Roberto Di Marco

Metabotropic glutamate receptor-4 modulates adaptive immunity and restrains neuroinflammation

High amounts of glutamate are found in the brains of people with multiple sclerosis, an inflammatory disease marked by progressive demyelination. Glutamate might affect neuroinflammation via effects on immune cells. Knockout mice lacking metabotropic glutamate receptor-4 (mGluR4) were markedly vulnerable to experimental autoimmune encephalomyelitis (EAE, a mouse model of multiple sclerosis) and developed responses dominated by interleukin-17–producing T helper (TH17) cells. In dendritic cells (DCs) from those mice, defective mGluR4 signaling—which would normally decrease intracellular cAMP formation—biased TH cell commitment to the TH17 phenotype. In wild-type mice, mGluR4 was constitutively expressed in all peripheral DCs, and this expression increased after cell activation. Treatment of wild-type mice with a selective mGluR4 enhancer increased EAE resistance via regulatory T (Treg) cells. The high amounts of glutamate in neuroinflammation might reflect a counterregulatory mechanism that is protective in nature and might be harnessed therapeutically for restricting immunopathology in multiple sclerosis.

Potential Role of Chitotriosidase Gene in Nonalcoholic Fatty Liver Disease Evolution

BACKGROUND:Nonalcoholic steatohepatitis (NASH) is a liver disease characterized by steatosis and periportal and lobular inflammation. The molecular mechanisms involved in the anomalous behavior of liver cells have only partially been disclosed. Human Chitotriosidase (Chit) is a member of the chitinase family that it is mainly synthesized by activated macrophages. We investigated chitotriosidase gene expression in Kupffer cells to determine the potential implication of this enzyme in the inflammation and in the progression from uncomplicated steatosis to steatohepatitis with progressive fibrosis.METHODS:Seventy-five liver biopsies from 40 subjects with NASH, 20 with simple steatosis, and 15 controls were used to detect CHIT expression, tumor necrosis factor-alpha (TNF-α), alpha-smooth muscle actin (α-SMA), and lipid peroxidation.RESULTS:CHIT was expressed exclusively by Kupffer cells. The levels of CHIT expression were significantly higher in NASH patients than in simple steatosis patients and in the control group. In addition, we found that CHIT over-expression influenced hepatic stellate cells activation, as demonstrated by the significant correlation between CHIT and α-SMA expression in NASH patients. A significant correlation was observed also between CHIT, TNF-α and lipid peroxidation in both NASH and simple steatosis.CONCLUSION:These results suggest that CHIT over-produced by Kupffer cells may contribute to the progression of hepatic fibrosis.

Prevention of Spontaneous Autoimmune Diabetes in Diabetes-Prone BB Rats by Prophylactic Treatment with Antirat Interferon-γ Antibody

The role of endogenous interferon-γ (IFNγ) in the development of insulin-dependent diabetes mellitus (IDDM) in diabetes-prone BB rats was evaluated. Several groups of these animals were treated under different experimental conditions with a purified polyclonal antibody (Ab), antirat IFNγ. The results show that when administered at doses of 100 or 200 μg/week from the 30/33th until the 105th day of age, the anti-IFNγ Ab reversibly reduced the incidence of IDDM compared to that in control rats treated with either irrelevant rabbit IgG or PBS. Moreover, when given up to the 105th day of age, these doses of anti-IFNγ Abs exerted comparable preventive effects regardless of whether application started as early as within 24 h after birth or at the end of the prediabetic period (e.g. 70/75 days). In contrast, under none of the above experimental conditions did larger doses of anti-IFNγ Ab (500 μg or 1 mg/week) exert antidiabetogenic effects in the BB rats. Apparently, this was due to the exuberant production of n...

