Identification of SNPs associated with methotrexate treatment outcomes in patients with early rheumatoid arthritis.

Methotrexate is one of the cornerstones of rheumatoid arthritis (RA) therapy. Genetic factors or single nucleotide polymorphisms (SNPs) are responsible for 15%-30% of the variation in drug response. Identification of clinically effective SNP biomarkers for predicting methotrexate (MTX) sensitivity has been a challenge. The aim of this study was to explore the association between the disease related outcome of MTX treatment and 23 SNPs in 8 genes of the MTX pathway, as well as one pro-inflammatory related gene in RA patients naïve to MTX. Categorical outcomes such as Disease Activity Score (DAS)-based European Alliance of Associations for Rheumatology (EULAR) non-response at 4 months, The American College of Rheumatology and EULAR (ACR/EULAR) non-remission at 6 months, and failure to sustain MTX monotherapy from 12 to 24 months were assessed, together with continuous outcomes of disease activity, joint pain and fatigue. We found that the SNPs rs1801394 in the MTRR gene, rs408626 in DHFR gene, and rs2259571 in AIF-1 gene were significantly associated with disease activity relevant continuous outcomes. Additionally, SNP rs1801133 in the MTHFR gene was identified to be associated with improved fatigue. Moreover, associations with p values at uncorrected significance level were found in SNPs and different categorical outcomes: 1) rs1476413 in the MTHFR gene and rs3784864 in ABCC1 gene are associated with ACR/EULAR non-remission; 2) rs1801133 in the MTHFR gene is associated with EULAR response; 3) rs246240 in the ABCC1 gene, rs2259571 in the AIF-1 gene, rs2274808 in the SLC19A1 gene and rs1476413 in the MTHFR gene are associated with failure to MTX monotherapy after 12-24 months. The results suggest that SNPs in genes associated with MTX activity may be used to predict MTX relevant-clinical outcomes in patients with RA.

Endogenous glutamine is rate-limiting for anti-CD3 and anti-CD28 induced CD4+ T-cell proliferation and glycolytic activity under hypoxia and normoxia.

To meet the demand for energy and biomass, T lymphocytes (T cells) activated to proliferation and clonal expansion, require uptake and metabolism of glucose (Gluc) and the amino acid (AA) glutamine (Gln). Whereas exogenous Gln is converted to glutamate (Glu) by glutaminase (GLS), Gln is also synthesized from the endogenous pool of AA through Glu and activity of glutamine synthase (GS). Most of this knowledge comes from studies on cell cultures under ambient oxygen conditions (normoxia, 21% O2). However, in vivo, antigen induced T-cell activation often occurs under moderately hypoxic (1-4% O2) conditions and at various levels of exogenous nutrients. Here, CD4+ T cells were stimulated for 72 h with antibodies targeting the CD3 and CD28 markers at normoxia and hypoxia (1% O2). This was done in the presence and absence of the GLS and GS inhibitors, Bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl) ethyl sulfide (BPTES) and methionine sulfoximine (MSO) and at various combinations of exogenous Gluc, Gln and pyruvate (Pyr) for the last 12 h of stimulation. We found that T-cell proliferation, viability and levels of endogenous AA were significantly influenced by the availability of exogenous Gln, Gluc and Pyr as well as inhibition of GLS and GS. Moreover, inhibition of GLS and GS and levels of oxygen differentially influenced oxygen consumption rate (OCR) and extracellular acidification rate (ECAR). Finally, BPTES-dependent down-regulation of ECAR was associated with reduced hexokinase (HK) activity at both normoxia and hypoxia. Our results demonstrate that Gln availability and metabolism is rate-limiting for CD4+ T-cell activity.

Identification and characterization of a novel glutaminase inhibitor.

In humans, there are two forms of glutaminase (GLS), designated GLS1 and GLS2. These enzymes catalyse the conversion of glutamine to glutamate. GLS1 exists as two isozymes: kidney glutaminase (KGA) and glutaminase C (GAC). Several GLS inhibitors have been identified, of which DON (6-diazo-5-oxonorleucine), BPTES (bis-2-(5-phenylacetamido-1, 3, 4-thiadiazol-2-yl) ethyl sulphide), 968 (5-(3-Bromo-4-(dimethylamino)phenyl)-2,2-dimethyl-2,3,5,6-tetrahydrobenzo[a]phenanthridin-4(1H)-one) and CB839 (Telaglenastat) are the most widely used. However, these inhibitors have variable efficacy, specificity and bioavailability in research and clinical settings, implying the need for novel and improved GLS inhibitors. Based on this need, a diverse library of 28,000 compounds from Enamine was screened for inhibition of recombinant, purified GAC. From this library, one inhibitor designated compound 19 (C19) was identified with kinetic features revealing allosteric inhibition of GAC in the µm range. Moreover, C19 inhibits anti-CD3/CD28-induced CD4+ T-cell proliferation and cytokine production with similar or greater potency as compared to BPTES. Taken together, our data suggest that C19 has the potential to modulate GLS1 activity and alter metabolic activity of T cells.

