Mild hypothermia combined with dexmedetomidine reduced brain, lung, and kidney damage in experimental acute focal ischemic stroke

Abstract

Background: Sedatives and mild hypothermia alone may yield neuroprotective effects in acute ischemic stroke (AIS). However, the impact of this combination is still under investigation. We compared the effects of the combination of mild hypothermia or normothermia with propofol or dexmedetomidine on brain, lung, and kidney in experimental AIS. AIS-induced Wistar rats (n = 30) were randomly assigned, after 24 h, to normothermia or mild hypothermia (32-35 °C) with propofol or dexmedetomidine. Histologic injury score and molecular biomarkers were evaluated not only in brain, but also in lung and kidney. Hemodynamics, ventilatory parameters, and carotid Doppler ultrasonography were analyzed for 60 min.

Results: In brain: (1) hypothermia compared to normothermia, regardless of sedative, decreased tumor necrosis factor (TNF)-α expression and histologic injury score; (2) normothermia + dexmedetomidine reduced TNF-α and histologic injury score compared to normothermia + propofol; (3) hypothermia + dexmedetomidine increased zonula occludens-1 expression compared to normothermia + dexmedetomidine. In lungs: (1) hypothermia + propofol compared to normothermia + propofol reduced TNF-α and histologic injury score; (2) hypothermia + dexmedetomidine compared to normothermia + dexmedetomidine reduced histologic injury score. In kidneys: (1) hypothermia + dexmedetomidine compared to normothermia + dexmedetomidine decreased syndecan expression and histologic injury score; (2) hypothermia + dexmedetomidine compared to hypothermia + propofol decreased histologic injury score.

Conclusions: In experimental AIS, the combination of mild hypothermia with dexmedetomidine reduced brain, lung, and kidney damage.

Keywords: Animal model; Hypothermia; Ischemic stroke; Kidney; Neuroprotection.

Fig. 1

Schematic flowchart of the study design (top) and timeline representation of the experimental protocol (bottom). A Animals were randomly assigned to normothermia (NORMO) or mild hypothermia (HYPO) combined with propofol (PRO) or dexmedetomidine (DEX): NORMO + PRO, HYPO + PRO, NORMO + DEX, HYPO + DEX groups (n = 6, each). B Study timeline from the time of stroke induction to the end of the experimental protocol. BGA blood gas analysis, cCT continuous core temperature, CD carotidal Doppler, cMAP continuous mean arterial pressure, cRT continuous rectal temperature, T0 baseline, T1, T2, and T3 = 15, 30, and 60 min after temperature stabilization

Fig. 2

Real-time polymerase chain reaction analysis of proinflammatory biological markers in the brain perilesional, lung, and kidney tissues. Relative gene expression was calculated as the ratio of average gene expression levels compared with the reference gene (36B4) and expressed as fold change relative to controls (C). In the brain perilesional tissue: interleukin-6 (IL-6), IL-1, intercellular adhesion molecule (ICAM), and zonula occludens-1 (ZO-1); in the lung tissue: IL-6, tumor necrosis factor-α, E-selectin, and ICAM; in the kidney tissue: IL-6, kidney injury molecule-1 (KIM1), ZO-1, and syndecan. Data are presented as box plots of medians and interquartile ranges with 6 animals in each group. Statistical significance was considered for p < 0.0125. DEX dexmedetomidine, HYPO hypothermia, NORMO normothermia, PRO propofol

Fig. 3

A Representative photomicrographs (light microscopy) of brain, lung, and kidney stained with hematoxylin–eosin stain in normothermia propofol (NORMO + PRO), normothermia dexmedetomidine (NORMO + DEX), hypothermia propofol (HYPO + PRO), and hypothermia dexmedetomidine (HYPO + DEX) rats. Decrease in cortex neurons pyroptosis and neuropil edema (A arrowheads and hash, inset) were observed in the HYPO + DEX and HYPO + PRO groups. Decrease in inflammatory thickening of the alveolar septa (E double arrowheads, inset) and renal tubular necrosis (I double asterisks, inset) in the HYPO + DEX and HYPO + PRO groups; more prominent in the NORMO + DEX group. The marked decrease in pyroptosis in cortical neurons (C arrowheads, inset), inflammatory alveolar septa (G double arrowheads, inset), and renal tubular necrosis (K double asterisks, inset) in HYPO + DEX and HYPO + PRO rats (D–L). Magnification × 400; inset × 1000. B: Brain, lung and kidney injury score. Boxes show the interquartile (25–75%) range, whiskers encompass the range (minimum to maximum), and horizontal lines represent median values of six animals/group. DEX dexmedetomidine, HYPO hypothermia, NORMO normothermia, PRO propofol. Histologic injury score in brain, lung and kidney was calculated by multiplying the severity and extent of organ injury (minimum score = 0 and maximum score = 16) and the total was calculated as the sum of each score for apoptosis, edema, inflammation, and necrosis (minimum score = 0 to maximum score = 64)

Fig. 4

Upper panel. Histology of the heart visualized by hematoxylin–eosin staining in normothermia (NORMO), hypothermia (HYPO), propofol (PRO), dexmedetomidine (DEX) rats. Hyalin necrosis of heart fibers (A–D asterisks, inset). Magnification × 400; inset × 1000. Lower panel. Data are expressed as median (interquartile range quartiles). Mann–Whitney test with Bonferroni multiple comparison between groups was adopted. A p level < 0.0125 was considered statistically significant. Points for severity and extent varied between 0 (no severity/extent) to 4 (maximum severity/extent). The heart injury score was calculated by multiplying the severity and extent of injury (minimum score = 0 and maximum score = 16) and was calculated by the sum of each score for apoptosis, edema, inflammation, and necrosis (minimum score = 0 to maximum score = 64). Magnification × 400; inset × 1000