Attenuation of TNF production and experimentally induced inflammation by PDE4 inhibitor rolipram is mediated by MAPK phosphatase-1

Mechanism of oxidized phospholipid-related inflammatory response in vascular ageing

Vascular ageing is an important factor in the morbidity and mortality of the elderly. Atherosclerosis is a characteristic disease of vascular ageing, which is closely related to the enhancement of vascular inflammation. Phospholipid oxidation products are important factors in inducing cellular inflammation. Through interactions with vascular cells and immune cells, they regulate intracellular signaling pathways, activate the expression of various cytokines, and affect cell behavior, such as metabolic level, proliferation, apoptosis, etc. Intervention in lipid metabolism and anti-inflammation are the two key pathways of drugs for the treatment of atherosclerosis. This review aims to sort out the signaling pathway of oxidized phospholipids-induced inflammatory factors in vascular cells and immune cells and the mechanism leading to changes in cell behavior, and summarize the therapeutic targets in the inflammatory signaling pathway for the development of atherosclerosis drugs.

MKP-1 Deficiency Exacerbates Skin Fibrosis in a Mouse Model of Scleroderma

Scleroderma is a chronic fibrotic disease, where proinflammatory and profibrotic events precede collagen accumulation. MKP-1 [mitogen-activated protein kinase (MAPK) phosphatase-1] downregulates inflammatory MAPK pathways suppressing inflammation. MKP-1 also supports Th1 polarization, which could shift Th1/Th2 balance away from profibrotic Th2 profile prevalent in scleroderma. In the present study, we investigated the potential protective role of MKP-1 in scleroderma. We utilized bleomycin-induced dermal fibrosis model as a well-characterized experimental model of scleroderma. Dermal fibrosis and collagen deposition as well as the expression of inflammatory and profibrotic mediators were analyzed in the skin samples. Bleomycin-induced dermal thickness and lipodystrophy were increased in MKP-1-deficient mice. MKP-1 deficiency enhanced collagen accumulation and increased expression of collagens, 1A1 and 3A1, in the dermis. Bleomycin-treated skin from MKP-1-deficient mice also showed enhanced expression of inflammatory and profibrotic factors IL-6, TGF-β1, fibronectin-1 and YKL-40, and chemokines MCP-1, MIP-1α and MIP-2, as compared to wild-type mice. The results show, for the first time, that MKP-1 protects from bleomycin-induced dermal fibrosis, suggesting that MKP-1 favorably modifies inflammation and fibrotic processes that drive the pathogenesis of scleroderma. Compounds enhancing the expression or activity of MKP-1 could thus prevent fibrotic processes in scleroderma and possess potential as a novel immunomodulative drug.

TRPA1 as a potential factor and drug target in scleroderma: dermal fibrosis and alternative macrophage activation are attenuated in TRPA1-deficient mice in bleomycin-induced experimental model of scleroderma

BACKGROUND

Systemic sclerosis is a rheumatoid disease best known for its fibrotic skin manifestations called scleroderma. Alternatively activated (M2-type) macrophages are normally involved in the resolution of inflammation and wound healing but also in fibrosing diseases such as scleroderma. TRPA1 is a non-selective cation channel, activation of which causes pain and neurogenic inflammation. In the present study, we investigated the role of TRPA1 in bleomycin-induced skin fibrosis mimicking scleroderma.

METHODS

Wild type and TRPA1-deficient mice were challenged with intradermal bleomycin injections to induce a scleroderma-mimicking disease. Macrophages were investigated in vitro to evaluate the underlying mechanisms.

RESULTS

Bleomycin induced dermal thickening and collagen accumulation in wild type mice and that was significantly attenuated in TRPA1-deficient animals. Accordingly, the expression of collagens 1A1, 1A2, and 3A1 as well as pro-fibrotic factors TGF-beta, CTGF, fibronectin-1 and YKL-40, and M2 macrophage markers Arg1 and MRC1 were lower in TRPA1-deficient than wild type mice. Furthermore, bleomycin was discovered to significantly enhance M2-marker expression particularly in the presence of IL-4 in wild type macrophages in vitro, but not in macrophages harvested from TRPA1-deficient mice. IL-4-induced PPARγ-expression in macrophages was increased by bleomycin, providing a possible mechanism behind the phenomenon.

CONCLUSIONS

In conclusion, the results indicate that interfering TRPA1 attenuates fibrotic and inflammatory responses in bleomycin-induced scleroderma. Therefore, TRPA1-blocking treatment could potentially alleviate M2 macrophage driven diseases like systemic sclerosis and scleroderma.

Salicylate Sodium Suppresses Monocyte Chemoattractant Protein-1 Production by Directly Inhibiting Phosphodiesterase 3B in TNF-α-Stimulated Adipocytes

As a worldwide health issue, obesity is associated with the infiltration of monocytes/macrophages into the adipose tissue causing unresolved inflammation. Monocyte chemoattractant protein-1 (MCP-1) exerts a crucial effect on obesity-related monocytes/macrophages infiltration. Clinically, aspirin and salsalate are beneficial for the treatment of metabolic diseases in which adipose tissue inflammation plays an essential role. Herein, we investigated the effect and precise mechanism of their active metabolite salicylate on TNF-α-elevated MCP-1 in adipocytes. The results indicated that salicylate sodium (SAS) could lower the level of MCP-1 in TNF-α-stimulated adipocytes, which resulted from a previously unrecognized target phosphodiesterase (PDE), 3B (PDE3B), rather than its known targets IKKβ and AMPK. The SAS directly bound to the PDE3B to inactivate it, thus elevating the intracellular cAMP level and activating PKA. Subsequently, the expression of MKP-1 was increased, which led to the decrease in p-EKR and p-p38. Both PDE3B silencing and the pharmacological inhibition of cAMP/PKA compromised the suppressive effect of SAS on MCP-1. In addition to PDE3B, the PDE3A and PDE4B activity was also inhibited by SAS. Our findings identify a previously unrecognized pathway through which SAS is capable of attenuating the inflammation of adipocytes.

Phosphodiesterase-4 Inhibitor Roflumilast-Mediated Protective Effect in Sepsis-Induced Late-Phase Event of Acute Kidney Injury: A Narrative Review

Severe infections such as viral, bacterial, or fungal sepsis can cause an inflammatory response in the host, leading to organ failure and septic shock—phosphodiesterase-4 (PDE-4) inhibiting related agents from suppressing cyclic adenosine monophosphate (cAMP) degradation. Regulatory organisations have approved some substances in this category to reduce the risk of chronic obstructive pulmonary disease (COPD) exacerbations in patients with chronic bronchitis and a history of COPD exacerbations. Roflumilast has been shown to alleviate inflammatory responses, thus regulating airway inflammation. Additionally, roflumilast therapy dramatically enhanced B-cell lymphoma 2 (Bcl-2) expression, an anti-apoptotic marker lowered in septic animals. Previous research has indicated that roflumilast may help reverse sepsis-induced liver and lung harm, but whether it is also effective in reversing sepsis-induced renal impairment remains unknown. Therefore, this review determines whether roflumilast protects against renal dysfunction, inflammatory response, and apoptosis in sepsis-induced kidney damage. Additionally, we discussed the molecular mechanism through which roflumilast exerts its protective effect to uncover a possible treatment agent for sepsis-induced renal impairment.

