Xiaochaihutang Improves the Cortical Astrocyte Edema in Thioacetamide-Induced Rat Acute Hepatic Encephalopathy by Activating NRF2 Pathway

Abstract

Oxidative stress induced by high ammonia, which leads to astrocyte edema, is the key to acute hepatic encephalopathy (AHE). Nuclear factor erythroid 2-related factor 2 (NRF2) has been implicated in oxidative stress, but the mechanism of NRF2 against ammoniainduced astrocytes edema has not been fully studied. We confirmed that the NRF2 pathway is related to brain edema caused by AHE and found that Xiaochaihutang (XCHT) could effectively activate the NRF2 pathway to treat AHE. The model of AHE was established with thioacetamide (TAA) in rats. Rat behaviors were observed, brain water content, blood ammonia levels, glutamine synthetase (GS), malondialdehyde (MDA), and total superoxide dismutase (T-SOD) were determined after XCHT treatment. Furthermore, the expression of NRF2 pathway proteins and mRNA, glial fibrillary acidic protein (GFAP) and aquaporins 4 (AQP4) were examined. In order to determine whether XCHT has a direct effect on cerebral edema caused by high ammonia, we examined the effect of XCHT compound serum on cortical astrocytes in the presence of ammonia, through microscopic observation and immunofluorescence (IF). Results showed that AHE induced by TAA changed the behavior of the rats, and increased brain water content, blood ammonia levels, GS and MDA content meanwhile decreasing T-SOD, but these symptoms were improved by treatment with XCHT. XCHT protected brain edema by activating the NRF2 pathway and increasing the expression of downstream proteins and genes. Astrocytes treated with 5 mM ammonia also showed an increase in the AQP4 protein expression but a decrease in XCHT compound serum and ammonia-induced cell edema groups. This study demonstrates that the NRF2 pathway is involved in the brain edema in AHE, and XCHT may represent a useful prescription for the treatment of AHE.

Thymol ameliorated neurotoxicity and cognitive deterioration in a thioacetamide-induced hepatic encephalopathy rat model; involvement of the BDNF/CREB signaling pathway

“…These findings are in harmony with previous reports. 60,62 This reduction of GFAP protein could be the result of the destabilization of GFAP mRNA in hyperammonemic conditions. 63 Reduced GFAP could partly explain the observed cytotoxic cell swelling and brain edema in the HE group.…”

2021 ISHEN guidelines on animal models of hepatic encephalopathy

“…Rodents: TAA’s toxicity is induced by the production of thioacetamide‐s‐oxide (a reactive oxygen species) through flavin adenine dinucleotide monooxygenase 44 . The TAA‐treated rat model of Type A HE has been well‐established relative to the clinical status, liver function and brain oedema development 45‐52 . In this model, rats are given TAA in doses ranging from 300 to 500 mg/kg by ip injection on consecutive days for 2‐3 days.…”

Astrocytes profiling in acute hepatic encephalopathy: Possible enrolling of glial fibrillary acidic protein, tumor necrosis factor-alpha, inwardly rectifying potassium channel (Kir 4.1) and aquaporin-4 in rat cerebral cortex

“…In mice, an acute administration of TAA raises brain water content and causes cerebral edema ( Grant et al, 2018 ). Neuroinflammation and ammonia-dependent events might be involved in increased water content in TAA-treated rats ( Heidari et al, 2016 ; Jia et al, 2020 ). This was ascertained in our study by increased plasma ammonia level along with increased TNFα expression in astrocytes.…”