The specific p38 mitogen-activated protein kinase pathway inhibitor FR167653 keeps insulitis benign in nonobese diabetic mice

GABA Administration Ameliorates Sjogren’s Syndrome in Two Different Mouse Models

Sjögren’s syndrome (SS) is a chronic autoimmune disease characterized by lymphocytic infiltrates in the salivary and lachrymal glands resulting in oral and ocular dryness. There are no clinically approved therapies to slow the progression of SS. Immune cells possess receptors for the neurotransmitter GABA (GABA-Rs) and their activation has immunoregulatory actions. We tested whether GABA administration has potential for amelioration of SS in NOD.B10-H2^b and C57BL/6.NOD-Aec1Aec2 mice, two spontaneous SS models. Oral GABA treatment was initiated (1) after the development of sialadenitis but before the onset of overt symptoms, or (2) after the appearance of overt symptoms. When assessed weeks later, GABA-treated mice had greater saliva and tear production, as well as quicker times to salvia flow, in both SS mouse models. This was especially evident when GABA treatment was initiated after the onset of overt disease. This preservation of exocrine function was not accompanied by significant changes in the number or area of lymphocytic foci in the salivary or lachrymal glands of GABA-treated mice and we discuss the possible reasons for these observations. Given that GABA-treatment preserved saliva and tear production which are the most salient symptoms of SS and is safe for consumption, it may provide a new approach to help ameliorate SS.

β-Catenin stabilization in NOD dendritic cells increases IL-12 production and subsequent induction of IFN-γ-producing T cells

Dendritic cells (DC) from diabetes-prone NOD mice and patients with type 1 diabetes (T1D) produce excess IL-12 that drives development of β-cell-destroying IFN-γ-producing T cells. The molecular mechanisms that control IL-12 production in T1D are unclear. In this study, we report that β-catenin, a multifunctional protein involved in inflammation, is dramatically increased in DC from NOD mice. We further investigated the mechanisms leading to accumulation of β-catenin in NOD DC and its role in the inflammatory pathogenic responses associated with T1D. Hyperphosphorylation of β-catenin at a stabilizing residue, serine 552, mediated by activation of Akt, appears to lead to β-catenin accumulation in NOD DC. Elevated β-catenin in DC correlated with IL-12 production and induction of IFN-γ-producing CD4 cells. On the one hand, knockdown/inhibition of β-catenin significantly reduced NOD DC production of IL-12 and their ability to induce IFN-γ-producing CD4 cells. On the other hand, overexpression of β-catenin in control DC resulted in increased IL-12 production and induction of IFN-γ-production in T cells. Additionally, we found that β-catenin inhibitors decreased NF-κB activation in NOD DC and IFN-γ production by NOD T cells in vivo. These data strongly suggest that accumulation of β-catenin in DC from NOD mice drives IL-12 production, and consequently, development of pathogenic IFN-γ-producing T cells. Targeting the defect responsible for β-catenin accumulation and subsequent overproduction of pro-inflammatory cytokines by NOD DC could be an effective therapeutic strategy for the prevention and/or treatment of T1D.

Deletion of serum amyloid A3 improves high fat high sucrose diet-induced adipose tissue inflammation and hyperlipidemia in female mice

Serum amyloid A (SAA) increases in response to acute inflammatory stimuli and is modestly and chronically elevated in obesity. SAA3, an inducible form of SAA, is highly expressed in adipose tissue in obese mice where it promotes monocyte chemotaxis, providing a mechanism for the macrophage accumulation that occurs with adipose tissue expansion in obesity. Humans do not express functional SAA3 protein, but instead express SAA1 and SAA2 in hepatic as well as extrahepatic tissues, making it difficult to distinguish between liver and adipose tissue-specific SAA effects. SAA3 does not circulate in plasma, but may exert local effects that impact systemic inflammation. We tested the hypothesis that SAA3 contributes to chronic systemic inflammation and adipose tissue macrophage accumulation in obesity using mice deficient for Saa3 (Saa3(-/-)). Mice were rendered obese by feeding a pro-inflammatory high fat, high sucrose diet with added cholesterol (HFHSC). Both male and female Saa3(-/-) mice gained less weight on the HFHSC diet compared to Saa3(+/+) littermate controls, with no differences in body composition or resting metabolism. Female Saa3(-/-) mice, but not males, had reduced HFHSC diet-induced adipose tissue inflammation and macrophage content. Both male and female Saa3(-/-) mice had reduced liver Saa1 and Saa2 expression in association with reduced plasma SAA. Additionally, female Saa3(-/-) mice, but not males, showed improved plasma cholesterol, triglycerides, and lipoprotein profiles, with no changes in glucose metabolism. Taken together, these results suggest that the absence of Saa3 attenuates liver-specific SAA (i.e., SAA1/2) secretion into plasma and blunts weight gain induced by an obesogenic diet. Furthermore, adipose tissue-specific inflammation and macrophage accumulation are attenuated in female Saa3(-/-) mice, suggesting a novel sexually dimorphic role for this protein. These results also suggest that Saa3 influences liver-specific SAA1/2 expression, and that SAA3 could play a larger role in the acute phase response than previously thought.

