Inhibition of IFN-gamma-induced janus kinase-1-STAT1 activation in macrophages by vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide

Inhibition of IFN-gamma-mediated inducible nitric oxide synthase induction by the peroxisome proliferator-activated receptor gamma agonist, 15-deoxy-delta 12,14-prostaglandin J2, involves inhibition of the upstream Janus kinase/STAT1 signaling pathway

Peroxisome proliferator-activated receptor gamma (PPARgamma) ligands have been reported to exert anti-inflammatory activities in macrophages by competition for transcriptional coactivators with some transcriptional factors, including NF-kappaB. In the present study the influence of PPARgamma activators on IFN-gamma-elicited macrophage stimulation and signaling cascades was investigated. The results show that IFN-gamma-induced inducible NO synthase (iNOS) gene transcription, iNOS protein induction, and NO production are more sensitive to inhibition by 15-deoxy-Delta(12,14)-prostaglandin J(2) (15dPGJ(2)) than by the other two PPARgamma agonists, GW1929 and ciglitazone. Delayed addition of 15dPGJ(2) for 2 h resulted in reduced inhibition, suggesting action by 15dPGJ(2) on the upstream signaling cascades. Immunoblotting, DNA binding, and reporter gene assays consistently revealed the inhibitory ability of 15dPGJ(2), but not GW1929 or ciglitazone, on IFN-gamma-elicited signaling cascades, including tyrosine phosphorylation of Janus tyrosine protein kinase 2 and STAT1, DNA binding, and IFN regulatory factor-1 trans-activation of STAT1. These effects of 15dPGJ(2) were not abrogated by the PPARgamma antagonist, bisphenol A diglycidyl ether, indicating the PPARgamma-independent actions. 15dPGJ(2) also attenuated IL-6-induced tyrosine phosphorylation of STAT1 and STAT3 in Hep3B hepatoma cells. Consistent with the inhibitory effect of reactive oxygen species on STAT1 signaling, STAT1 inhibition by 15dPGJ(2) was abrogated by N-acetylcysteine, glutathione, superoxide dismutase, and catalase. Furthermore, 15dPGJ(2)-induced inhibition of STAT1 phosphorylation and NO production still occurred in the presence of peroxovanadate, ruling out the action mechanism of 15dPGJ(2) on tyrosine phosphatase. Taken together, for the first time in this study we demonstrate that 15dPGJ(2) can inhibit cytokine-stimulated Janus kinase 2-STAT signaling through a PPARgamma-independent, reactive oxygen species-dependent mechanism. These data provide a novel molecular mechanism of iNOS inhibition by 15dPGJ(2) and confirm its physiological role in anti-inflammation.

PACAP in immunity and inflammation

The pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide belonging to the VIP/secretin/glucagon family of peptides, produced by the lymphoid cells, which exerts a wide spectrum of immunological functions controlling the homeostasis of immune system through different receptors expressed in various immunocompetent cells. In the last decade, PACAP has been clearly identified as a potent anti-inflammatory factor that exerts its function by regulating the production of both anti- and proinflammatory mediators. In this sense, PACAP prevents death by septic shock, an acute inflammatory disease with a high mortality. In addition, PACAP regulates the expression of costimulatory molecules, inasmuch as this related to the modulation in the shift from Th1 towards Th2 differentiation. We recently reported that PACAP prevents the deleterious effects of arthritis by downregulating both inflammatory and autoimmune components of the disease. Therefore, PACAP and analogs have been proposed as very promising candidates, alternative to other existing treatments, for treating acute and chronic inflammatory and autoimmune diseases, such as septic shock, arthritis, multiple sclerosis, Crohn's disease, or autoimmune diabetes.

