Background A better understanding about the mechanisms involved in the pathogenesis of type 2 diabetes mellitus (T2DM) showed that inflammatory cytokines such as tumor TNF-α and IL-1β play a pivotal role, mirroring data largely reported in rheumatoid arthritis (RA) . Both preclinical and clinical studies confirmed the usefulness of IL-1β antagonism therapy in both diseases . IL-1β is mainly produced by monocytes/macrophages. Hyperglycaemia may be able to modulate, in the cytoplasm of these cells, the assembly of a cytosolic multiprotein platforms, composed by 3 molecules: NLRP3 sensor protein; ASC adaptor protein; caspase-1, the so called NLRP3-inflammasome, where, the inactive pro-IL-1β is cleaved into active form, via caspase-1 activity .
Objectives We evaluated the production of IL-1 β and TNF-α, in peripheral blood monocytes (MO) of patients affected by RA or T2DM or both diseases, in order to understand if, an alteration of the glucose metabolism may influence their pro-inflammatory status.
Methods We enrolled 10 RA patients, 10 T2DM patients and 10 patients affected by both the diseases (T2DM/RA patients), and 5 healthy controls (HC). From these patients, MO were isolated from human peripheral blood mononuclear cells using CD14 selection. After that MO were incubated with 11 mmol/1 glucose (11G) and 33 mmol/1 glucose (33G), for 24 hours, and we evaluated by ELISA the concentration of both IL-1β and TNF-α released in cultured MO supernatants, the relative mRNA expression by qRT-PCR and the western blot analysis of NLRP3. Due to the non parametric distribution of our data the Mann-Whitney U test was used as appropriate for analyses. Statistical significance was expressed by a p value <0.05.
Results Our data showed, after 24 hours of incubation with 11G, a significantly increase of IL-1β in supernatants of T2DM, RA, and T2DM/RA cultured MO, when compared with HC (p<0.01 for each comparison). Our data showed that after 24 hours of incubation with 33G a significant increase of IL-1β secretion by T2DM/RA MO of patients when compared with other groups (p<0.01 for each comparison). We observed after 24 hours of incubation with both 11G and 33G an increase of TNF-α in supernatants, in all groups when compared with HC (p<0.01 for each comparison). We did not observed significant differences in TNF-α secretion among T2DM, RA and T2DM/RA patients. The analysis of relative mRNA expression confirmed these data. Our results showed after 24 hours of incubation with both 11G and 33G a significant increase in relative NLRP3 mRNA expression when we compared T2DM/RA patients and the other groups (p<0.001 for each comparison). The results of western blot analyses for NLRP3 mirrored these data.
Conclusions Our study showed an increased production of IL-1β by MO obtained from patients affected by both RA and T2DM via NLRP3-inflammasome activation suggesting a potential IL-1β target therapy.
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Disclosure of Interest None declared