The Effects of Rolipram, a Selective Phosphodiesterase Inhibitor, on Immortalized Schwann Cell Proliferation, AKAP95 and Cyclin D3 Expression

Schwann cells are a vital component of the Peripheral Nervous System and aid in the repair of axons following injury. The regulation of Schwann cell growth in vitro is facilitated by heregulin, a neuron-secreted growth factor, and an unknown mitogen that activates the cyclic adenosine monophosphate (cAMP) pathway. The abundance of intracellular cAMP is regulated by a family of enzymes called phosphodiesterases (PDEs). PDE inhibitors such as rolipram have therapeutic potential in various disorders and function by increasing the levels of intracellular cAMP. A-Kinase anchoring proteins (AKAPs), a family of scaffolding proteins that belong to the cAMP/Protein Kinase A (PKA) pathway are known to bind both PDE and PKA to regulate cAMP concentration in cardiac myocytes. Previous studies have shown that AKAP95, a nuclear AKAP, known for scaffolding cyclins, is essential for Schwann cell growth. Based on these reports, it was hypothesized that increasing the concentration of rolipram would elicit a dose-dependent increase in Schwann cell proliferation by augmenting the expression of AKAP95 and cyclin D3. Immortalized Schwann cells were cultured with no mitogens, 12.5 ng/mL heregulin, 1 µM of forskolin (a pharmacological activator of cAMP), heregulin + forskolin, and various doses of rolipram at 0, 0.5, 1, 5, 10, 25, and 50 µM for 12 or 24 hours. Using the MTT assay, preliminary results indicate that cells incubated for 12 hours and 24 hours exhibited the highest rate of proliferation at a dose of 5µM and 10 µM rolipram, respectively. Meanwhile, immunoblot analysis revealed that in cells treated with heregulin + forskolin, the expression of cyclin D3 and AKAP95 was highest when incubated with 25 µM and 50 µM of rolipram, respectively. These results suggest that increasing the concentration of cAMP by inhibiting phosphodiesterases augments Schwann cell proliferation by amplifying the expression of proteins regulating cell division.https://digitalcommons.misericordia.edu/research_posters2021/1020/thumbnail.jp