Inhibition of Phosphodiesterase 4 by FCPR03 Alleviates Lipopolysaccharide-Induced Depressive-Like Behaviors in Mice: Involvement of p38 and JNK Signaling Pathways.

Inflammatory responses induced by peripheral administration of lipopolysaccharide (LPS) triggers depressive-like behavioral syndrome in rodents. Inhibition of phosphodiesterase 4 (PDE4) produces a robust anti-inflammatory effect in inflammatory cells. Unfortunately, archetypal PDE4 inhibitors cause intolerable gastrointestinal side-effects, such as vomiting and nausea. N-isopropyl-3-(cyclopropylmethoxy)-4-difluoromethoxy benzamide (FCPR03) is a novel, selective PDE4 inhibitor with little, or no, emetic potency. Our previous studies show that FCPR03 is effective in attenuating neuroinflammation in mice treated with LPS. However, whether FCPR03 could exert antidepressant-like effect induced by LPS is largely unknown. In the present study, mice injected intraperitoneally (i.p.) with LPS was established as an in vivo animal model of depression. The antidepressant-like activities of FCPR03 were evaluated using a tail suspension test, forced swimming test, and sucrose preference test. We demonstrated that administration of FCPR03 (1 mg/kg) produced antidepressant-like effects in mice challenged by LPS, as evidenced by decreases in the duration of immobility in the forced swim and tail suspension tests, while no significant changes in locomotor activity were observed. FCPR03 also increased sucrose preference in mice treated with LPS. In addition, treatment with FCPR03 abolished the downregulation of brain-derived neurotrophic factor induced by LPS and decreased the level of corticosterone in plasma. Meanwhile, periphery immune challenge by LPS induced enhanced phosphorylation of p38-mitogen activated protein kinase (p38) and c-Jun N-terminal kinase (JNK) in both the cerebral cortex and hippocampus in mice. Interestingly, treatment with FCPR03 significantly blocked the role of LPS and reduced the levels of phosphorylated p38 and JNK. Collectively, these results indicate that FCPR03 shows antidepressant-like effects in mice challenged by LPS, and the p38/JNK signaling pathway is possibly involved in this process. Our findings suggest that FCPR03 is a potential compound for the prevention or treatment of depression.

The phosphodiesterase-4 inhibitor, FCPR16, attenuates ischemia-reperfusion injury in rats subjected to middle cerebral artery occlusion and reperfusion.

Current phosphodiesterase-4 (PDE4) inhibitors exert beneficial effects in central nervous system diseases via anti-inflammatory and anti-apoptotic properties, but many of them are plagued by side effects like nausea and emesis. FCPR16, a novel PDE4 inhibitor synthesized in our lab, has potential anti-inflammatory property. In the present study, we aimed to investigate the effects of FCPR16 in a rat model of ischemic stroke and evaluate its emetogenic potential. Our results showed that FCPR16 treatment improved neurological function, reduced cerebral infarct volume, and attenuated brain histological changes in rats subjected to middle cerebral artery occlusion and reperfusion (MCAO/R). Furthermore, levels of proinflammatory cytokines tumor necrosis factor α, interleukin-6 and interleukin-1ß were decreased after FCPR16 treatment, as well as the ionized calcium-binding adapter molecule 1 and glial fibrillary acidic protein in MCAO/R rats. TUNEL staining and Western blot results showed that FCPR16 reduced apoptosis and regulated apoptotic-related proteins, with increased level of phosphorylated protein kinase B. Moreover, FCPR16 treatment increased cyclic adenosine monophosphate (cAMP) levels and cAMP-response element binding protein (CREB) phosphorylation in ischemic tissue. In addition, oral administration of 3mg/kg FCPR16 did not cause vomiting in beagle dogs. This study indicates that FCPR16 has protective effects against cerebral ischemia-reperfusion injury through inhibiting inflammation and apoptosis via the cAMP/CREB pathway, while it has low emetogenic potential.

Roflumilast reverses polymicrobial sepsis-induced liver damage by inhibiting inflammation in mice.

