Injury/ischemia-induced stem cells: up-to-date knowledge and future perspectives for neural regeneration

Brain injuries like ischemic stroke induce endogenous stem cell production. Although the precise traits of stem cells in pathological brains remain unclear, we previously demonstrated that injury/ischemia-induced stem cells(iSCs)are present in the post-stroke mouse(Nakagomi et al.,2009)and human brains(Beppu et al.,2019).

Endoplasmic reticulum stress and autophagy in cerebral ischemia/reperfusion injury:PERK as a potential target for intervention

Several studies have shown that activation of unfolded protein response and endoplasmic reticulum(ER)stress plays a crucial role in severe cerebral ischemia/reperfusion injury.Autophagy occurs within hours after cerebral ischemia,but the relationship between ER stress and autophagy remains unclear.In this study,we established experimental models using oxygen-glucose deprivation/reoxygenation in PC12 cells and primary neurons to simulate cerebral ischemia/reperfusion injury.We found that prolongation of oxygen-glucose deprivation activated the ER stress pathway protein kinase-like endoplasmic reticulum kinase(PERK)/eukaryotic translation initiation factor 2 subunit alpha(e IF2α)-activating transcription factor 4(ATF4)-C/EBP homologous protein(CHOP),increased neuronal apoptosis,and induced autophagy.Furthermore,inhibition of ER stress using inhibitors or by si RNA knockdown of the PERK gene significantly attenuated excessive autophagy and neuronal apoptosis,indicating an interaction between autophagy and ER stress and suggesting PERK as an essential target for regulating autophagy.Blocking autophagy with chloroquine exacerbated ER stress-induced apoptosis,indicating that normal levels of autophagy play a protective role in neuronal injury following cerebral ischemia/reperfusion injury.Findings from this study indicate that cerebral ischemia/reperfusion injury can trigger neuronal ER stress and promote autophagy,and suggest that PERK is a possible target for inhibiting excessive autophagy in cerebral ischemia/reperfusion injury.

A matrix metalloproteinase-responsive hydrogel system controls angiogenic peptide release for repair of cerebral ischemia/reperfusion injury

Vascular endothelial growth factor and its mimic peptide KLTWQELYQLKYKGI(QK)are widely used as the most potent angiogenic factors for the treatment of multiple ischemic diseases.However,conventional topical drug delivery often results in a burst release of the drug,leading to transient retention(inefficacy)and undesirable diffusion(toxicity)in vivo.Therefore,a drug delivery system that responds to changes in the microenvironment of tissue regeneration and controls vascular endothelial growth factor release is crucial to improve the treatment of ischemic stroke.Matrix metalloproteinase-2(MMP-2)is gradually upregulated after cerebral ischemia.Herein,vascular endothelial growth factor mimic peptide QK was self-assembled with MMP-2-cleaved peptide PLGLAG(TIMP)and customizable peptide amphiphilic(PA)molecules to construct nanofiber hydrogel PA-TIMP-QK.PA-TIMP-QK was found to control the delivery of QK by MMP-2 upregulation after cerebral ischemia/reperfusion and had a similar biological activity with vascular endothelial growth factor in vitro.The results indicated that PA-TIMP-QK promoted neuronal survival,restored local blood circulation,reduced blood-brain barrier permeability,and restored motor function.These findings suggest that the self-assembling nanofiber hydrogel PA-TIMP-QK may provide an intelligent drug delivery system that responds to the microenvironment and promotes regeneration and repair after cerebral ischemia/reperfusion injury.

Role of nitric oxide in cerebral ischemia/reperfusion injury:A biomolecular overview

Nitric oxide(NO)is a gaseous molecule produced by 3 different NO synthase(NOS)isoforms:Neural/brain NOS(nNOS/bNOS,type 1),endothelial NOS(eNOS,type 3)and inducible NOS(type 2).Type 1 and 3 NOS are constitutively expressed.NO can serve different purposes:As a vasoactive molecule,as a neurotransmitter or as an immunomodulator.It plays a key role in cerebral ischemia/reperfusion injury(CIRI).Hypoxic episodes simulate the production of oxygen free radicals,leading to mitochondrial and phospholipid damage.Upon reperfusion,increased levels of oxygen trigger oxide synthases;whose products are associated with neuronal damage by promoting lipid peroxidation,nitrosylation and excitotoxicity.Molecular pathways in CIRI can be altered by NOS.Neuroprotective effects are observed with eNOS activity.While nNOS interplay is prone to endothelial inflammation,oxidative stress and apoptosis.Therefore,nNOS appears to be detrimental.The interaction between NO and other free radicals develops peroxynitrite;which is a cytotoxic agent.It plays a main role in the likelihood of hemorrhagic events by tissue plasminogen activator(t-PA).Peroxynitrite scavengers are currently being studied as potential targets to prevent hemorrhagic transformation in CIRI.

