Opposite function of p38MAPK/MK2 on ROS generation and circadian oscillations of circulating mouse and human leukocyte. (A-B) Blood samples were taken from points ZT7 and ZT19 in 10-week-old NSG and humanized mice (n = 6). Shown are representative stain and statistical analysis of phosphorylated p38MAPK (phospho-P38) (A) and phosphorylated MK2 (phospho-MK2) (B). (C-H) Blood samples were taken from 10-week-old humanized mice treated with PBS or LY228820 (n = 6). The number counts of mCD45⁺ (C) and hCD45⁺ (D) cells at each point in individual mice were normalized to the initial number at time ZT1. Shown are fold changes of cell number. The ROS MFI in mCD45⁺ (E) and hCD45⁺ (F) cells at points ZT7 and ZT19 were analyzed. The 24-h circadian oscillations of HIF-1α mRNA in mCD45⁺ (G) and hCD45⁺ (H) cells are shown. *P < .05; **P < .01.