p38 MAPK Endogenous Inhibition Improves Neurological Deficits in Global Cerebral Ischemia/Reperfusion Mice

Cerebral ischemia/reperfusion (I/R) injury is a complex pathophysiological process that can lead to neurological function damage and the formation of cerebral infarction. The p38 MAPK pathway has attracted considerable attention in cerebral I/R injury (IRI), but little research has been carried out on its direct role in vivo. In this study, to observe the effects of p38 MAPK endogenous inhibition on cerebral IRI, p38 heterozygous knockdown (p38KI/+) mice were used. We hypothesized that p38 signaling might be involved in I/R injury and neurological damage reduction and that neurological behavioral deficits improve when p38 MAPK is inhibited. First, we examined the neurological damage and neurological behavioral deficit effects of I/R injury in WT mice. Cerebral I/R injury was induced by the bilateral common carotid artery occlusion (BCCAO) method. The cerebral infarction area and volume were assessed and analyzed by 2,3,5-triphenyltetrazolium chloride (TTC) staining. p38 MAPK and caspase-3 were detected by western blotting. Neuronal apoptosis was measured using TUNEL staining. Neurological deficits were detected by behavioral testing. Furthermore, to assess whether these neuroprotective effects occurred when p38 MAPK was inhibited, p38 heterozygous knockdown (p38KI/+) mice were used. We found that p38 MAPK endogenous inhibition rescued hippocampal cell apoptosis, reduced ischemic penumbra, and improved neurological behavioral deficits. These findings showed that p38 MAPK endogenous inhibition had a neuroprotective effect on IRI and that p38 MAPK may be a potential therapeutic target for cerebral IRI.

Dexamethasone Attenuates the Expression of MMP-13 in Chondrocytes through MKP-1

Mitogen-activated protein kinase phosphatase-1 (MKP-1) is upregulated in inflammation and reduces the activity of proinflammatory mitogen-activated protein kinases (MAP kinases) by dephosphorylation. MAP kinases are intracellular signaling pathways that mediate the cellular effects of proinflammatory cytokines. In the present study, we investigated the effects of the glucocorticoid dexamethasone on the expression of catabolic enzymes in chondrocytes and tested the hypothesis that these effects are mediated through MKP-1. Dexamethasone was found to significantly attenuate the expression of matrix metalloproteinase (MMP)-13 in human OA chondrocytes as well as in chondrocytes from MKP-1 WT mice, but not in chondrocytes from MKP-1 KO mice. Dexamethasone also increased the expression of MKP-1 in murine and human OA chondrocytes. Furthermore, p38 MAP kinase inhibitors significantly attenuated MMP-13 expression in human OA chondrocytes, while JNK MAP kinase inhibitors had no effect. The results indicate that the effect of dexamethasone on MMP-13 expression in chondrocytes was mediated by an MKP-1 and p38 MAP kinase-dependent manner. These findings, together with previous results, support the concept of MKP-1 as a protective factor in articular chondrocytes in inflammatory conditions and as a potential drug target to treat OA.

Potent PDE4 inhibitor activates AMPK and Sirt1 to induce mitochondrial biogenesis

AMP-activated protein kinase (AMPK) is an evolutionarily conserved energy sensor. Activation of AMPK leads to a number of metabolic benefits, including improved mitochondrial function in skeletal muscle and lowering of serum glucose levels in type-2 diabetes models. However, direct activation of AMPK leads to cardiac enlargement, and an alternative strategy that activates AMPK without affecting the heart is needed. Inhibition of phosphodiesterase 4 (PDE4), which is poorly expressed in the human heart, activates AMPK in other tissues. In a screen to identify novel PDE4 inhibitors, we discovered compound CBU91, which is 5-10 fold more potent than rolipram, the best characterized PDE4 inhibitor. CBU91, like rolipram, is able to activate AMPK and Sirt1 and increase mitochondrial function in myotubes. These findings suggest that activation of AMPK in myotubes is a general property of PDE4 inhibition and that PDE4 inhibition may activate AMPK in metabolically relevant tissues without affecting the heart.

Phosphodiesterase 4 inhibition restrains muscle proteolysis in diabetic rats by activating PKA and EPAC/Akt effectors and inhibiting FoxO factors

AIM

There is growing evidence about the ability of cyclic adenosine monophosphate (cAMP) signaling and nonselective phosphodiesterase (PDE) inhibitors on mitigate muscle atrophy. PDE4 accounts for the major cAMP hydrolyzing activity in skeletal muscles, therefore advances are necessary about the consequences of treatment with PDE4 inhibitors on protein breakdown in atrophied muscles. We postulated that rolipram (selective PDE4 inhibitor) may activate cAMP downstream effectors, inhibiting proteolytic systems in skeletal muscles of diabetic rats.

MAIN METHODS

Streptozotocin-induced diabetic rats were treated with 2 mg/kg rolipram for 3 days. Changes in the levels of components belonging to the proteolytic machineries in soleus and extensor digitorum longus (EDL) muscles were investigated, as well as cAMP effectors.

KEY FINDINGS

Treatment of diabetic rats with rolipram decreased the levels of atrogin-1 and MuRF-1 in soleus and EDL, and reduced the activities of calpains and caspase-3; these findings partially explains the low ubiquitin conjugates levels and the decreased proteasome activity. The inhibition of muscle proteolysis may be occurring due to phosphorylation and inhibition of forkhead box O (FoxO) factors, probably as a consequence of the increased cAMP levels, followed by the activation of PKA and Akt effectors. Akt activation may be associated with the increased levels of exchange protein directly activated by cAMP (EPAC). As a result, rolipram treatment spared muscle mass in diabetic rats.

SIGNIFICANCE

The antiproteolytic responses associated with PDE4 inhibition may be helpful to motivate future investigations about the repositioning of PDE4 inhibitors for the treatment of muscle wasting conditions.

Phosphodiesterase-4 enzyme as a therapeutic target in neurological disorders

Phosphodiesterases (PDE) are a diverse family of enzymes (11 isoforms so far identified) responsible for the degradation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) which are involved in several cellular and biochemical functions. Phosphodiesterase 4 (PDE4) is the major isoform within this group and is highly expressed in the mammalian brain. An inverse association between PDE4 and cAMP levels is the key mechanism in various pathophysiological conditions like airway inflammatory diseases-chronic obstruction pulmonary disease (COPD), asthma, psoriasis, rheumatoid arthritis, and neurological disorders etc. In 2011, roflumilast, a PDE4 inhibitor (PDE4I) was approved for the treatment of COPD. Subsequently, other PDE4 inhibitors (PDE4Is) like apremilast and crisaborole were approved by the Food and Drug Administration (FDA) for psoriasis, atopic dermatitis etc. Due to the adverse effects like unbearable nausea and vomiting, dose intolerance and diarrhoea, PDE4 inhibitors have very less clinical compliance. Efforts are being made to develop allosteric modulation with high specificity to PDE4 isoforms having better efficacy and lesser adverse effects. Interestingly, repositioning PDE4Is towards neurological disorders including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), multiple sclerosis (MS) and sleep disorders, is gaining attention. This review is an attempt to summarize the data on the effects of PDE4 overexpression in neurological disorders and the use of PDE4Is and newer allosteric modulators as therapeutic options. We have also compiled a list of on-going clinical trials on PDE4 inhibitors in neurological disorders.

