Glibenclamide Produces Region-Dependent Effects on Cerebral Edema in a Combined Injury Model of Traumatic Brain Injury and Hemorrhagic Shock in Mice

Abstract

Cerebral edema is critical to morbidity/mortality in traumatic brain injury (TBI) and is worsened by hypotension. Glibenclamide may reduce cerebral edema by inhibiting sulfonylurea receptor-1 (Sur1); its effect on diffuse cerebral edema exacerbated by hypotension/resuscitation is unknown. We aimed to determine if glibenclamide improves pericontusional and/or diffuse edema in controlled cortical impact (CCI) (5m/sec, 1 mm depth) plus hemorrhagic shock (HS) (35 min), and compare its effects in CCI alone. C57BL/6 mice were divided into five groups (n = 10/group): naïve, CCI+vehicle, CCI+glibenclamide, CCI+HS+vehicle, and CCI+HS+glibenclamide. Intravenous glibenclamide (10 min post-injury) was followed by a subcutaneous infusion for 24 h. Brain edema in injured and contralateral hemispheres was subsequently quantified (wet-dry weight). This protocol brain water (BW) = 80.4% vehicle vs. 78.3% naïve, p < 0.01) but was not reduced by glibenclamide (I%BW = 80.4%). Ipsilateral edema also developed in CCI alone (I%BW = 80.2% vehicle vs. 78.3% naïve, p < 0.01); again unaffected by glibenclamide (I%BW = 80.5%). Contralateral (C) %BW in CCI+HS was increased in vehicle (78.6%) versus naive (78.3%, p = 0.02) but unchanged in CCI (78.3%). At 24 h, glibenclamide treatment in CCI+HS eliminated contralateral cerebral edema (C%BW = 78.3%) with no difference versus naïve. By 72 h, contralateral cerebral edema had resolved (C%BW = 78.5 ± 0.09% vehicle vs. 78.3 ± 0.05% naïve). Glibenclamide decreased 24 h contralateral cerebral edema in CCI+HS. This beneficial effect merits additional exploration in the important setting of TBI with polytrauma, shock, and resuscitation. Contralateral edema did not develop in CCI alone. Surprisingly, 24 h of glibenclamide treatment failed to decrease ipsilateral edema in either model. Interspecies dosing differences versus prior studies may play an important role in these findings. Mechanisms underlying brain edema may differ regionally, with pericontusional/osmolar swelling refractory to glibenclamide but diffuse edema (via Sur1) from combined injury and/or resuscitation responsive to this therapy. TBI phenotype may mandate precision medicine approaches to treat brain edema.

Keywords: HS; Sur1; TBI; cerebral edema; glibenclamide/glyburide.

FIG. 1.

Studies of glibenclamide pharmacokinetics (A) demonstrating immediate post-load levels of glibenclamide (3808 ± 611 pg/mL) and 4 day steady state concentrations (10170 ± 1823 pg/mL). Levels were not detectible in vehicle animals and are therefore not visible in the figure. Therapeutic levels did not influence normoglycemia. (B) Glucose levels were recorded in vehicle- and glibenclamide-treated animals at baseline, and at four subsequent time points: the end of the hemorrhagic shock phase, the end of the pre-hospital phase, the end of the hospital phase, and at 24 h. Glucose levels were not significantly different than in their vehicle counterparts, or than in naïve.

FIG. 2.

(A) At 24 h, %brain water (%BW) in the hemisphere ipsilateral to the contusion was significantly increased in both controlled cortical impact (CCI) (i, vehicle: black bar 80.20 ± 0.15) and CCI+hemorrhagic shock (HS) (ii, vehicle: black bar 80.46 ± 0.14%) versus naïve (white bar, 78.31 ± 0.04%; *p < 0.01). Glibenclamide treatment (shaded gray bar) did not reduce %BW in the hemisphere ipsilateral to contusion in either model. (B) At 24h, %BW in the hemisphere contralateral to the contusion was significantly increased in controlled cortical impact + hemorrhagic shock (CCI+HS) (ii, vehicle: black bar, 78.65 ± 0.10%) versus naive (white bar: 78.24 ± 0.05%, *p = 0.014) but unchanged in CCI alone (i, vehicle: black bar, 78.28 ± 0.08%, p = 1.0). Glibenclamide treatment (shaded gray bar) in CCI+HS (ii) returned %BW to naïve levels (78.25 ± 0.10%, p = 0.011). GLI, glibenclamide.

FIG. 3.

Continuous recordings of mean arterial pressure (A) were documented during the three phases of the combined injury experiments: hemorrhagic shock (shock, 35 min), pre-hospital phase (90 min), and hospital phase (15 min). Sodium concentration (B) and serum osmolarity (C) were also measured at the following time points: baseline, at the end of each phase of combined injury (“shock” at 35 min, “pre-hospital” at 125 min,“hospital” at 140 min), and at 24 h in the high-dose experiments. These measurements were performed comparing vehicle- with glibenclamide-treated animals for 24 h (A-i, B-i, C-i) and for 72 h (A-ii, B-ii, C-ii).

FIG. 4.

At 72 h, (A) in the hemisphere ipsilateral to contusion, %brain water (BW) was increased in vehicle (black bar, 80.37 ± 0.04%) versus naïve (white bar, 78.31 ± 0.04% naïve, p < 0.001). Glibenclamide treatment (shaded gray bar) did not reduce ipsilateral %BW. (B) At this time point, %BW in the hemisphere contralateral to the contusion had resolved (vehicle 78.45 ± 0.09% vs. naïve 78.26 ± 0.05%, p < 0.24).