Restriction of de novo pyrimidine biosynthesis inhibits Th1 cell activation and promotes Th2 cell differentiation

Blocking M2-Like Macrophage Polarization Using Decoy Oligodeoxynucleotide-Based Gene Therapy Prevents Immune Evasion for Pancreatic Cancer Treatment

M2-like macrophages exhibit immunosuppressive activity and promote pancreatic cancer progression. Reactive oxygen species (ROS) affect macrophage polarization; however, the mechanism remains unclear. This study aimed to elucidate the underlying molecular basis and design a gene therapy to inhibit M2-like polarization. Microarray analysis and immunofluorescence staining were performed in M1-like and M2-like macrophages to ascertain the expression of CYBB, a major intracellular ROS source. Coculture assay and syngeneic orthotopic pancreatic cancer mice models were used to study the mechanism of M2-like skewing. Decoy oligodeoxynucleotides (ODNs) were designed to manipulate CYBB transcription to inhibit M2-like polarization and control tumor growth. Lipopolysaccharide treatment polarized U937 cells to M1-like macrophages in which CYBB expression was increased. In contrast, coculture with PANC-1 cells induced M2-like polarization in U937 cells with CYBB downregulation. High CD204 M2-like expression in combination with low CYBB expression was associated with the worst prognosis in patients with pancreatic cancer. STAT6 and HDAC2 in U937 cells were activated by cancer cell-derived IL4 after coculture and then bound to the CYBB promoter to repress CYBB expression, resulting in M2-like polarization. Diphenyleneiodonium, 8λ³-iodatricyclo[7.4.0.02,⁷]trideca-1(13),2,4,6,9,11-hexaen-8-ylium chloride that inhibits ROS production could block this action. Knockdown of STAT6 and HDAC2 also inhibited M2-like polarization and maintained the M1-like phenotype of U937 cells after coculture. Decoy ODNs interrupting the binding of STAT6 to the CYBB promoter counteracted M2-like polarization and tumor growth and triggered antitumor immunity in vivo. Gene therapy using STAT6-CYBB decoy ODNs can inhibit M2-like polarization, representing a potential therapeutic tool for pancreatic cancer.

Disease Modifying Strategies in Multiple Sclerosis: New Rays of Hope to Combat Disability?

Multiple sclerosis (MS) is the most prevalent chronic autoimmune inflammatory- demyelinating disorder of the central nervous system (CNS). It usually begins in young adulthood, mainly between the second and fourth decades of life. Usually, the clinical course is characterized by the involvement of multiple CNS functional systems and by different, often overlapping phenotypes. In the last decades, remarkable results have been achieved in the treatment of MS, particularly in the relapsing- remitting (RRMS) form, thus improving the long-term outcome for many patients. As deeper knowledge of MS pathogenesis and respective molecular targets keeps growing, nowadays, several lines of disease-modifying treatments (DMT) are available, an impressive change compared to the relative poverty of options available in the past. Current MS management by DMTs is aimed at reducing relapse frequency, ameliorating symptoms, and preventing clinical disability and progression. Notwithstanding the relevant increase in pharmacological options for the management of RRMS, research is now increasingly pointing to identify new molecules with high efficacy, particularly in progressive forms. Hence, future efforts should be concentrated on achieving a more extensive, if not exhaustive, understanding of the pathogenetic mechanisms underlying this phase of the disease in order to characterize novel molecules for therapeutic intervention. The purpose of this review is to provide a compact overview of the numerous currently approved treatments and future innovative approaches, including neuroprotective treatments as anti-LINGO-1 monoclonal antibody and cell therapies, for effective and safe management of MS, potentially leading to a cure for this disease.

Identification of Potent hDHODH Inhibitors for Lung Cancer via Virtual Screening of a Rationally Designed Small Combinatorial Library

Cancer is characterized by altered cellular metabolism, and metabolic enzymes are considered as a promising target for anticancer therapy. Pyrimidine metabolism dysregulation is associated with various types of cancer, particularly lung cancer, which is one of the leading causes of cancer-related mortality worldwide. Recent studies have shown that small-cell lung cancer cells are particularly reliant on the pyrimidine biosynthesis pathway and are sensitive to its disruption. DHODH, the rate-limiting enzyme of the de novo pyrimidine production pathway, is essential in the production of RNA and DNA and is overexpressed in malignancies such as AML, skin cancer, breast cancer, and lung cancer, thereby highlighting DHODH as a viable target for developing drugs to combat lung cancer. Herein, rational drug design and computational techniques were used to discover novel DHODH inhibitors. A small combinatorial library was generated, and the top hits were synthesized and tested for anticancer activity against three lung cancer cell lines. Among the tested compounds, compound 5c possessed a stronger cytotoxicity (TC₅₀ of 11 μM) compared to the standard FDA-approved drug (Regorafenib, TC₅₀ of 13 μM) on the A549 cell line. Furthermore, compound 5c demonstrated potent inhibitory activity against hDHODH at a nanomolar level of 421 nM. DFT, molecular docking, molecular dynamic simulations, and free energy calculations were also carried out to understand the inhibitory mechanisms of the synthesized scaffolds. These in silico studies identified key mechanisms and structural features that will be crucial for future studies.

Teriflunomide modulates both innate and adaptive immune capacities in multiple sclerosis

BACKGROUND

Teriflunomide (TER) (Aubagio™) is an FDA-approved disease-modifying therapy (DMT) for relapsing-remitting multiple sclerosis (RRMS). The mechanism of action of TER is thought to be related to the inhibition of dihydroorotate dehydrogenase (DHODH), a key mitochondrial enzyme in the de novo pyrimidine synthesis pathway required by rapidly dividing lymphocytes. Several large pivotal studies have established the efficacy and safety of TER in patients with RRMS. Despite this, little is known about how the adaptive and innate immune cell subsets are affected by the treatment in patients with MS.

METHODS

We recruited 20 patients with RRMS who were newly started on TER and performed multicolor flow cytometry and functional assays on peripheral blood samples. A paired t-test was used for the statistical analysis and comparison.

RESULTS

Our data showed that TER promoted a tolerogenic environment by shifting the balance between activated pathogenic and naïve or immunosuppressive immune cell subsets. In our cohort, TER increased the expression of the immunosuppressive marker CD39 on regulatory T cells (Tregs) while it decreased the expression of the activation marker CXCR3 on CD4⁺ T helper cells. TER treatment also reduced switched memory (sm) B cells while it increased naïve B cells and downregulated the expression of co-stimulatory molecules CD80 and CD86. Additionally, TER reduced the percentage and absolute numbers of natural killer T (NKT) cells, as well as the percentage of natural killer (NK) cells and showed a trend toward reducing the CD56^dim NK pathogenic subset.

CONCLUSION

TER promotes the tolerogenic immune response and suppresses the pathogenic immune response in patients with RRMS.

