The effect of vesnarinone on TNF alpha production in human peripheral blood mononuclear cells and microglia: a preclinical study for the treatment of multiple sclerosis

siRNA-mediated silencing of phosphodiesterase 4B expression affects the production of cytokines in endotoxin-stimulated primary cultured microglia

Phosphodiesterase 4 (PDE4) has four subtypes: PDE4A, PDE4B, PDE4C and PDE4D. The expression of PDE4 subtypes in microglial cells and the specific contribution of each subtype to inflammation remain unclear. In this study, the expression of PDE4 subtypes in primary microglial cells was assayed. Primary microglial cells were then transfected with specific small interfering RNA (siRNA) against each PDE4 subtype. PDE4 subtype A-D knockdown was confirmed by quantitative polymerase chain reaction. Secreted cytokines in the supernatant and intracellular cyclic adenosine monophosphate (cAMP) levels of transfected cells were measured. The effect of PDE4B siRNA on the activation of extracellular regulated protein kinase (ERK) induced by lipopolysaccharide (LPS) in microglia was further tested by western blotting. Results showed that the primary microglial cells expressed all four types of PDE4s at the protein level. Transfection with the four siRNAs inhibited PDE4 subtype A-D mRNA expression, respectively. In primary microglial cells, treatment with PDE4B siRNA significantly inhibited the expression of tumor necrosis factor-α and interleukin (IL)-1β, and enhanced the expression of cAMP, while siRNAs to other subtypes had no significant effects. However, none of the four siRNAs had any significant effect on the expression of IL-10. Furthermore, in the PDE4B group, the level of phosphorylated ERK was reduced. Among the four PDE4 subtypes, PDE4B plays an important role in regulating inflammatory responses in microglia, potentially through initially regulating the intracellular cAMP concentration.

Inhibition of endogenous phosphodiesterase 7 promotes oligodendrocyte precursor differentiation and survival

During the development of the central nervous system (CNS), oligodendrocyte precursors (OPCs) are generated in specific sites within the neural tube and then migrate to colonize the entire CNS, where they differentiate into myelin-forming oligodendrocytes. Demyelinating diseases such as multiple sclerosis (MS) are characterized by the death of these cells. The CNS reacts to demyelination and by promoting spontaneous remyelination, an effect mediated by endogenous OPCs, cells that represent approximately 5-7 % of the cells in the adult brain. Numerous factors influence oligodendrogliogenesis and oligodendrocyte differentiation, including morphogens, growth factors, chemotropic molecules, extracellular matrix proteins, and intracellular cAMP levels. Here, we show that during development and in early adulthood, OPCs in the murine cerebral cortex contain phosphodiesterase-7 (PDE7) that metabolizes cAMP. We investigated the effects of different PDE7 inhibitors (the well-known BRL-50481 and two new ones, TC3.6 and VP1.15) on OPC proliferation, survival, and differentiation. While none of the PDE7 inhibitors analyzed altered OPC proliferation, TC3.6 and VP1.15 enhanced OPC survival and differentiation, processes in which ERK intracellular signaling played a key role. PDE7 expression was also observed in OPCs isolated from adult human brains and the differentiation of these OPCs into more mature oligodendroglial phenotypes was accelerated by treatment with both new PDE7 inhibitors. These findings reveal new roles for PDE7 in regulating OPC survival and differentiation during brain development and in adulthood, and they may further our understanding of myelination and facilitate the development of therapeutic remyelination strategies for the treatment of MS.

Vesnarinone: a differentiation-inducing anti-cancer drug

Vesnarinone has been shown to be a unique anti-proliferating, differentiation-inducing and apoptosis inducing drug against several human malignancies, including leukemia and several solid tumors. Furthermore, vesnarinone potentiates the effect of conventional cytotoxic chemotherapy or radiation therapy. Combination of differentiation-inducing therapy by vesnarinone with conventional chemotherapy or radiation therapy might be second- or third-line therapy in patients with advanced cancer. Analysis of the molecular mechanisms of the tumor differentiation therapy by vesnarinone might provide selective and targeted molecules for novel tumor dormancy therapy.

Vesnarinone causes oxidative damage by inhibiting catalase function through ceramide action in myeloid cell apoptosis

Vesnarinone is an effective inotropic agent for treating congestive heart failure, but its clinical usage is restricted because of the severe side effect of agranulocytosis. In myeloid HL-60 cells, vesnarinone increased the intracellular content of a proapoptotic lipid mediator, ceramide, in a time- and dose-dependent manner. Vesnarinone-induced apoptosis was significantly enhanced by simultaneous treatment with a cell-permeable N-acetyl sphingosine (C2-ceramide). Treatment with neither vesnarinone, C2-ceramide, nor simultaneously with vesnarinone and C2-ceramide caused a marked increase of reactive oxygen intermediates (ROI) generation measured by the 2',7'-dichlorofluorescin method. However, oxidative damage judged by the production of lipid peroxidates and the nitroblue tetrazolium-reducing ability were enhanced more significantly by simultaneous treatment with vesnarinone and C2-ceramide than by vesnarinone alone. Moreover, vesnarinone inhibited catalase function both at the protein and activity level, and this inhibition was synergistically enhanced by C2-ceramide, and vesnarinone-induced oxidative damage and apoptosis were significantly suppressed by treatment of HL-60 cells with purified catalase. C2-ceramide enhanced vesnarinone-induced inhibition of the ROI-scavenging enzyme catalase at the levels of protein and activity in HL-60 cells; in contrast, however, vesnarinone did not induce ceramide generation, oxidative damage, or catalase depletion in HL-60/ves cells, where vesnarinone could not induce apoptosis. Taken together, the results suggest that vesnarinone induces myeloid cell apoptosis by increasing oxidative damage via ceramide-induced inhibition of catalase function.

