Systemic Administration of Carbon Monoxide-Releasing Molecule-3 Protects the Skeletal Muscle in Porcine Model of Compartment Syndrome

ACETYL-COA PRODUCTION BY OCTANOIC ACID ALLEVIATES ACUTE COMPARTMENT SYNDROME-INDUCED SKELETAL MUSCLE INJURY THROUGH REGULATING MITOPHAGY

ABSTRACT

Background: Treatment of acute compartment syndrome (ACS)-induced skeletal muscle injury remains a challenge. Previous studies have shown that octanoic acid is a promising treatment for ACS owing to its potential ability to regulate metabolic/epigenetic pathways in ischemic injury. The present study was designed to investigate the efficacy and underlying mechanism of octanoic acid in ACS-induced skeletal muscle injury. Methods: In this study, we established a saline infusion ACS rat model. Subsequently, we assessed the protective effects of sodium octanoate (NaO, sodium salt of octanoic acid) on ACS-induced skeletal muscle injury. Afterward, the level of acetyl-coenzyme A and histone acetylation in the skeletal muscle tissue were quantified. Moreover, we investigated the activation of the AMP-activated protein kinas pathway and the occurrence of mitophagy in the skeletal muscle tissue. Lastly, we scrutinized the expression of proteins associated with mitochondrial dynamics in the skeletal muscle tissue. Results: The administration of NaO attenuated muscle inflammation, alleviating oxidative stress and muscle edema. Moreover, NaO treatment enhanced muscle blood perfusion, leading to the inhibition of apoptosis-related skeletal muscle cell death after ACS. In addition, NaO demonstrated the ability to halt skeletal muscle fibrosis and enhance the functional recovery of muscle post-ACS. Further analysis indicates that NaO treatment increases the acetyl-CoA level in muscle and the process of histone acetylation by acetyl-CoA. Lastly, we found NaO treatment exerts a stimulatory impact on the activation of the AMPK pathway, thus promoting mitophagy and improving mitochondrial dynamics. Conclusion: Our findings indicate that octanoic acid may ameliorate skeletal muscle injury induced by ACS. Its protective effects may be attributed to the promotion of acetyl-CoA synthesis and histone acetylation within the muscular tissue, as well as its activation of the AMPK-related mitophagy pathway.

Establishment and pathophysiological evaluation of a novel model of acute compartment syndrome in rats

BACKGROUND

Researches have used intra-compartmental infusion and ballon tourniquest to create high intra-compartmental pressure in animal models of Acute Compartment Syndrome (ACS). However, due to the large differences in the modeling methods and the evaluation criteria of ACS, further researches of its pathophysiology and pathogenesis are hindered. Currently, there is no ideal animal model for ACS and this study aimed to establish a reproducible, clinically relevant animal model.

METHODS

Blunt trauma and fracture were caused by the free falling of weights (0.5 kg, 1 kg, 2 kg) from a height of 40 cm onto the lower legs of rats, and the application of pressures of 100 mmHg, 200 mmHg, 300 mmHg and 400 mmHg to the lower limbs of rats using a modified pressurizing device for 6 h. The intra-compartmental pressure (ICP) and the pressure change (ΔP) of rats with single and combined injury were continuously recorded, and the pathophysiology of the rats was assessed based on serum biochemistry, histological and hemodynamic changes.

RESULTS

The ΔP caused by single injury method of different weights falling onto the lower leg did not meet the diagnosis criteria for ACS (< 30 mmHg). On the other hand, a combined injury method of a falling weight of 1.0 kg and the use of a pressurizing device with pressure of 300 mmHg or 400 mmHg for 6 h resulted in the desired ACS diagnosis criteria with a ΔP value of less than 30 mmHg. The serum analytes, histological damage score, and fibrosis level of the combined injury group were significantly increased compared with control group, while the blood flow was significantly decreased compared with control group.

CONCLUSION

We successfully established a new preclinical ACS-like rat model, by the compression of the lower leg of rats with 300 mmHg pressure for 6 h and blunt trauma by 1.0 kg weight falling.