Sex-specific control of central nervous system autoimmunity by p38 mitogen-activated protein kinase signaling in myeloid cells

OBJECTIVE

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS), characterized by a global increasing incidence driven by relapsing-remitting disease in females. Investigators have described p38 mitogen-activated protein kinase (MAPK) as a key regulator of inflammatory responses in autoimmunity, but its role in the sexual dimorphism in MS or MS models remains unexplored.

METHODS

Toward this end, we used experimental autoimmune encephalomyelitis (EAE), the principal animal model of MS, combined with pharmacologic and genetic inhibition of p38 MAPK activity and transcriptomic analyses.

RESULTS

Pharmacologic inhibition of p38 MAPK selectively ameliorated EAE in female mice. Conditional deletion studies demonstrated that p38α signaling in macrophages/myeloid cells, but not T cells or dendritic cells, mediated this sexual dimorphism, which was dependent on the presence of adult sex hormones. Analysis of CNS inflammatory infiltrates showed that female but not male mice lacking p38α in myeloid cells exhibited reduced immune cell activation compared with controls, whereas peripheral T-cell priming was unaffected in both sexes. Transcriptomic analyses of myeloid cells revealed differences in p38α-controlled transcripts comprising female- and male-specific gene modules, with greater p38α dependence of proinflammatory gene expression in females.

INTERPRETATION

Our findings demonstrate a key role for p38α in myeloid cells in CNS autoimmunity and uncover important molecular mechanisms underlying sex differences in disease pathogenesis. Taken together, our results suggest that the p38 MAPK signaling pathway represents a novel target for much needed disease-modifying therapies for MS.

Activation of p38 MAPK in CD4 T cells controls IL-17 production and autoimmune encephalomyelitis

Although several transcription factors have been shown to be critical for the induction and maintenance of IL-17 expression by CD4 Th cells, less is known about the role of nontranscriptional mechanisms. Here we show that the p38 MAPK signaling pathway is essential for in vitro and in vivo IL-17 production by regulating IL-17 synthesis in CD4 T cells through the activation of the eukaryotic translation initiation factor 4E/MAPK-interacting kinase (eIF-4E/MNK) pathway. We also show that p38 MAPK activation is required for the development and progression of both chronic and relapsing-remitting forms of experimental allergic encephalomyelitis (EAE), the principal autoimmune model of multiple sclerosis. Furthermore, we show that regulation of p38 MAPK activity specifically in T cells is sufficient to modulate EAE severity. Thus, mechanisms other than the regulation of gene expression also contribute to Th17 cell effector functions and, potentially, to the pathogenesis of other Th17 cell-mediated diseases.

Role of MKK3-p38 MAPK signalling in the development of type 2 diabetes and renal injury in obese db/db mice

AIMS/HYPOTHESIS

Obesity and diabetes are associated with increased intracellular p38 mitogen-activated protein kinase (MAPK) signalling, which may promote tissue inflammation and injury. Activation of p38 MAPK can be induced by either of the immediate upstream kinases, MAP kinase kinase (MKK)3 or MKK6, and recent evidence suggests that MKK3 has non-redundant roles in the pathology attributed to p38 MAPK activation. Therefore, this study examined whether MKK3 signalling influences the development of obesity, type 2 diabetes and diabetic nephropathy.

METHODS

Wild-type and Mkk3 (also known as Map2k3) gene-deficient db/db mice were assessed for the development of obesity, type 2 diabetes and renal injury from 8 to 32 weeks of age.

