A mutation in ß-amyloid precursor protein renders SH­SY5Y cells vulnerable to isoflurane toxicity: The role of inositol 1,4,5­trisphosphate receptors.

Isoflurane is a commonly used inhaled anesthetic, which induces apoptosis of SH­SY5Y cells in a dose­ and time­dependent manner; however, the underlying mechanisms remain unknown. The authors of the present study hypothesized that a mutation in ß­amyloid precursor protein (APP), which is a gene associated with familial Alzheimer's disease, may render cells vulnerable to isoflurane­induced cytotoxicity via activation of inositol 1,4,5­trisphosphate receptors (IP3R). In the present study, SH­SY5Y cells were transfected with a vector or with mutated APP, and were treated with the equivalent of 1 minimum alveolar concentration (MAC) isoflurane for 8 h. Cell apoptosis rate, alterations to cytosolic calcium concentrations ([Ca2+]c), and protein levels of IP3R were determined following exposure of cells to isoflurane. In addition, the effects of the IP3R antagonist xestospongin C were determined on isoflurane­induced cytotoxicity and calcium release from the endoplasmic reticulum (ER) of mutated APP­ and vector­transfected SH­SY5Y cells. Treatment with isoflurane (1 MAC) for 8 h induced a higher degree of cytotoxicity, and a marked increase in [Ca2+]c and IP3R protein levels in mutated APP­transfected SH­SY5Y cells compared with vector­transfected SH­SY5Y cells. Xestospongin C significantly attenuated isoflurane­mediated cytotoxicity and inhibited calcium release from the ER of SH­SY5Y cells. These results indicated that the APP mutation may render SH­SY5Y cells vulnerable to isoflurane neurotoxicity, and the underlying mechanism may be associated with Ca2+ dysregulation via overactivation of IP3R.

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.

[Effects of 7.5% hypertonic saline pre-injection on postoperative cognitive dysfunction in senile rats].

OBJECTIVE: To explore the effects of hypertonic saline (7.5% NaCl) pre-injection on postoperative cognitive function in senile rats. METHODS: A total of 60 healthy male Sprague-Dawley rats, aged 18 months, weighting 450-500 g, were randomly divided into 3 groups of control (C); model (M) and hypertonic saline (HS) (n = 20 each). At 30 min pre-operation, the rats of groups C and HS received an injection of 7.5% hypertonic sodium 4 ml/kg via tail vein. And the same volume of saline was injected in group M. Rats of groups M and HS were anesthetized by inhaling 3% sevoflourane and underwent splenectomy while group C inhaled merely pure oxygen. Escape latency and frequency of crossing original platform were assessed by Morris water maze on 1 day pre-operation and 1, 3, 7 days post-operation. The rats were randomly taken for detecting the intracellular [Ca²âº]i and apoptotic rate of hippocampal neuron with flow cytometry. And ultrastructures of hippocampal neurons were observed with transmission electron microscope at 1 day pre-operation and 1, 7 days post-operation. RESULTS: Compared with pre-dosing value, escape latency was significantly prolonged, the frequency of crossing original platform decreased and apoptotic rate and [Ca²âº]i increased at each time point post-operation in groups M and HS. And no significant changes were found in the above-mentioned parameters in group C. Compared with group M, escape latency was significantly shortened, the frequency of crossing original platform increased and apoptotic rate and [Ca²âº]i decreased at each time point post-operation in group HS. Pathological changes were found in groups M and HS and the damage was more severe in group M than that in group HS. And no significant pathological change was found in group C. CONCLUSION: Infusing 7.5% hypertonic saline can improve postoperative cognitive function of senile rats. And it may be due to a decreased apoptotic rate of hippocampal neurons.