Alteration in Lactate Production and Decrease in MTT Dye Reduction in Serum-starved Human Peripheral Blood Mononuclear Cells (PBMCs)

Abstract

Background: Immunometabolism targeting therapy of auto-inflammatory diseases is an emerging strategy compared to immune system global suppression. However, our knowledge in this field needs promotion. Objectives: We examined the effects of serum starvation stress on metabolic activity in human peripheral blood mononuclear cells (PBMCs). Methods: Fresh immune cells were isolated from four healthy adult volunteers and cultivated with or without fetal bovine serum (FBS) at various time points under standard conditions. Glucose and intra- and extracellular lactate levels were assessed using routine techniques, and 3-(4, 5 -dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) reduction assay was used to determine mitochondrial function. Results: Spindle shape macrophage-like cells, which appeared early, were replaced at 96 h by large round monocytes/macrophage-like cells, with more frequency in the non-starved group. Interestingly, serum starvation dictated a status, especially in monocyte/macrophage-like cells, that led to prolong decrement in mitochondrial dehydrogenase-mediated reduction of MTT. This difference was confirmed with the MTT assay quantitatively (P < 0.05). Moreover, the intra- and extracellular lactate concentrations were lower in starved cells than in non-starved controls (P < 0.05), and glucose levels were higher in 72 h starved cell culture supernatants than in non-starved control cells (P < 0.05). Conclusions: This study showed that under serum starvation-induced metabolic stress, lactate production is altered in immune cells, and total oxidative mitochondrial activity is reduced in macrophage-like cells. These findings open a new window to target immune cell metabolism for the treatment of autoinflammatory and autoimmune diseases.