ORIGINAL ARTICLE Role of serine protease inhibitor, ulinastatin, in rat model of hepatic encephalopathy: aquaporin 4 molecular targeting and therapeutic implication Rehab E. Abo El gheit 1 & Marwa Mohamed Atef 2 & Ghada A. Badawi 3 & Walaa M. Elwan 4 & H. A. Alshenawy 5 & Marwa Nagy Emam 1 Received: 14 January 2020 /Accepted: 9 August 2020 # University of Navarra 2020 Abstract Hepatic encephalopathy (HE) is a devastating neuropsychiatric presentation of the advanced hepatic insufficiency. It is associated with high morbidity and mortality. Aquaporin-4 (AQP4), the principal astrocyte water channel, is primarily involved in brain edema development. Ulinastatin (ULI) is a potent protease inhibitor, extracted from fresh human urine. We hypothesized that ULI could be neuroprotective in acute HE through molecular targeting of brain AQP4, which is known to be upregulated in HE. To induce acute liver failure (ALF), the rats were acutely intoxicated with thioacetamide (TAA). Animals were randomized into HE- and ULI-treated HE groups, with control normal group. Total bilirubin, albumin, serum aminotransferases, and serum/brain ammonia/proinflammatory cytokines, blood–brain barrier (BBB) integrity/tight junction proteins, brain water content, and neurological scores were assessed. Additionally, brain AQP4 and α-Syntrophin mRNA expression and protein levels were evaluated by quantitative real-time PCR and enzyme-linked immunosorbent assay, respectively. Brain and liver tissues were stripped and processed for further microscopic and histological analyses. ULI exerted potent dual neuro/hepato protective potential, improved neurological score, animals’ survival, ameliorated brain edema, probably via anti-inflammatory activity, preserved BBB integrity, down-regulated AQP4 expression, and membrane polarization by decreased α-syntrophin level, with rescued brain bioenergetics. ULI could be tooled as a possible therapeutic option in HE in ALF. Keywords Ulinastatin . Aquaporin 4 . Acute liver failure . Ammonia . Hepatic encephalopathy Introduction Acute liver failure (ALF) is a clinical syndrome of severe and sudden hepatic injury, associated with massive hepatocellular necrosis and dysfunction. It is characterized typically by co- agulopathy, jaundice, and encephalopathy [9]. Hepatic encephalopathy (HE) is developed as a devastating complication of advanced hepatic insufficiency. Pathologically, it is clarified by rapid onset brain edema that is encountered in 50% of ALF cases, increased intracranial tension, and consequently cerebral herniation [ 17 ]. Clinically, HE is presented with a wide spectrum of neuropsy- chiatric abnormalities ranging from subclinical alterations up to coma. It has an extremely poor prognosis with very high rate of mortality [30]. Emergence of brain edema and coma setting diverts HE to a lethal course. Although the underlying mechanisms of brain edema remain incompletely understood, it is primarily catego- rized as cytotoxic phenomena, correlated with alterations in Key points • Targeting AQP4 might be an appropriate focal point to combat brain edema in fulminant ALF. • ULI neuroprotective effects with improved neurological outcome could be designed as a novel mechanism-based therapeutic modality to control brain edema. * Rehab E. Abo El gheit rehab.abouelghait@med.TanTa.edu.eg; extrasystole.2003@gmail.com 1 Physiology Department, Faculty of Medicine, Tanta University, El Geesh Street, Tanta, Egypt 2 Medical Biochemistry Department, Faculty of Medicine, Tanta University, Tanta, Egypt 3 Pharmacology and Toxicology Department, Faculty of Pharmacy and Pharmaceutical Industries, Sinai University, El-Arish, Egypt 4 Histology Department, Faculty of Medicine, Tanta University, Tanta, Egypt 5 Pathology Department, Faculty of Medicine, Tanta University, Tanta, Egypt Journal of Physiology and Biochemistry https://doi.org/10.1007/s13105-020-00762-0