Effect of 2-aminoethoxydiphenyl borate on the functions of mouse skeletal muscle mitochondria

This work examined the effect of 2-aminoethoxydiphenyl borate (2-APB) on the functioning of isolated mouse skeletal muscle mitochondria and modeled its putative interaction with mitochondrial proteins. We have shown that 2-APB is able to dose-dependently suppress mitochondrial respiration in state 3 and 3UDNP driven by substrates of complex I and II. This effect of 2-APB was accompanied by a slight dose-dependent decrease in mitochondrial membrane potential and appears to be due to inhibition of complex I and complex III of the electron transport chain (ETC) with IC50 values of 200 and 120 μM, respectively. The results of molecular docking identified putative 2-APB interaction sites in these ETC complexes. 2-APB was shown to dose-dependently inhibit both mitochondrial Ca2+ uptake and Ca2+ efflux, which seems to be caused by a decrease in the membrane potential of the organelles. We have found that 2-APB has no significant effect on mitochondrial calcium retention capacity. On the other hand, 2-APB exhibited antioxidant effect by reducing mitochondrial hydrogen peroxide production but without affecting superoxide generation. It is concluded that the effect of 2-APB on mitochondrial targets should be taken into account when interpreting the results of cell and in vivo experiments.

Effects of intracellular Ca2+ on developmental potential and ultrastructure of cryopreserved-warmed oocyte in mouse

Maintaining appropriate intracellular calcium of oocytes is necessary to prevent ultrastructure and organelle damage caused by freezing and cryoprotectants. The present study aimed to investigate whether cryoprotectant-induced changes in the calcium concentrations of oocytes can be regulated to reduce damage to developmental potential and ultrastructure. A total of 33 mice and 1381 oocytes were used to explore the effects of intracellular calcium on the development and ultrastructures of oocytes subjected to 2-aminoethoxydiphenyl borate (2-APB) inhibition or thapsigargin (TG) stimulation. Results suggested that high levels intracellular calcium interfered with TG compromised oocyte survival (84.4 % vs. 93.4 %, p < 0.01) and blastocyst formation in fresh and cryopreservation oocytes (78.1 % vs. 86.4 %, and 60.5 % vs. 72.5 %, p < 0.05) compared with that of 2-APB pretreated oocytes in which Ca2+ was stabilized even though no differences in fertilization and cleavage was detected (p > 0.05). Examination by transmission electron microscopy indicated that the microvilli decreased and shortened, cortical granules considerably decreased in the cortex area, mitochondrial vesicles and vacuoles increased, and the proportion of vacuole mitochondria increased after oocytes were exposed to cryoprotectants. The cryopreservation-warming process deteriorated the negative effects on organelles of survival oocytes. By contrast, a low level of intracellular calcium mediated with 2-APB was supposed to contribute to the protection of organelles. These findings suggested oocyte injuries induced by cryoprotectants and low temperatures can be alleviated. More studies are necessary to confirm the relationship among Ca2+ concentration of the cytoplasm, ultrastructural injuries, and disrupted developmental potential in oocytes subjected to cryopreservation and warming.

2-Aminoethoxydiphenyl borate ameliorates functional and structural abnormalities in cisplatin-induced peripheral neuropathy

AIM OF THE STUDY

Cisplatin is a platinum-derived chemotherapeutic agent commonly used in the treatment of various tumors. Ototoxicity, nephrotoxicity, and peripheral neuropathy are the most common side effects of this drug. 2-Aminoethoxydiphenyl borate (2-APB), boron- containing compound, has some protective effects against various tissue damage. The present study aimed to investigate the potential protective effects of 2-APB on in vitro and in vivo cisplatin-induced neurotoxicity.

MATERIALS AND METHODS

MTT assay was used to determine cell viability in DRG cells. Peripheral neuropathy was induced in forty male Sprague-Dawley rats (200-250g) by administering cisplatin (3 mg/kg/week) intraperitoneally (i.p) for five weeks. 2-APB (2, 4, and 8 mg/kg, i.p) was administered. Mechanical allodynia, thermal hyperalgesia, cold allodynia, mechanical stimuli, motor coordination, and locomotor activity tests were performed. DRG cells and sciatic nerves were analyzed histologically. NGF, BDNF, TNF-α, GSH, MDA, and LDH levels were investigated in rat DRG tissue homogenates.

RESULTS

Our results revealed that 2-APB ameliorated cisplatin-induced neurotoxicity by improving mechanical and cold allodynia and motor coordination impairment. It also reduced cisplatin-induced structural toxicity in peripheral tissues.

CONCLUSION

These findings demonstrated that 2-APB could be considered as a potential therapeutic strategy for the treatment of cisplatin-induced peripheral neuropathy.

