Low-Dose Sodium Nitrite Fluid Resuscitation Prevents Lethality From Crush Syndrome by Improving Nitric Oxide Consumption and Preventing Myoglobin Cytotoxicity in Kidney in A Rat Model

BREAKING NEW GROUND: STANDARDIZING RAT MODELS FOR CRUSH SYNDROME INVESTIGATIONS

ABSTRACT

Crush syndrome (CS), alternatively termed traumatic rhabdomyolysis, is a paramount posttraumatic complication. Given the infeasibility of conducting direct simulation research in humans, the role of animal models is pivotal. Regrettably, the dearth of standardized animal models persists. The objective of this study was to construct a repeatable standardized rat CS models and, based on this, simulate specific clinical scenarios. Methods: Using a self-developed multichannel intelligent small-animal crush injury platform, we applied a force of 5 kg to the hind limbs of 8-week-old rats (280-300 g), subjecting them to a continuous 12 h compression to establish the CS model. Continuous monitoring was conducted for both the lower limbs and the overall body status. After decompression, biochemical samples were collected at 3, 6, 12, and 24 h. In addition, we created a CS model after resection of the left kidney (UNx-CS), which was conceptualized to simulate a more challenging clinical scenario to investigate the physiological and pathological responses rats with renal insufficiency combined with crush injury. The results were compared with those of the normal CS model group. Results : Our experiments confirm the stability of the crush injury platform. We defined the standardized conditions for modeling and successfully established rats CS model in bulk. After 12 h of compression, only 40% of the rats in the CS group survived for 24 h. Systemically, there was clear evidence of insufficient perfusion, reflecting the progression of CS from localized to generalized. The injured limbs displayed swelling, localized perfusion deficits, and severe pathological alterations. Significant changes were observed in blood biochemical markers: aspartate transaminase, lactate dehydrogenase, K+, creatine kinase, creatinine, and blood urea nitrogen levels rose rapidly after decompression and were significantly higher than the sham group. The kidney demonstrated characteristic pathological changes consistent with established CS diagnostic criteria. Although the UNx-CS rat model did not exhibit significant biochemical differences and pathological scores when compared with the standard CS model, it did yield intriguing results with regard to kidney morphology. The UNx-CS group manifested a higher incidence of cortical and medullary protein casts compared with the NC-CS group. Conclusion: We developed and iteratively refined a novel digital platform, addressing the multiple uncontrollable variables that plagued prior models. This study validated the stability of the platform, defined the standardized conditions for modeling and successfully established the CS model with good repeatability in bulk. In addition, our innovative approach to model a clinically challenging scenario, the UNx-CS rat model. This offers an opportunity to delve deeper into understanding the combined effects of preexisting renal compromise and traumatic injury. In summary, the development of a standardized, reproducible CS model in rats represents a significant milestone in the study of Crush syndrome. This study is of paramount significance as it advances the standardization of the CS model, laying a solid foundation for subsequent studies in related domains, especially in CS-AKI.

Ferroptosis in acute kidney injury following crush syndrome: A novel target for treatment

BACKGROUND

Crush syndrome (CS) is a kind of traumatic and ischemic injury that seriously threatens life after prolonged compression. It is characterized by systemic inflammatory reaction, myoglobinuria, hyperkalemia and acute kidney injury (AKI). Especially AKI, it is the leading cause of death from CS. There are various cell death forms in AKI, among which ferroptosis is a typical form of cell death. However, the role of ferroptosis has not been fully revealed in CS-AKI.

AIM OF REVIEW

This review aimed to summarize the evidence of ferroptosis in CS-AKI and its related molecular mechanism, discuss the therapeutic significance of ferroptosis in CS-AKI, and open up new ideas for the treatment of CS-AKI.