Activated, Pro-Inflammatory Th1, Th17, and Memory CD4+ T Cells and B Cells Are Involved in Delayed-Type Hypersensitivity Arthritis (DTHA) Inflammation and Paw Swelling in Mice.

Delayed-type hypersensitivity arthritis (DTHA) is a recently established experimental model of rheumatoid arthritis (RA) in mice with pharmacological values. Despite an indispensable role of CD4+ T cells in inducing DTHA, a potential role for CD4+ T cell subsets is lacking. Here we have quantified CD4+ subsets during DTHA development and found that levels of activated, pro-inflammatory Th1, Th17, and memory CD4+ T cells in draining lymph nodes were increased with differential dynamic patterns after DTHA induction. Moreover, according to B-cell depletion experiments, it has been suggested that this cell type is not involved in DTHA. We show that DTHA is associated with increased levels of B cells in draining lymph nodes accompanied by increased levels of circulating IgG. Finally, using the anti-rheumatoid agents, methotrexate (MTX) and the anti-inflammatory drug dexamethasone (DEX), we show that MTX and DEX differentially suppressed DTHA-induced paw swelling and inflammation. The effects of MTX and DEX coincided with differential regulation of levels of Th1, Th17, and memory T cells as well as B cells. Our results implicate Th1, Th17, and memory T cells, together with activated B cells, to be involved and required for DTHA-induced paw swelling and inflammation.

Inflammatory activation of endothelial cells increases glycolysis and oxygen consumption despite inhibiting cell proliferation.

Endothelial cell function and metabolism are closely linked to differential use of energy substrate sources and combustion. While endothelial cell migration is promoted by 2-phosphofructokinase-6/fructose-2,6-bisphosphatase (PFKFB3)-driven glycolysis, proliferation also depends on fatty acid oxidation for dNTP synthesis. We show that inflammatory activation of human umbilical vein endothelial cells (HUVECs) by interleukin-1ß (IL-1ß), despite inhibiting proliferation, promotes a shift toward more metabolically active phenotype. This was reflected in increased cellular glucose uptake and consumption, which was preceded by an increase in PFKFB3 mRNA and protein expression. However, despite a modest increase in extracellular acidification rates, the increase in glycolysis did not correlate with extracellular lactate accumulation. Accordingly, IL-1ß stimulation also increased oxygen consumption rate, but without a concomitant rise in fatty acid oxidation. Together, this suggests that the IL-1ß-stimulated energy shift is driven by shunting of glucose-derived pyruvate into mitochondria to maintain elevated oxygen consumption in HUVECs. We also revealed a marked donor-dependent variation in the amplitude of the metabolic response to IL-1ß and postulate that the donor-specific response should be taken into account when considering targeting dysregulated endothelial cell metabolism.

Cellular metabolism dictates T cell effector function in health and disease.

In a healthy person, metabolically quiescent T lymphocytes (T cells) circulate between lymph nodes and peripheral tissues in search of antigens. Upon infection, some T cells will encounter cognate antigens followed by proliferation and clonal expansion in a context-dependent manner, to become effector T cells. These events are accompanied by changes in cellular metabolism, known as metabolic reprogramming. The magnitude and variation of metabolic reprogramming are, in addition to antigens, dependent on factors such as nutrients and oxygen to ensure host survival during various diseases. Herein, we describe how metabolic programmes define T cell subset identity and effector functions. In addition, we will discuss how metabolic programs can be modulated and affect T cell activity in health and disease using cancer and autoimmunity as examples.

Growth-inhibition of cell lines derived from B cell lymphomas through antagonism of serotonin receptor signaling.

A majority of lymphomas are derived from B cells and novel treatments are required to treat refractory disease. Neurotransmitters such as serotonin and dopamine influence activation of B cells and the effects of a selective serotonin 1A receptor (5HT1A) antagonist on growth of a number of B cell-derived lymphoma cell lines were investigated. We confirmed the expression of 5HT1A in human lymphoma tissue and in several well-defined experimental cell lines. We discovered that the pharmacological inhibition of 5HT1A led to the reduced proliferation of B cell-derived lymphoma cell lines together with DNA damage, ROS-independent caspase activation and apoptosis in a large fraction of cells. Residual live cells were found 'locked' in a non-proliferative state in which a selective transcriptional and translational shutdown of genes important for cell proliferation and metabolism occurred (e.g., AKT, GSK-3ß, cMYC and p53). Strikingly, inhibition of 5HT1A regulated mitochondrial activity through a rapid reduction of mitochondrial membrane potential and reducing dehydrogenase activity. Collectively, our data suggest 5HT1A antagonism as a novel adjuvant to established cancer treatment regimens to further inhibit lymphoma growth.

