Acute Phase Of Ischemia-reperfusion Injury Research Articles

Preconditioning improves muscle regeneration after ischemia-reperfusion injury.

Ischemia-reperfusion injury (IRI) is a critical condition associated with serious clinical manifestations. Extensive research has focused on the strategies increasing organ tolerance to IRI. Preconditioning (PC) has been shown to provide protection to various organs toward IRI. However, the underlying mechanisms remain unknown. This study aimed to evaluate the role of PC on muscle regeneration after IRI and the potential underlying mechanisms. Three-month-old male UCP-1 reporter mice underwent unilateral hindlimb IRI with or without PC, the tissue viability and injury index were measured at 24 h after IRI. Hindlimb gait, muscle contractility, muscle histology were analyzed at 2 weeks after IRI. In another group of animals, β3 adrenergic receptor (β3AR) agonist amibegron and β3AR antagonist SR-59230A were administrated before PC/IRI, the hindlimb function and muscle regeneration were evaluated at 2 weeks after IRI. Our results showed that PC has little effect on improving the tissue viability at the acute phase of IRI, but it showed a long-term beneficial role of improving hindlimb function and muscle regeneration as evidenced by increased central nuclei regenerating myofibers. The effects of PC are related to inducing muscle fibro-adipogenic progenitor (FAP) brown/beige-like adipocyte (BAT) differentiation. Amibegron treatment displayed a similar role of PC while SR-59230A abolished the effect of PC. This study suggests PC has a beneficial role in promoting muscle regeneration after IRI through β3AR signaling pathway-stimulated FAP-BAT differentiation.

HIGH-MOBILITY GROUP BOX 1 PROTEIN ANTAGONIZES THE IMMUNOSUPPRESSIVE CAPACITY AND THERAPEUTIC EFFECT OF MESENCHYMAL STEM CELLS IN ACUTE KIDNEY INJURY

Purpose: Kidney ischemia reperfusion injury (IRI) is a common cause of acute kidney injury and an unavoidable consequence of kidney transplantation and still lacks specific therapeutics. In recent years, mesenchymal stem cell (MSC) emerges as a promising cell-based therapy. The reparative effects of MSC largely dependent on its unique immunosuppressive property, which is primed and regulated by the microenvironments. Methods: We employed mice kidney IRI model and MSC cell line to monitor the IRI related checkpoints. siRNAs were utilized to knock down the potential key factors for function. Statistical analysis was performed by using one-way ANOVA with Tukey’s post hoc procedure by SPSS. Results: The expression of high-mobility group box 1 protein (HMGB1) is increased not only in the acute phase of IRI, but also during the recovery stage, and the HMGB1 upregulation is correlated with the injury severity. We found that HMGB1 could diminish the immunosuppressive capacity of MSC in the presence of pro-inflammatory cytokines in vitro and in vivo. Toll like receptor 4 (TLR4)-mediated inducible nitric oxide synthase (iNOS) inhibition might contribute to the effect of HMGB1 on MSCs. Importantly, we further demonstrated that HMGB1 blocking strategies would augment the therapeutic efficacy of MSCs on renal IRI. Conclusions: These findings demonstrate that HMGB1 plays a crucial role in shaping the immunoregulatory property of MSCs within the microenvironments, providing novel insights into the crosstalk between MSCs and microenvironment components, suggesting HMGB1 signals as a promising target to improve MSC-based therapy.

Abstract 312: SGLT1 is Essential for Cardioprotection During Ischemia-Reperfusion Injury via Enhanced Glucose Utilization in Diet-induced Obese Mice

Recent large clinical trials have shown that sodium-glucose cotransporter 2 (SGLT2) inhibitors reduced cardiovascular events in diabetic patients. However, the regulation and functional role of cardiac SGLTs (SGLT1 is the dominant isoform) compared with those of other glucose transporters (insulin-dependent GLUT4 is the major isoform) remain incompletely understood. Given that glucose is a preferential substrate for myocardial metabolism during ischemia-reperfusion injury (IRI), we hypothesized that SGLT1 contributes to cardioprotection during IRI via enhanced glucose transport, particularly in insulin-resistant phenotypes. The hearts from mice fed a high-fat diet (HFD) for 12 weeks or a normal-fat diet (NFD) were perfused with either non-selective SGLT-inhibitor phlorizin (to inhibit SGLT1) or selective SGLT2-inhibitors (tofogliflozin, ipragliflozin, canagliflozin) during IRI using Langendorff model. After ischemia-reperfusion, HFD impaired left ventricular developed pressure (LVDP) recovery compared with NFD. Although phlorizin-perfusion impaired LVDP recovery in NFD, a further impaired LVDP recovery and dramatically increased infarct size (indicated by CPK release into perfusate and TTC staining) were observed in HFD with phlorizin-perfusion. Meanwhile, none of the SGLT2-inhibitors significantly affected cardiac function or myocardial injury after ischemia-reperfusion under either diet condition. The plasma membrane expression of GLUT4 was significantly increased after IRI in NFD but was substantially attenuated in HFD, the latter of which was associated with a significant reduction in both myocardial glucose uptake and cardiac tissue ATP content. In contrast, regardless of the diet condition, SGLT1 expression remained constant during IRI, whereas SGLT2 was not detected. Of note, phlorizin considerably reduced myocardial glucose uptake and decreased cardiac tissue ATP content after IRI, particularly in HFD. In conclusion, cardiac SGLT1 but not SGLT2 plays a compensatory protective role and contributes to cardiac energy metabolism during acute phase of IRI via enhanced glucose utilization, particularly under insulin-resistant conditions, in which IRI-induced GLUT4 upregulation is compromised.

