To explore the mechanism of action by which icariin regulates the loss of immune tolerance to immune thrombocytopenia (ITP) through the microRNA (miRNA)-98-5p-mediated adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR)/Unc-51-like autophagy-activating kinase 1 (ULK1) signaling pathway.

The ITP model was established by intraperitoneal injection of guinea pig anti-mouse platelet serum into mice. Another 12 normal mice were taken as the control group. The mice with successful modeling were divided into model group, the experimental-low group, the experimental-high group and the positive drug group. The experimental-low and experimental-high groups and the positive drug group were gavaged with 1.25, 5.00 mg·kg^-1 icariin and 9.1 mg·kg^-1 prednisone acetate, respectively, after the mice were modeled. The levels of platelets (PLT) and hemoglobin (Hb) were detected by automatic blood analyzer; the levels of thrombopoietin (TPO) and inflammatory factors were detected by enzyme-linked immunosorbent assay; the pathological damage of spleen tissue was detected by hematoxylin-eosin staining; megakaryocytes were observed with sternum bone marrow smears; the relative expression level of miRNA-98-5p was detected by real-time fluorescence quantitative polymerase chain reaction; and the protein relative expression levels of the AMPK/mTOR/ULK1 signaling pathway was detected by Western blotting.

The PLT levels in control group, model group, experimental-low group, experimental-high group and positive drug group were (1 504.56±166.99), (752.68±80.33), (862.95±98.33), (1 212.35±134.23) and (1 363.23±155.33)×10·L^-1, respectively; the Hb levels were (151.33±18.96), (124.11±13.56), (138.32±14.02), (145.33±16.88) and (149.22±16.02) g·L^-1, respectively; the TPO levels were (12.05±1.33), (5.86±0.78), (6.62±0.96), (7.85±0.92) and (9.66±0.89) pg·mL^-1, respectively; the levels of interleukin-6 (IL-6) were (18.96±2.33), (44.33±5.39), (39.25±4.46), (32.32±4.33) and (22.98±3.78) ng·L^-1, respectively; the levels of IL-10 were (42.15±6.48), (23.12±3.56), (26.89±3.99), (31.02±4.65) and (33.66±4.86) ng·L^-1, respectively; the levels of tumor necrosis factor-α(TNF-α) were (31.02±4.65), (77.36±8.98), (67.65±7.88), (60.52±7.34) and (40.56±5.99) ng·L^-1, respectively; the levels of interferon-gamma (IFN-γ) were (4.33±0.68), (8.33±0.96), (7.35±0.89), (6.02±0.81) and (5.86±0.75) ng·L^-1, respectively; the relative expression levels of miRNA-98-5p were 1.00±0.16, 1.78±0.21, 1.51±0.18, 1.22±0.16 and 1.15±0.15, respectively; the relative expression levels of phosphorylated (p)-AMPK/AMPK were 1.00±0.14, 1.81±0.28, 1.60±0.19, 1.31±0.16 and 1.25±0.21, respectively; the relative expression levels of p-mTOR/β-actin were 1.00±0.16, 0.48±0.07, 0.59±0.09, 0.79±0.12 and 0.82±0.14, respectively; the relative expression levels of p-ULK1/β-actin were 1.00±0.15, 0.42±0.06, 0.53±0.09, 0.89±0.14 and 0.93±0.16, respectively. There were statistically significant differences when comparing the above indicators of model group with those of control group, and also when comparing the above indicators of the experimental-low, experimental-high groups and positive drug group with those of model group (P<0.05, P<0.01, P<0.001).

Icariin regulates the loss of immune tolerance in rats with ITP, inhibits autophagy, and thus elevates platelet levels by down-regulating the expression of miRNA-98-5p and modulating the AMPK/mTOR/ULK1 signaling pathway.