Extracellular Domains of CAR Reprogram T-Cell Metabolism Without Antigen Stimulation

Metabolism is an indispensable part of T-cell proliferation, activation, and exhaustion, yet the metabolism of chimeric antigen receptor (CAR)-T cells remains incompletely understood. CARs are comprised of extracellular domains that determine cancer specificity, often using single-chain variable fragments (scFvs), and intracellular domains that trigger signaling upon antigen binding. Here we show that CARs differing only in the scFv reprogram T-cell metabolism differently. Even in the absence of antigens, some CARs increase proliferation and nutrient uptake in T cells. Using stable isotope tracers and mass spectrometry, we observe basal metabolic fluxes through glycolysis doubling and amino acid uptake overtaking anaplerosis in CAR-T cells harboring rituximab scFv, unlike other similar anti-CD20 scFvs. Disparate rituximab and 14g2a-based anti-GD2 CAR-T cells are similarly hypermetabolic and channel excess nutrients to nitrogen overflow metabolism. Since CAR-dependent metabolic reprogramming alters cellular energetics, nutrient utilization, and proliferation, metabolic profiling should be an integral part of CAR-T cell development.

A prospective study of the infant gut microbiome in relation to vaccine response

BACKGROUND

The establishment of the gut microbiome plays a key symbiotic role in the developing immune system; however, its influence on vaccine response is yet uncertain. We prospectively investigated the composition and diversity of the early-life gut microbiome in relation to infant antibody response to two routinely administered vaccines.

METHODS

Eighty-three infants enrolled in the New Hampshire Birth Cohort Study were included in the analysis. We collected blood samples at 12 months of age and assayed the isolated serum to quantify total IgG and measured antibody to pneumococcal capsular polysaccharide and tetanus toxoid. Stool samples were collected from infants at 6 weeks of age and sequenced using 16S rRNA, and a subset of 61 samples were sequenced using shotgun metagenomics sequencing.

RESULTS

We observed differences in beta diversity for 16S 6-week stool microbiota and pneumococcal and tetanus IgG antibody responses. Metagenomics analyses identified species and metabolic pathways in 6-week stool associated with tetanus antibody response, in particular, negative associations with the relative abundance of Aeriscardovia aeriphila species and positive associations with the relative abundance of species associated with CDP-diacylglycerol biosynthesis pathways.

CONCLUSIONS

The early gut microbiome composition may influence an infant's vaccine response.

IMPACT

Early intestinal microbiome acquisition plays a critical role in immune maturation and in both adaptive and innate immune response in infancy. We identified associations between early life microbiome composition and response to two routinely administered vaccines-pneumococcal capsular polysaccharide and tetanus toxoid-measured at approximately 1 year of age. Our findings highlight the potential impact of the gut microbiome on infant immune response that may open up opportunities for future interventions.

Repurposing MS immunotherapies for CIDP and other autoimmune neuropathies: unfulfilled promise or efficient strategy?

Despite advances in the treatment of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and other common autoimmune neuropathies (AN), still-many patients with these diseases do not respond satisfactorily to the available treatments. Repurposing of disease-modifying therapies (DMTs) from other autoimmune conditions, particularly multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD), is a promising strategy that may accelerate the establishment of novel treatment choices for AN. This approach appears attractive due to homologies in the pathogenesis of these diseases and the extensive post-marketing experience that has been gathered from treating MS and NMOSD patients. The idea is also strengthened by a number of studies that explored the efficacy of DMTs in animal models of AN but also in some CIDP patients. We here review the available preclinical and clinical data of approved MS therapeutics in terms of their applicability to AN, especially CIDP. Promising therapeutic approaches appear to be B cell-directed and complement-targeting strategies, such as anti-CD20/anti-CD19 agents, Bruton's tyrosine kinase inhibitors and anti-C5 agents, as they exert their effects in the periphery. This is a major advantage because, in contrast to MS, their action in the periphery is sufficient to exert significant immunomodulation.

Persistent CAD activity in memory CD8+ T cells supports rRNA synthesis and ribosomal biogenesis required at rechallenge

Memory CD8⁺ T cells are characterized by their ability to persist long after the initial antigen encounter and their capacity to generate a rapid recall response. Recent studies have identified a role for metabolic reprogramming and mitochondrial function in promoting the longevity of memory T cells. However, detailed mechanisms involved in promoting their rapid recall response are incompletely understood. Here, we identify a role for the initial and continued activation of the trifunctional rate-limiting enzyme of the de novo pyrimidine synthesis pathway CAD (carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase) as critical in promoting the rapid recall response of previously activated CD8⁺ T cells. We found that CAD was rapidly phosphorylated upon naïve T cell activation in an mTORC1-dependent manner, yet remained phosphorylated long after initial activation. Previously activated CD8⁺ T cells displayed continued de novo pyrimidine synthesis in the absence of mitogenic signals, and interfering with this pathway diminished the speed and magnitude of cytokine production upon rechallenge. Inhibition of CAD did not affect cytokine transcript levels but diminished available pre-rRNA (ribosomal RNA), the polycistronic rRNA precursor whose synthesis is the rate-limiting step in ribosomal biogenesis. CAD inhibition additionally decreased levels of detectable ribosomal proteins in previously activated CD8⁺ T cells. Conversely, overexpression of CAD improved both the cytokine response and proliferation of memory T cells. Overall, our studies reveal a critical role for CAD-induced pyrimidine synthesis and ribosomal biogenesis in promoting the rapid recall response characteristic of memory T cells.

Mitochondrial-Linked De Novo Pyrimidine Biosynthesis Dictates Human T-Cell Proliferation but Not Expression of Effector Molecules

T-cell activation upon antigen stimulation is essential for the continuation of the adaptive immune response. Impairment of mitochondrial oxidative phosphorylation is a well-known disruptor of T-cell activation. Dihydroorotate dehydrogenase (DHODH) is a component of the de novo synthesis of pyrimidines, the activity of which depends on functional oxidative phosphorylation. Under circumstances of an inhibited oxidative phosphorylation, DHODH becomes rate-limiting. Inhibition of DHODH is known to block clonal expansion and expression of effector molecules of activated T cells. However, this effect has been suggested to be caused by downstream impairment of oxidative phosphorylation rather than a lower rate of pyrimidine synthesis. In this study, we successfully inhibit the DHODH of T cells with no residual effect on oxidative phosphorylation and demonstrate a dose-dependent inhibition of proliferation of activated CD3⁺ T cells. This block is fully rescued when uridine is supplemented. Inhibition of DHODH does not alter expression of effector molecules but results in decreased intracellular levels of deoxypyrimidines without decreasing cell viability. Our results clearly demonstrate the DHODH and mitochondrial linked pyrimidine synthesis as an independent and important cytostatic regulator of activated T cells.

Inflammation-type dysbiosis of the oral microbiome associates with the duration of COVID-19 symptoms and long COVID

In the COVID-19 pandemic, caused by SARS-CoV-2, many individuals experience prolonged symptoms, termed long-lasting COVID-19 symptoms (long COVID). Long COVID is thought to be linked to immune dysregulation due to harmful inflammation, with the exact causes being unknown. Given the role of the microbiome in mediating inflammation, we aimed to examine the relationship between the oral microbiome and the duration of long COVID symptoms. Tongue swabs were collected from patients presenting with COVID-19 symptoms. Confirmed infections were followed until resolution of all symptoms. Bacterial composition was determined by metagenomic sequencing. We used random forest modeling to identify microbiota and clinical covariates that are associated with long COVID symptoms. Of the patients followed, 63% developed ongoing symptomatic COVID-19 and 37% went on to long COVID. Patients with prolonged symptoms had significantly higher abundances of microbiota that induced inflammation, such as members of the genera Prevotella and Veillonella, which, of note, are species that produce LPS. The oral microbiome of patients with long COVID was similar to that of patients with chronic fatigue syndrome. Altogether, our findings suggest an association with the oral microbiome and long COVID, revealing the possibility that dysfunction of the oral microbiome may have contributed to this draining disease.