KEY SCIENTIFIC CONCEPTS OF REVIEW

One of the main pathological manifestations of CS-AKI is renal tubular epithelial cell dysfunction and cell death, which has been attributed to massive deposition of myoglobin. Large amounts of myoglobin released from damaged muscle deposited in the renal tubules, impeding the normal renal tubules function and directly damaging the tubules with oxidative stress and elevated iron levels. Lipid peroxidation damage and iron overload are the distinguishing features of ferroptosis. Moreover, high levels of pro-inflammatory cytokines and damage-associated molecule pattern molecules (HMGB1, double-strand DNA, and macrophage extracellular trap) in renal tissue have been shown to promote ferroptosis. However, how ferroptosis occurs in CS-AKI and whether it can be a therapeutic target remains unclear. In our current work, we systematically reviewed the occurrence and underlying mechanism of ferroptosis in CS-AKI.

Crush syndrome: a review for prehospital providers and emergency clinicians

INTRODUCTION

Disasters and accidents have occurred with increasing frequency in recent years. Primary disasters have the potential to result in mass casualty events involving crush syndrome (CS) and other serious injuries. Prehospital providers and emergency clinicians stand on the front lines of these patients' evaluation and treatment. However, the bulk of our current knowledge, derived from historical data, has remained unchanged for over ten years. In addition, no evidence-based treatment has been established to date.

OBJECTIVE

This narrative review aims to provide a focused overview of, and update on, CS for both prehospital providers and emergency clinicians.

DISCUSSION

CS is a severe systemic manifestation of trauma and ischemia involving soft tissue, principally skeletal muscle, due to prolonged crushing of tissues. Among earthquake survivors, the reported incidence of CS is 2-15%, and mortality is reported to be up to 48%. Patients with CS can develop cardiac failure, kidney dysfunction, shock, systemic inflammation, and sepsis. In addition, late presentations include life-threatening systemic effects such as hypovolemic shock, hyperkalemia, metabolic acidosis, and disseminated intravascular coagulation. Immediately beginning treatment is the single most important factor in reducing the mortality of disaster-situation CS. In order to reduce complications from CS, early, aggressive resuscitation is recommended in prehospital settings, ideally even before extrication. However, in large-scale natural disasters, it is difficult to diagnose CS, and to reach and start treatments such as continuous administration of massive amounts of fluid, diuresis, and hemodialysis, on time. This may lead to delayed diagnosis of, and high on-site mortality from, CS. To overcome these challenges, new diagnostic and therapeutic modalities in the CS animal model have recently been advanced.

CONCLUSIONS

Patient outcomes can be optimized by ensuring that prehospital providers and emergency clinicians maintain a comprehensive understanding of CS. The field is poised to undergo significant advances in coming years, given recent developments in what is considered possible both technologically and surgically; this only serves to further emphasize the importance of the field, and the need for ongoing research.

Systemic Review of Animal Models Used in the Study of Crush Syndrome

ABSTRACT

Crush syndrome (CS), also known as traumatic rhabdomyolysis, is the leading cause of death following extrication from structural collapse due to earthquakes. Due to the unfeasibility of human studies, animal models are used to study crush syndrome pathophysiology, including biochemistry and treatment regimes. The aim of this systematic literature review was to identify the differences and benefits of various animal models used in the study of CS and provide valuable information for design of future research. A systematic search was conducted in two methods: with the filters "(crush syndrome) AND (crush muscle injury)" and with the keywords "(crush syndrome) AND (animal model)" covering all articles in the PubMed databases. The search generated 378 articles. After screening abstracts, 91 articles were retrieved and read, then 11 repeated articles were removed and 2 reference papers were included. We finally reviewed 82 original articles. There appear to be two primary methods employed for inducing crush syndrome in animal models, which are chemically induced injury and physically induced injury. Chemical method mainly includes intramuscular (IM) injection of tissue extract solution and IM injection of 50% glycerine. Physical method can be classified into invasive and non-invasive physical compression by elasticated material, inflatable band and heavy load. Various species of animals have been used to study CS, including mice (13.4%), rats (68.3%), rabbits (11.0%), canines (4.9%), goats (1.2%), and pigs (1.2%). Small animals are suitable for researches exploring the mechanism of disease or drug efficacy while large animals can work better with clinical application-related researches. In regard to the choice of modeling method, compressing the certain muscle of animals by heavy things is superior to others to cause systemic trauma-related rhabdomyolysis signs. In addition, due to the significant burden of crush injuries on animals, further attention shall be paid to the selection of the most suitable anesthetics and appropriate analgesics.

