Figure 5.

3‐HB inhibits Ca²⁺ releasing from ER depended on 3‐HB–Gpr109a signaling‐activated Ca²⁺ influx. A,B) Change in cytosolic Ca²⁺ concentration in real time as detected by Fura‐2 fluorescence imaging. The isolated BMDMs from WT or Gpr109a ^−/− mice were loaded with Fura‐2 AM (10 × 10⁻⁶ m), and then perfused in Hank's buffer (with added Ca²⁺). 3‐HB (1 × 10⁻³, 5 × 10⁻³, and 10 × 10⁻³ m) or niacin (0.1 × 10⁻⁶ m) were added as indicated by the vertical lines in the Ca²⁺ tracings. C) Increases in intracellular Ca²⁺ concentration after the addition of 3‐HB (1 × 10⁻³, 5 ×10⁻³, and 10 × 10⁻³ m) or niacin (0.1 × 10⁻⁶ m) were calculated and plotted (n = 5). D) Change in cytosolic Ca²⁺ concentration in real time detected via Fluo‐4 fluorescence imaging. The isolated BMDMs from WT mice were loaded with Fluo‐4 AM (10 × 10⁻⁶ m), and then perfused in Hank's buffer (without addition of Ca²⁺). LPS (100 × 10⁻⁹ g mL⁻¹), LPS (100 × 10⁻⁹ g mL⁻¹) +3‐HB (10 × 10⁻³ m) or LPS (100 × 10⁻⁹ g mL⁻¹) +2‐APB (100 × 10⁻⁶ m) were added as indicated using Ca²⁺ tracking. E) Increases in intracellular Ca²⁺ concentration after the addition of LPS (100 × 10⁻⁹ g mL⁻¹) +3‐HB (10 × 10⁻³ m) or LPS (100 × 10⁻⁹ g mL⁻¹) +2‐APB (100 × 10⁻⁶ m) (n = 5). F,G) Changes of phosphorylation levels of protein PLC, IP3R, and CaMKII in BMDMs treated with LPS (100 × 10⁻⁹ g mL⁻¹) with or without 3‐HB (10 × 10⁻³ m) or the intracellular calcium chelater BAPTA‐AM (20 × 10⁻⁶ m). Data are presented as mean±SEM from at least three independent experiments, one‐way ANOVA. ** p <0.01, *** p <0.01, **** p <0.01; NS, no statistical significance.