Sepsis is a life-threatening syndrome accompanied by an overwhelming inflammatory response and organ dysfunction. Selective targeting of phosphodiesterase 4 (PDE4) is currently being investigated as an effective therapeutic approach for inflammation-associated diseases. Roflumilast is a selective PDE4 inhibitor, used for the treatment of severe chronic obstructive pulmonary disease in clinic. However, its role in the treatment of sepsis-induced liver damage remains unclear. In the present study, we evaluated the effects of roflumilast in mice with cecal ligation and puncture-induced sepsis, and investigated the underlying mechanism. We found that roflumilast treatment improved survival in septic mice by reducing bacterial load locally and systemically, inhibiting the expression of pro-inflammatory cytokines interleukin-6 and tumor necrosis factor alpha, and alleviating liver injury. These effects were associated with the inhibition of nuclear translocation of nuclear factor-kappa B (NF-κB), as well as degradation of NF-κB inhibitory protein alpha. The phosphorylation of p38 mitogen-activated protein kinase (MAPK) was also markedly inhibited by roflumilast. Moreover, roflumilast significantly suppressed the activation of signal transducer and activator of transcription 3 (STAT3) and its upstream Janus kinase 1 and Janus kinase 2. Taken together, these results indicate that roflumilast prevents polymicrobial sepsis likely by suppressing NF-κB, p38 MAPK, and STAT3 pathways.

Novel Phosphodiesterase 4 Inhibitor FCPR03 Alleviates Lipopolysaccharide-Induced Neuroinflammation by Regulation of the cAMP/PKA/CREB Signaling Pathway and NF-κB Inhibition.

Overactivation of microglia contributes to the induction of neuroinflammation, which is highly involved in the pathology of many neurodegenerative diseases. Phosphodiesterase 4 (PDE4) represents a promising therapeutic target for anti-inflammation; however, the dose-limiting side effects, such as nausea and emesis, have impeded their clinic application. FCPR03, a novel selective PDE4 inhibitor synthesized in our laboratory, shows little or no emetic potency; however, the anti-inflammatory activities of FCPR03 in vitro and in vivo and the molecular mechanisms are still not clearly understood. This study was undertaken to delineate the anti-inflammatory effects of FCPR03 both in vitro and in vivo and explore whether these effects are regulated by PDE4-mediated signaling pathway. BV-2 microglial cells stimulated by lipopolysaccharide (LPS) and mice injected i.p. with LPS were established as in vitro and in vivo models of inflammation. Our results showed that FCPR03 dose dependently suppressed the production of tumor necrosis factor α, interleukin-1ß, and iinterleukin-6 in BV-2 microglial cells treated with LPS. The role of FCPR03 in the production of proinflammatory factors was reversed by pretreatment with protein kinase A (PKA) inhibitor H89. In addition, FCPR03 reduced the levels of proinflammatory factors in the hippocampus and cortex of mice injected with LPS. Our results further demonstrated that FCPR03 effectively increased the production of cAMP, promoted cAMP response element binding protein (CREB) phosphorylation, and inhibited nuclear factor κB (NF-κB) activation both in vitro and in vivo. Our findings suggest that FCPR03 inhibits the neuroinflammatory response through the activation of cAMP/PKA/CREB signaling pathway and NF-κB inhibition.

FFPM, a PDE4 inhibitor, reverses learning and memory deficits in APP/PS1 transgenic mice via cAMP/PKA/CREB signaling and anti-inflammatory effects.

Thus far, phosphodiesterase-4 (PDE4) inhibitors have not been approved for application in Alzheimer's disease (AD) in a clinical setting due to severe side effects, such as nausea and vomiting. In this study, we investigated the effect of FFPM, a novel PDE4 inhibitor, on learning and memory abilities, as well as the underlying mechanism in the APP/PS1 mouse model of AD. Pharmacokinetic studies have revealed that FFPM efficiently permeates into the brain, and reached peak values in plasma 2 h after orally dosing. A 3-week treatment with FFPM, at doses of 0.25 mg/kg and 0.5 mg/kg, significantly improved the learning and memory abilities of APP/PS1 transgenic mice in the Morris water maze and the Step-down passive avoidance task. Interestingly, we found that while rolipram (0.5 mg/kg) reduced the duration of the α2 adrenergic receptor-mediated anesthesia induced by xylazine/ketamine, FFPM (0.5 mg/kg) or the vehicle did not have an evident effect. FFPM increased the cAMP, PKA and CREB phosphorylation and BDNF levels, and reduced the NF-κB p65, iNOS, TNF-α and IL-1ß levels in the hippocampi of APP/PS1 trangenic mice, as observed by ELISA and Western blot analysis. Taken together, our data demonstrated that the reversal effect of FFPM on cognitive deficits in APP/PS1 transgenic mice might be related to stimulation of the cAMP/PKA/CREB/BDNF pathway and anti-inflammatory effects. Moreover, FFPM appears to have potential as an effective PDE4 inhibitor in AD treatment with little emetic potential.