Protective effects of rolipram on endotoxic cardiac dysfunction via inhibition of the inflammatory response in cardiac fibroblasts

BACKGROUND

Cardiac fibroblasts, regarded as the immunomodulatory hub of the heart, have been thought to play an important role during sepsis-induced cardiomyopathy (SIC). However, the detailed molecular mechanism and targeted therapies for SIC are still lacking. Therefore, we sought to investigate the likely protective effects of rolipram, an anti-inflammatory drug, on lipopolysaccharide (LPS)-stimulated inflammatory responses in cardiac fibroblasts and on cardiac dysfunction in endotoxic mice.

METHOD

Cardiac fibroblasts were isolated and stimulated with 1 μg/ml LPS for 6 h, and 10 μmol/l rolipram was administered for 1 h before LPS stimulation. mRNA levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in fibroblasts and their protein concentrations in supernatant were measured with real-time PCR (rt-PCR) and enzyme-linked immunosorbent assay, respectively. The expression of dual specificity phosphatase 1 (DUSP1), an endogenous negative regulator that inactivates MAPK-mediated inflammatory pathways, was also measured by rt-PCR and western blotting. DUSP1-targeted small interfering RNA (siRNA) was used to examine the specific role of DUSP1. To evaluate the role of rolipram in vivo, an endotoxic mouse model was established by intraperitoneal injection of 15 mg/kg LPS, and 10 mg/kg rolipram was intraperitoneally injected 1 h before LPS injection. mRNA and protein levels of inflammatory cytokines and DUSP1 in heart, inflammatory cell infiltration and cardiac function were all examined at 6 h after LPS injection.

RESULTS

The results showed that LPS could increase the expression and secretion of inflammatory cytokines and decrease the transcription and expression of DUSP1 in cardiac fibroblasts. However, rolipram pretreatment significantly reversed the LPS-induced downregulation of DUSP1 and inhibited LPS-induced upregulation and secretion of TNF-α and IL-6 but not IL-1β. Moreover, DUSP1-targeted siRNA experiments indicated that the protective effect of rolipram on inflammatory response was specific dependent on DUSP1 expression. Moreover, rolipram could further reduce inflammatory cell infiltration scores as shown by pathological analysis and increase the ejection fraction (EF) detected with echocardiography in the hearts of endotoxic mice.

CONCLUSIONS

Rolipram could improve endotoxin-induced cardiac dysfunction by upregulating DUSP1 expression to inhibit the inflammatory response in cardiac fibroblasts, which may be a potential treatment for SIC.

The p38/MKP-1 signaling axis in oral cancer: Impact of tumor-associated macrophages

Oral squamous cell carcinomas (OSCC) constitute over 95% of all head and neck malignancies. As a key component of the tumor microenvironment (TME), chronic inflammation contributes towards the development, progression, and regional metastasis of OSCC. Tumor associated macrophages (TAMs) associated with OSSC promote tumorigenesis through the production of cytokines and pro-inflammatory factors that are critical role in the various steps of malignant transformation, including tumor growth, survival, invasion, angiogenesis, and metastasis. The mitogen-activated protein kinases (MAPKs) can regulate inflammation along with a wide range of cellular processes including cell metabolism, proliferation, motility, apoptosis, survival, differentiation and play a crucial role in cell growth and survival in physiological and pathological processes including innate and adaptive immune responses. Dual specificity MAPK phosphatases (MKPs) deactivates MAPKs. MKPs are considered as an important feedback control mechanism that limits MAPK signaling and subsequent target gene expression. This review outlines the role of MKP-1, the founding member of the MKP family, in OSCC and the TME. Herein, we summarize recent progress in understanding the regulation of p38 MAPK/MKP-1 signaling pathways via TAM-related immune responses in OSCC development, progression and treatment outcomes.

Rolipram Protects Mice from Gram-negative Bacterium Escherichia coli-induced Inflammation and Septic Shock

Sepsis is typically triggered by an overwhelming systemic inflammatory response to pathogens, and may lead to severe organ dysfunction and/or death. Sepsis consequently has a high mortality rate and a high rate of complications for survivors, despite modern medical advances. Therefore, drug identification and validation for the treatment of sepsis is of the utmost importance. As a selective phosphodiesterase-4 inhibitor, rolipram also exhibits the abilities of inhibiting multiple pro-inflammatory cytokines production in macrophages and toxin-induced inflammation in mice. However, this drug has never been studied as a sepsis treatment method. We found that rolipram significantly improves survival in mice challenged with gram-negative bacterium E. coli, CLP, or E. coli derived lipopolysaccharide. We have also found that rolipram inhibits organ damage, pro-inflammatory cytokine production, and intracellular migration of early-stage inflammatory elements. Our results also show that rolipram increases anti-inflammatory cytokine production. The protective effects of rolipram on septic mice may result from inhibition of the MAP kinase and NF-κB signaling pathways. Rolipram may therefore be a potential novel sepsis treatment, one that would bypass the time-consuming and costly drug-discovery process.

Phosphodiesterase 4 inhibitor activates AMPK-SIRT6 pathway to prevent aging-related adipose deposition induced by metabolic disorder

Rolipram is a selective phosphodiesterase 4 (PDE4) inhibitor that exerts a variety of effects, including anti-inflammatory, immunosuppressive, and anti-tumor effects. The aim of this study was to investigate the effect of rolipram on metabolic disorder and its underlying mechanisms. Metabolic disorder was induced in 8-week-old wild type BABL/c mice by administration of D-galactose for 4 weeks. Simultaneously the mice were administered vehicle or rolipram. Alternatively, beginning at 3 or 21 months, the mice were administered db-cAMP for 3 months, with or without a high-fat-diet (HFD) to induce metabolic disorder. In both models, better metabolic function was observed in rolipram-treated mice. Rolipram reduced adipose deposition and inflammation and reserved metabolic disorder. Treatment with rolipram increased the AMPK phosphorylation and SIRT6 levels in the liver and kidney while reducing NF-κB acetylation. In vitro, these effects were blocked by suppression of SIRT6 expression using specific siRNA. Increased cAMP levels reduced excessive adipose deposition, and improved adipose distribution in presenile mice. These findings provide a promising strategy for the treatment of aging-related metabolic dysfunctions and suggest that selective PDE4 inhibitors may be useful agents for the treatment of aging-related metabolic diseases.

Preterm Birth, Inflammation and Infection: New Alternative Strategies for their Prevention

BACKGROUND

Worldwide, the progress in reducing neonatal mortality has been very slow. The rate of preterm birth has increased over the last 20 years in low-income and middle-income countries. Its association with increased mortality and morbidity is based on experimental studies and neonatal outcomes from countries with socioeconomic differences, which have considered implementing alternative healthcare strategies to prevent and reduce preterm births.

