Bletilla striata Polysaccharide Promotes Diabetic Wound Healing Through Inhibition of the NLRP3 Inflammasome.

Yan Zhao,Haitao Zhu,Shan Yan,Liangyong Huang,Jun Zhou,Yonghong Zhang,Tao Zheng,Lin Chen,Qibin Wang,Li Chen,Fang Ye

doi:10.3389/fphar.2021.659215

Abstract

The aim of this study was to evaluate the therapeutic effects of Bletilla striata polysaccharide (BSP) on wound healing in diabetes mellitus (DM) and to explore the underlying mechanisms. DM mouse models were induced by high fat-diet feeding combined with low-dose streptozocin injection. To establish diabetic foot ulcer (DFU) models, DM mice were wounded on the dorsal surface. Subsequently, mice were treated with vehicle or BSP for 12 days and wound healing was monitored. The effects of BSP on the production of interleukin-1β (IL-1β), tumor necrosis factor-α, macrophages infiltration, angiogenesis, the activation of nucleotide-binding and oligomerization (NACHT) domain, leucine-rich repeat (LRR), and pyrin domain (PYD)-containing protein 3 (NLRP3) inflammasome, and insulin sensitivity in wound tissues were subsequently evaluated. Separated- and cultured- bone marrow-derived macrophages (BMDMs) and cardiac microvascular endothelial cells (CMECs) were isolated from mice and used to investigate the effects of BSP on cell viability, reactive oxygen species (ROS) generation, NLRP3 inflammasome activation and insulin sensitivity in vitro following exposure to high glucose (HG). BSP administration accelerated diabetic wound healing, suppressed macrophage infiltration, promoted angiogenesis, suppressed NLRP3 inflammasome activation, decreased IL-1β secretion, and improved insulin sensitivity in wound tissues in DM mice. In vitro, co-treatment with BSP protected against HG-induced ROS generation, NLRP3 inflammasome activation, and IL-1β secretion in BMDMs, and improved cell viability and decreased ROS levels in CMECs. Moreover, in HG exposed BMDMs-CMECs cultures, BSP treatment suppressed NLRP3 inflammasome activation and IL-1β secretion in BMDMs, and improved cell viability and insulin sensitivity in CMECs. Furthermore, treatment with IL-1β almost completely suppressed the beneficial effects of BSP on the NLRP3 inflammasome, IL-1β secretion, and insulin sensitivity in HG-treated BMDMs-CMECs. BSP promotes DFU healing through inhibition of the HG-activated NLRP3 inflammasome.

Highlights

Diabetes mellitus (DM) afflicts more than 382 million people globally (Basu et al, 2019)
UV spectra showed no absorption peaks at either 260 or 280 nm, which contrasted that of Adenosine 5′-triphosphate disodium salt hydrate (ATP) or bovine serum albumin (BSA) (Figure 1B) confirming that the Bletilla striata polysaccharide (BSP) sample was free of nucleic acids and protein
According to highperformance gel permeation chromatography (HPGPC) assays, one of the main polysaccharides was detected in BSP (Figure 1C), with the weight-average molecular weight (Mw) of 536789 g/mol

Summary

Introduction

Diabetes mellitus (DM) afflicts more than 382 million people globally (Basu et al, 2019). The nucleotide-binding and oligomerization (NACHT) domain, leucine-rich repeat (LRR), and pyrin domain (PYD)-containing protein 3 (NLRP3) inflammasome-mediated inflammatory cascade has been suggested to contribute to the deficiencies in angiogenesis and ulcer healing in DM patients (Mirza et al, 2013; Zhang et al, 2017; Liu et al, 2019; Huang et al, 2020). It is recognized that the IL-1β-mediated inflammatory response can reduce insulin sensitivity and damage vascular endothelial cells, leading to defective wound healing (Bitto et al, 2014; Zhang et al, 2017; Liu et al, 2019; Huang et al, 2020). Blocking either the NLRP3 inflammasome or IL-1β-mediated inflammatory reactions can effectively promote DFU healing (Mirza et al, 2013; Bitto et al, 2014; Mirza et al, 2014; Huang et al, 2020)

Objectives

Methods

Results

Conclusion