Calcineurin inhibitors down-regulate iNOS expression by destabilising mRNA

Insights into the modulatory role of cyclosporine A and its research advances in acute inflammation

Cyclosporine A(CsA), a classic immunosuppressant, is mainly applied for solid organ transplantation and some autoimmune diseases by suppressing T lymphocytes. Early studies showed that the application of CsA is primarily focused on chronic but not acute inflammation, nevertheless, increasing evidence supporting a role for CsA in acute inflammation, although most of proofs come from experimental models. It has long been known to us that the nuclear factor of activated T cells (NFAT) is the target of CsA to regulate T lymphocytes. However, NFAT also contributes to the regulation of innate immune cells, thus, CsA can not only target lymphocytes but also innate immune cells such as monocytes/macrophages, dendritic cells and neutrophils, which provides a basis for CsA to act on acute inflammation. Moreover, some other pathophysiological events in acute inflammation such as decreased vascular activity, mitochondrial dysfunction and endogenous cell apoptosis can also be alleviated by CsA. There being a moderate successes in the application of CsA for experimental acute inflammation such as sepsis, trauma/hemorrhagic shock and ischemic/reperfusion injury, yet data of the clinical treatment is not clear. In this review, we will critically analyze the existing hypotheses, summarize the application of CsA and its possible mechanisms in various acute inflammation over the past few decades, hope to provide some clues for the clinical treatment of acute inflammation.

Proposed mechanisms of relative bradycardia

Relative bradycardia is the term used to describe the mechanism where there is dissociation between pulse and temperature. This finding is important to recognize since it may provide further insights into the potential underlying causes of disease. There is no known proposed mechanism to explain this phenomenon. We hypothesize that relative bradycardia is the central mechanism reflecting and influenced potentially by the direct pathogenic effect on the sinoatrial node as well as cross-talk between the autonomic nervous system and immune system. Cardiac pacemaker cells may act as a target for inflammatory cytokines leading to alteration in heart rate dynamics or their responsiveness to neurotransmitters during systemic inflammation. These factors account for the important role of how the host response to infectious and non-infectious causes influences the appearance of relative bradycardia. We propose several methods that may be useful to confirm the proposed theoretical framework to further enhance our understanding of this paradoxical phenomenon. This includes measuring, during the episode of relative bradycardia, proinflammatory and anti-inflammatory cytokines, monitoring heart rate variability (HRV), and assessing underlying comorbidities and outcomes in patients with the same disease.

Activation of central GABAB receptors offsets the cyclosporine counteraction of endotoxic cardiovascular outcomes in conscious rats

We have previously shown that cyclosporine (CSA) counteracts cardiovascular manifestations induced by endotoxemia (lipopolysaccharide, LPS) such as hypotension and cardiac autonomic dysfunction in conscious rats. In this study, we investigated whether the facilitation of central γ-amino butyric acid (GABA) neurotransmission blunts these favorable influences of CSA. The LPS-CSA interaction was determined in the absence and presence of drugs that activate GABA_A or GABA_B receptors or elevate synaptic GABA levels in the central nervous system. The consequent i.v. administration of CSA (10 mg/kg) blunted the LPS-evoked hypotension, tachycardia, and reductions in time- and frequency-domain indices of heart rate variability (measures of cardiac autonomic control) evoked by LPS (10 mg/kg i.v.). The ability of CSA to reverse the LPS effects disappeared in rats treated intracisternally (i.c.) with baclofen (selective GABA_B agonist, 2 μg/rat) but not muscimol (selective GABA_A agonist, 1 μg/rat), indicating a preferential compromising action for central GABA_B receptors on the advantageous effects of CSA. Moreover, the improvement by CSA of LPS-evoked cardiovascular derangements was also eliminated after concurrent i.c. administration of vigabatrin (GABA transaminase inhibitor, 200 μg/rat) or tiagabine (GABA reuptake inhibitor, 100 μg/rat). These results demonstrate that the activation of central GABA_B receptors either directly via baclofen or indirectly following interventions that boost GABA levels in central synapses counterbalances the rectifying action of CSA on endotoxemia.