Drugs used in the treatment of multiple sclerosis during COVID-19 pandemic: a critical viewpoint

Since COVID-19 has emerged as a word public health problem, attention has been focused on how immune-suppressive drugs used for the treatment of autoimmune disorders influence the risk for SARS-CoV-2 infection and the development of acute respiratory distress syndrome (ARDS). Here, we discuss the disease-modifying agents approved for the treatment of multiple sclerosis (MS) within this context. Interferon (IFN)-β1a and -1b, which display antiviral activity, could be protective in the early stage of COVID-19 infection, although SARS-CoV-2 may have developed resistance to IFNs. However, in the hyperinflammation stage, IFNs may become detrimental by facilitating macrophage invasion in the lung and other organs. Glatiramer acetate and its analogues should not interfere with the development of COVID-19 and may be considered safe. Teriflunomide, a first-line oral drug used in the treatment of relapsing-remitting MS (RRMS), may display antiviral activity by depleting cellular nucleotides necessary for viral replication. The other first-line drug, dimethyl fumarate, may afford protection against SARS-CoV-2 by activating the Nrf-2 pathway and reinforcing the cellular defenses against oxidative stress. Concern has been raised regarding the use of second-line treatments for MS during the COVID-19 pandemic. However, this concern is not always justified. For example, fingolimod might be highly beneficial during the hyperinflammatory stage of COVID-19 for a number of mechanisms, including the reinforcement of the endothelial barrier. Caution is suggested for the use of natalizumab, cladribine, alemtuzumab, and ocrelizumab, although MS disease recurrence after discontinuation of these drugs may overcome a potential risk for COVID-19 infection.

Functional Analysis of Immune Signature Genes in Th1* Memory Cells Links ISOC1 and Pyrimidine Metabolism to IFN-γ and IL-17 Production

CCR6+CXCR3+CCR4-CD4+ memory T cells, termed Th1*, are important for long-term immunity to Mycobacterium tuberculosis and the pathogenesis of autoimmune diseases. Th1* cells express a unique set of lineage-specific transcription factors characteristic of both Th1 and Th17 cells and display distinct gene expression profiles compared with other CD4+ T cell subsets. To examine molecules and signaling pathways important for the effector function of Th1* cells, we performed loss-of-function screening of genes selectively enriched in the Th1* subset. The genetic screen yielded candidates whose depletion significantly impaired TCR-induced IFN-γ production. These included genes previously linked to IFN-γ or M. tuberculosis susceptibility and novel candidates, such as ISOC1, encoding a metabolic enzyme of unknown function in mammalian cells. ISOC1-depleted T cells, which produced less IFN-γ and IL-17, displayed defects in oxidative phosphorylation and glycolysis and impairment of pyrimidine metabolic pathway. Supplementation with extracellular pyrimidines rescued both bioenergetics and IFN-γ production in ISOC1-deficient T cells, indicating that pyrimidine metabolism is a key driver of effector functions in CD4+ T cells and Th1* cells. Results provide new insights into the immune-stimulatory function of ISOC1 as well as the particular metabolic requirements of human memory T cells, providing a novel resource for understanding long-term T cell-driven responses.

Global Metabolomics in Allogeneic Hematopoietic Cell Transplantation Recipients Discordant for Chronic Graft-versus-Host Disease

Chronic graft-versus-host disease (cGVHD) remains a significant late effect issue for allogeneic hematopoietic cell transplantation (allo-HCT) survivors, contributing to morbidity and mortality. The etiology of cGVHD is not well elucidated. Owing to a lack of early diagnostic tests and pathophysiology ambiguity, targeted treatments remain limited. Biomarkers for prediction, control response, or prognostication have not yet been identified. Metabolomics, the quantification of metabolites, is a potential biomarker of cGVHD but has not been evaluated in this population. In this study, we examined global metabolites of stored plasma to identify differentially expressed metabolites of individuals discordant for cGVHD following allo-HCT. A descriptive, comparative, cross-sectional study design was used to examine differentially expressed metabolites of plasma samples obtained from 40 adult allo-HCT recipients (20 with cGVHD and 20 without cGVHD) from 2 parent studies. Metabolomics profiling was conducted at the University of Florida's Southeast Center for Integrative Metabolomics. Full experimental methods followed a previously published method. All statistical analyses were performed by a PhD-prepared, trained bioinformatics statistician. There were 10 differentially expressed metabolites between participants with cGVHD and those without cGVHD. Differential metabolites included those related to energy metabolism (n = 3), amino acid metabolism (n = 3), lipid metabolism (n = 2), caffeine metabolism (n = 1), and neurotransmission (n = 1). Serotonin had the greatest fold change (21.01). This study suggests that cGVHD may be associated with expanded cellular energy and potentially mitochondrial dysfunction. The differential metabolic profile between patients with and without cGVHD indicates metabolic perturbations that merit further exploration as potential biomarkers of cGVHD. These findings support the need for further examination using a larger, prospective study design to identify metabolomic risk factors that may signal the need for earlier preventive measures and earlier treatment to reduce cGVHD.

Natural product piperine alleviates experimental allergic encephalomyelitis in mice by targeting dihydroorotate dehydrogenase

Multiple sclerosis (MS) is the most popular chronic and debilitating inflammatory disease of the central nervous system (CNS) that remains incurable. Dihydroorotate dehydrogenase (DHODH) is critical to the activity of T lymphocytes and represents a potential therapeutic target for MS. Here we identify piperine, a bioactive constituent of black pepper, as a potent inhibitor of DHODH with an IC₅₀ value of 0.88 μM. Isothermal titration calorimetry and thermofluor assay demonstrate the directly interaction between piperine and DHODH. The co-complex crystal structure of DHODH and piperine at 1.98 Å resolution further reveal that Tyr356 residue of DHODH is crucial for piperine binding. Importantly, we show that piperine can inhibit T cell overactivation in a DHODH-dependent manner in concanavalin A-triggered T-cell assay and mixed lymphocyte reaction assay. Finally, piperine exhibits strong preventive and therapeutic effect in the MOG-induced experimental allergic encephalomyelitis (EAE), a useful model for studying potential treatments for MS, by restricting inflammatory cells infiltration into the CNS and preventing myelin destruction and blood-brain barrier (BBB) disruption. Taken together, these findings highlight DHODH as a therapeutic target for autoimmune disease of the nervous system, and demonstrate a novel role for piperine in the treatment of MS.

