Immunohistochemical expression of gfap, gs, aqp4, alzheimer-2-astrocytosis and brain ammonia levels in deceased septic patients without liver failure and those with sepsis-associated liver injury

Sepsis-associated liver injury (SALI) induces secondary hepatotoxic brain damage, complementing the mechanisms of sepsis-associated encephalopathy. In these conditions, astrocytes play one of the central roles as being the main homeostatic glia and key cells to metabolize ammonia in the brain. The aim of the study was to determine the ammonia levels and reactive astroglial changes in the brain of deceased septic patients without liver failure and deceased patients with sepsis-associated liver injury. Materials and methods. Sectional material of 40 patients who died from abdominal sepsis was studied. Case histories were analyzed according to the SOFA scale with accent on the brain and liver disfunction confirmation and excluding kidney insufficiency. Septic cases designed two main comparison groups: 1) sepsis without SALI («non-SALI», n = 20); 2) sepsis with SALI («SALI», n = 20). Control group included autopsy material of 30 deceased patients with cardiovascular pathology with no inflammatory, metabolic or toxic comorbidity. In paraffin sections of the postmortem brain cortex, white matter, hippocampus, thalamus, striatum, and cerebellum, it was determined: i) immunohistochemical expression of GFAP, GS, and AQP4; ii) histochemical expression of tissue ammonia with Nessler's reagent according to V. Gutiérrez-de-Juan et al. (2017); iii) Що це за позначення ?numbers of Alzheimer type 2 astrocytes (AA2). Results. In the «non-SALI» group, it is found increased level of all the studied parameters: i) elevated GFAP in six brain regions with the highest growth in the cortex – by 8.46 times; ii) elevated GS in the thalamus and cerebellum (by 1.96 and 1.29 times, respectively); iii) elevated AQP4 in six brain regions with the highest rise in the cortex – by 3 times; iv) elevated histochemical ammonia expression in the thalamus, striatum, and cerebellum (by 1.29, 1.20, and 1.17 times, respectively); v) increased AA2 numbers in the cortex and thalamus (by 2.32 and 1.53 times, respectively). The «SALI» group is characterized by the decreased GFAP expression in six brain regions, with the lowest values in thalamus, striatum, and cerebellum. Herewith, in six brain regions increased levels are typical for: i) GS expression, with maximal aggravation in the cortex and thalamus (by 3.20 and 3.18 times, respectively); ii) AQP4 expression, with maximal increase in thalamus and white matter (by 4.37 and 4.21 times, respectively); iii) histochemical ammonia expression with maximal enhancement in thalamus and cerebellum (by 4.33 and 4.27 times, respectively); iv) severity of AA2-astrocytosis with maximal rates in the cortex and striatum (increase by 3.58 and 3.23 times, respectively). Conclusions. In the brain of deceased septic patients without liver failure, a heterogeneously increased expression of GFAP, AQP4 and GS is observed which is accompanied by a slight increase in the level of tissue ammonia and weak AA2-astrocytosis. In deceased septic patients with sepsis-associated liver injury, a higher level of ammonia in the brain is associated with a significantly reduced level of GFAP, which is accompanied by an enhanced expression of GS and AQP4, as well as more pronounced AA2-astrocytosis, which indicates significant structural and functional remodeling and aggravation of astroglial dystrophy under action of hepatogenic neurointoxicity, which contributes to the disruption of astroglial homeostatic functionality and exacerbates sepsis-associated brain damage.