Modulation of Human Immune Response by Fungal Biocontrol Agents

Although the vast majority of biological control agents is generally regarded as safe for humans and environment, the increased exposure of agriculture workers, and consumer population to fungal substances may affect the immune system. Those compounds may be associated with both intense stimulation, resulting in IgE-mediated allergy and immune downmodulation induced by molecules such as cyclosporin A and mycotoxins. This review discusses the potential effects of biocontrol fungal components on human immune responses, possibly associated to infectious, inflammatory diseases, and defective defenses.

CCL8 and the Immune Control of Cytomegalovirus in Organ Transplant Recipients

Monitoring of cytomegalovirus cell-mediated immunity is a promising tool for the refinement of preventative and therapeutic strategies posttransplantation. Typically, the interferon-γ response to T cell stimulation is measured. We evaluated a broad range of cytokine and chemokines to better characterize the ex vivo host-response to CMV peptide stimulation. In a cohort of CMV viremic organ transplant recipients, chemokine expression-specifically CCL8 (AUC 0.849 95% CI 0.721-0.978; p = 0.003) and CXCL10 (AUC 0.841, 95% CI 0.707-0.974; p = 0.004)-was associated with control of viral replication. In a second cohort of transplant recipients at high-risk for CMV, the presence of a polymorphism in the CCL8 promoter conferred an increased risk of viral replication after discontinuation of antiviral prophylaxis (logrank hazard ratio 3.6; 95% CI 2.077-51.88). Using cell-sorting experiments, we determined that the primary cell type producing CCL8 in response to CMV peptide stimulation was the monocyte fraction. Finally, in vitro experiments using standard immunosuppressive agents demonstrated a dose-dependent reduction in CCL8 production. Chemokines appear to be important elements of the cell-mediated response to CMV infection posttransplant, as here suggested for CCL8, and translation of this knowledge may allow for the tailoring and improvement of preventative strategies.

Identification and characterization of the cDNAs encoding the two subunits of Chinese mitten crab (Eriocheir sinensis) calcineurin: their implications in stress and immune response

Calcineurin (CN), the only Ca(2+)/calmodulin-activated serine/threonine protein phosphatase, is a key effector participating in Ca(2+)-dependent signal transduction pathways in a number of cellular processes under normal, stress and pathological conditions. However, the expression and the relevance of CN in stress and immune response have not been characterized in crustaceans. Here, we identified the cDNAs that encode the two subunits of CN (termed EsCN-A and EsCN-B, respectively) in Chinese mitten crab Eriocheir sinensis and analysed their expression patterns in response to stress and immune challenges. The catalytic subunit EsCN-A is comprised of 511 amino acids with a theoretical molecular mass of 57.5 kDa and shows 80% sequence identity with human beings CN-A alpha isoform, while the regulatory subunit EsCN-B protein is composed of 170 amino acids with an estimated molecular mass of 19.3 kDa and shares 88% sequence identity with human beings CN-B type 1. Tissue distribution analysis reveals that both EsCN-A and EsCN-B mRNA transcripts are expressed in all tested tissues with the greatest expression in hepatopancreas and the lowest expression in haemocytes. In addition, both EsCN-A and EsCN-B genes could be significantly up-regulated but with different expression patterns by ambient salinity (15‰ and 30‰ salinities) and pH (pH 6 and 8.5) stresses in gill, hepatopancreas, haemocytes, intestine and muscle. Furthermore, EsCN-A and EsCN-B were up-regulated by LPS and Poly(I:C) immune stimulations in E. sinensis haemocytes in vitro. Moreover, EsCN-A and EsCN-B mRNA were significantly up-regulated in haemocytes, gill, hepatopancreas, intestine and muscle in response to Edwardsiella tarda challenge in vivo. Finally, we revealed the importance of EsCN in LPS-induced nitric oxide production in E. sinensis haemocytes. Together our observations suggest that EsCN, the important downstream effector of CaM-mediated signalling pathway(s), may possess vital roles in stress and immune response in the Chinese mitten crab.

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

BACKGROUND AND PURPOSE

3',5'-Cyclic nucleotide PDE4 is expressed in several inflammatory and immune cells, and PDE4 catalyses the hydrolysis of cAMP to 5'AMP, down-regulating cAMP signalling in cells. MAPK phosphatase-1 (MKP-1) is an endogenous p38 MAPK signalling suppressor and limits inflammatory gene expression and inflammation. In the present study, we investigated the effect of a PDE4 inhibitor rolipram on MKP-1 expression and whether MKP-1 is involved in the anti-inflammatory effects of rolipram.

