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Our previous studies showed that the phosphodiesterase-5 (PDE5) inhibitor sildenafil inhibited the microglial activation induced by lipopolysaccharide (LPS). However, whether yonkenafil, a novel PDE5 inhibitor, also inhibits microglial activation and the underlying mechanism of inhibition remain elusive. Here we found that yonkenafil significantly suppressed the production of NO, interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) and the protein expression of inducible NO synthase (iNOS) induced by LPS in microglial cells in a concentration-dependent manner. Knockdown of PDE5 inhibits NO and iNOS protein expression in LPS-stimulated N9 microglia. Moreover, we observed that the nuclear factor-κB (NF-κB) transcriptionally upregulated PDE5 expression, which was inhibited by sildenafil and yonkenafil in LPS-stimulated N9 microglia. Therefore, sildenafil and yonkenafil may exert their inhibitory effects on microglial activation by reducing the expression of PDE5. Furthermore, sildenafil and yonkenafil increased the cyclic guanosine monophosphate (cGMP) level in N9 microglia, and 8-Br-cGMP, an analogue of cGMP, downregulates extracellular signal-regulated kinases 1 and 2 (ERK1/2)/the NF-κB pathway, suggesting that sildenafil and yonkenafil inhibit microglial activation by decreasing PDE5 expression and increasing the cGMP level. Importantly, sildenafil and yonkenafil significantly alleviated the death of SH-SY5Y neuroblastoma cells and primary cortical neurons induced by the conditioned medium from activated microglia. Together, these findings position PDE5 as a potential therapy target for the treatment of neuroinflammation accompanied by microglial activation.

Original publication

DOI

10.1007/s12035-015-9293-0

Type

Journal article

Journal

Mol Neurobiol

Publication Date

05/2016

Volume

53

Pages

2647 - 2658

Keywords

LPS, Microglial activation, NF-κB, PDE5, cGMP, Animals, Cell Line, Cyclic GMP, Cyclic Nucleotide Phosphodiesterases, Type 5, Extracellular Signal-Regulated MAP Kinases, Gene Expression Regulation, Enzymologic, Humans, Inflammation Mediators, Lipopolysaccharides, Mice, Microglia, NF-kappa B, Neurotoxins, Phosphodiesterase Inhibitors, Pyrimidinones, Pyrroles, RNA Interference, RNA, Messenger, Sildenafil Citrate, Up-Regulation