Amelioration of collagen II-induced arthritis in rats by the type IV phosphodiesterase inhibitor Rolipram

Comparative Assessment of the New PDE7 Inhibitor - GRMS-55 and Lisofylline in Animal Models of Immune-Related Disorders: A PK/PD Modeling Approach

Purpose

This study aimed to assess the activity of two phosphodiesterase (PDE) inhibitors, namely GRMS-55 and racemic lisofylline ((±)-LSF)) in vitro and in animal models of immune-mediated disorders.

Methods

Inhibition of human recombinant (hr)PDEs and TNF-alpha release from LPS-stimulated whole rat blood by the studied compounds were assessed in vitro. LPS-induced endotoxemia, concanavalin A (ConA)-induced hepatitis, and collagen-induced arthritis (CIA) animal models were used for in vivo evaluation. The potency of the investigated compounds was evaluated using PK/PD and PK/PD/disease progression modeling.

Results

GRMS-55 is a potent hrPDE7A and hrPDE1B inhibitor, while (±)-LSF most strongly inhibits hrPDE3A and hrPDE4B. GRMS-55 decreased TNF-alpha levels in vivo and CIA progression with IC₅₀ of 1.06 and 0.26 mg/L, while (±)-LSF with IC₅₀ of 5.80 and 1.06 mg/L, respectively. Moreover, GRMS-55 significantly ameliorated symptoms of ConA-induced hepatitis.

Conclusions

PDE4B but not PDE4D inhibition appears to be mainly engaged in anti-inflammatory activity of the studied compounds. GRMS-55 and (±)-LSF seem to be promising candidates for future studies on the treatment of immune-related diseases. The developed PK/PD models may be used to assess the anti-inflammatory and anti-arthritic potency of new compounds for the treatment of rheumatoid arthritis and other inflammatory disorders.

Electronic supplementary material

The online version of this article (10.1007/s11095-019-2727-z) contains supplementary material, which is available to authorized users.

Ciclamilast ameliorates adjuvant-induced arthritis in a rat model

We assessed the effect of a novel and selective phosphodiesterase 4 (PDE4) inhibitor, ciclamilast, on chronic inflammation in adjuvant-induced arthritis (AIA), a rat model of rheumatoid arthritis (RA), and acute inflammation in the rat and mouse model of carrageenan-induced paw edema and peritonitis. Our results showed that daily oral administration of ciclamilast at 1, 3, and 10 mg/kg dose-dependently inhibited the increase in hind paw volume of rats with AIA. The inhibition of paw edema was associated with inhibition of both the production of cytokines such as TNF-α, IL-1β, and IL-6 and cell infiltration assessed in subcutaneous paw tissue. Moreover, there was significantly less tissue destruction in the ciclamilast-treated rats compared to the vehicle-treated rats, as assessed by radiographic analysis and histopathological evaluation. In the two acute inflammation models, ciclamilast inhibited carrageenan-induced paw edema in rats and inflammatory cell migration into the peritoneal cavity in mice in a dose-dependent manner. These results not only suggest that ciclamilast, as a disease-modifying antirheumatic drug (DMARD), can attenuate RA but also provide proof of principle that a PDE4 inhibitor may be useful for the treatment of arthritis.

The selective phosphodiesterase 4 inhibitor roflumilast and phosphodiesterase 3/4 inhibitor pumafentrine reduce clinical score and TNF expression in experimental colitis in mice

OBJECTIVE

The specific inhibition of phosphodiesterase (PDE)4 and dual inhibition of PDE3 and PDE4 has been shown to decrease inflammation by suppression of pro-inflammatory cytokine synthesis. We examined the effect of roflumilast, a selective PDE4 inhibitor marketed for severe COPD, and the investigational compound pumafentrine, a dual PDE3/PDE4 inhibitor, in the preventive dextran sodium sulfate (DSS)-induced colitis model.

METHODS

The clinical score, colon length, histologic score and colon cytokine production from mice with DSS-induced colitis (3.5% DSS in drinking water for 11 days) receiving either roflumilast (1 or 5 mg/kg body weight/d p.o.) or pumafentrine (1.5 or 5 mg/kg/d p.o.) were determined and compared to vehicle treated control mice. In the pumafentrine-treated animals, splenocytes were analyzed for interferon-γ (IFNγ) production and CD69 expression.

RESULTS

Roflumilast treatment resulted in dose-dependent improvements of clinical score (weight loss, stool consistency and bleeding), colon length, and local tumor necrosis factor-α (TNFα) production in the colonic tissue. These findings, however, were not associated with an improvement of the histologic score. Administration of pumafentrine at 5 mg/kg/d alleviated the clinical score, the colon length shortening, and local TNFα production. In vitro stimulated splenocytes after in vivo treatment with pumafentrine showed a significantly lower state of activation and production of IFNγ compared to no treatment in vivo.

CONCLUSIONS

These series of experiments document the ameliorating effect of roflumilast and pumafentrine on the clinical score and TNF expression of experimental colitis in mice.

Paeoniflorin inhibits function of synoviocytes pretreated by rIL-1α and regulates EP4 receptor expression

ETHNOPHARMACOLOGICAL RELEVANCE

To investigate the effect of the Paeoniflorin (Pae), a main active component of total glucosides of paeony (TGP) extracted from the root of Paeonia lactiflora, on regulation of synoviocytes cultured from rats collagen-induced arthritis (CIA) in vitro.

MATERIALS AND METHODS

CIA was induced in male Sprague-Dawley rats immunized with chicken type II collagen (CCII) in Freund's complete adjuvant. The levels of interleukin-1 (IL-1), tumor necrosis factor α (TNF-α), prostaglandin E(2) (PGE(2)) and cyclic adenosine monophosphate (cAMP) were measured by radioimmunoassay. The proliferation responses was determined by the 3-(4,5-2dimethylthiazal-2yl) 2,5-diphenyltetrazoliumbromide (MTT) assay. Expression of E-prostanoid (EP(4)) receptor was detected by Western blotting technique.

RESULTS

Treatment of Pae (2.5, 12.5, 62.5 μg/ml) significantly decreased the production of IL-1 and TNF-α. Recombinant interleukin-1 (rIL-1α) (10 ng/ml) apparently stimulated synoviocyte, thymocyte and splenocyte proliferation, and Pae (12.5, 62.5 μg/ml) inhibited abnormal proliferation responses stimulated by rIL-1α. Moreover, rIL-1α time- and concentration-dependently increased production of PGE(2). The production of PGE(2) produced by synoviocytes from CIA rats significantly inhibited by administration of Pae (12.5, 62.5 μg/ml). rIL-1α (10 ng/ml) decreased cAMP of synoviocytes cells treated for 24h. Similarly rIL-1α (0.1, 1, 10 ng/ml) induced a concentration-dependent decrease in the production of cAMP at 24h. Pae (12.5, 62.5 μg/ml) increased the production of cAMP in synoviocytes. The immunoblot, Pae (12.5, 62.5 μg/ml) apparently increased the expression of EP(4) receptor in synoviocytes stimulated by rIL-1α (10 ng/ml).