Non-Hematopoietic and Hematopoietic SIRPα Signaling Differently Regulates Murine B Cell Maturation in Bone Marrow and Spleen.

B lymphocyte development occurs in the bone marrow, while final differentiation and maturation can occur in both the bone marrow and the spleen. Here we provide evidence that signal regulatory protein α (SIRPα), an Ig-superfamily ITIM-receptor expressed by myeloid but not by lymphoid cells, is involved in regulating B cell maturation. Lack of SIRPα signaling in adult SIRPα-mutant mice resulted in a reduced maturation of B cells in the bone marrow, evident by reduced numbers of semi-mature IgD+IgMhi follicular type-II (F-II) and mature IgD+IgMlo follicular type-I (F-I) B cells, as well as reduced blood B cell numbers. In addition, lack of SIRPα signaling also impaired follicular B cell maturation in the spleen. Maturing BM or splenic B cells of SIRPα-mutant mice were found to express higher levels of the pro-apoptotic protein BIM and apoptosis was increased among these B cells. Bone marrow reconstitution experiments revealed that the B cell maturation defect in bone marrow and blood was due to lack of SIRPα signaling in non-hematopoietic cells, while hematopoietic SIRPα signaling was important for follicular B cell maturation in the spleen. Adding on to our previous findings of a stromal cell defect in SIRPα-mutant mice was the finding that gene expression of receptor activator of nuclear factor-ĸB ligand (RANKL) was significantly lower in cultured bone marrow stromal cells of SIRPα mutant mice. These data suggest a novel and opposite contribution of SIRPα signaling within non-hematopoietic and hematopoietic cells, respectively, to maintain B cell maturation and to prevent apoptosis in the bone marrow and spleen of adult mice.

Lack of non-hematopoietic SIRPα signaling disturbs the splenic marginal zone architecture resulting in accumulation and displacement of marginal zone B cells.

Signal regulatory protein α (SIRPα) is an immunoglobulin super family protein predominantly expressed by myeloid but not lymphoid cells, and its role in lymphocyte homeostasis and function is still to be revealed. We demonstrate that mice bearing a mutant SIRPα lacking the cytoplasmic signaling domain (SIRPα MT) had an increased amount of splenic marginal zone (MZ) B cells compared to wild-type controls. Immunohistochemical analysis revealed an increased localization of MZB cells into B cell follicular areas of the white pulp in SIRPα MT spleens. However, we found no signs of an increased MZB cell activation level in MT mice. The immune response to T-independent antigens in vivo was slightly increased in SIRPα MT mice while sorted MZB from these mice responded normally to LPS in vitro. Bone marrow reconstitution experiments demonstrated that the MZB cell phenotype of SIRPα MT mice was due to lack of SIRPα signaling in non-hematopoietic cells. In contrast, MZ retention of MZ macrophages required hematopoietic SIRPα, while normal distribution of metallophilic macrophages required non-hematopoietic SIRPα signaling. In summary, these data identified SIRPα signaling in non-hematopoietic cells to play an important role in regulating the numbers and positioning MZB cell in the spleen.

Analysis of neurotrophic factors in limb and extraocular muscles of mouse model of amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is currently an incurable fatal motor neuron syndrome characterized by progressive weakness, muscle wasting and death ensuing 3-5 years after diagnosis. Neurotrophic factors (NTFs) are known to be important in both nervous system development and maintenance. However, the attempt to translate the potential of NTFs into the therapeutic options remains limited despite substantial number of approaches, which have been tested clinically. Using quantitative RT-PCR (qRT-PCR) technique, the present study investigated mRNA expression of four different NTFs: brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), neurotrophin-4/5 (NT-4) and glial cell line-derived neurotrophic factor (GDNF) in limb muscles and extraocular muscles (EOMs) from SOD1G93A transgenic mice at early and terminal stages of ALS. General morphological examination revealed that muscle fibres were well preserved in both limb muscles and EOMs in early stage ALS mice. However, in terminal ALS mice, most muscle fibres were either atrophied or hypertrophied in limb muscles but unaffected in EOMs. qRT-PCR analysis showed that in early stage ALS mice, NT-4 was significantly down-regulated in limb muscles whereas NT-3 and GDNF were markedly up-regulated in EOMs. In terminal ALS mice, only GDNF was significantly up-regulated in limb muscles. We concluded that the early down-regulation of NT-4 in limb muscles is closely associated with muscle dystrophy and dysfunction at late stage, whereas the early up-regulations of GDNF and NT-3 in EOMs are closely associated with the relatively well-preserved muscle morphology at late stage. Collectively, the data suggested that comparing NTFs expression between limb muscles and EOMs from different stages of ALS animal models is a useful method in revealing the patho-physiology and progression of ALS, and eventually rescuing motor neuron in ALS patients.