Ischemic postconditioning inhibits apoptosis after renal ischemia/reperfusion injury in rat

Treatment with a novel hypoxia-inducible factor hydroxylase inhibitor (TRC160334) ameliorates ischemic acute kidney injury

BACKGROUND

Hypoxia-inducible factor (HIF) transcriptional system plays a central role in cellular adaptation to low oxygen levels. Preconditional activation of HIF and/or expression of its individual target gene products leading to cytoprotection have been well established in hypoxic/ischemic renal injury. Increasing evidence indicate HIF activation is involved in hypoxic/ischemic postconditioning of heart, brain and kidney. Very few studies evaluated the potential benefits of postischemia HIF activation in renal injury employing a pharmacological agent. We hypothesized that postischemia augmentation of HIF activation with a pharmacological agent would protect renal ischemia/reperfusion injury. For this, TRC160334, a novel HIF hydroxylase inhibitor, was used.

METHODS

TRC160334, a novel HIF hydroxylase inhibitor, was synthesized. Ability of TRC160334 for stabilization of HIF-α and consequent HIF activation was evaluated in Hep3B cells. Efficacy of TRC160334 was evaluated in a rat model of ischemia/reperfusion-induced AKI. Two different treatment protocols were employed, one involved treatment with TRC160334 before onset of ischemia, the other involved treatment after the reperfusion of kidneys.

RESULTS

TRC160334 treatment results in stabilization of HIF-α leading to HIF activation in Hep3B cells. Significant reduction in renal injury was observed by both treatment protocols and remarkable reduction in serum creatinine (23 and 71% at 24 and 48 h, respectively, p < 0.01) was observed with TRC160334 treatment applied after reperfusion. Urine output was significantly improved up to 24 h by both treatment protocols.

CONCLUSION

The data presented here provide pharmacologic evidence for postischemia augmentation of HIF activation by TRC160334 as a promising and clinically feasible strategy for the treatment of renal ischemia/reperfusion injury.

Attenuation of endoplasmic reticulum stress and mitochondrial injury in kidney with ischemic postconditioning application and trimetazidine treatment

Background

Endoplasmic reticulum (ER) and mitochondria have been implicated in the pathology of renal ischemia/reperfusion (I/R). In the present study, we investigated whether the use of ischemic postconditioning (IPostC) and trimetazidine (TMZ) separately or combined could reduce ER stress and mitochondria damage after renal ischemia.

Methods

Kidneys of Wistar rats were subjected to 60-min of warm ischemia followed by 120-min of reperfusion (I/R group, n = 6), or to 6 cycles of ischemia/reperfusion (10-s each cycle) just after 60-min of warm ischemia (IPostC group, n = 6), or to i.p. injection of TMZ (3 mg/kg) 30-min before ischemia (TMZ group, n = 6), or to the combination of both treatments (IPostC+TMZ group, n = 6). The results of these experimental groups were compared to those of a sham-operated group in which rat renal pedicles were only dissected. Sodium reabsorption rate, creatinine clearance lactate deshydrogenase (LDH) activity in plasma, and concentration of malonedialdehyde (MDA) in tissue were determined. In addition, Western blot analysis was performed to identify the amounts of cytochrome c, c-JunNH2-terminal kinase (JNK), voltage-dependent anion channel (VDAC), glycogen synthase kinase 3-beta (GSK3-β), and ER stress parameters.

Results

IPostC or/and TMZ significantly decreased cytolysis, oxidative stress and improved renal function in comparison to I/R group. IPostC but not TMZ significantly attenuated ER stress parameters versus I/R group. Indeed, it down-regulated the glucose-regulated protein 78 (GRP78), the activating transcription factor 4 (ATF4), the RNA activated protein kinase (PKR)-like ER kinas (PERK), the X box binding protein-1 (XBP-1) and the caspase12 protein levels. TMZ treatment significantly augmented GSK3-β phosphorylation and reduced levels of cytochrome c and VDAC phosphorylation in comparison to IPostC application. The combination of both treatments gave a synergetic effect. It significantly improved the survival rate, attenuated cytolysis, oxidative stress and improved renal function.

Conclusion

This study revealed that IPostC protects kidney from I/R injury by suppressing ER stress while the beneficial effects of TMZ are mediated by mitochondria protection. The combination of both treatments ameliorated functional recovery.