RESULTS

Mkk3 (+/+) db/db and Mkk3 (-/-) db/db mice developed comparable obesity and were similar in terms of incidence and severity of type 2 diabetes. At 32 weeks, diabetic Mkk3 (+/+) db/db mice had increased kidney levels of phospho-p38 and MKK3 protein. In comparison, kidney levels of phospho-p38 in diabetic Mkk3 ( -/- ) db/db mice remained normal, despite a fourfold compensatory increase in MKK6 protein levels. The reduced levels of p38 MAPK signalling in the diabetic kidneys of Mkk3 ( -/- ) db/db mice was associated with protection against the following: declining renal function, increasing albuminuria, renal hypertrophy, podocyte loss, mesangial cell activation and glomerular fibrosis. Diabetic Mkk3 ( -/- ) db/db mice were also significantly protected from tubular injury and interstitial fibrosis, which was associated with reduced Ccl2 mRNA expression and interstitial macrophage accumulation.

CONCLUSIONS/INTERPRETATION

MKK3-p38 MAPK signalling is not required for the development of obesity or type 2 diabetes, but plays a distinct pathogenic role in the progression of diabetic nephropathy in db/db mice.

MKK3 signalling plays an essential role in leukocyte-mediated pancreatic injury in the multiple low-dose streptozotocin model

In vitro studies have implicated activation of the p38 mitogen-activated protein kinase (MAPK) signalling pathway in cytokine-mediated pancreatic beta-cell injury. Activation of the p38 MAPK occurs through two different upstream kinases, mitogen-activated protein kinase kinase 3 (MKK3) and MKK6. This study examined the role of MKK3 signalling in an in vivo model of cytokine-dependent pancreatic injury induced by multiple low doses of streptozotocin (MLD-STZ). Groups of wild-type (WT) or Mkk3-/- C57BL/6J mice received 5 daily injections of STZ (40 mg/kg) and were killed on day 5, week 2 or week 4. MLD-STZ in WT mice exhibited two distinct phases of pancreatic damage: islet cell apoptosis (immunostaining for cleaved caspase-3) on day 5 in the absence of leukocyte infiltration, and this was followed by islet inflammation (leukocyte infiltration and cytokine production) and further islet cell apoptosis on day 14 resulting in a loss of insulin-producing beta-cells and an 80% incidence of hyperglycaemia. Mkk3-/- mice were not protected from the initial phase of STZ-induced islet cell apoptosis day 5. However, Mkk3-/- mice were completely protected from the induction of hyperglycaemia. This was attributed to inhibition of leukocyte infiltration, production of pro-inflammatory cytokines and islet cell apoptosis at day 14 of MLD-STZ. In vitro studies showed that cultured islets from Mkk3-/- and WT mice are equally susceptible to STZ and cytokine-induced apoptosis. In conclusion, MKK3 signalling plays an essential role in the development of islet inflammation leading to destruction of beta-cells and hyperglycaemia in MLD-STZ-induced pancreatic injury.

Transforming growth factor-beta-activated protein kinase 1-binding protein (TAB)-1alpha, but not TAB1beta, mediates cytokine-induced p38 mitogen-activated protein kinase phosphorylation and cell death in insulin-producing cells

Previous studies have indicated that the p38 MAPK participates in signaling events that lead to the death of the insulin-producing beta-cell. The aim of the present study was to elucidate the role of the TGF-beta-activated protein kinase 1-binding protein 1 (TAB1) in the cytokine-induced activation of p38. Levels of TAB1 mRNA and protein were analyzed by real-time PCR and immunoblotting, and TAB1 expression in mouse and human islet cells was down-regulated using lipofection of diced-small interfering RNA. TAB1 overexpression in beta-TC6 cells was achieved by transient transfections followed by fluorescence activated cell sorting. Phosphorylation of p38, c-Jun N-terminal kinase, and ERK was assessed by immunoblotting, and viability was determined using vital staining with bisbenzimide and propidium iodide. We observed that TAB1 is expressed in insulin-producing cells. Cytokine (IL-1beta + interferon-gamma)-stimulated p38 phosphorylation was significantly increased by TAB1alpha overexpression, but not TAB1beta overexpression, in beta-TC6 cells. The TAB1alpha-augmented p38 phosphorylation was paralleled by an increased cell death rate. Treatment of islet cells with diced-small interfering RNA specific for TAB1, but not for TGF-beta-activated kinase 1, resulted in lowered cytokine-induced p38 phosphorylation and protection against cell death. The cytokine-induced phosphorylation of c-Jun N-terminal kinase and ERK was not affected by changes in TAB1 levels. Finally, TAB1 phosphorylation was decreased by the p38 inhibitor SB203580. We conclude that TAB1alpha, but not TAB1beta, plays an important role in the activation of p38 in insulin-producing cells and therefore also in cytokine-induced beta-cell death.

