Objective To study the effect of blood-letting puncture at "Well-points" of the twelve meridians on hippocampal mitophagy of hypobaric hypoxia-induced brain injury(HHIBI) rats

so as to explore its biological mechanisms underlying improvement of high altitude hypoxia-induced brain injury. Methods Male SD rats were randomly divided into normal control group(n=9)

and model and blood-letting groups which were further divided into 6

12

24

48 and 72 h subgroups(n=9 in each subgroup). The HHIBI model was established by putting the rats into a hypobaric hypoxia chamber(equivalent to 5 000 m above sea level).The blood-letting groups were given blood-letting therapy at "Shaoshang"(LU11)

"Shangyang"(LI1)

"Zhongchong"(PC9)

"Guanchong"(SJ1)

"Shaochong"(HT9)

"Shaoze"(SI9)

once a day for 7 days. H.E. staining was used to observe the histopatholo-gical changes of hippocampus tissue. Serum hypoxia inducible factor(HIF)-1α and vascular endothelial growth factor(VEGF) contents were assayed using ELISA

and the expression levels of hippocampal Beclin-1 and LC3-Ⅱ proteins detected using Western blot. Results Compared with the normal control group

the levels of serum HIF-1α and VEGF at each time point

and the expressions of hippocampal Beclin-1 at 12 and 24 h

LC3-Ⅱat each time point were significantly increased in the model group(P<0.05

P<0.01); while in comparison with the model group

the levels of serum HIF-1α and VEGF contents

and the expressions of Beclin-1 at 12 h

LC3-Ⅱ at 24

48 and 72 h were further significantly up-regulated in the blood-letting group(P<0.01

P<0.05). H.E. staining revealed that the pyramidal cells in the hippocampal CA1 region had a disordered arrangement

and some of them presented swelling with loose and pale cytoplasm or vacuolation at 6

12 and 24 h

and showed indistinct nucleolus

irregular shape

pyknosis and deep staining and an obvious edema at 48 and 72 h

which was relatively milder in the blood-letting group.Conclusion Blood-letting of "Well-points" can up-regulate serum HIF-1α and VEGF contents and hippocampal Beclin-1 and LC3-Ⅱ(mitophagy related proteins) expressions in HHIBI rats

which may contribute to its effect in reducing hypoxic brain injury.