CONCLUSIONS

The present study indicates that Pae might exert its anti-inflammatory effects through suppressing synoviocytes function and regulating immune cells responses in CIA rats, which might be associated with its ability to up-regulate the E-prostanoid (EP(4)) receptor protein expression and modulate intracellular cAMP level.

[New biologics and orally available compounds. What is still in the pipeline?]

Biologics have revolutionized the treatment of inflammatory joint disease in the last decade. By precisely targeting and inhibiting inflammatory cytokines as well as the blockade of cells centrally integrated in the immune system, inhibition of inflammation has become possible which had been unthinkable before. The medical need to improve our current approach with biologics even more is based on three observations: (1) even though the clinical effect of a given biologic is evident in the majority of patients, not all show a satisfactory response, (2) the blockade of important mediators of the immune system bears the risk of infection and potentially malignant events and (3) all current biologics need to be administered parenterally. The present review describes several innovative biologics and low molecular weight compounds which are currently being investigated in clinical trials in patients suffering from inflammatory rheumatic conditions. Some of them may become a part of our growing armamentarium to treat these diseases which still represent a major burden to the patients and society.

Enhancement of the anti-inflammatory and anti-arthritic effects of theophylline by a low dose of a nitric oxide donor or non-specific nitric oxide synthase inhibitor

BACKGROUND AND PURPOSE

Although there are many new specific phosphodiesterase inhibitors with anti-inflammatory activity, none have yet reached the market because of their low therapeutic efficacy. Our study was aimed to evaluate the anti-inflammatory and anti-arthritic effect of an established phosphodiesterase inhibitor, theophylline, and to investigate the effect of the nitric oxide (NO) donor, sodium nitroprusside (SNP) or NO synthase inhibitor, L-N(G)-monomethyl arginine (L-NMMA) on its actions.

EXPERIMENTAL APPROACH

The effects of theophylline alone and combined with SNP or L-NMMA on the pathogenesis of adjuvant-induced arthritis in rats were evaluated.

KEY RESULTS

Prophylactic or therapeutic doses of theophylline significantly ameliorated the pathogenesis of adjuvant arthritis in rats as evidenced by a significant decrease in the arthritis index, hind paws volume, ankle joint diameter, fever, body weight loss and hyperalgesia in a dose-dependent manner. Inflammatory cellular infiltrate in synovium of ankle joint and pannus formation were also markedly inhibited. Interleukin-10 (IL-10) levels were significantly increased in arthritic rats given theophylline alone or in combination with either SNP or L-NMMA. Co-administration of a low dose of SNP or L-NMMA enhanced significantly the anti-inflammatory and anti-arthritic effect of theophylline. In contrast, a high dose of SNP counteracted the anti-inflammatory and anti-arthritic effects of theophylline.

CONCLUSIONS AND IMPLICATION

These findings confirm the anti-inflammatory and anti-arthritic activities of theophylline and suggest a new approach to enhance the anti-inflammatory and anti-arthritic effects of theophylline would be to administer it in combination with a low dose of a NO donor or a non-specific NO synthase inhibitor.

Phosphodiesterase inhibitors in the management of autoimmune disease

Phophodiesterases inhibitors (PDEis) act by inhibiting the catabolism of cyclic nucleotides, cAMP and cGMP, which are ubiquitously expressed in cells of the immune system. Increased levels of cAMP and/or cGMP have been reported to decrease the activity of pro-inflammatory TH1 cells, attenuate experimental autoimmune encephalomyelitis and experimental arthritis. PDE5i like Sildenafil improves endothelial dysfunction and vascular remodelling in patients with pulmonary artery hypertension and refractory secondary Raynaud's phenomenon, with a potential to cause disease modification in the former. Studies in animal models of fibrosis suggest that these drugs have anti-fibrotic effect and may be potentially useful in conditions like scleroderma. They also have been shown to have renoprotective effect in animal models. The emerging trends make it necessary to exploit the full therapeutic potential of this class of drugs in various autoimmune diseases like rheumatoid arthritis, scleroderma, profibrotic conditions and PAH.

Treatment with the phosphodiesterase type-4 inhibitor rolipram fails to inhibit blood--brain barrier disruption in multiple sclerosis

Rolipram, a prototypic phosphodiesterase-4 inhibitor, is highly effective in suppressing Th1 autoimmunity in multiple animal models, including experimental autoimmune encephalomyelitis. In addition, rolipram has been extensively studied as a potential neuroprotective agent. Based on its anti-inflammatory activity, we tested the efficacy of rolipram in suppressing inflammatory disease activity in multiple sclerosis in a proof-of-principle phase I/II open-label clinical trial. Enrolled MS patients were evaluated by monthly MRI and clinical examinations during 3 months (four MRIs) of pretreatment baseline and 8 months of rolipram therapy. The primary outcome was a change in contrast-enhanced lesions between baseline and the last 4 months of rolipram therapy. Previously defined biomarkers of rolipram-mediated immunomodulation were evaluated during the study. The trial was stopped prematurely because the drug was poorly tolerated and because of safety concerns: we observed an increase, rather than decrease, in the brain inflammatory activity measured by contrast-enhanced lesions on brain MRI. At the administered doses rolipram was active in vivo as documented by immunological assays. We conclude that the reasons underlying the discrepancy between the therapeutic efficacy of rolipram in experimental autoimmune encephalomyelitis versus multiple sclerosis are at present not clear.

Gene expression profiling in neutrophils from children with polyarticular juvenile idiopathic arthritis

OBJECTIVE

We have previously reported a defect in neutrophil activation in children with polyarticular juvenile idiopathic arthritis (JIA). The current study was undertaken to determine whether gene expression abnormalities persist in JIA in remission and to use systems biology analysis to elucidate pathologic pathways in polyarticular JIA.

METHODS

We performed gene expression profiling on neutrophils from children with polyarticular JIA. Children were grouped according to disease status. We studied 14 children with active disease who were taking medication, 8 children with clinical remission of disease who were taking medication (CRM status), and 6 children with clinical remission of disease who were not taking medication (CR status). We also studied 13 healthy children whose age ranges overlapped those of the patients.

RESULTS

Neutrophil abnormalities persisted in children with polyarticular JIA even after disease remission was achieved. Children with active disease and those with CRM status showed no differences in expression of specific genes, although they could be separated on cluster analysis. A comparison of children with CR status and healthy control children revealed networks of pro- and antiinflammatory genes that suggested that remission is a state of homeostasis and balance rather than a return to normal immune function. Furthermore, gene overexpression in patients with CR status supports the hypothesis that neutrophils play a role in regulating adaptive immunity in this disease.

CONCLUSION

Neutrophil gene profiling in polyarticular JIA suggests important roles for neutrophils in disease pathogenesis. These findings suggest the presence of complex interactions between innate and adaptive immunity, that are not easily modeled in conventional, linear, reductionist systems.

