Marked difference in tumor necrosis factor-alpha expression in warm ischemia- and cold ischemia-reperfusion of the rat liver

Prompt Graft Cooling Enhances Cardioprotection during Heart Transplantation Procedures through the Regulation of Mitophagy

A complete and prompt cardiac arrest using a cold cardioplegic solution is routinely used in heart transplantation to protect the graft function. However, warm ischemic time is still inevitable during the procedure to isolate donor hearts in the clinical setting. Our knowledge of the mechanism changes prevented by cold storage, and how warm ischemia damages donor hearts, is extremely poor. The potential consequences of this inevitable warm ischemic time to grafts, and the underlying potential protective mechanism of prompt graft cooling, have been studied in order to explore an advanced graft protection strategy. To this end, a surgical procedure, including 10-15 min warm ischemic time during procurement, was performed in mouse models to mimic the clinical situation (Group I), and compared to a group of mice that had the procurement performed with prompt cooling procedures (Group II). The myocardial morphologic changes (including ultrastructure) were then assessed by electron and optical microscopy after 6 h of cold preservation. Furthermore, syngeneic heart transplantation was performed after 6 h of cold preservation to measure the graft heart function. An electron microscopy showed extensive damage, including hypercontracted myofibers with contraction bands, and damaged mitochondria that released mitochondrial contents in Group I mice, while similar patterns of damage were not observed in the mice from Group II. The results from both the electron microscopy and immunoblotting verified that cardiac mitophagy (protective mitochondrial autophagy) was present in the mice from Group II, but was absent in the mice from Group I. Moreover, the mice from Group II demonstrated faster rebeating times and higher beating scores, as compared to the mice from Group I. The pressure catheter system results indicated that the graft heart function was significantly more improved in the mice from Group II than in those from Group I, as demonstrated by the left ventricle systolic pressure (31.96 ± 6.54 vs. 26.12 ± 8.87 mmHg), the +dp/dt (815.6 ± 215.4 vs. 693.9 ± 153.8 mmHg/s), and the -dp/dt: (492.4 ± 92.98 vs. 418.5 ± 118.9 mmHg/s). In conclusion, the warm ischemic time during the procedure impaired the graft function and destroyed the activation of mitophagy. Thus, appropriate mitophagy activation has emerged as a promising therapeutic target that may be essential for graft protection and functional improvement during heart transplantation.

Mitochondrial Damage-Associated Molecular Patterns (MTDs) Are Released during Hepatic Ischemia Reperfusion and Induce Inflammatory Responses

Ischemia / reperfusion injury (IRI) during the course of liver transplantation enhances the immunogenicity of allografts and thus impacts overall graft outcome. This sterile inflammatory insult is known to activate innate immunity and propagate organ damage through the recognition of damage-associate molecular pattern (DAMP) molecules. The purpose of the present study was to investigate the role of mitochondrial DAMPs (MTDs) in the pathogenesis of hepatic IRI. Using in vitro models we observed that levels of MTDs were significantly higher in both transplantation-associated and warm IR, and that co-culture of MTDs with human and rat hepatocytes significantly increased cell death. MTDs were also released in an in vivo rat model of hepatic IRI and associated with increased secretion of inflammatory cytokines (TNF-α, IL-6, and IL-10) and increased liver injury compared to the sham group. Our results suggest that hepatic IR results in a significant increase of MTDs both in vitro and in vivo suggesting that MTDs may serve as a novel marker in hepatic IRI. Co-culture of MTDs with hepatocytes showed a decrease in cell viability in a concentration dependent manner, which indicates that MTDs is a toxic mediator participating in the pathogenesis of liver IR injury.

Mechanisms of Toll-like receptor 4 (TLR4)-mediated inflammation after cold ischemia/reperfusion in the heart

BACKGROUND

Toll-Like Receptor 4 (TLR4) signaling mediates early inflammation after cold ischemia-reperfusion (I/R). We hypothesized that the TLR4 coreceptor CD14, the intracellular adaptor proteins myeloid differentiation factor 88 (MyD88) and TIR domain-containing-adaptor inducing IFNbeta (TRIF) would be required for cold I/R induced inflammation. High mobility group box 1 (HMGB1) is a putative endogenous activator of TLR4. Therefore, we also assessed the contribution of HMGB1 in cold I/R induced inflammation.

