Lipid emulsion mitigates impaired pulmonary function induced by limb I/R in rats through attenuation of local cellular injury and the subsequent systemic inflammatory response/inflammation

Mechanisms and Interventions on Acute Lower Limb Ischemia/Reperfusion Injury: A Review and Insights from Cell to Clinical Investigations

AIM

This review aims to highlight mechanistic insights on skeletal muscle ischemia/reperfusion injury (IRI), a potentially life-threatening complication after acute lower limb ischemia. Lower limb IRI produces a wide spectrum of manifestations, ranging from local skeletal muscle necrosis to multi-organ failure. There is increasing evidence from both in vitro and in vivo reports to demonstrate several promising interventions that have successfully reduced IRI in skeletal muscle ischemic models. However, clinical studies to confirm their benefits are still lacking.

METHOD

We conducted a comprehensive search of English literature listed in the PubMed database (All related published articles shown in PubMed until September 2020 have been included in this review), using the following keywords: acute limb ischemia, acute arterial occlusion, compartment syndrome, ischemic reperfusion injury, revascularization and hypoxic reoxygenation.

RESULT

58 articles pertinent to acute limb ischemia models were identified. The underlying mechanisms associated with IRI in skeletal muscle are due to excessive mitochondrial production of reactive oxygen species (ROS), cellular apoptosis and activation of inflammatory cascades. Several therapeutic interventions including both pharmacological and non-pharmacological treatments have been investigated and some showed promising results. These interventions include antioxidation, anti-inflammation, anti-hypertension, controlled-reperfusion and ischemic preconditioning. Further clinical studies are needed to warrant their use in a clinical setting for lower limb IRI treatment.

CONCLUSION

This review comprehensively summarizes the mechanisms underlying IRI in lower limb ischemia. The reports currently available regarding the potential therapeutic interventions against lower limb IRI from in vitro, in vivo and clinical studies are presented and discussed. These findings may provide mechanistic insights for devising the strategies to improve the clinical outcomes in IRI patients in the near future. Further clinical studies are needed to warrant their use in a clinical setting for lower limb IRI treatment.

Lung injury after cardiopulmonary bypass: Alternative treatment prospects

Although the lung injury caused by cardiopulmonary bypass (CPB) has been extensively investigated, the incidence and mortality of lung injury after CPB remain a prominent clinical problem. The poor outcome has been attributed to multifactorial etiology, including the systemic inflammatory response and ischemia reperfusion (I/R) injury during CPB. Lung injury after CPB is a complex pathophysiological process and has many clinical manifestations of mild to severe disease. Which is associated with prognosis. To alleviate this lung injury, interventions that address the pathogenesis are particularly important. This review summarizes the pathogenesis, mechanism and treatment options of lung injury after CPB, such as lung protection with intralipid.

Apelin-13 protects the lungs from ischemia-reperfusion injury by attenuating inflammatory and oxidative stress

Apelin has been reported to regulate mitochondrial function in myocardial ischemia-reperfusion injury and cerebral ischemia-reperfusion injury. However, the role of apelin-13 in lung ischemia-reperfusion injury (LIRI) remains unclear. This study established an experimental rat model to evaluate the underlying mechanisms of apelin-13 on LIRI. Twenty-four rats were randomly divided to sham operation group (group SM), ischemia/reperfusion group (group IR), and apelin-13 treatment group (group APL). The effects of apelin-13 on LIRI were determined histologically using H&E staining, while the wet/dry weight ratio was used to assess lung edema caused by LIRI. Inflammatory cytokines were also detected in Bronchoalveolar lavage (BAL) fluid by ELISA. The protein expression of UCP2 and the morphological changes of mitochondria were determined by western blotting and electromicroscopy, respectively. The results demonstrated the structural damage of lung tissues and lung edema in group IR. An increased level of inflammatory cytokines including IL-1β, IL-6 and TNF-α was observed in rats with LIRI using ELISA. After that, oxidative stress and morphological damage of mitochondria were also shown in group IR. Yet, the application of apelin-13 reversed all these deleterious effects in group APL. The protective effects of apelin-13 were indicated by decreased reactive oxygen species (ROS) and elevated UCP2 expression levels in rats. In conclusion, this study revealed that apelin-13 had protective effects against LIRI via attenuating lung edema, the production of inflammatory cytokines, oxidative stress and mitochondrial dysfunction.

