Characterization of the effects of Chinese peony (Radix paeoniae Alba) and its active ingredients on the hematopoietic function of the Chinese mitten crab (Eriocheir sinensis)

Hematopoietic tissue (HPT) is crucial for the proliferation and release of newly produced hemocytes during infection in crustaceans. Very few studies have reported how herbs affected the hematopoietic function of crustaceans. Radix paeoniae Alba is a candidate immunopotentiator herb with the potential to be a bloodtonifying drug. In this study, the effects of Radix paeoniae Alba and its monomers (paeoniflorin, albiflorin, and paeonol) on HPT and hemocytes of Eriocheir sinensis were evaluated. After feeding them commercial diets containing different ingredients for three weeks, the HPT development was determined via morphological observation and hematopoietic tissue body index (HTBI) calculation. The count and classification of hemocytes were evaluated using the hemocytometer and flow cytometer. The expression of hematopoietic factor astakine, transglutaminase (TGase), and marker genes for different types of hemocytes (KPI and SOD) and undifferentiated HPT cells (PCNA) were detected using real-time quantitative PCR (qRT-PCR) assay. The results indicated that the HTBI in the Radix Paeoniae Alba, paeoniflorin, and albiflorin groups increased by 114.96%, 111.42%, and 112.50%, which were higher than the control group. The Radix Paeoniae Alba, paeoniflorin, albiflorin, and paeonol groups had higher proportions of ovoid lobules than the control group, especially in the Radix Paeoniae Alba group. The total hemocyte count (THC) of the crab in the Radix Paeoniae Alba, paeoniflorin, and paeonol groups were 8.12, 9.69, and 8.57x106 ind/mL, respectively, which were higher than the control group. Furthermore, all experimental groups showed a higher proportion of granulocytes than the control group, with increased astakine protein being simultaneously detected in the HPT. The qRT-PCR results showed a relatively higher KPI expression in all the experimental groups, and also higher SOD mRNA expression in the Radix Paeoniae Alba, paeoniflorin, and paeonol groups, as compared with the control group. Therefore, these results implied the potential effect of Radix Paeoniae Alba and its monomers on the hematopoietic function of E. sinensis. However, due to the complex ingredient composition in Radix Paeoniae Alba and their different activities in the hematopoietic process, further research needs to be conducted in the future.