Reasons to switch: a noninterventional study evaluating immunotherapy switches in a large German multicentre cohort of patients with relapsing-remitting multiple sclerosis.

BACKGROUND: With a large array of disease modifying therapies (DMTs) for relapsing-remitting MS (RRMS), identifying the optimal treatment option for the individual patient is challenging and switching of immunotherapies is often required. The objective of this study was to systematically investigate reasons for DMT switching in patients on immunotherapies for mild/moderate MS, and provide real-life insights into currently applied therapeutic strategies. METHODS: This noninterventional, cross-sectional study (ML29913) at 50 sites in Germany included RRMS patients on therapies for mild/moderate MS who switched immunotherapy in the years 2014-2017. The key outcome variable was the reason to switch, as documented in the medical charts, based on failure of current therapy, cognitive decline, adverse events (AEs), patient wish, or a woman's wish to become pregnant. Expectations of the new DMT and patients' assessment of the decision maker were also recorded. RESULTS: The core analysis population included 595 patients, with a mean age of 41.6 years, of which 69.7% were female. More than 60% of patients had at least one relapse within 12 months prior to the switch. The main reasons to switch DMT were failure of current therapy (53.9%), patient wish (22.4%), and AEs (19.0%). Most patients (54.3%) were switched within DMTs for mild/moderate MS; only 43.5% received a subsequent DMT for active/highly active MS. While clinical and outcome-oriented aspects were the most frequently mentioned expectations of the new DMT for physicians, aspects relating to quality of life played a major role for patients. CONCLUSIONS: Our data indicate suboptimal usage of DMTs, including monoclonal antibodies, for active/highly active MS in German patients. This illustrates the medical need for DMTs combining high efficacy, low safety risk, and low therapy burden.

Role of the receptor Mas in macrophage-mediated inflammation in vivo.

Recently, an alternative renin-angiotensin system pathway has been described, which involves binding of angiotensin-(1-7) to its receptor Mas. The Mas axis may counterbalance angiotensin-II-mediated proinflammatory effects, likely by affecting macrophage function. Here we investigate the role of Mas in murine models of autoimmune neuroinflammation and atherosclerosis, which both involve macrophage-driven pathomechanisms. Mas signaling affected macrophage polarization, migration, and macrophage-mediated T-cell activation. Mas deficiency exacerbated the course of experimental autoimmune encephalomyelitis and increased macrophage infiltration as well as proinflammatory gene expression in the spleen and spinal cord. Furthermore, Mas deficiency promoted atherosclerosis by affecting macrophage infiltration and migration and led to increased oxidative stress as well as impaired endothelial function in ApoE-deficient mice. In summary, we identified the Mas axis as an important factor in macrophage function during inflammation of the central nervous and vascular system in vivo. Modulating the Mas axis may constitute an interesting therapeutic target in multiple sclerosis and/or atherosclerosis.

Neprilysin is a Mediator of Alternative Renin-Angiotensin-System Activation in the Murine and Human Kidney.

Cardiovascular and renal pathologies are frequently associated with an activated renin-angiotensin-system (RAS) and increased levels of its main effector and vasoconstrictor hormone angiotensin II (Ang II). Angiotensin-converting-enzyme-2 (ACE2) has been described as a crucial enzymatic player in shifting the RAS towards its so-called alternative vasodilative and reno-protective axis by enzymatically converting Ang II to angiotensin-(1-7) (Ang-(1-7)). Yet, the relative contribution of ACE2 to Ang-(1-7) formation in vivo has not been elucidated. Mass spectrometry based quantification of angiotensin metabolites in the kidney and plasma of ACE2 KO mice surprisingly revealed an increase in Ang-(1-7), suggesting additional pathways to be responsible for alternative RAS activation in vivo. Following assessment of angiotensin metabolism in kidney homogenates, we identified neprilysin (NEP) to be a major source of renal Ang-(1-7) in mice and humans. These findings were supported by MALDI imaging, showing NEP mediated Ang-(1-7) formation in whole kidney cryo-sections in mice. Finally, pharmacologic inhibition of NEP resulted in strongly decreased Ang-(1-7) levels in murine kidneys. This unexpected new role of NEP may have implications for the combination therapy with NEP-inhibitors and angiotensin-receptor-blockade, which has been shown being a promising therapeutic approach for heart failure therapy.

High salt drives Th17 responses in experimental autoimmune encephalomyelitis without impacting myeloid dendritic cells.