Treatment with β-sitosterol ameliorates the effects of cerebral ischemia/reperfusion injury by suppressing cholesterol overload, endoplasmic reticulum stress, and apoptosis

β-Sitosterol is a type of phytosterol that occurs naturally in plants.Previous studies have shown that it has anti-oxidant,anti-hyperlipidemic,anti-inflammatory,immunomodulatory,and anti-tumor effects,but it is unknown whetherβ-sitosterol treatment reduces the effects of ischemic stroke.Here we found that,in a mouse model of ischemic stroke induced by middle cerebral artery occlusion,β-sitosterol reduced the volume of cerebral infarction and brain edema,reduced neuronal apoptosis in brain tissue,and alleviated neurological dysfunction;moreover,β-sitosterol increased the activity of oxygen-and glucose-deprived cerebral cortex neurons and reduced apoptosis.Further investigation showed that the neuroprotective effects ofβ-sitosterol may be related to inhibition of endoplasmic reticulum stress caused by intracellular cholesterol accumulation after ischemic stroke.In addition,β-sitosterol showed high affinity for NPC1L1,a key transporter of cholesterol,and antagonized its activity.In conclusion,β-sitosterol may help treat ischemic stroke by inhibiting neuronal intracellular cholesterol overload/endoplasmic reticulum stress/apoptosis signaling pathways.

The action mechanism by which C1q/tumor necrosis factor-related protein-6 alleviates cerebral ischemia/reperfusion injury in diabetic mice

Studies have shown that C1q/tumor necrosis factor-related protein-6 (CTRP6) can alleviate renal ischemia/reperfusion injury in mice. However, its role in the brain remains poorly understood. To investigate the role of CTRP6 in cerebral ischemia/reperfusion injury associated with diabetes mellitus, a diabetes mellitus mouse model of cerebral ischemia/reperfusion injury was established by occlusion of the middle cerebral artery. To overexpress CTRP6 in the brain, an adeno-associated virus carrying CTRP6 was injected into the lateral ventricle. The result was that oxygen injury and inflammation in brain tissue were clearly attenuated, and the number of neurons was greatly reduced. In vitro experiments showed that CTRP6 knockout exacerbated oxidative damage, inflammatory reaction, and apoptosis in cerebral cortical neurons in high glucose hypoxia-simulated diabetic cerebral ischemia/reperfusion injury. CTRP6 overexpression enhanced the sirtuin-1 signaling pathway in diabetic brains after ischemia/reperfusion injury. To investigate the mechanism underlying these effects, we examined mice with depletion of brain tissue-specific sirtuin-1. CTRP6-like protection was achieved by activating the sirtuin-1 signaling pathway. Taken together, these results indicate that CTRP6 likely attenuates cerebral ischemia/reperfusion injury through activation of the sirtuin-1 signaling pathway.