17beta-estradiol inhibits the production of interferon-induced protein of 10 kDa by human keratinocytes

The natural course of psoriasis is often modulated during pregnancy, indicating the regulatory effect of estrogen or progesterone on psoriasis. Interferon-induced protein of 10 kDa chemoattracts T helper 1 cells, and interferon-induced protein of 10 kDa production by keratinocytes is enhanced in psoriatic skin lesions. We examined in vitro effects of sex hormones on the interferon-induced protein of 10 kDa production by human keratinocytes. 17beta-estradiol inhibited interferon-gamma-induced interferon-induced protein of 10 kDa secretion, mRNA expression, and promoter activity. Interferon-stimulated response element on the promoter was responsible for the inhibition by 17beta-estradiol. Interferon-gamma-induced protein of 10 kDa production was also inhibited by anti-estrogens, ICI 182 780 and tamoxifen, and membrane-impermeable bovine serum albumin-conjugated 17beta-estradiol, suggesting the effects via membrane estrogen receptor, whereas 17alpha-estradiol, progesterone, and dihydrotestosterone had no effects. 17beta-estradiol and bovine serum albumin-conjugated 17beta-estradiol suppressed interferon-gamma-induced transcription through the interferon-stimulated response element and signal transducer and activator of transcription 1alpha binding to interferon-stimulated response element. 17beta-estradiol and bovine serum albumin-conjugated 17beta-estradiol suppressed interferon-gamma-induced tyrosine phosphorylation of signal transducer and activator of transcription 1alpha, and Janus tyrosine kinase 1 and 2. 17beta-estradiol-mediated suppression on the interferon-gamma-induced signal transducer and activator of transcription 1alpha activation and interferon-induced protein of 10 kDa synthesis was counteracted by adenylate cyclase inhibitor SQ22536. 17beta-estradiol, bovine serum albumin-conjugated 17beta-estradiol, ICI 182 780, and tamoxifen increased intracellular 3',5'-adenosine cyclic monophosphate level by activating adenylate cyclase in keratinocytes. Fluorescein isothiocyanate-labeled bovine serum albumin-conjugated 17beta-estradiol bound to the surface of keratinocytes, and mRNA for estrogen receptor beta but not for estrogen receptor alpha was detected in keratinocytes. These results suggest that 17beta-estradiol may interact with the membrane receptor on keratinocytes and generate 3',5'-adenosine cyclic monophosphate by activating adenylate cyclase, which may lead to the inhibition of interferon-gamma-induced signal transducer and activator of transcription 1alpha activation and interferon-induced protein of 10 kDa synthesis.

Regulation of the Expression of Inducible Nitric Oxide Synthase

Nitric oxide (NO), generated by the inducible isoform of nitric oxide synthase (iNOS), has been described to have beneficial microbicidal, antiviral, antiparasital, immunomodulatory, and antitumoral effects. However, aberrant iNOS induction at the wrong place or at the wrong time has detrimental consequences and seems to be involved in the pathophysiology of several human diseases. iNOS is primarily regulated at the expression level by transcriptional and post-transcriptional mechanisms. iNOS expression can be induced in many cell types with suitable agents such as bacterial lipopolysaccharides (LPS), cytokines, and other compounds. Pathways resulting in the induction of iNOS expression may vary in different cells or different species. Activation of the transcription factors NF-kappaB and STAT-1alpha, and thereby activation of the iNOS promoter, seems to be an essential step for iNOS induction in most cells. However, at least in the human system, also post-transcriptional mechanism are critically involved in the regulation of iNOS expression. The induction of iNOS can be inhibited by a wide variety of immunomodulatory compounds acting at the transcriptional levels and/or post-transcriptionally.

Histamine inhibits the production of interferon-induced protein of 10 kDa in human squamous cell carcinoma and melanoma