METHODS

Currently, there is no widely effective strategy to prevent preterm birth. Pharmacological therapies are directed at inhibiting myometrial contractions to prolong parturition. Some drugs, medicinal plants and microorganisms possess myorelaxant, anti-inflammatory and immunomodulatory properties that have proved useful in preventing preterm birth associated with inflammation and infection.

RESULTS

This review focuses on the existing literature regarding the use of different drugs, medicinal plants, and microorganisms that show promising benefits for the prevention of preterm birth associated with inflammation and infection. New alternative strategies involving the use of PDE-4 inhibitors, medicinal plants and probiotics could have a great impact on improving prenatal and neonatal outcomes and give babies the best start in life, ensuring lifelong health benefits.

CONCLUSION

Despite promising results from well-documented cases, only a small number of these alternative strategies have been studied in clinical trials. The development of new drugs and the use of medicinal plants and probiotics for the treatment and/or prevention of preterm birth is an area of growing interest due to their potential therapeutic benefits in the field of gynecology and obstetrics.

Progesterone and cAMP synergize to inhibit responsiveness of myometrial cells to pro-inflammatory/pro-labor stimuli

Progesterone (P4) acting through the P4 receptor (PR) isoforms, PR-A and PR-B, promotes uterine quiescence for most of pregnancy, in part, by inhibiting the response of myometrial cells to pro-labor inflammatory stimuli. This anti-inflammatory effect is inhibited by phosphorylation of PR-A at serine-344 and -345 (pSer^344/345-PRA). Activation of the cyclic adenosine monophosphate (cAMP) signaling pathway also promotes uterine quiescence and myometrial relaxation. This study examined the cross-talk between P4/PR and cAMP signaling to exert anti-inflammatory actions and control pSer^344/345-PRA generation in myometrial cells. In the hTERT-HM^A/B immortalized human myometrial cell line P4 inhibited responsiveness to interleukin (IL)-1β and forskolin (increases cAMP) and 8-Br-cAMP increased this effect in a concentration-dependent and synergistic manner that was mediated by activation of protein kinase A (PKA). Forskolin also inhibited the generation of pSer^344/345-PRA and expression of key contraction-associated genes. Generation of pSer^344/345-PRA was catalyzed by stress-activated protein kinase/c-Jun NH₂-terminal kinase (SAPK/JNK). Forskolin inhibited pSer^344/345-PRA generation, in part, by increasing the expression of dual specificity protein phosphatase 1 (DUSP1), a phosphatase that inactivates mitogen-activated protein kinases (MAPKs) including SAPK/JNK. P4/PR and forskolin increased DUSP1 expression. The data suggest that P4/PR promotes uterine quiescence via cross-talk and synergy with cAMP/PKA signaling in myometrial cells that involves DUSP1-mediated inhibition of SAPK/JNK activation.

MKP-1 promotes anti-inflammatory M(IL-4/IL-13) macrophage phenotype and mediates the anti-inflammatory effects of glucocorticoids

Macrophage polarization refers to the ability of these cells to adopt different functional phenotypes according to their environment. Mitogen-activated protein kinase phosphatase-1 (MKP-1) is known to regulate the classical lipopolysaccharide (LPS)-induced pro-inflammatory macrophage activation and the inflammatory response. Here, we investigated the effects of MKP-1 on the anti-inflammatory and healing-promoting macrophage phenotype induced by cytokines IL-4 and IL-13 and examined the potential mediator role of MKP-1 in glucocorticoid effects on the two macrophage phenotypes. In MKP-1-deficient macrophages treated with IL-4 and IL-13 to induce the anti-inflammatory phenotype, the expression of phenotypic markers arginase 1, Ym-1 and FGF2 was reduced as compared to wild-type cells. In contrast, LPS-induced expression of the pro-inflammatory factors IL-6 and iNOS was significantly higher in MKP-1-deficient macrophages. Dexamethasone suppressed the pro-inflammatory phenotype and enhanced the anti-inflammatory phenotype. Interestingly, both of these glucocorticoid effects were attenuated in macrophages from MKP-1-deficient mice. Accordingly, dexamethasone increased MKP-1 expression in both LPS- and IL4+13-treated wild-type cells. In conclusion, the findings support MKP-1 as an endogenous mechanism able to shift macrophage activation from the classical pro-inflammatory state towards the anti-inflammatory and healing-promoting phenotype. In addition, MKP-1 was found to mediate the anti-inflammatory effects of dexamethasone in a dualistic manner: by suppressing the pro-inflammatory macrophage activation and by enhancing the healing-promoting macrophage phenotype.

Phosphodiesterase 4 and 7 inhibitors produce protective effects against high glucose-induced neurotoxicity in PC12 cells via modulation of the oxidative stress, apoptosis and inflammation pathways

Diabetic neuropathy (DN) is the most common diabetic complication. It is estimated diabetic population will increase to 592 million by the year 2035. This is while at least 50-60% of all diabetic patients will suffer from neuropathy in their lifetime. Oxidative stress, mitochondrial dysfunction, apoptosis, and inflammation are crucial pathways in development and progression of DN. Since there is also no selective and effective therapeutic agent to prevent or treat high glucose (HG)-induced neuronal cell injury, it is crucial to explore tools by which one can reduce factors related to these pathways. Phosphodiesterase 4 and 7 (PDE 4 and 7) regulate oxidative damage, neurodegenaration, and inflammatory responses through modulation of cyclic adenosine monophosphate (cAMP) level, and thus can be as important drug targets for regulating DN. The aim of this study was to evaluate the protective effects of inhibitors of PDE 4 and 7, named rolipram and BRL5048, on HG-induced neurotoxicity in PC12 cells as an in vitro cellular model for DN and determine the possible mechanisms for theirs effects. We report that the PC12 cells pre-treatment with rolipram (2 μM) and/or BRL5048 (0.2 μM) for 60 min and then exposing the cells to HG (4.5 g/L for 72 h) or normal glucose (NG) (1 g/L for 72 h) condition show: (1) significant attenuation in ROS, MDA and TNF-a levels, Bax/Bcl-2 ratio, expression of caspase 3 and UCP2 proteins; (2) significant increase in viability, GSH/GSSG ratio, MMP and ATP levels. All these data together led us to propose PDE 4 and 7 inhibitors, and specifically, rolipram and BRL5048, as potential drugs candidate to be further studied for the prevention and treatment of DN.