Ischemic postconditioning inhibits the renal fibrosis induced by ischemia-reperfusion injury in rats

OBJECTIVE

To investigate whether ischemic postconditioning effects on the development of tubulointerstitial fibrosis follow acute renal ischemia-reperfusion.

METHODS

Rat models of warm renal I/R were established by clamping left pedicles for 45 minutes after right nephrectomy, both with and without treatment with ischemic postconditioning, and then reperfused for up to 12 weeks. Hematoxylin-eosin (H&E) and Masson's trichrome staining were used to assess renal fibrosis. The expression spot and protein levels of α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1), and phospho-Smad2 were also analyzed.

RESULTS

Our data showed that patchy inflammation and tubulointerstitial fibrosis were found 12 weeks later in rats subjected to I/R alone or with postconditioning. Tubulointerstitial fibrosis worsened further in rats subjected to 45-minute ischemia-reperfusion, accompanied by the increased expressions of α-SMA, TGF-β1, and phospho-Smad2 at the end of 12 weeks. In contrast, the above histologic changes and molecular expressions were significantly attenuated in rats of ischemic postconditioning group.

CONCLUSION

The results indicated that 45-minute I/R injury may cause tubulointerstitial fibrosis in the long term, and ischemic postconditioning has beneficial effects on renal fibrosis. Its mechanisms may involve inhibition of the TGF-β1/phospho-Smad2 pathway to exert protective effects.

Perconditioning and postconditioning: current knowledge, knowledge gaps, barriers to adoption, and future directions

The broad definition of "conditioning" is the application of a series of alternating intervals of brief ischemia (hypoxia) and reperfusion (reoxygenation) applied in the setting of prolonged ischemia causing myocardial infarction. While the conditioning stimulus is applied before the major (index) ischemic event in ischemic preconditioning, it is applied during the event in perconditioning, and applied after the event (reperfusion) in postconditioning. Studies on perconditioning have only recently demonstrated a reduction in infarct size by remote ischemia applied during transport of heart attack victims to the hospital before percutaneous coronary interventions (PCIs). The "conditioning" paradigm has been extended to include remote perconditioning and remote postconditioning. However, the biology of perconditioning is virtually unknown. Postconditioning has enjoyed enthusiastic attention from scientists that have done much to demonstrate that the model of triggers, mediators, and effectors used in preconditioning may also apply to postconditioning, with the addition and important contribution of physiological mechanisms resulting in cardioprotection, including gradual normalization of tissue pH, reduction in generation of reactive oxygen species, and avoidance of hypercontracture. This same schema has not been confirmed in perconditioning. However, the unknowns in both conditioning paradigms far outweigh the knowns. Why postconditioning does not exert cardioprotection in experimental models of comorbidities and aging, yet reduces postischemic injury and contractile dysfunction in older patients with multiple comorbidities is a conundrum for which no answers are forthcoming. The optimal algorithm is unknown, as is the interrelationship between the many molecular, cellular, and physiological pathways that purportedly "mediate" or "trigger" the conditioning responses. Whether there are common pathways engaged in all 3 forms of conditioning, and what nuances separate one form of conditioning from another are unanswered questions. Yet, the translational potential of per- and postconditioning will drive further experimental work and clinical trials, which will ask unprecedented cooperation and information sharing between basic and clinician scientists, and creative developments from industry.

Contributions of heme oxygenase-1 in postconditioning-protected ischemia-reperfusion injury in rat liver transplantation

BACKGROUND

Heme oxygenase-1 (HO-1), an oxidative stress-response gene up-regulated by various physiological and exogenous stimuli, has cytoprotective activities. Ischemic postconditioning (Postcon) can protect an organ from ischemia-reperfusion (I/R) injury. In the present study, we investigated the potential contributions of HO-1 to Postcon-dependent protection against I/R injury in rat liver transplantation models.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were randomly divided into four groups: sham group with laparotomy for liver exposure; I/R group with 24-hour cold ischemia of the donor liver; Postcon group with the same treatment as the I/R group plus ischemic Postcon; and zinc protoporphyrin (ZnPP HO-1 inhibitor) + Postcon group treated the same as the Postcon cohort with donors pretreated using ZnPP 24 hours before the I/R injury. We measured liver tissue and peripheral blood samples collected at 6 hours after reperfusion and serum transaminase levels, histopathology, liver tissue malondialdehyde (MDA) content, superoxide dismutase (SOD) activity and HO-1 expression in the liver.

