hypothermia and arterial thrombolysis in acute cerebral infarction

Objective

Herein, we evaluated the efficacy and safety of intra-arterial mild hypothermia in combination with arterial thrombolysis to treat acute cerebral infarction due to middle cerebral artery occlusion.

Methods

A total of 26 patients with acute middle cerebral artery occlusion were divided into a normothermia group (n = 15) and a mild hypothermia group (n = 11). The infarct volumes at 24 h and 7 days after the operation were compared between the normothermia group and the mild hypothermia group. Additionally, we compared neurological deficit scores between the two groups at 24 h, 7 days, and 1 mo after the operation.

Results

The infarct volumes and neurological deficit scores of the mild hypothermia group were significantly reduced compared to those in the normothermia group (p < 0.05). Furthermore, no adverse reactions or complications occurred in the mild hypothermia group.

Conclusion

Intra-arterial mild hypothermia reduced infarct volume after ischemia–reperfusion injury in the arterial thrombolysis of an acute cerebral infarction. Additionally, it improved the prognosis of patients with an acute middle cerebral artery occlusion, suggesting that this procedure is safe and effective for treating acute cerebral infarction.

Diazoxide Attenuates Postresuscitation Brain Injury in a Rat Model of Asphyxial Cardiac Arrest by Opening Mitochondrial ATP-Sensitive Potassium Channels

Objective. We investigated whether and how diazoxide can attenuate brain injury after cardiopulmonary resuscitation (CPR) by selective opening of mitochondrial ATP-sensitive potassium (mitoKATP) channels. Methods. Adult male Sprague-Dawley rats with induced cerebral ischemia (n = 10 per group) received an intraperitoneal injection of 0.1% dimethyl sulfoxide (1 mL; vehicle group), diazoxide (10 mg/kg; DZ group), or diazoxide (10 mg/kg) plus 5-hydroxydecanoate (5 mg/kg; DZ + 5-HD group) 30 min after CPR. The control group (sham group, n = 5) underwent sham operation, without cardiac arrest. Mitochondrial respiratory control rate (RCR) was determined. Brain cell apoptosis was assessed using TUNEL staining. Expression of Bcl-2, Bax, and protein kinase C epsilon (PKCε) in the cerebral cortex was determined by Western blotting and immunohistochemistry. Results. The neurological deficit scores (NDS) in the vehicle group decreased significantly at 24 h and 48 h after CPR. Diazoxide significantly improved NDS and mitochondrial RCR after CPR at both time points; 5-HD cotreatment abolished these effects. Diazoxide decreased TUNEL-positive cells following CPR, upregulated Bcl-2 and PKCε, downregulated Bax, and increased the Bcl-2/Bax ratio; 5-HD cotreatment reversed these effects. Conclusions. Diazoxide attenuates postresuscitation brain injury, protects mitochondrial function, inhibits brain cell apoptosis, and activates the PKC pathway by opening mitoKATP channels.

Neuroprotective effect of nicorandil through inhibition of apoptosis by the PI3K/Akt1 pathway in a mouse model of deep hypothermic low flow

OBJECTIVE

Nicorandil exerts a protective effect on ischemia-reperfusion (I/R) injury in the brain and kidney through anti-apoptotic mechanisms. However, the mechanism by which nicorandil protects against I/R injury induced by deep hypothermic low flow (DHLF) remains unclear.

METHODS

We used a cerebral I/R model induced by DHLF to determine the neuroprotective effects and possible mechanisms of nicorandil.

RESULTS

Hematoxylin-eosin (HE) staining and in situ terminal deoxynucleotidyl transferase UTP nick end labeling (TUNEL) assay were used to detect changes in cell morphology and the number of apoptotic cells in hippocampus, respectively. The apoptotic regulators including Bcl-2, Bax, Akt, and p-Akt (the active, phosphorylated form of Akt) were examined by Western blot (WB). Histopathological findings showed that nicorandil significantly alleviated morphological damage in hippocampal and reduced the number of TUNEL-positive nuclei induced by DHLF. Nicorandil also increased the expression of Bcl-2 and decreased the expression of Bax, while increasing p-Akt level. Consistent with these results, nicorandil-mediated neuroprotection was reduced in the Akt1+/- mutant mice and inhibited by LY294002, a PI3K inhibitor.

CONCLUSIONS

These findings showed that nicorandil provides a neuroprotective role in DHLF-induced I/R injury by inhibiting apoptosis via activation of the PI3K/Akt1 signaling pathway.

Diazoxide attenuates ischemia/reperfusion injury via upregulation of heme oxygenase-1 after liver transplantation in rats

AIM: To evaluate the effects of diazoxide on ischemia/reperfusion (I/R)-injured hepatocytes and further elucidate its underlying mechanisms.

METHODS: Male Sprague-Dawley rats were randomized (8 for donor and recipient per group) into five groups: I/R group (4 h of liver cold ischemia followed by 6 h of reperfusion); heme oxygenase-1 (HO-1) small interfering RNA (siRNA) group (injection of siRNA via donor portal vein 48 h prior to harvest); diazoxide (DZ) group (injection of DZ via donor portal vein 10 min prior to harvest); HO-1 siRNA + DZ group; and siRNA control group. Blood and liver samples were collected at 6 h after reperfusion. The mRNA expressions and protein levels of HO-1 were determined by reverse transcription polymerase chain reaction and Western blotting, and tissue morphology was examined by light and transmission electron microscopy. Serum transaminases level and cytokines concentration were also measured.

RESULTS: We observed that a significant reduction of HO-1 mRNA and protein levels in HO-1 siRNA and HO-1 siRNA + DZ group when compared with I/R group, while the increases were prominent in the DZ group. Light and transmission electron microscopy indicated severe disruption of tissue with lobular distortion and mitochondrial cristae damage in the HO-1 siRNA and HO-1 siRNA + DZ groups compared with DZ group. Serum alanine aminotransferase, aspartate transaminase, tumor necrosis factor-α and interleukin-6 levels increased in the HO-1 siRNA and HO-1 siRNA + DZ groups, and decreased in the DZ group.

CONCLUSION: The protective effect of DZ may be induced by upregulation of HO-1. By inhibiting expression of HO-1, this protection pretreated with DZ was abolished.

Bradykinin postconditioning protects pyramidal CA1 neurons against delayed neuronal death in rat hippocampus

AIMS

The present study was undertaken to evaluate possible neuroprotective effect of bradykinin against delayed neuronal death in hippocampal CA1 neurons if applied two days after transient forebrain ischemia in the rat.

METHODS

Transient forebrain ischemia was induced in male Wistar rats by four-vessel occlusion for 8 min. To assess efficacy of bradykinin as a new stressor for delayed postconditioning we used two experimental groups of animals: ischemia 8 min and 3 days of survival, and ischemia 8 min and 3 days of survival with i.p. injection of bradykinin (150 microg/kg) applied 48 h after ischemia.

RESULTS

We found extensive neuronal degeneration in the CA1 region at day 3 after ischemia/reperfusion. The postischemic neurodegeneration was preceded by increased activity of mitochondrial enzyme MnSOD in cytoplasm, indicating release of MnSOD from mitochondria in the process of delayed neuronal death. Increased cytosolic cytochrome c and subsequently caspase-3 activation are additional signs of neuronal death via the mitochondrial pathway. Bradykinin administration significantly attenuated ischemia-induced neuronal death, and also suppressed the release of MnSOD, and cytochrome c, and prevented caspase-3 activation.

CONCLUSIONS

Bradykinin can be used as an effective stressor able to prevent mitochondrial failure leading to apoptosis-like delayed neuronal death in postischemic rat hippocampus.