METHODS

Syngeneic heart transplants were performed in mice deficient in CD14, MyD88, TRIF, or wild-type mice. In other experiments, anti-HMGB1 neutralizing antibody or control IgG was administered at reperfusion. Donor hearts were subjected to 2 hr of cold ischemia and retrieved after 3 hr of reperfusion.

RESULTS

After cold I/R, grafts revealed striking translocation of HMGB1 out of the nucleus in cardiac myocytes. Administration of an anti-HMGB1 neutralizing antibody resulted in reduced systemic interleukin (IL)-6, tumor necrosis factor alpha (TNFalpha), and intercellular adhesion molecule-1 (ICAM-1) messenger RNA (mRNA) levels (P< or =0.05). Compared with controls, CD14 knock-out (KO) mice exhibited significantly lower (P< or =0.05) systemic IL-6 and JE/monocyte chemotractant protein-1 levels after cold I/R. Intragraft TNFalpha and IL-1beta mRNA levels were also significantly lower (P< or =0.05) in CD14 KO grafts. MyD88 KO mice exhibited significantly lower (P< or=0.05) systemic IL-6 levels compared with control mice after cold I/R. Intragraft TNFalpha, IL-6, and ICAM-1 mRNA levels were also significantly lower (P< or =0.05) in MyD88 KO grafts. Significantly lower levels (P< or =0.05) of serum IL-6, monocyte chemotractant protein-1 as well as intragraft TNFalpha, IL-6, IL-1beta, and ICAM-1 were observed after cold I/R in TRIF deficient animals compared with controls.

CONCLUSIONS

CD14, MyD88, TRIF, and HMGB1 contribute to the inflammatory response that occurs after cold I/R. These results provide insight into the mechanisms of TLR4-mediated inflammation after cold I/R.

Effects of anti-inflammatory cytokine agent (FR167653) and serine protease inhibitor on warm ischemia-reperfusion injury of the liver graft

BACKGROUND

The shortage of donors has become a serious problem. Some institutes have tried to use grafts retrieved from non-heart-beating donors (NHBDs), but the results have not been satisfactory. This study clarifies the effects of nafamostat mesilate (NM), a strong serine protease inhibitor, and FR167653, a suppressant of both tumor necrosis factor-alpha and interleukin-1beta release, on warm ischemia-reperfusion injury and establishes the procurement of the grafts for a successful liver transplant using uncontrolled NHBDs.

METHODS

Male Wistar rats were divided into five groups as follows (n = 5): (1) heart-beating (HB) group, in which livers were retrieved from heart-beating donors; (2) non-heart-beating (NHB) group, in which livers were retrieved from NHBDs; (3) NM group, in which livers were retrieved from NHBDs pretreated with NM (0.2 mg/kg/hr, for 30 min); (4) FR group, in which livers were retrieved from NHBDs pretreated with FR167653 (2 mg/kg); and (5) FR+NM group, in which livers were retrieved from NHBDs pretreated with FR167653 and NM. The livers were perfused for 60 min with Krebs-Henseleit bicarbonate buffer after cold preservation 6 hr.

RESULTS

In the NHB group, the values of interleukin-1beta, tumor necrosis factor-alpha, thromboxane B2, and leukotriene B4, and the expressions of nuclear factor-kappaB, activating protein 1, and cyclooxygenase-2 were significantly higher than those in the HB group. In the FR+NM group, those values were low, the structure of the sinusoids was preserved, and the sinusoidal lumen was maintained (the same as observed in the HB group).

CONCLUSIONS

FR167653 and NM inhibited the induction of inflammatory cytokines and arachidonic acid cascade mediators. This combined therapy was effective in preserving sinusoidal microcirculation in the liver grafts from NHBDs.

Attenuation of Kupffer cell activation in cold-preserved livers after pretreatment of rats with methylprednisolone or its macromolecular prodrug

PURPOSE

Activation of hepatic Kupffer cells (KCs) during organ preservation and subsequent reperfusion causes release of proinflammatory mediators and is responsible, at least in part, for rejection of transplanted livers. Our hypothesis was that donor pretreatment, before liver harvest, with methylprednisolone (MP) or its dextran prodrug (DMP) would reduce KC activation.

METHODS

Adult donor rats were administered a single 5-mg/kg (MP equivalent) IV dose of MP or DMP or saline 2 h before liver harvest. The livers were then stored in University of Wisconsin solution for 24, 48, or 96 h (n = 4/treatment/time). A recirculating perfusion model was used to study, for 180 min, the release of KC activation markers, tumor necrosis factor (TNF)-alpha and acid phosphatase, and other biochemical indices from the cold-preserved livers.