Effects and mechanisms of total glucosides of paeony on synoviocytes activities in rat collagen-induced arthritis

The aim of the study was to investigate the effects of TGP, an active compound extracted from the roots of Paeonia lactiflora Pall, on the activities of synoviocytes in rats with collagen-induced arthritis (CIA) and its possible mechanisms. CIA was induced in male Sprague-Dawley (SD) rats immunized with chicken type II collagen (CII) in Freund's complete adjuvant (FCA). Synoviocytes proliferation was determined by 3-(4, 5-2dimethylthiazal-2yl) 2, 5-diphenyltetrazoliumbromide (MTT) assay. Tumor necrosis factor alpha (TNF-alpha), interleukin-1 (IL-1), prostaglandin E(2) (PGE(2)) and cyclic adenosine monophosphate (cAMP) levels in synoviocytes were measured by radioimmunoassay (RIA). E-prostanoid (EP)(2) and EP(4) receptors were analyzed by Western blot analysis. The results showed that TGP significantly inhibited the proliferation of synoviocytes, decreased the production of IL-1, TNF-alpha and PGE(2) and elevated the levels of cAMP. Further study showed that TGP could up-regulate the expression of EP(2) and EP(4). These results indicated that TGP might exert its anti-inflammatory effects through inhibiting the production of pro-inflammatory mediators in synoviocytes of CIA rats, which might be associated with its ability to regulate cAMP-dependent EP(2)/EP(4)-mediated pathway.

Synthesis of pyrrolo[2,3-d]pyridazinones as potent, subtype selective PDE4 inhibitors

A series of pyrrolo [2,3-d]pyridazinones was synthesized and tested for their inhibitory activity on PDE4 subtypes A, B and D and selectivity toward Rolipram high affinity binding site (HARBS). New agents with interesting profile were reported; in particular compound 9e showed a good PDE4 subtype selectivity, being 8 times more potent (IC50 = 0.32 microM) for PDE4B (anti-inflammatory) than for PDE4D (IC50 = 2.5 microM), generally considered the subtype responsible for emesis. Moreover the ratio HARBS/PDE4B was particularly favourable for 9e (147), suggesting that the best arranged groups around the pyrrolopyridazinone core are an isopropyl at position-1, an ethoxycarbonyl at position-2, together with an ethyl group at position-6. For compounds 8 and 15a the ability to inhibit TNFalpha production in PBMC was evaluated and the results are consistent with their PDE4 inhibitory activity.

Amelioration of collagen-induced arthritis in mice by a novel phosphodiesterase 7 and 4 dual inhibitor, YM-393059

YM-393059 is a novel phosphodiesterase (PDE) 7 and PDE4 dual inhibitor that inhibits PDE7A with high potency (IC50=14 nM) and PDE4 with moderate potency (IC50=630 nM). It inhibits lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha production in mice with an ED50 value of 2.1 mg/kg [Yamamoto, S., Sugahara, S., Naito, R., Ichikawa, A., Ikeda, K., Yamada, T., Shimizu, Y., 2006. The effects of a novel phosphodiesterase 7A and -4 dual inhibitor, YM-393059, on T-cell-related cytokine production in vitro and in vivo. Eur. J. Pharmacol. 541, 106-114.]. In this study, we investigated the therapeutic potential of YM-393059 for the treatment of rheumatoid arthritis in several animal models. YM-393059 was found to inhibit LPS-induced interleukin (IL)-1beta production in mice with an ED50 value of 16.6 mg/kg, but it had only a slight effect on IL-6 production. YM-393059 and cyclosporine significantly suppressed arthritis development at doses of 30-100 mg/kg and 20 mg/kg, respectively, in the mice collagen-induced arthritis model. YM-393059 (100 mg/kg) significantly inhibited increases in the serum immunoglobulin G level that occurred in response to autoantigenic collagen in arthritic mice, whereas cyclosporine (20 mg/kg) did not. In contrast, cyclosporine completely suppressed the acute rejection of cardiac allografts in rats, whereas YM-393059 did not, even at a dose of 100 mg/kg. YM-393059 potently inhibited proinflammatory cytokine production and selectively suppressed the response to the autoantigen without affecting the response to alloantigens. These results suggest that YM-393059 is an attractive compound for the treatment of autoimmune disorders such as rheumatoid arthritis.

Analysing the effect of novel therapies on cytokine expression in experimental arthritis

Type II collagen-induced arthritis (CIA) is an animal model of rheumatoid arthritis that has been used extensively to address questions of disease pathogenesis and to validate novel therapeutic targets. Susceptibility to CIA is strongly associated with major histocompatibility complex class II genes, and the development of arthritis is accompanied by a robust T- and B-cell response to type II collagen. The main pathological features of CIA include proliferative synovitis with infiltration of inflammatory cells, pannus formation, cartilage degradation, erosion of bone and fibrosis. Pro-inflammatory cytokines, such as tumour necrosis factor alpha and interleukin-1beta, are expressed in the arthritic joints in both murine CIA and human rheumatoid arthritis, and blockade of these molecules results in amelioration of disease. Hence, there is a great deal of interest in the development of small-molecular-weight inhibitors of pro-inflammatory cytokines. There is also interest in the development and testing of drugs with the capacity to modulate the immune pathways involved in driving the inflammatory response in arthritis. For these reasons, there is a need to monitor the effect of novel treatments on cytokine expression in vivo. In this review, we outline the various techniques used to detect cytokines in experimental arthritis and describe how these techniques have been used to quantify changes in cytokine expression following therapeutic intervention.

Selective inhibition of phosphodiesterase-4 ameliorates chronic colitis and prevents intestinal fibrosis

The phosphodiesterase-4 (PDE4) inhibitors may be an important target in the treatment of several inflammatory conditions. The anti-inflammatory effect of PDE4 inhibitors bears similarities with that of steroids, without interfering with the hypophysary-adrenal-axis. We compared the effect of rolipram, a selective PDE4 inhibitor, with steroids on the clinical course of experimental colitis induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS). Three groups of rats (n = 20) received TNBS. One group received methylprednisolone from day 7, another group received rolipram from the same day, and control group received no further treatment. On days 14 and 21 after TNBS instillation, sets of 10 rats underwent colonic dialysis to measure eicosanoid release. Colonic lesions were blindly scored, and colons were homogenized for quantification of myeloperoxidase (MPO) activity and collagen content. Concentration of tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta1 (TGF-beta1) in colonic tissue was also measured. Both treatments reduced significantly the eicosanoid release and MPO activity. On day 14, both rolipram and methylprednisolone significantly reduced TNF-alpha content, but TGF-beta1 was only inhibited by rolipram. On day 21, lesion scores and collagen content were significantly reduced only in rolipram-treated group. In conclusion, PDE4 inhibition by rolipram markedly ameliorates the course of chronic colitis and it is superior to methylprednisolone in preventing late collagen deposition.

The therapeutic potential of PDE4 inhibitors

Phosphodiesterase enzymes are responsible for the inactivation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Phosphodiesterase 4 (PDE4) is a cAMP specific phosphodiesterase expressed in inflammatory cells such as eosinophils. Inhibition of PDE4 results in an elevation of cAMP in these cells, which in turn downregulates the inflammatory response. The anti-inflammatory effects of PDE4 inhibitors have been well documented both in vitro and in vivo in a variety of animal models. The potential use of PDE4 inhibitors as anti-inflammatory agents for the treatment of asthma and other inflammatory disorders has received considerable attention from the pharmaceutical industry, but to date, there are no selective PDE4 inhibitors on the market. Early PDE4 inhibitors, typified by rolipram, suffered from dose-limiting side effects, including nausea and emesis, which severely restricted their therapeutic utility. Second generation compounds, including CDP840 and SB207499 (Ariflo), have been identified with reduced side effect liability. Recent evidence suggests a correlation between side effects and the ability of compounds to bind at the so-called high affinity rolipram binding site (HPDE), whilst beneficial effects appear to correlate with binding at the catalytic site. A number of companies are actively pursuing compounds which exhibit improved affinity for the catalytic site and reduced affinity for the HPDE, in the expectation that this will provide compounds with an improved therapeutic index.