RESULTS

Postcon significantly diminished the elevation of serum transaminases levels after I/R injury when compared with I/R and ZnPP+Postcon groups. Postcon treated rats showed significantly lower MDA production and higher SOD activity. HO-1 was induced in rat livers exposed to Postcon; its levels were obviously overexpressed after 6 hours in Postcon rats. Inhibiting the expression of HO-1, negated the protective effects of Postcon.

CONCLUSIONS

Induction of HO-1 in the Postcon condition played a protective role against hepatic I/R injury and enhanced the early antioxidative activity. The protective effects of Postcon were significantly associated with greater intrahepatic HO-1 expression.

Ischemic postconditioning attenuates liver warm ischemia-reperfusion injury through Akt-eNOS-NO-HIF pathway

BACKGROUND

Ischemic postconditioning (IPO) has been demonstrated to attenuate ischemia/reperfusion (I/R) injury in the heart and brain, its roles to liver remain to be defined. The study was undertaken to determine if IPO would attenuate liver warm I/R injury and its protective mechanism.

METHODS

Mice were divided into sham, I/R, IPO+I/R (occlusing the porta hepatis for 60 min, then treated for three cycles of 10 sec brief reperfusion consecutively, followed by a persistent reperfusion); L-NAME+ sham (L-NAME, 16 mg/kg, i.v., 5 min before repefusion); L-NAME+I/R; and L-NAME+ IPO. Blood flow of caudate and left lobe of the liver was blocked. Functional and morphologic changes of livers were evaluated. Contents of nitric oxide, eNOS and iNOS in serum were assayed. Concentration of eNOS, iNOS, malondialdehyde (MDA) and activity of superoxide dismutase (SOD) in hepatic tissue were also measured. Expressions of Akt, p-Akt and HIF-1α protein were determined by western blot. Expressions of TNF-α and ICAM-1 were measured by immunohistochemistry and RT-PCR.

RESULTS

IPO attenuated the dramatically functional and morphological injuries. The levels of ALT was significantly reduced in IPO+I/R group (p < 0.05). Contents of nitric oxide and eNOS in serum were increased in the IPO+I/R group (p < 0.05). IPO also up-regulated the concentration of eNOS, activity of SOD in hepatic tissue (p < 0.05), while reduced the concentration of MDA (p < 0.05). Moreover, protein expressions of HIF-1α and p-Akt were markedly enhanced in IPO+I/R group. Protein and mRNA expression of TNF-α and ICAM-1 were markedly suppressed by IPO (p < 0.05). These protective effects of IPO could be abolished by L-NAME.

CONCLUSIONS

We found that IPO increased the content of NO and attenuated the overproduction of ROS and I/R-induced inflammation. Increased NO contents may contribute to increasing HIF-1α level, and HIF-1α and NO would simultaneously protect liver from I/R injury. These findings suggested IPO may have the therapeutic potential through Akt-eNOS-NO-HIF pathway for the better management of liver I/R injury.

Protective effects of ischemic postconditioning against ischemia/reperfusion injury in rats undergoing liver transplantation

AIM: To explore whether ischemic postconditioning protects against ischemia/reperfusion injury in rats undergoing liver transplantation.

METHODS: Male Sprague-Dawley rats were divided randomly into six groups: animals undergoing sham operation (sham), ischemia/reperfusion (I/R), and ischemic postconditioning consisting of 6 cycles of 10 s/10 s (post-10 s), 30 s/30 s (post-30 s), 60 s/60 s (post-60 s) or 90 s/90 s (post-90 s) reperfusion/reocclusion. At 2 and 6 h after portal vein reperfusion, blood and liver tissue samples were taken to determine liver function, histopathology, and liver homogenate MDA and SOD levels. Moreover, the survival rate of rats was measured.

