Mitochondrial function and energy metabolism in neuronal HT22 cells resistant to oxidative stress

Background and Purpose

The hippocampal cell line HT22 is an excellent model for studying the consequences of endogenous oxidative stress. Extracellular glutamate depletes cellular glutathione by blocking the glutamate/cystine antiporter system xc−. Glutathione depletion induces a well-defined programme of cell death characterized by an increase in reactive oxygen species and mitochondrial dysfunction.

Experimental Approach

We compared the mitochondrial shape, the abundance of mitochondrial complexes and the mitochondrial respiration of HT22 cells, selected based on their resistance to glutamate, with those of the glutamate-sensitive parental cell line.

Key Results

Glutamate-resistant mitochondria were less fragmented and displayed seemingly contradictory features: mitochondrial calcium and superoxide were increased while high-resolution respirometry suggested a reduction in mitochondrial respiration. This was interpreted as a reverse activity of the ATP synthase under oxidative stress, leading to hydrolysis of ATP to maintain or even elevate the mitochondrial membrane potential, suggesting these cells endure ineffective energy metabolism to protect their membrane potential. Glutamate-resistant cells were also resistant to oligomycin, an inhibitor of the ATP synthase, but sensitive to deoxyglucose, an inhibitor of hexokinases. Exchanging glucose with galactose rendered resistant cells 1000-fold more sensitive to oligomycin. These results, together with a strong increase in cytosolic hexokinase 1 and 2, a reduced lactate production and an increased activity of glucose-6-phosphate dehydrogenase, suggest that glutamate-resistant HT22 cells shuttle most available glucose towards the hexose monophosphate shunt to increase glutathione recovery.

Conclusions and Implications

These results indicate that mitochondrial and metabolic adaptations play an important role in the resistance of cells to oxidative stress.

Linked Articles

This article is part of a themed issue on Mitochondrial Pharmacology: Energy, Injury & Beyond. To view the other articles in this issue visit http://dx.doi.org/10.1111/bph.2014.171.issue-8     

Assessment of Demineralization Inhibition Effects of Dentin Desensitizers Using Swept-Source Optical Coherence Tomography

The purpose of this study was to evaluate the mechanism of action and the inhibiting effects of two types of desensitizers against dentin demineralization using pre-demineralized hypersensitivity tooth model in vitro. In this study, we confirmed that a hypersensitivity tooth model from our preliminary experiment could be prepared by immersing dentin discs in an acetic acid-based solution with pH 5.0 for three days. Dentin discs with three days of demineralization were prepared and applied by one of the desensitizers containing calcium fluoro-alumino-silicate glass (Nanoseal, NS) or fluoro-zinc-silicate glass (Caredyne Shield, CS), followed by an additional three days of demineralization. Dentin discs for three days of demineralization (de3) and six days of demineralization (de6) without the desensitizers were also prepared. The dentin discs after the experimental protocol were scanned using swept-source optical coherence tomography (SS-OCT) to image the cross-sectional (2D) view of the samples and evaluate the SS-OCT signal. The signal intensity profiles of SS-OCT from the region of interest of 300, 500, and 700 µm in depth were obtained to calculate the integrated signal intensity and signal attenuation coefficient. The morphological differences and remaining chemical elements of the dentin discs were also analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. SS-OCT images of CS and NS groups showed no obvious differences between the groups. However, SS-OCT signal profiles for both the CS and NS groups showed smaller attenuation coefficients and larger integrated signal intensities than those of the de6 group. Reactional deposits of the desensitizers even after the additional three days of demineralization were observed on the dentin surface in NS group, whereas remnants containing Zn were detected within the dentinal tubules in CS group. Consequently, both CS and NS groups showed inhibition effects against the additional three days of demineralization in this study. Our findings demonstrate that SS-OCT signal analysis can be used to monitor the dentin demineralization and inhibition effects of desensitizers against dentin demineralization in vitro.     

Evaluation of the efficacy of platelet-rich plasma on healing of clean diabetic foot ulcers: A randomized clinical trial in Tehran,Iran

Background and aimsDiabetic foot ulcers (DFUs) are among challenging hurdles both for the patient and the physician. There is a recent trend toward finding novel and clinically efficient modalities to treat this potentially hazardous complication of diabetes mellitus in a timely manner. Herein, we aim to appraise the efficacy of platelet-rich plasma (PRP) in healing of clean DFUs.Methods90 patients with clean DFUs consisting of 56 (62.2%) males and 34 (37.8%) females with mean age (±standard deviation) of 56.52 (±7.14) years were enrolled in this study between June 2017 and December 2018. They were randomly allocated into control group (47 patients who received conventional dressing along with silver sulfadiazine ointment twice daily), and case group (43 patients who received PRP gel twice weekly for 3 weeks). All the patients were followed up for 6 months.ResultsOur study showed that PRP significantly increased the healing rate of DFUs regardless of the age (p-value: 0.0), gender (p-value: 0.0), or smoking (p-value: 0.0) and blood pressure (p-value: 0.0) status of patients, but it did not have a significant impact on the need for amputation (p-value: 0.11), level of amputation (p-value: 0.16), or the need for further treatments such as graft or angioplasty (p-value: 0.52).ConclusionRegardless of the age, gender, or smoking and blood pressure status of patients, PRP can be efficiently used in diabetic patients to accelerate the healing rate of foot ulcers.     

Blood bezoar causing obstruction after laparoscopic Roux-en-Y gastric bypass

INTRODUCTION

Bowel obstruction is a known complication after bariatric surgery especially Roux-en-Y gastric bypass. The known etiologies include internal hernia, jejunojejunostomy stricture, ileus, intussusceptions, superior mesenteric artery syndrome, incarcerated port site hernia, and adhesions. Blood bezoar is a rare cause of small intestinal obstruction after Roux-en-Y gastric bypass.

PRESENTATION OF CASE

We are going to present two cases of small bowel obstruction after Roux-en-Y gastric bypass due to blood bezoar.

DISCUSSION

Blood clot as the etiology of small bowel obstruction after Roux-en-Y gastric bypass is an unusual event. In the presence of postoperative small intestinal obstruction an obstructive blood bezoar should be in differential diagnosis. As any other etiology of postoperative obstruction it should be treated immediately to prevent its adverse lethal complications.

CONCLUSION

The best way for prevention of blood bezoar is prevention of bleeding at staple line and doing hemostasis at stapler line.