Protection against doxorubicin cardiomyopathy in rats: role of phosphodiesterase inhibitors type 4

Selective cardiotoxicity of doxorubicin (DOX) remains a significant and dose-limiting clinical problem. The mechanisms implicated are not yet fully defined but may involve the production of reactive oxygen species or expression of cytokines. Although patients with advanced congestive heart failure express elevated circulating levels of tumour necrosis factor-alpha (TNFalpha), little is known about the prognostic importance and regulation of TNF in the heart in cardiac disease states. Here we tested whether the expression of TNFalpha, along with oxidative stress, is associated with the development of DOX-induced cardiomyopathy (DOX-CM) and whether concurrent treatment with taurine (Taur), an antioxidant, or rolipram (Rolp), a TNFalpha inhibitor, offer a certain protection against DOX cardiotoxic properties. DOX (cumulative dose, 12 mg kg(-1)) was administered to rats in six equal (intraperitoneal) injections over a period of 6 weeks. Cardiomyopathy was evident by myocardial cell damage, which was characterized by a dense indented nucleus with peripheral heterochromatin condensation and distorted mitochondria, as well as significant increase in serum levels of creatine kinase and lactate dehydrogenase. DOX also induced an increment (P<0.001) in serum TNF and plasma nitric oxide levels. The extent of left ventricular (LV) superoxide anion, lipid peroxide measured as malondialdehyde, catalase and calcium content were markedly elevated, whereas superoxide dismutase, total and non-protein-bound thiol were dramatically decreased in DOX-treated rats. Exaggeration of DOX-CM was achieved by intraperitoneal injection of lipopolysaccharide (LPS) (1 mg kg(-1)) 18 h before sampling and evaluated by highly significant increase in heart enzymes (P<0.001), oxidative stress biomarkers and TNFalpha production. Pre- and co-treatment of DOX or DOX-LPS rats with Taur (1% daily supplemented in drinking water, 10 days before and concurrent with DOX) or Rolp (3 mg kg(-1), intraperitoneally, one dose before DOX administration then every 2 weeks throughout the experimental period) ameliorated the deleterious effect of both DOX and LPS on the aforementioned parameters. Meanwhile, it is noteworthy that Rolp exhibited a more preferable effect on serum TNFalpha level. Taur and rolipram also restored the myocardial apoptosis induced by DOX. In conclusion, a cumulative dose of DOX affected free radical and TNFalpha production in the heart of an experimental cardiomyopathy animal model. The current results suggest that down-regulation of these radicals and cytokines could be maintained by using the free radical scavenger Taur or, more favourably, the TNFalpha inhibitor Rolp.

Impact of cAMP on the T-cell response to type II collagen

There is considerable interest in the possible use of cAMP-elevating agents in the treatment of autoimmune diseases such as rheumatoid arthritis. The objective of this study was to evaluate the impact of different cAMP-elevating agents on the T-cell response to type II collagen within the context of collagen-induced arthritis, a murine model of rheumatoid arthritis. Spleen cells or lymph node cells from type-II-collagen-immunized DBA/1 mice were cultured in the presence of type II collagen plus one of five different cAMP-elevating agents: rolipram, forskolin, prostaglandin E2, 8-bromo-cAMP, or cholera toxin. Levels of interferon-gamma (IFN-gamma), interleukin-4 (IL-4) and IL-5 were measured in culture supernatants by enzyme-linked immunosorbent assay. All of the cAMP-elevating agents tested were found to profoundly suppress IFN-gamma production in a dose-dependent manner. IL-4 and IL-5 production was slightly up-regulated at low concentrations of the cAMP-elevating agents and was modestly suppressed at the highest concentrations of cAMP-elevating agents. Experiments were then carried out to determine whether T cells were directly affected by cAMP-elevating agents or whether the immunomodulatory effects were mediated via antigen-presenting cells. Pulsing T cells alone for a brief period with cholera toxin produced an almost identical effect to pulsing antigen-presenting cells alone, i.e. down-regulation of proliferation, down-regulation of IFN-gamma production with little effect on IL-5 production. It was concluded that cAMP-elevating agents suppressed T helper type 1 responses to type II collagen to a greater extent than T helper type 2 responses. The cAMP-elevating agents could directly influence the activity of T cells but, in addition, influenced the ability of antigen-presenting cells to support T helper type 1 responses.

Phosphodiesterase Type IV Inhibitors Prevent Ischemia-Reperfusion-Induced Gastric Injury in Rats

The effects of selective inhibitors of phosphodiesterase type IV (PDE4) on ischemia-reperfusion-induced gastric injuries were investigated in rats. Gastric ischemia was induced by applying a small clamp to the celiac artery, and reoxygenation was performed by removal of the clamp. Ischemia-reperfusion produced gastric hemorrhagic injuries and increased the content of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) and myeloperoxidase (MPO) activity in gastric mucosa. Rolipram (0.03-0.3 mg/kg, s.c.) and Ro-20-1724 (0.3-3 mg/kg, s.c.) prevented the development of gastric injury in a dose-dependent manner, and it also inhibited the increase in mucosal TNF-alpha content and MPO activity induced by ischemia-reperfusion. The anti-ulcer drug irsogladine (1-10 mg/kg, p.o.), which is known to possess a PDE4 inhibitory action, also inhibited the gastric injury produced by ischemia-reperfusion, as well as the increase in TNF-alpha levels and MPO activity. It is concluded that the ability of PDE4 inhibitors to inhibit cytokine TNF-alpha synthesis and the infiltration of polymorphonuclear leukocytes underlies their gastroprotective effects in ischemia-reperfusion-induced gastric injury. Our experiments suggest that drugs that inhibit PDE4 isoenzyme, such as the anti-ulcer drug irsogladine, may be a useful adjunct therapy for the treatment of the gastric damage that follows ischemia-reperfusion.

Neural immune pathways and their connection to inflammatory diseases

Inflammation and inflammatory responses are modulated by a bidirectional communication between the neuroendocrine and immune system. Many lines of research have established the numerous routes by which the immune system and the central nervous system (CNS) communicate. The CNS signals the immune system through hormonal pathways, including the hypothalamic-pituitary-adrenal axis and the hormones of the neuroendocrine stress response, and through neuronal pathways, including the autonomic nervous system. The hypothalamic-pituitary-gonadal axis and sex hormones also have an important immunoregulatory role. The immune system signals the CNS through immune mediators and cytokines that can cross the blood-brain barrier, or signal indirectly through the vagus nerve or second messengers. Neuroendocrine regulation of immune function is essential for survival during stress or infection and to modulate immune responses in inflammatory disease. This review discusses neuroimmune interactions and evidence for the role of such neural immune regulation of inflammation, rather than a discussion of the individual inflammatory mediators, in rheumatoid arthritis.

