Possible mechanisms by which silkworm faeces extract ameliorates adenine-induced renal anaemia in rats

Abstract

Ethnopharmacological relevance: Silkworm faeces are the dry faeces of the insect Bombyx mori (Linnaeus) and have historically been used in traditional Chinese medicine to treat blood deficiency and rheumatic pain. Silkworm faeces extract (SFE) is derived from silkworm faeces.

Aim of the study: Clinical observations of patients in the Department of Nephrology have shown that SFE effectively improves renal anaemia. However, the molecular mechanism remains unclear. This article mainly explores the regulatory effects of SFE on erythropoietin (EPO) and hepcidin to identify the molecular mechanism of SFE.

Materials and methods: A rat model of renal anaemia was established by feeding rats food containing 0.75% adenine. SFE was orally administered to the rats, while recombinant human erythropoietin (rhEPO) was used as a positive control drug. Haematological parameters and inflammation levels were compared between rats from each group, and pathological kidney sections from each rat were observed. The serum EPO and hepcidin levels were detected using enzyme-linked immunosorbent assay (ELISA) kits, while Western blot analyses were performed to detect the levels of proteins involved in the EPO-related hypoxia-inducible factor 2α (HIF-2α)/prolyl hydroxylase 2 (PHD2) signalling pathway and hepcidin-related BMP6/SMAD4 and interleukin-6 (IL-6)/STAT3 signalling pathways.

Results: SFE significantly ameliorated haematological parameters, renal function, and inflammation levels in the rats. A mechanistic study showed that SFE promoted EPO expression by upregulating HIF-2α expression and inhibiting the expression of NF-κB and GATA2 both in vivo and in vitro. In particular, SFE inhibited PHD2 expression, resulting in a decrease in the enzymatic reaction of HIF-2α to increase EPO expression. Furthermore, SFE inhibited hepcidin expression by blocking the BMP6/SMAD4 and IL-6/STAT3 pathways.

Conclusions: SFE regulated iron metabolism by inhibiting hepcidin and simultaneously promoted EPO synthesis to improve renal anaemia in rats.

Keywords: Chronic kidney disease; Erythropoietin; HIF-2α; Hepcidin; Renal anaemia; Silkworm faeces extract.