Animal models in compartment syndrome: a review of existing literature

Objective:

Extremity compartment syndrome (ECS) is a morbid condition resulting in permanent myoneural damage. Currently, the diagnosis of compartment syndrome relies on clinical symptoms and/or intracompartment pressure measurements, both of which are poor predictors of ECS. Animal models have been used to better define cellular mechanisms, diagnosis, and treatment of ECS. However, no standardized model exists. The purpose of this study was to identify existing animal research on extremity compartment syndrome to summarize the current state of the literature and to identify weaknesses that could be improved with additional research.

Methods:

A MEDLINE database search and reverse inclusion protocol were utilized. We included all animal models of ECS.

Results:

Forty-one studies were included. Dogs were the most commonly used model species, followed by pigs and rats. Most studies sought to better define the pathophysiology of compartment syndrome. Other studies evaluated experimental diagnostic modalities or potential treatments. The most common compartment syndrome model was intracompartment infusion, followed by tourniquet and intracompartment balloon models. Few models incorporated additional soft tissue or osseous injury. Only 65.9% of the reviewed studies confirmed that their model created myoneural injury similar to extremity compartment syndrome.

Conclusions:

Study purpose, methodology, and outcome measures varied widely across included studies. A standardized definition for animal compartment syndrome would direct more consistent research in this field. Few animal models have investigated the pathophysiologic relationship between traumatic injury and the development of compartment syndrome. A validated, clinically relevant animal model of extremity compartment syndrome would spur improvement in diagnosis and therapeutic interventions.

Proteinase 3 contributes to endothelial dysfunction in an experimental model of sepsis

In sepsis-induced inflammation, polymorphonuclear neutrophils (PMNs) contribute to vascular dysfunction. The serine proteases proteinase 3 (PR3) and human leukocyte elastase (HLE) are abundant in PMNs and are released upon degranulation. While HLE's role in inflammation-induced endothelial dysfunction is well studied, PR3's role is largely uninvestigated. We hypothesized that PR3, similarly to HLE, contributes to vascular barrier dysfunction in sepsis. Plasma PR3 and HLE concentrations and their leukocyte mRNA levels were measured by ELISA and qPCR, respectively, in sepsis patients and controls. Exogenous PR3 or HLE was applied to human umbilical vein endothelial cells (HUVECs) and HUVEC dysfunction was assessed by FITC-dextran permeability and electrical resistance. Both PR3 and HLE protein and mRNA levels were significantly increased in sepsis patients (P < 0.0001 and P < 0.05, respectively). Additionally, each enzyme independently increased HUVEC monolayer FITC-dextran permeability (P < 0.01), and decreased electrical resistance in a time- and dose-dependent manner (P < 0.001), an effect that could be ameliorated by novel treatment with carbon monoxide-releasing molecule 3 (CORM-3). The serine protease PR3, in addition to HLE, lead to vascular dysfunction and increased endothelial permeability, a hallmark pathological consequence of sepsis-induced inflammation. CORMs may offer a new strategy to reduce serine protease-induced vascular dysfunction.

In Vivo Imaging and Tracking Carbon Monoxide-Releasing Molecule-3 with an NIR Fluorescent Probe

As a water-soluble carbon monoxide-releasing molecule, CORM-3 is widely used as a CO donor to study CO in the life system. CORM-3 can also replace gaseous CO as a therapeutic drug molecule to reveal the physiological and pathological effects of CO in life. Therefore, it is of great importance to visualize and track CORM-3 in the life system. We develop herein a near-infrared (NIR) fluorescent probe CORM3-NIR that can detect CORM-3 both in living cells and in vivo effectively. The probe is based on the unique fluorescent QCy7 and uses a 4-nitrobenzyl group to trap CORM-3, and importantly, it shows good water solubility and responds rapidly, selectively, and sensitively to CORM-3, releasing QCy-7 and producing distinct colorimetric and significant NIR fluorescence change signals at 743 nm. The Stokes shift is up to 81 nm. The probe is also able to detect CORM-3 ratiometrically with fluorescence at 743 and 600 nm. Besides, with low cytotoxicity, the probe also shows good NIR fluorescence bioimaging ability for CORM-3 in live cells and mice, which indicates that CORM3-NIR is an effective probe for tracking and studying CORM-3 in the life system.