PDE4 inhibitor rolipram inhibits the expression of microsomal prostaglandin E synthase-1 by a mechanism dependent on MAP kinase phosphatase-1

Phosphodiesterase‐4 (PDE4) inhibitors have recently been introduced to the treatment of COPD and psoriatic arthritis. Microsomal prostaglandin E synthase‐1 (mPGES‐1) is an inducible enzyme synthesizing PGE₂, the most abundant prostanoid related to inflammation and inflammatory pain. mPGES‐1 is a potential drug target for novel anti‐inflammatory treatments aiming at an improved safety profile as compared to NSAIDs. Here we investigated the effect of the PDE4 inhibitor rolipram on the expression of mPGES‐1 in macrophages; and a potential mediator role in the process for MAP kinase phosphatase‐1 (MKP‐1) which is an endogenous factor limiting the activity of the proinflammatory MAP kinases p38 and JNK. The expression of mPGES‐1 was decreased, whereas that of MKP‐1 was enhanced by rolipram in wild‐type murine macrophages. Interestingly, rolipram did not reduce mPGES‐1 expression in peritoneal macrophages from MKP‐1‐deficient mice. A reduced phosphorylation of JNK, but not p38 MAP kinase, was specifically associated with the decreased expression of mPGES‐1. Accordingly, mPGES‐1 expression was suppressed by JNK but not p38 inhibitor. These findings underline the significance of the increased MKP‐1 expression and decreased JNK phosphorylation associated with the downregulated expression of mPGES‐1 by PDE4 inhibitors in inflammation.

MKP-1 negative regulates Staphylococcus aureus induced inflammatory responses in Raw264.7 cells: roles of PKA-MKP-1 pathway and enhanced by rolipram

MAP phosphatases (MKP)-1 acts as an important regulator of innate immune response through a mechanism of control and attention both MAPK and NF-κB molecules during bacterial infection. However, the regulatory role of MKP-1 in the interplay between MAPK and NFκB pathway molecules is still not fully understood. In present study, we showed a direct interactions of p38, ERK or IκBα with MKP-1, and demonstrated that MKP-1 was a pivotal feedback control for both MAP kinases and NF-κB pathway in response to S. aureus. In addition, we found that rolipram had anti-inflammatory activity and repressed IκBα activation induced by S. aureus via PKA-MKP-1 pathway. Our report also demonstrated that PKA-cα can directly bind to IκBα upon S. aureus stimulation, which influenced the downstream signaling of PKA pathway, including altered the expression of MKP-1. These results presented a novel mechanism of PKA and IκB pathway, which may be targeted for treating S. aureus infection.

Microsomal Prostaglandin E Synthase-1 Expression in Inflammatory Conditions Is Downregulated by Dexamethasone: Seminal Role of the Regulatory Phosphatase MKP-1

Microsomal prostaglandin E synthase-1 (mPGES-1) is an inducible enzyme situated downstream of cyclo-oxygenase-2, promoting the excessive PGE₂ production in inflammation. Dexamethasone is known to suppress mPGES-1 but the mechanisms regulating mPGES-1 expression remain poorly known. MKP-1 is a phosphatase controlling the proinflammatory MAP kinase pathways p38 and JNK, thus limiting the inflammatory responses. We have now investigated the role of MKP-1 and MAP kinases p38 and JNK in the regulation of mPGES-1 expression by dexamethasone. Dexamethasone increased MKP-1 and decreased mPGES-1 expression in J774 macrophages and in peritoneal macrophages from wild-type but not from MKP-1 deficient mice. Dexamethasone also reduced p38 and JNK phosphorylation along with enhancement of MKP-1, while inhibition of JNK reduced mPGES-1 expression. These findings were also translated to in vivo conditions as dexamethasone downregulated mPGES-1 expression in paw inflammation in wild-type but not in MKP-1 deficient mice. In conclusion, dexamethasone was found to downregulate mPGES-1 expression through enhanced MKP-1 expression and reduced JNK phosphorylation in inflammatory conditions. The results extend the understanding on the regulation of mPGES-1 expression and highlight the potential of MKP-1 as an anti-inflammatory drug target.

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.

The isozyme selective phosphodiesterase-4 inhibitor, ABI-4, attenuates the effects of lipopolysaccharide in human cells and rodent models of peripheral and CNS inflammation

Inhibitors of phosphodiesterase-4 (PDE4) have been approved for the treatment of inflammatory disorders, but are associated with dose-limiting nausea and vomiting. These side effects are hypothesized to be mediated by inhibition of the PDE4D isozyme. Here we demonstrate the anti-inflammatory effects of the novel brain penetrant PDE4D-sparing PDE4 inhibitor, ABI-4. ABI-4 was a potent (EC₅₀∼14nM) inhibitor of lipopolysaccharide (LPS) induced TNF-α release from mouse microglia and human PBMCs. ABI-4 (0.32mg/kg) blocked LPS-induced release of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) in blood and brain of mice. In a rat model of endotoxin induced uveitis, ABI-4 (0.03-0.3mg/kg) demonstrated steroid-like efficacy in preventing leucocyte infiltration of the aqueous humor when administered 4h after LPS. LPS (0.32mg/kg×5days) caused a 30% upregulation of translocator protein (TSPO) binding which was prevented by co-administration of ABI-4 (0.32mg/kg). In a paradigm to assess motivation, LPS (0.32mg/kg) reduced the number of rewards received, whereas the effect was significantly blunted in mice dosed with ABI-4 (P<0.05) or in PDE4B-/- mice. PDE4B was also shown to modulate brain and plasma levels of TNF-α and IL-1β in aged mice. Aged mice dosed chronically with ABI-4 (0.32mg/kg) as well as aged PDE4B-/- mice, had significantly lower levels of TNF-α and IL-1β in brain and plasma relative to vehicle treated or PDE4+/+ mice. Together these data demonstrate that the PDE4D sparing, PDE4 inhibitor, ABI-4 retains potency and efficacy in exerting anti-inflammatory effects. This mechanism warrants further investigation in human disorders involving neuroinflammation.

Mitogen-activated protein kinase phosphatase 1 (MKP-1) in macrophage biology and cardiovascular disease. A redox-regulated master controller of monocyte function and macrophage phenotype

MAPK pathways play a critical role in the activation of monocytes and macrophages by pathogens, signaling molecules and environmental cues and in the regulation of macrophage function and plasticity. MAPK phosphatase 1 (MKP-1) has emerged as the main counter-regulator of MAPK signaling in monocytes and macrophages. Loss of MKP-1 in monocytes and macrophages in response to metabolic stress leads to dysregulation of monocyte adhesion and migration, and gives rise to dysfunctional, proatherogenic monocyte-derived macrophages. Here we review the properties of this redox-regulated dual-specificity MAPK phosphatase and the role of MKP-1 in monocyte and macrophage biology and cardiovascular diseases.

Inhibition of Phosphodiesterase-4 during Pneumococcal Pneumonia Reduces Inflammation and Lung Injury in Mice

Pneumococcal pneumonia is a leading cause of mortality worldwide. The inflammatory response to bacteria is necessary to control infection, but it may also contribute to tissue damage. Phosphodiesterase-4 inhibitors, such as rolipram (ROL), effectively reduce inflammation. Here, we examined the impact of ROL in a pneumococcal pneumonia murine model. Mice were infected intranasally with 10(5)-10(6) CFU of Streptococcus pneumoniae, treated with ROL in a prophylactic or therapeutic schedule in combination, or not, with the antibiotic ceftriaxone. Inflammation and bacteria counts were assessed, and ex vivo phagocytosis assays were performed. ROL treatment during S. pneumoniae infection decreased neutrophil recruitment into lungs and airways and reduced lung injury. Prophylactic ROL treatment also decreased cytokine levels in the airways. Although modulation of inflammation by ROL ameliorated pneumonia, bacteria burden was not reduced. On the other hand, antibiotic therapy reduced bacteria without reducing neutrophil infiltration, cytokine level, or lung injury. Combined ROL and ceftriaxone treatment decreased lethality rates and was more efficient in reducing inflammation, by increasing proresolving protein annexin A1 (AnxA1) expression, and bacterial burden by enhancing phagocytosis. Lack of AnxA1 increased inflammation and lethality induced by pneumococcal infection. These data show that immunomodulatory effects of phosphodiesterase-4 inhibitors are useful during severe pneumococcal pneumonia and suggest their potential benefit as adjunctive therapy during infectious diseases.