Effect of TNF-alpha inhibition on urinary albumin excretion in experimental diabetic rats

The objective is to assess the effect of TNF-alpha inhibition on urinary albumin excretion in experimental diabetic rats. Male Wistar rats, 8-week-old, were categorized into four groups, which were the control (n = 9), diabetes (n = 9), infliximab-treated diabetes (n = 10), and FR167653-treated diabetes (n = 9) groups. Diabetes was induced by intraperitoneal injection of STZ (40 mg/kg). Thereafter, infliximab was injected intraperitoneally once a month (5.5 mg/kg) and FR167653 was administered orally by mixing with the rat chow (0.08%). The effects of infliximab and FR167653 on urinary albumin excretion were observed for 12 weeks. Body weight, blood sugar, 24-h urinary TNF-alpha, and 24-h urinary albumin/creatinine ratio (Ualb/Ucr) levels were determined at 1, 4, 8, and 12 weeks after the STZ-injection. Treatment of rats with STZ caused a significant loss of body weight, as well as polyuria and hyperglycemia within 1 week, while the urinary excretions of albumin and TNF-alpha were increased. Neither infliximab nor FR167653 affected body weight or blood sugar levels, whereas both decreased urinary albumin excretion, together with a modest decrease in the urinary excretion of TNF-alpha. These results suggest a role of TNF-alpha in the pathogenesis of diabetic nephropathy and show that TNF-alpha inhibition is a potential therapeutic strategy.

Genetic variants of RANTES are associated with serum RANTES level and protection for type 1 diabetes

RANTES (regulated on activation, normal T-cell expressed and secreted) is a T-helper type 1 (Th1) chemokine that promotes T-cell activation and proliferation. RANTES is genetically associated with asthma, sarcoidosis and multiple sclerosis. The concentration of RANTES is increased at inflammation sites in different autoimmune diseases. Type 1 diabetes (T1D) is a Th1-mediated disease with complex genetic predisposition. We tested RANTES as a candidate gene for association with T1D using three single-nucleotide polymorphism (SNP) variants (rs4251719, rs2306630 and rs2107538) to capture haplotype information. The minor alleles of all SNPs were transmitted less frequently to T1D offspring (transmission rates 37.3% (P=0.002), 38.7% (P=0.007) and 41.0% (P=0.01)) and were less frequently present in patients compared to controls (P=0.009, 0.03 and 0.04, respectively). A similar protective effect was observed for the haplotype carrying three minor alleles (transmission disequilibrium test (TDT): P=0.003; odds ratio (OR)=0.55; confidence interval (CI): 0.37-0.83; case/control: P=0.03; OR=0.74; CI: 0.55-0.98). Both patients and controls carrying the protective haplotype express significantly lower serum levels of RANTES compared to non-carriers. Subsequently, we tested a cohort of 310 celiac disease patients, but failed to detect association. RANTES SNPs are significantly associated with RANTES serum concentration and development of T1D. The rs4251719*A-rs2306630*A-rs2107538*A haplotype associated with low RANTES production confers protection from T1D. Our data imply that RANTES is associated with T1D both genetically and functionally, and contributes to diabetes-prone Th1 cytokine profile.

Preventive and therapeutic potential of p38 alpha-selective mitogen-activated protein kinase inhibitor in nonobese diabetic mice with type 1 diabetes

Mitogen-activated protein kinases (MAPKs) and heat shock proteins (HSPs) are ubiquitous proteins that function within T cells in both normal and stress-related pathophysiological states, including type 1 diabetes. The nonobese diabetic (NOD) mouse spontaneously develops T cell-mediated autoimmune pancreatic beta cell destruction that is similar to type 1 diabetes in humans. Because p38 MAPKs have been shown to modulate T cell function, we studied the effects of a p38alpha MAPK-selective inhibitor, indole-5-carboxamide (SD-169), on the development and progression of type 1 diabetes in the NOD mouse. In preventive treatment studies, SD-169 significantly reduced p38 and HSP60 expression in T cells of the pancreatic beta islets. Following treatment, the incidence of diabetes as determined by blood glucose levels was significantly lower, and immuno-histochemistry of pancreatic beta islet tissue demonstrated significant reduction in CD5+ T cell infiltration in the SD-169 treatment group as compared with untreated NOD mice. In therapeutic studies using mildly and moderately hyperglycemic NOD mice, SD-169 treatment lowered blood glucose and improved glucose homeostasis. Furthermore, following cessation of SD-169 treatment, NOD mice showed significant arrest of diabetes. In conclusion, we report that this p38alpha-selective inhibitor prevents the development and progression of diabetes in NOD mice by inhibiting T cell infiltration and activation, thereby preserving beta cell mass via inhibition of the p38 MAPK signaling pathway. These results have bearing on current prophylactic and therapeutic protocols using p38alpha-selective inhibitors in the prediabetic period for children at high risk of type 1 diabetes, in the honeymoon period, and for adults with latent autoimmune diabetes.