Interferon-induced protein of (IP-10) inhibits tumor progression. Tumor cells can produce interferon-induced protein of IP-10 in response to interferon-g. Histamine in the vicinity of tumor cells may sustain the tumor progression. We examined the in vitro effects of histamine on interferon-induced protein of IP-10 production in human squamous cell carcinoma and melanoma. Histamine suppressed interferon-g-mediated interferon-induced protein of IP-10 secretion and mRNA expression in SV40-transformed keratinocytes, SCC15, SCC4, and melanoma WM115, WM266-4, and C32. Histamine suppressed interferon-g-induced interferon-mediated protein of IP-10 promoter activation in these cells, and the interferon-stimulated response element on the promoter was responsible for the suppression. Histamine suppressed interferon-g-mediated transcription through the interferon-stimulated response element and signal transducer and activator of transcription 1alpha binding to the interferon-stimulated response element. Histamine suppressed interferon-g-induced tyrosine phosphorylation of the signal transducer and activator of transcription 1alpha, Janus tyrosine kinase 1, and Janus tyrosine kinase 2. Histamine-mediated suppression on the interferon-g-induced interferon-mediated protein of IP-10 synthesis was counteracted by the H2 receptor antagonist cimetidine, adenylate cyclase inhibitor SQ22536, and protein kinase A inhibitor H-89, but were not affected by H1 receptor antagonist mepyramine. Cimetidine, SQ22536, and H-89 also counteracted histamine-mediated suppression on the interferon-g-induced transcription through the interferon-stimulated response element, signal transducer and activator of transcription 1alpha binding to the interferon-stimulated response element, and tyrosine phosphorylation of the signal transducer and activator of transcription 1alpha, Janus tyrosine kinase 1, and Janus tyrosine kinase 2. Histamine increased intracellular 3',5'-adenosine cyclic monophosphate level and protein kinase A activity in squamous cell carcinoma and melanoma, and the effects of histamine were blocked by cimetidine. These results suggest that histamine may interact with H2 receptor on squamous cell carcinoma and melanoma and generate 3',5'-adenosine cyclic monophosphate, which may activate protein kinase A. The cyclic 3',5'-adenosine monophosphate/protein kinase A signaling pathway induced by histamine may inhibit interferon-g-induced signal transducer and activator of transcription 1alpha activation and suppress interferon-induced protein of IP-10 synthesis.

Cyclooxygenase-2 inhibitor enhances whereas prostaglandin E2 inhibits the production of interferon-induced protein of 10 kDa in epidermoid carcinoma A431

Interferon-induced protein of 10 kDa (IP-10) induces antitumor immunity. Cyclooxygenase-2 and its metabolite prostaglandin E2 (PGE2) are overexpressed in tumor cells, which may suppress antitumor immunity. We examined the in vitro effects of cyclooxygenase-2 inhibitor NS398 on IP-10 production in human epidermoid carcinoma A431. NS398 enhanced interferon-gamma-induced IP-10 secretion, mRNA expression, and promoter activation in A431, and exogenous PGE2 antagonized the enhancement. Interferon-stimulated response element (ISRE) on IP-10 promoter was responsible for the transcriptional regulation by NS398 and PGE2. NS398 enhanced interferon-gamma-induced transcription through ISRE and binding of signal transducer and activator of transcription 1alpha (STAT1alpha to ISRE in A431, and PGE2 antagonized the enhancement. NS398 enhanced interferon-gamma-induced tyrosine phosphorylation of STAT1alpha, Janus tyrosine kinase 1, and Janus tyrosine kinase 2, and PGE2 antagonized the enhancement. PGE2-mediated suppression of IP-10 synthesis was counteracted by adenylate cyclase inhibitor SQ22536 and protein kinase A inhibitor H-89, and PGE2 receptor EP4 antagonist AH23848B. AH23848B, SQ22536, and H-89 counteracted the PGE2-mediated suppression of ISRE-dependent transcription, STAT1alpha binding to ISRE, and tyrosine phosphorylation of STAT1alpha, Janus tyrosine kinase 1, and Janus tyrosine kinase 2. PGE2 increased intracellular cAMP level and protein kinase A activity in A431 pretreated with NS398, and AH23848B blocked the effects of PGE2. These results suggest that A431-derived PGE2 may generate cAMP signal via EP4 in A431, which may activate protein kinase A, and may resultantly inhibit interferon-gamma-induced STAT1alpha activation and IP-10 synthesis. The results also suggest that NS398 may restore IP-10 synthesis by preventing PGE2 production in A431 and thus may be therapeutically useful for skin cancer.

