Journal: Cell Death & Disease
Article Title: Pasireotide protects mammalian cochlear hair cells from gentamicin ototoxicity by activating the PI3K–Akt pathway
doi: 10.1038/s41419-019-1386-7
Figure Lengend Snippet: a Mouse OCs were treated as described in the Materials and methods section. GM alone had no effect on the relative expression of NfkB, Akt 1 , or Pi3k, while pasireotide up-regulated the expression of all the three genes, which correlated with a significant improvement in cell protection. b To further elucidate the mechanisms by which pasireotide activated the PI3K–Akt survival signaling pathway, we examined the expression of Gab1 , G-protein receptor ( Gpr ), and PTPn7 genes. The relative expression levels of Gab1 , Gpr , and PTPn7 mRNA in untreated (control), GM-treated, and GM + pasireotide-treated murine OCs are shown. GM strongly induced Gab1 and Gpr mRNA. Thus, these two genes are up-regulated in stress situations, such as ischemia or ototoxicity. The reverse effect was seen with PTPn7 mRNA with the pasireotide co-treatment. c Western blots of lysates prepared from murine OCs that were untreated, treated with GM alone, or treated with GM + pasireotide were performed to detect the activation of Akt. Specific antibodies were used for phosphor-PTPB1 (p-PTPB1) and total PTPB1 (t-PTPB1). d Quantification of western blot signals represented by the ratio of p-PTPB1/t-PTPB1 signals for 10 explants per group ( n = 15), including pups of both sexes (*** p < 0.001 by Student’s t test). Values represent the mean ± one standard deviation of three biological replicates. e Schematic representation of the intracellular signaling pathway modulated by SSTRs. After binding to SSTR2 and SSTR5, pasireotide activated different phosphotyrosine phosphatases (PTPs), such as SHP2 or PTPn (PTPn7). Activated PTPn directly interacted with PTPη inducing phosphorylation and tyrosine activation. PTPη dephosphorylates intracellular effectors, such as the PI3K–Akt pathway involved in the protection of hair cells. GM, gentamicin; OCs, organs of Corti
Article Snippet: Hundred micromolar CYN-154806-SSTR2 antagonist (Sigma-Aldrich, Switzerland) and 100 µM BIM 23056-SSTR5 antagonist (Sigma-Aldrich, Switzerland) were added separately or together for 1 h followed by an additional 4 h incubation with pasireotide.
Techniques: Expressing, Western Blot, Activation Assay, Standard Deviation, Binding Assay
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