Dichotomic effects of IFN-γ on the development of systemic lupus erythematosus-like syndrome in MRL-lpr/lpr mice

Systemic lupus erythematosus (SLE)‐prone female MRL‐lpr / lpr (MRL‐lpr) mice were treated with mouse or rat IFN‐γ under different experimental conditions, both prophylactically in 6‐ to 8 week‐old animals and therapeutically in 12‐ to 18‐week‐old SLE‐affected mice. It was found that IFN‐γ heterogeneously modulated the course of the disease in MRL‐lpr mice. When administered prophylactically, IFN‐γ favorably modulated the histological, serological and clinical signs of the disease. Relative to untreated or PBS‐treated control animals, the MRL‐lpr mice which received IFN γ were virtually free of inflammatory infiltration of the kidneys and the lungs, had lower levels of azotemia with reduction of both circulating IgG1, IgG2a and IgG3 and anti‐double strand (ds) and single strand (ss) DNA antibodies, milder skin vasculitis, significantly reduced enlargment of their lymph nodes and lower weight of the spleens. IFN‐γ also lowered the rate of mortality of MRL‐lpr mice. In contrast to these findings, therapeutically administered IFN‐γ worsened the course of the disease in MRL‐lpr mice, which exhibited increased proteinuria, higher levels of IgG2a and IgG3 and anti‐ds and ‐ss DNA antibodies, more aggressive nephritis and died at an earlier age than PBS‐treated control mice. The dichotomic effect of IFN‐γ on disease manifestation in MRL‐lpr mice offers new insights into the complex role of this cytokine in the regulation of systemic autoimmunity such as SLE.

Metabotropic glutamate receptors: Beyond the regulation of synaptic transmission

Metabotropic glutamate (mGlu) receptors are G-protein coupled receptors activated by glutamate, the major excitatory neurotransmitter of the CNS. A growing body of evidence suggests that the function of mGlu receptors is not restricted to the regulation of synaptic transmission. mGlu receptors are expressed in a variety of peripheral cells, including inter alia hepatocytes, pancreatic cells, osteoblasts and immune cells. Within the immunological synapses, mGlu receptors expressed by T cells might contribute to the vast array of signals generated by the antigen-presenting cells. mGlu receptors are also found in embryonic and neural stem cells. This suggests their involvement in the pathophysiology of brain tumors, which likely originates from cancer stem cells similar to neural stem cells. Ligands of mGlu3 and mGlu4 receptors are potential candidates for the experimental treatment of malignant gliomas and medulloblastomas, respectively.

Essential pathogenic role of endogenous IL-18 in murine diabetes induced by multiple low doses of streptozotocin. Prevention of hyperglycemia and insulitis by a recombinant IL-18-binding protein: Fc construct

IL‐18 is a cytokine structurally and functionally related to IL‐1 that, in synergy with IL‐12, stimulates the synthesis of IFN‐γ from T lymphocytes and natural killer cells. Because IFN‐γ plays a key pathogenic role in the development of murine immunoinflammatory diabetes induced by multiple low doses of streptozotocin (STZ) we investigated the effect of negating the actions of endogenous IL‐18 in this model by administering recombinant IL‐18‐binding protein:Fc (IL‐18 bp:Fc). C57BL/6 mice were injected once daily with 40 mg/kg STZ for 5 consecutive days, day 0 being the first day of STZ challenge. Relative to control animals treated in parallel with either PBS or human IgG, mice treated from day –3 to day 7 with daily doses of 150 μg of IL‐18 bp:Fc exhibited lowerincidence of diabetes and milder insulitis. In contrast, mice that were treated with IL‐18 bp:Fc from day 7 to day 14 exhibited clinical and histological signs of STZ‐induced diabetes similar to those of control mice treated with IgG. The protective effect of IL‐18 bp:Fc was accompanied by modified ex vivo immune responses, in that spleen cells and peritoneal macrophages contained fewer IFN‐γ secreting cells and released lower amounts of nitrite (an index of nitric oxide production) and IL‐1β. We conclude that intact IL‐18 function is essential for the full diabetogenic effectof low dose STZ in C57BL/6 mice.

