Effect of inhalational anesthetics on cytotoxicity and intracellular calcium differently in rat pheochromocytoma cells (PC12)

AMPK‑SIRT1 pathway dysfunction contributes to neuron apoptosis and cognitive impairment induced by sevoflurane

The anesthetic sevoflurane (Sev) is widely used because of its low blood-gas partition coefficient and lack of pungency. However, the application of Sevmay lead to cognitive impairment later in life. Previous results have indicated that exposure to Sev-induced neuronal apoptosis and cognitive dysfunction in a rat model, but much work remains to elucidate the mechanism. In the present study, inhibition in the AMP-activated protein kinase/Sirtuin 1 (AMPK/SIRT1) signaling pathway and a decrease in AMPK/SIRT1 activity was found to occur concomitantly in neuronal apoptosis induced by Sev. AICAR, an activator of AMPK, was able to suppress Sev-induced neuronal apoptosis and SIRT1 activity reduction in vitro. Further animal studies also showed that AICAR treatment blocked the deleterious cognition and AMPK/SIRT1 activity reduction in the cognition impairment rats induced by Sev. Taken together, it was concluded that the AMPK/SIRT1 signaling pathway mediates neuronal apoptosis and cognition impairment induced by Sev. The study provides evidence that AMPK activation ameliorates Sev-induced cognitive deficits.

Neuroprotective effects of vitexin against isoflurane-induced neurotoxicity by targeting the TRPV1 and NR2B signaling pathways

Vitexin is a bioactive compound extracted from hawthorn leaves, which reduces blood pressure and has anti‑inflammatory and potential anticancer effects. However, the mechanisms underlying the protective effects of vitexin against isoflurane‑induced neurotoxicity remain elusive. Therefore, the aim of the present study was to investigate these mechanisms further. Sprague Dawley rats received 1.4% isoflurane in a 100% oxygen environment for 2 h. Human PC12 pheochromocytoma neurosecretory cells were exposed to 2% isoflurane for 12 h before they were treated with 1, 10 or 100 µM vitexin for a further 24 h. Vitexin inhibited the isoflurane-induced cell cytotoxicity and weakened isoflurane-induced neuroinflammation and oxidative stress pathways in PC12 cells. In addition, treatment with vitexin suppressed isoflurane‑induced caspase‑3 activation and increased β-secretase 1 levels in PC12 cells. Furthermore, vitexin treatment decreased the levels of isoflurane‑induced cytosolic calcium and reactive oxygen species, and downregulated the expression of transient receptor potential cation channel subfamily V member 1 (TRPV1) and glutamate ionotropic receptor NMDA type subunit 2B (NR2B) protein expression in isoflurane-treated PC12 cells. These results suggest that vitexin mediates its protective effects against isoflurane-induced neurotoxicity by targeting the TRPV1 and NR2B signaling pathways.

Effects of calpain on sevoflurane-induced aged rats hippocampal neuronal apoptosis

BACKGROUND

Sevoflurane is one of the most commonly used volatile anesthetics and it has been shown to induce widespread apoptotic neurodegeneration in aged rat. Calpain is also activated during apoptosis in several types of cells. We hypothesized that calpain resulted in apoptosis under long time sevoflurane exposure, and it might play a role in the sevoflurane-induced memory impairment in aged rats.

METHODS

Seventy-two 18-month-old male Sprague-Dawley rats were randomly divided into three groups (n = 24): Control group rats were exposed to simply humid 50 % O2 balanced by N2 for 3 h; While M group rats received calpain inhibitor 10 mg/kg via the tail vein intravenously at 30 min before the animals inhaled 3 % sevoflurane for 3 h, subsequently received MDL 28170 3.33 mg/kg/h for 3 h. Sev group rats were only exposed to 3 % sevoflurane for 3 h without calpain inhibitor. Morris Water Maze was used to test the ability of learning and memory. Cytosolic calcium concentration was measured by using flow cytometry. Annexin-V labeled with a fluorophore or biotin can identify apoptotic cells by binding to PS. The expression of calpain in the hippocampus of rats was tested by Western blots.

RESULTS

The results showed that the M group had a shorter latency and had a larger number of times crossing over the previous platform site than that of the Sev group. Compared with Sev group, apoptosis rate and 76/80 kDa ratio of μ-calpain were significantly decreased in M group on the 1st day.

CONCLUSIONS

Sevoflurane might induce apoptosis through increasing [Ca(2+)]c and the activity of μ-calpain, which might be identified at least partially the molecular mechanism by which sevoflurane induces apoptosis.

Apoptosis induced clustering of IP(3)R1 in nuclei of non-differentiated PC12 cells

Inositol 1,4,5-trisphosphate (IP(3)) receptors are emerging as key sites for regulation by pro- and anti-apoptotic factors. Induction of apoptosis for 3 h increased mRNA and protein levels of type 1 IP(3) receptors in non-differentiated (ND), but not in differentiated (D) PC12 cells. Inhibitors of the IP(3) R's calcium release-2-aminoethoxydiphenyl borate (2-APB) and xestospongin-completely prevented Bax and caspase-3 mRNA increase after treatment with the apoptosis inducer set (AIK), and this reinforces the importance of IP(3) R1 in the apoptosis of ND PC12 cells. Apoptosis induction not only increases the IP(3) R1 protein, but it also causes formation of IP(3) R1 clusters in the nucleus which most likely result from fusion of the nucleoplasmic reticulum and/or IP(3) R1 translocation to the nucleus. This is quite similar to the observations noted after overexpression of IP(3) R1 in PC12 cells. The amount of IP(3) induced calcium release was higher in control than in AIK-treated cells. From our results we propose that after the apoptosis induction the amount of intranuclear calcium decreased dramatically due to the increase of calcium permeability of the nuclear calcium store vesicles. Therefore, increase of the calcium permeability may result from IP(3) receptors translocation to nuclei that can boost the calcium transport through IP(3) receptors.