Figure 8. Role of opioid receptor in MA-mediated ER stress.

SVGA cells were pre-treated with either 20 μM of nor-BNI, a selective inhibitor for κ-opioid receptor or 10 μM of naltrexone, a general inhibitor for opioid receptor 1 H before the treatment with MA and the effect was observed on the mRNA and protein expressions of BiP and CHOP. A, C. Pre-treatment with nor-BNI reduced the levels of BiP (A) and CHOP (C) mRNA. B, D. Pre-treatment with naltrexone reduced the levels of BiP (B) and CHOP (D) mRNA. E-F. The involvement of opioid receptor in MA-mediated ER stress was assessed by western blotting on PERK, IRE1α, ATF6, BiP and CHOP. Both, nor-BNI (E) and naltrexone (F) reduced the levels of all these markers at variable extents. G. The effect of nor-BNI and naltrexone on MA-mediated cell death was assessed by MTT assay at 48 H after MA treatment. The RNA and protein expressions in all the experiments were normalized with HPRT and GAPDH as housekeeping genes, respectively. The results shown in bar graphs were obtained from at least 3 independent experiments with each treatment performed in triplicates. The bar graphs shown in the figure are represented in mean ± S.E., while the western blots are representative images. The numbers above the blots represent mean intensity of the respective bands. Statistical significance was calculated using one-way ANOVA with multiple comparisons and the values were considered significant if p-value ≤ 0.01 (**).