Noradrenergic regulation of inflammatory gene expression in brain

It is now well accepted that inflammatory events contribute to the pathogenesis of numerous neurological disorders, including multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease, and AID's dementia. Whereas inflammation in the periphery is subject to rapid down regulation by increases in anti-inflammatory molecules and the presence of scavenging soluble cytokine receptors, the presence of an intact blood-brain barrier may limit a similar autoregulation from occurring in brain. Mechanisms intrinsic to the brain may provide additional immunomodulatory functions, and whose dysregulation could contribute to increased inflammation in disease. The findings that noradrenaline (NA) reduces cytokine expression in microglial, astroglial, and brain endothelial cells in vitro, and that modification of the noradrenergic signaling system occurs in some brain diseases having an inflammatory component, suggests that NA could act as an endogenous immunomodulator in brain. Furthermore, accumulating studies indicate that modification of the noradrenergic signaling system occurs in some neurodiseases. In this article, we will briefly review the evidence that NA can modulate inflammatory gene expression in vitro, summarize data supporting a similar immunomodulatory role in brain, and present recent data implicating a role for NA in attenuating the cortical inflammatory response to beta amyloid protein.

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) as modulators of both innate and adaptive immunity

The structurally related neuropeptides VIP and PACAP are released within the lymphoid organs following antigenic stimulation, and modulate the function of inflammatory cells through specific receptors. In activated macrophages, VIP and PACAP inhibit the production of pro-inflammatory agents (cytokines, chemokines, and nitric oxide), and stimulate the production of the anti-inflammatory cytokine IL-10. These events are mediated through the VIP/PACAP effects on de novo expression or nuclear translocation of several transcription factors, i.e., NFkappaB, CREB, c-Jun, JunB, and IRF-1. The in vivo administration of VIP/PACAP results in a similar pattern of cytokine and chemokine modulation, which presumably mediates the protective effect of VIP/PACAP in septic shock. In addition, VIP/PACAP reduce the expression of the co-stimulatory molecules B7.1/B7.2, and the subsequent stimulatory activity of macrophages for T-helper cells. In T-cells expressing specific VIP/PACAP receptors, VIP and PACAP inhibit the expression of FasL through effects on NFkappaB, NFAT, and Egr2/3. The reduction of FasL expression has several biological consequences: inhibition of antigen-induced cell death in CD4 T-cells, inhibition of the FasL-mediated cytotoxicity of CD8 and CD4 effectors against direct and bystander targets, and promotion of long-term memory Th2 cells, through a positive effect on the survival of Th2, but not Th1, effectors. The various biological effects of VIP and PACAP are discussed within the range of a general anti-inflammatory model.

Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit LPS-stimulated MIP-1alpha production and mRNA expression

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are neuropeptides with immunomodulatory properties, including the regulation of several proinflammatory mediators. Such mediators, for example chemokines, influence trafficking of inflammatory cells and contribute to shaping the immune response. In the present work, we studied the effect of VIP and PACAP on the CC chemokine macrophage inflammatory protein-1 alpha (MIP-1alpha) production in LPS-stimulated RAW 264.7 macrophage cell line. VIP and PACAP inhibited the production of MIP-1alpha in a dose-dependent manner and over a broad spectrum of LPS concentrations. The use of selective agonists and antagonists of VIP/PACAP receptors showed that type 1 VIP receptor (VPAC1) is the major receptor involved, but the type 2 VIP receptor (VPAC2) may be also implicated. By using selective PKA and PKC inhibitors and cAMP mimicked agents, we demonstrated a cAMP-dependent signalling pathway for the inhibitory effect of VIP/PACAP on MIP-1alpha production, although a minor non-mediated cAMP pathway was also involved. mRNA expression studies showed a down-regulation of MIP-1alpha gene expression by VIP and PACAP. Taken together, the present work strongly supports an anti-inflammatory role of VIP and PACAP by a new mechanism associated with impairment of a key component of the chemokine network.