Homer1a reduces inflammatory response after retinal ischemia/reperfusion injury

Elevated intraocular pressure(IOP)is one of the causes of retinal ischemia/reperfusion injury,which results in NRP3 inflammasome activation and leads to visual damage.Homerla is repo rted to play a protective role in neuroinflammation in the cerebrum.However,the effects of Homerla on NLRP3inflammasomes in retinal ischemia/reperfusion injury caused by elevated IOP remain unknown.In our study,animal models we re constructed using C57BL/6J and Homer1^(flox/-)/Homerla^(+/-)/Nestin-Cre^(+/-)mice with elevated IOP-induced retinal ischemia/repe rfusion injury.For in vitro expe riments,the oxygen-glucose deprivation/repe rfusion injury model was constructed with M uller cells.We found that Homerla ove rexpression amelio rated the decreases in retinal thickness and Muller cell viability after ischemia/reperfusion injury.Furthermore,Homerla knockdown promoted NF-κB P65^(Ser536)activation via caspase-8,NF-κB P65 nuclear translocation,NLRP3 inflammasome formation,and the production and processing of interleukin-1βand inte rleukin-18.The opposite results we re observed with Homerla ove rexpression.Finally,the combined administration of Homerla protein and JSH-23 significantly inhibited the reduction in retinal thickness in Homer1^(flox/-)Homer1a^(+/-)/Nestin-Cre^(+/-)mice and apoptosis in M uller cells after ischemia/reperfusion injury.Taken together,these studies demonstrate that Homer1a exerts protective effects on retinal tissue and M uller cells via the caspase-8/NF-KB P65/NLRP3 pathway after I/R injury.

Extracellular vesicles for delivering therapeutic agents in ischemia/reperfusion injury

Ischemia/reperfusion(I/R)injury ismarked by the restriction and subsequent restoration of blood supply to an organ.This process can exacerbate the initial tissue damage,leading to further disorders,disability,and even death.Extracellular vesicles(EVs)are crucial in cell communication by releasing cargo that regulates the physiological state of recipient cells.The development of EVs presents a novel avenue for delivering therapeutic agents in I/R therapy.The therapeutic potential of EVs derived from stem cells,endothelial cells,and plasma in I/R injury has been actively investigated.Therefore,this review aims to provide an overview of the pathological process of I/R injury and the biophysical properties of EVs.We noted that EVs serve as nontoxic,flexible,and multifunctional carriers for delivering therapeutic agents capable of intervening in I/R injury progression.The therapeutic efficacy of EVs can be enhanced through various engineering strategies.Improving the tropism of EVs via surface modification and modulating their contents via preconditioning are widely investigated in preclinical studies.Finally,we summarize the challenges in the production and delivery of EV-based therapy in I/R injury and discuss how it can advance.This review will encourage further exploration in developing efficient EV-based delivery systems for I/R treatment.

Morphological and functional observations of a novel model of retinal ischemia injury induced by bilateral carotid artery stenosis in mice

AIM:To investigate the features of retinal ischemic injuries in a novel mouse model with bilateral carotid artery stenosis(BCAS).METHODS:BCAS was induced with microcoil implantation in 6-8-week-old C57BL6 mice.Cerebral blood flow was monitored at 2,7,and 28d postoperatively.Retinal morphological changes were evaluated by fundus photography and hematoxylin-eosin staining.Fluorescein fundus angiography(FFA)was performed to detect retinal vascular changes and circulation.The levels of apoptosis,activation of neurogliosis,and expression of hypoxiainducible factor(HIF)-1αin the retina were assessed by Western blotting and immunofluorescence staining,followed by retinal ganglion cell(RGC)density detection.Additionally,electrophysiological examinations including photopic negative response(PhNR)was also performed.RESULTS:The mice demonstrated an initial rapid decrease in cerebral blood flow,followed by a 4-week recovery period after BCAS.The ratio of retinal artery and vein was decreased under fundus photography and FFA.Compared with the sham mice,BCAS mice showed thinner retinal thickness on day 28.Additionally,apoptosis was increased and RGC density was decreased mainly in peripheral retinal region.Neurogliosis was mainly located in the inner retinal layers,with a stable increase in HIF-1αexpression.The dark-adapted electroretinogram showed a notable reduction in the a-,b-,and oscillatory potential(OP)wave amplitudes between days 2 and 7;this gradually recovered over the following 4wk.However,the b-and OPwave amplitudes were still significantly decreased on PhNR examination on day 28.CONCLUSION:BCAS can result in relatively mild retinal ischemia injuries in mice,mainly in the inner layer and peripheral region.Our study provides a novel animal model for investigating retinal ischemic diseases.