EXPERIMENTAL APPROACH

The effect of rolipram on TNF production was investigated in J774 mouse macrophage cell line and in primary mouse peritoneal macrophages (PM) from wild-type (WT) and MKP-1(-/-) mice. We also investigated the effect of rolipram on carrageenan-induced paw inflammation in WT and MKP-1(-/-) mice.

KEY RESULTS

MKP-1 expression was enhanced by rolipram, by a non-selective PDE inhibitor IBMX and by a cAMP analogue 8-Br-cAMP in J774 cells and in PM. Enhanced MKP-1 mRNA expression by rolipram was reversed by a PKA inhibitor. Rolipram, IBMX and 8-Br-cAMP also inhibited TNF production in activated macrophages. Accordingly, rolipram inhibited TNF production in PMs from WT mice but, interestingly, not in PMs from MKP-1(-/-) mice. Furthermore, rolipram attenuated carrageenan-induced paw inflammation in WT but not in MKP-1(-/-) mice.

CONCLUSIONS AND IMPLICATIONS

PDE4 inhibitor rolipram was found to enhance the expression of MKP-1, and MKP-1 mediated, at least partly, the anti-inflammatory effects of PDE4 inhibition. The results suggest that compounds that enhance MKP-1 expression and/or MKP-1 activity hold potential as novel anti-inflammatory drugs.

The calcineurin inhibitor cyclosporine A improves lipopolysaccharide-induced vascular dysfunction but does not rescue from cardiovascular collapse in endotoxemic mice

The calcineurin inhibitor cyclosporine A (CsA) improves survival in endotoxemic mice. It was hypothesized that CsA counteracts the bradycardia and hypotension characteristic of endotoxemia. Vascular reactivity was determined in lipopolysaccharide (LPS; 50 μg/mL)-treated mouse aortic rings suspended in a myograph. Arterial blood pressure and heart rate were measured continuously with indwelling catheters in conscious mice treated with CsA and a bolus injection of LPS (2 mg/kg). The α1-adrenoceptor agonist phenylephrine induced stable tension of aortic rings that were attenuated significantly by LPS. Co-incubation of rings with LPS and CsA (1 × 10(-7) mol/L-1 × 10(-5) mol/L) restored vascular reactivity to phenylephrine. Intravenous administration of CsA (20 and 40 mg/kg/day) to mice induced a significant increase (by approximately 10 mmHg) in mean arterial blood pressure (MAP), with no effect on heart rate. An LPS bolus led to significant decreases in MAP (by approximately 30 mmHg) and heart rate (to 50 % of baseline). CsA-treated LPS-mice exhibited higher MAP at some (20 mg/kg) or all (40 mg/kg) time points after LPS. The decrease in MAP (Δ pressure) was similar between vehicle- and CsA-treated groups. The 50 % decrease in heart rate was not affected by CsA. Inducible nitric oxide synthase (iNOS) mRNA and protein levels in LPS-treated mice organs and plasma NO x concentration were significantly reduced by CsA. It is concluded that in a murine model of endotoxemia, increased peripheral vascular resistance and suppression of systemic NO formation by cyclosporine A are not sufficient to prevent cardiovascular collapse, which is caused primarily by compromised cardiac function.

The expression of interleukin-12 is increased by MAP kinase phosphatase-1 through a mechanism related to interferon regulatory factor 1

Mitogen-activated protein kinase phosphatase-1 (MKP-1) is a nuclear tyrosine/threonine phosphatase that inhibits p38 mitogen-activated protein kinase (MAPK) activity. We and others have shown that MKP-1 deficiency leads to excessive activation of innate immunity and inflammatory gene expression. Surprisingly, the present study shows that MKP-1 is a positive regulator of IL-12 expression in macrophages suggesting a stimulatory effect on Th1 type immune response. In the present study, we found that LPS-induced expression of IL-12p40 was lower in primary mouse peritoneal macrophages (PMs) and bone marrow-derived macrophages from MKP-1 deficient mice than in cells from wild-type mice whereas TNF expression was enhanced as expected. Correspondingly, the inhibition of p38 MAPK by pharmacologic inhibitors BIRB 796 and SB 202190 enhanced LPS-induced IL-12p40 production. Silencing of interferon regulatory factor 1 (IRF1) by siRNA inhibited the expression of IL-12p40 in J774 macrophages, showing that IRF1 is an important factor regulating IL-12p40 expression. BIRB 796 enhanced LPS-induced expression of IRF1 in J774 macrophages and in PMs from wild-type mice, and IRF1 expression was reduced in PMs from MKP-1 deficient mice. In conclusions, our results show that MKP-1 increases and p38 MAPK decreases the expression of IL-12 by enhancing the expression of IRF1. MKP-1, through regulation of IRF1 and IL-12, therefore may be an important factor supporting the development of Th1 type of immune response and anti-microbial defense.