Receptors and transcriptional factors involved in the anti-inflammatory activity of VIP and PACAP

VIP and PACAP modulate the function of inflammatory cells through specific receptors. VIP/PACAP inhibit the production of TNF alpha, IL-6, IL-12, and nitric oxide (NO), and stimulate IL-10 in peritoneal macrophages and Raw 264.7 cells. Here we report on the specific VIP/PACAP receptors, transduction pathways, and transcriptional factors involved in the regulation of these macrophage factors by VIP and PACAP. Both neuropeptides inhibit IL-6 production mainly through PAC1 binding, PKC activation, and the subsequent shedding of the LPS receptor CD14 in macrophages. However, the effects on TNF alpha, IL-10, IL-12, and NO are mostly mediated through the constitutively expressed VPAC1 receptor, although the inducible expressed VPAC2 may also participate. VIP/PACAP binding to VPAC1 induces both a cAMP-dependent and a cAMP-independent pathways that regulate cytokine and NO production at the transcriptional level. VIP/PACAP inhibit TNF alpha through reduction in NFkB binding and changes in the composition of CRE-binding complexes; they inhibit IL-12 through reduction in NFkB binding and changes in the composition of the ets-2 complexes. VIP/PACAP inhibit iNOS expression through reduction in NFkB and IRF-1 binding, and augment IL-10 by increasing CREB-binding. Whereas the inhibition of IRF-1 and CRE-binding complexes seems to be mediated through the cAMP-dependent pathway, VIP/PACAP inhibition of NFkB nuclear translocation is mediated through a reduction in IkB alpha degradation mediated by the cAMP-independent pathway. This study provides new evidence for the understanding of the molecular mechanism by means of which VIP and PACAP attenuate the inflammatory response.

Inhibitory neuropeptide receptors on macrophages

The immune response, both in innate and adaptive immunity, is controlled at several levels, including signaling from the central nervous system. Neuropeptides released within the lymphoid organs modulate the immune response, either as stimulators or inhibitors. The subject of this review is the description of macrophage-expressed receptors of inhibitory neuropeptides. We describe the inhibitory effects on macrophage function for several neuropeptides, the receptors that mediate those activities, and the molecular mechanisms initiated by some of these receptors in terms of transduction pathways and transcriptional factors.

Vasoactive intestinal peptide and pituitary adenylate cyclase activating polypeptide inhibit the MEKK1/MEK4/JNK signaling pathway in LPS-stimulated macrophages

The vasoactive intestinal peptide (VIP) and the pituitary adenylate cyclase activating polypeptide (PACAP), two immunomodulatory neuropeptides that affect both innate and acquired immunity, downregulate TNFalpha expression in LPS-stimulated peritoneal macrophages and Raw 264.7 cells. We showed previously that VIP/PACAP change the composition of the CRE-binding complex in the TNFalpha promoter from highc-Jun/(low)CREB, characteristic for LPS-stimulated macrophages, to lowc-Jun/(high)CREB, characteristic for the unstimulated cells. In the present study we examined the effects of VIP/PACAP on the MEKK1/MEK4/JNK transduction pathway, and on the subsequent changes in Jun family members. Our studies indicate that VIP/PACAP inhibit MEKK1 activity, and the subsequent phosphorylation of MEK4, JNK, and c-Jun. Treatment with VIP or PACAP results in a decrease in AP-1 binding, and a marked change in the composition of the AP-1 complexes from c-Jun/c-Fos to JunB/c-Fos. Western blots confirm that VIP stimulates JunB production in LPS-stimulated macrophages. Both the inhibition of the MEKK1/MEK4/JNK pathway, leading to the reduction in phosphorylated c-Jun, and the stimulation of JunB, are mediated through the specific VPAC1 receptor and the cAMP/PKA pathway. The VIP/PACAP interference with the stress-induced SAPK/JNK pathway in stimulated macrophages may represent a significant element in the regulation of the inflammatory response by the endogenous neuropeptides.