Dihydroorotate dehydrogenase in oxidative phosphorylation and cancer

Dihydroorotate dehydrogenase (DHODH) is an enzyme of the de novo pyrimidine synthesis pathway that provides nucleotides for RNA/DNA synthesis essential for proliferation. In mammalian cells, DHODH is localized in mitochondria, linked to the respiratory chain via the coenzyme Q pool. Here we discuss the role of DHODH in the oxidative phosphorylation system and in the initiation and progression of cancer. We summarize recent findings on DHODH biology, the progress made in the development of new, specific inhibitors of DHODH intended for cancer therapy, and the mechanistic insights into the consequences of DHODH inhibition.

Teriflunomide induces a tolerogenic bias in blood immune cells of MS patients

Objectives

Teriflunomide, a disease‐modifying treatment approved for multiple sclerosis (MS), inhibits reversibly dihydroorotate dehydrogenase, an enzyme involved in de novo pyrimidine biosynthesis and down‐regulates proliferation of activated lymphocytes. We aimed to study the impact of this drug in the lymphocyte profiles of MS patients.

Methods

Fifty‐five patients with relapsing‐remitting MS who initiated teriflunomide treatment were included in the study. We studied peripheral blood mononuclear cells obtained before and 6 months after treatment initiation and explored effector, memory, and regulatory cells by flow cytometry. Wilcoxon matched pair tests were used to assess differences between basal and 6 months after treatment results. P‐values were corrected with Bonferroni test.

Results

When explored T and B cell subsets, we observed a decrease in the percentages of terminally differentiated CD4+ T cells (P = 0.001) and plasmablasts (P < 0.0001) after 6 months of treatment. These results were confirmed with the total cell number. When studied immunomodulatory cells, we observed a clear increase of monocytes expressing programmed death‐ligand 1 (PD‐L1) (P = 0.005), which correlated negatively with all effector CD8+ T cell subsets. We also observed an increase in the percentage of CD8+ T cells (P = 0.028) and monocytes (P = 0.04) producing IL‐10.

Conclusions

Teriflunomide induces a specific reduction in effector T and B cells that have shown to play a role in MS course and an increase in immunomodulatory cells. Particularly, this drug induces the expression of PD‐L1, a molecule involved in tolerance to autoantigens, which can contribute to inhibit the abnormal immune response taking place in MS.

Teriflunomide Modulates Vascular Permeability and Microglial Activation after Experimental Traumatic Brain Injury

Despite intensive research and clinical trials with numerous therapeutic treatments, traumatic brain injury (TBI) is a serious public health problem in the United States. There is no effective FDA-approved treatment to reduce morbidity and mortality associated with TBI. Inflammation plays a pivotal role in the pathogenesis of TBI. We looked to re-purpose existing drugs that reduce immune activation without broad immunosuppression. Teriflunomide, an FDA-approved drug, has been shown to modulate immunological responses outside of its ability to inhibit pyrimidine synthesis in rapidly proliferating cells. In this study, we tested the efficacy of teriflunomide to treat two different injury intensities in rat models of TBI. Our results show that teriflunomide restores blood-brain barrier integrity, decreases inflammation, and increases neurogenesis in the subgranular zone of the hippocampus. While we were unable to detect neurocognitive effects of treatment on memory and special learning abilities after treatment, a 2-week treatment following injury was sufficient to reduce neuroinflammation up to 120 days later.

Teriflunomide attenuates neuroinflammation-related neural damage in mice carrying human PLP1 mutations

BACKGROUND

Genetically caused neurological disorders of the central nervous system (CNS) are mostly characterized by poor or even fatal clinical outcome and few or no causative treatments are available. Often, these disorders are associated with low-grade, disease-promoting inflammation, another feature shared by progressive forms of multiple sclerosis (PMS). We previously generated two mouse lines carrying distinct mutations in the oligodendrocytic PLP1 gene that have initially been identified in patients diagnosed with MS. These mutations cause a loss of PLP function leading to a histopathological and clinical phenotype common to both PMS and genetic CNS disorders, like hereditary spastic paraplegias. Importantly, neuroinflammation promotes disease progression in these models, suggesting that pharmacological modulation of inflammation might ameliorate disease outcome.

METHODS

We applied teriflunomide, an approved medication for relapsing-remitting MS targeting activated T-lymphocytes, in the drinking water (10 mg/kg body weight/day). Experimental long-term treatment of PLP mutant mice was non-invasively monitored by longitudinal optical coherence tomography and by rotarod analysis. Immunomodulatory effects were subsequently analyzed by flow cytometry and immunohistochemistry and treatment effects regarding neural damage, and neurodegeneration were assessed by histology and immunohistochemistry.

RESULTS

Preventive treatment with teriflunomide attenuated the increase in number of CD8+ cytotoxic effector T cells and fostered the proliferation of CD8+ CD122+ PD-1+ regulatory T cells in the CNS. This led to an amelioration of axonopathic features and neuron loss in the retinotectal system, also reflected by reduced thinning of the innermost retinal composite layer in longitudinal studies and ameliorated clinical outcome upon preventive long-term treatment. Treatment of immune-incompetent PLP mutants did not provide evidence for a direct, neuroprotective effect of the medication. When treatment was terminated, no rebound of neuroinflammation occurred and histopathological improvement was preserved for at least 75 days without treatment. After disease onset, teriflunomide halted ongoing axonal perturbation and enabled a recovery of dendritic arborization by surviving ganglion cells. However, neither neuron loss nor clinical features were ameliorated, likely due to already advanced neurodegeneration before treatment onset.

CONCLUSIONS

We identify teriflunomide as a possible medication not only for PMS but also for inflammation-related genetic diseases of the nervous system for which causal treatment options are presently lacking.

Mechanism of action of three newly registered drugs for multiple sclerosis treatment

Multiple sclerosis (MS) is a disease of suspected autoimmune origin leading to neurodegeneration. The disease pathomechanism is considered to be primarily based on neuroinflammation directed against myelin antigens caused by autoreactive T cells. MS etiology remains still unknown, which makes it difficult to create an efficient therapy, therefore, MS treatment targets mechanisms involved in disease pathology. In this review, we present the mechanism of action of three newly registered drugs for MS. Dimethyl fumarate (DMF) is an agent presenting a broad spectrum of action. Its main activity is based on activating the nuclear factor E2 dependent pathway leading to antioxidant enzyme synthesis. DMF in general suppresses the pro-inflammatory immune activity and exerts a neuroprotective action. Teriflunomide is a more focused drug, acting as an inhibitor of pyrimidines synthesis, important for rapidly dividing cells such as activated lymphocytes. Similarly, alemtuzumab, an anti-CD52 antibody, causes depletion of mainly lymphocytes. Since in MS pathology, T and B cells are involved, this mode of action is promising.