N-acetylserotonin alleviates retinal ischemia-reperfusion injury via HMGB1/RAGE/NF-κB pathway in rats

AIM:To observe the effects of N-acetylserotonin(NAS)administration on retinal ischemia-reperfusion(RIR)injury in rats and explore the underlying mechanisms involving the high mobility group box 1(HMGB1)/receptor for advanced glycation end-products(RAGE)/nuclear factor-kappa B(NF-κB)signaling pathway.METHODS:A rat model of RIR was developed by increasing the pressure of the anterior chamber of the eye.Eighty male Sprague Dawley were randomly divided into five groups:sham group(n=8),RIR group(n=28),RIR+NAS group(n=28),RIR+FPS-ZM1 group(n=8)and RIR+NAS+FPS-ZM1 group(n=8).The therapeutic effects of NAS were examined by hematoxylin-eosin(H&E)staining,and retinal ganglion cells(RGCs)counting.The expression of interleukin 1 beta(IL-1β),HMGB1,RAGE,and nod-like receptor 3(NLRP3)proteins and the phosphorylation of nuclear factorkappa B(p-NF-κB)were analyzed by immunohistochemistry staining and Western blot analysis.The expression of HMGB1 protein was also detected by enzyme-linked immunosorbent assay(ELISA).RESULTS:H&E staining results showed that NAS significantly reduced retinal edema and increased the number of RGCs in RIR rats.With NAS therapy,the HMGB1 and RAGE expression decreased significantly,and the activation of the NF-κB/NLRP3 pathway was antagonized along with the inhibition of p-NF-κB and NLRP3 protein expression.Additionally,NAS exhibited an anti-inflammatory effect by reducing IL-1βexpression.The inhibitory of RAGE binding to HMGB1 by RAGE inhibitor FPS-ZM1 led to a significant decrease of p-NF-κB and NLRP3 expression,so as to the IL-1βexpression and retinal edema,accompanied by an increase of RGCs in RIR rats.CONCLUSION:NAS may exhibit a neuroprotective effect against RIR via the HMGB1/RAGE/NF-κB signaling pathway,which may be a useful therapeutic target for retinal disease.

Protective Effects of Zingiberis and Acniti Praeparatae Decoction on Myocardial IschemiaReperfusion Injury in Rats

This study aimed to investigate the protective effects of zin-giberis and acniti praeparatae decoction on oxidative stress injury induced by my-ocardial ischemia reperfusion in rats. [Method] Myocardial ischemia-reperfusion was performed by ligation of the left anterior descending coronary artery for 30 min, fol-lowed by reperfusion for 60 min. The effects of zingiberis and acniti praeparatae decoction on ECG ST segment, myocardial infarction percentage, malondialdehyde （MDA） content in the serum, superoxide dismutase （SOD） activity and other indica-tors were observed. [Result] Zingiberis and acniti praeparatae decoction could effec-tively inhibit ECG ST segment elevation caused by myocardial ischemia-reperfusion injuries, reduce the percentage of myocardial infarction, decline the content of MDA in the serum, and increase the activity of SOD. [Conclusion] Zingiberis and acniti praeparatae decoction exhibits protective effects on oxidative injuries caused by my-ocardial ischemia-reperfusion injuries in rats, which may be involved in reducing the formation of myocardial free radicals and enhancing antioxidant capacity of my-ocardium.

Ligustrazine monomer against cerebral ischemia/reperfusion injury

Ligustrazine （2,3,5,6-tetramethylpyrazine） is a major active ingredient of the Szechwan lovage rhizome and is extensively used in treatment of ischemic cerebrovascular disease. The mecha- nism of action of ligustrazine use against ischemic cerebrovascular diseases remains unclear at present. This study summarizes its protective effect, the optimum time window of administra- tion, and the most effective mode of administration for clinical treatment of cerebral ischemia/ reperfusion injury. We examine the effects of ligustrazine on suppressing excitatory amino acid release, promoting migration, differentiation and proliferation of endogenous neural stem cells. We also looked at its effects on angiogenesis and how it inhibits thrombosis, the inflammatory response, and apoptosis after cerebral ischemia. We consider that ligustrazine gives noticeable protection from cerebral ischemia/reperfusion injury. The time window of ligustrazine admin- istration is limited. The protective effect and time window of a series of derivative monomers of ligustrazine such as 2-[（1,1-dimethylethyl）oxidoimino]methyl]-3,5,6-trimethylpyrazine, CXC137 and CXC 195 after cerebral ischemia were better than ligustrazine.

