Western blot analysis of tight junction proteins ZO-1, claudin-5, and adherens junction protein VE-cadherin from cell lysates of four endothelial cell lines. The cells were lysed with RIPA buffer. 50 μg of total protein was subjected to SDS-PAGE and western blotting analysis for individual markers. Actin was used as loading control. The four cell lines all expressed the adherens junction protein VE-cadherin. The TJ protein ZO-1 was detected in hCMEC/D3, in hBMEC, and at much lower levels in BB19 and TY10 cell lines. Claudin-5 expression was detected in hCMEC/D3, TY10, and at a very low level in hBMEC cells.