Macrophage responses to lipopolysaccharide are modulated by a feedback loop involving prostaglandin E2, dual specificity phosphatase 1 and tristetraprolin

In many different cell types, pro-inflammatory agonists induce the expression of cyclooxygenase 2 (COX-2), an enzyme that catalyzes rate-limiting steps in the conversion of arachidonic acid to a variety of lipid signaling molecules, including prostaglandin E₂ (PGE₂). PGE₂ has key roles in many early inflammatory events, such as the changes of vascular function that promote or facilitate leukocyte recruitment to sites of inflammation. Depending on context, it also exerts many important anti-inflammatory effects, for example increasing the expression of the anti-inflammatory cytokine interleukin 10 (IL-10), and decreasing that of the pro-inflammatory cytokine tumor necrosis factor (TNF). The tight control of both biosynthesis of, and cellular responses to, PGE₂ are critical for the precise orchestration of the initiation and resolution of inflammatory responses. Here we describe evidence of a negative feedback loop, in which PGE₂ augments the expression of dual specificity phosphatase 1, impairs the activity of mitogen-activated protein kinase p38, increases the activity of the mRNA-destabilizing factor tristetraprolin, and thereby inhibits the expression of COX-2. The same feedback mechanism contributes to PGE₂-mediated suppression of TNF release. Engagement of the DUSP1-TTP regulatory axis by PGE₂ is likely to contribute to the switch between initiation and resolution phases of inflammation.

Suppression of cytokine production by glucocorticoids is mediated by MKP-1 in human lung epithelial cells

Mitogen-activated protein kinase phosphatase 1 (MKP-1) expression is induced by inflammatory factors and serves as an endogenous p38 MAPK suppressor to limit inflammatory response. Glucocorticoids are very effective anti-inflammatory drugs and they are used for the treatment of many inflammatory diseases, such as asthma and COPD. We investigated the role of MKP-1 in the inhibition of cytokine production by dexamethasone in human A549 bronchial epithelial cells. We found that dexamethasone increased MKP-1 expression, inhibited p38 MAPK phosphorylation, and suppressed TNF and MIP-3α production in A549 cells. Interestingly, the suppression of p38 MAPK phosphorylation and the inhibition of TNF expression by dexamethasone were attenuated in cells, where MKP-1 expression was silenced by siRNA. In conclusion, these data suggest that dexamethasone increases MKP-1 expression and this results in the suppression of p38 MAPK signaling leading to the inhibition of cytokine production in human bronchial epithelial cells. These results point to the role of MKP-1 as an important factor in the therapeutic effects of glucocorticoids in the treatment of inflammatory lung diseases.

β2-receptor agonists salbutamol and terbutaline attenuated cytokine production by suppressing ERK pathway through cAMP in macrophages

β₂-receptor agonists are used in the treatment of inflammatory obstructive lung diseases asthma and COPD as a symptomatic remedy, but they have been suggested to possess anti-inflammatory properties, also. β₂-receptor activation is considered to lead to the activation of ERK pathway through G-protein- and cAMP-independent mechanisms. In this study, we investigated the effects of β₂-receptor agonists salbutamol and terbutaline on the production of inflammatory factors in macrophages. We found that β₂-receptor agonists inhibited LPS-induced ERK phosphorylation and the production of MCP-1. A chemical cAMP analog 8-Br-cAMP also inhibited ERK phosphorylation and TNF and MCP-1 release. As expected, MAPK/ERK kinase (MEK)1/2 inhibitor PD0325901 inhibited ERK phosphorylation and suppressed both TNF and MCP-1 production. In conclusion, we suggest that β₂-receptor agonists salbutamol and terbutaline inhibit inflammatory gene expression partly by a mechanism dependent on cAMP leading to the inhibition of ERK signaling in macrophages. Observed anti-inflammatory effects of β₂-receptor agonists may contribute to the clinical effects of these drugs.

Understanding how long-acting β2 -adrenoceptor agonists enhance the clinical efficacy of inhaled corticosteroids in asthma - an update

In moderate-to-severe asthma, adding an inhaled long-acting β₂ -adenoceptor agonist (LABA) to an inhaled corticosteroid (ICS) provides better disease control than simply increasing the dose of ICS. Acting on the glucocorticoid receptor (GR, gene NR3C1), ICSs promote anti-inflammatory/anti-asthma gene expression. In vitro, LABAs synergistically enhance the maximal expression of many glucocorticoid-induced genes. Other genes, including dual-specificity phosphatase 1(DUSP1) in human airways smooth muscle (ASM) and epithelial cells, are up-regulated additively by both drug classes. Synergy may also occur for LABA-induced genes, as illustrated by the bronchoprotective gene, regulator of G-protein signalling 2 (RGS2) in ASM. Such effects cannot be produced by either drug alone and may explain the therapeutic efficacy of ICS/LABA combination therapies. While the molecular basis of synergy remains unclear, mechanistic interpretations must accommodate gene-specific regulation. We explore the concept that each glucocorticoid-induced gene is an independent signal transducer optimally activated by a specific, ligand-directed, GR conformation. In addition to explaining partial agonism, this realization provides opportunities to identify novel GR ligands that exhibit gene expression bias. Translating this into improved therapeutic ratios requires consideration of GR density in target tissues and further understanding of gene function. Similarly, the ability of a LABA to interact with a glucocorticoid may be suboptimal due to low β₂ -adrenoceptor density or biased β₂ -adrenoceptor signalling. Strategies to overcome these limitations include adding-on a phosphodiesterase inhibitor and using agonists of other Gs-coupled receptors. In all cases, the rational design of ICS/LABA, and derivative, combination therapies requires functional knowledge of induced (and repressed) genes for therapeutic benefit to be maximized.

