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Fig. 1. Glycine increases neutrophil bactericidal activity via enhanced intracellular reactive oxygen species (ROS) production. (A) Glycine concentration-dependently increases neutrophil bactericidal activity. Various concentrations of glycine were added to HBSS. Strychnine blocked glycine-induced enhancement of neutrophil bactericidal activity. The average of three experiments is shown (mean ± SE). (B) Glycine increases the clearance of intraperitoneally injected E. coli in mice. Mice were pretreated subcutaneously with PBS or strychnine (0.4 mg/kg) 30 min before an i.p. injection of E. coli (5 × 108). At 30 min after E. coli injection, vehicle (PBS) or glycine (30 mg/kg) was subcutaneously injected. Eight hours after E. coli injection, mice were killed and the number of CFUs in peritoneal lavage fluid was counted. n = 9−10 per group. *p < 0.05; **p < 0.01; ***p < 0.001 by Student’s t-test. (C) Effect of DPI on glycine-induced enhancement of bactericidal activity. Neutrophils were pretreated with DPI (1 μM) for 1 h before glycine (500 μM) treatment in HBSS medium. (D) Effects of glycine on ROS generation in neutrophils. Neutrophils were exposed to E. coli for 20 min. Unphagocytosed E. coli was washed away and neutrophils were further incubated with or without glycine (500 μM) for 15 min. ROS production in neutrophils was measured with DCF-DA. (E) GIyR-ROS-Ca2+ signaling pathway. (Left) Effect of glycine on [Ca2+]i in neutrophils exposed to E. coli. Neutrophils were exposed to E. coli for 20 min, and further incubated with or without glycine (1 mM). (Right) Neutrophils were pretreated with DPI (1 μM) for 15 min before E. coli exposure. CFUs, colony forming units; DPI, diphenylene iodonium; DCF-DA, 2’,7’-dichlorodihydrofluorescein diacetate; Gly, glycine; GlyR, glycine receptor.
Korean J Physiol Pharmacol 2022;26:229-238 https://doi.org/10.4196/kjpp.2022.26.4.229
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