Angiotensin II-induced mouse hippocampal neuronal HT22 cell apoptosis was inhibited by propofol: Role of neuronal nitric oxide synthase and metallothinonein-3

Abstract

Background: The activation of renin angiotensin system is involved in multiple pathological processes. The neuroprotective effect of propofol has been reported. We hypothesized that propofol may attenuate Angiotensin II (Ang II)-induced apoptosis in mouse hippocampal HT22 cells and aimed to identify the underlying mechanisms.

Methods: Mouse hippocampal HT22 cells were pre-treated with propofol, and stimulated with Ang II. Apoptosis was examined by transferase dUTP nick end labeling (TUNEL) staining and caspase-3 activity assay. The effect of propofol on Ang II-modulated neuronal nitric oxide synthase (nNOS) expression, nitric oxide (NO) production, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase expression and activity, caspase activity and metallothinonein-3 (MT-3) expression were measured.

Results: Compared with control, Ang II concentration- and time-dependently induced apoptosis, which was attenuated by propofol in a concentration-dependent manner. Ang II (1 μM, 3 h) induced the expression of nNOS and NADPH oxidase, caused NO and superoxide anion accumulation, thus leading to excessive oxidative stress. Ang II also induced cytochrome C release and the activation of caspase 9 as well as caspase 3. In addition, Ang II reduced the expression of MT-3. Importantly, these effects were alleviated by 50 μM propofol, nNOS inhibitor S-methyl-l-thiocitrulline (SMTC) and angiotensin type 1 receptor (AT1R) blocker losartan, but not AT2R blocker PD123319.

Conclusions: Ang II via AT1R induced oxidative stress and apoptosis in hippocampal HT22 cells, and the neuroprotective anti-apoptotic effect of propofol was mediated through inhibiting oxidative stress.

Keywords: angiotensin II; apoptosis; metallothinonein-3; nitric oxide synthase; propofol.