Aquaporin 9 in rat brain after severe traumatic brain injury

Abstract

Predominantly caused by motor vehicle accidents, the traumatic brain injury (TBI) is the leading cause of death and severe disability among people under the age of 45 in Western industrialized countries 1 . Almost all patients suffer from severe disorder of energy metabolism 2 , ionic dysfunction 3 , and water homeostasis 4 after TBI. Experimental evidences indicate that aquaporin 9 (AQP9), which is one member of the water channel family in brain, can facilitate the flow of water and permeate glycerol, monocarboxylates, and urea through the plasma membrane and it is involved in water homeostasis and neuronal energy metabolism in brain 5 . In brain ischemia models, the studies show that AQP9 may be a helper in the regulation of postischemic edema 6 . Yet, as far as we know, little is known about AQP9 in brain after TBI. The present study was performed to study whether brain AQP9 expression is altered and what are the possible roles of AQP9 in brain after TBI. ABSTRACT Objective: To reveal the expression and possible roles of aquaporin 9 (AQP9) in rat brain, after severe traumatic brain injury (TBI). Methods: Brain water content (BWC), tetrazolium chloride staining, Evans blue staining, immunohistochemistry (IHC), immunofluorescence (IF), western blot, and real-time polymerase chain reaction were used. Results: The BWC reached the first and second (highest) peaks at 6 and 72 hours, and the blood brain barrier (BBB) was severely destroyed at six hours after the TBI. The worst brain ischemia occurred at 72 hours after TBI. Widespread AQP9-positive astrocytes and neurons in the hypothalamus were detected by means of IHC and IF after TBI. The abundance of AQP9 and its mRNA increased after TBI and reached two peaks at 6 and 72 hours, respectively, after TBI. Conclusions: Increased AQP9 might contribute to clearance of excess water and lactate in the early stage of TBI. Widespread AQP9-positive astrocytes might help lactate move into neurons and result in cellular brain edema in the later stage of TBI. AQP9-positive neurons suggest that AQP9 plays a role in energy balance after TBI. METHODS Experimental animalKey words: aquaporin-9, traumatic brain injury, brain edema. RESuMOObjetivo: Revelar a expressão e os possíveis papéis da aquaporina 9 (AQP9) no cérebro de ratos após lesão cerebral traumática (LCT) grave. Métodos: Foram utilizados: determinação do conteúdo cerebral de água, corante cloreto de tetrazólio, corante azul de Evans, imunoistoquímica (IHQ), imunofluorescência (IF), western blot e PCR em tempo real. Resultados: O conteúdo cerebral de água alcançou o primeiro e o segundo (o mais alto) picos após 6 e 72 horas. A função da barreira hematoencefálica se mostrou muito prejudicada após 6 horas da LCT. A pior isquemia cerebral ocorreu após 72 horas da LCT. Astrócitos AQP9 positivos e neurônios no hipotálamo foram detectados difusamente pela IHQ e IF após LCT. A abundância de AQP9 e de sua mRNA aumentou após LCT e alcançou dois picos após 6 e 72 horas, respectivamente, da LCT. Conclusões: AQP9 aumentada pode contr...

Heterogeneity of Astrocytes: From Development to Injury – Single Cell Gene Expression

“…We found the expression of Kcnj10 (encoding the Kir4.1 channel) in the EGFP + cells to be rather constant, while higher levels of Kcnj16 (encoding Kir5.1) transcripts were found in cells from subpopulations A1 and A3. We did not see any correlation between Aqp4 and Kcnj10 expression on the cellular level in any of the subpopulations in agreement with previous data showing the lack of any direct interaction between Kir4.1 and AQP4 [46], [47] and their different regulations of expression [48]. In agreement with recent findings [25], [49] we showed that EGFP + mature cortical astrocytes from P30 and P50 (comprising the B3 subpopulation) express low levels of Grm5, as a result of a significant decrease in Grm5 expression towards astrocytic maturation, and a high level of Grm3.…”

Curcumin attenuates brain edema in mice with intracerebral hemorrhage through inhibition of AQP4 and AQP9 expression

“…One study [30] also found that hypertonicity affected AQP4, but not AQP1 expression, suggesting that AQP1 and AQP4 expression is regulated by different mechanisms. Several studies have shown that acute brain injuries, including ICH, ischemic stroke, and brain trauma, alter AQP4 and AQP9 expression, and that decreased expression or gene knockout of AQP4 and AQP9 ameliorates brain edema and neurological deficits [10,[20][21][22][23][24][25]31] . The level and duration of AQP4 expression was temporally correlated with the degree of brain edema in a middle cerebral artery (MCA) occlusion model.…”

“…AQP9 is not only a water channel; it also facilitates the transfer of several solutes, including glycerol, urea, and monocarboxylate, suggesting that it plays an additional role in energy metabolism [17] . Many studies have shown that AQP1, AQP4 and AQP9 are associated with cerebral edema induced by several types of brain injury, including ICH, subarachnoid hemorrhage, ischemic stroke and brain trauma [10,[20][21][22][23][24][25][26] . However, the relationship between curcumin and AQPs has not been studied in ICH.…”

Inhibition of Myosin Light-Chain Kinase Attenuates Cerebral Edema after Traumatic Brain Injury in Postnatal Mice

“…42 Aquaporins, matrix metalloproteinases, inflammatory mediators, and oxidative stress have all been implicated in the development of the cytotoxic cerebral edema that occurs after TBI. 8,11,[43][44][45][46][47][48] It would be reasonable to think that MLCK plays a role in the development of cytotoxic edema as well as vasogenic edema. The common thread between each of these mechanisms and MLCK is calcium calmodulin; however, how MLCK interacts with any of these pathways after TBI has yet to be determined.…”