Fluid Therapy During Cardiopulmonary Resuscitation

Cardiopulmonary arrest (CPA), the acute cessation of blood flow and ventilation, is fatal if left untreated. Cardiopulmonary resuscitation (CPR) is targeted at restoring oxygen delivery to tissues to mitigate ischemic injury and to provide energy substrate to the tissues in order to achieve return of spontaneous circulation (ROSC). In addition to basic life support (BLS), targeted at replacing the mechanical aspects of circulation and ventilation, adjunctive advanced life support (ALS) interventions, such as intravenous fluid therapy, can improve the likelihood of ROSC depending on the specific characteristics of the patient. In hypovolemic patients with CPA, intravenous fluid boluses to improve preload and cardiac output are likely beneficial, and the use of hypertonic saline may confer additional neuroprotective effects. However, in euvolemic patients, isotonic or hypertonic crystalloid boluses may be detrimental due to decreased tissue blood flow caused by compromised tissue perfusion pressures. Synthetic colloids have not been shown to be beneficial in patients in CPA, and given their documented potential for harm, they are not recommended. Patients with documented electrolyte abnormalities such as hypokalemia or hyperkalemia benefit from therapy targeted at those disturbances, and patients with CPA induced by lipid soluble toxins may benefit from intravenous lipid emulsion therapy. Patients with prolonged CPA that have developed significant acidemia may benefit from intravenous buffer therapy, but patients with acute CPA may be harmed by buffers. In general, ALS fluid therapies should be used only if specific indications are present in the individual patient.

The effects of amantadine on lung tissue in lower limb ischemia/reperfusion injury model in rats

Background

This study aims to evaluate the effect of amantadine on lung tissue of after lower limb ischemia/reperfusion injury in rats.

Methods

A total of 24 Wistar rats were divided into four equal groups including six rats in each: sham group (Group S), amantadine group (Group A), ischemia/reperfusion group (Group I/R), and ischemia/reperfusion + amantadine group (Group I/R-A). All groups underwent a midline abdominal incision. In Groups I/R and I/R-A, the infrarenal abdominal aorta was clamped for 120 min and, then, reperfused for 120 min after removal of the clamp. Amantadine hydrochloride 45 mg/kg was administered intraperitoneally to the rats of Groups A and Group I/R-A 15 min before surgery. At the end of reperfusion period (240 min), all rats were sacrificed, and their lung tissues were obtained. Lung tissue catalase and superoxide dismutase activities and glutathione S-transferase and malondialdehyde levels were analyzed. Lung tissues were examined histopathologically.

Results

Catalase activity was lower in Groups A, I/R, and I/R-A compared to Group S. Superoxide dismutase activity was higher in Group I/R than Group S. Superoxide dismutase activity in Groups I/R-A and A decreased, compared to Groups S and I/R. Glutathione S-transferase levels decreased in Groups I/R and A, compared to Group S. Glutathione S-transferase levels in Group I/R-A were higher than Groups I/R and A. The highest level of malondialdehyde was found in Group I/R and the lowest level was found in Group I/R-A. According to histopathological examination, infiltration scores were significantly lower in Group S than Groups I/R and I/R-A (p=0.009 and p=0.011, respectively). The alveolar wall thickening scores in Group I/R were also significantly higher than Groups S and Group A (p=0.001 and p=0.001, respectively).

Conclusion

Lung tissue can be affected histopathologically by ischemia/ reperfusion injury and this injury can be reversed by amantadine administration.