Impact of VIP and cAMP on the regulation of TNF-alpha and IL-10 production: implications for rheumatoid arthritis

Vasoactive intestinal peptide (VIP) is an anti-inflammatory immunomodulatory neuropeptide with therapeutic potential demonstrated for collagen-induced arthritis. The aim of this study was to characterise its potential anti-arthritic effect on human monocytes, macrophages, T cells, and rheumatoid arthritis synovial membrane cells. Monocytes, macrophages, and T cells derived from human peripheral blood were treated with VIP and compared with other cAMP-elevating drugs for a range of activating stimuli. Cytokine production was assessed for cell cultures and, in addition, the ability of VIPs to activate cAMP response element binding protein. VIP partially suppressed monocyte- and macrophage-derived tumour necrosis factor α (TNF-α) with no effect on IL-10, whereas VIP fails to regulate IL-10 and TNF-α production by T lymphocytes. No such modulation of cytokine profile was observed for rheumatoid arthritis synovial membrane cells. Elevation of intracellular cAMP, on the other hand, potently suppressed macrophage TNF-α production and modulated T-cell response by inhibiting TNF-α and IFN-γ. VIP's lack of effect on IL-10 and its slight effect on TNF-α results from cAMP being rapidly degraded as the phosphodiesterase IV inhibitor, rolipram, rescues cAMP-dependent activation of cAMP response element binding protein. Interestingly, macrophages stimulated with phorbol 12-myristate 13-acetate/ionomycin displayed an augmented IL-10 response upon addition of dibutyryl cAMP, with corresponding downregulation in TNF-α, suggesting a complex interaction between protein kinase C and protein kinase A in cytokine regulation. In conclusion, VIP may represent an efficaceous anti-arthritic treatment modulating macrophage and T-cell cytokine profiles when used alongside a phosphodiesterase inhibitor.

Synthesis and biological activities of 1-pyridylisoquinoline and 1-pyridyldihydroisoquinoline derivatives as PDE4 inhibitors

A novel series of 1-pyridylisoquinoline and 1-pyridyldihydroisoquinoline derivatives has been prepared. These compounds showed potent PDE4 inhibitory activities and a broad margin between the K(i) value of the rolipram binding affinity and the IC(50) value of PDE4 inhibition. They also exhibited potent inhibitory activities toward LPS-induced TNF-alpha production in mice.

The specific type-4 phosphodiesterase inhibitor mesopram alleviates experimental colitis in mice

Mesopram, a specific inhibitor of type-4 phosphodiesterase, decreases the synthesis of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). In the present study, we investigated the effect of mesopram in dextran sulfate sodium (DSS)-induced murine colitis. In the preventive model, colitis was induced by DSS simultaneously with the application of mesopram in BALB/c mice. In the therapeutic model, colitis was induced in BALB/c mice by DSS over 7 days. At day 8, DSS was discontinued, and treatment was started. Mesopram was applied intraperitoneally or orally. The clinical score was calculated daily during the course of each study. Post mortem, colon length, histologic score, and expression of TNF-alpha and IFN-gamma in colons were determined. In the preventive model, mesopram significantly reduced the maximal clinical score, decreased colon shortening, and the histologic score. A dose finding study, using the preventive model, showed that most clinical and post mortem benefit was achieved with 50 mg/kg mesopram compared with 2 and 10 mg/kg. In the therapeutic model, i.p. mesopram treatment led to a significant reduction of clinical score. Both, i.p. and p.o. mesopram significantly reversed DSS-induced colon shortening and reduced the ex vivo colonic production of IFN-gamma. We conclude that the specific type-4 phosphodiesterase inhibitor mesopram ameliorates murine colitis both in a preventive and a therapeutic setting.

Effect of phosphodiesterase inhibitor-4, rolipram, on new bone formations by recombinant human bone morphogenetic protein-2

Collagen sponge disks (6 mm diameter, 1 mm thickness) were impregnated with recombinant human bone morphogenetic protein-2 (rhBMP-2) (5 microg/disk) and implanted onto the back muscles of mice. Ten or 20 mg/kg per day of Rolipram, a selective inhibitory agent to phosphodiesterase type 4 (PDE-4), or vehicle, was injected subcutaneously into the host mice for 3 weeks. After treatment, rhBMP-2-induced ectopic ossicles were harvested and examined by radiographic and histologic methods to determine the size, bone quality, and mineral content of the ossicles. The ossicles from a group treated with 20 mg/kg per day Rolipram were significantly larger in size and higher in bone mineral density (BMD) and bone mineral content (BMC) than the control samples. No significant differences were noted in mice treated with 10 mg/kg per day of Rolipram. Histologically, ossicles from the high-dose (20 mg/kg per day) Rolipram-treated group showed densely packed, thicker trabeculae when compared with those from the control group. These experimental results indicate that the PDE-4 inhibitor, Rolipram, may enhance the bone-inducing capacity of BMP-2 in mesenchymal cells. This in turn may result in increased responsiveness to BMP-2 and point to a potential use of PDE-4 inhibitors for the promotion of rhBMP-dependent bone repair.

Polymorphisms of the tumor necrosis factor alpha locus among autoimmune disease susceptible and resistant inbred rat strains

Inbred rat strains manifest remarkable differences in susceptibility/severity to autoimmune disease. MHC alleles strongly influence the pathogenesis of autoimmune disease in rats, but the precise mechanism(s) remain inadequately defined. The TNFalpha gene is located in the class III region of the MHC. Polymorphisms, influencing either the structure or expression of the TNF protein, might contribute to differences in autoimmune disease susceptibility/severity. We therefore sequenced the Tnf locus using genomic DNA from ACI, BB(DR), BN, DA, F344, and LEW rats that vary in susceptibility/severity to autoimmune diseases. We found 42 polymorphisms among these six strains. Although none of these polymorphisms are predicted to change the amino acid sequence of the TNF protein, several reside in potential non-coding regulatory regions and may influence expression levels. These polymorphisms may serve as good candidates for analysis of TNF expression to elucidate the mechanism(s) by which the MHC regulates susceptibility and/or severity of autoimmune diseases.

Design of rolipram-loaded nanoparticles: comparison of two preparation methods

The aim of the present work was to investigate the preparation of nanoparticles as a potential drug carrier and targeting system for the treatment of inflammatory bowel disease. Rolipram was chosen as the model drug to be incorporated within nanoparticles. Pressure homogenization-emulsification (PHE) with a microfluidizer or a modified spontaneous emulsification solvent diffusion method (SESD) were used in order to select the most appropriate preparation method. Poly(epsilon-caprolactone) has been used for all preparations. The drug loading has been optimized by varying the concentration of the drug and polymer in the organic phase, the surfactants (polyvinyl alcohol, sodium cholate) as well as the volume of the external aqueous phase. The rolipram encapsulation efficiency was high (>85%) with the PHE method in all cases, whereas with the SESD method encapsulation efficiencies were lower (<40%) when lower surfactant concentrations and reduced volume of aqueous phase were used. Release profiles were characterized by a substantial initial burst release with the PHE method (25-35%) as well as with the SESD method (70-90%). A more controlled release was obtained after 2 days of dissolution with the PHE method (70-90%), no further significant drug release was observed with the SESD method.