Role of MKK3 and p38 MAPK in cytokine-induced death of insulin-producing cells

The aim of the present investigation was to elucidate further the importance of p38 MAPK (mitogen-activated protein kinase) in nitric oxide- and cytokine-induced beta-cell death. For this purpose, isolated human islets were treated with d-siRNA (diced small interfering RNA) and then exposed to the nitric oxide donor DETA/NONOate [2,2'-(hydroxynitrosohydrazono)bis-ethanamine]. We observed that cells treated with p38alpha-specific d-siRNA, but not with d-siRNA targeting GL3 (a firefly luciferase siRNA plasmid) or PKCdelta (protein kinase Cdelta), were protected against nitric oxide-induced death. This was paralleled by an increased level of Bcl-XL (B-cell leukaemia/lymphoma-X long). For an in-depth study of the mechanisms of p38 activation, MKK3 (MAPK kinase 3), MKK6 and their dominant-negative mutants were overexpressed in insulin-producing RIN-5AH cells. In transient transfections, MKK3 overexpression resulted in increased p38 phosphorylation, whereas in stable MKK3-overexpressing RIN-5AH clones, the protein levels of p38 and JNK (c-Jun N-terminal kinase) were decreased, resulting in unaffected phospho-p38 levels. In addition, a long-term MKK3 overexpression did not affect cell death rates in response to the cytokines interleukin-1beta and interferon-gamma, whereas a short-term MKK3 expression resulted in increased cytokine-induced RIN-5AH cell death. The MKK3-potentiating effect on cytokine-induced cell death was abolished by a nitric oxide synthase inhibitor, and MKK3-stimulated p38 phosphorylation was enhanced by inhibitors of phosphatases. Finally, as the dominant-negative mutant of MKK3 did not affect cytokine-induced p38 phosphorylation, and as wild-type MKK3 did not influence p38 autophosphorylation, it may be that p38 is activated by MKK3/6-independent pathways in response to cytokines and nitric oxide. In addition, it is likely that a long-term increase in p38 activity is counteracted by both a decreased expression of the p38, JNK and p42 genes as well as an increased dephosphorylation of p38.

A short-term diabetes induced changes of catecholamines and p38-MAPK in discrete areas of rat brain

Chronic diabetes is associated with the alteration of second messengers and CNS disorders. We have recently identified that protein kinases (CaMKII and PKC-alpha) and brain neurotransmitters are altered during diabetes as well as in hyperglycemic and acidotic conditions. In this study, we investigated the effects of acute diabetes on the levels of dopamine (DA), norepinephrine (NE), epinephrine (E) and p38-Mitogen-Activated Protein Kinase (p38-MAPK) in striatum (ST), hippocampus (HC), hypothalamus (HT), midbrain (MB), pons medulla (PM), cerebellum (CB) and cerebral cortex (CCX). Alloxan (45 mg/kg) diabetic untreated rats that showed hyperglycemia (>260 mg%), revealed significant increases of DA level in ST (1.5 fold), HC (2.2 fold) and PM (2.0 fold) and the E level also found to be increased significantly in HT (2.4 fold), whereas the NE level was decreased in CB (0.5 fold), after 7 days of diabetes. Immunoblotting study of p38-MAPK expression under identical conditions showed significant alterations in ST, HC, HT and PM (p<0.05) correlated with the changes of catecholamines (DA and E). On the other hand, the above changes were reversed in insulin-treated diabetic rats maintained under normal glucose level (80 -110 mg %). These results suggest that p38-MAPK may regulate the rate of either the synthesis or release of DA and E in corresponding brain areas, but not NE, under these conditions.

Mapping non-class II H2-linked loci for type 1 diabetes in nonobese diabetic mice

Major histocompatibility complex (MHC) plays a largely predominant role in the genetic predisposition to type 1 diabetes, in both humans and rodents. While class II loci have long been recognized as essential, they do not fully explain the MHC-linked genetic component of type 1 diabetes. In the present study, using new NOD congenic strains harboring defined chromosomal segments from C57BL/6 mice, we circumscribed three distinct loci influencing murine type 1 diabetes and tightly linked to but separated from the class II region. Our findings might guide the search for additional HLA-linked loci in human type 1 diabetes.