Recently, we have shown that high dietary salt intake aggravates T helper cell (Th) 17 responses and neuroinflammation. Here, we employed in vitro assays for myeloid dendritic cell (mDC) maturation, DC cytokine production, T cell activation and ex vivo analyses in murine experimental autoimmune encephalomyelitis (EAE) to investigate whether the salt effect on Th17 cells is further mediated through DCs in vivo. In cell culture, an excess of 40mM sodium chloride did neither affect the generation, maturation nor the function of DCs, but, in different assays, significantly increased Th17 differentiation. During the initiation phase of MOG35-55 EAE, we did not observe altered DC frequencies or co-stimulatory capacities in lymphoid organs, while IL-17A production and Th17 cells in the spleen were significantly increased. Complementary ex vivo analyses of the spinal cord during the effector phase of EAE showed increased frequencies of Th17 cells, but did not reveal differences in phenotypes of CNS invading DCs. Finally, adaption of transgenic mice harboring a MOG specific T cell receptor to a high-salt diet led to aggravated clinical disease only after active immunization. Wild-type mice adapted to a high-salt diet in the effector phase of EAE, bypassing the priming phase of T cells, only displayed mildly aggravated disease. In summary, our data argue for a direct effect of NaCl on Th17 cells in neuroinflammation rather than an effect primarily exerted via DCs. These data may further fuel our understanding on the dietary impact on different immune cell subsets in autoimmune diseases, such as multiple sclerosis.

High salt reduces the activation of IL-4- and IL-13-stimulated macrophages.

A high intake of dietary salt (NaCl) has been implicated in the development of hypertension, chronic inflammation, and autoimmune diseases. We have recently shown that salt has a proinflammatory effect and boosts the activation of Th17 cells and the activation of classical, LPS-induced macrophages (M1). Here, we examined how the activation of alternative (M2) macrophages is affected by salt. In stark contrast to Th17 cells and M1 macrophages, high salt blunted the alternative activation of BM-derived mouse macrophages stimulated with IL-4 and IL-13, M(IL-4+IL-13) macrophages. Salt-induced reduction of M(IL-4+IL-13) activation was not associated with increased polarization toward a proinflammatory M1 phenotype. In vitro, high salt decreased the ability of M(IL-4+IL-13) macrophages to suppress effector T cell proliferation. Moreover, mice fed a high salt diet exhibited reduced M2 activation following chitin injection and delayed wound healing compared with control animals. We further identified a high salt-induced reduction in glycolysis and mitochondrial metabolic output, coupled with blunted AKT and mTOR signaling, which indicates a mechanism by which NaCl inhibits full M2 macrophage activation. Collectively, this study provides evidence that high salt reduces noninflammatory innate immune cell activation and may thus lead to an overall imbalance in immune homeostasis.

Role of glial 14-3-3 gamma protein in autoimmune demyelination.

BACKGROUND: The family of 14-3-3 proteins plays an important role in the regulation of cell survival and death. Here, we investigate the role of the 14-3-3 gamma (14-3-3 γ) subunit for glial responses in autoimmune demyelination. METHODS: Expression of 14-3-3 γ in glial cell culture was investigated by reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemistry. 14-3-3 γ knockout mice were subjected to murine myelin oligodendrocyte-induced experimental autoimmune encephalomyelitis (MOG-EAE), an animal model mimicking inflammatory features and neurodegenerative aspects of multiple sclerosis (MS). RESULTS: Expression studies in cell culture confined expression of 14-3-3 γ to both, oligodendrocytes (OL) and astrocytes. RT-PCR analysis revealed an increased expression of 14-3-3 γ mRNA in the spinal cord during the late chronic phase of MOG-EAE. At that stage, EAE was more severe in 14-3-3 γ knockout mice as compared to age- and gender-matched controls. Histopathological analyses on day 56 post immunization (p.i.) revealed significantly enhanced myelin damage as well as OL injury and secondary, an increase in axonal injury and gliosis in 14-3-3 γ -/- mice. At the same time, deficiency in 14-3-3 γ protein did not influence the immune response. Further histological studies revealed an increased susceptibility towards apoptosis in 14-3-3 γ-deficient OL in the inflamed spinal cord. CONCLUSION: These data argue for a pivotal role of 14-3-3 γ-mediated signalling pathways for OL protection in neuroinflammation.

Dietary Fatty Acids Directly Impact Central Nervous System Autoimmunity via the Small Intestine.