Supplement of Lipid Emulsion to Epinephrine Improves Resuscitation Outcomes of Asphyxia-Induced Cardiac Arrest in Aged Rats

Objective

The goal of the study was to investigate the efficacy of lipid supplement to epinephrine-based therapy in resuscitation of asphyxia-induced cardiac arrest in aged rats.

Methods

The study included two parts: in experiment A, rats underwent asphyxial cardiac arrest and cardiopulmonary resuscitation, randomized to receive epinephrine and normal saline (control group, n=22), epinephrine and intralipid 20% (long-chain triglycerides (LCT) group, n=22) or epinephrine and lipovenoes 20% (LCT/medium-chain triglcerides (MCT) group, n=22). Return of spontaneous circulation, recurrence of asystole after resuscitation, hemodynamic metrics, arterial blood gas values, neurological assessment score and indexes of pulmonary transudation were recorded. In experiment B, rats using the same model and resuscitation protocol were randomly divided into 21 groups: Control ₀, Control ₂₀, Control ₄₀, Control ₆₀, Control ₈₀, Control ₁₀₀, Control ₁₂₀, LCT ₀, LCT ₂₀, LCT ₄₀, LCT ₆₀, LCT ₈₀, LCT ₁₀₀, LCT ₁₂₀, LCT/MCT ₀, LCT/MCT ₂₀, LCT/MCT ₄₀, LCT/MCT ₆₀, LCT/MCT ₈₀, LCT/MCT ₁₀₀ and LCT ₁₂₀ (n=10, the subscripts represent respective endpoint of observation in minutes). Myocardial bioenergetics were determined.

Results

In experiment A, the LCT and LCT/MCT groups had a shorter time to return of spontaneous circulation (ROSC) (P=0.001and P<0.001, respectively) and higher survival rate (P=0.033 and P=0.014, respectively) compared with the Control group. The LCT/MCT group had higher MAP (P<0.001 and P=0.001, respectively), HR (P<0.001 and P=0.004, respectively) and RPP (P<0.001 and P<0.001, respectively) compared with the Control and LCT groups, respectively. In experiment B, the LCT/MCT group had a higher energy charge compared with the control group at 20 (P<0.001) and 40 (P<0.001) minutes. The LCT group had higher energy charge compared with the Control group at 40 (P<0.001) and 60 (P<0.001) minutes.

Conclusion

The supplement of lipid emulsion to epinephrine improves resuscitation outcomes of asphyxia-induced cardiac arrest than epinephrine alone in our in vivo model of aged rat. LCT/MCT emulsion may be superior to LCT emulsion in epinephrine-based resuscitation.

Protective effects of HO-1 pathway on lung injury subsequent to limb ischemia reperfusion

Limb ischemia reperfusion (LIR) can activate endogenous cytoprotective mechanisms by generating specific proteins against reperfusion injury in remote organs. The present study investigated the roles of heme oxygenase-1 (HO-1) pathway and the molecular mechanisms underlying the regulation of this pathway on lung injury following LIR. LIR was induced by ischemia for 4 hours followed by reperfusion for 6 hours (LIR 6 hours) or 16 hours (LIR 16 hours) in male Sprague-Dawley rats. HO-1 inducer cobalt protoporphyrin (Copp) or HO-1 inhibitor zinc protoporphyrin (Znpp) was intravenously injected 24 hours before ischemia. The animals were randomly divided into nine groups, including normal control, LIR 6 hours, LIR 16 hours, Copp, Copp + LIR 6 hours, Copp + LIR 16 hours, and Znpp, Znpp+ LIR 6 hours, and Znpp + LIR 16 hours groups (each group included four samples). Lung injury was examined through histopathology. Quantitative real-time PCR, immunohistochemistry and Western blot were applied to detect the mRNA and protein levels of HO-1, Nrf2, and Bach1. Our study showed that LIR induced Nrf2 upregulation but Bach1 downregulation to promote HO-1 expression in lung tissues. Activation of HO-1 pathway by Copp potentially enhanced Nrf2 expression but inhibition of the pathway by Znpp promoted Bach1 expression. Inducer of HO-1 pathway, Copp injection improved the lung injury. Nevertheless, Znpp injection aggravated the lung injury following LIR. Our findings suggested that activated HO-1 pathway might exert protective effects on the lung injury following LIR.