Monoamine oxidase inhibitors for IgA nephropathy

IgA nephropathy (IgAN), characterized by renal mesangial deposits of antibodies (of the IgA subtype), is the most common glomerulonephritis worldwide. The cause of IgAN is not known. IgAN can often lead to end stage renal disease (ESRD), and there is no known treatment proven to prevent ESRD in IgAN. Long term use of steroids or other immunosuppressant drugs carry severe toxicities and other risks. IgAN patients have high serum levels of tumor necrosis factor-alpha (TNF). Increased monoamine levels, via increased cellular cyclic AMP, can decrease TNF elaboration. Monoamine oxidase inhibitors (MAO-Is) have been found effective in case studies for a number of diseases, e.g. rheumatoid arthritis and Crohn's disease, characterized by high TNF levels. Here I suggest that MAO-Is might be of utility in IgAN by decreasing TNF levels.

Amelioration of collagen-induced arthritis in DBA/1J mice by recombinant TSG-6, a tumor necrosis factor/interleukin-1-inducible protein

OBJECTIVE

To examine the effect of recombinant TSG-6 on collagen-induced arthritis (CIA) in DBA/1J mice. TSG-6 is a tumor necrosis factor (TNF)/ interleukin-1 (IL-1)-inducible hyaluronan-binding protein produced by synovial cells and chondrocytes that is present in synovial fluids of patients with rheumatoid arthritis.

METHODS

To determine the effect of TSG-6 on chronic inflammatory joint disease, we induced CIA in DBA/1J mice by immunization with bovine type II collagen. Animals were treated with 12 intraperitoneal doses of 200 microg of recombinant TSG-6, beginning 3 days before the expected onset of disease symptoms. Progression of arthritis was monitored by determining the disease incidence, arthritis index, and footpad swelling. Levels of IgG1, IgG2a, and IgG2b antibodies against bovine and murine type II collagen and serum concentrations of IL-6 were determined at various time points. Histologic examination of affected joints was performed approximately 20 days after the onset of arthritis.

RESULTS

Treatment with recombinant TSG-6 protein had a potent ameliorative effect, manifested by decreases in the disease incidence, arthritis index, and footpad swelling. Histologic examination of affected joints in TSG-6-treated animals revealed little pannus formation and cartilage erosion, features which were conspicuous in control mice. Animals treated with recombinant TSG-6 developed significantly reduced levels of IgG1, IgG2a, and IgG2b antibodies against bovine and murine type II collagen.

CONCLUSION

The antiinflammatory effect of the TNF/IL-1-inducible TSG-6 protein in murine CIA suggests a role for this protein as an endogenous regulator of the inflammatory process.

Future prospects for anti-cytokine treatment

The era of anti-cytokine treatment in rheumatology has just begun. The first generation therapeutic agents, biological agents that block tumour necrosis factor alpha such as monoclonal antibodies or receptor Ig fusion proteins are safe and effective, and so this has generated much interest in how to increase the benefit or deliver it more cost effectively. This article provides a personal view of the coming trends in anti-cytokine treatment. Which of these will be realised in the future will be of interest.

Anti-inflammatory and analgesic effects of the phosphodiesterase 4 inhibitor rolipram in a rat model of arthritis

There has been much interest in strategies which modulate tumour necrosis factor-alpha (TNF-alpha) levels and/or function in rheumatoid arthritis. The elevation of intracellular levels of cyclic AMP in leukocytes by phosphodiesterase 4 inhibitors is accompanied by significant inhibition of the production of TNF-alpha. Nevertheless, these drugs may enhance the hyperalgesia induced by a range of inflammatory mediators, including TNF-alpha. In the present study, we examined the effects of the phosphodiesterase 4 inhibitor rolipram on the local inflammatory infiltrate and hyperalgesia in a rat model of adjuvant-induced arthritis. Rolipram (3 mg/kg) was administered by oral gavage from day 10 to 14 after disease induction. Pretreatment with rolipram abrogated oedema formation and significantly inhibited hyperalgesia. Histopathological analysis revealed a marked inhibition of cellular influx as well as bone and cartilage destruction. Serum and local TNF-alpha levels were suppressed in treated animals whereas there were little changes in interleukin-1beta levels. Although cyclic AMP elevating agents may affect nociceptor threshold to increase the hyperalgesic responses acutely, they also possess significant anti-inflammatory activity, which may hinder local mediator release and/or action. The anti-inflammatory effects of rolipram predominate during this chronic arthritis model in the rat.

Phosphodiesterase 4 inhibitors, structurally unrelated to rolipram, as promising agents for the treatment of asthma and other pathologies

An increase of cyclic adenosine and guanosine monophosphate (cAMP and cGMP) level can be achieved by inhibition of phosphodiesterases (PDEs), which are the enzymes responsible for the conversion of these second messengers into the corresponding 5-monophosphate inactive counterparts. The high heterogeneity in PDE families and in their tissue distribution, as well as their different functional role, make these enzymes very attractive targets for medicinal chemists. The PDE 4 family is particularly abundant in immunocompetent cells, where an increase of cAMP leads to the inhibition of the synthesis and release of pro-inflammatory mediators, cytokines and active oxygen species. Moreover PDE 4 inhibitors are able to reduce bronchial smooth muscle tone in vitro and show bronchodilatory effects in vivo. Thus, the current therapy for asthma, which is based on a combination of beta(2) agonists and corticosteroids, could be replaced by treatment with PDE 4 inhibitors. This review mainly covers PDE 4 inhibitors structurally related to xanthines and Nitraquazone, which appear to be very attractive models for the synthesis of novel PDE 4 inhibitors potentially useful for the treatment of asthma, chronic pulmonary obstructive disease and some autoimmune diseases. These compounds could be devoid of the central side-effects (nausea, vomiting, headache) of the archetypal Rolipram, which hampered its development as a drug. The review also highlights the novel structural classes of PDE 4 inhibitors recently reported in the literature.

New phosphodiesterase inhibitors as therapeutics for the treatment of chronic lung disease

Phosphodiesterase 4 (PDE4) is a member of the growing family cyclic AMP and cyclic GMP. Earliest described inhibitors of PDE4, such as rolipram, demonstrate marked anti-inflammatory and bronchodilatory effects in vitro and in vivo. The clinical utility of these earlier compounds was limited by their propensity to elicit gastrointestinal side effects. This has led to an extensive effort to identify novel PDE4 inhibitors that maintain the anti-inflammatory activity and bronchodilatory activity of rolipram but with a reduced potential to produce side effects. This article summarizes the evidence supporting the utility of selective PDE4 inhibitors in the treatment of asthma and chronic obstructive pulmonary disease, discusses the recent results obtained in clinical trials with second-generation inhibitors, and presents two approaches designed to identify additional novel selective PDE4 inhibitors.