Growing empirical evidence suggests that nutrition and bacterial metabolites might impact the systemic immune response in the context of disease and autoimmunity. We report that long-chain fatty acids (LCFAs) enhanced differentiation and proliferation of T helper 1 (Th1) and/or Th17 cells and impaired their intestinal sequestration via p38-MAPK pathway. Alternatively, dietary short-chain FAs (SCFAs) expanded gut T regulatory (Treg) cells by suppression of the JNK1 and p38 pathway. We used experimental autoimmune encephalomyelitis (EAE) as a model of T cell-mediated autoimmunity to show that LCFAs consistently decreased SCFAs in the gut and exacerbated disease by expanding pathogenic Th1 and/or Th17 cell populations in the small intestine. Treatment with SCFAs ameliorated EAE and reduced axonal damage via long-lasting imprinting on lamina-propria-derived Treg cells. These data demonstrate a direct dietary impact on intestinal-specific, and subsequently central nervous system-specific, Th cell responses in autoimmunity, and thus might have therapeutic implications for autoimmune diseases such as multiple sclerosis.

New role for the (pro)renin receptor in T-cell development.

The (pro)renin receptor (PRR) was originally thought to be important for regulating blood pressure via the renin-angiotensin system. However, it is now emerging that PRR has instead a generic role in cellular development. Here, we have specifically deleted PRR from T cells. T-cell-specific PRR-knockout mice had a significant decrease in thymic cellularity, corresponding with a 100-fold decrease in the number of CD4(+) and CD8(+) thymocytes, and a large increase in double-negative (DN) precursors. Gene expression analysis on sorted DN3 thymocytes indicated that PRR-deficient thymocytes have perturbations in key cellular pathways essential at the DN3 stage, including transcription and translation. Further characterization of DN T-cell progenitors leads us to propose that PRR deletion affects thymocyte survival and development at multiple stages; from DN3 through to DN4, double-positive, and single-positive CD4 and CD8. Our study thus identifies a new role for PRR in T-cell development.

Pivotal role of choline metabolites in remyelination.

Neuroprotective approaches for central nervous system regeneration have not been successful in clinical practice so far and compounds that enhance remyelination are still not available for patients with multiple sclerosis. The objective of this study was to determine potential regenerative effects of the substance cytidine-5'-diphospho (CDP)-choline in two different murine animal models of multiple sclerosis. The effects of exogenously applied CDP-choline were tested in murine myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis. In addition, the cuprizone-induced mouse model of de- and remyelination was used to specifically test the hypothesis that CDP-choline directly increases remyelination. We found that CDP-choline ameliorated the disease course of experimental autoimmune encephalomyelitis and exerted beneficial effects on myelin, oligodendrocytes and axons. After cuprizone-induced demyelination, CDP-choline effectively enhanced myelin regeneration and reversed motor coordination deficits. The increased remyelination arose from an increase in the numbers of proliferating oligodendrocyte precursor cells and oligodendrocytes. Further in vitro studies suggest that this process is regulated by protein kinase C. We thus identified a new mechanism to enhance central nervous system remyelination via the choline pathway. Due to its regenerative action combined with an excellent safety profile, CDP-choline could become a promising substance for patients with multiple sclerosis as an add-on therapy.

Angiotensin IV is induced in experimental autoimmune encephalomyelitis but fails to influence the disease.

In multiple sclerosis (MS) and its corresponding animal models, over-activity of the renin-angiotensin system (RAS) has been reported and pharmacological RAS blockade exerts beneficial effects. The RAS generates a number of bioactive angiotensins, thereby primarily regulating the body's sodium homeostasis and blood pressure. In this regard, angiotensin IV (AngIV), a metabolite of the RAS has been shown to modulate inflammatory responses. Here we studied potential implications of AngIV signalling in myelin oligodendrocyte glycoprotein (MOG) peptide induced murine experimental autoimmune encephalomyelitis (EAE), a close-to-MS animal model. Mass spectrometry revealed elevated plasma levels of AngIV in EAE. Expression of cognate AT4 receptors was detected in macrophages and T cells as major drivers of pathology in EAE. Yet, AngIV did not modulate macrophage or T cell functions in vitro or displayed detectable effects on neuroantigen specific immune responses in vivo. The data argue against a major contribution of AngIV signalling in the immunopathogenesis of MOG-EAE.

Role of "Western diet" in inflammatory autoimmune diseases.

Developed societies, although having successfully reduced the burden of infectious disease, constitute an environment where metabolic, cardiovascular, and autoimmune diseases thrive. Living in westernized countries has not fundamentally changed the genetic basis on which these diseases emerge, but has strong impact on lifestyle and pathogen exposure. In particular, nutritional patterns collectively termed the "Western diet", including high-fat and cholesterol, high-protein, high-sugar, and excess salt intake, as well as frequent consumption of processed and 'fast foods', promote obesity, metabolic syndrome, and cardiovascular disease. These factors have also gained high interest as possible promoters of autoimmune diseases. Underlying metabolic and immunologic mechanisms are currently being intensively explored. This review discusses the current knowledge relative to the association of "Western diet" with autoimmunity, and highlights the role of T cells as central players linking dietary influences to autoimmune pathology.