Challenges to develop novel anti-inflammatory and analgesic drugs

Chronic inflammatory diseases and persistent pain of different origin represent common medical, social, and economic burden, and their pharmacotherapy is still an unresolved issue. Therefore, there is a great and urgent need to develop anti-inflammatory and analgesic agents with novel mechanisms of action, but it is a very challenging task. The main problem is the relatively large translational gap between the preclinical experimental data and the clinical results due to characteristics of the models, difficulties with the investigational techniques particularly for pain, as well as species differences in the mechanisms. We summarize here the current state-of-the-art medication and related ongoing strategies, and the novel targets with lead molecules under clinical development. The first members of the gold-standard categories, such as nonsteroidal anti-inflammatory drugs, glucocorticoids, and opioids, were introduced decades ago, and since then very few drugs with novel mechanisms of action have been successfully taken to the clinics despite considerable development efforts. Several biologics targeting different key molecules have provided breakthrough in some autoimmune/inflammatory diseases, but they are expensive, only parenterally available, their long-term side effects often limit their administration, and they do not effectively reduce pain. Some kinase inhibitors and phosphodiesterase-4 blockers have recently been introduced as new directions. There are in fact some promising novel approaches at different clinical stages of drug development focusing on transient receptor potential vanilloid 1/ankyrin 1 channel antagonism, inhibition of voltage-gated sodium/calcium channels, several enzymes (kinases, semicarbazide-sensitive amine oxidases, and matrix metalloproteinases), cytokines/chemokines, transcription factors, nerve growth factor, and modulation of several G protein-coupled receptors (cannabinoids, purinoceptors, and neuropeptides). WIREs Nanomed Nanobiotechnol 2017, 9:e1427. doi: 10.1002/wnan.1427 For further resources related to this article, please visit the WIREs website.

Anti-Inflammatory Effects of β2-Receptor Agonists Salbutamol and Terbutaline Are Mediated by MKP-1

Mitogen-activated protein kinase phosphatase 1 (MKP-1) expression is induced by inflammatory factors, and it is an endogenous suppressor of inflammatory response. MKP-1 expression is increased by PDE4 inhibitor rolipram suggesting that it is regulated by cAMP-enhancing compounds. Therefore, we investigated the effect of β₂-receptor agonists on MKP-1 expression and inflammatory response. We found that β₂-receptor agonists salbutamol and terbutaline, as well as 8-Br-cAMP, increased MKP-1 expression. Salbutamol and terbutaline also inhibited p38 MAPK phosphorylation and TNF production in J774 mouse macrophages. Interestingly, salbutamol suppressed carrageenan-induced paw inflammation in wild-type mice, but the effect was attenuated in MKP-1(-/-) mice. In conclusion, these data show that β₂-receptor agonists increase MKP-1 expression, which seems to mediate, at least partly, the observed anti-inflammatory effects of β₂-receptor agonists.

Inhibitors of Phosphodiesterase 4, but Not Phosphodiesterase 3, Increase β2-Agonist-Induced Expression of Antiinflammatory Mitogen-Activated Protein Kinase Phosphatase 1 in Airway Smooth Muscle Cells

β2-agonists are principally used in asthma to provide bronchodilation; however, they also have antiinflammatory properties, due, in part, to their ability to up-regulate mitogen-activated protein kinase phosphatase (MKP) 1 in a cAMP-dependent manner. Phosphodiesterases (PDEs) are attractive targets for potentiating the antiinflammatory response. There are 11 subfamilies of PDE enzymes; among these, inhibition of PDE3 and PDE4 are the main targets for airway smooth muscle (ASM). PDE enzymes are important intracellular regulators that catalyze the breakdown of cyclic adenosine monophosphate (cAMP) and/or 3',5'-cyclic guanosine monophosphate to their inactive forms. Given that MKP-1 is cAMP dependent, and inhibition of PDE acts to increase β2-agonist-induced cAMP, it is possible that the presence of PDE inhibitors may enhance β2-adrenoceptor-mediated responses. We address this herein by comparing the ability of a panel of inhibitors against PDE3 (cilostamide, cilostazol, milrinone) or PDE4 (cilomilast, piclamilast, rolipram) to increase cAMP, MKP-1 mRNA expression, and protein up-regulation in ASM cells induced in response to the β2-agonist formoterol. Our data show that inhibitors of PDE4, but not PDE3, increase β2-agonist-induced cAMP and induce MKP-1 mRNA expression and protein up-regulation. When cAMP was increased, there was a concomitant increase in MKP-1 levels and significant inhibition of TNF-α-induced CXCL8 (IL-8). This result was consistent with all PDE4 inhibitors examined but not for the PDE3 inhibitors. These findings reinforce cAMP-dependent control of MKP-1 expression, and suggest that PDE4 is the predominant PDE isoform responsible for formoterol-induced cAMP breakdown in ASM cells. Our study is the first to demonstrate that PDE4 inhibitors augment antiinflammatory effects of β2-agonists via increased MKP-1 expression in ASM cells.

Vinpocetine reduces carrageenan-induced inflammatory hyperalgesia in mice by inhibiting oxidative stress, cytokine production and NF-κB activation in the paw and spinal cord

Vinpocetine is a safe nootropic agent used for neurological and cerebrovascular diseases. The anti-inflammatory activity of vinpocetine has been shown in cell based assays and animal models, leading to suggestions as to its utility in analgesia. However, the mechanisms regarding its efficacy in inflammatory pain treatment are still not completely understood. Herein, the analgesic effect of vinpocetine and its anti-inflammatory and antioxidant mechanisms were addressed in murine inflammatory pain models. Firstly, we investigated the protective effects of vinpocetine in overt pain-like behavior induced by acetic acid, phenyl-p-benzoquinone (PBQ) and formalin. The intraplantar injection of carrageenan was then used to induce inflammatory hyperalgesia. Mechanical and thermal hyperalgesia were evaluated using the electronic von Frey and the hot plate tests, respectively, with neutrophil recruitment to the paw assessed by a myeloperoxidase activity assay. A number of factors were assessed, both peripherally and in the spinal cord, including: antioxidant capacity, reduced glutathione (GSH) levels, superoxide anion, tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) levels, as well as nuclear factor kappa B (NF-κB) activation. Vinpocetine inhibited the overt pain-like behavior induced by acetic acid, PBQ and formalin (at both phases), as well as the carrageenan-induced mechanical and thermal hyperalgesia and associated neutrophil recruitment. Both peripherally and in the spinal cord, vinpocetine also inhibited: antioxidant capacity and GSH depletion; increased superoxide anion; IL-1β and TNF-α levels; and NF-κB activation. As such, vinpocetine significantly reduces inflammatory pain by targeting oxidative stress, cytokine production and NF-κB activation at both peripheral and spinal cord levels.

Effects of FGF-2 and FGF receptor antagonists on MMP enzymes, aggrecan, and type II collagen in primary human OA chondrocytes

OBJECTIVES

Fibroblast growth factor (FGF)-2 is a member of the FGF family and is found in the synovial fluid of patients with osteoarthritis (OA). The aim of this study was to investigate the effects of FGF-2 on human OA cartilage/chondrocytes by examining the association between FGF-2 and the cartilage degrading enzymes matrix metalloproteinase (MMP)-1 and MMP-13 and the major cartilage matrix components aggrecan and collagen II.

METHOD

Cartilage samples were obtained from 97 OA patients undergoing total knee replacement surgery. Cartilage tissue cultures were conducted and levels of FGF-2, MMP-1, and MMP-13 released into the culture medium were measured by immunoassay. The effects of FGF-2 on the expression of MMP-1, MMP-13, aggrecan, and collagen II were further investigated in cultures of primary human OA chondrocytes.