Autophagy: novel insights into therapeutic target of electroacupuncture against cerebral ischemia/reperfusion injury

Electroacupuncture is known as an effective adjuvant therapy in ischemic cerebrovascular disease. However, its underlying mechanisms remain unclear. Studies suggest that autophagy, which is essential for cell survival and cell death, is involved in cerebral ischemia reperfusion injury and might be modulate by electroacupuncture therapy in key ways. This paper aims to provide novel insights into a therapeutic target of electroacupuncture against cerebral ischemia/reperfusion injury from the perspective of autophagy. Here we review recent studies on electroacupuncture regulation of autophagy-related markers such as UNC-51-like kinase-1 complex, Beclin1, microtubule-associated protein-1 light chain 3, p62, and autophagosomes for treating cerebral ischemia/reperfusion injury. The results of these studies show that electroacupuncture may affect the initiation of autophagy, vesicle nucleation, expansion and maturation of autophagosomes, as well as fusion and degradation of autophagolysosomes. Moreover, studies indicate that electroacupuncture probably modulates autophagy by activating the mammalian target of the rapamycin signaling pathway.This review thus indicates that autophagy is a therapeutic target of electroacupuncture treatment against ischemic cerebrovascular diseases.

Role of P-selectin and anti-P-selectin monoclonal antibody in apoptosis during hepatic/renal ischemia-reperfusion injury

AIM To evaluale the potential role of P-selectinand anti-P-selectin monoclonal antibody(mAb)in apoptosis during hepatic/renal ischemia-reperfusion injury.METHODS Plasma P-selectin level,hepatic/renal P-selectin expression and cell apoptosiswere detected in rat model of hepatic/ renalischemia-reperfusion injury.ELISA,immunohist-ochemistry and TUNEL were used.Someischemia-reperfusion rats were treated with anti-P-selectin mAb.RESULTS Hepatic/renal function insuffic-iency,up-regulated expression of P-selectin inplasma and hepatic/renal tissue,hepatic/renalhistopathological damages and cell apoptosiswere found in rats with hepatic/renal ischemia-reperfusion injury,while these changes becameless conspicuous in animals treated with anti-P-selectin mAb.CONCLUSION P-selectin might mediateneutrophil infiltration and cell apoptosis andcontribute to hepatic/renal ischemia-reperfusioninjury,anti-P-selectin mAb might be an efficientapproach for the prevention and treatment ofhepatic/renal ischemia-reperfusion injury.

Effect of peroxisome proliferator-activated receptor gamma agonist on heart of rabbits with acute myocardial ischemia/reperfusion injury

Objective:To explore protective effect of rosiglitazone on myocardial ischemia reperfusion injury.Methods:A total of 48 male SD rats were randomly divided into control group(A),I/R group(B),high dose of rosiglitazone(C),low dose of rosiglitazone(D).Plasm concentration of creatine kinase(CK),CK-MB,hsCRP,Superoxide dismutase(SOD),malondialdehyde(MDA),glutathione peroxidase(GSH-Px),nitric oxide(NO)and endothelin(ET)were measured 1 h later after I/R.24 h after I/R hearts were harvested to observe pathological and ultrastructural changes.Immunohistochemistry and western blotting was used to test CD40 expression in myocardial tissue.Area of myocardial infarction were tested,arrhythmia rate during I/R was recorded.Results:Plasm concentration of creatine kinase(CK),CK-MB,hsCRP,NO,MDA and ET were decreased in group C,D compared with group B.Plasm concentration of T-SOD and GSHPx was increased significantly in group C,D compared with group B.Compared with group B,pathological and ultrastructural changes in group C,D were slightly.Myocardial infarction area and arrhythmia rate were lower in group C,D compare with group B.Conclusions:Rosiglitazone can protect myocardium from I/R injury by enhancing T-SOD and GSH-Px concentration,inhibit inflammatory reaction,improve endothelial function,reduce oxidative stress and calcium overload.

