Limited expression of TLR9 on T cells and its functional consequences in patients with nonalcoholic fatty liver disease.

BACKGROUND/AIMS: Toll-like receptors (TLRs) modulate T cell responses in diverse diseases. Co-stimulation of T cell activation via TLR9 induces production of interferon gamma (IFN-γ), priming of which is critical for differentiation of pro-inflammatory macrophages. These macrophages have a crucial role in nonalcoholic fatty liver disease (NAFLD). We aimed to evaluate the expression of TLR9 protein on T cells and the consequences of TLR9-mediated triggering of these cells in patients with NAFLD. METHODS: Our study included 34 patients with simple steatosis, 34 patients with nonalcoholic steatohepatitis, eight patients with NAFLD who met general diagnostic criteria but lacked histological diagnosis, and 51 control subjects. We used a synthetic TLR9 ligand to co-stimulate T cells. We measured TLR9 expression in liver and peripheral T cells and CD69 and IFN-γ as phenotypic markers of T cell activation and differentiation by flow cytometry. RESULTS: TLR9 expression on liver and peripheral T cells was lowest in patients with simple steatosis and was positively associated with anthropometric, biochemical, and histopathological features of NAFLD. In vitro co-stimulation of T cells from patients with simple steatosis induced a limited number of IFN-γ-producing CD8+ T cells. At baseline, these patients showed a low frequency of circulating type 1 CD8+ cells. CONCLUSION: The positive associations between TLR9 and anthropometric, clinical, and histological features and the crucial role of IFN-γ-in NAFLD suggest that limited TLR9 expression and production of IFN-γ play a protective role in patients with simple steatosis.

Selective hemangioma cell dysfunction and apoptosis triggered by in vitro treatment with imiquimod.

Infantile hemangiomas are the most common benign tumors of infancy, characterized by unregulated angiogenesis and endothelial cells with high mitotic rate. Although spontaneous regression occurs, sometimes treatment is required and alternatives to corticosteroids should be considered to reduce side effects. Imiquimod is an imidazoquinoline, approved for some skin pathologies other than hemangioma. It is proposed that the effectiveness of imiquimod comes from the activation of immune cells at tumor microenvironment. However, the possibility to selectively kill different cell types and to directly impede angiogenesis has been scarcely explored in vitro for endothelial cells. In this work we showed a dramatic cytotoxicity on hemangioma cell, with a significant lower IC50 value in hemangioma compared to normal endothelial cells and melanoma (employed as a non-endothelial tumor cell line). Nuclear morphometric and flow-cytometry assays revealed imiquimod-induced apoptosis on hemangioma and melanoma cells but a small percentage of senescence on normal endothelial cells. At sub-lethal conditions, cell migration, a key step in angiogenesis turned out to be inhibited in a tumor-selective manner along with actin cytoskeleton disorganization on hemangioma cells. Altogether, these findings pointed out the selective cytotoxic effects of imiquimod on transformed endothelial cells, evidencing the potential for imiquimod to be a therapeutic alternative to reduce extensive superficial hemangioma lesions.