RESULTS

FGF-2, MMP-1, and MMP-13 were released into the culture medium from cartilage samples obtained from patients with OA. FGF-2 concentrations correlated positively with the concentrations of MMP-1 (r = 0.414, p < 0.001) and MMP-13 (r = 0.362, p < 0.001). FGF-2 also up-regulated the production of MMP-1 and MMP-13, and down-regulated the expression of aggrecan and collagen II, in human OA chondrocyte cultures. Furthermore, FGF receptor antagonists AZD4547 and NVP-BGJ398 down-regulated the expression of MMP-1 and MMP-13 and up-regulated aggrecan and collagen II both in the absence and in the presence of exogenous FGF-2.

CONCLUSIONS

Our results suggest that, in contrast to its growth factor-like effects in some other tissues, FGF-2 induces catabolic effects in human OA cartilage. Moreover, FGF receptor antagonists showed promising beneficial effects on the balance of catabolic and anabolic factors within OA cartilage.

Two faces of inflammation: an immunopharmacological view

Inflammation is a protective response intended to eliminate pathogens and other offending agents which have potential to cause cell injury, as well as malignant and necrotic cells. However, if the inflammatory response is dysregulated or inappropriately focused, it has considerable potential to cause harm and can lead to development of inflammatory diseases such as allergic and autoimmune diseases. Despite the recent success in cytokine-targeted therapies, for example by the use of specific biological drugs, there are still considerable unmet needs in the treatment of inflammatory diseases. Further, recent discoveries in many diseases in addition to the classical inflammatory diseases have revealed inflammation to be a major factor participating in the underlying pathophysiological processes, either through activation of inflammatory cells or through triggering of inflammatory signalling mechanisms in the tissue cells. Examples of such diseases and conditions are many cardiovascular, metabolic and degenerative diseases, as well as cancer, obesity and pain. This brings the immunopharmacological approach into a new perspective in the drug development in very wide therapeutic areas. Immunopharmacology investigates mechanisms of inflammation and potential molecules and targets to treat inflammatory diseases. The current issue of Basic and Clinical Pharmacology and Toxicology focuses on some of the novel inflammatory mechanisms with potential in anti-inflammatory drug development, including kinase pathways, TRP ion channels, eicosanoid system, obesity-related adipokines, autoantibodies against citrullinated proteins, eosinophils, platelets and pathways connecting nervous and immune systems. The MiniReviews are based on lectures given at the symposium "Novel Drugs and Drug Targets to Treat Inflammation" in Ylläs, Finland, in March 2013.

Inhibition of mitogen-activated protein kinase phosphatase-1 (MKP-1) increases experimental stroke injury

BACKGROUND AND PURPOSE

Activation of mitogen-activated protein kinases (MAPKs), particularly c-jun-N-terminal kinases (JNK) and p38 exacerbates stroke injury by provoking pro-apoptotic and pro-inflammatory cellular signaling. MAPK phosphatase-1 (MKP-1) restrains the over-activation of MAPKs via rapid de-phosphorylation of the MAPKs. We therefore examined the role of MKP-1 in stroke and studied its inhibitory effects on MAPKs after experimental stroke.

METHODS

Male mice were subjected to transient middle cerebral artery occlusion (MCAO). MKP-1 knockout (KO) mice and a MKP-1 pharmacological inhibitor were utilized. We utilized flow cytometry, immunohistochemistry (IHC), and Western blots analysis to explore MKP-1 signaling and its effects on apoptosis/inflammation in the brain and specifically in microglia after stroke.

RESULTS

MKP-1 was highly expressed in the nuclei of both neurons and microglia after stroke. MKP-1 genetic deletion exacerbated stroke outcome by increasing infarct, neurological deficits and hemorrhagic transformation. Additionally, delayed treatment of the MKP-1 pharmacological inhibitor worsened stroke outcome in wild type (WT) mice but had no effect in MKP-1 KO mice. Furthermore, MKP-1 deletion led to increased c-jun-N-terminal kinase (JNK) activation and microglial p38 activation after stroke. Finally, MKP-1 deletion or inhibition increased inflammatory and apoptotic response as evidenced by the increased levels of interleukin-6 (IL-6), tumor necrosis factor α (TNFα), ratio of p-c-jun/c-jun and cleaved caspase-3 following ischemia.

CONCLUSIONS

We have demonstrated that MKP-1 signaling is an endogenous protective mechanism in stroke. Our data imply that MKP-1 possesses anti-apoptotic and anti-inflammatory properties by simultaneously controlling the activities of JNK and microglial p38.

Phosphodiesterase type 4 inhibitor rolipram improves survival of spiral ganglion neurons in vitro

Sensorineural deafness is caused by damage of hair cells followed by degeneration of the spiral ganglion neurons and can be moderated by cochlear implants. However, the benefit of the cochlear implant depends on the excitability of the spiral ganglion neurons. Therefore, current research focuses on the identification of agents that will preserve their degeneration. In this project we investigated the neuroprotective effect of Rolipram as a promising agent to improve the viability of the auditory neurons. It is a pharmaceutical agent that acts by selective inhibition of the phosphodiesterase 4 leading to an increase in cyclic AMP. Different studies reported a neuroprotective effect of Rolipram. However, its significance for the survival of SGN has not been reported so far. Thus, we isolated spiral ganglion cells of neonatal rats for cultivation with different Rolipram concentrations and determined the neuronal survival rate. Furthermore, we examined immunocytologically distinct proteins that might be involved in the neuroprotective signalling pathway of Rolipram and determined endogenous BDNF by ELISA. When applied at a concentration of 0.1 nM, Rolipram improved the survival of SGN in vitro. According to previous studies, our immunocytological data showed that Rolipram application induces the phosphorylation and thereby activation of the transcription factor CREB. This activation can be mediated by the cAMP-PKA-signalling pathway as well as via ERK as a part of the MAP-kinase pathway. However, only in cultures pre-treated with BDNF, an endogenous increase of BDNF was detected. We conclude that Rolipram has the potential to improve the vitality of neonatal auditory nerve cells in vitro. Further investigations are necessary to prove the effect of Rolipram in vivo in the adult organism after lesion of the hair cells and insertion of cochlear implants.

Mitogen-activated protein kinase phosphatase 1 as an inflammatory factor and drug target

Mitogen-activated protein kinases (MAPKs) are signaling proteins that are activated through phosphorylation, and they regulate many physiological and pathophysiological processes in cells. Mitogen-activated protein kinase phosphatase 1 (MKP-1) is an inducible nuclear phosphatase that dephosphorylates MAPKs, and thus, it is a negative feedback regulator of MAPK activity. MKP-1 has been found as a key endogenous suppressor of innate immune responses, as well as a regulator of the onset and course of adaptive immune responses. Altered MKP-1 signaling is implicated in chronic inflammatory diseases in man. Interestingly, MKP-1 expression and protein function have been found to be regulated by certain anti-inflammatory drugs, namely by glucocorticoids, antirheumatic gold compounds and PDE4 inhibitors, and MKP-1 has been shown to mediate many of their anti-inflammatory effects. In this Mini Review, we summarize the effect of MKP-1 in the regulation of innate and adaptive immune responses and its role as a potential anti-inflammatory drug target and review recent findings concerning the role of MKP-1 in certain anti-inflammatory drug effects.