Discovery of N-Alkyl Catecholamides as Selective Phosphodiesterase-4 Inhibitors with Anti-neuroinflammation Potential Exhibiting Antidepressant-like Effects at Non-emetic Doses.

Depression involving neuroinflammation is one of the most common disabling and life-threatening psychiatric disorders. Phosphodiesterase 4 (PDE4) inhibitors produce potent antidepressant-like and cognition-enhancing effects. However, their clinical utility is limited by their major side effect of emesis. To obtain more selective PDE4 inhibitors with antidepressant and anti-neuroinflammation potential and less emesis, we designed and synthesized a series of N-alkyl catecholamides by modifying the 4-methoxybenzyl group of our hit compound, FCPE07, with an alkyl side chain. Among these compounds, 10 compounds displayed submicromolar IC50 values in the mid- to low-nanomolar range. Moreover, 4-difluoromethoxybenzamides 10g and 10j, bearing isopropyl groups, exhibited the highest PDE4 inhibitory activities, with IC50 values in the low-nanomolar range and with higher selectivities for PDE4 (approximately 5000-fold and 2100-fold over other PDEs, respectively). Furthermore, compound 10j displayed anti-neuroinflammation potential, promising antidepressant-like effects, and a zero incidence rate of emesis at 0.8 mg/kg within 180 min.

Inhibition of phosphodiesterase-4 reverses the cognitive dysfunction and oxidative stress induced by Aß25-35 in rats.

Phosphodiesterase-4 (PDE4) inhibitors prevent the breakdown of the second messenger cAMP and have been demonstrated to improve learning in several animal models of cognition. In this study, we explored the antioxidative effects of rolipram in Alzheimer's disease (AD) by using bilateral Aß25-35 injection into the hippocampus of rats, which were used as an AD model. Rats received 3 intraperitoneal (i.p.) doses of rolipram (0.1, 0.5 and 1.25 mg/kg) daily after the injection of Aß25-35 for 25 days. Chronic administration of rolipram prevented the memory impairments induced by Aß25-35, as assessed using the passive avoidance test and the Morris water maze test. Furthermore, rolipram significantly reduced the oxidative stress induced by Aß25-35, as evidenced by the decrease in the levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and restored the reduced GSH levels and superoxide dismutase (SOD) activity. Moreover, western blotting and real-time reverse transcription polymerase chain reaction (RT-PCR) analysis showed that rolipram remarkably upregulated thioredoxin (Trx) and inhibited the inducible nitric oxide synthase/nitric oxide (iNOS/NO) pathway in the hippocampus. These results demonstrated that rolipram improved the learning and memory abilities in an Aß25-35-induced AD rat model. The mechanism underlying these effects may be due to the noticeable antioxidative effects of rolipram.

C-Reactive Protein Induces Tau Hyperphosphorylation via GSK3ß Signaling Pathway in SH-SY5Y Cells.

Amyloid plaques and neurofibrillary tangles are the key pathological features of Alzheimer's disease (AD). Studies have shown that C-reactive protein (CRP) increases during inflammatory reactions and, therefore, has been associated with AD. However, there is no published report relating the impact of CRP to the regulation of tau phosphorylation. In the present study, we investigated the effects of CRP on the phosphorylation of tau protein in SH-SY5Y cells. Treatment of cells with CRP (5, 10, 20 µg/ml) resulted in neurotoxicity and apoptosis, as was observed by MTT assay and Hoechst staining, respectively. Western blot analysis showed that CRP, in a time- and concentration-dependent manner, induced the phosphorylation of tau at Ser202 and ser396 in SH-SY5Y cells. Phosphorylation of Akt (Ser473) and GSK3ß (Ser9) were decreased by CRP treatment, whereas phosphorylation of ERK and p38 were not affected. Pharmacological inhibition of GSK3ß reversed the effects induced by CRP, viz., cytotoxicity, apoptosis, and tau phosphorylation. Herein, we present a novel mechanism of cell death following CRP insult, which activates tau hyperphosphorylation by regulating GSK3ß activity. CRP could potentially be used as an important pathological factor for the therapeutic intervention of AD.