Paradoxical Antidiabetogenic Effect of γ-Interferon in DP-BB Rats

Previous studies have shown that anti-γ-interferon (IFN-γ) antibody reduces the frequency of autoimmune IDDM in the DP-BB rat. We tested the effects of systemically administered recombinant rat IFN-γ in both DP-BB and DR-BB rats. Unexpectedly, IFN-γ markedly reduced the incidence of IDDM as compared with control rats when administered six times per week at a dosage of 280,000 U between ages 30-35 to 105 days or ages 60-64 to 105 days. A lower dosage (28,000 U on alternate days) was also protective when administered to DP-BB rats between birth and age 60 days. However, long-lasting protection against IDDM development over the 1-year study period was achieved only by the highest dosage of IFN-γ administered from age 30 to 105 days. Ex vivo production of tumor necrosis factor-a from splenic lymphoid cells (SLCs) and peritoneal macrophages of the rats treated with IFN-γ was comparable with that of controls; however, SLCs from the IFN-γ-treated animals secreted lower amounts of IFN-γ after stimulation with concanavalin A. IFN-γ treatment also markedly reduced the frequency of phenotypically activated SLC-expressing class II antigens and interleukin-2 receptor. Finally, in agreement with the observed antidiabetogenic effects, exogenously administered IFN-γ induced neither insulitis nor IDDM development in DR-BB rats, a subline of DP-BB rats in which autoimmune diabetes rarely occurs spontaneously but can be induced by administration of polyinosinic-polycytidilic acid.

In vivo treatment with a monoclonal antibody to interferon-gamma neither affects the survival nor the incidence of lupus-nephritis in the MRL/lpr-lpr mouse

The effects of the in vitro treatment with a mAb (DB-1) that neutralizes mouse IFN-gamma on the development of the SLE-like syndrome in MRL/lpr-lpr (MRL-lpr) mice were studied. The results show that the i.p. administration of 2.6 mg/week of DB-1 from the 12th to the 20th week of age neither affected the survival nor the incidence and severity of lupus nephritis in MRL-lpr mice. This study argues against the pathogenic relevance of IFN-gamma in this experimental model of human SLE.

Heme oxygenase-1 expression in peripheral blood mononuclear cells correlates with disease activity in multiple sclerosis.

Multiple sclerosis (MS) is an immunoinflammatory disease that affects the central nervous system. Heme oxygenase-1 (HO-1) is one of the three isoforms of the heme oxygenase enzyme that catabolyzes the degradation of heme into biliverdin with the production of free iron and CO. We show in this study that HO-1 expression is reduced in PBMCs of MS patients and that during exacerbation of the disease there is a significant downregulation of this enzyme. We conclude that HO-1 may play a significant role in the maintenance of immune homeostasis which is disrupted in autoimmune disorders, such as MS.

Hypomethylating Agent 5-Aza-2′-deoxycytidine (DAC) Ameliorates Multiple Sclerosis in Mouse Models

Increasing evidence supports the role of epigenetics in the development of autoimmune disorders and the possibility of using epigenetic modifying drugs in the context of MS has not yet been investigated. We have explored the effect of the hypomethylating agent 5‐aza‐2′‐deoxycytidine (DAC) in two murine models of experimental allergic encephalomyelitis (EAE). DAC treatment was associated with a significant amelioration of the clinical and histological hallmarks of EAE in both models. These effects were observed both in prophylactic and therapeutic regimens. The milder course of the disease was associated with a reduction in the number of spinal cord infiltrating lymphocytes and amelioration of the histopathological signs associated with EAE. In addition, increased transcript levels of anti‐inflammatory cytokines and decreased mRNA expression of pro‐inflammatory mediators were also observed. Finally, DAC treatment increased the percentage of circulating regulatory T cells by inducing Foxp3 expression via demethylation of a CpG island in Foxp3. J. Cell. Physiol. 229: 1918–1925, 2014.