On-Site Laser Photobiomodulation Treatment of Crushed Muscle Due to Prolonged Pressure in Rats

BACKGROUND AND OBJECTIVES

Crush injuries and prolonged pressure on muscles lead to bruises and sprains and, in most of the cases, cause distraction of the muscle and release of particles into the blood stream, causing renal and systemic complications in severe cases. Laser photobiomodulation treatment (i.e., laser phototherapy) is a method suggested to decrease the pressure damage in the first 24-48 hours after muscle injury, allowing a faster and more complete physical rehabilitation. We studied the efficacy of non-invasive laser photobiomodulation treatment as an on-site treatment for crush-injured gastrocnemius muscles, developing a moderate muscle crush injury model and aiming at decreasing damage extent while regaining physical competence faster.

STUDY DESIGN/MATERIALS AND METHODS

Muscle crush injury was performed on 30 female Wistar rats using direct pressure for 10 minutes on the gastrocnemius muscle in both left and right hindlimbs. Immediately after the injury, only the left hindlimb were irradiated for 16 minutes (with 780 nm laser with a power of 250 mW, the energy at the target was 240 J, and the fluence was 1019 J/cm² ) for 1, 3, or 7 consecutive days, and sacrificed accordingly. During the follow-up period, 1, 3, or 7 days, both gastrocnemius muscles (of the treated and untreated hindlimbs) were evaluated for electrophysiology and functionality.

RESULTS

The laser photobiomodulation treatment showed a significant electrophysiological and functional recovery of the gastrocnemius muscle during the first 3 days after injury, in comparison with the untreated hindlimb.

CONCLUSIONS

These preliminary results are promising, showing a significant effect of the laser photobiomodulation treatment during the first 3 days after the induction of the muscle crush injury, which is the most critical period in the clinical aspect. These findings suggest a therapeutic approach, which may help restore the muscle after crush injury.

Emerging medical therapies in crush syndrome - progress report from basic sciences and potential future avenues

Crush injury is a disease that is commonly found in victims of earthquakes, debris flows, mine disasters, explosions, terrorist attacks, local wars, and other accidents. The complications that arise due to the crush injury inflicted on victims give rise to crush syndrome (CS). If not treated in time, the mortality rate of CS is very high. The most important measure that can be taken to reduce mortality in such situations is to immediately start treatment. However, the traditional treatment methods such as fluid resuscitation, diuresis, and hemodialysis are not feasible enough to be carried out at the disaster scene. So there is a need for developing new treatments that are efficient and convenient. Because it is difficult to diagnose in the disaster area and reach the treatment equipment and treat on time. It has become a new research needs to be directed into identifying new medical treatment targets and methods using the etiology and pathophysiological mechanisms of CS. In recent years, a large number of new anti-oxidant and anti-inflammatory drug therapies have been shown to be highly efficacious in CS rat/mouse models. Some of them are expected to become specific drugs for the emergency treatment of a large number of patients who may develop CS in the aftermath of earthquakes, wars, and other disasters in the future. Hence, we have reviewed the latest research on the medical therapy of CS as a source for anyone wishing to pursue research in this direction.

H2S- and NO-releasing gasotransmitter platform: A crosstalk signaling pathway in the treatment of acute kidney injury

Acute kidney injury (AKI) is a syndrome affecting most patients hospitalized due to kidney disease; it accounts for 15 % of patients hospitalized in intensive care units worldwide. AKI is mainly caused by ischemia and reperfusion (IR) injury, which temporarily obstructs the blood flow, increases inflammation processes and induces oxidative stress. AKI treatments available nowadays present notable disadvantages, mostly for patients with other comorbidities. Thus, it is important to investigate different approaches to help minimizing side effects such as the ones observed in patients subjected to the aforementioned treatments. Therefore, the aim of the current review is to highlight the potential of two endogenous gasotransmitters - hydrogen sulfide (H₂S) and nitric oxide (NO) - and their crosstalk in AKI treatment. Both H₂S and NO are endogenous signalling molecules involved in several physiological and pathophysiological processes, such as the ones taking place in the renal system. Overall, these molecules act by decreasing inflammation, controlling reactive oxygen species (ROS) concentrations, activating/inactivating pro-inflammatory cytokines, as well as promoting vasodilation and decreasing apoptosis, hypertrophy and autophagy. Since these gasotransmitters are found in gaseous state at environmental conditions, they can be directly applied by inhalation, or in combination with H₂S and NO donors, which are compounds capable of releasing these molecules at biological conditions, thus enabling higher stability and slow release of NO and H₂S. Moreover, the combination between these donor compounds and nanomaterials has the potential to enable targeted treatments, reduce side effects and increase the potential of H₂S and NO. Finally, it is essential highlighting challenges to, and perspectives in, pharmacological applications of H₂S and NO to treat AKI, mainly in combination with nanoparticulated delivery platforms.