Ischemic Duration and Frequency Determines AKI-to-CKD Progression Monitored by Dynamic Changes of Tubular Biomarkers in IRI Mice.

Ischemia reperfusion injury (IRI) is one of the most common causes of acute kidney injury (AKI). However, the pathogenesis and biomarkers predicting the progression of IRI-induced AKI to chronic kidney disease (CKD) remain unclear. A side-by-side comparison between different IRI animal models with variable ischemic duration and episodes was performed. The dynamic changes of KIM-1 and NGAL continuously from AKI to CKD phases were studied as well. Short-term duration of ischemia induced mild renal tubule-interstitial injury which was completely reversed at acute phase of kidney injury, while long-term duration of ischemia caused severe tubular damage, cell apoptosis and inflammatory infiltration at early disease stage, leading to permanent chronic kidney fibrosis at the late stage. Repeated attacks of moderate IRI accelerated the progression of AKI to CKD. Different from serum and urine levels of KIM-1 that increased at acute phase of IRI then declined gradually in chronic phase, NGAL increased continuously during AKI-to-CKD transition. Severity and frequency of ischemia injury determines the progression and outcome of ischemia-induced AKI. Inflammation, apoptosis and fibrogenesis likely participate in the progression of AKI to CKD. Both KIM-1 and NGAL enable noninvasive and early detection of AKI, but NGAL is associated better with the process of AKI-to-CKD progression.

Expression of SGLT1 in Human Hearts and Impairment of Cardiac Glucose Uptake by Phlorizin during Ischemia-Reperfusion Injury in Mice.

ObjectiveSodium-glucose cotransporter 1 (SGLT1) is thought to be expressed in the heart as the dominant isoform of cardiac SGLT, although more information is required to delineate the subtypes of SGLTs in human hearts. Moreover, the functional role of SGLTs in the heart remains to be fully elucidated. We herein investigated whether SGLT1 is expressed in human hearts and whether SGLTs significantly contribute to cardiac energy metabolism during ischemia-reperfusion injury (IRI) via enhanced glucose utilization in mice.Methods and ResultsWe determined that SGLT1 was highly expressed in both human autopsied hearts and murine perfused hearts, as assessed by immunostaining and immunoblotting with membrane fractionation. To test the functional significance of the substantial expression of SGLTs in the heart, we studied the effects of a non-selective SGLT inhibitor, phlorizin, on the baseline cardiac function and its response to ischemia-reperfusion using the murine Langendorff model. Although phlorizin perfusion did not affect baseline cardiac function, its administration during IRI significantly impaired the recovery in left ventricular contractions and rate pressure product, associated with an increased infarct size, as demonstrated by triphenyltetrazolium chloride staining and creatine phosphokinase activity released into the perfusate. The onset of ischemic contracture, which indicates the initiation of ATP depletion in myocardium, was earlier with phlorizin. Consistent with this finding, there was a significant decrease in the tissue ATP content associated with reductions in glucose uptake, as well as lactate output (indicating glycolytic flux), during ischemia-reperfusion in the phlorizin-perfused hearts.ConclusionsCardiac SGLTs, possibly SGLT1 in particular, appear to provide an important protective mechanism against IRI by replenishing ATP stores in ischemic cardiac tissues via enhancing availability of glucose. The present findings provide new insight into the significant role of SGLTs in optimizing cardiac energy metabolism, at least during the acute phase of IRI.

Systemic Inhibition of Angiopoietin-2 Prevents Endothelial Activation, and Acute Rejection in Rat Cardiac Allografts

