Korean J Neurotrauma.  2017 Oct;13(2):68-75. 10.13004/kjnt.2017.13.2.68.

Expression of Aquaporin 1 and 4 in the Choroid Plexus and Brain Parenchyma of Kaolin-Induced Hydrocephalic Rats

• Jeon T
• Park KS
• Park SH
• Hwang JH
• Hwang SK

• KMID: 2394537
• DOI: http://doi.org/10.13004/kjnt.2017.13.2.68

Abstract

OBJECTIVE
Aquaporin (AQP) is a recently discovered protein that regulates water homeostasis. The present study examines changes in AQP 1 and 4 in kaolin induced experimental hydrocephalic rats to elucidate the pathophysiology of water homeostasis in the disease.
METHODS
Hydrocephalus was induced by percutaneous intracisternal injection of kaolin. The brain parenchyma and choroid plexus were obtained at 3, 7, 14 and 30 days after injection. Protein expressions of AQP 1 and 4 were measured by western blot, immunohistochemistry (IHC) and immunofluorescence (IF) stains.
RESULTS
In the choroid plexus of the kaolin-induced hydrocephalus group, AQP 1 expression identified by western blot exhibited sharp decrease in the early stage (55% by the 3rd day and 22% by the 7th day), but indicated a 2.2-fold increase in the later stage (30th day) in comparison with control groups. In the parenchyma, a quantitative measurement of AQP 4 expression revealed variable results on the 3rd and 7th days, but indicated expression 2.1 times higher than the control in the later stage (30th day). In addition, the IHC and IF findings supported the patterns of expression of AQP 1 in the choroid plexus and AQP 4 in the parenchyma.
CONCLUSION
Expression of AQP 1 decreased sharply in the choroid plexus of acute hydrocephalus rats and increased at later stages. Expression of AQP 4 in the brain parenchyma was variable in the early stage in the hydrocephalus group, but was higher than in the control in the later stage. These findings suggest a compensating role of AQPs in water physiology in hydrocephalus.

Keyword

Aquaporins; Choroid plexus; Hydrocephalus; Rats

MeSH Terms

Animals
Aquaporin 1*
Aquaporins
Blotting, Western
Brain*
Choroid Plexus*
Choroid*
Coloring Agents
Fluorescent Antibody Technique
Homeostasis
Hydrocephalus
Immunohistochemistry
Kaolin
Physiology
Rats*
Water
Aquaporin 1
Aquaporins
Coloring Agents
Kaolin
Water

Figure

• 

  FIGURE 1 (A) Morphological changes in ventricle size and choroid plexus (hematoxylin and eosin stain [H & E], ×10) for the control group and (B) 30-day hydrocephalus group after kaolin injection showing enlargement of ventricles representing successful hydrocephalus models.

• 

  FIGURE 2 (A) Expression of aquaporin (AQP) 1 in the choroid plexus of hydrocephalic and control rats in western blot analysis of each experimental animal and (B) changes according to time interval after intracisternal kaolin injection. Expression decreased progressively on day 3 and day 7, but was higher than that of the control at day 14. (n=3, *p<0.05; for detailed p-value; Table 1). GAPDH: glyceraldehyde-3-phosphate dehydrogenase.

• 

  FIGURE 3 Aquaporin (AQP) 1 immunolabeling in the choroid plexus. (A) Immunohistochemical staining and (B) quantificative measurement by positive pixel count of AQP 1 of brain parenchyma revealed expression to be higher than in the control at 3 days and 30 days (n=3, *p<0.05).

• 

  FIGURE 4 (A) Expression of aquaporin (AQP) 4 in the brain parenchyma of hydrocephalic and control rats in western blot analysis of each experimental animal and (B) changes according to time interval after intracisternal kaolin injection. Expression decreased early after injection, but increased to higher levels than that of the control after 14 days (n=3, *p<0.05; for detailed p-value; Table 1). GAPDH: glyceraldehyde-3-phosphate dehydrogenase.

• 

  FIGURE 5 Aquaporin (AQP) 4 immunolabeling in the parenchyme. (A) Immunohistochemical staining and (B) quantificative measurement by positive pixel count of AQP4 of the brain parenchyma revealed expression to be higher than in the control at day 3 and day 30 (n=3, *p<0.05).

• 

  FIGURE 6 (A, B) Immunofluorescence staining of aquaporin (AQP) 1 and AQP 4 in the choroid plexus and brain parenchyma in hydrocephalic rats after 3 days and 30 days. AQP 1 was expressed in the choroid plexus both in control and in hydrocephalic rats, but was not expressed in the brain parenchyma. (C, D) In contrast, AQP 4 was expressed in the brain parenchyma, but not in the choroid plexus.

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