Proceedings of The Physiological Society
King's College London (2011) Proc Physiol Soc 22, PC12
The effects of streptozotocin-induced diabetes on tight junction protein expression in the choroid plexus epithelium and on the physical integrity of the blood-cerebrospinal fluid barrier in rat
F. Safar1, M. Al-Bader1, H. Al-Sarraf1, Z. Redzic1
1. Department of Physiology, Faculty of Medicine, Kuwait University, Kuwait, Kuwait.
It has been shown that streptozotocin (STZ) induced diabetes in rats altered expression of the BBB tight junction (TJ) proteins . This study investigated effects of the STZ-induced diabetes in rat on the expression of the TJ proteins occludin, claudin 1 and 2 in the choroid plexus epithelium (CPE) and on the physical integrity of blood-cerebrospinal fluid barrier (BCSFB). Methods. Diabetes was induced in Sprague-Dawley rats by i.p. injection of STZ, 55 mg/kg; control group (CG) animals received a vehicle. Only animals with blood glucose >17 mM were included in the diabetic group (DG). Animals from the DG groups and CG were used for the study at either 7 or 28 days after the STZ/vehicle injection. At the day of experiment rats were anesthetized with urethane (1.2-1.5 g/kg, i.p.), CSF samples were collected from Cistern Magna and choroid plexuses were collected. The expression of TJ proteins was explored at the transcript level by real-time PCR using hydrolysis probes, with 18S mRNA as an internal control and the CGs as calibrators. The fold change in mRNA expression was calculated as described earlier . The expression of TJ proteins at the protein level was explored by immunoblotting; rat β-actin was used as internal control. The physical integrity of the BCSFB was explored by estimating the CSF/perfusate ratio for [14C]sucrose after 10 min of in situ brain perfusion and the in vivo CSF/serum ratio for albumin. Statistical analysis was done using Student’s t -test. Results. The amount of mRNA for occludin in the DG after 7 days decreased to 64% of the amount in the CG; no significant change in the amount of mRNA for claudins were observed. After 28 days, amount of mRNA for all 3 TJ proteins decreased to <50% of the amount in the CG, (Table 1). No significant change in TJ proteins expression at the protein level, relative to expression of rat β-actin, was detected in DGs. Neither the CSF/perfusate ratio for [14C] sucrose nor the in vivo albumin CSF/serum ratio differed between the DGs and CGs at 7 and 28 days. Conclusion. STZ-induced diabetes has caused a decrease in the amount of occludin mRNA after 7 days and a decrease in the amount of mRNA for all three TJ proteinsa after 28 days. The relative expression of those proteins and the physical integrity of the BCSFB did not change.
Where applicable, experiments conform with Society ethical requirements