Reciprocal Regulation of Substance P and IL-12/IL-23 and the Associated Cytokines, IFNγ/IL-17: A Perspective on the Relevance of This Interaction to Multiple Sclerosis

The neuropeptide substance P (SP) exhibits cytokine-like properties and exerts different effects in autoimmune inflammation. Various immune cells express SP and its neurokinin-1 receptor (NK1R) isoforms. A role for SP has been demonstrated in a number of autoimmune conditions, including multiple sclerosis (MS). In this work, we studied the role of SP and NK1R in human immune cells with a focus on their relationship with IL-12/IL-23 family cytokines and the associated IFN-γ/IL-17. AIMS: (1) To determine the role of SP mediated effects on induction of various inflammatory cytokines in peripheral blood mononuclear cells (PBMC); (2) to investigate the expression of SP and its receptor in T cells and the effects of stimulation with IL-12 and IL-23. Quantitative real-time PCR, flow cytometry, ELISA, promoter studies on PBMC and primary T cells from healthy volunteers, and Jurkat cell line. Treatment with SP significantly increased the expression of IL-12/IL-23 subunit p40, IL-23 p19 and IL-12 p35 mRNA in human PBMC. Expression of NK1R and SP in T cells was upregulated by IL-23 but a trend was observed with IL-12. The IL-23 effect likely involves IL-17 production that additionally mediates IL-23 effects. Mutual interactions exist with SP enhancing the cytokines IL-23 and IL-12, and SP and NK1R expression being differentially but potentially synergistically regulated by these cytokines. These findings suggest a proinflammatory role for SP in autoimmune inflammation. We propose a model whereby immunocyte derived SP stimulates Th1 and Th17 autoreactive cells migrating to the central nervous system (CNS), enhances their crossing the blood brain barrier and perpetuates inflammation in the CNS by being released from damaged nerves and activating both resident glia and infiltrating immune cells. SP may be a therapeutic target in MS. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11481-015-9589-x) contains supplementary material, which is available to authorized users

Arthritis suppression by NADPH activation operates through an interferon-beta pathway

Background: A polymorphism in the activating component of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex, neutrophil cytosolic factor 1 (NCFI), has previously been identified as a regulator of arthritis severity in mice and rats. This discovery resulted in a search for NADPH oxidase- activating substances as a potential new approach to treat autoimmune disorders such as rheumatoid arthritis (RA). We have recently shown that compounds inducing NCFI- dependent oxidative burst, e. g. phytol, have a strong ameliorating effect on arthritis in rats. However, the underlying molecular mechanism is still not clearly understood. The aim of this study was to use gene- expression profiling to understand the protective effect against arthritis of activation of NADPH oxidase in the immune system. Results: Subcutaneous administration of phytol leads to an accumulation of the compound in the inguinal lymph nodes, with peak levels being reached approximately 10 days after administration. Hence, global gene- expression profiling on inguinal lymph nodes was performed 10 days after the induction of pristane-induced arthritis (PIA) and phytol administration. The differentially expressed genes could be divided into two pathways, consisting of genes regulated by different interferons. IFN-gamma regulated the pathway associated with arthritis development, whereas IFN-beta regulated the pathway associated with disease protection through phytol. Importantly, these two molecular pathways were also confirmed to differentiate between the arthritis-susceptible dark agouti (DA) rat, (with an Ncf-/(DA) allele that allows only low oxidative burst), and the arthritis-protected DA.Ncf-/(E3) rat (with an Ncf/(E3) allele that allows a stronger oxidative burst). Conclusion: Naturally occurring genetic polymorphisms in the Ncf-/ gene modulate the activity of the NADPH oxidase complex, which strongly regulates the severity of arthritis. We now show that the Ncf-/ allele that enhances oxidative burst and protects against arthritis is operating through an IFN-gamma-associated pathway, whereas the arthritis-driving allele operates through an IFN-gamma-associated pathway. Treatment of arthritis- susceptible rats with an NADPH oxidase- activating substance, phytol, protects against arthritis. Interestingly, the treatment led to a restoration of the oxidative- burst effect and induction of a strikingly similar IFN-beta-dependent pathway, as seen with the disease-protective Ncfl polymorphism