BACKGROUND:Intestinal acute graft-versus-host disease is one of the most aggressive complications after allogeneic hematopoietic stem cell transplantation with high lethality.How to improve intestinal inflammation and regulate autophagy by applying traditional Chinese medicine in order to treat intestinal acute graft-versus-host disease is a worthwhile research issue nowadays. OBJECTIVE:To investigate the mechanism of Huangqintang modulating intestinal flora for the treatment of intestinal acute graft-versus-host disease. METHODS:CB6F1 mice were irradiated with 60Co X radiation at a total dose of 8 Gy,and then single nucleated cell suspensions(bone marrow cells+splenocytes)from Balb/c H-2d mice were injected into the tail vein in order to prepare a model of intestinal acute graft-versus-host disease.These samples were randomly divided into the model group and the high-,moderate-,and low-dose Huangqintang groups.After modeling,the model,high-,moderate-,and low-dose groups received different doses of Huangqintang or an equal volume of saline by continuous gavage for 14 days.Clinical acute graft-versus-host disease grading,and survival time was recorded.Small intestinal tissues from each group were stained with hematoxylin and eosin for small intestinal mucosal pathology scoring.The intestinal flora of mice in each group was detected using 16S rDNA sequencing.Autophagy-related markers were detected using immunofluorescence,immunohistochemistry,and PCR. RESULTS AND CONCLUSION:(1)Compared with the model group,the survival time of mice was significantly prolonged(P<0.01);the clinical acute graft-versus-host disease scores were significantly reduced(P<0.01);the pathological grading scores of the small intestinal mucosa were significantly diminished(P<0.01);the levels of the small intestinal tissue inflammatory factors tumor necrosis factor-α,interleukin-1β,and interleukin-6,were significantly decreased(P<0.01);the structural integrity of the small intestinal mucosal epithelium was partially restored in mice after the intervention of moderate and high-dose Huangqintang.(2)The study of intestinal flora found that compared with the model group,the pro-inflammatory strain Enterococcus was significantly reduced(P<0.05),while beneficial bacteria such as Clostridium_innocuum and Rhodococcus,a pro-autophagy bacterium,were significantly elevated(P<0.05)in the moderate-dose Huangqintang group.(3)Compared with the model group,the autophagy markers were significantly elevated in the moderate-dose Huangqintang group(P<0.05);under transmission electron microscopy,the number of autophagic vacuoles of moderate-dose Huangqintang group increased significantly.(4)The results showed that Huangqintang significantly reduced the abundance of conditionally pathogenic bacteria and the level of inflammatory factors in small intestinal tissues,and increased the relative abundance of beneficial bacteria and promoted the expression of autophagy in the small intestinal mucosa,which resulted in a significant improvement of intestinal symptoms in mice with acute graft-versus-host disease.