Increased Calcitonin Gene-Related Peptide and Macrophages Are Involved in Astragalus membranaceus-Mediated Peripheral Nerve Regeneration in Rats
Abstract
Astragalus membranaceus (AM) is one of 50 fundamental herbs in traditional Chinese medicine. Previous studies have shown that AM extract can be a potential nerve growth-promoting factor, being beneficial for the growth of peripheral nerve axons. We further investigated the effects of AM extract on regeneration in a rat sciatic nerve transection model. Rats were divided into three groups (n=10): normal saline (intraperitoneal) as the control, and 1.5g/kg or 3.0g/kg of AM extract (every other day for four weeks), respectively. We evaluated neuronal electrophysiology, neuronal connectivity, macrophage infiltration, expression levels and location of calcitonin gene-related peptide (CGRP), and expression levels of both nerve growth factors (NGFs) and immunoregulatory factors. In the high-dose AM group, neuronal electrophysiological function (measured by nerve conductive velocity and its latency) was significantly improved (P<0.05). Expression levels of CGRP and macrophage density were also drastically enhanced (P<0.05). Expression levels of fibroblast growth factor (FGF), NGF, platelet-derived growth factor (PDGF), transforming growth factor-β, interleukin-1 (IL-1), and interferon (IFN)-γ were reduced in the high-dose AM group (P<0.05), while FGF, NGF, PDGF, IL-1, and IFN-γ were increased in the low-dose AM group (P<0.05). These results suggest that AM can modulate local inflammatory conditions, enhance nerve regeneration, and potentially increase recovery of a severe peripheral nerve injury.