Regional hypothermia attenuates secondary-injury caused by time-out application of tourniquets following limb fragments injury combined with hemorrhagic shock

Background

Tourniquet is the most widely used and effective first-aid equipment for controlling hemorrhage of injured limb in battlefield. However, time-out application of tourniquets leads to ischemic-necrosis of skeletal muscles and ischemia-reperfusion injury. Regional hypothermia (RH) on wounded limb can relieve the injury on local tissue and distant organs. We aimed to investigate the protective effects of RH on rabbits’ limbs injured by a steel-ball combined with hemorrhagic-shock, and then employed tourniquet over-time, tried to identify the optimal treatment RH.

Methods

Thirty rabbits were randomly divided into 5 groups. All rabbits were anesthetized, intubated femoral artery and vein in right-hind limbs. Sham operation group (Sham): only femoral arteriovenous cannula in right-hind limb. None RH group (NRH): rabbits were intubated as Sham group, then the soft tissues of rabbits’ left-hinds were injured by a steel-ball shooting, and were exsanguinated until shock, then bundled with rubber tourniquets for 4 h. Three RH subgroups: rabbits were injured as mentioned above, the injured limbs were bundled with rubber tourniquets and treated with different temperature (5 ± 1 °C, 10 ± 1 °C, and 20 ± 1 °C, respectively) for 4 h. The injury severity of lung and regional muscle was assessed by histologic examination. Activity of adenosine triphosphatase (ATPase) and content of malondialdehyde (MDA) in muscle, inflammatory cytokines, myoglobin, creatine kinase-MM (CK-MM), Heme, Heme oxygenase 1 (HO-1), lactic acid (Lac), and lectrolyte ion in serum were detected.

Results

Following with RH treatment, the injury of lung and local muscle tissue was alleviated evidencing by mitigation of histopathological changes, significant decrease of water-content and MDA content, and increase of ATPase activity. Lower level of Lac, Potassium (K⁺), inflammatory cytokines, Heme, CK-MM, myoglobin content, and higher level of Calcium (Ca²⁺), HO-1 content were shown in RH treatment. 10 °C was the most effective RH to increase ATPase activity, and decrease MDA, myoglobin, CK-MM content.

Conclusion

Transient RH (4 h) had a “long-term mitigation effects” (continued for 6 h) on time-out application of tourniquet with the fluid resuscitation and core temperature maintenance, and the most effective temperature for reducing the side effects on tourniquet time-out application was 10 °C.

Nitrite as a pharmacological intervention for the successful treatment of crush syndrome

Crush syndrome is characterized by ischemia/reperfusion injury (IRI). The protective effect of nitrite on experimentally induced IRI has been demonstrated in the heart, kidney, liver, and skeletal muscle. IRI in tissues and systemic organs occurs due to the massive generation of reactive oxygen species and subsequent systemic inflammation. Therefore, ischemic pre and postconditioning are performed in clinical practice. Intravenous administration of nitrite inhibits IRI through nitric oxide-mediated mechanisms. In this paper, we discuss the utility of nitrite as a pharmacological postconditioning agent in the treatment of crush syndrome.

