Iso-Oncotic Albumin Mitigates Brain and Kidney Injury in Experimental Focal Ischemic Stroke

Abstract

Background: There is widespread debate regarding the use of albumin in ischemic stroke. We tested the hypothesis that an iso-oncotic solution of albumin (5%), administered earlier after acute ischemic stroke (3 h), could provide neuroprotection without causing kidney damage, compared to a hyper-oncotic albumin (20%) and saline. Objective: To compare the effects of saline, iso-oncotic albumin, and hyper-oncotic albumin, all titrated to similar hemodynamic targets, on the brain and kidney. Methods: Ischemic stroke was induced in anesthetized male Wistar rats (n = 30; weight 437 ± 68 g) by thermocoagulation of pial blood vessels of the primary somatosensory, motor, and sensorimotor cortices. After 3 h, animals were anesthetized and randomly assigned (n = 8) to receive 0.9% NaCl (Saline), iso-oncotic albumin (5% ALB), and hyper-oncotic albumin (20% ALB), aiming to maintain hemodynamic stability (defined as distensibility index of inferior vena cava <25%, mean arterial pressure >80 mmHg). Rats were then ventilated using protective strategies for 2 h. Of these 30 animals, 6 were used as controls (focal ischemic stroke/no fluid). Results: The total fluid volume infused was higher in the Saline group than in the 5% ALB and 20% ALB groups (mean ± SD, 4.3 ± 1.6 vs. 2.7 ± 0.6 and 2.6 ± 0.5 mL, p = 0.03 and p = 0.02, respectively). The total albumin volume infused (g/kg) was higher in the 20% ALB group than in the 5% ALB group (1.4 ± 0.6 vs. 0.4 ± 0.2, p < 0.001). Saline increased neurodegeneration (Fluoro-Jade C staining), brain inflammation in the penumbra (higher tumor necrosis factor-alpha expression), and blood-brain barrier damage (lower gene expressions of claudin-1 and zona occludens-1) compared to both iso-oncotic and hyper-oncotic albumins, whereas it reduced the expression of brain-derived neurotrophic factor (a marker of neuroregeneration) compared only to iso-oncotic albumin. In the kidney, hyper-oncotic albumin led to greater damage as well as higher gene expressions of kidney injury molecule-1 and interleukin-6 than 5% ALB (p < 0.001). Conclusions: In this model of focal ischemic stroke, only iso-oncotic albumin had a protective effect against brain and kidney damage. Fluid therapy thus requires careful analysis of impact not only on the brain but also on the kidney.

Keywords: albumin; hemodynamic; inflammation; kidney damage; stroke.

Figure 1

Study randomization (A) and experimental design (B). Schematic illustration of the model of focal ischemic stroke by craniectomy and thermocoagulation of pial vessels over the right primary sensorimotor cortex is shown in the bottom left. dIVC, distensibility index of inferior vena cava; MAP, mean arterial pressure; V_T, tidal volume; PEEP, positive end-expiratory pressure; FiO₂, inspired fraction of oxygen; 5% ALB, 5% albumin; 20% ALB, 20% albumin.

Figure 2

Comparison of Fluoro-Jade C (FJC) staining between Saline (0.9% NaCl), 5% ALB (albumin), and 20% ALB groups. Long arrows point to FJC-positive cells, and short arrows, to vessels. Note representative diagram of a brain slice after ischemic brain injury, indicating the core and penumbra regions. Within the penumbra, a sample area from which FJC images were taken is highlighted. Comparisons among groups were performed by the Kruskal–Wallis test followed by Dunn's test. * vs. Saline; # vs. 5% ALB. Significance accepted at p < 0.05.

Figure 3

Expression of biologic markers associated with brain damage. Real-time polymerase chain reaction analysis of biologic markers associated with blood-brain barrier integrity (zonula occludens [ZO]-1 and claudin-1), brain inflammation (tumor necrosis factor [TNF]-α), and neurotrophic activity (brain-derived neurotrophic factor [BDNF]). Boxes show the interquartile range (25–75th percentile), while whiskers encompass the range (minimum-maximum) and horizontal lines represent the median in 8 animals/group. Scatter plots are also presented. Relative gene expression was calculated as a ratio of average expression of each gene to the reference gene (36B4) and expressed as fold change relative to Saline group. Comparisons among all groups were done using the Kruskal–Wallis test followed by Dunn's post hoc test. * vs. Saline. For all comparisons, significance accepted at p < 0.05.

Figure 4

Acute kidney injury (AKI) score (absence of brush border, presence of vacuolization, desquamation, cell debris, and hyaline casts). (A): Representative photomicrographs (light microscopy) of kidney tubules stained with periodic acid–Schiff reagent (PAS). Absence/derangement of the brush border in proximal tubular epithelia (▴), tubular cell vacuolization (→), and tubular obstruction due to the presence of cellular debris or casts (*) in kidney histological sections of 6–8 animals (original magnification, × 200). (B): AKI score. Data are shown as median [interquartile range]. Comparisons among all groups were done using the Kruskal–Wallis test followed by Dunn's post hoc test. Five percentage ALB: 5% albumin; 20% ALB: 20% albumin. * vs. Saline; # vs. 5% ALB. For all comparisons, significance accepted at p < 0.05.

Figure 5

Expression of biologic markers associated with kidney damage. (A) Interleukin (IL)-6 mRNA levels; (B) Kidney injury molecule-1 (KIM-1) mRNA levels. Comparisons among all groups were done using the Kruskal–Wallis test, with significance accepted at p < 0.05. Boxes show the interquartile range (25–75th percentile), while whiskers encompass the range (minimum-maximum) and horizontal lines represent the median in 8 animals/group. Scatter plots are also presented. Relative gene expression was calculated as a ratio of average expression of each gene to the reference gene (36B4) and expressed as fold change relative to Saline group. * vs. Saline 0.9%; # vs. 5% ALB.