Ruboxistaurin hydrochloride (LY 333531 hydrochloride) is an Isozyme-selective inhibitor of protein kinase C (PKC); competitively and reversibly inhibits PKCβI and PKCβII (IC50 values are 4.7 and 5.9 nM respectively). Selective for PKCβ over other PKC isozymes (IC50values are 0.052, 0.25, 0.30, 0.36, 0.60 and >100 μM for PKCη, -δ, -γ, -α, -ε and -ζ respectively). Exhibits selectivity for PKC over other ATP-dependent kinases, including protein kinase A, casein kinase and src).

PKCη:0.052 μM, PKCβ2:5.9 nM, PKCδ:0.25 μM, PKCβ1:4.7 nM, PKCγ:0.3 μM

Ruboxistaurin strikingly decreases the chance of HUVEC survival and the effect of Ruboxistaurin on apoptotic cell death in HUVEC significantly increases compared with the AGEs group. Blockade of PKC-beta up-regulates the expression of Bax and Bad proteins and down-regulates the expression of Bcl-2 protein. Moreover, Ruboxistaurin reduces the ratio of Bcl-2/Bax. Ruboxistaurin can further prompt AGEs-induced endothelial cells apoptosis. The increased expression of Bax, Bad and decreased expression of Bcl-2 and Bcl-2/Bax ratio are associated with the apoptotic process[3].

A significant up-regulation of TGF-b1, Smad2 and Smad3 mRNA expression was observed in diabetic rats, which was alleviated by administration of ruboxistaurin.

HUVECs are seeded into 96-well plates in low glucose DMEM with 10% FBS for 12 h. Afterwards, HUVECs are starved for 12 h and incubated with BSA (200 μg/ml), AGEs (200 μg/ml) and LY333531 (200 nM)+AGEs (200 μg/ml) for 48 h. Then, the medium is replaced with 0.5 mg/ml MTT and at 37 ?C in a 95% air/5% CO2 incubator for 4 h. Finally, the medium containing MTT is aspirated and replaced by dimethyl sulphoxide (DMSO). OD is measured with a Microplate spectrophotometer. AGEs:advanced glycation end products.(Only for Reference)