IL-22-producing CD4+T cells in the treatment response of rheumatoid arthritis to combination therapy with methotrexate and leflunomide

T cells are key players in immune-mediated rheumatoid arthritis (RA). We previously reported that interleukin (IL)-22+CD4+T helper (IL-22+ Th) cells and IL-22 critically control the pathogenesis of RA. Here we monitored circulating levels of different IL-22+ Th cell subsets and measured plasma levels of IL-22, IL-17, and interferon (IFN)-γ in 60 patients with active RA following 12-week combination methotrexate (MTX) and leflunomide (LEF) therapy (MTX+LEF) and 20 healthy individuals. We found the frequencies of circulating IFN-γ-IL-17-IL-22+ (Th22), IFN-γ-IL-17+ (total Th17), IFN-γ+IL-17-IL-22+ (IL-22+Th1) cells, and IFN-γ-IL-17+IL-22+ (IL-22+Th17) cells, as well as the plasma levels of IL-22, IL-17 and IFN-γ to be significantly reduced in RA patients that responded to treatment, but not in non-responders. Reductions in plasma IL-22 level significantly correlated with percentage of circulating Th22 cells and the decrease of plasma IL-22 level correlated with the reduction of DAS28 in responders. Our data suggests that circulating Th22 cells and plasma IL-22 level play a detrimental role in RA. The combination MTX+LEF therapy, by targeting Th22 cells and reducing IL-22 level, relieves the immune defects and ameliorates symptoms of RA. This study provides novel mechanistic understanding of the pathogenesis of RA, which may promote a design of better therapies for RA.

From Leflunomide to Teriflunomide: Drug Development and Immunosuppressive Oral Drugs in the Treatment of Multiple Sclerosis

BACKGROUND

Immunosuppressive drugs have been used in the treatment of multiple sclerosis (MS) for a long time. Today, orally available second generation immunosuppressive agents have been approved or are filed for licensing as MS therapeutics. Due to semi-selective targeting of cellular processes, these second-generation immunosuppressive compounds might rather be immunomodulatory. For example, Teriflunomide inhibits the de novo pyrimidine synthesis and thus only targets rapidly proliferating cells, including lymphocytes. It is used as first line disease modifying therapy (DMT) in relapsing-remitting MS (RRMS).

METHODS

Review of online content related to oral immunosuppressants in MS with an emphasis on Teriflunomide.

RESULTS

Teriflunomide and Cladribine are second-generation immunosuppressants that are efficient in the treatment of MS patients. For Teriflunomide, a daily dose of 14 mg reduces the annualized relapse rate (ARR) by more than 30% and disability progression by 30% compared to placebo. Cladribine reduces the ARR by about 50% compared to placebo but has not yet been licensed due to unresolved safety concerns. We also discuss the significance of older immunosuppressive compounds including Azathioprine, Mycophenolate mofetile, and Cyclophosphamide in current MS therapy.

CONCLUSION

Teriflunomide has shown a favorable safety and efficacy profile in RRMS and is a therapeutic option for a distinct group of adult patients with RRMS.

Dendritic cells as therapeutic targets in neuroinflammation

Multiple sclerosis (MS) is the most common chronic inflammatory demyelinating disorder of the central nervous system characterized by infiltration of immune cells and progressive damage to myelin sheaths and neurons. There is still no cure for the disease, but drug regimens can reduce the frequency of relapses and slightly delay progression. Myeloid cells or antigen-presenting cells (APCs) such as dendritic cells (DC), macrophages, and resident microglia, are key players in both mediating immune responses and inducing immune tolerance. Mounting evidence indicates a contribution of these myeloid cells to the pathogenesis of multiple sclerosis and to the effects of treatment, the understanding of which might provide strategies for more potent novel therapeutic interventions. Here, we review recent insights into the role of APCs, with specific focus on DCs in the modulation of neuroinflammation in MS.

Advantage of tacrolimus/mycophenolate mofetil regimen for cytotoxic T cell-mediated defence and its inhibition by additive steroid administration in high-risk liver transplant recipients

Our previous work revealed that the recipients with the highest pre-existing numbers of CD8(+) effector T cells (TE ) [hyperparathyroidism (HPT)E recipients] occupied approximately 30% of adult transplant recipients performed in our hospital. HPTE recipients demonstrated very poor clinical outcome compared with the remaining 70% of recipients with the lowest pre-existing TE (LPTE recipient). This study aimed to clarify the best combined immunosuppressive regimen related to function of cytotoxic T lymphocytes (CTLs) for HPTE recipients. Eighty-one HPTE recipients were classified into three types, according to the immunosuppressive regimens: type 1, tacrolimus (Tac)/glucocorticoid (GC); type 2, Tac/mycophenolate mofetil (MMF)/GC; and type 3, Tac/MMF. Frequencies of severe infection, rejection and hospital death were the highest in types 1 and 2, whereas the lowest occurred in type 3. The survival rate in type 3 was the highest (100%) during follow-up until post-operative day 2000. Regarding the immunological mechanism, in type 1 TE perforin and interferon (IFN)-γ were generated through the self-renewal of CD8(+) central memory T cells (TCM ), but decreased in the early post-transplant period due to marked down-regulation of interleukin (IL)-12 receptor beta-1 of TCM. In type 2, the self-renewal TCM did not develop, and the effector function could not be increased. In type 3, in contrast, the effectors and cytotoxicity were correlated inversely with IL-12Rβ1(+) TCM levels, and increased at the highest level around the pre-transplant levels of IL-12Rβ1(+) TCM . However, the immunological advantage of Tac/MMF therapy was inhibited strongly by additive steroid administration.

Role of the immunogenic and tolerogenic subsets of dendritic cells in multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated disorder in the central nervous system (CNS) characterized by inflammation and demyelination as well as axonal and neuronal degeneration. So far effective therapies to reverse the disease are still lacking; most therapeutic drugs can only ameliorate the symptoms or reduce the frequency of relapse. Dendritic cells (DCs) are professional antigen presenting cells (APCs) that are key players in both mediating immune responses and inducing immune tolerance. Increasing evidence indicates that DCs contribute to the pathogenesis of MS and might provide an avenue for therapeutic intervention. Here, we summarize the immunogenic and tolerogenic roles of DCs in MS and review medicinal drugs that may affect functions of DCs and have been applied in clinic for MS treatment. We also describe potential therapeutic molecules that can target DCs by inducing anti-inflammatory cytokines and inhibiting proinflammatory cytokines in MS.

Nimesulide improves the symptomatic and disease modifying effects of leflunomide in collagen induced arthritis

Nimesulide is a COX-2 inhibitor used for symptomatic relief of rheumatoid arthritis. Leflunomide is an anti-pyrimidine used to manage the progression of rheumatoid arthritis. Herein we studied the influence of nimesulide and leflunomide combination in terms of disease symptoms and progression using collagen-induced arthritis model in mice, as a model for rheumatoid arthritis. Collagen induced arthritis was induced by immunization with type II collagen. Assessment of joint stiffness and articular hyperalgesia were evaluated using a locomotor activity cage and the Hargreaves method, respectively. Disease progression was assessed via arthritic index scoring, X-ray imaging, myeloperoxidase enzyme activity and histopathologic examination. Nimesulide induced only transient symptomatic alleviation on the top of decreased leucocytic infiltration compared to arthritis group. However, nimesulide alone failed to induce any significant improvement in the radiological or pathological disease progression. Leflunomide alone moderately alleviates the symptoms of arthritis and moderately retarded the radiological and pathological disease progression. Combination of nimesulide and leflunomide significantly improved symptomatic (analgesia and joint stiffness) and arthritic disease progression (radiological, pathological and Myeloperoxidase enzyme activity) in collagen induced arthritis animal model.