A cell permeable peptide inhibitor of NFAT inhibits macrophage cytokine expression and ameliorates experimental colitis

Nuclear factor of activated T cells (NFAT) plays a critical role in the development and function of immune and non-immune cells. Although NFAT is a central transcriptional regulator of T cell cytokines, its role in macrophage specific gene expression is less defined. Previous work from our group demonstrated that NFAT regulates Il12b gene expression in macrophages. Here, we further investigate NFAT function in murine macrophages and determined the effects of a cell permeable NFAT inhibitor peptide 11R-VIVIT on experimental colitis in mice. Treatment of bone marrow derived macrophages (BMDMs) with tacrolimus or 11R-VIVIT significantly inhibited LPS and LPS plus IFN-γ induced IL-12 p40 mRNA and protein expression. IL-12 p70 and IL-23 secretion were also decreased. NFAT nuclear translocation and binding to the IL-12 p40 promoter was reduced by NFAT inhibition. Experiments in BMDMs from IL-10 deficient (Il10^−/−) mice demonstrate that inhibition of IL-12 expression by 11R-VIVIT was independent of IL-10 expression. To test its therapeutic potential, 11R-VIVIT was administered systemically to Il10^−/− mice with piroxicam-induced colitis. 11R-VIVIT treated mice demonstrated significant improvement in colitis compared to mice treated with an inactive peptide. Moreover, decreased spontaneous secretion of IL-12 p40 and TNF in supernatants from colon explant cultures was demonstrated. In summary, NFAT, widely recognized for its role in T cell biology, also regulates important innate inflammatory pathways in macrophages. Selective blocking of NFAT via a cell permeable inhibitory peptide is a promising therapeutic strategy for the treatment of inflammatory bowel diseases.

Mechanisms of rapid induction of interleukin-22 in activated T cells and its modulation by cyclosporin a

IL-22 is an immunoregulatory cytokine displaying pathological functions in models of autoimmunity like experimental psoriasis. Understanding molecular mechanisms driving IL-22, together with knowledge on the capacity of current immunosuppressive drugs to target this process, may open an avenue to novel therapeutic options. Here, we sought to characterize regulation of human IL22 gene expression with focus on the established model of Jurkat T cells. Moreover, effects of the prototypic immunosuppressant cyclosporin A (CsA) were investigated. We report that IL-22 induction by TPA/A23187 (T/A) or αCD3 is inhibited by CsA or related FK506. Similar data were obtained with peripheral blood mononuclear cells or purified CD3(+) T cells. IL22 promoter analysis (-1074 to +156 bp) revealed a role of an NF-AT (-95/-91 nt) and a CREB (-194/-190 nt) binding site for gene induction. Indeed, binding of CREB and NF-ATc2, but not c-Rel, under the influence of T/A to those elements could be proven by ChIP. Because CsA has the capability to impair IκB kinase (IKK) complex activation, the IKKα/β inhibitor IKKVII was evaluated. IKKVII likewise reduced IL-22 induction in Jurkat cells and peripheral blood mononuclear cells. Interestingly, transfection of Jurkat cells with siRNA directed against IKKα impaired IL22 gene expression. Data presented suggest that NF-AT, CREB, and IKKα contribute to rapid IL22 gene induction. In particular the crucial role of NF-AT detected herein may form the basis of direct action of CsA on IL-22 expression by T cells, which may contribute to therapeutic efficacy of the drug in autoimmunity.