Protective effect of hyperoside on cardiac ischemia reperfusion injury through inhibition of ER stress and activation of Nrf2 signaling

Objective:To study the protective effect of hyperoside(Hyp) on cardiac ischemia reperfusion injury and its potential mechanism.Methods:Rats were divided into two groups for the evaluation,the Hyp(50 uM Hyp;n=8) and the control group(n=8).Rat hearts were isolated and perfused with Krebs-Henseleit buffer(KHB) for 30 min.After being inhibited with cardioplegic solution,they were stored for 4 h in B21 solution at 4℃.Afterwards,rat hearts were perfused with KHB again for 45 min.In this period.Hyp was added into solutions of cardioplegia for storage and KHB.Parameters of cardiac functions,including heart rate,the systolic pressure of the left ventricle,the end-diastolic pressure of the left ventricle,the developed pressure of the left ventricle,the left-ventricular systolic pressure and the peak rise rate of the pressure of the left ventricle were recorded.The levels of adenosine triphosphate(ATP),the content of malondialdehyde and apoptotic cells were determined to evaluate the protective effect of Hyp on hearts suffered from ischemia reperfusion injury.Moreover,cultured cardiac myocytes were subjected to the process simulating ischemia/reperfusion.What were analyzed included the endoplasmic reticulum(ER) stress hallmarks expressions,such as binding immunoglobulin protein and C/EBP homologous protein,using the western blot and real-time PCR.Besides,the NF-E2-related factor 2(Nrf2) expression was measured to explore the potential mechanism.Results:Compared with the control group,the Hyp group had better cardiac functional parameters and higher ATP levels;pretreatment of Hyp greatly relieved the apoptosis of myocyte,decreased oxidative stress as well as ER stress and activated the signaling pathway of anti-oxidative Nrf2 to a further extent.Conclusions:Hyp plays an important role in preserving cardiac function by improving ATP levels of tissue,easing oxidative injury of myocardium and reducing apoptosis following IRI dramatically,while the ER stress inhibition and the downstream Nrf2 signaling activation may contribute to the effects of protection.

Ginsenoside Rd inhibits apoptosis following spinal cord ischemia/reperfusion injury

Ginsenoside Rd has a clear neuroprotective effect against ischemic stroke. We aimed to verify the neuroprotective effect of ginsenoside Rd in spinal cord ischemia/reperfusion injury and explore its anti-apoptotic mechanisms. We established a spinal cord ischemia/reperfusion injury model in rats through the occlusion of the abdominal aorta below the level of the renal artery for 1 hour. Successfully established models were injected intraperitoneally with 6.25, 12.5, 25 or 50 mg/kg per day ginsenoside Rd. Spinal cord morphology was observed at 1, 3, 5 and 7 days after spinal cord ischemia/reperfusion injury. Intraperitoneal injection of ginsenoside Rd in ischemia/reperfusion injury rats not only improved hindlimb motor function and the morphology of motor neurons in the anterior horn of the spinal cord, but it also reduced neuronal apoptosis. The optimal dose of ginsenoside Rd was 25 mg/kg per day and the optimal time point was 5 days after ischemia/ reperfusion. Immunohistochemistry and western blot analysis showed ginsenoside Rd dose-de- pendently inhibited expression of pro-apoptotic Caspase 3 and down-regulated the expression of the apoptotic proteins ASK1 and JNK in the spinal cord of rats with spinal cord ischemia/reper- fusion injury. These findings indicate that ginsenoside Rd exerts neuroprotective effects against spinal cord ischemia/reperfusion injury and the underlying mechanisms are achieved through the inhibition of ASK1-JNK pathway and the down-regulation of Caspase 3 expression.

Heme oxygenase-1 protects donor livers from ischemia/reperfusion injury:The role of Kupffer cells

AIM:To examine whether heme oxygenase (HO)-1 overexpression would exert direct or indirect effects on Kupffer cells activation, which lead to aggravation of reperfusion injury.METHODS: Donors were pretreated with cobalt protoporphyrin (CoPP) or zinc protoporphyrin (ZnPP), HO-1 inducer and antagonist, respectively. Livers were stored at 4℃ for 24 h before transplantation. Kupffer cells were isolated and cultured for 6 h after liver reperfusion.RESULTS: Postoperatively, serum transaminases were significantly lower and associated with less liver injury when donors were pretreated with CoPP, as compared with the ZnPP group. Production of the cytokines tumor necrosis factor-α and interleukin-6 generated by Kupffer cells decreased in the CoPP group. The CD14 expression levels (RT-PCR/Western blots) of Kupffer cells from CoPP-pretreated liver grafts reduced.CONCLUSION: The study suggests that the potential utility of HO-1 overexpression in preventing ischemia/reperfusion injury results from inhibition of Kupffer cells activation.