Magnetic field-induced Ca2+ intake by mesenchymal stem cells is mediated by intracellular Zn2+ and accompanied by a Zn2+ influx

Chronic exposure to magnetic fields (MFs) has a diverse range of effects on biological systems but definitive molecular mechanisms of the interaction remain largely unknown. One of the most frequently reported effects of MF exposure is an elevated concentration of intracellular Ca²⁺ through disputed pathways. Other prominent effects include increased oxidative stress and upregulation of neural markers through EGFR activation in stem cells. Further characterization of cascades triggered by MF exposure is hindered by the phenotype diversity of biological models used in the literature. In an attempt to reveal more mechanistic data in this field, we combined the most commonly used biological model and MF parameters with the most commonly reported effects of MFs. Based on clues from the pathways previously defined as sensitive to MFs (EGFR and Zn²⁺-binding enzymes), the roles of different types of channels (voltage gated Ca²⁺ channels, NMDA receptors, TRP channels) were inquired in the effects of 50 Hz MFs on bone marrow-derived mesenchymal stem cells. We report that, an influx of Zn²⁺ accompanies MF-induced Ca²⁺ intake, which is only attenuated by the broad-range inhibitor of TRP channels and store-operated Ca²⁺ entry (SOCE), 2-Aminoethoxydiphenyl borate (2-APB) among other blockers (memantine, nifedipine, ethosuximide and gabapentin). Interestingly, cation influx completely disappears when intracellular Zn²⁺ is chelated. Our results rule out voltage gated Ca²⁺ channels as a gateway to MF-induced Ca²⁺ intake and suggest Zn²⁺-related channels as a new focus in the field.

Effect of Sphingosine-1-Phosphate on Intracellular Free Ca²⁺ in Cat Esophageal Smooth Muscle Cells

A comprehensive collection of proteins senses local changes in intracellular Ca²⁺ concentrations ([Ca²⁺]_i) and transduces these signals into responses to agonists. In the present study, we examined the effect of sphingosine-1-phosphate (S1P) on modulation of intracellular Ca²⁺ concentrations in cat esophageal smooth muscle cells. To measure [Ca²⁺]_i levels in cat esophageal smooth muscle cells, we used a fluorescence microscopy with the Fura-2 loading method. S1P produced a concentration-dependent increase in [Ca²⁺]_i in the cells. Pretreatment with EGTA, an extracellular Ca²⁺ chelator, decreased the S1P-induced increase in [Ca²⁺]_i, and an L-type Ca²⁺-channel blocker, nimodipine, decreased the effect of S1P. This indicates that Ca²⁺ influx may be required for muscle contraction by S1P. When stimulated with thapsigargin, an intracellular calcium chelator, or 2-Aminoethoxydiphenyl borate (2-APB), an InsP₃ receptor blocker, the S1P-evoked increase in [Ca²⁺]_i was significantly decreased. Treatment with pertussis toxin (PTX), an inhibitor of G_i-protein, suppressed the increase in [Ca²⁺]_i evoked by S1P. These results suggest that the S1P-induced increase in [Ca²⁺]_i in cat esophageal smooth muscle cells occurs upon the activation of phospholipase C and subsequent release of Ca²⁺ from the InsP₃-sensitive Ca²⁺ pool in the sarcoplasmic reticulum. These results suggest that S1P utilized extracellular Ca²⁺ via the L type Ca²⁺ channel, which was dependent on activation of the S1P₄ receptor coupled to PTX-sensitive G_i protein, via phospholipase C-mediated Ca²⁺ release from the InsP₃-sensitive Ca²⁺ pool in cat esophageal smooth muscle cells.

In vivo assay to monitor flavonoid uptake across plant cell membranes

Flavonoids represent one of the most important molecules of plant secondary metabolism, playing many different biochemical and physiological roles. Although their essential role in plant life and human health has been elucidated by many studies, their subcellular transport and accumulation in plant tissues remains unclear. This is due to the absence of a convenient and simple method to monitor their transport. In the present work, we suggest an assay able to follow in vivo transport of quercetin, the most abundant flavonoid in plant tissues. This uptake was monitored using 2-aminoethoxydiphenyl borate (DPBA), a fluorescent probe, in non-pigmented Vitis vinifera cell cultures.

Modulation effect of Smilax glabra flavonoids on ryanodine receptor mediated intracellular Ca2+ release in cardiomyoblast cells

ETHNOPHARMACOLOGICAL RELEVANCE

Smilax glabra rhizome, a plant material from Liliaceae family, is a widely used traditional Chinese medicine for anti-cardiac hypertrophy treatment. We have previously found that Smilax glabra flavonoids (SGF) exerted such anti-cardiac hypertrophy activity. However, the mechanism of this activity of SGF has not been clarified yet.

MATERIALS AND METHODS

This study was aimed to investigate the inhibitory role of SGF on intracellular Ca(2+) release in rat cardiomyoblast cells (H9C2). Intracellular Ca(2+) release was determined by Ca(2+) indicator fluorescence (fluo 4-AM) in H9C2 cell line.

RESULTS

SGF at concentrations of 0.25, 0.5, 1.0mg/ml significantly inhibited the phenylephrine or angiotensin II induced intracellular Ca(2+) release in a dose-dependent manner. Furthermore, SGF could also inhibit ryanodine receptor (RyR) agonist caffeine induced Ca(2+) release and phenylephrine (PE)-induced Ca(2+) release under the condition in which inositol trisphosphate (IP3) receptors were blocked with 2-Aminoethoxydiphenyl borate (2-APB). Nevertheless, SGF had no impact on PE-induced Ca(2+) release under the condition in which RyRs were blocked with tetracaine.

CONCLUSIONS

Our results suggest that the protective effects of SGF are mediated via targeting inhibition of RyR mediated intracellular Ca(2+) release.