A novel method to assess the severity and prognosis in crush syndrome by assessment of skin damage in hairless rats

PURPOSE

Crush syndrome (CS), a serious medical condition characterised by damage to the muscle cells due to pressure, is associated with high mortality, even when patients receive fluid therapy during transit to the hospital or admission to the hospital. There is no standard triage approach for earthquake victims with crush injuries due to the scarcity of epidemiologic and quantitative data. We examined whether mortality can be predicted based on the severity of skin damage so that assess the severity and prognosis in crush syndrome by assessment of skin damage in hairless rats because we have previously observed that CS results in oedema and redness of the skin in rats.

METHODS

Anaesthetised rats were subjected to bilateral hind limb compression [1 kg (mild) and 2 kg (severe) loads] with a rubber tourniquet for 5 h. The rats were then randomly divided into three groups: sham, mild CS, and severe CS.

RESULTS

The mild and severe CS groups had mortality rates of 20 and 90%, respectively. The severe CS group demonstrated higher rates of hyperkalaemia, hypovolemic shock, acidosis, and inflammation. Skin damage was significantly worse in the severe CS group compared to the mild CS group. Skin damage showed good correlation with pathological severity.

CONCLUSIONS

Skin damage is a valid measure of transepidermal water loss and severity of CS. We suggest that these models may be useful to professionals who are not experienced in disaster management to identify earthquake victims at high risk of severe CS.

Low dose nitrite improves reoxygenation following renal ischemia in rats

In hypoxic and acidic tissue environments, nitrite is metabolised to nitric oxide, thus, bringing about novel therapeutic options in myocardial infarction, peripheral artery disease, stroke, and hypertension. Following renal ischemia, reperfusion of the kidney remains incomplete and tissue oxygenation is reduced for several minutes to hours. Thus, in renal ischemia-reperfusion injury, providing nitrite may have outstanding therapeutic value. Here we demonstrate nitrite's distinct potential to rapidly restore tissue oxygenation in the renal cortex and medulla after 45 minutes of complete unilateral kidney ischemia in the rat. Notably, tissue oxygenation was completely restored, while tissue perfusion did not fully reach pre-ischemia levels within 60 minutes of reperfusion. Nitrite was infused intravenously in a dose, which can be translated to the human. Specifically, methaemoglobin did not exceed 3%, which is biologically negligible. Hypotension was not observed. Providing nitrite well before ischemia and maintaining nitrite infusion throughout the reperfusion period prevented the increase in serum creatinine by ischemia reperfusion injury. In conclusion, low-dose nitrite restores renal tissue oxygenation in renal ischemia reperfusion injury and enhances regional kidney post-ischemic perfusion. As nitrite provides nitric oxide predominantly in hypoxic tissues, it may prove a specific measure to reduce renal ischemia reperfusion injury.

Astragaloside-IV prevents acute kidney injury and inflammation by normalizing muscular mitochondrial function associated with a nitric oxide protective mechanism in crush syndrome rats

Background

Crush syndrome (CS) is a serious medical condition characterized by muscle cell damage resulting from decompression after compression (i.e., ischemia/reperfusion injury). A large number of CS patients develop cardiac failure, kidney dysfunction, and systemic inflammation, even when fluid therapy is administered. We evaluated whether the administration of astragaloside-IV (AS)-containing fluid improved survival by preventing kidney and muscular mitochondrial dysfunction in a rat model of CS.

Results

The CS model was generated by subjecting anesthetized rats to bilateral hind limb compression with a rubber tourniquet for 5 h. Rats were then randomly divided into four groups: (1) sham; (2) CS with no treatment; (3) CS with normal saline treatment; and (4) CS with normal saline + 10 mg/kg AS. AS-containing fluid improved kidney function by improving shock and metabolic acidosis in CS rats. In addition, there was a reduction in oxidative damage. The attenuation of hyperkalemia was significantly related to improving muscle injury via preventing mitochondrial dysfunction. Moreover, this mitochondria protection mechanism was related to the nitric oxide (NO) generated by activation of endothelial nitric oxide synthase, which provided an anti-oxidative and anti-inflammatory effect.

Conclusions

Treatment with AS-containing fluid led to a dramatic improvement in survival following CS because of direct and indirect anti-oxidative effects in the kidney, and improvements in mitochondrial dysfunction and inflammation owing to AS acting as an NO donor in injured muscle.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-017-0313-2) contains supplementary material, which is available to authorized users.