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

The impact of ATP-sensitive potassium channel modulation on mitochondria in a Parkinson's disease model using SH-SY5Y cells depends on their differentiation state

Inward rectifying potassium channels sensitive to ATP levels (KATP) have been the subject of investigation for several decades. Modulators of KATP channels are well-established treatments for metabolic as well as cardiovascular diseases. Experimental studies have also shown the potential of KATP modulation in neurodegenerative disorders. However, to date, data regarding the effects of KATP antagonists/agonists in experiments related to neurodegeneration remain inconsistent. The main source of confusion in evaluating available data seems to be the choice of experimental models. The present study aims to provide a comprehensive understanding of the effects of both opening and blocking KATP channels in two forms of SH-SY5Y cells. Our results offer valuable insights into the significance of metabolic differences between differentiated and non-differentiated SH-SY5Y cells, particularly in the context of glibenclamide and diazoxide effects under normal conditions and during the initiation of pathological events simulating Parkinson's disease in vitro. We emphasize the analysis of mitochondrial functions and changes in mitochondrial network morphology. The heightened protein expression of KATP channels identified in non-differentiated SH-SY5Y cells seems to be a platform for a more significant impact of KATP modulators in this cell type. The efficiency of rotenone treatment in inducing morphological changes in the mitochondrial network depends on the differentiation status of SH-SY5Y cells.

[Protective effect of iridoid glycosides of radix scrophulariae on endoplasmic reticulum stress induced by oxygen-glucose deprivation and reperfusion in vitro model]

OBJECTIVE

To investigate the regulatory effect of iridoid glycoside of radix scrophulariae (IGRS) on endoplasmic reticulum stress induced by oxygen-glucose deprivation and reperfusion in vitro model.

METHODS

Rat pheochromocytoma PC12 cells were pretreated with IGRS (50, 100, 200 μg/mL) for 24h, and the in vitro model of oxygen-glucose deprivation/reoxygenation (OGD/R) was applied. The cell viability was determined by MTT and lactate dehydrogenase (LDH) assay. The apoptotic rate was detected by flow cytometry. The expression of B-cell lymphoma-2 (Bcl-2), Bcl-2 related X protein (Bax), C/EBP homologous protein (CHOP), caspase-12 protein, and glucose-regulated protein-78(GRP78)were detected by Western blotting. The mRNA expression levels of sarco/endoplasmic reticulum Ca2+-ATPase2 (SERCA2), 1, 4, 5-triphosphate inositol receptor 1 (IP3R1), and ryanodine receptor 2 (RyR2)were detected by real-time RT-PCR. Free Ca2+ concentration [Ca2+]i was determined by using laser scanning confocal microscopy.

RESULTS

The damage caused by OGD/R to PC12 cells was significantly reduced by IGRS, with significant effect on increasing survival rate and reducing LDH release (all P<0.01). The expression of GRP78, CHOP, Bax, and caspase-12 were down-regulated (all P<0.01), and the expression of Bcl-2 and Bcl-2/Bax ratio was up-regulated (all P<0.01); IGRS increased the expression of SERCA2 mRNA in PC12 cells after OGD/R injury (P<0.01), decreased [Ca2+]i and down-regulated the expression of RyR2 mRNA and IP3R1 mRNA.

CONCLUSIONS

IGRS has neuroprotective effect, which may alleviate cerebral ischemia-reperfusion injury by regulating SERCA2, maintaining calcium balance, and inhibiting endoplasmic reticulum stress-mediated apoptosis.

Upregulation of Nucleotide-Binding Oligomerization Domain-, LRR- and Pyrin Domain-Containing Protein 3 in Motoneurons Following Peripheral Nerve Injury in Mice

Neuronal injuries are accompanied by release and accumulation of damage-associated molecules, which in turn may contribute to activation of the immune system. Since a wide range of danger signals (including endogenous ones) are detected by the nucleotide-binding oligomerization domain-, LRR- and pyrin domain-containing protein 3 (NLRP3) pattern recognition receptor, we hypothesized that NLRP3 may become activated in response to motor neuron injury. Here we show that peripheral injury of the oculomotor and the hypoglossal nerves results in upregulation of NLRP3 in corresponding motor nuclei in the brainstem of mice. Although basal expression of NLRP3 was observed in microglia, astroglia and neurons as well, its upregulation and co-localization with apoptosis-associated speck-like protein containing a caspase activation and recruitment domain, suggesting inflammasome activation, was only detected in neurons. Consequently, increased production of active pro-inflammatory cytokines interleukin-1β and interleukin-18 were detected after hypoglossal nerve axotomy. Injury-sensitive hypoglossal neurons responded with a more pronounced NLRP3 upregulation than injury-resistant motor neurons of the oculomotor nucleus. We further demonstrated that the mitochondrial protector diazoxide was able to reduce NLRP3 upregulation in a post-operative treatment paradigm. Our results indicate that NLRP3 is activated in motoneurons following acute nerve injury. Blockade of NLRP3 activation might contribute to the previously observed anti-inflammatory and neuroprotective effects of diazoxide.

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.

Overexpression of COX6B1 protects against I/R‑induced neuronal injury in rat hippocampal neurons

Cerebrovascular disease (CVD) is one of the leading causes of mortality worldwide. The role of cytochrome c oxidase subunit 6B1 (COX6B1) in the central nervous system remains unclear. The present study aimed to analyze the role of COX6B1 in rat hippocampal neurons extracted from fetal rats. The subcellular localization of the neuron-specific marker microtubule-associated protein 2 was detected by immunofluorescence assay. Cell viability was assessed using a cell counting kit, and the levels of apoptosis and cytosolic Ca²⁺ were analyzed by flow cytometry. The expression levels of the molecular factors downstream to COX6B1 were determined using reverse transcription-quantitative polymerase chain reaction and western blotting. Reoxygenation following oxygen-glucose deprivation (OGD) decreased cell viability and the expression levels of COX6B1 in a time-dependent manner, and 60 min of reoxygenation was identified as the optimal time period for establishing an ischemia/reperfusion (I/R) model. Overexpression of COX6B1 was demonstrated to reverse the viability of hippocampal neurons following I/R treatment. Specifically, COX6B1 overexpression decreased the cytosolic concentration of Ca²⁺ and suppressed neuronal apoptosis, which were increased following I/R treatment. Furthermore, overexpression of COX6B1 increased the protein expression levels of apoptosis regulator BCL-2 and mitochondrial cytochrome c (cyt c), and decreased the protein expression levels of apoptosis regulator BCL2-associated X and cytosolic cyt c in I/R model cells. Collectively, the present study results suggested that COX6B1 overexpression may reverse I/R-induced neuronal damage by increasing the viability of neurons, by decreasing the cytosolic levels of Ca²⁺ and by suppressing apoptosis. These results may facilitate the development of novel strategies for the prevention and treatment of CVD.