Unfractionated Heparin Improves the Intestinal Microcirculation in a Canine Septic Shock Model

Heparin in sepsis: current clinical findings and possible mechanisms

Sepsis is a clinical syndrome resulting from the interaction between coagulation, inflammation, immunity and other systems. Coagulation activation is an initial factor for sepsis to develop into multiple organ dysfunction. Therefore, anticoagulant therapy may be beneficial for sepsis patients. Heparin possesses a variety of biological activities, so it has a broad prospect in sepsis. Previous studies suggested that patients with sepsis-induced disseminated intravascular coagulation and high disease severity might be suitable for anticoagulant therapy. With the development of artificial intelligence (AI), recent studies have shown that patients with severe coagulation activation represent the targeted patients for anticoagulant therapy in sepsis. However, it remains necessary to accurately define the relevant biomarkers indicative of this phenotype and validate their clinical utility by large randomized controlled trials (RCTs). Analyses of data from early small RCTs, subgroup analyses of large RCTs and meta-analyses have collectively suggested that anticoagulant therapy, particularly the use of heparin, may be an effective approach for managing sepsis patients. Concurrently, debate persists regarding the optimal selection of anticoagulants, proper timing, usage and dosage of administration that should be employed to assess treatment efficacy. The primary mechanisms of heparin are acting on heparan sulfate, histones, high mobility group box 1 and heparin-binding protein, which interfere with the regulation of inflammation, vascular permeability, coagulation, endothelial function and other biological activities. However, the underlying pathophysiological processes mediating the potential therapeutic effects of heparin in the context of sepsis remain incompletely understood and warrant additional rigorous investigation to establish the mechanism more conclusively.

Unfractionated Heparin Protects Microcirculation in Endotoxemic Rats by Antagonizing Histones

INTRODUCTION

Levels of extracellular histones are highly increased in sepsis and may facilitate microcirculatory dysfunction. Unfractionated heparin (UFH) binds histones and neutralizes their cytotoxicity. We investigated the effect of UFH on microcirculatory dysfunction by interacting with extracellular histones in endotoxemic rats.

METHODS

Twenty-four Wistar rats were randomly divided into three groups: control, lipopolysaccharide (LPS) group, and LPS + UFH group. In the LPS and LPS + UFH groups, 10 mg/kg LPS was injected to induce endotoxemia, and 100 IU/kg/h UFH was administered intravenously in the LPS + UFH group. The rats underwent midline laparotomy, and then intestinal microcirculation was evaluated using an incident dark field microscope. Circulating histones and microstructures of the rat intestinal microvascular endothelium were also detected. Additionally, the antagonistic effect of UFH on histone-induced cytotoxicity was investigated in human intestinal microvascular endothelial cells.

RESULTS

UFH protected the microcirculation of the intestinal serosa and mucosa in endotoxemic rats, as evidenced by increased total vessel density, perfused vessel density, and proportion of perfused vessels of both the serosa and mucosa, and increased microcirculatory flow index of the mucosa in the LPS + UFH group. UFH treatment decreased the levels of circulating histones and alleviated intestinal microvascular endothelial injuries in endotoxemic rats. Furthermore, UFH inhibited histone cytotoxicity in vitro.

CONCLUSIONS

UFH attenuated microcirculatory dysfunction in endotoxemic rats by antagonizing extracellular histones, thereby providing a potential therapeutic strategy for sepsis.