Therapeutic Potential of Heme Oxygenase-1 and Carbon Monoxide in Acute Organ Injury, Critical Illness, and Inflammatory Disorders

Heme oxygenase-1 (HO-1) is an inducible stress protein that catalyzes the oxidative conversion of heme to carbon monoxide (CO), iron, and biliverdin (BV), the latter of which is converted to bilirubin (BR) by biliverdin reductase. HO-1 has been implicated as a cytoprotectant in various models of acute organ injury and disease (i.e., lung, kidney, heart, liver). Thus, HO-1 may serve as a general therapeutic target in inflammatory diseases. HO-1 may function as a pleiotropic modulator of inflammatory signaling, via the removal of heme, and generation of its enzymatic degradation-products. Iron release from HO activity may exert pro-inflammatory effects unless sequestered, whereas BV/BR have well-established antioxidant properties. CO, derived from HO activity, has been identified as an endogenous mediator that can influence mitochondrial function and/or cellular signal transduction programs which culminate in the regulation of apoptosis, cellular proliferation, and inflammation. Much research has focused on the application of low concentration CO, whether administered in gaseous form by inhalation, or via the use of CO-releasing molecules (CORMs), for therapeutic benefit in disease. The development of novel CORMs for their translational potential remains an active area of investigation. Evidence has accumulated for therapeutic effects of both CO and CORMs in diseases associated with critical care, including acute lung injury/acute respiratory distress syndrome (ALI/ARDS), mechanical ventilation-induced lung injury, pneumonias, and sepsis. The therapeutic benefits of CO may extend to other diseases involving aberrant inflammatory processes such as transplant-associated ischemia/reperfusion injury and chronic graft rejection, and metabolic diseases. Current and planned clinical trials explore the therapeutic benefit of CO in ARDS and other lung diseases.

Protective effects of epigallocatechin gallate against ischemia reperfusion injury in rat skeletal muscle via activating Nrf2/HO-1 signaling pathway

AIMS

Previous studies have demonstrated that epigallocatechin gallate (EGCG) had certain protective effects on myocardial and renal ischemia reperfusion (I/R) injury. We aimed to research the special effects and underling mechanisms of EGCG on skeletal muscle I/R injury.

MAIN METHOD

We established an experimental rat model of I/R skeletal muscle injury and treated with different doses of EGCG. Hematoxylin eosin staining, TUNEL assay, ELISA, qRT-PCR and Western blotting were used to evaluate the effects of EGCG.

KEY FINDINDS

EGCG significantly improved skeletal muscle function of I/R injury rats. Moreover, EGCG had positive effects on decreasing apoptosis of skeletal muscle tissues, alleviating oxidative stress damage and suppressing the production of inflammatory cytokines. Further, EGCG had positive effects on activating Nrf2/HO-1 signaling pathway.

SIGNIFICANCE

EGCG might be a powerful candidate compound for alleviating I/R injury in rat skeletal muscle.

Carbon monoxide-releasing molecule-3 (CORM-3) offers protection in an in vitro model of compartment syndrome

OBJECTIVE

Limb compartment syndrome (CS), a complication of trauma, results in muscle necrosis and cell death; ischemia and inflammation contribute to microvascular dysfunction and parenchymal injury. Carbon monoxide-releasing molecule-3 (CORM-3) has been shown to protect microvascular perfusion and reduce inflammation in animal models of CS. The purpose of the study was to test the effect of CORM-3 in human in vitro CS model, allowing exploration of the mechanism(s) of CO protection and potential development of pharmacologic treatment.

METHODS

Confluent human vascular endothelial cells (HUVECs) were stimulated for 6 h with serum isolated from patients with CS. Intracellular oxidative stress (production of reactive oxygen species (ROS)) apoptosis, transendothelial resistance (TEER), polymorphonuclear leukocyte (PMN) activation and transmigration across the monolayer in response to the CS stimulus were assessed. All experiments were performed in the presence of CORM-3 (100 μM) or its inactive form, iCORM-3.

RESULTS

CS serum induced a significant increase in ROS, apoptosis and endothelial monolayer breakdown; it also increased PMN superoxide production, leukocyte rolling and adhesion/transmigration. CORM-3 completely prevented CS-induced ROS production, apoptosis, PMN adhesion, rolling and transmigration, while improving monolayer integrity.

CONCLUSION

CORM-3 offers potent anti-oxidant and anti-inflammatory effects, and may have a potential application to patients at risk of developing CS.