Inhibition of adjuvant-induced arthritis by nasal administration of novel synthetic peptides from heat shock protein 65

Background

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease mediated by T cells. The aim of the present study was to investigate the therapeutic efficacy of synthetic peptides (HP-R1, HP-R2 and HP-R3), derived from the sequence of 65-kD mycobacterial heat shock protein (HSP), in the treatment of RA using adjuvant-induced arthritis (AA) animal model.

Methods

AA was induced by a single intradermal injection Freund’s complete adjuvant in male Lewis rats. At the first clinical sign of disease, rats were administered nasally by micropipette of peptides or phosphate buffer saline (PBS). Disease progression was monitored by measurement of body weight, arthritis score and paw swelling. The changes of histopathology were assessed by hematoxylin eosin staining. The serum levels of tumor necrosis factor (TNF) - alpha and interleukin (IL)-4 were measured by enzyme-linked immunosorbent assay (ELISA).

Results

The peptides efficiently inhibited the footpad swelling and arthritic symptoms in AA rats. The synthetic peptides displayed significantly less inflammatory cellular infiltration and synovium hyperplasia than model controls. This effect was associated with a suppression of pro-inflammatory cytokine TNF-alpha production and an increase of anti-inflammatory cytokine IL-4 production after peptides treatment.

Conclusions

These results suggest that the synthetic peptides derived from HSP65 induce highly effective protection against AA, which is mediated in part by down-regulation of inflammatory cytokines, and support the view that the synthetic peptides is a potential therapy for RA that may help to diminish both joint inflammation and destruction.

Molecular pharmacodynamics of new oral drugs used in the treatment of multiple sclerosis

New oral drugs have considerably enriched the therapeutic armamentarium for the treatment of multiple sclerosis. This review focuses on the molecular pharmacodynamics of fingolimod, dimethyl fumarate (BG-12), laquinimod, and teriflunomide. We specifically comment on the action of these drugs at three levels: 1) the regulation of the immune system; 2) the permeability of the blood-brain barrier; and 3) the central nervous system. Fingolimod phosphate (the active metabolite of fingolimod) has a unique mechanism of action and represents the first ligand of G-protein-coupled receptors (sphingosine-1-phosphate receptors) active in the treatment of multiple sclerosis. Dimethyl fumarate activates the nuclear factor (erythroid-derived 2)-related factor 2 pathway of cell defense as a result of an initial depletion of reduced glutathione. We discuss how this mechanism lies on the border between cell protection and toxicity. Laquinimod has multiple (but less defined) mechanisms of action, which make the drug slightly more effective on disability progression than on annualized relapse rate in clinical studies. Teriflunomide acts as a specific inhibitor of the de novo pyrimidine biosynthesis. We also discuss new unexpected mechanisms of these drugs, such as the induction of brain-derived neurotrophic factor by fingolimod and the possibility that laquinimod and teriflunomide regulate the kynurenine pathway of tryptophan metabolism.

Teriflunomide and its mechanism of action in multiple sclerosis

Treatment of multiple sclerosis (MS) is challenging: disease-modifying treatments (DMTs) must both limit unwanted immune responses associated with disease initiation and propagation (as T and B lymphocytes are critical cellular mediators in the pathophysiology of relapsing MS), and also have minimal adverse impact on normal protective immune responses. In this review, we summarize key preclinical and clinical data relating to the proposed mechanism of action of the recently approved DMT teriflunomide in MS. Teriflunomide selectively and reversibly inhibits dihydro-orotate dehydrogenase, a key mitochondrial enzyme in the de novo pyrimidine synthesis pathway, leading to a reduction in proliferation of activated T and B lymphocytes without causing cell death. Results from animal experiments modelling the immune activation implicated in MS demonstrate reductions in disease symptoms with teriflunomide treatment, accompanied by reduced central nervous system lymphocyte infiltration, reduced axonal loss, and preserved neurological functioning. In agreement with the results obtained in these model systems, phase 3 clinical trials of teriflunomide in patients with MS have consistently shown that teriflunomide provides a therapeutic benefit, and importantly, does not cause clinical immune suppression. Taken together, these data demonstrate how teriflunomide acts as a selective immune therapy for patients with MS.

Teriflunomide for oral therapy in multiple sclerosis

Teriflunomide, the active metabolite of an approved antirheumatic drug, is an emerging oral therapy for multiple sclerosis (MS). Next to the inhibition of pyrimidine biosynthesis and proliferation of activated lymphocytes, it seems to have multiple anti-inflammatory and immunomodulating effects. Phase II and III clinical trials in relapsing MS demonstrated favorable safety and tolerability of the drug, as well as clinical efficacy, with a significant reduction of relapse rate, comparable with those of the available injectable immunomodulatory agents. While multiple other studies with teriflunomide are currently ongoing, its exact place in future treatment algorithms for MS is difficult to predict. It may be a good alternative for patients wishing to have an oral treatment with relatively large data regarding long-term safety.

An update of teriflunomide for treatment of multiple sclerosis

There are a number of oral agents emerging as potential disease-modifying agents in multiple sclerosis (MS). Among these investigational agents, teriflunomide has shown promise in large, multicenter, phase III clinical trials with respect to safety and efficacy in relapsing MS patients, and is the latest disease-modifying agent approved for use in MS patients in the United States. This review will summarize teriflunomide’s historical development, clinical pharmacology, studies in animals, clinical trials, and safety data, and will end with a discussion of the role of teriflunomide in MS in the context of existing treatment options.

Role of oral teriflunomide in the management of multiple sclerosis

The landscape of the treatment of relapsing-remitting multiple sclerosis is changing fast. Several oral treatments have shown benefit and generate much interest because of the convenience of their administration. Two oral compounds, fingolimod and teriflunomide, have been approved in relapsing-remitting multiple sclerosis, while others have completed Phase III trials and are awaiting review for registration. Teriflunomide is a pyrimidine synthesis inhibitor with selective immunomodulatory and immunosuppressive properties that have shown consistent efficacy in clinical trials, and a good safety profile. This paper provides an overview of the mechanisms of action and efficacy and safety results from clinical trials with this drug. The role of teriflunomide in the treatment of relapsing-remitting multiple sclerosis is discussed.

Influence of interleukin-4 gene polymorphisms and interleukin-4 serum level on susceptibility and severity of rheumatoid arthritis in Egyptian population

BACKGROUND

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease in which interleukin-4 (IL-4) plays an important role. This study aimed to investigate the influence of IL-4 variable number of tandem repeats (VNTRs) and IL-4-590 promoter polymorphisms on RA susceptibility, activity and severity in Egyptian population.

MATERIALS AND METHODS

One hundred and seventy-two RA patients and 172 controls were enrolled in this study. IL-4 VNTR and IL-4-590 promoter polymorphisms were genotyped using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Serum IL-4 and anti-cyclic citrullinated peptides (anti-CCPs) antibody concentrations were measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

Subjects with IL-4-590 TT genotype were significantly more likely to develop RA. IL-4 VNTR 1/1 genotype, IL-4-590 TT and CT genotypes were significantly more associated with erosive RA and positive anti-CCP antibody. RA severity parameters were significantly increased, while, IL-4 level was significantly decreased in RA patients with IL-4 VNTR 1/1 and IL-4-590 TT genotypes. Only patients with IL-4-590 TT genotype showed a significant increase of all RA activity parameters.