Sodium chloride drives autoimmune disease by the induction of pathogenic TH17 cells.

There has been a marked increase in the incidence of autoimmune diseases in the past half-century. Although the underlying genetic basis of this class of diseases has recently been elucidated, implicating predominantly immune-response genes, changes in environmental factors must ultimately be driving this increase. The newly identified population of interleukin (IL)-17-producing CD4(+) helper T cells (TH17 cells) has a pivotal role in autoimmune diseases. Pathogenic IL-23-dependent TH17 cells have been shown to be critical for the development of experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis, and genetic risk factors associated with multiple sclerosis are related to the IL-23-TH17 pathway. However, little is known about the environmental factors that directly influence TH17 cells. Here we show that increased salt (sodium chloride, NaCl) concentrations found locally under physiological conditions in vivo markedly boost the induction of murine and human TH17 cells. High-salt conditions activate the p38/MAPK pathway involving nuclear factor of activated T cells 5 (NFAT5; also called TONEBP) and serum/glucocorticoid-regulated kinase 1 (SGK1) during cytokine-induced TH17 polarization. Gene silencing or chemical inhibition of p38/MAPK, NFAT5 or SGK1 abrogates the high-salt-induced TH17 cell development. The TH17 cells generated under high-salt conditions display a highly pathogenic and stable phenotype characterized by the upregulation of the pro-inflammatory cytokines GM-CSF, TNF-α and IL-2. Moreover, mice fed with a high-salt diet develop a more severe form of EAE, in line with augmented central nervous system infiltrating and peripherally induced antigen-specific TH17 cells. Thus, increased dietary salt intake might represent an environmental risk factor for the development of autoimmune diseases through the induction of pathogenic TH17 cells.

Vascular pathology in multiple sclerosis: mind boosting or myth busting?

The investigation of central nervous system vascular changes in the pathophysiology of multiple sclerosis (MS) is a time-honored concept. Yet, recent reports on changes in venous cerebrospinal outflow, the advent of new magnetic resonance imaging techniques and the investigation of immunomodulatory properties of several vascular mediators on the molecular level have added new excitement to hypotheses centering around vascular pathology as determining factor in the pathophysiology of MS. Here we critically review the concept of chronic cerebrospinal venous insufficiency in MS patients and describe new imaging techniques including perfusion weighted imaging, susceptibility weighted imaging and diffusion weighted imaging which reveal central nervous system hypoperfusion, perivascular iron deposition and diffuse structural changes in the MS brain. On a molecular basis, vascular mediators represent interesting targets connecting vascular pathology with immunomodulation. In summary, the relation of venous changes to the pathophysiology of MS may not be as simple as initially described and it certainly seems awkward to think of the complex disease MS solely as result of a simple venous outflow obstruction. Yet, the investigation of new vascular concepts as one variable in the pathophysiology of the autoimmune attack seems very worthwhile and may add to a better understanding of this devastating disorder.

Role of the renin-angiotensin system in autoimmune inflammation of the central nervous system.

Angiotensin II is the principle effector molecule of the renin angiotensin system (RAS). It exerts its various actions on the cardiovascular and renal system, mainly via interaction with the angiotensin II type-1 receptor (AT1R), which contributes to blood pressure regulation and development of hypertension but may also mediate effects on the immune system. Here we study the role of the RAS in myelin-oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (MOG-EAE), a model mimicking many aspects of multiple sclerosis. Quantitative RT-PCR analyses showed an up-regulation of renin, angiotensin-converting enzyme, as well as AT1R in the inflamed spinal cord and the immune system, including antigen presenting cells (APC). Treatment with the renin inhibitor aliskiren, the angiotensin II converting-enzyme inhibitor enalapril, as well as preventive or therapeutic application of the AT1R antagonist losartan, resulted in a significantly ameliorated course of MOG-EAE. Blockade of AT1R did not directly impact on T-cell responses, but significantly reduced numbers of CD11b+ or CD11c+ APC in immune organs and in the inflamed spinal cord. Additionally, AT1R blockade impaired the expression of CCL2, CCL3, and CXCL10, and reduced CCL2-induced APC migration. Our findings suggest a pivotal role of the RAS in autoimmune inflammation of the central nervous system and identify RAS blockade as a potential new target for multiple sclerosis therapy.