Therapeutic potential of phosphodiesterase-4 and -3 inhibitors in Th1-mediated autoimmune diseases

Phosphodiesterase-4 (PDE4) inhibitors have the potential to modulate immune responses from the Th1 toward the Th2 phenotype and are considered candidate therapies for Th1-mediated autoimmune disorders. However, depending on the model and cell types employed, studies of atopic individuals have come to the opposite conclusion, i.e., that PDE inhibitors may be beneficial in asthma. Using in vitro immunopharmacologic techniques we analyzed the effects of PDE4 and PDE3 inhibitors on human immune cells to address these discrepancies and broaden our understanding of their mechanism of action. Our results indicate that PDE inhibitors have complex inhibitory effects within in vivo achievable concentration ranges on Th1-mediated immunity, whereas Th2-mediated responses are mostly unaffected or enhanced. The Th2 skewing of the developing immune response is explained by the effects of PDE inhibitors on several factors contributing to T cell priming: the cytokine milieu; the type of costimulatory signal, i.e., up-regulation of CD86 and down-regulation of CD80; and the Ag avidity. The combination of PDE4 and PDE3 inhibitors expresses synergistic effects and may broaden the therapeutic window. Finally, we observed a differential sensitivity to PDE inhibition in autoreactive vs foreign Ag-specific T cells and cells derived from multiple sclerosis patients vs those derived from healthy donors. This suggests that PDE inhibition weakens the strength of the T cell stimulus and corrects the underlying disease-associated cytokine skew in T cell-mediated autoimmune disorders. These new findings broaden the understanding of the immunomodulatory actions of PDE inhibitors and underscore their promising drug profile for the treatment of autoimmune disorders.

Phosphodiesterase 4 (PDE4) inhibitors in asthma and chronic obstructive pulmonary disease (COPD)

Phosphodiesterases (PDE) are a family of enzymes responsible for the metabolism of the intracellular second messengers cyclic AMP and cyclic GMP. PDE4 is a cyclic AMP specific PDE that is the major if not sole cyclic AMP metabolizing enzymes found in inflammatory and immune cells, and contributes significantly to cyclic AMP metabolism in smooth muscles. Based on its cellular and tissue distribution and the demonstration that selective inhibitors of this isozyme reduce bronchoconstriction in animals and suppress the activation of inflammatory cells, PDE4 has become an important molecular target for the development of novel therapies for asthma and COPD. This chapter will review the evidence demonstrating the ability of PDE4 inhibitors to modify airway obstruction, airway inflammation and airway remodelling and hyperreactivity, will present some preliminary findings obtained with theses compounds in clinical trials and and will discuss experimental approaches designed to identify novel compounds that maintain the beneficial activity of the initial selective PDE4 inhibitors but with a reduced tendency of elicit the gastrointestinal side effects observed with this class of compounds.

Rolipram suppresses experimental autoimmune neuritis and prevents relapses in Lewis rats

Rolipram, a phosphodiesterase type 4 inhibitor, can markedly down-regulate antigen-driven T cell proliferation and suppress TNF-alpha production in vitro and in vivo. Here we report the effects of Rolipram on experimental autoimmune neuritis (EAN), which can be induced by immunization with myelin components of the peripheral nervous system (PNS) combined with Freund's complete adjuvant (FCA), and which represents a CD4+ T cell-mediated animal model for human Guillain-Barré syndrome. EAN induced in Lewis rats by inoculation with the PNS P2 protein peptide 57-81 and FCA was strongly suppressed by Rolipram administered twice daily intraperitoneally from day 9 post immunization (p.i.), i.e. after onset of clinical EAN. Suppression of EAN was associated with down-regulated myelin antigen-induced T cell responses as well as down-regulated IFN-gamma and TNF-alpha production. A relapse of clinical EAN occurred upon treatment of a short duration (7 days), while prolongation of treatment resulted in the prevention of clinical EAN relapse. There was no relationship between clinical EAN relapse and high levels of TNF-alpha. The immunomodulatory effects of Rolipram call for further research into the potential role of drugs acting on the immune system in the treatment of autoimmune diseases.

Effects of the phosphodiesterase inhibitor rolipram on streptococcal cell wall-induced arthritis in rats

The phosphodiesterase-IV (PDE-IV) inhibitor, rolipram, is antiinflammatory in a number of animal models and inhibits the release of a variety of cytokines, including TNFalpha. Arthritis induced in rats by systemic reactivation with streptococcal cell walls (SCW) following intraarticular sensitization is a TNFalpha-dependent, delayed-type hypersensitivity (DTH) reaction. Rolipram administered during the reactivation phase dose-dependently inhibited hind paw edema through day 24, the day of peak swelling. PMN and T-cell recruitment to the arthritic joint were also attenuated in rolipram-treated rats. Histologic examination of ankle sections from rolipram-treated animals showed a marked attenuation of synovial inflammation. Mechanistic studies to determine the role of glucocorticoids in mediating rolipram action showed that the inhibitory effect of rolipram on swelling was not reversed by RU 486, a glucocorticoid antagonist. In contrast, RU 486 reversed the inhibitory effects of rolipram on TNFalpha secretion. To further evaluate the role of cAMP in the model, the beta-adrenergic receptor (betaAR) agonist isoproterenol was tested, and found to inhibit swelling but not the release of TNFalpha. These results are consistent with the view that the inhibitory effects of rolipram may be partially mediated by cAMP-dependent, but TNFalpha-independent, mechanisms. The betaAR antagonists propranolol and nadolol had no appreciable affect on the antiinflammatory effect of rolipram. However, rolipram reversed the lethal effects of the antagonists observed when either was administered alone. Apparently, beta-adrenergic mechanisms moderate the response to challenge, and rolipram treatment, presumably as a result of its effects on cAMP levels, reverses the toxic effect of the antagonists.

Differential regulation of rheumatoid synovial cell interleukin-12 production by tumor necrosis factor alpha and CD40 signals

OBJECTIVE

To investigate the roles of tumor necrosis factor alpha(TNFalpha) and the CD40-CD154 interaction in interleukin-12 (IL-12) production by rheumatoid synovial cells (SC).

METHODS

Levels of IL-12 (p40 and p70) in synovial tissue and culture supernatants of SC from patients with rheumatoid arthritis (RA), osteoarthritis (OA), and ankylosing spondylitis (AS) were assayed by enzyme-linked immunosorbent assay. Effects of anti-CD154 and anti-TNFalpha antibody on spontaneous and lipopolysaccharide (LPS)-stimulated IL-12 production by SC were examined. Effects of immobilized anti-CD3 treatment and depletion of CD4+ T cells on IL-12 production were also tested. CD154 expression by synovial T cells and intracellular IL-12 production during culture were analyzed by flow cytometry.

RESULTS

IL-12 p40 and p70 levels in RA synovial tissue and spontaneous IL-12 p40 production by SC from RA patients were significantly higher than the levels in OA and AS patients. Spontaneous IL-12 production by SC from RA patients significantly decreased after depletion of CD4+ T cells from SC or after application of anti-CD154 antibody, but not by treatment with anti-TNFalpha antibody. Anti-CD3 antibody stimulation increased spontaneous IL-12 p40 production and CD154 expression by synovial T cells. The increment of IL-12 p40 production by anti-CD3 was abrogated by anti-CD154 antibody. IL-12 p40 production was also increased by LPS stimulation. LPS-stimulated IL-12 production was inhibited by anti-TNFalpha antibody, but not by T cell depletion and anti-CD154 antibody treatment. The TNFalpha inhibitor rolipram inhibited LPS-stimulated IL-12 p40 production by RA SC more strongly than spontaneous production. TNFalpha restored LPS-stimulated IL-12 production that had been inhibited by rolipram.