RESULTS: At 2 and 6 h after reperfusion, post-30 s and post-60 s reperfusion/reocclusion markedly improved liver function, ameliorated hepatocellular damage, lowered MDA level, and elevated SOD activity compared with the I/R group (8.69 μmol/g ± 1.68 μmol/g vs 14.31 μmol/g ± 2.43 μmol/g, P = 0.0087; 10.01 UN/mg ± 0.89 UN/mg vs 6.92 UN/mg ± 1.19 UN/mg, P = 0.0092). In contrast, post-10 s and post-90 s reperfusion/reocclusion failed to protect against liver damage. Excluding the sham-operated group, rat survival rate was significantly higher in the post-60 s group than in the other groups.

CONCLUSION: Ischemic postconditioning can reduce reperfusion injury, attenuate oxidative stress, and improve survival in rats undergoing liver transplantation. Ischemic postconditioning consisting of 6 cycles of 60 s/60 s reperfusion/reocclusion exhibits the best protective effects against ischemia/reperfusion injury in rats undergoing liver transplantation.

Attenuation of renal ischemia-reperfusion injury by postconditioning involves adenosine receptor and protein kinase C activation

SUMMARY

Significant organ injury occurs after transplantation and reflow (i.e., reperfusion injury). Postconditioning (PoC), consisting of alternating periods of reperfusion and re-occlusion at onset of reperfusion, attenuates reperfusion injury in organs including heart and brain. We tested whether PoC attenuates renal ischemia-reperfusion (I/R) injury in the kidney by activating adenosine receptors (AR) and protein kinase C (PKC). The single kidney rat I/R model was used. Groups: (1) sham: time-matched surgical protocol only. In all others, the left renal artery (RA) was occluded for 45 min and reperfused for 24 h. (2) CONTROL: I/R with no intervention at R. All antagonists were administered 5 min before reperfusion. (3) PoC: I/R + four cycles of 45 s of R and 45 s of re-occlusion before full R. (4) PoC + ARi: PoC plus the AR antagonist 8-rho-(sulfophenyl) theophylline (8-SPT). (5) PoC + PKCi: PoC plus the PKC antagonist chelerythrine (Che). In shams, plasma blood urea nitrogen (BUN mg/dl) at 24 h averaged 23.2 +/- 5.3 and creatinine (Cr mg/dl) averaged 1.28 +/- 0.2. PoC reduced BUN (87.2 +/- 10 in CONTROL vs. 38.8 +/- 9, P = 0.001) and Cr (4.2 +/- 0.6 in CONTROL vs. 1.5 +/- 0.2, P < 0.001). 8-SPT and Che reversed renal protection indices after PoC. I/R increased apoptosis, which was reduced by PoC, which was reversed by 8-SPT and Che. Postconditioning attenuates renal I/R injury by adenosine receptor activation and PKC signaling.

Ischemia/reperfusion injury in kidney transplantation: mechanisms and prevention

Ischemia has been an inevitable event accompanying kidney transplantation. Ischemic changes start with brain death, which is associated with severe hemodynamic disturbances: increasing intracranial pressure results in bradycardia and decreased cardiac output; the Cushing reflex causes tachycardia and increased blood pressure; and after a short period of stabilization, systemic vascular resistance declines with hypotension leading to cardiac arrest. Free radical-mediated injury releases proinflammatory cytokines and activates innate immunity. It has been suggested that all of these changes-the early innate response and the ischemic tissue damage-play roles in the development of adaptive responses, which in turn may lead to an acute font of kidney rejection. Hypothermic kidney storage of various durations before transplantation add to ischemic tissue damage. The final stage of ischemic injury occurs during reperfusion. Reperfusion injury, the effector phase of ischemic injury, develops hours or days after the initial insult. Repair and regeneration processes occur together with cellular apoptosis, autophagy, and necrosis; the fate of the organ depends on whether cell death or regeneration prevails. The whole process has been described as the ischemia-reperfusion (I-R) injury. It has a profound influence on not only the early but also the late function of a transplanted kidney. Prevention of I-R injury should be started before organ recovery by donor pretreatment. The organ shortage has become one of the most important factors limiting extension of deceased donor kidney transplantation worldwide. It has caused increasing use of suboptimal deceased donors (high risk, extended criteria [ECD], marginal donors) and uncontrolled non-heart-beating (NHBD) donors. Kidneys from such donors are exposed to much greater ischemic damage before recovery and show reduced chances for proper early as well as long-term function. Storage of kidneys, especially those recovered from ECD (or NHBD) donors, should use machine perfusion.