Similar to the ratio of the oxygen solubility at these two pO2, which is 4.2. Given that the rates of oxygen uptake of the cells grown at each pO2 were not dramatically different, the major determinant of the steady-state concentration of oxygen around the cells is the solubility of this gas at each of the pO2.DiscussionOur data demonstrate that adapting conventional culture conditions to more physiologically relevant conditions significantlyOxygen Tension Influences THP-1 Cell PhysiologyFigure 7. Oxygen tension influences redox in LPS-induced NF-kB activation in PMA-Bromopyruvic acid web differentiated THP-1 cells. Undifferentiated THP-1 XBlue cells, which express an NF-kB reporter gene linked to secreted embryonic alkaline phosphatase (SEAP) were synchronized by serum deprivation for 48 h, and then differentiated with PMA (20 ng/ml) for 48 h. Differentiated THP-1 XBlue cells were then cultured in varying concentrations of DPI (A) or NGA (B) for 4 h followed by LPS (1 mg/ml) stimulation for an additional 24 h in either 18 or 5 O2. SEAP activity was quantified by QuantiBlue at 630 nm. Data are presented as the mean 6 SEM (n = 2 independent experiments). *Significantly different from baseline (SEAP activity in the absence of inhibitor) at the same oxygen tension; **p,0.01; ***p,0.001 (one-way ANOVA with post hoc Tukey’s test). #Significantly different from 5 O2 at same antioxidant concentration; #p,0.05; ##p,0.01 (Student’s t-test). doi:10.1371/journal.pone.0054926.galters THP-1 cell physiology. Specifically, we observed that while lowering oxygen tension from 18 O2 to 5 O2 had no effect on the proliferation of undifferentiated THP-1 cells, this endpoint was significantly altered by the removal of serum from the culture medium. Changing the oxygen tension from hyperoxic to normoxic did, however, significantly increase metabolic activity in both undifferentiated and differentiated THP-1 cells as well as enhance the differentiation of THP-1 cells and signficantly influence key aspects of macrophage function in differentiated THP-1 cells. Quantification of cellular uptake of oxygen in THP-1 cells grown under 18 O2 versus 5 O2 confirmed that the major determinant of the steady-state concentration of oxygen around these cells was the solubility of this gas at each pO2 and not cellular oxygen order CAL120 consumption. Removing 2-ME from the culture media had negligible effect on these endpoints. In contrast, removing both 2-ME and serum had significant effects on THP-1 metabolism, differentiation and macrophage functions under both conditions of oxygen tension, with more pronounced effects observed in THP-1 cells cultured under 5 O2. Serum is commonly used as a supplement in cell culture to improve cell viability; however, there are a number of downsides including cost and the fact that serum is chemically undefined with high variability between batches. Adapting THP-1 cells 24786787 to serumfree culture conditions would, therefore, significantly decrease costs and potentially increase culture consistency and experimental reproducibility. Removal of serum decreased proliferation of undifferentiated THP-1 cells; however, this effect was largely ameliorated by lowering the oxygen tension from 18 to 5 O2. This is consistent with previous studies demonstrating that the proliferation rate of peripheral blood mononuclear cells (PBMC) cultured in medium supplemented with a very low serum concentration was enhanced under normoxic conditions relative to hyperoxic conditions [32]. The.Similar to the ratio of the oxygen solubility at these two pO2, which is 4.2. Given that the rates of oxygen uptake of the cells grown at each pO2 were not dramatically different, the major determinant of the steady-state concentration of oxygen around the cells is the solubility of this gas at each of the pO2.DiscussionOur data demonstrate that adapting conventional culture conditions to more physiologically relevant conditions significantlyOxygen Tension Influences THP-1 Cell PhysiologyFigure 7. Oxygen tension influences redox in LPS-induced NF-kB activation in PMA-differentiated THP-1 cells. Undifferentiated THP-1 XBlue cells, which express an NF-kB reporter gene linked to secreted embryonic alkaline phosphatase (SEAP) were synchronized by serum deprivation for 48 h, and then differentiated with PMA (20 ng/ml) for 48 h. Differentiated THP-1 XBlue cells were then cultured in varying concentrations of DPI (A) or NGA (B) for 4 h followed by LPS (1 mg/ml) stimulation for an additional 24 h in either 18 or 5 O2. SEAP activity was quantified by QuantiBlue at 630 nm. Data are presented as the mean 6 SEM (n = 2 independent experiments). *Significantly different from baseline (SEAP activity in the absence of inhibitor) at the same oxygen tension; **p,0.01; ***p,0.001 (one-way ANOVA with post hoc Tukey’s test). #Significantly different from 5 O2 at same antioxidant concentration; #p,0.05; ##p,0.01 (Student’s t-test). doi:10.1371/journal.pone.0054926.galters THP-1 cell physiology. Specifically, we observed that while lowering oxygen tension from 18 O2 to 5 O2 had no effect on the proliferation of undifferentiated THP-1 cells, this endpoint was significantly altered by the removal of serum from the culture medium. Changing the oxygen tension from hyperoxic to normoxic did, however, significantly increase metabolic activity in both undifferentiated and differentiated THP-1 cells as well as enhance the differentiation of THP-1 cells and signficantly influence key aspects of macrophage function in differentiated THP-1 cells. Quantification of cellular uptake of oxygen in THP-1 cells grown under 18 O2 versus 5 O2 confirmed that the major determinant of the steady-state concentration of oxygen around these cells was the solubility of this gas at each pO2 and not cellular oxygen consumption. Removing 2-ME from the culture media had negligible effect on these endpoints. In contrast, removing both 2-ME and serum had significant effects on THP-1 metabolism, differentiation and macrophage functions under both conditions of oxygen tension, with more pronounced effects observed in THP-1 cells cultured under 5 O2. Serum is commonly used as a supplement in cell culture to improve cell viability; however, there are a number of downsides including cost and the fact that serum is chemically undefined with high variability between batches. Adapting THP-1 cells 24786787 to serumfree culture conditions would, therefore, significantly decrease costs and potentially increase culture consistency and experimental reproducibility. Removal of serum decreased proliferation of undifferentiated THP-1 cells; however, this effect was largely ameliorated by lowering the oxygen tension from 18 to 5 O2. This is consistent with previous studies demonstrating that the proliferation rate of peripheral blood mononuclear cells (PBMC) cultured in medium supplemented with a very low serum concentration was enhanced under normoxic conditions relative to hyperoxic conditions [32]. The.