CONCLUSION

IL-4 VNTR and IL-4-590 promoter polymorphisms may be helpful for assessing RA severity in Egyptian population. Moreover, IL-4-590 promoter polymorphism may be associated with increased risk and activity of RA.

What do effective treatments for multiple sclerosis tell us about the molecular mechanisms involved in pathogenesis?

Multiple sclerosis is a potentially debilitating disease of the central nervous system. A concerted program of research by many centers around the world has consistently demonstrated the importance of the immune system in its pathogenesis. This knowledge has led to the formal testing of a number of therapeutic agents in both animal models and humans. These clinical trials have shed yet further light on the pathogenesis of MS through their sometimes unexpected effects and by their differential effects in terms of impact on relapses, progression of the disease, paraclinical parameters (MRI) and the adverse events that are experienced. Here we review the currently approved medications for the commonest form of multiple sclerosis (relapsing-remitting) and the emerging therapies for which preliminary results from phase II/III clinical trials are available. A detailed analysis of the molecular mechanisms responsible for the efficacy of these medications in multiple sclerosis indicates that blockade or modulation of both T- and B-cell activation and migration pathways in the periphery or CNS can lead to amelioration of the disease. It is hoped that further therapeutic trials will better delineate the pathogenesis of MS, ultimately leading to even better treatments with fewer adverse effects.

Emerging oral immunomodulating agents - focus on teriflunomide for the treatment of multiple sclerosis

Treatment for multiple sclerosis (MS), a chronic disease of the central nervous system, has historically relied exclusively on the use of injectable therapies. As the disease requires lifelong therapy, the development of oral therapies that are safe and effective would provide a more convenient dosage form that may improve patient compliance. One oral medication (fingolimod) was recently approved for treatment of MS. Teriflunomide, an immunomodulator, is one of four oral therapies currently undergoing Phase III trials. Teriflunomide exerts its clinical effects via selective inhibition of de novo pyrimidine synthesis, primarily targeting proliferating T and B lymphocytes in the periphery. Teriflunomide was effective as monotherapy in reducing magnetic resonance imaging lesions and annual relapse rates in Phase II and Phase III trials. When teriflunomide was added to interferon or glatiramer acetate therapy in Phase II trials, teriflunomide reduced magnetic resonance imaging lesions significantly more than either interferon or glatiramer acetate alone. Treatment-emergent adverse events occurred at similar rates among all groups in teriflunomide studies, with a trend towards a higher treatment emergent adverse events rate in the higher dosage group of teriflunomide (14 mg daily). Treatment discontinuations in teriflunomide trials were relatively low, suggesting that teriflunomide monotherapy is well tolerated. This article reviews the mode of action of teriflunomide, its pharmacokinetic, clinical efficacy, and safety profiles.

Preventive effects of 1,25-(OH)2VD3 against ConA-induced mouse hepatitis through promoting vitamin D receptor gene expression

AIM

To investigate the immunosuppressive effects of 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)VD(3)) on concanavalin A (ConA)-induced hepatitis and elucidate the action mechanism.

METHODS

Female BALB/C mice were intravenously administered ConA (20 mg/kg) to induce acute immunological liver injury. Liver damage was evaluated in respect to serum alanine transaminase (ALT) level and liver histological changes. The proliferation of splenocytes was measured by using [(3)H]-thymidine incorporation. The cytokine level in the cultured splenocyte supernatant was determined by using enzyme-linked immunosorbent assays (ELISAs). The percentage of different splenic T cell subtypes was analyzed by using flow cytometry. The expression of splenic vitamin D receptor (VDR) mRNA and protein was detected by using real-time qRT-PCR and Western blot, respectively.

RESULTS

1,25-(OH)(2)VD(3) (2.5 microg/kg, ip) significantly decreased the serum ALT levels and markedly attenuated the histological liver damage. The beneficial effect of 1,25-(OH)(2)VD(3) was associated with: (i) inhibition of CD4(+) T cell activation; (ii) reduction of interferon-gamma (IFN-gamma) and elevation of both IL-4 and IL-5 in supernatants of cultured splenocytes; and (iii) elimination of activated T cells by increasing VDR mRNA and protein expression in the spleen.

CONCLUSION

1,25-(OH)(2)VD(3) had a significant protective effect against ConA-induced hepatitis, and its mechanism of action was associated with down-regulation of T cell-mediated immunity and up-regulation of VDR gene expression.

Association of polymorphisms in the human IL-10 and IL-18 genes with rheumatoid arthritis

The decrease of anti-inflammatory cytokine and increase of pro-inflammatory cytokine was observed in rheumatoid arthritis (RA). Interleukin-10 (IL-10), a potent anti-inflammatory cytokine, has been demonstrated to suppress joint swelling and deformation in RA animal model. Interleukin-18 (IL-18), a widely distributed pro-inflammatory cytokine, induces the production of IFN-γ, activate NK cells, and promote inflammation. Recent studies demonstrated that the serum IL-10 and IL-18 levels may be influenced by genetics and related to susceptibility to several autoimmune diseases. In the present study, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing techniques, we analyzed the genotype and allele distributions of two single nucleotide polymorphisms (SNP) loci in the promoter region of IL-10 and IL-18 genes (IL-10-592 A/C and IL-18-607 A/C loci, respectively). Our results indicated that IL-10-592 allelic and genotypic frequencies were significantly different between the RA patients and normal subjects (P<0.05). In addition, significant differences of IL-10-592 allelic and genotypic frequencies were also detected between the patients with or without anti-cyclic citrullinated peptide antibody (anti-CCP) (P<0.05). In contrast, allelic and genotypic frequencies of IL-18-607 did not show significant difference between RA patients and normal subjects (P>0.05) or between anti-CCP-positive and anti-CCP-negative RA patients (P>0.05). Furthermore, ELISA detection of IL-10 and IL-18 serum levels revealed that the genotype of IL-10-592 was associated with IL-10 serum level (P<0.05), but the genotype and allele frequency of IL-18-607 was not associated with IL-18 serum level (P>0.05). Taken together, our findings provide new insight for the polymorphism of IL-10 gene in the pathogenesis of RA.

Recent developments in multiple sclerosis therapeutics

Multiple sclerosis, the most common neurologic disorder of young adults, is traditionally considered to be an inflammatory, autoimmune, demyelinating disease of the central nervous system. Based on this understanding, the initial therapeutic strategies were directed at immune modulation and inflammation control. These approaches, including high-dose corticosteroids for acute relapses and long-term use of parenteral interferon-beta, glatiramer acetate or natalizumab for disease modification, are at best moderately effective. Growing evidence supports that, while an inflammatory pathology characterizes the early relapsing stage of multiple sclerosis, neurodegenerative pathology dominates the later progressive stage of the disease. Multiple sclerosis disease-modifying therapies currently in development attempt to specifically target the underlying pathology at each stage of the disease, while avoiding frequent self-injection. These include a variety of oral medications and monoclonal antibodies to reduce inflammation in relapsing multiple sclerosis and agents intended to promote neuroprotection and neurorepair in progressive multiple sclerosis. Although newer therapies for relapsing MS have the potential to be more effective and easier to administer than current therapies, they also carry greater risks. Effective treatments for progressive multiple sclerosis are still being sought.