Suppressive effects of phosphodiesterase type IV inhibitors on rat cultured microglial cells: comparison with other types of cAMP-elevating agents

We investigated the effects of inhibitors of cAMP-specific phosphodiesterase type IV (PDE IV) on cultured rat microglial cells. Microglial cells expressed mRNA encoding PDE IV. Rolipram and RO-20-1724, specific inhibitors of PDE IV, elevated the intracellular cAMP level much higher than the other types of PDE inhibitors. cAMP in astrocytes but not in cerebrocortical neurons was similarly increased in response to treatment with PDE IV inhibitors examined. The PDE IV inhibitors, a beta-adrenergic agonist isoproterenol and an adenylyl cyclase stimulant forskolin suppressed the proliferation of microglial cells as revealed by PCNA-immunocytochemical staining. The PDE IV inhibitors suppressed release of TNF alpha and nitric oxide (NO) from lipopolysaccharide-activated microglial cells in pure culture, while they did not affect NO release from microglial cells in neuron-microglia coculture. The PDE IV inhibitors also suppressed superoxide anion production by phorbol ester-treated microglial cells. Isoproterenol and forskolin similarly suppressed the macrophage-like functions of activated microglial cells. However, the PDE IV inhibitors displayed novel effects distinct from those of isoproterenol, forskolin and 8Br-cAMP, regarding expression of mRNAs encoding PDE IV, metallothionein-1 and hemeoxigenase-1. The present data showed that the PDE IV inhibitors can be available to control microglial function and that their effects on glial cells should be taken into account when PDE IV inhibitors are used for treatment of brain diseases, such as multiple sclerosis.

Effects of vesnarinone on peripheral circulating levels of cytokines and cytokine receptors in patients with heart failure: a report from the Vesnarinone Trial

STUDY OBJECTIVES

Proinflammatory cytokines may contribute to disease progression in heart failure by virtue of the direct toxic effects that these molecules exert on the heart and the circulation. Accordingly, there is interest in developing therapeutic agents with anticytokine properties that might be used as adjunctive therapy to modulate proinflammatory cytokine levels in patients with heart failure. Previous experimental studies suggested that vesnarinone has potent anticytokine properties in vitro. Therefore, we examined the effects of vesnarinone on circulating levels of cytokines and cytokine receptors in a large-scale, multicenter, clinical trial of patients with moderate-to-advanced heart failure: the Vesnarinone Trial (VEST).

METHODS

Circulating levels of tumor necrosis factor (TNF)-alpha, soluble TNF-receptor type 1, soluble TNF-receptor type 2, as well as interleukin (IL)-6 and soluble IL-6 receptor (sIL-6R) were measured on plasma samples by enzyme-linked immunosorbent assay at baseline and at 24 weeks in patients who were receiving placebo (n = 352), 30 mg of vesnarinone (n = 367), and 60 mg of vesnarinone (n = 327).

RESULTS

Treatment with 30 mg and 60 mg of vesnarinone had no effect on circulating levels of cytokines or cytokine receptors in patients with advanced heart failure over a 24-week period.

CONCLUSIONS

In contrast to the potent anticytokine effects observed with vesnarinone in experimental studies in vitro, the results of this clinical study suggest that vesnarinone does not have any measurable anticytokine effects in vivo in patients with moderate-to-advanced heart failure.

Vesnarinone suppresses TNF-induced activation of NF-kappa B, c-Jun kinase, and apoptosis

Vesnarinone, a synthetic quinolinone derivative used in the treatment of cardiac failure, exhibits immunomodulatory, anti-inflammatory, and cell growth regulatory properties. The mechanisms underlying these properties are not understood, but due to the critical role of nuclear transcription factor NF-kappa B in these responses, we hypothesized that vesnarinone must modulate NF-kappa B activation. We investigated the effect of vesnarinone on NF-kappa B activation induced by inflammatory agents. Vesnarinone blocked TNF-induced activation of NF-kappa B in a concentration- and time-dependent manner. This effect was mediated through inhibition of phosphorylation and degradation of I kappa B alpha, an inhibitor of NF-kappa B. The effects of vesnarinone were not cell type specific, as it blocked TNF-induced NF-kappa B activation in a variety of cells. NF-kappa B-dependent reporter gene transcription activated by TNF was also suppressed by vesnarinone. The TNF-induced NF-kappa B activation cascade involving TNF receptor 1-TNF receptor associated death domain-TNF receptor associated factor 2 NF-kappa B-inducing kinase-IKK was interrupted at the TNF receptor associated factor 2 and NF-kappa B-inducing kinase sites by vesnarinone, thus suppressing NF-kappa B reporter gene expression. Vesnarinone also blocked NF-kappa B activation induced by several other inflammatory agents, inhibited the TNF-induced activation of transcription factor AP-1, and suppressed the TNF-induced activation of c-Jun N-terminal kinase and mitogen-activated protein kinase kinase. TNF-induced cytotoxicity, caspase activation, and lipid peroxidation were also abolished by vesnarinone. Overall, our results indicate that vesnarinone inhibits activation of NF-kappa B and AP-1 and their associated kinases. This may provide a molecular basis for vesnarinone's ability to suppress inflammation, immunomodulation, and growth regulation.

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.