Figure 3.

Persistent activation of β-cell MT receptor signaling protects against β-cell proteotoxicity. A, Graphical illustration of the experimental work flow. B and C, Cleaved caspase-3, phospho-JNK, and GAPDH (loading control) protein levels in control INS 832/13 cells and in cells transduced at 400 MOI with h-IAPP adenovirus for 48 hours and exposed for the final 12–14 hours to media containing either MT (10 nM) or vehicle (DMSO). The graph represents the quantification of the cleaved form of caspase-3 and JNK phosphorylation at threonine 183 and tyrosine 185 (n = 3–5 independent experiments). Data are expressed as mean ± SEM. *, P < .05. D, Immunoblot detection of carbonyl groups introduced into proteins due to oxidative stress and derivatized to DNP in INS 832/13 cells transduced at 400 MOI with h-IAPP adenovirus for 48 hours and exposed for the final 12–14 hours to media containing either MT (10 nM) or vehicle (DMSO) (a representative example of five independent experiments is shown). DMSO vehicle treatment was administered to all non-MT conditions to correct for potential confounding effects of DMSO, which was used to prepare melatonin solutions.