RESULTS

Cold ischemia-reperfusion resulted in release of substantial levels of TNF-alpha in untreated groups. Pretreatment of rats with MP or DMP caused a significant (p < 0.0001) reduction in TNF-alpha AUC in the perfusate, with no significant differences between MP and DMP. The maximum inhibitory effect of MP (77.5 +/- 10.2%) was observed after 48 h of preservation, whereas DMP showed maximal inhibition of TNF-alpha AUC at both 24 (74.5 +/- 15.8%) and 48 (74.8 +/- 12.6%) h of preservation. Similarly, both MP and DMP resulted in a significant (p < 0.0004) decrease in acid phosphatase levels of cold-preserved livers. However, neither pretreatment had any substantial effect on the levels of other biochemical markers.

CONCLUSIONS

Both MP and DMP pretreatments decreased the release of TNF-alpha and acid phosphatase from livers subjected to cold ischemia preservation. Therefore, pretreatment of liver donors with MP or its prodrug decreases KC activation by cold ischemia-reperfusion.

The interplay of collagen IV, tumor necrosis factor-alpha, gelatinase B (matrix metalloprotease-9), and tissue inhibitor of metalloproteases-1 in the basal lamina regulates Sertoli cell-tight junction dynamics in the rat testis

During spermatogenesis, preleptotene and leptotene spermatocytes must translocate across the blood-testis barrier formed by inter-Sertoli cell-tight junctions (TJs) from the basal compartment of the seminiferous epithelium adjacent to the basement membrane to the adluminal compartment at stages VIII-IX for further development. Because of the close proximity between extracellular matrix (ECM) that constitutes the basement membrane and the blood-testis barrier, we sought to investigate the role of ECM in Sertoli cell TJ dynamics. When Sertoli cells were cultured in vitro to initiate the assembly of the Sertoli cell TJ-permeability barrier, the presence of an anticollagen IV antibody indeed perturbed the barrier. Because ECM is known to maintain a pool of cytokines and TNFalpha has been shown to regulate TJ dynamics in other epithelia, we investigated whether TNFalpha can regulate Sertoli cell TJ function via its effects on collagen alpha3(IV) and other proteins that maintain the homeostasis of ECM. As expected, recombinant TNFalpha perturbed the Sertoli cell TJ-barrier assembly in vitro dose dependently. TNFalpha also inhibited the timely induction of occludin, which is known to associate with the Sertoli cell TJ-barrier assembly. Furthermore, TNFalpha induced the expression of Sertoli cell collagen alpha3(IV), gelatinase B (matrix metalloprotease-9, MMP-9) and tissue inhibitor of metalloproteases-1 but not gelatinase A (matrix metalloprotease-2), and promoted the activation of pro-MMP-9. These results thus suggest that the activated MMP-9 induced by TNFalpha is used to cleave the existing collagen network in the ECM, thereby perturbing the TJ-barrier. This in turn creates a negative feedback that causes TNFalpha to induce collagen alpha3(IV) and tissue inhibitor of metalloproteases-1 expression so as to replenish the collagen network in the disrupted TJ-barrier and limit the activity of MMP-9. Taken collectively, these observations strengthen the notion that ECM is involved in the regulation of junction dynamics in addition to its structural role in the testis.

Improvement of rat liver function by energy repletion after the preservation period: implications for hepatic graft management

We very recently showed (using a blood-free perfusion model) that cold preservation sensitized rat hepatocyte functions to rewarming ischemic injury and that the injury can be prevented by repleting high-energy adenylates in the liver by short-term oxygenated warm reperfusion. Here we investigated whether short-term reperfusion after the preservation period can improve hepatic graft function in a blood reperfusion model. Eighteen-hour cold-preserved rat livers either untreated (Group A) or pretreated by 30-min oxygenated warm reperfusion after preservation (Group B) were subjected to 20-min ischemic rewarming and then reperfused with blood. Livers in Group B compared to Group A exhibited approx. three times increased bile production and bromosulfophthalein excretion, nearly 7-fold decreased swelling, and 1.2-fold improved blood flow. These results suggest that repletion of the energy by short-term oxygenated reperfusion after prolonged preservation may improve markedly initial hepatic graft function.