Biliary tract injury caused by different relative warm ischemia time in liver transplantation in rats

BACKGROUND: There is a controversy over the degree of liver and biliary injury caused by the period of secondary warm ischemia. A liver autotransplantation model was adopted because it excludes the effects of infection and immunological rejection on bile duct injury. This study was undertaken to assess biliary tract injury caused by relative warm ischemia (secondary warm ischemia time in the biliary tract) and reperfusion. METHODS: One hundred and two rats were randomly divided into 5 groups: group I (control); groups 11 to V, relative warm ischemia times of 0 minute, 30 minutes, I hour and 2 hours. In addition to the levels of serum alkaline phosphatase, and total bilirubin, pathomorphology assessment and TUNEL assay were performed to evaluate biliary tract damage. RESULTS: Under the conditions that there were no significant differences in warm ischemia time, cold perfusion time and anhepatic phase, group comparisons showed statistically significant differences. The least injury occurred in group H (portal vein and hepatic artery reperfused simultaneously) but the most severe injury occurred in group V (biliary tract relative warm ischemia time 2 hours). CONCLUSIONS: Relative warm ischemia is one of the factors that result in bile duct injury, and the relationship between relative warm ischemia time the bile injury degree is time-dependent. Simultaneous arterial and portal reperfusion is the best choice to avoid the bile duct injury caused by relative warm ischemia. (Hepatobiliary Pancreat Dis Int 2009; 8: 247-254)

Heme oxygenase-1 protects rat liver against warm ischemia/reperfusion injury via TLR2/TLR4-triggered signaling pathways

AIM:To investigate the efficacy and molecularmechanisms of induced heme oxygenase(HO)-1 in protecting liver from warm ischemia/reperfusion(I/R)injury.METHODS:Partial warm ischemia was produced in the left and middle hepatic lobes of SD rats for 75min,followed by 6 h of reperfusion.Rats were treated with saline,cobalt protoporphyrin(Co PP)or zinc protoporphyrin(Zn PP)at 24 h prior to the ischemia insult.Blood and samples of ischemic lobes subjected to ischemia were collected at 6 h after reperfusion.Serum transaminases level,plasma lactate dehydrogenase and myeloperoxidase activity in liver were measured.Liver histological injury and inflammatory cell infiltration were evaluated by tissue section and liver immunohistochemical analysis.We used quantitative reverse transcription polymerase chain reaction to analyze liver expression of inflammatory cytokines and chemokines.The cell lysates were subjected to immunoprecipitation with anti-Toll-IL-1R-containing adaptor inducing interferon-β(TRIF)and anti-myeloid differentiation factor 88(My D88),and then the immunoprecipitates were analyzed by SDS-PAGE and immunoblotted with the indicated antibodies.RESULTS:HO-1 protected livers from I/R injury,as evidenced by diminished liver enzymes and wellpreserved tissue architecture.In comparison with Zn PP livers 6 h after surgery,Co PP treatment livers showed a significant increase inflammatory cell infiltration of lymphocytes,plasma cells,neutrophils and macrophages.The Toll-like receptor(TLR)-4 and TANK binding kinase1 protein levels of rats treated with Co PP significantly reduced in TRIF-immunoprecipitated complex,as compared with Zn PP treatment.In addition,pretreatment with Co PP reduced the expression levels of TLR2,TLR4,IL-1R-associated kinase(IRAK)-1 and tumor necrosis factor receptor-associated factor 6 in My D88-immunoprecipitated complex.The inflammatory cytokines and chemokines m RNA expression rapidly decreased inCo PP-pretreated liver,compared with the Zn PP-treated group.However,the expression of negative regulators Tollinteracting protein,suppressor of cytokine signaling-1,IRAK-M and Src homology 2 domain-containing inositol-5-phosphatase-1 in Co PP treatment rats were markedly up-regulated as compared with Zn PP-treated rats.CONCLUSION:HO-1 protects liver against I/R injury by inhibiting TLR2/TLR4-triggered My D88-and TRIFdependent signaling pathways and increasing expression of negative regulators of TLR signaling in rats.