Purpose Angiopoietin-2 (Ang2) is vascular growth factor promoting vascular instability and inflammation. In our previous study, heart-targeted Ang2-inhibition prevented ischemia-reperfusion injury (IRI). Ang2 production and release, however, continues after the acute phase of IRI, and activates endothelium to attract inflammatory cells. We investigated in allogeneic rat cardiac transplantation (Tx) model the effects of preop and postop systemic recipient treatment with anti-Ang2 antibody (Ab). Methods and Materials DA donor hearts were preserved in +4 °C PBS for 4h and then transplanted to fully MHC-mismatched WF recipient rats. The recipients received anti-Ang2 Ab or control-IgG i.p. 4h prior to the Tx and, in survival studies, consecutive doses on days 1, 3, and 5. We analyzed IRI-induced endothelial activation, myocardial damage and inflammation at 6h after the Tx. In survival experiments, the recipients received additional mild CyA (1mg/kg/d) and allograft survival was evaluated by daily palpation. Results The preop recipient anti-Ang2 Ab treatment reduced IRI-induced myocardial damage, microvascular VCAM1 and ICAM1 expression, and inflammatory cell influx at 6h after the Tx. Furthermore, when the anti-Ang2 Ab treatment was continued on days 1, 3, and 5 after the Tx, the allograft survival was significantly prolonged, while single preop treatment dose failed to prolong the survival. [ figure 1 ] Conclusions In conclusion, we show that systemic recipient treatment with anti-Ang2 Ab reduces endothelial activation, inflammatory cell influx, myocardial injury, and when continued after the Tx, prolongs allograft survival. These results suggest that Ang2 is important in IRI, but also in sustaining inflammation after IRI.

Evidence that estrogen receptors play a limited role in mediating enhanced recovery of bile flow in female rats in the acute phase of liver ischemia reperfusion injury

Introduction. Female patients exhibit better survival and less hepatic damage from ischemia reperfusion (IR) injury following surgery. However, the effects of sex and estrogens on liver function in the acute phase of IR are not well understood.Objective. The aim was to investigate this question.Material and methods. A rat model of segmental hepatic ischemia was employed. Rats were pre-treated with the estrogen receptor antagonist ICI182,780 and/or the estrogen receptor agonist 17β-estradiol. Bile flow, blood concentrations of bilirubin and liver enzymes were measured, and liver histology was assessed.Results. Bile flow recovery immediately after the initiation of reperfusion was faster in females than in males. ICI182,780 reduced the rate of bile flow recovery in females but this reduction was not reversed by co-administration of 17 β-estradiol. In males, 17 β-estradiol alone did not enhance bile flow recovery. The changes in bile flow recovery observed under a given condition were correlated with small changes in blood liver enzymes and liver histology.Conclusions. Sex has a significant influence on the early recovery of liver function in the acute phase of IR injury. However, in female rats estrogen receptors play only a limited role in mediating enhanced recovery of liver function.

Rapamycin Induces Heme Oxygenase-1 in Liver but Inhibits Bile Flow Recovery after Ischemia

Rapamycin, which is employed in the management of patients undergoing liver surgery, induces the synthesis of heme oxygenase-1 (HO-1) in some non-liver cell types. The aim was to investigate whether rapamycin can induce HO-1 expression in the liver, and to test the effects of rapamycin on liver function in the early phase of ischemia reperfusion (IR) injury. Isolated rat hepatocytes and a rat model of segmental hepatic ischemia and reperfusion were employed. Bile flow was measured gravimetrically or by using indocyanine green. mRNA and protein (by quantitative PCR and Western blot, respectively) and blood concentrations of rapamycin, bilirubin, and liver marker enzymes were measured. In isolated hepatocytes, rapamycin induced a 6-fold increase in HO-1, comparable to that induced by cobalt proporphyrin (CoPP), and a 2-fold increase in peroxiredoxin-1. Pretreatment of rats with rapamycin resulted in a small increase in liver HO-1 expression, a 20% inhibition of the basal rate of bile flow, and a 50% inhibition in the rate of bile flow recovery after ischemia. CoPP increased basal bile flow by 20% and inhibited bile flow recovery by 50%. These effects were associated with small increases in the blood concentrations of bilirubin and liver marker enzymes. Rapamycin, through HO-1 induction, has the potential to protect the liver against damage in the late phase of IR. The inhibition by rapamycin of bile flow indicates that its actions on liver function in the acute phase of IR injury are complex.

Effects of Ischemia-Reperfusion Injury on Apolipoprotein M Expression in the Liver

The present study investigated the expression pattern of apolipoprotein M (apoM) mRNA in a rat model of hepatic ischemia-reperfusion injury (IRI). Animals were ischemic for 1 hour followed by various reperfusion times. As expected, serum alanine aminotransferase levels were significantly increased under IRI, which indicated the severity of liver injury. Hepatic mRNA levels of HSP70, which is the most common characterized protein within the family of heat-shock proteins (HSP), were significantly increased after 0.5 to 3 hours of IRI. Plasma C-reactive protein, high-density lipoprotein-cholesterol, and lipoprotein (a) levels were significantly increased after 1-hour ischemia followed by 0.5 to 3 hours of reperfusion. Interestingly, similar to HSP70, apoM mRNA levels in the liver were gradually increased after 0.5 to 3 hours of IRI, whereas it returned to a lower level after 6 or 24 hours of IRI, which indicated that hepatic apoM expression was significantly influenced by the acute phase of IRI. However, plasma apoM levels were not increased in parallel, even slightly decreasing after 0.5 or 1 hour of IRI. We concluded that apoM mRNA expression pattern, like HSP70, in the liver showed rapid, significant changes during hepatic local IRI.