Somatostatin is involved in the regulation of multiple signaling pathways and affords neuroprotection in response to neurotoxins. In the present study, we investigated the role of Somatostatin-14 (SST) in cell viability and the regulation of phosphorylation of Collapsin Response Mediator Protein 2 (CRMP2) (Ser522) via the blockade of Ca2+ accumulation, along with the inhibition of cyclin-dependent kinase 5 (CDK5) and Calpain activation in differentiated SH-SY5Y cells. Cell Viability and Caspase 3/7 assays suggest that the presence of SST ameliorates mitochondrial stability and cell survival pathways while augmenting pro-apoptotic pathways activated by Aβ. SST inhibits the phosphorylation of CRMP2 at Ser522 site, which is primarily activated by CDK5. Furthermore, SST effectively regulates Ca2+ influx in the presence of Aβ, directly affecting the activity of calpain in differentiated SH-SY5Y cells. We also demonstrated that SSTR2 mediates the protective effects of SST. In conclusion, our results highlight the regulatory role of SST in intracellular Ca2+ homeostasis. The neuroprotective role of SST via axonal regeneration and synaptic integrity is corroborated by regulating changes in CRMP2; however, SST-mediated changes in the blockade of Ca2+ influx, calpain expression, and toxicity did not correlate with CDK5 expression and p35/25 accumulation. To summarize, our findings suggest two independent mechanisms by which SST mediates neuroprotection and confirms the therapeutic implications of SST in AD as well as in other neurodegenerative diseases where the effective regulation of calcium homeostasis is required for a better prognosis.

No abstract

Purpose: Cushing’s disease is associated with significant morbidity, thus additional tumor-directed drugs with the potential to exert antineoplastic effects on corticotroph adenoma cells are desired. The PI3K (phosphoinositide-3-kinase)/AKT (protein kinase B) pathway, which plays regulatory roles in cell survival and proliferation, is activated in pituitary adenomas. The present study evaluated the effects of BKM120 (Buparlisib), an oral PI3K inhibitor, in corticotroph tumor cells. Methods: AtT-20/D16v-F2 mouse pituitary corticotroph tumor cells were treated with increasing concentrations of BKM120 or vehicle. Cell viability was measured using MTS-based assay. Apoptosis was evaluated by Annexin V staining. ACTH levels were measured in the culture supernatants by chemiluminescent immunometric assay. Cell cycle analysis was performed by propidium iodide DNA staining and flow cytometry. Gene expression of cell cycle regulators (Cdkn1b, Rb1, Ccnd1, Cdk4, Cdk2, and Myc) was assessed by qPCR. Protein expression of p27, p70 S6 Kinase, p85 S6 Kinase, and phosphorylated AKT was assessed by Western blot. Results: Treatment with BKM120 decreased AtT-20/D16v-F2 cell proliferation and ACTH levels in the cell culture supernatants. Furthermore, BKM120 treatment diminished the phosphorylation of AKT at residue 473, increased p27 expression and induced a G0/G1 cell cycle arrest. Conclusion:In vitro inhibition of PI3K/AKT pathway by BKM120 resulted in antiproliferative effects on corticotroph tumor cells, decreasing cell viability and ACTH production. These encouraging findings shape the path for further experiments with the inhibition of PI3K/AKT pathway in Cushing’s disease.