Schizandrin A protects against cerebral ischemia-reperfusion injury by suppressing inflammation and oxidative stress and regulating the AMPK/Nrf2 pathway regulation

Inflammation and oxidative stress are considered major factors in the pathogenesis of ischemic stroke. Increasing evidence has demonstrated that Schizandrin A (Sch A), a lignin compound isolated from Schisandra chinesnesis, exhibits prominent anti-inflammatory and antioxidant activities. In this study, we investigated the anti-inflammatory and antioxidant effects of Sch A against cerebral ischemia/reperfusion (I/R) injury as well as the underlying molecular mechanisms. Sch A treatment significantly improved the neurological score and reduced infarct volume 24 h after reperfusion. It dose-dependently inhibited the expression of cyclooxygenase-2 and inducible nitric oxide synthase, reduced the release of pro-inflammatory cytokines (tumor necrosis factor-α interleukin [IL]-1β and IL-6), and increased anti-inflammatory cytokines (transforming growth factor-β and interleukin-10). Furthermore, it increased the activity of superoxide dismutase and catalase, decreased reactive oxygen species production and 4-hydroxynonenal and 8-hydroxy-2'-deoxyguanosine levels. Transcription of nuclear factor erythroid 2-related factor 2 (Nrf2) and downstream genes (heme oxygenase-1 and NAD[P]H: quinone oxidoreductase 1) increased. Knockdown of Nrf2 by siRNA inhibited the neuroprotective effects of Sch A. In addition, Sch A increased phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) both in vivo and in vitro. Activation of the Nrf2 pathway as well as the protective effects of Sch A in an oxygen and glucose deprivation-induced injury model was abolished by AMPK knockdown. Our study indicates that Sch A protects against cerebral I/R injury by suppressing inflammation and oxidative stress, and that this effect is regulated by the AMPK/Nrf2 pathway.

Effect of intralipid on myocardial injury during valve replacement surgery with concomitant radiofrequency ablation: A randomized controlled trial

BACKGROUND

This study aimed to evaluate the effect of intralipid postconditioning (ILPC) on myocardial damage in patients undergoing valve replacement surgery with concomitant radiofrequency ablation (RFA) for atrial fibrillation (AF).

METHODS

Randomized patient and assessor-blind controlled trial conducted in adult patients undergoing valve replacement surgery with concomitant RFA. Sixty-nine patients were randomly assigned to ILPC group (n = 34) or control group (n = 35): ILPC group received an intravenous infusion of 20% intralipid (2 mL/kg) just 10 minutes before aortic cross-unclamping, and control group received an equivalent volume of normal saline. Serum cardiac troponin-T (cTnT) and creatine kinase-MB (CK-MB) was measured before surgery and at 4, 12, 24, 48, and 72 hours after surgery. The primary endpoints were the 72-hour area under the curve (AUC) for cTnT and CK-MB.

RESULTS

The total 72-hour AUC of cTnT (P = .33) and CK-MB (P = .52) were comparable between 2 groups. The left ventricle ejection fraction at discharge (P = .011) was higher in the ILPC group than that in the control group, while the AF recurrence did not differ significantly between 2 groups.

CONCLUSIONS

There was no observed beneficial effect of ILPC on myocardial injury documented by the cardiac biomarkers in patients undergoing valve replacement surgery with concomitant RFA, and the effect of intralipid against myocardial I/R injury is undetectable within the background of massive biomarker release following ablation owing to localized myocardial necrosis. Besides, there are no other published data about the cardioprotective role of intralipid in patients undergoing this procedure and benefits of this protection need further studies to validate.