Blood leucocyte cytokine production after LPS stimulation at different concentrations of glucose and/or insulin

The Intracellular Growth of M. tuberculosis Is More Associated with High Glucose Levels Than with Impaired Responses of Monocytes from T2D Patients

Diabetes mellitus, a metabolic disease characterized by hyperglycemia and poor glucose control, is a risk factor for Mycobacterium tuberculosis (M. tuberculosis) infection and the development of active tuberculosis. To evaluate whether M. tuberculosis infection susceptibility is associated with an intrinsic factor in monocytes from type 2 diabetes (T2D) patients or it is associated with hyperglycemia per se, we analyzed TLR-2 and TLR-4 expression by flow cytometry and the cytokines IL-1β, IL-6, IL-8, IL-10, and TNF-α by cytometric bead array assays, either stimulated with TLR-2 and TLR-4 ligands or infected with M. tuberculosis in the whole blood from T2D patients (n = 43) and healthy subjects (n = 26) or in CD14+ monocytes from healthy subjects cultured in high glucose (HG) (30 mM). The intracellular growth of M. tuberculosis was evaluated by CFU counts at 0, 1, and 3 days in both monocytes from T2D patients and monocytes from healthy subjects cultured in HG. We did not find significant differences in TLR expression, cytokine production, or growth of M. tuberculosis in monocytes from T2D patients compared with those in monocytes from healthy subjects. Despite these results, in vitro assays of monocytes cultured with 30 mM glucose led to significantly increased TLR-2 and TLR-4 basal expression compared to those of monocytes cultured with 11 mM glucose (P < 0.05). Conversely, the production of IL-6 by TLR-2 ligand stimulation, of IL-1β, IL-6, and IL-8 by TLR-4 ligand stimulation, and of IL-8 by M. tuberculosis infection significantly decreased in monocytes cultured in HG (P < 0.05). Additionally, the intracellular survival of M. tuberculosis increased in monocytes in HG after day 3 of culture (P < 0.05). In conclusion, HG decreased IL-8 production and the intracellular growth control of M. tuberculosis by monocytes, supporting the hypothesis that hyperglycemia plays an important role in the impaired immune responses to M. tuberculosis in patients with T2D.

Delayed addition of glucocorticoids selectively suppresses cytokine production in stimulated human whole blood

Glucocorticoids (GC) are potent drugs proven to effectively treat inflammatory diseases, although patients typically begin therapy after the onset of symptoms. Clinical studies with cytokine inhibitors prove that these mediators drive inflammatory responses in diseases such as rheumatoid arthritis and Crohn's disease. Despite the clear sequence of cytokine-induced inflammation followed by effective GC treatment, most basic science investigations have examined the ability of GC to prevent an inflammatory response rather than halt its progression. The current studies used the Toll-like receptor 2 (TLR2) agonist palmitoyl(3)-cysteine-serine-lysine(4) (PAM) or the TLR4 agonist lipopolysaccharide (LPS) to stimulate human whole blood and determine whether postponing the addition of the GC dexamethasone (DEX) limits its ability to decrease cytokine production. Twenty-four hours after stimulation, tumor necrosis factor (TNF), interleukin-1beta (IL-1beta), IL-6, and IL-8 levels were measured, in addition to the cytokine inhibitors IL-1 soluble receptor II (SRII), IL-1 receptor antagonist, and TNF SRII. LPS rapidly induced all of the proinflammatory mediators over 24 h while failing to induce any of the cytokine inhibitors. PAM stimulation also induced IL-1beta, IL-6, and IL-8. Concomitant addition of DEX plus LPS or PAM significantly suppressed all cytokine levels. Delaying the addition of DEX until 6 h after LPS stimulation failed to decrease TNF or IL-6. In contrast, delayed DEX addition significantly suppressed PAM-induced IL-1beta, IL-6, or IL-8 and also suppressed LPS-induced IL-1beta and IL-8. Our results show that cytokines which typically increase in concentration between 6 and 24 h after stimulation were significantly suppressed by the addition of DEX 6 h after stimulation.