Critical periods for the teratogenicity of immune-suppressant Leflunomide in mice

Leflunomide has inhibitory effects on dihydroorotate-dehydrogenase activity and protein tyrosine kinase activity. In the present study, a single dose of 50 mg/kg Leflunomide was administered to pregnant mice on one of gestation days (GD)6-11. Characteristic external malformations were craniofacial defects following dosing on GD7, cleft palate on GD9, cleft palate and limb and tail deformities on GD10, and limb deformities on GD11. Skeletal examination revealed cervical to caudal vertebral malformations after treatment on GD7, GD8, GD9 or GD10. In the viscera, cardiovascular deformities were observed in the GD7 and GD9 Leflunomide-treated groups. These results demonstrate that multiple malformations were seen in various organs and most of the malformations observed appeared to be developmental stage-specific responses to Leflunomide treatment.

Systemic administration of tolerogenic dendritic cells ameliorates murine inflammatory arthritis

The expression of various cell surface molecules and the production of certain cytokines are important mechanisms by which dendritic cells (DC) are able to bias immune responses. This paper describes the effects of the inflammatory cytokine tumor necrosis factor (TNF)-α on DC phenotype and function. TNF-α treatment resulted in upregulation of MHC class II and CD86 in the absence of increased cell surface CD40 and CD80 or the production of IL-12. Additionally TNF-α treated cells were able to bias T cell responses towards an anti-inflammatory profile. On a note of caution this tolerogenic phenotype of the DC was not stable upon subsequent TLR-4 ligation as a 4 hour pulse of the TNF-α treated DC with lipopolysaccharide (LPS) resulted in the restoration of IL-12 production and an enhancement of their T cell stimulatory capacity which resulted in an increased IFN-γ production. However, TNF-α treated DC, when administered in vivo, were shown to ameliorate disease in collagen induced arthritis, an experimental model of inflammatory joint disease. Mice receiving TNF-α treated DC but not LPS matured DC had a delayed onset, and significantly reduced severity, of arthritis. Disease suppression was associated with reduced levels of collagen specific IgG2a and decreased inflammatory cell infiltration into affected joints. In summary the treatment of DC with TNF-α generates an antigen presenting cell with a phenotype that can reduce the pro-inflammatory response and direct the immune system towards a disease modifying, anti-inflammatory state.

AHR-mediated immunomodulation: the role of altered gene transcription

The immune system is a sensitive target for aryl hydrocarbon receptor (AHR)-mediated transcriptional regulation. Most of the cells that participate in immune responses express AHR protein, and many genes involved in their responses contain multiple DRE sequences in their promoters. However, the potential involvement of many of these candidate genes in AHR-mediated immunomodulation has never been investigated. Many obstacles to understanding the transcriptional effects of AHR activation exist, owing to the complexities of pathogen-driven inflammatory and adaptive immune responses, and to the fact that activation of AHR often influences the expression of genes that are already being regulated by other transcriptional events in responding cells. Studies with TCDD as the most potent, non-metabolized AHR ligand indicate that AHR activation alters many inflammatory signals that shape the adaptive immune response, contributing to altered differentiation of antigen-specific CD4(+) T helper (TH) cells and altered adaptive immune responses. With TCDD, most adaptive immune responses are highly suppressed, which has been recently linked to the AHR-dependent induction of CD4(+)CD25(+) regulatory T cells. However activation of AHR by certain non-TCDD ligands may result in other immune outcomes, as a result of metabolism of the ligand to active metabolites or to unknown ligand-specific effects on AHR-mediated gene transcription. Based on studies using AHR(-/-) mice, evidence for a role of endogenous AHR ligands in regulation of the immune response is growing, with bilirubin and lipoxinA4 representing two promising candidates.

Identification and development of new therapeutics for multiple sclerosis

In recent years, large efforts have been undertaken to establish new therapeutic options for the treatment of multiple sclerosis (MS). So far, all of these strategies more or less specifically target subsets of the immune response in MS, including not only activation and expansion of T cells, their circulation and transmigration over the blood-brain barrier but also other cell types such as B cells and probably also natural killer cells. Here, we review available data on the most promising (at present) new therapeutic approaches. These involve the orally available compounds cladribine, FTY720, fumaric-acid esters, laquinimod and teriflunomide in addition to the monoclonal antibodies alemtuzumab, daclizumab, natalizumab and rituximab. After successful completion of Phase III studies, these compounds might have the potential to add to the current therapeutic armentarium especially for relapsing remitting disease courses in the near future, possibly opening the way to a more individualized treatment.

The Immunology of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is represents the most common chronic inflammatory joint disease and is still a major medical challenge because of unsolved issues related to the etiologic and pathogenetic questions. Intensive research has been conducted over the last years that focused on the inappropriate activation of the immune system: although T cells have long been deemed to play a central role in the origin and propagation of joint inflammation, data accumulated so far have widened this perspective recognizing the contribution of other cells, as well as the major histocompatibility complex class II proteins and a composite set of costimulatory signals responsible for the production of proinflammatory cytokines and other soluble mediators implicated in tissue destruction typical of the disease. This paper will provide an insight into the immune system in RA, dissecting cellular and humoral aspects both in serum and in synovium of patients.

Safety and efficacy of leflunomide in primary Sjögren's syndrome: a phase II pilot study

BACKGROUND

For invalidating symptoms in primary Sjögren's syndrome (pSS), there is still a need for easy-to-administer, cost-effective and well-tolerated systemic treatment. Leflunomide (LEF) is structurally unrelated to other immunomodulatory drugs and might be efficacious in pSS, given its characteristic immunoregulatory modes of action.

OBJECTIVE

To investigate the safety and efficacy of LEF in pSS in a phase II open-label pilot study.

METHODS

15 patients with pSS with early and active disease received LEF 20 mg once daily for 24 weeks. Tolerability, safety and efficacy of LEF were evaluated every 8 weeks. Additional safety visits were performed every fortnight.

RESULTS

Mild gastrointestinal discomfort (including diarrhoea) and hair loss were mainly reported. Five patients developed lupus-like skin lesions on the face, arms or trunk, responding well to topical corticosteroids, nevertheless causing the withdrawal of one patient. Two patients with pre-existing hypertension had to increase dosages of anti-hypertensive drugs. Increased levels of alanine aminotransferase normalised after dose reduction in two patients. A decrease in general fatigue and an increase in physical functioning were observed after 24 weeks. Serum IgG levels decreased from 8 weeks onwards. Schirmer test values increased, not reaching statistical significance, whereas sialometry values did not change. In four of five repeated biopsies, the lymphocytic focus score decreased at the rate of 1 focus/4 mm(2). A remarkable amelioration of leucocytoclastic vasculitis was observed in three patients.

CONCLUSIONS

Although the safety profile seems fairly acceptable, the observed indications for efficacy were modest and may be doubtful in justifying a randomised controlled trial of LEF in pSS.