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• Treatment with CBD attenuated microglial activation in vitro and in vivo. • CBD enhanced the level of Mfn2 and improved mitochondrial function in microglia. • Mfn2 knockdown abolished the role of CBD in LPS-triggered in vitro and in vivo models. • Mfn2 knockdown abolished the role of CBD in the EAE animal model. Currently, there is increasing attention on the regulatory effects of cannabidiol (CBD) on the inflammatory response and the immune system. However, the mechanisms have not yet been completely revealed. Mitofusin 2 (Mfn2) is a mitochondrial fusion protein involved in the inflammatory response. Here, we investigated whether Mfn2 confers the anti-inflammatory effects of CBD. We found that treatment with CBD decreased the levels of tumor necrosis factor α, interleukin 6, inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and ionized calcium-binding adaptor molecule-1 (Iba1) in lipopolysaccharide (LPS)-challenged microglia. CBD also significantly suppressed the increase in reactive oxygen species (ROS) and the decline of mitochondrial membrane potential in BV-2 cells subjected to LPS. Interestingly, CBD treatment increased the expression of Mfn2, while knockdown of Mfn2 blocked the effect of CBD. By contrast, overexpression of Mfn2 reversed the increase in the levels of iNOS, COX-2, and Iba1 induced by Mfn2 small interfering RNA. In mice challenged with LPS, we found that CBD ameliorated the anxiety responses and cognitive deficits, increased the level of Mfn2, and decreased the expression of Iba1. Since neuro-inflammation and microglial activation are the common events that are observed in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis, we treated EAE mice with CBD. Mice that received CBD showed amelioration of clinical signs, reduced inflammatory response, and increased myelin basic protein level. Most importantly, the adeno-associated virus delivery of short hairpin RNA against Mfn2 reversed the protective effects of CBD. Altogether, these results indicate that Mfn2 is an essential immunomodulator conferring the anti-inflammatory effects of CBD. Our results also shed new light on the mechanisms underlying the protective effects of CBD against inflammatory diseases including multiple sclerosis. [ABSTRACT FROM AUTHOR]

We have previously shown that inhibition of cAMP-specific 3′,5′-cyclic phosphodiesterase 4 (PDE4) protects against cellular toxicity in neuronal cells. Since α-synuclein (α-syn) toxicity contributes to the neurodegeneration of Parkinson's disease (PD). The aim of this study was to explore the effects and mechanisms of PDE4 on α-syn-induced neuronal toxicity. Using mutant human A53T α-syn overexpressed SH-SY5Y cells, we found that PDE4B knockdown reduced cellular apoptosis. Roflupram (ROF, 20 μM), a selective PDE4 inhibitor, produced similar protective effects and restored the morphological alterations of mitochondria. Mechanistic studies identified that α-syn enhanced the phosphorylation of Parkin at Ser131, followed by the decreased mitochondrial translocation of Parkin. Whereas both PDE4B knockdown and PDE4 inhibition by ROF blocked the effects of α-syn on Parkin phosphorylation and mitochondrial translocation. Moreover, PDE4 inhibition reversed the increase in the phosphorylation of p38 mitogen-activated protein kinase (MAPK) induced by α-syn. ROF treatment also reduced the binding of p38 MAPK to Parkin. Consistently, overexpression of PDE4B blocked the roles of ROF on p38 MAPK phosphorylation, Parkin phosphorylation, and the subsequent mitochondrial translocation of parkin. Furthermore, PDE4B overexpression attenuated the protective role of ROF, as evidenced by reduced mitochondria membrane potential and increased cellular apoptosis. Interestingly, ROF failed to suppress α-syn-induced cytotoxicity in the presence of a protein kinase A (PKA) inhibitor H-89. Our findings indicate that PDE4 facilitates α-syn-induced cytotoxicity via the PKA/p38 MAPK/Parkin pathway in SH-SY5Y cells overexpressing A53T mutant α-synuclein. PDE4 inhibition by ROF is a promising strategy for the prevention and treatment of α-syn-induced neurodegeneration. • PDE4 inhibition by roflupram attenuated cellular apoptosis in the α-syn A53T model • Roflupram inhibited the phosphorylation of Parkin and p38 MAPK • Roflupram decreased the interaction between p38 MAPK and Parkin • Roflupram promoted the mitochondrial translocation of Parkin • The protective effects of roflupram were mediated in a PKA-dependent way [ABSTRACT FROM AUTHOR]

• PDE4 inhibition inhibited HMGB1 signaling in the brain of CMUS-exposed mice. • PDE4 inhibition reduced the activation of p38 MAPK and NF-κB. • PDE4 inhibition inhibited the activation of NLRP3 inflammasome. • PDE4 inhibition ameliorated microglial morphology in the hippocampus. Inhibition of phosphodiesterase-4 (PDE4) produces robust anti-inflammatory and antidepressant-like effects in multiple animal models. However, the detailed mechanisms have not been well studied. Receptor for advanced glycation endproducts (RAGE) and inflammasome activation are implicated in the etiology of depression. Here, we aimed to investigate the involvement of RAGE and nucleotide-binding domain (NOD)–like receptor protein 3 (NLRP3) inflammasome in the antidepressant-like effects of PDE4 inhibition in mice. We found that inhibition of PDE4 by roflupram (ROF, 0.5, and 1.0 mg/kg, i.g.) exerted antidepressant-like effects in mice subjected to chronic unpredictable mild stress (CUMS). Simultaneously, ROF inhibited CUMS-induced microglial activation and restored the morphology of microglial cells in the hippocampus, as evidenced by reduced total process length, area, volume, number of branching points, number of terminal points and total sholl intersections of microglia. ROF also decreased the expression of ionized calcium-binding adapter molecule-1 and the level of interleukin-1β. Western blot analysis showed that PDE4 inhibition suppressed the high-mobility group box 1 protein (HMGB1)/RAGE signaling pathway, as the levels of HMGB1, RAGE, toll-like receptor 4, phosphorylated p38 mitogen-activated protein kinase, and nuclear factor κ-B were decreased in both hippocampus and cortex in mice after treatment with ROF. Moreover, ROF also attenuated the protein levels of NLRP3, the apoptosis-associated speck-like protein containing (ASC), and cysteine-requiring aspartate protease-1 (Caspase-1), which are key proteins in the NLRP3-mediated inflammasome signaling pathway. In summary, these results demonstrate that the down-regulation of HMGB1/RAGE signaling pathway and inflammasome suppression possibly contribute to the antidepressant-like effects of PDE4 inhibitors. And, ROF has potential as a candidate drug in the treatment of depression. [ABSTRACT FROM AUTHOR]