Sustained Surface ICAM-1 Expression and Transient PDGF-B Production by Phorbol Myristate Acetate-Activated THP-1 Cells Harboring Blau Syndrome-Associated NOD2 Mutations

Objectives: Blau syndrome is a distinct class of autoinflammatory syndrome presenting with early-onset systemic granulomatosis. Blau syndrome-causing NOD2 mutations located in the central nucleotide-oligomerization domain induce ligand-independent basal NF-κB activation in an in vitro reporter assay. However, the precise role of this signaling on granuloma formation has not yet been clarified. Methods: Blau syndrome-causing NOD2 mutations were introduced into human monocytic THP-1 cells, and their morphological and molecular changes from parental cells were analyzed. Identified molecules with altered expression were examined in the patient’s lesional skin by immunostaining. Results: Although the production of proinflammatory cytokines was not altered without stimulation, mutant NOD2-expressing THP-1 cells attached persistently to the culture plate after stimulation with phorbol myristate acetate. Sustained surface ICAM-1 expression was observed in association with this phenomenon, but neither persistent ICAM-1 mRNA expression nor impaired ADAM17 mRNA expression was revealed. However, the transient induction of PDGF-B mRNA expression was specifically observed in stimulated THP-1 derivatives. In the granulomatous skin lesion of a Blau syndrome patient, ICAM-1 and PDGF-B were positively immunostained in NOD2-expressing giant cells. Conclusions: Sustained surface ICAM-1 expression and transient PDGF-B production by newly differentiating macrophages harboring mutant NOD2 might play a role in granuloma formation in Blau syndrome.

Dietary antioxidants significantly reduced phorbol myristate acetate induced oxidative stress of peripheral blood mononuclear cells of patients with rheumatoid arthritis

Background: Rheumatoid arthritis (RA) is an auto immune disease responsible for maximum human morbidity in modern life whereas oxidative stress is the ultimate potential biomarker for determining disease activity in patients with RA. Objective: The present study scientifically validated the effectiveness of antioxidant commonly present in different food supplement as to neutralize the free radicals mediated oxidativestress in isolated peripheral blood mononuclear lymphocytes (PBML) of patients with RA. Methods: The study population included the patients with Rheumatoid arthritis, RA (n =15) who fulfilled the American College of Rheumatology criteria for RA. Peripheral blood was collected and isolated mononuclear lymphocyte cells (PBML) were pretreated with phorbol myristate acetate (PMS) and furthermore incubated with different concentration of Naringenin, β carotene and N-acetyl cysteine (NAC) in an ex vivo condition. Resultant cell lysate was used for further studies for determination of other oxidative biomarkers. Increase of superoxide and nitric oxide production was observed when PBML were treated PMS. Results: Importantly, the increased oxidative stress was effectively decreased by the selected plant derived compounds β-carotene and naringenin. Conclusion: The study scientifically evaluated the efficacy of the molecules validated by one-way ANOVA followed by Dunnett’s post hoc test of significance. Collectively, our results indicate that both β carotene and naringenin may be a promising non-toxic food supplement in attenuating the oxidative stress associated pathology in RA, meriting further pharmacological studies on other inflammatory cells like neutrophils.

Induction of tryptophan 2,3-dioxygenase expression in human monocytic leukemia/lymphoma cell lines THP-1 and U937

Tumor-associated macrophages are immune cells with diverse functions in tumor development. Among other functions, they downregulate immune-mediated tumor rejection by depriving lymphocytes of nutrients. The essential amino acid tryptophan is metabolized by the enzymes indoleamine 2,3-dioxygenase 1 and tryptophan 2,3-dioxygenase (TDO). Indoleamine 2,3-dioxygenase 1 is expressed in a large number of human tumors, and inhibitors are in development to improve immunotherapy. Tryptophan 2,3-dioxygenase was also found in human tumors and preclinical working models confirmed its immunosuppressive power. We explored a potential expression of TDO by macrophages. This enzyme could be induced in two human cell lines, THP-1 and U937, by incubation with phorbol myristate acetate, lipopolysaccharide, and interferon gamma. Phorbol-myristate-acetate-mediated induction was inhibited by rottlerin, a protein kinase C inhibitor. In contrast to these monocytic cell lines, other cell lines or fresh human monocytes isolated from peripheral blood mononuclear cells and differentiated into proinflammatory or anti-inflammatory macrophages could not be induced to express TDO. Our results suggest that TDO might play an immunosuppressive role in human monocytic leukemias but not in untransformed macrophages.