CONCLUSION

IL-12 production in RA is regulated by 2 different pathways. One pathway is T cell dependent, predominantly through a CD40-CD154 interaction, while the other is T cell independent, mediated through TNFalpha. Inhibition of IL-12 production by interference with CD40-CD154 interaction and TNFalpha production may be a potential therapeutic strategy for treating RA.

Regulation of IL-15-Stimulated TNF-α Production by Rolipram

Agents that increase intracellular cAMP have been shown to reduce joint inflammation in experimental arthritis, presumably by lowering the release of proinflammatory cytokines, such as TNF-α. Recent studies suggest that, in joints of patients with rheumatoid arthritis, TNF-α release from macrophages is triggered by their interaction with IL-15-stimulated T lymphocytes. In this report, we analyze the effect of rolipram, a cAMP-specific phosphodiesterase inhibitor, on TNF-α production in this experimental system. Cocultures of U937 cells with IL-15-stimulated T cells, but not control T cells, resulted in increased release of TNF-α. Pretreatment of T cells with rolipram or cAMP analogues inhibited the IL-15-stimulated increases in proliferation, expression of cell surface molecules CD69, ICAM-1, and LFA-1, and release of TNF-α from macrophages. Addition of PMA to T cells dramatically increased the expression of cell surface molecules, but had little or no effect on TNF-α release from either T cells or from cocultures, suggesting that other surface molecules must also be involved in T cell/macrophage contact-mediated production of TNF-α. Addition of PMA synergistically increased the proliferation of IL-15-stimulated T cells and the secretion of TNF-α from IL-15-stimulated T cell/macrophage cocultures. Rolipram and 8-(4-chlorophenylthio)-cAMP (CPT-cAMP) blocked these increases. Measurement of protein kinase A (PKA) activity and the use of inhibitory cAMP analogues (RpCPT-cAMP) confirmed that rolipram worked by stimulating PKA. These data suggest that PKA-activating agents, such as rolipram, can block secretion of TNF-α from macrophages by inhibiting T cell activation and expression of surface molecules.

Differential effects of phosphodiesterase type 4-specific inhibition on human autoreactive myelin-specific T cell clones

Proinflammatory cytokines, secreted by autoreactive CD4+ T lymphocytes may contribute to the pathogenesis of several human autoimmune diseases, including multiple sclerosis (MS). Since the antigen specificities of these T cells are not known at present, therapeutic strategies aiming at common effector pathways, in particular cytokine secretion, may be more feasible in the near future. We have studied the influence of the isoenzyme-specific phosphodiesterase inhibitor rolipram on the proliferation and cytokine secretion of human myelin basic protein-specific T cell clones. The inhibition of proliferation correlated with interference with the IL-2/IL-2 receptor system, while the effects of rolipram on several T helper 1-(TNF-alpha, TNF-beta, IFN-gamma) and T helper 2-like cytokines (IL-4, IL-13) as well as IL-10 revealed an interesting drug profile, with preferential inhibition of TNF-beta, TNF-alpha and IL-10. This profile suggest that rolipram differs from other currently used immunomodulatory drugs.

Phosphodiesterase 4 inhibitors as novel anti-inflammatory agents

Preclinical and clinical studies of phosphodiesterase 4 inhibitors have shown that these agents may find utility in a wide range of inflammatory disorders, including asthma, chronic obstructive pulmonary disease, atopic dermatitis, rheumatoid arthritis, multiple sclerosis and various neurological disorders. The future of this class of drugs will depend upon the ability to demonstrate a reasonable safety margin against emesis and other typical phosphodieserase (PDE4) side effects, as well as in identification of the inflammatory disorder(s) most relevant to PDE4 inhibition.

Prevention by rolipram of concanavalin A-induced T-cell-dependent hepatitis in mice

Rolipram is a type IV phosphodiesterase inhibitor endowed with powerful immunomodulatory properties. In this study, we evaluated the effects of this drug on the development of the T-cell-mediated hepatitis inducible in mice by concanavalin A. The results indicated that prophylactic treatment with either 5 or 10 mg/kg rolipram injected intraperitoneally 24 h and 1 h prior to intravenous (i.v.) challenge with 20 mg/kg concanavalin A successfully ameliorated serological and histological signs of liver damage, so that the treated mice showed lower transaminase levels in the plasma and milder mononuclear cell infiltration of the liver as compared to vehicle-treated controls. Moreover, this effect was associated with profound modifications of circulating levels of cytokines released after concanavalin A injection, with the blood levels of interferon-gamma and tumor necrosis factor-alpha being significantly lower and those of interleukin-10 higher than those of the control mice. In particular, the increased blood levels of interleukin-10 might play an important role in the anti-hepatitic effects of rolipram as coadministering this compound with anti-interleukin-10 monoclonal antibody significantly reduced its anti-inflammatory action. These results suggest that rolipram may be useful in the clinical setting for the treatment of cell-mediated immunoinflammatory diseases such as immunoinflammatory hepatitis.

Cyclic-3',5'-nucleotide phosphodiesterase isozymes in cell biology and pathophysiology of the kidney

Investigations of recent years revealed that isozymes of cyclic-3', 5'-nucleotide phosphodiesterase (PDE) are a critically important component of the cyclic-3',5'-adenosine monophosphate (cAMP) protein kinase A (PKA) signaling pathway. The superfamily of cyclic-3', 5'-phosphodiesterase (PDE) isozymes consists of at least nine gene families (types): PDE1 to PDE9. Some PDE families are very diverse and consist of several subtypes and numerous PDE isoform-splice variants. PDE isozymes differ in molecular structure, catalytic properties, intracellular regulation and location, and sensitivity to selective inhibitors, as well as differential expression in various cell types. A number of type-specific "second-generation" PDE inhibitors have been developed. Current evidence indicates that PDE isozymes play a role in several pathobiologic processes in kidney cells. In rat mesangial cells, PDE3 and PDE4 compartmentalize cAMP signaling to the PDE3-linked cAMP-PKA pathway that modulates mitogenesis and PDE4-linked cAMP-PKA pathway that modulates generation of reactive oxygen species. Administration of selective PDE isozyme inhibitors in vivo suppresses proteinuria and pathologic changes in experimental anti-Thy-1.1 mesangial proliferative glomerulonephritis in rats. Increased activity of PDE5 (and perhaps also PDE9) in glomeruli and in cells of collecting ducts in sodium-retaining states, such as nephrotic syndrome, accounts for renal resistance to atriopeptin; diminished ability to excrete sodium can be corrected by administration of the selective PDE5 inhibitor zaprinast. Anomalously high PDE4 activity in collecting ducts is a basis of unresponsiveness to vasopressin in mice with hereditary nephrogenic diabetes insipidus. Apparently, PDE isozymes apparently also play an important role in the pathogenesis of acute renal failure of different origins. Administration of PDE isozyme-selective inhibitors suppresses some components of immune responses to allograft transplant and improves preservation and survival of transplanted organ. PDE isozymes are a target for action of numerous novel selective PDE inhibitors, which are key components in the design of novel "signal transduction" pharmacotherapies of kidney diseases.