Attenuation of the acute inflammatory response by dual specificity phosphatase 1 by inhibition of p38 MAP kinase

Dual specificity phosphatase 1 (DUSP1) dephosphorylates and, hence, regulates the activity of MAP kinases. The present study investigated the effect of DUSP1 on inflammatory gene expression and on the development of carrageenan-induced inflammation. It was found that DUSP1 expression was increased by LPS, and the down-regulation of DUSP1 by siRNA enhanced the phosphorylation of p38 MAPK, while JNK phosphorylation was not affected in murine macrophages. LPS-induced interleukin (IL)-6, tumor-necrosis factor (TNF) and cyclooxygenase-2 (COX2) expression were enhanced in bone marrow-derived macrophages (BMMs) from DUSP1(-/-) mice as compared to those from wild-type mice. In addition, down-regulation of DUSP1 by siRNA enhanced IL-6, TNF and COX2 expression in J774 macrophages, while p38 MAPK inhibitors SB202190 and BIRB 796 inhibited the expression of those inflammatory factors. In vivo, the intensity of the carrageenan-induced paw edema reaction was increased in DUSP1(-/-) mice as compared to the wild-type animals. In conclusion, DUSP1 is an important negative regulator of the acute inflammatory response by limiting p38 MAPK, and compounds which enhance DUSP1 expression or activity may hold a promise as anti-inflammatory drugs.

Dual specificity phosphatase 1 regulates human inducible nitric oxide synthase expression by p38 MAP kinase

The role of dual specificity phosphatase 1 (DUSP1) in inducible nitric oxide synthase (iNOS) expression in A549 human pulmonary epithelial cells, J774 mouse macrophages and primary mouse bone marrow-derived macrophages (BMMs) was investigated. iNOS expression was induced by a cytokine mixture (TNF, IFNγ and IL-1β) in A549 cells and by LPS in J774 cells, and it was inhibited by p38 MAPK inhibitors SB202190 and BIRB 796. Stimulation with cytokine mixture or LPS enhanced also DUSP1 expression. Down-regulation of DUSP1 by siRNA increased p38 MAPK phosphorylation and iNOS expression in A549 and J774 cells. In addition, LPS-induced iNOS expression was enhanced in BMMs from DUSP1^(−/−) mice as compared to that in BMMs from wild-type mice. The results indicate that DUSP1 suppresses iNOS expression by limiting p38 MAPK activity in human and mouse cells. Compounds that enhance DUSP1 expression or modulate its function may be beneficial in diseases complicated with increased iNOS-mediated NO production.

Cyclosporin A and atherosclerosis--cellular pathways in atherogenesis

Cyclosporin A (CsA) is an immunosuppressant drug widely used in organ transplant recipients and people with autoimmune disorders. Long term treatment with CsA is associated with many side effects including hyperlipidemia and an increased risk of atherosclerosis. While its immunosuppressive effects are closely linked to its effects on T cell activation via the inhibition of the nuclear factor of activated T cells (NFAT) pathway, the precise mechanisms underlying its cardiovascular effects appear to involve multiple pathways additional to those relevant for immunosuppression. These include inhibition of calcineurin activity and intracellular cyclophilin peptidylprolyl isomerase and chaperone activities, inhibition of pro-inflammatory extracellular cyclophilin A, and NFAT-independent transcriptional effects. CsA demonstrates complex effects on lipoprotein metabolism and bile acid production, and affects endothelial cells, smooth muscle cells and macrophages, all of which are critical to the atherosclerotic process. Interpretation of the available data is hampered as many experimental models are used to study the effects of CsA in vivo and in vitro, leading to diverse and often contradictory findings. In this review we will describe the cellular mechanisms related to CsA-induced hyperlipidemia and atherosclerosis, with a focus on identifying pro-atherogenic pathways that are distinct from those relevant to its immunosuppressant effects. The potential of CsA analogues to avoid such sequelae will be discussed.

The calcineurin inhibitor, FK506, does not alter glutamate transport in the ischaemic mouse retina

The protein phosphatase 2B inhibitor, FK506, is an immunomodulatory polypeptide that has neuroprotective properties, the mechanisms of which have not been elucidated. A possible mechanism may be phosphorylation-mediated regulation of glutamate transporter activity. In the present study, we investigated the effect of FK506 on glutamate transporter localization and activity in the ischaemic mouse retina. FK506 did not appear to modulate the localization or activity of glutamate transporters under simulated ischaemic conditions. Our present data suggest that the mechanism by which FK506 exerts its neuroprotective action is not attributable to alterations in retinal glutamate transport.