Effects of HE-precipitating factors on nuclear volume and morphology in cultured rat astrocytes
03 January 2018 (online)
Hepatic encephalopathy (HE) is a neuropsychiatric syndrome and a serious complication of acute or chronic liver failure. HE is triggered by a heterogenous set of factors such as ammonia, pro-inflammatory cytokines or sedatives of the benzodiazepine type. Recent evidence suggests that nuclear morphology strongly affects gene transcription. In the present study we examined effects of ammonia, TNFα and diazepam on nuclear volume and morphology in cultured rat astrocytes. Moreover, we analyzed whether TNFα or diazepam in synergism with ammonia alter nuclear volume and morphology, respectively.
Astrocytes were exposed to NH4Cl (5mM), diazepam (10µM) or TNFα (10 ng/ml) for 24, 48, 72, 120 or 168 hours. In a second set of experiments, astrocytes were coexposed to NH4Cl (5mM) TNFa (10 ng/ml) or NH4Cl (5mM) diazepam (10µM) for 72 hours. For analysis of nuclear shape and morphology vital astrocytes were stained with the nucleic acid stain Syto11 (5µM) and z-stack picture series were acquired using a fluorescence microscope equipped with a VivaTomeTM device. Nuclear volume and morphology were calculated by bioinformatic analysis. Statistical analysis was performed using unpaired t-test and one-way ANOVA.
Exposure to NH4Cl significantly decreased the nuclear volume in astrocytes after 72, 120 and 168 hours. Nuclear morphology changes were observed 24 hours after exposure to NH4Cl and these effects remained stable over an observation period of 168 hours: The nuclear shape became more circular and the nuclear area as well as the nuclear perimeter decreased. TNFα or diazepam had only minor and transient effects on nuclear volume and morphology in astrocytes. Coexposure to NH4Cl TNFα or NH4Cl diazepam had no effect on NH4Cl-induced nuclear volume and morphology changes.
The results of the present study show that long-term exposure to ammonia decreases the volume and modifies the morphology of the nucleus of cultured rat astrocytes. Ammonia-induced nuclear volume and morphology changes may alter transcription and underly gene expression changes observed in HE.